Cambridge Üniversitesinden Martin Haehnelt ve meslektaşları, dünyanın en güçlü teleskoplarından biriyle yaptıkları 92 saatlik gözlem sırasında keşfettikleri 27 “yeni yetme” veya “proto-galaksi”nin, Samanyolu gibi gökadaların, daha küçük gaz ve toz bulutlarından meydana geldiğinin kanıtı olduğunu belirtti.
Şimdiye dek bu genç galaksilerden gelen ışığın çok zayıf olması nedeniyle bunların varlıklarını ispatlamakta sıkıntı çektiklerini belirten bilim adamları, “Bu galaksilerin daha küçük yığınların birleşmesiyle oluştuğunu düşünüyoruz. Önceden yığınların daha büyük galaksileri oluşturduğunu görmüştük, ama ilk kez bizim galaksimizdeki gibi bir şeylerin birleşmesine yetecek kadar küçük kümeleri gözlemledik” diye konuştu.
Astronomlar, milyarlarca yıl önce evreni son derece ince ve neredeyse sadece gaz çiminde olduğunu, sonra gazların birleşerek zayıf proto-galaksilerin oluşmaya başlamasını sağladığını düşünüyor. Birleşme ve çarpışmalarla bir araya gelen bu bileşenlerin daha sonra olgun galaksileri oluşturduğu sanılıyor. Avrupa Güney Gözlemevinin Şili’deki teleskoplarıyla yapılan gözlemlerde tespit edilen genç galaksilerin çok uzakta olduğu ve evrenin sadece 2 milyar yaşına tarihlendiği belirtiliyor
Wednesday, November 28, 2007
Users give up privacy in exchange for trust
With the public concern over online fraud, new research, funded by the Economic and Social Research Council, has revealed that internet users will reveal more personal information online if they believe they can trust the organisation that requests the information. ‘Even people who have previously demonstrated a high level of caution regarding online privacy will accept losses to their privacy if they trust the recipient of their personal information’ says Dr Adam Joinson, who led the study.
The findings of the study are vital for those aiming to create online services that pose a potential privacy threat, such as Government agencies involved in developing ID cards. The project found that even those people who declared themselves unconcerned about privacy would soon become opposed to ID cards if the way that they were asked for information made them feel that their privacy was threatened.
The ‘Privacy and Self-Disclosure Online’ project is the first of its kind, in that rigorous methods were used to measure internet users actual behaviour. Dr Joinson explains; ‘For the first time we have research which actually analyses what people do online, rather than just looking at what they say they do.’
56 % of internet users stated that they have concerns about privacy when they are online. The central issue was whether websites were seen as particularly trustworthy – or untrustworthy – causing users to alter their behaviour. When a website is designed to look trustworthy, people are willing to accept privacy violations. But, the same actions by an untrustworthy site leads to people behaving in a much more guarded manner.
In addition, the researchers looked at how the wording of questions and the design of response options further influenced levels of self-disclosure. If the response ‘I prefer not to say’ appears at the top of an options list, users are far less likely to disclose information. Similarly, if given the opportunity to remain vague in their responses, for instance in choosing how wide the scale that represents their salary is, they are more likely to opt for less disclosure – in this case, users tended to opt for a broad scale, such as £10,000 - £50,000 per year.
‘One of the most interesting aspects of our findings,’ says Dr Joinson, ‘is that even people who genuinely have a high level of concern regarding privacy online may act in a way that is contrary to their stated attitudes when they come across a particular set of conditions.’
The implications of this are wide ranging. Many services now require a level of online disclosure. According to this research, how a user assesses the trustworthiness of a website may have a real impact on the success of that service. In addition, research findings will be used to guide policy regarding how the public can be encouraged to make informed choices regarding online privacy.
The project has targeted a number of groups who can benefit from the findings, including health professionals, higher education professionals and survey bodies.
The findings of the study are vital for those aiming to create online services that pose a potential privacy threat, such as Government agencies involved in developing ID cards. The project found that even those people who declared themselves unconcerned about privacy would soon become opposed to ID cards if the way that they were asked for information made them feel that their privacy was threatened.
The ‘Privacy and Self-Disclosure Online’ project is the first of its kind, in that rigorous methods were used to measure internet users actual behaviour. Dr Joinson explains; ‘For the first time we have research which actually analyses what people do online, rather than just looking at what they say they do.’
56 % of internet users stated that they have concerns about privacy when they are online. The central issue was whether websites were seen as particularly trustworthy – or untrustworthy – causing users to alter their behaviour. When a website is designed to look trustworthy, people are willing to accept privacy violations. But, the same actions by an untrustworthy site leads to people behaving in a much more guarded manner.
In addition, the researchers looked at how the wording of questions and the design of response options further influenced levels of self-disclosure. If the response ‘I prefer not to say’ appears at the top of an options list, users are far less likely to disclose information. Similarly, if given the opportunity to remain vague in their responses, for instance in choosing how wide the scale that represents their salary is, they are more likely to opt for less disclosure – in this case, users tended to opt for a broad scale, such as £10,000 - £50,000 per year.
‘One of the most interesting aspects of our findings,’ says Dr Joinson, ‘is that even people who genuinely have a high level of concern regarding privacy online may act in a way that is contrary to their stated attitudes when they come across a particular set of conditions.’
The implications of this are wide ranging. Many services now require a level of online disclosure. According to this research, how a user assesses the trustworthiness of a website may have a real impact on the success of that service. In addition, research findings will be used to guide policy regarding how the public can be encouraged to make informed choices regarding online privacy.
The project has targeted a number of groups who can benefit from the findings, including health professionals, higher education professionals and survey bodies.
Researchers produce high performance field effect transitors with thin film of Carbon(60)
Using room-temperature processing, researchers at the Georgia Institute of Technology have fabricated high-performance field effect transistors with thin films of Carbon 60, also known as fullerene. The ability to produce devices with such performance with an organic semiconductor represents another milestone toward practical applications for large area, low-cost electronic circuits on flexible organic substrates.
The new devices – which have electron-mobility values higher than amorphous silicon, low threshold voltages, large on-off ratios and high operational stability – could encourage more designers to begin working on such circuitry for displays, active electronic billboards, RFID tags and other applications that use flexible substrates. “If you open a textbook and look at what a thin-film transistor should do, we are pretty close now,” said Bernard Kippelen, a professor in Georgia Tech’s School of Electrical and Computer Engineering and the Center for Organic Photonics and Electronics. “Now that we have shown very nice single transistors, we want to demonstrate functional devices that are combinations of multiple components. We have everything ready to do that.”
Fabrication of the Carbon60 transistors was reported August 27 th in the journal Applied Physics Letters. The research was supported by the U.S. National Science Foundation through the STC program MDITR, and the U.S. Office of Naval Research.
Researchers have been interested in making field-effect transistors and other devices from organic semiconductors that can be processed onto various substrates, including flexible plastic materials. As an organic semiconductor material, C60 is attractive because it can provide high electron mobility – a measure of how fast current can flow. Previous reports have shown that Carbon60 can yield mobility values as high as six square centimeters per volt-second (6 cm2/V/s). However, that record was achieved using a hot-wall epitaxy process requiring processing temperatures of 250 degrees Celsius – too hot for most flexible plastic substrates.
Though the transistors produced by Kippelen’s research team display slightly lower electron mobility – 2.7 to 5 cm2/V/s – they can be produced at room temperature.
“If you want to deposit transistors on a plastic substrate, you really can’t have any process at a temperature of more than 150 degrees Celsius,” Kippelen said. “With room temperature deposition, you can be compatible with many different substrates. For low-cost, large area electronics, that is an essential component.”
Because they are sensitive to contact with oxygen, the C60 transistors must operate under a nitrogen atmosphere. Kippelen expects to address that limitation by using other fullerene molecules – and properly packaging the devices.
The new transistors were fabricated on silicon for convenience. While Kippelen isn’t underestimating the potential difficulty of moving to an organic substrate, he says that challenge can be overcome.
Though their performance is impressive, the C60 transistors won’t threaten conventional CMOS chips based on silicon. That’s because the applications Kippelen has in mind don’t require high performance.
“There are a lot of applications where you don’t necessarily need millions of fast transistors,” he said. “The performance we need is by far much lower than what you can get in a CMOS chip. But whereas CMOS is extremely powerful and can be relatively low in cost because you can make a lot of circuits on a wafer, for large area applications CMOS is not economical.”
A different set of goals drives electronic components for use with low-cost organic displays, active billboards and similar applications.
“If you look at a video display, which has a refresh rate of 60 Hz, than means you have to refresh the screen every 16 milliseconds,” he noted. “That is a fairly low speed compared to a Pentium processor in your computer. There is no point in trying to use organic materials for high-speed processing because silicon is already very advanced and has much higher carrier mobility.”
Now that they have demonstrated attractive field-effect C60 transistors, Kippelen and collaborators Xiao-Hong Zhang and Benoit Domercq plan to produce other electronic components such as inverters, ring oscillators, logic gates, and drivers for active matrix displays and imaging devices. Assembling these more complex systems will showcase the advantages of the Carbon60 devices.
“The goal is to increase the complexity of the circuits to see how that high mobility can be used to make more complex structures with unprecedented performance,” Kippelen said.
The researchers fabricated the transistors by depositing C60 molecules from the vapor phase into a thin film atop a silicon substrate onto which a gate electrode and gate dielectric had already been fabricated. The source and drain electrodes were then deposited on top of the C60 films through a shadow mask.
Kippelen’s team has been working with C60 for nearly ten years, and is also using the material in photovoltaic cells. Beyond the technical advance, Kippelen believes this new work demonstrates the growing maturity of organic electronics.
“This progress may trigger interest among more conventional electronic engineers,” he said.
“Most engineers would like to work with the latest technology platform, but they would like to see a level of performance showing they could actually implement these circuits. If you can demonstrate – as we have – that you can get transistors with good reproducibility, good stability, near-zero threshold voltages, large on-off current ratios and performance levels higher than amorphous silicon, that may convince designers to consider this technology"
The new devices – which have electron-mobility values higher than amorphous silicon, low threshold voltages, large on-off ratios and high operational stability – could encourage more designers to begin working on such circuitry for displays, active electronic billboards, RFID tags and other applications that use flexible substrates. “If you open a textbook and look at what a thin-film transistor should do, we are pretty close now,” said Bernard Kippelen, a professor in Georgia Tech’s School of Electrical and Computer Engineering and the Center for Organic Photonics and Electronics. “Now that we have shown very nice single transistors, we want to demonstrate functional devices that are combinations of multiple components. We have everything ready to do that.”
Fabrication of the Carbon60 transistors was reported August 27 th in the journal Applied Physics Letters. The research was supported by the U.S. National Science Foundation through the STC program MDITR, and the U.S. Office of Naval Research.
Researchers have been interested in making field-effect transistors and other devices from organic semiconductors that can be processed onto various substrates, including flexible plastic materials. As an organic semiconductor material, C60 is attractive because it can provide high electron mobility – a measure of how fast current can flow. Previous reports have shown that Carbon60 can yield mobility values as high as six square centimeters per volt-second (6 cm2/V/s). However, that record was achieved using a hot-wall epitaxy process requiring processing temperatures of 250 degrees Celsius – too hot for most flexible plastic substrates.
Though the transistors produced by Kippelen’s research team display slightly lower electron mobility – 2.7 to 5 cm2/V/s – they can be produced at room temperature.
“If you want to deposit transistors on a plastic substrate, you really can’t have any process at a temperature of more than 150 degrees Celsius,” Kippelen said. “With room temperature deposition, you can be compatible with many different substrates. For low-cost, large area electronics, that is an essential component.”
Because they are sensitive to contact with oxygen, the C60 transistors must operate under a nitrogen atmosphere. Kippelen expects to address that limitation by using other fullerene molecules – and properly packaging the devices.
The new transistors were fabricated on silicon for convenience. While Kippelen isn’t underestimating the potential difficulty of moving to an organic substrate, he says that challenge can be overcome.
Though their performance is impressive, the C60 transistors won’t threaten conventional CMOS chips based on silicon. That’s because the applications Kippelen has in mind don’t require high performance.
“There are a lot of applications where you don’t necessarily need millions of fast transistors,” he said. “The performance we need is by far much lower than what you can get in a CMOS chip. But whereas CMOS is extremely powerful and can be relatively low in cost because you can make a lot of circuits on a wafer, for large area applications CMOS is not economical.”
A different set of goals drives electronic components for use with low-cost organic displays, active billboards and similar applications.
“If you look at a video display, which has a refresh rate of 60 Hz, than means you have to refresh the screen every 16 milliseconds,” he noted. “That is a fairly low speed compared to a Pentium processor in your computer. There is no point in trying to use organic materials for high-speed processing because silicon is already very advanced and has much higher carrier mobility.”
Now that they have demonstrated attractive field-effect C60 transistors, Kippelen and collaborators Xiao-Hong Zhang and Benoit Domercq plan to produce other electronic components such as inverters, ring oscillators, logic gates, and drivers for active matrix displays and imaging devices. Assembling these more complex systems will showcase the advantages of the Carbon60 devices.
“The goal is to increase the complexity of the circuits to see how that high mobility can be used to make more complex structures with unprecedented performance,” Kippelen said.
The researchers fabricated the transistors by depositing C60 molecules from the vapor phase into a thin film atop a silicon substrate onto which a gate electrode and gate dielectric had already been fabricated. The source and drain electrodes were then deposited on top of the C60 films through a shadow mask.
Kippelen’s team has been working with C60 for nearly ten years, and is also using the material in photovoltaic cells. Beyond the technical advance, Kippelen believes this new work demonstrates the growing maturity of organic electronics.
“This progress may trigger interest among more conventional electronic engineers,” he said.
“Most engineers would like to work with the latest technology platform, but they would like to see a level of performance showing they could actually implement these circuits. If you can demonstrate – as we have – that you can get transistors with good reproducibility, good stability, near-zero threshold voltages, large on-off current ratios and performance levels higher than amorphous silicon, that may convince designers to consider this technology"
Planting carbon deep in the earth rather than the greenhouse
STORING carbon dioxide deep below the earth’s surface could be a safe, long-term solution to one of the planet’s major contributors to climate change.
University of Leeds research shows that porous sandstone, drained of oil by the energy giants, could provide a safe reservoir for carbon dioxide. The study found that sandstone reacts with injected fluids more quickly than had been predicted - such reactions are essential if the captured CO2 is not to leak back to the surface.
The study looked at data from the Miller oilfield in the North Sea, where BP had been pumping seawater into the oil reservoir to enhance the flow of oil. As oil was extracted, the water that was pumped out with it was analysed and this showed that minerals had grown and dissolved as the water travelled through the field.
Significantly, PhD student Stephanie Houston found that water pumped out with the oil was especially rich in silica. This showed that silicates, usually thought of as very slow to react, had dissolved in the newly-injected seawater over less than a year. This is the type of reaction that would be needed to make carbon dioxide stable in the pore waters, rather like the dissolved carbonate found in still mineral water.
The study gives a clear indication that carbon dioxide sequestered deep underground could also react quickly with ordinary rocks to become assimilated into the deep formation water.
The work was supervised by Bruce Yardley, Professor in the School of Earth and Environment at the University, who explained: “If CO2 is injected underground we hope that it will react with the water and minerals there in order to be stabilized. That way it spreads into its local environment rather than remaining as a giant gas bubble which might ultimately seep to the surface.
“It had been thought that reaction might take place over hundreds or thousands of years, but there’s a clear implication in this study that if we inject carbon dioxide into rocks, these reactions will happen quite quickly making it far less likely to escape.”
Although extracting CO2 from power stations and storing it underground has been suggested as a long-term measure for tackling climate change, it has not yet been put to work for this purpose on a large scale. “There is one storage project in place at Sleipner, in the Norwegian sector of the North Sea, and some oil companies have actually used CO2 sequestration as a means of pushing out more oil from existing oilfields,” said Prof Yardley.
In the UK the Prime Minister has recently announced a major expansion of energy from renewable sources and the launch of a competition to build one of the world's first carbon capture and storage plants. The Leeds study suggests the technique has long-term potential for safely storing this major by-product of our power stations, rather than allowing it to escape and further contribute to global warming.
University of Leeds research shows that porous sandstone, drained of oil by the energy giants, could provide a safe reservoir for carbon dioxide. The study found that sandstone reacts with injected fluids more quickly than had been predicted - such reactions are essential if the captured CO2 is not to leak back to the surface.
The study looked at data from the Miller oilfield in the North Sea, where BP had been pumping seawater into the oil reservoir to enhance the flow of oil. As oil was extracted, the water that was pumped out with it was analysed and this showed that minerals had grown and dissolved as the water travelled through the field.
Significantly, PhD student Stephanie Houston found that water pumped out with the oil was especially rich in silica. This showed that silicates, usually thought of as very slow to react, had dissolved in the newly-injected seawater over less than a year. This is the type of reaction that would be needed to make carbon dioxide stable in the pore waters, rather like the dissolved carbonate found in still mineral water.
The study gives a clear indication that carbon dioxide sequestered deep underground could also react quickly with ordinary rocks to become assimilated into the deep formation water.
The work was supervised by Bruce Yardley, Professor in the School of Earth and Environment at the University, who explained: “If CO2 is injected underground we hope that it will react with the water and minerals there in order to be stabilized. That way it spreads into its local environment rather than remaining as a giant gas bubble which might ultimately seep to the surface.
“It had been thought that reaction might take place over hundreds or thousands of years, but there’s a clear implication in this study that if we inject carbon dioxide into rocks, these reactions will happen quite quickly making it far less likely to escape.”
Although extracting CO2 from power stations and storing it underground has been suggested as a long-term measure for tackling climate change, it has not yet been put to work for this purpose on a large scale. “There is one storage project in place at Sleipner, in the Norwegian sector of the North Sea, and some oil companies have actually used CO2 sequestration as a means of pushing out more oil from existing oilfields,” said Prof Yardley.
In the UK the Prime Minister has recently announced a major expansion of energy from renewable sources and the launch of a competition to build one of the world's first carbon capture and storage plants. The Leeds study suggests the technique has long-term potential for safely storing this major by-product of our power stations, rather than allowing it to escape and further contribute to global warming.
Wednesday, November 21, 2007
Bioclocks work by controlling chromosome coiling
There is a new twist on the question of how biological clocks work.
In recent years, scientists have discovered that biological clocks help organize a dizzying array of biochemical processes in the body. Despite a number of hypotheses, exactly how the microscopic pacemakers in every cell in the body exert such a widespread influence has remained a mystery.
Now, a new study provides direct evidence that biological clocks can influence the activity of a large number of different genes in an ingenious fashion, simply by causing chromosomes to coil more tightly during the day and to relax at night.
“The idea that the whole genome is oscillating is really cool,” enthuses Vanderbilt Professor of Biological Sciences Carl Johnson, who headed the research that was published online Nov. 13 in the Proceedings of the National Academy of Sciences. “The fact that oscillations can act as a regulatory mechanism is telling us something important about how DNA works: It is something DNA jockeys really need to think about.”
Johnson’s team, which consisted of Senior Lecturer Mark A Woelfle, Assistant Research Professor Yao Xu and graduate student Ximing Qin, performed the study with cyanobacteria (blue-green algae), the simplest organism known to possess a biological clock. The chromosomes in cyanobacteria are organized in circular molecules of DNA. In their relaxed state, they form a single loop. But, within the cell, they are usually “supercoiled” into a series of small helical loops. There are even two families of special enzymes, called gyrases and topoisomerases, whose function is coiling and uncoiling DNA.
The researchers focused on small, non-essential pieces of DNA in the cyanobacteria called plasmids that occur naturally in the cyanobacteria. Because a plasmid should behave in the same fashion as the larger and more unwieldy chromosome, the scientists consider it to be a good proxy of the behavior of the chromosome itself.
When the plasmid is relaxed, it is open and uncoiled and, when it is supercoiled, it is twisted into a smaller, more condensed state. So, the researchers used a standard method, called gel electrophoresis, to measure the extent of a plasmid’s supercoiling during different points in the day/night cycle.
The researchers found a distinct day/night cycle: The plasmid is smaller and more tightly wound during periods of light than they are during periods of darkness. They also found that this rhythmic condensation disappears when the cyanobacteria are kept in constant darkness.
“This is one of the first pieces of evidence that the biological clock exerts its effect on DNA structure through the coiling of the chromosome and that this, in turn, allows it to regulate all the genes in the organism,” says Woelfle.
Some cyanobacteria use their biological clocks to control two basic processes. During the day, they use photosynthesis to turn sunlight into chemical energy. During the night, they remove nitrogen from the atmosphere and incorporate it into a chemical compound that they can use to make proteins.
According to the Johnson lab’s “oscilloid model,” the genes that are involved in photosynthesis should be located in regions of the chromosome that are “turned on” by the tighter coiling in the DNA during the day and “turned off” during the night when the DNA is more relaxed. By the same token, the genes that are involved in nitrogen fixation should be located in regions of the chromosome that are “turned off” during the day when the DNA is tightly coiled and “turned on” during the night when it is more relaxed.
The researchers see no reason why the bioclocks in higher organisms, including humans, do not operate in a similar fashion. “This could be a universal theme that we are just starting to decipher,” says Woelfle.
The DNA in higher organisms is much larger than that in cyanobacteria and it is linear, not circular. Stretched end-to-end, the genome in a mammalian cell is about six feet long. In order to fit into a microscopic cell, the DNA must be tightly packed into a series of small coils, something like microscopic Slinkies.
Previous studies have shown that in higher organisms between 5 to 10 percent of genes in the genome are controlled by the bioclock, compared to 100 percent of genes in the cyanobacteria. In the case of the higher organisms, the bioclock’s control is likely to be local rather than the global situation in cyanobacteria.
With a circular chromosome (as in cyanobacteria), twisting it at any point affects the entire molecule. When you twist a linear chromosome at a certain point, however, the effect only extends for a limited distance in either direction because the ends are not connected. That fits neatly with the idea that the bioclock’s influence on linear chromosomes is limited to certain specific regions, regions where the specific genes that it regulates are located.
In recent years, scientists have discovered that biological clocks help organize a dizzying array of biochemical processes in the body. Despite a number of hypotheses, exactly how the microscopic pacemakers in every cell in the body exert such a widespread influence has remained a mystery.
Now, a new study provides direct evidence that biological clocks can influence the activity of a large number of different genes in an ingenious fashion, simply by causing chromosomes to coil more tightly during the day and to relax at night.
“The idea that the whole genome is oscillating is really cool,” enthuses Vanderbilt Professor of Biological Sciences Carl Johnson, who headed the research that was published online Nov. 13 in the Proceedings of the National Academy of Sciences. “The fact that oscillations can act as a regulatory mechanism is telling us something important about how DNA works: It is something DNA jockeys really need to think about.”
Johnson’s team, which consisted of Senior Lecturer Mark A Woelfle, Assistant Research Professor Yao Xu and graduate student Ximing Qin, performed the study with cyanobacteria (blue-green algae), the simplest organism known to possess a biological clock. The chromosomes in cyanobacteria are organized in circular molecules of DNA. In their relaxed state, they form a single loop. But, within the cell, they are usually “supercoiled” into a series of small helical loops. There are even two families of special enzymes, called gyrases and topoisomerases, whose function is coiling and uncoiling DNA.
The researchers focused on small, non-essential pieces of DNA in the cyanobacteria called plasmids that occur naturally in the cyanobacteria. Because a plasmid should behave in the same fashion as the larger and more unwieldy chromosome, the scientists consider it to be a good proxy of the behavior of the chromosome itself.
When the plasmid is relaxed, it is open and uncoiled and, when it is supercoiled, it is twisted into a smaller, more condensed state. So, the researchers used a standard method, called gel electrophoresis, to measure the extent of a plasmid’s supercoiling during different points in the day/night cycle.
The researchers found a distinct day/night cycle: The plasmid is smaller and more tightly wound during periods of light than they are during periods of darkness. They also found that this rhythmic condensation disappears when the cyanobacteria are kept in constant darkness.
“This is one of the first pieces of evidence that the biological clock exerts its effect on DNA structure through the coiling of the chromosome and that this, in turn, allows it to regulate all the genes in the organism,” says Woelfle.
Some cyanobacteria use their biological clocks to control two basic processes. During the day, they use photosynthesis to turn sunlight into chemical energy. During the night, they remove nitrogen from the atmosphere and incorporate it into a chemical compound that they can use to make proteins.
According to the Johnson lab’s “oscilloid model,” the genes that are involved in photosynthesis should be located in regions of the chromosome that are “turned on” by the tighter coiling in the DNA during the day and “turned off” during the night when the DNA is more relaxed. By the same token, the genes that are involved in nitrogen fixation should be located in regions of the chromosome that are “turned off” during the day when the DNA is tightly coiled and “turned on” during the night when it is more relaxed.
The researchers see no reason why the bioclocks in higher organisms, including humans, do not operate in a similar fashion. “This could be a universal theme that we are just starting to decipher,” says Woelfle.
The DNA in higher organisms is much larger than that in cyanobacteria and it is linear, not circular. Stretched end-to-end, the genome in a mammalian cell is about six feet long. In order to fit into a microscopic cell, the DNA must be tightly packed into a series of small coils, something like microscopic Slinkies.
Previous studies have shown that in higher organisms between 5 to 10 percent of genes in the genome are controlled by the bioclock, compared to 100 percent of genes in the cyanobacteria. In the case of the higher organisms, the bioclock’s control is likely to be local rather than the global situation in cyanobacteria.
With a circular chromosome (as in cyanobacteria), twisting it at any point affects the entire molecule. When you twist a linear chromosome at a certain point, however, the effect only extends for a limited distance in either direction because the ends are not connected. That fits neatly with the idea that the bioclock’s influence on linear chromosomes is limited to certain specific regions, regions where the specific genes that it regulates are located.
MIT: Thermoelectric materials are 1 key to energy savings
Breathing new life into an old idea, MIT Institute Professor Mildred S. Dresselhaus and co-workers are developing innovative materials for controlling temperatures that could lead to substantial energy savings by allowing more efficient car engines, photovoltaic cells and electronic devices.
Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air conditioning and energy costs.
The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor (and former president) Paul Gray, among others.
Dresselhaus and colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She’ll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26, at the annual meeting of the Materials Research Society in Boston.
Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. Conversely, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and especially well with semiconductors — the materials from which computer chips are made. But it always had one big drawback: it is very inefficient.
The fundamental problem in creating efficient thermoelectric materials is that they need to be very good at conducting electricity, but not heat. That way, one end of the apparatus can get hot while the other remains cold, instead of the material quickly equalizing the temperature. In most materials, electrical and thermal conductivity go hand in hand. So researchers had to find ways of modifying materials to separate the two properties.
The key to making it more practical, Dresselhaus explains, was in creating engineered semiconductor materials in which tiny patterns have been created to alter the materials’ behavior. This might include embedding nanoscale particles or wires in a matrix of another material. These nanoscale structures — just a few billionths of a meter across — interfere with the flow of heat, while allowing electricity to flow freely. “Making a nanostructure allows you to independently control these qualities,” Dresselhaus says.
She and her MIT collaborators started working on these developments in the 1990s, and soon drew interest from the US Navy because of the potential for making quieter submarines (power generation and air conditioning are some of the noisiest functions on existing subs). “From that research, we came up with a lot of new materials that nobody had looked into,” Dresselhaus says.
After some early work conducted with Ted Harman of MIT Lincoln Labs, Harman, Dresselhaus, and her student Lyndon Hicks published an experimental paper on the new materials in the mid 1990s. “People saw that paper and the field started,” she says. “Now there are conferences devoted to it.”
Her work in finding new thermoelectric materials, including a collaboration with MIT professor of Mechanical Engineering Gang Chen, invigorated the field, and now there are real applications like seat coolers in cars. Last year, a small company in California sold a million of the units worldwide.
OTHER POTENTIAL APPLICATIONS
The same principle can be used to design cooling systems that could be built right into microchips, reducing or eliminating the need for separate cooling systems and improving their efficiency.
The technology could also be used in cars to make the engines themselves more efficient. In conventional cars, about 80 percent of the fuel’s energy is wasted as heat. Thermoelectric systems could perhaps be used to generate electricity directly from this wasted heat. Because the amount of fuel used for transportation is such a huge part of the world’s energy use, even a small percentage improvement in efficiency can have a great impact, Dresselhaus explains. “It’s very practical,” she says, “and the car companies are getting interested.”
The same materials might also play a role in improving the efficiency of photovoltaic cells, harnessing some of the sun’s heat as well as its light to make electricity. The key will be finding materials that have the right properties but are not too expensive to produce.
Dresselhaus and colleagues are continuing to probe the thermoelectric properties of a variety of semiconductor materials and nanostructures such as superlattices and quantum dots. Her research on thermoelectric materials is presently sponsored by NASA.
Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air conditioning and energy costs.
The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor (and former president) Paul Gray, among others.
Dresselhaus and colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She’ll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26, at the annual meeting of the Materials Research Society in Boston.
Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. Conversely, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and especially well with semiconductors — the materials from which computer chips are made. But it always had one big drawback: it is very inefficient.
The fundamental problem in creating efficient thermoelectric materials is that they need to be very good at conducting electricity, but not heat. That way, one end of the apparatus can get hot while the other remains cold, instead of the material quickly equalizing the temperature. In most materials, electrical and thermal conductivity go hand in hand. So researchers had to find ways of modifying materials to separate the two properties.
The key to making it more practical, Dresselhaus explains, was in creating engineered semiconductor materials in which tiny patterns have been created to alter the materials’ behavior. This might include embedding nanoscale particles or wires in a matrix of another material. These nanoscale structures — just a few billionths of a meter across — interfere with the flow of heat, while allowing electricity to flow freely. “Making a nanostructure allows you to independently control these qualities,” Dresselhaus says.
She and her MIT collaborators started working on these developments in the 1990s, and soon drew interest from the US Navy because of the potential for making quieter submarines (power generation and air conditioning are some of the noisiest functions on existing subs). “From that research, we came up with a lot of new materials that nobody had looked into,” Dresselhaus says.
After some early work conducted with Ted Harman of MIT Lincoln Labs, Harman, Dresselhaus, and her student Lyndon Hicks published an experimental paper on the new materials in the mid 1990s. “People saw that paper and the field started,” she says. “Now there are conferences devoted to it.”
Her work in finding new thermoelectric materials, including a collaboration with MIT professor of Mechanical Engineering Gang Chen, invigorated the field, and now there are real applications like seat coolers in cars. Last year, a small company in California sold a million of the units worldwide.
OTHER POTENTIAL APPLICATIONS
The same principle can be used to design cooling systems that could be built right into microchips, reducing or eliminating the need for separate cooling systems and improving their efficiency.
The technology could also be used in cars to make the engines themselves more efficient. In conventional cars, about 80 percent of the fuel’s energy is wasted as heat. Thermoelectric systems could perhaps be used to generate electricity directly from this wasted heat. Because the amount of fuel used for transportation is such a huge part of the world’s energy use, even a small percentage improvement in efficiency can have a great impact, Dresselhaus explains. “It’s very practical,” she says, “and the car companies are getting interested.”
The same materials might also play a role in improving the efficiency of photovoltaic cells, harnessing some of the sun’s heat as well as its light to make electricity. The key will be finding materials that have the right properties but are not too expensive to produce.
Dresselhaus and colleagues are continuing to probe the thermoelectric properties of a variety of semiconductor materials and nanostructures such as superlattices and quantum dots. Her research on thermoelectric materials is presently sponsored by NASA.
New research shows climate change triggers wars and population decline
Climate change may be one of the most significant threats facing humankind. A new study shows that long-term climate change may ultimately lead to wars and population decline.
The study, published November 19 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS), revealed that as temperatures decreased centuries ago during a period called the Little Ice Age, the number of wars increased, famine occurred and the population declined.
Data on past climates may help accurately predict and design strategies for future large and persistent climate changes, but acknowledging the historic social impact of these severe events is an important step toward that goal, according to the study’s authors.
“Even though temperatures are increasing now, the same resulting conflicts may occur since we still greatly depend on the land as our food source,” said Peter Brecke, associate professor in the Georgia Institute of Technology’s Sam Nunn School of International Affairs and co-author of the study.
This new study expands previous work by David Zhang of the University of Hong Kong and lead author of the study.
“My previous research just focused on Eastern China. This current study covers a much larger spatial area and the conclusions from the current research could be considered general principles,” said Zhang.
Brecke, Zhang and colleagues in Hong Kong, China and the United Kingdom perceived a possible connection between temperature change and wars because changes in climate affect water supplies, growing seasons and land fertility, prompting food shortages. These shortages could lead to conflict – local uprisings, government destabilization and invasions from neighboring regions – and population decline due to bloodshed during the wars and starvation.
To study whether changes in temperature affected the number of wars, the researchers examined the time period between 1400 and 1900. This period recorded the lowest average global temperatures around 1450, 1650 and 1820, each separated by slight warming intervals.The researchers collected war data from multiple sources, including a database of 4,500 wars worldwide that Brecke began developing in 1995 with funding from the U.S. Institute of Peace. They also used climate change records that paleoclimatologists reconstructed by consulting historical documents and examining indicators of temperature change like tree rings, as well as oxygen isotopes in ice cores and coral skeletons.
Results showed a cyclic pattern of turbulent periods when temperatures were low followed by tranquil ones when temperatures were higher. The number of wars per year worldwide during cold centuries was almost twice that of the mild 18th century.
The study also showed population declines following each high war peak, according to population data Brecke assembled. The population growth rate of the Northern Hemisphere was elevated from 1400-1600, despite a short cooling period beginning in the middle of the 15th century. However, during the colder 17th century, Europe and Asia experienced more wars of great magnitude and population declines.
In China, the population plummeted 43 percent between 1620 and 1650. Then, a dramatic increase in population occurred from 1650 until a cooling period beginning in 1800 caused a worldwide demographic shock.
The researchers examined whether these average temperature differences of less than one degree Celsius were enough to cause food shortages. By assuming that agricultural production decreases triggered price increases, they showed that when grain prices reached a certain level, wars erupted. The ecological stress on agricultural production triggered by climate change did in fact induce population shrinkages, according to Brecke.
Global temperatures are expected to rise in the future and the world’s growing population may be unable to adequately adapt to the ecological changes, according to Brecke.
“The warmer temperatures are probably good for a while, but beyond some level plants will be stressed,” explained Brecke. “With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water.”
The study, published November 19 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS), revealed that as temperatures decreased centuries ago during a period called the Little Ice Age, the number of wars increased, famine occurred and the population declined.
Data on past climates may help accurately predict and design strategies for future large and persistent climate changes, but acknowledging the historic social impact of these severe events is an important step toward that goal, according to the study’s authors.
“Even though temperatures are increasing now, the same resulting conflicts may occur since we still greatly depend on the land as our food source,” said Peter Brecke, associate professor in the Georgia Institute of Technology’s Sam Nunn School of International Affairs and co-author of the study.
This new study expands previous work by David Zhang of the University of Hong Kong and lead author of the study.
“My previous research just focused on Eastern China. This current study covers a much larger spatial area and the conclusions from the current research could be considered general principles,” said Zhang.
Brecke, Zhang and colleagues in Hong Kong, China and the United Kingdom perceived a possible connection between temperature change and wars because changes in climate affect water supplies, growing seasons and land fertility, prompting food shortages. These shortages could lead to conflict – local uprisings, government destabilization and invasions from neighboring regions – and population decline due to bloodshed during the wars and starvation.
To study whether changes in temperature affected the number of wars, the researchers examined the time period between 1400 and 1900. This period recorded the lowest average global temperatures around 1450, 1650 and 1820, each separated by slight warming intervals.The researchers collected war data from multiple sources, including a database of 4,500 wars worldwide that Brecke began developing in 1995 with funding from the U.S. Institute of Peace. They also used climate change records that paleoclimatologists reconstructed by consulting historical documents and examining indicators of temperature change like tree rings, as well as oxygen isotopes in ice cores and coral skeletons.
Results showed a cyclic pattern of turbulent periods when temperatures were low followed by tranquil ones when temperatures were higher. The number of wars per year worldwide during cold centuries was almost twice that of the mild 18th century.
The study also showed population declines following each high war peak, according to population data Brecke assembled. The population growth rate of the Northern Hemisphere was elevated from 1400-1600, despite a short cooling period beginning in the middle of the 15th century. However, during the colder 17th century, Europe and Asia experienced more wars of great magnitude and population declines.
In China, the population plummeted 43 percent between 1620 and 1650. Then, a dramatic increase in population occurred from 1650 until a cooling period beginning in 1800 caused a worldwide demographic shock.
The researchers examined whether these average temperature differences of less than one degree Celsius were enough to cause food shortages. By assuming that agricultural production decreases triggered price increases, they showed that when grain prices reached a certain level, wars erupted. The ecological stress on agricultural production triggered by climate change did in fact induce population shrinkages, according to Brecke.
Global temperatures are expected to rise in the future and the world’s growing population may be unable to adequately adapt to the ecological changes, according to Brecke.
“The warmer temperatures are probably good for a while, but beyond some level plants will be stressed,” explained Brecke. “With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water.”
Monday, November 19, 2007
Sunbathing tree frogs' future under a cloud
Animal conservationists in Manchester are turning to physics to investigate whether global warming is responsible for killing sun-loving South American tree frogs.
In a unique collaborative project, researchers in The Photon Science Institute (PSI) at The University of Manchester have joined forces with The Manchester Museum, which boasts an amazing collection of colourful tree frogs.
Physicist Dr Mark Dickinson, working with Andrew Gray, Curator of Herpetology at the museum, and Dr Richard Preziosi from The Faculty of Life Sciences, has started using a technique called Optical Coherence Tomography (OCT) to investigate the properties of the tree frogs’ skin.
This non-invasive technique, which does not cause harm or distress to the frogs, allows images to be obtained from within tissue – and the Manchester team believe this innovative application of OCT could hold the key to understanding the alarming global decline in amphibians.
When in their natural habitat, the Costa Rican tree frogs being studied in Manchester prefer to live on leaves and branches high above the ground.
They enjoy basking in the hot sun – which is unusual because frogs normally avoid prolonged exposure to high levels of light due to the risk of overheating and dehydration.
The Manchester team’s hypothesis is that global warming is leading to more cloud cover in the frogs’ natural habitat.
They believe this is denying them the opportunity to 'sunbathe' and kill off fatal Chytrid fungal infections, leading to many species dying out.
In their work so far, the team have observed that the skin of basking tree frogs sometimes undergoes a visible change and becomes almost metallic in texture. They think that when this happens, the level of absorption and reflection and the skin temperature also changes.
The Manchester team believe tree frogs are able to bask happily under a fierce sun because they have the ability to regulate their body temperature and prevent overheating through the unique structure and properties of their skin.
Gray, Dickinson and Preziosi are now seeking further funding to do more comprehensive research using the OCT technique – which is more commonly used to examine the human retina – and put their hypothesis to the test.
As part of their studies, they want to use OCT to compare structural changes in the skin of tree frogs with the structural changes in the skin of frogs that do not have the same high levels of infrared reflectance.
This reflectance is associated with a pigment called pterorhodin, and allows the tree frogs to camouflage themselves from predators by adjusting the infrared reflection of their skin to match the infrared reflection of the leaves they laze upon.
They team are hoping to work with and support the important work being carried by the eminent climatologist, Alan Pounds, who has theorised that global warming is a major factor in amphibian declines.
The team plan to travel out to Costa Rica next year and to apply spectral reflectance techniques to tree frogs living in their natural habitat.
Dr Mark Dickinson said: "This is a great example of an exciting interdisciplinary research project that draws on expertise right across the university. It is proof that interdisciplinary research is not just a fashionable expression we band around, but something we actually do."
Andrew Gray said: “With a third of the world’s amphibians currently under threat it’s vitally important we do our utmost to investigate the reasons why they are dying out at such an alarming rate.
"The imaging technique we use is completely non-invasive and does not harm the frogs in any way. As an animal conservationist, I simply would not allow any research that distressed these amazing creatures."
In a unique collaborative project, researchers in The Photon Science Institute (PSI) at The University of Manchester have joined forces with The Manchester Museum, which boasts an amazing collection of colourful tree frogs.
Physicist Dr Mark Dickinson, working with Andrew Gray, Curator of Herpetology at the museum, and Dr Richard Preziosi from The Faculty of Life Sciences, has started using a technique called Optical Coherence Tomography (OCT) to investigate the properties of the tree frogs’ skin.
This non-invasive technique, which does not cause harm or distress to the frogs, allows images to be obtained from within tissue – and the Manchester team believe this innovative application of OCT could hold the key to understanding the alarming global decline in amphibians.
When in their natural habitat, the Costa Rican tree frogs being studied in Manchester prefer to live on leaves and branches high above the ground.
They enjoy basking in the hot sun – which is unusual because frogs normally avoid prolonged exposure to high levels of light due to the risk of overheating and dehydration.
The Manchester team’s hypothesis is that global warming is leading to more cloud cover in the frogs’ natural habitat.
They believe this is denying them the opportunity to 'sunbathe' and kill off fatal Chytrid fungal infections, leading to many species dying out.
In their work so far, the team have observed that the skin of basking tree frogs sometimes undergoes a visible change and becomes almost metallic in texture. They think that when this happens, the level of absorption and reflection and the skin temperature also changes.
The Manchester team believe tree frogs are able to bask happily under a fierce sun because they have the ability to regulate their body temperature and prevent overheating through the unique structure and properties of their skin.
Gray, Dickinson and Preziosi are now seeking further funding to do more comprehensive research using the OCT technique – which is more commonly used to examine the human retina – and put their hypothesis to the test.
As part of their studies, they want to use OCT to compare structural changes in the skin of tree frogs with the structural changes in the skin of frogs that do not have the same high levels of infrared reflectance.
This reflectance is associated with a pigment called pterorhodin, and allows the tree frogs to camouflage themselves from predators by adjusting the infrared reflection of their skin to match the infrared reflection of the leaves they laze upon.
They team are hoping to work with and support the important work being carried by the eminent climatologist, Alan Pounds, who has theorised that global warming is a major factor in amphibian declines.
The team plan to travel out to Costa Rica next year and to apply spectral reflectance techniques to tree frogs living in their natural habitat.
Dr Mark Dickinson said: "This is a great example of an exciting interdisciplinary research project that draws on expertise right across the university. It is proof that interdisciplinary research is not just a fashionable expression we band around, but something we actually do."
Andrew Gray said: “With a third of the world’s amphibians currently under threat it’s vitally important we do our utmost to investigate the reasons why they are dying out at such an alarming rate.
"The imaging technique we use is completely non-invasive and does not harm the frogs in any way. As an animal conservationist, I simply would not allow any research that distressed these amazing creatures."
MIT: 'Micro' livers could aid drug screening
MIT researchers have devised a novel way to create tiny colonies of living human liver cells that model the full-sized organ. The work could allow better screening of new drugs that are potentially harmful to the liver and reduce the costs associated with their development.
Liver toxicity is one of the main reasons pharmaceutical companies pull drugs off the market. These dangerous drugs slip through approval processes due in part to the shortcomings of liver toxicity tests. Existing tests rely on liver cells from rats, which do not always respond to toxins the way human cells do. Or they rely on dying human cells that survive for only a few days in the lab.
The new technology arranges human liver cells into tiny colonies only 500 micrometers (millionths of a meter) in diameter that act much like a real liver and survive for up to six weeks.
Sangeeta Bhatia, associate professor in the Harvard-MIT Division of Health Sciences and Technology (HST) and MIT's Department of Electrical Engineering and Computer Science, and HST postdoctoral associate Salman Khetani describe their model liver tissue and its behavior in the November 18 online issue of Nature Biotechnology.
To build these model livers, Khetani uses micropatterning technology—the same technology used to place tiny copper wires on computer chips—to precisely arrange human liver cells and other supporting cells on a plate. Khetani adapted this method from Bhatia’s early work as an HST graduate student building micropatterned co-cultures of rat liver cells and supporting cells.
Such precisely arranged cells results in what Bhatia calls a “high-fidelity tissue model” because it so closely mimics the behavior of a human liver. For example, each model “organ” secretes the blood protein albumin, synthesizes urea, and produces the enzymes necessary to break down drugs and toxins.
To predict how close their model tissue is to real liver tissue, which has over 500 different functions, they also evaluated its gene expression profiles, measures of the levels of gene activation in the tissues. They found that these profiles are very similar to those of fresh liver cells, “giving us confidence that other [liver] functions are preserved,” said Khetani.
For drug testing purposes, this affinity to the human liver allows each colony to provide a window into the human liver’s response to a drug without having to expose human patients to the drug in a clinical trial, said Bhatia.
Further, because the engineered tissue lives for so long, it has the potential to make new types of toxicity tests possible. For instance, it opens the door to testing the effects of long-term drug use akin to taking one pill a day over multiple weeks. It also will allow more extensive testing of drug-drug interactions.
In addition to being a good biological model, the engineered tissue is designed to be seamlessly integrated into an industrial pharmaceutical science setting.
To mass-produce plates of the miniature liver models, Khetani relies on a technique called soft lithography. This technique fashions a reusable micropatterned rubber stencil from a silicon master. Each stencil contains an array of 24 wells, and each well contains a matrix of 37 tiny holes. Khetani “peels and sticks” the stencil onto plates and places the liver cells into the holes, patterning over 888 miniature model livers across the microwells in a matter of minutes.
In tests of drugs with a range of well-known toxicity levels, assays (chemical detection tests) on the miniature liver models showed the expected levels of toxicity. “Our platform was able to predict the relative toxicity of these drugs as seen in the clinic,” said Khetani. For instance, troglitazone, a drug withdrawn from the market by the FDA due to liver toxicity, showed toxicity levels much higher than its FDA-approved analogues, Rosiglitazone and Pioglitazone.
The model uses a fraction of the costly human liver cells used in other test platforms and can be assembled using frozen cells. Moreover, the expanded toxicity testing capabilities have the potential to allow drug developers to identify toxicity earlier in the development process, thereby avoiding the expense of investing in formulas that are bound to fail.
A startup company called Hepregen has licensed the technology and is working to introduce it into the pharmaceutical marketplace.
“My hope is that this new model will make drugs safer, cheaper, and better labeled,” said Bhatia.
Liver toxicity is one of the main reasons pharmaceutical companies pull drugs off the market. These dangerous drugs slip through approval processes due in part to the shortcomings of liver toxicity tests. Existing tests rely on liver cells from rats, which do not always respond to toxins the way human cells do. Or they rely on dying human cells that survive for only a few days in the lab.
The new technology arranges human liver cells into tiny colonies only 500 micrometers (millionths of a meter) in diameter that act much like a real liver and survive for up to six weeks.
Sangeeta Bhatia, associate professor in the Harvard-MIT Division of Health Sciences and Technology (HST) and MIT's Department of Electrical Engineering and Computer Science, and HST postdoctoral associate Salman Khetani describe their model liver tissue and its behavior in the November 18 online issue of Nature Biotechnology.
To build these model livers, Khetani uses micropatterning technology—the same technology used to place tiny copper wires on computer chips—to precisely arrange human liver cells and other supporting cells on a plate. Khetani adapted this method from Bhatia’s early work as an HST graduate student building micropatterned co-cultures of rat liver cells and supporting cells.
Such precisely arranged cells results in what Bhatia calls a “high-fidelity tissue model” because it so closely mimics the behavior of a human liver. For example, each model “organ” secretes the blood protein albumin, synthesizes urea, and produces the enzymes necessary to break down drugs and toxins.
To predict how close their model tissue is to real liver tissue, which has over 500 different functions, they also evaluated its gene expression profiles, measures of the levels of gene activation in the tissues. They found that these profiles are very similar to those of fresh liver cells, “giving us confidence that other [liver] functions are preserved,” said Khetani.
For drug testing purposes, this affinity to the human liver allows each colony to provide a window into the human liver’s response to a drug without having to expose human patients to the drug in a clinical trial, said Bhatia.
Further, because the engineered tissue lives for so long, it has the potential to make new types of toxicity tests possible. For instance, it opens the door to testing the effects of long-term drug use akin to taking one pill a day over multiple weeks. It also will allow more extensive testing of drug-drug interactions.
In addition to being a good biological model, the engineered tissue is designed to be seamlessly integrated into an industrial pharmaceutical science setting.
To mass-produce plates of the miniature liver models, Khetani relies on a technique called soft lithography. This technique fashions a reusable micropatterned rubber stencil from a silicon master. Each stencil contains an array of 24 wells, and each well contains a matrix of 37 tiny holes. Khetani “peels and sticks” the stencil onto plates and places the liver cells into the holes, patterning over 888 miniature model livers across the microwells in a matter of minutes.
In tests of drugs with a range of well-known toxicity levels, assays (chemical detection tests) on the miniature liver models showed the expected levels of toxicity. “Our platform was able to predict the relative toxicity of these drugs as seen in the clinic,” said Khetani. For instance, troglitazone, a drug withdrawn from the market by the FDA due to liver toxicity, showed toxicity levels much higher than its FDA-approved analogues, Rosiglitazone and Pioglitazone.
The model uses a fraction of the costly human liver cells used in other test platforms and can be assembled using frozen cells. Moreover, the expanded toxicity testing capabilities have the potential to allow drug developers to identify toxicity earlier in the development process, thereby avoiding the expense of investing in formulas that are bound to fail.
A startup company called Hepregen has licensed the technology and is working to introduce it into the pharmaceutical marketplace.
“My hope is that this new model will make drugs safer, cheaper, and better labeled,” said Bhatia.
Sunday, November 18, 2007
Mutation Fired Outbreak of Deadly Tropical Virus
What a difference a nucleotide makes. A simple change in the genetic sequence of the chikungunya virus may have triggered a massive outbreak of the deadly tropical disease on an island in the Indian Ocean in 2005 and 2006. The mutation made it easier for the virus to reproduce inside the mosquitoes that transmit it to humans, researchers report in the current issue of PLOS One.
Chikungunya kills about one in every 1000 infected people; in the rest, it can cause rash, fever, and crippling joint and muscle pains. The outbreak at La Réunion, a French island 700 kilometers east of Madagascar, sickened at least a third of the 800,000 inhabitants (ScienceNOW, 17 February 2006). "The scope and magnitude were really unprecedented," says Ann Powers, an expert in insect-borne viruses at the Centers for Disease Control and Prevention in Fort Collins, Colorado. The virus was spread mainly by the Asian tiger mosquito, Aedes albopictus, although it wasn't known at the time as a prominent chikungunya vector.
From sequencing the RNA genomes of viruses isolated from patients, researchers knew that chikungunya had undergone a mutation early on in the epidemic. The mutation led to a one-amino-acid change within E1, a protein sitting on the viral coat. About September 2005, most patients still had the amino acid alanine at a certain position within E1. But from about December on, when the outbreak really got going, more than 90% had valine at that same position. Researchers suspected that the change had facilitated spread, but this was mostly speculation.
Now they have proof. A group led by Anna-Bella Failloux of the Pasteur Institute in Paris bred populations of A. albopictus mosquitoes from La Réunion and nearby Mayotte and fed them a blood meal spiked with virus having one or the other version of E1. The scientists then ground up the insect bodies at different time intervals after the feeding and measured the amount of virus inside. In mosquitoes fed with the valine-substituted E1, the virus occurred in quantities almost 100 times higher than in those without. This mutated virus was also better able to pass the wall of a mosquito's midgut and make its way to the salivary glands, from where it could pass to a new victim with the insect's next bite. Apparently, the mutation made the virus a much better fit for La Réunion's Asian tiger mosquito population and thus made the epidemic soar, says Failloux.
"It's an elegant study," says Powers. "They did a very nice job of showing that there is a difference in what was occurring early in the outbreak and later on." That said, many other factors must have conspired to fuel the epidemic, Powers says, from zero immunity in the human population--La Réunion was virgin territory for chikungunya--to the fact that the mosquitoes were apparently thriving at the time.
Chikungunya kills about one in every 1000 infected people; in the rest, it can cause rash, fever, and crippling joint and muscle pains. The outbreak at La Réunion, a French island 700 kilometers east of Madagascar, sickened at least a third of the 800,000 inhabitants (ScienceNOW, 17 February 2006). "The scope and magnitude were really unprecedented," says Ann Powers, an expert in insect-borne viruses at the Centers for Disease Control and Prevention in Fort Collins, Colorado. The virus was spread mainly by the Asian tiger mosquito, Aedes albopictus, although it wasn't known at the time as a prominent chikungunya vector.
From sequencing the RNA genomes of viruses isolated from patients, researchers knew that chikungunya had undergone a mutation early on in the epidemic. The mutation led to a one-amino-acid change within E1, a protein sitting on the viral coat. About September 2005, most patients still had the amino acid alanine at a certain position within E1. But from about December on, when the outbreak really got going, more than 90% had valine at that same position. Researchers suspected that the change had facilitated spread, but this was mostly speculation.
Now they have proof. A group led by Anna-Bella Failloux of the Pasteur Institute in Paris bred populations of A. albopictus mosquitoes from La Réunion and nearby Mayotte and fed them a blood meal spiked with virus having one or the other version of E1. The scientists then ground up the insect bodies at different time intervals after the feeding and measured the amount of virus inside. In mosquitoes fed with the valine-substituted E1, the virus occurred in quantities almost 100 times higher than in those without. This mutated virus was also better able to pass the wall of a mosquito's midgut and make its way to the salivary glands, from where it could pass to a new victim with the insect's next bite. Apparently, the mutation made the virus a much better fit for La Réunion's Asian tiger mosquito population and thus made the epidemic soar, says Failloux.
"It's an elegant study," says Powers. "They did a very nice job of showing that there is a difference in what was occurring early in the outbreak and later on." That said, many other factors must have conspired to fuel the epidemic, Powers says, from zero immunity in the human population--La Réunion was virgin territory for chikungunya--to the fact that the mosquitoes were apparently thriving at the time.
Shrewd Snake Savors Deadly Meal
Your mother may have warned that you'd get a tummy ache if you scarfed down your food, but for one Australian snake, eating too fast could be deadly. The death adder dines on frogs, but some of them are poisonous. So the snake has learned patience: After striking a particular poisonous frog, it waits for its victim's toxin to degrade before it dines. The finding could help ecologists decipher how one species can outevolve another.
The death adder stabs unsuspecting frogs with its fangs, injecting venom to kill its supper. The frogs have fought back, however, evolving various defenses--longer legs for bigger jumps or chemical substances that taste nasty and can kill. Ecologists Ben Phillips and Richard Shine, both of the University of Sydney, Australia, decided to study the snake's general feeding behavior. And when they did, they stumbled upon a strange twist in this evolutionary arms race.
The team dropped frogs of various species in the snakes' glass pens and kept a video camera rolling to record the action as the snakes captured their prey. The snakes gobbled up nontoxic frogs right after injecting them with venom, but they took more time with two other species, the researchers report in the December issue of The American Naturalist. The snake waited 10 minutes before munching on the marbled frog, which produces a gluelike substance on its skin when irritated. (Mouth full of goo? No, thank you!) Further studies revealed that the gunk loses its stickiness after 10 minutes. The snakes waited even longer--40 minutes--before eating the deadly Dahl's aquatic frog. Shine says that by letting the frogs' chemical defenses break down, the snakes have found an unbeatable strategy. "Any predator eating prey whose defenses will terminate after death can simply wait around," Shine says.
The results reveal an unusual adaptation on the part of the snakes, says Wolfgang Wüster, a zoologist at Bangor University in the U.K. He says the frogs may find another strategy to continue the evolutionary battle: "It is hard to say, however, how it would happen easily."
The death adder stabs unsuspecting frogs with its fangs, injecting venom to kill its supper. The frogs have fought back, however, evolving various defenses--longer legs for bigger jumps or chemical substances that taste nasty and can kill. Ecologists Ben Phillips and Richard Shine, both of the University of Sydney, Australia, decided to study the snake's general feeding behavior. And when they did, they stumbled upon a strange twist in this evolutionary arms race.
The team dropped frogs of various species in the snakes' glass pens and kept a video camera rolling to record the action as the snakes captured their prey. The snakes gobbled up nontoxic frogs right after injecting them with venom, but they took more time with two other species, the researchers report in the December issue of The American Naturalist. The snake waited 10 minutes before munching on the marbled frog, which produces a gluelike substance on its skin when irritated. (Mouth full of goo? No, thank you!) Further studies revealed that the gunk loses its stickiness after 10 minutes. The snakes waited even longer--40 minutes--before eating the deadly Dahl's aquatic frog. Shine says that by letting the frogs' chemical defenses break down, the snakes have found an unbeatable strategy. "Any predator eating prey whose defenses will terminate after death can simply wait around," Shine says.
The results reveal an unusual adaptation on the part of the snakes, says Wolfgang Wüster, a zoologist at Bangor University in the U.K. He says the frogs may find another strategy to continue the evolutionary battle: "It is hard to say, however, how it would happen easily."
New Material Doubles Record for Holding Hydrogen
If the hoped-for hydrogen economy is ever to become a reality, researchers must devise efficient ways to produce and store the gas. That will require a series of breakthroughs that have been slow in coming. But researchers in the United States have hit upon a material for storing hydrogen that could be far better than the competition--just the sort of break hydrogen researchers are looking for.
Hydrogen has long been seen as a potentially green alternative to gasoline, which is produced from fossil fuels and gives off the greenhouse gas carbon dioxide when burned. When piped through a fuel cell, hydrogen molecules (H2) combine with oxygen, producing only electricity and water. At room temperature, however, hydrogen is a gas, which makes it difficult to store enough of it on board a car to drive long distances. The gas can be compressed in high-pressure tanks or cooled to a liquid at ultracold temperatures. But both of those strategies require large amounts of energy themselves.
As an alternative, researchers have been searching for materials that can hold large amounts of H2 and release it on demand. But so far the best performers, which are known as metal hydrides, hold only about 2% of their weight in hydrogen at room temperature, well below what is needed for a practical gas tank. Other materials can get up to 7% but require either high or low temperatures, and thus added energy and cost.
Last year, however, researchers led by Taner Yildirim at the National Institute of Standards and Technology in Gaithersburg, Maryland, calculated that a material made from certain metals, such as titanium, and a small hydrocarbon called ethylene should form a stable complex that could bind up to 14% of its weight in hydrogen. Adam Phillips, a physicist and postdoc in the lab of Bellave Shivaram at the University of Virginia, Charlottesville, decided to give the proposal a try.
Phillips used a laser to vaporize titanium in a gas of ethylene. The combined material settled out of the gas and on to a substrate to form a film. When Phillips added hydrogen at room temperature and weighed the result, he found the 14% added weight, just as predicted. After running a series of successful control studies, Phillips and Shivaram reported their new material on Monday at the International Symposium on Materials Issues in a Hydrogen Economy in Richmond, Virginia.
The new result is "extremely interesting," says Gholam-Abbas Nazri, a hydrogen storage expert at the General Motors Research and Development Center in Warren, Michigan. However, Nazri adds, "we have to be very cautious." There have been numerous false starts in the field before, he says. And researchers still must make the material in bulk, demonstrate that it works in that form, and show that it will release hydrogen as easily as it sops it up.
Even with those caveats, George Crabtree, a physicist at Argonne National Laboratory in Illinois, says the result "is one of the most promising developments of the last few years."
Hydrogen has long been seen as a potentially green alternative to gasoline, which is produced from fossil fuels and gives off the greenhouse gas carbon dioxide when burned. When piped through a fuel cell, hydrogen molecules (H2) combine with oxygen, producing only electricity and water. At room temperature, however, hydrogen is a gas, which makes it difficult to store enough of it on board a car to drive long distances. The gas can be compressed in high-pressure tanks or cooled to a liquid at ultracold temperatures. But both of those strategies require large amounts of energy themselves.
As an alternative, researchers have been searching for materials that can hold large amounts of H2 and release it on demand. But so far the best performers, which are known as metal hydrides, hold only about 2% of their weight in hydrogen at room temperature, well below what is needed for a practical gas tank. Other materials can get up to 7% but require either high or low temperatures, and thus added energy and cost.
Last year, however, researchers led by Taner Yildirim at the National Institute of Standards and Technology in Gaithersburg, Maryland, calculated that a material made from certain metals, such as titanium, and a small hydrocarbon called ethylene should form a stable complex that could bind up to 14% of its weight in hydrogen. Adam Phillips, a physicist and postdoc in the lab of Bellave Shivaram at the University of Virginia, Charlottesville, decided to give the proposal a try.
Phillips used a laser to vaporize titanium in a gas of ethylene. The combined material settled out of the gas and on to a substrate to form a film. When Phillips added hydrogen at room temperature and weighed the result, he found the 14% added weight, just as predicted. After running a series of successful control studies, Phillips and Shivaram reported their new material on Monday at the International Symposium on Materials Issues in a Hydrogen Economy in Richmond, Virginia.
The new result is "extremely interesting," says Gholam-Abbas Nazri, a hydrogen storage expert at the General Motors Research and Development Center in Warren, Michigan. However, Nazri adds, "we have to be very cautious." There have been numerous false starts in the field before, he says. And researchers still must make the material in bulk, demonstrate that it works in that form, and show that it will release hydrogen as easily as it sops it up.
Even with those caveats, George Crabtree, a physicist at Argonne National Laboratory in Illinois, says the result "is one of the most promising developments of the last few years."
Japan fleet sets off to hunt humpbacks
SHIMONOSEKI, Japan - A defiant Japan embarked on its largest whaling expedition in decades Sunday, targeting protected humpbacks for the first time since the 1960s despite international opposition. An anti-whaling protest boat awaited the fleBid farewell in a festive ceremony in the southern port of Shimonoseki, four ships headed for the waters off Antarctica, resuming a hunt that was cut short by a deadly fire last February that crippled the fleet's mother ship.
Families waved little flags emblazoned with smiling whales and the crew raised a toast with cans of beer, while a brass band played "Popeye the Sailor Man." Officials told the crowd that Japan should not give into militant activists and preserve its whale-eating culture.
"They're violent environmental terrorists," mission leader Hajime Ishikawa told the ceremony. "Their violence is unforgivable ... we must fight against their hypocrisy and lies."
The whalers plan to kill up to 50 humpbacks in what is believed to be the first large-scale hunt for the once nearly extinct species since a 1963 moratorium in the Southern Pacific put the giant marine mammals under international protection.
The mission also aims to take as many as 935 minke whales and up to 50 fin whales in what Japan's Fisheries Agency says is its largest-ever scientific whale hunt. The expedition lasts through April.
Japan says it needs to kill the animals in order to conduct research on their reproductive and feeding patterns.
While scientific whale hunts are allowed by the International Whaling Commission, or IWC, critics say Japan is simply using science as a cover for commercial whaling.
The anti-whaling group Greenpeace said its protest ship, Esperanza, was moored just outside Japan's territorial waters and would chase the fleet to the southern ocean. There was no immediate word Sunday of an offshore confrontation.
"We are going to do everything in our power to reduce their catch," Karli Thomas, expedition leader on the Esperanza, told The Associated Press by telephone. "Japan's research program is a sham. We demand that the Japanese government cancel it."
An IWC moratorium on commercial whaling took effect in 1986, but Japan — where coastal villages have hunted whales for hundreds of years — has killed almost 10,500 mostly minke and Brydes whales under research permits since then. Tokyo has argued unsuccessfully for years for the IWC to overturn the moratorium.
The Japanese hunt, which puts meat from the whales on the commercial market, is growing rapidly despite an increasingly vocal anti-whaling movement. This winter season's target of up to 1,035 whales is more than double the number the country hunted a decade ago.
Japan argues that it should have the right to hunt whales as long as they are not in danger of extinction.
The head of Japan's Fisheries Agency said Sunday the fruits of Tokyo's research would help prove that sustainable whaling is possible.
"The scientific research we carry out will pave the way to overturning the moratorium on commercial whaling, which will better help us to utilize whale resources," Shuji Yamada told the ceremony.
The focus on this year's hunt is the humpback, which was in serious danger of extinction just a few decades ago. They are now a favorite of whale-watchers for their playful antics at sea, where the beasts — which grow as large as 40 tons — throw themselves out of the water.
Humpbacks feed, mate and give birth near shore, making them easy prey for whalers, who by some estimates depleted the global population to just 1,200 before the 1963 moratorium. The southern moratorium was followed by a worldwide ban in 1966.
Since then, only Greenland and the Caribbean nation of Saint Vincent and the Grenadines have been allowed to catch humpbacks under an IWC aboriginal subsistence program. Each caught one humpback last year, according to the commission.
The American Cetacean Society estimates the humpback population has recovered to about 30,000-40,000 — about a third of the number before modern whaling. The species is listed as "vulnerable" by the World Conservation Union.
Japanese fisheries officials insist the population has returned to a sustainable level and that taking 50 of them will have no impact.et offshore.
Families waved little flags emblazoned with smiling whales and the crew raised a toast with cans of beer, while a brass band played "Popeye the Sailor Man." Officials told the crowd that Japan should not give into militant activists and preserve its whale-eating culture.
"They're violent environmental terrorists," mission leader Hajime Ishikawa told the ceremony. "Their violence is unforgivable ... we must fight against their hypocrisy and lies."
The whalers plan to kill up to 50 humpbacks in what is believed to be the first large-scale hunt for the once nearly extinct species since a 1963 moratorium in the Southern Pacific put the giant marine mammals under international protection.
The mission also aims to take as many as 935 minke whales and up to 50 fin whales in what Japan's Fisheries Agency says is its largest-ever scientific whale hunt. The expedition lasts through April.
Japan says it needs to kill the animals in order to conduct research on their reproductive and feeding patterns.
While scientific whale hunts are allowed by the International Whaling Commission, or IWC, critics say Japan is simply using science as a cover for commercial whaling.
The anti-whaling group Greenpeace said its protest ship, Esperanza, was moored just outside Japan's territorial waters and would chase the fleet to the southern ocean. There was no immediate word Sunday of an offshore confrontation.
"We are going to do everything in our power to reduce their catch," Karli Thomas, expedition leader on the Esperanza, told The Associated Press by telephone. "Japan's research program is a sham. We demand that the Japanese government cancel it."
An IWC moratorium on commercial whaling took effect in 1986, but Japan — where coastal villages have hunted whales for hundreds of years — has killed almost 10,500 mostly minke and Brydes whales under research permits since then. Tokyo has argued unsuccessfully for years for the IWC to overturn the moratorium.
The Japanese hunt, which puts meat from the whales on the commercial market, is growing rapidly despite an increasingly vocal anti-whaling movement. This winter season's target of up to 1,035 whales is more than double the number the country hunted a decade ago.
Japan argues that it should have the right to hunt whales as long as they are not in danger of extinction.
The head of Japan's Fisheries Agency said Sunday the fruits of Tokyo's research would help prove that sustainable whaling is possible.
"The scientific research we carry out will pave the way to overturning the moratorium on commercial whaling, which will better help us to utilize whale resources," Shuji Yamada told the ceremony.
The focus on this year's hunt is the humpback, which was in serious danger of extinction just a few decades ago. They are now a favorite of whale-watchers for their playful antics at sea, where the beasts — which grow as large as 40 tons — throw themselves out of the water.
Humpbacks feed, mate and give birth near shore, making them easy prey for whalers, who by some estimates depleted the global population to just 1,200 before the 1963 moratorium. The southern moratorium was followed by a worldwide ban in 1966.
Since then, only Greenland and the Caribbean nation of Saint Vincent and the Grenadines have been allowed to catch humpbacks under an IWC aboriginal subsistence program. Each caught one humpback last year, according to the commission.
The American Cetacean Society estimates the humpback population has recovered to about 30,000-40,000 — about a third of the number before modern whaling. The species is listed as "vulnerable" by the World Conservation Union.
Japanese fisheries officials insist the population has returned to a sustainable level and that taking 50 of them will have no impact.et offshore.
Diesel pollution clogs arteries, raises risk of heart disease
Diesel fumes interact with fatty acids found in LDL ("bad") cholesterol to raise the risk of heart disease, according to a study published in the online journal "Genome Biology."On their own, both diesel fumes and certain fatty acids contained in LDL cholesterol create free radicals in the body. These free radicals damage cells and tissue, leading to the inflammation that can cause cardiovascular disease. In the new study, researchers at the University of California-Los Angeles found that the combination of diesel and the fats was far more dangerous than either factor separately."Their combination creates a dangerous synergy that wreaks cardiovascular havoc far beyond what's caused by the diesel or cholesterol alone," said lead researcher André Nel.The researchers first combined diesel pollutants with the fatty acids and added them to a culture of cells from the inside of human blood vessels. They found that the mixture activated the genes that promote cellular inflammation. Then the researchers exposed mice with high cholesterol to diesel particles. In response, many of the same genes were activated in the mice's bodies.Researchers said that the exact mechanism by which pollution leads to heart disease is still unknown."We do know that these particles are coated with chemicals that damage tissue and cause inflammation of the nose and lungs," Nel said. "Vascular inflammation in turn leads to cholesterol deposits and clogged arteries, which can give rise to blood clots and trigger heart attack or stroke."According to Cathy Ross, a cardiac nurse at the British Heart Foundation, it has long been known that air pollution increases a person's risk of death from cardiovascular disease. "Anyone with chronic lung disease or coronary heart disease should avoid staying outside for long periods when pollution levels are high," she said.
Evolutionary Biology Research on Plant Shows Significance of Maternal Effects
When habitat changes, animals migrate. But how do immobile organisms like plants cope when faced with alterations to their environment? This is an increasingly important question in light of new environmental conditions brought on by global climate change.A University of Virginia study, published in the Nov. 16 issue of the journal Science, demonstrates that plants grown in the same setting as their maternal plant performed almost 3½ times better than those raised in a different environment — indicating that maternal plants give cues to their offspring that help them adapt to their environmental conditions.Evolutionary biologist Laura Galloway, an associate professor of biology at the University of Virginia, recently completed a study of the American bellflower, a native wildflower that commonly grows in both shaded areas and areas that receive full sunlight for at least part of the day. She focused on the transmission of environmental information between maternal plants and their offspring.Galloway planted some seeds in light conditions similar to their maternal plants and some in different light. She found that plants growing in the same setting as their maternal plant outperformed those planted in a different environment. The work was conducted in a natural habitat at the University of Virginia’s Mountain Lake Biological Station in Southwest Virginia.Since seeds typically fall close to their maternal plant, they grow in a similar environment. When seeds are dispersed to different environments, Galloway found that the plants may suffer for one generation, but as long as the seeds of those plants grow locally, their offspring will recover. “We found a temporary mechanism of adaptation to local environmental conditions,” says Galloway. Since plant adaptation is typically studied on a permanent, genetic level rather than in direct response to environmental conditions, Galloway’s insights are unique. Galloway was led to this line of inquiry by chance. She was surprised to observe a number of years ago that plants that had experienced drought had smaller seeds than those that had not. This highly visible physiological change within only one generation intrigued her. “Historically maternal effects have been viewed as a complicating factor — an inconvenience,” explains Galloway. “But we have found that they can dramatically influence the performance of an individual.”
Human ancestors: more gatherers than hunters?
Chimpanzees crave roots and tubers even when food is plentiful above ground, according to a new study that raises questions about the relative importance of meat for brain evolution.
Appearing online the week of Nov. 12 in the early edition of the Proceedings of the National Academy of Sciences, the study documents a novel use of tools by chimps to dig for tubers and roots in the savanna woodlands of western Tanzania.
The chimps’ eagerness for buried treats offers new insights in an ongoing debate about the role of meat versus potato-like foods in the diet of our hominid ancestors, said first author Adriana Hernandez-Aguilar, who collected the field data for her doctoral research at the University of Southern California.
The debate centers on the diet followed by early hominids as their brain and body size slowly increased towards a human level. Was it meat-and-potatoes, or potatoes-and-meat"
“Some researchers have suggested that what made us human was actually the tubers,” Hernandez-Aguilar said.
Anthropologists had speculated that roots and tubers were mere fallback foods for hominids trying to survive the harsh dry season in the savanna 3.5 million years ago and later (hominids are known to have consumed meat at least as early as 2.5 million years ago).
But the study found that modern chimps only dig for roots during the rainy season, when other food sources abound.
The finding suggests, but does not prove, that hominids behaved the same way. Researchers view modern chimps as proxies for hominids because of similarities in habitat, brain mass and body size.
“We look at chimps for the way that we could have behaved when our ancestors were chimp-like,” Hernandez-Aguilar said.
Corresponding author Travis Pickering, of the University of Wisconsin-Madison, said: “Savanna chimps, we would contend, are dealing with environmental constraints and problems – evolutionary pressures – that our earliest relatives would have dealt with as well.”
The tuber-digging chimps “suggest that underground resources were within reach of our ancestors,” added co-author James Moore of the University of California at San Diego.
The study was based on observation of 11 digging sites in the Ugalla savanna woodland of western Tanzania.
Chimpanzees were linked to the excavated tubers and roots through knuckle prints, feces, and spit-out wads of fibers from those underground foods.
Seven tools were found at three of the sites, with worn edges and dirt marking implying their use as digging implements.
Because chimpanzees in the area are not habituated to humans, Hernandez-Aguilar was unable to observe them directly. She plans to conduct further observations in the area and to advocate for greater protection for the savanna chimps.
“Chimpanzees in savannas have not been considered a priority in conservation plans because they live in low densities compared to chimps in forests,” she said.
“We hope that discoveries such as this will show the value of conserving the savanna populations.”
Hernandez-Aguilar conducted her thesis work under Craig Stanford, professor of anthropology at USC.
The research was funded by the LSB Leakey Foundation, the National Science Foundation, the Jane Goodall Center at the University of Southern California, the University of California Committee on Research, the Palaeontology Scientific Trust and the Ugalla Primate Lab from UCSD. James Moore is the coordinator of the Ugalla Primate Project.
Appearing online the week of Nov. 12 in the early edition of the Proceedings of the National Academy of Sciences, the study documents a novel use of tools by chimps to dig for tubers and roots in the savanna woodlands of western Tanzania.
The chimps’ eagerness for buried treats offers new insights in an ongoing debate about the role of meat versus potato-like foods in the diet of our hominid ancestors, said first author Adriana Hernandez-Aguilar, who collected the field data for her doctoral research at the University of Southern California.
The debate centers on the diet followed by early hominids as their brain and body size slowly increased towards a human level. Was it meat-and-potatoes, or potatoes-and-meat"
“Some researchers have suggested that what made us human was actually the tubers,” Hernandez-Aguilar said.
Anthropologists had speculated that roots and tubers were mere fallback foods for hominids trying to survive the harsh dry season in the savanna 3.5 million years ago and later (hominids are known to have consumed meat at least as early as 2.5 million years ago).
But the study found that modern chimps only dig for roots during the rainy season, when other food sources abound.
The finding suggests, but does not prove, that hominids behaved the same way. Researchers view modern chimps as proxies for hominids because of similarities in habitat, brain mass and body size.
“We look at chimps for the way that we could have behaved when our ancestors were chimp-like,” Hernandez-Aguilar said.
Corresponding author Travis Pickering, of the University of Wisconsin-Madison, said: “Savanna chimps, we would contend, are dealing with environmental constraints and problems – evolutionary pressures – that our earliest relatives would have dealt with as well.”
The tuber-digging chimps “suggest that underground resources were within reach of our ancestors,” added co-author James Moore of the University of California at San Diego.
The study was based on observation of 11 digging sites in the Ugalla savanna woodland of western Tanzania.
Chimpanzees were linked to the excavated tubers and roots through knuckle prints, feces, and spit-out wads of fibers from those underground foods.
Seven tools were found at three of the sites, with worn edges and dirt marking implying their use as digging implements.
Because chimpanzees in the area are not habituated to humans, Hernandez-Aguilar was unable to observe them directly. She plans to conduct further observations in the area and to advocate for greater protection for the savanna chimps.
“Chimpanzees in savannas have not been considered a priority in conservation plans because they live in low densities compared to chimps in forests,” she said.
“We hope that discoveries such as this will show the value of conserving the savanna populations.”
Hernandez-Aguilar conducted her thesis work under Craig Stanford, professor of anthropology at USC.
The research was funded by the LSB Leakey Foundation, the National Science Foundation, the Jane Goodall Center at the University of Southern California, the University of California Committee on Research, the Palaeontology Scientific Trust and the Ugalla Primate Lab from UCSD. James Moore is the coordinator of the Ugalla Primate Project.
Saturday, November 17, 2007
Avrupa’ya büyük örümcek göçü
Avrupa’ya 150 yıldan beri 87 yeni tür örümceğin yerleştiği ve dünya ticaretinin yoğunluk kazanmasıyla da yeni örümceklerin giderek Avrupa’yı daha çok mesken tutacağı açıklandı.
Bern Üniversitesi Zooloji Enstitüsü araştırmacıları tarafından yapılan ve yayımlanan bir çalışmada, her iki yılda bir Avrupa’ya yeni bir tür örümcek geldiği ve bunun yakında her yıl bir örümcek rakamına ulaşacağı belirtilirken, genellikle Asya ülkelerinden gelen bu örümceklerin yerli örümceklere nazaran daha büyük olduğu kaydedildi.
Bunun nedeni, “yolculuğun stresine” büyük boy örümceklerin daha iyi dayanabilmesi olarak açıklanırken, yakın bir gelecekte her yıl yeni bir tür örümceğin Avrupa’ya gelmesinin beklendiğinin altı çizildi.Avrupa’da iklimin değişmesinin Asya’dan gelen örümceklere daha iyi bir yaşam koşulu sunduğu da belirtilen çalışmada, yeni türlerin gelişinin tehlikeli olabileceği de ima edildi.Çalışmada, şimdiye kadar Avrupa’da zehirli örümceğe rastlanmadığı da kaydedildi.
Bern Üniversitesi Zooloji Enstitüsü araştırmacıları tarafından yapılan ve yayımlanan bir çalışmada, her iki yılda bir Avrupa’ya yeni bir tür örümcek geldiği ve bunun yakında her yıl bir örümcek rakamına ulaşacağı belirtilirken, genellikle Asya ülkelerinden gelen bu örümceklerin yerli örümceklere nazaran daha büyük olduğu kaydedildi.
Bunun nedeni, “yolculuğun stresine” büyük boy örümceklerin daha iyi dayanabilmesi olarak açıklanırken, yakın bir gelecekte her yıl yeni bir tür örümceğin Avrupa’ya gelmesinin beklendiğinin altı çizildi.Avrupa’da iklimin değişmesinin Asya’dan gelen örümceklere daha iyi bir yaşam koşulu sunduğu da belirtilen çalışmada, yeni türlerin gelişinin tehlikeli olabileceği de ima edildi.Çalışmada, şimdiye kadar Avrupa’da zehirli örümceğe rastlanmadığı da kaydedildi.
Akdeniz’de köpekbalığını bekleyen tehdit
IUCN’nin açıklamasında, bölgede 30 türün soyunun tükenme tehlikesiyle karşı karşıya olduğu ve dünya genelinde en büyük yok olma tehdidiyle karşı karşıya olan köpek balığı ve kedi balığı türlerinin bu bölgede bulunduğu belirtildi. Açıklamada, Birliğin uzmanlarının 71 türü incelediği ve konuyla ilgili bir raporun yarın yayımlanacağı belirtildi.
Raporda, bu türlerin özellikle aşırı avlanmaları nedeniyle soyunun tükenebileceği kaydedildi. Türlerin soyunun tükenmesine yol açan nedenler arasında, çevre koşullarının kötüye gitmesi ve hobi amacıyla yapılan balıkçılık da yer aldı.IUCN’nin açıklamasında, derin sularda avlanmada uygulanacak bazı yasaklarla bu türlerin soyunun tükenmesinin engellenebileceği belirtildi.
Raporda, bu türlerin özellikle aşırı avlanmaları nedeniyle soyunun tükenebileceği kaydedildi. Türlerin soyunun tükenmesine yol açan nedenler arasında, çevre koşullarının kötüye gitmesi ve hobi amacıyla yapılan balıkçılık da yer aldı.IUCN’nin açıklamasında, derin sularda avlanmada uygulanacak bazı yasaklarla bu türlerin soyunun tükenmesinin engellenebileceği belirtildi.
Go with the flow-Traffic control Systems
Dr. Helbing, Professor of Sociology at the ETH Zurich Chair of Sociology, a specialist in modelling and simulation, supports his claim with a recent study called ‘Efficient Self-Control of Traffic Flows in Urban Networks Using Short-Sighted Anticipation’. Professor Helbing and co-author, Stefan Lämmer of the Institute for Transport and Economics at Dresden University of Technology, propose a self-organized control system for traffic lights that could improve vehicular traffic flow significantly. The system relies on the joining of two distinct strategies.
Traffic light system antiquated
The problem, Professor Helbing explains, is that heavy investments in traffic light systems were made in the 1960s and 70s rendering most systems today, due to use, age and technological advancement, antiquated. Forty to fifty years ago when traffic volume was lighter, the main job of traffic light systems was to manage peak traffic during the day or, for example, sporting events. The lights were centrally controlled, and not programmed to adjust in real time. Rather, they were mostly optimised for pre-established assumed situations, meaning for situations that traffic planners had faced in the past.
The disadvantage of this strategy, especially today, is that the more traffic lights there are to coordinate, the more difficult it is to optimize control of the lights. Why? The dilemma is well-known: the larger the number of nodes, or lights, in a system the more computation is necessary until finally computational time “explodes”. “Even for normal-sized cities, super computers are just not fast enough to compute all of the different options that exist for controlling traffic lights. So the number of choices actually considered by the optimization program is significantly reduced,” says Professor Helbing.
Most traffic lights, therefore, continue to be programmed offline, regardless of the realities of the road. Unfortunately, “the variation in the number of vehicles that queue up at a traffic light at any minute of the day is huge,” Professor Helbing says. None of this variation is considered when optimizing for typical Monday or Friday traffic volume curves. “You are optimizing for a situation that basically is true on average but that is never true for any single day or minute: essentially for a situation that never exists. Plus, even adaptive traffic lights in modern control schemes are usually restricted to a variation of cycle-based control.”
One strategy is not enough
Professor Helbing and Stefan Lämmer propose a decentralized system instead that would make travel time more predictable, though traffic light sequence less so. First, the researchers tried to optimize the flow of traffic at one light of an intersection. This localized approach worked well as long as traffic flow through the intersection was not too high. Once volume rose, however, locally programmed lights did not clear traffic off of side roads fast enough and led to back-ups at other intersections. Professor Helbing concluded “On its own, this optimizing strategy was worse than traffic light controls already in place.”
Another component, a stabilizing strategy, was then studied. This strategy cleared traffic when it reached a critical threshold, but it was inconsistent with travel time minimization. Unlike the optimization strategy, the stabilizing strategy performed poorly at all volumes. On its own, it too could not compete with today’s traffic light control systems.
However, “it turns out that the two strategies properly combined perform better than today’s traffic light controls at all traffic volumes. So the combination of two inferior strategies can perform much better – if we do it right,” Professor Helbing says.
Simulation tests show the combined strategies work well. With non-periodic - not cyclically repeated - traffic lights releasing long traffic queues, travel time even becomes more predictable. Flow is kept stable, fuel consumption and emissions are reduced.
Succes depends on motorists
However, the success of the new system will depend on how motorists react, Professor Helbing points out. Drivers are used to the present cycle of traffic lights and anticipate ‘their turn’ to enter an intersection. The combined strategy would disrupt such expectations: if the traffic load is heavy in one direction, that road will be served two times, while others will be served only once. To support driver acceptance and avoid undesirable side effects, such as increased frustration or even accidents, any new traffic control system would need government support and funding by way of a well-publicised awareness campaign directed to the general public during the system’s introductory phase.
In Asian countries, where infrastructure is still being built, is where Professor Helbing thinks investment in the combined strategies might first take place. In Europe the “pain and pressure for change may still not be great enough”. In the end, cost will be a determining factor. The new technologies will have to show that they are cheaper to run than the present system.
Testings ahead
The need to lower CO2 emissions could, however, accelerate the development, suggests Professor Helbing. “You have to decide whether it is necessary to force people to use their cars less, or if the same goals can be achieved through coordinating traffic flows better. If the answer is coordination, then let’s go for the better technology.”
Politicians need to be informed of the options. And the traffic light systems themselves must now be tested through practical application. Professor Helbing is nonetheless optimistic that they will out-perform the systems of today. “What we don’t know is how big an advantage the news systems will be. But all the facts point to decentralised traffic control. This will be the paradigm of the future.”
Traffic light system antiquated
The problem, Professor Helbing explains, is that heavy investments in traffic light systems were made in the 1960s and 70s rendering most systems today, due to use, age and technological advancement, antiquated. Forty to fifty years ago when traffic volume was lighter, the main job of traffic light systems was to manage peak traffic during the day or, for example, sporting events. The lights were centrally controlled, and not programmed to adjust in real time. Rather, they were mostly optimised for pre-established assumed situations, meaning for situations that traffic planners had faced in the past.
The disadvantage of this strategy, especially today, is that the more traffic lights there are to coordinate, the more difficult it is to optimize control of the lights. Why? The dilemma is well-known: the larger the number of nodes, or lights, in a system the more computation is necessary until finally computational time “explodes”. “Even for normal-sized cities, super computers are just not fast enough to compute all of the different options that exist for controlling traffic lights. So the number of choices actually considered by the optimization program is significantly reduced,” says Professor Helbing.
Most traffic lights, therefore, continue to be programmed offline, regardless of the realities of the road. Unfortunately, “the variation in the number of vehicles that queue up at a traffic light at any minute of the day is huge,” Professor Helbing says. None of this variation is considered when optimizing for typical Monday or Friday traffic volume curves. “You are optimizing for a situation that basically is true on average but that is never true for any single day or minute: essentially for a situation that never exists. Plus, even adaptive traffic lights in modern control schemes are usually restricted to a variation of cycle-based control.”
One strategy is not enough
Professor Helbing and Stefan Lämmer propose a decentralized system instead that would make travel time more predictable, though traffic light sequence less so. First, the researchers tried to optimize the flow of traffic at one light of an intersection. This localized approach worked well as long as traffic flow through the intersection was not too high. Once volume rose, however, locally programmed lights did not clear traffic off of side roads fast enough and led to back-ups at other intersections. Professor Helbing concluded “On its own, this optimizing strategy was worse than traffic light controls already in place.”
Another component, a stabilizing strategy, was then studied. This strategy cleared traffic when it reached a critical threshold, but it was inconsistent with travel time minimization. Unlike the optimization strategy, the stabilizing strategy performed poorly at all volumes. On its own, it too could not compete with today’s traffic light control systems.
However, “it turns out that the two strategies properly combined perform better than today’s traffic light controls at all traffic volumes. So the combination of two inferior strategies can perform much better – if we do it right,” Professor Helbing says.
Simulation tests show the combined strategies work well. With non-periodic - not cyclically repeated - traffic lights releasing long traffic queues, travel time even becomes more predictable. Flow is kept stable, fuel consumption and emissions are reduced.
Succes depends on motorists
However, the success of the new system will depend on how motorists react, Professor Helbing points out. Drivers are used to the present cycle of traffic lights and anticipate ‘their turn’ to enter an intersection. The combined strategy would disrupt such expectations: if the traffic load is heavy in one direction, that road will be served two times, while others will be served only once. To support driver acceptance and avoid undesirable side effects, such as increased frustration or even accidents, any new traffic control system would need government support and funding by way of a well-publicised awareness campaign directed to the general public during the system’s introductory phase.
In Asian countries, where infrastructure is still being built, is where Professor Helbing thinks investment in the combined strategies might first take place. In Europe the “pain and pressure for change may still not be great enough”. In the end, cost will be a determining factor. The new technologies will have to show that they are cheaper to run than the present system.
Testings ahead
The need to lower CO2 emissions could, however, accelerate the development, suggests Professor Helbing. “You have to decide whether it is necessary to force people to use their cars less, or if the same goals can be achieved through coordinating traffic flows better. If the answer is coordination, then let’s go for the better technology.”
Politicians need to be informed of the options. And the traffic light systems themselves must now be tested through practical application. Professor Helbing is nonetheless optimistic that they will out-perform the systems of today. “What we don’t know is how big an advantage the news systems will be. But all the facts point to decentralised traffic control. This will be the paradigm of the future.”
A discovery of a new way to manipulate light a million times more efficiently than before
Using a special hollow-core photonic crystal fibre, a team at the University of Bath, UK, has opened the door to what could prove to be a new sub-branch of photonics, the science of light guidance and trapping.
The team, led by Dr Fetah Benabid, reports on the discovery, which relates to the emerging attotechnology, the ability to send out pulses of light that last only an attosecond, a billion billionth of a second.
These pulses are so brief that they allow researchers to more accurately measure the movement of sub-atomic particles such as the electron, the tiny negatively-charged entity which moves outside the nucleus of an atom. Attosecond technology may throw light, literally, upon the strange quantum world where such particles have no definite position,only probable locations.
To make attosecond pulses, researchers create a broad spectrum of light from visible wavelengths to x-rays through an inert gas. This normally requires a gigawatt of power, which puts the technique beyond any commercial or industrial use.
But Dr Benabid’s team used a photonic crystal fibre (pcf), the width of a human hair, which traps light and the gas together in an efficient way. Until now the spectrum produced by photonic crystal fibre has been too narrow for use in attosecond technology, but the team have now produced a broad spectrum, using what is called a Kagomé lattice, using about a millionth of the power used by non-pcf methods.
“This new way of using photonic crystal fibre has meant that the goal of attosecond technology is much closer," said Dr Benabid, of the University of Bath’s Department of Physics, who worked with students Mr Francois Couny and Mr Phil Light, and with Dr John Roberts of the Technical University of Denmark and Dr Michael Raymer of the University of Oregon, USA.
“The greatly reduced cost and size of producing these phenomenally short and powerful pulses makes exploring matter at an even smaller detail a realistic prospect.”
Dr Benabid’s team has not only made an important step in applied physics, but has contributed to the theory of photonics too. The effectiveness of photonic crystal fibre has lain so far in its exploitation of what is called photonic band gap, which stops photons of light from “existing” in the fibre cladding and enabled them to be trapped in the inside core of the fibre.
Instead, the team makes use of the fact that light can exist in different ‘modes’ without strongly interacting. This creates a situation whereby light can be trapped inside the fibre core without the need of photonic bandgap. Physicists call these modes bound states within a continuum.
The existence of these bound states between photons was predicted at the beginning of quantum mechanics in the 1930s, but this is the first time it has been noted in reality, and marks a theoretical breakthrough.
The team, led by Dr Fetah Benabid, reports on the discovery, which relates to the emerging attotechnology, the ability to send out pulses of light that last only an attosecond, a billion billionth of a second.
These pulses are so brief that they allow researchers to more accurately measure the movement of sub-atomic particles such as the electron, the tiny negatively-charged entity which moves outside the nucleus of an atom. Attosecond technology may throw light, literally, upon the strange quantum world where such particles have no definite position,only probable locations.
To make attosecond pulses, researchers create a broad spectrum of light from visible wavelengths to x-rays through an inert gas. This normally requires a gigawatt of power, which puts the technique beyond any commercial or industrial use.
But Dr Benabid’s team used a photonic crystal fibre (pcf), the width of a human hair, which traps light and the gas together in an efficient way. Until now the spectrum produced by photonic crystal fibre has been too narrow for use in attosecond technology, but the team have now produced a broad spectrum, using what is called a Kagomé lattice, using about a millionth of the power used by non-pcf methods.
“This new way of using photonic crystal fibre has meant that the goal of attosecond technology is much closer," said Dr Benabid, of the University of Bath’s Department of Physics, who worked with students Mr Francois Couny and Mr Phil Light, and with Dr John Roberts of the Technical University of Denmark and Dr Michael Raymer of the University of Oregon, USA.
“The greatly reduced cost and size of producing these phenomenally short and powerful pulses makes exploring matter at an even smaller detail a realistic prospect.”
Dr Benabid’s team has not only made an important step in applied physics, but has contributed to the theory of photonics too. The effectiveness of photonic crystal fibre has lain so far in its exploitation of what is called photonic band gap, which stops photons of light from “existing” in the fibre cladding and enabled them to be trapped in the inside core of the fibre.
Instead, the team makes use of the fact that light can exist in different ‘modes’ without strongly interacting. This creates a situation whereby light can be trapped inside the fibre core without the need of photonic bandgap. Physicists call these modes bound states within a continuum.
The existence of these bound states between photons was predicted at the beginning of quantum mechanics in the 1930s, but this is the first time it has been noted in reality, and marks a theoretical breakthrough.
MIT: Remote-control nanoparticles deliver drugs directly into tumors
MIT scientists have devised remotely controlled nanoparticles that, when pulsed with an electromagnetic field, release drugs to attack tumors. The innovation, reported in the Nov. 15 online issue of Advanced Materials, could lead to the improved diagnosis and targeted treatment of cancer.
In earlier work the team, led by Sangeeta Bhatia, M.D.,Ph.D., an associate professor in the Harvard-MIT Division of Health Sciences & Technology (HST) and in MIT's Department of Electrical Engineering and Computer Science, developed injectable multi-functional nanoparticles designed to flow through the bloodstream, home to tumors and clump together. Clumped particles help clinicians visualize tumors through magnetic resonance imaging (MRI).
With the ability to see the clumped particles, Bhatia’s co-author in the current work, Geoff von Maltzahn, asked the next question: “Can we talk back to them?”
The answer is yes, the team found. The system that makes it possible consists of tiny particles (billionths of a meter in size) that are superparamagnetic, a property that causes them to give off heat when they are exposed to a magnetic field. Tethered to these particles are active molecules, such as therapeutic drugs.
Exposing the particles to a low-frequency electromagnetic field causes the particles to radiate heat that, in turn, melts the tethers and releases the drugs. The waves in this magnetic field have frequencies between 350 and 400 kilohertz—the same range as radio waves. These waves pass harmlessly through the body and heat only the nanoparticles. For comparison, microwaves, which will cook tissue, have frequencies measured in gigahertz, or about a million times more powerful.
The tethers in the system consist of strands of DNA, “a classical heat sensitive material,” said von Maltzahn, a graduate student in HST. Two strands of DNA link together through hydrogen bonds that break when heated. In the presence of the magnetic field, heat generated by the nanoparticles breaks these, leaving one strand attached to the particle and allowing the other to float away with its cargo.
One advantage of a DNA tether is that its melting point is tunable. Longer strands and differently coded strands require different amounts of heat to break. This heat-sensitive tuneability makes it possible for a single particle to simultaneously carry many different types of cargo, each of which can be released at different times or in various combinations by applying different frequencies or durations of electromagnetic pulses.
To test the particles, the researchers implanted mice with a tumor-like gel saturated with nanoparticles. They placed the implanted mouse into the well of a cup-shaped electrical coil and activated the magnetic pulse. The results confirm that without the pulse, the tethers remain unbroken. With the pulse, the tethers break and release the drugs into the surrounding tissue.
The experiment is a proof of principal demonstrating a safe and effective means of tunable remote activation. However, work remains to be done before such therapies become viable in the clinic.
To heat the region, for example, a critical mass of injected particles must clump together inside the tumor. The team is still working to make intravenously injected particles clump effectively enough to achieve this critical mass.
“Our overall goal is to create multifunctional nanoparticles that home to a tumor, accumulate, and provide customizable remotely activated drug delivery right at the site of the disease,” said Bhatia.
Co-authors on the paper are Austin M. Derfus, a graduate student at the University of California at San Diego; Todd Harris, an HST graduate student; Erkki Ruoslahti and Tasmia Duza of The Burnham Institute in La Jolla, CA; and Kenneth S. Vecchio of the University of San Diego.
The research was supported by grants from the David and Lucile Packard Foundation, the National Cancer Institute of the National Institutes of Health. Dervis was supported by a G.R.E.A.T fellowship from the University of California Biotechnology Research and Educational Program.
Written by Elizabeth Dougherty, Harvard-MIT Division of Health Sciences and Technology
In earlier work the team, led by Sangeeta Bhatia, M.D.,Ph.D., an associate professor in the Harvard-MIT Division of Health Sciences & Technology (HST) and in MIT's Department of Electrical Engineering and Computer Science, developed injectable multi-functional nanoparticles designed to flow through the bloodstream, home to tumors and clump together. Clumped particles help clinicians visualize tumors through magnetic resonance imaging (MRI).
With the ability to see the clumped particles, Bhatia’s co-author in the current work, Geoff von Maltzahn, asked the next question: “Can we talk back to them?”
The answer is yes, the team found. The system that makes it possible consists of tiny particles (billionths of a meter in size) that are superparamagnetic, a property that causes them to give off heat when they are exposed to a magnetic field. Tethered to these particles are active molecules, such as therapeutic drugs.
Exposing the particles to a low-frequency electromagnetic field causes the particles to radiate heat that, in turn, melts the tethers and releases the drugs. The waves in this magnetic field have frequencies between 350 and 400 kilohertz—the same range as radio waves. These waves pass harmlessly through the body and heat only the nanoparticles. For comparison, microwaves, which will cook tissue, have frequencies measured in gigahertz, or about a million times more powerful.
The tethers in the system consist of strands of DNA, “a classical heat sensitive material,” said von Maltzahn, a graduate student in HST. Two strands of DNA link together through hydrogen bonds that break when heated. In the presence of the magnetic field, heat generated by the nanoparticles breaks these, leaving one strand attached to the particle and allowing the other to float away with its cargo.
One advantage of a DNA tether is that its melting point is tunable. Longer strands and differently coded strands require different amounts of heat to break. This heat-sensitive tuneability makes it possible for a single particle to simultaneously carry many different types of cargo, each of which can be released at different times or in various combinations by applying different frequencies or durations of electromagnetic pulses.
To test the particles, the researchers implanted mice with a tumor-like gel saturated with nanoparticles. They placed the implanted mouse into the well of a cup-shaped electrical coil and activated the magnetic pulse. The results confirm that without the pulse, the tethers remain unbroken. With the pulse, the tethers break and release the drugs into the surrounding tissue.
The experiment is a proof of principal demonstrating a safe and effective means of tunable remote activation. However, work remains to be done before such therapies become viable in the clinic.
To heat the region, for example, a critical mass of injected particles must clump together inside the tumor. The team is still working to make intravenously injected particles clump effectively enough to achieve this critical mass.
“Our overall goal is to create multifunctional nanoparticles that home to a tumor, accumulate, and provide customizable remotely activated drug delivery right at the site of the disease,” said Bhatia.
Co-authors on the paper are Austin M. Derfus, a graduate student at the University of California at San Diego; Todd Harris, an HST graduate student; Erkki Ruoslahti and Tasmia Duza of The Burnham Institute in La Jolla, CA; and Kenneth S. Vecchio of the University of San Diego.
The research was supported by grants from the David and Lucile Packard Foundation, the National Cancer Institute of the National Institutes of Health. Dervis was supported by a G.R.E.A.T fellowship from the University of California Biotechnology Research and Educational Program.
Written by Elizabeth Dougherty, Harvard-MIT Division of Health Sciences and Technology
Kopya insanların türemesi an meselesi
Uluslararası toplumun, üreme amaçlı insan kopyalamayı (klonlama) yasaklamaya ya da muhtemel ayrımcılığa, hatta suistimale karşı gelecekte ortaya çıkabilecek klonlanmış insanların haklarını korumaya hazırlanması yönünde acilen bir anlaşmaya varması gerekebileceği bildirildi.
İrlanda Ulusal Üniversitesi İnsan Hakları Merkezi’nden Brendam Tobin ve ekibinin yayımladığı rapor, BM’nin üreme amaçlı kopyalamayı yasa dışı ilan etmekte başarısız olmasının, araştırmalardaki hızlı gelişmeler yüzünden kopyalanmış insanların ortaya çıkması ve çoğalmasının an meselesi olduğunu anlamına geldiğini ortaya koydu.Tobin, tedavi amaçlı denetimli kopyalama araştırmalarına izin verilirken, üreme amaçlı insan kopyalamasının yasa gücüyle dünya çapında yasaklanmasının en arzu edilen seçenek olduğunu söyledi.Brendam Tobin, uluslararası toplumun uzlaşma bulamamaya direnmesi halinde, sorumluluğu kabul etmesi ve kopyalanmış her bireyin aynı insan haklarından bütünüyle yararlanmasını sağlaması gerekebileceğini ifade etti.BM’nin, kopyalanmış insanlara saygı gösterilmesi ve kopyalanmış insanların ön yargı, suistimal ya da ayrımcılığa karşı koruması yönünde halkın duyarlılığını artırmak için büyük çaplı programlar başlatması gerekebileceğini de ifade etti.Fransa ve Almanya, BM’den üreme amaçlı kopyalama girişimlerine küresel bir yasak getirilmesini istemiş, ancak tedavi amaçlı klonlama deneylerine izin verilmesini talep etmişti.BM’deki tartışmalar sırasında, birçok hükümet bu görüşe sahip çıkmış, ancak aralarında ABD ve Vietnam’ın da bulunduğu bazı ülkeler amacı ne olursa olsun her türlü klonlama çalışmasına karşı çıkmıştı.
İrlanda Ulusal Üniversitesi İnsan Hakları Merkezi’nden Brendam Tobin ve ekibinin yayımladığı rapor, BM’nin üreme amaçlı kopyalamayı yasa dışı ilan etmekte başarısız olmasının, araştırmalardaki hızlı gelişmeler yüzünden kopyalanmış insanların ortaya çıkması ve çoğalmasının an meselesi olduğunu anlamına geldiğini ortaya koydu.Tobin, tedavi amaçlı denetimli kopyalama araştırmalarına izin verilirken, üreme amaçlı insan kopyalamasının yasa gücüyle dünya çapında yasaklanmasının en arzu edilen seçenek olduğunu söyledi.Brendam Tobin, uluslararası toplumun uzlaşma bulamamaya direnmesi halinde, sorumluluğu kabul etmesi ve kopyalanmış her bireyin aynı insan haklarından bütünüyle yararlanmasını sağlaması gerekebileceğini ifade etti.BM’nin, kopyalanmış insanlara saygı gösterilmesi ve kopyalanmış insanların ön yargı, suistimal ya da ayrımcılığa karşı koruması yönünde halkın duyarlılığını artırmak için büyük çaplı programlar başlatması gerekebileceğini de ifade etti.Fransa ve Almanya, BM’den üreme amaçlı kopyalama girişimlerine küresel bir yasak getirilmesini istemiş, ancak tedavi amaçlı klonlama deneylerine izin verilmesini talep etmişti.BM’deki tartışmalar sırasında, birçok hükümet bu görüşe sahip çıkmış, ancak aralarında ABD ve Vietnam’ın da bulunduğu bazı ülkeler amacı ne olursa olsun her türlü klonlama çalışmasına karşı çıkmıştı.
Preserving One Web
Increasingly, people connect to the Internet through mobile phones, video-game consoles, or televisions. The problem is that a lot of Internet content isn't available for all of these devices, and many websites crash when loaded on a mobile device. Tim Berners-Lee, director of the World Wide Web Consortium (W3C) and father of the Internet, worries that this is effectively cutting some people off from the information that is freely shared on the Internet. Speaking at the Mobile Internet World conference in Boston earlier this week, Berners-Lee said that the W3C is working on defining a set of standards that developers can use to build websites that work with mobile devices, as well as with desktop computers, so that the mobile Web doesn't break apart from the World Wide Web. This week, the W3C also launched a new tool that developers can use to test their websites for compatibility with mobile devices.
The overarching goal of the initiative, according to Berners-Lee, is to keep content available regardless of the devices available to a person. "I like being able to choose my hardware separately from choosing my software, and separately from choosing my content," Berners-Lee said at the conference. There needs to be just one Web, he explained, and it needs to work on phones.
Many websites are far from Berners-Lee's vision. Some developers don't have websites that work with mobile devices and don't make mobile versions of their sites, seeing this as an added technical headache. For developers who do want their websites to be available everywhere, a common practice is to build special versions of sites for mobile devices, with pared-down features and, sometimes, content.
In some parts of the world, the mobile phone is the primary way that people access the Internet, and content should be available to those people as much as it is to people using a desktop computer. The system doesn't work well for those in wealthier nations, either. Users with devices such as the iPhone want to be able to access sites from their mobile device at the full capability that the iPhone has, says Matt Womer, the W3C's mobile-Web-initiative lead for North America. Users don't want to see a pared-down site.
On the other hand, Womer notes that mobile-device users shouldn't be forced to download large images or be redirected to several different pages, since users pay by the kilobyte.
Mobile sites can also be hard to find, because there are no standards for creating domain names. Some sites use the prefix "mobile" instead of "www," for example, while other sites use the prefix "wap." Womer says that the result can be confusing for users, who shouldn't have to know to look for special prefixes. "I think in the end, what's best for the user is one URL that works everywhere," he says.
The W3C's current suggestion for people writing Web pages, Womer says, is to separate information about how to present content from the content itself. The content can be described through hypertext markup language (HTML), the language traditionally used to describe Web pages, while the presentation can be handled with separate style sheets. Womer says that the W3C is collecting information about devices so that developers can tailor the presentation to the capabilities of the hardware.
The W3C's new tool, called the mobileOK checker, will look over code to see how well it follows the W3C's guidelines. Womer says that the tool won't be able to assess everything--some things, such as determining the readability of text against a background color, require human judgment--but it will consider a great deal of variables and provide specific instructions for what needs to be fixed.
"The importance of standards cannot be overestimated," says Jon von Tetzchner, CEO of Opera Software, who is working with the W3C's mobile-Web initiative. In addition to making browsers for desktop computers and mobile devices, Opera makes browsers for the Nintendo Wii and other game systems. "To deal with the complexity that is out there, there can only be one Web," von Tetzchner says.
The overarching goal of the initiative, according to Berners-Lee, is to keep content available regardless of the devices available to a person. "I like being able to choose my hardware separately from choosing my software, and separately from choosing my content," Berners-Lee said at the conference. There needs to be just one Web, he explained, and it needs to work on phones.
Many websites are far from Berners-Lee's vision. Some developers don't have websites that work with mobile devices and don't make mobile versions of their sites, seeing this as an added technical headache. For developers who do want their websites to be available everywhere, a common practice is to build special versions of sites for mobile devices, with pared-down features and, sometimes, content.
In some parts of the world, the mobile phone is the primary way that people access the Internet, and content should be available to those people as much as it is to people using a desktop computer. The system doesn't work well for those in wealthier nations, either. Users with devices such as the iPhone want to be able to access sites from their mobile device at the full capability that the iPhone has, says Matt Womer, the W3C's mobile-Web-initiative lead for North America. Users don't want to see a pared-down site.
On the other hand, Womer notes that mobile-device users shouldn't be forced to download large images or be redirected to several different pages, since users pay by the kilobyte.
Mobile sites can also be hard to find, because there are no standards for creating domain names. Some sites use the prefix "mobile" instead of "www," for example, while other sites use the prefix "wap." Womer says that the result can be confusing for users, who shouldn't have to know to look for special prefixes. "I think in the end, what's best for the user is one URL that works everywhere," he says.
The W3C's current suggestion for people writing Web pages, Womer says, is to separate information about how to present content from the content itself. The content can be described through hypertext markup language (HTML), the language traditionally used to describe Web pages, while the presentation can be handled with separate style sheets. Womer says that the W3C is collecting information about devices so that developers can tailor the presentation to the capabilities of the hardware.
The W3C's new tool, called the mobileOK checker, will look over code to see how well it follows the W3C's guidelines. Womer says that the tool won't be able to assess everything--some things, such as determining the readability of text against a background color, require human judgment--but it will consider a great deal of variables and provide specific instructions for what needs to be fixed.
"The importance of standards cannot be overestimated," says Jon von Tetzchner, CEO of Opera Software, who is working with the W3C's mobile-Web initiative. In addition to making browsers for desktop computers and mobile devices, Opera makes browsers for the Nintendo Wii and other game systems. "To deal with the complexity that is out there, there can only be one Web," von Tetzchner says.
Oil from Wood
Dutch biofuels startup Bioecon and Khosla Ventures have launched a joint venture called Kior, which will commercialize Bioecon's process for converting agricultural waste directly into "biocrude," a mixture of small hydrocarbon molecules that can be processed into fuels such as gasoline or diesel in existing oil refineries. The process, Kior claims, boasts numerous advantages over other methods of producing biofuels: it could prove relatively cheap, relies on a nontoxic catalyst, taps into the present fuel-refining and transportation infrastructure, and produces clean-burning fuels that can be used in existing engines.
Biofuels are widely seen as a key stepping-stone on the path from fossil fuels to renewable energy sources, particularly for transportation. Their use could also reduce emissions of carbon dioxide and other greenhouse gases. But ethanol, the most widely produced biofuel, contains little energy compared with gasoline or diesel. And a great deal of energy goes into its production: growing the grain from which it is fermented, distilling it, and transporting it. Many biofuels boosters have pinned their hopes on finding ways to produce ethanol from cellulose, the tough polymer that makes up much of plant stems and wood. In practice, though, cellulose must be broken down into simple sugars before it can be fermented into ethanol or converted into synthetic gas and turned into fuels. Despite three decades of research, these remain difficult, expensive, and energy-intensive processes that are not yet commercially viable. Additionally, recent research shows that ethanol, which is highly volatile, may actually exacerbate smog problems when it evaporates directly into the air instead of burning in vehicle engines.
The way to make cellulosic biofuels viable, says Bioecon's founder, Paul O'Connor, is to use catalysts to convert biomass into a hydrocarbon biocrude that can be processed into gasoline and diesel in existing petroleum refineries. After decades developing catalysts for the petroleum industry, O'Connor started Bioecon in early 2006 to develop methods for converting biomass directly into biofuels. His first success is a catalytic process that can convert cellulosic biomass into short-chain hydrocarbons about six to thirteen carbon atoms long. Khosla Ventures agreed to provide an undisclosed amount of series A funding to spinoff Kior in order to commercialize the process. Vinod Khosla, founder of the venture fund, believes that converting biomass into liquid transportation fuels is key to decreasing greenhouse-gas emissions and compensating for dwindling petroleum reserves. Khosla is funding a number of biofuels startups with competing technologies and says that Kior's approach is unique. "They have some very clever proprietary catalytic approaches that are pretty compelling," he says. "They can produce relatively cheap crude oil--that's attractive."
The most effective method of converting biomass into fuel is to subject it to high temperatures and high pressure to produce synthetic gas, or syngas. In the presence of a catalyst, the syngas reacts to produce fuels such as ethanol or methanol (used as an additive in biodiesel). But this is a costly process, and catalysts able to withstand the high temperature of the syngas are expensive and frequently toxic.
Attempts to produce fuel by directly exposing agricultural cellulose to a catalyst have had little success because most of the cellulose is trapped inside plant stems and stalks. O'Connor says that while the Bioecon researchers are developing new catalysts, their "biomass cracking" process is the real breakthrough. Using proprietary methods, they have been able to insert a catalyst inside the structure of the biomass, improving the contact between the materials and increasing the efficiency of the process. While O'Connor won't go into details, he says that the most basic version of the technique might involve impregnating the biomass with a solution containing the catalyst; the catalyst would then be recrystallized. "What we're doing now is improving the method to make it easier and cheaper," O'Connor says
Biofuels are widely seen as a key stepping-stone on the path from fossil fuels to renewable energy sources, particularly for transportation. Their use could also reduce emissions of carbon dioxide and other greenhouse gases. But ethanol, the most widely produced biofuel, contains little energy compared with gasoline or diesel. And a great deal of energy goes into its production: growing the grain from which it is fermented, distilling it, and transporting it. Many biofuels boosters have pinned their hopes on finding ways to produce ethanol from cellulose, the tough polymer that makes up much of plant stems and wood. In practice, though, cellulose must be broken down into simple sugars before it can be fermented into ethanol or converted into synthetic gas and turned into fuels. Despite three decades of research, these remain difficult, expensive, and energy-intensive processes that are not yet commercially viable. Additionally, recent research shows that ethanol, which is highly volatile, may actually exacerbate smog problems when it evaporates directly into the air instead of burning in vehicle engines.
The way to make cellulosic biofuels viable, says Bioecon's founder, Paul O'Connor, is to use catalysts to convert biomass into a hydrocarbon biocrude that can be processed into gasoline and diesel in existing petroleum refineries. After decades developing catalysts for the petroleum industry, O'Connor started Bioecon in early 2006 to develop methods for converting biomass directly into biofuels. His first success is a catalytic process that can convert cellulosic biomass into short-chain hydrocarbons about six to thirteen carbon atoms long. Khosla Ventures agreed to provide an undisclosed amount of series A funding to spinoff Kior in order to commercialize the process. Vinod Khosla, founder of the venture fund, believes that converting biomass into liquid transportation fuels is key to decreasing greenhouse-gas emissions and compensating for dwindling petroleum reserves. Khosla is funding a number of biofuels startups with competing technologies and says that Kior's approach is unique. "They have some very clever proprietary catalytic approaches that are pretty compelling," he says. "They can produce relatively cheap crude oil--that's attractive."
The most effective method of converting biomass into fuel is to subject it to high temperatures and high pressure to produce synthetic gas, or syngas. In the presence of a catalyst, the syngas reacts to produce fuels such as ethanol or methanol (used as an additive in biodiesel). But this is a costly process, and catalysts able to withstand the high temperature of the syngas are expensive and frequently toxic.
Attempts to produce fuel by directly exposing agricultural cellulose to a catalyst have had little success because most of the cellulose is trapped inside plant stems and stalks. O'Connor says that while the Bioecon researchers are developing new catalysts, their "biomass cracking" process is the real breakthrough. Using proprietary methods, they have been able to insert a catalyst inside the structure of the biomass, improving the contact between the materials and increasing the efficiency of the process. While O'Connor won't go into details, he says that the most basic version of the technique might involve impregnating the biomass with a solution containing the catalyst; the catalyst would then be recrystallized. "What we're doing now is improving the method to make it easier and cheaper," O'Connor says
Tiny, Sensitive Magnetic-Field Detectors
Researchers at the National Institute of Standards and Technology (NIST) have developed a new type of magnetometer--or magnetic-field detector--that rivals the sensitivity of its predecessors but is small and cheap, and uses very little power.
Magnetometers have a wide range of potential applications: where there is an electrical current, there is a magnetic field. Measurements of magnetic fields can reveal information about the electrical activity of the human heart and brain, the chemical identity of a spinning atom, or simply the presence or absence of metal. Because of their small size and sensitivity, the new sensors promise to improve detection of bombs and fetal heartbeats, and could be incorporated into future magnetic resonance imaging (MRI) scanners.
The new sensor, developed by NIST physicistJohn Kitching consists of a laser, a cell containing vaporized metal atoms, and a light detector. When the metal atoms are illuminated by the laser, they align such that they don't absorb any of the light. The presence of even a very weak magnetic field, however, disrupts their alignment, and they absorb some of the light. This change is recorded by the detector.
Other researchers have made similar magnetometers, but Kitching and his team used microfabrication techniques to miniaturize the vapor cell, which in their device consists of a cubic millimeter of silicon. The laser is an infrared diode similar to those in CD drives, so all three components can be mounted on silicon chips, making them easier to work with.
For applications such as the detection of improvised explosive devices or unexploded ordnance in minefields, the small size and low power consumption of the NIST sensors could make a big difference. The sensors could be grouped in arrays, making it possible to gain more data in a given amount of time. Commercially available laser-based magnetic detectors are the size of soda cans, require 20 watts of power, and cost $20,000 each, so grouping them in arrays is impracticable.
Remediation workers use these large sensors to detect unexploded land mines and other weapons in former battlefields, but it's a "tedious procedure," says Mark Prouty, president of Geometrics, a San Jose, CA, company that makes magnetic sensors. The heavy sensors must be carried back and forth across a field, then carried back to an office, where magnetic data is synthesized with GPS data to make maps. Then the workers must go back to the field with the maps to dig up the weapons.
With an array of smaller sensors, it would be possible to "gather data in a snapshot and dig [weapons] up in the field," says Prouty.
The detection of improvised explosive devices is also a big problem for the military, says Prouty. It's difficult to detect these bombs with individual magnetic sensors because "everything shows up, including the vehicle the sensor is mounted on," he explains. Single sensors take point measurements; they can detect a metal-containing object like a bomb but can't give any information about its location or shape. An array of magnetic sensors could "give an answer on the spot," says Prouty.
Magnetometers have a wide range of potential applications: where there is an electrical current, there is a magnetic field. Measurements of magnetic fields can reveal information about the electrical activity of the human heart and brain, the chemical identity of a spinning atom, or simply the presence or absence of metal. Because of their small size and sensitivity, the new sensors promise to improve detection of bombs and fetal heartbeats, and could be incorporated into future magnetic resonance imaging (MRI) scanners.
The new sensor, developed by NIST physicistJohn Kitching consists of a laser, a cell containing vaporized metal atoms, and a light detector. When the metal atoms are illuminated by the laser, they align such that they don't absorb any of the light. The presence of even a very weak magnetic field, however, disrupts their alignment, and they absorb some of the light. This change is recorded by the detector.
Other researchers have made similar magnetometers, but Kitching and his team used microfabrication techniques to miniaturize the vapor cell, which in their device consists of a cubic millimeter of silicon. The laser is an infrared diode similar to those in CD drives, so all three components can be mounted on silicon chips, making them easier to work with.
For applications such as the detection of improvised explosive devices or unexploded ordnance in minefields, the small size and low power consumption of the NIST sensors could make a big difference. The sensors could be grouped in arrays, making it possible to gain more data in a given amount of time. Commercially available laser-based magnetic detectors are the size of soda cans, require 20 watts of power, and cost $20,000 each, so grouping them in arrays is impracticable.
Remediation workers use these large sensors to detect unexploded land mines and other weapons in former battlefields, but it's a "tedious procedure," says Mark Prouty, president of Geometrics, a San Jose, CA, company that makes magnetic sensors. The heavy sensors must be carried back and forth across a field, then carried back to an office, where magnetic data is synthesized with GPS data to make maps. Then the workers must go back to the field with the maps to dig up the weapons.
With an array of smaller sensors, it would be possible to "gather data in a snapshot and dig [weapons] up in the field," says Prouty.
The detection of improvised explosive devices is also a big problem for the military, says Prouty. It's difficult to detect these bombs with individual magnetic sensors because "everything shows up, including the vehicle the sensor is mounted on," he explains. Single sensors take point measurements; they can detect a metal-containing object like a bomb but can't give any information about its location or shape. An array of magnetic sensors could "give an answer on the spot," says Prouty.
'Speed of thought' guides brain's memory consolidation
November 16, 2007 - Research shows the brain's processing speed is significantly faster than real timeScientists at The University of Arizona have added another piece of the puzzle of how the brain processes memory.Bruce McNaughton, a professor of psychology and physiology, and his colleague David Euston have shown that, during sleep, the reactivated memories of real-time experiences are processed within the brain at a higher rate of speed. That rate can be as much as six or seven times faster, and what McNaughton calls "thought speed."Memory stores patterns of activity in modular form in the brain's cortex. Different modules in the cortex process different kinds of information - sounds, sights, tastes, smells, etc. The cortex sends these networks of activity to a region called the hippocampus. The hippocampus then creates and assigns a tag, a kind of temporary bar code, that is unique to every memory and sends that signal back to the cortex.Each module in the cortex uses the tag to retrieve its own part of the activity. A memory of having lunch, for example, would involve a number of modules, each of which might record where the diner sat, what was served, the noise level in the restaurant or the financial transaction to pay for the meal.But while an actual dining experience might have taken up an hour of actual time, replaying the memory of it would only take 8 to 10 minutes. The reason, McNaughton said, is that the speed of the consolidation process isn't constrained by the real world physical laws that regulate activity in time and space.The brain uses this biological trick because there is no way for all of its neurons to connect with and interact with every other neuron. It is still an expensive task for the hippocampus to make all of those connections. The retrieval tags the hippocampus generates are only temporary until the cortex can carry a given memory on its own."It's a slow process," said McNaughton."The initial creation of the tag is made through existing connections. In order to do the rewiring necessary to have the intermodular connections carry the burden takes time. What you have to do is reinstate those memories multiple times. Every time you reinstate the memory, the modules make a little shift in the connection . . . something grows this way, grows that way, a connection gets made here, gets broken there. And eventually, after you do this multiple times, then an optimal set of connections gets constructed," Mc Naughton said.The brain is generally thought to do all of this during sleep, specifically slow-wave sleep, when the brain is not busy with processing real-time inputs. McNaughton has developed the technology to record from multiple probes, each of which can track the activity of a dozen or more brain cells."We need groups of cells because in order to identify a pattern, you have to look at the collected activity of many neurons," McNaughton said. His previous research has show that cells that fired during activity prior to sleep, also fired in the same sequential patterns during sleep. During sleep, the hippocampus sends little, 100-millisecond bursts of activity to the cortex as much as three times per second.What remains is finding an experiment that will enable researchers to demonstrate that changes in the memory reactivation process would affect memory consolidation but not damage the brain in the process."The more practical point, I think, is that this methodology, the ability to measure how fast the brain is processing at the level of changing the state of the brain from one 10- millisecond epoch to the next, how fast the internal state is sweeping through its memories or its allowable patterns is, I think, a model for thought speed," McNaughton said.Knowing the determinants for the speed of thought, he said, might allow studies of the effects of drugs, developmental anomalies and the behavioral therapies that might improve them.
Friday, November 16, 2007
Japonlardan “sağlık-ölçer” telefon
Japonya’da kullanıcısının nabzını ve kolestrolünü ölçen, stres seviyesini azaltmak için sohbet eden, ve ağız kokusuna karşı uyaran bir telefon üretildi.
Japonya’da NTT DoCoMo Inc. ve Mitsubishi ortaklığında üretilen cep telefonu, yoğun stres altında çalışırken sağlığını da ihmal etmek istemeyenlere hitap ediyor.
Kullanıcı “Wellness Phone”u vücudundaki yağ oranını tesbit etmek için de kullanabiliyor. Telefondaki sensör parmak ucundan nabzı ölçüyor.
Telefonun bir de “breathanalyzer” (nefes analizi) özelliği bulunuyor. Üzerinde bulunan ufak deliğe 3 saniye boyunca üflendiğinde, telefon ekranında ağız kokusu olup olmadığına dair bir mesaj gösteriyor.
Wellness Phone, “Kendinizi aşırı halsiz hissediyor musunuz?”, “Geceyarısınan sonra mı uyuyorsunuz?” gibi sorularla stres seviyesini de belirliyor ve ekranda “Üzülme, yarın yeni bir gün olacak!” mesajıyla da kullanıcısına destek oluyor.
Japonya’da NTT DoCoMo Inc. ve Mitsubishi ortaklığında üretilen cep telefonu, yoğun stres altında çalışırken sağlığını da ihmal etmek istemeyenlere hitap ediyor.
Kullanıcı “Wellness Phone”u vücudundaki yağ oranını tesbit etmek için de kullanabiliyor. Telefondaki sensör parmak ucundan nabzı ölçüyor.
Telefonun bir de “breathanalyzer” (nefes analizi) özelliği bulunuyor. Üzerinde bulunan ufak deliğe 3 saniye boyunca üflendiğinde, telefon ekranında ağız kokusu olup olmadığına dair bir mesaj gösteriyor.
Wellness Phone, “Kendinizi aşırı halsiz hissediyor musunuz?”, “Geceyarısınan sonra mı uyuyorsunuz?” gibi sorularla stres seviyesini de belirliyor ve ekranda “Üzülme, yarın yeni bir gün olacak!” mesajıyla da kullanıcısına destek oluyor.
Himalayalar karbondioksit ‘pompalıyor’
Fransızların Nancy üniversitesinden araştırmacılar, kıtasal erozyonun yeryüzü karbondioksit çevriminde çok önemli yer tuttuğunu gösterdi. İnsanoğlunun faaliyetleri sonucu atmosfere salınan karbon gazları yüzünden dengesi artık bozulmaya yüz tutan bu çevrimde, yanardağ patlamalarıyla yayılan karbondioksit biyokimyasal süreçlerle yok ediliyor.
Fransızların araştırmasına göre, Himalayaların erozyonu sonucu açığa çıkan organik karbonun küçük bir kısmı atmosfere karışıyor ve yüzde 70 ila 85’i, şiddetli yağmurlar ve nehirlerle Bengal körfezinde birikiyor. Bu da, yeryüzündeki bütün okyanuslara karalardan akan organik karbonun yüzde 10 ila 20’sini oluşturuyor.Himalaya gibi genç dağ zincirlerinde erozyonun fazla olduğunu belirleyen uzmanlar, muson yağmurları ve nehirlerle Himalayalardan yılda 1 milyar tondan fazla toprak ve organik maddenin okyanusa taşındığını düşünüyor ve bunu, Dünya’yla Ay arasındaki uzaklığın birbuçuk katı mesafeye kamyonların kum taşımasına benzetiyor.Araştırmacılar, bu manzaradan şu sonucu çıkarıyor: Himalayaların güney eteklerindeki havzalar, topraktaki organik maddeleri okyanusa taşıyor, okyanus dibinde biriken organik atıklar zamanla bozunuyor ve okyanustan atmosfere karbondioksit “pompalanıyor.”Milyonlarca yıla yayılan bu süreç, iklimin soğumasına yardımcı oluyor.
Fransızların araştırmasına göre, Himalayaların erozyonu sonucu açığa çıkan organik karbonun küçük bir kısmı atmosfere karışıyor ve yüzde 70 ila 85’i, şiddetli yağmurlar ve nehirlerle Bengal körfezinde birikiyor. Bu da, yeryüzündeki bütün okyanuslara karalardan akan organik karbonun yüzde 10 ila 20’sini oluşturuyor.Himalaya gibi genç dağ zincirlerinde erozyonun fazla olduğunu belirleyen uzmanlar, muson yağmurları ve nehirlerle Himalayalardan yılda 1 milyar tondan fazla toprak ve organik maddenin okyanusa taşındığını düşünüyor ve bunu, Dünya’yla Ay arasındaki uzaklığın birbuçuk katı mesafeye kamyonların kum taşımasına benzetiyor.Araştırmacılar, bu manzaradan şu sonucu çıkarıyor: Himalayaların güney eteklerindeki havzalar, topraktaki organik maddeleri okyanusa taşıyor, okyanus dibinde biriken organik atıklar zamanla bozunuyor ve okyanustan atmosfere karbondioksit “pompalanıyor.”Milyonlarca yıla yayılan bu süreç, iklimin soğumasına yardımcı oluyor.
Küresel Isınma ve Buz Dağları
Antartika Okyanusu’nda son 10 yıldır yüksek sıcaklıklar nedeniyle buz kütleleri giderek daha sık ana karadan kopuyor. Bu da buz dağlarının sayılarında artış görüldüğü anlamına geliyor.Bu buz dağlarının çevreye ne gibi etkileri olduğu üzerine ilk kez bir araştırma yapıldı. Science dergisinde yayımlanan bu araştırmaya göre, aslında buz dağları çevre üzerinde olumlu bir rol oynuyorlar. Araştırmayı yürüten bilim adamları, buz dağlarının eridikleri sırada demir yönünden zengin bir madde saçtığını söylüyor. Bu madde deniz canlılarını kendisine çeken bir plankton türünün yetişmesini sağlıyor.Bilim adamları buz dağları üzerinde kuş, balık, yosun ve kril gruplarının yaşadığını tespit etti. Bu eko sistemler, özellikle de yosun ve kril, atmosferdeki karbondioksitin emilmesine büyük oranda yardımcı olabilir. Çalışmanın baş yazarlarından Doktor Ken Smith, araştırmanın henüz ilk aşamalarında olduğunu söylüyor. Ancak buz dağlarının karbondioksit gazı üzerindeki etkisinin şüphe götürmez olduğunu ifade ediyor. Araştırmada yer alan bilim adamları, çalışmalarını iki büyük buz dağını inceleyerek tamamlamış. İncelemeler, buz dağlarının hayli uzağında, deniz altında bir araç kullanılması süretiyle gerçekleştirilmiş. Ve araştırmaları ışığında, bu buz dağlarının çevresinde üç kilometrelik alan boyunca kuşların ve deniz canlılarının biriktiği tespit edilmiş.
New battery technology converts sugar water into electricity
Researchers at St. Louis University in Missouri have developed a type of fuel cell that can produce electricity from almost any type of sugar. The scientists successfully tested the new cell with a glucose solution, carbonated soft drinks, sweetened drink mixes and even tree sap.The biodegradable cell runs best off of the simple glucose solution, and it runs worst off of carbonated beverages, which caused it to weaken.The research was funded by the Department of Defense, which is interested in developing ways to charge portable electronic devices in battlefield or emergency situations where electricity is not readily available. But the researchers have also suggested that the fuel cell could be used to replace lithium-ion batteries in portable electronics such as computers and cell phones. Lead researcher Shelley Minteer estimates that the cell could be ready for consumer use within three to five years.Fuel cells are distinct from the electrochemical cells commonly used in batteries; electrochemical cells generate electricity from a closed system (metal rods in ionic solutions), whereas fuel cells actually consume their fuel source, which must be periodically replaced. The cell developed by Minteer's team consumes sugar and leaves behind a handful of byproducts, primarily water. The researchers have suggested that a battery constructed from the cell could contain easily replaceable cartridges filled with a sugar solution.Minteer said that she has successfully used the prototype battery -- about the size of a postage stamp -- to power a handheld calculator.Fuel cells running off of hydrogen or hydrocarbons have become a popular area of alternative energy research -- but, in many cases, technical problems have ruled them out as a practical energy source. The smallest commercially available fuel cell is one made by Toshiba, which uses undiluted methanol as fuel. In December 2006, Samsung announced that it would make methanol fuel cells for laptops commercially available by the end of this year.
Butterflies inspire new LED illumination technology
An ingenious method of efficiently emitting light has come from a unique inspiration: butterflies.
The science behind higher-emission light emitting diodes (LED) comes from the fluorescent patches found on the wings of the African swallowtail butterfly. LED technology has been around for decades, but this new method of LED manufacture allows the diode to shine brighter.
The realization for the new form of diode comes from the wing structure of the butterfly. African swallowtails are dark colored with small spots of bright blue or green on their wings. The wings have scales that act like photonic crystals that provide intense fluorescent light. The scales have mirrors under them to direct light. With the butterflies, pigment in their wings absorbs ultra-violet light and emits it as a bright blue-green shade. The butterflies use the scales to signal to each other.
For the LEDs, scientists at MIT used actual photonic crystals to get the same effect. A lattice design etched into the crystals, implanted in the upper levels of LED’s design, makes the light emitted shine brighter.
LED technology has made advances to a point where LEDs could soon emit enough light to be considered an alternative to incandescent light bulbs. While LEDs are much more expensive, they also last a lot longer: approximately 100,000 hours. It also would save energy compared to conventional lighting.
LEDs date back to the 1950s, when an engineer at RCA observed that gallium arsenide emits an infrared light. The first infrared LED was developed soon afterward in 1961 by engineers at Texas Instruments, who accomplished this by electrifying gallium arsenide. A year later, the first visible-light LEDs appeared thanks to Nick Holonyak, Jr. of General Electric.
The most popular material for LEDs today is still gallium arsenide – which is used to make red and infrared LEDs – but gallium phosphide and gallium nitrite is used for other colors. LEDs are used for electronic signage, traffic lights and car taillights, among other uses.
The science behind higher-emission light emitting diodes (LED) comes from the fluorescent patches found on the wings of the African swallowtail butterfly. LED technology has been around for decades, but this new method of LED manufacture allows the diode to shine brighter.
The realization for the new form of diode comes from the wing structure of the butterfly. African swallowtails are dark colored with small spots of bright blue or green on their wings. The wings have scales that act like photonic crystals that provide intense fluorescent light. The scales have mirrors under them to direct light. With the butterflies, pigment in their wings absorbs ultra-violet light and emits it as a bright blue-green shade. The butterflies use the scales to signal to each other.
For the LEDs, scientists at MIT used actual photonic crystals to get the same effect. A lattice design etched into the crystals, implanted in the upper levels of LED’s design, makes the light emitted shine brighter.
LED technology has made advances to a point where LEDs could soon emit enough light to be considered an alternative to incandescent light bulbs. While LEDs are much more expensive, they also last a lot longer: approximately 100,000 hours. It also would save energy compared to conventional lighting.
LEDs date back to the 1950s, when an engineer at RCA observed that gallium arsenide emits an infrared light. The first infrared LED was developed soon afterward in 1961 by engineers at Texas Instruments, who accomplished this by electrifying gallium arsenide. A year later, the first visible-light LEDs appeared thanks to Nick Holonyak, Jr. of General Electric.
The most popular material for LEDs today is still gallium arsenide – which is used to make red and infrared LEDs – but gallium phosphide and gallium nitrite is used for other colors. LEDs are used for electronic signage, traffic lights and car taillights, among other uses.
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