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.
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