New snapshot of the universe

Deep in the bowels of the earth –100 metres below ground in Geneva, Switzerland – lies a supermachine of 27 km circumference called the Large Hadron Collider (LHC) that has been built to unlock the mysteries of the universe.

Claude Leroy, a Université de Montréal physics professor, was among the 2,500 scientists from 37 countries recruited to help design, test and build the ATLAS detector at the supermachine that will provide a new perspective into what occurred at the time of the Big Bang and immediately after. Designed for CERN, the European Organization for Nuclear Research, the ATLAS detector, the largest among the four detectors operating at the supermachine in question, is 46 metres in length, 25 metres in height and 7000 tonnes in weight – or the size of three football fields.

Prof. Leroy was responsible for the radiation and irradiation studies conducted to ensure the ATLAS detector will run smoothly. His investigations also led to the creation of MPX, a small device attached throughout the supermachine and ATLAS that uses pixel silicon detectors to perform real-time measurements of the spectral characteristics and composition of radiation inside and around the ATLAS detector. The small devices essentially capture images of what’s inside the detector and its environment, such neutrons and photons, a world-first.

He also participated in physics studies that targeted the production of heavy leptons, excited leptons, quarks and supersymmetry, in particular the study of neutralinos as dark matter candidates. Prof. Leroy’s experiments were critical in ensuring the viability of the ATLAS detector at the core of the supermachine, which is the world’s biggest particles physics detector. Indeed, before the LHC can be started up, some 38,000 tons of equipment of the supermachine must be cooled down to minus 456 degrees Fahrenheit for the magnets to operate in a superconducting state. This will be achieved by using liquid helium for magnet. Parts of the ATLAS calorimeters use liquid argon cooled at minus 312 degrees Fahrenheit. “The radiation field produced by the operation of the machine and ATLAS is stronger than a nuclear reactor, so it is vital that its design master all aspects of physics,” said Prof. Leroy.

Supermachine’s Big Bang

The LHC will recreate conditions akin to the Big Bang – which many scientists believe gave birth to the universe – by colliding two beams of particles at close to the speed of light. Since it is estimated that only 4 percent of the universe has been charted, the supermachine will help answer the following questions in physics when it is turned on in summer

Use of powerful anticoagulants to prevent pulmonary embolism may actually lead to more deaths after surgery

Anticoagulants are routinely prescribed before and after total hip and knee replacement operations to reduce the risk of thrombosis, and death from pulmonary embolism in particular, as recommended by the Chest Physicians Consensus Statement. During the last decades, deaths from pulmonary embolism have fallen significantly due to a combination of advancements in anesthesia, better surgical techniques and care pre- and post-surgery, as well as a better understanding of how thrombosis develops as a result of surgery. In light of these developments, Sharock and his team looked at whether the prescription of potent anticoagulants by surgeons who perform joint replacement operations is still warranted, as these drugs also have side effects.

The authors reviewed 20 studies among a total of just over 28,000 patients undergoing joint replacement surgery who were prescribed medication to reduce the risk of thrombosis. They compared the total number of deaths and cases of non-fatal pulmonary embolism between three frequently used prevention protocols worldwide. Patients in group A received potent anticoagulants such as low molecular weight heparin; those in group B received local spinal or epidural anesthesia, pneumatic compression and aspirin; patients in group C were prescribed slow-acting oral anticoagulants such as warfarin.

The lowest number of deaths occurred in patients in group B. Patients in groups A and C were more than twice as likely to have died as those in group B. There was no difference in the number of deaths between groups A and C. Patients in group A were also at 60-70% greater risk of non-fatal pulmonary embolism than those in group B, indicating that pulmonary embolism occurs despite the use of powerful anticoagulants.

Sharock and colleagues conclude that “the American College of Chest Physicians should reconsider their guidelines to reflect the fact that pulmonary embolism occurs despite the use of potent anticoagulants and may, in fact, expose patients to increased mortality after surgery.” In their view, the current recommendations often result in physicians feeling compelled to prescribe these anticoagulants to avoid potential litigation when, in reality, these drugs could be doing more harm than good.