Monday, February 8, 2010
2/08/2010 03:26:00 AM Publicado por Alquimia
Most people know that diamond is one of the hardest solids on Earth, so strong that it can easily cut through glass and steel. Surprisingly, very little is known about the strength of diamond at extreme conditions. But new research by Lawrence Livermore National Laboratory scientists shows that diamond becomes even stronger during rapid compression.
Using the Janus laser at LLNL and the Omega laser at the University of Rochester, Livermore scientists and Rochester and UC Berkeley colleagues showed that when shock waves are applied to diamond with powerful lasers, it can support almost a million times atmospheric pressure before being crushed.
The research has implications for the technological uses of diamond.
“It could also provide insights into the ancient history of natural diamonds found on Earth and in meteorites, where shock waves caused by impact are common,” said Stewart McWilliams, lead author of a paper appearing in the upcoming edition of the journal, Physical Review B.
McWilliams conducted the experiments as a graduate student at UC Berkeley while on a Student Employee Graduate Research Fellowship (SEGRF) at LLNL.
Most natural diamonds are formed at high-pressure, high-temperature conditions existing at depths of 87 to 120 miles in the Earth’s mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years (25 percent to 75 percent of the age of the Earth).
In the recent research, the team measured the behavior of natural diamond crystals under shock-wave compression between 1 million and 10 million atmospheres of pressure, and the diamonds were crushed and melted in just a nanosecond (one billionth of a second).
“What we found is that diamond exhibits considerable strength right up to the point it melts,” McWilliams said.
“We reached some surprising conclusions about the strength of diamond,” said LLNL co-author Jon Eggert. “This type of research informs us about the interiors of the gas giants as well our own planet.”
Earlier research conducted by Livermore scientists show that diamond melts at around 6 million atmospheres of pressure and 14,000 degrees Fahrenheit. Their experiments mimicked conditions on the icy gas giant planets (Uranus and Neptune) where, according to their research, icebergs of diamond could float on a sea of liquid carbon.
(Photo: Eugene Kowaluk/LLE)
Lawrence Livermore National Laboratory
2/08/2010 03:25:00 AM Publicado por Alquimia
Caucasians and Asians don't examine faces in the same way, according to new research. PhD student Caroline Blais, of the Université de Montréal Department of Psychology, has published two studies on the subject: one in Current Biology and the other in PLoS One.
Previous studies have shown that people collect information by mostly studying the eyes as well as the mouth of a face. "The problem is that these studies always used Caucasian test subjects," says Blais.
Questioning the universality of facial recognition began after studies showed that Asians study faces in an overall fashion, while Caucasians break down faces into distinct parts.
Blais used a camera designed to track eye movements to study 14 Caucasian and 14 Asian participants. As part of the experiment, subjects were shown 112 Caucasian and Asian faces and asked to report if they had seen the face before and to name the dominating trait. The study confirmed that Caucasians study the triangle of the eyes and mouth, while Asians focus on the nose.
Caucasian and Asian subjects excelled at recognizing someone of their race, yet both had the same level of difficulty in identifying someone of another ethnic group. According to Blais, this says more about the analytical approach of Caucasians and the holistic approach of Asians.
In a second experiment, test subjects had to pinpoint an emotion: surprise, fear, disgust or joy. Asians mostly focused on the eyes and not enough on the mouth, which meant some emotions were wrongly identified.
"Asians had particular problems with negative emotions. They confused fear and surprise as well as disgust and anger," says Blais. "This is because they avoided looking at the mouth which provides a lot of information about these emotions."
Cultural or biological causes, Blais says, might explain why humans don't read faces in a universal fashion.
(Photo: Université de Montréal)
Université de Montréal
2/08/2010 03:24:00 AM Publicado por Alquimia
A Université de Montréal research team is developing a pill composed of leptin, the protein that tells our brain to stop eating.
"Mice deprived of leptin will not stop eating. They become so big they have trouble moving around," says Moïse Bendayan, a pathology professor at the Université de Montréal Faculty of Medicine who has studied the leptin protein extensively.
Leptin regulates appetite in mammals and its levels decrease when fasting and rise during meals. It has been proven to be an appetite suppressant when administered intravenously to pathologically obese people.
Postdoctoral student Philippe Cammisotto is leading the charge for a leptin-based, appetite suppressing pill with Dr. Bendayan and Émile Levy, a professor from the Department of Nutrition. "Taken orally, such a pill would provide obese people with the sensation of being full. They would eat less and in turn lose weight," says Dr. Cammisotto.
"We hope to start animal testing in 2010," says Bendayan. "The molecule is easy to synthesize and the protocol is ready."
After decades of building his reputation in fundamental research, Bendayan is happy to collaborate on something more tangible. "Obesity is a big problem in our society, no pun intended," says Bendayan. "To develop medication to combat obesity would be a great way for our laboratory to contribute to public health."
The new pill is being created based on a startling Université de Montréal discovery from 2006: leptin isn't only secreted by fatty tissues. "From the first bite of any meal, leptin levels skyrocket in the bloodstream. Yet this has nothing to do with the leptin stored in the fatty tissues," says Bendayan. "In the lab, we proved that up to 80 percent of cells in our stomach also produce leptin. Those are the ones that regulate appetite."
The Université de Montréal finding led to a different understanding of how the protein works, since leptin alone can't survive in an acidic stomach without assistance. Indeed, leptin protects itself with an accomplice that acts as its bodyguard and accompanies the protein through the digestive system until it can be absorbed into the bloodstream.
(Photo: Université de Montréal)
Université de Montréal