[Most Recent Entries] [Calendar View]
Monday, November 5th, 2012
| Time | Event |
| 4:00a | Clearing the air  Susan Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science Photo: Dominick Reuter Solomon points out that recent decades have seen major environmental progress: In the 1970s, the United States banned indoor leaded paint following evidence that it was poisoning children. In the 1990s, the United States put in place regulations to reduce emissions of sulfur dioxide — a move that significantly reduced acid rain. Beginning in the 1970s, countries around the world began to phase out leaded gasoline; blood lead levels in children dropped dramatically in response. During this period, Solomon herself contributed to a milestone in environmental protection: In 1985, scientists discovered that the Earth’s protective ozone layer was thinning over Antarctica. In response, Solomon led an expedition whose atmospheric measurements helped show that chlorofluorocarbons (CFCs) — chemicals then used in aerosols and as coolants in refrigerators and air conditioners — were to blame for ozone depletion. Her discovery ultimately contributed to the basis for the United Nations’ Montreal Protocol, an international treaty designed to protect the ozone layer by phasing out CFCs and other ozone-depleting chemicals. “I find it tremendously uplifting to look back at how our world has changed,” says Solomon, now the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT. Solomon, a renowned atmospheric chemist who worked for 30 years in Boulder, Colo., at the National Oceanic and Atmospheric Administration (NOAA) and as an adjunct professor at the University of Colorado, is continuing her work in climate research at MIT, where she joined the Department of Earth, Atmospheric and Planetary Sciences in January. In addition to her research, Solomon is teaching a course, 12.085/12.885 (Environmental Science and Society), exploring how society has tackled a range of past environmental challenges through science, engineering, policy, public engagement and politics. “I think young people today are growing up at a time when they don’t know that we actually have made tremendous progress on a whole series of past environmental challenges,” Solomon says. “Climate change has been called the mother of all environmental issues … and I think our approach to this problem can only be better informed if we understand better what we’ve done in the past.” Heading west Born in Chicago, Solomon was completely taken, from a young age, with “The Undersea World of Jacques Cousteau,” a documentary series that followed the legendary marine explorer on his seafaring expeditions. “I pretty much never wavered from the decision right then that I was going to be a scientist,” she recalls. After high school, Solomon enrolled at the Illinois Institute of Technology, where she received a bachelor’s degree in chemistry. Continuing her studies in atmospheric chemistry, Solomon moved west, to the University of California at Berkeley. “I had a 1977 Gremlin,” Solomon recalls. “It was one of the most awful cars, I think, ever made, but it was really cheap, and I was young and poor. I remember listening to … ‘California Dreamin’’ as I drove out west.” Solomon received her PhD in chemistry from Berkeley in 1981, and went to work as a research scientist at NOAA. In 1985, scientists with the British Antarctic Survey discovered the ozone hole above Antarctica, prompting Solomon to lead expeditions to the icy continent in 1986 and 1987. “It’s the next-best thing to going to another planet,” Solomon says of the harsh yet exhilarating experience. “It is the place on our planet that is the most unexplored, the most remote, the most hostile in terms of what the weather and climate is. It is so viciously cold. I just thought it was fantastic exploration, and it’s that spirit of exploration that I think is so endemic to science, and is fundamental to everything about Antarctica.” In 2001, Solomon chronicled perhaps the most dramatic exploration of that continent in a bestselling book, “The Coldest March”: She used scientific data to examine long-held myths about Robert Falcon Scott, an early-20th-century English explorer who trekked more than 1,000 miles on foot in an effort to become the first to reach the South Pole. But Roald Amundsen, a rival explorer, beat him to the pole by a month, and Scott, along with several team members, perished on the long trek back. While Scott’s expedition had been ridiculed — for example, by some who painted him as a “dyed-in-the-wool Englishman who only wanted to eat tinned mutton,” and therefore died of scurvy — letters and diaries from his crew told a different story. Many members of the team described eating fresh seal meat and seal liver, which have been shown to be a good source of the vitamins that ward off the disease. Solomon also analyzed weather data from 1912, and discovered that the crew likely would have survived had they not encountered extreme and unpredictable weather conditions. “It just seemed to me that somebody needed to go back and take a closer look, with all the diaries of all the guys, and what we know from modern science,” Solomon says. Changing the climate In 2002, Solomon took on another monumental task: leading an international assessment of the scientific work related to climate change. Over six years, she served as co-chair of Working Group 1 of the Intergovernmental Panel on Climate Change (IPCC). In 2007, the group released a comprehensive report on the scientific basis of climate change. Later that year, based in part on the report, the IPCC and former vice president Al Gore received the Nobel Peace Prize. Solomon continues to seek answers to the most pressing climate challenges. In a widely cited 2009 paper published in the journal Proceedings of the National Academy of Sciences, Solomon and her co-authors determined that, even if humans were to immediately and completely stop emitting carbon dioxide, it would take more than 1,000 years to undo existing changes in Earth’s surface temperatures, rainfall and sea levels. This news, while sobering, has not deterred the chemist in her scientific goals. Solomon is currently probing which places on the planet are likely to be the most affected by anthropogenic warming in the near future. In addition to her climate research, she also continues to study the stratosphere — the layer of the atmosphere in which the ozone layer is found. “There are still fantastic surprises in the stratosphere, as there are in any field, no matter how much has been done on it,” Solomon says. “There’s always something to discover, and I love that feeling.” |
| 8:00p | A step toward stronger polymers Many of the objects we encounter are made of polymers — long chains of repeating molecules. Networks of polymers form manmade materials such as plastics, as well as natural products such as rubber and cellulose. Within all of these polymeric materials, there are structural flaws at the molecular level. To form an ideal network, each polymer chain would bind only to another chain. However, in any real polymeric material, a significant fraction of the chains instead bind to themselves, forming floppy loops. “If your material properties depend on having polymers connected to each other to form a network, but you have polymers folded around and connected to themselves, then those polymers are not part of the network. They weaken it,” says Jeremiah A. Johnson, an assistant professor of chemistry at MIT. Johnson and his colleagues have now developed, for the first time, a way to measure how many loops are present in a given polymer network, an advance they believe is the first step toward creating better materials that don’t contain those weak spots. Huaxing Zhou, an MIT postdoc, is the lead author of a paper describing the new technique in this week’s issue of the Proceedings of the National Academy of Sciences. Other authors are visiting researcher Jiyeon Woo, chemistry graduate student Alexandra Cok, chemical engineering graduate student Muzhou Wang, and Bradley Olsen, an assistant professor of chemical engineering. Although polymer chemists have known about these loops since the 1940s, they have had no way to count them until now. In the new paper, the researchers measured the percentage of loops in a gel, but their approach could be used for nearly any type of polymer network, Johnson says. To measure the number of loops, the researchers first design polymer chains that incorporate a chemical bond, in a specific location, that can be broken using hydrolysis. Once the polymer crosslinks into a gel network, the researchers treat it with a base that cleaves this chemical bond, known as an ester. (Other degradation methods, such as enzymes or light, could also be used.) Because they know where the break points are, the researchers can predict the percentages of the four different degradation products they should expect to find in an ideal, no-loop network. By measuring the quantity of each degradation product and comparing it with the ideal, they can figure out what fraction of the polymer formed loops. They found that the percentage of polymer loops ranges from about 9 percent to nearly 100 percent, depending on the concentration of polymers in the starting material and other factors. “Even in the best material we can make, 9 percent of its junctions are wasted as loops, which tells us that if can figure out a way to reduce loop formation, we’d have a 9 percent improvement in material properties,” Johnson says. Christopher Bielawski, a professor of chemistry at the University of Texas at Austin, says the new technique overcomes longstanding limitations in chemists’ understanding of the exact structures of polymers. “The technique is a beautiful combination of experiment, theory and state-of-the-art analytics that takes the field a giant step toward sorting out a problem of tremendous importance,” says Bielawski, who was not part of the research team. The researchers are now looking for ways to reduce the number of loops by altering the mixture of polymers used to produce a material, as well as the reaction conditions. They are also planning to use their method to study interactions between cells and biological materials. It has already been shown that at the micron scale, cells behave differently depending on the mechanical properties of their environment, such as stiffness. In their new studies, the MIT researchers want to look at nanoscale interactions between cells and specific protein sequences found in the extracellular matrix, which provides structural support for cells. The researchers hope to uncover what happens when a cell grabs on to a protein that is looped on itself rather than being attached to the extracellular matrix. The research was funded by the MIT Department of Chemistry, MIT’s Institute for Soldier Nanotechnologies, and a National Defense Science and Engineering Graduate Fellowship. |
| 8:00p | Inside the unconscious brain A new study from MIT and Massachusetts General Hospital (MGH) reveals, for the first time, what happens inside the brain as patients lose consciousness during anesthesia. By monitoring brain activity as patients were given a common anesthetic, the researchers were able to identify a distinctive brain activity pattern that marked the loss of consciousness. This pattern, characterized by very slow oscillation, corresponds to a breakdown of communication between different brain regions, each of which experiences short bursts of activity interrupted by longer silences. “Within a small area, things can look pretty normal, but because of this periodic silencing, everything gets interrupted every few hundred milliseconds, and that prevents any communication,” says Laura Lewis, a graduate student in MIT’s Department of Brain and Cognitive Sciences (BCS) and one of the lead authors of a paper describing the findings in the Proceedings of the National Academy of Sciences this week. This pattern may help anesthesiologists to better monitor patients as they receive anesthesia, preventing rare cases where patients awaken during surgery or stop breathing after excessive doses of anesthesia drugs. “We now finally have an objective physiological signal for measuring when someone’s unconscious under anesthesia,” says Patrick Purdon, an instructor of anesthesia at MGH and Harvard Medical School and senior author on the paper. “Now clinicians will know what to look for in the EEG when they are putting someone under anesthesia.” Other MIT authors of the PNAS paper are co-lead author Veronica Weiner, a graduate student in BCS, and Emery Brown, professor of brain and cognitive sciences and health sciences and technology at MIT and an anesthesiologist at MGH. Breakdown of communication For this study, the researchers focused on propofol, one of the most commonly used anesthesia drugs. Propofol activates receptors found on neurons that are likely to make the neurons less active, but its precise effects on the brain were not known. The researchers studied epileptic patients who had electrodes implanted in their brains to monitor their seizures, and were undergoing surgery to have the electrodes removed. Loss of consciousness occurred within 40 seconds of propofol administration, and was defined by the moment when patients stopped responding to sounds that were played every four seconds. Using two different-sized electrodes, the researchers were able to obtain two different readings of brain activity. The larger electrodes, slightly bigger than a penny, were spaced about a centimeter apart and recorded the overall EEG, or brain-wave pattern. Smaller electrodes, in an array only 4 millimeters wide, recorded from individual neurons, marking the first time anyone has recorded from individual neurons in human patients as they lost consciousness. Between 50 and 100 electrodes were implanted in each patient, clustered in different regions. From the large electrodes, the researchers observed that within a couple of seconds of losing consciousness, the brain EEG abruptly took on a pattern of low-frequency oscillation, about one cycle per second. At the same time, the electrodes recording from individual neurons revealed that within localized brain regions, neurons were active for a few hundred milliseconds, then shut off again for a few hundred milliseconds. This “flickering” of activity created the slow oscillation seen in the EEG. “When one area was active, it was likely that another brain area that it was trying to communicate with was not active. Even when the neurons were on, they still couldn’t send information to other brain regions,” Lewis says. Michael Avidan, a professor of anesthesiology at Washington University School of Medicine, says the findings are exciting because they offer neurobiological evidence for one of the theories of how the brain gives rise to consciousness. That theory, known as information integration theory, suggests that large-scale brain networks integrate many types of sensory input to generate our overall experience of the world. When consciousness is lost, “there may still be information coming into the brain, but that information is remaining localized and doesn’t get integrated into a coherent picture,” says Avidan, who was not part of the research team. Failure of information integration had previously been suggested as a possible mechanism for loss of consciousness, but no one was sure how that might happen. “This finding really narrows it down quite a bit,” Brown says. “It really does, in a very fundamental way, constrain the possibilities of what the mechanisms could be." A delicate balance Patients who receive too little anesthesia risk awakening in the middle of their surgery, while too much drug can cause respiratory problems and even halt breathing. Anesthesiologists must give just the right amount of drugs to keep patients in the appropriate state. Currently, anesthesiologists monitor anesthesia with recordings that compute an index from the EEG. That index obscures the physiology that can be observed directly in the slow waves. “What this study says is that you should be looking at raw EEG in order to observe the oscillations and interpret them. If you do that, you have a physiologically linked way to know when someone is unconscious,” Brown says. “We can take this into the operating room today and give better patient care.” The team is now planning to study what happens to brain activity as consciousness is regained. They have also begun studies of other anesthesia drugs, to see if they produce the same slow oscillation. “There are many other drugs — based on EEG studies — that seem like they might be producing slow oscillations. But there are other drugs that seem to be doing something totally different,” Purdon says. The research was funded by an NIH Director’s New Innovator Award, an NIH Director’s Pioneer Award, a fellowship from the Canadian Research Foundation, and the National Institute of Neurological Disorders and Stroke. |
| << Previous Day |
2012/11/05 [Calendar] |
Next Day >> |