Last modified: 09/16/2013
"There has been much excitement the last couple of years precipitated by reports by the two experimental collaborations working at the Tevatron (at Fermilab, outside Chicago) that a much larger-than-expected top-quark forward-backward asymmetry is seen," Grinstein told Phys.org. "Several models have been proposed to explain this unexpected result. Our paper suggests a way to distinguish among the various models that have been proposed, since these models give very different bottom-quark forward-backward asymmetries. When a sufficiently precise measurement of the bottom-quark forward-backward asymmetry is performed, we will be able to narrow down significantly the new physics that the Tevatron experiments seem to have uncovered.
"But perhaps more importantly, observations of the bottom-quark forward-backward asymmetry in disagreement with expectations from the Standard Model, when put together with the top-quark forward-backward asymmetry, would demonstrate fairly conclusively that there is new physics in the form of new particles and interactions not included in the Standard Model, and would point the way toward its direct experimental confirmation. So, as you can see, this would go to the heart of the question in particle physics."
As the physicists explain, a quark's forward-backward asymmetry refers to the likelihood that the quark is moving in the forward or backward direction after it is produced in a proton-antiproton collision.
"The Tevatron is a large circular particle accelerator in which protons and antiprotons travel in opposite directions," Murphy said. "The direction of travel of a proton at the point it collides with an antiproton is called the 'forward' direction. Often a b-quark and an anti-b-quark are produced as a result of the proton-antiproton collision. There are several ways to define a 'bottom-quark forward-backward asymmetry,' but they all are a measure of how more (or less) likely it is for the produced b-quark to be moving preferentially in the forward direction. For example, one may count the number of collisions with a forward-moving b-quark, subtract the number of collisions with a backwards-moving b-quark, and divide this by the total number of collisions that produce b-quarks. It should be noted that the asymmetry is not just a single number because it can be determined for various values of the energies of the produced b-quarks. So in fact the asymmetry is a function of the energy of the b-quarks."
This is the second plot showing the predicted bottom-quark forward-backward asymmetry (in percentage) plotted against the energy (in GeV units) of the bottom quark-antiquark pair produced in the proton-antiproton collision at the Tevatron. ...more If new physics is involved, as the physicists expect, then the bottom-quark forward-backward asymmetry might be larger than predicted by the Standard Model, or the asymmetry may even be reversed.
"The Standard Model of electroweak and strong interactions predicts a very small bottom-quark forward-backward asymmetry at the Tevatron, of the order of a few percent," Grinstein said. "What we have shown in our work is that new physics can change this number dramatically. One of the interesting features we discovered is that when the energy of the b-quark and b-antiquark sum to the rest energy of the Z-boson (one of the particles responsible for weak interactions), the asymmetry is enhanced. We furthermore showed that, at this particular energy, the effects of new physics can be greatly amplified. For example, in one popular class of models the sign of the asymmetry is reversed, relative to that predicted by the Standard Model, in the energy region corresponding to the Z-boson's rest energy."
The plots in the physicists' paper tell a more detailed story of the possibilities for new physics. The two plots included here show the predicted bottom-quark forward-backward asymmetry (in percentage) plotted against the energy (in GeV units) of the bottom quark-antiquark pair produced in the proton-antiproton collision at the Tevatron.
In both plots, the orange line represents the Standard Model prediction, while the other colors correspond to predictions from proposed extensions of the Standard Model. The plots are not continuous, but instead they are bar graphs in which the quark pairs of energies in given "bins" are collected together. The black vertical bars indicate what the CDF experiment at Fermilab predicts as its sensitivity, meaning they will be able to distinguish between colored lines that are separated by more than the size of the black bar.
Last modified: 08/27/2013
Cells obey simple "growth laws" that describe linear relationships between cell growth and protein expression, Terence T. Hwa and colleagues at the University of California, San Diego, report (Science, DOI: 10.1126/science.1192588). Their findings could ease the ability to predict cell growth in synthetic biology experiments, fermentation processes, and other areas.
"Hwa and colleagues have used an integrated computational and experimental approach to show that protein expression influences cell growth and vice versa," says James J. Collins, who studies synthetic biology at Boston University. "That's important because efforts in synthetic biology assume that synthetic circuits and other constructs are in most cases isolated and independent of other actions in cells."
The researchers changed the state of Escherichia coli cells by inhibiting their ribosomes, which tends to suppress protein expression, or by varying their nutrient levels. They found that when the growth rate increases by boosting nutrients, the ribosome content of cells likewise increases linearly, increasing protein expression. Another linear relationship they found was that "when you slow down the ribosome, the cell makes more ribosome and less of other proteins," Hwa notes.
On the basis of these growth laws, they divided the bacterium's proteome into three broad categories: ribosomal, metabolic, and housekeeping. Housekeeping proteins, which account for about 50% of the proteome, don't change with growth state, but the cell varies in the other two categories, depending on growth conditions.
"The rule is extremely simple," Hwa says. "If you have poor nutrients, then you devote more resources to the metabolic portion. If your ribosome is having trouble translating, you devote more resources to the ribosomes.
The findings also help explain why engineered pathways in bacteria slow down cell growth: Because "unnecessary" proteins produced by engineered genes reduce the production of both metabolic and ribosomal portions of the proteome. "We predicted that the growth rate would drop linearly with the amount of these unnecessary proteins in the cell," Hwa says. They found that growth slowed down just as predicted when engineered E. coli expressed ß-galactosidase in large quantities.
"The authors have shown that the cell cycle itself, and the general growth state of the cell, plays a big role in the output of your circuit," Collins says.
Chemical & Engineering News
Copyright © 2013 American Chemical Society
Last modified: 07/23/2013
Strains of bacteria able to resist multiple antibiotics pose a growing threat to public health, yet the means by which resistance quickly emerges aren't well understood.
Scientists led by physics professor Terence Hwa at the University of California, San Diego, thought that the variety of environments in which bacteria encounter antibiotic drugs could play an important role. They have developed a mathematical model, published in the June 18 early online edition of the Proceedings of the National Academy of Sciences, that demonstrates how that would work.Drug levels can vary widely between different organs and tissues in the human body, or between different individuals in a hospital. To account for that, their model considers a matrix of "compartments" with differing concentrations of a drug.
The bacteria in their model can move randomly from one compartment to the next. Their survival and rates of proliferation depend on the concentration of antibiotic within each compartment. And mutations that allow the bacteria to survive and thrive in environments with slightly higher concentrations were allowed to emerge randomly as well.
The system, designed to represent the varying environment of the human body, showed that drug-resistant mutants could evade competition by invading parts of the body, compartments in the model, with slightly higher drug concentrations where other bacteria fail to thrive.
When the process is repeated, the bacterial population can quickly adapt to components with much higher drug concentrations, with adaptation rates that would be very unlikely impossible in a uniform environment.
Although Hwa's team created this model to study the evolution of antibiotic resistance, its formulation quite general. It could be applied to any example of adaptive expansion of an organism's range, a general feature of biological systems that has allowed living things to populate every corner of the Earth, they write.
"Our mathematical model quantifies hypotheses, makes falsifiable predictions and suggests experiments on this vast subject in which many words have been said but few quantitative statements can be found," Hwa said. "The next step is quantitative experimentations which are being carried out in our lab and elsewhere."
The iteration of quantitative prediction, experimental characterization and model refinement characterizes quantitative biology, an emerging discipline that aims to fundamentally change biological research from discipline that is descriptive in nature to one that is quantitative and predictive. prerequisite for engineering and synthesis that promise to be the fruit of this century of biology.
Co-authors include postdoc Rutger Hermsen and graduate student Barret Deris, both members of Hwa's research group. This work was supported by the Center for Theoretical Biological Physics (National Science Foundation) and the National Cancer Institute's Physical Science-Oncology program. Deris holds a National Science Foundation Research Fellowship.
Last modified: 07/23/2013
Now a team of scientists has designed a simple genetic circuit that creates a striped pattern that they can control by tweaking a single gene.
With multiple starting points, bacteria guided by a simple genetic circuit can create intricate patterns.
"The essential components can be buried in a complex physiological context," said Terence Hwa, a professor of physics at the University of California, San Diego, and one of the leaders of the study published October 14 in Science. "Natural systems make all kinds of wonderful patterns, but the problem is you never know what's really controlling it."
With genes taken from one species of bacterium and inserted into another, Hwa and colleagues from the University of Hong Kong assembled a genetic loop from two linked modules that senses how crowded a group of cells has become and responds by controlling their movements.
One of the modules secretes a chemical signal called acyl-homoserine lactone (AHL). As the bacterial colony grows, AHL floods the accumulating cells, causing them to tumble in place rather than swim. Stuck in the agar of their dish, they pile up.
Because AHL doesn't diffuse very far, a few cells escape and swim away to begin the process again.
Left to grow overnight, the cells create a target-like pattern of concentric rings of crowded and dispersed bacterial cells. By tweaking just one gene that limits how fast and far cells can swim, the researchers were able to control the number of rings the bacteria made. They can also manipulate the pattern by modifying how long AHL lasts before it degrades.
A colony of bacteria with a "synthetic" genetic circuit develops a pattern of strips over 24 hours.
Although individual bacteria are single cells, as colonies they can act like a multicellular organism, sending and receiving signals to coordinate the growth and other functions of the colony. That means fundamental rules that govern the development of these patterns could well apply to critical steps in the development of other organisms.
To uncover these fundamental rules, Hwa and colleagues characterized the performance of their synthetic genetic circuit in two ways.
First, they precisely measured both the activity of individual genes in the circuit throughout the tumble-and-swim cycle. Then they derived a mathematical equation that describes the probability of cells flipping between swim and tumble motions.
Additional equations describe other aspects of the system, such as the dynamics of the synthesis, diffusion and deactivation of one of the cell-to-cell chemical signal AHL.
This three-pronged approach of "wet-lab" experiments, precise measurements of the results, and mathematical modeling of the system, characterize the emerging discipline of quantitative biology, Hwa said. "This is a prototype, a model of the kind of biology we want to do."
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Prof. Burgasser will be partnering with Prof. Willie Rockward, Chair of Department of Physics and Dual-Degree Engineering at Morehouse College, a historically black college based in Atlanta, GA and one of the largest producers of African-American Physics Bachelors in the US.
In each of the next three years, 3-5 Morehouse undergraduate Physics majors will travel to UCSD for a summer research and graduate training program, co-mentored by UCSD and Morehouse faculty. In addition, support will be provided for faculty to visit each others' institutions to establish and develop research collaborations.
Students selected for the program who subsequently apply and are admitted for graduate study at any UC will also receive graduate stipend support through the Initiative. This is the second UC-HBCU program to be awarded to UCSD; last year the "Pathways to UC San Diego" program was established to link UCSD with Howard University.
Last modified: 07/03/2013
David Kleinfeld (Ph.D. '84), professor of physics and neurobiology at UC San Diego, and colleagues mapped blood vessels in an area of the mouse brain that receives sensory signals from the whiskers.The study, published June 9 in the early online edition of Nature Neuroscience, describes vascular architecture within a well-known region of the cerebral cortex and explores what that structure means for functional imaging of the brain and the onset of a kind of dementia.
The brain area is part of the cerebral cortex, which is fed by small arteries that plunge from the surface of the brain and is drained by small veins that return from the depths to the surface. The network of capillaries in between was uncharted though these tiny vessels deliver crucial oxygen and nutrients to energy-hungry brain cells and carry away wastes.
The team traced this fine network by filling the vessels with a fluorescent gel. Then, using an automated system, developed by co-author Philbert Tsai (B.S. '94, Ph.D. '04), a project scientist in physics, reconstructed the three-dimensional network of tiny vessels. The system, which removes thin layers of tissue with a laser while capturing a series of images, will be instrumental to the rapid mapping planned by the recently announced BRAIN initiative.
This project focused on a region of the cerebral cortex in which the nerve cells are so well known they can be traced to individual whiskers. These neurons cluster in "barrels," one per whisker, a pattern of organization seen in other sensory areas as well.
The scientists expected each whisker barrel to match up with its own discrete blood supply, but that was not the case.
"This was a surprise, because the blood vessels develop in tandem with neural tissue," Kleinfeld said. Instead, microvessels beneath the surface loop and connect in patterns that don't obviously correspond to the barrels.
To search for hidden patterns, they turned to a branch of mathematics called graph theory, which describes systems as connecting paths. Using this approach, led by Harry Suhl, professor emeritus of physics and a founding faculty member who joined the campus in 1961, they determined that the mesh indeed forms a continous network they call the "angiome."
The vascular maps traced in this study raise a question of what we're actually seeing in a widely used kind of brain imaging called functional MRI, which in one form measures brain activity by recording changes in oxygen levels in the blood. The idea is that activity will locally deplete oxygen. But without a discrete blood supply, they wondered how precisely that optical signal would match the sites of neural activity.
To find out, they wiggled whiskers on individual mice and found that optical signals associated with depleted oxygen indeed centered on the barrels, where electrical recordings confirmed neural activity.
The researchers also went a step further to calculate patterns of blood flow based on the diameters and connections of the vessels and asked how this would change if a feeder arteriole were blocked. The map allowed them to identify "perfusion domains," which predict the volumes of lesions that result when a clot occludes a vessel. Critically, they were able to build a physical model of how these lesions form, as may occur in cases of human vascular dementia.
Additional co-authors include Pablo Blinder, John Kaufhold and Per Knutsen. This work was funded by the National Institutes of Health, including a Director's Pioneer Award to Kleinfeld.
Last modified: 06/27/2013
One of the most satisfying aspects of condensed matter physics is that a variety of condensed matter systems show universal behavior, i.e. behavior that appears to be common to a wide variety of unrelated systems. A jamming transition occurs when the density of particles becomes large enough and the motion of the particles is restricted by the surrounding particles (think traffic jams!). In this regime, the particles cannot fluctuate freely but move collectively via long range interactions. Examples are colloidal gels or polymer emulsions. Recent work carried out in the Sinha group (S.-W. Chen, H. Guo, K. A. Seu, K. Dumesnil, S. Roy, and S. K. Sinha, Physical Review Letters 110, 217201 (2013) ) using X-ray scattering show that magnetic domains in an antiferromagnet have dynamical behavior very similar to that exhibited by several other jammed systems. The magnetic spins in the rare earth element dysprosium undergo a phase transition from a disordered state to a spiral ordered structure at a temperature of 180 K. When the temperature is slightly above the phase transition temperature, the spins start to form clusters which eventually become magnetic domains below the transition temperature. These domains are head to head with each other and the domain walls form a disordered network, which mimics the jammed state in a soft matter system. As the temperature is further lowered, the sizes of the domains increase and eventually the dynamics are kinetically arrested, as happens when a material becomes a glass.
Last modified: 05/24/2013
Scholars from San Diego State University to the University of California San Diego to California State University San Marcos are preparing to travel the globe. They will explore subjects as varied as water quality in Uganda to tuberculosis in Brazil to religious issues in Germany.
We've pulled together a sample of the research, some of which will be explained in greater depth this summer in dispatches sent to U-T San Diego by the scientists.
TOM ROCKWELL, seismologist, San Diego State University, will dig trenches on the Sudetic marginal fault in the Czech Republic in early July. He's examining whether the fault is active and could produce future earthquakes, which may have implications for nuclear power plants in Poland.
BIANCA MOTHE, biologist, Cal State San Marcos, will spend much of the spring and summer in Rio de Janeiro, Brazil, studying immune-system responses in patients who are infected with multi-drug and extreme-drug resistant tuberculosis.
DAN CAYAN, research meteorologist, Scripps Institution of Oceanography in La Jolla, will travel to the Sierra Nevada and the White Mountains in June to explore climate change and variability.
BRIAN KEATING, astrophysicist, UC San Diego, will visit Chile's Atacama Desert in September to study the cosmos from the university's James Ax Observatory, home of the POLARBEAR telescope.
DREW TALLEY, biological oceanographer, University of San Diego, will spend part of June in Bahia San Quintin, Baja California, comparing bivalve populations to historic records from the 1960s
FOREST ROWHER, microbial ecologist, San Diego State, will be diving in the Galapagos, Franz Josef Land (Arctic) and Line Islands in the central Pacific throughout the summer. He will study how human activities increase microbes in the world's oceans.
GENO PAWLAK, mechanical engineer, UC San Diego, will spend part of August and September on the leeward side of Oahu, Hawaii to help improve computerized models that simulate how currents and waves behave when they encounter coral reefs.
MARC MEYERS, materials scientist, UC San Diego, will spend part of August on the Roosevelt River in Brazil trying to obtain the scales of armored catfish, as well as a different fish whose teeth look almost human-like. The goal is to find inspiration for the design of new, better, lighter, tougher and stronger manmade materials.
GEORGE VOURLITIS, ecologist, Cal State San Marcos, will spend part of June and July in Cuiaba, Mato Grosso, Brazil, with undergraduates examining soil fertility and biodiversity in the Brazilian savannah, the country's second-largest and most vulnerable ecosystem.
BETH O'SHEA, geochemist, University of San Diego, will spend part of June at the European Synchrotron Radiation Facility in Grenoble, France, studying how arsenic is released from rocks into household well water.
JOHN HAVILAND, linguistic anthropologist, UC San Diego, will spend part of June and July in northeastern Italy analyzing the Rhaeto-Romance language Friulian, and parts of July and August in Chiapas, Mexico, studying a previously unknown sign language in a Tzotzil (Mayan) speaking village.
ANDRE KUNDGEN, mathematician, Cal State San Marcos, will spend June in Copenhagen, Denmark, exploring new directions in the study of graphs on surfaces. He'll work with renowned mathematician Carsten Thomassen.
JULIE JAMESON, biologist, Cal State San Marcos, will visit Manila, Philippines in June to help educators learn better ways to teach science, technology, engineering and mathematics.
ESRA OZYUREK, anthropologist, UC San Diego, will spend July, August and September in Berlin, doing research on Germans who convert to Islam.
PAUL ETZEL, astronomer, San Diego State University, will spent part of the late summer installing the new 50-inch Phillips Claud Telescope on Mt. Laguna. The telescope will greatly improve the university's ability to study deep space.
CAROLYN KURLE, biologist, UC San Diego, will spend the summer working in bays and estuaries in the San Diego area to study how certain pollution from runoff and stream outfalls is becoming incorporated into coastal food webs.
Copyright 2013 The San Diego Union-Tribune, LLC. An MLIM LLC Company. All rights reserved.
Last modified: 05/06/2013
"What is unique about this particular galaxy is that it is forming stars so rapidly with such a tiny supply of gas," said Aleksandar Diamond-Stanic, a fellow at the University of California's Southern California Center for Galaxy Evolution who helped make the discovery. A team of nine astrophysicists recently reported the finding in Astrophysical Journal Letters.
The team of astronomers estimated the amount of gas in the galaxy using the IRAM Plateau de Bure Interferometer, a telescope in the French Alps that detects a light signal associated with hydrogen gas, the fuel of stars. Images from the Hubble Space Telescope show gas concentrated in a zone just a few hundred light years across, yet that gas is condensing and igniting new stars at a rate hundreds of times that of our own Milky Way galaxy.
The distant galaxy, 6 billion light years away, initially popped out of an image captured by a satellite-based NASA instrument called WISE, for Wide-field Infrared Survey Explorer. The image revealed infrared light, an indication of star formation, pouring out of the galaxy.
That rate of star formation combined with the estimate of available fuel indicates an efficiency close to the theoretical maximum, called the Eddington limit.
"This galaxy is like a highly tuned sports car, converting gas to stars at the most efficient rate thought to be possible," said Jim Geach, an astrophysicist at McGill University who led the study.
"We've caught it just before it runs out of gas," adds Diamond-Stanic, a member the research group led by Alison Coil, a physics professor at UC San Diego who also co-authored the report. This rate of star birth is so ferocious that most of the galaxy's gas will be gone in just a few tens of millions of years, a brief episode in the course of its evolution.
That's why they think no galaxy quite like this one has ever been seen before. Once star formation abates, the team expects the galaxy to mature into a steadier state: an ordinary reddish, elliptical galaxy.
Last modified: 05/06/2013
The Department of Energy Computational Science Graduate Fellowship (DOE CSGF) program provides outstanding benefits and opportunities to students pursuing doctoral degrees in fields of study that use high performance computing to solve complex science and engineering problems.
The program fosters a community of bright, energetic and committed Ph.D. students, alumni, DOE laboratory staff and other scientists who share a common desire to impact the nation while advancing their science. Fellowship students represent diverse scientific and engineering disciplines but the common thread is their use of mathematical and computing techniques for their research.
Funded by the Department of Energy's Office of Science and National Nuclear Security Administration, the DOE CSGF trains scientists to meet U.S. workforce needs and helps to create a nationwide interdisciplinary community.
The specific objectives of the DOE CSGF program are:
To help ensure an adequate supply of scientists and engineers appropriately trained to meet national workforce needs, including those of the DOE, in computational sciences.
To make national DOE laboratories available for practical work experiences for fellows ensuring cross-disciplinary experience in highly productive work teams.
To strengthen collaborative ties between the national academic community and DOE laboratories so that the multidisciplinary nature of the fellowship builds the national community of scientists.
To raise the visibility of careers in the computational sciences and to encourage talented students to pursue such careers, thus building the next generation of leaders in computational science.
Read the 2004 article (updated July 2009), Building a Community of Leaders to find out more about why the DOE CSGF program is important to the nation.
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See link for details.
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The department congratulates him on this important milestone in his career and wishes him continued success in teaching and research in the future.
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A professor at the University of California, San Diego, Dr. Sharma had to spend months at a time away from home, coordinating a team of physicists at the Large Hadron Collider, here just outside Geneva. But on April 15, 2011, Meera Sharma's 7th birthday, he flew to California for some much-needed family time. "We had a fine birthday, a beautiful day," he recalled.
Then Dr. Sharma was alerted to a blog post. There it was reported that a rival team of physicists had beaten his team to the discovery of the Higgs boson - the long-sought "God particle."
If his rivals were right, it would mean a cascade of Nobel Prizes flowing in the wrong direction and, even more vexingly, that Dr. Sharma and his colleagues had missed one of nature's clues and thus one of its greatest prizes; that the dream of any physicist - to know something that nobody else has ever known - was happening to someone else.
He flew back to Geneva the next day. "My wife was stunned," he recalled.
He would not see them again for months.
Last modified: 03/06/2013
Well, maybe not.
Smith, who earned a doctorate in physics at the University of California San Diego, is a professor at Duke University, where he's stirring attention with his efforts to cloak things with the use of common materials. Smith doesn't make objects literally disappear. But the materials effectively make small things invisible to microwave energy.
It's trippy research that Smith will discuss on Wednesday, February 27, during a free public lecture at UC San Diego. He'll take to the podium at the Great Hall in the International House at 7 p.m., and explain how cloaking works and explore how it might be used to improve our lives. He gave us a preview of his talk during a recent phone call.
Q: Many people think of Harry Potter's fictional invisibility cloak when the subject of invisibility comes up. Is this the kind of thing you're working on?
A: Harry Potter's magical cloak can seemingly make someone completely invisible to detection, whether they're sitting still or moving around. We're not trying to make people invisible. But we are working on a closely related concept that could help make things like your cellphone and certain electronic systems in automobiles work better and more reliably.
Our experiment involves microwaves, an electromagnetic form of energy. Humans can't see microwaves, but they're there and they can get blocked by objects. For example, if you're sitting in an airport trying to use your cellphone your wireless signal might get blocked by the big column that helps hold up the roof of the terminal. That could disrupt your call, or it could make it hard to do something like call up Netflix on the Internet. We're working on ways to make that column 'invisible' to microwaves. We do that by bending the microwaves around blockages.
Q: How do you do that?
A: We cloak objects with meta-materials. These materials cause the microwaves to go around objects. Think of water flowing in a stream. The water flows around things like rocks. In a similar way, microwaves go around things that would block their movement.
Q: And what are meta-materials?
A: They're basically copper circuits that are placed on things like plastic and Teflon. The copper can be arranged in a pattern that causes microwaves to refract. We want to use meta-materials to cloak things that can become an obstruction. This is becoming increasingly important with things like automobiles because they're taking on more and more electronic systems, from wireless Internet to collision-avoidance sensors. We might be able to cloak the grill on a car to prevent it from blocking the signals that come from the collision-avoidance system.
Q: It sounds like this would have a lot of applications for the military. Does it?
A: Yes. The military uses a lot of antennas and they are putting more and more of them together in smaller spaces. We might be able to cloak one antenna to prevent it from blocking the signal of another.
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Last modified: 02/12/2013
Where do we come from? What is the universe made of? Will the universe exist only for a finite time or will it last forever? These are just some of the questions that University of California, San Diego physicists are working to answer in the high desert of northern Chile.
Armed with a massive 3.5 meter (11.5 foot) diameter telescope designed to measure space-time fluctuations produced immediately after the Big Bang, the research team will soon be one step closer to understanding the origin of the universe. The Simons Foundation has recently awarded the team a $4.3 million grant to build and install two more telescopes. Together, the three telescopes will be known as the Simons Array.
"The Simons Array will inform our knowledge of the universe in a completely new way," said Brian Keating, associate professor of Physics at UC San Diego's Center for Astrophysics and Space Sciences. Keating will lead the project with Professor Adrian Lee of UC Berkeley.
Fluctuations in space-time, also known as "gravitational waves," are gravitational perturbations that propagate at the speed of light and can penetrate "through" matter, like an x-ray. The gravitational waves are thought to have imprinted the "primordial soup" of matter and photons that later coalesced to become gases, stars and galaxies-all the structures that we now see. The photons left over from the Big Bang will be captured by the telescopes to give scientists a unique view back to the universe's beginning.
The telescopes of the Simons Array-named in recognition of the grant-will focus light onto more than 20,000 detectors, each of which must be cooled nearly to absolute zero. The result will provide an unmatched combination of sensitivity, frequency coverage and sky coverage.
Last modified: 01/09/2013
Ride was in charge of the Grail mission's MoonKam project, which let students from around the world select targets for the probes' cameras. MIT's Maria Zuber, the mission's principal investigator, announced just after today's double whammy that her team received clearance from NASA to name the crash site after Ride.Read More:
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The article can be read here: October 2012 Nature Materials
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We know, of course, that tigers are not apt to vanish into thin air; we know that such magic tricks are more trick than magic. But how is it possible that our eyes can be deceived so easily?
The answer has much to do with the way our sense of sight works. As we look around a room, our eyes detect the light that bounces off nearby people or objects, and our brains interpret the images formed from the patterns of light received. We can even figure out what material something is made of based on the way it reflects and transmits light: metal is opaque and typically very reflective; plastic, which is more dull and often translucent, absorbs some of the light and reflects the rest in all directions. Our brains, then, turn these signals from reflections into breathtakingly complex pictures of the world around us. And it all happens faster than the blink of an eye. Indeed, after every blink of an eye.
Such lightning-fast cognitions are possible partly because the brain makes certain automatic assumptions: it figures that light has traveled in a straight line from the object to our eyes. Remarkably, in that built-in assumption is the recipe for a bit of magic that humans (and mythical humans) have sought, from the time of Plato to the age of Harry Potter: invisibility.
The trick involves the ability to bend and distort light as it travels through space - in other words, to make it do what the brain assumes it won't. In some ways, it's the same sleight of hand that the magician uses with the tiger. He uses a mirror angled in such a way that when we think we're looking into an empty box, we're actually seeing the reflection from the bottom of the box and assuming it's the back. Since we don't expect that the light reaching our eyes has swerved, making a 90-degree turn along the way, our eyes "tell" us the tiger has vanished. (In reality, he's hiding comfortably in the box.)
Now we've found a way to one-up this neat trick with science: changing the trajectory of light without using mirrors. We do it with the science of materials - designing a "cloak" that can make light curve around an object, and then emerge just as if it had passed in a straight line through space. (Think of it like water flowing past a rock in a stream.)
The phenomenon is indeed supernatural. That's because nature doesn't appear to offer any materials that can accomplish this feat. The reason is that light has both electric and magnetic components - and to make it swerve around an object, one has to redirect both of these very different components and have them sync up immediately after the detour. That's impossible to do with metals, fabrics or any other traditional materials.
But research findings over the past decade have shown us how to develop artificially structured "metamaterials" - in which tiny electrical circuits serve as the building blocks in much the same way that atoms and molecules provide the structure of natural substances. By changing the geometry and other parameters of those circuits, we can give these materials properties beyond what nature offers, letting us simultaneously manipulate both the electric and magnetic aspects of light in striking harmony.
This year, with one such metamaterial, we built the world's first invisibility cloak capable of managing both components of light.
There is a catch, admittedly. Our cloak works only on microwaves, not on visible light. And humans don't "see" microwaves in the first place, making the idea of invisibility seem, well, a little extraneous.
Still, even if we mortals don't see them, many essential devices do. Nearly every time you walk through security at an airport, your body is scanned with microwaves. Also, your cellphone, iPad and other devices make a similar kind of virtual eye contact with one another. So, even in the microwave realm, cloaking can potentially be used to remove obstacles from the paths of direct microwave communications (or hide things we don't want detected).
More important, microwaves are part of the same electromagnetic spectrum as visible light. In principle, if cloaks can be made to work at microwave frequencies, they might one day be made to work at visible wavelengths.
This will be far more difficult: the wavelengths of visible light are more than 10,000 times smaller than those of microwaves, meaning that the corresponding metamaterials would have to be equally reduced in size.
What excites scientists and Harry Potter fans alike, though, is that our microwave cloak proves there's no theoretical limitation that would prevent someone from building a visible-light cloak.
There are some tricky technological barriers to work out. But in this case, at least, not seeing is believing.
David R. Smith is a professor of electrical and computer engineering at Duke University, where Nathan Landy is a graduate student.
Last modified: 11/17/2012
Sifting through images and data from three telescopes, a team of astronomers found 29 objects with outflowing winds measuring up to 2,500 kilometers per second, an order of magnitude faster than most observed galactic winds.
"They're nearly blowing themselves apart," said Aleksandar Diamond-Stanic, a fellow at the University of California's Southern California Center for Galaxy Evolution, who led the study. "Most galactic winds are more like fountains; the outflowing gas will fall back onto the galaxies. With the high-velocity winds we've observed the outflowing gas will escape the galaxy and never return." Diamond-Stanic and colleagues published their findings in Astrophysical Journal Letters.
The galaxies they observed are a few billion light years away with outflowing winds of 500 to 2,500 kilometers per second. Initially they thought the winds might be coming from quasars, but a closer look revealed these winds emanate from entire galaxies.
Young, bright and compact, these massive galaxies are in the midst of or just completing a period of star formation as intense as anyone has ever observed.
"These galactic-scale crazy-fast winds are probably driven by the really massive stars exploding and pushing out the gas around them," said Alison Coil, professor in UC San Diego's Center for Astrophysics and Space Sciences and a co-author of the paper. "There's just such a high density of those stars it's like all these bombs went off near each other at the same time. Each bomb evacuates the area around it, then the next can push gas out further until they're evacuating gas on the scale of the whole galaxy."
Galaxies with winds this fast are also quite rare, opening up the question of whether these are unusual events or part of a common phase in the evolution of massive galaxies that is seldom observed because it is so brief.
Astrophysicists still lack an explanation for how and why starmaking ends. Theorists who model the evolution of galaxies often invoke supermassive black holes called active galactic nuclei, which can also generate savage winds, to explain how gas needed to form stars can be depleted.
These new observations demonstrate that black holes may not be neccesary to account for how these kinds galaxies run out of gas. "The winds seem to be powered by the starburst," Diamond-Stanic said. "The central supermassive black hole is apparently just a spectator for these massive stellar fireworks."
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This is the first time anyone has observed plasmons on graphene, sheets of carbon just one atom thick with a host of intriguing physical properties, and an important step toward using plasmons to process and transmit information in spaces too tight to use light.
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This feat will allow scientists to better study the physical properties of excitons, which exist only fleetingly yet offer promising applications as diverse as efficient harvesting of solar energy and ultrafast computing.
"The realization of the exciton condensate in a trap opens the opportunity to study this interesting state. Traps allow control of the condensate, providing a new way to study fundamental properties of light and matter," said Leonid Butov, professor of physics at the University of California, San Diego. A paper reporting his team's success was recently published in the scientific journal Nano Letters.
Excitons are composite particles made up of an electron and a "hole" left by a missing electron in a semiconductor. Created by light, these coupled pairs exist in nature. The formation and dynamics of excitons play a critical role in photosynthesis, for example.
Like other matter, excitons have a dual nature of both particle and wave, in a quantum mechanical view. The waves are usually unsynchronized, but when particles are cooled enough to condense, their waves synchronize and combine to form a giant matter wave, a state that others have observed for atoms.
Scientists can easily create excitons by shining light on a semiconductor, but in order for the excitons to condense they must be chilled before they recombine.
The key to the team's success was to separate the electrons far enough from their holes so that excitons could last long enough for the scientists to cool them into a condensate. They accomplished this by creating structures called "coupled quantum wells" that separate electrons from holes in different layers of alloys made of gallium, arsenic and aluminum.
Then they set an electrostatic trap made by a diamond-shaped electrode and chilled their special semiconducting material in an optical dilution refrigerator to as cold as 50 milli-Kelvin, just a fraction of a degree above absolute zero.
A laser focused on the surface of the material created excitons, which began to accumulate at the bottom of the trap as they cooled. Below 1 Kelvin, the entire cloud of excitons cohered to form a single matter wave, a signature of a state called a Bose-Einstein condensate.
Other scientists have seen whole atoms do this when confined in a trap and cooled, but this is the first time that scientists have seen subatomic particles form coherent matter waves in a trap.
Varying the size and depth of the trap will alter the coherent exciton state, providing this team, and others, the opportunity to study the properties of light and mater in a new way.
This most recent discovery stems from an ongoing collaboration between Leonid Butov's research group in UC San Diego's Division of Physical Sciences, including Alexander High, Jason Leonard and Mikas Remeika, and Micah Hanson and Arthur Gossard in UC Santa Barbara's Materials Department. The Army Research Office and the National Science Foundation funded the experiments, and the Department of Energy supported the development of spectroscopy in the optical dilution refrigerator, the technique used to observe the exciton condensate in a trap.
Last modified: 05/29/2012
The innovative research effort, which is being funded by the Office of Naval Research under the Defense Department's MultiUniversity Research Initiative, or MURI, will also involve scientists at UC Berkeley and the University of Chicago.
The team plans to conduct basic research on how collective action in the brain learns, modulates and produces coherent functional neural activity for coordinated behavior of complex systems.
"This research will tie together theoretical ideas, hardware implementation of structural models and experimental investigations of human and animal behavior to develop a quantitative understanding and a predictive language for discussing complex physical and biological systems," said Henry Abarbanel, a physics professor at UC San Diego who is heading the collaboration.
The grant will pay for the costs of new laboratory facilities at UC San Diego and the University Chicago, create powerful parallel computing capabilities for the three universities involved and employ 10 or more postdoctoral research fellows. Key UC San Diego researchers participating in the effort are Katja Lindenberg, professor of chemistry and biochemistry; Tim Gentner, associate professor of psychology; Gert Cauwenberghs, professor of bioengineering; Misha Rabinovich, research physicist in the BioCircuits Institute; and Terry Sejnowski, professor of biology.
This is the fourth MURI award led by Abarbanel. The first focused on theory and experiment in complex fluid flows and was funded by the Defense Advanced Research and Projects Agency from 1988 to 1993. The second investigated chaotic communications strategies from 1998 to 2003 under sponsorship by the Army Research Office. The third developed advanced chemical sensing methodologies using animal olfactory dynamics and was funded by the Office of Naval Research from 2007 to 2012.
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Doesn't look too exciting at first glance but it's the start of big things for the project and team!
It's an amazing place to be... very much like being an astronaut on Mars due to the high altitude (17,000') and the terrain. To complete the astronaut analogy most of us need to be on supplemental oxygen most of the time, which makes manual labor quite hard. But it sure beats the alternative!
Thanks to the whole collaboration and especially to the UCSD team (Darcy Barron, Dave Boettger, Frederick Matsuda, Nathan Miller, Stephanie Moyerman, Dr. Nathan Stebor, Praween Siritanasak) for all of their hard work and dedication!
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Single-molecule force spectroscopy, which measures how a molecule responds to mechanical forces pulling it apart, is an important tool in the study of biomolecules and other polymers. Experiments have shown that for weak forces molecules end up in two or more states, depending on the amount of stretching, which researchers attribute to how molecules fold and unfold. However, they have found it difficult to close in on a theoretical explanation. One recent study maintains that these experiments monitor a barrierless process, rather than one where the barrier is known to exist. It concluded that what the experiments are actually observing is merely the collapse of the molecules, and not folding per se.
In their paper in Physical Review Letters, Olga Dudko at the University of California, San Diego, and co-workers appear to resolve this gap in our understanding of this fundamental mechanism in biomolecular interactions. From molecular simulation studies of molecular energy surfaces ("energy landscapes"), they find that there is indeed a barrier to folding, and it is this barrier that is probed by the experiments. It is just that the barrier appeared to be absent-hidden, as it were-in the earlier theoretical work, partly because of the method chosen to project a complicated, multidimensional folding scenario onto a single dimension (the "reaction coordinate"). A more robust choice of a folding coordinate ends up revealing the barrier.
This resolution of a central discrepancy between theory and observations in the important field of molecular-particularly protein-folding should bring about a collective sigh of relief among many biological physicists and physical chemists. - Sami Mitra, Physical Review Letters, American Physical Society
Link to the online publication: http://prl.aps.org/abstract/PRL/v107/i20/e208301
Last modified: 11/07/2011
Supermassive black holes millions to billions times the mass of our Sun lie at the heart of most, maybe all large galaxies. Some of these power brilliantly luminous, rapidly growing objects called active galactic nuclei that gather and condense enormous quantities of dust, gas and stars.
Because astronomers had seen these objects primarily in the oldest, most massive galaxies that glow with the red light of aging stars, many thought active galactic nuclei might help to bring an end to the formation of new stars, though the evidence was always circumstantial.
That idea has now been overturned by a new survey of the sky that found active galactic nuclei in all kinds and sizes of galaxies, including young, blue, star-making factories.
“The misconception was simply due to observational biases in the data,” said Alison Coil, assistant professor of physics at the University of California, San Diego and an author of the new report, which will be published in The Astrophysical Journal.
“Before this study, people found active galactic nuclei predominantly at the centers of the most massive galaxies, which are also the oldest and are making no new stars,” said James Aird, a postdoc at the University of California, San Diego’s Center for Astrophysics and Space Sciences, who led the study.
Black holes, such as those at the centers of active galactic nuclei, can’t be observed directly as not even light escapes their gravitational field. But as material swirls toward the event horizon, before it’s sucked into the void, it releases intense radiation across the electromagnetic spectrum, including visible light. Of these, X-rays are often the brightest as they can penetrate the dust and gas that sometimes obscures other wavelengths.
“When we take into account variations in the strength of the X-ray signal, which can be relatively weak even from extremely fast-growing black holes, we find them over a whole range of galaxies,” Aird said
He searched the sky for X-rays from active galactic nuclei using two orbiting telescopes, the XMM-Newton and the Chandra X-ray Observatory, and compared those signals to a large-scale survey of about 100,000 galaxies that mapped their colors and distances.
Coil led that survey, called PRIMUS, along with colleagues now at New York University and the Harvard College Observatory. Using the twin Magellan telescopes at Las Campanas Observatory in Chile, they detected the faint light of faraway galaxies.
They measured both the color of each galaxy and how much the spectrum of that light had shifted as the galaxies receded in our expanding universe – an estimate of their distance from Earth. Because distances in space reach back in time, they’ve captured nearly two-thirds of the history of the universe in particular segments of the sky.
Galaxies can be distinguished by the color of their light. Younger galaxies glow with the bluish light of young stars. As starmaking ceases, and stars burn through their fuel, the color of their light shifts toward red.
In a sample of about 25,000 of the galaxies from the PRIMUS survey, Aird found 264 X-ray signals emanating from galaxies of every kind: massive and smaller, old elliptical red galaxies and younger blue spirals. They’re everywhere.
So as suspects in the quenching of star formation, active galactic nuclei have been exonerated. And because the astronomers saw similar signals stretching far back into time, they conclude that the physical processes that trigger and fuel active galactic nuclei haven’t changed much in the last half of the universe’s existence.
Yet starmaking has ceased in many galaxies, probably when they ran out of gas, though it’s not clear how that happens. The interstellar gas could all be used up, turned into stars, but Coil studies another possibility: fierce galactic winds that have been seen blowing gas and dust from so-called starburst galaxies.
The source of those winds, and their influence on the evolution of galaxies, is one of Coil’s main areas of current investigation.
Alison Coil is an Alfred P. Sloan Foundation Fellow. The National Science Foundation and NASA provided funding for the PRIMUS survey.
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The scientists who made the discovery, published in this week's advance online publication of Nature, found that the process bacteria use to quickly adapt to metabolize preferred energy sources such as glucose--a process called "catabolite repression"--is controlled not just by glucose, as had long been known and taught, but just as much by other essential nutrients, such as nitrogen and sulfur, available to bacteria in their growth medium.
"This is one of the most studied processes in molecular biology; it's in every textbook," says Terence Hwa, a professor of physics and biology at UC San Diego, who headed the team of scientists. "We showed that this process doesn't work the way most people thought it did for the past several decades, and its purpose is different from what had generally been assumed."
The basic phenomenon, Hwa says, is analogous to a balanced diet: To reduce an individual's sugar uptake, common wisdom is to reduce the availability of sugar. This strategy backfires on bacteria because they would increase their appetite for sugars -- the process of catabolite repression would direct the bacteria to increase the production of their sugar uptake system to counteract the scarcity of sugar in the environment. However, by figuring out that catabolite repression actually works by sensing the difference between the influx of sugar and that of other essential nutrients such as nitrogen, it is possible to drastically lower the bacteria's appetite for sugar by simply rationing the supply of nitrogen.
Hwa and his team arrived at their surprising finding by employing a new approach called "quantitative biology," in which scientists quantify biological data and discover mathematical patterns, which in turn guide them to develop predictive models of the underlying processes.
"This mode of research, an iterative dialogue between data quantitation and model building, has driven the progress of physics for the past several centuries, starting with Kepler's discovery of the law of planetary motion," explains Hwa. "However, it was long thought that biology is so laden with historical accidents which render the application of quantitative deduction intractable."
The significance of the study, according to Hwa, is that it demonstrates that the physicists' quantitative approach can also effectively probe and elucidate biological processes, even a classic problem that has been heavily scrutinized.
"Molecular biology gives us a collection of parts and interactions," says Hwa. "But how do you make sense of those interactions? You need to examine them in their physiological context. Quantitative patterns in physiological responses, together with mathematical analysis, provide important clues that can reveal the functions of molecular components and interactions, and in this case, also pinpoint the existence of previously unknown interactions."
"It is remarkable that after so many years of studying these cells there are more fascinating things to be discovered by simple experiments and theory," says Krastan B. Blagoev, a program director in the National Science Foundation's Division of Physics, which jointly funded the research with the agency's Molecular and Cellular Biology Division.
Hwa and his team of physicists and biologists at UC San Diego are among the world's leaders in quantitative biology, which is gaining an upsurge of interest and importance in the life sciences. According to a recent National Academy of Sciences report, advances in quantitative biology are a necessary ingredient to ensure our nation continues to make future progress in medicine, genetics and other life science disciplines. By quantifying the complex behavior of living organisms, for example, researchers can develop reliable models that could allow them to more accurately predict processes like drug interactions before untested pharmaceuticals are used in human clinical trials. UC San Diego is in the middle of a major expansion in quantitative biology, with plans to hire 15 to 20 faculty members in this new discipline in different departments over a three-year period.
In their study, the UC San Diego scientists collaborated with colleagues at Peking University in China, the University of Marburg in Germany and the Indiana University of School of Medicine--an international research team formed six years ago with the help of a grant from the Human Frontier Science Program, headquartered in Strasbourg, France.
Biologists have long known that when glucose is the primary carbon source for cells, bacteria such as E. coli repress genes that allow the organism to metabolize other kinds of sugars. This catabolite repression effect is controlled by a small molecule known as "cyclic adenosine monophosphate"--or cAMP.
"Previously, it was thought that glucose uptake sets the cAMP level in the cell," says Hwa. "But we discovered that in reality, it's the difference between carbon uptake and the uptake of other essential nutrients such as nitrogen. So the picture now is very different."
The UC San Diego scientists unraveled this relationship by measuring the level of cAMP and the level of enzymes that break down sugar molecules in bacterial cells against the growth rates of the bacteria, while subjecting these cells to limiting supplies of carbon, nitrogen and other compounds.
"When we plotted our results, our jaws dropped," recalls Hwa. "The levels of the sugar uptake and utilization enzymes lined up remarkably into two crossing lines when plotted with the corresponding growth rates, with the enzyme level increasing upon carbon limitation and decreasing upon nitrogen and sulfur limitation. The enzyme levels followed the simple mathematical rules like a machine." "From the overall pattern, it is clear that there's nothing special about glucose," he adds. "Now we know this process is not about the preference of glucose over other carbon compounds, but rather the fine coordination of carbon uptake in the cell with other minor, but essential nutrient elements such as nitrogen and sulfur."
Hwa points out that the physiological insights derived from simple mathematical relations guided them to figuring out both the strategy and molecular mechanisms their bacteria employ to coordinate carbon metabolism with those of other elements. Such knowledge may be very valuable to the fermentation industry, where metabolic engineers strive to rewire the genetic programs of industrial microorganisms to increase their yield of desirable products, such as insulin for biomedical applications and ethanol for bioenergy.
Hwa further speculates that by similarly quantifying how the human metabolic control system deals with different types of nutrient limitations, one may envision novel strategies to combat diseases such as obesity, which involves an imbalance of macronutrient composition, or even cancer, which requires a full suite of nutrient elements to fuel its rapid growth.
While quantitative biology papers are often filled with complicated mathematical formulas and involved heavy number crunching by computers, Hwa says the mathematics used in this discovery was surprisingly simple.
"We just used line plots," he says. "Our entire study involves just three linear equations. They're the kind of things my 10-year-old daughter should be able to do. Quantitative biology doesn't have to be fancy." Like their mathematical approach, Hwa says his team's experiments were simple enough most of them could have been done 50 years ago. In fact, one prominent scientist was on the right track to discovering the same thing nearly 40 years ago. The Nobel-Prizewinning French scientist Jacques Monod, who was the first to study the effects of catabolite repression quantitatively during World War II 70 years ago and whose study led eventually to the birth of molecular biology 20 years later, wrote a paper published months after his death in 1976 that questioned the standard understanding of catabolite repression--a publication that had been long forgotten until Hwa mentioned his team's results recently to some colleagues from France.
"Monod knew that something was not quite right with the standard picture of cyclic AMP," says Hwa, who was directed to that 1976 paper. "He knew that nitrogen was having an effect on the input and he knew that somehow it was very important."
Hwa says he and his team are now applying the same quantitative approaches to learn more about the response of bacteria to antibiotics and how cells transition from one state to another. "This kind of quantitative, physiological approach is really underutilized in biology," he adds. "Because it's so easy to manipulate molecules, biologists as well as biophysicists tend to jump immediately to a molecular view, often decoupled from the physiological context. Certainly the parts list is important and we could not have gotten to the bottom of our study without all of the molecular work that had been done before. But that in of itself is not enough, because the very same parts can be put to work in different ways to make systems with very different functions."
Other authors of the paper were UC San Diego scientists Conghui You, Hiroyuki Okano, Sheng Hui, Zhongge Zhang, Minsu Kim and Carl Gunderson; Yi-Ping Wang of Peking University in China; Peter Lenz of the University of Marburg in Germany; and Dalai Yan of the Indiana University School of Medicine in Indianapolis.
Last modified: 08/22/2011
In the fourth year of the Outstanding Graduate/Professional Student Award, eighteen nominations were submitted by students, faculty, and alumni who felt it was important to acknowledge the most talented and gifted graduate/professional students at UC San Diego. With the high quantity of outstanding nominations the awards committee had tremendous difficulty selecting one graduate recipient. However, it was noted that Alexander's stewardship, leadership, and scholarship will continue to make a mark on campus life for future generations of students after graduation.
Vice Chancellor of Student Affairs, Penny Rue comments in her letter to Alexander, "My experience working with students shows that the chance to make a difference is the primary reason you give of yourself, and for that I thank you. Your work on the undergraduate scholarship council is a forecast of what I know will be lifelong involvement at UC San Diego. In addition to receiving this award, you will also receive $1,000 and a lifetime membership to the UC San Diego Alumni Association."
The Outstanding Graduate/Professional Student Award will be presented at the 20 I 1 All Campus Graduation Celebration on Friday, June 10 at 7:00 p.m. on RIMAC field.
Last modified: 01/23/2011
All of the images will be displayed in the S&E Library beginning Friday, May
27, and continuing through the summer. Please stop by and take a look. They
will also be posted on the S&E Flickr page
And the winners are...
1st place - Tadel Matevz, Physics
2nd place - Adam Burgasser, Physics
3rd place - David Rideout, Mathematics
1st place - Rick Wagner, Physics
2nd place - Christopher Doran, ECE
3rd place - Kim Wright, MAE
Honorable Mention - Alireza Kargar, ECE
ChaOss Begets Order I. (1st place - Tadel Matevz, Physics)
The image shows a Z-boson decaying into electron-positron pair inside the Compact Muon Selenoid (CMS) detector at CERN, European Organization for Nuclear Research in Geneva, Switzerland. The event was produced as a result of lead-lead ion collisions at the Large Hadron Collider and is in fact one of the first events in the world where Z-boson production was observed in heavy-ion collisions. The two opposite, dominant red towers show energy depositions of the electron and positron in the electro-magnetic calorimeter of CMS while other smaller red and blue towers represent the energy deposited by remaining low-energy particles in the electro-magnetic (red) and hadronic (blue) calorimeters of CMS.
Stellar Orbits Dragonfly (2nd place - Adam Burgasser, Physics)
Everything in the Universe moves. Moons, planets, stars, even whole galaxies careen through the cosmos, carrying us along. These motions tell us about the origins of celestial objects, how they have evolved, and the medium of matter, dark matter and dark energy they move through.
In my research, I study our nearest brown dwarf neighbors - very low-mass, low-temperature stars they are a "mere" 10-50 light-years away. These stars orbit our galactic system - the Milky Way Galaxy - along many paths that reveal their diverse ages and origins. The image shows the orbital paths of 200 such brown dwarfs based on data collected from the Two Micron All Sky Survey and the Sloan Digital Sky Survey, projected to show radial and vertical motions. Some of the orbits are clustered, indicating stellar groups that orbit around the Milky Way together; others are very wide, indicating old stars that are just passing through the Solar Neighborhood.
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Please click on the following link for more information:
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His talk, "Taming Dirac's Particle," led off the session entitled "Through the Looking Glass: Recent Adventures in Antimatter," at 1:30 pm on February 18. Surko said that since "positrons"--the anti-electrons predicted by English physicist Paul Dirac some 80 years ago-- disappear in a burst of gamma rays whenever they come in contact with ordinary matter, accumulating and storing these antimatter particles is no small feat. But over the past few years, he added, researchers have developed new techniques to store billions of positrons for hours or more and cool them to low temperatures in order to slow their movements so they can be studied. Surko said physicists are now able to slow positrons from radioactive sources to low energy and accumulate and store them for days in specially designed "bottles" that have magnetic and electric fields as walls rather than matter. They have also developed methods to cool them to temperatures as low as that of liquid helium and to compress them to high densities. "One can then carefully push them out of the bottle in a thin stream, a beam, much like squeezing a tube of toothpaste," said Surko, adding that there are a variety of uses for such positrons.
A familiar positron technique that does not use this new technology is the PET scan, also known as Positron Emission Tomography, which is now used routinely to study human metabolic processes and help design new drugs. In the new methods being developed by physicists, beams of positrons will be used in other ways. "These beams provide new ways to study how antiparticles interact or react with ordinary matter," said Surko. "They are very useful, for example, in understanding the properties of material surfaces." Surko and his collaborators at UC San Diego are studying how positrons bind to ordinary matter, such as atoms and molecules. "While these complexes only last a billionth of a second or so," he said, "the 'stickiness' of the positron is an important facet of the chemistry of matter and antimatter." Surko and his colleagues are building the world's largest trap for low-energy positrons in his laboratory at UC San Diego, capable of storing more than a trillion antimatter particles at one time. "We are now working to accumulate trillions of positrons or more in a novel 'multi-cell' trap--an array of magnetic bottles akin to a hotel with many rooms, with each room containing tens of billions of antiparticles," he said.
"These developments are enabling many new studies of nature. Examples include the formation and study of antihydrogen, the antimatter counterpart of hydrogen; the investigation of electron-positron plasmas, similar to those believed to be present at the magnetic poles of neutron stars, using a device now being developed at Columbia University; and the creation of much larger bursts of positrons which could eventually enable the creation of an annihilation gamma ray laser." "An exciting long-term goal of the work is the creation of portable traps for antimatter," added Surko. "This would increase greatly the ability to use and exploit antiparticles in our matter world in situations where radioisotope- or accelerator-based positron sources are inconvenient to arrange." Professor Surko's work is funded by the National Science Foundation, the U.S. Department of Energy and the Defense Threat Reduction Agency.
Last modified: 01/23/2011
The link below includes all scheduled air dates/times, as well as different options to view the program online once it's uploaded to the site just prior to the premiere date. This will include embeddable Flash video and audio and video podcasts.
Last modified: 01/23/2011
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One of the greatest successes of the former Soviet space program was a lunar rover called Lunokhod 1 Russian for "moonwalker." Landing on the moon on November 17, 1970 with a laser reflector, it wandered around the moon's surface for 11 months then mysteriously disappeared -- until last spring.
On April 22, nearly 40 years after Lunokhod 1 disappeared, a team headed by Tom Murphy found the reflector and pinpointed its distance from earth to within one centimeter.
The discovery came as part of a long-term project Murphy heads to send pulses of laser light to the moon from a telescope in New Mexico. The purpose, which he will describe in his talk, is to look for deviations of Einstein's theory of general relativity by measuring the shape of the lunar orbit to within the accuracy of one millimeter, or about the thickness of a paperclip.
The talk is free and the public welcome. Light refreshments will be served afterwards. If you have questions, please contact
Last modified: 10/21/2010
Last modified: 10/21/2010
Following a successful "first-light" four-month observing run, UCSD's POLARBEAR experiment on the Huan Tran Telescope at the James Ax Observatory located in the Inyo National Forest near Bishop, CA, is moving to its permanent location in the Atacama Desert, Chile.
POLARBEAR is a collaboration between UC San Diego,
UC Berkeley, University of Colorado, McGill University, Imperial College, the Japanese High Energy Research Organization, and the University of Paris.
Polarbear's goal is to detect the gravitational waves produced during the era of inflation, shortly after the Big Bang by observing unique patterns of polarization of the Cosmic Microwave Background (CMB) radiation. These gravitational waves would be a telltale sign that inflation indeed took place. Additionally, measurement of the small angular scale polarization patterns have the capability to constrain the properties of Dark Matter and the mass of the neutrinos.
POLARBEAR's receiver is able to detect the polarization of the CMB radiation through an array of over 1200 superconducting transition edge sensor bolometers cooled to 0.25 degrees Kelvin to reduce noise. Many months of observations must be combined to improve the signal to noise enough to observe the desired signals. Atmospheric water vapor is the enemy of ground-based
microwave background measurements, hence the move to one of the driest sites on earth: the Atacama Desert, Chile where at an altitude of 16,500 feet, water vapor is greatly reduced.
The POLARBEAR team has begun decommissioning the temporary observatory in the Inyo mountains which will be reassembled in Atacama for observations starting in early 2011.
Polarbear team members from UC San Diego are David Boettger, George Fuller, Brian Keating, Nathan Miller, Hans Paar, and Ian Schanning.
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UCSD physics Professor Oleg Shpyrko has received an NSF Faculty Early Career Development Program (CAREER) Grant. The CAREER Program offers the National Science Foundation's most prestigious awards in support of junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research within the context of the mission of their organizations. This Faculty Early Career Award will support research aiming to investigate the relationship between dynamical, mechanical, and structural properties of nanoscale-thick films, using synchrotron x-ray surface scattering probes at both the existing and the next generation light sources. Understanding the fundamental relationship between structure and function of materials such as biological membranes, self-assembled monolayers and thin polymer films at the nanoscale is crucial for many disciplines ranging from condensed matter and chemistry to biology, engineering and nanotechnology. More information on Prof. Shpyrko's research is available at http://oleg.ucsd.edu.
Last modified: 05/31/2010
The French-built laser reflector was sent aboard the unmanned Luna 17 mission, which landed on the moon November 17, 1970, releasing a robotic rover that roamed the lunar surface and carried the missing laser reflector. The Soviet lander and its rover, called Lunokhod 1, were last heard from on September 14, 1971.
"No one had seen the reflector since 1971," said Tom Murphy, an associate professor of physics at UCSD. He heads a team of scientists engaged in a long-term effort to look for deviations of Einstein's theory of general relativity by measuring the shape of the lunar orbit to within an accuracy of one millimeter, or about the thickness of a paperclip. This is accomplished by timing the reflections of pulses of laser light from reflectors left on the moon by Apollo astronauts and turning the timing measurement into a distance.
"We routinely use the three hardy reflectors placed on the moon by the Apollo 11, 14 and 15 missions," said Murphy, "and occasionally the Soviet-landed Lunokhod 2 reflector--though it does not work well enough to use when illuminated by sunlight. But we yearned to find Lunokhod 1."
Three reflectors are required to lock down the orientation of the moon. A fourth adds information about tidal distortion of the moon, and a fifth enhances that information.
"Lunokhod 1, by virtue of its location, would provide the best leverage for understanding the liquid lunar core, and for producing an accurate estimate of the position of the center of the moon--which is of paramount importance in mapping out the orbit and putting Einstein's gravity to a test," said Murphy.
Murphy said his team had occasionally looked for the Lunokhod 1 reflector over the last two years, but faced tall odds against finding it until recently. The breakthrough came last month when the high-resolution camera on NASA's Lunar Reconnaissance Orbiter, or LRO, obtained images of the landing site. The camera team, led by Mark Robinson at Arizona State University, identified the rover as a sunlit speck on the image--miles from where Murphy and his team had been searching. (see:http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20100318.html ) But until now the existence of the reflector or its precise location was unknown.
"It turns out we were searching around a position miles from the rover," said Murphy. "We could only search one football-field-sized region at a time. The recent images from LRO, together with laser altimetry of the surface, provided coordinates within 100 meters, and then we were in business and only had to wait for time on the telescope in good observing conditions."
On April 22, his team sent pulses of laser light from the 3.5 meter telescope at the Apache Point Observatory in New Mexico, zeroing in on the target coordinates provided by the LRO images. Murphy, together with Russet McMillan of the Apache Point Observatory in Sunspot, NM, and UCSD physics graduate student Eric Michelsen found the long lost Lunokhod 1 reflector and pinpointed its distance from earth to within one centimeter. They then made a second observation less than 30 minutes later that allowed the team to triangulate the reflector's latitude and longitude on the moon, in other words its exact spot on the moon, to within 10 meters--"not bad for a half-hour's work," said Murphy. In the coming months, he estimates it will be possible to establish the reflector's coordinates to better than one-centimeter precision.
The return signal from the reflector was measured by Murphy's team as a collection of individual particles, or photons, of laser light.
"We quickly verified the signal to be real and found it to be surprisingly bright: at least five times brighter than the other Soviet reflector, on the Lunokhod 2 rover, to which we routinely send laser pulses," Murphy said. "The best signal we've seen from Lunokhod 2 in several years of effort is 750 return photons, but we got about 2,000 photons from Lunokhod 1 on our first try. It's got a lot to say after almost 40 years of silence."
The discovery of the Soviet reflector came as a surprise, because scientists had actively searched for it for nearly four decades without success. Many scientists had speculated that the Lunokhod 1 rover might have fallen into a crater or parked badly, with its reflector not facing the earth, which would have prevented it from being located by laser pulses.
"Not only now do we know that Lunokhod 1 is there, we also know that it is parked perfectly so that its reflector faces earth," said Murphy. "In fact, the signal is so surprisingly strong that the rover could not be in anything but a level parking spot with its last commanded roll on the lunar surface deliberately oriented toward the earth."
Murphy and his colleagues found in a study they published this month that lunar dust may be obscuring the reflectors on the moon. see: Moon Dust His team found that the laser light they bounce off reflectors on the moon is fainter than expected and dims even more whenever the moon is full.
"Near full moon, the strength of the returning light decreases by a factor of ten," he adds. "We need to understand what is causing this if we are contemplating putting additional scientific equipment on the moon. Finding the Lunokhod 1 reflector will add important clues to this study."
Murphy's project, dubbed APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation), is supported by the National Science Foundation and NASA, and includes scientists at the University of Washington, Harvard University, the Massachusetts Institute of Technology, Humboldt State University and the Apache Point Observatory.
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Founded in 1652, the Leopoldina is the "world's oldest academy involved in the natural sciences that has been permanently in existence." The number of members is limited to 1,000 total in 28 subject sections. Wolynes will belong to the subsection of Theoretical Physics.
Wolynes has developed the leading theory of how proteins fold, which has led to computer algorithms that allow one to predict the three-dimensional structure of a protein from its amino acid sequence. His work on the theory of energy landscapes has also impacted condensed matter physics, notably illuminating the nature of glasses and liquids.
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Prof. Ruderman is a distinguished theoretical astrophysicist who pioneered the science of neutron stars and pulsars; he has also contributed to elementary particle physics and to understanding of the earth's atmosphere. He has worked intensively on problems associated with collapsed objects in astrophysics, especially neutron stars. Recent work has focused on how neutron stars convert so much of their initial spin-energy into beams of high energy radiation. Prof. Ruderman received his PhD. from Cal Tech in 1951. He was elected to the National Academy of Sciences in 1972 and to the American Academy of Arts & Sciences in 1974.
Talk Abstract: Forty years after the discovery of the first pulsars important questions still remain about the structure and dynamics of these strongly magnetized, rapidly spinning neutron stars. Expected properties and observable phenomena will be presented for a "standard model" of them. It assumes a near solar mass core of superfluid neutrons, superconducting protons and very relativistic degenerate electrons, all enclosed by a thin solid metal crust. The model describes a distinctive evolution of neutron star magnetic fields during prolonged stellar spin-down (or spin-up) and, associated with it, two families of sudden jumps in the star's spin-down torque and spin-rate. Model expectations are consistent with observations. However, understanding other kinds of observations, commonly interpreted as evidence for very long period neutron star precession, and also presumed thermal x-ray emission from the stellar surface, raise problems for this standard model. Other interpretations of these observations will be suggested.
The Physics Department Memorial Lecture series was organized in memory of Prof. Norman M. Kroll, a pioneer in quantum physics and a founding member of the UCSD Physics department. During his forty year career at UCSD, Prof. Kroll made brilliant contributions to research in quantum electrodynamics, atomic physics, particle physics, free electron lasers and subatomic particle accelerators.
This lecture is generously supported by financial contributions from the Kroll family and friends, the Department of Physics, and the Institute of Physics & Applied Physical Sciences. The event is free and open to the public.
Last modified: 04/10/2007
The Institute of Low Temperature and Structure Research was established in 1966 and is named after Professor W. Trzebiatowski, who played a key role in the establishment of the Institute, served as its first Director, and later became the President of the Polish Academy of Sciences. Professor Trzebiatowski is known for the discovery in 1952 of ferromagnetism in uranium hydride UH3. This came as a great surprise since metallic uranium was known to be completely nonmagnetic and, at that time, ferromagnetic ordering had only been found in metals and alloys of the iron group, as well as in gadolinium, one of the rare earth metals.
Professor Maple has collaborated with researchers at the W. Trzebiatowski Institute since 1976 and coauthored eight joint papers. His most recent projects with the Institute concern the nonmagnetic Kondo effect in actinides and the physics of strongly correlated electron behavior in lanthanide and actinide filled skutterudite arsenide compounds.See full article here: http://physicalsciences.ucsd.edu/news_events/news_archives/2007_Archive/07.26.02.maple.poland.htm
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George Feher, a research professor at UCSD, will share the $100,000 prize with Ada Yonath of Israel's Weizmann Institute of Science" for ingenious structural discoveries of the ribosomal machinery of peptide-bond formation and the light-driven primary processes in photosynthesis." The award will be presented to the two scientists by the President of Israel at a formal ceremony at the Knesset, or parliament, in Jerusalem, on May 13.
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From the Article:
"The mediators of the weak interaction, the massive W and Z gauge bosons, are readily produced at the Tevatron and have been studied extensively by the CDF and DZero experiments. But producing pairs of heavy gauge bosons is far more rare. While one W boson is produced in every 3 million Tevatron collisions, and one Z boson in every 10 million, WZ pairs are produced only once per 20 billion events. Facing these odds, it is no wonder that WZ has never been observed--that is, until now. The elusive WZ has finally been netted at CDF. We found it by searching for WZ production in its most easily observable signature, where 3 charged leptons are produced along with missing energy from a neutrino. CDF observed 16 of these signatures, and about 13 of them are expected to be WZ events. If WZ production was not actually happening in the Tevatron, the probability of getting this result would only be 2 in a billion. This indicates that our results are significant; and we have, in fact, observed WZ production. Finding the WZ pair is important because it teaches us about how gauge bosons interact with each other, and it confirms Standard Model predictions. Observing such a rare process at CDF also represents an important experimental milestone in our pursuit of the Higgs particle and new physics at the Tevatron. We look forward to a bright future as we continue to collect data from Run II!"
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A team led by Physicist Massimiliano Di Ventra at the University of California, San Diego has shown the feasibility of a fast, inexpensive technique to sequence DNA as it passes through tiny pores. The advance brings personalized, genome-based medicine closer to reality.Full Article
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David R. Smith, a physicist formerly at the University of California, San Diego, has been awarded the European Union's Descartes Prize for Excellence in Scientific Research for developing at UCSD a new class of composite materials with unusual physical properties that scientists theorized might be possible, but had never before been able to produce in nature.
Complete story at http://ucsdnews.ucsd.edu/newsrel/science/mcdescartes.asp
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Professors Margaret Burbidge and Sally Ride were named to Smithsonian Magazine's "35 Innovators of Our Time" in the November 2005 issue. The article marks the 35th anniversary of the magazine by "...revisiting scientists, artists and scholars who've enriched the magazine and our lives."Article Summary
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Kenneth Burch, UCSD Physics student, has been chosen for a GMAG Outstanding Dissertation in Magnetism Award for 2006. The award consists of a cash prize, certificate and invited talk in an appropriate session at the 2006 March meeting in Baltimore.
More information can be found at: http://www.aps.org/units/gmag/
Last modified: 10/18/2005
Each year the Physics Department and its faculty host a number of undergraduates in its Research Experience for Undergraduates program. The students are selected from approximately 450 applicants. The program is funded by an NSF Grant (with Dmitri Basov and Hans Paar co-PIs).
Besides working hard in the labs and attending seminars and workshops, the students also take the Physics of Sailing course. The course consists of a classroom lecture and a laboratory component that takes place on the San Diego Bay in a 42' Catalina sailboat. The photograph shows the students, Charmaine Samahin and her husband Randy, and the instructor (Hans Paar).
Last modified: 09/14/2005
The Department of Physics is pleased to announce the winners of this year's Ma and Malmberg awards, our department's awards to the top undergraduate physics majors.
This years Ma award goes to Kyle Armour. Kyle is graduating with a GPA of ... ok, university regulations prohibit me from telling you. Let's just say its within epsilon of 4.0, where epsilon is a small number. Also, he garnered 10 A+ grades in physics courses! He has already done significant research in particle physics in Jim Branson's group, and is heading to graduate school at U. Washington where he intends to continue working in particle theory.
The Malmberg award goes to Tyson Kim. Tyson has distinguished himself in our biophysics program, and is the lead author on an applied physics letter (along with David Kleinfeld and Alex Groisman) that is soon to appear. Tyson has not yet decided between biophysics/MD-PhD programs at Harvard, U. San Francisco and UCSD. (We hope he chooses to stay in San Diego!)
Congratulations and best wishes to Tyson and Kyle!
Attribution: Dan Dubin - Vice Chair for Undergraduate Education
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Both programs recognize and support outstanding graduate students in the relevant science, technology, and mathematics disciplines. Fellows are expected to become experts who can contribute significantly to research, teaching, and innovations in science and engineering. The CSGF recipients receive payments of all tuition and required fees for up to 4 years of study, a yearly stipend, matching funds for a computer workstation, a yearly academic allowance, and yearly conferences. Among the requirements and benefits are a plan of study which includes course work in Applied Mathematics, Science and Computer Science, and a practicum at a national DOE laboratory. NSF fellows receive tuition, fees, a yearly stipend for up to 3 years of study, with no requirement beyond annual reporting.
Last modified: 05/04/2005
Five faculty members at the University of California, San Diego have been named fellows of the American Academy of Arts and Sciences, the academy has announced. The five are among 196 new fellows and 17 new foreign honorary members in the academy's 225th class.
The new fellows from UCSD are Jack Keil Wolf, professor of electrical and computer engineering at the Jacobs School of Engineering; Ajit P. Varki, professor of medicine and cellular and molecular medicine; Linda Preiss Rothschild and M. Salah Baouendi, professors of mathematics; and Michael L. Norman, professor of physics.
They join 76 current AAAS fellows on the UCSD faculty.
It gives me great pleasure to welcome these outstanding leaders in their fields, said Academy President Patricia Meyer Spacks. Fellows are selected through a highly competitive process that recognizes individuals who have made preeminent contributions to their disciplines and to society at large.
Fellows and members are nominated and elected by current members, comprising scholars and practitioners from mathematics, physics, biological sciences, humanities and the arts, public affairs and business. The academy will welcome this years fellows and honorary members at its annual induction ceremony on October 8 in Cambridge, Mass.
Last modified: 04/28/2005
Prof. David Gross, recipient of the 2004 Nobel Prize in Physics will speak on The Future of Physics in the inaugural lecture of the Physics Department Memorial Lecture series. This event will be held at 4:00 pm on Thursday, April 21 at the Liebow Auditorium in Basic Science Building.
This annual lecture series organized in the memory of Prof. Norman M. Kroll, a brilliant pioneer in Quantum physics and a founding member of the UCSD Physics department. During his forty year career at the UCSD, Professor Kroll made brilliant contributions to research in quantum electrodynamics, atomic physics, particle physics, free electron lasers and subatomic particle accelerators. He served as the chair of the physics department from 1963 to 1965 and from 1983 to 1988. A short description of Prof. Kroll's life is at http://ucsdnews.ucsd.edu/newsrel/science/mckroll.asp
This lecture series is generously supported by the financial contributions from the friends and family of Prof. Norman Kroll. The event is free and open to the public. Parking is $3.
David J. Gross is Director of the Kavli Institute for Theoretical Physics (KITP) and the first incumbent of the Frederick W. Gluck Chair in Theoretical Physics at the University of California at Santa Barbara. Professor Gross was awarded the 2004 Nobel Prize in Physics for solving, in 1973, the last great remaining problem of what has since come to be called the Standard Model of the quantum mechanical picture of reality and discovered along with his co-recipients how the nucleus of atoms works. This lecture is also a part of the worldwide celebration of 2005 as the year of physics.