Rotating light provides indirect look into the nucleus

Results reported in TheJournal of Chemical Physicsintroduce an alternative path to this information, by using light to observe nuclei indirectly via the orbitingelectrons.

"We are not looking at a way to replace the conventional technique but there are a number of applications in which optical detection could provide complementary information,"says author Carlos Meriles of the City University of New York.

The new technique is based on Optical Faraday Rotation (OFR), a phenomenon in which the plane of linearly polarized light rotates upon crossing a material immersed in amagnetic field. When nuclei are sufficiently polarized, the extra magnetic field they produce is 'felt' by the electrons in the sample thus leading to Faraday rotation of their own. Because the interaction between electrons and nuclei depends on the local molecular structure, OFR-detected NMR spectroscopy provides complementary information to conventional detection.

Another interesting facet of the technique is that, unlike conventional NMR, the signal response is proportional to the sample length, but not its volume."Although we have not yet demonstrated it, our calculations show that we could magnify the signal by creating a very long optical path in a short, thin tube,"Meriles says. This signal magnification would use mirrors at both ends of a channel in a microfluidics device to reflectlaser lightrepeatedly through the sample, increasing the signal amplitude with each pass.

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Tempest in a teapot: Scientists describe swirling natural phenomena

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The earth's atmosphere and its molten outer core have one thing in common: Both contain powerful, swirling vortices. While in the atmosphere these vortices include cyclones and hurricanes, in the outer core they are essential for the formation of the earth's magnetic field. These phenomena in earth's interior and its atmosphere are both governed by the same natural mechanisms, according to experimental physicists at UC Santa Barbara working with a computation team in the Netherlands.

Using laboratory cylinders from 4 to 40 inches high, the team studied these underlying physical processes. The results are published in the journalPhysical Review Letters.

"To study the atmosphere would be too complicated for our purposes,"said Guenter Ahlers, senior author and professor of physics at UCSB."Physicists like to take one ingredient of a complicated situation and study it in a quantitative way under ideal conditions."The research team, including first author Stephan Weiss, a postdoctoral fellow at UCSB, filled the laboratory cylinders with water, and heated the water from below and cooled it from above.

Due to that temperature difference, the warm fluid at the bottom plate rose, while the cold fluid at the top sank–– a phenomenon known as convection. In addition, the whole cylinder was rotated around its own axis; this had a strong influence on how the water flowed inside the cylinder.Rotation, such as the earth's rotation, is a key factor in the development of vortices. The temperature difference between the top and the bottom of the cylinder is another causal factor since it drives the flow in the first place. Finally, the relation of the diameter of the cylinder to the height is also significant.

Ahlers and his team discovered a new unexpected phenomenon that was not known before for turbulent flows like this. When spinning the container slowly enough, no vortices occurred at first. But, at a certain critical rotation speed, the flow structure changed. Vortices then occurred inside the flow and the warm fluid was transported faster from the bottom to the top than at lower rotation rates."It is remarkable that this point exists,"Ahlers said."You must rotate at a certain speed to get to this critical point."

The rotation rate at which the first vortices appeared depended on the relation between the diameter and the height of the cylinder. For wide cylinders that are not very high, this transition appeared at relatively low rotation rates, while for narrow but high cylinders, the cylinder had to rotate relatively fast in order to produce vortices. Further, it was found that vortices do not exist very close to the sidewall of the cylinder. Instead they always stayed a certain distance away from it. That characteristic distance is called the"healing length."

"You can't go from nothing to something quickly,"said Ahlers."The change must occur over a characteristic length. We found that when you slow down to a smaller rotation rate, the healing length increases."

The authors showed that their experimental findings are in keeping with a theoretical model similar to the one first developed by Vitaly Lazarevich Ginzburg and Lev Landau in the theory of superconductivity. That same model is also applicable to other areas of physics such as pattern formation and critical phenomena. The model explains that the very existence of the transition from the state without vortices to the one with them is due to the presence of the sidewalls of the container. For a sample so wide (relative to its height) that the walls become unimportant, the vortices would start to form even for very slow rotation. The model makes it possible to describe the experimental discoveries, reported in the article, in precise mathematical language.

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When bird meets machine, bioinspired flight

IOP Publishing'sBioinspiration&Biomimeticspublishes a special edition today, Wednesday 24 November 2010, entitled Bioinspired Flight, comprising of nine journal papers which display the wealth of knowledge being accrued by researchers in the field.

Nature outclasses man's best efforts at robotic flight, as even the geometry and descent dynamics of a simple maple seed lead one research team from the University of Maryland, led by Dr. Evan Ulrich, to show that micro helicopters could be much simplified by imitating the maple seed's wing pitch for controlled hovering and, surprisingly, forward flight.

The issue, starting with two papers on tactics employed for controlled descent by geckoes and flying snakes, is accompanied by a selection of films - four of which areavailable on YouTube.

The first film, from a team led by graduate student Ardian Jusufi from UC Berkeley, shows how researchers have studied the gecko's trick of employing its tail to right and turn itself mid-air, helping it always fall on its feet, and have now made a robot model gecko which can employ the same grace on descent.

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Gecko fall. How mid-air righting gecko inspires robot gecko that can right itself during free fall. Credits: Ardian Jusufi and co-workers

A second film from Professor Jake Socha and his team at Virginia Tech displays themystifying skills of flying snakes, which direct their flight mid-air by slithering.

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Compilation of high-speed video's of flying snakes Chrysopelea paradisi. Credits: Courtesy of National Geographic Television; compiled by Jake Socha

Moving on from tactical descent, the special edition also covers humming birds' perfect hover; birds' intuitive exploitation of thermal updrafts; the mechanical motion of insects' wings, and seagulls' magnificent sense of flight environment, which allows them incredible angles of attack and increased control in crosswinds.

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Thorax design of the Harvard robot fly for powering and controlling its wingbeat. Credit: Benjamin Finio and Robert Wood

As the special edition's editor, Professor David Lentink from Wageningen University, writes in an accompanying editorial,"Because biologists and engineers are typically trained quite differently, there is a gap between the understanding of naturalflightof biologists and the engineer's expertise in designing vehicles that function well. In the middle however is a few pioneering engineers who are able to bridge both fields."

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Extreme lasers at work

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The researchers focused on the behavior of argon atoms, which is easy to handle and well-characterized, under illumination bylaser lightabout one hundred trillion times brighter than the noonday sun, and containing about seven times more energy per photon than the bluest light visible to the human eye. Previous work by other researchers showed that such intense, energetic light removes multiple electrons from target atoms, resulting in highly chargedions. While the mechanism of the ionization process was partially understood from observations of the yields and momenta of these ions, important details were missing.

Hikosaka, Nagasono and colleagues chose to observe the electrons emitted during the ionization process (Fig. 1), instead of the ions themselves. Not only do theseelectronscarry unique information about the ionization process, but they can be measured after each ultra-short laser pulse. Since the laser spectrum and power are constantly fluctuating, the fine details of the ionization process are averaged or‘smeared’ during a continuous measurement. A shot-by-shot measurement, however, can account for laser fluctuations.

The experiment showed that the dominant ionization pathway of the argon atoms has two steps: first, a single laser photon is absorbed to create singly-ionized argon, and then two more photons are absorbed to create doubly-ionized argon. The researchers also found that the intermediate argon ion states had energy levels, or energy resonances, that induced this pathway.

The research leverages the recent development of free electron lasers, which are uniquely capable of producing very bright, energetic and short pulses of radiation. The work also illustrates that energy resonances are key to multi-photon, multiple ionization processes, a finding that is likely to be relevant to a variety of research programs. Hikosaka says that the research team will continue to focus on the basic science, as well as applications:“Our goal is to develop and leverage a deep understanding of the mechanism and dynamics of non-linear processes in order to manipulate or control these processes and their final products.”

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Large Hadron Collider experiments bring new insight into primordial universe

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This result is reported in a paper from the ATLAS collaboration accepted for publication yesterday in the scientific journalPhysical Review Letters. A CMS paper will follow shortly, and results from all of the experiments will be presented at a seminar on Thursday 2 December at CERN. Data taking with ions continues to 6 December.

“It is impressive how fast the experiments have arrived at these results, which deal with very complex physics,” said CERN’s Research Director Sergio Bertolucci.“The experiments are competing with each other to publish first, but then working together to assemble the full picture and cross check their results. It’s a beautiful example of how competition and collaboration is a key feature of this field of research.”

One of the primary goals of the lead-ion programme at CERN is to create matter as it would have been at the birth of the Universe. Back then, the ordinary nuclear matter of which we and the visible universe are made could not have existed: conditions would have been too hot and turbulent for quarks to be bound up by gluons into protons and neutrons, the building blocks of the elements. Instead, these elementary particles would have roamed freely in a sort of quark gluon plasma. Showing beyond doubt that we can produce and study quark gluon plasma will bring important insights into the evolution of the early Universe, and the nature of the strong force that binds quarks and gluons together into protons, neutrons and ultimately all the nuclei of the periodic table of the elements.

When lead-ions collide in the LHC, they can concentrate enough energy in a tiny volume to produce tiny droplets of this primordial state of matter, which signal their presence by a wide range of measureable signals. The ALICE papers point to a large increase in the number of particles produced in the collisions compared to previous experiments, and confirm that the much hotter plasma produced at the LHC behaves as a very low viscosity liquid (a perfect fluid), in keeping with earlier observations from Brookhaven’s RHIC collider. Taken together, these results have already ruled out some theories about how the primordial Universe behaved.

“With nuclear collisions, the LHC has become a fantastic 'Big Bang' machine,” said ALICE spokesperson Jürgen Schukraft.“In some respects, the quark-gluon matter looks familiar, still the ideal liquid seen at RHIC, but we’re also starting to see glimpses of something new.”

The ATLAS and CMS experiments play to the strength of their detectors, which both have very powerful and hermetic energy measuring capability. This allows them to measure jets of particles that emerge from collisions. Jets are formed as the basic constituents of nuclear matter, quarks and gluons, fly away from the collision point. In proton collisions, jets usually appear in pairs, emerging back to back. However, in heavy ion collisions the jets interact in the tumultuous conditions of the hot dense medium. This leads to a very characteristic signal, known as jet quenching, in which the energy of the jets can be severely degraded, signalling interactions with the medium more intense than ever seen before. Jet quenching is a powerful tool for studying the behaviour of the plasma in detail.

“ATLAS is the first experiment to report direct observation of jet quenching,” said ATLAS Spokesperson Fabiola Gianotti.“The excellent capabilities of ATLAS to determine jet energies enabled us to observe a striking imbalance in energies of pairs of jets, where one jet is almost completely absorbed by the medium. It’s a very exciting result of which the Collaboration is proud, obtained in a very short time thanks in particular to the dedication and enthusiasm of young scientists.”

“It is truly amazing to be looking, albeit on a microscopic scale, at the conditions and state of matter that existed at the dawn of time,” said CMS Spokesperson Guido Tonelli.“Since the very first days of lead-ion collisions the quenching of jets appeared in our data while other striking features, like the observation of Z particles, never seen before in heavy-ion collisions, are under investigation. The challenge is now to put together all possible studies that could lead us to a much better understanding of the properties of this new, extraordinary state of matter"

The ATLAS and CMS measurements herald a new era in the use of jets to probe the quark gluon plasma. Future jet quenching and other measurements from the three LHC experiments will provide powerful insight into the properties of the primordial plasma and the interactions among its quarks and gluons.

With data taking continuing for over one more week, and the LHC already having delivered the programmed amount of data for 2010, the heavy-ion community at the LHC is looking forward to further analysing their data, which will greatly contribute to the emergence of a more complete model ofquark gluon plasma, and consequently the very early Universe.

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Optimizing large wind farms

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Charles Meneveau, who studies fluid dynamics at Johns Hopkins University, and his collaborator Johan Meyers from Leuven University in Belgium, have developed a model to calculate the optimal spacing of turbines for the very largewind farmsof the future. They will present their work today at the American Physical Society Division ofFluid Dynamics(DFD) meeting in Long Beach, CA.

"The optimal spacing between individual wind turbines is actually a little farther apart than what people use these days,"said Meneveau.

The blades of a turbine distort wind, creating eddies of turbulence that can affect otherwind turbinesfarther downwind. Most previous studies have used computer models to calculate the wake effect of one individual turbine on another.

Starting with large-scalecomputer simulationsand small-scale experiments in awind tunnel, Meneveau's model considers the cumulative effects of hundreds or thousands of turbines interacting with the atmosphere.

"There's relatively little knowledge about what happens when you put lots of these together,"said Meneveau.

The energy a large wind farm can produce, he and his coworkers discovered, depends less on horizontal winds and more on entraining strong winds from higher in the atmosphere. A 100-meter turbine in a large wind farm must harness energy drawn from the atmospheric boundary layer thousands of feet up.

In the right configuration, lots of turbines essentially change the roughness of the land -- much in the same way that trees do -- and create turbulence. Turbulence, in this case, isn't a bad thing. It mixes the air and helps to pull downkinetic energyfrom above.

Using as example 5 megawatt-rated machines and some reasonable economic figures, Meneveau calculates that the optimal spacing between turbines should be about 15 rotor diameters instead of the currently prevalent figure of 7 rotor diameters.

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When Belgium sneezes, the world catches a cold

Using data from Bureau Van Dijk - the company information and business intelligence provider - to assess the reach and size of different countries' economies, and applying the Susceptible-Infected-Recovered (SIR) model, physicists from universities in Greece, Switzerland and Israel have identified the twelve countries with greatest power to spread a crisis globally.

The research published today, Thursday 25 November 2010, inNew Journal of Physics(co-owned by the Institute of Physics and German Physical Society), groups Belgium and Luxembourg alongside more obviously impactful economies such as the USA in the top twelve.

Using a statistical physics approach, the researchers from the Universities of Thessaloniki, Lausanne and Bar-Ilan used two different databases to model the effect of hypothetical economic crashes in different countries. The use of two different databases aided the avoidance of bias but threw up very similar results.

The data used allowed the physicists to identify links between the different countries, by mapping theglobal economyto acomplex network, and gauge the likelihood of one failed economy having an effect on another.

One network was created using data on the 4000 world corporations with highest turnover and a second using data onimportandexportrelations between 82 countries.

The SIR model, successfully used previously to model the spreading of disease epidemics, is applied to these two networks taking into consideration the strength of links between countries, the size of the crash, and the economic strength of the country in potential danger.

When put to the test with the corporate data, the USA, the UK, France, Germany, Netherlands, Japan, Sweden, Italy, Switzerland, Spain, Belgium and Luxembourg were part of an inner core of countries that would individually cause the most economic damage globally if their economies were to fail.

Using the import/export data, China, Russia, Japan, Spain, UK, Netherlands, Italy, Germany, Belgium, Luxembourg, USA, and France formed the inner core, with the researchers explaining that the difference– particularly the addition of China to this second list– is due to a large fraction of Chinese trade volume coming from subsidiaries of western corporations based in China.

The researchers write,"Surprisingly, not all 12 countries have the largest total weights or the largest GDP. Nevertheless, our results suggest that they do play an important role in the global economic network. This is explained by the fact that these smallercountriesdo not support only their local economy, but they are a haven for foreign investments."

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The physics of coffee rings

You might thinkcoffeering formation, first described quantitatively by Deegan et al in a heavily cited article, is the most widely and ritualistically performed experiment in the world, given the prevalence of caffeine in cultures. But most of us lack thescanning electron microscopeand mathematical models to evaluate our stain data properly, or reach meaningful conclusions beyond"Use a coaster."

Now Shreyas Mandre of Brown University, Ning Wu from Colorado School of Mines and L. Mahadevan and Joanna Aizenberg from Harvard University have devised apredictive modelthat combines laboratory studies of microscopic glass particles in solution with mathematical theories to predict the existence, thickness and length of the banded ring patterns that formed.

Their results, presented today at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, CA, suggest the patterned deposition of particles can be controlled by altering physical parameters such as evaporation andsurface tension-- and perhaps one day manipulated to create small-particle tools.

"Controlling the ring deposition process would be useful for creating such things as new microphysics tools operating at a scale where pliers or other traditional tools for moving particles cannot operate,"notes Mandre.

The team found that during ring deposition, a particle layer of uniform thickness is deposited if the concentration is above a certain threshold. Below that threshold the deposits form non-uniform bands. The threshold is formed because evaporation at the solid-liquid interface of the rim occurs faster than a replenishing flow of water from the center of the droplet can replace the evaporating rim fluid. This leaves the particles on the rim high, dry -- and deposited.

Exploiting this competition between evaporation and replenishment is the key to controlling the process as a microtool, says Mandre. Potential applications include printing, making industrial coatings, fabricating electronics, and designing new medicines.

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Scientists glimpse universe before the Big Bang

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The CMB is the radiation that exists everywhere in the universe, thought to be left over from when the universe was only 300,000 years old. In the early 1990s, scientists discovered that the CMB temperature has anisotropies, meaning that the temperature fluctuates at the level of about 1 part in 100,000. These fluctuations provide one of the strongest pieces of observational evidence for the Big Bang theory, since the tiny fluctuations are thought to have grown into the large-scale structures we see today. Importantly, these fluctuations are considered to be random due to the period of inflation that is thought to have occurred in the fraction of a second after the Big Bang, which made the radiation nearly uniform.

However, Penrose and Gurzadyan have now discovered concentric circles within the CMB in which the temperature variation is much lower than expected, implying that CMB anisotropies are not completely random. The scientists think that these circles stem from the results of collisions between supermassive black holes that released huge, mostly isotropic bursts of energy. The bursts have much more energy than the normal local variations in temperature. The strange part is that the scientists calculated that some of the larger of these nearly isotropic circles must have occurred before the time of the Big Bang.

The discovery doesn't suggest that there wasn't a Big Bang - rather, it supports the idea that there could have been many of them. The scientists explain that the CMB circles support the possibility that we live in a cyclic universe, in which the end of one“aeon” or universe triggers anotherBig Bangthat starts another aeon, and the process repeats indefinitely. The black hole encounters that caused the circles likely occurred within the later stages of the aeon right before ours, according to the scientists.

In the past, Penrose has investigated cyclic cosmology models because he has noticed another shortcoming of the much more widely accepted inflationary theory: it cannot explain why there was such low entropy at the beginning of the universe. The low entropy state (or high degree of order) was essential for making complex matter possible. The cyclic cosmology idea is that, when a universe expands to its full extent, black holes will evaporate and all the information they contain will somehow vanish, removing entropy from theuniverse. At this point, a new aeon with a low entropy state will begin.

Because of the great significance of these little circles, the scientists will do further work to confirm their existence and see which models can best explain them. Already, Penrose and Gurzadyan used data from two experiments - WMAP and BOOMERanG98 - to detect the circles and eliminate the possibility of an instrumental cause for the effects. But even if the circles really do stem from sources in a pre-Big Bang era, cyclic cosmology may not offer the best explanation for them. Among its challenges, cyclic cosmology still needs to explain the vast shift of scale between aeons, as well as why it requires all particles to lose their mass at some point in the future.

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Enhancing the efficiency of wind turbines

New ideas for enhancing the efficiency ofwind turbinesare being presented this week at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, CA.

One issue confronting the efficiency of wind energy is the wind itself -- specifically, its changeability. The aerodynamic performance of a wind turbine is best under steady wind flow, and the efficiency of the blades degrades when exposed to conditions such as wind gusts, turbulent flow, upstream turbine wakes, and wind shear.

Now a new type of air-flow technology may soon increase the efficiency of large wind turbines under many different wind conditions.

Syracuse University researchers Guannan Wang, Basman El Hadidi, Jakub Walczak, Mark Glauser and Hiroshi Higuchi are testing new intelligent-systems-based active flow control methods with support from the U.S. Department of Energy through the University of Minnesota Wind Energy Consortium. The approach estimates the flow conditions over the blade surfaces from surface measurements and then feeds this information to an intelligent controller to implement real-time actuation on the blades to control the airflow and increase the overall efficiency of the wind turbine system. The work may also reduce excessive noise and vibration due to flow separation.

Initial simulation results suggest that flow control applied on the outboard side of the blade beyond the half radius could significantly enlarge the overall operational range of the wind turbine with the same rated power output or considerably increase the rated output power for the same level of operational range. The team is also investigating a characteristic airfoil in a new anechoic wind tunnel facility at Syracuse University to determine the airfoil lift and drag characteristics with appropriate flow control while exposed to large-scale flow unsteadiness. In addition, the effects of flow control on the noise spectrum of the wind turbine will be also assessed and measured in the anechoic chamber.

Another problem with wind energy is drag, the resistance felt by the turbine blades as they beat the air. Scientists at the University of Minnesota have been looking at the drag-reduction effect of placing tiny grooves on turbine blades. The grooves are in the form of triangular riblets scored into a coating on the blade surface. They are so shallow (between 40 and 225 microns) that they can't be seen by the human eye -- leaving the blades looking perfectly smooth.

Using wind-tunnel tests of 2.5 megawatt turbine airfoil surfaces (becoming one of the popular industry standards) and computer simulations, they are looking at the efficacies of various groove geometries and angles of attack (how the blades are positioned relative to the air stream).

Riblets like these have been used before, in the sails on sailboats taking part in the last America's Cup regatta and on the Airbus airliner, where they produced a drag reduction of about 6 percent. The design of wind turbine blades was, at first, closely analogous to that of airplane wings. But owing to different engineering concerns, such asturbine bladeshaving a much thicker cross section close to the hub and wind turbines having to cope with peculiar turbulence near the ground, drag reduction won't be quite the same for wind turbines.

University of Minnesota researchers Roger Arndt, Leonardo P. Chamorro and Fotis Sotiropoulos believe that riblets will increase wind turbine efficiency by about 3 percent.

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Pitt physicist wins 2011 Einstein Prize for lifetime unraveling, reshaping general relativity theory

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To recognize Newman's lifetime of work at the forefront of general relativity, the American Physical Society has awarded him the 2011 Einstein Prize for his part in devising the renowned Newman-Penrose formalism—an extension of Einstein'stheory of general relativity—as well as for composing a variety of solutions to Einstein's equations, particularly the Kerr-Newman black hole. The prize also commends Newman's ongoing work to explain the significance of far-flung light energy.

Newman joins a select roster of physicists who have received the biennial $10,000 prize since its 2003 inception, including noted Einstein collaborators John A. Wheeler of Princeton University, and Syracuse University (SU) physicist Peter Bergmann, Newman's mentor when he pursued his PhD degree at SU, which he earned in 1956.

In 1962, six years after Newman joined Pitt's Department of Physics andAstronomy, he and University of Oxford professor Roger Penrose developed the Newman-Penrose formalism, one of the most-cited sets of equations in relativity. In short, the formalism is an alternative method for describing Einstein's equations that replaces Einstein's own version, Newman explained.

The significance of the Newman-Penrose formalism is that it allows for special conditions to be imposed before one even attempts to solve an equation—conditions for which Einstein's original theory does not allow. Instead of using the four standard space-time coordinates, the Newman-Penrose equations use four different vectors to describe the geometric constructions of the theory that arise from massive objects in motion.

"We knew we had something good,"Newman recalled."We performed the Goldberg-Sachs theorem, which originally required a great deal of effort, at the drop of a hat. We knew it was a powerful technique then. I've used it virtually every day since the original paper, and when I lecture now to a technical audience, I assume that most people are familiar with it."

Three years later, in 1965, Newman inadvertently took part in constructing another important solution, the Kerr-Newman black hole.

As a hotshot young physicist, Newman stated in the Journal of Mathematical Physics that a class of solutions to Einstein's equations did not exist. In all of Newman's mathematics, however, there was one lowly plus-sign that should have been a minus. Roy Kerr, then a professor of physics at the University of Texas at Austin, discovered the error and found that the class of solutions did in fact exist. But it turned out that the now-correct equation easily allowed Newman to solve the Einstein-Maxwell equations for describing rotating, electrically charged black holes and their surrounding region. The Kerr-Newman stands as one of four solutions of Einstein's equations describing black holes.

In his more recent work, Newman investigates null foliation, or the patterns light rays form as they fill space-time. In 1980, Newman first identified a property known as H-space that occurs at the outer reaches of light's range when light rays no longer have physical contact—like the fingertips of a splayed hand. Newman is currently working on possible applications of H-space theory for explaining observable phenomena. {Also known as Heaven theory after a good-natured play on the"H"coined fittingly at a lecture Newman gave in Israel, the work gained notoriety after antipork-spending crusader Sen. William Proxmire (D-Wisconsin) took the name seriously and decried Newman's National Science Foundation grant application for a project to find"Heaven."Newman got the grant anyway.}

Newman's outpouring of research and many collaborations characterize the spirit of the golden age of general relativity that fell approximately between 1955 and 1975, he said.

Contemporary audiences may struggle to imagine a time when Einstein's theories were not highly regarded. Yet, when Newman entered Syracuse in 1951 as a graduate student in Bergmann's lab, general relativity was out of fashion, having been superseded since the mid-1920s by quantum theory. There were rumblings, however, partly attributable to Einstein's dismissal of major quantum principles, that quantum theory had serious shortcomings. Bergmann—who collaborated with Einstein on his unified field theory work—and his group began to revisit general relativity along with research groups at Princeton, in the United Kingdom, and in Eastern Europe.

"When I joined Bergmann's group, general relativity was in the doldrums. No one worked on it and Einstein, though honored as a great thinker, was considered to be passé, a fogey,"Newman said.

"But groups in a handful of institutions around the world began accepting Einstein's theory of relativity as relevant to thephysicsof the day. There was an open exchange of ideas among the different groups that stimulated a rapid revitalization of relativity,"Newman continued."Soon, a deeper understanding of the Einstein equations was developed and predictions of the existence and properties of gravitational waves were made. The theory of relativity became mainstream.

"Those were wonderful years of friendship and collaboration."

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Physicists study behavior of enzyme linked to Alzheimer's, cancer

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Margaret Cheung, assistant professor of physics at UH, and Antonios Samiotakis, a physics Ph.D. student, described their findings in a paper titled"Structure, function, and folding of phosphoglycerate kinase (PGK) are strongly perturbed by macromolecular crowding,"published in a recent issue of the journalProceedings of the National Academy of Sciences, one of the world's most-cited multidisciplinary scientific serials.

"Imagine you're walking down the aisle toward an exit after a movie in a crowded theatre. The pace of your motion would be slowed down by the moving crowd and narrow space between the aisles. However, you can still maneuver your arm, stretch out and pat your friend on the shoulder who slept through the movie,"Cheung said."This can be the same environment inside a crowded cell from the viewpoint of a protein, the workhorse of all living systems. Proteins always 'talk' to each other inside cells, and they pass information about what happens to the cell and how to respond promptly. Failure to do so may cause uncontrollable cell growth that leads to cancer or cause malfunction of a cell that leads to Alzheimer's disease. Understanding a protein inside cells– in terms of structures and enzymatic activity– is important to shed light on preventing, managing or curing these diseases at a molecular level."

Cheung, a theoretical physicist, and Martin Gruebele, her experimental collaborator at the University of Illinois at Urbana-Champaign, led a team that unlocked this mystery. Studying the PGK enzyme, Cheung used computer models that simulate the environment inside a cell. Biochemists typically study proteins in water, but such test tube research is limited because it cannot gauge how a protein actually functions inside a crowded cell, where it can interact with DNA, ribosomes and other molecules.

The PGK enzyme plays a key role in the process of glycolysis, which is the metabolic breakdown of glucose and other sugars that releases energy in the form of ATP. ATP molecules are basically like packets of fuel that power biological molecular motors. This conversion of food to energy is present in every organism, from yeast to humans. Malfunction of the glycolytic pathway has been linked to Alzheimer's disease and cancer. Patients with reduced metabolic rates in the brain have been found to be at risk for Alzheimer's disease, while out-of-control metabolic rates are believed to fuel the growth of malignant tumor cells.

Scientists had previously believed that a PGK enzyme shaped like Pac-Man had to undergo a dynamic hinge motion to perform its metabolic function. However, in the computer models mimicking the cell interior, Cheung found that the enzyme was already functioning in its closed Pac-Man state in the jam-packed surrounding. In fact, theenzymewas 15 times more active in the tight spaces of a crowded cell. This shows that in cell-like conditions the function of aproteinis more active and efficient than in a dilute condition, such as a test tube. This finding can drastically transform how scientists view proteins and their behavior when the environment of a cell is taken into account.

"This work deepens researchers' understanding of how proteins function, or don't function, in real cell conditions,"Samiotakis said."By understanding the impact of a crowded cell on the structure, dynamics of proteins can help researchers design efficient therapeutic means that will work better inside cells, with the goal to prevent diseases and improve human health."

Cheung and Samiotakis'computer simulations– performed using the supercomputers at the Texas Learning and Computation Center (TLC2)– were coupled with in vitro experiments by Gruebele and his team. Using the high-performance computing resources of TLC2 factored significantly in the success of their work.

"Picture having a type of medicine that can precisely recognize and target a key that causes Alzheimer's or cancer inside a crowded cell. Envision, then, the ability to switch a sick cell like this back to its healthy form of interaction at a molecular level,"Cheung said."This may become a reality in the near future. Our lab at UH is working toward that vision."

The research was funded by a nearly $224,000 National Science Foundation grant in support of Samiotakis' dissertation.

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New look at relativity: Electrons can't exceed the speed of light -- thanks to light itself, says biologist

Any space with a temperature aboveabsolute zeroconsists ofphotons. As a result of theDoppler effect, the moving electron experiences the photons crashing into the front of it as being blue-shifted, and the photons colliding with the back of it as being red-shifted. Since blue-shifted photons exert more momentum than red-shifted photons, the photons themselves exert a counterforce on the moving electron, just as the cytoplasm in a cell exerts a viscous force on the moving organelles. The viscous force that arises from the Doppler-shifted photons prevents electrons from exceeding the speed of light, according to Randy Wayne, associate professor of plant biology.

Wayne's research,"Charged Particles Are Prevented From Going Faster Than the Speed of Light by Light Itself: A Biophysical Cell Biologist's Contribution to Physics,"appears in the November 2010 issue ofActa Physica Polonica B.

On determining whether electrons can surpass the speed of light, Albert Einstein's specialtheory of relativitycontends that electrons are prevented from exceeding the speed of light as a result of the relativity of time. But Wayne contends that Einstein didn't take the environment through which theelectronsmove into account.

"Given the prominence of viscous forces within and around cells and the experience of identifying and quantifying such resistive forces, biophysical cell biologists have an unique perspective in discovering the viscous forces that cause moving particles to respond to an applied force in a nonlinear manner,"he explained."Consequently, light itself prevents charged particles from moving faster than thespeed of light."

Wayne will publish a related paper,"The Relativity of Simultaneity: An Analysis Based on the Properties of Electromagnetic Waves,"in a forthcoming volume of theAfrican Physical Review, which is a juried publication.

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Light bending by a black hole may offer proof of extra dimensions

Most of the work by astrophysicists studying the effects ofgravitational lensing, or light bending, relates togalaxiesand galaxy clusters. New research from Penn makes use of thesupermassive black holebelieved to exist at the center of theMilky Waygalaxy.

The analysis was carried out by Amitai Y. Bin-Nun, a theoretical astrophysics and cosmology graduate student at Penn, with guidance from Justin Khoury, assistant professor, and Ravi K. Sheth, professor, both in the Physics and Astronomy Department in Penn’s School of Arts and Sciences. The article appears in the journalPhysical Review D.

“We found that, if our universe is described by a theory incorporating extra dimensions, light near the black hole at the center of our galaxy may appear brighter than it would if we live in a universe without extra dimensions,” Bin-Nun said.“Detecting images at the brighter intensity would represent evidence ofextra dimensionsand would be an incredibly important development.”

Bin-Nun studied the effect of gravitational lensing on the stars orbiting Sagittarius A*, or Sgr A*, a radio source in the center of the Milky Way. Sgr A* was chosen because it hosts the supermassive black hole hypothesized to exist at the center of the Milky Way. The strong gravitational pull of the black hole distorts the light from Sgr A* before it reaches Earth, creating the illusion of multiple images of the same star.

Bin-Nun simulated the orbits of stars near the black hole and treated each star as a source lensed by the black hole, solving for the location and brightness of the“secondary” image which appears near the black hole. For each individual star, Bin-Nun found that the brightness of the secondary image would change over time and would peak in brightness when the star is nearly aligned with Sgr A*.

Next, he repeated the lensing analysis assuming the black hole was described by a metric coming from the theoretical Randall-Sundrum II braneworld scenario, which prescribes an extra fifth dimension. If that description of the black hole is correct, then the seconday image of the star S2 will be up to 44 percent brighter in early 2018 when it reaches its peak brightness, providing evidence for the presence of a fifth dimension where gravity is severely diluted. If not, then the four dimensional description of the black hole should be seen as more accurate.

Even if the exact universe is not five dimensional, or this analysis breaks down at other points,“we have shown alternative gravity theories have the possibility of creating a large gravitational lensing effect and we should look into lensing as a test for gravity theories,” Bin-Nun said.

The findings come with several caveats.

Certain assumptions on the form of the black hole were made as the shape of space around a five dimensional black hole is not known. Researchers did not take into account the spin of the black hole, which confounds the analysis. It’s also highly probable that, because the image is so close to the black hole and resolution of available ground-based telescopes are limited, the light from larger, nearby objects could obscure the image of the star, meaning observers won’t be able to isolate the effects of this particular iamge.

“These findings illustrate how the opportunities provided by the Penn physics Ph.D. program and its new Center for Particle Cosmology allow its students to make important contributions at the cutting edge of discovery,” Sheth said.

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Cleaner stoves for developing countries, thanks to heat-powered fan design

At an upcoming meeting of the 2nd Pan-American/Iberian Meeting on Acoustics in Cancun, Mexico, he will present a simple heat-powered fan that could help to make these stoves more efficient and combat the serious health problems associated with cooking in unventilated spaces.

How important is this? In a speech in September 2010 U.S. Secretary of State Hillary Clinton made a speech in which she underscored the impact of simple stoves on living standards in many parts of the world. More than 3 billion people use open fire cooking to eat daily, she said. But such cooking is very energy inefficient; finding fuel itself is a laborious; the combustion contributes disproportionately togreenhouse warming; and, worst of all, the fumes (often gathering in unventilated rooms) produce air that often exceeds EPA guidelines for healthful air by a factor of 200.

The fumes kill an estimated 1.9 million people a year, according to the United Nations. TheWorld Health Organizationcites this smoke as one of the five greatest killers indeveloping countries. Ms. Clinton's speech launched a worldwide effort called the Global Alliance for Clean Cookstoves.

Some moderate-sized devices generate combined heat and power, or CHP. The smallest of these highly-efficient machines can make, for example, 2 kilowatts of heat and 1 kilowatt of electricity. But even this is too much for a person in a rural area to use and too expensive, so Montgomery is trying to make a simple appliance that is 100 times smaller still.

His device, still at the experimental stage, captures some of the stove'swaste heatand converts the heat intosound wavesin a simple thermo-acoustic engine. Then theacoustic energyis converted into a tiny bit of electricity in an electro-acoustic transducer. The electricity in turn can partly charge a battery (delivering well-needed lighting after dark) and operate a fan directed at the combustion of the stove's biofuel, making the whole process more energy efficient.

The more efficient combustion, the less biomass must be burned to cook and the less smoke produced.

"Although a thermo-acoustic cogeneration cook stove would produce only on the order of ten watts of electrical power,"he says,"there are probably two billion biomass-fueled cook stoves in use worldwide that might benefit from nano-CHP technology."

The target price for the device that attaches to the stove is $25, says Montgomery, who will report on his ongoing engineering research in Cancun.

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Foucault, revisited: Scientists show how to build a pendulum for any classroom

The only problem, according to Argentinean researcher Horacio Salva, is that the devices are generally large and unwieldy, making them impractical to install in places where space is at a premium. This limitation was something he and his colleagues at the Centro Atómico Bariloche in Argentina wanted to address.

Now in the American Institute of Physics journalReview of Scientific Instruments, Salva and colleagues report success in what he acknowledges was a fun side project -- building two pendulums precisely enough to make measurements of the spinning Earth yet compact enough to fit in a lobby or classroom of just about any science building.

By definition, Foucault pendulums -- which are named after the French physicist Léon Foucault who first conceived of one in the middle of the 19th century -- count as a simple technology. Generally, a metal orb is suspended by a wire and hung from a height that can be dozens and dozens of feet. The orb is pulled back and released, and as it swings back and forth over the course of a day, it appears to slowly rotate in a circle. In fact what's observed is the Earth moving underneath the pendulum, which swings back and forth in a fixed plane, like a gyroscope.

Or rather, it's more accurate to say that pendulums swing in a mostly fixed plane. That's because, as anyone who pushes a child in a swing can attest, it's tough to keep a pendulum swinging in a straight line. Over time, due to the vagaries of friction and other forces, a pendulum will start to travel in an ellipse, an effect that can easily garble evidence of the Earth's rotation, which for generations has been novel enough to astonish when first observed. Here's the beginning of a February 23, 1908 article in The New York Times describing a Foucault pendulum display in the Big Apple:"Perhaps you were one of the crowd of people who saw the great Foucault pendulum experiment last week at Columbia University. Probably you watched it like the rest with openmouthed wonder."

The heavier the suspended orb and the longer the wire, the more limited the elliptical drift. Similarly, older children on taller swings tend to fly straighter than younger children in the shorter toddler swings.

Consider the dimensions of an 80-year-old Foucault pendulum on display at Philadelphia's Franklin Institute: a 180-pound-orb hangs from a wire 85 feet long and swings back and forth once every 10 seconds. The two pendulums built by Salva are kiddie-sized in comparison. In the case of the first, a 27-pound weight swings back and forth on a 16-foot-long piano wire once every 4 and a half seconds. The second pendulum uses the same weight and an even shorter wire. Using a copper ring underneath each orb to damp down the drift, Salva was able to easily observe and measure precession, the technical name for the movement of the Earth relative to the fixed swinging of the pendulums. Indeed his jiggering of the pendulums was able to tune out all but one percent of the elliptical"noise,"at least in the case of his longer pendulum.

Admittedly, says Salva, this new pendulum by no means has the precision necessary to make any groundbreaking new measurements. But the design, he says, is sophisticated enough to be a useful tool for teaching basic physics concepts to physics students and the general public.

"There's obviously no pressure to do work like this,"said Salva, who in his day job studies far more sophisticated"pendulums"involving the elasticity of various materials."It's mostly for fun, though I think it may well help students in the future, too."

Pointing to one possible application, the paper notes that the device was able to detect earthquakes of medium intensity that took place as far away as 765 km."Some earthquakes can be seen, because the seismic wave moves the support of thependulumincreasing the ellipse of the moment and changing the precession speed,"said Salva.

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Study reveals the subtle dynamics underpinning how cats drink (w/ Video)

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Researchers at MIT, Virginia Tech and Princeton University analyzed the way domestic and big cats lap and found thatfelinesof all sizes take advantage of a perfect balance between two physical forces. The results will be published in the November 11 online issue of the journalScience.

It was known that when they lap, cats extend their tongues straight down toward the bowl with the tip of the tongue curled backwards like a capital"J"to form a ladle, so that the top surface of the tongue actually touches the liquid first. We know this because another MIT engineer, the renowned Doc Edgerton, who first used strobe lights in photography to stop action, filmed a domestic cat lapping milk in 1940.

But recent high-speed videos made by this team clearly revealed that the top surface of the cat's tongue is the only surface to touch the liquid. Cats, unlike dogs, aren't dipping their tongues into the liquid like ladles after all. Instead, the cat's lapping mechanism is far more subtle and elegant. The smooth tip of the tongue barely brushes the surface of the liquid before the cat rapidly draws its tongue back up. As it does so, a column of milk forms between the moving tongue and the liquid's surface. The cat then closes its mouth, pinching off the top of the column for a nice drink, while keeping its chin dry.

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The liquid column, it turns out, is created by a delicate balance between gravity, which pulls the liquid back to the bowl, and inertia, which in physics, refers to the tendency of the liquid or any matter, to continue moving in a direction unless another force interferes. The cat instinctively knows just how quickly to lap in order to balance these two forces, and just when to close its mouth. If it waits another fraction of a second, the force of gravity will overtake inertia, causing the column to break, the liquid to fall back into the bowl, and the cat's tongue to come up empty.

While the domestic cat averages about four laps per second, with each lap bringing in about 0.1 milliliters of liquid, the big cats, such as tigers, know to slow down. They naturally lap more slowly to maintain the balance of gravity and inertia.

Analyzing the mechanics

In this research, Roman Stocker of MIT's Department of Civil and Environmental Engineering (CEE), Pedro Reis of CEE and the Department of Mechanical Engineering, Sunghwan Jung of Virginia Tech's Department of Engineering Science and Mechanics, and Jeffrey Aristoff of Princeton's Department of Mechanical and Aerospace Engineering used observational data gathered from high-speed digital videos of domestic cats, including Stocker's family cat, and a range of big cats (tiger, lion and jaguar) from the Boston-area zoos, thanks to a collaboration with Zoo New England's mammal curator John Piazza and assistant curator Pearl Yusuf. And, in what could be a first for a paper published inScience, the researchers also gathered additional data by analyzing existing YouTube.com videos of big cats lapping.

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With these videos slowed way down, the researchers established the speed of the tongue's movement and the frequency of lapping. Knowing the size and speed of the tongue, the researchers then developed a mathematical model involving the Froude number, a dimensionless number that characterizes the ratio between gravity and inertia. For cats of all sizes, that number is almost exactly one, indicating a perfect balance.

To better understand the subtle dynamics of lapping, they also created a robotic version of a cat's tongue that moves up and down over a dish of water, enabling the researchers to systematically explore different aspects of lapping, and ultimately, to identify the mechanism underpinning it.

"The amount of liquid available for the cat to capture each time it closes its mouth depends on the size and speed of thetongue. Our research— the experimental measurements and theoretical predictions— suggests that the cat chooses the speed in order to maximize the amount of liquid ingested per lap,"said Aristoff, a mathematician who studies liquid surfaces."This suggests thatcatsare smarter than many people think, at least when it comes to hydrodynamics."

Aristoff said the team benefitted from the diverse scientific backgrounds of its members: engineering, physics and mathematics.

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The researchers needed to be able to change a cat's lapping speed in order to test their theory. So they developed a robotic version of a cat's tongue— a mechanical column with a 1-inch glass disk at the tip. This device allowed the researchers to study the liquid column for different lapping speeds using a high-speed digital camera. The initial image was taken at 1000 frames per second. The video above is slowed to 15 frames per second. Video /Pedro M. Reis, Sunghwan Jung, Jeffrey M. Aristoff and Roman Stocker

"In the beginning of the project, we weren't fully confident that fluid mechanics played a role in cat's drinking. But as the project went on, we were surprised and amused by the beauty of the fluid mechanics involved in this system,"said Jung, an engineer whose research focuses on soft bodies, like fish, and the fluids surrounding them.

The work began three-and-a-half years ago when Stocker, who studies the fluid mechanics of the movements of ocean microbes, was watching his cat lap milk. That cat, eight-year-old Cutta Cutta, stars in the researchers' best videos and still pictures. And like all movie stars (Cutta Cutta means"stars stars"in an Australian aboriginal language), he likes being waited on. With their cameras trained on Cutta Cutta's bowl, Stocker and Reis said they spent hours at the Stocker home waiting on Cutta Cutta… to drink, that is. But the wait didn't dampen their enthusiasm for the project, which very appropriately originated from a sense of curiosity.

"Science allows us to look at natural processes with a different eye and to understand how things work, even if that's figuring out how my cat laps his breakfast,"Stocker said."It's a job, but also a passion, and this project for me was a high point in teamwork and creativity. We did it without any funding, without any graduate students, without much of the usual apparatus that science is done with nowadays."

"Our process in this work was typical, archetypal really, of any new scientific study of a natural phenomenon. You begin with an observation and a broad question, 'How does the cat drink?' and then try to answer it through careful experimentation and mathematical modeling,"said Reis, a physicist who works on the mechanics of soft solids."To us, this study provides further confirmation of how exciting it is to explore the scientific unknown, especially when this unknown is something that's part of our everyday experiences."

Besides their obvious enthusiasm for the work itself, the researchers are also delighted that it builds on Edgerton's 1940 film of the cat lapping. That film appeared as part of an MGM-released movie called"Quicker'n a Wink,"which won an Academy Award in 1941. Reis and Stocker say they're moving on to other collaborations closer to their usual areas of research. But their feline friend Cutta Cutta might have Oscar hopes.

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