bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced heteroepitaxial growth of CoCrPt–SiO2 perpendicular magnetic recording media on optimized Ru intermediate layers
Authors: Srinivasan Kumar , Piramanayagam S. N.
Published: January 2008

The crystallographic growth, interfacial roughness, and magnetic properties of CoCrPt–SiO2 perpendicular magnetic recording media prepared on various types of Ru intermediate growth layers were systematically investigated based on high angle and omega offset x-ray diffraction scans, rocking curve scans, synchrotron radiation based grazing incidence reflectivity scans, and magneto-optical Kerr hysteresis loops. For samples that make use of one Ru growth layer, voltage bias applied on the Ru layer was seen to have two observable effects: (1) the dispersion in the Ru(00⋅2) perpendicular texture increased, but that of the Co(00⋅2) remained unchanged, leading to identical layered growth and (2) the in-plane a-lattice parameter of the Ru decreased leading to enhanced heteroepitaxy with the Co. There was no significant change in the Ru–Co interfacial roughness with changing the bias on the Ru layer. The bias effect can be used to optimize the design of the Ru intermediate layers. A scheme that makes use of two Ru growth layers consisting of a bottom Ru layer prepared under zero bias, which is inserted below a second Ru layer prepared under biased conditions, is shown to lead to significant benefits such as improved texture without affecting the magnetic properties. This is due to the different functional roles ascribed to each of the Ru growth layers.
X-ray diffraction from shock-loaded polycrystals
Authors: Swift Damian C.
Published: January 2008

X-ray diffraction was demonstrated from shock-compressed polycrystalline metals on nanosecond time scales. Laser ablation was used to induce shock waves in polycrystalline foils of Be, 25–125μm thick. A second laser pulse was used to generate a plasma x-ray source by irradiation of a Ti foil. The x-ray source was collimated to produce a beam of controllable diameter, which was directed at the Be sample. X-rays were diffracted from the sample, and detected using films and x-ray streak cameras. The diffraction angle was observed to change with shock pressure. The diffraction angles were consistent with the uniaxial (elastic) and isotropic (plastic) compressions expected for the loading conditions used. Polycrystalline diffraction will be used to measure the response of the crystal lattice to high shock pressures and through phase changes.
Frequency dispersion in capacitance-voltage characteristics of AlGaN∕GaN heterostructures
Authors: Shealy James R. , Brown Richard J.
Published: January 2008

Capacitance-voltage (CV) characterization of AlGaN∕GaN heterostructures is a widely used method for determining the depletion characteristics of the two-dimensional electron gas at the heterointerface. In combination with the Hg probe, these measurements are considered nondestructive. The technique can provide accurate determination of the sheet electron density, the concentration profile, the AlGaN barrier thickness, and the pinch off voltage. If the measurement conditions are not chosen properly, significant errors result from the effects of the series resistance, the backside Hg contact, and the electron generation lifetime. The best conditions (bias and frequency) for CV data acquisition are identified.
Observation of delayed fluorescence in CdSxSe1−x nanobelts by femtosecond time-resolved fluorescence spectroscopy
Authors: Han Xiao-Feng , Weng Yu-Xiang , Pan Anlian , Zou Bingsuo , Zhang Jing-Yuan
Published: January 2008

The time-resolved fluorescence spectra as well as the decay kinetics for CdSxSe1−x single crystal nanobelts without and with the presence of structural disorders have been investigated by femtosecond time-resolved fluorescence spectrometer based on optical parametric fluorescence amplifier technique. The structural disorders in the crystal give rise to an inhomogeneous broadening of the steady-state fluorescence spectra and also to a distinct time-dependent redshift in the transient photoluminescence spectra, due to the carrier relaxation from the conduction band to the trapped states. The delayed fluorescence was observed and it can be attributed to several mechanisms including the electron-phonon interaction and the Auger effect.
Migration and luminescence enhancement effects of deuterium in ZnO∕ZnCdO quantum wells
Authors: Lim W. , Norton D. P. , Pearton S. J. , Wang X. J. , Chen W. M. , Buyanova I. A. , Osinsky A. , Dong J. W. , Hertog B. , Thompson A. V. , Schoenfeld W. V. , Wang Y. L. , Ren F.
Published: January 2008

Zn O ∕ Zn Cd O ∕ Zn O multiple quantum well samples grown on sapphire substrates by molecular beam epitaxy and annealed in situ were exposed to D2 plasmas at 150°C. The deuterium showed migration depths of ∼0.8μm for 30min plasma exposures, with accumulation of H2 in the ZnCdO wells. The photoluminescence (PL) intensity from the samples was increased by factors of 5 at 5K and ∼20 at 300K as a result of the deuteration, most likely due to passivation of competing nonradiative centers. Annealing up to 300°C led to increased migration of H2 toward the substrate but no loss of deuterium from the sample and little change in the PL intensity. The initial PL intensities were restored by annealing at ⩾400°C as H2 was evolved from the sample (∼90% loss by 500°C). By contrast, samples without in situ annealing showed a decrease in PL intensity with deuteration. This suggests that even moderate annealing temperatures lead to degradation of ZnCdO quantum wells.
Music from Oil Drums: The Acoustics of the Steel Pan
Authors: Rossing Thomas D. , Hampton D. Scott , Hansen Uwe J.
Published: January 2008

The steel pan—made from the end of an oil drum—is probably the most important new acoustical (that is, nonelectronic) musical instrument developed in the 20th century. In addition to being the foremost musical instrument in its home country, Trinidad and Tobago, the steel pan is becoming increasingly popular in North America and Europe. (See figure 1). The modern family of steel pans now covers a five-octave range, and steel bands of today use them to perform calypso, jazz, and popular and classical music.
Liverpool and Berkeley: The Chadwick–Lawrence Letters
Authors: Brown Andrew P.
Published: January 2008

Research procedures at Cambridge University's famous Cavendish Laboratory underwent some visible changes in the 1920s. An influx of men with electrical engineering backgrounds, such as John Cockcroft, T. E. Allibone and Ernest Walton, led to work on prototype particle accelerators. The goal was to attack the atomic nucleus with something other than Lord Rutherford's beloved alpha particles.
Quantum Cascade Laser Makes Progress
Authors: Levi Barbara Goss
Published: January 2008

Two years after a group of researchers at Bell Labs successfully operated a novel infrared, semiconductor laser, they have the device putting out hundreds of milliwatts of power at temperatures near 50 °C. That's 40 °C warmer than the highest temperature at which its competitors in this wavelength region can operate, and then only at much lower power. The new laser is a quantum cascade laser developed by Jerome Faist, Federico Capasso and their colleagues at Bell Labs. Their modifications of the 1994 design have produced a laser that operates in a pulsed mode at 5.2 μm and generates maximum peak powers of about 200 mW at 27 °C and 100 mW at 47 °C.
Memories of Richard Feynman
Authors: Hey Anthony J. G.
Published: January 2008

I well remember my arrival at Caltech on a sunny October morning in 1970. Fresh from the University of Oxford where even graduate students at that time wore ties and shirts, I was unsure what to wear for my first meeting with Murray Gell-Mann. I gambled, wrongly, on a suit, and arrived at the office of the theory group secretary, Julie Curcio, feeling more and more overdressed and as if I had a large label dangling from my collar saying “New PhD from Oxford.” I had seen Gell-Mann once before in England but was unsure if the bearded individual dressed in an open-necked shirt and sitting in Julie's office was indeed the eminent professor, A moment after I had introduced myself, my doubts were dispelled by the man putting out his hand and saying “Hi, I'm Murray.” This episode illustrates only a small part of the healthy culture shock I experienced in California. Six years in Oxford had left me used to calling my professor “Professor Dalitz, sir.” At that time, I would certainly not have dared to address Richard Dalitz as “Dick.”
With New Funding, Antimatter Research to Continue at CERN
Authors: Feder Toni
Published: January 2008

Thanks to external funding, antimater research at CERN will continue. CERN's antiproton complex, which in the fall of 1995 was the first to produce antihydrogen, was closed at the end of last year to free up money for the Large Hadron Collider. Now, however, one part of this complex, the antiproton collector, is to be upgraded and rechristened the “antiproton decelerator,” scheduled to begin operating in early 1999.
The Moses of Silicon Valley
Authors: Riordan Michael , Hoddeson Lillian
Published: January 2008

Forty years ago the southern part of the San Francisco Bay area was predominantly an agricultural valley filled with apricot orchards. Today this region is the bustling high-technology capital of the world—envied by governments around the globe for its creativity and productivity. How did this remarkable technological transformation occur? And why is Silicon Valley located southeast of San Francisco rather than in, say, northern New Jersey, the Boston area or near Dallas?
Physicists in Finance
Authors: Pimbley Joseph M.
Published: January 2008

To a physicist facing significant difficulty in the job market, the allure of a career in finance is obvious: The industry has numerous opportunities that demand the physicist's quantitative skills, and pay handsomely for them. Those contemplating such a move, however, need to look beyond these immediate considerations, for the culture of finance differs markedly from that of physics, having different goals and philosophies, work styles, even dress codes. Tb be successful on Wall Street, the physicist must willingly adapt to Wall Streets ways.
The Discovery of the Risk of Global Warming
Authors: Weart Spencer R.
Published: January 2008

It is now a century since Syante Arrhenius published the idea: As human activity puts ever more carbon dioxide into the atmosphere, global warming becomes ever more likely. (See figure 1 and the box on page 36.) His paper attracted notice, and one might suppose that knowledge of the so-called “greenhouse effect” has grown steadily ever since. But that is not in fact how the science proceeded. During more than half a century after 1896 almost nothing of value was learned about global warming. Only in the late 1950s did scientists at last begin to regard it as a serious possibility, indeed a potential danger.
In a Quantum Hall System, Is the Insulator Really a Conductor in Vortex Clothing?
Authors: Levi Barbara Goss
Published: January 2008

Dan Shahar, Daniel Tsui and Mansour Shayegan at Princeton University were studying the liquid-to-insulator transitions in a quantum Hall system recently when they noticed a surprising symmetry in the plot of longitudinal voltage versus current: For each point close to the phase transition in the liquid phase, they could find a corresponding point in the insulating phase such that the (normalized) I–V curve for one fell precisely on the V-I curve of the other—that is, the curve with the voltage and current coordinates switched. Such behavior suggests that the underlying dynamics of the liquid and insulator phases must be intimately related, despite their overtly different transport characteristics.
String Theory Is Testable, Even Supertestable
Authors: Kane Gordon
Published: January 2008

Suppose we could understand the laws of nature that govern the particles and their interactions, and in addition why the laws are as they are, and also how the universe evolved and perhaps even how it originated—an active research area today That understanding—a theory—would be formulated not in terms of everyday units, but rather units built from constants such as the speed of light, Planck's constant and Newton's constant. From these constants one obtains the natural scales: the Planck length (∼10−33 cm) and the Planck mass (MP∼1019 GeV/c2). I will call this theory the primary theory, a name I like because it suggests that as we go through a hierarchy of effective theories, from macroscopic sizes to atoms to nuclei, we end at a primary one that is not related to another at a deeper level.
Transient Stellar X-Ray Sources Yield Evidence that Black Holes Really Do Have Event Horizons
Authors: Schwarzschild Bertram
Published: January 2008

X-ray astronomy has already provided us with about a dozen rather convincing stellar black hole candidates. (See PHYSICS TODAY, November 1995, page 58.) But until now the evidence was simply that an object too compact to be an ordinary star was too massive to be just another neutron star. So, by elimination, what else could it be but a black hole? Convincing as that kind of evidence is, it does not address the defining exotic properties that general relativity attributes to black holes: the remorseless event horizon and the strongly curved spacetime leading down to it.
Nuclear Waste Disposal: The Technical Challenges
Authors: Crowley Kevin D.
Published: January 2008

In this sixth decade of the nuclear age, the US and many other nations face daunting technical challenges to the disposal of nuclear waste. There are many contributing factors, not the least of which are the sheer volumes of waste and the great number of chemical and physical forms in which it exists at defense and civilian sites both here and abroad. (See figure 1, for example, and see also John Ahearne's article on page 24.)
Nuclear Waste Management Worldwide
Authors: McCombie Charles
Published: January 2008

The proper management of radioactive wastes involves a broad array of activities. Residues must be minimized and conditioned; waste packages must be safely handled, transported and kept in interim storage prior to their safe disposal. Further major challenges arise in cleaning up sites that have been contaminated in the course of mining uranium, producing reactor fuel and fabricating nuclear weapons. Accomplishing these tasks requires not only the development and deployment of technological processes but also the solution of obstinate socioeconomic and organizational problems: Necessary resources must be made available and—most important—acceptable sites must be found for waste management facilities.
Harness the Hubris: Useful Things Physicists Could Do in Biology
Authors: Parsegian V. Adrian
Published: January 2008

I once asked my father why he chose physics when he started at MIT. “Everybody said it was the hardest course, so I decided to do it.”
Geophysical Dynamics at the Center of the Earth
Authors: Jeanloz Raymond , Romanowicz Barbara
Published: January 2008

New studies are revealing the dynamics of the Earth's deep interior to a degree that could hardly be imagined even a few years ago. A combination of geophysical observations (mostly seismological, geomagnetic and geodetic) and new laboratory and computational results has revolutionized our ability to understand what happens at the core of our planet.
Blending Education and Research in Atmospheric Science—A Case Study
Authors: Cohn Stephen A. , Hallett John , Koracin Darko
Published: January 2008

Our atmosphere is a great natural laboratory. Atmospheric scientists can use this laboratory to look for physical phenomena, to teach physical ideas and to develop practical technologies.
Hipparcos Parallax Data May Reconcile Ages of Globular Clusters and the Universe
Authors: Schwarzschild Bertram
Published: January 2008

In the summer of 1989, the European Space Agency launched the High Precision Parallax Collecting Satellite—Hipparcos, for short. The name of this first automated astrometry orbiter honors Hipparchus of Nicea, who diligently compiled a catalog of the celestial positions and brightnesses of more than a thousand stars in the second century BC.
Infrared Laser Illustrates Another Way to Achieve Gain
Authors: Levi Barbara Goss
Published: January 2008

The standard way to build a laser is to produce a population inversion between an upper and a lower energy level. But laser gain is proportional not only to the population difference between two states but also to the oscillator strength, which depends on both the energy difference between the upper and lower states and the probability of a transition between them. By focusing on these often-overlooked factors, a group at Bell Laboratories, Lucent Technologies, has made a semiconductor infrared laser with a unique property: It is electrically tunable over a 6% range.
A Nobel Tale of Postwar Injustice
Authors: Crawford Elisabeth , Sime Ruth Lewin , Walker Mark
Published: January 2008

In November 1945, three months after the end of World War II, a narrow majority of the members of the Royal Swedish Academy of Sciences decided to award the 1944 Nobel Prize in Chemistry to Otto Hahn for the discovery of nuclear fission. The award was and still remains controversial, primarily because Hahn's Berlin colleagues, the chemist Fritz Strassmann and the physicist Lise Meitner, were not included. Probably, Strassmann was ignored because he was not a senior scientist. Meitner's exclusion, however, points to other flaws in the decision process, and to four factors in particular: the difficulty of evaluating an interdisciplinary discovery, a lack of expertise in theoretical physics, Sweden's scientific and political isolation during the war, and a general failure of the evaluation committees to appreciate the extent to which German persecution of Jews skewed the published scientific record.
Information Warfare: A Brief Guide to Defense Preparedness
Authors: Libicki Martin C.
Published: January 2008

With the cold war over, we Americans could justifiably think that our world is safer. As a nation, we could turn from hostile pursuits and begin to enlist private and public support for other great efforts—such as building a national, nay global, information infrastructure. Such an infrastructure, besides making our lives more productive and pleasant, might also serve as a bridge to global comity.
The Leptons After 100 Years
Authors: Perl Martin L.
Published: January 2008

Over the course of a century, six leptons have been discovered in the universe of elementary particles. Three—the electron, muon and tau—each have one unit of electric charge; the other three—the neutrinos—have no charge.
On Some Modern Uses of the Electron in Logic and Memory
Authors: Fowler Alan
Published: January 2008

The electron plays a role in many facets of modern life—lighting, heating, welding and so on. Here, I concentrate on the use of electrons primarily in logic and memory. I generally skip the early history—that of electronic tubes—and start instead with the modern integrated circuit and then go on to explore possible alternatives to the now-dominant silicon MOSFET technology. (MOSFET stands for metal oxide semiconductor field-effect transistor.) This approach is enforced not only by space considerations, but also by the fact that the passing years have erased triodes, power pentodes, klystrons, traveling-wave tubes and the like from my memory. Not that they are no longer used; clones of the 6L6, EL34 and KT88 are still used in some of the best audio amplifiers. Microwaves and power applications still rely heavily on tubes. Cathode-ray tubes are still the standard display, although their days may be numbered—at least at the large and small ends. Electron microscopes and lithography tools are, in a sense, large demountable vacuum tubes. (They are the subject of Murray Gibson's article on page 56 in this special issue.) However, over the past 40 years, the vacuum tube has been displaced by solid-state devices as the basis of most computer, low-power amplifier, communications and control circuits. (See figure 1, which shows a computer processing unit.)
Exhaustive Searching Is Less Tiring with a Bit of Quantum Magic
Authors: Collins Graham P.
Published: January 2008

The elementary particle of information used by modern digital computers is the bit—a register or memory element that can be in one of two distinct states, 0 or 1. But we live in a quantum world, and one can design computers in which each elementary unit of information is a quantum bit, or qubit, which can be in any superposition of two quantum states, |0〉 and |1〉. A quantum computer built with n such components could itself be in a superposition of 2n distinct states, each splinter of the superposition performing its own computation in parallel with all the rest.
Quantum Oscillations Ring Out Loud and Clear
Authors: Levi Barbara Goss
Published: January 2008

At the Symposium on Quantum Fluids and Solids in Paris this past July, Richard Packard of the University of California, Berkeley, entertained the audience by playing a brief recording: The sound on the tape began as a high-pitched whistle and slid down the frequency scale over a period of a few seconds. What people were hearing was the sound of a superfluid surging rapidly back and forth through the holes in a membrane1 in response to a pressure difference applied across the membrane. This phenomenon is the superfluid analog of the AC Josephson effect for superconductors, according to which a supercurrent will oscillate across a thin tunnel junction under an applied voltage. (A French group had earlier reported evidence of this phenomenon.) In addition to recording the sounds of the mass oscillations, Packard and Seamus Davis and their respective groups at Berkeley found that the measured frequencies agreed with those predicted by the Josephson equations.
Are There Really Electrons? Experiment and Reality
Authors: Franklin Allan
Published: January 2008

Discussing the existence of electrons, philosopher of science Ian Hacking has written, “So far as I'm concerned, if you can spray them, then they are real.” He went on to elaborate this view: “We are completely convinced of the reality of electrons when we set out to build—and often enough succeed in building—new kinds of device that use various well-understood causal properties of electrons to interfere in other more hypothetical parts of nature.”
From Ethane to Benzene through a Supersonic Nozzle
Authors: Levi Barbara Goss
Published: January 2008

Organic chemists have long been challenged to find an easy way to break apart, or activate, the single bonds in methane so that they could use this very abundant compound as a building block to synthesize organic compounds. But methane is stubbornly unreactive. Recently, Dudley Herschbach and his colleagues at Harvard University found that they could use a catalytic supersonic nozzle to produce high yields of more reactive intermediaries starting with ethane—a cousin of methane. The new method is tantalizing, although it has not yet worked with methane—and even if it were to, it would have to be scaled up from producing thimblefuls to churning out millions of barrels of hydrocarbons before it would be of interest to the petroleum industry. Short of that, the catalytic supersonic nozzle is of 1nterest as a way to do nonequilibrium chemisty.
Ancient Stardust in the Laboratory
Authors: Bernatowicz Thomas J. , Walker Robert M.
Published: January 2008

A mazingly, individual grains of dust from stars that existed before the Sun was born have made their way to Earth in meteorites. When subjected to a battery of cutting-edge laboratory techniques, these tiny grains provide thrilling new insights into such topics as the dynamics of supernova explosions, the age and chemical evolution of the Galaxy, fundamental nuclear physics and processes in the outer envelopes of stars. The path from dust grain to astrophysical insight is the subject of this article.
Fractionally Charged Quasiparticles Signal Their Presence with Noise
Authors: Collins Graham P.
Published: January 2008

To particle physicists, the electron is the quintessential example of an elementary particle: The highest energy experiments to date have revealed no evidence of any internal structure, no evidence that an electron is made up of some other, more fundamental components. But for condensed matter physicists studying the behavior of matter at low temperatures in semiconductor crystals, electrons can play by a different (although ultimately equivalent) set of rules. The fractional quantum Hall effect, for example, can be explained by invoking quasiparticles, which behave like distinct particles that each carry a fraction of an electron's charge. (On a more fundamental level, quasiparticles are collective excitations of interacting electrons.) Two recent experiments in Israel and France have added to the evidence that these quasiparticles exist.
Molecules Are Magnetically Trapped
Authors: Lubkin Gloria B.
Published: January 2008

The techniques of magnetic trapping and evaporative cooling of atoms to nanokelvin temperatures have led to Bose–Einstein condensation in alkali atoms and atomic hydrogen and to studies of ultracold atomic collisions. But none of the optical cooling methods has worked for molecules because it hasn't seemed possible to keep the molecules from being optically pumped into inaccessible states.
Kondo Physics Seen in a Quantum Dot
Authors: Levi Barbara Goss
Published: January 2008

A quantum dot, as its name implies, is a minuscule region of metallic or semiconductor material whose dimensions can be as small as a few tens of nanometers on a side. It has been likened to an artificial atom because it carries a discrete charge and quantized electronic energy levels (see the article by Marc Kastner in PHYSICS TODAY, January 1993, page 24). That analogy has now been taken a step further with the demonstration that a quantum dot interacts with nearby metallic leads in much the same way that a single magnetic impurity interacts with a surrounding metallic substance—in the phenomenon known as the Kondo effect.
The Highest-Energy Cosmic Rays
Authors: O'Halloran Thomas , Sokolsky Pierre , Yoshida Shigeru
Published: January 2008

The unexpected discovery of the cosmic microwave background by Arno Penzias and Robert Wilson in 1965 is now the centerpiece of our understanding of the Big Bang and the subsequent evolution of the universe. (See PHYSICS TODAY, November 1997, page 32.) The discovery also set off something of a race to verify one of its implications for cosmic rays. In 1966, Kenneth Greisen (Cornell University) pointed out that the most energetic cosmic-ray particles would be affected by interaction with the ubiquitous photons of this microwave background. Greisen predicted that, if cosmic-ray sources were far enough away from us and if their energy spectrum extended beyond 1020 eV, then the ultra-high-energy protons and nuclei would interact inelastically with the backgound radiation.
An Ion Clock Reaches the Accuracy of the Best Atomic Fountain
Authors: Levi Barbara Goss
Published: January 2008

The most accurate primary frequency standards in the world today reside in the national standards laboratories of several countries: They are an atomic-fountain clock at the Paris Observatory's Bureau National de Métrologie—Laboratoire Primaire de Temps et Fréquences and two atomic-beam clocks, one run by the US National Institute of Standards and Technology (NIST) in Boulder, Colorado, and another by the German Federal Institute of Physics and Metrology in Braunschweig.
The New Gamma-Ray Astronomy
Authors: Gehrels Neil , Paul Jacques
Published: January 2008

Our understanding of the gamma-ray sky is being revolutionized. Seven years ago, gamma-ray astronomers knew of only a scattering of very bright sources. Now, thanks to two international observatories, the gamma-ray sky appears to be teeming with variety—unstable sources that change violently on short time scales, steady sources that glow radioactively and others whose nature we barely understand.
Science and Politics in Early Nuclear Test Ban Negotiations
Authors: Barth Kai-Henrik
Published: January 2008

Scientists are no strangers to politics. Newspapers report daily about scientific experts participating in controversies such as low-level radiation, DNA testing, cloning or global warming. We find scientists testifying in congressional hearings, courtrooms and various committees on issues requiring both technical expertise and political judgment. This inseparability of science and politics is particularly visible in highly contested areas such as national security and nuclear arms control.
Researchers Find Extraordinarily High Temperature Superconductivity in Bio-Inspired Nanopolymer
Authors: Grant Paul M.
Published: January 2008

Forty-two years ago, Johannes Georg Bednorz and Karl Alex M̈ller startled the world with their unexpected discovery of superconductivity in layered copper oxide perovskites at temperatures substantially higher than previously thought possible. The history of this breakthrough is well known, and a large number of related compounds were found over the succeeding years, culminating in 2002 with Au-2223—a triple-layer CuO complex with an ambient-pressure transition temperature of 175 K, synthesized by Paul Chu and his collaborators in Houston. Such materials have found a number of communications and electric power applications, especially in distribution cables, transformers and passive RF filters, but remain limited by the need for cryogenic packaging.
A Personal Look Back at Physics Today
Authors: Lubkin Gloria B.
Published: January 2008

The idea of a magazine for physicists probably dates back to the 1930s, to early debates on the Reviews of Modern Physics, to the creation of a short-lived American Physical Society (APS) journal called Physics and later to a short-lived section within Review of Scientific Instruments, By 1944 the American Institute of Physics (AJP) had begun to seriously consider a magazine for physicists. Proposals ranged from a mimeographed newsletter to a slick magazine.
How Physics Today Hatched
Authors: Katcher David A.
Published: January 2008

Fifty years? Hard to believe… Among the joys of physics is knowing physicists. In the absence today of any connection whatsoever with the field, I read the autobiographies that are sprouting and relive the heroics before teams and chunk physics (as Matt Sands called it) on big machines took over.
Very Distant Supernovae Suggest that the Cosmic Expansion is Speeding Up
Authors: Schwarzschild Bertram
Published: January 2008

To determine the rate at which the cosmos is expanding, one has to measure the redshifts and brightnesses of objects very far away. To seek out the derivative of that rate—the expected deceleration, or perhaps even an acceleration, of the cosmic expansion—one has to look out much farther still. That's precisely what two competing groups of astronomers and physicists undertook to do a few years ago. And now both groups have come up with the same astonishing, if still somewhat tentative, conclusion: The present mean mass density (ρ0) that acts to slow down the Hubble expansion by gravitational braking appears to be overmatched by some ethereal agency that is actually speeding it up.
Strings May Tie Quantum Gravity to Quantum Chromodynamics
Authors: Levi Barbara Goss
Published: January 2008

Although string theorists explore bizarre multidimensional spaces filled with tiny loops and membranelike objects, they are ultimately seeking a description of the real world. They may have come close with a recent hypothesis that links a ten-dimensional string theory to a gauge field theory in the four dimensions of our ordinary world. The theorists' great hope is that this connection extends to the specific gauge theory describing quantum chromodynamics (QCD), which governs the strong interactions.
Berlin–Heidelberg Group Reports Phase Transition in Glass at Millikelvins in Presence of Microtesla Field
Authors: Lubkin Gloria B.
Published: January 2008

Peter Strehlow of the Physikalisch-Technische Bundesanstadt (the German counterpart of the National Institute of Standards and Technology), and Christian Enss and Siegfried Hunklinger of the University of Heidelberg, have recently reported a phase transition in glass at very low temperature. The experiments were done at the PTB low-temperature lab in Berlin.
Fiscal Physicists
Authors: Kannenberg Lloyd
Published: January 2008

I think it was Ernest Rutherford who once stated, “Science is divided into two categories, physics and stamp-collecting.” If this were true, physicists who dabbled in philately on the side could claim sweeping scientific expertise. Alas, it isn't and we can't. But many physicists, in fact, are avid collectors of stamps (Hans Bethe among them, I understand) and of other things.
Two Experiments Observe Explicit Violation of Time-Reversal Symmetry
Authors: Schwarzschild Bertram
Published: January 2008

It is hard to imagine that nature might violate the CPT theorem. Its proof invokes only rock-bottom assumptions of quantum field theory, and many of its consequences have been tested to very high precision. The theorem, independently discovered in the mid-1950s by Gerhardt Lüders, Wolfgang Pauli and John Bell, asserts that any local field theory that is invariant under the “proper” Lorentz transformations must also be invariant under the combined operation of the three discrete (improper) transformations: time reversal (T), parity inversion (P) and charge conjugation (C).
Phase Synchronization May Reveal Communication Pathways in Brain Activity
Authors: Fitzgerald Richard
Published: January 2008

Employing experiments that range from studying isolated pairs of lobster neurons to looking at electrical and magnetic signals from human test subjects, physicists are applying concepts from nonlinear systems, chaos and control theory to improve our understanding of neuronal dynamics. Exemplifying this approach, a collaboration in Germany between neurologists at the University of Düsseldorf and physicists at the University of Potsdam has recently demonstrated the potential of a new nonlinear analysis technique—phase synchronization—for neuronal studies. With this tool, the researchers found evidence in magnetoencephalography (MEG) data for synchronous activity between different parts of the brain and between the brain and the muscles during the tremor of a patient with Parkinson's disease (see the figure below).
Deep Under the South Pole, a Novel Telescope Records Ultrahigh-Energy Astrophysical Neutrinos
Authors: Schwarzschild Bertram
Published: January 2008

A neutrino telescope buried, under a mile of ice at the South Pole has been recording the interception of very high energy neutrinos (typically 1012 electron volts, or 1 TeV) for two years now. The AMANDA (Antarctic Muon And Neutrino Detector Array) collaboration has begun reporting its first results at meetings in recent weeks. A preliminary pass through the first four months of data harvested in 1997 has already yielded about 20 unambiguous neutrino events. So one can expect AMANDA, in its present configuration, to yield about 100 events per year above its neutrino-energy threshold of roughly 50 GeV
Electron Cryomicroscopy Comes of Age
Authors: Day Charles
Published: January 2008

Evolution has so purposefully crafted biological molecules that their function is often revealed by their structure. Much of what we know about the molecular basis of life has come from determining the structures of the molecular participants.
Traveling-Wave Thermoacoustic Heat Engines Attain High Efficiency
Authors: Fitzgerald Richard
Published: January 2008

With continued concerns about greenhouse gases and ozonedepleting refrigerants, the quest for efficient and environmentally benign engines, heat pumps, and refrigerators remains important. For 20 years, one field of exploration has been thermoacoustics, which involves the interplay between thermodynamics and sound waves. Thermoacoustic engine research has focused almost exclusively on standing-wave engines. Now Scott Backhaus and Greg Swift of Los Alamos National Laboratory have reported a new implementation of a traveling-wave thermoacoustic engine—a pistonless Stirling engine that's almost twice as efficient as standing-wave thermoacoustic engines.
Adiabatic Quantum Electron Pump Produces DC Current
Authors: Lubkin Gloria B.
Published: January 2008

If you know what you're doing and have suitable equipment, you can make a quantum dot, a tiny conducting region that contains anywhere from a handful to several thousand electrons. A number of experimenters have studied the electron transport properties of such dots. Now a group at Stanford University and the University of California, Santa Barbara, has made an open quantum dot, changed the shape of the system cyclically, and found that a finite current flows. This surprising effect requires quantum phase coherence and is observable only at a temperature low enough to preserve quantum phase. The effect was recently reported by Michael Switkes and Charles Marcus (Stanford), and Kenneth Campman and Arthur Gossard (UCSB).
Experiments at Jefferson Lab and MIT Probe for Strange Quarks in the Proton
Authors: Schwarzschild Bertram
Published: January 2008

The simplest description of the proton in terms of constituents regards it as a bound state of the three “Valence” quarks that account for its quantum numbers: two up quarks, each with charge +23e, and one down quark, with charge −13e. But we know that's too naive. Experiments over many years have shown that quarks carry only about half the proton's linear momentum and a quarter of its angular momentum.
New Data from Mars Hint at a Dynamic Past
Authors: Levi Barbara Goss
Published: January 2008

As the Mars Global Surveyor orbits the Red Planet, magnetometers aboard the spacecraft have been sending home some astounding data. The instruments have confirmed indications from earlier missions that, if Mars has a global magnetic dipole at all, it is more than 10 000 times weaker than Earth's. Nevertheless, the magnetometers find, Mars's surface is dotted with local regions where the magnetic fields are over ten times greater than any perturbations in Earth's global field. Most likely, the local fields stem from an early time when the planet's core was still molten and a magnetic dynamo imprinted its field in the rocks. But the most intriguing discovery by far is the large, linear magnetic structure evident in Mars's southern hemisphere: Along a band extending nearly 2000 km from east to west, the crustal magnetic moments are aligned in one direction; those in adjacent bands appear to be magnetized in the reverse direction, and so forth—for five or six flips of the magnetic field.
Ultraslow Light Pulse Propagation Observed in Atoms—Both Cold and Hot
Authors: Fitzgerald Richard
Published: January 2008

Earlier this year, Lene Hau (Rowland Institute for Science and Harvard University) and her coworkers captured the media spotlight with their announcement of having slowed the speed of light pulses through a Bose—Einstein condensate to a mere 17 m/s, down by a factor of nearly 20 million from light's speed in vacuum. (See Physics Today, April 1999, page 9.) Marian Scully and his colleagues at Texas A&M University, the National Institute for Standards and Technology in Boulder, Colorado, and the Harvard-Smithsonian Center for Astrophysics have recently reported comparable results using an ensemble of rubidium atoms that, at a temperature of 360 K, are a billion times hotter than Hau's sodium atoms. And Dmitry Budker's group at the University of California, Berkeley has seen even slower speeds in rubidium at room temperature. Accompanying the slow speeds are extremely nonlinear optical properties, as well.
First Events Seen at Sudbury Neutrino Observatory
Authors: Fitzgerald Richard
Published: January 2008

Fifteen years after it was initially proposed, the Sudbury Neutrino Observatory (SNO) has begun collecting data on solar and atmospheric neutrinos. Built by a collaboration of scientists from Canada, the US, and the UK, SNO is the second of a new generation of powerful neutrino detectors (see Physics Today, July 1996, page 30 and December 1997, page 56). It consists of an acrylic container holding 1000 metric tons of heavy water, surrounded by an array of about 9600 photo-multiplier tubes (PMTs) in ordinary water and buried 2 km underground in a nickel mine near Sudbury, Ontario.
Adaptive Optics at the New 8-Meter Gemini Telescope
Authors: Schwarzschild Bertram
Published: January 2008

These two extraordinarily detailed near-infrared images of the elegant planetary’ nebula prosaically named BD+30 3639 were produced by two very different instruments. The right-hand panel shows an image recently made with an adaptive-optics system on the 8.1 meter Gemini North Telescope, dedicated just three months ago on Hawaii's Mauna Kea.1 (Gemini's southern twin is nearing completion in the Chilean Andes.) The left-hand panel shows, for comparison, an image taken in 1994 with the recently corrected Hubble Space Telescope (HST),2
Computational Materials Science: The Era of Applied Quantum Mechanics
Authors: Bernholc Jerzy
Published: January 2008

For many centuries, materials were discovered, mined, and processed in a largely serendipitous way. However, the characterization of the atom and the progress made in x-ray diffraction during the early years of this century started a quest for a theory of materials in terms of their atomic constituents. Later decades saw scientists developing many qualitative and semi-quantitative models that explained the principles of atomic cohesion and the basic properties of semiconductors, metals, and salts. Considering their simplicity, some of the models were surprisingly accurate and led to remarkable progress. However, for most materials of current interest, the interatomic interactions are intricate enough to require fairly elaborate models. Fortunately, we are entering an era in which high-performance computing is coming into its own, allowing true predictive simulations of complex materials to be made from information on their individual atoms.
Femtosecond Laser Excites Novel Surface Chemistry
Authors: Day Charles
Published: January 2008

It's possible to map the stages of surface reactions by using the latest scanning probe techniques, but if you want to investigate the ultrafast dynamics of the atoms and molecules involved, you'll need something faster—like a femtosecond laser.
Composite Materials—Reflections on the First Half Century
Authors: Kelly Tony , Clyne Bill
Published: January 2008

Nature tends to use composites in building strong structures. Timber, for instance, is a composite made up of strong cellulose fibers in soft lignin. Bone consists of hydroxyapatite in collagen. Although people don't always recognize them, composites are everywhere. Only in the last 50 years or so has mankind purposely imitated these natural materials by developing artificial composites.
Nobel Prize to 't Hooft and Veltman for Putting Electroweak Theory on Firmer Foundation
Authors: Lubkin Gloria B.
Published: January 2008

The Royal Swedish Academy of Sciences has awarded the 1999 Nobel Prize in Physics jointly to Gerard 't Hooft of the University of Utrecht and Martinus J. G. Veltman, now retired from the University of Michigan, “for elucidating the quantum structure of electroweak interactions in physics.” The Academy's announcement stressed that the two Dutch theorists were honored “for having placed particle physics theory on a firmer mathematical foundation.” They developed a technique with which one can calculate radiative corrections to the electroweak theory, and, says the Academy, “they have in particular shown how the theory may be used for precise calculations of physical quantities. Experiments at accelerator laboratories in Europe and the USA have recently confirmed many of the calculated results.”
MerTK is required for apoptotic cell–induced T cell tolerance
Authors: Wallet Mark A. , Sen Pradip , Flores Rafael R. , Wang Yaming , Yi Zuoan , Huang Yingsu , Mathews Clayton E. , Earp H. Shelton , Matsushima Glenn , Wang Bo , Tisch Roland
Published: January 2008

Self-antigens expressed by apoptotic cells (ACs) may become targets for autoimmunity. Tolerance to these antigens is partly established by an ill-defined capacity of ACs to inhibit antigen-presenting cells such as dendritic cells (DCs). We present evidence that the receptor tyrosine kinase Mer (MerTK) has a key role in mediating AC-induced inhibition of DC activation/maturation. Pretreatment of DCs prepared from nonobese diabetic (NOD) mice with AC blocked secretion of proinflammatory cytokines, up-regulation of costimulatory molecule expression, and T cell activation. The effect of ACs on DCs was dependent on Gas6, which is a MerTK ligand. NOD DCs lacking MerTK expression (NOD.MerTKKD/KD) were resistant to AC-induced inhibition. Notably, autoimmune diabetes was exacerbated in NOD.MerTKKD/KD versus NOD mice expressing the transgenic BDC T cell receptor. In addition, β cell–specific CD4+ T cells adoptively transferred into NOD.MerTKKD/KD mice in which β cell apoptosis was induced with streptozotocin exhibited increased expansion and differentiation into type 1 T cell effectors. In both models, the lack of MerTK expression was associated with an increased frequency of activated pancreatic CD11c+CD8α+ DCs, which exhibited an enhanced T cell stimulatory capacity. These findings demonstrate that MerTK plays a critical role in regulating self-tolerance mediated between ACs, DCs, and T cells.
Development of all CD4 T lineages requires nuclear factor TOX
Authors: Aliahmad Parinaz , Kaye Jonathan
Published: January 2008

CD8+ cytotoxic and CD4+ helper/inducer T cells develop from common thymocyte precursors that express both CD4 and CD8 molecules. Upon T cell receptor signaling, these cells initiate a differentiation program that includes complex changes in CD4 and CD8 expression, allowing identification of transitional intermediates in this developmental pathway. Little is known about regulation of these early transitions or their specific importance to CD4 and CD8 T cell development. Here, we show a severe block at the CD4loCD8lo transitional stage of positive selection caused by loss of the nuclear HMG box protein TOX. As a result, CD4 lineage T cells, including regulatory T and CD1d-dependent natural killer T cells, fail to develop. In contrast, functional CD8+ T cells develop in TOX-deficient mice. Our data suggest that TOX-dependent transition to the CD4+CD8lo stage is required for continued development of class II major histocompatibility complex–specific T cells, regardless of ultimate lineage fate.
INTRODUCTION
Authors: Pearsall Cornelia
Published: January 2008

This introduction argues that Alfred Tennyson’s conception of “rapt oration” is critical to the understanding of a quartet of his major dramatic monologues, “St. Simeon Stylites,” “Ulysses,” “Tithonus,” and “Tiresias,” all drafted after the death in 1833 of his friend, Arthur Henry Hallam, though published over the course of the ensuing half-century. An examination of a variety of Tennyson’s works, in particular In Memoriam, establishes “rapt oration” as a state in which both speaker and listener are “transported” by the speaker’s oratorical prowess. A desire for rapture, characterized by both personal and political transformation, motivates the speech and actions of each of Tennyson’s speakers in these dramatic monologues. This introduction additionally argues that these dramatic monologues should be considered in the context of nineteenth-century rapture theology, reform politics, classical scholarship (in particular theories on Homer), and sexological theory, as well as in the context of Tennyson’s relationships with a range of contemporaries, including Thomas Carlyle, William Gladstone, John Stuart Mill, and Heinrich Schliemann.