bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of shear and deviatoric stress on the evolution of permeability in fractured rock
Authors: Faoro Igor , Niemeijer Andre , Marone Chris , Elsworth Derek
Published: December 2008

The evolution of permeability in fractured rock as a function of effective normal stress, shear displacement, and damage remains a complex issue. In this contribution, we report on experiments in which rock surfaces were subject to direct shear under controlled pore pressure and true triaxial stress conditions while permeability was monitored continuously via flow parallel to the shear direction. Shear tests were performed in a pressure vessel under drained conditions on samples of novaculite (Arkansas) and diorite (Coso geothermal field, California). The sample pairs were sheared to 18 mm of total displacement at 5 μm/s at room temperature and at effective normal stresses on the shear plane ranging from 5 to 20 MPa. Permeability evolution was measured throughout shearing via flow of distilled water from an upstream reservoir discharging downstream of the sample at atmospheric pressure. For diorite and novaculite, initial (preshear) fracture permeability is 0.5–1 × 10−14 m2 and largely independent of the applied effective normal stresses. These permeabilities correspond to equivalent hydraulic apertures of 15–20 μm. Because of the progressive formation of gouge during shear, the postshear permeability of the diorite fracture drops to a final steady value of 0.5 × 10−17 m2. The behavior is similar in novaculite but the final permeability of 0.5 × 10−16 m2 is obtained only at an effective normal stress of 20 MPa.
Changes in cloud and aerosol cover (1980–2006) from reflectivity time series using SeaWiFS, N7‐TOMS, EP‐TOMS, SBUV‐2, and OMI radiance data
Authors: Herman J. R. , Labow G. , Hsu N. C. , Larko D.
Published: December 2008

The amount of solar radiation reflected back to space or reaching the Earth's surface is primarily governed by the amount of cloud cover and, to a much lesser extent, by Rayleigh scattering, aerosols, and various absorbing gases (e.g., O3, NO2, H2O). A useful measure of the effect of cloud plus aerosol cover is given by the amount that the 331 nm Lambert Equivalent Reflectivity (LER) of a scene exceeds the surface reflectivity for snow/ice‐free scenes after Rayleigh scattering has been removed. Twenty‐eight years of reflectivity data are available by overlapping data from several satellites: N7 (Nimbus 7, TOMS; 331 nm) from 1979 to 1992, SBUV‐2 series (Solar Backscatter Ultraviolet, NOAA; 331 nm) 1985 to 2007, EP (Earth‐Probe, TOMS; 331 nm) 1997 to 2006, SW (SeaWiFS; 412 nm) 1998 to 2006, and OMI (Ozone Measuring Instrument; 331 nm) 2004–2007. Only N7 and SW have a sufficiently long data record, Sun‐synchronous orbits, and are adequately calibrated for long‐term reflectivity trend estimation. Reflectivity data derived from these instruments and the SBUV‐2 series are compared during the overlapping years. Key issues in determining long‐term reflectivity changes that have occurred during the N7 and SW operating periods are discussed. The largest reflectivity changes in the 412 nm SW LER and 331 nm EP LER are found to occur near the equator and are associated with a large El Nino‐Southern Oscillation event. Most other changes that have occurred are regional, such as the apparent cloud decrease over northern Europe since 1998. The fractional occurrence (fraction of days) of high reflectivity values over Hudson Bay, Canada (snow/ice and clouds) appears to have decreased when comparing reflectivity data from 1980 to 1992 to 1997–2006, suggesting shorter duration of ice in Hudson Bay since 1980.
Ventilation changes in intermediate water on millennial time scales in the SE Nordic seas, 65‐14 kyr BP
Authors: Rasmussen Tine L. , Thomsen Erik
Published: December 2008

A glacial epibenthic δ13C record from 773 m water depth in the SE Nordic seas reveals moderate, but distinct changes in the ventilation ∼65,000−14,000 years ago. The Last Glacial Maximum, the warm interstadials, and the shorter stadials are characterized by high δ13C values indicating well‐ventilated intermediate water masses in the Nordic seas. Decreasing δ13C values during the cold Heinrich events signify a reduction in intermediate water ventilation. We attribute the reduction to the development of a halocline causing a stop in convection and outflow from the Nordic seas. The well‐ventilated outflow water is replaced by warmer Atlantic water, which due to the stratification is isolated from the atmosphere. Its initial high δ13C values are reduced due to 'ageing'. We ascribe the lack of response in the subsurface Atlantic Water during the stadials to the smaller geographical extent of these events as compared to the Heinrich events.
Expression of Hemoglobin in Rodent Neurons
Authors: Schelshorn Dominik W , Schneider Armin , Kuschinsky Wolfgang , Weber Daniela , Krüger Carola , Dittgen Tanjew , Bürgers Heinrich F , Sabouri Fatemeh , Gassler Nikolaus , Bach Alfred , Maurer Martin H
Published: December 2008

Hemoglobin is the major protein in red blood cells and transports oxygen from the lungs to oxygen-demanding tissues, like the brain. Mechanisms that facilitate the uptake of oxygen in the vertebrate brain are unknown. In invertebrates, neuronal hemoglobin serves as intracellular storage molecule for oxygen. Here, we show by immunohistochemistry that hemoglobin is specifically expressed in neurons of the cortex, hippocampus, and cerebellum of the rodent brain, but not in astrocytes and oligodendrocytes. The neuronal hemoglobin distribution is distinct from the neuroglobin expression pattern on both cellular and subcellular levels. Probing for low oxygen levels in the tissue, we provide evidence that hemoglobin α-positive cells in direct neighborhood with hemoglobin α-negative cells display a better oxygenation than their neighbors and can be sharply distinguished from those. Neuronal hemoglobin expression is upregulated by injection or transgenic overexpression of erythropoietin and is accompanied by enhanced brain oxygenation under physiologic and hypoxic conditions. Thus we provide a novel mechanism for the neuroprotective actions of erythropoietin under ischemic—hypoxic conditions. We propose that neuronal hemoglobin expression is connected to facilitated oxygen uptake in neurons, and hemoglobin might serve as oxygen capacitator molecule.
Charge-transport-induced dissociation in donor-bridge-acceptor complexes
Authors: Brisker Daria , Peskin Uri
Published: December 2008

Possible mechanisms for charge-transport-induced dissociation in donor-bridge-acceptor complexes are studied. Two mechanisms for dissociation at the molecular bridge are captured within a simple model of an anharmonic bridge vibration coupled nonlinearly to an electronic degree of freedom. A direct mechanism is associated with vibronic excitations to the nuclear continuum and an alternative dissociation mechanism involves intermediate quasibound vibrational states (Feshbach resonances). The two different mechanisms of charge-transport-induced dissociation are analyzed and their interplay as a function of the system parameters is examined. A parameter regime is suggested where the phenomenon should be experimentally accessible.
Characterization of nonthermal Ne–N2 mixture radio frequency discharge
Authors: Rehman N. U. , Zakaullah M. , Khan F. U. , Naseer S.
Published: December 2008

This paper deals with optical emission spectroscopic studies of low pressure (p=0.1⇒0.5 mbar) Ne–N2 capacitively coupled radio frequency (rf) plasma that can be used for plasma nitriding, etc. It reports the methods to calculate the electron temperature (Te) in nonthermal plasmas. Since, the selected Ne I lines, used to calculate electron temperature, are found in corona balance; therefore, it allows us to use modified Boltzmann technique to calculate electron temperature. Langmuir probe is also used to calculate electron temperature and electron energy distribution functions (EEDFs). The measurements are worked out for different discharge parameters like neon percentage, filling pressure and RF power. It is found that electron temperature increases with the increase in neon percentage and decreases with the increase in pressure, whereas excitation temperature (Texc) increases with power, neon percentage, and decreases with pressure. It is also observed that electron temperature measured by Langmuir probe technique is slightly greater than the one measured via modified Boltzmann plot method. The tails of the EEDFs gain height and extend toward the higher energy with the increase in neon percentage in the mixture.
Photochromics
Authors: Kiss Zoltan J.
Published: December 2008

A GREEN MATERIAL MAY TURN BLUE; a pale blue material may turn purple and a white material may turn red as different colors of light shine upon them. This photochromic effect is a property of certain types of inorganic materials. Among those that have been studied are single crystals of calcium fluoride doped with rare-earth elements, and strontium titanate doped with transition metals, and the alkali halide, potassium chloride. If these materials are to be used as light-sensitive media, their sensitivity to light, their rate of switching color and their resolution are of particular importance. Once the photochromic mechanism is completely understood, its technical applications may range from computer memories to three-dimensional television.
Cosmology: A search for two numbers
Authors: Sandage Allan R.
Published: December 2008

AS RECENTLY AS THE 1950's about all that observational cosmology had succeeded in establishing was that galaxies exist and the universe expands. But beginning in the 1960's a flood of new discoveries has enriched our picture of the universe and has begun to provide a basis on which to distinguish between competing cosmological models. There has been a 30-year effort, now drawing to a close, to get precise measurements of two parameters that will provide a crucial test for cosmological models. The two key numbers are the rate of expansion (the Hubble constant H0) and the deceleration in the expansion (q0). The hope is that current research, by determining the extragalactic distance scale for nearby galaxies and searching for exceedingly distant clusters where the redshift is large, will measure both of these numbers to a precision of 15%.
Natural coordinates for electrons in solids
Authors: Zak Joshua
Published: December 2008

THE DESCRIPTION OF A PROBLEM in physics can often be significantly simplified by a suitable choice of coordinates. Usually the choice of the best coördinates is dictated by the symmetry of the problem. Thus for a spherically symmetric potential it is most convenient to use spherical coordinates. In some cases it is very easy to choose the right coordinates; in other cases, the problem is not trivial at all. Here we will discuss the choice of suitable coördinates for the motion of electrons in solids.
Neutron Scattering Verifies Dynamic Scaling
Authors: Lubkin Gloria B.
Published: December 2008

A Brookhaven group has observed the time-dependent behavior of rubidium manganese fluoride near the critical point, and their results agree with dynamic-scaling predictions made by Bertrand Halperin and Pierre Hohenberg (Bell Telephone Laboratories); the agreement is the latest in a series of successes that scaling laws have achieved in predicting critical-point behavior.
Can equations of motion be used in high-energy physics?
Authors: Dirac P. A. M.
Published: December 2008

THE PHENOMENA of high-energy physics have stimulated the development of several new mathematical approaches to calculate and explain the experimental results. Many of these approaches bear little relation to methods used in other areas of physics and many have incomplete or unsatisfactory aspects to them. They have been used with varying success. Methods based on the equations of motion, so necessary for low-energy physics, have been largely abandoned as being intractable to this latest branch of physics. Yet if we believe in the unity of physics, we should believe that the same basic ideas universally apply to all fields of physics. Should we not then use the equations of motion in high-energy as well as low-energy physics? I say we should. A theory with mathematical beauty is more likely to be correct than an ugly one that fits some experimental data.
The stability of the bicycle
Authors: Jones David E. H.
Published: December 2008

ALMOST EVERYONE can ride a bicycle, yet apparently no one knows how they do it. I believe that the apparent simplicity and ease of the trick conceals much unrecognized subtlety, and I have spent some time and effort trying to discover the reasons for the bicycle's stability. Published theory on the topic is sketchy and presented mainly without experimental verification. In my investigations I hoped to identify the stabilizing features of normal bicycles by constructing abnormal ones lacking selected features (see figure 1). The failure of early unridable bicycles led me to a careful consideration of steering geometry, from which—with the aid of computer calculations—I designed and constructed an inherently unstable bicycle.
Magnetic resonance in biology
Authors: Wüthrich Kurt , Shulman Robert G.
Published: December 2008

DURING THE LAST FEW YEARS high-resolution nuclear magnetic-resonance (NMR) spectroscopy has become a powerful technique for investigating the molecular and electronic structure of biological compounds. The high sensitivity and resolution of recently developed spectrometers with superconducting solenoids has made possible many new applications and has yielded data not obtainable by other methods. NMR experiments can be done under conditions similar to the physiological environment of the molecules: in aqueous solution and at body temperature. Thus with NMR it is often possible to establish relations between data on the structure of biological compounds in the solid state, obtained by techniques like x-ray crystallography, and the corresponding molecular properties in solution.
A Visit with Paul McDaniel of the AEC
Authors: Lubkin Gloria B.
Published: December 2008

The AEC Division of Research has an annual budget of $400 million (including capital items), of which about 3/4 goes for physics and the rest to the other physical sciences. That sum makes the division the largest supporter of physics research in the US. To find out how funds are allocated and what the major directions of AEC-funded research are, we spent the day at AEC headquarters with Paul W. McDaniel, director of the division, deputy director Daniel R. Miller, senior associate director Arthur E. Ruark (now retired), Walter E. Hughes (assistant director for administration) and the five assistant program directors.
Long-chain polymer crystals
Authors: Keller Andrew
Published: December 2008

CHAIN FOLDING is one of several unexpected features of long-chain polymer crystals that have come to light during the last decade or so. The polymers that exhibit these features are among our most important synthetic products—nylon and polyethylene, for example—and also abound in nature. The organization of their long-chain molecules therefore has practical as well as fundamental significance. Along with the new discoveries we find simplifications that make certain phenomena more reproducible experimentally, as well as more amenable to theoretical treatment, in polymers than in simpler substances.
Current State of Physics: AEC's View
Authors: Lubkin Gloria B.
Published: December 2008

Because the AEC Division of Research is the largest source of basic-physics support in the US, we asked division director Paul McDaniel and the five assistant program directors, “Where's the action in your field?”
Negative differential conductivity
Authors: Conwell Esther M.
Published: December 2008

UNIQUE ELECTRICAL BEHAVIOR results when a system operates in a region of negative differential conductivity, where current density falls rather than rises with increasing electric fields. This type of conductivity is not infrequently found in semiconductors, where both factors that determine conductivity—density of carriers and their mobility (drift velocity developed per unit field)—may be easily varied. Under conditions of negative differential conductivity there is a tendency to enhance nonuniformities that would otherwise be damped. One of the many dramatic examples of such behavior is the Gunn effect.
Report on AIP—1969
Authors: Scott John T.
Published: December 2008

TRENDS BECAME REALITIES, and 1968's plans turned into 1969's achievements. This was the kind of year it was for the American Institute of Physics, as procedures started or planned during 1968 matured and tendencies observed earlier showed up more strongly.
New Alloy Shows Promise as High-Field Superconducting Magnet
Authors: Lubkin Gloria B.
Published: December 2008

An alloy of niobium, germanium and aluminum, Nb0.8(Al0.75Ge0.25)0.2, has remained superconducting in a 410-kG field at a temperature of 4.2 K. The alloy has the highest known transition temperature, 20.7 K. If the alloy can be made into a wire or tape that can maintain a high current density, it could be used to build a high-field superconducting dc magnet (provided one could make a structure that would hold together under the enormous forces produced by the fields). The best material previously tested, Nb3Sn, has a critical field of about 220 kG at 4.2 K and has been used in commercial magnets for several years.
Computer display systems
Authors: Michael George A.
Published: December 2008

COMPUTER GRAPHICS has been defined in many ways. The clearest definition, however, is still that it is an efficient (perhaps the most efficient) technique for exchanging useful information between computer and user, primarily through pictures. We will be interested here in exploring the uses of computer graphics in physics: the techniques now used and their strengths and weaknesses.
Experimental Relativity Hits the Big Time
Authors: Lubkin Gloria B.
Published: December 2008

The turnout for the third “Cambridge” Conference on Relativity was so large that one speaker complained: “I was told that the meeting would just be a few guys standing around a blackboard. Now I see that even the physics press is here.” At the meeting, held at the Goddard Institute for Space Studies on 8 June, experimenters discussed measurements of gravity waves, bending of electromagnetic waves by the sun, relativistic time delays and the dragging of an inertial frame by the earth.
Second-class currents in beta decay?
Authors: Lubkin Gloria B.
Published: December 2008

Denys Wilkinson has recently raised again the issue of whether or not second-class currents exist in the weak interaction. Second-class currents are defined as having the opposite behavior under G-parity as first-class currents. The G-parity operation is the product of charge conjugation and charge symmetry (which rotates the isotopic spin through 180 deg). Although known to be conserved in strong interactions, G parity might very well not be a useful symmetry for the discussion of weak interactions.
Atmospheric dust increase could lower Earth's temperature
Authors: Lubkin Gloria B.
Published: December 2008

By increasing the dust content of the atmosphere, mankind is risking a significant decrease in the surface temperature of Earth, conceivably sufficient to speed up the onset of the next ice age. So say Ichtiaque Rasool and Stephen Schneider of the Goddard Institute for Space Studies (Science 173, 138, 1971).
Low-temperature thermometers discussed at symposium
Authors: Lubkin Gloria B.
Published: December 2008

A thermometer can be a glass-ceramic capacitor, a superconducting tunnel junction, the He3 melting curve or a paramagnetic salt. These approaches were all discussed at the Fifth Symposium on “Temperature—Its Measurement and Control in Science and Industry,” which was held in Washington at the end of June. They are attempts to find additional ways of measuring temperatures below the range of the platinum resistance thermometer—below about 14 K.
SLAC proposes to boost energy above 50 GeV without superconductors
Authors: Heim Steven M.
Published: December 2008

The plan to fit Stanford's 20-GeV electron linac with superconducting cavities has been dropped, and a new proposal to upgrade performance has been submitted to the AEC. SLAC director Wolfgang Panofsky told us that at present a complete conversion to superconducting cavities would be noncompetitive, both in terms of time and money.
Keeping up with what's going on in physics
Authors: Herschman Arthur
Published: December 2008

In an earlier incarnation, it seems, when I did things in physics rather than for physics, I was dimly aware of having an information problem although I doubt that I would have used that term. I scanned Phys Rev and certain other journals; I attended APS meetings. But somehow key items kept getting lost in the chinks—I found out about them much too late to use them properly. This frustration was compounded every time I decided to work on a new topic; tracking down the basic references was maddening. Later, when I became involved in physics information to the exclusion of physics research, I discovered a quote from Lord Rayleigh that summed up my feelings better than I could:
Surface microtopography
Authors: Young Russell D.
Published: December 2008

It is difficult to imagine a scientist or engineer who has not become painfully aware of the importance of metal surfaces in today's technological world. Indeed, most of the work in surface science has been initiated to explain puzzling surface problems encountered in other fields of science and engineering. An important aspect of this problem has involved the determination of the detailed topography of metal surfaces.
Radio interferometer at Stanford undergoes tests
Authors: Hein Steven M.
Published: December 2008

A high-resolution radio interferometer built at the Stanford Radio Astronomy Institute is now undergoing final tests and calibration. Under development for four years, the array of five 60-ft diameter dish antennas will permit observation of a large number of catalogued radio sources at wavelengths of 2.8 cm.
Shape isomers and the double-humped barrier
Authors: Clark David D.
Published: December 2008

Efforts to express the total binding energy of the nucleus in terms of the atomic number, the number of neutrons and the shape of the nucleus form an old and continuing search. An accurate expression for this function would help us understand many nuclear phenomena, for example the fission barrier: Under what conditions and in what ways do nuclei fly apart?
Polarized light from white-dwarf star
Authors: Lubkin Gloria B.
Published: December 2008

Circularly polarized light has been found in a peculiar white dwarf star; the result suggests that its magnetic field is between 10 million and 100 million gauss, a value to be expected on theoretical grounds. Further observations show that with increasing wavelength the percentage circular polarization rises in the ultraviolet, drops somewhat and then rises sharply again in the infrared at 12 000 Å. There is also a linear polarization, which is present in the uv, disappears at about 6000 Å, then reappears at about 8000 Å perpendicular to the first direction.
APS-AAPT meet in New York
Authors: Rothenberg Marian S.
Published: December 2008

More papers are scheduled for the joint American Physical Society—American Association of Physics Teachers meeting in New York this year than for each of the two previous meetings. The meeting, to be held 1–4 February at the New York Hilton, will probably be better attended than its organizers originally expected; if the number of contributed papers is any guide to attendance, then cuts in funds will probably not keep as many physicists from participating as was earlier believed. According to William W. Havens Jr, executive secretary of the APS, a rush of contributed-paper abstracts descended on the APS office at the deadline date.
The parton: “It works even if you don't believe in it”
Authors: Lubkin Gloria B.
Published: December 2008

A picture of the proton at high energies is emerging from the work of many theorists trying to explain the deep inelastic scattering observed with the SLAC electron linac. These theories visualize the proton as consisting of pointlike constituents with charge less than the electron charge and a spin of 1/2. The deep inelastic scattering, they say, measures the momentum distribution within the proton of these pointlike constituents, be they quarks, partons or “stratons” (a term coined by the Chinese to refer to the stratification of atoms, nuclei and nucleons).
LAMPF meson factory calls for beam-time proposals
Authors: Scott John T.
Published: December 2008

Do you have an idea for an experiment that needs an 800-MeV meson-factory beam? If so, it is time to submit it to the Los Alamos Meson Physics Facility. Louis Rosen, LAMPF director, recently summed up the current status of the accelerator and experimental areas, issued a call for proposals for beam time, and announced the formation of a program committee to consider proposals. The 11-member program committee, plus Rosen as chairman and Darragh Nagle (LAMPF deputy director) as alternate chairman, will hold its first meeting during March.
Frontiers of laser development
Authors: Emmett John L.
Published: December 2008

Early lasers had an extremely limited range of operational parameters, and so were of only limited usefulness. Now, however, laser action has been achieved in almost everything from semiconductor diodes to quinine water. What are some of the results of 12 years of laser research?
Applications in physics research
Authors: Armstrong John A.
Published: December 2008

Now firmly established as a versatile tool in many branches of science, the laser has taken little more than a decade to develop from a research project itself into an instrument for the support of other research. The number of laser applications in industry, technology and pure science is now so great that no one article could possibly cover them all. Here I will be concentrating on scientific applications only, but even so I must adopt a limited scope. The choice of topics has been restricted by posing the question: Of the many scientific investigations conducted with help from lasers, which ones are feasible only because lasers are available? Applications that satisfy this criterion should be the ones that best emphasize the unique capabilities of the laser as a tool of science.
Junction lasers
Authors: D'Asaro L. A. , Ripper José E.
Published: December 2008

Junction lasers are devices in which laser action is produced by a high, nonequilibrium concentration of electrons and holes within the same small region of a semiconductor. Why do we want junction lasers? They are interesting not only from the viewpoint of the physics involved; their properties suit them for industrial application as well. The advantages include:

▸ Smallness: Dimensions of the active region are typically one to two microns, with the largest dimension usually no more than a fraction of a millimeter.

▸ Mechanical stability: The mirrors are an integral part of the laser structure, and are usually formed by cleaving the crystal.

▸ High efficiency: Pulsed junction lasers have operated at as much as 40% external quantum efficiency.

▸ Reasonable power: Continuous output of 40 mW has been obtained at room temperature, with much higher powers at low temperatures. The record peakpower output in a 100-nanosec pulse is about 100 watts.

▸ Versatility: Junction lasers are conveniently pumped with direct current, and their output can be amplitude, frequency or pulse-position modulated into the GHz range. They can lase at wavelengths from 20 to 0.75 microns with the proper choice of semiconductor alloy, and can operate in a single mode. Within the last year, junction lasers have been operated continuously at room temperature.
X-ray parametric conversion—two photons for one
Authors: Rothenberg Marian S.
Published: December 2008

Nonlinear optical effects with visible light have long been known; the first laser was developed 12 years ago. Now Peter Eisenberger and Samuel McCall of Bell Telephone Laboratories have demonstrated nonlinear optical effects at x-ray frequencies. In an experiment that verifies the calculations of Isaac Freund and Barry F. Levine, Eisenberger and McCall have achieved the x-ray analog of optical parametric conversion. They have shown that a single x-ray photon of frequency ωp incident on a crystal can result in the coincidental emission of two x-ray photons ω1 and ω2, where ω1+ω2 = ωp, and the crystal as a whole takes up the recoil, so that both energy and momentum are conserved. A prime reason for interest in the result is the anticipation that the work might be extended to a mixed x-ray–visible experiment that could reveal microscopic details of the behavior of outer-shell electrons in these nonlinear interactions.
ISR collisions at CERN; experiments start this summer
Authors: Lubkin Gloria B.
Published: December 2008

CERN's Intersecting Storage Rings have produced collisions between protons several months ahead of schedule, and experiments are scheduled to begin with the rings around the middle of the year. The first successful collisions occurred on 27 January with 15-GeV protons, and by 17 February the energy had been boosted to 22.5 GeV. When operated at the full energy of 28 GeV, the collisions will correspond to a beam of 1700 GeV hitting a stationary target.
How scientists can really help
Authors: Gell-Mann Murray
Published: December 2008

Last fall I had the honor of speaking at the dedication of a new physics building on the University of California campus at Santa Barbara. As I arrived for the occasion, it struck me how lucky the physicists at Santa Barbara are to be living and working in such a glorious place. The day was clear and I could see the mountains, which contain the surviving frayed specimens of the majestic California condor, and the channel, with the islands on the other side. I had been sailing in the channel and had seen it sometimes sparkling in the sunlight, sometimes shrouded with fog, full of dolphins and sea lions. The campus is built on what used to be my favorite bird-watching place in Southern California, with its curlews, godwits, and phalaropes. Now, for the males of our species, it is a favorite girl-watching place. In any case it is bustling with young Californians presumably seeking knowledge and wisdom, and some older people who are supposed to be able to impart such things.
Latest work on the A2 meson sees no split
Authors: Lubkin Gloria B.
Published: December 2008

Interest ran high at the special session on the A2 meson, held at the Washington APS meeting. Many of those who crowded into the room hoped that a new experiment designed to duplicate the original CERN experiment would at last settle the question of whether or not the A2 is split, that is, does it exist as two identical particles differing only in mass by 3%?
Surprising proton–proton data from CERN
Authors: Lubkin Gloria B.
Published: December 2008

Although the CERN Intersecting Storage Rings have barely been turned on, exciting experimental data are already pouring out. Carlo Rubbia (Harvard) reported, first at the Washington APS meeting and more recently, with additional data, at the Amsterdam International Conference on Elementary Particles on 2 July, surprising results from elastic proton–proton scattering. The experiment was done by a collaboration from Aachen, CERN, Harvard, Genoa and Torino. They measured the scattering for center-of-mass energies of 30.4, 45.0 and, more recently at 56 GeV (which is equivalent to performing a conventional high-energy scattering experiment at about 1400 GeV). Their determination of the slope parameter is in complete contradiction with the predictions of a naive formulation of Regge theory.
The search for high-temperature superconductors
Authors: Matthias Bernd T.
Published: December 2008

Since 1911 superconductivity at room temperature has been the dream of scientists and science-fiction writers alike. Unfortunately for superconductivity, the boundary between these two dream worlds has become totally blurred during the last decade. Still, today, superconductivity at room temperature together with controlled thermonuclear fusion are often mentioned as the two most important and crucial problems in physics relevant to the needs of society. Controlled fusion has now become a distinct possibility, and its progress over the last twenty years has covered many orders of magnitude. During this same time, superconducting transition temperatures have expanded from a range of 0.4 K to 16 K to a range stretching from 0.0002 K to 21 K. If this upper limit could be further increased, not by another order of magnitude, but by a factor of as little as 1.2, or as large as 1.5, superconductivity, while still far from room temperature, would revolutionize our technology. This revolution would encompass electric power transmission, electric motors, high-field electromagnets, and the metallurgy of magnetic suspensions as a whole. In this article I will explain why I believe that this factor of 1.5 is a distinct possibility. I will also explain why room-temperature superconductivity (regardless of a thousand statements by theorists and an equal number of theories) is—in my opinion—pure science fiction.
Electronics with superconducting junctions
Authors: Clarke John
Published: December 2008

Josephson tunneling, an effect predicted and discovered within the last decade, has already formed the basis of a new technology. The “Josephson devices” are ultrasensitive electronic measuring devices that operate at liquid-helium temperatures (1–4K) and exploit the macroscopic-scale quantum properties of superconducting junctions. They have been used to measure, for example, smaller low-frequency voltages and magnetic fields than can be measured with any other methods, and are also being investigated as possible high-frequency detectors and mixers, as thermometers and as computer elements. One of the most important applications of the Josephson effect has been in the precision measurement of e/h in an experiment that avoids any assumptions from quantum electrodynamics (QED); results from this experiment give a convenient and accurate way to express the standard of electromotive force.
ISR experiment shows scaling behavior
Authors: Lubkin Gloria B.
Published: December 2008

One of the first experiments to be done at the new CERN Intersecting Storage Rings has verified certain scaling laws developed by Richard Feynman (Cal Tech) and by C. N. Yang (State University of New York at Stony Brook) and his collaborators. The experiment was just reported by Lazarus G. Ratner (Argonne), Richard J. Ellis and Gianni Vannini (University of Bologna), Bryce A. Babcock, Alan D. Krisch and Jabus B. Roberts (University of Michigan) in the 5 July issue of Physical Review Letters.
A resolution of the clock paradox
Authors: Sachs Mendel
Published: December 2008

Ever since the initial successes of the theory of relativity, physicists and philosophers of science have written a great deal about a paradox that seems to arise when theory tries to answer the question: If two identical stationary clocks in the same inertial frame of reference are synchronized, and if one of them is accelerated away into different inertial frames and then returned to the original inertial frame, would the time readings of the clocks still be synchronized at this later rendezvous?
Five satellites observe short, intense x-ray bursts
Authors: Lubkin Gloria B.
Published: December 2008

“June is busting out all over,” goes the old song. And now it seems that the x-ray sky is doing the same. In December a group using the Astronomical Netherlands satellite reported seeing x-ray bursts from a source in a globular cluster. Soon after, an MIT group, using SAS-3, determined that the bursts from that source were roughly periodic. A Los Alamos team found what appear to be x-ray bursts in several spots. Then the MIT workers and a Harvard group found additional sources of x-ray bursts, some of which are close to the center of our galaxy.
The state of US physics—1976
Authors: Wu Chien-Shiung
Published: December 2008

There are cycles in the history of scientific development just as there are in the affairs of men. To keep a Society such as The American Physical Society healthy and strong in the face of these changes, we must review our objectives periodically and adjust to the demands and needs of the present. In preparing this report on the State of Physics I sought to acquire some sense of the historical development of American physics by browsing through two famous addresses given by Henry Augustus Rowland, the founder and first president of our Society.
Neutron molecular spectroscopy
Authors: Chen Sow-Hsin , Yip Sidney
Published: December 2008

Neutron scattering is playing an increasingly important, and sometimes even unique, role in molecular spectroscopy. In this article we describe a unified approach to the study of molecular forces, correlating thermodynamic, conformational, structural and spectroscopic data on atomic and molecular systems. Our emphasis is on the basic information on the intermolecular potential function that can be extracted from the study of the dynamical properties of these systems. In particular we will describe the development of empirical potentials for chemical systems and discuss current techniques in neutron spectroscopy.
Large-angular separation of particles induced by cascaded deflection angles in optical sorting
Authors: Yuan X.-C. , Zhu S. W. , Bu J. , Sun Y. Y. , Lin J. , Gao Bruce Z.
Published: December 2008

A composite microlens array (MLA) with two cascaded guiding axes has been fabricated to achieve a large lateral separation of an object with different refractive indices or sizes. The MLA projects a composite pattern formed by its focal spots into a microchamber for optical sorting in a microscopic system. This approach enables passive, high power, efficient, and continuous microfluidic sorting without requiring complicated optical assembly. Separation of particles with different refractive indices to a lateral angle of 40° is experimentally demonstrated with moderate laser power.
Variational, V-representable, and variable-occupation-number perturbation theories
Authors: Dunlap Brett I.
Published: December 2008

Density-functional perturbation theory with variationally fitted Kohn–Sham (KS) potentials is described. Requiring the Fock matrix and density matrix to commute through each order of perturbation theory determines the off-diagonal elements of the density matrix, and thus the effect of changing occupation numbers in density-functional perturbation theory. At each order of perturbation theory, the change in occupation numbers at that order enters only the diagonal part of the density matrix. The theory contains no phases, and a limiting process relates the rest of the diagonal density matrix element, obtained from wave function perturbation theory, to the off-diagonal part, obtained by commutation. V-representable density-functional theory is most practical when the KS potential is expanded in a finite basis to create the Sambe–Felton (SF) potential of analytic density-functional theory. This reduces the dimensionality of perturbation theory from order N2 in the orbital basis to order N in the SF basis. Computing the (occupied-virtual)2, i.e., N4, sum over states once at the end of a self-consistent-field molecular orbital calculation removes the orbitals from all higher orders of perturbation theory. The rank-N2 iterative coupled-perturbed equations are replaced by rank-N matrix inversion, to fit variationally the perturbed SF potential at each order. As an example of the 2n+1 rule of perturbation theory, the variational, first-order potential is used to give precise second and third derivatives of the energy with respect to occupation number. The hardness and hyperhardness are computed for a standard set of molecules. Both are essentially independent of how the variational SF potential is constrained for four different constraint combinations. With variational fitting, the precision of derivatives and the fidelity of the fit to the SF potential are not related. Analytic derivatives are accurate to machine precision for any constraint and all fitting basis sets.
Evolution of electron holes in two electron population plasmas
Authors: Saharia K. , Goswami K. S.
Published: December 2008

Formations and existence conditions of electron holes from one-dimensional Vlasov simulations in a collisionless unmagnetized two component plasma are presented. Kinetic simulation results quantitatively confirm the Fast Auroral SnapshoT (FAST) observations of large amplitude (up to 500mV∕m) solitary waves at the edge of the auroral kilometric radiation (AKR) source region.
Surface stress effect on bending resonance of nanowires with different boundary conditions
Authors: He Jin , Lilley Carmen M.
Published: December 2008

The influence of surface stress on the resonance frequencies of bending nanowires was studied by incorporating the generalized Young–Laplace equation into Euler–Bernoulli beam theory. Theoretical solutions are presented for three different boundary conditions. The overall Young’s modulus was used to study the surface stress influenced mechanical behavior of bending nanowires and a comparison was made for the overall Young’s modulus calculated from nanowires in resonance and static bending. It was found that the overall Young’s modulus can be simply related to a nondimensional surface effect factor via empirical formulae.
Sound generation by a vortex ring collision with a wall
Authors: Nakashima Yoshitaka , Inoue Osamu
Published: December 2008

Sound generation by a collision of a vortex ring with a free-slip/no-slip wall is investigated by using a direct numerical simulation. The three-dimensional, unsteady, compressible Navier–Stokes equations are solved by a finite difference method, not only for a near-vortical flow field but also for a far-acoustic field. By comparing free-slip and no-slip problems, we discuss the effects of the no-slip boundary condition at the wall surface on the near and far fields. In addition, a new three-dimensional expression to predict the far-field sound pressure is proposed based on the theory of vortex sound. Then, by using the new expression, we discuss the relation between the vortical phenomenon and the acoustic wave modes. For normal collision with a no-slip wall, a secondary vorticity layer is produced on the wall surface because of the no-slip condition, and then forms secondary and tertiary vortex rings. The mutual interaction between the primary and secondary/tertiary vortex rings induces a rebounding motion of the primary vortex ring. The sound pressure radiated by the collision has a quadrupolar nature, and its generation is closely related to the rebounding motion. For oblique collision with a no-slip wall, the secondary vortical structure consists of helical vortex lines. The variations in vorticity moment associated with the formation of the helical vortex lines affect the quadrupole emission. In this case, in addition to the quadrupole and octupole modes, the dipole mode is also observed which is not observed in the free-slip case. The new expression proposed shows that the generation of the dipole in the no-slip case is related to the wall shear stress and the velocity distribution.
Electron density topology of cubic structure I Xe clathrate hydrate at high pressure
Authors: Flacau Roxana , Desgreniers Serge , Tse John S.
Published: December 2008

In this report, we present a detailed powder x-ray diffraction study of the structural properties and charge density topology of structure I Xe clathrate hydrate under high pressure and room temperature. The pressure dependence of the structural parameters was determined by applying a Rietveld analysis to the experimental data. The combined Rietveld/maximum entropy method was used to derive the most probable charge density distribution at each pressure. Our results show that the charge density distribution of the encaged Xe atoms differs depending on the type of host cage at all pressures. Spherical electron density distributions were observed for the Xe atoms in the small cages while the atoms in the large cages showed longitudinal elongated electronic distributions. Along with the observed cage deformations, the change in electronic density distribution represents a clear indication that the guest-host interaction differs significantly between the small and large cages at high pressures. A similar behavior has been previously reported in low-temperature studies of methane clathrate hydrate.
Crystal structure and multiferroic properties of Gd-substituted BiFeO3
Authors: Khomchenko V. A. , Kiselev D. A. , Bdikin I. K. , Shvartsman V. V. , Borisov P. , Kleemann W. , Vieira J. M. , Kholkin A. L.
Published: December 2008

Room-temperature crystal structure, local ferroelectric, and magnetic properties of the Bi1−xGdxFeO3 (x=0.1,0.2,0.3) polycrystalline samples have been investigated by x-ray diffraction, piezoresponse force microscopy, and magnetometry techniques. Performed measurements have revealed a sequence of the composition-driven structural phase transitions R3c→Pn21a (occurs at x∼0.1) and Pn21a→Pnma (takes place within the concentrational range of 0.2<x<0.3). The latter structural transformation is attributed to the substitution-induced suppression of the polar displacements. Gd substitution has been shown to effectively induce the appearance of the spontaneous magnetization, thus indicating a promising way for improving multiferroic properties of antiferromagnetic BiFeO3.
More laser power with electron-beam control
Authors: Scott John T.
Published: December 2008

Our best hope for an ultrahigh-power laser with good beam quality appears to lie with molecular gas-discharge devices. The development of these lasers has so far been limited by the difficulty of maintaining stable discharge conditions and by the impossibility of producing a design scalable in all its parameters—size, pressure, and so on. That is, a certain discharge device that runs well cannot in general be rebuilt twice the size for increased power. Now at least three groups in the US and one in Russia are experimenting with devices embodying electron-beam-controlled discharges to solve some of these problems.
Introducing scale symmetry
Authors: Jackiw Roman
Published: December 2008

When symmetries are present the solution of almost any physical problem is simplified, because we can get at the properties of a system without completely solving all the equations that describe the system. In high-energy physics, symmetry principles have been studied with an eye to circumventing two obstacles to the understanding of elementary particles: lack of precise knowledge about interparticle forces (with the exception of electromagnetism) and the mathematical intractability of any realistic models that propose to explain observed particle phenomena.
Electron Spectroscopy or Chemical Analysis
Authors: Carlson Thomas A.
Published: December 2008

Although electron energy spectra have been studied for years, only more recently has their usefulness in chemical-structure problems been appreciated. Now we appear to have a new analytic method that can describe the complete electronic structure of a molecule by measuring binding energies for all the orbitals. Optical spectroscopy, in comparison, measures only the first ionization potentials, except for the very simplest molecules. And electron emission spectra, we shall see, are also useful in such applied work as protein structure analysis and investigations of environmental pollutants.
Joint meeting goes West
Authors: Rothenberg Marian S.
Published: December 2008

This year the joint annual meeting of The American Physical Society and the American Association of Physics Teachers will be in San Francisco for the first time. What will be special about this meeting other than its location? This is the first year that the new APS Forum on Physics and Society has participated; three symposia have been arranged by the group. Energy sources and production will be the topic at two other related sessions. And two sessions, one organized by AAPT and the other by APS, will deal with alternative directions for physics education.