bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of New Superconductors Revive Old Questions
Authors: Khurana Anil
Published: January 2008

Lanthanum copper oxide, which is now regarded as the prototype for the new high-temperature superconductors, undergoes a phase transition to an antiferromagnetic state. The critical temperature for this transition, at which the magnetic moments on copper ions begin to order antiferromagnetically, depends sensitively on the oxygen concentration. Confirmation of the existence of this antiferromagnetic phase in La2CuO4−y and the determination, using neutron scattering, of the arrangement of magnetic moments in it provided definitive evidence last summer for the importance of magnetic phenomena in the new superconducting oxides. Philip Anderson (Princeton University) had proposed in January 1987 that superconductivity in La2CuO4−y doped with barium or strontium, which had been confirmed only two months earlier, arose from novel, short-range antiferromagnetic correlations between copper spins.
CLEO '88 To Be Held In Anaheim
Authors: Marynowski Margaret
Published: January 2008

The eighth Conference on Losers and Electro-Optics will feature technical sessions on laser technologies and applications, awards and the year's largest exhibit of laser and electro-optical equipment.
Negative Calcium Ions Are Stable—In Spite of the Conventional Wisdom
Authors: Schwarzschild Bertram
Published: January 2008

Most atomic species—roughly 80% of the periodic table—can form stable negative ions in their gaseous phase. The most notable and easily understood exceptions are the noble gas atoms, the symmetry of whose completely filled electron shells offers no handhold for a would-be extra tenant. The alkaline earths—calcium, strontium, barium and their group IIA cousins—are similarly inhospitable, or so the standard textbooks assure us. Two back-to-back reports in a recent issue of Physical Review Letters have now disabused us of this venerable assurance.
Are the Ultra-Energetic Cosmic Gammas Really Photons?
Authors: Schwarzschild Bertram
Published: January 2008

A renaissance of cosmic-ray physics in this decade has been doling out tantalizing bits of evidence for extraordinary phenomena involving photons far more energetic than one can make in the laboratory. A 1983 report of observations at the University of Kiel's extensive-air-shower array argued that the mysterious x-ray and radio source Cygnus X-3 was sending us photons of energy exceeding 1015 electron volts (1000 TeV) from half way across the Galaxy. Cosmic photons of more than a few TeV had never before been seen to come from “point sources.” Nor could such energies be explained by conventional models of cosmic-ray acceleration. Furthermore, it appeared that these ultrahigh-energy photons, when they hit the upper atmosphere, were behaving very differently from the confident expectations of particle theory.
Ballistic Electron Transport Through a Narrow Channel is Quantized
Authors: Khurana Anil
Published: January 2008

The electrical conductance of a short and narrow conducting channel is quantized in units of 2e2/h, a team of experimenters from the Netherlands recently reported. The effect was independently observed by experimenters at Cambridge University at much the same time as its discovery by the Dutch group. In the new effect the conductance of the channel, which connects two-dimensional reservoirs of electrons, remains constant at an integral multiple of 2e2/h for a range of channel widths but jumps sharply to the next higher integral multiple of 2e2/h at some critical values of the width.
Committe Reviews DOE Inertial-Confinement Fusion Program
Authors: Schwarzschild Bertram
Published: January 2008

Inertial-confinement fusion clearly works. It's demonstrated every time a hydrogen bomb is detonated. But is it possible to ignite a small deuteriumtritium pellet under controlled conditions in the laboratory—driving the requisite implosion with anything less drastic than a fission bomb?
Two-dimensional symmetry breaking of fluid density distribution in closed nanoslits
Authors: Berim Gersh O. , Ruckenstein Eli
Published: January 2008

Stable and metastable fluid density distributions (FDDs) in a closed nanoslit between two identical parallel solid walls have been identified on the basis of a nonlocal canonical ensemble density functional theory. Similar to Monte Carlo simulations, periodicity of the FDD in one of the lateral (parallel to the walls surfaces) directions, denoted as the x direction, was assumed. In the other lateral direction, y direction, the FDD was considered uniform. It was found that depending on the average fluid density in the slit, both uniform as well as nonuniform FDDs in the x direction can occur. The uniform FDDs are either symmetric or asymmetric about the middle plane between walls; the latter FDD being the consequence of a symmetry breaking across the slit. The nonuniform FDDs in the x direction occur either in the form of a bump on a thin liquid film covering the walls or as a liquid bridge between those walls and provide symmetry breaking in the x direction. For small and large average densities, the stable state is uniform in the x direction and is symmetric about the middle plane between walls. In the intermediate range of the average density and depending on the length Lx of the FDD period, the stable state can be represented either by a FDD, which is uniform in the x direction and asymmetric about the middle of the slit (small values of Lx), or by a bump- and bridgelike FDD for intermediate and large values of Lx, respectively. These results are in agreement with the Monte Carlo simulations performed earlier by other authors. Because the free energy of the stable state decreases monotonically with increasing Lx, one can conclude that the real period is very large (infinite) and that for the values of the parameters employed, a single bridge of finite length over the entire slit is generated.
Phase separation in three-component lipid membranes: From Monte Carlo simulations to Ginzburg-Landau equations
Authors: Reigada Ramon , Buceta Javier , Gómez Jordi , Sagués Francesc , Lindenberg Katja
Published: January 2008

Preferential affinity of cholesterol for saturated rather than unsaturated lipids underlies the thermodynamic process of the formation of lipid nanostructures in cell membranes, that is, of rafts. In this context, phase segregation of two-dimensional ternary lipid mixtures is formally studied from two different perspectives. The simplest approach is based on Monte Carlo simulations of an Ising model corresponding to two interconnected lattices, from which the basic features of the phenomenon are investigated. Then, the coarse-graining mean field procedure of the discrete Hamiltonian is adapted and a Ginzburg-Landau-like free energy expression is obtained. From this latter description, we construct kinetic equations that enable us to perform numerical simulations and to establish analytical phase separation criteria. Application of our formalism in the biological context is also discussed.
Effect of ionized protein residues on the nucleation pathway of protein folding
Authors: Djikaev Y. S. , Ruckenstein Eli
Published: January 2008

Using a ternary nucleation formalism, we have recently [Y. S. Djikaev and E. Ruckenstein, J. Chem. Phys. 126, 175103 (2007)] proposed a kinetic model for the nucleation mechanism of protein folding. A protein was considered as a heteropolymer consisting of hydrophobic, hydrophilic, and neutral beads with all the bonds having the same constant length and all the bond angles equal and fixed. In this paper, we further develop that model by taking into account of the ionizability of some of the protein residues. As previously, an overall potential around the cluster wherein a protein residue performs a chaotic motion is considered to be a combination of the average dihedral and average pairwise potentials (the latter now including an electrostatic contribution for ionized residues) assigned to the residue and the confining potential due to the polymer connectivity constraint. The overall potential as a function of the distance from the cluster has a double well shape (even for ionized beads) which allows one to determine the rates of emission and absorption of residues by the cluster by using a first passage time analysis. Assuming the equality of the ratios of the numbers of negatively and positively ionized residues in the cluster and in the entire protein, one can keep the modified model within the framework of the ternary nucleation formalism and evaluate the size and composition of the nucleus and the protein folding time as in the previous model. As an illustration, the model is again applied to the folding of bovine pancreatic ribonuclease consisting of 124 amino acids, whereof 40 are hydrophobic, 81 hydrophilic (of which 10 are negatively and 18 positively ionizable), and 3 neutral. Numerical calculations at pH=6.3, pH=7.3, and pH=8.3 show that for this protein the time of folding via nucleation is significantly affected by electrostatic interactions only for the unusually low pH of 6.3 and that among all pH’s considered pH=7.3 provides the lowest folding time.
Dielectric-loaded surface plasmon-polariton waveguides at telecommunication wavelengths: Excitation and characterization
Authors: Holmgaard Tobias , Bozhevolnyi Sergey I. , Markey Laurent , Dereux Alain
Published: January 2008

The excitation and propagation of strongly confined surface plasmon-polariton (SPP) waveguide modes, supported by 500-nm-wide and 550-nm-high dielectric ridges fabricated on smooth gold films, are investigated at telecommunication wavelengths using a scanning near-field optical microscope. Different tapering structures for coupling of SPPs, excited at bare gold surfaces, into dielectric-loaded SPP waveguide (DLSPPW) modes are considered. The DLSPPW mode confinement and propagation loss are characterized. The DLSPPW mode propagation along an S bend having the smallest curvature radius of 2.48μm is shown, demonstrating the potential of DLSPPW technology for the realization of high-density photonic integrated circuits.
Martensitic phase transformation in rapidly solidified Mn50Ni40In10 alloy ribbons
Authors: Sánchez Llamazares J. L. , Sanchez T. , Santos J. D. , Pérez M. J. , Sanchez M. L. , Hernando B. , Escoda Ll. , Suñol J. J. , Varga R.
Published: January 2008

Heusler alloy Mn50Ni40In10 was produced as preferentially textured ribbon flakes by melt spinning, finding the existence of martensitic-austenic transformation with both phases exhibiting ferromagnetic ordering. A microcrystalline three-layered microstructure of ordered columnar grains grown perpendicularly to ribbon plane was formed between two thin layers of smaller grains. The characteristic temperatures of the martensitic transformation were MS=213K, Mf=173K, AS=222K, and Af=243K. Austenite phase shows a cubic L21 structure (a=0.6013(3)nm at 298K and a Curie point of 311K), transforming into a modulated fourteen-layer modulation monoclinic martensite.
Critical and slow dynamics in a bulk metallic glass exhibiting strong random magnetic anisotropy
Authors: Luo Q. , Zhao D. Q. , Pan M. X. , Wang W. H.
Published: January 2008

The nature of the magnetic state of strong random magnetic anisotropy (RMA) remains elusive. It is unclear whether the RMA and the Ising spin glass systems belong to the same class or not. Here, we demonstrate, by investigations of the static, critical, and slow dynamic properties of a Dy-base bulk metallic glass (BMG), the RMA can be classified to a universal class of glass different from Ising spin glass. The results have implication for understanding the connection between RMA and spin glass and the subtle role of anisotropy in the magnetic transition of disorder and frustrated systems. On the other hand, our study has the significance in developing efficient BMGs for functional applications.
Optical manipulation of paramagnetic particles with on-chip detection using spin valve sensors
Authors: Lui L. W. Y. , Li K. B. , O’Shea S. J. , Sow C. H.
Published: January 2008

In this work, we present a combinatory approach where optical tweezers were used to trap and position a single superparamagnetic particle over a spin valve sensor, with the particle then detected by the sensor. This approach is demonstrated using superparamagnetic particles of 2μm together with a spin valve sensor with dimensions of 2×4μm2, whereby a single magnetic particle was positioned over the sensor and a corresponding drop in the voltage across the sensor was detected. The results are explained using a simple model where the particle is treated as a pure magnetic dipole.
Existence of universal entangler
Authors: Chen Jianxin , Duan Runyao , Ji Zhengfeng , Ying Mingsheng , Yu Jun
Published: January 2008

A gate is called an entangler if it transforms some (pure) product states to entangled states. A universal entangler is a gate which transforms all product states to entangled states. In practice, a universal entangler is a very powerful device for generating entanglements, and thus provides important physical resources for accomplishing many tasks in quantum computing and quantum information. This paper demonstrates that a universal entangler always exists except for a degenerated case. Nevertheless, the problem how to find a universal entangler remains open.
Vacuum Tunneling: A New Technique for Microscopy
Authors: Quate Calvin F.
Published: January 2008

I was introduced to vacuum tunneling high over the Atlantic while flying to London in April 1982. For months prior to that flight I had been fretting about the future work of our microscopy research group at Stanford. We had just completed our work in acoustic microscopy and were looking for new directions. I was considering a variety of problems, such as the building of an x-ray microscope, but nothing would fall into place. I thought that a trip to a conference in London might provide some time to get away and think. On the way to the airport I stopped by my office and picked up the latest issue of this magazine. I think we were over Iceland when I opened it and found a report (PHYSICS TODAY, April 1982, page 21) on a new form of scanning microscopy being developed in Zurich. In London, I changed my travel plans and went to Zurich. It proved to be the start of an adventure for our group, an adventure that still continues, undiminished in excitement.
The Birth of the Solid-State Physics Community
Authors: Weart Spencer R.
Published: January 2008

In 1930 solid-state physics did not exist. The very term was unknown; nor was there any intellectual or social entity to which the term could have applied. Certainly there flourished a number of specialties—for example, the electron theory of metals—that would eventually fall within the field of solid-state physics. However, there was no feeling that physicists who studied solids should be distinguished as a group from those who studied gas spectra, for instance, or nuclear reactions. Thirty years later the situation had entirely changed. The term “solid-state physics” not only was familiar in 1960, but could be attached to a number of institutions: university chairs, journals, research groups and even buildings devoted entirely to the subject.
Reflections on Early Work on ‘Big Bang’ Cosmology
Authors: Alpher Ralph A. , Herman Robert
Published: January 2008

Primordial nucleosynthesis of the lightest elements in the early universe and stellar nucleosynthesis of the heavier elements are by now both reasonably well understood. The classic paper on stellar nucleosynthesis of elements heavier than helium was published in 1957 by Margaret Burbidge, Geoffrey Burbidge, William Fowler and Fred Hoyle, and that on light-element primordial nucleosynthesis in 1967 by Robert V. Wagoner, Fowler and Hoyle. The physical conditions required for primordial element-building also provide useful insights into—and constraints on—the allowable number, type and degeneracy of neutrinos, the number and properties of weakly interacting particles, the mean density of luminous matter, and the entropy per baryon, or photon-to-baryon ratio. For many years that ratio was the one “free” parameter in the canonical Big Bang model, although we, with George Gamow, and others had long since suggested that it should not be considered free, but should be explained as a natural consequence of the physics of the very early universe.
Atomic Spectroscopy and Astrophysics
Authors: Goldberg Leo
Published: January 2008

Most of our knowledge of the universe has come from the study of spectral lines emitted by astronomical objects. The wavelengths of the lines identify unequivocally the elements that are present, their states of ionization and the velocities with which they are moving. Thus the shifts to lower energy of the spectral line wavelengths for distant galaxies—the redshifts—demonstrate that the universe is expanding (see the article by Ralph Alpher and Robert Herman on page 24). The intensities of spectral lines give us information on the densities, temperatures and abundances of the elements in the environment in which the lines are emitted or absorbed. However, to determine these physical quantities we also need to know atomic and molecular parameters such as transition probabilities and oscillator strengths, so it is no accident that much of laboratory spectroscopy has come to be known as laboratory astrophysics. Millions of spectral lines are useful as diagnostic probes, and the assembly of reliable tables of atomic and molecular data is an essential part of astronomical spectroscopy.
Clouds of Trapped Cooled Ions Condense into Crystals
Authors: Levi Barbara Goss
Published: January 2008

Photographs of ions trapped by electric and magnetic fields are revealing ordered structures ranging from a few ions in crystalline arrays to thousands of ions arranged on the surfaces of concentric shells. In some experiments with a handful of singly charged ions, varying certain parameters of the trap causes the regular structures to dissolve rapidly into clouds and just as rapidly to recrystallize—behavior resembling a phase change or an order-to-chaos transition. All these regular structures occur in systems with well-defined constituents and interactions. As such they can provide useful insights into collective phenomena such as cluster formation, Wigner crystallization and other strongly coupled plasmas.
Universal Singular Behavior is Observed in Quantum Hall Effect
Authors: Khurana Anil
Published: January 2008

Almost eight years after the discovery of the quantum Hall effect, a group led by Daniel Tsui (Princeton University) has observed universal scaling behavior that might provide an important clue to how the effect could be reconciled with the quantum theory of electrical resistance. At issue is a scaling law of that theory. As enunciated in 1979, the law applies only to electrons in the absence of a magnetic field. If, however, the law also applied to electrons in the presence of the strong magnetic fields used in quantum Hall effect measurements, then both the Hall conductance and the longitudinal conductance of electrons confined in a plane would have a vanishingly small value. (In Hall effect measurements, the sample is placed in perpendicular electric and magnetic fields. The Hall conductance is a measure of the current flow in a direction normal to both the electric field and the magnetic field.)
Pions to Quarks: Particle Physics in the 1950s
Authors: Brown Laurie M. , Dresden Max , Hoddeson Lillian
Published: January 2008

The years 1947 to 1963, here freely referred to as “the fifties,” form a well-marked period in the history of particle physics, not only in scientific discoveries, but also in technical developments, the scale and cost of projects, and social organization.
Theory of Random Magnets
Authors: Fisher Daniel S. , Grinstein Geoffrey M. , Khurana Anil
Published: January 2008

Much of the enormous increase in our understanding of collective phenomena during the past few decades has arisen from the study of magnetic systems. The formulation of concepts such as universality, broken symmetry, and scaling near continuous phase transitions, as well as the development of the powerful ideas of the renormalization group, have been strongly influenced by research in magnetism. This is due in part to the availability of a host of experimentally accessible magnetic systems, and in part to the remarkable fact that simple models of magnetism capture the essential physics of the phases and ordering transitions in more complicated systems.
Edmond Halley, Geophysicist
Authors: Evans Michael E.
Published: January 2008

The recent passage of Comet Halley produced a great deal of scientific activity as well as the usual plethora of books, articles and diverse paraphernalia. So why add more? My excuse is that although Edmond Halley is famous for his comet—and rightly so—his contributions to scientific knowledge were much wider than is generally appreciated. Indeed, cometary matters represent a very small fraction of his work. Even if he had made none of his astronomical and other contributions, however, Halley would have left us an important legacy as one of the world's first geophysicists.
Merle Antony Tuve: Pioneer Nuclear Physicist
Authors: Cornell Thomas D.
Published: January 2008

Despite the effects of the Depression on the institutions that supported its work, the American physics community of the 1930s was booming intellectually. In particular, many of its members were contributing significantly to the rapid emergence of nuclear physics as a distinctive field of research. Among the most active of these participants was Merle Antony Tuve.
The Birth of the Laser
Authors: Bromberg Joan Lisa
Published: January 2008

In a recent study of early radio, Hugh G. J. Aitken (Amherst College) wrote: “We are inclined to think of invention as an act rather than a process because of the bias built into our patent laws. If property rights in a new discovery are to be secured, it is important to be able to establish priority in time…. This bias, however, should not be allowed to corrupt our historical interpretations…. [Invention is] a process with considerable duration in time, one to which many individuals contribute in a substantial way.” The birth of the laser was such a process. In this account, which I confine to events in the United States, I take the duration of the process to be the period between September 1957, when Charles H. Townes of Columbia University first wrote into his notebook his preliminary ideas for “a maser at optical frequencies,” and December 1960, when Ali Javan, William Bennett and Donald Herriott of Bell Telephone Laboratories operated the first continuous laser. The people I include will be those who had initiated substantial laser research programs before July 1960, when Theodore H. Maiman of Hughes Research Laboratories announced his ruby laser. I shall review the work of these scientists and address two questions: First, what drew these people into laser research? Second, why were they able to command the resources needed to pursue it?
Medical Applications of Lasers
Authors: Deutsch Thomas F.
Published: January 2008

The use of lasers in medicine began soon after the first ruby laser was invented in 1960. In recent years the number and variety of applications of lasers to biology and medicine has been increasing rapidly. I will review some of these applications, with emphasis on the physical mechanisms and the technology. After an overview of the various types of laser-tissue interactions, I give some examples of how these interactions are exploited in medicine.
Chaos: How Regular Can It Be?
Authors: Chernikov Alexander A. , Sagdeev Roald Z. , Zaslavsky George M.
Published: January 2008

Forty years ago Albert Einstein wrote to Max Born, “God does not play dice.” Their correspondence dealt with the probabilistic interpretation of quantum theory, which Einstein opposed. He searched for a more direct analogy with classical mechanics that would consider deterministic processes free from probabilistic uncertainty.
AAPT's Physics Teaching Resource Agent Program
Authors: Von Hise Yverte A. , Nelson Jim
Published: January 2008

The problem we have come to call scientific and mathematical illiteracy will produce repercussions for many years unless we address it promptly. Many states have attempted to remedy the situation by increasing their high-school graduation requirements in science and mathematics. Unfortunately, this effort may fail, for two reasons. Not only are there too few qualified science teachers to teach the new classes, but the average age of science teachers in the system is increasing—and no source of new teachers is immediately identifiable.
Climate and the Earth's Radiation Budget
Authors: Ramanathan V. , Barkstrom Bruce R. , Harrison Edwin F.
Published: January 2008

Among the first payloads aboard satellites in the early 1960s were instruments for measuring the Earth's radiation budget. The radiation budget consists of the incident and reflected sunlight and the long-wave (infrared and far infrared) radiation emitted to space. The source for the recent spurt in scientific and public interest in the greenhouse effect and global warming is the alteration of the radiation budget by the anthropogenic emission of trace gases into the atmosphere.
Reminiscences of Landau
Authors: Khalatnikov I. M.
Published: January 2008

In 1932 Lev Davidovich Landau moved from Leningrad to Kharkov. The lectures he started giving at Kharkov University immediately drew the attention of the students. Those who knew Landau can readily imagine the charisma he emanated. Besides, those years were the golden age of theoretical physics. Quantum mechanics had already been created, but the wide field of its applications was still to be explored. In particular, the quantum theory of the solid state began to sprout around that time. Landau's sociable disposition and his readiness to discuss physics immediately stimulated the formation of a group of young physicists and students who were keen on working with him.
Landau's Attitude Toward Physics and Physicists
Authors: Ginzburg Vitaly L.
Published: January 2008

On 22 January 1988 in Moscow, we celebrated Lev Davidovich Landau's 80th birthday in the same hall at the Institute of Physical Problems where Landau held his seminars and where I used to see him. Perhaps that is why the thought haunted me at that memorable meeting that Landau might have been among us that day, sitting there in the front row as he used to, and I expressed it in my opening remarks. But, alas, more than 27 years have already passed since Landau conducted his last seminar: On 7 January 1962, Landau met with a car accident and was disabled for the rest of his life. He died on 1 April 1968.
The Concept of Mass
Authors: Okun Lev B.
Published: January 2008

Mass is one of the most fundamental concepts of physics. Understanding and calculating the masses of the elementary particles is the central problem of modern physics, and is intimately connected with other fundamental problems such as the origin of CP violation, the mystery of the energy scales that determine the properties of the weak and gravitational interactions, the compositeness of particles, supersymmetry theory and the properties of the not-yet-discovered Higgs bosons.
Neutrino Oscillations and Solar Neutrinos
Authors: Wolfenstein Lincoln , Beier Eugene W.
Published: January 2008

The neutrino is the elementary particle postulated by Wolfgang Pauli to account for the apparent nonconservation of energy in nuclear beta decay. Neutrinos are now believed to exist in at least three varieties, or “flavors,” labeled νe, νμ and ντ and distinguished by the way they interact. There are also three antineutrinos, ν̄e, ν̄μ and ν̄τ.
Remote Sensing Of The Earth: A Synoptic View
Authors: Schott John W.
Published: January 2008

Remote sensing of the Earth may be traced back to the first prehistoric explorer who climbed a nearby hill to study the lay of the land. But it was not until 150 years ago that Louis Jacques Mande Daguerre and Joseph Nicéphore Niepce invented the daguerreotype, which provided the foundation for modern photography and, through it, a means to record a remotely sensed image. Twenty years later, in 1859, Gaspard Félix Tournachon Clateu (later known in the literature as Félix Nadar) took the first known aerial image from a balloon. That set the stage for the use of balloon-based cameras by Union troops to photograph Confederate defenses around Richmond, Virginia, during the Civil War. Kites were also used as platforms for early photography. A particularly notable example is a very-large-format image (1.4×2.4 m) taken by G. R. Lawrence after the 1906 San Francisco earthquake and fire. A cluster of 17 kites flown from a ship in the bay carried the camera aloft. The first known photos from an aircraft were taken in 1909 in Italy by a passenger in a plane piloted by Wilbur Wright. Aerial photography was used for reconnaissance during World War I and was further developed for that purpose during World War II, resulting in the creation of special cameras and films, including color and color infrared film for detecting camouflage.
Feynman and Partons
Authors: Bjorken James D.
Published: January 2008

For me, as for so many others, Richard Feynman is a special hero. He became so while I was learning quantum electrodynamics in graduate school at Stanford. The course happened to be organized historically, and for several months it was taught in the 1930s style out of Heitler's classic text, using old-fashioned perturbation theory and Dirac matrices α and β (but not γ). After this trial by fire came a seemingly endless, gloomy, turgid mass of field-quantization formalism. When Feynman diagrams arrived, it was the sun breaking through the clouds, complete with rainbow and pot of gold. Brilliant! Physical and profound! It was instant conversion to discipleship.
Richard Feynman and Condensed Matter Physics
Authors: Pines David
Published: January 2008

From 1953 to 1958 Richard Feynman worked primarily on problems in condensed matter physics. Of the 14 scientific papers he published during this period, ten are devoted to the physics of liquid helium, one discusses the relation between superconductivity and superfluidity, and one deals with the motion of slow electrons in polar crystals, the “polaron” problem; the remaining two describe work Feynman had carried out on quantum electrodynamics and hadron physics earlier at Cornell. He brought to the condensed matter problems the same remarkable originality and physical insight that characterized his earlier work on quantum electrodynamics and the path integral method, and through his contributions he made a lasting impact on the subfields of low-temperature physics and statistical mechanics.
Cavity Quantum Electrodynamics
Authors: Haroche Serge , Kleppner Daniel
Published: January 2008

Ever since Einstein demonstrated that spontaneous emission must occur if matter and radiation are to achieve thermal equilibrium, physicists have generally believed that excited atoms inevitably radiate. Spontaneous emission is so fundamental that it is usually regarded as an inherent property of matter. This view, however, overlooks the fact that spontaneous emission is not a property of an isolated atom but of an atom-vacuum system. The most distinctive feature of such emission, irreversibility, comes about because an infinity of vacuum states is available to the radiated photon. If these states are modified—for instance, by placing the excited atom between mirrors or in a cavity—spontaneous emission can be greatly inhibited or enhanced.
In Defense of Confidentiality
Authors: Lazarus David
Published: January 2008

On 15 March 1989 the principle of confidentiality in peer review received a strong legal foundation, in the form of a unanimous decision of the United States Court of Appeals for the Federal Circuit. Important principles frequently get established with little trumpeting and under innocuous rubrics: Roe v. Wade, Brown v. Board of Education. This decision goes by the name of Solarex Corporation and RCA Corporation v. Arco Solar Inc v. The American Physical Society, Fed. Cir. No. 88-1542. The consequences of the judgment on the side issue between Arco Solar and APS that arose from this suit should go far beyond the immediate case, into the realm of protection of the confidentiality of all the thousands of referees who have reviewed and will review papers for the journals of The American Physical Society and for other scholarly journals.
US-Soviet Research in Arms Control
Authors: Sweet William
Published: January 2008

Much of the excitement may seem to have gone out of arms control since the high drama of Reykjavik—the October 1986 summit meeting in which President Reagan and General Secretary Gorbachev came close to reaching a historic agreement. Yet even in these much more quiet times the US and Soviet governments continue to conduct promising negotiations across a broad range of arms control issues. And still more quietly, but not far behind the scenes, scientists from the US and USSR carry on more informal but increasingly well-organized discussions of more distant and more daring ways of strengthening limits on nuclear arms and of furthering a long-term process of disarmament
Arms Control Physics: The New Soviet Connection
Authors: Von Hippel Frank
Published: January 2008

US and Soviet scientists have been holding quiet discussions on matters like missile defense since the first International Pugwash Conference on Science and World Affairs in 1957 (see PHYSICS TODAY, September, page 81). Sometimes these discussions have constituted an informal “backchannel” between the governments for consideration of possible arms control initiatives. Thus in conversations between US and Soviet scientists in 1964, US scientists argued that ABM systems would not be effective against a determined adversary and that their deployment would stimulate an offense-defense arms race; they accordingly proposed a treaty to limit ABM systems. Two high-level Soviet scientists, Lev Artsimovich (who was head of the Soviet fusion program) and Mikhail Millionshchikov (who was vice president for applied physics and mathematics of the Soviet Academy of Sciences), subsequently helped bring their government around to this position, thereby contributing to the achievement in 1972 of the ABM Treaty.
Heinrich Hertz and the Development of Physics
Authors: Mulligan Joseph F.
Published: January 2008

The discovery that electromagnetic radiation in the microwave and radio regions of the spectrum displays the same basic behavior as visible light—reflection, refraction, diffraction, interference, polarization—was made in Karlsruhe in 1888 by Heinrich Rudolf Hertz. Some special events last year marked the centennial of Hertz's momentous discovery. The Technical University in Karlsruhe, at which Hertz did his electromagnetic research, held a symposium on Hertz and the consequences of his work, and devoted one complete volume of its publication Fridericiana to him. In the US, the Microwave Theory and Techniques Society of the Institute of Electrical and Electronics Engineers held a symposium in New York City to celebrate Hertz's achievements. On display at this meeting, from the Science Museum in London, was a refurbished set of replicas of Hertz's original apparatus. These replicas were exhibited at the MIT Museum in Cambridge, Massachusetts, before returning to London late last year.
The First Texas Symposium on Relativistic Astrophysics
Authors: Schucking Engelbert L.
Published: January 2008

Someone—I do not remember who—discovered that this is the 25th anniversary of the first Texas Symposium on Relativistic Astrophysics. The discovery is the more remarkable since the conference is held every two years and the number 25 is, I believe, odd. Undoubtedly, this fact could, should and presumably will be explained by historians of science—thus I will not bother.
On BC1 RNA and the fragile X mental retardation protein
Authors: Iacoangeli Anna , Rozhdestvensky Timofey S. , Dolzhanskaya Natalia , Tournier Barthélémy , Schütt Janin , Brosius Jürgen , Denman Robert B. , Khandjian Edouard W. , Kindler Stefan , Tiedge Henri
Published: January 2008

The fragile X mental retardation protein (FMRP), the functional absence of which causes fragile X syndrome, is an RNA-binding protein that has been implicated in the regulation of local protein synthesis at the synapse. The mechanism of FMRP's interaction with its target mRNAs, however, has remained controversial. In one model, it has been proposed that BC1 RNA, a small non-protein-coding RNA that localizes to synaptodendritic domains, operates as a requisite adaptor by specifically binding to both FMRP and, via direct base-pairing, to FMRP target mRNAs. Other models posit that FMRP interacts with its target mRNAs directly, i.e., in a BC1-independent manner. Here five laboratories independently set out to test the BC1–FMRP model. We report that specific BC1–FMRP interactions could be documented neither
in vitro
nor
in vivo
. Interactions between BC1 RNA and FMRP target mRNAs were determined to be of a nonspecific nature. Significantly, the association of FMRP with bona fide target mRNAs was independent of the presence of BC1 RNA
in vivo
. The combined experimental evidence is discordant with a proposed scenario in which BC1 RNA acts as a bridge between FMRP and its target mRNAs and rather supports a model in which BC1 RNA and FMRP are translational repressors that operate independently.
SIRT1 Acts as a Nutrient-sensitive Growth Suppressor and Its Loss Is Associated with Increased AMPK and Telomerase Activity
Authors: Narala Swami R. , Allsopp Richard C. , Wells Trystan B. , Zhang Guanglei , Prasad Prerna , Coussens Matthew J. , Rossi Derrick J. , Weissman Irving L. , Vaziri Homayoun
Published: January 2008

SIRT1, the mammalian homolog of SIR2 in Saccharomyces cerevisiae, is an NAD-dependent deacetylase implicated in regulation of lifespan. By designing effective short hairpin RNAs and a silent shRNA-resistant mutant SIRT1 in a genetically defined system, we show that efficient inhibition of SIRT1 in telomerase-immortalized human cells enhanced cell growth under normal and nutrient limiting conditions. Hematopoietic stem cells obtained from SIRT1-deficient mice also showed increased growth capacity and decreased dependency on growth factors. Consistent with this, SIRT1 inhibition was associated with increased telomerase activity in human cells. We also observed a significant increase in AMPK levels up on SIRT1 inhibition under glucose limiting conditions. Although SIRT1 suppression cooperated with hTERT to promote cell growth, either overexpression or suppression of SIRT1 alone had no effect on life span of human diploid fibroblasts. Our findings challenge certain models and connect nutrient sensing enzymes to the immortalization process. Furthermore, they show that in certain cell lineages, SIRT1 can act as a growth suppressor gene.
Discovery of candidate KEN-box motifs using Cell Cycle keyword enrichment combined with native disorder prediction and motif conservation
Authors: Michael Sushama , Travé Gilles , Ramu Chenna , Chica Claudia , Gibson Toby J.
Published: January 2008

Motivation: KEN-box-mediated target selection is one of the mechanisms used in the proteasomal destruction of mitotic cell cycle proteins via the APC/C complex. While annotating the Eukaryotic Linear Motif resource (ELM, http://elm.eu.org/), we found that KEN motifs were significantly enriched in human protein entries with cell cycle keywords in the UniProt/Swiss-Prot database—implying that KEN-boxes might be more common than reported.

Results: Matches to short linear motifs in protein database searches are not, per se, significant. KEN-box enrichment with cell cycle Gene Ontology terms suggests that collectively these motifs are functional but does not prove that any given instance is so. Candidates were surveyed for native disorder prediction using GlobPlot and IUPred and for motif conservation in homologues. Among >25 strong new candidates, the most notable are human HIPK2, CHFR, CDC27, Dab2, Upf2, kinesin Eg5, DNA Topoisomerase 1 and yeast Cdc5 and Swi5. A similar number of weaker candidates were present. These proteins have yet to be tested for APC/C targeted destruction, providing potential new avenues of research.

Contact:  toby.gibson@embl.de

Supplementary information: Tables of KEN-box candidates and keyword/conservation significance assessments are available as supplementary data at Bioinformatics online.
A hybrid model for robust detection of transcription factor binding sites
Authors: Gunewardena Sumedha , Zhang Zhaolei
Published: January 2008

Motivation: The short and degenerate nature of transcription factor (TF) binding sites contributes towards a low signal to noise ratio making it very difficult to separate them from their background. In order to tackle this problem one needs to look at ways of capturing the underlying biophysical properties that best discriminates TF binding sites from their background DNA. One such discriminatory property lies in the observed compositional differences in the nucleotide levels of TF binding sites and background DNA which are a result of processes such as purifying selection and selective preferences of TF binding sites for particular nucleotides or a combination of nucleotides over others.

Results: In this article, we present a hybrid model, referred to as a MonoDi-nucleotide model for robustly detecting TF binding sites. It incorporates both mono- and dinucleotide statistics to optimally partition the base positions of an aligned set of TF binding sites (motif) into a non-redundant sequence of mono and/or dinucleotide segments that maximizes the odds ratio of the binding sites relative to their background DNA. We tested the MonoDi-nucleotide model on the benchmark dataset compiled by Tompa et al. (2005) for assessing computational tools that predict TF binding sites. The performance of the MonoDi-nucleotide model on this data set compares well to, and in many cases exceeds, the performance of existing tools. This is in part attributed to the significant role played by dinucleotides in discriminating TF binding sites from background DNA.

Availability: A Matlab implementation of the MonoDi-nucleotide model can be found at http://www.utoronto.ca/zhanglab/MonoDi/.

Contact:  sumedha@cantab.net, Zhaolei.Zhang@utoronto.ca

Supplementary information: Supplementary data are available at Bioinformatics online.
Interpool: interpreting smart-pooling results
Authors: Thierry-Mieg Nicolas , Bailly Gilles
Published: January 2008

Motivation: In high-throughput projects aiming to identify rare positives using a binary assay, smart-pooling constitutes an appealing strategy liable of significantly reducing the number of tests while correcting for experimental noise. In order to perform simulations for choosing an appropriate set of pools, and later to interpret the experimental results, the pool outcomes must be ‘decoded’. The intuitive aim is clearly to identify the positives that gave rise to an observation, whether real or simulated. However, this goal is not well-formalized and has been the focus of very few studies.

Results: We first provide a clear combinatorial formalization of the ‘decoding problem’. We then present interpool, an exact algorithm to solve this problem. An efficient implementation is freely available. Its usefulness is illustrated in the context of yeast-two-hybrid interactome mapping with the Shifted Transversal Design.

Availability: The implementation, licensed under the GNU GPL, can be downloaded from http://www-timc.imag.fr/Nicolas.Thierry-Mieg/

Contact:  nicolas.thierry-mieg@imag.fr

Supplementary information: Supplementary data are available at Bioinformatics online.
Molecular Characterization of the Fusarium graminearum Species Complex in Japan
Authors: Suga H. , Karugia G. W. , Ward T. , Gale L. R. , Tomimura K. , Nakajima T. , Miyasaka A. , Koizumi S. , Kageyama K. , Hyakumachi M.
Published: January 2008

Members of the Fusarium graminearum species complex are important cereal pathogens worldwide and belong to one of at least nine phylogenetically distinct species. We examined 298 strains of the F. graminearum species complex collected from wheat or barley in Japan to determine the species and trichothecene chemotype. Phylogenetic analyses and species-diagnostic polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLPs) revealed the presence and differential distribution of F. graminearum sensu stricto (s. str.) and F. asiaticum in Japan. F. graminearum s. str. is predominant in the north, especially in the Hokkaido area, while F. asiaticum is predominant in southern regions. In the Tohoku area, these species co-occurred. Trichothecene chemotyping of all strains by multiplex PCR revealed significantly different chemotype compositions of these species. All 50 strains of F. graminearum s. str. were of a 15- or 3-acetyl deoxynivalenol type, while 173 (70%) out of 246 strains of F. asiaticum were of a nivalenol type. The possibility of gene flow between the two species was investigated by use of 15 PCR-RFLP markers developed in this study. However, no obvious hybrids were detected from 98 strains examined, including strains collected from regions where both species co-occur.
Biological and Molecular Analyses of the Acibenzolar-S-Methyl-Induced Systemic Acquired Resistance in Flue-Cured Tobacco Against Tomato spotted wilt virus
Authors: Mandal B. , Mandal S. , Csinos A. S. , Martinez N. , Culbreath A. K. , Pappu H. R.
Published: January 2008

Tomato spotted wilt virus (TSWV) is an economically important virus of flue-cured tobacco. Activation of systemic acquired resistance (SAR) by acibenzolar-S-methyl (ASM) in flue-cured tobacco was studied under greenhouse conditions by challenge inoculation with a severe isolate of TSWV. ASM restricted virus replication and movement, and as a result reduced systemic infection. Activation of resistance was observed within 2 days after treatment with ASM and a high level of resistance was observed at 5 days onward. Expression of the pathogenesis-related (PR) protein gene, PR-3, and different classes of PR proteins such as PR-1, PR-3, and PR-5 were detected at 2 days post-ASM treatment which inversely correlated with the reduction in the number of local lesions caused by TSWV. Tobacco plants treated with increased quantities of ASM (0.25, 0.5, 1.0, 2.0, and 4.0 g a.i./7,000 plants) showed increased levels of SAR as indicated by the reduction of both local and systemic infections by TSWV. The highest level of resistance was at 4 g a.i., but this rate of ASM also caused phytotoxicity resulting in temporary foliar spotting and stunting of plants. An inverse correlation between the TSWV reduction and phytotoxicity was observed with the increase of ASM concentration. ASM at the rate of 1 to 2 g a.i./7,000 plants activated a high level of resistance and minimized the phytotoxicity. Use of gibberellic acid in combination with ASM reduced the stunting caused by ASM. Present findings together with previous field experiments demonstrate that ASM is a potential option for management of TSWV in flue-cured tobacco.