bluuebunny/crossref_metadata_2025 huggingface dataset:
Parameters necessary for the adequate characterization of a solid-state material
Authors: Roy Rustum
Published: April 2009

A large number of scientists are caught up in the greatly expanded and accelerated national effort in materials science and technology. The impetus for this push came largely from members of one branch of the field—the solid-state physicists concerned with the properties of a material or the phenomena observable in a particular solid. It is, therefore, understandable that the initial emphasis of “materials science” programs stressed the solid-state physics or “measurement of properties” aspects. Only during the last two or three years has the recognition grown beyond verbal acquiescence that in order to have a flourishing program of measuring and interpreting properties of solids, it was essential to have “good” materials. In other words, the necessity to support and develop the whole science of “materials preparation” became apparent. This note is concerned with the third stage of the development of solid-state materials science and technology. Hardly had the effort in materials preparation been launched that it became apparent that one essential was still lacking—that which can be summarized in the expression “characterization of materials”. Some definition is in order: this term is used herein to include the whole spectrum of analyses, tests, measurements, etc., which must be carried out in order to be able to describe both accurately and precisely a particular solid. Another way of putting it is to say that it concerns the specifications necessary in order that another specimen can be established as being sensibly the same as a given model.
IQSY-EQEX cosmic-ray expedition to India
Authors: Korff Serge A.
Published: April 2009

Traditionally, the study of cosmic radiation has involved problems in geographical distribution, and the studies carried out during the recent “EQEX” expedition are no exception. The necessity of such studies comes about since the primary cosmic radiation is a mixed radiation with a wide energy spectrum. If one wishes to study the effects of some one portion of this spectrum, it is possible to use the earth's magnetic field as a magnetic spectrograph to sort out certain energy intervals of the radiation. By this means one can narrow down the energy-intervals, at least to some extent. It has therefore been customary to make observations at various latitudes. The latitude of southern India is one which restricts the incident radiation to the band of incident primary energies in excess of about 15 GeV, the so-called “Stoermer cutoff” here. Since the geomagnetic equator is north of the geographic equator at these longitudes, in India one is some eight or ten degrees further south geomagnetically than geographically.
Relativistic astrophysics—A report on the Second Texas Symposium
Authors: Robinson I. , Schild A. , Schucking E. L.
Published: April 2009

Scientists of 1965 see the universe with diverse eyes. They look with the two-hundred-inch pyrex mirror on top of Mount Palomar, with a hundred thousand gallons of cleaning fluid buried more than a mile underground, with scintillation counters flying in rockets and satellites, with a retina covering several square miles of the New Mexico desert at Volcano Ranch, with a steel bowl two hundred and ten feet across at Parkes in Australia, and with a gently swinging aluminum bar in Maryland, waiting patiently for the tremor of a gravitational wave.
Electron spin resonance of stable free radicals
Authors: Turkevich John
Published: April 2009

Electron spin resonance is a relatively new phenomenon in physics and chemistry while free radicals are substances long familiar to organic chemists. Electron spin resonance, discovered by the Soviet physicist Zavoiski in 1945, is the absorption of radiation in a magnetic field of certain definite strength by materials having unpaired electrons. The absorption has the characteristics of a resonance phenomenon because the differences in the energy levels of the unpaired electron or electrons due to the Zeeman splitting are sharp. This splitting is given by gβH where g is the gyromagnetic ratio (equal to 2.0023 for “spin only” case), β the value of the Bohr magneton, and H the intensity of the magnetic field. On the other hand, this energy difference is equal to hv where h is Planck's constant and v is the frequency of the absorbed radiation. Equating these two conditions, we obtain the resonance condition in conventional units of F = 2.80 H, with F being given in megacycles and H in oersteds. Such resonance absorption is observed in many chemical systems, transition metal ions, rare earth and actinide ions, conduction electrons, charred materials, radiation damaged materials, and the free radicals of the organic chemist. Not only can free radicals be detected with high sensitivity by electron spin resonance, but various aspects of this resonance absorption have given the chemist a powerful tool for the elucidation of the structure of organic molecules and of the mechanism of chemical reactions.
AAPT apparatus competition 1965
Authors: Christensen F. E.
Published: April 2009

During the middle of January 1965, equipment arrived at the Hotel Statler-Hilton in New York City for another physics apparatus exhibit and competition. One entry was received from Switzerland, the others from the United States. The entries, with one exception, were submitted by physicists from academic institutions.
Wavefront reconstruction photography
Authors: Leith Emmett , Upatnieks Juris
Published: April 2009

Wavefront reconstruction, or holography, is a fascinating photographic process which is a major departure from conventional photography. In this process, discovered in 1947 by D. Gabor of Imperial College, London, the photosensitive device does not directly record an image of the subject; instead, the electromagnetic waves reflected or scattered from the subject are recorded as a standing wave pattern. The resulting photographic record is called a hologram (from the Greek word holos, meaning whole), a name given by Professor Gabor to indicate that the whole, or entirety, of the wave pattern is recorded.
Of time and the atom…
Authors: Hudson George E.
Published: April 2009

In 1952, Harold Lyons of the National Bureau of Standards put into brief operation an atomic clock of the ammonia-absorption type, and thus reflected the intense interest in devising atomic standards for measuring time intervals. This interest has grown rather than diminished. As progress continued with the advent of cesium-beam frequency controls—first with L. Essen and J. V. L. Parry at the National Physical Laboratory in England, and later with the models investigated at the Boulder Laboratories of the NBS, and by Bonanomi in Neuchatel, Switzerland, by Kalra in Canada, and by McCoubrey and Holloway of the National Company in the United States—the standard for time measurement of highest possible accuracy was removed in effect from the astronomic realm to the atomic. In collaborating with Essen, W. Markowitz of the US Naval Obsevatory determined in 1958 the frequency characteristic of the cesium standard in terms of the accepted international unit of time, the ephemeris second. Since the international adoption of a temporary atomic standard to realize the unit of time, the figure they gave with a considerable uncertainty, 9 192 631 770 Hz, must be regarded not as a measured value, but rather as an exactly defined one, accurate to any number of significant figures. The uncertainty of 2 or 3 parts in 109 that originally attached to the measurement was evidently due to the uncertainties and inconvenience in the methods used to realize the ephemeris second; that is, the limitation lay in the astronomical observations, not in the atomic device.
Atomic spectra and radiation processes
Authors: Bradley L. C. , Foley H. M.
Published: April 2009

The Conference on Atomic Spectra and Radiation Processes (April 12–14, 1965) brought together in Oxford some 160 participants from 13 countries. This attendance reflected the recent increase of interest in the topics of the conference.
The structure of nucleons
Authors: Foldy L. L.
Published: April 2009

The urge to reduce the seemingly infinite variety and complexity of the visible world to some aesthetically satisfactory order has been a part of man's intellectual life since ancient times. In ancient philosophy and in modern science the natural orientation of this drive has been in the direction of understanding this variety and complexity as the natural outcome of the enormous number of combinatorial possibilities available to even a small number of basic entities subject to fixed laws of behavior. The search for these basic entities and for the strict formulation of the laws which govern them is still very much the essential fabric of physics today.
Ferrimagnetism in strained Fe2As thin films on Si(001)
Authors: Hwang Younghun , Choi Jeongyong , Cho Sunglae , Ketterson John B. , Tsai C.-C.
Published: April 2009

We present the structural and magnetic properties of Fe2As thin films grown on Si(100) by molecular beam epitaxy. From the reflection high-energy electron diffraction and x-ray diffraction patterns, the orientation of Fe2As film on Si(100) was found to be a c-axis in the tetragonal crystal structure. The tetragonal Fe2As thin film exhibited ferrimagnetic (FIM) ordering at room temperature. The magnetic moment of Fe2As was 0.1 μB/unit cell determined from the saturated magnetic moment. The observed FIM in Fe2As films was attributed to the strain in the film.
Noise pollution—what can be done?
Authors: Shaw Edgar A. G.
Published: April 2009

“An old riddle asked, ‘What comes with a carriage and goes with a carriage, is of no use to the carriage and yet the carriage cannot move without it?’ The answer: ‘A noise.’
New techniques advance hypernuclear spectroscopy
Authors: Levi Barbara G.
Published: April 2009

A feasible and fruitful way to study the spectroscopy of hypernuclei has been demonstrated by two experiments that applied counter techniques to measure hypernuclear reactions induced by K− mesons in flight. Such studies have been made possible in recent years by the development of intense, low-momentum K− beams. They were further stimulated by the suggestions of theorists that production of hypernuclei by K− mesons in flight might favor the formation of states in which a nucleon of the parent nucleus is replaced by a lambda hyperon without otherwise changing the wave functions. Comparison of such a hypernuclear state with the corresponding nuclear state could yield useful information about the lambda–nucleon interaction.
Crystallography and the future
Authors: Guinier André
Published: April 2009

Crystallography is a marvelous science for a young man or woman beginning a research career, and I would like to tell them some reasons why embarking in that discipline can be a good choice.
Prospects for a gamma-ray laser
Authors: Baldwin G. C. , Khokhlov R. V.
Published: April 2009

Lasers generating wavelengths shorter than one angstrom unit would have many important applications. Ever since the discovery of the Mössbauer effect it has been realized that we would be able to stimulate nuclear transitions suitable for lasers in this range if we could prepare the population inversion on which lasers depend, and it has also long been known that some nuclear isomers are producible in a state of population inversion. Why then do we not yet have any operating gamma-ray lasers?
Problems with fuel pellets for laser-induced fusion
Authors: Goss Levi Barbara
Published: April 2009

The nature of fuel pellets and their implications for laser-induced fusion are a little less mysterious since the AEC declassification of information regarding them. (See PHYSICS TODAY, February, page 78.) This previously withheld information was quickly disseminated because the secrecy was lifted just before two pertinent conferences—the meeting of the APS Plasma Division in Albuquerque, N. M. during 28–31 October and the Fifth IAEA Conference on Plasma Physics and Controlled Nuclear Fusion Research held in Tokyo, Japan 1–15 November.
Nucleon–antinucleon bound states suggested
Authors: Goss Levi Barbara
Published: April 2009

Does positronium have an analogy in the nucleon–antinucleon system? The existence of such narrow bound states is a possible explanation for results of a recent experiment that seem to contradict predictions of charge independence. Specifically, a team from Syracuse University, New York and from the Nuclear Research Center Demokritos in Athens, Greece found that in pionic annihilations at rest of antiprotons on deuterium, the resulting charged pions carried away less energy than is expected if the strong interaction forces are independent of charge. The Syracuse–Athens team then gathered evidence that the “missing” energy is taken away by an excess number of gamma rays; that is, more gamma rays than should be produced by decay of the neutral pions into two gammas. The experimenters feel that these extra gammas represent electromagnetic transitions between narrow nucleon–antinucleon resonances or bound states, which they have named “cosmion.” If their interpretation is correct then perhaps such narrow nucleon–antinucleon resonances or bound states are connected to the newly discovered J or ψ particles at 3.1 and 3.7 GeV; such is the suggestion of Alfred Goldhaber and Maurice Goldhaber. Another interesting feature of such possible states is that their characteristic gamma rays could identify regions of the universe where antimatter (if it exists) meets matter.
The geometry of surface layers
Authors: Estrup Peder J.
Published: April 2009

If we wish to understand the properties of a solid surface, we must begin with some picture of the geometrical arrangement of atoms in the outermost layers of the solid. Such a structural model represents an essential ingredient in any microscopic description of a material.
Positronium reveals its first excited state
Authors: Levi Barbara G.
Published: April 2009

The way has been paved to test quantum electrodynamical predictions of the Lamb-shift-like transitions in positronium. Karl F. Canter, Allen P. Mills Jr and Stephan Berko of Brandeis University recently observed1 the long-sought radiation from the first excited state of positronium with a method that makes it feasible to measure the fine structure of the n = 2 state. That measurement is now in progress.
Analysis shows Skylab tore hole in ionosphere
Authors: Levi Barbara G.
Published: April 2009

The launch of Skylab on 14 May 1973 created a temporary, large-scale hole in the ionosphere. The “hole,” a depletion of the total electron content of the ionosphere that spanned a spatial region of 1000 to 2000 km and a time period of 2 to 3 hours, was observed and subsequently analyzed by Michael Mendillo (Boston University), Gerald S. Hawkins (Smithsonian Astrophysical Observatory) and John A. Klobuchar (Air Force Cambridge Research Laboratory). They assert that the electrons were lost because of exceptionally rapid chemical recombination of the electrons with oxygen ions that was caused by the molecular hydrogen and water vapor from the exhaust of the Saturn V rocket engines.
Two laboratories develop lasers pumped by reactors
Authors: Rothenberg Marian S.
Published: April 2009

The first lasers pumped solely by nuclear reaction products have been developed independently at two laboratories. This news has been welcomed partly because producing any phenomenon in a new way is of scientific interest. But part of the welcome has a more pragmatic flavor: If the large amounts of energy produced in a reactor could be efficiently channeled into a laser, the resulting device might be powerful enough for applications ranging from isotope separation, to laser fusion, to communications in space. These first reports, from Sandia Laboratories in Albuquerque, New Mexico, and from Los Alamos Scientific Laboratory in Los Alamos, New Mexico, indicate that such lasers are in principle possible although as yet far from practical. David McArthur and Philip Tollefsrud (Sandia) described their carbon monoxide laser in the 15 February issue of Applied Physics Letters, and Herbert Helmick (Los Alamos), James Fuller and Richard Schneider (both of the University of Florida, Gainesville) reported lasing from xenon in the 15 March issue of the same journal. Both of these lasers are excited by U235 fission fragments that result from irradiating uranium foil with neutrons from a fast-burst reactor.
High-current electron beams
Authors: Fleischmann Hans H.
Published: April 2009

The rapid development of new technologies over the past decade has greatly expanded the capabilities of relativistic electron beams. While electron beams constitute one of the oldest particle beams available to physicists, the strengths of such beams were limited to a few amperes up to the early 1960's. Since then, however, a new type of accelerator has been developed that permits electron-beam bursts of many kiloamperes—and even megamperes—to be accelerated to energies of several megavolts. The most recent facility of this type at Cornell University, shown on the cover of this issue of PHYSICS TODAY, is capable of accelerating a 15-kA beam of electrons to 5 MeV. Figure 1 shows Aurora, the largest facility of this type presently operating, which is able to accelerate 160-nanosecond pulses of electron beams of up to 1.6 megamperes to energies as high as 12 MeV.
Metallic glasses
Authors: Gilman John J.
Published: April 2009

A piece of ordinary glass is a silicate material that did not crystallize when cooled from its liquid state to ambient temperature. Other substances, especially those whose molecules tend to polymerize, can also be cooled to ambient temperatures without crystallization. With metals, however, this could not be done until rather recently, and doing it continuously to make materials of interest to engineering is a very recent development. Metal alloys that can be quenched without crystallization form metallic glasses—solids with unusual, and in some cases outstanding, physical properties. Because their atoms are bound together by long-range metallic bonding, these glasses are malleable and good electrical conductors (comparable to stainless steels), unlike covalently bonded silicate glasses.
Superconductivity in novel sulfur–nitrogen polymer
Authors: Rothenberg Marian S.
Published: April 2009

Can a polymer of sulfur and nitrogen be metallic, even superconducting? Apparently yes, is the answer for polysulfur nitride, (SN)x, a highly anisotropic, quasi-one-dimensional polymer that looks like a metal, has the transport properties of a metal and becomes superconducting at around 0.3 K. The idea of finding superconductivity in a new part of the periodic table is of course exciting, whether or not practical applications ever arise. So the important questions are the nature of the polymer—its transport properties, crystallographic structure and band structure—as well as speculations about future technological uses. Some of the facts about (SN)x were exchanged and clarified during a special session at the March meeting of The American Physical Society. At that meeting, which took place in Denver from 31 March to 3 April, two groups active in recent studies of the transport properties each described their work. One group is at IBM, San Jose (the group that first saw superconductivity); the other is at the University of Pennsylvania, Philadelphia. A third group actively studying (SN)x is at Temple University (Philadelphia).
Electrons exhibit periodic density distribution
Authors: Levi Barbara G.
Published: April 2009

Although the electron distribution at the Fermi surface of a metal has long been considered to be well understood, some anomalies of electronic behavior such as magnetoresistivity have hinted that this understanding was not complete. In 1968 Albert W. Overhauser (Purdue University) proposed a model of a Fermi-surface instability that he called “charge density waves.”1 However, the validity of charge density wave theory has only now been established by the experimental observation of periodic structural distortions—unique consequences of this type of instability.
Alcator team reports good plasma parameters
Authors: Levi Barbara G.
Published: April 2009

Alcator—the high-field toroidal plasma experiment at MIT—has achieved very successful operating conditions since last summer. Its plasma density is the highest of any Tokamak-like plasma-containment device, and its Lawson number (product of density and containment time) is competitive for the high ion temperatures at which it runs (see box). Several unique features of this device are its high current density and the wide ranges of such parameters as density and plasma current. Alcator's staff is all the more pleased because the project had initially been making a slow start.
Cosmic background radiation reveals its blackbody shape
Authors: Rothenberg Marian S.
Published: April 2009

Experimenters from Berkeley, California, have measured the spectral shape of the submillimeter cosmic background radiation beyond the 6 cm−1 peak and found it to be consistent with the emission from a blackbody at 2.99 K (+0.07, −0.14 K at the 90% confidence limits). Their work comes several months after the balloon flights of a group from Queen Mary College, London, who studied the same spectral region and also found a blackbody shape. The QMC and Berkeley studies, however, disagree in their observations of, and correction for, atmospheric and (in the QMC case) window emission, and the Berkeley results are believed by most workers in the field to give a more likely picture of the nature of the detected radiation. The British group (E. I. Robson, D. G. Vickers, J. S. Huizinga, J. E. Beckman and P. E. Clegg) reported their studies in the 18 October 1974 issue of Nature Physical Science.1 The Berkeley group—David Woody, John Mather (now at the Goddard Institute for Space Studies, New York), Norman Nishioka and Paul Richards of the University of California, Berkeley and the Lawrence Berkeley Laboratory—reported their balloon-borne experiments in the 21 April issue of Physical Review Letters2 and at the Washington, D.C. meeting of The American Physical Society. Although the first measurements to point out the existence of a 3-K background were done over a decade ago, these two new studies are the first continuous measurements of the spectrum of this radiation in the far infrared and so provide direct evidence that the spectrum “turns over” on the short-wavelength side of the 6 cm−1 peak, in exactly the way a 3-K blackbody should.
Extended range for ultrashort laser pulses
Authors: Goss Levi Barbara
Published: April 2009

New areas of interest may be opening for ultrashort, or picosecond duration, laser pulses. These pulses have already been used for many years in research ranging from molecular lifetime studies to nonlinear optics (see PHYSICS TODAY, July 1971, page 19). Recent applications to biophysics, condensed matter and plasma physics are reviewed in the article that begins on page 30 of this issue. One new area, recently reported by David H. Auston of Bell Labs,1 is the application of these optical pulses to electronic switching functions; they can switch a signal in about 10 picoseconds, one or two orders of magnitude faster than semiconductor junction devices. A second area is the development of ultrafast pulses from the highly efficient carbon dioxide laser, thus extending the ultrafast pulses from the visible and near infrared, where they are currently available, toward the far infrared. Most recently at the Conference on Laser Engineering and Applications in Washington, DC from 28–30 May, one group announced a technique for fast optical switching of pulses from a carbon-dioxide laser.
Nuclear proliferation-thirty years after Hiroshima
Authors: Feld Bernard T.
Published: April 2009

Nowadays there is a tendency among historians and social scientists to think of the postwar scientists' movement as a quaint aberration, and to dismiss the ideas we developed in the late 1940's as politically naive or irrelevant. Some go even further and would have us believe that time has shown the wisdom of those politicians who insisted on the need for maintaining American preeminence in nuclear armaments, despite our urgent warnings that this was a futile and dangerous course. As evidence, they cite the facts that for thirty years nuclear war has been averted, in spite of recurrent international crises, and that the number of nuclear-weapons states has remained much smaller than the number that we predicted would be able to produce nuclear weapons on a time scale of thirty years.
Nuclear reactor safety—the APS submits its report
Authors: Lewis Harold W.
Published: April 2009

On 28 April at the Washington meeting of The American Physical Society, the results of a year-long study of light-water-reactor safety were released. The study group, consisting of a dozen physicists, chemists and engineers, was chaired by Harold W. Lewis of the University of California at Santa Barbara; it reported to the Physical Society Council through a Steering–Review Committee consisting of Wolfgang K. H. Panofsky (chairman), Hans A. Bethe, and Victor F. Weisskopf. The study was jointly financed by the former Atomic Energy Commission and the National Science Foundation.
Man-made square wells offer insight and applications
Authors: Leuchtag H. Richard
Published: April 2009

Thanks to teams at two laboratories, that textbook abstraction of quantum mechanics, the one-dimensional square well, has become realized in a physical object. Known as a “heterostructure,” this object consists of accurately deposited thin layers of two different semiconductors of matching lattice constants. When these man-made square wells are built up into stacks of 10–100 periods, they constitute essentially an infinite configuration (because of the finite mean free path of the carriers) known as a “superlattice” (PHYSICS TODAY, August 1973, page 20). These structures open the possibility of creating quantum states with predetermined energy levels and bandwidths.
Magnetic fields of the human body
Authors: Cohen David
Published: April 2009

In France, around 1780, many Parisians believed in curing their illnesses by magnetism. To perform this cure, they sat in a group around a tub containing “mesmerized” water and iron filings; this was part of the cult introduced to Paris by Dr Franz Mesmer. He proclaimed that animal magnetism of the human body controlled the flow of a universal fluid through the body and that illness resulted when there was an obstacle to that flow. The illness would be cured by magnetically redirecting the fluid with arrangements such as the filings and water.
Sequel to the psi: DESY, SLAC see intermediate states
Authors: Lubkin Gloria B.
Published: April 2009

After the first rush of discovery last fall in which the J or psi particle, with mass of 3.1 GeV was discovered, almost immediately followed by the psi prime, with mass of 3.7 GeV, there has been no new obviously related particle discovered. That is, until now, when an intermediate state, dubbed the “Pc particle” was observed at the DESY electron–positron storage ring, DORIS. The particle apparently has a mass of either 3.5 or 3.3 GeV, but the experimenters cannot tell which.
Two forms of amorphous solid water reported
Authors: Lubkin Gloria B.
Published: April 2009

The structure of solid water has intrigued physicists and chemists since the nineteenth century. By now it is known that solid water has at least eight crystalline forms. In 1935 E. F. Burton and W. F. Oliver (University of Toronto) reported seeing an amorphous form of solid water, and since then a few other experimenters have said they had observed it. Now Stuart Rice (University of Chicago) and his collaborators have done careful, quantitative x-ray diffraction, neutron diffraction and Raman-scattering studies of water prepared in two different ways, and they believe they have observed two distinct forms of amorphous solid water.
Fusion reactors
Authors: Kadomtsev Boris B. , Fowler T. Kenneth
Published: April 2009

The Soviet fusion program is a broadly based effort with work in progress at several centers on tokamaks, stellarators and open systems, coupled with a strong background in the theory necessary for an understanding of these machines and their limitations. In addition, some exploratory efforts are being carried out on new ideas and new technologies, such as laser-induced fusion and pulsed systems. In this article we will briefly survey the present status of each component of this extensive yet well balanced program.
Laser research
Authors: Leuchtag H. Richard
Published: April 2009

An impressive amount of research is carried out in the Soviet Union in the areas of laser physics and quantum electronics. PHYSICS TODAY asked a number of leading US physicists who have worked closely with the Soviets in these fields to give us their impressions of this work. They are Michael Feld, an associate professor of physics at MIT; Aram Mooradian, the leader, and Paul Kelley, the associate leader of the Quantum Electronics Group at the MIT Lincoln Laboratory; Keith Boyer, division leader for laser fusion at Los Alamos Scientific Laboratory, and Ali Javan, a professor of physics at MIT and an inventor of the helium–neon laser.
Power-line radiation affects Earth's magnetosphere
Authors: Leuchtag H. Richard
Published: April 2009

Electromagnetic radiation from the Canadian power system is entering the Earth's magnetosphere, according to a recent report1 in the Journal of Geophysical Research. The authors, a team from the Stanford Radioscience Laboratory headed by Robert Helliwell, have also found evidence that these power-line emissions are amplified within the magnetosphere and cause the precipitation of electrons from it. Further studies of these phenomena, including satellite experiments, are under way.
The Earth's magnetosphere
Authors: Akasofu Syun-Ichi , Lanzerotti Louis J.
Published: April 2009

The growth of satellite observations over the last 15 years, together with increasingly sophisticated ground-based measurements, has brought the study of Earth's electromagnetic environment to a new era of development. This study has grown to a broad discipline that overlaps magnetism, astrophysics and plasma physics. Important understandings have been achieved in many areas including auroral phenomena, distributions and interactions of plasmas and waves in the magnetosphere, the physics of wave–energetic-particle interactions, and the identification of magnetic-field-aligned currents.
Physics in combustion research
Authors: Hartley Danny , Hardesty Donald , Lapp Marshall
Published: April 2009

Virtually all the energy we derive from fossil fuels is obtained through some form of combustion. Any technical advance that can result in more efficient combustion systems without sacrificing environmental quality would therefore be a major contribution to energy conservation. For example, every one-percent increase in auto engine combustion efficiency saves about 14.5 million barrels of oil per year, gaining the US over 150 million dollars per year in balance of payments. Although research in specific technological areas is usually difficult to justify from economic arguments, this is not the case for combustion research, as these figures show. The return on the investment pays for combustion research many times over. In addition, improved control of combustion processes should result in lower pollutant emissions and thereby reduce such hidden costs of burning fossil fuels as exhaust-gas cleanup and damages to health and environment. However, combustion devices, like most other engineering systems, face performance limitations of an inherently scientific nature.
Structural and physical properties of room temperature stable multiferroic properties of single-phase (Bi0.9La0.1)FeO3–Pb(Fe0.5Nb0.5)O3 solid solution systems
Authors: Paik Hanjong , Kim Hyung-Chul , No Kwangsoo , Kim Yong-Il , Cann David P. , Hong Jongin
Published: April 2009

( 1 − x ) ( Bi 0.9 La 0.1 ) FeO 3 – x Pb ( Fe 0.5 Nb 0.5 ) O 3 (BLFO-PFNO) (x=0.2, 0.7, and 0.8), are investigated as an A-site substituted counterpart multiferroic solid solution of previous (Bi0.9La0.1)FeO3–Ba(Fe0.5Nb0.5)O3 (BLFO-BFNO). The unique BLFO-PFNO solid solution system enables soft ferromagnetism at room temperature and macroscopic polarization with the ferroelectric domain evolution due to nanoscale ordered single grains at high composition of relaxor-type ferroelectric PFNO.
Electronic structures and magnetic properties of a ferromagnetic insulator: La2MnNiO6
Authors: Kim Bongjae , Lee Jieun , Kim Beom Hyun , Choi Hong Chul , Kim Kyoo , Kang J.-S. , Min B. I.
Published: April 2009

We have investigated the electronic structures and magnetic properties of La2MnNiO6 that is a typical ferromagnetic insulator with the double perovskite structure. We have examined the valence states of Mn and Ni ions using the full-potential linearized augmented plane wave band method. The density of states as well as the charge density plot are in good agreement with the reported experimental and theoretical results. We have examined the ferromagnetic mechanism in terms of the superexchange interaction. We have calculated the x-ray absorption spectrum based on the band structure results and compared it with the experiment.
Electrical transport measurements of highly conductive carbon nanotube/poly(bisphenol A carbonate) composite
Authors: Curran Seamus A. , Talla Jamal , Dias Sampath , Zhang Donghui , Carroll David , Birx Donald
Published: April 2009

Acid-treated and pristine chemical vapor deposition grown multiwalled carbon nanotube (MWNT) and poly(bisphenol A carbonate) (PC) composites were prepared through a simple solution blending with varied nanotube weight fractions. The electrical conductivities of the composites can be described by the scaling law based on percolation theory with unprecedented high saturated ac conductivity of pristine nanotubes (σsat=1598.4 S cm−1, pc=0.19 wt %) and acid-treated nanotubes (σsat=435.4 S cm−1, pc=0.3 wt %), which correlates well with the dc behavior. We attribute the high saturated conductivities to managing the dispersions, rather than looking to have a well dispersed three-dimensional network thin film. The comparison was made between acid-treated nanotubes and pristine nanotube, both dispersed in PC at various loadings. It was found that the pristine nanotubes in PC possessed an even higher conductivity than the more evenly dispersed composites consisting of lightly acid-treated MWNT in PC.
An exact accelerated stochastic simulation algorithm
Authors: Mjolsness Eric , Orendorff David , Chatelain Philippe , Koumoutsakos Petros
Published: April 2009

An exact method for stochastic simulation of chemical reaction networks, which accelerates the stochastic simulation algorithm (SSA), is proposed. The present “ER-leap” algorithm is derived from analytic upper and lower bounds on the multireaction probabilities sampled by SSA, together with rejection sampling and an adaptive multiplicity for reactions. The algorithm is tested on a number of well-quantified reaction networks and is found experimentally to be very accurate on test problems including a chaotic reaction network. At the same time ER-leap offers a substantial speedup over SSA with a simulation time proportional to the 2∕3 power of the number of reaction events in a Galton–Watson process.
Effect of nanorods on the mesophase structure of diblock copolymers
Authors: He Linli , Zhang Linxi , Xia Agen , Liang Haojun
Published: April 2009

Mixtures of symmetric diblock copolymers and rigid nanorods (NRs) that are preferentially wetted by one of the blocks (A) are systematically investigated via dissipative particle dynamics simulations. The morphology of such composites depends not only on the characteristics of the copolymers, but also on the physical or chemical features of the NRs, such as NR volume fraction, size, and polymer-NR interaction. We find that the presence of NRs influences the phase behavior of copolymers and the phase-separated domains of copolymers in turn confine the NRs spatial distribution and positional orientation. The morphologies and phase transitions of hybrids and the corresponding NRs distributed and oriented regularities can be rationalized on the basis of the relative enthalpic and entropic effects involving all of the species, A and B blocks, and NRs. These results suggest that by choosing appropriate parameters, our model systems may provide a prediction to control and design the high-performance composites.
Semiconductor lasers with integrated plasmonic polarizers
Authors: Yu Nanfang , Wang Qi Jie , Pflügl Christian , Diehl Laurent , Capasso Federico , Edamura Tadataka , Furuta Shinichi , Yamanishi Masamichi , Kan Hirofumi
Published: April 2009

The authors reported the plasmonic control of semiconductor laser polarization by means of metallic gratings and subwavelength apertures patterned on the laser emission facet. An integrated plasmonic polarizer can project the polarization of a semiconductor laser onto other directions. By designing a facet with two orthogonal grating-aperture structures, a polarization state consisting of a superposition of a linearly and right-circularly polarized light was demonstrated in a quantum cascade laser; a first step toward a circularly polarized laser.
Thermal transport properties of polycrystalline tin-doped indium oxide films
Authors: Ashida Toru , Miyamura Amica , Oka Nobuto , Sato Yasushi , Yagi Takashi , Taketoshi Naoyuki , Baba Tetsuya , Shigesato Yuzo
Published: April 2009

Thermal diffusivity of polycrystalline tin-doped indium oxide (ITO) films with a thickness of 200 nm has been characterized quantitatively by subnanosecond laser pulse irradiation and thermoreflectance measurement. ITO films sandwiched by molybdenum (Mo) films were prepared on a fused silica substrate by dc magnetron sputtering using an oxide ceramic ITO target (90 wt % In2O3 and 10 wt % SnO2). The resistivity and carrier density of the ITO films ranged from 2.9×10−4 to 3.2×10−3 Ω cm and from 1.9×1020 to 1.2×1021 cm−3, respectively. The thermal diffusivity of the ITO films was (1.5–2.2)×10−6 m2/s, depending on the electrical conductivity. The thermal conductivity carried by free electrons was estimated using the Wiedemann–Franz law. The phonon contribution to the heat transfer in ITO films with various resistivities was found to be almost constant (λph=3.95 W/m K), which was about twice that for amorphous indium zinc oxide films.
Existence, uniqueness, and equivalence theorems for magnetic monopoles in general (4p−1)-dimensional Yang–Mills theory
Authors: Gao Zhifeng , Zhang Jing
Published: April 2009

In this paper, we use the method of calculus of variations to establish the existence of energy-minimizing radially symmetric magnetic monopole solutions in the general (4p−1)-dimensional Yang–Mills gauge field theory developed recently by Radu and Tchrakian. We also show that these solutions are either self-dual or anti-self-dual and, hence, unique. Our study extends the existence work of Belavin, Polyakov, Schwartz, and Tyupin and the equivalence and uniqueness work of Maison in three dimensions and the work of Yang in seven dimensions to the situation of arbitrary (4p−1) dimensions.
Intramolecular energy transfer and the driving mechanisms for large-amplitude collective motions of clusters
Authors: Yanao Tomohiro , Koon Wang Sang , Marsden Jerrold E.
Published: April 2009

This paper uncovers novel and specific dynamical mechanisms that initiate large-amplitude collective motions in polyatomic molecules. These mechanisms are understood in terms of intramolecular energy transfer between modes and driving forces. Structural transition dynamics of a six-atom cluster between a symmetric and an elongated isomer is highlighted as an illustrative example of what is a general message. First, we introduce a general method of hyperspherical mode analysis to analyze the energy transfer among internal modes of polyatomic molecules. In this method, the (3n−6) internal modes of an n-atom molecule are classified generally into three coarse level gyration-radius modes, three fine level twisting modes, and (3n−12) fine level shearing modes. We show that a large amount of kinetic energy flows into the gyration-radius modes when the cluster undergoes structural transitions by changing its mass distribution. Based on this fact, we construct a reactive mode as a linear combination of the three gyration-radius modes. It is shown that before the reactive mode acquires a large amount of kinetic energy, activation or inactivation of the twisting modes, depending on the geometry of the isomer, plays crucial roles for the onset of a structural transition. Specifically, in a symmetric isomer with a spherical mass distribution, activation of specific twisting modes drives the structural transition into an elongated isomer by inducing a strong internal centrifugal force, which has the effect of elongating the mass distribution of the system. On the other hand, in an elongated isomer, inactivation of specific twisting modes initiates the structural transition into a symmetric isomer with lower potential energy by suppressing the elongation effect of the internal centrifugal force and making the effects of the potential force dominant. This driving mechanism for reactions as well as the present method of hyperspherical mode analysis should be widely applicable to molecular reactions in which a system changes its overall mass distribution in a significant way.
Ionization energy measurements and spectroscopy of HfO and HfO+
Authors: Merritt Jeremy M. , Bondybey Vladimir E. , Heaven Michael C.
Published: April 2009

Rotationally resolved spectra for the HfO+ cation have been recorded using the pulsed field ionization zero electron kinetic energy (PFI-ZEKE) technique. Resonant excitation of the F(0+)←X Σ1+ band system of HfO was used as an intermediate level providing molecule and rovibrational state selectivity in the ionization process. The ionization energy (IE) of HfO, derived from the PFI-ZEKE spectrum, was determined to be 7.916 87(10) eV, which is 0.37 eV higher than the value reported from electron impact measurements. Underestimation of the IE in the previous studies is attributed to ionization of thermally excited states. A progression in the HfO+ stretch vibration up to ν+=4 was observed in the PFI-ZEKE spectrum, allowing for the determination of the ground electronic state vibrational frequency of ωe+=1017.7(10) cm−1 and anharmonicity of ωexe+=3.2(2) cm−1. The rotational constant of HfO+ was determined to be 0.403(5) cm−1. Benchmark theoretical ab initio calculations were carried out in order to explore the effects of electron correlation on the predicted molecular properties. Survey scans utilizing laser induced fluorescence and resonance enhanced multiphoton ionization detection revealed many previously unassigned bands in the region of the F-X and G-X bands of HfO, which we attribute to nominally forbidden singlet-triplet transitions of HfO.
Retrieving the vertical column density of NO2 by using multiaxis differential optical absorption spectroscopy technique
Authors: Zuo H. Y. , Luo S. R. , Liu Q. J.
Published: April 2009

A rigorous technique of monitoring the vertical column density (VCD) of NO2 by using the scattered solar radiation is reported. By analyzing the optical path, the method of collecting the useful scattered solar radiation is achieved. By using this method, the collecting equipment and procedure of solar radiation could be greatly simplified. And through the actual measurement, it is proved that the VCD of NO2 measured by using the scattered solar radiation is very close to that from the direct solar radiation.
Laser-induced aligned self-assembly on water surfaces
Authors: Nevo Iftach , Kapishnikov Sergey , Birman Atalia , Dong Mingdong , Cohen Sidney R. , Kjaer Kristian , Besenbacher Flemming , Stapelfeldt Henrik , Seideman Tamar , Leiserowitz Leslie
Published: April 2009

The key to functionalize of engineered molecularly nanometer thick films lies in the ability to reproducibly control their structure. A number of factors influence the film morphology of self-assembled films on solid or liquid surfaces, such as the structure of the molecules/particles, wetting, solvent hydrodynamics, and evaporation. An important example is the deposition of amphiphilic molecules from a volatile solution, self-assembled onto a water surface at monolayer coverage. Upon evaporation, a myriad of microscopic two-dimensional (2D) crystallites forms a ruptured film lying in random orientation on the surface, resulting in “2D powders.” Here we present a general technique, employing linearly polarized laser pulses and varying solvent composition to influence the assembly of molecules such as poly-benzyl-L-glutamate and alamethicin on water surfaces, resulting in ultrathin molecular films with aligned regions that point in the same direction, though macroscopically separated. The experimental results are tentatively explained by a mechanism that is based on excluded volume forces and “kick model” for the effect of laser pulses to induce molecular rotation that eventually results in an aligned pattern when the system is at a collective state.
A Fourier transform spectrometer without a beam splitter for the vacuum ultraviolet range: From the optical design to the first UV spectrum
Authors: de Oliveira N. , Joyeux D. , Phalippou D. , Rodier J. C. , Polack F. , Vervloet M. , Nahon L.
Published: April 2009

We describe a Fourier transform (FT) spectrometer designed to operate down to 60 nm (20 eV) on a synchrotron radiation beamline for high resolution absorption spectrometry. As far as we know, such an instrument is not available below 140 nm mainly because manufacturing accurate and efficient beam splitters remains a major problem at these wavelengths, especially if a wide bandwidth operation is desired. In order to overcome this difficulty, we developed an interferometer based on wave front division instead of amplitude division. It relies on a modified Fresnel bimirror configuration that requires only flat mirrors. The instrument provides path difference scanning through the translation of one reflector. During the scanning, the moving reflector is controlled by an optical system that keeps its direction constant within a tolerable value and provides an accurate interferometric measurement of the path difference variation. Therefore, a regular interferogram sampling is obtained, producing a nominal spectral impulse response and an accurate spectral calibration. The first results presented in this paper show a measured spectral resolution of δσ=0.33 cm−1 (interval between spectral samples). This was obtained with a sampling interval of 29 nm (path difference) and 512 K samples from a one-sided interferogram using a cosine FT. Such a sampling interval should allow the recording of large bandwidth spectra down to λ̣=58 nm with an ultimate resolving power of 500 000 at this wavelength. In order to check the instrument performances, we first recorded an interferogram from a He–Ne stabilized laser. This provided the actual spectral impulse function, which was found to be fully satisfactory. The determination of the impulse response distortion and of the noise on the vacuum ultraviolet (VUV) spectral range provided accurate information in the sampling error profile over a typical scan. Finally, the instrument has been moved to the SU5 undulator-based synchrotron radiation beamline (Super-ACO facility, LURE, Orsay, France). A high resolution spectrum of O2 (the Schumann–Runge absorption bands, 185–200 nm) was computed from recorded interferograms using the beamline monochromator at the zeroth order to feed the instrument with an 11% relative bandwidth “white” beam (2003). These UV measurements are very close to those found in the literature, showing nominal performances of the FT spectrometer that should translate into an unprecedented resolving power at shortest VUV wavelengths. A recent upgrade (2007) and future developments will be discussed in light of the current installation of the upgraded FT spectrometer as a permanent endstation for ultrahigh resolution absorption spectrometry on the VUV beamline DESIRS at SOLEIL, the new French third generation synchrotron facility.