bluuebunny/crossref_metadata_2025 huggingface dataset:
Exchange-biased planar Hall effect sensor optimized for biosensor applications
Authors: Damsgaard Christian D. , Freitas Susana C. , Freitas Paulo P. , Hansen Mikkel F.
Published: January 2008

This article presents experimental investigations of exchange-biased Permalloy planar Hall effect sensor crosses with a fixed active area of w×w=40×40μm2 and Permalloy thicknesses of t=20, 30, and 50nm. It is shown that a single domain model describes the system well and that the thicker film will have a higher signal as well as a lower noise. It is estimated that the signal-to-noise ratio for bead detection increases by a factor 2.1 when t is increased from 20to50nm and hence a higher t is beneficial for biosensor applications. This is exemplified with calculations on M-280 Dynabeads®.
Off-center magnetic resonance imaging with permanent magnets
Authors: Abele Manlio G. , Rusinek Henry
Published: January 2008

Magnets for magnetic resonance imaging are currently designed as structures that are symmetric with respect to the geometric center O of the magnet cavity. This symmetry results in a symmetric field configuration, where point O coincides with the imaging center S defined as the point where the field gradient is zero. However, in many clinical applications such as breast or spine imaging, the region of interest is displaced from the geometric center. We present a design method for yokeless permanent magnets, where the position of point S is dictated by the imaging requirements. The magnet is composed of uniformly magnetized triangular prisms and it does not require a ferromagnetic yoke to channel the magnetic flux. Given an arbitrary polygonal cavity, the design depends on the position of point F, where the magnetostatic potential is assumed to be equal to the magnetostatic potential of the external medium. For a long magnet, the position of the imaging center S coincides with point F. As an example of the off-center design, we analyze a three-dimensional yokeless magnet with cavity of width=length=80cm and height=45cm. The magnet generates a field above 0.5T when constructed using the NdFeB alloy of remanence larger than 1.3T. The off-center configuration offers flexibility in magnet design that makes it possible to focus on a particular region of the human body, without increasing magnet cavity, magnet size, or its weight
Fabrication of L11 type Co-Pt ordered alloy films by sputter deposition
Authors: Sato H. , Shimatsu T. , Okazaki Y. , Muraoka H. , Aoi H. , Okamoto S. , Kitakami O.
Published: January 2008

L 1 1 type Co-Pt ordered alloy films with a large uniaxial magnetic anisotropy, Ku, of the order of 107erg∕cm3 were successfully fabricated at relatively low substrate temperatures of 270–390°C using ultrahigh vacuum sputter film deposition. L11 type ordered Co-Pt films, with the ⟨111⟩ direction (easy axis of magnetization) perpendicular to the film plane, were fabricated on MgO(111) single crystal substrates and glass disks. The ordered structure was formed in a wide Pt content region of 40–75at.%, and Ku showed a maximum at around 50at.% Pt content. The values of the order parameter S and Ku for L11 type Co50Pt50 films increased as the substrate temperature Ts, increased. Ku reached about 3.7×107erg∕cm3 (S=0.54) at Ts=360°C for the single crystal films deposited on MgO(111) substrates, indicating a potential increase in Ku by enhancing the ordering. The values of Ku for polycrystalline films deposited on glass disks were smaller than those for the single crystal films on MgO(111) substrates, however, Ku reached 1.9×107erg∕cm3 at Ts=360°C. The experimental results demonstrate the potential of L11 type Co50Pt50 films for use in data storage applications, because of their very high Ku, comparable to L10 type Fe50Pt50 films, the relatively low fabrication temperature, and good controllability of the grain orientation.
Tunneling magnetoresistance in CoFeB∕GaAs∕(Ga,Mn)As hybrid magnetic tunnel junctions
Authors: Du G. X. , Han X. F. , Deng J. J. , Wang W. Z. , Zhao J. H.
Published: January 2008

We reported the all electronic demonstration of spin injection and detection in the trilayers with hybrid structure of CoFeB∕GaAs∕(Ga,Mn)As (metal/insulator semiconductor) by probing the magnetoresistance at low temperature from 1.8to30K. Tunneling magnetoresistance (TMR) ratios of 3.8%, 4.7%, 2.9%, and 1.4% at 1.8, 10, 20, and 30K, respectively, were observed. Bias dependence of both the junction resistance and TMR ratio was studied systematically. Vhalf at which TMR drops to half of its maximum is 6.3mV, being much smaller compared to that observed in (Ga,Mn)As∕ZnSe∕Fe and (Ga,Mn)As∕AlAs∕MnAs hybrid structures, indicating lower Fermi energy of (Ga,Mn)As.
Moment fluctuations in 7nm γ-Fe2O3 nanoparticles probed at the atomic level using Mössbauer spectroscopy
Authors: Desautels R. D. , Skoropata E. , van Lierop J.
Published: January 2008

We have examined the local magnetism of 7nm γ-Fe2O3 nanoparticles as a function of temperature using transmission Mössbauer spectroscopy. Spectra indicate that the nanoparticles exhibit two different spin populations: one is due to the core Fe moments, while the other is from the surface moments. We find that the uniaxial anisotropy of the core increases with temperature from 5to75K, whereupon it remains constant. Simultaneously, the surface moment fluctuations increase in frequency with warming.
Constrained subgrid-scale stress model for large eddy simulation
Authors: Shi Yipeng , Xiao Zuoli , Chen Shiyi
Published: January 2008

In this letter, we propose to impose physical constraints in the dynamic procedure of the dynamic subgrid-scale (SGS) stress model in large eddy simulation, and to calculate the SGS model coefficients using a constrained variation. Numerical simulations of forced and decaying isotropic turbulence demonstrate that the constrained dynamic mixed model predicts the energy evolution and the SGS energy dissipation well. The constrained SGS model also shows a strong correlation with the real stress and is able to capture the energy backscatter, manifesting a desirable feature of combining the advantages of dynamics Smagorinsky and mixed models.
Faraday magneto-optical rotation in compositionally graded films
Authors: Miao X. P. , Gao L. , Xu P.
Published: January 2008

We present a two-step homogenization method for studying the Faraday magneto-optical effect in graded metal-dielectric composite films of width W, in which the volume fraction of metal particles in a slice varies along the direction perpendicular to the film surface. First, we adopt the effective-medium theory to formulate the equivalent (local) dielectric permittivity tensor for a z slice. Second, the graded composite films are homogenized with an effective (overall) dielectric permittivity tensor including the diagonal and off-diagonal elements. Faraday rotation is studied as a function of the graded profile p(z) with the same total volume fraction. For a power-law form p(z)=a(z/W)m with different m, it is found that with increasing m, the magnitude of Faraday rotation becomes weak near the surface plasmon resonant band, accompanied with the redshift of the resonant center. Interestingly, it is possible to achieve strongly enhanced Faraday rotation in the high-frequency region, and to change the direction of rotation in the low-frequency one. Moreover, the magnitude can be further enhanced for needle-like particles. In the dilute limit, we show that Faraday rotation is indeed independent of m within Maxwell-Garnett theory.
A miniature tunable coupled-cavity laser constructed by micromachining technology
Authors: Cai H. , Liu A. Q. , Zhang X. M. , Tamil J. , Tang D. Y. , Zhang Q. X. , Lu C.
Published: January 2008

This letter presents a miniature tunable coupled-cavity laser by integrating a Fabry-Pérot chip, a gain chip and a deep-etched parabolic mirror using micromachining technology. The mirror is to actively adjust the gap between chips, enabling the optimal mode selection. Single-mode operation with a tuning range of 16.55nm and a side-mode-suppression ratio of >25.1dB is demonstrated. The device overcomes phase mismatching and instability problems encountered in conventional fixed-gap coupled-cavity lasers.
Oxidation processes of surface hydrogenated silicon nanocrystallites prepared by pulsed laser ablation and their effects on the photoluminescence wavelength
Authors: Umezu Ikurou , Sugimura Akira , Makino Toshiharu , Inada Mitsuru , Matsumoto Kimihisa
Published: January 2008

Natural oxidation processes of surface hydrogenated silicon nanocrystallites prepared by pulsed laser ablation under various hydrogen gas pressures are discussed by measuring the vibrational frequency of Si–Hn units on the surface and intensity of Si–O–Si stretching vibration. The surfaces of nanocrystallites are predominantly composed of Si–H bonds and oxidation starts from backbonds of these bonds. The deposited nanocrystal films have a porous secondary structure which depends on the background gas pressure. The oxidation rate observed by infrared absorption measurements depended on this porous secondary structure. The oxidation process is discussed by the correlation between oxidation rate and porous structure of nanocrystal film. We found that Si–O bond density increases with covering the surface of the nanocrystallites during the diffusion of oxygen-related molecules through the void spaces in the porous structure. The surface oxidation of each nanocrystallite is not homogeneous; after the coverage of easy-to-oxidize sites, oxidation continues to gradually progress at the post-coverage stage. We point out that the oxidation process at coverage and post-coverage stages result in different photoluminescence (PL) wavelengths. Adsorption of the water molecule before oxidation also affects the PL wavelength. Defect PL centers which have light emission around 600 and 400 nm are generated during the coverage and post-coverage oxidation processes, respectively.
Experimental and theoretical studies on gadolinium doping in ZnTe
Authors: Ma Zhixun , Liu Lei , Yu Kin Man , Walukiewicz Wladek , Perry Dale L. , Yu Peter Y. , Mao Samuel S.
Published: January 2008

We studied the effects of Gd doping on the structural and optical properties of ZnTe films grown by pulsed laser deposition. We found that a small amount of Gd doping yields a reduction in the ZnTe lattice constant with no change in the fundamental band gap of the material. When the doping level increases above 7% the lattice constant becomes more or less constant, while the band gap increases abruptly (by as much as 50 meV). Theoretical calculations based on ZnTe supercells containing either isolated defects or defect complexes show that the reduced lattice constant can be attributed to the presence of defect complexes involving substitutional Gd ions and neighboring vacancies. The insensitivity of the band gap to low Gd concentration can be explained by self-compensation of these defects, while the band-filling effect probably explains the increase in the band gap energy.
Neutron diffraction study of magnetic structure in DyCu under magnetic field
Authors: Yasui Motoyoshi , Terai Tomoyuki , Kakeshita Tomoyuki , Matsuda Masaaki , Metoki Naoto , Nojiri Hiroyuki
Published: January 2008

We have investigated the magnetic structure of the first field-induced phase (FM-I111) of DyCu under a magnetic field applied in the [1 1 1] direction at 2.8K, which is below TN=63.0K, by means of neutron diffraction experiments using a single crystal. With the magnetic transition from the antiferromagnetic (AFM) phase to the FM-I111 phase at 8.0T, the intensity of 121¯20 reflection decreases sharply. The intensity in the FM-I111 phase is about three-fourths of the intensity in the AFM phase. This experimental result suggests that the magnetic structure model proposed by Amara et al. [J. Phys. Condens. Matter 9, 7441 (1997)] is appropriate for the FM-I111 phase. Considering the present results and the previous results reported by Amara et al., we have quantitatively evaluated the exchange and quadrupolar interaction energies based on a mean-field approximation. These interaction energies in the AFM and FM-I111 phases are found to be comparable.
The turbulence dissipation constant is not universal because of its universal dependence on large-scale flow topology
Authors: Mazellier N. , Vassilicos J. C.
Published: January 2008

The dimensionless dissipation rate constant Cϵ of homogeneous isotropic turbulence is such that Cϵ=f(logReλ)Cs′3, where f(logReλ) is a dimensionless function of logReλ which tends to 0.26 (by extrapolation) in the limit where logReλ⪢1 (as opposed to just Reλ⪢1) if the assumption is made that a finite such limit exists. The dimensionless number Cs′ reflects the number of large-scale eddies and is therefore nonuniversal. The nonuniversal asymptotic values of Cϵ stem, therefore, from its universal dependence on Cs′. The Reynolds number dependence of Cϵ at values of logReλ close to and not much larger than 1 is primarily governed by the slow growth (with Reynolds number) of the range of viscous scales of the turbulence. An eventual Reynolds number independence of Cϵ can be achieved, in principle, by an eventual balance between this slow growth and the increasing non-Gaussianity of the small scales. The turbulence is characterized by five length-scales in the following order of increasing magnitude: the Kolmogorov microscale η, the inner cutoff scale η*≈η(7.8+9.1logReλ), the Taylor microscale λ∼Reλ1∕2η, the voids length scale λv∼Reλ1∕3λ, and the integral length scale L∼Reλ2∕3λv.
Metal-semiconductor transition and magnetic properties of epitaxially grown MnAs∕GaAs superlattices
Authors: Song J. H. , Cui Y. , Lee J. J. , Cho S. L. , Ketterson J. B.
Published: January 2008

We successfully grew epitaxial MnAs∕GaAs superlattices at various growth temperatures (Tg) with a periodicity of 5∕5nm using molecular-beam epitaxy and characterized their magnetic and electrical transport properties. Structural analysis shows that the magnetic anisotropy originates from the crystal domain structure of the MnAs layers. The metallic behavior for the sample with Tg=375°C systematically changed to semiconducting on increasing Tg up to 540°C. The transport properties of thin single layered MnAs films with a thickness of 20nm showed the same Tg dependency. These observations indicate that the semiconducting characteristics of MnAs∕GaAs superlattices are attributable to a radical alteration of the electronic structure of the MnAs layers.
Nonlinear filamentation of a current-carrying plasma
Authors: Niknam A. R. , Shokri B.
Published: January 2008

The nonlinear filamentation in a nonrelativistic collisional current-carrying plasma in the diffusion frequency region is investigated. It is shown that by using the two-fluid plasma equations and Ampere’s law and assuming that the plasma is nonisothermal and inhomogeneous, the spatial evolution of the magnetic field in a plasma is described by the Lienard nonlinear differential equation. Also, it is shown that a transverse filamentation and density steepening can occur in the static limit. Furthermore, the profiles of magnetic field and the electron density variation have a nonsinusoidal shape in the nonlinear regime. Moreover it is shown that the shape of the transverse filamentation varies due to the nonlinear effect in the static limit.
Ge 3d core-level shifts at (100)Ge∕Ge(Hf)O2 interfaces: A first-principles investigation
Authors: Pourtois G. , Houssa M. , Delabie A. , Conard T. , Caymax M. , Meuris M. , Heyns M. M.
Published: January 2008

First-principles calculations of Ge 3d core-level shifts on (100)Ge∕Ge(Hf)O2 interface models, presenting a GeOx transition region that samples different possible oxidation states for Ge atoms near the interface are reported. The fractional densities of these different oxidation states present in the modeled structures are consistent with those inferred from x-ray photoelectron spectroscopy data on thermally oxidized (100)Ge surfaces. The computed relative Ge 3d core-level shifts are in overall fair agreement with the experimental values reported in the literature, especially for the Ge–O–Hf bonds that are likely formed at the GeO2∕HfO2 interface. The computed core-level shifts increase linearly with the partial atomic charges on the Ge atoms, consistently with a classical charge-transfer model usually used for the interpretation of experimental data on (100)Ge∕Ge(Hf)O2 interfaces.
Detection of the magnetostructural phase coexistence in MnAs epilayers at a very early stage
Authors: Milano J. , Steren L. B. , Repetto Llamazares A. H. V. , Garcia V. , Marangolo M. , Eddrief M. , Etgens V. H.
Published: January 2008

We report on the appearance of magnetic stripes in MnAs∕GaAs(100) epilayers at temperatures well below the ferromagnetic transition of the system. The study has been performed by ferromagnetic resonance (FMR) experiments on MnAs epilayers grown on the (100) and (111) GaAs substrates. The FMR spectra of the MnAs∕GaAs(100) samples at 180K reveal the appearance of zones of different magnetic behaviors with respect to the low-temperature homogeneous ferromagnetic phase. The angular and the temperature dependences of the spectra serve us to detect the intergrowth of the nonmagnetic phase into the ferromagnetic phase at a very early stage of the process. The experimental data show that the paramagnetic phase nucleates in a self-arranged array of stripes in MnAs∕GaAs(100) thin films while it grows randomly in the same films grown on GaAs(111).
The rf magnetic-field vector detector based on the spin rectification effect
Authors: Bai L. H. , Gui Y. S. , Wirthmann A. , Recksiedler E. , Mecking N. , Hu C.-M. , Chen Z. H. , Shen S. C.
Published: January 2008

Ferromagnetic resonances on three Permalloy strips under an in-plane external magnetic field are detected electrically. By measuring and analyzing the angular dependence of the photovoltage induced by the spin rectification effect, an approach is demonstrated for making microwave detectors capable of detecting the rf magnetic field vector at subwavelength scale.
High quality passivation for heterojunction solar cells by hydrogenated amorphous silicon suboxide films
Authors: Mueller Thomas , Schwertheim Stefan , Scherff Maximilian , Fahrner Wolfgang R.
Published: January 2008

In this letter, we report on our investigations of hydrogenated amorphous silicon suboxides (a-SiOx:H) used as a high quality passivation scheme for heterojunction solar cells. The a-SiOx:H films were deposited using high frequency (70MHz) plasma enhanced chemical vapor deposition by decomposition of carbon dioxide, hydrogen, and silane at a substrate temperature of around 155°C. High effective lifetimes of outstanding 4ms on 1Ωcm n-type float-zone material and a surface recombination velocity of ⩽2.6cm∕s have been repeatedly obtained. Optical analysis revealed a distinct decrease of blue light absorption in the a-SiOx:H films compared to commonly used intrinsic amorphous silicon passivation used in heterojunction cells.
Rabi splitting and ac-Stark shift of a charged exciton
Authors: Kroner M. , Lux C. , Seidl S. , Holleitner A. W. , Karrai K. , Badolato A. , Petroff P. M. , Warburton R. J.
Published: January 2008

The Rabi splitting of the negatively charged exciton in a single InGaAs quantum dot is observed in resonance transmission spectroscopy. We use a pump laser excitation to drive strongly the unpolarized trion transition in a quantum dot and detect its modified absorption spectrum with a second weak probe laser. By tuning the pump laser near resonance, we observe an ac-Stark effect dispersion, with a power dependent Rabi splitting on resonance, both signatures of a strongly coupled two level system. Although the pump and probe laser fields are resonant with the same transition, we do not observe all features in the Mollow spectrum. We combine the results of pump probe with saturation spectroscopy data to deduce the individual contributions to the low power linewidth.
Integrated organic electronic based optochemical sensors using polarization filters
Authors: Kraker Elke , Haase Anja , Lamprecht Bernhard , Jakopic Georg , Konrad Christian , Köstler Stefan
Published: January 2008

A compact, integrated photoluminescence based oxygen and pH sensor, utilizing an organic light emitting device (OLED) as the light source and an organic photodiode (OPD) as the detection unit, is described. The main challenge in such an integrated sensor is the suppression of the excitation light at the detector, which is typically by many orders of magnitude higher in intensity than the emitted fluorescence. In our approach, we refrain from utilizing edge filters which require narrow band excitation sources and dyes with an adequate large Stokes shift. We rather developed an integrated sensor concept relying on two polarizers to separate the emission and excitation light. One polarizer is located right after the OLED, while the other one, oriented at 90° to the first, is placed in front of the OPD. The main advantage of this solution is that any combination of excitation and emission light is acceptable, even if the two signals overlap spectrally. This is especially important for the use of OLEDs as the excitation sources, as these devices typically exhibit a broad spectral emission.
Self-similar neutral-plasma isothermal expansion into a vacuum
Authors: Huang Yongsheng , Bi Yuanjie , Duan Xiaojiao , Lan Xiaofei , Wang Naiyan , Tang Xiuzhang , He Yexi
Published: January 2008

The self-similar solutions are obtained for isothermal expansions of neutral plasmas into a vacuum. The classic solution given by Mora [Phys. Fluids 22, 12 (1979)] corresponds to a special case of our solution. Some special solutions have been pointed out by Gurevich et al. [Phys. Rev. Lett. 42, 769 (1979)] and observed by a lot of experiments. The formulation of ion velocity with respect to the acceleration time is proposed for the general solution, and the numerical result can be obtained easily. The electric field and ion velocity at the ion front have been achieved.
Photothermal thickness measurement of multilayered structures: An experimental and numerical analysis
Authors: Suter P. , Graf T.
Published: February 2008

The evolution of the surface temperature of flash-illuminated layered structures was studied by means of photothermal radiometry, the finite element method, and the Green’s formalism. The potential of a simple tabletop experiment to extract the sequence and thickness of the layers was investigated. Keeping the complexity low, only one parameter can be determined independently, for instance the absolute value and small variations of the top layer thickness. Our method is straightforward, accurate, and well-suited for online thickness detection.
Postmodern Quantum Mechanics
Authors: Heller Eric J. , Tomsovic Steven
Published: January 2008

Postmodern movements are well known in the arts. After a major artistic revolution, and after the “modern” innovations have been assimilated, the threads of premodern thought are always reconsidered. Much of value may be rediscovered and put to new use. The modern context casts new light on premodern thought, which in turn shades perspectives on modernism.
The Fluid Physics of Parachut Inflation
Authors: Peterson Carl W.
Published: January 2008

Parachutes have a fascinating history and a promising future. They were born long before airplanes, in ancient China. Leonardo da Vinci made sketches of a parachutelike device at the end of the 15th century, and Fauste Veranzio parachuted from a Venetian tower in 1617. By the time airplanes arrived on the scene, parachutes were older than Methuselah.
Einstein and the Press
Authors: Pais Abraham
Published: January 2008

Nearly four decades after Albert Einstein's death, his role as a mythical figure in our culture continues undiminished. Articles centering on him still appear in the press. He is the main character in plays and operas, and is pictured in advertisements, some witty, some vulgar.
Sonoluminescence
Authors: Crum Lawrence A.
Published: January 2008

In 1896 Henri Becquerel discovered that a uranium salt could darken a photographic plate, and from this effect he went on to discover radioactivity. In 1934 H. Frenzel and H. Schultes exposed a photographic plate to acoustic waves generated in a water bath and also observed a darkening of the plate. They attributed that result to luminescence from the sound field—an effect that has come to be known as sonoluminescence. The uminescence they observed did not result from the sound field directly but arose through a process called cavitation, in which voids filled with gas and vapor are generated within the liquid during the tensile portion of the pressure variation. The subsequent collapse of these voids during the compression portion of the acoustic cycle can be extremely violent and represents a remarkable degree of energy concentration—as high as 12 orders of magnitude. This energy concentration results principally from the fact that cavitation-bubble collapse obeys spherical symmetry, at least until the final stages, when instabilities in the interface may develop. This spherical symmetry is apparently preserved to submicron-size dimensions in single-bubble sonoluminescence, resulting in another remarkable phenomenon: Extremely short bursts of light are emitted from the bubble with clock-like precision.
Electrosensory Organisms
Authors: Bastian Joseph
Published: January 2008

Many aquatic animals have the ability to sense very weak electric fields. This electric sense is found in numerous species of marine and freshwater fish and in several amphibian species. Electrosensory abilities have also been reported in “higher” animals including the platypus and a semiaquatic mole.
Biomolecules: Where the Physics of Complexity and Simplicity Meet
Authors: Frauenfelder Hans , Wolynes Peter G.
Published: January 2008

Are we moving toward a time when no new and exciting problems appear in physics? Would the vaunted “theory of everything” mean the end of creative physics? A similar scenario was played out at the end of the last century, when some great physicists declared that only minor problems remained to be solved.
Resonance Ionization Spectroscopy
Authors: Samuel Hurst G. , Letokhov Vladilen S.
Published: January 2008

More than two decades ago a laser-based spectroscopic technique was developed that has since proved effective in solving problems no other spectroscopic method, conventional or laser based, can tackle. Known as resonance ionization spectroscopy, it has become a very useful tool for pure and applied research in physics and chemistry (see an example in figure 1), and it has found application in many other fields, including microelectronics, the Earth sciences and biomedicine.
Human Impacts on the Nitrogen Cycle
Authors: Kinzig Ann P. , Socolow Robert H.
Published: January 2008

Humans are greatly perturbing the global nitrogen cycle. Perhaps the best evidence for this perturbation comes from air trapped in layers of quasipermanent ice in the Arctic and the Antarctic. Ice cores taken from these two polar regions give us a 2000-year record of the Earth's atmospheric composition. This record indicates a striking constancy in nitrous oxide concentrations, at approximately 285 parts per billion, for nearly 1500 years. (See figure 2.) Since about 1600 AD, however, nitrous oxide concentrations have been increasing, and the present-day atmospheric burden of this gas is greater than at any other time in the past two millennia. Furthermore, nitrous oxide concentrations continue to increase, currently at a rate of about 0.3% per year. These variations indicate that many nitrogen flows are now larger than in preindustrial times, and other evidence suggests that human activity is responsible. (See figure 1.).
Fuel Cells: Energy Conversion for the Next Century
Authors: Kartha Sivan , Grimes Patrick
Published: January 2008

Fossil fuel combustion, the technology on which the world relies most heavily for power generation, heating and transportation, was adopted long before its environmental burdens had been fully recognized. The results of our recent efforts to mitigate these environmental costs are perceptible, but still modest and very costly. Despite the use of sulfur scrubbers, acid rain remains a serious regional threat, especially with the increased use of lowquality coals. Catalytic converters have reduced nitrogen oxide and carbon monoxide emissions from automobiles in some countries, but the poor air quality of many of the world's urban areas nonetheless constitutes a severe health threat. New, more efficient power plants and automobiles generate less carbon dioxide per unit of useful energy than did their predecessors, but atmospheric carbon dioxide concentrations continue to rise, intensifying the threat of global warming. Despite our diligent efforts, a major strategic shift in energy production may be required to achieve more than incremental and perhaps inadequate advances. What is needed is an energy conversion technology that is inherently clean, efficient and compatible with renewable energy sources.
Teaching and Learning Physics with Interactive Video
Authors: Zollman Dean A. , Fuller Robert G.
Published: January 2008

In 1961 the psychologist Jerome Bruner concluded a discussion of innovative teaching materials of the late 1950s by saying, “The intelligent use of [audiovisual] resources will depend upon how well we are able to integrate the technique of the filmmaker or the program producer with the technique and wisdom of the skillful teacher.” The Physical Sciences Study Committee had just completed a series of films that attempted to bring together current film technology, the expertise of the film producer and the knowledge and experience of outstanding physics teachers. Today a critic of pedagogical films would find much to change in the PSSC films. Yet they did open new territory for physics teachers, and parts of these films survive today in the videodisc series Physics: Cinema Classics.
Special Issue: Nonlinear Optics
Authors: Garmire Elsa
Published: January 2008

Before the advent of lasers, transparent optical materials were assumed to be essentially passive, unaffected by light traveling through them. The high powers of laser beams made it possible for the first time to observe that the presence of light can indeed affect the medium. Intense light can, for example, change the refractive index or absorption of an optical material.
Nonlinear Optical Frequency Conversion
Authors: Fejer Martin M.
Published: January 2008

The colored rings shown in figure 1 are a spectacular manifestation of one type of nonlinear optical frequency conversion: parametric amplification of quantum noise. The amplification in this case is produced by the propagation of an intense pulse of ultraviolet radiation through a crystal of barium borate. When intense electromagnetic radiation propagates through such a material, whose polarization response at optical frequencies manifests a strongly nonlinear dependence on electric field amplitude, nonlinear mixing of the input radiation generates new spectral components. We can exploit this phenomenon to generate coherent radiation at frequencies for which we have no convenient laser sources.
Yakov Il'ich Frenkel
Authors: Peierls Rudolf
Published: January 2008

February 1994 saw the centenary of the birth of Yakov Il'ich Frenkel, a distinguished Russian theoretical physicist. His was one of the well-known names among physicists in the first half of the century. He belonged to the generation of universalists, and his contributions range from condensed matter to nuclear physics, and from classical electrodynamics to geophysics and biophysics. He was a prolific writer, and his books, translated into German and English, were widely used texts. He educated many graduate students and played an important part in building up physics institutions in the Soviet Union in the late 1920s and '30s
The Origin of the Earth
Authors: Ahrens Thomas J.
Published: January 2008

The question of the origin of the blue planet pictured in figure 1 is related to other questions about our beginnings. These include the origin of the universe, the evolution of galaxies and stars, the origin of life and the ascent of humankind. In the late 1700s both Pierre-Simon Laplace and Immanuel Kant suggested that Earth and the other planets in the solar system had condensed from a flattened nebular disk surrounding the Sun. Since these astute hypotheses were suggested, a series of well-known physical scientists including James Jeans, Gerald Kuiper and Harold Urey have developed a now widely accepted theory of the accretion of the Earth and planets. Their theory, which I describe below, was based on telescopic observations of the solar system, theoretical calculations and the study of meteorites. Now referred to as the Schmidt theory (after Otto Yu. Schmidt of the Institute of the Earth, Moscow), it explains the formation of the planets as resulting from the accretion of already solid bodies.
Complex Dynamics of Mesoscopic Magnets
Authors: Awschalom David D. , DiVincenzo David P.
Published: January 2008

For many years physicists thought small structures would be nearly ideal systems in which to explore and manipulate magnetic interactions. On a small enough length scale the interactions between individual atomic spins cause their magnetic moments to align in the ordered pattern of a single domain, without the complication of domain walls separating regions of varying orientation. For particle sizes at or below that of a single domain, many theoretical models of dynamical behavior predict simple, stable magnets with controllable classical properties. However, as with advances in semiconductor physics, the process of miniaturizing magnetic materials has unexpectedly revealed fascinating new classical and quantum mechanical phenomena. Even the simplest magnetic system, the isolated single-domain particle, exhibits a wealth of exotic behavior that pushes us to the limits of our present understanding of the fundamentals of magnetism.
Interactions of Ultra-Intense Laser Light with Matter
Authors: Joshi Chandrashekhar J. , Corkum Paul B.
Published: January 2008

When the laser made its debut in 1960, it was often called a solution looking for a problem. Today the laser is hailed as one of the most significant inventions of the 20th century. Lasers are used in almost all fields of science and technology, and they have become commonplace in daily life, from supermarket scanners to CD players. The recent development of ultrahigh-power lasers has opened exciting research opportunities in the field of laser-matter interactions. They range from the interaction of laser light with single atoms to collective effects in plasmas.
Quantum Information and Computation
Authors: Bennett Charles H.
Published: January 2008

Thpheoretical computer scientists, like their counterparts in physics, suffer and benefit from a high level of intellectual machismo. They believe they have some of the biggest brains around, which they need to think about some of the hardest problems. Like mathematicians, they prove theorems and doubt the seriousness of those who don't. Lately, however, theoretical computer scientists have sought the help of physicists in understanding quantum mechanics, a hard part of physics which they now believe has great significance for their own field.
Fissile Material Security in the Post-Cold-War World
Authors: von Hippel Frank
Published: January 2008

During the cold war, the US and the Soviet Union each produced enough fissile material to make tens of thousands of nuclear weapons—between 100 and 200 metric tons of plutonium and about 1000 tonnes of highly enriched uranium (uranium enriched to more than 20% in U-235). This weapons-usable fissile material seemed invulnerable to theft until the collapse of the Soviet Union in 1991. Since then, subkilogram quantities of plutonium and multikilogram quantities of highly-enriched uranium have been intercepted in Russia, the Czech Republic and Germany—apparently stolen from Russian nuclear facilities and intended for sale. the old Soviet security system for fissile material, which focused on the surveillance and control of those in contact with such material, has been largely swept away. Gone too is the economic security of nuclear workers, who may now be tempted or threatened by predatory criminal groups. the situation poses a grave risk to global security, because the biggest obstacle facing non-nuclear-weapons states or even terrorist groups interested in acquiring nuclear weapons is lack of access to the bomb material.
Bethe Fest: A Tribute to a Titan of Modern Physics
Authors: Goodwin Irwin
Published: January 2008

Even at the age of 88, Hans Albrecht Bethe is one of the world's most resourceful and responsible physicists. He also is one of the most universally admired—not only for his scientific accomplishments but also for his courage in taking on many sensitive political issues and his ability to attract some of the best and brightest students. So his colleagues, students and friends found it irresistible to mark his 60 years at Cornell University, where he arrived in 1935 as an emigré from Nazi Germany and where he has remained ever since. In just about every respect the Bethe Fest on the Cornell campus on 31 March and 1 April was a fitting reflection of the man himself: scientific talks on the frontiers of physics and astrophysics and an abundance of cordiality, warmth, humor and good food.
Where Does the Proton Really Get Its Spin?
Authors: Jaffe Robert L.
Published: January 2008

In 1987 the European Muon Collaboration, which had been scattering muons off polarized protons at CERN, shocked the particle physics community with the announcement that little or none of the proton's spin can be attributed to the spins of its three constituent quarks—two “up” quarks and one “down” quark. That report precipitated what became known as “the spin crisis.”
The Role of Science in Our Society
Authors: Richter Burton
Published: January 2008

Science, particularly physics, has been in a relatively privileged position in the United States since the end of World War II. Support by the government has been generous, and those of us whose careers have spanned the period since World War II have, until recently, seen research funding increasing in real terms. Our support rested on two assumptions: Science would improve the lives of the citizens, and science would make us secure in a world that seemed very dangerous because of the US-USSR confrontation.
Eugene Paul Wigner: A Towering Figure of Modern Physics
Authors: Vogt Erich
Published: January 2008

With the death on 1 January 1995 of Eugene Wigner, at the age of 92, we lost one of the towering figures who built the edifice of quantum mechanics. Both his scientific work and his personality have become legendary. His own recollections, recorded late in his long life, and his earlier book of “Reflections,” help give us insight into his singular view of science, his role as a teacher at Princeton, his strong personal style and the great depth and breadth of his scientific knowledge.
Magnetoelectronics Today and Tomorrow
Authors: Simonds John L.
Published: January 2008

Mention magnetics and an image arises of musty physics labs peopled by old codgers with iron filings under their fingernails—good science, this, but not the stuff from which career dreams are spun. Yes, you say, but what about the giant magnetic recording industry—it's still healthy, isn't it? Not according to some. The popular press has made statements about magnetic recording being a technology that has reached its maturity and has limited growth potential. Aficionados of semiconductor memory even advised a few years ago that memory cards based on semiconductor technology would become price competitive with magnetic hard-disk drives by 1995. This prediction has fallen short by two orders of magnitude.
The Industrialization of American Astronomy, 1880–1940
Authors: Lankford John , Slavings Ricky L.
Published: January 2008

The rise of big science is often linked to World War II and the cold war. However, such an interpretation ignores the historical roots of big science in the six decades preceding the war. Here we discuss one aspect of the development of big science in America: the industrialization of astronomy and astronomy's emergence as the biggest of the sciences in an age of little science.
Special Issue: New Light on Early Soviet Bomb Secrets
Authors: Holloway David
Published: January 2008

Nuclear history has opened up remarkably since the end of the cold war and the collapse of the Soviet Union. The Soviet nuclear program and the history of the US-Soviet nuclear arms race can now be studied in quite a new way, thanks to information from Russian archives and from participants in the program itself.
Thermonuclear Milestones: (2) Beginnings of the Soviet H-Bomb Program
Authors: Goncharov German A.
Published: January 2008

In late 1945 Soviet physicist Yakov Il'ich Frenkel suggested that fission bombs might be used to fuse light nuclei and thus release even greater energies. In a memo addressed to Igor Vasilievich Kurchatov dated 22 September 1945, he pointed out that “it would be in our best interest to utilize the high, billion-degree temperatures developed in the explosion of an atomic bomb in application to synthetic reactions (for example, to produce helium from hydrogen), which are the energy source of stars and which could even further increase the energy released in the explosion of the principal substance (uranium, bismuth, lead),” Despite the error in estimating the temperatures in an atomic explosion and the fallacy of suggesting that bismuth and lead nuclei are fissionable, the thought expressed by Frenkel is significant as the first documented Soviet communication on the topic.
Nobel Chemistry Prize Goes to Curl, Kroto and Smalley for Discovering Fullerenes
Authors: Schwarzschild Bertram
Published: January 2008

On 10 December, the 100th anniversary of Alfred Nobel's death, the king of Sweden will award the 1996 Nobel Prize in Chemistry to Robert F. Curl, Harold W. Kroto and Richard E. Smalley, “for their discovery of fullerenes.” Curl and Smalley are professors of chemistry at Rice University, in Houston, where the three made the discovery in 1985. Kroto is a Royal Society research professor at the University of Sussex in Brighton, England.
Electronic Publishing of Scientific Journals
Authors: Boyce Peter B. , Dalterio Heather
Published: January 2008

Scientific societies were founded to foster communication among their members. As we move into the era of enhanced electronic communication, the research community is seeking to make the exchange of information among scientists faster and better, at reasonable cost. The Internet offers a wide variety of possibilities for accomplishing this goal.
From Mars to Minerva: The Origins of Scientific Computing in the AEC Labs
Authors: Seidel Robert W.
Published: January 2008

In the 50 years since the ENIAC (Electronic Numerical Integrator and Computer) was publicly announced at the Moore School of Electrical Engineering at the University of Pennsylvania, computers have transformed the natural sciences and even become the subject of their own science. Designed to be a tool of Mars rather than Minerva, the ENIAC was finished too late to be of use for its intended purpose of calculating ballistic tables in World War II. It was initially applied instead to the “Los Alamos problem,” a calculation of the behavior of Edward Teller's thermonuclear weapon design, known as the “Super.” However, after the formation of the Atomic Energy Commission (AEC) in 1946. Los Alamos and the other AEC laboratories actively developed computers and applied them to a wide variety of physical problems in a fruitful partnership with industry and academia.
Effect of oestradiol and progesterone on the instant and directional velocity of microsphere movements in the rat oviduct: gap junctions mediate the kinetic effect of oestradiol
Authors: Ríos Mariana , Hermoso Marcela , Sánchez Trinidad M. , Croxatto Horacio B. , Villalón Manuel J.
Published: January 2008

The oviducal transport of eggs to the uterus normally takes 72–96 h in the rat, but this is reduced to less than 20 h after a single injection of oestradiol (E2). This accelerated transport is associated with an increased frequency of pendular movements in the isthmic segment of the oviduct, with increased levels of the gap junction (GJ) component Connexin (Cx) 43, and is antagonised by progesterone (P). In the present study, we investigated the effect of these hormones on the instant and directional velocity of pendular movements and the role of the GJ and its Cx43 component in the kinetic response of the oviduct to E2 and P. Using microspheres as egg surrogates, microsphere instant velocity (MIV) was measured following treatment with E2, P or P + E2, which accelerate or delay egg transport. Microspheres were delivered into the oviduct of rats on Day 1 of pregnancy and their movement within the isthmic segment was recorded. Oestrogen increased MIV with faster movement towards the uterus. After P or P + E2, MIV was similar to that in the control group. Two GJ uncouplers, namely 18α- and 18β-glycyrrhetinic acid, blocked the effect of E2 on MIV. Connexin 43 mRNA levels increased over that seen in control with all treatments. In conclusion, the effects of E2 on MIV resulted in faster movements that produced accelerated egg transport towards the uterus. Gap junctions are probably involved as smooth muscle synchronisers in this kinetic effect of E2, but the opposing effects of E2 and P are not exerted at the level of Cx43 transcription.
Pregnancy and calving rates following transfer of in-vitro-produced river and F1 (river × swamp) buffalo (Bubalus bubalis) embryos in recipients on natural oestrus or synchronised for ovulation
Authors: Liang Xianwei , Zhang Xiufang , Yang Bingzhuang , Cheng Mingtang , Huang Fenxiang , Pang Chunying , Qing Guangsheng , Liao Chaohui , Wei Shengju , Senatore Elena M. , Bella Antonino , Presicce Giorgio A.
Published: January 2008

The main objective of this study was to compare pregnancy and calving rates following transfer of in-vitro-produced fresh river and F1 (river × swamp) buffalo embryos in recipients synchronised by Ovsynch protocol or following natural oestrus. River embryos were produced from cumulus–oocyte complexes (COCs) derived by ovum pick up (OPU) on 40 Murrah and Nili-Ravi donor buffaloes over a twice-weekly collection schedule for 120 single OPUs. F1 embryos were produced by fertilisation of swamp COCs recovered from abattoir ovaries coincubated with river sperm cells. Both groups of embryos were produced following the same protocol for in vitro production. With regard to the OPU source of COCs, 923 antral follicles were punctured and 647 COCs were recovered (70%). From 462 selected COCs for IVM, 257 (55.6%) cleaved zygotes were recorded leading to 93 blastocysts (20.1%). In total, 590 swamp COCs were aspirated from abattoir ovaries and 476 were selected for IVM leading to 270 (56.7%) cleaved zygotes and resulting in 137 blastocysts (28.8%). River and F1 embryos were transferred between Day 6 to 7 of in vitro development, corresponding to blastocyst–expanding blastocyst, into F1 recipients synchronised by Ovsynch and swamp buffaloes following natural oestrus, respectively, each of them receiving two embryos. According to palpation per rectum of the ovaries at the time of embryo transfer, 26 of the 47 (55.3%) F1 recipients synchronised by Ovsynch were considered suitable for transfer, resulting in seven pregnancies (26.9%) and four calvings (15.3%) owing to three abortions occurring between 2 and 3 months of pregnancy. In total, 29 swamp recipients following natural oestrus were judged suitable as recipients, resulting in 12 pregnancies (41.4%) and 10 calvings (34.5%) owing to two abortions at 2 and 3 months of gestation respectively. Pregnancy and calving rates following transfer of river and F1 embryos were similar. Likewise, weight at birth of calves derived from transfer of river and F1 embryos was not different: 30.5 ± 1.4 and 32.9 ± 2.4 respectively. Pregnancy and calving rates following AI in a group of river and swamp buffaloes considered for reference in this study were similar to recipients carrying in-vitro-produced embryos. Collectively, no apparent postnatal complications were recorded in resulting live calves.