bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of nuclear weapons
Authors: Sartori Leo
Published: August 2008

The intensity of public debate on issues involving nuclear weapons and strategic policy is currently at an all-time high. This is surely a welcome development. Although the issues are largely political, they cannot be addressed without some knowledge of the properties of nuclear weapons and of the destruction that their use could bring about It is our particular responsibility as technically trained citizens to be informed of the basic facts concerning nuclear weapons and to help our fellow citizens understand them so that they can contribute more effectively to the debate It is my hope that this article—a presentation of the fundamental principles governing nuclear explosions and their effects—will be useful to those interested in carrying out this responsibility for education on nuclear war.
Physics and the world in 1982
Authors: Goldhaber Maurice
Published: August 2008

Physicists and organizations of physicists, like all individuals and groups, are subject to the influence of events in this country and throughout the world. It is interesting to examine how physicists and The American Physical Society, through its elected council, committees, president and professional staff, have reacted to and become involved in some of these events. A quick glance at the last year shows physicists active along a broad front of important issues—working to increase the number of women in physics, trying to improve our knowledge of the Washington scene, joining in an effort to minimize government control over the flow of technical information when national security is not at stake, standing up for physicists and other scientists in difficulty in many countries, and organizing educational activities concerning nuclear-arms control. At the same time, within budgetary limits, physicists have vigorously continued to pursue research.
Computations in plasma physics
Authors: Cohen Bruce I. , Killeen John
Published: August 2008

Physicists around the world are today vigorously pursuing research in plasma physics, not only because nearly all matter in the Universe is in the plasma state, but because plasma physics has many important terrestrial applications. Researchers in the field quickly recognized the complexity of phenomena supported by collections of charged particles, and by using computers they have significantly accelerated the maturation of plasma science. Recent advances in computational models and computer hardware have greatly improved the correspondence of computer calculations with experimental data.
Superlattices from mismatched materials
Authors: Schwarzschild Bertram M.
Published: September 2008

Leo Esaki and Raphael Tsu at IBM pointed out in 1970 that imposing an artificial periodicity one or two orders of magnitude larger than the natural lattice spacing on a semiconductor crystal ought to yield novel and potentially useful electrical and optical effects. Since then, considerable work has been done on fabricating and investigating the properties of superlattices—epitaxially grown stacks of alternating thin layers (on the order of a hundred angstroms) of two different semiconductor materials. But until recently the requirement of good, defect-free crystal matching at the interfaces has severely restricted the choice of materials used to grow such artificially periodic structures. Almost all superlattices were grown with alternating layers of GaAs and Alx Ga1−x As with the lattice constants (spacings) of the two materials differing by only about a part in a thousand.
Directed energy weapons—where are they headed?
Authors: Levi Barbara G.
Published: September 2008

A futuristic look at the nation's defensive weapons systems sometimes includes visions of space-based lasers or particle beams, able to direct their energy precisely and devastatingly upon any target. The Defense Department has several technology programs that deal with these directed-energy weapons, although practical implementation appears to be at least a decade away. President Reagan may now wish to place more stress on such programs. In a speech to the nation on 23 March, the President proposed a “comprehensive and intensive effort to define the long-term R&D program” on defensive weapons against ballistic missiles. He hoped to ensure peace by rendering such nuclear weapons launchers “impotent and inoperative.” One ingredient of such a program might be a land- or space-based system of lasers and particle beams.
Less-elusive neutrinos to look for oil and gas deposits
Authors: Lubkin Gloria B.
Published: September 2008

Four well-known particle physicists recently went public with a far-out scheme using high-energy neutrinos to explore far into the depths of the Earth. The group—Alvaro De Rujula (CERN), Sheldon Glashow (Harvard), Robert R. Wilson (Columbia) and Georges Charpak (CERN)—suggested a number of such geological studies: exploration for oil, natural gas and high-Z ores, and determination of the vertical density profile of the Earth.
Physics research organization, Italian style
Authors: Rizzuto Carlo
Published: September 2008

Most physics research in Italy is organized and conducted through six national research groups. This way of organizing research through national groups has proved very successful and may in part explain how it is that Italian physicists have been able to remain competitive with their international colleagues despite their much lower levels of funding. (For example, in 1981 the total government funding for non-nuclear physics in Italy was about $16 million and $75 million for nuclear physics, of which about $33 million was for CERN.) Our experience has been that the structure provided by the national groups enables the highest productivity possible under difficult financial constraints. The structure has also proved to be valuable in starting and carrying out scientific and technical programs requiring high levels of exchange between many different locations and across geographical, institutional and disciplinary barriers. I suggest that a similar approach could be used to advantage by developing countries and for specific fields in Europe or elsewhere, to counteract the difficult periods connected with funding and student enrollment expected in the near future. It might also be applied on an international basis for specific purposes and programs.
Proton decay not seen at predicted rate
Authors: Schwarzschild Bertram M.
Published: September 2008

In the year that has already seen the discovery of the three intermediate vector bosons of electroweak unification, it would be wonderful to report that proton decay has also been verified—establishing a grand unification of the weak, electromagnetic and strong interactions in one encompassing theory. But, alas, it appears we will have to be patient.
Construction of the e–p collider HERA under way in Hamburg
Authors: Lubkin Gloria B.
Published: September 2008

Construction has begun at DESY on an electron–proton collider, the first of its kind in the world. This Hadron Electron Ring Accelerator, or HERA, will collide 820-GeV protons with 30-GeV electrons, providing 314 GeV in the center of mass. The proton storage ring uses 4.53-T superconducting magnets. The electron storage ring, on the other hand, uses conventional technology. But the ring will produce longitudinally polarized electrons, a capability never achieved in a storage ring before. Because of this capability and its high center-of-mass energy, when HERA starts running experiments in 1990, it should shed new light on the weak interaction by charged and neutral currents with quarks
Special issue: Materials research
Authors: Dresselhaus Mildred S.
Published: September 2008

In the past few years, the focus of research in condensed-matter physics has shifted to exotic materials, novel structural arrangements, surfaces, interfaces and imperfect systems. Advances leading to the fabrication of metal oxide–semiconductor devices and superlattice structures, for example, have made possible the study of quantum-well structures and the discovery of the quantum Hall effect. After a decade of progress with this technology, combined with advances in computer-controlled processing, we can now tailor composition and impurity profiles at an atomic level, monitor the effects that a fraction of a monolayer of atoms has on a surface and control the deposition of atoms layer by layer, capabilities that have already led to the discovery of new physics, such as the fractional quantum Hall effect. (See PHYSICS TODAY, July 1983, page 19.) Venkatesh Narayanamurti, in his article on page 24, captures the excitement of the strong interplay between basic physics and technology in condensed matter physics.
Crystalline semiconductor heterostructures
Authors: Narayanamurti Venkatesh
Published: September 2008

The great advances in solid-state electronics can be traced to a unique combination of basic conceptual advances, the perfection of new materials and the development of new device principles. Ever since the invention of the transistor at Bell Laboratories almost forty years ago, we have witnessed a spectacular growth in silicon technology, leading to increasingly higher densities of devices and more complex functions. Almost as revolutionary as the invention of the transistor in 1947 was the invention of the laser a decade later. Thus, nearly concurrent with the electronics revolution, we have seen another technological revolution, the so-called photonics revolution: using beams of laser light for information transmission. The lasers that provide light for today's lightwave communication systems are made not from silicon but from compound semiconductors. These are generally compounds of elements from group III of the periodic table, such as Ga, Al and In, along with elements from group V, most notably As, P and Sb.
Superconducting materials
Authors: Beasley Malcolm R. , Geballe Theodore H.
Published: September 2008

Superconductivity almost from its beginning has depended upon an interplay between materials research and condensed-matter physics. This interplay continues unabatedly today. The seemingly eternal fascination with the phenomenon of superconductivity lies in the spectacular electrical and magnetic properties exhibited by superconductors—zero resistance, the Meissner effect and the various macroscopic quantum aspects of superconductivity. Equally important to the practitioners of the trade is the fact that these striking electrical and magnetic properties make superconductivity easy to detect. In short, the evidence of superconductivity broadcasts itself, even when present only in trace amounts.
NSAC recommends a relativistic heavy-ion collider
Authors: Schwarzschild Bertram M.
Published: September 2008

The Nuclear Science Advisory Committee submitted its new Long Range Plan for Nuclear Science to DOE and NSF last month. The “highest priority” major new facility recommended in the 1983 NSAC Plan appears already to have aroused considerable excitement beyond the borders of the traditional nuclear-physics community. NSAC is urging the construction of an ultrarelativistic heavy-ion collider—a double ring of counter-circulating 30-GeV-per-nucleon beams of ions all the way up to uranium.
Special issue: Fluids out of equilibrium
Authors: Hanley H. J. M.
Published: September 2008

We live in a world of fluids—air, water, blood, gasoline. In fact, fluids are so vital and familiar to everyday life that one can easily take their varied and fascinating properties for granted. Many household products exist because they make use of some exotic flow phenomena. A cookbook is a storehouse of fluid facts. Our industrial civilization began when the change of water to steam—really an extraordinary occurrence in its own right—was appreciated and applied. Fluids, then, have intrigued scientists for hundreds of years and their diverse behavior means that their study is rich in concepts and models and draws upon and contributes to many fields; it is truly multidisciplinary, in fact.
Fascinating polymeric liquids
Authors: Bird R. Byron , Curtiss Charles F.
Published: September 2008

Fluid dynamics is an old subject. In 1687, Isaac Newton wrote a simple equation defining the viscosity of a fluid as the coefficient of proportionality between the shear stress and the velocity gradient. Newton's equation does well at describing gases and liquids made up of “light” molecules—those of molecular weight less than about 1000. By the middle of the last century the mathematical description of the flow of such “Newtonian” fluids was well established. This description is based on use of the laws of conservation of mass and momentum.
Generalized hydrodynamics
Authors: Alder Berni J. , Alley W. Edward
Published: September 2008

The object of generalized hydrodynamics is to extend from the macroscopic scale to the microscopic scale the domain in which ordinary hydrodynamics applies. With this extension, under well-defined conditions, we will then, among other things, be able to predict the momentum with which neutrons are scattered at various angles by the fluid; neutron scattering is one of the principal methods by which the dynamic structure of fluids is investigated experimentally.
Atomic physics with synchrotron radiation
Authors: Crasemann Bernd , Wuilleumier François
Published: September 2008

Atomic and molecular science has grown dramatically in the last two decades. Today, the combined membership of the APS Division of Electron and Atomic Physics and Division of Chemical Physics rivals that of the society's largest Division, Condensed Matter.
Visualization of nanoscale peeling of carbon nanotube on graphite
Authors: Ishikawa Makoto , Harada Ryuichi , Sasaki Naruo , Miura Kouji
Published: September 2008

We have fabricated a manipulation system with a force detection, which uses a self-detective cantilever, in a chamber of a scanning electron microscope. This system can simultaneously manipulate a nanoparticle and detect a force needed to move it, a detective resolution of which is approximately 1nN. In this work, nanoscale peeling processes of a multiwalled carbon nanotube (MWCNT) on the graphite substrate have been studied. We have first experimentally obtained the vertical force-distance curve with the characteristic hysteresis loop which exhibits the multistable states between line contact and point contact of the MWCNT shape during the peeling processes.
Electron thermal transport analysis in Tokamak à Configuration Variable
Authors: Asp E. , Kim J.-H. , Horton W. , Porte L. , Alberti S. , Karpushov A. , Martin Y. , Sauter O. , Turri G. ,   the TCV TEAM
Published: September 2008

A Tokamak à Configuration Variable (TCV) [G. Tonetti, A. Heym, F. Hofmann et al., in Proceedings of the 16th Symposium on Fusion Technology, London, U.K., edited by R. Hemsworth (North-Holland, Amsterdam, 1991), p. 587] plasma with high power density (up to 8MW∕m3) core deposited electron cyclotron resonance heating at significant plasma densities (⩽7×1019m−3) is analyzed for the electron thermal transport. The discharge distinguishes itself as it has four distinct high confinement mode (H-mode) phases. An Ohmic H-mode with type III edge localized modes (ELMs), which turns into a type I ELMy H-mode when the ECRH is switched on. The ELMs then vanish, which gives rise to a quasistationary ELM-free H-mode. This ELM-free phase can be divided into two, one without magnetohydrodynamics (MHD) and one with. The MHD mode in the latter case causes the confinement to drop by ∼15%. For all four phases both large-scale trapped electron (TEM) and ion temperature gradient (ITG) modes and small-scale electron temperature gradient (ETG) modes are analyzed. The analytical TEM formulas have difficulty in explaining both the magnitude and the radial profile of the electron thermal flux. Collisionality governs the drive of the TEM, which for the discharge in question implies it can be driven by either the temperature or density gradient. The TEM response function is derived and it is shown to be relatively small and to have sharp resonances in its energy dependence. The ETG turbulence, predicted by the Institute for Fusion Studies electron gyrofluid code, is on the other hand driven solely by the electron temperature gradient. Both trapped and passing electrons add to the ETG instability and turbulent thermal flux. For easy comparison of the results of the above approaches and also with the Weiland model, a dimensionless error measure, the so-called average relative variance is introduced. According to this method the ETG model explains 70% of the variation in the electron heat diffusivity whereas the predictive capabilities of the TEM-ITG models are poor. These results for TCV support the conclusion that the ETG model is able to explain a wide range of anomalous electron transport data, in addition to existing evidence from ASDEX [F. Ryter, F. Leuterer, G. Pereverzev, H.-U. Fahrbach, J. Stober, W. Suttrop, and the ASDEX Upgrade Team, Phys. Rev. Lett. 86, 2325 (2001)], Tore Supra [G. T. Hoang, W. Horton, C. Bourdelle, B. Hu, X. Garbet, and M. Ottaviani, Phys. Plasmas 10, 405 (2003)] and the Frascati Tokamak Upgrade [A. Jacchia, F. D. Luca, S. Cirant, C. Sozzi, G. Bracco, A. Brushi, P. Buratti, S. Podda, and O. Tudisco, Nucl. Fusion 42, 1116 (2002)].
Theory of photoemission from cesium antimonide using an alpha-semiconductor model
Authors: Jensen Kevin L. , Jensen Barbara L. , Montgomery Eric J. , Feldman Donald W. , O’Shea Patrick G. , Moody Nathan
Published: September 2008

A model of photoemission from cesium antimonide (Cs3Sb) that does not rely on adjustable parameters is proposed and compared to the experimental data of Spicer [Phys. Rev. 112, 114 (1958)] and Taft and Philipp [Phys. Rev. 115, 1583 (1959)]. It relies on the following components for the evaluation of all relevant parameters: (i) a multidimensional evaluation of the escape probability from a step-function surface barrier, (ii) scattering rates determined using a recently developed alpha-semiconductor model, and (iii) evaluation of the complex refractive index using a harmonic oscillator model for the evaluation of reflectivity and extinction coefficient.
Laser-heated emissive plasma probe
Authors: Schrittwieser Roman , Ionita Codrina , Balan Petru , Gstrein Ramona , Grulke Olaf , Windisch Thomas , Brandt Christian , Klinger Thomas , Madani Ramin , Amarandei George , Sarma Arun K.
Published: September 2008

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808nm wavelength and an output power up to 50W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.
The effects of anomalous diffusion on power-law blinking statistics of CdSe nanorods
Authors: Tang Jau
Published: September 2008

In this study of fluorescence blinking statistics for nanorods, we present a diffusion-controlled reaction model that leads to a more general formula: t−mexp[−(Γt)n]. This formula describes a short-time power law with a crossover to a stretched exponential decay at later times. Based on quantum Brownian motion for a coupled central harmonic oscillator coupled to heat bath oscillators, we show that the position distribution follows anomalous diffusion with time-dependent diffusion coefficient and drift coefficient. The first and the second moments of the energy fluctuations are shown to be related to the exponent m and n for the blinking statistics.
Simulations of remanence and field distributions of permanent magnet array with rectangular cavity
Authors: Xu X. N. , Lu D. W. , Xu X. B. , Zang W. C. , Madireddi Sesha
Published: September 2008

The magnetic phenomena of a Halbach-type permanent magnet array under a strong self-field such as demagnetization, saturation, deflection, and rotation of remanence vectors occur deep in the interior of the magnets, and thus lead to an inhomogeneous field even for a hollow cylindrical permanent magnet array with circular cavity. Considering the anisotropic magnetization loops of commercially available permanent magnets, the self-consistent remanence and field distributions of a 16 piece hollow cylindrical permanent magnet array with rectangular cavity (HCPMARC) are presented here to simulate the magnetic phenomena inside the magnets. The field distribution of a HCPMARC can be modulated by array structure while keeping both the cross sectional areas of the cavity and the magnets constant. At the expense of field uniformity, a HCPMARC acquires greater center field uniformity than a HCPMACC does. Furthermore, we simulated the magnetization and field distributions for a yoked HCPMARC obtained by replacing the partial permanent magnets with soft ones on both magnetic poles of a yokeless HCPMARC. Such substitution always enhances field uniformity but depresses the center field. This, in turn, causes changes in the average magnitude of the field in the entire rectangular cavity.
Dynamic simulation of atomic force microscope cantilevers oscillating in liquid
Authors: Martin Michael James , Fathy Hosam K. , Houston Brian H.
Published: September 2008

To simulate the behavior of an atomic force microscope (AFM) operating in liquid, a lumped-parameter model of a 40×5 μm2 thick silicon cantilever with natural frequencies ranging from 3.0 to 6.0×105 rad/s was combined with a transient Navier–Stokes solver. The equations of motion were solved simultaneously with the time-dependent flow field. The simulations successfully capture known characteristics of the AFM in liquid, including large viscous losses, reduced peak resonant frequencies, and frequency-dependent damping. From these simulations, the transfer function G(s) of the system was obtained. While the transfer function shares many of the characteristics of a second-order system at higher frequencies, the frequency-dependent damping means that a second-order model cannot be applied. The viscous damping of the system is investigated in greater depth. A phase difference between the peak velocity and peak damping force is observed. Both the phase difference and the magnitude of the damping are shown to be functions of the excitation frequency. Finally, the damping is shown to be strongly dependent on the liquid viscosity and weakly dependent on the liquid density.
Influence of ZnO on the crystallization kinetics and properties of diopside-Ca-Tschermak based glasses and glass-ceramics
Authors: Goel Ashutosh , Tulyaganov Dilshat U. , Shaaban Essam R. , Basu Rajendra N. , Ferreira José M. F.
Published: September 2008

We report on the influence of ZnO on the structural, thermal, and crystallization behavior of the diopside-Ca-Tschermak based glasses, and on the processing, microstructure, and the properties of the sintered glass ceramics. Four glasses with nominal compositions of CaMg0.8Al0.4Si1.8O6, CaMg0.75Zn0.05Al0.4Si1.8O6, CaMg0.70Zn0.10Al0.4Si1.8O6, and CaMg0.60Zn0.20Al0.4Si1.8O6 were obtained by melting at 1580 °C for 1 h. Structural and thermal behavior of the glasses was investigated by Fourier-transform infrared spectroscopy, density measurements, dilatometry, and differential thermal analysis. Nonisothermal crystallization kinetics has been employed to study the crystallization mechanism in the glasses. Sintering, crystallization, microstructure, and properties of the glass ceramics were investigated under nonisothermal heating conditions in the temperature range of 850–1000 °C.
Indium incorporation dynamics into AlInN ternary alloys for laser structures lattice matched to GaN
Authors: Schenk H. P. D. , Nemoz M. , Korytov M. , Vennéguès P. , Dräger A. D. , Hangleiter A.
Published: September 2008

Al 1 − x In x N ternary alloys with solid phase indium compositions between x=0.15 and 0.28 have been grown by metal organic chemical vapor deposition under indium rich conditions within the growth temperature range of 750–810 °C. A thermally activated process with activation energy of 1.05±0.05eV is found to compete with indium incorporation. Smooth epitaxial layers with root mean-squares surface roughness of 0.3–0.8nm are obtained. (Al,In)N films lattice matched to GaN have been introduced into laser diode structures for optical confinement. Optical gain is observed.
Electrorheological response and orientational bistability of a homogeneously aligned nematic capillary
Authors: Reyes J. Adrián , Corella-Madueño A. , Mendoza Carlos I.
Published: September 2008

We consider a homogeneously aligned nematic liquid crystal confined in the region between two rotating coaxial cylinders. We study the nematic’s director and velocity profiles induced by the imposed Couette flow and an applied radial electric field. We present calculations for the specific flow-aligning nematic liquid crystal 4′-n-pentyl-4-cyanobiphenyl and numerically solve a hydrodynamic model assuming hard anchoring and nonslip boundary conditions. We calculate a phase diagram in the parameter space showing a region where there exist multiple equilibrium solutions for the nematic’s configuration and a region where there exists only one stationary solution. We also study the rheology of the system by calculating the apparent viscosity and the first normal stress difference. We find that the competition between the Couette flow and the electric field gives rise to an interesting non-Newtonian response which switches its behavior from shear thickening to shear thinning by exceeding a critical field.
Origin of open circuit voltage in planar and bulk heterojunction organic thin-film photovoltaics depending on doped transport layers
Authors: Uhrich Christian , Wynands David , Olthof Selina , Riede Moritz K. , Leo Karl , Sonntag Stefan , Maennig Bert , Pfeiffer Martin
Published: September 2008

The aim of this article is to investigate the origin of the open circuit voltage (Voc) in organic heterojunction solar cells. The studied devices consist of buckminsterfullerene C60 as acceptor material and an oligophenyl-derivative 4,4′-bis-(N,N-diphenylamino)quaterphenyl (4P-TPD) as donor material. These photoactive materials are sandwiched between indium tin oxide and p-doped hole transport layers. Using two different p-doped hole transport layers, the built-in voltage of the solar cells is independently changed from the metal contacts. The influence of the built-in voltage on the Voc is investigated in bulk and planar heterojunctions. In bulk heterojunctions, in which doped transport layers border directly on the photoactive blend layer, Voc cannot exceed the built-in voltage significantly. Though, in planar heterojunctions, Voc is identical with the splitting of quasi-Fermi levels at the donor-acceptor interface and is thus primarily determined by the difference of the lowest unoccupied molecular orbital of C60 and the highest occupied molecular orbital of 4P-TPD. In planar heterojunctions, the open circuit voltage can exceed the built-in voltage. Furthermore, the investigations show that the efficiency of organic solar cells can be improved by using p-doped charge transport layers with optimized energy level alignment to the active materials. The optimized planar heterojunction shows a fill factor of up to 65.5% and a Voc of 0.95 V. For solar cells with insufficient energy level alignment between the photoactive layer system and the hole transport layer, a reduced Voc in bulk heterojunction cells and a characteristic S shape of the I-V characteristics in planar heterojunction cells are observed.
Neutral and charged excitations in carbon fullerenes from first-principles many-body theories
Authors: Tiago Murilo L. , Kent P. R. C. , Hood Randolph Q. , Reboredo Fernando A.
Published: September 2008

We investigate the accuracy of first-principles many-body theories at the nanoscale by comparing the low-energy excitations of the carbon fullerenes C20, C24, C50, C60, C70, and C80 with experiment. Properties are calculated via the GW–Bethe–Salpeter equation and diffusion quantum Monte Carlo methods. We critically compare these theories and assess their accuracy against available photoabsorption and photoelectron spectroscopy data. The first ionization potentials are consistently well reproduced and are similar for all the fullerenes and methods studied. The electron affinities and first triplet excitation energies show substantial method and geometry dependence. These results establish the validity of many-body theories as viable alternative to density-functional theory in describing electronic properties of confined carbon nanostructures. We find a correlation between energy gap and stability of fullerenes. We also find that the electron affinity of fullerenes is very high and size independent, which explains their tendency to form compounds with electron-donor cations.
Preparation of oriented and aligned H2 and HD by stimulated Raman pumping
Authors: Bartlett Nate C. M. , Miller Daniel J. , Zare Richard N. , Sofikitis Dimitris , Peter Rakitzis T. , Alexander Andrew J.
Published: September 2008

Stimulated Raman pumping has been used to prepare oriented and aligned samples of H2(ν=1,J=1,2,3) and HD(ν=1,J=2) under collision-free conditions using the (1,0) S(0), S(1), Q(1), Q(2), and O(3) lines. The M-sublevel anisotropies were interrogated by polarized [2+1] resonance-enhanced multiphoton ionization via the (0,1) O(2), O(3), and S(1) lines of the E,FΣg+1−XΣg+1 system. The optical excitation schemes employed in this study generate highly oriented and aligned molecular ensembles. We show that the H2(ν=1,J=2,M=0) and H2(ν=1,J=2,M=2) samples retain their initial polarization for greater than 100ns and are therefore suitable candidates for targets or projectiles in future scattering experiments.
Video tracking algorithm of long-term experiment using stand-alone recording system
Authors: Chen Yu-Jen , Li Yan-Chay , Huang Ke-Nung , Jen Sun-Lon , Young Ming-Shing
Published: September 2008

Many medical and behavioral applications require the ability to monitor and quantify the behavior of small animals. In general these animals are confined in small cages. Often these situations involve very large numbers of cages. Modern research facilities commonly monitor simultaneously thousands of animals over long periods of time. However, conventional systems require one personal computer per monitoring platform, which is too complex, expensive, and increases power consumption for large laboratory applications. This paper presents a simplified video tracking algorithm for long-term recording using a stand-alone system. The feature of the presented tracking algorithm revealed that computation speed is very fast data storage requirements are small, and hardware requirements are minimal. The stand-alone system automatically performs tracking and saving acquired data to a secure digital card. The proposed system is designed for video collected at a 640×480 pixel with 16 bit color resolution. The tracking result is updated every 30 frames/s. Only the locomotive data are stored. Therefore, the data storage requirements could be minimized. In addition, detection via the designed algorithm uses the Cb and Cr values of a colored marker affixed to the target to define the tracked position and allows multiobject tracking against complex backgrounds. Preliminary experiment showed that such tracking information stored by the portable and stand-alone system could provide comprehensive information on the animal’s activity.
High throughput system for magnetic manipulation of cells, polymers, and biomaterials
Authors: Spero Richard Chasen , Vicci Leandra , Cribb Jeremy , Bober David , Swaminathan Vinay , O’Brien E. Timothy , Rogers Stephen L. , Superfine R.
Published: September 2008

In the past decade, high throughput screening (HTS) has changed the way biochemical assays are performed, but manipulation and mechanical measurement of micro- and nanoscale systems have not benefited from this trend. Techniques using microbeads (particles ∼0.1–10 μm) show promise for enabling high throughput mechanical measurements of microscopic systems. We demonstrate instrumentation to magnetically drive microbeads in a biocompatible, multiwell magnetic force system. It is based on commercial HTS standards and is scalable to 96 wells. Cells can be cultured in this magnetic high throughput system (MHTS). The MHTS can apply independently controlled forces to 16 specimen wells. Force calibrations demonstrate forces in excess of 1 nN, predicted force saturation as a function of pole material, and powerlaw dependence of F∼r−2.7±0.1. We employ this system to measure the stiffness of SR2+ Drosophila cells. MHTS technology is a key step toward a high throughput screening system for micro- and nanoscale biophysical experiments.
Complex magnetically insulated transmission line oscillator
Authors: Fan Yu-Wei , Zhong Hui-Huang , Shu Ting , Li Zhi-Qiang
Published: September 2008

A magnetically insulated transmission line oscillator (MILO) is a crossed-field device designed specifically to generate microwave power at the gigawatt level, which is a major hotspot in the field of high-power microwaves (HPM) research at present. It is one of the major thrust for MILO development to improve the power conversion efficiency. In order to improve the power conversion efficiency of MILO, a complex MILO is presented and investigated theoretically and numerically, which comprises the MILO-1 and MILO-2. The MILO-2 is used as the load of the MILO-1. The theoretical analyses show that the maximum power conversion efficiency of the complex MILO has an increase of about 50% over the conventional load-limited MILO. The complex MILO is optimized with KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992), and the simulation results agree with the theoretical results.
Interstitial-based boron diffusion dynamics in amorphous silicon
Authors: Kong Ning , Kirichenko Taras A. , Hwang Gyeong S. , Banerjee Sanjay K.
Published: September 2008

Using density-functional theory calculations we identified an interstitial-based fast boron diffusion mechanism in amorphous silicon. We found that interstitial-like point defects, omnipresent in as-implanted silicon, to be very stable in an amorphous network and can form highly mobile pair with Boron atoms. The transient existence of such point defects in amorphous silicon is suggested to play an important role in boron diffusion. We found the activation energy for this pathway to be 2.73 eV, in good agreement with experimental results. In addition, this mechanism is consistent with the experimentally reported transient and concentration-dependent features of boron diffusion in amorphous silicon.
Carrier doping in anatase TiO2 film by perovskite overlayer deposition
Authors: Takahashi K. S. , Hwang H. Y.
Published: September 2008

Heterostructures composed of perovskite overlayers on anatase TiO2 films were fabricated on LaAlO3 substrates. By depositing LaTiO3 and LaAlO3 thin films on the insulating anatase TiO2 films, metallic conduction was induced in the anatase layer with the increasing thickness of the perovskite overlayer. This perovskite overlayer deposition on TiO2 provides a method to induce free carriers, which may be applied to the development of transparent conducting oxides.
Gain optimization in ion sensitive field-effect transistor based sensor with fully depleted silicon on insulator
Authors: Shalev Gil , Doron Amihood , Virobnik Udi , Cohen Ariel , Sanhedrai Yosi , Levy Ilan
Published: September 2008

The sensitivity in bulk silicon (Si) and in silicon-on-insulator (SOI) ion sensitive field-effect transistor (ISFET) is determined according to its manufacturing process, geometry, and the selected materials. However, in SOI ISFETs the back gate biasing plays a major part in device sensitivity. It is shown that in fully depleted SOI ISFET the existing charge coupling between the front and back interfaces allows for gain optimization in terms of both gain increase and widening of the conventional gain peak. This stands in contrast with bulk Si ISFET where only a single channel exists. Here we report gain increase in ∼40% and increase in gain peak width of ∼250%.
Valence band offset of ZnO/Zn0.85Mg0.15O heterojunction measured by x-ray photoelectron spectroscopy
Authors: Su S. C. , Lu Y. M. , Zhang Z. Z. , Shan C. X. , Li B. H. , Shen D. Z. , Yao B. , Zhang J. Y. , Zhao D. X. , Fan X. W.
Published: September 2008

X-ray photoelectron spectroscopy was used to measure the valence band offset at the ZnO/Zn0.85Mg0.15O heterojunction grown by plasma-assisted molecular beam epitaxy. The valence band offset (ΔEV) is determined to be 0.13 eV. According to the experimental band gap of 3.68 eV for the Zn0.85Mg0.15O, the conduction band offset (ΔEC) in this system was calculated to be 0.18 eV. The ΔEc:ΔEv in ZnO/Zn0.85Mg0.15O heterojunction was estimated to be 3:2.
Germanium-induced stabilization of a very high-k zirconia phase in ZrO2/GeO2 gate stacks
Authors: Tsipas P. , Volkos S. N. , Sotiropoulos A. , Galata S. F. , Mavrou G. , Tsoutsou D. , Panayiotatos Y. , Dimoulas A. , Marchiori C. , Fompeyrine J.
Published: September 2008

Electrical data on ZrO2/GeO2 stacks prepared by atomic oxygen beam deposition on Ge at 225 °C reveal a relatively weak dependence of the stack equivalent oxide thickness upon the ZrO2 thickness. This trend points to a very high zirconia dielectric permittivity (k) value which is estimated to be around 44. This is indicative of zirconia crystallization into a tetragonal phase which is also supported by x-ray diffraction data. X-ray photoelectron spectroscopy analysis is in line with the assumption that due to a finite GeO2 decomposition, Ge is incorporated into the growing ZrO2, thus, stabilizing the high-k tetragonal phase.
The gas centrifuge and nuclear weapons proliferation
Authors: Wood Houston G. , Glaser Alexander , Kemp R. Scott
Published: September 2008

Uranium enrichment by centrifugation is the basis for the quick and efficient production of nuclear fuel—or nuclear weapons.
HLA class I alleles tag
HLA-DRB1
*
1501
haplotypes for differential risk in multiple sclerosis susceptibility
Authors: Chao Michael J. , Barnardo Martin C. N. M. , Lincoln Matthew R. , Ramagopalan Sreeram V. , Herrera Blanca M. , Dyment David A. , Montpetit Alexandre , Sadovnick A. Dessa , Knight Julian C. , Ebers George C.
Published: September 2008

The major locus for multiple sclerosis (MS) susceptibility is located within the class II region of the Major Histocompatibility Complex (MHC).
HLA-DRB1
alleles, constituting the strongest MS susceptibility factors, have been widely exploited in research including construction of transgenic animal models of MS. Many studies have concluded that
HLA-DRB1
*
15
allele itself determines MS-associated susceptibility. If this were true, haplotypes bearing this allele would confer equal risk. If
HLA-DRB1
*
15
bearing haplotypes differed for risk, roles for other loci in this region would be implied and further study of the fine structure of this locus would be compelling. We have tested the hypothesis comparing haplotypes stratified by HLA class I tagging. We show here that
HLA-DRB1
*
15
-bearing-haplotypes in 1970 individuals from 494 MS families are indeed heterogeneous. Some
HLA-DRB1
*
15
haplotypes determine susceptibility while others do not. Three groups of class I tagged
HLA-DRB1
*
15
haplotypes were
not
over-transmitted: (
i
)
HLA-DRB1
*
15-HLA-B
*
08
(TR = 25, NT = 23, Odds Ratio = 1.09), (
ii
)
-HLA-B
*
27
(TR = 18, NT = 17, Odds Ratio = 1.06), and (
iii
) rare
HLA-DRB1
*
15
haplotypes (frequency <0.02). Rare haplotypes were significantly different from common haplotypes, and transmissions were remarkably similar to those for class-I-matched non-
HLA-DRB1
*
15
haplotypes. These results unambiguously indicate that
HLA-DRB1
*
15
is part of a susceptibility haplotype but cannot be the susceptibility allele itself, requiring either epistatic interactions, epigenetic modifications on some haplotypes, or nearby structural variation. These findings strongly imply that differences among
HLA-DRB1
*
15
haplotypes will furnish the basis for MHC-associated susceptibility in MS and raise the possibility that the MHC haplotype is the fundamental unit of genetic control of immune response.
Age-related top-down suppression deficit in the early stages of cortical visual memory processing
Authors: Gazzaley Adam , Clapp Wesley , Kelley Jon , McEvoy Kevin , Knight Robert T. , D'Esposito Mark
Published: September 2008

In this study, electroencephalography (EEG) was used to examine the relationship between two leading hypotheses of cognitive aging, the inhibitory deficit and the processing speed hypothesis. We show that older adults exhibit a selective deficit in suppressing task-irrelevant information during visual working memory encoding, but only in the early stages of visual processing. Thus, the employment of suppressive mechanisms are not abolished with aging but rather delayed in time, revealing a decline in processing speed that is selective for the inhibition of irrelevant information. EEG spectral analysis of signals from frontal regions suggests that this results from excessive attention to distracting information early in the time course of viewing irrelevant stimuli. Subdividing the older population based on working memory performance revealed that impaired suppression of distracting information early in the visual processing stream is associated with poorer memory of task-relevant information. Thus, these data reconcile two cognitive aging hypotheses by revealing that an interaction of deficits in inhibition and processing speed contributes to age-related cognitive impairment.
View From Iran
Authors: Ebadi Shirin
Published: August 2008

Nobel Peace Prize laureate Shirin Ebadi reflects on the state of free expression
The Politics of Terror
Authors: Gearty Conor
Published: August 2008

In the drive to tackle extremism, debate is being undermined and fear is driving the agenda. Conor Gearty makes the case for common sense
Interpreting conjunctions
Authors: Bott Lewis , Frisson Steven , Murphy Gregory L.
Published: September 2008

The interpretation generated from a sentence of the form P and Q can often be different to that generated by Q and P, despite the fact that and has a symmetric truth-conditional meaning. We experimentally investigated to what extent this difference in meaning is due to the connective and and to what extent it is due to order of mention of the events in the sentence. In three experiments, we collected interpretations of sentences in which we varied the presence of the conjunction, the order of mention of the events, and the type of relation holding between the events (temporally vs. causally related events). The results indicated that the effect of using a conjunction was dependent on the discourse relation between the events. Our findings contradict a narrative marker theory of and, but provide partial support for a single-unit theory derived from Carston (2002). The results are discussed in terms of conjunction processing and implicatures of temporal order.
Regulation of chromatin binding by a conformational switch in the tail of the Ran exchange factor RCC1
Authors: Hao Yi , Macara Ian G.
Published: September 2008

RCC1 is the only known exchange factor for the Ran guanosine triphosphatase and performs essential roles in nuclear transport, spindle organization, and nuclear envelope formation. RCC1 binds to chromatin through a bimodal attachment to DNA and histones, and defects in binding cause chromosome missegregation. Chromatin binding is enhanced by apo-Ran. However, the mechanism underlying this regulation has been unclear. We now demonstrate that the N-terminal tail of RCC1 is essential for association with DNA but inhibits histone binding. Apo-Ran significantly promotes RCC1 binding to both DNA and histones, and these effects are tail mediated. Using a fluorescence resonance energy transfer biosensor, we detect conformational changes in the tail of RCC1 coupled to the two binding modes and in response to interactions with Ran and importin-α. The biosensor also reports changes accompanying mitosis in living cells. We propose that Ran induces an allosteric conformational switch in the tail that exposes the histone-binding surface on RCC1 and facilitates association of the positively charged tail with DNA.
Delayed maturation of an IL-12–producing dendritic cell subset explains the early Th2 bias in neonatal immunity
Authors: Lee Hyun-Hee , Hoeman Christine M. , Hardaway John C. , Guloglu F. Betul , Ellis Jason S. , Jain Renu , Divekar Rohit , Tartar Danielle M. , Haymaker Cara L. , Zaghouani Habib
Published: September 2008

Primary neonatal T cell responses comprise both T helper (Th) cell subsets, but Th1 cells express high levels of interleukin 13 receptor α1 (IL-13Rα1), which heterodimerizes with IL-4Rα. During secondary antigen challenge, Th2-produced IL-4 triggers the apoptosis of Th1 cells via IL-4Rα/IL-13Rα1, thus explaining the Th2 bias in neonates. We show that neonates acquire the ability to overcome the Th2 bias and generate Th1 responses starting 6 d after birth. This transition was caused by the developmental maturation of CD8α+CD4− dendritic cells (DCs), which were minimal in number during the first few days of birth and produced low levels of IL-12. This lack of IL-12 sustained the expression of IL-13Rα1 on Th1 cells. By day 6 after birth, however, a significant number of CD8α+CD4− DCs accumulated in the spleen and produced IL-12, which triggered the down-regulation of IL-13Rα1 expression on Th1 cells, thus protecting them against IL-4–driven apoptosis.
miR-181b negatively regulates activation-induced cytidine deaminase in B cells
Authors: de Yébenes Virginia G. , Belver Laura , Pisano David G. , González Susana , Villasante Aranzazu , Croce Carlo , He Lin , Ramiro Almudena R.
Published: September 2008

Activated B cells reshape their primary antibody repertoire after antigen encounter by two molecular mechanisms: somatic hypermutation (SHM) and class switch recombination (CSR). SHM and CSR are initiated by activation-induced cytidine deaminase (AID) through the deamination of cytosine residues on the immunoglobulin loci, which leads to the generation of DNA mutations or double-strand break intermediates. As a bystander effect, endogenous AID levels can also promote the generation of chromosome translocations, suggesting that the fine tuning of AID expression may be critical to restrict B cell lymphomagenesis. To determine whether microRNAs (miRNAs) play a role in the regulation of AID expression, we performed a functional screening of an miRNA library and identified miRNAs that regulate CSR. One such miRNA, miR-181b, impairs CSR when expressed in activated B cells, and results in the down-regulation of AID mRNA and protein levels. We found that the AID 3′ untranslated region contains multiple putative binding sequences for miR-181b and that these sequences can be directly targeted by miR-181b. Overall, our results provide evidence for a new regulatory mechanism that restricts AID activity and can therefore be relevant to prevent B cell malignant transformation.