bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a light-emitting diode tachistoscope
Authors: Thurgood Clementine , Patterson John , Simpson David , Whitfield T. W. Allan
Published: April 2010

This paper describes a new method for rapid visual stimulus delivery, the light-emitting diode (LED) tachistoscope. An array of white LEDs provided a luminous intensity greater than 1 000 000 mcd. This array was placed behind a liquid crystal display (LCD) to function as a backlight; switching it on and off determined the visibility of the display. Commands to illuminate for periods from 1 ms to continuously on were relayed from a computer to the LED array. Changes in luminous intensity at the surface of a LED and the LCD were recorded via oscilloscope. The required duration of light pulses consistently matched the durations displayed, with only microsecond discrepancies due to turn-on and turn-off delays. Images were illuminated on the LCD screen for as little as 1 ms, with the amplitude of the luminance consistent across trials. The LED tachistoscope can be used with any computer to display images extremely briefly, potentially at the submillisecond level, providing superior performance to traditional and computer monitor tachistoscopes.
Optical and scintillation characteristics of Y2O3 transparent ceramic
Authors: Fukabori Akihiro , Yanagida Takayuki , Pejchal Jan , Maeo Shuji , Yokota Yuui , Yoshikawa Akira , Ikegami Takayasu , Moretti Federico , Kamada Kei
Published: April 2010

Various fundamental characteristics of Y2O3 ceramics, such as optical transmittance, reflectivity, absorption coefficient, refractive index, and dielectric constant, were investigated. Furthermore, in order to evaluate the possible application of this material as γ-ray scintillator, other radiation responses, like the α-ray excited emission spectrum, the γ-ray excited pulse height spectrum, the light yield, the nonproportionality, the energy resolution, and the γ-ray excited scintillation decay curves were obtained. The light yield of Y2O3 ceramics was evaluated in about 1.13 times higher than that of Bi4Ge3O12(BGO):Ce single crystals and was estimated in 9300 photon/MeV. The nonproportionality measurements showed a good proportionality. The scintillation decay curve could be fitted by an exponential function characterized by a fast component of about 34 ns.
Anomalous magnetic field dependence of magnetocaloric effect at low temperature in Pr0.52Sr0.48MnO3 single crystal
Authors: Patra M. , Majumdar S. , Giri S. , Iles G. N. , Chatterji T.
Published: April 2010

We report the magnetocaloric effect (MCE) in a Pr0.52Sr0.48MnO3 single crystal. A peak in the temperature dependence of magnetic entropy change (ΔSM) with a fairly large negative value (≈3.8 J/kg K) is observed at 275 K close to Curie temperature. MCE is spread over a wide temperature range resulting in a considerable refrigerant capacity (≈293 J/kg). At low temperature the sign of ΔSM changes, below which anomalous field dependence of ΔSM is observed indicating the coexistence of ferromagnetic and antiferromagnetic interactions. Interplay between the interactions is strongly influenced by direction and magnitude of applied magnetic field in the ordered state.
The quantum N-body problem and the auxiliary field method
Authors: Silvestre-Brac Bernard , Semay Claude , Buisseret Fabien , Brau Fabian
Published: April 2010

Approximate analytical energy formulas for N-body semirelativistic Hamiltonians with one- and two-body interactions are obtained within the framework of the auxiliary field method. This method has already been proven to be a powerful technique in the case of two-body problems. A general procedure is given and applied to various Hamiltonians of interest, in atomic and hadronic physics in particular. A test of formulas is performed for baryons described as a three-quark system.
Statistical behavior of electrical breakdown in insulating polymers
Authors: Wu Kai , Wang Yang , Cheng Yonghong , Dissado L. A. , Liu Xiaojun
Published: April 2010

A simulation model to investigate the statistical property of electrical breakdown is presented based on the field-assisted percolation model for dielectric breakdown, by expressing the disorder in morphology as randomly distributed trap barriers. The effects of sample area and large defects on the statistical property of breakdown are also studied, and the statistical behavior of the lifetime is investigated by considering the stochastic development of deteriorated regions. In addition an equation describing the breakdown probability in homogeneous materials is derived from percolation theory, which we show fits well to the simulation data. The breakdown probability is expressed in terms of trap distribution, and thus provides a way to connect the disorder in polymer morphology with the stochastic nature of breakdown.
Physics of proximity Josephson sensor
Authors: Voutilainen J. , Laakso M. A. , Heikkilä T. T.
Published: April 2010

We study the proximity Josephson sensor in both bolometric and calorimetric operation and optimize it for different temperature ranges between 25 mK and a few kelvin. We investigate how the radiation power is absorbed in the sensor and find that the irradiated system is typically in a weak nonequilibrium state. We show in detail how the proximity of the superconductors affects the device response: for example, via changes in electron-phonon coupling and out-of-equilibrium noise. In addition, we estimate the applicability of graphene as the absorber material.
Raman scattering of cadmium oxide epilayers grown by metal-organic vapor phase epitaxy
Authors: Cuscó R. , Ibáñez J. , Domenech-Amador N. , Artús L. , Zúñiga-Pérez J. , Muñoz-Sanjosé V.
Published: April 2010

We present a lattice-dynamics study of rocksalt cadmium oxide (CdO). We use Raman scattering to investigate a series of high-quality CdO epilayers grown on sapphire substrates by means of metal-organic vapor phase epitaxy. Two main features are found to dominate the Raman spectra of CdO: a sharp peak at ∼265 cm−1 and a broad feature at ∼390 cm−1. To assign these and other weaker second-order features that appear in the Raman spectra, we have carried out an ab initio calculation of the phonon dispersion in CdO. From the calculated two-phonon density of states (PDOS) we tentatively assign the peak at 265 cm−1 to a 2TA(L) mode. The broadband centered at ∼390 cm−1 seems to reflect the high two-PDOS in the 300–450 cm−1 spectral region.
Magnetoresistance in a hybrid ferromagnetic/semiconductor device
Authors: Papp G. , Peeters F. M.
Published: April 2010

Ballistic transport of a two-dimensional electron gas (2DEG) in a rectangle shaped wire, subjected to a local nonhomogeneous magnetic field that results from an in-plane magnetized ferromagnetic (FM) strip deposited above the 2DEG, is investigated theoretically. We found a positive magnetoresistance (MR), which exhibits hysteresis behavior with respect to the direction of the magnetic field sweep, in agreement with a recent experiment. This positive MR can be tuned by applying a gate voltage to the FM strip.
Electronic structure of LaO based on frozen-core four-component relativistic multiconfigurational quasidegenerate perturbation theory
Authors: Moriyama Hiroko , Watanabe Yoshihiro , Nakano Haruyuki , Yamamoto Shigeyoshi , Tatewaki Hiroshi
Published: April 2010

The electronic structure of the LaO molecule is studied using frozen-core four-component multiconfigurational quasidegenerate perturbation theory. The ground state and nine experimentally observed excited states are examined. The ground state is Σ21/2+ and its gross atomic orbital population is La(5p5.766s0.836p0.14p∗0.21d∗1.17f∗0.26) O(2p4.63), where p∗, d∗, and f∗ are the polarization functions of La that form molecular spinors with O 2ps. We found that it is not necessary to consider the excitation from the O 2p electrons when analyzing the experimental spectra. This validates the foundation of the ligand field theory on diatomic molecules, including the La atom where only one electron is considered. The spectroscopic constants Re, ωe, and T0 calculated for the ground state and low-lying excited states A′(Δ23/2), A′(Δ25/2) A(Π21/2), and A(Π23/2) are in good agreement with the experimental values.
A coarse-grained model for amorphous and crystalline fatty acids
Authors: Hadley K. R. , McCabe C.
Published: April 2010

Fatty acids constitute one of the main components of the lipid lamellae in the top layer of the skin, known as the stratum corneum, which acts as a barrier to foreign substances entering the body and to water leaving the body. To better understand the mechanics of the skin, a molecular-level understanding of the structure of the lamellae needs to be investigated. As a first step toward this goal, the current work involves the development of a coarse-grained model for fatty acids in an amorphous and a crystalline state. In order to retain the structural details of the atomistic molecules, radial distribution functions have been used to provide target data against which the coarse-grained force field is optimized. The optimization was achieved using the method developed by Reith, Pütz, and Müller-Plathe with a damping factor introduced into the updating scheme to facilitate the convergence against the crystalline radial distribution functions. Using this approach, a transferable force field has been developed for both crystalline and amorphous systems that can be used to describe fatty acids of different chain lengths. We are unaware of any other coarse-grained model in the literature that has been developed to study solid phases. Additionally, the amorphous force field has been shown to accurately model mixtures of different free fatty acids based on the potentials derived from pure lipid systems.
Communications: Electron polarization critically stabilizes the Mg2+ complex in the catalytic core domain of HIV-1 integrase
Authors: Lu Yunpeng , Mei Ye , Zhang John Z. H. , Zhang Dawei
Published: April 2010

In this paper, we present a detailed dynamics study of the catalytic core domain (CCD) of HIV-1 integrase using both polarized and nonpolarized force fields. The numerical results reveal the critical role of protein polarization in stabilizing Mg2+ coordination complex in CCD. Specifically, when nonpolarized force field is used, a remarkable drift of the Mg2+ complex away from its equilibrium position is observed, which causes the binding site blocked by the Mg2+ complex. In contrast, when polarized force field is employed in MD simulation, HIV-1 integrase CCD structure is stabilized and both the position of the Mg2+ complex and the binding site are well preserved. The detailed analysis shows the transition of α-helix to 310-helix adjacent to the catalytic loop (residues 139–147), which correlates with the dislocation of the Mg2+ complex. The current study demonstrates the importance of electronic polarization of protein in stabilizing the metal complex in the catalytic core domain of HIV-1 integrase.
Rayleigh instability of charged drops and vesicles in the presence of counterions
Authors: Thaokar R. M. , Deshmukh S. D.
Published: April 2010

Rayleigh instability of charged conducting drops, in the viscous regime, is analyzed in the presence of counterions in the surrounding fluid. The Rayleigh criterion for the instability is derived in the Debye–Huckel approximation. It is found that the critical charge for the instability is reduced in the presence of counterions. The analysis is carried out for charged vesicles, with symmetric double layers across the bilayer, and the critical charge for the instability is determined. It is found that vesicles can indeed become unstable at high surface potentials. These results should be important in biological systems, where cells, with charged membranes, are immersed in electrolyte solutions. Additionally, the expression for the decay rate for vesicles with charged bilayers should give better estimates for the correlation time of the shape fluctuations.
Anomalous thermal expansion of Pb–Te system semiconductors
Authors: Yoneda Seiji , Kato Masahiko , Ohsugi Isao J.
Published: April 2010

The thermal expansion properties of sintered samples of PbTe doped with 0.5 mass % PbI2 and those of Pb0.5Sn0.5Te were evaluated by two different methods such as: (1) by determining the apparent expansion coefficient obtained from dimensional changes and (2) by estimating the crystal lattice expansion coefficient calculated from the crystal lattice spacing. Abnormally large values of the apparent expansion coefficients were observed only for samples prepared from fine powders with a particle size of 25 μm or less at high temperatures above 400 °C, while such large values were not obtained for other samples in that temperature range. No significant differences were observed between the lattice expansion coefficients of the samples prepared from the fine powders and those of the other samples. Thermogravimetric analysis revealed that the abnormally large expansion developed in the crystal grain boundaries. The grain boundary effects were estimated by comparing the apparent expansion coefficients and the lattice expansion coefficients. Some substances were found to be deposited in the apparatus during the experiment, and they were identified as compounds that including tellurium by the x-ray diffraction analysis. It was concluded that this curious expansion phenomenon was caused by decomposition and sublimation of tellurium from the telluride samples at the high temperature range.
Dynamic simulations of colloids by core-modified dissipative particle dynamics
Authors: Whittle Martin , Travis Karl P.
Published: April 2010

We develop a core-modified dissipative particle dynamics model of colloidal systems which includes an extra term to counteract depletion forces. Results are presented covering the full range of volume fractions. Radial distribution functions for the suspending fluid are shown to change significantly as the volume fraction of colloid increases. Equilibrium results for the long-time diffusion coefficient behave as expected, but the short-time coefficient is anomalous. The form of the equilibrium stress correlation functions is discussed and the derived Green–Kubo viscosities are compared with expected semiempirical forms. For nonequilibrium shear-field simulations we find that the system temperature is not adequately controlled by the dissipative particle dynamics (DPD) thermostat alone. Results using three alternative auxiliary thermostats are compared; a naïve choice leading to a string phase at high shear rate. Using a thermostat based on relative particle velocities, the model reproduced the four classical regions of colloid rheology: a first Newtonian plateau, a shear-thinning region, a second Newtonian plateau, and finally a shear-thickening region at high strain rate. The most unexpected result of this exercise is that the core-modified DPD model without auxiliary thermostat almost exactly follows the same curve despite recording a temperature increase of a factor ∼2.5 over the range.
Temperature and composition dependence of the Soret coefficient in Lennard-Jones mixtures presenting consolute critical phenomena
Authors: Leonardi Erminia , D’Aguanno Bruno , Angeli Celestino
Published: April 2010

Nonequilibrium molecular dynamics calculations have been carried out o Lennard-Jones binary mixtures with the aim to investigate the dependence of the Soret coefficient on the temperature and on the composition for systems presenting phase transitions. By an appropriate choice of the cross interaction parameter, ε12 (0<ε12<min{ε11,ε22}), these systems show a mixing/demixing (consolute) phase transition. The other parameters are those of a binary mixture of Argon and Krypton. This system has been considered over a wide range of temperatures (up to ≃1000 K), of compositions (0.1≤x1≤0.9), and of cross interaction parameter (0<ε12<min{ε11,ε22}). The study allows the formulation of a very simple expression for the Soret coefficient, ST, as a function of temperature and composition. Indeed the computed values of ST in the one phase region outside the critical region are closely fitted by the function [T−Tc(x1)]−1 where Tc(x1) is the demixing temperature of the mixture under study. This result indicates for this type of systems a dependence of ST, as a function of the temperature, on a unique characteristic property of the fluid mixture, the demixing temperature Tc, which, in turn, is a function of the binary mixture composition x1.
Characterization of charge transfer excitations in hexacyanomanganate(III) with Mn K-edge resonant inelastic x-ray scattering
Authors: Meyer Drew A. , Zhang Xuena , Bergmann Uwe , Gaffney Kelly J.
Published: April 2010

We use hard x-ray resonant inelastic x-ray scattering (RIXS) and density functional theory (DFT) calculations to characterize charge transfer excitations in K3Mn(CN)6. The combination of RIXS measurements and DFT calculations allows us to characterize the strength of the ligand-metal electronic interaction and assign the Raman resonances in the RIXS spectra to charge transfer excitations. With x-ray excitation energies resonant with the T2g and Eg pre-edge peaks derived predominantly from the Mn 3d orbitals, we observe Raman resonances in the energy transfer range from 2 to 12 eV, which results from the filling of the 1s core-hole from T1u-symmetry occupied orbitals. DFT calculations indicate that these orbitals exhibit primarily ligand character, supporting the assignment of the energy transfer resonances to ligand-to-metal charge transfer excitations. Our RIXS measurements and DFT calculations also indicate that the Eg-orbital spin-splits by roughly 0.8 eV, though we do not cleanly resolve the two absorption peaks in the RIXS spectra. We also see evidence for a metal-to-ligand charge transfer (MLCT) excitation when exciting with a 6545.0 eV incident photon, roughly 4 eV above the Eg absorption peaks. The 6545.0 eV resonant emission spectrum shows a 6.0 eV energy transfer resonance, which corresponds to a final state hole in the T2g partially occupied orbital. DFT calculations indicate that excitation at 6545.0 eV populates an unoccupied T1u-symmetry orbital of primarily ligand character. Given the predominantly metal character of the final state hole, we assign the 6.0 eV Raman resonance to a MLCT excitation. These measurements demonstrate the ability of hard x-ray RIXS to characterize the valence electronic structure of coordination compounds.
Molecular dynamics simulation and identification of the truly interfacial molecules (ITIM) analysis of the liquid-vapor interface of dimethyl sulfoxide
Authors: Darvas Mária , Pojják Katalin , Horvai George , Jedlovszky Pál
Published: April 2010

The liquid-vapor interface of dimethyl sulfoxide (DMSO) is investigated by molecular dynamics computer simulation and by the novel method of the identification of the truly interfacial molecules (ITIM). With this method, it is possible to consider in the analysis specifically those molecules that are located right at the boundary of the two phases. The obtained results show that the orientation of the surface molecules is driven by the requirement that these molecules should be able to maintain their strong dipole-dipole and π-π interactions with each other, such as in the bulk liquid phase. This requirement leads to the preference of the polar SO double bonds for laying parallel with the surface, and of the apolar CH3 groups for pointing rather flatly out of the liquid phase. As a result, the surface of liquid DMSO is only mildly corrugated, in terms of the molecular size. Similarly to the bulk liquid phase, the DMSO molecules are also found to form long dipole chains of head-to-tail oriented neighbors even within the surface layer. The results also indicate that, at least from the point of view of the dynamics of the individual molecules, the division of the system beneath the truly surface layer into further subsurface molecular layers is already physically meaningless.
Traveling electric field probed by a fine particle above voltage-modulated strips in a striped electrode device
Authors: Li Yang-fang , Zhang Wen-gui , Ma J. X. , Jiang Ke , Thomas H. M. , Morfill G. E.
Published: April 2010

It is described that the distribution of the horizontal electric field above a striped electrode can be inferred from the trajectory of a single fine particle with known mass and diameter. The striped electrode consists of 100 segmented stainless steel strips, each electrically insulated. A traveling periodic potential profile is produced above the striped electrode by modulating the voltage signals on the strips. When the voltage modulation is on, the fine particle, which is originally levitated in the sheath region above the striped electrode, experiences a periodic oscillation along both the vertical and the horizontal directions because of the periodic electric force arising from the modulation voltages. Tracking the motion of the fine particles, the electric force is obtained from the momentum equation including the gravity and the neutral gas friction. With the particle charge estimated by the vertical oscillation method, the electric field can be derived. The horizontal electric field obtained by this method is in agreement with the result predicted by a collisional particle-in-cell simulation.
The anomalously high melting temperature of bilayer ice
Authors: Kastelowitz Noah , Johnston Jessica C. , Molinero Valeria
Published: April 2010

Confinement of water usually depresses its melting temperature. Here we use molecular dynamics simulations to determine the liquid-crystal equilibrium temperature for water confined between parallel hydrophobic or mildly hydrophilic plates as a function of the distance between the surfaces. We find that bilayer ice, an ice polymorph in which the local environment of each water molecule strongly departs from the most stable tetrahedral structure, has the highest melting temperature (Tm) of the series of l-layer ices. The melting temperature of bilayer ice is not only unusually high compared to the other confined ices, but also above the melting point of bulk hexagonal ice. Recent force microscopy experiments of water confined between graphite and a tungsten tip reveal the formation of ice at room temperature [K. B. Jinesh and J. W. M. Frenken, Phys. Rev. Lett. 101, 036101 (2008)]. Our results suggest that bilayer ice, for which we compute a Tm as high as 310 K in hydrophobic confinement, is the crystal formed in those experiments.
Statistics of magnetic reconnection in two-dimensional magnetohydrodynamic turbulence
Authors: Servidio S. , Matthaeus W. H. , Shay M. A. , Dmitruk P. , Cassak P. A. , Wan M.
Published: April 2010

The nonlinear dynamics of magnetic reconnection in turbulence is investigated through direct numerical simulations of decaying, incompressible, two-dimensional magnetohydrodynamics. Recently, it was shown by Servidio et al. [Phys. Rev. Lett. 102, 115003 (2009)] that in fully developed turbulence complex processes of reconnection occur locally. Here, the main statistical features of these multiscale reconnection events are further described, providing details on the methodology. It is found that is possible to describe the reconnection process in turbulence as a generalized local Sweet–Parker process in which the parameters are locally controlled by the turbulence cascade, thus providing a step toward reconciling classical turbulence analysis with reconnection theory. This general description of reconnection may be useful for laboratory and space plasmas, where the presence of turbulence plays a crucial role.
A note on the metallization of compressed liquid hydrogen
Authors: Tamblyn Isaac , Bonev Stanimir A.
Published: April 2010

We examine the molecular-atomic transition in liquid hydrogen as it relates to metallization. Pair potentials are obtained from first principles molecular dynamics and compared with potentials derived from quadratic response. The results provide insight into the nature of covalent bonding under extreme conditions. Based on this analysis, we construct a schematic dissociation-metallization phase diagram and suggest experimental approaches that should significantly reduce the pressures necessary for the realization of the elusive metallic phase of hydrogen.
Crystallization of hard aspherical particles
Authors: Miller William L. , Bozorgui Behnaz , Cacciuto Angelo
Published: April 2010

We use numerical simulations to study the crystallization of monodisperse systems of hard aspherical particles. We find that particle shape and crystallizability can be easily related to each other when particles are characterized in terms of two simple and experimentally accessible order parameters: one based on the particle surface-to-volume ratio and the other on the angular distribution of the perturbations away from the ideal spherical shape. We present a phase diagram obtained by exploring the crystallizability of 487 different particle shapes across the two-order-parameter spectrum. Finally, we consider the physical properties of the crystalline structures accessible to aspherical particles and discuss limits and relevance of our results.
Structure of entangled polymer network from primitive chain network simulations
Authors: Masubuchi Yuichi , Uneyama Takashi , Watanabe Hiroshi , Ianniruberto Giovanni , Greco Francesco , Marrucci Giuseppe
Published: April 2010

The primitive chain network (PCN) model successfully employed to simulate the rheology of entangled polymers is here tested versus less coarse-grained (lattice or atomistic) models for what concerns the structure of the network at equilibrium (i.e., in the absence of flow). By network structure, we mean the distributions of some relevant quantities such as subchain length in space or in monomer number. Indeed, lattice and atomistic simulations are obviously more accurate, but are also more difficult to use in nonequilibrium flow situations, especially for long entangled polymers. Conversely, the coarse-grained PCN model that deals more easily with rheology lacks, strictly speaking, a rigorous foundation. It is therefore important to verify whether or not the equilibrium structure of the network predicted by the PCN model is consistent with the results recently obtained by using lattice and atomistic simulations. In this work, we focus on single chain properties of the entangled network. Considering the significant differences in modeling the polymer molecules, the results here obtained appear encouraging, thus providing a more solid foundation to Brownian simulations based on the PCN model. Comparison with the existing theories also proves favorable.
Effect of polar discontinuity on the growth of LaNiO3/LaAlO3 superlattices
Authors: Liu Jian , Kareev M. , Prosandeev S. , Gray B. , Ryan P. , Freeland J. W. , Chakhalian J.
Published: April 2010

We have conducted a detailed microscopic investigation of [LaNiO3(1 u.c.)/LaAlO3(1 u.c.)]N superlattices grown on (001) SrTiO3 and LaAlO3 to explore the influence of polar mismatch on the resulting electronic and structural properties. Our data demonstrate that the initial growth on the nonpolar SrTiO3 surface leads to a rough morphology and unusual 2+ valence of Ni in the initial LaNiO3 layer, which is not observed after growth on the polar surface of LaAlO3. A devised model suggests that the polar mismatch can be resolved if the perovskite layers grow with an excess of LaO, which also accounts for the observed electronic, chemical, and structural effects.
Effect of free-stream turbulence on the flow over a sphere
Authors: Son Kwangmin , Choi Jin , Jeon Woo-Pyung , Choi Haecheon
Published: April 2010

In this paper, the effect of free-stream turbulence (FST) on the flow over a sphere is experimentally investigated at the Reynolds numbers of 0.5×105–2.8×105. Three levels of FST are generated in a wind tunnel by installing three different types of grids upstream of the sphere. It is found that FST triggers the boundary layer instability above the sphere surface and delays the separation. Once laminar separation occurs, the disturbances both from the boundary-layer instability and FST trigger the shear-layer instability. Then, high momentum is entrained toward the sphere surface and the separated flow is reattached, forming a separation bubble on the sphere surface. Due to high momentum near the surface, the main separation is delayed and the drag is reduced. The critical Reynolds number, at which the drag coefficient decreases rapidly, decreases as the FST intensity increases. With increasing Reynolds number, the first separation point moves downstream, but the reattachment and main separation points are nearly fixed, resulting in a constant drag coefficient. As the Reynolds number further increases, the separation bubble finally disappears but the main separation point is still nearly unchanged, resulting in a constant drag coefficient within the Reynolds number range considered. Therefore, the formation, regression, and disappearance of a separation bubble on the sphere surface are the key mechanisms of the drag change by FST.
Electric field distributions in CdZnTe due to reduced temperature and x-ray irradiation
Authors: Sellin P. J. , Prekas G. , Franc J. , Grill R.
Published: April 2010

Real-time Pockels imaging is performed on semi-insulating CdZnTe to measure the electric field profile in the material bulk. In steady-state room temperature conditions the measured electric field profile is uniform, consistent with a low space charge concentration. At temperatures <270 K a significant nonuniform electric field profile is observed, which we explain in terms of temperature-induced band bending at the metal-semiconductor interface, causing the formation of positive space charge in the bulk. Similar electric field distortion effects are observed when room temperature CdZnTe is irradiated by x-rays, causing a high rate of photoinduced charge injection.
Multihit mode direct-detection laser radar system using a Geiger-mode avalanche photodiode
Authors: Oh Min Seok , Kong Hong Jin , Kim Tae Hoon , Hong Keun Ho , Kim Byung Wook , Park Dong Jo
Published: April 2010

In this paper, a direct-detection laser radar system that uses a Geiger-mode avalanche photodiode (GAPD) of relatively short dead time (45 ns) is described. A passively Q-switched microchip laser is used as a laser source and a compact peripheral component interconnect system, which includes a time-to-digital converter (TDC), is set up for fast signal processing. With both the GAPD and the TDC functioning multistop acquisition, the system operates in a multihit mode. The software for the three-dimensional visualization and an algorithm for the removal of noise are developed. It is shown that the single-shot precision of the system is ∼10 cm (σ) and the precision is improved by increasing the number of laser pulses to be averaged so that the precision of ∼1 cm (σ) was acquired with more than 150 laser pulses scattered from the target. The accuracy of the system is measured to be 12 cm when the energy of the emitted laser pulse varies with a factor of 7.
Energetic distribution of oxide traps created under negative bias temperature stress and their relation to hydrogen
Authors: Aichinger Thomas , Nelhiebel Michael , Decker Stefan , Grasser Tibor
Published: April 2010

By applying an incremental sweep technique to silicon devices subjected to negative bias temperature stress, we identify two significant peaks of recoverable oxide defects located energetically within the silicon band gap. The first peak is near midgap and is almost fully developed after ten seconds of stress while the second peak is found in the upper half of the silicon band gap and develops gradually as a function of stress time. We obtain very similar density-of-state profiles for two samples having vastly different hydrogen concentrations within the gate oxide indicating that the precursor for oxide trap creation is independent of hydrogen.
All-optical switching in an optofluidic polydimethylsiloxane: Liquid crystal grating defined by cast-molding
Authors: De Sio Luciano , Cuennet Julien G. , Vasdekis Andreas E. , Psaltis Demetri
Published: April 2010

We report an optofluidic photoswitchable grating, based on a polydimethylsiloxane periodic structure on a glass substrate, separated by a thin liquid crystal film. The polydimethylsiloxane microstructure was realized via high resolution replica molding and was employed to both confine and align a photosensitive nematic liquid crystal. In the absence of any surface treatment, the liquid crystal exhibited homeotropic alignment. By inducing planar alignment on the glass substrate, a hybrid orientation of the liquid crystal was achieved, inducing polarization sensitive transmission. The photosensitivity of the liquid crystal enabled the all-optical control of the grating transmission and 20% diffraction efficiency was measured.
Study of electric characteristics and diffusion effects of 2-methyl-9,10-di(2-naphthyl)anthracene doped with cesium fluoride by admittance spectroscopy
Authors: Hsieh Ming-Ta , Ho Meng-Huan , Lin Kuan-Heng , Chen Jenn-Fang , Chen Teng-Ming , Chen Chin H.
Published: April 2010

In this work, the admittance spectroscopy studies show that doping cesium fluoride (CsF) into 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) can greatly decrease the resistance of MADN and raises the Fermi level from deep level to only 0.1 eV below the lowest unoccupied molecular orbital, resulting in enhancing the electron injection. In addition, the diffusion width of CsF from doped MADN layer into tris(8-quinolinolato)aluminium is clearly observed by capacitance-frequency measurement and is about 9.4 nm. Moreover, the diffusion width is significant to be affected by external thermal.
Twinned Fano interferences induced by hybridized plasmons in Au–Ag nanorod heterodimers
Authors: Yang Zhong-Jian , Zhang Zong-Suo , Zhang Wei , Hao Zhong-Hua , Wang Qu-Quan
Published: April 2010

We theoretically investigated the plasmon interferences and hybridization in the Au–Ag nanorod heterodimers. Twinned Fanolike profiles are observed in the absorption cross sections of the gold and silver nanorods in the heterodimers, the Fano factors of which have the opposite signs near the antibonding resonances, which are found to be induced by the destructive interferences of two hybridized local surface plasmons. Both the value and sign of the Fano factors could be tuned by adjusting rod-lengths, which could find the applications in the design of plasmonic nanodevices.
Optical refrigeration sets solid-state cooling record
Authors: Miller Johanna
Published: April 2010

Certain high-purity solid materials can be cooled by an all-solid-state laser-based system.
Mercury isotopes in Arctic snow exhibit mass-independent fractionation
Authors: Miller Johanna
Published: April 2010

Magnetic and nonmagnetic isotopes behave differently in chemical reactions initiated by sunlight.
ITER collaboration defuses standoff
Authors: Feder Toni
Published: April 2010

The multinational, multicultural, multibillion-dollar fusion test reactor is set to get back on track with a shorter-than-proposed additional delay.
Special report: Obama’s 2011 budget proposes one more year of growth for science and technology
Authors: Kramer David
Published: April 2010

Swollen with stimulus monies, 2010 R&D totals are a tough act to follow. And the president’s call for a spending freeze points to austere times ahead.
The tangled tale of phase space
Authors: Nolte David D.
Published: April 2010

Phase space has been called one of the most powerful inventions of modern science. But its historical origins are clouded in a tangle of independent discovery and misattributions that persist today.
Crystal structure of HLA-DP2 and implications for chronic beryllium disease
Authors: Dai Shaodong , Murphy Guinevere A. , Crawford Frances , Mack Douglas G. , Falta Michael T. , Marrack Philippa , Kappler John W. , Fontenot Andrew P.
Published: April 2010

Chronic beryllium disease (CBD) is a fibrotic lung disorder caused by beryllium (Be) exposure and is characterized by granulomatous inflammation and the accumulation of Be-responsive CD4+T cells in the lung. Genetic susceptibility to CBD has been associated with certain alleles of the MHCII molecule HLA-DP, especiallyHLA-DPB1*0201and other alleles that contain a glutamic acid residue at position 69 of the β-chain (βGlu69). The HLA-DP alleles that can present Be to T cells match those implicated in the genetic susceptibility, suggesting that the HLA contribution to disease is based on the ability of those molecules to bind and present Be to T cells. The structure of HLA-DP2 and its interaction with Be are unknown. Here, we present the HLA-DP2 structure with its antigen-binding groove occupied by a self-peptide derived from the HLA-DR α-chain. The most striking feature of the structure is an unusual solvent exposed acidic pocket formed between the peptide backbone and the HLA-DP2 β-chain α-helix and containing three glutamic acids from the β-chain, including βGlu69. In the crystal packing, this pocket has been filled with the guanidinium group of an arginine from a neighboring molecule. This positively charged moiety forms an extensive H-bond/salt bridge network with the three glutamic acids, offering a plausible model for how Be-containing complexes might occupy this site. This idea is strengthened by the demonstration that mutation of any of the three glutamic acids in this pocket results in loss of the ability of DP2 to present Be to T cells.
The Haves and the Have Nots: A Historical Study of Disability in Modern Iran
Authors: Kashani-Sabet Firoozeh
Published: April 2010

This essay provides a historical analysis of Iranian experiences with disability. I will begin by reviewing the literary application of the term in various contexts. Next, I will examine the social milieux in which local observers, medical professionals, and policy makers talked about and treated disability. As state-run institutions emerged to address disability needs, health professionals often drew a distinction between physical disability and intellectual or psychological disability, raising ethical and legal questions about the status of the disabled in modern Iranian society. Finally, an attempt will be made to situate disability politics in contemporary Iran, where the disabled population has increased significantly as a consequence of the Iran–Iraq War (1980–88). Although this paper concentrates on Iranian experiences with disability, comparisons can be drawn with other Islamic societies.
Iranian Studies in the United Kingdom in the Twentieth Century
Authors: Bonakdarian Mansour
Published: April 2010

This essay provides a general introductory survey of Iranian and Iran-related studies in the United Kingdom in the twentieth century (including languages, literature, and the arts), with a very brief preliminary foray into earlier Iran-related scholarship and wide-ranging imaginations of Iran in Britain and Ireland, as well as some concluding remarks on contemporary knowledge production about Britain in Iran. Among other themes covered in the essay are the varied contributions of non-Britons and non-Irish to Iran-related scholarship and imaginations in the United Kingdom, underscoring the overall transnational production, dissemination, reception, and utilization of knowledge (history, geography, archaeology, cultures, ethnography and anthropology, art and architecture, Iran-related Persian-language literatures and poetry, etc.). In particular, the essay highlights the contributions made by individuals from, and institutions in, the Indian subcontinent to “British” scholarship and knowledge about Iran.
Dyslexia and the school counsellor: A Maltese case study
Authors: Falzon Ruth , Camilleri Stephen
Published: April 2010

Aim: This paper seeks to understand whether Maltese school counsellors are equipped to deal with dyslexic clients, considers whether specific strategies need to be used, and what positive effects, if any, counselling has on these clients. Previous studies: A literature review on self‐concept and techniques on how to improve the self‐concept of children with Learning Disabilities (LD)/Specific Learning Difficulties (SpLD) will place the current study in context. Method: Questionnaires (available from the authors on request) were distributed to all school counsellors on the island and analysed using content analysis. Findings: Findings from respondents indicate a need for more training, evidence‐based knowledge of specific techniques when dealing effectively and successfully with dyslexic clients, specific specialised training to understand dyslexic clients and that counselling has a positive effect on dyslexic clients.
The challenge of counselling and psychotherapy research
Authors: Cooper Mick
Published: April 2010

Aims: The purpose of this commentary is to argue that the value of counselling and psychotherapy research lies, not only in what it teaches us as therapists, but also in its ability to challenge us and our assumptions. Method: The paper identifies eight beliefs that may be prevalent in sections of the counselling and psychotherapy community, and presents evidence that challenges them. Findings: While many of our beliefs may hold true for some clients some of the time, the research evidence suggests that they are unlikely to be true for all clients all of the time. Discussion: By questioning and challenging therapists' a priori assumptions, research findings can help counsellors and psychotherapists to be less set in their beliefs; and more open to the unique experiences, characteristics and wants of each individual client.
Why argue? Towards a cost–benefit analysis of argumentation
Authors: Paglieri Fabio , Castelfranchi Cristiano
Published: April 2010

This article proposes a cost–benefit analysis of argumentation, with the aim of highlighting the strategic considerations that govern the agent's decision to argue or not. In spite of its paramount importance, the topic of argumentative decision-making has not received substantial attention in argumentation theories so far. We offer an explanation for this lack of consideration and propose a tripartite taxonomy and detailed description of the strategic reasons considered by arguers in their decision-making: benefits, costs, and dangers. We insist that the implications of acknowledging the strategic dimension of arguing are far-reaching, including promising insights on how to develop better argumentation technologies.
Modular argumentation for modelling legal doctrines of performance relief
Authors: Dung Phan Minh , Thang Phan Minh , Hung Nguyen Duy
Published: April 2010

We present an argument-based formalism of contract dispute resolution following a modern view that the court would resolve a contract dispute by enforcing an interpretation of contract that reasonably represents the mutual intention of contract parties. Legal doctrines provide principles, rules and guidelines for the court to objectively arrive at such an interpretation. In this paper, we establish the appropriateness of the formalism by applying it to resolve disputes about performance relief with the legal doctrines of impossibility and frustration of purpose in common laws of contract. The formalism is based on modular argumentation, a recently proposed extension of assumption-based argumentation for modelling contract dispute resolution.
Adsorption of methanol and atomic oxygen on the Pt(100) surface: a first-principles periodic density functional theory study
Authors: Moussounda P S , Haroun M F , Légaré P
Published: April 2010

Adsorption of methanol and atomic oxygen at three sites (top, bridge and hollow) on the Pt(100) surface has been investigated by the density functional theory (DFT) method at the generalized gradient approximation (GGA-PW91) level. Methanol can be molecularly adsorbed via its oxygen atom. At 25% surface coverage, methanol adsorption at the hollow site is favoured over that at the top and bridge sites. Calculations of oxygen atomic adsorption were performed in a wide range of coverages. The most favoured adsorption site for atomic oxygen on the Pt(100) surface is the bridge site at all coverages (from 0.25 to 1 ML). At an oxygen surface coverage of 0.25 ML, the calculated adsorption energies are in good agreement with the experimental observations and the previous theoretical calculations.
The irreducibility of symmetric Yagzhev maps
Authors: Bakalarski Sławomir
Published: April 2010

Let

F
:

C

n

→

C

n

F:\mathbb {C}^n \rightarrow \mathbb {C}^n

be a polynomial mapping in Yagzhev form, i.e.
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper F left-parenthesis x 1 comma ellipsis comma x Subscript n Baseline right-parenthesis equals left-parenthesis x 1 plus upper H 1 left-parenthesis x 1 comma ellipsis comma x Subscript n Baseline right-parenthesis comma ellipsis comma x Subscript n Baseline plus upper H Subscript n Baseline left-parenthesis x 1 comma ellipsis comma x Subscript n Baseline right-parenthesis right-parenthesis comma">

F
(

x
1

,
…
,

x
n

)
=
(

x
1

+

H
1

(

x
1

,
…
,

x
n

)
,
…
,

x
n

+

H
n

(

x
1

,
…
,

x
n

)
)
,

F(x_1,\ldots ,x_n)=(x_1+H_1(x_1,\ldots ,x_n),\ldots ,x_n+H_n(x_1,\ldots ,x_n)),

\]
where

H
i

H_i

are homogeneous polynomials of degree 3. We show that if

J
a
c

(
F
)
∈

C

∗

\mathrm {Jac}(F) \in \mathbb {C}^*

and the Jacobian matrix of

F
F

is symmetric, then the polynomials

x
i

+

H
i

(

x
1

,
…
,

x
n

)

x_i+H_i(x_1,\ldots ,x_n)

are irreducible as elements of the ring

C

[

x
1

,
…
,

x
n

]

\mathbb {C}[x_1,\ldots ,x_n]

.
Upper bounds for series involving moderate and small deviations
Authors: Spătaru Aurel
Published: April 2010

Let

X
,
 

X

1

,
 

X

2

,
.
.
.

X,~X_{1},~X_{2},...

be i.i.d. random variables with

0
>
E

X

2

=

σ

2

>
∞

0>EX^{2}=\sigma ^{2}>\infty

and

E
X
=
0
,

EX=0,

and set

S

n

=

X

1

+
⋯
+

X

n

.

S_{n}=X_{1}+\cdots +X_{n}.

We prove Paley-type inequalities for series involving probabilities of moderate deviations

P
(

|

S

n

|

≥
λ

n
log
⁡
n

)
,

P(\left \vert S_{n}\right \vert \geq \lambda \sqrt {n\log n}),

λ
>
0
,

\lambda >0,

and probabilities of small deviations

P
(

|

S

n

|

≥

P(\left \vert S_{n}\right \vert \geq

λ

n
log
⁡
log
⁡
n

)

\lambda \sqrt {n\log \log n})

,

λ
>
σ

2

.

\lambda >\sigma \sqrt {2}.
The defect index of singular symmetric linear difference equations with real coefficients
Authors: Ren Guojing , Shi Yuming
Published: April 2010

This paper is concerned with the defect index of singular symmetric linear difference equations of order

2
n

2n

with real coefficients and one singular endpoint. We show that their defect index

d
d

satisfies the inequalities

n
≤
d
≤
2
n

n\leq d \leq 2n

and that all values of

d
d

in this range are realized. This parallels the well known result of Glazman for differential equations established about 1950. In addition, several criteria of the limit point and strong limit point cases are established.
On an exponential predicate in polynomials over finite fields
Authors: Sirokofskich Alla
Published: April 2010

We show that the theory of the set of polynomials in

F

q

[
t
]

\mathbb {F}_q[t]

, where

F

q

\mathbb {F}_q

is a finite field, in a language including addition and a predicate for the relation “

x
x

is a power of

t
t

” is model-complete and therefore decidable.