bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of plumes on measuring the large scale circulation in turbulent Rayleigh-Bénard convection
Authors: Stevens Richard J. A. M. , Clercx Herman J. H. , Lohse Detlef
Published: September 2011

We studied the properties of the large-scale circulation (LSC) in turbulent Rayleigh-Bénard (RB) convection by using results from direct numerical simulations in which we placed a large number of numerical probes close to the sidewall. The LSC orientation is determined by either a cosine or a polynomial fit to the azimuthal temperature or azimuthal vertical velocity profile measured with the probes. We study the LSC in Γ = D/L = 1/2 and Γ = 1 samples, where D is the diameter and L is the height. For Pr = 6.4 in an aspect ratio Γ = 1 sample at Ra = 1 × 108 and 5 × 108, the obtained LSC orientation is the same, irrespective of whether the data of only 8 or all 64 probes per horizontal plane are considered. In a Γ = 1/2 sample with Pr = 0.7 at Ra = 1 × 108, the influence of plumes on the azimuthal temperature and azimuthal vertical velocity profiles is stronger. Due to passing plumes and/or the corner flow, the apparent LSC orientation obtained using a cosine fit can result in a misinterpretation of the character of the large-scale flow. We introduce the relative LSC strength, which we define as the ratio between the energy in the first Fourier mode and the energy in all modes that can be determined from the azimuthal temperature and azimuthal vertical velocity profiles, to further quantify the large-scale flow. For Ra = 1 × 108, we find that this relative LSC strength is significantly lower in a Γ = 1/2 sample than in a Γ = 1 sample, reflecting that the LSC is much more pronounced in a Γ = 1 sample than in a Γ = 1/2 sample. The determination of the relative LSC strength can be applied directly to available experimental data to study high Rayleigh number thermal convection and rotating RB convection.
Static voltage distribution between turns of secondary winding of air-core spiral strip transformer and its application
Authors: Zhang Hong-bo , Liu Jin-liang , Cheng Xin-bing , Zhang Yu
Published: September 2011

The static voltage distribution between winding turns has great impact on output characteristics and lifetime of the air-core spiral strip pulse transformer (ACSSPT). In this paper, winding inductance was calculated by electromagnetic theory, so that the static voltage distribution between turns of secondary winding of ACSSPT was analyzed conveniently. According to theoretical analysis, a voltage gradient because of the turn-to-turn capacitance was clearly noticeable across the ground turns. Simulation results of Pspice and CST EM Studio codes showed that the voltage distribution between turns of secondary winding had linear increments from the output turn to the ground turn. In experiment, the difference in increased voltage between the ground turns and the output turns of a 20-turns secondary winding is almost 50%, which is believed to be responsible for premature breakdown of the insulation, particularly between the ground turns. The experimental results demonstrated the theoretical analysis and simulation results, which had important value for stable and long lifetime ACSSPT design. A new ACSSPT with improved structure has been used successfully in intense electron beam accelerators steadily.
A unified model of grain-boundary segregation kinetics
Authors: Wu Jian , Song Shenhua
Published: September 2011

A unified model of grain-boundary segregation kinetics is established, which can simulate the equilibrium and non-equilibrium grain-boundary segregation kinetics during isothermal ageing. The results of model fittings/predictions are in a good consistence with those of the experiments. Values of several important parameters, such as vacancy formation energy, vacancy migration energy, and complex migration energy derived by model fittings, show a reasonably good agreement with those in the references. Relationship between the equilibrium and non-equilibrium grain-boundary segregation mechanisms is discussed in detail. The segregation peak/depletion trough observed in the non-equilibrium segregation kinetics may be ascribed to the vacancy flux. The equilibrium segregation kinetics is considered as a special case in non-equilibrium segregation kinetics with the zero vacancy flux. Both the equilibrium and non-equilibrium segregation kinetics are believed to be dominated by vacancy-solute complex flux. The proposed unified model can be a significant progress in grain-boundary segregation theory, with applications in guiding the design of materials.
GaN/SiC avalanche photodiodes
Authors: Zhou Qiugui , McIntosh Dion C. , Lu Zhiwen , Campbell Joe C. , Sampath Anand V. , Shen Hongen , Wraback Michael
Published: September 2011

Near ultraviolet-sensitive separate absorption and multiplication avalanche photodiodes with GaN/SiC epitaxial layers grown on SiC substrate were fabricated. Dark current < 1 pA at 90% breakdown voltage, maximum multiplication gain of ∼105, and responsivity exceeding 4.2 A/W at 365 nm were achieved.
The Gould-Hopper polynomials in the Novikov-Veselov equation
Authors: Chang Jen-Hsu
Published: September 2011

We use the Gould-Hopper (GH) polynomials to investigate the Novikov-Veselov (NV) equation. The root dynamics of the σ-flow in the NV equation is studied using the GH polynomials and then the Lax pair is found. In particular, when N = 3, 4, 5, one can get the Gold-fish model. The smooth rational solutions of the NV equation are also constructed via the extended Moutard transformation and the GH polynomials. The asymptotic behavior is discussed and then the smooth rational solution of the Liouville equation is obtained.
Analytic treatment of the precessional (ballistic) contribution to the conventional magnetic switching
Authors: Bazaliy Ya. B.
Published: September 2011

We consider a uniformly magnetized particle (i.e., a macroscopic magnetic moment) with an easy axis anisotropy. The particle’s moment is switched from “up” to “down” direction by an external magnetic field applied parallel to the easy axis and continuously swept from a positive to a negative value. In addition, a small constant perpendicular bias field is present. It is shown that while the driving field switches the particle’s moment in a conventional damped way, the perpendicular field creates an admixture of the precessional (ballistic) switching that speeds up the switching process. Precessional contribution produces a non-monotonic dependence of the switching time on the field sweep time with a minimum at a particular sweep time value. We derive analytic expressions for the optimal point, and for the entire dependence of the switching time on the field sweep time. Our approximation is valid in a wide parameter range and can be used to engineer and optimize of the magnetic memory devices.
Spherically symmetric solutions to a model for phase transitions driven by configurational forces
Authors: Ou Yaobin , Zhu Peicheng
Published: September 2011

We prove the global-in-time existence of spherically symmetric solutions to an initial-boundary value problem for a system of partial differential equations, which consists of the equations of linear elasticity and a nonlinear, non-uniformly parabolic equation of second order. This problem models the evolutional behavior of materials in which martensitic phase transitions, driven by configurational forces, take place. Moreover, it can be considered to be a regularization of the corresponding sharp interface model. By assuming that the solutions are spherically symmetric, we reduce the original multi-dimensional problem to the one in one space dimension, then prove the existence of spherically symmetric solutions. Our proof is valid due to the essential feature that the resulting problem is one-dimensional.
Relaxation of internal temperature and volume viscosity
Authors: Bruno Domenico , Giovangigli Vincent
Published: September 2011

We investigate the relaxation of internal temperature and the concept of volume viscosity in nonequilibrium gas models derived from the kinetic theory. We first investigate a nonequilibrium gas model with two temperatures—translational and internal—where the volume viscosity is absent. We establish that in a relaxation regime, the temperature difference becomes proportional to the divergence of the velocity fields and define a nonequilibrium, multitemperature, volume viscosity coefficient. We next analyze the convergence of the two temperature model towards the one temperature model when the relaxation is fast. We then investigate a nonequilibrium two temperature gas model with a fast and a slow internal energy mode. We establish that in a relaxation regime, there are four contributions to the volume viscosity, namely, the fast internal mode volume viscosity, the slow internal mode volume viscosity, the relaxation pressure, and the perturbed source term. In the thermodynamic equilibrium limit, the sum of these four terms converges toward the one-temperature two-mode volume viscosity. We finally perform Monte Carlo simulations of spontaneous fluctuations near thermodynamic equilibrium. The numerical results obtained from the Boltzmann equation are compared to the predictions of the one and two temperature fluid models, and the agreement between theory and calculations is complete.
Spectroscopy and thermochemistry of a jet-cooled open-shell polyene: 1,4-pentadienyl radical
Authors: Chalyavi Nahid , Bacskay George B. , Menon Ambili S. , Troy Tyler P. , Davis Nathaniel J. L. K. , Radom Leo , Reid Scott A. , Schmidt Timothy W.
Published: September 2011

The 1,4-pentadienyl (vinylallyl) radical has been observed for the first time by optical spectroscopy. An excitation spectrum is recorded on m/z 67 by resonant two-color two-photon ionization spectroscopy. Several bands are observed with the origin transition identified at 19 449 cm−1. The spectrum is assigned by a comparison with ab initio frequencies calculated at the CASPT2/cc-pVTZ level of theory, with an accompanying Franck-Condon calculation of the excitation spectrum, including Dushinsky mixing. The b1 and a2 outer C–C bond torsional modes are calculated to halve in frequency upon electronic excitation, bringing about their appearance in the excitation spectrum. This can be readily understood by considering the torsional sensitivity of the frontier molecular orbital energies. High-level quantum chemical calculations of the radical stabilization energy, resulting in a value of nearly 120 kJ mol−1, provide quantitative confirmation that this radical is highly stabilized.
Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak
Authors: Ogata R. , Hanada K. , Nishino N. , Liu H. Q. , Zushi H. , Ishiguro M. , Ikeda T. , Nakamura K. , Fujisawa A. , Idei H. , Hasegawa M. , Kawasaki S. , Nakashima H. , Higashijima A. ,   QUEST Group
Published: September 2011

A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E × B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed.
Bogomolny-Prasad-Sommerfeld monopoles and open spin chains
Authors: Doikou Anastasia , Ioannidou Theodora
Published: September 2011

We construct SU(n + 1) Bogomolny-Prasad-Sommerfeld (BPS) spherically symmetric monopoles with minimal symmetry breaking by solving the full Weyl equation. In this context, we explore and discuss the existence of open spin chainlike part within the Weyl equation. For instance, in the SU(3) case the relevant spin chain is the 2-site spin 1/2 XXX chain with open boundary conditions. We exploit the existence of such a spin chain part in order to solve the full Weyl equation.
High resolution quantum cascade laser studies of the ν3 band of methyl fluoride in solid para-hydrogen
Authors: McKellar A. R. W. , Mizoguchi Asao , Kanamori Hideto
Published: September 2011

Spectra of solid para-H2 doped with CH3F at 1.8 K are studied in the ν3 region (∼1040 cm−1) using a quantum cascade laser source. As shown previously, residual ortho-H2 in the sample (∼1000 ppm) gives rise to distinct spectral features due to clusters of the form CH3F–(ortho-H2)N, with N = 0, 1, 2, 3, etc. Brief annealing at 7 K is found to give narrower spectral lines (≥0.006 cm−1) than conventional (5 K) annealing, and causes the N = 3 and 4 lines to fragment into two or more components. The N = 3 line is observed to be particularly stable and persistent. The N = 0 line (no ortho-H2 neighbors) is resolved into two closely spaced (≈0.007 cm−1) components which are assigned to the K = 0 and 1 states of CH3F rotating around its C3v symmetry axis (ortho- and para-CH3F, respectively). Similar K-structure is also evident for other lines. Weak but persistent features (“N = 1/2 lines”) are observed mid way between N = 0 and 1.
A broadband ferromagnetic resonance spectrometer to measure thin films up to 70 GHz
Authors: Harward I. , O’Keevan T. , Hutchison A. , Zagorodnii V. , Celinski Z.
Published: September 2011

We report the development of a broadband ferromagnetic resonance (FMR) system operating in the frequency range from 10 MHz to 70 GHz using a closed-cycle He refrigeration system for measurements of thin films and micron/nano structures. The system is capable of carrying out measurements in frequency and field domain. Using two coplanar waveguides, it is capable of simultaneously measuring two samples in the out of plane and in plane FMR geometries. The system operates in the temperature range of 27–350 K and is sensitive to less than one atomic monolayer of a single crystal Fe film.
A low energy electron microscopy study of the initial growth, structure, and thermal stability of 4,4′-biphenyldicarboxylic acid domains on Cu(001)
Authors: Khokhar Fawad S. , van Gastel Raoul , Schwarz Daniel , Zandvliet Harold J. W. , Poelsema Bene
Published: September 2011

The growth of 4,4′-biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene rings of adsorbed BDA are twisted along the molecular axis. Unconventional growth of the domains, followed by a second nucleation stage, is observed at room temperature. This unanticipated feature is attributed to the accumulation of stress in the islands. Ostwald ripening in the films and the decay of BDA domains at 448 K exhibits features that are consistent with diffusion limited behavior.
C-N coupling on transition metal surfaces: A density functional theory study
Authors: Gómez-Díaz Jaime , Vargas-Fuentes Crisa , López Núria
Published: September 2011

We have investigated the formation of C-N bonds from individual atoms and single hydrogenated moieties on a series of transition metals. These reactions play a role in HCN formation at high oxygen coverage, also known as Andrussow oxidation, and they are fundamental to understand the ability of other materials to form part of alloys where Pt is the major component. Dehydrogenations take place quite easily under these high oxygen conditions and thus, the C+N, HC+N, and N+CH recombinations to form HCN or its isomer CNH might represent the rate-limiting steps for the reaction. For all the metals in the present study we have found that the activation energy for the reactions between HxC and NHy (x,y = 0,1) involved in C-N formation follow a linear relationship with the adsorption energy of the N atom. This is due to the common nature of all these transition states, where N-containing fragments get activated from three-fold hollow sites to bridge positions. The slopes of the linear dependence, though, depend on the valence of the N fragment, i.e., smaller slopes are found for NH moieties with respect to N ones.
Shear waves in an inhomogeneous strongly coupled dusty plasma
Authors: Janaki M. S. , Banerjee D. , Chakrabarti N.
Published: September 2011

The properties of electrostatic transverse shear waves propagating in a strongly coupled dusty plasma with an equilibrium density gradient are examined using the generalized hydrodynamic (GH) equation. In the usual kinetic limit, the resulting equation has similarity to zero energy Schrodinger’s equation. This has helped in obtaining some exact eigenmode solutions in both Cartesian and cylindrical geometries for certain nontrivial density profiles. The corresponding velocity profiles and the discrete eigenfrequencies are obtained for several interesting situations and their physics discussed.
High-β equilibria in tokamaks with toroidal flow
Authors: Fitzgerald Michael , Sharapov Sergei , Hole Matthew
Published: September 2011

We extend existing 2-D analytical high-β equilibrium solutions obtained by Cowley et al. [Phys. Fluids B 3, 2066 (1991)] and Hsu et al. [Phys. Plasmas 3, 266 (1996)] to the case of toroidally flowing plasma, assuming ideal magnetohydrodynamics and isothermal magnetic surfaces. Invoking the ordering βq2>>ε2 and Mφ2q2>>ε, we solve the boundary layer problem, re-obtaining the static solution in the zero flow limit. The phenomenon of extreme plasma diamagnetism in the static solution was found to be reduced due to centrifugal drift currents for significant toroidal flow. Example equilibrium calculations are presented using plasma parameters which are approaching attainable values in next generation spherical tokamaks.
Lensing by Kerr black holes. I. General lens equation and magnification formula
Authors: Aazami Amir B. , Keeton Charles R. , Petters A. O.
Published: September 2011

We develop a unified, analytic framework for gravitational lensing by Kerr black holes. In this first paper, we present a new, general lens equation and magnification formula governing lensing by a compact object. Our lens equation assumes that the source and observer are in the asymptotically flat region and does not require a small angle approximation. Furthermore, it takes into account the displacement that occurs when the light ray's tangent lines at the source and observer do not meet on the lens plane. We then explore our lens equation in the case when the compact object is a Kerr black hole. Specifically, we give an explicit expression for the displacement when the observer is in the equatorial plane of the Kerr black hole as well as for the case of spherical symmetry.
Optoelectronic properties of Mg2Si semiconducting layers with high absorption coefficients
Authors: Kato Takashi , Sago Yuichiro , Fujiwara Hiroyuki
Published: September 2011

In an attempt to develop a low-cost material for solar cell devices, polycrystalline magnesium silicide (poly-Mg2Si) semiconducting layers have been prepared by applying rf magnetron sputtering using a Mg2Si target. The optimum substrate temperature for the poly-Mg2Si growth was found to be Ts = 200 °C; the film deposition at higher temperatures leads to desorption of Mg atoms from the growing surface, while the amorphous phase formation occurs at room temperature. The poly-Mg2Si layer deposited at Ts = 200 °C shows the (111) preferential orientation with a uniform grain size of ∼50 nm. The dielectric function of the poly-Mg2Si layer has been determined accurately by spectroscopic ellipsometry. From the analysis, quite high absorption coefficients and an indirect gap of 0.77 eV in the poly-Mg2Si layer have been confirmed. The above poly-Mg2Si layer shows clear photoconductivity and can be applied as a narrow-gap bottom layer in multi-junction solar cell devices.
Three-dimensional optical analyses and optimizations of a vertical alignment color-filters-embedded liquid-crystal-on-silicon microdisplay
Authors: Zhang Baolong , Li Dan , Dai Fengzhi , Yang Shifeng , Kwok Hoising
Published: September 2011

The process of vertical alignment (VA) mode color filter liquid crystal on silicon (CF-LCoS) microdisplay was developed. In order to minimize the fringing field effect in small color pixels, a three dimensional (3D) optical model was established and performed to analyze this VA mode CF-LCoS microdisplay. The simulated result was compared with the experimental data and they coincided well. Optimization of this breed of VA mode CF-LCoS microdisplay was proposed with optimal pretilt angle and pixel size. With the pretilt angle of 86 degrees and the pixel size of 15 μm, the color purity of the VA mode CF-LCoS microdisplay could attain more than 60% National Television Standards Committee (NTSC) level, and the contrast was larger than 400.
Roughness influence in the barrier quality of ferroelectric/ferromagnetic tunnel junctions, model, and experiments
Authors: Sirena M.
Published: September 2011

In this work, a phenomenological approach is proposed to analyze the electrical transport through an insulating barrier in insulating/metallic bilayer systems using conductive atomic force microscopy. The influence of the substrate in the electrical properties of ferroelectric/ferromagnetic bilayers was studied in the frame of this model. The substrate roughness was found to increase the barrier height distribution and increase the attenuation length in the material, reducing the barrier quality for the developing of multiferroic tunnel junctions.
Tunable and absolute electromagnetic vacuum in two-dimensional photonic-band-gap Based on multiferroic materials
Authors: Chen Kai , Jia Wei , Chen Yanbin , Lu Minghui , Zhang Xirui , Yang Wei , Wu Yong , Huang Chenxi , Li Xiangyin , Su Jie , Liu Junming , Lu Xiaomei , Zhu Jinsong , Liu Yun
Published: September 2011

When multiferroic terbium manganite (TbMnO3) crystal cylinders are periodically arranged in a square lattice, the resulting two-dimensional (2D) system exhibits photonic band gaps (PBGs). The absolute PBG originating from the Mie resonance is modulated from closed to open by applying an external static magnetic field, which is attributed to the electromagnon depression of the dielectric constant by the rearrangement of antiferromagnetic order. Tunable electromagnetic band structure may be realized by controlling the magnetic transition of manganese spins in TbMnO3.
Implications of the effective one-component analysis of pair correlations in colloidal fluids with polydispersity
Authors: Pond Mark J. , Errington Jeffrey R. , Truskett Thomas M.
Published: September 2011

Partial pair-correlation functions of colloidal suspensions with continuous polydispersity can be challenging to characterize from optical microscopy or computer simulation data due to inadequate sampling. As a result, it is common to adopt an effective one-component description of the structure that ignores the differences between particle types. Unfortunately, whether this kind of simplified description preserves or averages out information important for understanding the behavior of the fluid depends on the degree of polydispersity and can be difficult to assess, especially when the corresponding multicomponent description of the pair correlations is unavailable for comparison. Here, we present a computer simulation study that examines the implications of adopting an effective one-component structural description of a polydisperse fluid. The square-well model that we investigate mimics key aspects of the experimental behavior of suspended colloids with short-range, polymer-mediated attractions. To characterize the partial pair-correlation functions and thermodynamic excess entropy of this system, we introduce a Monte Carlo sampling strategy appropriate for fluids with a large number of pseudo-components. The data from our simulations at high particle concentrations, as well as exact theoretical results for dilute systems, show how qualitatively different trends between structural order and particle attractions emerge from the multicomponent and effective one-component treatments, even with systems characterized by moderate polydispersity. We examine consequences of these differences for excess-entropy based scalings of shear viscosity, and we discuss how use of the multicomponent treatment reveals similarities between the corresponding dynamic scaling behaviors of attractive colloids and liquid water that the effective one-component analysis does not capture.
The curious case of thin-body Ge crystallization
Authors: Duffy R. , Shayesteh M. , McCarthy B. , Blake A. , White M. , Scully J. , Yu R. , Kelleher A.-M. , Schmidt M. , Petkov N. , Pelaz L. , Marqués L. A.
Published: September 2011

The authors investigate the templated crystallization of thin-body Ge fin structures with high aspect ratios. Experimental variables include fin thickness and thermal treatments, with fin structures oriented in the 〈110〉 direction. Transmission electron microscopy determined that various crystal defects form during crystallization of amorphous Ge regions, most notably {111} stacking faults, twin boundaries, and small crystallites. In all cases, the nature of the defects is dependent on the fin thickness and thermal treatments applied. Using a standard 600 °C rapid-thermal-anneal, Ge structures with high aspect ratios crystallize with better crystal quality and fewer uncured defects than the equivalent Si case, which is a cause for optimism for thin-film Ge devices.
Nature of phase transitions in crystalline and amorphous GeTe-Sb2Te3 phase change materials
Authors: Kalkan B. , Sen S. , Clark S. M.
Published: September 2011

The thermodynamic nature of phase stabilities and transformations are investigated in crystalline and amorphous Ge1Sb2Te4 (GST124) phase change materials as a function of pressure and temperature using high-resolution synchrotron x-ray diffraction in a diamond anvil cell. The phase transformation sequences upon compression, for cubic and hexagonal GST124 phases are found to be: cubic → amorphous → orthorhombic → bcc and hexagonal → orthorhombic → bcc. The Clapeyron slopes for melting of the hexagonal and bcc phases are negative and positive, respectively, resulting in a pressure dependent minimum in the liquidus. When taken together, the phase equilibria relations are consistent with the presence of polyamorphism in this system with the as-deposited amorphous GST phase being the low entropy low-density amorphous phase and the laser melt-quenched and high-pressure amorphized GST being the high entropy high-density amorphous phase. The metastable phase boundary between these two polyamorphic phases is expected to have a negative Clapeyron slope.
Resistive switching at manganite/manganite interfaces
Authors: Kalkert Christin , Krisponeit Jon-Olaf , Esseling Markus , Lebedev Oleg I. , Moshnyaga Vasily , Damaschke Bernd , van Tendeloo Gustaaf , Samwer Konrad
Published: September 2011

We report bipolar resistive switching between the interfaces of manganite nanocolumns. La0.7Sr0.3MnO3 films were prepared on Al2O3 substrates, where the films grow in nanocolumns from the substrate to the surface. Conductive atomic force microscopy directly detects that the resistive switching is located at the boundaries of the grains. Furthermore, mesoscopic transport measurements reveal a tunnel magnetoresistance. In combination with the resistive switching, this leads to a total of four different resistive states.
Performance characteristics according to the channel length and magnetic fields of cylindrical Hall thrusters
Authors: Lee Jongsub , Seo Mihui , Seon Jongho , June Lee Hae , Choe Wonho
Published: September 2011

Performance characteristics of low power cylindrical Hall thrusters are investigated in terms of the length of the discharge channel. Thrust, efficiency, discharge current, and propellant utilization are evaluated for different channel lengths of 19, 22, and 25 mm. It is found that the propellant utilization and ion energy distribution function are strongly associated with the channel length. Increase of thrust and efficiency are also found with increasing channel lengths. These characteristics of the thruster are interpreted with possible generation of multi-charged ions due to increased residing time within the extended space inside the channel.
Monolayer graphene film/silicon nanowire array Schottky junction solar cells
Authors: Xie Chao , Lv Peng , Nie Biao , Jie Jiansheng , Zhang Xiwei , Wang Zhi , Jiang Peng , Hu Zhizhong , Luo Linbao , Zhu Zhifeng , Wang Li , Wu Chunyan
Published: September 2011

Schottky junction solar cells were constructed by combining the monolayer graphene (MLG) films and the Si nanowire (SiNW) arrays. Pronounced photovoltaic characteristics were investigated for devices with both p-MLG/n-SiNWs and n-MLG/p-SiNWs structures. Due to the balance between light absorption and surface carrier recombination, devices made of SiNW arrays with a medium length showed better performance and could be further improved by enhancing the MLG conductivity via appropriate surface treatment or doping. Eventually, a photoconversion efficiency up to 2.15% is obtained by the means of filling the interspace of SiNW array with graphene suspension.
Influences of sub-Alfvénic shear flows on nonlinear evolution of magnetic reconnection in compressible plasmas
Authors: Zhang X. , Li L. J. , Wang L. C. , Li J. H. , Ma Z. W.
Published: September 2011

Influences of sub-Alfvénic shear flows on the nonlinear evolution of the magnetic reconnection are studied in the framework of compressible resistive MHD and compressible Hall MHD. It is found for the first time that the sub-Alfvénic shear flow can either stabilize or destabilize magnetic reconnection, which is mainly determined by the plasma beta and the half thickness of the shear flow (λv). The shear flow exhibits a suppressing effect on magnetic reconnection and the boosting effect nearly disappears for the beta plasma β ≲1, which is associated with the presence of a pair of discontinuities in the upper and lower inflow region. The shear flow has the boosting effect on magnetic reconnection when the half thickness of the shear flow exceeds a critical value in the high beta plasma which is in a good agreement with the results from incompressible simulation. With the inclusion of the Hall effect, shear flow can still either stabilize or destabilize magnetic reconnection, but the boosting effect becomes weaker as the ion inertial length di increases.
Managing magnetic force applied to a magnetic device by a rotating dipole field
Authors: Mahoney Arthur W. , Abbott Jake J.
Published: September 2011

We demonstrate that the attractive magnetic force acting on a rotating magnetic device (e.g., a magnetic microrobot), actuated using a rotating magnet dipole, can be converted into a lateral force by rotating the actuator dipole according to a specific open-loop trajectory. Results show rotating magnetic devices can be rolled and simultaneously pushed along a surface by the lateral force, resulting in significant increase in velocity. We also demonstrate that the lateral force magnitude can be sufficient to levitate the magnetic device. The results apply to rotating magnetic devices of any size provided inertia has a negligible contribution to its dynamics.
Enhanced photovoltaic properties in graphene/polycrystalline BiFeO3/Pt heterojunction structure
Authors: Zang Yongyuan , Xie Dan , Wu Xiao , Chen Yu , Lin Yuxuan , Li Mohan , Tian He , Li Xiao , Li Zhen , Zhu Hongwei , Ren Tianling , Plant David
Published: September 2011

We report the enhanced photovoltaic properties in polycrystalline BiFeO3 (BFO) thin films with graphene as top electrodes. The short circuit current density (Jsc) and open circuit voltage of the heterojunction are measured to be 25 μA/cm2 and 0.44 V, respectively, much higher than the reported values for polycrystalline BFO with indium tin oxide (ITO) as top electrodes. Influence of HNO3 treatment on the photovoltaic properties is studied, and a significant photocurrent density improvement from 25 μA/cm2 to 2.8 mA/cm2 is observed. A metal-intrinsic semiconductor-metal model is proposed to explain the graphene induced enhancement comparing with traditional ITO.
Manipulating the spin of single-molecule magnet by thermal spin-transfer torque
Authors: Zhang Zhengzhong , Jiang Liang , Wang Ruiqiang , Wang Baigeng , Xing D. Y.
Published: September 2011

We investigate thermally driven electronic transport through a single-molecule magnet (SMM) coupled to a ferromagnetic (FM) lead and a normal-metallic lead. Due to the thermal spin-transfer torque effect, the orientation of the SMM’s spin can be manipulated by temperature bias or gate voltage to be parallel or antiparallel to the FM lead’s magnetization. The present device can be realized by current technologies and has potential application in molecular spintronics or quantum information processing.
Origin of characteristic variability in metal-oxide-semiconductor field-effect transistors revealed by three-dimensional atom imaging
Authors: Takamizawa H. , Shimizu Y. , Inoue K. , Toyama T. , Okada N. , Kato M. , Uchida H. , Yano F. , Nishida A. , Mogami T. , Nagai Y.
Published: September 2011

The greater variability in the electrical properties of n-type metal-oxide-semiconductor field-effect transistors (MOSFETs) compared with those of p-type MOSFETs poses problems for scaling of silicon based large-scale integration technology. We have elucidated the origin of the variability difference between n- and p-type transistors by using laser-assisted atom probe tomography to directly count the number of discrete atoms in local regions. We found that ion implantation and activation annealing for source/drain extension fabrication enhances anomalous dopant fluctuations of boron atoms in n-MOSFET channel regions, interpreted by fast migration of boron atoms.
Evidence of lattice tilt and slip in m-plane InGaN/GaN heterostructure
Authors: Yoshida Shunji , Yokogawa Toshiya , Imai Yasuhiko , Kimura Shigeru , Sakata Osami
Published: September 2011

Using high-resolution microbeam x-ray diffraction and cross-section transmission electron microscopy, we investigated in-plane anisotropy resulting from epilayer lattice tilts in heteroepitaxial InGaN on a m-plane GaN substrate. The in-plane structure consists of two lattice tilts along the [112¯0] direction corresponding to (101¯0) and (01¯10) slip planes inclined at roughly 60° from the m-plane. Based on the Peierls-Nabarro model, we explain this structure by proposing a slip system via the {101¯0} prism plane with 〈112¯0〉-type slip directions.
Fast relaxation of the velocity distribution function of neutral and ionized species in high-power impulse magnetron sputtering
Authors: Britun Nikolay , Palmucci Maria , Snyders Rony
Published: September 2011

A super-exponential time-relaxation of the full width at half maximum of Ti and Ti+ spectral lines was found during the off-time in a high-power impulse magnetron sputtering discharge studied by laser-induced fluorescence. After the estimation of the possible broadening mechanisms, the main contribution to the determined linewidths appeared to be the broadening due to ballistic motion of sputtered species with a minor contribution of the instrumental and Doppler broadenings. The deconvoluted linewidths depend both on pressure and distance from target, and their time-decay was attributed to the fast energy relaxation of the sputtered neutrals and ions during the off-time.
Nonlinear electrical properties of carbon nanotube forests
Authors: Kozlov Mikhail E.
Published: September 2011

Differential conductance of vertically aligned arrays of multi-walled carbon nanotubes (MWNT forests) reveals a zero bias anomaly at room temperature. The anomaly becomes narrower and sharper upon cooling sample down reaching magnitude of 25% of average conductance at 244 K. Further cooling results in decrease of its magnitude that correlates with the slope of temperature dependence of sample’s electrical conductance. The anomaly can be caused by tunneling of charge carriers through nanotube junctions enhanced by temperature gradients induced by measuring currents. Observed phenomenon can be used for the characterization of junction network created by carbon nanotubes in MWNT forests.
Photoluminescence due to inelastic exciton-exciton scattering in ZnMgO-alloy thin film
Authors: Chia C. H. , Chen J. N. , Hu Y. M.
Published: September 2011

We studied the photoluminescence of ZnMgO thin film, grown by the radiofrequency sputtering method, as a function of excitation intensity and temperature. As the excitation intensity increases, a nonlinear emission band caused by the radiative recombination of the inelastic exciton-exciton scattering was detected at low temperature. We found that the inelastic exciton-exciton scattering process can only persist up to T ∼ 260 K. The nonlinear emission band observed at room temperature is due to the radiative recombination of the electron-hole plasma.
Antiapoptotic protein Lifeguard is required for survival and maintenance of Purkinje and granular cells
Authors: Hurtado de Mendoza Tatiana , Perez-Garcia Carlos G. , Kroll Todd T. , Hoong Nien H. , O'Leary Dennis D. M. , Verma Inder M.
Published: September 2011

Lifeguard (LFG) is an inhibitor of Fas-mediated cell death and is highly expressed in the cerebellum. We investigated the biological role of LFG in the cerebellum in vivo, using mice with reduced LFG expression generated by shRNA lentiviral transgenesis (shLFG mice) as well as LFG null mice. We found that LFG plays a role in cerebellar development by affecting cerebellar size, internal granular layer (IGL) thickness, and Purkinje cell (PC) development. All these features are more severe in early developmental stages and show substantial recovery overtime, providing a remarkable example of cerebellar plasticity. In adult mice, LFG plays a role in PC maintenance shown by reduced cellular density and abnormal morphology with increased active caspase 8 and caspase 3 immunostaining in shLFG and knockout (KO) PCs. We studied the mechanism of action of LFG as an inhibitor of the Fas pathway and provided evidence of the neuroprotective role of LFG in cerebellar granule neurons (CGNs) and PCs in an organotypic cerebellar culture system. Biochemical analysis of the Fas pathway revealed that LFG inhibits Fas-mediated cell death by interfering with caspase 8 activation. This result is supported by the increased number of active caspase 8-positive PCs in adult mice lacking LFG. These data demonstrate that LFG is required for proper development and survival of granular and Purkinje cells and suggest LFG may play a role in cerebellar disorders.
Sources for the Study of Iran
Authors: Mottahedeh Roy
Published: September 2011

Oliver Wendell Holmes when he taught anatomy at the Harvard Medical School in the 19th century used to begin his lecture on the skull by picking up each bone and describing its position: “The frontal bone borders on the parietal bone, the parietal bone borders on the occipital bone,” and so on, until he came to the sphenoid bone, a bone composed of many pieces that seem to border on everything and assume all shapes. He is supposed to have picked up the sphenoid and said in annoyance, “Gentlemen, curse the sphenoid bone!” No such uncharitable words would come from the student of Iran, but how often the primitive state of his science, like the anatomy of an earlier century, makes Iran seem the most complex and indefinable of all the bones in the greater body politic of the world.
Theism and Pantheism in Rumi
Authors: Bausani Alessandro
Published: September 2011

Pantheism is generally defined as “all is God and God is all (I) but it can therotically assume two different forms. First, it is said that the finite and temporal world is nothing in front of God, and it is swallowad up by the sole absolute Reality of God, or in the second instance, God is considered as dissolved in the world, poetically sung or scientifically demonstrated as a Whole, in which an immanent Life-Energy acts. In both cases, however, what most sharply distinguishes pantheism from non-pantheism (or theism) is the fact that God is always considered by pantheists as something impersonal; pantheists generally affirm the superiority of their view on theistic “inferior” forms of religion pointing out that (a) calling God a “person” restricts and diminishes His greatness, as it necessarily implies a body and a limitation, (b) pantheistic piety is not a feeling of devotion of an Ego to a Thou, but rather the sensation of being a part belonging to a Whole, a wave in the immense sea of Being.
Someone Else's Child
Authors: Al-i-Ahmad Jalal
Published: September 2011

Well, what could I do? My husband wouldn't keep me and the child both—a child who was not his own. The boy was my former husband's who had divorced me and never come to take him. If someone else were in my place, what would she do? Well, I had to live too. If this new husband divorces me what would I do? I had to get rid of the child.

A woman like me who doesn't know her way around wouldn't think of anything else. I didn't know any place or any way out of the thing. But it wasn't that I didn't know any place, really. I knew you could put the child in a nursery or stick him in some other place. But where would they take him? Where could I be sure they wouldn't keep me waiting and then not pay any attention to me and call me and the child a thousand names? Where? I couldn't have it end that way.
The rigidity of Dolbeault-type operators and symplectic circle actions
Authors: Li Ping
Published: September 2011

Following the idea of Lusztig, Atiyah-Hirzebruch and Kosniowski, we note that the Dolbeault-type operators on compact, almost-complex manifolds are rigid. When the circle action has isolated fixed points, this rigidity result will produce many identities concerning the weights on the fixed points. In particular, it gives a criterion to determine whether or not a symplectic circle action with isolated fixed points is Hamiltonian. As applications, we simplify the proofs of some known results related to symplectic circle actions, due to Godinho, Tolman-Weitsman and Pelayo-Tolman, and generalize some of them to more general cases.
Viperin inhibits hepatitis C virus replication by interfering with binding of NS5A to host protein hVAP-33
Authors: Wang Shanshan , Wu Xianfang , Pan Tingting , Song Wuhui , Wang Yaohui , Zhang Fei , Yuan Zhenghong
Published: September 2011

Viperin is a type-I and -II interferon-inducible intracytoplasmic protein that mediates antiviral activity against several viruses. A previous study has reported that viperin could limit hepatitis C virus (HCV) replicationin vitro. However, the underlying mechanism remains elusive. In the present study, we found that overexpression of viperin could inhibit HCV replication in a dose-dependent manner in both the replicon and HCVcc systems. Furthermore, through co-immunoprecipitation and laser confocal microscopic analysis, viperin was found to interact with the host protein hVAP-33. Mutagenesis analysis demonstrated that the anti-HCV activity of viperin was located to its C terminus, which was required for the interaction with the C-terminal domain of hVAP-33. Competitive co-immunoprecipitation analysis showed that viperin could interact competitively with hVAP-33, and could therefore interfere with its interactions with HCV NS5A. In summary, these findings suggest a novel mechanism by which viperin inhibits HCV replication, possibly through binding to host protein hVAP-33 and interfering with its interaction with NS5A.
Do components of current ‘hardcore smoker’ definitions predict quitting behaviour?
Authors: Ip David T. , Cohen Joanna E. , Bondy Susan J. , Chaiton Michael O. , Selby Peter , Schwartz Robert , McDonald Paul , Garcia John , Ferrence Roberta
Published: September 2011

Aims  It has been hypothesized that the smoking population is represented by an increasingly ‘hardcore’ group of smokers who are resistant to quitting. Many definitions of ‘hardcore smokers’ have been used, but their predictive validity is unknown. To evaluate whether ‘hardcore smoker’ definition components predict quitting behaviours and which combinations of ‘hardcore’ components are most predictive.

Design, setting and participants  Longitudinal, random telephone survey of a representative sample of adult smokers in Ontario, Canada (n = 4130, recruited 2005–08 and followed for 1 year).

Measurements  Multiple logistic regression models were compared to evaluate the predictive ability of ‘hardcore’ components (high daily cigarette consumption, high nicotine dependence, being a daily smoker, history of long‐term smoking, no quit intention and no life‐time quit attempt) on three outcomes [continued smoking, not attempting to quit and having unsuccessful quit attempt(s)].

Findings  All ‘hardcore’ components predicted having no quit attempt and continued smoking during follow‐up (P < 0.05), except for history of long‐term smoking and no life‐time quit attempt (for continued smoking). Among respondents who made 1 + quit attempts during follow‐up, only high nicotine dependence, high daily cigarette consumption and being a daily smoker were predictive of quitting failure (P < 0.01). The best combination of components depended on the outcome.

Conclusions  Measures of ‘hardcore’ include a mixture of motivational, dependence and behavioural variables. As found previously, motivational and behavioural measures, such as intention to quit, predict failure to make quit attempts. However, dependence components best predicted continued smoking and thus would be best for further exploring the hardening hypothesis.
A damage/benefit evaluation of addictive product use
Authors: Bourgain Catherine , Falissard Bruno , Blecha Lisa , Benyamina Amine , Karila Laurent , Reynaud Michel
Published: September 2011

Aims  To obtain damage/benefit assessments of eight commonly used addictive products and one addictive behaviour from French addiction experts and link these to overall evaluations.

Design and setting  Criteria‐based evaluation by experts in addiction. Specific statistical modelling to estimate the relative contribution of various criteria to formulating expert general opinion on products.

Participants  Forty‐eight French experts in addiction.

Measurements  Twelve criteria covering the whole spectrum of damages and benefits to users and to society evaluated using visual analogue scales (VAS). Direct measure of expert overall subjective opinions on products from user and from social perspectives.

Findings  Damage scoring identified alcohol (damage score = 48.1), heroin (damage score = 44.9) and cocaine (damage score = 38.5) as the most harmful products to users and to society; gambling was considered the least harmful (score = 22.5), replicating previous results. Damage scoring correlated poorly with legal status or with overall subjective expert opinions of products. Benefit perception scores indicated alcohol as a clear outlier (benefit score = 45.5) followed by tobacco (benefit score = 34.3) and cannabis (benefit score = 31.1). Statistical modelling suggested that experts attributed 10 times more importance to benefit perception than to damages when making their subjective opinion from a user perspective and two times more importance to benefit perception than to damages in formulating their opinion from a social perspective.

Conclusions  The perceived benefits of addictive products appear to have a major impact on the opinion of those products expressed by a number of French addiction experts.