bluuebunny/crossref_metadata_2025 huggingface dataset:
X-pinch radiography for the radiation suppressed tungsten and aluminum planar wire array
Authors: Wu J. , Wang L. P. , Han J. J. , Li M. , Sheng L. , Li Y. , Zhang M. , Guo N. , Lei T. S. , Qiu A. C. , Lv M.
Published: February 2012

X-pinch radiography experiments were carried out on the 1 MA QiangGuang-1 facility to investigate the wire core behaviors of the tungsten and aluminum planar wire array. An axial quencher and over-massed loads were used to suppress keV radiation from the planar wire array. Two-wire 30 μm Mo and/or 25 μm W X-pinches were used as backlighters. The x-ray point-projection images showed quite uneven characteristics of the dense wire cores and the current distribution in the linear array. For the W single planar wire array (SPWA), Wire core diameter profiles are likely to reveal that the initial current distributed inductively among the wires with the same diameter in the array, and both inductively and resistively among the wires with different diameters. For the Al SPWA, wires in different positions were in quite different ablation processes. No correlations of stratifications or plasma jets between adjacent wires were observed.
Dynamics of H+ + CO at ELab = 30 eV
Authors: Stopera Christopher , Maiti Buddhadev , Grimes Thomas V. , McLaurin Patrick M. , Morales Jorge A.
Published: February 2012

The astrophysically relevant system H+ + CO (vi = 0) → H+ + CO (vf) at ELab = 30 eV is studied with the simplest-level electron nuclear dynamics (SLEND) method. This investigation follows previous successful SLEND studies of H+ + H2 and H+ + N2 at ELab = 30 eV [J. Morales, A. Diz, E. Deumens, and Y. Öhrn, J. Chem. Phys. 103(23), 9968 (1995)10.1063/1.469886; C. Stopera, B. Maiti, T. V. Grimes, P. M. McLaurin, and J. A. Morales, J. Chem. Phys. 134(22), 224308 (2011)10.1063/1.3598511]. SLEND is a direct, time-dependent, variational, and non-adiabatic method that adopts a classical-mechanics description for the nuclei and a single-determinantal wavefunction for the electrons. A canonical coherent-states (CS) procedure associated with SLEND reconstructs quantum vibrational properties from the SLEND classical dynamics. Present SLEND results include reactivity predictions, snapshots of the electron density evolution, average vibrational energy transfers, rainbow angle predictions, total and vibrationally resolved differential cross sections (DCS), and average vibrational excitation probabilities. SLEND results are compared with available data from experiments and vibrational close-coupling rotational infinite-order sudden (VCC-RIOS) approximation calculations. Present simulations employ four basis sets: STO-3G, 6-31G, 6-31G**, and cc-pVDZ to determine their effect on the results. SLEND simulations predict non-charge-transfer scattering and CO collision-induced dissociation as the main reactions. SLEND/6-31G, /6-31G**, and /cc-pVDZ predict rainbow angles and total DCS in excellent agreement with experiments and more accurate than their VCC-RIOS counterparts. SLEND/6-31G** and /cc-pVDZ predict vibrationally resolved DCS for vf = 0–2 in satisfactory experimental agreement, but less accurate than their comparable H+ + CO VCC-RIOS and H+ + H2 and H+ + N2 SLEND results. SLEND/6-31G** and /cc-pVDZ predict qualitatively correct average vibrational excitation probabilities, which are quantitatively correct for vf = 2, but under(over)estimated for vf = 0(1). Discrepancies in some H+ + CO SLEND vibrational properties, not observed in H+ + H2 and H+ + N2 SLEND results, are attributed to the moderately overestimated SLEND vibrational energy through its effect upon the canonical CS probabilities. Correction of that energy to its experimental values produces a remarkable improvement in the average vibrational excitation probabilities. Ways to obtain more accurate vibrational properties with higher-level versions of electron nuclear dynamics are discussed.
Microstructure and low-temperature plastic deformation of Al–Li alloy
Authors: Isaev N. V. , Zabrodin P. A. , Spuskanyuk V. Z. , Davydenko A. A. , Pustovalov V. V. , Fomenko V. S. , Braude I. S.
Published: February 2012

Features of the plastic deformation of solid Al–Li solutions with microstructures formed by direct and angular hydroextrusion are studied under tension at temperatures of 4.2–350 K. It is found that the grain size reductions, increases in the average density of defects, and changes in the orientational textures during combined hydroextrusion lead to increased strength and reduced plasticity of the microcrystalline alloy relative to initially large-grained samples. The high yield stress of the microcrystalline alloy is explained by a higher grain density and the evolution of an orientational texture. The strong temperature dependence of the yield stress is typical of thermally activated interactions between dislocations and local obstacles in the form of deformation defects produced during hydroextrusion. The low plasticity of the microcrystalline alloy, which already shows up as a localization of plastic deformation with small deformations, is caused by a low rate of work hardening owing to enhanced dynamic recovery of fine grains even at low temperatures. The rate of dynamic recovery decreases, while uniform deformation increases, at temperatures of 77 K and below. Based on data on the high stress rate sensitivity at temperatures above 77 K and the low activation volume for plastic deformation of microcrystalline Al–Li, it is proposed that high-angle grain boundaries may serve as highly efficient sources and sinks of mobile dislocations.
Violation of a logarithmic trend of magnetization relaxation in HTSCs with strong pinning centers
Authors: Monarkha V. Y. , Timofeev V. P. , Shablo A. A.
Published: February 2012

The dynamics of magnetic fluxes trapped in small constant magnetic fields, of the order of the Earth’s field, were experimentally investigated in single crystals of YBCO with strong pinning centers formed in the structure of unidirectional twinning boundaries. A significant deviation of the isothermal magnetization relaxation from the logarithmic behavior observed previously only in strong magnetic fields was found for the first time in the region of strong thermal fluctuations near the superconducting phase transition. Within the Anderson-Kim linear model of the thermally activated creep and using experimental data, an effective pinning potential was estimated. It is shown that at the temperatures close to critical one the inverse logarithmic model of Zeldov describes better the magnetization drop, in particular, at long measurements times.
Dynamic phase transitions in a two-dimensional electronic crystal and in a two-dimensional helium film
Authors: Syvokon V. E. , Nasedkin K. A.
Published: February 2012

The phase transitions induced by an electric field in the plane of the electron layer (dynamic transitions) in a two-dimensional (2D) electronic crystal over liquid helium are investigated experimentally. They are compared with the superfluid transition in thin helium films at nonlinear conditions (at high velocities of a substrate). A qualitative correspondence between the transitions is found. Because the melting of the two-dimensional crystal and the superfluid transition in the two-dimensional film belong to one type of phase transitions, the correspondence found indicates that the dynamic phase transition in the 2D electronic crystal can be considered as a nonlinear or dynamic melting.
Three-dimensional control of Tetrahymena pyriformis using artificial magnetotaxis
Authors: Hyung Kim Dal , Seung Soo Kim Paul , Agung Julius Anak , Jun Kim Min
Published: February 2012

We demonstrate three-dimensional control with the eukaryotic cell Tetrahymena pyriformis (T. pyriformis) using two sets of Helmholtz coils for xy-plane motion and a single electromagnet for z-direction motion. T. pyriformis is modified to have artificial magnetotaxis with internalized magnetite. To track the cell’s z-axis position, intensity profiles of non-motile cells at varying distances from the focal plane are used. During vertical motion along the z-axis, the intensity difference is used to determine the position of the cell. The three-dimensional control of the live microorganism T. pyriformis as a cellular robot shows great potential for practical applications in microscale tasks, such as target transport and cell therapy.
Structure, magnetization, and low-temperature impedance response of polycrystalline InSe intercalated with nickel
Authors: Stakhira Y. M. , Tovstyuk N. K. , Fomenko V. L. , Grigorchak I. I. , Borysyuk A. K. , Seredyuk B. A.
Published: February 2012

A solid-phase mechanochemical technology of production of polycrystalline InSе intercalated with Ni up to 1.25 at. % has been developed. The x-ray and phase analyses of the produced NixInSe samples confirm their homogeneity and demonstrate a nonmonotonic Ni-content dependence of the lattice constant along the axis normal to the layers. Analysis of the low-temperature (77 K) impedance response within the frequency region 10–3–106 Hz shows a good correlation between the change in interlayer distance and in the band conductivity observed with increasing Ni concentration. However, the Ni concentration dependence of specific magnetization demonstrates an irregular increase at x ∼ 1 and does not coincide with the former. Such behavior is explained by the proposed theoretical model, which at the same time unveiled the mechanism behind the increasing contribution of free carrier concentration to conductivity – hybridization of electron orbitals of guest nickel and the lattice layers.
Modeling of silicon nanocrystals based down-shifter for enhanced silicon solar cell performance
Authors: Sgrignuoli F. , Paternoster G. , Marconi A. , Ingenhoven P. , Anopchenko A. , Pucker G. , Pavesi L.
Published: February 2012

A transfer matrix model of a luminescent down-shifter (LDS) layer, consisting of silicon nanocrystals (Si-NCs) embedded in a silicon oxide matrix, on a silicon solar cells is presented. To enhance the efficiency of the silicon solar cell, we propose using a SiO2/Si-NCs double layer stack, as an anti-reflection-coating (ARC) and as a LDS material. The optical characteristics of this stack have been simulated and optimized as a front surface coating. The cell performances have been simulated by means of a two-dimensional device simulator and compared with the performances of a reference silicon solar cell. We found a 6% relative enhancement of the energy conversion efficiency with respect to the reference cell. We demonstrate that this enhancement results from the lower reflectance and from the down-shifter effect of the Si-NCs activated coating stack.
Strain enhanced spin polarization in graphene with Rashba spin-orbit coupling and exchange effects
Authors: Zhang Ying-Tao , Zhai Feng
Published: February 2012

We investigate spin polarization and valley-dependent transport in bulk graphene in the presence of the exchange splitting field, the pseudo magnetic field, and Rashba spin-orbit coupling (SOC). It is demonstrated that Rashba SOC and the pseudo magnetic field cannot produce a spin polarization component perpendicular to the graphene sheet, but the exchange field can. However, the Rashba SOC leads to a finite in-plane spin polarization, which can be modulated by the pseudo magnetic field. Furthermore, it is also demonstrated that the valley polarization current cannot be produced in the considered system due to the mirror symmetry property of transmission probability for valley K and K′.
Effect of dimensionality on the continuum percolation of overlapping hyperspheres and hypercubes
Authors: Torquato S.
Published: February 2012

We show analytically that the [0, 1], [1, 1], and [2, 1] Padé approximants of the mean cluster number S for both overlapping hyperspheres and overlapping oriented hypercubes are upper bounds on this quantity in any Euclidean dimension d. These results lead to lower bounds on the percolation threshold density ηc, which become progressively tighter as d increases and exact asymptotically as d → ∞, i.e., ηc → 2−d. Our analysis is aided by a certain remarkable duality between the equilibrium hard-hypersphere (hypercube) fluid system and the continuum percolation model of overlapping hyperspheres (hypercubes). Analogies between these two seemingly different problems are described. We also obtain Percus-Yevick-like approximations for the mean cluster number S in any dimension d that also become asymptotically exact as d → ∞. We infer that as the space dimension increases, finite-sized clusters become more ramified or “branch-like.” These analytical estimates are used to assess simulation results for ηc up to 20 dimensions in the case of hyperspheres and up to 15 dimensions in the case of hypercubes. Our analysis sheds light on the radius of convergence of the density expansion for S and naturally leads to an analytical approximation for ηc that applies across all dimensions for both hyperspheres and oriented hypercubes. Finally, we describe the extension of our results to the case of overlapping particles of general anisotropic shape in d dimensions with a specified orientational probability distribution.
Competing effects of rare gas atoms in matrix isolation spectroscopy: A case study of vibrational shift of BeO in Xe and Ar matrices
Authors: Nakayama Akira , Niimi Keisuke , Ono Yuriko , Taketsugu Tetsuya
Published: February 2012

We investigate the vibrational shift of beryllium oxide (BeO) in Xe matrix as well as in Ar matrix environments by mixed quantum-classical simulation and examine the origin of spectral shift in details. BeO is known to form strong chemical complex with single rare gas atom, and it is predicted from the gas phase calculations that vibrational frequencies are blueshifted by 78 cm−1 and 80 cm−1 upon formation of XeBeO and ArBeO, respectively. When the effects of other surrounding rare gas atoms are included by Monte Carlo simulations, it is found that the vibrational frequencies are redshifted by 21 cm−1 and 8 cm−1 from the isolated XeBeO and ArBeO complexes, respectively. The vibrational shift of XeBeO in Ar matrix is also calculated and compared with experimental data. In all simulations examined in this paper, the calculated vibrational frequency shifts from the isolated BeO molecule are in reasonable agreement with experimental values. The spectral shift due to the rare-gas-complex formation of RgBeO (Rg = Xe or Ar) is not negligible as seen in the previous studies, but it is shown in this paper that the effects of other surrounding rare gas atoms should be carefully taken into account for quantitative description of the spectral shifts and that these two effects are competing in vibrational spectroscopy of BeO in matrix environments.
Nonadiabatic excited-state molecular dynamics: Numerical tests of convergence and parameters
Authors: Nelson Tammie , Fernandez-Alberti Sebastian , Chernyak Vladimir , Roitberg Adrian E. , Tretiak Sergei
Published: February 2012

Nonadiabatic molecular dynamics simulations, involving multiple Born-Oppenheimer potential energy surfaces, often require a large number of independent trajectories in order to achieve the desired convergence of the results, and simulation relies on different parameters that should be tested and compared. In addition to influencing the speed of the simulation, the chosen parameters combined with the frequently reduced number of trajectories can sometimes lead to unanticipated changes in the accuracy of the simulated dynamics. We have previously developed a nonadiabatic excited state molecular dynamics methodology employing Tully's fewest switches surface hopping algorithm. In this study, we seek to investigate the impact of the number of trajectories and the various parameters on the simulation of the photoinduced dynamics of distyrylbenzene (a small oligomer of polyphenylene vinylene) within our developed framework. Various user-defined parameters are analyzed: classical and quantum integration time steps, the value of the friction coefficient for Langevin dynamics, and the initial seed used for stochastic thermostat and hopping algorithms. Common approximations such as reduced number of nonadiabatic coupling terms and the classical path approximation are also investigated. Our analysis shows that, at least for the considered molecular system, a minimum of ∼400 independent trajectories should be calculated in order to achieve statistical averaging necessary for convergence of the calculated relaxation timescales.
Dipole evolution in rotating two-dimensional flow with bottom friction
Authors: Makarov V. G.
Published: February 2012

The evolution of a dipolar vortex in a quasi-two-dimensional rotating flow of barotropic fluid over a flat surface with a no-slip condition in the Ekman bottom layer is considered. The vorticity equation in this case becomes nonlinear. An effect of bottom friction is displayed mainly in cyclone-anticyclone asymmetry, which results in the expansion (diminution) of cyclonic (anticyclonic) local structures and in the stronger decay of positive vorticity. When a lateral viscosity is omitted, the vorticity equation has a solution in the form of vortex patches and hence a contour dynamics method may be used for numerical simulation. An approach of point vortices with decaying strengths is also discussed. In an approximation of two patches of opposite uniform vorticity, a three-parameter family of stationary (in an ideal fluid) orbital dipoles [V. G. Makarov and Z. Kizner, “Stability and evolution of uniform-vorticity dipoles,” J. Fluid Mech. 672, 307 (2011)]10.1017/S0022112010006026 consisting of patches with unequal areas and absolute values of vorticity is considered. A three-dimensional domain of instability for this family is numerically constructed. It is shown that the evolution of such dipoles in a flow with bottom friction is described with good accuracy by a properly matched trajectory in parameter space of ideal-fluid steady states. Explicit time-dependent formulae for this phase trajectory are obtained. All characteristics (including the patch's shapes) of the evolutionary dipole, and the same characteristics for the corresponding ideal-fluid stationary dipole, almost completely coincide, at least while the phase trajectory remains in the stability region. The evolution of stationary translating dipoles (with zero net circulation) that have continuously distributed vorticity inside a quasi-elliptical finite region is also examined. When the circular Lamb dipole is used as the initial condition, good qualitative agreement is observed between the asymmetric dipoles obtained during evolution and the chain of the exact solutions from the known one-parameter family of non-symmetrical Chaplygin dipoles.
Velocity slip coefficients based on the hard-sphere Boltzmann equation
Authors: Gibelli Livio
Published: February 2012

We present a kinetic theory derivation of higher-order slip boundary conditions. The situation studied is that of a pressure driven isothermal gas flowing through a plane microchannel. The distribution function is expanded in terms of half-range Hermite polynomials and the system of moment equations in the expansion coefficients is analytically solved. The velocity slip coefficients, as well as their Knudsen-layer corrections, are obtained by evaluating the solution in the near continuum limit. The proposed approach is accurate and easy to implement. The results are presented for the hard-sphere Boltzmann equation and Maxwell's diffuse-specular boundary conditions, but can be extended to arbitrary intermolecular interactions and more general scattering kernels.
1D/2D switchable grating based on field-induced polymer stabilized blue phase liquid crystal
Authors: Zhu Ji-Liang , Lu Jian-Gang , Qiang Jing , Zhong En-Wei , Ye Zhi-Cheng , He Zhenghong , Guo Xiaojun , Dong Cheng-Yuan , Su Yikai , Shieh Han-Ping D.
Published: February 2012

We present a 1D/2D switchable grating based on field-induced polymer stabilized blue phase liquid crystal (PSBPLC). For 1D grating, the diffraction efficiency of the first order is 37.2% and the phase modulation depth of the 1D grating can achieve 2π. For 2D grating, more than 90% of light intensity is distributed to the surrounding orders of zero order and the phase modulation depth is about 3.67π. Furthermore it shows fast phase modulation and 1D/2D switching time.
Model of dissipative dielectric elastomers
Authors: Chiang Foo Choon , Cai Shengqiang , Jin Adrian Koh Soo , Bauer Siegfried , Suo Zhigang
Published: February 2012

The dynamic performance of dielectric elastomer transducers and their capability of electromechanical energy conversion are affected by dissipative processes, such as viscoelasticity, dielectric relaxation, and current leakage. This paper describes a method to construct a model of dissipative dielectric elastomers on the basis of nonequilibrium thermodynamics. We characterize the state of the dielectric elastomer with kinematic variables through which external loads do work, and internal variables that measure the progress of the dissipative processes. The method is illustrated with examples motivated by existing experiments of polyacrylate very-high-bond dielectric elastomers. This model predicts the dynamic response of the dielectric elastomer and the leakage current behavior. We show that current leakage can be significant under large deformation and for long durations. Furthermore, current leakage can result in significant hysteresis for dielectric elastomers under cyclic voltage.
Recombination lifetime of free polarons in polymer/fullerene bulk heterojunction solar cells
Authors: Li Kejia , Li Lijun , Campbell Joe C.
Published: February 2012

The recombination lifetime of free polarons was measured using three different methods: electrical field–dependent photoresponse, transient photoconductivity, and forward-to-zero bias transient-current response. The average free polaron recombination lifetime is estimated to be a few microseconds for poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) solar cells. The competition between sweep-out by the internal field and the loss of photogenerated carriers by recombination is analyzed. The short-circuit free polaron collection efficiency for P3HT:PCBM bulk heterojunction material was determined to be in the range of 80% to 90%.
Iterative diagonalization in the state-averaged multi-configurational time-dependent Hartree approach: Excited state tunneling splittings in malonaldehyde
Authors: Hammer Thorsten , Manthe Uwe
Published: February 2012

An iterative block Lanczos-type diagonalization scheme utilizing the state-averaged multi-configurational time-dependent Hartree (MCTDH) approach is introduced. Combining propagation in real and imaginary time and using a set of initial seed wavefunctions corresponding to excitations via the different components of the dipole moment vector, the scheme can favorably be used to selectively compute vibrational states which show high intensities in vibrational absorption spectra. Tunneling splitted vibrational states in double well systems can be described particularly efficient employing an increased set of seed wavefunctions which includes symmetric and anti-symmetric wavefunctions simultaneously. The new approach is used to study the tunneling splittings of the vibrationally excited states of malonaldehyde. Full-dimensional multi-layer MCTDH calculations are performed and results for the tunneling splittings of several excited vibrational states can be obtained. The calculated tunneling splittings agree reasonably well with available experimental data. Order of magnitude differences between tunneling splittings of different vibrationally excited states are found and interpreted.
Extrinsic and intrinsic nonlinear current-voltage characteristics in charge ordered oxides
Authors: Wang F. , Zou T. , Liu Y. , Yan L.-Q. , Sun Y.
Published: February 2012

We present a systematic study to clarify the origin of nonlinear I-V characteristics widely observed in charge ordered oxides. The experiments performed on the charge ordered YbFe2O4 single crystals demonstrate that the I-V behavior strongly depends on the measurement parameters, such as the width and strength of applied voltage/current pulse, the time interval between two subsequent pulses, and the time delay before reading a data. Correspondingly, three regimes are identified: (i) steep nonlinear I-V behavior induced by self-heating when the pulse width is big and/or the time interval is short; (ii) smooth nonlinear I-V characteristic in the low field range when the electric pulse width is small and the time interval is long enough, owing to sliding of charge density wave; (iii) abrupt collapse of charge order/charge density wave at high electric fields. A proper measurement scheme must be employed in order to distinguish the intrinsic effects associated with electric field modulation of charge order from the extrinsic self-heating effect.
Tailoring of electro-optical properties of ferroelectric liquid crystals by doping Pd nanoparticles
Authors: Kumar A. , Singh G. , Joshi T. , Rao G. K. , Singh A. K. , Biradar A. M.
Published: February 2012

We demonstrate here the tailoring of electro-optical properties of ferroelectric liquid crystals (FLCs) by doping different concentrations of Selenium Docosane (SD) capped palladium nanoparticles (PdNPs). The operating voltage is lowered by ∼50% in doped FLC as compared to undoped one. The remarkable increment in optical tilt angle of doped FLC is monitored, which is concentration-dependent. The steric interactions among alkyl chains of SD capped PdNPs and FLC molecules could be the probable reason for enhanced optical tilt angle. More importantly, present investigations on doped FLCs are indicative of their indispensible impact on next generation FLCs-based electro-optical devices.
A quantum model for light emission performance of carbon nanotube field effect transistor
Authors: Aziziyan M. R. , Ahmadi V. , Moghadam N.
Published: February 2012

We propose a full quantum model based on non-equilibrium Green function method to simulate short channel, ohmic-carbon nanotube field effect transistor as light emitter. We consider carrier annihilation using self-energy concept in non-ballistic regime, regarding current conservation. Using this model, we calculate radiative recombination rate and electroluminescence spectrum of device. Since, higher bias voltage causes higher carrier injection, we expect to observe more recombination rate by increasing drain or gate voltage. Variation of gate voltage can shift the electroluminescence peak due to slight band gap change. The device current confirms that the electrical and optical properties of device are correlated.
Anisotropic magnetoresistance and weak spin-orbital coupling in doped ZnO thin films
Authors: Tian Yufeng , Lin Weinan , Wu Tom
Published: February 2012

Both out-of-plane and in-plane anisotropic magnetoresistance (AMR) of Cu-doped ZnO thin films with different crystalline orientations are studied. Comparative data of angular dependent AMR suggest that the out-of-plane AMR comes from the geometric effect, while the in-plane AMR can be attributed to the field-dependent path-length effect. Moreover, the small magnitude of AMR and the negligible magnetocrystalline anisotropy suggest that the spin-orbit coupling in Cu-doped ZnO is relatively weak.
Dielectric relaxation in the DyMn1−xFexO3 system
Authors: Hong Fang , Cheng Zhenxiang , Zhang Shujun , Wang Xiaolin
Published: February 2012

The dielectric constant and loss of perovskite DyMn1−xFexO3 samples show strong dispersion in various frequencies, which is indicative of relaxation. The activation energies were obtained through Arrhenius law fitting and range from 0.213 eV to 0.385 eV. The Fe content dependence of the characteristic frequency f0 and the activation energy Eα shows two transitions that are well consistent with the change in orbital ordering. Meanwhile, different magnetic orderings could affect the relaxation and induce the change in Eα.
The holonomy group at infinity of the Painlevé VI equation
Authors: Ben Hamed Bassem , Gavrilov Lubomir , Klughertz Martine
Published: February 2012

We prove that the holonomy group at infinity of the Painlevé VI equation is virtually commutative.
Enhancement of critical heat flux in pool boiling using atomic layer deposition of alumina
Authors: Feng Bo , Weaver Keith , Peterson G. P.
Published: February 2012

Alumina nano coatings on platinum (Pt) micro wires were fabricated using atomic layer deposition. During the pool boiling heat transfer, the critical heat flux (CHF) of Pt/Alumina in de-ionized water was found to have a two-fold enhancement compared to that of the same Pt bare wire. The CHF was shown to increase with coating thickness of alumina up to a thickness of 20 nm. Coating thicknesses in excess of 20 nm had no additional influence on the CHF. The enhancement of the CHF is the result of the superwetting property of the amorphous alumina coatings, which significantly increases the liquid film thickness, enhancing the rewetting of the “hot spot.”
The effect of an externally attached neutrally buoyant transmitter on mortal injury during simulated hydroturbine passage
Authors: Brown Richard S. , Pflugrath Brett D. , Carlson Thomas J. , Daniel Deng Z.
Published: February 2012

On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing through hydroturbines experience a rapid decrease in pressure as they pass by the turbine blade. The severity of this decompression can be highly variable but can result in injuries such as swim bladder rupture, exophthalmia, and emboli and hemorrhaging in the fins and tissues. Recent research indicates that the presence of a telemetry tag (acoustic, radio, inductive) implanted inside the coelom of a juvenile salmon increases the likelihood that the fish will be injured or die during turbine passage. Thus, previous turbine passage survival research conducted using telemetry tags implanted into the coelom of fish may have been inaccurate. Therefore, a new technique is needed to provide unbiased estimates of survival through turbines. This study evaluated the effectiveness of a neutrally buoyant externally attached acoustic transmitter on decompression-stressed juvenile Chinook salmon. Both nontagged fish and fish tagged with a neutrally buoyant external transmitter were exposed to a range of rapid decompressions simulating turbine passage. Juvenile Chinook salmon tagged with a neutrally buoyant externally attached acoustic transmitter did not experience a higher degree of barotrauma-induced injuries than their nontagged counterparts. We suggest that future research include field-based comparisons of survival and behavior among fish tagged with a neutrally buoyant external transmitter and those internally implanted with transmitters.
Impacts of aerosols on available solar energy at Mbour, Senegal
Authors: Drame Mamadou , Ould Bilal Boudy , Camara Moctar , Sambou Vincent , Gaye Amadou
Published: February 2012

This study aims to evaluate the available solar potential (direct normal on the overall horizontal plane) and to estimate the observed impact of aerosols on solar radiation at Mbour, Senegal (16.958 °W; 14. 394 °N) using observations from solar instruments and AERONET during 2006. The results show the presence of a good available solar potential. At intra-seasonal timescale, the total and direct normal energy are stronger in May with a mean value of 7 kWh/m2/day and February with an average value of 5.50 kWh/m2/day. The lower available total and direct normal solar energies are, respectively, found in August (5.31 kWh/m2/day) and July (2.90 kWh/m2/day). The observations of AERONET show that aerosol optical depth values are higher in June (0.7) and lower in February (0.16). These results are consistent with the observed trends of total and direct normal energy during those months. Case studies of the influence of aerosols on available solar energy show a mean decrease of 10% and 28%, respectively, for the total and direct normal energies. This decrease does not vary much from the rainy season to the dry season, but there is a strong diurnal fluctuation in the rainy season probably due to the presence of cloud droplets.
Observation of conductivity type conversion in undoped ZnO films grown by pulsed laser deposition on silicon (100) substrates
Authors: Esmaili-Sardari Saeed , Berkovich Andrew , Iliadis Agis A.
Published: February 2012

We report a conductivity type conversion of ZnO films from n to p-type for films grown on silicon (100) substrates by pulsed laser deposition under low constant oxygen overpressure. Conductivity conversion is attributed to a competition between donor and acceptor-like native defects correlating with growth conditions and surface differences between phosphorus doped n-type and boron doped p-Si substrates. Effects of growth temperature on intrinsic defects including oxygen vacancies, zinc vacancies and hydrogen impurity contamination are discussed. Our results show that the interplay of defect-related centers is critical to the electrical behavior and conductivity type of ZnO grown on Si substrates.
Spacelike hypersurfaces with negative total energy in de Sitter spacetime
Authors: Liang Zhuobin , Zhang Xiao
Published: February 2012

De Sitter spacetime can be separated into two parts along two kinds of hypersurfaces and the half-de Sitter spacetimes are covered by the planar and hyperbolic coordinates, respectively. Two positive energy theorems were proved previously for certain \documentclass[12pt]{minimal}\begin{document}$\mathcal P$\end{document}P-asymptotically de Sitter and \documentclass[12pt]{minimal}\begin{document}$\mathcal H$\end{document}H-asymptotically de Sitter initial data sets by the second author and collaborators. These initial data sets are asymptotic to time slices of the two kinds of half-de Sitter spacetimes, respectively, and their mean curvatures are bounded from above by certain constants. While the mean curvatures violate these conditions, the spacelike hypersurfaces with negative total energy in the two kinds of half-de Sitter spacetimes are constructed in this short paper.
Superconducting low-inductance undulatory galvanometer microwave amplifier
Authors: Hover D. , Chen Y.-F. , Ribeill G. J. , Zhu S. , Sendelbach S. , McDermott R.
Published: February 2012

We describe a microwave amplifier based on the superconducting low-inductance undulatory galvanometer (SLUG). The SLUG is embedded in a microstrip resonator, and the signal current is injected directly into the device loop. Measurements at 30 mK show gains of 25 dB at 3 GHz and 15 dB at 9 GHz. Amplifier performance is well described by a simple numerical model based on the Josephson junction phase dynamics. We expect optimized devices based on high critical current junctions to achieve gain greater than 15 dB, bandwidth of several hundred MHz, and added noise of order one quantum in the frequency range of 5-10 GHz.
Quadrupole-bound anions: Efficacy of positive versus negative quadrupole moments
Authors: Garrett W. R.
Published: February 2012

A pseudopotential method is utilized to study the critical stability of model anions formed by long-range quadrupolar molecular potentials. Results indicate that critical quadrupole moments of simple point-charge triads do not serve well as predictors of real quadrupole-bound anions of systems with negative moments.
Thermal conductivity and photoluminescence of light-emitting silicon nitride films
Authors: Marconnet Amy , Panzer Matt , Yerci Selçuk , Minissale Salvatore , Wang X. , Zhang X. , Dal Negro Luca , Goodson K. E.
Published: February 2012

Silicon-rich and rare-earth-doped nitride materials are promising candidates for silicon-compatible photonic sources. This work investigates the thermal conductivity and photoluminescence (PL) of light emitting samples fabricated with a range of excess silicon concentrations and annealing temperatures using time-domain picosecond thermoreflectance and time-resolved photoluminescence. A direct correlation between the thermal conductivity and photoluminescence dynamics is demonstrated, as well as a significant reduction of thermal conductivity upon incorporation of erbium ions. These findings highlight the role of annealing and stoichiometry control in the optimization of light emitting microstructures suitable for the demonstration of efficient Si-compatible light sources based on the silicon nitride platform.
Restrictions on definiteness in
second language acquisition
Authors: White Lydia , Belikova Alyona , Hagstrom Paul , Kupisch Tanja , Özçelik Öner
Published: February 2012

In this paper we investigate whether learners of L2 English show knowledge of the Definiteness Effect (Milsark, 1977), which restricts definite expressions from appearing in the existential there-insertion construction. There are crosslinguistic differences in how restrictions on definiteness play out. In English, definite expressions may not occur in either affirmative or negative existentials (e.g. There is a/*the mouse in my soup; There isn’t a/*the mouse in my soup). In Turkish and Russian, affirmative existentials observe a restriction similar to English, whereas negative existentials do not. We report on a series of experiments conducted with learners of English whose L1s are Turkish and Russian, of intermediate and advanced proficiency. Native speakers also took the test in English, Turkish, and Russian. The task involved acceptability judgments. Subjects were presented with short contexts, each followed by a sentence to be judged as natural/unnatural. Test items included affirmative and negative existentials, as well as items testing apparent exceptions to definiteness restrictions. Results show that both intermediate and advanced L2ers respond like English native speakers, crucially rejecting definites in negative existentials. A comparison with the groups taking the test in Russian and Turkish confirms that judgments in the L2 are quite different from the L1, suggesting that transfer cannot provide the explanation for learner success.
Assessing multilingual lexical incorporation hypotheses through a primed picture-naming task*
Authors: Gonzàlez Alonso Jorge
Published: February 2012

The incorporation of new representations into the mental lexicon has raised numerous questions about the organisational principles that govern the process. A number of studies have argued that similarity between the new L3 items and existing representations in the L1 and L2 is the main incorporating force (Hall & Ecke, 2003;Herwig, 2001). Experimental evidence obtained through a primed picture-naming task with L1 Polish-L2 English learners of L3 Russian supports Hall and Ecke’s Parasitic Model of L3 vocabulary acquisition, displaying a significant main effect for both priming and proficiency. These results complement current models of vocabulary acquisition and lexical access in multilingual speakers.
The development of structural characteristics of Brahmi script in derivative writing systems
Authors: Fedorova Liudmila L.
Published: February 2012

Indian writing systems reveal a great variety of graphic forms, proceeding from the unique source which is Brahmi script. These graphic forms render structural oppositions developed in phonographic writing systems which stem from Brahmi. This paper aims to highlight the changes scripts underwent to satisfy demands of language structure. The comparison raises the issue of the complexity of writing systems. Keywords: writing system; grapheme; typology; Brahmi; abugida; alphasyllabary; akshara; diacritic; graphon; vowel differentiation
The relation between spelling and pronunciation
Authors: Brissaud Catherine , Fisher Carole , Negro Isabelle
Published: February 2012

This paper presents a study of the impact of pronunciation on the spelling of /E/ verb endings in French. The pronunciation of /E/ endings varies according to which areas the French language is used. In some areas, the /E/ verb endings are pronounced either /e/ or /ε/, according to the verb tense, whereas in others this opposition has progressively disappeared in time. Since the opposition /e/ ~ /ε/ leads to spelling distinctions, it is hypothesized that contrasting phonological forms may help the writer to avoid spelling errors. To test this hypothesis, 136 fifth-graders from specific different regions were required to transcribe different verb endings in /E/. The transcriptions from areas where the phonological opposition is usually observed were compared with those from areas where the opposition is neutralized. The data reveals that, although there is a tendency for students in areas where phonological opposition is still present to use phonologically compatible endings, the absence of neutralization does not necessarily guarantee the correct selection of verb endings. Keywords: pronunciation; spelling; phonological neutralization; French; verb endings
How adolescents with dyslexia dysorthographia use texting
Authors: Simoës-Perlant Aurélie , Thibault Marie-Pierre , Lanchantin Tonia , Combes Céline , Volckaert-Legrier Olga , Largy Pierre
Published: February 2012

Adolescents with dyslexia dysorthographia have some phonological skill deficiency and/or visual-attention deficit. Knowing that these same skills are required to use SMS codes, the main objective of this study is to understand how these subjects use texting language. To understand this, we compared the SMSs of adolescents with dyslexia dysorthographia with the SMSs of typical writers in a dictation task. We analyzed the number and the type of SMS codes used by the subjects. This study shows less use of SMS codes in quantitative terms in adolescents with dyslexia dysorthographia (DD), but globally equivalent use in terms of quality, in comparison with normal writers. Keywords: adolescent; SMS language; dyslexia; dysorthographia; writing; development
The blueberry industry.
Authors: Hancock J. , Retamales J.
Published: February 2012

This chapter provides information on the history of blueberry (Vaccinium spp.) cultivation, and the most important locations, species and cultural practices employed in the different production regions (within and outside North America). The climatic conditions in the major production regions are also covered.
Blueberry taxonomy and breeding.
Authors: Hancock J. , Retamales J.
Published: February 2012

This chapter focuses on the taxonomy of blueberry (Vaccinium spp.) species, the history of improvement and current breeding efforts, tools and goals (improvement of fruit and flowering characteristics, plant architecture, physiological adaptations, and pest resistance), and describes the most important blueberry cultivars grown worldwide.
Blueberry field management and harvesting.
Authors: Hancock J. , Retamales J.
Published: February 2012

This chapter covers various management practices that are important in blueberry (Vaccinium spp.) cultivation, including mulching (with plastic film or organic mulch), irrigation, pruning, pollination and mechanical harvesting. Plant water relations, and blueberry response to water stress and water excess (flooding) are briefly discussed.
Electronic-Eye Faucets:LegionellaSpecies Contamination in Healthcare Settings
Authors: Sydnor Emily R. M. , Bova Gregory , Gimburg Anatoly , Cosgrove Sara E. , Perl Trish M. , Maragakis Lisa L.
Published: February 2012

Objective.

To compare heterotrophic plate counts (HPCs) andLegionellaspecies growth from electronic and manual faucet water samples.

Design.

Proportions of water samples with growth and colony-forming units were compared using Fisher's exact test and the Wilcoxon rank-sum test, respectively.

Setting.

Two psychiatric units and 1 medical unit in a 1,000-bed university hospital.

Methods.

Water samples were collected from 20 newly installed electronic faucets and 20 existing manual faucets in 3 hospital units. Manual faucets were located in rooms adjacent to the electronic faucets and received water from the same source. Water samples were collected between December 15, 2008, and January 29, 2009. Four electronic faucets were dismantled, and faucet components were cultured.Legionellaspecies and HPC cultures were performed using standard methods.

Results.

Nearly all electronic faucets (19/20 [95%]) grewLegionellaspecies from at least 1 water sample, compared with less than half (9/20 [45%]) of manual faucets (P= .001). Fifty-four (50%) of 108 electronic faucet water cultures grewLegionellaspecies, compared with 11 (15%) of 75 manual faucet water cultures (P< .001). After chlorine dioxide remediation, 4 (14%) of 28 electronic faucet and 1 (3%) of 30 manual faucet water cultures grewLegionellaspecies (P= .19), and 8 (29%) electronic faucet and 2 (7%) manual faucet cultures had significant HPC growth (P= .04). All 12 (100%) of die internal faucet components from 2 electronic faucets grewLegionellaspecies.

Conclusions.

Electronic faucets were more commonly contaminated withLegionellaspecies and other bacteria and were less likely to be disinfected after chlorine dioxide remediation. Electronic faucet components may provide points of concentrated bacterial growth.

Infect Control Hosp Epidemiol2012;33(3):235-240
Effect of finite electrode area ratio on high-frequency Langmuir probe measurements
Authors: Shimoyama M , Oyama K-I , Abe T , Yau A W
Published: February 2012

Langmuir probe (LP) measurement generally requires a reference electrode with large surface area compared with that of a probe. Whereas a reference electrode with large surface area is available in laboratory experiments, surface area of the reference electrode is limited when the probe is installed on a small spacecraft such as a sounding rocket. Insufficient electrode area ratio of the reference electrode to the probe leads to distortion of the current–voltage (I–V) characteristics and therefore the derived electron temperature and density might be erroneous. In order to investigate the effect of finite electrode area ratio on LP measurements, we have carried out a laboratory simulation by setting up a model sounding rocket with whole apparatus for LP measurement in a vacuum chamber. By changing the frequency of sweep voltage applied to the probe from 0.1 Hz to 3 kHz, we have derived an equivalent resistance and capacitance of the reference electrode sheath, which was thought to be the principal cause of distortion in I–V characteristics. The result shows that when the electrode area ratio is 124, the electron temperature is unaffected by the impedance of the reference electrode while the electron density is underestimated by 50%. In addition, the high sweep frequency method introduced here turned out to be an effective approach to make measurements with LP possible even when a sufficient surface area ratio cannot be achieved.
Tunable energy filtering of ballistic electrons in graphene
Authors: Zubarev A , Dragoman D
Published: February 2012

We show, by employing the scattering matrix approach, that a magnetic field applied over a graphene strip can select obliquely incident ballistic electrons with definite energies, corresponding to specific Landau levels. The energy range in which filtering is possible depends on the position of the obliquely placed electrodes, which emit and collect the filtered electrons. Energy tuning is achieved by modifying the magnetic field strength.