bluuebunny/crossref_metadata_2025 huggingface dataset:
Anharmonic vibrational analysis of water with traditional and explicitly correlated coupled cluster methods
Authors: Kahn Kalju , Kirtman Bernard , Noga Jozef , Ten-no Seiichiro
Published: August 2010

It is well known that the convergence of harmonic frequencies with respect to the basis set size in traditional correlated calculations is slow. We now report that the convergence of cubic and quartic force constants in traditional CCSD(T) calculations on H2O with Dunning’s cc-pVXZ family of basis sets is also frustratingly slow. As an alternative, we explore the performance of R12-based explicitly correlated methods at the CCSD(T) level. Excellent convergence of harmonic frequencies and cubic force constants is provided by these explicitly correlated methods with R12-suited basis irrespective of the used standard approximation and/or the correlation factor. The Slater type geminal, however, outperforms the linear r12 for quartic force constants and vibrational anharmonicity constants. The converged force constants from explicitly correlated CCSD(T) calculations succeed in reproducing the fundamental frequencies of water molecule with spectroscopic accuracy after corrections for post-CCSD(T) effects are made.
Tensile properties of helical auxetic structures: A numerical study
Authors: Wright J. R. , Sloan M. R. , Evans K. E.
Published: August 2010

This paper discusses a helical auxetic structure which has a diverse range of practical applications. The mechanical properties of the system can be determined by particular combinations of geometry and component material properties; finite element analysis is used to investigate the static behavior of these structures under tension. Modeling criteria are determined and design issues are discussed. A description of the different strain-dependent mechanical phases is provided. It is shown that the stiffnesses of the component fibers and the initial helical wrap angle are critical design parameters, and that strain-dependent changes in cross-section must be taken into consideration: we observe that the structures exhibit nonlinear behavior due to nonzero component Poisson’s ratios. Negative Poisson’s ratios for the helical structures as low as −5 are shown. While we focus here on the structure as a yarn our findings are, in principle, scaleable.
Influence of quenching rate on the magnetic and martensitic properties of Ni–Fe–Ga melt-spun ribbons
Authors: Okumura H. , Uemura K.
Published: August 2010

We have fabricated Ni–Fe–Ga β single phase alloy ribbons with Ga content less than 25 at. %. Higher spinning rate of melt-spinning technique can produce β single phase alloys without precipitation of γ particles, whereas lower spinning rate results in the β+γ two phase structure. This higher quenching rate is found to be able to fully suppress the formation of γ phase during fabrication. The martensitic and magnetic transition temperatures of β phase ribbons are both above room temperature, and the ribbon show saturation magnetization as high as 56.5 emu/g at room temperature. These features are attractive for practical applications. The effects of quenching rate on microstructure, martensitic transformation, and magnetic properties are discussed.
Second-order Møller–Plesset perturbation theory applied to extended systems. II. Structural and energetic properties
Authors: Grüneis Andreas , Marsman Martijn , Kresse Georg
Published: August 2010

Results for the lattice constants, atomization energies, and band gaps of typical semiconductors and insulators are presented for Hartree–Fock and second-order Møller–Plesset perturbation theory (MP2). We find that MP2 tends to undercorrelate weakly polarizable systems and overcorrelates strongly polarizable systems. As a result, lattice constants are overestimated for large gap systems and underestimated for small gap systems. The volume dependence of the MP2 correlation energy and the dependence of the MP2 band gaps on the static dielectric screening properties are discussed in detail. Moreover, the relationship between MP2 and the G0W0 quasiparticle energies is elucidated and discussed. Finally, we demonstrate explicitly that the correlation energy diverges with decreasing k-point spacing for metals.
Enhancement of photovoltaic cell response due to high-refractive-index encapsulants
Authors: Ma Ming , Mont Frank W. , Poxson David J. , Cho Jaehee , Schubert E. Fred , Welser Roger E. , Sood Ashok K.
Published: August 2010

This study compares the electrical output of photovoltaic (PV) cells encapsulated with silicones having different refractive indices to unencapsulated PV cells. It is demonstrated that the optical concentration ratio of dome-shaped concentrator PV systems can be increased by using a higher refractive-index encapsulant. The short-circuit photocurrent of the PV cell having high-refractive-index encapsulation (n=1.57) is 71% higher than that of the PV cell having a low-refractive-index encapsulation (n=1.41), and 316% higher than that of the unencapsulated PV cell. These experimental concentration-ratio enhancements are consistent with the theoretical estimates of concentration ratio dependence on the refractive index of the PV concentrator.
Pressure and arc voltage coupling in dc plasma torches: Identification and extraction of oscillation modes
Authors: Rat V. , Coudert J. F.
Published: August 2010

This work is devoted to the instabilities occurring in a plasma torch, such as those found in plasma spraying. These instabilities are responsible for a lack of reproducibility of coatings properties, especially in the case of suspension plasma spraying that is an innovative way to obtain thin coatings of submicron-sized particles. Strong Helmholtz oscillations are highlighted in the plasma flow and it is demonstrated that they overlap with different acoustic modes in addition with the more commonly admitted “restrike” mode, the later being due to rearcing events in the arc region. The instabilities occur in the arc voltage but it is experimentally shown in this paper that the pressure within the torch body presents the same kind of instabilities. Besides, a numerical filtering technique has been adapted to isolate the different instability components. The operating parameters of the plasma torch were varied in order to highlight their influence on the amplitude of the different modes, both for the arc voltage and the pressure.
Time-resolved investigation of dual high power impulse magnetron sputtering with closed magnetic field during deposition of Ti–Cu thin films
Authors: Stranak Vitezslav , Cada Martin , Hubicka Zdenek , Tichy Milan , Hippler Rainer
Published: August 2010

Time-resolved comparative study of dual magnetron sputtering (dual-MS) and dual high power impulse magnetron sputtering (dual-HiPIMS) systems arranged with closed magnetic field is presented. The dual-MS system was operated with a repetition frequency 4.65 kHz (duty cycle ≈50%). The frequency during dual-HiPIMS is lower as well as its duty cycle (f=100 Hz, duty 1%). Different metallic targets (Ti, Cu) and different cathode voltages were applied to get required stoichiometry of Ti–Cu thin films. The plasma parameters of the interspace between magnetrons in the substrate position were investigated by time-resolved optical emission spectroscopy, Langmuir probe technique, and measurement of ion fluxes to the substrate. It is shown that plasma density as well as ion flux is higher about two orders of magnitude in dual-HiPIMS system. This fact is partially caused by low diffusion of ionized sputtered particles (Ti+,Cu+) which creates a preionized medium.
Stability of convective patterns in reaction fronts: A comparison of three models
Authors: Vasquez Desiderio A. , Coroian Dan I.
Published: August 2010

Autocatalytic reaction fronts generate density gradients that may lead to convection. Fronts propagating in vertical tubes can be flat, axisymmetric, or nonaxisymmetric, depending on the diameter of the tube. In this paper, we study the transitions to convection as well as the stability of different types of fronts. We analyze the stability of the convective reaction fronts using three different models for front propagation. We use a model based on a reaction-diffusion-advection equation coupled to the Navier–Stokes equations to account for fluid flow. A second model replaces the reaction-diffusion equation with a thin front approximation where the front speed depends on the front curvature. We also introduce a new low-dimensional model based on a finite mode truncation. This model allows a complete analysis of all stable and unstable fronts.
Polarization behavior of water in extreme aqueous environments: A molecular dynamics study based on the Gaussian charge polarizable water model
Authors: Chialvo Ariel A. , Horita Juske
Published: August 2010

We study the polarization behavior of water under geologically relevant extreme aqueous environments along four equidistant supercritical isotherms, 773≤T(K)≤1373, and over a wide pressure range, 0<P(GPa)≤30, by isobaric-isothermal molecular dynamics simulations of the Gaussian charge polarizable water model, to unravel and discuss the underlying link between two precisely defined orientational order parameters and the magnitude of the average induced dipole moment of water. The predicted behavior indicates an isothermal linear dependence (a) between the magnitude of the average induced dipole moment μind and the average system density ρ, (b) between the magnitude of the average induced dipole μind and that of the total dipole μtot, resulting from (c), a compensating (inverse) dependence between the permanent-to-induced dipolar angle ϑ and the magnitude of the average induced dipole moment μind. Moreover, we interpret this behavior in terms of the evolution of the state dependent tetrahedral order parameter qT and the corresponding bond-order parameter Q6, supplemented by the microstructural analysis based on the three site-site radial distribution functions of water and the distance-ranked nearest-neighbor distributions. Finally, we show that while water exhibits a dramatic microstructural transformation from an open four-coordinated hydrogen-bonded network at normal conditions to a quasi-close-packed coordination, it still preserves a significant degree of hydrogen bonding.
The accuracy of liquid-liquid phase transition temperatures determined from semiautomated light scattering measurements
Authors: Dean Kevin M. , Babayco Christopher B. , Sluss Daniel R. B. , Williamson J. Charles
Published: August 2010

The synthetic-method determination of liquid-liquid coexistence curves using semiautomated light scattering instrumentation and stirred samples is based on identifying the coexistence curve transition temperatures (Tcx) from sudden changes in turbidity associated with droplet formation. Here we use a thorough set of such measurements to evaluate the accuracy of several different analysis methods reported in the literature for assigning Tcx. More than 20 samples each of weakly opalescent isobutyric acid+water and strongly opalescent aniline+hexane were tested with our instrumentation. Transmitted light and scattering intensities at 2°, 24°, and 90° were collected simultaneously as a function of temperature for each stirred sample, and the data were compared with visual observations and light scattering theory. We find that assigning Tcx to the onset of decreased transmitted light or increased 2° scattering has a potential accuracy of 0.01 K or better for many samples. However, the turbidity due to critical opalescence obscures the identification of Tcx from the light scattering data of near-critical stirred samples, and no simple rule of interpretation can be applied regardless of collection geometry. At best, when 90° scattering is collected along with transmitted or 2° data, the accuracy of Tcx is limited to 0.05 K for near-critical samples. Visual determination of Tcx remains the more accurate approach in this case.
A minimal model of nanoparticle crystallization in polar solvents via steric effects
Authors: Kung William , Gonzalez-Mozuelos Pedro , Olvera de la Cruz Monica
Published: August 2010

Motivated by recent experimental findings, we present here a minimal analytical model illustrating that the steric interactions among the ionic components can provide a simple, generic mechanism for like-charge crystallization in prototypical nanoparticle systems with counterions in polar solvents. In particular, the underlying steric interactions among these ionic components arise from the structural organization of the polar solvent molecules surrounding these ions as molecular dipole moments that may cooperatively enhance or counteract existing entropic depletion and electrostatic forces. Phenomenologically capturing these steric effects, we assume only the existence of a short-range pairwise Gaussian interaction, which has already been employed usefully for nanoparticles with hydrophillic surfaces or grafted-polymer coatings, among these ionic components (nanoparticles and counterions). The corresponding Gaussian interaction parameters characterize tunable interaction strengths. Making use of an analytically obtained effective pairwise potential between two nanoparticles, upon the contraction of counterions, we derive phase diagrams for nanoparticle systems of varying charge- and size-ratios as a function of particle densities, and observe crystallization for a range of parameters. We further demonstrate that our minimal model is compatible with the phenomenon of charge asymmetry.
Interfacial layering and capillary roughness in immiscible liquids
Authors: Geysermans P. , Pontikis V.
Published: August 2010

The capillary roughness and the atomic density profiles of extended interfaces between immiscible liquids are determined as a function of the interface area by using molecular dynamics and Lennard-Jones (12-6) potentials. We found that with increasing area, the interface roughness diverges logarithmically, thus fitting the theoretical mean-field prediction. In systems small enough for the interfacial roughness not to blur the structural details, atomic density profiles across the fluid interface are layered with correlation length in the range of molecular correlations in liquids. On increasing the system size, the amplitude of the thermally excited position fluctuations of the interface increases, thus causing layering to rapidly vanish, if density profiles are computed without special care. In this work, we present and validate a simple method, operating in the direct space, for extracting from molecular dynamics trajectories the “intrinsic” structure of a fluid interface that is the local density profile of the interface cleaned from capillary wave effects. Estimated values of interfacial properties such as the tension, the intrinsic width, and the lower wavelength limit of position fluctuations are in agreement with results collected from the literature.
Axial magnetic field generation by intense circularly polarized laser pulses in underdense plasmas
Authors: Naseri N. , Bychenkov V. Yu. , Rozmus W.
Published: August 2010

Axial magnetic field generation by intense circularly polarized laser beams in underdense plasmas has been studied with three-dimensional particle-in-cell simulations and by means of theoretical analysis. Comparisons between analytical models and simulation results have identified an inverse Faraday effect as the main mechanism of the magnetic field generation in inhomogeneous plasmas. The source of azimuthal nonlinear currents and of the axial magnetic field depends on the transverse inhomogeneities of the electron density and laser intensity. The fields reach a maximum strength of several tens of megagauss for laser pulses undergoing relativistic self-focusing and channeling in moderately relativistic regime. Ultrarelativistic laser conditions inhibit magnetic field generation by directly reducing a source term and by generating fully evacuated plasma channels.
Oxygen incorporation in Ti2AlC: Tuning of anisotropic conductivity
Authors: Rosen J. , Dahlqvist M. , Simak S. I. , McKenzie D. R. , Bilek M. M. M.
Published: August 2010

The substitution of oxygen for carbon in Ti2AlC M(n+1)AXn (MAX) phase, forming Ti2AlC1−xOx, has recently been reported. In this paper we simulate the effect of oxygen incorporation on mechanical and electronic properties using ab initio calculations. While the mechanical properties are not sensitive to the change in composition, the electronic properties can be tuned by varying the oxygen concentration. As the concentration increases, the conduction changes from in plane, typical of MAX phases, to conduction also in the c-direction. The conduction along c passes from insulating to n-type and then finally to p-type. These findings reveal an anisotropic semiconducting material.
CO
2
capture properties of alkaline earth metal oxides and hydroxides: A combined density functional theory and lattice phonon dynamics study
Authors: Duan Yuhua , Sorescu Dan C.
Published: August 2010

By combining density functional theory and lattice phonon dynamics, the thermodynamic properties of CO2 absorption/desorption reactions with alkaline earth metal oxides MO and hydroxides M(OH)2 (where M=Be,Mg,Ca,Sr,Ba) are analyzed. The heats of reaction and the chemical potential changes of these solids upon CO2 capture reactions have been calculated and used to evaluate the energy costs. Relative to CaO, a widely used system in practical applications, MgO and Mg(OH)2 systems were found to be better candidates for CO2 sorbent applications due to their lower operating temperatures (600–700 K). In the presence of H2O, MgCO3 can be regenerated into Mg(OH)2 at low temperatures or into MgO at high temperatures. This transition temperature depends not only on the CO2 pressure but also on the H2O pressure. Based on our calculated results and by comparing with available experimental data, we propose a general computational search methodology which can be used as a general scheme for screening a large number of solids for use as CO2 sorbents.
Imaging the dynamics of chlorine atom reactions with alkenes
Authors: Estillore Armando D. , Visger Laura M. , Suits Arthur G.
Published: August 2010

We report a study of chlorine atom reactions with a series of target monounsaturated alkene molecules: 1-pentene, 1-hexene, 2-hexene, and cyclohexene. These reactions were studied using crossed-beam dc slice ion imaging at collision energies of 4 and 7 kcal/mol. Images of the reactively scattered alkenyl radical products were obtained via single photon ionization at 157 nm. The angular distributions at low collision energy are largely isotropic, suggesting the formation of a complex that has a lifetime comparable to or longer than its rotational period, followed by HCl elimination. At high collision energy, the distributions show a sharp forward peak superimposed on the isotropic component accounting for ∼13% of the product flux. The translational energy distributions peak near zero for the backscattered product, in sharp contrast to the results for alkanes. In the forward direction, the translational energy distributions change dramatically with collision energy. At the high collision energy, a sharp forward peak at ∼80% of the collision energy appears, quite reminiscent of results of our recent study of Cl+pentane reactions. The scattering distributions for all target molecules are similar, suggesting similarity of the reaction dynamics among these molecules. Ab initio calculations of the energetics and ionization energies for the various product channels were performed at the CBS-QB3 level to aid in interpreting the results.
Experimental determination of wave function spread in Si inversion layers
Authors: Majumdar Amlan
Published: August 2010

We have experimentally determined the extent of wave function spread TQM in Si inversion layers on (100)-oriented surface in metal-oxide-semiconductor field-effect transistors (MOSFETs) using the back gate bias sensitivity of front gate threshold voltage of planar fully depleted silicon-on-insulator (SOI) MOSFETs. We show that the sum of TQM for large positive and negative F is an electrically determined value of the SOI thickness TSI. We find that the electric field dependence of TQM for electrons and holes is given by TQM∼F−0.4 and F−0.6, respectively, at high electric fields with TQM being larger for holes at a given F. Larger TQM for holes can be explained by the fact that holes have a smaller effective mass along the confinement direction than electrons in (100) Si. The field dependences of TQM are, however, not consistent with the results of variational calculations that assume single-subband occupancy and predict TQM∼F−1/3. The discrepancy likely indicates that the effects of multiple-subband occupation are significant at room temperature, especially for holes.
Surface carrier recombination of a silicon tip under high electric field
Authors: Mazumder B. , Vella A. , Vurpillot F. , Martel G. , Deconihout B.
Published: August 2010

Using laser assisted atom probe tomography, we investigate the surface recombination processes of a subwavelength Si tip illuminated by an ultrashort laser pulse under high electric field. In practice, by changing the laser wavelength, we demonstrate the presence of a very long electron-phonon relaxation time at the surface. It is experimentally shown that this behavior is common to indirect band gap semiconductors. Furthermore, a simple model is developed in this paper to explain laser wavelength dependence of our experimental results and estimate the surface recombination time.
Small angle neutron scattering from 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids ([Cnmim][PF6], n=4, 6, and 8)
Authors: Hardacre Christopher , Holbrey John D. , Mullan Claire L. , Youngs Tristan G. A. , Bowron Daniel T.
Published: August 2010

The presence of local anisotropy in the bulk, isotropic, and ionic liquid phases—leading to local mesoscopic inhomogeneity—with nanoscale segregation and expanding nonpolar domains on increasing the length of the cation alkyl-substituents has been proposed on the basis of molecular dynamics (MD) simulations. However, there has been little conclusive experimental evidence for the existence of intermediate mesoscopic structure between the first/second shell correlations shown by neutron scattering on short chain length based materials and the mesophase structure of the long chain length ionic liquid crystals. Herein, small angle neutron scattering measurements have been performed on selectively H/D-isotopically substituted 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids with butyl, hexyl, and octyl substituents. The data show the unambiguous existence of a diffraction peak in the low-Q region for all three liquids which moves to longer distances (lower Q), sharpens, and increases in intensity with increasing length of the alkyl substituent. It is notable, however, that this peak occurs at lower values of Q (longer length scale) than predicted in any of the previously published MD simulations of ionic liquids, and that the magnitude of the scattering from this peak is comparable with that from the remainder of the amorphous ionic liquid. This strongly suggests that the peak arises from the second coordination shells of the ions along the vector of alkyl-chain substituents as a consequence of increasing the anisotropy of the cation, and that there is little or no long-range correlated nanostructure in these ionic liquids.
Two-dimensional Stokes flow due to a pair of vortices below the free surface
Authors: Jeong Jae-Tack
Published: August 2010

A two-dimensional Stokes flow due to a pair of counter-rotating vortices of equal strength below the free surface is analyzed, and the streamline pattern and free-surface deformation are discussed. Two vortices are placed at a fixed depth and an arbitrary distance between each other. In the analysis, Stokes’ approximation is used and surface tension effects are included, but gravity is neglected. The solution is obtained by using conformal mapping and complex function theory. From the solution, typical flow patterns are seen, depending on the capillary number, Ca, and the distance between the two vortices, and some interesting results are obtained. For separation distances below a critical distance, a cusp occurs at the center of the free surface as Ca→∞, following the results of Jeong and Moffatt [“Free-surface cusps associated with flow at low Reynolds number,” J. Fluid Mech. 241, 1 (1992)] for no separation (distance of zero). However, above the critical distance, the cusp disappears and a smooth, trough-shaped interface is formed. At even greater separation distances, a pair of viscous eddies exists near the free surface beyond some critical values of Ca. As the capillary number vanishes, the solution is reduced to that of a linearized potential flow.
Role of surrounding oxygen on oxide nanowire growth
Authors: Klamchuen Annop , Yanagida Takeshi , Kanai Masaki , Nagashima Kazuki , Oka Keisuke , Kawai Tomoji , Suzuki Masaru , Hidaka Yoshiki , Kai Shoichi
Published: August 2010

The ability to control oxide nanowires via vapor-liquid-solid (VLS) mechanism remains an important challenge to explore various applications of oxide nanowires. Here we demonstrate the crucial roles of surrounding oxygen on VLS grown SnO2 nanowires. When the partial pressure of surrounding oxygen is relatively low, the oxygen mainly acts as an oxygen source, promoting VLS growth. While for relatively high oxygen partial pressures, vapor-solid (VS) growth emerges, suppressing nanowire growth. The findings as to the roles of surrounding oxygen on the inherent competition between VLS and VS growths are in principle rather universal for VLS grown nanowires of various oxides.
Low temperature plasma enhanced chemical vapor deposition of thin films combining mechanical stiffness, electrical insulation, and homogeneity in microcavities
Authors: Peter S. , Günther M. , Hauschild D. , Richter F.
Published: August 2010

The deposition of hydrogenated amorphous carbon (a-C:H) as well as hydrogenated amorphous silicon carbonitride (SiCN:H) films was investigated in view of a simultaneous realization of a minimum Young’s modulus (>70 GPa), a high electrical insulation (≥1 MV/cm), a low permittivity and the uniform coverage of microcavities with submillimeter dimensions. For the a-C:H deposition the precursors methane (CH4) and acetylene (C2H2) were used, while SiCN:H films were deposited from mixtures of trimethylsilane [SiH(CH3)3] with nitrogen and argon. To realize the deposition of micrometer thick films with the aforementioned complex requirements at substrate temperatures ≤200 °C, several plasma enhanced chemical vapor deposition methods were investigated: the capacitively coupled rf discharge and the microwave electron cyclotron resonance (ECR) plasma, combined with two types of pulsed substrate bias. SiCN:H films deposited at about 1 Pa from ECR plasmas with pulsed high-voltage bias best met the requirements. Pulsed biasing with pulse periods of about 1 μs and amplitudes of about −2 kV was found to be most advantageous for the conformal low temperature coating of the microtrenches, thereby ensuring the required mechanical and insulating film properties.
Direct measurement of the magnetic field effects on carrier mobilities and recombination in tri-(8-hydroxyquinoline)-aluminum based light-emitting diodes
Authors: Li Feng , Xin Linyuan , Liu Shiyong , Hu Bin
Published: August 2010

The magnetic field effects on the carrier mobilities and recombination in tri-(8-hydroxyquinoline)-aluminum (Alq3) based light-emitting diodes have been measured by the method of transient electroluminescence. It is confirmed that the magnetic field has no effect on the electron and hole mobilities in Alq3 layers and can decrease the electron-hole recombination coefficient. The results imply that the dominant mechanism for the magnetic field effects in Alq3 based light-emitting diodes is the interconversion between singlet e-h pairs and triplet e-h pairs modulated by the magnetic field when the driving voltage is larger than the onset voltage of the electroluminescence.
Sputtering formation of p-type SnO thin-film transistors on glass toward oxide complimentary circuits
Authors: Yabuta Hisato , Kaji Nobuyuki , Hayashi Ryo , Kumomi Hideya , Nomura Kenji , Kamiya Toshio , Hirano Masahiro , Hosono Hideo
Published: August 2010

Thin film transistors (TFTs) using polycrystalline tin oxides (SnO–SnO2) channels were formed on glass by a conventional sputtering method and subsequent annealing treatments. SnO-channel TFTs showed p-type operation with on/off current ratios of ∼102 and field-effect mobilities of 0.24 cm2 V−1 s−1. Incorporation of excess oxygen to SnO channel layers did not generate holes but did electrons, which in turn led to n-type operation. This result is explained by transformation to a local SnO2-like structure and finally to SnO2. We propose a simple method to fabricate complimentary circuits by simultaneous selective formation of p- and n-channel TFTs.
Foucault pendulum and sub-Riemannian geometry
Authors: Anzaldo-Meneses A. , Monroy-Pérez F.
Published: August 2010

The well known Foucault nonsymmetrical pendulum is studied as a problem of sub-Riemannian geometry on nilpotent Lie groups. It is shown that in a rotating frame a sub-Riemannian structure can be naturally introduced. For small oscillations, three dimensional horizontal trajectories are computed and displayed in detail. The fiber bundle structure is explicitly shown. The underlying Lie structure is described together with the corresponding holonomy group, which turns out to be given by the center of the Heisenberg group. Other related physical problems that can be treated in a similar way are also mentioned.
Anisotropic etching of diamond by molten Ni particles
Authors: Smirnov W. , Hees J. J. , Brink D. , Müller-Sebert W. , Kriele A. , Williams O. A. , Nebel C. E.
Published: August 2010

Nanopores in insulating solid state membranes have recently attracted much interest in the field of probing, characterizing, and manipulating single linear polymers such as DNA/RNA and proteins in their native environment. Here a low cost, fast, and effective way to produce nanostructures such as pyramidal shaped nanopores and nanochannels with dimensions down to about 15 nm in diamond membranes without any need for electron-beam lithography is demonstrated. By use of a catalytic process, anisotropic etching of diamond with self-organized Ni nanoparticles in hydrogen atmosphere at 900 °C is achieved and possible etching mechanisms are discussed. It is shown that diamond planes with the crystallographic orientation of [111] are etched slowest with this method.
Doping- and size-dependent photovoltaic properties of p-type Si-quantum-dot heterojunction solar cells: correlation with photoluminescence
Authors: Hong Seung Hui , Park Jae Hee , Shin Dong Hee , Kim Chang Oh , Choi Suk-Ho , Kim Kyung Joong
Published: August 2010

Boron-doped SiOx/SiO2 superlattices have been prepared on n-type Si (100) wafers by ion beam sputtering and subsequently annealed to form p-type Si quantum dots (QDs)/n-type Si-wafer heterojunction solar cells. Systematic studies on photoluminescence (PL) and photovoltaic effects show that optimum formation of Si QDs, proper doping concentration (nB), and minimization of defects are crucial factors for enhancing energy-conversion efficiency of the solar cells. Highest efficiency of 9.5% is obtained under the conditions of x=1.0 (QD size: ∼5 nm) and nB=6.3×1020 cm−3. Possible physical mechanisms are discussed to explain the correlation of the photovoltaic parameters and the QD-/defect-PL intensities. The demonstration of the photovoltaic effects in the Si-QD heterojunction solar cells is promising for the development of next-generation all-Si-QD solar cells.
Mid-infrared transmission properties of amorphous germanium optical fibers
Authors: Mehta Priyanth , Krishnamurthi Mahesh , Healy Noel , Baril Neil F. , Sparks Justin R. , Sazio Pier J. A. , Gopalan Venkatraman , Badding John V. , Peacock Anna C.
Published: August 2010

Germanium optical fibers have been fabricated using a high pressure chemical deposition technique to deposit the semiconductor material inside a silica capillary. The amorphous germanium core material has a small percentage of hydrogen that saturates the dangling bonds to reduce absorption loss. Optical transmission measurements were performed to determine the linear losses over a broad mid-infrared wavelength range with the lowest loss recorded at 10.6 μm. The extended transmission range measured in the germanium fibers demonstrates their potential for use in mid-infrared applications.
InGaN/GaN multiple quantum well concentrator solar cells
Authors: Dahal R. , Li J. , Aryal K. , Lin J. Y. , Jiang H. X.
Published: August 2010

We present the growth, fabrication, and photovoltaic characteristics of Inx Ga1−xN/GaN(x∼0.35) multiple quantum well solar cells for concentrator applications. The open circuit voltage, short circuit current density, and solar-energy-to-electricity conversion efficiency were found to increase under concentrated sunlight. The overall efficiency increases from 2.95% to 3.03% when solar concentration increases from 1 to 30 suns and could be enhanced by further improving the material quality.
The Perceptual Salience of Symmetrical and Asymmetrical Sections of a Line
Authors: Stucchi Natale , Graci Valentina , Toneatto Carlo , Scocchia Lisa
Published: August 2010

A vertical line segment intersecting a horizontal one at different crossing points generates line sections. Visual perception of such line sections was investigated here in two experiments. In both experiments participants were most accurate and precise when they had to reproduce symmetrical sections. Interestingly, the different asymmetrical sections of a line were not equivalent in terms of participants' performance: constant errors changed as a function of sections and the error curve was nicely interpolated by the composition of two harmonics of the line length. In consistence with the harmonic fitting of the data, we propose that the perceptual salience of specific asymmetrical sections is a byproduct of the automatic triggering of a line midpoint identification process. Being perceptually tuned to symmetry warps our visual representation of the line, which results in systematic misperceptions. The way of bringing present and past experimental findings into a unitary whole is proposed.
National survey of general practitioners' experience of delivering the National Human Papillomavirus Vaccination Program
Authors: Brotherton Julia M. L. , Leask Julie , Jackson Cath , McCaffery Kirsten , Trevena Lyndal J.
Published: August 2010

Background: Between 2007 and 2009, Australian general practitioners (GPs) were involved in implementing a population-based human papillomavirus (HPV) vaccination program. We investigated GPs’ experiences of delivering the HPV vaccine to women aged 18–26. Methods: We posted a survey to 1000 GPs. The survey was informed by 12 domains incorporating constructs from psychological theories that focus on individual and environmental barriers and facilitators to effective implementation of evidence-based practice by health professionals. Results: The response rate was 32%. The 298 vaccinating GPs were positive about HPV vaccine implementation as part of their professional role as a worthwhile initiative within existing general practice infrastructure. They had more negative views about some aspects of program organisation, such as the timelines and potential adverse impacts on cervical screening rates. Vaccine safety was not a key concern. Actual levels of knowledge about HPV were moderate (mean score 3.41 out of 6 (s.d. 0.99)) and contrasted with self-rated knowledge, which was high (93% perceived their knowledge to be adequate). Notably, there were unrealistic expectations about the likely reduction in Pap abnormalities due to vaccination, which is important to clarify to avoid loss of confidence in the vaccine when this reduction does not eventuate. Conclusions: Australian GPs viewed HPV vaccination of women aged 18–26 years as an integrated part of their routine practice, with positive attitudes regarding its benefits and achievability. GPs are well placed to implement mass immunisation programs as long as they are supported by effective and timely communication strategies and resources.
Estimating the prevalence of and treatment patterns for juvenile onset recurrent respiratory papillomatosis in Australia pre-vaccination: a pilot study
Authors: Novakovic Daniel , Cheng Alan T. L. , Cope Daron H. , Brotherton Julia M. L.
Published: August 2010

Background: Recurrent respiratory papillomatosis (RRP) causes serious morbidity. RRP in Australia may be eliminated in the near future following the implementation of a national vaccination program using a human papillomavirus (HPV) vaccine that protects against infection with HPV types 6 and 11, those responsible for RRP. Baseline data on RRP prevalence and disease burden in Australia are lacking. Methods: Three study methods were used to estimate the burden of juvenile onset RRP in Australia. We conducted a retrospective chart review of RRP cases treated at The Children’s Hospital at Westmead over 10 years, examined the coding of these cases, and then calculated and applied the positive predictive value of the codes to national data to estimate the prevalence of RRP in Australia. We also conducted an online survey of otolaryngologists in Australia who manage RRP. Results: Nineteen patients were treated at the hospital over 10 years, involving 359 admissions. We estimate that between 33 and 56 RRP cases aged <20 are being treated nationally per year (0.6–1.1 per 100 000 persons), with children 5–9 years having a higher estimated rate of 1.2–1.8 per 100 000. Among 39 otolaryngologists treating juvenile onset RRP, the majority (73%) treated RRP in a paediatric tertiary hospital, and used the microdebrider for ablation of lesions. Conclusions: Our estimates of RRP disease burden agree with international estimates. As a small number of clinicians treat RRP nationally, we believe that establishment of a national RRP register is both feasible and necessary to monitor the impact of vaccination.
Models of cervical screening in the era of human papillomavirus vaccination
Authors: Canfell Karen
Published: August 2010

Epidemiologic and economic evaluation using simulation modelling can support complex policy decisions, and is an important tool in predicting the future interaction between human papillomavirus vaccination and cervical screening. Several categories of screening program evaluation are of interest, including: (1) changes to screening considered over the short term, over which the effects of vaccination should be confined to the youngest age groups (<30 years old); (2) the medium and long-term effect of vaccination on the screening program; and (3) changes to screening in context of vaccination. This review considers some of the policy questions in each category and discusses the modelling implications, with particular focus on the Australian context.
A brief history of economic evaluation for human papillomavirus vaccination policy
Authors: Beutels Philippe , Jit Mark
Published: August 2010

Background: This commentary discusses key issues for health economic evaluation and modelling, applied to human papillomavirus (HPV) vaccine programs. Methods: We outline some of the specific features of HPV disease and vaccination, and associated policy questions in light of a literature search for economic evaluations on HPV vaccination. Results: We observe that some policy questions could not be reliably addressed by many of the 43 published economic evaluations we found. Despite this, policy making on universal HPV vaccination followed shortly after vaccine licensure in many developed countries, so the role economic evaluation played in informing these decisions (pre-dating 2008) seems to have been fairly limited. For more recent decisions, however, economic evaluation is likely to have been used more widely and more intensively. Conclusions: We expect future cost-effectiveness analyses to be more instrumental in policy making regarding vaccines covering more HPV types, therapeutic HPV vaccines, and novel diagnostic tests for biomarkers of HPV infection and disease integrated with cervical screening programs.
Quantitative 3D elemental microtomography ofCyclotella meneghinianaat 400-nm resolution
Authors: de Jonge Martin D. , Holzner Christian , Baines Stephen B. , Twining Benjamin S. , Ignatyev Konstantin , Diaz Julia , Howard Daryl L. , Legnini Daniel , Miceli Antonino , McNulty Ian , Jacobsen Chris J. , Vogt Stefan
Published: August 2010

X-ray fluorescence tomography promises to map elemental distributions in unstained and unfixed biological specimens in three dimensions at high resolution and sensitivity, offering unparalleled insight in medical, biological, and environmental sciences. X-ray fluorescence tomography of biological specimens has been viewed as impractical—and perhaps even impossible for routine application—due to the large time required for scanning tomography and significant radiation dose delivered to the specimen during the imaging process. Here, we demonstrate submicron resolution X-ray fluorescence tomography of a whole unstained biological specimen, quantifying three-dimensional distributions of the elements Si, P, S, Cl, K, Ca, Mn, Fe, Cu, and Zn in the freshwater diatomCyclotella meneghinianawith 400-nm resolution, improving the spatial resolution by over an order of magnitude. The resulting maps faithfully reproduce cellular structure revealing unexpected patterns that may elucidate the role of metals in diatom biology and of diatoms in global element cycles. With anticipated improvements in data acquisition and detector sensitivity, such measurements could become routine in the near future.
Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice
Authors: Liu Jiping , Curry Judith A.
Published: August 2010

The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models’ internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.
Mechanism for pH-dependent gene regulation by amino-terminus-mediated homooligomerization of
Bacillus subtilis
anti-
trp
RNA-binding attenuation protein
Authors: Sachleben Joseph R. , McElroy Craig A. , Gollnick Paul , Foster Mark P.
Published: August 2010

Anti-TRAP (AT) is a small zinc-binding protein that regulates tryptophan biosynthesis in
Bacillus subtilis
by binding to tryptophan-bound
trp
RNA-binding attenuation protein (TRAP), thereby preventing it from binding RNA, and allowing transcription and translation of the
trp
EDCFBA operon. Crystallographic and sedimentation studies have shown that AT can homooligomerize to form a dodecamer, AT
12
, composed of a tetramer of trimers, AT
3
. Structural and biochemical studies suggest that only trimeric AT is active for binding to TRAP. Our chromatographic and spectroscopic data revealed that a large fraction of recombinantly overexpressed AT retains the N-formyl group (fAT), presumably due to incomplete N-formyl-methionine processing by peptide deformylase. Hydrodynamic parameters from NMR relaxation and diffusion measurements showed that fAT is exclusively trimeric (AT
3
), while (deformylated) AT exhibits slow exchange between both trimeric and dodecameric forms. We examined this equilibrium using NMR spectroscopy and found that oligomerization of active AT
3
to form inactive AT
12
is linked to protonation of the amino terminus. Global analysis of the pH dependence of the trimer-dodecamer equilibrium revealed a near physiological
pK

a

for the N-terminal amine of AT and yielded a pH-dependent oligomerization equilibrium constant. Estimates of excluded volume effects due to molecular crowding suggest the oligomerization equilibrium may be physiologically important. Because deprotonation favors “active” trimeric AT and protonation favors “inactive” dodecameric AT, our findings illuminate a possible mechanism for sensing and responding to changes in cellular pH.
On the aesthetic ablation of fuzziness in Chinese expressions in Chinese–English translation
Authors: Wuqiu Fan
Published: August 2010

Although fuzziness is one of the innate characteristics of language, shared by both Chinese and English, there do exist apparent differentiations between them as far as their roles in aesthetic-effect-generating, representation mode, application field suitability and aesthetic impact are concerned, which has remained a great challenge and regret in either English to Chinese (E–C) or Chinese to English (C–E) translation, particularly in the latter. It’s no exaggeration to say that translation is a profession with no lack of regret and translators are professional regret-tasters. The most impressive regret in C–E translation might lie in the fact that the talent and capability of the translators is painfully restricted in reproducing and conveying the aesthetic effect of Chinese fuzzy expressions.

As an artistically conceived language, Chinese invites macro-induction in terms of linguistic features while English, being logic-oriented, analysis-based and hypotaxis-dependent, is largely ignorant of what is called macro-induction. Hence abundant aesthetic genius of Chinese fuzzy expressions can hardly find its way into the English version. It can be said that generally the process of C–E translation is one of complementing continuously “meaning blank”, of changing “indeterminacy of meaning” into “determinacy of meaning”, with the E–C translation as the opposite. Many language problems in communication are essentially closely related to nationality psychologic archetype complex, which may be a significant try in translation study.
Notes on the verbal system of Gulf Pidgin Arabic
Authors: Bakir Murtadha J.
Published: August 2010

This is a description of one of the essential constituents of sentence structure in one reduced linguistic system in use in various countries of the western coast of the Arab Gulf and Saudi Arabia, that has been given the name Gulf Pidgin Arabic (GPA) in the very little that has been written about it. The paper starts with locating this reduced linguistic form in its sociolinguistic background. This is followed by a description of the morphological characteristics of the verbs used in this system. The discussion also involves how the grammatical categories that form part of the verbal system are signaled, when and if they are (e.g. tense, aspect, mood, modality, and those that mark agreement like gender, person, and number). Furthermore, the paper deals with the status of the copulative element and predication marker fii and sentence negation in relation to the verbal system. It ends with a discussion of the properties of GPA compared to the general characteristics of world pidgins and to other Arabic-based pidgins and creoles.