bluuebunny/crossref_metadata_2025 huggingface dataset:
Extraesophageal Reflux: How Patient Compliance Affects Diagnosis and Treatment
Authors: Musser Joy , Kelchner Lisa
Published: November 2010

Extraesophageal reflux can be a significant yet elusive issue in the diagnosis and treatment of voice, swallowing, and airway disorders. This paper explores the role of patient compliance during 24-hour dual pH probe monitoring as a confounding factor in the poor agreement amongst current clinical tools. Supporting data from a recent research study are provided.
Translating Exercise Science Into Voice Care
Authors: Sandage Mary J. , Pascoe David D.
Published: November 2010

The basic principles of exercise training for skeletal muscle adaptations have been applied to voice training for some time. To date, the use of the basic principles of muscle training for designing a voice rehabilitation program or advising voice clients about the role of voice rest and modified voice use following surgical intervention has not been well developed. Voice training is a complex process of skill acquisition through application of motor learning principles and the concurrent coordinated use of many physiologic systems. However, the translation of exercise science literature to voice training and recovery needs to be undertaken with caution, because the function and performance of laryngeal skeletal muscle can be different from those of skeletal muscles used for other types of movement. This discussion will be confined to the basic adaptations of the muscle tissue itself. A brief review of basic principles of muscle training as understood for skeletal muscle will be followed by a more extensive discussion of the neurologic, metabolic, and physiologic adaptations of muscle training and detraining. Translation of this body of literature will be considered in the contexts of post-surgical voice recovery, voice rehabilitation, and maintenance of professional voice requirements.
Numerical simulations of Stokes–Brinkman equations for permeability prediction of dual scale fibrous porous media
Authors: Hwang Wook Ryol , Advani Suresh G.
Published: November 2010

A new finite-element scheme to solve the Stokes–Brinkman equation for flow analyses in dual scale porous media is presented and has been applied to predict the effective permeability of dual scale fibrous media. Both continuous and discontinuous stress conditions at the interface between a porous media and a surrounding fluid are explored by introducing an equivalent momentum equation for the Brinkman equation. The proposed scheme uses a uniform structured regular rectangular mesh to discretize the domain and employs the level-set method to describe the porous media allowing for inclusion of complex geometrical features easily. Biperiodic boundary conditions have been applied to conduct the flow analysis in a representative volume of mesoscale porous structures. Numerical solutions in a parallel channel flow over a porous media are presented and compared with analytic solutions to assess the accuracy of the proposed scheme. The scheme is then applied to flow past two regular periodic geometries of elliptic porous media in two dimension, representing unidirectional fiber tow (bundle of aligned fibers) in a textile fabric, to predict the effective permeability and its dependence on the fiber volume fraction, the aspect ratio, the fiber tow permeability, and the degree of compaction of the fiber tows. In addition, we propose a simple relationship between the effective permeability and the permeability of fiber tow, based on numerical and analytic results.
Study on Langevin model parameters of velocity in turbulent shear flows
Authors: Tanière Anne , Arcen Boris , Oesterlé Benoît , Pozorski Jacek
Published: November 2010

This paper deals with the stochastic equation used to predict the fluctuating velocity of a fluid particle in a nonhomogeneous turbulent flow, in the frame of probability density function (PDF) approaches. It is shown that a Langevin-type equation is appropriate provided its parameters (drift and diffusion matrices) are suitably specified. By following the approach proposed in the literature for homogeneous turbulent shear flows, these parameters have been identified using data from direct numerical simulations (DNS) of both channel and pipe flows. Using statistics extracted from the computation of the channel flow, it is shown that the drift matrix of the stochastic differential equation can reasonably be assumed to be diagonal but not spherical. This behavior of the drift coefficients is confirmed by the available results for a turbulent pipe flow at low Reynolds number. Concerning the diffusion matrix, it is found that this matrix is anisotropic for low Reynolds number flows, a property which has been observed earlier for a homogeneous turbulent shear flow. The pertinence of the present estimation of the drift and diffusion tensors is assessed through different kinds of tests including the incorporation of these parameters in a purely Lagrangian, or stand-alone, PDF computation.
Structure and photoabsorption properties of cationic alkali dimers solvated in neon clusters
Authors: Zanuttini D. , Douady J. , Jacquet E. , Giglio E. , Gervais B.
Published: November 2010

We present a theoretical investigation of the structure and optical absorption of M2+ alkali dimers (M=Li,Na,K) solvated in Nen clusters for n=1 to a few tens Ne atoms. For all these alkali, the lowest-energy isomers are obtained by aggregation of the first Ne atoms at the extremity of the alkali molecule. This particular geometry, common to other M2+-rare gas clusters, is intimately related to the shape of the electronic density of the X Σ2g+ ground state of the bare M2+ molecules. The structure of the first solvation shell presents equilateral Ne3 and capped pentagonal Ne6 motifs, which are characteristic of pure rare gas clusters. The size and geometry of the complete solvation shell depend on the alkali and were obtained at n=22 with a D4h symmetry for Li and at n=27 with a D5h symmetry for Na. For K, our study suggests that the closure of the first solvation shell occurs well beyond n=36. We show that the atomic arrangement of these clusters has a profound influence on their optical absorption spectrum. In particular, the XΣ transition from the X Σ2g+ ground state to the first excited Σ2u+ state is strongly blueshifted in the Frank–Condon area.
Highly rarefied two-dimensional jet impingement on a flat plate
Authors: Khasawneh Khaleel , Liu Hongli , Cai Chunpei
Published: November 2010

In this paper, we investigate highly rarefied jet gas flows out of a two-dimensional slit that impinges on a flat plate which is set vertically to the plume flow direction. The plate is assumed to be completely diffusive and the gaseous plume flow out of the slit is modeled with a Maxwellian distribution function which is characterized with known number density, nonzero exit velocity, and temperature. We present some analytical collisionless flow properties for a free plume and the impingement on the plate. The outcomes include simple results of the largest shear stress on the plate and the corresponding location. Numerical simulation results obtained with the direct simulation Monte Carlo method validate the analytical collisionless flow solutions.
Nonlocal description of evaporating drops
Authors: Eggers J. , Pismen L. M.
Published: November 2010

We present a theoretical study of the evolution of a drop of pure liquid on a solid substrate, which it wets completely. In a situation where evaporation is significant, the drop does not spread, but instead the drop radius goes to zero in finite time. Our description couples the viscous flow problem to a self-consistent thermodynamic description of evaporation from the drop and its precursor film. The evaporation rate is limited by the diffusion of vapor into the surrounding atmosphere. For flat drops, we compute the evaporation rate as a nonlocal integral operator of the drop shape. Together with a lubrication description of the flow, this permits an efficient numerical description of the final stages of the evaporation problem. We find that the drop radius goes to zero like R∝(t0−t)α, where α has value close to 1/2, in agreement with experiment.
On Koopmans’ theorem in density functional theory
Authors: Tsuneda Takao , Song Jong-Won , Suzuki Satoshi , Hirao Kimihiko
Published: November 2010

This paper clarifies why long-range corrected (LC) density functional theory gives orbital energies quantitatively. First, the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies of typical molecules are compared with the minus vertical ionization potentials (IPs) and electron affinities (EAs), respectively. Consequently, only LC exchange functionals are found to give the orbital energies close to the minus IPs and EAs, while other functionals considerably underestimate them. The reproducibility of orbital energies is hardly affected by the difference in the short-range part of LC functionals. Fractional occupation calculations are then carried out to clarify the reason for the accurate orbital energies of LC functionals. As a result, only LC functionals are found to keep the orbital energies almost constant for fractional occupied orbitals. The direct orbital energy dependence on the fractional occupation is expressed by the exchange self-interaction (SI) energy through the potential derivative of the exchange functional plus the Coulomb SI energy. On the basis of this, the exchange SI energies through the potential derivatives are compared with the minus Coulomb SI energy. Consequently, these are revealed to be cancelled out only by LC functionals except for H, He, and Ne atoms.
The reweighted path ensemble
Authors: Rogal Jutta , Lechner Wolfgang , Juraszek Jarek , Ensing Bernd , Bolhuis Peter G.
Published: November 2010

We introduce a reweighting scheme for the path ensembles in the transition interface sampling framework. The reweighting allows for the analysis of free energy landscapes and committor projections in any collective variable space. We illustrate the reweighting scheme on a two dimensional potential with a nonlinear reaction coordinate and on a more realistic simulation of the Trp-cage folding process. We suggest that the reweighted path ensemble can be used to optimize possible nonlinear reaction coordinates.
Watching solvent friction impede ultrafast barrier crossings: A direct test of Kramers theory
Authors: Anna Jessica M. , Kubarych Kevin J.
Published: November 2010

A systematic investigation of the solvent’s dynamic influence on activated barrier crossings on an electronic ground state is performed using ultrafast two-dimensional infrared chemical exchange spectroscopy. These measurements facilitate a direct comparison with the widely adopted Kramers theory of condensed phase reaction kinetics, and for the first time avoid the significant complication of electronic excitation to probe directly in the time domain a ground electronic state reaction with a well-defined transition state. The picosecond timescale interconversion between two stable isomers of the metal carbonyl complex Co2(CO)8 in a series of linear alkane solvents shows negligible energetic variation with solvent carbon chain length, providing an exclusive probe of the effects of solvent friction. Relative to the linear alkane series, cyclohexane does alter the potential energy surface by preferentially stabilizing one of the isomers. Despite this pronounced modification of the reaction barrier energetics, combination of experiment and computation enables the removal of the nondynamical barrier contribution to the rate constant, isolating the dynamical influence of solvent friction. The experimental data, supported with quantum and classical computations, show agreement with a simple Markovian Kramers theory for the isomerization rate constant’s dependence on solvent viscosity.
State-dependent biasing method for importance sampling in the weighted stochastic simulation algorithm
Authors: Roh Min K. , Gillespie Dan T. , Petzold Linda R.
Published: November 2010

The weighted stochastic simulation algorithm (wSSA) was developed by Kuwahara and Mura [J. Chem. Phys. 129, 165101 (2008)] to efficiently estimate the probabilities of rare events in discrete stochastic systems. The wSSA uses importance sampling to enhance the statistical accuracy in the estimation of the probability of the rare event. The original algorithm biases the reaction selection step with a fixed importance sampling parameter. In this paper, we introduce a novel method where the biasing parameter is state-dependent. The new method features improved accuracy, efficiency, and robustness.
The rotational spectrum of CuCCH(X̃ Σ1+): A Fourier transform microwave discharge assisted laser ablation spectroscopy and millimeter/submillimeter study
Authors: Sun M. , Halfen D. T. , Min J. , Harris B. , Clouthier D. J. , Ziurys L. M.
Published: November 2010

The pure rotational spectrum of CuCCH in its ground electronic state (X̃ Σ1+) has been measured in the frequency range of 7–305 GHz using Fourier transform microwave (FTMW) and direct absorption millimeter/submillimeter methods. This work is the first spectroscopic study of CuCCH, a model system for copper acetylides. The molecule was synthesized using a new technique, discharge assisted laser ablation spectroscopy (DALAS). Four to five rotational transitions were measured for this species in six isotopologues (C63uCCH, C65uCCH, C63uC13CH, C63uCC13H, C63uC13C13H, and C63uCCD); hyperfine interactions arising from the copper nucleus were resolved, as well as smaller splittings in CuCCD due to deuterium quadrupole coupling. Five rotational transitions were also recorded in the millimeter region for C63uCCH and C65uCCH, using a Broida oven source. The combined FTMW and millimeter spectra were analyzed with an effective Hamiltonian, and rotational, electric quadrupole (Cu and D) and copper nuclear spin-rotation constants were determined. From the rotational constants, an rm(2) structure for CuCCH was established, with rCuC=1.8177(6) Å, rCC=1.2174(6) Å, and rCH=1.046(2) Å. The geometry suggests that CuCCH is primarily a covalent species with the copper atom singly bonded to the CCH moiety. The copper quadrupole constant indicates that the bonding orbital of this atom may be sp hybridized. The DALAS technique promises to be fruitful in the study of other small, metal-containing molecules of chemical interest.
Design of an infrared laser pulse to control the multiphoton dissociation of the Fe–CO bond in CO-heme compounds
Authors: Sharma Sitansh , Singh Harjinder , Harvey Jeremy N. , Balint-Kurti Gabriel G.
Published: November 2010

Optimal control theory is used to design a laser pulse for the multiphoton dissociation of the Fe–CO bond in the CO-heme compounds. The study uses a hexacoordinated iron–porphyrin–imidazole–CO complex in its ground electronic state as a model for CO liganded to the heme group. The potential energy and dipole moment surfaces for the interaction of the CO ligand with the heme group are calculated using density functional theory. Optimal control theory, combined with a time-dependent quantum dynamical treatment of the laser-molecule interaction, is then used to design a laser pulse capable of efficiently dissociating the CO-heme complex model. The genetic algorithm method is used within the mathematical framework of optimal control theory to perform the optimization process. This method provides good control over the parameters of the laser pulse, allowing optimized pulses with simple time and frequency structures to be designed. The dependence of photodissociation yield on the choice of initial vibrational state and of initial laser field parameters is also investigated. The current work uses a reduced dimensionality model in which only the Fe–C and C–O stretching coordinates are explicitly taken into account in the time-dependent quantum dynamical calculations. The limitations arising from this are discussed in Sec. IV.
Segmented contracted basis sets for one- and two-component Dirac–Fock effective core potentials
Authors: Weigend Florian , Baldes Alexander
Published: November 2010

Segmented contracted basis sets for 4d, 5d, 5s, and 6s elements of split (double zeta) valence to quadruple zeta valence quality optimized for Dirac–Fock effective core potentials (ECPs) are presented. They were obtained from previous bases optimized for Wood–Boring ECPs by comparably small modifications and reoptimizations. Additionally extensions for two-component self-consistent-field treatments accounting for spin-orbit (SO) coupling were designed and optimized. Reliability for chemical applications was assessed by comparing results to those obtained with a very large (19s16p17d7f6g) reference basis for a set of more than 80 representatively chosen 5s-5d compounds. Moreover, the effect of different types of ECPs and that of the SO-coupling at the basis set limit of density functional theory is documented for the above set of molecules extended by 40 5p-6p compounds.
Simulations of high-dielectric Stockmayer fluids in hyperspherical geometry
Authors: Trulsson Martin
Published: November 2010

The static dielectric properties of Stockmayer fluids are investigated in the hyperspherical geometry, S3. Different methods of obtaining the static dielectric constant εr are compared. Tested methods include the evaluation of the Kirkwood factor, fluctuations of the total dipole moment, and a two-center potential correlation formula to obtain the dielectric constant through effective interactions. With no coupling to the “surrounding,” the different methods give consistent estimates of the dielectric constant. Adding a coupling to the surrounding gives large size dependencies and the two-center potential correlation formula breaks down. For low dipole moments, there is a good agreement in the dielectric constant with previous studies.
The generation of azimuthal magnetic field in laser-induced plasma bubbles
Authors: Zhou Suyun , Yu Wei , Yuan Xiao , Xu Han , Wang Xin , Ma Guangjing
Published: November 2010

A two-dimensional (2D) analytical model for a laser-induced bubble is rebuilt by taking into account the generation of azimuthal magnetic field. It is shown that the azimuthal magnetic field surrounds the bubble transversely, whose amplitude peaks at the bubble edge and vanishes at laser axis. In a laser wakefield acceleration scheme, the longitudinal electric field accelerates the electrons injected from the rear of the bubble, while the azimuthal magnetic field makes the resulting energetic-electron beam converge. The analytical model is justified by a 2D Particle in Cell (PIC) simulation.
Full-dimensional quantum dynamics of vibrationally highly excited NHD2
Authors: Marquardt Roberto , Sanrey Michael , Gatti Fabien , Le Quéré Frédéric
Published: November 2010

We report on full-dimensional vibrational quantum dynamics of the highly excited ammonia isotopologue NHD2 using a newly developed potential energy surface and the MCTDH program package. The calculations allow to realistically simulate an infrared laser induced stereomutation reaction at the pyramidal nitrogen atom in the femtosecond time domain. Our results allow for a thorough qualitative and quantitative understanding of infrared photoinduced stereomutation kinetics, the underlying quantum dynamics, and the reaction mechanisms. Comparison is made with a previous, reduced dimensionality study of the same reaction [R. Marquardt, M. Quack, I. Thanopulos, and D. Luckhaus, J. Chem. Phys. 118, 643 (2003)], and it is shown that slight variances of reduced spaces lead to significantly different kinetics. Because the quantum dynamics depends subtly on variances of reduced spaces, reduced dimensionality treatments are not reliable even for qualitative predictions of the stereomutation kinetics. The first direct comparison between the Multiconfigurational Time Dependent Hartree [M. H. Beck, A. Jäckle, G. A. Worth et al., Phys. Rep. 324, 1 (2000)] and Unimolecular Reactions Induced by Monochromatic Infrared Radiation [M. Quack and E. Sutcliffe, QCPE Bulletin 6, 98 (1986)] program packages on a specific, four dimensional quantum dynamical problem allows for their full validation in the present work.
On spontaneous formation of current sheets: Untwisted magnetic fields
Authors: Bhattacharyya R. , Low B. C. , Smolarkiewicz P. K.
Published: November 2010

This is a study of the spontaneous formation of electric current sheets in an incompressible viscous fluid with perfect electrical conductivity, governed by the magnetohydrodynamic Navier–Stokes equations. Numerical solutions to two initial value problems are presented for a three-dimensional, periodic, untwisted magnetic field evolving, with no change in magnetic topology under the frozen-in condition and at characteristic fluid Reynolds numbers of the order of 500, from a nonequilibrium initial state with the fluid at rest. The evolution converts magnetic free energy into kinetic energy to be all dissipated away by viscosity so that the field settles into a minimum-energy, static equilibrium. The solutions demonstrate that, as a consequence of the frozen-in condition, current sheets must form during the evolution despite the geometric simplicity of the prescribed initial fields. In addition to the current sheets associated with magnetic neutral points and field reversal layers, other sheets not associated with such magnetic features are also in evidence. These current sheets form on magnetic flux surfaces. This property is used to achieve a high degree of the frozen-in condition in the simulations, by describing the magnetic field entirely in terms of the advection of its flux surfaces and integrating the resulting governing equations with a customized version of a general-purpose high-resolution (viz., nonoscillatory) hydrodynamical simulation code EULAG [J. M. Prusa et al., Comput. Fluids 37, 1193 (2008)]. Incompressibility imposes the additional global constraint that the flux surfaces must evolve with no change in the spatial volumes they enclose. In this approach, current sheet formation is demonstrated graphically by the progressive pressing together of suitably selected flux surfaces until their separation has diminished below the minimal resolved distance on a fixed grid. The frozen-in condition then fails in the simulation as the field reconnects through an effecting numerical resistivity. The principal results are related to the Parker theory of current-sheet formation and dissipation in the solar corona.
Field-theoretic model of inhomogeneous supramolecular polymer networks and gels
Authors: Mohan Aruna , Elliot Richard , Fredrickson Glenn H.
Published: November 2010

We present a field-theoretic model of the gelation transition in inhomogeneous reversibly bonding systems and demonstrate that our model reproduces the classical Flory–Stockmayer theory of gelation in the homogeneous limit. As an illustration of our model in the context of inhomogeneous gelation, we analyze the mean-field behavior of an equilibrium system of reacting trifunctional units in a good solvent confined within a slit bounded by parallel, repulsive walls. Our results indicate higher conversions and, consequently, higher concentrations of gel following the gelation transition near the center of the slit relative to the edges.
Measuring diffusivity in supercooled liquid nanoscale films using inert gas permeation. II. Diffusion of Ar, Kr, Xe, and CH4 through Methanol
Authors: Matthiesen Jesper , Smith R. Scott , Kay Bruce D.
Published: November 2010

We present an experimental technique to measure the diffusivity of supercooled liquids at temperatures near their Tg. The approach uses the permeation of inert gases through supercooled liquid overlayers as a measure of the diffusivity of the supercooled liquid itself. The desorption spectra of the probe gas are used to extract the low temperature supercooled liquid diffusivities. In the preceding companion paper, we derived equations using ideal model simulations from which the diffusivity could be extracted using the desorption peak times for isothermal or peak temperatures for temperature programmed desorption experiments. Here, we discuss the experimental conditions for which these equations are valid and demonstrate their utility using amorphous methanol with Ar, Kr, Xe, and CH4 as probe gases. The approach offers a new method by which the diffusivities of supercooled liquids can be measured in the experimentally challenging temperature regime near the glass transition temperature.
Measuring diffusivity in supercooled liquid nanoscale films using inert gas permeation. I. Kinetic model and scaling methods
Authors: Smith R. Scott , Matthiesen Jesper , Kay Bruce D.
Published: November 2010

We describe in detail a diffusion model used to simulate inert gas transport through supercooled liquid overlayers. In recent work, the transport of the inert gas has been shown to be an effective probe of the diffusivity of supercooled liquid methanol in the experimentally challenging regime near the glass transition temperature. The model simulations accurately and quantitatively describe the inert gas permeation desorption spectra. The simulation results are used to validate universal scaling relationships between the diffusivity, overlayer thickness, and the temperature ramp rate for isothermal and temperature programmed desorption. From these scaling relationships we derive simple equations from which the diffusivity can be obtained using the peak desorption time or temperature for an isothermal or set of TPD experiments, respectively, without numerical simulation. The results presented here demonstrate that the permeation of gases through amorphous overlayers has the potential to be a powerful technique to obtain diffusivity data in deeply supercooled liquids.
Fast reciprocating probe system on the EAST superconducting tokamak
Authors: Zhang W. , Chang J. F. , Wan B. N. , Xu G. S. , Xiao C. J. , Li B. , Xu C. S. , Yan N. , Wang L. , Liu S. C. , Jiang M. , Liu P.
Published: November 2010

A new fast reciprocating probe system (FRPS) has been built and installed on the outer midplane of the EAST tokamak to investigate the profiles of the boundary plasma parameters such as electron density and temperature. The system consists of a two-stage motion drive mechanism: slow motion and fast motion. The fast motion is powered by a servo motor, which drives the probe horizontally up to 50 cm to scan the edge region of the EAST tokamak. The maximum velocity achieved is 2 m/s. High velocity and flexible control of the fast motion are the remarkable features of this FRPS. A specially designed connector installed at the front end of the probe shaft makes it easy to install or replace the probe head on FRPS. During the latest experimental campaign in the spring of 2010, a probe head with seven tips, including two tips for a Mach probe, has been used. An example is given for simultaneous profile measurements of the plasma temperature, plasma density, and the plasma flow velocity.
Computation of nucleation at a nonequilibrium first-order phase transition using a rare-event algorithm
Authors: Adams David A. , Ziff Robert M. , Sander Leonard M.
Published: November 2010

We introduce a new forward flux sampling in time algorithm to efficiently measure transition times in rare-event processes in nonequilibrium systems and apply it to study the first-order (discontinuous) kinetic transition in the Ziff–Gulari–Barshad model of catalytic surface reaction. The average time for the transition to take place, as well as both the spinodal and transition points, is efficiently found by this method.
Quantitative temperature measurement of an electrically heated carbon nanotube using the null-point method
Authors: Chung Jaehun , Kim Kyeongtae , Hwang Gwangseok , Kwon Ohmyoung , Jung Seungwon , Lee Junghoon , Lee Jae Woo , Kim Gyu Tae
Published: November 2010

Previously, we introduced the double scan technique, which enables quantitative temperature profiling with a scanning thermal microscope (SThM) without distortion arising from heat transfer through the air. However, if the tip-sample thermal conductance is disturbed due to the extremely small size of the sample, such as carbon nanotubes, or an abrupt change in the topography, then quantitative measurement becomes difficult even with the double scan technique. Here, we developed the null-point method by which one can quantitatively measure the temperature of a sample without disturbances arising from the tip-sample thermal conductance, based on the principle of the double scan technique. We first checked the effectiveness and accuracy of the null-point method using 5 μm and 400 nm wide aluminum lines. Then, we quantitatively measured the temperature of electrically heated multiwall carbon nanotubes using the null-point method. Since the null-point method has an extremely high spatial resolution of SThM and is free from disturbance due to the tip-sample thermal contact resistance, and distortion due to heat transfer through the air, the method is expected to be widely applicable for the thermal characterization of many nanomaterials and nanodevices.
Can theory quantitatively model stratospheric photolysis?Ab initioestimate of absolute absorption cross sections of ClOOCl
Authors: Ončák Milan , Šištík Lukáš , Slavíček Petr
Published: November 2010

We have calculated the absorption spectrum of dichlorine peroxide (ClOOCl) in the spectral range 250–400 nm. We have employed five different approaches to quantitatively model the absorption cross section (empirical broadening scheme, linearized harmonic reflection principle and full reflection principle with ground state density calculated using harmonic approximation, classical molecular dynamics, and path-integral molecular dynamics). We have also tested various single and multireference methods. We found that (i) the excitation characteristics of ClOOCl are sensitive on molecular geometries and therefore the ground state density has to be properly sampled and that (ii) single-reference methods tend to overestimate the absorption cross section and lead to a blueshift in the absorption maximum. The absorption spectrum calculated at the CASPT2 level with complete active space-configuration interaction (CAS-SCF) transition dipole moment with the ground state sampled via path-integral molecular dynamics is in a good agreement with the experiment. We, however, did not reach full agreement in the atmospherically relevant low-energy tail of the spectrum. The general message is that quantitative predictions are difficult even for a relatively small molecule as ClOOCl and the convergence, with respect to the electronic structure method, basis set used, and ground state sampling, needs to be carefully examined.
UEDGE simulation of edge plasmas in DIII-D double null configurations
Authors: Porter G. D. , Petrie T. W. , Rognlien T. D. , Rensink M. E.
Published: November 2010

Analysis of plasma flow in the edge of double null hybrid mode DIII-D plasmas is reported. The two dimension fluid plasma code UEDGE [T. Rognlien et al., J. Nucl. Mater. 196–198, 347 (1992)] is used for the analysis. The effect of impurity radiation from intrinsic carbon sputtered from plasma facing surfaces is included as is the effect of plasma drifts. Two discharges in which the flux surfaces through the poloidal field nulls (X-points) are separated by 1 cm at the outer midplane are analyzed. The discharges differ only in the direction of the ion ∇B drift. It is shown that the flow of both primary ions and intrinsic impurities is dominated by the effect of plasma drifts. Variations in the recycling of deuterium ions, as seen in Dα emission profiles, are qualitatively consistent with experiment and are driven by the effect of E×B drifts associated with radial gradients of the electron temperature at the secondary separatrix. Trace argon impurity is introduced to simulate the transport of argon used in the experiment to enhance divertor radiation power. Penetration of the trace argon to the closed field lines depends on the direction of the ion ∇B drift, consistent with experiment. The analysis described here includes the effect of a deuterium gas puff to establish the “puff and pump” configuration. The poloidal flow of impurities is a balance between the projection of the parallel flow and poloidal drifts, primarily from E×B. It is shown that the effect of the gas puff is primarily to alter the electron temperature profile and thus affects impurity flow via alteration of E×B drifts, not via entrainment in deuterium ion parallel flow.
Negative refraction in three-dimensional point-dipolelike polaritonic crystals
Authors: Rose A. , Kempa K.
Published: November 2010

We propose two practical realizations of the point-dipole crystal, shown previously to be capable of negative refraction and other metamaterial and plasmonic properties. These are: an array of highly polarizable spheres, and the complementary array of spherical cavities in a highly polarizable medium. We study light propagation through these polaritonic crystals and show that they are capable of negative refraction, and can be constructed from available materials for experimental demonstrations at both microwave and optical frequencies.
Observation of the missing mode effect in a poly-phenylenevinylene derivative: Effect of solvent, chain packing, and composition
Authors: Wise Adam J. , Martin Thomas P. , Gao Jian , VanDerGeest Kori , Grey John K.
Published: November 2010

Optical emission spectra of poly[2-methoxy-5-[3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) in dilute solutions exhibit a vibronic progression interval (∼1225 cm−1) that does not correspond to any ground state vibrational mode frequency. This phenomenon is assigned as the missing mode effect (MIME) in which five key displaced polymer backbone vibrational modes in the range of 800–1600 cm−1 contribute to the MIME interval. Emission spectra are calculated by analytically solving the time-dependent Schrödinger equation using estimates of mode-specific vibrational displacements determined independently from preresonance Raman intensities. Emission spectra of MDMO-PPV thin films and nanoparticles are measured and lineshapes show an increase of the MIME frequency to ∼1340 cm−1 in addition to changes in vibronic intensity distributions and energies. Composite blend thin films consisting of MDMO-PPV and a fullerene derivative (1:1 w/w) exhibit a substantially larger MIME interval (∼1450 cm−1) that arises from an increase in polymer chain planarity. This structural change is most apparent from large decreases of the excited state displacement of an out-of-plane CH bending mode (961 cm−1) that becomes forbidden in the planar structure.
Microwave spectrum and structural parameters for the formamide-formic acid dimer
Authors: Daly Adam M. , Sargus Bryan A. , Kukolich Stephen G.
Published: November 2010

The rotational spectra for six isotopologues of the complex formed between formamide and formic acid have been measured using a pulsed-beam Fourier transform microwave spectrometer and analyzed to obtain rotational constants and quadrupole coupling parameters. The rotational constants and quadrupole coupling strengths obtained for H C12OOH–H2 N14COH are A=5889.465(2), B=2148.7409(7), 1575.1234(6), eQqaa=1.014(5), eQqbb=1.99(1), and eQqcc=−3.00(1) MHz. Using the 15 rotational constants obtained for the H C13OOH, HCOOD, DCOOH, and H2 N15CHO isotopologues, key structural parameters were obtained from a least-squares structure fit. Hydrogen bond distances of 1.78 Å for R(O3⋯H1) and 1.79 Å for R(H4⋯O1) were obtained. The “best fit” value for the ∠(C–O–H) of formic acid is significantly larger than the monomer value of 106.9° with an optimum value of 121.7(3)°. The complex is nearly planar with inertial defect Δ=−0.158 amu Å2. The formamide proton is moved out of the molecular plane by 15(3)° for the best fit structure. Density functional theory using B3PW91, HCTH407, and TPSS as well as MP2 and CCSD calculations were performed using 6-311++G(d,p) and the results were compared to experimentally determined parameters.
Three-dimensional linear instability in pressure-driven two-layer channel flow of a Newtonian and a Herschel–Bulkley fluid
Authors: Sahu K. C. , Matar O. K.
Published: November 2010

The three-dimensional linear stability characteristics of pressure-driven two-layer channel flow are considered, wherein a Newtonian fluid layer overlies a layer of a Herschel–Bulkley fluid. We focus on the parameter ranges for which Squire’s theorem for the two-layer Newtonian problem does not exist. The modified Orr–Sommerfeld and Squire equations in each layer are derived and solved using an efficient spectral collocation method. Our results demonstrate the presence of three-dimensional instabilities for situations where the square root of the viscosity ratio is larger than the thickness ratio of the two layers; these “interfacial” mode instabilities are also present when density stratification is destabilizing. These results may be of particular interest to researchers studying the transient growth and nonlinear stability of two-fluid non-Newtonian flows. We also show that the “shear” modes, which are present at sufficiently large Reynolds numbers, are most unstable to two-dimensional disturbances.
Structure of poly(ethylene glycol)–water mixture studied by polymer reference interaction site model theory
Authors: Xu Qinzhi , Mi Jianguo , Zhong Chongli
Published: November 2010

In this work, the polymer reference interaction site model is applied to investigate the structure of poly(ethylene glycol) (PEG) aqueous solution with the strong hydrogen-bond interactions. In the theoretical model, the renormalized technique of electrostatic potentials is combined with our recently proposed multisite semiflexible chain model to describe the inter- and intramolecular correlations. To test the model for the description of hydrogen bonding, the intermolecular correlation functions of water, ethylene glycol (EG), and EG-water binary mixture are calculated. The results are in good agreement with the corresponding simulation or experimental data. The validated model is then employed to predict the intermolecular correlation functions of different sites of the PEG and its aqueous solution. Another priority of the model is that it can obtain the corresponding direct correlation functions directly.
Nonvolatile multiple-valued memory device using lateral spin valve
Authors: Kimura T. , Hara M.
Published: November 2010

The authors propose a nonvolatile multiple-valued memory based on a nonlocal spin valve structure. Multibit informations are formed by changing the magnetization configuration in a nonlocal voltage probe consisting of a magnetic multilayer. A simple calculation method for the spin-accumulation voltage induced in lateral ferromagnetic/nonmagnetic multilayered hybrid structures is also developed on the basis of the spin resistance model. The developed model enables us to find the thickness of each ferromagnetic layer for the optimized operation of the multiple-valued memory.
Chain contraction and nonlinear stress damping in primitive chain network simulations
Authors: Furuichi Kenji , Nonomura Chisato , Masubuchi Yuichi , Watanabe Hiroshi
Published: November 2010

Doi and Edwards (DE) proposed that the relaxation of entangled linear polymers under large deformation occurs in two steps: the fast chain contraction (via the longitudinal Rouse mode of the chain backbone) and the slow orientational relaxation (due to reptation). The DE model assumes these relaxation processes to be independent and decoupled. However, this decoupling is invalid for a generalized convective constraint release (CCR) mechanism that releases the entanglement on every occasion of the contraction of surrounding chains. Indeed, the decoupling does not occur in the sliplink models where the entanglement is represented by the binary interaction (hooking) of chains. Thus, we conducted primitive chain network simulations based on a multichain sliplink model to investigate the chain contraction under step shear. The simulation quantitatively reproduced experimental features of the nonlinear relaxation modulus G(t,γ). Namely, G(t,γ) was cast in the time-strain separable form, G(t,γ)=h(γ)G(t) with h(γ)=damping function and G(t)=linear modulus, but this rigorous separability was valid only at times t comparable to the terminal relaxation time, although a deviation from this form was rather small (within ±10%) at t>τR (longest Rouse relaxation time). A molecular origin of this delicate failure of time-strain separability at t∼τR was examined for the chain contour length, subchain length, and subchain stretch. These quantities were found to relax in three steps, the fast, intermediate, and terminal steps, governed by the local force balance between the subchains, the longitudinal Rouse relaxation, and the reptation, respectively. The contributions of the terminal reptative mode to the chain length relaxation as well as the subchain length/stretch relaxation, not considered in the original DE model, emerged because the sliplinks (entanglement) were removed via the generalized CCR mechanism explained above and the reformation of the sliplinks was slow at around the chain center compared to the more rapidly fluctuating chain end. The number of monomers in the subchain were kept larger at the chain center than at the chain end because of the slow entanglement reformation at the center, thereby reducing the tension of the stretched subchain at the chain center compared to the DE prediction. This reduction of the tension at the chain center prevented completion of the length equilibration of subchains at t∼τR (which contradicts to the DE prediction), and it forces the equilibration to complete through the reptative mode at t⪢τR. The delicate failure of time-strain separability seen for G(t,γ) at t∼τR reflects this retarded length equilibration.
Electrical characterization of PMN–28%PT(001) crystals used as thin-film substrates
Authors: Herklotz Andreas , Plumhof Johannes D. , Rastelli Armando , Schmidt Oliver G. , Schultz Ludwig , Dörr Kathrin
Published: November 2010

Ferroelectric and piezoelectric properties of (001) 0.72PbMg1/3Nb2/3O3–0.28PbTiO3 (PMN–28%PT) single crystals have been investigated from cryogenic temperatures to 475 K. PMN–28%PT is used as piezoelectric substrate, e.g., in multiferroic heterostructures. Electric field-induced phase transformations have been examined by electrical characterization including measurements of polarization loops, dielectric permitivitty, and the resistance change in La0.7Sr0.3MnO3 films deposited on the (001) face. The relaxor ferroelectric transition behavior was studied by means of time-dependent current measurements. A phase diagram is set up. PMN–28%PT is found to be at the border of the appearance of the monoclinc phase (MC) bridging the rhombohedral-tetragonal (R-T) transformation at higher PbTiO3 contents. Measurements of the lattice expansion reveal that a high piezoelectric effect persists down to low temperatures. Therefore, PMN–28%PT single crystals are found to be appropriate substrates for application of piezoelectric strain to thin films over a broad temperature range.
Growth and characteristics of tantalum oxide thin films deposited using thermionic vacuum arc technology
Authors: Vladoiu Rodica , Ciupina Victor , Mandes Aurelia , Dinca Virginia , Prodan Madalina , Musa Geavit
Published: November 2010

Tantalum pentoxide (Ta2O5) thin films were synthesized using thermionic vacuum arc (TVA) technology. TVA is an original deposition method using a combination of anodic arc and electron gun system for the growth of thin films from solid precursors under vacuum of 10−6 Torr. The properties of the deposited Ta2O5 thin films were investigated in terms of wettability, refractive index, morphology, and structure. The surface free energy was determined by means of surface energy evaluation system indicating a hydrophilic character and the refractive index was measured by Filmetrics F20 device. The morphology was determined from bright field transmission electron microscopy (TEM) image performed by Philips CM 120 ST TEM system. It exhibits nanoparticles of 3–6 nm diameter smoothly distributed. Selected area electron diffraction pattern revealed the contrast fringes given by complex polycrystalline particles included in the amorphous film. The measured fringes could be indexed using monoclinic structure of Ta2O5.
Noise temperature and beam pattern of an NbN hot electron bolometer mixer at 5.25 THz
Authors: Zhang W. , Khosropanah P. , Gao J. R. , Bansal T. , Klapwijk T. M. , Miao W. , Shi S. C.
Published: November 2010

We report the measured sensitivities of a superconducting NbN hot electron bolometer (HEB) heterodyne receiver at 5.25 THz. Terahertz (THz) radiation is quasioptically coupled to a HEB mixer with a lens and a spiral antenna. Using a measurement setup with black body calibration sources and a beam splitter in vacuo, and an antireflection coated Si lens, we obtained a double sideband (DSB) receiver noise temperature (TrecDSB) of 1150 K, which is nine times hν/2k, where h is the Planck constant, ν the frequency, and k the Boltzmann constant. In addition, the measured far field beam patterns of the integrated lens antenna show nearly collimated beams from 2.5 to 5.3 THz that allow reliable measurement of TrecDSB using the vacuum setup. Our experimental results in combination with an antenna-to-bolometer coupling simulation suggest that the HEB mixer can work well at least up to 6 THz, making it suitable for next generation of high-resolution spectroscopic space telescopes and, in particular, for the detection of the neutral atomic oxygen line at 4.7 THz.
Nb / Al – AlO x – Nb superconducting heterostructures: A promising class of self-shunted Josephson junctions
Authors: Lacquaniti V. , De Leo N. , Fretto M. , Sosso A. , Belogolovskii M.
Published: November 2010

The measurements of dc Josephson and quasiparticle current-voltage characteristics of four-layered Nb/Al–AlOx–Nb devices with a fixed Nb thickness of 270 nm and Al thicknesses ranging from 40 to 120 nm are reported and analyzed in the framework of a microscopic model developed to determine stationary properties of dirty limit double-barrier junctions. It is shown that the temperature dependence of the supercurrent as well as the values of characteristic voltages are well reproduced by the model calculations with only one fitting parameter. We have revealed a hysteretic-to-nonhysteretic transition in the current-voltage characteristics of our junctions at temperatures near 4.2 K and argue that this effect is caused by two factors: high-transparency insulating barrier with a broad distribution of the transmission coefficient and the temperature as a tuning parameter, which decreases the McCumber–Stewart parameter from values above unity at low temperatures to less than one above 4.2 K. Finally, we show how and why the temperature stability of the proposed Josephson devices can be significantly improved by choosing an appropriate Al thickness.
Kane-like electrons in type II/III heterostructures versus Dirac-like electrons in graphene
Authors: Dragoman D.
Published: November 2010

The propagation of charge carriers in graphene is compared to that in type II/III heterostructures for which a two-band Kane model is appropriate. In particular, conditions for a quantitative analogy between these two cases are searched for and found to be quite restrictive. The analysis in this paper shows that the essential property of graphene is not the spinor character of its wave function but the linear dispersion relation, which does not hold in finite-gap two-band Kane-type semiconductors. Therefore, Kane-like and Dirac-like charge carriers behave differently, except in zero-band gap semiconductor superlattices.