bluuebunny/crossref_metadata_2025 huggingface dataset:
Stabilität und Variabilitätvon Wettkampfangst
Authors: Ehrlenspiel Felix , Graf Karla , Kühn Christian , Brand Ralf
Published: February 2011

Zusammenfassung. Die Trait-State Theorie der Angst ( Spielberger, 1972 ) postuliert Ängstlichkeit (A-Trait) als überdauerndes Merkmal einer Person in verschiedenen Situationen mit Angst zu reagieren und den Angstzustand (A-State) als situativ variierendes Merkmal einer Reaktion auf aktuell als bedrohlich wahrgenommene Situationen. Mit nicht-sportspezifischen Messverfahren konnten zentrale Annahmen der Theorie im Bereich des Sports nur teilweise bestätigt werden ( Schwenkmezger, 1985 ). Die vorliegende Untersuchung überprüft diese Annahmen nun mit Hilfe weiterentwickelter diagnostischer und statistischer Methoden. Die sportspezifischen, multidimensionalen und auf einen Wettkampf bezogenen Messungen von Angst und Ängstlichkeit bestätigen theoriekonform die Annahmen zur Stabilität von A-Trait und zur Variabilität von A-State, wobei A-Trait offenbar nicht nur das Ausmaß sondern auch die Veränderung von A-State beeinflusst. Jedoch deuten Untersuchungen mit wiederholter Messung von A-State vor verschiedenen Wettkämpfen auf geringe relative Konsistenz (d. h. interindividuelle Unterschiede waren transsituational wenig stabil). Für die Praxis bedeuten die Ergebnisse, dass zur genaueren Beschreibung des Wettkampfangsterlebens von Sportlerinnen und Sportlern die einfache Erfassung des A-Trait durch eine mehrmalige Erfassung des A-State ergänzt werden sollte.
Parameter estimation of coupled water and energy balance models based on stationary constraints of surface states
Authors: Sun Jian , Salvucci Guido D. , Entekhabi Dara , Farhadi Leila
Published: February 2011

We use a conditional averaging approach to estimate the parameters of a land surface water and energy balance model and then use the estimated parameters to partition net radiation into latent, sensible, and ground heat fluxes and precipitation into evapotranspiration and drainage plus runoff. Through conditional averaging of the modeled fluxes with respect to soil moisture and temperature, we write an objective function that approximates the temperature‐ and moisture‐dependent errors of the modeled fluxes in terms of atmospheric forcing (e.g., precipitation and radiation), surface states (moisture (S) and temperature (Ts)), and model parameters. The novelty of the approach is that the error term is estimated without comparison to measured fluxes. Instead, it is inferred from the deviation of the conditionally averaged tendency terms (expectation and expectation ) from zero since each of these terms equals zero in stationary systems but diverges from zero in the presence of misspecified parameters. Minimization of the approximated error yields parameters for model applications. This strategy was previously studied for simple water balance models using soil moisture conditional averaging. Here we extend the idea to include energy balance fluxes and surface temperature conditioning. The method is tested at two AmeriFlux sites, Vaira Ranch (California) and Kendall Grassland (Arizona). The estimated fluxes (using only observed forcing and state variables) are in reasonable agreement with field measurements. Because this method is based on conditional averages, it can be applied to situations with subsampled or missing data; that is, continuous integration in time is not required.
Academic doping or Viagra for the brain?
Authors: Lucke Jayne C , Bell Stephanie K , Partridge Bradley J , Hall Wayne D
Published: February 2011

The use of neuropharmaceuticals for recreation and mental enhancement is set to increase. Can we learn from past experiences with other drugs, to predict the response of the public and regulators?
Intra- and Multicenter Reproducibility of Pulsed, Continuous and Pseudo-Continuous Arterial Spin Labeling Methods for Measuring Cerebral Perfusion
Authors: Gevers Sanna , van Osch Matthias J , Bokkers Reinoud PH , Kies Dennis A , Teeuwisse Wouter M , Majoie Charles B , Hendrikse Jeroen , Nederveen Aart J
Published: February 2011

Intra- and multicenter reproducibility of currently used arterial spin labeling (ASL) methods were assessed at three imaging centers in the Netherlands, equipped with Philips 3TMR scanners. Six healthy participants were scanned twice at each site. The imaging protocol consisted of continuous ASL (CASL), pseudo-continuous ASL (p-CASL) with and without background suppression, pulsed ASL (PASL) with single and multiple inversion times (TIs), and selective ASL for segmentation. Reproducibility was expressed in terms of the coefficient of repeatability and the repeatability index. Voxelwise analysis of variance was performed, yielding brain maps that reflected regional variability. Intra- and multicenter reproducibility were comparable for all methods, except for single TI PASL, with better intracenter reproducibility (F-test of equality of two variances, P < 0.05). Pseudo-continuous ASL and multi TI PASL varied least between sites. Variability maps of all methods showed most variability near brain-feeding arteries within sessions and in gray matter between sessions. On the basis of the results of this study, one could consider the use of reference values in clinical routine, with whole-brain p-CASL perfusion varying < 20% over repeated measurements within the same individuals considered to be normal. Knowledge on regional variability allows for the use of perfusion-weighted images in the assessment of local cerebral pathology.
Pressure cell for investigations of solid–liquid interfaces by neutron reflectivity
Authors: Kreuzer Martin , Kaltofen Thomas , Steitz Roland , Zehnder Beat H. , Dahint Reiner
Published: February 2011

We describe an apparatus for measuring scattering length density and structure of molecular layers at planar solid–liquid interfaces under high hydrostatic pressure conditions. The device is designed for in situ characterizations utilizing neutron reflectometry in the pressure range 0.1–100 MPa at temperatures between 5 and 60 °C. The pressure cell is constructed such that stratified molecular layers on crystalline substrates of silicon, quartz, or sapphire with a surface area of 28 cm2 can be investigated against noncorrosive liquid phases. The large substrate surface area enables reflectivity to be measured down to 10−5 (without background correction) and thus facilitates determination of the scattering length density profile across the interface as a function of applied load. Our current interest is on the stability of oligolamellar lipid coatings on silicon surfaces against aqueous phases as a function of applied hydrostatic pressure and temperature but the device can also be employed to probe the structure of any other solid–liquid interface.
Permittivity scaling in Ba1−xSrxTiO3 thin films and ceramics
Authors: Aygün Seymen M. , Ihlefeld Jon F. , Borland William J. , Maria Jon-Paul
Published: February 2011

A dramatic enhancement in the electromechanical response of barium titanate thin films is demonstrated by understanding and optimizing the relationship between organic removal, crystallization, and microstructure, which therefore results in pore elimination, larger grain sizes, and superior densification. The combination enables one to produce bulk-like dielectric properties in a thin film with a room temperature permittivity value above 3000. This advancement in complex oxide thin film processing science creates a new perspective from which to compare, parameterize, and better understand a collection of literature data concerning the manner in which the dielectric response of BaTiO3 depends upon physical dimensions. We are consequently able to apply a single physical model to bulk ceramic and thin film systems, and so demonstrate that the existence of parasitic interfacial layers are not needed to explain dielectric scaling. This work is instrumental in illustrating that extrinsic contributions to scaling are predominant, and that a fundamental understanding of material synthesis provides important opportunities to broaden the spectrum of nonlinear electromechanical properties that can be achieved in ferroelectric thin films.
Structural studies of water in hydrophilic and hydrophobic mesoporous silicas: An x-ray and neutron diffraction study at 297 K
Authors: Jelassi J. , Grosz T. , Bako I. , Bellissent-Funel M.-C. , Dore J. C. , Castricum H. L. , Sridi-Dorbez R.
Published: February 2011

Water confined in a sol–gel network has been characterized by x-ray and neutron diffraction for two samples of mesoporous silica: one with a hydrophilic character (a nonmodified one) and another with a hydrophobic character (a modified one with a methylated internal pore surface). The pore size has been previously characterized [J. Jelassi et al., Phys. Chem. Chem. Phys. 134, 1039 (2010)] to have a mean pore diameter of approximately 55 Å. The diffraction measurements presented in this paper have been made at room temperature [293 K] for a filling factor of 0.45, giving a mean thickness of 8–9 Å for the water layer. The results show that the local order of the confined water molecules in the intermediate region of 3–6 Å is significantly different from that of the bulk water and also for the two different environments. For the hydrophilic sample, the siloxyl groups at the surface modify the water structure through the effects of interfacial hydrogen-bonding, which influences the orientational configuration of local water molecules and creates a modified spatial arrangement in the pore. In the case of the hydrophobic sample, there is no specific interaction with the pore wall, which is primarily van der Waals type, and the water molecules at the interface are differently oriented to create a hydrogen-bonded network linked more directly to the rest of the water volume. In the present circumstances, the thickness of the water layer has a relatively small dimension so that the interpretation of the measured diffraction pattern is not as straightforward as for the bulk liquids, and it is necessary to consider the effects of diffraction-broadening from a distributed sample volume and also the contribution from cross-terms that remain after conducting a “wet-minus-dry” analysis procedure. These analytic difficulties are discussed in the context of the present measurements and compared with the work of other groups engaged in the study of water confined in different environments. The present results, again, emphasize the complexity influencing the properties of water in a confined geometry and the strong influence of surface interactions on its behavior.
Laser control of free-carrier density in solids through field-enhanced multiphonon tunneling recombination
Authors: Zheltikov A. M. , Shneider M. N. , Voronin A. A. , Miles R. B.
Published: February 2011

Enhancement of multiphonon tunneling recombination of free carriers in strong laser fields is shown to offer a mechanism whereby ultrafast carrier-density dynamics in a semiconductor can be controlled by properly shaped laser pulses. This regime of laser–solid interaction enables an ultrafast switching of optical and electric properties of semiconductor materials, suggesting new strategies for laser micromachining and nanomachining, optical data processing, and ultrafast plasmonics.
Internal stresses and formation of switchable nanowires at thin silica film edges
Authors: Phillips J. C.
Published: February 2011

At vertical edges, thin films of silicon oxide (SiO2−x) can contain defect-free semiconductive c-Si layered nanocrystals (Si NC) embedded in and supported by an insulating g-SiO2 matrix. Yaoet al. [Appl. Phys. A (in press)] have shown that a trenched thin film geometry enables the NC to form switchable nanowires (SNW) when trained by an applied field. The field required to form SNW decreases rapidly within a few cycles, or by annealing at 600 °C in even fewer cycles, and is stable to 700 °C. Here we describe the intrinsic evolution of Si NC and SNW in terms of the competition between internal stresses and electro-osmosis. The analysis relies heavily on experimental data from a wide range of thin film studies, and it explains why a vertical edge across the planar polySi-SiO2−x interface is necessary to form SNW. The discussion also shows that the formation mechanisms of Si NC and polySi/SiO2−x SNW are intrinsic and result from optimization of nanowire connectivity in the presence of residual host misfit stresses.
Transmission line based short pulse generation circuits in a 0.13 μm complementary metal–oxide–semiconductor technology
Authors: Zou Huan , Geng Yongtao , Wang Pingshan
Published: February 2011

A few traditional pulse forming circuits are implemented and compared in a commercial 0.13 μm digital CMOS technology. Standard on-chip transmission lines are used as pulse forming lines (PFLs), while CMOS transistors are used as switches. The shortest output pulses of these circuits are analyzed and compared through Cadence Spectre simulations. All the CMOS circuits are fabricated in the commercial technology. Pulses of ∼170 ps durations and 120–400 mV amplitudes are obtained when the power supply is tuned from 1.2 to 2 V. The results show that these traditional PFL based circuits can be implemented in standard CMOS technology for high power short pulse generations. Furthermore, the PFL circuits significantly extend the short pulse generation capabilities of CMOS technologies.
Response to “Comment on ‘A versatile thermoelectric temperature controller with 10 mK reproducibility and 100 mK absolute accuracy”’ [Rev. Sci. Instrum. 80, 126107 (2009)]
Authors: Libbrecht K. G. , Libbrecht A. W.
Published: February 2011

The preceding comment by Sloman points out that the absolute accuracy of a temperature controller may be compromised by thermistor self-heating. We measured the self-heating of the thermistor used in our temperature controller, verifying a systematic error of nearly 200 mK. However, this error is reduced by over an order of magnitude with a slight change in our original circuit design. With this change, our controller does achieve an absolute temperature accuracy of 100 mK, limited mainly by the stated absolute accuracy of the thermistor used in the circuit.
Photoionization of epichlorohydrin enantiomers and clusters studied with circularly polarized vacuum ultraviolet radiation
Authors: Daly Steven , Powis Ivan , Garcia Gustavo A. , Soldi-Lose Héloïse , Nahon Laurent
Published: February 2011

The photoionization of enantiomerically pure epichlorohydrin (C3H5OCl) has been studied using linearly and circularly polarized vacuum ultraviolet synchrotron radiation. The threshold photoelectron spectrum was recorded and the first three bands assigned using molecular orbital calculations for the expected conformers, although uncertain experimental conformer populations and an anticipated breakdown in Koopmans’ theorem leave some ambiguity. Measurements of the photoelectron circular dichroism (PECD) were obtained across a range of photon energies for each of these bands, using electron velocity map imaging to record the angular distributions, during which a record PECD chiral asymmetry factor of 32% was observed. A comparison with calculated PECD curves clarifies the assignment achieved using ionization energies alone and further suggests a likely relative population of the conformers. Threshold photoelectron–photoion coincidence methods were used to study the ionic fragmentation of epichlorohydrin. Fragment ion appearance energies show nonstatistical behavior with clear indications that the cationic epoxide ring is unstable and lower energy decay channels proceeding via ring breaking are generally open. Extensive neutral homochiral clusters of epichlorohydrin may be formed in supersonic molecular beam expansions seeded in Ar. Electron angular distribution measurements made in coincidence with dimer and trimer ions are used to effect an examination of the PECD associated with ionization of size-selected neutral cluster species, and these results differ clearly from PECD of the neutral monomer. The shifted ionization thresholds of the n-mers (n = 2, …, 7) are shown to follow a simple linear relationship, but under intense beam expansion conditions the monomer deviates from this relationship, and the monomer electron spectra tail to below the expected monomer adiabatic ionization potential (IP). PECD measurements made in coincidence with monomer ions obtained under different beam expansion conditions were used to identify unambiguously a contribution from dissociative photoionization of larger clusters to the monomer parent mass ion yield above and below its adiabatic IP.
Orientational dynamics for an amphiphilic-solvent solution
Authors: Heinzelmann G. , Figueiredo W. , Girardi M.
Published: February 2011

In this work, we performed Monte Carlo simulations on a lattice model for spontaneous amphiphilic aggregation, in order to study the orientational and hydrogen-bonding dynamics of water on different regions inside the micellar solution. We employed an associating lattice gas model that mimics the aqueous solvent, which presents a rich phase diagram with first- and second-order transition lines. Even though this is a simplified model, it makes possible to investigate the orientational dynamics of water in an equilibrium solution of amphiphiles, as well as the influence of the different phases of the solvent in the interfacial and bulk water dynamics. By means of extensive simulations, we showed that, at high temperatures, the behavior of the orientational relaxation and hydrogen bonding of water molecules in the bulk, first, and second hydration shells are considerable different. We observe the appearance of a very slow component for water molecules in the first hydration shell of micelles when the system reaches a high-density phase, consistent with previous theoretical and experimental studies concerning biological water. Also, at high temperatures, we find that water molecules in the second hydration shell of micelles have an orientational decay similar to that of bulk water, but with a generally slower dynamics. Otherwise, at low temperatures, we have two components for the orientational relaxation of bulk water in the low density liquid phase, and only a single component in the high density liquid (HDL) phase, which reflect the symmetry properties of the different phases of the solvent model. In the very dense region of water molecules in the first hydration shell of micelles at low temperatures, we find two components for the orientational relaxation on both liquid phases, one of them much slower than that in the single component of bulk water in the HDL phase. This happens even though our model does not present any hindrance to the water rotational freedom caused by the presence of the amphiphiles.
Implementation of Lees–Edwards periodic boundary conditions for direct numerical simulations of particle dispersions under shear flow
Authors: Kobayashi Hideki , Yamamoto Ryoichi
Published: February 2011

A general methodology is presented to perform direct numerical simulations of particle dispersions in a shear flow with Lees–Edwards periodic boundary conditions. The Navier–Stokes equation is solved in oblique coordinates to resolve the incompatibility of the fluid motions with the sheared geometry, and the force coupling between colloidal particles and the host fluid is imposed by using a smoothed profile method. The validity of the method is carefully examined by comparing the present numerical results with experimental viscosity data for particle dispersions in a wide range of volume fractions and shear rates including nonlinear shear-thinning regimes.
Mechanism of plasma-induced damage to low-k SiOCH films during plasma ashing of organic resists
Authors: Takeda Keigo , Miyawaki Yudai , Takashima Seigo , Fukasawa Masanaga , Oshima Keiji , Nagahata Kazunori , Tatsumi Tetsuya , Hori Masaru
Published: February 2011

Plasma-induced damage to porous SiOCH (p-SiOCH) films during organic resist film ashing using dual-frequency capacitively coupled O2 plasmas was investigated using the pallet for plasma evaluation method developed by our group. The damage was characterized by ellipsometry and Fourier-transform infrared spectroscopy. Individual and synergetic damage associated with vacuum ultraviolet (VUV) and UV radiation, radicals, and ions in the O2 plasma were clarified. It was found that the damage was caused not only by radicals but also by synergetic reactions of radicals with VUV and UV radiation emitted by the plasmas. It is noteworthy that the damage induced by plasma exposure without ion bombardment was larger than the damage with ion bombardment. These results differed from those obtained using an H2/N2 plasma for resist ashing. Finally, the mechanism of damage to p-SiOCH caused by O2 and H2/N2 plasma ashing of organic resist films is discussed. These results are very important in understanding the mechanism of plasma-induced damage to p-SiOCH films.
Current sharing between the metallic and superconducting layers of high temperature superconductor coated conductors operated above their critical current
Authors: Bernstein Pierre , McLoughlin Conor , Thimont Yohann , Sirois Frédéric , Coulombe Jonathan
Published: February 2011

In this contribution, we report and discuss the physical meaning of pulse current measurements carried out on coated conductors (CCs) consisting of a superconducting YBCO film deposited on a Hastelloy substrate and coated with a thin metallic layer. The high current (up to 1000 A) and short duration pulses have allowed us to determine the current-voltage characteristics of two different samples in a situation near that of zero injected energy and therefore remove the bias resulting from the temperature rise during the measurement. The characteristics obtained show a flux creep region and two linear regimes. The first linear regime is the flux flow regime. In this regime, we show that there is a constant vortex velocity that depends on the metal film resistivity. The second linear regime is also a vortex regime, but its precise nature is less clear. We propose models describing both linear regimes, in agreement with the measurements. Finally, we discuss the consequences of these results for the applications of CCs in devices for power systems, especially fault current limiters and power transmission cables.
Fluctuating lattice-Boltzmann model for complex fluids
Authors: Ollila Santtu T. T. , Denniston Colin , Karttunen Mikko , Ala-Nissila Tapio
Published: February 2011

We develop and test numerically a lattice-Boltzmann (LB) model for nonideal fluids that incorporates thermal fluctuations. The fluid model is a momentum-conserving thermostat, for which we demonstrate how the temperature can be made equal at all length scales present in the system by having noise both locally in the stress tensor and by shaking the whole system in accord with the local temperature. The validity of the model is extended to a broad range of sound velocities. Our model features a consistent coupling scheme between the fluid and solid molecular dynamics objects, allowing us to use the LB fluid as a heat bath for solutes evolving in time without external Langevin noise added to the solute. This property expands the applicability of LB models to dense, strongly correlated systems with thermal fluctuations and potentially nonideal equations of state. Tests on the fluid itself and on static and dynamic properties of a coarse-grained polymer chain under strong hydrodynamic interactions are used to benchmark the model. The model produces results for single-chain diffusion that are in quantitative agreement with theory.
Effects of Bi doping on the thermoelectric properties of β-Zn4Sb3
Authors: Qin X. Y. , Liu M. , Pan L. , Xin H. X. , Sun J. H. , Wang Q. Q.
Published: February 2011

The thermoelectric properties of Bi-doped compounds (Zn1−xBix)4Sb3 (x=0,0.0025,0.005,0.01) were studied experimentally as well as theoretically. The results indicate that low-temperature (T<300 K) thermal conductivity of moderately doped (Zn0.9975Bi0.0025)4Sb3 reduces remarkably as compared with that of Zn4Sb3 due to enhanced phonon scattering of impurity (dopant). Electrical resistivity and Seebeck coefficient increase monotonically with increase in the Bi content resulting mainly from decrease in carrier concentration. Moreover, first-principle calculations were performed on the occupation options of Bi atoms in β-Zn4Sb3, which show that Bi will preferentially occupy the Zn sites and not Sb sites and act as donors, being consistent with the experimental observations. In addition, the lightly doped compound (Zn0.9975Bi0.0025)4Sb3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient, whose figure of merit, ZT, is about 1.5 times larger than that of β-Zn4Sb3 at 300 K.
Lead-free high-temperature dielectrics with wide operational range
Authors: Dittmer Robert , Jo Wook , Damjanovic Dragan , Rödel Jürgen
Published: February 2011

The dielectric, electrical and structural properties of (1–x)(0.94Bi1/2Na1/2TiO3–0.06BaTiO3)–xK0.5Na0.5NbO3 (BNT–BT–xKNN) with x=0.09, 0.12, 0.15, and 0.18 were investigated as potential candidates for high-temperature capacitors with a working temperature far beyond 200 °C. Temperature dependent dielectric permittivity (ε) showed two local broad maxima that at the optimal composition of KNN (x=0.18) are combined to form a plateau. This then results in a highly temperature-insensitive permittivity up to ∼300 °C at the expense of a small reduction in absolute permittivity values. High-temperature in situ x-ray diffraction study showed pseudocubic symmetry without obvious structural changes, which implies that the dielectric anomalies observed could only be a consequence of a slight change in space group. BNT–BT–0.18KNN showed a permittivity of ∼2150 at the frequency of 1 kHz at 150 °C with a normalized permittivity ε/ε150 °C varying no more than ±10% from 43 to 319 °C. With very good electrical properties persisting up to 300 °C, i.e., a resistivity on the order of magnitude of 108 Ω m and the RC constant of about 1 s, the examined BNT–BT–xKNN compositions present a good starting point for the development of high-temperature capacitor materials.
Numerical model of current-voltage characteristics and efficiency of GaAs nanowire solar cells
Authors: LaPierre R. R.
Published: February 2011

Numerical simulation of current-voltage (J-V) characteristics of III-V nanowire core-shell p-n junction diodes under illuminated conditions is presented with an emphasis on optimizing the nanowire design for photoconversion efficiency. Surface recombination and depletion effects are found to play a dominant role in the J-V characteristics. The impact of surface charge density, surface recombination velocity, doping concentration, and nanowire geometry are investigated. Investigation of contacting methodology indicated that solar cell efficiency is degraded with electrical contacts on the sidewalls of the nanowire due to Fermi level pinning at the metal/semiconductor interface. On the other hand, contacts on the top of nanowires with sidewall passivation provide solar cell performance close to the detailed balance efficiency limit of ∼30%. Elimination of the thin film between nanowires produces a smaller dark current and improved cell performance.
Two interacting particles in a spherical pore
Authors: Urrutia Ignacio , Castelletti Gabriela
Published: February 2011

In this work we analytically evaluate, for the first time, the exact canonical partition function for two interacting spherical particles into a spherical pore. The interaction with the spherical substrate and between particles is described by an attractive square-well and a square-shoulder potential. In addition, we obtain exact expressions for both the one particle and an averaged two particle density distribution. We develop a thermodynamic approach to few-body systems by introducing a method based on thermodynamic measures [I. Urrutia, J. Chem. Phys. 134, 104503 (2010)] for nonhard interaction potentials. This analysis enables us to obtain expressions for the pressure, the surface tension, and the equivalent magnitudes for the total and Gaussian curvatures. As a by-product, we solve systems composed of two particles outside a fixed spherical obstacle. We study the low density limit for a many-body system confined to a spherical cavity and a many-body system surrounding a spherical obstacle. From this analysis we derive the exact first order dependence of the surface tension and Tolman length. Our findings show that the Tolman length goes to zero in the case of a purely hard wall spherical substrate, but contains a zero order term in density for square-well and square-shoulder wall-fluid potentials. This suggests that any nonhard wall-fluid potential should produce a non-null zero order term in the Tolman length.
A semilinear wave equation with space–time dependent coefficients and a memory boundarylike antiperiodic condition: A low-frequency asymptotic expansion
Authors: Lê Út V.
Published: February 2011

This paper studies a low-frequency asymptotic expansion for a unique strong solution to an initial-boundary value problem of a semilinear wave equation. This equation admits space–time dependent coefficients and a memory boundarylike antiperiodic condition. For some small parameters from coefficients of this semilinear wave equation and of boundary conditions, we approximate a unique strong solution to this problem by a polynomial of these parameters, and coefficients of this polynomial are strong solutions of a sequence of well-defined linear initial-boundary value problems.
Gaussian fluctuations in tethered DNA chains
Authors: Zhao Shuang-Liang , Wu Jiamin , Gao Di , Wu Jianzhong
Published: February 2011

In a recent work [Gao et al., Appl. Phys. Lett. 134, 113902 (2007)], we reported a novel DNA separation method by tethering DNA chains to a solid surface and then stretching the DNA chains with an electric field. The anchor is such designed that the critical force to detach a DNA chain is independent of its length. Because the stretching force is proportional to the DNA net charge, a gradual increase of the electric field leads to size-based removal of the DNA strands from the surface and thus DNA separation. Originally proposed for separation of long double-stranded DNA chains (>10 000 bps), this method has been proven useful also for short single-stranded DNA fragments (<100 bases) for which the fluctuation force induced by the solvent becomes significant. Here we show that the fluctuation force can be approximately represented by a Gaussian model for tethered DNA chains. Analytical expressions have been derived to account for the dependence of the fluctuation force on the surface confinement, the polymer chain length, and the DNA tethering potential. The theoretical predictions are found to coincide with experiment.
Experimental and theoretical study on generalized oscillator strengths of the valence-shell electronic excitations in CF4
Authors: Watanabe Noboru , Suzuki Daisuke , Takahashi Masahiko
Published: February 2011

We report an angle-resolved electron energy loss spectroscopy (EELS) study on the valence-shell electronic excitations in CF4. Experimentally momentum-transfer-dependent generalized oscillator strengths (GOSs) or GOS profiles for low-lying electronic excitations at 12.6, 13.8, and 14.8 eV are derived from EELS spectra measured at an incident electron energy of 3 keV. We also calculate GOS profiles using theoretical wave functions at the equation-of-motion coupled cluster singles and doubles level. There are good agreements between experiment and theory except for a significant discrepancy at small momentum transfer for the 1tl → 3s Rydberg excitation at 12.6 eV. The experimental GOS profile for 1tl → 3s exhibits a shape that is typical of a dipole allowed transition, while the excitation is formally dipole forbidden. This symmetry breaking behavior is rationally accounted for by qualitatively analyzing the nature of vibronic coupling effects. For the excitation band at 13.8 eV, a shoulder and extrema are observed in the GOS profile and are then found to be mainly due to the 21T2 transition. Furthermore, the theoretical GOS profile for the 21T2 transition exhibits a remarkable oscillatory pattern; its origin is discussed by considering multicenter interference effects. For the 14.8 eV excitation band, the predominant nondipole nature of the underlying transitions are revealed and comparisons with the theoretical calculations show that major contributions to this band come from the 4t2 → 3p excitation.
Triaxial stress distributions in Cu/low-k interconnect features
Authors: Murray Conal E. , Besser Paul R. , Ryan E. Todd , Jordan-Sweet Jean L.
Published: February 2011

The distribution of triaxial stresses within single damascene Cu/organosilicate interconnect structures as a function of linewidth, ranging from 45 to 250 nm, was measured using x-ray diffraction. Least-squares minimization techniques were employed to determine the volume-averaged stress tensors of the Cu features. Longitudinal Cu stress values increased for linewidths below 100 nm, while transverse stresses decreased with decreasing linewidth below 100 nm due to the interplay between the Cu microstructure and the feature geometry. Large tensile out-of-plane stresses were observed in all of the lines demonstrating the constraint imposed by the barrier layers that encapsulate the Cu.
Interface proximity effects on ionic conductivity in nanoscale oxide-ion conducting yttria stabilized zirconia: An atomistic simulation study
Authors: Sankaranarayanan Subramanian K. R. S. , Ramanathan Shriram
Published: February 2011

We present an atomistic simulation study on the size dependence of dopant distribution and the influence of nanoscale film thickness on carrier transport properties of the model oxide-ion conductor yttria stabilized zirconia (YSZ). Simulated amorphization and recrystallization approach was utilized to generate YSZ films with varying thicknesses (3–9 nm) on insulating MgO substrates. The atomic trajectories generated in the molecular dynamics simulations are used to study the structural evolution of the YSZ thin films and correlate the resulting microstructure with ionic transport properties at the nanoscale. The interfacial conductivity increases by 2 orders of magnitude as the YSZ film size decreases from 9 to 3 nm owing to a decrease in activation energy barrier from 0.54 to 0.35 eV in the 1200–2000 K temperature range. Analysis of dopant distribution indicates surface enrichment, the extent of which depends on the film thickness. The mechanisms of oxygen conductivity for the various film thicknesses at the nanoscale are discussed in detail and comparisons with experimental and other modeling studies are presented where possible. The study offers insights into mesoscopic ion conduction mechanisms in low-dimensional solid oxide electrolytes.
Effects of polydisperse crowders on aggregation reactions: A molecular thermodynamic analysis
Authors: Shah Dhawal , Tan Aik Lee , Ramakrishnan Vigneshwar , Jiang Jianwen , Rajagopalan Raj
Published: February 2011

Intracellular crowding in biological systems is usually mimicked in in vitro experiments by adding single crowders at high volume fractions, without taking into consideration the polydispersity of the crowders in the cellular environment. Here, we develop a molecular thermodynamic formalism to examine the effects of size-polydispersity of crowders on aggregation reaction equilibria. Although the predominantly common practice so far has been to appeal to the entropic (excluded-volume) effects in describing crowding effects, we show that the internal energy (hence, the enthalpy) of the system could dramatically alter the effects, even qualitatively, particularly in the case of a mixture of crowders, depending on the changes in the covolume of the products relative to that of the reactants and on the preferential binding or exclusion of the crowders by the reactants and products. We also show that in the case of polydisperse crowders the crowders with the largest size difference dominate the overall changes in the yield of the reaction, depending on the individual concentrations of the crowders.
Convergence of vibrational angular momentum terms within the Watson Hamiltonian
Authors: Neff Michael , Hrenar Tomica , Oschetzki Dominik , Rauhut Guntram
Published: February 2011

Vibrational angular momentum terms within the Watson Hamiltonian are often considered negligible or are approximated by the zeroth order term of an expansion of the inverse of the effective moment of inertia tensor. A multimode expansion of this tensor up to second order has been used to study the impact of first and second order terms on the vibrational transitions of N2H2 and HBeH2BeH. Comparison with experimental data is provided. The expansion of the tensor can be exploited to introduce efficient prescreening techniques.
De Haas–van Alphen effect in 2D systems: application to mono- and bilayer graphene
Authors: Luk’yanchuk Igor A.
Published: February 2011

A generalization of the Shoenberg theory of de Haas–van Alphen magnetic oscillations in 2D metals to the case of electrons with arbitrary spectral dispersion is used to propose a method for determining the nature of charge carriers in the 2D conducting systems mono- and bilayer graphene. We analyze an analytical expression for the oscillating susceptibility as a function of chemical potential and determine its behavior for carriers with normal parabolic and Dirac-like linear spectra, which can be detected experimentally.
The interaction of electromagnetic wave and plasma wave in an electron beam-ion channel system
Authors: Su D. , Tang C. J.
Published: February 2011

The features of the waves and the instability induced by the interaction of electromagnetic (EM) wave with plasma wave in the electron beam-ion channel system are studied. Characteristics of waves in the system are displayed through the dispersion relation and two kinds of EM instabilities are found. The first one is excited by the interaction of the fast plasma wave and the forward EM wave, and the other one is induced by the coupling of the fast plasma wave and the backward EM wave, the numerical results show that this is caused by the virtual cathode oscillation. The conditions of these EM instabilities are given and the related physical mechanisms have been discussed in detail.
Free-boundary magnetohydrodynamic equilibria with flow
Authors: Schmitt R. F. , Guazzotto L. , Strauss H. , Park G. Y. , Chang C.-S.
Published: February 2011

The finite-element M3D code [W. Park et al., Phys. Plasmas 6, 1796 (1999)] has been modified to include a free-boundary equilibrium solver with arbitrary toroidal and poloidal flows. With this modification, the M3D code now has the capability to self-consistently model two essential ingredients necessary for equilibrium calculations in the edge region, namely, free-boundary and arbitrary flow. As a free-boundary code, M3D includes the separatrix and scrape-off layer regions in the equilibrium calculation. Poloidal flows in the subsonic, supersonic, and transonic regimes can be calculated with the new version of the M3D code. Calculation results show that the presence of equilibrium flows, in particular those next to the plasma boundary, can considerably influence the position of the X-point and magnetic separatrix shape/location and hence the position of the strike point on the divertor plates. Moreover, it is shown that poloidal flow is not a rigid-body rotation, with the fastest flows occurring on the inboard side of the plasma. A numerical confirmation of the “de Laval nozzle” model of Betti and Freidberg [R. Betti and J. P. Freidberg, Phys. Plasmas 7, 2439 (2000)] for free-boundary equilibrium calculations is obtained, with the formation of the predicted discontinuities between regions of subsonic and supersonic flows (with respect to the poloidal sound speed). Finally, a detailed comparison between isentropic and isothermal equilibria is presented, showing qualitative analogies and quantitative differences.
Impact of plasma poloidal rotation on resistive wall mode instability in toroidally rotating plasmas
Authors: Aiba N. , Shiraishi J. , Tokuda S.
Published: February 2011

Stability of resistive wall mode (RWM) is investigated in a cylindrical plasma and an axisymmetric toroidal plasma by taking into account not only toroidal rotation but also poloidal rotation. Since the Doppler shifted frequency is responsible for the RWM stability, the modification of this Doppler shifted frequency by poloidal rotation affects the rotation effect on RWM. When a poloidal rotation frequency is not so large, the effect of poloidal rotation on the RWM stability can be approximately treated with the modified toroidal rotation frequency. In a toroidal plasma, this modified frequency is determined by subtracting a toroidal component of the rotation parallel to the magnetic field from the toroidal rotation frequency. The poloidal rotation that counteracts the effect of the Doppler shift strongly reduces the stabilizing effect of toroidal rotation, but by changing the rotational direction, the poloidal rotation enhances this stabilizing effect. This trend is confirmed in not only a cylindrical plasma but also a toroidal plasma. This result indicates that poloidal rotation produces the dependence of the critical toroidal rotation frequency for stabilizing RWM on the rotational direction of toroidal rotation in the same magnetic configuration.
Relativistic collision operators for modeling noninductive current drive by waves
Authors: Hu Y. J. , Hu Y. M. , Lin-Liu Y. R.
Published: February 2011

A weakly relativistic Fokker–Planck operator for electron-electron collision was first used by Karney and Fisch to calculate the efficiencies of current drive by waves with fast phase velocity [C. F. F. Karney and N. J. Fisch, Phys. Fluids 28, 116 (1985)]. The present work extends Karney and Fisch’s work by expressing the weakly relativistic collision operator in potential form, and working out a general Legendre expansion of the potential functions. This general Legendre expansion reproduces the results in Karney and Fisch’s paper and is useful in implementing the weakly relativistic operator in Fokker–Planck codes. To justify the use of the weakly relativistic collision operator for current drive applications under ITER conditions, a comparison is made of current drive efficiencies predicted by this operator and a fully relativistic collision operator. Good agreement between efficiencies predicted by these two models is found. This suggests that the weakly relativistic collision operator is sufficiently precise for modeling the current drive schemes under ITER conditions.
Modified magnetic field distribution in relativistic magnetron with diffraction output for compact operation
Authors: Li Wei , Liu Yong-gui
Published: February 2011

A modified magnetic field distribution in relativistic magnetron with diffraction output (MDO) for compact operation is proposed in this paper. The principle of how the modified magnetic field confines electrons drifting out of the interaction space is analyzed. The results of the particle-in-cell (PIC) simulations of the MDO with the modified magnetic field distribution show that the output power of the MDO is improved, and the long cylindrical waveguide used for collecting the drifting electrons can be omitted. The latter measure allows the horn antenna of the MDO to produce more focused energy with better directivity in the far field than it does with the long cylindrical waveguide. The MDO with the modified magnetic field distribution promises to be the real most compact narrow band high power microwave source.
Thin film flow on the inside surface of a horizontally rotating cylinder: Steady state solutions and their stability
Authors: Pougatch K. , Frigaard I.
Published: February 2011

We present an approximate evolution equation for the film thickness on the inner surface of a horizontally rotating cylinder and solve it numerically by a collocation method. The influences of gravity, inertia, viscous and surface tension forces, and liquid volume fraction are included in the model. We investigate steady two-dimensional solutions and their linear stability to both axially uniform and two-dimensional perturbations and map stable and unstable regions depending on the relevant dimensionless numbers. It is shown that while an increase of the liquid volume fraction or surface tension always has a destabilizing effect on the solution, inertia may stabilize or destabilize the flow depending on the values of other parameters. At the same time, the inertial influence on the solution itself is relatively small. To obtain more insights into the flow after the loss of stability, we examine the growth rate of disturbances and demonstrate that it varies significantly through the considered parameter range. In addition, we obtain the most unstable wave numbers. This provides a means to distinguish between capillary and inertial instabilities. Finally, we present some steady three-dimensional solutions to illustrate possible film shapes that can be obtained after the loss of stability.
Treecode-based generalized Born method
Authors: Xu Zhenli , Cheng Xiaolin , Yang Haizhao
Published: February 2011

We have developed a treecode-based O(Nlog N) algorithm for the generalized Born (GB) implicit solvation model. Our treecode-based GB (tGB) is based on the GBr6 [J. Phys. Chem. B 111, 3055 (2007)], an analytical GB method with a pairwise descreening approximation for the R6 volume integral expression. The algorithm is composed of a cutoff scheme for the effective Born radii calculation, and a treecode implementation of the GB charge–charge pair interactions. Test results demonstrate that the tGB algorithm can reproduce the vdW surface based Poisson solvation energy with an average relative error less than 0.6% while providing an almost linear-scaling calculation for a representative set of 25 proteins with different sizes (from 2815 atoms to 65456 atoms). For a typical system of 10k atoms, the tGB calculation is three times faster than the direct summation as implemented in the original GBr6 model. Thus, our tGB method provides an efficient way for performing implicit solvent GB simulations of larger biomolecular systems at longer time scales.