bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of the magnetization in pre-patterned half-metallic La0.7Sr0.3MnO3 nanostructures
Authors: Heidler J. , Rhensius J. , Vaz C. A. F. , Wohlhüter P. , Körner H. S. , Bisig A. , Schweitzer S. , Farhan A. , Méchin L. , Le Guyader L. , Nolting F. , Locatelli A. , Menteş T. O. , Niño M. Á. , Kronast F. , Heyderman L. J. , Kläui M.
Published: November 2012

The evolution of the magnetization configurations in highly spin polarized La0.7Sr0.3MnO3 (LSMO) thin film elements (20–60 nm in thickness) as a function of external magnetic field and temperature is studied by direct magnetic imaging using x-ray magnetic circular dichroism photoemission electron microscopy. The sample structuring is done via a pre-patterning process using a Cr mask layer. The LSMO grows amorphous on the Cr layer for the 20 nm thick film but polycrystalline at larger thicknesses. Temperature dependent studies allow for a direct comparison of the properties of the strained and unstrained LSMO regions on a single sample and show that the polycrystalline areas exhibit a higher TC compared to the epitaxial areas. The single crystalline areas are largely magnetically decoupled from the matrix. The magnetic switching between domain states and domain wall spin structures is determined for LSMO ring elements of varying size and thickness. We find that the magnetic field values required to depin domain walls or to nucleate domains increase with decreasing ring width due to the increasing role of shape anisotropy and edge defects. Both transverse and vortex domain walls are stable spin configurations at room temperature and at zero field. In particular, we demonstrate that the desired domain wall type can be selected by applying an appropriate field sequence.
Powder diffraction from solids in the terapascal regime
Authors: Rygg J. R. , Eggert J. H. , Lazicki A. E. , Coppari F. , Hawreliak J. A. , Hicks D. G. , Smith R. F. , Sorce C. M. , Uphaus T. M. , Yaakobi B. , Collins G. W.
Published: November 2012

A method of obtaining powder diffraction data on dynamically compressed solids has been implemented at the Jupiter and OMEGA laser facilities. Thin powdered samples are sandwiched between diamond plates and ramp compressed in the solid phase using a gradual increase in the drive-laser intensity. The pressure history in the sample is determined by back-propagation of the measured diamond free-surface velocity. A pulse of x rays is produced at the time of peak pressure by laser illumination of a thin Cu or Fe foil and collimated at the sample plane by a pinhole cut in a Ta substrate. The diffracted signal is recorded on x-ray sensitive material, with a typical d-spacing uncertainty of ∼0.01 Å. This diagnostic has been used up to 0.9 TPa (9 Mbar) to verify the solidity, measure the density, constrain the crystal structure, and evaluate the strain-induced texturing of a variety of compressed samples spanning atomic numbers from 6 (carbon) to 82 (lead). Further refinement of the technique will soon enable diffraction measurements in solid samples at pressures exceeding 1 TPa.
Quantum dynamics study of the competing ultrafast intersystem crossing and internal conversion in the “channel 3” region of benzene
Authors: Penfold T. J. , Spesyvtsev R. , Kirkby O. M. , Minns R. S. , Parker D. S. N. , Fielding H. H. , Worth G. A.
Published: November 2012

Time-resolved photoelectron spectroscopy can obtain detailed information about the dynamics of a chemical process on the femtosecond timescale. The resulting signal from such detailed experiments is often difficult to analyze and therefore theoretical calculations are important in providing support. In this paper we continue our work on the competing pathways in the photophysics and photochemistry of benzene after excitation into the “channel 3” region [R. S. Minns, D. S. N. Parker, T. J. Penfold, G. A. Worth, and H. H. Fielding, Phys. Chem. Chem. Phys. 12, 15607 (2010)]10.1039/c001671c with details of the calculations shown previously, building on a vibronic coupling Hamiltonian [T. J. Penfold and G. A. Worth, J. Chem. Phys. 131, 064303 (2009)]10.1063/1.3197555 to include the triplet manifold. New experimental data are also presented suggesting that an oscillatory signal is due to a hot band excitation. The experiments show that signals are obtained from three regions of the potential surfaces, three open channels, which are assigned with the help of simulations showing that following excitation into vibrationally excited-states of S1 the wavepacket not only crosses through the prefulvenoid conical intersection back to the singlet ground state, but also undergoes ultrafast intersystem crossing to low lying triplet states. The model is, however, not detailed enough to capture the full details of the oscillatory signal due to the hot band.
Accurate measurement of the through-plane water content of proton-exchange membranes using neutron radiography
Authors: Hussey D. S. , Spernjak D. , Weber A. Z. , Mukundan R. , Fairweather J. , Brosha E. L. , Davey J. , Spendelow J. S. , Jacobson D. L. , Borup R. L.
Published: November 2012

The water sorption of proton-exchange membranes (PEMs) was measured in situ using high-resolution neutron imaging in small-scale fuel cell test sections. A detailed characterization of the measurement uncertainties and corrections associated with the technique is presented. An image-processing procedure resolved a previously reported discrepancy between the measured and predicted membrane water content. With high-resolution neutron-imaging detectors, the water distributions across N1140 and N117 Nafion membranes are resolved in vapor-sorption experiments and during fuel cell and hydrogen-pump operation. The measured in situ water content of a restricted membrane at 80 °C is shown to agree with ex situ gravimetric measurements of free-swelling membranes over a water activity range of 0.5 to 1.0 including at liquid equilibration. Schroeder's paradox was verified by in situ water-content measurements which go from a high value at supersaturated or liquid conditions to a lower one with fully saturated vapor. At open circuit and during fuel cell operation, the measured water content indicates that the membrane is operating between the vapor- and liquid-equilibrated states.
Thermal surface signatures of ship propeller wakes in stratified waters
Authors: Voropayev S. I. , Nath C. , Fernando H. J. S.
Published: November 2012

When a ship moves in temperature stratified water, e.g., in the ocean diurnal thermocline, the propeller(s) as well as the turbulent boundary layer of the hull mix the surface water with underlying colder fluid. As a result, when observed from above, a temperature “wake signature” of ∼1–2 °C may be detected at the water surface. To quantify this phenomenon, theoretical modeling and physical experiments were conducted. The dominant processes responsible for thermal wake generation were identified and parameterized. Most important similarity parameters were derived and estimates for wake signature contrast were made. To verify model predictions, scaled experiments were conducted, with the water surface temperature measured using a sensitive infrared camera. Comparison of laboratory measurements with model estimates has shown satisfactory agreement, both qualitative and quantitatively. Estimates for ocean ship-wake scenarios are also given, which are supported by available field observations.
Band-engineered SrTiO3 nanowires for visible light photocatalysis
Authors: Fu Q. , He T. , Li J. L. , Yang G. W.
Published: November 2012

We have theoretically investigated the structural, electronic, and optical properties of perovskite SrTiO3 nanowires for use in visible light photocatalytic applications using pseudopotential density-functional theory calculations. The electronic structure calculations show that the band gap is modified in the SrTiO3 nanowires compared with that of the bulk. For TiO2-terminated nanowires, the mid-band states induced by the combination of oxygen and strontium atoms on the surface lead to a shift in the valence band toward the conduction band without interference from the edge of the conduction band, which reduces the band gap. On the contrary, the electronic states induced by the combination of oxygen and strontium atoms on the surface of SrO-terminated nanowires lead to a shift in the conduction band toward the valence band. The calculated optical results indicate that the absorption edge of the nanowires shift towards the red-light region. These theoretical results suggest that perovskite SrTiO3 nanowires are promising candidates for use in visible light photocatalytic processes such as solar-assisted water splitting reactions.
Apparatus to measure adsorption of condensable solvents on technical surfaces by photothermal deflection
Authors: Plimmer M. D. , du Colombier D. , Iraqi Houssaini N. , Silvestri Z. , Pinot P. , Hannachi R.
Published: November 2012

This article describes an instrument for the measurement of the mirage effect as a tool to determine the molar adsorption per unit surface area Y1 of condensable solvents in the presence of a non-condensable carrier gas. The present apparatus is a much improved version of previous prototypes developed in our laboratory and elsewhere with a higher surface bake-out temperature (150 °C rather than 40 °C), lower residual vacuum (3 Pa versus 100 Pa), greater sample surface (40 mm diameter instead of 10 mm), more powerful optical pump beam (150 W cf. 50 W), and larger saturated vapour preparation volume (4 L instead of 1 L). The new set-up also includes the in situ monitoring of the surface via a reflected HeNe laser beam for the real-time detection of the onset of condensation. Here, we give a detailed description of the various components, outline the experimental procedure, show typical results, and suggest some straightforward improvements.
Note: Silicon carbide telescope dimensional stability for space-based gravitational wave detectors
Authors: Sanjuán J. , Korytov D. , Mueller G. , Spannagel R. , Braxmaier C. , Preston A. , Livas J.
Published: November 2012

Space-based gravitational wave detectors are conceived to detect gravitational waves in the low frequency range by measuring the distance between proof masses in spacecraft separated by millions of kilometers. One of the key elements is the telescope which has to have a dimensional stability better than 1 pm Hz−1/2 at 3 mHz. In addition, the telescope structure must be light, strong, and stiff. For this reason a potential telescope structure consisting of a silicon carbide quadpod has been designed, constructed, and tested. We present dimensional stability results meeting the requirements at room temperature. Results at −60 °C are also shown although the requirements are not met due to temperature fluctuations in the setup.
An automated spin-assisted approach for molecular layer-by-layer assembly of crosslinked polymer thin films
Authors: Chan Edwin P. , Lee Jung-Hyun , Chung Jun Young , Stafford Christopher M.
Published: November 2012

We present the design of an automated spin-coater that facilitates fabrication of polymer films based on molecular layer-by-layer (mLbL) assembly. Specifically, we demonstrate the synthesis of ultrathin crosslinked fully-aromatic polyamide (PA) films that are chemically identical to polymer membranes used in water desalination applications as measured by X-ray photoelectron spectroscopy. X-ray reflectivity measurements indicate that the automated mLbL assembly creates films with a constant film growth rate and minimal roughness compared with the traditional interfacial polymerization of PA. This automated spin-coater improves the scalability and sample-to-sample consistency by reducing human involvement in the mLbL assembly.
Role of the dimensionality of the [GaX]2 network in the Zintl phases EuGa2X2
Authors: Singh Nirpendra , Pöttgen Rainer , Schwingenschlögl Udo
Published: November 2012

The structural, electronic, magnetic, optical, and thermoelectric properties of EuGa2X2 (X = P, As, and Sb) are investigated using first principles calculations (taking into account the onsite Coulomb interaction) and the semi-classical Boltzmann theory. The divalent nature of Eu fulfils the Zintl principle as is confirmed by the calculated total magnetic moments of ∼7 μB. A metallic behavior is obtained for all compounds. The optical spectra originate mainly from the transitions between occupied Eu 4f states and unoccupied Eu 5d states. It is demonstrated that the two-dimensional [Ga(P/As)]2 network in EuGa2P2 and EuGa2As2 is favorable for thermoelectric applications as compared to the three-dimensional [GaSb]2 network in EuGa2Sb2.
Correlation between deep-level defects and turn-on recovery characteristics in AlGaN/GaN hetero-structures
Authors: Nakano Yoshitaka , Irokawa Yoshihiro , Sumida Yasunobu , Yagi Shuichi , Kawai Hiroji
Published: November 2012

We report on a correlation between deep-level defects and turn-on recovery characteristics in AlGaN/GaN hetero-structures, employing Schottky barrier diodes. Photo-capacitance spectroscopy measurements reveal three specific deep levels located at ∼2.07, ∼2.80, and ∼3.23 eV below the conduction band, presumably attributable to Ga vacancies and/or impurity C present in the GaN buffer layer. Additionally, from photo-assisted turn-on current recovery measurements, by using 390 and 370 nm long-pass filters, the recovery time becomes significantly faster due to inactivation of their corresponding deep-level traps. Therefore, the ∼2.80 and ∼3.23 eV levels are probably responsible for the carrier-trapping phenomena in the bulk region.
Frequency lock-in phenomenon for self-sustained roll oscillations of rectangular wings undergoing a forced periodic pitching motion
Authors: Tregidgo L. , Wang Z. , Gursul I.
Published: November 2012

The free-to-roll behaviour of rigid and membrane rectangular wings with an aspect ratio of two was studied in wind tunnel experiments conducted at a chord Reynolds number of Rec = 46 000. Self-excited roll oscillations resulting from the fluid-structure interaction were studied in forced sinusoidal pitching motion in order to simulate gust encounters of small air vehicles. For the dynamic pitching cases, the frequency and phase of the self-excited roll oscillations can become synchronized (or locked-in) with the fundamental pitching frequency and its subharmonics. This is believed to be the first documented example of synchronization for this type of fluid-structure interaction. Depending on the amplitude and frequency of excitation (pitching motion), there are regions of decreased roll oscillations, which may be important for the gust response of small vehicles.
Band structure calculations of InP wurtzite/zinc-blende quantum wells
Authors: Faria Junior P. E. , Sipahi G. M.
Published: November 2012

Semiconductor nanowhiskers (NWs) made of III-V compounds exhibit great potential for technological applications. Controlling the growth conditions, such as temperature and diameter, it is possible to alternate between zinc-blende (ZB) and wurtzite (WZ) crystalline phases, giving origin to the so called polytypism. This effect has great influence in the electronic and optical properties of the system, generating new forms of confinement to the carriers. A theoretical model capable to accurately describe electronic and optical properties in these polytypical nanostructures can be used to study and develop new kinds of nanodevices. In this study, we present the development of a wurtzite/zinc-blende polytypical model to calculate the electronic band structure of nanowhiskers based on group theory concepts and the k·p method. Although the interest is in polytypical superlattices, the proposed model was applied to a single quantum well of InP to study the physics of the wurtzite/zinc-blende polytypism. By the analysis of our results, some trends can be predicted: spatial carriers' separation, predominance of perpendicular polarization (xy plane) in the luminescence spectra, and interband transition blueshifts with strain. Also, a possible range of values for the wurtzite InP spontaneous polarization is suggested.
Cooperativity in self-limiting equilibrium self-associating systems
Authors: Freed Karl F.
Published: November 2012

A wide variety of highly cooperative self-assembly processes in biological and synthetic systems involve the assembly of a large number (m) of units into clusters, with m narrowly peaked about a large size m0 ≫ 1 and with a second peak centered about the m = 1 unassembled monomers. While very specific models have been proposed for the assembly of, for example, viral capsids and core-shell micelles of ß-casein, no available theory describes a thermodynamically general mechanism for this double peaked, highly cooperative equilibrium assembly process. This study provides a general mechanism for these cooperative processes by developing a minimal Flory-Huggins type theory. Beginning from the simplest non-cooperative, free association model in which the equilibrium constant for addition of a monomer to a cluster is independent of cluster size, the new model merely allows more favorable growth for clusters of intermediate sizes. The theory is illustrated by computing the phase diagram for cases of self-assembly on cooling or heating and for the mass distribution of the two phases.
Numerical simulation of flow around a circular cylinder having porous surface
Authors: Naito Hiroshi , Fukagata Koji
Published: November 2012

Flow around a circular cylinder having porous surface is studied numerically by means of direct numerical simulation and large eddy simulation. The flow in the porous media is represented by a spatially averaged model. First, the properties of the most effective porous media are found from a preliminary two-dimensional parametric test. Subsequently, the dependency of flow modification on the Reynolds number (Re = 100, 1000, 3900, and 1.0 × 105) and the porous layer thickness is investigated in detail. It is found that the porous surface works to suppress the velocity and pressure fluctuations and such effect is more significant at higher Reynolds number. In particular, the vortex shedding is found to be completely suppressed at Re = 1.0 × 105. The mechanism of flow modification is explained by slip velocity and energy dissipation process.
Proton vibrational dynamics in lithium imide investigated through incoherent inelastic and Compton neutron scattering
Authors: Pietropaolo A. , Colognesi D. , Catti M. , Nale A.-C. , Adams M. A. , Ramirez-Cuesta A. J. , Mayers J.
Published: November 2012

In the present study we report neutron spectroscopic measurements on polycrystalline lithium imide, namely, incoherent inelastic neutron scattering at 20 K, and neutron Compton scattering from 10 K up to room temperature. From the former technique the H-projected density of phonon states up to 100 meV is derived, while the latter works out the spherically averaged single-particle (i.e., H, Li, and N) momentum distributions and, from this, the mean kinetic energies. Only for H at the lowest investigated temperature, non-Gaussian components of its momentum distribution are detected. However, these components do not seem directly connected to the system anharmonicity, being fully compatible with the simple N-H bond anisotropy. Neutron data are also complemented by ab initio lattice dynamics simulations, both harmonic and, at room temperature, carried out in the framework of the so-called “quantum colored noise thermostat” method. The single-particle mean kinetic energies in lithium imide as a function of temperature show a quite peculiar behavior at the moment not reproduced by ab initio lattice dynamics methods, at least as far as H and Li are concerned. As matter of fact, neither their low temperature values nor their temperature trends can be precisely explained in terms of standard phonon calculations.
Quantitative determination of the lateral density and intermolecular correlation between proteins anchored on the membrane surfaces using grazing incidence small-angle X-ray scattering and grazing incidence X-ray fluorescence
Authors: Abuillan Wasim , Vorobiev Alexei , Hartel Andreas , Jones Nicola G. , Engstler Markus , Tanaka Motomu
Published: November 2012

As a physical model of the surface of cells coated with densely packed, non-crystalline proteins coupled to lipid anchors, we functionalized the surface of phospholipid membranes by coupling of neutravidin to biotinylated lipid anchors. After the characterization of fine structures perpendicular to the plane of membrane using specular X-ray reflectivity, the same membrane was characterized by grazing incidence small angle X-ray scattering (GISAXS). Within the framework of distorted wave Born approximation and two-dimensional Percus-Yevick function, we can analyze the form and structure factors of the non-crystalline, membrane-anchored proteins for the first time. As a new experimental technique to quantify the surface density of proteins on the membrane surface, we utilized grazing incidence X-ray fluorescence (GIXF). Here, the mean intermolecular distance between proteins from the sulfur peak intensities can be calculated by applying Abelé's matrix formalism. The characteristic correlation distance between non-crystalline neutravidin obtained by the GISAXS analysis agrees well with the intermolecular distance calculated by GIXF, suggesting a large potential of the combination of GISAXS and GIXF in probing the lateral density and correlation of non-crystalline proteins displayed on the membrane surface.
Physical understanding of negative bias temperature instability below room temperature
Authors: Ji Xiaoli , Liao Yiming , Yan Feng , Zhu Chenxin , Shi Yi , Guo Qiang
Published: November 2012

The physical mechanism of VT degradations under negative bias temperature stress below room temperature has been studied for SiO2 and plasma nitrided oxide (PNO-based) pMOSFETs. It is found that VT degradations in both devices exhibit strong dependence on the electric field and temperature. The analysis shows that this strong dependence follows multi-phonon field-assisted tunneling theory, which indicates the inelastic hole trapping mechanism in the low temperature negative bias temperature instability (NBTI). On the other hand, by applying a low temperature sweeping technique, the energy distribution of these NBTI-induced hole traps below room temperature is indentified. The energy distribution of hole traps has two obvious peaks, one in the lower and one in the upper half of the silicon band gap. Both peaks gradually develop with increasing the stress time and temperature. We attempt to compare the energy profile for SiO2 and PNO devices to identify the trap precursors in NBTI below room temperature.
Resonant-magnetic-perturbation-induced plasma transport in H-mode pedestals
Authors: Callen J. D. , Cole A. J. , Hegna C. C.
Published: November 2012

Plasma toroidal rotation reduces reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational (q = m/n) magnetic flux surfaces. Hence, it causes radial perturbations δBρm/n to be small there, and thus inhibits magnetic island formation and stochasticity in the edge of high (H-) mode confinement tokamak plasmas. However, electron collisional damping combined with the spatial magnetic flutter δBρm/n induced by RMPs in the vicinity of rational surfaces causes a radial electron heat diffusivity χeRMP∼(1/2)∑m,n[δB̂ρm/n(x)/B0]2χe∥eff(x) in which χe∥eff∼(vTe2/νe)/(1+x2/δ∥2) is an effective parallel electron thermal diffusivity. These effects are reduced by magnetic shear effects at a distance x from rational surfaces for |x|>δ∥ but amplified for δB̂ρm/n(x)>δB̂ρm/n(0). A kinetic, toroidal model of these RMP-flutter-induced plasma transport effects is developed and compared to a previously developed cylindrical model. The RMP-induced increases in plasma transport can be large enough to reduce plasma gradients in H-mode pedestals. Thus, they may contribute to suppressing edge localized modes in tokamak plasmas.
Finite-temperature corrections to the time-domain equations of motion for perpendicular propagation in nonuniform magnetized plasmas
Authors: Tierens W. , De Zutter D.
Published: November 2012

In this paper we extend the new techniques of W. Tierens and D. D. Zutter, J. Comput. Phys. 231, 5144 (2012) to include finite Larmor radius effects up to second order in the Larmor radius. We limit ourselves to the case of propagation perpendicular to the background magnetic field B→0. We show that our time-domain technique is able to produce the lowest-order Bernstein wave (a wave believed to be useful for heating fusion devices [H. P. Laqua, Plasma Phys. Controlled Fusion 49, R1 (2007)]). The discrete equations retain many of the favourable properties described in W. Tierens and D. D. Zutter, J. Comput. Phys. 231, 5144 (2012), i.e., unconditional stability and a straightforward relation between the second-order accurate continuous dispersion relation and the dispersion relation of the discretized problem. The theory is illustrated by a place-independent and a place-dependent temperature numerical example.
Threshold for electron trapping nonlinearity in Langmuir waves
Authors: Strozzi D. J. , Williams E. A. , Rose H. A. , Hinkel D. E. , Langdon A. B. , Banks J. W.
Published: November 2012

We assess when electron trapping nonlinearity is expected to be important in Langmuir waves. The basic criterion is that the inverse of the detrapping rate νd of electrons in the trapping region of velocity space must exceed the bounce period of deeply trapped electrons, τB≡(ne/δn)1/22π/ωpe. A unitless figure of merit, the “bounce number” NB≡1/νdτB, encapsulates this condition and defines a trapping threshold amplitude for which NB=1. The detrapping rate is found for convective loss (transverse and longitudinal) out of a spatially finite Langmuir wave. Simulations of driven waves with a finite transverse profile, using the 2D-2V Vlasov code LOKI, show trapping nonlinearity increases continuously with NB for transverse loss, and is significant for NB≈1. The detrapping rate due to Coulomb collisions (both electron-electron and electron-ion) is also found, with pitch-angle scattering and parallel drag and diffusion treated in a unified manner. A simple way to combine convective and collisional detrapping is given. Application to underdense plasma conditions in inertial confinement fusion targets is presented. The results show that convective transverse loss is usually the most potent detrapping process in a single f/8 laser speckle. For typical plasma and laser conditions on the inner laser cones of the National Ignition Facility, local reflectivities ∼3% are estimated to produce significant trapping effects.
Effect of secondary convective cells on turbulence intensity profiles, flow generation, and transport
Authors: Yi S. , Kwon J. M. , Diamond P. H. , Rhee T.
Published: November 2012

This paper reports the results of gyrokinetic simulation studies of ion temperature gradient driven turbulence which investigate the role of non-resonant modes in turbulence spreading, turbulence regulation, and self-generated plasma rotation. Non-resonant modes, which are those without a rational surface within the simulation domain, are identified as nonlinearly driven, radially extended convective cells. Even though the amplitudes of such convective cells are much smaller than that of the resonant, localized turbulence eddies, we find from bicoherence analysis that the mode-mode interactions in the presence of such convective cells increase the efficiency of turbulence spreading associated with nonlocality phenomena. Artificial suppression of the convective cells shows that turbulence spreading is reduced, and that the turbulence intensity profile is more localized. The more localized turbulence intensity profile produces stronger Reynolds stress and E × B shear flows, which in turn results in more effective turbulence self-regulation. This suggests that models without non-resonant modes may significantly underestimate turbulent fluctuation levels and transport.
The effect of size ratio on the sphere structure factor in colloidal sphere-plate mixtures
Authors: Cinacchi G. , Doshi N. , Prescott S. W. , Cosgrove T. , Grillo I. , Lindner P. , Phipps J. S. , Gittins D. , van Duijneveldt J. S.
Published: November 2012

Binary mixtures of colloidal particles of sufficiently different sizes or shapes tend to demix at high concentration. Already at low concentration, excluded volume interactions between the two species give rise to structuring effects. Here, a new theoretical description is proposed of the structure of colloidal sphere-plate mixtures, based on a density expansion of the work needed to insert a pair of spheres and a single sphere in a sea of them, in the presence or not of plates. The theory is first validated using computer simulations. The predictions are then compared to experimental observations using silica spheres and gibbsite platelets. Small-angle neutron scattering was used to determine the change of the structure factor of spheres on addition of platelets, under solvent contrast conditions where the platelets were invisible. Theory and experiment agreed very well for a platelet/sphere diameter ratio D/d = 2.2 and reasonably well for D/d = 5. The sphere structure factor increases at low scattering vector Q in the presence of platelets; a weak reduction of the sphere structure factor was predicted at larger Q, and for the system with D/d = 2.2 was indeed observed experimentally. At fixed particle volume fraction, an increase in diameter ratio leads to a large change in structure factor. Systems with a larger diameter ratio also phase separate at lower concentrations.
A sealed capsule system for biological and liquid shock-recovery experiments
Authors: Leighs James A. , Appleby-Thomas Gareth J. , Stennett Chris , Hameed Amer , Wilgeroth James M. , Hazell Paul J.
Published: November 2012

This paper presents an experimental method designed to one-dimensionally shock load and subsequently recover liquid samples. Resultant loading profiles have been interrogated via hydrocode simulation as the nature of the target did not allow for direct application of the diagnostics typically employed in shock physics (e.g., manganin stress gauges or Heterodyne velocimeter (Het-V)). The target setup has been experimentally tested using aluminium flyer plates accelerated by a 50-mm bore single-stage gas-gun reaching projectile impact velocities of up to ∼500 ms−1 (corresponding to peak pressures of up to ca. 4 GPa being experienced by fluid samples). Recovered capsules survived well showing only minor signs of damage. Modelled gauge traces have been validated through the use of a (slightly modified) experiment in which a Het-V facing the rear of the inner capsule was employed. In these tests, good correlation between simulated and experimental traces was observed.
Landau damping effects on the scattering spin-asymmetry and channel preference in election-hole plasmas
Authors: Jung Young-Dae , Hong Woo-Pyo
Published: November 2012

The scattering spin-asymmetry and spin channel preference in electron collisions are investigated in electron-hole plasmas. It is found that the Landau damping effect enhances the scattering channel preference for the spin-singlet electron scattering and suppresses the spin-triplet electron scattering except the scattering angle θ=π/2. It is also found that the spin-singlet electron scattering decreases with an increase of the quantum shielding distance. In addition, the Landau damping effect on the spin-asymmetry parameter is found to be more significant in the intermediate domain of the quantum Debye length.
Note: Precision viscosity measurement using suspended microchannel resonators
Authors: Lee I. , Park K. , Lee J.
Published: November 2012

We report the characterization of a suspended microchannel resonator (SMR) for viscosity measurements in a low viscosity regime (<10 mPa s) using two measurement schemes. First, the quality factor (Q-factor) of the SMR was characterized with glycerol-water mixtures. The measured Q-factor at 20 °C exhibits a bilinear behavior with the sensitivity of 1281 (mPa s)−1 for a lower (1-4 mPa s) and 355 (mPa s)−1 for a higher viscosity range (4-8 mPa s), respectively. The second scheme is the vibration amplitude monitoring of the SMR running in a closed loop feedback. When compared in terms of the measurement time, the amplitude-based measurement takes only 0.1 ∼ 1 ms while the Q-factor-based measurement takes ∼30 s. However, the viscosity resolution of the Q-factor-based measurement is at least three times better than the amplitude-based measurement. By comparing the Q-factors of heavy water and 9.65 wt.% glycerol-water mixture that have very similar viscosities but different densities, we confirmed that the SMR can measure the dynamic viscosity without the density correction. The obtained results demonstrate that the SMR can measure the fluid viscosity with high precision and even real-time monitoring of the viscosity change is possible with the amplitude-based measurement scheme.
A compact holographic optical tweezers instrument
Authors: Gibson G. M. , Bowman R. W. , Linnenberger A. , Dienerowitz M. , Phillips D. B. , Carberry D. M. , Miles M. J. , Padgett M. J.
Published: November 2012

Holographic optical tweezers have found many applications including the construction of complex micron-scale 3D structures and the control of tools and probes for position, force, and viscosity measurement. We have developed a compact, stable, holographic optical tweezers instrument which can be easily transported and is compatible with a wide range of microscopy techniques, making it a valuable tool for collaborative research. The instrument measures approximately 30×30×35 cm and is designed around a custom inverted microscope, incorporating a fibre laser operating at 1070 nm. We designed the control software to be easily accessible for the non-specialist, and have further improved its ease of use with a multi-touch iPad interface. A high-speed camera allows multiple trapped objects to be tracked simultaneously. We demonstrate that the compact instrument is stable to 0.5 nm for a 10 s measurement time by plotting the Allan variance of the measured position of a trapped 2 μm silica bead. We also present a range of objects that have been successfully manipulated.
High precision deflection measurement of microcantilever in an optical pickup head based atomic force microscopy
Authors: Lee Sang Heon
Published: November 2012

This paper presents the methodology to measure the precise deflection of microcantilever in an optical pickup head based atomic force microscopy. In this paper, three types of calibration methods have been proposed: full linearization, sectioned linearization, and the method based on astigmatism. In addition, the probe heads for easy calibration of optical pickup head and fast replacement of optical pickup head have been developed. The performances of each method have been compared through a set of experiments and constant height mode operation which was not possible in the optical pickup head based atomic force microscopy has been carried out successfully.
Integrability and supersymmetry of Schrödinger-Pauli equations for neutral particles
Authors: Nikitin A. G.
Published: November 2012

Integrable quantum mechanical systems for neutral particles with spin \documentclass[12pt]{minimal}\begin{document}$\frac{1}{2}$\end{document}12 and nontrivial dipole momentum are classified. It is demonstrated that such systems give rise to new exactly solvable problems of quantum mechanics with clear physical content. Solutions for three of them are given in explicit form. The related symmetry algebras and superalgebras are discussed. The presented classification is restricted to two-dimensional systems, which admit matrix integrals of motion linear in momenta.
Improved charge breeding efficiency of light ions with an electron cyclotron resonance ion source
Authors: Vondrasek R. , Delahaye P. , Kutsaev Sergey , Maunoury L.
Published: November 2012

The Californium Rare Isotope Breeder Upgrade is a new radioactive beam facility for the Argonne Tandem Linac Accelerator System (ATLAS). The facility utilizes a 252Cf fission source coupled with an electron cyclotron resonance ion source to provide radioactive beam species for the ATLAS experimental program. The californium fission fragment distribution provides nuclei in the mid-mass range which are difficult to extract from production targets using the isotope separation on line technique and are not well populated by low-energy fission of uranium. To date the charge breeding program has focused on optimizing these mid-mass beams, achieving high charge breeding efficiencies of both gaseous and solid species including 14.7% for the radioactive species 143Ba27+. In an effort to better understand the charge breeding mechanism, we have recently focused on the low-mass species sodium and potassium which up to present have been difficult to charge breed efficiently. Unprecedented charge breeding efficiencies of 10.1% for 23Na7+ and 17.9% for 39K10+ were obtained injecting stable Na+ and K+ beams from a surface ionization source.
High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy
Authors: Miyashita Naoya , Ahsan Nazmul , Inagaki Makoto , Monirul Islam Muhammad , Yamaguchi Masafumi , Okada Yoshitaka
Published: November 2012

We report the highest mobility values above 2000 cm2/Vs in Si doped GaNAs film grown by molecular beam epitaxy. To understand the feature of the origin which limits the electron mobility in GaNAs, temperature dependences of mobility were measured for high mobility GaNAs and referential low mobility GaInNAs. Temperature dependent mobility for high mobility GaNAs is similar to the GaAs case, while that for low mobility GaInNAs shows large decrease in lower temperature region. The electron mobility of high quality GaNAs can be explained by intrinsic limiting factor of random alloy scattering and extrinsic factor of ionized impurity scattering.
A superhigh-frequency optoelectromechanical system based on a slotted photonic crystal cavity
Authors: Sun Xiankai , Zhang Xufeng , Poot Menno , Xiong Chi , Tang Hong X.
Published: November 2012

We develop an all-integrated optoelectromechanical system that operates in the superhigh frequency band. This system is based on an ultrahigh-Q slotted photonic crystal (PhC) nanocavity formed by two PhC membranes, one of which is patterned with electrode and capacitively driven. The strong simultaneous electromechanical and optomechanical interactions yield efficient electrical excitation and sensitive optical transduction of the bulk acoustic modes of the PhC membrane. These modes are identified up to a frequency of 4.20 GHz, with their mechanical Q factors ranging from 240 to 1730. Directly linking signals in microwave and optical domains, such optoelectromechanical systems will find applications in microwave photonics in addition to those that utilize the electromechanical and optomechanical interactions separately.
A fast-converging iterative method for X-ray in-line phase contrast tomography
Authors: Vo Nghia T. , Atwood Robert C. , Moser Herbert O. , Lee Peter D. , Breese Mark B. H. , Drakopoulos Michael
Published: November 2012

X-ray in-line phase contrast tomography holds great promise for the quantitative analysis of soft materials. However, its applications have been limited, so far, by the fact that direct methods based on the transport-of-intensity equation and the contrast transfer function are sensitive to noise and applicable only to limited types of samples. Here, we propose an iterative method based on the Gerchberg-Saxton algorithm (R. W. Gerchberg and W. O. Saxton, Optik 35, 237 (1972)), but overcoming its slow convergence by an acceleration technique, named random signed feedback, which shows an excellent performance, both in numerical simulation and tomographic experiment, of discriminating various polymers even when using 53 keV synchrotron X-rays.
Abundant traveling wave solutions of the compound KdV-Burgers equation via the improved (G′/G)-expansion method
Authors: Naher Hasibun , Abdullah Farah Aini , Bekir Ahmet
Published: November 2012

In this article, we investigate the compound KdV-Burgers equation involving parameters by applying the improved (G′/G)-expansion method for constructing some new exact traveling wave solutions including solitons and periodic solutions. The second order linear ordinary differential equation with constant coefficients is used, in this method. The obtained solutions are presented through the hyperbolic, the trigonometric and the rational functions. Further, it is significant to point out that some of our solutions are in good agreement for special cases with the existing results which validates our other solutions. Moreover, some of the obtained solutions are described in the figures.
The study of dielectric, pyroelectric and piezoelectric properties on hot pressed PZT-PMN systems
Authors: Srivastava Geetika , Maglione Mario , Umarji A. M.
Published: November 2012

Hot uniaxial pressing technique has been adopted for the densification of PZT-PMN system with an aim to yield dense ceramics and to lower the sintering temperature and time for achieving better and reproducible electronic properties. The ceramics having >97% theoretical density and micron size grains are investigated for their dielectric, pyroelectric and piezoelectric properties. The effect of Li and Mn addition has also been studied.
The peaks and troughs of corpus-based contextual analysis
Authors: Gabrielatos Costas , McEnery Tony , Diggle Peter J. , Baker Paul
Published: November 2012

This paper focuses upon two issues. Firstly, the question of identifying diachronic trends, and more importantly significant outliers, in corpora which permit an investigation of a feature at many sampling points over time. Secondly, we consider how best to combine more qualitatively oriented approaches to corpus data with the type of trends that can be observed in a corpus using quantitative techniques. The work uses a recently completed ESRC-funded project as a case study, the representation of Islam in the UK press, in order to demonstrate the potential of the approach taken to establishing significant peaks in diachronic frequency development, and the fruitful interface that may be created between qualitative and quantitative techniques.
Actually, Genuinely, Really, and Truly
Authors: Liu Dilin , Espino Maggie
Published: November 2012

Using the 400+ million-word Corpus of Contemporary American English (COCA) as data and a behavioral profile analysis approach, this study examines the semantic and usage differences among actually, genuinely, really, and truly, four near-synonymous adverbs notorious for their complex functional and syntactic usage patterns. In addition to examining the collocates of the adverbs (i.e. the common types of adjectives/verbs they each modify), the study also investigated the positions the adverbs typically occupy in the sentence structure and their functional implications. The data analysis yields an informative delineation of the internal semantic structure of the synonym set, which includes some interesting new findings compared with existing descriptions of the adverbs. The results also show the need for the BP approach to go beyond collocational analysis in the study of synonymous adverbs. Finally, the study also demonstrates the viability of a corpus-based BP approach in the study of synonymous adverbs.
The language of Islamic extremism
Authors: Prentice Sheryl , Rayson Paul , Taylor Paul J.
Published: November 2012

Recent studies have sought to understand individuals’ motivations for terrorism through terrorist material content. To date, these studies have not capitalised on automated language analysis techniques, particularly those of corpus linguistics. In this paper, we demonstrate how applying three corpus-linguistic techniques to extremist statements can provide insights into their ideology. Our data consisted of 250 statements (approximately 500,000 words) promoting terrorist violence. Using the online software tool WMatrix, we submitted these data to frequency count, key word and key concept, and concordance analyses. Results showed that authors centre their rhetoric on themes of morality, social proof, inspiration and appeals to religion, and refer to the world via contrasting concepts, suggesting a polarised way of thinking compared to a general population usage. Additionally, we show how collocation can aid the establishment of networks between people and places. We discuss how such analyses might support the formulation of evidence based counter-terrorism strategies.
Linking critical discourse analysis with translation studies
Authors: Al-Hejin Bandar
Published: November 2012

This paper argues for closer interdisciplinarity between critical discourse analysis (CDA) and translation studies (TS). There has been very little CDA investigating discursive representations by news organisations across linguistic, political and cultural boundaries. Similarly researchers in TS have pointed out that the sensitive role news translation plays in discursive phenomena such as globalisation and political discourse remains largely underestimated. To address this gap, three methodological models are proposed for linking the dialectical-relational approach to CDA (Fairclough 1992, 1995, 2003) with text-based approaches in TS. A mini-case study will illustrate such links by analysing talks by Saudi women translated by BBC News into Standard Arabic and English. Findings reveal substantial transformations which cannot be dismissed as inevitable constraints of the news genre or translation, but are more likely to reflect prevailing narratives of Muslim women being ‘submissive’ and ‘oppressed’.
Not just any order!
Authors: Jørgensen Signe Kjær
Published: November 2012

The article analyses how the Mohammad cartoons enforced stereotypes of Muslims. It provides in-depth analysis of the cartoons based on opinion material from public debate and cognitive discourse analysis of “common sense knowledge”. The article shows that the main themes of interpretation were Muslim male and female identities. These were presented in a stereotypical way, downplaying agency and critical reflection among Muslim believers. Moreover, many citizens pointed out similarities between the Abrahamic religions. Such interpretations may be traced to mental models that perceived the cartoons as either humorous, a matter of Freedom of speech, or as an expression of values supportive to multiculturalism. Thereby the public debate drew on discourses about terrorism, veiling, child marriages, mother tongue education, and Turkey’s possible EU-accession. In general, the cartoons as well as the public debate about them enforced new racist ideas of Muslims.
Do verb bias effects on sentence production reflect sensitivity to comprehension or production factors?
Authors: Ferreira Victor S. , Schotter Elizabeth R.
Published: November 2012

Speakers should be motivated to produce easy-to-understand sentences, but they must successfully say sentences that are harder to produce. Four experiments assessed how verb bias influences the mention of the optional “that” in sentence-complement structures. Without the “that”, such sentences can be incorrectly interpreted as including direct objects ( garden paths), and especially so after direct-object-biased verbs (compared to embedded-clause-biased verbs). But direct-object-biased verbs are rarely produced as sentence-complement structures, and so they might be harder to produce as such. Experiments 1 and 2 show that speakers mention the “that” more after direct-object-biased verbs than after embedded-clause-biased verbs. Experiment 3a shows that sentences with verbs biased toward neither direct objects nor embedded subjects were often produced with the “that”, and Experiment 3b shows that postverbal noun phrases after neither-biased verbs are interpreted as direct objects less than direct-object-biased verbs and so should cause a milder garden path. Thus, frequent “that” mention is not sensitive to the tendency of a verb to be followed by a direct object, but by how rarely the verb has been produced in the formulated structure.