bluuebunny/crossref_metadata_2025 huggingface dataset:
Elasticity of phase D and implication for the degree of hydration of deep subducted slabs
Authors: Rosa Angelika D. , Sanchez‐Valle Carmen , Ghosh Sujoy
Published: March 2012

Seismic anomalies in subducted slabs, including low velocity zones and shear wave splitting, have often been related to hydrous regions. Phase D (MgSi2H2O6, 10–18 wt.% H2O) may be the ultimate water carrier in hydrous subducted peridotite and its seismic properties are thus essential for interpreting observed anomalies in terms of hydration. Here, we report the sound velocities and elasticity of Mg‐ and Al‐Fe‐bearing phase D single‐crystals measured by Brillouin spectroscopy. The room conditions adiabatic bulk and shear modulus are: KS0 = 154.8(3.2) GPa and μ = 104.3(2.1) GPa for Mg‐phase D and KS0 = 158.4(3.9) GPa and μ = 104.7(2.7) GPa for AlFe‐phase D, suggesting minor effect of cation substitution on the elasticity of phase D. Based on the seismic velocity data, we found that 16 vol.% of AlFe‐phase D in hydrous subducted peridotite with 1.2 wt.% H2O could provide a plausible explanation for the negative velocity anomalies of 3% observed in fragments of the Tonga slab below the transition zone.
Perpendicular magnetic anisotropy of Ni/Cu(001) films with surface passivation
Authors: Pan Wei , Shih Ying-Ta , Lee Kuo-Long , Shen Wen-He , Tsai Chung-Wei , Wei Der-Hsin , Chan Yuet-Loy , Chang Hui-Ching
Published: March 2012

A 13 monolayer Ni film was deposited on Cu(001) and followed by oxygen exposure at 300 K. It was confirmed that the surface contained Ni oxide with an amorphous atomic arrangement. The magnetization is perpendicular after surface oxidation. The coercivity is substantially enhanced without shifting of the hysteresis loop after field cooling. This could indicate that the NiO is randomly antiferromagnetic or that the Neél temperature of the NiO is above 300 K. This surface oxide leads to surface passivation so that the film is magnetically alive under ambient conditions, which could have useful applications in the future.
Valence and inner-valence shell dissociative photoionization of CO in the 26–33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions
Authors: Lebech M. , Houver J. C. , Raseev G. , dos Santos A. S. , Dowek D. , Lucchese Robert R.
Published: March 2012

Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative photoionization measurements where the velocities of the ionic fragment and photoelectron were detected in coincidence, are compared to RFPADs computed using the multichannel Schwinger configuration interaction method. The formalism for including a finite lifetime of the predissociative ion state is presented for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 eV, and 32.5 eV. A comparison of experimental and theoretical RFPADs allows us to identify the ionic states detected in the experimental studies. In addition to previously identified states, we found evidence for the 2 2Δ state with an ionization potential of 25.3 eV and 2Σ+ states with ionization potentials near 32.5 eV. A comparison of the experimental and theoretical RFPADs permits us to estimate predissociative lifetimes of 0.25–1 ps for some of the ion states. Consideration of the MFPADs of a series of 2Π ion states indicates the importance of inter-channel coupling at low photoelectron kinetic energy and the limitations of a single-channel analysis based on the corresponding Dyson orbitals.
Improved fake mode free plane-wave expansion and three planar-slab waveguides method
Authors: Jiang Bin , Zhou Wenjun , Chen Wei , Liu Anjin , Zheng Wanhua
Published: March 2012

We compare the extra modes introduced by plane-wave expansion with the two-dimensional (2D) and the three-dimensional (3D) supercell approximation method, and analyze the differences between those two kinds of extra modes. In the band structure of 2D photonic crystal (PhC) using the 2D supercell approximation, the extra modes are created through band folding, and those extra modes can really exist in the 2D PhC. However, in the band structure of a 2D PhC slab using the 3D supercell approximation, the extra modes are mainly generated by the coupling between supercells, and cannot exist in the real 2D PhC slab, thus these extra modes are defined as fake modes in our paper. Through a detailed analysis of the origin of the fake modes and of the energy distribution of the fake modes and of the real modes, we propose an improved fake mode free plane-wave expansion and three planar slab waveguides method which removes the fake modes. This is the first time such a fake mode free band structure is presented. This result can be definitely helpful in designing 3D devices.
Molecular packing in highly stable glasses of vapor-deposited tris-naphthylbenzene isomers
Authors: Dawson Kevin , Kopff Laura A. , Zhu Lei , McMahon Robert J. , Yu Lian , Richert Ranko , Ediger M. D.
Published: March 2012

Physical vapor deposition of organic molecules can produce glasses with high kinetic stability and low enthalpy. Previous experiments utilizing wide-angle x-ray scattering (WAXS) have shown that, relative to the ordinary glasses prepared by cooling the supercooled liquid, such glasses exhibit excess scattering characteristic of anisotropic packing. We have used vapor deposition to prepare glasses of four isomers of tris-naphthylbenzene (TNB), and measured both the WAXS patterns and the kinetic stability. While vapor-deposited glasses of all four TNB isomers exhibit high and nearly uniform kinetic stability, the level of excess scattering varies significantly. In addition, for α,α,β-TNB, glasses of essentially identical kinetic stability can have excess scattering levels that vary by a factor of two. These results indicate that anisotropic packing is not the source of kinetic stability in vapor-deposited glasses but rather a secondary feature that depends upon the chemical structure of the glass-forming molecules. We also show that the time required for these stable vapor-deposited glasses to transform into the supercooled liquid greatly exceeds the structural relaxation time τα of the liquid and scales approximately as τα0.6. The kinetic stability of the vapor-deposited TNB glasses matches that expected for ordinary glasses that have been aged for 102 to 107 years.
Fully coupled discrete energy-averaged model for Terfenol-D
Authors: Chakrabarti S. , Dapino M. J.
Published: March 2012

A fully coupled 3D energy-avaraged model is presented which describes the magnetomechanical behavior of Terfenol-D. Conventional energy averaging with eight easy axis orientations yields an unphysical kink in the magnetization response and fails to describe the gradual approach to saturation present in Terfenol-D magnetostriction. Superposition of an empirically weighted global anisotropy energy onto an anisotropy energy locally defined around each easy axis eliminates the unphysical kink in the response, while an implicit definition of the domain volume fraction describes the gradual approach to saturation. Anhysteretic bulk material response is described through a weighted sum of individual domains; the weights (or domain volume fractions) are calculated using Boltzmann-type energy averaging. A hysteretic extension is built from an evolution equation for the domain volume fractions. Although solution of the implicit equation for the anhysteretic domain volume fractions requires iteration, the model takes only 20% longer than its original non-iterative version because of the small size of the iteration loop. Comparison of the model with sensing and actuation measurements reveals an average modeling error below 3%. A reduced version of the model, proposed by eliminating certain easy axis orientations, has a 30% lower computational time, with an average modeling error below 6%.
Hydrogel discs for digital microfluidics
Authors: Fiddes Lindsey K. , Luk Vivienne N. , Au Sam H. , Ng Alphonsus H. C. , Luk Victoria , Kumacheva Eugenia , Wheeler Aaron R.
Published: March 2012

Hydrogels are networks of hydrophilic polymer chains that are swollen with water, and they are useful for a wide range of applications because they provide stable niches for immobilizing proteins and cells. We report here the marriage of hydrogels with digital microfluidic devices. Until recently, digital microfluidics, a fluid handling technique in which discrete droplets are manipulated electromechanically on the surface of an array of electrodes, has been used only for homogeneous systems involving liquid reagents. Here, we demonstrate for the first time that the cylindrical hydrogel discs can be incorporated into digital microfluidic systems and that these discs can be systematically addressed by droplets of reagents. Droplet movement is observed to be unimpeded by interaction with the gel discs, and gel discs remain stationary when droplets pass through them. Analyte transport into gel discs is observed to be identical to diffusion in cases in which droplets are incubated with gels passively, but transport is enhanced when droplets are continually actuated through the gels. The system is useful for generating integrated enzymatic microreactors and for three-dimensional cell culture. This paper demonstrates a new combination of techniques for lab-on-a-chip systems which we propose will be useful for a wide range of applications.
Criticality of flow transition behind two side-by-side elliptic cylinders
Authors: Peng Y. F. , Sau Amalendu , Hwang Robert R. , Yang W. C. , Hsieh Chih-Min
Published: March 2012

In this study, near-critical bifurcations of low Reynolds number (Re) flows past a pair of elliptic cylinders in the side-by-side arrangement are numerically investigated, and onsets of several distinct transition scenarios are addressed. A nested Cartesian-grid formulation, in combination with an effective immersed boundary method and a two-step fractional-step procedure, has been adopted to simulate the flows. The transition scenarios associated with various periodic, quasi-periodic, and biased flows, their bifurcation characteristics, corresponding critical Reynolds numbers, and phase-portraits are exploited to better understand the governing physics. From the global point of view, there appear variety of flow patterns within the investigated parameter space, 40 ⩽ Re ⩽ 300, 0.2 ⩽ G ⩽ 3.0 (G being the gap-ratio of the cylinders), and 1.5 ⩽ A ⩽ 3 (A is the cylinder aspect-ratio), which include, symmetric vortex shedding mode, semi-single/twin vortex street formations, asymmetric/deflected flows, stationary/biased flip-flopped-type vortex shedding, weakly-chaotic flows, and in-phase/anti-phase vortex synchronizations. We numerically present these flows by tuning Re quasi-stationary, and provide a broader understanding of the entire transition process. A comprehensive analysis of effects of Reynolds number, the gap-ratio, and the angle of incidence on different flow-induced forces on the cylinders is included in this regard. On the other hand, our simulated wakes with various non-zero incidence-angles are found to reveal a rich variety of instability induced weakly synchronized physical evolution characteristics, which remained virtually unexplored.
Evolution of structural and thermoelectric properties of indium-ion-implanted epitaxial GaAs
Authors: Warren M. V. , Wood A. W. , Canniff J. C. , Naab F. , Uher C. , Goldman R. S.
Published: March 2012

We have examined the structural and thermoelectric properties of nanocomposites prepared by matrix-seeded growth, which consists of ion-beam-amorphization, followed by nanoscale recrystallization via annealing. We use a sputter-mask to increase the retained concentration of In+ ions in GaAs as a path towards the formation of nanoscale InAs crystals in an amorphous GaAs matrix. For the highest ion fluence, an enormous Seebeck coefficient of −12 mV/K is observed at 4 K. We discuss the temperature-dependence of the resistivity, Seebeck coefficient, and thermoelectric power factor in terms of the microstructure of the layers.
The accuracy of parameter estimation by curve fitting in the presence of noise
Authors: Spengen W. M. van
Published: March 2012

Curve fitting of a spectrum or intensity line by chi-square minimization to obtain estimates of parameters is commonly used in fields ranging from (Raman) spectroscopy to position detection. The error or noise in the parameters such as peak position, obtained by the fitting procedure, depends on three error sources in the original data. The limited number of counts in the signal, a systematic error due to binning the data (e.g., to detector pixels), and background noise are identified as the main contributors to the inaccuracy of the estimated parameters after the fitting procedure has been completed. An analysis using analytical calculations and Monte Carlo simulations shows that the effects of limited signal counts and binning both favor a spread of the signal over as many bins as possible, while the background noise has least influence if the signal is concentrated in very few bins. These conflicting demands define a minimum attainable noise level. Hence an optimal situation can be identified where the signal is spread over a definite amount of bins to obtain minimal noise in the extracted parameters such as peak position. A good strategy is presented to obtain this optimum spread of the signal over the bins. This is very relevant to all scientific fields that make use of curve fitting, as it enables a thorough assessment and minimization of the uncertainty in the values obtained.
Discharge impedance evolution, stray capacitance effect, and correlation with the particles size in a dusty plasma
Authors: Wattieaux Gaëtan , Boufendi Laïfa
Published: March 2012

Dust particles growing or injected in a plasma modify significantly the impedance of capacitively coupled radio frequency discharges. The principal modifications are the increase of the plasma bulk resistance and of the plasma sheath capacitance. In this work, we propose a method to evaluate the impedance of the discharge (sheath + plasma bulk) during the growth of dust particles in a plasma. This method does not require the measurement of any current/voltage phase shift. Then, the evolution of the power coupled into the plasma as well as the voltage drop across the plasma bulk are derived. It follows that the plasma coupled power increases by a factor of five during the dust growth. The effect of the reactor stray capacitance on the power coupled to the plasma is underlined. Finally, a perfect correlation between the evolution of the size of the dust particles in the plasma and the increase of the plasma/electrode sheath capacitance suggests that charged dust particles induce an electrostatic force on the plasma sheath. An analytical model is proposed in order to take this phenomenon into account in future dusty plasma electrical modelling.
Near-wall velocity structures that drive turbulent transport from a line source at the wall
Authors: Karna Anjani Kalyan , Papavassiliou Dimitrios V.
Published: March 2012

This work involves numerical experiments that were conducted in a turbulent channel flow using direct numerical simulation in conjunction with the tracking of thermal markers released from a single instantaneous line source at the wall of the channel. The simulations were conducted at Reτ = 300 and for different Prandtl number fluids (Pr = 0.1, 0.7, 6, 20, and 50), in order to investigate the physical mechanism of turbulent transport and the flow structures that promote turbulent transport. The behavior of these heat markers was observed in 12 locations ranging from 1 to 12 half-channel heights downstream from the source. In each of these locations the flow structures that carried thermal markers towards the channel center (i.e., those that transfer heat away from the wall) and flow structures that carried thermal markers towards the channel wall (i.e., those that transfer heat towards the wall) were identified and characterized as a function of the Prandtl number. The characteristic time and length scales were obtained based on the calculation of correlation coefficients for the markers that were captured in each of the downstream locations. The average width of the heat-transferring plumes that have positive vertical velocity fluctuations is larger than the plumes with negative vertical velocity. Even though areas where heat markers are present extend for a long distance downstream, consistent with a sheet-like behavior of thermal plumes, it is found that the eddies associated with these thermal structures are considerably shorter and a synergism among these short eddies, both close and farther away from the wall, is needed in order to transport heat.
Miniature active damping stage for scanning probe applications in ultra high vacuum
Authors: Assig Maximilian , Koch Andreas , Stiepany Wolfgang , Straßer Carola , Ast Alexandra , Kern Klaus , Ast Christian R.
Published: March 2012

Scanning probe microscope (SPM) experiments demand a low vibration level to minimize the external influence on the measured signal. We present a miniature six-degree of freedom active damping stage based on a Gough-Stewart platform (hexapod) which is positioned in ultra high vacuum as close to the SPM as possible. In this way, vibrations originating from the experimental setup can be effectively reduced providing a quiet environment for the SPM. In addition, the hexapod provides a rigid reference point, which facilitates wiring as well as sample transfer. We outline the main working principle and show that for scanning tunneling microscopy (STM) measurements of a Si(111) 7 × 7 surface, the hexapod significantly improves the stability and quality of the topographic images.
Theory of ionization-induced trapping in laser-plasma accelerators
Authors: Chen M. , Esarey E. , Schroeder C. B. , Geddes C. G. R. , Leemans W. P.
Published: March 2012

Ionization injection in a laser-plasma accelerator is studied analytically and by multi-dimensional particle-in-cell (PIC) simulations. To enable the production of low energy spread beams, we consider a short region containing a high atomic number gas (e.g., nitrogen) for ionization-induced trapping, followed by a longer region using a low atomic number gas (e.g., hydrogen), that is, free of additional trapping, for post acceleration. For a broad laser pulse, ionization injection requires a minimum normalized laser field of a0≃1.7, assuming a resonant Gaussian laser pulse. Effects of gas mix parameters, including species, concentration, and length of the mixture region, on the final electron injection number and beam quality are studied. The minimum energy spread is determined by the spread in initial ionized phases of the electrons in the wakefield due to the tunneling ionization process within the laser pulse. Laser polarization and intensity effects on injection number and final electron emittance are examined. Two-dimensional PIC simulations are used to study the ionization injection process and the transverse beam structure. With proper laser-plasma parameters, mono-energetic electron beams with 10 pC charge, a central energy at GeV level, and energy spread less than 1% can be produced in a mixed gas with ionized electron density of 1018cm-3. Lower density can give a higher final accelerated beam energy and reduce the final relative energy spread even further.
Mixed initial-boundary value problem for intermediate long-wave equation
Authors: Kaikina Elena I.
Published: March 2012

We consider the mixed initial-boundary value problem for intermediate long-wave equation on the half-line. We study the several rigorous aspects of this problem including global in time existence of solutions and the asymptotic behavior of solutions for large time. The type of existence results derived here plays a crucial role in the rigorous investigation of integrable equations.
Liquid crystal phase shifters at millimeter wave frequencies
Authors: Garbovskiy Yu. , Zagorodnii V. , Krivosik P. , Lovejoy J. , Camley R. E. , Celinski Z. , Glushchenko A. , Dziaduszek J. , Dąbrowski R.
Published: March 2012

We demonstrate an on-wafer liquid crystal phase shifter which has a tunable 0–300°/cm phase shift at 110 GHz. The results show no dispersion over the entire frequency range indicating a tunable “true time delay” of up to 2.5 ps/cm at all frequencies. The inherent losses in the liquid crystal are small, less than 1 dB/cm over the range of 1–110 GHz. The full tunability is achieved using small voltages, close to 10 V. We anticipate that one could achieve a phase shift of 600°/cm at 220 GHz.
Pressure effects on phase equilibria and solid solubility in MgO-Y2O3 nanocomposites
Authors: Akdoğan E. K. , Şavklιyιldιz İ. , Berke B. , Zhong Z. , Wang L. , Weidner D. , Croft M. C. , Tsakalakos T.
Published: March 2012

We study the temperature and pressure dependence of phase evolution in the 0.5MgO-0.5Y2O3 nanocomposite system using a diamond anvil apparatus in conjunction with in situ synchrotron energy dispersive x-ray diffraction at 7 GPa hydrostatic pressure. At (298 K, 7.0 GPa), structural transformations in the Y2O3 phase are observed, giving rise to the co-existence of its cubic, hexagonal, and monoclinic polymorphs together with cubic MgO. An increase in temperature to 1273 K causes the crystallinity of the Y2O3 hexagonal and monoclinic phases to increase. Isothermal and isobaric hold at (1273 K, 7.0 GPa) for 60 min results in yttrium dissolution in cubic MgO, causing ∼1.0% expansive volumetric lattice strain despite the large differences in the ionic radii of the cations. Cooling the nanocomposite to (298 K, 0 GPa) after a 60 min soak yields four phase co-existence among cubic MgO and cubic, hexagonal, and monoclinic Y2O3. The residual MgO unit cell volume expansion is 0.69% at 298 K, indicating solid solution formation at room temperature despite large differences in the ionic radii of Mg2+ and Y3+. The macroscopic shrinkage due to densification is 3% by volume. Thermodynamic considerations suggest that the relative molar partial volume of Y3+ in MgO is a negative quantity, indicating that the partial molar volume of Y3+ in the solid solution is smaller than its molar volume in the pure state. Aging of the nanocomposites for 240 h does not change the observed 4 phase co-existence. We propose a crystallographic model in which the observed volumetric expansion of the MgO unit cell is primarily attributed to two hydrostatic expansive strain components accompanying solid solution formation: (i) Coulomb repulsion among O2− ions in the immediate vicinity of Mg2+ vacancies, and (ii) misfit strain due to differences in ionic radii upon Y3+ substitution on Mg2+ sites.
A new analytical potential energy surface for the singlet state of He2H+
Authors: Liang Jing-Juan , Yang Chuan-Lu , Wang Li-Zhi , Zhang Qing-Gang
Published: March 2012

The analytic potential energy surface (APES) for the exchange reaction of HeH+ (X1Σ+) + He at the lowest singlet state 11A/ has been built. The APES is expressed as Aguado-Paniagua function based on the many-body expansion. Using the adaptive non-linear least-squares algorithm, the APES is fitted from 15 682 ab initio energy points calculated with the multireference configuration interaction calculation with a large d-aug-cc-pV5Z basis set. To testify the new APES, we calculate the integral cross sections for He + H+He (v = 0, 1, 2, j = 0) → HeH+ + He by means of quasi-classical trajectory and compare them with the previous result in literature.
Direct imaging and optical activities of stacking faults in 4H-SiC homoepitaxial films
Authors: Chen Bin , Matsuhata Hirofumi , Kumagai Kazuhiro , Sekiguchi Takashi , Ichinoseki Kyouichi , Okumura Hajime
Published: March 2012

Both Shockley- and Frank-type stacking faults (SFs) in 4H-SiC were directly observed by scanning electron microscopy (SEM) and their optical activities were investigated by cathodoluminescence technique. The Shockley-type SFs identified by transmission electron microscopy show strong luminescence at wavelength of 471 nm while the Frank-type ones emit the luminescence at 482 nm. Both types of SFs present bright contrast in in-lens SEM images while no obvious contrast in out-lens images. The positions of the SFs observed by SEM correlate well with those detected in cathodoluminescence images. The bright SF contrast in SEM is discussed.
Emitter injection in terahertz quantum cascade lasers: Simulation of an open system
Authors: Wang F. , Guo X. G. , Li H. , Cao J. C.
Published: March 2012

We investigate the carrier transport properties of a three-well terahertz quantum cascade laser which is considered as an open system by using self-consistent Bloch-Poisson equations. The simulation results show that a dynamic equilibrium is achieved, and the electric potential of each period slightly changes with time. Compared to other simulation methods with the cyclic boundary condition approximation, our open system modeling gives more reliable results on the current density-applied electric field and population inversion-applied electric field characteristics. Our modeling method can give more realistic results of working terahertz quantum cascade lasers without increasing the simulation complexity.
Atom probe tomography characterisation of a laser diode structure grown by molecular beam epitaxy
Authors: Bennett Samantha E. , Smeeton Tim M. , Saxey David W. , Smith George D. W. , Hooper Stewart E. , Heffernan Jonathan , Humphreys Colin J. , Oliver Rachel A.
Published: March 2012

Atom probe tomography (APT) has been used to achieve three-dimensional characterization of a III-nitride laser diode (LD) structure grown by molecular beam epitaxy (MBE). Four APT data sets have been obtained, with fields of view up to 400 nm in depth and 120 nm in diameter. These data sets contain material from the InGaN quantum well (QW) active region, as well as the surrounding p- and n-doped waveguide and cladding layers, enabling comprehensive study of the structure and composition of the LD structure. Two regions of the same sample, with different average indium contents (18% and 16%) in the QW region, were studied. The APT data are shown to provide easy access to the p-type dopant levels, and the composition of a thin AlGaN barrier layer. Next, the distribution of indium within the InGaN QW was analyzed, to assess any possible inhomogeneity of the distribution of indium (“indium clustering”). No evidence for a statistically significant deviation from a random distribution was found, indicating that these MBE-grown InGaN QWs do not require indium clusters for carrier localization. However, the APT data show steps in the QW interfaces, leading to well-width fluctuations, which may act to localize carriers. Additionally, the unexpected presence of a small amount (x = 0.005) of indium in a layer grown intentionally as GaN was revealed. Finally, the same statistical method applied to the QW was used to show that the indium distribution within a thick InGaN waveguide layer in the n-doped region did not show any deviation from randomness.
Thermal stability of patterned Co/Pd nanodot arrays
Authors: Tudosa I. , Lubarda Marko V. , Chan K. T. , Escobar M. A. , Lomakin Vitaliy , Fullerton E. E.
Published: March 2012

We have studied the magnetic reversal and thermal stability of [Co(0.3 nm)/Pd(0.7 nm)]N multilayers patterned into 35-nm-diameter nanodot arrays. The short-time coercive fields are relatively constant with N while the room-temperature thermal stability parameter increases nearly linearly with N. However the magnetic switching volume extracted from the thermal stability is significantly less than the physical volume of the samples. The experimental results are in quantitative agreement with micromagnetic modeling, which indicates that reversal and thermal stability is controlled by nucleation and propagation of edge domains.
Direct piezoelectric properties of (100) and (111) BiFeO3 epitaxial thin films
Authors: Ujimoto K. , Yoshimura T. , Ashida A. , Fujimura N.
Published: March 2012

The direct piezoelectric properties of BiFeO3 epitaxial thin films with different crystal orientation were investigated. Epitaxial films of (100) and (111) rhombohedral BiFeO3 fabricated using pulsed laser deposition showed rectangular hysteresis loops with remanent polarizations of 54 and 83 μC/cm2, respectively. Effective transverse piezoelectric coefficients (e31,f) of −3.5 and −1.3 C/m2 were obtained, for (100) and (111) films, respectively. Results suggest that the strong direct piezoelectric response of the (100) rhombohedral film results from the effects of the engineered-domain configuration.
Aesthetic Valence of Visual Illusions
Authors: Stevanov Jasmina , Marković Slobodan , Kitaoka Akiyoshi
Published: March 2012

Visual illusions constitute an interesting perceptual phenomenon, but they also have an aesthetic and affective dimension. We hypothesized that the illusive nature itself causes the increased aesthetic and affective valence of illusions compared with their non-illusory counterparts. We created pairs of stimuli. One qualified as a standard visual illusion whereas the other one did not, although they were matched in as many perceptual dimensions as possible. The phenomenal quality of being an illusion had significant effects on “Aesthetic Experience” (fascinating, irresistible, exceptional, etc), “Evaluation” (pleasant, cheerful, clear, bright, etc), “Arousal” (interesting, imaginative, complex, diverse, etc), and “Regularity” (balanced, coherent, clear, realistic, etc). A subsequent multiple regression analysis suggested that Arousal was a better predictor of Aesthetic Experience than Evaluation. The findings of this study demonstrate that illusion is a phenomenal quality of the percept which has measurable aesthetic and affective valence.
Beef cattle breeding in Australia with genomics: opportunities and needs
Authors: Johnston D. J. , Tier B. , Graser H.-U.
Published: March 2012

Opportunities exist in beef cattle breeding to significantly increase the rates of genetic gain by increasing the accuracy of selection at earlier ages. Currently, selection of young beef bulls incorporates several economically important traits but estimated breeding values for these traits have a large range in accuracies. While there is potential to increase accuracy through increased levels of performance recording, several traits cannot be recorded on the young bull. Increasing the accuracy of these traits is where genomic selection can offer substantial improvements in current rates of genetic gain for beef. The immediate challenge for beef is to increase the genetic variation explained by the genomic predictions for those traits of high economic value that have low accuracies at the time of selection. Currently, the accuracies of genomic predictions are low in beef, compared with those in dairy cattle. This is likely to be due to the relatively low number of animals with genotypes and phenotypes that have been used in developing genomic prediction equations. Improving the accuracy of genomic predictions will require the collection of genotypes and phenotypes on many more animals, with even greater numbers needed for lowly heritable traits, such as female reproduction and other fitness traits. Further challenges exist in beef to have genomic predictions for the large number of important breeds and also for multi-breed populations. Results suggest that single-nucleotide polymorphism (SNP) chips that are denser than 50 000 SNPs in the current use will be required to achieve this goal. For genomic selection to contribute to genetic progress, the information needs to be correctly combined with traditional pedigree and performance data. Several methods have emerged for combining the two sources of data into current genetic evaluation systems; however, challenges exist for the beef industry to implement these effectively. Changes will also be needed to the structure of the breeding sector to allow optimal use of genomic information for the benefit of the industry. Genomic information will need to be cost effective and a major driver of this will be increasing the accuracy of the predictions, which requires the collection of much more phenotypic data than are currently available.
Uses of genomics in livestock agriculture
Authors: Goddard M. E.
Published: March 2012

World demand for livestock products is likely to increase in coming decades but the cost of production could escalate faster than the price due to competition for land, water, grain and fertiliser and the effects of climate change and its mitigation. To remain competitive for these resources, livestock agriculture has to dramatically increase in efficiency of production. Genetic gain is one mechanism to achieve increased efficiency and there is the opportunity to utilise the scientific advances in genomics. Three ways in which genomics can be used are in additive genetic improvement, exploitation of non-additive genetic variance and management which exploits genotype by environment interactions to optimise management. Genomic selection is already being widely implemented in dairy cattle and beef cattle and sheep will follow in the future once the accuracy of genomic selection is high enough. The accuracy of equations that predict breeding value from DNA genotypes can be increased by increasing the size of the reference population from which the equations are estimated, increasing the density of markers, using genome sequences instead of markers, using more appropriate statistical procedures and incorporating biological information into the prediction. In the long term, genomic selection combined with reproductive technology that reduces the minimum age at breeding will greatly increase the rate of genetic gain. This will allow long-term increases in biological efficiency and short-term tailoring of livestock to meet the demands of particular markets and opportunities.
Droplet formation and scaling in dense suspensions
Authors: Miskin Marc Z. , Jaeger Heinrich M.
Published: March 2012

When a dense suspension is squeezed from a nozzle, droplet detachment can occur similar to that of pure liquids. While in pure liquids the process of droplet detachment is well characterized through self-similar profiles and known scaling laws, we show here the simple presence of particles causes suspensions to break up in a new fashion. Using high-speed imaging, we find that detachment of a suspension drop is described by a power law; specifically we find the neck minimum radius,
r

m

, scales like

near breakup at time
τ
 = 0. We demonstrate data collapse in a variety of particle/liquid combinations, packing fractions, solvent viscosities, and initial conditions. We argue that this scaling is a consequence of particles deforming the neck surface, thereby creating a pressure that is balanced by inertia, and show how it emerges from topological constraints that relate particle configurations with macroscopic Gaussian curvature. This new type of scaling, uniquely enforced by geometry and regulated by the particles, displays memory of its initial conditions, fails to be self-similar, and has implications for the pressure given at generic suspension interfaces.
Neuronal mRNAs travel singly into dendrites
Authors: Batish Mona , van den Bogaard Patrick , Kramer Fred Russell , Tyagi Sanjay
Published: March 2012

RNA transport granules deliver translationally repressed mRNAs to synaptic sites in dendrites, where synaptic activity promotes their localized translation. Although the identity of many proteins that make up the neuronal granules is known, the stoichiometry of their core component, the mRNA, is poorly understood. By imaging nine different dendritically localized mRNA species with single-molecule sensitivity and subdiffraction-limit resolution in cultured hippocampal neurons, we show that two molecules of the same or different mRNA species do not assemble in common structures. Even mRNA species with a common dendritic localization element, the sequence that is believed to mediate the incorporation of these mRNAs into common complexes, do not colocalize. These results suggest that mRNA molecules traffic to the distal reaches of dendrites singly and independently of others, a model that permits a finer control of mRNA content within a synapse for synaptic plasticity.
RelA protein stimulates the activity of RyhB small RNA by acting on RNA-binding protein Hfq
Authors: Argaman Liron , Elgrably-Weiss Maya , Hershko Tal , Vogel Jörg , Altuvia Shoshy
Published: March 2012

The conserved RNA-binding protein Hfq and its associated small regulatory RNAs (sRNAs) are increasingly recognized as the players of a large network of posttranscriptional control of gene expression in Gram-negative bacteria. The role of Hfq in this network is to facilitate base pairing between sRNAs and their
trans
-encoded target mRNAs. Although the number of known sRNA–mRNA interactions has grown steadily, cellular factors that influence Hfq, the mediator of these interactions, have remained unknown. We report that RelA, a protein long known as the central regulator of the bacterial-stringent response, acts on Hfq and thereby affects the physiological activity of RyhB sRNA as a regulator of iron homeostasis. RyhB requires RelA in vivo to arrest growth during iron depletion and to down-regulate a subset of its target mRNAs (
fdoG
,
nuoA
, and
sodA
), whereas the
sodB
and
sdhC
targets are barely affected by RelA. In vitro studies with recombinant proteins show that RelA enhances multimerization of Hfq monomers and stimulates Hfq binding of RyhB and other sRNAs. Hfq from polysomes extracted from wild-type cells binds RyhB in vitro, whereas Hfq from polysomes of a
relA
mutant strain shows no binding. We propose that, by increasing the level of the hexameric form of Hfq, RelA enables binding of RNAs whose affinity for Hfq is low. Our results suggest that, under specific conditions and/or environments, Hfq concentrations are limiting for RNA binding, which thereby provides an opportunity for cellular proteins such as RelA to impact sRNA-mediated responses by modulating the activity of Hfq.
Transferred melanoma-specific CD8
+
T cells persist, mediate tumor regression, and acquire central memory phenotype
Authors: Chapuis Aude G. , Thompson John A. , Margolin Kim A. , Rodmyre Rebecca , Lai Ivy P. , Dowdy Kaye , Farrar Erik A. , Bhatia Shailender , Sabath Daniel E. , Cao Jianhong , Li Yongqing , Yee Cassian
Published: March 2012

Adoptively transferred tumor-specific T cells offer the potential for non–cross-resistant therapy and long-term immunoprotection. Strategies to enhance in vivo persistence of transferred T cells can lead to improved antitumor efficacy. However, the extrinsic (patient conditioning) and intrinsic (effector cell) factors contributing to long-term in vivo persistence are not well-defined. As a means to enhance persistence of infused T cells in vivo and limit toxicity, 11 patients with refractory, progressive metastatic melanoma received cyclophosphamide alone as conditioning before the infusion of peripheral blood mononuclear cell-derived, antigen-specific, CD8
+
cytotoxic T-lymphocyte (CTL) clones followed by low-dose or high-dose IL-2. No life-threatening toxicities occurred with low-dose IL-2. Five of 10 evaluable patients had stable disease at 8 wk, and 1 of 11 had a complete remission that continued for longer than 3 y. On-target autoimmune events with the early appearance of skin rashes were observed in patients with stable disease or complete remission at 4 wk or longer. In vivo tracking revealed that the conditioning regimen provided a favorable milieu that enabled CTL proliferation early after transfer and localization to nonvascular compartments, such as skin and lymph nodes. CTL clones, on infusion, were characterized by an effector memory phenotype, and CTL that persisted long term acquired phenotypic and/or functional qualities of central memory type CTLs in vivo. The use of a T-cell product composed of a clonal population of antigen-specific CTLs afforded the opportunity to demonstrate phenotypic and/or functional conversion to a central memory type with the potential for sustained clinical benefit.
Stoichiometry of proton translocation by respiratory complex I and its mechanistic implications
Authors: Wikström Mårten , Hummer Gerhard
Published: March 2012

Complex I (NADH-ubiquinone oxidoreductase) in the respiratory chain of mitochondria and several bacteria functions as a redox-driven proton pump that contributes to the generation of the protonmotive force across the inner mitochondrial or bacterial membrane and thus to the aerobic synthesis of ATP. The stoichiometry of proton translocation is thought to be 4 H
+
per NADH oxidized (2 e
-
). Here we show that a H
+
/2 e
-
ratio of 3 appears more likely on the basis of the recently determined H
+
/ATP ratio of the mitochondrial
F
1
F

o

-ATP synthase of animal mitochondria and of a set of carefully determined ATP/2 e
-
ratios for different segments of the mitochondrial respiratory chain. This lower H
+
/2 e
-
ratio of 3 is independently supported by thermodynamic analyses of experiments with both mitochondria and submitochondrial particles. A reduced H
+
/2 e
-
stoichiometry of 3 has important mechanistic implications for this proton pump. In a rough mechanistic model, we suggest a concerted proton translocation mechanism in the three homologous and tightly packed antiporter-like subunits L, M, and N of the proton-translocating membrane domain of complex I.
Participation, progression and value added: business and economics for 14–19‐year‐olds in England
Authors: Brant Jacek , Cullimore Duncan
Published: March 2012

This article attempts to map the business and economics curriculum and explain some of the reasons for it being as it is; and to examine the number of students choosing to study the subjects and the ‘perceived relative value' of studying economics and business studies. In 1988 a National Curriculum was introduced for all 5–16‐year‐olds in state schools in England but curiously neither business studies nor economics were mandatory subjects. In England, government education policy has influenced the development of the business and economics school curriculum in four main ways: first, in defining a core curriculum; second, in changes in school type; third, in the treatment of the academic/vocational divide; and, finally, in the development of a qualifications framework. With a new government elected, changes in education policy will therefore have an impact on the study of these subjects. We argue that while business and economics are very popular options for study by 14–19‐year‐olds, this area of the English curriculum needs further strengthening, and that all students should have the opportunity to study business and economics in some form to develop their own economic wellbeing and to better understand the world in which they live.
Young people's process of engagement in school counselling
Authors: Prior Seamus
Published: March 2012

Background: Adolescent reluctance to engage in help‐seeking for psychological and emotional problems is well documented. Despite a significant expansion in counselling provision in UK secondary schools, young people's experience of accessing counselling remains under‐researched. Aim: The present study aimed to elucidate the key features and stages of the help‐seeking process as defined by young people accessing school counselling. Method: Semi‐structured interviews were conducted with young people who had successfully completed a course of counselling at school. Thematic narrative analysis focusing on help‐seeking was then applied to the interview transcripts. Results: The analysis proposes a multi‐staged socially‐mediated process of disclosure and engagement, from initial acknowledgement of a problem through to full disclosure to the counsellor. Discussion: Analysis of young people's narratives highlights: the complex process of negotiation and evaluation which they undertake to engage fully in school counselling; the careful management of stigmatisation concerns both through practical access arrangements and the language in which school counselling is framed; the significant balanced position of the counsellor as both integrated and separate within the school community; and the key role of facilitators in enabling young people to access counselling, both practically and psychologically.
Effect of hole transporting layers on the performance of PCPDTBT : PCBM organic solar cells
Authors: Kettle J , Waters H , Horie M , Chang S-W
Published: March 2012

We study the performance of PCPDTBT : C71-PCBM organic photovoltaics (OPVs) for three hole transporting layers (HTL); PEDOT : PSS, nickel oxide (NiO) and molybdenum trioxide (MoO3). We show that devices fabricated with nickel oxide HTL demonstrate the highest power conversion efficiency and theoretical data using a transfer matrix model confirms that this is as a result of increased absorption in the active layer as well as a result of improved series resistance and improved matching of energy levels. Device degradation is studied and lifetime is highest for the NiO and MoO3 based devices, proving that OPVs with this material system are less sensitive to the environmental effects of water, oxygen and irradiance.
Elastic and vibrational properties of monoclinic HfO2 from
first-principles study
Authors: Wu Rui , Zhou Bo , Li Qian , Jiang ZhenYi , Wang WenBo , Ma WenYan , Zhang XiaoDong
Published: March 2012

The elastic and vibrational properties of crystalline monoclinic HfO2 have been
investigated using density functional perturbation theory. Using the Voigt and Reuss theory, we
estimate the bulk, shear and Young's modulus for polycrystalline HfO2, which agree
very well with the available experimental and theoretical data. Additionally, we present a
systematic analysis of the elastic properties of HfO2 polymorphs and find the trends
in the elastic parameters for the HfO2 structures are consistent with those for the
ZrO2 structures. The choice of exchange-correlation functional has an important
effect on the results of elastic and vibrational properties. The utilization of
Hartwigzen–Goedecker–Hutter type functional is a great improvement on calculation
of the zone-centre phonon frequencies, and shows the root-mean-square absolute deviation of
7 cm−1 with experiments. A rigorous assignment of all the Raman modes is
achieved by combining symmetry analysis with the first-principles calculations, which helps us
to identify the main peak and some other features of Raman spectra. Furthermore, the Raman
spectrum of HfO2 powder has been simulated for the first time, providing a
theoretical benchmark for the interpretation of the unresolved problems in experimental
studies.
The effect of non-axisymmetric wall geometry on 13C transport in ASDEX Upgrade
Authors: Miettunen J. , Kurki-Suonio T. , Makkonen T. , Groth M. , Hakola A. , Hirvijoki E. , Krieger K. , Likonen J. , Äkäslompolo S.
Published: March 2012

We present the first results of 3D simulations of global 13C transport in ASDEX Upgrade (AUG) indicating that the deposition profile of 13C exhibits toroidal asymmetry in the main chamber.

In 2007, the migration of carbon in AUG was studied with a methane (13CH4) injection experiment (A. Hakola et al and the ASDEX Upgrade Team 2010 Plasma Phys. Control. Fusion
52 065006). The total amount of deposited 13C was estimated by assuming toroidally symmetric deposition. Remarkably, the total number of deposited atoms was observed to be less than 10% of the number of injected atoms.

The experiment has been simulated with the 3D orbit-following Monte Carlo code ASCOT using both a realistic 3D wall geometry of AUG and a 3D magnetic field with toroidal ripple. The simulations indicate that the non-axisymmetric wall geometry causes notable toroidal asymmetry in the deposition profile in the outer (low-field side) midplane region which can provide a partial explanation for the missing carbon inferred from post-mortem analysis of 13C deposition.