bluuebunny/crossref_metadata_2025 huggingface dataset:
Colloidal asphaltene deposition in laminar pipe flow: Flow rate and parametric effects
Authors: Hashmi S. M. , Loewenberg M. , Firoozabadi A.
Published: August 2015

Deposition from a suspended phase onto a surface can aversely affect everyday transport processes on a variety of scales, from mineral scale corrosion of household plumbing systems to asphaltene deposition in large-scale pipelines in the petroleum industry. While petroleum may be a single fluid phase under reservoir conditions, depressurization upon production often induces a phase transition in the fluid, resulting in the precipitation of asphaltene material which readily aggregates to the colloidal scale and deposits on metallic surfaces. Colloidal asphaltene deposition in wellbores and pipelines can be especially problematic for industrial purposes, where cleanup processes necessitate costly operational shutdowns. In order to better understand the parametric dependence of deposition which leads to flow blockages, we carry out lab-scale experiments under a variety of material and flow conditions. We develop a parametric scaling model to understand the fluid dynamics and transport considerations governing deposition. The lab-scale experiments are performed by injecting precipitating petroleum fluid mixtures into a small metal pipe, which results in deposition and clogging, assessed by measuring the pressure drop across the pipe. Parametric scaling arguments suggest that the clogging behavior is determined by a combination of the Peclet number, volume fraction of depositing material, and the volume of the injection itself.
Dielectric microwave properties of Si-integrated pulsed laser deposited (Ba, Sr)TiO3 thin films up to 110 GHz
Authors: Ning Xi , Chen Shuming , Zhang Jinying , Huang Hui , Wang Lei
Published: August 2015

Ba0.6Sr0.4TiO3 thin films with a thickness of 339 nm are deposited directly on the high resistivity silicon through pulsed laser deposition. Coplanar waveguides with a slot width of 4.5 μm are designed to extract the complex permittivity of ferroelectric thin film in the frequency range from 1 GHz to 110 GHz. A fast three-dimensional (3D) finite element method (FEM) model is proposed to implement the permittivity extraction based on the propagation-constant matching, i.e., narrowing the difference between measured and simulated propagation-constants by adjusting the changeable permittivity in the fast 3D FEM model. In order to reduce the calculation overhead, the quasi transverse electromagnetic mode and conformal mapping analysis are introduced to realize the adjusting. The relative difference between measured and simulated propagation-constants is defined to describe the precision of the result. Experimental results show that the relative difference is less than 1.1%. The relative dielectric permittivity of BST films equals 332.6 at 1 GHz and reduces to 240.1 at 110 GHz. The loss tangent is about 17.5% at 110 GHz.
Effect of channel thickness, electrolyte ions, and dissolved oxygen on the performance of organic electrochemical transistors
Authors: Kumar Prajwal , Yi Zhihui , Zhang Shiming , Sekar Arvindh , Soavi Francesca , Cicoira Fabio
Published: August 2015

We investigated the device characteristics of organic electrochemical transistors based on thin films of poly(3,4-ethylenedioxythiophene) doped with poly(styrene-sulfonate). We employed various channel thicknesses and two different electrolytes: the micelle forming surfactant cetyltrimethyl ammonium bromide (CTAB) and NaCl. The highest ON/OFF ratios were achieved at low film thicknesses using CTAB as the electrolyte. Cyclic voltammetry suggests that a redox reaction between oxygen dissolved in the electrolytes and PEDOT:PSS leads to low ON/OFF ratios when NaCl is used as the electrolyte. Electrochemical impedance spectroscopy reveals that doping/dedoping of the channel becomes slower at high film thickness and in the presence of bulky ions.
Black phosphorus saturable absorber for ultrashort pulse generation
Authors: Sotor J. , Sobon G. , Macherzynski W. , Paletko P. , Abramski K. M.
Published: August 2015

Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics.
On the neighborhood of an inhomogeneous stable stationary solution of the Vlasov equation—Case of an attractive cosine potential
Authors: Barré Julien , Yamaguchi Yoshiyuki Y.
Published: August 2015

We consider the one-dimensional Vlasov equation with an attractive cosine potential, and its non-homogeneous stable stationary states that are decreasing functions of the energy. We show that in the Sobolev space W1,p (p > 2) neighborhood of such a state, all stationary states that are decreasing functions of the energy are stable. This is in sharp contrast with the situation for homogeneous stationary states of a Vlasov equation, where a control over strictly more than one derivative is needed to ensure the absence of unstable stationary states in a neighborhood of a reference stationary state [Z. Lin and C. Zeng, Commun. Math. Phys. 306, 291-331 (2011)].
Electrochemical strain microscopy time spectroscopy: Model and experiment on LiMn2O4
Authors: Amanieu Hugues-Yanis , Thai Huy N. M. , Luchkin Sergey Yu. , Rosato Daniele , Lupascu Doru C. , Keip Marc-André , Schröder Jörg , Kholkin Andrei L.
Published: August 2015

Electrochemical Strain Microscopy (ESM) can provide useful information on ionic diffusion in solids at the local scale. In this work, a finite element model of ESM measurements was developed and applied to commercial lithium manganese (III,IV) oxide (LiMn2O4) particles. ESM time spectroscopy was used, where a direct current (DC) voltage pulse locally disturbs the spatial distribution of mobile ions. After the pulse is off, the ions return to equilibrium at a rate which depends on the Li diffusivity in the material. At each stage, Li diffusivity is monitored by measuring the ESM response to a small alternative current (AC) voltage simultaneously applied to the tip. The model separates two different mechanisms, one linked to the response to DC bias and another one related to the AC excitation. It is argued that the second one is not diffusion-driven but is rather a contribution of the sum of several mechanisms with at least one depending on the lithium ion concentration explaining the relaxation process. With proper fitting of this decay, diffusion coefficients of lithium hosts could be extracted. Additionally, the effect of phase transition in LiMn2O4 is taken into account, explaining some experimental observations.
On the avalanche generation of runaway electrons during tokamak disruptions
Authors: Martín-Solís J. R. , Loarte A. , Lehnen M.
Published: August 2015

A simple zero dimensional model for a tokamak disruption is developed to evaluate the avalanche multiplication of a runaway primary seed during the current quench phase of a fast disruptive event. Analytical expressions for the plateau runaway current, the energy of the runaway beam, and the runaway energy distribution function are obtained allowing the identification of the parameters dominating the formation of the runaway current during disruptions. The effect of the electromagnetic coupling to the vessel and the penetration of the external magnetic energy during the disruption current quench as well as of the collisional dissipation of the runaway current at high densities are investigated. Current profile shape effects during the formation of the runaway beam are also addressed by means of an upgraded one-dimensional model.
Electric field stimulation setup for photoemission electron microscopes
Authors: Buzzi M. , Vaz C. A. F. , Raabe J. , Nolting F.
Published: August 2015

Manipulating magnetisation by the application of an electric field in magnetoelectric multiferroics represents a timely issue due to the potential applications in low power electronics and the novel physics involved. Thanks to its element sensitivity and high spatial resolution, X-ray photoemission electron microscopy is a uniquely suited technique for the investigation of magnetoelectric coupling in multiferroic materials. In this work, we present a setup that allows for the application of in situ electric and magnetic fields while the sample is analysed in the microscope. As an example of the performances of the setup, we present measurements on Ni/Pb(Mg0.66Nb0.33)O3-PbTiO3 and La0.7Sr0.3MnO3/PMN-PT artificial multiferroic nanostructures.
Nonlinearity of local dynamics promotes multi-chimeras
Authors: Omelchenko Iryna , Zakharova Anna , Hövel Philipp , Siebert Julien , Schöll Eckehard
Published: August 2015

Chimera states are complex spatio-temporal patterns in which domains of synchronous and asynchronous dynamics coexist in coupled systems of oscillators. We examine how the character of the individual elements influences chimera states by studying networks of nonlocally coupled Van der Pol oscillators. Varying the bifurcation parameter of the Van der Pol system, we can interpolate between regular sinusoidal and strongly nonlinear relaxation oscillations and demonstrate that more pronounced nonlinearity induces multi-chimera states with multiple incoherent domains. We show that the stability regimes for multi-chimera states and the mean phase velocity profiles of the oscillators change significantly as the nonlinearity becomes stronger. Furthermore, we reveal the influence of time delay on chimera patterns.
Surface impacts and collisions of particle-laden nanodrops
Authors: Koplik Joel
Published: August 2015

The surface impact and collisions of particle-laden nanodrops are studied using molecular dynamics computer simulations. The drops are composed of Lennard-Jones dimers and the particles are rigid spherical sections of a cubic lattice, with radii about 11 nm and 0.6 nm, respectively. Uniform suspensions of 21% and 42% particle concentrations and particle-coated drops are studied, and their behavior is compared to that of pure fluid drops of the same size. The relative velocities studied span the transition to splashing, and both wetting/miscible and non-wetting/immiscible cases are considered. Impacts normal to the surface and head-on collisions are studied and compared. In surface impact, the behavior of low-density suspensions and liquid marble drops is qualitatively similar to that of pure liquid, while the concentrated drops are solid-like on impact. Collisions produce a splash only at velocities significantly higher than in impact, but the resulting drop morphology shows a similar dependence on solid concentration as in impact. In all cases, the collision or impact produces a strong local enhancement in the kinetic energy density and temperature but not in the particle or potential energy densities. Mixing of the two colliding species is not enhanced by collisions, unless the velocity is so high as to cause drop disintegration.
Breaking Gaussian incompatibility on continuous variable quantum systems
Authors: Heinosaari Teiko , Kiukas Jukka , Schultz Jussi
Published: August 2015

We characterise Gaussian quantum channels that are Gaussian incompatibility breaking, that is, transform every set of Gaussian measurements into a set obtainable from a joint Gaussian observable via Gaussian postprocessing. Such channels represent local noise which renders measurements useless for Gaussian EPR-steering, providing the appropriate generalisation of entanglement breaking channels for this scenario. Understanding the structure of Gaussian incompatibility breaking channels contributes to the resource theory of noisy continuous variable quantum information protocols.
Relaxations in the metastable rotator phase of n-eicosane
Authors: Di Giambattista C. , Sanctuary R. , Perigo E. , Baller J.
Published: August 2015

We present relaxations in the metastable rotator phase of the n-alkane eicosane (C20H42). The relaxation times found by calorimetry increase with increasing temperature on approaching the melting temperature of the rotator phase. This is the opposite behavior than the one found for classical activated processes. The relaxation behavior found by calorimetry is confirmed by investigations of the lattice structure with X-ray diffraction. It is shown that one lattice parameter of the orthorhombic phase relaxes on the same time scales found in calorimetry, whereas another lattice parameter reacts almost instantly on temperature perturbations. Increasing cooperativity for the creation of conformational defects in the alkane chains is proposed to be responsible for the observed behaviour.
Enhanced surface modification engineering (H, F, Cl, Br, and NO2) of CdS nanowires with and without surface dangling bonds
Authors: Zeng Yijie , Xing Huaizhong , Huang Yan , Lu Aijiang , Wang Chunrui , Xu Xiaofeng , Wang Jiqing , Chen Xiaoshuang
Published: August 2015

Semiconductor nanowires (NWs) can be applied in gas sensing and cell detection, but the sensing mechanism is not clearly understood. In this study, surface modification effect on the electronic properties of CdS NWs for different diameters with several species (H, F, Cl, Br, and NO2) is investigated by first principles calculations. The surface dangling bonds and halogen elements are chosen to represent the environment of the surface. Halogen passivation drastically changes the band gaps due to the strong electronegativity and the energy level of halogen atoms. Density of states analysis indicates that valence band maximum (VBM) of halogen-passivated NWs is formed by the p states of halogen atoms, while VBM of H-passivated NWs is originated from Cd 4d and S 3p orbitals. To illustrate that surface modification can be applied in gas sensing, NO2-absorbed NWs with different coverage are calculated. Low coverage of NO2 introduces a deep p-type dopant-like level, while high coverage introduces a shallow n-type dopant-like level into the band structure. The transformation is due to that at low coverage the adsorption is chemical while at high coverage is physical. These findings might promote the understanding of surface modification effect and the sensing mechanism of NWs as gas sensors.
Reaction-in-flight neutrons as a test of stopping power in degenerate plasmas
Authors: Hayes A. C. , Jungman Gerard , Schulz A. E. , Boswell M. , Fowler M. M. , Grim G. , Klein A. , Rundberg R. S. , Wilhelmy J. B. , Wilson D. , Cerjan C. , Schneider D. , Sepke S. M. , Tonchev A. , Yeamans C.
Published: August 2015

We present the first measurements of reaction-in-flight (RIF) neutrons in an inertial confinement fusion system. The experiments were carried out at the National Ignition Facility, using both Low Foot and High Foot drives and cryogenic plastic capsules. In both cases, the high-energy RIF (En> 15 MeV) component of the neutron spectrum was found to be about 10−4 of the total. The majority of the RIF neutrons were produced in the dense cold fuel surrounding the burning hotspot of the capsule, and the data are consistent with a compressed cold fuel that is moderately to strongly coupled (Γ∼ 0.6) and electron degenerate (θFermi/θe∼ 4). The production of RIF neutrons is controlled by the stopping power in the plasma. Thus, the current RIF measurements provide a unique test of stopping power models in an experimentally unexplored plasma regime. We find that the measured RIF data strongly constrain stopping models in warm dense plasma conditions, and some models are ruled out by our analysis of these experiments.
Muon detection studied by pulse-height energy analysis: Novel converter arrangements
Authors: Holmlid Leif , Olafsson Sveinn
Published: August 2015

Muons are conventionally measured by a plastic scintillator–photomultiplier detector. Muons from processes in ultra-dense hydrogen H(0) are detected here by a novel type of converter in front of a photomultiplier. The muon detection yield can be increased relative to that observed with a plastic scintillator by at least a factor of 100, using a converter of metal, semiconductor (Ge), or glass for interaction with the muons penetrating through the metal housing of the detector. This detection process is due to transient formation of excited nuclei by the well-known process of muon capture, giving beta decay. The main experimental results shown here are in the form of beta electron energy spectra detected directly by the photomultiplier. Events which give a high-energy tail in the energy spectra are probably due to gamma photons from the muons. Sharp and intense x-ray peaks from a muonic aluminium converter or housing material are observed. The detection conversion in glass and Ge converters has a time constant of the order of many minutes to reach the final conversion level, while the process in metal converters is stabilized faster. The time constants are not due to lifetimes of the excited nuclei or neutrons but are due to internal charging in the insulating converter material. Interaction of this charging with the high voltage in the photomultiplier is observed.
Electric field-induced tuning of magnetism in PbFe0.5Nb0.5O3 at room temperature
Authors: Rayaprol S. , Mukherjee S. , Kaushik S. D. , Matteppanavar S. , Angadi B.
Published: August 2015

We study the influence of electrical poling, carried out at room temperature, on the structure and magnetism of Pb(Fe0.5Nb0.5)O3 by analyzing the differences observed in structural and magnetic properties before and after the electrical poling. The changes observed in magnetization of Pb(Fe0.5Nb0.5)O3 before and after electrical poling exhibit considerably strong converse magnetoelectric effect at room temperature. In addition, the strengthening of Fe/Nb-O bond due to electrical poling is discussed on the basis of Raman spectral studies and analysis of neutron diffraction patterns. The potential tunability of magnetization with electrical poling can be an ideal tool for realization of application potential of this multiferroic material.
Lifetime analysis of laser crystallized silicon films on glass
Authors: Kühnapfel Sven , Huang Jialiang , Teal Anthony , Kampwerth Henner , Amkreutz Daniel , Gall Stefan , Varlamov Sergey
Published: August 2015

Only recently, the quality of liquid phase crystallized silicon directly on glass substrates made a huge leap towards the quality of multi-crystalline wafers with open circuit voltages well above 600 mV. In this paper, we investigate the material quality in order to identify the factors limiting further performance improvements. We employ photoluminescence imaging on a state of the art test structure with lifetime calibration by transient photoluminescence. The resulting lifetime map is converted into an effective diffusion length map and the origin of regions with short lifetimes is investigated with electron backscattering and transmission electron microscopy. High local dislocation densities in areas with dissociated coincidence site lattice boundaries were found to be responsible for the localised quenching of the photoluminescence signal.
Communication: Maximum caliber is a general variational principle for nonequilibrium statistical mechanics
Authors: Hazoglou Michael J. , Walther Valentin , Dixit Purushottam D. , Dill Ken A.
Published: August 2015

There has been interest in finding a general variational principle for non-equilibrium statistical mechanics. We give evidence that Maximum Caliber (Max Cal) is such a principle. Max Cal, a variant of maximum entropy, predicts dynamical distribution functions by maximizing a path entropy subject to dynamical constraints, such as average fluxes. We first show that Max Cal leads to standard near-equilibrium results—including the Green-Kubo relations, Onsager’s reciprocal relations of coupled flows, and Prigogine’s principle of minimum entropy production—in a way that is particularly simple. We develop some generalizations of the Onsager and Prigogine results that apply arbitrarily far from equilibrium. Because Max Cal does not require any notion of “local equilibrium,” or any notion of entropy dissipation, or temperature, or even any restriction to material physics, it is more general than many traditional approaches. It also applicable to flows and traffic on networks, for example.
Spin-transfer-torque efficiency enhanced by edge-damage of perpendicular magnetic random access memories
Authors: Song Kyungmi , Lee Kyung-Jin
Published: August 2015

We numerically investigate the effect of magnetic and electrical damages at the edge of a perpendicular magnetic random access memory (MRAM) cell on the spin-transfer-torque (STT) efficiency that is defined by the ratio of thermal stability factor to switching current. We find that the switching mode of an edge-damaged cell is different from that of an undamaged cell, which results in a sizable reduction in the switching current. Together with a marginal reduction of the thermal stability factor of an edge-damaged cell, this feature makes the STT efficiency large. Our results suggest that a precise edge control is viable for the optimization of STT-MRAM.
Localized surface plasmon induced enhancement of electron-hole generation with silver metal island at n-Al:ZnO/p-Cu2O heterojunction
Authors: Kaur Gurpreet , Yadav K. L. , Mitra Anirban
Published: August 2015

Localized surface plasmon induced generation of electron-hole pairs with inclusion of metal islands of noble metal like Ag can enhance the photocurrent. A heterostructure of n-Al:ZnO/p-Cu2O with inclusion of Ag metalislands at the junction has been fabricated. I-V characteristic curve of these heterostructures shows a significant enhancement of photocurrent under the illumination (1.5 AMU). This enhancement of photocurrent is attributed to the supply of hot electrons generated in silver metal nanoislands. It has also been shown that inclusion of metal islands increases the absorption of solar spectrum in visible region at 500 nm. Enhancement of photocurrent may also be due to the direct resonance energy transfer from Localized Surface Plasmons of metal islands to Cu2O.
Ultrasound sensing using the acousto-optic effect in polymer dispersed liquid crystals
Authors: Trushkevych O. , Eriksson T. J. R. , Ramadas S. N. , Dixon S. , Edwards R. S.
Published: August 2015

Acousto-optic effects are demonstrated in polymer dispersed liquid crystal (PDLC) films, showing promise for applications in ultrasound sensing. The PDLC films are used to image two displacement profiles of air-coupled flexural transducers' resonant modes at 295 kHz and 730 kHz. Results are confirmed using laser vibrometry. The regions on the transducers with the largest displacements are clearly imaged by the PDLC films, with the resolution agreeing well with laser vibrometry scanning. Imaging takes significantly less time than a scanning system (switching time of a few seconds, as compared to 8 h for laser vibrometry). Heating effects are carefully monitored using thermal imaging and are found not to be the main cause of PDLC clearing.
Determination of transition metal ion distribution in cubic spinel Co1.5Fe1.5O4 using anomalous x-ray diffraction
Authors: Singh M. N. , Sinha A. K. , Ghosh Haranath
Published: August 2015

We report anomalous x-ray diffraction studies on Co ferrite with composition Co1.5Fe1.5O4 to obtain the distribution of transition metal ions in tetrahedral and octahedral sites. We synthesize spinel oxide (Co1.5Fe1.5O4) through co-precipitation and subsequent annealing route. The imaginary part (absorption) of the energy dependent anomalous form factor is measured and the real part is calculated theoretically through Kramers–Krönig transformation to analyze anomalous x-ray diffraction peak intensities. Fe and Co K-edge x-ray absorption near edge structure (XANES) spectra are used to estimate charge states of transition metals. Our analysis, within experimental errors, suggests 44% of the tetrahedral sites contain Co in +2 oxidation state and the rest 56% sites contain Fe in +2 and +3 oxidation states. Similarly, 47% of the octahedral sites contain Fe in +3 oxidation states, whereas, the rest of the sites contain Co in +2 and +3 oxidation states. While a distinct pre-edge feature in the Fe K-edge XANES is observed, Co pre-edge remains featureless. Implications of these results to magnetism are briefly discussed.
Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles
Authors: Ravikumar Patta , Kisan Bhagaban , Perumal A.
Published: August 2015

We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO) band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μB/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (TC) around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR) studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high TC and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.
Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal
Authors: Lu Qieni , Han Jinxin , Dai Haitao , Ge Baozhen , Zhao Shuang
Published: August 2015

We measure temperature dependence on Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal simultaneously in this work, based on digital holographic interferometry (DHI). And the spatial distribution of the field-induced refractive index change can also be visualized and estimated by numerically retrieving sequential phase maps of Mn:Fe:KTN crystal from recording digital holograms in different states. The refractive indices decrease with increasing temperature and quadratic polarized optical coefficient is insensitive to temperature. The experimental results suggest that the DHI method presented here is highly applicable in both visualizing the temporal and spatial behavior of the internal electric field and accurately measuring electro-optic coefficient for electrooptical media.
Theoretical analysis of uranium-doped thorium dioxide: Introduction of a thoria force field with explicit polarization
Authors: Shields A. E. , Ruiz Hernandez S. E. , de Leeuw N. H.
Published: August 2015

Thorium dioxide is used industrially in high temperature applications, but more insight is needed into the behavior of the material as part of a mixed-oxide (MOX) nuclear fuel, incorporating uranium. We have developed a new interatomic potential model including polarizability via a shell model, and commensurate with a prominent existing UO2 potential, to conduct configurational analyses and to investigate the thermophysical properties of uranium-doped ThO2. Using the GULP and Site Occupancy Disorder (SOD) computational codes, we have analyzed the distribution of low concentrations of uranium in the bulk material, where we have not observed the formation of uranium clusters or the dominance of a single preferred configuration. We have calculated thermophysical properties of pure thorium dioxide and Th(1−x)UxO2 which generated values in very good agreement with experimental data.
Atomistic tensile deformation mechanisms of Fe with gradient nano-grained structure
Authors: Li Wenbin , Yuan Fuping , Wu Xiaolei
Published: August 2015

Large-scale molecular dynamics (MD) simulations have been performed to investigate the tensile properties and the related atomistic deformation mechanisms of the gradient nano-grained (GNG) structure of bcc Fe (gradient grains with d from 25 nm to 105 nm), and comparisons were made with the uniform nano-grained (NG) structure of bcc Fe (grains with d = 25 nm). The grain size gradient in the nano-scale converts the applied uniaxial stress to multi-axial stresses and promotes the dislocation behaviors in the GNG structure, which results in extra hardening and flow strength. Thus, the GNG structure shows slightly higher flow stress at the early plastic deformation stage when compared to the uniform NG structure (even with smaller grain size). In the GNG structure, the dominant deformation mechanisms are closely related to the grain sizes. For grains with d = 25 nm, the deformation mechanisms are dominated by GB migration, grain rotation and grain coalescence although a few dislocations are observed. For grains with d = 54 nm, dislocation nucleation, propagation and formation of dislocation wall near GBs are observed. Moreover, formation of dislocation wall and dislocation pile-up near GBs are observed for grains with d = 105 nm, which is the first observation by MD simulations to our best knowledge. The strain compatibility among different layers with various grain sizes in the GNG structure should promote the dislocation behaviors and the flow stress of the whole structure, and the present results should provide insights to design the microstructures for developing strong-and-ductile metals.
Hysteresis phenomena of the two dimensional electron gas density in lattice-matched InAlN/GaN heterostructures
Authors: Sang Ling , Yang Xuelin , Cheng Jianpeng , Jia Lifang , He Zhi , Guo Lei , Hu Anqi , Xiang Yong , Yu Tongjun , Wang Maojun , Xu Fujun , Tang Ning , Wang Xinqiang , Ge Weikun , Shen Bo
Published: August 2015

High-temperature transport properties in high-mobility lattice-matched InAlN/GaN heterostructures have been investigated. An interesting hysteresis phenomenon of the two dimensional electron gas (2DEG) density is observed in the temperature-dependent Hall measurements. After high-temperature thermal cycles treatment, the reduction of the 2DEG density is observed, which is more serious in thinner InAlN barrier samples. This reduction can then be recovered by light illumination. We attribute these behaviors to the shallow trap states with energy level above the Fermi level in the GaN buffer layer. The electrons in the 2DEG are thermal-excited when temperature is increased and then trapped by these shallow trap states in the buffer layer, resulting in the reduction and hysteresis phenomenon of their density. Three trap states are observed in the GaN buffer layer and CGa may be one of the candidates responsible for the observed behaviors. Our results provide an alternative approach to assess the quality of InAlN/GaN heterostructures for applications in high-temperature electronic devices.
Band gap engineering in finite elongated graphene nanoribbon heterojunctions: Tight-binding model
Authors: Tayo Benjamin O.
Published: August 2015

A simple model based on the divide and conquer rule and tight-binding (TB) approximation is employed for studying the role of finite size effect on the electronic properties of elongated graphene nanoribbon (GNR) heterojunctions. In our model, the GNR heterojunction is divided into three parts: a left (L) part, middle (M) part, and right (R) part. The left part is a GNR of width WL, the middle part is a GNR of width WM, and the right part is a GNR of width WR. We assume that the left and right parts of the GNR heterojunction interact with the middle part only. Under this approximation, the Hamiltonian of the system can be expressed as a block tridiagonal matrix. The matrix elements of the tridiagonal matrix are computed using real space nearest neighbor orthogonal TB approximation. The electronic structure of the GNR heterojunction is analyzed by computing the density of states. We demonstrate that for heterojunctions for which WL = WR, the band gap of the system can be tuned continuously by varying the length of the middle part, thus providing a new approach to band gap engineering in GNRs. Our TB results were compared with calculations employing divide and conquer rule in combination with density functional theory (DFT) and were found to agree nicely.
Seasonal oestrous cycle activity of captive female koalas in south-east Queensland
Authors: Ballantyne K. , Lisle A. , Mucci A. , Johnston S. D.
Published: August 2015

This study investigated the seasonality of behavioural oestrus in a captive koala population in south-east Queensland. A total of 33 sexually mature koalas were examined over a 4-year period (2009–12) to determine the possible influence of temperature, photoperiod and rainfall on the incidence of expression of behavioural oestrus without the confounding effect of lactation or limiting food resource availability. Although signs of behavioural oestrus were detected throughout the year, an obvious seasonality was apparent, with significantly fewer females displaying behavioural oestrus in late autumn and winter (May–August) than September to April (P < 0.0001). While average monthly photoperiod (P < 0.0001) and average monthly temperature (P < 0.0001) were significantly related to oestrous behaviour, rainfall was not (P > 0.05). A better understanding of the seasonality of reproductive function in the female koala will facilitate the use of reproductive management-assisted breeding technology to enable improved genetic management in captive populations.
Necrotic enteritis in chickens: an important disease caused by Clostridium perfringens
Authors: Moore Robert J
Published: August 2015

Clostridium perfringens, a spore-forming, Gram-positive, anaerobic bacterium, causes a variety of diseases throughout the animal kingdom. Each disease in each animal species tends to be caused by particular strains of C. perfringens and is defined by the tissue tropism and toxin profile of the bacteria. In chickens toxinotype A strains cause necrotic enteritis; a disease characterised by tissue damage to the proximal regions of the small intestine. In extreme cases the disease can be lethal but is more commonly seen as a sub-clinical disease that causes welfare issues and productivity losses within the poultry industry. The disease is currently well controlled in Australia by good management practices and, for some poultry producers, the use of antibiotics in the feed. However, the disease does cause significant issues in other regions including North America and Europe. In Europe there was a spike of necrotic enteritis disease when antibiotics were withdrawn from animal feeds. It is probable that the disease will become more of an issue in the Australian poultry industry as in-feed antibiotic use is reduced. Therefore, other methods of disease control are under investigation, including the development of vaccines.
The manufacture of veterinary clostridial vaccines
Authors: Dempster Robert
Published: August 2015

Clostridial vaccines are commonly used in most countries where farming of cattle, sheep, goats and horses occurs on a commercial scale. Vaccines to protect against clostridial diseases make up the second largest group of ruminant vaccines sold globally. In Australia the sales value of these vaccines makes up $46m of the $96m sheep and cattle vaccine market (Baron market data). This group of vaccines has become so ubiquitous, and competition between competitors so fierce, that they have been reduced to the status of commodities where they can sell for less than 20c/dose. However, this definition does not do justice to the enormous value they have generated for many decades ‘behind the farm gate'.
Morphologically similar, coexisting hard corals (Porites lobata and P. solida) display similar trophic isotopic ratios across reefs and depths
Authors: Plass-Johnson Jeremiah G. , McQuaid Christopher D. , Hill Jaclyn M.
Published: August 2015

Recent studies using stable isotope analysis in scleractinian corals have highlighted strong inter- and intra-specific variability in isotopic ratios, but few have excluded the effects of morphology, which affects resource acquisition, potentially confounding this with metabolic differences among species. Differences in the stable isotopic (δ13C and δ15N) ratios of the coral host tissue and photosymbionts of two co-existing, morphologically similar Porites corals (P. lobata and P. solida) were examined across nested spatial scales (inter-reefs and intra-reef) and across depths in Zanzibar, Tanzania. There were few differences between species in either coral host or photosymbiont isotopic ratios, but the two tissues showed different spatial patterns. Photosymbionts showed variation only in their δ13C ratios, which differed among reefs, but not by depth. In contrast, the coral hosts differed in δ13C and δ15N values among reefs and also by depth. Within-reef differences among sites occurred only for photosymbionts at one reef. The absence of differences in isotopic ratios between the two Porites species across reefs and depths, confirms that highly related and morphologically similar scleractinian corals may occupy similar ecosystem niches, metabolising resources in a similar fashion. This suggests that resource partitioning among corals, and subsequent isotopic variability, is most likely driven by resource acquisition, rather than being inherently species-specific.
Comparison of in situ and satellite sea surface-temperature data from South Australia and Tasmania: how reliable are satellite data as a proxy for coastal temperatures in temperate southern Australia?
Authors: Stobart B. , Mayfield S. , Mundy C. , Hobday A. J. , Hartog J. R.
Published: August 2015

Satellite sea-surface temperature (SST) is widely used for biological modelling and ecological studies, assuming it represents subsurface in situ temperature (IST). We tested this assumption at 32 coastal sites in southern Australia, spanning a wide geographic range. Annual IST regimes are described and were demonstrated to be highly correlated with SST. Mean annual daily temperature differences between SST and IST (DTD) were generally small, varying spatially and seasonally (range 0–1°C). No correlation between DTDs and a range of site attributes was found, indicating the importance of site-specific factors. Seasonal DTDs were not geographically consistent, being higher in South Australia during the summer (mean 1.4°C) than in Tasmania (mean 0.5°C). Generally, small annual mean DTDs justify using SST for broad-scale ecological and climate-change studies, although considerable DTDs at some sites suggest that using SST at smaller spatial and temporal scales is unlikely to be appropriate. In addition, SST data lack information on daily temperature fluctuation that may be biologically relevant. Excepting South Australia, where spatially consistent summer DTDs would allow a correction factor, this site-specific variation is hard to correct. In spite of this, studies that rely on SST should consider the implications of such variation on the level of certainty associated with temperature-based predictions.
Catatonia and Cannabis Withdrawal: A Case Report
Authors: Caudron Mathieu , Rolland Benjamin , Deheul Sylvie , Geoffroy Pierre Alexis , Thomas Pierre , Amad Ali
Published: August 2015

Background

Catatonia is a severe motor syndrome found in approximately 10% of all acute psychiatric hospital admissions. It can occur in various psychiatric diseases. The authors report the first case report of catatonia during cannabis withdrawal. Case Presentation: Mr. A, a 32-year-old man, reported to have smoked approximately 20 g of cannabis daily since the age of 11. Mr. A was incarcerated and was reported 3 weeks later to the medical department for having completely ceased talking and eating. At admission in the authors’ department, the patient presented with classical catatonia symptoms (Bush-Francis Catatonia Rating Scale [BFCRS] score = 39/69). All laboratory results and brain magnetic resonance imaging (MRI) were normal. Six weeks after his admission and treatments by lorazepam and memantine, his BFCRS score was 0/69. Discussion: This single case study highlights the previously underreported emergence of physical and motor symptoms following cannabis withdrawal. Pathophysiological aspects of abrupt cannabis cessation contributing to γ-aminobutyric acid (GABA)/glutamate balance dysregulation and to catatonia are discussed.
Heart Rate Recovery is an Important Predictor of Outcomes in Patients with Connective Tissue Disease–Associated Pulmonary Hypertension
Authors: Minai Omar A. , Nguyen Quyen , Mummadi Srinivas , Walker Esteban , McCarthy Kevin , Dweik Raed A.
Published: August 2015

Reduced heart rate recovery (HRR) after exercise is associated with increased mortality in cardiac and pulmonary diseases. We sought to evaluate the association between HRR after the 6‐minute walk test (6MWT) and outcomes in patients with connective tissue disease–associated pulmonary hypertension (CTD‐PH). Data were obtained by review of the medical records. HRR was defined as the difference in heart rate at the end of the 6MWT and after 1 minute (HRR1), 2 minutes (HRR2), and 3 minutes (HRR3) of rest. All patients with pulmonary hypertension and a diagnosis of systemic sclerosis, systemic lupus erythematosus, or mixed connective tissue disease who underwent the 6MWT between August 1, 2009, and October 30, 2011, were included (n = 66). By Kaplan‐Meier analysis, HRR1, HRR2, and HRR3 at different cutoff points were all good predictors, with HRR1 of <16 being the best predictor of time to clinical worsening (log‐rank P < 0.0001), hospitalization (log‐rank P = 0.0001), and survival (log‐rank P < 0.003). By proportional hazards regression, patients with HRR1 of <16 were at increased risk of clinical worsening (hazard ratio [HR]: 6.4 [95% confidence interval (CI): 2.6–19.2]; P < 0.0001], hospitalization (HR: 6.6 [95% CI: 2.4–23]; P < 0.0001), and death (HR: 4.5 [95% CI: 1.6–15.7]; P = 0.003). Patients in the highest tercile (HRR1 of ≥19) were unlikely to have a clinical worsening event (HR: 0.1 [95% CI: 0.04–0.5]; P = 0.001], to be hospitalized (HR: 0.1 [95% CI: 0.02–0.5]; P = 0.001), or to die (HR: 0.3 [95% CI: 0.07–0.9]; P = 0.04]. In conclusion, in patients with CTD‐PH, abnormal HRR1 (defined as HRR1 of <16) after the 6MWT is a strong predictor of clinical worsening, time to clinical worsening, survival, and hospitalization.
Ezrin regulates focal adhesion and invadopodia dynamics by altering calpain activity to promote breast cancer cell invasion
Authors: Hoskin Victoria , Szeto Alvin , Ghaffari Abdi , Greer Peter A. , Côté Graham P. , Elliott Bruce E.
Published: August 2015

Up-regulation of the cytoskeleton linker protein ezrin frequently occurs in aggressive cancer types and is closely linked with metastatic progression. However, the underlying molecular mechanisms detailing how ezrin is involved in the invasive and metastatic phenotype remain unclear. Here we report a novel function of ezrin in regulating focal adhesion (FA) and invadopodia dynamics, two key processes required for efficient invasion to occur. We show that depletion of ezrin expression in invasive breast cancer cells impairs both FA and invadopodia turnover. We also demonstrate that ezrin-depleted cells display reduced calpain-mediated cleavage of the FA and invadopodia-associated proteins talin, focal adhesion kinase (FAK), and cortactin and reduced calpain-1–specific membrane localization, suggesting a requirement for ezrin in maintaining proper localization and activity of calpain-1. Furthermore, we show that ezrin is required for cell directionality, early lung seeding, and distant organ colonization but not primary tumor growth. Collectively our results unveil a novel mechanism by which ezrin regulates breast cancer cell invasion and metastasis.
(En) corps sonore
: Jean-Luc Nancy's ‘Sonotropism’
Authors: Hickmott Sarah
Published: August 2015

This article offers a critical, feminist, and interdisciplinary account of the question of listening in Jean-Luc Nancy's 2002 text,
À l'écoute
. Nancy's text is at once an auditory counterpart to his larger philosophical project; an articulation of the specifically sonorous subject; and a more expressly musicological contribution to his other work on the literary and visual arts. While Nancy's — among others' — attempts at steering philosophy away from or beyond a visual bias proliferate, considerably less commentary has been devoted to the way in which inherited ideas about aesthetic ‘objects’ — in this case music— already inhabit certain conceptions of the senses. By paying close attention to the characterization and inclusion of music in the
corps sonore
, and by tracing the genealogies of Nancy's thought on music (and sound), this article will finally offer a rereading of Nancy's oto-iconographical reading of Titian's
Venus and Cupid with an Organist
; one that highlights the ethical and political dimensions of Nancy's position. I shall argue that problematic and preconceived notions about the supposed nature of music abound in Nancy's philosophy of listening, revealing a metaphysical (sono)tropism that is all too familiar.
Escape conditions of radiative-driven strati from luminous accretion disks
Authors: Nakai Takuya , Fukue Jun
Published: August 2015

We examine the dynamical motion and escape conditions of continuum-driven strati (flat cloud) with finite optical depth from luminous accretion disks around a black hole. We adopt the near-disk approximation, and treat the problem in the framework of special relativity, where the radiation drag force as well as the radiation pressure are included. We find that the optically thin strati are easy to accelerate, compared with the particles, and the escape condition of the stratus is reduced. That is, when the disk luminosity is around the Eddington luminosity, the optically thin strati can escape from the inner disk (≲ 20 rg; rg being the Schwarzschild radius). When the disk luminosity is about half the Eddington luminosity, it can escape at around 5 rg. This is due to the translucent effect. In addition, the trajectories of the strati are not vertical, but a funnel-like shape due to the centrifugal force. Stratus outflow could easily blow out from usual accretion disks with sub-Eddington luminosities, and this may explain outflows observed in broad absorption line quasars and ultra-fast outflow objects.