bluuebunny/crossref_metadata_2025 huggingface dataset:
Transformer inrush mitigation for dynamic voltage restorer using direct flux linkage control
Authors: Gao Shan , Lin Xinchun , Ye Shangjun , Lei He , Kang Yong
Published: September 2015

Dynamic voltage restorer (DVR) based on transformer‐coupled topology is the most cost‐effective solution to protect consumer from voltage sags. However, an important issue about this topology is the transformer saturation. Magnetic saturation of the transformer will generate large inrush current which may greatly distort the compensation voltage or even trigger the over‐current protection. To prevent the transformer from saturation, this study proposes a novel direct magnetising flux linkage control strategy. Distinguished from existing DVR models which ignored the transformer magnetising branch, this study establishes a comprehensive DVR model by adopting the magnetising flux linkage as a state‐variable. Therefore, by adopting flux linkage feedback, the magnetising flux linkage would be directly controlled. Otherwise, to implement the flux linkage control, this study proposes a robust flux estimation method to carry out the proposed control scheme. Finally, the whole system is verified on a 380 V/10 kVA three‐phase experimental DVR prototype.
Noninvasively probing the light-emitting diode temperature by magnetic nanoparticles
Authors: Hu Run , Du Zhongzhou , Cheng Ting , Huang Zhixing , Liu Wenzhong , Luo Xiaobing
Published: September 2015

The precise measurement of temperature information is of great importance in the thermal management of light-emitting diodes (LEDs). Hitherto, many methods have been proposed to measure the LED temperature, but none of them involve with magnetics. Herein, we developed a noninvasive and precise method to probe the LED temperatures based on magnetic nanoparticles (MNPs). Detailed measurement principle and experimental setup were introduced. Through this setup, the heating and cooling characteristics of LEDs were investigated with different voltage inputs. It is found that higher voltage input leads to higher LED temperature. When the input voltage is 5.2 V, the LED temperature is 326.8 K. The present noninvasive and precise method supplements the existing techniques of temperature measurement in terms of magnetics and opens up new avenues to measure the temperature information where conventional approaches may fail.
Fokker Planck and Krook theory of energetic electron transport in a laser produced plasma
Authors: Manheimer Wallace , Colombant Denis
Published: September 2015

Various laser plasma instabilities, such as the two plasma decay instability and the stimulated Raman scatter instability, produce large quantities of energetic electrons. How these electrons are transported and heat the plasma are crucial questions for laser fusion. This paper works out a Fokker Planck and Krook theory for such transport and heating. The result is a set of equations, for which one can find a simple asymptotic approximation for the solution, for the Fokker Planck case, and an exact solution for the Krook case. These solutions are evaluated and compared with one another. They give rise to expressions for the spatially dependent heating of the background plasma, as a function of the instantaneous laser and plasma parameters, in either planar or spherical geometry. These formulas are simple, universal (depending weakly only on the single parameter Z, the charge state), and can be easily be incorporated into a fluid simulation.
Gravity current flow over sinusoidal topography in a two-layer ambient
Authors: Nicholson Mitchell , Flynn Morris R.
Published: September 2015

We report upon a laboratory experimental study of dense full- and partial-depth locks released gravity currents propagating through a two-layer ambient and over sinusoidal topography of amplitude A and wavelength λ. Attention is restricted to a Boussinesq flow regime and the initial (or slumping) stage of motion. Because of the presence of the topography, the lower layer depth and channel depth vary in the downstream direction by as much as ±52% and ±40%, respectively. Despite such large variations, the instantaneous gravity current front speed typically changes by only a small amount from its average value, Ū. We conclude that the reason for this unexpected observation is a counterbalancing between the contraction/expansion of the channel on one hand and along-slope variations of the buoyancy force on the other hand. Compared to the case of gravity current flow over a horizontal surface, the topography has a retarding effect on Ū; we characterize the variation of Ū with the following parameters: A, A/λ, the interface height, the height of gravity current fluid inside the lock, and the layer densities as characterized by S ≡ (ρ1 − ρ2)/(ρ0 − ρ2) where ρ0 is the gravity current density, ρ1 is the lower ambient layer density, and ρ2 is the upper ambient layer density. The topography also alters the structure of the gravity current head by inducing large-scale Kelvin-Helmholtz (K-H) vortices directly downstream of regions of significant shear. These vortices are transient flow features; after formation and saturation, they relax at which point gravity current fluid sloshes back and forth in the topographic troughs. A simple geometric model is presented that prescribes the minimum number of topographic peaks a gravity current fluid will overcome. As in the horizontal bottom case, the forward advance of the gravity current can excite a downstream-propagating interfacial disturbance, which is more prominent for larger S. We identify when the gravity current front will travel faster (supercritical flow) or slower (subcritical flow) than the interfacial disturbance based on S and A/λ. Unlike in the horizontal-bottom case, however, we typically also observe interfacial oscillations far ahead of the gravity current front. These have wavelength approximately equal to λ and are due to spatial variations in the speed of the ambient return flow.
Runaway electron dynamics in tokamak plasmas with high impurity content
Authors: Martín-Solís J. R. , Loarte A. , Lehnen M.
Published: September 2015

The dynamics of high energy runaway electrons is analyzed for plasmas with high impurity content. It is shown that modified collision terms are required in order to account for the collisions of the relativistic runaway electrons with partially stripped impurity ions, including the effect of the collisions with free and bound electrons, as well as the scattering by the full nuclear and the electron-shielded ion charge. The effect of the impurities on the avalanche runaway growth rate is discussed. The results are applied, for illustration, to the interpretation of the runaway electron behavior during disruptions, where large amounts of impurities are expected, particularly during disruption mitigation by massive gas injection. The consequences for the electron synchrotron radiation losses and the resulting runaway electron dynamics are also analyzed.
Modeling of inelastic collisions in a multifluid plasma: Excitation and deexcitation
Authors: Le Hai P. , Cambier Jean-Luc
Published: September 2015

We describe here a model for inelastic collisions for electronic excitation and deexcitation processes in a general, multifluid plasma. The model is derived from kinetic theory, and applicable to any mixture and mass ratio. The principle of detailed balance is strictly enforced, and the model is consistent with all asymptotic limits. The results are verified with direct Monte Carlo calculations, and various numerical tests are conducted for the case of an electron-hydrogen two-fluid system, using a generic, semi-classical model of collision cross sections. We find that in some cases, the contribution of inelastic collisions to the momentum and thermal resistance coefficients is not negligible, in contrast to the assumptions of current multifluid models. This fundamental model is also applied to ionization and recombination processes, the studies on which are currently underway.
Effects of laser radiation field on energies of hydrogen atom in plasmas
Authors: Bahar M. K.
Published: September 2015

In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye and quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.
Vertical electric field induced suppression of fine structure splitting of excited state excitons in a single GaAs/AlGaAs island quantum dots
Authors: Ghali Mohsen , Ohno Yuzo , Ohno Hideo
Published: September 2015

We report experimentally on fine structure splitting (FSS) of various excitonic transitions in single GaAs island quantum dots, formed by a monolayer thickness fluctuation in the narrow GaAs/AlGaAs quantum well, and embedded in an n-i-Schottky diode device. By applying a forward vertical electric field (F) between the top metallic contact and the sample substrate, we observed an in-plane polarization rotation of both the ground and the excited state excitons with increasing the electric field. The polarization rotations were accompanied with a strong decrease in the FSS of the ground as well as the excited state excitons with the field, until the FSS vanished as F approached 30 kV/cm.
Dimensional crossover of free exciton diffusion in etched GaAs wire structures
Authors: Bieker S. , Stühler R. , Kiessling T. , Ossau W. , Molenkamp L. W.
Published: September 2015

We report on low-temperature spatially resolved photoluminescence spectroscopy to study the diffusion of free excitons in etched wire structures of high-purity GaAs. We assess the stationary diffusion profiles by the free exciton second LO-phonon replica to circumvent the inherent interpretation ambiguities of the previously investigated free exciton zero-phonon line. Moreover, strictly resonant optical excitation prevents the distortion of the diffusion profiles due to local heating in the carrier system. We observe a dimensional crossover from 2D to 1D exciton diffusion when the lateral wire width falls below the diffusion length.
Dry efficient cleaning of poly-methyl-methacrylate residues from graphene with high-density H2 and H2-N2 plasmas
Authors: Cunge G. , Ferrah D. , Petit-Etienne C. , Davydova A. , Okuno H. , Kalita D. , Bouchiat V. , Renault O.
Published: September 2015

Graphene is the first engineering electronic material, which is purely two-dimensional: it consists of two exposed sp2-hybridized carbon surfaces and has no bulk. Therefore, surface effects such as contamination by adsorbed polymer residues have a critical influence on its electrical properties and can drastically hamper its widespread use in devices fabrication. These contaminants, originating from mandatory technological processes of graphene synthesis and transfer, also impact fundamental studies of the electronic and structural properties at the atomic scale. Therefore, graphene-based technology and research requires “soft” and selective surface cleaning techniques dedicated to limit or to suppress this surface contamination. Here, we show that a high-density H2 and H2-N2 plasmas can be used to selectively remove polymeric residues from monolayer graphene without any damage on the graphene surface. The efficiency of this dry-cleaning process is evidenced unambiguously by a set of spectroscopic and microscopic methods, providing unprecedented insights on the cleaning mechanisms and highlighting the role of specific poly-methyl-methacrylate residues at the graphene interface. The plasma is shown to perform much better cleaning than solvents and has the advantage to be an industrially mature technology adapted to large area substrates. The process is transferable to other kinds of two-dimensional material and heterostructures.
Fluid-solid transition in simple systems using density functional theory
Authors: Bharadwaj Atul S. , Singh Yashwant
Published: September 2015

A free energy functional for a crystal which contains both the symmetry-conserved and symmetry-broken parts of the direct pair correlation function has been used to investigate the fluid-solid transition in systems interacting via purely repulsive Weeks-Chandler-Anderson Lennard–Jones potential and the full Lennard–Jones potential. The results found for freezing parameters for the fluid-face centred cubic crystal transition are in very good agreement with simulation results. It is shown that although the contribution made by the symmetry broken part to the grand thermodynamic potential at the freezing point is small compared to that of the symmetry conserving part, its role is crucial in stabilizing the crystalline structure and on values of the freezing parameters.
Metallic nanoparticle shape and size effects on aluminum oxide-induced enhancement of exciton-plasmon coupling and quantum dot emission
Authors: Wing Waylin J. , Sadeghi Seyed M. , Gutha Rithvik R. , Campbell Quinn , Mao Chuanbin
Published: September 2015

We investigate the shape and size effects of gold metallic nanoparticles on the enhancement of exciton-plasmon coupling and emission of semiconductor quantum dots induced via the simultaneous impact of metal-oxide and plasmonic effects. This enhancement occurs when metallic nanoparticle arrays are separated from the quantum dots by a layered thin film consisting of a high index dielectric material (silicon) and aluminum oxide. Our results show that adding the aluminum oxide layer can increase the degree of polarization of quantum dot emission induced by metallic nanorods by nearly two times, when these nanorods have large aspect ratios. We show when the aspect ratio of these nanorods is reduced to half, the aluminum oxide loses its impact, leading to no improvement in the degree of polarization. These results suggest that a silicon/aluminum oxide layer can significantly enhance exciton-plasmon coupling when quantum dots are in the vicinity of metallic nanoantennas with high aspect ratios.
Dissemination stability and phase noise characteristics in a cascaded, fiber-based long-haul radio frequency dissemination network
Authors: Gao C. , Wang B. , Zhu X. , Yuan Y. B. , Wang L. J.
Published: September 2015

To study the dissemination stability and phase noise characteristics of the cascaded fiber-based RF dissemination, we perform an experiment using three sets of RF modulated frequency dissemination systems. The experimental results show that the total transfer stability of the cascaded system can be given by σT2=∑i=1Nσi2 (σi is the frequency dissemination stability of the ith segment and N is the quantity of segments). Furthermore, for each segment, the phase noise of recovered frequency signal is also measured. The results show that for an N-segment, cascaded dissemination system, its stability degrades only by a factor of N. This sub-linear relation makes the cascaded, RF-dissemination method a very attractive one for long-haul, time and frequency dissemination network.
Directed HK propagator
Authors: Kocia Lucas , Heller Eric J.
Published: September 2015

We offer a more formal justification for the successes of our recently communicated “directed Heller-Herman-Kluk-Kay” (DHK) time propagator by examining its performance in one-dimensional bound systems which exhibit at least quasi-periodic motion. DHK is distinguished by its single one-dimensional integral—a vast simplification over the usual 2N-dimensional integral in full Heller-Herman-Kluk-Kay (for an N-dimensional system). We find that DHK accurately captures particular coherent state autocorrelations when its single integral is chosen to lie along these states’ fastest growing manifold, as long as it is not perpendicular to their action gradient. Moreover, the larger the action gradient, the better DHK will perform. We numerically examine DHK’s accuracy in a one-dimensional quartic oscillator and illustrate that these conditions are frequently satisfied such that the method performs well. This lends some explanation for why DHK frequently seems to work so well and suggests that it may be applicable to systems exhibiting quite strong anharmonicity.
Optical activity and defect/dopant evolution in ZnO implanted with Er
Authors: Azarov Alexander , Galeckas Augustinas , Hallén Anders , Kuznetsov Andrej , Monakhov Edouard , Svensson Bengt G.
Published: September 2015

The effects of annealing on the optical properties and defect/dopant evolution in wurtzite (0001) ZnO single crystals implanted with Er ions are studied using a combination of Rutherford backscattering/channeling spectrometry and photoluminescence measurements. The results suggest a lattice recovery behavior dependent on ion dose and involving formation/evolution of an anomalous multipeak defect distribution, thermal stability of optically active Er complexes, and Er outdiffusion. An intermediate defect band occurring between the surface and ion-induced defects in the bulk is stable up to 900 °C and has a photoluminescence signature around 420 nm well corresponding to Zn interstitials. The optical activity of the Er atoms reaches a maximum after annealing at 700 °C but is not directly associated to the ideal Zn site configuration, since the Er substitutional fraction is maximal already in the as-implanted state. In its turn, annealing at temperatures above 700 °C leads to dissociation of the optically active Er complexes with subsequent outdiffusion of Er accompanied by the efficient lattice recovery.
Electron beam induced growth of tin whiskers
Authors: Vasko A. C. , Warrell G. R. , Parsai E. I. , Karpov V. G. , Shvydka Diana
Published: September 2015

We have investigated the influence of electron irradiation on tin whisker growth. Sputtered tin samples exposed to electron beam of 6 MeV energy exhibited fast whisker growth, while control samples did not grow any whiskers. The statistics of e-beam induced whiskers was found to follow the log-normal distribution. The observed accelerated whisker growth is attributed to electrostatic effects due to charges trapped in an insulating substrate. These results offer promise for establishing whisker-related accelerated life testing protocols.
Simultaneous negative refraction and focusing of fundamental frequency and second-harmonic fields by two-dimensional photonic crystals
Authors: Zhang Jun , Zhang Xiangdong
Published: September 2015

Simultaneous negative refraction for both the fundamental frequency (FF) and second-harmonic (SH) fields in two-dimensional nonlinear photonic crystals have been found through both the physical analysis and exact numerical simulation. By combining such a property with the phase-matching condition and strong second-order susceptibility, we have designed a SH lens to realize focusing for both the FF and SH fields at the same time. Good-quality non-near field images for both FF and SH fields have been observed. The physical mechanism for such SH focusing phenomena has been disclosed, which is different from the backward SH generation as has been pointed out in the previous investigations. In addition, the effect of absorption losses on the phenomena has also been discussed. Thus, potential applications of these phenomena to biphotonic microscopy technique are anticipated.
Influence of pretreatment processes onto bio-methanation of wheat straw
Authors: Sharma Rajan , Singhal Shailey , Tiwari Avanish K. , Agarwal Shilpi , Arora Shefali , Singhal Naveen
Published: September 2015

Lignocellulosic wastes, inexpensive and potential sources of bioenergy were explored for delignification and production of biogas. Wheat straw was subjected to chemical and biological treatment methods for removal of lignin, facilitating bio-methanation. Pretreatment produced remarkable results with an enhanced amount of methane. Bio-methanation of wheat straw after pretreatment produced biogas with an appreciable methane content (acid treatment 80%, alkaline treatment 74%, thermal treatment 77%, and fungal treatment 92%). Among all, fungal treatment responded to maximum delignification and biogas generation. The method has the potential to be converted to technology for large scale operations.
Hyper-Rayleigh scattering in centrosymmetric systems
Authors: Williams Mathew D. , Ford Jack S. , Andrews David L.
Published: September 2015

Hyper-Rayleigh scattering (HRS) is an incoherent mechanism for optical second harmonic generation. The frequency-doubled light that emerges from this mechanism is not emitted in a laser-like manner, in the forward direction; it is scattered in all directions. The underlying theory for this effect involves terms that are quadratic in the incident field and involves an even-order optical susceptibility (for a molecule, its associated hyperpolarizability). In consequence, HRS is often regarded as formally forbidden in centrosymmetric media. However, for the fundamental three-photon interaction, theory based on the standard electric dipole approximation, representable as E13, does not account for all experimental observations. The relevant results emerge upon extending the theory to include E12M1 and E12E2 contributions, incorporating one magnetic dipolar or electric quadrupolar interaction, respectively, to a consistent level of multipolar expansion. Both additional interactions require the deployment of higher orders in the multipole expansion, with the E12E2 interaction analogous in rank and parity to a four-wave susceptibility. To elicit the correct form of response from fluid or disordered media invites a tensor representation which does not oversimplify the molecular components, yet which can produce results to facilitate the interpretation of experimental observations. The detailed derivation in this work leads to results which are summarized for the following: perpendicular detection of polarization components both parallel and perpendicular to the pump radiation, leading to distinct polarization ratio results, as well as a reversal ratio for forward scattered circular polarizations. The results provide a route to handling data with direct physical interpretation, to enable the more sophisticated design of molecules with sought nonlinear optical properties.
Internal quantum efficiency in yellow-amber light emitting AlGaN-InGaN-GaN heterostructures
Authors: Ngo Thi Huong , Gil Bernard , Valvin Pierre , Damilano Benjamin , Lekhal Kaddour , De Mierry Philippe
Published: September 2015

We determine the internal quantum efficiency of strain-balanced AlGaN-InGaN-GaN hetero-structures designed for yellow-amber light emission, by using a recent model based on the kinetics of the photoluminescence decay initiated by Iwata et al. [J. Appl. Phys. 117, 075701 (2015)]. Our results indicate that low temperature internal quantum efficiencies sit in the 50% range and we measure that adding an AlGaN layer increases the internal quantum efficiency from 50% up to 57% with respect to the GaN-InGaN case. More dramatic, it almost doubles from 2.5% up to 4.3% at room temperature.
Experimental implementation of phase locking in a nonlinear interferometer
Authors: Wang Hailong , Marino A. M. , Jing Jietai
Published: September 2015

Based upon two cascade four-wave mixing processes in two identical hot rubidium vapor cells, a nonlinear interferometer has been experimentally realized [Jing et al., Appl. Phys. Lett. 99, 011110 (2011); Hudelist et al., Nat. Commun. 5, 3049 (2014)]. It has a higher degree of phase sensitivity than a traditional linear interferometer and has many potential applications in quantum metrology. Phase locking of the nonlinear interferometer is needed before it can find its way into applications. In this letter, we investigate the experimental implementation of phase locking of the relative phase between the three beams at different frequencies involved in such a nonlinear interferometer. We have utilized two different methods, namely, beat note locking and coherent modulation locking. We find that coherent modulation locking can achieve much better phase stability than beat note locking in our system. Our results pave the way for real applications of a nonlinear interferometer in precision measurement and quantum manipulation, for example, phase control in phase-sensitive N-wave mixing process, N-port nonlinear interferometer and quantum-enhanced real-time phase tracking.
Accurate on-chip measurement of the Seebeck coefficient of high mobility small molecule organic semiconductors
Authors: Warwick C. N. , Venkateshvaran D. , Sirringhaus H.
Published: September 2015

We present measurements of the Seebeck coefficient in two high mobility organic small molecules, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) and 2,9-didecyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (C10-DNTT). The measurements are performed in a field effect transistor structure with high field effect mobilities of approximately 3 cm2/V s. This allows us to observe both the charge concentration and temperature dependence of the Seebeck coefficient. We find a strong logarithmic dependence upon charge concentration and a temperature dependence within the measurement uncertainty. Despite performing the measurements on highly polycrystalline evaporated films, we see an agreement in the Seebeck coefficient with modelled values from Shi et al. [Chem. Mater. 26, 2669 (2014)] at high charge concentrations. We attribute deviations from the model at lower charge concentrations to charge trapping.
Magnonic crystal as a delay line for low-noise auto-oscillators
Authors: Bankowski Elena , Meitzler Thomas , Khymyn Roman S. , Tiberkevich Vasil S. , Slavin Andrei N. , Tang Hong X.
Published: September 2015

It is demonstrated that a delay line based on a one-dimensional magnonic crystal used in a feedback loop of a microwave auto-oscillator can substantially reduce the phase noise figure and improve other vital performance characteristics of the auto-oscillator. The advantage is achieved due to the increase of the effective delay time in the magnonic crystal, compared to the case of an un-patterned yttrium iron garnet (YIG) film, and improvement of the power-handling characteristics due to the now possible increase of the YIG film thickness. The internal modes of a magnonic crystal caused by the periodic energy exchange between the incident and reflected spin waves play the dominant role in the described effect.
Existence of the β-tin structure in Sr: First evidence from computational approach
Authors: Tsuppayakorn-aek P. , Chaimayo W. , Pinsook U. , Bovornratanaraks T.
Published: September 2015

Molecular Dynamics (MD) calculation is one of the most powerful theoretical methods widely used to predict and to confirm structural phase transitions. In this work, the MD method has been used to verify phase transition from body-centered cubic (bcc) to β-tin structure, then, to the Cmcm and hexagonal close-packed (hcp) structure, respectively. The transition sequence from previous theoretical works has been confirmed. In this study, Density Functional Theory (DFT), has been used to calculate phonon dispersion to confirm the stability of β-tin and hcp phases. The long time discrepancies in transition sequence between the calculation and the experimental works has been explained by conventional DFT calculation using screened exchange local density approximation (sX-LDA). More importantly, the existence of β-tin structure is finally predicted and the transition nature of Sr has also been revealed.
Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO
Authors: Huang Zheng , Lü Tie-Yu , Wang Hui-Qiong , Zheng Jin-Cheng
Published: September 2015

We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type) semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature, indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.
Magnetic moment directions and distributions of cations in Cr (Co) substituted spinel ferrites Ni0.7Fe2.3O4
Authors: Xue L. C. , Lang L. L. , Xu J. , Li Z. Z. , Qi W. H. , Tang G. D. , Wu L. Q.
Published: September 2015

Powder samples of the spinel ferrites MxNi0.7−xFe2.3O4 (M = Cr, Co and 0.0 ≤ x ≤ 0.3) and CrxNi0.7Fe2.3−xO4 (0.0 ≤ x ≤ 0.3) were synthesized using the chemical co-precipitation method. The XRD spectra confirmed that the samples had a single-phase cubic spinel structure. Magnetic measurements showed that the magnetic moments (μexp) per formula both at 10 K and 300 K increased with Co substitution, while the values of μexp decreased with Cr substitution. Applying the assumption that the magnetic moments of Cr2+ and Cr3+ lie antiparallel to those of the divalent and trivalent Fe, Co, and Ni cations in the same sublattice of spinel ferrites, these interesting behaviors could be easily interpreted. The cation distributions of the three series of samples were estimated successfully by fitting the dependences of μexp, measured at 10 K, on the doping level x, using a quantum-mechanical potential barrier model earlier proposed by our group. The results obtained for the Cr cation distributions at the (A) and [B] sites are very close to those obtained elsewhere using neutron diffraction.
Electronic structure of the (Nd1−xDyx)2Fe14B (0 ≤ x ≤ 1) system studied by X-ray photoelectron spectroscopy
Authors: Wang Jing , Yang Bin , Liang Le , Sun Li-min , Zhang Lan-ting , Hirano Shin-ichi
Published: September 2015

Systematic characterization of electronic structures in the (Nd1−xDyx)2Fe14B system, especially the 4f behavior, provides an insight to the physical nature of the evolution of magnetic properties. A series of X-ray photoelectron spectroscopy (XPS) core-level and valence-band spectra were used to study the electronic structures. It was found that substitution of Dy for Nd in Nd2Fe14B results in a nonlinear variation in the evolution of electronic structures. Only the finite coupling between the Nd 4f states and the Fe 3d states is found at both the Nd-rich regime and the Dy-rich regime. When the Dy concentration and the Nd concentration approach to be equal, a strong coupling between the Nd 4f states and the Fe 3d states is found, which results in a bonding state between them. Additionally, the 4f components in the (Nd1−xDyx)2Fe14B system are ascribed to three parts: 1) the individual contribution of the Dy 4f states, which emerges just after the Dy-substitution; 2) the contribution of the coupling between the Nd 4f states and the Dy 4f states, which arises only when 0.4 ≤ x ≤ 0.6; 3) the associated contributions of the Nd 4f states and the Dy 4f states, where the contribution of the Nd 4f states and that of the Dy 4f states are prominent in the Nd-rich regime and Dy-rich regime, respectively.
Controlled formation of anatase and rutile TiO2 thin films by reactive magnetron sputtering
Authors: Rafieian Damon , Ogieglo Wojciech , Savenije Tom , Lammertink Rob G. H.
Published: September 2015

We discuss the formation of TiO2 thin films via DC reactive magnetron sputtering. The oxygen concentration during sputtering proved to be a crucial parameter with respect to the final film structure and properties. The initial deposition provided amorphous films that crystallise upon annealing to anatase or rutile, depending on the initial sputtering conditions. Substoichiometric films (TiOx<2), obtained by sputtering at relatively low oxygen concentration, formed rutile upon annealing in air, whereas stoichiometric films formed anatase. This route therefore presents a formation route for rutile films via lower (<500 °C) temperature pathways. The dynamics of the annealing process were followed by in situ ellipsometry, showing the optical properties transformation. The final crystal structures were identified by XRD. The anatase film obtained by this deposition method displayed high carriers mobility as measured by time-resolved microwave conductance. This also confirms the high photocatalytic activity of the anatase films.
Direct evidence that suspensor cells have embryogenic potential that is suppressed by the embryo proper during normal embryogenesis
Authors: Liu Yuan , Li Xinbo , Zhao Jing , Tang Xingchun , Tian Shujuan , Chen Junyi , Shi Ce , Wang Wei , Zhang Liyao , Feng Xianzhong , Sun Meng-Xiang
Published: September 2015

Significance

The suspensor is a temporary structure that undergoes programmed cell death during seed maturation. It has been suggested that suspensor cells have embryogenic potential that is suppressed by the embryo. Using an established in vivo living cell laser ablation system, we confirmed the embryogenic potential of the
Arabidopsis
suspensor and the role of the embryo proper in imposing suspensor cell identity. We also showed that auxin redistribution in suspensor cells after laser ablation of embryos may play an essential role in the initiation of suspensor embryos.
Effects of coffee and caffeine anhydrous on strength and sprint performance
Authors: Trexler Eric T. , Smith‐Ryan Abbie E. , Roelofs Erica J. , Hirsch Katie R. , Mock Meredith G.
Published: September 2015

Caffeine and coffee are widely used among active individuals to enhance performance. The purpose of the current study was to compare the effects of acute coffee (COF) and caffeine anhydrous (CAF) intake on strength and sprint performance. Fifty‐four resistance‐trained males completed strength testing, consisting of one‐rep max (1RM) and repetitions to fatigue (RTF) at 80% of 1RM for leg press (LP) and bench press (BP). Participants then completed five, 10‐second cycle ergometer sprints separated by one minute of rest. Peak power (PP) and total work (TW) were recorded for each sprint. At least 48 hours later, participants returned and ingested a beverage containing CAF (300 mg flat dose; yielding 3–5 mg/kg bodyweight), COF (8.9 g; 303 mg caffeine), or placebo (PLA; 3.8 g non‐caloric flavouring) 30 minutes before testing. LP 1RM was improved more by COF than CAF (p = .04), but not PLA (p = .99). Significant interactions were not observed for BP 1RM, BP RTF, or LP RTF (p > .05). There were no sprint × treatment interactions for PP or TW (p > .05). 95% confidence intervals revealed a significant improvement in sprint 1 TW for CAF, but not COF or PLA. For PLA, significant reductions were observed in sprint 4 PP, sprint 2 TW, sprint 4 TW, and average TW; significant reductions were not observed with CAF or COF. Neither COF nor CAF improved strength outcomes more than PLA, while both groups attenuated sprint power reductions to a similar degree. Coffee and caffeine anhydrous may be considered suitable pre‐exercise caffeine sources for high‐intensity exercise.
Ontogenetic and Sex-Specific Shifts in the Feeding Habits of the Barndoor Skate
Authors: Schmitt Joseph D. , Gedamke Todd , DuPaul William D. , Musick John A.
Published: September 2015

Diet analysis is critical in understanding the flow of energy within marine food webs and is necessary for trophic ecosystem modeling and subsequent ecosystem-based management recommendations. This study represents the first comprehensive diet description for the Barndoor Skate Dipturus laevis, the largest rajid species found on the continental shelf in the northwestern Atlantic Ocean. Stomach contents were extracted from 273 individual skate caught as bycatch in the commercial scallop fishery on Georges Bank and a total of 31 prey species were identified. The Barndoor Skate feeds primarily upon sand shrimp Crangon septemspinosa, the rock crab Cancer irroratus, the Acadian hermit crab Pagurus acadianus, and teleost fish. Length-specific analysis revealed four significant feeding groups (ANOVA: P < 0.01). Skate < 35 cm TL were specialized feeders foraging solely on caridean shrimp, and as size increased (35–75 cm TL), they began to feed upon rock crab and then the Acadian hermit crab. At lengths ranging from 85 to 105 cm TL, no caridean shrimp were found in the skate's diet and the prevalence of crustaceans decreased. Large skate (>105 cm TL) began to prey heavily upon teleost fish, yet also continued to consume larger crustaceans. Significant sex-specific differences in food habits were also observed in the biggest skate (>105 cm TL): males fed primarily on teleost fish (∼80%); however, females maintained a diet of approximately equal amounts of fish and crustaceans. These sex-specific feeding patterns and differential food niche utilization may be mitigated by sexually dimorphic dentition.

Received November 18, 2014; accepted June 11, 2015
Exploring peptide/MHC detachment processes using hierarchical natural move Monte Carlo
Authors: Knapp Bernhard , Demharter Samuel , Deane Charlotte M. , Minary Peter
Published: September 2015

Motivation: The binding between a peptide and a major histocompatibility complex (MHC) is one of the most important processes for the induction of an adaptive immune response. Many algorithms have been developed to predict peptide/MHC (pMHC) binding. However, no approach has yet been able to give structural insight into how peptides detach from the MHC.

Results: In this study, we used a combination of coarse graining, hierarchical natural move Monte Carlo and stochastic conformational optimization to explore the detachment processes of 32 different peptides from HLA-A*02:01. We performed 100 independent repeats of each stochastic simulation and found that the presence of experimentally known anchor amino acids affects the detachment trajectories of our peptides. Comparison with experimental binding affinity data indicates the reliability of our approach (area under the receiver operating characteristic curve 0.85). We also compared to a 1000 ns molecular dynamics simulation of a non-binding peptide (AAAKTPVIV) and HLA-A*02:01. Even in this simulation, the longest published for pMHC, the peptide does not fully detach. Our approach is orders of magnitude faster and as such allows us to explore pMHC detachment processes in a way not possible with all-atom molecular dynamics simulations.

Availability and implementation: The source code is freely available for download at http://www.cs.ox.ac.uk/mosaics/.

Contact:  bernhard.knapp@stats.ox.ac.uk

Supplementary information:  Supplementary data are available at Bioinformatics online.
Infertility and reproductive disorders: impact of hormonal and inflammatory mechanisms on pregnancy outcome
Authors: Vannuccini Silvia , Clifton Vicki L. , Fraser Ian S. , Taylor Hugh S. , Critchley Hilary , Giudice Linda C. , Petraglia Felice
Published: September 2015

BACKGROUND

Reproductive disorders and infertility are associated with the risk of obstetric complications and have a negative impact on pregnancy outcome. Affected patients often require assisted reproductive technologies (ART) to conceive, and advanced maternal age is a further confounding factor. The challenge is to dissect causation, correlation and confounders in determining how infertility and reproductive disorders individually or together predispose women to poor pregnancy outcomes.

METHODS

The published literature, to June 2015, was searched using PubMed, summarizing all evidences concerning the perinatal outcome of women with infertility and reproductive disorders and the potential mechanisms that may influence poor pregnancy outcome.

RESULTS

Reproductive disorders (endometriosis, adenomyosis, polycystic ovary syndrome and uterine fibroids) and unexplained infertility share inflammatory pathways, hormonal aberrations, decidual senescence and vascular abnormalities that may impair pregnancy success through common mechanisms. Either in combination or alone, these disorders results in an increased risk of preterm birth, fetal growth restriction, placental pathologies and hypertensive disorders. Systemic hormonal aberrations, and inflammatory and metabolic factors acting on endometrium, myometrium, cervix and placenta are all associated with an aberrant milieu during implantation and pregnancy, thus contributing to the genesis of obstetric complications. Some of these features have been also described in placentas from ART.

CONCLUSIONS

Reproductive disorders are common in women of childbearing age and rarely occur in isolation. Inflammatory, endocrine and metabolic mechanisms associated with these disorders are responsible for an increased incidence of obstetric complications. These patients should be recognized as ‘high risk’ for poor pregnancy outcomes and monitored with specialized follow-up. There is a real need for development of evidence-based recommendations about clinical management and specific obstetric care pathways for the introduction of prompt preventative care measures.
Lidocaine Reduces Acute Postoperative Pain After Supratentorial Tumor Surgery in the PACU: A Secondary Finding From a Randomized, Controlled Trial
Authors: Peng Yuming , Zhang Wei , Kass Ira S. , Han Ruquan
Published: September 2015

Background:

Perioperative lidocaine infusion has been reported to reduce postoperative pain in patients after abdominal surgery; however, no study has examined lidocaine’s effect on acute postoperative pain after supratentorial tumor surgery.

Methods:

A total of 94 patients scheduled for supratentorial craniotomy were enrolled. Patients received either lidocaine through an intravenous bolus (1.5 mg/kg) after induction followed by infusion at a rate of 2 mg/kg/h until the end of surgery or the same volume of normal saline. Mean arterial blood pressure, heart rate, and bispectral index were recorded at different intraoperative time points. Patients were assessed for pain in the postoperative anesthesia care unit (PACU) by the numeric rating scale (NRS). Other complications including hypertension, tachycardia, dysphoria, and postoperative nausea and vomiting (PONV) were reported.

Results:

There was no significant difference between the normal saline and lidocaine group for mean arterial blood pressure, heart rate, and bispectral index at any time point (P>0.05). There was no significant difference in the incidence of hypertension, tachycardia, dysphoria, and PONV between groups (P>0.05). The incidence of mild pain (NRS between 1 and 3) after surgery in PACU was lower in lidocaine group than that in the normal saline group (P=0.014); the number of patients with an NRS pain score of 0 before leaving the PACU was significantly greater in the lidocaine group. No patient in either group had moderate or severe pain.

Conclusions:

Intraoperative infusion of lidocaine significantly decreases the proportion of patients with acute pain after supratentorial tumor surgery in the PACU.
Real-Time Measurement of Dynamic Changes of Anterior Segment Biometry and Wavefront Aberrations During Accommodation
Authors: Zhu Dexi , Shao Yilei , Peng Yu , Chen Qi , Wang Jianhua , Lu Fan , Shen Meixiao
Published: September 2015

Objectives:

To analyze the dynamic relationship between ocular geometrical structure and high-order aberrations (HOAs) in teal-time during accommodation of human eye.

Methods:

A custom-built spectral domain optical coherence tomography (OCT) system with high-speed and ultra-long scan depth was used to image the anterior segment, whereas a Shack–Hartmann wavefront sensor was used to detect the whole-eye aberration. A Badal optometer with switched visual targets was integrated with this system to induce 0 and 3.00 D accommodative stimuli. Three young adult subjects were measured and the structural parameters of anterior segment were measured from OCT images and accommodative response and HOAs were calculated and exponentially fitted in real time during the accommodation.

Results:

The dynamic process from nonaccommodation to 3.00 D accommodation results in reduced pupil diameter, shallower anterior chamber depth, and increased crystalline lens thickness. After an accommodative active time, the RMS of the HOAs changes sharply when an accommodative stimulus is introduced and then tends to be stable. The accommodative response time and velocity are characterized by fitted parameters. The individual differences of changing in HOAs between subjects can be explained by the different sign and changing tendency of certain terms of aberration coefficients in form of Zernike polynomials during the accommodation.

Conclusions:

Based on the integrated ocular measurement platform including OCT system and wavefront sensor, our research demonstrated how the morphology of the human anterior segment affect the aberration in real time during accommodation. The dynamic relationship between them helps us to deeply understand the mechanism of accommodation.
Use of Sugammadex in Patients With Obesity: A Pooled Analysis
Authors: Monk Terri G. , Rietbergen Henk , Woo Tiffany , Fennema Hein
Published: September 2015

A growing proportion of patients undergoing surgical procedures are obese, providing anesthesiologists with numerous challenges for patient management. The current pooled analysis evaluated recovery times following sugammadex reversal of neuromuscular blockade by body mass index (BMI) in general, and in particular, in patients with BMIs ≥30 kg/m2 (defined as obese) and <30 kg/m2 (defined as non-obese). Data were pooled from 27 trials evaluating recommended sugammadex doses for reversal of moderate [reappearance of the second twitch of the train-of-four (TOF); sugammadex 2 mg/kg] or deep (1–2 post-tetanic counts or 15 minutes after rocuronium; sugammadex 4 mg/kg) rocuronium- or vecuronium-induced neuromuscular blockade. All doses of sugammadex were administered based on actual body weight. The recovery time from sugammadex administration to a TOF ratio ≥0.9 was the primary efficacy variable in all individual studies and in the pooled analysis. This analysis comprised a total of 1418 adult patients treated with sugammadex; 267 (18.8%) of these patients had a BMI ≥30 kg/m2. The average time to recovery of the TOF ratio to 0.9 was 1.9 minutes for rocuronium-induced blockade and 3.0 minutes for vecuronium-induced blockade. No clinically relevant correlation was observed between BMI and recovery time. The recommended sugammadex doses based on actual body weight provide rapid recovery from neuromuscular blockade in both obese and non-obese patients; no dose adjustments are required in the obese patient.