bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon-nanoparticles isolated by in situ grown polycrystalline graphene hollow spheres for enhanced lithium-ion storage
Authors: Zhang Juan , Zhang Li , Xue Peng , Zhang Liya , Zhang Xianlin , Hao Weiwei , Tian Jinghua , Shen Ming , Zheng Honghe
Published: March 2015

Graphene hollow sphere isolated Si nanoparticle nanocomposites arein situsynthesized for the first time and used as high-performance Li-ion anodes.
Co3S4 porous nanosheets embedded in graphene sheets as high-performance anode materials for lithium and sodium storage
Authors: Du Yichen , Zhu Xiaoshu , Zhou Xiaosi , Hu Lingyun , Dai Zhihui , Bao Jianchun
Published: March 2015

A robust three-dimensional sandwich-like Co3S4 porous nanosheet/graphene sheet composite exhibits improved rate performance and cycling stability for both lithium and sodium storage.
In3Se4 and S-doped In3Se4 nano/micro-structures as new anode materials for Li-ion batteries
Authors: Han Guang , Chen Zhi-Gang , Ye Delai , Wang Bei , Yang Lei , Zou Yichao , Wang Lianzhou , Drennan John , Zou Jin
Published: March 2015

In3Se4 and S-doped In3Se4 nano/micro-structures consisting of thin nanosheets have been explored as new anode materials for Li-ion batteries.
Dendrite-free lithium metal anodes: stable solid electrolyte interphases for high-efficiency batteries
Authors: Cheng Xin-Bing , Zhang Qiang
Published: March 2015

A more superior cycling stability and a higher utilization ratio of the Li metal anode have been achieved by additive- and nanostructure-stabilized SEI layers. A profound understanding of the composition, internal structure, and evolution of the SEI film sheds new light on dendrite-free high-efficiency lithium metal batteries.
Flexible all-solid-state asymmetric supercapacitors with three-dimensional CoSe2/carbon cloth electrodes
Authors: Yu Neng , Zhu Ming-Qiang , Chen Di
Published: March 2015

Hierarchical CoSe2 nanostructures are successfully grown on conductive carbon fabrics as binder-free electrodes for flexible all-solid-state asymmetric supercapacitors with improved performances.
Graphene aerogel prepared by thermal evaporation of graphene oxide suspension containing sodium bicarbonate
Authors: Yang Shaolin , Zhang Li , Yang Qiuyun , Zhang Zihan , Chen Bo , Lv Peng , Zhu Wei , Wang Guanzhong
Published: March 2015

We present a new type of in situ reduction-assembly approach to construct graphene hydrogel through simultaneous water evaporation and graphene oxide reduction.
Intelligent position control of permanent magnet synchronous motor using recurrent fuzzy neural cerebellar model articulation network
Authors: Lin Faa‐Jeng , Yang Kai‐Jie , Sun I‐Fan , Chang Jin‐Kuan
Published: March 2015

A recurrent fuzzy neural cerebellar model articulation network (RFNCMAN) control is proposed in this paper for position servo drive systems to track various periodical position references with robustness. The adopted position servo drive system is designed using a six‐phase PMSM and equipped with a fault‐tolerant control scheme. First, an ideal computed torque controller is designed for the tracking of the rotor position reference command. Since the uncertainties of the PMSM position servo drive system are difficult to know in advance, it is impossible to design an ideal computed control law for practical applications. Therefore, the RFNCMAN is proposed to mimic the ideal computed torque controller with a compensated controller to compensate the approximation error. In the RFNCMAN, a recurrent fuzzy cerebellar model articulation network (RFCMAN) is adopted in the first dimension to enhance the online learning rate and localisation learning capability. Moreover, a general recurrent fuzzy neural network (RFNN) is adopted in the second dimension to enhance the generalisation performance and to reduce the required memory and rule numbers. Finally, the proposed position control system is implemented in a 32‐bit floating‐point DSP. The effectiveness of the proposed RFNCMAN control system is verified by some experimental results.
Integrated battery charger with power factor correction for electric‐propulsion systems
Authors: Liu Tian‐Hua , Chen Yi , Yi Pei‐Heng , Chen Jui‐Ling
Published: March 2015

This paper proposes an on‐board integrated battery charger for an electric‐propulsion system. The system includes a rectifying diode bridge, an inverter, a permanent magnet motor, a digital signal processor, a battery set and three relays. By suitably controlling the three relays and the power switches of the inverter, the proposed system can be operated as either an electric‐propulsion system or a battery charger. The integrated battery charger can be used to charge a 48 V battery set or a 192 V battery set from a single‐phase 110 Vrms grid. The battery charger can be operated in a boost‐converter charging mode or in buck‐converter charging mode with input power factor higher than 0.9 when operating with 48 V battery or 192 V battery, which can meet the IEC 1000‐3‐2 standard. Only a diode bridge, an inductance‐capacitance (LC) filter, and three additional relays are required in addition to the components for propulsion. The windings of the motor and the power switches of the inverter are shared for both the electric‐propulsion system and the battery charger. A digital signal processor, TMS‐320‐F‐2808, is used to execute all of the control algorithms. Experimental results validate the theoretical analysis and separately show the correctness and feasibility of the proposed method.
Effect of pressure on the parameters of the superconducting transition in In-doped PbzSn1−zTe semiconducting solid solutions
Authors: Parfeniev R. V. , Kozub V. I. , Andrianov G. O. , Shamshur D. V. , Chernyaev A. V. , Mikhailin N. Yu. , Nemov S. A.
Published: March 2015

The effect of hydrostatic pressures up to 10 kbar and lead content on the superconducting and electrical characteristics of indium-doped (5 at. %) PbzSn1−zTe semiconducting solid solutions is studied. Experimental correlations are found for these pressure dependences. When the pressure is raised to P = 6.8 kbar in this material with a lead content z = 0.45 the superconductivity threshold increases to Tc = 1.7 K, which is typical of the compound with z = 0.05 at atmospheric pressure. Increasing the hydrostatic pressure P > 3 kbar in (Pb0.05Sn0.95)0.95In0.05Te causes Tc to fall below 1 K. These features, along with the bell-shaped Tc(P) curve for z = 0.3, are explained by a shift in the energy EIn of the quasilocal states and the Fermi level which is stabilized by them, from the L-band into the Σ-valence band with a high density of states (most noticeable for z = 0.45). A concentration threshold for emergence of the Fermi level from the Σ-valence band with increasing lead content was found using Hall effect measurements at T = 77 K.
New manifestations of a pseudogap state and electron spin scattering in the low-temperature thermal properties of near-stoichiometric iron-vanadium-aluminum alloys
Authors: Lonchakov A. T. , Marchenkov V. V. , Okulov V. I. , Okulova K. A. , Govorkova T. E. , Podgornykh S. M.
Published: March 2015

The temperature dependences of the specific heat and thermal conductivity, as well as magnetic-field induced changes in the thermal conductivity, are studied in iron-vanadium-aluminum alloys that exhibit anomalous electron properties for certain near-stoichiometric compositions. Based on previous work, we develop some ideas regarding particular features of the electron structure in these alloys (narrow pseudogap, strong spin scattering, etc.) that may be of interest both for discovering new classes of materials and for technical applications.
Properties of solid solutions, doped film, and nanocomposite structures based on zinc oxide
Authors: Lashkarev G. V. , Shtepliuk I. I. , Ievtushenko A. I. , Khyzhun O. Y. , Kartuzov V. V. , Ovsiannikova L. I. , Karpyna V. A. , Myroniuk D. V. , Khomyak V. V. , Tkach V. N. , Timofeeva I. I. , Popovich V. I. , Dranchuk N. V. , Khranovskyy V. D. , Demydiuk P. V.
Published: March 2015

A study of the properties of materials based on the wide bandgap zinc oxide semiconductor, which are promising for application in optoelectronics, photovoltaics and nanoplasmonics. The structural and optical properties of solid solution Zn1−xCdxO films with different cadmium content, are studied. The samples are grown using magnetron sputtering on sapphire backing. Low-temperature photoluminescence spectra revealed emission peaks associated with radiative recombination processes in those areas of the film that have varying amounts of cadmium. X-ray phase analysis showed the presence of a cadmium oxide cubic phase in these films. Theoretical studies of the solid solution thermodynamic properties allowed for a qualitative interpretation of the observed experimental phenomena. It is established that the growth of the homogeneous solid solution film is possible only at high temperatures, whereas regions of inhomogeneous composition can be narrowed through elastic deformation, caused by the mismatch of the film-backing lattice constants. The driving forces of the spinodal decomposition of the Zn1−xCdxO system are identified. Fullerene-like clusters of Znn−xCdxOn are used to calculate the bandgap and the cohesive energy of ZnCdO solid solutions. The properties of transparent conductive ZnO films, doped with Group III donor impurities (Al, Ga, In), are examined. It is shown that oxygen vacancies are responsible for the hole trap centers in the zinc oxide photoconductivity process. We also examine the photoluminescence properties of metal-ZnO nanocomposite structures, caused by surface plasmons.
Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide
Authors: Bondi Robert J. , Marinella Matthew J.
Published: March 2015

First-principles density-functional theory calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (VOn; n = 0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta2O5), and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. VOn of all oxidation states preferentially segregates at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta2O5, VO0 is characterized by structural contraction and electron density localization, while VO2+ promotes structural expansion and is depleted of electron density. In contrast, interfacial VO0 and VO2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced VO center. Interfacial VO2+ extracts electron density from metallic Ta, indicating that VO2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.
Characteristics of temperature rise in variable inductor employing magnetorheological fluid driven by a high-frequency pulsed voltage source
Authors: Lee Ho-Young , Kang In Man , Shon Chae-Hwa , Lee Se-Hee
Published: March 2015

A variable inductor with magnetorheological (MR) fluid has been successfully applied to power electronics applications; however, its thermal characteristics have not been investigated. To evaluate the performance of the variable inductor with respect to temperature, we measured the characteristics of temperature rise and developed a numerical analysis technique. The characteristics of temperature rise were determined experimentally and verified numerically by adopting a multiphysics analysis technique. In order to accurately estimate the temperature distribution in a variable inductor with an MR fluid-gap, the thermal solver should import the heat source from the electromagnetic solver to solve the eddy current problem. To improve accuracy, the B–H curves of the MR fluid under operating temperature were obtained using the magnetic property measurement system. In addition, the Steinmetz equation was applied to evaluate the core loss in a ferrite core. The predicted temperature rise for a variable inductor showed good agreement with the experimental data and the developed numerical technique can be employed to design a variable inductor with a high-frequency pulsed voltage source.
Formation of buffer-gas-trap based positron beams
Authors: Natisin M. R. , Danielson J. R. , Surko C. M.
Published: March 2015

Presented here are experimental measurements, analytic expressions, and simulation results for pulsed, magnetically guided positron beams formed using a Penning-Malmberg style buffer gas trap. In the relevant limit, particle motion can be separated into motion along the magnetic field and gyro-motion in the plane perpendicular to the field. Analytic expressions are developed which describe the evolution of the beam energy distributions, both parallel and perpendicular to the magnetic field, as the beam propagates through regions of varying magnetic field. Simulations of the beam formation process are presented, with the parameters chosen to accurately replicate experimental conditions. The initial conditions and ejection parameters are varied systematically in both experiment and simulation, allowing the relevant processes involved in beam formation to be explored. These studies provide new insights into the underlying physics, including significant adiabatic cooling, due to the time-dependent beam-formation potential. Methods to improve the beam energy and temporal resolution are discussed.
Suppression of roll-off characteristics of organic light-emitting diodes by narrowing current injection/transport area to 50 nm
Authors: Hayashi Kyohei , Nakanotani Hajime , Inoue Munetomo , Yoshida Kou , Mikhnenko Oleksandr , Nguyen Thuc-Quyen , Adachi Chihaya
Published: March 2015

Using e-beam nanolithography, the current injection/transport area in organic light-emitting diodes (OLEDs) was confined into a narrow linear structure with a minimum width of 50 nm. This caused suppression of Joule heating and partial separation of polarons and excitons, so the charge density where the electroluminescent efficiency decays to the half of the initial value (J0) was significantly improved. A device with a narrow current injection width of 50 nm exhibited a J0 that was almost two orders of magnitude higher compared with that of the unpatterned OLED.
Origins of low energy-transfer efficiency between patterned GaN quantum well and CdSe quantum dots
Authors: Xu Xingsheng
Published: March 2015

For hybrid light emitting devices (LEDs) consisting of GaN quantum wells and colloidal quantum dots, it is necessary to explore the physical mechanisms causing decreases in the quantum efficiencies and the energy transfer efficiency between a GaN quantum well and CdSe quantum dots. This study investigated the electro-luminescence for a hybrid LED consisting of colloidal quantum dots and a GaN quantum well patterned with photonic crystals. It was found that both the quantum efficiency of colloidal quantum dots on a GaN quantum well and the energy transfer efficiency between the patterned GaN quantum well and the colloidal quantum dots decreased with increases in the driving voltage or the driving time. Under high driving voltages, the decreases in the quantum efficiency of the colloidal quantum dots and the energy transfer efficiency can be attributed to Auger recombination, while those decreases under long driving time are due to photo-bleaching and Auger recombination.
A stochastic perturbation method to generate inflow turbulence in large-eddy simulation models: Application to neutrally stratified atmospheric boundary layers
Authors: Muñoz-Esparza D. , Kosović B. , van Beeck J. , Mirocha J.
Published: March 2015

Despite the variety of existing methods, efficient generation of turbulent inflow conditions for large-eddy simulation (LES) models remains a challenging and active research area. Herein, we extend our previous research on the cell perturbation method, which uses a novel stochastic approach based upon finite amplitude perturbations of the potential temperature field applied within a region near the inflow boundaries of the LES domain [Muñoz-Esparza et al., “Bridging the transition from mesoscale to microscale turbulence in numerical weather prediction models,” Boundary-Layer Meteorol., 153, 409–440 (2014)]. The objective was twofold: (i) to identify the governing parameters of the method and their optimum values and (ii) to generalize the results over a broad range of atmospheric large-scale forcing conditions, Ug = 5 − 25 m s−1, where Ug is the geostrophic wind. We identified the perturbation Eckert number, Ec=Ug2/ρcpθ̃pm, to be the parameter governing the flow transition to turbulence in neutrally stratified boundary layers. Here, θ̃pm is the maximum perturbation amplitude applied, cp is the specific heat capacity at constant pressure, and ρ is the density. The optimal Eckert number was found for nonlinear perturbations allowed by Ec ≈ 0.16, which instigate formation of hairpin-like vortices that most rapidly transition to a developed turbulent state. Larger Ec numbers (linear small-amplitude perturbations) result in streaky structures requiring larger fetches to reach the quasi-equilibrium solution, while smaller Ec numbers lead to buoyancy dominated perturbations exhibiting difficulties for hairpin-like vortices to emerge. Cell perturbations with wavelengths within the inertial range of three-dimensional turbulence achieved identical quasi-equilibrium values of resolved turbulent kinetic energy, q, and Reynolds-shear stress, 〈w′u′〉. In contrast, large-scale perturbations acting at the production range exhibited reduced levels of 〈w′u′〉, due to the formation of coherent streamwise structures, while q was maintained, requiring larger fetches for the turbulent solution to stabilize. Additionally, the cell perturbation method was compared to a synthetic turbulence generator. The proposed stochastic approach provided at least the same efficiency in developing realistic turbulence, while accelerating the formation of large-scales associated with production of turbulent kinetic energy. Also, it is computationally inexpensive and does not require any turbulent information.
Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy
Authors: Miaja-Avila L. , O'Neil G. C. , Uhlig J. , Cromer C. L. , Dowell M. L. , Jimenez R. , Hoover A. S. , Silverman K. L. , Ullom J. N.
Published: March 2015

We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.
First-principles investigation of thermodynamic, elastic and electronic properties of Al3V and Al3Nb intermetallics under pressures
Authors: Chen Zhe , Zhang Peng , Chen Dong , Wu Yi , Wang Mingliang , Ma Naiheng , Wang Haowei
Published: March 2015

The thermodynamic, elastic, and electronic properties of D022-type Al3V and Al3Nb intermetallics were studied using the first-principle method. The results showed the pressure has profound effects on the structural, mechanical and electronic properties in both Al3V and Al3Nb. Thermodynamically, the formation enthalpies for Al3V and Al3Nb were derived, which agreed well with available experimental and theoretical values. Comparably, Al3Nb was a more stable phase with the more negative Hf than Al3V. Mechanically, the calculated elastic constants showed linearly increasing tendencies, and satisfied the Born's criteria from 0–20 GPa, indicating the mechanically stability of Al3V and Al3Nb under this pressure range. Further, the mechanical parameters (i.e., bulk modulus (B), shear modulus (G), and Young's modulus (E)) were derived using the Voigt-Reuss-Hill (VRH) method, and in good agreement with available experimental results at the ground state. All these parameters presented the linearly increasing dependences on the external pressure. The B/G ratios and Poisson's ratio indicated that the Al3V and Al3Nb crystals should exhibit brittle behavior at 0–20 GPa. Additionally, the bulk modulus can be obtained through fitting the Birch-Murnaghan equation (B0), computing by VRH method (BH), and deriving from the elastic theory (Brelax) in both intermetallics. The uniformity of these calculated bulk moduli in each compound exhibited the excellent reliability and self-consistency. In addition, Debye temperature was estimated from the average sound velocity. The Debye temperature showed an increasing dependence on the pressures. Finally, through density of states analysis, Al3V and Al3Nb were suggested to possess naturally metallic behavior. Under pressures, it was noted that the shapes of peaks and pseudogaps exhibited relative few changes, suggesting Al3V and Al3Nb has kept structurally stable up to 20 GPa. At zero pressure, Al3Nb was considered as a more structurally stable phase with the more number of bonding electrons per atom than Al3V. This conclusion was in consistent with the one drawn from the thermodynamic analysis.
Demonstration of cathode emittance dominated high bunch charge beams in a DC gun-based photoinjector
Authors: Gulliford Colwyn , Bartnik Adam , Bazarov Ivan , Dunham Bruce , Cultrera Luca
Published: March 2015

We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9–9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers.
Electroluminescence from GeSn heterostructure pin diodes at the indirect to direct transition
Authors: Gallagher J. D. , Senaratne C. L. , Sims P. , Aoki T. , Menéndez J. , Kouvetakis J.
Published: March 2015

The emission properties of GeSn heterostructure pin diodes have been investigated. The devices contain thick (400–600 nm) Ge1−ySny i-layers spanning a broad compositional range below and above the crossover Sn concentration yc where the Ge1−ySny alloy becomes a direct-gap material. These results are made possible by an optimized device architecture containing a single defected interface thereby mitigating the deleterious effects of mismatch-induced defects. The observed emission intensities as a function of composition show the contributions from two separate trends: an increase in direct gap emission as the Sn concentration is increased, as expected from the reduction and eventual reversal of the separation between the direct and indirect edges, and a parallel increase in non-radiative recombination when the mismatch strains between the structure components is partially relaxed by the generation of misfit dislocations. An estimation of recombination times based on the observed electroluminescence intensities is found to be strongly correlated with the reverse-bias dark current measured in the same devices.
Electronic band structure of ZnO-rich highly mismatched ZnO1−xTex alloys
Authors: Ting M. , dos Reis R. , Jaquez M. , Dubon O. D. , Mao S. S. , Yu K. M. , Walukiewicz W.
Published: March 2015

We synthesized ZnO1−xTex alloys with Te composition x < 0.23 by using pulsed laser deposition. Alloys with x < 0.06 are crystalline with a columnar growth structure while samples with higher Te content are polycrystalline with random grain orientation. Electron microscopy images show a random distribution of Te atoms with no observable clustering. We found that the incorporation of a small concentration of Te (x ∼ 0.003) redshifts the ZnO optical absorption edge by more than 1 eV. The minimum band gap obtained in this work is 1.8 eV for x = 0.23. The optical properties of the alloys are explained by the modification of the valence band of ZnO, due to the anticrossing interactions of the localized Te states with the ZnO valence band extended states. Hence, the observed large band gap reduction is primarily originating from the upward shift of the valence band edge. We show that the optical data can be explained by the band anticrossing model with the localized level of Te located at 0.95 eV above the ZnO valence band and the band anticrossing coupling constant of 1.35 eV. These parameters allow the prediction of the compositional dependence of the band gap as well as the conduction and the valence band offsets in the full composition range of ZnO1−xTex alloys.
Lateral buckling and mechanical stretchability of fractal interconnects partially bonded onto an elastomeric substrate
Authors: Fu Haoran , Xu Sheng , Xu Renxiao , Jiang Jianqun , Zhang Yihui , Rogers John A. , Huang Yonggang
Published: March 2015

Fractal-inspired designs for interconnects that join rigid, functional devices can ensure mechanical integrity in stretchable electronic systems under extreme deformations. The bonding configuration of such interconnects with the elastomer substrate is crucial to the resulting deformation modes, and therefore the stretchability of the entire system. In this study, both theoretical and experimental analyses are performed for postbuckling of fractal serpentine interconnects partially bonded to the substrate. The deformation behaviors and the elastic stretchability of such systems are systematically explored, and compared to counterparts that are not bonded at all to the substrate.
Ultra-short longitudinal spatial coherence length of laser light with the combined effect of spatial, angular, and temporal diversity
Authors: Ahmad Azeem , Srivastava Vishal , Dubey Vishesh , Mehta D. S.
Published: March 2015

We demonstrate ultra-high axial-resolution topography and tomography of multilayered objects using pseudo thermal light source, i.e., laser. The longitudinal spatial coherence (LSC) length of light was significantly reduced by synthesizing a pseudo thermal source with the combined effect of spatial, angular, and temporal diversity. Thus, generating a low spatially coherent (i.e., broad angular frequency spectrum) light source having narrow temporal frequency spectrum. The LSC length was reduced less than 10 μm using a very low magnification lens. Experimental results of optical sectioning of multilayer objects with high axial-resolution of the order of 4 μm was achieved which is comparable to broadband light source. The present system does not require any dispersion compensation optical system for biological samples as a highly monochromatic light source is used.
Research on energy extraction characteristics of an adaptive deformation oscillating-wing
Authors: Zhu Bing , Han Wei , Sun Xiaojing , Wang Ying , Cao Yang , Wu Guoqing , Huang Diangui , Zheng Zhongquan Charlie
Published: March 2015

Oscillating foil machines represent a type of flow energy harvesters which perform pitching and plunging motions simultaneously to harness the energy from incoming stream. In this paper, a new adaptive deformation oscillating wing was proposed and the theoretical performance of such a concept was studied here through unsteady two-dimensional simulations using an in-house developed computational fluid dynamics code. During operation, the proposed oscillating foil whose initial shape is symmetric can be deformed into a cambered foil, which aims to produce large lift force. Our numerical results suggest that the power efficiency of the proposed oscillating foil can be about 16.1% higher than the conventional oscillating foil without deformation. In addition, the effects of the maximum bending displacement and effective angle of attack on the efficiency of proposed oscillating foil were also discussed in this work.
Mitigating the volatility of renewable distributed generators with plug-in electric vehicles in optimal operation of active distribution networks
Authors: Zhang Hong , Zhao Dongmei , Gu Chenghong , Li Furong
Published: March 2015

Active distribution networks (ADNs) are becoming popular worldwide, where renewable distributed generators (DGs) are responsible to support system operation and allowed to be integrated to networks under non-firm connection agreements. With the increasing penetration of renewable DGs, their power volatility cannot be neglected any more. In order to overcome the negative influences caused by the volatility of renewable DGs, a strategy for mitigating the volatility with plug-in electric vehicles (PEVs) is proposed for economic and safe operation of ADNs. First, a PEV aggregator is proposed to control a group of PEVs, which can act as demand response in ADNs by charging/discharging power. Then, a volatility index (VI) is defined to measure the volatile degree of power from renewable DGs in a certain time period. Based on VI, the formulation of union volatility index is derived, considering the power charged/discharged by PEV aggregators. Thereafter, an optimal operation model of ADN operation with volatility constraints is proposed. Its objective is to minimize the operation cost of ADNs. This optimal model is solved by a novel algorithm–disruption bare-bones particle swarm optimization algorithm, which integrates disruption strategies into the bare-bones particle swarm optimization algorithm. The proposed model is demonstrated on a 37-node radial distribution system with a PEV aggregator. Five scenarios are carefully designed to certify the necessity of mitigating the volatility of renewable DGs in network economic operation. It is concluded that mitigating the volatility of renewable DGs and adopting real-time pricing schemes on PEV aggregators are particularly effective for optimal operation of ADNs.
Hopping conduction and piezoelectricity in Fe-doped GaN studied by non-contacting resonant ultrasound spectroscopy
Authors: Ogi H. , Tsutsui Y. , Nakamura N. , Nagakubo A. , Hirao M. , Imade M. , Yoshimura M. , Mori Y.
Published: March 2015

Using the antenna-transmission acoustic-resonance technique, we measured temperature dependencies of mechanical resonance frequencies and attenuation of an Fe-doped GaN. A strong internal-friction peak appears during temperature change, at which reduction in frequency occurs. The peak temperature rises as frequency increases, indicating the phonon-assisted hopping conduction of carriers between Fe centers. The Arrhenius plot yields the activation energy of the hopping conduction to be 0.23 ± 0.05 eV. The frequency reduction of a quasi-plane-shear resonance mode yields the piezoelectric coefficient e15 = 0.332 ± 0.03 C/m2.
High magnetic-refrigeration performance of plate-shaped La0.5Pr0.5Fe11.4Si1.6 hydrides sintered in high-pressure H2 atmosphere
Authors: Sun N. K. , Guo J. , Zhao X. G. , Si P. Z. , Huang J. H. , Zhang Z. D.
Published: March 2015

La(Fe, Si)13 hydride is regarded as one of the most promising room-temperature refrigerants. However, to use the alloys in an active magnetic regenerator machine, it is vital to prepare thin refrigerants. In this work, a high H2 gas pressure of 50 MPa was employed to suppress the desorption of hydrogen atoms during the sintering process of plate-shaped La0.5Pr0.5Fe11.4Si1.6 hydrides. At 330 K, a high-density sintered thin plate shows a large magnetic-entropy change ΔSm of 15.5 J/kg K (106 mJ/cm3 K) for a field change of 2 T. The volumetric ΔSm is almost twice as large as that of bonded La(Fe,Si)13 hydrides. Favorably, hysteresis is almost absent due to the existence of micropores with a porosity of 0.69% which has been analyzed with high-resolution X-ray microtomography.
Stiff yet supple hydrogel mimics cartilage
Authors: Smart Ashley G.
Published: March 2015

Magnetically aligned nanosheets give the material its rare combination of mechanical traits.
From Congress to AAAS, Rush Holt reflects on science policy
Authors: Kramer David
Published: March 2015

The one-time fusion researcher worries that public understanding of climate change is slipping, and says political attacks on social sciences are misguided.
New park will honor US atomic heritage
Authors: Kramer David
Published: March 2015

Provision ensures preservation of World War II–era structures.
Do little embryos make big decisions? How maternal dietary protein restriction can permanently change an embryo’s potential, affecting adult health
Authors: Fleming Tom P. , Watkins Adam J. , Sun Congshan , Velazquez Miguel A. , Smyth Neil R. , Eckert Judith J.
Published: March 2015

Periconceptional environment may influence embryo development, ultimately affecting adult health. Here, we review the rodent model of maternal low-protein diet specifically during the preimplantation period (Emb-LPD) with normal nutrition during subsequent gestation and postnatally. This model, studied mainly in the mouse, leads to cardiovascular, metabolic and behavioural disease in adult offspring, with females more susceptible. We evaluate the sequence of events from diet administration that may lead to adult disease. Emb-LPD changes maternal serum and/or uterine fluid metabolite composition, notably with reduced insulin and branched-chain amino acids. This is sensed by blastocysts through reduced mammalian target of rapamycin complex 1 signalling. Embryos respond by permanently changing the pattern of development of their extra-embryonic lineages, trophectoderm and primitive endoderm, to enhance maternal nutrient retrieval during subsequent gestation. These compensatory changes include stimulation in proliferation, endocytosis and cellular motility, and epigenetic mechanisms underlying them are being identified. Collectively, these responses act to protect fetal growth and likely contribute to offspring competitive fitness. However, the resulting growth adversely affects long-term health because perinatal weight positively correlates with adult disease risk. We argue that periconception environmental responses reflect developmental plasticity and ‘decisions’ made by embryos to optimise their own development, but with lasting consequences.
Elemental diet induces the proliferation of sialomucin goblet cells in the rat duodenum and jejunum
Authors: Hino Shingo , Ito Ayano , Kondo Takashi , Morita Tatsuya
Published: March 2015

We histologically examined the effects of elemental diet (ED) on the goblet cell profile in the rat small intestine. The sulfomucin goblet cells were predominant throughout the small intestine in the control group, while sialomucin goblet cells were manifest in the duodenum and jejunum in the ED group. Next, we investigated the possible relevance of luminal osmolality to the goblet cell profile. Gastric osmolality in the ED group was within the physiological range. Meanwhile, ingestion of high glucose diet elevated gastric osmolality and increased the number of sialomucin goblet cells in the duodenum and jejunum. Further, it turned out that the lower sulfur contents in ED was not related to the unique goblet cell profile by ED ingestion. It is inductively suggested that the influx of high concentrations of low molecular nutrients into the small intestine could be associated with the goblet cell alteration, but the alteration was not necessarily due to the changes in the gastric osmolality by ED ingestion.
Causal judgements about temporal sequences of events in single individuals
Authors: White Peter A.
Published: March 2015

Stimuli were presented in which values of an outcome variable for a single individual were recorded over 24 time periods, and an intervention was introduced at one of the time periods. Participants judged whether and how much the intervention affected the outcome. Judgements were affected by manipulations of the temporal relation between the intervention and a gradual increase in values on the outcome variable, by the size of the increase, by the time taken for the increase to occur, and by variance in the preincrease data. Most results were predicted by a simple model in which the mean outcome value for the preintervention time periods is subtracted from the mean outcome value for the postintervention time periods, though there was also an effect of temporal contiguity that is not predicted by the simple model. This form of information, which is a kind of quasiexperimental design, is more representative of the kind of information generally available for causal judgement than the more commonly investigated binary variables in which the cause is either present or absent, and the outcome either occurs or does not; as such, it is more revealing of how causal judgements are made under the conditions that prevail in the world.
Testosterone-to-oestradiol ratio is associated with female facial attractiveness
Authors: Probst Fabian , Bobst Cora , Lobmaier Janek S.
Published: March 2015

The relationship between facial shape and attractiveness has been extensively studied, yet few studies have investigated the underlying biological factors of an attractive face. Many researchers have proposed a link between female attractiveness and sex hormones, but there is little empirical evidence in support of this assumption. In the present study we investigated the relationship between circulating sex hormones and attractiveness. We created prototypes by separately averaging photographs of 15 women with high and low levels of testosterone, oestradiol, and testosterone-to-oestradiol ratio levels, respectively. An independent set of facial images was then shape transformed toward these prototypes. We paired the resulting images in such a way that one face depicted a female with high hormone level and the other one with a low hormone level. Fifty participants were asked to choose the more attractive face of each pair. We found that low testosterone-to-oestradiol ratio and low testosterone were positively associated with female facial attractiveness. There was no preference for faces with high oestradiol levels. In an additional experiment with 36 participants we confirmed that a low testosterone-to-oestradiol ratio plays a larger role than low testosterone alone. These results provide empirical evidence that an attractive female face is shaped by interacting effects of testosterone and oestradiol.
GSK3- and PRMT-1–dependent modifications of desmoplakin control desmoplakin–cytoskeleton dynamics
Authors: Albrecht Lauren V. , Zhang Lichao , Shabanowitz Jeffrey , Purevjav Enkhsaikhan , Towbin Jeffrey A. , Hunt Donald F. , Green Kathleen J.
Published: March 2015

Intermediate filament (IF) attachment to intercellular junctions is required for skin and heart integrity, but how the strength and dynamics of this attachment are modulated during normal and pathological remodeling is poorly understood. We show that glycogen synthase kinase 3 (GSK3) and protein arginine methyltransferase 1 (PRMT-1) cooperate to orchestrate a series of posttranslational modifications on the IF-anchoring protein desmoplakin (DP) that play an essential role in coordinating cytoskeletal dynamics and cellular adhesion. Front-end electron transfer dissociation mass spectrometry analyses of DP revealed six novel serine phosphorylation sites dependent on GSK3 signaling and four novel arginine methylation sites including R2834, the mutation of which has been associated with arrhythmogenic cardiomyopathy (AC). Inhibition of GSK3 or PRMT-1 or overexpression of the AC-associated mutant R2834H enhanced DP–IF associations and delayed junction assembly. R2834H blocked the GSK3 phosphorylation cascade and reduced DP–GSK3 interactions in cultured keratinocytes and in the hearts of transgenic R2834H DP mice. Interference with this regulatory machinery may contribute to skin and heart diseases.
Rad51-mediated replication fork reversal is a global response to genotoxic treatments in human cells
Authors: Zellweger Ralph , Dalcher Damian , Mutreja Karun , Berti Matteo , Schmid Jonas A. , Herrador Raquel , Vindigni Alessandro , Lopes Massimo
Published: March 2015

Replication fork reversal protects forks from breakage after poisoning of Topoisomerase 1. We here investigated fork progression and chromosomal breakage in human cells in response to a panel of sublethal genotoxic treatments, using other topoisomerase poisons, DNA synthesis inhibitors, interstrand cross-linking inducers, and base-damaging agents. We used electron microscopy to visualize fork architecture under these conditions and analyzed the association of specific molecular features with checkpoint activation. Our data identify replication fork uncoupling and reversal as global responses to genotoxic treatments. Both events are frequent even after mild treatments that do not affect fork integrity, nor activate checkpoints. Fork reversal was found to be dependent on the central homologous recombination factor RAD51, which is consistently present at replication forks independently of their breakage, and to be antagonized by poly (ADP-ribose) polymerase/RECQ1-regulated restart. Our work establishes remodeling of uncoupled forks as a pivotal RAD51-regulated response to genotoxic stress in human cells and as a promising target to potentiate cancer chemotherapy.
Stemness factor Sall4 is required for DNA damage response in embryonic stem cells
Authors: Xiong Jianhua , Todorova Dilyana , Su Ning-Yuan , Kim Jinchul , Lee Pei-Jen , Shen Zhouxin , Briggs Steven P. , Xu Yang
Published: March 2015

Mouse embryonic stem cells (ESCs) are genetically more stable than somatic cells, thereby preventing the passage of genomic abnormalities to their derivatives including germ cells. The underlying mechanisms, however, remain largely unclear. In this paper, we show that the stemness factor Sall4 is required for activating the critical Ataxia Telangiectasia Mutated (ATM)–dependent cellular responses to DNA double-stranded breaks (DSBs) in mouse ESCs and confer their resistance to DSB-induced cytotoxicity. Sall4 is rapidly mobilized to the sites of DSBs after DNA damage. Furthermore, Sall4 interacts with Rad50 and stabilizes the Mre11–Rad50–Nbs1 complex for the efficient recruitment and activation of ATM. Sall4 also interacts with Baf60a, a member of the SWI/SNF (switch/sucrose nonfermentable) ATP-dependent chromatin-remodeling complex, which is responsible for recruiting Sall4 to the site of DNA DSB damage. Our findings provide novel mechanisms to coordinate stemness of ESCs with DNA damage response, ensuring genomic stability during the expansion of ESCs.
A fresh start for stalled forks
Authors: Leslie Mitch
Published: March 2015

Studies reveal mechanisms that reverse and then reactivate replication forks.
Some existence and regularity results for porous media and fast diffusion equations with a gradient term
Authors: Abdellaoui Boumediene , Peral Ireneo , Walias Magdalena
Published: March 2015

In this article we consider the problem
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartLayout 1st Row with Label left-parenthesis reverse-solidus textit left-brace upper P right-brace right-parenthesis EndLabel StartLayout Enlarged left-brace 1st Row 1st Column u Subscript t Baseline minus normal upper Delta u Superscript m 2nd Column a m p semicolon equals 3rd Column a m p semicolon StartAbsoluteValue nabla u EndAbsoluteValue Superscript q Baseline plus f left-parenthesis x comma t right-parenthesis comma u greater-than-or-equal-to 0 4th Column a m p semicolon in normal upper Omega Subscript upper T Baseline identical-to normal upper Omega times left-parenthesis 0 comma upper T right-parenthesis comma 2nd Row 1st Column u left-parenthesis x comma t right-parenthesis 2nd Column a m p semicolon equals 3rd Column a m p semicolon 0 4th Column a m p semicolon on partial-differential normal upper Omega times left-parenthesis 0 comma upper T right-parenthesis comma 3rd Row 1st Column u left-parenthesis x comma 0 right-parenthesis 2nd Column a m p semicolon equals 3rd Column a m p semicolon u 0 left-parenthesis x right-parenthesis 4th Column a m p semicolon in normal upper Omega comma EndLayout EndLayout">

(\textit {P})

{

u
t

−
Δ

u
m

a
m
p
;
=

a
m
p
;

|

∇
u

|

q

+

f
(
x
,
t
)
,

u
≥
0

a
m
p
;

 in 

Ω
T

≡
Ω
×
(
0
,
T
)
,

u
(
x
,
t
)

a
m
p
;
=

a
m
p
;
0

a
m
p
;

 on 

∂
Ω
×
(
0
,
T
)
,

u
(
x
,
0
)

a
m
p
;
=

a
m
p
;

u
0

(
x
)

a
m
p
;

 in 

Ω
,

\begin{equation}\tag {\textit {P}} \left \{\begin {array}{rclll} u_t-\Delta u^m&=&|\nabla u|^q +\,f(x,t),\quad u\ge 0 &\hbox { in } \Omega _T\equiv \Omega \times (0,T),\\ u(x,t)&=&0 &\quad \hbox { on } \partial \Omega \times (0,T),\\ u(x,0)&=&u_0(x)&\quad \hbox { in } \Omega , \end{array} \right . \end{equation}

where

Ω
⊂

R

N

\Omega \subset \mathbb {R}^N

is a bounded regular domain,

N
≥
1

N\ge 1

,

1
>
q
≤
2

1>q\le 2

, and

f
≥
0

f\ge 0

,

u
0

≥
0

u_0\ge 0

are in a suitable class of measurable functions.

We obtain some results for the so-called elliptic-parabolic problems with measure data related to problem

(
P
)

(P)

that we use to study the existence of solutions to problem

(
P
)

(P)

according with the values of the parameters

q
q

and

m
m

.
Quantum cluster characters for valued quivers
Authors: Rupel Dylan
Published: March 2015

Let

F

\mathbb {F}

be a finite field and

(
Q
,

d

)

(Q,\mathbf {d})

an acyclic valued quiver with associated exchange matrix

B
~

\tilde {B}

. We follow Hubery’s approach to prove our main conjecture from 2011: the quantum cluster character gives a bijection from the isoclasses of indecomposable rigid valued representations of

Q
Q

to the set of non-initial quantum cluster variables for the quantum cluster algebra

A

|

F

|

(

B
~

,
Λ
)

\mathcal {A}_{|\mathbb {F}|}(\tilde {B},\Lambda )

. As a corollary we find that for any rigid valued representation

V
V

of

Q
Q

, all Grassmannians of subrepresentations

G

r

e

V

Gr_{\mathbf {e}}^V

have counting polynomials.
A ‘classic’ case of heavy menstrual bleeding?
Authors: Shruti Mohan , Jasmine Tay , Jenny Higham , Hamady Mohamad
Published: March 2015

Clinicians are increasingly faced with women who delay pregnancy until later in life, a significant proportion of whom seek treatment for severe heavy menstrual bleeding. This case describes a case of heavy menstrual bleeding in a 41-year-old women with a fibroid uterus who initially wishes to preserve her fertility. It describes the progressive treatment ladder for symptomatic uterine fibroids suggested by the clinician as in cases where symptoms fail to respond to initial therapy or recur after a period of time. In particular, the challenge of counselling for uterine artery embolization with respect to fertility, as well as risks of repeated surgery in a woman with previous intra-abdominal surgery (in this case, 3 previous caesarean sections) is highlighted.