bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid measurement of charged particle beam profiles using a current flux grating
Authors: Paul Samit , Chowdhury Abhishek , Bhattacharjee Sudeep
Published: February 2015

The principle and physics issues of charged particle beam diagnostics using a current flux grating are presented. Unidirectional array of conducting channels with interstitial insulating layers of spacing d is placed in the beam path to capture flux of charge and electronically reproduce an exact beam current profile with density variation. The role of secondary electrons due to the impinging particle beam (both electron and ion) on the probe is addressed and a correction factor is introduced. A 2-dimensional profile of the electron beam is obtained by rotating the probe about the beam axis. Finally, a comparison of measured beam profile with a Gaussian is presented.
An efficient, movable single-particle detector for use in cryogenic ultra-high vacuum environments
Authors: Spruck Kaija , Becker Arno , Fellenberger Florian , Grieser Manfred , von Hahn Robert , Klinkhamer Vincent , Novotný Oldřich , Schippers Stefan , Vogel Stephen , Wolf Andreas , Krantz Claude
Published: February 2015

A compact, highly efficient single-particle counting detector for ions of keV/u kinetic energy, movable by a long-stroke mechanical translation stage, has been developed at the Max-Planck-Institut für Kernphysik (Max Planck Institute for Nuclear Physics, MPIK). Both, detector and translation mechanics, can operate at ambient temperatures down to ∼10 K and consist fully of ultra-high vacuum compatible, high-temperature bakeable, and non-magnetic materials. The set-up is designed to meet the technical demands of MPIK’s Cryogenic Storage Ring. We present a series of functional tests that demonstrate full suitability for this application and characterise the set-up with regard to its particle detection efficiency.
Structural evolution during fragile-to-strong transition in CuZr(Al) glass-forming liquids
Authors: Zhou Chao , Hu Lina , Sun Qijing , Zheng Haijiao , Zhang Chunzhi , Yue Yuanzheng
Published: February 2015

In the present work, we show experimental evidence for the dynamic fragile-to-strong (F-S) transition in a series of CuZr(Al) glass-forming liquids (GFLs). A detailed analysis of the dynamics of 98 glass-forming liquids indicates that the F-S transition occurs around Tf-s ≈ 1.36 Tg. Using the hyperquenching-annealing-x-ray scattering approach, we have observed a three-stage evolution pattern of medium-range ordering (MRO) structures during the F-S transition, indicating a dramatic change of the MRO clusters around Tf-s upon cooling. The F-S transition in CuZr(Al) GFLs is attributed to the competition among the MRO clusters composed of different locally ordering configurations. A phenomenological scenario has been proposed to explain the structural evolution from the fragile to the strong phase in the CuZr(Al) GFLs.
Conservative weak solutions of the periodic Cauchy problem for μHS equation
Authors: Tığlay Feride
Published: February 2015

We prove the existence and uniqueness of conservative weak solutions of the periodic Cauchy problem for an integrable evolution equation from mathematical physics. Our method is to first prove the existence and uniqueness of solutions for all time in Lagrangian coordinates and construct the maps to carry this result to the Eulerian coordinates.
A sample holder with integrated laser optics for an ELMITEC photoemission electron microscope
Authors: Gierster L. , Pape L. , Ünal A. A. , Kronast F.
Published: February 2015

We present a new sample holder compatible with ELMITEC Photoemission Electron Microscopes (PEEMs) containing an optical lens and a mirror. With the integrated optical elements, a laser beam is focused from the back side of the sample at normal incidence, yielding a minimum spot size of about 1 μm. This opens up new possibilities for local laser excitations in PEEM experiments such as imaging all-optical magnetization switching at a small length scale.
Monolithically integrated two-axis microgripper for polarization maintaining in optical fiber assembly
Authors: Zhang Jianbin , Lu Kangkang , Chen Weihai , Jiang Jun , Chen Wenjie
Published: February 2015

Polarization maintaining optical fiber (PMOF) is a kind of special optical fiber that is designed to transmit the linearly polarized light. Unlike the general optical fiber, it is critical to conduct the rotational alignment between two PMOFs to guarantee the efficiency of light transmission. Until now, this alignment task still cannot be addressed with an efficient and economical way. Hence, we propose a monolithically integrated two-axis flexure-based microgripper that has the grasping and rubbing functions. To achieve a compact structure, the microgripper is designed with an asymmetric architecture. In this paper, the pseudo-rigid body model approach and finite element analysis are conducted to provide the essential guideline to accomplish the theoretical design. The prototype is fabricated by wire electrical discharge machining, with which two experiments are conducted to validate the performance of the microgripper. The experimental results demonstrate that the proposed microgripper can firmly grasp the optical fiber with the diameter of 250 μm and meanwhile can rub it more than 90° accurately and effectively, which indicate that it can satisfy the operating requirements well in the PMOF assembly.
Short-time diffusion in concentrated bidisperse hard-sphere suspensions
Authors: Wang Mu , Heinen Marco , Brady John F.
Published: February 2015

Diffusion in bidisperse Brownian hard-sphere suspensions is studied by Stokesian Dynamics (SD) computer simulations and a semi-analytical theoretical scheme for colloidal short-time dynamics, based on Beenakker and Mazur’s method [Physica A 120, 388–410 (1983); 126, 349–370 (1984)]. Two species of hard spheres are suspended in an overdamped viscous solvent that mediates the salient hydrodynamic interactions among all particles. In a comprehensive parameter scan that covers various packing fractions and suspension compositions, we employ numerically accurate SD simulations to compute the initial diffusive relaxation of density modulations at the Brownian time scale, quantified by the partial hydrodynamic functions. A revised version of Beenakker and Mazur’s δγ-scheme for monodisperse suspensions is found to exhibit surprisingly good accuracy, when simple rescaling laws are invoked in its application to mixtures. The so-modified δγ scheme predicts hydrodynamic functions in very good agreement with our SD simulation results, for all densities from the very dilute limit up to packing fractions as high as 40%.
Isotropic-nematic phase equilibria of hard-sphere chain fluids—Pure components and binary mixtures
Authors: Oyarzún Bernardo , van Westen Thijs , Vlugt Thijs J. H.
Published: February 2015

The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components.
A phenomenological theory of rotating turbulence
Authors: Baqui Yasir Bin , Davidson P. A.
Published: February 2015

We present direct numerical simulations of statistically homogeneous, freely decaying, rotating turbulence in which the Rossby number, Ro = u⊥/2Ωℓ⊥, is of order unity. This is the regime normally encountered in laboratory experiments. The initial condition consists of fully developed turbulence in which Ro is sufficiently high for rotational effects to be weak. However, as the kinetic energy falls, so also does Ro, and quite quickly, we enter a regime in which the Coriolis force is relatively strong and anisotropy grows rapidly, with ℓ⊥ ≪ ℓ∥. This regime occurs when Ro ∼ 0.4 and is characterised by an almost constant perpendicular integral scale, ℓ⊥ ∼ constant, a rapid linear growth in the integral scale parallel to the rotation axis, ℓ∥ ∼ ℓ⊥Ωt, and a slow decline in the value of Ro. We observe that the rate of dissipation of energy scales as ε ∼ u3/ℓ∥ and that both the perpendicular and parallel energy spectra exhibit a k−5/3 inertial range; Ek⊥∼ε2/3k⊥−5/3 and Ek∥∼ε2/3k∥−5/3. We show that these power-law spectra have nothing to do with Kolmogorov’s theory, since the equivalent non-rotating turbulence, which has the same initial condition and Reynolds number, does not exhibit a k−5/3 inertial range, the Reynolds number being too low. Nor are the spectra a manifestation of traditional critical balance theory, as this requires ε ∼ u3/ℓ⊥. We develop a phenomenological theory of the inertial range that assumes that the observed linear growth in anisotropy, ℓ∥/ℓ⊥ ∼ Ωt, also occurs on a scale-by-scale basis most of the way down to the Zeman scale, the linear growth in ℓ∥ being a consequence of inertial wave propagation. Below the Zeman scale, however, inertial waves cannot propagate, and so there is necessarily a transition in spectral behaviour around this scale. The observed spectra are consistent with the predictions of our phenomenological theory.
The effects of mean atmospheric forcings of the stable atmospheric boundary layer on wind turbine wake
Authors: Bhaganagar Kiran , Debnath Mithu
Published: February 2015

Interactions between the nocturnal atmospheric boundary layer (ABL) and wind turbines (WTs) can be complicated due to the presence of low level jets (LLJ), a region which creates wind speeds higher than geostrophic wind speed. A study has been performed to isolate the effect of mean forcings of the ABL on turbulence energetics and structures in the wake of WT. Large eddy simulation with an actuator line model has been used as a tool to simulate a full-scale 5-MW WT under two different realistic atmospheric states of the stable ABL corresponding to low- and high-stratification. The study clearly demonstrates that the large-scale forcings of thermally stratified atmospheric boundary characterized by shear- and buoyancy-driven turbulence significantly influence the wake structure of a wind turbine. For the WT in low-stratified ABL, the jets occur above the WT resulting in a strong mixed layer behind the WT. High turbulence results in a faster wake recovery. For the WT in high-stratified ABL, the jets occur near the hub-height resulting in an asymmetric wake structure. The jets confine the mixing to hub-height resulting in a slower wake recovery. Vertical shear causes the interaction of the root- and lower-tip vortices resulting in the instability of the root vortex leading to an enhanced shear stress and turbulent kinetic energy. The tip vortices exhibit mutual inductance between adjacent vortex filaments resulting in vortex merging. LLJs are an important metric associated with mean atmospheric forcings that dictate the turbulence generated in WT wake and the wake recovery of a WT in a stable ABL.
Temperature dependent thermal conductivity of a suspended submicron graphene ribbon
Authors: Li Qin-Yi , Takahashi Koji , Ago Hiroki , Zhang Xing , Ikuta Tatsuya , Nishiyama Takashi , Kawahara Kenji
Published: February 2015

Thermophysical characterization of graphene is very important for both fundamental and technological research. While most of the existing thermal conductivity measurements are for graphene sheets with sizes larger than 1 μm, the thermal conductivities for suspended submicron graphene ribbons are still very few, although the thermal conductivity of graphene ribbons at the submicron scale is predicted to be much smaller than large graphene and strongly size dependent for both length and width due to the 2D nature of phonon transport. Here, we report the temperature dependent thermal conductivity of a 169-nm wide and 846-nm long graphene ribbon measured by the electrical self-heating method. The measured thermal conductivities range from (12.7 ± 2.95) W/m/K at 80 K to (932 ± 333) W/m/K at 380 K, being (349 ± 63) W/m/K at 300 K, following a ∼ T2.79 law for the full temperature range of 80 K to 380 K and a ∼ T1.23 law at low temperatures. The comparison of the measured thermal conductance with the ballistic transport limit indicates diffusive transport in this narrow and short ribbon due to phonon-edge as well as phonon-defect scattering. The data were also combined with an empirical model to predict possible width dependence of thermal conductivity for suspended graphene ribbons. These results help understand the 2D phonon transport in suspended submicron graphene ribbons and provide knowledge for controlling thermophysical properties of suspended graphene nanoribbons through size manipulation.
Experimental study of complex mixed-mode oscillations generated in a Bonhoeffer-van der Pol oscillator under weak periodic perturbation
Authors: Shimizu Kuniyasu , Sekikawa Munehisa , Inaba Naohiko
Published: February 2015

Bifurcations of complex mixed-mode oscillations denoted as mixed-mode oscillation-incrementing bifurcations (MMOIBs) have frequently been observed in chemical experiments. In a previous study [K. Shimizu et al., Physica D 241, 1518 (2012)], we discovered an extremely simple dynamical circuit that exhibits MMOIBs. Our model was represented by a slow/fast Bonhoeffer-van der Pol circuit under weak periodic perturbation near a subcritical Andronov-Hopf bifurcation point. In this study, we experimentally and numerically verify that our dynamical circuit captures the essence of the underlying mechanism causing MMOIBs, and we observe MMOIBs and chaos with distinctive waveforms in real circuit experiments.
Electric field modification of magnetotransport in Ni thin films on (011) PMN-PT piezosubstrates
Authors: Tkach Alexander , Kehlberger Andreas , Büttner Felix , Jakob Gerhard , Eisebitt Stefan , Kläui Mathias
Published: February 2015

This study reports the magnetotransport and magnetic properties of 20 nm-thick polycrystalline Ni films deposited by magnetron sputtering on unpoled piezoelectric (011) [PbMg1/3Nb2/3O3]0.68-[PbTiO3]0.32 (PMN-PT) substrates. The longitudinal magnetoresistance (MR) of the Ni films on (011) PMN-PT, measured at room temperature in the magnetic field range of −0.3 T < μ0H < 0.3 T, is found to depend on the crystallographic direction and polarization state of piezosubstrate. Upon poling the PMN-PT substrate, which results in a transfer of strain to the Ni film, the MR value decreases by factor of 20 for the current along [100] of PMN-PT and slightly increases for the [011¯] current direction. Simultaneously, a strong increase (decrease) in the field value, where the MR saturates, is observed for the [011¯] ([100]) current direction. The anisotropic magnetoresistance is also strongly affected by the remanent strain induced by the electric field pulses applied to the PMN-PT in the non-linear regime revealing a large (132 mT) magnetic anisotropy field. Applying a critical electric field of 2.4 kV/cm, the anisotropy field value changes back to the original value, opening a path to voltage-tuned magnetic field sensor or storage devices. This strain mediated voltage control of the MR and its dependence on the crystallographic direction is correlated with the results of magnetization reversal measurements.
A parity-time symmetric coherent plasmonic absorber-amplifier
Authors: Baum Brian , Alaeian Hadiseh , Dionne Jennifer
Published: February 2015

Non-Hermitian parity-time (PT)-symmetric optical potentials have led to a new class of unidirectional photonic components based on the spatially symmetric and balanced inclusion of loss and gain. While most proposed and implemented PT-symmetric optical devices have wavelength-scale dimensions, no physical constraints preclude development of subwavelength PT-symmetric components. We theoretically demonstrate a nanoscale PT-symmetric, all-optical plasmonic modulator capable of phase-controlled amplification and directional absorption. The modulator consists of two deeply subwavelength channels composed of either gain or loss dielectric material, embedded in a metallic cladding. When illuminating on-resonance by two counter-propagating plane waves, the aperture's total output can be modulated by changing the phase offset between the two waves. Modulation depths are greater than 10 dB, with output power varying from less than one half of the incident power to more than six times amplification. Off-resonance, the aperture possesses strong phase-controlled directionality with the output from one side varying from perfect absorption to strong scattering and transmission. The device design provides a platform for nanoscale all-optical modulators with gain while potentially enabling coherent perfect absorption and lasing in a single, compact structure.
Parasitic modulation of electromagnetic signals caused by time-varying plasma
Authors: Yang Min , Li Xiaoping , Xie Kai , Liu Yanming
Published: February 2015

An experiment on the propagation of electromagnetic (EM) signals in continuous time-varying plasma is described. The time-varying characteristics of plasma are considered to cause a parasitic modulation in both amplitude and phase, and the strength of this modulation, which carries the information of the electron density profile, is closely related to the plasma frequency and the incident wave frequency. Through theoretical analysis, we give an explanation and mechanism of the interaction between the continuous time-varying plasma and EM waves, which is verified by a comparative analysis with experiments performed under the same conditions. The effects of this modulation on the EM signals in the plasma sheath cannot be ignored.
Coherent thermoelectric transport in single, double, and U-bend structures
Authors: Pye A. J. , Faux D. A. , Kearney M. J.
Published: February 2015

Coherent, i.e., ballistic, thermoelectric transport in electron waveguide structures containing right-angle bends in single, double, and U-bend configurations is investigated. A theory based on Green's functions is used to derive the transmission function (and from that the transport coefficients) and allows for the inclusion of realistic models of spatially distributed imperfections. The results for the single and double-bend structures are presented in more detail than elsewhere in the literature. In the U-bend structure, sharp resonances in the stop-band region of the transmission function lead to large-magnitude peaks in the thermopower and consequently a large thermoelectric figure of merit (of order ten in some instances). These properties are still readily apparent even in the presence of moderate edge roughness or Anderson disorder.
Electrode size and boundary condition independent measurement of the effective piezoelectric coefficient of thin films
Authors: Stewart M. , Lepadatu S. , McCartney L. N. , Cain M. G. , Wright L. , Crain J. , Newns D. M. , Martyna G. J.
Published: February 2015

The determination of the piezoelectric coefficient of thin films using interferometry is hindered by bending contributions. Using finite element analysis (FEA) simulations, we show that the Lefki and Dormans approximations using either single or double-beam measurements cannot be used with finite top electrode sizes. We introduce a novel method for characterising piezoelectric thin films which uses a differential measurement over the discontinuity at the electrode edge as an internal reference, thereby eliminating bending contributions. This step height is shown to be electrode size and boundary condition independent. An analytical expression is derived which gives good agreement with FEA predictions of the step height.
A valve-less microfluidic peristaltic pumping method
Authors: Zhang Xiannian , Chen Zitian , Huang Yanyi
Published: February 2015

We demonstrate a valve-less microfluidic peristaltic pumping method which enables the delivery of continuous nanoliter-scale flow with high precision. The fluid is driven by squeezing the microchannels embedded in a poly(dimethylsiloxane) device with rolling cams or bearings. We achieve continuous and uniform flow with velocity range from 1 to 500 nl/s, with outflow volume error within 3 nl. The devices show enhanced backpressure resistance up to 340 kPa. This method also shows great flexibility. By altering the channels' layout, emulsions and plugs can be generated easily. These low-cost and easy-to-fabricate micro-pumps offer novel approaches for liquid actuation in various microfluidic applications.
Origin of the smaller conductances of Rh, Pb, and Co atomic junctions in hydrogen environment
Authors: Li Xue , Chen Mingyan , Ye Xiang , Xie Yi-qun , Ke San-huang
Published: February 2015

We study theoretically the structural and electronic origins of the smaller conductances (one conductance quantum, G0, and smaller) of Rh, Pb, and Co metal atomic junctions (MAJs) in a hydrogen environment, as were measured in recent experiments. For the Rh MAJs, the 1G0 conductance is attributed to a stable contact bridged by a single hydrogen molecule whose antibonding state provides a single transport channel. For the Pb and Co MAJs the 1G0 conductance is, however, ascribed to a linear atomic chain adsorbing two dissociated H atoms, which largely reduces the density of states at the Fermi energy with respect to the pure ones. On the other hand, the small conductances of 0.3G0 (Rh) and 0.2G0 (Co) are due to H-decorated atomic chains connected to electrodes by a H atom.
Selective growth of Pb islands on graphene/SiC buffer layers
Authors: Liu X. T. , Hu T. W. , Miao Y. P. , Ma D. Y. , Chu Paul K. , Ma F. , Xu K. W.
Published: February 2015

Graphene is fabricated by thermal decomposition of silicon carbide (SiC) and Pb islands are deposited by Pb flux in molecular beam epitaxy chamber. It is found that graphene domains and SiC buffer layer coexist. Selective growth of Pb islands on SiC buffer layer rather than on graphene domains is observed. It can be ascribed to the higher adsorption energy of Pb atoms on the 63 reconstruction of SiC. However, once Pb islands nucleate on graphene domains, they will grow very large owing to the lower diffusion barrier of Pb atoms on graphene. The results are consistent with first-principle calculations. Since Pb atoms on graphene are nearly free-standing, Pb islands grow in even-number mode.
Acoustic focusing by metal circular ring structure
Authors: Xia Jian-Ping , Sun Hong-Xiang
Published: February 2015

We report an exotic acoustic focusing effect through a simple brass circular ring structure immersed in water. The acoustic waves can be focused on a prefect point at the centre of the ring structure. This exotic acoustic focusing phenomenon arises from the intrinsic modes in the ring structure at some special eigenfrequencies, which is essentially distinct from the previous studies originating from the negative refraction. The focusing effect is closely related to the size and shape of the ring structure. Interesting applications of the focusing mechanism in black box detectors in the sea and medical ultrasound treatment are further discussed.
On the AlGaInP-bulk and AlGaInP/GaAs-superlattice confinement effects for heterostructure-emitter bipolar transistors
Authors: Tsai Jung-Hui
Published: February 2015

The confinement effect and electrical characteristics of heterostructure-emitter bipolar transistors with an AlGaInP bulk-confinement layer and an AlGaInP/GaAs superlattice-confinement layer are first demonstrated and compared by experimentally results. In the two devices, the relatively large valence band discontinuity at AlGaInP/GaAs heterojunction provides excellent confinement effect for holes to enhance current gain. As to the AlGaInP/GaAs superlattice-confinement device, part of thermionic-emission electrons will be trapped in the GaAs quantum wells of the superlattice. This will result in lower collector current and current gain as compared with the bulk-confinement device. Nevertheless, the superlattice-confinement device exhibits a larger current-gain cutoff frequency, which can be attributed that the tunneling behavior is included in the carrier transportation and transporting time across the emitter region could be substantially reduced.
Non-uniform depth distributions of Sn concentration induced by Sn migration and desorption during GeSnSi layer formation
Authors: Taoka Noriyuki , Asano Takanori , Yamaha Takashi , Terashima Tatsuya , Nakatsuka Osamu , Costina Ioan , Zaumseil Peter , Capellini Giovanni , Zaima Shigeaki , Schroeder Thomas
Published: February 2015

The distributions of Sn concentration in GeSnSi layers formed on Ge substrate at various temperatures were investigated. High deposition temperature (Td) induces significant Sn migration and desorption, which have activation energies of 0.75 eV and 0.27 eV, respectively. A model quantitatively clarified the Sn migration fluxes during the deposition, which increase not only with increasing Td but also with the layer thickness. A non-negligible Sn flux compared with the supplied flux was found at 350 °C at the surface of the 200-nm-thick layer. Consequently, designs of layer thickness and Td taking into account the appropriate Sn flux are important to form a GeSnSi layer with uniform Sn content for future optoelectronics.
Improving magnetic properties of ultrasmall magnetic nanoparticles by biocompatible coatings
Authors: Costo R. , Morales M. P. , Veintemillas-Verdaguer S.
Published: February 2015

This paper deals with the effect of a biocompatible surface coating layer on the magnetic properties of ultrasmall iron oxide nanoparticles. Particles were synthesized by laser pyrolysis and fully oxidized to maghemite by acid treatment. The surface of the magnetic nanoparticles was systematically coated with either phosphonate (phosphonoacetic acid or pamidronic acid) or carboxylate-based (carboxymethyl dextran) molecules and the binding to the nanoparticle surface was analyzed. Magnetic properties at low temperature show a decrease in coercivity and an increase in magnetization after the coating process. Hysteresis loop displacement after field cooling is significantly reduced by the coating, in particular, for particles coated with pamidronic acid, which show a 10% reduction of the displacement of the loop. We conclude that the chemical coordination of carboxylates and phosphonates reduces the surface disorder and enhances the magnetic properties of ultrasmall maghemite nanoparticles.
Fermi surface distortion induced by interaction between Rashba and Zeeman effects
Authors: Choi Won Young , Chang Joonyeon , Kim Hyung-jun , Lee Kyung-Jin , Koo Hyun Cheol
Published: February 2015

To evaluate Fermi surface distortion induced by interaction between Rashba and Zeeman effects, the channel resistance in an InAs quantum well layer is investigated with an in-plane magnetic field transverse to the current direction. In the magnetoresistance curve, the critical point occurs at ∼3.5 T, which is approximately half of the independently measured Rashba field. To get an insight into the correlation between the critical point in magnetoresistance curve and the Rashba strength, the channel conductivity is calculated using a two-dimensional free-electron model with relaxation time approximation. The critical point obtained from the model calculation is in agreement with the experiment, suggesting that the observation of critical point can be an alternative method to experimentally determine the Rashba parameter.
Lithography-free, broadband, omnidirectional, and polarization-insensitive thin optical absorber
Authors: Ding Fei , Mo Lei , Zhu Jianfei , He Sailing
Published: February 2015

We have proposed and experimentally demonstrated a lithography-free, broadband, thin optical absorber composed of planar multilayered dielectric and metal films, which can cover the total visible wavelength range with simulated and experimental absorption efficiencies higher than 90%. Moreover, the absorption is insensitive to the polarization and angle of incidence. Such a planar device is much easier to fabricate compared with other broadband absorbers with complicated structures and may have potential applications in solar energy harvesting and controllable thermal emission.
Statistical features of magnetic noise in mixed-type impact fracture
Authors: Danku Zs. , Lenkey Gy. B. , Kun F.
Published: February 2015

We study the statistical features of magnetic noise accompanying the dynamic fracture of steel samples during mixed type fracture, where the overall ductile character of crack propagation is interrupted by a sudden brittle jump. The structure of the voltage time series is investigated by identifying discrete peaks which correspond to elementary steps of the jerky cracking process. We show that the height, duration, area, and energy of peaks have power law distributions with exponents falling close to the corresponding values of pure ductile fracture. For single peaks, a power law correlation of the height and area with the width is evidenced; however, the mixed nature of fracture gives rise to a crossover between two regimes of different exponents. The average pulse shape of micro-cracking events has a parabolic form with a right handed asymmetry similarly to quasi-static fracture propagation. The asymmetry emerges due to stress localization at the advancing crack front.
Different effect of quenching temperature on Fe1+σTe0.5Se0.5 and β-FeSe
Authors: Guo Zhongnan , Zhang Huanhuan , Han Bingling , Feng Xiaojing , Yuan Wenxia
Published: February 2015

In this work, we have demonstrated a different effect on Fe1+σTe0.5Se0.5 and β-FeSe by changing the quenching temperature. Tc is clearly reduced in Fe1+σTe0.5Se0.5 after increasing the quenching temperature from 300 °C to 500 °C, while that of β-FeSe is almost unchanged. Structure refinement indicates that after quenched at 500 °C, FeTe4 tetrahedron exhibits an expansion with the stretched Fe-Te bond, together with the increased amount of interstitial iron. These particular changes on structure are believed to be responsible for the suppression of superconductivity in Fe1+σTe0.5Se0.5.
Investigation of CuGaSe2/CuInSe2 double heterojunction interfaces grown by molecular beam epitaxy
Authors: Thiru Sathiabama , Asakawa Masaki , Honda Kazuki , Kawaharazuka Atsushi , Tackeuchi Atsushi , Makimoto Toshiki , Horikoshi Yoshiji
Published: February 2015

In-situ reflection high-energy electron diffraction (RHEED) observation and X-ray diffraction measurements were performed on heterojunction interfaces of CuGaSe2/CnInSe2/CuGaSe2 grown on GaAs (001) using migration-enhanced epitaxy. The streaky RHEED pattern and persistent RHEED intensity oscillations caused by the alternate deposition of migration-enhanced epitaxy sequence are observed and the growths of smooth surfaces are confirmed. RHEED observation results also confirmed constituent material interdiffusion at the heterointerface. Cross-sectional transmission electron microscopy showed a flat and abrupt heterointerface when the substrate temperature is as low as 400 °C. These have been confirmed even by X-ray diffraction and photoluminescence measurements.
Two-step weaning in beef calves: permanence of nose flaps for 7 or 21 days does not influence the behaviour response
Authors: Alvez P. , Quintans G. , Hötzel M. J. , Ungerfeld R.
Published: February 2015

Two-step weaning with nose flaps is used to minimise the stress of weaning in beef calves. Farmers leave the nose flaps for 7–30 days, basing the period on practical considerations. Thus, the objective of this study was to compare the behavioural response of 6-month-old beef calves fitted with nose flaps during 7 or 21 days before permanent separation from the dam, or abruptly weaned. Angus × Hereford cow-calf pairs were assigned to: (1) calves fitted with nose flaps on Day –7 and permanently separated from their mothers on Day 0 (NF7), (2) calves fitted with nose flaps on Day –21 and permanently separated from their mothers on Day 0 (NF21), and (3) calves abruptly weaned on Day 0 (CON). Behaviours (standing, lying, walking pacing, grazing, ruminating and vocalisations) were recorded during 3 days before and 5 days after permanent separation from the dam. On Days 1–3, standing and grazing behaviours decreased, whereas walking, pacing and vocalising increased in CON calves but not in NF7 or NF21 calves. Control calves differed from NF7 and NF21 calves for all these behaviours. The two nose flap treatments differed only on Day 1, when the changes in the frequency of walking, lying and standing were smaller in NF7 than NF21 calves. In conclusion, nose flaps can be used for periods from 7 to 21 days before permanent separation from the dam, diminishing the behavioural indicators of distress provoked by weaning.
Occupy
Authors: Martín Rojo Luisa
Published: February 2015

Large-scale protests have recently transformed urban common spaces into sites of resistance. Squares and urban places, monumentally designed as political and economic centres, have been reclaimed as places for discussion anddecision-making, for increasing participation and intervention in the governance of the community. Through banners and signs, open assemblies, and other communicative practices in the encampments and interconnecting physical and virtual spaces, participants permanently reconfigure the spatial context discursively. The attempt to account for on-going social phenomena from the moment they first happen, and with an international perspective, undoubtedly represents a theoretical and methodological challenge. This special issue focuses on this complex interplay between social, spatial, and communicative practices, drawing on complementary and alternative methods.
Taking over the Square
Authors: Martín Rojo Luisa
Published: February 2015

In this paper I study the extent to which the 15-M or Spanish Indignados movement has transformed the discourses of social movements, not only in terms of their content, but also in the way their communicative practices are produced and circulate. Thus, this paper firstly explores how changes in the conditions of production and circulation of linguistic practices contribute to the “deterritorialisation” and “reterritorialisation” of space, by means of which protestors replace the traditional organisation and uses of space with their own beliefs, ideologies and communicative practices. Secondly, I examine the extent to which this “reterritorialisation” leads to an in-depth transformation of the forms of communication, which could be, in their turn, not only transforming public spaces, but also social movements themselves, and the way of doing politics. The paper addresses whether these practices, in projecting themselves onto a public space which they transform, prefigure in the present moment the kind of society being proposed and fought for.
The Occupy Assembly
Authors: Steinberg R. Lila
Published: February 2015

A key feature of the Occupy movement has been the General Assembly (GA), in which participants, gathered in outdoor public space, engaged in emergent forms of direct deliberative democratic practice. GAs created opportunities for renewed, co-constructed discourses about human rights, collectivity and autonomy, and the nature of fairness. The physical, durative occupation of public space and establishment of encampments enabled participants to converse and collaborate meaningfully about these matters and their implications for action. An attested ideology of horizontalism was produced and reflected in practices of decision-making within a direct participatory democratic framework. The generation of local intersubjectivity and global solidarity as well as the embodied augmentation of personal and group agency were lodged within face-to-face interactions at Occupy GAs. Participants developed and adapted specific embodied tools for assembly use, including hand signals and the human mic, to facilitate a discursive praxis of egalitarianism within the context of a speech exchange system suited to a large outdoor deliberative body. These practices are central to the Occupy movement, as they constitute the discursive experiments in direct democracy set in motion by a shared recognition of social crisis and systemic injustice felt increasingly around the world. This paper examines how several embodied practices at Occupy Los Angeles attend to participants’ attested ideologies and the practical problems of open, large-group direct democracy.
A Long-Term Longitudinal Examination of the Effect of Early Onset of Alcohol and Drug use on Later Alcohol Abuse
Authors: Ohannessian Christine McCauley , Finan Laura J. , Schulz Jessica , Hesselbrock Victor
Published: February 2015

Background

Early onset of alcohol use has been linked to later alcohol problems in adulthood. Currently, it is not clear whether early onset of marijuana and tobacco use similarly predicts alcohol problems. Moreover, most studies examining the effect of early substance use onset on later problems only have followed youth into their early 20s. Therefore, the primary goal of this study was to examine whether early onset of alcohol, marijuana, and tobacco use predicts alcohol problems beyond the transition to adulthood.

Methods

The sample included 225 15–19-year-old youth (60% girls; 62% Caucasian) who were surveyed in three time periods: 1993–1998 (Time 1), 1998–2003 (Time 2), and 2003–2007 (Time 3). Participants reported their age of onset for regular drinking, tobacco use, and marijuana use. At each time of measurement, they also completed surveys relating to their alcohol use and abuse.

Results

Participants with an earlier age of onset of drinking regularly scored higher on the Michigan Alcoholism Screening Test (MAST) and drank more frequently to get high and drunk throughout their 20s. Tobacco use onset and marijuana use onset were not associated with later alcohol use or abuse.

Conclusions

Results from this study suggest that the relationship between the onset of substance use and later substance abuse may be substance specific. Of note, early onset of regular drinking was associated with alcohol problems during adulthood, underscoring the importance of delaying the onset of regular alcohol use among youth.
Pharmaceutical Opioids in the Home and Youth: Implications for Adult Medical Practice
Authors: Binswanger Ingrid A. , Glanz Jason M.
Published: February 2015

Pharmaceutical opioid prescribing, opioid use disorders, and related poisonings have increased substantially in the last decade. In particular, pharmaceutical opioid deaths among youth have markedly increased. One area that has received relatively little attention is the role of home safety, given that parents are an important source of opioids for youth. Parents may intentionally share opioids with youth, due to low perceived risks or limited knowledge, and youth may divert opioids from parents’ medicine cabinets. Safe medication storage has long been mandated by treatment programs that provide pharmacologically supported treatment of opioid use disorders, but it is not generally encouraged or required for pharmaceutical opioids prescribed for pain. Greater attention is needed on the development, evaluation, and implementation of 3 preventive strategies. These 3 strategies can be delivered in or supported by adult medical practices: (1) fully informing adults prescribed opioids about the risks of opioids to family members and others; (2) providing locked medication safe storage devices; and (3) educating parents on safe disposal options. However, a critical evidence base is still lacking for these opioid safety interventions.
Defining Nonmedical Use of Prescription Opioids within Health Care Claims: A Systematic Review
Authors: Cochran Gerald , Woo Bongki , Lo-Ciganic Wei-Hsuan , Gordon Adam J. , Donohue Julie M. , Gellad Walid F.
Published: February 2015

Background

Health insurance claims data may play an important role for health care systems and payers in monitoring the nonmedical use of prescription opioids (NMPO) among patients. However, these systems require valid methods for identifying NMPO if they are to target individuals for intervention. Limited efforts have been made to define NMPO using administrative data available to health systems and payers. We conducted a systematic review of publications that defined and measured NMPO within health insurance claims databases in order to describe definitions of NMPO and identify areas for improvement.

Methods

We searched 8 electronic databases for articles that included terms related to NMPO and health insurance claims. A total of 2613 articles were identified in our search. Titles, abstracts, and article full texts were assessed according to predetermined inclusion/exclusion criteria. Following article selection, we extracted general information, conceptual and operational definitions of NMPO, methods used to validate operational definitions of NMPO, and rates of NMPO.

Results

A total of 7 studies met all inclusion criteria. A range of conceptual NMPO definitions emerged, from concrete concepts of abuse to qualified definitions of probable misuse. Operational definitions also varied, ranging from variables that rely on diagnostic codes to those that rely on opioid dosage and/or filling patterns. Quantitative validation of NMPO definitions was reported in 3 studies (e.g., receiver operating curves or logistic regression), with each study indicating adequate validity. Three studies reported qualitative validation, using face and content validity. One study reported no validation efforts. Rates of NMPO among the studies’ populations ranged from 0.75% to 10.32%.

Conclusions

Disparate definitions of NMPO emerged from the literature, with little uniformity in conceptualization and operationalization. Validation approaches were also limited, and rates of NMPO varied across studies. Future research should prospectively test and validate a construct of NMPO to disseminate to payers and health officials.
Gesture is More Effective than Spatial Language in Encoding Spatial Information
Authors: So Wing-Chee , Shum Priscilla Lok-Chee , Wong Miranda Kit-Yi
Published: February 2015

The present research investigates whether producing gestures with and without speech facilitates route learning at different levels of route complexity and in learners with different levels of spatial skills. It also examines whether the facilitation effect of gesture is stronger than that of spatial language. Adults studied routes with 10, 13, and 16 steps and reconstructed them with sticks, either without rehearsal or after rehearsal by producing gestures with speech, gestures alone, or speech only. For all levels of route complexity and spatial skills, participants who were encouraged to gesture (with or without speech) during rehearsal had the best recall. Additionally, we found that number of steps rehearsed in gesture, but not that rehearsed in speech, predicted the recall accuracy. Thus, gesture is more effective than spatial language in encoding spatial information, and thereby enhancing spatial recall. These results further corroborate the beneficial nature of gesture in processing spatial information.
Are There Qualitative Differences in the Representation of Abstract and Concrete Words? Within-Language and Cross-Language Evidence from the Semantic Priming Paradigm
Authors: Ferré Pilar , Guasch Marc , García-Chico Teófilo , Sánchez-Casas Rosa
Published: February 2015

The different organizational frameworks theory proposes that there is a qualitative difference between the representation of concrete and abstract words in memory: Concrete concepts would be primarily organized in terms of semantic similarity whereas abstract concepts would be mainly organized by their association with other concepts. Evidence in support of this proposal has been mostly obtained with neuropsychological populations and, to a lesser extent, with healthy participants. In the present work, we tested the different organizational frameworks theory by using, for the first time, a semantic priming paradigm both within language and across languages. The results revealed that there was priming for both semantically similar and associative relations when words were concrete. However, with abstract words, priming was only observed when pairs and targets were associated. These results do not support the proposal of Crutch and coworkers, suggesting that the experimental paradigm as well as the type of relations tested may modulate the pattern of effects obtained with concrete and abstract words.
Face learning with multiple images leads to fast acquisition of familiarity for specific individuals
Authors: Dowsett A. J. , Sandford A. , Burton A. Mike
Published: February 2015

Matching unfamiliar faces is a difficult task. Here we ask whether it is possible to improve performance by providing multiple images to support matching. In two experiments we observe that accuracy improves as viewers are provided with additional images on which to base their match. This technique leads to fast learning of an individual, but the effect is identity-specific: Despite large improvements in viewers’ ability to match a particular person's face, these improvements do not generalize to other faces. Experiment 2 demonstrated that trial-by-trial feedback provided no additional benefits over the provision of multiple images. We discuss these results in terms of familiar and unfamiliar face processing and draw out some implications for training regimes.