bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and optimization of illumination vector for contouring surface form and feature using DSPI
Authors: Song Chaolong , Prasad A. S. Guru , Chan Kelvin H. K. , Murukeshan Vadakke Matham
Published: June 2016

Surface defect or damage is one of the critical factors leading to the failure of engineering materials and structures. The methodologies for the measurement of surface shape and feature or defect have been extensively explored and developed over the past few decades, including both contact and non-contact methods. Speckle pattern interferometry, as a non-contact optical method, has been demonstrated to effectively contour the surface shape through adjusting the illumination vector. However, few studies have been made to investigate the effect of the initial position of the illumination source as well as the source translation direction. In this paper, we report to carry out a study of measuring the surface form and feature using digital speckle pattern interferometry system via a slight translation of illumination source. Through theoretically analyzing the sensitivity factor along with the experimental validation, it is shown that the contouring fringe is more sensitive to the surface height with an off-axis illumination than the paraxial illumination. It is also found that translating the source along axial and lateral direction can be both used for the surface shape re-construction.
The cryogenic storage ring CSR
Authors: von Hahn R. , Becker A. , Berg F. , Blaum K. , Breitenfeldt C. , Fadil H. , Fellenberger F. , Froese M. , George S. , Göck J. , Grieser M. , Grussie F. , Guerin E. A. , Heber O. , Herwig P. , Karthein J. , Krantz C. , Kreckel H. , Lange M. , Laux F. , Lohmann S. , Menk S. , Meyer C. , Mishra P. M. , Novotný O. , O’Connor A. P. , Orlov D. A. , Rappaport M. L. , Repnow R. , Saurabh S. , Schippers S. , Schröter C. D. , Schwalm D. , Schweikhard L. , Sieber T. , Shornikov A. , Spruck K. , Sunil Kumar S. , Ullrich J. , Urbain X. , Vogel S. , Wilhelm P. , Wolf A. , Zajfman D.
Published: June 2016

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm−3 is derived, equivalent to a room-temperature pressure below 10−14 mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.
Ultra-thin flexible GaAs photovoltaics in vertical forms printed on metal surfaces without interlayer adhesives
Authors: Kim Juho , Hwang Jeongwoo , Song Kwangsun , Kim Namyun , Shin Jae Cheol , Lee Jongho
Published: June 2016

Wearable flexible electronics often require sustainable power sources that are also mechanically flexible to survive the extreme bending that accompanies their general use. In general, thinner microelectronic devices are under less strain when bent. This paper describes strategies to realize ultra-thin GaAs photovoltaics through the interlayer adhesiveless transfer-printing of vertical-type devices onto metal surfaces. The vertical-type GaAs photovoltaic devices recycle reflected photons by means of bottom electrodes. Systematic studies with four different types of solar microcells indicate that the vertical-type solar microcells, at only a quarter of the thickness of similarly designed lateral-type cells, generate a level of electric power similar to that of thicker cells. The experimental results along with the theoretical analysis conducted here show that the ultra-thin vertical-type solar microcells are durable under extreme bending and thus suitable for use in the manufacturing of wearable flexible electronics.
Electrode-stress-induced nanoscale disorder in Si quantum electronic devices
Authors: Park J. , Ahn Y. , Tilka J. A. , Sampson K. C. , Savage D. E. , Prance J. R. , Simmons C. B. , Lagally M. G. , Coppersmith S. N. , Eriksson M. A. , Holt M. V. , Evans P. G.
Published: June 2016

Disorder in the potential-energy landscape presents a major obstacle to the more rapid development of semiconductor quantum device technologies. We report a large-magnitude source of disorder, beyond commonly considered unintentional background doping or fixed charge in oxide layers: nanoscale strain fields induced by residual stresses in nanopatterned metal gates. Quantitative analysis of synchrotron coherent hard x-ray nanobeam diffraction patterns reveals gate-induced curvature and strains up to 0.03% in a buried Si quantum well within a Si/SiGe heterostructure. Electrode stress presents both challenges to the design of devices and opportunities associated with the lateral manipulation of electronic energy levels.
Effective short-range Coulomb correction to model the aggregation behavior of ionic surfactants
Authors: Burgos-Mármol J. Javier , Solans Conxita , Patti Alessandro
Published: June 2016

We present a short-range correction to the Coulomb potential to investigate the aggregation of amphiphilic molecules in aqueous solutions. The proposed modification allows to quantitatively reproduce the distribution of counterions above the critical micelle concentration (CMC) or, equivalently, the degree of ionization, α, of the micellar clusters. In particular, our theoretical framework has been applied to unveil the behavior of the cationic surfactant C24H49N2O2+ CH3SO4−, which offers a wide range of applications in the thriving and growing personal care market. A reliable and unambiguous estimation of α is essential to correctly understand many crucial features of the micellar solutions, such as their viscoelastic behavior and transport properties, in order to provide sound formulations for the above mentioned personal care solutions. We have validated our theory by performing extensive lattice Monte Carlo simulations, which show an excellent agreement with experimental observations. More specifically, our coarse-grained model is able to reproduce and predict the complex morphology of the micelles observed at equilibrium. Additionally, our simulation results disclose the existence of a transition from a monodisperse to a bidisperse size distribution of aggregates, unveiling the intriguing existence of a second CMC.
Electric multipole moments calculation with explicitly correlated coupled-cluster wavefunctions
Authors: Bokhan Denis , Trubnikov Dmitrii N. , Bartlett Rodney J.
Published: June 2016

A method of calculation of expectation values of dipole and quadrupole moments with wavefunctions, corresponding to linearly approximated explicitly correlated coupled-cluster singles and doubles [CCSD(F12)] model has been formulated and implemented. As a part of algorithm, explicitly correlated version of Λ equations has also been derived and implemented. Numerical tests, conducted for sets of molecules, show that explicitly correlated results for expectation values of dipole moment are accurate up to 0.01 a.u. already at a double-ζ level compared to those in the complete basis set limit. The corresponding results for quadrupole moments at double-ζ level are accurate up to 0.1 a.u., while for the triple-ζ bases errors do not exceed 0.01 a.u.
Fabrication of FeSi and Fe3Si compounds by electron beam induced mixing of [Fe/Si]2 and [Fe3/Si]2 multilayers grown by focused electron beam induced deposition
Authors: Porrati F. , Sachser R. , Gazzadi G. C. , Frabboni S. , Huth M.
Published: June 2016

Fe-Si binary compounds have been fabricated by focused electron beam induced deposition by the alternating use of iron pentacarbonyl, Fe(CO)5, and neopentasilane, Si5H12 as precursor gases. The fabrication procedure consisted in preparing multilayer structures which were treated by low-energy electron irradiation and annealing to induce atomic species intermixing. In this way, we are able to fabricate FeSi and Fe3Si binary compounds from [Fe/Si]2 and [Fe3/Si]2 multilayers, as shown by transmission electron microscopy investigations. This fabrication procedure is useful to obtain nanostructured binary alloys from precursors which compete for adsorption sites during growth and, therefore, cannot be used simultaneously.
The Wentzel–Kramers–Brillouin approximation method applied to the Wigner function
Authors: Tosiek J. , Cordero R. , Turrubiates F. J.
Published: June 2016

An adaptation of the Wentzel–Kramers–Brilluoin method in the deformation quantization formalism is presented with the aim to obtain an approximate technique of solving the eigenvalue problem for energy in the phase space quantum approach. A relationship between the phase σ(r→) of a wave function expiħσ(r→) and its respective Wigner function is derived. Formulas to calculate the Wigner function of a product and of a superposition of wave functions are proposed. Properties of a Wigner function of interfering states are also investigated. Examples of this quasi–classical approximation in deformation quantization are analysed. A strict form of the Wigner function for states represented by tempered generalised functions has been derived. Wigner functions of unbound states in the Poeschl–Teller potential have been found.
Argon metastable production in argon-helium microplasmas
Authors: Hoskinson Alan R. , Gregorío José , Hopwood Jeffrey , Galbally-Kinney Kristin , Davis Steven J. , Rawlins Wilson T.
Published: June 2016

Microwave resonator-driven microplasmas are a promising technology for generating the high density of rare-gas metastable states required for optically pumped rare gas laser systems. We measure the density of argon 1s5 states (Paschen notation) in argon-helium plasmas between 100 Torr and atmospheric pressure using diode laser absorption. The metastable state density is observed to rise with helium mole fraction at lower pressures but to instead fall slightly when tested near atmospheric pressure. A 0-D model of the discharge suggests that these distinct behaviors result from the discharge being diffusion-controlled at lower pressures, but with losses occurring primarily through dissociative recombination at high pressures. In all cases, the argon metastable density falls sharply when the neutral argon gas fraction is reduced below approximately 2%.
LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window
Authors: Ximendes Erving Clayton , Rocha Uéslen , Kumar Kagola Upendra , Jacinto Carlos , Jaque Daniel
Published: June 2016

We report on Ytterbium and Neodymium codoped LaF3 core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd3+ → Yb3+ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.
On-chip interference of single photons from an embedded quantum dot and an external laser
Authors: Prtljaga N. , Bentham C. , O'Hara J. , Royall B. , Clarke E. , Wilson L. R. , Skolnick M. S. , Fox A. M.
Published: June 2016

In this work, we demonstrate the on-chip two-photon interference between single photons emitted by a single self-assembled InGaAs quantum dot and an external laser. The quantum dot is embedded within one arm of an air-clad directional coupler which acts as a beam-splitter for incoming light. Photons originating from an attenuated external laser are coupled to the second arm of the beam-splitter and then combined with the quantum dot photons, giving rise to two-photon quantum interference between dissimilar sources. We verify the occurrence of on-chip Hong-Ou-Mandel interference by cross-correlating the optical signal from the separate output ports of the directional coupler. This experimental approach allows us to use a classical light source (laser) to assess in a single step the overall device performance in the quantum regime and probe quantum dot photon indistinguishability on application realistic time scales.
Chemical free device fabrication of two dimensional van der Waals materials based transistors by using one-off stamping
Authors: Lee Young Tack , Choi Won Kook , Hwang Do Kyung
Published: June 2016

We report on a chemical free one-off imprinting method to fabricate two dimensional (2D) van der Waals (vdWs) materials based transistors. Such one-off imprinting technique is the simplest and effective way to prevent unintentional chemical reaction or damage of 2D vdWs active channel during device fabrication process. 2D MoS2 nanosheets based transistors with a hexagonal-boron-nitride (h-BN) passivation layer, prepared by one-off imprinting, show negligible variations of transfer characteristics after chemical vapor deposition process. In addition, this method enables the fabrication of all 2D MoS2 transistors consisting of h-BN gate insulator, and graphene source/drain and gate electrodes without any chemical damage.
Comparative studies of efficiency droop in polar and non-polar InGaN quantum wells
Authors: Davies M. J. , Dawson P. , Hammersley S. , Zhu T. , Kappers M. J. , Humphreys C. J. , Oliver R. A.
Published: June 2016

We report on a comparative study of efficiency droop in polar and non-polar InGaN quantum well structures at T = 10 K. To ensure that the experiments were carried out with identical carrier densities for any particular excitation power density, we used laser pulses of duration ∼100 fs at a repetition rate of 400 kHz. For both types of structures, efficiency droop was observed to occur for carrier densities of above 7 × 1011 cm−2 pulse−1 per quantum well; also both structures exhibited similar spectral broadening in the droop regime. These results show that efficiency droop is intrinsic in InGaN quantum wells, whether polar or non-polar, and is a function, specifically, of carrier density.
Generating photon pairs from a silicon microring resonator using an electronic step recovery diode for pump pulse generation
Authors: Savanier Marc , Mookherjea Shayan
Published: June 2016

Generation of photon pairs from compact, manufacturable, and inexpensive silicon (Si) photonic devices at room temperature may help develop practical applications of quantum photonics. An important characteristic of photon-pair generation is the two-photon joint spectral intensity, which describes the frequency correlations of the photon pair. Recent attempts to generate a factorizable photon-pair state suitable for heralding have used short optical pump pulses from mode-locked lasers, which are much more expensive and bigger table-top or rack-sized instruments compared with the Si microchip used for generating photon pairs, and thus dominate the cost and inhibit the miniaturization of the source. Here, we generate photon pairs from an Si microring resonator by using an electronic step-recovery diode to drive an electro-optic modulator which carves the pump light from a continuous-wave laser diode into pulses of the appropriate width, thus potentially eliminating the need for optical mode-locked lasers.
Experimental investigation of resonant MEMS switch with ac actuation
Authors: Pal Jitendra , Zhu Yong , Wang Boyi , Lu Junwei , Khan Fahimullah , Viet Dao Dzung , Wang Yifan
Published: June 2016

In this letter, modeling, analysis, and experimental investigation for a resonant MEMS switch are presented. The resonant switch harnesses its mechanical resonance to lower the required actuation voltage by a substantial factor over the switch with static actuation. With alternating actuation voltage at its mechanical resonance frequency of 6.6 kHz, the average capacitance is tuned by changing the gap between fixed and movable electrodes. Based on the proposed actuation method, the device offers 57.44% lower actuation voltage compared with the switch with static actuation.
Thermal poling of ferroelectrets: How does the gas temperature influence dielectric barrier discharges in cavities?
Authors: Qiu Xunlin , Wirges Werner , Gerhard Reimund
Published: June 2016

The influence of the temperature in the gas-filled cavities on the charging process of ferroelectret film systems has been studied in hysteresis measurements. The threshold voltage and the effective polarization of the ferroelectrets were determined as functions of the charging temperature TP. With increasing TP, the threshold voltage for triggering dielectric barrier discharges in ferroelectrets decreases. Thus, increasing the temperature facilitates the charging of ferroelectrets. However, a lower threshold voltage reduces the attainable remanent polarization because back discharges occur at lower charge levels, as soon as the charging voltage is turned off. The results are discussed in view of Paschen's law for electrical breakdown, taking into account the respective gas temperature and a simplified model for ferroelectrets. Our results indicate that the thermal poling scheme widely used for conventional ferroelectrics is also useful for electrically charging ferroelectrets.
Is organic photovoltaics promising for indoor applications?
Authors: Lee Harrison K. H. , Li Zhe , Durrant James R. , Tsoi Wing C.
Published: June 2016

This work utilizes organic photovoltaics (OPV) for indoor applications, such as powering small electronic devices or wireless connected Internet of Things. Three representative polymer-based OPV systems, namely, poly(3-hexylthiophene-2,5-diyl), poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)], and poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]], were selected as the donor materials in blend with fullerene derivatives for comparison under low light level condition using fluorescent lamps. PCDTBT based devices are found to be the best performing system, generating 13.9 μW/cm2 corresponding to 16.6% power conversion efficiency at 300 lx, although PTB7 based devices show the highest efficiency under one sun conditions. This high performance suggests that OPV is competitive to the other PV technologies under low light condition despite much lower performance under one sun condition. Different properties of these devices are studied to explain the competitive performance at low light level. A low energy consuming method for maximum power point tracking is introduced for the operation of the OPV devices. Finally, a 14 cm × 14 cm OPV module with 100 cm2 active area is demonstrated for real applications. These findings suggest that OPV, in particular, PCDTBT based devices, could be a promising candidate for indoor applications.
Giant linear magneto-resistance in nonmagnetic PtBi2
Authors: Yang Xiaojun , Bai Hua , Wang Zhen , Li Yupeng , Chen Qian , Chen Jian , Li Yuke , Feng Chunmu , Zheng Yi , Xu Zhu-an
Published: June 2016

We synthesized nonmagnetic PtBi2 single crystals and observed a giant linear magneto-resistance (MR) up to 684% under a magnetic field μ0H = 15 T at T = 2 K. The linear MR decreases with increasing temperature, but it is still as large as 61% under μ0H of 15 T at room temperature. Such a giant linear MR is unlikely to be described by the quantum model as the quantum condition is not satisfied. Instead, we found that the slope of MR scales with the Hall mobility, and it can be well explained by a classical disorder model.
Decoupling indirect topographic cross-talk in band excitation piezoresponse force microscopy imaging and spectroscopy
Authors: Yang Sang Mo , Mazet Lucie , Okatan M. Baris , Jesse Stephen , Niu Gang , Schroeder Thomas , Schamm-Chardon Sylvie , Dubourdieu Catherine , Baddorf Arthur P. , Kalinin Sergei V.
Published: June 2016

All scanning probe microscopies are subjected to topographic cross-talk, meaning the topography-related contrast in functional images. Here, we investigate the signatures of indirect topographic cross-talk in piezoresponse force microscopy (PFM) imaging and spectroscopy and its decoupling using band excitation (BE) method in ferroelectric BaTiO3 deposited on the Si substrates with free standing nanopillars of diameter 50 nm. Comparison between the single-frequency PFM and BE-PFM results shows that the measured signal can be significantly distorted by topography-induced shifts in the contact resonance frequency and cantilever transfer function. However, with proper correction, such shifts do not affect PFM imaging and hysteresis loop measurements. This suggests the necessity of an advanced approach, such as BE-PFM, for detection of intrinsic sample piezoresponse on the topographically non-uniform surfaces.
Band structure characterization of WS2 grown by chemical vapor deposition
Authors: Tanabe Iori , Gomez Michael , Coley William C. , Le Duy , Echeverria Elena M. , Stecklein Gordon , Kandyba Viktor , Balijepalli Santosh K. , Klee Velveth , Nguyen Ariana E. , Preciado Edwin , Lu I-Hsi , Bobek Sarah , Barroso David , Martinez-Ta Dominic , Barinov Alexei , Rahman Talat S. , Dowben Peter A. , Crowell Paul A. , Bartels Ludwig
Published: June 2016

Growth by chemical vapor deposition (CVD) leads to multilayer WS2 of very high quality, based on high-resolution angle-resolved photoemission spectroscopy. The experimental valence band electronic structure is considered to be in good agreement with that obtained from density functional theory calculations. We find the spin-orbit splitting at the K¯ point to be 420 ± 20 meV with a hole effective mass of −0.35 ± 0.02 me for the upper spin-orbit component (the branch closer to the Fermi level) and −0.43 ± 0.07 me for the lower spin-orbit component. As predicted by theory, a thickness-dependent increase of bandwidth is observed at the top of the valence band, in the region of the Brillouin zone center. The top of the valence band of the CVD-prepared films exhibits a substantial binding energy, consistent with n-type behavior, and in agreement with transistor characteristics acquired using devices incorporating the same WS2 material.
Pressure-induced transformations in carbon nano-onions
Authors: Yao Mingguang , Zhang Weiwei , Dong Jiajun , Liu Ran , Liu Bingbing
Published: June 2016

Carbon nano-onions (CNOs) with an average diameter of 43 nm have been studied under pressure. The interlayer d-spacings of the CNOs are expanded by about 3% compared to those of the larger CNOs with average diameter of 150 nm studied earlier. High pressure study on the G-band of the small CNOs indicates that a bonding change was initiated at 23.4 GPa, which is higher than that of the larger CNOs. The small CNOs were destroyed into amorphous fragments at above 48 GPa with a large applied deviatoric stress, showing a lower high pressure stability compared with the larger CNOs. These features are qualitatively similar to the size effects observed in the compression behavior of some nanocrystalline materials, showing that a reduced cluster size gives similar physical effects in the two classes of materials. The present results for CNOs can be rationalized by the interlayer expansion and the highly turbostratic layer structure of the studied material. The fact that CNOs with different diameters behave differently upon compression is important when selecting materials for applications.
Growth kinetics and island evolution during double-pulsed molecular beam epitaxy of InN
Authors: Kraus A. , Hein C. , Bremers H. , Rossow U. , Hangleiter A.
Published: June 2016

The kinetic processes of InN growth using alternating source fluxes with sub-monolayer In pulses in plasma-assisted molecular beam epitaxy have been investigated. Growth at various temperatures reveals the existence of two growth regimes. While growth at low temperatures is solely governed by surface diffusion, a combination of decomposition, desorption, and diffusion becomes decisive at growth temperatures of 470 °C and above. At this critical temperature, the surface morphology changes from a grainy structure to a structure made of huge islands. The formation of those islands is attributed to the development of an indium adlayer, which can be observed via reflection high energy electron diffraction monitoring. Based on the growth experiments conducted at temperatures below TGrowth = 470 °C, an activation energy for diffusion of 0.54 ± 0.02 eV has been determined from the decreasing InN island density. A comparison between growth on metalorganic vapor phase epitaxy GaN templates and pseudo bulk GaN indicates that step edges and dislocations are favorable nucleation sites. Based on the results, we developed a growth model, which describes the main mechanisms of the growth.
Vacuum arcing behavior between transverse magnetic field contacts subjected to variable axial magnetic field
Authors: Ma Hui , Wang Jianhua , Liu Zhiyuan , Geng Yingsan , Wang Zhenxing , Yan Jing
Published: June 2016

The objective of this work is to reveal the effects of an axial magnetic field (AMF) on the vacuum arc characteristics between transverse magnetic field (TMF) contacts. These vacuum arc characteristics include the vacuum arcing behavior and the arc voltage waveform. In the experiments, an external AMF was applied to a pair of TMF contacts. The external AMF flux density BAMF can be adjusted from 0 to 110 mT. The arc current in the tests varied over a range from 0 to 20 kA rms at 45 Hz. The contact material was CuCr25 (25% Cr). A high-speed charge-coupled device video camera was used to record the vacuum arc evolution. The experimental results show that the application of the AMF effectively reduces the TMF arc voltage noise component and reduces the formation of liquid metal drops between the contacts. The diffuse arc duration increases linearly with increasing AMF flux density, but it also decreases linearly with increasing arc current under application of the external AMF. The results also indicate that the diffuse arc duration before the current zero is usually more than 1 ms under the condition that the value of the AMF per kiloampere is more than 2.0 mT/kA. Finally, under application of the AMF, the arc column of the TMF contacts may constrict and remain in the center region without transverse rotation. Therefore, the combined TMF–AMF contacts should be designed such that they guarantee that the AMF is not so strong as to oppose transverse rotation of the arc column.
The kinetic origin of delayed yielding in metallic glasses
Authors: Ye Y. F. , Liu X. D. , Wang S. , Fan J. , Liu C. T. , Yang Y.
Published: June 2016

Recent experiments showed that irreversible structural change or plasticity could occur in metallic glasses (MGs) even within the apparent elastic limit after a sufficiently long waiting time. To explain this phenomenon, a stochastic shear transformation model is developed based on a unified rate theory to predict delayed yielding in MGs, which is validated afterwards through extensive atomistic simulations carried out on different MGs. On a fundamental level, an analytic framework is established in this work that links time, stress, and temperature altogether into a general yielding criterion for MGs.
Flash Kα radiography of laser-driven solid sphere compression for fast ignition
Authors: Sawada H. , Lee S. , Shiroto T. , Nagatomo H. , Arikawa Y. , Nishimura H. , Ueda T. , Shigemori K. , Sunahara A. , Ohnishi N. , Beg F. N. , Theobald W. , Pérez F. , Patel P. K. , Fujioka S.
Published: June 2016

Time-resolved compression of a laser-driven solid deuterated plastic sphere with a cone was measured with flash Kα x-ray radiography. A spherically converging shockwave launched by nanosecond GEKKO XII beams was used for compression while a flash of 4.51 keV Ti Kα x-ray backlighter was produced by a high-intensity, picosecond laser LFEX (Laser for Fast ignition EXperiment) near peak compression for radiography. Areal densities of the compressed core were inferred from two-dimensional backlit x-ray images recorded with a narrow-band spherical crystal imager. The maximum areal density in the experiment was estimated to be 87 ± 26 mg/cm2. The temporal evolution of the experimental and simulated areal densities with a 2-D radiation-hydrodynamics code is in good agreement.
Temperature independent infrared responsivity of a quantum dot quantum cascade photodetector
Authors: Wang Feng-Jiao , Zhuo Ning , Liu Shu-Man , Ren Fei , Ning Zhen-Dong , Ye Xiao-Ling , Liu Jun-Qi , Zhai Shen-Qiang , Liu Feng-Qi , Wang Zhan-Guo
Published: June 2016

We demonstrate a quantum dot quantum cascade photodetector with a hybrid active region of InAs quantum dots and an InGaAs quantum well, which exhibited a temperature independent response at 4.5 μm. The normal incident responsivity reached 10.3 mA/W at 120 K and maintained a value of 9 mA/W up to 260 K. It exhibited a specific detectivity above 1011 cm Hz1/2 W−1 at 77 K, which remained at 108 cm Hz1/2 W−1 at 260 K. We ascribe the device's good thermal stability of infrared response to the three-dimensional quantum confinement of the InAs quantum dots incorporated in the active region.
Integrating superconducting phase and topological crystalline quantum spin Hall effect in hafnium intercalated gallium film
Authors: Zhou Jian , Zhang Shunhong , Wang Qian , Jena Puru
Published: June 2016

Motivated by the growth of superconducting atomic hexagonal Ga layers on GaN surface we have calculated the electronic properties of Hf intercalated honeycomb Ga layers using first-principles theory. In contrast to the hexagonal Ga layers where substrate is necessary for their stability, we find the above structure to be dynamically stable in its freestanding form with small formation energy. In particular, six Dirac cones composed of Hf-dxy/dx2-y2 orbitals are observed in the first Brillouin zone, slightly below the Fermi energy. Spin-orbit coupling opens a large band gap of 177 meV on these Dirac cones. By calculating its mirror Chern number, we demonstrate that this band gap is topologically nontrivial and protected by mirror symmetry. Such mirror symmetry protected band gaps are rare in hexagonal lattice. A large topological crystalline quantum spin Hall conductance σSH ∼ −4 e2/h is also revealed. Moreover, electron-phonon coupling calculations reveal that this material is superconducting with a transition temperature Tc = 2.4 K, mainly contributed by Ga out-of-plane vibrations. Our results provide a route toward manipulating quantum spin Hall and superconducting behaviors in a single material which helps to realize Majorana fermions and topological superconductors.
Band gap engineering of N-alloyed Ga2O3 thin films
Authors: Song Dongyu , Li Li , Li Bingsheng , Sui Yu , Shen Aidong
Published: June 2016

The authors report the tuning of band gap of GaON ternary alloy in a wide range of 2.75 eV. The samples were prepared by a two-step nitridation method. First, the samples were deposited on 2-inch fused silica substrates by megnetron sputtering with NH3 and Ar gas for 60 minutes. Then they were annealed in NH3 ambience at different temperatures. The optical band gap energies are calculated from transmittance measurements. With the increase of nitridation temperature, the band gap gradually decreases from 4.8 eV to 2.05 eV. X-ray diffraction results indicate that as-deposited amorphous samples can crystallize into monoclinic and hexagonal structures after they were annealed in oxygen or ammonia ambience, respectively. The narrowing of the band gap is attributed to the enhanced repulsion of N2p -Ga3d orbits and formation of hexagonal structure.
Local Peltier-effect-induced reversible metal–insulator transition in VO2 nanowires
Authors: Takami Hidefumi , Kanki Teruo , Tanaka Hidekazu
Published: June 2016

We report anomalous resistance leaps and drops in VO2 nanowires with operating current density and direction, showing reversible and nonvolatile switching. This event is associated with the metal–insulator phase transition (MIT) of local nanodomains with coexistence states of metallic and insulating phases induced by thermoelectric cooling and heating effects. Because the interface of metal and insulator domains has much different Peltier coefficient, it is possible that a significant Peltier effect would be a source of the local MIT. This operation can be realized by one-dimensional domain configuration in VO2 nanowires because one straight current path through the electronic domain-interface enables theoretical control of thermoelectric effects. This result will open a new method of reversible control of electronic states in correlated electron materials.
Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals
Authors: Liang Xiaogang , Hamid Ilyar , Duan Haiming
Published: June 2016

The dynamic stabilities of the icosahedral-like clusters containing up to 2200 atoms are investigated for 15 metal elements. The clusters originate from five different initial structures (icosahedron, truncated decahedron, octahedron, closed-shell fragment of an HCP structure, and non-closed-shell fragment of an HCP structure). The obtained order of the dynamic stabilities of the icosahedral-like clusters can be assigned to three groups, from stronger to weaker, according to the size ranges involved: (Zr, Al, Ti) > (Cu, Fe, Co, Ni, Mg, Ag) > (Pb, Au, Pd, Pt, Rh, Ir), which correspond to the predicted formation ability of the quasicrystals. Thedifferences of the sequences can be explained by analyzing the parameters of the Gupta-type many-body inter-atomic potentials.
Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers
Authors: Sun Rui , Makise Kazumasa , Zhang Lu , Terai Hirotaka , Wang Zhen
Published: June 2016

We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100) substrates with a TiN buffer layer. A 50-nm-thick (200)-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large IcRN product of 3.8 mV, a sharp quasiparticle current rise with a ΔVg of 0.4 mV, and a small subgap leakage current. The junction quality factor Rsg/RN was about 23 for the junction with a Jc of 47 A/cm2 and was about 6 for the junction with a Jc of 3.0 kA/cm2. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200)-orientated TiN buffer layer and had a highly crystalline structure with the (200) orientation.
Broadband reflected wavefronts manipulation using structured phase gradient metasurfaces
Authors: Wang Xiao-Peng , Wan Le-Le , Chen Tian-Ning , Song Ai-Ling , Du Xiao-Wen
Published: June 2016

Acoustic metasurface (AMS) is a good candidate to manipulate acoustic waves due to special acoustic performs that cannot be realized by traditional materials. In this paper, we design the AMS by using circular-holed cubic arrays. The advantages of our AMS are easy assemble, subwavelength thickness, and low energy loss for manipulating acoustic waves. According to the generalized Snell’s law, acoustic waves can be manipulated arbitrarily by using AMS with different phase gradients. By selecting suitable hole diameter of circular-holed cube (CHC), some interesting phenomena are demonstrated by our simulations based on finite element method, such as the conversion of incoming waves into surface waves, anomalous reflections (including negative reflection), acoustic focusing lens, and acoustic carpet cloak. Our results can provide a simple approach to design AMSes and use them in wavefront manipulation and manufacturing of acoustic devices.
Gallium antimonide texturing for enhanced light extraction from infrared optoelectronics devices
Authors: Wassweiler Ella , Toor Fatima
Published: June 2016

The use of gallium antimonide (GaSb) is increasing, especially for optoelectronic devices in the infrared wavelengths. It has been demonstrated in gallium nitride (GaN) devices operating at ultraviolet (UV) wavelengths, that surface textures increase the overall device efficiency. In this work, we fabricated eight different surface textures in GaSb to be used in enhancing efficiency in infrared wavelength devices. Through chemical etching with hydrofluoric acid, hydrogen peroxide, and tartaric acid we characterize the types of surface textures formed and the removal rate of entire layers of GaSb. Through optimization of the etching recipes we lower the reflectivity from 35.7% to 1% at 4 μm wavelength for bare and textured GaSb, respectively. In addition, we simulate surface textures using ray optics in finite element method solver software to provide explanation of our experimental findings.
Ruminal fermentation, nutrient digestibility and microbial protein synthesis in sheep fed diets with different levels of date pulp
Authors: Khezri A. , Javidan S. , Dayani O. , Tahmasbi R.
Published: June 2016

Four ruminally cannulated mature Kermani sheep (50 ± 2.3 kg and 40 ± 2.1 months old) were used in a 4 × 4 Latin square design to determine the effects of diets with different levels of date pulp (DP) on ruminal fermentation, nutrient digestibility and microbial protein synthesis. DP was replaced for wheat bran in diets at no DP (0 DP), 7 (7 DP), 14 (14 DP) and 21% (21 DP) of diet dry matter (DM) and were fed twice daily (0800 hours and 1800 hours). In this study, increasing the amount of DP in diets of sheep did not affect DM intake and apparent digestibility of nutrient (P > 0.05). Inclusion of DP in diets increased ruminal pH linearly (P < 0.05), but did not influence total volatile fatty acids and molar proportion of individual volatile fatty acids (P > 0.05). Ruminal ammonia nitrogen concentration (6.04 vs 10.13 mmol/L), and blood urea nitrogen (8.59 vs 13.10 mg/dL) were affected by diets (P < 0.05). Moreover, urinary nitrogen excretion was higher (P < 0.05) for Control diet (no DP) than the 21 DP diet. In this study, urinary excretion of purine derivatives and microbial protein synthesis were affected by experimental diets (P < 0.05). In conclusion, this study showed that DP at 14% can be used as an alternative feed resource in sheep nutrition especially in semiarid areas.
Pigs experimentally infected with an enterotoxigenic strain of Escherichia coli have improved feed efficiency and indicators of inflammation with dietary supplementation of tryptophan and methionine in the immediate post-weaning period
Authors: Capozzalo M. M. , Kim J. C. , Htoo J. K. , de Lange C. F. M. , Mullan B. P. , Hansen C. F. , Resink J. W. , Pluske J. R.
Published: June 2016

This experiment tested the hypothesis that pigs challenged with an enterotoxigenic strain of E. coli (ETEC) will improve performance by dietary supplementation of sulfur amino acids (SAA) and tryptophan (Trp) above the current recommended levels in the immediate post-weaning period. Male pigs (n = 96) weighing 6.2 ± 0.78 kg (mean ± s.d.) and weaned at 21 days were stratified into one of four treatments based on weaning weight (n = 24). Four diets were formulated [11.2 MJ NE/kg; 20.1% crude protein, 1.25% standardised ileal digestible (SID) lysine (Lys)] according to a 2 × 2 factorial arrangement of treatments with two levels of SID SAA : Lys ratio (0.52 vs 0.60) and two levels of SID Trp : Lys ratio (0.16 vs 0.24). Diets did not contain any antimicrobial compounds. Pigs were individually housed and were fed diets for 14 days after weaning. Pigs were infected with ETEC (3.44 × 108 CFU/mL, serotype O149 : K91 : K88) on Days 5, 6, and 7 after weaning. Pigs were bled on Days 5, 8 and 14 and subsequently analysed for plasma levels of acute-phase proteins, urea, cytokines (Days 5 and 8 only) and amino acids (Days 5 and 8 only). Increasing Trp (P = 0.036) and SAA (P = 0.028) improved feed conversion ratio, and combined supplementation of SAA and Trp further improved FCR than individual supplementation of either SAA or Trp (P = 0.092). Dietary treatments had no impact on the incidence of post-weaning diarrhoea (P > 0.05). Increasing SAA increased shedding of ETEC on Days 12 and 14 after weaning (P < 0.019). Increasing dietary Trp reduced the intensity of inflammation (as measured by APP Index = [(C-reactive protein × PigMAP)/apolipoprotein A1]) immediately after infection with ETEC (P < 0.05), while increasing dietary SAA reduced the APP index on 24 h and 7 days after ETEC infection (P < 0.05). Increasing dietary SAA reduced plasma levels of interferon-gamma regardless of dietary Trp or day of sampling (P = 0.043). Increasing dietary SAA decreased plasma urea (PU) levels on Days 5, 8 and 14 (P < 0.05). These data indicate that Trp supplementation reduced the intensity of inflammation and SAA supplementation decreased the pro-inflammatory interferon-gamma response and improved protein utilisation, as measured by PU, whereas supplementation with both Trp and SAA improved feed conversion ratio.
Smoking status and associated factors among male Chinese restaurant workers in metropolitan Sydney
Authors: Jiang Wei , Leung Brenda , Tam Nancy , Xu Huilan , Gleeson Suzanne , Wen Li Ming
Published: June 2016

Issue addressed

The smoking rate among male Chinese migrants in Australia is higher than among the general population. This study investigated the smoking rate of male Chinese restaurant workers in metropolitan Sydney, and explored factors associated with smoking and quitting.

Methods

A self‐administered questionnaire survey was completed by Chinese workers in selected Chinese restaurants in metropolitan Sydney from October‐December 2012. Eighty‐nine Chinese restaurants were approached and 54 (61%) took part in the study. The questionnaire asked participants about their smoking status, knowledge of and attitudes to smoking and quitting as well as socio‐demographic information. Multivariable logistic regression was built to assess the associated factors.

Results

Of the 382 participants who completed the survey, 171 (45%) were current smokers and 50% of current smokers wanted to quit smoking. Participants who spoke Mandarin, had lower English proficiency, did not realise environmental smoke harms children, did not prefer a smoke‐free environment or had more than 50% of relatives or friends who smoked were more likely to be current smokers. Participants who were aged 18–29 years, did not understand the benefits of quitting smoking or did not prefer a smoke‐free environment were less likely to want to quit.

Conclusions

Nearly 50% of male Chinese restaurant workers surveyed in this study were current smokers. Key factors associated with the participants' smoking or quitting status are: aged 18–29 years; speaking Mandarin; lower English literacy; and not knowing the dangers of smoking.

So what?

Tobacco control programs targetted at male Chinese restaurant workers that raise awareness of the harm caused by smoking and the benefits of quitting smoking are required to enhance intention to quit smoking within this population.
Increasing instruction time in school does increase learning
Authors: Andersen Simon Calmar , Humlum Maria Knoth , Nandrup Anne Brink
Published: June 2016

Significance

Across the Organization for Economic Co-operation and Development countries, the instruction time at age 10 y old varies by a factor of two, reflecting, at least in part, differences in beliefs about the value of additional instruction time. Because educational resources are typically not randomly allocated, it has proven to be a major challenge to determine how different educational resources, such as instruction time, affect student learning. We present evidence from a large-scale, randomized trial that increasing instruction time in school increases student learning. Importantly, a regime with no formal requirements on how the extra time is spent is at least as efficient as an increase in instruction time with a detailed teaching program.
Role and structural mechanism of WASP-triggered conformational changes in branched actin filament nucleation by Arp2/3 complex
Authors: Rodnick-Smith Max , Luan Qing , Liu Su-Ling , Nolen Brad J.
Published: June 2016

Significance

Assembly of actin filaments is tightly regulated to orchestrate basic cellular processes such as motility, division, and differentiation. To control when and where actin filaments assemble, cells rely on actin filament nucleators including the Arp2/3 (Actin-related proteins 2/3) complex, a seven-subunit protein assembly that nucleates branched actin filaments to create dendritic actin networks. Activity of the Arp2/3 complex is controlled by WASP (Wiskott–Aldrich syndrome protein) proteins, which bind directly to it to activate nucleation. To understand how WASP proteins activate the complex, we used chemical cross-linking to engineer an Arp2/3 complex that is locked into an “on” state without WASP. In addition, we used biochemical experiments to determine how WASP proteins stimulate the on state. These results have important implications for understanding how cells control the actin cytoskeleton.
Working memory is not fixed-capacity: More active storage capacity for real-world objects than for simple stimuli
Authors: Brady Timothy F. , Störmer Viola S. , Alvarez George A.
Published: June 2016

Significance

Visual working memory is the cognitive system that holds visual information in an active state, making it available for cognitive processing and protecting it against interference. Here, we demonstrate that visual working memory has a greater capacity than previously measured. In particular, we use EEG to show that, contrary to existing theories, enhanced performance with real-world objects relative to simple stimuli in short-term memory tasks is reflected in active storage in working memory and is not entirely due to the independent usage of episodic long-term memory systems. These data demonstrate that working memory and its capacity limitations are dependent upon our knowledge. Thus, working memory is not fixed-capacity; instead, its capacity is dependent on exactly what is being remembered.
Long-term genetic stability and a high-altitude East Asian origin for the peoples of the high valleys of the Himalayan arc
Authors: Jeong Choongwon , Ozga Andrew T. , Witonsky David B. , Malmström Helena , Edlund Hanna , Hofman Courtney A. , Hagan Richard W. , Jakobsson Mattias , Lewis Cecil M. , Aldenderfer Mark S. , Di Rienzo Anna , Warinner Christina
Published: June 2016

Significance

Since prehistory, the Himalayan mountain range has presented a formidable barrier to population migration, whereas at the same time its transverse valleys have long served as conduits for trade and exchange. Yet, despite the economic and cultural importance of Himalayan trade routes, little is known about the region’s peopling and early population history. In this study, we conduct to our knowledge the first ancient DNA investigation of the Himalayan arc and generate genome data for eight individuals ranging in time from the earliest known human settlements to the establishment of the Tibetan Empire. We demonstrate that the region was colonized by East Asians of likely high-altitude origin, followed by millennia of genetic continuity despite marked changes in material culture and mortuary behavior.