bluuebunny/crossref_metadata_2025 huggingface dataset:
Fibronectin remodelling: cell-mediated regulation of the microenvironment
Authors: Wolanska Katarzyna I. , Morgan Mark R.
Published: January 2015

The biophysical, mechanical and chemical characteristics of extracellular matrixes influence many cellular functions to control tissue homoeostasis and drive progression of cancer and inflammatory diseases. To maintain normal tissue function, fibronectin-rich matrixes are subject to dynamic cell-mediated structural and chemical modification. In this article, we discuss how localized application of mechanical force, heterodimer-specific integrin engagement and matrix proteolysis regulate fibronectin assembly and turnover. We also speculate that recently identified integrin trafficking, syndecan signalling and adhesion receptor–growth factor receptor cross-talk mechanisms might dynamically control the function, assembly and mechanical properties of a viable, and mechanoresponsive, fibronectin network.
Low‐cost memory data scheduling method for reconfigurable FFT bit‐reversal circuits
Authors: Gao Wei , Kwong Sam , Sang Hongshi
Published: January 2015

A low‐cost memory data scheduling method based on two N/2‐depth single‐port memories is proposed for reconfigurable fast Fourier transform (FFT) bit‐reversed data reordering tasks. To make single‐port memories have the equivalent ability to read and write data simultaneously, two types of read and write address generation methods are proposed. Based on the proposed data scheduling method, the bit‐reversal circuits are designed for continuous data reordering tasks. The proposed bit‐reversal design is implemented for a maximum 8 k flexible length FFT processor. Compared with the other two conventional methods, the proposed bit‐reversal method can reduce memory area cost by 53.8 and 46.1%, respectively.
Link scheduling schemes with on‐off interference map for device‐to‐device communications
Authors: Kang Jin‐Whan , Hussain Ayaz , Kim Sang‐Hyo
Published: January 2015

New distributed link scheduling schemes based on a recently proposed device‐to‐device (D2D) communication technology, FlashLinQ are studied. FlashLinQ is an orthogonal frequency division multiplexing‐based synchronous D2D communication system, which achieves a high data rate at longer communication ranges over a licensed spectrum. In this method, some links are selected for data traffic for efficient frequency reuse to avoid interference in D2D links. Where every link is assigned a scheduling priority, so in TX (transmitter) and RX (receiver) yielding, the links which are highly interfered by higher priority links give up communication. However, this technique causes inefficiency in the resource reuse from the cascade yielding problem because link scheduling is performed individually by its RX and TX nodes. To deal with this problem, the authors propose two new link scheduling schemes based on a binary matrix called on‐off interference map (I‐Map), which indicates strong interference between links. In these schemes, each TX generates a binary I‐Map matrix with the collective information from TX and RX blocks. With the common I‐Map matrix that displays inter‐link interference between D2D links, the proposed schemes achieve better performance as compared to the conventional distributed FlashLinQ scheduling scheme.
Radial photovoltaic junction with single Si nanowire core–shell structure
Authors: Dupré Ludovic , Buttard Denis , Solanki A. , Pauc Nicolas , Gentile Pascal
Published: January 2015

A single silicon nanowire core–shell structure has been elaborated. Technological stages of the process are presented. The device results in a P‐i‐N radial junction: the core is a P‐type silicon nanowire encapsulated in an intrinsic thin silicon layer and an N‐type doped silicon layer. Scanning electron microscopy observations, as well as the electrical I(V) characterisation on single nanowires, are presented.
One‐pot synthesis of polypyrrole/AgCl composite nanotubes and their antibacterial properties
Authors: Liu Jingya , Wang Jijiang , Yu Xianghua , Li Liang , Shang Songmin
Published: January 2015

Polypyrrole/silver chloride (PPy/AgCl) composite nanotubes have been successfully prepared via a reactive self‐degrade template. By introducing ammonium peroxysulphate, AgNO3 and pyrrole monomer into the acidic methyl orange solution in sequence, AgCl nanoparticles could be uniformly distributed into the matrix of PPy nanotubes without aggregation in the one‐pot reaction. The formation mechanism, morphology and structure of the nanocomposites were studied by transmission electron microscopy, Fourier transform infrared spectra and X‐ray diffraction. The presented results suggest that the one‐dimensional hollow PPy/AgCl nanocomposites have significant antibacterial activity. The conducting PPy/AgCl nanotube composites may be used to fabricate the antistatic coatings with an antibacterial property in potential applications.
Absorption and emission of silicon nanocrystals embedded in SiC: Eliminating Fabry-Pérot interference
Authors: Schnabel M. , Summonte C. , Dyakov S. A. , Canino M. , López-Conesa L. , Löper P. , Janz S. , Wilshaw P. R.
Published: January 2015

Silicon nanocrystals embedded in SiC are studied by spectrophotometry and photoluminescence (PL) spectroscopy. Absorptivities are found to be affected by residual Fabry-Pérot interference arising from measurements of reflection and transmission at locations of different film thickness. Multiple computational and experimental methods to avoid these errors in thin film measurements, in general, are discussed. Corrected absorptivity depends on the quantity of Si embedded in the SiC but is independent of the Si crystallinity, indicating a relaxation of the k-conservation criterion for optical transitions in the nanocrystals. Tauc gaps of 1.8–2.0 and 2.12 eV are determined for Si nanoclusters and SiC, respectively. PL spectra exhibit a red-shift of ∼100 nm per nm nominal Si nanocluster diameter, which is in agreement with quantum confinement but revealed to be an artifact entirely due to Fabry-Pérot interference. Several simple experimental methods to diagnose or avoid interference in PL measurements are developed that are applicable to all thin films. Corrected PL is rather weak and invariant with passivation, indicating that non-paramagnetic defects are responsible for rapid non-radiative recombination. They are also responsible for the broad, sub-gap PL of the SiC, and can wholly account for the form of the PL of samples with Si nanoclusters. The PL intensity of samples with Si nanoclusters, however, can only be explained with an increased density of luminescent defects in the SiC due to Si nanoclusters, efficient tunneling of photogenerated carriers from Si nanoclusters to SiC defects, or with emission from a-Si nanoclusters. Films prepared on Si exhibit much weaker PL than the same films prepared on quartz substrates.
Resistive switching and synaptic properties of fully atomic layer deposition grown TiN/HfO2/TiN devices
Authors: Matveyev Yu. , Egorov K. , Markeev A. , Zenkevich A.
Published: January 2015

Recently proposed novel neural network hardware designs imply the use of memristors as electronic synapses in 3D cross-bar architecture. Atomic layer deposition (ALD) is the most feasible technique to fabricate such arrays. In this work, we present the results of the detailed investigation of the gradual resistive switching (memristive) effect in nanometer thick fully ALD grown TiN/HfO2/TiN stacks. The modelling of the I-V curves confirms interface limited trap-assisted-tunneling mechanism along the oxygen vacancies in HfO2 in all conduction states. The resistivity of the stack is found to critically depend upon the distance from the interface to the first trap in HfO2. The memristive properties of ALD grown TiN/HfO2/TiN devices are correlated with the demonstrated neuromorphic functionalities, such as long-term potentiation/depression and spike-timing dependent plasticity, thus indicating their potential as electronic synapses in neuromorphic hardware.
Free surfaces in open capillary channels—Parallel plates
Authors: Bronowicki P. , Canfield P. , Grah A. , Dreyer M.
Published: January 2015

This paper is concerned with forced flow through partially open capillary channels under microgravity conditions. The investigated channel consists of two parallel plates and is bounded by free liquid surfaces along the open sides. The curvature of the channel’s gas-liquid interface, which is exposed to the ambient pressure, adjusts to the pressure difference across the interface in accordance with the Young-Laplace equation. Flow within the channel becomes unstable when the free surface collapses and gas ingestion into the flow path occurs—a process that is also referred to as the “choking” phenomenon. During stable flow, the behavior of the free surface is influenced by flow conditions, geometric properties of the channel, and the pre-defined system pressure. In this work, a previously published stability theory is verified for a wide range of model parameters. A detailed study is provided for stable flow in capillary channels, including static and dynamic solutions. The results of the Capillary Channel Flow (CCF) experiment are evaluated and are found to agree well with numerical predictions. A clear limit is determined between stable and unstable flows. It is shown that the model can predict the shape of the free surface under various flow conditions. A numerical tool is employed to exploit the mathematical model, and the general behavior of free surfaces in said capillary channels is studied. Studies are conducted in both viscous and convective flow regimes and in the transition area between the two. The validity of the model is confirmed for a wide range of geometrical configurations and parameters.
High-precision laser spectroscopy of the CO A1Π - X1Σ+ (2,0), (3,0), and (4,0) bands
Authors: Niu M. L. , Ramirez F. , Salumbides E. J. , Ubachs W.
Published: January 2015

High-precision two-photon Doppler-free frequency measurements have been performed on the CO A1Π - X1Σ+ fourth-positive system (2,0), (3,0), and (4,0) bands. Absolute frequencies of forty-three transitions, for rotational quantum numbers up to J = 5, have been determined at an accuracy of 1.6 × 10−3 cm−1, using advanced techniques of two-color 2  +  1’ resonance-enhanced multi-photon ionization, Sagnac interferometry, frequency-chirp analysis on the laser pulses, and correction for AC-Stark shifts. The accurate transition frequencies of the CO A1Π - X1Σ+ system are of relevance for comparison with astronomical data in the search for possible drifts of fundamental constants in the early universe. The present accuracies in laboratory wavelengths of Δλ/λ = 2 × 10−8 may be considered exact for the purpose of such comparisons.
Time-resolved spectroscopy using a chopper wheel as a fast shutter
Authors: Wang Shicong , Wendt Amy E. , Boffard John B. , Lin Chun C.
Published: January 2015

Widely available, small form-factor, fiber-coupled spectrometers typically have a minimum exposure time measured in milliseconds, and thus cannot be used directly for time-resolved measurements at the microsecond level. Spectroscopy at these faster time scales is typically done with an intensified charge coupled device (CCD) system where the image intensifier acts as a “fast” electronic shutter for the slower CCD array. In this paper, we describe simple modifications to a commercially available chopper wheel system to allow it to be used as a “fast” mechanical shutter for gating a fiber-coupled spectrometer to achieve microsecond-scale time-resolved optical measurements of a periodically pulsed light source. With the chopper wheel synchronized to the pulsing of the light source, the time resolution can be set to a small fraction of the pulse period by using a chopper wheel with narrow slots separated by wide spokes. Different methods of synchronizing the chopper wheel and pulsing of the light sources are explored. The capability of the chopper wheel system is illustrated with time-resolved measurements of pulsed plasmas.
Reaction and internal energy relaxation rates in viscous thermochemically non-equilibrium gas flows
Authors: Kustova E. V. , Oblapenko G. P.
Published: January 2015

In the present paper, reaction and energy relaxation rates as well as the normal stress are studied for viscous gas flows with vibrational and chemical non-equilibrium. Using the modified Chapman-Enskog method, multi-temperature models based on the Treanor and Boltzmann vibrational distributions are developed for the general case taking into account all kinds of vibrational energy transitions, exchange reactions, dissociation, and recombination. Integral equations specifying the first-order corrections to the normal mean stress and reaction rates are derived, as well as approximate systems of linear equations for their numerical computation. Generalized thermodynamic driving forces associated with all non-equilibrium processes are introduced. It is shown that normal stresses and rates of non-equilibrium processes can be expressed in terms of the same driving forces; the symmetry of kinetic coefficients in these expressions is proven. The developed general model is applied to a particular case of a pure N2 viscous flow with slow VT relaxation. Normal stress and rates of vibrational relaxation are studied for various ratios of vibrational and translational temperatures. The cross effects between different vibrational transitions in viscous flows are evaluated, along with the influence of anharmonicity and flow compressibility on the first-order corrections to the relaxation rate. Limits of validity for the widely used Landau–Teller model of vibrational relaxation are indicated.
Poisson's ratio of collagen fibrils measured by small angle X-ray scattering of strained bovine pericardium
Authors: Wells Hannah C. , Sizeland Katie H. , Kayed Hanan R. , Kirby Nigel , Hawley Adrian , Mudie Stephen T. , Haverkamp Richard G.
Published: January 2015

Type I collagen is the main structural component of skin, tendons, and skin products, such as leather. Understanding the mechanical performance of collagen fibrils is important for understanding the mechanical performance of the tissues that they make up, while the mechanical properties of bulk tissue are well characterized, less is known about the mechanical behavior of individual collagen fibrils. In this study, bovine pericardium is subjected to strain while small angle X-ray scattering (SAXS) patterns are recorded using synchrotron radiation. The change in d-spacing, which is a measure of fibril extension, and the change in fibril diameter are determined from SAXS. The tissue is strained 0.25 (25%) with a corresponding strain in the collagen fibrils of 0.045 observed. The ratio of collagen fibril width contraction to length extension, or the Poisson's ratio, is 2.1 ± 0.7 for a tissue strain from 0 to 0.25. This Poisson's ratio indicates that the volume of individual collagen fibrils decreases with increasing strain, which is quite unlike most engineering materials. This high Poisson's ratio of individual fibrils may contribute to high Poisson's ratio observed for tissues, contributing to some of the remarkable properties of collagen-based materials.
Effects of forcing time scale on the simulated turbulent flows and turbulent collision statistics of inertial particles
Authors: Rosa B. , Parishani H. , Ayala O. , Wang L.-P.
Published: January 2015

In this paper, we study systematically the effects of forcing time scale in the large-scale stochastic forcing scheme of Eswaran and Pope [“An examination of forcing in direct numerical simulations of turbulence,” Comput. Fluids 16, 257 (1988)] on the simulated flow structures and statistics of forced turbulence. Using direct numerical simulations, we find that the forcing time scale affects the flow dissipation rate and flow Reynolds number. Other flow statistics can be predicted using the altered flow dissipation rate and flow Reynolds number, except when the forcing time scale is made unrealistically large to yield a Taylor microscale flow Reynolds number of 30 and less. We then study the effects of forcing time scale on the kinematic collision statistics of inertial particles. We show that the radial distribution function and the radial relative velocity may depend on the forcing time scale when it becomes comparable to the eddy turnover time. This dependence, however, can be largely explained in terms of altered flow Reynolds number and the changing range of flow length scales present in the turbulent flow. We argue that removing this dependence is important when studying the Reynolds number dependence of the turbulent collision statistics. The results are also compared to those based on a deterministic forcing scheme to better understand the role of large-scale forcing, relative to that of the small-scale turbulence, on turbulent collision of inertial particles. To further elucidate the correlation between the altered flow structures and dynamics of inertial particles, a conditional analysis has been performed, showing that the regions of higher collision rate of inertial particles are well correlated with the regions of lower vorticity. Regions of higher concentration of pairs at contact are found to be highly correlated with the region of high energy dissipation rate.
A study of transport properties in Cu and P doped ZnSb
Authors: Valset K. , Song X. , Finstad T. G.
Published: January 2015

ZnSb samples have been doped with copper and phosphorus and sintered at 798 K. Electronic transport properties are interpreted as being influenced by an impurity band close to the valence band. At low Cu dopant concentrations, this impurity band degrades the thermoelectric properties as the Seebeck coefficient and effective mass are reduced. At carrier concentrations above 1 × 1019 cm−3, the Seebeck coefficient in Cu doped samples can be described by a single parabolic band.
Organic molecules deposited on graphene: A computational investigation of self-assembly and electronic structure
Authors: de Oliveira I. S. S. , Miwa R. H.
Published: January 2015

We use ab initio simulations to investigate the adsorption and the self-assembly processes of tetracyanoquinodimethane (TCNQ), tetrafluoro-tetracyanoquinodimethane (F4-TCNQ), and tetrasodium 1,3,6,8-pyrenetetrasulfonic acid (TPA) on the graphene surface. We find that there are no chemical bonds at the molecule–graphene interface, even at the presence of grain boundaries on the graphene surface. The molecules bond to graphene through van der Waals interactions. In addition to the molecule–graphene interaction, we performed a detailed study of the role played by the (lateral) molecule–molecule interaction in the formation of the, experimentally verified, self-assembled layers of TCNQ and TPA on graphene. Regarding the electronic properties, we calculate the electronic charge transfer from the graphene sheet to the TCNQ and F4-TCNQ molecules, leading to a p-doping of graphene. Meanwhile, such charge transfer is reduced by an order of magnitude for TPA molecules on graphene. In this case, it is not expected a significant doping process upon the formation of self-assembled layer of TPA molecules on the graphene sheet.
A crawling and drilling microrobot driven by an external oscillating or precessional magnetic field in tubular environments
Authors: Kim S. J. , Jang G. H. , Jeon S. M. , Nam J. K.
Published: January 2015

We propose a crawling and drilling microrobot actuated by an external precessional magnetic field (EPMF) to effectively unclog obstructed blood vessels. Conventional crawling microrobots can only generate crawling motions using an external oscillating magnetic field. The proposed microrobot can generate navigating (crawling) and drilling motions selectively or simultaneously by controlling the EPMFs. We prototyped the proposed microrobot, and conducted several experiments to verify the efficacy of the crawling and drilling ability of the microrobot in a tubular environment.
Comprehensive study of the electronic and optical behavior of highly degenerate p-type Mg-doped GaN and AlGaN
Authors: Gunning Brendan P. , Fabien Chloe A. M. , Merola Joseph J. , Clinton Evan A. , Doolittle W. Alan , Wang Shuo , Fischer Alec M. , Ponce Fernando A.
Published: January 2015

The bulk and 2-dimensional (2D) electrical transport properties of heavily Mg-doped p-type GaN films grown on AlN buffer layers by Metal Modulated Epitaxy are explored. Distinctions are made between three primary p-type conduction mechanisms: traditional valence band conduction, impurity band conduction, and 2D conduction within a 2D hole gas at a hetero-interface. The bulk and 2D contributions to the overall carrier transport are identified and the relative contributions are found to vary strongly with growth conditions. Films grown with III/V ratio less than 1.5 exhibit high hole concentrations exceeding 2 × 1019 cm−3 with effective acceptor activation energies of 51 meV. Films with III/V ratios greater than 1.5 exhibit lower overall hole concentrations and significant contributions from 2D transport at the hetero-interface. Films grown with III/V ratio of 1.2 and Mg concentrations exceeding 2 × 1020 cm−3 show no detectable inversion domains or Mg precipitation. Highly Mg-doped p-GaN and p-AlGaN with Al fractions up to 27% similarly exhibit hole concentrations exceeding 2 × 1019 cm−3. The p-GaN and p-Al0.11Ga0.89N films show broad ultraviolet (UV) photoluminescence peaks, which intercept the valence band, supporting the presence of a Mg acceptor band. Finally, a multi-quantum-well light-emitting diode (LED) and p-i-n diode are grown, both of which demonstrate rectifying behavior with turn-on voltages of 3–3.5 V and series resistances of 6–10 Ω without the need for any post-metallization annealing. The LED exhibits violet-blue luminescence at 425 nm, while the p-i-n diode shows UV luminescence at 381 nm, and both devices still show substantial light emission even when submerged in liquid nitrogen at 77 K.
Giant magnetoimpedance effect and domain wall dynamics in Co-rich amorphous microwires
Authors: Zhukov A. , Chizhik A. , Ipatov M. , Talaat A. , Blanco J. M. , Stupakiewicz A. , Zhukova V.
Published: January 2015

The giant magnetoimpedance (GMI) effect, as well as the magnetic and magneto-optical properties, of Co69.2Fe4.1B11.8Si13.8C1.1 and Fe73.8Cu1Nb3.1B9.1Si13 amorphous microwires is studied. It is observed that the magnetic properties and the GMI effect of the Co-rich microwire can be tuned by heat treatment. A high GMI effect has been observed in as-prepared Co-rich microwires. After appropriate annealing of the Co-rich microwires, fast domain wall propagation and a GMI effect can be simultaneously observed in the same sample, and annealing is seen to affect both the diagonal and off-diagonal GMI components. Using complementary studies of the bulk and surface magnetic properties, an attempt is made to explain the great difference observed in the GMI properties of Co- and Fe-based microwires exhibiting very similar bulk hysteresis loops.
Optical spectroscopy of sputtered nanometer-thick yttrium iron garnet films
Authors: Jakubisova-Liskova Eva , Visnovsky Stefan , Chang Houchen , Wu Mingzhong
Published: January 2015

Nanometer (nm)-thick yttrium iron garnet (Y3Fe5O12, YIG) films present interest for spintronics. This work employs spectral ellipsometry and magneto-optic Kerr effect (MOKE) spectra to characterize nm-thick YIG films grown on single-crystal Gd3Ga5O12 substrates by magnetron sputtering. The thickness (t) of the films ranges between 10 nm and 40 nm. Independent on t, the polar MOKE hysteresis loops saturate in the field of about 1.8 kOe, consistent with the saturation magnetization in bulk YIG (4πMs ≈ 1.75 kG). The MOKE spectrum measured at photon energies between 1.3 eV and 4.5 eV on the 38-nm-thick film agrees with that measured on single-crystal YIG bulk materials. The MOKE spectrum of the 12-nm-thick film still preserves the structure of the bulk YIG but its amplitude at lower photon energies is modified due to the fact that the radiation penetration depth exceeds 20 nm. The t dependence of the MOKE amplitude is consistent with MOKE calculations. The results indicate that the films are stoichiometric, strain free, without Fe2+, and preserve bulk YIG properties down to t ≈ 10 nm.
Quasiperiodic AlGaAs superlattices for neuromorphic networks and nonlinear control systems
Authors: Malyshev K. V.
Published: January 2015

The application of quasiperiodic AlGaAs superlattices as a nonlinear element of the FitzHugh–Nagumo neuromorphic network is proposed and theoretically investigated on the example of Fibonacci and figurate superlattices. The sequences of symbols for the figurate superlattices were produced by decomposition of the Fibonacci superlattices' symbolic sequences. A length of each segment of the decomposition was equal to the corresponding figurate number. It is shown that a nonlinear network based upon Fibonacci and figurate superlattices provides better parallel filtration of a half-tone picture; then, a network based upon traditional diodes which have cubic voltage-current characteristics. It was found that the figurate superlattice F011(1) as a nonlinear network's element provides the filtration error almost twice less than the conventional “cubic” diode. These advantages are explained by a wavelike shape of the decreasing part of the quasiperiodic superlattice's voltage-current characteristic, which leads to multistability of the network's cell. This multistability promises new interesting nonlinear dynamical phenomena. A variety of wavy forms of voltage-current characteristics opens up new interesting possibilities for quasiperiodic superlattices and especially for figurate superlattices in many areas—from nervous system modeling to nonlinear control systems development.
Inhomogeneous thermal expansion of metallic glasses in atomic-scale studied by in-situ synchrotron X-ray diffraction
Authors: Taghvaei Amir Hossein , Shakur Shahabi Hamed , Bednarčik Jozef , Eckert Jürgen
Published: January 2015

Numerous investigations have demonstrated that the elastic strain in metallic glasses subjected to mechanical loading could be inhomogeneous in the atomic-scale and it increases with distance from an average atom and eventually reaches the macroscopic strain at larger inter-atomic distances. We have observed a similar behavior for the thermal strain imposed by heating of Co40Fe22Ta8B30 glassy particles below the glass transition temperature by analysis of the scattering data obtained by in-situ high-energy synchrotron X-ray diffraction (XRD). The results imply that the volumetric thermal strains calculated from the shift in position of the principal diffraction maximum and reduced pair correlation function (PDF) peaks are in good agreement for the length scales beyond 0.6 nm, corresponding to the atoms located over the third near-neighbor shell. However, smaller and even negative volumetric thermal strains have been calculated based on the shifts in the positions of the second and first PDF peaks, respectively. The structural changes of Co40Fe22Ta8B30 glassy particles are accompanied by decreasing the average coordination number of the first near-neighbor shell, which manifests the occurrence of local changes in the short-range order upon heating. It is believed that the detected length-scale dependence of the volumetric thermal strain is correlated with the local atomic rearrangements taking place in the topologically unstable regions of the glass governed by variations in the atomic-level stresses.
Impact of nanomechanical resonances on lasing from electrically pumped quantum dot micropillars
Authors: Czerniuk T. , Tepper J. , Akimov A. V. , Unsleber S. , Schneider C. , Kamp M. , Höfling S. , Yakovlev D. R. , Bayer M.
Published: January 2015

We use a picosecond acoustics technique to modulate the laser output of electrically pumped GaAs/AlAs micropillar lasers with InGaAs quantum dots. The modulation of the emission wavelength takes place on the frequencies of the nanomechanical extensional and breathing (radial) modes of the micropillars. The amplitude of the modulation for various nanomechanical modes is different for every micropillar which is explained by a various elastic contact between the micropillar walls and polymer environment.
A pseudo-single-crystalline germanium film for flexible electronics
Authors: Higashi H. , Kasahara K. , Kudo K. , Okamoto H. , Moto K. , Park J.-H. , Yamada S. , Kanashima T. , Miyao M. , Tsunoda I. , Hamaya K.
Published: January 2015

We demonstrate large-area (∼600 μm), (111)-oriented, and high-crystallinity, i.e., pseudo-single-crystalline, germanium (Ge) films at 275 °C, where the temperature is lower than the softening temperature of a flexible substrate. A modulated gold-induced layer exchange crystallization method with an atomic-layer deposited Al2O3 barrier and amorphous-Ge/Au multilayers is established. From the Raman measurements, we can judge that the crystallinity of the obtained Ge films is higher than those grown by aluminum-induced-crystallization methods. Even on a flexible substrate, the pseudo-single-crystalline Ge films for the circuit with thin-film transistor arrays can be achieved, leading to high-performance flexible electronics based on an inorganic-semiconductor channel.
Epi-cleaning of Ge/GeSn heterostructures
Authors: Di Gaspare L. , Sabbagh D. , De Seta M. , Sodo A. , Wirths S. , Buca D. , Zaumseil P. , Schroeder T. , Capellini G.
Published: January 2015

We demonstrate a very-low temperature cleaning technique based on atomic hydrogen irradiation for highly (1%) tensile strained Ge epilayers grown on metastable, partially strain relaxed GeSn buffer layers. Atomic hydrogen is obtained by catalytic cracking of hydrogen gas on a hot tungsten filament in an ultra-high vacuum chamber. X-ray photoemission spectroscopy, reflection high energy electron spectroscopy, atomic force microscopy, secondary ion mass spectroscopy, and micro-Raman showed that an O- and C-free Ge surface was achieved, while maintaining the same roughness and strain condition of the as-deposited sample and without any Sn segregation, at a process temperature in the 100–300 °C range.
The electron spin resonance study of heavily nitrogen doped 6H SiC crystals
Authors: Savchenko D. V.
Published: January 2015

The magnetic and electronic properties of heavily doped n-type 6H SiC samples with a nitrogen concentration of 1019 and 4 × 1019 cm−3 were studied with electron spin resonance (ESR) at 5–150 K. The observed ESR line with a Dysonian lineshape was attributed to the conduction electrons (CE). The CE ESR (CESR) line was fitted by Lorentzian (insulating phase) (T < 40 K) and by Dysonian lineshape (metallic phase) above 40 K, demonstrating that Mott insulator-metal (IM) transition takes place at ∼40 K, accompanied by significant change in the microwave conductivity. The temperature dependence of CESR linewidth follows the linear Korringa law below 40 K, caused by the coupling of the localized electrons (LE) and CE, and is described by the exponential law above 40 K related to the direct relaxation of the LE magnetic moments via excited levels driven by the exchange interaction of LE with CE. The g-factor of the CESR line (g‖ = 2.0047(3), g⊥ = 2.0034(3)) is governed by the coupling of the LE of nitrogen donors at hexagonal and quasi-cubic sites with the CE. The sharp drop in CESR line intensity (25–30 K) was explained by the formation of antiferromagnetic ordering in the spin system close to the IM transition. The second broad ESR line overlapped with CESR signal (5–25 K) was attributed to the exchange line caused by the hopping motion of electrons between occupied and non-occupied positions of the nitrogen donors. Two mechanisms of conduction, hopping and band conduction, were distinguished in the range of T = 10–25 K and T > 50 K, respectively.
Diffusion of Cd and Te adatoms on CdTe(111) surfaces: A computational study using density functional theory
Authors: Naderi Ebadollah , Nanavati Sachin , Majumder Chiranjib , Ghaisas S. V.
Published: January 2015

CdTe is one of the most promising semiconductor for thin-film based solar cells. Here we report a computational study of Cd and Te adatom diffusion on the CdTe (111) A-type (Cd terminated) and B-type (Te terminated) surfaces and their migration paths. The atomic and electronic structure calculations are performed under the DFT formalism and climbing Nudge Elastic Band (cNEB) method has been applied to evaluate the potential barrier of the Te and Cd diffusion. In general the minimum energy site on the surface is labeled as Aa site. In case of Te and Cd on B-type surface, the sub-surface site (a site just below the top surface) is very close in energy to the A site. This is responsible for the subsurface accumulation of adatoms and therefore, expected to influence the defect formation during growth. The diffusion process of adatoms is considered from Aa (occupied) to Aa (empty) site at the nearest distance. We have explored three possible migration paths for the adatom diffusion. The adatom surface interaction is highly dependent on the type of the surface. Typically, Te interaction with both type (5.2 eV for A-type and 3.8 eV for B-type) is stronger than Cd interactions(2.4 eV for B-type and 0.39 eV for A-type). Cd interaction with the A-type surface is very weak. The distinct behavior of the A-type and B-type surfaces perceived in our study explain the need of maintaining the A-type surface during growth for smooth and stoichiometric growth.
Electrocaloric effect of metal-insulator transition in VO2
Authors: Matsunami Daichi , Fujita Asaya
Published: January 2015

The electrocaloric effect was observed in association with an electric-field induced metal-insulator transition in VO2 using a calorimetric measurement under an applied voltage. For a VO2 plate with a 0.4 mm thickness located in the center of a capacitor-like structure, the metal-insulator transition was manipulated by applying a few volts. The occurrence of a transition in such a thick sample with relatively low voltage indicates that a surface charge accumulation mechanism is effective. The isothermal entropy change reached 94 J kg−1 K−1, while the adiabatic temperature change was calculated as −3.8 K under a voltage change of 0–3 V. The large entropy change is attributed to correlation of the complex freedom among spin, charge, and lattice.
Probing temperature-driven spin reorientation transition of GdFeCo film by Kerr loops and ferromagnetic resonance
Authors: He Wei , Liu Hao-Liang , Wu Hong-Ye , Cai Jian-Wang , Cheng Zhao-Hua
Published: January 2015

The magnetic anisotropy is of both scientific and technological interest for magneto-optical material GdFeCo film. We characterize the magnetic anisotropy of a 20 nm GdFeCo film from 265 K to 320 K via Kerr loops and ferromagnetic resonance. With increasing temperature, both of the first-order uniaxial magnetic anisotropy and shape anisotropy increase. However, the competition between them causes a temperature-driven spin reorientation transition (SRT) and the effective perpendicular magnetic anisotropy decrease from 2.22 × 104 ergs/cm3 (288 K) to −1.56 × 104 ergs/cm3 (317 K). The positive second-order uniaxial magnetic anisotropy determines an easy-cone state as the mediated state during SRT.
Near-field behavior of electrified jet under moving substrate constrains
Authors: Bu Ningbin , Huang YongAn , Duan Yongqing , Ding Yajiang , Yin Zhouping
Published: January 2015

We investigate the dynamics and shapes of electrified jet deposited onto a moving substrate in near-field electrospinning. At low speed, drag effect imposes on the jet and makes it buckling to a ‘heel’. As the ‘heel’ continues to move far away, a restoring force is accumulated until it is large enough to make an ‘out of the plane deformation’, which will also introduce torsion for the jet and turns it into a rotation state. When the speed increases, stretching effect makes jet drawing to a stable catenary shape. The ‘heel’ is a transition stage between catenary and rotation state due to the buckling of the jet. Moreover, the transformation from the ‘heel’ to ‘catenary’ is validated by modeling the jet as electrified filament. The simulation results show that the speed brings the pulling force exerted on the jet tail and it only depends on the substrate speed. The works provide a better understanding the effect mechanism of the substrate speed on the fiber morphology.
Multicarrier chaotic communications in multipath fading channels without channel estimation
Authors: Wang Shilian , Zhang Zhili
Published: January 2015

A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.
Survival, age estimation and sexual maturity of pouch young of the brush-tailed bettong (Bettongia penicillata) in captivity
Authors: Thompson Craig K. , Wayne Adrian F. , Godfrey Stephanie S. , Thompson R. C. Andrew
Published: January 2015

The brush-tailed bettong or woylie (Bettongia penicillata) is a continuous and rapid breeder. However, research investigating the monthly survival and development of young woylies from parturition to parental independence is incomplete. The reproductive biology of eight female woylies was observed for 22 consecutive months within a purpose-built enclosure. Adult female woylies bred continuously and were observed caring for a dependant young 96% of the time. Pouch life of the young was ~102 days, with sexual maturity of female offspring reached as early as 122 days post partum. Crown–rump measurement was an accurate predictor of age for young restricted to the pouch, while skeletal morphometrics were a better predictor of age for ejected pouch young, young-at-foot and subadults. A four-month period between May and August of each study year accounted for 85% of pouch young mortality and 61% of pouch young births where the neonate went on to survive to subadult age. Here we discuss the possibility that pouch young born during the cooler, wetter months of May to August may have an increased chance of survival in the wild, resulting from an increased maternal investment being directed towards the rearing of ‘fitter’ progeny.
Roles of gibberellins and cytokinins in regulation of morphological and physiological traits in Polygonum cuspidatum responding to light and nitrogen availabilities
Authors: Sugiura Daisuke , Sawakami Koichiro , Kojima Mikiko , Sakakibara Hitoshi , Terashima Ichiro , Tateno Masaki
Published: January 2015

We evaluated the roles of gibberellins (GAs) and cytokinins (CKs) in regulation of morphological traits such as biomass allocation and leaf mass per area (LMA). Seedlings of Polygonum cuspidatum Siebold & Zucc. were grown under various light and N availabilities. We exogenously sprayed solutions of gibberellin (GA3), benzyl adenine (BA), uniconazole (an inhibitor of GA biosynthesis) or their mixtures on the aboveground parts, and changes in morphological and physiological traits and relative growth rate (RGR) were analysed. Endogenous levels of GAs and CKs in the control plants were also quantified. The morphological traits were changed markedly by the spraying. Biomass allocation to leaves was increased by GA3 and BA, whereas it decreased by uniconazole. GA3 decreased LMA, whereas uniconazole increased it. We found close relationships among morphological and physiological traits such as photosynthetic rate and net assimilation rate, and RGR under all growth conditions. Seedlings with high levels of endogenous GAs or CKs and low levels of endogenous GAs or CKs showed morphologies similar to those sprayed with GA3 or BA, and those sprayed with uniconazole, respectively. Thus we concluded these phytohormones are involved in the regulation of biomass allocation responding to either light or N availability.
Image based phenotyping during winter: a powerful tool to assess wheat genetic variation in growth response to temperature
Authors: Grieder Christoph , Hund Andreas , Walter Achim
Published: January 2015

Having a strong effect on plant growth, temperature adaption has become a major breeding aim. Due to a lack of efficient methods, we developed an image-based approach to characterise genotypes for their temperature behaviour in the field. Twenty-nine winter wheat (Triticum aestivum L.) genotypes were continuously monitored at 3-day intervals on a plot basis during early growth from November to March using a modified digital camera. Canopy cover (CC) was determined by segmentation of leaves in calibrated images. Relative growth rates (RGR) of CC were then calculated for each measurement interval and related to the respective temperature. Also, classical traits used in plant breeding were assessed. Measurements of CC at single dates were highly repeatable with respect to genotype. For the tested range of temperatures (0−7°C), a linear relation between RGR and temperature was observed. Genotypes differed for base temperature and increase in RGR with rising temperature, these two traits showing a strong positive correlation with each other but being independent of CC at a single date. Our simple approach is suitable to screen large populations for differences in growth response to environmental stimuli. Furthermore, the derived parameters reveal additional information that cannot be assessed by usual measurements of static size.
Changes in rangeland cover associated with livestock grazing in Altun National Nature Reserve, northwest Qinghai-Tibetan Plateau
Authors: Su Xukun , Dong Shikui , Liu Shiliang , Wu Yu , Zhao Haidi , Zhang Xiang , Weng Jin , Tang Lin , Wu Xiaoyu , Hou Peng
Published: January 2015

The Altun National Nature Reserve, located on the northern edge of the Qinghai-Tibetan Plateau of China, is one of 35 most important biodiversity sites worldwide. Land-use and cover change are affecting this alpine ecosystem. A supervised classification was used to classify types containing meadow, steppe, sparse rangeland, and non-rangeland environments based on Landsat Thematic Mapper (TM) imagery data. By conducting an aggregation analysis using a Geographic Information System an analysis of changes from 1990 to 2010 was conducted. The results demonstrated that sparse rangeland was the most widespread vegetation type and underwent significant changes over the period. The area of sparse rangeland increased by 64.4 km2 from 1990 to 1995 and by 49.3 km2 from 1995 to 2000. However, the area of sparse rangeland decreased by 99.2 km2 from 2000 to 2005 and by 247.4 km2 from 2005 to 2010. The major areas of change were primarily located in the vicinities of the Yishakipati central inspection station, the Kardun inspection station, and Ayakkum, Aqqikkol and Jingyu Lakes. There was a positive correlation between the change in area of sparse rangeland and the amount of livestock grazing. The change in non-rangeland was significantly negatively correlated with the amount of livestock grazing during the period in the grazing area. Appropriate livestock grazing may be essential for promoting the resilience of the predominant ecosystems and key habitats of wildlife in the Altun National Nature Reserve.
Sexual practices, partner concurrency and high rates of sexually transmissible infections among male sex workers in three cities in Vietnam
Authors: Clatts Michael C. , Goldsamt Lloyd A. , Giang Le Minh , Yu Gary
Published: January 2015

Background
This paper examines sexual practices, partner concurrency and sexually transmissible infections (STI)/HIV infection among male sex workers (MSWs) in Vietnam. Methods: Six hundred and fifty-four MSWs, aged 16–35 years, were recruited in Hanoi, Nha Trang and Ho Chi Minh City between 2009 and 2011. Survey measures included demographic characteristics, drug use, types of sexual partners and sexual practices. Subjects were screened for STIs, including HIV. Results: MSWs in Ho Chi Minh City (33%) were more likely than those from the other two sites to be current users of one or more types of illegal drugs (P < 0.001). MSWs with both male and female elective partners (compared with other partnership types) were more likely to have anal sex with male client partners (P < 0.001), elective male partners (P = 0.045) and elective female partners (P = 0.025). At last sex with a male client partner, only 30% used a condom during anal intercourse. At last sex with an elective female partner, only 31% used a condom during vaginal sex and only 3% during anal sex. Although rates of HIV are low (4%), other STIs are high, including chlamydia (17%), gonorrhoea (29%) and human papillomavirus (33%). Most (57.3%) have never been tested for HIV and only 17% have ever disclosed to a healthcare provider that they have sex with men. Conclusions: Complex patterns of sexual concurrency, coupled with high rates of STIs, signal the urgent need for health services interventions among MSWs, both to improve individual health outcomes and to reduce secondary STI/HIV transmission among sexual partner networks.
Proclus’ prolegomena on the ontological status of time
Authors: Terezis Christos , Tempelis Elias
Published: January 2015

This paper attempts at showing the basic principles according to which the Neoplatonist philosopher Proclus (412–485) formulated his theory on time. The argumentation basically focuses on his methodology, since whatever is included in this analysis is used by the Neoplatonist philosopher in almost all his references to the notion of time. His basic position is that time is not simply a cosmological factor, but possesses properties which connect it closely with the metaphysical world. Also, that it is essential to examine its relation with the Soul, as an ontological factor which connects the metaphysical with the natural world, and that this examination is necessary, so that the production of the natural world can be clarified with due exactness. The topics dealt with are included in Proclus’ treatise In Platonis Timaeum, i.e. his extensive commentary on the Platonic dialogue Timaeus, on the basis of the new scientific and philosophical finds, which had became available since the time of Plato.
Philosophiekritik als Aufklärung?
Authors: Schick Stefan
Published: January 2015

Some contemporary readings of Averroes put special emphasis on the philosophical and critical character of the work of the Muslim theologian and mystic al-Ġazālī, who is also known as the “Proof of Islam”. They even regard him as some pioneer of Enlightenment thought. This paper therefore investigates the thesis of Averroes as a critical philosopher. It sets forth that one can indeed find some essential elements of critical thought in al-Ġazālī’s writings: for example Ġazālī’s critique of reason and especially his rejection of تقليد (taqlīd), which means the nonreflective imitation of a teacher, authority or tradition, especially in matters pertaining to religion. Nevertheless, comparing him to both, Kant and Descartes, we will try to show that his thought falls short of critical thinking and even of philosophy itself. To this end we will proceed as follows: First, we analyze his critique of taqlīd. Secondly, we investigate his critique of Aristotelian Arabic philosophy as a variety of taqlīd. Thirdly, we consider his skeptical suspension of reason in favor of immediate prophetic perception. Fourthly, we look upon the relationship between the super-rational perception and reason. Fifthly, we show that Ġazālī dismisses the idea of autonomous reason.