bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyphenols from pinecones of Pinus koraiensis induce apoptosis in colon cancer cells through the activation of caspase in vitro
Authors: Yi Juanjuan , Wang Zhenyu , Bai Haina , Li Lu , Zhao Haitian , Cheng Cuilin , Zhang Hua , Li Jingtong
Published: January 2016

The present study reports the antitumor effects of PPP-40 (the purified polyphenols fromP. koraiensispinecones by 40% ethanol) on LOVO cells and revealed its antitumor mechanism, which involved the apoptosis of cells associated with the activation of the caspase pathway.
Correction: In vitro drug controlled-release behavior of an electrospun modified poly(lactic acid)/bacitracin drug delivery system
Authors: Yao Junyan , Zhang Shijie , Li Wudan , Du Zhi , Li Yujie
Published: January 2016

Correction for ‘In vitro drug controlled-release behavior of an electrospun modified poly(lactic acid)/bacitracin drug delivery system’ by Junyan Yao et al., RSC Adv., 2016, 6, 515–521.
Bond fission in monocationic frameworks: diverse fragmentation pathways for phosphinophosphonium cations
Authors: Bamford Karlee L. , Chitnis Saurabh S. , Stoddard Rhonda L. , McIndoe J. Scott , Burford Neil
Published: January 2016

Bond dissociation pathways for phosphinophosphonium cations have been addressed through the concerted application of ESI-CID-MS/MS and DFT modelling.
The importance of nickel oxyhydroxide deprotonation on its activity towards electrochemical water oxidation
Authors: Diaz-Morales Oscar , Ferrus-Suspedra David , Koper Marc T. M.
Published: January 2016

The OER activity of NiOOH enhances at pH > 11 due to formation of superoxo-like species on its surface.
“Nanotraps” in porous electrospun fibers for effective removal of lead(ii) in water
Authors: Senthamizhan Anitha , Balusamy Brabu , Celebioglu Asli , Uyar Tamer
Published: January 2016

In this report, we demonstrated a synthetic strategy for the effective removal of Pb2+in water by creating stable “nanotraps” in electrospun porous cellulose acetate fibers encapsulated with dithiothreitol capped gold nanoclusters.
Micro/nanostructured surfaces for self-powered and multifunctional electronic skins
Authors: Park Jonghwa , Lee Youngoh , Ha Minjeong , Cho Seungse , Ko Hyunhyub
Published: January 2016

We introduce recent advances in the design of bioinspired micro/nanostructures and 2D/3D structures for the enhancement of energy harvesting and multifunctional sensing properties of flexible electronic skins.
Restricted access to a conical intersection to explain aggregation induced emission in dimethyl tetraphenylsilole
Authors: Peng Xing-Liang , Ruiz-Barragan Sergi , Li Ze-Sheng , Li Quan-Song , Blancafort Lluís
Published: January 2016

Aggregation-induced emission of dimethyl tetraphenylsilole is due to restricted access to a conical intersection. The intersection allows for radiationless decay in solution but is not reachable in the aggregate phase.
7,7′-Diazaisoindigo: a novel building block for organic electronics
Authors: de Miguel Gustavo , Camacho Luis , García-Frutos Eva M.
Published: January 2016

A new family of 7,7′-diazaisoindigo is presented. Theoretical calculations and photophysical studies demonstrate that it could be a good candidate for organic electronics.
The synthesis of novel AIE emitters with the triphenylethene-carbazole skeleton and para-/meta-substituted arylboron groups and their application in efficient non-doped OLEDs
Authors: Shi Heping , Xin Dehua , Gu Xinggui , Zhang Pengfei , Peng Huiren , Chen Shuming , Lin Gengwei , Zhao Zujin , Tang Ben Zhong
Published: January 2016

Four novel aggregation-induced emission (AIE)-active luminogens (p-DPDECZ, p-DBPDECZ, m-DPDECZ and m-DBPDECZ) with triphenylethene-carbazole skeleton and para-/meta-substituted arylboron groups have been synthesized.
Multilayer MoS2 growth by metal and metal oxide sulfurization
Authors: Heyne M. H. , Chiappe D. , Meersschaut J. , Nuytten T. , Conard T. , Bender H. , Huyghebaert C. , Radu I. P. , Caymax M. , de Marneffe J.-F. , Neyts E. C. , De Gendt S.
Published: January 2016

The H2S sulfurization of metal and metal oxide molybdenum films and the H2 influence on their morphology is described.
Synthetic transmit aperture focusing using optimal sparse receive array for reducing computational complexity
Authors: Park J. , Song T.‐K.
Published: January 2016

Synthetic transmit aperture focusing (STAF) has the problem of high computational complexity. An STAF scheme with greatly reduced computational complexity by using an optimal periodic sparse receive array (SRA) is proposed. An analytic method to design optimal SRAs that provide minimum main lobe width and grating lobe levels for a given number of active receive elements is also suggested. The experiment results show that the proposed STAF method can reduce computational complexity by up to 66.67% compared with conventional STAF.
Design and fabrication of compact fluorescent lamp igniter using TRIAC‐assisted high‐voltage DC source
Authors: Rana M. , Kabir A. , Rafi Md. , MRazib M. , Jarin S. , Khan A.G.
Published: January 2016

A potential approach for designing and fabricating igniter for compact fluorescent lamp is introduced using high‐voltage DC (HVDC) source which is controlled by gate pulse obtained from TRIAC‐based firing circuit. The Cockroft–Walton voltage multiplier circuit is used to design HVDC (2 kV) source where initially optimal rating of capacitance for each stage was considered based on experimental analysis. This design was further simulated by Multisim 11 and characterised experimentally. The response obtained by this method reveals that the HVDC source is able to ignite the fluorescence lamp potentially than the conventional available ignition processes. The major advantages of using HVDC are lower power to ignite fluorescence lamp, longer life and cost effective.
Railway infrastructure asset management: the whole‐system life cost analysis
Authors: Rama Dovile , Andrews John D
Published: January 2016

Delivering the railway infrastructure whose functionality is sustainable and uncompromised in terms of safety and availability under ever decreasing budget constraints is a great challenge. The successful accomplishment of this task relies on the effective management of individual assets within a wider whole system perspective. This is a highly complex decision‐making task where mathematical models are required to enable well‐informed choices. In this study, a novel modelling framework is proposed for performing the whole system lifecycle cost analysis. The framework is based on two models: railway network performance and costs. Using the former model investigations of the effects of decisions can be carried out for the individual asset and the whole system. A Petri net modelling technique is used to construct the model. A form of Monte Carlo simulation is then used to obtain model results. The infrastructure performance model is then integrated with the cost model to perform the lifecycle cost analysis. A superstructure example is presented to demonstrate the application of the approach. The results show that taking into account interdependencies among the intervention activities greatly influences, not only the performance of the infrastructure, but also its lifecycle costs and thus should be included in the cost analysis.
Development and testing of an automatic remote condition monitoring system for train wheels
Authors: Hyde Paul , Defossez Francois , Ulianov Cristian
Published: January 2016

The safe guidance of railway vehicles is dependent on the contact geometry between the wheel and the rail as defects in the running surface of the wheels can increase the risk of derailments and wheel catastrophic failures, and significantly increase the damage done by the vehicle to the track. An automatic optical based system for detecting wheel defects of rail vehicles passing in service has been developed and tested. The system is described, detailing the process of capturing consistent high resolution and quality images of the wheel tread and flange suitable for processing to detect defects. Tests of the system have been carried out with a wide variety of different rail vehicles, some with defects created artificially on the test wheel to test the image capturing capability of the system and its ability to automatically detect the defects. The prototype system was successfully installed in an operational railway site and captured high‐resolution images of the tread and flanges of the entire circumference of rail vehicle wheels as they passed through the system. The system was also shown to be successful at automatically analysing the captured images to detect wheel surface defects.
Delay management and energy consumption minimisation on a single‐track railway
Authors: Umiliacchi Silvia , Nicholson Gemma , Zhao Ning , Schmid Felix , Roberts Clive
Published: January 2016

To become more competitive, railways are developing methods and technologies that enable cost reduction, higher capacity, better punctuality and greater sustainability. The authors of this study address the last two objectives and propose a method that can be used to minimise the impact of a single delay on the system by reducing both the deviation from timetabled arrival at timing points and the energy consumed by trains. The technique uses a combined macro‐ and microscopic level approach in an optimisation algorithm to calculate the maximum speed a train should travel at on different sections of its route, so that the train meets time constraints and saves energy. The algorithm interacts with the traffic management system to obtain the applicable time constraints. The initial results from a case study based on a single‐track railway line show that applying this method to a freight train that needs to pass a late running passenger train at a loop and to arrive on time at its last station allows a 9% reduction in energy use by comparison with a situation where the freight train trajectory is not adjusted as a function of the actual traffic conditions.
Hybrid quantum particle swarm optimisation to calculate wideband Green's functions for microstrip structures
Authors: Hedayati Maziar , Firouzeh Zaker Hossein , Khayam Nekoei Hamed
Published: January 2016

This study presents wideband analytical Green's functions of microstrip structures using a two‐dimensional (2D) complex images method. The unknown coefficients of exponential terms are obtained using different particle swarm optimisation (PSO) algorithms such standard PSO, meta PSO, binary PSO, quantum PSO (QPSO) and ramped convergence PSO (RCPSO). The simulation results of both the magnetic vector and electric scalar potentials obtained by the PSO methods are compared and discussed. It is shown that the QPSO and RCPSO methods give considerably better solutions to the problem compared with other PSO algorithms. Then, a hybrid QPSO‐gradient‐based technique is used to improve the precision of the 2D complex images. The closed‐form Green's functions are valid over a wide range of frequencies and regions. The numerical results show close agreement with the rigorous numerical integration of Sommerfeld integrals.
A time-implicit numerical method and benchmarks for the relativistic Vlasov–Ampere equations
Authors: Carrié Michael , Shadwick B. A.
Published: January 2016

We present a time-implicit numerical method to solve the relativistic Vlasov–Ampere system of equations on a two dimensional phase space grid. The time-splitting algorithm we use allows the generalization of the work presented here to higher dimensions keeping the linear aspect of the resulting discrete set of equations. The implicit method is benchmarked against linear theory results for the relativistic Landau damping for which analytical expressions using the Maxwell-Jüttner distribution function are derived. We note that, independently from the shape of the distribution function, the relativistic treatment features collective behaviours that do not exist in the nonrelativistic case. The numerical study of the relativistic two-stream instability completes the set of benchmarking tests.
Theoretical description of the gaseous Knudsen layer in Couette flow based on the second-order constitutive and slip-jump models
Authors: Myong R. S.
Published: January 2016

The Knudsen layer, found in the region of gas flow very close (in order of a few mean free paths) to the solid surfaces, plays a critical role in accurately modeling rarefied and micro-scale gases. In various previous investigations, abnormal behaviors at high Knudsen numbers such as nonlinear velocity profile, velocity gradient singularity, and pronounced thermal effect are identified to exist in the Knudsen layer. However, some behaviors, in particular, the velocity gradient singularity near the surface and higher temperature, remain elusive in the continuum framework. In this study, based on the second-order macroscopic constitutive equation recently derived from the kinetic Boltzmann equation via the balanced closure and cumulant expansion [R. S. Myong, “On the high Mach number shock structure singularity caused by overreach of Maxwellian molecules,” Phys. Fluids 26(5), 056102 (2014)], the macroscopic second-order constitutive and slip-jump models that are able to explain qualitatively all the known non-classical and non-isothermal behaviors are proposed. As a result, new analytical solutions to the Knudsen layer in Couette flow, in conjunction with the algebraic nonlinearly coupled second-order constitutive and Maxwell velocity slip and Smoluchowski temperature jump models, are derived. It was shown that the velocity gradient singularity in the Knudsen layer can be explained within the continuum framework, when the nonlinearity of the constitutive model is morphed into the determination of the velocity slip in the nonlinear slip and jump model. Also, the smaller velocity slip and shear stress are shown to be caused by the shear-thinning property of the second-order constitutive model, that is, vanishing effective viscosity at high Knudsen number.
Spherical fused silica cells filled with pure helium for nuclear magnetic resonance-magnetometry
Authors: Maul Andreas , Blümler Peter , Heil Werner , Nikiel Anna , Otten Ernst , Petrich Andreas , Schmidt Thomas
Published: January 2016

High magnetic fields (>1 T) are measured by NMR magnetometers with unrivaled precision if the precessing spin sample provides long coherence times. The longest coherence times are found in diluted 3He samples, which can be hyperpolarized for sufficient signal strength. In order to have minimal influence on the homogeneity and value of the measured magnetic field, the optimal container for the 3He should be a perfect sphere. A fused silica sphere with an inner diameter of 8 mm and an outer diameter of 12 mm was made from two hemispheres by diffusion bonding leaving only a small hole for cleaning and evacuation. This hole was closed in vacuum by a CO2 laser and the inner volume was filled with a few mbars of 3He via wall permeation. NMR-measurements on such a sample had coherence times of 5 min. While the hemispheres were produced with <1 μm deviation from sphericity, the bonding left a step of ca. 50 μm at maximum. The influence of such a mismatch, its orientation, and the immediate environment of the sample is analyzed by FEM-simulations and discussed in view of coherence times and absolute field measurements.
First-principles calculations of thermoelectric properties of TiN/MgO superlattices: The route for an enhancement of thermoelectric effects in artificial nanostructures
Authors: Takaki Hirokazu , Kobayashi Kazuaki , Shimono Masato , Kobayashi Nobuhiko , Hirose Kenji
Published: January 2016

We present the thermoelectric properties of TiN/MgO superlattices employing first-principles calculation techniques. The Seebeck coefficients, the electrical conductances, the thermal conductances, and the figure of merit are investigated employing electrical and thermal transport calculations based on density functional theory combined with the nonequilibrium Green's function and nonequilibrium molecular dynamics simulation methods. The TiN/MgO superlattices with a small lattice mismatch at the interfaces are ideal systems to study the way for an enhancement of thermoelectric properties in artificial nanostructures. We find that the interfacial scattering between the two materials in the metal/insulator superlattices causes the electrical conductance to change rapidly, which enhances the Seebeck coefficient significantly. We show that the figure of merit for the artificial superlattice nanostructures has a much larger value compared with that of the bulk material and changes drastically with the superlattice configurations at the atomistic level.
Absolute energy distributions of Al, Cu, and Ta ions produced by nanosecond laser-generated plasmas at 1013 W cm−2
Authors: Comet M. , Versteegen M. , Gobet F. , Denis-Petit D. , Hannachi F. , Meot V. , Tarisien M.
Published: January 2016

The charge state and energy distributions of ions produced by a pulsed 1 J, 9 ns Nd:YAG laser focused onto solid aluminum, copper, and tantalum targets were measured with an electrostatic analyzer coupled with a windowless electron multiplier detector. Special attention was paid to the detector response function measurements and to the determination of the analyzer transmission. Space charge effects are shown to strongly affect this transmission. Measured absolute energy distributions are presented for several charge states. They follow Boltzmann-like functions characterized by an effective ion temperature and an equivalent accelerating voltage. These parameters exhibit power laws as a function of I λ2 which open the possibility to predict the expected shape of the relative energy distributions of ions on a large range of laser intensities (106–1016 W cm−2 μm2).
The origins of intra- and inter-molecular vibrational couplings: A case study of H2O-Ar on full and reduced-dimensional potential energy surface
Authors: Hou Dan , Ma Yong-Tao , Zhang Xiao-Long , Li Hui
Published: January 2016

The origin and strength of intra- and inter-molecular vibrational coupling is difficult to probe by direct experimental observations. However, explicitly including or not including some specific intramolecular vibrational modes to study intermolecular interaction provides a precise theoretical way to examine the effects of anharmonic coupling between modes. In this work, a full-dimension intra- and inter-molecular ab initio potential energy surface (PES) for H2O–Ar, which explicitly incorporates interdependence on the intramolecular (Q1,  Q2,  Q3) normal-mode coordinates of the H2O monomer, has been calculated. In addition, four analytic vibrational-quantum-state-specific PESs are obtained by least-squares fitting vibrationally averaged interaction energies for the (v1,  v2,  v3) =  (0,  0,  0), (0,  0,  1), (1,  0,  0), (0,  1,  0) states of H2O to the three-dimensional Morse/long-range potential function. Each vibrationally averaged PES fitted to 442 points has root-mean-square (rms) deviation smaller than 0.15 cm−1, and required only 58 parameters. With the 3D PESs of H2O–Ar dimer system, we employed the combined radial discrete variable representation/angular finite basis representation method and Lanczos algorithm to calculate rovibrational energy levels. This showed that the resulting vibrationally averaged PESs provide good representations of the experimental infrared data, with rms discrepancies smaller than 0.02 cm−1 for all three rotational branches of the asymmetric stretch fundamental transitions. The infrared band origin shifts associated with three fundamental bands of H2O in H2O–Ar complex are predicted for the first time and are found to be in good agreement with the (extrapolated) experimental values. Upon introduction of additional intramolecular degrees of freedom into the intermolecular potential energy surface, there is clear spectroscopic evidence of intra- and intermolecular vibrational couplings.
Optical absorption and small-polaron hopping in oxygen deficient and lithium-ion-intercalated amorphous titanium oxide films
Authors: Triana C. A. , Granqvist C. G. , Niklasson G. A.
Published: January 2016

Optical absorption in oxygen-deficient and Li+-ion inserted titanium oxide films was studied in the framework of small-polaron hopping. Non-stoichiometric TiOy films with 1.68 ≤ y ≤ 2.00 were deposited by reactive DC magnetron sputtering and were subjected to electrochemical intercalation of Li+-ions and charge-balancing electrons to obtain LixTiOy films with 0.12 ≤ x ≤ 0.34. Dispersion analysis was applied to calculate the complex dielectric function ε(ℏω) ≡ ε1(ℏω) + iε2(ℏω) from numerical inversion of optical transmittance and reflectance spectra; a superposition of Tauc-Lorentz and Lorentz oscillator models was used for this purpose. Data on ε2(ℏω) were employed to calculate the optical conductivity and fit this property to a small-polaron model for disordered systems with strong electron-phonon interaction and involving transitions near the Fermi level. The introduction of oxygen vacancies and/or Li+ insertion yielded band gap widening by ∼0.20–0.35 eV, and both processes induced similar low-energy optical absorption. The small-polaron-based analysis indicated increases in the Fermi level by ∼0.15–0.3 eV for sub-stoichiometric and/or Li+-inserted films. This suggests the existence of polaronic Ti3+ states in the lower part of the conduction band arising from transfer of electrons from oxygen vacancies and/or inserted Li+ species. The present article is a sequel to an earlier paper on oxygen-deficient and/or Li+-inserted amorphous WOy thin films and forms part of a comprehensive investigation of optical absorption in amorphous transition metal oxides with different valence states of the metallic ions.
An FPGA-based instrumentation platform for use at deep cryogenic temperatures
Authors: Conway Lamb I. D. , Colless J. I. , Hornibrook J. M. , Pauka S. J. , Waddy S. J. , Frechtling M. K. , Reilly D. J.
Published: January 2016

We describe the operation of a cryogenic instrumentation platform incorporating commercially available field-programmable gate arrays (FPGAs). The functionality of the FPGAs at temperatures approaching 4 K enables signal routing, multiplexing, and complex digital signal processing in close proximity to cooled devices or detectors within the cryostat. The performance of the FPGAs in a cryogenic environment is evaluated, including clock speed, error rates, and power consumption. Although constructed for the purpose of controlling and reading out quantum computing devices with low latency, the instrument is generic enough to be of broad use in a range of cryogenic applications.
Electrical and structural characterizations of crystallized Al2O3/GaN interfaces formed by in situ metalorganic chemical vapor deposition
Authors: Liu X. , Jackson C. M. , Wu F. , Mazumder B. , Yeluri R. , Kim J. , Keller S. , Arehart A. R. , Ringel S. A. , Speck J. S. , Mishra U. K.
Published: January 2016

Al2O3 films were grown in situ by metalorganic chemical vapor deposition at 900 °C on GaN of both Ga- and N-face polarities. High-resolution transmission electron microscopy revealed that the Al2O3 films were crystalline and primarily γ-phase. The Al2O3/Ga-GaN and Al2O3/N-GaN interfaces were both atomically sharp, and the latter further exhibited a biatomic step feature. The corresponding current-voltage (J-V) characteristics were measured on a metal-Al2O3-semiconductor capacitor (MOSCAP) structure. The leakage current was very high when the Al2O3 thickness was comparable with the size of the crystalline defects, but was suppressed to the order of 1 × 10−8 A/cm2 with larger Al2O3 thicknesses. The interface states densities (Dit) were measured on the same MOSCAPs by using combined ultraviolet (UV)-assisted capacitance-voltage (C-V), constant capacitance deep level transient spectroscopy (CC-DLTS), and constant capacitance deep level optical spectroscopy (CC-DLOS) techniques. The average Dit measured by CC-DLTS and CC-DLOS were 6.6 × 1012 and 8.8 × 1012 cm−2 eV−1 for Al2O3/Ga-GaN and 8.6 × 1012 and 8.6 × 1012 cm−2 eV−1 for Al2O3/N-GaN, respectively. The possible origins of the positive (negative) polarization compensation charges in Al2O3/Ga-GaN (Al2O3/N-GaN), including the filling of interface states and the existence of structure defects and impurities in the Al2O3 layer, were discussed in accordance with the experimental results and relevant studies in the literature.
Coherence property of mid-infrared supercontinuum generation in tapered chalcogenide fibers with different structures
Authors: Liu Lai , Nagasaka Kenshiro , Qin Guanshi , Suzuki Takenobu , Ohishi Yasutake
Published: January 2016

We have numerically investigated the coherence property of mid-infrared supercontinuum generation in tapered step-index chalcogenide fibers with different structures. The pump source is a 4 μm laser with pulse width of 500 fs and peak power of 1 kW. The length ratio is the ratio of transition region length near the laser input to the other transition region length near the output. We calculate the bandwidth and the spectrally averaged coherence of the supercontinuum spectra generated in fibers with different length ratios under the same pumping condition. Numerical results show that as the length ratio increases, the bandwidth decreases from 4.84 μm to 4.11 μm while the spectrally averaged coherence increases from 0.53 to 0.9 and then jitters near the maximum. The length ratio within 1–1.5 is preferable to keep a balance between bandwidth and coherence.
The determination of the elastic constants of isotropic solids by means of transient thermal surface gratings
Authors: Fivez J.
Published: January 2016

Starting from the coupled thermoelastic equations, an analytic formula is obtained for the surface deformation of a semi-infinite homogeneous and isotropic solid in an impulsive stimulated scattering (ISS) experiment. The surface ripple consists of a transient diffusive grating and a standing Rayleigh wave. The time evolution of the diffusive part directly reveals the thermal diffusivity. The oscillatory part then reveals the elastic properties, and explicit formulae are presented for retrieving the elastic moduli as a function of the frequency and amplitude of the standing Rayleigh wave. The analytic formulae not only allow to avoid time-consuming and delicate numerical integration but they also demonstrate the uniqueness of the inversion from signal to material parameters and offer direct insight into the error propagation. The formulae are applied to real experimental data, illustrating the strength and the limitations of the ISS technique.
Involvement of a low-lying Rydberg state in the ultrafast relaxation dynamics of ethylene
Authors: Champenois Elio G. , Shivaram Niranjan H. , Wright Travis W. , Yang Chan-Shan , Belkacem Ali , Cryan James P.
Published: January 2016

We present a measurement of the time-resolved photoelectron kinetic energy spectrum of ethylene using 156 nm and 260 nm laser pulses. The 156 nm pulse first excites ethylene to the 1B1u (ππ∗) electronic state where 260 nm light photoionizes the system to probe the relaxation dynamics with sub-30 fs resolution. Recent ab initio calculations by Mori et al. [J. Phys. Chem. A 116, 2808-2818 (2012)] have predicted an ultrafast population transfer from the initially excited state to a low-lying Rydberg state during the relaxation of photoexcited ethylene. The measured photoelectron kinetic energy spectrum reveals wave packet motion on the valence state and shows indications that the low-lying π3s Rydberg state is indeed transiently populated via internal conversion following excitation to the ππ∗ state, supporting the theoretical predictions.
Prediction of binary nanoparticle superlattices from soft potentials
Authors: Horst Nathan , Travesset Alex
Published: January 2016

Driven by the hypothesis that a sufficiently continuous short-ranged potential is able to account for shell flexibility and phonon modes and therefore provides a more realistic description of nanoparticle interactions than a hard sphere model, we compute the solid phase diagram of particles of different radii interacting with an inverse power law potential. From a pool of 24 candidate lattices, the free energy is optimized with respect to additional internal parameters and the p-exponent, determining the short-range properties of the potential, is varied between p = 12 and p = 6. The phase diagrams contain the phases found in ongoing self-assembly experiments, including DNA programmable self-assembly and nanoparticles with capping ligands assembled by evaporation from an organic solvent. The resulting phase diagrams can be mapped quantitatively to existing experiments as a function of only two parameters: Nanoparticle radius ratio (γ) and softness asymmetry.
Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films
Authors: Li Xiaopu , Ma Chung T. , Lu Jiwei , Devaraj Arun , Spurgeon Steven R. , Comes Ryan B. , Poon S. Joseph
Published: January 2016

Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.
Evaluation of reconstruction errors and identification of artefacts for JET gamma and neutron tomography
Authors: Craciunescu Teddy , Murari Andrea , Kiptily Vasily , Lupelli Ivan , Fernandes Ana , Sharapov Sergei , Tiseanu Ion , Zoita Vasile ,   JET Contributors
Published: January 2016

The Joint European Torus (JET) neutron profile monitor ensures 2D coverage of the gamma and neutron emissive region that enables tomographic reconstruction. Due to the availability of only two projection angles and to the coarse sampling, tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET, but the problem of evaluating the errors associated with the reconstructed emissivity profile is still open. The reconstruction technique based on the maximum likelihood principle, that proved already to be a powerful tool for JET tomography, has been used to develop a method for the numerical evaluation of the statistical properties of the uncertainties in gamma and neutron emissivity reconstructions. The image covariance calculation takes into account the additional techniques introduced in the reconstruction process for tackling with the limited data set (projection resampling, smoothness regularization depending on magnetic field). The method has been validated by numerically simulations and applied to JET data. Different sources of artefacts that may significantly influence the quality of reconstructions and the accuracy of variance calculation have been identified.
Loss mechanisms in superconducting thin film microwave resonators
Authors: Goetz Jan , Deppe Frank , Haeberlein Max , Wulschner Friedrich , Zollitsch Christoph W. , Meier Sebastian , Fischer Michael , Eder Peter , Xie Edwar , Fedorov Kirill G. , Menzel Edwin P. , Marx Achim , Gross Rudolf
Published: January 2016

We present a systematic analysis of the internal losses of superconducting coplanar waveguide microwave resonators based on niobium thin films on silicon substrates. In particular, we investigate losses introduced by Nb/Al interfaces in the center conductor, which is important for experiments where Al based Josephson junctions are integrated into Nb based circuits. We find that these interfaces can be a strong source for two-level state (TLS) losses, when the interfaces are not positioned at current nodes of the resonator. In addition to TLS losses, for resonators including Al, quasiparticle losses become relevant above 200 mK. Finally, we investigate how losses generated by eddy currents in conductive material on the backside of the substrate can be minimized by using thick enough substrates or metals with high conductivity on the substrate backside.
Tunable electronic and magnetism of SrTiO3/BiFeO3 (001) superlattice: For electrochemical applications
Authors: Xu Qiang , Sopiha Kostiantyn , Sobhan Mushtaq , Anariba Franklin , Ong Khuong Phuong , Zheng Jian Wei , Wu Ping
Published: January 2016

Practical strategy in tuning the conductivity and magnetism of SrTiO3/BiFeO3 (STO/BFO) (001) superlattice is investigated using the first-principles method based on density functional theory. Our calculated results show that both the conductivity and magnetism of this superlattice can be tuned via a control of its interface terminations. The STO layers maintain semiconducting, while the BFO layers demonstrate metallic character. Therefore, the conductivity of STO/BFO is controlled by the BFO layers. Furthermore, a magnetic STO/BFO (001) superlattice can be found in n-type TiO2/BiO interface but with heavy electron carriers. The thickness of BFO does not change the electronic structure and character of STO/BFO (001) superlattice. This study provides a fundamental understanding of the chemically turned conductivity and magnetism of BFO thin films, which may further advance electrochemical applications like magnetic-field aided chemical gas sensing, solar cells, and photo-catalytic chemical reactions.
Compact CH4 sensor system based on a continuous-wave, low power consumption, room temperature interband cascade laser
Authors: Dong Lei , Li Chunguang , Sanchez Nancy P. , Gluszek Aleksander K. , Griffin Robert J. , Tittel Frank K.
Published: January 2016

A tunable diode laser absorption spectroscopy-based methane sensor, employing a dense-pattern multi-pass gas cell and a 3.3 μm, CW, DFB, room temperature interband cascade laser (ICL), is reported. The optical integration based on an advanced folded optical path design and an efficient ICL control system with appropriate electrical power management resulted in a CH4 sensor with a small footprint (32 × 20 × 17 cm3) and low-power consumption (6 W). Polynomial and least-squares fit algorithms are employed to remove the baseline of the spectral scan and retrieve CH4 concentrations, respectively. An Allan-Werle deviation analysis shows that the measurement precision can reach 1.4 ppb for a 60 s averaging time. Continuous measurements covering a seven-day period were performed to demonstrate the stability and robustness of the reported CH4 sensor system.
Low-resistance gateless high electron mobility transistors using three-dimensional inverted pyramidal AlGaN/GaN surfaces
Authors: So Hongyun , Senesky Debbie G.
Published: January 2016

In this letter, three-dimensional gateless AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated with 54% reduction in electrical resistance and 73% increase in surface area compared with conventional gateless HEMTs on planar substrates. Inverted pyramidal AlGaN/GaN surfaces were microfabricated using potassium hydroxide etched silicon with exposed (111) surfaces and metal-organic chemical vapor deposition of coherent AlGaN/GaN thin films. In addition, electrical characterization of the devices showed that a combination of series and parallel connections of the highly conductive two-dimensional electron gas along the pyramidal geometry resulted in a significant reduction in electrical resistance at both room and high temperatures (up to 300 °C). This three-dimensional HEMT architecture can be leveraged to realize low-power and reliable power electronics, as well as harsh environment sensors with increased surface area.
Theoretical prediction of the band offsets at the ZnO/anatase TiO2 and GaN/ZnO heterojunctions using the self-consistent ab initio DFT/GGA-1/2 method
Authors: Fang D. Q. , Zhang S. L.
Published: January 2016

The band offsets of the ZnO/anatase TiO2 and GaN/ZnO heterojunctions are calculated using the density functional theory/generalized gradient approximation (DFT/GGA)-1/2 method, which takes into account the self-energy corrections and can give an approximate description to the quasiparticle characteristics of the electronic structure of semiconductors. We present the results of the ionization potential (IP)-based and interfacial offset-based band alignments. In the interfacial offset-based band alignment, to get the natural band offset, we use the surface calculations to estimate the change of reference level due to the interfacial strain. Based on the interface models and GGA-1/2 calculations, we find that the valence band maximum and conduction band minimum of ZnO, respectively, lie 0.64 eV and 0.57 eV above those of anatase TiO2, while lie 0.84 eV and 1.09 eV below those of GaN, which agree well with the experimental data. However, a large discrepancy exists between the IP-based band offset and the calculated natural band offset, the mechanism of which is discussed. Our results clarify band alignment of the ZnO/anatase TiO2 heterojunction and show good agreement with the GW calculations for the GaN/ZnO heterojunction.
IR-induced conformational isomerization of a helical peptide in a cold ion trap
Authors: Seaiby Caroline , Zabuga Aleksandra V. , Svendsen Annette , Rizzo Thomas R.
Published: January 2016

In this work, we use laser-induced population transfer techniques to study the conformational isomerization of a helical peptide, Ac-Phe-(Ala)5-LysH+, in a cold ion trap. In one scheme, called IR-UV hole-filling spectroscopy, a single conformation is selectively excited with an IR pump laser via a distinct NH stretch vibration. After giving the vibrationally excited ions sufficient time to isomerize and re-cool in the trap, the new conformational redistribution is detected by UV photofragment spectroscopy. While we clearly observe a redistribution of the conformer populations due to isomerization, only those conformations that initially have population participate in this redistribution—we do not form conformers that were not initially present in the trap. In a second scheme, called IR-induced population transfer spectroscopy, we determine the fractional populations of the four stable conformations of Ac-Phe-(Ala)5-LysH+ by scanning the IR laser while selectively detecting a specific conformation using UV photofragment spectroscopy.
Impurity-induced divertor plasma oscillations
Authors: Smirnov R. D. , Kukushkin A. S. , Krasheninnikov S. I. , Pigarov A. Yu. , Rognlien T. D.
Published: January 2016

Two different oscillatory plasma regimes induced by seeding the plasma with high- and low-Z impurities are found for ITER-like divertor plasmas, using computer modeling with the DUSTT/UEDGE and SOLPS4.3 plasma-impurity transport codes. The oscillations are characterized by significant variations of the impurity-radiated power and of the peak heat load on the divertor targets. Qualitative analysis of the divertor plasma oscillations reveals different mechanisms driving the oscillations in the cases of high- and low-Z impurity seeding. The oscillations caused by the high-Z impurities are excited near the X-point by an impurity-related instability of the radiation-condensation type, accompanied by parallel impurity ion transport affected by the thermal and plasma friction forces. The driving mechanism of the oscillations induced by the low-Z impurities is related to the cross-field transport of the impurity atoms, causing alteration between the high and low plasma temperature regimes in the plasma recycling region near the divertor targets. The implications of the impurity-induced plasma oscillations for divertor operation in the next generation tokamaks are also discussed.
Green laser induced terahertz tuning range expanding in KTiOPO4 terahertz parametric oscillator
Authors: Yan Chao , Wang Yuye , Xu Degang , Xu Wentao , Liu Pengxiang , Yan Dexian , Duan Pan , Zhong Kai , Shi Wei , Yao Jianquan
Published: January 2016

532 nm green laser is utilized to achieve terahertz tuning range expanding in KTiOPO4 terahertz parametric oscillator. With the theoretical analysis of the stimulated polariton scattering, an expanded tunability of the KTiOPO4 terahertz parametric oscillator can be realized. A wide terahertz output tuning range from 5.7 to 6.1 THz, from 7.4 to 7.8 THz, from 11.5 to 11.8 THz, and from 13.3 to 13.5 THz was demonstrated in our experiment, and the result well matched the analysis. The maximum terahertz output energy was 1.61 μJ under the pump energy of 140 mJ, corresponding to the maximum THz wave conversion efficiency of 1.3 × 10−5, and the threshold pump energy is about 30 mJ.
Negative bias temperature instability of SiC MOSFET induced by interface trap assisted hole trapping
Authors: Yen Cheng-Tyng , Hung Chien-Chung , Hung Hsiang-Ting , Lee Chwan-Ying , Lee Lurng-Shehng , Huang Yao-Feng , Hsu Fu-Jen
Published: January 2016

We investigated the negative bias temperature instability (NBTI) characteristics of 4H-SiC metal oxide semiconductor field effect transistor (MOSFET) and metal oxide semiconductor capacitor (MOSCAP). The shift of threshold voltage approached saturation with time, and the different magnitude of mid-gap voltage shift with different starting biases observed in capacitance-voltage (CV) curves taken from MOSCAP and MOSFET suggested that the hole trapping was the primary mechanism contributing to the NBTI in this study. The trend of mid-gap voltage shift with starting bias and threshold voltage shift with stress bias showed steep change before −10 V and approached saturation after −10 V which can be explained by a process where the hole trapping was assisted by positively charged interface states. The positively charged interface states may have acted as an intermediate state which reduced the overall energy barrier and facilitated the process of hole trapping. The split-CV sweeps with 0 s and 655 s of hold time were essentially overlapped which was consistent with the time evolution characteristic of hole trapping and supported the interface trap assisted hole trapping mechanism.
Theoretical description of magnetocaloric effect in the shape memory alloy exhibiting metamagnetic behavior
Authors: L'vov Victor A. , Kosogor Anna , Barandiaran Jose M. , Chernenko Volodymyr A.
Published: January 2016

A simple thermodynamic theory is proposed for the quantitative description of giant magnetocaloric effect observed in metamagnetic shape memory alloys. Both the conventional magnetocaloric effect at the Curie temperature and the inverse magnetocaloric effect at the transition from the ferromagnetic austenite to a weakly magnetic martensite are considered. These effects are evaluated from the Landau-type free energy expression involving exchange interactions in a system of a two magnetic sublattices. The findings of the thermodynamic theory agree with first-principles calculations and experimental results from Ni-Mn-In-Co and Ni-Mn-Sn alloys, respectively.
In situ transmission electron microscopy observation of ZnO polar and non-polar surfaces structure evolution under electron beam irradiation
Authors: Ding Yong , Pradel Ken C. , Wang Zhong Lin
Published: January 2016

Using in situ transmission electron microscopy, we investigated the dynamic reconstruction and evolution of ZnO polar and non-polar surfaces under high-energy electron beam irradiation. Electron beam radiolysis creates oxygen vacancies and a Zn rich (0001) surface. Positive polar charges at the (0001) surface expel loosely bonded Zn ions to diffuse away from the (0001) polar surface. As a result, mass loss was observed around the (0001) surface. Dehydration by the electron beam breaks the charge balance on the (0001¯) polar surface. The negative charges on the (0001¯) surface suppress the radiolysis effect and further absorb Zn ions to the surface to neutral the polar charges. The ideal stacking sequences of Zn ions in hexagonal ZnO structure can be considered as ABAB… along its c axis, while the absorbed individual Zn ion on the (0001¯) surface occupies the C site to form three bonds with surface O ions beneath, instead of one bond in the ideal structure. With more Zn ion absorption and surface oxidization, new nanocrystals grow up from the (0001¯) polar surface. New nanocrystals nucleated at the (011¯0) non-polar surface are driven by the electric field of the polar charges as well, for the Zn ions were always observed to absorb on the negatively charged [0001¯] end of the newly formed (011¯0) surface layer.
Electrical, luminescent, and deep trap properties of Si doped n-GaN grown by pendeo epitaxy
Authors: Polyakov A. Y. , Smirnov N. B. , Yakimov E. B. , Lee In-Hwan , Pearton S. J.
Published: January 2016

Electrical and luminescent properties and deep trap spectra of Si doped GaN films grown by maskless epitaxial lateral overgrowth (MELO) are reported. The dislocation density in the wing region of the structure was 106 cm−2, while in the seed region it was 108 cm−2. The major electron traps present had activation energy of 0.56 eV and concentrations in the high 1015 cm−3 range. A comparison of diffusion length values and 0.56 eV trap concentration in MELO GaN and epitaxial lateral overgrowth (ELOG) GaN showed a good correlation, suggesting these traps could be effective in carrier recombination. The doped MELO films were more uniform in their electrical properties than either ELOG films or undoped MELO films. We also discuss the differences in deep trap spectra and luminescence spectra of low-dislocation-density MELO, ELOG, and bulk n-GaN samples grown by hydride vapor phase epitaxy. It is suggested that the observed differences could be caused by the differences in oxygen and carbon contamination levels.
Species composition and hybridisation of mussel species (Bivalvia: Mytilidae) in Australia
Authors: Ab Rahim Emi S. , Nguyen Thuy T. T. , Ingram Brett , Riginos Cynthia , Weston Kim J. , Sherman Craig D. H.
Published: January 2016

Mussels belonging to the Mytilus edulis species complex have been the focus of numerous studies exploring the systematics and origin of this commercially and ecologically important genus. Species have wide geographical ranges and hybridise where their distributions overlap, making identification difficult. Several molecular markers have been used to distinguish between the species within the M. edulis species complex; however, no single marker system has been found to be completely diagnostic, and a combination of markers are used. Here, we used a combination of three nuclear genes and a mitochondrial gene region to assess the species composition of Mytilus mussels collected across its geographical range in Australia. Our results show that the majority (98.5%) of individuals sampled from Australian populations are Mytilus galloprovincialis, with 56.2% of them displaying a southern hemisphere haplotype, 10.3% displaying a putatively northern hemisphere haplotype, and 32% having M. galloprovincialis genotypes consistent with either northern or southern hemisphere M. galloprovincialis lineages. The taxonomic origin of the remaining 1.5% of samples (n=3) could not be conclusively determined. Our results suggest that there have been significant introductions of non-native M. galloprovincialis lineages into both southern and northern hemisphere populations.