bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfuration of the C(sp2)–H bond of enaminones: a protocol for the synthesis of thioether using elemental sulfur as a sulfurating reagent
Authors: Yang Li-Fang , Liu Cheng-Guo , Xu Xiao-Ping , Ji Shun-Jun
Published: February 2016

Sulfuration reaction of the C(sp2)–H bond of enaminones with elemental sulfur in the presence of CuBr/K3PO4 was carried out. It provided an efficient method for the synthesis of thioethers and selenides in moderate to good yields.
Highly sensitive and selective colorimetric detection of sulphide using Ag–Au nanoalloys: a DFT study
Authors: Chang Le , Fisher Adrian , Liu Zhiping , Cheng Daojian
Published: February 2016

For the colorimetric detection of S, SH, cysteine, and H2S, the sensitivity of Ag–Au nanoalloy is better than pure Ag cluster, and both of them possess high selectivity for the detection of S.
Comb-shaped phenolphthalein-based poly(ether sulfone)s as anion exchange membranes for alkaline fuel cells
Authors: Lin Chen Xiao , Zhuo Yi Zhi , Lai Ao Nan , Zhang Qiu Gen , Zhu Ai Mei , Liu Qing Lin
Published: February 2016

A series of novel comb-shaped phenolphthalein-based poly(ether sulfone)s was synthesized for preparing anion exchange membranes (AEMs).
Exploration of interactions between decyl-β-d-glucopyranoside and bovine serum albumin in aqueous solution
Authors: Wang Gongke , Hou Huimin , Chen Ye , Yan Changling , Bai Guangyue , Lu Yan
Published: February 2016

The interactions between decyl-β-d-glucopyranoside (DG) and bovine serum albumin (BSA), in aqueous media, were investigated through the use of surface tension, steady-state fluorescence, and UV-vis absorption spectroscopy measurements.
Hydration lubrication and shear-induced self-healing of lipid bilayer boundary lubricants in phosphatidylcholine dispersions
Authors: Sorkin Raya , Kampf Nir , Zhu Linyi , Klein Jacob
Published: February 2016

In the presence of a lipid reservoir, softer lipid layers can self heal and provide enhanced lubricationviathe hydration lubrication mechanism.
Towards stable deep-blue emission and low efficiency roll-off in OLEDs based on phenanthroimidazole dimers
Authors: Wang Zhiming , Li Xueying , Xue Kaiqi , Li Hui , Zhang Xiaojuan , Liu Yulong , Yu Zhenqiang , Lu Ping , Chen Ping
Published: February 2016

Stable deep-blue emitters were prepared via meta–meta tailoring, and low roll-off was realized after cyano-substitution.
Ultrafast double-quantum NMR spectroscopy with optimized sensitivity for the analysis of mixtures
Authors: Rouger Laetitia , Gouilleux Boris , Pourchet-Gellez Mariane , Dumez Jean-Nicolas , Giraudeau Patrick
Published: February 2016

UF-DQS is an accurate 2D NMR approach for the quantification of analytes in complex mixtures characterized by strong peak overlaps.
Current control by electrode coatings formed by polymerization of dopamine at prussian blue-modified electrodes
Authors: Gao Bowen , Su Lei , Yang Hankun , Shu Tong , Zhang Xueji
Published: February 2016

Electrode coating with polydopamine (PDA) is fast becoming a popular surface modification technique.
Global optimization of small bimetallic Pd–Co binary nanoalloy clusters: a genetic algorithm approach at the DFT level
Authors: Aslan Mikail , Davis Jack B. A. , Johnston Roy L.
Published: February 2016

The global optimisation of small bimetallic PdCo binary nanoalloys are systematically investigated using the Birmingham Cluster Genetic Algorithm (BCGA).
Bio-inspired stabilization of sulfenyl iodide RS-I in a Zr(iv)-based metal–organic framework
Authors: Yee Ka-Kit , Wong Yan-Lung , Xu Zhengtao
Published: February 2016

Distance lends stability: a solid framework constrains S-I groups from approaching each other, emulating protein scaffolds in iodine thyroid chemistry.
Phthalocyanine-cRGD conjugate: synthesis, photophysical properties and in vitro biological activity for targeting photodynamic therapy
Authors: Luan Liqiang , Fang Wenjuan , Liu Wei , Tian Minggang , Ni Yuxing , Chen Xi , Yu Xiaoqiang
Published: February 2016

Phthalocyanine-RGD conjugate was synthesized and examined for its two-photon absorption cross section (TPACS), cellular uptake, and photocytotoxicity.
Palladium-catalyzed paraformaldehyde insertion: a three-component synthesis of benzofurans
Authors: Cheng Xiufang , Peng Yi , Wu Jun , Deng Guo-Jun
Published: February 2016

2-Aroylbenzofurans were prepared from 2-bromophenols, phenacyl bromides and paraformaldehyde under palladium catalysis conditions.
First principles calculations on the hydrogen atom passivation of TiO2 nanotubes
Authors: Dai Jianhong , Song Yan
Published: February 2016

Both charge and hydrogen atom passivation could metallize TiO2 nanotubes.
Reduced free-standing Co3O4@Ni cathode for lithium–oxygen batteries with enhanced electrochemical performance
Authors: Shen Chen , Wen Zhaoyin , Wang Fan , Huang Xiao , Rui Kun , Wu Xiangwei
Published: February 2016

The electrochemical activity of Co3O4 in lithium–oxygen battery is significantly improved by partial reduction of Co3+ to Co2+.
H/He interaction with vacancy-type defects in α-Al2O3 single crystals studied by positron annihilation
Authors: Zhang Guikai , Xiang Xin , Yang Feilong , Liu Lang , Tang Tao , Shi Yan , Wang Xiaolin
Published: February 2016

The first evidence that Al vacancies can be stabilized by H and filled with He is provided.
Emergence of comparable covalency in isostructural cerium(iv)– and uranium(iv)–carbon multiple bonds
Authors: Gregson Matthew , Lu Erli , Tuna Floriana , McInnes Eric J. L. , Hennig Christoph , Scheinost Andreas C. , McMaster Jonathan , Lewis William , Blake Alexander J. , Kerridge Andrew , Liddle Stephen T.
Published: February 2016

Against expectations the covalency in a cerium(iv)–carbon multiple bond interaction is essentially as covalent as the uranium(iv) analogue.
Analysis of derivative control based virtual inertia in multi‐area high‐voltage direct current interconnected power systems
Authors: Rakhshani Elyas , Remon Daniel , Mir Cantarellas Antoni , Rodriguez Pedro
Published: February 2016

Due to increasing level of power converter‐based component and consequently the lack of inertia, automatic generation control (AGC) of interconnected systems is experiencing different challenges. To cope with this challenging issue, a derivative control‐based virtual inertia for simulating the dynamic effects of inertia emulations by HVDC (high‐voltage direct current) interconnected systems is introduced and reflected in the multi‐area AGC system. Derivative control technique is used for higher level applications of inertia emulation. The virtual inertia will add an additional degree of freedom to the system dynamics which makes a considerable improvement on first overshoot responses in addition to damping characteristics of HVDC links. Complete trajectory sensitivities are used to analyse the effects of virtual inertia and derivative control gains on the system stability. The effectiveness of the proposed concept on dynamic improvements is tested through Matlab simulation of two‐area test system for different contingencies.
Cellular automata‐based artificial life system of horizontal gene transfer
Authors: Liu Ji‐xin
Published: February 2016

Mutation and natural selection is the core of Darwin's idea about evolution. Many algorithms and models are based on this idea. However, in the evolution of prokaryotes, more and more researches have indicated that horizontal gene transfer (HGT) would be much more important and universal than the authors had imagined. Owing to this mechanism, the prokaryotes not only become adaptable in nearly any environment on Earth, but also form a global genetic bank and a super communication network with all the genes of the prokaryotic world. Under this background, they present a novel cellular automata model general gene transfer to simulate and study the vertical gene transfer and HGT in the prokaryotes. At the same time, they use Schrodinger's life theory to formulate some evaluation indices and to discuss the intelligence and cognition of prokaryotes which is derived from HGT.
Hydrothermal synthesis of spindle shaped hierarchical ZnGa2O4 architectures and their photocatalytic activity
Authors: Yin Jingzhou , Jiang Zhengjing , Wang Hongyan , Li Rongqing , Zhang Yu , Zhong Hui , Zhang LiLi , Zhang Weiguang
Published: February 2016

The formation of spindle shaped hierarchical zinc gallate (ZnGa2O4) architectures was obtained through a simple hydrothermal process without the presence of any surface‐active agent. The X‐ray powder diffraction pattern indicated the formation of well crystallised in ZnGa2O4. The field emission scanning electron microscopy and high resolution transmission electron microscopy images showed that the spindle shaped hierarchical ZnGa2O4 architectures were constructed by octahedral ZnGa2O4. A feasible formation mechanism for the obtained spindle shaped ZnGa2O4 structure was proposed. The photocatalytic performance of the obtained ZnGa2O4 architectures was tested by the degradation of methylene blue under UV light irradiation. The result shows that spindle shaped ZnGa2O4 architectures have good photocatalytic performance.
Hollow carbon microfibres fabricated using coaxial centrifugal spinning
Authors: Xu Wei , Xia Lei , Zhou Xing‐hai , Xi Peng , Cheng Bo‐wen , Liang Yu‐xia
Published: February 2016

A novel method for preparing coaxial polyacrylonitrile (PAN)/polyvinyl pyrrolidone (PVP) microfibres is proposed. Further, the obtained composite fibres are subsequently processed using pre‐oxidation and carbonisation treatments in order to obtain hollow carbon microfibres. The effects of different respective PVP and PAN concentrations in the inner and outer solutions (the solutions injected into the inner and outer centrifugal tubes, respectively) on the product morphology are discussed. It is found that hollow carbon microfibres can only be fabricated for concurrent inner PVP and outer PAN solution concentrations of 14–17 and 13–16 wt%, respectively. If either of the solution concentrations is too low, droplets are formed, whereas the spinneret becomes blocked and cannot spin if either of these concentrations is too high. The diameters of the coaxial fibres and hollow carbon fibres can be controlled between 3 and 10 μm. This novel coaxial centrifugal spinning strategy can potentially be applied in the rapid fabrication of coaxial and hollow fibres.
Microcrystalline diamond cylindrical resonators with quality-factor up to 0.5 million
Authors: Saito Daisuke , Yang Chen , Heidari Amir , Najar Hadi , Lin Liwei , Horsley David A.
Published: February 2016

We demonstrate high quality-factor 1.5 mm diameter batch-fabricated microcrystalline diamond cylindrical resonators (CR) with quality-factors limited by thermoelastic damping (TED) and surface loss. Resonators were fabricated 2.6 and 5.3 μm thick in-situ boron-doped microcrystalline diamond films deposited using hot filament chemical vapor deposition. The quality-factor (Q) of as-fabricated CR's was found to increase with the resonator diameter and diamond thickness. Annealing the CRs at 700 °C in a nitrogen atmosphere led to a three-fold increase in Q, a result we attribute to thinning of the diamond layer via reaction with residual O2 in the annealing furnace. Post-anneal Q exceeding 0.5 million (528 000) was measured at the 19 kHz elliptical wineglass modes, producing a ring-down time of 8.9 s. A model for Q versus diamond thickness and resonance frequency is developed including the effects of TED and surface loss. Measured quality factors are shown to agree with the predictions of this model.
A note on spectral properties of the p-adic tree
Authors: Klimek Slawomir , Rathnayake Sumedha , Sakai Kaoru
Published: February 2016

We study the spectrum of the operator D∗D, where the operator D, introduced in Klimek et al. [e-print arXiv:1403.7263v2], is a forward derivative on the p-adic tree, a weighted rooted tree associated to ℤp via Michon’s correspondence. We show that the spectrum is closely related to the roots of a certain q − hypergeometric function and discuss the analytic continuation of the zeta function associated with D∗D.
Complex multireference configuration interaction calculations for the K-vacancy Auger states of N
q+ (q = 2-5) ions
Authors: Peng Yi-Geng , Wu Yong , Zhu Lin-Fan , Zhang Song Bin , Wang Jian-Guo , Liebermann H.-P. , Buenker R. J.
Published: February 2016

K-vacancy Auger states of Nq+ (q = 2-5) ions are studied by using the complex multireference single- and double-excitation configuration interaction (CMRD-CI) method. The calculated resonance parameters are in good agreement with the available experimental and theoretical data. It shows that the resonance positions and widths converge quickly with the increase of the atomic basis sets in the CMRD-CI calculations; the standard atomic basis set can be employed to describe the atomic K-vacancy Auger states well. The strong correlations between the valence and core electrons play important roles in accurately determining those resonance parameters, Rydberg electrons contribute negligibly in the calculations. Note that it is the first time that the complex scaling method has been successfully applied for the B-like nitrogen. CMRD-CI is readily extended to treat the resonance states of molecules in the near future.
High pressure dielectric studies on the structural and orientational glass
Authors: Kaminska E. , Tarnacka M. , Jurkiewicz K. , Kaminski K. , Paluch M.
Published: February 2016

High pressure dielectric studies on the H-bonded liquid d-glucose and Orientationally Disordered Crystal (ODIC) 1,6-anhydro-d-glucose (levoglucosan) were carried out. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. It is well reflected in the low pressure coefficient of the glass transition and orientational glass transition temperatures which is equal to 60 K/GPa for both d-glucose and 1,6-anhydro-d-glucose. Although it should be noted that ∂Tg0/∂p evaluated for the latter compound seems to be enormously high with respect to other systems forming ODIC phase. We also found that the shape of the α-loss peak stays constant for the given relaxation time independently on the thermodynamic condition. Consequently, the Time Temperature Pressure (TTP) rule is satisfied. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index (mp) drops with pressure. Interestingly, this change is much more significant in the case of d-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC–crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J. Chem. Phys. 142, 104501 (2015)] have shown that ODIC phase in 1,6-anhydro-d-glucose is stable in the wide range of temperatures and there is no tendency to form more ordered phase at ambient pressure. On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid (ODIC)–solid (crystal) transition in 1,6-anhydro-d-glucose. This result mimics the impact of pressure on the crystallization of fully disordered supercooled van der Waals liquids.
A theoretical simulation of the resonant Raman spectroscopy of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes
Authors: Franklin-Mergarejo Ricardo , Rubayo-Soneira Jesús , Halberstadt Nadine , Janda Kenneth C. , Apkarian V. Ara
Published: February 2016

The resonant Raman spectra of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes have been studied in the framework of a 2-dimensional model previously used in the simulation of their UV-visible absorption spectra using time-dependent techniques. In addition to the vibrational progression along the dihalogen mode, a progression is observed along the intermolecular mode and its combination with the intramolecular one. The relative intensity of the inter to intramolecular vibrational progressions is about 15% for H2O⋯Cl2 and 33% for H2O⋯Br2. These results make resonant Raman spectra a potential tool for detecting the presence of halogen bonded complexes in condensed phase media such as clathrates and ice.
Magneto-convective instabilities in horizontal cavities
Authors: Mistrangelo Chiara , Bühler Leo
Published: February 2016

A linear stability analysis is performed to investigate the onset of convective motions in a flat cavity filled with liquid metal. A volumetric heat source is uniformly distributed in the fluid and a horizontal magnetic field is imposed. Walls perpendicular to the magnetic field are thermally insulating, and the top wall is isothermal and the bottom adiabatic. When a magnetic field is applied, electromagnetic forces tend to transform 3D convective flow structures into quasi-2D rolls aligned to the magnetic field. By integrating 3D equations along magnetic field lines, a quasi-2D mathematical model has been derived. A dissipation term in the 2D equations accounts for 3D viscous effects in boundary layers at Hartmann walls perpendicular to the magnetic field. The influence of various parameters on flow stability is investigated. The flow is stabilized by increasing the magnetic field intensity or the electric conductance of Hartmann walls and by reducing the aspect ratio of the cavity. Numerical simulations are performed to verify the analytical results and to describe the main convective flow patterns in the non-linear regime.
Sub-10 pW/Hz0.5 room temperature Ni nano-bolometer
Authors: Yang Hyun-Ho , Rebeiz Gabriel M.
Published: February 2016

In this letter, we report on room temperature Ni nano-bolometers with a measured electrical noise equivalent power of 8.7 pW/Hz0.5 based on air-suspended and self-aligned nano-stack (SiO2/Ni/SiO2) structures, which is an outstanding electrical performance among uncooled micro/nano-bolometers. This result, together with electrical resistances of 172.6 Ω and modulation frequencies of 15–30 kHz, shows that Ni nano-bolometers can be easily coupled to terahertz antennas and are appropriate for fast passive imaging applications.
Direct simulation Monte Carlo modeling of relaxation processes in polyatomic gases
Authors: Pfeiffer M. , Nizenkov P. , Mirza A. , Fasoulas S.
Published: February 2016

Relaxation processes of polyatomic molecules are modeled and implemented in an in-house Direct Simulation Monte Carlo code in order to enable the simulation of atmospheric entry maneuvers at Mars and Saturn’s Titan. The description of rotational and vibrational relaxation processes is derived from basic quantum-mechanics using a rigid rotator and a simple harmonic oscillator, respectively. Strategies regarding the vibrational relaxation process are investigated, where good agreement for the relaxation time according to the Landau-Teller expression is found for both methods, the established prohibiting double relaxation method and the new proposed multi-mode relaxation. Differences and applications areas of these two methods are discussed. Consequently, two numerical methods used for sampling of energy values from multi-dimensional distribution functions are compared. The proposed random-walk Metropolis algorithm enables the efficient treatment of multiple vibrational modes within a time step with reasonable computational effort. The implemented model is verified and validated by means of simple reservoir simulations and the comparison to experimental measurements of a hypersonic, carbon-dioxide flow around a flat-faced cylinder.
Dressing method and quadratic bundles related to symmetric spaces. Vanishing boundary conditions
Authors: Valchev T. I.
Published: February 2016

We consider quadratic bundles related to Hermitian symmetric spaces of the type SU(m + n)/S(U(m) × U(n)). The simplest representative of the corresponding integrable hierarchy is given by a multi-component Kaup-Newell derivative nonlinear Schrödinger equation which serves as a motivational example for our general considerations. We extensively discuss how one can apply Zakharov-Shabat’s dressing procedure to derive reflectionless potentials obeying zero boundary conditions. Those could be used for one to construct fast decaying solutions to any nonlinear equation belonging to the same hierarchy. One can distinguish between generic soliton type solutions and rational solutions.
Transition and separation process in brine channels formation
Authors: Berti Alessia , Bochicchio Ivana , Fabrizio Mauro
Published: February 2016

In this paper, we discuss the formation of brine channels in sea ice. The model includes a time-dependent Ginzburg-Landau equation for the solid-liquid phase change, a diffusion equation of the Cahn-Hilliard kind for the solute dynamics, and the heat equation for the temperature change. The macroscopic motion of the fluid is also considered, so the resulting differential system couples with the Navier-Stokes equation. The compatibility of this system with the thermodynamic laws and a maximum theorem is proved.
Constructive spin-orbital angular momentum coupling can twist materials to create spiral structures in optical vortex illumination
Authors: Barada Daisuke , Juman Guzhaliayi , Yoshida Itsuki , Miyamoto Katsuhiko , Kawata Shigeo , Ohno Seigo , Omatsu Takashige
Published: February 2016

It was discovered that optical vortices twist isotropic and homogenous materials, e.g., azo-polymer films to form spiral structures on a nano- or micro-scale. However, the formation mechanism has not yet been established theoretically. To understand the mechanism of the spiral surface relief formation in the azo-polymer film, we theoretically investigate the optical radiation force induced in an isotropic and homogeneous material under irradiation using a continuous-wave optical vortex with arbitrary topological charge and polarization. It is revealed that the spiral surface relief formation in azo-polymer films requires the irradiation of optical vortices with a positive (negative) spin angular momentum and a positive (negative) orbital angular momentum (constructive spin-orbital angular momentum coupling), i.e., the degeneracy among the optical vortices with the same total angular momentum is resolved.
Observation of Fano line shapes in infrared vibrational spectra of CO2 adsorbed on Cu(997) and Cu(111)
Authors: Koitaya Takanori , Shiozawa Yuichiro , Mukai Kozo , Yoshimoto Shinya , Yoshinobu Jun
Published: February 2016

Adsorption states of carbon dioxide on the Cu(997) and Cu(111) surfaces were investigated by infrared reflection absorption spectroscopy, temperature programmed desorption, and X-ray photoelectron spectroscopy. CO2 molecules are physisorbed on the Cu(997) surface at temperatures below 70 K; neither chemisorption nor dissociation of CO2 occurs on the Cu(997) surface at this low temperature. However, the vibrational spectra of adsorbed CO2 depend significantly on the substrate temperature and coverage. IR spectra of CO2 vibrational modes at 70 K show asymmetric Fano line shapes, while only normal absorption bands are observed when CO2 is adsorbed at 20 K. Fano line shapes are also observed for CO2 on Cu(111) at 85 K. The observation of Fano effect indicates the coupling between the electronic continuum states of the Cu surface and the internal vibrational modes of CO2 even in such physisorbed system.
Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators
Authors: Slutz S. A. , Stygar W. A. , Gomez M. R. , Peterson K. J. , Sefkow A. B. , Sinars D. B. , Vesey R. A. , Campbell E. M. , Betti R.
Published: February 2016

The MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values: i.e., peak current = 25 MA, deposited preheat energy = 5 kJ, and Bz = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.
Design of a polymer thermoelectric generator using radial architecture
Authors: Menon Akanksha K. , Yee Shannon K.
Published: February 2016

Thermoelectric generators (TEGs) are solid-state heat engines consisting of p-type and n-type semiconductors that convert heat into electricity via the Seebeck effect. Conducting polymers are a viable alternative with intrinsic advantages over their inorganic counterparts, since they are abundant, flexible as thick-films, and have reduced manufacturing costs due to solution processing. Furthermore, polymers have an inherently low thermal conductivity, thus affording them the option of forgoing some heat exchanger costs. Current examples of polymer TE devices have been limited to traditional flat-plate geometries with power densities on the μW/cm2 scale, where their potential is not fully realized. Herein, we report a novel radial device architecture and model the improved performance of polymer-based TEG based on this architecture. Our radial architecture accommodates a fluid as the heat source and can operate under natural convection alone due to heat spreading. Analytical heat transfer and electrical models are presented that optimize the device for maximum power density, and for the first time we obtain the geometry matching condition that maximizes the efficiency. We predict high power densities of ∼1 mW/cm2 using state-of-the-art polymer TEs subjected to a temperature difference of 100 K, which is nearly 1000× higher than polymer flat-plate architectures reported in literature.
Elastic metamaterial beam with remotely tunable stiffness
Authors: Qian Wei , Yu Zhengyue , Wang Xiaole , Lai Yun , Yellen Benjamin B.
Published: February 2016

We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ∼30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves.
Self-pulsing in a low-current hollow cathode discharge: From Townsend to glow discharge
Authors: Qin Yu , Xie Kan , Zhang Yu , Ouyang Jiting
Published: February 2016

We investigate the self-pulsing phenomenon of a low current cavity discharge in a cylindrical hollow cathode in pure argon. The waveforms of pulsed current and voltage are measured, and the time-averaged and time-resolved images of hollow cathode discharge are recorded by using high-speed intensified charge coupled device camera. The results show that the self-pulsing is a mode transition between low-current stage of Townsend discharge and high-current stage of glow discharge. During the self-pulsing, the current rising time relates to the dissipation of space charges, and the decay time relates to the reconstruction of the virtual anode by the accumulation of positive ions. Whether or not space charges can form and keep the virtual anode is responsible for the discharge mode and hence plays an important role in the self-pulsing phenomenon in low current hollow cathode discharge.
Effective electrostatic interactions among charged thermo-responsive microgels immersed in a simple electrolyte
Authors: González-Mozuelos P.
Published: February 2016

This work explores the nature and thermodynamic behavior of the effective electrostatic interactions among charged microgels immersed in a simple electrolyte, taking special interest in the effects due to the thermally induced variation of the microgel size while the remaining parameters (microgel charge and concentration, plus the amount of added salt) are kept constant. To this end, the rigorous approach obtained from applying the precise methodology of the dressed ion theory to the proper definition of the effective direct correlation functions, which emerge from tracing-out the degrees of freedom of the microscopic ions, is employed to provide an exact description of the parameters characterizing such interactions: screening length, effective permittivity, and renormalized charges. A model solution with three components is assumed: large permeable anionic spheres for the microgels, plus small charged hard spheres of equal size for the monovalent cations and anions. The two-body correlations among the components of this model suspension, used as the input for the determination of the effective interaction parameters, are here calculated by using the hyper-netted chain approximation. It is then found that at finite microgel concentrations the values of these parameters change as the microgel size increases, even though the ionic strength of the supporting electrolyte and the bare charge of the microgels remain fixed during this process. The variation of the screening length, as well as that of the effective permittivity, is rather small, but still interesting in view of the fact that the corresponding Debye length stays constant. The renormalized charges, in contrast, increase markedly as the microgels swell. The ratio of the renormalized charge to the corresponding analytic result obtained in the context of an extended linear response theory allows us to introduce an effective charge that accounts for the non-linear effects induced by the short-ranged association of microions to the microgels. The behavior of these effective charges as a function of the amount of added salt and the macroion charge, size, and concentration reveals the interplay among all these system parameters.
Metal particle compaction during drop-substrate impact for inkjet printing and drop-casting processes
Authors: Clancy I. , Amarandei G. , Nash C. , Glowacki B. A.
Published: February 2016

Direct coating methods using metal particles from aqueous solutions or solvent-based inks become central in the roll-to-roll fabrication processes as these methods can lead to continuous or pre-defined conductive layers on a large variety of substrates. For good electrical conductivity, the metal particles have to be brought into contact, and traditionally, additional sintering treatments are required. Such treatments can degrade the sensitive substrates as paper or polymer films. In this study, the possibility of obtaining conductive layers at room temperature is investigated for direct coating methods with an emphasis on drop-casting and inkjet printing. Thus, it is shown that electrical conductive layers can be achieved if the metal particles can compact during the drop-substrate impact interaction. It is theoretically shown that the compaction process is directly related to the particle and ink drop size, the initial fractional particle loading of the ink, solvent viscosity, and drop velocity. The theoretical predictions on compaction are experimentally validated, and the particle compaction's influence on changes in the electrical conductivity of the resulting layers is demonstrated.
Dependence of the scatter of the electrical properties on local non-uniformities of the tunnel barrier in Nb/Al-AlOx/Nb junctions
Authors: Yadranjee Aghdam Parisa , Rashid Hawal Marouf , Pavolotsky Alexey , Desmaris Vincent , Belitsky Victor
Published: February 2016

In this paper, we study the effect of the tunnel barrier thickness non-uniformity in Nb/Al-AlOx/Nb tunnel junctions using the measurement results of the junction capacitance (C) and the normal resistance (Rn). The local thickness distribution of the AlOx tunnel barrier in Nb/Al-AlOx/Nb trilayer (RnA ∼ 30 Ω μm2) was studied by high resolution transmission electron microscopy. The specific resistance (RnA) values of the measured junctions range from 8.8 to 68 Ω μm2. We observed scatter in both the junction specific resistance and capacitance data, which is considerably higher than the measurement uncertainty. We also observed noticeable scatter in the RnC product, which does not stem from junction area estimation uncertainties. We discuss the possible reasons that contribute to this scatter. We suggest that the local thickness non-uniformity of the tunnel barrier significantly contributes to the scatter in the RnC product. We confirm this conclusion through an illustrative model based on the barrier imaging data, which results in the variation of the RnC data consistent with the measurements in this paper.
Schottky barrier heights at the interfaces between pure-phase InAs nanowires and metal contacts
Authors: Feng Boyong , Huang Shaoyun , Wang Jiyin , Pan Dong , Zhao Jianghua , Xu H. Q.
Published: February 2016

Understanding of the Schottky barriers formed at metal contact-InAs nanowire interfaces is of great importance for the development of high-performance InAs nanowire nanoelectronic and quantum devices. Here, we report a systematical study of InAs nanowire field-effect transistors (FETs) and the Schottky barrier heights formed at the contact-nanowire interfaces. The InAs nanowires employed are grown by molecular beam epitaxy and are high material quality single crystals, and the devices are made by directly contacting the nanowires with a series of metals of different work functions. The fabricated InAs nanowire FET devices are characterized by electrical measurements at different temperatures and the Schottky barrier heights are extracted from the measured temperature and gate-voltage dependences of the channel current. We show that although the work functions of the contact metals are widely spread, the Schottky barrier heights are determined to be distributed over 35–55 meV, showing a weak but not negligible dependence on the metals. The deduced Fermi level in the InAs nanowire channels is found to be in the band gap and very close to the conduction band. The physical origin of the results is discussed in terms of Fermi level pinning by the surface states of the InAs nanowires and a shift in pinned Fermi level induced by the metal-related interface states.
Tunable multipole resonances in plasmonic crystals made by four-beam holographic lithography
Authors: Luo Y. , Li X. , Zhang X. , Prybolsky S. , Shepard G. D. , Strauf S.
Published: February 2016

Plasmonic nanostructures confine light to sub-wavelength scales, resulting in drastically enhanced light-matter interactions. Recent interest has focused on controlled symmetry breaking to create higher-order multipole plasmonic modes that store electromagnetic energy more efficiently than dipole modes. Here we demonstrate that four-beam holographic lithography enables fabrication of large-area plasmonic crystals with near-field coupled plasmons as well as deliberately broken symmetry to sustain multipole modes and Fano-resonances. Compared with the spectrally broad dipole modes we demonstrate an order of magnitude improved Q-factors (Q = 21) when the quadrupole mode is activated. We further demonstrate continuous tuning of the Fano-resonances using the polarization state of the incident light beam. The demonstrated technique opens possibilities to extend the rich physics of multipole plasmonic modes to wafer-scale applications that demand low-cost and high-throughput.
A conductive scanning study of La0.67Sr0.33MnO3/Nb:SrTiO3 hetero-junction
Authors: Lu H. X. , Zhang J. , Zhang H. R. , Li Y. , Chen Y. S. , Shen B. G. , Sun J. R.
Published: February 2016

Basing on conductive atomic force microscopy, we presented a direct conductance mapping for the interface of the La0.67Sr0.33MnO3/Nb:SrTiO3 hetero-junction. The most remarkable observation is the presence of an interfacial layer in Nb:SrTiO3 adjacent to the manganite film. Within this layer, the AFM tip/Nb:SrTiO3 contact shows a current-voltage dependence that strongly deviates from Shockley equation, unlike a Schottky diode. Spatial extension of this layer is explored and possible transport mechanism in or outside this interfacial layer is discussed. The present work gives a direct intuitional image on the interface of manganite junction. The principle proven here can be extended to other complex oxide interfaces.
The origins of near band-edge transitions in hexagonal boron nitride epilayers
Authors: Du X. Z. , Li J. , Lin J. Y. , Jiang H. X.
Published: February 2016

Photoluminescence spectroscopy has been employed to probe the near band-edge transitions in hexagonal BN (h-BN) epilayers synthesized under varying ammonia flow rates. The results suggest that the quasi-donor-acceptor pair emission line at 5.3 eV is due to the transition between the nitrogen vacancy and a deep acceptor, whereas the 5.5 eV emission line is due to the recombination of an exciton bound to a deep acceptor formed by carbon impurity occupying the nitrogen site. By growing h-BN under high ammonia flow rates, nitrogen vacancy related peaks can be eliminated and epilayers exhibiting pure free exciton emission have been obtained.
Transfer into L3 English
Authors: Lloyd-Smith Anika , Gyllstad Henrik , Kupisch Tanja
Published: February 2016

This study is concerned with L3 acquisition in heritage speakers (HSs). The goals are to incorporate HSs into L3 acquisition research and investigate the role of language dominance for predicting L3 transfer. We analyze global accent in German-Turkish early bilinguals, HSs of Turkish, who acquired English as their L3. Twenty native-speaker judges determined accent strength and accent source in the speech of 18 bilinguals as well as 15 controls (L1 English, L1 German, L1 Turkish) when speaking English. Results show, firstly, that bilinguals are perceived as less accented than L1 Turkish speakers and similar to L1 German speakers. Secondly, unlike L1 controls, there is no uniform accent source for HSs when speaking their L3. Our results question the role of age of acquisition, while being generally consistent with the TPM. However, HSs seem to benefit from bilingual experience and structure-based transfer can be overpowered by high proficiency.
Main Pulmonary Arterial Wall Shear Stress Correlates with Invasive Hemodynamics and Stiffness in Pulmonary Hypertension
Authors: Schäfer Michal , Kheyfets Vitaly O. , Schroeder Joyce D. , Dunning Jamie , Shandas Robin , Buckner J. Kern , Browning James , Hertzberg Jean , Hunter Kendall S. , Fenster Brett E.
Published: February 2016

Pulmonary hypertension (PH) is associated with proximal pulmonary arterial remodeling characterized by increased vessel diameter, wall thickening, and stiffness. In vivo assessment of wall shear stress (WSS) may provide insights into the relationships between pulmonary hemodynamics and vascular remodeling. We investigated the relationship between main pulmonary artery (MPA) WSS and pulmonary hemodynamics as well as markers of stiffness. As part of a prospective study, 17 PH patients and 5 controls underwent same‐day four‐dimensional flow cardiac magnetic resonance imaging (4‐D CMR) and right heart catheterization. Streamwise velocity profiles were generated in the cross‐sectional MPA in 45° increments from velocity vector fields determined by 4‐D CMR. WSS was calculated as the product of hematocrit‐dependent viscosity and shear rate generated from the spatial gradient of the velocity profiles. In‐plane average MPA WSS was significantly decreased in the PH cohort compared with that in controls (0.18 ± 0.07 vs. 0.32 ± 0.08 N/m2; P = 0.01). In‐plane MPA WSS showed strong inverse correlations with multiple hemodynamic indices, including pulmonary resistance (ρ = –0.74, P < 0.001), mean pulmonary pressure (ρ = –0.64, P = 0.006), and elastance (ρ = –0.70, P < 0.001). In addition, MPA WSS had significant associations with markers of stiffness, including capacitance (ρ = 0.67, P < 0.001), distensibility (ρ = 0.52, P = 0.013), and elastic modulus (ρ = –0.54, P = 0.01). In conclusion, MPA WSS is decreased in PH and is significantly associated with invasive hemodynamic indices and markers of stiffness. 4‐D CMR‐based assessment of WSS may represent a novel methodology to study blood‐vessel wall interactions in PH.
Diagnosis of Pulmonary Hypertension from Magnetic Resonance Imaging–Based Computational Models and Decision Tree Analysis
Authors: Lungu Angela , Swift Andrew J. , Capener David , Kiely David , Hose Rod , Wild Jim M.
Published: February 2016

Accurately identifying patients with pulmonary hypertension (PH) using noninvasive methods is challenging, and right heart catheterization (RHC) is the gold standard. Magnetic resonance imaging (MRI) has been proposed as an alternative to echocardiography and RHC in the assessment of cardiac function and pulmonary hemodynamics in patients with suspected PH. The aim of this study was to assess whether machine learning using computational modeling techniques and image‐based metrics of PH can improve the diagnostic accuracy of MRI in PH. Seventy‐two patients with suspected PH attending a referral center underwent RHC and MRI within 48 hours. Fifty‐seven patients were diagnosed with PH, and 15 had no PH. A number of functional and structural cardiac and cardiovascular markers derived from 2 mathematical models and also solely from MRI of the main pulmonary artery and heart were integrated into a classification algorithm to investigate the diagnostic utility of the combination of the individual markers. A physiological marker based on the quantification of wave reflection in the pulmonary artery was shown to perform best individually, but optimal diagnostic performance was found by the combination of several image‐based markers. Classifier results, validated using leave‐one‐out cross validation, demonstrated that combining computation‐derived metrics reflecting hemodynamic changes in the pulmonary vasculature with measurement of right ventricular morphology and function, in a decision support algorithm, provides a method to noninvasively diagnose PH with high accuracy (92%). The high diagnostic accuracy of these MRI‐based model parameters may reduce the need for RHC in patients with suspected PH.
Fusing geophysical signatures of locally recorded surface explosions to improve blast detection
Authors: Carmichael Joshua D. , Nemzek Robert , Arrowsmith Stephen , Sentz Kari
Published: February 2016

We recorded acoustic, seismic and radio-frequency signatures of 70 solid charge (∼2–12 kg) surface explosions (shots) at local distances (0.1–1.5 km) to determine if such signals could be fused for blast monitoring. We observed that each geophysical signature was sufficiently repeatable between similar shots to be identifiable with multichannel correlation detectors. Using template signals from a large explosion, we then processed heavily contaminated data recording a smaller shot with these detectors, and missed or marginally detected the resultant target signals. By then fusing the p-values of these statistics through Fisher's combined probability test, we clearly identified the same explosion signals at thresholds consistent with the false alarm on noise rates of the correlation detectors. This resulting Fisher test thereby provided high-probability detections, zero false alarms and higher theoretical detection capability.
Application of a predator–prey overlap metric to determine the impact of sub-grid scale feeding dynamics on ecosystem productivity
Authors: Greer Adam T. , Woodson C. Brock
Published: February 2016

Marine ecosystem models assume spatially homogeneous population dynamics at sub-grid scale resolution, despite evidence that marine systems are highly structured on fine scales. This structuring can influence the predator–prey interactions driving trophic transfer and thereby overall ecosystem production. Here we apply a statistic, the AB ratio (ζAB), to quantify increased predator production due to fine-scale overlap with its prey. We calculated ζAB from available literature sources (spatial observations of predator and prey) and from data obtained with a towed plankton imaging system, demonstrating that organisms from a range of trophic levels and oceanographic regions tended to overlap with their prey both in the horizontal and vertical dimensions. The values of ζAB indicate that spatially homogeneous calculations underestimate productivity. This pattern was accentuated when accounting for swimming over a diel cycle and by increasing sampling resolution, especially when prey were highly aggregated. We recommend that ecosystem models incorporate more fine-scale information both to more accurately capture trophic transfer processes and to capitalize on the increasing sampling resolution, data volume, and data sharing platforms from empirical studies.