Search Results - (Author, Cooperation:H. Yao)

2018-02-03

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-01-06

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

2011-03-26

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2018-07-06

American Physical Society (APS)

0556-2813

1089-490X

Physics

Nuclear Structure

2012-06-09

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Action Potentials/drug effects ; Animals ; Animals, Newborn ; *Cell Lineage ; *Electric Conductivity ; Electrical Synapses/metabolism/*physiology ; Gap Junctions/drug effects/*metabolism ; Meclofenamic Acid/pharmacology ; Mice ; Models, Neurological ; Neocortex/*cytology ; Neurons/*cytology/drug effects/*physiology ; Synaptic Transmission

2018-03-12

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

2018-06-22

The American Society for Microbiology (ASM)

0019-9567

1098-5522

Medicine

2018-05-17

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-11-03

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

1089-7550

AIP Digital Archive

Physics

Anisotropic dielectric functions of sapphire have been determined by both reflection and transmission variable angle spectroscopic ellipsometry. The measurements were made on a-plane (21¯1¯0) sapphire substrates in the energy range of 0.75–6.5 eV at room temperature. The orientation of the optic axis of the a-plane sapphire sample was determined by polarized Raman scattering based on which the Euler angles are set for the fitting model. Two pairs of Cauchy user-defined functions were constructed to describe the optical constants of both ordinary n⊥(ω) and extraordinary n(parallel)(ω) rays, respectively. As a result the optical constants from the generalized ellipsometry analysis are in good agreement with the reported data. The Kramers–Kronig (KK) relation between the real and the imaginary part have been carefully checked for both ordinary and extraordinary rays. The perfect fitting between the calculated and experimental ε1(ω) function indicates that both functions of ordinary and extraordinary rays are KK consistent. The refractive index difference between the ordinary and extraordinary rays is close to a constant (+0.008), which is determined mainly by the off-diagonal signal of the transmission ellipsometry data. The extinction coefficients are zero below 6 eV, and increase rapidly above 6 eV. © 1999 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Using variable angle spectroscopic ellipsometry, optical constants for AlAs (1.4–5.0 eV) are presented which are simultaneously compatible with measured data from four different samples. The below-gap index values are compatible with published prism measured values. The second derivative spectrum are compatible with published values above the direct band gap. The AlAs spectra is Kramers–Kronig self-consistent over the measured range and is compatible with published values from 0.6 to 1.4 eV. The optical constants for thin (〈50 A(ring)) GaAs caps on AlAs are shown to be different from bulk GaAs values and require special consideration when fitting ellipsometric data. For the thin GaAs caps, the E1 and E1+Δ1 critical-point structure is shifted to higher energies as previously observed for GaAs quantum wells. Bulk AlAs optical constants are shown to be different from those of a thin (∼20 A(ring)) AlAs barrier layer embedded in GaAs. The thin barrier layer exhibits a highly broadened critical-point structure. This barrier broadening effect (AlAs) and the thin cap shifting effects (GaAs) have implications for in situ growth control schemes which make use of the E1 and E1+Δ1 critical-point region. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Room temperature continuous wave operation of ZnSe-based blue/green laser diodes grown homoepitaxially on conductive ZnSe substrates with threshold current densities as low as 176 A/cm2 has been demonstrated. This is the lowest reported threshold among all short wavelength lasers in the blue/green region. Lifetimes at room temperature of up to 2.1 h have been obtained for lasers with pre-existing defect densities lower than 3×104 cm−2. © 1998 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Standard variable angle spectroscopic ellipsometry (VASE) has been employed to study the ordinary optical dielectric response of hexagonal gallium nitride (GaN) thin films—an important material for blue and ultraviolet light emitting device applications. The GaN films were grown by molecular beam epitaxy on c-plane sapphire substrates (α-Al2O3). Room temperature isotropic and anisotropic mode VASE measurements were made at angles of incidence between of 20° and 80°. Evidence of anisotropy was observed from the anisotropic mode measurements, reflecting the nature of wurtzite crystal structure of GaN. The sizable off-diagonal elements (Aps and Asp) of the Jones matrix indicate that the optical axis 〈c〉 of the c-plane sample are slightly off from the surface normal due to a small miscut of substrates. VASE data simulations by isotropic and anisotropic models indicate that the anisotropic effect on both diagonal and off-diagonal elements of the Jones matrix can be minimized to a negligible level at small angle of incidence. Thus the ordinary optical dielectric functions (E⊥〈c〉) are precisely determined by the isotropic mode VASE measurements at angles of incidence between 20° and 40° in the range of 0.75–6.5 eV. The VASE data were analyzed by a model dielectric function based on the GaN critical point structure, which allows for a nonzero extinction coefficient k below the band gap. The thicknesses of these GaN films are accurately determined via the analysis as well. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Carrier concentrations exceeding 1019/cm3 in GaAs implanted with Si (2×1014/cm2 at 140 keV) have been obtained by pulsed laser annealing with either a dye laser (λ=728 nm) or a XeCl excimer laser (λ=308 nm). Dye-laser annealing through a ∼55-nm-thick Si3N4 cap consistently produced higher activations than excimer-laser annealing with or without the cap. Carrier densities were measured by phonon-Raman and plasmon-Raman scattering.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The optical properties of silicon nitride and gallium arsenide were studied at temperatures up to and beyond the melting point of GaAs by means of laser heating. XeCl excimer and pulsed dye laser pulses, ∼10 ns in duration, were used to heat the semiconductor under nitride capping layers of varying thickness. The transient reflectivity response at 514.5 nm was used together with a multilayer interference analysis to obtain the optical constants of solid and molten GaAs and of solid Si3N4 near the 1513-K melting point of GaAs. In addition, we report the melt duration as a function of laser pulse energy for GaAs with and without capping layers.

Electronic Resource

1089-7666

AIP Digital Archive

Physics

Hyperdiffusion, a simple linear eddy diffusivity scheme, is commonly used in atmospheric and oceanic simulations because it increases the range of inertially behaving spatial scales for a given model resolution. Compared with molecular diffusion (which is utterly negligible in the atmosphere and oceans), hyperdiffusion more sharply confines the dissipation to the smallest scales of the numerical model. But is this all that hyperdiffusion does? In this paper, the inelastic interaction of two distributed vortices of unequal size is examined. Contour surgery (CS) simulations are compared with pseudospectral (PS) simulations employing hyperdiffusion or molecular diffusion. The example illustrates what is believed to be the most fundamental characteristic of two-dimensional (2-D) (and layerwise-2-D) vortex dynamics, namely, the formation of exceedingly high vorticity gradients. There is an excellent agreement between the hyperdiffusive PS and CS calculations at early times (i.e., for a few vortex rotation periods). Thereafter, significant discrepancies develop, beginning abruptly from the time when vorticity-gradient intensification is arrested by diffusion. A rapid inward erosion of the smaller of the two vortices then takes place. This erosion takes place under the joint action of (hyper) diffusion and stripping (the peeling of the vortex periphery by the external flow). With hyperdiffusion, the erosion is accompanied by a serious numerical artifact: a climb in the peak vorticity by 30% in this example. Eventually, the erosion reaches the vortex center and the vortex is sheared into a filament. In the CS calculation, there is no erosion, no climb in peak vorticity, and the vortex appears to last indefinitely.In the PS calculations, the viscosity or hyperdiffusion is adjusted according to the resolution to give the largest possible inertial range while ensuring numerical stability. It is found that vortices that are spanned by fewer than 10–20 grid points are eroded away in only a few vortex rotation periods (a time scale that is very much shorter than one would estimate from pure viscous decay). These findings bring into question the results of many 2- turbulence simulations using hyperdiffusion, for hyperdiffusion simulates neither inviscid dynamics nor molecular-diffusive dynamics. © 1995 American Institute of Physics.

Electronic Resource

1089-7666

AIP Digital Archive

Physics

In numerical studies, we observe the essentially inviscid approach to axisymmetry of an isolated-and-perturbed monopolar and uniformly decreasing distributed vortex region in a two-dimensional incompressible fluid. In particular, an initial small-but-finite amplitude, 3-fold, "edge''-located hole or depletion perturbation of a monopole evolves into a 2-fold state. This occurs through the nonlinear processes of hole stretching, splitting and partial merger. The initial growth rate for this downward cascade is proportional to the initial perturbation magnitude. Near-inviscid simulations are made with surgery-regularized contour dynamics codes (CDS), using from 5 to 11 contours. Pseudospectral (PS) simulations with varying Newtonian and hyperviscosities, that is considering continuum and dissipation effects, yield consistent results. Our numerical results are in agreement with small-but-finite amplitude perturbations that were used in recent laboratory experiments on magnetized electron columns. This process may also occur in late time evolutions associated with the "bump-on-tail'' initial condition in Vlasov plasmas. © 1996 American Institute of Physics.

Electronic Resource

1365-2389

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

In methanogenic rice-field soil, organic matter (SOM) is anaerobically fermented to acetate, CO2 and H2 which then serve as substrates for methanogenesis. The whole process is a disproportionation reaction in which part of the SOM is oxidized to CO2 and part is reduced to CH4. We were interested in the electron balance during this process. The rates VCO2 and VCH4 at which CO2 and CH4 are produced by anaerobic degradation of SOM, and the fraction RH2 of the CH4 produced by reduction of CO2 with H2 (as opposed to acetotrophic methanogenesis), depend on (i) the presence or absence of inorganic oxidants and (ii) the electron balance ΔZ. Under pseudo steady-state conditions, where inorganic oxidants are exhausted and the rate of SOM degradation is small compared with the size of the pool, VCO2, VCH4 and RH2 are constrained by ΔZ. Conversely, ΔZ may be determined from VCO2, VCH4 and RH2, all of which may be independently measured. We measured VCO2 (0.149–0.308 μmol g−1 day−1), VCH4 (0.169–0.466 μmol g−1 day−1) and RH2 (0.19–0.35) in eight soils and obtained values of ΔZ ranging from −0.918 to 0.035 μmol g−1 day−1. The majority (six) were negative, indicating a decrease in the oxidation state of the SOM carbon on degradation. This could be caused by humic acids acting as an electron acceptor and allowing more of the SOM to be oxidized to CO2 rather than reduced to CH4. Direct measurement of SOM carbon oxidation state Z produced values around zero (−0.1 ± 0.1), but is too insensitive to reveal changes of the magnitude of ΔZ.

Electronic Resource

1750-3841

Blackwell Publishing Journal Backfiles 1879-2005

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Process Engineering, Biotechnology, Nutrition Technology

: Yield, gelation, viscosity, emulsifying properties, and sugar composition of polysaccharides extracted from tofu processing wastewater under acidic conditions at different temperature levels and incubation times were determined. Optimum extraction for water-soluble polysaccharides was at pH 1.5 and 100 °C over an incubation period of 6 hours. Extraction ratio (%) and yield of high-molecular-weight polysaccharides were higher at pH ranges of 1.5 to 3.0 with extraction temperatures of 80 to 100 °C. Most water-soluble polysaccharides extracted under strong acidic conditions and above 80 °C remained fluid, while most extracted within the range of 45 to 80 °C gelled. Pure polysaccharides exhibited better emulsifying properties than water-soluble polysaccharides. Apparent viscosities of water-soluble polysaccharides were dependent on sugar concentration.

Electronic Resource

0005-2760

AC calorimetry ; Heat capacity spectroscopy ; Lipid ; Membrane ; Relaxation process

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Medicine

Physics

Electronic Resource