Time-frequency analysis of auditory-nerve-fiber and basilar-membrane click responses reveal glide irregularities and non-characteristic-frequency skirts

Although many properties of click responses can be accounted for by a single, frequency-dispersive traveling wave exciting a single, characteristic-frequency (CF) resonance, some properties, such as waxing and waning cannot. Joint time-frequency distributions (TFDs) were used to help understand click responses of cat single auditory-nerve (AN) fibers (CFs<4 kHz) and published measurements of chinchilla basilar-membrane (BM) motion. For CFs> 800 Hz, the peak energy of the response decreased in latency and frequency as the level increased, as expected. However, at high levels the trend reversed for AN, but not BM, responses. Normalized TFDs, which show the frequency with the peak energy at each response time, revealed glides, as previously reported. Classical theory predicts smooth, upward glides. Instead, at low CFs there were downward glides, and at other CFs glides had substantial irregularities. Finally, click skirts, defined as the longest-latency part of click responses, sometimes showed deviations from CF for above-threshold sound levels. Most of these phenomena are not explained by a single, frequency-dispersive traveling wave exciting a single CF resonance, but they can be accounted for by the interaction of two (or more) excitation drives with different latencies and frequency contents.     

High-pressure combinatorial screening of homogeneous catalysts: hydrogenation of carbon dioxide

A simple method for high-pressure combinatorial catalyst discovery with visual (dye-based) assay is described. With this method, the first highly active catalyst, incorporating metals outside the platinum group, has been identified for CO(2) hydrogenation.     

On the reduction of S-alkyl-thionocarbonates (xanthates) with phosphorus compounds

[reaction: see text] Reductive cleavage of the carbon-sulfur bond present in S-alkyl-thionocarbonates (xanthates) was achieved by high-yielding, tin-free radical reactions based on phosphorus reagents. The combination hypophosphorous acid/triethylamine/AIBN led to fast, efficient, and smooth formation of the alkane. Reduction with diethyl phosphite was sufficiently slow to permit sequential intermolecular addition of a 2-oxoalkyl xanthate onto an olefin followed by cleavage of the newly formed carbon-sulfur bond.     

A capacitary weak type inequality for Sobolev functions and its applications

In this paper a capacitary weak type inequality for Sobolev functions is established and is applied to reprove some well-known results concerning Lebesgue points, Taylor expansions in the -sense, and the Lusin type approximation of Sobolev functions.

     

Cardiac glycosides from Erysimum cheiranthoides

Two new cardiac glycosides called cheiranthosides VI (2) and VII (3) were isolated together with a known one, glucoerysimoside (1) from the seeds of Erysimum cheiranthoides. Based on spectroscopic data, the structures of 2 and 3 were characterized as periplogenin 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-fucopyranoside and periplogenin 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-antiaropyranoside, respectively.     

Potential PDP phosphors with strong absorption around 172 nm: Rare earth doped NaLaP2O7 and NaGdP2O7

NaLaP₂O₇ and NaGdP₂O₇ powder samples are prepared by solid-state reactions at 750 and 600 °C, respectively, and the VUV-excited luminescence properties of Ln³⁺ (Ln=Ce, Pr, Tb, Tm, Eu) in both diphosphates are studied. Ln³⁺ ions in both hosts show analogous luminescence. For Ce³⁺-doped samples, the five Ce³⁺ 5d levels can be clearly identified. As for Pr³⁺ and Tb³⁺-doped samples, strong 4f-5d absorption band around 172 nm is observed, which matches well with Xe-He excimer in plasma display panel (PDP) devices. As a result, Pr³⁺ can be utilized as sensitizer to absorb 172 nm VUV photon and transfer energy to appropriate activators, and Tb³⁺-doped NaREP₂O₇(RE=La, Gd) are potential 172 nm excited green PDP phosphors. For Tm³⁺ and Eu³⁺-doped samples, the Tm³⁺-O²⁻ charge transfer band (CTB) is observed to be at 177 nm, but the CTB of Eu³⁺ is observed at abnormally low energy position, which might originate from multi-position of Eu³⁺ ions. The similarity in luminescence properties of Ln³⁺ in both hosts indicates certain structural resemblance of coordination environment of Ln³⁺ in the two sodium rare earth diphosphates.     

A direct‐forcing pressure‐based lattice Boltzmann method for solving fluid–particle interaction problems

A direct‐forcing immersed boundary‐lattice Boltzmann method (IB–LBM) is developed to simulate fluid–particle interaction problems. This method uses the pressure‐based LBM to solve the incompressible flow field and the immersed boundary method to handle the fluid–particle interactions. The pressure‐based LBM uses the pressure distribution functions instead of the density distribution functions as the independent dynamic variables. The main idea is to explicitly eliminate the compressible effect due to the density fluctuation. In the IB method, a direct‐forcing method is introduced to capture the particle motion. It directly computes an IB force density at each lattice grid from the differences between the pressure distribution functions obtained by the LBM and the equilibrium pressure distribution functions computed from the particle velocity. By applying this direct‐forcing method, the IB–LBM becomes a purely LBM version. Also, by applying the Gauss theorem, the formulas for computing the force and the torque acting on the particle from the flows are derived from the volume integrals over the particle volume instead of from the surface integrals over the particle surface. The order of accuracy of the IB–LBM is demonstrated on the errors of velocity field, wall stress, and gradients of velocity and pressure. As a demonstration of the efficiency and capabilities of the new method, sedimentation of a large number of spherical particles in an enclosure is simulated. Copyright © 2010 John Wiley & Sons, Ltd.     

RESERVOIR DESCRIPTION BY USING A PIECEWISE CONSTANT LEVEL SET METHOD

We consider the permeability estimation problem in two-phase porous media flow. We try to identify the permeability field by utilizing both the production data from wells as well as inverted seismic data. The permeability field is assumed to be piecewise constant, or can be approximated well by a piecewise constant function. A variant of the level set method, called Piecewise Constant Level Set Method is used to represent the interfaces between the regions with different permeability levels. The inverse problem is solved by minimizing a functional, and TV norm regularization is used to deal with the ill-posedness. We also use the operator-splitting technique to decompose the constraint term from the fidelity term. This gives us more flexibility to deal with the constraint and helps to stabilize the algorithm.     

研究金属切削中组织变化的网格高速摄影装置

研究金属切削过程中的变化,对改进切削工艺、实现高速、自动化和精密加工具有重要意义。高速显微摄影是实现从宏观到微观、从定性到定量、从静态到动态研究的有效方法。