A Multimoment Finite-Volume Shallow-Water Model On The Yin-Yang Overset Spherical Grid

A numerical model for shallow-water equations has been built and tested on the Yin-Yang overset spherical grid. A high-order multimoment finite-volume method is used for the spatial discretization in which two kinds of so-called moments of the physical field [i.e., the volume integrated average ( VIA) and the point value (PV)] are treated as the model variables and updated separately in time. In the present model, the PV is computed by the semi-implicit semi-Lagrangian formulation, whereas the VIA is predicted in time via a flux-based finite-volume method and is numerically conserved on each component grid. The concept of including an extra moment (i.e., the volume-integrated value) to enforce the numerical conservativeness provides a general methodology and applies to the existing semi-implicit semi-Lagrangian formulations. Based on both VIA and PV, the high-order interpolation reconstruction can only be done over a single grid cell, which then minimizes the overlapping zone between the Yin and Yang components and effectively reduces the numerical errors introduced in the interpolation required to communicate the data between the two components. The present model completely gets around the singularity and grid convergence in the polar regions of the conventional longitude-latitude grid. Being an issue demanding further investigation, the high-order interpolation across the overlapping region of the Yin-Yang grid in the current model does not rigorously guarantee the numerical conservativeness. Nevertheless, these numerical tests show that the global conservation error in the present model is negligibly small. The model has competitive accuracy and efficiency.

Calculations of bond dissociation energies and dipole moments in energetic materials using density-functional methods

We compare the effectiveness of six exchange/correlation functional combinations (Becke/Lee, Yang and Parr; Becke-3/Lee, Yang and Parr; Becke/Perdew-Wang 91; Becke-3/Perdew-Wang 91; Becke/Perdew 86; Becke-3/Perdew 86) for computing C-N, O-O and N-NO2 dissociation energies and dipole moments of five compounds. The studied compounds are hexabydro-1,3,5-trinitro-1,3,5-triazine (RDX), dimethylnitramine, cyanogen, nitromethane and ozone. The Becke-3/Perdew 86 in conjunction with 6-31G

Biological activities of skin secretions of the salamander Tylototriton verrucosus

Water-soluble skin secretions of salamander Tylototriton venucosus, first described by Anderson in 1871, were studied for their biological and enzymatic activities. They were found to be toxic to mice with an intraperitoneal LD50 of 11.5 mg/kg. Using Sephadex G-75 gel filtration, it was proven that the toxic components of the secretions are proteins with molecular weights ranging from 30,000 to 50,000 Da. The secretions of T. venucosus display a wide spectrum of antimicrobial activities and also contain both proteolytic activity and trypsin inhibitory activity. In contrast, neither hemolytic nor hemorrhagic activities were found. The secretions were determined to have phospholipase A(2) activity; however, no acetylcholine esterase activity was detectable under the assay conditions.

A novel heme-containing protein with anti-HIV-1 activity from skin secretions of Bufo andrewsi

A novel protein, named BAS-AH, was purified and characterized from the skin of the toad Bufo andrewsi. BAS-AH is a single chain protein and the apparent molecular weight is about 63 kDa as judged by SDS-PAGE. BAS-AH was determined to bind heme (0.89 mol heme/mol protein) as determined by pyridine haemochrome analysis. Fifty percentage cytotoxic concentration (CC50) of BAS-AH on C8166 cells was 9.5 mu M. However, at concentrations that showed little effect oil cell viability, BAS-AH displayed dose dependent inhibition oil HIV-1 infection and replication. The antiviral selectivity indexes corresponding to the measurements of syncytium formation and HIV-1 p24 (CC50/EC50) were 14.4 and 11.4, respectively, corresponding to the . BAS-AH also showed an inhibitory effect on the activity of recombinant HIV-1 reverse transcriptase (IC50 = 1.32 mu M). The N-terminal sequence of BAS-AH was determined to be NAKXKADVIGKISILLGQDNLSNIVAM, which exhibited little identity with other known anti-HIV-1 proteins. BAS-AH is devoid of antibacterial, protcolytic, trypsin inhibitory activity, (L)-amino acid oxidase activity and catalase activity. (c) 2005 Elsevier Ltd. All rights reserved.

Some new bounds on eigenvalues of the Hadamard product and the Fan product of matrices

Let A and B be nonsingular M-matrices. A lower bound on the minimum eigenvalue q(B circle A(-1)) for the Hadamard product of A(-1) and B, and a lower bound on the minimum eigenvalue q(A star B) for the Fan product of A and B are given. In addition, an upper bound on the spectral radius rho(A circle B) of nonnegative matrices A and B is also obtained. These bounds improve several existing results in some cases and the estimating formulas are easier to calculate for they are only depending on the entries of matrices A and B. (C) 2009 Elsevier Inc. All rights reserved.

Theoretical studies on conformation comparison of braid-like and triplex DNA

Based on the experimental data of scanning tunneling microscopy (STM), models of three-stranded braid-like DNAs composed by three kinds of base triplets AAA, TAT and GCA were constructed. We investigated the braid-like DNAs and their comparative tripler DNAs using a molecular mechanics method. The three strands of braid-like DNAs are proven equivalent, while those of tripler DNAs are not. The conformational energies for braid-like DNAs were found to be higher than that for tripler DNAs. Each period in one strand of braid-like DNA has 18 nucleotides, half of which are right-handed, while the other half are left-handed. Additional discussions concerning sugar puckering modes and the H-bonds are also included. (C) 1999 Elsevier Science B.V. All rights reserved.

A traveling-wave electroabsorption modulator with a large optical cavity and intrastep quantum wells

This paper reports a novel traveling-wave electroabsorption modulator (TWEAM) with a large optical cavity waveguide and an intrastep quantum well structure designed to achieve a high bandwidth, high saturation power and better fiber-matched optical profile, which is good for high coupling efficiency. The optical mode characteristic shows a great improvement in matching the circular mode of the fiber and the saturation power of 21 dBm, and a 3 dB bandwidth of 23 GHz was achieved for the fabricated TWEAM.

Ion bombardment as the initial stage of diamond film growth

It is believed that during the initial stage of diamond film growth by chemical-vapor deposition (CVD), ion bombardment is the main mechanism in the bias-enhanced-nucleation (BEN) process. To verify such a statement, experiments by using mass-separated ion-beam deposition were carried out, in which a pure carbon ion beam, with precisely defined low energy, was selected for investigating the ion-bombardment effect on a Si substrate. The results are similar to those of the BEN process, which supports the ion-bombardment-enhanced-nucleation mechanism. The formation of sp(3) bonding is based on the presumption that the time of stress generation is much shorter than the duration of the relaxation process. The ion-bombarded Si is expected to enhance the CVD diamond nucleation density because the film contains amorphous carbon embedded with nanocrystalline diamond and defective graphite. (C) 2001 American Institute of Physics.

Carbon film deposited by mass-selected low energy ion beam technique and ion bombardment effect

By mass-selected low energy ion beam deposition, amorphous carbon film was obtained. X-ray diffraction, Raman and Auger electron spectroscopy depth line shape measurements showed that such carbon films contained diamond particles. The main growth mechanism is subsurface implantation. Furthermore, it was indicated in a different way that ion bombardment played a decisive role in bias enhanced nucleation of chemical vapor deposition diamond.