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We investigate an optimal fourth-order staggered-grid finite-difference scheme for 3D frequency-domain viscoelastic wave modeling. An anti-lumped mass strategy is incorporated to minimize the numerical dispersion. The optimal finite-difference coefficients and the mass weighting coefficients are obtained by minimizing the misfit between the normalized phase velocities and the unity. An iterative damped least-squares method, the Levenberg–Marquardt algorithm, is utilized for the optimization. Dispersion analysis shows that the optimal fourth-order scheme presents less grid dispersion and anisotropy than the conventional fourth-order scheme with respect to different Poisson's ratios. Moreover, only 3.7 grid-points per minimum shear wavelength are required to keep the error of the group velocities below 1%. The memory cost is then greatly reduced due to a coarser sampling. A parallel iterative method named CARP-CG is used to solve the large ill-conditioned linear system for the frequency-domain modeling. Validations are conducted with respect to both the analytic viscoacoustic and viscoelastic solutions. Compared with the conventional fourth-order scheme, the optimal scheme generates wavefields having smaller error under the same discretization setups. Profiles of the wavefields are presented to confirm better agreement between the optimal results and the analytic solutions. [ABSTRACT FROM AUTHOR]

Abstract: Activity of the pterin- and folate-salvaging enzymes pteridine reductase 1 (PTR1) and dihydrofolate reductase–thymidylate synthetase (DHFR-TS) is commonly measured as a decrease in absorbance at 340nm, corresponding to oxidation of nicotinamide adenine dinucleotide phosphate (NADPH). Although this assay has been adequate to study the biology of these enzymes, it is not amenable to support any degree of routine inhibitor assessment because its restricted linearity is incompatible with enhanced throughput microtiter plate screening. In this article, we report the development and validation of a nonenzymatically coupled screening assay in which the product of the enzymatic reaction reduces cytochrome c, causing an increase in absorbance at 550nm. We demonstrate this assay to be robust and accurate, and we describe its utility in supporting a structure-based design, small-molecule inhibitor campaign against Trypanosoma brucei PTR1 and DHFR-TS. [Copyright &y& Elsevier]

A study was conducted to investigate the changes of pH, total cell number, soluble peptide patterns, free amino acid patterns, total phenolics, digestibility and antioxidant activities in vitro and in vivo of fermented extruded-pretreatment rapeseed meal with selected Bacillus subtilis (YY-1) and Saccharomyces cerevisiae (YY-2) (fermented extruded-pretreatment rapeseed meal, FERSM) with fermentation time. The objective was to develop a functional food/feed ingredient to contribute to healthy improvement. The results showed that the small peptide (molecular weight<3 kDa), total phenolic contents and digestibility of FERSM at 48th h increased to the highest level, and the subunit band intensities of 2S albumin and 12S globulin had almost entirely disappeared. The DPPH radical scavenging activity of FERSM at 48th h was higher (p <.05), and the T-SOD levels in serum and liver of weaned rats fed FERSM at 48th h was higher and MDA levels were lower (p <.05). The novel approach was effective for improving antioxidant properties. • The rapeseed meal was firstly fermented with self-selected Bacillus and Saccharomyces. • The rapeseed meal was firstly processed by combination of extrusion and fermentation.. • The extrusion destroyed the structure to facilitate to the release of substances.. • The phenolics contributed for antioxidant activity more than soluble peptides. • Rapeseed peptides (<3 KDa) play important role for antioxidant activity. [ABSTRACT FROM AUTHOR]

Abstract: Biomass was measured at 48 undefoliated grassland sites on a 1900-km transect in Inner Mongolia. Above-ground biomass was separated into leaf, stem, flower and fruit, and dead matter, and into the five dominant species at each site. Below-ground biomass was measured to a depth of 30cm and separated into 10-cm layers. Changes of these biomass components and their ratios were examined in relation to gradients of temperature and precipitation, and to the classification of the sites into five grassland types. Total biomass decreased markedly as site mean annual temperature increased and to a smaller extent as mean annual precipitation decreased. Averaged over all sites 92% of biomass was below ground. The proportion of below-ground biomass increased as temperature decreased, and was least and distributed more deeply in desert grassland. As aridity of the grassland types increased, the proportion of biomass in the first dominant species and in stem relative to leaf tissue increased. The biomass measurements provide baseline data required for monitoring sustainable use of Inner Mongolia grassland for livestock production and its storage of carbon. [Copyright &y& Elsevier]