Stability Analysis for Discrete Biological Models Using Algebraic Methods

This paper is concerned with stability analysis of biological networks modeled as discrete and finite dynamical systems. We show how to use algebraic methods based on quantifier elimination, real solution classification and discriminant varieties to detect steady states and to analyze their stability and bifurcations for discrete dynamical systems. For finite dynamical systems, methods based on Gr?bner bases and triangular sets are applied to detect steady states. The feasibility of our approach is demonstrated by the analysis of stability and bifurcations of several discrete biological models using implementations of algebraic methods.     

本地传输网承载WCDMA PS域业务方式探讨

根据工程实践经验,深入探讨了本地传输网承载WCDMA PS域业务方式,分析了现有传输承载方式及传输网存在的问题,提出了近期、远期及目标阶段的承载方案。     

N-甲基吡咯烷酮与H_nXW_(12)O_(40)·mH_2O(X=P,Si,Ge)电荷转移盐的合成、表征及非线性光学性质研究

由N -甲基吡咯烷酮和HnXW1 2 O40 ·mH2 O(X =P ,Si,Ge)合成了具有非线性光学性质的电荷转移盐 ,(NMPH) 3PW1 2 O40 ·CH3CN(I) ,(NMPH) 4 SiW1 2 O40 ·CH3CN(Ⅱ )和 (NMPH) 4 GeW1 2 O40 ·CH3CN(Ⅲ ) .并由元素分析 ,红外光谱 ,漫反射电子光谱进行了表征。结果表明杂多酸形成电荷转移盐后其阴离子结构未变 ;N -甲基吡咯烷酮通过N原子与酸中的质子H+结合成阳离子而成盐 ,光激发下阴阳离子之间可以发生电荷转移 ,非线性光学性性质研究表明 ,电荷转移盐的倍频效应强度分别为I2ωⅠ =0 .6IKDP,I2ωⅡ =0 .85和I2ωⅢ =0 .41IKDP,三阶非线性系数分别为 χ(3)Ⅰ =1 .60× 1 0 - 1 2 esu ,χ(3)Ⅱ =3.6× 1 0 - 1 2 esu ,χ(3)Ⅲ =1 .2× 1 0 - 1 1 esu .     

Synthesis and shapes of gold nanoparticles by using transition metal monosubstituted heteropolyanions as photocatalysts and stabilizers

Gold nanoparticles were prepared via a simple photoreduction technique in the presence of transition metal monosubstituted Keggin heteropolyanions (PW11M, M= Cu²⁺, Ni²⁺, Zn²⁺, Fe³⁺), in which PW11M acted as reducing agent, photocatalyst and stabilizer. The results indicated that the formation rate and morphology of the nanoparticles strongly depended on the kind of transition metal substituted in heteropolyacid and the preparation conditions, such as irradiation time and propan-2-ol amount. The photoreduction rates of PW11Zn and PW11Fe were faster than those of PW11Ni and PW11Cu. The shapes of the nanoparticles synthesized in the presence of PW11Fe and PW11Zn were nearly uniform spheres, whereas the morphologies of the nanoparticles synthesized in the presence of PW11Ni and PW11Cu were found to contain a mixture of flat triangular/hexagonal structures as well as spheres. Increases in the irradiation time and the propan-2-ol amount could make the morphology of nanoparticles uniform and shorten the formation time of the nanoparticles. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24(7) (in Chinese)     

V2O5/C catalyst for liquid phase oxidation of glyoxal to glyoxylic acid

Science China Chemistry - A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH...     

变频器过电压故障原因分析及对策

本文对变频器中间直流回路过电压原因进行了分析，提出了解决该故障的处理方案。     

Synthesis and Application of Graphitic Carbon with High Surface Area

Nanostructured graphitic carbons have widespread applications. However, the synthesis of such materials with a high surface area is still a great challenge. In this study, we demonstrate a new approach for improving the surface area. Graphitic carbon nanocages (CNCs) are prepared by spray pyrolysis of ethanol with dissolved iron carbonyl at high temperature. Ammonium thiocyanate is added to form iron sulfide as a less active catalyst and a template with less carbon dissolution and precipitation than single‐phase Fe. This addition leads to an apparent reduction in cage size from 60 to 40 nm and wall thickness from 5–10 nm to 2–4 nm and a significant increase in surface area from 227 to 550 m² g^?1 at 800 °C. As an example of a potential application, the CNCs with a thin wall and high surface area are demonstrated to be a superb material for supporting the Pt catalyst used in low‐temperature fuel cells. It is suggested that the present approach may be integrated with previous methods for improving the surface area of graphitic carbons and their performance in many areas of interest.     

Tailoring the d‐Band Centers Enables Co4N Nanosheets To Be Highly Active for Hydrogen Evolution Catalysis

Endowing materials with specific functions that are not readily available is always of great importance, but extremely challenging. Co₄N, with its beneficial metallic characteristics, has been proved to be highly active for the oxidation of water, while it is notoriously poor for catalyzing the hydrogen evolution reaction (HER), because of its unfavorable d‐band energy level. Herein, we successfully endow Co₄N with prominent HER catalytic capability by tailoring the positions of the d‐band center through transition‐metal doping. The V‐doped Co₄N nanosheets display an overpotential of 37 mV at 10 mA cm^?2, which is substantially better than Co₄N and even close to the benchmark Pt/C catalysts. XANES, UPS, and DFT calculations consistently reveal the enhanced performance is attributed to the downshift of the d‐band center, which helps facilitate the H desorption. This concept could provide valuable insights into the design of other catalysts for HER and beyond.