Synthesis and crystal structure of nickel(Ⅱ) and zinc(Ⅱ) complexes with 2,4-bis(3,5-dimethylpyrazol-1-yl)-6-methoxyl-1,3,5-triazine

2,4-Bis(3,5-dimethylpyrazol-1-yl)-6-methoxyl-1,3,5-triazine(bpt) has been synthesized by using a new, simple and general method with high yields. Reactions of bpt with Ni(CIO4)2 · 6H2O and Zn(CIO4)2 · 6H2O in methanol gave mononuclear complex [Ni(bpt)2] · (CIO4)2 · H2O and ternary complex [Zn(mpt)2(dmp)](CIO4)2 respectively, where mpt (2,4-dimethoxy-6-(3,5-dimethyl-pyrazol-1-yl)-1,3,5-triazine) and dmp(3,5-dimethylpyrazole) are the alcoholysis products of bpt in the presence of Zn2+ ion. A possible mechanism for this catalytic reaction was proposed. X-ray crystal structure for ligand bpt, Ni and Zn complexes are reported. The protonated form of the ligand bpt crystallizes as its perchlorate salt including one molecule of water, [Hbpt · H2O · CIO4]. The proton is located on one pyrazole N-atom. [Hbpt ?H2O ?CIO4], in which [Hbpt]+ is in cis-cis conformation, are packed in slipped stacks of approximately parallel layers. The π-π overlap interactions between the non-protonized pyrazoles of the adjace     

关于货币市场结构转换利率期限结构的实证研究

基本的利率期限结构模型均未能将结构转换效应考虑进来,因此为了探讨结构转换架构下利率期限结构模型的特性,本文在中国货币市场利率数据的基础上对基本利率期限结构模型和结构转换利率期限结构模型进行了比较研究,结果发现中国货币市场利率动态中存在明显的结构转换效应,且在结构转换效应中其本身也存在着不稳定性,这充分反映了中国货币市场在发展过程中的不成熟特征.     

Performance Study and Analysis of Parallel Multilevel Preconditioners

The significant gap between peak and realized performance of parallel systems motivates the need for performance analysis. In order to predict the performance of a class of parallel multilevel ILU preconditioner (PBILUM), we build two performance prediction models for both the preconditioner construction phase and the solution phase. These models combine theoretical features of the preconditioners with estimates on computation cost, communications overhead, etc. Experimental simulations show that our model predication based on certain reasonable assumptions is close to the simulation results. The models may be used to predict the performance of this class of parallel preconditioners.*The research work of the authors was supported in part by the U.S. National Science Foundation under grants CCR-9988165, CCR-0092532, ACR-0202934, and ACR-234270, by the U.S. Department of Energy Office of Science under grant DE-FG02-02ER45961, by the Kentucky Science & Engineering Foundation under grant KSEF-02-264-RED-002.     

Precise Supramolecular Polymerization of Liquid Crystalline Block Copolymer Initiated by Heavy Metallic Salts

Chinese Journal of Polymer Science - Heavy metallic salts are capable to bind with proteins and cause detrimental fibrilization in living cells. Herein, we report a similar case of supramolecular...     

Antioxidant and cytotoxic activity of lichens collected from Bidoup Nui Ba National Park,Vietnam

Research on Chemical Intermediates - Lichens were some of the earliest colonizers of terrestrial habitats on Earth. They represent a unique symbiont between fungi (mycobionts) and algae and/or...     

Preparation of polyacrylonitrile-based activated carbon fiber for CS2 adsorption

Research on Chemical Intermediates - Polyacrylonitrile (PAN)-based activated carbon fiber (ACF) was prepared by CO2 and KOH activation method, respectively, and used for the adsorption of CS2 at...     

Thermodynamic analysis of an ejector–vapour compressor cascade refrigeration system

Using the framework of the first and second law of thermodynamics, an ejector–vapour compressor cascade refrigeration system is studied. The criteria for refrigerant selection are examined, with R134a and R410A selected as the refrigerant for the ejector and compressor sub-cycle, respectively. The effects of generator temperature, evaporator temperature, condenser temperature, intercooler temperature and intercooler temperature difference are examined. The results demonstrate that a combined cycle can improve 30.8% when compared to the COP of single compressor cycle and 122% when compared to the single ejector cycle. In addition, intercooler temperature can be set at 26.5 °C for minimizing total exergy loss.

     

Salicyaldehyde-based fluorescent sensors with high sensitivity for amino acids

Structurally simple salicylaldehyde-based fluoreseent sensors for amino acids have been obtained by one-step or two-step synthesis.These sensors show significant fluorescence enhancement in the presence of many amino acids at concentrations as low as 10~5 mol/L.The reversible reaction of the aldehydes with amino acids to form imines in aqueous solution is proposed to account for the observed fluorescence enhancement.     

Effects of size and location of distal tear on hemodynamics and wave propagation in type B aortic dissection

Applied Mathematics and Mechanics - The type B aortic dissection (TBAD) is a perilous disease with high morbidity and mortality rates. The hemodynamics of TBAD in different scenarios has been...