Interaction between explosive and analyte layers in explosive matrix-assisted plasma desorption mass spectrometry

An HMX/insulin two-layer system was chosen as a model for further investigation of the matrix properties of explosive materials for protein analytes in plasma desorption mass spectrometry. The dependencies of the molecular ion yield and average charge state as a function of the analyte thickness were studied. An increase in the charge state of multiply protonated molecular species was confirmed as the major matrix effect, with the average charge state z at the smallest thickness studied being higher than in matrix-assisted laser desorption/ionization and closer to the value obtained in electrospray ionization under standard acidic conditions. Observed charge state distributions are significantly narrower than the corresponding Poisson distributions, which suggests that the protonation of insulin is limited in plasma desorption by the number of basic sites in the molecule, similar to electrospray ionization. Both the curve displaying total molecular ion yield and the one showing the total charge (proton) yield as a function of the insulin thickness have maxima at a thickness different from an insulin monolayer. These observations diminish the significance of a matrix/analyte interface mechanism for the explosive matrix assistance. Instead, a mechanism related to the chemical energy release during conversion of the explosive after the ion impact is proposed. As additional mechanisms, enhanced protonation of the analyte through collisions with products of the explosive decay is considered, as well as electron scavenging by other products, which leads to a higher survival probability of positively charged protein molecular ions. Copyright 1999 John Wiley & Sons, Ltd.     

地下结构物外加电流阴极保护用阳极评述

本文分析了地下结构物外加电流阴极保护用阳极的工况环境条件 ;并对各类阳极材料的性能特点进行了评述 ;探讨了埋地辅助阳极材料的发展与应用方向 .     

Wave scattering effects in elastic percolation models

The study of the propagation of waves in randomly diluted models is presented. Porosity (crack-like) models are simulated by constructing typical elastic percolation networks with random microscopic heterogeneities in order to resemble rock media. Central and bond-bending forces (Born Hamiltonian) models are considered. For each experimental case, the elastic energy of the system is relaxed in equilibrium and then the model is excited by a pulse source in order to produce wave propagation. First, a review is presented of the well established velocity-porosity relationship from rock physics, which shows a linear trend from small porosities up to the critical porosity (percolation threshold) where the rocks fall apart. From the wave propagation analysis a general trend is observed for the attenuation of waves, from the small to the large porosity models, suggesting multiple scattering effects similar to those reported from effective-medium approximations of wave scattering due to random heterogeneities. Finally, the results are compared with those obtained from laboratory experiments on dry rocks with different porosities and different applied stress regimes.     

GOx signaling triggered by aptamer-based ATP detection

Aptamer based ATP binding leads to the release of the co-factor FAD, which acts as a trigger to 'turn-on' the activity of apo-GOx and thus generates a measurable response.     

Synthesis,spectral studies,thermal behavior,and antibacterial activity of Ni(Ⅱ),Cu(Ⅱ),and Zn(Ⅱ) complexes with an ONO tridentate Schiff base

Three new transition metal complexes have been synthesized with a Schiff base,3-(2-hydroxy-5-chlorophenylimino)-l,3- diphenylpropen-1-one.In all complexes Schiff base is completely deprotonated and coordinated to metal as tridentate ligand via phenolic and enolic oxygens and imine nitrogen.Thermal decomposition of the complexes has been studied by thermogravimetry. The in vitro antibacterial activity of Schiff bases and their complexes has been evaluated and compared with the standard drugs.     

Adsorption of nitrous oxide on the(6,0) magnesium oxide nanotube

Nitrous oxide adsorption on the pristine（6,0） magnesium oxide nanotube was studied by using density functional theory calculations.We present the nature of the N₂O interaction in selected sites of the nanotube.Adsorption energies corresponding to adsorption of the N₂O on the nanotube were calculated to be in the range -11.67 to -22.21 kJ mol^-1.Our results indicate that the N₂O molecule has a weak physical adsorption on the pristine models due to weak Van der Waals interaction between the nanotubes and N₂O molecule.The important results can be useful in production of the N₂O sensors.     

A comparative lipidomics platform for chemotaxonomic analysis of Mycobacterium tuberculosis

The lipidic envelope of Mycobacterium tuberculosis promotes virulence in many ways, so we developed a lipidomics platform for a broad survey of cell walls. Here we report two new databases (MycoMass, MycoMap), 30 lipid fine maps, and mass spectrometry datasets that comprise a static lipidome. Further, by rapidly regenerating lipidomic datasets during biological processes, comparative lipidomics provides statistically valid, organism-wide comparisons that broadly assess lipid changes during infection or among clinical strains of mycobacteria. Using stringent data filters, we tracked more than 5,000 molecular features in parallel with few or no false-positive molecular discoveries. The low error rates allowed chemotaxonomic analyses of mycobacteria, which describe the extent of chemical change in each strain and identified particular strain-specific molecules for use as biomarkers.     

钻井液添加剂对形成天然气水合物的影响

针对深水钻井中水基钻井液易形成天然气水合物从而导致钻井作业无法正常进行的问题,利用自行设计研制的气体水合物反应装置,模拟深水钻井温度压力条件,对水基钻井液添加剂进行了天然气水合物形成的实验研究。分析了各实验体系形成水合物的过冷度。以过冷度为评价指标,评价了各种钻井液添加剂在深水钻井水合物形成过程中的作用。结果表明,在钻井液使用的加量范围内,阳离子聚丙烯酰胺CPAM、两性离子聚合物FA367等对天然气水合物的形成有抑制作用,且随着加量的增加抑制作用增强;磺甲基丹宁SMT、木质素磺酸盐FCLS对天然气水合物的形成有微弱的促进作用,但影响不大。聚合物添加剂的离子类型对天然气水合物的形成影响不大。     

1,3-Dibromo 5,5-dimethylhydantoin (DBH):A novel and efficient catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j] xanthenes under solvent-free conditions

An atom-efficient and environment-friendly approach for the synthesis of aryl-14H-dibenzo[a,j]xanthenes (3a–o) via the one-pot reaction of β-naphthol and aryl aldehydes (1) catalyzed by DBH has been developed. The present approach offers several advantages such as reduced reaction times, moderate temperature, higher yields, solvent free, eco-friendly reaction condition, easy purification and economic availability of the catalyst.     

Velocity-dependent symmetries and non-Noether conserved quantities of electromechanical systems

The theory of velocity-dependent symmetries(or Lie symmetry) and non-Noether conserved quantities are presented corresponding to both the continuous and discrete electromechanical systems.Firstly,based on the invariance of Lagrange-Maxwell equations under infinitesimal transformations with respect to generalized coordinates and generalized charge quantities,the definition and the determining equations of velocity-dependent symmetry are obtained for continuous electromechanical systems;the Lie's theorem and ...