Matrix Isolation ir Spectra of Methyl Acetate II.Stoechiometry of Methyl Acetate…H2O Complexes in AR Matrices. Comparison with Methyl Benzoate…H20

The earlier reported matrix system methylacetate/ H₂O/Ar has been reinvestigated by IR spectroscopy. The complex band pattern of the ester ν _c=0 and the water ν₃, ν₁ and ν₂ modes can be explained by the coexistence of 1:1, linear 1:2 and linear 2:1 H-bonded complexes. The study of methyl benzoate/H₂O/Ar supports the proposed interpretation.     

用于虚拟化环境的进程隔离方法研究与实现

针对虚拟化环境中用户进程运行安全问题,提出一种适用于虚拟化环境的进程隔离方法.该方法引入安全域作为进程隔离保护的基本单元,安全域是进程以及进程运行过程中依赖的环境构成的整体,通过建立安全域之间的依赖关系和安全域之间信息的交换规则,确保进程初始安全和运行过程中的隔离性.给出了安全域的相关概念和形式化描述,以及安全域之间信息流交换和依赖关系的建立方法和相关证明.以Xen虚拟化系统为基础,给出了该保护方法的具体实现以及实验结果,实验结果分析表明:该方法在虚拟化环境中能够抵御多种攻击手段,额外执行开销不超过10%.     

Purification of angiotensin‐converting enzyme from human plasma and investigation of the effect of some active ingredients isolated from Nigella sativa L. extract on the enzyme activity

In the present study, one‐step purification of angiotensin‐converting enzyme (ACE, peptidyldipeptidase A, EC 3.4.15.1), responsible for regulation of blood pressure, was achieved using affinity chromatography from human plasma. The enzyme was purified 12,860‐fold with a specific activtiy of 5080 EU/mg protein. Optimum temperature and pH were determined for the enzyme as 35–40°C and pH 7.4–7.5, respectively. The purity of ACE was determined by SDS–PAGE and the enzyme showed two bands at 60 and 70 kDa on the gel. The native molecular weight of ACE was found to be 260 kDa by gel filtration chromatography, demonstrating that the enzyme has a heterodimeric structure. Natural fatty acids of Nigella sativa (Ranunculaceae) were isolated by means of column chromatography. The structures of these compounds were determined using NMR and GC‐MS. The results showed that high concentrations of linoleic, oleic and palmitic acids were isolated from the plant. The effect of six fractions (Fr 1–6) on ACE activity was examined. Fraction 3 increased the ACE activity while the other fractions decreased the enzyme activity. The concentrations of the fractions inhibiting the half‐maximum activity of the enzyme were calculated as 1.597 mg/mL for Fr 1, 0.053 mg/mL for Fr 2, 0.527 mg/mL for Fr 4, 0.044 mg/mL for Fr 5 and 0.136 mg/mL for Fr 6 using a Lineweaver–Burk graph.     

New designed DNA light switch Ruthenium complexes as DNA photocleavers and Topoisomerase I inhibitors

Two ruthenium complexes containing a new ligand phipz (phipz = 2‐(1,10‐phenanthroline)‐1H‐imidazo[4,5‐b]phenazine) were designed and synthesized. These complexes were found to inhibit the DNA supercoiled relaxation mediated by topoisomerase I (topo I), cleave DNA under irradiation and bind to calf thymus DNA through intercalative mode. Furthermore, complex 2 shows higher photocleavage activity, topo I inhibition activity and DNA affinity than complex 1 . Additionally, introduction of phenazine unit may be the reason that two complexes exhibit DNA ‘light switch’ behavior. The present work shows that two complexes might be potential as new DNA ‘light switches’, DNA photocleavers and topo I inhibitors.     

Flash Vacuum Pyrolysis: Techniques and Reactions

Flash vacuum pyrolysis (FVP) had its beginnings in the 1940s and 1950s, mainly through mass spectrometric detection of pyrolytically formed free radicals. In the 1960s many organic chemists started performing FVP experiments with the purpose of isolating new and interesting compounds and understanding pyrolysis processes. Meanwhile, many different types of apparatus and techniques have been developed, and it is the purpose of this review to present the most important methods as well as a survey of typical reactions and observations that can be achieved with the various techniques. This includes preparative FVP, chemical trapping reactions, matrix isolation, and low temperature spectroscopy of reactive intermediates and unstable molecules, the use of online mass, photoelectron, microwave, and millimeterwave spectroscopies, gas‐phase laser pyrolysis, pulsed pyrolysis with supersonic jet expansion, very low pressure pyrolysis for kinetic investigations, solution‐spray and falling‐solid FVP for involatile compounds, and pyrolysis over solid supports and reagents. Moreover, the combination of FVP with matrix isolation and photochemistry is a powerful tool for investigations of reaction mechanism.     

衰减振荡电流下火花电阻的光谱诊断

气体开关是脉冲功率系统的关键部件,开关的火花通道阻抗直接影响负载电压的陡度及其能量传输效率。提出一种光谱学诊断方法,通过对火花通道成像光谱的时空分辨测量,获得通道半径及电导率,从而计算时变的火花电阻。光谱测量结果表明,氮气间隙火花放电通道电子温度为2~3eV,通道电导率先增大后减小,最大值约16 000S,随着放电发展,火花通道电阻从绝缘状态快速跌落并趋于稳定值,时变趋势与电学计算结果基本吻合。3~100kPa范围内,随着气压增大,放电通道半径减小,火花通道电阻增大。     

Double rolling isolation systems: A mathematical model and experimental validation

Rolling isolation systems (RISs) protect fragile building contents from earthquake hazards by decoupling horizontal floor motions from the horizontal responses of the isolated object. The RISs in use today have displacement capacities of about 20 cm. This displacement capacity can be increased by stacking two systems. This paper presents and evaluates a complete non-linear model of the coupled dynamics of double RISs. The model is derived through the fundamental form of Lagrange׳s equation and involves the non-holonomic constraints of spheres rolling between non-parallel surfaces. The derivation requires the use of two translating and rotating reference frames. The proposed model is validated through comparisons between experimentally measured and numerically predicted time histories and peak response quantities—total acceleration and relative displacement. The effects of the initial conditions, the mass of the isolated object, and the amplitude and period of the disturbance on the system׳s performance are assessed.     

Heavy-Atom Tunneling in Semibullvalenes: How Driving Force,Substituents, and Environment Influence the Tunneling Rates

The Cope rearrangement of selectively deuterated isotopomers of 1,5-dimethylsemibullvalene 2 a and 3,7-dicyano-1,5-dimethylsemibullvalene 2 b were studied in cryogenic matrices. In both semibullvalenes the Cope rearrangement is governed by heavy-atom tunneling. The driving force for the rearrangements is the small difference in the zero-point vibrational energies of the isotopomers. To evaluate the effect of the driving force on the tunneling probability in 2 a and 2 b , two different pairs of isotopomers were studied for each of the semibullvalenes. The reaction rates for the rearrangement of 2 b in cryogenic matrices were found to be smaller than the ones of 2 a under similar conditions, whereas differences in the driving force do not influence the rates. Small curvature tunneling (SCT) calculations suggest that the reduced tunneling rate of 2 b compared to that of 2 a results from a change in the shape of the potential energy barrier. The tunneling probability of the semibullvalenes strongly depends on the matrix environment; however, for 2 a in a qualitatively different way than for 2 b .