The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。     

Dynamic wetting: hydrodynamic or molecular-kinetic?

The dynamic wetting behavior of simple liquids (water, glycerin, formamide, ethylene glycol, and a mixture of water and ethylene glycol) and polydimethylsiloxane (PDMS) oils with different viscosities has been investigated. The hydrodynamic, molecular-kinetic, and combined molecular-hydrodynamic models have been applied to the experimental results to evaluate the models' adequacy. Our work suggests that the molecular displacement, i.e., the adsorption and desorption process, seems to be dominant for the simple liquids investigated. For polydimethylsiloxanes, our work suggests that none of the evaluated models is sufficient to explain the experimentally observed dependence of the dynamic contact angle on contact velocity. This work, to the best of our knowledge, provides the first extensive comparison of the three models with experimental data over a wide range of viscosity. In addition, we have investigated the contact angle hysteresis and conclude that it is a strong function of the contact speed, the interactions between the fluids and the substrate, and the fluid viscosity.     

Mobility and in situ aggregation of charged microparticles at oil-water interfaces

Particle mobility, aggregate structure, and the mechanism of aggregate growth at the two-dimensional level have been of long-standing interest. Here, we use solid-stabilized emulsions as a model system to investigate the mobility of charged microparticles at poly(dimethylsiloxane) (oil)-water interfaces using confocal laser scanning microscopy. Remarkably, the rate of diffusion of the charged colloidal-sized polystyrene particles at the oil-water interface is only moderately slower than that in the bulk water phase. The ambient diffusion constant of solid particles is significantly reduced from 1.1 x 10(-9) cm2/s to 2.1 x 10(-11) cm2/s when the viscosity of the oil phase increases from 5 cSt to 350 cSt. In addition, we successfully observe the in situ structural formation of solid particles at the oil-water interface.     

In silico targeting PAD4 for the treatment of rheumatoid arthritis

Structural Chemistry - Rheumatoid arthritis (RA) is an autoimmune disorder that causes chronic inflammation with periodic bursts of activity in multiple synovial joints which lead to irreversible...     

Nuclear orbiting and anomalies in nuclear reactions

In this paper, we report our measurements of back-angle oxygen and carbon particle yields from ¹⁶O+⁸⁹Y, ¹²C+⁹³Nb reactions forming the same compound nucleus ¹⁰⁵Ag at the same excitation energy and spin distribution. We find anomalously large oxygen yield and entrance channel dependence at high excitation energies from ¹⁶O+⁸⁹Y reaction implying formation of a dinuclear orbiting complex. Possible connection between nuclear orbiting and fast fission is also discussed.