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.     

Monitoring of total antimony and its species by ICP-MS and on-line ion chromatography in biological samples from patients treated for leishmaniasis

Results from a study are reported in which patients with leishmaniasis were monitored by whole blood, blood plasma, urine, and hair analysis, before, during, and after intramuscular administration of N-methyl meglumine antimoniate. Quadrupole ICP-MS was used for the detection of antimony and on-line ion chromatography for the separation of its species. After typically 30 consecutive daily injections of 5 mg antimony per kg of body weight, Sb concentrations of up to 250 microg L(-1) in whole blood and plasma, and 60 mg of Sb per gram of creatinine in urine, were measured 24 h after drug administration. Antimony in hair samples of these patients showed concentrations of up to 24 microg g(-1). Speciation studies of Sb5+ and Sb3+ in drug, urine, and plasma samples were performed by ion chromatography using a Hamilton PRP-100X anion exchange column and EDTA (2 or 20 mM, pH 4.7) as the mobile phases. Repeatability of elution time and peak area measurements for a 0.125 ng spike were <1.2% and <3.5%, respectively. Method detection limits for both species, using a 1:10 diluted urine or plasma sample, were typically 1.6 microg L(-1). The procedure was capable of separating the very intense drug peak from its inorganic species, thus permitting the first studies on the bio-transformation of N-methyl meglumine antimoniate to Sb5+ and Sb3+ in the human body.     

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.     

Momentum analysis of kaon and pion pairs produced from time-like photons at 1.6 GeV energy

We present results for the total cross section of e⁺e^? annihilation into two hadrons at 1.6 GeV: σ_ππ = σ_KK = (1.8 ± 1.1) × 10^-33 cm².From these values we obtain the time-like electromagnetic form factors these mesons: |F_π|² = 0.24 ± 0.14 and |F_K|² = 0.46 ± 0.26.     

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。     

A Simple Procedure for Decomposition of Human Hair Using Polypropylene Vials for Selenium Determination by Hydride Generation Atomic Absorption Spectrometry

Two procedures for wet decomposition of human hair samples were compared for selenium determination by hydride generation atomic absorption spectrometry (HGAAS). These procedures involve treatment with HNO₃/H₂O₂ and H₂SO₄/HNO₃, respectively, using small disposable polypropylene (PP) vials. Analytical steps from weighing to dilution were performed in the same individual PP vial. After sample weighing (10±3mg) and reagent addition, decomposition was performed in a conventional oven (20h, 100°C). Addition of sulfamic acid prior to HGAAS measurements was necessary to minimize interference due to residual nitrogen oxides from the decomposition step. The accuracy was estimated using certified hair reference analysis which yielded an agreement higher than 97% (recovery tests). The absolute limit of detection was 1.2ng (3 s; n=10), corresponding to 0.12µgg^–1 in the dry sample.     

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.     

Search for narrow resonances in e+e− annihilation into hadrons at adone in the mass region 2.5–3.0 GeV/c2

The mass region 2.5 to 3.0 GeV/c² has been searched for evidence of ψ-like narrow resonance in e⁺e^? annihilation into hadrons. No evidence for new narrow resonances has been found with a sensitivity of about the 10% of the integrated cross section of the J/ψ (3100).