Rate constants for chemical exchange between water and hydroxyl protons in natural compounds evaluated with NMR two-dimensional exchange spectroscopy and geometric average method

Nuclear magnetic resonance two-dimensional exchange spectroscopy has been applied to measure the chemical exchange rate constants between water and hydroxyl protons in three natural organic compounds which contain four to eight hydroxyl groups. In data treatment, the simple geometric average method has been used. Application of the geometric average method to assumed exchange systems has indicated that the method is reliable.     

计算氢同位素水分子汽化焓的比较法

本文首次提出计算氢同位素水分子汽化焓的比较法,得到0～374℃时H2O,D2O,DTO和T2O的汽化焓,并提出用D2从含氚重水中分离出DT气的适宜温度.     

Study of the glow discharge in inert gases with water vapor

The behavior of the water vapor concentrations and fragments in wet plasma is studied. The results of plasma-chemical modeling are compared with the results of direct measurements of water molecule dissociation in plasma.     

A continuous stream flash evaporator for the calibration of an IR cavity ring-down spectrometer for the isotopic analysis of water

A new technique for high-resolution simultaneous isotopic analysis of δ1?O and δD in liquid water is presented. A continuous stream flash evaporator has been designed that is able to vapourise a stream of liquid water in a continuous mode and deliver a stable and finely controlled water vapour sample to a commercially available infrared cavity ring-down spectrometer. Injection of sub-microlitre amounts of the liquid water is achieved by pumping liquid water sample through a fused silica capillary and instantaneously vapourising it with 100% efficiency in a home-made oven at a temperature of 170 °C. The system's simplicity, low power consumption and low dead volume together with the possibility for automated unattended operation provides a solution for the calibration of laser instruments performing isotopic analysis of water vapour. Our work is mainly driven by the possibility to perform high-resolution online water isotopic analysis on continuous-flow analysis (CFA) systems typically used to analyse the chemical composition of ice cores drilled in polar regions. In the following, we describe the system's precision and stability and sensitivity to varying levels of sample size and we assess the observed memory effects. A test run with standard waters of different isotopic compositions is presented, demonstrating the ability to calibrate the spectrometer's measurements on a VSMOW scale with a relatively simple and fast procedure.     

A continuous stream flash evaporator for the calibration of an IR cavity ring-down spectrometer for the isotopic analysis of water

A new technique for high-resolution simultaneous isotopic analysis of δ¹⁸O and δD in liquid water is presented. A continuous stream flash evaporator has been designed that is able to vapourise a stream of liquid water in a continuous mode and deliver a stable and finely controlled water vapour sample to a commercially available infrared cavity ring-down spectrometer. Injection of sub-microlitre amounts of the liquid water is achieved by pumping liquid water sample through a fused silica capillary and instantaneously vapourising it with 100% efficiency in a home-made oven at a temperature of 170?°C. The system's simplicity, low power consumption and low dead volume together with the possibility for automated unattended operation provides a solution for the calibration of laser instruments performing isotopic analysis of water vapour. Our work is mainly driven by the possibility to perform high-resolution online water isotopic analysis on continuous-flow analysis (CFA) systems typically used to analyse the chemical composition of ice cores drilled in polar regions. In the following, we describe the system's precision and stability and sensitivity to varying levels of sample size and we assess the observed memory effects. A test run with standard waters of different isotopic compositions is presented, demonstrating the ability to calibrate the spectrometer's measurements on a VSMOW scale with a relatively simple and fast procedure.     

A new DWBA method for two-nucleon transfer with heavy ions

A formalism is developed for calculating two-nucleon transfer cross sections. It is intended mainly for heavy-ion induced reactions. The single-nucleon wave functions are expanded in a harmonic oscillator series. A Moshinsky transformation then yields a series of terms containing the relative and c.m. coordinates. It is found that only a limited number of these terms are needed.     

Fine hexaferrite particles for perpendicular recording prepared by the coprecipitation method in the presence of an inert component

The modified coprecipitation method has been shown to be suitable for preparing BaFe_2y−2χCo_χTi_χO₁₉ powder with narrow particle size distribution (50–80 nm). The phase composition of the intermediate products during the synthesis has been investigated by DTA, TG, X-ray analysis and Mössbauer spectroscopy. The dependence of the dc measured specific magnetization and coercivity on the Ti-Co content and annealing temperature is presented.     

Numerical study of tidal water mass exchange in an inland sea with archipelago

The tidal water mass exchange in an inland sea with archipelago is numerically studied adopting the control volume based 2-dimensional finite element method to cope with the complex coastline. Yatusiro Sea situated in the south-west of Kyushu, Japan is the model inland sea of our study. Water mass exchange by semi-diurnal (M ₂) tidal flow is investigated by the dispersion of Lagrangean particles and by the Eulerean tidal residual flow. Main results are as follows: i) Except the southern part of Ariake Sea and Nagashima Strait, the most part of Lagrangean particles still stay in the areas after 20 periods. ii) The particles in Ariake Sea (Yatusiro Sea) flow into Yatusiro Sea (Ariake Sea) through Yanagi-seto (Misumi-seto). iii) The particles in Hachiman-seto flow into Yatusiro Sea through Oh-seto and Gannojiri-seto. iv) The particles in the south part of Yatusiro Sea flow into Nagashima Strait through Mebuki-seto and Ikara-seto. v) In the Eulerean tidal residual flow, there exists a clock-wise vortex around Shishijima island in Yatusiro Sea.     

A spectroscopic method of determining the isotopic composition of magnesium

The composition is determined from the isotopic shift of the Mgl 880.68 nm line. The coefficient of variation for magnesium metal is 1.8%, but 4% for magnesium oxide. Several spectroscopic analyses can be performed in the time needed for one mass-spectrometer analysis, which reduces the error of analysis by a factor two or three.We are indebted to Professor A.N. Zaidel for valuable advice and to N. A. Novozhilova for assistance with the measurements.     

Emission characteristics and parameters of gas-discharge plasma in mixtures of heavy inert gases with chlorine

The ultraviolet (UV) radiation from longitudinal glow-discharge plasma in three- and four-component mixtures of argon, krypton, and xenon with chlorine has been investigated. The total radiation of Ar, Kr, and Xe monochlorides and chlorine molecules in the spectral range 170–310 nm has been optimized with respect to the composition and the pressure of gas mixtures, as well as the discharge current. The mean output power, the electric power of discharge, and the efficiency of a broadband low-pressure exciplex halogen lamp have been determined. Parameters of the glow discharge in Ar-Kr-Cl₂ and Kr-Xe-Cl₂ mixtures have been simulated numerically. The electron energy distribution functions have been determined through the solution of the Boltzmann kinetic equation. These functions have been used to calculate the plasma parameters, namely, electron transfer characteristics, specific losses of discharge power for electronic processes, and ionization and attachment coefficients.     

A simple water model in the presence of inert Lennard-Jones obstacles II: the hydrophobic effect

Using Monte Carlo computer simulations, hydrophobic effect for a non-polar particle with the diameter of a water molecule was studied in water, confined within a disordered matrix. Freely mobile two-dimensional Mercedes-Benz water was put in a disordered, but fixed, matrix of Lennard-Jones disks. Influence of temperature and matrix properties on the thermodynamic quantities of a non-polar solute solvation was studied. The hydrophobic effect is changed by the presence of the obstacles. Smaller matrix particles change the solute–water structure and thermodynamics drastically, as it was also observed for the properties of pure confined water. The study is bringing new scientific important observations in understanding the role of hydrophobic forces under confinement.     

水体重金属激光诱导击穿光谱定量分析方法对比研究

建立了适用于激光诱导击穿光谱探测的多元线性回归、神经网络回归和支持向量机回归三种定量反演算法模型, 以水体重金属Ni为例进行了回归实验测试和对比分析. 多元线性回归、神经网络回归和支持向量机回归的平均相对标准偏差分别为7.60%, 4.86%, 2.35%; 最大相对标准偏差分别为23.35%, 15.20%, 8.29%; 平均相对误差分别为25.98%, 10.58%, 2.72%, 最大相对误差分别为116.47%, 47.38%, 9.89%. 研究为进一步实现水中痕量金属元素的快速定量分析提供了方法和数据参考. 关键词： 光谱学 激光诱导击穿光谱 支持向量机回归 重金属     

超声波在金属溶剂萃取及离子交换中的应用

本文综述了超声波在金属溶剂萃取和离子交换中的最新应用研究成果，展望了声化学在该领域中的应用前景。     

Emission characteristics of a glow discharge in a mixture of heavy inert gases with iodine vapor

The results of a systematic investigation of the emission characteristics of a low-pressure UV excimer-halogen lamp pumped by a longitudinal dc glow discharge are presented. The discharge was initiated in mixtures of heavy inert gases with iodine vapor at a total pressure of 100–2000 Pa and a power deposited into the plasma of 10–100 W. Current-voltage characteristics of the glow discharge and emission spectra of the plasma in the region of 190–360 nm are studied. The radiation intensity at the resonance line of the iodine atom (206.2 nm) and the intensity at the peaks of the XeI(B-X) (253 nm) and I₂(B-X) (342 nm) emission bands are analyzed as functions of the pressure and partial composition of the mixtures of Ar, Kr, and Xe with iodine vapor, as well as the electric power of the glow discharge. The most efficient gas mixtures are determined for an electric-discharge UV iodine vapor lamp with continuous-wave emission and a long service life before a change of the mixture is required.     

Study of the heavy molecular states in the quark model with meson exchange interaction

Some charmonium-like resonances such as X(3872) can be interpreted as possible D^(*)D^(*) molecular states. Within the quark model, we study the structure of such molecular states and the similar B^(*)D^(*) molecular states by taking into account the light meson exchange (π, η, ρ, ω and σ) between two light quarks from different mesons.     

On one pion exchange potential with quark exchange in the resonating group method

The effect of quark exchange between different nucleons on the one pion exchange potential is studied in the framework of the resonating group method. The calculated phase shifts including the one pion exchange potential with quark exchange in addition to the one gluon plusσ meson exchange are shown to be consistent with experiments. Especially thep-wave phase shifts are improved by taking into account the quark exchange on the one pion exchange potential.