Application of radioactive tracer technique to study the kinetics and mechanism of reversible ion-isotope exchange with strongly basic anion-exchange resin Indion-850

The kinetics of reversible bromide ion-isotope exchange with Indion-850 resin was studied in the concentrations range from 0.0025 to 0.100 M and the temperature varied from 27.0 to 48.0°C. Two sets of experiments were performed: exchange of the inactive resin in the bromide form with the bromide solution spiked with ⁸²Br tracer and exchange of the labeled resin with an inactive bromide solution. For both forward and reverse bromide ion-isotope exchange reactions, the rate constants, amount of bromide ions exchanged, and initial rate of bromide ion exchange were calculated. The rate constants of the forward and reverse reactions are essentially equal. In both cases, the amount of bromide ion exchanged and the initial rate of bromide ion exchange increase with temperature. Published in Russian in Radiokhimiya, 2008, Vol. 50, No. 6, pp. 555–557. The test was submitted by the authors in English.     

Formulation of ternary complexes of glyburide with hydroxypropyl-β-cyclodextrin and other solubilizing agents and their effect on release behavior of glyburide in aqueous and buffered media at different agitation speeds

Glyburide, a sulfonylurea derivative, widely used as hypoglycaemic agent. In the present study, an attempt has been made to investigate the most effective third component which can be used with hydroxylpropyl-β-cyclodextrin (HPβCd) to form a ternary complex with glyburide in order to enhance its dissolution rate, as well as reduce the amount of HPβCd used for formulating the binary complex with glyburide. Moreover, the objective of this study was also to develop a discriminatory dissolution media in order to discriminate the effect of the different solubilizing agents used for formulating the ternary complex system. Sodium lauryl sulphate, Poloxamer-188, Polyvinylpyrrolidone K-30, lactose and l-arginine were used to formulate ternary system along with HPβCd and glyburide. The ternary system formulated with glyburide:HPβCd:l-arginine in a proportion of 1:1:0.5 has shown the fastest dissolution rate when compared to other solubilizing agents. Unbuffered aqueous media with stirring speed 50?rpm has produced the most discriminatory dissolution profiles. The DSC thermograms and the powder X-ray analysis revealed the decrease in crystallinity of the drug. This was an indication of amorphous solid dispersion or molecular encapsulation of the drug into the cyclodextrin cavity.     

45钢送丝激光熔覆成型基础工艺

45钢送丝激光熔覆成型工艺将通过单道及搭接熔覆实验进行研究.送丝方向和角度、送丝速度、激光扫描速度和功率对熔覆质量和效率的影响将首先得到研究.搭接实验旨在研究45钢的最佳搭接率.熔道微观硬度和微观组织的研究旨在证明基于送丝技术的激光熔覆成型可得到致密的金属组织,为后续激光熔覆修复和激光熔覆快速成型打下基础.     

基于逆向工程与快速成型的假体设计和制造

在传统的义耳制作中,通常采用人工雕刻自身软肋骨来完成,其精度及制作效率取决于雕刻师的技巧、经验及审美水平。文章介绍了一种基于激光扫描和快速成形技术制作假体的方法。以义耳设计和制造为例,采用激光扫描仪获取耳朵的轮廓数据,并通过逆向软件生成曲面,最后在快速成型系统中加工出模型。研究结果表明,该集成制造方法可以快速制作出准确逼真的造型,从而为手术的规划提供直接的参考。     

Analysis of mineral content of some medicinal plants by NAA and AAS techniques

Elemental analysis of some medicinal plants used in the Indian Ayurvedic system was performed by employing instrumental neutron activation analysis and atomic absorption spectroscopy. The samples were irradiated with thermal neutrons in a nuclear reactor and the induced activity was counted by γ-ray spectrometry using an efficiency calibrated high resolution high purity germanium detector. Most of the medicinal plants were found to be rich in one or more of the elements under study. The elemental concentration in different medicinal plants and their biological effects on humans are discussed. Published in Russian in Radiokhimiya, 2009, Vol. 51, No. 3, pp. 282–285. The text was submitted by the authors in English.     

基于有限元法的聚碳酸酯激光焊接性能研究

为了揭示焊接参量对焊接质量的影响机理,优化焊接工艺参量,利用超景深显微镜和拉伸试验机对不同功率、焊接速率和材料厚度参量下的焊接强度进行了观察和测试。采用ABAQUS建立3维轴对称物理模型,对焊接过程中的温度分布进行了有限元模拟,并通过正交试验获得了各参量对焊接质量的影响规律。结果表明,激光功率是影响焊接强度的首要因素,其次是焊接速率,材料厚度影响最小;焊接过程中焊接温度越高,焊缝的宽度越大,可能导致熔池材料分解,焊缝中的气泡增多,影响焊接强度。     

Comparative study on iodide and bromide isotopic exchange reactions by application of radioactive tracer technique

In the present investigation, a short lived radioactive tracer isotopes ¹³¹I and ⁸²Br were used to study the kinetics of isotopic exchange reactions. For bromide isotopic exchange reaction, the calculated values of specific reaction rate (min⁻¹), and amount of bromide ions exchanged (mmol) were obtained higher than that for iodide isotopic exchange reaction under identical experimental conditions. For both the exchange reactions it was observed that when the concentration of ionic solution was increased twice, the␣percentage of ions exchanged increases sharply at nearly same specific reaction rate, indicating that concentration greatly influences the exchange reactions.     

Application of radioactive tracer technique for characterization of strongly basic anion-exchange resins duolite A 101D and duolite A 102D<Superscript>1</Superscript>

The radioactive ⁸²Br was used as a tracer to study the bromide self-diffusion reactions. The effect of temperature, concentration of ionic solution, and amount of ion-exchange resin on the kinetics of exchange reactions was examined. Under identical experimental conditions, the specific reaction rate, amount of bromide ions exchanged, and initial rate of bromide ion exchange calculated for Duolite A 101D resin were higher than those calculated for Duolite A 102D resin. The difference in the values calculated for the two resins was attributed to their water-holding capacities. The probable mechanism of bromide isotope exchange reaction was also predicted by comparing the specific reaction rate of rapid and slow exchange process. It is expected that the same technique can be employed to assess the efficiency of various ion exchangers under different operating conditions.     

Influence of formulation parameters on dissolution rate enhancement of glyburide using liquisolid technique

The aim of this study was to investigate the use of liquisolid technique in improving the dissolution of glyburide in a solid dosage form. This study was designed to evaluate the effects of different formulation variables, i.e. type of non-volatile liquid vehicles and drug concentrations, on drug dissolution rates. The liquisolid tablets were formulated with Propylene glycol, as liquid vehicle. Microcrystalline cellulose was used as a carrier material, silica as a coating material and croscaremellose as a disintegrant. In vitro drug dissolution profiles of the liquisolid formulations were studied and compared with direct compressed non-micronized and micronized tablets of glyburide using USP II, paddle apparatus at 50 rpm for 60 min using 900 ml of 0.05 M Phosphate Buffer, pH 7.5. The stability studies showed that the dissolution profiles of liquisolid tablets prepared with propylene glycol were not affected by ageing significantly, as f2 value found between aged and fresh samples was 51.92. Differential scanning calorimetry revealed that the drug has got solubilized in the liquid vehicle. This was further supported by the powder X-ray diffraction studies of pure drug and the liquisolid powder system. It can be concluded that it is possible to load poorly soluble drug into liquisolid tablets by addition of PVP to the liquid vehicle. This is valuable for the preparation of liquisolid tablets of poorly soluble drugs. The liquisolid tablets prepared with PVP showed a remarkably improved dissolution rate in comparison with DC tablet and other formulations.     

45钢送丝激光熔覆温度场及应力场模拟

针对激光熔覆过程的特点,基于有限元分析软件ANSYS,对45钢送丝激光熔覆过程的温度场和应力场进行三维数值动态模拟.建模时采用实体单元和表面单元相结合的方式,采用参数化设计划分网格,施加热源载荷,设定初始条件和基本边界条件,对流边界条件进行求解.分析了激光熔覆过程中温度场在工件上的分布规律,揭示了整个时间历程上应力强度的变化规律,为提高激光熔覆质量提供了理论依据.