Flow-injection chemical vapor-generating procedure for the determination of Au by atomic absorption spectrometry

Volatile Au species in an acidified medium were generated at room temperature by reduction with NaBH₄ in acidified aqueous medium using a flow-injection chemical vapor-generation atomic absorption spectrometric (FI–CVG–AAS) system in the presence of micro amounts of sodium diethyldithiocarbamate (DDTC). Precision of 2.0% RSD (n = 11, 2.0 mg L^–1 level) was obtained at a sample throughput of 180 h^–1. A detection limit of 24 ng mL^–1 (3σ) was obtained with 300 μL sample solution. The method was used for the determination of gold in ore sample digests, and the results obtained agreed well with those obtained by flame AAS.     

Study on air pollution monitoring in Korea using low volume air sampler by instrumental neutron activation analysis

The aim of this research was to enhance the use of nuclear analytical techniques for air pollution studies and to study the feasibility of the use of instrumental neutron activation analysis (INAA) as a routine monitoring tool to reveal environmental pollution sources. For the collection of air particulate samples, the Gent stacked filter unit, low volume sampler with Nucleopore membrane filters were used. Trace elements in samples collected at two suburban residential sites, Taejon and Wonju city in the Republic of Korea, were analyzed by INAA. Variations of the elemental concentrations were measured monthly and the enrichment factors were calculated for the fine (<2 μm EAD) and coarse size (2–10 μm EAD) fractions. The analytical data were treated statistically to estimate the relationship between the two variables, the concentrations of elements and the total suspended particulate matter. The results were used to describe the emission source and their correlation.     

Ni0.8Co0.2-SiO2颗粒膜中的Hall效应

对用离子束溅射制备的Ni_0.8Co_0.2-SiO₂颗粒膜的Hall效应进行了研究.当Ni_0.8Co_0.2合金的含量为43vol%时,在9.5×10⁵A/m的外磁场下,样品的室温Hall电阻率达6.3μΩ·cm ,高于普通磁性金属两个数量级以上,还研究了不同NiCo组分样品的电阻率与温度的关系（95—300K）,发现x＜x_c(逾渗组分)时,电阻率与-logT成正比,电阻温度系数为负;当x＜x_c时,逐渐呈现金属性;而当x≈x_c时,为过渡态.还用透射电子显微镜和振动样品磁强计等手段对样品的微结构和磁性进行了对比研究,表明金属-绝缘体颗粒膜中在逾渗阈值附近有较大的Hall效应,这与样品的微结构有密切关系. 关键词：     

退火对Co35(SiO2)65颗粒膜巨磁电阻效应的影响

采用多靶离子束溅射镀膜机制备了一系列不同退火温度的Co₃₅(SiO₂)₆₅（体积百分数）颗粒膜样品,发现样品的巨磁电阻效应随着退火温度T_a的升高而单调下降.应用磁力显微镜对样品的磁结构进行了观测,发现随着退火温度的升高,近邻的Co颗粒的磁矩倾向于平行排列,形成磁畴结构,从而导致Co₃₅(SiO₂)₆₅颗粒膜巨磁电阻效应单调下降. 关键词：     

Peremolv SU(1,1)相干叠加态的二阶量子关联特性研究

本文首先讨论了Barut-GirardelloSU(1,1)相干叠加态在Bargmann指数k≠1/2时的二阶量子关联特性。发现随着Bargmann指数的增大,Barut-Girardello奇相干态呈现反关联的区域变大。然后提出并研究了PeremolovSU(1,1)相干叠加态。Peremolov奇相干态可呈现反关联,并且随着Bargmann指数的增加,反关联程度变弱,反关联区域变小。     

The kinetics of polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol using benzyltriethylammonium chloride as a phase‐transfer catalyst

The phase‐transfer catalyzed polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol was carried out using benzylethylammonium chloride in a two‐phase system of an aqueous alkaline solution and benzene at 60 °C under nitrogen atmosphere. The rate of polycondensation was expressed as the combined terms of quaternary onium cation and 4,4′‐isopropylidenediphenolate anion rather than the feed concentration of catalyst and 4,4′‐isopropylidenediphenol. The measured concentrations of hydroxide and chloride anion in the aqueous solution and α,α′‐dichloro‐p‐xylene in the organic phase were used to obtain the reaction rate constant with the integral method, and to analyze the polycondensation mechanism with a cyclic phase‐transfer initiation step in the heterogeneous liquid–liquid system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3059–3066, 2000     

A thermodynamic theory on the nonlinear viscoelasticity of glassy polymers, 1. Constitutive equation

We have developed a nonlinear viscoelastic constitutive equation, which can predict the yield behavior of polymers. This constitutive equation results from the viewpoints that the plastic flow of glassy polymers can be described by a soliton, which is expected to unify the existing concepts for viscoelasticity and yield of glassy polymers, such as dislocation, disclination and free volume. Although our approach is based on molecular concepts and irreversible thermodynamics, it is phenomenological.     

Controlled Release of Insulin Based on Temperature and Glucose Dual Responsive Biomicrocapsules

The treatment of diabetes lies in developing novel functional carriers, which are expected to have the unique capability of monitoring blood glucose levels continuously and dispensing insulin correctly and timely. Hence, this study is proposing to create a smart self-regulated insulin delivery system according to changes in glucose concentration. Temperature and glucose dual responsive copolymer microcapsules bearing N-isopropylacrylamide and 3-acrylamidophenylboronic acid as main components were developed by bottom-spray coating technology and template method. The insulinoma β-TC6 cells were trapped in the copolymer microcapsules by use of temperature sensitivity, and then growth, proliferation, and glucose-responsive insulin secretion of microencapsulated cells were successively monitored. The copolymer microcapsules showed favorable structural stability and good biocompatibility against β-TC6 cells. Compared with free cells, the biomicrocapsules presented a more effective and safer glucose-dependent insulin release behavior. The bioactivity of secreted and released insulin did not differ between free and encapsulated β-TC6 cells. The results demonstrated that the copolymer microcapsules had a positive effect on real-time sensing of glucose and precise controlled release of insulin. The intelligent drug delivery system is supposed to mimic insulin secretion in a physiological manner, and further provide new perspectives and technical support for the development of artificial pancreas.