Investigations with the finite element method on the Cyber 205

We are trying to investigate systematically the application of the finite element method (FEM) for solving the Schrödinger equation. The present paper is devoted to the calculation of vibrational transition probabilities for the collinear reactive system A + BC (i.e. H+H₂ and their isotopes). The calculations are fully two-dimensional and the results are compared with earlier FEM calculations and conventional basis set expansion methods using the the R-matrix or S-matrix propagation.We made extensive analysis of FEM on the vector-computer Cyber 205 and developed a vector code for the efficient use in two dimensions, so that in the near future applications even in three dimensions will be possible.For the hydrogen exchange reactions we investigated the following isotope combinations: (a) H + H₂, b) H + DH, D + HD and H + MuH (symmetric reaction), (c) D + HH, H + DD and Mu + DD (asymmetric reaction). We calculated the transition probabilities for up to five open vibrational channels and found excellent agreement with known exact values.     

Comparison of the sequential simplex method and linear solvent strength theory in HPLC gradient elution optimization of multicomponent flavonoid mixtures

Summary Using a camomile flavonoid extract as the sample and four different reversed-phase partition systems, the ability of the Simplex procedure to produce optimum gradient separation of unknown multicomponent mixtures was checked against the linear solvent strength (LSS) gradient elution theory. On the same partition systems the mean solvent strenghts were measured by experimentally determined logk vs. mobile phase composition plots. These mean solvent strengths are compared to those inferred from the optimum gradients and the usefulness of LSS theory in multicomponent mixture gradient elution optimization is discussed.Dadicated to Prof. Dr. A Liberti on the occasion of his 70th birthday.     

Structure, Stability and Vibrational Spectra of LaC_5~n(n=-1,0,+1) Clusters

用密度泛含方法研究了ＬａＣ５ｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性及振动光谱，对这个六原子体系提出了三种可能构型，点群结构为Ｃ２ｖ对称性．第一个构型为Ｌａ接在弯曲的Ｃ５链上，第二个是Ｌａ通过二个键与Ｃ５环相连第三个是Ｌａ通过一个键与Ｃ５环相连；结果表明，第一个构型即当Ｌａ接在弯曲的Ｃ５链上时能量最低．振动光谱分析指出，当ｎ＝－１时，第二个构型为局域极小值；当ｎ＝＋１时，第一个和第二个构型为局域极小值；对ｎ＝０，局域极小值没有找到．     

用石墨炉原子吸收法测定水质中微量砷,硒的探讨

采用石墨炉原子吸收法测定水中微量砷，硒，经大量实验条件摸索，选择不同仪器分析工作条件，找出了最佳升温程序条件，特别是原子化时气流控制，使分析方法的检出限降低为：Ａｓ０．６μｇ／Ｌ，Ｓｅ０．５μｇ／Ｌ。线性范围；Ａｓ０．０００－０．１２０ｍｇ／Ｌ，Ｓｅ０．０００－０．０２４ｍｇ／Ｌ；精密度，相对标准偏差分别为：Ａｓ１．２６％，３．６７％，Ｓｅ２．５６％，４．５７％，回收率为：Ａｓ９８．０％－１１０．     

Developing On-Site Trace Level Speciation of Lead,Cadmium and Zinc by Stripping Chronopotentiometry (SCP): Fast Screening and Quantification of Total Metal Concentrations

Electrochemical stripping techniques are interesting candidates for carrying out onsite speciation of environmentally relevant trace metals due to the existing low-cost portable instrumentation available and the low detection limits that can be achieved. In this work, we describe the initial analytical technique method development by quantifying the total metal concentrations using Stripping Chronopotentiometry (SCP). Carbon paste screen-printed electrodes were modified with thin films of mercury and used to quantify sub-nanomolar concentrations of lead and cadmium and sub-micromolar concentrations of zinc in river water. Low detection limits of 0.06 nM for Pb(II) and 0.04 nM for Cd(II) were obtained by the standard addition method using a SCP deposition time of 180 s. The SCP results obtained for Pb(II) and Cd(II) agreed with those of inductively coupled plasma mass spectrometry (ICP-MS). The coupling of SCP with screen-printed electrodes opens up excellent potential for the development of onsite speciation of trace metals. Due to the low analysis throughput obtained for the standard addition method, we also propose a new, more rapid screening Cd(II) internal standard methodology to significantly increase the number of samples that can be analyzed per day.     

Supercritical Fluid Extraction of Phenolic Compounds from Mango (Mangifera indica L.) Seed Kernels and Their Application as an Antioxidant in an Edible Oil

Phenolic compounds from mango (M. indica) seed kernels (MSK) var. Sugar were obtained using supercritical CO₂ and EtOH as an extraction solvent. For this purpose, a central composite design was carried out to evaluate the effect of extraction pressure (11–21 MPa), temperature (40–60 °C), and co-solvent contribution (5–15% w/w EtOH) on (i) extraction yield, (ii) oxidative stability (OS) of sunflower edible oil (SEO) with added extract using the Rancimat method, (iii) total phenolics content, (iv) total flavonoids content, and (v) DPPH radical assay. The most influential variable of the supercritical fluid extraction (SFE) process was the concentration of the co-solvent. The best OS of SEO was reached with the extract obtained at 21.0 MPa, 60 °C and 15% EtOH. Under these conditions, the extract increased the OS of SEO by up to 6.1 ± 0.2 h (OS of SEO without antioxidant, Control, was 3.5 h). The composition of the extract influenced the oxidative stability of the sunflower edible oil. By SFE it was possible to obtain extracts from mango seed kernels (MSK) var. Sugar that transfer OS to the SEO. These promissory extracts could be applied to foods and other products.     

炼铝用碳阳极中碱金属氧化物作用机理的量子化学研究

本文应用CNDO/2法研究了炼铝用碳阳极中添加碱金属氧化物的吸附行为, 通过优化得到了吸附的最佳模型, 考察了吸附结合能随分子间距的变化, 进而给出了碱金属氧化物在碳阳极中作用的机理。量子化学计算结果表明: 碱金属氧化物添加到炼铝用碳阳极中起传输电子的电桥作用, 是碳阳极在空气中氧化反应以及铝电解时生成氧气的氧化反应的催化剂; 理论计算和实验结果二者吻合较好, 可以用来解释若干实验结果。     

Analysis of Mercury in Skin Lightening Cream by Microwave Plasma Atomic Emission Spectroscopy (MP-AES)

This research aimed at developing an analysis method, which was optimized and validated to determine the content of mercury in skin lightening cream discovered in the market in Bandar Lampung, Indonesia, through the use of microwave plasma atomic emission spectroscopy (MP-AES). The optimization on the analysis method was conducted on pump rate, viewing position, and reductant concentration in order to obtain the highest mercury emission intensity, while the solution stability was optimized to know the stability of mercury in the solution. The result showed that the method developed had precision with a relative standard deviation of 2.67%, recovery value of 92.78%, and linearity with an r value of 0.993, respectively. The sensitivity of the instrument detection had a limit of analysis method detection and quantification of 0.59 and 1.98 µg/L, respectively. The results of the test of the lightening cream (8 of 16 samples) positively contained mercury in the range of 422.61–44,960.79 ng/g. Therefore the method of analysis developed may be used for routine analysis of chemicals in any cosmetics products.     

Fabrication of Alginate-Based O/W Nanoemulsions for Transdermal Drug Delivery of Lidocaine: Influence of the Oil Phase and Surfactant

Transdermal drug delivery of lidocaine is a good choice for local anesthetic delivery. Microemulsions have shown great effectiveness for the transdermal transport of lidocaine. Oil-in-water nanoemulsions are particularly suitable for encapsulation of lipophilic molecules because of their ability to form stable and transparent delivery systems with good skin permeation. However, fabrication of nanoemulsions containing lidocaine to provide an extended local anesthetic effect is challenging. Hence, the aim of this study was to address this issue by employing alginate-based o/w nanocarriers using nanoemulsion template that is prepared by combined approaches of ultrasound and phase inversion temperature (PIT). In this study, the influence of system composition such as oil type, oil and surfactant concentration on the particle size, in vitro release and skin permeation of lidocaine nanoemulsions was investigated. Structural characterization of lidocaine nanoemulsions as a function of water dilution was done using DSC. Nanoemulsions with small droplet diameters (d < 150 nm) were obtained as demonstrated by dynamic light scattering (DLS) and cryo-TEM. These nanoemulsions were also able to release 90% of their content within 24-h through PDMS and pig skin and able to the drug release over a 48-h. This extended-release profile is highly favorable in transdermal drug delivery and shows the great potential of this nanoemulsion as delivery system.     

High-vacuum pyrolysis of 1,1,1-trifluoro-2-bromo-2-chloroethane. IR spectrum of 1,1,1-trifluoro-2-chloroethyl radical in an argon matrix

The products of high-vacuum pyrolysis of 1,1,1-trifluoro-2-bromo-2-chloroethane were studied by matrix IR spectroscopy. The decomposition of 1,1,1-trifluoro-2-bromo-2-chloroethane was shown to occur predominantlyvia two directions: to form the 1,1,1-trifluoro-2-chloroethyl radical and trifluoromethylcarbene isomerizing to trifluoroethylene. The CF₃CHCl radical has been detected in the matrix for the first time. The bands observed in the IR spectrum were calculated by the quantum-chemical B3LYP/6-311 G(d,p) method and assigned to normal vibrations of the radical. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2085–2088, October, 1998.