Thermodynamic derivative properties and densities for hyperbaric gas condensates: SRK equation of state predictions versus Monte Carlo data

The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, a_ij, and three expressions of the crossed terms of the repulsive parameter, b_ij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of a_ij and b_ij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations.     

Retention,enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column

Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an ₁-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.     

Alpha稳定分布噪声下MPSK信号调制识别算法研究

针对Alpha稳定分布噪声中信号四次方谱失效的问题,提出了广义四次方谱的概念,在此基础上研究了基于广义四次方谱的多进制相移键控(M-ary Phase Shift Keying,MPSK)信号调制识别算法.首先分析了待识别信号的广义四次方谱,然后提取广义四次方谱中二倍载频和四倍载频处的谱线作为特征参数,最后通过判断谱线是否被冲击来实现信号的分类.仿真结果表明,这种算法在Alpha稳定分布噪声下的性能优于基于四次方谱的算法,且该算法在高斯噪声下也具有良好的性能.     

Evaluation of in vitro,in silico antidiabetic and antioxidant potential of bioactivity based isolated “Pakistanine” from Berberis baluchistanica

Bioassay based fractionation of methanolic extract of Berberis baluchistanica (Berberidaceae), used traditionally for internal injuries, led to the isolation of known compounds (1–4). The structure of these compounds was elucidated by different spectroscopic analysis and available literature data. Antidiabetic and antioxidant potentials of B. baluchistanica fractions and isolated compounds were evaluated using in vitro alpha- amylase and DPPH assays. The isolated compounds were identified as obamegine (1), pakistanine (2), 8-oxyberberine (3) and baluchistine (4). Obamegine was reported from many other species of this genus but it is first time isolated from B. baluchistanica in present study. Moreover, in vitro pakistanine (2) was found as bioactive lead molecule for hypoglycemic (IC₅₀:40.26 µg/ml) and antioxidant (IC₅₀:14.15 µg/ml) activities compared to acarbose (IC₅₀:33.68 µg/ml) and ascorbic acid (IC₅₀:0.41 µg/ml). To the best of our knowledge, no previous data were available for these biological activities. Additionally, in silico antidiabetic and antioxidant activity of pakistanine against two proteins, α-amylase (-9.7 kcal/mol) and tyrosinase (-8.7 kcal/mol) are reported here for the first time. The molecular docking binding interactions authenticate and support the above-mentioned activities and are helpful in predicting the mechanism of action of pakistanine (2).     

Alpha稳定分布噪声环境下新的类RLS自适应算法

给出在分数低阶Alpha稳定分布环境中一种新的类RLS自适应算法.由于Alpha稳定分布信号不存在有限的二阶和二阶以上矩,因此用最小p范数准则代替了传统的最小均方准则,并利用矩阵求逆定理提出一种直接递推的类RLS算法,避免了以往类RLS算法中的IRLS迭代计算,从而使算法的计算复杂度大大降低.最后对几种自适应算法进行仿真,并对其收敛特性进行了分析.结果表明,算法的收敛速度明显快于LMP和NLMP算法.     

Heavy-element chemistry --Status and perspectives

In the past ten years, nuclear chemists have made considerable progress in developing fast on-line separation techniques, which allowed to chemically characterize the first four transactinide elements Rf (rutherfordium, Z = 104), Db (dubnium, Z = 105), Sg (seaborgium, Z = 106), and recently also Bh (bohrium, Z = 107). In all cases the isolated nuclides were unambiguously identified by observing genetically linked decay chains. Nuclides with production cross-sections of less than 100 pb and half-lives as short as a few seconds have been chemically isolated. Thus, chemists have discovered or significantly contributed to the characterization of the nuclear-decay properties of a number of transactinide nuclei. New techniques with greatly improved overall efficiencies should allow chemists to extend their studies to even heavier elements such as Hs (hassium, Z = 108) and to the recently discovered superheavy elements with Z = 112 and 114, which can be produced only with picobarn cross-sections. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: andreas.tuerler@psi.ch     

Nanoindentation and the indentation size effect: Kinetics of deformation and strain gradient plasticity

A study of the indentation size effect (ISE) in aluminum and alpha brass is presented. The study employs rate effects to examine the fundamental mechanisms responsible for the ISE. These rate effects are characterized in terms of the rate sensitivity of the hardness, , where H is the hardness and is an effective strain rate in the plastic volume beneath the indenter. can be measured using indentation creep, load relaxation, or rate change experiments. The activation volume V∗, calculated based on which can traditionally be used to compare rate sensitivity data from a hardness test to conventional uniaxial testing, is calculated. Using materials with different stacking fault energy and specimens with different levels of work hardening, we demonstrate how increasing the dislocation density affects V∗; these effects may be taken as a kinetic signature of dislocation strengthening mechanisms. We noticed both H and exhibit an ISE. The course of V∗ vs. H as a result of the ISE is consistent with the course of testing specimens with different level of work hardening. This result was observed in both materials. This suggests that a dislocation mechanism is responsible for the ISE. When the results are fitted to a strain gradient plasticity model, the data at deep indents (microhardness and large nanoindentation) exhibit a straight-line behavior closely identical to literature data. However, for shallow indents (nanoindentation data), the slope of the line severely changes, decreasing by a factor of 10, resulting in a “bilinear behavior”.     

Swelling and structure of radiation induced near-surface damage in CR-39 and its chemical etching

Systematic measurements of swelling of CR-39 nuclear track detector (NTD) due to irradiation with fission fragments and alpha particles over a wide range of fluences from ²⁵²Cf are presented here. Precisely designed and optimized exposure and chemical etching experiments were employed to unfold the structure of radiation induced surface damage. Delays in the startup of the chemical etching of latent tracks in low radiation fluence detectors are measured and are found to contain important information about structure of the surface damage. Simple atomic scale pictures of radiation induced surface damage and its chemical etching are developed using measurements of radiation induced swelling of CR-39 detectors and nuclear track parameters. The computer code SRIM2010 was utilized for the calculations of basic features of latent tracks of fission fragments and alpha particles in CR-39. Another computer code TRACK_VISION was used to compute parameters of etched tracks. Computations and experimental findings in the paper coherently compose a realistic picture of radiation damage.     

Capillary electrophoresis enzyme immunoassay for alpha-fetoprotein and thyroxine in human serum with electrochemical detection

A novel CE-based enzyme immunoassay (CE-EIA) method was developed in o-aminophenol (OAP)-H(2)O(2)-horseradish peroxidase (HRP) system and applied to benign liver disease and hyperthyroidism research in the clinical practical field. In the presented method, after the enzyme immunoreaction, the HRP-labeled antibody or HRP-labeled antigen catalyzed the enzyme substrate OAP and H(2)O(2). The product of the enzymatic catalysis reaction 2-aminophenoxazine-3-one (AP) was determined using electrochemical detection on a Pt electrode at the outlet of the reaction capillary. Factors influencing the performance, including running buffer concentration, separation, and detection voltage, were investigated to the optimum conditions. Noncompetitive and competitive models were utilized to detect alpha-fetoprotein (AFP) and thyroxine (T(4)) in human sera, respectively. The linear ranges and the detection limits (S/N = 3) were from 1.5 to 66.6 ng/mL and 0.48 ng/mL for AFP, and from 1.7 to 260.0 ng/mL and 1.0 ng/mL for T(4). The results of this method were linear proportional to those of spectrophotometric ELISA method, giving a good prospect for a new clinical diagnostic instrument.     

Differentiation between tracks and damages in SSNTD under the atomic force microscope

We have observed three-dimensional sponge-like structures as well as strips of connecting pits on the surface of the LR 115 detector after etching, which can be confused with the small tracks formed after short etching time. We have employed an atomic force microscope (AFM) to study these “damages” as well as genuine alpha tracks for short etching time. It was found that while the track and damage openings could be similar in size and shape, the depths for the damages were consistently smaller. Therefore, the depth of the pits will serve as a clear criterion to differentiate between tracks and other damages. The ability to discriminate between genuine tracks from other damages is most important for etching for short time intervals.