Chemometric analysis of groundwater quality data of alluvial aquifer of Gangetic plain, North India

Water quality data set from the alluvial region in the Gangetic plain in northern India, which is known for high fluoride levels in soil and groundwater, has been analysed by chemometric techniques, such as principal component analysis (PCA), discriminant analysis (DA) and partial least squares (PLS) in order to investigate the compositional differences between surface and groundwater samples, spatial variations in groundwater composition and influence of natural and anthropogenic factors. Trilinear plots of major ions showed that the groundwater in this region is mainly of Na/K-bicarbonate type. PCA performed on complete data matrix yielded six significant PCs explaining 65% of the data variance. Although, PCA rendered considerable data reduction, it could not clearly group and distinguish the sample types (dug well, hand-pump and surface water). However, a visible differentiation between the water samples pertaining to two watersheds (Khar and Loni) was obtained. DA identified six discriminating variables between surface and groundwater and also between different types of samples (dug well, hand pump and surface water). Distinct grouping of the surface and groundwater samples was achieved using the PLS technique. It further showed that the groundwater samples are dominated by variables having origin both in natural and anthropogenic sources in the region, whereas, variables of industrial origin dominate the surface water samples. It also suggested that the groundwater sources are contaminated with various industrial contaminants in the region.     

Electrochemical characterization of solid materials in volume range I. Chemical effects on the matrix-phase separation

The electrochemical phase isolation (EPI) is described as a preparation method for determining specific precipitations in solid materials in microamounts and microdimensions. Fundamental criteria are examined as a function of the main parameter (polarization current) on the system Fe₃C in a Fe-matrix. The influence of the electrolyte composition on the electrochemical behaviour of the matrix, on the one hand, and of the phase, on the other hand, are investigated and utilized.     

修正PRP共轭梯度方法求解无约束最优化问题

基于著名的PRP共轭梯度方法,利用CG_DESCENT共轭梯度方法的结构,本文提出了一种求解大规模无约束最优化问题的修正PRP共轭梯度方法。该方法在每一步迭代中均能够产生一个充分下降的搜索方向,且独立于任何线搜索条件。在标准Wolfe线搜索条件下,证明了修正PRP共轭梯度方法的全局收敛性和线性收敛速度。数值结果展示了修正PRP方法对给定的测试问题是非常有效的。     

供应商不确定情景下药品物流多中心选址优化研究

根据国家4+7药品带量集中采购评审标准,基于药品生产企业生产质量、供应能力、相关资质和同类药品参标结果等数据进行梳理和分析,针对药品供应商不确定情景下药品物流多中心选址问题,构建药品物流整体费用最优的多中心选址模型,设计多阶段改进禁忌搜索算法,最后通过4+7带量集中采购具体算例对模型和算法进行验证,结果显示该模型和算法是可行和有效的。     

Nonmonotone stabilization methods for nonlinear equations

We are concerned with defining new globalization criteria for solution methods of nonlinear equations. The current criteria used in these methods require a sufficient decrease of a particular merit function at each iteration of the algorithm. As was observed in the field of smooth unconstrained optimization, this descent requirement can considerably slow the rate of convergence of the sequence of points produced and, in some cases, can heavily deteriorate the performance of algorithms. The aim of this paper is to show that the global convergence of most methods proposed in the literature for solving systems of nonlinear equations can be obtained using less restrictive criteria that do not enforce a monotonic decrease of the chosen merit function. In particular, we show that a general stabilization scheme, recently proposed for the unconstrained minimization of continuously differentiable functions, can be extended to methods for the solution of nonlinear (nonsmooth) equations. This scheme includes different kinds of relaxation of the descent requirement and opens up the possibility of describing new classes of algorithms where the old monotone linesearch techniques are replace with more flexible nonmonotone stabilization procedures. As in the case of smooth unconstrained optimization, this should be the basis for defining more efficient algorithms with very good practical rates of convergence.This material is partially based on research supported by the Air Force Office of Scientific Research Grant AFOSR-89-0410, National Science Foundation Grant CCR-91-57632, and Istituto di Analisi dei Sistemi ed Informatica del CNR.     

Electron microprobe analysis of micro amount powder samples: A case study on high purity coal

For the major, minor and trace element analysis of the inorganic compounds of a Ruhr-Saar coal different preparation techniques are investigated with X-ray fluorescence analysis, electron microprobe and classical wet chemical methods minimizing sample weight at standard preparation times and analytical accuracies. Considering accuracy as well as preparation efforts, determinations by electron microprobe on small sample amounts (<50 mg) proved to be superior to the other methods.Abbreviations AAS atomic absorbtion spectrometry - EMA electron microprobe analysis - IC ion chromatography - ISE ion sensitive electrode - PHOT photometry - WCA wet chemical analysis - XRF X-ray fluorescence analysis - LTA low temperature plasma ashing - HTA high temperature ashing - l.o.i. loss on ignition     

Implementation and efficiency of an automatic peak-purity-control procedure in HPLC-UV-VIS-coupling based on principal component analysis

Summary Based on a thorough knowledge of the actual system precision significance testing of the primary eigen values, resulting from principal component analysis of the two-dimensional data array of HPLC with photodiode-array detection, is a powerful means to uncover unresolved chromatographic peaks. The implementation of this chemometric technique for assuring peak homogeneity and results showing the efficiency for two-component peaks in regard to spectral characteristics, chromatographic resolution and absorbance ratio of the investigated compounds are presented.     

Cadmium speciation in Arabidopsis thaliana as a strategy to study metal accumulation system in plants

The strategy to identify cadmium deactivation mechanism in Arabidopsis thaliana has been developed using selective and sensitive hyphenated techniques. Cadmium concentrations, in main parts of the plant, were determined by ICP-MS and total amount was found as 0.43-0.44 μg g⁻¹ in leaves and 3.3-3.4 μg g⁻¹ in roots. Speciation of the metal complexes in cells was investigated by SEC-ICP-MS in order to estimate the accumulation process. Phytochelatins, desglycyl-phytochelatins and phytochelatins homologues lacking the N-terminal γ-linked glutamic acid were extracted from plant and were identified by RPLC-ESI-MS. Two-dimensional chromatography allowed to link the metal complexes separated by SEC with isoforms of phytochelatins analyzed by high resolution RPLC and confirm their significant responsibility for metal accumulation. The potential of the cadmium complexes speciation indicates that obtained results could be reliable source of knowledge to confirm the information coming from the well-known genomic sequence of Arabidopsis and to estimate the role of γ-glutamyl transpeptidase in metabolism of glutathione.     

Sample preparation in analysis of pharmaceuticals

Sample preparation is a very important and essential step in environmental analysis. This article presents an overview of extraction methods for environmental samples, focusing especially on pharmaceuticals as there is great concern about them as pollutants.     

Lattice models of peptide aggregation: evaluation of conformational search algorithms

We present a series of conformational search calculations on the aggregation of short peptide fragments that form fibrils similar to those seen in many protein mis-folding diseases. The proteins were represented by a face-centered cubic lattice model with the conformational energies calculated using the Miyazawa-Jernigan potential. The searches were performed using algorithms based on the Metropolis Monte Carlo method, including simulated annealing and replica exchange. We also present the results of searches using the tabu search method, an algorithm that has been used for many optimization problems, but has rarely been used in protein conformational searches. The replica exchange algorithm consistently found more stable structures then the other algorithms, and was particularly effective for the octamers and larger systems.