Chemometric and trend analysis of water quality of the South Chennai lakes: an integrated environmental study

In order to bring out the nature of the factors influencing lake water composition, multivariate statistical analysis and trend analysis were performed based on the hydrochemical data of the study area, namely, South Chennai. Change in land use pattern and settlements along the banks of the lakes alters the quality and quantity of the surface water. In the present study, the R‐mode factor analysis and cluster analysis were applied to the geochemical parameters of the water to identify the factors affecting the chemical composition of the lake water. Dendograms of both the seasons give three major clusters, reflecting the groups of unpolluted to moderately polluted, polluted, and heavily polluted stations. The movement of stations from one cluster to another clearly brings out the seasonal variation in the chemical composition of the lake water. The complex hydrochemical data of the surface water were interpreted by condensing them into three major factors. Factor score analysis was used successfully to delineate the stations under study and the role of the contributing factors, and the nature of factors responsible for the variation in chemical composition of the water has been clearly brought out. Results of trend analysis using ArcGIS clearly indicate that the trend in water quality is deteriorating at a faster rate in the eastern part of the study area. It is understood that although natural shifts probably can account for some of the variation, it is most likely that human activities play a major role in affecting the water quality on a regional scale. Copyright © 2014 John Wiley & Sons, Ltd.     

SnCl4/Sn catalyzed chemoselective reduction of glycopyranosyl azides for the synthesis of diversely functionalized glycopyranosyl chloroacetamides

A method for the chemoselective reduction of glycopyranosyl azides using SnCl₄ and tin metal as the reducing agent followed by in situ chloroacetylation of the synthesized glycopyranosyl amine was developed. This reaction is applicable to diversely functionalized glycopyranosyl azides for the synthesis of glycopyranosyl chloroacetamides.     

Development and validation of a hydrophilic interaction liquid chromatography with tandem mass spectrometry method for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine

A sensitive hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine. The method is highly sensitive and specific with good precision and accuracy. In plasma the limit of detection and limit of quantification are 0.03 and 0.1 ng/mL, respectively, for both analytes. In urine the limit of detection and limit of quantification are 0.3 and 1 ng/mL, respectively, for both analytes. The suitability of the method for doping control analysis in equine species is demonstrated by analyzing postadministration samples collected after a single intravenous administration of 50 mg etilefrine to a standardbred mare. Etilefrine was detected up to 120 h in urine and up to 48 h in plasma. Etilefrine is highly conjugated in equine urine whereas it exists in the free form in equine plasma. Therefore, enzyme hydrolysis prior to sample preparation is recommended for the detection and quantification of etilefrine and oxilofrine in equine urine.     

Effective Relaxations and Partitioning Schemes for Solving Water Distribution Network Design Problems to Global Optimality

In this paper, we address the development of a global optimization procedure for the problem of designing a water distribution network, including the case of expanding an already existing system, that satisfies specified flow demands at stated pressure head requirements. The proposed approach significantly improves upon a previous method of Sherali et al. (1998) by way of adopting tighter polyhedral relaxations, and more effective partitioning strategies in concert with a maximal spanning tree-based branching variable selection procedure. Computational experience on three standard test problems from the literature is provided to evaluate the proposed procedure. For all these problems, proven global optimal solutions within a tolerance of 10^–4% and/or within 1$ of optimality are obtained. In particular, the two larger instances of the Hanoi and the New York test networks are solved to global optimality for the very first time in the literature. A new real network design test problem based on the Town of Blacksburg Water Distribution System is also offered to be included in the available library of test cases, and related computational results are presented.     

Regular semigroups with a split map

Communicated by R. B. McFadden     

Stannoxanes and phosphonates: New approaches in organometallic and transition metal assemblies

Phosphonate ligands, [RPO₃]^2-, are extremely versatile in the assembly of multi-tin and multi-copper architectures. We have used organostannoxane cores for supporting multi-ferrocene and multi-porphyrin peripheries. The copper-metalated multi-porphyrin compound is an excellent reagent for facile cleavage of DNA, even in the absence of a co-oxidant. Reaction oft-BuPO₃H₂ with Cu(C10₄)₂. 6H₂O in the presence of 2-pyridylpyrazole (2-Pypz) leads to the synthesis of a decanuclear copper (II) assembly.     

Conformational preferences of the aglycon moiety in models and analogs of GlcNAc-Asn linkage: crystal structures and ab initio quantum chemical calculations of N-(beta-D-glycopyranosyl)haloacetamides

The biological addition of oligosaccharide structures to asparagine residues of N-glycoproteins influences the properties and bioactivities of these macromolecules. The linkage region constituents, 2-acetamino-2-deoxy-beta-D-glucopyranose monosaccharide (GlcNAc) and L-asparagine amino acid (Asn), are conserved in the N-glycoproteins of all eukaryotes. In order to gain information about the structure and dynamics of glycosylated proteins, two chloroacetamido sugars, Glc betaNAcNHCOCH2Cl and Man betaNHCOCH2Cl, have been synthesized, and their crystal structures have been solved. Structural comparison with a series of other models and analogs gives insight about the influence of the N-acetyl group at position C2 on the conformation of the glycan-peptide linkage at C1. Interestingly, this N-acetyl group also influences the packing and network of hydrogen bonds with involvement in weak hydrogen bonds C-H...X that are of biological importance. DFT ab initio calculations performed on a series of models and analogs also confirm that the GlcNAc derivatives present different preferred conformation about the N-CO-CH2-X (chi2) torsion angle of the glycan-peptide linkage, when compared to other monosaccharide derivatives. The energy profiles that have been obtained will be useful for parametrization of molecular mechanics force-field. The conjunction of crystallographic and computational chemistry studies provides arguments for the structural effect of the N-acetyl group at C2 in establishing an extended conformation that presents the oligosaccharide away from the protein surface.