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Ionic Solutions (ionic + solution)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Many-body effects on structure and dynamics of aqueous ionic solutions

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2003
Hannes H. Loeffler
Abstract We performed several molecular dynamic studies of metal cations in aqueous solution. The alkali metal ion Li+ and the first-row transition metal ion Mn2+ have been chosen as model systems. Two different three-body corrections are proposed to mimic the crucial many-body effects of electrolyte solutions. The correction function, which includes attractive features of the three-body potential, performs considerably better than the purely repulsive interaction function. Structural and dynamic results show that this simple enhancement is able to satisfactorily reproduce experimental and higher-level results for the first hydration shell. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1232,1239, 2003 [source]

EXAFS and molecular dynamics studies of ionic solutions

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
Paola D'Angelo
This paper focuses on recent advances in the X-ray absorption spectroscopy (XAS) analysis of ionic solutions. The asymmetry of radial distribution functions associated with the solvent molecules surrounding the ions has to be taken into account to perform a reliable structural analysis. Molecular dynamics (MD) simulations provide reliable 's which can be used as starting models in the XAS data analysis. The combined MD-XAS investigation reduces meaningfully the indetermination of the structural parameters, especially for coordination numbers and Debye,Waller factors. Double-electron excitation channels can be present in the XAS spectra of ionic solutions and they have to be accounted for in the background extraction. The ability of the XAS technique to probe three-body correlation functions in ionic solutions with the aid of MD has been shown. The analysis of the low- k region of the spectra allows the detection of a weak but significant hydrogen structural signal. The XAS technique is especially well suited to determine the detailed shape of the nearest-neighbor peak in the atom,atom pair correlation functions of disordered systems. The information that they contain about the short-range atom,atom pairwise interactions can be very helpful for specifying and properly modifying model potentials used in MD simulations. [source]

Spatio-temporal inhomogeneities of laser induced plasma on surface solutions

LASER PHYSICS LETTERS, Issue 11 2004
J. Ben Ahmed
Abstract A transient plasma created by focusing a nanosecond laser pulse on the surface of ionic solutions of Ca++ and Mg++ is studied spectroscopically. This kind of plasma has a properties which vary significantly with time and over its extended volume. The emissions of ionic and atomic line of calcium and magnesium are analyzed to get information on the electronic temperature, the electronic density and on the kinetics of the population of low atomic and ionic states: 4P1 of CaI, 5S1/2 of CaII, 3P1 of MgII and 3P1/2 of MgII. The temperature is maximal at the plasma center and it drops at the edges. The study of the term as a function of time, where r is the radial position, shows a continue decreasing with time, which implies that the inhomogeneity of the temperature develops with time. On the another side, the electronic density deceases exponentially with time and does not vary significantly with space. These measurements allow us to follow the kinetics of the transformation of calcium (magnesium) from Ca++Mg++ to Ca+(Mg+) to give at the end Ca (Mg) and to understand the behavior of self-absorption phenomena which is observed in the resonance line of CaII at t , 2000 ns to increase with time. The experimental results are simulated by a kinetics model of LTE laser induced plasma in its late relaxation period. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Preparation of Functionalized Polysilsesquioxane and Polysilsesquioxane-Metal Nanoparticle Composite Spheres,

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2006
Young Baek Kim
Abstract Summary: Network polysilsesquioxane spheres made solely of poly(vinylsilsesquioxane) (PVSQ) and poly(3-mercaptopropylsilsesquioxane) (PMPSQ) were prepared from heterogeneous mixtures of triethylamine (TEA), water, and either vinyltrimethoxysilane (VTMS), or 3-mercaptopropyltrimethoxysilane (MPTMS). The microscopic, macroscopic observations, and the relationship between the diameters of spheres and the amount of each ingredient in the reaction system, showed that spheres formed via a mechanism similar to emulsion polymerization and suspension polymerization, depending on the reaction conditions. Diameters of spheres could be controlled from tens of nanometers to a few micrometers by adjusting the amounts of TEA, water, and a surfactant. Heating aqueous solutions of metal ions with these spheres produced polysilsesquioxanes (PSQ)-metal nanoparticle composite spheres. The spheres prepared in this study were characterized by scanning electron microscopy, transmission electron microscopy, solid state NMR spectroscopy, IR spectroscopy, elemental analysis, and differential thermal analysis. These spheres would be useful in recovering metals from their ionic solutions and probes after chemical modifications. An image of the spheres of poly(vinylsilsesquioxane)-gold nanoparticle composite. [source]

Fast and novel purification method to obtain the prostate specific antigen (PSA) from human seminal plasma

THE PROSTATE, Issue 10 2006
Boris Acevedo
Abstract Background Prostate specific antigen (PSA) is a relevant antigen in diagnosis; follow-up, and therapeutic approaches for fighting the prostate cancer. Several methods have been published previously to obtain a high purity preparation of PSA. In general, these methods are expensive, time-consuming, laborious, and in some cases produce low yields. Methods Based on a panel of 7 anti-PSA Mab's we carried on binding and elution experiments of PSA antigen in 96-well plates. The selected Mab were immobilized in a Sepharose CL-4B activated matrix with the purpose of purify PSA from human seminal fluid. In order to optimize the purification procedure, we test several washing and elution conditions (chaotropic agents, high ionic strength solution, and extreme pH). Results We selected a high ionic strength solution (2 M MgCl2) as elution condition, and a previous washing step with a mix of two ionic solutions (2.5 M NaCl pH 8/1 M MgCl2 pH 5.5) in order to purify PSA. Using such conditions we obtained a PSA preparation with 90% of purity and 50% of recovery. Conclusion In this article, we report a simple, quickly, and non-expensive procedure to obtain free-PSA from human seminal plasma at high purity levels. Prostate 66: 1029,1036, 2006. © 2006 Wiley-Liss, Inc. [source]