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Method Makes (method + make)
Selected AbstractsEnantioseparation of nuarimol by affinity electrokinetic chromatography-partial filling technique using human serum albumin as chiral selectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2008Maria Amparo Martínez-Gómez Abstract The present paper deals with the enantiomeric separation of nuarimol enantiomers by affinity EKC-partial filling technique using HSA as chiral selector. Firstly, a study of nuarimol interactions with HSA by CE-frontal analysis was performed. The binding parameters obtained for the first site of interaction were n1 = 0.84; K1 = 9.7 ± 0.3×103 M,1 and the protein binding percentage of nuarimol at physiological concentration of HSA was 75.2 ± 0.2%. Due to the moderate affinity of nuarimol towards HSA the possibility of using this protein as chiral selector for the separation of nuarimol using the partial filling technique was evaluated. A multivariate optimization approach of the most critical experimental variables in enantioresolution, running pH, HSA concentration and plug length was carried out. Separation of nuarimol enantiomers was obtained under the following selected conditions: electrophoretic buffer composed of 50 mM Tris at pH 7.3; 160 ,M HSA solution applied at 50 mbar for 156 s as chiral selector; nuarimol solutions in the range of 2,8×10,4 M injected hydrodynamically at 30 mbar for 2 s and the electrophoretic runs performed at 30°C applying 15 kV voltage. Resolution, accuracy, reproducibility speed and cost of the proposed method make it suitable for quality control of the enantiomeric composition of nuarimol in formulations and for further toxicological studies. The results showed a different affinity between nuarimol enantiomers towards HSA. [source] Efficient generation of Heisenberg Hamiltonian matrices for VB calculations of potential energy surfacesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2009A. M. Tokmachev Abstract The spin-Hamiltonian valence bond theory relies upon covalent configurations formed by singly occupied orbitals differing by their spin counterparts. This theory has been proven to be successful in studying potential energy surfaces of the ground and lowest excited states in organic molecules when used as a part of the hybrid molecular mechanics,valence bond method. The method allows one to consider systems with large active spaces formed by n electrons in n orbitals and relies upon a specially proposed graphical unitary group approach. At the same time, the restriction of the equality of the numbers of electrons and orbitals in the active space is too severe: it excludes from the consideration a lot of interesting applications. We can mention here carbocations and systems with heteroatoms. Moreover, the structure of the method makes it difficult to study charge-transfer excited states because they are formed by ionic configurations. In the present work we tackle these problems by significant extension of the spin-Hamiltonian approach. We consider (i) more general active space formed by n ± m electrons in n orbitals and (ii) states with the charge transfer. The main problem addressed is the generation of Hamiltonian matrices for these general cases. We propose a scheme combining operators of electron exchange and hopping, generating all nonzero matrix elements step-by-step. This scheme provides a very efficient way to generate the Hamiltonians, thus extending the applicability of spin-Hamiltonian valence bond theory. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Wavelet-based functional mixed modelsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 2 2006Jeffrey S. Morris Summary., Increasingly, scientific studies yield functional data, in which the ideal units of observation are curves and the observed data consist of sets of curves that are sampled on a fine grid. We present new methodology that generalizes the linear mixed model to the functional mixed model framework, with model fitting done by using a Bayesian wavelet-based approach. This method is flexible, allowing functions of arbitrary form and the full range of fixed effects structures and between-curve covariance structures that are available in the mixed model framework. It yields nonparametric estimates of the fixed and random-effects functions as well as the various between-curve and within-curve covariance matrices. The functional fixed effects are adaptively regularized as a result of the non-linear shrinkage prior that is imposed on the fixed effects' wavelet coefficients, and the random-effect functions experience a form of adaptive regularization because of the separately estimated variance components for each wavelet coefficient. Because we have posterior samples for all model quantities, we can perform pointwise or joint Bayesian inference or prediction on the quantities of the model. The adaptiveness of the method makes it especially appropriate for modelling irregular functional data that are characterized by numerous local features like peaks. [source] Solid Phase Extraction of Thallium(III) on Micro Crystalline Naphthalene Modified with N,N, -Bis(3-methylsalicylidene)- ortho -phenylenediamine and Determination by SpectrophotometryCHINESE JOURNAL OF CHEMISTRY, Issue 10 2008Ali MOGHIMI Abstract A novel, simple, sensitive and effective method has been developed for preconcentration of thallium on N,N, -bis(3-methylsalicylidene)- ortho -phenylenediamine (MSOPD) adsorbent in a pH range 5.0,10.0, prior to its spectrophotometric determination, based on the oxidation of bromopyrogallol red at ,=520 nm. This method makes it possible to quantitize thallium in a range of 3.6×10,9 to 2.0×10,5 mol/L, with a detection limit (S/N=3) of 1.42×10,9 mol/L. This procedure has been successfully applied to determine the ultra trace levels of thallium in the environmental samples, free from the interference of some diverse ions. The precision, expressed as relative standard deviation of three measurements, is better than 2.9%. 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