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201.
Rasim Batmaz Nishil Mohammed Masuduz Zaman Gagan Minhas Richard M. Berry Kam C. Tam 《Cellulose (London, England)》2014,21(3):1655-1665
Cellulose nanocrystals (CNCs) prepared from cellulose fibre via sulfuric acid hydrolysis was used as an adsorbent for the removal of methylene blue (MB) from aqueous solution. The effects of pH, adsorbent dosage, temperature, ionic strength, initial dye concentration were studied to optimize the conditions for the maximum adsorption of dye. Adsorption equilibrium data was fitted to both Langmuir and Freundlich isotherm models, where the Langmuir model better described the adsorption process. The maximum adsorption capacity was 118 mg dye/g CNC at 25 °C and pH 9. Calculated thermodynamic parameters, such as free energy change (ΔG = ?20.8 kJ/mol), enthalpy change (ΔH = ?3.45 kJ/mol), and entropy change (ΔS = 0.58 kJ/mol K) indicates that MB adsorption on CNCs is a spontaneous exothermic process. Tunability of the adsorption capacity by surface modification of CNCs was shown by oxidizing the primary hydroxyl groups on the CNC surface with TEMPO reagent and the adsorption capacity was increased from 118 to 769 mg dye/g CNC. 相似文献
202.
Elyes Dahmane Julien Boccard Chantal Csajka Serge Rudaz Laurent Décosterd Eric Genin Bénédicte Duretz Maciej Bromirski Khalil Zaman Bernard Testa Bertrand Rochat 《Analytical and bioanalytical chemistry》2014,406(11):2627-2640
Liquid-chromatography (LC) high-resolution (HR) mass spectrometry (MS) analysis can record HR full scans, a technique of detection that shows comparable selectivity and sensitivity to ion transitions (SRM) performed with triple-quadrupole (TQ)-MS but that allows de facto determination of “all” ions including drug metabolites. This could be of potential utility in in vivo drug metabolism and pharmacovigilance studies in order to have a more comprehensive insight in drug biotransformation profile differences in patients. This simultaneous quantitative and qualitative (Quan/Qual) approach has been tested with 20 patients chronically treated with tamoxifen (TAM). The absolute quantification of TAM and three metabolites in plasma was realized using HR- and TQ-MS and compared. The same LC-HR-MS analysis allowed the identification and relative quantification of 37 additional TAM metabolites. A number of new metabolites were detected in patients’ plasma including metabolites identified as didemethyl-trihydroxy-TAM-glucoside and didemethyl-tetrahydroxy-TAM-glucoside conjugates corresponding to TAM with six and seven biotransformation steps, respectively. Multivariate analysis allowed relevant patterns of metabolites and ratios to be associated with TAM administration and CYP2D6 genotype. Two hydroxylated metabolites, α-OH-TAM and 4′-OH-TAM, were newly identified as putative CYP2D6 substrates. The relative quantification was precise (<20 %), and the semiquantitative estimation suggests that metabolite levels are non-negligible. Metabolites could play an important role in drug toxicity, but their impact on drug-related side effects has been partially neglected due to the tremendous effort needed with previous MS technologies. Using present HR-MS, this situation should evolve with the straightforward determination of drug metabolites, enlarging the possibilities in studying inter- and intra-patients drug metabolism variability and related effects. Figure
? 相似文献
203.
Mohammad Zaman Kassaee Farnaz Alipour Shakib Mohammad Reza Momeni Mehdi Ghambarian Seyed Majid Musavi 《Monatshefte für Chemie / Chemical Monthly》2009,9(4):33-38
Abstract
Based on geometries and relative energies, three different mechanisms are proposed for the rearrangements of five isomers of silacyclohexadienylidenes to silabenzene at B3LYP and MP2 levels: (1) [1,2]-hydrogen migration through a planar transition state, (2) [1,4]-hydrogen migration through a boat transition state, and (3) zip-zap mechanism, comprised of three successive [1,2]-hydrogen migrations. The above results are compared and contrasted to rearrangements of the corresponding cyclohexadienylidenes to benzene. 相似文献204.
An analytical formulation is developed to predict the flexural behavior of a cylindrical liquid storage tank resting on an isotropic elastic soil medium, which is modelled as a half space. The interface between the plate foundation and the soil medium is considered to be smooth and continuous. The plate deflection function is assumed in the form of a power series expansion in terms of the radial coordinate. The procedure accounts for the interactions between the tank wall and the plate foundation, and between the plate foundation and the soil medium. The principle of minimum potential energy is used to evaluate the unknown coefficients appearing in the assumed power series expansion and also the unknown interacting forces at the tank wall-plate foundation junction. Any number of terms can be considered in the assumed deflection function. Analytical expressions are obtained for the plate foundation deflections and radial moment, the contact stress distribution, the tank wall displacements, and the tank wall stress resultants. The results obtained compare well with the finite element analysis of a similar problem. Results of a parametric study are also presented to demonstrate the effect of the various geometric and material parameters on the flexural behavior of the system. 相似文献
205.
M. R. Zaman 《Journal of Radioanalytical and Nuclear Chemistry》1995,199(1):15-19
Reactions between aniline and dibromomethane (DBM) or 1,2-dibromoethane (DBE) produce fine glassy crystals at ordinary temperature. Due to these product formation processes, aniline fails to exert its scavenging action on bromine recoil reactions in these media. 相似文献
206.
207.
Sorption of metal ions on oxide/hydroxide surfaces mediates the fate and transport of these ions in many natural systems. These metallic ions often exist in bulk in the aqueous phase as complexes with inorganic and organic ligands. In the present study, we investigated the sorption properties of manganese dioxide in the presence of phosphate which is thought to be one of the most important complex forming species. The surface area, point of zero charge and structural morphology of the solid manganese dioxide were determined. Cd(2+) sorption studies were carried out on manganese dioxide as a function of pH, temperature and phosphate concentration. Cd(2+) sorption increased with increasing pH, temperature and phosphate concentration. It was found that phosphate formed both outer and inner sphere complexes via metal and ligand-like adsorption. The Langmuir equation was applied to describe the data and from the constants of this equation different thermodynamic parameters such as DeltaH(0), DeltaS(0) and DeltaG(0) were evaluated. 相似文献
208.
A highly robust and recyclable Hoveyda-Grubbs’ second generation ruthenium type catalyst immobilised on polyethylene glycol is conveniently prepared from Grubbs’ second generation catalyst. The catalyst performs ring-closing metathesis of various di-and tri-substituted olefins efficiently in dichloromethane in air. 相似文献
209.
We examine the problem of flow and heat transfer in a second grade fluid over a stretching sheet [K. Vajravelu, T. Roper,
Int. J. Nonlinear Mech. 34, 1031 (1999)]. The equations considered by Vajravelu and Roper [K. Vajravelu, T. Roper, Int. J.
Nonlinear Mech. 34, 1031 (1999)], are found to be incorrect in the literature. In this paper, we not only corrected the equation
but found a useful analytic solution to this important problem. We also extended the problem for hydromagnetic flow and heat
transfer with Hall effect. The explicit analytic homotopy solution for the velocity field and heat transfer are presented.
Graphs for the velocity field, skin friction coefficient, and rate of heat transfer are presented. Tables for the skin friction
coefficient and rate of heat transfer are also presented. The convergence of the solution is also properly checked and discussed. 相似文献
210.