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71.
S. Yasin P. F. Luckham T. Iqbal M. Zafar 《Journal of Dispersion Science and Technology》2013,34(2):268-272
For making stable dispersions of graphitic carbon black (Monarch 700), the effectiveness of three dispersants/polymers (hypermer LP1, hypermer B246, and OLOA 11000) in xylene is investigated. Hypermer LP1 (polyhydroxystearic acid) is a homopolymer and hypermer B246 (PEG 30-dipolyhydroxystearate) is a polyhydroxystearic acid/polyethylene oxide/polyhydroxystearic acid ABA block copolymer, while OLOA 11000 (polyisobutylene succinimide) has a polar head group (polyamine) attached to a hydrocarbon chain (polyisobutylene). Well-dispersed graphitic carbon black dispersions were prepared using dispersants at optimum concentrations. Percolation threshold and rheological threshold were determined by analyzing the variations in electrical conductivity and elastic modulus with concentration of carbon black. Above threshold concentration, scaling law was applied to experimental data of rheology (dynamic measurements) and electrical conductivity measurements to evaluate quality of the system. Effectiveness of polymers was investigated on the basis of value of critical exponent (t and t′, respectively) in scaling power law. Hypermer LP1 was proved to be a poor dispersant for Monarch 700 dispersions while other two polymers were found to be effective stabilizers. 相似文献
72.
Ahmed A. K. Mohammed Peter A. Limacher Benoît Champagne 《Journal of computational chemistry》2013,34(17):1497-1507
The finite field method, widely used for the calculation of static dipole polarizabilities or the first and second hyperpolarizabilities of molecules and polymers, is thoroughly explored. The application of different field strengths and the impact on the precision of the calculations were investigated. Borders could be defined and characterized, establishing a range of feasible field strengths that guarantee reliable numerical results. The quality of different types of meshes to screen the feasible region is assessed. Extrapolation schemes are presented that reduce the truncation error and allow to increase the precision of finite field calculations by one to three orders of magnitude. © 2013 Wiley Periodicals, Inc. 相似文献
73.
A.-H. Abdel-Rahman Adel E. El Aassy Ibrahim Y. Ahmed Fadia F. Hamza Mohammed 《Journal of Dispersion Science and Technology》2013,34(8):1128-1135
Synthesis of poly(acrylamidoxime) resin from polyacrylonitrile performed with different crosslinking ratios 2, 5, and 10 wt% of divinylbenzene as crosslinking agent, using methylbenzoate and dioctylphthalate as pore producing solvent, the reaction mixture occurred under nitrogen. Studies carried out on diluted solution from rare earth elements (REEs) concentrate contains impurities as Cu2+, Ni2+, Zn2+, Fe3+, Al3+, Si4+, Th4+, U6+, Ca2+, and K+. Changing some parameters as pH of the solution, time of feeding and type of acid as HCl, HNO3, H2SO4. The adsorption efficiency of resin is in the order pH 6 > pH 5 > pH 4 > pH 2 with excluding pH 6 due to the precipitation of some of REEs with the impurities and complete precipitation of Dy ion during pH adjustment, the adsorption in HNO3 > HCl > H2SO4 media. 相似文献
74.
Mohammed Taghi Zafarani-Moattar Roghayeh Majdan-Cegincara 《Colloid and polymer science》2013,291(8):1977-1987
The Fe3O4 nanoparticles and Fe3O4 nanoparticles coated with oleic acid have been dispersed in base fluid of poly(ethylene glycol) (PEG). Stability and particle size distribution of these nanofluids have been studied by result analysis of UV–Vis spectroscopy, zeta potential and dynamic light scattering. Blue shift of UV–Vis spectra has been related to quantum effects such as band gap enlargement with particle size decreasing and also to effect of oleic acid on the ultraviolet wavelength. Flow behavior and suspension structure of Fe3O4 nanoparticles dispersed in PEG have been determined by rheological properties. Viscosity values of Fe3O4-PEG nanofluid as a function of temperature have also been investigated. The chain-like structure of Fe3O4 nanoparticles coated with oleic acid in base fluid of PEG has been verified by measuring the magnetorheological properties. The effect of temperature on magnetorheological properties of Fe3O4 nanoparticles coated with oleic acid has also been investigated in base fluid of PEG. The volumetric properties of Fe3O4-PEG and Fe3O4 coated with oleic acid–PEG nanofluids and PEG–oleic acid solution have also been measured at different temperatures to specify the suspension structure and also interactions of Fe3O4, PEG and oleic acid molecules. 相似文献
75.
A simple, rapid, sensitive, and inexpensive method for spectrophotometric determination of chromium(VI), based on the absorbance of its complex with 1,4,8,11-tetraazacyclotetradecane (cyclam) is presented. The complex showed a molar absorbtivity of 1.5?×?104?L?mol?1?cm?1 at 379?nm. Under optimum experimental conditions, a pH of 4.5 and 1.960?×?103?mg?L?1 cyclam were selected, and all measurements were performed 10?min after mixing. Major cations and anions did not show any interference; Beer's law was applicable in the concentration range 0.2–20?mg?L?1 with a detection limit of 0.001?mg?L?1. The standard deviation in the determination is ±0.5?mg?L?1 for a 15.0?mg?L?1 solution (n?=?7). The described method provides a simple and reliable means for determination of Cr(VI) in real samples. 相似文献
76.
Treatment of the 1,6‐anhydrosugar epoxide 5 with a cyano‐Gilman cuprate [(CuCN (6 eq.), MeLi (12 eq.)] surprisingly led to the open chain rearranged (2S,3R)‐1,2‐dihydroxy‐3,6‐dimethylheptan‐4‐one (7), structurally confirmed by conversion to the corresponding diacetate 8. Another unusual reaction was found by hydrogenation of the 2‐tosyl‐1‐bromosugar 11, leading in one operation to the twofold deoxygenated chiral pyran derivative 14. This procedure might prove to be useful in the rapid deoxygenation of sugar derivatives. 相似文献
77.
78.
79.
Mohammed?M?Hefnawy Atef?M?Homoda Mohammed?A?Abounassif Amer?M?Alanazi Abdulrahaman?Al-Majed Gamal?A?MostafaEmail author 《Chemistry Central journal》2014,8(1):59
Background
The construction and electrochemical response characteristics of Poly (vinyl chloride) membrane sensors for moxifloxacin HCl (MOX) are described. The sensing membranes incorporate ion association complexes of moxifloxacin cation and sodium tetraphenyl borate (NaTPB) (sensor 1), phosphomolybdic acid (PMA) (sensor 2) or phosphotungstic acid (PTA) (sensor 3) as electroactive materials.Results
The sensors display a fast, stable and near-Nernstian response over a relative wide moxifloxacin concentration range (1 × 10-2 - 4.0 × 10-6, 1 × 10-2 - 5.0 × 10-6, 1 × 10-2 - 5.0 × 10-6 M), with detection limits of 3 × 10-6, 4 × 10-6 and 4.0 × 10-6 M for sensor 1, 2 and 3, respectively over a pH range of 6.0 - 9.0. The sensors show good discrimination of moxifloxacin from several inorganic and organic compounds. The direct determination of 400 μg/ml of moxifloxacin show an average recovery of 98.5, 99.1 and 98.6% and a mean relative standard deviation of 1.8, 1.6 and 1.8% for sensors 1, 2 and 3 respectively.Conclusions
The proposed sensors have been applied for direct determination of moxifloxacin in some pharmaceutical preparations. The results obtained by determination of moxifloxacin in tablets using the proposed sensors are comparable favorably with those obtained using the US Pharmacopeia method. The sensors have been used as indicator electrodes for potentiometric titration of moxifloxacin.80.
Bhaskar R. Aluri Mohammed Ghalib Markus K. Kindermann Peter G. Jones Joachim W. Heinicke 《Heteroatom Chemistry》2015,26(6):426-435
The reactivity of tBuLi (pentane) toward the N‐neopentyl‐substituted π‐excess P=CH–N heterocycle 1 depends on the solvent (tetrahydrofuran, diethyl ether, hexane, and toluene) and reaction conditions. Trapping of the resulting organolithium compounds with CO2/ClSiMe3, ClSiMe3, or EtI led to various products indicating CH lithiation ( 1a , b ), normal addition of tBuLi at the P=C bond (E/Z ‐2a , b ), inverse addition of the primary addition product 2Li at the P=C bond of a second molecule 1 , affording 3‐tert‐butyl‐2,2’‐bis(1,3‐benzazaphospholines) 3 , or inverse addition of tBuLi ( 4b,c ). The formation of 3 demonstrates a novel route to asymmetric heterocyclic 1,2‐diphosphine ligands. The structure elucidation of the new compounds is based on their 31P and 13C NMR data with conclusive chemical shifts and P–C coupling constants, that of the isolated PH‐functionalized diphosphine 3 on crystal structure analysis. 相似文献