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101.
Suresh K. Bhargava Kunihiko Kitadai Steven H. Privér Jörg Wagler 《Journal of organometallic chemistry》2010,695(14):1787-1793
[Au2Cl2{μ-2,2′-Ph2As(5,5′-Me2C6H3C6H3)AsPh2}] reacts with phenylacetylene or ethynylferrocene to give the corresponding digold(I) bis(alkynyl) derivatives [Au2(CCR)2{μ-2,2′-Ph2As(5,5′-Me2C6H3C6H3)AsPh2}] [R = Ph (4), Fc (5)]. In contrast, products resulting from the reaction with 1,3- or 1,4-diethynylbenzene (deb) depend markedly on the dichlorodigold(I) complex to ligand ratio. When an excess of alkyne is used, the expected bis(alkynyl) complexes [Au2X2{μ-2,2′-Ph2As(5,5′-Me2C6H3C6H3)AsPh2}] [X = 1,3-deb (6), 1,4-deb (7)] are obtained, but when using a 1:1 molar ratio poorly soluble, presumably polymeric, species are formed. Attempts to prepare a digold(II) bis(alkynyl) derivative by treatment of [Au2Cl2(μ-C6H3-5-Me-2-PPh2)2] with ethynylferrocene in the presence of NaOMe gives a mixture of species, the recrystallization of which yielded a crystal of [{2-(FcCC)-4-MeC6H3PPh2}Au(CCFc)] (1). The reaction of [Au2Cl2(μ-C6H3-5-Me-2-AsPh2)2] with phenylacetylene, 1,3- or 1,4-deb gives a mixture of unidentified products. 相似文献
102.
We report on the sol-gel synthesis of Zn1−xCrxO (x=0.0, 0.05, 0.10, 0.15 and 0.20) nanoparticles. These nanoparticles were characterized by using thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and Photoluminescence (PL). Electronegativity of Cr ions (Cr3+) reduces the final decomposition temperature by 40 °C and activation energy of the reaction when Cr is doped into ZnO. Doping of higher Cr concentration (x≥0.10) into ZnO shows formation of secondary spinel (ZnCr2O4) phase along with the hexagonal (ZnO) and is revealed by XRD. Formation of secondary phase changes the activation energy of the reaction and thus the strain in ZnO lattice. In Raman spectra, additional Raman modes have been observed for Zn1−xCrxO nanoparticles, which can be assigned to the modes generated due to Cr doping. The Cr doping into ZnO is also supported by PL, in which vacancies are formed with Cr ion incorporation and emission band shifts towards higher wavelength. 相似文献
103.
O. Anwar Bg Lik Sim J. Zueco R. Bhargava 《Communications in Nonlinear Science & Numerical Simulation》2010,15(2):345-359
A numerical solution is developed for the viscous, incompressible, magnetohydrodynamic flow in a rotating channel comprising two infinite parallel plates and containing a Darcian porous medium, the plates lying in the x–z plane, under constant pressure gradient. The system is subjected to a strong, inclined magnetic field orientated to the positive direction of the y-axis (rotational axis, normal to the x–z plane). The Navier–Stokes flow equations for a general rotating hydromagnetic flow are reduced to a pair of linear, viscous partial differential equations neglecting convective acceleration terms, for primary velocity (u′) and secondary velocity (v′) where these velocities are directed along the x and y axes. Only viscous terms are retained in the momenta equations. The model is non-dimensionalized and shown to be controlled by a number of dimensionless parameters. The resulting dimensionless ordinary differential equations are solved using a robust numerical method, Network Simulation Methodology. Full details of the numerics are provided. The present solutions are also benchmarked against the analytical solutions presented recently by Ghosh and Pop [Ghosh SK, Pop I. An analytical approach to MHD plasma behaviour of a rotating environment in the presence of an inclined magnetic field as compared to excitation frequency. Int J Appl Mech Eng 2006;11(4):845–856] for the case of a purely fluid medium (infinite permeability). We study graphically the influence of Hartmann number (Ha, magnetic field parameter), Ekman number (Ek, rotation parameter), Hall current parameter (Nh), Darcy number (Da, permeability parameter), pressure gradient (Np) and also magnetic field inclination (θ) on primary and secondary velocity fields. Additionally we investigate the effects of these multiphysical parameters on the dimensionless shear stresses at the plates. Both primary and secondary velocity are seen to be increased with a rise in Darcy number, owing to a simultaneous reduction in Darcian drag force. Primary velocity is seen to decrease with an increase in Hall current parameter (Nh) but there is a decrease in secondary velocity. The study finds important applications in magnetic materials processing, hydromagnetic plasma energy generators, magneto-geophysics and planetary astrophysics. 相似文献
104.
A rapid method for determining total iron in iron ores, sinter and related materials without use of mercury compounds is described. Fusion of the sample with sodium peroxide in a zirconium crucible and subsequent treatment with acid yields total decomposition and a solution amenable to direct reduction to ferrous iron with a silver reductor and subsequent titration with dichromate. Results for NBS, BCS and ISO reference standard ores demonstrate the universal applicability of the method both for routine and referee analysis. There is no interference from vanadium and two samples can be analysed in 30 min. 相似文献
105.
Suman Mehrotra J. P. Barthwal A. K. Saxena K. P. Bhargava S. S. Parmar 《Journal of heterocyclic chemistry》1981,18(6):1157-1159
Twelve 6-substituted-2-(1′-mercaptoacetyl-3′-arylurea)-3-phenyl-4-quinazolones were synthesized by condensation of 6-substituted anthranilic acids and aryl isothiocyanates followed by reaction with chloroacetyl arylurea. These compounds were characterized by their sharp melting points and elemental analyses. All compounds were evaluated for their enzyme inhibitory activity. It was found that all substituted quinazolones at a final concentration of 2 × 10?4 M inhibited in vitro monoamine oxidase and succinate dehydrogenase activity of rat brain homogenates and the degree of inhibition ranged from 11–77% and 25–53%, respectively. 相似文献
106.
V. K. Bhargava V. K. Rao S. G. Marathe S. M. Sahakundu R. H. Iyer 《Journal of Radioanalytical and Nuclear Chemistry》1978,47(1-2):5-15
A radiochemical method is described for the separation of heavier rare earths from the fission of uranium. The method is particularly
suitable for the separation of low yield (10−5%–10−7%), highly asymmetric rare earth fission products viz.179,177Lu,175Yb,173Tm,172,171Er,167Ho and161,160Tb in the neutron induced fission of natural and depleted uranium targets. Additional separation steps have been incorporated
for decontamination from239Np (an activation product) and93-90Y (a high fission-yield product) which show similar chemical behaviour to rare earths. Separation of individual rare earths
is achieved by a cation exchange method performed at 80°C by elution with α-hydroxyisobutyric acid (α-HIBA). 相似文献
107.
Jos Luis Mata‐Mata J. Alfredo Gutirrez M. Angeles Paz‐Sandoval Amira R. Madrigal Antonio Martínez‐Richa 《Journal of polymer science. Part A, Polymer chemistry》2006,44(24):6926-6942
End‐functionalized polyesters have been synthesized by ring‐opening polymerization (ROP) of ?‐caprolactone (CL) initiated with five different ruthenium derivatives in the presence of a series of alcohols as transfer agents. Mechanistic studies were performed for ROP of CL with RuCl2(PPh3)3 ( I ), TpRuCl(PPh3)2 ( II ), and TpRuCl(PHPh2)(PPh3) ( III ) as catalysts in the presence or absence of benzyl alcohol (BzOH). Obtained molecular weights are proportional to CL/BzOH ratio, but there is not a direct relationship with CL/ruthenium complex ratios. 1H and 13C NMR spectroscopy revealed the existence of benzyl ester end‐groups. Catalysis involves (a) dissociation of ruthenium complexes, (b) coordination of the lactone CL, (c) coordination of the BzOH with the formation of a metal alkoxide, (d) transfer from the alkoxyl ligand to the coordinated lactone, and (e) ring‐opening of CL by oxygen‐acyl bond cleavage. The proposed mechanism is supported by 1H, 13C, and 31P NMR, gel permeation chromatography (GPC), and MALDI‐TOF analysis of the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6926–6942, 2006 相似文献
108.
Karla A. Barrera‐Rivera Ángel Marcos‐Fernández Ricardo Vera‐Graziano Antonio Martínez‐Richa 《Journal of polymer science. Part A, Polymer chemistry》2009,47(21):5792-5805
Yarrowia lipolytica (YLL), Candida rugosa (CRL), and porcine pancreatic lipase (PPL) were employed successfully as catalysts in the enzymatic ring‐opening polymerization (ROP) of ε‐caprolactone in the presence of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1‐butylpyridinium tetrafluoroborate ([BuPy][BF4]), 1‐butylpyridinium trifluoroacetate ([BuPy][CF3COO]), 1‐ethyl‐3‐methylimidazolium nitrate ([EMIM][NO3]) ionic liquids. Poly(ε‐caprolactone)s (PCLs) with molecular weights (Mn) in the range of 300–9000 Da were obtained. 1H‐ and 13C‐NMR analyses on PCLs formed by YLL, CRL, and PPL showed asymmetric telechelic α‐hydroxy‐ω‐carboxylic acid end groups. Differences between CP‐MAS and MAS spectra are observed and discussed in terms of morphology. MALDI‐TOF spectra show the formation of at least seven species. Differential scanning calorimetry (DSC) and Wide Angle X‐Ray Scattering (WAXS) results demonstrate the high degree of crystallinity present in all the polyesters. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5792–5805, 2009 相似文献
109.
110.
The linear and nonlinear low field AC susceptibilities of Zn0.75Co0.25Fe0.5Cr1.5O4 show peaks due to non-critical contributions, which mask the peak due to spin glass ordering. They extend into the region of temperatures in which Mössbauer spectra do not show any magnetic component. When a DC field of 200 Oe suppresses the non-critical contributions, peak due to spin glass ordering is clearly visible. The spin glass ordering is thus shown to be a thermodynamic transition. The critical exponent is found to fall within the range found using other spin glasses. Mössbauer spectra in zero fields provide TSG, which agrees with the peak temperature of AC susceptibilities in the absence of non-critical contributions. 〈SZ〉 determined using Mössbauer spectra does not show any anomaly. In the presence of a field of 5 T, the spectra show SG ordering at 4.2 K, which converts into ferrimagnetic ordering at higher temperatures. 相似文献