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排序方式: 共有215条查询结果,搜索用时 15 毫秒
191.
S. P. Elangovan V. Krishnasamy V. Murugesan 《Reaction Kinetics and Catalysis Letters》1995,55(1):153-159
SAPO-5 and SAPO-11 were synthesized using aluminium isopropoxide and tetraethyl orthosilicate as source materials for aluminium and silicon, respectively, adopting a modified procedure. The as-synthesized materials were characterized by XRD and chemical analysis. Acidity was found by temperature-programmed desorption using TGA. Unit cell parameters were calculated for both as-synthesized and calcined materials. The catalytic activity of SAPO-5 and SAPO-11 in camphene isomerization was studied and selective formation of tricyclene was achieved. 相似文献
192.
Kenneth A. Rubinson John A. Cook James B. Mitchell R. Murugesan Murali C. Krishna Sankaran Subramanian 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,132(2):255-259
A truncated transmission line probe (TLP) has been utilized to excite and detect time domain responses after pulsed excitation in electron paramagnetic resonance (EPR) spectroscopic experiments in the frequency range 200–400 MHz. The TLP device is a modified short-circuited coaxial line, which allows the irradiation of the sample by the traveling waveB1fields in the frequency range of kilohertz to 30 GHz. In EPR studies at 300 MHz carrier frequency, with 10 W incident power, a 45° pulse is 45 ns in duration. This corresponds to a 0.9-GB1field. Using the TLP, time-domain responses from the solidN-methyl pyridiniumtetra-cyanoquinodimethane (TCNQ) were collected at 200, 250, 300, and 350 MHz, with the range limited by the amplifiers. In addition two tubes containing TCNQ placed side-by-side vertically along the axis of the probe were used to collect time domain responses in the presence of magnetic field gradients to test the feasibility of two-dimensional imaging using a TLP. The magnetic field gradient was steered in thexzplane and 36 projections were collected at 5° intervals. Using filtered back-projection image reconstruction, the two-dimensional spatial image in thexzplane was obtained at good resolution. 相似文献
193.
R. Murugesan A. Thamaraichelvan P. Sami 《Journal of inclusion phenomena and macrocyclic chemistry》1999,34(3):235-243
Synthesis and IR spectra of novel Hofmann-T
d
-type aniline clathrates, M(NH3)2Zn(CN)4· 2C6H5NH2 (M = Zn or Cd) are reported for the first time. All the vibrational modes of aniline are characterised. The shifts in
a
(NH2) and
s
(NH2) reveal hydrogen bonding between the NH2 group of aniline and the cyanide group of the host lattice to be stronger than in Hofmann-type aniline clathrates. However, the out of plane deformation mode of aniline indicates absence of hydrogen bonding between ammonia and the -cloud of the aniline ring. The related aniline clathrates with bridging Cd(CN)4 M(NH3)2Cd(CN)4· 2C6H5NH2 (M=Zn or Cd), exhibit similar behaviour. 相似文献
194.
Chandran Karunakaran K.R. Justin Thomas Arunachalam Shunmugasundaram Ramachandran Murugesan 《Journal of chemical crystallography》1999,29(4):413-420
Single crystals of the title Cu(II) complex, [Cu(stpy)4(ONO2)(ONO2)] [stpy = trans-4-styryl-pyridine] have been prepared and characterized by elemental and thermal analyses, IR, electronic and EPR spectral measurements, and X-ray crystal structure determination. The complex crystallizes in the monoclinic space group P21/c with unit-cell parameters, a = 12.985(2), b = 22.865(8), c = 17.024(10) Å, = 112.29(3)°, and Z = 4. The structure consists of discrete monomeric units of [Cu(stpy)4(ONO2)(ONO2)]. The equatorial positions of the Cu(II) polyhedron are occupied by nitrogen atoms of the four stpy ligands and the axial positions by the oxygens of two unidentate nitrate anions. One of these oxygens is at rather longer distance [2.609(3) Å] and may be considered to be semicoordinated. If this semibond is ignored, the coordination geometry lies closer to an idealized square pyramid than to the trigonal bipyramid geometry. IR spectra reveal nitrogen coordination from stpy and asymmetry in the monodentate oxygen binding of the two nitrate ligands. The optical reflectance band at 600 nm suggests pseudo-square-based pyramidal geometry around Cu(II). Well-resolved Cu(II) hyperfine features in the EPR spectra reveal the absence of exchange interactions between adjacent copper centers. Optical and EPR spectra of a methanolic solution of the complex indicate solvent interactions. Thermogravimetric analysis shows the complex to be stable up to 175°C. 相似文献
195.
196.
Benial AM Ramakrishnan V Murugesan R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,56(14):1088-2781
Single crystal electron paramagnetic resonance (EPR) of Cu(C5H5NO)6(BF4)2 is studied at 300 K. The spin Hamiltonian parameters obtained at 300 K are A11 = -149.8, A22 = -50.7 and A33 = -37.7 (all in units of 10(-4) cm(-1)), g11 = 2.3452, g22 = 2.0679 and g33 = 2.0695. Angular variation of hyperfine structure lines shows the presence of a single magnetic site. The low magnitude of the A11 value for Cu(C5H5NO)6(BF4)2 is rationalized in terms of a mixed d(x2-y2)/d(z2) ground state. 相似文献
197.
Oxidation of palmatine () choride with -chloroperbenzoic acid in methylene chloride in the presence of sodium bicarbonate at near ?78° C yields polycarpine (). A new biogenetic route to the aporphines is proposed which does not involve phenolic oxidative coupling, and proceeds through the intermediacy of protoberberinium salts. 相似文献
198.
Anderson EH Ruegsegger MA Murugesan G Kottke-Marchant K Marchant RE 《Macromolecular bioscience》2004,4(8):766-775
We report on a novel series of biomimetic polymers exhibiting interfacial properties similar to the extracellular matrix. A series of well-defined surfactant polymers were synthesized by simultaneously incorporating arginine-glycine-aspartic acid (RGD) peptide, dextran oligosaccharide, and hexyl ligands with controlled feed ratios onto a poly(vinyl amine) (PVAm) backbone. The peptide sequence was H-GSSSGRGDSPA-NH(2) (Pep) having a hydrophilic extender at the amino terminus and capped carboxy terminus. The peptide-to-dextran (Pep:Dex) ratios were varied to create surfactants having 0, 25, 50, 75, and 100 mol-% peptide relative to dextran. The surfactants were characterized by IR, NMR and atomic force microscopy (AFM) for composition and surface active properties. AFM confirmed full surface coverage of PVAm(Pep)(100%) on graphite, and supported the mechanism of interdigitation of hexyl ligands between surfactant molecules within a specified range of hexyl chain densities. the attachment and growth of human pulmonary artery endothelial cells on the PVAm(Pep)(100%) surface was identical to the fibronectin positive control. Cell adhesion decreased dramatically with decreasing peptide density on the surfactant polymers. Molecular model of a peptide surfactant polymer, consisting of poly(vinyl amine) backbone with peptide, dextran oligosaccharide and hexyl branches coupled to the polymer chain. 相似文献
199.
200.
Polyaniline (PANI) is one of the most studied and most stable electrically conductive polymers, with the conductive form being the navy blue emeraldine salt. However, PANI is very difficult to process and displays poor mechanical performance, which suggests improving its properties by developing composite systems. In the present approach, PANI was generated in situ in poly(dimethylsiloxane) (PDMS) networks. The color of the composites varied from brown, to blue, to greenish blue, with the blue samples being the most conductive. The chemical structures of the samples were studied using FT-IR/ATR spectroscopy, which confirmed that there was more conjugation in the more conductive samples.This paper is dedicated to Mike Owen on occasion of his winning the DeBruyn medal, the first silicon chemist to do so. 相似文献