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21.
Ramesh P Okazaki T Taniguchi R Kimura J Sugai T Sato K Ozeki Y Shinohara H 《The journal of physical chemistry. B》2005,109(3):1141-1147
Double-wall carbon nanotubes (DWNTs) have been selectively synthesized over Fe/Co loaded mesoporous silica by catalytic chemical vapor deposition of alcohol. Several silica materials with desired pore diameter and morphology have been investigated for the DWNT growth. The diameter distribution and selectivity of the DWNT are found to depend on the reaction temperature, pore size, and thermal stability of the support material. A high-yield synthesis of DWNTs has been achieved at 900 degrees C over high-temperature stable mesoporous silica. The outer diameter of DWNTs is found to be in the range of 1.5-5.4 nm with a "d" spacing of 0.38 +/- 0.02 nm between inner and outer layers, which is much larger than those of multiwall carbon nanotubes. 相似文献
22.
The purpose of this paper is to compare and contrast the modeling capabilities of seven algebraic modeling languages (ML) available today, namely, AMPL, GAMS, LINGO, LPL, MPL, PC-PROG and XPRESS-LP. In general, these MLs do an excellent job of providing an interface with which the modeler can specify an algebraically formatted linear program (LP). That is, each ML provides a substantial improvement in time and convenience over the matrix generator/report writers of the last few decades. Further, each of the MLs provides: (1) significant flexibility in model specification, instantiation and modification, (2) effective and efficient conversion from algebraic to solver format, and (3) an understandable and, for the most part, self-documenting model representation. In addition, each of the MLs is constantly being updated and upgraded to provide additional capabilities sought by practitioners and users. However, as shown in the fifteen tables provided in the body of this paper, each ML has its own set of competitive advantages. For example, the most integrated environments (i.e. those integrating the modeling language with a full-screen editor, data import capabilities and a solver) are provided by LINGO and PC-PROG. The most user-friendly interfaces are provided by MPL and PC-PROG, both of which provide window-based interfaces to create models and pop-up windows to display error messages; MPL also uses pull-down menus to specify various operations, whereas PC-PROG uses function keys for operational control. Package costs are led by a current (March, 1991) introductory offer from LINGO. Modeling effectiveness, especially with respect to flexibility in specifying arithmetic statements, is led by GAMS and LPL. Model compactness, as measured by the number of lines required to specify a model, is led by AMPL, LPL, MPL and PC-PROG; LPL, MPL and PC-PROG also provide context sensitive editors which automatically position the cursor where the error was detected. And finally, the most comprehensive user documentation is provided by GAMS, whereas GAMS, LINGO and LPL provide extensive libraries of sample models for those users who learn by example. 相似文献
23.
The synthesis and structure-activity-relationship (SAR) for a series of N-substituted piperazinyl carbamoyl 7-15 and piperazinyl acetyl 18-26 derivatives of tetrahydropapaverine have been carried out. The general synthetic methods of carbamoyl tetrahydropapaverine analogues involve N-substituted piperazines and carbamoyl imidazole tetrahydropapaverine as starting materials. Another route for synthesizing these compounds, involving the formation of carbamoyl imidazole piperazine has also been explored. Acylation of tetrahydropapaverine followed by substitution with various piperazinyl moities afforded the acetyl tetrahydropapaverine derivatives. Variously substituted piperazines have been used to monitor the effect of electron releasing and electron withdrawing substituents upon the antispasmodic activity of the molecules. Effect of varying electron densities on the antispasmodic activity, by altering the position of these groups on the benzene ring has also been monitored. Pharmacological methods involve the in vitro antispasmodic activity studies on a freshly removed guinea pig ileum using a force displacement transducer amplifier connected to a physiograph. Among the analogues synthesized in the present study, a promising compound 7, a potent muscle relaxant as compared to papaverine has been obtained. 相似文献
24.
Ramapanicker Ramesh 《Tetrahedron》2007,63(37):9153-9162
The base catalyzed cyclization of N-aryl and N-alkyl-O-propargyl carbamates is studied in detail. The effect of various bases and solvents on the efficacy of this cyclization reaction is analyzed and a new base-solvent system (LiOH in DMF) for effective cyclization of these carbamates is reported. A number of differentially substituted O-propargyl carbamates were cyclized to the corresponding 2-oxazolidinones under these conditions. The reaction conditions reported here are mild and no side reactions were observed in any of the substrates studied. A propargyl carbonate group was unaffected during the course of the cyclization of the O-propargyl carbamate group. The propargyl carbamates were prepared from the corresponding alkyl or aryl amines and the corresponding propargyl chloroformate, resulting in oxazolidinones diversely substituted at the nitrogen atom. N-Aryl-O-propargyl carbamates cyclized readily to the corresponding oxazolidinones with LiOH in DMF, whereas N-alkyl-O-propargyl carbamates reacted slowly under the same conditions. O-Propargyl carbamates substituted at the 1-position tend to cyclize faster whereas those substituted at 3-position cyclize considerably slower than the unsubstituted carbamates. 相似文献
25.
Summary The binuclear iron(III) compound, Fe2Cl(OH)2(MeCO2)3 2 AcOH combines with pyridine, -picoline and 2,2-bipyridyl (B) to form Fe2Cl(OH)2(AcO)3·B adducts. The secondary bases, pyrrolidine and diethylamine (RNH), on the other hand, combine with the complete elimination of chlorine to form, Fe2(NR)(OH)2(AcO)3. These products have been characterised by molecular weight, i.r. spectra, magnetic susceptibility and Mössbauer measurements. 相似文献
26.
Venkatachalam G Ramesh R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(9):2081-2087
A series of stable low spin Ru(III) complexes of the type [RuX2(EPh3)2(L)] (where E = P or As; X = Cl or Br; L = mono basic bidentate Schiff bases) have been synthesized and were characterized by analytical, spectral and electrochemical data. A distorted octahedral geometry has been proposed for all the complexes. These complexes catalyze oxidation of primary alcohols and secondary alcohol with high yields in the presence of N-methylmorpholine-N-oxide (NMO). The ruthenium(III) Schiff base complexes show growth inhibitory activity against the bacteria Staphylococcus aureus (209p) and E. coli ESS (2231). 相似文献
27.
An enantioselective total synthesis of the novel natural product (+)-panepophenanthrin has been accomplished in which a biomimetic Diels-Alder dimerisation is a key step. The monomeric precursor 2 was assembled from the readily available Diels-Alder adduct of cyclopentadiene and p-benzoquinone through a short, simple sequence employing chemo- and stereoselective operations. 相似文献
28.
Ramesh Chitrakar Hirofumi KanohYoshitaka Miyai Kenta Ooi 《Journal of solid state chemistry》2002,163(1):1-4
Microwave irradiation of a suspension of γ-MnOOH in a 4 mol dm−3 LiOH solution brought about a rapid formation of semicrystalline orthorhombic LiMnO2 (o-LiMnO2) within 30 min at 120°C. Cubic Li1.6Mn1.6O4 was obtained by heating o-LiMnO2 at 400°C; lithium could be topotactically extracted from Li1.6Mn1.6O4 with acid to form cubic H1.6Mn1.6O4. 相似文献
29.
A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines () from 3-(3-methylbut-1-enyl)-2-quinolones () is described. A neat synthesis of the alkaloids (±)-lunacrine (), (±)-lunasine () and (±)-demethoxylunacrine () is also reported. 相似文献
30.
V. Balaram S. L. Ramesh K. V. Anjaiah 《Fresenius' Journal of Analytical Chemistry》1995,353(2):176-182
ICP-MS has been used for the determination of over 30 geochemically significant trace elements (Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th, U and REEs) in anorthosites and related rock reference samples. Open acid digestion, pressure decomposition using HF, HNO3 and HClO4, and a fusion method using lithium metaborate and subsequent dissolution in dil. HNO3 were adopted for the decomposition of these rock samples before analysis. The dissolution problems and interference effects are discussed. Rh and Bi were used as internal standards. The first set of data on several rare earths and other trace elements in the Russian anorthosite reference sample, MO-6 are presented along with data on other samples. The data are compared with the available data. The results obtained with different dissolution methods were found to be in good agreement for the majority of the trace elements. The accuracy and precision achieved (better than 6% RSD in most cases) suggested that the data obtained by ICP-MS for such samples are best suited for geochemical interpretations. 相似文献