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1.
I. Kawabe T. Tanaka V. Ekambaram A. M. Davis L. Grossman 《Journal of Radioanalytical and Nuclear Chemistry》1986,102(1):227-238
Second-order neutron activation becomes a serious interference in NAA determinations of REE in submilligram samples of meteoritic and terrestrial materials when neutron fluences reach levels of 1020 n·cm–2 or more. The Dy-interference to Ho determination and the Eu-interference to Gd determination are quite, large. We discuss the importance of second-order activation interferences in REE determinations, and present an experimental method to correct the Dy-interference to Ho determination by INAA. Ho concentrations in splits of less than 0.2 mg of BCR-1 and SP can be accurately determined by INAA with a neutron fluence of 2·1020 n·cm–2 in spite of large Dy interferences of up to 200%. It is necessary for NAA determinations of REE with high neutron fluences that each REE standard be separated from its neighboring REE, in order to correct the second-order activation interferences experimentally. 相似文献
2.
Coupled thermo-mechanical modelling of bulk-metallic glasses: Theory, finite-element simulations and experimental verification 总被引:1,自引:0,他引:1
A three-dimensional, finite-deformation-based constitutive model to describe the behavior of metallic glasses in the supercooled liquid region has been developed. By formulating the theory using the principles of thermodynamics and the concept of micro-force balance [Gurtin, M., 2000. On the plasticity of single crystals: free energy, microforces, plastic-strain gradients. J. Mech. Phys. Solids 48, 989-1036], a kinetic equation for the free volume concentration is derived by augmenting the Helmholtz free energy used for a conventional metallic alloy with a flow-defect free energy which depends on the free volume concentration and its spatial gradient. The developed constitutive model has also been implemented in the commercially available finite-element program ABAQUS/Explicit (2005) by writing a user-material subroutine. The constitutive parameters/functions in the model were calibrated by fitting the constitutive model to the experimental simple compression stress-strain curves conducted under a variety of strain-rates at a temperature in the supercooled liquid region [Lu, J., Ravichandran, G., Johnson, W., 2003. Deformation behavior of the Zr-Ti-Cu-Ni-Be bulk metallic glass over a wide range of strain-rates and temperatures. Acta Mater. 51, 3429-3443].With the model calibrated, the constitutive model was able to reproduce the simple compression stress-strain curves for jump-in-strain-rate experiments to good accuracy. Furthermore stress-strain responses for simple compression experiments conducted at different ambient temperatures within the supercooled liquid region were also accurately reproduced by the constitutive model. Finally, shear localization studies also show that the constitutive model can reasonably well predict the orientation of shear bands for compression experiments conducted at temperatures within the supercooled liquid region [Wang, G., Shen, J., Sun, J., Lu, Z., Stachurski, Z., Zhou, B., 2005. Compressive fracture characteristics of a Zr-based bulk metallic glass at high test temperatures. Mater. Sci. Eng. A 398, 82-87]. 相似文献
3.
Livanov K Madhu V Balaraman E Shimon LJ Diskin-Posner Y Neumann R 《Inorganic chemistry》2011,50(22):11273-11275
The catalytic photocleavage of CS(2) to S(8) and a (C(x)S(y))(n) polymer with visible light using a dinuclear ruthenium(II) compound with a bipyridine units for photoactivity and a vicinal tertiary amine binding site for CS(2) activation was studied. The catalyst was characterized by X-ray diffraction, (1)H NMR, and (13)C NMR, ESI-MS and elemental analysis. CS(2) photocleavage was significant (240 turnovers, 20 h) to yield isolable S(8) and a (C(x)S(y))(n) polymer. A mononuclear catalyst or one without an amine binding site showed significantly less activity. XPS of the (C(x)S(y))(n) polymer showed a carbon/sulfur ratio ~1.5-1.6 indicating that in part both C-S bonds of CS(2) had been cleaved. Catalyst was also included within the polymer. The absence of peaks in the (1)H NMR verified the (C(x)S(y))(n) nature of the polymer, while (13)C NMR and IR indicated that the polymer had multiple types of C-S and C-C bonds. 相似文献
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5.
Murugan Subaramanian Vinod G. Landge Akash Mondal Virendrakumar Gupta Ekambaram Balaraman 《化学:亚洲杂志》2019,14(24):4557-4562
A molecularly defined NiII‐complex catalyzing the chemoselective acetalization of aldehydes with alcohols under neutral conditions is reported. The reaction is general, efficient and showed a wide substrate scope (including aliphatic aldehydes) as well as excellent functional group tolerance. Reusability of the present nickel catalyst is also demonstrated. 相似文献
6.
Sambandan Ekambaram Masaru Yanagisawa Satoshi Uchida Yoshinobu Fujishiro Tsugio Sato 《Molecular Crystals and Liquid Crystals》2013,570(2):213-218
Abstract TiO2 and Pt have been intercalated in hectorite and H4Nb6O17. The height of TiO2 and Pt pillars was less than 0.8 nm and the band gap energy of TiO2 pillars was ca. 3.3 eV. Both hectorite/TiO2 and H4Nb6O17(Pt, TiO2) were capable of hydrogen evolution following irradiation from a high pressure mercury are (λ > 290 nm) in the presence of methanol as a sacrificial hole acceptor and the hydrogen evolution was enhanced by co-incorporation of Pt, although hectorite and hectorite/Pt did not show photocatalytic activity. Incorporation of Pt or Pt and TiO2 in the interlayer of H4Nb6O17 has resulted in enhanced photo evolution of hydrogen, however, TiO2 alone in the interlayer of H4Nb6O17 showed adverse photocatalytic activity. 相似文献
7.
Balaraman E Gnanaprakasam B Shimon LJ Milstein D 《Journal of the American Chemical Society》2010,132(47):16756-16758
The selective, direct hydrogenation of amides to the corresponding alcohols and amines with cleavage of the C-N bond was discovered. The expected products of C-O cleavage are not formed (except as traces in the case of anilides). The reaction proceeds under mild pressure and neutral, homogeneous conditions using a dearomatized, bipyridyl-based PNN Ru(II) pincer complex as a catalyst. The postulated mechanism involves metal-ligand cooperation by aromatization-dearomatization of the heteroaromatic pincer core and does not involve hydrolytic cleavage of the amide. The simplicity, generality, and efficiency of this environmentally benign process make it attractive for the direct transformations of amides to alcohols and amines in good to excellent yields. 相似文献
8.
Sambandan Ekambaram Slavi C. Sevov 《Angewandte Chemie (International ed. in English)》1999,38(3):372-375
The first large‐pore, mixed‐valent titanium phosphate was hydrothermally synthesized by using elemental titanium as a starting material, and 1,3‐diaminopropane as a template. The structure displays an open framework containing octahedrally coordinated TiIII and TiIV centers and tetrahedrally coordinated P centers; the diamine molecules are located within the zigzag channels (the picture shows a polyhedral representation of the structure). 相似文献
9.
Ekambaram Ramesh 《Tetrahedron letters》2008,49(17):2810-2814
A facile synthesis of pyrano/thiopyranoquinolines is accomplished in excellent yields through imino Diels-Alder reaction using silica gel impregnated with indium trichloride as catalyst. 相似文献
10.
Boopathy Gnanaprakasam Ekambaram Balaraman Chidambaram Gunanathan David Milstein 《Journal of polymer science. Part A, Polymer chemistry》2012,50(9):1755-1765
The amidation reaction based on catalytic coupling of alcohols with amines previously reported by us, using the pincer complexes 1 and 2 as catalysts, was applied to the generation of polyamides from nonactivated diols and diamines. A range of polymers was prepared, with Mn up to 26.9 kDa. Unlike the traditional syntheses of polyamides based on carboxylic acid derivatives, which require the use of toxic reagents and generate stoichiometric amounts of waste, this process generates only molecular hydrogen as byproduct. Both aromatic and aliphatic diols and diamines were used. Gel permeation chromatography measurements of the dimethylformamide‐soluble polymers and thermal studies of the polyamides were performed. Matrix assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) spectra are also reported. Thermogravimetric analyses studies indicate that the aromatic polyamides (with the exception of the pyridine‐based polyamide) are more thermally stable than the aliphatic ones. This general, environmentally benign method for the synthesis of polyamides is homogeneously catalyzed under neutral conditions by dearomatized ruthenium‐pincer complexes 1 and 2 and proceeds in 1,4‐dioxane under an inert atmosphere. Conditions for polyamidation in the absence of solvent are also reported, using the pincer complex 2 as catalyst. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献