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71.
Naresh Kumar Shiva Prasad D.S. Misra N. Venkataramani Murtaza Bohra R. Krishnan 《Journal of magnetism and magnetic materials》2008
Yttrium iron garnet (YIG) thin films were deposited on fused quartz substrate at different substrate temperatures (Ts) varying from room temperature (RT) to 850 °C using pulsed laser deposition (PLD) technique. All the films in the as-deposited state were X-ray amorphous and non-magnetic at RT. The film deposited at RT after annealing at temperatures Ta?700 °C showed both X-ray peaks and the magnetic order. The films deposited at higher Ts (500–850 °C) and then annealed at 700 °C resulted in better-quality films with higher 4πMs value. The highest value of magnetization was for the sample deposited at 850 °C and annealed at 700 °C, which is 68% of the bulk 4πMs value. 相似文献
72.
73.
Shiva K. Rastogi Robert A. Rogers Justin Shi Christopher T. Brown Cindy Salinas Katherine M. Martin Jacob Armitage Christopher Dorsey Gao Chun Peter Rinaldi William J. Brittain 《Magnetic resonance in chemistry : MRC》2016,54(2):126-131
We report through‐space (TS) 19F–19F coupling for ortho‐fluoro‐substituted Z ‐azobenzenes. The magnitude of the TS‐coupling constant (TSJFF) ranged from 2.2–5.9 Hz. Using empirical formulas reported in the literature, these coupling constants correspond to non‐bonded F–F distances (dFF) of 3.0–3.5 Å. These non‐bonded distances are significantly smaller than those determined by X‐ray crystallography or density functional theory, which argues that simple models of 19F–19F TS spin–spin coupling solely based dFF are not applicable. 1H, 13C and 19F data are reported for both the E and Z isomers of ten fluorinated azobenzenes. Density functional theory [B3YLP/6‐311++G(d,p)] was used to calculate 19F chemical shifts, and the calculated values deviated 0.3–10.0 ppm compared with experimental values. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
74.
M. Chandrappa G. V. Shiva Reddy Rahaman Fazlur B. Narasimha Murthy Phani Kumar Pullela S. Girish Kumar 《Chemical Papers》2017,71(12):2445-2453
Terpyridines are unique class of functional compounds that is extensively spotlighted in diverse fields like synthesis of supramolecular chemistry, nanomaterials, medicinal chemistry intermediates, drugs and active pharmaceutical ingredients and so on. The key challenges for the production of terpyridine lie in the bulk scale synthesis of intermediates. The expansively used synthon for terpyridine synthesis is 4′-chloro-2,2′:6′,2″-terpyridine and their bulk scale synthesis under the ambient conditions using a Fe3O4@SiO2 magnetic nanomaterial catalyst is investigated in the present work. In the protocol stabilized, ethyl-2-pinacolate and acetone were reacted in the presence of NaH to obtain 1,5-bis(2-pyridinyl) pentane-1,3,5-trione. The enolate of acetone is difficult to generate even with NaH and we used Fe3O4@SiO2 to increase the rate of H2 gas evolution. The triketone is cyclized with CH3COONH4 to obtain 2,6-bis(2-pyridinyl)-4-pyridine. This reaction proceeds quantitatively and the off-white solid was easy to isolate from the reaction medium. The subsequent aromatization was observed with PCl5/POCl3 and acidic silica gel promoted the product yield to reach ~78%. The crux of the present protocol is that it does not involve any column purification and significant yield of 4′-chloro-2,2′:6′,2″-terpyridine can be conveniently attained. The Fe3O4@SiO2 aids in the stabilization of carbonyl on the solid support and abstraction of hydrogen from methyl group of acetone. The 40 nm sized Fe3O4@SiO2 favored the maximum yield attributed to the density of active sites to promote the reactions. Due to high value nature of 4′-chloro-2,2′:6′,2″-terpyridine, the nominal 30% yield improvement achieved at the bulk scale gauges significant at the industrial scale. 相似文献
75.
76.
M. Lakshmi Kantam G.T. Venkanna Ch. Sridhar K.B. Shiva Kumar 《Tetrahedron letters》2006,47(23):3897-3899
Copper exchanged fluorapatite (CuFAP) is an effective heterogeneous catalyst for N-arylation of heterocycles with bromo- or iodoarenes using K2CO3 as base. N-Arylated products were isolated in good to excellent yields, demonstrating the versatility of the reaction. 相似文献
77.
Shiva Mittal Niraj K. Shukla Nadya A. S. Atlouba 《Numerical Functional Analysis & Optimization》2016,37(2):253-276
In this article, we study the theory of nonuniform minimally supported frequency multiwavelets and nonuniform multiscaling sets. A characterization of nonuniform multiwavelet sets is obtained which generalizes a result of Yu and Gabardo. After introducing a notion of generalized nonuniform scaling set, we obtain a characterization of nonuniform multiscaling sets associated with nonuniform multiresolution analysis having finite multiplicity. In addition, we provide a geometric construction to find families of symmetric nonuniform multiwavelet sets. 相似文献
78.
Mannepalli Lakshmi Kantam Vura Bala Subrahmanyam Kota Balaji Shiva Kumar Gopaladasu T. Venkanna Bojja Sreedhar 《Helvetica chimica acta》2008,91(10):1947-1953
Rhodium fluoroapatite (RhFAP) is an efficient catalyst for conjugate addition of organoboron reagents to α,β‐unsaturated carbonyl compounds. A variety of arylboronic acids and α,β‐unsaturated carbonyl compounds were converted to the corresponding conjugate‐addition products, demonstrating the versatility of the reaction. The reaction is highly selective. RhFAP was recovered quantitatively by simple filtration, and reused for four cycles. 相似文献
79.
Catalytic decomposition of CH4 over Ni-Al2O3-SiO2 catalysts: Influence of pretreatment conditions for the production of H2
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Jangam Ashok Gangadhara Raju Padigapati Shiva Reddy Machiraju Subrahmanyam Akula Venugopal 《天然气化学杂志》2008,17(2):113-119
This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, and effect of reductive pretreatment on the decomposition of methane activity is investigated. The physico-chemical characteristics of fresh and deactivated samples were characterized using BET-SA, XRD, TPR, SEM/TEM, CHNS analyses and correlated with the methane decomposition results obtained. The Ni-Al-Si (4 : 0.5 : 1.5) catalyst reduced with hydrazine hydrate produced better H2 yields of ca. 1815 mol H2/mol Ni than the catalyst reduced with 5% H2/N2. 相似文献
80.
Solvent-free aerobic oxidation of ethylbenzene over supported Ni catalysts using molecular oxygen at atmospheric pressure
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We investigated the aerobic oxidation of ethylbenzene in the absence of solvent or any additive carried out over Ni on different types of supports namely SiO2, hydroxyapatite, SBA-15, and USY Zeolites. The oxidation of ethylbenzene activities was measured in a round bottom flask immersed in oil bath at known reaction temperature. The physicochemical characteristics of the catalysts were examined by BET surface area, XRD, FT-IR and the oxidation activities were correlated with the acidities of the catalysts obtained by TPD of NH3. It was observed that both hydroxyapatite and USY (13% Na2O) supported Ni catalysts displayed higher ethylbenzene conversion and 80% selectivity towards acetophenone. 相似文献