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91.
The transient response of composite plates, with and without central circular holes, to blast loading is studied. The modal-analysis approach has been used in the computation of numerical results, which have been obtained for isotropic and orthotropic plates, with and without holes. In order to verify the theoretical results, experiments have been conducted on aluminum and unidirectionally reinforced E-glassepoxy plates, using a shock tube as the loading device. The experimental peak dynamic strains (normalized with respect to the pressure) are compared with the theoretical values. The strain-time history is also shown for a particular gage location in the composite plate. Finally, a comparison of dynamic-amplification factors, defined as the ratio of the peak dynamic strains to the static strains, has been made between the isotropic and the composite plates. 相似文献
92.
Pullukat T. Joseph Chorappan Pavithran Krishnan G. K. Warrier Chathakudam P. Prabhakaran 《Transition Metal Chemistry》1978,3(1):286-288
Summary Iron(II) complexes of 1-benzyl-2-phenylbenzimidazole (BPBI) and 2-coumarinylbenzimidazole (CBI) have been prepared and characterised. The chloride, bromide, iodide and thiocyanate complexes have the general formula FeL2X2 (where L = BPBI or CBI) while the perchlorate complex of CBI has the composition [Fe(CBI)3](CIO4)2. The perchlorate complex behaves as a 1 : 2 electrolyte in nitrobenzene and methanol; Fe(BPBI)2I2 shows considerable dissociation in nitrobenzene while the other complexes behave as nonelectrolytes. The i.r. spectra of the complexes suggest that N(3) of BPBI and N(3) together with the CO group of CBI are the coordination sites. The magnetic and spectral evidence suggests a regular octahedral geometry for the perchlorate complex and pseudotetrahedral configuration for the iodide and thiocyanate complexes. The other complexes appear to be distorted octahedral with halide bridging.Author to whom all correspondence should be addressed. 相似文献
93.
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95.
T. A. W. Beale S. B. Wilkins R. D. Johnson D. Prabhakaran A. T. Boothroyd P. Steadman S. S. Dhesi P. D. Hatton 《The European physical journal. Special topics》2012,208(1):99-106
The magneto-electric multiferroic TbMn2O5 has a complex magnetic structure in three different magnetically ordered phases. We have determined the nature of the induced
magnetic order on the oxygen sites in the commensurate magnetic phase through full linear X-ray polarisation analysis at the
oxygen K edge. This has been achieved rotating the linear polarisation of the incident beam at the source, and using multilayers to
analyse the polarisation state of the scattered X-ray beam. We have confirmed that the anisotropy of the magnetic scattering
at the oxygen edge is consistent with the anisotropy of the manganese magnetic structure. 相似文献
96.
Ramkrishna Mandal Meenakshi Singh Amrutha A.V. Krishnan Yogita H. Dahat V. Ravichandiran 《Natural product research》2020,34(15):2208-2218
AbstractA facile, atom-economic synthesis of isoxazilidino withaferin, a novel hybrid of withaferin A, has been accomplished via two-step reaction of nitrone synthesis followed by nitrone 1,3-dipolar cycloaddition. The reaction is highly chemoselective (preferential reaction only on one of the two double bonds present on withaferin A) and diastereoselective affording exclusively the cis-fused products. The structure was determined by detailed analysis of 1D, 2D NMR and mass spectral data. 相似文献
97.
Piet Schönherr Shilei Zhang Yuanqian Liu Patryk Kusch Stephanie Reich Terence Giles Dominik Daisenberger Dharmalingam Prabhakaran Yulin Chen Thorsten Hesjedal 《固体物理学:研究快报》2015,9(2):130-135
A novel topological insulator with orthorhombic crystal structure is demonstrated. It is characterized by quasi one‐dimensional, conducting atomic chains instead of the layered, two‐dimensional sheets known from the established Bi2(Se,Te)3 system. The Sb‐doped Bi2Se3 nanowires are grown in a TiO2‐catalyzed process by chemical vapor deposition. The binary Bi2Se3 is transformed from rhombohedral to orthorhombic by substituting Sb on ~38% of the Bi sites. Pure Sb2Se3 is a topologically trivial band insulator with an orthorhombic crystal structure at ambient conditions, and it is known to transform into a topological insulator at high pressure. Angle‐resolved photoemission spectroscopy shows a topological surface state, while Sb doping also tunes the Fermi level to reside in the bandgap. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
98.
Bending at the valence angle N–Cα–C′ (τ) is a known control feature for attenuating the stability of the rare intramolecular i→i hydrogen bonded pseudo five-membered ring C5 structures, the so called 2.05 helices, at Aib. The competitive 310-helical structures still predominate over the C5 structures at Aib for most values of τ. However at Aib∗, a mimic of Aib where the carbonyl O of Aib is replaced with an imidate N (in 5,6-dihydro-4H-1,3-oxazine = Oxa), in the peptidomimic Piv-Pro-Aib∗-Oxa (1), the C5i structure is persistent in both crystals and in solution. Here we show that the i→i hydrogen bond energy is a more determinant control for the relative stability of the C5 structure and estimate its value to be 18.5 ± 0.7 kJ/mol at Aib∗ in 1, through the computational isodesmic reaction approach, using two independent sets of theoretical isodesmic reactions. 相似文献
99.
Reddy DN Thirupathi R Prabhakaran EN 《Chemical communications (Cambridge, England)》2011,47(33):9417-9419
Selective modification of the C-terminal amide in peptides to dihydrooxazine (a novel stable imidate isostere) by intramolecular nucleophilic cyclo-O-alkylation of the corresponding N-(3-bromopropyl)amides results in constraining of the C-terminal residue in natively disallowed conformations both in crystals and in solution. 相似文献
100.
Johnson RD Nair S Chapon LC Bombardi A Vecchini C Prabhakaran D Boothroyd AT Radaelli PG 《Physical review letters》2011,107(13):137205
By combining bulk properties, neutron diffraction, and nonresonant x-ray diffraction measurements, we demonstrate that the new multiferroic Cu(3)Nb(2)O(8) becomes polar simultaneously with the appearance of generalized helicoidal magnetic ordering. The electrical polarization is oriented perpendicularly to the common plane of rotation of the spins-an observation that cannot be reconciled with the conventional theory developed for cycloidal multiferroics. Our results are consistent with coupling between a macroscopic structural rotation, which is allowed in the paramagnetic group, and magnetically induced structural chirality. 相似文献