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排序方式: 共有101条查询结果,搜索用时 15 毫秒
81.
Adamovich MI Aggarwal MM Alexandrov YA Andreeva NP Anson ZV Arora R Badyal SK Basova ES Bhalla KB Bhasin A Bhatia VS Bogdanov VG Bubnov VI Burnett TH Cai X Chasnikov IY Chernova LP Chernyavski MM Eligbaeva GZ Eremenko LE Gaitinov AS Ganssauge ER Garpman S Gerassimov SG Grote J Gulamov KG Gupta SK Heckman HH Huang H Jakobsson B Judek B Kachroo S Kadyrov FG Kalyachina GS Kanygina EK Karlsson L Kaul GL Kharlamov SP Koss T Kumar V Lal P Larionova VG Lepetan VN Liu LS Lokanathan S Lord J Lukicheva S 《Physical review letters》1991,67(10):1201-1205
82.
Jenkins HD Glasser L Klapötke TM Crawford MJ Bhasin KK Lee J Schrobilgen GJ Sunderlin LS Liebman JF 《Inorganic chemistry》2004,43(20):6238-6248
By virtue of our recently established relationships, knowledge of the formula unit volume, V(m), of a solid ionic material permits estimation of thermodynamic properties such as standard entropy, lattice potential energy, and, hence, enthalpy and Gibbs energy changes for reactions. Accordingly, development of an approach to obtain currently unavailable ion volumes can expose compounds containing these ions to thermodynamic scrutiny, such as predictions regarding stability and synthesis. The isomegethic rule, introduced in this paper, states that the formula unit volumes, V(m), of isomeric ionic salts are approximately the same; this rule then forms the basis for a powerful and successful means of predicting unknown ion volumes (as well as providing a means of validating existing volume and density data) and, thereby, providing solid state thermodynamic data. The rule is exploited to generate unknown ion and (by additivity) corresponding formula unit volumes. 相似文献
83.
An effective one-pot synthesis of polyhydroxylated quinolizidines from 1-C-(2'-oxo-4'-pentenyl)-5-azido-C-glycofuranosides was developed. Reduction of the 5-azido group using triphenylphosphine followed by base treatment produced quinolizidines in good yield. The base-mediated ring-opening beta-elimination produced an acyclic alpha,beta-conjugated ketone as a Michael acceptor, which was followed by an intramolecular nitrogen conjugate addition to form an aza-C-glycopyranoside intermediate. Meanwhile, the beta,gamma-double bond of the aglycon migrated under the basic conditions to form another alpha,beta-conjugated ketone. The subsequent intramolecular conjugate addition by the azasugar nitrogen led to the formation of the quinolizidines in a highly stereoselective manner. The stereoselectivity of the first conjugate addition giving azasugar is affected by the stereochemistry of the monosaccharide substrate, whereas the stereoselectivity in the second conjugate addition was likely directed entirely by steric repulsion from the azasugar. 相似文献
84.
K. K. Bhasin P. Venugopalan J. Singh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2579-2587
A convenient method for the preparation of various methyl substituted 2,2'-dipyridyl diselenides and -ditellurides by the aerial oxidation of lithium 2-pyridylselenolate/tellurolate, prepared from the lithium-halogen exchange between n-butyllithium and 2-bromo methyl substituted pyridines is reported. All the compounds prepared are new and have been characterized by elemental analysis, IR, 1 H, 13 C, 11 Se NMR, and mass spectral studies. Crystal structure of 6,6'-dimethyl-2,2'-dipyridyl diselenide has been determined. 相似文献
85.
In this work, we report the size tunable synthesis of selenium (Se) nanoparticles with an average particle size ~16 nm by
using hydrazine hydrate as the reducing agent. The solution of selenium dioxide was taken as the precursor and hexadecyltrimethylammonium
bromide (CTAB) a cationic surfactant, which helps in providing sufficient stabilization to the Se nanoparticles. The synthesized
Se nanoparticles were characterized by the UV–vis, X-ray diffraction (XRD), and transmission electron microscopic techniques,
which demonstrated high stability of Se nanoparticles in aqueous media. The particle sizes estimated from the band gap values
using effective mass approximation (EMA) agreed fairly well with those calculated from the XRD measurements. The concentration
effects of Se and CTAB on the particle size have also been examined. The capping ability of the CTAB has been quantitatively
evaluated from FTIR studies. 相似文献
86.
K. K. Bhasin S. Pundir S. Neogy D. Mehta S. K. Mehta 《Phosphorus, sulfur, and silicon and the related elements》2018,193(5):273-279
Bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)telluride (2) has been synthesised in good yield by reacting 1-(2-chloroethyl)-3,5-dimethylpyrazole with in situ prepared sodium telluride, Na2Te in an aqueous solution. A number of new organotellurium halides from bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)telluride have been synthesised by using different halogenating reagents. Reaction of 2 with bromine gave bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)telluride dibromide (5a) in addition to unexpected product bis(2-(4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)ethyl)telluride dibromide (5b). All compounds were characterized by different spectroscopic techniques viz., 1H, 13C, 125Te NMR, Mass spectroscopy, IR and CHN analysis. EDXRF studies have also been employed to confirm the identity of 5a and 5b. Thermal gravimetric analysis of bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)telluride (IV) chloride (4) and bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)telluride (IV) iodide (5c) reveals the thermal stability of these molecules above 100°C. The X-ray studies of 5c shows trigonal bipyramidal geometry around tellurium atom and intermolecular secondary interaction viz., C-H π stacking between H23A and C22 showing a supramolecular packing between two molecules. 相似文献
87.
Fracture toughness of metals depends strongly on the state of stress near the crack tip. The existing standards (like R-6, SINTAP) are being modified to account for the influence of stress triaxiality in the flaw assessment procedures. These modifications are based on the ability of so-called ‘constraint parameters’ to describe near tip stresses. Crack tip stresses in homogeneous fracture specimens are successfully described in terms of two parameters like J–Q or J–T. For fracture specimens having a weld center crack, strength mismatch ratio between base and weld material and weld width are the additional variables, along with the magnitude of applied loading, type of loading, and geometry of specimen that affect the crack tip stresses. In this work, a novel three-parameter scheme was proposed to estimate the crack tip opening stress accounting for the above-mentioned variables. The first and second parameters represent the crack tip opening stress in a homogeneous fracture specimen under small-scale yielding and are well known. The third parameter accounts for the effect of constraint developed due to weld strength mismatch. It comprises of weld strength mismatch ratio (M, i.e. ratio of yield strength of weld material to that of base material), and a plastic interaction factor (Ip) that scales the size of the plastic zone with the width of the weld material. The plastic interaction factor represents the degree of influence of weld strength mismatch on crack tip constraint for a given mismatch ratio. The proposed scheme was validated with detailed FE analysis using the Modified Boundary Layer formulation. 相似文献
88.
In this work, we report the size tunable synthesis of water-dispersed gold nanoparticles by using octadecylamine (ODA) as the reducing agent, that electrostatically complexes with the chloroaurate ions, reduces them, and subsequently caps the gold nanoparticles. Amine-capped gold nanoparticles, thus formed, were subsequently coordinated with a secondary monolayer of an anionic surfactant, sodium bis(2-ethylhexyl)-sulfosuccinate (AOT) which helps in providing sufficient hydrophilicity to the gold nanoparticles. Functionalized gold nanoparticles were characterized by UV-vis, IR spectrophotometric, dynamic light scattering, zeta-potential and transmission electron microscopic techniques, which demonstrated high stability of gold nanoparticles in aqueous media, indicating stabilization via bilayers of ODA and AOT. The gold nanoparticles were further conjugated with a protein (bovine serum albumin) and the interaction was investigated by circular dichroism studies as well as by measuring the fluorescence quenching of the tryptophan residues of protein molecules after the binding of nanoparticles to specific sites of the protein. The binding constant and the stoichiometry values indicated that the particles with larger core size are less site-specific but show higher binding affinity with protein molecules. The use of a bio-compatible synthetic process and the stabilization of the gold nanoparticles by ODA and AOT are interesting from the point of view of making bioprobes for life science applications. 相似文献
89.
Adams J Aggarwal MM Ahammed Z Amonett J Anderson BD Arkhipkin D Averichev GS Badyal SK Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Berger J Bezverkhny BI Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Billmeier A Bland LC Blyth CO Blyth S Bonner BE Botje M Boucham A Bouchet J Brandin AV Bravar A Bystersky M Cadman RV Cai XZ Caines H de la Barca Sánchez MC Castillo J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S 《Physical review letters》2005,95(6):062301
We present the first measurement of pseudorapidity distribution of photons in the region 2.3 < or = eta < or = 3.7 for different centralities in Au+Au collisions at square root of (S(NN)) = 62.4 GeV. We find that the photon yield scales with the number of participating nucleons at all collision centralities studied. The pseudorapidity distribution of photons, dominated by pi0 decays, has been compared to those of charged pions, photons, and inclusive charged particles from heavy-ion and nucleon-nucleon collisions at various energies. The photon production has been shown to be consistent with the energy and centrality independent limiting fragmentation scenario. 相似文献
90.
K. K. Bhasin N. Singh V. Trehan P. K. Jain Jaspreet Singh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):753-759
Reductive cleavage of tellurium-tellurium bond in various 2,2'-dipyridyl ditellurides using hydrazine hydrate (100%) both in the presence and absence of phase transfer catalyst is reported. A tentative mechanism of the reaction is also proposed. 相似文献