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排序方式: 共有230条查询结果,搜索用时 31 毫秒
221.
We study the limiting spectral distribution for a class of circulant type random matrices with heavy tailed input sequence. Unlike the light tailed case where the limit is nonrandom, here the limit is a random probability distribution. We provide an explicit representation of the limit. 相似文献
222.
Majumder P Baksi S Halder S Tadesse H Blake AJ Drew MG Bhattacharya S 《Dalton transactions (Cambridge, England : 2003)》2011,40(20):5423-5425
Reaction of a potential NCN-pincer ligand, viz. 1,3-di(phenylazo)benzene (L), with [Rh(PPh(3))(3)Cl] affords, via a C-H bond activation, an interesting dinuclear Rh(II) complex (1), and with RhCl(3)·3H(2)O affords a mononuclear Rh(III) complex (2) containing a catalytically useful Rh-OH(2) fragment. 相似文献
223.
Sulphated galactan (SF(A)) containing alpha (alpha), iota (i) and pyruvated alpha-carrageenans (17.6:18.8:25.3 mol %) was extracted and characterized from Sarconema filiforme of Indian waters. The SF(A) and its alkali modified derivative (SF(AM)) were composed of D-galactose, 3, 6-anhydro-D-galactose, 6-O-methylated-D-galactose (64.5:23.0:9.8 and 59.6:29.8:7.6 mol %) respectively. The linkage analysis, physicochemical analysis, infra red and 13C nuclear magnetic resonance spectra of SFA along with linkage analysis of the desulphated derivative (SF(D)) of SFA, reveals that it was a hybrid/combination of alpha/iota carrageenan as well as 3-linked 4',6'-O-(1-carboxyethylidene)-galactose (pyruvated alpha carrageenan) and 6-O-methylated alpha-carrageenan. The flow behavior of SF(A) obtained from rheological measurements suggested strong network formation in presence of 1% aqueous KCl and CaCl2 solutions. 相似文献
224.
Pathak AK 《Chemphyschem》2011,12(14):2641-2645
Structures and photoelectron spectral properties of I??nCO2 (n=1–7) clusters are presented at the level of second‐order Møller–Plesset perturbation theory with relativistic corrections. Triple split‐valence 6‐311++G(d,p) basis set functions are employed herein. It is observed that the CO2 molecules approach the I? anion from one side in all the clusters and that I??nCO2 clusters prefer the surface structure. The calculated vertical detachment energy of these clusters is in excellent agreement with the reported experimentally measured values (within 4 %). Efforts are also made to extract vertical detachment energy of large size of clusters, including the bulk. The extracted vertical detachment energy values for larger clusters (n=8–13) by employing the microscopic theory‐based expression are also close (within 4 %) to that of the experimentally measured values. 相似文献
225.
Premamoy Ghosh Dilip Kumar Chowdhury Arup Rat Bandyopadhyay 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5-6):549-555
Preliminary studies on the suitability of some organic acids and amines, separately and in combination with each other, as photo-initiators for the polymerization of methyl methacrylate were made. Combinations of maleic acid or phthalic acid with any of the tertiary amines–triethyl amine, demethyl aniline, and diethylaniline-proved to be interesting photoinitiator systems in view of the fact that the initiator components in each combination were ineffective as initiators when used separately. The rate of photopolymerization in each of the above acid-amine combination system was much enhanced and the respective inhibition period largely reduced when benzophenone was used as the photoinitiator. Aliphatic diamine or polyamines such as ethylene diamine, diethylene triamine, and tri-ethylene tetramine, were ineffective as photoinitiators when used alone or in combination with maleic acid, but became effective 相似文献
226.
An expeditious one-pot synthesis of substituted pyrimidinone derivatives with aromatic aldehydes, cyclopentanone, and urea (or thiourea) was developed with boric acid (10 mol%) and glycerol (0.1 mL) in aqueous medium at 45–50 °C. The methodology is simple, highly efficient, and high yielding. The idea behind this methodology is that boric acid, being a weak acid, behaves as a strong acid in presence of glycerol in aqueous medium. 相似文献
227.
Ananya Baksi Prof. Dr. Thalappil Pradeep Dr. Bokwon Yoon Dr. Constantine Yannouleas Prof. Dr. Uzi Landman 《Chemphyschem》2013,14(6):1272-1282
A discrete sequence of bare gold clusters of well‐defined nuclearity, namely Au25+, Au38+ and Au102+, formed in a process that starts from gold‐bound adducts of the protein lysozyme, were detected in the gas phase. It is proposed that subsequent to laser desorption ionization, gold clusters form in the gas phase, with the protein serving as a confining growth environment that provides an effective reservoir for dissipation of the cluster aggregation and stabilization energy. First‐principles calculations reveal that the growing gold clusters can be electronically stabilized in the protein environment, achieving electronic closed‐shell structures as a result of bonding interactions with the protein. Calculations for a cluster with 38 gold atoms reveal that gold interaction with the protein results in breaking of the disulfide bonds of the cystine units, and that the binding of the cysteine residues to the cluster depletes the number of delocalized electrons in the cluster, resulting in opening of a super‐atom electronic gap. This shell‐closure stabilization mechanism confers enhanced stability to the gold clusters. Once formed as stable magic number aggregates in the protein growth medium, the gold clusters become detached from the protein template and are observed as bare Aun+ (n=25, 38, and 102) clusters. 相似文献
228.
Arup Sinha 《Journal of organometallic chemistry》2011,696(6):1248-1257
A mononuclear Ru(II)-N-heterocyclic carbene (NHC) complex [RuII(CO)2(κ2C,N-BIN)(H2O)Br][OTf] (OTf = trifluoromethane sulphonate) (1) has been synthesized in high-yield by the oxidative cleavage of the metal-metal singly-bonded diruthenium(I) precursor [Ru2(CO)4(CH3CN)6(OTf)2] with 1,8-naphthyridine functionalized NHC precursor 1-benzyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (BIN·HBr) at room temperature. Compound 1 catalyzes transfer hydrogenation of ketones to alcohols, and carbene-transfer from ethyl diazoacetate to a variety of substrates. It is shown to be an excellent catalyst for the insertion of carbene into the O-H and N-H bonds of alcohols and amines. 相似文献
229.
Arup Ghorai Somnath Mahato Sudarshan Singh Shaona Bose Baidyanath Roy Unyong Jeong Samit Kumar Ray 《Angewandte Chemie (International ed. in English)》2023,62(22):e202302852
Although α-CsPbI3 is regarded as an attractive optical luminophore, it is readily degraded to the optically inactive δ-phase under ambient conditions. Here, we present a simple approach to revive degraded (“optically sick”) α-CsPbI3 through “medication” with thiol-containing ligands. The effect of different types of thiols is systematically studied through optical spectroscopy. The structural reconstruction of degraded α-CsPbI3 nanocrystals to cubic crystals in the presence of thiol-containing ligands is visualized through high-resolution transmission electron microscopy and supported by X-ray diffraction analysis. We found that 1-dodecanethiol (DSH) effectively revives degraded CsPbI3 and results in high immunity towards moisture and oxygen, hitherto unreported. DSH facilitates the passivation of surface defects and etching of degraded Cs4PbI6 phase, thus reverting them back to the cubic CsPbI3 phase, leading to enhanced PL and environmental stability. 相似文献
230.