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排序方式: 共有880条查询结果,搜索用时 15 毫秒
791.
YX Chen A Lavacchi SP Chen F di Benedetto M Bevilacqua C Bianchini P Fornasiero M Innocenti M Marelli W Oberhauser SG Sun F Vizza 《Angewandte Chemie (International ed. in English)》2012,51(34):8500-8504
Improved performance through milling: A method for enhancing the catalytic activity of supported metal nanoparticles is reported. This method enhances the activity for the ethanol electro-oxidation of a supported palladium catalyst. The much higher catalytic performance is ascribed to the increased electrochemically active surface area as well as the generation of high-index facets at the milled nanoparticle surface. 相似文献
792.
Mebs S Weber M Luger P Schmidt BM Sakurai H Higashibayashi S Onogi S Lentz D 《Organic & biomolecular chemistry》2012,10(11):2218-2222
The experimental electron density of sumanene, C(21)H(12), was extracted from a high resolution X-ray data set measured at 100 K and topologically analyzed. In addition to bond topological and atomic properties, information about the density distribution between adjacent molecules, which show close C···C approaches of ~3.4 ? within the columnar π-stacks in the crystal lattice, are discussed. A comparison is made with the electron density of the related corannulene molecule based also on the analysis of Electron Localizability Indicator (ELI-D) calculations. 相似文献
793.
Angelo Zinellu Salvatore Sotgia Elisabetta Pisanu Bastianina Scanu Manuela Sanna Maria Franca Usai Roberto Chessa Luca Deiana Ciriaco Carru 《Analytical and bioanalytical chemistry》2010,398(5):1973-1978
The role of neurotransmitter amino acids (NAAs) in the functioning of the nervous system has been the focus of increasingly
intense research over the past several years. Among the various amino acids that have important roles as neurotransmitters,
there are alanine (Ala), glutamic acid (Glu), aspartic acid (Asp), serine (Ser), taurine (Tau) and glycine (Gly). NAAs are
present in plasma, cells and—at trace levels—in all biological fluids, but complex components in biological matrices make
it difficult to determine them in biological samples. We describe a new capillary electrophoresis (CE) method with laser-induced
fluorescence detection by which analytes are resolved in less than 12 minutes in a 18 mmol/L phosphate run buffer at pH 11.6.
The use of elevated temperatures during sample derivatization leads to a drastic reduction in the reaction time, down to 20 min,
compared to the 6–14 h usually described for reactions between FITC and amino acids at room temperature. In order to demonstrate
its wide range of applications, the method was applied to the analysis of NAA in human plasma and in other sample types, such
as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva and vitreous humor, thus avoiding the typical limitations
of other methods, which are normally suitable for use with only one or two matrix types. 相似文献
794.
Timo Bollermann Ganesan Prabusankar Dr. Christian Gemel Dr. Rüdiger W. Seidel Dr. Manuela Winter Roland A. Fischer Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8846-8853
The synthesis and structural characterisation of low‐valent dinuclear copper(I) and copper(0) complexes supported by organogallium ligands has been accomplished for the first time by the reductive coordination reaction of [GaCp*] (Cp*=pentamethylcyclopentadienyl) and [Ga(ddp)] (ddp=HC(CMeNC6H3‐2,6‐iPr2)2 2‐diisopropylphenylamino‐4‐diisopropylphenylimino‐2‐pentene) with readily available copper(II) and copper(I) precursors. The treatment of CuBr2 and Cu(OTf)2 (OTf=CF3SO3) with [Ga(ddp)] under mild conditions resulted in elimination of [Ga(L)2(ddp)] (L=Br, OTf) and afforded the novel gallium(I)/copper(I) compounds [{(ddp)GaCu(L)}2] (L=Br ( 1 ), OTf ( 2 )). The single‐crystal X‐ray structure determinations of 1 and 2 reveal that these molecules are composed of {(ddp)GaCu(L)} dimeric units, with planar CuI? GaI four‐membered rings and short CuI???CuI distances, with 2 exhibiting the shortest CuI???CuI contact reported to date of 2.277(3) Å. The all‐gallium coordinated dinuclear [Cu2(GaCp*)(μ‐GaCp*)3Ga(OTf)3] ( 3 ) is formed when Cu(OTf)2 is combined with [GaCp*] instead of [Ga(ddp)]. Notably, in the course of this redox reaction Lewis acidic Ga(OTf)3 is formed, which coordinates to one of the electron‐rich copper(0) centres. Compound 3 is suggested as the first case of a structurally characterised complex of copper(0). By changing the copper(II) to a copper(I) source, that is, [Cu(cod)2][OTf] (cod=1,5‐cyclooctadiene), the salt [Cu2(GaCp*)3(μ‐GaCp*)2][OTf]2 ( 4 ) is formed, the cationic part of which is related to previously described isoelectronic dinuclear d10 complexes of the type [M2(GaCp*)5] (M=Pd, Pt). 相似文献
795.
Manuela Nees 《Numerical Functional Analysis & Optimization》2013,34(9-10):903-910
The two-sided deconvolution problem, for a certain class of a bandlimited kernels, is reduced to a discrete deconvolution problem by the sampling theorem, yielding a bandlimited solution. For this solution, in addition, a Galerkin type approximation is given. In general, the solution of the convolutioon equation for bandlimited kernels is not bandlimited. This follows from a characterization of the general solution 相似文献
796.
Albano VG Bandini M Barbarella G Melucci M Monari M Piccinelli F Tommasi S Umani-Ronchi A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(3):667-675
The synthesis, characterization, and structure-guided application of a new class of highly versatile chiral C(2)-symmetric diamine-oligothiophene ligands in Pd-catalyzed asymmetric transformations are presented. Experimental investigations of the intimate role of pendant pi-conjugate oligothiophenes in determining the catalytic activity of the corresponding chiral Pd complexes are described. Their unusual behavior opens up new routes toward the logical design of finely tuned organometallic catalysts by remote structural functionalizations. 相似文献
797.
An enantioselective CE assay for the simultaneous determination of the enantiomeric purity and of related substances of etomidate has been developed and validated using a binary chiral selector system employing 30 mg/mL beta-CD and 4.6 mg/mL sulfated-beta-CD in a 150 mM potassium phosphate buffer, pH 2.1. The method was validated with respect to specificity, range, linearity, LOQ and LOD, precision and accuracy. The assay allowed the detection and determination of related substances including (S)-etomidate at the 0.05% w/w level, the reporting threshold as defined by the International Conference on Harmonisation guidelines as well as the European Pharmacopoeia. Robustness testing was carried out by an "Augmented Plackett-Burman" design. Quantitation of the compounds was performed by calibration graphs with respect to lidocaine hydrochloride as internal standard and by peak area normalization, the procedure usually applied by pharmacopoeias. Although data obtained from the calibration graphs constructed with the aid of the internal standard were more accurate based on compound recovery, peak area normalization may also be used without significant loss of accuracy and precision. 相似文献
798.
Ravikovitch PI Vishnyakov A Neimark AV Ribeiro Carrott MM Russo PA Carrott PJ 《Langmuir : the ACS journal of surfaces and colloids》2006,22(2):513-516
Universal mechanisms of adsorption and capillary condensation of toluene and nitrogen on ordered MCM-41 and PHTS materials are studied by means of high-resolution experiments and Monte Carlo molecular simulations. A molecular simulation model of toluene adsorption in silica nanopores, which accounts for surface heterogeneity, and a hybrid molecular-macsroscopic method for pore size distribution (PSD) calculations have been developed. For a range of reference materials, the PSD results obtained from toluene isotherms are consistent with the results of nitrogen adsorption using the nonlocal density functional theory method. 相似文献
799.
Baunemann A Kim Y Winter M Fischer RA 《Dalton transactions (Cambridge, England : 2003)》2006,(1):121-128
The coordination chemistry of the hydrazine derivatives dimethylhydrazine (Hdmh) and N-trimethylsilyl-N'N'-dimethylhydrazine (Htdmh) at Ta, Zr and Hf was investigated aiming at volatile mixed ligand all-nitrogen coordinated compounds. The hydrazido ligands were introduced either by salt metathesis employing the Li salts of the hydrazines and the tetrachlorides MCl(4) (M = Zr, Hf) or by amine substitution using M(NR(2))(4) (R = Me, Et) and [(t-BuN)Ta(NR(2))(3)]. The new complexes were fully characterised including (1)H/(13)C NMR, mass spectrometry and a study of their thermal behaviour. The crystal structures of [ZrCl(tdmh)(3)] and the all-nitrogen coordinated complex [Ta(N-t-Bu)(NMe(2))(2)(tdmh)] are discussed as well as the structure of the by-product [Li(tdmh)(py)](2). Preliminary MOCVD experiments of the liquid compound [Ta(NEt(2))(2)(N-t-Bu)(tdmh)] were performed and the deposited TaN(Si) films were analysed by RBS and SEM. 相似文献
800.
A novel phosphoramidite, N,N-diisopropylamino-2-cyanoethyl-9-anthracenemethyl phosphoramidite 1, was prepared and coupled with the terminal 5′-hydroxyl of support-bound T10 and the putative phosphite triester intermediate was subsequently reacted with iodine in the presence of either water or a series of primary and secondary amines. The reactivity of 1 compared to a previously reported benzyl phosphoramidite 2 was also investigated: oxidation of the product of coupling 2 with CPG-T10-5′OH under aqueous conditions resulted in greater than 30% of the benzyl moiety being retained. In contrast, essentially complete loss of the 9-anthracenemethyl group was observed using 1 under the same conditions. Oligonucleotides modified with a terminal phosphate monoester, lipophilic, fluorescent or cationic groups were thus prepared. 相似文献