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排序方式: 共有109条查询结果,搜索用时 39 毫秒
1.
Abstract— C18 formate ester (5) [2-(6-methyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3E,5E,7E-octatrienyl formate], a highly reactive analog of retinal, was synthesized and its interaction with bacterioopsin studied. The formate ester, in the absence of purple or bleached membrane, undergoes very rapid reaction (tl/2 = 0.9 min) in neutral buffer but with membrane present it diffuses more rapidly into the membrane where it reacts slowly. Incorporation of 5 in the membrane results in a 38 nm (3900 cm-1 ) red shift which remains after reconstitution with retinal. Similar experiments with the corresponding C18 alcohol (4) results in a red shift, but this absorption blue shifts upon reconstitution with retinal. Washing the formate ester-treated membrane with bovine serum albumin or the corresponding lyophilized preparation with hexane, treatments that remove retinal oxime, fails to remove the UV-visible absorption, suggesting that a covalent bond between the C18 moiety and a nucleophilic group of the protein has probably formed. 相似文献
2.
Zusammenfassung Eine Methode der Identifizierung von Alkyl- und Arylgruppen organischer Sulfide wurde ausgearbeitet, die die Spaltung dieser Stoffe mit Raney-Nickel zur gaschromatographischen Bestimmung der dabei entstandenen Kohlenwasserstoffe ausnützt.
Die Autoren danken den Kollegen Dr.M. Veea, Ing.J. Petránek und Ing.J. Gaspari für die Überlassung von Proben organischer Sulfide. 相似文献
Summary A method was developed for identifying alkyl- and aryl groups of organic sulfides. The method employs the cleavage of these materials with Raney nickel for the gas chromatographic determination of the resulting hydrocarbons.
Résumé On a mis au point une méthode d'identification des groupes alkylés et arylés des sulfures organiques exploitant la dissociation de ceux-ci par le nickel Raney pour le dosage par chromatographic en phase gazeuse des carbures d'hydrogène qui se forment.
Die Autoren danken den Kollegen Dr.M. Veea, Ing.J. Petránek und Ing.J. Gaspari für die Überlassung von Proben organischer Sulfide. 相似文献
3.
A number of reporter molecules of the structure R-(CH2)n-N+(CH3)2(CH2)mN+(CH3)3·2Br?, where R is a chromophore absorbing in the 300–500 mp region, have been synthesized. The effect of DNA and RNA on the absorption, induced circular dichroism, and proton magnetic resonance spectra is reported. A red shift and a hypochromic effect on the absorption spectra of the bound chromophore is observed. In all cases where R is an “unsymmetrical” 4-nitroaniline chromophore, it is found that DNA and RNA induce an opposite CD in the absorption band of the bound reporter molecules. These results together with PMR studies are interpreted in terms of the structure of the nucleic acid systems in solutions. 相似文献
4.
Levine D 《Chaos (Woodbury, N.Y.)》1999,9(3):573-580
When mixtures of granular materials are rotated, it is often found that they segregate into bands, along the axis of rotation, which are rich in the various components. This effect is discussed experimentally and theoretically, with emphasis on a mechanism based on surface flow. The complimentary phenomenon of radial segregation is reviewed, and a mechanism is proposed. Finally, we consider the long-time behavior of rotating mixtures, particularly their anomolous coarsening. (c) 1999 American Institute of Physics. 相似文献
5.
Dov M. Gabbay 《Israel Journal of Mathematics》1971,10(2):135-146
A Kripke type semantics is given to a large class of tense logics with statability operators (including PriorsQK
t) in such a manner as to obtain their decidability using Rabin’s theorem.
Dedicated to the Memory of A. N. Prior 相似文献
6.
7.
Dov Aharonov 《Journal d'Analyse Mathématique》1986,46(1):13-15
Recently deBranges gave a very remarkable proof of Milin’s conjecture. This implies both the conjectures of Robertson and
Bieberbach. It is our aim to show that the statement of equality case in both Robertson’s and Bierbach’s conjectures may be
proved by a different and easier method. 相似文献
8.
Edna Furman-Haran Dov Grobgeld Hadassa Degani 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,128(2):161-171
High resolution, dynamic GdDTPA-enhanced images of MCF7 human breast tumors in immunodeficient mice were analyzed at pixel resolution. The analysis, based on a physiological model, was performed by applying a nonlinear least-square algorithm using a color coded scale. The final output mapped at pixel resolution capillary permeability times surface area and fraction of extracellular volume, for each tumor slice. In addition, the output included assessment of the fit to the model by determining the proportion of variability (R2) for each pixel. The spatial variation in theR2values served to identify regions where the predominant mechanism of enhancement was leakage from the intravascular volume to the extracellular volume (R2close to 1). In regions with lowR2other mechanisms of enhancement appear to be dominating presumably diffusion within the extracellular space. As expected, in necrotic regions lacking microcapillaries and identified by analyzingT2-weighted images of the same tumors, the model failed to fit the dynamic contrast enhanced data. The heterogeneous distribution of the determined pathophysiological features demonstrates the importance of recording and analyzing breast tumor images at high spatial resolution. 相似文献
9.
A set of cleavage experiments with strip-shaped single-crystal silicon specimens subjected to three-point bending is reported. The experiments enabled examination of the relationships between the dynamic energy release rate, the velocity, the orientation-dependent cleavage energy, and the cleavage plane of propagation.Dynamic crack propagation experiments show that when a [0 0 1] silicon single crystal is fractured under three-point bending at ‘parallel’ velocity (directly measured at the bottom surface of the specimen) of up to , it prefers to cleave along the vertical (1 1 0) plane, while when the specimen is fractured under the same conditions but at a velocity higher than , it cleaves along the inclined (1 1 1) plane. At intermediate velocities, the crack will deflect from the (1 1 0) plane to the (1 1 1) plane. Crack velocity was determined by the initial notch length. The local (calculated) velocity of deflection between the cleavage planes ranges from , for a crack propagating on the (1 1 0) plane in the direction, to about , for a crack on the (1 1 0) plane, but in the [0 0 1] direction.It is suggested that the cause of the deflection phenomenon is the anisotropic, velocity-dependent cleavage energy, resulted phonon radiation caused by anisotropic, velocity-dependent lattice vibrations. We have studied the effect of material properties and propose selection criteria to explain the deflection phenomenon: the crack will deflect to the plane of least-energy, for which G−Γi(V)=max, or to the plane with maximum crack tip velocity, Vi(Γ)=max. 相似文献
10.
Taís Vanessa Gabbay Alves Eraldo José Madureira Tavares Fauze Ahmad Aouada Charles Alberto Brito Negrão Marcos Enê Chaves Oliveira Anivaldo Pereira Duarte Júnior Carlos Emmerson Ferreira da Costa José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2011,106(3):717-724
This paper reports the thermal characterization of polyacrylamide-co-methylcellulose hydrogels and the constituent monomers (acrylamide and methylcellulose). Polymeric materials can be used
to produce hydrogels, which can be natural, synthetic, or a mixture. The hydrogels described here were obtained by free radical
polymerization, in the presence of N,N′-methylene-bis-acrylamide as a cross-linker agent. Four acrylamide concentrations were used for the synthesis of hydrogels:
3.6, 7.2, 14.7, and 21.7% (w/v). The materials so obtained were analyzed by TG, DTG, DSC, and FT-IR. The TG curves of acrylamide
and methylcellulose showed three mass loss events. In DSC curves, the acrylamide exhibited one melting peak at 84.5 °C, and
methylcellulose indicated one exothermic event. Nevertheless, acrylamide was considered more stable than methylcellulose.
The TG curves of the hydrogels exhibited three mass loss events, and on the DSC curves, three endothermic events were observed.
It was verified that the different acrylamide proportions influenced the thermic behavior of hydrogels, and that the authors
considered the 7.2% hydrogel a promising drug carrier system. The absorption bands were well defined, confirming the presence
of the functional groups in the samples. 相似文献