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排序方式: 共有218条查询结果,搜索用时 15 毫秒
91.
92.
El-Sadek RI Roushdy M Magda JJ 《Langmuir : the ACS journal of surfaces and colloids》2007,23(15):7907-7910
Axisymmetric oscillating pendant drop shape analysis has been used to study the interfacial rheology of the liquid crystal 4'-pentyl-4-biphenylcarbonitrile (5CB) in water with homeotropic anchoring. Nearly spherical 5CB droplets were subjected to low frequency (1-5 mHz) volume oscillations, and the increase in tension with surface dilation was used to calculate the complex modulus. The droplet interface response is completely elastic, with no relaxations occurring on the experimental time scale. This surprising result is attributed to droplet storage of elastic energy in the form of distorted orientational distributions within the bulk (Frank elasticity) and on the surface (anchoring elasticity). 相似文献
93.
Orozco D Skamarack J Reins K Titlow B Lunetta S Li F Roman M 《Journal of AOAC International》2007,90(5):1227-1236
A method based on high-performance liquid chromatography with ultraviolet detection has been developed to quantify ubidecarenone [coenzyme Q10 (CoQ10)] in raw materials and dietary supplements. Single-laboratory validation has been performed on the method to determine repeatability, accuracy, selectivity, limits of detection and quantification (LOQ), ruggedness, and linearity for CoQ10. As CoQ10 can exist as the biologically active reduced form, the application of an oxidizing agent, ferric chloride, drives the equilibrium mechanics to the fully oxidized state and allows for exact quantification of total CoQ10 in the sample. This method was found to be fit and linear for the testing of materials containing CoQ10 in the range of approximately equal 50-1000 mg/g. Repeatability precision for CoQ10 was between 2.15 and 5.00% relative standard deviation. Observed recovery of CoQ10 was found to be between 93.8 and 100.9%. LOQ was found to be 9 microg/mL. Further, limited studies showed that some adulterants and degraded material could be satisfactorily separated from CoQ10 and identified. 相似文献
94.
Jie Liu Maaike J. G. Schotman Marco M. R. M. Hendrix Xianwen Lou Patricia P. Marín San Román Ilja K. Voets Rint P. Sijbesma 《Journal of polymer science. Part A, Polymer chemistry》2021,59(12):1162-1170
We report on the self-assembly in water of a set of bis-urea amphiphiles. A range of techniques, including dynamic light scattering, Cryo-TEM, SAXS, and MS are used to study the effect of structural variation on the morphology of the assemblies. The length, dispersity, and end-group of the ethylene glycol hydrophilic part of the molecule, as well as of the alkyl chain length are varied to tailor the morphology towards soluble wormlike micelles. Slight modification on molecular structures gave a large difference in self-assembly behavior in water, giving guidelines for the design of rodlike supramolecular fibers with novel functionalities, such as strain-stiffening and bioactivity. 相似文献
95.
Christian Deffo Tassak Jules Sadefo Kamdem Louis Aimé Fono Nicolas Gabriel Andjiga 《The Journal of the Operational Research Society》2017,68(12):1491-1502
Peng et al (Int J Uncertain Fuzziness Knowl Based Syst 15:29–41, 2007) introduced, by means of the credibility measure, two dominance relations on fuzzy variables, namely the first- and the second-order dominances. In this paper, we characterize each of these dominance relations, and we justify that they satisfy six well-known properties of comparison methods. We propose a Game Theory approach for the determination of optimal portfolios when returns are fuzzy by introducing the set of best portfolios with respect to the first- and the second-order dominances. Based on the characterization of the first-order dominance, we numerically display some of the best portfolios of the classical set of portfolios of seven independent assets described by triangular fuzzy numbers. 相似文献
96.
Alaaeddin Alsbaiee Mustapha St. Jules Rachel L. Beingessner Jae-Young Cho Takeshi Yamazaki Hicham Fenniri 《Tetrahedron letters》2012,53(13):1645-1651
Rosette nanotubes (RNTs) are discrete nanostructures self-assembled from a guanine–cytosine hybrid motif (G∧C) under aqueous conditions. These materials have substantial design flexibility and a range of applications, which are partly attributed to their diverse surface functionalization. Given the potential for interesting properties resulting from a metal-RNT construct, here we describe an oxorhenium-functionalized RNT. More specifically, we present the synthesis of a twin G∧C motif expressing the mercaptoacetyl triglycine (MAG3) ligand. We then examine the chelation reaction of the MAG3 with ReOCl3(PPh3)2 and self-assemble the resulting ReO-MAG3-G∧C conjugate into RNTs under DMSO and aqueous conditions. 相似文献
97.
Emil B. Milosavljević Ljiljana Solujić John H. Nelson James L. Hendrix 《Mikrochimica acta》1985,87(5-6):353-360
Summary
Simultaneous Determination of Chromium(VI) and Chromium(III) by Flame Atomic Absorption Spectrometry with a Chelating Ion-Exchange Flow Injection System
A simple method is described for the simultaneous determination of chromium(VI) and chromium(III) in a flow injection system comprising chelating ion-exchange and flame atomic absorption spectrometry. Sampling rates for 2001 and 1 ml sample volumes were 120 and 60 h–1 (240 and 120 speciations per hour), respectively. Typical relative standard deviations were 0.52% for Cr(VI) (0.50g ml–1 and 0.67% for Cr(III) (0.10,g ml–1) and the corresponding limits of detection were 85 ng ml–1, and 16 ng ml–1, respectively.On leave from University of Belgrade. 相似文献
98.
Joseph Tsemeugne Emmanuel Sopbué Fondjo Jean-de-Dieu Tamokou Ignas Tonle Irene Chinda Kengne Arnaud Djintchui Ngongang Stephen Tamekou Lacmata Taoufik Rohand Jules Roger Kuiate Beibam Luc Sondengam 《Chemistry Central journal》2017,11(1):119
Background
A series of recently reported phenolic azo dyes 7a–e were prepared by coupling the thienyl diazonium sulfate of 3-Amino-4H-benzo[f]thieno[3,4-c](2H)chromen-4-one with selected diversely substituted phenolic and naphtholic derivatives. These compounds were evaluated for their antibacterial and antifungal activities. Furthermore their voltammetric behavior was compared at a glassy carbon electrode.Results
The voltammetric behavior of the five recently reported azo dyes has been compared at a glassy carbon electrode. It is shown that the azo dyes 7a–e with a hydroxyl group in the ortho position with respect to the azo bridge give rise to well defined, irreversible peaks for the oxidation and reduction process within a pH range of 2–7. The mechanisms of electrochemical oxidation of compound 7a–c and 7e are proposed. For the hydroxyl-substituted dyes, re-oxidation peaks were obtained in the subsequent scan. The antimicrobial activities of the reported compounds 7a–e along with the entire precursors 1–4 and 6a–e were performed against selected bacterial and fungal species and their activities compared to those of nystatin, griseofulvin and ciprofloxacin used as reference drugs.Conclusions
The present study showed significant antimicrobial activity of compounds 6d, 7a and 7c,e against the tested microorganisms; this result confirms the antimicrobial potency of azo compounds and some of their precursors.99.
Omemah Gliah Boguslaw Kruczek Seyed Gh. Etemad Jules Thibault 《Heat and Mass Transfer》2011,47(9):1171-1180
To properly simulate the condensation process and design a water recovery system from condensation of atmospheric water vapour
on a surface maintained below the dew point by radiative heat loss from the surface to night sky, an accurate estimation of
the effective sky temperature is required. To estimate the effective night sky temperature, an experimental system consisting
of a series of metal plates embedded on a heat transfer panel, a weather station and a control system was used. The results
obtained from theoretical analyses and preliminary experiments are presented and discussed. A special emphasis is given to
a mathematical solution of the system of equations that need to be solved to obtain the effective sky temperature. It is shown
that although the system of equations works well for the direct heat transfer problem, there is a serious difficulty to solve
the inverse heat transfer problem to retrieve the desired parameters. 相似文献
100.
Bean DE Muya JT Fowler PW Nguyen MT Ceulemans A 《Physical chemistry chemical physics : PCCP》2011,13(46):20855-20862
The ipsocentric method at the coupled Hartree-Fock level is used for the calculation of magnetically induced ring currents in the boron buckyball B(80), for both I(h) and distorted T(h) geometries. A close similarity between the current patterns in boron and carbon buckyballs is noted, but with a higher current density in B(80). Paratropic currents on the pentagons are predominant in the boron buckyball, and the central NICS value is positive. These observations support the conclusion that B(80) should be considered (weakly) anti-aromatic. The largest orbital contributions to the ring currents in both molecules are identified and related to specific excitations in the frontier orbital region. 相似文献