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1.
ZnO nanoparticles were synthesized by the continuous spray pyrolysis technique (CoSP) and the effect of applied voltage across the spray nozzle and an annular ground electrode during spray has been studied. X-ray diffraction and transmission electron microscopy studies showed that the product has (hexagonal) wurtzite structure with the average particle size decreasing from 18.5?nm to 12.9?nm in the presence of a high DC voltage (1?kV). The higher value of the absorption peak for the nanoparticles synthesized without voltage is supportive of this behavior. The films deposited by spin coating using these nanoparticles can be used for a variety of applications, particularly as photoelectrodes for dye-sensitized solar cells. 相似文献
2.
Michael Veith Charu Mathur Volker Hugh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):489-492
The synthesis of the new heteroleptic heterotrimetallic cluster, [(C5H5)Sn(μ-OBut)2Ge(OBut)Mo(CO)5] (1) has been achieved by a thermally induced CO substitution of the transition metal derivative, Mo(CO)6, by the basic germanium atom of the cyclopentadienyl heterobimetallic alkoxide, [(C5H5)Sn(μ-OBut)2Ge(OBut)]. The microanalysis, molecular weight (monomer in benzene), IR and multinuclear NMR data and X-ray diffraction study is consistent with the formulation of 1. The Sn atom has a trigonal pyramidal coordination environment formed by a aysmmterically π-bonded terminal C5H5 ring and two symmetrically bridged tert-butoxy groups. The four-coordinate Ge atom lies at the centre of a distorted tetrahedron and is terminally attached to a tert-butoxy group and a Mo(CO)55? fragment. 相似文献
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Force-length relations at ambient temperature have been determined for a set of polyethylenes which represent a wide range in molecular weight and molecular constitution. Taking advantage of previous work from this laboratory, samples have been prepared in such a manner that the important independent structural variables can be identified and isolated and their influence on the different aspects of the deformation process assessed. Partial melting-recrystallization processes appear to play an important role. For the linear polymers there is a direct influence of molecular weight. The influence of molecular weight manifests itself in the structure of the interlamellar zone which has a major influence on the initial modulus as well as the ultimate properties. Copolymers and branched copolymers display quite different behavior. The most striking difference is the invariance of the ultimate properties with molecular weight, branching, and level of crystallinity. From the set of experimental results that are presented the molecular factors involved in the deformation process can be sorted out. It becomes quite evident that all of the basic structural regions, characteristic of semicrystalline polymers, contribute to the observations. Focus solely on the changes in the crystallite, in analogy to the deformation of small-molecule crystalline systems, is inadequate in the case of crystalline polymers. 相似文献
5.
JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid method has been established for indirect separation of the enantiomers of (R,S)-metoprolol and (R,S)-carvedilol... 相似文献
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Chiral assay of enantiomers of fluoxetine was achieved in pharmaceutical formulations using direct and indirect methods. L-tartaric acid was used as a mobile phase additive in thin-layer chromatography; the enantiomers were separated and isolated and were used to determine the elution order in HPLC. (R,S)-flouxetine was derivatized with (S)-N-(4-nitrophenoxycarbonyl)phenylalanine methoxyethyl ester [(S)-NIFE], Marfey's reagent and 1-fluoro-2,4-dinitrophenyl-L-methionine amide (FDNP-L-Met-NH?. The diastereomers were separated using RP-HPLC. The effect of flow rate and TFA concentration on resolution was studied. The diastereomers obtained by derivatization with FDNP-L-Met-NH? were also separated by RP-TLC. 相似文献
7.
Hari M. Gupta José R. Campanha Daniela R. de Aguiar Gabriel A. Queiroz Charu G. Raheja 《Physica A》2007
We study the statistical distribution of firm size for USA and Brazilian publicly traded firms through the Zipf plot technique. Sale size is used to measure firm size. The Brazilian firm size distribution is given by a log-normal distribution without any adjustable parameter. However, we also need to consider different parameters of log-normal distribution for the largest firms in the distribution, which are mostly foreign firms. The log-normal distribution has to be gradually truncated after a certain critical value for USA firms. Therefore, the original hypothesis of proportional effect proposed by Gibrat is valid with some modification for very large firms. We also consider the possible mechanisms behind this distribution. 相似文献
8.
D. E. Axelson L. Mandelkern R. Popli P. Mathieu 《Journal of Polymer Science.Polymer Physics》1983,21(11):2319-2335
The carbon-13 spin-lattice relaxation times T1 of the crystalline portion of a set of polyethylenes have been studied. Chain structure and crystallization conditions have been varied over the widest possible extremes so that large differences are developed in the level of crystallinity, the supermolecular structure, and the crystallite thickness. Concomitantly, the observed crystalline T1 values cover the extraordinarily wide range of about 40–4500 s. They bear a one-to-one relation with the crystallite thickness, which is found to be the key structural variable determining this property. A correlation with the temperature for the α-transition can be established, which implies a similar type of segmental motions for the two phenomena. Major changes in the interfacial structure can also have a drastic influence on the value for the crystalline T1. Analysis of the magnetization decay curve also allows for a quantitative determination of the degree of crystallinity, which is found to be in excellent agreement with the corresponding value found from Raman spectroscopy. 相似文献
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DL-Penicillamine has been resolved into its enantiomers by normal-phase TLC using L-tartaric acid as chiral impregnating reagent as well as chiral mobile phase additive, while (R)-mandelic acid has been found to be successful as a chiral impregnating reagent. The solvent system acetonitrile-methanol-water (5:1:1, v/v) was found to be successful when L-tartaric acid was used as impregnating agent while the solvent combination acetonitrile-methanol-(0.5% l-tartaric acid in water, pH 5)-glacial acetic acid (7:1:1.1:0.7, v/v) was successful as mobile phase as it contained L-tartaric acid as the chiral additive. (R)-mandelic acid was successful as chiral impregnating reagent with ethyl acetate-methanol-water (3:1:1, v/v), as the mobile phase. The effects of concentration of chiral selectors, temperature and pH were examined on enantiomeric resolution. The spots were detected with iodine vapors and the detection limits were found to be 0.12 microg for each enantiomer of penicillamine with L-tartaric acid, under both the conditions, and 0.11 microg with (R)-mandelic acid. 相似文献
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Direct resolution of the enantiomers of the racemic drugs ketamine and lisinopril has been achieved by TLC. Enantiomerically pure tartaric acid and mandelic acid were used as chiral impregnating reagents and as mobile phase additives. When (?)-mandelic acid was used as chiral impregnating reagent use of ethyl acetate–methanol–water 3:1:1 (v/v) as mobile phase enabled successful resolution of the enantiomers of both compounds. For lisinopril, the mobile phase acetonitrile–methanol–water–dichloromethane 7:1:1:0.5 (v/v) was successful when (+)-tartaric acid was used as impregnating agent. When (+)-tartaric acid was used as mobile phase additive the mobile phase acetonitrile–methanol–(+)-tartaric acid (0.5% in water, pH 5)–glacial acetic acid 7:1:1.1:0.7 (v/v) enabled successful resolution of the enantiomers of lisinopril. The effects on resolution of temperature, pH, and the amount of chiral selector were also studied. The separated enantiomers were isolated and identified. Spots were detected with iodine vapour. LODs were 0.25 and 0.27 μg for each enantiomer of ketamine with (+)-tartaric acid and (?)-mandelic acid, respectively, whereas for lisinopril LODs were 0.14 and 0.16 μg for each enantiomer with (+)-tartaric acid (both conditions) and (?)-mandelic acid, respectively. 相似文献