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排序方式: 共有277条查询结果,搜索用时 15 毫秒
1.
Riaan Schmuhl Sankhanilay Roy Chowdhury Johan E. ten Elshof Albert van den Berg Dave H.A. Blank 《Journal of Sol-Gel Science and Technology》2004,31(1-3):249-252
Templated MCM-48 silica was prepared using CTAB as surfactant. The MCM-48 powders and thin films were characterized by different techniques. MCM-48 layers were deposited on macroporous α-alumina supports and silicon nitride microsieves. The water permeability of MCM-48 was compared with the permeability of conventional mesoporous γ-alumina membranes. The applicability of MCM-48 as ion-selective electric field-driven switchable interconnect for microfluidic devices was demonstrated. 相似文献
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F. C. ten Doornkaat Koolman J. Traube Jandell Henderson Donald G. Russell und H. Bunzel 《Fresenius' Journal of Analytical Chemistry》1914,53(6):404
Ohne Zusammenfassung 相似文献
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Witte PT Chowdhury SR ten Elshof JE Sloboda-Rozner D Neumann R Alsters PL 《Chemical communications (Cambridge, England)》2005,(9):1206-1208
A "sandwich" type polyoxometalate catalyst ([MeN(n-C8H17)3]12[WZn3(ZnW9O34)2]) was very efficiently recycled by nanofiltration with almost quantitative retention, using an alpha-alumina supported mesoporous gamma-alumina membrane. 相似文献
6.
ten Cate AT Kooijman H Spek AL Sijbesma RP Meijer EW 《Journal of the American Chemical Society》2004,126(12):3801-3808
Bifunctional 2-ureido-4[1H]-pyrimidinone (UPy) derivatives can form small cyclic oligomers as well as long supramolecular polymers in chloroform solutions using the quadruple hydrogen-bonding motif. Ring-chain equilibria of a set of supramolecular monomers containing methyl-substituted alkyl linkers between the hydrogen-bonding UPy moieties were investigated by (1)H NMR spectroscopy and viscometry. The data were characterized in terms of critical concentration (CC, denoting the onset of polymerization) and equilibrium cyclic dimer concentration (EDC, representing preorganization of the monomer toward selective formation of cyclic dimer). Methyl substituents in the monomer were found to promote conformations favorable for cyclic dimerization, leading to an increase in both the EDC and the CC with respect to unsubstituted monomer. Furthermore, we observed an odd-even effect in the CC and EDC with increasing length of the linker between the hydrogen-bonding units. The combined results allow tuning of the critical concentration over a broad range and offer detailed information on the correlation between monomer structure, conformation, and polymerizability which may provide new insights for the study and design of other ring-chain equilibria or helix-random coil transitions. 相似文献
7.
The partial energies and entropies of O2in perovskite-type oxides La0.6Sr0.4Co1−yFeyO3−δ(y=0, 0.1, 0.25, 0.4, 0.6) were determined as a function of nonstoichiometryδby coulometric titration of oxygen in the temperature range 650–950°C. An absolute reference value ofδwas obtained by thermogravimetry in air. The nonstoichiometry at a given oxygen pressure and temperature decreases with iron contenty. At low nonstoichiometries the oxygen chemical potential decreases withδ. The observed behavior can be interpreted by assuming random distribution of oxygen vacancies, an electronic structure with both localized donor states on Fe, and a partially filled itinerant electron band, of which the density of states at the Fermi level scales with the Co content. The energy of the Fe states is close to the energy at the Fermi level in the conduction band. The observed trends of the thermodynamic quantities can be interpreted in terms of the itinerant electron model only when the iron content is small. At high values ofδthe chemical potential of O2becomes constant, indicating partial decomposition of the perovskite phase. The maximum value ofδat which the compositions are single-phase increases with temperature. 相似文献
8.
U Aebi R K Bijlenga B ten Heggeler J Kistler A C Steven P R Smith 《Journal of supramolecular structure》1976,5(4):475-495
A study has been made of the structure of the capsids of T4D giant phage produced from mutants in gene 23 and temperature-sensitive mutants in gene 24, and T4D and T2L giant phage formed by the addition of L-canavanine followed by an Larginine chase in the growth medium. All the giant phage capsids have been shown to be built according to the same geometrical architecture. This consists of a near-hexagonal surface net, lattice constant 129.5 A, folded into a left-handed T = 13 prolate icosahedron elongated along one of its fivefold symmetry axes. Their only apparent difference from wild-type T-even phage capsids is their abnormally elongated tubular part. A comparison of the capsomere morphologies and protein compositions of the giant phage capsids showed that all T4D giants are identical but differ from T2L: The T4D capsomere has a complex (6 + 6 + 1)-type morphology, whereas the T2L has a simple 6-type. T2L phage, however, lack two capsid proteins, "soc" and "hoc", present in T4D. The difference in capsomere morphology can therefore be related to the difference in the protein compositions of these two phage. Possible differences between the initiation and means of length regulation of giant phage heads and the aberrant polyheads are discussed. 相似文献
9.
ten Cate AT Dankers PY Kooijman H Spek AL Sijbesma RP Meijer EW 《Journal of the American Chemical Society》2003,125(23):6860-6861
Homochiral hydrogen-bonded cyclic assemblies are formed in dilute solutions of racemic supramolecular polymers based on the quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidinone unit, as observed by 1H NMR and SEC experiments. Preorganization of the monomers and the combined binding strength of the eight hydrogen bonds result in a very high stability of the cyclic aggregates with pronounced selectivity between homochiral and heterochiral cyclic species, usually only observed in crystalline or liquid crystalline phases. 相似文献
10.
O van Tellingen J H Beijnen R Baurain W W ten Bokkel Huinink H R van der Woude W J Nooyen 《Journal of chromatography. A》1991,553(1-2):47-53
Procedures for the determination of vinblastine (VBL), 4-O-deacetylvinblastine (DVBL) and 4-O-deacetylvinblastine-3-oic acid (DVBLA) in biological samples using high-performance liquid chromatography (HPLC) combined with selective sample clean-up are presented. VBL and DVBL were determined in plasma and urine using ion-exchange normal-phase HPLC with fluorescence detection. The limit of detection was 1 microgram/l for both compounds using a 500-microliter sample. Successful chromatographic analyses of DVBLA were achieved by using a glass column packed with 5-microns Hypersil ODS and acetonitrile-0.05 M phosphate buffer (pH 2.7) (23:77, v/v). Positive identification was supported by the use of diode-array detection. The limit of detection (at 270 nm) was 10 micrograms/l using 1-ml samples. 相似文献