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991.
992.
993.
Nicholson PG Ruiz V Macpherson JV Unwin PR 《Chemical communications (Cambridge, England)》2005,(8):1052-1054
Incorporation of non-luminescent dodecanethiolate-protected gold clusters into regioregular poly(3-hexylthiophene) films results in a 6-fold increase in the visible photoluminescence (PL) of the polymer, which arises predominantly from NP-induced structural changes in the composite films. 相似文献
994.
Beevers AP Fettes KJ O'Neil IA Roberts SM Arnold JR Cosstick R Fisher J 《Chemical communications (Cambridge, England)》2002,(14):1458-1459
The effects of a single 3'-S-phosphorothiolate link in the DNA strand of a DNA:RNA dodecamer duplex is described; the sulfur induces a conformational shift in the (attached) sugar pucker, as shown by 1H NMR studies, and increases the thermal stability of the duplex compared to the non-modified system. 相似文献
995.
Richard A. Newmark Michael L. Runge Julie A. Chermack 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1329-1336
Reaction of pentaerythritol (1) or dipentaerythritol with caprolactone yields prepolymers of the general structure for i = 1, 2, 3, and 4 (2)-(5). The 13C chemical shifts of the quaternary carbons in (1)-(5) differ by more than 0.5 ppm. Conditions were determined to obtain quantitative intensity ratios of these carbons. The relative intensities give the distribution of the various branched structures and permit calculations of the average number of caprolactones per branch. Results are reported for caprolactone/polyol mole ratics of 3-66. 相似文献
996.
997.
[reaction: see text] A new class of bis(oxazoline) ligands are introduced that feature o-alkoxyaryl substituents and provide the highest enantioselectivities yet reported for the copper-catalyzed asymmetric dienosilane aldol addition to pyruvate and glyoxylate esters. Enantioselectivities up to 98% ee (before recrystallization) and isolated yields up to 91% were observed. Additionally, chloride counterions were found to be superior to triflate for this reaction. 相似文献
998.
Ji QC Zhou JY Gonzales RJ Gage EM El-Shourbagy TA 《Rapid communications in mass spectrometry : RCM》2004,18(15):1753-1760
Dexmedetomidine (Dex) (Precedex) is a novel lipophilic imidazole derivative with a high affinity for alpha-2 adrenergic receptors, which exhibits sedative, analgesic-sparing, and sympatholytic properties. The pharmacological effects and therapeutic benefits of this drug have drawn continued interest from the medical community. Here we report a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method to simultaneously measure the concentrations of dexmedetomidine and its glucoronide metabolites, G-Dex-1 and G-Dex-2, in human plasma samples. A solid-phase extraction method was developed to effectively extract Dex, G-Dex-1, and G-Dex-2 from plasma matrices. An isocratic chromatographic method was developed to achieve baseline separation of G-Dex-1 and G-Dex-2. The linear dynamic range evaluated was 19.08-1908.56 pg/mL for Dex, 65.17-6518.17 pg/mL for G-Dex-1, and 29.42-2943.28 pg/mL for G-Dex-2. The linear correlation coefficient (r) ranged from 0.9944-0.9979 for Dex, from 0.9966-0.9984 for G-Dex-1, and from 0.9939-0.9966 for G-Dex-2. The intra-assay coefficient of variation (CV) was between 2.5-12.5% for Dex, between 5.2-11.0% for G-Dex-1, and between 3.5-12.1% for G-Dex-2. The inter-assay precision of QC samples give % CV ranges from 6.5-9.3% for Dex, from 7.1-10.6% for G-Dex-1, and from 8.2-10.2% for G-Dex-2. The inter-assay accuracies ranged from 102.0-109.3% for Dex, from 95.4-105.6% for G-Dex-1, and from 98.7-115.0% for G-Dex-2. 相似文献
999.
Cryopreservation using a winter vegetative bud method is being applied to the Malus collection maintained in the field at the USDA-ARS Plant Genetic Resources Unit, Geneva, New York. Winter hardy materials are sent to the USDA-ARS National Center for Genetic Resources Preservation, Fort Collins, CO, for processing. To date 1915 accessions, representing 30 species and 16 interspecific hybrids, have been tested. The NCGRP minimum standard for cryopreservation is 40% viable buds, as determined by grafting. For M. x domestica 95% of the accessions tested have been cryopreserved. For species other than M. x domestica, 83% have met the criterion. Eight lines were collected, cryopreserved and recovered through grafting each year. Data from this set showed an affect of year and cultivar on success. There was no strong relationship between viability after cryopreservation and phylogeny. For North American species success after cryopreservation was related to geographical origin. 相似文献
1000.
Huang W Jin C Derzon DK Huber TA Last JA Provencio PP Gopalan AS Dugger M Sasaki DY 《Journal of colloid and interface science》2004,272(2):457-464
A series of single- and double-tailed hydrocarbon-fluorocarbon (HF) surfactants were prepared to evaluate the effect of molecular structure on aggregate formation in organic solvents. The molecules were designed with ether linkages to permit facile syntheses of both sets of molecules. Solvent foaming studies were used to rapidly assess the surface-active properties of the surfactants, while dynamic light scattering provided quantitative critical micelle concentrations (CMC) and hydrodynamic radius (R(h)) measurements of the aggregates in solution. The single-tailed surfactants did not produce any foaming action in a number of hydrocarbon solvents, nor was any micellar formation observed up to 100 mM concentrations. Double-tailed surfactants, on the other hand, gave low CMC values in dodecane but with R(h) values that indicated a tight micelle structure. Bilayer formation was expected but not observed for these molecules, which is believed to be due to their unusual structural geometry, imparted by the glycerol backbone. No thermotropic liquid crystalline (LC) behavior was observed for any of the single- or double-tailed molecules. These data contrast with the known behavior of perfluorinated alkanes and other fluorinated surfactants, suggesting that the ether linkage plays an important role in the self-organizing behavior of these molecules. 相似文献