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991.
992.
[reaction: see text]. SmI2/H2O/amine provides selective cleavage of unsubstituted allyl ethers in good to excellent yields. This method is therefore useful in deprotection of alcohols and carbohydrates. 相似文献
993.
Schonecker B Lange C Kotteritzsch M Gunther W Weston J Anders E Gorls H 《The Journal of organic chemistry》2000,65(18):5487-5497
The diastereomeric 16-bromo- and 16-azido-17-alcohols 5-8, 11, 12, 16, and 17 and 17-ketones 3, 4, 9, and 10 of the 13alpha-estra-1,3, 5(10)-triene series were synthesized as precursors for biologically active compounds and chiral ligands for metal complexation. Conformational investigations of these and some other compounds via X-ray analysis and (1)H NMR spectroscopy show the existence of compounds with the classical steroid conformation (ring C chair, restricted conformation of ring D) and such with an atypical ring C twist-boat and a flexible ring D conformation. It could be shown that 17beta-substituents or flattening of the D-ring are responsible for the twist-boat conformation, whereas compounds containing a 17alpha-substituent or 17-keto group possess the classical conformation. By varying the substituents, compounds with either of these conformations can be intentionally synthesized. MO calculations confirmed the relative stability of the twist-boat conformation. 相似文献
994.
Thomas Tanggaard Alkeskjold Lara Scolari Danny Noordegraaf Jesper Lægsgaard Johannes Weirich Lei Wei Giovanni Tartarini Paolo Bassi Sebastian Gauza Shin-Tson Wu Anders Bjarklev 《Optical and Quantum Electronics》2007,39(12-13):1009-1019
Liquid crystal photonic bandgap fibers form a versatile and robust platform for designing optical fiber devices, which are highly tunable and exhibit novel optical properties for manipulation of guided light. We present fiber devices for spectral filtering and polarization control/analysis. 相似文献
995.
S.H. Mohamed André Anders L. Galán 《Journal of Physics and Chemistry of Solids》2007,68(12):2227-2232
Thin films of tungsten oxynitrides were deposited on substrates preheated at 300 °C from metallic tungsten target using reactive pulsed d.c. magnetron sputtering. The deposition was carried out at different nitrogen to total reactive gas partial pressures ratios. The energy dispersive analysis of X-ray showed that significant incorporation of nitrogen occurred only when the nitrogen partial pressure exceeded 74% of the total reactive gas pressure. X-ray diffraction analysis revealed that the formation of a specific crystalline phase is affected by the composition and the possibility of competitive growth of different phases. The increase of nitrogen content into the films increases the optical absorption and decreases the optical band gap. The refractive index was determined from the transmittance spectra using Swanepoel's method. It was found that the refractive index increases with increasing nitrogen content over the entire spectral range. The values of the tungsten effective coordination number, Nc, was estimated from the analysis of the dispersion of the refractive index, and an increase in Nc with increasing nitrogen content was observed. 相似文献
996.
Lone B Madsen Bo Thomsen Knud Larsen Christian Bendixen Ida E Holm Merete Fredholm Arne L Jørgensen Anders L Nielsen 《BMC neuroscience》2007,8(1):72
Background
The transmembrane presenilin (PSEN) proteins, PSEN1 and PSEN2, have been proposed to be the catalytic components of the γ-secretase protein complex, which is an intramembranous multimeric protease involved in development, cell regulatory processes, and neurodegeneration in Alzheimer's disease. Here we describe the sequencing, chromosomal mapping, and polymorphism analysis of PSEN1 and PSEN2 in the domestic pig (Sus scrofa domesticus). 相似文献997.
Dendritic cells (DCs) are potent antigen-presenting cells and critical for the priming of CD8+ T cells. Therefore the use
of these cells as adjuvant cells has been tested in a large number of experimental and clinical vaccination studies, in particular
cancer vaccine studies. A number of protocols are emerging that combine vaccination with CTL expanding strategies, such as
e.g. blockade of CTLA-4 signalling. On the other hand, the lifespan and in vivo survival of therapeutic DCs have only been addressed in a few studies, although this is of importance for the kinetics of
CTL induction during vaccination. We have previously reported that DCs loaded with specific antigens are eliminated by antigen
specific CTLs in vivo and that this elimination affects the potential for in vivo CTL generation. We now show that CTLA-4 blockade increases the number of DC vaccine induced LCMV gp33 specific CTLs and the
lysis of relevant in vivo targets. However, the CTLA-4 blockage dependent expansion of CTLs also affect DC survival during booster DC injections and
our data suggest that during a booster DC vaccine, the largest increase in CTL levels is already obtained during the first
vaccination. 相似文献
998.
Anders Melin 《Arkiv f?r Matematik》1971,9(1-2):117-140
999.
A detailed comparison of the simplex method for linear programming with a recent interval linear programming algorithm reveals that the methods are identical in the sense that the same sequence of extreme points can be generated by either algorithm. 相似文献
1000.