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101.
K. Vince Fernando 《Numerische Mathematik》1989,56(1):73-91
Summary Linear convergence of the row cyclic Jacobi and Kogbetliantz methods can be guaranteed if certain constraints concerning the angles of rotations are implemented. Unlike the results of Forsythe and Henrici, convergence can be achieved without under-rotations.This work was carried out under the MOD Contract No. A94C/2243 in collaboration with the Royal Signals and Radar Establishment 相似文献
102.
K. Vince Fernando Beresford N. Parlett 《Numerical Linear Algebra with Applications》1995,2(6):507-531
The implicit Cholesky algorithm has been developed by several authors during the last 10 years but under different names. We identify the algorithm with a special version of Rutishauser's LR algorithm. Intermediate quantities in the transformation furnish several attractive approximations to the smallest singular value. The paper extols the advantages of using shifts with the algorithm. The nonorthogonal transformations improve accuracy. 相似文献
103.
104.
It is known that a lexicographically shellable poset is shellable, and it has been asked whether the two concepts are equivalent.
We provide a counterexample, a shellable graded poset that is not lexicographically shellable. 相似文献
105.
Carbocyclic ribofuranosylamine, a key intermediate for the synthesis of carbocyclic ribonucleosides, was synthesized by a facile route from the lactam, 2-azabicyclo[2.2.1]hept5-ene-3-one. 相似文献
106.
Carbovir is a novel carbocyclic guanosine derivative that has potent in vitro activity against human immunodeficiency virus, the causative agent of acquired immunodeficiency syndrome (AIDS). Two methods of sample preparation were developed for the analysis of carbovir in rat blood. Solid-phase extraction on C18 extraction columns proved to be the most effective. Whole rat blood (200 microliters) was diluted with 0.8 ml of distilled water containing the internal standard. After two freeze-thaw cycles to lyse the red blood cells and subsequent centrifugation at 13,000 g, the supernatant was loaded on the C18 extraction columns. Carbovir and the internal standard were eluted with methanol-water (60:40). The extract was evaporated and reconstituted in mobile phase and the samples were injected onto a high-capacity reversed-phase column. The compounds were detected at 252 nm. Other nucleosides that could be used in the treatment of AIDS such as zidovudine and acyclovir did not interfere. Standard curves were linear over the concentration range 0.156-28.0 micrograms/ml (r2 greater than 0.99). The within-day coefficient of variation was less than 7.6% at all concentrations (n = 4). The between-day coefficient of variation ranged from 16.7 to 2.0% (n = 14). The limit of sensitivity was 0.05 micrograms/ml with a 200-microliters blood sample and the average extraction recovery was 74%. Carbovir was stable in rat blood for at least 4 h at 37 degrees C. The assay was used to determine the blood levels of carbovir in a rat after a 20 mg/kg intravenous dose. 相似文献
107.
A new, efficient, and mild protocol is presented for the coupling of saccharides to proteins. First, a heterobifunctional aminooxy-thiol linker is coupled to the bromoacylated protein to introduce aminooxy groups through thioether linkages. Condensation of the aminooxylated protein and aldehydo/keto-derivatized carbohydrates affords covalent saccharide-protein constructs. Uncoupled saccharide can be recovered in its original form. The scope of our protocol is exemplified by the coupling of neutral mono- and tetrasaccharides and a negatively charged ribitol-phosphate construct to BSA. 相似文献
108.
Sanjay?Awasthi Kerri?L?Hallene Vince?Fazio Sharad?S?Singhal Luca?Cucullo Yogesh?C?Awasthi Gabriele?Dini Damir?JanigroEmail author 《BMC neuroscience》2005,6(1):61
Background
Permeability of the blood-brain barrier is one of the factors determining the bioavailability of therapeutic drugs and resistance to chemically different antiepileptic drugs is a consequence of decreased intracerebral accumulation. The ABC transporters, particularly P-glycoprotein, are known to play a role in antiepileptic drug extrusion, but are not by themselves sufficient to fully explain the phenomenon of drug-resistant epilepsy. Proteomic analyses of membrane protein differentially expressed in epileptic foci brain tissue revealed the frequently increased expression of RLIP76/RALBP1, a recently described non-ABC multi-specific transporter. Because of a significant overlap in substrates between P-glycoprotein and RLIP76, present studies were carried out to determine the potential role of RLIP76 in AED transport in the brain. 相似文献109.
[reaction: see text] A general strategy for the formation of 1,3-cis-substituted tetrahydroisoquinolines is described from ortho-iodo imines involving Larock isoquinoline synthesis, addition of organolithium compounds to unactivated isoquinolines, and ionic hydrogenation. In addition, a new synthesis of lactams via an unprecedented azide cyclization in the presence of a sulfonium ion is described. 相似文献
110.
In the nucleophilic reaction of chromone () with NH2OH·HC1 in anhydrous methanol a new compound 2-methoxychromanone () appeared as an intermediate in the formation of chromone oxime () and 2-methoxychromanone oxine (). 相似文献