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991.
4-Methyl-5-methylimino-1,2,4-dithiazolidine-3-thione ( l )and 2,4-dimethyl-1,2,4-thiadiazolidine-3,5-dithione ( 2 ) are interconvertible in acetone at 50°. They react with ketenes and electrophilic acetylenes to give the thiazole derivatives 6 and 7 after elimination of methyl isothiocyanate or carbon disulfide. Electrophilic isothiocyanates and phenylsulfonyl isocyanate transform the C = S function of 1 in an imine function ( 8 ), and a similar transformation of the thiourea C = S function of 2 is observed on reaction with phenylsulfonyl isocyanate, giving 9 . 相似文献
992.
993.
It has been claimed that Lyapunov exponents computed from electroencephalogram or electrocorticogram (ECoG) time series are useful for early prediction of epileptic seizures. We show, by utilizing a paradigmatic chaotic system, that there are two major obstacles that can fundamentally hinder the predictive power of Lyapunov exponents computed from time series: finite-time statistical fluctuations and noise. A case study with an ECoG signal recorded from a patient with epilepsy is presented. 相似文献
994.
Stochastic synchronization analysis is applied to intracellular calcium oscillations in astrocyte cultures prepared from epileptic human temporal lobe. The same methods are applied to astrocyte cultures prepared from normal rat hippocampus. Our results indicate that phase-repulsive coupling in epileptic human astrocyte cultures is stronger, leading to an increased synchronization in epileptic human compared to normal rat astrocyte cultures. 相似文献
995.
Ann?M?Peiffer R?Holly?Fitch Jennifer?J?Thomas Alexandra?N?Yurkovic Glenn?D?RosenEmail author 《BMC neuroscience》2003,4(1):12
Background
Disrupting neural migration with bilateral focal freezing necrosis on postnatal day 1 (P1) results in the formation of 4-layered microgyria. This developmental injury triggers a pervasive neural reorganization, which is evident at the electrophysiological, behavioral, and anatomical levels. In this experiment, we investigated changes in brain weight as an index of global disruption of neural systems caused by focal damage to the developing cortical plate. 相似文献996.
Inhibition study of angiotensin converting enzyme by capillary electrophoresis after enzymatic reaction at capillary inlet 总被引:1,自引:0,他引:1
Van Dyck S Nováková S Van Schepdael A Hoogmartens J 《Journal of chromatography. A》2003,1013(1-2):149-156
Capillary electrophoresis was used to study the inhibition of angiotensin-converting enzyme (ACE) by different inhibitors. Reaction occurred at the capillary inlet during a predetermined waiting period, followed by the electrophoretic separation of the reaction compounds. ACE activity was determined by the quantification of the reaction product, hippuric acid, at 230 nm. The technique was used to study the potency of five different inhibitors (captopril, lisinopril, perindoprilat, quinaprilat and benazeprilat). During a kinetic study, the Ki value of captopril was estimated to be 55.4 +/- 8.8 nM, a value consistent with previously reported values. 相似文献
997.
Van Dyck S Kaale E Nováková S Glatz Z Hoogmartens J Van Schepdael A 《Electrophoresis》2003,24(22-23):3868-3878
Recent developments in the use of capillary electrophoretic techniques for the in-line study of enzyme reactions and derivatization protocols are reviewed. The article is divided into two parts: (i) in-line enzyme reactions and (ii) in-line derivatization. The first part introduces electrophoretically mediated microanalysis (EMMA) and discusses and illustrates the different modes of EMMA. A literature overview is provided, starting from 1996, and the investigated enzymes are classified into two tables based on the mode of engagement (i.e., continuous or transient) of the developed EMMA-based assay. The second part starts with an introduction of the procedures and the nomenclature used in the area of in-line derivatization protocols based on EMMA. Reported derivatization procedures are discussed and classified in tables, according to the functional group that is derivatized. 相似文献
998.
Ann Anderson 《School science and mathematics》1994,94(3):146-150
The purpose of this article is to present illustrative examples which will help teachers and teacher educators combine mathematics and science through the activities which involve higher order thinking and worthwhile tasks. Packaging provides an important and meaningful context for exploring important mathematics and an important environmental issue. 相似文献
999.
Maged H. M. Sharaf Paul L. Schiff Albert N. Tackie Charles H. Phoebe Ann O. Davis C. Webster Andrews Ronald C. Crouch Gary E. Martin 《Journal of heterocyclic chemistry》1995,32(5):1631-1636
The structure of a new indolobenzazepine alkaloid, homocryptolepinone, isolated from extracts of the roots of the indigenous Ghanaian medicinal plant Cryptolepis sanguinolenta, is reported. The structure was determined using mass spectrometric, one-dimensional nOe difference nmr, and inverse-detected two-dimensional nmr experiments which included HMQC, IDR-(Inverted Direct Response)-HMQC-TOCSY, and HMBC experiments. The structure of homocryptolepinone is significant in that it may provide insight into the biogenesis of the benzpyrrolizinobenzazepine portion of the structure of the complex spiro nona-cyclic alkaloid cryptospirolepine previously isolated in these laboratories from C. sanguinolenta, and which has no precedent in alkaloid chemistry. 相似文献
1000.
A classical model for electronically non-adiabatic collision processes is applied to E → V energy transfer in a collinear system, A + BC (v = 1) → A1 + BC (v = 0), resembling Br-H2.The model, which treats electronic as well as translational, rotational, and vibrational degrees of freedom by classical mechanics, describes the resonance features in this process reasonably well. 相似文献