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排序方式: 共有107条查询结果,搜索用时 15 毫秒
1.
Gábor Blaskó S.Fazal Hussain Alan J. Freyer Maurice Shamma 《Tetrahedron letters》1981,22(33):3127-3130
The dark yellow indenobenzazepine alkaloids lahorine () and lahoramine () have been found in Lam. (Fumariaceae). In a transformation with biogenetic implications, treatment of the spirobenzylisoquinolines dihydrofumariline () and dihydroparfumidine () with methanesulfonyl chloride and triethylamine in dry THF, followed by iodine oxidation, provided and , respectively. 相似文献
2.
Armstrong A Ahmed G Dominguez-Fernandez B Hayter BR Wailes JS 《The Journal of organic chemistry》2002,67(24):8610-8617
Several alpha-substituted N-carbethoxytropinones have been evaluated as catalysts for asymmetric epoxidation of alkenes with Oxone, via a dioxirane intermediate. alpha-Fluoro-N-carbethoxytropinone (2) has been studied in detail and is an efficient catalyst which does not suffer from Baeyer-Villiger decomposition and can be used in relatively low loadings. This ketone was prepared in enantiomerically pure form using chiral base desymmetrization of N-carbethoxytropinone. Asymmetric epoxidation catalyzed by 2 affords epoxides with up to 83% ee. Among other derivatives tested, the alpha-acetoxy derivative 7 affords the highest enantioselectivities. 相似文献
3.
Two-dimensional capillary electrophoresis was used for the separation of proteins and biogenic amines from the mouse AtT-20 cell line. The first-dimension capillary contained a TRIS–CHES–SDS–dextran buffer to perform capillary sieving electrophoresis, which is based on molecular weight of proteins. The second-dimension capillary contained a TRIS–CHES–SDS buffer for micellar electrokinetic capillary chromatography. After a 61-s preliminary separation, fractions from the first-dimension capillary were successively transferred to the second-dimension capillary, where they further separated by MECC. The two-dimensional separation required 60 min. 相似文献
4.
In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise. 相似文献
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7.
Célestin Wafo Soh Fazal M. Mahomed 《Mathematical Methods in the Applied Sciences》2016,39(14):4139-4157
We review the theory of hypercomplex numbers and hypercomplex analysis with the ultimate goal of applying them to issues related to the integration of systems of ordinary differential equations (ODEs). We introduce the notion of hypercomplexification, which allows the lifting of some results known for scalar ODEs to systems of ODEs. In particular, we provide another approach to the construction of superposition laws for some Riccati‐type systems, we obtain invariants of Abel‐type systems, we derive integrable Ermakov systems through hypercomplexification, we address the problem of linearization by hypercomplexification, and we provide a solution to the inverse problem of the calculus of variations for some systems of ODEs. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
8.
(+)-Parviflorine (), found in Lam. (Fumariaceae), is the first known glycosidic spirobenzylisoquinoline alkaloid. Its acid hydrolysis yields (+)-parfumine () and D-glucose. Klyne's rule indicates that is a β-D-glucoside. The absolute configuration shown in expressions is predominant among spirobenzylisoquinolines. A generalization has been drawn between plant source and the oxygenation pattern of ring C for the spirobenzylisoquinoline alkaloids. 相似文献
9.
Iqbal Saeed Raza Aadil Butt Muhammad Fasih Uddin Mirza Jawad Iqbal Muhammad Ghafoor Salman El-Hajjar Mohammed 《Optical Review》2021,28(3):278-288
Optical Review - In this paper, we propose a full duplex architecture based on a hybrid link composed of free space optics (FSO) and multimode plastic optical fiber (MMPOF) for short-range wireless... 相似文献
10.
Atif Fazal Sahar Al-Fayez Laila H. Abdel-Rahman Zaki S. Seddigi Abdul Rahman Al-Arfaj Bassam El Ali Mohammad A. Dastageer Mohammad A. Gondal Mohammed Fettouhi 《Polyhedron》2009,28(18):4072-4076
New copper(I) mixed-ligand complexes 1–4 of the formula Cu(N–N)PR3X, where N–N = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′dimbpy) and PR3 = tricyclohexylphosphine, tris(2-cyanoethyl)phosphine and isopropyldiphenylphosphine, have been synthesized. The complexes were characterized by EA, IR, NMR and single crystal X-ray diffraction. The solution fluorescence emission spectra were measured. The single crystal X-ray analysis showed that the copper(I) ion is four-coordinate with a distorted tetrahedral geometry. The complexes catalyze the formation of diphenylacetylene from the coupling of halobenzene with phenylacetylene. The complex Cu(5,5′-dimethylbpy)P{(cyhexyl)3}I showed the highest catalytic activity. At room temperature all four complexes exhibit, in dichloromethane, emission maxima in the 329–344 nm range, corresponding to intra-ligand excited states. 相似文献