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排序方式: 共有234条查询结果,搜索用时 15 毫秒
41.
Kavita Pathak Irshad Ahmad Sayed H.R. Abdi Rukhsana I. Kureshy Noor-ul H. Khan Raksh V. Jasra 《Journal of molecular catalysis. A, Chemical》2008,280(1-2):106-114
Chiral BINOL was covalently anchored on two different pore sized mesoporous silica (SBA-15 (7.5 nm) and MCF (14 nm)). These heterogenized ligands were used in Ti-catalyzed asymmetric addition of diethylzinc to aldehydes. High catalytic activity with excellent enantioselectivity (up to 94% ee) for secondary alcohols was achieved using MCF supported chiral BINOL under heterogeneous reaction conditions. Good to excellent enantioselectivity (ee, 68–91%) was also achieved with various small to bulkier aldehydes. The MCF supported catalyst was reused in multiple catalytic runs without loss of enantioselectivity. 相似文献
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Material forces govern the behavior and evolution of defects in solids. In elastic materials these forces which are associated with the Eshelby stress tensor are used to describe fracture sensitivities and can be employed to compute the J‐integral [2]. Since crack propagation begins with a variety of fundamental processes which occur within highly localized ultra–fine volume of material that constitute the fracture process zone surrounding a crack tip [3], the question of appropriate growth criteria, i.e. how far and in which direction a crack will glide under a certain loading condition is implied by the material force. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Mahnaz M.Abdi H.N.M.Ekramul Mahmud Luqman Chuah Abdullah Anuar Kassim Mohamad Zaki Ab.Rahman Josephine Liew Ying Chyi 《高分子科学》2012,(1):93-100
Electrical conductivity and optical properties of polypyrrole-chitosan(PPy-CHI) conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films.The two electrode method and I-V characteristic technique were used to measure the conductivity of the PPy-CHI thin films,and the optical band gap was obtained from their ultraviolet absorption edges.Depending upon experimental parameter,the optical band gap(Eg) was found within 1.30-2.32 eV as estimated from optical absorption data.The band gap of the composite films decreased as the CHI content increased.The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84×10-7-15.25×10-7 S·cm-1 depending on the chitosan content.The thermogravimetry analysis(TGA) showed that the CHI can improve the thermal stability of PPy-CHI composite films. 相似文献
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Tamal Roy Rukhsana I. Kureshy Noor-ul H. Khan Sayed H.R. Abdi Arghya Sadhukhan Hari C. Bajaj 《Tetrahedron》2012,68(31):6314-6322
Chiral dimeric Mn(III) salen complex with 1R, 2R-(?)-diaminocyclohexane collar was immobilized on short channel large pore sized silica through a long linker of {(CH2)3–NH–melamine–piperazine} to investigate its performance in enantioselective epoxidation of chromenes, indene, styrene and cis β-methyl styrene in the presence of pyridine N-oxide (PyNO) as an axial base using aqueous NaOCl as an oxidant at 0 °C. The immobilized catalyst system showed high turnover frequency (TOF) and enantioselectivity for the smaller and bulkier alkenes like styrene, indene, 2,2-dimethylchromene and 6-cyano-2,2-dimethylchromene (ee up to 98%). These results are the best reported for heterogeneous catalyst under biphasic reaction conditions and were comparable to the dimeric Mn(III) salen system under homogeneous condition. The performance of the immobilized catalyst was retained for six reuse experiments. This protocol was extended to the synthesis of an antihypertensive drug (S)-Levchromakalim (ee 98%) at 1 g level. 相似文献
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Rony Abdi Syahputra Urip Harahap Aminah Dalimunthe M. Pandapotan Nasution Denny Satria 《Molecules (Basel, Switzerland)》2022,27(4)
Doxorubicin is a widely used and promising anticancer drug; however, a severe dose-dependent cardiotoxicity hampers its therapeutic value. Doxorubicin may cause acute and chronic issues, depending on the duration of toxicity. In clinical practice, the accumulative toxic dose is up to 400 mg/m2 and increasing the dose will increase the probability of cardiac toxicity. Several molecular mechanisms underlying the pathogenesis of doxorubicin cardiotoxicity have been proposed, including oxidative stress, topoisomerase beta II inhibition, mitochondrial dysfunction, Ca2+ homeostasis dysregulation, intracellular iron accumulation, ensuing cell death (apoptosis and necrosis), autophagy, and myofibrillar disarray and loss. Natural products including flavonoids have been widely studied both in cell, animal, and human models which proves that flavonoids alleviate cardiac toxicity caused by doxorubicin. This review comprehensively summarizes cardioprotective activity flavonoids including quercetin, luteolin, rutin, apigenin, naringenin, and hesperidin against doxorubicin, both in in vitro and in vivo models. 相似文献
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S. Wali Abdi 《School science and mathematics》1994,94(2):104-105
Book reviewed in this article: Minerals of the World , Walter Schumann. A-Z of Snake Keeping , Chris Mattison. 相似文献