排序方式: 共有39条查询结果,搜索用时 31 毫秒
31.
Estelle Piquer Marie-Catherine Charrier-Mojtabi Mejdi Azaiez Abdelkader Mojtabi 《Comptes Rendus Mecanique》2005,333(2):179-186
This Note deals with mixed convection in binary fluid with Soret effect in a rectangular duct heated from below. In particular, we study the transition towards transverse 2D rolls appearing at low Reynolds and Rayleigh numbers. The linear stability analysis of Poiseuille flow, with linearly stratified temperature and concentration fields, shows the influence of the separation ratio on the critical Rayleigh number at the transition towards the transversal 2D convective patterns. It highlights the presence, at low Reynolds numbers, of propagating transverse rolls in the downwards as well as in the upwards direction. Finally, we point out that, under these conditions, the propagating frequency of the rolls is the sum of two well defined frequencies: the first related to the Reynolds, the second to the separation ratio. To cite this article: E. Piquer et al., C. R. Mecanique 333 (2005). 相似文献
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The low-temperature single-crystal polarized absorption and the luminescence spectra of Cs2[CrCl2(H2O)4]Cl3 are theoretically analyzed in order to determine the electronic structure of the trans-[CrCl2(H2O)4]+ complex. This study, based on the Racah theory, leads to a good agreement between the theoretical and experimental energy levels. The electronic-exited state 4T2g(Oh) is split into 4Eg and 4B2g components due to the lowering of the symmetry from Oh to D4h. The polarized absorption spectrum and the theoretical energies show that the 4Eg(D4h) state is lower in energy than the 4B2g(D4h) state. The resolved vibronic structure in the luminescence spectrum reveals a progression in a non-totally symmetric b1g mode, a manifestation of a Jahn-Teller effect in the emitting state 4T2g(Oh). Both Jahn-Teller and spin-orbit coupling in the orbitally degenerated 4Eg(D4h) state are necessary to account for the spectroscopic observations. 相似文献
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Samira El Ghammarti Benoít Rigo Hechmi Mejdi Jean‐Pierre Hnichart Daniel Couturier 《Journal of heterocyclic chemistry》2000,37(1):143-150
Tetrahydro‐2H‐pyrrolo[1,2‐c]quinazoline‐3‐ones are easily obtained from the Friedel‐Crafts cyclization of N‐arylaminomethyl pyroglutamic acids. This reaction occurrs via an acyliminium salt formed by decarboxylation of the acid function. 相似文献
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A theoretical energy-level analysis was based on parametric Hamiltonian for the 4f11 electronic configuration of Er3+ ions in C3v center, and it permitted a phenomenological characterization of crystal-field (CF) Hamiltonian parameters. This characterization allowed us to calculate the energy of the missing stark levels of the 4I15/2 and 4I13/2 states and to confirm the presence of a single emission center with C3v symmetry. The calculated CF and strength parameters are compared with those obtained for Sm3+, Pr3+ and Yb3+ ions in the same host and with Er3+ in other isostructural hosts. 相似文献
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2-Amino-4-(2-hydroxynaphthyl)-4H-chromene-3-carbonitriles were synthesized by Michael addition of various 3-cyanoiminocoumarins and β-naphthol in good yield. The heterocyclization of these materials in an acidic medium leads new heterocyclic compounds, which have not previously been described, in moderate to good yields and good selectivity. The synthesized compounds were characterized by infrared, 1H NMR, 13C NMR, two-dimensional NMR, and elemental analysis. 相似文献
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Maher Kammoun Imed Koubaa Yassine Ben Ali Raoudha Jarraya Youssef Gargouri Mohamed Damak Sofiane Bezzine 《Applied biochemistry and biotechnology》2010,162(3):662-670
The aim of the present work was to evaluate the anti-inflammatory properties of Cynara cardunculus L. (Asteraceae) during its growth using various solvents such as n-hexane, dichloromethane, acetone, and methanol for air-dried leaves and stems. The anti-inflammatory activities of crude
extracts were evaluated by measuring the inhibition potency of mammalian non-pancreatic phospholipases A2 (hG-IIA). The methanol
and acetone extracts of leaves harvested in February exhibit potent inhibition of hG-IIA (IC50 = 50 and 70 μg/ml, respectively). However, the acetone extract of stems harvested in December inhibits the hG-IIA with a
lower IC50 around 130 μg/ml. Fractionation on silica gel and hydrophobic gel of the methanol extract of leaves harvested in February
increases the inhibitory effect, and the IC50 reached 10 μg/ml. 相似文献
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Bandar Hamad Aloufi Mejdi Snoussi Abdel Moneim E. Sulieman 《Molecules (Basel, Switzerland)》2022,27(8)
SARS-CoV-2 is a highly virulent coronavirus that first surfaced in late 2019 and has since created a pandemic of the acute respiratory sickness known as “coronavirus disease 2019” (COVID-19), posing a threat to human health and public safety. S-RBD is a coronaviral protein that is essential for a coronavirus (CoV) to bind and penetrate into host cells. As a result, it has become a popular pharmacological target. The goal of this study was to find potential candidates for anti-coronavirus disease 2019 (COVID-19) drugs by targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) S-RBD with novel bioactive compounds and molecular interaction studies of 15,000 phytochemicals belonging to different flavonoid subgroups. A spike protein crystal structure attached to the ACE2 structure was obtained from the PDB database. A library of 15,000 phytochemicals was made by collecting compounds from different databases, such as the Zinc-database, PubChem-database, and MPD3-database. This library was docked against a receptor binding domain of a spike glycoprotein through the Molecular Operating Environment (MOE). The top drug candidates Phylloflavan, Milk thistle, Ilexin B and Isosilybin B, after virtual screening, were selected on the basis of the least binding score. Phylloflavan ranked as the top compound because of its least binding affinity score of −14.09 kcal/mol. In silico studies showed that all those compounds showed good activity and could be used as an immunological response with no bioavailability issues. Absorption, distribution, metabolism, excretion and a toxicological analysis were conducted through SwissADME. Stability and effectiveness of the docked complexes were elucidated by performing the 100 ns molecular dynamic simulation through the Desmond package. 相似文献