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排序方式: 共有1191条查询结果,搜索用时 218 毫秒
941.
S. Thinagar D. Velmurugan S. Shanmuga Sundara Raj Hoong‐Kun Fun S. C. Gupta H. Merazig S. Bouacida 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o181-o183
The title compound 3,3′‐[o‐phenylenebis(methyleneoxy)]bis(6‐chloroflavone), C38H24Cl2O6, (I), crystallizes in the monoclinic space group C2/c, with the molecules lying across twofold rotation axes so that there is half a molecule in the asymmetric unit, while the other title compound, 3,3′‐propylenedioxybis[6‐chloro‐2‐(2‐furyl)‐4H‐1‐benzopyran‐4‐one], C29H18Cl2O8, (II), crystallizes in monoclinic space group P21/n with one molecule in the asymmetric unit. In both compounds, the benzopyran moiety is nearly planar, with dihedral angles between the two fused rings of 1.43 (8)° in (I), and 2.54 (7) and 3.00 (6)° with respect to the benzopyran moieties in the two halves of (II). The furan rings are twisted by 8.3 (1) and 8.4 (1)° in the two halves of (II). In both compounds, the molecular structure is stabilized by intramolecular C—H⃛O hydrogen bonds, while the crystal packing is stabilized by C—H⃛Cl and C—H⃛O intermolecular hydrogen bonds in (I) and (II), respectively. 相似文献
942.
943.
Pema Raj Sijo Joseph Thandapilly Jeffrey Wigle Shelley Zieroth Thomas Netticadan 《Molecules (Basel, Switzerland)》2021,26(21)
Atherosclerosis, myocardial infarction (MI) and heart failure (HF) are the main causes of mortality and morbidity around the globe. New therapies are needed to better manage ischemic heart disease and HF as existing strategies are not curative. Resveratrol is a stilbene polyphenolic compound with favorable biological effects that counter chronic diseases. Current evidence suggests that resveratrol is cardioprotective in animal models of atherosclerosis, ischemic heart disease, and HF. Though clinical studies for resveratrol have been promising, evidence remains inadequate to introduce it to the clinical setting. In this narrative review, we have comprehensively discussed the relevant compelling evidence regarding the efficacy of resveratrol as a new therapeutic agent for the management of atherosclerosis, MI and HF. 相似文献
944.
The cycloaddition reactions namely, [2 + 4], [4 + 2], [2 + 3] and [1 + 4] given by the heterophospholes, which are five-membered 6π aromatic heterocycles containing at least one σ2, λ3 phosphorus, are reviewed in the present article. Different aspects of these reactions such as stereoselectivity, regioselectivity, relative reactivities and theoretical correlations thereof are included. The literature has been surveyed up to December 2003. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:271–287, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20002 相似文献
945.
Miguel Lagos & Raj Das 《advances in applied mathematics and mechanics.》2016,8(3):485-498
Common silicate glasses are among the most brittle of the materials. However,
on warming beyond the glass transition temperature $T_g$ glass transforms into
one of the most plastic known materials. Bulk metallic glasses exhibit similar phenomenology,
indicating that it rests on the disordered structure instead on the nature
of the chemical bonds. The micromechanics of a solid with bulk amorphous structure
is examined in order to determine the most basic conditions the system must satisfy
to be able of plastic flow. The equations for the macroscopic flow, consistent with the
constrictions imposed at the atomic scale, prove that a randomly structured bulk material
must be either a brittle solid or a liquid, but not a ductile solid. The theory permits
to identify a single parameter determining the difference between the brittle solid and
the liquid. However, the system is able of perfect ductility if the plastic flow proceeds
in two dimensional plane layers that concentrate the strain. Insight is gained on the
nature of the glass transition, and the phase occurring between glass transition and
melting. 相似文献
946.
Bianchi type I string dust cosmological models in the presence and absence of magnetic field in the frame work of Lyra geometry are investigated. To get the deterministic model of the universe, we assume that the eigenvalue (σ11 ) of shear tensor (σi j ) is proportional to expansion (θ ). This leads to A =(BC)n, where A, B, C are metric potentials and n is a constant. To discuss the results in terms of cosmic time t, we have considered n = 1. The physical and geometrical aspects of the models and singularities in the models are also discussed. 相似文献
947.
The absorption and emission spectral properties of thioflavin T (TFT+) in Nafion (Nf) and cellulose matrices have been studied. Formation of the emittive dimer is observed in both matrices. The monomer TFT+ emission is blueshifted in Nafion membrane (Nf), whereas it is red-shifted in cellulose membrane when compared with the emission in aqueous solution. The dimer emission of TFT+ in the Na+-Nf membrane undergoes off-on switching with acids and alkalis. The TFT+ molecule undergoes protonation in the H+-Nf and the protonated dye is fluorescent. The dimer emission of TFT+ is not observed in the dry H+-Nf membrane because of the protonation of the TFT+ molecule. The diffusion coefficient and the free energy of hydrophobic interaction for the TFT+ molecule in the Nf membrane are calculated. The TFT+ molecule experiences hydrophobic and electrostatic interactions in the Nf matrix, whereas it experiences a polar environment in the cellulose membrane. The 3D emission spectral studies support the formation of the emittive dimer in both Nf and cellulose matrices. 相似文献
948.
Tirtha Raj Acharya Pradeep Lamichhane Rizwan Wahab Dinesh Kumar Chaudhary Bhanu Shrestha Leela Pradhan Joshi Nagendra Kumar Kaushik Eun Ha Choi 《Molecules (Basel, Switzerland)》2021,26(24)
This paper compared the effects of A. indica plant proteins over chemical methods in the morphology of zinc oxide nanoparticles (ZnO NPs) prepared by a co-precipitation method, and ethanol sensing performance of prepared thin films deposited over a fluorene-doped tin oxide (FTO) bind glass substrate using spray pyrolysis technique. The average crystallite sizes and diameters of the grain-sized cluster ZnO NPs were 25 and (701.79 ± 176.21) nm for an undoped sample and 20 and (489.99 ± 112.96) nm for A. india dye-doped sample. The fourier transform infrared spectroscopy (FTIR) analysis confirmed the formation of the Zn–O bond at 450 cm−1, and also showed the presence of plant proteins due to A. indica dye extracts. ZnO NPs films exhibited good response (up to 51 and 72% for without and with A. indica dye-doped extracts, respectively) toward ethanol vapors with quick response-recovery characteristics at a temperature of 250 °C for undoped and 225 °C for A. indica dye-doped ZnO thin films. The interaction of A. indica dye extracts helps to decrease the operating temperature and increased the response and recovery rates of the sensor, which may be due to an increase in the specific surface area, resulting in adsorption of more oxygen and hence high response results. 相似文献
949.
Polypropylene (PP) was reinforced with chemi-thermomechanical (CTMP) pulp and wood flour. Different chemical treatment of the fiber a) polyethylene-poly-(phenyl isocyanate), b) silane A-172 and c) epolene was carried out to improve the bonding between the polymer and fiber. PP reinforced with CTMP pulp and wood flour showed a decrease in stress values as the concentration of fiber increased in the composite. Tensile modulus generally increased with filler loading and was not much affected by fiber treatment. Experimental results of the composites were compared with theoretically predicted values. 相似文献
950.
One novel triply-bridged dicopper(II) complex formulated as [Cu2(dpa)2(μ-Cl)(μ-OH)(μ-HCOO)]·(ClO4) 1 and two terephthalate anions bridged 2,2′-bipyridine (2,2′-bpy) dicopper(II) complexes with formulae of [Cu2(2,2′-bpy)4(μ-terephthalate)]·(NO3)22 and [Cu2(2,2′-bpy)4(μ-terephthalate)]·(terephthalate) 3, respectively, have been synthesized and characterized by infrared and electrospray mass spectra as well as X-ray single-crystal determination. In addition, thermal properties of all compounds have been studied. 相似文献