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Structural Chemistry - This work provides a comprehensive DFT study on the conversion mechanism and photoisomerization of the effective and commonly used nonsteroidal anti-inflammatory medicine... 相似文献
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Dr. Elena Meirzadeh Shiri Dishon Dr. Isabelle Weissbuch Dr. David Ehre Prof. Dr. Meir Lahav Prof. Dr. Igor Lubomirsky 《Angewandte Chemie (International ed. in English)》2018,57(18):4965-4969
Metastable polymorphs commonly emerge when the formation of the stable analogues is inhibited by using different solvents or auxiliaries. Herein, we report that when glycine is grown in aqueous solutions in the presence of low concentrations of different co‐solvents, only alcohols and acetone, unlike water and acetic acid, are selectively incorporated in minute amounts within the bulk of the α‐polymorph. These findings demonstrate that although water binds more strongly to the growing face of the crystal, alcohols and acetone are exclusively incorporated, and thus serve as efficient inhibitors of this polymorph, leading to the precipitation of the β‐form. These solvents then create polar domains detectable by pyroelectric measurements and impedance spectroscopy. These results suggest that in the control of crystal polymorphism with co‐solvents, one should consider also the different desolvation rates in addition to the energy of binding to the growing faces of the crystal. 相似文献
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A new magnetically separable nickel catalyst (Ni(NO3)2?Imine/Thiophene‐Fe3O4@SiO2) was readily prepared and structurally characterized by Fourier transform infrared spectroscopy (FT‐IR), Scanning electron microscopy (SEM), Energy‐dispersive X‐ray spectroscopy (EDX), Vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD) and Atomic absorption spectroscopy (AAS). The Ni(NO3)2?Imine/Thiophene‐Fe3O4@SiO2 exhibited efficient catalytic activity in the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐ones and polyhydroquinolines. Catalysis research under water and solvent‐free conditions makes also this synthetic protocol ideal and fascinating from the environmental point of view. The catalyst can be magnetically recovered after the reaction and can be reused for many times without appreciable decrease in activity. 相似文献
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Many of the surprising phenomena occurring in high dimensions are proved by use of probabilistic arguments, which show the existence of organized and regular structures but do not hint as to where exactly do these structures lie. It is an intriguing question whether some of them could be realized explicitly. In this paper we show that the amount of randomness used can be reduced significantly in many of these questions from asymptotic convex geometry, and most of the random steps can be substituted by completely explicit algorithmic steps. The main tool we use is random walks on expander graphs. 相似文献
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Sofia Curland Christoph Allolio Leah Javitt Shiri Dishon Ben‐Ami Isabelle Weissbuch David Ehre Daniel Harries Meir Lahav Igor Lubomirsky 《Angewandte Chemie (International ed. in English)》2020,59(36):15575-15579
Electrofreezing experiments of super‐cooled water (SCW) with different ions, performed directly on the charged hemihedral faces of pyroelectric LiTaO3 and AgI crystals, in the presence and in the absence of pyroelectric charge are reported. It is demonstrated that bicarbonate (HCO3?) ions elevate the icing temperature near the positively charged faces. In contrast, the hydronium (H3O+) slightly reduces the icing temperature. Molecular dynamics simulations suggest that the hydrated trigonal planar HCO3? ions self‐assemble with water molecules near the surface of the AgI crystal as clusters of slightly different configuration from those of the ice‐like hexagons. These clusters, however, have a tendency to serve as embryonic nuclei for ice crystallization. Consequently, we predicted and experimentally confirmed that the trigonal planar ions of NO3? and guanidinium (Gdm+), at appropriate concentrations, elevate the icing temperature near the positive and negative charged surfaces, respectively. On the other hand, the Cl? and SO42? ions of different configurations reduce the icing temperature. 相似文献
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A novel and atom-economic protocol for the synthesis of thiazole-2-imine derivatives was developed. Synthesis of thiazole-2-imine derivatives from primary amines, phenyl isothiocyanate and phenacyl bromide derivatives by the CoFe2O4@SiO2-PA-CC-Guanidine-SA magnetic nanocatalyst in excellent yields was reported. This nanocatalyst is easily separated from the reaction mixture and can be reused for several times. For the characterization of the catalyst used of Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and vibrating-sample magnetometry (VSM) techniques. 相似文献
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Shiri?ArtsteinEmail author Keith M.?Ball Franck?Barthe Assaf?Naor 《Probability Theory and Related Fields》2004,129(3):381-390
We study the rate at which entropy is produced by linear combinations of independent random variables which satisfy a spectral gap condition.Mathematics Subjects Classification (2000):94A17; 60F05Supported in part by the EU Grant HPMT-CT-2000-00037, The Minkowski center for Geometry and the Israel Science Foundation.Supported in part by NSF Grant DMS-9796221.Supported in part by EPSRC Grant GR/R37210.Supported in part by the BSF, Clore Foundation and EU Grant HPMT-CT-2000-00037. 相似文献
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A methodology for the preparation of asmarine analogues has been developed. The asmarines are cytotoxic marine alkaloids with a unique tetrahydro[1,4]diazepino[1,2,3-g,h]purine (THDAP) structure. Three cyclization methods were applied for the preparation of the 9,9-disubstituted 10-hydroxy-THDAP system, namely, aminomercurization, iodocyclization, and acid-catalyzed cyclization. The DMPM group of the NOH functionality and cyanoethyl group of the N-9 atom were found to be the most suitable protecting groups. The structures of all compounds were mainly determined from NMR measurements including (15)N chemical shifts obtained from (15)NH HMBC spectra. The end products are at least about 1 order of magnitude less active than the natural product asmarine B. 相似文献