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排序方式: 共有144条查询结果,搜索用时 15 毫秒
101.
Rao CN Kulkarni GU Agrawal VV Gautam UK Ghosh M Tumkurkar U 《Journal of colloid and interface science》2005,289(2):305-318
The air-water interface has traditionally been employed to prepare particle assemblies and films of metals and semiconductors. The interface between water and an organic liquid, however, has not been investigated sufficiently for possible use in preparing nanocrystals and thin films of materials. In this article, we demonstrate the use of the liquid-liquid interface as a medium for preparing ultrathin films of metals, chalcogenides and oxides. The method involves the reaction at the interface between a metal-organic compound in the organic layer and an appropriate reagent for reduction, sulfidation, etc. in the aqueous layer. Some of the materials discussed are nanocrystalline films of gold, CuS, CuSe, CuO, and Cu(OH)2 formed at the liquid-liquid interface. The results reported in this article should demonstrate the versatility and potential of the liquid-liquid interface for preparing nanomaterials and ultrathin films and encourage further research in this area. 相似文献
102.
Interfacial stabilization of organic-aqueous two-phase microflows for a miniaturized DNA extraction module 总被引:1,自引:0,他引:1
Organic-aqueous liquid (phenol) extraction is one of many standard techniques to efficiently purify DNA directly from cells. The cell components naturally distribute themselves into the two fluid phases in order to minimize interaction energies of the biological components with the surrounding solvents. The membrane components and protein partition to the interface between the organic and aqueous phases while the DNA stays in the aqueous phase. The aqueous phase is then removed with a purified DNA sample. This work studies the first steps towards miniaturizing this liquid extraction technique in a microfluidic device. The first step is to understand how the two liquid phases behave in microchannels. Due to the interfacial tension between the two liquid phases, novel approaches must be examined in order to obtain interfacial stability under flow conditions. The stability of the organic-aqueous interface is improved by reducing the interfacial tension between the two phases by incorporating a surfactant into the aqueous phase. The variation of the interfacial tension as a function of surfactant concentration is also quantified in this work. This has led to the ability to create stable stratified microflows in both a dual inlet and three inlet microfluidic systems. Also, the first step in understanding biological interactions at the organic-aqueous interface is investigated using a fluorescently labeled bovine serum albumin protein. 相似文献
103.
Bhattacharyya Suvanjan Vishwakarma Devendra Kumar Goel Varun Chamoli Sunil Issakhov Alibek Meyer Josua P. 《Journal of Thermal Analysis and Calorimetry》2021,145(3):1445-1465
Journal of Thermal Analysis and Calorimetry - Baffles are used for heat transfer enhancement in heat exchanger tubes. However, they also increase the friction factor in the flow channel.... 相似文献
104.
Kumari Akriti Karnatak Manvika Sen Debanjan Rawat Varun Khan Shahnawaz Verma Ved Prakash 《Structural chemistry》2022,33(3):907-919
Structural Chemistry - Malaria infection continues to pose a substantial threat to human health in the twenty-first century. The parasites’ resistance against conventional antimalarial drugs... 相似文献
105.
Collagen type I is an AAB heterotrimer assembled from two alpha1 chains and one alpha2 chain. Missense mutations in either of these chains that substitute a glycine residue in the ubiquitous X-Y-Gly repeat with a bulky amino acid leads to osteogenesis imperfecta (OI) of varying severity. These mutations have been studied in the past using collagen-like peptide homotrimers as a model system. However, homotrimers, which by definition will contain glycine mutations in all the three chains, do not accurately mimic the mutations in their native form and result in an exaggerated effect on stability and folding. In this article, we report the design of a novel model system based upon collagen-like heterotrimers that can mimic the glycine mutations present in either the alpha1 or alpha2 chains of type I collagen. This design utilizes an electrostatic recognition motif in three chains that can force the interaction of any three peptides, including AAA (all same), AAB (two same and one different), or ABC (all different) triple helices. Therefore, the component peptides can be designed in such a way that glycine mutations are present in zero, one, two, or all three chains of the triple helix. With this design, we for the first time report collagen mutants containing one or two glycine substitutions with structures relevant to native forms of OI. Furthermore, we demonstrate the difference in thermal stability and refolding half-life times between triple helices that vary only in the frequency of glycine mutations at a particular position. 相似文献
106.
Akhilesh K. Verma Pankaj Attri Varun Chopra Rakesh K. Tiwari Ramesh Chandra 《Monatshefte für Chemie / Chemical Monthly》2008,139(9):1041-1047
A new, highly efficient, inexpensive, recyclable, mild, convenient, and green protocol for chemoselective aza/thia-Michael addition reactions of amines/thiols to α,β-unsaturated compounds using triethylammonium acetate (TEAA) ionic liquid was developed. The catalyst can be recycled ten times and obviate the need for toxic and expensive catalysts.
Correspondence: Akhilesh K. Verma, Green Organic Chemistry Research Laboratory, Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi 110007, India. 相似文献
107.
Waldemar Hujo B. Shadrack Jabes Varun K. Rana Charusita Chakravarty Valeria Molinero 《Journal of statistical physics》2011,145(2):293-312
The thermodynamic liquid-state anomalies and associated structural changes of the Stillinger-Weber family of liquids are mapped out as a function of the degree of tetrahedrality of the interaction potential, focusing in particular on tetrahedrality values suitable for modeling C, H2O, Si, Ge and Sn. We show that the density anomaly, associated with a rise in molar volume on isobaric cooling, emerges at intermediate tetrahedralities (e.g. Ge, Si and H2O) but is absent in the low (e.g. Sn) and high (e.g. C) tetrahedrality liquids. The rise in entropy on isothermal compression associated with the density anomaly is related to the structural changes in the liquid using the pair correlation entropy. An anomalous increase in the heat capacity on isobaric cooling exists at high tetrahedralities but is absent at low tetrahedralities (e.g. Sn). Structurally, this heat capacity anomaly originates in a sharp rise in the fraction of four-coordinated particles and local tetrahedral order in the liquid as its structure approaches that of the tetrahedral crystal. 相似文献
108.
Effects of non-uniform strains on tensile fracture of fiber-reinforced ceramic–matrix composites have not been satisfactorily explained by existing mechanics-based models. In this paper, we use an exact model of fiber fragmentation under global load sharing conditions to predict fracture in three model problems in which non-uniform strains occur: (i) an end-constrained plate subject to a linear transverse temperature gradient; (ii) an internally-pressurized cylindrical tube with a linear through-thickness temperature gradient; and (iii) a rectangular beam under combined bending and tension. Fracture is assumed to occur when the global load reaches a maximum value. Approximations to the exact fragmentation model are also assessed, with the goal of decoupling the effects of two important parts of the computed stress–strain response: the rate of post-peak strain softening and the magnitude of the plateau “flow” stress once fiber fragmentation is complete. We find that for cases in which the fiber Weibull modulus is low and hence its plateau strength is high relative to its peak and the loading yields a sufficiently high strain gradient, the failure strain lies in the plateau regime. Consequently, the results can be predicted with good accuracy using a perfectly-plastic representation of the post-peak response. In contrast, for cases in which the fiber Weibull modulus is high, the failure strain lies in the softening portion of the curve. Here a linear-softening model is found to yield accurate results. A preliminary assessment of the model has been made by comparing predicted and measured bending/tension strength and failure strain ratios for one specific composite. The correlations appear good, though additional experiments are required in order to critically assess the model predictions over a range of loading scenarios. 相似文献
109.
Nitin A. Randive Varun Kumar Vipin A. Nair 《Monatshefte für Chemie / Chemical Monthly》2010,43(7):1329-1332
Abstract
Water-promoted hydrothiolation and hydroamination of ethyl propiolate leading to highly regioselective and stereoselective formation of thioacrylates and β-enamino esters in excellent yields, by a simple, efficient, and environmentally friendly reaction procedure without employing any hazardous reagent or solvent is reported. 相似文献110.