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71.
Sijo Sebastian Manesh Michael Sreekala G. Anu Varghese Chandu Venugopal 《Brazilian Journal of Physics》2017,47(1):46-54
We have investigated fast- and slow-mode solitary profiles in a five-component plasma consisting of positively and negatively charged pair ions, hydrogen ions, and hotter and colder electrons. Of these, the heavier ions and colder photoelectrons are of cometary origin while the other components are of solar origin; the electrons are described by kappa distributions. The Zakharov-Kuznetsov (ZK) equation is derived, and solutions for fast- and slow-mode solitary structures are plotted for parameters relevant to comet Halley. We found that the presence of hydrogen ions determines the polarity of the fast- and slow-mode solitary structures. Also, variations of equilibrium number density of hydrogen ions and charge numbers on the heavier pair ions act differently on the fast- and slow-mode solitary structures. The addition of hydrogen ions significantly affects the amplitude of the solitary structures for the fast mode. Further, the cyclotron frequency of the lighter and heavier ions has a noticeable effect on the width of the solitary waves. 相似文献
72.
Varghese N Shetye GS Bandyopadhyay D Gobalasingham N Seo J Wang JH Theiler B Luk YY 《Langmuir : the ACS journal of surfaces and colloids》2012,28(29):10797-10807
Single-chain surfactants usually emulsify and stabilize oily substances into droplets in an aqueous solution. Here, we report a coassembly system, in which single types of anionic or non-ionic surfactants emulsify a class of water-soluble nonamphiphilic organic salts with fused aromatic rings in aqueous solutions. The nonamphiphilic organic salts are in turn promoted to form droplets of water-based liquid crystals (chromonic liquid crystals) encapsulated by single-chain surfactants. The droplets, stabilized against coalescence by encapsulated in a layer (or layers) of single chain surfactants, are of both nonspherical tactoid (elongated ellipsoid with pointy ends) and spherical shapes. The tactoids have an average long axis of ~9 μm and a short axis of ~3.5 μm with the liquid crystal aligning parallel to the droplet surface. The spherical droplets are 5-10 μm in diameter and have the liquid crystal aligning perpendicular to the droplet surface and a point defect in the center. Cationic and zwitterionic surfactants studied in this work did not promote the organic salt to form droplets. These results illustrate the complex interplay of self-association and thermodynamic incompatibility of molecules in water, which can cause new assembly behavior, including potential formation of vesicles or other assemblies, from surfactants that usually form only micelles. These unprecedented tactoidal shaped droplets also provide potential for the fabrication of new soft organic microcapsules. 相似文献
73.
Raveendran Sindhu Mathiyazhakan Kuttiraja Parameswaran Binod Varghese Elizabeth Preeti Soolankandath Variem Sandhya Sankar Vani Rajeev Kumar Sukumaran Ashok Pandey 《Applied biochemistry and biotechnology》2012,167(6):1513-1526
Sugarcane tops is one of the largest biomass resources in India and in tropical countries such as Brazil in terms of surplus availability. Conversion of this feedstock to ethanol requires pretreatment to make it more accessible for the enzymes used in saccharification. Though several pretreatment regimens have been developed for addressing biomass recalcitrance, very few seem to be promising as an industrial process. A novel hybrid method involving use of mild acid and surfactant was developed which could effectively remove lignin and improve the sugar yield from sugar cane tops. Operational parameters that affect the pretreatment efficiency (measured as yield of sugars) were studied and optimized. Changes in structural properties of the biomass were studied in relation to the pretreatment process using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared (FTIR) analysis, and the changes in chemical composition was also monitored. The biomass pretreated with the optimized novel method could yield 0.798?g of reducing sugars per gram of pretreated biomass upon enzymatic hydrolysis. 相似文献
74.
Bablu Mukherjee Binni Varghese Minrui Zheng K.R.G. Karthik Nripan Mathews Subodh G. Mhaisalkar Eng Soon Tok Chorng Haur Sow 《Journal of Crystal Growth》2012,346(1):32-39
We report the syntheses of vertically aligned, beaded zinc germinate (Zn2GeO4)/zinc oxide (ZnO) hybrid nanowire arrays via a catalyst-free approach. Vertically aligned ZnO nanowire is used as a lattice matching reactive template for the growth of Zn2GeO4/ZnO nanowire. The morphology and structure of the as-prepared samples were characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). TEM studies revealed the beaded microstructures of the Zn2GeO4/ZnO nanowire. The thickness and microstructures of crystalline beads could be easily controlled by tuning the growth duration and temperature. The photoluminescence spectrum of the Zn2GeO4/ZnO nanowires is composed of two peaks, i.e., the ultraviolet (UV) peak and the defect peak. For longer treatment duration of the samples, both the UV and defect peak intensities decrease dramatically. One application of the as-prepared Zn2GeO4/ZnO nanowire is to use the nanowire as template for the growth of three-dimensionally (3D) aligned, high-density ZnO nanobranches en route to hierarchical structure. The study of field emission properties of the as-prepared samples revealed the low turn-on voltage and high current density electron emission from the 3D ZnO nanobranches as compared to the ZnO nanowires and Zn2GeO4/ZnO nanowires. Furthermore, the electrical transport behavior of single hybrid nanowire device indicates the formation of back-to-back Schottky barriers (SBs) formation at the contacts and its application in white-light response has been demonstrated. 相似文献
75.
Qin DD Tao CL Friesen SA Wang TH Varghese OK Bao NZ Yang ZY Mallouk TE Grimes CA 《Chemical communications (Cambridge, England)》2012,48(5):729-731
Films of crystalline WO(3) nanosheets oriented perpendicular to tungsten substrates were grown by a surfactant-free hydrothermal method, followed by sintering. The films exhibit photoelectrochemical oxygen evolution at low overpotential. 相似文献
76.
JPC – Journal of Planar Chromatography – Modern TLC - A simple, accurate and precise high-performance thin-layer chromatography (HPTLC) method was developed and validated for the... 相似文献
77.
Shaji Varghese Samuthira Nagarajan Mercy R. Benzigar Ajayan Mano Zeid A. ALOthman George Allen Gnana Raj Ajayan Vinu 《Tetrahedron letters》2012,53(12):1485-1489
A novel bimetallic nanoporous FeAl-KIT-5 catalyst with a cage type porous structure and a high surface area has been prepared for the hydroarylation of styrene and arylacetylenes to afford 1,1-diarylalkanes and 1,1-diarylalkenes, respectively. The catalyst was found to be highly active, and selective, affording a high yield of substituted alkanes and alkenes. The catalyst also showed much higher activity as compared to those of other nanoporous catalysts such as AlSBA-15, AlKIT-5, and FeKIT-5, and can be reused several times without much loss of its activity. 相似文献
78.
In order to examine the applicability of the diffusion-limited Ostwald ripening model to the growth kinetics of nanocrystals, platinum nanocrystals prepared by two different methods have been investigated by a combined use of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). One of the methods of synthesis involved the reduction of chloroplatinic acid by sodium citrate while in the other method reduction was carried out in the presence of polyvinylpyrrolidone (PVP) as a capping agent. The growth of platinum nanocrystals prepared by citrate reduction in the absence of any capping agent follows a Ostwald ripening growth with a D(3) dependence. In the presence of PVP, the growth of platinum nanocrystals does not completely follow the Ostwald ripening model, making it necessary to include a surface reaction term in the growth equation. Thus, the growth of platinum nanocrystals in the presence of PVP has contributions both from diffusion and surface reaction, exhibiting a D(3)+D(2) type behavior. 相似文献
79.
Hema Tresa Varghese C. Yohannan Panicker Daizy Philip Joydeep Chowdhury Manash Ghosh 《Journal of Raman spectroscopy : JRS》2007,38(3):323-331
IR, Raman and surface enhanced Raman scattering (SERS) spectra of 3,5‐dinitrosalicylic acid (DNSA) were recorded and analysed. The vibrational wavenumbers were computed by the ab initio method using RHF/6–21G* basis and they were found to be in good agreement with the experimental values. The effect of the concentration dependence on the SERS intensity of the molecule was studied. The molecular plane assumes a tilted orientation with respect to the silver surface. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
80.
R. V. Krishnakumar M. Subha Nandhini S. Natarajan K. Sivakumar Babu Varghese 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1149-1150
The glycine molecule in the title compound, Na(NO3)·C2H5NO2, exists in the zwitterionic form. The Na atom exhibits eightfold coordination and the polyhedron may be visualized as a distorted hexagonal bipyramid. The glycine molecules are linked through head-to-tail hydrogen bonds and are found `sandwiched' between the Na(NO3) layers. 相似文献