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101.
102.
103.
Harsh Kumar Meenu Singla Rajeev Jindal 《Monatshefte für Chemie / Chemical Monthly》2014,145(4):565-575
104.
A. Asthana K. Momeni A. Prasad Y. K. Yap R. S. Yassar 《Applied Physics A: Materials Science & Processing》2011,102(4):909-914
The energetics and dynamics of electromigration of the oxygen vacancy is investigated with first-principles calculations and
kinetic Monte Carlo methods. To simulate the charged oxygen vacancy under external fields within the first-principles approach,
we introduce a slab model with electron-accepting dopants in the surface. The analysis of the density of states confirms that
the oxygen vacancies are positively charged. When the external field is applied, the total energy of the slab linearly changes
with respect to the position of the charged vacancy in the field direction, which allows for probing local permittivity around
the vacancy site. The activation energy of vacancy migration is lowered along the field direction in a manner that the charge
state of the vacancy is maintained along the migration path. Kinetic Monte Carlo simulations based on the first-principles
inputs are also carried out and it is shown that the high-temperature condition is important for the fast redistribution of
charged vacancies. 相似文献
105.
Garg BS Nandan Kumar D Sarbhai M Reddy MJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(12):2775-2783
Dimeric (hydrated and anhydrated) complexes of Cu(II) with N,N'-bis(3-carboxy-1-oxo-2-prop-2-enyl)ethylenediamine(BCOPENH(2), A) and N,N'-bis(2-carboxy-1-oxo-phenylenyl)ethylenediamine(BCOPHENH(2), B) have been prepared and characterised by elemental analysis, magnetic susceptibility measurements, EPR, thermal and spectral (IR, UV/Vis) studies. EPR parameters and magnetic behaviour indicates that the complexes are antiferromagnetic in nature and most likely adopt the typical carboxylate cage structure. Interesting amide bonding patterns have been observed and various EPR parameters have been evaluated on the basis of these studies, tentative probable structures of the complexes have been proposed. 相似文献
106.
Given a sequence of bound-state energies, the inverse Gel'fand-Levitan theory for the one-dimensional Schrödinger equation enables us to uniquely construct a symmetric reflectionless potential which supports those bound states. We test the reliability of this technique by applying it to some known symmetric potentials (confining and non-confining) in one dimension. We also study the systematics under which the method may be reliable. 相似文献
107.
G. S. Deshmukh O. P. Asthana V. S. N. Pillai 《Fresenius' Journal of Analytical Chemistry》1962,185(6):429-434
Summary An amperometric titration procedure for the determination of vanadium as selenite in 0.044 M ammonium acetate and 50–55 per cent alcohol at a pH between 5.3–5.5 has been described. The titration is carried out at –1.10 V versus S.C.E. A V-shaped curve is obtained. The molar ratio of Se:V (11) supports the formation of a normal selenite VOSeO3.
Zusammenfassung Es wird eine Methode zur amperometrischen Titration von Vanadium beschrieben. Das Verfahren beruht auf der Fällung des Vanadiums als Vanadylselenit aus 0,044 m Ammoniumacetatlösung mit 50–55% Alkohol bei pH 5,3–5,5. Es wird ein Potential von –1,10 V (gegen die gesätt. Kalomelelektrode) angewendet. Man erhält eine V-förmige Titrationskurve. Das molare Verhältnis Se:V=11 läßt auf die Bildung eines normalen Selenits (VOSeO3) schließen.相似文献
108.
Archana Asthana Richard A. Larson Karen A. Marley R. W. Tuveson 《Photochemistry and photobiology》1992,56(2):211-222
Citral, a monoterpene aldehyde synthesized by several plant genera, has been reported to exhibit antimicrobial activity. For the first time, we report that critral exhibits UV-A (315-400 nm) light enhanced oxygen-dependent toxicity against a series of Escherichia coli strains differing in DNA repair and catalase proficiency. Those E. coli strains carrying a gene leading to catalase deficiency (katF) are particularly sensitized to inactivation by citral and UV-A treatment when compared to catalase proficient strains (katF+). Consistent with these in vivo observations, citral when treated with UV-A in vitro produces H2O2. When tested against Fusarium oxysporum and F. solani, fungal root pathogens of Citrus, enhanced toxicity by citral in the presence of UV-A was demonstrated, while dark toxicity was negligible. When the plasmid pBR322 was treated with citral in the presence of UV-A, a change in conformation from the covalently closed circular to the open circular and, ultimately, the linear form was observed. The change in plasmid conformation corresponded to a reduction in transforming activity. Holding plasmid DNA which had been treated with UV-A light in the presence of citral at 4 degrees C for 22 h in the dark resulted in continued degradation of the DNA and loss of transforming activity. Holding plasmid DNA treated with UV-A or citral alone under identical conditions had no detectable effect on either plasmid conformation or transforming activity. 相似文献
109.
The oxidation of hexacyanoferrate(II) by periodate ion has been studied spectrophotometrically by registering an increase in absorbance at 420 nm (λmax of yellow colored [Fe(CN)6 3?] complex under pseudo first-order conditions by taking excess of [IO4 ?] over [Fe(CN)6 4?]. The reaction conditions were: pH = 9.5 ± 0.02, I = 0.1 M (NaCl) and Temp. = 25 ± 0.1 °C. The reaction exhibited first-order dependence on each [IO4 ?] and [Fe(CN)6 4?]. The effects of variations of pH, ionic strength and temperature were also studied. The experimental observations revealed that the periodate ion exists in its protonated forms viz. [H2IO6]3? and [H3IO6]2? while [Fe(CN)6]4? is present in its deprotonated form throughout the pH region selected for the present study. It has also been observed that deprotonated form of [Fe(CN)6 4?] and protonated forms of periodate ion are the most reactive species towards oxidation of [Fe(CN)6 4?]. The repetitive spectral scan is provided as an evidence to prove the conversion of [Fe(CN)6 4?] to [Fe(CN)6 3?] in the present reaction. The activation parameters have also been computed using the Eyring’s plot and found to be, ΔH? = 51.53 ± 0.06 kJ mol?1, ΔS? = ?97.12 ± 1.57 J K?1 mol?1 and provided in support of a most plausible mechanistic scheme for the reaction under study. 相似文献
110.
Jung S. Shim Siddhartha Asthana Naoki Omura Joseph P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》1998,36(17):2997-3012
The synthesis and characterization of novel thermoplastic elastomers consisting of multiple polystyrene-b-polyisobutylene (PSt-b-PIB) arms emanating from cyclosiloxane cores is described. The synthesis involved the sequential living cationic block copolymerization of styrene (St) and isobutylene (IB), followed by quantitative allylic end-functionalization of the living PSt-b-PIB+ to produce PSt-b-PIB CH2 CHCH2 prearms, and finally linking by hydrosilation of these prearms with Si H-containing cyclosiloxanes (e.g., 2,4,6,8,10,12-hexamethylcyclohexasiloxane, D). Two types of star-blocks, namely primary and higher-order star-blocks, were prepared: Primary star-blocks containing 3–9 PSt-b-PIB arms were obtained by using various cyclosiloxanes (D to D) and a close to exact stoichiometry between the Si H and allyl groups, [Si H]/[CC] ∼ 1, in the essential absence of moisture ([H2O] ∼ 100 ppm). Higher-order star-blocks consisting of 13–24 PSt-b-PIB arms radiating from complex coupled cyclosiloxanes were prepared by the use of Si H/allyl ratios significantly larger than unity ([Si H]/[CC] = 2–3) in the presence of controlled amounts of moisture ([H2O] ∼ 600 ppm). Reaction conditions (temperature, concentration, stoichiometry, solvent nature, catalyst concentration, etc.) for efficient syntheses have been developed. The products were characterized by 200 and 600 MHz 1H-NMR spectroscopy and triple-detector (RI, UV, LLS) GPC. The microstructure of the condensed cores in the higher-order star-blocks was studied by 2D-NMR (HMQC) spectroscopy, and the number of cyclosiloxane rings in the cores (i.e., the content (wt %) of cores in the star-blocks) was determined. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2997–3012, 1998 相似文献