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61.
Using hydrodynamical model of the two-electron-temperatere plasma, the analytical investigation of parametric instability of electron-acoustic wave has been made. It is found that the growth rate decreases with increasing concentration ratio of the hot to the total electrons nh0/n0. The growth rate is found to be more for 相似文献
62.
R. S. Misra C. Dwivedi S. S. Parmar S. P. Singh 《Journal of heterocyclic chemistry》1978,15(4):681-682
Six 1-(N-acetylpiperidino)-4-aryl semicarbazides were synthesized from ethyl-N-piperidino-aeetatc which on treatment with hydrazine hydrate was converted into N-piperidinoacethydrazide. The resulting hydrazide on treatment with the appropriate arylisoeyanales formed l -(N-acelyl-piperidino)-4-aryl semicarbazides. Amongst these piperidinosemicarbazides, three compound possessed low anticonvulsanl activity and provided 20-40% protection against pentylenetetrazol-induced convulsions in mice. All piperidino semicarbazides (0.1 mM) possessed antihemolytic activity (13-35%) and caused 40-72% inhibition of monoamine oxidase activity of rat brain homogenates at a final concentration of 0.3 mM. 相似文献
63.
Sandeep K. Dwivedi 《Tetrahedron letters》2007,48(31):5375-5377
An efficient synthesis of amino ethers and amino thioethers has been achieved via the ring cleavage of N-tosylazetidines with alcohols or thiols. The reactions were studied in the presence of various Lewis acids and BF3·OEt2 was found to be the most efficient. The products were obtained in modest to good yields under very mild conditions in 5-15 min. 相似文献
64.
The Lorenz model has been widely used for exploring many real world problems. In this paper we obtain, with the help of an invariant manifold technique, the return map for the maximum value of the variable x of the model and use this return map to derive the simple, empirically obtained, regime transition rules for forecasting regime changes and length in the new regime for the model. The probability distribution for number of cycles between successive regime transitions of the Lorenz model may be of interest in many disciplines. We apply the Perron-Frobenius algorithm over the return map to estimate the probability distribution for the number of cycles between successive regime transitions. These probabilities are also estimated for the forced Lorenz model, which is a conceptual model to explore the effects of sea surface temperature on seasonal rainfall. 相似文献
65.
Brijesh Pandey Veda P. Pandey A. K. Shasany U. N. Dwivedi 《Applied biochemistry and biotechnology》2014,172(7):3414-3423
A cinnamyl alcohol dehydrogenase (CAD) from the secondary xylem of Leucaena leucocephala has been purified to homogeneity through successive steps of ammonium sulfate fractionation, DEAE cellulose, Sephadex G-75, and Blue Sepharose CL-6B affinity column chromatographies. CAD was purified to 514.2 folds with overall recovery of 13 % and specific activity of 812. 5 nkat/mg. Native and subunit molecular masses of the purified enzyme were found to be ~76 and ~38 kDa, respectively, suggesting it to be a homodimer. The enzyme exhibited highest catalytic efficiency (Kcat/Km 3.75 μM?1 s?1) with cinnamyl aldehyde among all the substrates investigated. The pH and temperature optima of the purified CAD were pH 8.8 and 40 °C, respectively. The enzyme activity was enhanced in the presence of 2.0 mM Mg2+, while Zn2+ at the same concentration exerted an inhibitory effect. The inclusion of 2.0 mM EDTA in the assay system activated the enzyme. The enzyme was inhibited with caffeic acid and ferulic acid in a concentration-dependent manner, while no inhibition was observed with salicylic acid. Peptide mass analysis of the purified CAD by MALDI-TOF showed a significant homology to alcohol dehydrogenases of MDR superfamily. 相似文献
66.
Free radical copolymerization of an acyclic monoterpenoid linalool (LIN) and methyl methacrylate (MMA) in dioxan was carried out in dilatometer under an inert atmosphere of nitrogen for 90 min at 60 ± 1°C by using diphenyl selenonium 2,3,4,5‐tetraphenylcyclopentadienylide (selenonium ylide) as an initiator. The kinetic expression of the reaction is Rp ∝ [ylide]0.5[MMA]1.0[LIN]1.0. The activation energy of copolymerization was estimated to be 43.7 kJ mol?1. The formation of a functional copolymer is evidenced by spectral analysis. The copolymer was characterized by FTIR, 1H NMR, 13C NMR, DSC, and TGA analysis. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 43–52, 2011 相似文献
67.
P. C. Srivastava Rama Dwivedi A. Srivastava Surendra Kumar Manoj Shrivastva 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):149-151
Labile pool (E-value) of Mn and extractable soil Mn content using six multinutrient extractants were estimated in fifty surface (0–15 cm) soil samples. Labile pool of Mn was poorly correlated to the general soil properties and modified Olsen’s-; 0.01 M CaCl2- and 1 M MgCl2-extractable Mn contents but it was positively and significantly correlated to diethylene triamine pentaacetic acid (DTPA), pH 7.3; ammonium bicarbonate + DTPA (pH 7.6); and Mehlich-3-extractable soil Mn contents. The multinutrient extractants involving only simple salt solutions were not useful to assess the availability of Mn in soils. 相似文献
68.
69.
Ambient UVA‐Induced Expression of p53 and Apoptosis in Human Skin Melanoma A375 Cell Line by Quinine
Neera Yadav Ashish Dwivedi Syed Faiz Mujtaba Hari Narayan Kushwaha Shio Kumar Singh Ratan Singh Ray 《Photochemistry and photobiology》2013,89(3):655-664
This study aimed to analyze the phototoxic mechanism and photostability of quinine in human skin cell line A375 under ambient intensities of UVA (320–400 nm). Photosensitized quinine produced a photoproduct 6‐methoxy‐quinoline‐4‐ylmethyl‐oxonium identified through LC‐MS/MS. Generation of 1O2, O2??, and ?OH was measured and further substantiated through their respective quenchers. Photosensitized Quinine (Q) caused degradation of 2‐deoxyguanosine, the most sensitive nucleotide to UV radiation. The intracellular ROS was increased in a concentration‐dependent manner. Significant reduction in metabolic status measured in terms of cell viability (54%) at 25 μg mL?1 was observed through MTT assay. Results of MTT assay accord NRU assay. Single strand DNA breaks and apoptosis were increased significantly (P < 0.01) as observed through comet assay and EB/AO double staining. Photosensitized quinine caused cells to arrest in G2 phase of cell cycle and induced apoptosis (5.08%) as revealed through FACS. Real‐Time PCR showed upregulation of p21 (4.56 folds) and p53 (2.811 folds) genes expression. Thus, our study suggests that generation of reactive oxygen species by quinine under ambient intensity of UVA may result into deleterious phototoxic effects among human population. 相似文献
70.
S. A. Siddiqui A. Dwivedi P. K. Singh T. Hasan S. Jain O. Prasad N. Misra 《Journal of Structural Chemistry》2009,50(3):411-420
This work is devoted to theoretical study on molecular structure of protopine. The equilibrium geometry, harmonic vibrational frequencies and infrared intensities were calculated by ab initio Hartree-Fock and density functional B3LYP methods with the 6-31G(d) basis set and were interpreted in terms of potential energy distribution (PED) analysis. The internal coordinates were optimized repeatedly for many times to maximize the PED contributions. A detailed interpretation of the infrared spectra of protopine is reported. The calculations are in agreement with experiment. The thermodynamic functions of the title compound were also performed at HF/6-31G(d) and B3LYP/6-31G(d) level of theory. The FT-IR spectra of protopine were recorded in solid phase. 相似文献