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21.
Hiba Kottayil Shaibuna Machingal Sherly mole Parackal B. Shebitha Alungal M. Letcy V. Theresa Avudaiappan Govindan Sreekumar Krishnapillai 《Journal of heterocyclic chemistry》2020,57(9):3310-3317
A new polyamine was prepared by the ring opening polymerization of epichlorohydrin and properly characterized. The catalytic property of the prepared polymer was assessed by synthesizing 2-aryl-substituted benzimidazole and benzoxazole derivatives by the conjugation of o-phenylenediamine/o-aminophenol with various aromatic aldehydes in the presence of atmospheric oxygen. Significant attributes of the present synthesis include short reaction time, good to excellent yield, high purity, easy reusability, and room temperature reaction. The reaction was carried out in the absence of any metal catalyst and other cooxidants. 相似文献
22.
Meyyappan M. Govindan T.R. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(2):122-129
A continuum model is presented for low-pressure, radio-frequency electronegative discharges commonly encountered in reactive ion etching and plasma-deposition applications. The model is based on the moments of the Boltzmann transport equations. Local and convective acceleration terms are retained in the momentum equations for the electrons and ions as it allows nonlocal transport in weakly collisional regions. A stable numerical scheme to solve these equations is also presented. A chlorine discharge at 13.56 MHz is simulated as a case study. The simulation results reproduce features observed experimentally in Cl2 discharges under similar conditions. Of particular importance is the simulated excitation and ionization waveforms. In the bulk, the waveforms peak twice per cycle, which is essentially due to the modulation of electron temperature; in the sheath regions, the waveforms peak only during the anodic part of the cycle when the electrons are accelerated toward the electrode 相似文献
23.
S. Sukumar Pradeep Kumar Sharma P. Govindan R. V. Subba Rao 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):191-196
Acetohydroxamic acid (AHA) based uranium product purification process to remove plutonium was optimized. For this process, equilibrium data was generated to optimize AHA concentration and acidity of stripping agent/scrubbing agent. Two options namely (i) Pu complexation in aqueous phase followed by extraction and scrubbing ii) extraction followed by scrubbing with AHA were studied. Results of these studies indicate that U product obtained in AHA purification is near to the table top specification and also quantitative Pu recovery from the AHA strip product is possible by oxalate precipitation. 相似文献
24.
N. Vishnu Priya M. Senthilvelan Govindan Rangarajan M. Lakshmanan 《Physics letters. A》2019,383(1):15-26
We construct symmetry preserving and symmetry broken N-bright, dark and antidark soliton solutions of a nonlocal nonlinear Schrödinger equation. To obtain these solutions, we use appropriate eigenfunctions in Darboux transformation (DT) method. We present explicit one and two bright soliton solutions and show that they exhibit stable structures only when we combine the field and parity transformed complex conjugate field. Further, we derive two dark/antidark soliton solution with the help of DT method. Unlike the bright soliton case, dark/antidark soliton solution exhibits stable structure for the field and the parity transformed conjugate field separately. In the dark/antidark soliton solution case we observe a contrasting behaviour between the envelope of the field and parity transformed complex conjugate envelope of the field. For a particular parametric choice, we get dark (antidark) soliton for the field while the parity transformed complex conjugate field exhibits antidark (dark) soliton. Due to this surprising result, both the field and PT transformed complex conjugate field exhibit sixteen different combinations of collision scenario. We classify the parametric regions of dark and antidark solitons in both the field and parity transformed complex conjugate field by carrying out relevant asymptotic analysis. Further we present 2N-dark/antidark soliton solution formula and demonstrate that this solution may have combinations of collisions. 相似文献
25.
Benzopyran fused tetra and pentacyclic frameworks have been synthesized by the domino Knoevenagel hetero Diels–Alder (DKHDA) reaction using various 1,3-diones with O-allylated salicylaldehydes and O-propargylated salicylaldehydes in a solvent and catalyst free condition via Solid-State Melt Reaction (SSMR). The reaction requires only a single step operation thus providing potentially bioactive polycyclic heterocycles in high yields. 相似文献
26.
R. Venkata Krishnan Hrudananda Jena K. V. Govindan Kutty K. Nagarajan 《Journal of Thermal Analysis and Calorimetry》2010,101(1):371-377
Rare earth uranates Nd6UO12, Gd6UO12 and Eu6UO12 were prepared by combustion synthesis and characterized by XRD. Single-phase rhombohedral structure was observed for all
the above compounds. Heat capacity measurements were carried out on Nd6UO12 and Gd6UO12 with differential scanning calorimetry in the temperature range 298–800 K. Enthalpy, entropy and Gibbs energy functions were
computed. Heat capacity values of Nd6UO12 and Gd6UO12 at 298 K are 436 and 400 J K−1 mol−1, respectively. Thermal expansion characteristics were studied using high temperature X-ray diffraction (HTXRD) in the temperature
range 298–873 K. The coefficients of thermal expansion measured for Eu6UO12 are 10.5 × 10−6 and 7.3 × 10−6 K−1 along a- and c-axis, respectively. Similarly, the coefficients of thermal expansion of Gd6UO12 along a-axis are 10.0 × 10−6 K−1 and along c-axis is 9.7 × 10−6 K−1. 相似文献
27.
28.
Krishna?Kishore?Kottapalli Kalyan?Kumar?Adari Parvataneni?VaniEmail author Sudarsan?Kochu?Govindan 《Transition Metal Chemistry》2005,30(7):773-777
The kinetics of oxidation of L-Cysteine in aqueous HClO4 medium were studied using a one-equivalent oxidant, hexachloroiridate(IV). The reaction exhibits second-order dependence
with respect to hexachloroiridate(IV) and first-order in cysteine. The rate decreases with increase in hydrogen ion concentration
indicating that the zwitterionic form of cysteine is more reactive. Cysteic acid is identified as the product of oxidation.
A suitable mechanism involving the formation of [IrCl6]2− – sulphur bonded intermediate is proposed. The activation parameters of the reaction are computed using the linear least
squares method and the values of Ea and ΔS# are found to be 27.97±1.82 kJ mol−1 and −51.30±6.0 J K−1mol−1, respectively. 相似文献
29.
Ruslan M. Minyaev Wolfgang Quapp Govindan Subramanian Paul von R. Schleyer Yirong Mo 《Journal of computational chemistry》1997,18(14):1792-1803
The paths of correlated internal disrotation (barrier less than 0.4 kcal/mol) and conrotation (barrier around 1.9 kcal/mol) of the two BH2 groups in H2BCH2BH2 have been computed employing ab initio [MP2(full)/6–31G**] and density functional theory (Becke3LYP/6–311+G**) methods. Two B(SINGLE BOND)C(DOTTED BOND)B(p) hyperconjugative interactions stabilize the Cs symmetric H2BCH2BH2 isomer ( 1 ). The B(SINGLE BOND)C(DOTTED BOND)B(p) hyperconjugative stabilization, evaluated by homodesmotic reactions and using the orbital deletion procedure (which “deactivates” the “vacant” born p orbital), is less than 6 kcal/mol in diborylmethane. The B(SINGLE BOND)C(DOTTED BOND)B(p) stabilization is shown to be remarkably large in C4B6H10 (Td). At MP2(fu)/6–31G**, disproportionation into 1 and methane is only 5.6 kcal/mol exothermic. The 1,3 H exchange in diborylmethane is an asynchronous process and proceeds via a doubly bridged cyclic intermediate with 9.3 kcal/mol barrier. Structures with “planar tetracoordinate” carbon are stabilized considerably by BH2 substituents, but they are still high in energy. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1792–1803, 1997 相似文献
30.