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21.
N Barik  P Das  A R Panda 《Pramana》1995,44(2):145-152
Magnetic moments of decuplet baryons have been calculated in a relativistic independent quark model with a phenomenological potential in equally mixed scalar-vector harmonic form. Such a model has been successful in describing wide ranging hadronic phenomena in mesonic and baryonic sectors. Using the solutions of the constituent quark orbitals with the model parameters taken from its earlier applications, the magnetic moments of decuplet baryons Δ++ and Ω have been obtained which are in good agreement with the available experimental data. However, the agreement is found to be much better when the magnetic moment ratios such as μδ++/μ p and μΩ-/μΛ are considered. Model predictions for the magnetic moments of other decuplet baryons together with the charge radii have also been calculated which may be verified in future experiments.  相似文献   
22.
N Barik  S Kar  P C Dash 《Pramana》1997,48(5):985-995
We investigate the weak leptonic decays of light and heavy pseudoscalar mesons in a relativistic quark model of independent quarks. We perform a static calculation of the decay constantf M purely on grounds of simplicity. In order to minimize the possible uncertainty in the static calculation, we estimate the ratios of the decay constants which are found to be in good agreement, in the heavy flavor sector, with the predictions of other models available in the literature and existing experimental data. However, there is a noticeable discrepancy in the current prediction for pion decay constant which demonstrates the inherent limitations of the static approximation in the study of non-strange light mesons.  相似文献   
23.
Two new pyrimidine based NNS tridentate Schiff base ligands S-methyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL1] and S-benzyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL2] have been synthesised by the 1:1 condensation of 2-S-methylmercapto-6-methylpyrimidine-4-carbaldehyde and S-methyl/S-benzyl dithiocarbazate. A Ni(II) complex of HL1 and Co(III) and Fe(III) complexes of HL2 have been prepared and characterized by elemental analyses, molar conductivities, magnetic susceptibilities and spectroscopic studies. All the bis-chelate complexes have a distorted octahedral arrangement with an N4S2 chromophore around the central metal ion. Each ligand molecule binds the metal ion using the pyrimidyl and azomethine nitrogen and thiolato sulfur atoms (except in the nickel complex, one ligand molecule uses the thione sulfur in lieu of thiolato sulfur atom). In the Ni(II) complex, one of the ligand molecules behaves as a neutral tridentate and the other molecule functions as a uninegative tridentate, whereas in the Co(III) and Fe(III) complexes, the ligand molecules behave as monoanionic tridentate. All the complexes were analyzed by single crystal X-ray diffraction and significant differences concerning the distortion from an octahedral geometry of the coordination environment were observed.  相似文献   
24.
N Barik  B K Dash  P C Dash 《Pramana》1987,29(6):543-557
Pion mass and its decay constant have been studied in a chiral symmetric potential model of independent quarks. The non-perturbative multi-gluon interaction which is responsible for quark confinement in a hadron is phenomenologically represented here by an effective potentialU(r) = 1/2(1 +γ 0)(ar 2 +V 0). The residual interactions due to quark-pion coupling arising out of the chiral symmetry preservation and that due to quark-gluon coupling arising out of single-gluon exchange are treated as low order perturbations. The centre of mass correction is also taken into account appropriately. This leads to the mass in consistency with that of the PCAC-pion and the pion decay constant in reasonable agreement with experiment.  相似文献   
25.
Biological conversion of low-Btu coal synthesis gas to higher Btu methane was demonstrated using both pure co-cultures and/or adapted-mixed anaerobic bacteria.Peptostreptococcus productus metabolized coal gas to mainly acetate and CO2. The co-cultures containing methanogens converted these products to methane. In mixed culture studies, CH4 and small amounts of acetate were produced. Reactor studies using stirred-tank and immobilized cell reactors exhibited excellent potential to convert CO, CO2 and H2 to methane at higher gas flow rates. Gas retention times ranging from 0.7 to 2 hours and high agitation were required for 90 percent CO conversion in these systems. This paper also illustrates the potential of biological methanation and demonstrates the need for good mass transfer in converting gas phase substrates.  相似文献   
26.
The kinetics of photopolymerization by ultraviolet-light with acriflavine as the sensitizer was studied in nonaqueous medium. The reducing agent used was alcohol. The rates of the photopolymerization were determined dilatometrically. The order of the reaction with respect to the sensitizer concentration was 0.14 while that with respect to the reducing agent concentration was 0.8 × 10?1. These results are interpreted in terms of a kinetic scheme which involves a competitive ground-state deactivation of the dye triplet and photoreduction. A low initiator efficiency of the primary radicals (cage recombination) and bimolecular termination processes are assumed.  相似文献   
27.
A novel solvent free synthetic method has been designed by using rice husk ash (RHA) as solid support for the selective functionalization of ferrocenyl derivatives and described the synthesis of a 1,1′‐unsymmetrically bi‐functionalized ferrocenyl compounds for their biological evaluation. Single crystal X‐ray structural evaluation showed some interesting intra‐molecular hydrogen bonding interactions across the chains of the ferrocenyl molecule, while DFT calculation revealed the significance of the orientation between the two cyclopentadienyl rings for the hydrogen bonding interaction. Redox and antibacterial properties have been studied to understand the electronic and biological effect of different hydrazone system and their potential for future application.  相似文献   
28.
We have applied density functional theory to study the electronic structure changes caused by Nb incorporation in BiVO4 and the application of external pressure. The overall solubility of Nb in BiVO4 is usually high, and the presence of oxygen vacancies affect the dopability of Nb in BiVO4. Through the analyses of the chemical-potential landscape, we have determined the single-phase stability zone of BiVO4 with the Nb doping. The most favorable Nb doping is simultaneous substitutions at both V- and Bi-sites. Even though Nb substitution at only V-site is next favorable, the band gap change is not very significant which agrees with an earlier experiment. However, it does change the electron effective mass by 20 % owing to the presence of Nb 4d bands in the conduction bands, which explains better catalytic activity by Nb-doped BiVO4. In addition, application of external pressure the single-phase stability zone in the chemical-potential landscape. We have also focused on the local structural distortions near the Nb doping site, especially on the BiO8 octahedra. We have shown here that pressure-induced symmetrization of BiO8 dodecahedron lowers the electron's effective mass further and therefore can help to improve the photoconduction property of BiVO4.  相似文献   
29.
1 The single stranded-helicate Vanadium(IV) complex [V2O2Cl4(L)(H2O)2] (1) involving heterocyclic bis-bidentate ligand viz. 3,3/-dipyridine-2-yl-[1.1/]bi[imidazo[1,5-a]pyridineyl] (L) with biological relevance is prepared and characterized by X-ray diffraction analysis. The compound lacks molecular center of symmetry where coordination environments around V(1) and V(2) centres are distorted octahedral (V···V# separation of 5.827 Å). Structure of the compound in the solid state structure shows anion?π interactions, classical and Carene-H---anion non-classical H-bonding interactions. These interactions play significant roles in shaping the extended structure of this molecule.  相似文献   
30.
The European Physical Journal E - We discuss the lateral dynamics of two active force dipoles, which interact with each other via hydrodynamic interactions in a thin fluid layer that is active and...  相似文献   
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