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41.
Molecular structure, and phase behaviour of 2-Cyano-N-[4-(4-n-pentyloxybenzoyloxy)-benzylidene] aniline (CPBBA) has been reported with respect to translational and orientational motions. The atomic net charge and dipole moment components at each atomic centre have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger perturbation theory along with multicentered–multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a ‘6-exp’ potential function has been assumed for short-range interactions. The interaction energy values obtained through these computations have been used as input to calculate the configurational probability at room temperature (300 K), and nematic–isotropic transition temperature (396.5 K). On the basis of stacking, in-plane, and terminal interaction energy calculations, all possible geometrical arrangements between the molecular pairs have been considered. Molecular arrangements inside a bulk of materials have been discussed in terms of their relative order. Further, translational rigidity parameter has been estimated as a function of temperature to understand the phase behaviour of the compound. The present model is helpful to understand the effect of molecular motions on ordering, and phase behaviour of the mesogenic compounds. 相似文献
42.
Umaprasana Ojha Pallavi Kulkarni David Cozzens Rudolf Faust 《Journal of polymer science. Part A, Polymer chemistry》2010,48(17):3767-3774
The hydrolytic degradation of a series of poly‐L ‐lactide (PLLA)‐polyisobutylene (PIB) multiblock copolymers was studied in phosphate buffer solution (pH = 7.4) at 37 °C. The multiblock copolymers were synthesized by chain extension of PLLA‐b‐PIB‐b‐PLLA triblock copolymers, which were obtained by ring‐opening polymerization of L ‐lactide initiated by hydroxyallyl telechelic PIB. The degradation strongly depended on the PLLA segment length. At constant PIB segment length, the multiblock copolymer with the shortest PLLA segment length (DPn = 10), showed significant weight loss after 8 weeks, whereas weight loss for DPn = 36 was only observed after 24 weeks. The gel‐permeation chromatographic analysis showed a similar decrease in the number‐average molecular weight (Mn) with time further supporting the weight loss data. Dynamic mechanical analysis showed a decrease in ultimate stress and modulus with time. The crystallinity of multiblock copolymers changed significantly with degradation time as indicated from differential scanning calorimetric analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3767–3774, 2010 相似文献
43.
Lakshmi Praveen P. Ajeetha N. Ojha Durga P. 《Russian Journal of General Chemistry》2009,79(10):2267-2271
Russian Journal of General Chemistry - A computational analysis of ordering in N-(4-n-alkoxy benzylidene)-4′-alkyl aniline ( n O m ) with n = 7, m = 6 carbon atoms in alkyl chain has been... 相似文献
44.
Mithlesh Pawan K. Pareek Ravi Kant Sanjeev K. Shukla Krishan G. Ojha 《Central European Journal of Chemistry》2010,8(1):163-173
A series of N-(6-methylbenzothiazolyl)-2,3,5,6-tetrasubstituted-4-(aryl)-1,4-dihydropyridines were synthesized by reaction
of 2-amino-6-methylbenzothiazole, aromatic aldehyde and active methylene compound in methanol by conventional, as well as,
microwave irradiation (solvent free and solid support) methods. The microwave irradiation technique gives better yield and
shorter reaction time. Among solid supported microwave irradiation better yields are obtained in acidic alumina as compared
to silica, neutral alumina, and basic alumina. All compounds were tested for antibacterial and antifungal activities and results
have been compared with standard drugs. Entomological activities were also tested. The results showed that a change in the
substitution pattern in 1,4-dihydropyridine derivatives may cause a marked effect on their antimicrobial activity. 相似文献
45.
M.I. Adamovich E.S. Basova M.M. Chernyavsky A. Dirner K.G. Gulamov B. Jakobsson L. Just S.P. Kharlamov S.A. Krasnov A. Kravčáková V.G. Larionova S.Z. Nasyrov V.S. Navotny I.D. Ojha G.I. Orlova N.G. Peresadko N.V. Petrov V.V. Rusakova N.A. Salmanova B.K. Singh V. Singh K. Söderström M. TóthovᆠM.I. Tretyakova T.P. Trofimova U.I. Tuleeva S.K. Tuli B.P. Tursunov S. Vokál J. Vrláková B.S. Yuldashev 《The European Physical Journal A - Hadrons and Nuclei》1999,6(4):427-430
Using emulsion detector the collective flow signals in inelastic interactions of 84Kr nuclei with Ag(Br) at 950 MeV/nucleon are studied. A transverse momentum analysis is performed to determine the reaction
plane. The bounce-off of spectator fragments is observed. In azimuthal distributions relative to the reaction plane squeeze-out
and side-splash of participants are seen.
Received: 27 September 1999 相似文献
46.
Laser photochromic velocimetry was successfully used to determine details of a steady two-dimensional flow field. In the
plane of symmetry of a 90° curved tube at a Reynolds number of 250, the axial and radial velocity fields were measured using
laser photochromic velocimetry combined with a technique involving interpolation of the photochromic data. The wall shear
stress, vorticity, and pressure field were also estimated. The experimental results were compared with those from numerical
simulation. The agreement was remarkably good lending validity to the interpolation method used for this flow field.
Received: 29 May 1997 / Accepted: 13 November 1997 相似文献
47.
D. P. Ojha 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(3):361-365
A computational analysis of ordering in p-ethoxybenzylidene-p-n-butylaniline (2O.4) has been carried out based on quantum mechanics and intermolecular forces. The evaluation of atomic charges and dipole moments at each atomic center has been carried out using the CNDO/2 method. The configuration energy has been computed using the modified Rayleigh-Schrödinger perturbation method at an interval of 1 Å in translation and 10° in rotations. The various possible geometrical arrangements of molecular pairs during the different modes of interactions have been considered, and the most favorable configuration of pairing has been obtained. A comparative picture of the molecular parameters, such as the total energy, binding energy, and total dipole moment of 2O.4 with other nematogen 4-4′-di-n-propoxy-azoxybenzene (DPAB) and 5-(trans-4-ethylcyclohexyl)-2-(4-cyanophenyl)-pyrimidine (ECCPP), has been given. The results are discussed in the light of experimental and other theoretical observations. 相似文献
48.
V. K. Rastogi M. A. Palafox Surabhi Singhal S. P. Ojha W. Kiefer 《International journal of quantum chemistry》2007,107(5):1099-1114
The geometry, vibrational wavenumbers, and thermodynamical parameters have been calculated using density functional methods (DFT) for benzonitrile (BN) and the six difluorobenzonitriles (DFBNs) of the series. The results were compared with the available experimental data, and correlations were established for the ? C?N and C? F moieties between the natural atomic charges and the geometrical parameters of the compounds. These relations were found as linear or slightly parabolic in most cases. Investigations were carried out to examine the effect of substituents on structural deformations and other properties. Correlations were also determined with the stretching vibrations. Other general conclusions have also been drawn. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
49.
The surface enhanced Raman spectra of tyrosine in colloidal Ag solution have been recorded over a range of pH. A line shape analysis of the bands at 1359, 1505 and 1577 cm−1 was performed between pH 3.5 and 8.5. The variation of spectral linewidth (FWHM) of the band at 1359 cm−1 with pH is explained in terms of two mechanisms in solution: (i) the fluctuation of the pH of a microscopic volume in a solution with an overall uniform pH and/or (ii) the role of changing viscosity and solvation at different pH values due to the intermolecular ionic interactions between different charged states of the tyrosine molecule. The blue shift in three bands with increasing pH has been explained in terms of charge transfer between the different charged states of tyrosine and metal ions upon chemisorption. The experimental spectra are compared with ab initio/DFT calculations of vibrational wavenumbers, bond geometries, binding energy and charge distributions obtained by means of Hartree–Fock (HF) analysis, the nonlocal density functional method (BLYP) and the hybrid functional method (B3LYP). Two basis sets, CEP-31G and lanl2DZ, were used for all calculations. 相似文献
50.
A quantum mechanical analysis has been carried out to determine the association energy of five homologous of 4‐Cyano‐4'‐Alkylbiphenyls series with alkyl group: propyl (3CB) ; butyl (4CB) ; pentyl (5CB) ; hexyl (6CB) ; hepty (7CB) using Rayleigh‐Schrodinger perturbation method for different nearest neighbour configurations of interacting pairs. The net atomic charges and dipoles have been computed using the CNDO/2 method. The complete association energy with all its components has been reported. An attempt has been made to explain the odd‐even effects at the molecular level on the basis of these results. 相似文献