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81.
Density functional theory (DFT) of freezing is used to study the isotropic–nematic, isotropic–smectic A and nematic–smectic A phase transitions in a system of large, semi-flexible conjugated oligomers parameterised within Gay–Berne (GB) potential. The pair correlation functions of the isotropic fluid, used as structural inputs in the DFT, are calculated by solving the Percus–Yevick integral equation theory. Large number of spherical harmonic coefficients of each orientation-dependent functions has been considered to ensure the numerical accuracy at different densities and temperatures for the system of these model GB ellipsoids having large aspect ratio (length-to-breadth ratio). We found that the system of GB ellipsoids parameterised for conjugated oligomers shows stable isotropic, nematic and smectic A phases. At low temperatures, on increasing the density, isotropic fluid makes a direct transition to smectic A phase. Nematic phase get stabilised in between the isotropic and smectic A phases on increasing the temperature. Using the transition parameter obtained through the DFT, we have plotted the temperature–density and pressure–temperature phase diagrams which are found to be qualitatively similar to the one obtained in simulations for the systems with low aspect ratio GB particles. 相似文献
82.
Gupta Abhishek Verma Shikhar Dwivedi Harinath Rawat Ajay Kumar Singh 《平面色谱法杂志一现代薄层色谱法》2016,29(6):423-428
JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography (HPTLC) method for the simultaneous quantitative determination of lupeol and ursolic... 相似文献
83.
K. K. Dwivedi S. Ghosh D. Fink R. Mishra S. P. Tripathy A. Kulshreshtha D. T. Khating 《Radiation measurements》1999,31(1-6):127-132
It has been well established that different ionising radiations modify the track registration properties of dielectric solids. In an effort to study the response of Polyallyl diglycol carbonate (PADC Homalite) detector towards fission fragment, PADC detectors were exposed to 104 Gy dose of 62 MeV protons and then one set of samples were exposed to fission fragments from a 252Cf source. Two of these detectors were containing a thin layer of Buckminsterfullerene (C60). The study of the etched tracks by Leitz Optical Microscope reveals that the track diameters are enhanced by more than 70% in the proton irradiated zone as compared to that in the unirradiated zone. Scanning Electron Microscopy was performed after etching the sample in 6 N NaOH at 55°C for different etching times, to study the details of the surface modifications due to proton irradiation of PADC detectors with and without C60 layer. Our observations revealed that the diameters and density of proton tracks have increased with etching time on the surface facing the fullerene layer as well as the other surface. However, a relatively more open structure of the etched surface containing C60 as compared to the bare one may be an indication of the extra damage caused by the energy released upon the destruction of C60 molecules by energetic protons. 相似文献
84.
Jaya Chakraborty 《应用光谱学评论》2017,52(1):1-38
Microbes are the most fascinating group, with huge diversity devising myriad functional applications in the field of medicine, pharmaceuticals, environmental remediation, and industries. Quantitative and qualitative determination of biomolecules and microbial assisted phenomena by spectroscopy is a pioneer approach. It facilitates the study of atomic and molecular geometries, energy levels, chemical bonds, and interactions between molecules and microbes. It produces fingerprints of the microbial species serving to characterize, differentiate, and identify microorganisms, in both the environment and at single-cell level. Spectroscopy-based bioremediation techniques like Fourier transform infrared spectroscopy, mass spectroscopy, force spectroscopy, Raman spectroscopy, photoemission spectroscopy, and laser-induced breakdown spectroscopy have been very well represented and linked with the microbial applications. This review summarizes the traditional spectroscopic techniques used for the study of microbes and microbial-assisted products as well as illustrates its application in the field of microbial diversity and remediation. This will provide an outlook for the intricate characterization and dimension of microbes to be used for effective application in bioremediation. 相似文献
85.
86.
A. Dwivedi S. A. Siddiqui O. Prasad L. Sinhal N. Misra 《Journal of Applied Spectroscopy》2009,76(5):623-629
The molecular geometry and vibrational frequencies of 5-phenyl-2-(4-pyridyl)pyrimidine in the ground state have been calculated
by the density functional theory with B3LYP/6-311G(d) as the basis set. The observed frequencies of 5-phenyl-2-(4-pyridyl)pyrimidine
and those calculated are nearly the same. The form of the modes for all fundamentals is based on potential energy distribution
calculations. 相似文献
87.
Energy transfer has been studied from Er3+ to Eu3+ ions on excitation with NIR photons (796 and 980 nm) with and without Yb3+ ions. It is found that in one case the presence of Yb3+ enhances the fluorescence yield (980 nm excitation) whereas in the other case it quenches (796 nm excitation). Energy transfer from Er3+ ion's levels 4S3/2 and 2H11/2 is verified by decay curve analysis in both the cases. The nature of interaction between the donor (Er) and the acceptor (Eu) ions is found to be dipole-dipole. The energy transfer parameters viz. transfer probability, critical distance etc. have been calculated. 相似文献
88.
89.
In this note we define the Chern–Simons classes of a flat superconnection, D+L, on a complex Z/2Z-graded vector bundle E on a manifold such that D preserves the grading and L is an odd endomorphism of E. As an application, we obtain a definition of Chern–Simons classes of a (not necessarily flat) morphism between flat vector bundles on a smooth manifold. An application of Reznikov's theorem shows the triviality of these classes when the manifold is a compact Kähler manifold or a smooth complex quasi-projective variety in degrees >1. 相似文献
90.
Z Irani Y K Dwivedi M D Williams 《The Journal of the Operational Research Society》2009,60(10):1322-1334
Broadband offers several benefits to consumers over its preceding technology ‘narrowband’. Despite it offering such benefits, many countries are still experiencing low levels of adoption of broadband technology by consumers. This study presents an extended technology acceptance model (TAM) that integrates perceived resources, self-efficacy and social influence into the TAM in order to investigate factors determining consumer adoption of broadband. The model was empirically tested employing data collected from a survey of broadband consumers in the United Kingdom. A regression analysis was conducted to evaluate the influence of predictive constructs on behavioural intention to adopt broadband and actual adoption behaviour. Findings of the study indicated that all variables significantly affected consumers' behavioural intention to adopt broadband. The outcomes of the paper will be useful for the stakeholders such as internet service providers and governments interested in encouraging the adoption of broadband. The implications of this work to both researchers and practitioners is discussed. 相似文献