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141.
Netaji K. Desai Prasad G. Mahajan Dhanaji P. Bhopate Dattatray K. Dalavi Avinash A. Kamble Anil H. Gore Tukaram D. Dongale Govind B. Kolekar Shivajirao R. Patil 《Journal of fluorescence》2018,28(1):51-63
A simple solid state reaction technique was employed for the preparation of polycrystalline luminophors of p-terphenyl containing different amounts of perylene followed by spectral characterization techniques viz. XRD, SEM, TGA-DSC, UV–Visible spectroscopy, thermo-electrical conductivity, fluorescence spectroscopy, fluorescence life time spectroscopy and temperature dependent fluorescence. X-ray diffraction profiles of the doped p-terphenyl reveal well-defined and sharp peaks indicate homogeneity and crystallinity. The SEM micrograph of pure p-terphenyl exhibit flakes like grains and then compact and finally gets separately with perylene amounts. The observed results indicate that closed packed crystal structures of doped p-terphenyl during crystal formation. The band gaps estimated from UV–visible spectroscopy decreased from 5.20 to 4.10 eV, while thermo-electrical conductivity increases with perylene content. The fluorescence spectra showed partial quenching of p-terphenyl fluorescence and simultaneously sensitization of perylene fluorescence at the excitation wavelength of p-terphenyl (290 nm) due to excitation energy transfer from p-terphenyl to perylene. The observed sensitization results are in harmony with intense blue color seen in fluorescence microscopy images and has high demand in scintillation process. 相似文献
142.
Physical ageing of amorphous polymers well below their glass transition temperature leads to changes in almost all physical properties. Of particular interest is the increase in yield stress and post-yield strain softening that accompanies ageing of these materials. Moreover, at larger strain polymers seem to rejuvenate, i.e. aged and non-aged samples have identical stress-strain responses. Also, plastically deforming an aged sample seems to rejuvenate the polymer. In this work we use molecular dynamic simulations with a detailed force field suitable for macromolecular ensembles to simulate and understand the effects of ageing on the mechanical response of these materials. We show that within the timescales of these simulations it is possible to simulate both ageing and rejuvenation. The short range potentials play an important role in ageing and rejuvenation. A typical yield drop exhibited by glassy polymers is a manifestation of a sudden relaxation in the short range structure of an aged polymer. Moreover, the aged polymers are known to be brittle. We show that this is intimately related to its typical stress-strain response which allows it to carry arbitrarily large mean stresses ahead of a notch. 相似文献
143.
The quantum theory of a harmonic oscillator with a time dependent frequency arises in several important physical problems,
especially in the study of quantum field theory in an external background. While the mathematics of this system is straightforward,
several conceptual issues arise in such a study. We present a general formalism to address some of the conceptual issues like
the emergence of classicality, definition of particle content, back reaction etc. In particular, we parameterize the wave
function in terms of a complex number (which we call excitation parameter) and express all physically relevant quantities
in terms it. Many of the notions—like those of particle number density, effective Lagrangian etc., which are usually defined
using asymptotic in–out states—are generalized as time-dependent concepts and we show that these generalized definitions lead
to useful and reasonable results. Having developed the general formalism we apply it to several examples. Exact analytic expressions
are found for a particular toy model and approximate analytic solutions are obtained in the extreme cases of adiabatic and
highly non-adiabatic evolution. We then work out the exact results numerically for a variety of models and compare them with
the analytic results and approximations. The formalism is useful in addressing the question of emergence of classicality of
the quantum state, its relation to particle production and to clarify several conceptual issues related to this. In Paper
II which is a sequel to this, the formalism will be applied to analyze the corresponding issues in the context of quantum
field theory in background cosmological models and electric fields. 相似文献
144.
Sachini Rodrigo Disni Gunasekera Jyoti P. Mahajan Long Luo 《Current Opinion in Electrochemistry》2021
Electrochemical organic synthesis has recently attracted much attention because of its unique reactivity and environmentally benign approach. Conventional electrosynthesis uses either constant current or constant potential, known as direct current electrolysis. However, recently, alternating current electrolysis has begun receiving more attention. The purpose of this study is to give a short overview of the history and recent advances in the field of alternating current electrolysis for organic synthesis. 相似文献
145.
146.
147.
The compactification of 10-dimensional supergravity, coupled to super Yang-Mills theory, to curved 4-dimensional spacetimes
is investigated. The requirement of unbroken supersymmetry leads to a set of consistency conditions. These are fairly restrictive,
but nevertheless permit some nontrivial solutions, including the Milne universe. More general time-dependent metrics are also
not ruled out. 相似文献
148.
Srubabati Goswami Raghavan Rangarajan K. Agashe A. Bandyopadhyay K. Bhattacharya B. Brahmachari C. Burgess E. J. Chun D. Choudhury P. K. Das A. Dighe R. Godbole S. Goswami N. Gupta M. Kaplinghat D. Indumathi J. Forshaw Y. Y. Keum B. Layek D. Majumdar N. Mahajan P. Mehta R. N. Mohapatra N. Mondai S. More Y. Nir S. Pakvasa M. K. Parida M. Ravikumar G. Rajasekaran P. Ramadevi R. Rangarajan S. D. Rindani D. P. Roy P. Roy N. Sahu A. Samanta Y. Shadmi A. M. Srivastava S. Uma Sankar R. Vaidya U. Yajnik 《Pramana》2004,63(6):1391-1405
This is the report of neutrino and astroparticle physics working group at WHEPP-8. We present the discussions carried out
during the workshop on selected topics in the above fields and also indicate progress made subsequently. The neutrino physics
subgroup studied the possibilities of constraining neutrino masses, mixing and CPT violation in lepton sector from future
experiments. Neutrino mass models in the context of Abelian horizontal symmetries, warped extra dimensions and in the presence
of triplet Higgs were studied. Effect of threshold corrections on radiative magnification of mixing angles was investigated.
The astroparticle physics subgroup focused on how various particle physics inputs affect the CMBR fluctuation spectrum, and
on brane cosmology. This report also contains an introduction on how to use the publicly available code CMBFAST to calculate
the CMBR fluctuations. 相似文献
149.
V. N. Bhoraskar S. Y. Mahajan S. S. Jayanthakumar V. D. Gogate 《Journal of Radioanalytical and Nuclear Chemistry》1985,95(2):73-79
Ancient iron objects excavated from five different sites around Nagpur city in Maharashtra State /India/ were cut into small pieces and samples were prepared. Each sample was irradiated with 14 MeV neutrons for 8 min. From the recorded gamma ray spectrum for each sample, the presence of trace elements Cu, Si, Al, Mg and Mn were detected and their mutual ratios of activities were determined. The results show that all the iron objects obtained from five different sites are of the same origin. 相似文献
150.