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91.
Large shifts (~50 cm-1) to lower energies in the C=C and C≡C stretching modes of the Raman spectra of Langmuir-Blodgett deposted thin films of 15-8 polydiacetylene polymer are observed as the film thickness changes from a monolayer or one bilayer to two or more bilayers. The spectra of two or more bilayers are found to be identical to bulk material. These large shifts, observed by surface enhanced Raman scattering from the silver island substrate on which the films are deposited are attributed to delocalization of the electronic states in the backbone of the polydiacetylene polymer. 相似文献
92.
T. Takahashi P. Miller Y. M. Chen L. Samuelson D. Galotti B. K. Mandal J. Kumar S. K. Tripathy 《Journal of Polymer Science.Polymer Physics》1993,31(2):165-173
Langmuir-Blodgett (LB) film formation has been investigated for polymers in which non-linear optical (NLO) moieties are attached to the side chain of a polymethacrylate (PMA) backbone. Polymer monolayers were successfully transferred onto hydrophilic glass substrates using a moving-wall type LB trough. The LB films were characterized by pressure-area isotherms, polarized ultraviolet visible spectra, ellipsometry, and second harmonic generation measurements. The characterization shows that NLO moieties in the side chain are inclined at a shallow angle to the plane of the substrate. The second-order nonlinear optical coefficient and molecular hyperpolarizability were also calculated. © 1993 John Wiley & Sons, Inc. 相似文献
93.
Effect of high gamma irradiation on track properties of PADC (Homalite) has been studied in the dose range of 101–106 Gy. The properties like bulk-etch rates and track-etch rates of the detector are found to increase due to gamma exposure. Etching efficiency of the detector increases due to exposure and it is significant at the dose higher than 103 Gy. Another track property, the critical angle, is also influenced by gamma exposure and is found to decrease with increasing dose. In all cases it is observed that the post-gamma exposure has greater effect than the pre-gamma exposure. The experimental results are presented and discussed in details. 相似文献
94.
A. V. Rama Rao M. K. Gurjar S. V. S. Lalitha Sasmita Tripathy 《Journal of Chemical Sciences》1994,106(6):1415-1421
β-thymidine is a key intermediate in the manufacturing of anti-AIDS agents- AZT and d4 T. A practical and economically viable route to β-thymidine starting from inexpensive D-xylose has been described. This synthetic
route is based on a new rearrangement leading to 2,2′-anhydro-formation with concomitant epimerisation at C-3′, observed for
the first time in nucleoside chemistry.
Dedicated to Prof C N R Rao on the occasion of his 60th birthday
IICT Communication No. 3435 相似文献
95.
A. K. Tripathy 《Mathematica Slovaca》2008,58(5):581-604
Oscillatory and asymptotic behaviour of solutions of a class of fourth order nonlinear neutral difference equations of the
form
and
are studied under the assumption < ∞, for different ranges of p(n). Sufficient conditions are obtained for the existence of positive bounded solutions of (E).
相似文献
96.
Statistically convergent difference double sequence spaces 总被引:1,自引:0,他引:1
In this article we define the notion of statistically convergent difference double sequence spaces. We examine the spaces 2l∞(△, q), 2c(△, q), 2cB(△, q), 2cR(△, q), 2cBR(△,q) etc. being symmetric, solid, monotone, etc. We prove some inclusion results too. 相似文献
97.
Debasish Kundu Manisha Tripathy Pintu Maity Prof. Dr. Brindaban C. Ranu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8727-8732
Cobalt(II)‐catalyzed C(sp2)?O cross‐coupling between aryl/heteroaryl alcohols and vinyl/aryl halides in the presence of CuI has been achieved under ligand‐free conditions. In this reaction, copper plays a significant role in transmetalation rather than being directly involved in the C?O coupling. This unique Co/Cu‐dual catalyst system provides an easy access to a library of aryl–vinyl, heteroaryl–styryl, aryl–aryl, and heteroaryl–heteroaryl ethers in the absence of any ligand or additive. 相似文献
98.
Thin films of polypropylene have been irradiated with different doses of gamma radiation from a 60Co source. IR, UV-VIS spectra of this polymer before and after irradiation have been recorded and from the spectral data some modifications in the properties have been investigated. The spectra indicated that polypropylene film was oxidised at the dose of 106 Gy. Due to the removal of additives, total destruction of the polymer takes place at this dose. Isotactic arrangement of the polymer is no longer present after irradiation. Growth of carbon cluster takes place above a gamma dose of 102 Gy. Thermal stability of the polymer changes due to irradiation and the polymer seems to decompose in four different steps at the highest dose of 106 Gy. 相似文献
99.
S. P. Tripathy R. Mishra K. K. Dwivedi S. Ghosh D. Fink D. T. Khathing 《辐射效应与固体损伤》2013,168(8):583-591
Optical and thermal responses of two cellulose detectors, Cellulose triacetate (Triafol-TN) and Cellulose acetate butyrate (Triafol-BN), to four different doses of 62 MeV protons were studied using spectroscopic, thermal and track-etching techniques. The spectroscopic analysis revealed that though the optical band-gap in the polymers was affected by proton irradiation, the polymers showed high resistance against any major structural modification by radiation. The thermal stability of the polymers was found to be affected by proton irradiation. The activation energy of etching was found to be almost constant for both the polymers even after irradiation. It is hoped that the findings in this work would be of significant relevance to material science and applications of polymers. 相似文献
100.
H. F. Liu A. Huang S. Tripathy S. J. Chua 《Journal of Raman spectroscopy : JRS》2011,42(12):2179-2182
Effects of Ag and Ti nanoparticle coatings on resonant Raman scattering in various ZnO thin films are presented. The longitudinal optical (LO) phonons, irrespective of the ZnO quality, exhibit an enhancement and a weakening by the Ag and Ti nanoparticle coatings, respectively. The enhancement (weakening) is always accompanied by a reduced (an increased) intensity ratio of the second to first‐order LO phonons, which can be associated with changes in the electron‐phonon coupling strength in the probed area of ZnO. Angle‐resolved X‐ray photoelectron spectroscopy provides evidence for the bending of the surface energy bands and their changes induced by the metal coatings. The effect of metal nanoparticle coatings on the Raman scattering of ZnO is thus attributed to the changes in the surface electric field. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献