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31.
S. Radhakrishnan N. Somanathan T. Narasimhaswamy 《Journal of Polymer Science.Polymer Physics》2008,46(14):1463-1477
Liquid crystalline materials display unique properties, which can be exploited in organic light emitting diodes. Polythiophene model compounds containing phenyl groups linked with azomethine, ester, and alkoxy groups [thiophene‐3‐alkyloxy benzoyloxy aniline series (N series) and thiophene‐3‐alkoxy phenoxy amino benzoate series (R Series)] were synthesized. Molecular orbital calculations were performed and the predicted band gaps compared to understand the effects of spacer length and linkage. The experimental photoabsorption characteristics are compared with the theoretically predicted band gap. Photoabsorption and emission studies on N series and R series polymers as the function of polarizer angle suggest that polymers of both series emit polarized light in all base color ranges. The electroemission characteristics of the above‐synthesized polymers were also recorded as the function of polarizer angle. The results show that the compounds also emit polarized electroemission, and the EL polarization ratio decreases with the increase of alkoxy chain length for N and R polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1463–1477, 2008 相似文献
32.
D. Mohan Ganga Radhakrishnan S. Rajadurai K. Venkata Rao Gordon G. Cameron 《Journal of polymer science. Part A, Polymer chemistry》1989,27(6):2123-2133
Polyacrylamide has been grafted onto casein in phosphate buffer medium using potassium peroxodisulfate as initiator. The influence of synthetic variables on percent grafting, grafting efficiency, rates of conversion of monomer, and the rates of graft copolymerization have been discussed. A possible kinetic scheme based on experimental results has been derived. 相似文献
33.
Amit Deshpande Rahul Jain T. Kavitha Satyanarayana V. Lokam Jaikumar Radhakrishnan 《Random Structures and Algorithms》2005,27(3):358-378
An error‐correcting code is said to be locally decodable if a randomized algorithm can recover any single bit of a message by reading only a small number of symbols of a possibly corrupted encoding of the message. Katz and Trevisan 12 showed that any such code C : {0, 1}n → Σm with a decoding algorithm that makes at most q probes must satisfy m = Ω((n/log |Σ|)q/(q?1)). They assumed that the decoding algorithm is non‐adaptive, and left open the question of proving similar bounds for adaptive decoders. We show m = Ω((n/log |Σ|)q/(q?1)) without assuming that the decoder is nonadaptive. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005 相似文献
34.
This paper presents an optical approach to measure the oxygen gradients in biofilms grown on stainless-steel 316L. The sensor is constructed by immobilizing an oxygen-quenchable fluorophore at the tip of an optical fiber. The response time and reversibility of fiber-optic sensor have been analyzed. By mounting the optical fiber using a computerized micromanipulator, the vertical profiles of oxygen are measured with 10 μm depth resolution across biofilms on metal coupons. Steep concentration gradients of oxygen have been observed within the biofilm, both perpendicular and parallel to the metal surface. Optical response of the biofilm grown metal surface is found to be a consistent measure of the oxygen profiles within biofilms. 相似文献
35.
Radhakrishnan Sivakumar Vijayaragavan Reena Nallamuthu Ananthi Muthiya Babu Sambandam Anandan Sivan Velmathi 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(3):1146-1151
Salicylaldimine based schiff base receptors with different substituents showing fluorescent enhancement in the presence of fluoride anion was visualized through naked eye as well as by change in spectral properties (UV–vis and fluorescent techniques). The reason for such fluorescence enhancement may be due to hydrogen bond interaction between receptor recognition site and fluoride anion. Such a hydrogen bond interaction creates a six-membered transition state, which avoids quenching processes. To support this, fluorescence enhancement factor (FEF) was calculated and it was found to be more (FEF = 652) for –NO2 substituted receptor compared to other receptors. 相似文献
36.
Litty Irimpan A. Deepthy Bindu Krishnan V.P.N. Nampoori P. Radhakrishnan 《Applied physics. B, Lasers and optics》2008,90(3-4):547-556
In the present work, we have investigated the nonlinear optical properties of self-assembled films formed from ZnO colloidal
spheres by z-scan technique. The sign of the nonlinear component of refractive index of the material remains the same; however,
a switching from reverse saturable absorption to saturable absorption has been observed as the material changes from colloid
to self-assembled film. These different nonlinear characteristics can be mainly attributed to ZnO defect states and electronic
effects when the colloidal solution is transformed into self-assembled monolayers. We investigated the intensity, wavelength
and size dependence of saturable and reverse saturable absorption of ZnO self-assembled films and colloids. Values of the
imaginary part of third-order susceptibility are calculated for particles of size in the range 20–300 nm at different intensity
levels ranging from 40 to 325 MW/cm2 within the wavelength range of 450–650 nm.
PACS 81.16.Dn; 42.65.-k; 42.65.An; 42.70.-a; 42.70.Nq; 78.20.Ci 相似文献
37.
Ch. G. Chandaluri A. Patra Dr. T. P. Radhakrishnan Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8699-8706
A polyelectrolyte‐assisted reprecipitation method is developed to fabricate nanoparticles of highly soluble molecules. The approach is demonstrated by using a zwitterionic diaminodicyanoquinodimethane molecule bearing remote ammonium functionalities with high solubility in water as well as organic solvents. Nanoparticles are prepared by injecting aqueous solutions of this compound containing an optimum concentration of sodium poly(styrenesulfonate) into methanol. The strong fluorescence exhibited by the compound in the aggregated state is reflected in the enhanced fluorescence of the polyelectrolyte complex in water. The nanoparticles formed in the colloidal state manifest even stronger fluorescence, which leads to an overall enhancement by about 90 times relative to aqueous solutions of the pure compound. The conditions for achieving the emission enhancement are optimized and a model for the molecular‐level interactions and aggregation effects is developed through a range of spectroscopy, microscopy, and calorimetry investigations and control experiments. 相似文献
38.
39.
R. Renuka S. Rajasekaran Ganga Radhakrishnan 《Applied biochemistry and biotechnology》2001,96(1-3):83-92
Among the possible new materials for microelectronics, quinones have a number of significant advantages. Similarly, polymers
with quinone functionality possess biodegradability. Because natural polymers are promising candidates for functional materials
for the future, we have initiated studies on the polymers of natural products. In the present study, a natural quinone (a
plant substance) extracted from Embelier libes distributed in the Kerala state of India was electrochemically polymerized and its properties were investigated. The redox
activity, electrical conductivity, and biodegradability are discussed. 相似文献
40.
Radhakrishnan Srinivasan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1995,46(4):524-545
The problem considered here is the steady, incompressible plane Stokes flow in a rectangular cavity generated by uniform translation of the upper wall. An exact analytical solution of the governing biharmonic equation is derived which not only contains the leading term of the required singularities at the upper corners, but also approximately satisfies the boundary conditions at all four walls. A standard numerical algorithm is employed to correct the small deviations in the boundary conditions satisfied by the analytical solution. This technique enables accurate computation of the solution uniformly throughout the domain; in particular, near the singular corners and in those regions where the flow is extremely weak, for example, in the secondary vortex regions of the deep cavity. The method is illustrated for the square cavity and also for a deep cavity with a depth-to-width ratio of five, and the results are compared with previous analytical and numerical solutions. 相似文献