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51.
Wayne W.-Y. Yang C. G. Overberger C. M. Venkatachalam 《Journal of polymer science. Part A, Polymer chemistry》1983,21(6):1751-1761
Two possible conformations for poly(cis-5-ethyl-D -proline) have been identified and characterized by using combinations of 1H- and 13C-NMR, CD, and ORD spectroscopic techniques. Both forms have helical conformations similar to those of poly(L -proline) characterized by different amide bonds (cis and trans). However, the carbonyl group of the amide in poly(cis-5-ethyl-D -proline) form II (trans) seems to be closer to perpendicular orientation with respect to the helical axis than in poly(L -proline) form II. The pyrrolidine ring conformation of form I (cis) is probably β+γ?-puckered, whereas for form II it is probably β+-puckered in nature. The side-chain ethyl groups prefer to adopt anti conformations to the C5? H bond, or prefer to have χ = 180°, regardless which of the two forms poly(cis-5-ethyl-D -proline) may like to assume. The experimental results agree well with our previous theoretical conformational energy calculations. 相似文献
52.
Bhuvaneswari N. Priyadharsini N. Sivakumar S. Venkatachalam K. Siva V. 《Journal of Thermal Analysis and Calorimetry》2019,136(1):411-417
Journal of Thermal Analysis and Calorimetry - Single crystals of tetramethylammonium cadmium chloride were grown by slow evaporation technique. The single-crystal X-ray diffraction revealed that... 相似文献
53.
Jianfeng Wang Venkatachalam M. Yuguang Fang 《Selected Areas in Communications, IEEE Journal on》2007,25(4):712-721
Video broadcast and mobile TV have received significant interests from both academia and industry recently. The emerging mobile WiMAX (802.16e) is capable of providing high data rate and flexible quality of service (QoS) mechanisms, making the support of mobile TV very attractive. However, how to efficiently deliver video broadcast over WiMAX is not straightforward, especially in the multi-BS mode. The multi-BS mode requires multiple BSs to be synchronized in the transmission of common multicast/broadcast data. In this paper, we first identify the key design issues for video broadcast over WiMAX in the multi-BS mode. Then, we present an end-to-end solution which fully addresses key issues such as synchronization, energy efficiency and robust video quality. Moreover, we propose a methodology to optimize the coverage, the spectrum efficiency and the video quality. Results show that our proposed scheme can significantly improve the coverage and spectrum efficiency while satisfying video quality requirements. 相似文献
54.
T. Priyamvada Devi C. Kalidas C.S. Venkatachalam 《Journal of Electroanalytical Chemistry》1980,113(2):285-291
Electrochemical reduction of 4-thienylquinazoline (4-TQ) at the dropping mercury electrode in dimethylformamide solutions containing 0.1 M tetrabutyl ammonium iodide supporting electrolyte gave two well-defined diffusion-controlled waves. The first wave was found to be quasi-reversible and the second irreversible, on the basis of the usual criteria. The controlled potential electrolysis experiments carried out at the limiting regions of the frist and the total waves of 4-TQ yielded the same number of electrons, namely two, in both cases. Mechanisms corresponding to the total wave and the first wave were proposed based on the results obtained. 相似文献
55.
Avi Shalav Dinesh K. Venkatachalam Robert G. Elliman 《Applied Physics A: Materials Science & Processing》2012,107(3):749-754
Silica nanowires, grown via the active oxidation of a silicon substrate, have been coated with TiO2 using two coating methods: solution-based deposition of Ti-alkoxides and atomic layer deposition. Analysis of as-deposited and annealed films shows that it is possible to produce stable conformal coatings of either the anatase or rutile phases of TiO2 on nanowires with diameters greater than 100 nm when annealed between 500–600°C and 800–900°C, respectively, with annealing at higher temperatures (1050°C) producing coatings with a highly facetted rutile morphology. The efficacy of the process is shown to depend on nanowire diameter, with nanowires having diameters less than about 100 nm fusing together during solution-based coating and decomposing during TiO2 atomic layer deposition. The use of a suitable buffer layer is shown to be an effective means of minimizing nanowire decomposition. Finally, annealing coated nanowires under active oxidation conditions (1100°C) is shown to be an effective technique for depositing additional conformal SiO x coatings, thereby providing a means of fabricating multi-layered coaxial nanostructures. 相似文献
56.
Harekrushna Behera Venkatachalam Ramkumar Dr. Nandita Madhavan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10179-10184
Protein pores that selectively transport ions across membranes are among nature’s most efficient machines. The selectivity of these pores can be exploited for ion sensing and water purification. Since it is difficult to reconstitute membrane proteins in their active form for practical applications it is desirable to develop robust synthetic compounds that selectively transport ions across cell membranes. One can envision tuning the selectivity of pores by incorporating functional groups inside the pore. Readily accessible octapeptides containing (aminomethyl)benzoic acid and alanine are reported here that preferentially transport cations over halides across the lipid bilayer. Ion transport is hypothesized through pores formed by stable assemblies of the peptides. The aromatic ring(s) appear to be proximal to the pore and could be potentially utilized for functionalizing the pore interior. 相似文献
57.
Contribution of exogenous polyamines (PAs) and polyamine-inhibitors on plantlet regeneration patterns of banana (cv. Nanjanagudu Rasabale-AAB) was studied and the performance of regenerated shoots in temporary immersion system was evaluated. The rhizome explants (without shoot bud) of in vitro shoots produced a mixture of embryogenic and nonembryogenic calli on modified MS medium. The analyses of endogenous pools of polyamines showed higher levels of PAs in embryogenic than in nonembryogenic calli. Supplementation of various levels of (10-50 microM) spermine (Spm), spermidine (Spd), and putrescine (Put) to cultures with secondary embryogenesis showed that about 50% of embryogenic calli rapidly produced secondary embryos only in the presence 40 microM Spm but not in other treatments. The crucial role of Spm was further confirmed by the use of 0.1 mM each of alpha-DL-Difluromethylornithine and alpha-DL-Difluromethylarginine along with Spm where the presence of inhibitors concomitantly inhibited the secondary embryogenesis. The shoots obtained from the embryogenic cultures were checked for their performance on solid medium (SM) and partial immersion system (PIS). The rate of shoot multiplication was higher in PIS than in SM throughout 6 weeks culture period. Uniformity in elongation of all the shoot buds was observed in PIS but not in SM. Evaluation for the acclimatization, survival under greenhouse conditions revealed the better performance of PIS-derived plants than those from SM. 相似文献
58.
Perumal Venkatachalam Narayanasamypillai Jayabalam 《Applied biochemistry and biotechnology》1997,61(3):351-364
Callus cultures were established from immature leaf expiants ofArachis hypogaea on MS medium supplemented with 2.0 mg/L of NAA and 0.5 mg/L of BAP of the susceptible cultivars namely VRI-2 and TMV-7. Three-week-old
calli were subjected to mutagenic treatments (gamma rays: 50–250 Gy and EMS: 5–25 mM). Mutagen-treated calli were subcultured
to fresh medium containing various concentrations (25–100% v/v) of pathotoxic culture filtrates. Calli were challenged in
vitro with pathotoxic culture filtrate of the fungal pathogen and were assessed by visible growth ratings expressed as the
percent response to the doses/concentrations of mutagen. Selected mutagen-treated calli showed resistance in vitro on media
containingCercosporidium personatum pathotoxic culture filtrate. Resistance calli were then transferred to MS regeneration medium supplemented with BAP (2.0
mg/L) and NAA (0.5 mg/L) for shoot bud regeneration. The progeny of the plants produced 13 disease-resistant plants (R2) in both the cultivars. Among the eight R2 populations studied, 70.2–82.5% of the plants exhibited enhanced resistance. This study suggested that groundnut plants with
resistance to C.personatum can be selected 相似文献
59.
Perumal Venkatachalam Narayanasamipillai Jayabalan 《Applied biochemistry and biotechnology》1997,67(3):237-247
Tissue cultures were established from cotyledon and cotyledonarynode segments ofArachis hypogaea L. on Murashige and Skoog (MS) medium supplemented with different concentrations of auxins (IAA, NAA, IBA, and 2, 4-D) and
cytokinins (KIN and BAP). For callus initiation, high concentration of auxins and low concentration of cytokinins were used,
whereas high concentration of cytokinins and low concentration of auxins were used for shoot-bud differentiation. Callus induction
and shoot-bud regeneration frequency, however, varied with genotype, expiant, and the different plant-growth regulators combination
in the medium. The shoot-bud multiplication was also influenced by genotype, explant type, and growth regulators. The combination
of BAP and NAA produced more shoots than other combinations. The maximum number of shoots was obtained from cotyledonary-node
segments on a medium containing BAP (5.0 mg/L) and IBA (1.0 mg/L). Rooting of regenerated shoots was achieved on a medium
augmented with NAA or IBA (2.0 mg/L) in combination with KIN (0.5 mg/L). Rooted plantlets were successfully established in
the soil, where 95% of them survived.
Tissue-culture studies of these expiants suggests the shoots to be ofde nova origin, which would make the system suitable for gene-transfer technology. 相似文献
60.