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181.
Anirban Ganguly M. De Sarkar Anil K. Bhowmick 《Journal of Polymer Science.Polymer Physics》2007,45(1):52-66
Atomic force microscopy was successfully applied for comprehensive nanoscale surface and bulk morphological characterization of thermoplastic elastomeric triblock copolymers: poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) having different block lengths and their clay based nanocomposites. Commercially available Cloisite®20A and octadecyl (C18) ammonium ion modified montmorillonite clay (OC) prepared in our laboratory by cation exchange reaction were used. The phase detected images in the tapping mode atomic force microscopy exhibited a well‐ordered phase separated morphology consisting of bright nanophasic domains corresponding to hard component and darker domains corresponding to softer rubbery ethylene‐co‐butylene (PEB) lamella for all the neat triblock copolymers. This lamellar morphology gave a domain width of 19–23 nm for styrenic nanophase and 12–15 nm for ethylene‐co‐butylene phase of SEBS having end to mid block length ratio of 30:70 and block molecular weights of 8800–41,200–8800. On increasing the ratio of block lengths of the polymer matrix and the selectivity of the solvent toward the blocks used for casting, the morphological features of the resultant films altered along with change in domain thickness. The phase images showed position and distribution of the brightest clay stacks in the dark‐bright contrast of the base matrix of the nanocomposite. Exfoliated and intercalated‐exfoliated morphology obtained in the case of Cloisite®20A and OC‐based SEBS nanocomposites, respectively, is further supported by X‐ ray diffraction and transmission electron microscopy studies. The lamellar thickness of the soft phases widened to 50–75 nm, where the layered clay silicates (40–54 nm in length and 4–17 nm in width) were embedded in the soft rubbery phases in the block copolymeric matrix of the nanocomposite. The marginally thicker width of the hard styrenic phases and slightly shrinked width of the soft rubbery lamella can be observed from the regions where no nanofiller is present. Distinct differences in bulk morphologies of the nanocomposites prepared in the melt and the solution processes were obtained with nanocomposites. The presence of clay particles was evident from the almost zero pull‐off and snap‐in force in the force‐distance analysis of SEBS based nanocomposite. This analysis also revealed stronger tip interaction resulting in highest contact and adhesive forces with the softer PEB region relative to the harder PS region. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 52–66, 2007 相似文献
182.
Summary A computational scheme for determining the dynamic stiffness coefficients of a linear, inclined, translating and viscously/hysteretically damped cable element is outlined. Also taken into account is the coupling between inplane transverse and longitudinal forms of cable vibration. The scheme is based on conversion of the governing set of quasistatic boundary value problems into a larger equivalent set of initial value problems, which are subsequently numerically integrated in a spatial domain using marching algorithms. Numerical results which bring out the nature of the dynamic stiffness coefficients are presented. A specific example of random vibration analysis of a long span cable subjected to earthquake support motions modeled as vector gaussian random processes is also discussed. The approach presented is versatile and capable of handling many complicating effects in cable dynamics in a unified manner.The work reported in this paper has been carried out as a part of a research project on dynamics of extensible cables funded by the Department of Science and Technology, Government of India. The financial support received is gratefully acknowledged. 相似文献
183.
Biswajoy Brahmachari Patrick J. O’Donnell Utpal Sarkar 《Zeitschrift fur Physik C Particles and Fields》1997,74(1):171-178
An extension of the left-right symmetric model has been constructed which gives in a natural way the three lepton decay modes of the proton which have been suggested as an explanation for the atmospheric neutrino anomaly. We write down the potential which after minimization gives the proper choice of the Higgs spectrum. With this Higgs spectrum we then study the evolution of the gauge coupling constants and point out that for consistency one has to include effects of gravity. 相似文献
184.
The problem of nonlinear optimization is encountered while fitting the observed response of certain radiation detectors. In
this paper the development of an optimizing technique based on quasi random search is described. The performance of this technique
is compared with other existing methods of gradient search and linear Taylor differential correction technique in the case
of fitting the photopeak responses of Nal(Tl) detectors. Our results are favourable especially when the observed data are
associated with poor statistics. 相似文献
185.
We have synthesized, by enzymic and chemical means, a variety of novel polyaromatic-enzyme complexes that are extremely stable
and show promise in the conversion of cellulose to glucose. Thus we have prepared a number of homo- and heteropolymeric supports
(involvingl-tyrosine, pyrogallol, resorcinol, phloroglucinol, orcinol, catechol, protocatechuic acid, and various hydroxybenzoic acids)
and discovered that, for example, a resorcinol-Β-d-glucosidase copolymer has high stability combined with lowK
m (10.5 mM vs commercial soluble (3-d-glucosidase 9.3 mM) and high Vmax values (104 Μmol ρNP mg-1H-1 vs 85 Μmol ρNP mg-1H-1). These properties are enhanced when the copolymer is complexed with bentonite clay. The kinetic constants of the resorcinol-Β-d-glucosidase copolymer-bentonite complex wereK
m = 9.6 mM andV
max = 73.5 Μmol ρNP mg-1H-1. Stability has been assessed against proteolysis, organic solvents, elevated temperatures, storage, and incorporation into
fresh soil.
A cellulase preparation fromTrichoderma viride has also been copolymerized with a variety of phenolic macromolecules and displays varying degrees of stability and activity
against carboxymethyl cellulose.
The resorcinol Β-d-glucosidase-copolymer was immobilized on a PM10 ultrafiltration membrane (K
m = 16.8 mM; Vmax = 42.4 (Μmol ρNP mg-1H-1) and showed enhanced thermostability, a broader pH range for maximal activity, and could be reused without loss of activity.
An ultrafiltration cell, containing the membrane-immobilized resorcinol-Β-d-glucosida se copolymer, can be operated as a continuous reactor with substrate flow rates from 0.1 to 0.7 mL min-1 without decrease in product formation. 相似文献
186.
A study of effective implementation of threshold activation technique for neutron spectral analysis in the environment of
an alpha-cyclotron target is presented. The activation data are analysed using LOUHI-82 code. Optimal choices of the regularization
parameters of the code are studied and discussed. Energy distribution of neutrons emitted from thick targets of Be, C and
Ta irradiated by 40–45 MeV alphas is discussed. 相似文献
187.
Some new complexes of tetravalent molybdenum containing acetylacetone have been synthesized by the reaction of acetylacetone with hydrated molybdenum(IV) oxide. Two series of complexes having varied coordination linkages for acetylacetone have been isolated under appropriate conditions. All the compounds were characterized through their elemental analyses, spectral data, magnetic moment and conductance measurement. 相似文献
188.
Somenath Sarkar Arun Kumar I.C. Goyal Enakshi K. Sharma Ramanand Tewari 《Optics Communications》1985,53(2):91-94
We present an analytical method to evaluate the auxiliary function and spot sizes determining microbending loss in single mode fibers with arbitrary refractive index profiles. Comparison with the exact numerical results shows that the present method gives very accurate results for spot sizes. The method is simple and requires relatively less computational effort. 相似文献
189.
Pratul Bandyopadhyay Brahmananda Bhattacharya Harish Sarkar 《International Journal of Theoretical Physics》1983,22(8):677-689
In quantum neutrinodynamics (photon-neutrino weak coupling) all the renormalization constants vanish and therefore the field equations cannot be expressed in terms of unrenormalized field quantities. This helps us to formulate quantum neutrinodynamics as a convergent quantum field theory. It is also pointed out that from the viewpoint of the unified model of weak and electromagnetic interaction as developed on the basis of the photon-neutrino weak coupling by Bandyopadhyay, quantum electrodynamics also manifests itself as a convergent field theory. 相似文献
190.