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251.
The effects of ultrasonication on the chemical polymerization of aniline leading to the formation of conducting polyaniline colloids were examined. The formation rate of the colloids was significantly increased under ultrasonication. Furthermore, it was also observed that the morphological structure of the colloids thus prepared was greatly affected by the sonication. The polyaniline colloids were further characterized by a range of techniques including electric resistance meter, gel permeation chromatography, FT-IR and cyclic voltammetry. It is noteworthy that the application of ultrasound to the polymerization resulted in a marked increase in the doping level, which reflected to the high electroconductivity of polyaniline colloids. 相似文献
252.
The use of hexamethylphosphoramide (HMPA) in the osmium-thiocyanate system makes the method more sensitive and selective. The blue colour formed by osmium(VIII) with thiocyanate in 1.5M hydrochloric acid is intensified in the presence of HMPA and the complex becomes readily extractable into chloroform. The colour system has its absorption maximum at 595 nm and obeys Beer's law over the range 0.5-16 mug of Os per ml. The optimum range is 2-10 mug/ml. The molar absorptivity is 2.09 x 10(4)l.mole(-1).cm(-1). The method is simple, sensitive and free from interference from many metal ions, including ruthenium and other platinum metals. 相似文献
253.
K. L. Chowdhury 《Journal of Elasticity》1983,13(1):87-90
Similarity transformations are constructed and used to obtain an exact solution for the axisymmetric boundary value problem of a homogeneous isotropic elastic semi-space subjected to a concentrated torque normal to its surface. 相似文献
254.
A dynamical model of normal immune response has been formulated in terms of cellular automata by Kaufmanet al. We generalize this model incorporating the antigens as a dynamical variable. This generalized model not only describes the kinetics of primary and secondary responses of humoral immunity, together with the appropriate memory cells, but also describes the vaccinated state as well as the states of low-dose and high-dose paralysis. Recently models of autoimmune response have also been developed in terms of discrete automata. But the models are underdetermined by the experimental facts, i.e., several models can account for the same set of observed biological facts. With an aim to find out how large this underdeterminacy is and how it can be reduced systematically, we have carried out an exhaustive computer-aided search of all those discrete three-cell and five-cell models of autoimmune response which at present cannot be ruled out by the existing biological informations. Out of the 325 possible five-cell models, only one fulfilled our criteria. We also carried out simulations of the dynamics of some of these models on a discrete lattice. We discuss the relevance of random interactions in the context of autoimmune disease. 相似文献
255.
On the gate-controlled surface capacitance of MOS structures of Si having n-channel inversion layers
D. R. Choudhury A. K. Chowdhury A. N. Chakravarti 《Czechoslovak Journal of Physics》1980,30(10):1157-1160
An attempt is made to work out a simple theory of gate-controlled MOS capacitance based on the triangular potential-well approximation. The predicted dependence of the capacitance on gate voltage is in excellent qualitative agreement with the recent experimental observation reported elsewhere.On leave of absence fromthe Dept. of Physics, University of Patna, Patna, India. 相似文献
256.
Using an elimination technique, the non-linear compatibility equations for the theory of elastic dielectrics including polarization gradient effects are established. The corresponding Bianchi-type identities are constructed and used to establish the number of independent compatibility conditions consistent with the number of unknown field variables for a stress-like boundary value problem. 相似文献
257.
The polarised optical spectra of single crystal of K3Mn(CN)6 is reported at liquid nitrogen temperature. A new system of transition is located along with its hot components which is verified by temperature variation studies. The crystal field parameters to reproduce the bands are given. 相似文献
258.
Generation of fluorescent adducts of malondialdehyde and amino acids: toward an understanding of lipofuscin 总被引:2,自引:0,他引:2
Chowdhury PK Halder M Choudhury PK Kraus GA Desai MJ Armstrong DW Casey TA Rasmussen MA Petrich JW 《Photochemistry and photobiology》2004,79(1):21-25
Lipofuscin is a yellow-brown, highly fluorescent pigment that undergoes an age-related progressive accumulation in animal cells, mainly in postmitotic cells. It is a heterogeneous, high-molecular weight material associated with proteins, lipids and nucleic acids. Lipofuscin is implicated in many aspects of human health, including aging, oxidative stress, macular degeneration, lipid peroxidation, atherosclerosis, dementia (Alzheimer's Disease) and diseases associated with prions. Although the fluorescent properties of lipofuscin have long been recognized, neither histologists nor chemists have yet isolated the pigments themselves or characterized their optical properties. We have prepared lipofuscinlike species by reacting malondialdehyde (MDA) with cysteine (Cys). MDA:Cys adducts 3:2 and 2:2 are two of those that have been identified among the many that were present in the reaction. Whereas previous attempts to synthesize lipofuscinlike species resulted in compounds that were either nonfluorescent or emitted principally in the blue, the MDA:Cys adducts reported in this study are not only fluorescent but also emit over a broader range. 相似文献
259.
A. Z. M. Shaifullah Chowdhury Yasuyuki Shibata 《Journal of heterocyclic chemistry》2001,38(3):743-747
A variety of tri‐ and tetracyclic hetero systems were obtained by reaction of heteroaromatic ortho‐aminoesters or ortho‐aminonitriles with iminothioether, yielding double‐annelation of a thiazolo[3,2‐a]‐pyrimidine, pyrimido[2,l‐b]thiazine, imidazo[1,2‐a]pyrimidine, and pyrimido[1,2‐a]pyrimidine moieties in a one‐pot process. 相似文献
260.
Summary The silica-supported comb-shaped polymer (Sil-ODA18) with a “crystalline-to-isotropic” phase transition showed the characteristic behaviors of both polymeric and monomeric ODS
phases. This was examined using a SRM 869 test mixture. Furthermore, Sil-ODA18 exhibited a specific selectivity towards the critical pairs of polycyclic aromatic hydrocarbons (PAHs), such as acenaphthene
and fluorene, or benz(a)anthracene and chrysene, or benzo(ghi)perylene, indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene.
The separation of these solutes was controlled by selecting temperature and solvent systems. The selectivity on Sil-ODA18 was also compared with a conventional ODS (octadecylsilyl silica gel) column. The selectivity on a Sil-ODA18 matrix is attributable to an orientation change of the long-chain alkyl substituents on the surface of the silica base material
on transition from crystalline to isotropic state. 相似文献