Showing papers by "North Eastern Hill University published in 1999"

The effects of swift heavy ion irradiation on the radiochemistry and melting characteristics of PET

Abstract: High electronic excitation (∼10 keV/nm) induced effects on the radiochemistry and melting behaviour of semicrystalline polyethylene terephthalate (PET) have been studied by FTIR and differential scanning calorimetry (DSC) techniques. After irradiation with a 180 MeV Ag 14+ ion beam, DSC measurements of PET films exhibited significant change in their melting behaviour. The gradual increase in the melting enthalpy of irradiated PET with the ion fluence is observed for the first time, which reaches a maximum when track overlapping sets in, and decreases exponentially thereafter. FTIR measurements of irradiated PET at different ion fluences have also shown partly different trend of amorphisation than the earlier observations. X-ray diffraction results of irradiated PET reveal both a shift and a reduction of the main peak, along with the appearance of a new small peak. Possible reasons for these findings are discussed.

Measuring the Trilinear Couplings of MSSM Neutral Higgs Bosons at High-Energy e + e Colliders

Abstract: We present a detailed analysis of multiple production of the lightest $\mathrm{CP}$-even Higgs boson $(h)$ of the minimal supersymmetric standard model (MSSM) at high-energy ${e}^{+}{e}^{\ensuremath{-}}$ colliders. We consider the production of the heavier $\mathrm{CP}$-even Higgs boson $(H)$ via Higgs-strahlung ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}ZH,$ in association with the $\mathrm{CP}$-odd Higgs boson $(A)$ in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}AH,$ or via the fusion mechanism ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{ u}}_{e}{\overline{\ensuremath{ u}}}_{e}H,$ with $H$ subsequently decaying through $\stackrel{\ensuremath{\rightarrow}}{H}hh,$ thereby resulting in a pair of lighter Higgs bosons $(h)$ in the final state. These processes can enable one to measure the trilinear Higgs couplings ${\ensuremath{\lambda}}_{\mathrm{Hhh}}$ and ${\ensuremath{\lambda}}_{\mathrm{hhh}},$ which can be used to theoretically reconstruct the Higgs potential. We delineate the regions of the MSSM parameter space in which these trilinear Higgs couplings could be measured at a future ${e}^{+}{e}^{\ensuremath{-}}$ collider. In our calculations, we include in detail the radiative corrections to the Higgs sector of the MSSM, especially the mixing in the squark sector.

Types of carbamyl phosphate synthetases and subcellular localization of urea cycle and related enzymes in air-breathing walking catfish, Clarias batrachus

Abstract: The types of carbamyl phosphate synthetase (CPS), the subcellular localization of urea cycle enzymes and glutamine synthetase (GS) in liver and kidney (potential ureogenic tis- sues) and also the possible involvement of some extra-hepatic tissues for urea synthesis via the urea cycle were studied in an Indian ureogenic amphibious air-breathing walking catfish, Clarias batrachus. Mitochondrial CPS III (glutamine- and N-acetyl-L-glutamate (NAG)-dependent) and cytosolic CPS II (glutamine-dependent) activities were found to be present in liver, analogous to that described for two other teleosts that have CPS III activity. The same activities and subcellu- lar localization were found in kidney. Unexpectedly, a CPS I-like (ammonia- and NAG-dependent) activity was found to be present at levels higher than the CPS III activity in the mitochondrial fraction of both liver and kidney analogous to another Indian amphibious air-breathing teleost fish, Heteropneustes fossilis. The two other urea cycle enzymes, ornithine transcarbamylase (OTC) and arginase (ARG), and GS were found to be localized primarily in the mitochondria, and argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) in the cytosol analogous to H. fossilis and elasmobranchs. Significant levels of urea cycle enzymes along with GS activity could also be detected in muscle, intestine and brain tissues, except ASL in muscle and ASS in brain. Our results also indicated that probably all three different types of CPS activities are also expressed in all three extra-hepatic tissues. The urea cycle-related CPS III found in invertebrates and fish is considered to be the evolutionary precursor of the urea cycle-related CPS I in ureotelic mammalian and amphibian species. Whether or not the CPS I-like activity reported here (1) is due to the presence of a separate CPS I gene in addition to a CPS III gene or (2) represents an adapted CPS III activity in C. batrachus, these results suggest that the presence of both CPS I- like and CPS III activities along with the presence of urea cycle enzymes in extra-hepatic tissues may play an important physiological adaptive role for survival of these walking catfish in higher ambient ammonia or living in air or while burrowing inside mud during habitat drying. J. Exp. Zool. 283:121n130, 1999. © 1999 Wiley-Liss, Inc. Most teleost fishes are ammoniotelic in terms of nitrogen excretion and, until recently, the pres- ence of a functional urea cycle was not known to exist in teleosts (for reviews, see Campbell and Anderson, '91; Wood, '93; Anderson, '95a; Wright,

Modulation of the clastogenic activity of gamma-irradiation in buthionine sulphoximine-mediated glutathione depleted mammalian cells.

Abstract: enzyme c-glutamylcysteine synthetase and increases Purpose: Chromosome aberrations (CA) were used as an end- cellular radiosensitivity. GSH is an important factor point to investigate the eU ect of buthionine sulphoximine (BSO), in the radiosensitization of hypoxic cells and it has a potent glutathione-depleting agent, on the radiosensitivity of been described as a chemical repair agent in mammamammalian cells. The aim was to obtain information about the lian cells (Midander 1982, Clark et al. 1984, Revesz role of glutathione (GSH) in physicochemical and biochemical processes in irradiated cells.

Resonant Electron Tunneling in Single Quantum well Heterostructure junction of Electrodeposited metal Semiconductor nanostructures using Nuclear track filters.

Abstract: We report on resonant electron tunneling through a Cu–Se heterostructure junction grown electrochemically in the submicron size pores (0.8 μm) of a nuclear track filter (Polycarbonate). The prominent feature of negative differential resistance (NDR) has been observed in the current–voltage ( I – V ) characteristic of the so-fabricated array of resonant tunneling diodes (RTDs) even at room temperature, along with a significant peak to valley current ratio (2.5) of the resonance. Tunneling structures of the nanofabricated RTDs around zero bias are also observed at room temperature. Our results show that the low cost and relatively easy electrodeposition method can be a very effective way to prepare resonant quantum tunneling devices, using the pores of nuclear track filters.

New ways of polymeric ion track characterization

Abstract: New ways have been applied for characterization of ion tracks in polymers in the last few years, which are essentially related to depth profile determinations of ions, molecules, or positrons penetrating into these tracks In combination with tomography, the first three-dimensional results have been obtained Extensive diffusion simulations accompanying the measurements have enabled us to obtain a better understanding of the transport processes going on in ion tracks This paper gives an overview about the range of new possibilities accessible by these techniques, and summarizes the presently obtained understanding of ion tracks in polymers

Stimulation of ureogenesis in the perfused liver of an Indian air-breathing catfish, Clarias batrachus, infused with different concentrations of ammonium chloride

Abstract: The pattern of changes of activity of the urea cycle enzymes and the rate of urea-N excretion were studied in the perfused liver of an Indian air-breathing ureogenic walking catfish, Clarias batrachus. The liver was perfused with different concentrations of NH4Cl for a period of 60 min to determine the role of ammonia for stimulation of hepatic ureogenesis and the threshold level of ammonia loading needed to cause such stimulation. Both the urea-N excretion and the ammonia uptake by the perfused liver were found to be a saturable process. Ammonia accumulated significantly in the liver infused with 1.25 μmoles g liver −1 min−1 of NH4Cl, followed by a maximum accumulation of about 28.5 μmoles g wet wt−1 with the infusion of 5.08 μmoles g liver−1 min−1. The Vmax of the urea-N excretion (0.47 μmol g liver−1 min−1) was obtained with the addition of 5.08 μmoles g liver−1 min−1 of NH4Cl. Both the tissue and the specific activity of the urea cycle enzymes, except ornithine transcarbamylase and arginase, were stimulated significantly with the infusion of either 1.25 or 5.08 μmoles g liver−1 min−1 of NH4Cl. Maximum stimulation of tissue activity of carbamoyl phosphate synthetase (about 120%) was seen with the infusion of 5.08 μmol g liver−1 min−1, and for argininosuccinate synthetase (about 135%), and argininosuccinate lyase (about 50%) with the infusion of 10.81 μmol g liver−1 min−1 of NH4Cl. Higher accumulation of ammonia of about 10–15 μmol g wet wt−1 from the physiological level in the perfused liver while infusing with NH4Cl was suggested to be one of the major causes of stimulation of ureogenesis. The presence of such physiological adaptive strategy is probably necessary in this unique group of air-breathing walking catfish to survive under hyper-ammonia stress in their normal habitat or while living outside water or while burrowing inside mud.

Asymmetric parabolic effective barrier model for heavy ion fusion and its relation to coupled channel effects

Abstract: Using the exact transmission coefficient across an asymmetric parabolic barrier derived by Zafar Ahmed and the ideas used earlier in our effective fusion barrier transmission model we develop a new asymmetric parabolic effective fusion barrier model for heavy ion fusion. A closed form expression for fusion cross section (F) depending only on the s-wave characteristics of the fusion barrier is derived. The expected change of shape of the barrier in the interior side due to channel coupling is represented by a variable curvature parameter 2 whereas the outer curvature 1 is kept unchanged. We apply this model to fit the fusion data, namely fusion cross section, spin distribution, average angular momenta and barrier distribution, in the cases of the following representative pairs of nuclei at energies around the Coulomb barrier: 16O+ 144Sm, 16O+ 152Sm, 40Ca+ 46,48,50Ti, 58Ni+ 64Ni and 64Ni+ 92Zr. These examples include cases of symmetric, asymmetric and nearly symmetric fusion. We obtain good fits to the experimental data. The asymmetry parameter = (2/1) 1/2 used in the present macroscopic formulation is correlated to the order of coupling in coupled channel calculations.

Highly regioselective nucleophilic/cycloaddition reactions of N-arylamino 1,3-diazabuta-1,3-dienes with α-nitrosostyrenes: synthesis of functionalised imidazoles and imidazole oxides

Abstract: The α-nitrosostyrenes 2, generated in situ from α-halogeno oximes, underwent regioselective cycloadditon/nucleophilic reactions with N-arylamino 1,3-diazabuta-1,3-dienes 1 leading to a mixture of imidazoles and cyclic nitrones shown to have structures 3 and 4, respectively, by X-ray crystallographic analysis. The structure 4 for cyclic nitrones was also supported by their 1,3-dipolar cycloaddition with dimethyl acetylenedicarboxylate (DMAD). The thermolysis of nitrones 4 gives imidazoles 3 via oxadiazine intermediates 6.

Effect of cisplatin on the lactate dehydrogenase activity and its isozyme pattern in dalton's lymphoma bearing mice

Abstract: Lactate dehydrogenase (LDH) activity and its isozyme patterns were determined in various tissues of normal, Dalton's lymphoma (DL) bearing and cisplatin treated tumorous mice. Tumorbearing hosts showed about two fold higher serum LDH activity than that in the normal animals and following cisplatin treatment (8 mg/kg body wt, i.p.) for 1-4. days, serum LDH activity further increased. In kidney, as compared to normal mice, there was no significant change in the enzyme activity in tumor bearing hosts, but liver LDH activity increased in tumorous condition. After cisplatin treatment overall 20-30% decrease in the activity was noted in kidney and liver, with slight increase on the day 2 of treatment. LDH isozyme analysis revealed that in serum and kidney, all the five isozyme constituents were present, whereas, in liver and ascites tumor supernatant only LDH-3, -4 and-5 were observed with the predominance of LDH-5. In liver, after cisplatin treatment LDH-3 and-4 expression gradually decreased. In DL cells, LDH-5 was the only isozyme form present and after cisplatin treatment its activity increased.Thus, it is suggested that LDH activity is definitely affected in the tissues of tumor bearing hosts and during tumor regression after cisplatin treatment. The changes in LDH activity could be very useful parameter in malignancy and cisplatin-mediated chemotherapy against murine Dalton's lymphoma in particular and cancer in general. LDH isozyme patterns revealed the presence of tissue specificity of different isozymes, with only LDH-5 in tumor cells and appearance of some specific isozyme variant, named here as LDH-T, in the serum of tumor bearing hosts.

The lysine and methionine rich basic subunit of buckwheat grain legumin: some results of a structural study.

Abstract: Summary. The 26 kD basic subunit of 280 kD buckwheat grain legumin has been partially characterized by measurement of its fluorescence and CD spectra. The protein has 22% a-helix, 36% 13-sheet, 12% 13-turn and 30% random coil secondary structure. In comparison with the basic subunits of other legumin-type proteins, the buckwheat legumin subunit has a high content of lysine and methionine. The protein also has higher ratios of lysine to arginine and methionine to arginine.

The Riccion, the Instanton and Primordial Inflation

Abstract: It is shown that R2 and R3 terms dominate over the Einstein–Hilbert term in the gravitational action till the energy mass scale M ≥ 8.4 × 108 GeV. In the presence of these higher derivative terms, the action for Riccions is obtained with quartic self-interaction potential. It is interesting to see that the instanton solution for Riccions gives rise to primordial inflation without any phase transition or symmetry breaking.

Raman anisotropic linewidth dependence on the van der Waals volume of the interacting systems

Abstract: The anisotropic components of the Raman band corresponding to the CO stretching mode of the p-methylacetophenone, benzaldehyde, cyclohexanone, N,N-dimethylacetamide and N,N-dimethylformamide were studied in acetonitrile and benzene solvents. For the first time it has been shown that the van der Waals volume plays a significant role in the line broadening mechanism. The interpretation of the data has been attempted keeping in view van der Waals volume and multipole–multipole interactions. Copyright © 1999 John Wiley & Sons, Ltd.

Dual Nature of Ricci Scalar and Models of the Early Universe

Abstract: In some of the earlier papers, it was noticed that at a high energy level Ricci scalar behaved in dual manner: (a) like a matter field and (b) like a geometrical field. In this letter, dual nature of the Ricci scalar is also obtained from a gravitational action where R2 and R3 terms dominate the Einstein–Hilbert Lagrangian in the gravitational action. Cosmological models are derived using dual role of the Ricci scalar. In an expanding model of the universe, local gravitational effect of a compact object is ignored. These models are interesting in the sense that these have capability of exhibiting gravitational effect of compact objects also in an expanding universe. Moreover, these models provide an inhomogeneous generalization of Robertson–Walker type models. Another important feature of the letter is the derivation of these models through physical theories like phase transition and spontaneous symmetry breaking, not through conventional approach of solving complicated Einstein's field equations.