Showing papers by "North Eastern Hill University published in 1995"

Predictions for the proton lifetime in minimal nonsupersymmetric SO(10) models: An update.

Abstract: We present our best estimates of the uncertainties due to heavy particle threshold corrections on the unification scale ${\mathit{M}}_{\mathit{U}}$, intermediate scale ${\mathit{M}}_{\mathit{I}}$, and coupling constant ${\mathrm{\ensuremath{\alpha}}}_{\mathit{U}}$ in the minimal nonsupersymmetric SO(10) models. Using recent data from the CERN ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ collider LEP on ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathit{W}}$ and ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{strong}}$ to obtain the two-loop-level predictions for ${\mathit{M}}_{\mathit{U}}$ and ${\mathrm{\ensuremath{\alpha}}}_{\mathit{U}}$, we update the predictions for the proton lifetime in minimal nonsupersymmetric SO(10) models.

Induction of ureogenesis in perfused liver of a freshwater teleost, Heteropneustes fossilis, infused with different concentrations of ammonium chloride

Abstract: The induction pattern of urea cycle enzymes and the rate of urea-N excretion were studied with relation to ammonia load in the perfused liver of a freshwater ammoniotelic teleost, Heteropneustes fossilis , when infused with different concentrations of ammonium chloride for 60 min. Both urea-N excretion and uptake of ammonia by the perfused liver were found to be a saturable process. The V max of urea-N excretion (0.45 μmol/g liver/min) was obtained at ammonium chloride addition of 1.18 μmol/g liver/min. The maximum induction of carbamyl phosphate synthetase (ammonia dependent), ∼200%, and of ornithine transcarbamylase, ∼120%, was seen by the addition of 0.58 μmol/g liver/min, and for argininosuccinate synthetase and argininosuccinate lyase of ∼150% and 115%, respectively, by the addition of 2.8 μmol/g liver/min of ammonium chloride. However, arginase activity did not alter in any of the concentrations of ammonium chloride added. An increase of ammonia load of 3–5 μmol/g wet wt from the physiological level in the perfused liver was sufficient to initiate and to cause maximum induction of most of the urea cycle enzymes activitty. These results further confirm the capacity of transition from ammoniotelism to ureotelism in this unique freshwater air-breathing teleost to tolerate a very high ambient ammonia.

Effect of glutathione on sister-chromatid exchanges in normal and buthionine sulfoximine-treated mice

Abstract: Based on their ability to induce sister-chromatid exchanges (SCEs) it is evident that thiol-containing radioprotectors can induce DNA damage. However, there were contradictory findings when reduced glutathione (GSH) was tested using two cell lines. The present study demonstrated that GSH can induce SCEs and also delay in cell proliferation in mouse bone marrow cells in vivo. The presence of catalase significantly reduced GSH-induced SCE frequency down to catalase alone levels. An attempt was made to evaluate the effect of GSH treatment in buthionine sulfoximine (BSO)-treated mice (GSH-depleted mice) and the data indicate that induction of SCEs takes place without inducing a delay in cell proliferation or the generation of hydrogen peroxide. Probably, some unknown route is involved by which GSH-degraded product(s) induce SCEs in BSO-treated mice. Therefore, the induction of SCEs by GSH in normal mice may be largely due to hydrogen peroxide generation; however, the involvement of the binding ability of GSH to chromatin and the probable (unknown) route by which GSH-degraded product(s) may cause smaller fraction of SCEs cannot be ruled out.

Structure of some arylazophenols and arylazonaphthols in the solid state: A resonance Raman study

Abstract: A resonance Raman study of (2-hydroxy-5-metheylphenylazo)benzene and (2-hydroxynaphthylazo)benzene and their derivatives is presented. The characteristic modes in the azo and hydrazone forms are identified. Structures for both types of compounds in the solid state are proposed. It is shown that hydroxy substitution at the ortho position forms a hydrogen bond with the nitrogen atom of the azo group in arylazophenols. The effect of ring substitution on the characteristic modes is also discussed.

Contribution of lethal mutations to excision assays for tumour cell survival

Abstract: Conventional assays of cell survival determine only the proportion of colony-forming cells, assuming that all such cells are equivalent. However, cells surviving irradiation are reported to have lower plating efficiencies than unirradiated controls, suggesting an additional component of cellular damage that is ignored in conventional survival assays, but which could contribute to therapeutic outcome. Therefore we have examined the contribution of this additional form of damage to excision assays for cell survival in experimental tumours following both single dose and fractionated irradiation (10F/5 days) in vivo. Plating efficiencies were considerably lower for the long-term descendents of irradiated compared with non-irradiated cells. Expression of delayed reproductive death was reduced after fractionated radiation doses, only appearing after a substantial number of 3.4 Gy fractions had accumulated. Thus estimates of survival derived from single clonogenicity assays may underestimate the reduction in cell viability from a particular treatment. This could compromise assays for intrinsic radiosensitivity and mathematical modelling of the efficacy of treatment regimens.

2-Mercaptopropionylglycine Affords Enhanced Radioprotection After a Liposome Encapsulation

Abstract: Use of radioprotective drugs in radiotherapy is desirable to protect normal tissues. 2-mercaptopropionylglycine (MPG) has shown promising results in experimental radioprotection. In this report, a liposome drug delivery system for MPG has been used in Swiss albino mice exposed to 1 to 8 Gy whole body Gamma-irradiation to test whether or not this modality enhances the MPG afforded radioprotection. A statistically significant, dose dependent enhancement of protection by liposome encapsulated MPG (LEM) was observed. LEM, as compared to free MPG, improved the viabilities of spleen and bone marrow cells by factors between 1.11 and 2.23 for different doses of radiation.

Structural characterization of some quinolin‐8‐ol‐containing azo dyes in solid and solution state as probed by resonance Raman, fourier transform IR and electronic spectroscopic techniques

Abstract: Some 5-(aryl)azoquinolin-8-ol derivatives were studied by resonance Raman, Fourier transform IR and electronic spectroscopic techniques. Analysis of vibrational and electronic spectra was used to determine the azo and hydrazone forms in both the solid and solution states. In the solid state, the compounds remain dominantly in one form and the characteristic bands due to each resonating form were identified. Various structural motifs for protonated, neutral and deprotonated states were proposed based on pH-dependent studies. The effect of H-bonding in stabilizing a particular type of structure is also discussed.

NEUTRON GENERATION IN MASSIVE Cu-TARGETS DURING THE IRRADIATION WITH 22 AND 44 GeV CARBON IONS

Abstract: An extended Cu-target was irradiated with 22 and 44 GeV carbon ions for about 11.3 and 14.7 hours, respectively. The upper side of the target was in contact with a paraffin-block for the moderation of secondary neutrons. Small holes in the moderator were filled with either lanthanum salts or uranium oxide. The reaction\({}^{139}La(n,\gamma ){}^{140}La\mathop \to \limits^{\beta - } \) was studied via the decay of140La(40h) using radiochemical methods, as has been published. The reaction\({}^{238}U(n,\gamma )^{239} U\mathop \to \limits^{\beta - } {}^{239}Np\mathop \to \limits^{\beta - } \) was studied via the decay of239Np(2.3 d) as well as the reaction U(n,f) using radiochemical methods. In addition, solid state nuclear track detectors were used for fission studies in gold. The yields for the formation of (n,γ) products agree essentially with other experiments on extended targets carried out at the Dubna Synchrophasotron (LHE, JINR). To a first approximation, the breeding rate of (n, γ) products doubles when the carbon energy increases from 22 to 44 GeV. If, however, results at 44 GeV are compared in detail to those at 22 GeV, we observe an excess of (37±9)% in the experimentally observed239Np-breeding rate over theoretical estimations. Experiments using solid state nuclear track detectors give similar results. We present a conception for the interpretation of this fact: There is the evident connection between anomalies we observe in the yield of secondary particles in relativistic heavy ion interactions above a total energy of approximately 30–35 GeV and increased yield of neutrons in this energy region.

Preliminary test estimators in double sampling with two auxiliary variables

Abstract: An attempt has been mads to suggest some estimators for population mean in double sampling with two auxiliary variables., alternative to the usual regression estimator. When the experimenter has partial Information about the mean of the auxiliary variable or variables, preliminary test estimators can be used. The bias, mean square error, relative efficiency and optimum allocation of sample sizes are obtained for the suggested estimators.

Low-mass right-handed gauge bosons, proton decay, and other observable predictions in SU(8)L x SU(8)R and SU(16).

Abstract: The prospects of an alternative method of decoupling the parity and SU(2){sub {ital R}} breaking are reexamined under the constraints of CERN LEP measurements in the minimal chains of SU(8){sub {ital L}}{times}SU(8){sub {ital R}} and SU(16) grand unified theories. Including the uncertainties in the input parameters, one chain permits the SU(2){sub {ital L}}{times}SU(2){sub {ital R}}{times}SU(4){sub {ital C}}-breaking scale {ital M}{sub {ital C}}=10{sup 5.6{plus_minus}0.6} GeV leading to the {Delta}({ital B}{minus}{ital L})={minus}2 nucleon-decay modes possibly accessible to the ongoing experiments and observable branching ratios for rare kaon decays. Uncertainties in the Higgs scalar masses near {ital M}{sub {ital C}} result in wider ranges of predictions on the proton lifetime and mixing times for {ital n}-{ital {bar n}} and {ital H}-{ital {bar H}} oscillations. In a separate chain the SU(2){sub {ital L}}{times}SU(2){sub {ital R}}{times}U(1){sub {ital B}{minus}{ital L}}{times}SU(3){sub {ital C}}-breaking scale corresponding to the masses of right-handed gauge bosons could be {ital M}{sub {ital R}}=10{sup 2.8{plus_minus}0.7} GeV, which seems to be the lowest value predicted so far in a non-SUSY GUT consistent with minimal fine-tuning of parameters.

Upper bound on the mass of lightest higgs boson in the supersymmetric singlet majoran model

Abstract: We calculate an upper bound on the lightest Higgs boson mass in the supersymmetric singlet majoran model containing SU(2)×U(1) singlet right-handed neutrino fields and a chiral singlet having two units of lepton number. We show that although the singlet vacuum expectation values and supersymmetry breaking masses do not decouple from the upper bound, even at the tree level, their effect is small, thereby reducing the bound to the corresponding bound in the minimal supersymmetric standard model. Radiative corrections to the bound are similar to those in the minimal model. We also show that the couplings of the lightest Higgs boson to the majorans are suppressed in this model.

Fundamental constants in singularity-free five-dimensional Kaluza-Klein cosmological model

Abstract: Expressions for the time dependence of the fundamental constants are derived through dimensional reduction and one-loop quantum corrections to scalar fields. Moreover, singularity-free solutions of Einstein's field equations are obtained. Using these solutions, we discuss the time dependence of fundamental constants. It is interesting to see that the fine structure constant asymptotically approaches to 1/137,G eff (effective four-dimensional constant) approachesG N (Newtonian gravitational constant), and λeff vanishes. Graphical representations of these results are also given for a special case.