Showing papers by "Banaras Hindu University published in 1990"

Defluoridation of water by adsorption on fly ash

Abstract: The ability of fly ash to remove fluoride from water and wastewaters has been studied at different concentrations, times, temperatures and pH of the solution. The rate constants of adsorption, intraparticle transport, mass transfer coefficients and thermodynamic parameters have been calculated at 30, 40, and 50 °C. The empirical model has been tested at various concentration for the present system. The removal of fluoride is favorable at low concentration, high temperature and acidic pH.

Use of wollastonite in the removal of Ni(II) from aqueous solutions

Abstract: The ability of wollastonite to adsorb Ni (II) from water has been carried out. A removal of 92% of Ni (II) with 20 g L−1 of adsorbent was observed at 50 mg L−1 adsorbate concentration, 6.5 pH and 30 °C. The process follows a first order rate kinetics with diffusion controlled nature and the data fits the Langmuir adsorption isotherm. Removal of Ni increases from 10 to 92% with the rise of pH from 3.0 to 8.0 and thereafter it remains almost unchanged. This change has been explained on the basis of aqueous-complex formation and the subsequent acid base dissociation at the solid-solution interface.

Tensile and fracture properties of epoxy resin filled with flyash particles

Abstract: The ultimate tensile strength, modulus of elasticity and fracture properties of epoxy resin filled with flyash particles have been evaluated by the tensile test. The tensile strength of epoxy resin filled with flyash particles decreases the fracture properties and the modulus of elasticity increases with increasing percentage of flyash. It is advisable to use flyash when the void formation cannot be controlled effectively.

Formation Kinetics of Calcium Aluminates

Abstract: The kinetics of formation of calcium aluminates was studied by firing the reaction mixes in the temperature range 12000° to 1460°C for reaction times from 15 to 360 min. Phases formed were determined by taking X-ray diffractograms of the samples. It was observed that all stable calcium aluminates were formed and that monocalcium aluminate (CA) grew with calcium dialuminate (CA2) in a 1:2 reaction mix of CaO and Al2O3. CA reacted further with Al2O3 to form CA2. The formation of CA2 obeyed the rate law equation 1 - (1 - x)1/3=Kt/r2. The activation energy for the system (140 kJ·mol−1 (33.4 kcal · mol−1)) was determined by the Arrhenius equation.

In vitro micropropagation of the tropical fruit tree Syzygium cuminii L.

Abstract: Multiple shoots were obtained from nodal and shoot tip segments of 10 to 15-day-old seedlings of Syzygium cuminii L. on Murashige & Skoog (MS) revised medium supplemented with 6-benzyladenine (BA) (0.23–8.90 μM) singly or in combination with α-naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA) or indole-3-butyric acid (IBA). Excised shoots were placed for root induction on MS medium containing NAA and/or IBA and then transferred to MS basal medium to form complete plantlets. The regenerated plantlets have been acclimatized and successfully transferred into the soil.

Duality for fractional minimax programming problems

Abstract: Duality theory is discussed for fractional minimax programming problems. Two dual problems are proposed for the minimax fractional problem: minimize max y∈Υ f(x, y)/h(x, y) , subject to g(x) ≤ 0. For each dual problem a duality theorm is established. Mainly these are generalisations of the results of Tanimoto [14] for minimax fractional programming problems. It is noteworthy here that these problems are intimately related to a class of nondifferentiable fractional programming problems.

Soret effects on free-convection and mass transfer flow in the stokes problem for a infinite vertical plate

Abstract: An analytical study is performed to examine the free-convection and mass transfer flow for the Sokes problem for an infinite vertical plate on taking into account the Soret effect (thermal diffusion effect). The Laplace transform technique is used to obtain the expressions for velocity and skin-friction. The effect of Soret numberS on velocity field and skin-friction is extensively discussed with the help of graphs and table.

Nitrogen release from decomposing litter of Leucaena leucocephala in the dry tropics

Abstract: Experiments were made on a 2-yr old Leucaena leucocephala stand to measure the litterfall and decomposition rates. Annual litterfall was 10 t ha−1 and was maximal in the dry summer months (≈50% of total litterfall). The seasonal peaks were in June and December (15 and 11% of total litterfall, respectively). Leaves comprised 88% of the total litterfall. Litter decomposition in the field was examined using leaf, twig and fruit fractions of above-ground litter. Roots were also studied for loss of mass and N release below-ground. Loss of mass was in the order fruit > root > twig > leaf. The inital mass loss was high and there was rapid loss in the rainy season (July-September). Annual above-ground litter N content was high (256 kg ha−1) with an annual release of 208 kg ha−1 i.e. 81% of the total litterfall. N release from litter per unit area was leaves (13.2gm−2), fruits (10.5 gm−2), twigs (4.4g m−2) and roots (3.4g m−2). Litter decomposition and N release from the decomposing litter was dependent on the C-N ratio and environmental factors. N turnover time was < 1 yr for all litter fractions.

Effect of radiation and surface recombination on the characteristics of an ion-implanted GaAs MESFET

Abstract: The effects of optical radiation and surface recombination on the characteristics of an ion-implanted GaAs MESFET are studied analytically in the below-pinchoff region. Results show that optical radiation significantly enhances the drain-source current of the GaAs MESFET when only electron-hole pair generation is considered. However, the surface recombination, which in turn results in a gate leakage current, reduces the drain-source current, with the reduction depending on the density of trap centers. The threshold voltage is found to decrease under the normally OFF condition and increase under the normally ON condition due to photogenerated carriers. The surface recombination reverses the effect, i.e. threshold voltage increases under the normally OFF condition and decreases under the normally ON condition, with an increase in the trap center density at a particular ion dose compared to those cases where the effect of recombination is not considered. >

TEM investigation of γ′ free bands in nimonic PE16 under LCF loading at room temperature

Abstract: The cyclic stress strain behavior of nickel base alloy Nimonic PE16 has been studied at room temperature under constant strain rate of 4 × 10 −3 s −1 and at a strain amplitude of 0.57% for different γ′ particle sizes. Fatigue softening is observed for all microstructures. Detailed TEM investigations reveal γ′ free bands in all specimens. Evolution of these bands is studied as a function of cumulative deformation the specimen has bee subjected to γ′ particles within deformation bands are initially sliced by movement of dislocations and on further deformation slices are fragmented by cross slip of dislocations within bands. A conceptual model for reduction in size of γ′ particles during fatigue is proposed on the basis of these results. Reaging studies of deformed samples reveal nucleation of very fine γ′ particles within bands. Comparison of γ′ particle size within these bands with those formed after ageing in specimens deformed in solution treated condition indicates that γ′ particles have completely dissolved in the specimen containing smallest γ′ precipitates. These results are explained on the basis of the concept of particle fragmentation under cyclic loading.

Lateral asymmetry in identification and expression of facial emotions

Abstract: Ninety normal subjects were asked to identify, in a split-plot repeated measures design, photographs displaying facial expression of four negative emotions, sadness, fear, anger, and disgust, presented tachistoscopically. Experimental manipulations involved in visual field (left-right), hemiface composition of expression (normal representation or right-left, left-left, right-right), and task (matching labelling). A left visual field (LVF) superiority was found for identifying the facial emotions; and sad facial emotion was identified with greatest accuracy followed by fear, disgust, and anger. The main effects of facial composite and task remained nonsignificant. However, a taskwise analysis of the data revealed that normal facial representations (RL) were identified with greater accuracy than left-left (LL) or right-right (RR) facial composites in matching task.

Factors regulating copper uptake in a cyanobacterium

Abstract: Copper uptake in the diazotrophic cyanobacteriumNostoc calcicola was found to be typically biphasic, comprising rapid binding of the cations to the cell wall (during the first 10 min) followed by the subsequent metabolism-dependent intracellular uptake for at least 1 h, with a curvilinear kinetics saturating at 40 µM (Km 25.0 µM, Vmax 3.0 nmol Cu mg−1 protein min−1). The cellular Cu uptake was light- and ATP-dependent, and the addition of 3(3,4-dichlorophenyl)-1,1-dimethylurea or exogenous ATP proved that the energy to drive Cu transport was derived mainly through PS II reactions. The application of metabolic inhibitors and uncouplers like carbonylcyanidep-nitrofluoromethoxylphenyl hydrazone, N,N′-dicyclohexycarbodiimide, azide, and p-chloromercuribenzoate revealed that -SH group(s), proton gradient across the cell membrane, and ATP hydrolysis were involved in the transmembrane movement of Cu inN. calcicola. While monothiol (2-mercaptoethanol) caused a twofold reduction in Cu uptake rate, dithiol (dithiothreitol) contributed towards a further drop in the cation uptake rate.

Effect of four heavy metals on the biology of Nostoc muscorum.

Abstract: This study presents the effects of Cr, Pb, Ni and Ag on growth, pigments, protein, DNA, RNA, heterocyst frequency, uptake of NH4+ and N03−, loss of electrolytes (Na+ and K+), nitrate reductase and glutamine synthetase activities ofNostoc muscorum. The statistical tests revealed a direct positive correlation between the metal concentration and inhibition of different processes. Ni was found to be more toxic against growth, pigments and heterocyst differentiation compared to the other metals. Inhibition of pigment showed the following trend: chlorophyll > phycocyanin > carotenoid. No generalized trend for inhibition of macromolecules was observed. The loss of K+ and Na+ as affected by Cr, Ni and Pb was similar but more pronounced for K+ than Na+. The inhibition of physiological variables depicted the following trend: Na+ loss > K+ loss > glutamine synthetase > NH4 uptake > growth > N03− uptake > nitrate reductase > heterocyst frequency. This study therefore suggests that loss of electrolytes can be used as a first signal of metal toxicity in cyanobacteria. However, further study is needed to confirm whether the abnormality induced by nickel (branch formation) is a physiological or genetic phenomenon.

Influence of carbon concentration and reaction temperature upon bainite morphology in Fe-C-2 Pct Mn alloys

Abstract: Isothermal transformation of austenite to bainite was studied by optical, replication, and thin foil transmission electron microscopy (TEM) in both hypo- and hypereutectoid Fe-C-2 wt pct Mn alloys (and a single 3 pct Mn alloy) containing from 0.1 to 1.37 wt pct C in order to characterize and explain the transitions which occur in bainite morphology as a function of carbon content and reaction temperature. A “morphology map” was constructed showing the temperaturecarbon composition(T-x) regions in which four different bainite morphologies predominate: upper bainite, lower bainite, nodular bainite, and inverse bainite. Calculations of the volume free energy changes associated with the nucleation of ferrite, †G v α , and cementite, †G v c , and the parabolic rate constant for growth of ferrite, αα, and cementite, αc, were performed in order to explain the observed morphological transitions. In hypoeutectoid alloys, where |†G v α | ≫ |ΔG v c | and αα ≫ α c , the Widmanstatten ferrite-dominated morphologies of upper and lower bainite predominate. The upper-to-lower bainite transition appears to be associated with the emergence of edge-to-face sympathetic nucleation at high values of |ΔG v α |. In hypereutectoid alloys, the ratios ΔG v α /ΔG v c and αα/αc are considerably smaller; hence, cementite can compete much more readily with ferrite during both nucleation and growth, resulting in the formation of nodular bainite. With decreasing temperature in the hypereutectoid regime,ΔG v α /ΔG v c , and especially αga/αc, increase, resulting in the replacement of nodular bainite by lower bainite at temperatures below about 250 °C to 275°C.

The effect of different temporal relationships of 5‐hydroxytryptophan (5‐HTP) and l‐dihydroxyphenylalanine (L‐DOPA) on reproductive and metabolic responses of migratory red‐headed bunting (Emberiza bruniceps)

Abstract: To study the reproductive and metabolic effects of circadian serotonergic and Dopaminergic activities, 5‐hydroxytryptophan (5‐HTP, serotonin precursor) and L‐dihydroxyphenylalanine (L‐DOPA, dopamine precursor) were administered daily in different temporal relationships in Red‐headed bunting (Emberiza bruniceps) during the preparatory phase of annual gonadal cycle. L‐DOPA given daily after 12 hours of 5‐HTP injection (12‐hr relationship) induced full gonadal development and fat deposition. But, L‐DOPA given after 4 hours of 5‐HTP administration (4‐hr relationship) stimulated only fat deposition without any gonadal effect. On the other hand, these two drugs injected 8‐hour apart led to significant decrease in gonadal growth as well as fat deposition. The findings manifested that 12 hour relationship of these two neural oscillations may induce breeding conditions (summer), 8 hour relationship induced post reproductive regressive/photorefractory condition (late summer) and 4‐hour relationship induced...