Showing papers by "Indian Institute of Science published in 1972"
TL;DR: In this paper, the peristaltic motion of a power law fluid in a tube, with a sinusoidal wave of small amplitude travelling down its wall, was modeled as a power series in terms of the amplitude of the wave.
Abstract: To understand theoretically the flow properties of physiological fluids, we have considered as a model the peristaltic motion of a power law fluid in a tube, with a sinusoidal wave of small amplitude travelling down its wall. The solution for the stream function is obtained as a power series in terms of the amplitude of the wave. The stream function and the velocity components are evaluated by solving numerically two point boundary value problems with a singular point at the origin. The influence of the applied pressure gradient along with non-Newtonian parameters on the streamlines and velocity profiles are discussed in detail.
157 citations
TL;DR: In this article, it is shown that a flow satisfying the conditions required by a self-preservation analysis will exhibit equilibrium only if the relaxation length is small compared with a characteristic streamwise length scale of the flow.
Abstract: In order to study the memory of the larger eddies in turbulent shear flow, experiments have been conducted on plane turbulent wakes undergoing transition from an initial (carefully prepared) equilibrium state to a different final one, as a result of a nearly impulsive pressure gradient. It is shown that under the conditions of the experiments the equations of motion possess self-preserving solutions in the sense of Townsend (1956), but the observed behaviour of the wake is appreciably different when the pressure gradient is not very small, as the flow goes through a slow relaxation process before reaching final equilibrium. Measurements of the Reynolds stresse show that the approach to a new equilibrium state is exponential, with a relaxation length of the order of 103 momentum thicknesses. It is suggested that a flow satisfying the conditions required by a self-preservation analysis will exhibit equilibrium only if the relaxation length is small compared with a characteristic streamwise length scale of the flow.
91 citations
TL;DR: An enzyme responsible for the conversion of p-coumarate into caffeate was purified 97-fold from Streptomyces nigrifaciens and the relationship of the enzyme to other hydroxylases is discussed.
Abstract: 1. An enzyme responsible for the conversion of p-coumarate into caffeate was purified 97-fold from Streptomyces nigrifaciens. The enzyme had a molecular weight of 18000 as determined by Sephadex G-100 gel filtration and was homogeneous on polyacrylamide-gel electrophoresis. 2. The preparation exhibited both p-coumarate hydroxylase and caffeate oxidase activities. 3. Stoicheiometry of the reaction indicated a mono-oxygenase-mediated catalysis consuming 1mol of O(2)/mol of substrate hydroxylated. 4. NADH, NADPH, tetrahydropteroylglutamate or ascorbate act as electron donors for the reaction, ascorbate being inhibitory at higher concentrations. 5. The optimum enzyme activity was at about pH7.7 and 40 degrees C, with an activation energy of 39kJ/mol. 6. Monophenols such as p-hydroxyphenylpropionate, p-hydroxyphenylacetate, l-tyrosine and dl-p-hydroxyphenyl-lactate were also hydroxylated by the preparation, in addition to p-coumarate. 7. The enzyme was a copper protein having 0.38% copper in a bound form. 8. Thiol-group inhibitors did not affect the reaction. 9. The relationship of the enzyme to other hydroxylases is discussed.
43 citations
TL;DR: Clofenapate fed to the rat in the diet increased the content of mitochondrial protein in the liver by 50-60% and resembled the related compound clofibrate, which is widely used as an antihypercholesterolaemic drug.
Abstract: 1. Clofenapate (methyl 2-[4-(p-chlorophenyl)phenoxy]-2-methylpropionate) fed to the rat in the diet increased the content of mitochondrial protein in the liver by 50–60%. In this respect it resembled the related compound clofibrate (ethyl α-p-chlorophenoxyisobutyrate), which is widely used as an antihypercholesterolaemic drug. 2. Both compounds when fed to the rat enhanced the activity of α-glycerol phosphate dehydrogenase in the liver mitochondria manyfold, but were without effect on the enzyme in the soluble fraction. 3. On the other hand, the catalase activity in the supernatant fraction increased twofold after administration of the drugs. The mitochondrial catalase activity showed a consistent decrease. 4. It was unlikely that under the influence of the drug the increase in catalase activity took place in the mitochondrial particles and was leached into the cytosol during isolation. 5. The increase in catalase activity in the cytosol under the influence of the drug is best explained on the assumption that peroxisomes which contain this enzyme, and which are known to increase on administration of the drug, were broken during the process of cellular fractionation and released the enzyme into the cytosol. 6. All the above effects shown by both drugs were fully reversed when drugs were withdrawn from the diet. 7. Clofenapate was effective in bringing about the above changes when administered to the animal at one-hundredth the concentration of clofibrate.
43 citations
39 citations
TL;DR: In this paper, a method is developed by which the input leading to the highest possible response in an interval of time can be determined for a class of non-linear systems, where the input, if deterministic, is constrained to have a known finite energy (or norm) in the interval under consideration.
38 citations
TL;DR: In this article, the normal vibrational analysis of the DMA skeleton as well as the entire molecule was carried out employing the Urey-Bradley and modified UreyBradley force fields.
36 citations
TL;DR: A computer-aided procedure is described for analyzing the reliability of complicated networks, which breaks down a network into small subnetworks whose reliability can be more readily calculated.
Abstract: A computer-aided procedure is described for analyzing the reliability of complicated networks. This procedure breaks down a network into small subnetworks whose reliability can be more readily calculated. The subnetworks which are searched for are those with only two nodes; this allows the original network to be considerably simplified.
36 citations
TL;DR: In studies on the reaction of o-benzoquinone with amino-acids and proteins, a new reaction is observed at the thioether group of methionine that is related to the inactivation of some enzymes.
Abstract: Ortho-quinones such as o-benzoquinone, DOPA quinone, indole-5,6-quinone, adrenoquinone and flavonol quinones are highly reactive and unstable compounds present in biological systems1. Their reactions with proteins are intimately connected with such biochemical processes as formation of melanin2–4, tanning of insect cuticle5, 6 and tanning of plant proteins7–9. The reaction of o-benzoquinone with some of the enzymes results in their inactivation10, 11. The principal functional groups of proteins that have been implicated in these cases are the amino, imino and the sulphydryl groups1. In our studies on the reaction of o-benzoquinone with amino-acids and proteins we have observed a new reaction of o-benzoquinone at the thioether group of methionine.
34 citations
TL;DR: The present studies show that the fungicide hexachlorobenzene, when administered to female rats, can lead to enhanced amounts and rate of synthesis of cytochrome P-450 under conditions when the rate of total haem synthesis has not appreciably altered.
Abstract: Several drugs are known to induce the liver microsomal mixed-function oxidase system when administered in vivo or even in vitro in cell culture. A sequence of events has been suggested in which the drug is visualized to induce delta-aminolaevulinate synthetase, the first and rate-limiting enzyme of the haem-biosynthetic pathway, which is followed by enhanced haem synthesis and cytochrome P-450 content, facilitating the increase in the drug-metabolizing activity of the liver microsomal fraction. The present studies show that the fungicide hexachlorobenzene, when administered to female rats, can lead to enhanced amounts and rate of synthesis of cytochrome P-450 under conditions when the rate of total haem synthesis has not appreciably altered. The subsequent increase in the rate of total haem synthesis as well as the initial increase in amounts of cytochrome P-450 are brought about under conditions when delta-aminolaevulinate synthetase activity remains constant. However, manifestation of porphyria due to prolonged drug administration is accompanied by a twofold increase in delta-aminolaevulinate synthetase activity. The increase in enzyme activity appears to be due to a decreased degradation rate of the enzyme.
33 citations
TL;DR: In this paper, new criteria in the multiplier form are presented for the input-output stability in the L 2 -space of a linear system with a time-varying element k(t) in a feedback loop.
Abstract: New criteria in the multiplier form are presented for the input-output stability in the L 2 -space of a linear system with a time-varying element k(t) in a feedback loop. These are sufficient conditions for the system stability and involve conditions on the shifted imaginary-axis behavior of the multipliers. The criteria permit the use of noncausal multipliers, and it is shown that this necessitates dk/dt to be bounded from above as well as from below. The method of derivation draws on the theory of positivity of compositions of operators and time-varying gains, and the results are shown to be more general than the existing criteria.
TL;DR: In this article, a coordinate transformation in the radial direction has been used to obtain effective solutions by the classical Rayleigh-Ritz method, particularly for large hole sizes, over direct analysis.
01 Jul 1972
TL;DR: A simple procedure based on the transformation properties of the nonlinear susceptibility tensors of different ranks referred to appropriate coordinate systems is given for studying the selection rules and polarization characters in regard to all orders of harmonics as mentioned in this paper.
Abstract: A simple procedure, based on the transformation properties of the nonlinear susceptibility tensors of different ranks referred to appropriate coordinate systems, is given for studying the selection rules and polarization characters in regard to all orders of harmonics. By this procedure, results covering both linearly and circularly polarized incident light for all the 32 crystal classes with some simplifying restrictions are obtained and listed in the paper. Attention is drawn to special features in each case. There is complete agreement with what has been reported earlier by Tang and Herbert Rabin for circularly polarized incident light.
TL;DR: In this article, the activation area and activation enthalpy were determined as a function of stress and temperature for alpha titanium, and the experimental data support a lattice hardening mechanism as controlling the low-temperature deformation in alpha titanium.
TL;DR: Hydroxylation of aromatic compounds was observed in NADH-phenazine methosulfate-O2 model system known to generate superoxide anions, suggesting an involvement of O2− in aromatic hydroxylations.
TL;DR: In this paper, the authors present a historical review of the history of speckle patterns in Optica Acta: International Journal of Optics: Vol. 19, No. 9, pp. 791-793.
Abstract: (1972). Speckle Patterns: A Historical Retrospect. Optica Acta: International Journal of Optics: Vol. 19, No. 9, pp. 791-793.
TL;DR: The activity of delta-aminolaevulinate dehydratase is very low in the mould Neurospora crassa compared with the activities detected in bacterial and animal systems and the properties of the purified enzyme indicate its allosteric nature and susceptibility to feedback inhibition by coproporphyrinogen III.
Abstract: The activity of δ-aminolaevulinate dehydratase is very low in the mould Neurospora crassa compared with the activities detected in bacterial and animal systems. The enzyme is inducible in iron-deficient cultures by addition of iron and is repressed by protoporphyrin. The properties of the purified enzyme indicate its allosteric nature and susceptibility to feedback inhibition by coproporphyrinogen III. Neurospora extracts also contain a protein inhibitor of the enzyme and a small-molecule activator, which appears to be associated with the enzyme. The regulatory function of this enzyme in vivo is correlated with the accumulation of δ-aminolaevulinic acid in normal cultures of N. crassa. The decay curve of the iron-induced enzyme in vivo shows a biphasic pattern, with one of the components showing a half-life of 4–5 min.
TL;DR: In this paper, the natural modes of a non-linear system with two degrees of freedom are investigated, which may contain either hard or soft springs, and the system is shown to possess three modes of vibration one of which does not have any counterpart in the linear theory.
Abstract: The natural modes of a non-linear system with two degrees of freedom are investigated. The system, which may contain either hard or soft springs, is shown to possess three modes of vibration one of which does not have any counterpart in the linear theory. The stability analysis indicates the existence of seven different modal stability patterns depending on the values of two parameters of non-linearity.
TL;DR: Two optimal non- linear reinforcement schemes for the two-state automaton functioning in a stationary random environment are considered and very simple conditions of symmetry of the non-linear function figuring in the reinforcement scheme are shown to be necessary and sufficient for optimality.
TL;DR: In this paper, Fe(Apy)6]-ClO4)2 and Fe(PyO)6]I2 have been characterized and characterized for 1-phenyl-2,3-dimethyl-5-pyrazolone (antipyrine, Apy) and pyridine N-oxide (PyO).
TL;DR: The mechanism of hydroxylation reactions catalyzed by m-hydroxybenzoate-4-hydroxylase and anthranilate hydroxolase from Aspergillus niger was investigated using superoxide dismutase from ovine erythrocytes, indicating the possible involvement of superoxide anions (O2−) in these reactions.
TL;DR: The enzyme laccase has been partially purified from the culture fluid of Ganoderma lucidum by acetone precipitation, ammonium sulphate fractionation and adsorption on alumina Cγ gel and is shown to be specific for ortho and para hydroxyphenolic compounds.
Abstract: The enzyme laccase has been partially purified from the culture fluid of Ganoderma lucidum by acetone precipitation, ammonium sulphate fractionation and adsorption on alumina Cγ gel. The enzyme has been shown to be specific for ortho and para hydroxyphenolic compounds, having Km values of 5.5×10-5 M and 2.86×10-5 M for catechol and hydroquinone respectively. The optimum pH for the oxidation of catechol and hydroquinone are 5.4 and 5.0 respectively. The enzyme is inactivated above 60°C and is inhibited by enzyme inhibitors and metal chelating agents like azide, cyanide etc.
TL;DR: In this paper, a detailed application of a model Reynolds stress equation (Narasimha 1969) to plane turbulent wakes subjected to pressure gradients is considered, which is a transport equation for the stress exhibiting relaxation and diffusion, is found to be consistent with the observed response of a wake to a nearly impulsive pressure gradient.
Abstract: We consider here the detailed application of a model Reynolds stress equation (Narasimha 1969) to plane turbulent wakes subjected to pressure gradients. The model, which is a transport equation for the stress exhibiting relaxation and diffusion, is found to be consistent with the observed response of a wake to a nearly impulsive pressure gradient (Narasimha & Prabhu 1971). It implies in particular that a wake can be in equilibrium only if the longitudinal strain rate is appreciably less than the wake shear.
We then describe a further series of experiments, undertaken to investigate the range of validity of the model. It is found that, with an appropriate convergence correction when necessary, the model provides excellent predictions of wake development under favourable, adverse and mixed pressure gradients. Furthermore, the behaviour of constant-pressure distorted wakes, as reported by Keffer (1965, 1967), is also explained very well by the model when account is taken of the effective flow convergence produced by the distortion. In all these calculations, only a simple version of the model is used, involving two non-dimensional constants both of which have been estimated from a single relaxation experiment.
TL;DR: The effect of longitudinal harmonic oscillations on free convective heat transfer from an elec- trically heated vertical plate is considered in this paper, where experiments have been performed for frequencies ranging from 10 to 20 cps at an amplitude of 0.25 in.
TL;DR: Negative cooperative interactions observed at low concentrations of FAD were abolished by the addition of Pi and the inhibition by AMP was sigmoid and Pi abolished this sigmoidal response.
TL;DR: Decomposition of chitin by Cytophaga johnsonii was investigated and the nature of some of the products formed and the steps involved in their transformations by the resting cells and the cell-free extracts suggested that N-acetylglucosamine first gets deacetylated to glucosamine before it is further oxidized to glucoaminic acid by these strains.
Abstract: Decomposition of chitin by Cytophaga johnsonii was investigated. Unlike other chitinolytic bacteria, some strains of C. johnsonii did not liberate chitinase extracellularly; instead the cells of such strains had need for close contact with the chitin particles in order to hydrolyze them. The cell-free extract of one of these strains, viz., C. johnsonii C35 did show presence of chitinase. The remaining strains liberated an extracellular chitinase and a chitobiase. The partially purified chitinase from the culture filtrates of C. johnsonii C31 was most active at pH 6.3–6.5 and at 40°C. Metabolism of N-acetylglucosamine, a product of chitin hydrolysis, by C. johnsonii C35 and C31 was investigated. The nature of some of the products formed and the steps involved in their transformations by the resting cells and the cell-free extracts suggested that N-acetylglucosamine first gets deacetylated to glucosamine before it is further oxidized to glucosaminic acid by these strains. Both strains were also able to dehydrogenate gluconate to 2-ketogluconate, the former being in all probability the product of deamination of glucosaminic acid.
01 Jan 1972-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the thermal conductivity data of liquid metals have been correlated based on the cell theory of liquids, and the temperature dependence of thermal conductivities is predicted in the case of thirteen metals for which experimental data are available.
Abstract: The thermal conductivity data of liquid metals have been correlated based on the cell theory of liquids. The temperature dependence of thermal conductivity is predicted in the case of thirteen metals for which experimental data are available. The overall average absolute deviation of predicted values is 4.25 pct. The method has been extended to alloys.
TL;DR: The Raman and i.r. spectra of antiferroelectric copper formate tetrahydrate at liquid air temperature (the phase transition is at −38·9°C) did not show any striking changes from the room temperature spectrum except for intensity variations as discussed by the authors.
TL;DR: It is interesting to find that the control steps in the isoprene pathway are located in particulate systems of microsomes or mitochondria, and the enzyme, HMG-CoA reductase is shown to exhibit latent activity on removal of the lipid by acetone or deoxycholate.
Abstract: Publisher Summary It is interesting to find that the control steps in the isoprene pathway are located in particulate systems of microsomes or mitochondria. This is particularly appropriate because of the lipid nature of the products synthesized by the pathway. In fact for the very same reason study of end-product inhibition with isolated enzyme systems is complicated by the uncertain interactions between the lipid reactants and particulate enzymes. On the other hand, location in the lipid-rich membrane offers scope for regulation by modification of membrane structure or by displacement of the products thereof. The enzyme, HMG-CoA reductase is shown to exhibit latent activity on removal of the lipid by acetone or deoxycholate. This property of masking-unmasking of activity by the lipid can be used for fine control. The diverse types of controls operate in cholesterol biogenesis. These have been classified into three types. Of these types I and III signify the two extremes of the same mechanism. The type II alteration is more significant in the reduction of serum cholesterol and merits intensive study in view of its relationship to the problem of atherosclerosis.