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Showing papers by "Indian Institute of Science published in 1973"


Journal ArticleDOI
TL;DR: In this article, a sufficiently accurate analysis for statics and dynamics of composite laminates is presented, where the displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and rotary inertia are included.

343 citations


Journal ArticleDOI
TL;DR: In this article, the mean flow development in an initially turbulent boundary layer subjected to a large favourable pressure gradient beginning at a point x0 is examined through analyses expected a priori to be valid on either side of relaminarization.
Abstract: The mean flow development in an initially turbulent boundary layer subjected to a large favourable pressure gradient beginning at a point x0 is examined through analyses expected a priori to be valid on either side of relaminarization. The ‘quasi-laminar’ flow in the later stages of reversion, where the Reynolds stresses have by definition no significant effect on the mean flow, is described by an asymptotic theory constructed for large values of a pressure-gradient parameter Λ, scaled on a characteristic Reynolds stress gradient. The limiting flow consists of an inner laminar boundary layer and a matching inviscid (but rotational) outer layer. There is consequently no entrainment to lowest order in Λ−1, and the boundary layer thins down to conserve outer vorticity. In fact, the predictions of the theory for the common measures of boundary-layer thickness are in excellent agreement with experimental results, almost all the way from x0. On the other hand the development of wall parameters like the skin friction suggests the presence of a short bubble-shaped reverse-transitional region on the wall, where neither turbulent nor quasi-laminar calculations are valid. The random velocity fluctuations inherited from the original turbulence decay with distance, in the inner layer, according to inverse-power laws characteristic of quasi-steady perturbations on a laminar flow. In the outer layer, there is evidence that the dominant physical mechanism is a rapid distortion of the turbulence, with viscous and inertia forces playing a secondary role. All the observations available suggest that final retransition to turbulence quickly follows the onset of instability in the inner layer.It is concluded that reversion in highly accelerated flows is essentially due to domination of pressure forces over the slowly responding Reynolds stresses in an originally turbulent flow, accompanied by the generation of a new laminar boundary layer stabilized by the favourable pressure gradient.

205 citations


Journal ArticleDOI
TL;DR: It is proposed that, in addition to stabilizing the collagen triple-helical structure due to the stereochemical properties of the pyrrolidine ring, hydroxyproline gives added stability by the formation of an extra hydrogen bond.

182 citations


Journal ArticleDOI
TL;DR: A systematic trend is observable in the experimental data, slightly deviating from theory, which indicates that some deformations occur in the shapes of the peptide units forming the bend, differing from that of the standard planar peptide unit.

129 citations


Journal ArticleDOI
TL;DR: In this article, an examination of all the available data available on incompressible (nominally) plane wall jets in still air, supplementing these when necessary with some additional measurements.
Abstract: An examination has been made of all the data available on incompressible (nominally) plane wall jets in still air, supplementing these when necessary with some additional measurements. For a wall jet in still air, the chief mean flow qualities of interest are the maximum velocity, the inner length scale, and a total thickness, in addition to the wall stress. On the basis of the analysis, a (nominally) plane wall jet flow can be divided into an initial region, a fully developed flow region, and a confined wall jet flow region.

85 citations


Journal ArticleDOI
TL;DR: By means of CNDO/2 calculations on N- methyl acetamide, it is shown that the state of minimum energy of the trans-peptide unit is a non-planar conformation, with the NH and NC 2 α bonds being significantly out of the plane formed by the atoms C 1 α, C′, O and N.

75 citations


Journal ArticleDOI
TL;DR: In this paper, the vibration problems of skew plates with different edge conditions involving simple support and clamping have been considered by using the variational method of Ritz, a double series of beam characteristic functions being employed appropriate to the combination of the edge conditions.

74 citations



Journal ArticleDOI
TL;DR: It is shown that the dihedral angles θ N and Δω are correlated, while θ C, is small and is uncorrelated with Δω, showing that the non-planar distortion at C′ is generally small.

61 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used the Rayleigh-Ritz method with simple polynomials as admissible functions for obtaining natural frequencies of transversely vibrating polar orthotropic annular plates.

50 citations


Journal ArticleDOI
TL;DR: In this paper, the interaction of DNA with gold(III) has been considered, which does not occur as $Au^{3+}$ in solution, but rather exists in square planar $complexes^{11}$.
Abstract: Metal $ions^{1..10}$ are known to bind to DNA. A number of metal ions have been studied and their binding established. $Cu(II)^{8,9,10}$ and $Ag(I)^4$ have been widely studied and ample literature exists on these two metals. On the other hand, the interaction of DNA with gold(III) (which does not occur as $Au^{3+}$ in solution, but rather exists in square planar $complexes^{11}$) has seldom been considered. During the course of our work on this phenomenon Gibson and $co-workers^{12}$ have published a paper recently reporting the results on binding of gold(III) with adenine nucleotides.

Journal ArticleDOI
TL;DR: Anti-deoxyadenylate antibodies were produced in rabbits by injecting a conjugate of deoxyadenosine 5′-phosphate with bovine serum albumin and showed hapten-specific antibodies, finding a high degree of specificity for the whole nucleotide, the base, sugar and phosphate playing almost equally important roles.

Journal ArticleDOI
TL;DR: From the data presented here it is concluded that Mg 2+ ion is dircctfy involved in binding to counteract efcctmstatk repulsions between npa-tiveiy charged pho~hate group of DNA anJ anioni.

Journal ArticleDOI
TL;DR: In this paper, a clarification of some of these questions as regards rectangular and skew plates is presented by making use of concepts from physics dealing with molecular vibrations, which may be referred to as quasi-degeneracies.

Journal ArticleDOI
TL;DR: In one low-level streptomycin-resistant mutant, the in vitro amino acid-incorporating system was as sensitive to various concentrations of strePTomycin as the parental type, and a possible involvement of a membrane site in the development of low- level resistance was indicated.
Abstract: An efficient in vitro amino acid-incorporating system from Mycobacterium tuberculosis H37Rv was standardized. Ribonucleic acid (RNA) isolated from phage-infected M. smegmatis cells served as natural messenger RNA and directed the incorporation of 14C-amino acids into protein. The effects of various antitubercular drugs and “known inhibitors” of protein synthesis on amino acid incorporation were studied. Antibiotics like chloramphenicol and tetracycline inhibited mycobacterial protein synthesis, though they failed to prevent the growth of the organism. This failure was shown to be due to the impermeability of mycobacteria to these drugs by use of “membrane-active” agents along with the antibiotics in growth inhibition studies. Several independent streptomycin-resistant mutants of M. tuberculosis H37Rv were isolated. Streptomycin inhibited the incorporation of 14C-amino acids into proteins by whole cells of a streptomycin-susceptible strain by more than 90%, whereas very little or no inhibition was observed in either high-level or low-level streptomycin-resistant strains.

Journal ArticleDOI
TL;DR: A model is proposed for the regulation of δ-aminolaevulinate synthetase induction in rat liver and there is evidence for the formation of drug-resistant protein-bound haem in liver microsomal material under these conditions.
Abstract: A reciprocal relationship exists between the cytochrome P-450 content and δ-aminolaevulinate synthetase activity in adult rats. In young rats the basal δ-aminolaevulinate synthetase activity is higher and the cytochrome P-450 content is lower compared with the adult rat liver. Administration of allylisopropylacetamide neither induces the enzyme nor causes degradation of cytochrome P-450 in the young rat liver, unlike adult rat liver. Allylisopropylacetamide fails to induce δ-aminolaevulinate synthetase in adrenalectomized–ovariectomized animals or intact animals pretreated with successive doses of the drug, in the absence of cortisol. The cortisol-mediated induction of the enzyme is sensitive to actinomycin D. Allylisopropylacetamide administration degrades microsomal haem but not nuclear haem. Haem does not counteract the decrease in cytochrome P-450 content caused by allylisopropylacetamide administration, but there is evidence for the formation of drug-resistant protein-bound haem in liver microsomal material under these conditions. Phenobarbital induces δ-aminolaevulinate synthetase under conditions when there is no breakdown of cytochrome P-450. On the basis of these results and those already published, a model is proposed for the regulation of δ-aminolaevulinate synthetase induction in rat liver.

Journal ArticleDOI
TL;DR: Algorithms are described for the basic arithmetic operations and square rooting in a negative base and a new operation called polarization that reverses the sign of a number facilitates subtraction, using addition.
Abstract: Algorithms are described for the basic arithmetic operations and square rooting in a negative base. A new operation called polarization that reverses the sign of a number facilitates subtraction, using addition. Some special features of the negative-base arithmetic are also mentioned.

Journal ArticleDOI
TL;DR: In this article, the pulsatile flow of an incompressible viscous fluid in a cylindrical tube of varying cross section is investigated for small Reynolds numbers and the shear stress distribution on the wall is evaluated and discussed in detail for special geometries like tapered tubes, locally constricted tubes and peristaltic tubes.
Abstract: The pulsatile flow of an incompressible viscous fluid in a cylindrical tube of varying cross section is investigated for small Reynolds numbers. The solutions consist of a stedy and an oscillatory part. The shear stress distribution on the wall is evaluated and discussed in detail for special geometries like tapered tubes, locally constricted tubes and peristaltic tubes. The existence of separation in the flow field is noticed.

Journal ArticleDOI
TL;DR: The changes in the net amounts of retinol, retinyl esters and retinal in both the developing chick embryo and the newly hatched chick were investigated and Retinal virtually disappeared from the extra-embryonic tissue after day 17 of incubation.
Abstract: 1. The changes in the net amounts of retinol, retinyl esters and retinal in both the developing chick embryo and the newly hatched chick were investigated. The embryo requires about 68nmol of the vitamin for its growth, whereas the baby chick requires about 108nmol during the first 7 days after hatching. 2. Retinal was present in the egg in fairly high concentrations at the beginning of the incubation but it virtually disappeared from the extra-embryonic tissue after day 17 of incubation. It was not found in the liver of the embryo or of the newly hatched chick up until day 7.

Journal ArticleDOI
TL;DR: In this article, the authors considered the identification of a non-linear system in terms of a Hammerstein model, with a zero-memory nonlinear gain followed by a linear system.
Abstract: This paper considers the on-line identification of a non-linear system in terms of a Hammerstein model, with a zero-memory non-linear gain followed by a linear system. The linear part is represented by a Laguerre expansion of its impulse response and the non-linear part by a polynomial. The identification procedure involves determination of the coefficients of the Laguerre expansion of correlation functions and an iterative adjustment of the parameters of the non-linear gain by gradient methods. The method is applicable to situations involving a wide class of input signals. Even in the presence of additive correlated noise, satisfactory performance is achieved with the variance of the error converging to a value close to the variance of the noise. Digital computer simulation establishes the practicability of the scheme in different situations.

Journal ArticleDOI
TL;DR: Several alkylidene malononitriles (1b,1d,1e,2b and4b) and alkylsidene cyanoacetates (1a,2a and4a) studied exhibit a long wavelength UV absorption band around 355 nm which shows a hyperchromic effect in the presence of ethanolic alkali as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this paper, general expressions for various aspects of analysis-viz., natural frequency equation, modal vectors, forced response and filter performance have been evaluated in terms of a single parameter, referred to as velocity ratio.

Journal ArticleDOI
Abstract: Empirical energy calculations on cyclo-Gly-X with X- Phe, Tyr, Val, and Leu as a function of the side-chain torsion angles X indicate that the conformation of minimum energy are characterized by $X^1$ = 60 °, $X^2$ = 90 ° for Phe and Try, $X^1$ = -60 ° for Val and $X^1$ = -60 °, $X^2$ = 180 ° and $X^1$ = 60 ° and $X^2$ = 150 ° for Leu. The minimum energy conformation of cyclo-Gly-Phe and cyclo-Gly-Val have the side chains of Phe and Val stacked over the poperazinedione ring as suggested by NMR and found for cyclo-Gly-Tyr crystal structure. In contrast, the Leu side chain is expected to exist in an extended or a quasi-folded form.

Journal ArticleDOI
TL;DR: In this paper, normal coordinate analysis was used to assign the infrared frequencies of methyl and ethyl xanthato complexes of nickel(II) with the aid of normal coordinate analyses.

Journal ArticleDOI
TL;DR: The acetone powders prepared from leaf extracts of Tecoma stans L. were found to catalyze the oxidation of catechol to 3,4,3',4'-tetrahydroxydiphenyl, and the purified enzyme was remarkably specific forcatechol.

Journal ArticleDOI
TL;DR: The cholesterol side-chain cleavage enzyme activity is decreased considerably at the mild stage of vitamin A deficiency in rat testes and ovaries and the decrease in activity becomes more pronounced with progress of deficiency.
Abstract: The cholesterol side-chain cleavage enzyme activity is decreased considerably at the mild stage of vitamin A deficiency in rat testes and ovaries and the decrease in activity becomes more pronounced with progress of deficiency. Supplementation of the deficient rats with retinyl acetate, but not retinoic acid, restores the enzyme activity to normal values. The cholesterol side-chain cleavage enzyme of adrenals is not affected by any of the above treatments.


Journal ArticleDOI
TL;DR: Transduction of resistance to isoniazid and streptomycin as well as susceptibility in Mycobacterium smegmatis SN2 has been demonstrated and a method has been described for the selection of isoniaZid-susceptible variants after transduction of susceptibility.
Abstract: Transduction of resistance to isoniazid and streptomycin as well as susceptibility to isoniazid in Mycobacterium smegmatis SN2 has been demonstrated. A method has been described for the selection of isoniazid-susceptible variants after transduction of susceptibility.

Journal ArticleDOI
TL;DR: It is shown that the terms constituting velocity ratio can be readily determined by means of an algebraic algorithm developed from a heuristic study of the process of transfer matrix multiplication.

Journal ArticleDOI
TL;DR: It is concluded that the catabolism of homoarginine through homoagmatine represents a major pathway of metabolism of the arnino acid.