Showing papers by "University of Madras published in 1978"

Hydrophobic character of amino acid residues in globular proteins

Abstract: PREDICTIVE studies on the secondary structure of globular proteins aimed at locating ordered structural segments have provided little information about spatial orientations or even as to whether residues are exposed or buried. However, the physico-chemical properties1 of residues can be used to obtain such information. In particular the hydrophobic character2, is a useful parameter in these studies. The hydrophobic character as defined by the indices given by Tanford3 and Jones4 does not reflect hydrophobic environment within protein structures, but we introduce here a new parameter, the ‘bulk hydrophobic character’ obtained from an analysis of the surrounding hydrophobic environment of amino acid residues in protein crystals. This is a better index of protein hydrophobicity, showing very good correlation with the extent to which residues are buried5 (correlation coefficient r = 0.9) compared with the hydrophobic indices used previously, and it could be used to characterise tertiary structures.

Hydrodynamics and mass transport in rotary disk contactors

Abstract: This paper reports a detailed study of the hydrodynamics involved in the operation of rotary disk contactors (RDC). New information is presented regarding the ‘critical rotor speed’ which divides the two hydrodynamic regimes of near constant and varying characteristic velocity of the dispersed droplet phase. Generalized correlations for prediction of characteristic velocity both above and below the critical rotor speed have been proposed under conditions of no solute transfer as well as solute transfer between the dispersed and continuous phases. Experimental data on mass transfer obtained in the two hydrodynamic regimes of RDC operation have also been correlated by the application of mass transport theory taking into account the factors affecting the interfacial area of contact, drop size, characteristic velocity and dispersed phase holdup. On rapporte dans le present travail une etude detaillee de l'hydrodynamique mise en jeu dans le fonctionnement de contacteurs a disques rotatifs (RDC). On presente des informations nouvelles sur la “vitesse critique des rotors”, qui divise les deux systemes hydrodynamiques a base respective d'une vitesse caracteristique constante et variable de la phase dispersee des gouttelettes. On a propose des correlations generalisees pour prevoir la vitesse caracteristique au-dessus et audessous de la vitesse critique du rotor, dans des conditions ou il y a ou non transfert du solute de la phase dispersee a la phase continue. On a aussi etabli une correlation entre les resultats experimentaux qu'on a obtenus sur le transfert de masse dans les deux systemes hydrodynamiques mis en jeu dans le fonctionnement des contacteurs a disques; on a employe a cette fin la theorie du transport de masse qui considere les facteurs qui influent sur la zone interfaciale de contact, les dimensions des gouttes, la vitesse caracteristique et la retention de la phase dispersee.

Studies on the reproductive biology

Abstract: Therea petiveriana (L.), the seven white spotted fessorial roach of the scrub jungles of South India is seasonal, univoltine and is very restricted in its distribution. The males emerge earlier than the females, soon after the first rain in summer. The cryptic nymphs are subterranean and the adults are predominantly crepuscular. The males that play the active role in courtship and mating, start the process by the characteristic antennal caressing. Depending on the intensity of receptivity of the relatively passive partner, he spares no time in backing into her genitalia to achieve the end to end position of genital connection. Mated couples go subterranean forthwith. The females choose reasonably wet substratum for resting as well as for ootheca deposition. The ootheca rotation is invariably dextral. Senescent females as well as virgins oviposit single eggs and the number of eggs in each completed ootheca ranges from 12–16. The process of oviposition starts early in the mornings as well as late in the evenings and the oothecae are carried longer when the substratutum remains dry. The pairedpleural pouches are elaborate development of the pleuron of the second and third abdominal segments. These pouches are kept withdrawn into the body cavity by a set of retractor muscles that originates at the bottom of the pouch and gets inserted at the antecosta of the corresponding segment. Young adults, when perturbed, instantaneously lift the wings and fling open the tergites and sternites in order to expose the hairy pleats of the fully projected plural pouches. Projection is brought about by the haemocoelic fluid pressure. The well developed hypodermis of the pleural pouches of young adults has an outer tier of cuticle secreting small compactly packed cells and a basal tier of large secretory cells, the secretion of which is considered to function as alerting pheromone.

Particles of half-integral or integral helicity by quantization of a nonrelativistic free particle, and related topics

Abstract: It is known that the equations of motion of a classical system do not in general determine its canonical description uniquely. Thus the corresponding quantum system obtained by canonical quantization is also ambiguous. We use this freedom to quantize a free nonrelativistic particle so that the corresponding quantum particle has half-integral or integral helicity. Methods are developed for finding inequivalent canonical descriptions of a given classical system. It is emphasized that classical symmetries can be broken at the quantum level by a suitable choice of the canonical formalism prior to quantization. It is suggested that this may provide a new mechanism for breaking internal symmetries at the quantum level.

Generation of gluons from quark confinement

Abstract: We study a model of quark confinement defined by the vanishing of colour currents. The model is shown to be equivalent to quantum chromodynamics and this equivalence is interpreted as due to the compositeness of the colour gluons. The Green’s functions of the theory are found to contain nontrivial structure only for colour singlet composites which can be identified with hadrons.

Nonbonded interactions in membrane active cyclic biopolymers. II. Ion binding by valinomycin

Abstract: A possible mode for the capture of a cation by the carrier molecule valinomycin has been simulated. The intramolecular nonbonded energy and the binding energy for a centrally located potassium ion at different stages in the capture process have been evaluated using a method proposed earlier. Contrary to intuitive expectations the open conformation of valinomycin is also found to have a strong affinity for K+. There appears to be a rather high potential barrier between the open and closed symmetric conformations.

South Indian Agaricales IV. A New Species of Psathyrella

Abstract: Berkeley, M. J., and C. E. Broome. 1883. List of fungi from Brisbane, Queensland. Trans. Linn. Soc. London, Bot. 2: 53-75. Cunningham, G. H. pref. 1942. The Gasteromycetes of Australia and New Zealand. Printed privately by J. Mclndoe, Dunedin, New Zealand. xv + 236 p. Kobayasi, Y. 1938. Hymenogastrineae et Phallineae. (Nova flora Japonica, no. 2). Sanseido Co., Tokyo. 90 p. Reid, D. A. 1977. Some Gasteromycetes from Trinidad and Tobago. Kew Bull. 31: 657-690.

Quantum Point Process Model for Photodetection

Abstract: In classical physics, phenomena which involve a random sequence of events in time have been successfully investigated by means of the theory of classical point processes (CPP)[1]. Hence, it is not surprising that most of the theoretical approaches [2–6] to the photon-counting problem are also based on the theory of CPP. The central objective of these investigations is to derive an expression (referred to as the counting formula) for the probability p((t,t+T],m) that m counts are observed in the time interval (t,t+T]. This naturally leads to the study of a situation where the detector performs continuous measurements on the electromagnetic field in the interval (t,t+T].

Pyridoxine and its relation to lipids. Studies with pyridoxineless mutants of Aspergillus nidulans.

Abstract: The effect of pyridoxine deficiency on fat metabolism was studied using mutant strains of Aspergillus nidulans requiring pyridoxine for growth. Under pyridoxine deficiency the mutants exhibited increased levels of total lipid, sterols, phospholipids, and triacylglycerols. Total fatty acids were found to decrease with pyridoxine deficiency. An increase in saturated fatty acids and decrease in unsaturated fatty acids were seen with deficiency. Pyridoxine deficiency also increased lower carbon chain fatty acids. A possible involvement of pyridoxine in the elongation of fatty acid chain and in the desaturation of fatty acids in Aspergillus nidulans is suggested.

Putagraivam, a new genus of the hyphomycetes

Abstract: A synnematous hyphomycetePutagraivam sundaram gen. et sp. nov. collected on dead twigs ofMacaranga indica Wight from India is described and illustrated. It is the conidial state of a hypocreaceous fungus.

Chromatographic separation of nitrite and nitrate ions

Abstract: The influence of solvents on the migration of nitrite and nitrate ions on paper chromatograms was studied. The differential migration and separation is based upon differential solubilization of the ions by virtue of differential polarity of the ions and the solvents. The separated ions are estimated photometrically.

Effect of the epidermal secretions of Hemichordate,Ptychodera flava on growth ofAmphora coffeaeformis andCyclotella meneghiniana (Diatoms)

Abstract: The effect of epidermal secretions ofPtychodera flava collected during nonbreeding and breeding seasons on growth of two diatomsAmphora coffeaeformis andCyclotella meneghiniana is studied. Differential effect of the secretions on growth rate of the diatoms indicates differences in their potency. Low concentrations tend to stimulate growth. The ecological significance of the secretions has been briefly commented upon.

Influence of atomic mass on the coriolis coupling constants in some XY6-type molecules. I-XCl6

Abstract: The symmetric force constants F33, F34 and F44 are determined using the Thirugnanasambandam method of “kinetic constant constraint” for some octahedral XCl6 molecules and ions. The Coriolis coupling constants ζ33 and ζ44 evaluated using these force constants are observed to vary with the mass of the X-atom. Empirical relationships between the atomic mass of the X-atom and ζ44 values have been proposed. These relations are compared with those for the tetrahedral XCl4 molecules and ions which were suggested earlier.

Crystal structure of 1-amino-2-phenyl benzocycloheptanol hydrobromide monohydrate

Abstract: Crystals of 1-amino 2-phenyl benzocycloheptanol hydrobromide monohydrate are orthorhombic witha=6·927(17),b=30·947(40),c=30·990(40) A,z=16 and the space group is Iba2.ρ=1·41 gm/ccρ cal=1·403 gm/cc,μ for CuKα=37.06 cm−1. The structure was solved by heavy atom method using three dimensional x-ray intensity data and refined by block diagonal and full matrix least squares method to anR-index of 0·106. The structure is stabilised by a number of hydrogen bonds of the type N-H…O, O-H…Br, N-H…Br. The heptane rings in this molecule are in chair conformation.

Classical solutions of a model of quark confinement

Abstract: We find the classical solutions of a model of quark confinement defined by the vanishing of colour currents. Both plane-wave type of solutions extending all over space as well as string-type of solutions confined to restricted regions of space are found.

Taxonomic studies on the genusAulosira kirchner

Abstract: Two isolates ofAulosira were cultured under uniform laboratory conditions in order to make a taxonomic investigation. The isolates were grown in Chu 10 and biphasic soil water media, and identified using well known manuals. Study of the isolates revealed differential behaviour of the same isolate and identical behaviour of dissimilar isolates in different environments (culture conditions). A revision of the genus is suggested.