Browsing by Issue Date, starting with "1987"

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An electron microscopic study of the decagonal phase in a melt-spun Al-26 wt.% Co alloy
(1987) C. Suryanarayana; Jyothi Menon
[No abstract available]
Influence of certain environmental factors on spore germination and spore differentiation in Pithophora oedogonia
(Springer Netherlands, 1987) B.R. Chaudhary; H.V. Singh
Of the light- and dark-stored spores of Pithophora oedogonia for over a period of one and half years, the latter exhibited complete failure of germination under controlled culture conditions. pH 8, blue light and 1 klx intensity of white light proved to be ideal conditions as they resulted in optimum germination of akinetes. pH 5, green light and 0.25 klx light intensity delayed the initiation of sporulation and also reduced percentage sporulation. All filaments died before sporulation in pH 4. © 1987 Institute of Microbiology, Academy of Sciences of the Czech Republic.
ELECTROCHEMICAL AND AES INVESTIGATIONS OF SOME METALLIC GLASSES IN SULPHURIC ACID SOLUTION.
(1987) I.B. Singh; R.D.K. Misra; T.K.G. Namboodhiri; R.S. Chaudhary
No passivation is observed for 0040 alloy whereas all the other alloys passivated in sulphuric acid solutions. Initial dissolution of the alloy in the active region is essential for passivation in molybdenum containing alloys and the concentration of Mo in the passive film is less than that of in the bulk of the alloys. Better passivation is observed in 2826 alloy when the dissolution rate is high in the active region. Prepassive film on 2826MB and 2826 alloys is nickel rich which changes to iron rich passive film at higher anodic potentials. In 2826A alloy, chromium and phosphorous concentrations are higher in the passive film.
An investigation into the effect of blast geometry on rock fragmentation
(International Society for Rock Mechanics and Rock Engineering, 1987) D.P. Singh; V.R. Sastry
S Reck fragmentation due to blasting is dependent on geomechanical, explosive and blast geometry parameters. A laboratory scale study was made to evaluate the effect of some blast geometry parameters (burden, spacing and bench height) on rock blasting. Experiments were divided into two groups-single hole tests to evaluate the effect of burden and bench height, and double hole tests to find out the effect of spacing and bench height. Optimum fragmentation burden was found to be 51 per cent of bench height. Significant increase in optimum breakage and fragmentation burdens vas observed with increase in the bench height. The rate of fall in fragmentation with increase in burden was greater in smaller benches because of increased stiffness of burden rock. Spacing to burden ratio of 3.0 to 4.0 gave optimum fragmentation. Fragmentation at less than optimum fragmentation burden even at a spacing to burden ratio of 5.0 was finer compared to the values obtained at optimum and greater than optimum fragmentation burdens for all spacing to burden ratios, suggesting smaller burdens even with larger spacings for finer fragmentation. Considerable improvement in fragmentation was achieved both qualitatively and quantitatively with increase in bench height. © 6th ISRM Congress 1987. All rights reserved.
Dielectric behaviour of glasses and glass ceramics in the system BaO-PbO-TiO2-B2O3-SiO2
(Springer India, 1987) R.K. Mandal; Ch. Durga Prasad; O.M. Parkash; Devendra Kumar
Glasses with varying molar ratios of PbO/BaO in the system BaO-PbO-TiO2-B2O3-SiO2 were prepared keeping (BaO + PbO)/TiO2 ratio equal to one. The glasses were ceramized by two-stage heat treatment. X-ray diffraction indicates that PbTiO3 crystallizes in lead-rich glasses while BaTiO3 precipitates in barium-rich compositions. Solid solution (Ba, Pb)TiO3 does not seem to crystallize over the entire range of compositions. Simultaneous presence of PbO and BaO in the initial glass composition reduces the yield of ferroelectric phase. Dielectric properties have been interpreted in terms of microstructural features. © 1987 Indian Academy of Sciences.
X‐ray investigation of the mechanism of phase transformation in single crystals of ZnS, ZnxCd1−xS and ZnxMn1−xS (I). Calculation of diffraction effects by a three parameter model
(1987) M.T. Sebastian; P. Krishna
Hexagonal close‐packed (2H) single crystals of ZnS, ZnxCd1−xS and ZnxMn1−xS are known to undergo solid state transformation to the cubic close‐packed (3C) and 6H‐structures on annealing at elevated temperatures. The transformations occur by the non‐random nucleation of stacking faults on individual close‐packed layers parallel to (0001). The nature of the faults involved and their probability distribution during transformation determine the diffraction effects produced along the 10. L reciprocal lattice row by a crystal quenched in an intermediate state of transformation. We have investigated the mechanism of the transformation by comparing the diffraction effects recorded from such crystals on a single crystal diffractometer, with those calculated for an assumed model of the transformation. It is known that in these materials the faults involved in the transformation are deformation faults. To explain the observed diffraction effects we develop a three parameter theoretical model employing a fult probability α for the radom insertion of a deformation fault in the 2H structure, a fault probability β for the deformation faults to occur at three layer separations and a fault probability γ of their occcurrence at 2‐layer separations. The probability α corresponds to the development of a fresh nucleus, the probability β to the growth of the 6H nucleus and the probability γ to the growth of a 3C nucleus. This paper develops the necessary theory of X‐ray scattering for such a model of the transformation and predicts the diffraction effects for different values of α, β, and γ. The next paper compares these results with experimental observations. Copyright © 1987 WILEY‐VCH Verlag GmbH & Co. KGaA
Finite difference analysis of unsteady free convective flow through a porous medium adjacent to a semi-infinite vertical plate
(1987) A. Raptis; A.K. Singh; K.D. Rai
Explicit finite-difference analysis of free convective flow through a porous medium bounded by a semi-infinite vertical plate is carried out. The transient and steady state velocity and temperature profiles are shown on graphs and table. It has been observed that the velocity components increases with permeability parameter where as temperature decreases with it. © 1987.
Search for anomalous interaction mean free paths of charge, 2≦Z≦18 projectile fragments in emulsions exposed to 1.8 A GeV40Ar ions
(Springer-Verlag, 1987) S.B. Beri; K.B. Bhalla; R. Bhanja; A. Bharti; V.S. Bhatia; G. Claesson; S. Garpman; S.K. Gupta; V.K. Gupta; N.Y. Herrstrom; B. Jakobsson; R. Joseph; G.L. Kaul; G. Kaur; M. Kaur; S. Kitroo; V. Kumar; S. Lokanathan; I. Lund; L.K. Mangotra; I.S. Mitra; S. Mookerjee; B. Norén; A. Oskarsson; I. Otterlund; Y. Prakash; S. Persson; N.K. Rao; S. Sankhyadhar; S. Satti; M.M. Sherif; K. Söderström; S.K. Tuli
40Ar-emulsion interactions are studied, to investigate the question of anomalons, in two G- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect, Nh dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level. © 1987 Springer-Verlag.
Sativanine-k: An additional N-formyl cyclopeptide alkaloid from Zizyphus sativa
(1987) A.H. Shah; M.A. Al-Yahya; S. Devi; V.B. Pandey
From the bark of Zizyphus sativa a 13-membered N-formyl cyclopeptide alkaloid containing a short side chain has been isolated for the first time. The structure was determined by spectroscopic methods and chemical degradation. © 1987.
Ab initio calculations of fundamental frequencies for isomeric difluorobenzenes
(1987) O.P. Singh; J.S. Yadav; R.A. Yadav
Ab initio computations of harmonic frequencies for the three isomeric difluorobenzenes have been carried out using the MO technique with split valence 3–21 G basis set. The computed frequencies have been compared with the experimental frequencies. The computed frequencies have been scaled with empirical scale factors in order to correct for the systematic errors originating in the limitations of the theoretical model. It was found necessary to use different scaling factors for the planar and non-planar modes. © 1981, Indian Academy of Sciences. All rights reserved.
Effect of temperature on the photoresponse of chlorophyll photoelectrochemical solar cell
(1987) Neeraj Khare
Photoresponses of chlorophyll Photoelectrochemical Solar Cell have been studied at different temperatures. Observed decrease in the photovoltage/ photocurrent has been attributed to the decrease in the population of the excited state of chlorophyll at high temperature. Nature of the variation of the photoresponse has been explained in terms of a theoretical model in which the photoinduced charge transfer responsible for the photovoltage/photocurrent is supposed to take place between the triplet excited state of chlorophyll and oxidised energy levels of the electrolyte. © 1987.
The male-induced pregnancy block (the Bruce effect) in mice: Re-evaluation of the ability of exogenous progesterone in preventing implantation failure
(1987) G. Rajendren; C.J. Dominic
The ability of exogenous progesterone administration to prevent implantation failure in newly inseminated females exposed to alien males for 3 days (from 10.00 hr on day 1 to 10.00 hr on day 4 post coitum) was evaluated. Administration of progesterone, 1 mg/female/day, for 5 days beginning at 10.00 hr on day 1 or at 10.00 hr on day 2 prevented the return of oestrus and induced implantation of blastocysts in alien male-exposed females. Administration of progesterone beginning at 22.00 hr on day 2 was only partially effective in preventing return of oestrus in the male-exposed females; however, the majority of the females which exhibited vaginal oestrus showed implanted embryos. Progesterone injection beginning at 10.00 hr on day 3 or later was totally ineffective in preventing return of oestrus in the females. Administration of progesterone beginning at 10.00 hr or at 22.00 hr on day 3 failed to induce implantation in the male-exposed females which returned to oestrus on day 3; however, the treatment induced implantation in the majority of the females which returned to oestrus on day 4. Progesterone administration beginning at 10.00 hr on day 4 was totally ineffective in inducing implantation in the male-exposed females exhibiting the Bruce effect. The results indicate that administration of progesterone beginning at any time prior to the appearance of oestrus facilitates implantation of blastocysts in male-exposed females; however, progesterone administration beginning after the onset of oestrus is totally ineffective in inducing implantation in females. The results also strongly suggest that in females exhibiting the Bruce effect there is a total loss of blastocysts.
Chemical-bath-deposited CdS and CdS: Li films and their use in photoelectrochemical solar cells
(1987) S.N. Sahu; S. Chandra
A chemical bath deposition technique was used to obtain n-CdS and lithium-doped CdS films. Lithium doping apparently decreases the band gap and lowers the resistivity, which are responsible for better performance of photoelectrochemical solar cells with the geometry CdS or CdS:Li/S2- S22-/ Pt. The CdS-S2-,S22- interface was electrochemically characterized. © 1987.
HARDNESS AND STRUCTURE OF NICKEL ELECTRODEPOSITED FROM ITS CHLORIDE AND ACETATE SALTS DISSOLVED IN PURE DIMETHYSULFOXIDE.
(1987) H.K. Srivastava; P.K. Tikoo
Earlier studies on the electrodeposition of nickel from nickel chloride or nickel borofluoride dissolved in pure dimethylsulfoxide did not lead to satisfactory results. However, nickel acetate/DMSO bath resulted in deposition but conductivity of the bath was too low. Addition of ammonium acetate improved the conductivity of the bath and quality of the deposit. As an extension of this work, deposition was studied with nickel chloride solutions in presence of varying concentration of ammonium acetate.
Electro-deposited gallium arsenide film: I. Preparation, structural, optical and electrical studies
(1987) S. Chandra; N. Khare
The preparation of GaAs films using an electro-co-deposition technique' is described. An aqueous solution containing Ga and As ions in proper ratios was electrolysed at low currents. The deposited material was identified and characterised by EDAX and electron microscopic studies. Optical absorption study shows that the band gap of the deposited material is approximately 1./5 eV. The resistivity and trap density of electro-deposited film are approximately 103 Omega cm and approximately 1014 cm-3 respectively as determined by I-V characteristics.
Pentobarbitone stimulation of protein phosphorylation in rat brain in vitro
(1987) S. Kumar; R. Shankar
Effect of pentobarbitone on protein phosphorylation in rat brain in vitro was investigated. It was observed that at short term incubations pentobarbitone greatly enhanced incorporation of 32P into cerebral phosphoproteins which came to lower level after prolonged incubation. Dose response curve of the drug on protein phosphorylation was unconventional. The drug did not appreciably affect lipid peroxidation in brain homogenates. Effect of pentobarbitone on protein phosphorylation is not due to its inhibition of mitochondrial electron flow which would have given opposite results. © 1987.
Dexamethasone-induced phosphorylation of high mobility group nonhistone proteins of aging rats
(Martinus Nijhoff/Dr. W. Junk Publishers, 1987) S. Prasad; M.K. Thakur
Phosphorylation of high mobility group (HMG) proteins and its modulation by dexamethasone were examined in vitro by incubating liver slices of young (15- ) and old (138-week) male rats with (32P) orthophosphate. HMG proteins were extracted and analyzed by acid-urea polyacrylamide gel electrophoresis. Phosphorylation of HMG proteins, particularly of HMG 2, 14 and 17 decreases drastically in old rats. Dexamethasone stimulates the phosphorylation of total HMG proteins in both ages. Individual HMG proteins vary in the extent of 32P incorporation. Such differential phosphorylation of HMG proteins and its modulation by dexamethasone may affect chromatin organization and gene expression during aging. © 1987 Martinus Nijhoff Publishers.
EFFECT OF SLAG AND FLY ASH ON PROPERTIES OF CONCRETE.
(1987) T.P. Agrawal; P.K. Singh; M.L.K. Rao
Pure slag was mixed as 20%, 30%, 40% and 50% of the total cementitious material. Other proportions considered are 20% fly ash, 10% slag and 10% fly ash, and 15% slag and 5% fly ash. The consistency and setting times have been studied. Fly ash and slag increase the setting times. Slag reduces the normal consistency whereas fly ash increases it. At 56 days, concrete with 20% fly ash has strength that is comparable to ordinary concrete. Fly ash and slag give more strength to concrete when used separately.
Intracerebroventricular chloride infusion enhances water intake in rats
(1987) Rajendra Dhar Badgaiyan
Central anionic influences on dipsogenic response was studied in 54 euhydrated rats. Quantity of water consumed following third ventricular infusions of equimolar hypertonic chloride and bicarbonate solutions of sodium, potassium, calcium, and barium was compared. Control group (n=6) was given artificial cerebrospinal fluid infusion while rats of the remaining 8 groups (n=6 each) received one of the test solutions. All the chloride solutions, irrespective of the cations to which they were associated, elicited significantly greater dipsogenic response as compared to the control, or the bicarbonate solutions. Response of the bicarbonate solutions was more than the control only in the observation taken 30 min after the infusions. In the later observations, there was no significant difference. Drinking was not affected significantly by the cationic composition of the infusion fluids. Anionic concentration of the solutions has predominantly influenced the dipsogenic response. Enhancement of drinking following infusions of chloride solutions suggests the possibility of the CSF anions exerting active physiological influences over the juxtacerebroventricular sensors. © 1987.
Chromosomal organization of Drosophila tumours - I. Polytene chromosome organization and DNA synthesis in ovarian pseudonurse cells in otu mutants of D. melanogaster
(Springer-Verlag, 1987) P. Sinha; Arati Mishra; S.C. Lakhotia
In otu mutants of Drosophila melanogaster ovarian tumours develop because of the high mitotic activity of the mutant cystocytes; the latter are normally endopolyploid. In certain alleles of otu, however, a varying proportion of the mutant ovarian cystocytes undergo polyteny. Mutant cystocytes with polytene chromosomes are termed pseudonurse cells (PNC). Polytene chromosome morphology and banding patterns in PNC of otu1/otu3 flies were cytologically analysed. Extensive variability was noted in the quality of the banding pattern of the PNC chromosomes which ranged from highly condensed (condensed PNC chromosomes) to those with a banding pattern (banded PNC chromosomes) similar to that in larval salivary gland cells (SGC). Both the condensed and banded PNC chromosomes frequently enter into a diffuse state characterised by weakened synapsis of the polytene chromatids and alterations in their banding pattern (diffuse PNC chromosomes). Analysis of DNA synthesis patterns in the various morphological forms of PNC polytene chromosomes by 3H-thymidine autoradiography revealed a basic similarity to the pattern seen in polytene nuclei of larval SGC. Independently replicating sites, however, could be unambiguously identified only in banded PNC chromosomes. Comparison of late replicating sites in such PNC chromosomes with those of larval SGC showed a remarkable similarity in the two cell types. These results suggest a close correlation between the polytene chromosome banding pattern and its replicative organization. © 1987 Springer-Verlag.