Showing papers by "Banaras Hindu University published in 1971"

Inverse filter coefficients for the computation of apparent resistivity standard curves for a horizontally stratified earth

Abstract: In this paper a fast method is developed for computing apparent resistivity curves for known layer configurations. The method is based on the application of a linear filter to determine the apparent resistivity curve from, the kernel function.

Review: A decade of quenching from the melt

Abstract: The technique of rapidly quenching metals and alloys from the melt developed in 1960 by Duwez and his collaborators has gained wide popularity. The extremely high cooling rates (106 to 108° C/sec) attainable with these techniques have yielded supersaturated solid solutions, non-equilibrium crystalline phases and also amorphous alloys. The fascinating results obtained so far, particularly the unusual structures and properties of the new products, are extensively reviewed in this article.

A comparative study of the structure of the skin of certain air-breathing fresh-water teleosts

Abstract: A comparative study of the skin, based on the micro-anatomical investigation of skin fragments taken from a specific region of the body, has been made of three air-breathing fishes, namely, Heteropneustes fossilis, Amphipnous cuchia and Mastacembelus pancalus. On the basis of their structure and histochemical nature, five types of skin glands have been distinguished in the epidermis of these fishes. The relative thickness of the epidermis (A. cuchia–119 μm (average value), H. fossilis– 98 μm (average value), M. pancalus–34 μm (average value)) and its vascularization has been considered and compared with other fishes and amphibians. The possibilities of cutaneous respiration in these air-breathing fishes has been discussed. The presence of a well-defined lymphatic system, comprising a series of lymph spaces containing small lymphocytes, in the stratum germinativum layer of the epidermis of these fishes has been established. The stratum laxum layer of the dermis in Amphipnous is characterized by the presence of definite areas containing “Substantia amorpha” having acidic mucopolysaccharides which may be related with the amphibious habit of the fishes. This is an adaptation against desiccation similar to that found in the Anura. In Mastacembelus elliptical areas of the stratum laxum penetrate into the epidermis thus making these areas of the epidermis considerably thin (about 7 μm) for cutaneous respiration. There is an inverse relationship between the thickness of the stratum compactum and squamation.

Evolution of sex-chromosomes and formation of W-chromatin in snakes

Abstract: The analysis of sex-chromosome complexes and formation of W-chromatin in 16 species of snakes of the families Boidae, Colubridae, Elapidae, and Hydrophiidae, reveal three very pertinent facts. First, the snakes exhibit various states of the differentiation of the Z and W chromosomes, apparently according to the evolutionary status of the families, being homomorphic in primitive families and well differentiated in highly evolved ones. Second, the demonstration of a heteropycnotic body in the interphase nuclei of the families of a large number of species of snakes has definitely shown that the nuclear sexing is possible not only in those species of snakes where the W chromosome is morphologically distinguishable from the Z, but also in those species where it is not so, but shows an asynchrony in the replicating pattern of W. It is suggested that development of allocycly rather than establishment of structural changes is the first step in the differentiation of the W from the Z in snakes. Third, the absence of coexistence of nucleolus and W-chromatin in a condensed state in the interphase nuclei of different tissues in a few species of snakes reported in this paper suggests that the W-chromatin is responsible for the synthesis of the nucleolus in these snakes.

Three-Phonon Scattering and Guthrie's Limits for Its Temperature Dependence

Abstract: It is shown that one can explain the temperature dependence of the phonon conductivity of Ge in the entire range from 2 to 1000 \ifmmode^\circ\else\textdegree\fi{}K if the three-phonon relaxation rate is given by $\ensuremath{\tau}_{3\mathrm{ph}}^{\ensuremath{-}1}\ensuremath{\propto}g(\ensuremath{\omega}){T}^{m(T)}{e}^{\ensuremath{-}\frac{\ensuremath{\Theta}}{\ensuremath{\alpha}T}}$. Three-phonon scattering processes are classified, after Guthrie, into two groups: class I, which involves the annihilation of carrier phonons by combination, and class II, which involves splitting of carrier phonons. At all temperatures, the values of $m(T)$ for both classes of processes lie either definitely below or close to the upper limit of $m(T)$ as obtained by Guthrie.

Phonon Conductivity of InSb and GaAs in the Temperature Range 2-300 °K

Abstract: The recent modification of Holland's model of two-mode conduction, as proposed by us, has been applied to explain the phonon conductivity of InSb and GaAs. This model, Known as the Sharma-Dubey-Verma model, makes use of Guthrie's classification of three-phonon scattering events. In this model, the exponent $m$ of the temperature, i.e., ${T}^{m(T)}$ is a continuous function of temperature and approaches unity in the high-temperature region for both the longitudinal phonons as well as transverse phonons. The dispersion of acoustic branches is taken into account in replacing $\frac{{v}_{g}}{v_{p}^{2}}$ in the conductivity integrals and this forms the basis of the division of the conductivity integrals for the different polarization branches. The present model gives excellent agreement between the theoretical and experimental values of phonon conductivity except near the maximum where the scattering of phonons by point defects dominates over phonon-phonon scattering as well as boundary scattering of phonons.

Studies on the Physiology of Host‐parasite Relationship in Orobanche. II. Growth and Mineral Nutrition of Host and Parasite

Abstract: The effects of Orobanche infection on the growth and mineral compostition of the host were studied. Parallel observations were made in host and parasite. Orobanche infection reduces the height of main shoot, the length of root, the number of branches, and the number and total area leaves per plant. Consequently the fresh and dry weight of the host is also decreased. Infection affects NAR and LAR only slightly but reduces RGR and RLGR at a later period of infection. The retardation in the growth of host seems to be due mainly to a continuous extraction of metabolites and inorganic nutrients. Infection increases the nitrogen, calcium and magnesium content in the host, especially in the leaves. This fact is connected with the retarded growth in the host. The process of absorption is probably not changed. The phosphorus and potassium contents diminish in the infected host, a fact related to the higher translocation to the parasite. The Orobanche plants grow faster during early stages and accumulate 88 % of total dry matter before flowering, The growth stages of Orobanche do not coincide with those of the host suggesting that the parasite is capable of synthesizing its own growth substances. Studies with 32P show that the flow of minerals is mainly in the direction from host to parasite. The major part of the requirement of the parasite is met by the host. Orobanche maintains a higher phosphorus and potassium content in its tissues than the host, while the nitrogen, calcium and magnesium content is lower.

Karyotypes of Five Indian Species of Microchiroptera

Abstract: SUMMARYTaphozous melanopogon and T. l. longimanus (family Emballonuridae, have 2N=42, Megaderma I. lyra (family Megadermatidae) has 2N = 54 and Hipposideros fulvus and H. a. ater (family Hipposideridae) have 2N=32. The chromosomes of Megadermatidae and Hipposideridae have been studied for the first time. Interrelationships on the basis of available chromosome data and also the probable mechanisms of karyotype evolution in these Indian species of Microchiroptera are discussed.

Studies on the Physiology of Host-parasite Relationship in Orobanche. I. Respiratory Metabolism of Host and Parasite

Abstract: The respiratory rate of the roots of mustard (Brassica cam-pestris L.) and tomato (Lycopersicum esculentum Mill.) serving as hosts for the total root parasites Orobanche aegyptiaca Pers. and O.cernua Loefll. was measured using Warburg manometric technique. At the same time determinations were made of the respiration of the apical, basal and root regions of the parasites. The effects of sodium fluoride, malonic acid, sodium azide and DNP (2,4-dinitrophenol) on the rate of respiration of the host roots as well as of the parasites were studied. The Orobanche infection results in a marked increase in the respiratory rate near the host-parasite contact region. The damaging effect of infection seems to be due mainly to a continuous flow of water, minerals and metabolites from host to parasite. The haustorial invasion creates an obstruction in the translocation of metabolites. The respiration rate is lower in Orobanche than in the host, which might be related to its slower growth rate, inefficient oxidative processes and an escaping of certain energy-requiring interconversion processes. Roots of O. aegyptiaca are more well-developed and have higher rate of respiration. They can absorb more water and minerals from the soil. This fact might be connected with the specificity of the two species. NaF and malonic acid inhibit the respiration to a similar extent in healthy and infected roots. This indicates that the pathway of respiration does not change materially after infection. The EMP and Krebs cycle seem to operate at a lower intensity in Orobanche, which is proved by the lower inhibition of the respiration as compared to in the host. Azide causes a stronger reduction of the respiration in infected than in healthy roots. It would imply that the infection stimulates the activity of metal containing oxidases. The weaker inhibition of the respiration in Orobanche tissues indicates a mediation of other enzymes in the oxidation processes than in the host. The respiration is less stimulated by DNP in infected than in healthy roots. Contrary to the general effect of DNP, this substance decreases the O2 uptake in the parasite tissues. This fact may be explained by the occurrence of exceptionally high amounts of endogenous phenolic compounds and an insufficient production of ATP in the parasite.

Some Observations on the Morphology and Cytology of Indian Charophyta

Abstract: Out of the several Indian Charophyta studied cytologically from seven States, ten taxa, five belonging to the genus Nitella and five to the genus Chara, are new records for which brief morphological descriptions have been given. Chromosome numbers in eighteen taxa are new reports. The nuclear characters of these taxa also have been summarised. Occurrence of cytological races in N. tenuissima f. transilis and C. fibrosa has been recorded.

Foliar spray of gibberellic acid and its influence on the rhizosphere and rhizoplane mycoflora

Abstract: The effect of foliar spray of Gibberellic acid in different concentrations was studied. The variation in the number of fungi/g of dry soil in rhizosphere was found to be significant in case ofD. alba andO. sanctum and insignificant in case ofW. somnifera. Qualitatively, no marked difference was observed in the rhizosphere fungal flora of sprayed and control plants.

Induced crossing-over in the males of Drosophila melanogaster sensitivity of the three life-cycle stages

Abstract: Radiosensitivity of Drosophila germ cells to the induction of recombination in males at different life-cycle stages was studied using a uniform dose of 1000 R of X-rays. Heterozygous males were mated individually for 10–15 days with 7 or 8 virgins each day. Daily broods with recombination frequency agreeing with the Poisson distribution among families were considered to have arisen from independent exchanges. Variation in crossover frequencies between the homogeneous broods was not significant. Similarly, there was no significant intra-stage variation in independent cross-over production of the four larval, the two pupal and the three adult ages. However, there was a very significant inter-stage variation for irradiation at different stages. The recombination frequency was much higher in experiments with pupae than in those with larvae and adults. Possible interpretations of these observations with regard to the origin of independent crossovers are discussed.

Induction and repression of L-arabinose isomerase in Salmonella typhimurium.

Abstract: As with other inducible enzymes, the induced synthesis of l-arabinose isomerase (l-arabinose ketol isomerase, EC 5.3.1.4) in Salmonella typhimurium is subject to catabolite repression. Of the three catabolite repressors tested, glucose produces maximum repression. Analogues of catabolite repressors like 2-deoxy-d-glucose and d-fucose also inhibit the synthesis of the enzyme. The catabolite repression is completely reversed in the presence of 1.5 × 10−3m cyclic 3′,5′-adenosine monophosphate (AMP). The maximum repression is produced in glucose-grown cells in glucose-containing induction medium. Cyclic 3′,5-AMP reverses this repression provided that the cells are treated with ethylenediaminetetraacetic acid (EDTA). In normal cells, cyclic 3′,5′-AMP has no effect on the induction but in EDTA-treated cells the cyclic nucleotide enhances synthesis of the enzyme. The inhibition produced by d-fucose cannot be reversed by cyclic 3′,5′-AMP. d-Fucose competes with the inducer l-arabinose in some step(s) involved in the process of induction.

Direct gravity interpretation of sedimentary basin using digital computer — Part I

Abstract: A method is developed for rapid gravity interpretation of a sedimentary basin using a digital computer. Assuming a linear variable density contrast (both vertically and horizontally), expressions have been derived for the gravitational attraction of a rectangular strip. An interpretation of the structure of Godavari Valley (India) has been made using these expressions.

Riser Whistlers at a Ground Station at Low Latitude

Abstract: THIS communication reports riser whistlers observed for the first time in a ground station. They were noticed during the routine recording of whistlers at our low latitude station, the High Altitude Research Laboratory, Gulmarg (geomagnetic latitude 24° 10′ N, geomagnetic longitude 147° 24′ E). Because these whistlers appear as rising tones in the sonagrams, they resemble the “riser whistlers” reported by Pfeiffer et al.1, from the Injun III satellite observations.

Magmatic differentiation of the volcanics at Pavagarh, Gujarat, India

Abstract: Magmatic differentiation in Pavagarh adopted the courses corresponding to the olivine-basalt trend including olivine-basalt, mugearite, latite and pitch-stone and the normal basalt trend comprising tholeiitic basalts, andesite, dellenite, and rhyolite. The dellenite-rhyolite assemblage is not consanguineous. Their average composition corresponds with the petrochemical field of the basalt-andesite-dacite-rhyolite association or the calc-alkaline series of Nockolds. It lies in between plateau and tholeiitic basalts of different provinces and shows alkali enrichment in the initial phases of differentiation.