Browsing by Author "Y. Singh"

Now showing 1 - 20 of 67

A simple and exactly solvable model for a semiflexible polymer chain interacting with a surface
(2003) P.K. Mishra; S. Kumar; Y. Singh
We use the lattice model of directed walks to investigate the conformational as well as the adsorption properties of a semiflexible homopolymer chain immersed in a good solvent in 2D and 3D. To account for the stiffness in the chain we have introduced energy barrier for each bend in the walk and have calculated the persistent length as a function of this energy. For the adsorption on an impenetrable surface perpendicular to the preferred direction of the walk we have solved the model exactly and have found the critical value of the surface attractions for the adsorption in both 2D and 3D. We have also enumerated all possible walks on square and cubic lattices for the number of steps N≤30 for 2D and N≤20 for 3D and have used ratio method for extrapolation. The transition located using this method is in excellent agreement with the results found from the analytical method. We have compared the results of surface adsorption for two different surface orientations. In one of the orientation, surface is considered parallel to the preferred direction and in another it is perpendicular to the preferred direction. Results found in both the cases indicate that for stiffer chains adsorption transition takes place at higher temperature compared to that of flexible chain © 2003 Elsevier Science B.V. All rights reserved.
Adaptation of a strain of Spirulina platensis to grow in cobalt‐and iodine‐enriched media
(1994) Y. Singh; H.D. Kumar
Cobalt‐ and iodide‐enriched (adapted, tolerant) strains of the protein‐rich cyanobacterium, Spirulina platensis, were produced by repeated sub‐culturing in increasing concentrations of the two trace elements. The strains enriched with cobalt and iodide showed higher uptake of these elements than the controls. The LD50 values for the parent and cobalt‐adapted strains were 95 and 231 μmol 1‐1 Co2+, respectively. Likewise, the LD50 values for parent and iodide‐adapted strains were 12 and 42 mmol‐1 I‐1. The carotenoid : chlorophyll a ratio of the parent strains increased after cobalt addition. The cobalt‐adapted strain showed a much higher ratio than the cobalt‐grown parent (sensitive) cells which remained unchanged after cobalt addition. Intracellular Co2+ uptake by the cells was concentration‐dependent and followed Michaelis‐Menten kinetics with saturation in uptake occurring in the parent and adapted strains at 126 and 189 μmol 1‐1 Co2, respectively. At saturating concentrations, the maximum Co2+ uptake was 39.73 and 158.43 nmol Co2+ mg‐1 protein, respectively for the parent and adapted strains. The adapted strain also showed greater cobalt adsorption. The Km of intracellular Co2+ uptake was lower in the case of adapted cells as compared with the parent, whereas Vmax showed an opposite trend. Thus, the adapted cells appear to be more efficient than the parent strain in intracellular uptake of cobalt. Differences between kinetic constants of both the strains suggest that the strains may be physiologically different. Likewise, iodide uptake was significantly higher in iodide‐adapted cells than in controls. Copyright © 1994, Wiley Blackwell. All rights reserved
Cluster expansion of the distribution functions for a ground state Fermi system
(1982) S.K. Sinha; Y. Singh
The spin-averaged Slater sum of the fermion system is expanded in terms of the square of the ground state wavefunction of a boson system and the "antisymmetry" Ursell function. This expansion is used to obtain the cluster series for the radial distribution function of the fermion system in terms off (-script c sign(n)/S ), where script c sign(n) is sum of chains of (-f/S) and (-fh2B/S) bonds. The series is further expressed in a more compact form using a function L(n) defined by Eq. (55), and the "modified" FHNC approximation for the radial distribution function is presented. © 1983 American Institute of Physics.
Collapsed and adsorbed states of a directed polymer chain in two dimensions
(2002) P.K. Mishra; Y. Singh
A phase diagram for a surface-interacting long flexible partially-directed polymer chain in a two-dimensional poor solvent, where the possibility of collapse in the bulk exists, is determined using exact enumeration methods. We used a model of self-attracting self-avoiding walks and evaluated 30 steps in series. An intermediate phase between the desorbed collapsed and adsorbed expanded phases, having the conformation of a surface-attached globule, is found. The four phases, viz., (i) desorbed expanded (DE), (ii) desorbed collapsed (DC), (iii) adsorbed expanded (AE), (iv) surface-attached globule (SAG), are found to meet at a multicritical point. These features are in agreement with those of an Isotropic (or non-directed) polymer chain.
Comments on "perturbation theory of quantum fluids at high temperature"
(1982) S.K. Sinha; Y. Singh
[No abstract available]
Critical behaviour of two interacting linear polymer chains: Exact results for a state of interpenetration of chains on a fractal lattice
(1993) S. Kumar; Y. Singh
A model of two interacting (chemically different) linear polymer chains on a fractal lattice is proposed, to study segregation and interpenetration of chains. Using the real space renormalization group transformation, the value of the contact exponent at the point of the interpenetration transition is calculated exactly for the 2D Sierpinski gasket.
Critical exponents of self-avoiding walks on a family of truncated n-simplex lattices
(1990) S. Kumar; Y. Singh; Y.P. Joshi
The authors have studied self-avoiding walks (SAWs) on a family of truncated n-simplex lattices which provide a family of fractals in which the fractal dimension d can be varied to a wide range while the spectral dimension d is held almost fixed. By means of exact renormalisation group transformations, they have calculated the critical exponents nu , alpha and gamma and the connectivity constant mu of the SAWs for n=5 and 6. They propose an approximate theory for calculating the critical exponents of the SAWs on fractals which is expected to be accurate at large values of n. They show that the theory gives results which are in good agreement with exact values even for small values of n and leads to simple closed relations for the exponents.
Cytogenetic aberrations and morphological changes induced by insecticide treatments of barley seeds
(1977) B.D. Singh; Y. Singh; R.B. Singh
[No abstract available]
Does a surface attached globule phase exist?
(2003) P.K. Mishra; D. Giri; S. Kumar; Y. Singh
A long flexible neutral polymer chain immersed in a poor solvent and interacting with an impenetrable attractive surface exhibits a phase known as surface attached globule (SAG) in addition to other adsorbed and desorbed phases. In the thermodynamic limit, the SAG phase has the same free energy per monomer as the globular phase, and the transition between them is a surface transition. We have investigated the phase diagrams of such a chain in both two- and three-dimensions and calculated the distribution of monomers in different domains of the phase diagram. © 2002 Elsevier Science B.V. All rights reserved.
Effect of defects on thermal denaturation of DNA oligomers
(2001) N. Singh; Y. Singh
Effect of defects on the melting profile of short heterogeneous DNA chains was analyzed using Peyrard-Bishop Hamiltonian. The analytical investigation of nonlinear dynamics of the model shows the initiation of denaturation by intrinsic energy localization. The results show that the melting profile of the DNA chain does not depend on the location of the defect site of the oligomer crystals.
Effect of genome sequence on the force-induced unzipping of a DNA molecule
(2006) N. Singh; Y. Singh
We considered a dsDNA polymer in which distribution of bases are random at the base pair level but ordered at a length of 18 base pairs and calculated its force elongation behaviour in the constant extension ensemble. The unzipping force F(y) vs. extension y is found to have a series of maxima and minima. By changing base pairs at selected places in the molecule we calculated the change in F(y) curve and found that the change in the value of force is of the order of few pN and the range of the effect depending on the temperature, can spread over several base pairs. We have also discussed briefly how to calculate in the constant force ensemble a pause or a jump in the extension-time curve from the knowledge of F(y).
Effect of insecticides on germination, early growth and cytogenetic behavior of barley (Hordeum vulgare)
(1979) B.D. Singh; R.B. Singh; R.M. Singh; Y. Singh; J. Singh
Seeds of barley (Hordeum vulgare L. cv. "Ratna") were treated for 3 hr with 0.1% solutions of the active ingredients of commercial formulas of six systemic (Dimecron, Citrolane, Thimet, Counter, Furadon and Disyston) and three nonsystemic (Endrin, Cythion and Ambithion) insecticides, and ethylmethane sulphonate (EMS). In general, insecticide treatments did not reduce germination (except for Ambithion), but did reduce seedling height, pollen fertility and chiasma frequency. Different cytological aberrations, viz., chromosome fragments at mitotic metaphase; chromatin bridges, fragments, laggards, bridges with fragments and/or laggards at mitotic anaphase; univalents, precocious separation and nonorientation of bivalents at meiotic metaphase I; and laggards, bridges, bridges with laggards, tripolar divisions and unequal separation of chromosomes at anaphase I, were observed in the treated populations in frequencies significantly higher than those in the control. Some insecticides induced significantly greater cytological aberrations and other detrimental effects, such as reduction in germination, seedling height and pollen fertility, than EMS. © 1979.
Effect of organic nitrogen sources and biofertilizers on production potential and energy budgeting of rice (Oryza sativa)-based cropping systems
(Indian Society of Agronomy, 2013) S.K. Yadav; Subhash Babu; Y. Singh; G.S. Yadav; Kalyan Singh; Raghavendra Singh; Harvir Singh
A field experiment was conducted during 2005-06 and 2006-07 at Varanasi, Uttar Pradesh, to find out the effect of organic nitrogen sources and biofertilizers on system productivity and energy budgeting of rice (Oryza sativa L.)-based cropping system. Rice-potato [Solanum tubersoum (L.)]-onion [Allium cepa (L.)] system recorded significantly higher production efficiency (97.5 kg/ha/day), land-utilization efficiency (91.4%), economic efficiency (738/ha/day), energy input (61.08×103MJ/ha) and energy output (187.09×103MJ/ha). The lowest (39.4 × 103MJ/ ha) energy intensiveness was recorded in rice-table pea (Pisum sativum var. hortense)-cowpea [Vigna unguiculata (L.) Walp.] cropping system. However, the organic nutrition with biofertilizers (Azotobacter and phosphate-solubilizing bacteria) had the highest rice-equivalent grain yield (35.3 t/ha), production efficiency (96.7kg/ha/ day), land utilization efficiency (89.8%), economic efficiency (803 ha/day) and energy-use efficiency (3.15) of system, followed by organic nitrogen sources alone (3.0). Recommended dose of N @100% through organic nitrogen sources alone was the next best treatment resulting in higher productivity and system efficiency. Rice-potato-onion cropping system was found most productive, profitable and energy efficient with application of 100% recommended dose of nitrogen through organic sources along with biofertilizers. © 2013, Indian Society of Agronomy. All rights reserved.
Effect of polyolefin resin coated slow release iron fertilizer and its methods of application on rice production in calcareous soil
(2004) K. Singh; H.C. Sharma; C.S. Singh; Y. Singh; N.K. Nishizawa; S. Mori; S. Mori
Experiment was carried out to evaluate the, efficiency of different iron sources including polyolefin resin coated slow release Fe fertilizer (PRCCFe) and its methods of application on the performance of rice var. Swarna during rainy seasons of 2001 and 2002 under calcareous soil at Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The pots were filled with 10 kg calcareous soil having high CaCO3 (36.32%) and low iron contents (1.45 pp—less than critical limit). The experimental treatments comprised five iron sources (NPK + 100% pyrite, NPK + 100% polyolefin resin coated slow release Fe (PRCSRFe), NPK + 50% pyrite + 50% PRCSRFe, NPK + 75% pyrite + 25% PCRSRFe, and NPK + 25% pyrite + 75% PCRSRFe and two methods of application (uniform and co-situs) including one control (NPK only). These 11 treatment combinations were laid out in Completely Randomized Block Design (CRBD) replicated thrice. The two methods of iron application did not differ significantly with respect to crop yield though higher yield was recorded with co-situs application. Among the Fe sources, application of iron 75% through to + 25% through polyolefin resin coated slow release Fe fertilizer produced the highest grain yield. © 2004 Taylor & Francis Group, LLC.
Effect of shape of molecules on transport and equilibrium properties of nonpolar polyatomic gases
(1973) A. Das Gupta; Y. Singh; S. Singh
Collision integrals for nonpolar polyatomic gases have been evaluated on the assumption of fixed relative orientation per collision, with a 12-12-6 potential model, for a range of reduced temperatures and shape parameters. The effect of shape of molecules on diffusion and viscosity is small but not negligible. Thermal diffusion factors are most strongly affected; the presence of interaction due to nonsphericity in the shape of molecules can wipe out the thermal-diffusion inversion temperatures. The parameters of the spherical component of the potential have been obtained from the viscosity data for nine gases. These parameters have been used in conjunction with the second viral coefficient data to determine the quadrupole moments and shape parameters of the molecules. The quadrupole moments and shape parameters obtained are very reasonable.
Effect of tillage, inter-terrace and mulching on yield and nutrient uptake by maize (Zea mays)-chickpea (Cicer arietinum) cropping system
(2002) Kalyan Singh; U.N. Singh; Y. Singh; S.R. Singh; R.S. Chandel
A field experiment was conducted during 1997-98 to 1999-2000 at the Research Farm of University situated at Barkachha (Mirzapur) under Vindhyan hills, to study the effect of tillage, inter-terrace and mulching on yield and nutrient uptake by maize (Zea mays L)-chickpea (Cicer arietinum L.) cropping system. Deep tillage was more remunerative than off-season and conventional tillage with respect to maize yield (6.21 tonnes/ha), chickpea yield (1.15 tonnes/ha) and nutrient uptake (262.79 N, 49.84 P, 219.37 K kg/ha) in maize-chickpea cropping system. Earthen bund was superior to live bund as well as live bund + small section bund. Under mulching treatments stover mulch was superior to soil mulch and control (no mulch).
Equilibrium properties of a hard-disk fluid via the hypernetted chain integral equation theory
(1983) Y.S. Sainger; S.K. Sinha; Y. Singh
Quantum corrections to the radial distribution function (RDF) and thermodynamic properties for a hard-disk fluid in the semiclassical limit are calculated by means of perturbation method using the extended hypernetted-chain integral equation theory. Numerical results are given for the first order correction to the RDF and for the first and second order corrections to the free energy and equation of state. It is found that quantum effect increases with density and makes the qualitative difference to the RDF near the hard core. © 1983 American Institute of Physics.
Equilibrium properties of dense simple fluids in the presence of three-body forces
(1977) S.K. Sinha; J. Ram; Y. Singh
Computationally convenient theoretical methods for calculating the structural and thermodynamic properties of a classical fluid in the presence of three-body forces are presented. The concept of the effective pair potential has been used to develop two approximations, one known as the Exp approximation for the pair correlation function and the other known as ORPA+B2 for the Helmholtz free energy. The theory has been applied to calculate the effect of the triplet potential on the radial distribution function for the hard-sphere and the Lennard-Jones fluids. At densities and temperatures away from the triple point the effect of the dipole-dipole-dipole and dipole-dipole-quadrupole interactions on the structure of fluids have been found to be small. It is shown that the direct correlation function outside the hard core is significantly affected by the presence of the three-body forces. Copyright © 1977 American Institute of Physics.
Equilibrium properties of fluids in the semiclassical limit
(1976) S.K. Sinha; Y. Singh
The problem of calculating the equilibrium properties of dense fluids in the semiclassical limit when the quantum effects are small is studied. Expressions are given for the pressure, free energy, and the radial distribution function in terms of the properties and correlation functions of the classical system and s-body "modified" Mayer functions Finite Part integral sign1,2,...,ss. It is shown that the correct radial distribution function of a fluid in the semiclassical limit is generated from the classical radial distribution function if we replace in turn each Finite Part integral sign0 bond (Finite Part integral sign12 0 = e-βø(1,2) -1) by an effective Finite Part integral signeff bond, where Finite Part integral signeff = Finite Part integral sign0+(1+Finite Part integral sign 0)Finite Part integral signII +(1+Finite Part integral sign0)(1+Finite Part integral signII)〈 and where 〈 is subset of the line-irreducible graphs each of which contain one Finite Part integral signIII bond. The effective pair bond correct to the second order in thermal wavelength λ ( = {2πℏ2β /m} 1/2) for a fluid of hard spheres is calculated for λ/d = 0.1, and 0.2 at reduced densities ρ* = 0.3 and 0.6. The most striking effect of the quantum mechanics on the structure of a hard-sphere fluid is found at and near the point of contact of the hard spheres. Copyright © 1977 American Institute of Physics.
Equilibrium properties of fluids in the semiclassical limit. II. Application to hard-sphere fluids
(1977) S.K. Sinha; Y. Singh
We present computationally convenient theoretical methods for calculating the structural and thermodynamic properties of a fluid in the semiclassical limit where quantum effects are small. The concept of the effective two-body Mayer functions has been used to develop two approximations, one for the pair correlation function and the other for the Helmholtz free energy. The theory has been applied to the calculation of quantum effects on the radial distribution function and Helmholtz free energy of a fluid of hard spheres. It is shown that because of quantum effects a significant change in the structure of a hard-sphere fluid takes place in the neighborhood of the point of contact. © 1977 The American Physical Society.