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Search Results: 1 - 10 of 14266 matches for " Yashwant Singh Rawat "
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Van Panchayats as an Effective Tool in Conserving Biodiversity at Local Level  [PDF]
Vardan Singh Rawat, Yashwant Singh Rawat
Journal of Environmental Protection (JEP) , 2010, DOI: 10.4236/jep.2010.13033
Abstract: Forest vegetation of a community managed forest was studied along four aspects. Quercus leucotrichophora and Pinus roxburghii was the dominant species on each of the two aspects. Across the aspects the total tree density ranged between 193 to 324.3 ind/ha, sapling density between 119 to 258.6 ind/ha and seedling density from 249.98 to 845 ind/ha. The shrub density varied from 199.99 to 406.32 ind/ha and herb density from 9466.66 to 52483.33 ind/ha. The total basal area varied from 0.06 to 7.15 m2/ha at eastern and north facing aspect for Quercus leucotrichophora and Pinus roxburghii respectively showing that the forest is in young stage. Species diversity value for tree layer varied from 0.21 to 1.23 while concentration of dominance value ranged from 0.56 to 0.94. It was noticed that with an increase in species diversity concentration of dominance value decreases indicating inverse relationship between diversity and dominance.
Partition function of a bubble formed in double stranded DNA
Yashwant Singh
Physics , 2009,
Abstract: We calculate the entropic part of partition function of a bubble embedded in a double stranded DNA (dsDNA) by considering the total weights of possible configurations of a system of two single stranded DNA (ssDNA) of given length which start from a point along the contour of dsDNA and reunite at a position vector {\bf r} measured from the first point and the distribution function of the position vector {\bf r} which separates the two zipper forks of the bubble in dsDNA. For the distribution function of position vector {\bf r} we use the distribution of the end-to-end vector {\bf r} of strands of given length of dsDNA found from the wormlike chain model. We show that when the chains forming the bubble are assumed to be Gaussian the so called loop closure exponent $c$ is 3 and when we made correction by including self avoidence in each chain the value of $c$ becames 3.2.
On the generalization of Gurland distribution
Yashwant Singh
Mathematics , 2008,
Abstract: In the present paper a generalization of Gurland distribution [3] is obtained as a beta mixture of the generalized Poisson distribution (GPD) of Consul and Jain [2]. The first two moments of the distribution and a recurrence relation among probabilities are obtained. The present distribution is supposed to be more general in nature and wider in scope.
Statistical Mechanics of thermal denaturation of DNA oligomers
Navin Singh,Yashwant Singh
Physics , 2004,
Abstract: Double stranded DNA chain is known to have nontrivial elasticity. We study the effect of this elasticity on the denaturation profile of DNA oligomer by constraining one base pair at one end of the oligomer to remain in unstretched (or intact) state. The effect of this constraint on the denaturation profile of the oligomer has been calculated using the Peyrard-Bishop Hamiltonian. The denaturation profile is found to be very different from the free (i.e. without the constraint) oligomer. We have also examined how this constraint affects the denaturation profile of the oligomer having a segment of defect sites located at different parts of the chain.
Statistical Theory of Force Induced Unzipping of DNA
Navin Singh,Yashwant Singh
Physics , 2004, DOI: 10.1140/epje/i2004-10100-7
Abstract: The unzipping transition under the influence of external force of a dsDNA molecule has been studied using the Peyrard-Bishop Hamiltonian. The critical force $F_c(T)$ is found to depend on the potential parameters $k$, represents the stiffness of single strand of DNA and the potential depth $D$. We used constant extension ensemble to calculate the average force needed to stretch a base pair $y$ distance apart. A very large peak around $y = 1 {\rm \AA}$ is found. The value of $F(y)$ needed to stretch a base pair located far away from the ends of a dsDNA molecule is found twice the value of the force needed to stretch a base pair located at one of the ends to the same distance. The effect of mismatching in the base pairs on the peak height and position is investigated. The formation and behaviour of a loop of Y shape when one of the ends base pair is stretched and a bubble of ssDNA with the shape of "an eye" when a base pair far from ends is stretched are investigated.
Effect of genome sequence on the force-induced unzipping of a DNA molecule
Navin Singh,Yashwant Singh
Physics , 2006, DOI: 10.1140/epje/e2006-00023-6
Abstract: 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 defects on thermal denaturation of DNA Oligomers
Navin Singh,Yashwant Singh
Quantitative Biology , 2001, DOI: 10.1103/PhysRevE.64.042901
Abstract: The effect of defects on the melting profile of short heterogeneous DNA chains are calculated using the Peyrard-Bishop Hamiltonian. The on-site potential on a defect site is represented by a potential which has only the short-range repulsion and the flat part without well of the Morse potential. The stacking energy between the two neigbouring pairs involving a defect site is also modified. The results are found to be in good agreement with the experiments.
Dynamics of a bubble formed in double stranded DNA
Shikha Srivastava,Yashwant Singh
Physics , 2008, DOI: 10.1209/0295-5075/85/38001
Abstract: We study the fluctuational dynamics of a tagged base-pair in double stranded DNA. We calculate the drift force which acts on the tagged base-pair using a potential model that describes interactions at base pairs level and use it to construct a Fokker-Planck equation.The calculated displacement autocorrelation function is found to be in very good agreement with the experimental result of Altan-Bonnet {\it et. al.} Phys. Rev. Lett. {\bf 90}, 138101 (2003) over the entire time range of measurement. We calculate the most probable displacements which predominately contribute to the autocorrelation function and the half-time history of these displacements.
Linear and branched polymers on fractals
Deepak Dhar,Yashwant Singh
Physics , 2005,
Abstract: This is a pedagogical review of the subject of linear polymers on deterministic finitely ramified fractals. For these, one can determine the critical properties exactly by real-space renormalization group technique. We show how this is used to determine the critical exponents of self-avoiding walks on different fractals. The behavior of critical exponents for the $n$-simplex lattice in the limit of large $n$ is determined. We study self-avoiding walks when the fractal dimension of the underlying lattice is just below 2. We then consider the case of linear polymers with attractive interactions, which on some fractals leads to a collapse transition. The fractals also provide a setting where the adsorption of a linear chain near on attractive substrate surface and the zipping-unzipping transition of two mutually interacting chains can be studied analytically. We also discuss briefly the critical properties of branched polymers on fractals.
Molecular theory of elastic constants of liquid crystals. III. Application to smectic phases with tilted orientational order
Yashwant Singh,Jokhan Ram
Physics , 2001, DOI: 10.1103/PhysRevE.64.051705
Abstract: Using the density functional formalism we derive expression for the distortion free energy for systems with continuous broken symmetry and use it to derive expression for the elastic constants of smectic phases in which director is tilted with respect to the smectic layer normal. As in the previous papers of the series (Phys. Rev. A {\bf 45}, 974 (1992), E {\bf 49}, 501, (1994)) the expressions for the elastic constants are written in terms of order and structural parameters. The structural parameters involve the generalised spherical harmonic coefficients of the direct pair correlation function of an effective isotropic liquid. The density of this effective isotropic liquid depends on the nature and amount of ordering present in the system and is evaluated self- consistently. We estimate the value of elastic constants using reasonable guess for the order and structural- parameters.
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