Computation of Kolmogorov's Constant in Magnetohydrodynamic Turbulence

In this paper we calculate Kolmogorov's constant for magnetohydrodynamic turbulence to one loop order in perturbation theory using the direct interaction approximation technique of Kraichnan. We have computed the constants for various $E^u(k)/E^b(k)$, i.e., fluid to magnetic energy ratios when the normalized cross helicity is zero. We find that $K$ increases from 1.47 to 4.12 as we go from fully fluid case $(E^b=0)$ to a situation when $E^u/E^b=0.5$, then it decreases to 3.55 in a fully magnetic limit $(E^u=0)$. When $E^u/E^b=1$, we find that $K=3.43$.Comment: Latex, 10 pages, no figures, To appear in Euro. Phys. Lett., 199

Algebraic Aspects of Abelian Sandpile Models

The abelian sandpile models feature a finite abelian group G generated by the operators corresponding to particle addition at various sites. We study the canonical decomposition of G as a product of cyclic groups G = Z_{d_1} X Z_{d_2} X Z_{d_3}...X Z_{d_g}, where g is the least number of generators of G, and d_i is a multiple of d_{i+1}. The structure of G is determined in terms of toppling matrix. We construct scalar functions, linear in height variables of the pile, that are invariant toppling at any site. These invariants provide convenient coordinates to label the recurrent configurations of the sandpile. For an L X L square lattice, we show that g = L. In this case, we observe that the system has nontrivial symmetries coming from the action of the cyclotomic Galois group of the (2L+2)th roots of unity which operates on the set of eigenvalues of the toppling matrix. These eigenvalues are algebraic integers, whose product is the order |G|. With the help of this Galois group, we obtain an explicit factorizaration of |G|. We also use it to define other simpler, though under-complete, sets of toppling invariants.Comment: 39 pages, TIFR/TH/94-3

Biochemical genetic polymorphism in Indian mackerel (Rastrelliger kanagurta)

Six enzymes glucose 6 phosphate dehydrogenase (G6PD), xanthene de hydrogenase (XDH), alcohol dehydrogenase (ADH), peroxidase (PO), lactate dehydrogenase (LDH) and isocitric dehydrogenase (lDH) were examined to discover the genetic variation in Indian mackerel through polyacrylamide gel electrophoresis. A significant difference in allelic frequency at XDH locus was observed between the eachin and Thotapally populations. Thotapally stocks exhibited a significant deviation (P< 0.05) from Hardy weinberg equillibrium. The proportion of polymorphic Joci was 0.777. The coefficient of identity and the genetic distance estimated were 0.9262 and 0.076 respectively

Biochemical genetic polymorphism in the Indian mackerel Rastrelliger kanagurta from Mangalore region

Electrophoresis is the modern and most popular technique used for studying the genetic variability within and among the populations of plants and animals. Genetically controlled tissue enzymes are the most suitable parameters for genetic variability studies. In the present study Polyacrylamide Gel Electrophoresis was used to study the genetic variability in Indian mackerel

A comparative DFT study of electronic properties of 2H-, 4H- and 6H-SiC(0001) and SiC(000-1) clean surfaces: Significance of the surface Stark effect

Electric field, uniform within the slab, emerging due to Fermi level pinning at its both sides is analyzed using DFT simulations of the SiC surface slabs of different thickness. It is shown that for thicker slab the field is nonuniform and this fact is related to the surface state charge. Using the electron density and potential profiles it is proved that for high precision simulations it is necessary to take into account enough number of the Si-C layers. We show that using 12 diatomic layers leads to satisfactory results. It is also demonstrated that the change of the opposite side slab termination, both by different type of atoms or by their location, can be used to adjust electric field within the slab, creating a tool for simulation of surface properties, depending on the doping in the bulk of semiconductor. Using these simulations it was found that, depending on the electric field, the energy of the surface states changes in a different way than energy of the bulk states. This criterion can be used to distinguish Shockley and Tamm surface states. The electronic properties, i.e. energy and type of surface states of the three clean surfaces: 2H-, 4H-, 6H-SiC(0001), and SiC($000 \bar{1}$) are analyzed and compared using field dependent DFT simulations.Comment: 18 pages, 10 figures, 4 table