Spin-excitations of the quantum Hall ferromagnet of composite fermions

The spin-excitations of a fractional quantum Hall system are evaluated within a bosonization approach. In a first step, we generalize Murthy and Shankar's Hamiltonian theory of the fractional quantum Hall effect to the case of composite fermions with an extra discrete degree of freedom. Here, we mainly investigate the spin degrees of freedom, but the proposed formalism may be useful also in the study of bilayer quantum-Hall systems, where the layer index may formally be treated as an isospin. In a second step, we apply a bosonization scheme, recently developed for the study of the two-dimensional electron gas, to the interacting composite-fermion Hamiltonian. The dispersion of the bosons, which represent quasiparticle-quasihole excitations, is analytically evaluated for fractional quantum Hall systems at \nu = 1/3 and \nu = 1/5. The finite width of the two-dimensional electron gas is also taken into account explicitly. In addition, we consider the interacting bosonic model and calculate the lowest-energy state for two bosons. Besides a continuum describing scattering states, we find a bound-state of two bosons. This state is interpreted as a pair excitation, which consists of a skyrmion of composite fermions and an antiskyrmion of composite fermions. The dispersion relation of the two-boson state is evaluated for \nu = 1/3 and \nu = 1/5. Finally, we show that our theory provides the microscopic basis for a phenomenological non-linear sigma-model for studying the skyrmion of composite fermions.Comment: Revised version, 14 pages, 4 figures, accepted to Phys. Rev.

A Network Flow Model for Irrigation Water Management

Irrigation water management plays a crucial role in the growth and prosperity of countries like India. Optimization Techniques can be effectively used in the management of irrigation water. Motivated by a real crisis in Andhra Pradesh, India, the authors made an attempt to provide scientific solution to the problem of management of Pennar Delta System of Nellore District in Andhra Pradesh. The problem concerns the management of water distribution and scheduling for given requirements and availabilities of water at various nodes of the irrigation network of the system. This article provides a model and framework for the problem in question. The problem is formulated as a dynamic minimum cost network flow problem and provides an approach to solve the problem using static network flow models. A need based software is also developed to solve the network flow problems. Some issues in the programming are discussed

Room temperature soft ferromagnetism in the nanocrystalline form of YCo2 - a well-known bulk Pauli paramagnet

The Laves phase compound, YCo2, is a well-known exchange-enahnced Pauli paramagnet. We report here that, in the nanocrystalline form, this compound interestingly is an itinerant ferromagnet at room temperature with a low coercive-field. The magnitude of the saturation moment (about 1 Bohr-magneton per formula unit) is large enough to infer that the ferromagnetism is not a surface phenomenon in these nanocrystallites. Since these ferromagnetic nanocrystallines are easy to synthesize with a stable form in air, one can explore applications, particularly where hysteresis is a disadvantage

Effect of lead on metallothionein concentration in lead-resistant bacteria Bacillus cereus isolated from industrial effluent

Metallothioneins (MTs) are cysteine-rich metal-binding proteins found in a wide variety of organisms including bacteria, fungi as well as all eukaryotic plant and animal species. MTs bind essential and nonessential heavy metals. MTs production was evaluated by a simple spectrophotometry methodology. The study elucidated that the metallothionein concentration in Bacillus cereus treated with different concentrations of lead increased with increasing lead concentration. The protein samples from B.cereus treated with different concentrations of lead were isolated and electrophoresed on SDS-PAGE and 2-D gels. The study of gels revealed that a thick protein band appeared around 14.3KD in case of B. cereus treated with lead unlike the control samples. © 2011 Academic Journals