4,434 research outputs found
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
Use of epoxysepharose for protein immobilisation
Epoxy Sepharose, an activated affinity matrix which has been used for immobilisation of carbohydrates has been tried for immobilisation of proteins. Under normal conditions of coupling at neutral or alkaline pH proteins do not couple to epoxy Sepharose. However, a very high salt concentration during coupling allows the binding of proteins to epoxy Sepharose at a pH as low as 8.5. Increasing ionic strength and/or pH facilitates the binding. The bioactivity of the proteins is not destroyed by the immobilisation. This matrix, unlike cyanogen bromide-Sepharose, retains its ability to bind albumin by 80-90% even after 60 days of storage in aqueous suspension at 4°C. Its capacity to bind proteins is comparable to that of cyanogen bromide-Sepharose
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.
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
Finite Temperature Magnetism in Fractional Quantum Hall Systems: Composite Fermion Hartree-Fock and Beyond
Using the Hamiltonian formulation of Composite Fermions developed recently,
the temperature dependence of the spin polarization is computed for the
translationally invariant fractional quantum Hall states at and
in two steps. In the first step, the effect of particle-hole
excitations on the spin polarization is computed in a Composite Fermion
Hartree-Fock approximation. The computed magnetization for lies above
the experimental results for intermediate temperatures indicating the
importance of long wavelength spin fluctuations which are not correctly treated
in Hartree-Fock. In the second step, spin fluctuations beyond Hartree-Fock are
included for by mapping the problem on to the coarse-grained
continuum quantum ferromagnet. The parameters of the effective continuum
quantum ferromagnet description are extracted from the preceding Hartree-Fock
analysis. After the inclusion of spin fluctuations in a large-N approach, the
results for the finite-temperature spin polarization are in quite good
agreement with the experiments.Comment: 10 pages, 8 eps figures. Two references adde
Radioimmunoassay of polypeptide hormones using immunochemically coated plastic tubes
A method has been developed for immobilisation of antisera on fresh plastic tubes through an immunochemical bridge. This type of immobilisation has been shown to be more consistent than direct adsorption on plastic. Such immunochemically coated antisera on plastic tube has been used in the development of a noncentrifugation radioimmunoassay. This assay system has been found to be technically as sound as the conventional method
Magnetic phenomena at and near nu =1/2 and 1/4: theory, experiment and interpretation
I show that the hamiltonian theory of Composite Fermions (CF) is capable of
yielding a unified description in fair agreement with recent experiments on
polarization P and relaxation rate 1/T_1 in quantum Hall states at filling nu =
p/(2ps+1), at and near nu = 1/2 and 1/4, at zero and nonzero temperatures. I
show how rotational invariance and two dimensionality can make the underlying
interacting theory behave like a free one in a limited context.Comment: Latex 4 pages, 2 figure
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