7,291 research outputs found
Domain Growth in Random Magnets
We study the kinetics of domain growth in ferromagnets with random exchange
interactions. We present detailed Monte Carlo results for the nonconserved
random-bond Ising model, which are consistent with power-law growth with a
variable exponent. These results are interpreted in the context of disorder
barriers with a logarithmic dependence on the domain size. Further, we clarify
the implications of logarithmic barriers for both nonconserved and conserved
domain growth.Comment: 7 pages, 4 figure
Crossover in Growth Law and Violation of Superuniversality in the Random Field Ising Model
We study the nonconserved phase ordering dynamics of the d = 2, 3 random
field Ising model, quenched to below the critical temperature. Motivated by the
puzzling results of previous work in two and three di- mensions, reporting a
crossover from power-law to logarithmic growth, together with superuniversal
behavior of the correlation function, we have undertaken a careful
investigation of both the domain growth law and the autocorrelation function.
Our main results are as follows: We confirm the crossover to asymptotic
logarithmic behavior in the growth law, but, at variance with previous
findings, the exponent in the preasymptotic power law is disorder-dependent,
rather than being the one of the pure system. Furthermore, we find that the
autocorre- lation function does not display superuniversal behavior. This
restores consistency with previous results for the d = 1 system, and fits
nicely into the unifying scaling scheme we have recently proposed in the study
of the random bond Ising model.Comment: To be published in Physical Review
Spinodal Decomposition in Thin Films: Molecular Dynamics Simulations of a Binary Lennard-Jones Fluid Mixture
We use molecular dynamics (MD) to simulate an unstable homogeneous mixture of
binary fluids (AB), confined in a slit pore of width . The pore walls are
assumed to be flat and structureless, and attract one component of the mixture
(A) with the same strength. The pair-wise interactions between the particles is
modeled by the Lennard-Jones potential, with symmetric parameters that lead to
a miscibility gap in the bulk. In the thin-film geometry, an interesting
interplay occurs between surface enrichment and phase separation.
We study the evolution of a mixture with equal amounts of A and B, which is
rendered unstable by a temperature quench. We find that A-rich surface
enrichment layers form quickly during the early stages of the evolution,
causing a depletion of A in the inner regions of the film. These
surface-directed concentration profiles propagate from the walls towards the
center of the film, resulting in a transient layered structure. This layered
state breaks up into a columnar state, which is characterized by the lateral
coarsening of cylindrical domains. The qualitative features of this process
resemble results from previous studies of diffusive Ginzburg-Landau-type models
[S.~K. Das, S. Puri, J. Horbach, and K. Binder, Phys. Rev. E {\bf 72}, 061603
(2005)], but quantitative aspects differ markedly. The relation to spinodal
decomposition in a strictly 2- geometry is also discussed.Comment: 37 pages, 11 figures, to appear in Phys. Rev.
Investigating the ‘mission and profit’ paradox: Case study of an ecopreneurial organisation in India
Based on a case study of a waste management services provider in India, this paper sets out to investigate how an ecopreneurial organisation balances the competing demands of environmental mission and profit generation. Results indicate that two internal organisational mechanisms, namely Leadership, and Organisational Processes, are instrumental in achieving the dual goals. The paper highlights the role of contextual factors in supporting such organisations, and in doing so, it responds to the call for research to examine social entrepreneurship in wider contexts including Asia, Latin America, and Africa, to address ‘marginalisation’ of studies in the field
The study of multifragmentation around transition energy in intermediate energy heavy-ion collisions
Fragmentation of light charged particles is studied for various systems at
different incident energies between 50 and 1000 MeV/nucleon. We analyze
fragment production at incident energies above, below and at transition
energies using the isospin dependent quantum molecular dynamics(IQMD) model.
The trends observed for the fragment production and rapidity distributions
depend upon the incident energy, size of the fragments, composite mass of the
reacting system as well as on the impact parameter of the reaction. The free
nucleons and light charged particles show continous homogeneous changes
irrespective of the transition energies indicating that there is no relation
between the transition energy and production of the free as well as light
charged particles
Scaling Behavior of Response Functions in the Coarsening Dynamics of Disordered Ferromagnets
We study coarsening dynamics in the ferromagnetic random bond Ising model in
d = 1; 2. We focus on the validity of super-universality and the scaling
properties of the response functions. In the d = 1 case, we obtain a complete
understanding of the evolution, from pre- asymptotic to asymptotic behavior.
The corresponding response function shows a clear violation of
super-universality. Further, our results for d = 1; 2 settle the controversy
regarding the decay exponent which characterizes the response function
Phase separation driven by surface diffusion: a Monte Carlo study
We propose a kinetic Ising model to study phase separation driven by surface
diffusion. This model is referred to as "Model S", and consists of the usual
Kawasaki spin-exchange kinetics ("Model B") in conjunction with a kinetic
constraint. We use novel multi-spin coding techniques to develop fast
algorithms for Monte Carlo simulations of Models B and S. We use these
algorithms to study the late stages of pattern dynamics in these systems.Comment: 25 pages, 9 figure
Circulating nucleic acids as a diagnostic and prognostic marker in various malignant and benign diseases
Elevated levels of circulating nucleic acids have been found in a variety of benign and malignant pathological conditions. The ability to detect and quantitate specific DNA, RNA and micro-RNA sequences in serum/ plasma has opened up the possibilities of non-invasive diagnosis and monitoring of diseases. Circulating nucleic acids have now been shown to be useful in other conditions, such as diabetes mellitus, stroke and myocardial infarction. Plasma DNA is already in use for fetal blood group typing in many countries.With the rapid development in molecular biology techniques the application of circulating nucleic acids in diagnostics especially in cancer and prenatal diagnosis is expected to be revolutionized
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