11,591 research outputs found
Persistence of a Brownian particle in a Time Dependent Potential
We investigate the persistence probability of a Brownian particle in a
harmonic potential, which decays to zero at long times -- leading to an
unbounded motion of the Brownian particle. We consider two functional forms for
the decay of the confinement, an exponential and an algebraic decay. Analytical
calculations and numerical simulations show, that for the case of the
exponential relaxation, the dynamics of Brownian particle at short and long
times are independent of the parameters of the relaxation. On the contrary, for
the algebraic decay of the confinement, the dynamics at long times is
determined by the exponent of the decay. Finally, using the two-time
correlation function for the position of the Brownian particle, we construct
the persistence probability for the Brownian walker in such a scenario.Comment: 7 pages, 5 figures, Accepted for publication in Phys. Rev.
Global Persistence Exponent in Critical Dynamics: Finite Size induced Crossover
We extend the definition of a global order parameter to the case of a
critical system confined between two infinite parallel plates separated by a
finite distance . For a quench to the critical point we study the
persistence property of the global order parameter and show that there is a
crossover behaviour characterized by a non universal exponent which depends on
the ratio of the system size to a dynamic length scale
PGPR in Managing Root Rot Disease and Enhancing Growth in Mandarin (Citrus reticulata Blanco.) Seedlings
Decline in general plant-health and fruit production in mandarin influenced by abiotic and biotic factors is a major threat to cultivars grown in Darjeeling and Sikkim hills. Fusarium root rot, caused by F. oxysporum, is one of the most serious diseases afflicted during early plant growth stage in Citrus. To address this, seven PGPR isolates - Pseudomonas poae (RMK03), Bacillus stratosphericus (RHS/CL-01), Ochrobactrum anthropi, Paenibacillus lentimorbus, Bacillus pumilus, Bacillus megaterium and Bacillus amyloliquefaciens were isolated from the rhizosphere of Citrus reticulata, C. limonia and Camellia sinensis, and used for evaluating their effect on growth of mandarin seedlings. Pseudomonas poae showed in vitro antagonism to Fusarium oxysporum. Better growth enhancement was noticed with P. poae, B. stratosphericus, O. anthropi and B. pumilus. Enhanced activity of chlorophyll, total protein, phenol, four major defense enzymeschitinase, β-1, 3-glucanase, peroxidase and phenyalanine ammonia lyase was observed upon application of PGPR. P. poae also suppressed root rot caused by Fusarium oxysporum. Use of PGPR, which promote growth besides reducing disease severity to some extent, may lead to use of eco-friendly approaches for controlling plant diseases
Finite Size Effect in Persistence
We have investigated the random walk problem in a finite system and studied
the crossover induced in the the persistence probability scales by the system
size.Analytical and numerical work show that the scaling function is an
exponentially decaying function.The particle here is trapped with in a box of
size . We have also considered the problem when the particle in trapped in
a potential. Direct calculation and numerical result show that the scaling
function here also an exponentially decaying function. We also present
numerical works on harmonically trapped randomly accelerated particle and
randomly accelerated particle with viscous drag.Comment: revtex4, 4 pages, 4 figure
Temperature dependence of spin polarizations at higher Landau Levels
We report our results on temperature dependence of spin polarizations at
in the lowest as well as in the next higher Landau level that compare
well with recent experimental results. At , except having a much smaller
magnitude the behavior of spin polarization is not much influenced by higher
Landau levels. In sharp contrast, for filling factor we predict
that unlike the case of the system remains fully spin polarized
even at vanishingly small Zeeman energies.Comment: 4 pages, REVTEX, and 3 .ps files, To be published in Physical Review
Letter
On the Complexity of Temporal-Logic Path Checking
Given a formula in a temporal logic such as LTL or MTL, a fundamental problem
is the complexity of evaluating the formula on a given finite word. For LTL,
the complexity of this task was recently shown to be in NC. In this paper, we
present an NC algorithm for MTL, a quantitative (or metric) extension of LTL,
and give an NCC algorithm for UTL, the unary fragment of LTL. At the time of
writing, MTL is the most expressive logic with an NC path-checking algorithm,
and UTL is the most expressive fragment of LTL with a more efficient
path-checking algorithm than for full LTL (subject to standard
complexity-theoretic assumptions). We then establish a connection between LTL
path checking and planar circuits, which we exploit to show that any further
progress in determining the precise complexity of LTL path checking would
immediately entail more efficient evaluation algorithms than are known for a
certain class of planar circuits. The connection further implies that the
complexity of LTL path checking depends on the Boolean connectives allowed:
adding Boolean exclusive or yields a temporal logic with P-complete
path-checking problem
Persistence in Advection of Passive Scalar
We consider the persistence phenomenon in advectecd passive scalar equation
in 1-dimension. The velocity field is random with the
. In presence of the
non-linearity the complete Green's function becomes
. We determine self-consistently from the
correlation function which gives , with
. The effect of the non-linear term in the equation in the
is to replace the diffusion term due to molecular
viscosity by an effective term of the form . The stationary
correlator for this system is . Using the
self-consistent theory we have determined the relation between and
. Finally, IIA is used to determine the persistent exponent.Comment: 4 page
Reduction of Chromite ore at different flow rates of inert gas
Pre-reduction of chromite outside the submerged-arc furnace(SAF) can significantly lower the specific power
consumption in the SAF process. Conventional processes for the pre-reduction of the ore operate at relatively
high temperatures, at 1400-1500°C. It is possible to enhance the rate of reduction at low temperatures by optimizing the flow rate of inert gas over the reaction site. The influence of the flow rate of inert gas on the rate
of reduction of chromite ore was investigated. The rate of reduction initially decreased wit the flow rate of the
gas. It increased subsequently at higher flow rates to be followed by a decrease again. There was an optimum
flow rate at which maximum reduction could be obtained. It was possible to achieve high levels of reduction
at 1200°C by optimising the flow rate of the gas. The degree of reduction obtained was comparable to that
obtained at 1400-1500°C, by conventional process routes
High-spin structure and Band Termination in Cd
Excited states of the neutron deficient Cd nucleus have been
investigated via the Ge(Cl, p3n) reaction at beam energy of 135
MeV by use of in-beam spectroscopic methods. Gamma rays depopulating the
excited states were detected using the Gammasphere spectrometer with high-fold
-ray coincidences. A quadrupole -ray coincidence analysis
() has been used to extend the known level scheme. The positive
parity levels have been established up to and
MeV. In addition to the observation of highly-fragmented level scheme belonging
to the positive-parity sequences at E 5 MeV, the termination of a
negative-parity sequence connected by transitions has been established at
and MeV. The experimental results
corresponding to both the positive- and negative-parity sequences have been
theoretically interpreted in the framework of the core particle coupling model.
Evidence is presented for a shape change from collective prolate to
non-collective oblate above the (8011 keV) level and for a
smooth termination of the negative-parity band.Comment: 19 pages, 8 figures. Submitted to Phys. Rev.
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