1,566 research outputs found
Surface crossover exponent for branched polymers in two dimensions
Transfer-matrix methods on finite-width strips with free boundary conditions
are applied to lattice site animals, which provide a model for randomly
branched polymers in a good solvent. By assigning a distinct fugacity to sites
along the strip edges, critical properties at the special (adsorption) and
ordinary transitions are assessed. The crossover exponent at the adsorption
point is estimated as , consistent with recent
predictions that exactly for all space dimensionalities.Comment: 10 pages, LaTeX with Institute of Physics macros, to appear in
Journal of Physics
Kosterlitz-Thouless transition in three-state mixed Potts ferro-antiferromagnets
We study three-state Potts spins on a square lattice, in which all bonds are
ferromagnetic along one of the lattice directions, and antiferromagnetic along
the other. Numerical transfer-matrix are used, on infinite strips of width
sites, . Based on the analysis of the ratio of scaled mass
gaps (inverse correlation lengths) and scaled domain-wall free energies, we
provide strong evidence that a critical (Kosterlitz-Thouless) phase is present,
whose upper limit is, in our best estimate, . From analysis
of the (extremely anisotropic) nature of excitations below , we argue that
the critical phase extends all the way down to T=0. While domain walls parallel
to the ferromagnetic direction are soft for the whole extent of the critical
phase, those along the antiferromagnetic direction seem to undergo a softening
transition at a finite temperature. Assuming a bulk correlation length varying,
for , as , , we attempt finite-size scaling plots of our finite-width
correlation lengths. Our best results are for . We propose a
scenario in which such inconsistency is attributed to the extreme narrowness of
the critical region.Comment: 11 pages, 6 .eps figures, LaTeX with IoP macros, to be published in J
Phys
Chromosome instability in intergeneric hybrids of Triticum aestivum;× tritordeum (amphiploid Hordeum chilense×Triticum turgidum) with high dosage of Ph1 gene of wheat
In somatic cells of intergencric hybrids Truicum uestirum (mono-isosomic 5BL, 2n=6x=4f)x trinordum 12n = 6x = 42, amphiploid Hordeum clulense x Triticum turgidnm)it was observed that high dosage of the long arm of 5B induced chromosome instability in hybrids 2n=42, in hybrids 2n=41 with only one dose of 5BL from the normal 5B genome of the teteaploed wheat, all cells have consistently 2n=41 chromosomes and no rmal 5B genome of the tetraploid wheat all cells have consistently 2n=41 plant differenttation in plants with 2n=42 which carry three doses of 5BL (one isochromosome 5BL and one 5B chromosome)most of the metaphase cells had 2n=42 chromosomes. However other cells in a reasonable frequency varying from 19% to 40% carried from 2n=6 to 2n=44. and showed marked desturbances in all phases of the cell cycle leading to final failure in plant development. It is suggested that the Ph1 geng of wheat. Located on 5BL regulates chromosome stability in the somatic cells of those hybrids
Pair of Heavy-Exotic-Quarks at LHC
We study the production and signatures of heavy exotic quarks pairs at LHC in
the framework of the vector singlet model (VSM), vector doublet model (VDM) and
fermion-mirror-fermion (FMF) model. The pair production cross sections for the
electroweak and strong sector are computed.Comment: 7 pages, 6 figures. accept at Int. Jour. of Mod. Phy
On surface properties of two-dimensional percolation clusters
The two-dimensional site percolation problem is studied by transfer-matrix
methods on finite-width strips with free boundary conditions. The relationship
between correlation-length amplitudes and critical indices, predicted by
conformal invariance, allows a very precise determination of the surface
decay-of-correlations exponent, , consistent with
the analytical value . It is found that a special transition does
not occur in the case, corroborating earlier series results. At the ordinary
transition, numerical estimates are consistent with the exact value
for the irrelevant exponent.Comment: 8 pages, LaTeX with Institute of Physics macros, to appear in Journal
of Physics
Domain scaling and marginality breaking in the random field Ising model
A scaling description is obtained for the --dimensional random field Ising
model from domains in a bar geometry. Wall roughening removes the marginality
of the case, giving the correlation length in , and for power law behaviour with
, . Here, (lattice, continuum) is one of four rough wall exponents provided by the
theory. The analysis is substantiated by three different numerical techniques
(transfer matrix, Monte Carlo, ground state algorithm). These provide for
strips up to width basic ingredients of the theory, namely free energy,
domain size, and roughening data and exponents.Comment: ReVTeX v3.0, 19 pages plus 19 figures uuencoded in a separate file.
These are self-unpacking via a shell scrip
Boundary critical behaviour of two-dimensional random Ising models
Using Monte Carlo techniques and a star-triangle transformation, Ising models
with random, 'strong' and 'weak', nearest-neighbour ferromagnetic couplings on
a square lattice with a (1,1) surface are studied near the phase transition.
Both surface and bulk critical properties are investigated. In particular, the
critical exponents of the surface magnetization, 'beta_1', of the correlation
length, 'nu', and of the critical surface correlations, 'eta_{\parallel}', are
analysed.Comment: 16 pages in ioplppt style, 7 ps figures, submitted to J. Phys.
Dietary supplementation of heat-treated Gracilaria and Ulva seaweeds enhanced acute hypoxia tolerance in gilthead sea bream (Sparus aurata)
Intensive aquaculture practices involve rearing fish at high densities. In these conditions, fish may be exposed to suboptimal dissolved O2 levels with an increased formation of reactive O2 species (ROS) in tissues. Seaweeds (SW) contain biologically active substances with efficient antioxidant capacities. This study evaluated the effects of dietary supplementation of heat-treated SW (5% Gracilaria vermiculophylla or 5% Ulva lactuca) on stress bioindicators in sea bream subjected to a hypoxic challenge. 168 fish (104.5 g average weight) were distributed in 24 tanks, in which eight tanks were fed one of three experimental diets for 34 days: (i) a control diet without SW supplementation, (ii) a control diet supplemented with Ulva, or (iii) a control diet with Gracilaria. Thereafter, fish from 12 tanks (n=4 tanks/dietary treatment) were subjected to 24 h hypoxia (1.3 mg O2 l-1) and subsequent recovery normoxia (8.6 mg O2 l-1). Hypoxic fish showed an increase in hematocrit values regardless of dietary treatment. Dietary modulation of the O2-carrying capacity was conspicuous during recovery, as fish fed SW supplemented diets displayed significantly higher haemoglobin concentration than fish fed the control diet. After the challenge, survival rates in both groups of fish fed SW were higher, which was consistent with a decrease in hepatic lipid peroxidation in these groups. Furthermore, the hepatic antioxidant enzyme activities were modulated differently by changes in environmental O2 condition, particularly in sea bream fed the Gracilaria diet. After being subjected to hypoxia, the gene expression of antioxidant enzymes and molecular chaperones in liver and heart were down regulated in sea bream fed SW diets. This study suggests that the antioxidant properties of heat-treated SW may have a protective role against oxidative stress. The nature of these compounds and possible mechanisms implied are currently being investigated.Fil: Magnoni, Leonardo Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentina. Universidad de Porto; PortugalFil: Martos Sitcha, Juan Antonio. Consejo Superior de Investigaciones Científicas; EspañaFil: Queiroz, Augusto. Universidad de Porto; PortugalFil: Calduch Giner, Josep Alvar. Consejo Superior de Investigaciones Científicas; EspañaFil: Magalhaes Gonçalves, Jose Fernando. Universidad de Porto; PortugalFil: Rocha, Cristina M.R.. Universidad de Porto; PortugalFil: Abreu, Helena T.. ALGAplus; PortugalFil: Schrama, Johan W.. Wageningen University; Países BajosFil: Ozorio, Rodrigo O.A.. Universidad de Porto; PortugalFil: Perez Sanchez, Jaume. Consejo Superior de Investigaciones Científicas; Españ
Evaluación de accesiones de calabaza para características agronómicas y nutricionales - ciclo II.
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