3,027 research outputs found
Experimental rearing of Nile tilapia fry (Oreochromis niloticus) for saltwater culture
Represents a preliminary evaluation of the utility of various approaches of early salinity exposure for saltwater culture of tilapias. Studies the reproductive performance of Nile tilapia under laboratory conditions at various salinities; salinity tolerance of progeny; survivorship of fertilized eggs, spawned in freshwater but removed from the mouth of the parent female and artificially incubated at various salinities.Rearing, Experimental culture, Tilapia culture, Salinity tolerance, Salinity effects Oreochromis niloticus
Salinity tolerance of the tilapias Oreochromis aureus, O. niloticus and an O. mossambicus X O. niloticus hybrid
Studies ontogenetic changes in salinity tolerance in tilapias spawned and reared in freshwater using the indices of median lethal salinity, mean survival time and median survival time. Discusses implications of findings for brackish - and seawater culture of tilapias.Salinity tolerance, Hybrids, Tilapia Oreochromis aureus, Oreochromis niloticus, Oreochromis mossambicus
Electronic damping of molecular motion at metal surfaces
A method for the calculation of the damping rate due to electron-hole pair
excitation for atomic and molecular motion at metal surfaces is presented. The
theoretical basis is provided by Time Dependent Density Functional Theory
(TDDFT) in the quasi-static limit and calculations are performed within a
standard plane-wave, pseudopotential framework. The artificial periodicity
introduced by using a super-cell geometry is removed to derive results for the
motion of an isolated atom or molecule, rather than for the coherent motion of
an ordered over-layer. The algorithm is implemented in parallel, distributed
across both and space, and in a form compatible with the
CASTEP code. Test results for the damping of the motion of hydrogen atoms above
the Cu(111) surface are presented.Comment: 10 pages, 3 figure
Nonlinear Modulation of Multi-Dimensional Lattice Waves
The equations governing weakly nonlinear modulations of -dimensional
lattices are considered using a quasi-discrete multiple-scale approach. It is
found that the evolution of a short wave packet for a lattice system with cubic
and quartic interatomic potentials is governed by generalized Davey-Stewartson
(GDS) equations, which include mean motion induced by the oscillatory wave
packet through cubic interatomic interaction. The GDS equations derived here
are more general than those known in the theory of water waves because of the
anisotropy inherent in lattices. Generalized Kadomtsev-Petviashvili equations
describing the evolution of long wavelength acoustic modes in two and three
dimensional lattices are also presented. Then the modulational instability of a
-dimensional Stokes lattice wave is discussed based on the -dimensional
GDS equations obtained. Finally, the one- and two-soliton solutions of
two-dimensional GDS equations are provided by means of Hirota's bilinear
transformation method.Comment: Submitted to PR
Evolution of Non-Equilibrium Profile in Adsorbate Layer under Compressive Strain
We investigate the time evolution of an initial step profile separating a
bare substrate region from the rest of the compressively strained adsorbate
layer near a commensurate to incommensurate transition. The rate of profile
evolution as a function of the mismatch, coverage and the strength of the
substrate potential are determined by Brownian molecular dynamics simulations.
We find that the results are qualitatively similar to those observed for the
Pb/Si(111) system. The anomalously fast time evolution and sharpness of the
non-equilibrium profile can be understood through the domain wall creation at
the boundary and its subsequent diffusion into the interior of the adsorbate
layer.Comment: 6 pages, 7 figures, Tribology Letter
LES of non-Newtonian physiological blood flow in a model of arterial stenosis
Large Eddy Simulation (LES) is performed to study the physiological pulsatile transition-to-turbulent non-Newtonian blood flow through a 3D model of arterial stenosis by using five different blood viscosity models: (i) Power-law, (ii) Carreau, (iii) Quemada, (iv) Cross and (v) modified-Casson. The computational domain has been chosen is a simple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the first four harmonic series of the physiological pressure pulse (Loudon and Tordesillas [1]). The effects of the various viscosity models are investigated in terms of the global maximum shear rate, post-stenotic re-circulation zone, mean shear stress, mean pressure, and turbulent kinetic energy. We find that the non-Newtonian viscosity models enlarge the length of the post-stenotic re-circulation region by moving the reattachment point of the shear layer separating from the upper wall further downstream. But the turbulent kinetic energy at the immediate post-lip of the stenosis drops due to the effects of the non-Newtonian viscosity. The importance of using LES in modelling the non-Newtonian physiological pulsatile blood flow is also assessed for the different viscosity models in terms of the results of the dynamic subgrid-scale (SGS) stress Smagorinsky model constant, C<sub>s</sub>, and the corresponding SGS normalised viscosity
A simple model for magnetism in itinerant electron systems
A new lattice model of interacting electrons is presented. It can be viewed
as a classical Hubbard model in which the energy associated to electron
itinerance is proportional to the total number of possible electron jumps.
Symmetry properties of the Hubbard model are preserved. In the half-filled band
with strong interaction the model becomes the Ising model. The main features of
the magnetic behavior of the model in the one-dimensional and mean-field cases
are studied.Comment: 9 pages, 3 figures, to be published in Physica
Distribution and density of the partition function zeros for the diamond-decorated Ising model
Exact renormalization map of temperature between two successive decorated
lattices is given, and the distribution of the partition function zeros in the
complex temperature plane is obtained for any decoration-level. The rule
governing the variation of the distribution pattern as the decoration-level
changes is given. The densities of the zeros for the first two
decoration-levels are calculated explicitly, and the qualitative features about
the densities of higher decoration-levels are given by conjecture. The Julia
set associated with the renormalization map is contained in the distribution of
the zeros in the limit of infinite decoration level, and the formation of the
Julia set in the course of increasing the decoration-level is given in terms of
the variations of the zero density.Comment: 8 pages,8figure
Continuous Monitoring of Dynamical Systems and Master Equations
We illustrate the equivalence between the non-unitary evolution of an open
quantum system governed by a Markovian master equation and a process of
continuous measurements involving this system. We investigate a system of two
coupled modes, only one of them interacting with external degrees of freedom,
represented, in the first case, by a finite number of harmonic oscillators,
and, in the second, by a sequence of atoms where each one interacts with a
single mode during a limited time. Two distinct regimes appear, one of them
corresponding to a Zeno-like behavior in the limit of large dissipation
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