710 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
Quantum Fluctuations of Radiation Pressure
Quantum fluctuations of electromagnetic radiation pressure are discussed. We
use an approach based on the quantum stress tensor to calculate the
fluctuations in velocity and position of a mirror subjected to electromagnetic
radiation. Our approach reveals that radiation pressure fluctuations are due to
a cross term between vacuum and state dependent terms in a stress tensor
operator product. Thus observation of these fluctuations would entail
experimental confirmation of this cross term. We first analyze the pressure
fluctuations on a single, perfectly reflecting mirror, and then study the case
of an interferometer. This involves a study of the effects of multiple bounces
in one arm, as well as the correlations of the pressure fluctuations between
arms of the interferometer. In all cases, our results are consistent with those
previously obtained by Caves using different mehods.Comment: 23 pages, 3 figures, RevTe
Gravitons and Lightcone Fluctuations
Gravitons in a squeezed vacuum state, the natural result of quantum creation
in the early universe or by black holes, will introduce metric fluctuations.
These metric fluctuations will introduce fluctuations of the lightcone. It is
shown that when the various two-point functions of a quantized field are
averaged over the metric fluctuations, the lightcone singularity disappears for
distinct points. The metric averaged functions remain singular in the limit of
coincident points. The metric averaged retarded Green's function for a massless
field becomes a Gaussian which is nonzero both inside and outside of the
classical lightcone. This implies some photons propagate faster than the
classical light speed, whereas others propagate slower. The possible effects of
metric fluctuations upon one-loop quantum processes are discussed and
illustrated by the calculation of the one-loop electron self-energy.Comment: 18pp, LATEX, TUTP-94-1
Solar Neutrinos: What We Have Learned
The four operating solar neutrino experiments confirm the hypothesis that the
energy source for solar luminosity is hydrogen fusion. However, the measured
rate for each of the four solar neutrino experiments differs significantly (by
factors of 2.0 to 3.5) from the corresponding theoretical prediction that is
based upon the standard solar model and the simplest version of the standard
electroweak theory. If standard electroweak theory is correct, the energy
spectrum for \b8 neutrinos created in the solar interior must be the same (to
one part in ) as the known laboratory \b8 neutrino energy spectrum.
Direct comparison of the chlorine and the Kamiokande experiments, both
sensitive to \b8 neutrinos, suggests that the discrepancy between theory and
observations depends upon neutrino energy, in conflict with standard
expectations. Monte Carlo studies with 1000 implementations of the standard
solar model confirm that the chlorine and the Kamiokande experiments cannot be
reconciled unless new weak interaction physics changes the shape of the \b8
neutrino energy spectrum. The results of the two gallium solar neutrino
experiments strengthen the conclusion that new physics is required and help
determine a relatively small allowed region for the MSW neutrino parameters.Comment: LaTeX file, 19 pages. For hardcopy with figures contact
[email protected]. Institute for Advanced Study number AST 93/6
Evidence of Final-State Suppression of High-p_T Hadrons in Au + Au Collisions Using d + Au Measurements at RHIC
Transverse momentum spectra of charged hadrons with 6 GeV/c have
been measured near mid-rapidity (0.2 1.4) by the PHOBOS experiment
at RHIC in Au + Au and d + Au collisions at . The spectra for different collision centralities are compared to collisions at the same energy. The resulting nuclear modification
factor for central Au + Au collisions shows evidence of strong suppression of
charged hadrons in the high- region ( GeV/c). In contrast, the d +
Au nuclear modification factor exhibits no suppression of the high-
yields. These measurements suggest a large energy loss of the high-
particles in the highly interacting medium created in the central Au + Au
collisions. The lack of suppression in d + Au collisions suggests that it is
unlikely that initial state effects can explain the suppression in the central
Au + Au collisions.Comment: 3 pages, 4 figures, International Europhysics Conference on High
Energy Physics EPS (July 17th-23rd 2003) in Aachen, German
Identified particles in Au+Au collisions at sqrt{s_NN} = 200 GeV
The yields of identified particles have been measured at RHIC for Au+Au
collisions at sqrt{s_NN} = 200 GeV using the PHOBOS spectrometer. The ratios of
antiparticle to particle yields near mid-rapidity are presented. The first
measurements of the invariant yields of charged pions, kaons and protons at
very low transverse momenta are also shown.Comment: 4 pages, 4 figures, Contribution to Quark Matter 2002, Nantes,
France, July 200
Model Independent Information On Solar Neutrino Oscillations
We present the results of a Bayesian analysis of solar neutrino data in terms
of nu_e->nu_{mu,tau} oscillations, independent from the Standard Solar Model
predictions for the solar neutrino fluxes. We show that such a model
independent analysis allows to constraint the values of the neutrino mixing
parameters in limited regions around the usual SMA, LMA, LOW and VO regions.
Furthermore, there is a strong indication in favor of large neutrino mixing and
large values of Delta m^2 (LMA region). We calculate also the allowed ranges of
the neutrino fluxes and we show that they are in good agreement with the
Standard Solar Model prediction. In particular, the ratio of the 8B flux with
its Standard Solar Model prediction is constrained in the interval [0.45,1.42]
with 99.73% probability. Finally, we show that the hypothesis of no neutrino
oscillations is strongly disfavored in a model independent way with respect to
the hypothesis of neutrino oscillations.Comment: 40 pages, 20 figures. Added references and improved figure
Universal Behavior of Charged Particle Production in Heavy Ion Collisions
The PHOBOS experiment at RHIC has measured the multiplicity of primary
charged particles as a function of centrality and pseudorapidity in Au+Au
collisions at sqrt(s_NN) = 19.6, 130 and 200 GeV. Two kinds of universal
behavior are observed in charged particle production in heavy ion collisions.
The first is that forward particle production, over a range of energies,
follows a universal limiting curve with a non-trivial centrality dependence.
The second arises from comparisons with pp/pbar-p and e+e- data.
N_tot/(N_part/2) in nuclear collisions at high energy scales with sqrt(s) in a
similar way as N_tot in e+e- collisions and has a very weak centrality
dependence. This feature may be related to a reduction in the leading particle
effect due to the multiple collisions suffered per participant in heavy ion
collisions.Comment: 4 Pages, 5 Figures, contributed to the Proceedings of Quark Matter
2002, Nantes, France, 18-24 July 200
Recent Results from PHOBOS at RHIC
The PHOBOS experiment at RHIC has recorded measurements for Au-Au collisions
spanning nucleon-nucleon center-of-mass energies from 19.6 GeV to 200 GeV.
Global observables such as elliptic flow and charged particle multiplicity
provide important constraints on model predictions that characterize the state
of matter produced in these collisions. The nearly 4 pi acceptance of the
PHOBOS experiment provides excellent coverage for complete flow and
multiplicity measurements. Results including beam energy and centrality
dependencies are presented and compared to elementary systems.Comment: 4 pages, 4 figures, proceedings from PANIC02 in Osaka, Japa
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