408 research outputs found
Salinity tolerance and fishery of mud shrimp Solenocera crassicornis (H. Milne Edwards) in the coastal waters of Mumbai
Salinity tolerance of mud shrimp Solenocera crassicornis investigated at different salinities ranging
from 15‰ to 55‰ showed that shrimps in the salinity range 30‰ - 42‰ survived but those in lower and
higher salinities died soon after the transfer. Ionic concentration in the hemolymph and free amino acids
in the body muscle in response to different salinity ranges showed hypo-regulation initially but later
became hyposmotic to the medium and died eventually when the salinity decreased. The abundance of
shrimp showed inverse relationship with rainfall and consequent lowering of salinity in the inshore
waters. The study showed that S. crassicornis can regulate osmotic and ionic concentrations of body
fluids efficiently in the salinity range of 30 - 42‰ but unlike euryhaline penaeid shrimps it is a poor
regulator at lower salinities and therefore it migrates offshore during monsoon months
Gamma-radiation with E gamma 5 MeV detected from Seyfert galaxy 3C120 and region with 1" = 190 deg and b" = 20 deg
The observation of the Galaxy anticenter region in gamma-rays with E gamma = 5 / 100 MeV was made by gamma-telescope Natalya-1 in a balloon flight. The flight was performed at the ceiling 5.1 + or - 0.1 g/sq cm, magnetic cutoff being 17 GV. The description of the instrument and the analysis of the experiment conditions are given. The tracks of electron-positron pairs generated by gamma-quanta in the convertors were detected by wire spark chambers. The recorded events were classified manually by an operator using a graphic display into three classes: pairs, single and bad events. The arrival angle of gamma-quanta and their energy for selected gamma-ray events (pairs and singles) were determined through multiple scattering of pair components in the convertors. On the basis of the data obtained the celestial maps were made in gamma-rays for E sub gamma 5 MeV and E gamma 20 MeV energy ranges
Balloon observations of hard X-rays from NGC 4151 and an X-ray transient source
An X-ray telescope consisting of 400 sq cm phoswich detectors (NaI(Tl)/CsI(Na)) was flown from Hyderabad (India) on 31 October 1980; the field of view was 11 deg x 1 deg FWHM. During a five hour observation at 5 millibars two X-ray sources were seen: (1) the variable Seyfert Galaxy NGC 4151; and (2) a transident of approximately 8 minutes duration in the vicinity of the variable source 4U1444 43 which may be associated with the galaxy NGC 5608. X-ray fluxes and spectra in 18-120 keV X-rays are presented
Balloon observations of hard X-rays from some galactic X-ray sources
An X-ray telescope consisting of 400 cm phoswich detectors (NaI(T1)/CsI(Na)) was flown from Hyderabad (India) on 18 December 1984. The field of view was 5 deg x 5 deg FWHM. In a 10 hour float at 4 MB several galactic X-ray sources were tracked by the telescope using an on-board microprocessor. Fluxes and spectra in 18-120 keV X-rays for SCO X-1, GX 1+4, Gx 5-1, GX 17+2, SCT X-1, CYC X-1 an CYG X-3 will be presented
Non-equilibrium Gross-Pitaevskii dynamics of boson lattice models
Motivated by recent experiments on trapped ultra-cold bosonic atoms in an
optical lattice potential, we consider the non-equilibrium dynamic properties
of such bosonic systems for a number of experimentally relevant situations.
When the number of bosons per lattice site is large, there is a wide parameter
regime where the effective boson interactions are strong, but the ground state
remains a superfluid (and not a Mott insulator): we describe the conditions
under which the dynamics in this regime can be described by a discrete
Gross-Pitaevskii equation. We describe the evolution of the phase coherence
after the system is initially prepared in a Mott insulating state, and then
allowed to evolve after a sudden change in parameters places it in a regime
with a superfluid ground state. We also consider initial conditions with a "pi
phase" imprint on a superfluid ground state (i.e. the initial phases of
neighboring wells differ by pi), and discuss the subsequent appearance of
density wave order and "Schrodinger cat" states.Comment: 16 pages, 11 figures; (v2) added reference
Electrostatic potential profiles of molecular conductors
The electrostatic potential across a short ballistic molecular conductor
depends sensitively on the geometry of its environment, and can affect its
conduction significantly by influencing its energy levels and wave functions.
We illustrate some of the issues involved by evaluating the potential profiles
for a conducting gold wire and an aromatic phenyl dithiol molecule in various
geometries. The potential profile is obtained by solving Poisson's equation
with boundary conditions set by the contact electrochemical potentials and
coupling the result self-consistently with a nonequilibrium Green's function
(NEGF) formulation of transport. The overall shape of the potential profile
(ramp vs. flat) depends on the feasibility of transverse screening of electric
fields. Accordingly, the screening is better for a thick wire, a multiwalled
nanotube or a close-packed self-assembled monolayer (SAM), in comparison to a
thin wire, a single-walled nanotube or an isolated molecular conductor. The
electrostatic potential further governs the alignment or misalignment of
intramolecular levels, which can strongly influence the molecular I-V
characteristic. An external gate voltage can modify the overall potential
profile, changing the current-voltage (I-V) characteristic from a resonant
conducting to a saturating one. The degree of saturation and gate modulation
depends on the metal-induced-gap states (MIGS) and on the electrostatic gate
control parameter set by the ratio of the gate oxide thickness to the channel
length.Comment: to be published in Phys. Rev. B 69, No.3, 0353XX (2004
Multicritical crossovers near the dilute Bose gas quantum critical point
Many zero temperature transitions, involving the deviation in the value of a
conserved charge from a quantized value, are described by the dilute
Bose gas quantum critical point. On such transitions, we study the consequences
of perturbations which break the symmetry down to in spatial
dimensions. For the case , , we obtain exact, finite temperature,
multicritical crossover functions by a mapping to an integrable lattice model.Comment: 10 pages, REVTEX 3.0, 2 EPS figure
Scaling and thermodynamics of a trapped Bose-condensed gas
We investigate the thermodynamics of a Bose gas interacting with repulsive
forces and confined in a harmonic trap. We show that the relevant parameters of
the system (temperature, number N of atoms, harmonic oscillator length,
deformation of the trap, s-wave scattering length) fix its large N
thermodynamic behaviour through two dimensionless scaling parameters. These are
the reduced temperature t=T/T^0_c and the ratio \eta between the T=0 value of
the chemical potential, evaluated in the Thomas-Fermi limit, and the critical
temperature T_c^0 of the non-interacting model. The scaling functions relative
to the condensate fraction, energy, chemical potential and moment of inertia
are calculated within the Popov approximation.Comment: 10 pages, REVTEX, 5 figures, also available at
http://anubis.science.unitn.it/~oss/bec/BEC.htm
Fast, broad-band magnetic resonance spectroscopy with diamond widefield relaxometry
We present an alternative to conventional Electron Paramagnetic Resonance
spectroscopy equipment. Avoiding the use of bulky magnets and magnetron
equipment, we use the photoluminescence of an ensemble of Nitrogen-Vacancy
centers at the surface of a diamond. Monitoring their relaxation time (or T1),
we detected their cross-relaxation with the compound of interest. In addition,
the EPR spectra is encoded through a localized magnetic field gradient. While
12 minutes was necessary to record each data point of the spectrum with
previous individual NV center's technics, we are able to reconstruct a full
spectrum at once in 3 seconds, over a range from 3 to 11 gauss. In term of
sensitivity, only 0.5 microliter of a hexaaquacopper (II) ion solution with 1
micromole per liter concentration was necessary.Comment: Main text (15 pages, 6 Figures) + Supplementary (6 Pages, 7 Figures
Fluctuation Conductivity in Insulator-Superconductor Transitions with Dissipation
We analyze here the fluctuation conductivity in the vicinity of the critical
point in a 2D Josephson junction array shunted by an Ohmic resistor.We find
that at the Gaussian level, the conductivity acquires a logarithmic dependence
on when the dissipation is sufficiently small. In the renormalized
classical regime, this logarithmic dependence gives rise to a leveling-off of
the resistivity at low to intermediate temperatures when fluctuations are
included. We show, however, that this trend does not persist to T=0 at which
point the resistivity vanishes. The possible relationship of the leveling of
the resistivity to the low temperature transport in granlar superconductors is
discussed.Comment: 4 page
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