756 research outputs found
Evolution of induced axial magnetization in a two-component magnetized plasma
In this paper, the evolution of the induced axial magnetization due to the
propagation of an electromagnetic (em) wave along the static background
magnetic field in a two-component plasma has been investigated using the Block
equation. The evolution process induces a strong magnetic anisotropy in the
plasma medium, depending nonlinearly on the incident wave amplitude. This
induced magnetic anisotropy can modify the dispersion relation of the incident
em wave, which has been obtained in this paper. In the low frequency Alfven
wave limit, this dispersion relation shows that the resulting phase velocity of
the incident wave depends on the square of the incident wave amplitude and on
the static background magnetic field of plasma. The analytical results are in
well agreement with the numerically estimated values in solar corona and
sunspots.Comment: 7 pages, 1 figur
Relativistic semiclassical approach in strong-field nonlinear photoionization
Nonlinear relativistic ionization phenomena induced by a strong laser
radiation with elliptically polarization are considered. The starting point is
the classical relativistic action for a free electron moving in the
electromagnetic field created by a strong laser beam. The application of the
relativistic action to the classical barrier-suppression ionization is briefly
discussed. Further the relativistic version of the Landau-Dykhne formula is
employed to consider the semiclassical sub-barrier ionization. Simple
analytical expressions have been found for: (i) the rates of the strong-field
nonlinear ionization including relativistic initial and final state effects;
(ii) the most probable value of the components of the photoelectron final state
momentum; (iii) the most probable direction of photoelectron emission and (iv)
the distribution of the photoelectron momentum near its maximum value.Comment: 13 pages, 3 figures, to be published in Phys. Rev.
Relativistic photoelectron spectra in the ionization of atoms by elliptically polarized light
Relativistic tunnel ionization of atoms by intense, elliptically polarized
light is considered. The relativistic version of the Landau-Dykhne formula is
employed. The general analytical expression is obtained for the relativistic
photoelectron spectra. The most probable angle of electron emission, the
angular distribution near this angle, the position of the maximum and the width
of the energy spectrum are calculated. In the weak field limit we obtain the
familiar non-relativistic results. For the case of circular polarization our
analytical results are in agreement with recent derivations of Krainov [V.P.
Krainov, J. Phys. B, {\bf 32}, 1607 (1999)].Comment: 8 pages, 2 figures, accepted for publication in Journal of Physics
On the variational limits of lattice energies on prestrained elastic bodies
We study the asymptotic behaviour of the discrete elastic energies in
presence of the prestrain metric , assigned on the continuum reference
configuration . When the mesh size of the discrete lattice in
goes to zero, we obtain the variational bounds on the limiting (in the sense of
-limit) energy. In case of the nearest-neighbour and
next-to-nearest-neibghour interactions, we derive a precise asymptotic formula,
and compare it with the non-Euclidean model energy relative to
The Gulf Stream Front, Its Role in Larval Fish Survival and Recruitment in Florida: Hydrographic Station and Plankton Data
The goal of this project was to develop a clearer understanding of the role that the Gulf Stream system plays in larval fish survival and recruitment in Florida waters. The specific objectives of this study were to: Determine whether the biomass of fish larva, other zooplankton, microzooplankton and phytoplankton is higher at the shoreward front of the Gulf Stream than on either side of it. Characterize the assemblages of fish larvae predators and prey both at the front and on either side of it. Determine if the composition, abundance and size frequency distribution of larval and juvenile fishes in the front is different from that in the coastal zone or in the Gulf Stream. Monitor the position of the Gulf Stream by continuous measurements of physical variables at moorings located in the Gulf Stream off Fort Lauderdale and within Port Everglades.
This project was a first effort to characterize the coupling between physical and biological processes that may influence the early life histories of fishes in Florida\u27s coastal waters. This report contains the hydrographic and plankton data from the project. It is intended to facilitate data access by the scientific and management communities. Interpretations and detailed analyses of these data are being given in meeting presentations, peer-reviewed journal articles (Stone et al. draft manuscript, Braker et al. draft manuscript, Frazel et al. in preparation) and graduate theses (Stone 1993; Braker 1993)
Accommodation of tin in tetragonal ZrO2
Atomic scale computer simulations using density functional theory were used to investigate the behaviour of tin in the tetragonal phase oxide layer on Zr-based alloys. The Sn×ZrSnZr× defect was shown to be dominant across most oxygen partial pressures, with Sn′′ZrSnZr″ charge compensated by V∙∙OVO•• occurring at partial pressures below 10−31 atm. Insertion of additional positive charge into the system was shown to significantly increase the critical partial pressure at which Sn′′ZrSnZr″ is stable. Recently developed low-Sn nuclear fuel cladding alloys have demonstrated an improved corrosion resistance and a delayed transition compared to Sn-containing alloys, such as Zircaloy-4. The interaction between the positive charge and the tin defect is discussed in the context of alloying additions, such as niobium and their influence on corrosion of cladding alloys
Mesoscale subduction at the Almeria-Oran front. Part 2: biophysical interactions.
This paper presents a detailed diagnostic analysis of hydrographic and current meter data from three, rapidly repeated, fine-scale surveys of the Almeria–Oran front. Instability of the frontal boundary, between surface waters of Atlantic and Mediterranean origin, is shown to provide a mechanism for significant heat transfer from the surface layers to the deep ocean in winter. The data were collected during the second observational phase of the EU funded OMEGA project on RRS Discovery cruise 224 during December 1996. High resolution hydrographic measurements using the towed undulating CTD vehicle, SeaSoar, traced the subduction of Mediterranean Surface Water across the Almeria–Oran front. This subduction is shown to result from a significant baroclinic component to the instability of the frontal jet. The Q-vector formulation of the omega equation is combined with a scale analysis to quantitatively diagnose vertical transport resulting from mesoscale ageostrophic circulation. The analyses are presented and discussed in the presence of satellite and airborne remotely sensed data; which provide the basis for a thorough and novel approach to the determination of observational error
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