1,800 research outputs found
Alien Registration- Babin, John S. (Fort Kent, Aroostook County)
https://digitalmaine.com/alien_docs/36266/thumbnail.jp
Alien Registration- Babin, John S. (Fort Kent, Aroostook County)
https://digitalmaine.com/alien_docs/36266/thumbnail.jp
Giant Coulomb broadening and Raman lasing on ionic transitions
CW generation of anti-Stokes Raman laser on a number of blue-green argon-ion
lines (4p-4s, 4p-3d) has been demonstrated with optical pumping from metastable
levels 3d'^2G, 3d^4F. It is found, that the population transfer rate is
increased by a factor of 3-5 (and hence, the output power of such Raman laser)
owing to Coulomb diffusion in the velocity space. Measured are the excitation
and relaxation rates for the metastable level. The Bennett hole on the
metastable level has been recorded using the probe field technique. It has been
shown that the Coulomb diffusion changes shape of the contour to exponential
cusp profile while its width becomes 100 times the Lorentzian one and reaches
values close to the Doppler width. Such a giant broadening is also confirmed by
the shape of the absorption saturation curve.Comment: RevTex 18 pages, 5 figure
Trajectory and smooth attractors for Cahn-Hilliard equations with inertial term
The paper is devoted to a modification of the classical Cahn-Hilliard
equation proposed by some physicists. This modification is obtained by adding
the second time derivative of the order parameter multiplied by an inertial
coefficient which is usually small in comparison to the other physical
constants. The main feature of this equation is the fact that even a globally
bounded nonlinearity is "supercritical" in the case of two and three space
dimensions. Thus the standard methods used for studying semilinear hyperbolic
equations are not very effective in the present case. Nevertheless, we have
recently proven the global existence and dissipativity of strong solutions in
the 2D case (with a cubic controlled growth nonlinearity) and for the 3D case
with small inertial coefficient and arbitrary growth rate of the nonlinearity.
The present contribution studies the long-time behavior of rather weak (energy)
solutions of that equation and it is a natural complement of the results of our
previous papers. Namely, we prove here that the attractors for energy and
strong solutions coincide for both the cases mentioned above. Thus, the energy
solutions are asymptotically smooth. In addition, we show that the non-smooth
part of any energy solution decays exponentially in time and deduce that the
(smooth) exponential attractor for the strong solutions constructed previously
is simultaneously the exponential attractor for the energy solutions as well
Virulent bacterial infection improves aversive learning performance in Drosophila melanogaster.
Virulent infections are expected to impair learning ability, either as a direct consequence of stressed physiological state or as an adaptive response that minimizes diversion of energy from immune defense. This prediction has been well supported for mammals and bees. Here, we report an opposite result in Drosophila melanogaster. Using an odor-mechanical shock conditioning paradigm, we found that intestinal infection with bacterial pathogens Pseudomonas entomophila or Erwinia c. carotovora improved flies' learning performance after a 1h retention interval. Infection with P. entomophila (but not E. c. carotovora) also improved learning performance after 5 min retention. No effect on learning performance was detected for intestinal infections with an avirulent GacA mutant of P. entomophila or for virulent systemic (hemocoel) infection with E. c. carotovora. Assays of unconditioned responses to odorants and shock do not support a major role for changes in general responsiveness to stimuli in explaining the changes in learning performance, although differences in their specific salience for learning cannot be excluded. Our results demonstrate that the effects of pathogens on learning performance in insects are less predictable than suggested by previous studies, and support the notion that immune stress can sometimes boost cognitive abilities
Experimental demonstration of mode structure in ultralong Raman fiber lasers
We present the first experimental demonstration of a resolvable mode structure with spacing c/2nL in the RF spectra of ultralong Raman fiber lasers. The longest ever demonstrated laser cavity (L=84km), RF peaks of ∼100 Hz width and spacing ∼1 kHz have been observed at low intracavity powers. The width of the peaks increases linearly with growing intracavity power and is almost independent of fiber length. © 2007 Optical Society of America
Random raman fiber laser based on a twin-core fiber with FBGs inscribed by femtosecond radiation
Narrowband Raman lasing in a polarization-maintaining two-core fiber (TCF) is demonstrated. Femtosecond point-by-point inscription of fiber Bragg gratings (FBGs) in individual cores produces a half-open cavity with random distributed feedback. The laser linewidth in the cavity with a single FBG inscribed in one core of the TCF reduced by ∼2 times with respect to the cavity with a fiber loop mirror. It is shown that the inscription of two FBGs in different cores leads to the formation of a Michelson-type interferometer, leading to the modulation of generation spectra near threshold. This technique offers new possibilities for spectral filtering or multi-wavelength generation
Beam self-cleaning in multimode optical fibers and hydrodynamic 2D turbulence
We experimentally demonstrate the conservation of the average mode number in the process of Kerr beam self-cleaning in a graded-index multimode optical fiber, in analogy with wave condensation in hydrodynamic 2D turbulence
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