2,846 research outputs found
Homing orientation in salamanders: A mechanism involving chemical cues
A detailed description is given of experiments made to determine the senses and chemical cues used by salamanders for homing orientation. Sensory impairment and cue manipulative techniques were used in the investigation. All experiments were carried out at night. Results show that sense impaired animals did not home as readily as those who were blind but retained their sensory mechanism. This fact suggests that the olfactory mechanism is necessary for homing in the salamander. It was determined that after the impaired salamander regenerated its sensory mechanism it too returned home. It was concluded that homing ability in salamanders is direction independent, distant dependent, and vision independent
Semiclassical description of the kinematically complete experiments
Based on the semiclassical, impact parameter method a theoretical model is
constructed to calculate totally differential cross sections for single
ionization of helium by impact with fast C ions. Good agreement with the
experiment is achieved in the scattering plane, while in the perpendicular
plane a similar structure to that observed experimentally is obtained. The
contribution of different partial waves to the cross section is also
investigated.Comment: 9 pages, 6 figure
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Multifaceted Changes in Synaptic Composition and Astrocytic Involvement in a Mouse Model of Fragile X Syndrome.
Fragile X Syndrome (FXS), a common inheritable form of intellectual disability, is known to alter neocortical circuits. However, its impact on the diverse synapse types comprising these circuits, or on the involvement of astrocytes, is not well known. We used immunofluorescent array tomography to quantify different synaptic populations and their association with astrocytes in layers 1 through 4 of the adult somatosensory cortex of a FXS mouse model, the FMR1 knockout mouse. The collected multi-channel data contained approximately 1.6 million synapses which were analyzed using a probabilistic synapse detector. Our study reveals complex, synapse-type and layer specific changes in the neocortical circuitry of FMR1 knockout mice. We report an increase of small glutamatergic VGluT1 synapses in layer 4 accompanied by a decrease in large VGluT1 synapses in layers 1 and 4. VGluT2 synapses show a rather consistent decrease in density in layers 1 and 2/3. In all layers, we observe the loss of large inhibitory synapses. Lastly, astrocytic association of excitatory synapses decreases. The ability to dissect the circuit deficits by synapse type and astrocytic involvement will be crucial for understanding how these changes affect circuit function, and ultimately defining targets for therapeutic intervention
Periodically-dressed Bose-Einstein condensates: a superfluid with an anisotropic and variable critical velocity
Two intersecting laser beams can produce a spatially-periodic coupling
between two components of an atomic gas and thereby modify the dispersion
relation of the gas according to a dressed-state formalism. Properties of a
Bose-Einstein condensate of such a gas are strongly affected by this
modification. A Bogoliubov transformation is presented which accounts for
interparticle interactions to obtain the quasiparticle excitation spectrum in
such a condensate. The Landau critical velocity is found to be anisotropic and
can be widely tuned by varying properties of the dressing laser beams.Comment: 5 pages, 4 figure
Calibration of distorted wave Born approximation for electron impact excitation of Ne and Ar at incident energies below 100 eV
We calibrate the distorted wave Born approximation (DWBA) for electron impact
excitation processes empirically. Differential cross sections (DCS) for the
excitation of the , ,, and configurations of
Ne and the and configurations of Ar by electron impact are
calculated using DWBA for incident energies between 20 and 100 eV. The
calculated results are compared with the absolute experimental measurements and
other theoretical results. We found that the structure of the DCS can be well
reproduced by the DWBA model while the magnitude is overestimated for most
cases considered here. The differences in magnitude between DWBA and experiment
are used to test the calibration of DWBA such that the DWBA can be used to
describe laser-induced electron impact excitation processes. These processes
are involved in the non-sequential double ionization of atoms in strong laser
fields.Comment: 10 pages, 8 figure
Comparison of theoretical and absolute experimental fully differential cross sections for ion-atom impact ionization
We report fully differential cross section (FDCS) calculations and absolute measurements for ion-atom impact ionization. Using the COLTRIMS (cold target recoil ion momentum spectroscopy) method we have obtained absolute FDCS both in the scattering plane as well as out of the scattering plane for 100 MeV amu(- 1) C6+ ionization of helium FDCS results are presented for different projectile scattering angles and ejected electron energies. The measurements are compared with a theoretical calculation employing an asymptotically exact three body final state wavefunction that contains all active two particle subsystem interactions to infinite order in perturbation theory. For the active electron a Hartree-Fock (HF) bound state wavefunction is used for the initial state and numerical continuum state eigenfunctions of a HF potential for the ion are used for the final state In the scattering plane these theoretical results are in very good agreement with experiment for small and intermediate momentum transfer. However some significant discrepancies are found for large momentum transfer and outside the scattering plane. These discrepancies disappear upon comparison with successively less differential cross sections
Dissipative dynamics of vortex arrays in trapped Bose-condensed gases: neutron stars physics on K scale
We develop a theory of dissipative dynamics of large vortex arrays in trapped
Bose-condensed gases. We show that in a static trap the interaction of the
vortex array with thermal excitations leads to a non-exponential decay of the
vortex structure, and the characteristic lifetime depends on the initial
density of vortices. Drawing an analogy with physics of pulsar glitches, we
propose an experiment which employs the heating of the thermal cloud in the
course of the decay of the vortex array as a tool for a non-destructive study
of the vortex dynamics.Comment: 4 pages, revtex; revised versio
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