619 research outputs found
Quantal analysis of long-term potentiation of combined neuronal postsynaptic potentials on hippocampal slices in vitro.
10.1007/BF0105247
Quantal analysis of long-term posttetanic changes in minimal postsynaptic potentials of hippocampal slices in vitro
Antiproton-Hydrogen annihilation at sub-kelvin temperatures
The main properties of the interaction of ultra low-energy antiprotons ( a.u.) with atomic hydrogen are established. They include the
elastic and inelastic cross sections and Protonium (Pn) formation spectrum. The
inverse Auger process () is taken into account in the
framework of an unitary coupled-channels model. The annihilation cross-section
is found to be several times smaller than the predictions made by the black
sphere absorption models. A family of nearthreshold metastable
states is predicited. The dependence of Protonium formation probability on the
position of such nearthreshold S-matrix singularities is analysed. An
estimation for the annihilation cross section is obtained.Comment: latex.tar.gz file, 22 pages, 9 figure
Whispering Gallery States of Antihydrogen
We study theoretically interference of the long-living quasistationary
quantum states of antihydrogen atoms, localized near a concave material
surface. Such states are an antimatter analog of the whispering gallery states
of neutrons and matter atoms, and similar to the whispering gallery modes of
sound and electro-magnetic waves. Quantum states of antihydrogen are formed by
the combined effect of quantum reflection from van der Waals/Casimir-Polder
(vdW/CP) potential of the surface and the centrifugal potential. We point out a
method for precision studies of quantum reflection of antiatoms from vdW/CP
potential; this method uses interference of the whispering gallery states of
antihydrogen.Comment: 13 pages 7 figure
Neutron diffraction constraint on spin-dependent short range interaction
The direct constraint on the parameters of short range pseudomagnetic
interaction of free neutron with matter is obtained from the recent test
experiment on a search for neutron EDM by crystal-diffraction method. It is
shown that this constraint on a product of scalar to pseudo-scalar coupling
constants is better than that of any other method for the range
cm
SUSY approach to Pauli Hamiltonians with an axial symmetry
A two-dimensional Pauli Hamiltonian describing the interaction of a neutral
spin-1/2 particle with a magnetic field having axial and second order
symmetries, is considered. After separation of variables, the one-dimensional
matrix Hamiltonian is analyzed from the point of view of supersymmetric quantum
mechanics. Attention is paid to the discrete symmetries of the Hamiltonian and
also to the Hamiltonian hierarchies generated by intertwining operators. The
spectrum is studied by means of the associated matrix shape-invariance. The
relation between the intertwining operators and the second order symmetries is
established and the full set of ladder operators that complete the dynamical
algebra is constructed.Comment: 18 pages, 3 figure
GRANIT project: a trap for gravitational quantum states of UCN
Previous studies of gravitationally bound states of ultracold neutrons showed
the quantization of energy levels, and confirmed quantum mechanical predictions
for the average size of the two lowest energy states wave functions.
Improvements in position-like measurements can increase the accuracy by an
order of magnitude only. We therefore develop another approach, consisting in
accurate measurements of the energy levels. The GRANIT experiment is devoted to
the study of resonant transitions between quantum states induced by an
oscillating perturbation.
According to Heisenberg's uncertainty relations, the accuracy of measurement
of the energy levels is limited by the time available to perform the
transitions. Thus, trapping quantum states will be necessary, and each source
of losses has to be controlled in order to maximize the lifetime of the states.
We discuss the general principles of transitions between quantum states, and
consider the main systematical losses of neutrons in a trap.Comment: presented in ISINN 15 seminar, Dubn
Study of the neutron quantum states in the gravity field
We have studied neutron quantum states in the potential well formed by the
earth's gravitational field and a horizontal mirror. The estimated
characteristic sizes of the neutron wave functions in the two lowest quantum
states correspond to expectations with an experimental accuracy. A
position-sensitive neutron detector with an extra-high spatial resolution of ~2
microns was developed and tested for this particular experiment, to be used to
measure the spatial density distribution in a standing neutron wave above a
mirror for a set of some of the lowest quantum states. The present experiment
can be used to set an upper limit for an additional short-range fundamental
force. We studied methodological uncertainties as well as the feasibility of
improving further the accuracy of this experiment
Increased distractibility in schizotypy: Independent of individual differences in working memory capacity?
Individuals with schizophrenia typically show increased levels of distractibility. This has been attributed to impaired working memory capacity (WMC), since lower WMC is typically associated with higher distractibility, and schizophrenia is typically associated with impoverished WMC. Here, participants performed verbal and spatial serial recall tasks that were accompanied by to-be-ignored speech tokens. For the few trials wherein one speech token was replaced with a different token, impairment was produced to task scores (a deviation effect). Participants subsequently completed a schizotypy questionnaire and a WMC measure. Higher schizotypy scores were associated with lower WMC (as measured with operation span, OSPAN), but WMC and schizotypy scores explained unique variance in relation to the mean magnitude of the deviation effect. These results suggest that schizotypy is associated with heightened domain-general distractibility, but that this is independent of its relationship with WMC
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