10,308 research outputs found
Glutamatergic-dopaminergic balance in the brain. Its importance in motor disorders and schizophrenia
Dopamine appears to be of less importance in the regulation of psychomotor functions than was previously thought. A central dopaminergic-glutamatergic balance may be important for both akinetic motor disorders and psychosis. In Parkinson's disease glutamate antagonists may counteract central glutamatergic hyperactivity and may be of value as anti-parkinsonian drugs. An increase of dopaminergic activity and/or a reduction of glutamatergic activity may contribute to the development of paranoid hallucinatory psychosis in schizophrenic patients and of pharmacotoxic psychosis in Parkinson's disease. Because of possibly severe side-effects of glutamatergic antagonists and agonists in the treatment of akinesia and psychosis, the development of partial glutamate agonists/antagonists could be an alternative strategy capable of producing antipsychotic or anti-kinetic effects with only mild adverse reaction
Storage by trapping and spatial staggering of multiple interacting solitons in -type media
In this paper we investigate the properties of self induced transparency
(SIT) solitons, propagating in a -type medium. It was found that the
interaction between SIT solitons can lead to trapping with their phase
preserved in the ground state coherence of the medium. These phases can be
altered in a systematic way by the application of appropriate light fields,
such as additional SIT solitons. Furthermore, multiple independent SIT solitons
can be made to propagate as bi-solitons through their mutual interaction with a
separate light field. Finally, we demonstrate that control of the SIT soliton
phase can be used to implement an optical exclusive-or gate.Comment: 7 pages, 7 figure
A gain-coefficient switched Alexandrite laser
We report on a gain-coefficient switched Alexandrite laser. An electro-optic
modulator is used to switch between high and low gain states by making use of
the polarization dependent gain of Alexandrite. In gain-coefficient switched
mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a
repetition rate of 5 Hz.Comment: 8 pages, 5 figure
Microscopic theory for interface fluctuations in binary liquid mixtures
Thermally excited capillary waves at fluid interfaces in binary liquid
mixtures exhibit simultaneously both density and composition fluctuations.
Based on a density functional theory for inhomogeneous binary liquid mixtures
we derive an effective wavelength dependent Hamiltonian for fluid interfaces in
these systems beyond the standard capillary-wave model. Explicit expressions
are obtained for the surface tension, the bending rigidities, and the coupling
constants of compositional capillary waves in terms of the profiles of the two
number densities characterizing the mixture. These results lead to predictions
for grazing-incidence x-ray scattering experiments at such interfaces.Comment: 23 pages, 11 figure
Local orientations of fluctuating fluid interfaces
Thermal fluctuations cause the local normal vectors of fluid interfaces to
deviate from the vertical direction defined by the flat mean interface
position. This leads to a nonzero mean value of the corresponding polar tilt
angle which renders a characterization of the thermal state of an interface.
Based on the concept of an effective interface Hamiltonian we determine the
variances of the local interface position and of its lateral derivatives. This
leads to the probability distribution functions for the metric of the interface
and for the tilt angle which allows us to calculate its mean value and its mean
square deviation. We compare the temperature dependences of these quantities as
predicted by the simple capillary wave model, by an improved phenomenological
model, and by the microscopic effective interface Hamiltonian derived from
density functional theory. The mean tilt angle discriminates clearly between
these theoretical approaches and emphasizes the importance of the variation of
the surface tension at small wave lengths. Also the tilt angle two-point
correlation function is determined which renders an additional structural
characterization of interfacial fluctuations. Various experimental accesses to
measure the local orientational fluctuations are discussed.Comment: 29 pages, 12 figure
Programmable two-photon quantum interference in channels in opaque scattering media
We investigate two-photon quantum interference in an opaque scattering medium
that intrinsically supports transmission channels. By adaptive spatial
phase-modulation of the incident wavefronts, the photons are directed at
targeted speckle spots or output channels. From experimentally available
coupled channels, we select two channels and enhance their transmission, to
realize the equivalent of a fully programmable beam splitter. By
sending pairs of single photons from a parametric down-conversion source
through the opaque scattering medium, we observe two-photon quantum
interference. The programmed beam splitter need not fulfill energy conservation
over the two selected output channels and hence could be non-unitary.
Consequently, we have the freedom to tune the quantum interference from
bunching (Hong-Ou-Mandel-like) to antibunching. Our results establish opaque
scattering media as a platform for high-dimensional quantum interference that
is notably relevant for boson sampling and physical-key-based authentication
Production of Neutral Pions and Eta-mesons in pp Collisions Measured with ALICE
Invariant cross sections for neutral pions and eta mesons in pp collisions at
sqrt(s) = 0.9, 2.76, and 7 TeV were measured by the ALICE detector at the Large
Hadron Collider. Next-to-leading order (NLO) perturbative QCD calculations
describe the pi0 and eta spectra at 0.9 TeV, but overestimate the measured
cross sections at 2.76 TeV and 7 TeV. The measured eta/pi0 ratio is consistent
with mT scaling at 2.76 TeV. At 7 TeV indications for a violation of mT scaling
were found.Comment: 4 pages, 2 figures, to appear in the proceedings of the XXII
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions,
Quark Matter 2011, Annec
Liquid n-hexane condensed in silica nanochannels: A combined optical birefringence and vapor sorption isotherm study
The optical birefringence of liquid n-hexane condensed in an array of
parallel silica channels of 7nm diameter and 400 micrometer length is studied
as a function of filling of the channels via the vapor phase. By an analysis
with the generalized Bruggeman effective medium equation we demonstrate that
such measurements are insensitive to the detailed geometrical (positional)
arrangement of the adsorbed liquid inside the channels. However, this technique
is particularly suitable to search for any optical anisotropies and thus
collective orientational order as a function of channel filling. Nevertheless,
no hints for such anisotropies are found in liquid n-hexane. The n-hexane
molecules in the silica nanochannels are totally orientationally disordered in
all condensation regimes, in particular in the film growth as well as in the
the capillary condensed regime. Thus, the peculiar molecular arrangement found
upon freezing of liquid n-hexane in nanochannel-confinement, where the
molecules are collectively aligned perpendicularly to the channels' long axes,
does not originate in any pre-alignment effects in the nanoconfined liquid due
to capillary nematization.Comment: 7 pages, 5 figure
An S-shaped outflow from IRAS 03256+3055 in NGC 1333
The IRAS source 03256+3055 in the NGC 1333 star forming region is associated
with extended sub-millimeter emission of complex morphology, showing multiple
clumps. One of these is found to coincide with the driving source of a bipolar
jet of S-shaped morphology seen in the emission lines of H_alpha and [SII] as
well as in the H2 emission lines in the K-band. Detailed images of the driving
source at the wavelengths of H_alpha and [SII] and in the I, J, H, and K bands
as well as a K-band spectrum and polarimetry are discussed. The near-infrared
morphology is characterized by a combination of line emission from the jet and
scattered light from a source with a steep continuum spectrum. The morphology
and proper motion of the jet are discussed in the context of a binary system
with a precessing disk. We conclude that the molecular core associated with
IRAS 03256+3055 consists of several clumps, only one of which shows evidence of
recent star formation at optical and near-infrared wavelengths.We also briefly
discuss a second, newly found near-infrared source associated with a compact
sub-millimeter continuum source near IRAS 03256+3055, and conclude that this
source may be physically unrelated the cluster of molecular clumps.Comment: 25 pages, including 5 figures. Accepted for publication in The
Astronomical Journa
Stability of bubble nuclei through Shell-Effects
We investigate the shell structure of bubble nuclei in simple
phenomenological shell models and study their binding energy as a function of
the radii and of the number of neutron and protons using Strutinsky's method.
Shell effects come about, on the one hand, by the high degeneracy of levels
with large angular momentum and, on the other, by the big energy gaps between
states with a different number of radial nodes. Shell energies down to -40 MeV
are shown to occur for certain magic nuclei. Estimates demonstrate that the
calculated shell effects for certain magic numbers of constituents are probably
large enough to produce stability against fission, alpha-, and beta-decay. No
bubble solutions are found for mass number A < 450.Comment: 9 pages and 9 figures in the eps format include
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