1,909 research outputs found
Dopamine: A Marker of Psychosis and Final Common Driver of Schizophrenia Psychosis
Our attempt to understand schizophrenia in neurochemical terms began with the landmark studies of Carlsson and Lindqvist (1) in the 1960s. The results of these studies, based on the action of chlorpromazine, were strengthened by the binding studies carried out in both Seeman's (2) and Synder's (3) laboratories, which showed that antipsychotic potency was correlated with dopamine D2 receptor binding. The one major exception to this correlation is clozapine, which appears to be the most effective available drug for treating schizophrenia symptoms. The most recent version of the resulting dopamine hypothesis suggests that genetic, environmental, and developmental variables play major etiological roles in schizophrenia, but that striatal dopamine presynaptic overactivity remains the final trigger resulting in psychosis.....
Scattering into the fifth dimension of N=4 super Yang-Mills
We study an alternative to dimensional regularisation of planar scattering
amplitudes in N=4 super Yang-Mills theory by going to the Coulomb phase of the
theory. The infrared divergences are regulated by masses obtained from a Higgs
mechanism, allowing us to work in four dimensions. The corresponding string
theory set-up suggests that the amplitudes have an exact dual conformal
symmetry. The latter acts on the kinematical variables of the amplitudes as
well as on the Higgs masses in an effectively five dimensional space. We
confirm this expectation by an explicit calculation in the gauge theory. A
consequence of this exact dual conformal symmetry is a significantly reduced
set of scalar basis integrals that are allowed to appear in an amplitude. For
example, triangle sub-graphs are ruled out. We argue that the study of
exponentiation of amplitudes is simpler in the Higgsed theory because
evanescent terms in the mass regulator can be consistently dropped. We
illustrate this by showing the exponentiation of a four-point amplitude to two
loops. Finally, we also analytically compute the small mass expansion of a
two-loop master integral with an internal mass.Comment: 35 pages, many figures. v2: typos and references fixed. v3: minor
changes, version to be published in JHE
Emergence of turbulence in an oscillating Bose-Einstein condensate
We report on the experimental observation of vortices tangle in an atomic BEC
of Rb-87 atoms when an external oscillatory perturbation is introduced in the
trap. The vortices tangle configuration is a signature of the presence of a
turbulent regime in the cloud. We also show that this turbulent cloud has
suppression of the aspect ratio inversion typically observed in quantum
degenerate bosonic gases during free expansion. Instead, the cloud expands
keeping the ratio between their axis constant. Turbulence in atomic superfluids
may constitute an alternative system to investigate decay mechanisms as well as
to test fundamental theoretical aspects in this field.Comment: accepted for Phys. Rev. Let
Polls and the political process: the use of opinion polls by political parties and mass media organizations in European post‐communist societies (1990–95)
Opinion polling occupies a significant role within the political process of most liberal-capitalist societies, where it is used by governments, parties and the mass media alike. This paper examines the extent to which polls are used for the same purposes in the post-communist countries of Central and Eastern Europe, and in particular, for bringing political elites and citizens together. It argues that these political elites are more concerned with using opinion polls for gaining competitive advantage over their rivals and for reaffirming their political power, than for devolving political power to citizens and improving the general processes of democratization
Generation of vortices and observation of Quantum Turbulence in an oscillating Bose-Einstein Condensate
We report on the experimental observation of vortex formation and production
of tangled vortex distribution in an atomic BEC of Rb-87 atoms submitted to an
external oscillatory perturbation. The oscillatory perturbations start by
exciting quadrupolar and scissors modes of the condensate. Then regular
vortices are observed finally evolving to a vortex tangle configuration. The
vortex tangle is a signature of the presence of a turbulent regime in the
cloud. We also show that this turbulent cloud has suppression of the aspect
ratio inversion typically observed in quantum degenerate bosonic gases during
free expansion.Comment: to appear in JLTP - QFS 200
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