2,453 research outputs found
Theory of anomalous magnetic interference pattern in mesoscopic SNS Josephson junctions
The magnetic interference pattern in mesoscopic SNS Josephson junctions is
sensitive to the scattering in the normal part of the system. In this paper we
investigate it, generalizing Ishii's formula for current-phase dependence to
the case of normal scattering at NS boundaries in an SNS junction of finite
width. The resulting flattening of the first diffraction peak is consistent
with experimental data for S-2DEG-S mesoscopic junctions.Comment: 6 pages, 5 figures. Phys. Rev. B 68, 144514 (2003
Musical hallucinations and their relation with epilepsy
Musical hallucinations are poorly understood phenomena. Their relation with epilepsy was first described over a century ago, but never systematically explored. We, therefore, reviewed the literature, and assessed all descriptions of musical hallucinations attributed to epileptic activity. Our search yielded 191 articles, which together describe 983 unique patients, with 24 detailed descriptions of musical hallucinations related to epilepsy. We also describe six of our own patients. Based on the phenomenological descriptions and neurophysiological data, we distinguish four subgroups of epilepsy-related musical hallucination, comprising auras/ictal, inter-ictal and post-ictal phenomena, and phenomena related to brain stimulation. The case descriptions suggest that musical hallucinations in epilepsy can be conceptualised as lying on a continuum with other auditory hallucinations, including verbal auditory hallucinations, and—notably—tinnitus. To account for the underlying mechanism we propose a Bayesian model involving top-down and bottom-up prediction errors within the auditory network that incorporates findings from EEG and MEG studies. An analysis of phenomenological characteristics, pharmacological triggers, and treatment effects suggests wider ramifications for understanding musical hallucinations. We, therefore, conclude that musical hallucinations in epilepsy open a window to understanding these phenomena in a variety of conditions.Stress and Psychopatholog
Charge and Spin Effects in Mesoscopic Josephson Junctions
We consider the charge and spin effects in low dimensional superconducting
weak links. The first part of the review deals with the effects of
electron-electron interaction in Superconductor/Luttinger liquid/Superconductor
junctions. The experimental realization of this mesoscopic hybrid system can be
the individual single wall carbon nanotube that bridges the gap between two
bulk superconductors. The dc Josephson current through a Luttinger liquid in
the limits of perfectly and poorly transmitting junctions is evaluated. The
relationship between the Josephson effect in a long SNS junction and the
Casimir effect is discussed. In the second part of the paper we review the
recent results concerning the influence of the Zeeman and Rashba interactions
on the thermodynamical properties of ballistic S/QW/S junction fabricated in
two dimensional electron gas. It is shown that in magnetically controlled
junction there are conditions for resonant Cooper pair transition which results
in giant supercurrent through a tunnel junction and a giant magnetic response
of a multichannel SNS junction. The supercurrent induced by the joint action of
the Zeeman and Rashba interactions in 1D quantum wires connected to bulk
superconductors is predicted.Comment: 36 pages, 8 figures; minor changes in reference
Donor states in modulation-doped Si/SiGe heterostructures
We present a unified approach for calculating the properties of shallow
donors inside or outside heterostructure quantum wells. The method allows us to
obtain not only the binding energies of all localized states of any symmetry,
but also the energy width of the resonant states which may appear when a
localized state becomes degenerate with the continuous quantum well subbands.
The approach is non-variational, and we are therefore also able to evaluate the
wave functions. This is used to calculate the optical absorption spectrum,
which is strongly non-isotropic due to the selection rules. The results
obtained from calculations for Si/SiGe quantum wells allow us to
present the general behavior of the impurity states, as the donor position is
varied from the center of the well to deep inside the barrier. The influence on
the donor ground state from both the central-cell effect and the strain arising
from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure
Resonant transmission of normal electrons through Andreev states in ferromagnets
Giant oscillations of the conductance of a superconductor - ferromagnet -
superconductor Andreev interferometer are predicted. The effect is due to the
resonant transmission of normal electrons through Andreev levels when the
voltage applied to the ferromagnet is close to ( is the
spin-dependant part of the electron energy). The effect of bias voltage and
phase difference between the superconductors on the current and the
differential conductance is presented. These efects allow a direct spectroscopy
of Andreev levels in the ferromagnet.Comment: 4 pages, 4 figure
Issues in Vendor/Library Relations-The Sales Call
We re-take a coding theoretic notion which goes back to Cl. Shannon: codeword distinguishability. This notion is standard in zero-error information theory, but its bearing is definitely wider and it may help to better understand new forms of coding, e.g. DNA word design.
In our approach, the underlying decoding principle is very simple and very general: one decodes by trying to minimise the diversity (in the simplest case the Hamming distance) between a codeword and the output sequence observed at the end of the noisy transmission channel. Symmetrically and equivalently, one may use maximum-similarity decoders and and codeword confusabilities. The operational meaning of codewoord distinguishability is made clear by a reliability criterion, which generalises the well-known criterion on minimum Hamming distance for error-correcting codes. We investigate the formal properties of distinguishabilities versus diversities; these two notions are deeply related, and yet essentially different. An encoding theorem is put forward; as a case study we examine a channel of cryptographic interest
Auditory hallucinations, not necessarily a hallmark of psychotic disorder
Auditory hallucinations (AH) are often considered a sign of a psychotic disorder. This is promoted by the DSM-5 category of Other Specified Schizophrenia Spectrum And Other Psychotic Disorder (OSSSOPD), the diagnostic criteria for which are fulfilled with the sole presence of persistent AH, in the absence of any other psychotic symptoms. And yet, persistent AH are not synonymous with having a psychotic disorder, and should therefore not be uncritically treated as such. Many people who seek treatment for persistent AH have no other psychotic symptoms, have preserved realitytesting capacities, and will never develop a schizophrenia spectrum disorder. Instead, hallucinations may be the result of many different causes, including borderline personality disorder, post-traumatic stress disorder (PTSD), hearing loss, sleep disorders or brain lesions, and they may even occur outside the context of any demonstrable pathology. In such cases, the usage of the DSM-5 diagnosis of OSSSOPD would be incorrect, and it may prompt unwarranted treatment with antipsychotic medication. We therefore argue that a DSM-5 diagnosis of Schizophrenia Spectrum Disorder (or any other type of psychotic disorder) characterized by AH should require at least one more symptom listed under the A-criterion (i.e. delusions, disorganized speech, disorganized or catatonic behavior or negative symptoms). Adhering to these more stringent criteria may help to distinguish between individuals with persistent AH which are part of a psychotic disorder, for whom antipsychotic medication may be helpful, and individuals with AH in the absence of such a disorder who may benefit from other approaches (e.g. different pharmacological interventions, improving coping style, trauma-related therapy)
Free-electron Model for Mesoscopic Force Fluctuations in Nanowires
When two metal electrodes are separated, a nanometer sized wire (nanowire) is
formed just before the contact breaks. The electrical conduction measured
during this retraction process shows signs of quantized conductance in units of
G_0=2e^2/h. Recent experiments show that the force acting on the wire during
separation fluctuates, which has been interpreted as being due to atomic
rearrangements. In this report we use a simple free electron model, for two
simple geometries, and show that the electronic contribution to the force
fluctuations is comparable to the experimentally found values, about 2 nN.Comment: 4 pages, 3 figures, reference correcte
A luminosity constraint on the origin of unidentified high energy sources
The identification of point sources poses a great challenge for the high
energy community. We present a new approach to evaluate the likelihood of a set
of sources being a Galactic population based on the simple assumption that
galaxies similar to the Milky Way host comparable populations of gamma-ray
emitters. We propose a luminosity constraint on Galactic source populations
which complements existing approaches by constraining the abundance and spatial
distribution of any objects of Galactic origin, rather than focusing on the
properties of a specific candidate emitter. We use M31 as a proxy for the Milky
Way, and demonstrate this technique by applying it to the unidentified EGRET
sources. We find that it is highly improbable that the majority of the
unidentified EGRET sources are members of a Galactic halo population (e.g.,
dark matter subhalos), but that current observations do not provide any
constraints on all of these sources being Galactic objects if they reside
entirely in the disk and bulge. Applying this method to upcoming observations
by the Fermi Gamma-ray Space Telescope has the potential to exclude association
of an even larger number of unidentified sources with any Galactic source
class.Comment: 18 pages, 4 figures, to appear in JPhys
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