5,972 research outputs found
DĂ©jĂ vu and the entorhinal cortex: dissociating recollective from familiarity disruptions in a single case patient
Past research has demonstrated a relationship between déjà vu and the entorhinal cortex in patients with wider medial temporal lobe damage. The aim of the present research was to investigate this crucial link in a patient (MR) with a selective lesion to the left lateral entorhinal cortex to provide a more direct exploration of this relationship. Two experiments investigated the experiences of déjà vécu (using the IDEA questionnaire) and déjà vu (using an adapted DRM paradigm) in MR and a set of matched controls. The results demonstrated that MR had quantitatively more and qualitatively richer recollective experiences of déjà vécu. In addition, under laboratory-based déjà vu conditions designed to elicit both false recollection (critical lures) and false familiarity (weakly-associated lures), MR only revealed greater memory impairments for the latter. The present results are therefore the first to demonstrate a direct relationship between the entorhinal cortex and the experience of both déjà vu and déjà vécu. They furthermore suggest that the entorhinal cortex is involved in both weakly-associative false memory as well as strongly-associative memory under conditions that promote familiarity-based processing
X-ray bright active galactic nuclei in massive galaxy clusters III: New insights into the triggering mechanisms of cluster AGN
We present the results of a new analysis of the X-ray selected Active
Galactic Nuclei (AGN) population in the vicinity of 135 of the most massive
galaxy clusters in the redshift range of 0.2 < z < 0.9 observed with Chandra.
With a sample of more than 11,000 X-ray point sources, we are able to measure,
for the first time, evidence for evolution in the cluster AGN population beyond
the expected evolution of field AGN. Our analysis shows that overall number
density of cluster AGN scales with the cluster mass as .
There is no evidence for the overall number density of cluster member X-ray AGN
depending on the cluster redshift in a manner different than field AGN, nor
there is any evidence that the spatial distribution of cluster AGN (given in
units of the cluster overdensity radius r_500) strongly depends on the cluster
mass or redshift. The scaling relation we measure is
consistent with theoretical predictions of the galaxy merger rate in clusters,
which is expected to scale with the cluster velocity dispersion, , as or . This consistency suggests that AGN in
clusters may be predominantly triggered by galaxy mergers, a result that is
further corroborated by visual inspection of Hubble images for 23
spectroscopically confirmed cluster member AGN in our sample. A merger-driven
scenario for the triggering of X-ray AGN is not strongly favored by studies of
field galaxies, however, suggesting that different mechanisms may be primarily
responsible for the triggering of cluster and field X-ray AGN.Comment: 21 Pages, 8 figures, 5 tables. Submitted to MNRAS. Comments are
welcome, and please request Steven Ehlert for higher resolution figure
X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters II: The Fraction of Galaxies Hosting Active Nuclei
We present a measurement of the fraction of cluster galaxies hosting X-ray
bright Active Galactic Nuclei (AGN) as a function of clustercentric distance
scaled in units of . Our analysis employs high quality Chandra X-ray
and Subaru optical imaging for 42 massive X-ray selected galaxy cluster fields
spanning the redshift range of . In total, our study involves
176 AGN with bright () optical counterparts above a keV flux
limit of . When excluding
central dominant galaxies from the calculation, we measure a cluster-galaxy AGN
fraction in the central regions of the clusters that is times lower
that the field value. This fraction increases with clustercentric distance
before becoming consistent with the field at . Our data
exhibit similar radial trends to those observed for star formation and
optically selected AGN in cluster member galaxies, both of which are also
suppressed near cluster centers to a comparable extent. These results strongly
support the idea that X-ray AGN activity and strong star formation are linked
through their common dependence on available reservoirs of cold gas.Comment: 9 Pages, 4 Figures, accepted for publication in MNRAS, please contact
Steven Ehlert ([email protected]) with any querie
Existence of two-channel Kondo regime for tunneling impurities with resonant scattering
Dynamical tunneling systems have been proposed earlier to display a
two-channel Kondo effect, the orbital index of the particle playing the role of
a pseudospin in the equivalent Kondo problem, and the spin being a silent
channel index. However, as shown recently by Aleiner et al. [Phys. Rev. Lett.
86, 2629 (2001)], the predicted two-channel Kondo behavior can never be
observed in the weak coupling regime, where the tunneling induced splitting of
the levels of the tunneling system always dominates the physics. Here we show
that the above scenario changes completely if the conduction electrons are
scattered by resonant scattering off the tunneling impurity; Then - as a
non-perturbative analysis reveals - the two-channel Kondo regime can easily be
reached.Comment: 10 PRB page
A variational approach to the macroscopic electrodynamics of anisotropic hard superconductors
We consider the Bean's critical state model for anisotropic superconductors.
A variational problem solved by the quasi--static evolution of the internal
magnetic field is obtained as the -limit of functionals arising from
the Maxwell's equations combined with a power law for the dissipation.
Moreover, the quasi--static approximation of the internal electric field is
recovered, using a first order necessary condition. If the sample is a long
cylinder subjected to an axial uniform external field, the macroscopic
electrodynamics is explicitly determined.Comment: 24 pages, 15 figure
INTEGRAL upper limits on gamma-ray emission associated with the gravitational wave event GW150914
Using observations of the INTErnational Gamma-Ray Astrophysics Laboratory
(INTEGRAL), we put upper limits on the gamma-ray and hard X-ray prompt emission
associated with the gravitational wave event GW150914, discovered by the
LIGO/Virgo collaboration. The omni-directional view of the INTEGRAL/SPI-ACS has
allowed us to constrain the fraction of energy emitted in the hard X-ray
electromagnetic component for the full high-probability sky region of LIGO
trigger. Our upper limits on the hard X-ray fluence at the time of the event
range from erg cm to
erg cm in the 75 keV - 2 MeV energy range for typical spectral models.
Our results constrain the ratio of the energy promptly released in gamma-rays
in the direction of the observer to the gravitational wave energy
EE. We discuss the implication of gamma-ray
limits on the characteristics of the gravitational wave source, based on the
available predictions for prompt electromagnetic emission.Comment: accepted for publication in ApJ
X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters I: Number Counts and Spatial Distribution
We present an analysis of the X-ray bright point source population in 43
massive clusters of galaxies observed with the Chandra X-ray Observatory. We
have constructed a catalog of 4210 rigorously selected X-ray point sources in
these fields, which span a survey area of 4.2 square degrees. This catalog
reveals a clear excess of sources when compared to deep blank-field surveys,
which amounts to roughly 1 additional source per cluster, likely Active
Galactic Nuclei (AGN) associated with the clusters. The excess sources are
concentrated within the virial radii of the clusters, with the largest excess
observed near the cluster centers. The average radial profile of the excess
X-ray sources of the cluster are well described by a power law (N(r) ~ r^\beta)
with an index of \beta ~ -0.5. An initial analysis using literature results on
the mean profile of member galaxies in massive X-ray selected clusters
indicates that the fraction of galaxies hosting X-ray AGN rises with increasing
clustercentric radius, being approximately 5 to 10 times higher near the virial
radius than in the central regions. This trend is qualitatively similar to that
observed for star formation in cluster member galaxies.Comment: 18 Pages, 10 Figures, Submitted to MNRAS. Please contact Steven
Ehlert ([email protected]) for higher resolution figures. Updated to
reflect small changes requested by referee. This version has been accepted
into MNRA
Optical Observations of GRO J1655-40 in Quiescence I: A Precise Mass for the Black Hole Primary
We report photometric and spectroscopic observations of the black hole binary
GRO J1655-40 in complete quiescence. In contrast to the 1995 photometry, the
light curves from 1996 are almost completely dominated by ellipsoidal
modulations from the secondary star. Model fits to the light curves, which take
into account the temperature profile of the accretion disk and eclipse effects,
yield an inclination of i=69.50 +/- 0.08 degrees and a mass ratio of Q=2.99 +/-
0.08. The precision of our determinations of i and Q allow us to determine the
black hole mass to an accuracy of approximately 4% (7.02 +/- 0.22 solar
masses). The secondary star's mass is 2.34 +/- 0.12 solar masses. The position
of the secondary on the Hertzsprung-Russell diagram is consistent with that of
a 2.3 solar mass star which has evolved off the main sequence and is halfway to
the start of the giant branch. Using the new spectra we present an improved
value of the spectroscopic period (2.62157 +/- 0.00015 days), radial velocity
semiamplitude (228.2 +/- 2.2 km/sec), and mass function (3.24 +/- 0.09 solar
masses). Evolutionary models suggest an average mass transfer rate for such a
system of 3.4E-9 solar masses per year (2.16E+17 grams per second), which is
much larger than the average mass transfer rates implied in the other six
transient black hole systems, but still barely below the critical mass transfer
rate required for stability.Comment: 30 pages, 12 figures, LaTeX (uses orosztwo.sty), to appear in ApJ,
vol. 474 (March 10, 1997
Quantized Detector Networks: A review of recent developments
QDN (quantized detector networks) is a description of quantum processes in
which the principal focus is on observers and their apparatus, rather than on
states of SUOs (systems under observation). It is a realization of Heisenberg's
original instrumentalist approach to quantum physics and can deal with time
dependent apparatus, multiple observers and inter-frame physics. QDN is most
naturally expressed in the mathematical language of quantum computation, a
language ideally suited to describe quantum experiments as processes of
information exchange between observers and their apparatus. Examples in quantum
optics are given, showing how the formalism deals with quantum interference,
non-locality and entanglement. Particle decays, relativity and non-linearity in
quantum mechanics are discussed.Comment: 59 pages, 14 figures, to be published in Int. J. Mod. Phys.
The INTEGRAL view of the Soft Gamma-ray Repeater SGR 1806-20
We present the results obtained by INTEGRAL on the Soft-Gamma Ray Repeater
SGR 1806-20. In particular we report on the temporal and spectral properties of
the bursts detected during a moderately active period of the source in
September and October 2003 and on the search for quiescent emission.Comment: To appear in the proceedings (ESA-SP) of the 5th INTEGRAL Workshop,
"The INTEGRAL UNIVERSE", Munich, 16-20 February 200
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