3,653 research outputs found
Consistent discretizations: the Gowdy spacetimes
We apply the consistent discretization scheme to general relativity
particularized to the Gowdy space-times. This is the first time the framework
has been applied in detail in a non-linear generally-covariant gravitational
situation with local degrees of freedom. We show that the scheme can be
correctly used to numerically evolve the space-times. We show that the
resulting numerical schemes are convergent and preserve approximately the
constraints as expected.Comment: 10 pages, 8 figure
A Study of Gaussianity in CMB band maps
The detection of non-Gaussianity in the CMB data would rule out a number of
inflationary models. A null detection of non-Gaussianity, instead, would
exclude alternative models for the early universe. Thus, a detection or
non-detection of primordial non-Gaussianity in the CMB data is crucial to
discriminate among inflationary models, and to test alternative scenarios.
However, there are various non-cosmological sources of non-Gaussianity. This
makes important to employ different indicators in order to detect distinct
forms of non-Gaussianity in CMB data. Recently, we proposed two new indicators
to measure deviation from Gaussianity on large angular scales, and used them to
study the Gaussianity of the raw band WMAP maps with and without the KQ75 mask.
Here we extend this work by using these indicators to perform similar analyses
of deviation from Gaussianity of the foreground-reduced Q, V, and W band maps.
We show that there is a significant deviation from Gaussianity in the
considered full-sky maps, which is reduced to a level consistent with
Gaussianity when the KQ75 mask is employed.Comment: 5 pages, 2 PS figures, uses ws-ijmpd.cls ; to be published in the
International Journal of Modern Physics
Non-Gaussianity in the HILC foreground-reduced three-year WMAP CMB map
A detection or nondetection of primordial non-Gaussianity in the CMB data is
essential not only to test alternative models of the physics of the early
universe but also to discriminate among classes of inflationary models. Given
this far reaching consequences of such a non-Gaussianity detection for our
understanding of the physics of the early universe, it is important to employ
alternative indicators in order to have further information about the
Gaussianity features of CMB that may be helpful for identifying their origins.
In this way, a considerable effort has recently gone into the design of
non-Gaussianity indicators, and in their application in the search for
deviation from Gaussianity in the CMB data. Recently we have proposed two new
large-angle non-Gaussianity indicators which provide measures of the departure
from Gaussianity on large angular scales. We have used these indicators to
carry out analyses of Gaussianity of the single frequency bands and of the
available foreground-reduced {\it five-year} maps with and without the KQ75
mask. Here we extend and complement these studies by performing a new analysis
of deviation from Gaussianity of the {\it three-year} harmonic ILC (HILC)
foreground-reduced full-sky and KQ75 masked maps obtained from WMAP data. We
show that this full-sky foreground-reduced maps presents a significant
deviation from Gaussianity, which is brought down to a level of consistency
with Gaussianity when the KQ75 mask is employed.Comment: 6 pages, 1 figure. To appear in IJMPD (2010). V2: Corrected ref.[8]
A Computational Theory for the Learning of Equivalence Relations
Equivalence relations (ERs) are logical entities that emerge concurrently with
the development of language capabilities. In this work we propose a
computational model that learns to build ERs by learning simple conditional
rules. The model includes visual areas, dopaminergic, and noradrenergic
structures as well as prefrontal and motor areas, each of them modeled as a
group of continuous valued units that simulate clusters of real neurons. In the
model, lateral interaction between neurons of visual structures and top-down
modulation of prefrontal/premotor structures over the activity of neurons in
visual structures are necessary conditions for learning the paradigm. In terms
of the number of neurons and their interaction, we show that a minimal
structural complexity is required for learning ERs among conditioned stimuli.
Paradoxically, the emergence of the ER drives a reduction in the number of
neurons needed to maintain those previously specific stimulusâresponse
learned rules, allowing an efficient use of neuronal resources
Performance of Shored Earth Retaining Systems During the January 17, 1994, Northridge Earthquake
The performance of several temporary deep shored earth retaining systems during the January 17, 1994 Northridge earthquake in Southern California is documented. These shoring systems ranged from 30 to 70 feet in depth and were subjected to severe ground motions with little deflection or distress
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Serotonergic innervation of the amygdala is increased in autism spectrum disorder and decreased in Williams syndrome.
BackgroundWilliams syndrome (WS) and autism spectrum disorder (ASD) are neurodevelopmental disorders that demonstrate overlapping genetic associations, dichotomous sociobehavioral phenotypes, and dichotomous pathological differences in neuronal distribution in key social brain areas, including the prefrontal cortex and the amygdala. The serotonergic system is critical to many processes underlying neurodevelopment and is additionally an important neuromodulator associated with behavioral variation. The amygdala is heavily innervated by serotonergic projections, suggesting that the serotonergic system is a significant mediator of neuronal activity. Disruptions to the serotonergic system, and atypical structure and function of the amygdala, are implicated in both WS and ASD.MethodsWe quantified the serotonergic axon density in the four major subdivisions of the amygdala in the postmortem brains of individuals diagnosed with ASD and WS and neurotypical (NT) brains.ResultsWe found opposing directions of change in serotonergic innervation in the two disorders, with ASD displaying an increase in serotonergic axons compared to NT and WS displaying a decrease. Significant differences (pâ<â0.05) were observed between WS and ASD data sets across multiple amygdala nuclei.LimitationsThis study is limited by the availability of human postmortem tissue. Small sample size is an unavoidable limitation of most postmortem human brain research and particularly postmortem research in rare disorders.ConclusionsDifferential alterations to serotonergic innervation of the amygdala may contribute to differences in sociobehavioral phenotype in WS and ASD. These findings will inform future work identifying targets for future therapeutics in these and other disorders characterized by atypical social behavior
Osterberg Load Cell Testing of a Deep Reinforced Concrete Pile
A pedestrian bridge was constructed between two portions of a hospital in Southern California. Potentially liquefiable soils were present to a depth of about 72 feet below the ground surface. Because of the liquefiable soils, the bridge was to be supported on 30- inch-diameter cast-in-place piles drilled to a depth of approximately 90 feet below the ground surface. A test pile was constructed to confirm the soil capacities for the bridge. An Osterberg Load cell (O-cell) was placed near the middle of the test pile, and the downward load capacities of the deeper soils (below the elevation of potentially liquefiable soils) were tested using the upper portion of the pile to provide reaction. Instrumentation of the test pile consisted of four pairs of vibrating wire strain gages mounted on the pile reinforcing cage at four depths. The strain gages were connected to a data acquisition unit used to record data during the pile load test. A pair of tell-tale rods connected to electronic dial gages monitored the movement of the lower plate of the O-cell. Another pair of tell-tale rods was used to monitor the movement of the top of pile during the test while a third pair of tell-tale rods was used to monitor the compression of the upper portion of the pile. The pile load test was successful in confirming the predicted pile capacities, and the production piles were installed. The Osterberg Load cell was an economical method of testing the pile for this particular application
Method and apparatus for detecting flaws and defects in heat seals
Flaws and defects in heat seals formed between sheets of translucent film are identified by optically examining consecutive lateral sections of the seal along the seal length. Each lateral seal section is illuminated and an optical sensor array detects the intensity of light transmitted through the seal section for the purpose of detecting and locating edges in the heat seal. A line profile for each consecutive seal section is derived having an amplitude proportional to the change in light intensity across the seal section. Instances in the derived line profile where the amplitude is greater than a threshold level indicate the detection of a seal edge. The detected edges in each derived line profile are then compared to a preset profile edge standard to identify the existence of a flaw or defect
A test of the Poincare dodecahedral space topology hypothesis with the WMAP CMB data
It has been suggested by Roukema and coworkers (hereafter R04) that the
topology of the Universe as probed by the ``matched circles'' method using the
first year release of the WMAP CMB data, might be that of the Poincar\'e
dodecahedral space (PDS) model. An excess in the correlation of the
``identified circles'' was reported by R04, for circles of angular radius of
~11 deg for a relative phase twist -36deg, hinting that this could be due to a
Clifford translation, if the hypothesized model were true.
R04 did not however specify the statistical significance of the correlation
signal.
We investigate the statistical significance of the signal using Monte Carlo
CMB simulations in a simply connected Universe, and present an updated analysis
using the three-year WMAP data. We find that our analyses of the first and
three year WMAP data provide results that are consistent with the simply
connected space at a confidence level as low as 68%.Comment: 8 pages, 6 figures, typo corrected/replaced to match version
published in A&
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