4,025 research outputs found
Three Dimensional Distorted Black Holes: Initial Data and Evolution
We present a new class of 3D black hole initial data sets for numerical
relativity. These data sets go beyond the axisymmetric, ``gravity wave plus
rotating black hole'' single black hole data sets by creating a dynamic,
distorted hole with adjustable distortion parameters in 3D. These data sets
extend our existing test beds for 3D numerical relativity, representing the
late stages of binary black hole collisions resulting from on-axis collision or
3D spiralling coalescence, and should provide insight into the physics of such
systems. We describe the construction of these sets, the properties for a
number of example cases, and report on progress evolving them.Comment: 3 pages, 2 postscript figures, LaTeX, uses mprocl.sty (available at
http://shemesh.fiz.huji.ac.il/MG8/submission.html) To appear in the
proceedings of the Marcel Grossmann 8 (Jerusalem, 1997
A systematic review of neuropsychiatric symptoms in mild cognitive impairment
Mild cognitive impairment (MCI) is a clinical concept proposed as an intermediate state between normal aging and dementia. This condition has multiple heterogeneous sources, including clinical presentation, etiology, and prognosis. Recently, the prevalence and associated features of neuropsychiatric symptoms (NPS) in MCI have been described. We systematically searched the PubMed database (last accessed on August 31, 2008) for articles on NPS in MCI. Included articles used strict selection criteria, and outcome variables were extracted in duplicate; of the 27 articles included, 14 (52%) used prospective cohorts. The global prevalence of NPS in MCI ranged from 35% to 85%. The most common behavioral symptoms were depression, anxiety, and irritability. Hospital-based samples reported a higher global prevalence of NPS than population-based studies; this discrepancy probably reflected differences in demographics, study setting, MCI diagnostic criteria, and behavioral instruments used. Prospective studies showed that NPS, particularly depression, may represent risk factors for MCI or predictors for the conversion of MCI to Alzheimer's disease (AD). NPS are very prevalent in subjects with MCI, displaying a similar pattern of symptoms compared to dementia and AD. Large cohort studies using standardized MCI criteria and behavioral instruments are required to evaluate the prognostic role of NPS in MCI.Mild cognitive impairment (MCI) is a clinical concept proposed as an intermediate state between normal aging and
dementia. This condition has multiple heterogeneous sources, including clinical presentation, etiology, and prognosis. Recently,
the prevalence and associated features of neuropsychiatric symptoms (NPS) in MCI have been described. We systematically
searched the PubMed database (last accessed on August 31, 2008) for articles on NPS in MCI. Included articles used strict
selection criteria, and outcome variables were extracted in duplicate; of the 27 articles included, 14 (52%) used prospective
cohorts. The global prevalence of NPS in MCI ranged from 35% to 85%. The most common behavioral symptoms were
depression, anxiety, and irritability. Hospital-based samples reported a higher global prevalence of NPS than population-based
studies; this discrepancy probably reflected differences in demographics, study setting, MCI diagnostic criteria, and behavioral
instruments used. Prospective studies showed that NPS, particularly depression, may represent risk factors for MCI or predictors
for the conversion of MCI to Alzheimer’s disease (AD). NPS are very prevalent in subjects with MCI, displaying a similar pattern
of symptoms compared to dementia and AD. Large cohort studies using standardized MCI criteria and behavioral instruments
are required to evaluate the prognostic role of NPS in MC
Movements execution in amnestic mild cognitive impairment and Alzheimer's disease.
We evaluated the relationship between motor and neuropsychological deficits in subjects affected by amnestic Mild Cognitive Impairment (aMCI) and {early} Alzheimer's Disease (AD). Kinematics of goal-directed movement of aMCI and AD subjects were compared to those of age-matched control subjects. AD showed a slowing down of motor performance compared to aMCI and controls. No relationships were found between motor and cognitive performances in both AD and aMCI. Our results suggest that the different motor behaviour between AD and aMCI cannot be related to memory deficits, probably reflecting the initial degeneration of parietal-frontal circuits for movement planning. The onset of motor dysfunction in early AD could represent the transition from aMCI to AD
Continuous monitoring of hydrogen and carbon dioxide at Mt Etna
This study assessed the use of an H2 fuel cell as an H2-selective sensor for volcano monitoring. The resolution,
repeatability, and cross-sensitivity of the sensor were investigated and evaluated under known laboratory
conditions. A tailor-made device was developed and used for continuously monitoring H2 and CO2 at Mt Etna
throughout 2009 and 2010. The temporal variations of both parameters were strongly correlated with the
evolution of the volcanic activity during the monitoring period. In particular, the CO2 flux exhibited long-term
variations, while H2 exhibited pulses immediately before the explosive activity that occurred at Mt Etna during
2010
Global-Local Finite Element Analysis for Thermo-Mechanical Stresses in Bonded Joints
An analysis of adhesively bonded joints using conventional finite elements does not capture the singular behavior of the stress field in regions where two or three dissimilar materials form a junction with or without free edges. However, these regions are characteristic of the bonded joints and are prone to failure initiation. This study presents a method to capture the singular stress field arising from the geometric and material discontinuities in bonded composites. It is achieved by coupling the local (conventional) elements with global (special) elements whose interpolation functions are constructed from the asymptotic solution
Three Dimensional Distorted Black Holes
We present three-dimensional, {\it non-axisymmetric} distorted black hole
initial data which generalizes the axisymmetric, distorted, non-rotating
[Bernstein93a] and rotating [Brandt94a] single black hole data developed by
Bernstein, Brandt, and Seidel. These initial data should be useful for studying
the dynamics of fully 3D, distorted black holes, such as those created by the
spiraling coalescence of two black holes. We describe the mathematical
construction of several families of such data sets, and show how to construct
numerical solutions. We survey quantities associated with the numerically
constructed solutions, such as ADM masses, apparent horizons, measurements of
the horizon distortion, and the maximum possible radiation loss ().Comment: 23 pages, 12 figures, accepted for publication in Classical and
Quantum Gravit
Taxonomic revision of the Astragalus genargenteus complex (Fabaceae)
Within the Astragalus genargenteus complex three morphologically, ecologically and chorologically
well differentiated taxa are distinguished: A. genargenteus from siliceous substrate in the Gennargentu
massif (central Sardinia) and two species described as new to science, A. gennarii from limestone on
Monte Albo (NE Sardinia) and A. greuteri, widespread on siliceous substrate in the Corsican mountains.
The relationship of these species with the allied, spine cushion-like A. sirinicus and A. angustifolius
is examined. A key to the species and illustrations are given
Symmetry without Symmetry: Numerical Simulation of Axisymmetric Systems using Cartesian Grids
We present a new technique for the numerical simulation of axisymmetric
systems. This technique avoids the coordinate singularities which often arise
when cylindrical or polar-spherical coordinate finite difference grids are
used, particularly in simulating tensor partial differential equations like
those of 3+1 numerical relativity. For a system axisymmetric about the z axis,
the basic idea is to use a 3-dimensional Cartesian (x,y,z) coordinate grid
which covers (say) the y=0 plane, but is only one
finite-difference-molecule--width thick in the y direction. The field variables
in the central y=0 grid plane can be updated using normal (x,y,z)--coordinate
finite differencing, while those in the y \neq 0 grid planes can be computed
from those in the central plane by using the axisymmetry assumption and
interpolation. We demonstrate the effectiveness of the approach on a set of
fully nonlinear test computations in 3+1 numerical general relativity,
involving both black holes and collapsing gravitational waves.Comment: 17 pages, 4 figure
Overview about E-Mobility Conducted Immunity Tests on ESA Communication Lines
Due to the complexity of the Automotive Electromagnetic Compatibility legislation in force, this article aims to describe a simplified overview of several technical standards relating to conducted immunity tests on electronic sub-assemblies, where communication lines are involved. The discussed automotive standards reported in this article are: ISO 11452-1 and ISO 11452-4 for continuous narrowband electromagnetic fields immunity test, bulk current injection and tubular wave coupler, IEC 61000-4-5 for immunity against surge events, IEC 61000-4-4 for electrical fast transient/burst events immunity, ISO 10605 for electrostatic discharge events immunity, ISO 7637-2 and ISO 7637-3 for transient disturbances events immunity. For each cited standard, disturbance bandwidth evaluation was performed. Practical examples are reported, with analysis and discussion of some of the adoptable disturbance countermeasures applicable on controlled area network communication lines, and possible design advantages and disadvantages with different types of filtering and suppression circuit solutions
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