5,272 research outputs found
Executive function in first-episode schizophrenia
BACKGROUND: We tested the hypothesis that schizophrenia is primarily a frontostriatal disorder by examining executive function in first-episode patients. Previous studies have shown either equal decrements in many cognitive domains or specific deficits in memory. Such studies have grouped test results or have used few executive measures, thus, possibly losing information. We, therefore, measured a range of executive ability with tests known to be sensitive to frontal lobe function.
METHODS: Thirty first-episode schizophrenic patients and 30 normal volunteers, matched for age and NART IQ, were tested on computerized test of planning, spatial working memory and attentional set shifting from the Cambridge Automated Neuropsychological Test Battery. Computerized and traditional tests of memory were also administered for comparison. RESULTS: Patients were worse on all tests but the profile was non-uniform. A componential analysis indicated that the patients were characterized by a poor ability to think ahead and organize responses but an intact ability to switch attention and inhibit prepotent responses. Patients also demonstrated poor memory, especially for free recall of a story and associate learning of unrelated word pairs.
CONCLUSIONS: In contradistinction to previous studies, schizophrenic patients do have profound executive impairments at the beginning of the illness. However, these concern planning and strategy use rather than attentional set shifting, which is generally unimpaired. Previous findings in more chronic patients, of severe attentional set shifting impairment, suggest that executive cognitive deficits are progressive during the course of schizophrenia. The finding of severe mnemonic impairment at first episode suggests that cognitive deficits are not restricted to one cognitive domain
The population of Comet candidates among quasi-Hilda objects revisited and updated
In this paper, we perform a dynamical study of the population of objects in
the unstable quasi-Hilda region. The aim of this work is to make an update of
the population of quasi-Hilda comets (QHCs) that have recently arrived from the
Centaurs region. To achieve our goal, we have applied a dynamical criteria to
constrain the unstable quasi-Hilda region that allowed us to select 828
potential candidates. The orbital data of the potential candidates was take
from the ASTORB database and we apply backward integration to search by those
that have recently arrived from the outer regions of the Solar System. Then we
studied the dynamical evolution of the candidates from a statistical point of
view by calculating the time-averaged distribution of a number of clones of
each candidate as a function of aphelion and perihelion distances. We found
that 47 objects could have been recently injected into the inner Solar System
from the Centaur or transneptunian regions. These objects may have preserved
volatile material and are candidates to exhibit cometary activity.Comment: 7 pages 3 figure
Susceptibility of Vitis vinifera 'Semillon' and 'Chardonnay' to the root-knot nematode Meloidogyne javanica
A study to assess the effect of the initial population (Pi) densities (0, 200, 400, 600 and 800 second stage juveniles (J2) kg-1 dry soil) of the root knot nematode, Meloidogyne javanica, on the growth, yield and juice characteristics of two white wine grapevine (Vitis vinifera) cvs. 'Semillon' and 'Chardonnay' was conducted in a vineyard located at the Centre for Irrigated Agriculture, Riverina, NSW, Australia. M. javanica J2 population densities in soil after harvest during 2004-2008 growing seasons increased gradually, year by year, and in most cases were higher where the initial densities were higher. Regression analysis revealed that yield, in general, was reduced significantly with the increase of the nematode population densities·kg-1 soil for both cultivars. After six years, the nematode population had increased by ca. 9.0-22.4 fold for 'Semillon' and 6.7-18.5 fold for 'Chardonnay'. All Pi densities significantly reduced Semillon yields in all years but only the highest level (800 J2·kg-1 dry soil) affected 'Chardonnay' yields. At the end of the experiment, M. javanica decreased yields by 15-20 % in Semillon but only 7-13 % in 'Chardonnay'. The nematode inoculation also caused a decrease in bunch numbers in 'Semillon' but not in 'Chardonnay'. This is the first study showing that 'Chardonnay' is less susceptible to M. javanica than 'Semillon'.
Buckling mediated by mobile localized elastic excitations
Experiments reveal that structural transitions in thin sheets are mediated by
the passage of transient and stable mobile localized elastic excitations. These
``crumples'' or ``d-cones'' nucleate, propagate, interact, annihilate, and
escape. Much of the dynamics occurs on millisecond time scales. Nucleation
sites correspond to regions where generators of the ideal unstretched surface
converge. Additional stable intermediate states illustrate two forms of
quasistatic inter-crumple interaction through ridges or valleys. These
interactions create pairs from which extended patterns may be constructed in
larger specimens. The onset of localized transient deformation with increasing
sheet size is correlated with a characteristic stable crumple size, whose
measured scaling with thickness is consistent with prior theory and experiment
for localized elastic features in thin sheets. We offer a new theoretical
justification of this scaling.Comment: contains link to video
The first confirmation of V-type asteroids among the Mars crosser population
The Mars crossing region constitutes a path to deliver asteroids from the
Inner Main Belt to the Earth crossing space. While both the Inner Main Belt and
the population of Earth crossing asteroids contains a significant fraction of
asteroids belonging to the V taxonomic class, only two of such V-type asteroids
has been detected in the Mars crossing region up to now. In this work, we
searched for asteroids belonging to the V class among the population of Mars
crossing asteroids, in order to support alternative paths to the delivery of
this bodies into the Earth crossing region. We selected 18 candidate V-type
asteroids in the Mars crossing region using observations contained in the Sloan
Digital Sky Survey Moving Objects Catalog. Then, we observed 4 of these
candidates to take their visible spectra using the Southern Astrophysical
Research Telescope (SOAR). We also performed the numerical simulation of the
orbital evolution of the observed asteroids. We confirmed that 3 of the
observed asteroids belong to the V class, and one of these may follow a path
that drives it to an Earth collision in some tens of million years
Magnetic variation anomalies in northern England and southern Scotland
Single-station transfer functions linking the time variations of the vertical and horizontal components of the magnetic field at stations in northern England and southern Scotland have been compiled into a uniform data set. From hypothetical event analysis we show here that there are two distinct anomalies in the Borders region. One runs south-west to north-east, immediately to the south-east of the Southern Uplands Fault; the second follows the Northumberland Basin, and seems to exist because the conductive sedimentary rocks filling the basin create a link between the Irish and North Seas. If the Iapetus suture is marked by a conductivity anomaly, as has been suggested, these results place it beneath the Southern Uplands, unless it is masked by the surface conductor in the Northumberland Basin
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Thorium Energy Futures
The potential for thorium as an alternative or supplement to uranium in fission power generation has long been recognised, and several reactors, of various types, have already operated using thorium-based fuels. Accelerator Driven Subcritical (ADS) systems have benefits and drawbacks when compared to conventional critical thorium reactors, for both solid and molten salt fuels. None of the four options – liquid or solid, with or without an accelerator – can yet be rated as better or worse than the other three, given today's knowledge. We outline the research that will be necessary to lead to an informed choice
Development of a Superconducting Twin Axis Cavity
Superconducting cavities with two separate accelerating axes have been proposed in the past for energy recovery linac applications. While the study showed the advantages of such cavity, the designs present serious fabrication challenges. Hence the proposed cavities have never been built. The new design, elliptical twin cavity, proposed by Jefferson Lab and optimized by Center for Accelerator Science at Old Dominion University, allows similar level of engineering and fabrication techniques of a typical elliptical cavity. This paper describes preliminary LOM and HOM spectrum, engineering and fabrication processes of the twin axis cavity
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