42,859 research outputs found
Radio Images of 3C 58: Expansion and Motion of its Wisp
New 1.4 GHz VLA observations of the pulsar-powered supernova remnant 3C 58
have resulted in the highest-quality radio images of this object to date. The
images show filamentary structure over the body of the nebula. The present
observations were combined with earlier ones from 1984 and 1991 to investigate
the variability of the radio emission on a variety of time-scales. No
significant changes are seen over a 110 day interval. In particular, the upper
limit on the apparent projected velocity of the wisp is 0.05c. The expansion
rate of the radio nebula was determined between 1984 and 2004, and is
0.014+/-0.003%/year, corresponding to a velocity of 630+/-70 km/s along the
major axis. If 3C 58 is the remnant of SN 1181, it must have been strongly
decelerated, which is unlikely given the absence of emission from the supernova
shell. Alternatively, the low expansion speed and a number of other arguments
suggest that 3C 58 may be several thousand years old and not be the remnant of
SN 1181.Comment: 12 pages; accepted for publication in the Astrophysical Journa
Disturbances in the spontaneous attribution of social meaning in schizophrenia
Background. Schizophrenia patients show disturbances on a range of tasks that assess mentalizing or 'Theory of Mind' (ToM). However, these tasks are often developmentally inappropriate, make large demands on verbal abilities and explicit problem-solving skills, and involve after-the-fact reflection as opposed to spontaneous mentalizing.
Method. To address these limitations, 55 clinically stable schizophrenia out-patients and 44 healthy controls completed a validated Animations Task designed to assess spontaneous attributions of social meaning to ambiguous
abstract visual stimuli. In this paradigm, 12 animations depict two geometric shapes' interacting' with each other in three conditions: (1) ToM interactions that elicit attributions of mental states to the agents, (2) Goal-Directed (GO) interactions that elicit attributions of simple actions, and (3) Random scenes in which no interaction occurs. Verbal
descriptions of each animation are rated for the degree of Intentionality attributed to the agents and for accuracy.
Results. Patients had lower Intentionality ratings than controls for ToM and GO scenes but the groups did not significantly differ for Random scenes. The descriptions of the patients less closely matched the situations intended by the developers of the task. Within the schizophrenia group, performance on the Animations Task showed minimal
associations with clinical symptoms.
Conclusions. Patients demonstrated disturbances in the spontaneous attribution of mental states to abstract visual stimuli that normally evoke such attributions. Hence, in addition to previously established impairment on mentalizing tasks that require logical inferences about others' mental states, individuals with schizophrenia show disturbances in implicit aspects of mentalizing
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The neurophysiology of biological motion perception in schizophrenia.
IntroductionThe ability to recognize human biological motion is a fundamental aspect of social cognition that is impaired in people with schizophrenia. However, little is known about the neural substrates of impaired biological motion perception in schizophrenia. In the current study, we assessed event-related potentials (ERPs) to human and nonhuman movement in schizophrenia.MethodsTwenty-four subjects with schizophrenia and 18 healthy controls completed a biological motion task while their electroencephalography (EEG) was simultaneously recorded. Subjects watched clips of point-light animations containing 100%, 85%, or 70% biological motion, and were asked to decide whether the clip resembled human or nonhuman movement. Three ERPs were examined: P1, N1, and the late positive potential (LPP).ResultsBehaviorally, schizophrenia subjects identified significantly fewer stimuli as human movement compared to healthy controls in the 100% and 85% conditions. At the neural level, P1 was reduced in the schizophrenia group but did not differ among conditions in either group. There were no group differences in N1 but both groups had the largest N1 in the 70% condition. There was a condition Ă— group interaction for the LPP: Healthy controls had a larger LPP to 100% versus 85% and 70% biological motion; there was no difference among conditions in schizophrenia subjects.ConclusionsConsistent with previous findings, schizophrenia subjects were impaired in their ability to recognize biological motion. The EEG results showed that biological motion did not influence the earliest stage of visual processing (P1). Although schizophrenia subjects showed the same pattern of N1 results relative to healthy controls, they were impaired at a later stage (LPP), reflecting a dysfunction in the identification of human form in biological versus nonbiological motion stimuli
Coulomb screening in mesoscopic noise: a kinetic approach
Coulomb screening, together with degeneracy, is characteristic of the
metallic electron gas. While there is little trace of its effects in transport
and noise in the bulk, at mesoscopic scales the electronic fluctuations start
to show appreciable Coulomb correlations. Within a strictly standard Boltzmann
and Fermi-liquid framework, we analyze these phenomena and their relation to
the mesoscopic fluctuation-dissipation theorem, which we prove. We identify two
distinct screening mechanisms for mesoscopic fluctuations. One is the
self-consistent response of the contact potential in a non-uniform system. The
other couples to scattering, and is an exclusively non-equilibrium process.
Contact-potential effects renormalize all thermal fluctuations, at all scales.
Collisional effects are relatively short-ranged and modify non-equilibrium
noise. We discuss ways to detect these differences experimentally.Comment: Source: REVTEX. 16 pp.; 7 Postscript figs. Accepted for publication
in J. Phys.: Cond. Ma
Family health narratives : midlife women’s concepts of vulnerability to illness
Perceptions of vulnerability to illness are strongly influenced by the salience given to personal experience of illness in the family. This article proposes that this salience is created through autobiographical narrative, both as individual life story and collectively shaped family history. The paper focuses on responses related to health in the family drawn from semi-structured interviews with women in a qualitative study exploring midlife women’s health. Uncertainty about the future was a major emergent theme. Most respondents were worried about a specified condition such as heart disease or breast cancer. Many women were uncertain about whether illness in the family was inherited. Some felt certain that illness in the family meant that they were more vulnerable to illness or that their relatives’ ageing would be mirrored in their own inevitable decline, while a few expressed cautious optimism about the future. In order to elucidate these responses, we focused on narratives in which family members’ appearance was discussed and compared to that of others in the family. The visualisation of both kinship and the effects of illness, led to strong similarities being seen as grounds for worry. This led to some women distancing themselves from the legacies of illness in their families. Women tended to look at the whole family as the context for their perceptions of vulnerability, developing complex patterns of resemblance or difference within their families
Social Determinants of Smoke Exposure During Pregnancy: Findings From Waves 1 & 2 of the Population Assessment of Tobacco and Health (PATH) Study
Maternal smoking during pregnancy (MSDP) and secondhand smoke (SHS) exposure are associated with a myriad of negative health effects for both mother and child. However, less is known regarding social determinants for SHS exposure, which may differ from those of maternal smoking during pregnancy (MSDP). To identify social determinants for SHS exposure only, MSDP only, and MSDP and SHS exposure, data were obtained from all pregnant women (18–54 years; N = 726) in waves 1 and 2 of the Population Assessment of Tobacco and Health Study (2014–2015). Multiple logistic regressions were conducted using SAS 9.4. Smoke exposure during pregnancy was common; 23.0% reported SHS exposure only, 6.1% reported MSDP only, and 11.8% reported both SHS exposure and MSDP. Results demonstrate that relationships between smoke exposure during pregnancy and social determinants vary by type of exposure. Women at risk for any smoke exposure during pregnancy include those who are unmarried and allow the use of combustible tobacco products within the home. Those who are at higher risk for SHS exposure include those who are younger in age, and those who are earlier in their pregnancy. Those who are at higher risk for maternal smoking include those with fair/poor mental health status and those who believe that others\u27 view tobacco use more positively. These results suggest the need for implementing more comprehensive policies that promote smoke-free environments. Implementing these strategies have the potential to improve maternal and fetal health outcomes associated with tobacco smoke exposure
High-field noise in metallic diffusive conductors
We analyze high-field current fluctuations in degenerate conductors by
mapping the electronic Fermi-liquid correlations at equilibrium to their
semiclassical non-equilibrium form. Our resulting Boltzmann description is
applicable to diffusive mesoscopic wires. We derive a non-equilibrium
connection between thermal fluctuations of the current and resistive
dissipation. In the weak-field limit this is the canonical fluctuation-
dissipation theorem. Away from equilibrium, the connection enables explicit
calculation of the excess ``hot-electron'' contribution to the thermal
spectrum. We show that excess thermal noise is strongly inhibited by Pauli
exclusion. This behaviour is generic to the semiclassical metallic regime.Comment: 13 pp, one fig. Companion paper to cond-mat/9911251. Final version,
to appear in J. Phys.: Cond. Ma
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