8,024 research outputs found
Curvature Radiation in Rotating Pulsar Magnetosphere
We consider the curvature emission properties from relativistic particles
streaming along magnetic field lines and co-rotating with pulsar magnetosphere.
The co-rotation affects the trajectories of the particles and hence the
emission properties, especially the polarization. We consider the modification
of the particle velocity and acceleration due to the co-rotation. Curvature
radiation from a single particle is calculated using the approximation of a
circular path to the particle trajectory. Curvature radiation from particles at
a given height actually contains the contributions from particles streaming
along all the nearby field lines around the tangential point, forming the
emission cone of 1/{\gamma}. The polarization patterns from the emission cone
are distorted by the additional rotation, more serious for emission from a
larger height. Net circular polarization can be generated by the density
gradient in the emission cone. For three typical density models in the form of
core, cone and patches, we calculate the polarization profiles for emission
generated at a given height. We find that the circular polarization could have
a single sign or sign reversal, depending on the density gradient along the
rotation phase. The polarization profiles of the total curvature radiation from
the whole open field line region, calculated by adding the emission from all
possible heights, are similar to that from a dominating emission height. The
circular polarization of curvature radiation has sign reversals in the patchy
emission, while it has a single sign for the core emission, and is negligible
for the cone emission.Comment: 13pages,20figure
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Dementia assessment and management in primary care settings: a survey of current provider practices in the United States.
BACKGROUND:Primary care providers (PCPs) are typically the first to screen and evaluate patients for neurocognitive disorders (NCDs), including mild cognitive impairment and dementia. However, data on PCP attitudes and evaluation and management practices are sparse. Our objective was to quantify perspectives and behaviors of PCPs and neurologists with respect to NCD evaluation and management. METHODS:A cross-sectional survey with 150 PCPs and 50 neurologists in the United States who evaluated more than 10 patients over age 55 per month. The 51-item survey assessed clinical practice characteristics, and confidence, perceived barriers, and typical practices when diagnosing and managing patients with NCDs. RESULTS:PCPs and neurologists reported similar confidence and approaches to general medical care and laboratory testing. Though over half of PCPs performed cognitive screening or referred patients for cognitive testing in over 50% of their patients, only 20% reported high confidence in interpreting results of cognitive tests. PCPs were more likely to order CT scans than MRIs, and only 14% of PCPs reported high confidence interpreting brain imaging findings, compared to 70% of specialists. Only 21% of PCPs were highly confident that they correctly recognized when a patient had an NCD, and only 13% were highly confident in making a specific NCD diagnosis (compared to 72 and 44% for neurologists, both p < 0.001). A quarter of all providers identified lack of familiarity with diagnostic criteria for NCD syndromes as a barrier to clinical practice. CONCLUSIONS:This study demonstrates how PCPs approach diagnosis and management of patients with NCDs, and identified areas for improvement in regards to cognitive testing and neuroimaging. This study also identified all providers' lack of familiarity with published diagnostic criteria for NCD syndromes. These findings may inform the development of new policies and interventions to help providers improve the efficacy of their decision processes and deliver better quality care to patients with NCDs
On the connection between gamma and radio radiation spectra in pulsars
The model of pulsar radio emission is discussed in which a coherent radio
emis-sion is excited in a vacuum gap above polar cap of neutron star. Pulsar X
and gamma radiation are considered as the result of low-frequency radio
emission inverse Comp-ton scattering on ultra relativistic electrons
accelerated in the gap. The influence of the pulsar magnetic field on Compton
scattering is taken into account. The relation of radio and gamma radiation
spectra has been found in the framework of the model.Comment: 15 pages, 3 figures, Russian version accepted to JETP, partly
published in JETP Letters, Vol. 85, #6 (2007
A funding model for the residential aged care sector. The Resource Utilisation and Classification Study: Report 5
This is one of a series of reports that presents the results of an important national study commissioned by the Department of Health (the Department) to inform the development of a new funding model for residential aged care in Australia. The purpose of this report is to provide an outline of the key design features of the proposed new funding model. Also discussed are the anticipated impacts of the model for both government and the aged care sector, and a recommended approach to implementation
Electronic band structure and carrier effective mass in calcium aluminates
First-principles electronic band structure investigations of five compounds
of the CaO-Al2O3 family, 3CaO.Al2O3, 12CaO.7Al2O3, CaO.Al2O3, CaO.2Al2O3 and
CaO.6Al2O3, as well as CaO and alpha-, theta- and kappa-Al2O3 are performed. We
find that the conduction band in the complex oxides is formed from the oxygen
antibonding p-states and, although the band gap in Al2O3 is almost twice larger
than in CaO, the s-states of both cations. Such a hybrid nature of the
conduction band leads to isotropic electron effective masses which are nearly
the same for all compounds investigated. This insensitivity of the effective
mass to variations in the composition and structure suggests that upon a proper
degenerate doping, both amorphous and crystalline phases of the materials will
possess mobile extra electrons
Chromatic number, clique subdivisions, and the conjectures of Haj\'os and Erd\H{o}s-Fajtlowicz
For a graph , let denote its chromatic number and
denote the order of the largest clique subdivision in . Let H(n) be the
maximum of over all -vertex graphs . A famous
conjecture of Haj\'os from 1961 states that for every
graph . That is, for all positive integers . This
conjecture was disproved by Catlin in 1979. Erd\H{o}s and Fajtlowicz further
showed by considering a random graph that for some
absolute constant . In 1981 they conjectured that this bound is tight up
to a constant factor in that there is some absolute constant such that
for all -vertex graphs . In this
paper we prove the Erd\H{o}s-Fajtlowicz conjecture. The main ingredient in our
proof, which might be of independent interest, is an estimate on the order of
the largest clique subdivision which one can find in every graph on
vertices with independence number .Comment: 14 page
A deep campaign to characterize the synchronous radio/X-ray mode switching of PSR B0943+10
We report on simultaneous X-ray and radio observations of the mode-switching
pulsar PSR B0943+10 obtained with the XMM-Newton satellite and the LOFAR, LWA
and Arecibo radio telescopes in November 2014. We confirm the synchronous
X-ray/radio switching between a radio-bright (B) and a radio-quiet (Q) mode, in
which the X-ray flux is a factor ~2.4 higher than in the B-mode. We discovered
X-ray pulsations, with pulsed fraction of 38+/-5% (0.5-2 keV), during the
B-mode, and confirm their presence in Q-mode, where the pulsed fraction
increases with energy from ~20% up to ~65% at 2 keV. We found marginal evidence
for an increase in the X-ray pulsed fraction during B-mode on a timescale of
hours. The Q-mode X-ray spectrum requires a fit with a two-component model
(either a power-law plus blackbody or the sum of two blackbodies), while the
B-mode spectrum is well fit by a single blackbody (a single power-law is
rejected). With a maximum likelihood analysis, we found that in Q-mode the
pulsed emission has a thermal blackbody spectrum with temperature ~3.4x10^6 K
and the unpulsed emission is a power-law with photon index ~2.5, while during
B-mode both the pulsed and unpulsed emission can be fit by either a blackbody
or a power law with similar values of temperature and photon index. A Chandra
image shows no evidence for diffuse X-ray emission. These results support a
scenario in which both unpulsed non-thermal emission, likely of magnetospheric
origin, and pulsed thermal emission from a small polar cap (~1500 m^2) with a
strong non-dipolar magnetic field (~10^{14} G), are present during both radio
modes and vary in intensity in a correlated way. This is broadly consistent
with the predictions of the partially screened gap model and does not
necessarily imply global magnetospheric rearrangements to explain the mode
switching.Comment: To be published on The Astrophysical Journa
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Empathic Accuracy Deficits in Patients with Neurodegenerative Disease: Association with Caregiver Depression.
OBJECTIVES:To investigate whether deficits in empathic accuracy (i.e., ability to recognize emotion in others) in patients with neurodegenerative disease are associated with greater depression in their caregivers. DESIGN:Two cross-sectional studies. SETTING:Academic medical center and research university. PARTICIPANTS:Two independent samples (N = 172, N = 63) of patients with a variety of neurodegenerative diseases and their caregivers; comparison group of healthy couples. MEASUREMENT:Patients' empathic accuracy was assessed in the laboratory using a novel dynamic tracking task (rating another person's changing emotions over time) and more traditional measures (recognizing the emotion expressed in photographs of facial expressions and by characters in films). Caregivers completed self-report inventories of depression. RESULTS:Lower empathic accuracy in patients was associated with greater depression in caregivers in both studies. In study 1, this association was found when empathic accuracy was measured using the dynamic tracking measure but not when measured using the more traditional photograph and film measures. In study 2, we found preliminary support for our theoretical model wherein lower empathic accuracy in patients is associated with increased caregiver stress (loneliness, strain, and burden), which in turn is associated with greater caregiver depression. CONCLUSIONS:Caring for a patient with deficits in empathic accuracy is associated with greater loneliness, strain, and burden for caregivers, and increased depression. Caregivers may benefit from interventions designed to compensate for the stress and interpersonal loss associated with patients' declining empathic accuracy
Derivation of the Semi-circle Law from the Law of Corresponding States
We show that, for the transition between any two quantum Hall states, the
semi-circle law and the existence of a duality symmetry follow solely from the
consistency of the law of corresponding states with the two-dimensional scaling
flow. This puts these two effects on a sound theoretical footing, implying that
both should hold exactly at zero temperature, independently of the details of
the microscopic electron dynamics. This derivation also shows how the
experimental evidence favours taking the two-dimensional flow seriously for the
whole transition, and not just near the critical points.Comment: 4 pages, 1 figure, typeset in LaTeX (uses revtex
Neuropsychological, Behavioral, and Anatomical Evolution in Right Temporal Variant Frontotemporal Dementia: A Longitudinal Single Case Analysis
We examine longitudinal clinical and anatomical data for a patient with the right temporal variant of frontotemporal dementia. The patient received comprehensive clinical evaluations and structural MRI scans over three years. She presented with early behavioral deficits and ultimately developed semantic impairments consistent with the semantic variant of primary progressive aphasia. Imaging revealed early atrophy of the right temporal lobe, with later involvement of the left, and pathology confirmed bilateral temporal involvement. Findings support the view that right and left temporal variants reflect early asymmetry of atrophy that may become more bilateral over time, resulting in a mixed clinical picture
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