78 research outputs found
A Faraday Rotation Template for the Galactic Sky
Using a set of compilations of measurements for extragalactic radio sources
we construct all-sky maps of the Faraday Rotation produced by the Galactic
magnetic field. In order to generate the maps we treat the radio source
positions as a kind of "mask" and construct combinations of spherical harmonic
modes that are orthogonal on the masked sky. As long as relatively small
multipoles are used the resulting maps are quite stable to changes in selection
criteria for the sources, and show clearly the structure of the local Galactic
magnetic field. We also suggest the use of these maps as templates for CMB
foreground analysis, illustrating the idea with a cross-correlation analysis
between the Wilkinson Microwave Anisotropy Probe (WMAP) data and our maps. We
find a significant cross-correlation, indicating the presence of significant
residual contamination.Comment: 9 pages, 9 figures, accepted for publication in MNRA
Non-Random Phases in Non-Trivial Topologies
We present a new technique for constraining the topology of the universe. The
method exploits the existence of correlations in the phases of the spherical
harmonic coefficients of the CMB temperature pattern associated with matched
pairs of circles seen in the sky in universes with non-trivial topology. The
method is computationally faster than all other statistics developed to hunt
for these matched circles. We applied the method to a range of simulations with
topologies of various forms and on different scales. A characteristic form of
phase correlation is found in the simulations. We also applied the method to
preliminary CMB maps derived from WMAP, but the separation of topological
effects from, e.g., foregrounds is not straightforward.Comment: 5 pages, accepted for publication in MNRA
Phase Correlations in Cosmic Microwave Background Temperature Maps
We study the statistical properties of spherical harmonic modes of
temperature maps of the cosmic microwave background. Unlike other studies,
which focus mainly on properties of the amplitudes of these modes, we look
instead at their phases. In particular, we present a simple measure of phase
correlation that can be diagnostic of departures from the standard assumption
that primordial density fluctuations constitute a statistically homogeneous and
isotropic Gaussian random field, which should possess phases that are uniformly
random on the unit circle. The method we discuss checks for the uniformity of
the distribution of phase angles using a non-parametric descriptor based on the
use order statistics, which is known as Kuiper's statistic. The particular
advantage of the method we present is that, when coupled to the judicious use
of Monte Carlo simulations, it can deliver very interesting results from small
data samples. In particular, it is useful for studying the properties of
spherical harmonics at low l for which there are only small number of
independent values of m and which therefore furnish only a small number of
phases for analysis. We apply the method to the COBE-DMR and WMAP sky maps, and
find departures from uniformity in both. In the case of WMAP, our results
probably reflect Galactic contamination or the known variation of
signal-to-noise across the sky rather than primordial non-Gaussianity.Comment: 18 pages, 4 figures, accepted for publication in MNRA
Statistical Characterization of Temperature Patterns in Anisotropic Cosmologies
We consider the issue of characterizing the coherent large-scale patterns
from CMB temperature maps in globally anisotropic cosmologies. The methods we
investigate are reasonably general; the particular models we test them on are
the homogeneous but anisotropic relativistic cosmologies described by the
Bianchi classification. Although the temperature variations produced in these
models are not stochastic, they give rise to a "non-Gaussian" distribution of
temperature fluctuations over the sky that is a partial diagnostic of the
model. We explore two methods for quantifying non-Gaussian and/or
non-stationary fluctuation fields in order to see how they respond to the
Bianchi models.We first investigate the behavior of phase correlations between
the spherical harmonic modes of the maps. Then we examine the behavior of the
multipole vectors of the temperature distribution which, though defined in
harmonic space, can indicate the presence of a preferred direction in real
space, i.e. on the 2-sphere. These methods give extremely clear signals of the
presence of anisotropy when applied to the models we discuss, suggesting that
they have some promise as diagnostics of the presence of global asymmetry in
the Universe.Comment: 14 pages, 10 figures, 4 tables, accepted by MNRA
Faraday Rotation as a Diagnostic of Galactic Foreground Contamination of CMB Maps
We present a diagnostic test of possible Galactic contamination of cosmic
microwave background sky maps designed to provide an independent check on the
methods used to compile these maps. The method involves a non-parametric
measurement of cross-correlation between the Faraday rotation measure (RM) of
extragalactic sources and the measured microwave signal at the same angular
position. We argue that statistical properties of the observed distribution of
rotation measures are consistent with a Galactic origin, an argument reinforced
by a direct measurement of cross-correlation between dust, free-free and
synchrotron foreground maps and RM values with the strongest correlation being
for dust and free-free. We do not find any statistically compelling evidence
for correlations between the RM values and the COBE DMR maps at any frequency,
so there is no evidence of residual contamination in these CMB maps. On the
other hand, there is a statistically significant correlation of RM with the
preliminary WMAP individual frequency maps which remains significant in the
Tegmark et al. Wiener-filtered map but not in the Internal Linear Combination
map produced by the WMAP team.Comment: 8 pages, 1 figure, accepted for publication in MNRA
Beyond Functional Diversity: The Importance of Trophic Position to Understanding Functional Processes in Community Evolution
Ecosystem structure—that is the species present, the functions they represent, and how those functions interact—is an important determinant of community stability. This in turn aects how ecosystems respond to natural and anthropogenic crises, and whether species or the ecological functions that they represent are able to persist. Here we use fossil data from museum collections, literature, and the Paleobiology Database to reconstruct trophic networks of Tethyan paleocommunities fromthe Anisian and Carnian (Triassic), Bathonian (Jurassic), and Aptian (Cretaceous) stages, and compare these to a previously reconstructed trophic network from a modern Jamaican reef community. We generated model food webs consistent with functional structure and taxon richnesses of communities, and compared distributions of guild level parameters among communities, to assess the eect of the Mesozoic Marine Revolution on ecosystem dynamics. We found that the trophic space of communities expanded from the Anisian to the Aptian, but this pattern was notmonotonic.We also found that trophic position for a given guild was subject to variation depending on what other guilds were present in that stage. The Bathonian showed the lowest degree of trophic omnivory by top consumers among all Mesozoic networks, and was dominated by longer food chains. In contrast, the Aptian network displayed a greater degree of short food chains and trophic omnivory that we attribute to the presence of large predatory guilds, such as sharks and bony fish. Interestingly, the modern Jamaican community appeared to have a higher proportion of long chains, as was the case in the Bathonian. Overall, results indicate that trophic structure is highly dependent on the taxa and ecological functions present, primary production experienced by the community, and activity of top consumers. Results from this study point to a need to better understand trophic position when planning restoration activities because a community may be so altered by human activity that restoring a species or its interactions may no longer be possible, and alternatives must be considered to restore an important function. Further work may also focus on elucidating the precise roles of top consumers in moderating network structure and community stability
Investigating hyper-vigilance for social threat of lonely children
The hypothesis that lonely children show hypervigilance for social threat was examined in a series of three studies that employed different methods including advanced eye-tracking technology. Hypervigilance for social threat was operationalized as hostility to ambiguously motivated social exclusion in a variation of the hostile attribution paradigm (Study 1), scores on the Children’s Rejection-Sensitivity Questionnaire (Study 2), and visual attention to socially rejecting stimuli (Study 3). The participants were 185 children (11 years-7 months to 12 years-6 months), 248 children (9 years-4 months to 11 years-8 months) and 140 children (8 years-10 months to 12 years-10 months) in the three studies, respectively. Regression analyses showed that, with depressive symptoms covaried, there were quadratic relations between loneliness and these different measures of hypervigilance to social threat. As hypothesized, only children in the upper range of loneliness demonstrated elevated hostility to ambiguously motivated social exclusion, higher scores on the rejection sensitivity questionnaire, and disengagement difficulties when viewing socially rejecting stimuli. We found that very lonely children are hypersensitive to social threat
Determinants of workload-related clinician stress levels in general hospital consultation liaison psychiatry services during the COVID-19 pandemic in England and Ireland. Short report
OBJECTIVE: To explore workload-related stress levels experienced by consultation liaison psychiatry (CLP) staff in England and Ireland, and factors relevant to such a burden, during the COVID-19 pandemic. METHODS: Data were obtained for England and Ireland from a European survey among CLP services in general hospitals spread via CLP networks (11th June - 3rd October 2021). The heads of respective CLP services in general hospitals responded on behalf of each service, on 100 CLP hospital staff in total. DEPENDENT VARIABLE: workload-related stress levels in CLP services due to COVID-19 (0-10 point scale). INDEPENDENT VARIABLES: hospital size, CLP service size, degree of hospital involvement in COVID-19-related care, and the number of support options available to hospital staff. Spearman's rho correlation analyses were performed. RESULTS: There was a significant association between the hospital's involvement in COVID-19-related care and workload-related stress levels as reported by CLP staff: r(22) = 0.41, p = 0.045, R2 = 0.17. There were no significant associations between workload-related stress levels and other variables including staff support (p = 0.74). CONCLUSION: Our findings suggest that perceived workload-related stress levels of CLP staff during the COVID-19 pandemic can be an indicator of COVID-19 involvement of the hospitals. Staff support seemed not to alleviate work stress in the context of the pandemic. Healthcare policies should improve working conditions for CLP hospital staff that play an essential role from a population health perspective. Rigorous measures may be needed to ensure mental healthcare provision remains tenable and sustainable in the long term
Surgical Treatment of Renal Cell Cancer Liver Metastases: A Population-Based Study
Background: To evaluate outcomes of surgical treatment in patients with hepatic metastases from renal-cell carcinoma in the Netherlands, and to identify prognostic factors for survival after resection. Renal-cell carcinoma has an incidence of 2,000 new patients in the Netherlands each year (12.5/100,000 inhabitants). According to literature, half of these patients ultimately develop distant metastases with 20% involvement of the liver. Resection of renal-cell carcinoma liver metastases (RCCLM) is performed in only a minority of patients. Hence, little is known about outcome of resectable RCCLM. Methods: Patients were retrieved from local databases of theNetherlands Task Force for Liver Surgery (14 centers) and from the Dutch collective pathology database. Survival and prognostic factors were determined by Kaplan-Meier analysis and log rank test. Results: Thirty-three patients were identified who underwent resection (n = 29) or local ablation (n = 4) of RCCLM in the Netherlands between 1990 and 2008. These patients comprise 0.5% to 1% of the total population of patients diagnosed with RCCLM in that period. There was no operative mortality. The overall survival at 1, 3, and 5 years was 79, 47, and 43%, respectively. Metachronous metastases (n = 23, P = 0.03) and radical resection (n = 19, P < 0.001) were statistically significant prognosticators of ov
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