9,168 research outputs found
Results from a Second RXTE Observation of the Coma Cluster
The RXTE satellite observed the Coma cluster for 177 ksec during November and
December 2000, a second observation motivated by the intriguing results from
the first 87 ksec observation in 1996. Analysis of the new dataset confirms
that thermal emission from isothermal gas does not provide a good fit to the
spectral distribution of the emission from the inner 1 degree radial region.
While the observed spectrum may be fit by emission from gas with a substantial
temperature gradient, it is more likely that the emission includes also a
secondary non-thermal component. If so, non-thermal emission comprises ~8% of
the total 4--20 keV flux. Interpreting this emission as due to Compton
scattering of relativistic electrons (which produce the known extended radio
emission) by the cosmic microwave background radiation, we determine that the
mean, volume-averaged magnetic field in the central region of Coma is B =
0.1-0.3 microgauss.Comment: 10 pages, 1 figure; APJ, in pres
Trailing Edge Noise Reduction by Passive and Active Flow Controls
This paper presents the results on the use of porous metal foams (passive control) and dielectric barrier surface plasma actuations (active control) for the reduction of vortex shedding tonal noises from the nonflat plate type trailing edge serration in a NACA0012 airfoil previously discussed in Chong et al. (AIAA J. Vol. 51, 2013, pp. 2665-2677). The use of porous metal foams to fill the interstices between adjacent members of the sawtooth can almost completely suppress the vortex shedding tonal noise, whilst the serration effect on the broadband noise reduction is retained. This concept will promote the nonflat plate type serrated trailing edge to become a genuine alternative to the conventional flat plate type serrated trailing edge, which is known to have drawbacks in the structural stability, aerodynamic performances and implementation issues. For the plasma actuators, configuration which produces electric wind in a tangential direction is found to be not very effective in suppressing the vortices emanated from the serration blunt root. On the other hand, for the plasma configuration which produces electric wind in a vertical direction, good level of vortex shedding tonal noise reduction has been demonstrated. However, the self noise produced by the plasma actuators negates the noise benefits on the tonal noise reduction. This characteristic illustrates the need to further develop the plasma actuators in a two pronged approach. First is to increase the electric wind speed, thereby allowing the plasma actuators to be used in a higher free jet velocity which naturally produces a larger level of jet noise. Second, the self noise radiated by the plasma actuators should be reduced
The impact of satellite temperature soundings on the forecasts of a small national meteorological service
The impact of introducing satellite temperature sounding data on a numerical weather prediction model of a national weather service is evaluated. A dry five level, primitive equation model which covers most of the Northern Hemisphere, is used for these experiments. Series of parallel forecast runs out to 48 hours are made with three different sets of initial conditions: (1) NOSAT runs, only conventional surface and upper air observations are used; (2) SAT runs, satellite soundings are added to the conventional data over oceanic regions and North Africa; and (3) ALLSAT runs, the conventional upper air observations are replaced by satellite soundings over the entire model domain. The impact on the forecasts is evaluated by three verification methods: the RMS errors in sea level pressure forecasts, systematic errors in sea level pressure forecasts, and errors in subjective forecasts of significant weather elements for a selected portion of the model domain. For the relatively short range of the present forecasts, the major beneficial impacts on the sea level pressure forecasts are found precisely in those areas where the satellite sounding are inserted and where conventional upper air observations are sparse. The RMS and systematic errors are reduced in these regions. The subjective forecasts of significant weather elements are improved with the use of the satellite data. It is found that the ALLSAT forecasts are of a quality comparable to the SAR forecasts
Influence of peptidylarginine deiminase type 4 genotype and shared epitope on clinical characteristics and autoantibody profile of rheumatoid arthritis.
Background: Recent evidence suggests that distinction
of subsets of rheumatoid arthritis (RA) depending on anticyclic
citrullinated peptide antibody (anti-CCP) status may
be helpful in distinguishing distinct aetiopathologies and in
predicting the course of disease. HLA-DRB1 shared
epitope (SE) and peptidylarginine deiminase type 4
(PADI4) genotype, both of which have been implicated in
anti-CCP generation, are assumed to be associated with
RA.
Objectives: To elucidate whether PADI4 affects the
clinical characteristics of RA, and whether it would
modulate the effect of anti-CCPs on clinical course. The
combined effect of SE and PADI4 on autoantibody profile
was also analysed.
Methods: 373 patients with RA were studied. SE,
padi4_94C.T, rheumatoid factor, anti-CCPs and antinuclear
antibodies (ANAs) were determined. Disease
severity was characterised by cumulative therapy
intensity classified into ordinal categories (CTI-1 to CTI-3)
and by Steinbrocker score.
Results: CTI was significantly associated with disease
duration, erosive disease, disease activity score (DAS) 28
and anti-CCPs. The association of anti-CCPs with CTI was
considerably influenced by padi4_94C.T genotype (C/C:
ORadj=0.93, padj=0.92; C/T: ORadj=2.92,
padj=0.093; T/T: ORadj=15.3, padj=0.002). Carriage of
padi4_94T exhibited a significant trend towards higher
Steinbrocker scores in univariate and multivariate
analyses. An association of padi4_94C.T with ANAs
was observed, with noteworthy differences depending on
SE status (SE2: ORadj=6.20, padj,0.04; SE+:
ORadj=0.36, padj=0.02) and significant heterogeneity
between the two SE strata (p=0.006).
Conclusions: PADI4 genotype in combination with anti-
CCPs and SE modulates clinical and serological characteristics
of RA
Phase Separation and Charge-Ordered Phases of the d = 3 Falicov-Kimball Model at T>0: Temperature-Density-Chemical Potential Global Phase Diagram from Renormalization-Group Theory
The global phase diagram of the spinless Falicov-Kimball model in d = 3
spatial dimensions is obtained by renormalization-group theory. This global
phase diagram exhibits five distinct phases. Four of these phases are
charge-ordered (CO) phases, in which the system forms two sublattices with
different electron densities. The CO phases occur at and near half filling of
the conduction electrons for the entire range of localized electron densities.
The phase boundaries are second order, except for the intermediate and large
interaction regimes, where a first-order phase boundary occurs in the central
region of the phase diagram, resulting in phase coexistence at and near half
filling of both localized and conduction electrons. These two-phase or
three-phase coexistence regions are between different charge-ordered phases,
between charge-ordered and disordered phases, and between dense and dilute
disordered phases. The second-order phase boundaries terminate on the
first-order phase transitions via critical endpoints and double critical
endpoints. The first-order phase boundary is delimited by critical points. The
cross-sections of the global phase diagram with respect to the chemical
potentials and densities of the localized and conduction electrons, at all
representative interactions strengths, hopping strengths, and temperatures, are
calculated and exhibit ten distinct topologies.Comment: Calculated density phase diagrams. Added discussions and references.
14 pages, 9 figures, 4 table
Effects of age and eccentricity on visual target detection
The aim of this study was to examine the effects of aging and target eccentricity on a visual search task comprising 30 images of everyday life projected into a hemisphere, realizing a ±90° visual field. The task performed binocularly allowed participants to freely move their eyes to scan images for an appearing target or distractor stimulus (presented at 10°; 30°, and 50° eccentricity). The distractor stimulus required no response, while the target stimulus required acknowledgment by pressing the response button. One hundred and seventeen healthy subjects (mean age = 49.63 years, SD = 17.40 years, age range 20–78 years) were studied. The results show that target detection performance decreases with age as well as with increasing eccentricity, especially for older subjects. Reaction time also increases with age and eccentricity, but in contrast to target detection, there is no interaction between age and eccentricity. Eye movement analysis showed that younger subjects exhibited a passive search strategy while older subjects exhibited an active search strategy probably as a compensation for their reduced peripheral detection performance
Ontology-based Domain Diversity Profiling of User Comments
Diversity has been the subject of study in various disciplines from biology to social science and computing. Respecting and utilising the diversity of the population is increasingly important to broadening knowledge. This paper describes a pipeline for diversity profiling of a pool of text in order to understand its coverage of an underpinning domain. The application is illustrated by using a domain ontology on presentation skills in a case study with 38 postgraduates who made comments while learning pitch presentations with the Active Video Watching system (AVW-Space). The outcome shows different patterns of coverage on the domain by the comments in each of the eight videos
Social network analysis shows direct evidence for social transmission of tool use in wild chimpanzees
The authors are grateful to the Royal Zoological Society of Scotland for providing core funding for the Budongo Conservation Field Station. The fieldwork of CH was funded by the Leverhulme Trust, the Lucie Burgers Stichting, and the British Academy. TP was funded by the Canadian Research Chair in Continental Ecosystem Ecology, and received computational support from the Theoretical Ecosystem Ecology group at UQAR. The research leading to these results has received funding from the People Programme (Marie Curie Actions) and from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013) REA grant agreement n°329197 awarded to TG, ERC grant agreement n° 283871 awarded to KZ. WH was funded by a BBSRC grant (BB/I007997/1).Social network analysis methods have made it possible to test whether novel behaviors in animals spread through individual or social learning. To date, however, social network analysis of wild populations has been limited to static models that cannot precisely reflect the dynamics of learning, for instance, the impact of multiple observations across time. Here, we present a novel dynamic version of network analysis that is capable of capturing temporal aspects of acquisition-that is, how successive observations by an individual influence its acquisition of the novel behavior. We apply this model to studying the spread of two novel tool-use variants, "moss-sponging'' and "leaf-sponge re-use,'' in the Sonso chimpanzee community of Budongo Forest, Uganda. Chimpanzees are widely considered the most "cultural'' of all animal species, with 39 behaviors suspected as socially acquired, most of them in the domain of tool-use. The cultural hypothesis is supported by experimental data from captive chimpanzees and a range of observational data. However, for wild groups, there is still no direct experimental evidence for social learning, nor has there been any direct observation of social diffusion of behavioral innovations. Here, we tested both a static and a dynamic network model and found strong evidence that diffusion patterns of moss-sponging, but not leaf-sponge re-use, were significantly better explained by social than individual learning. The most conservative estimate of social transmission accounted for 85% of observed events, with an estimated 15-fold increase in learning rate for each time a novice observed an informed individual moss-sponging. We conclude that group-specific behavioral variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, long before the advent of modern humans.Publisher PDFPeer reviewe
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