922 research outputs found
Can stellar mass black holes be quark stars?
We investigate the possibility that stellar mass black holes, with masses in
the range of and , respectively, could be in fact
quark stars in the Color-Flavor-Locked (CFL) phase. Depending on the value of
the gap parameter, rapidly rotating CFL quark stars can achieve much higher
masses than standard neutron stars, thus making them possible stellar mass
black hole candidates. Moreover, quark stars have a very low luminosity and a
completely absorbing surface - the infalling matter on the surface of the quark
star is converted into quark matter. A possibility of distinguishing CFL quark
stars from stellar mass black holes could be through the study of thin
accretion disks around rapidly rotating quark stars and Kerr type black holes,
respectively. Furthermore, we show that the radiation properties of accretion
disks around black holes and CFL quark stars are also very similar. However,
strange stars exhibit a low luminosity, but high temperature bremsstrahlung
spectrum, which, in combination with the emission properties of the accretion
disk, may be the key signature to differentiate massive strange stars from
black hole.Comment: 27 pages, 5 figures, accepted for publication in MNRA
Health services research in the public healthcare system in Hong Kong: An analysis of over 1 million antihypertensive prescriptions between 2004-2007 as an example of the potential and pitfalls of using routinely collected electronic patient data
<b>Objectives</b> Increasing use is being made of routinely collected electronic patient data in health services research. The aim of the present study was to evaluate the potential usefulness of a comprehensive database used routinely in the public healthcare system in Hong Kong, using antihypertensive drug prescriptions in primary care as an example.<p></p>
<b>Methods</b> Data on antihypertensive drug prescriptions were retrieved from the electronic Clinical Management System (e-CMS) of all primary care clinics run by the Health Authority (HA) in the New Territory East (NTE) cluster of Hong Kong between January 2004 and June 2007. Information was also retrieved on patientsâ demographic and socioeconomic characteristics, visit type (new or follow-up), and relevant diseases (International Classification of Primary Care, ICPC codes). <p></p>
<b>Results</b> 1,096,282 visit episodes were accessed, representing 93,450 patients. Patientsâ demographic and socio-economic details were recorded in all cases. Prescription details for anti-hypertensive drugs were missing in only 18 patients (0.02%). However, ICPC-code was missing for 36,409 patients (39%). Significant independent predictors of whether disease codes were applied included patient age > 70 years (OR 2.18), female gender (OR 1.20), district of residence (range of ORs in more rural districts; 0.32-0.41), type of clinic (OR in Family Medicine Specialist Clinics; 1.45) and type of visit (OR follow-up visit; 2.39). <p></p>
In the 57,041 patients with an ICPC-code, uncomplicated hypertension (ICPC K86) was recorded in 45,859 patients (82.1%). The characteristics of these patients were very similar to those of the non-coded group, suggesting that most non-coded patients on antihypertensive drugs are likely to have uncomplicated hypertension. <p></p>
<b>Conclusion</b> The e-CMS database of the HA in Hong Kong varies in quality in terms of recorded information. Potential future health services research using demographic and prescription information is highly feasible but for disease-specific research dependant on ICPC codes some caution is warranted. In the case of uncomplicated hypertension, future research on pharmaco-epidemiology (such as prescription patterns) and clinical issues (such as side-effects of medications on metabolic parameters) seems feasible given the large size of the data set and the comparability of coded and non-coded patients
Auditory temporal resolution and evoked responses to pulsed sounds for the Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis)
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology 197 (2011): 1149-1158, doi:10.1007/s00359-011-0677-y.Temporal cues are important for some forms of auditory processing, such as
echolocation. Among odontocetes (toothed whales, dolphins, and porpoises), it has been
suggested that porpoises may have temporal processing abilities which differ from other
odontocetes because of their relatively narrow auditory filters and longer duration echolocation
signals. This study examined auditory temporal resolution in two Yangtze finless porpoises
(Neophocaena phocaenoides asiaeorientalis) using auditory evoked potentials (AEPs) to
measure: (i) rate following responses and modulation rate transfer function for 100 kHz centered
pulse sounds and (ii) hearing thresholds and response amplitudes generated by individual pulses
of different durations. The animals followed pulses well at modulation rates up to 1250 Hz, after
which response amplitudes declined until extinguished beyond 2500 Hz. The subjects had
significantly better hearing thresholds for longer, narrower-band pulses similar to porpoise
echolocation signals compared to brief, broadband sounds resembling dolphin clicks. Results
indicate that the Yangtze finless porpoise follows individual acoustic signals at rates similar to
other odontocetes tested. Relatively good sensitivity for longer duration, narrow-band signals
suggests that finless porpoise hearing is well-suited to detect their unique echolocation signals.The work was supported by the Office of Naval Research, a WHOI
Mellon Joint Initiatives Award , the Chinese National Natural Science Foundation (grant No:
30730018) and the Institute of Hydrobiology of the Chinese Academy of Sciences2012-09-1
NuSTAR and XMM-Newton observations of NGC 1365: Extreme absorption variability and a constant inner accretion disk
We present a spectral analysis of four coordinated NuSTAR+XMM-Newton
observations of the Seyfert galaxy NGC 1365. These exhibit an extreme level of
spectral variability, which is primarily due to variable line-of-sight
absorption, revealing relatively unobscured states in this source for the first
time. Despite the diverse range of absorption states, each of the observations
displays the same characteristic signatures of relativistic reflection from the
inner accretion disk. Through time-resolved spectroscopy we find that the
strength of the relativistic iron line and the Compton reflection hump relative
to the intrinsic continuum are well correlated, as expected if they are two
aspects of the same broadband reflection spectrum. We apply self-consistent
disk reflection models to these time-resolved spectra in order to constrain the
inner disk parameters, allowing for variable, partially covering absorption to
account for the vastly different absorption states observed. Each of the four
observations is treated independently to test the consistency of the results
obtained for the black hole spin and the disk inclination, which should not
vary on observable timescales. We find both the spin and the inclination
determined from the reflection spectrum to be consistent, confirming NGC 1365
hosts a rapidly rotating black hole; in all cases the dimensionless spin
parameter is constrained to be a* > 0.97 (at 90% statistical confidence or
better)
How the co-benefits of addressing climate change can motivate action across the world
It is traditionally thought that the public must be convinced of the reality and importance of anthropogenic climate change in order to take personal and political action. However, convincing the broad public involves overcoming powerful ideological obstacles1-4, and in many places climate change is slipping in public importance5,6. Here we examined whether beliefs about the âco-benefitsâ of mitigating climate change7 can avoid these obstacles by motivating behavior in both those who accept climate change and those who are unconvinced or unconcerned. We describe an integrative framework for assessing co-benefits8, distinguishing sociological dimensions (e.g., pollution, disease, economic development), and community character (e.g., benevolence, competence). Data from all inhabited continents (24 countries; N=6059), showed that two types of co-benefits, Development (economic and scientific advancement) and Benevolence (a more moral and caring community), rivalled climate change importance in the strength of their relationships with motivations to act. These co-benefits showed effects independent of climate change importance beliefs, and showed similar effects for both climate change believers and skeptics. Communicating these co-benefits of addressing climate change can help motivate action on climate change where traditional approaches have stalled
Inferring fish escape behaviour in trawls based on catch comparison data: Model development and evaluation based on data from Skagerrak, Denmark
During the fishing process, fish react to a trawl with a series of behaviours that often are species and size specific. Thus, a thorough understanding of fish behaviour in relation to fishing gear and a scientific understanding of the ability of different gear designs to utilize or stimulate various behavioural patterns during the catching process are essential for developing more efficient, selective, and environmentally friendly trawls. Although many behavioural studies using optical and acoustic observation systems have been conducted, harsh observation conditions on the fishing grounds often hamper the ability to directly observe fish behaviour in relation to fishing gear. As an alternative to optical and acoustic methods, we developed and applied a new mathematical model to catch data to extract detailed and quantitative information about species- and size-dependent escape behaviour in towed fishing gear such as trawls. We used catch comparison data collected with a twin trawl setup; the only difference between the two trawls was that a 12 m long upper section was replaced with 800 mm diamond meshes in one of them. We investigated the length-based escape behaviour of cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), witch flounder (Glyptocephalus cynoglossus), and lemon sole (Microstomus kitt) and quantified the extent to which behavioural responses set limits for the large mesh panel's selective efficiency. Around 85% of saithe, 80% of haddock, 44% of witch flounder, 55% of lemon sole, and 55% of cod (below 68 cm) contacted the large mesh panel and escaped. We also demonstrated the need to account for potential selectivity in the trawl body, as it can bias the assessment of length-based escape behaviour. Our indirect assessment of fish behaviour was in agreement with the direct observations made for the same species in a similar section of the trawl body reported in the literature
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Methane emission by Camelids
Methane emissions from ruminant livestock have been intensively studied in order to reduce contribution to the greenhouse effect. Ruminants were found to produce more enteric methane than other mammalian herbivores. As camelids share some features of their digestive anatomy and physiology with ruminants, it has been proposed that they produce similar amounts of methane per unit of body mass. This is of special relevance for countrywide greenhouse gas budgets of countries that harbor large populations of camelids like Australia. However, hardly any quantitative methane emission measurements have been performed in camelids. In order to fill this gap, we carried out respiration chamber measurements with three camelid species (Vicugna pacos, Lama glama, Camelus bactrianus; n = 16 in total), all kept on a diet consisting of food produced from alfalfa only. The camelids produced less methane expressed on the basis of body mass (0.3260.11 L kg21 d21) when compared to literature data on domestic ruminants fed on roughage diets (0.5860.16 L kg21 d21). However, there was no significant difference between the two suborders when methane emission was expressed on the basis of digestible neutral detergent fiber intake (92.7633.9 L kg21 in camelids vs. 86.2612.1 L kg21 in ruminants). This implies that the pathways of methanogenesis forming part of the microbial digestion of fiber in the foregut are similar between the groups, and that the lower methane emission of camelids can be explained by their generally lower relative food intake. Our results suggest that the methane emission of Australiaâs feral camels corresponds only to 1 to 2% of the methane amount produced by the countriesâ domestic ruminants and that calculations of greenhouse gas budgets of countries with large camelid populations based on equations developed for ruminants are generally overestimating the actual levels
A rapidly spinning supermassive black hole at the centre of NGCâ1365
Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims that the black hole (2âĂâ10^6 solar masses) at the centre of the galaxy NGCâ1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGCâ1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10â30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds
Toward characterization and definition of fibromyalgia severity
<p>Abstract</p> <p>Background</p> <p>There are no standard criteria for defining or assessing severity of fibromyalgia (FM) as a condition as fibromyalgia is associated with multiple symptom domains. The objective of this study was to evaluate whether patient self-reported severity of FM is associated with severity of pain and sleep interference and the presence of core co-morbidities.</p> <p>Methods</p> <p>We recruited individuals ℠18 years of age with a clinician-confirmed diagnosis of FM ℠3 months and a current pain rating >2 on a 0-10 numeric rating scale (NRS). Patients completed a questionnaire by mail in which they self-rated their FM severity (very mild, mild, moderate, and severe), their current pain severity and extent of sleep interference (NRS; mild, 0-3; moderate, 4-6, severe, 7-10), and provided information (yes/no) on the presence of core comorbidities (symptoms of depression, anxiety, sleep problems, back pain, neck pain) and medication use for FM. The core symptoms of FM were stratified to assist with patient characterization. Analysis of variance (ANOVA) was used to explore the relationship between self-reported FM severity and continuous variables (pain severity and sleep interference), and Mantel-Haenszel chi-square analysis was used to evaluate the trend in the proportions of patients reporting use of medications and core symptoms of FM by severity of FM. To complement patient-reported FM severity and to understand physicians' perspectives, a survey was performed among 28 physician specialists (rheumatology, neurology, anesthesiology/pain management, family practice, internal medicine, and psychiatry) to determine what they assessed when evaluating FM severity in clinical practice.</p> <p>Results</p> <p>The population (N = 129) of FM patients was predominantly female (89.1%), with a mean age of 49.4 ± 11.0 years, and 81.4% reported duration ℠2 years. Self-reported FM severity was moderate/severe in 86.0% of patients; mean current pain score was 6.40 ± 2.19 (moderate), and mean sleep interference score was 7.28 ± 2.23 (severe). Greater FM severity was significantly associated with higher levels of current pain and sleep interference (p < 0.0001), the proportion of patients reporting FM medication use (p = 0.0001), and the presence of core comorbidities (p < 0.05). Pain, functional disability, and fatigue severity were ranked as the top three criteria by the highest proportion of physicians when evaluating FM severity.</p> <p>Conclusion</p> <p>With higher self-reported FM severity, patients have greater pain and sleep interference as well as increased frequency of core comorbidities. Further investigation into understanding FM severity is warranted.</p
Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at âs = 7 TeV with the ATLAS detector
This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of âs = 7 TeV;{\rm Te}{\rm V}4.6\;{\rm f}{{{\rm b}}^{-1}}{{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}|\eta |\lt 1.9{{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques
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