5,487 research outputs found
Radio Band Observations of Blazar Variability
The properties of blazar variability in the radio band are studied using the
unique combination of temporal resolution from single dish monitoring and
spatial resolution from VLBA imaging; such measurements, now available in all
four Stokes parameters, together with theoretical simulations, identify the
origin of radio band variability and probe the characteristics of the radio jet
where the broadband blazar emission originates. Outbursts in total flux density
and linear polarization in the optical-to-radio bands are attributed to shocks
propagating within the jet spine, in part based on limited modeling invoking
transverse shocks; new radiative transfer simulations allowing for shocks at
arbitrary angle to the flow direction confirm this picture by reproducing the
observed centimeter-band variations observed more generally, and are of current
interest since these shocks may play a role in the gamma-ray flaring detected
by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars
identify the spectral variability properties of circular polarization for the
first time and demonstrate that polarity flips are relatively common.
All-Stokes data are consistent with the production of circular polarization by
linear-to-circular mode conversion in a region that is at least partially
self-absorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes
VLBA observations of 3C 279 support this physical picture and are best
explained by emission from an electron-proton plasma.Comment: 6 pages, 5 figures, uses, jaa.sty. Invited talk presented at the
conference Multifrequency Variability of Blazars, Guangzhou, China, September
22-24, 2010. To appear in J. Astrophys. Ast
Detection of high levels of congenital transmission of toxoplasma gondii in natural urban populations of mus domesticus
The relative importance of different transmission routes of Toxoplasma gondii has been a matter for debate. This ubiquitous parasite is generally thought to be transmitted by infective oocysts excreted by the definitive host, the cat. Ingestion of undercooked meat has also been considered an important route of transmission in many mammals while congenital transmission has generally been considered relatively rare. Experimental studies demonstrate the ability of T. gondii to be transmitted congenitally, but few studies have investigated the frequency of this transmission route in natural populations. We use PCR amplification of the SAG1 gene to investigate the frequency of congenital transmission in a wild population of mice (Mus domesticus) and show that congenital transmission is occurring in 75% of pregnancies in this population. Furthermore, for infected pregnant mice, transmission occurs to at least one foetus in 100% of cases while variable penetrance of congenital infection is observed. These high levels of congenital transmission in this wild population of mice, taken together with other recent data on congenital transmission in sheep, suggests that this phenomenon might be more widespread than previously thought
Luminosities of AGB Variables
The prevailing evidence suggests that most large-amplitude AGB variables
follow the period luminosity (PL) relation that has been established for Miras
in the LMC and galactic globular clusters. Hipparcos observations indicate that
most Miras in the solar neighbourhood are consistent with such a relation.
There are two groups of stars with luminosities that are apparently greater
than the PL relation would predict: (1) in the LMC and SMC there are large
amplitude variables, with long periods, P> 420 days, which are probably
undergoing hot bottom burning, but which are very clearly more luminous than
the PL relation (these are visually bright and are likely to be among the first
stars discovered in more distant intermediate age populations); (2) in the
solar neighbourhood there are short period, P<235 days, red stars which are
probably more luminous than the PL relation. Similar short-period red stars,
with high luminosities, have not been identified in the Magellanic Clouds.Comment: 8 pages, 2 figure, to be published in Mass-Losing Pulsating Stars and
their Circumstellar Matter, Y. Nakada & M. Honma (eds) Kluwer ASSL serie
Metabolism and Disposition of Fluticasone Furoate, an Enhanced-Affinity Glucocorticoid, in Humans
ABSTRACT: The purpose of this study was to investigate the metabolism and disposition of fluticasone furoate, an enhanced-affinity glucocorticoid receptor agonist, in humans. In a two-part, open-label design study, five healthy male subjects received a p. Fluticasone furoate [(6␣,11,16␣,17␣)-6,9-difluoro-17-{[(fluoromethyl)-thio]carbonyl}-11-hydroxy-16-methyl-3-oxoandrosta-1,4-dien-17-yl-2-furancarboxylate] is a new enhanced-affinity glucocorticoid receptor agonist. It is a synthetic fluorinated corticosteroid that has been developed as an intranasal treatment for patients with symptoms of rhinitis. Fluticasone furoate, otherwise known as GW685698X, is not a salt or prodrug because the entire molecule is required for pharmacological activity. It has similar or greater potency than other clinically used corticosteroids (including mometasone furoate, budesonide, fluticasone propionate, and the active principle of ciclesonide) for the glucocorticoid receptor and against the proinflammatory transcription factors nuclear factor B (NF-B), activation protein-1, and tumor necrosis factorinduced interleukin-8 cytokine productio
Evaluating the translation of implementation science to clinical artificial intelligence: a bibliometric study of qualitative research
INTRODUCTION: Whilst a theoretical basis for implementation research is seen as advantageous, there is little clarity over if and how the application of theories, models or frameworks (TMF) impact implementation outcomes. Clinical artificial intelligence (AI) continues to receive multi-stakeholder interest and investment, yet a significant implementation gap remains. This bibliometric study aims to measure and characterize TMF application in qualitative clinical AI research to identify opportunities to improve research practice and its impact on clinical AI implementation. METHODS: Qualitative research of stakeholder perspectives on clinical AI published between January 2014 and October 2022 was systematically identified. Eligible studies were characterized by their publication type, clinical and geographical context, type of clinical AI studied, data collection method, participants and application of any TMF. Each TMF applied by eligible studies, its justification and mode of application was characterized. RESULTS: Of 202 eligible studies, 70 (34.7%) applied a TMF. There was an 8-fold increase in the number of publications between 2014 and 2022 but no significant increase in the proportion applying TMFs. Of the 50 TMFs applied, 40 (80%) were only applied once, with the Technology Acceptance Model applied most frequently (n = 9). Seven TMFs were novel contributions embedded within an eligible study. A minority of studies justified TMF application (n = 51,58.6%) and it was uncommon to discuss an alternative TMF or the limitations of the one selected (n = 11,12.6%). The most common way in which a TMF was applied in eligible studies was data analysis (n = 44,50.6%). Implementation guidelines or tools were explicitly referenced by 2 reports (1.0%). CONCLUSION: TMFs have not been commonly applied in qualitative research of clinical AI. When TMFs have been applied there has been (i) little consensus on TMF selection (ii) limited description of selection rationale and (iii) lack of clarity over how TMFs inform research. We consider this to represent an opportunity to improve implementation science's translation to clinical AI research and clinical AI into practice by promoting the rigor and frequency of TMF application. We recommend that the finite resources of the implementation science community are diverted toward increasing accessibility and engagement with theory informed practices. The considered application of theories, models and frameworks (TMF) are thought to contribute to the impact of implementation science on the translation of innovations into real-world care. The frequency and nature of TMF use are yet to be described within digital health innovations, including the prominent field of clinical AI. A well-known implementation gap, coined as the "AI chasm" continues to limit the impact of clinical AI on real-world care. From this bibliometric study of the frequency and quality of TMF use within qualitative clinical AI research, we found that TMFs are usually not applied, their selection is highly varied between studies and there is not often a convincing rationale for their selection. Promoting the rigor and frequency of TMF use appears to present an opportunity to improve the translation of clinical AI into practice
Evaluating the translation of implementation science to clinical artificial intelligence: a bibliometric study of qualitative research
2023 Hogg, Al-Zubaidy, Keane, Hughes, Beyer and Maniatopoulos.Introduction: Whilst a theoretical basis for implementation research is seen as advantageous, there is little clarity over if and how the application of theories, models or frameworks (TMF) impact implementation outcomes. Clinical artificial intelligence (AI) continues to receive multi-stakeholder interest and investment, yet a significant implementation gap remains. This bibliometric study aims to measure and characterize TMF application in qualitative clinical AI research to identify opportunities to improve research practice and its impact on clinical AI implementation. Methods: Qualitative research of stakeholder perspectives on clinical AI published between January 2014 and October 2022 was systematically identified. Eligible studies were characterized by their publication type, clinical and geographical context, type of clinical AI studied, data collection method, participants and application of any TMF. Each TMF applied by eligible studies, its justification and mode of application was characterized. Results: Of 202 eligible studies, 70 (34.7%) applied a TMF. There was an 8-fold increase in the number of publications between 2014 and 2022 but no significant increase in the proportion applying TMFs. Of the 50 TMFs applied, 40 (80%) were only applied once, with the Technology Acceptance Model applied most frequently (n = 9). Seven TMFs were novel contributions embedded within an eligible study. A minority of studies justified TMF application (n = 51,58.6%) and it was uncommon to discuss an alternative TMF or the limitations of the one selected (n = 11,12.6%). The most common way in which a TMF was applied in eligible studies was data analysis (n = 44,50.6%). Implementation guidelines or tools were explicitly referenced by 2 reports (1.0%). Conclusion: TMFs have not been commonly applied in qualitative research of clinical AI. When TMFs have been applied there has been (i) little consensus on TMF selection (ii) limited description of selection rationale and (iii) lack of clarity over how TMFs inform research. We consider this to represent an opportunity to improve implementation science\u27s translation to clinical AI research and clinical AI into practice by promoting the rigor and frequency of TMF application. We recommend that the finite resources of the implementation science community are diverted toward increasing accessibility and engagement with theory informed practices. The considered application of theories, models and frameworks (TMF) are thought to contribute to the impact of implementation science on the translation of innovations into real-world care. The frequency and nature of TMF use are yet to be described within digital health innovations, including the prominent field of clinical AI. A well-known implementation gap, coined as the “AI chasm” continues to limit the impact of clinical AI on real-world care. From this bibliometric study of the frequency and quality of TMF use within qualitative clinical AI research, we found that TMFs are usually not applied, their selection is highly varied between studies and there is not often a convincing rationale for their selection. Promoting the rigor and frequency of TMF use appears to present an opportunity to improve the translation of clinical AI into practice
Comparative study of nonlinear properties of EEG signals of a normal person and an epileptic patient
Background: Investigation of the functioning of the brain in living systems
has been a major effort amongst scientists and medical practitioners. Amongst
the various disorder of the brain, epilepsy has drawn the most attention
because this disorder can affect the quality of life of a person. In this paper
we have reinvestigated the EEGs for normal and epileptic patients using
surrogate analysis, probability distribution function and Hurst exponent.
Results: Using random shuffled surrogate analysis, we have obtained some of
the nonlinear features that was obtained by Andrzejak \textit{et al.} [Phys Rev
E 2001, 64:061907], for the epileptic patients during seizure. Probability
distribution function shows that the activity of an epileptic brain is
nongaussian in nature. Hurst exponent has been shown to be useful to
characterize a normal and an epileptic brain and it shows that the epileptic
brain is long term anticorrelated whereas, the normal brain is more or less
stochastic. Among all the techniques, used here, Hurst exponent is found very
useful for characterization different cases.
Conclusions: In this article, differences in characteristics for normal
subjects with eyes open and closed, epileptic subjects during seizure and
seizure free intervals have been shown mainly using Hurst exponent. The H shows
that the brain activity of a normal man is uncorrelated in nature whereas,
epileptic brain activity shows long range anticorrelation.Comment: Keywords:EEG, epilepsy, Correlation dimension, Surrogate analysis,
Hurst exponent. 9 page
Observations of 'wisps' in magnetohydrodynamic simulations of the Crab Nebula
In this paper, we describe results of new high-resolution axisymmetric relativistic magnetohydrodynamic (MHD) simulations of pulsar wind nebulae. The simulations reveal strong breakdown of the equatorial symmetry and highly variable structure of the pulsar wind-termination shock. The synthetic synchrotron maps, constructed using a new more accurate approach, show striking similarity with the well-known images of the Crab Nebula obtained by Chandra and the Hubble Space Telescope. In addition to the jet–torus structure, these maps reproduce the Crab's famous moving wisps whose speed and rate of production agree with the observations. The variability is then analysed using various statistical methods, including the method of structure function and wavelet transform. The results point towards the quasi-periodic behaviour with the periods of 1.5–3 years and MHD turbulence on scales below 1 year. The full account of this study will be presented in a follow-up paper
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