198 research outputs found
Systematic and Stochastic Variations in Pulsar Dispersion Measures
We analyze deterministic and random temporal variations in dispersion measure
(DM) from the full three-dimensional velocities of pulsars with respect to the
solar system, combined with electron-density variations on a wide range of
length scales. Previous treatments have largely ignored the pulsar's changing
distance while favoring interpretations involving the change in sky position
from transverse motion. Linear trends in pulsar DMs seen over 5-10~year
timescales may signify sizable DM gradients in the interstellar medium (ISM)
sampled by the changing direction of the line of sight to the pulsar. We show
that motions parallel to the line of sight can also account for linear trends,
for the apparent excess of DM variance over that extrapolated from
scintillation measurements, and for the apparent non-Kolmogorov scalings of DM
structure functions inferred in some cases. Pulsar motions through atomic gas
may produce bow-shock ionized gas that also contributes to DM variations. We
discuss possible causes of periodic or quasi-periodic changes in DM, including
seasonal changes in the ionosphere, annual variation of the solar elongation
angle, structure in the heliosphere-ISM boundary, and substructure in the ISM.
We assess the solar cycle's role on the amplitude of ionospheric and solar-wind
variations. Interstellar refraction can produce cyclic timing variations from
the error in transforming arrival times to the solar system barycenter. We
apply our methods to DM time series and DM gradient measurements in the
literature and assess consistency with a Kolmogorov medium. Finally, we discuss
the implications of DM modeling in precision pulsar timing experiments.Comment: 24 pages, 17 figures, published in Ap
Measures of fidelity of delivery and engagement in self-management interventions: A systematic review of measures
BACKGROUND: Self-management interventions are increasingly being developed and researched to improve long-term condition outcomes. To understand and interpret findings, it is essential that fidelity of intervention delivery and participant engagement are measured and reported. Before developing fidelity checklists to assess treatment fidelity of interventions, current recommendations suggest that a synthesis of fidelity measures reported in the literature is completed. Therefore, here we aim to identify what the current measures of fidelity of intervention delivery and engagement for self-management interventions for long-term conditions are and whether there is treatment fidelity. METHODS: Four databases (MEDLINE, PubMed, CINAHL Plus and ScienceDirect) and the journal implementation science were systematically searched to identify published reports from inception to December 2020 for experimental studies measuring fidelity of intervention delivery and/or participant engagement in self-management interventions for long-term conditions. Data on fidelity of delivery and engagement measures and the findings were extracted and synthesised. RESULTS: Thirty-nine articles were identified as eligible, with 25 studies measuring fidelity of delivery, 19 reporting engagement and 5 measuring both. For fidelity of delivery, measures included structured checklists, participant completed measures and researcher observations/notes. These were completed by researchers, participants and intervention leaders. Often there was little information around the development of these measures, particularly when the measure had been developed by the researchers, rather than building on others work. Eighteen of 25 studies reported there was fidelity of intervention delivery. For engagement, measures included data analytics, participant completed measures and researcher observations. Ten out of 19 studies reported participants were engaged with the intervention. CONCLUSION: In complex self-management interventions, it is essential to assess whether treatment fidelity of each core component of interventions is delivered, as outlined in the protocol, to understand which components are having an effect. Treatment fidelity checklists comparing what was planned to be delivered, with what was delivered should be developed with pre-defined cut-offs for when fidelity has been achieved. Similarly, when measuring engagement, while data analytics continue to rise with the increase in digital interventions, clear cut-offs for participant use and content engaged with to be considered an engagement participant need to be pre-determined
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Dentate gyrus abnormalities in sudden unexplained death in infants: morphological marker of underlying brain vulnerability
Sudden unexplained death in infants, including the sudden infant death syndrome, is likely due to heterogeneous causes that involve different intrinsic vulnerabilities and/or environmental factors. Neuropathologic research focuses upon the role of brain regions, particularly the brainstem, that regulate or modulate autonomic and respiratory control during sleep or transitions to waking. The hippocampus is a key component of the forebrainâlimbic network that modulates autonomic/respiratory control via brainstem connections, but its role in sudden infant death has received little attention. We tested the hypothesis that a well-established marker of hippocampal pathology in temporal lobe epilepsyâfocal granule cell bilamination in the dentate, a variant of granule cell dispersionâis associated with sudden unexplained death in infants. In a blinded study of hippocampal morphology in 153 infants with sudden and unexpected death autopsied in the San Diego County medical examinerâs office, deaths were classified as unexplained or explained based upon autopsy and scene investigation. Focal granule cell bilamination was present in 41.2 % (47/114) of the unexplained group compared to 7.7 % (3/39) of the explained (control) group (p < 0.001). It was associated with a cluster of other dentate developmental abnormalities that reflect defective neuronal proliferation, migration, and/or survival. Dentate lesions in a large subset of infants with sudden unexplained death may represent a developmental vulnerability that leads to autonomic/respiratory instability or autonomic seizures, and sleep-related death when the infants are challenged with homeostatic stressors. Importantly, these lesions can be recognized in microscopic sections prepared in current forensic practice. Future research is needed to determine the relationship between hippocampal and previously reported brainstem pathology in sudden infant death. Electronic supplementary material The online version of this article (doi:10.1007/s00401-014-1357-0) contains supplementary material, which is available to authorized users
Optimal spatiotemporal scales to aggregate satellite ocean color data for nearshore reefs and tropical coastal waters: two case studies
Remotely sensed ocean color data are useful for monitoring water quality in coastal environments. However, moderate resolution (hundreds of meters to a few kilometers) satellite data are underutilized in these environments because of frequent data gaps from cloud cover and algorithm complexities in shallow waters. Aggregating satellite data over larger space and time scales is a common method to reduce data gaps and generate a more complete time series, but potentially smooths out the small-scale, episodic changes in water quality that can have ecological influences. By comparing aggregated satellite estimates of Kd(490) with related in-water measurements, we can understand the extent to which aggregation methods are viable for filling gaps while being able to characterize ecologically relevant water quality conditions. In this study, we tested a combination of six spatial and seven temporal scales for aggregating data from the VIIRS instrument at several coral reef locations in Maui, Hawaiâi and Puerto Rico and compared these with in situ measurements of Kd(490) and turbidity. In Maui, we found that the median value of a 5-pixels, 7-days spatiotemporal cube of satellite data yielded a robust result capable of differentiating observations across small space and time domains and had the best correlation among spatiotemporal cubes when compared with in situ Kd(490) across 11 nearshore sites (R2 = 0.84). We also found long-term averages (i.e., chronic condition) of VIIRS data using this aggregation method follow a similar spatial pattern to onshore turbidity measurements along the Maui coast over a three-year period. In Puerto Rico, we found that the median of a 13-pixels, 13-days spatiotemporal cube of satellite data yielded the best overall result with an R2 = 0.54 when compared with in situ Kd(490) measurements for one nearshore site with measurement dates spanning 2016â2019. As spatiotemporal cubes of different dimensions yielded optimum results in the two locations, we recommend local analysis of spatial and temporal optima when applying this technique elsewhere. The use of satellite data and in situ water quality measurements provide complementary information, each enhancing understanding of the issues affecting coastal ecosystems, including coral reefs, and the success of management efforts
What's in a message? Delivering sexual health promotion to young people in Australia via text messaging
<p>Abstract</p> <p>Background</p> <p>Advances in communication technologies have dramatically changed how individuals access information and communicate. Recent studies have found that mobile phone text messages (SMS) can be used successfully for short-term behaviour change. However there is no published information examining the acceptability, utility and efficacy of different characteristics of health promotion SMS. This paper presents the results of evaluation focus groups among participants who received twelve sexual health related SMS as part of a study examining the impact of text messaging for sexual health promotion to on young people in Victoria, Australia.</p> <p>Methods</p> <p>Eight gender-segregated focus groups were held with 21 males and 22 females in August 2008. Transcripts of audio recordings were analysed using thematic analysis. Data were coded under one or more themes.</p> <p>Results</p> <p>Text messages were viewed as an acceptable and 'personal' means of health promotion, with participants particularly valuing the informal language. There was a preference for messages that were positive, relevant and short and for messages to cover a variety of topics. Participants were more likely to remember and share messages that were funny, rhymed and/or tied into particular annual events. The message broadcasting, generally fortnightly on Friday afternoons, was viewed as appropriate. Participants said the messages provided new information, a reminder of existing information and reduced apprehension about testing for sexually transmitted infections.</p> <p>Conclusions</p> <p>Mobile phones, in particular SMS, offer health promoters an exciting opportunity to engage personally with a huge number of individuals for low cost. The key elements emerging from this evaluation, such as message style, language and broadcast schedule are directly relevant to future studies using SMS for health promotion, as well as for future health promotion interventions in other mediums that require short formats, such as social networking sites.</p
Circadian control of mouse heart rate and blood pressure by the suprachiasmatic nuclei:behavioral effects are more significant than direct outputs
Diurnal variations in the incidence of events such as heart attack and stroke suggest a role for circadian rhythms in the etiology of cardiovascular disease. The aim of this study was to assess the influence of the suprachiasmatic nucleus (SCN) circadian clock on cardiovascular function. mice and WT. However, there was also a modest circadian rhythm of resting HR and BP that was independent of LA.If appropriate methods of analysis are used that take into account sleep and locomotor activity level, mice are a good model for understanding the contribution of circadian timing to cardiovascular function. Future studies of the influence of sleep and wakefulness on cardiovascular physiology may help to explain accumulating evidence linking disrupted sleep with cardiovascular disease in man
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Revealing the progenitor of SN 2021zby through analysis of the shock-cooling light curve
We present early observations and analysis of the double-peaked Type IIb
supernova (SN IIb) 2021zby. captured the prominent early shock cooling
peak of SN 2021zby within the first 10 days after explosion with a
30-minute cadence. We present optical and near-infrared spectral series of SN
2021zby, including three spectra during the shock cooling phase. Using a
multi-band model fit, we find that the inferred properties of its progenitor
are consistent with a red supergiant or yellow supergiant, with an envelope
mass of 0.3-3.0 M and an envelope radius of 50-350. These inferred progenitor properties are similar to those of other
SNe IIb with double-peak feature, such as SNe 1993J, 2011dh, 2016gkg and
2017jgh. This study further validates the importance of the high cadence and
early coverage in resolving the shape of the shock cooling light curve, while
the multi-band observations, especially UV, is also necessary to fully
constrain the progenitor properties.Comment: 12 pages, 5 figures, 2 tables, submitted to ApJ
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