542 research outputs found
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Ready exerciser one: examining the efficacy of immersive technologies in the exercise domain
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe present programme of research sought to examine the effects of audio-visual stimuli during exercise, using immersive, commercially available technologies. Three original studies were conducted using a range of settings (i.e., real-world, laboratory), methodologies (i.e., qualitative and quantitative), exercise modalities (i.e., gym workouts, cycle ergometry) and consumer products (e.g., music-video channels, virtual reality head-mounted displays) in order to explore the main research question from various perspectives. A substantive theory was proposed in Study 1 that sought to explain and predict the social process of exercising in the presence of a music-video channel. The model provides support for a three-stage process
that commences with the content of the music-video channel. The second stage depicts a series of moderators that revolve around the core category, appraisal of appropriateness. Lastly, a range of effects pertaining to exercisers and facility staff are predicted. Study 2 sought to examine the influence of a range of audio-visual stimuli on cycle ergometer exercise at the ventilatory threshold. The findings indicated that a 360-degree video with music condition elicited the most positive affective valence, greatest perceived activation, most dissociative thoughts, and highest ratings of perceived enjoyment. Study 3 sought to
veer towards greater ecological validity with the inclusion of a commercially available virtual reality-enabled cycle ergometer. The findings demonstrated the efficacy of such technology, as conditions that entailed virtual reality elicited the most positive affective valence, highest perceived activation, largest number of dissociative thoughts, and greatest perceived enjoyment. Taken holistically, the present body of work demonstrates that audio-visual stimuli can serve as a catalyst for several affective, cognitive, and behavioural effects across various exercise modes and intensities. Researchers are beginning to recognise the importance of affective responses in shaping future exercise behaviours. The addition of audio-visual stimuli within the exercise environment represents a cost-effective and easily implementable intervention that might encourage individuals to partake in regular exercise
Lessons to be learned from test evaluations during the Covid-19 pandemic:RSS Working Groupâs Report on Diagnostic Tests
The coronavirus disease (Covid-19) pandemic raised challenges for everyday life. Development of new diagnostic tests was necessary, but under such enormous pressure risking inadequate evaluation. Against a background of concern about standards applied to the evaluation of in vitro diagnostic tests (IVDs), clear statistical thinking was needed on the principles of diagnostic testing in general, and their application in a pandemic. Therefore, in July 2020, the Royal Statistical Society convened a Working Group of six biostatisticians to review the statistical evidence needed to ensure the performance of new tests, especially IVDs for infectious diseasesâfor regulators, decision-makers, and the public. The Working Groupâs review was undertaken when the Covid-19 pandemic shone an unforgiving light on current processes for evaluating and regulating IVDs for infectious diseases. The reportâs findings apply more broadly than to the pandemic and IVDs, to diagnostic test evaluations in general. A section of the report focussed on lessons learned during the pandemic and aimed to contribute to the UK Covid-19 Inquiryâs examination of the response to, and impact of, the Covid-19 pandemic to learn lessons for the future. The review made 22 recommendations on what matters for study design, transparency, and regulation
Gamma-Ray Bursts and Magnetars as Possible Sources of Ultra High Energy Cosmic Rays: Correlation of Cosmic Ray Event Positions with IRAS Galaxies
We use the two-dimensional Kolmogorov-Smirnov (KS) test to study the
correlation between the 60 cosmic ray events above 4x10^19 eV from the AGASA
experiment and the positions of infrared luminous galaxies from the IRAS PSCz
catalog. These galaxies are expected to be hosts to gamma ray bursts (GRB) and
magnetars, both of which are associated with core collapse supernovae and have
been proposed as possible acceleration sites for ultra high energy cosmic rays.
We find consistency between the models and the AGASA events to have been drawn
from the same underlying distribution of positions on the sky with KS
probabilities ~50%. Application of the same test to the 11 highest AGASA events
above 10^20 eV, however, yields a KS probability of < 0.5%, rejecting the
models at >99.5% significance level. Taken at face value, these highest energy
results suggest that the existing cosmic ray events above 10^20 eV do not owe
their origin to long burst GRBs, rapidly rotating magnetars, or any other
events associated with core collapse supernovae. The larger data set expected
from the AUGER experiment will test whether this conclusion is real or is a
statistical fluke that we estimate to be at the 2 sigma level.Comment: 15 pages, 4 figures. Final Version to be published in Phys. Rev.
Stellar migration and chemical enrichment in the milky way disc: a hybrid model
We develop a hybrid model of galactic chemical evolution that combines a multiring computation of chemical enrichment with a prescription for stellar migration and the vertical distribution of stellar populations informed by a cosmological hydrodynamic disc galaxy simulation. Our fiducial model adopts empirically motivated forms of the star formation law and star formation history, with a gradient in outflow mass loading tuned to reproduce the observed metallicity gradient. With this approach, the model reproduces many of the striking qualitative features of the Milky Way discâs abundance structure: (i) the dependence of the [O/Fe]â[Fe/H] distribution on radius Rgal and mid-plane distance |z|; (ii) the changing shapes of the [O/H] and [Fe/H] distributions with Rgal and |z|; (iii) a broad distribution of [O/Fe] at sub-solar metallicity and changes in the [O/Fe] distribution with Rgal, |z|, and [Fe/H]; (iv) a tight correlation between [O/Fe] and stellar age for [O/Fe] > 0.1; (v) a population of young and intermediate-age α-enhanced stars caused by migration-induced variability in the Type Ia supernova rate; (vi) non-monotonic ageâ[O/H] and ageâ[Fe/H] relations, with large scatter and a median age of âŒ4 Gyr near solar metallicity. Observationally motivated models with an enhanced star formation rate âŒ2 Gyr ago improve agreement with the observed ageâ[Fe/H] and ageâ[O/H] relations, but worsen agreement with the observed ageâ[O/Fe] relation. None of our models predict an [O/Fe] distribution with the distinct bimodality seen in the observations, suggesting that more dramatic evolutionary pathways are required. All code and tables used for our models are publicly available through the Versatile Integrator for Chemical Evolution (VICE; https://pypi.org/project/vice)
The Lifetime of FRIIs in Groups and Clusters: Implications for Radio-Mode Feedback
We determine the maximum lifetime t_max of 52 FRII radio sources found in 26
central group galaxies from cross correlation of the Berlind SDSS group catalog
with the VLA FIRST survey. Mock catalogs of FRII sources were produced to match
the selection criteria of FIRST and the redshift distribution of our parent
sample, while an analytical model was used to calculate source sizes and
luminosities. The maximum lifetime of FRII sources was then determined via a
comparison of the observed and model projected length distributions. We
estimate the average FRII lifetime is 1.5x10^7 years and the duty cycle is
~8x10^8 years. Degeneracies between t_max and the model parameters: jet power
distribution, axial ratio, energy injection index, and ambient density
introduce at most a factor of two uncertainty in our lifetime estimate. In
addition, we calculate the radio active galactic nuclei (AGN) fraction in
central group galaxies as a function of several group and host galaxy
properties. The lifetime of radio sources recorded here is consistent with the
quasar lifetime, even though these FRIIs have substantially sub-Eddington
accretion. These results suggest a fiducial time frame for energy injection
from AGN in feedback models. If the morphology of a given extended radio source
is set by large-scale environment, while the lifetime is determined by the
details of the accretion physics, this FRII lifetime is relevant for all
extended radio sources.Comment: 18 pages, 7 figures. Accepted for publication in ApJ. High resolution
paper available at http://www.astronomy.ohio-state.edu/~bird/BMK07.pd
Numerical Study of Magnetoaerodynamic Flow Around a Hemisphere
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83560/1/AIAA-49278-455.pd
Structural basis for tunable control of actin dynamics by myosin-15 in mechanosensory stereocilia
The motor protein myosin-15 is necessary for the development and maintenance of mechanosensory stereocilia, and mutations in myosin-15 cause hereditary deafness. In addition to transporting actin regulatory machinery to stereocilia tips, myosin-15 directly nucleates actin filament (âF-actinâ) assembly, which is disrupted by a progressive hearing loss mutation (p.D1647G, âjordanâ). Here, we present cryoâelectron microscopy structures of myosin-15 bound to F-actin, providing a framework for interpreting the impacts of deafness mutations on motor activity and actin nucleation. Rigor myosin-15 evokes conformational changes in F-actin yet maintains flexibility in actinâs D-loop, which mediates inter-subunit contacts, while the jordan mutant locks the D-loop in a single conformation. Adenosine diphosphateâbound myosin-15 also locks the D-loop, which correspondingly blunts actin-polymerization stimulation. We propose myosin-15 enhances polymerization by bridging actin protomers, regulating nucleation efficiency by modulating actinâs structural plasticity in a myosin nucleotide stateâdependent manner. This tunable regulation of actin polymerization could be harnessed to precisely control stereocilium height
Inflation and the Scale Dependent Spectral Index: Prospects and Strategies
We consider the running of the spectral index as a probe of both inflation
itself, and of the overall evolution of the very early universe. Surveying a
collection of simple single field inflationary models, we confirm that the
magnitude of the running is relatively consistent, unlike the tensor amplitude,
which varies by orders of magnitude. Given this target, we confirm that the
running is potentially detectable by future large scale structure or 21 cm
observations, but that only the most futuristic measurements can distinguish
between these models on the basis of their running. For any specified
inflationary scenario, the combination of the running index and unknown
post-inflationary expansion history induces a theoretical uncertainty in the
predicted value of the spectral index. This effect can easily dominate the
statistical uncertainty with which Planck and its successors are expected to
measure the spectral index. More positively, upcoming cosmological experiments
thus provide an intriguing probe of physics between TeV and GUT scales by
constraining the reheating history associated with any specified inflationary
model, opening a window into the "primordial dark age" that follows the end of
inflation.Comment: 32 pages. v2 and v3 Minor reference updates /clarification
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Isolation of Angola-like Marburg virus from Egyptian rousette bats from West Africa.
Marburg virus (MARV) causes sporadic outbreaks of severe Marburg virus disease (MVD). Most MVD outbreaks originated in East Africa and field studies in East Africa, South Africa, Zambia, and Gabon identified the Egyptian rousette bat (ERB; Rousettus aegyptiacus) as a natural reservoir. However, the largest recorded MVD outbreak with the highest case-fatality ratio happened in 2005 in Angola, where direct spillover from bats was not shown. Here, collaborative studies by the Centers for Disease Control and Prevention, Njala University, University of California, Davis USAID-PREDICT, and the University of Makeni identify MARV circulating in ERBs in Sierra Leone. PCR, antibody and virus isolation data from 1755 bats of 42 species shows active MARV infection in approximately 2.5% of ERBs. Phylogenetic analysis identifies MARVs that are similar to the Angola strain. These results provide evidence of MARV circulation in West Africa and demonstrate the value of pathogen surveillance to identify previously undetected threats
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