3,290 research outputs found
On the equivalence between standard and sequentially ordered hidden Markov models
Chopin (2007) introduced a sequentially ordered hidden Markov model, for
which states are ordered according to their order of appearance, and claimed
that such a model is a re-parametrisation of a standard Markov model. This note
gives a formal proof that this equivalence holds in Bayesian terms, as both
formulations generate equivalent posterior distributions, but does not hold in
Frequentist terms, as both formulations generate incompatible likelihood
functions. Perhaps surprisingly, this shows that Bayesian re-parametrisation
and Frequentist re-parametrisation are not identical concepts
Characterizing Tool-Selective Areas With Human Neuroimaging
Humans, unlike any other species, use tools to achieve complex goals. New Caledonian Crows, among the best of avian tool-makers, use twigs to retrieve food in crevices, and veined octopuses use coconut shells as shelters. Humans, however, go above and beyond these simple behaviours. Even when compared to orders that are evolutionarily closest to humans such as non-human primates, tool use is indisputably more advanced in humans. Conventionally, neuroimaging researchers who have studied complex tool use in humans do so by presenting pictures of tools and measuring the brain activity evoked by actions potentiated by the tools. This method has revealed tool-selective regions that activate in response to pictures of tools but, critically, also activate in response to real actions with real tools. Though there is overlap between regions that respond to both pictures of tools and to real tool use, it is unclear whether tool pictures are indeed an effective proxy for real tool use. In light of this, the overarching goals of this thesis were, 1) from a methodological perspective, to determine whether different proxies for studying tool use are more effective than using pictures but less technically challenging than using real actions on real tools; and 2) from a theoretical perspective, to determine what these proxies can reveal about tool-related processing, particularly in brain regions involved in visuomotor control. In sum, the results from this thesis revealed, 1) that presenting videos of familiar tool actions is an optimal proxy to study tool use, and 2) that tool-selective regions are areas selective for actions afforded by tools, for the characteristic motion associated with tools, and for familiar tools of which functional associations are well-established. Taken together, this thesis offers support to the notion that tool-selective regions process information with the purpose of predicting upcoming actions and reasoning possible ways to use a tool to interact with a target. In agreement with the affordance perspective, tool-selective regions do so even when there is no intent to act on a tool
The Cooperative Participatory Evaluation of Renewable Technologies on Ecosystem Services (CORPORATES)
Publisher PD
Towards a satellite system for archaeology? Simulation of an optical satellite mission with ideal spatial and temporal resolution, illustrated by a case study in Scotland
Applications of remote sensing data for archaeology rely heavily on repurposed data, which carry inherent limitations in their suitability to help address archaeological questions. Through a case study framed around archaeological imperatives in a Scottish context, this work investigates the potential for existing satellite systems to provide remote sensing data that meet defined specifications for archaeological prospection, considering both spatial and temporal resolution, concluding that the availability of commercial data is currently insufficient. Tasking a commercial constellation of 12 spacecraft to collect images of a 150 km 2 region in Scotland through the month of July 2020 provided 26 images with less than 50% cloud cover. Following an analysis of existing systems, this paper presents a high-level mission architecture for a bespoke satellite system designed from an archaeological specification. This study focuses on orbit design and the number of spacecraft needed to meet the spatial and temporal resolution requirements for archaeological site detection and monitoring in a case study of Scotland, using existing imaging technology. By exploring what an ideal scenario might look like from a satellite mission planning perspective, this paper presents a simulation analysis that foregrounds archaeological imperatives and specifies a satellite constellation design on that basis. High-level design suggests that a system of eight 100 kg spacecraft in a 581 km altitude orbit could provide coverage at a desired temporal and spatial resolution of two-weekly revisit and <1 m ground sampling distance, respectively. The potential for such a system to be more widely applied in regions of similar latitude and climate is discussed
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Sunspot observations on 10 and 11 February 1917: a case study in collating known and previously undocumented records
An extensive investigation of ships’ logs, as part of the ‘Old Weather’ citizen-science project,
identified a sunspot observation made from HMS Hilary on 10 February 1917. This sunspot record was accompanied by detailed meteorological records that have enabled a reconstruction of the conditions under which the observation was made (overcast with detached clouds). Although there is no incontrovertible evidence that this was an unaided-eye observation, comparison with an unaided-eye observation recorded on the 11 February 1917 in a local
treatise from Hénán province in China confirms that this sunspot group was visible to the unaided eye. White-light photographs from the Dehra Dun Observatory confirm the detailed description of the sunspot group provided by the naval observer. Moreover, comparisons with tabular data published by the Royal Observatory, Greenwich, confirm the statement that this was an unusually large sunspot group. Indeed, on 11 February 1917 the area of the sunspot group was greater than the area of any sunspot group recorded previously at the Royal Observatory, Greenwich. A comparison with a modern unaided-eye observation confirms that it is possible to observe sunspots under meteorological conditions similar to those experienced on-board HMS Hilary
Fifteen-year prospective longitudinal cohort study of outcomes following single radius total knee arthroplasty
Aims This prospective study reports longitudinal, within-patient, patient-reported outcome measures (PROMs) over a 15-year period following cemented single radius total knee arthroplasty (TKA). Secondary aims included reporting PROMs trajectory, 15-year implant survival, and patient attrition from follow-up. Methods From 2006 to 2007, 462 consecutive cemented cruciate-retaining Triathlon TKAs were implanted in 426 patients (mean age 69 years (21 to 89); 290 (62.7%) female). PROMs (12-item Short Form Survey (SF-12), Oxford Knee Score (OKS), and satisfaction) were assessed preoperatively and at one, five, ten, and 15 years. Kaplan-Meier survival and univariate analysis were performed. Results At 15 years, 28 patients were lost to follow-up (6.1%) and 221 patients (51.9%) had died, with the mean age of the remaining cohort reducing by four years. PROMs response rates among surviving patients were: one-year 63%; five-year 72%; ten-year 94%; and 15-year 59%. OKS and SF-12 scores changed significantly over 15 years (p < 0.001). The mean improvement in OKS was 18.8 (95% confidence (CI) 16.7 to 19.0) at one year. OKS peaked at five years (median 43 years) declining thereafter (p < 0.001), though at 15 years it remained 17.5 better than preoperatively. Age and sex did not alter this trajectory. A quarter of patients experienced a clinically significant decline (≥ 7) in OKS from five to ten years and from ten to 15 years. The SF-12 physical component score displayed a similar trajectory, peaking at one year (p < 0.001). Patient satisfaction was 88% at one, five, and ten years, and 94% at 15 years. In all, 15-year Kaplan-Meier survival was 97.6% (95% CI 96.0% to 99.2%) for any revision, and 98.9% (95% CI 97.9% to 99.9%) for aseptic revision. Conclusion Improvements in PROMs were significant and maintained following single radius TKA, with OKS peaking at five years, and generic physical health peaking at one year. Patient satisfaction remained high at 15 years, at which point 2.4% had been revised.</p
CHANG-ES XI: Circular Polarization in the Cores of Nearby Galaxies
We detect 5 galaxies in the CHANG-ES (Continuum Halos in Nearby Galaxies --
an EVLA Survey) sample that show circular polarization (CP) at L-band in our
high resolution data sets. Two of the galaxies (NGC~4388 and NGC~4845) show
strong Stokes \%, two (NGC~660 and NGC~3628) have
values of \%, and NGC~3079 is a marginal detection at \%. The two strongest galaxies also have the most luminous X-ray
cores and the strongest internal absorption in X-rays. We have expanded on our
previous Faraday conversion interpretation and analysis and provide analytical
expressions for the expected signal for a general case in which the cosmic
ray electron energy spectral index can take on any value. We provide examples
as to how such expressions could be used to estimate magnetic field strengths
and the lower energy cutoff for CR electrons. Four out of our detections are
{\it resolved}, showing unique structures, including a {\it jet} in NGC~4388
and a CP `conversion disk' in NGC~4845. The conversion disk is inclined to the
galactic disk but is perpendicular to a possible outflow direction. Such CP
structures have never before been seen in any galaxy to our knowledge. None of
the galaxy cores show linear polarization at L-band. Thus CP may provide a
unique probe of physical conditions deep into radio AGNs.Comment: 30 pages, 4 figures, accepted to MNRA
Representation of Multiple Body Parts in the Missing-Hand Territory of Congenital One-Handers.
Individuals born without one hand (congenital one-handers) provide a unique model for understanding the relationship between focal reorganization in the sensorimotor cortex and everyday behavior. We previously reported that the missing hand\u27s territory of one-handers becomes utilized by its cortical neighbor (residual arm representation), depending on residual arm usage in daily life to substitute for the missing hand\u27s function [1, 2]. However, the repertoire of compensatory behaviors may involve utilization of other body parts that do not cortically neighbor the hand territory. Accordingly, the pattern of brain reorganization may be more extensive [3]. Here we studied unconstrained compensatory strategies under ecological conditions in one-handers, as well as changes in activation, connectivity, and neurochemical profile in their missing hand\u27s cortical territory. We found that compensatory behaviors in one-handers involved multiple body parts (residual arm, lips, and feet). This diversified compensatory profile was associated with large-scale cortical reorganization, regardless of cortical proximity to the hand territory. Representations of those body parts used to substitute hand function all mapped onto the cortical territory of the missing hand, as evidenced by task-based and resting-state fMRI. The missing-hand territory also exhibited reduced GABA levels, suggesting a reduction in connectional selectivity to enable the expression of diverse cortical inputs. Because the same body parts used for compensatory purposes are those showing increased representation in the missing hand\u27s territory, we suggest that the typical hand territory may not necessarily represent the hand per se, but rather any other body part that shares the functionality of the missing hand [4]
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