| 44271. |
- Jones, E.P., et al.
(författare)
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Sources and distribution of fresh water in the East Greenland Current
- 2008
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611. ; 78:1, s. 37-44
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Tidskriftsartikel (refereegranskat)abstract
- Fresh water flowing from the Arctic Ocean via the East Greenland Current influences deep water formation in the Nordic Seas as well as the salinity of the surface and deep waters flowing from there. This fresh water has three sources: Pacific water (relatively fresh cf. Atlantic water), river runoff, and sea ice meltwater. To determine the relative amounts of the three sources of fresh water, in May 2002 we collected water samples across the East Greenland Current in sections from 81.5°N to the Irminger Sea south of Denmark Strait. We used nitrate–phosphate relationships to distinguish Pacific waters from Atlantic waters, salinity to obtain the sum of sea ice melt water and river runoff water, and total alkalinity to distinguish the latter. River runoff contributed the largest part of the total fresh water component, in some regions with some inventories exceeding 12 m. Pacific fresh water (Pacific source water S 32 cf. Atlantic source water S 34.9) typically provided about 1/3 of the river runoff contribution. Sea ice meltwater was very nearly non-existent in the surface waters of all sections, likely at least in part as a result of the samples being collected before the onset of the melt season. The fresh water from the Arctic Ocean was strongly confined to near the Greenland coast. We thus conjecture that the main source of fresh water from the Arctic Ocean most strongly impacting deep convection in the Nordic Seas would be sea ice as opposed to fresh water in the liquid phase, i.e., river runoff, Pacific fresh water, and sea ice meltwater.
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| 44272. |
- Jones, Graham
(författare)
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Algorithmic improvements to species delimitation and phylogeny estimation under the multispecies coalescent
- 2017
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Ingår i: Journal of Mathematical Biology. - : Springer Science and Business Media LLC. - 0303-6812 .- 1432-1416. ; 74:1, s. 447-467
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Tidskriftsartikel (refereegranskat)abstract
- The focus of this article is a Bayesian method for inferring both species delimitations and species trees under the multispecies coalescent model using molecular sequences from multiple loci. The species delimitation requires no a priori assignment of individuals to species, and no guide tree. The method is implemented in a package called STACEY for BEAST2, and is a extension of the author's DISSECT package. Here we demonstrate considerable efficiency improvements by using three new operators for sampling from the posterior using the Markov chain Monte Carlo algorithm, and by using a model for the population size parameters along the branches of the species tree which allows these parameters to be integrated out. The correctness of the moves is demonstrated by tests of the implementation. The practice of using a pipeline approach to species delimitation under the multispecies coalescent, has been shown to have major problems on simulated data (Olave et al. in Syst Biol 63:263-271. doi:10.1093/sysbio/syt106, 2014). The same simulated data set is used to demonstrate the accuracy and improved convergence of the present method. We also compare performance with *BEAST for a fixed delimitation analysis on a large data set, and again show improved convergence.
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| 44273. |
- Jones, Graham, et al.
(författare)
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DISSECT: an assignment-free Bayesian discovery method for species delimitation under the multispecies coalescent
- 2015
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Ingår i: Bioinformatics. - : Oxford University Press (OUP). - 1367-4803 .- 1367-4811. ; 31:7, s. 991-998
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Tidskriftsartikel (refereegranskat)abstract
- Motivation: The multispecies coalescent model provides a formal framework for the assignment of individual organisms to species, where the species are modeled as the branches of the species tree. None of the available approaches so far have simultaneously co-estimated all the relevant parameters in the model, without restricting the parameter space by requiring a guide tree and/or prior assignment of individuals to clusters or species. Results: We present DISSECT, which explores the full space of possible clusterings of individuals and species tree topologies in a Bayesian framework. It uses an approximation to avoid the need for reversible-jump MCMC, in the form of a prior that is a modification of the birth-death prior for the species tree. It incorporates a spike near zero in the density for node heights. The model has two extra parameters: one controls the degree of approximation, and the second controls the prior distribution on the numbers of species. It is implemented as part of BEAST and requires only a few changes from a standard *BEAST analysis. The method is evaluated on simulated data and demonstrated on an empirical data set. The method is shown to be insensitive to the degree of approximation, but quite sensitive to the second parameter, suggesting that large numbers of sequences are needed to draw firm conclusions.
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| 44274. |
- Jones, Graham
(författare)
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Divergence Estimation in the Presence of Incomplete Lineage Sorting and Migration
- 2019
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Ingår i: Systematic biology. - : Oxford University Press (OUP). - 1076-836X .- 1063-5157. ; 68:1, s. 19-31
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Tidskriftsartikel (refereegranskat)abstract
- This article focuses on the problem of estimating a species tree from multilocus data in the presence of incomplete lineage sorting and migration. I develop a mathematical model similar to IMa2 (Hey 2010) for the relevant evolutionary processes which allows both the population size parameters and the migration rates between pairs of species tree branches to be integrated out. I then describe a BEAST2 package DENIM (Divergence estimation notwithstanding ILS and migration) which is based on this model and which uses an approximation to sample from the posterior. The approximation is based on the assumption that migrations are rare, and it only samples from certain regions of the posterior which seem likely given this assumption. The method breaks down if there is a lot of migration. Using simulations, Leaché et al. (2014) showed that using the standard multispecies coalescent model to infer a species tree can result in poor accuracy if migration is present. I reanalyze this simulated data to explore DENIM's performance and demonstrate substantial improvements in accuracy over *BEAST. I also reanalyze an empirical data set.
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| 44275. |
- Jones, G., et al.
(författare)
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Genome-wide meta-analysis of muscle weakness identifies 15 susceptibility loci in older men and women
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Low muscle strength is an important heritable indicator of poor health linked to morbidity and mortality in older people. In a genome-wide association study meta-analysis of 256,523 Europeans aged 60 years and over from 22 cohorts we identify 15 loci associated with muscle weakness (European Working Group on Sarcopenia in Older People definition: n=48,596 cases, 18.9% of total), including 12 loci not implicated in previous analyses of continuous measures of grip strength. Loci include genes reportedly involved in autoimmune disease (HLA-DQA1p=4x10(-17)), arthritis (GDF5p=4x10(-13)), cell cycle control and cancer protection, regulation of transcription, and others involved in the development and maintenance of the musculoskeletal system. Using Mendelian randomization we report possible overlapping causal pathways, including diabetes susceptibility, haematological parameters, and the immune system. We conclude that muscle weakness in older adults has distinct mechanisms from continuous strength, including several pathways considered to be hallmarks of ageing. Muscle weakness has been associated with morbidity and mortality in older people. Here, the authors have investigated this trait further by performing a genome-wide meta-analysis of grip strength and Mendelian randomization to discover causal relationships between muscle weakness and other diseases.
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| 44276. |
- Jones, J. W., et al.
(författare)
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Longitudinal correspondence between subjective and objective memory in the oldest old: A parallel process model by gender
- 2019
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Ingår i: European Journal of Ageing. - : Springer Science and Business Media LLC. - 1613-9372 .- 1613-9380. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- Subjective memory and objective memory performance have predictive utility for clinically relevant outcomes in older adults. Previous research supports certain overlap between objective performance and subjective ratings of memory. These studies are typically cross-sectional or use baseline data only to predict subsequent change. The current study uses a parallel process model to examine concurrent changes in objective memory and subjective memory. We combined data from two population-based Swedish studies of individuals aged 80 + years, assessed every 2 years (OCTO—3 measurement occasions, OCTO-Twin—5 measurement occasions) yielding 607 participants (66% female). The results confirmed that both objective and subjective memory declined over time. The association between the slope of objective memory and subjective memory was statistically significant for women but not for men. This pattern remained after accounting for age and depressive symptoms. Our findings suggest that, in population-based samples of the oldest old, women seem to show better metacognitive abilities in detecting and reporting changes in memory. Memory changes for men may be better identified by objective performance as their self-assessment of memory changes is not associated with actual change in memory performance. © 2019, Springer Nature B.V.
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| 44277. |
- Jones, K. A., et al.
(författare)
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Chronic stress exacerbates neuronal loss associated with secondary neurodegeneration and suppresses microglial-like cells following focal motor cortex ischemia in the mouse
- 2015
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Ingår i: Brain Behavior and Immunity. - : Elsevier BV. - 0889-1591. ; 48, s. 57-67
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Tidskriftsartikel (refereegranskat)abstract
- Post-stroke patients describe suffering from persistent and unremitting levels of distress. Using an experimental model of focal cortical ischemia in adult male C57BL/6 mice, we examined whether exposure to chronic stress could modify the development of secondary thalamic neurodegeneration (STND), which is commonly reported to be associated with impaired functional recovery. We were particularly focused on the modulatory role of microglia-like cells, as several clinical studies have linked microglial activation to the development of STND. One month following the induction of cortical ischemia we identified that numbers of microglial-like cells, as well as putative markers of microglial structural reorganization (Iba-1), complement processing (CD11b), phagocytosis (CD68), and antigen presentation (MHC-II) were all significantly elevated in response to occlusion. We further identified that these changes co-occurred with a decrease in the numbers of mature neurons within the thalamus. Occluded animals that were also exposed to chronic stress exhibited significantly lower levels of Iba-1 positive cells and a reduced expression of Iba-1 and CD11b compared to the 'occlusion-alone' group. Interestingly, the dampened expression of microglial/monocyte markers observed in stressed animals was associated with significant additional loss of neurons. These findings indicate that the process of STND can be negatively modified, potentially in a microglial dependent manner, by exposure to chronic stress. (C) 2015 Elsevier Inc. All rights reserved.
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| 44278. |
- Jones, K E, et al.
(författare)
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Directional tuning of human forearm muscle afferents during voluntary wrist movements.
- 2001
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Ingår i: The Journal of physiology. - 0022-3751. ; 536:Pt 2, s. 635-47
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Tidskriftsartikel (refereegranskat)abstract
- 1. Single unit activity was recorded with the microneurography technique from sixteen spindle afferents and one Golgi tendon organ afferent originating from the forearm extensor muscles. Impulse rates were studied while subjects performed unobstructed aiming movements at the wrist in eight different directions 45 deg apart. In addition, similar imposed movements were performed while the subject was instructed to remain relaxed. Movement amplitudes were about 5 deg and the speed 10-30 deg x s(-1). Joint movements were translated to movements of a cursor on a monitor to provide visual feedback. 2. Individual spindle afferents modulated their activity over a number of targets, i.e. were broadly tuned, during these aiming movements. The preferred direction for a spindle afferent was the same during both passive and active movements, indicating that the fusimotor effects associated with active contractions had little or no effect on the direction of tuning. 3. The direction of tuning of individual spindle afferents could be predicted from the biomechanically inferred length changes of the parent muscle. Thus spindle afferents responded as stretch receptors, i.e. impulse rates increased with lengthening and decreased with shortening, in active as well as passive movements. 4. Spindles from muscles, which continuously counteracted gravity exhibited a stretch response and directional tuning during the phase of movement alone whereas their position sensitivity was poor. In contrast, spindle afferents from the muscles that had no or minimal antigravity role were directionally tuned during both the dynamic and the static phase of the aiming task and their position sensitivity was substantially higher. 5. In spite of the limited data base from three extensor muscles it could be demonstrated that wrist joint position was remarkably well encoded in the ensemble muscle spindle data. In some cases the ensemble muscle spindle data encoded the instantaneous trajectory of movement as well.
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| 44279. |
- Jones, K E, et al.
(författare)
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Proprioceptive feedback is reduced during adaptation to a visuomotor transformation: preliminary findings.
- 2001
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Ingår i: Neuroreport. - 0959-4965. ; 12:18, s. 4029-33
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Tidskriftsartikel (refereegranskat)abstract
- Adapting movements in relation to visual feedback is a ubiquitous characteristic of sensorimotor control and involves the integration of multiple sources of sensory information. We recorded sensory feedback from muscle spindle afferents during visuomotor adaptation while subjects performed an aiming task to investigate whether the activity of the muscle spindles was modulated by the fusimotor system under these learning conditions. None of the muscle spindles showed an increase in activity, rather in 83% of the trials the firing rates were decreased. These preliminary results suggest that the CNS reduces the sensory signals arising from muscle spindles perhaps as a means of resolving the conflict between visual and proprioceptive feedback during the task.
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| 44280. |
- Jones, K. L., et al.
(författare)
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The unintended consequences of school inspection: the prevalence of inspection side-effects in Austria, the Czech Republic, England, Ireland, the Netherlands, Sweden, and Switzerland
- 2017
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Ingår i: Oxford Review of Education. - : Informa UK Limited. - 0305-4985 .- 1465-3915. ; 43:6, s. 805-822
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Tidskriftsartikel (refereegranskat)abstract
- It has been widely documented that accountability systems, including school inspections, bring with them unintended side effects. These unintended effects are often negative and have the potential to undo the intended positive effects. However the empirical evidence is limited. Through a European comparative study we have had the rare opportunity to collect empirical evidence and study the effects (both intended and unintended) of school inspections (a key system of accountability) in a systematic way, across seven countries. We present the findings of the unintended effects in this paper. Survey self-report responses from school principals in each country, with differing school inspection systems, are analysed to measure the prevalence of these unintended effects and to investigate the part played by pressure to do well in inspections. A key finding is that increasing pressure in school inspection systems is associated with the undesired effect of the narrowing and refocusing of the curriculum and instructional strategies. We also show that a proportion of school principals admit to misrepresenting the school in data sent to the inspectorate and show evidence for formalisation/proceduralisation (excessive focus on records) and ossification (fear of experimentation in teaching), although these factors are less related to changes in pressure.
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