4,412 research outputs found
Mammalian models of extended healthy lifespan
Over the last two centuries, there has been a significant increase in average lifespan expectancy in the developed world. One unambiguous clinical implication of getting older is the risk of experiencing age-related diseases including various cancers, dementia, type-2 diabetes, cataracts and osteoporosis. Historically, the ageing process and its consequences were thought to be intractable. However, over the last two decades or so, a wealth of empirical data has been generated which demonstrates that longevity in model organisms can be extended through the manipulation of individual genes. In particular, many pathological conditions associated with the ageing process in model organisms, and importantly conserved from nematodes to humans, are attenuated in long-lived genetic mutants. For example, several long-lived genetic mouse models show attenuation in age-related cognitive decline, adiposity, cancer and glucose intolerance. Therefore, these long-lived mice enjoy a longer period without suffering the various sequelae of ageing. The greatest challenge in the biology of ageing is to now identify the mechanisms underlying increased healthy lifespan in these model organisms. Given that the elderly are making up an increasingly greater proportion of society, this focused approach in model organisms should help identify tractable interventions that can ultimately be translated to humans
Inhibition of Tendon Cell Proliferation and Matrix Glycosaminoglycan Synthesis by Non-Steroidal Anti-Inflammatory Drugs in vitro
The purpose of this study was to investigate the effects of some commonly used non-steroidal anti-inflammatory drugs (NSAIDs) on human tendon. Explants of human digital flexor and patella tendons were cultured in medium containing pharmacological concentrations of NSAIDs. Cell proliferation was measured by incorporation of 3H-thymidine and glycosaminoglycan synthesis was measured by incorporation of 35S-Sulphate. Diclofenac and aceclofenac had no significant effect either on tendon cell proliferation or glycosaminoglycan synthesis. Indomethacin and naproxen inhibited cell proliferation in patella tendons and inhibited glycosaminoglycan synthesis in both digital flexor and patella tendons. If applicable to the in vivo situation, these NSAIDs should be used with caution in the treatment of pain after tendon injury and surgery
Coronary steal syndrome after coronary artery bypass for anomalous aortic origin of a coronary artery.
Anomalous aortic origin of a coronary artery found in a symptomatic 9-year-old boy was initially treated with coronary artery bypass grafting using a left internal mammary artery anastomoses to the left anterior descending coronary artery, but resulted in coronary ischemia, likely from a steal phenomenon. Subsequent transection of the proximal left internal mammary artery with anastomosis to the ascending aorta, and coronary ostial enlargement, resulted in a durable treatment. We recommend caution in choosing coronary artery bypass grafting using a left internal mammary artery pedicle graft for the treatment of anomalous aortic origin of a coronary artery
Simulating the Multi-Epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-Transiting Hot Jupiter HD187123B
We report the 6.5 detection of water from the hot Jupiter HD187123b
with a Keplerian orbital velocity of 53 13 km/s. This high
confidence detection is made using a multi-epoch, high resolution, cross
correlation technique, and corresponds to a planetary mass of
1.4 and an orbital inclination of 21 5.
The technique works by treating the planet/star system as a spectroscopic
binary and obtaining high signal-to-noise, high resolution observations at
multiple points across the planet's orbit to constrain the system's binary
dynamical motion. All together, seven epochs of Keck/NIRSPEC -band
observations were obtained, with five before the instrument upgrade and two
after. Using high resolution SCARLET planetary and PHOENIX stellar spectral
models, along with a line-by-line telluric absorption model, we were able to
drastically increase the confidence of the detection by running simulations
that could reproduce, and thus remove, the non-random structured noise in the
final likelihood space well. The ability to predict multi-epoch results will be
extremely useful for furthering the technique. Here, we use these simulations
to compare three different approaches to combining the cross correlations of
high resolution spectra and find that the Zucker 2003 log(L) approach is least
affected by unwanted planet/star correlation for our HD187123 data set.
Furthermore, we find that the same total S/N spread across an orbit in many,
lower S/N epochs rather than fewer, higher S/N epochs could provide a more
efficient detection. This work provides a necessary validation of multi-epoch
simulations which can be used to guide future observations and will be key to
studying the atmospheres of further separated, non-transiting exoplanets.Comment: Accepted to AJ, 14 pages, 10 figure
Transport of Cosmic Rays in Chaotic Magnetic Fields
The transport of charged particles in disorganised magnetic fields is an
important issue which concerns the propagation of cosmic rays of all energies
in a variety of astrophysical environments, such as the interplanetary,
interstellar and even extra-galactic media, as well as the efficiency of Fermi
acceleration processes. We have performed detailed numerical experiments using
Monte-Carlo simulations of particle propagation in stochastic magnetic fields
in order to measure the parallel and transverse spatial diffusion coefficients
and the pitch angle scattering time as a function of rigidity and strength of
the turbulent magnetic component. We confirm the extrapolation to high
turbulence levels of the scaling predicted by the quasi-linear approximation
for the scattering frequency and parallel diffusion coefficient at low
rigidity. We show that the widely used Bohm diffusion coefficient does not
provide a satisfactory approximation to diffusion even in the extreme case
where the mean field vanishes. We find that diffusion also takes place for
particles with Larmor radii larger than the coherence length of the turbulence.
We argue that transverse diffusion is much more effective than predicted by the
quasi-linear approximation, and appears compatible with chaotic magnetic
diffusion of the field lines. We provide numerical estimates of the Kolmogorov
length and magnetic line diffusion coefficient as a function of the level of
turbulence. Finally we comment on applications of our results to astrophysical
turbulence and the acceleration of high energy cosmic rays in supernovae
remnants, in super-bubbles, and in jets and hot spots of powerful
radio-galaxies.Comment: To be published in Physical Review D, 20 pages 9 figure
Pair Plasma Dominance in the Parsec-Scale Relativistic Jet of 3C345
We investigate whether a pc-scale jet of 3C345 is dominated by a normal
plasma or an electron-positron plasma. We present a general condition that a
jet component becomes optically thick for synchrotron self-absorption, by
extending the method originally developed by Reynolds et al. The general
condition gives a lower limit of the electron number density, with the aid of
the surface brightness condition, which enables us to compute the magnetic
field density. Comparing the lower limit with another independent constraint
for the electron density that is deduced from the kinetic luminosity, we can
distinguish the matter content. We apply the procedure to the five components
of 3C345 (C2, C3, C4, C5, and C7) of which angular diameters and radio fluxes
at the peak frequencies were obtainable from literature. Evaluating the
representative values of Doppler beaming factors by their equipartition values,
we find that all the five components are likely dominated by an
electron-positron plasma. The conclusion does not depend on the lower cutoff
energy of the power-law distribution of radiating particles.Comment: 17 page
Setting the stage: social-environmental and motivational predictors of optimal training engagement
In this paper, we will firstly explore the central tenets of SDT. Research that has examined the social-environmental and motivation-related correlates of optimal training, performance and health-related engagement through the theoretical lens of SDT will be reviewed. Drawing from SDT-driven work undertaken in educational, sport and dance settings, we will draw conclusions and suggest future directions from a research and applied perspective
On the Concept of a Notational Variant
In the study of modal and nonclassical logics, translations have frequently been employed as a way of measuring the inferential capabilities of a logic. It is sometimes claimed that two logics are “notational variants” if they are translationally equivalent. However, we will show that this cannot be quite right, since first-order logic and propositional logic are translationally equivalent. Others have claimed that for two logics to be notational variants, they must at least be compositionally intertranslatable. The definition of compositionality these accounts use, however, is too strong, as the standard translation from modal logic to first-order logic is not compositional in this sense. In light of this, we will explore a weaker version of this notion that we will call schematicity and show that there is no schematic translation either from first-order logic to propositional logic or from intuitionistic logic to classical logic
Estimating the functional form for the density dependence from life history data
Two contrasting approaches to the analysis of population dynamics are currently popular: demographic approaches where the associations between demographic rates and statistics summarizing the population dynamics are identified; and time series approaches where the associations between population dynamics, population density, and environmental covariates are investigated. In this paper, we develop an approach to combine these methods and apply it to detailed data from Soay sheep (Ovis aries). We examine how density dependence and climate contribute to fluctuations in population size via age- and sex-specific demographic rates, and how fluctuations in demographic structure influence population dynamics. Density dependence contributes most, followed by climatic variation, age structure fluctuations and interactions between density and climate. We then simplify the density-dependent, stochastic, age-structured demographic model and derive a new phenomenological time series which captures the dynamics better than previously selected functions. The simple method we develop has potential to provide substantial insight into the relative contributions of population and individual-level processes to the dynamics of populations in stochastic environments
Étude microsystémique des facteurs influençant l’anxiété de performance de l’élève athlète
Résumé
Cette étude caractérise les facteurs de protection et de risque de l’anxiété de performance associés aux parents, aux entraîneurs et aux enseignants des élèves athlètes des programmes de Sport-études québécois. Le devis qualitatif interprétatif est ancré dans le modèle écologique de Bronfenbrenner. Seize entretiens semi-dirigés individuels documentent le point de vue de quatre trios (élève athlète, parent et entraîneur), celui d’une dyade (élève athlète et parent) et de deux personnes en direction sportive et scolaire. L’analyse thématique révèle plus de facteurs de protection que de facteurs de risque. Les résultats soulignent l’importance d’améliorer les savoirs des enseignants et de mieux définir les attentes académiques envers les élèves athlètes liées au programme de Sport-études. Ils mettent de l’avant la nécessité d’aider les élèves athlètes à modifier leurs schémas de pensées et de promouvoir l’apprentissage par erreur. Finalement, cette étude démontre l’importance de considérer les multiples sources d’influence de l’anxiété de performance.
Abstract
This study characterizes the protective and risk factors of performance anxiety associated with parents, coaches and teachers of student athletes in Quebec Sport-studies programs. The interpretative qualitative study is anchored in Bronfenbrenner's ecological model. Sixteen semi-structured individual interviews document the perspective of four trios (student athlete, parent and coach), that of a dyad (student athlete and parent) and two people in sports and school management. The thematic analysis reveals more protective factors than risk factors. The results underline the importance of improving the knowledge of teachers and of better defining the academic expectations of student athletes related to the Sport-studies program. They emphasize the need to help student athletes change their thought patterns and promote learning through mistake. Finally, this study demonstrates the importance of considering the multiple sources of influence of performance anxiety
- …