109 research outputs found
A Differential Spectroscopic Analysis of 16 Cygni A and B
We utilize high-resolution, high signal-to-noise spectra to perform a
differential analysis of Fe abundances in the common proper-motion pair 16 Cyg
A and B. We confirm that both stars are slightly metal-rich compared to the
Sun, and we show for the first time that the primary is enhanced in Fe relative
to the secondary by a significant amount. We find Delta[Fe/H]=+0.025\pm0.009.
This tends to support the ``self-pollution'' scenario proposed by Gonzalez
(1998), though lack of a complete understanding of small primordial metallicity
variations among binaries and open cluster members prevents a definitive
conclusion
The effect of heavy element opacity on pre-main sequence Li depletion
Recent 3-D analysis of the solar spectrum data suggests a significant change
of the solar chemical composition. This may affect the temporal evolution of
the surface abundance of light elements since the extension of the convective
envelope is largely affected by the internal opacity value. We analyse the
influence of the adopted solar mixture on the opacity in the convective
envelope of pre-main sequence (PMS) stars and thus on PMS lithium depletion.
The surface Li abundance depends on the relative efficiency of several
processes, some of them still not known with the required precision; this paper
thus analyses one of the aspects of this ``puzzle''. Focusing on PMS evolution,
where the largest amount of Li burning occurs, we computed stellar models for
three selected masses (0.8, 1.0 and 1.2 Msun, with Z=0.013, Y=0.27, alpha=1.9)
by varying the chemical mixture, that is the internal element distribution in
Z. We analysed the contribution of the single elements to the opacity at the
temperatures and densities of interest for Li depletion. Several mixtures were
obtained by varying the abundance of the most important elements one at a time;
we then calculated the corresponding PMS Li abundance evolution. We found that
a mixture variation does change the Li abundance: at fixed total metallicity,
the Li depletion increases when increasing the fraction of elements heavier
than O.Comment: A&A accepted, 11 pages, 18 eps figure
Mass transfer from a giant star to a main sequence companion and its contribution to long-orbital-period blue stragglers
Binary population synthesis shows that mass transfer from a giant star to a
main-sequence (MS) companion may account for some observed long-orbital period
blue stragglers. However, little attention {\bf is paid to this blue straggler
formation scenario} as dynamical instability often happens when the mass donor
is a giant star. In this paper, we have studied the critical mass ratio,
, for dynamically stable mass transfer from a giant star to a MS
companion using detailed evolution calculations. The results show that a more
evolved star is generally less stable for Roche lobe overflow. Meanwhile,
almost linearly increases with the amount of the mass and angular
momentum {\bf lost} during mass transfer, but has little dependance on stellar
wind. To conveniently use the result, we give a fit of as a
function of the stellar radius at the onset of Roche lobe overflow and of the
mass transfer efficiency during the Roche lobe overflow.
To examine the formation of blue stragglers from mass transfer between giants
and MS stars, we have performed Monte Carlo simulations with various . {\bf The simulations show that some binaries with the mass donor on the
first giant branch may contribute to blue stragglers with obtained
in this paper but will not from previous . Meanwhile, from our
, blue stragglers from the mass transfer between an AGB star and a
MS companion may be more numerous and have a wider range of orbital periods
than those from the other .Comment: 16 pages, 17 figures. accepted by MNRA
Are changes in Australian national primary healthcare policy likely to promote or impede equity of access? A narrative review
Copyright La Trobe University 2017, published by CSIROSignificant changes have occurred in Australia’s national primary healthcare (PHC) policy over the last decade, but little assessment has been made of implications for equity. This research aimed to identify key recent changes in national PHC policy and assess implications for equity of access to PHC. Academic literature was reviewed to identify issues affecting equity of access in national PHC policy, and grey literature was also reviewed to identify significant policy changes during 2005–16 with implications for equitable access. Equity implications of four areas of policy change, set against the existing Medicare system, were assessed. It was found that Medicare supports equitable access to general practice, but there is a risk of reduced equity under current policy settings. Four changes in PHC policy were selected as having particular implications for equity of access and these were assessed as follows: increased involvement of private health insurance presents risks for equity; equity implications of new models of coordinated care are unclear; and regional primary health organisations and current policy on Aboriginal and Torres Strait Islander health have potential equity benefits, but these will depend on further implementation
EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2013 . Scientific O pinion on Dietary Reference Values for molybdenum
Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) derived Dietary Reference Values (DRVs) for molybdenum. Molybdenum is efficiently and rapidly absorbed at a wide range of intakes, and the body is able to maintain homeostasis through the regulation of excretion via the urine. Molybdenum deficiency in otherwise healthy humans has not been observed and there are no biomarkers of molybdenum status. Various metabolic balance studies have been performed to establish molybdenum requirements. However, only one balance study, which was performed with a constant diet and under controlled conditions in adult men, was considered to be of sufficient duration. In this small study, balance was reported to be near zero when molybdenum intakes were 22 µg/day. Biochemical changes or symptoms suggestive of molybdenum deficiency were not observed, and it is possible that humans may be able to achieve molybdenum balance at even lower intakes. Data on molybdenum intakes and health outcomes were unavailable for the setting of DRVs for molybdenum. As the evidence required to derive an Average Requirement and a Population Reference Intake was considered insufficient, an Adequate Intake (AI) is proposed. Observed molybdenum intakes from mixed diets in Europe were taken into consideration in setting this value. An AI of 65 µg/day is proposed for adults; a figure that is based on molybdenum intakes at the lower end of the wide range of observed intakes. It is suggested that the adult AI also applies to pregnant and lactating women. An AI is also proposed for infants from seven months and for children based on extrapolation from the adult AI using isometric scaling and the reference body weights of the respective age groups
Low and intermediate mass star yields: The evolution of carbon abundances
We present a set of low and intermediate mass star yields based on a modeling
of the TP--AGB phase which affects the production of nitrogen and carbon. These
yields are evaluated by using them in a Galaxy Chemical Evolution model, with
which we analyze the evolution of carbon abundances. By comparing the results
with those obtained with other yield sets, and with a large amount of
observational data, we conclude that the model using these yields combined with
those from Woosley & Weaver (1995) for massive stars properly reproduce all the
data. The model reproduces well the increase of C/O with increasing O/H
abundances. Since these massive star yields do not include winds, it implies
that these stellar winds might have a smoother dependence on metallicity than
usually assumed and that a significant quantity of carbon proceeds from LIM
stars.Comment: 21 pages, 11 figures. To be published in Astronomy and Astrophysic
Improving the Accuracy of Demographic and Molecular Clock Model Comparison While Accommodating Phylogenetic Uncertainty
status: publishe
Short-term effects of unilateral lesion of the primary motor cortex (M1) on ipsilesional hand dexterity in adult macaque monkeys
Although the arrangement of the corticospinal projection in primates is consistent with a more prominent role of the ipsilateral motor cortex on proximal muscles, rather than on distal muscles involved in manual dexterity, the role played by the primary motor cortex on the control of manual dexterity for the ipsilateral hand remains a matter a debate, either in the normal function or after a lesion. We, therefore, tested the impact of permanent unilateral motor cortex lesion on the manual dexterity of the ipsilateral hand in 11 macaque monkeys, within a time window of 60 days post-lesion. For comparison, unilateral reversible pharmacological inactivation of the motor cortex was produced in an additional monkey. Manual dexterity was assessed quantitatively based on three motor parameters derived from two reach and grasp manual tasks. In contrast to the expected dramatic, complete deficit of manual dexterity of the contralesional hand that persists for several weeks, the impact on the manual dexterity of the ipsilesional hand was generally moderate (but statistically significant) and, when present, lasted less than 20 days. Out of the 11 monkeys, only 3 showed a deficit of the ipsilesional hand for 2 of the 3 motor parameters, and 4 animals had a deficit for only one motor parameter. Four monkeys did not show any deficit. The reversible inactivation experiment yielded results consistent with the permanent lesion data. In conclusion, the primary motor cortex exerts a modest role on ipsilateral manual dexterity, most likely in the form of indirect hand postural control
Impact of early applied upper limb stimulation: The EXPLICIT-stroke programme design
Main claims of the literature are that functional recovery of the paretic upper limb is mainly defined within the first month post stroke and that rehabilitation services should preferably be applied intensively and in a task-oriented way within this particular time window. EXplaining PLastICITy after stroke (acronym EXPLICIT-stroke) aims to explore the underlying mechanisms of post stroke upper limb recovery. Two randomized single blinded trials form the core of the programme, investigating the effects of early modified Constraint-Induced Movement Therapy (modified CIMT) and EMG-triggered Neuro-Muscular Stimulation (EMG-NMS) in patients with respectively a favourable or poor probability for recovery of dexterity.BioMechanical EngineeringMechanical, Maritime and Materials Engineerin
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