The impact of metallicity on the mass-loss rate from red giant branch (RGB) stars is studied through its effect on the parameters of horizontal branch (HB) stars. The scaling factors from Reimers and ...Schröder and Cuntz are used to measure the efficiency of RGB mass-loss for typical stars in 56 well-studied Galactic globular clusters (GCs). The median values among clusters are, respectively,
$\eta _{\rm R} = 0.477 \pm 0.070 ^{+0.050}_{-0.062}$
and
$\eta _{\rm SC} = 0.172 \pm 0.024 ^{+0.018}_{-0.023}$
(standard deviation and systematic uncertainties, respectively). Over a factor of 200 in iron abundance, η varies by ≲30 per cent, thus mass-loss mechanisms on the RGB have very little metallicity dependence. Any remaining dependence is within the current systematic uncertainties on cluster ages and evolution models. The low standard deviation of η among clusters (≈14 per cent) contrasts with the variety of HB morphologies. Since η incorporates cluster age, this suggests that age accounts for the majority of the ‘second parameter problem’, and that a Reimers-like law provides a good mass-loss model. The remaining spread in η correlates with cluster mass and density, suggesting helium enrichment provides the third parameter explaining HB morphology of GCs. We close by discussing asymptotic giant branch (AGB) mass-loss, finding that the AGB tip luminosity is better reproduced and η has less metallicity dependence if GCs are more co-eval than generally thought.
ABSTRACT
We derive the fundamental parameters (temperature and luminosity) of 107 619 Hipparcos stars and place these stars on a true Hertzsprung–Russell diagram. This is achieved by comparing ...bt‐settl model atmospheres to spectral energy distributions (SEDs) created from Hipparcos, Tycho, Sloan Digital Sky Survey, DENIS, Two Micron All Sky Survey, MSX, AKARI, IRAS and Wide‐field Infrared Survey Explorer data. We also identify and quantify from these SEDs any infrared excesses attributable to circumstellar matter. We compare our results to known types of objects, focusing on the giant branch stars. Giant star dust production (as traced by infrared excess) is found to start in earnest around 680 L⊙.
Objectives
To determine the long‐term effects of three strength and balance exercise interventions on physical performance, fall‐related psychological outcomes, and falls in older people.
Design
A ...single‐blinded, four‐group, randomized controlled trial.
Setting
Community, Germany.
Participants
Community‐dwelling adults aged 70 to 90 who had fallen in the past 6 months or reported fear of falling.
Intervention
After baseline assessment, 280 participants were randomly assigned to the control group (CG; no intervention; n = 80) or one of three strength and balance exercise interventions (the strength and balance group (SBG; strength and balance only; n = 63), the fitness group (FG; strength and balance plus endurance training; n = 64), or the multifaceted group (MG; strength and balance plus fall risk education; n = 73). The interventions consisted of 32 one‐hour group sessions in 16 weeks.
Measurements
Data on physical performance, fall‐related psychological outcomes, and falls were collected for 24 months.
Results
Mixed‐effects regression analyses showed improved short‐ and long‐term (12 and 24 months, respectively) physical performance for the SBG and FG, particularly regarding mobility, balance, and walking speed (P < .05). The improvements in physical performance outcomes were most prominent in the FG. Fall‐related psychological outcomes, number of falls, and injurious falls were not significantly different from in the control group.
Conclusion
Training focusing on strength, balance, and endurance can enhance physical performance for up to 24 months in community‐dwelling older adults. These findings did not translate to improved fall‐related psychological outcomes or reduced incidence of falls. This demonstrates the need for a different approach (e.g., regarding intervention dose and components) to gain intervention benefits in the multiple domains that contribute to independence and well‐being in older adults.
Ultraviolet radiation from white dwarfs can efficiently clear Galactic globular clusters (GCs) of their intracluster medium (ICM). This solves the problem of the missing ICM in clusters, which is ...otherwise expected to build up to easily observable quantities. To show this, we recreate the ionizing flux in 47 Tuc, following randomly generated stars through their asymptotic giant branch (AGB), post-AGB and white dwarf evolution. Each white dwarf can ionize all the material injected into the cluster by stellar winds for similar to 3 Myr of its evolution: similar to 40 such white dwarfs exist at any point. Every GC's ICM should be ionized. The neutral cloud in M15 should be caused by a temporary overdensity. A pressure-supported ICM will expand over the cluster's tidal radius, where it will be truncated, allowing Jeans escape. The modelled Jeans mass-loss rate approximates the total stellar mass-loss rate, allowing efficient clearing of ICM. Any cluster's ICM mass should equal the mass injected by its stars over the sound travel time between the cluster core and tidal radius. We predict similar to 11.3 M. of ICM within 47 Tuc, cleared over similar to 4 Myr, compared to a dynamical time-scale of 4.3 Myr. We present a new mass hierarchy, discussing the transition between GCs dwarf galaxies.
Most older people wish to age in place, for which functional status or being able to perform activities of daily living (ADLs) is an important precondition. However, along with the substantial growth ...of the (oldest) old, the number of people who develop limitations in ADLs or have functional decline dramatically increases in this part of the population. Therefore, it is important to gain insight into factors that can contribute to developing intervention strategies at older ages. As a first step, this systematic review was conducted to identify risk and protective factors as predictors for developing limitations in ADLs in community-dwelling people aged 75 and over.
Four electronic databases (CINAHL (EBSCO), EMBASE, PsycINFO and PubMed) were searched systematically for potentially relevant studies published between January 1998 and March 2016.
After a careful selection process, 6,910 studies were identified and 25 were included. By far most factors were examined in one study only, and most were considered risk factors. Several factors do not seem to be able to predict the development of limitations in ADLs in people aged 75 years and over, and for some factors ambiguous associations were found. The following risk factors were found in at least two studies: higher age, female gender, diabetes, hypertension, and stroke. A high level of physical activity and being married were protective in multiple studies. Notwithstanding the fact that research in people aged 65 years and over is more extensive, risk and protective factors seem to differ between the 'younger' and 'older' olds.
Only a few risk and protective factors in community-dwelling people aged 75 years and over have been analysed in multiple studies. However, the identified factors could serve both detection and prevention purposes, and implications for future research are given as well.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
AbstractObjectiveTo test whether StandingTall, a home based, e-health balance exercise programme delivered through an app, could provide an effective, self-managed fall prevention programme for ...community dwelling older people.DesignAssessor blinded, randomised controlled trial.SettingOlder people living independently in the community in Sydney, Australia.Participants503 people aged 70 years and older who were independent in activities of daily living, without cognitive impairment, progressive neurological disease, or any other unstable or acute medical condition precluding exercise.InterventionsParticipants were block randomised to an intervention group (two hours of StandingTall per week and health education; n=254) or a control group (health education; n=249) for two years.Main outcome measuresThe primary outcomes were the rate of falls (number of falls per person year) and the proportion of people who had a fall over 12 months. Secondary outcomes were the number of people who had a fall and the number who had an injurious fall (resulting in any injury or requiring medical care), adherence, mood, health related quality of life, and activity levels over 24 months; and balance and mobility outcomes over 12 months.ResultsThe fall rates were not statistically different in the two groups after the first 12 months (0.60 falls per year (standard deviation 1.05) in the intervention group; 0.76 (1.25) in the control group; incidence rate ratio 0.84, 95% confidence interval 0.62 to 1.13, P=0.071). Additionally, the proportion of people who fell was not statistically different at 12 months (34.6% in intervention group, 40.2% in control group; relative risk 0.90, 95% confidence interval 0.67 to 1.20, P=0.461). However, the intervention group had a 16% lower rate of falls over 24 months compared with the control group (incidence rate ratio 0.84, 95% confidence interval 0.72 to 0.98, P=0.027). Both groups had a similar proportion of people who fell over 24 months (relative risk 0.87, 95% confidence interval 0.68 to 1.10, P=0.239), but the proportion of people who had an injurious fall over 24 months was 20% lower in the intervention group compared with the control group (relative risk 0.80, 95% confidence interval 0.66 to 0.98, P=0.031). In the intervention group, 68.1% and 52.0% of participants exercised for a median of 114.0 min/week (interquartile range 53.5) after 12 months and 120.4 min/week (38.6) after 24 months, respectively. Groups remained similar in mood and activity levels. The intervention group had a 0.03 (95% confidence interval 0.01 to 0.06) improvement on the EQ-5D-5L (EuroQol five dimension five level) utility score at six months, and an improvement in standing balance of 11 s (95% confidence interval 2 to 19 s) at six months and 10 s (1 to 19 s) at 12 months. No serious training related adverse events occurred.ConclusionsThe StandingTall balance exercise programme did not significantly affect the primary outcomes of this study. However, the programme significantly reduced the rate of falls and the number of injurious falls over two years, with similar but not statistically significant effects at 12 months. E-health exercise programmes could provide promising scalable fall prevention strategies.Trial registrationACTRN12615000138583
Background: the 16-item Falls Efficacy Scale-International (FES-I) has been shown to have excellent reliability and construct validity. However, for practical and clinical purposes, a shortened ...version of the FES-I would be useful. Objective: to develop and validate a shortened version of FES-I while preserving good psychometric properties. Design: initial development of a shortened version using data from a UK survey (Short FES-I; n = 704), test of reliability and validity of the Short FES-I using data from a Dutch survey (n = 300). Setting: community samples. Methods: comparison of reliability and validity of the Short FES-I and the FES-I in a random sample of 193 people aged between 70 and 92. Results: the internal and 4-week test–retest reliability of the Short FES-I is excellent (Cronbach's alpha 0.92, intra-class coefficient 0.83) and comparable to the FES-I. The correlation between the Short FES-I and the FES-I is 0.97. Patterns in differences with respect to mean scores according to age, sex, falls history, and overall fear of falling are similar for the Short FES-I and the FES-I. The FES-I had slightly better power to discriminate between groups differentiated by age, sex, falls history, and fear falling, but differences are small. Conclusions: the Short FES-I is a good and feasible measure to assess fear of falling in older persons. However, if researchers or clinicians are particularly interested in the distributions of specific fear of falling-related activities not included in the Short FES-I, the use of the full FES-I is recommended.
ABSTRACT Low- and intermediate-mass stars eject much of their mass during the late, red giant branch (RGB) phase of evolution. The physics of their strong stellar winds is still poorly understood. In ...the standard model, stellar pulsations extend the atmosphere, allowing a wind to be driven through radiation pressure on condensing dust particles. Here, we investigate the onset of the wind, using nearby RGB stars drawn from the Hipparcos catalog. We find a sharp onset of dust production when the star first reaches a pulsation period of 60 days. This approximately coincides with the point where the star transitions to the first overtone pulsation mode. Models of the spectral energy distributions show stellar mass-loss rate suddenly increasing at this point, by a factor of ∼10 over the existing (chromospherically driven) wind. The dust emission is strongly correlated with both pulsation period and amplitude, indicating stellar pulsation is the main trigger for the strong mass loss, and determines the mass-loss rate. Dust emission does not strongly correlate with stellar luminosity, indicating radiation pressure on dust has little effect on the mass-loss rate. RGB stars do not normally appear to produce dust, whereas dust production by asymptotic giant branch stars appears commonplace, and is probably ubiquitous above the RGB-tip luminosity. We conclude that the strong wind begins with a step change in mass-loss rate and is triggered by stellar pulsations. A second rapid mass-loss-rate enhancement is suggested when the star transitions to the fundamental pulsation mode at a period of ∼300 days.
ABSTRACT
We present three-dimensional (3D) dust mapping of 12 supernova remnants (SNRs) in the Galactic anticentre (Galactic longitude l between 150○ and 210○) based on a recent 3D interstellar ...extinction map. The dust distribution of the regions, which cover the full extents in the radio continuum for the individual SNRs, is discussed. Four SNRs show significant spatial coincidences between molecular clouds (MCs) revealed from the 3D extinction mapping and the corresponding radio features. The results confirm the interactions between these SNRs and their surrounding MCs. Based on these correlations, we provide new distance estimates of the four SNRs, G189.1+3.0 (IC443, $d=1729^{+116}_{-94} \rm \, pc$), G190.9–2.2 ($d=1036^{+17}_{-81} \rm \, pc$), G205.5+0.5 ($d=941^{+96}_{-94}$ or $1257^{+92}_{-101} \rm \, pc$), and G213.0–0.6 ($d=1146^{+79}_{-80} \rm \, pc$). In addition, we find indirect evidences of potential interactions between SNRs and MCs for three other SNRs. New distance constraints are also given for these three SNRs.
We present the results of our survey of 1612-MHz circumstellar OH maser emission from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC). We have ...discovered four new circumstellar maser sources in the LMC, and increased the number of reliable wind speeds from infrared (IR) stars in the LMC from 5 to 13. Using our new wind speeds, as well as those from Galactic sources, we have derived an updated relation for dust-driven winds: ... We compare the subsolar metallicity LMC OH/IR stars with carefully selected samples of more metal-rich OH/IR stars, also at known distances, in the Galactic Centre and Galactic bulge. We derive pulsation periods for eight of the bulge stars for the first time by using near-IR photometry from the Vista Variables in the Via Lactea survey. We have modelled our LMC OH/IR stars and developed an empirical method of deriving gas-to-dust ratios and mass-loss rates by scaling the models to the results from maser profiles. We have done this also for samples in the Galactic Centre and bulge and derived a new mass-loss prescription which includes luminosity, pulsation period, and gas-to-dust ratio ... The tightest correlation is found between mass-loss rate and luminosity. We find that the gas-to-dust ratio has little effect on the mass-loss of oxygen-rich AGB stars and RSGs within the Galaxy and the LMC. This suggests that the mass-loss of oxygen-rich AGB stars and RSGs is (nearly) independent of metallicity between a half and twice solar. (ProQuest: ... denotes formulae/symbols omitted.)
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