Physical activity and functional performance in Iranian 75-year-olds : a cross-sectional population study compared with a Swedish study

Background: Population ageing is highly complex and varies with the context. For instance, people’s health can be influenced by behavioral and cultural factors and economic resources. Cross-national comparisons are helpful when exploring these factors. Aims: To provide a Persian version of the Falls Efficacy Scale, Swedish version (FES(S)) and explore its validity and reliability in an Iranian population. To investigate whether Iranian 75-year-olds differ from their Swedish peers with respect to physical activity level, physical performance and certain health-related factors. To explore if walking for at least 30 min a day is related to health, fitness, physiological capacity and functional performance in older Iranians. To establish whether health-related behavior (HRB) and independence (I) intermediate the link between the socioeconomic status (SES) and the health status (HS) of older adults in Iran. Material and methods: A representative sample of 637 Swedish 75-year olds, from the longitudinal Gerontological and Geriatric Population Studies in Gothenburg, and an Iranian sample of 851 75-year-olds, living in Tehran, were included. Physical activity level, health-related factors, and the results of functional tests including walking speed, muscle strength and balance function were evaluated. SPSS and Mplus 5 softwares were used for data analysis. Results: The Persian FES (S) was shown to be a culturally relevant, valid, and reliable tool for measuring fall-related self-perceived confidence in Iranian older adults. Iranian 75-year-olds had a lower physical activity level, a worse physical function apart from a better grip strength, a worse physical health status but smoked less than their Swedish counterparts. There were no differences between the two cohorts regarding vertigo or falls. The extent of gender differences was about the same in most aspects and to the disadvantage of women. Iranian old people who walked at least 30 minutes daily/almost daily were better in most health-related outcomes, ADL and functional performance than people who walked less. A structural equation model showed that older people with a high SES had a higher level of physical activity and were more independent in ADL than others. SES was a positive predictor of HS, not directly but through the intermediation of HRB and I. Conclusions: The Persian version of FES(S) was shown to be a valid and reliable tool. 75-year-old Iranians were less physically active than their Swedish peers and their functional performance, apart from grip strength, was worse, while similar gender differences were found, mainly to the advantage of men. Iranians who took a daily walk of at least 30 min a day showed better results in most health-related outcomes, ADL and functional performance than persons who walked less. As physical activity is a strong determinant of functional performance and health, activities like taking a daily walk of at least 30 minutes should be promoted. Gender-specific discrepancies found in relation to physical activity and performance call for longitudinal studies to clarify the causes

The influence of outflow in supercritical accretion flows

We solve the radiation-hydrodynamic (RHD) equations of supercritical accretion flows in the presence of radiation force and outflow by using self similar solutions. Compare with the pioneer works, in this paper we consider power-law function for mass inflow rate as $\dot{M} \propto r^{s}$. We found that $s = 1$ when the radiative cooling term is included in the energy equation. Correspondingly, the effective temperature profile with respect to the radius was obtained as $T_{\text{eff}} \varpropto r^{-1/2}$. In addition, we investigated the influence of the outflow on the dynamics of the accretion flow. We also calculated the continuum spectrum emitted from the disk surface as well as the bolometric luminosity of the accretion flow. Furthermore, our results show that the advection parameter, $f$, strongly depends on mass inflow rate.Comment: Accepted for publication in Astrophysical Journa

Numerical Simulation of Hot Accretion Flow around Bondi Radius

Previous numerical simulations have shown that strong winds can be produced in the hot accretion flows around black holes. Most of those studies focus only on the region close to the central black hole, therefore it is unclear whether the wind production stops at large radii around Bondi radius. Bu et al. 2016 studied the hot accretion flow around the Bondi radius in the presence of nuclear star gravity. They find that when the nuclear stars gravity is important/comparable to the black hole gravity, winds can not be produced around the Bondi radius. However, for some galaxies, the nuclear stars gravity around Bondi radius may not be strong. In this case, whether winds can be produced around Bondi radius is not clear. We study the hot accretion flow around Bondi radius with and without thermal conduction by performing hydrodynamical simulations. We use the virtual particles trajectory method to study whether winds exist based on the simulation data. Our numerical results show that in the absence of nuclear stars gravity, winds can be produced around Bondi radius, which causes the mass inflow rate decreasing inwards. We confirm the results of Yuan et al. which indicates this is due to the mass loss of gas via wind rather convectional motions.Comment: 15 pages, 8 figures, accepted for publication in Ap