Hemodialysis (HD) is the most common form of kidney replacement therapy. This study aimed to examine the use, availability, accessibility, affordability, and quality of HD care worldwide.
A ...cross-sectional survey.
Stakeholders (clinicians, policy makers, and consumer representatives) in 182 countries were convened by the International Society of Nephrology from July to September 2018.
Use, availability, accessibility, affordability, and quality of HD care.
Descriptive statistics.
Overall, representatives from 160 (88%) countries participated. Median country-specific use of maintenance HD was 298.4 (IQR, 80.5-599.4) per million population (pmp). Global median HD use among incident patients with kidney failure was 98.0 (IQR, 81.5-140.8) pmp and median number of HD centers was 4.5 (IQR, 1.2–9.9) pmp. Adequate HD services (3-4 hours 3 times weekly) were generally available in 27% of low-income countries. Home HD was generally available in 36% of high-income countries. 32% of countries performed monitoring of patient-reported outcomes; 61%, monitoring of small-solute clearance; 60%, monitoring of bone mineral markers; 51%, monitoring of technique survival; and 60%, monitoring of patient survival. At initiation of maintenance dialysis, only 5% of countries used an arteriovenous access in almost all patients. Vascular access education was suboptimal, funding for vascular access procedures was not uniform, and copayments were greater in countries with lower levels of income. Patients in 23% of the low-income countries had to pay >75% of HD costs compared with patients in only 4% of high-income countries.
A cross-sectional survey with possibility of response bias, social desirability bias, and limited data collection preventing in-depth analysis.
In summary, findings reveal substantial variations in global HD use, availability, accessibility, quality, and affordability worldwide, with the lowest use evident in low- and lower-middle–income countries.
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Are Debris Disks and Massive Planets Correlated? Moro-Martín, Amaya; Carpenter, John M; Meyer, Michael R ...
Astrophysical journal/The Astrophysical journal,
04/2007, Letnik:
658, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Using data from the Spitzer Space Telescope Legacy Science Program Formation and Evolution of Planetary Systems (FEPS), we have searched for debris disks around nine FGK stars (2-10 Gyr), known from ...radial velocity (RV) studies to have one or more massive planets. Only one of the sources, HD 38529, has excess emission above the stellar photosphere; at 70 km the signal-to-noise ratio in the excess is 4.7, while at l< 30 k m there is no evidence of excess. The remaining sources show no excesses at any Spitzer wavelengths. Applying survival tests to the FEPS sample and the results for the FGK survey recently published in Bryden et al., we do not find a significant correlation between the frequency and properties of debris disks and the presence of close-in planets. We discuss possible reasons for the lack of a correlation.
ABSTRACT
Coherent radio emission via electron cyclotron maser emission (ECME) from hot magnetic stars was discovered more than two decades ago, but the physical conditions that make the generation of ...ECME favourable remain uncertain. Only recently was an empirical relation, connecting ECME luminosity with the stellar magnetic field and temperature, proposed to explain what makes a hot magnetic star capable of producing ECME. This relation was, however, obtained with just 14 stars. Therefore, it is important to examine whether this relation is robust. With the aim of testing the robustness, we conducted radio observations of five hot magnetic stars. This led to the discovery of three more stars producing ECME. We find that the proposed scaling relation remains valid after the addition of the newly discovered stars. However, we discovered that the magnetic field and effective temperature correlate for Teff ≲ 16 kK (likely an artefact of the small sample size), rendering the proposed connection between ECME luminosity and Teff unreliable. By examining the empirical relation in light of the scaling law for incoherent radio emission, we arrive at the conclusion that both types of emission are powered by the same magnetospheric phenomenon. Like the incoherent emission, coherent radio emission is indifferent to Teff for late-B and A-type stars, but Teff appears to become important for early-B type stars, possibly due to higher absorption, or higher plasma density at the emission sites suppressing the production of the emission.
Abstract
We report the detection of radial velocity (RV) variations in nine evolved G- and K-type giant stars. The observations were conducted at Okayama Astrophysical Observatory. Planets or planet ...candidates can best explain these regular variations. However, a coincidence of near 280 d variability among five of them prevents us from fully ruling out stellar origins for some of the variations, since all nine stars behave similarly in stellar properties. In the planet hypotheses for the RV variations, the planets (including one candidate) may survive close to the boundary of the so-called “planet desert” around evolved stars, having orbital periods between 255 and 555 d. Besides, they are the least-massive giant planets detected around G- and K-type giant stars, with minimum masses between 0.45 MJ and 1.34 MJ. We further investigated other hypotheses for our detection, yet none of them can better explain regular RV variation. With our detection, we can be convinced that year-long regular variation with amplitude down to 15 m s−1 for G- and K-type giant stars is detectable. Moreover, we performed simulations to further confirm the detectability of planets around these stars. Finally, we explored giant planets around intermediate-mass stars, and likewise found a four-Jupiter-mass gap (e.g., Santos et al. 2017, A&A, 603, A30), which is probably a boundary of the giant planet population.
The elements germanium (Ge, Z = 32), arsenic (As, Z = 33), and selenium (Se, Z = 34) span the transition from charged-particle or explosive synthesis of the iron-group elements to neutron-capture ...synthesis of heavier elements. Among these three elements, only the chemical evolution of germanium has been studied previously. Here we use archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope and observations from several ground-based facilities to study the chemical enrichment histories of seven stars with metallicities -2.6 < or =, slant Fe/H < or =, slant -0.4. We perform a standard abundance analysis of germanium, arsenic, selenium, and several other elements produced by neutron-capture reactions. When combined with previous derivations of germanium abundances in metal-poor stars, our sample reveals an increase in the Ge/Fe ratios at higher metallicities. This could mark the onset of the weak s-process contribution to germanium. In contrast, the As/Fe and Se/Fe ratios remain roughly constant. These data do not directly indicate the origin of germanium, arsenic, and selenium at low metallicity, but they suggest that the weak and main components of the s-process are not likely sources.
We have spectroscopically studied the last six stars in the northern sky from our preliminary list of candidates for wide non-coeval pairs, and we have found no evidence of non-coevality. Thus, ...considering our previous research, which found one such binary system, we confirm that our preliminary estimate of the fraction of binaries in the solar neighborhood formed by capture is no more than 0.03%.
We have carried out abundance analysis for a sample of high galactic latitude supergiants in search of evolved stars. We find that HD 27381 has atmospheric parameters and an abundance pattern very ...similar to that of the post-AGB star HD 107369. HD 10285 and HD 25291 are moderately metal-poor and show the influence of mixing that has brought the products of NeNa cycle to the surface. The high galactic latitude B supergiant HD 137569 shows selective depletion of refractory elements normally seen in post-AGB stars. We find that the high velocity B type star HD 172324 shows moderate deficiency of Fe group elements but the CNO abundances are very similar to that of disk B supergiants. The observed variations in the radial velocities, transient appearance of emission components in hydrogen line profiles and doubling of O I lines at 7774 Å support the possibility of this star being a pulsating variable or a binary star.
A Spectroscopic Study of Field and Runaway OB Stars McSwain, M. Virginia; Boyajian, Tabetha S; Grundstrom, Erika D ...
Astrophysical journal/The Astrophysical journal,
01/2007, Letnik:
655, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Identifying binaries among runaway O- and B-type stars offers valuable insight into the evolution of open clusters and close binary stars. Here we present a spectroscopic investigation of 12 known or ...suspected binaries among field and runaway OB stars. We find new orbital solutions for five single-lined spectroscopic binaries (HD 1976, HD 14633, HD 15137, HD 37737, and HD 52533), and we classify two stars thought to be binaries (HD 30614 and HD 188001) as single stars. In addition, we reinvestigate their runaway status using our new radial velocity data with the UCAC2 proper-motion catalogs. Seven stars in our study appear to have been ejected from their birthplaces, and at least three of these runaways are spectroscopic binaries and are of great interest for future study.
Context.
The advent of asteroseismology as the golden path to precisely characterize single stars naturally led to synergies with the field of exoplanetology. Today, the precise determination of ...stellar masses, radii and ages for exoplanet-host stars is a driving force in the development of dedicated software and techniques to achieve this goal. However, as various approaches exist, it is clear that they all have advantages and inconveniences and that there is a trade-off between accuracy, efficiency, and robustness of the techniques.
Aims.
We aim to compare and discuss various modelling techniques for exoplanet-host red giant stars for which TESS data are available. The results of the seismic modelling are then used to study the dynamical evolution and atmospheric evaporation of the planetary systems.
Methods.
We study, in detail, the robustness, accuracy and precision of various seismic modelling techniques when applied to four exoplanet-host red giants observed by TESS. We discuss the use of global seismic indexes, the use of individual radial frequencies and that of non-radial oscillations. In each case, we discuss the advantages and inconveniences of the modelling technique.
Results.
We determine precise and accurate masses of exoplanet-host red giant stars orbited by long-period Jupiter-like planets using various modelling techniques. For each target, we also provide a model-independent estimate of the mass from a mean density inversion combined with radii values from
Gaia
and spectroscopic data. We show that no engulfment or migration is observed for these targets, even if their evolution is extended beyond their estimated seismic ages up the red giant branch.
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