Iron K-alpha echoes from the circumnuclear disk orbiting Sgr A*

Molecular clouds in the Galactic center (GC) reprocess radiation from past outbursts of nearby high-energy sources, generating a bright Fe K-alpha fluorescence at 6.4 keV. The closest clouds to the GC are only $\simeq 1.5$ pc from Sgr A*, forming a torus-like structure known as the circumnuclear disk (CND). The study of fluorescence emission can lead to a characterization of the illuminating source(s), the reflecting clouds, and the global geometry of such a system lying in the GC. The primary purpose of our study is to analyze possible fluorescence signals arising in the CND. This signal would allow us to constrain the CND's physical properties and the source-reflector system's geometry. By exploiting the last $\simeq 20$ years of XMM-Newton observations of the GC, we studied the variability of the Fe K-alpha line in the region around Sgr A*. We identified regions with a flux excess and computed the spectrum therein. We then derived the hydrogen column density of the CND after relating the intensity of the 6.4 keV line to the total energy emitted by known transient sources in the region. Starting from data collected in 2019, we find significant line excesses in a region compatible with the eastern portion of the CND. The echo radiation can be linked to the 2013 outburst of the magnetar SGR J1745-2900. We derive a mean effective hydrogen column density of the CND in the eastern region of $\simeq 10^{23}$ cm$^{-2}$. The scenario depicted is physically plausible, given the luminosity, the position of the illuminating source, and the expected density of the CND.Comment: 15 pages, 18 figures, to be published in Astronomy & Astrophysic

Применение метода матричной прогонки для моделирования процесса пневматической обработки угольного пласта

Розглянуто чисельне рішення системи рівнянь математичної фізики, покладених в основу математичної моделі пневматичної дії на вугільний пласт, за допомогою методу матричної прогонки.The numerical solution of system of mathematical physics equations, formed the base of mathematical model of process of pneumatic action on coal stratum, using the method of matrix drive is considered

Occupational choice, number of entrepreneurs and output: theory and empirical evidence with Spanish data

This paper extends the (Lucas, Bell J Econ 9:508–523,1978) model of occupational choices by individuals with different skills, beyond the simple options of self-employment or wage-employment, by including a second choice for the self-employed. That is, an option to hire employees and so become self-employed with employees (SEWEs), or to be self-employed without employees (SEWNEs). We solve for the market equilibrium and examine the sensitivity of relative sizes of occupational groups, and of the level of productivity, to changes in the exogenous parameters. The results show that the positive (negative) association between number of SEWEs (SEWNEs) and productivity, observed in the Spanish data, can be explained, under certain conditions, as the result of cross-region and time differences in average skills. These findings point to the importance of distinguishing between SEWEs and SEWNEs in drawing valid conclusions concerning any link between entrepreneurship and economic development

Is there a U-shaped association between physical activity and falling in older persons?

Summary: This study tests whether the relationship between physical activity and (recurrent) falling is U-shaped. Among 1,337 community-dwelling older persons, no evidence for a nonlinear association was found. If all older persons increase their physical activity level with 100 units, 4% may be prevented to become recurrent fallers. Introduction: Previous studies suggest a U-shaped relationship between physical activity and falling. This study tests this hypothesis and examines whether this relationship is modified by level of physical functioning. Methods: Community-dwelling persons (65+) from the Longitudinal Aging Study Amsterdam (LASA) were prospectively followed on falls for 3 years after baseline assessment in 1995/1996 (n=1,337). Outcome measures were time to first fall and time to recurrent falling. The LASA Physical Activity Questionnaire was used to calculate physical activity in minutes per day weighted for intensity (range 0-2000). Physical functioning was measured with physical performance tests and self reported functional limitations. Confounders were age, sex, body mass index, chronic diseases, psychotropic medication, cognitive functioning, depressive symptoms, and fear of falling. Results: No evidence for a nonlinear association was found (p for physical activity > 0.20). No significant association was found between physical activity and time to first fall. An increase in physical activity of 100 units led to a 4% decrease in risk of recurrent falling (adjusted hazard ratio 0.96, 95% confidence interval 0.92, 0.99). No interactions with physical performance or functional limitations were found (p>0.50). Conclusions: The hypothesized U-shaped relationship between physical activity and falling could not be confirmed. At higher levels of physical activity, the risk of recurrent falling decreased, while no association was found with fall risk

Health claims databases used for kidney research around the world

Health claims databases offer opportunities for studies on large populations of patients with kidney disease and health outcomes in a non-experimental setting. Among others, their unique features enable studies on healthcare costs or on longitudinal, epidemiological data with nationwide coverage. However, health claims databases also have several limitations. Because clinical data and information on renal function are often lacking, the identification of patients with kidney disease depends on the actual presence of diagnosis codes only. Investigating the validity of these data is therefore crucial to assess whether outcomes derived from health claims data are truly meaningful. Also, one should take into account the coverage and content of a health claims database, especially when making international comparisons. In this article, an overview is provided of international health claims databases and their main publications in the area of nephrology. The structure and contents of the Dutch health claims database will be described, as well as an initiative to use the outcomes for research and the development of the Dutch Kidney Atlas. Finally, we will discuss to what extent one might be able to identify patients with kidney disease using health claims databases, as well as their strengths and limitations

Polypharmacy and medication use in patients with chronic kidney disease with and without kidney replacement therapy compared to matched controls

BACKGROUND: This study aims to examine polypharmacy (PP) prevalence in patients with chronic kidney disease (CKD) Stage G4/G5 and patients with kidney replacement therapy (KRT) compared with matched controls from the general population. Furthermore, we examine risk factors for PP and describe the most commonly dispensed medications. METHODS: Dutch health claims data were used to identify three patient groups: CKD Stage G4/G5, dialysis and kidney transplant patients. Each patient was matched to two controls based on age, sex and socio-economic status (SES) score. We differentiated between ‘all medication use’ and ‘chronic medication use’. PP was defined at three levels: use of ≥5 medications (PP), ≥10 medications [excessive PP (EPP)] and ≥15 medications [hyper PP (HPP)]. RESULTS: The PP prevalence for all medication use was 87, 93 and 95% in CKD Stage G4/G5, dialysis and kidney transplant patients, respectively. For chronic medication use, this was 66, 70 and 75%, respectively. PP and comorbidity prevalence were higher in patients than in controls. EPP was 42 times more common in young CKD Stage G4/G5 patients (ages 20–44 years) than in controls, while this ratio was 3.8 in patients ≥75 years. Older age (64–75 and ≥75 years) was a risk factor for PP in CKD Stage G4/G5 and kidney transplant patients. Dialysis patients ≥75 years of age had a lower risk of PP compared with their younger counterparts. Additional risk factors in all patients were low SES, diabetes mellitus, vascular disease, hospitalization and an emergency room visit. The most commonly dispensed medications were proton pump inhibitors (PPIs) and statins. CONCLUSIONS: CKD Stage G4/G5 patients and patients on KRT have a high medication burden, far beyond that of individuals from the general population, as a result of their kidney disease and a large burden of comorbidities. A critical approach to medication prescription in general, and of specific medications like PPIs and statins (in the dialysis population), could be a first step towards more appropriate medication use