3,074 research outputs found
Identification of Young Stellar Object candidates in the DR2 x AllWISE catalogue with machine learning methods
The second Data Release (DR2) contains astrometric and photometric
data for more than 1.6 billion objects with mean magnitude 20.7,
including many Young Stellar Objects (YSOs) in different evolutionary stages.
In order to explore the YSO population of the Milky Way, we combined the
DR2 database with WISE and Planck measurements and made an all-sky
probabilistic catalogue of YSOs using machine learning techniques, such as
Support Vector Machines, Random Forests, or Neural Networks. Our input
catalogue contains 103 million objects from the DR2xAllWISE cross-match table.
We classified each object into four main classes: YSOs, extragalactic objects,
main-sequence stars and evolved stars. At a 90% probability threshold we
identified 1,129,295 YSO candidates. To demonstrate the quality and potential
of our YSO catalogue, here we present two applications of it. (1) We explore
the 3D structure of the Orion A star forming complex and show that the spatial
distribution of the YSOs classified by our procedure is in agreement with
recent results from the literature. (2) We use our catalogue to classify
published Science Alerts. As measures the sources at multiple
epochs, it can efficiently discover transient events, including sudden
brightness changes of YSOs caused by dynamic processes of their circumstellar
disk. However, in many cases the physical nature of the published alert sources
are not known. A cross-check with our new catalogue shows that about 30% more
of the published alerts can most likely be attributed to YSO activity.
The catalogue can be also useful to identify YSOs among future alerts.Comment: 19 pages, 12 figures, 3 table
Asteroseismology of the heartbeat star KIC 5006817
This paper summarizes the project work on asteroseismology at the ERASMUS+
GATE 2020 Summer school on space satellite data. The aim was to do a global
asteroseismic analysis of KIC 5006817 and quantify its stellar properties using
the high-quality, state of the art space missions data. We employed the
aperture photometry to analyze the data from the Kepler space telescope and the
Transiting Exoplanet Survey Satellite (TESS). Using the lightkurve Python
package, we have derived the asteroseismic parameters and calculated the
stellar parameters using the scaling relations. Our analysis of KIC 5006817
confirmed its classification as a heartbeat binary. The rich oscillation
spectrum facilitate estimating power excess () at
145.500.50 Hz and large frequency separation () to be
11.630.10 Hz. Our results showed that the primary component is a
low-luminosity, red-giant branch star with a mass, radius, surface gravity, and
luminosity of 1.530.07 M, 5.910.12 R, 3.080.01
dex, and 19.660.73 L, respectively. The orbital period of the
system is 94.830.05 d.Comment: 13 pages, 4 figures, 2 tables; Based on the project work at ERASMUS+
GATE 2020 Summer school; To be published in Contrib. Astron. Obs. Skalnat\'e
Ples
Depression in Mid- and Later-Life and Risk of Dementia in Women: A Prospective Study within the Danish Nurses Cohort
BACKGROUND: Depression and dementia confer substantial global health burdens, particularly in women. Understanding the association between depression and dementia may inform new targets for prevention and/or early intervention. OBJECTIVE: To investigate the association between depression in mid- and later-life and dementia (all-cause, Alzheimer's disease (AD) or vascular dementia (VaD)) in women. METHODS: A prospective study design. Nurses were followed from age 60 years or entry into the cohort, whichever came last, until date of dementia, death, emigration, or end of follow-up, whichever came first. Cox regression models with age as the underlying timeline were used to estimate the associations between time-varying depression and incident dementia. RESULTS: The study included 25,651 female Danish nurses (≥45 years) participating in the Danish Nurse Cohort. During an average of 23 years of follow-up, 1,232 (4.8%) nurses developed dementia and 8,086 (31.5%) were identified with at least two episodes of treated depression. In adjusted analyses, nurses with depression were at a statistically significant 5.23-fold higher risk of all-cause dementia (aHR 5.23:95% CI, 4.64-5.91) compared to those with no history of depression. The differential effects of depression were greater for VaD (aHR 7.96:95% CI, 5.26-12.0) than AD (aHR 4.64:95% CI, 3.97-5.42). Later life depression (>60 years) (aHR 5.85:95% CI, 5.17-6.64) and recurrent depression (aHR 3.51:95% CI, 2.67-4.61) elevated dementia risk. Severe depression tripled the risk of all cause dementia (aHR 3.14:95% CI, 2.62-3.76). CONCLUSION: Both later life and severe depression substantially increase dementia risk in women, particularly VaD
The age of anxiety? It depends where you look: changes in STAI trait anxiety, 1970–2010
Purpose
Population-level surveys suggest that anxiety has been increasing in several nations, including the USA and UK. We sought to verify the apparent anxiety increases by looking for systematic changes in mean anxiety questionnaire scores from research publications.
Methods
We analyzed all available mean State–Trait Anxiety Inventory scores published between 1970 and 2010. We collected 1703 samples, representing more than 205,000 participants from 57 nations.
Results
Results showed a significant anxiety increase worldwide, but the pattern was less clear in many individual nations. Our analyses suggest that any increase in anxiety in the USA and Canada may be limited to students, anxiety has decreased in the UK, and has remained stable in Australia.
Conclusions
Although anxiety may have increased worldwide, it might not be increasing as dramatically as previously thought, except in specific populations, such as North American students. Our results seem to contradict survey results from the USA and UK in particular. We do not claim that our results are more reliable than those of large population surveys. However, we do suggest that mental health surveys and other governmental sources of disorder prevalence data may be partially biased by changing attitudes toward mental health: if respondents are more aware and less ashamed of their anxiety, they are more likely to report it to survey takers. Analyses such as ours provide a useful means of double-checking apparent trends in large population surveys
A novel role for Lyl1 in primitive erythropoiesis
© 2018. Published by The Company of Biologists Ltd. Stem cell leukemia (Scl or Tal1) and lymphoblastic leukemia 1 (Lyl1) encode highly related members of the basic helix-loop-helix family of transcription factors that are co-expressed in the erythroid lineage. Previous studies have suggested that Scl is essential for primitive erythropoiesis. However, analysis of single-cell RNA-seq data of early embryos showed that primitive erythroid cells express both Scl and Lyl1. Therefore, to determine whether Lyl1 can function in primitive erythropoiesis, we crossed conditional Scl knockout mice with mice expressing a Cre recombinase under the control of the Epo receptor, active in erythroid progenitors. Embryos with 20% expression of Scl from E9.5 survived to adulthood. However, mice with reduced expression of Scl and absence of Lyl1 (double knockout; DKO) died at E10.5 because of progressive loss of erythropoiesis. Gene expression profiling of DKO yolk sacs revealed loss of Gata1 and many of the known target genes of the SCL-GATA1 complex. ChIP-seq analyses in a human erythroleukemia cell line showed that LYL1 exclusively bound a small subset of SCL targets including GATA1. Together, these data show for the first time that Lyl1 can maintain primitive erythropoiesis
The changing nature of risk and risk management: the challenge of borders, uncertainty and resilience
No abstract available
External sources of clean technology: evidence from the clean development mechanism
New technology is fundamental to sustainable development. However, inventors from industrialized countries often refuse technology transfer because they worry about reverse-engineering. When can clean technology transfer succeed? We develop a formal model of the political economy of North–South technology transfer. According to the model, technology transfer is possible if (1) the technology in focus has limited global commercial potential or (2) the host developing country does not have the capacity to absorb new technologies for commercial use. If both conditions fail, inventors from industrialized countries worry about the adverse competitiveness effects of reverse-engineering, so technology transfer fails. Data analysis of technology transfer in 4,894 projects implemented under the Kyoto Protocol’s Clean Development Mechanism during the 2004–2010 period provides evidence in support of the model
Invasion speeds for structured populations in fluctuating environments
We live in a time where climate models predict future increases in
environmental variability and biological invasions are becoming increasingly
frequent. A key to developing effective responses to biological invasions in
increasingly variable environments will be estimates of their rates of spatial
spread and the associated uncertainty of these estimates. Using stochastic,
stage-structured, integro-difference equation models, we show analytically that
invasion speeds are asymptotically normally distributed with a variance that
decreases in time. We apply our methods to a simple juvenile-adult model with
stochastic variation in reproduction and an illustrative example with published
data for the perennial herb, \emph{Calathea ovandensis}. These examples
buttressed by additional analysis reveal that increased variability in vital
rates simultaneously slow down invasions yet generate greater uncertainty about
rates of spatial spread. Moreover, while temporal autocorrelations in vital
rates inflate variability in invasion speeds, the effect of these
autocorrelations on the average invasion speed can be positive or negative
depending on life history traits and how well vital rates ``remember'' the
past
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