396 research outputs found
Eclipsing binaries in the MACHO database: New periods and classifications for 3031 systems in the Large Magellanic Cloud
Eclipsing binaries offer a unique opportunity to determine fundamental
physical parameters of stars using the constraints on the geometry of the
systems. Here we present a reanalysis of publicly available two-color
observations of about 6800 stars in the Large Magellanic Cloud, obtained by the
MACHO project between 1992 and 2000 and classified as eclipsing variable stars.
Of these, less than half are genuine eclipsing binaries. We determined new
periods and classified the stars, 3031 in total, using the Fourier parameters
of the phased light curves. The period distribution is clearly bimodal,
reflecting refer to the separate groups of more massive blue main sequence
objects and low mass red giants. The latter resemble contact binaries and obey
a period-luminosity relation. Using evolutionary models, we identified
foreground stars. The presented database has been cleaned of artifacts and
misclassified variables, thus allowing searches for apsidal motion, tertiary
components, pulsating stars in binary systems and secular variations with
time-scales of several years.Comment: 11 figures, 9 pages, accepted for publication in Ap
On the formation process of silicon carbide nanophases via hydrogenated thermally induced templated synthesis
A thermally induced templated synthesis for SiC nanotubes and nanofibers
using ammonia or nitrogen as a carrier gas, single wall carbon nanotubes
(SWCNT) as templates as well as gaseous Si is presented. The bundles of SWCNT
act as both the carbon source and as a nanoframe from which SiC structuctures
form. Depending on the duration of the thermally induced templated reaction,
for a fixed temperature, carrier gas, and gas pressure, various SiC
nanostructures are obtained. These structures include SiC nanorods coated in C,
SiC nanorods, SiC nanotubes, and SiC nanocrytals. From our analysis using
transmission electron microscopy (TEM) and scanning electron microscopy (SEM),
electron energy-loss spectroscopy (EELS), electron diffraction (EDX), optical
absorption spectroscopy and Raman spectroscopy as probes we prove that H has a
key role on the morphology and stochiometry of the different SiC
nanostructures.Comment: 9 pages, 2 Figure
Predictors for adherence to action plans for self-treatment of COPD exacerbations
Introduction/Aim: A minority of patients with chronic obstructive pulmonary disease (COPD) derives benefit fromself-management interventions that include action plans for self-treatment of COPD exacerbations. The aimof this studywas to identify predictors for adherence to action plans for self-treatment of exacerbations in COPD patients. Methods: Self-reported diary data from a subset of COPD patients who participated in a randomized controlled trial (COPE-II study) in the Netherlands was used to assess adherence to COPD action plans within a self-management intervention. Only patients with exacerbations were included. Successful self-treatment was defined as self-initiating a course of oral steroids/antibiotics within 2 days from the start of an exacerbation. A patient was defined as being adherent when in â„75% of all exacerbations the self-treatment action plan was followed. Patient-level factors that showed a univariate association (P <0.10) with adherence were included in a multivariate logistic regression model to identify the predictors for adherence toCOPD self-treatment action plans (P <0.05). Results: Data from 66 patients (mean age 63.6 ± 8.0;men 56.1%) showed 387 exacerbations within 2 years of follow-up. Adherence to the action plans was observed in 37.9% of the patients and in 216 COPD exacerbations. Multivariate logistic regression analyses showed that being male (OR: 5.1; 95% CI: 1.5-17.3) and having no walking problems (EQ5D mobility, OR: 4.9; 95%CI: 1.5-16.4) were positively associatedwith being adherent to the action plan for self-treatment of COPD exacerbations. Conclusion: Our study results indicate that being male and having no walking problems are predictors for better adherence to COPD exacerbation action plans. This implies that exploring patients' mobility and offering more support to femaleCOPDpatients who are lessmobilemay positively influence the adherence to COPD exacerbation self-treatment action plans. More research is, however, required to confirm this
Facilitators and Barriers of Adherence to Multi-Disease Exacerbation Action Plans in COPD Patients - A Qualitative Study
Functional or not functional; that's the question Can we predict the diagnosis functional movement disorder based on associated features?
Background and purpose Functional movement disorders (FMDs) pose a diagnostic challenge for clinicians. Over the years several associated features have been shown to be suggestive for FMDs. Which features mentioned in the literature are discriminative between FMDs and non-FMDs were examined in a large cohort. In addition, a preliminary prediction model distinguishing these disorders was developed based on differentiating features. Method Medical records of all consecutive patients who visited our hyperkinetic outpatient clinic from 2012 to 2019 were retrospectively reviewed and 12 associated features in FMDs versus non-FMDs were compared. An independentttest for age of onset and Pearson chi-squared analyses for all categorical variables were performed. Multivariate logistic regression analysis was performed to develop a preliminary predictive model for FMDs. Results A total of 874 patients were eligible for inclusion, of whom 320 had an FMD and 554 a non-FMD. Differentiating features between these groups were age of onset, sex, psychiatric history, family history, more than one motor phenotype, pain, fatigue, abrupt onset, waxing and waning over long term, and fluctuations during the day. Based on these a preliminary predictive model was computed with a discriminative value of 91%. Discussion Ten associated features are shown to be not only suggestive but also discriminative between hyperkinetic FMDs and non-FMDs. Clinicians can use these features to identify patients suspected for FMDs and can subsequently alert them to test for positive symptoms at examination. Although a first preliminary model has good predictive accuracy, further validation should be performed prospectively in a multi-center study
Predicting Mortality in COPD with Validated and Sensitive Biomarkers; Fibrinogen and Mid-Range-Proadrenomedullin (MR-proADM)
Although fibrinogen is a FDA qualified prognostic biomarker in COPD, it still lacks sufficient resolution to be clinically useful. Next to replication of findings in different cohorts also the combination with other validated biomarkers should be investigated. Therefore, the aim of this study was to confirm in a large well-defined population of COPD patients whether fibrinogen can predict mortality and whether a combination with the biomarker MR-proADM can increase prognostic accuracy. From the COMIC cohort study we included COPD patients with a blood sample obtained in stable state (nâ=â640) and/or at hospitalization for an acute exacerbation of COPD (nâ=â262). Risk of death during 3âyears of follow up for the separate and combined biomarker models was analyzed with Cox regression. Furthermore, logistic regression models for death after one year were constructed. When both fibrinogen and MR-proADM were included in the survival model, a doubling in fibrinogen and MR-proADM levels gave a 2.2 (95% CI 1.3-3.7) and 2.1 (95% CI 1.5-3.0) fold increased risk of dying, respectively. The prediction model for death after 1âyear improved significantly when MR-proADM was added to the model with fibrinogen (AUC increased from 0.78 to 0.83; pâ=â0.02). However, the combined model was not significantly more adequate than the model with solely MR-proADM (AUC 0.83 vs 0.82; pâ=â0.34). The study suggests that MR-proADM is more promising than fibrinogen in prediciting mortality. Adding fibrinogen to a model containing MR-proADM does not significantly increase the predictive capacity of the model
Pressure dependence of Raman modes in double wall carbon nanotubes filled with α-Fe.
The preparation of highly anisotropic one-dimensional (1D) structures confined into carbon nanotubes (CNTs) in general is a key objective in CNTs research. In this work, the capillary effect was used to fill double wall carbon nanotubes with iron. The samples are characterized by Mössbauer and Raman spectroscopy, transmission electron microscopy, scanning area electron diffraction, and magnetization. In order to investigate their structural stability and compare it with that of single wall carbon nanotubes (SWNTs), elucidating the differences induced by the inner-outer tube interaction, unpolarized Raman spectra of tangential modes of double wall carbon nanotubes (DWNTs) filled with 1D nanocrystallin α-Fe excited with 514 nm were studied at room temperature and elevated pressure. Up to 16 GPa we find a pressure coefficient for the internal tube of 4.3 cmâ1 GPaâ1 and for the external tube of 5.5 cmâ1 GPaâ1. In addition, the tangential band of the external and internal tubes broadens and decreases in amplitude. All findings lead to the conclusion that the outer tube acts as a protection shield for the inner tubes (at least up 16 GPa). Structural phase transitions were not observed in this range of pressure
Circular Polarization of Water Masers in the Circumstellar Envelopes of Late Type Stars
We present circular polarization measurements of circumstellar H_2O masers.
The circular polarization detected in the (6_{16}-5_{23}) rotational transition
of the H_{2}O maser can be attributed to Zeeman splitting in the intermediate
temperature and density regime. The magnetic fields are derived using a
general, LTE Zeeman analysis as well as a full radiative transfer method
(non-LTE), which includes a treatment of all hyperfine components
simultaneously as well as the effects of saturation and unequal populations of
the magnetic substates. The differences and relevances of these interpretations
are discussed extensively. The field strengths are compared with previous
detections of the magnetic field on the SiO and OH masers. We show that the
magnetic pressure dominates the thermal pressure by a factor of 20 or more.Comment: 15 pages, 15 figures; accepted for publication in A&A; (Abstract
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