63 research outputs found
Analytical line geometry of the plane
Thesis (M.A.)--University of Kansas, Mathematics, 1927
Radio emission models of Colliding-Wind Binary Systems
We present calculations of the spatial and spectral distribution of the radio
emission from a wide WR+OB colliding-wind binary system based on
high-resolution hydrodynamical simulations and solutions to the radiative
transfer equation. We account for both thermal and synchrotron radio emission,
free-free absorption in both the unshocked stellar wind envelopes and the
shocked gas, synchrotron self-absorption, and the Razin effect. The
applicability of these calculations to modelling radio images and spectra of
colliding-wind systems is demonstrated with models of the radio emission from
the wide WR+OB binary WR147. Its synchrotron spectrum follows a power-law
between 5 and 15 GHz but turns down to below this at lower and higher
frequencies. We find that while free-free opacity from the circum-binary
stellar winds can potentially account for the low-frequency turnover, models
that also include a combination of synchrotron self-absorption and Razin effect
are favoured. We argue that the high-frequency turn down is a consequence of
inverse-Compton cooling. We present our resulting spectra and intensity
distributions, along with simulated MERLIN observations of these intensity
distributions. From these we argue that the inclination of the WR147 system to
the plane of the sky is low. We summarise by considering extensions of the
current model that are important for models of the emission from closer
colliding wind binaries, in particular the dramatically varying radio emission
of WR140.Comment: 18 pages, 18 figures; Accepted by Astronomy and Astrophysics, July 8,
200
XMM-Newton X-ray Observations of the Wolf-Rayet Binary System WR 147
We present results of a 20 ksec X-ray observation of the Wolf-Rayet (WR)
binary system WR 147 obtained with XMM-Newton. Previous studies have shown that
this system consists of a nitrogen-type WN8 star plus an OB companion whose
winds are interacting to produce a colliding wind shock. X-ray spectra from the
pn and MOS detectors confirm the high extinction reported from IR studies and
reveal hot plasma including the first detection of the Fe K-alpha line complex
at 6.67 keV. Spectral fits with a constant-temperature plane-parallel shock
model give a shock temperature kT(shock) = 2.7 keV [T(shock) ~ 31 MK], close to
but slightly hotter than the maximum temperature predicted for a colliding wind
shock. Optically thin plasma models suggest even higher temperatures, which are
not yet ruled out. The X-ray spectra are harder than can be accounted for using
2D numerical colliding wind shock models based on nominal mass-loss parameters.
Possible explanations include: (i) underestimates of the terminal wind speeds
or wind abundances, (ii) overly simplistic colliding wind models, or (iii) the
presence of other X-ray emission mechanisms besides colliding wind shocks.
Further improvement of the numerical models to include potentially important
physics such as non-equilibrium ionization will be needed to rigorously test
the colliding wind interpretation.Comment: 8 pages, 7 figure
The Solar--Stellar Connection
Stars have proven to be surprisingly prolific radio sources and the added
sensitivity of the Square Kilometer Array will lead to advances in many
directions. This chapter discusses prospects for studying the physics of
stellar atmospheres and stellar winds across the HR diagram.Comment: to appear in "Science with the Square Kilometer Array," eds. C.
Carilli and S. Rawlings, New Astronomy Reviews (Elsevier: Amsterdam
Pycallingcards: An integrated environment for visualizing, analyzing, and interpreting Calling Cards data
MOTIVATION: Unraveling the transcriptional programs that control how cells divide, differentiate, and respond to their environments requires a precise understanding of transcription factors\u27 (TFs) DNA-binding activities. Calling cards (CC) technology uses transposons to capture transient TF binding events at one instant in time and then read them out at a later time. This methodology can also be used to simultaneously measure TF binding and mRNA expression from single-cell CC and to record and integrate TF binding events across time in any cell type of interest without the need for purification. Despite these advantages, there has been a lack of dedicated bioinformatics tools for the detailed analysis of CC data.
RESULTS: We introduce Pycallingcards, a comprehensive Python module specifically designed for the analysis of single-cell and bulk CC data across multiple species. Pycallingcards introduces two innovative peak callers, CCcaller and MACCs, enhancing the accuracy and speed of pinpointing TF binding sites from CC data. Pycallingcards offers a fully integrated environment for data visualization, motif finding, and comparative analysis with RNA-seq and ChIP-seq datasets. To illustrate its practical application, we have reanalyzed previously published mouse cortex and glioblastoma datasets. This analysis revealed novel cell-type-specific binding sites and potential sex-linked TF regulators, furthering our understanding of TF binding and gene expression relationships. Thus, Pycallingcards, with its user-friendly design and seamless interface with the Python data science ecosystem, stands as a critical tool for advancing the analysis of TF functions via CC data.
AVAILABILITY AND IMPLEMENTATION: Pycallingcards can be accessed on the GitHub repository: https://github.com/The-Mitra-Lab/pycallingcards
Switching to Glycerol Phenylbutyrate in 48 Patients with Urea Cycle Disorders: Clinical Experience in Spain
Clinical practice; Glycerol phenylbutyrate; Urea cycle disordersPráctica clinica; Fenilbutirato de glicerol; Trastornos del ciclo de la ureaPràctica clínica; Fenilbutirat de glicerol; Trastorns del cicle de la ureaBackground and objectives: Glycerol phenylbutyrate (GPB) has demonstrated safety and efficacy in patients with urea cycle disorders (UCDs) by means of its clinical trial program, but there are limited data in clinical practice. In order to analyze the efficacy and safety of GPB in clinical practice, here we present a national Spanish experience after direct switching from another nitrogen scavenger to GPB. Methods: This observational, retrospective, multicenter study was performed in 48 UCD patients (age 11.7 ± 8.2 years) switching to GPB in 13 centers from nine Spanish regions. Clinical, biochemical, and nutritional data were collected at three different times: prior to GPB introduction, at first follow-up assessment, and after one year of GPB treatment. Number of related adverse effects and hyperammonemic crisis 12 months before and after GPB introduction were recorded. Results: GPB was administered at a 247.8 ± 102.1 mg/kg/day dose, compared to 262.6 ± 126.1 mg/kg/day of previous scavenger (46/48 Na-phenylbutyrate). At first follow-up (79 ± 59 days), a statistically significant reduction in ammonia (from 40.2 ± 17.3 to 32.6 ± 13.9 μmol/L, p < 0.001) and glutamine levels (from 791.4 ± 289.8 to 648.6 ± 247.41 μmol/L, p < 0.001) was observed. After one year of GPB treatment (411 ± 92 days), we observed an improved metabolic control (maintenance of ammonia and glutamine reduction, with improved branched chain amino acids profile), and a reduction in hyperammonemic crisis rate (from 0.3 ± 0.7 to less than 0.1 ± 0.3 crisis/patients/year, p = 0.02) and related adverse effects (RAE, from 0.5 to less than 0.1 RAEs/patients/year p < 0.001). Conclusions: This study demonstrates the safety of direct switching from other nitrogen scavengers to GPB in clinical practice, which improves efficacy, metabolic control, and RAE compared to previous treatments.This study was funded by AECOM (Spanish Association for the Study of Inborn Errors of Metabolism). Immedica Pharma Spain funded medical writing support and article processing charges
Non-thermal emission processes in massive binaries
In this paper, I present a general discussion of several astrophysical
processes likely to play a role in the production of non-thermal emission in
massive stars, with emphasis on massive binaries. Even though the discussion
will start in the radio domain where the non-thermal emission was first
detected, the census of physical processes involved in the non-thermal emission
from massive stars shows that many spectral domains are concerned, from the
radio to the very high energies.
First, the theoretical aspects of the non-thermal emission from early-type
stars will be addressed. The main topics that will be discussed are
respectively the physics of individual stellar winds and their interaction in
binary systems, the acceleration of relativistic electrons, the magnetic field
of massive stars, and finally the non-thermal emission processes relevant to
the case of massive stars. Second, this general qualitative discussion will be
followed by a more quantitative one, devoted to the most probable scenario
where non-thermal radio emitters are massive binaries. I will show how several
stellar, wind and orbital parameters can be combined in order to make some
semi-quantitative predictions on the high-energy counterpart to the non-thermal
emission detected in the radio domain.
These theoretical considerations will be followed by a census of results
obtained so far, and related to this topic... (see paper for full abstract)Comment: 47 pages, 5 postscript figures, accepted for publication in Astronomy
and Astrophysics Review. Astronomy and Astrophysics Review, in pres
Switching to Glycerol Phenylbutyrate in 48 Patients with Urea Cycle Disorders: Clinical Experience in Spain
Background and objectives: Glycerol phenylbutyrate (GPB) has demonstrated safety and efficacy in patients with urea cycle disorders (UCDs) by means of its clinical trial program, but there are limited data in clinical practice. In order to analyze the efficacy and safety of GPB in clinical practice, here we present a national Spanish experience after direct switching from another nitrogen scavenger to GPB. Methods: This observational, retrospective, multicenter study was performed in 48 UCD patients (age 11.7 ± 8.2 years) switching to GPB in 13 centers from nine Spanish regions. Clinical, biochemical, and nutritional data were collected at three different times: prior to GPB introduction, at first follow-up assessment, and after one year of GPB treatment. Number of related adverse effects and hyperammonemic crisis 12 months before and after GPB introduction were recorded. Results: GPB was administered at a 247.8 ± 102.1 mg/kg/day dose, compared to 262.6 ± 126.1 mg/kg/day of previous scavenger (46/48 Na-phenylbutyrate). At first follow-up (79 ± 59 days), a statistically significant reduction in ammonia (from 40.2 ± 17.3 to 32.6 ± 13.9 μmol/L, p < 0.001) and glutamine levels (from 791.4 ± 289.8 to 648.6 ± 247.41 μmol/L, p < 0.001) was observed. After one year of GPB treatment (411 ± 92 days), we observed an improved metabolic control (maintenance of ammonia and glutamine reduction, with improved branched chain amino acids profile), and a reduction in hyperammonemic crisis rate (from 0.3 ± 0.7 to less than 0.1 ± 0.3 crisis/patients/year, p = 0.02) and related adverse effects (RAE, from 0.5 to less than 0.1 RAEs/patients/year p < 0.001). Conclusions: This study demonstrates the safety of direct switching from other nitrogen scavengers to GPB in clinical practice, which improves efficacy, metabolic control, and RAE compared to previous treatments.This study was funded by AECOM (Spanish Association for the Study of Inborn Errors of
Metabolism). Immedica Pharma Spain funded medical writing support and article processing charges
Quantifying direct and indirect contacts for the potential transmission of infection between species using a multilayer contact network
Detecting opportunities for between-species transmission of pathogens can be challenging, particularly if rare behaviours or environmental transmission are involved. We present a multilayer network framework to quantify transmission potential in multi-host systems, incorporating environmental transmission, by using empirical data on direct and indirect contacts between European badgers Meles meles and domestic cattle. We identify that indirect contacts via the environment at badger latrines on pasture are likely to be important for transmission within badger populations and between badgers and cattle. We also find a positive correlation between the role of individual badgers within the badger social network, and their role in the overall badger-cattle-environment network, suggesting that the same behavioural traits contribute to the role of individual badgers in within- and between-species transmission. These findings have implications for disease management interventions in this system, and our novel network approach can provide general insights into transmission in other multi-host disease systems
Unveiling the X-ray point source population of the Young Massive Cluster Westerlund 1
Aims.We investigate the nature of the X-ray point source population within the Young Massive Cluster Westerlund 1.
Methods.Chandra observations of 18 ks and 42 ks were used to determine the X-ray properties of emitters within Wd 1, while a comprehensive multiwavelength dataset was employed to constrain their nature.
Results.We find X-ray emission from a multitude of different stellar sources within Wd 1, including both evolved high mass and low mass pre-MS stars. We attribute the X-ray emission from the high mass component to both single stars and colliding wind binaries on the basis of their observed flux and spectral properties, with binaries being systematically harder and more luminous than single stars. We are able to infer a high binary fraction for both WN (10/16) and WC stars (7/8), resulting in a combined Wolf Rayet binary fraction of ≳ 70%. These represent the most stringent limits currently placed on the binary fraction of very massive (>45 M⊙) stars. We place the first observational constraints on X-ray emission from stars transitioning between the Main Sequence and Wolf Rayet phases, finding that both hot (B hypergiants) and cool (yellow hypergiants and red supergiants) spectral types appear to be intrinsically X-ray faint. The B[e] star W9 is found to be X-ray bright and shows similarities to both the X-ray binary SS433 and the Luminous Blue Variable η Carinae. Globally, we find the point source population to be systematically fainter than those found in younger massive star forming regions such as NGC 3603 and R136 / 30 Doradus , consistent with a loss of the most massive stars to SNe and a reduction in emissivity from the low mass pre-Main Sequence stars. No unambiguous evidence for X-ray emission due to accretion onto relativistic objects of any mass is found, although the current data do not exclude the presence of either a High Mass X-ray Binary or an Intermediate Mass Black Hole accreting at a low rate. Finally, we suggest the progenitor mass for the magnetar CXOU J164710.2-455216 is comparable to that of SGR 1806-20 (~55 M⊙), while that for SGR 1900+14 appears significantly lower (~15 M⊙), implying that magnetars may form from stars with a wide range of initial masses
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