Results 101 to 110 of about 4,406,721 (399)

The Ca ii Lines as Tracers of Disk Structure in T Tauri Stars: The Chamaeleon I Region

The Astrophysical Journal, 2023
We present a study of the Ca ii K and IR triplet lines in a sample of classical T Tauri stars in the Chamaeleon I star-forming region. We study X-shooter spectra of the stars in the sample and find that in some of these stars the Ca ii lines are much ...
Marbely Micolta, Nuria Calvet, Thanawuth Thanathibodee, Gladis Magris C., María José Colmenares, Jesús V. Díaz, Jairo Alzate-Trujillo   +6 more
doaj   +1 more source

Chemical abundances and metallicity of Planetary Nebulae [PDF]

Symposium - International Astronomical Union, 1997
Confrontations of the dredge-up theory with observed patterns of chemical abundances of planetary nebulae (PNs) have been carried out by many authors (see, e.g., Kaler & Jacoby 1990, 1991; Stasińska & Tylenda 1990). Although these studies suggest that the observational abundance ratios of PNs can qualitatively be explained by the current dredge-
C. Y. Zhang, Sun Kwok
openaire   +2 more sources

High-precision chemical abundances of Galactic building blocks

Astronomy & Astrophysics, 2022
Context. Sequoia is a retrograde kinematic substructure in the nearby Galactic halo, whose properties are a matter of debate. For example, previous studies do not necessarily agree on the chemical abundances of Sequoia stars, which are important for understanding its nature. Aims.
Matsuno, Tadafumi, Koppelman, Helmer H., Helmi, Amina, Aoki, Wako, Ishigaki, Miho N., Suda, Takuma, Yuan, Zhen, Hattori, Kohei   +7 more
openaire   +3 more sources

Unraveling Mycobacterium tuberculosis acid resistance and pH homeostasis mechanisms

FEBS Letters, EarlyView.
Mycobacterium tuberculosis exhibits a remarkable resilience to acid stress. In this Review, we discuss some of the molecular mechanisms and metabolic pathways used by the tubercle bacilli to adapt and resist host‐mediated acid stress. Mycobacterium tuberculosis (Mtb) is a successful pathogen that has developed a variety of strategies to survive and ...
Janïs Laudouze, Stéphane Canaan, Alexandre Gouzy, Pierre Santucci   +3 more
wiley   +1 more source

The Missing Link of Sulfur Chemistry in TMC-1: The Detection of c-C3H2S from the GOTHAM Survey

The Astrophysical Journal
We present the spectroscopic characterization of cyclopropenethione in the laboratory and detect it in space using the Green Bank Telescope Observations of TMC-1: Hunting Aromatic Molecules survey.
Anthony J. Remijan, P. Bryan Changala, Ci Xue, Elsa Q. H. Yuan, Miya Duffy, Haley N. Scolati, Christopher N. Shingledecker, Thomas H. Speak, Ilsa R. Cooke, Ryan Loomis, Andrew M. Burkhardt, Zachary T. P. Fried, Gabi Wenzel, Andrew Lipnicky, Michael C. McCarthy, Brett A. McGuire   +15 more
doaj   +1 more source

The ¹⁷O/¹⁸O Ratio of Post-AGB Sources: Canonical and Non-Canonical Populations

Galaxies
Stellar evolution models serve as tools to derive stellar parameters from elemental and isotopic abundance ratios. For low-to-intermediate mass evolved stars, C/O, 12C/13C, and 17O/18O ratios are proxies of the initial mass, a largely unknown parameter ...
Javier Alcolea, Elisa Masa, Theo Khouri, Miguel Santander-García, Iván Gallardo Cava, Hans Olofsson, Carmen Sánchez Contreras, Valentín Bujarrabal, Wouter H. T. Vlemmings, Daniel Tafoya   +9 more
doaj   +1 more source

The Influence of Radial Stellar Migration on the Chemical Evolution of the Milky Way [PDF]

, 2013
Stellar migration is an important dynamical process in Galactic disk. Here we model the radial stellar migration in the Galactic disk with an analytical method, then add it to detailed Galactic chemical evolution model to study the influence of radial stellar migration on the chemical evolution of the Milky Way, especially for the abundance gradients ...
arxiv   +1 more source

Properties of six short-period massive binaries: a study of the effects of binarity on surface chemical abundances [PDF]

, 2017
A significant fraction of massive stars are found in multiple systems. The effect of binarity on stellar evolution is poorly constrained. In particular, the role of tides and mass transfer on surface chemical abundances is not constrained observationally.
F. Martins, L. Mahy, Anthony Herv'e Lupm, CNRSMontpellier University, S. Sciences, Technologies, A. R. Institute, L. University, Instituut voor Sterrenkunde, K. Leuven   +9 more
semanticscholar   +1 more source

Chemical Abundances in Galactic Bulge Pn [PDF]

Symposium - International Astronomical Union, 1993
We present abundance determinations, in particular of carbon, and C/O ratios, for 11 Galactic bulge planetary nebulae (PN) based on our low resolution UV data from IUE observations and optical spectrophotometry from the Anglo-Australian Telescope. We compare the observed abundances with those predicted by dredge-up theory for the high metallicity ...
R. E. S. Clegg, Nicholas A. Walton, M. J. Barlow   +2 more
openaire   +2 more sources

Unconventional mRNA processing and degradation pathways for the polycistronic yrzI (spyTA) mRNA in Bacillus subtilis

FEBS Letters, EarlyView.
The S1025 peptide is the major antidote to the YrzI toxin, which we renamed here as SpyT (Small Peptide YrzI Toxin) and SpyA (Small Peptide YrzI Antitoxin) (1). Degradation of the toxin–antitoxin spyTA mRNA, either by a translation‐dependent cleavage by the endoribonuclease Rae1 (2) or by direct attack by 3′‐exoribonucleases (3), also contributes to ...
Laetitia Gilet, Magali Leroy, Alexandre Maes, Ciarán Condon, Frédérique Braun   +4 more
wiley   +1 more source