Objetivos: determinar los factores asociados a la supervivencia de pacientes con cáncer y VIH en Cali, Colombia.Métodos: se realizó un estudio de cohorte retrospectivo en la Fundación Valle del Lili, ...Cali, Colombia. Se cruzaron datos de la base de datos de VIH con datos del Registro Poblacional de Cáncer de Cali (PCRC) entre 2011 y 2019. Se excluyeron pacientes menores de 18 años y aquellos con información limitada en la historia clínica. Se realizó un análisis de supervivencia mediante el método de Kaplan-Meier y se ajustó un modelo de regresión de Cox.
We explore the sensitivity of the nucleosynthesis due to type Ia supernovae with respect to uncertainties in nuclear reaction rates. We have adopted a standard one-dimensional delayed detonation ...model of the explosion of a Chandrasekhar-mass white dwarf, and have post-processed the thermodynamic trajectories of every mass-shell with a nucleosynthetic code, with increases (decreases) by a factor of ten on the rates of 1196 nuclear reactions. We have computed as well hydrodynamic models for different rates of the fusion reactions of 12C and of 16O. For selected reactions, we have recomputed the nucleosynthesis with alternative prescriptions for their rates taken from the JINA REACLIB database, and have analyzed the temperature ranges where modifications of their rates have the strongest effect on nucleosynthesis. The nucleosynthesis resulting from the Type Ia supernova models is quite robust with respect to variations of nuclear reaction rates, with the exception of the reaction of fusion of 12C nuclei. The energy of the explosion changes by less than \sim4%. The changes in the nucleosynthesis due to the modification of the rates of fusion reactions are as well quite modest, for instance no species with a mass fraction larger than 0.02 experiences a variation of its yield larger than a factor of two. We provide the sensitivity of the yields of the most abundant species with respect to the rates of the most intense reactions with protons, neutrons, and alphas. In general, the yields of Fe-group nuclei are more robust than the yields of intermediate-mass elements. Among the charged particle reactions, the most influential on supernova nucleosynthesis are 30Si + p \rightleftarrows 31P + {\gamma}, 20Ne + {\alpha} \rightleftarrows 24Mg + {\gamma}, and 24Mg + {\alpha} \rightleftarrows 27Al + p. The temperatures at which a modification of their rate has a larger impact are in the range 2 < T < 4 GK. (abridged)
Production of intermediate-mass and heavy nuclei Thielemann, F.-K.; Fröhlich, C.; Hirschi, R. ...
Progress in particle and nuclear physics,
07/2007, Volume:
59, Issue:
1
Journal Article, Publication
Peer reviewed
Open access
Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big ...bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the evolution of the elemental and isotopic compositions found in galaxies, and especially the mixture found in the solar system. Different timescales due to the progenitor mass dependence of the endpoints of stellar evolution (type II supernova explosions — SNe II vs. planetary nebulae) or single vs. binary stellar systems (the latter being responsible for novae, type Ia supernovae — SNe Ia, or X-ray bursts) are the keys to understand galactic evolution. At very early times, the role of explosion energies of events, polluting pristine matter with a composition originating only from the big bang, might also play a role. We also speculate on the role of very massive stars not undergoing SN II explosions but rather causing “hypernovae” after the formation of a central black hole via core collapse.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
36.
Nucleosynthesis in neutrino-driven supernovae Fröhlich, C.; Hix, W.R.; Martínez-Pinedo, G. ...
New astronomy reviews,
October 2006, 2006-10-00, 2006-10, Volume:
50, Issue:
7-8
Journal Article, Publication
Peer reviewed
Open access
Core collapse supernovae are the leading actor in the story of the cosmic origin of the chemical elements. Existing models, which generally assume spherical symmetry and parameterize the explosion, ...have been able to broadly replicate the observed elemental pattern. However, inclusion of neutrino interactions produces noticeable improvements in the iron peak composition of the ejecta when compared to observations. Neutrino interactions may also provide a supernova source for light p-process nuclei.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Type Ia supernovae originate from the explosion of carbon-oxygen white dwarfs in binary systems, but the exact nature of their progenitors remains elusive. The bulk properties of Type Ia supernova ...remnants, such as the radius and the centroid energy of the Fe K\(\alpha\) blend in the X-ray spectrum, are determined by the properties of the supernova ejecta and the ambient medium. We model the interaction between Chandrasekhar and sub-Chandrasekhar models for Type Ia supernova ejecta and a range of uniform ambient medium densities in one dimension up to an age of 5000 years. We generate synthetic X-ray spectra from these supernova remnant models and compare their bulk properties at different expansion ages with X-ray observations from \textit{Chandra} and \textit{Suzaku}. We find that our models can successfully reproduce the bulk properties of most observed remnants, suggesting that Type Ia SN progenitors do not modify their surroundings significantly on scales of a few pc. Ambient medium density and expansion age are the main contributors to the diversity of the bulk properties in our models. Chandrasekhar and sub-Chandrasekhar progenitors make similar predictions for the bulk remnant properties, but detailed fits to X-ray spectra have the power to discriminate explosion energetics and progenitor scenarios.
We ensure successful explosions (of otherwise non-explosive models) by enhancing the neutrino luminosity via reducing the neutrino scattering cross sections or by increasing the heating efficiency ...via enhancing the neutrino absorption cross sections in the heating region. Our investigations show that the resulting electron fraction
Y
e
in the innermost ejecta is close to 0.5, in some areas even exceeding 0.5. We present the effects of the resulting values for
Y
e
on the nucleosynthesis yields of the innermost zones of core collapse Supernovae.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The ultimate understanding of Type Ia Supernovae diversity is one of the most urgent issues to exploit thermonuclear explosions of accreted White Dwarfs (WDs) as cosmological yardsticks. In ...particular, we investigate the impact of the progenitor system metallicity on the physical and chemical properties of the WD at the explosion epoch. We analyze the evolution of CO WDs through the accretion and simmering phases by using evolutionary models based on time-dependent convective mixing and an extended nuclear network including the most important electron captures, beta decays and URCA processes. We find that, due to URCA processes and electron-captures, the neutron excess and density at which the thermal runaway occurs are substantially larger than previously claimed. Moreover, we find that the higher the progenitor metallicity, the larger the neutron excess variation during the accretion and simmering phases and the higher the central density and the convective velocity at the explosion. Hence, the simmering phase acts as an amplifier of the differences existing in SNe Ia progenitors. When applying our results to the neutron excess estimated for the Tycho and Kepler young Supernova remnants, we derive that the metallicity of the progenitors should be in the range Z=0.030-0.032, close to the average metallicity value of the thin disk of the Milky Way. As the amount of \({^{56}}\)Ni produced in the explosion depends on the neutron excess and central density at the thermal runaway, our results suggest that the light curve properties depend on the progenitor metallicity.
The physical process whereby a carbon--oxygen white dwarf explodes as a Type Ia supernova (SN Ia) remains highly uncertain. The degree of neutronization in SN Ia ejecta holds clues to this process ...because it depends on the mass and the metallicity of the stellar progenitor, and on the thermodynamic history prior to the explosion. We report on a new method to determine ejecta neutronization using Ca and S lines in the X-ray spectra of Type Ia supernova remnants (SNRs). Applying this method to \textit{Suzaku} data of Tycho, Kepler, 3C 397 and G337.2\(-\)0.7 in the Milky Way, and N103B in the Large Magellanic Cloud, we find that the neutronization of the ejecta in N103B is comparable to that of Tycho and Kepler, which suggests that progenitor metallicity is not the only source of neutronization in SNe Ia. We then use a grid of SN Ia explosion models to infer the metallicities of the stellar progenitors of our SNRs. The implied metallicities of 3C 397, G337.2\(-\)0.7, and N103B are major outliers compared to the local stellar metallicity distribution functions, indicating that progenitor metallicity can be ruled out as the origin of neutronization for these SNRs. Although the relationship between ejecta neutronization and equivalent progenitor metallicity is subject to uncertainties stemming from the \(^{12}\)C\(\,\)+\(^{16}\)O reaction rate, which affects the Ca/S mass ratio, our main results are not sensitive to these details.
PDF