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Search Results: 1 - 10 of 102 matches for " Chieffi "
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Interrelationship between Schistosomiasis and concomitant diseases
Chieffi, Pedro Paulo;
Memórias do Instituto Oswaldo Cruz , 1992, DOI: 10.1590/S0074-02761992000800045
Abstract: the biological literature contains many examples of mutual influences between different species of parasites, especially with respect to concomitant helminth infections. several situations are known in wich the association of infection by shistosoma mansoni with other pathogens in the same host results in a type of disease wich differs from the simple summation of the individual effects of each infection. the present study concerns concomitant infections involving s. mansoni and enterobacteriaceae; s. mansoni and other helmints such as ascaris lumbricoides, ancylostomids, toxocara canis and species of the genus hymenolepis; s. mansoni and different protozoa such as trypanosoma cruzi, t. brucei, toxoplasma gondii and plasmodium berghei. the interaction between hepatitis b virus and s. mansoni, leading to prolonged viremia and worsening of liver damage, is also discussed. the paper also treats the simultaneous occurrence of schistosomiasis and other aggravating factors such as malnutrition and neoplasias wich may alter the host's response to the trematode.
Book review
Chieffi Pedro Paulo
Revista do Instituto de Medicina Tropical de S?o Paulo , 2001,
Chieffi Pedro Paulo
Revista do Instituto de Medicina Tropical de S?o Paulo , 1999,
Evolution, Explosion and Nucleosynthesis of Core Collapse Supernovae
M. Limongi,A. Chieffi
Physics , 2003, DOI: 10.1086/375703
Abstract: We present a new set of presupernova evolutions and explosive yields of massive stars of initial solar composition (Y=0.285, Z=0.02) in the mass range 13-35 Msun. All the models have been computed with the latest version (4.97) of the FRANEC code that now includes a nuclear network extending from neutrons to Mo98. The explosive nucleosynthesis has been computed twice: a first one with an hydro code and a second one following the simpler radiation dominated shock approximation (RDA).
Presupernova evolution and explosive nucleosynthesis of zero metal massive stars
M. Limongi,A. Chieffi
Physics , 2012, DOI: 10.1088/0067-0049/199/2/38
Abstract: We present a new set of zero metallicity models in the range 13-80 $\rm M_\odot$ together to the associated explosive nucleosynthesis. These models are fully homogeneous with the solar metallicity set we published in Limongi & Chieffi (2006) and will be freely available at the web site http://www.iasf-roma.inaf.it./orfeo/public{\_}html. A comparison between these yields and an average star that represents the average behavior of most of the very metal poor stars in the range $\rm -5.0<[Fe/H]<-2.5$ confirms previous findings that only a fraction of the elemental [X/Fe] may be fitted by the ejecta of $\it standard$ core collapse supernovae.
The evolution of rotating solar metallicity stars extending in mass from 13 to 120 msun: the hydrostatic evolution and the explosive yields
Alessandro Chieffi,Marco Limongi
Physics , 2012,
Abstract: We present the first set of a new generation of models of massive stars of solar composition extending between 13 and 120 \msun, computed with and without the effects of rotation. We included two instabilities induced by rotation, namely the meridional circulation and the shear instability. We implemented two alternative schemes to treat the transport of the angular momentum: the advection-diffusion formalism and the simpler purely diffusive one. The full evolution from the Pre Main Sequence up to the presupernova stage is followed in detail with a very extended nuclear network. The explosive yields are provided for a variety of possible mass cut and are available at the website \url{http://www.iasf-roma.inaf.it/orfeo/public{\_}html}. We find that both the He and the CO core masses are larger than those of their non rotating counterparts. Also the C abundance left by the He burning is lower than in the non rotating case, especially for stars of initial mass 13-25 \msun, and this affects the final Mass-Radius relation, basically the final binding energy, at the presupernova stage. The elemental yields produced by a generation of stars rotating initially at 300 km/s do not change substantially with respect to those produced by a generation of non rotating massive stars, the main differences being a slight overproduction of the weak s-component and a larger production of F. Since rotation also affects the mass loss rate, either directly and indirectly, we find substantial differences in the lifetimes as O-type and WR-subtypes between rotating and non rotating models. The maximum mass exploding as type IIP supernova ranges between 15 and 20\msun in both sets of models (this value depending basically on the larger mass loss rates in the Red Super Giant phase due to the inclusion of the dust driven wind). This limiting value is in remarkable good agreement with current estimates.
Radioactivities in Low- and Intermediate-Mass Stars
Maria Lugaro,Alessandro Chieffi
Physics , 2010,
Abstract: Energy in stars is provided by nuclear reactions, which, in many cases, produce radioactive nuclei. When stable nuclei are irradiated by a flux of protons or neutrons, capture reactions push stable matter out of stability into the regime of unstable species. The ongoing production of radioactive nuclei in the deep interior of the Sun via proton-capture reactions is recorded by neutrinos emitted during radioactive decay and detected on Earth. Radioactive nuclei that have relatively long half lives may also be detected in stars via spectroscopic observations and in stardust recovered from primitive meteorites via laboratory analysis. The vast majority of these stardust grains originated from Asymptotic Giant Branch (AGB) stars. This is the final phase in the evolution of stars initially less massive than ~10 solar masses, during which nuclear energy is produced by alternate hydrogen and helium burning in shells above the core. The long-lived radioactive nucleus 26Al is produced in massive AGB stars (>4:5 solar masses), where the base of the convective envelope reaches high temperatures. Several other long-lived radioactive nuclei, including 60Fe, 87Rb, and 99Tc, are produced in AGB stars when matter is exposed to a significant neutron flux leading to the synthesis of elements heavier than iron. Here, neutron captures occur on a timescale that is typically slower than beta-decay timescales, resulting slow neutron captures (the s-process). However, when radioactive nuclei with half lives greater than a few days are produced they may either decay or capture a neutron, thus branching up the path of neutron captures and defining the final s-process abundance distribution. This nucleosynthesis in AGB stars could produce some long-living radioactive nuclei in relative abundances that resemble those observed in the early solar system.
The Explosive Yields Produced by the First Generation of Core Collapse Supernovae and the Chemical Composition of Extremely Metal Poor Stars
Alessandro Chieffi,Marco Limongi
Physics , 2002, DOI: 10.1086/342170
Abstract: We present a detailed comparison between an extended set of elemental abundances observed in some of the most metal poor stars presently known and the ejecta produced by a generation of primordial core collapse supernovae. We used five stars which form our initial database and define a "template" ultra metal poor star which is then compared to the theoretical predictions. Our main findings are as follows: a) the fit to [Si/Mg] and [Ca/Mg] of these very metal poor stars seems to favor the presence of a rather large C abundance at the end of the central He burning; in a classical scenario in which the border of the convective core is strictly determined by the Schwarzschild criterion, such a large C abundance would imply a rather low C12(alpha,gamma)O16 reaction rate; b) a low C abundance left by the central He burning would imply a low [Al/Mg] (<-1.2 dex) independently on the initial mass of the exploding star while a rather large C abundance would produce such a low [Al/Mg] only for the most massive stellar model; c) at variance with current beliefs that it is difficult to interpret the observed overabundance of [Co/Fe], we find that a mildly large C abundance in the He exhausted core (well within the present range of uncertainty) easily and naturally allows a very good fit to [Co/Fe]; d) our yields allow a reasonable fit to 8 out of the 11 available elemental abundances; e) within the present grid of models it is not possible to find a good match of the remaining three elements, Ti, Cr and Ni (even for an arbitrary choice of the mass cut); f) the adoption of other yields available in the literature does not improve the fit; g) since no mass in our grid provides a satisfactory fit to these three elements, even an arbitrary choice of the initial mass function would not improve their fit.
The Chemical Yields Produced by Zero Metal Massive Stars
Marco Limongi,Alessandro Chieffi
Physics , 2002, DOI: 10.1071/AS01091
Abstract: In this review we compare the three existing sets of theoretical yields of zero metal massive stars available in the literature. We also show how each of these three different sets of yields fits the element abundance ratios observed in the extremely metal poor star CD 38245. We find that, at present, no theoretical set of yields of zero metal massive stars is able to satisfactorily reproduce the elemental ratios [X/Fe] of this star.
Judicializa??o da política pública de assistência farmacêutica e eqüidade
Chieffi, Ana Luiza;Barata, Rita Barradas;
Cadernos de Saúde Pública , 2009, DOI: 10.1590/S0102-311X2009000800020
Abstract: the supply of medicines in response to court orders or injunctions has become a common practice in the state of s?o paulo, brazil. this "judicialization" of the health system clashes with basic principles of the brazilian unified national health system (sus), such as equal opportunity to access health services. the aim of this paper is to analyze the legal action used to obtain medicines through the s?o paulo state health department, from two main angles: judicialization of public policies and breach of the equity principle. this is a descriptive study of legal action taken to obtain medicines through the s?o state health department, as listed in the electronic court docket system for the year 2006. most cases were filed through private attorneys; 47% of the patients had obtained their prescriptions through private care; and 73% of the cases involved patients from the three wealthiest areas in the city of s?o paulo. the data demonstrate that such legal action violates key principles of the sus such as equity, thereby privileging individuals with higher purchasing power and more access to information.
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