1,269 research outputs found
Un ampliamento dell'idea di presente : Musica antica a Milano attraverso ricordi, esperienze, testimonianze
No full textAtomic diffusion in solar-like stars with MESA
No full textContext. The stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA) is public and is widely used by the community. It includes the possibility of taking several non-standard processes such as atomic diffusion into account. Even if the effect of gravitational settling is considered a standard ingredient in stellar modelling today, this is not the case for radiative accelerations. The specific treatment of atomic diffusion along with the radiative accelerations has never been compared with other stellar evolution codes. Benchmarking these codes is important because improved accuracy is required in order to analyse data from present and future space missions, such as the Kepler, Transiting Exoplanet Survey Satellite, and PLAnetary Transits and Oscillations of stars missions.
Aims. The aim of this paper is to compare MESA models including atomic diffusion (with radiative accelerations) with models computed with the Montreal/Montpellier stellar evolution code and with the Code d’Evolution Stellaire Adaptatif et Modulaire (CESTAM). Additionally, we assess the impact of some MESA options related to atomic diffusion.
Methods. We calculated atomic diffusion, including radiative accelerations, following the abundance profiles of 14 elements with MESA models. This was then compared with 1.1 and 1.4 M⊙ models computed with the Montreal/Montpellier and CESTAM codes. Various tests of MESA options for atomic diffusion were also carried out by varying only one of them at a time.
Results. We find that the abundance profiles of the considered elements in the MESA models compare rather well with the models computed with the two other codes when atomic diffusion options are carefully set. We also show that some options in MESA are crucial for a proper treatment of atomic diffusion
Testing the cores of first ascent red giant stars using the period spacing of g modes
No full textIn the context of the determination of stellar properties using asteroseismology, we study the influence of rotation and convective-core overshooting on the properties of red giant stars. We used models in order to investigate the effects of these mechanisms on the asymptotic period spacing of gravity modes (ΔΠ1) of red-giant stars that ignite He burning in degenerate conditions (M ≤ 2.0 M⊙). We also compare the predictions of these models with Kepler observations. For a given Δv, ΔΠ1 depends not only on the stellar mass, but also on mixing processes that can affect the structure of the core. We find that in the case of more evolved red-giant-branch stars and regardless of the transport processes occurring in their interiors, the observed ΔΠ1 can provide information as to their stellar luminosity, within ~10-20 per cent. In general, the trends of ΔΠ1 with respect to mass and metallicity that are observed in Kepler red-giant stars are well reproduced by the models
Characterising the AGB bump and its potential to constrain mixing processes in stellar interiors
No full textContext. In the 1990s, theoretical studies motivated the use of the asymptotic giant branch bump (AGBb) as a standard candle given the weak dependence between its luminosity and stellar metallicity. Because of the small size of observed asymptotic giant branch (AGB) samples, detecting the AGBb is not an easy task. However, this has now been made possible thanks to the wealth of data collected by the CoRoT, Kepler, and TESS space-borne missions. Aims. It is well-known that the AGB bump provides valuable information on the internal structure of low-mass stars, particularly on mixing processes such as core overshooting during the core He-burning phase. Here, we investigate the dependence of the AGBb position on stellar parameters such as the stellar mass and metallicity based on the calibration of stellar models to observations. Methods. In this context, we analysed ∼4000 evolved giants observed by Kepler and TESS, including red giant branch (RGB) stars and AGB stars, for which asteroseismic and spectrometric data are available. By using statistical mixture models, we detected the AGBb both in frequency at maximum oscillation power, ?max, and in effective temperature, Teff. Then, we used the Modules for Experiments in Stellar Astrophysics (MESA) stellar evolution code to model AGB stars and match the AGBb occurrence with observations. Results. From the observations, we were able to derive the AGBb location in 15 bins of mass and metallicity. We noted that the higher the mass, the later the AGBb occurs in the evolutionary track, which agrees with theoretical works. Moreover, we found a slight increase in the luminosity at the AGBb when the metallicity increases. By fitting those observations with stellar models, we noticed that low-mass stars (M = 1:0 M ) require a small core overshooting region during the core He-burning phase. This core overshooting extent increases toward high mass; however, above M = 1:5 M , we found that the AGBb location cannot be reproduced with a realistic He-core overshooting alone. Thus, additional mixing processes have to be invoked instead. Conclusions. The observed dependence on metallicity complicates the application of the AGBb as a standard candle. Moreover, different mixing processes may occur according to stellar mass. At low mass (M = 1:5 M ), the AGBb location can be used to constrain the He-core overshooting. At high mass (M = 1:5 M ), an additional mixing induced, for instance, by rotation is needed to reproduce what is seen in observations
P.2.f.004 Effects of combined treatment between trazodone and selective serotonin reuptake inhibitors
No full textPost-traumatic stress disorder in victims of terrorist attacks: a comparison with the impact of other traumatic events on patients' lives
No full text
Off-Label Uses of Trazodone: a Review
No full textIntroduction: Trazodone is an antidepressant belonging to the class of serotonin receptor antagonists and reuptake inhibitors. It is approved by the FDA for the treatment of depression. Insomnia is the most frequent reason for prescription of trazodone. It has also been proven useful in the treatment of anxiety disorders. Other off-label uses include the treatment of bulimia, benzodiazepine/alcohol dependence, fibromyalgia, central nervous system degenerative diseases (behavioral disorders in dementia and other organic disorders), schizophrenia, chronic pain disease and diabetic neuropathy, sexual dysfunction. Areas covered: This paper evaluates trazodone's efficacy and safety in its off-label uses. It also discusses the possibility that a combination of trazodone with SSRIs may prevent or treat some of the SSRI side effects, such as anxiety, insomnia and sexual dysfunction, in addition to synergically increasing SSRIs' antidepressant activity. Expert opinion: Few clinical trials have been conducted to evaluate trazodone's efficacy in the treatment of the diseases and symptoms for which it is often used in clinical practice. More studies are necessary to investigate possible new therapeutic indications, and to scientifically demonstrate the risk/benefit ratio for the many conditions for which trazodone is used, but not approved by the FDA. © 2012 Informa UK, Ltd
Diagnostic mistakes in post-traumatic stress disorder. The problem of symptom overlap with depression [Błędy popełniane w diagnostyce zaburzenia stresowego pourazowego – problem nakładania się objawów tego zaburzenia i depresji]
No full textObjectives. The overlap between symptoms of PTSD and MDD is substantial. PTSD symptoms arise after a traumatic experience and the trauma is present in all of the diagnostic clusters. In individuals who have experienced a trauma a long time before, it is difficult to establish the exact moment of onset of their symptoms in relation to the trauma suffered. We proposed to raise awareness among operators who may encounter this problem, with the aim of providing them with valuable help in order to achieve a correct differential diagnosis. Methods. A sample of subjects suffering from PTSD without comorbidity was assessed to confirm the diagnosis and the severity of post-traumatic symptoms. The Kruskal-Wallis test was used to compare any modifications in the parameters analyzed through the Davidson Trauma Scale with the presence and severity of depressive symptoms as evaluated by the Hamilton-D scale. Results. Half of the PSTD patients recruited showed values of HAM-D > 18, although an active Major Depressive Episode was clinically excluded. Symptom of "numbing", despite being different from the apathy experienced in depression, is identified as a depressive symptom by the HAM-D. Conclusions. Giving prevalence to depressive symptoms may be misleading for diagnosis and may ultimately result in inappropriate treatment
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