Understanding the rate at which stars form is central to studies of galaxy formation. Observationally, the star formation rates (SFRs) of galaxies are measured using the luminosity in different frequency bands, often under the assumption of a time-steady SFR in the recent past. We use star formation histories (SFHs) extracted from cosmological simulations of star-forming galaxies from the FIRE project to analyse the time-scales to which the H α and far-ultraviolet (FUV) continuum SFR indicators are sensitive. In these simulations, the SFRs are highly time variable for all galaxies at high redshift, and continue to be bursty to z = 0 in dwarf galaxies. When FIRE SFHs are partitioned into their bursty and time-steady phases, the best-fitting FUV time-scale fluctuates from its ∼10 Myr value when the SFR is time-steady to ≳100 Myr immediately following particularly extreme bursts of star formation during the bursty phase. On the other hand, the best-fitting averaging time-scale for H α is generally insensitive to the SFR variability in the FIRE simulations and remains ∼5 Myr at all times. These time-scales are shorter than the 100 and 10 Myr time-scales sometimes assumed in the literature for FUV and H α, respectively, because while the FUV emission persists for stellar populations older than 100 Myr, the time-dependent luminosities are strongly dominated by younger stars. Our results confirm that the ratio of SFRs inferred using H α versus FUV can be used to probe the burstiness of star formation in galaxies.

We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 105.5 and 108.6 M⊙. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flatter gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady ‘puffing’ of old, metal-poor stars by feedback-driven potential fluctuations and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the ‘puffing’ process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.

BackgroundChronic Kidney Disease disproportionately affects the poor in Low and Middle Income Countries (LMICs). Mexico exemplifies the difficulties faced in supporting Renal Replacement Therapy (RRT) and providing equitable patient care, despite recent attempts at health reform. The objective of this study is to document the challenges faced by uninsured, poor Mexican families when attempting to access RRT.MethodsThe article takes an ethnographic approach, using interviewing and observation to generate detailed accounts of the problems that accompany attempts to secure care. The study, based in the state of Jalisco, comprised interviews with patients, their caregivers, health and social care professionals, among others. Observations were carried out in both clinical and social settings.ResultsIn the absence of organised health information and stable pathways to renal care, patients and their families work extraordinarily hard and at great expense to secure care in a mixed public-private healthcare system. As part of this work, they must navigate challenging health and social care environments, negotiate treatments and costs, resource and finance healthcare and manage a wide range of formal and informal health information.ConclusionsExamining commonalities across pathways to adequate healthcare reveals major failings in the Mexican system. These systemic problems serve to reproduce and deepen health inequalities. A system, in which the costs of renal care are disproportionately borne by those who can least afford them, faces major difficulties around the sustainability and resourcing of RRTs. Attempts to increase access to renal therapies, therefore, need to take into account the complex social and economic demands this places on those who need access most. This paper further shows that ethnographic studies of the concrete ways in which healthcare is accessed in practice provide important insights into the plight of CKD patients and so constitute an important source of evidence in that effort.

The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics (stellar masses, sizes, velocity dispersions and morphologies). Here we show that the standard paradigm naturally pro-Bird

We use FIRE-2 zoom cosmological simulations of Milky Way size galaxy haloes to calculate astrophysical J-factors for dark matter annihilation and indirect detection studies. In addition to velocity-independent (s-wave) annihilation cross sections ⟨σv⟩, we also calculate effective J-factors for velocity-dependent models, where the annihilation cross-section is either either p-wave (∝v2/c2) or d-wave (∝v4/c4). We use 12 pairs of simulations, each run with dark-matter-only (DMO) physics and FIRE-2 physics. We observe FIRE runs produce central dark matter velocity dispersions that are systematically larger than in DMO runs by factors of ∼2.5 − 4. They also have a larger range of central (∼400 pc) dark matter densities than the DMO runs (ρFIRE/ρDMO ≃ 0.5 − 3) owing to the competing effects of baryonic contraction and feedback. At 3 degrees from the Galactic Center, FIRE J-factors are 3 − 60 (p-wave) and 10 − 500 (d-wave) times higher than in the DMO runs. The change in s-wave signal at 3 degrees is more modest and can be higher or lower (∼0.3 − 7), though the shape of the emission profile is flatter (less peaked towards the Galactic Center) and more circular on the sky in FIRE runs. Our results for s-wave are broadly consistent with the range of assumptions in most indirect detection studies. We observe p-wave J-factors that are significantly enhanced compared to most past estimates. We find that thermal models with p-wave annihilation may be within range of detection in the near future.

OPINIÓN / OPINION RESUMEN La investigación cualitativa se difunde en el área de la salud en Iberoamérica en las últimas décadas.Numerosos programas de enseñanza y capacitación se han organizado en la región; pero son inexistentes los trabajos cuyo objetivo sea evaluar los avances y dificultades en su enseñanza. Este artículo presenta el diálogo de cinco académicos iberoamericanos sobre la enseñanza de la investigación cualitativa en salud. La reflexión gira en torno a cuatro temas: su acercamiento al campo y a su enseñanza; las fortalezas, logros de las iniciativas educativas en que han participado; las dificultades y obstáculos enfrentados, y los retos y prioridades de su enseñanza en el futuro. Los académicos participantes fueron elegidos por su experiencia en el tema y por su procedencia geográfica. El diálogo se estableció vía Internet, empleando una variante del método FODA y la técnica Delphi.Los participantes, separados geográficamente, con diferentes trayectorias profesionales y antecedentes académicos, exponen los motivos por los cuales esta forma de investigación ha tenido éxito: el entusiasmo de la gente joven y las mujeres, el interés creciente, el rigor académico, la interdisciplinariedad y la legitimación que ha ganado como forma válida de hacer ciencia. Entre los problemas y dificultades destacan la poca consolidación y madurez de las propuestas educativas, y un medio que poco le favorece. Los mismos plantean impulsar su enseñanza en diálogo con la orientación cuantitativa, formulan propuestas al interior de los programas educativos y haciendo uso de tecnologías. Sugieren tomar en cuenta las particularidades sociales para la enseñanza de este campo.

Las enfermedades crónicas han pasado a ser objeto de creciente atención por parte de investigadores con una orientación cualitativa. Pocos trabajos, sin embargo, han profundizado en las decisiones metodológicas empleadas en los estudios. El objetivo de este artículo es presentar algunas reflexiones sobre la metodología empleada en un estudio cualitativo multicéntrico centrado en las perspectivas sobre las enfermedades crónicas y su atención. Los temas objeto de reflexión son la orientación del estudio, la selección del área y la muestra, el empleo de los grupos focales y las relaciones entre los participantes. Concluimos sustentando que las opciones y estrategias metodológicas empleadas, más que ser un asunto de índole técnico, están íntimamente vinculadas al objeto de estudio, a las relaciones sociales establecidas entre los participantes y al contexto del estudio.

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