Context. The identification of the sources that reionized the Universe and their specific contribution to this process are key missing pieces of our knowledge of the early Universe. Faint star-forming galaxies may be the main contributors to the ionizing photon budget during the epoch of reionization, but their escaping photons cannot be detected directly due to inter-galactic medium opacity. Hence, it is essential to characterize the properties of faint galaxies with significant Lyman continuum photon leakage up to z 4 to (...) define indirect indicators allowing analogues to be found at the highest redshift. Aims. Long gamma-ray bursts explode typically in star-forming regions of faint, star-forming galaxies. Through LGRB afterglow spectroscopy it is possible to detect directly LyC photons. Our aim is to use LGRBs as tools to study LyC leakage from faint, star-forming galaxies at high redshift. Methods. Here we present the observations of LyC emission in the afterglow spectra of GRB 191004B at z = 3:5055, together with those of the other two previously known LyC-emitting LGRB, to determine their LyC escape fraction and compare their properties. Results. From the afterglow spectrum of GRB 191004B we determine a neutral hydrogen column density at the LGRB redshift of og =17:2 0:15, and negligible extinction. The only metal absorption lines detected are C iv and Si iv. In contrast to GRB 050908 and GRB 060607A, the host galaxy of GRB 191004B displays significant Ly emission. From its Ly emission and the non-detection of Balmer emission lines we constrain its star-formation rate to 1 SFR 4:7 M yr. 1. We fit the Ly emission with a shell model and find parameters values consistent with the observed ones. The absolute LyC escape fractions we find for GRB 191004B, GRB 050908 and GRB 060607A are of 0:35+0:10.0:11, 0:08+0:05.0:04 and :20+0:05.0:05, respectively. We compare the LyC escape fraction of LGRBs to the values of other LyC emitters found from the literature, showing that LGRB afterglows can be powerful tools to study LyC escape for faint high-redshift star-forming galaxies. Indeed we could push LyC leakage studies to much higher absolute magnitudes. The host galaxies of the three LGRB presented here have all M1600 >.19:5 mag, with the GRB 060607A host at M1600 >.16 mag. LGRB hosts may therefore be particularly suitable for exploring the ionizing escape fraction in galaxies that are too faint or distant for conventional techniques. Furthermore the time investment is very small compared to galaxy studies. (shrink)

Introdução a Levinas a partir da discussão sobre a problemática da subjetividade.

When the COVID-19 surge hit New York City hospitals, the Division of Medical Ethics at Weill Cornell Medical College, and our affiliated ethics consultation services, faced waves of ethical issues sweeping forward with intensity and urgency. In this article, we describe our experience over an eight-week period (16 March through 10 May 2020), and describe three types of services: clinical ethics consultation (CEC); service practice communications/interventions (SPCI); and organizational ethics advisement (OEA). We tell this narrative through the prism of time, (...) describing the evolution of ethical issues and trends as the pandemic unfolded. We delineate three phases: anticipation and preparation, crisis management, and reflection and adjustment. The first phase focused predominantly on ways to address impending resource shortages and to plan for remote ethics consultation, and CECs focused on code status discussions with surrogates. The second phase was characterized by the dramatic convergence of a rapid increase in the number of critically ill patients, a growing scarcity of resources, and the reassignment/ redeployment of staff outside their specialty areas. The third phase was characterized by the recognition that while the worst of the crisis was waning, its medium- and long-term consequences continued to pose immense challenges. We note that there were times during the crisis that serving in the role of clinical ethics consultant created a sense of dis-ease as novel as the coronavirus itself. In retrospect we learned that our activities far exceeded the familiar terrain of clinical ethics consultation and extended into other spheres of organizational life in novel ways that were unanticipated before this pandemic. To that end, we defined and categorized a middle level of ethics consultation, which we have termed service practice communication intervention (SPCI). This is an underappreciated dimension of the work that ethics consult services are capable of in times of crisis. We believe that the pandemic has revealed the many enduring ways that ethics consultation services can more robustly contribute to the ethical life of their institutions moving forward. (shrink)