Mapping discrete galaxies at cosmic dawn with 21-centimeter observations

At cosmic dawn, the 21-centimeter signal from intergalactic hydrogen was driven by Lyman-$\alpha$ photons from some of the earliest stars, producing a spatial pattern that reflected the distribution of galaxies at that time. Due to the large foreground, it is thought that around redshift 20 it is only observationally feasible to detect 21-cm fluctuations statistically, yielding a limited, indirect probe of early galaxies. Here we show that 21-cm images at cosmic dawn should actually be dominated by large (tens of comoving megaparsecs), high contrast bubbles surrounding individual galaxies. We demonstrate this using a substantially upgraded semi-numerical simulation code that realistically captures the formation and 21-cm effects of the small galaxies expected during this era. Small number statistics associated with the rarity of early galaxies, combined with the multiple scattering of photons in the blue wing of the Lyman-$\alpha$ line, create the large bubbles and also enhance the 21-cm power spectrum by a factor of 2--7 and add to it a feature that measures the typical brightness of galaxies. These various signatures of discrete early galaxies are potentially detectable with planned experiments such as the Square Kilometer Array or the Hydrogen Epoch of Reionization Array, even if the early stars formed in dark matter halos with masses as low as $10^8\, M_\odot$, ten thousand times smaller than the Milky Way halo.Comment: First submitted for publication on Apr. 5th, 202

Mineralogical and geochemical characterization of gold mining tailings and their potential to generate acid mine drainage (Minas Gerais, Brazil)

For more than 30 years, sulfide gold ores were treated in metallurgic plants located in Nova Lima, Minas Gerais, Brazil, and accumulated in the Cocoruto tailings dam. Both flotation and leaching tailings from a deactivated circuit, as well as roasted and leaching tailings from an ongoing plant, were studied for their acid mine drainage potential and elements’ mobility. Detailed characterization of both tailings types indicates the presence of fine-grain size material hosting substantial amounts of sulfides that exhibit distinct geochemical and mineralogical characteristics. The samples from the ongoing plant show high grades of Fe in the form of oxides, cyanide, and sulfates. Differently, samples from the old circuit shave higher average concentrations of Al (0.88%), Ca (2.4%), Mg (0.96%), and Mn (0.17%), present as silicates and carbonates. These samples also show relics of preserved sulfides, such as pyrite and pyrrhotite. Concentrations of Zn, Cu, Au, and As are higher in the tailings of the ongoing circuit, while Cr and Hg stand out in the tailings of the deactivated circuit. Although the obtained results show that the sulfide wastes do not tend to generate acid mine drainage, leaching tests indicate the possibility of mobilization of toxic elements, namely As and Mn in the old circuit, and Sb, As, Fe, Ni, and Se in the tailings of the plant that still works. This work highlights the need for proper management and control of tailing dams even in alkaline drainage environments such as the one of the Cocoruto dam. Furthermore, strong knowledge of the tailings’ dynamics in terms of geochemistry and mineralogy would be pivotal to support long-term decisions on wastes management and disposal.This work was funded by FCT—Fundação para a Ciência e a Tecnologia through projects UIDB/04683/2020 e UIDP/04683/2020 and Nano-MINENV 029259 (PTDC/CTA-AMB/29259/2017, and by AngloGold Ashanti Brazil

Characterization of Arsenical Mud from Effluent Treatment of Au Concentration Plants, Minas Gerais – Brazil.

The determination of the general properties of arsenical mud was carried out in effluent treatment plant of an Au metallurgical facility, located in Nova Lima, Minas Gerais, Brazil. This effluent, which comes from the calcination stage, is treated via Fe-coprecipitation / lime-neutralization and thus mud with high As concentration is generated. Instrumental methods were applied to investigate physical-chemical characteristics, such as pH, in addition to the forms of occurrence of As and its associations. The results indicated that the mud has an alkaline pH (≈ 8.5), particles with grain size below 20 µm, and As, Fe, S and Al concentrations above 5%. The element As is essentially associated with Fe, Ca, S, and Al, forming phases with wide compositional variation as major and minor constituents generically classified as “complex sulfates” and “compounds with S”. The obtained results could assist optimization of the treatment routes in the plant and even to consider the potential reuse of this arsenic mud as a potential valuable produc

Donation of organs and tissues for transplantation: Theoretical contributions.

This bibliographic review study aimed to make theoretical considerations related to the process of organ and tissue donation for transplantation in Brazil. The information source was composed of relevant publications from the Brazilian Association of Organ Transplants, as well as articles found in Latin and American databases, in addition to the current legislation. The increase in the donation rate depends on a broad and systematic look at the technical and legal issues inherent to the donation process. To strengthen this process, it is recommended to incorporate the social approach and the ethical perspective, based on technical and legal understanding and respect for the right of autonomy of potential donors and their families. Actions that ensure ethical-legal management presuppose a commitment to the quality and safety of the donation process, which must be strictly pursued by professionals in this context.This bibliographic review study aimed to make theoretical considerations related to the process of organ and tissue donation for transplantation in Brazil. The information source was composed of relevant publications from the Brazilian Association of Organ Transplants, as well as articles found in Latin and American databases, in addition to the current legislation. The increase in the donation rate depends on a broad and systematic look at the technical and legal issues inherent to the donation process. To strengthen this process, it is recommended to incorporate the social approach and the ethical perspective, based on technical and legal understanding and respect for the right of autonomy of potential donors and their families. Actions that ensure ethical-legal management presuppose a commitment to the quality and safety of the donation process, which must be strictly pursued by professionals in this context

Geoenvironmental characterization of gold mine tailings from Minas Gerais and Goiás, Brazil

For more than two centuries, sulfide gold ores have been treated at metallurgical plants located in Nova Lima, Santa Barbara and Crixás. Brazil. In this study, geochemical, mineralogical, and textural properties of tailings from eight tailings deposits were analysed. The samples show high concentration of Au, hosted in different minerals. In addition, samples contain S, Fe, and As. Sulfides, oxides, and sulfates are present, some as preserved relics. This work highlights different geochemistry and mineralogy, dependent on the nature of the tailings. Such information is critical to support long-term decisions about tailings management and circular economy.This work was supported by FCT through projects UIDB/04683/2020 and UIDP/04683/2020, and the Nano-MINENV project 029259 (PTDC/CTA-AMB/29259/2017), and by AngloGold Ashanti Brasil. Our colleagues at ICT, Centro de Microscopy at Universidade Federal de Minas Gerais (CM-UFMG) and AngloGold Ashanti provide insights and knowledge that greatly aid the research