Participating as a research team during the COVID-19 pandemic benefits mental health of undergraduate medical students in Brazil.

During the COVID-19 pandemic, undergraduate medical students (UMS) exposed to isolation, social distancing and complete or partial face-to-face educational activities interruption may present increased stress, depression and anxiety. This study was undertaken to evaluate if, during isolation, UMS involved in online group activities as investigators of a research project (volunteer group) would present better mental health than their colleagues, not involved in that research (control group). A Web-based survey, via the Google Forms platform, including details on demographic data, life habits, previous health conditions, worries with the COVID-19 pandemic, sleep pattern modifications and depression, anxiety and mental stress, using the DASS-21 (Depression, Anxiety and Stress Scale) was implemented from 20 July to 31 August 2020.

Determination of fluorine in copper concentrate via high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis - Comparison of three target molecules.

The chemical composition of complex inorganic materials, such as copper concentrate, may influence the economics of their further processing because most smelters, and particularly the producers of high-purity electrolyte copper, have strict limitations for the permissible concentration of impurities. These components might be harmful to the quality of the products, impair the production process and be hazardous to the environment. The goal of the present work is the development of a method for the determination of fluorine in copper concentrate using high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis.

Determination of lead in biomass and products of the pyrolysis process by direct solid or liquid sample analysis using HR-CS GF AAS.

A method has been developed for the determination of lead in biomass, bio-oil, pyrolysis aqueous phase, and biomass ashes by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) and direct solid or liquid sample analysis. All measurements were performed without chemical modifier and calibration could be carried out using aqueous standard solutions. A pyrolysis temperature of 800°C and an atomization temperature of 2200°C were applied.

Transformation of tributyltin in zebrafish eleutheroembryos (Danio rerio).

Organotin compounds are highly versatile group of organometallic chemicals used in industrial and agricultural applications. Their endocrine-disrupting effects are well known and their extensive uses as biocide materials, e.g.

Optimisation and application of the voltammetric technique for speciation of chromium in the Patos Lagoon Estuary--Brazil.

The chemical speciation analysis of chromium in one of the most important South American Estuary was performed for the first time. Samples were collected in Patos Lagoon Estuary (Brazil) and were analysed by adsorptive cathodic stripping voltammetry, with the following analytical figures of merit: limit of detection, 0.1 nmol L(-1); precision RSD = 3%, n = 7; linearity, from limit of quantitation up to 20 nmol L(-1); and accuracy of 99.

Determination of cadmium and lead in beverages after leaching from pewter cups using graphite furnace atomic absorption spectrometry.

Two simple methods have been developed to determine cadmium and lead in different kinds of beverages and vinegar leached from pewter cups produced in Brazil. Leaching experiments have been carried out with different solutions: beer, sugar cane spirit, red and white wine, vinegar and a 3% acetic acid solution. The solutions were kept in cups with and without solder for 24h.