Analysis of the Chemical Modification of Dental Enamel Submitted to 35% Hydrogen Peroxide “In-Office” Whitening, with or without Calcium

Purpose. The purpose of this study was to evaluate changes in calcium and phosphorus content in dental enamel when subjected to “in-office” whitening for an extended time by using a 35% hydrogen peroxide solution, with and without calcium. Materials and Methods. 10 human teeth, from which the roots had been removed, were embedded in epoxy resin, and their surfaces were smoothed. The specimens were divided into two groups; in group 1, a whitening solution without calcium was used, while in group 2, the solution included calcium. Each specimen was evaluated at 6 different points before the bleaching treatment, and these points were reassessed after each session. A total of five sessions were carried out. Concentrations of calcium and phosphorus were measured by using the technique of X-ray fluorescence. Results. After performing a statistical analysis, it was found that there was no statistically significant loss of calcium and phosphorus during the whitening treatment, and the groups showed no statistical differences. Conclusion. Excessive use of hydrogen peroxide, with or without calcium, causes no loss of calcium and phosphorus

Multielement analysis in beer cans using X-ray fluorescence

In this study the elemental concentrations of twenty-three beer cans of different brands and nationalities were determined using X-ray fluorescence technique. Beer cans from Brazil (20 beer cans), Germany, the United Kingdom and Colombia were analyzed, totalizing 15 different breweries. It was possible to calculate the concentration of 15 elements in the beer cans samples: Mg, Al, Si, S, Cl, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Zr and Pb. The results showed that aluminum concentrations ranged from 94 % to 96 %. Other's elements can be considered trace elements, being the highest concentrations of them for Mg (approximately 2%) and Mn (approximately 1%). Some elements showed differences between cans from different nationalities, with Zn being much higher in samples from Brazil. The Zr element showed similarities between German and UK beer cans. In addition, the beer can sample from Colombian had lower concentrations of Cl and Ga. This study shows that the values found are comparable to those found in the literature and that the concentrations of some trace elements in beer cans may represent signs of impurities brought during the recycling process

Non-invasive characterization of the painting Saint John the Evangelist by means spectroscopic methods

In this work, the pigments and ground layers of the Saint John the Evangelist painting were analyzed using the techniques of computed radiography, X-ray fluorescence (XRF), and micro-Raman spectroscopy. The painting was purchased by a collector at auction as a 19th-century work of art of unknown authorship. XRF analyzes were performed with a voltage of 40 kV, current of 50 µA, and acquisition time of 60 s. Micro-Raman spectroscopy measurements of a black fragment sample were performed with the Thermo Scientific – DXR2 Raman microscope equipment. The sample was excited by the adjusted 785 nm laser source with a power of 4 mW, focused on the sample using a 100x objective. It was possible to characterize the pigments used in the painting of São João Evangelista as Lead White, Vermilion, Carbon Black, and Ocher. No areas of repainting and modern pigments were identified that could suggest any type of intervention

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Energy-dispersive X-ray fluorescence analysis of a pre-Columbian funerary gold mask from the Museum of Sicán, Peru

A funerary gold mask from the Museum of Sicán, Ferrañafe, Peru was analyzed in 30 different areas using a portable equipment using energy-dispersive X-ray fluorescence. It was deduced from the measurements that the main sheet of the mask and the majority of the pendants have a similar composition and are made of tumbaga, which means a poor gold alloy enriched at the surface by depletion gilding, and have a similar ‘equivalent’ gilding thickness of about 5 µm. The nose, also on tumbaga, has different composition and a thickness of about 8 µm. The clamps are on gilded or on silvered copper. The red pigment dispersed on the surface of the mask is cinnabar

Portable equipment for a non-destructive analysis of pre-Columbian metal artefacts from the Royal Tombs of Sipán by energy-dispersive X-ray fluorescence spectrometry

On the north coast of present-day Peru flourished approximately between 50 and 700 AD the Moche civilisation. They were sophisticated metalworkers and are considered the finest producers of jewels and artefacts of the region. The Moche metalworking ability was impressively demonstrated by the excavations of the ‘Tumbas Reales de Sipán’, carried out by Walter Alva et al. in 1987. About 50 metal objects from these excavations, now at the Museum ‘Tumbas Reales de Sipán’, in Lambayeque, North of Peru, were analysed with a portable equipment which uses energy-dispersive X-ray fluorescence (EDXRF). This portable equipment is mainly composed of a small-sized X-ray tube and a thermoelectrically cooled, small-sized X-ray detector. Standard samples of gold and silver alloys were employed for calibration and quantitative determination. The analysed artefacts are mainly gold, silver and copper alloys, gilded copper and tumbaga, the last being a poor gold alloy enriched at the surface by depletion gilding, i.e. by removing copper and silver from the surface. In the case of gold, silver and copper alloys, their composition was determined by the EDXRF analysis in the usual manner, i.e. by employing standard alloys. In the case of gilded copper or tumbaga, the ratios Cu(Kα/Kβ) and (Au-Lα/Cu-Kα) were accurately determined from the X-ray spectra, first to clearly distinguish gilded copper from tumbaga and then to determine the gilding thickness or an ‘equivalent gilding thickness’ in the case of tumbaga. The combination of the two ratios is a clear indication of the nature of the alloy (gold, gilded Cu or tumbaga) and allows an accurate measurement of the gilding thickness in the case of gilded copper objects or, in the case of tumbaga, the ‘equivalent’ gold thickness was measured to be &#126;2.8 µm. From all measurements, the mean approximate composition and thickness of Sipán alloys is the following: 1.Gold: Au = &#126;70%, Ag = &#126;20% and Cu = &#126;10% 2.Gilding of gilded copper: Au = &#126;97.5% and Ag = &#126;2.5%; thickness = &#126;0.6 µm 3.Tumbaga: ‘equivalent’ Au thickness = &#126;2.5 µm 4.Silver: Ag = &#126;92%, Cu = &#126;5% and Au = &#126;3% 5.Copper: Cu = &#126;99% with traces of iron and nickel</ul

Determination of the chemical composition and functional properties of shrimp waste protein concentrate and lyophilized flour Determinação da composição química e das propriedades funcionais de concentrado protéico e de farinha liofilizada de resíduos de camarão

Wastes from the seafood industry can be easily processed into products with new forms of use. The present study was aimed at determining the chemical composition and functional properties of shrimp waste protein concentrate and lyophilized flour. The raw material used in this study consisted of waste (head) of Litopenaeus vannamei. The protein concentrate was obtained by ethanolic extraction, being subsequently submitted to drying in oven at 70° C, while the flour was obtained by lyophilization of shrimp wastes. Moisture, ash, protein and calcium contents showed significant difference between fresh shrimp head waste samples (IN) and protein concentrate and lyophilized flour samples. The protein content for protein concentrate (PC) and lyophilized flour (LF) showed significant increase in relation to protein content in the waste (IN), thus showing that the process for obtaining the protein concentrate was efficient.<br>Resíduos provenientes da indústria do pescado podem ser facilmente transformados em produtos com novas formas de aproveitamento. No presente estudo, objetivou-se determinar a composição química e as propriedades funcionais de farinha liofilizada e concentrado proteico provenientes de resíduos de camarão. A matéria-prima empregada neste estudo foi constituída de resíduos (cabeça) de camarão Litopenaeus vannamei. O concentrado proteico foi obtido por extração etanólica e, posteriormente, submetido à secagem em estufa a 70° C, enquanto a farinha foi obtida pelo processo de liofilização do resíduo. Os teores de umidade, cinzas, proteínas e cálcio apresentaram diferença significativa entre as amostras de resíduo de cabeça de camarão in natura (IN) e as amostras de concentrado proteico e farinha liofilizada. O teor de proteínas para concentrado protéico (CP) e para a farinha liofilizada (FL) apresentou aumento significativo em relação ao teor proteico do resíduo (IN), mostrando, assim, que o processo de elaboração do concentrado proteico foi eficiente