Semiconductors (LEDs) quality control based in high-resolution 3D X-ray microscope

Electronic devices are getting smaller each time and the technology, increasingly complex. Commonly found problems such as reflow soldering and open solder connections, which are mostly difficult to detect by conventional means like X-ray images or physical cut on the transverse section. Along with the challenge of finding these flaws, there are also some problems that may arise on the exposure of them using destructive analysis techniques, such as the fiscal transversal cut and chemical decapsulation. Both techniques may induce damage not relevant to where that flaw is located or remove evidence of a flaw or a damaged place. The high-resolution 3D x-ray computerized microtomography provides a powerful alternative solution and non-invasive to issues that involve the analysis of semiconductor devices. This research contemplates the study of semiconductor’s integrity (LED’s) based of X-ray computerized microtomography. The SkyScan 1272 Bruker commercial equipment was used for analysis of the P-N junction in a set with 10 LEDs, under non polarized conditions and upon electrical overstress effects on its contact terminals. The P-N junction had their dimensions analyzed on the three spatial directions (x, y and z) and studied on the effects that occur when a LED is damaged. The study methodology of integrity regarding computerized microtomography have shown consist outcomes that allowed the understanding of what occurs on the LED's structure and investigates matters that allows decisions to be made regarding its quality, and so, accomplishing the goals designated on this research

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

Evaluation of mass attenuation coefficient of concrete sample for different traits

Concrete is widely used in the world and is the main material for civil construction. Due to its properties, it has different uses such as structural, filling and shielding. The aim of this work is to compare experimental and theoretical mass attenuation coefficient for concrete with different traits and determine the one with the best performance. For this, density, X-ray diffraction, mass attenuation coefficient (experimental with a Cs137 source, simulated by MCNP and theoretical determined with XCOM platform) and compressive strength were determined for three different traits of cement mortar (standardized sand, conventional sand and artificial sand). The X-ray diffraction showed more compounds for artificial sand’s samples. Density showed no significant variation. The samples showed a good agreement for experimental, simulated and theoretical mass attenuation coefficient. Standardized sand’s samples had the best performance for mechanical test, with a compressive strength 47.4% higher than artificial sand’s samples and 38.2% higher than conventional sand’s samples. It is possible to conclude that, since mass attenuation coefficient showed no significant difference, standardized sand’s samples is more indicated to be used for shielding than the others

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

Avaliação do estado de hidratação de um time de atletas de futebol americano do sertão brasileiro

O Futebol americano é caracterizado como um esporte que proporciona uma demanda física específica aos atletas e suas necessidades de água durante o treinamento e os jogos aumentam. O presente estudo teve como objetivo avaliar o estado nutricional e o estado de hidratação de atletas de uma equipe de futebol americano do Sertão Brasileiro. A amostra foi composta por 28 atletas amadores saudáveis. Os parâmetros de hidratação foram avaliados com a intervenção de água mineral e água de coco, coleta pré e pós-treinamento de urina para averiguar parâmetros bioquímicos como pH, densidade, Coloração e pré e pós-treino e verificação de peso, para cálculo de % perda de peso e temperatura e umidade relativa do ar.  A avaliação nutricional foi realizada por meio de medidas de peso, IMC, circunferências, Razão-Cintura-Quadril, percentual de gordura e músculo. Também foram avaliados pressão arterial, frequência cardíaca, saturação de oxigênio e glicemia. O estudo mostrou hidratação dos atletas de acordo com a perda de peso menor que 1%, contudo, os aspectos de densidade e pH urinário após intervenção com água mineral e água de coco, possibilitaram identificar o estado de desidratação dos atletas no, pós treino. Além disso, as condições climáticas da região podem ter impactado diretamente os resultados obtidos. Ambos os grupos de atletas, apresentaram-se com peso e IMC elevado de acordo com sexo e idade, assim como o percentual de gordura e o de massa muscular. Sendo necessário o acompanhamento individual destes atletas, a fim de evitar o desenvolvimento de agravos à saúde

Pre-Columbian alloys from the royal tombs of Sipán and from the Museum of Sicán

On the north coast of present-day Peru, approximately between 50 and 700 AD, flourished the Moche civilization. It was an advanced culture, and the Moche were sophisticated metalsmiths. The Moche metal working ability was impressively shown by the excavations of the “Tumbas Reales de Sipán”, discovered by W. Alva and co-workers in 1987. The Sicán culture is a successive civilization (750-1375 AD) which extended as far as present day Piura in the north and Trujillo in the south. The Sicán culture was strongly influenced by the Moche culture, particularly in its metallurgical development (Shimada and Griffin, 1994). The metal objects from the Museums of Sipán and Sicán were analyzed with a portable equipment which uses energy-dispersive X-ray fluorescence (XRF). This portable equipment is composed of a small size X-ray tube and a Si-PIN thermoelectrically cooled X-ray detector. It was determined that the analyzed artefacts are composed of gold, silver and copper alloys, of gilded copper, of silvered gold, and of tumbaga, the last being a poor gold alloy enriched at the surface by depletion gilding, i.e. removing copper from the surface. In the case of gold, silver and copper alloys, their composition was determined by EDXRF analysis employing standard alloys. In the case of gilded copper, silvered copper and of tumbaga, the ratio Cu(Ka/Kb) was accurately determined from the X-ray spectra, first in order to clearly distinguish them, and subsequently in order to determine the thickness of the gilding. Mean values of 0.4 µm and 2.7 µm were determined for gilded copper and tumbaga, respectively. For gilded silver, the ratio Ag(Ka /Kb) was measured. The ratios Au-Ka/Cu-Ka, Ag-Ka/Cu-Ka and Au-Ka/Ag-Ka (gilded copper, silvered copper, and gilded silver, respectively) also depend on the thickness of gilding or silvering, and were employed to this aim.Sur la côte nord de l’actuel Pérou, entre environ 50 et 700 AD, prospérait la civilisation Moche. Cette culture était très avancée et les Moches étaient des métallurgistes avertis. Leur talent pour travailler le métal est illustré par les fouilles du site des “Tumbas Reales de Sipán”, découvert par W. Alva et collaborateurs en 1987. La culture Sicán est une civilisation qui se succède de 750 à 1375 AD et qui s’étend au nord jusqu’à Piura et au sud jusqu’à Trujillo. La culture Sicán a été fortement influencée par la culture Moche, et tout particulièrement leur métallurgie (Shimada et Griffin, 1994). Les objets métalliques des musées de Sipán et Sicán ont été analysés avec un spectromètre portable à fluorescence X à dispersion d’énergie. Cet équipement est constitué d’un tube à rayons-X miniaturisé et d’un détecteur de rayons-X de type Si-PIN à refroidissement thermoélectrique.  Nous avons pu montrer que les objets sont fabriqués avec des alliages d’or, argent et cuivre, avec du cuivre et de l’argent doré ainsi qu’avec du tumbaga, alliage d’or enrichi par mise en couleur, c’est-à-dire par appauvrissement en surface du cuivre. Les compositions des alliages en or, argent et cuivre ont été déterminées par ED-FX au moyen de standards d’or. Pour différencier les cuivres et les argents dorés ainsi que les tumbaga et ensuite déterminer l’épaisseur de la dorure, le rapport Cu(Ka/Kb) a été déterminé avec précision à partir des spectres à rayons X. Des valeurs moyennes de, respectivement, 0,4µm et 2,7µm ont été déterminées pour les cuivres dorés et les tumbaga. Pour les argents dorés, c’est le rapport Ag(Ka/Kb) qui a été mesuré. Les rapports Au-Ka/Cu-Ka, Ag-Ka/Cu-Ka et Au-Ka/Ag-Ka (cuivres dorés, cuivres argentés et argents dorés, respectivement) dépendent aussi de l’épaisseur de la dorure et de l’argenture

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