Effect of drill speed on the strain distribution during drilling of bovine and human bones

Drilling is an operation commonly required in orthopaedic surgery for insertion of screws and internal fixation of bone fractures. Induced damage is one of the undesired effects of drilling mainly due to the use of inadequate drilling parameters. During the recent years, scientists have been trying to describe the relationship between drilling parameters and bone injury. However, no studies have examined the level of strain generated in the bone during the drilling process. This paper focuses on the analysis of different drill speeds during drilling of fresh bovine femora and human cadaveric tibiae. The main contribution of this work is to determine how differences in applied drill speeds affect the strain of cortical tissue near the drilling site and the drill bit temperature. Strains were measured in ex-vivo material during the osteotomy preparation with three drill speeds (520, 900 and 1370 r.p.m.). Additionally, a thermographic camera was used to measure the drill bit temperature. As the drilling operations are blind in nature with unknown depth, the osteotomies were performed using a drill press machine without control of the feed rate or depth. Drill bit geometry was kept constant with 4 mm of diameter, point angle 120⁰ and helix angle 30⁰. The tests were conducted at room temperature without applying cooling at the drilling zone. Bone strains near to the drilling sites were recorded with high accuracy using linear strain gages mounted around the diaphyseal cortex. It was noted that the bone strain and drill bit temperature increased with an increasing drill speed. Human and bovine bone samples presented significantly different levels of strain and temperature. Both strain and temperature were higher when drilling bovine femora than when drilling human cadaveric tibiae

Environmental risk assessment in a contaminated estuary: an integrated weight of evidence approach as a decision support tool

Environmental risk assessment of complex ecosystems such as estuaries is a challenge, where innovative and integrated approaches are needed. The present work aimed at developing an innovative integrative methodology to evaluate in an impacted estuary (the Sado, in Portugal, was taken as case study), the adverse effects onto both ecosystem and human health. For the purpose, new standardized lines of evidence based on multiple quantitative data were integrated into a weight of evidence according to a best expert judgment approach. The best professional judgment for a weight of evidence approach in the present study was based on the following lines of evidence: i) human contamination pathways; ii) human health effects: chronic disease; iii) human health effects: reproductive health; iv) human health effects: health care; v) human exposure through consumption of local agriculture produce; vi) exposure to contaminated of water wells and agriculture soils; vii) contamination of the estuarine sedimentary environment (metal and organic contaminants); viii) effects on benthic organisms with commercial value; and ix) genotoxic potential of sediments. Each line of evidence was then ordinally ranked by levels of ecological or human health risk, according to a tabular decision matrix and expert judgment. Fifteen experts scored two fishing areas of the Sado estuary and a control estuarine area, in a scale of increasing environmental risk and management actions to be taken. The integrated assessment allowed concluding that the estuary should not be regarded as impacted by a specific toxicant, such as metals and organic compounds hitherto measured, but by the cumulative risk of a complex mixture of contaminants. The proven adverse effects on species with commercial value may be used to witness the environmental quality of the estuarine ecosystem. This method argues in favor of expert judgment and qualitative assessment as a decision support tool to the integrative management of estuaries. Namely it allows communicating environmental risk and proposing mitigation measures to local authorities and population under a holistic perspective as an alternative to narrow single line of evidence approaches, which is mandatory to understand cause and effect relationships in complex areas like estuaries.info:eu-repo/semantics/publishedVersio

Fuel Starvation: irreversible degradation mechanisms in PEM Fuel Cells

PEM fuel cell operates under very aggressive conditions in both anode and cathode. Failure modes and mechanism in PEM fuel cells include those related to thermal, chemical or mechanical issues that may constrain stability, power and lifetime. In this work, the case of fuel starvation is examined. The anode potential may rise to levels compatible with the oxidization of water. If water is not available, oxidation of the carbon support will accelerate catalyst sintering. Diagnostics methods used for in-situ and ex-situ analysis of PEM fuel cells are selected in order to better categorize irreversible changes of the cell. Electrochemical Impedance Spectroscopy (EIS) is found instrumental in the identification of fuel cell flooding conditions and membrane dehydration associated to mass transport limitations / reactant starvation and protonic conductivity decrease, respectively. Furthermore, it indicates that water electrolysis might happen at the anode. Cross sections of the membrane catalyst and gas diffusion layers examined by scanning electron microscopy indicate electrode thickness reduction as a result of reactions taking place during hydrogen starvation. Catalyst particles are found to migrate outwards and located on carbon backings. Membrane degradation in fuel cell environment is analyzed in terms of the mechanism for fluoride release which is considered an early predictor of membrane degradation

Synthesis and characterization of novel thieno[3,2-b]thiophene based metal-free organic dyes with different heteroaromatic donor moieties as sensitizers for dye-sensitized solar cells

Four novel heterocycle dyes 3a-d were synthesized in order to study the variations produced in the optical, electronic and photovoltaic properties by substitution of different electron-rich heterocyclic groups to the thieno[3,2-b]thiophene system. The final push-pull conjugated dyes 3a-d were synthesized by Suzuki-Miyaura coupling reaction followed by Knoevenagel condensation of the corresponding aldehyde precursors with cyanoacrylic acid 2a-d. These new push-pull systems are based on a thieno[3,2-b]thiophene spacer, a cyanoacetic acid anchoring group and several electron-rich heterocycles (thiophene, pyrrole and furan) as donor groups. The multidisciplinary study concerning the optical, redox and photovoltaic characterization of the dyes reveals that compound 3b bearing a hexyl-bithiophene donor group/heterocyclic spacer exhibits the best overall conversion efficiency (2.49%) as sensitizer in nanocrystalline TiO2 dye sensitized solar cells. Co-adsorption studies between N719 and 3b revealed that upon addition of N719 co-adsorbent, the optimized cell efficiencies were improved by 16–77%. The best efficiency was 4.40%, corresponding to 54% of the photovoltaic performance of the N719-based DSSC fabricated and measured under similar conditions.FCTFEDERQRENEuropean Research Council (Contract no: 321315

Spatial behavior of acid mine drainage in a peculiar stream : physical-chemical evolution from the source until the temporarlly receptor in the Iberian Pyrite Belt

Publicado em "Proceedings of the Energy and Environment Knowledge Week 2014 (E2KW2014), ISBN 978-84-697-1162-0"The Iberian Pyrite Belt is a vast concentration of massive sulphide, located in the SW of the Iberian Peninsula. Historically, this area has undergone an intense mining activity, which has left a huge amount of mining facilities and unrestored waste dumps. Mineral-water interaction in the waste dumps is responsible for the generation of acid mine drainage (AMD), causing a strong impact in the water systems. The AMD occurs when the sulfide minerals are in the presence of atmospheric oxygen and humidity, suffering oxidation reactions. As a consequence, metals and acidity are mobilized into the receiving watercourses. Such conditions have created a unique scenario in the world by the extreme degradation that characterizes the network of channels and streams in the IPB. In this context, widely described in the scientific literature, the present study aims to monitoring a singular channel affected by AMD (Campanario stream), from its origin (in the waste dump) to its confluence with an unpolluted stream. Such monitoring procedure will allow characterizing the physicochemical evolution and the mineral-water processes that regulate it

Four abandoned mines, one acid mine drainage affected river and an unsolved issue for a water supply reservoir

Publicado em "Proceedings of the Energy and Environment Knowledge Week 2014(E2KW2014)". ISBN 978-84-697-1162-

Removal of the hormones 17β-estradiol and 17α-ethinylestradiol from aqueous solutions employing a decomposed peat as adsorbent material

REMOVAL OF THE HORMONES 17b-ESTRADIOL AND 17a-ETHINYLESTRADIOL FROM AQUEOUS SOLUTIONS EMPLOYING A DECOMPOSED PEAT AS ADSORBENT MATERIAL. This paper describes the adsorption of 17b-estradiol (E2) and 17a-ethinylestradiol (EE2) from aqueous solution by decomposed peat. The peat presented a good adsorption process, close to 76.2% for E2 removal and approximately 55.0% for EE2. Moreover, the results indicated a probable multi-layered process. Adsorption isotherms were well fitted by Freundlich model. The data were evaluated considering the pseudo-first-order and pseudo-second-order approaches, being the second more significant mechanism in the rate-controlling step. Thermodynamic data revealed that hormones adsorption onto peat is spontaneous under the employed experimental conditions. The results confirmed the potential of this adsorbent to be employed for effluents treatment

Constipação intestinal na criança

  Objective: To present an update review of intestinal constipation in children, analysing the principal clinic characteristics and its diagnostic and therapeutic approachs. Methods: Recent articles on the topic were reviewed, supplemented by the clinical experience of the Gastroenterology Unit, of the Pediatric Departament- HCRP- USP. Results: The intestinal constipation is a commun problem in the pediatric clinics. Its definition is based on the elimination of painful, difficulted and dry feces. Infants usually present crying during the evacuations. In some children it can be observed important facael retention with or without soiling. The diagnosis is based on a deitailed clinical history and physical examination of the children. The diagnosis in the most of the cases may be done with a carefully clinical history and phisical examination. The treatment must be done according to the basal cause and in the most of the cases dietetic and comportamental changes are necessary. Conclusões: The diagnosis of the intestinal constipation must be done earlier because it is important for the therapeutic sucess, that depends on a adequate diet and a behavioral program to regulate bowel habits.   Objetivo: Apresentar uma revisão sobre a constipação intestinal na criança, analisando as principais características clínicas bem como sua abordagem diagnóstica e terapêutica. Métodos: Revisão bibliográfica atualizada e experiência da Unidade de Gastroenterologia do Departamento de Pediatria- HCRP- USP. Resultados: A constipação intestinal constitui um problema comum na prática pediátrica. Sua definição está baseada na eliminação de fezes ressecadas, com esforço e dor. É comum as crianças pequenas apresentarem choro durante as evacuações. Em algumas crianças, pode ser observada retenção fecal importante, com ou sem escape fecal. O diagnóstico, na maioria dos casos, pode ser feito através de dados de história clínica e exame físico cuidadoso dos pacientes. O tratamento deve ser direcionado à causa básica, necessitando, na maioria dos casos, mudanças dietéticas e comportamentais. Conclusões: O diagnóstico da constipação intestinal deve ser precoce, pois interfere no sucesso terapêutico, que depende de uma adequada alimentação e do recondicionamento esfincteriano. &nbsp

Geoenvironmental study of gold mining tailings in a circular economy context: Santa Barbara, Minas Gerais, Brazil

We characterized the tailings from the Santa Barbara tailings dam, which is located in Minas Gerais, southeastern Brazil, to: (i) identify its chemical, mineralogical, and metallurgical properties, and (ii) perform an environmental evaluation of the water at the surface of the tailings facility. The potential recovery of elements such as Sb, As, and Au was also considered for potential tailings reuse. The water was alkaline, with maximum pH values of ≈ 10, and contained potentially toxic elements, such as Sb (up to 0.500 mg/L), As (up to 0.080 mg/L), and Cu (up to 20 mg/L). Gold enrichment areas were found in the tailings dam, with concentrations up to 0.5 g/t. Alignment exists among tailings management, demand for critical raw materials, and increased interest in the processing of low-grade ores and mining waste, which is important in the context of the circular economy. They suggest that valorisation of tailings, although challenging, can be achieved by economic recovery of the more valuable metals.This work was funded the Fundação para a Ciência e a Tecnologia (FCT) through projects UIDB/04683/2020, UIDP/04683/2020, Nano-MINENV 029259 (PTDC/CTAAMB/29259/2017), and by AngloGold Ashanti Brazil