Design optimization of cruciform specimens for biaxial fatigue loading

In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS) method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests. © 2014, Gruppo Italiano Frattura. All rights reserved.

Exposição profissional a chumbo : utilização da protoporfirina-zinco (PPZ) na vigilância de saúde de trabalhadores ex

Resumo Uma estratégia de avaliação e prevenção de riscos na exposição a agentes químicos deve ter sempre em conta que a vigilância do ambiente de trabalho e a da saúde dos trabalhadores são aspectos complementares de uma mesma realidade – os riscos resultantes da interacção entre um agente químico e os trabalhadores a ele expostos. Se à Vigilância Ambiental compete apreciar o risco, pela caracterização do agente no ambiente de trabalho, a Vigilância Biológica pronuncia-se sobre a interacção entre o tóxico e o organismo, avaliando a resposta à agressão química e a evolução das reacções de adaptação ou de desajuste face à absorção do tóxico. Os Indicadores Biológicos, deste modo, assumem um estatuto de instrumento privilegiado na vigilância da saúde dos trabalhadores expostos, na medida em que medem a quantidade de tóxico que efectivamente penetrou e foi absorvido, ou o resultado (efeito) determinado por essa mesma dose. O presente estudo procura contribuir para a definição de um quadro metodológico de utilização dos Indicadores Biológicos na avaliação/gestão da exposição profissional ao chumbo, designadamente apreciando a variação da protoporfirina-zinco (PPZ), indicador até ao presente ainda não utilizado em Portugal. O chumbo é um metal de ocorrência natural, cujos níveis nos diversos ecossistemas resultam, principalmente, das actividades antropogénicas de natureza doméstica e industrial. A sua capacidade poluente é assinalável, representando uma fonte de exposição permanente para o homem, demonstrável pela sua constante presença no organismo apesar de não desempenhar qualquer tipo de função fisiológica. São actualmente inúmeras as suas aplicações, tornando a exposição profissional ao chumbo uma realidade vasta: indústrias de acumuladores eléctricos, de vidros, de plásticos e de munições, construção civil, manutenção e reparação automóvel e de navios, fabrico de tintas, indústrias electrónicas, fundições e actividades de soldadura são, entre outras, situações onde é uma realidade a ter em conta. A penetração dos compostos inorgânicos de chumbo no organismo efectua-se principalmente por via respiratória, não sendo, no entanto, desprezável, a sua penetração por via digestiva. As partículas absorvidas são transportadas pelo sangue principalmente ligadas aos eritrocitos (95%), distribuem-se pelos tecidos moles e depositam-se essencialmente no tecido ósseo, onde representam mais de 90% da carga corporal do total absorvido e tendo aí um elevado tempo de semi-vida (mais de 20 anos). Não é metabolizado no organismo e a sua eliminação efectua-se essencialmente por via renal,sendo igualmente excretado, em menor escala, através das fezes, do suor, da saliva, das faneras e do leite materno. O conhecimento científico evidencia que concentrações sanguíneas de chumbo entre 20 e 50 mg/dL são susceptíveis de determinar efeitos adversos no homem, podendo ser afectados o sistema hematopoiético, o sistema nervoso, o sistema cardiovascular, o sistema reprodutor e o sistema imunitário. Contudo, ainda muito há a clarificar no âmbito da toxicidade do chumbo. Os níveis de exposição a que correspondem as alterações nos diversos órgãos e sistemas continuam a ser motivo de alguma controvérsia. As características carcinogénicas e mutagénicas do chumbo são, ainda, um campo de vasta exigência de investigação. A intoxicação por chumbo e seus sais (Saturnismo) de origem ocupacional é reconhecida em Portugal como doença profissional (grupo 1 - Doenças Provocadas por Agentes Químicos, da Lista das Doenças Profissionais). É uma intoxicação do tipo crónico, fruto da absorção contínua de doses relativamente pequenas durante longo período, evidenciando-se no seu início por sinais e sintomas vagos e difusos de grande inespecificidade, que podem incluir, nomeadamente, perda de apetite, sabor metálico na boca, palidez, mal-estar e fadiga, cefaleias, mialgias e artralgias, irritabilidade, tremores finos, obstipação, cólicas abdominais, insónias, déficit da memória de curto prazo e da capacidade de concentração. Um importante conjunto de indicadores biológicos pode ser utilizado na vigilância periódica da saúde de trabalhadores nestas condições de exposição. Tais indicadores (de dose ou de efeito), encerram diferentes significados e comportam distintas exigências, competindo ao Médico do Trabalho, no âmbito dos programas de prevenção dos efeitos adversos relacionados com a exposição profissional a chumbo, seleccionar a sua utilização e interpretar a sua informação, de modo a avaliar a interacção do tóxico com o organismo numa fase de reversibilidade. O presente estudo envolveu 180 trabalhadores dos quais 110 apresentavam plumbémias (Pb-S) iguais ou superiores a 40 mg/dL. Além da Pb-S, a todos foi doseada a protoporfirina-zinco (PPZ) e efectuado o Hemograma e a cerca de 25% foi determinada a concentração do ácido d-aminolevulínico urinário (ALA-U). Os doseamentos da PPZ efectuados em amostra de sangue capilar através de um hematofluorímetro portátil revelaram-se de total fiabilidade, dando significado a uma técnica de fácil execução e baixo custo. A avaliação do tipo de colheita urinária para doseamento do ALA-U concluiu pela necessidade de recurso a urinas de 24 horas.Os resultados do estudo evidenciaram uma elevada associação entre a PPZ e a Pb-S, com uma maior magnitude e de início mais precoce do que o que registado na associação da Pb-S com o ALA-U. Revelaram, ainda, fracos níveis de associação da hemoglobina (e outros parâmetros hematológicos) com a Pb-S. E demonstraram para um cut-off de 100 mg/ dL de PPZ, taxa de falsos negativos e falsos positivos, para plumbémias a partir de 70 mg/dL, inferiores a 20%. Assim, concluiu-se que, nos protocolos de vigilância de saúde de trabalhadores expostos a chumbo, o doseamento da PPZ por hematofluorímetro, em sangue de colheita capilar, é adequado, fiável e de realização preferencial em relação ao do ALA-U. Concluiu-se, também, que a realização do hemograma apenas se justifica em situações individuais que clinicamente o tornem aconselhável. E que estes protocolos devem incluir a realização da Pb-S e da PPZ, podendo, em situações de controlo rigoroso (ambiental, biológico e clínico), basear-se apenas na determinação da PPZ reservando os outros indicadores para aprofundar a investigação médica nos casos de taxas elevadas desta ou de situações limitantes. ■ Résumée Une stratégie d’évaluation et de prévention des risques d’exposition aux agents chimiques doit toujours tenir en considération que la vigilance du lieu de travail et de la santé des travailleurs sont des aspects complémentaires d’une même réalité – les risques résultant d’une interaction entre l’agent chimique et les travailleurs exposés. Si c’est à la Vigilance Ambiantale de juger le risque, par la caractérisation de l’agent dans le lieu de travail, la Vigilance Biologique, elle, se prononce sur l’interaction entre le toxique et l’organisme, évaluant la réponse à l’agression chimique et l’évolution des réactions d’adaptation ou de rupture face à l’absorption du toxique. Les Indicateurs Biologiques assument ainsi un statut d’instrument privilégié de vigilance de la santé des travailleurs exposés, dans la mesure où ils déterminent la quantité de toxique qui a effectivement été pénétré et absorbé, ou le résultat (effet) déterminé par cette dose. Cette étude-ci cherche à contribuer à la définition d’un cadre méthodologique d’utilisation des Indicateurs Biologiques dans l’évaluation/ gestion de l’exposition professionnelle au plomb inorganique, évaluant spécialement le comportement de la protoporphirine-zinc (PPZ), indicateur pas encore utilisé au Portugal.Le plomb est un métal d’occurrence naturelle dont les niveaux dans les différents écosystèmes en résultent, principalement, des activités anthropogéniques de nature domestique et industrielle. Sa capacité polluante peut être signalée, représentant une source d’exposition permanente pour l’homme, celle-ci démontrable par sa présence continue dans l’organisme, même si elle n’y accomplit aucune fonction physiologique. Actuellement ses applications sont innombrables, faisant de l’exposition professionnelle au plomb une réalité de grande ampleur : industries d’accumulateurs électriques, de verre, de plastique et de munitions, bâtiments, manutention et réparation automobile et navale, fabrication d’encres, industries électroniques, fontes et activités de soudure sont, entre autres, des situations réelles a en tenir compte. La pénétration du plomb inorganique dans l’organisme se fait principalement par voie respiratoire, pouvant se faire également par voie digestive. Les particules absorbées sont transportées par le sang, surtout liées aux érythrocytes (95%), se repartent à travers les tissus mous et se déposent essentiellement dans le tissu osseux, où elles représentent plus de 90% de la charge corporelle de ce qui a été absorbé et ont un temps de demi-vie élevé (plus de 20 ans). Le plomb n’est pas métabolisé dans l’organisme et son élimination se fait essentiellement par voie rénale, pouvant tout de même, à une moindre échelle, être excrété dans les fèces, de la sueur, de la salive, des ongles, des cheveux et du lait maternel. La connaissance scientifique met en évidence que des concentrations sanguines de plomb entre 20 et 50 mg/dL sont susceptibles de déterminer des effets adverses dans l’homme, pouvant les systèmes hématopoïétique, nerveux, cardiovasculaire, reproducteur et immunitaire en être affectés. Cependant, il en reste beaucoup à éclaircir dans le domaine de la toxicité du plomb. Les niveaux d’exposition auxquels correspondent les modifications des divers organes et systèmes, demeurent toujours sujet de quelque controverse. Les caractéristiques carcinogèniques et mutagèniques du plomb restent toujours un champ d’investigation d’une grande exigence. L’intoxication par le plomb et ses sels (Saturnisme) d’origine occupationnelle est reconnue, au Portugal, comme une maladie professionnelle (groupe 1- Maladies Provoquées par des Agents Chimiques, de la Liste des Maladies Professionnelles). C’est une intoxication du tipe chronique, due à l’absorption continue de doses relativement petites pendant une longue période, mise en évidence à travers des signes et des symptômes vagues et diffus sans grande spécificité, lesquels peuvent inclure, particulièrement, le manque d’appétit, goût métallique dans la bouche, pâleur, malaise et fatigue, céphalées, myalgies et arthralgies, irritabilité, tremblements fins, constipation, coliques abdominales, insomnies, déficit de la mémoire à court terme et de la capacité de concentration.Un ensemble important d’indicateurs biologiques peut être employé dans la vigilance périodique de la santé des travailleurs dans ces conditions d’exposition. Ces indicateurs (de dose ou d’effet) renferment différentes significations et comportent diverses exigences, devant le Médecin de Travail, dans le domaine des programmes de prévention des effets adverses qui sont en relation avec l’exposition professionnelle au plomb, sélectionner son utilisation et interpréter son information de façon à évaluer l’interaction de l’élément toxique avec l’organisme à un stade de réversibilité. L’étude ci-présent engloba 180 travailleurs desquels 110 présentaient des plombémies (Pb-S) égales ou supérieures à 40 mg/dL. À part la Pb-S, la protoporphyrine-zinc (PPZ) leur a été prise en dosage et un Hémogramme fut effectué et fut déterminé l’acide d- aminolévulinique urinaire (ALA-U) sur environ 25% des travailleurs. Le dosage de la PPZ efectué en échantillon de sang capillaire par un fluorimètre portable, s’est accomplit d’une fiabilité total, donnant du sgnificat à une téchnique de facile execution et bas prix. L’évaluation de la prise urinaire par dosage du ALA-U conclut au besoin d’un recours aux urines de 24 heures Les résultats de l’étude ont mis en évidence une association élevée entre la PPZ et la Pb- S, avec une intensité majeure et de début plus précoce par rapport à celui qui fut registré lors de l’association de la Pb-S avec la ALA-U. Ces résultats ont également montré de faibles niveaux d’association entre l’hémoglobine (et autres paramètres hématologiques) et la Pb-S. Ils ont démontré aussi, une valeur de cut-off de 100 mg/dL de PPZ, des taux de faux négatifs et faux positifs, pour des plombémies de 70 mg/dL, inférieurs à 20%. On peut donc conclure que dans les protocoles de vigilance de la santé des travailleurs exposés au plomb, le dosage de la PPZ par fluorimetrie dans le sang capillaire est adéquat, fiable et de réalisation préférentielle par rapport à celui du ALA-U. On peut également conclure que la réalisation de l’hémogramme ne se justifie que dans les cas individuels où, cliniquement, celui-ci est conseillé. De plus, ces protocoles doivent inclure la réalisation de la Pb-S et de la PPZ, pouvant, en cas de contrôle rigoureux (ambiantal, biologique et clinique), s’appuyer que dans la détermination de la PPZ réservant les autres indicateurs pour approfondir l’investigation médicale dans les cas où les taux de celle-ci sont élevés ou dans les cas de situations limitantes. ■ Summary Any strategy to evaluate and prevent the risks of chemical agents exposure must always regard the work environment and workers health as complementary aspects of one reality - the resulting risks from the interaction between the chemical agent and the exposed workers. It is the responsibility of Environmental Monitoring to evaluate the risks of exposure by the characterization of the chemical agent in the work environment. Biological Monitoring, on the other hand, pronounces itself over the toxin and body interaction, evaluating human response to the chemical aggression and the body adaptations to the toxic absorption. Biological Exposure Indices (BEI) assume, therefore, a privileged status among exposed workers' health monitoring instruments, as they measure the actual penetrated and absorbed toxic quantity and the effect it produces. This research study aims to contribute to the definition of a methodological strategy on the utilization of BEI’s in evaluating inorganic lead's occupational exposure, more specifically appreciating the zinc protoporphyrin (ZPP) variation, an index that has never been taken under consideration in Portugal until now. Lead is a natural metal whose ecosystem’s levels are mainly due to domestic and industrial anthropogenic activities. Its pollutant capacity is notable, representing a permanent exposure risk shown by its constant presence in the human body, although it has no physiologic function. Nowadays, lead's applications are countless, turning its professional exposure a huge reality: storage batteries industries, glass industries, plasterers and munitions industries, building construction, ships and motor car maintenance and repairing, ink manufacture, electronics industries, foundries and other soldering activities are, among so many other, realities to attend to. Respiration is the main cause of human body's inorganic lead absorption, although digestive pathway must not to be ignored. The absorbed particles are transported by blood, essentially bounded to erythrocytes (95%). It is distributed by soft tissues and settled mainly on bone tissues, where it represents approximately 90% of the total body charge and has a high half-life time (more than 20 years). It is not metabolized by the organism, its elimination being effectuated by renal activity and, in smaller scale, through lees, sweat, saliva, nails, hair and maternal milk.Scientific knowledge shows that concentrations of lead in blood between 20 e 50 mg/dL are susceptible to determine adverse effects in man and able to affect the hematopoietic system, the nervous system, the cardiovascular system, the reproductive system and the immunological system. Nevertheless, there's still much to be learned and clarified about lead's toxicity. The correlation between exposure levels and human's systems and organs alteration levels continues to be a centre of controversies. Still, lead's carcinogenic and mutagenic characteristics continue to be a high demanding research field. Intoxication by lead and its compounds (saturnism), from occupational origin, is recognized in Portugal as an occupational disease, included in Group 1 - Chemical Agents Caused Diseases, on the Occupational Diseases List. It is a chronic intoxication caused by a continuous absorption of small doses, throughout a long period of time. Its signs and symptoms are diffuse and imprecise, of great unspecificity, such as loss of appetite, metallic flavor in the mouth, paleness, ailment and fatigue, headaches, myalgia and arthralgia, irritability, thin tremors, constipation, abdominal pain, insomnias, short memory loses and inability to concentrate. A considered number of BEI’s can be used in Periodic Health Monitoring of workers in such exposure conditions. Such BEI (dose indices or effect indices) provide different meanings and imply different procedures, being Occupational Doctors responsibility, in the context of lead related adverse effects preventive programmes, to select and interpret its information, in order to evaluate the interaction between toxic and organism in a reversible phase of the toxic action. The present research study involved 180 workers, 110 of which presented blood lead levels (PbB) above or equal to 40 mg/dL. Besides PbB, all workers has been evaluated for zinc protoporphyrin levels (PPZ) and submitted to a haemogram. About 25% of the workers were selected for d-aminolevulinic urinary acid (ALA-U) determination. The evaluation of PPZ, by a portable hematofluorometer using capillary blood samples, turned out to be an easy procedure with low costs and total warrantability. As in regard for ALA- U procedure, it was concluded the necessity of 24 hours urine samples. This research results underlined a strong connection between ZPP and PbB, which was found to to be stringer and to begin earlier than it was registered for PbB and ALA-U association. The same study also revealed a low association level between PbB and hemoglobin or other hematological indices. It was also verified less than 20% of false negatives and false positives cases when admitted a ZPP 100 mg/dL cut off value for PbB³ 70 mg/dL. As in result it was concluded that in Health Monit

Protein folding, metal ions and conformational states: the case of a di-cluster ferredoxin

Dissertation presented to obtain the PhD degree in Biochemistry at the Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

Noble metal nanoparticles - Au and Ag - for biodetection

Dissertation submitted for obtainment of the Master’s Degree in Biotechnology, by the Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

Greener Selective Cycloalkane Oxidations with Hydrogen Peroxide Catalyzed by Copper-5-(4-pyridyl)tetrazolate Metal-Organic Frameworks

Microwave assisted synthesis of the Cu(I) compound [Cu(µ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2]n∙(DMF)2n (2) and [Cu(µ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h−1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1–3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity.

Hydrogenating activity of Pt/zeolite catalysts focusing acid support and metal dispersion influence

Toluene hydrogenation was studied over catalysts based on Pt supported on large pore zeolites (HUSY and HBEA) with different metal/acid ratios. Acidity of zeolites was assessed by pyridine adsorption followed by FTIR showing only small changes before and after Pt introduction. Metal dispersion was determined by H2–O2 titration and verified by a linear correlation with the intensity of Pt0–CO band obtained by in situ FTIR. It was also observed that the electronic properties of Pt0 clusters were similar for the different catalysts. Catalytic tests showed rapid catalyst deactivation with an activity loss of 80–95% after 60 min of reaction. The turnover frequency of fresh catalysts depended both on metal dispersion and the support. For the same support, it changed by a 1.7-fold (HBEA) and 4.0-fold (HUSY) showing that toluene hydrogenation is structure-sensitive, i.e. hydrogenating activity is not a unique function of accessible metal. This was proposed to be due to the contribution to the overall activity of the hydrogenation of adsorbed toluene on acid sites via hydrogen spillover. Taking into account the role of zeolite acidity, the catalysts series were compared by the activity per total adsorbing sites which was observed to increase steadily with nPt/(nPt + nA). An increase of the accessible Pt atoms leads to an increase on the amount of spilled over hydrogen available in acid sites therefore increasing the overall activity. Pt/HBEA catalysts were found to be more active per total adsorbing site than Pt/HUSY which is proposed to be due to an augmentation in the efficiency of spilled over hydrogen diffusion related to the proximity between Pt clusters and acid sites. The intervention of Lewis acid sites in a greater extent than that measured by pyridine adsorption may also contribute to this higher activity of Pt/HBEA catalysts. These results reinforce the importance of model reactions as a closer perspective to the relevant catalyst properties in reaction conditions.

Integrated biomarker responses of an estuarine invertebrate to high abiotic stress and decreased metal contamination

An integrated chemical-biological effects monitoring was performed in 2010 and 2012 in two NW Iberian estuaries under different anthropogenic pressure. One is low impacted and the other is contaminated by metals. The aim was to verify the usefulness of a multibiomarker approach, using Carcinus maenas as bioindicator species, to reflect diminishing environmental contamination and improved health status under abiotic variation. Sampling sites were assessed for metal levels in sediments and C. maenas, water abiotic factors and biomarkers (neurotoxicity, energy metabolism, biotransformation, anti-oxidant defences, oxidative damage). High inter-annual and seasonal abiotic variation was observed. Metal levels in sediments and crab tissues were markedly higher in 2010 than in 2012 in the contaminated estuary. Biomarkers indicated differences between the study sites and seasons and an improvement of effects measured in C. maenas from the polluted estuary in 2012. Integrated Biomarker Response (IBR) index depicted sites with higher stress levels whereas Principal Component Analysis (PCA) showed associations between biomarker responses and environmental variables. The multibiomarker approach and integrated assessments proved to be useful to the early diagnosis of remediation measures in impacted sites.

Modification of cell volume and proliferative capacity of Pseudokirchneriella subcapitata cells exposed to metal stress

The impact of metals (Cd, Cr, Cu and Zn) on growth, cell volume and cell division of the freshwateralga Pseudokirchneriella subcapitata exposed over a period of 72 h was investigated. The algal cells wereexposed to three nominal concentrations of each metal: low (closed to 72 h-EC10values), intermediate(closed to 72 h-EC50values) and high (upper than 72 h-EC90values). The exposure to low metal concen-trations resulted in a decrease of cell volume. On the contrary, for the highest metal concentrations anincrease of cell volume was observed; this effect was particularly notorious for Cd and less pronouncedfor Zn. Two behaviours were found when algal cells were exposed to intermediate concentrations ofmetals: Cu(II) and Cr(VI) induced a reduction of cell volume, while Cd(II) and Zn(II) provoked an oppositeeffect. The simultaneous nucleus staining and cell image analysis, allowed distinguishing three phases inP. subcapitata cell cycle: growth of mother cell; cell division, which includes two divisions of the nucleus;and, release of four autospores. The exposure of P. subcapitata cells to the highest metal concentrationsresulted in the arrest of cell growth before the first nucleus division [for Cr(VI) and Cu(II)] or after thesecond nucleus division but before the cytokinesis (release of autospores) when exposed to Cd(II). Thedifferent impact of metals on algal cell volume and cell-cycle progression, suggests that different toxic-ity mechanisms underlie the action of different metals studied. The simultaneous nucleus staining andcell image analysis, used in the present work, can be a useful tool in the analysis of the toxicity of thepollutants, in P. subcapitata, and help in the elucidation of their different modes of action.

Optimization of cruciform specimens for biaxial fatigue loading with direct multi search

In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriate for the load capacity installed. At the present time there are no standard specimen's geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriate for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress distributions on the loading directions are uniform and maximum with two limit phase shift loading conditions (delta = 0 degrees and (delta = 180 degrees). Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS) method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests

Metal ions and protein folding: conformational and functional interplay

Dissertation presented to obtain a PhD degree in Biochemistry at Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

Metal ions modulate the folding and stability of the tumor suppressor protein S100A2

Febs Journal (2009)276:1776-1786

Stress Ratio Effects on the fatigue Properties of Biaxially Loaded Tubular FRP-Specimens – Experimental Study

In this work tubular fiber reinforced specimens are tested for fatigue life. The specimens are biaxially loaded with tension and shear stresses, with a load angle β of 30° and 60° and a load ratio of R=0,1. There are many factors that affect fatigue life of a fiber reinforced material and the main goal of this work is to study the effects of load ratio R by obtaining S-N curves and compare them to the previous works (1). All the other parameters, such as specimen production, fatigue loading frequency and temperature, will be the same as for the previous tests. For every specimen, stiffness, temperature of the specimen during testing, crack counting and final fracture mode are obtained. Prior to testing, a study if the literature regarding the load ratio effects on composites fatigue life and with that review estimate the initial stresses to be applied in testing. In previous works (1) similar specimens have only been tested for a load ratio of R=-1 and therefore the behaviour of this tubular specimens for a different load ratio is unknown. All the data acquired will be analysed and compared to the previous works, emphasizing the differences found and discussing the possible explanations for those differences. The crack counting software, developed at the institute, has shown useful before, however different adjustments to the software parameters lead to different cracks numbers for the same picture, and therefore a better methodology will be discussed to improve the crack counting results. After the specimen’s failure, all the data will be collected and stored and fibre volume content for every specimen is also determinate. The number of tests required to make the S-N curves are obtained according to the existent standards. Additionally are also identified some improvements to the testing machine setup and to the procedures for future testing.

Heavy-metal resistance in Marinobacter aquaeolei 617 insights into copper resistance

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Biotecnologia

The influence of task design on upper limb muscles fatigue during low-load repetitive work: A systematic review

Ergonomic interventions such as increased scheduled breaks or job rotation have been proposed to reduce upper limb muscle fatigue in repetitive low-load work. This review was performed to summarize and analyze the studies investigating the effect of job rotation and work-rest schemes, as well as, work pace, cycle time and duty cycle, on upper limb muscle fatigue. The effects of these work organization factors on subjective fatigue or discomfort were also analyzed. This review was based on relevant articles published in PubMed, Scopus and Web of Science. The studies included in this review were performed in humans and assessed muscle fatigue in upper limbs. 14 articles were included in the systematic review. Few studies were performed in a real work environment and the most common methods used to assess muscle fatigue were surface electromyography (EMG). No consistent results were found related to the effects of job rotation on muscle activity and subjective measurements of fatigue. Rest breaks had some positive effects, particularly in perceived discomfort. The increase in work pace reveals a higher muscular load in specific muscles. The duration of experiments and characteristics of participants appear to be the factors that most have influenced the results. Future research should be focused on the improvement of the experimental protocols and instrumentation, in order to the outcomes represent adequately the actual working conditions. Relevance to industry: Introducing more physical workload variation in low-load repetitive work is considered an effective ergonomic intervention against muscle fatigue and musculoskeletal disorders in industry. Results will be useful to identify the need of future research, which will eventually lead to the adoption of best industrial work practices according to the workers capabilities.

The influence of pauses on the fatigue of upper limb muscles during the task of ironing

The aim of this study was to analyze the influence of position and pauses on muscle activity and fatigue during the task of ironing. Ten female participants performed the task of ironing in two different positions (standing and sitting) for 10 min each with a 1-min pause at the end of each task. Muscle activity and fatigue from the upper trapezium, anterior deltoid, and pectoralis major were analyzed using surface electromyography. The results showed that the positions had no significant influence on muscle activity; nevertheless, they had significant influence on muscular fatigue. In addition, the pauses were possibly beneficial in decreasing the muscle fatigue, but the results were not conclusive.