Characterization of aluminium single-lap joints for high temperature applications

In this study, an experimental investigation into the shear strength behaviour of aluminium alloy single-lap adhesive joints was carried out in order to understand the effect of temperature on the strength of adhesively bonding joints. Single lap joints (SLJs) were fabricated and tested at RT and high temperatures (100ºC, 125ºC, 150ºC, 175ºC and 200ºC). Results showed that the failure loads of the single-lap joint test specimens vary with temperature and this needs to be considered in any design procedure. It is shown that, although the tensile stress decreased with temperature, the lap-shear strength of the adhesive increased with increasing of temperature up to the glass transition of the adhesive (Tg) and decreased for tests above the Tg.

Using a cohesive damage model to predict the tensile behaviour of CFRP single-strap repairs

This work addresses both experimental and numerical analyses regarding the tensile behaviour of CFRP single-strap repairs. Two fundamental geometrical parameters were studied: overlap length and patch thickness. The numerical model used ABAQUS® software and a developed cohesive mixed-mode damage model adequate for ductile adhesives, and implemented within interface finite elements. Stress analyses and strength predictions were carried out. Experimental and numerical comparisons were performed on failure modes, failure load and equivalent stiffness of the repair. Good correlation was found between experimental and numerical results, showing that the proposed model can be successfully applied to bonded joints or repairs.

Occupational stress and coping resources in physiotherapists: a survey of physiotherapists in three general hospitals

Objectives - To identify occupational stressors and coping resources in a group of physiotherapists, and to analyse interactions between subjective levels of stress, efficacy in stress resolution and coping resources used by these professionals. Design - A sample of 55 physiotherapists working in three general hospitals in Portugal completed the Coping Resources Inventory for Stress, the Occupational Stressors Inventory and two subjective scales for stress and stress resolution. Main results - Most physiotherapists perceived that they were moderately stressed (19/55, 35%) or stressed (20/55, 36%) due to work, and reported that their efficacy in stress resolution was moderate (25/54, 46%) or efficient (23/54, 42%). Issues related to lack of professional autonomy, lack of organisation in the hierarchical command chain, lack of professional and social recognition, disorganisation in task distribution and interpersonal conflicts with superiors were identified as the main sources of stress. The most frequently used coping resources were social support, stress monitoring, physical health and structuring. Perceived efficacy in stress resolution was inversely related to perceived level of occupational stress (r = −0.61, P < 0.01). Significant correlations were found between several coping resources and the perceived level of stress and efficacy in stress resolution. Associations between problem solving, cognitive restructuring and stress monitoring and both low levels of perceived stress and high levels of perceived efficacy were particularly strong. Implications for practice - The importance of identifying stressors and coping resources related to physiotherapists’ occupational stress, and the need for the development of specific training programmes to cope with stress are supported.

Buckling strength of adhesively-bonded single and double-strap repairs on carbon-epoxy structures

This work reports on an experimental and finite element method (FEM) parametric study of adhesively-bonded single and double-strap repairs on carbon-epoxy structures under buckling unrestrained compression. The influence of the overlap length and patch thickness was evaluated. This loading gains a particular significance from the additional characteristic mechanisms of structures under compression, such as fibres microbuckling, for buckling restrained structures, or global buckling of the assembly, if no transverse restriction exists. The FEM analysis is based on the use of cohesive elements including mixed-mode criteria to simulate a cohesive fracture of the adhesive layer. Trapezoidal laws in pure modes I and II were used to account for the ductility of most structural adhesives. These laws were estimated for the adhesive used from double cantilever beam (DCB) and end-notched flexure (ENF) tests, respectively, using an inverse technique. The pure mode III cohesive law was equalled to the pure mode II one. Compression failure in the laminates was predicted using a stress-based criterion. The accurate FEM predictions open a good prospect for the reduction of the extensive experimentation in the design of carbon-epoxy repairs. Design principles were also established for these repairs under buckling.

Strength improvement of adhesively-bonded joints using a reverse-bent geometry

Adhesive bonding of components has become more efficient in recent years due to the developments in adhesive technology, which has resulted in higher peel and shear strengths, and also in allowable ductility up to failure. As a result, fastening and riveting methods are being progressively replaced by adhesive bonding, allowing a big step towards stronger and lighter unions. However, single-lap bonded joints still generate substantial peel and shear stress concentrations at the overlap edges that can be harmful to the structure, especially when using brittle adhesives that do not allow plasticization in these regions. In this work, a numerical and experimental study is performed to evaluate the feasibility of bending the adherends at the ends of the overlap for the strength improvement of single-lap aluminium joints bonded with a brittle and a ductile adhesive. Different combinations of joint eccentricity were tested, including absence of eccentricity, allowing the optimization of the joint. A Finite Element stress and failure analysis in ABAQUS® was also carried out to provide a better understanding of the bent configuration. Results showed a major advantage of using the proposed modification for the brittle adhesive, but the joints with the ductile adhesive were not much affected by the bending technique.

Effect of hole drilling at the overlap on the strength of single-lap joints

Bonded unions are gaining importance in many fields of manufacturing owing to a significant number of advantages to the traditional fastening, riveting, bolting and welding techniques. Between the available bonding configurations, the single-lap joint is the most commonly used and studied by the scientific community due to its simplicity, although it endures significant bending due to the non-collinear load path, which negatively affects its load bearing capabilities. The use of material or geometric changes in single-lap joints is widely documented in the literature to reduce this handicap, acting by reduction of peel and shear peak stresses at the damage initiation sites in structures or alterations of the failure mechanism emerging from local modifications. In this work, the effect of hole drilling at the overlap on the strength of single-lap joints was analyzed experimentally with two main purposes: (1) to check whether or not the anchorage effect of the adhesive within the holes is more preponderant than the stress concentrations near the holes, arising from the sharp edges, and modification of the joints straining behaviour (strength improvement or reduction, respectively) and (2) picturing a real scenario on which the components to be bonded are modified by some external factor (e.g. retrofitting of decaying/old-fashioned fastened unions). Tests were made with two adhesives (a brittle and a ductile one) varying the adherend thickness and the number, layout and diameter of the holes. Experimental testing showed that the joints strength never increases from the un-modified condition, showing a varying degree of weakening, depending on the selected adhesive and hole drilling configuration.

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.

Acute renal failure after rifampicin

A patient with miliary tuberculosis and a chronic urogenital focus is described, who had a borderline renal function at diagnosis and developed overt renal failure upon daily treatment with rifampin (RMP), isoniazid (INH) and ethambutol (EMB). This is the first Brazilian report of BMP induced renal damage. A renal biopsy taken on the third day of oliguria showed recent tubular necrosis with acute interstitial inflammation and granuloma formation. The aspect of the granulomatous lesion hightly suggested drug etiology because of the lack of palisading, high incidence of neutrophils and absence of facid-fast bacilli. This is the first presentation of an acute granulomatous interstitial nephritis probably due to RMP. Furthermore the pathogenesis of the renal damage caused by tuberculosis and RMP are discussed.

The influence of geometric factors on the wall shear stress distribution in realistic human coronary arteries

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Biomédica. A presente dissertação foi desenvolvida no Erasmus Medical Center em Roterdão, Holanda

Efeito de alterações geométricas na resistência de juntas de sobreposição

A utilização de juntas coladas em aplicações industriais tem vindo a aumentar nos últimos anos, em detrimento dos métodos tradicionais de ligação tais como a soldadura, brasagem, ligações aparafusadas e rebitadas. As juntas de sobreposição simples são o tipo de juntas mais frequentemente utilizadas em aplicações industriais, porque são as mais simples de fabricar. No entanto, a aplicação descentrada da carga neste tipo de junta provoca efeitos de flexão que originam o aparecimento de tensões normais na direção da espessura do adesivo (arrancamento), reduzindo assim a resistência da junta colada. De uma maneira geral, existem dois tipos de métodos para reduzir as concentrações de tensões. O primeiro é utilizar alterações no próprio material, otimizando as propriedades do adesivo e do substrato, enquanto o segundo método envolve alterar a geometria da junta, como por exemplo utilizando filetes de adesivo, chanfros nas extremidades dos substratos, aplicar uma geometria ondulada ou dobrar os substratos na zona de sobreposição, ou ainda utilizar rasgos nos substratos ao longo da sobreposição. Neste trabalho é realizado um estudo experimental e numérico por Elementos Finitos de duas alterações efetuadas à geometria de juntas de sobreposição simples, de modo a aumentar a sua resistência comparativamente às juntas sem alteração geométrica. A primeira condição efetuada foi a utilização de rasgos nas extremidades do comprimento de sobreposição e a segunda foi a utilização de rasgos a meio do comprimento de sobreposição. No final do estudo experimental, verificou-se que a resistência da ligação foi significativamente melhorada com algumas das configurações testadas para cada alteração, e foi possível estabelecer em ambos os casos a configuração ótima. Numa fase posterior, procedeu-se à simulação numérica, que incluiu uma análise de tensões e previsão do comportamento das juntas através de modelos de dano coesivo. A análise permitiu obter os modos de rotura, as curvas força-deslocamento e a resistência das juntas. Obteve-se uma concordância bastante boa com os resultados experimentais, o que mostrou a adequabilidade do método de previsão proposto para estimar o comportamento das juntas.

Tuberculosis in patients with chronic renal failure

Nine cases of tuberculosis (TB) were diagnosed among 800 uremic patients, followed-up during 11 years, a prevalence of 1125%, 2.5 times higher than that in the general population. Six patients (66.7%) had lymph node involvement (4 cervical and 2 mediastinal). Three patients (33.3%) had pulmonary involvement (2 pleuro-pulmonary and 1 bilateral apical pulmonary). Eight patients were undergoing dialysis and 1 was pre-dialytic. The duration of dialysis ranged from 1 to 60 months. Three patients had previously received immunosuppressive drugs for unsuccessful renal transplantation. Daily fever was present in all but one patient; he was asymptomatic and TB was suspected after routine chest radiography. Biopsy was the diagnostic procedure in 7 patients (77.8%), four by direct cervical lymph node biopsy, 2 by mediastinal, performed by mediastinoscopy and 1 by pleural biopsy. In 2 other patients TB was confirmed by the presence of tubercle bacilli; in sputum (1 patient) and in a bronchial flushing specimen (the other patient). Triple therapy was used in all patients (isoniazid and ethambutol in all), plus rifampicin in 8 and streptomycin in 1. One patient had jaundice and another had optical neuritis. Five patients were cured. The other four died during treatment of causes unrelated to TB or its treatment.

Contributo para o estudo da influência do stress na resposta imunitária à vacina contra a gripe em profissionais de saúde

Resumo: Os profissionais de saúde podem estar expostos a vários factores indutores de stress crónico nomeadamente de natureza profissional destacando-se, entre os seus possíveis efeitos, a diminuição da resposta de anticorpos após administração de vacinas, entre as quais, a vacina contra a gripe. Uma vez que os trabalhadores da saúde estão expostos a factores indutores de stress e, simultaneamente, a agentes biológicos cujos efeitos poderão ser prevenidos pela vacinação, é pertinente estudar a influência do stress na resposta imunitária à vacina contra a gripe em enfermeiros. Constituíram objectivos deste trabalho: (1) estudar a associação entre a presença de stress crónico em enfermeiros hospitalares e a “insuficiente” resposta imunitária à vacina contra a gripe, avaliada um mês após a vacinação (T1); (2) estudar a associação entre a presença de stress crónico em enfermeiros hospitalares e a redução dos títulos de anticorpos dirigidos às hemaglutininas seis meses após a vacinação (T6) e (3) identificar algumas características das unidades de internamento e do trabalho dos participantes que possam estar associadas à presença de stress crónico e estudar a sua possível associação com a resposta imunitária à vacina contra a gripe. Realizou-se um estudo caso-controlo incorporado num estudo de coortes e a amostra em estudo foi constituída por 136 enfermeiros saudáveis (83,8% sexo feminino; média de idades de 33anos) de um hospital universitário. Realizaram-se entrevistas individuais e aplicaram-se as versões portuguesas dos questionários The General Health Questionnaire (GHQ12) e Maslach Burnout Inventory – Human Services Survey (MBI-HSS) para determinação da presença de stress crónico pelo método da triangulação, no início do estudo (T0) e realizou-se a recolha de dados relativos à caracterização de elementos de trabalho nas unidades de internamento. Foi administrada a vacina contra a gripe e determinou-se os títulos de anticorpos dirigidos às hemaglutininas de cada estirpe componentes da vacina contra a gripe utilizada em 2007, antes da vacinação, um mês e seis meses após a vacinação. Não se encontrou associação, ao nível de significância de 5%, entre a presença de stress e a “insuficiente” resposta à vacina contra a gripe, avaliada pela taxa de indivíduos que apresentaram um aumento, ao fim de um mês, inferior a quatro vezes os títulos de anticorpos antes da vacinação. No entanto, encontrou-se uma maior proporção de indivíduos com stress no grupo de participantes em que ocorreu uma diminuição do título de anticorpos dirigidos à hemaglutinina AH1 (ac AH1) em T6, quando comparado com o respectivo grupo controlo. A diferença entre grupos foi estatisticamente significativa, quando se avaliou a presença de stress pelo método da triangulação usando a entrevista (p=0,006), pelo método da triangulação usando o GHQ12 (p=0,045) e ainda usando a combinação dos três critérios (p=0,001). Após análise multivariada, verificou-se que a associação entre a presença de XXVI stress e a redução dos ac AH1 em T6 manteve significado estatístico (respectivamente, p= 0,010, p= 0,042 e p=0,002) e apresentou odds ratio ajustados, em função de cada um dos métodos de avaliação da presença de stress, de 3,643, de 2,733 e de 5,223. A quantidade de trabalho percepcionada como sobrecarga constituiu o factor indutor de stress mais vezes referido (58,8% da amostra e 61,8% dos enfermeiros de unidades de internamento), seguida dos conflitos entre profissionais. O contacto com o sofrimento e a morte de doentes foram identificados em quarto lugar pela amostra, mas em segundo pelos enfermeiros de unidades de internamento. Nesses, verificou-se uma associação positiva entre trabalhar em Serviços onde o número de doentes falecidos foi muito elevado e a presença de stress, medido pelo método da triangulação usando a entrevista (p=0,039), usando o GHQ12 (p=0,019), usando a escala de exaustão emocional do MBI-HSS (p=0,012) e pela combinação dos três métodos (p=0,014). Verificou-se também uma associação positiva entre a presença de stress, identificada pelo método da triangulação usando a escala de exaustão emocional do MBI-HSS, e o trabalho em serviços de internamento onde a percentagem de doentes idosos (p=0,025) e a taxa de letalidade (p=0,036) foram elevadas. Contudo, não se encontrou associação entre a exposição muito frequente ao sofrimento e à morte de doentes e a redução do título de ac AH1 em T6. Possivelmente, a exposição a esse factor indutor de stress, apesar de estar relacionada com a presença de stress nos enfermeiros de serviços de internamento, não foi suficientemente intenso para, por si só, estar associada à redução do título de ac AH1 em T6. A associação encontrada entre a presença de stress crónico e a redução do título de anticorpos AH1 em T6 vem apoiar a resposta à questão de investigação inicialmente colocada de que o stress poderá influenciar negativamente a manutenção dos títulos de anticorpos, mesmo em indivíduos adultos não idosos. Assim, o risco de um enfermeiro com stress apresentar redução do título de anticorpos dirigidos à hemaglutinina da estirpe AH1N1 – A/Solomon Islands/3/2006 ao fim dos seis meses do estudo, foi 3,6, 2,7 ou 5,2 vezes superior ao de um enfermeiro sem stress, consoante o critério de stress ter sido determinado, respectivamente, pelo método da triangulação usando a entrevista, pelo método da triangulação utilizando o GHQ12 ou pela combinação dos três critérios. Summary: Health workers may be exposed to various factors causing chronic stress namely those related directly to their activity, in particular the decrease in the capacity of the response of antibodies after the administration of the vaccines, amongst others the Influenza vaccine. Since health workers are exposed to factors causing stress and at the same time biological agents, whose effects may be prevented through vaccination, it is important to study the influence of stress in the immunity response to the Influenza vaccine on nurses. The aims of this study are: (1) to examine the relation between chronic stress in hospital nurses and the “insufficient” immunity response to the Influenza vaccine, assessed at one month after vaccination (T1); (2) to examine the relation between chronic stress in hospital nurses and the decrease of the hemagglutinin titles of antibodies six months after vaccination (T6); (3) to identify some characteristics of internment units and the work of the participants that may be related to the presence of chronic stress and to study its possible relation with the immunity response to the Influenza vaccine. A control-case study, integrated in a coortes study, was carried out and the sample under analysis consisted of 136 healthy nurses (83,8% female; average age 33 years old) from a university hospital. Several individual interviews were conducted and the portuguese versions of General Health Questionnaire (GHQ12) and Maslach Burnout Inventory – Human Services Survey (MBI-HSS) was applied in order to determine the presence of chronic stress, using the triangulation method at the beginning of the study (T0). Data concerning the particular features of the internment units was collected. The Influenza vaccine was administered and the titles of hemagglutinin antibodies of each strain composing the Influenza vaccine used in 2007, before vaccination, and a month and six months after vaccination, were determined. There was no statistically relevant (5%) relation between stress and the “insufficient” immune response to the Influenza vaccine, according to the rate of individuals that showed, after a month, a level of antibodies concentration lower than four times the level prior to the vaccination. Nevertheless, there was a greater number of individuals with stress in the group of participants in which there was a decrease of the hemagglutinin titles of antibodies AH1 (ac AH1) in T6, when compared to the control group under study. The difference between groups was statistically relevant when assessing the presence of stress by triangulation method using the interview (p=0,006), by triangulation method using the GHQ12 (p=0,045) and by the combination of the three criteria (p=0,001). After multivariate analysis, it was verified that the XXVIII relation between the presence of stress and the reduction of the ac AH1 in T6 was statistically relevant (respectively, p= 0,010, p= 0,042 and p=0,002) and the odds ratio were, according to each of the methods used to assess the presence of stress, 3,643, 2,733 and 5,223. Overwork was the most emphasised stress-causing factor (58,8% of the sample and 61,8% of the nurses working in the Internment Units), followed by conflicts arousing among co-workers. Witnessing the suffering and death of patients was ranked as the fourth cause of stress, but the second by the nurses of the internment units. The former revealed a positive connection between working in the services, where there was a high rate of deaths, and the presence of stress, when assessing the presence of stress by triangulation method using the interview (p=0,039), the GHQ12 (p=0,019), the MBI-HSS emotional exhaustion scale (p=0,012) and by the combination of the three criteria (p=0,014).There was also a connection between the presence of stress, identified by the method of triangulation using the MBI-HSS emotional exhaustion scale, and working in the internment units, where the percentage of elderly people (p=0,025) and the mortality rate (p=0,036) were high. However, there was no connection between frequent exposure to suffering and death in patients and the reduction of ac AH1 titles, in T6. Although one can establish a connection between stress in nurses working in the internment units and the aforementioned stress-causing factor, the exposure to that factor was not, per se, intense enough to reduce the ac AH1 title in T6. The relation found between the presence of chronic stress and the reduction of AH1 antibodies titles in T6, corroborates the hypothesis that stress can negatively influence the title of antibodies, even in non-elderly adults. Thus, and according to the criteria used to define stress, by the triangulation method using the interview, by the triangulation method using the GHQ12 or the combination of the three criteria respectively, the risk of a nurse suffering from stress showing a reduction in the title of hemagglutinin antibodies for the strain AH1N1 – A/Solomon Islands/3/2006 six-month after Influenza vaccine was 3,6, 2,7 or 5,2 times greater than on a nurse suffering from no stress at all. Résumé: Les professionnels de la santé peuvent être exposés à différents facteurs inducteurs de stress chronique de nature professionnelle. On remarque, parmi les effets possibles, une baisse de la réponse des anticorps après l´administration de vaccins, comme en particulier, le vaccin de la grippe. Lorsque les professionnels de la santé ont été exposés à des facteurs inducteurs de stress, et de manière simultanée, à des agents biologiques dont les effets pourront être prévenus par la vaccination, il est pertinent d´étudier l´influence du stress dans la réponse immunitaire au vaccin de la grippe chez les infirmiers. Ils ont constitué des objectifs d´études et de discussion : (1) étudier l´association entre la présence de stress chronique chez les infirmiers, en milieu hospitalier, et la “insuffisant” réponse immunitaire au vaccin de la grippe, vérifiée à un mois après la vaccination (T1); (2) étudier l´association entre la présence de stress chronique chez les infirmiers, en milieu hospitalier, et la réduction de la teneur des anticorps dirigé à la hémaglutinina six mois après la vaccination (T6) (3) identifier certaines caractéristiques des unités d´internement, et étudier les aspects du travail des participants, qui puissent être associée à la présence de stress chronique et étudier sa possible association avec la réponse immunitaire au vaccin de la grippe. Une étude cas-contrôle incorporée dans une étude de groupe a été réalisée et un échantillon, pour étude, a été constitué par 136 infirmiers sains (83,8% de sexe féminin, âge moyen 33 ans) travaillant dans un hôpital universitaire. Des entretiens individuels ont été réalisés et les versions portugaises des questionnaires de General Health Questionnaire (GHQ12) et Maslach Burnout Inventory- Human Service Survey (MBI-HSS) ont été utilisés pour déterminer la présence de stress chronique grâce à la méthode de triangulation, au début de l´étude (T0) et un relevé de données relatives à la caractérisation d´éléments de travail dans les unités d´internement a été fait. Le vaccin de la grippe a été administré et les teneurs en anticorps dirigés aux hémaglutininas de chaque composant du vaccin de la grippe pour 2007 ont été déterminés, avant la vaccination et un mois et six mois après. On n´a pas trouvé d´association, à un niveau significatif de au moins 5%, entre la présence de stress et la “insuffisant” réponse au vaccin de la grippe, évaluée par le taux d´individus qui ont présenté une augmentation, à la fin du mois, inférieur à quatre fois la teneur des anticorps par rapport à avant la vaccination. Cependant , on a trouvé une plus grande proportion d´individus victimes de stress dans le groupe des participants où il y a eu une baisse de la teneur des anticorps dirigé à la hémaglutinina AH1 (ac AH1) en T6, après comparaison avec le respectif groupe de contrôle. La différence entre les groupes a été statistiquement significative lorsqu´on a vérifié la présence de stress grâce à la méthode de triangulation, en utilisant l´entretien (p=0,006), par la méthode de triangulation en utilisant le GHQ12 (p=0,045) et en utilisant aussi la combinaison des trois critères (p=0,001). Après une analyse XXX multivariée, on a vérifié que l´association entre la présence de stress et la réduction des ac AH1 en T6 a conservé un signifié statistique (respectivement, p=0,010, p=0,042 et p=0,002) et a présenté des odds ratio ajustés, en fonction de chacune des méthodes de vérification de la présence de stress de 3,643, de 2,733 et de 5,223. La quantité de travail perçue comme une surcharge constitue le facteur inducteur de stress le plus souvent cité (58,8% de l´échantillon et 61,8% des infirmiers des unités d´internement), suivi par les conflits entre professionnels. Le contact avec la souffrance et la mort des patients a été placé en quatrième position par l´échantillon, mais en deuxième position par les infirmiers des unités d´internement. Dans ces cas, on a vérifié une association évidente entre le fait de travailler dans des services où le nombre de patients décédés a été très élevé et la présence de stress, identifiée par la méthode de triangulation, en utilisant l´entretien (p=0,039), le GHQ12 (p=0,019), l´échelle de fatigue émotionnelle du MBI-HSS (p=0,012) et en utilisant aussi la combinaison des trois critères (p=0,014). On a aussi vérifié une association positive entre la présence de stress, identifiée par la méthode de triangulation, en utilisant l´échelle de fatigue émotionnelle du MBI-HSS et le travail dans des services d´internement où le pourcentage de malade âgés (p=0,025) et le taux de mortalité ont été élevés (p=0,036). Malgré tout, on n´a pas trouvé d´association entre l´exposition très fréquente à la souffrance et à la mort des patients et la réduction de la teneur de ac AH1 en T6. Probablement l´exposition à ce facteur inducteur de stress, bien qu´elle soit liée à la présence de stress chez les infirmiers des services d´internement, n´a pas été suffisamment intense pour, en elle-même, être associée à la réduction de la teneur ac AH1 enT6. L´association trouvée entre la présence de stress chronique et la réduction de la teneur des anticorps AH1 en T6 vient renforcer l´hypothèse que le stress pourra influencer négativement la manutention des teneurs en anticorps même chez les individus adultes jeunes. Donc le risque qu´un infirmier stressé présente une réduction de la teneur en anticorps dirigés à la hémaglutinina de le composant AH1N1-A/Solomon Island/3/2006 à la fin des six mois d´études a été 3,6, 2,7 ou 5,2 fois supérieure à celui d´un infirmier sans stress, après avoir déterminé le critère de stress, respectivement par la méthode de triangulation utilisant l´entretien, par la méthode de triangulation utilisant le GHQ12 ou par la combinaison des trois critères.

Deciphering the role of Yap4 phosphorylation under stress conditions

The existence of molecular mechanisms of response, repair and adaptation, many of which are greatly conserved across nature, gives to the cell with the plasticity it requires to adjust to its ever-changing environment, a homeostatic event that is termed the stress response. In the budding yeast Saccharomyces cerevisiae there is a particular family of transcription factors, the Yap family, which has been shown to have a relevant role in yeast adaptation to several stress conditions. In particular, Yap1 is the major regulator of the transcriptional response to oxidative stress and Yap2 and Yap8 play important roles upon cadmium and arsenic exposure, respectively.(...)

Stress in university students and cardiovascular response to academic stressors

Introduction: University students are frequently exposed to events that can cause stress and anxiety, producing elevated cardiovascular responses. Repeated exposure to academic stress has implications to students’ success and well-being and may contribute to the development of long-term health problems. Objective: To identify stress levels and coping strategies in university students and assess the impact of stress experience in heart rate variability (HRV). Methods: 17 university students, 19-23 years, completed the University Students Stress Inventory, the Depression Anxiety Stress Scales and the Ways of Coping Questionnaire. Two 24h-Holter recordings were performed, on academic activity days, including one of them an exam situation. Results: Students tend to present moderate stress levels, and prefer problem-focused coping strategies in order to manage stress. Exam situations are perceived as significant stressors. Although we found no significant differences in HRV (SDNN), between days with and without an exam, we registered a lower SDNN score and a variation in heart rate (HR) related to exam situation (maximum HR peak at 10 minutes before the exam, and total HR recovery 20 minutes after the exam), reflecting sympathetic activation due to stress. Conclusions: These results suggest that academic events, especially those related to exam situations, are the cause of stress in university students, with implications at cardiovascular level, underlying the importance of interventions that help these students improve their coping skills and optimize stress management, in order to improve academic achievement and promote well-being and quality of life.

The use of the boundary element method in the analysis of single lap joints

The most common techniques for stress analysis/strength prediction of adhesive joints involve analytical or numerical methods such as the Finite Element Method (FEM). However, the Boundary Element Method (BEM) is an alternative numerical technique that has been successfully applied for the solution of a wide variety of engineering problems. This work evaluates the applicability of the boundary elem ent code BEASY as a design tool to analyze adhesive joints. The linearity of peak shear and peel stresses with the applied displacement is studied and compared between BEASY and the analytical model of Frostig et al., considering a bonded single-lap joint under tensile loading. The BEM results are also compared with FEM in terms of stress distributions. To evaluate the mesh convergence of BEASY, the influence of the mesh refinement on peak shear and peel stress distributions is assessed. Joint stress predictions are carried out numerically in BEASY and ABAQUS®, and analytically by the models of Volkersen, Goland, and Reissner and Frostig et al. The failure loads for each model are compared with experimental results. The preparation, processing, and mesh creation times are compared for all models. BEASY results presented a good agreement with the conventional methods.