Thermal conditions affecting heat transfer in FDM/FFE: a contribution towards the numerical modelling of the process

The performance of parts produced by Free Form Extrusion (FFE), an increasingly popular additive manufacturing technique, depends mainly on their dimensional accuracy, surface quality and mechanical performance. These attributes are strongly influenced by the evolution of the filament temperature and deformation during deposition and solidification. Consequently, the availability of adequate process modelling software would offer a powerful tool to support efficient process set-up and optimisation. This work examines the contribution to the overall heat transfer of various thermal phenomena developing during the manufacturing sequence, including convection and radiation with the environment, conduction with support and between adjacent filaments, radiation between adjacent filaments and convection with entrapped air. The magnitude of the mechanical deformation is also studied. Once this exercise is completed, it is possible to select the material properties, process variables and thermal phenomena that should be taken in for effective numerical modelling of FFE.

Effects of clove oil on the stress response of matrinxã (Brycon cephalus) subjected to transport

Fish transport is one of the most stressful procedures in aquaculture facilities. The present work evaluated the stress response of matrinxã to transportation procedures, and the use of clove oil as an alternative to reduce the stress response to transport in matrinxã (Brycon cephalus). Clove oil solutions were tested in concentrations of 0, 1, 5 and 10 mg/L during matrinxã transportation in plastic bags, supplied with water and oxygen as the usual field procedures in Brazil. Clove oil reduced some of the physiological stress responses (plasma cortisol, glucose and ions) that we measured. The high energetic cost to matrinxã cope with the transport stress was clear by the decrease of liver glycogen after transport. Our results suggest that clove oil (5 mg/l) can mitigate the stress response in matrinxã subjected to transport.

Studying conformally flat spacetimes with an elastic stress energy tensor using 1+3 formalism

Conformally flat spacetimes with an elastic stress energy tensor having diagonal trace-free anisotropic pressure are investigated using 1+3 formalism. The 1+3 Bianchi and Jacobi identities and Einstein field equations are written for a particular case with a conformal factor dependent on only one spatial coordinate. Solutions with non null anisotropic pressure are obtained.

Stress, personalidade, coping e bem-estar: relação com o sucesso e excelência em contextos de realização desportiva

Dissertação de mestrado integrado em Psicologia

Autocontrolo, coping e controlo atencional em situações de stress e pressão competitiva: estudo exploratório no basquetebol

Dissertação de mestrado em Psicologia Aplicada

Physiological responses of pirarucu (Arapaima gigas) to acute handling stress

Pirarucu (Arapaima gigas) is an obligatory air-breathing fish from the Amazon basin. Previous study showed that pirarucu juveniles present a latency period in their response to moderate stress (transportation). Therefore the objective of this study was to verify the effects of a prolonged air exposure stress in lactate, glucose, cortisol, haematocrit, haemoglobin, and liver glycogen in pirarucu. Thirty-six fish were handled by netting and subjected to air exposure for 75-min. Six fish were sampled before handling and at 0, 6, 24, 48, and 96h after handling. Fish cortisol, lactate and haematocrit rose after handling, returning to previous unstressed values on the following sampling (6h after handling). Glucose increased significantly after handling and that was maintained for 24 h. There were no changes in haemoglobin and liver glycogen as a consequence of handling. The results demonstrate a quick response when exposed to an acute stressor and a fast recovery, suggesting that pirarucu does not use their glycogen reserves during an acute stress. The results suggest that pirarucu exhibit physiological stress responses to handling similar in magnitude to those previously documented for many teleostean fishes, including salmonids.

Physiological stress responses in the warm-water fish matrinxã (Brycon amazonicus ) subjected to a sudden cold shock

The present work evaluated several aspects of the generalized stress response [endocrine (cortisol), metabolic (glucose), hematologic (hematocrit and hemoglobin) and cellular (HSP70)] in the Amazonian warm-water fish matrinxã (Brycon amazonicus ) subjected to an acute cold shock. This species farming has been done in South America, and growth and feed conversion rates have been interesting. However, in subtropical areas of Brazil, where the water temperature can rapidly change, high rates of matrinxã mortality have been associated with abrupt decrease in the water temperature. Thus, we subjected matrinxã to a sudden cold shock by transferring the fish directly to tanks in which the water temperature was 10ºC below the initial conditions (cold shock from 28ºC to 18ºC). After 1h the fish were returned to the original tanks (28ºC). The handling associated with tank transfer was also imposed on control groups (not exposed to cold shock). While exposure to cold shock did not alter the measured physiological conditions within 1h, fish returned to the ambient condition (water at 28º C) significantly increased plasma cortisol and glucose levels. Exposure to cold shock and return to the warm water did not affect HSP70 levels. The increased plasma cortisol and glucose levels after returning the fish to warm water suggest that matrinxã requires cortisol and glucose for adaptation to increased temperature.

Qualidade de vida, morbilidade psicológica e stress familiar em idosos residentes na comunidade

Este estudo procurou investigar as relações existentes entre morbilidade psicológica, stress familiar e qualidade de vida (QV) da pessoa idosa. A amostra foi constituída por 126 idosos. Os instrumentos utilizados foram: The Lawton Instrumental Activities of Daily Living (IADL), Quality of Life (WHOQOL-Bref), Geriatric Anxiety Inventory (GSI), Geriatric Depression Scale (GDS); e Index of Family Relations (IFR). Os resultados revelaram a importância da idade, estado civil, escolaridade e número de patologias assim como o género na capacidade funcional, morbilidade, stress familiar e QV. Ao nível dos preditores, a depressão foi a variável que mais contribuiu para a QV. Não foram encontradas variáveis moderadoras no modelo. A discussão e implicações dos resultados são abordadas bem como a intervenção psicológica nesta população.

An efficient chronic unpredictable stress protocol to induce stress-related responses in C57BL/6 mice

Exposure to chronic stress can have broad effects on health ranging from increased predisposition for neuropsychiatric disorders to deregulation of immune responses. The chronic unpredictable stress (CUS) protocol has been widely used to study the impact of stress exposure in several animal models and consists in the random, intermittent, and unpredictable exposure to a variety of stressors during several weeks. CUS has consistently been shown to induce behavioral and immunological alterations typical of the chronic stress-response. Unfortunately C57BL/6 mice, one of the most widely used mouse strains, due to the great variety of genetically modified lines, seem to be resistant to the commonly used 4-week-long CUS protocol. The definition of an alternative CUS protocol allowing the use of C57BL/6 mice in chronic stress experiments is a need. Here, we show that by extending the CUS protocol to 8?weeks is possible to induce a chronic stress-response in C57BL/6 mice, as revealed by abrogated body weight gain, increased adrenals weight, and an overactive hypothalamic-pituitary-adrenal axis with increased levels of serum corticosterone. Moreover, we also observed stress-associated behavioral alterations, including the potentiation of anxious-like and depressive-like behaviors and a reduction of exploratory behavior, as well as subtle stress-related changes in the cell population of the thymus and of the spleen. The present protocol for C57BL/6 mice consistently triggers the spectrum of CUS-induced changes observed in rats and, thus, will be highly useful to researchers that need to use this particular mouse strain as an animal model of neuropsychiatric disorders and/or immune deregulation related to CUS.

Does nitrogen availability have greater control over the formation of tropical heath forests than water stress?A hypothesis based on nitrogen isotope ratios

Global scale analyses of soil and foliage δ15N have found positive relationships between δ15N and ecosystem N loss (suggesting an open N cycle) and a negative relationship between δ15N and water availability. We show here that soils and leaves from tropical heath forests are depleted in 15N relative to 'typical' forests suggesting that they have a tight N cycle and are therefore limited by N rather than by, often suggested, water availability.

Occupational stress and coping among portuguese military police officers

This study describes the professional experience of military police officers from the Portuguese Republican National Guard (N = 95). We focused on the main sources and consequences of stress and the coping strategies used to deal with stress. The evaluation protocol included one closed-ended question and four open-ended questions. Data analysis of meaningful text segments was conceptually based and data categorization followed deductive content analysis. Results allowed the identification of 483 meaning units. Factors intrinsic to the job and the relationships at work were the main stressors referred by participants. The consequences of stressors were evident at an individual level, affecting family, psychological, and physical/health domains. The coping strategies used to deal with the main source of stress in the professional career were focused on problem solving (e.g., active confrontation) and emotional regulation (e.g., situation acceptance). Practical implications and future avenues of research with these professionals are discussed.

Photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress

Light and water are important factors that may limit the growth and development of higher plants. The aim of this study was to evaluate photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress. I used six independent pre-acclimation treatments (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) and 720 min (06h00-18h00)) varying the time of exposure to full sunlight (PFS) during 30 days, followed by whole-day outdoor exposure for 120 days. Before PFS, the plants were kept in a greenhouse at low light levels (0.8 mol m-2 day-1). The PFS of 0 min corresponded to plants constantly kept under greenhouse conditions. From the beginning to the end of the experiment, each PFS treatment was submitted to two water regimes: moderate water stress (MWS, pre-dawn leaf water potential (ΨL) of -500 to -700 kPa) and without water stress (WWS, ΨL of -300 kPa, soil kept at field capacity). Plants under MWS received only a fraction of the amount of water applied to the well-watered ones. At the end of the 120-day-period under outdoor conditions, I evaluated light saturated photosynthesis (Amax), stomatal conductance (g s), transpiration (E) and plant growth. Both Amax and g s were higher for all plants under the PFS treatment. Stem diameter growth rate and Amax were higher for C. guianensis subjected to MWS than in well-watered plants. The contrary was true for B. excelsa. The growth of seedlings was enhanced by exposure to full sunlight for 180 minutes in both species. However, plants of B. excelsa were sensitive to moderate water stress. The higher photosynthetic rates and faster growth of C. guianensis under full sun and moderate water stress make this species a promissory candidate to be tested in reforestation programs.

Natural gaps associated with oxidative stress in Willisornis poecilinotus (Aves: Thamnophilidae) in a tropical forest

Natural disturbances in tropical forests modify the availability and quality of resources and alter the patterns of bird distribution. These environmental changes increase the metabolic rate and disrupt the redox balance promoting oxidative stress. This study aimed to compare the abundance of Willisornis poecilinotus between gaps and the understory of a forest with undisturbed canopy at Caxiuanã National Forest. The abundance was correlated with vegetation heights. The oxidative stress and the stress promoting factors were determined in both sites of sampling. We captured 81 specimens of W. poecilinotus. The number of captures was high in gaps. The specimens sampled at gaps showed high levels of oxidative stress. The biomarkers of oxidative stress were significantly correlated in gaps. The variability of oxidative stress and oxidative damage were explained only by site of sampling. These results suggest that gaps are stressors sites to W. poecilinotus, which probably can be due to an increase of metabolic rate to deal with new flight strategies of foraging and avoid predation