456 research outputs found
Processing of continuous fibre reinforced thermoplastics
ECCM15 - 15TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June 2012Towpregs
based on different fibres and thermoplastic matrices were processed for highly
demanding and more commercial applications by different composite processing
technologies. In the technologies used, compression moulding and pultrusion, the final
composite pr
ocessing parameters were studied in order to obtain composites with adequate
properties at industrial compatible production rates. The produced towpregs were tested to
verify its polymer content and degree of impregnation. The obtained results have shown t
hat
the coating line enabled to produce, with efficiency and industrial scale speed rates,
thermoplastic matrix towpregs
that may be used to manufacture
composites for
advanced and
larger volume commercial markets
Processing of carbon reinforced thermoplastic pre-impregnated materials
The aim of this work is to produce and optimize the processing of carbon fibres thermoplastic matrix pre-impregnated materials (towpregs and PCT´s). Pultrusion and heated compression moulding were the selected manufacturing methods for processing all carbon fibres thermoplastic matrix pre-impregnated materials into composite parts.
The optimization of those processes was made by studying the influence of the most relevant processing parameters in the final properties of the produced carbon fibres thermoplastic matrix pre-impregnated materials and composites. The method of Taguchi / DOE (Design of Experiments) was used to achieve this aim as it allowed making more rational choices of processing windows.
The composite relevant mechanical properties were determined and studied. The final composites were also submitted to SEM microscopy analysis.info:eu-repo/semantics/publishedVersio
Compression molding of pultruded carbon reinforced thermoplastic composites
Historically, thermoset resins have dominated the composite industry but they start to be replaced
by thermoplastics. In this study two different thermoplastic matrix carbon reinforced pre-impregnated
materials were used, one produced in our laboratories (towpreg) and another obtained from coextrusion
process (PCT). Carbon fibre and two different thermoplastic matrices (polypropylene and
PRIMOSPIRE®) were selected for the production of the pre-impregnated materials.
Heated compression moulding and pultrusion were the two manufacturing technologies used to
obtain composite plates and profiles for study. The optimization of those processes was made by
studying the influence of the most relevant processing parameters in the final properties of the
produced carbon fibres thermoplastic matrix pre-impregnated materials and composites.
The composite relevant mechanical properties were determined and the final composites were
submitted to Dynamic Mechanical Analysis (DMA), Scanning Electron Microscope (SEM), optical
microscopy and calcination tests.
The determination of the fiber volume fraction of all studied composite was obtained comparing
the results of thermogravimetric analysis (TGA), SEM and calcination tests.info:eu-repo/semantics/publishedVersio
Assessing the effects of temperature and salinity oscillations on a key mesopredator fish from European coastal systems
Abstract
A population dynamics model was developed to assess the short and long-term effects of
temperature and salinity variations in the common goby Pomatoschistus microps in a
Portuguese estuary (Minho estuary, NW Portugal). The population was divided into juveniles,
females and males, which constituted the model’s state variables. Linear regressions between
the observed and the predicted density of juveniles, females and the total population were
significant. Parameter’s sensitivity and uncertainty analysis were estimated. The model was able
to satisfactory describe the P. microps population dynamics, and thus was used to simulate the
effects of climatic changes on the fish population. Simulations indicated that the common goby
population is sensitive to both temperature and salinity changes. Overall, scenarios of + 4°C
increase caused significant population decreases. Similarly, increased salinities led to a
population shrinkage, whereas scenarios of salinity decrease generated an opposite variation on
the population. According to the IPCC predictions for climatic tendencies, the population of the
common goby will tend to decrease in the near future, experiencing marked oscillations
(decrease or increase) during climatic extremes, namely droughts and floods, respectively.
These results may be a useful tool for future planning and management of estuarine systems
given that the common goby is an important species of estuarine food webs in many temperate
ecosystems.
Keywords: Population modelling, Pomatoschistus microps, climate change, uncertainty,
estuary, Portuga
Culex quinquefasciatus mosquitoes do not support replication of Zika virus
The rapid spread of Zika virus (ZIKV) in the Americas raised many questions about the role of Culex quinquefasciatus mosquitoes in transmission, in addition to the key role played by the vector Aedes aegypti. Here we analysed the competence of Cx. quinquefasciatus (with or without Wolbachia endosymbionts) for a ZIKV isolate. We also examined the induction of RNA interference pathways after viral challenge and the production of small virus-derived RNAs. We did not observe any infection nor such small virus-derived RNAs, regardless of the presence or absence of Wolbachia. Thus, Cx. quinquefasciatus does not support ZIKV replication and Wolbachia is not involved in producing this phenotype. In short, these mosquitoes are very unlikely to play a role in transmission of ZIKV
Damage assessment of drilled hybrid composite laminates
Hole drilling operations are common in fibre reinforced plastics - FRP’s - to facilitate fastener assembly
to other parts in more complex structures. As these materials are non-homogeneous, drilling causes some
damages, like delamination, for example. Delamination can be reduced by a careful selection of drilling
parameters, drill material and drill bit geometry. In this work two types of laminates are drilled using
different machining parameters and comparing drill geometries. Results show the importance of a
cautious selection of these variables when composites’ drilling is involved
Estudo da influência da pré-furação no dano em laminados carbono/epóxido
Na furação de placas em materiais compósitos é corrente o uso de técnicas tradicionais de furação adaptadas. O defeito mais grave é a delaminação, que nem sempre é visÃvel à superfÃcie e pode causar o colapso prematuro das estruturas. Para a avaliação dos danos provocados nas peças utilizam-se meios de controlo não-destrutivo. Neste artigo são analisados os resultados obtidos através do recurso à pré-furação em placas carbono/epóxido e de duas técnicas de controlo. Os resultados obtidos permitem estabelecer a influência da pré-furação na delaminação Neste trabalho, utilizam-se técnicas de Visão Computacional no processamento e análise das imagens obtidas nos ensaios experimentais
In situ measurement of hydraulic conductivity of mountain soils: a case study in Serra da Estrela mountain (Central Portugal)
Understanding the role of the vadose zone is essential to accurately assess hydrogeological systems
and the respective groundwater resources. The study area (Manteigas – Nave de Santo António – Torre
sector, Serra da Estrela Mountain, Central Portugal) presents specific geological, morphotectonical
and climatic characteristics with significant influence on the hydrogeologic regime. The vadose zone has particular features that contribute to control both the quantity and the quality of the
groundwater resources. In situ hydraulic conductivity tests were carried out in A and H soil horizons,
by means of the constant head permeameter (Guelph permeameter) method. The mean value of the
field saturated hydraulic conductivity is high (around 6 cm/h) and is typical of coarse textured soils.
Unsaturated hydraulic conductivity was estimated using the Gardner mathematical model
Low Bone Mass Density Is Associated With Hemolysis In Brazilian Patients With Sickle Cell Disease.
To determine whether kidney disease and hemolysis are associated with bone mass density in a population of adult Brazilian patients with sickle cell disease. Bone involvement is a frequent clinical manifestation of sickle cell disease, and it has multiple causes; however, there are few consistent clinical associations between bone involvement and sickle cell disease. Patients over 20 years of age with sickle cell disease who were regularly followed at the Hematology and Hemotherapy Center of Campinas, Brazil, were sorted into three groups, including those with normal bone mass density, those with osteopenia, and those with osteoporosis, according to the World Health Organization criteria. The clinical data of the patients were compared using statistical analyses. In total, 65 patients were included in this study: 12 (18.5%) with normal bone mass density, 37 (57%) with osteopenia and 16 (24.5%) with osteoporosis. Overall, 53 patients (81.5%) had bone mass densities below normal standards. Osteopenia and osteoporosis patients had increased lactate dehydrogenase levels and reticulocyte counts compared to patients with normal bone mass density (p<0.05). Osteoporosis patients also had decreased hemoglobin levels (p<0.05). Hemolysis was significantly increased in patients with osteoporosis compared with patients with osteopenia, as indicated by increased lactate dehydrogenase levels and reticulocyte counts as well as decreased hemoglobin levels. Osteoporosis patients were older, with lower glomerular filtration rates than patients with osteopenia. There was no significant difference between the groups with regard to gender, body mass index, serum creatinine levels, estimated creatinine clearance, or microalbuminuria. A high prevalence of reduced bone mass density that was associated with hemolysis was found in this population, as indicated by the high lactate dehydrogenase levels, increased reticulocyte counts and low hemoglobin levels.66801-
The dynamics of stress: a longitudinal MRI study of rat brain structure and connectome
Stress is a well-established trigger for a number of neuropsychiatric disorders, as it alters both structure and function of several brain regions and its networks. Herein, we conduct a longitudinal neuroimaging study to assess how a chronic unpredictable stress protocol impacts the structure of the rat brain and its functional connectome in both high and low responders to stress. Our results reveal the changes that stress triggers in the brain, with structural atrophy affecting key regions such as the prelimbic, cingulate, insular and retrosplenial, somatosensory, motor, auditory and perirhinal/entorhinal cortices, the hippocampus, the dorsomedial striatum, nucleus accumbens, the septum, the bed nucleus of the stria terminalis, the thalamus and several brain stem nuclei. These structural changes are associated with increasing functional connectivity within a network composed by these regions. Moreover, using a clustering based on endocrine and behavioural outcomes, animals were classified as high and low responders to stress. We reveal that susceptible animals (high responders) develop local atrophy of the ventral tegmental area and an increase in functional connectivity between this area and the thalamus, further spreading to other areas that link the cognitive system with the fight-or-flight system. Through a longitudinal approach we were able to establish two distinct patterns, with functional changes occurring during the exposure to stress, but with an inflection point after the first week of stress when more prominent changes were seen. Finally, our study revealed differences in functional connectivity in a brainstem-limbic network that distinguishes resistant and susceptible responders before any exposure to stress, providing the first potential imaging-based predictive biomarkers of an individual's resilience/vulnerability to stressful conditions.This work is part of the Sigma project with the reference FCT-ANR/NEU-OSD/
0258/2012 co-financed by the French public funding agency ANR (Agence National
pour la Recherche, APP Blanc International II 2012), the Portuguese FCT (Fundação
para a Ciência e Tecnologia) and by the Portuguese North Regional Operational
Program (ON.2 – O Novo Norte) under the National Strategic Reference Framework
(QREN), through the European Regional Development Fund (FEDER) as well as the
Projecto Estratégico co-funded by FCT (PEst-C/SAU/LA0026-/2013) and the European
Regional Development Fund COMPETE (FCOMP-01-0124-FEDER-037298). DAB and
AN were funded by grants from FCT-ANR/NEU-OSD/0258/2012. RM is supported by
the FCT fellowship grant with the reference PDE/BDE/113604/2015 from the PhDiHES program; AC was supported by a grant from the foundation NRJ. PM was funded
by Fundação Calouste Gulbenkian (Portugal; ‘Better mental health during ageing
based on temporal prediction of individual brain ageing trajectories (TEMPO)’), Grant
Number P-139977. We thank Drs PatrÃcio Costa and Pedro Moreira for support on the
various statistical analyses.info:eu-repo/semantics/publishedVersio
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