The Quaternary pyroclastic succession of southeast Tenerife, Canary Islands: Explosive eruptions, related caldera subsidence, and sector collapse

A much-revised Quaternary stratigraphy is presented for ignimbrites and pumice fall deposits of the Bandas del Sur, in southern Tenerife. New Ar-41/Ar-39 data obtained for the Arico, Granadilla, Fasnia, Poris, La Caleta and Abrigo formations are presented, allowing correlation with previously dated offshore marine ashfall layers and volcaniclastic sediments. We also provide a minimum age of 287 +/- 7 ka for a major sector collapse event at the Gaimar valley. The Bandas del Sur succession includes more than seven widespread ignimbrite sheets that have similar characteristics, including widespread basal Plinian layers, predominantly phonolite composition, ignimbrites with similar extensive geographic distributions, thin condensed veneers with abundant diffuse bedding and complex lateral and vertical grading patterns, lateral gradations into localized massive facies within palaeo-wadis, and widespread lithic breccia layers that probably record caldera-forming eruptions. Each ignimbrite sheet records substantial bypassing of pyroclastic material into the ocean. The succession indicates that Las Canadas volcano underwent a series of major explosive eruptions, each starting with a Plinian phase followed by emplacement of ignimbrites and thin ash layers, some of coignimbrite origin. Several of the ignimbrite sheets are compositionally zoned and contain subordinate mafic pumices and banded pumices indicative of magma mingling immediately prior to eruption. Because passage of each pyroclastic density current was characterized by phases of non-deposition and erosion, the entire course of each eruption is incompletely recorded at any one location, accounting for some previously perceived differences between the units. Because each current passed into the ocean, estimating eruption volumes is virtually impossible. Nevertheless, the consistent widespread distributions and the presence of lithic breccias within most of the ignimbrite sheets suggest that at least seven caldera collapse eruptions are recorded in the Bandas del Sur succession and probably formed a complex, nested collapse structure. Detailed field relationships show that extensive ignimbrite sheets (e.g. the Arico, Poris and La Caleta formations) relate to previously unrecognized caldera collapse events. We envisage that the evolution of the nested Las Cahadas caldera is more complex than previously thought and involved a protracted history of successive ignimbrite-related caldera collapse events, and large sector collapse events, interspersed with edifice-building phases.

Some aspects of the microbiological properties of polymers and composite materials

The interaction of microorganisms with glass-reinforced polyester resins(GRP), both under laboratory and simulated operating conditions, has been examined following reports of severl! fungal biodeterioration. Although GRP was not previously associated with substantial microbial growth, small amounts of microbial activity would pose problems for products associated with comestible materials. The microbiology of the raw materials was investigated, two ingredients were supportive to microbial populations whilst five materials were biostatic or inhibitory in their action. Production laminate was not susceptible to microbial deterioration or inhibitory to microbes. Incorporation of zinc stearate, one of the supportive ingredients, at 300% manufacturing level or drastic undercuring produced laminate capable of supporting microbial growth but only after a non-biotic stage of degradation. Study of the long-term population dynamics of cisterns of GRP and competitive materials under conditions simulating in-service conditions, monitoring microbial numbers within the experimental vessels and comparing with the populations of the supply water, suggests that the performance of GRP cisterns is slightly superior to conventional competitive materials. An investigation of the biological performance of GRP cisterns in an isolated area of known microbiological hazard was conducted. Severe biodeterioration had been experienced with Preform GRP articles moulded using different production techniques, but substitution of current GRP articles resulted in no recurrence of the problem. All attempts to establish the fungal isolate responsible for the phenomena in cisterns under controlled conditions failed. Scanning Electron Microscopy of GRP surfaces showed that although differences exist between current and Preform laminates, these could not satisfactorily explain the differences in service behaviour. These results and the results of the British Plastics Federation Expert Working Group interlaboratory study are discussed in relation to the original report of gross fungal biodeterioration and, to the design of future testing programmes for the products of industrial concerns.

Influência da absorção de umidade no comportamento mecânico nos compósitos poliméricos híbridos Kevlar/vidro quando imerso em água do mar e petróleo

The polymer matrix composite materials are being used on a large scale in the most different industrial fields such as aerospace, automotive, oil, among others, since the industrial perspectives is currently working with materials which have a good mechanical performance at high service life and cost / benefit. Thus, the determination of the mechanical properties is indispensable for the characterization of waste resulting in greater expansion of this type of material. Thus, this work will be obtained three plates laminated with tereftálica polymeric matrix reinforced by a bidirectional woven E-glass and kevlar both industrially made, where the plates are manufactured by manual lamination process (hand lay-up), all laminates have five enhancement layers, the first hybrid laminate will consist of bidirectional woven E-glass fiber, kevlar fiber interspersed with layers, is formed by the second bidirectional woven kevlar fiber at the ends of the laminate (two layers), and in the center the glass fiber fabric (three layers), the third plate is composed of only the bidirectional woven E-glass fiber. Then were prepared specimens (CP) by standard, to determine the mechanical properties of tensile and bending in three points. After fabrication of the specimens, they were immersed in oil and seawater. After that, there was a comparison of the mechanical properties for the test condition in the dry state. Showing that there was a considerable increase in the properties studied because the effect of hybridization in laminates.

The disappearing of palheiros in Aveiro lagoon

Palheiros are traditional timber constructions existing in the littoral centre region of Portugal. This is particularly the case of the Aveiro lagoon region where for many years many such constructions have existed. They were originally built to store working tools related with lagoon activity (fishing and sea salt extraction) and to give shelter for the fishermen during the fishing season. These constructions were built with superimposed veneers in vertical or horizontal directions. Since they are mostly located near the sea, they have started to be used as holiday houses and are often painted in vivid colours. Most of these buildings are being replaced by concrete constructions, since their preservation state is rather unsatisfactory or simply because there is a need to increase their size. Additionally, little knowledge about the possibilities of maintenance and building in timber structures exists. In some cases, although the structures were changed from timber to concrete, the exterior appearance of the palheiros remains the same, which might be interesting from the pictorial point of view but it isn’t certainly from a heritage preservation perspective. However in many other situations, they are being substituted by “modern” constructions that were not valuable in any of the previous viewpoints. Fortunately, there are also cases where palheiros have been preserved and remain in good condition. For how long these examples will remain is certainly the major question that must be answered since these are only on the dependence of owner’s will and not based on local authorities concern. A consciousness of local authorities and citizens is mandatory in order to preserve this heritage because it is perfectly possible to preserve the traditional constructions offering all the comfort of modern houses. Keywords: timber construction, vernacular construction, preservation.

Resistive Embedded Heating for Homogeneous Curing of Composite Damage Repair

Thesis (Ph.D.)--University of Washington, 2016-08

Reabilitação estética com facetas em pacientes com amelogénese imperfeita

A Amelogénese Imperfeita é uma anomalia hereditária que interfere no desenvolvimento do esmalte, pode variar em seu grau de intensidade, podendo afetar o esmalte tanto na sua qualidade, quanto na sua quantidade e em ambas as dentições. Existem pelo menos catorze subtipos diferentes de amelogénese imperfeita, sendo as do tipo hipoplásico, hipomaturado, hipocalcificado e hipoplásico ou hipomaturado com taurodontia segundo o seu fenótipo e quinze subtipos, segundo o seu modo de transmissão. Segundo a literatura, os pacientes com amelogénese imperfeita, independentemente do subtipo presente, apresentam complicações orais semelhantes: estética dentária comprometida, sensibilidade dentária e diminuição da dimensão vertical de oclusão. O tratamento destes pacientes assume um papel relevante, na medida em que requer cuidados especiais, já que esta doença acarreta, por norma, problemas psicológicos e interfere com o autoestima do individuo. É notória, atualmente, uma oferta variada de opções reabilitadoras ao dispor do Médico Dentista, que ajudarão o mesmo a restabelecer a estética e função. Os tratamentos são variados e por vezes complexos, podem ser desenvolvidos de forma conservadora ou invasiva. Contudo, a escolha do melhor tratamento será consequência da gravidade da patologia e de fatores inerentes ao próprio paciente. Neste estudo, abordamos as facetas, como uma alternativa reabilitadora, que com o avanço e melhorias na área da Dentisteria Estética, nomeadamente no que diz respeito à adesão à dentina, parecem ser uma opção credível. Assim, o objetivo desta dissertação é demonstrar e elucidar a reabilitação dos defeitos associados a esta doença com a utilização de facetas diretas e indiretas. Foram efetuadas pesquisas e consulta de livros, monografias, dissertações, artigos em base de dados como o Pubmed/Medline, para que conseguíssemos realizar uma discussão sobre o mesmo tema e desta forma encontrar uma adequada resposta a todas as nossas inquietações sobre esta questão.

Comparação de materiais usados na confeção de facetas dentárias

A demanda na procura da reabilitação estética é um dos focos da história da humanidade ao longo das eras, mas que teve a sua acentuação nestes últimos dois séculos. Sendo a face um dos pontos que nos permite avaliar esteticamente uma pessoa, cabe ao médico dentista, como um dos profissionais que trabalha nessa zona do corpo humano, avaliar e procurar satisfazer as necessidades estéticas da população. Assim, por parte dos profissionais de Medicina Dentária, tem de haver uma procura constante para a satisfação das exigências estéticas, não só no conhecimento como no aprimoramento da técnica. Nos últimos tempos, com a necessidade de desenvolvimento de materiais para colmatar a cada vez maior busca para a perfeição estética, as facetas surgiram como tratamento de excelência. O presente trabalho teve como objectivo a comparação entre resina composta e cerâmica, na elaboração de restaurações estéticas. Para os dois tipos de materiais foram avaliados a estética e o comportamento biomecânico. Foram comparados benefícios e desvantagens, contra-indicações, indicações, plano de tratamento, diagnóstico e procedimentos clínicos dos dois materiais, utilizados na confecção das facetas cerâmicas e de resina composta. Foram utilizados os seguintes parâmetros de comparação: biocompatibilidade, adaptação marginal, preparação, resistência, cor, acabamento, potencial de reparação, custo e estética. A utilização de facetas cerâmicas tem sido um dos principais focos de desenvolvimento da Medicina Dentária no âmbito científico. A sua utilização permite uma maior predictibilidade e uma maior longevidade clínica. A sua qualidade estética, resistência à fractura, biodisponibilidade e estabilidade de cor, são as suas maiores vantagens na utilização clínica. Em sentido inverso, as facetas de resina composta apresentam menor custo, maior resistência à abrasão, possibilidade de reparação fácil e menor desgaste de estrutura dentária durante a sua preparação. Contudo apresentam menor estabilidade de cor. Portanto, torna-se esclarecedor que a escolha do material a utilizar na confecção de facetas, deve ser adaptada às especificidades de cada caso.

Compósitos poliméricos a base de fibras de licuri: efeitos da hibridização e do envelhecimento ambiental acelerado

The gradual replacement of conventional materials by the ones called composite materials is becoming a concern about the response of these composites against adverse environmental conditions, such as ultraviolet radiation, high temperature and moist. Also the search for new composite using natural fibers or a blend of it with synthetic fibers as reinforcement has been studied. In this sense, this research begins with a thorough study of microstructural characterization of licuri fiber, as a proposal of alternative reinforcement to polymeric composites. Thus, a study about the development of two composite laminates was done. The first one, involving only the fiber of licuri and the second comprising a hybrid composite based of fiber glass E and the fiber of licuri, in order to know the performance of the fiber when of fiber across the hybridization process. The laminates were made in the form of plates using the tereftálica ortho-polyester resin as matrix. The composite laminate made only by licuri fiber had two reinforcing fabric layers of unidirectional licuri and the hybrid composite had two reinforcing layers of unidirectional licuri fabric and three layers of fiber short glass-E mat. Finally, both laminates was exposed to aging acceleration in order to study the influence of environmental degradation involving the mechanical properties and fracture characteristics thereof. Regarding the mechanical properties of composites, these were determined through uniaxial tensile tests, uniaxial compression and three bending points for both laminates in original state, and uniaxial tensile tests and three bending points after accelerated aging. As regards the study of structural degradation due to aging of the laminates, it was carried out based on microscopic analysis and microstructure, as well as measuring weight loss. The characteristics of the fracture was performed by macroscopic and microscopic (optical and SEM) analysis. In general, the laminated composites based on fiber licuri showed some advantages in their responses to environmental aging. These advantages are observed in the behavior related to stiffness as well as the microstructural degradation and photo-oxidation processes. However, the structural integrity of this laminate was more affected in case the action of uniaxial tensile loads, where it was noted a lower rate of withholding his last resistance property

Ocorrência e tratamento de monogenoides em alevinos de pampo (Trachinotus carolinus) cultivados experimentalmente na região norte do estado de São Paulo

This work had as objective tests therapeutic treatments seeking the monogenea eradication in fingerlings Florida Pompano (Trachinotus carolinus) servants in cage net in the area of Ubatuba, State of São Paulo. The fingerlings presented an accentuated weigh loss and strong discoloration and through observation of scraped of gills under light microscope were identified a high amount of monogenea. Three treatments were tested in form of baths: T1 (fresh water for 5 minutes); T2 (formalin: 1: 1.000 for 20 minutes) and T3: (formalin: 1:4.000 for 30 minutes). The treatments were appraised through scraped of gills, mounted among you laminate and laminulas and observed to the light microscope. It was observed that in the tested conditions all of the treatments were efficient in the elimination of the monogenea without presenting lethality to the fish. The treatment is recommended T I (take a bath in fresh water for 5 minutes) for the facility in the application and for the absence of use of chemical products.

Multi-scale simulation using a hybrid mass-spring system and finite element model

Ply-scale finite element (FE) models are widely used to predict the performance of a composite structure based on material properties of individual plies. When simulating damage, these models neglect microscopic fracture processes which may have a significant effect on how a crack progresses within and between plies of a multidirectional laminate. To overcome this resolution limitation a multi-scale modelling technique is employed to simulate the effect micro-scale damage events have on the macro-scale response of a structure. The current paper discusses the development and validation of a hybrid mass-spring system and finite element modelling technique for multi-scale analysis. The model developed here is limited to elastic deformations; however, it is the first key step towards an efficient multi-scale damage model well suited to simulation of fracture in fibre reinforced composite materials. Various load cases have been simulated using the model developed here which show excellent accuracy compared to analytical and FE results. Future work is discussed, including extension of the model to incorporate damage modelling.

Simulation of progressive damage in composites using the enhanced embedded element technique

Analysis of complex composite structures requires a fine contiguous mesh of threedimensional (3D) solid elements. The embedded element technique is a promising technique for predicting stiffness and stress. This paper presents a new method for enhancing the embedded element with continuum damage mechanics methods for predicting the evolution of damage in fiber reinforced composite structures. Comparison of the model prediction with experimental results reveals an excellent correlation between the tensile strength of quasi-isotropic laminate with an open hole. The embedded element technique allows the fiber reinforcement and matrix domains to be meshed independently and failure is evaluated separately in each domain. The enhanced embedded element approach allows the failure modes to be observed, specifically, the evolution of matrix cracking and fiber rupture. Compared to the traditional contiguous mesh finite element method, the present modelling technique demonstrates a clear advantage in predicting the experimentally observed failure modes and accurate characterisation of intralaminar fracture.

The influence of processing techniques on the matrix distribution and filtration of clay in a fibre reinforced nanocomposite

A nano-modified matrix based on an epoxy resin and montmorillonite (MMT) layered silicates, was successfully infiltrated through 10 ply of carbon fibre preform. A combined fabrication process of a vacuum assisted resin infusion method (VARIM) followed by a rapid heating rate and mechanical vibration during cure, facilitated the infiltration of the nano-modified matrix through the preform. This was achieved by dispersing the MMT clay in the resin and ensuring that the viscosity of the nano-modified matrix remained low during fabrication. SEM-EDX (energy dispersive X-ray spectroscopy) spectra showed that chemical constituents within MMT clay including silicon, aluminium and magnesium elements had permeated through the fibre preform and were detected throughout the laminate. A homogeneous resin/particle distribution was achieved with the size of clay particles ranging from 100 nm to 1 μm.

Prediction of mode I delamination resistance of z-pinned laminates using the embedded finite element technique

A new finite modelling approach is presented to analyse the mode I delamination fracture toughness of z-pinned laminates using the computationally efficient embedded element technique. In the FE model,each z-pin is represented by a single one-dimensional truss element that is embedded within the laminate. Each truss is given the material, geometric and spatial properties associated with the global crackbridging traction response of a z-pin in the laminate; this simplification provides a computationally efficient and flexible model where pin elements are independent of the underlying structural mesh for thelaminate. The accuracy of the FE modelling approach is assessed using mode I interlaminar fracture toughness data for a carbon-epoxy laminate reinforced with z-pins made of copper, titanium or stainless steel. The model is able to predict with good accuracy the crack growth resistance curves and fracture toughness properties for the different types of z-pinned laminate.

Defeitos de desenvolvimento do esmalte e respetivo tratamento

As estruturas dentárias são revestidas pelo esmalte dentário. O esmalte é um tecido de alta dureza, avascular e predominantemente branco. No entanto, distingue-se dos outros tecidos mineralizados do corpo pela sua incapacidade de remodelação. Devido a esse facto qualquer alteração que ocorra, quer ao longo da vida, quer no seu desenvolvimento fica, permanentemente, registada (Seow, 1997). Procurou-se nesta monografia aprofundar os conhecimentos sobre os mais comuns defeitos de desenvolvimento do esmalte existentes, assim como o respetivo tratamento. Para a realização desta monografia foram utilizados os seguintes motores de busca B-on, PubMed, Science Direct e Sci-elo, para a realização da pesquisa de informação, aplicando-se um critério de seleção temporal dos últimos 10 anos. As palavras-chaves e combinações de palavras utilizadas nos motores de busca referidos para a realização da pesquisa foram “Enamel”, “Enamel Development”, “Enamel Defects”, “Amelogenisis Imperfecta”, “Hypoplasia”. Dos 300 artigos encontrados nesta pesquisa, foram selecionados 68. O desenvolvimento dos tecidos dentários é um processo complexo conhecido por odontogénese, podendo ser simplisticamente dividido em três fases Fase de Botão, Fase de Capuz e por último a Fase de Campânula (Thesleff et al.,2009) Existem inúmeros defeitos de desenvolvimento do esmalte registados na literatura, não sendo mesmo possível em muitos casos enquadrar indubitavelmente o referido defeito numa categoria, ou até atribuir-lhe uma designação (Seow, 1997). Optou-se pela sua relevância e epidemiologia abordar nesta monografia os seguintes defeitos: Defeitos de desenvolvimento do esmalte; Opacidades; Opacidade difusa; Hipoplasia; Amelogenese imperfeita e todas as suas categorias; Fluorose e manchas por tetraciclinas assim como os seus respectivos tratamentos. Os defeitos de desenvolvimento de esmalte apresentam diversas características próprias e outras semelhantes entre si, verificando-se assim diversas possibilidades de tratamentos a realizar, uns mais invasivos e outros menos, que vão desde microabrasões na superfície do esmalte, à colocação de cerâmicas, dependendo sempre da preferência do paciente e do seu poder socioeconómico (Azevedo DT et al., 2011). Conclui-se que apesar de todos os problemas que acarretam quer a nível estético quer a nível funcional para os indivíduos nos quais não existe uma grande gravidade das lesões esses casos podem ser resolvidos por um Médico Dentista generalista desde que este tenha o conhecimento adequado dos protocolos de atuação.