Biologia com humor: utilização de charges na divulgação científica

Anais do 3° Encontro Nacional de Jogos e Atividades Lúdicas no Ensino de Química, Física e Biologia (Jalequim - Level III) - Núcleo de Desenvolvimento de Pesquisas em Ensino de Química/Ciências da UNILA (NuDDEQ)O campo das Ciências Biológicas apresenta linguajar e conceitos que, muitas vezes, soam como estranhos ao público em geral. Tal aspecto pode contribuir para um afastamento das pessoas em relação a esta área do conhecimento (SASSERON & CARVALHO, 2011). Desta maneira, é interessante se pensar estratégias de aproximação do linguajar biológico com o cotidiano das pessoas, contribuindo assim para a divulgação científica. Entre as várias possibilidades de estratégias de divulgação científica, o presente trabalho optou por trabalhar a mesma relacionando-a com o humor, utilizando-se charges

Natural and amyloid self-assembly of S100 proteins: structural basis of functional diversity

The S100 proteins are 10-12 kDa EF-hand proteins that act as central regulators in a multitude of cellular processes including cell survival, proliferation, differentiation and motility. Consequently, many S100 proteins are implicated and display marked changes in their expression levels in many types of cancer, neurodegenerative disorders, inflammatory and autoimmune diseases. The structure and function of S100 proteins are modulated by metal ions via Ca2+ binding through EF-hand motifs and binding of Zn2+ and Cu2+ at additional sites, usually at the homodimer interfaces. Ca2+ binding modulates S100 conformational opening and thus promotes and affects the interaction with p53, the receptor for advanced glycation endproducts and Toll-like receptor 4, among many others. Structural plasticity also occurs at the quaternary level, where several S100 proteins self-assemble into multiple oligomeric states, many being functionally relevant. Recently, we have found that the S100A8/A9 proteins are involved in amyloidogenic processes in corpora amylacea of prostate cancer patients, and undergo metal-mediated amyloid oligomerization and fibrillation in vitro. Here we review the unique chemical and structural properties of S100 proteins that underlie the conformational changes resulting in their oligomerization upon metal ion binding and ultimately in functional control. The possibility that S100 proteins have intrinsic amyloid-forming capacity is also addressed, as well as the hypothesis that amyloid self-assemblies may, under particular physiological conditions, affect the S100 functions within the cellular milieu

Utilização de bender elements na determinação do módulo de distorção

Este trabalho apresenta a utilização de bender elements na determinação do módulo de distorção de uma areia. A amostra foi preparada para um determinado índice de vazios e ensaiada à compressão isotrópica até 400 kPa. Baseada na medição e interpretação de velocidades de ondas sísmicas, a técnica dos bender elements foi utilizada para a determinação do módulo de distorção no âmbito das muito pequenas deformações. Para melhorar a consistência dos resultados, foram utilizadas em simultâneo análises no domínio do tempo e da frequência na determinação do módulo de distorção. São feitas recomendações relativas à redução da subjetividade na determinação da velocidade de propagação das ondas sísmicas. A relação do módulo de distorção com a tensão normal média efetiva é avaliada e comparada com expressões empíricas.Fundação para a Ciência e Tecnologia (FCT), projeto de investigação WaveSoil (PTDC/ECM/122751/2010) do projeto FCOMOP-01-0124-FEDER-02036

Small strain stiffness of a sand by means of bender elements and accelerometers: measuring principles and applications

Ao longo dos anos têm-se assistido ao desenvolvimento de novas técnicas para a determinação da rigidez dos solos em laboratório, baseadas na determinação direta da velocidade de propagação de ondas sísmicas. Neste contexto, este trabalho apresenta a medição e interpretação de velocidades de ondas sísmicas em ensaios realizados numa areia através do uso combinado de bender elements e acelerómetros. A interpretação das medições do tempo de propagação e da aceleração foi realizada no domínio do tempo e no domínio da frequência. No final, são tecidas considerações relativas aos valores de rigidez obtidos e a uma potencial expansão do setup apresentado para aplicações a uma vasta gama de geomateriais.In the last decades, the development of new laboratory techniques to assess soil stiffness throughout the use of seismic wave-based techniques, have received significant attention. In this context, this paper presents measurements and interpretation of seismic wave velocities from tests performed on a sand and based on the combined use of bender elements with accelerometers. The interpretation of the travel time measurements were performed using time and frequency-domain methods. Finally, considerations concerning stiffness results and an enlarged application of the presented setup to a wide range of geomaterials are made.Fundação para a Ciência e Tecnologia (FCT), projeto de investigação WaveSoil (PTDC/ECM/122751/2010) do projeto FCOMOP-01-0124-FEDER-02036

Optimal cruciform specimen design using the direct multi-search method and design variable influence study

Nowadays the development of new testing machines and the optimization of new specimen geometries are two very demanding activities. In order to study complex material stress and strain distributions, as in-plane biaxial loading, one must develop new technical solutions. A new type of testing machine has been developed by the present authors, for the fatigue testing of cruciform specimens, but the low capacity of the testing machine requires the optimization of the specimen in order to achieve higher but uniform stress and strain distributions on the specimen center. In this paper, the authors describe the procedure to optimize one possible geometry for cruciform specimens, able to determine the fatigue initiation life of material subjected to out of phase in-plane biaxial fatigue loadings. The high number of design variables were optimized using the direct multi-search method, considering two objective functions, the stress level on the specimen center and the uniformity of the strain distribution on a 1.0 mm radius of the specimen center. Several Pareto Fronts were obtained for different material thickness, considering the commercially available sheet metal thickness. With the optimal solution, the influence of every design variable was studied in order to provide others with a powerful tool that allows selecting the optimal geometry for the desired application. The results are presented in the form of design equations considering that the main design variable, the material thickness, was chosen from a Renard series of preferred numbers. The end user is then able to configure the optimal specimen for the required fatigue test.info:eu-repo/semantics/publishedVersio

Assessment of shear modulus by different seismic wave-based techniques

Using combined setup of bender elements and accelerometers, tests were conducted on Coimbra sand specimens in order to measure and interpret seismic wave velocities to assess initial shear modulus. For these tests both time and frequency domain analyses were performed. Resonant column tests were also performed on the same sand to validate the results obtained with the bender elements and accelerometers setup. As is well known, in the last decades the development of new laboratory techniques to assess soil stiffness through the use of seismic wave-based techniques, has received significant attention due to its simplicity and versatility of the equipment setup. One of these techniques is the bender elements test which have been one of the most widely used, although some limitations concerning its usage. In this context, the combined use of bender elements with other seismic wave-based testing techniques, such as accelerometers or the resonant column, is quite important to compare and validate the testing techniques. Given its miniature size, the installation of accelerometers on the side of the sample is considered feasible without significant disturbance on the other measuring techniques. The resonant column is a widely used and accurate testing technique due to its reliability and repeatability. Finally, the results of this combined tests allow a critical discussion on the advantages and limitations of the use of bender elements and accelerometers, in contrast with the resonant-column for the assessment of the shear modulus in sand.This work was developed with the financial support provided by FCT (Portuguese Foundation for Science and Technology) under the research project WaveSoil - PTDC/ECM/122751/2010 from FCOMOP-01-0124-FEDER-020365 project

Avaliação do comportamento mecânico de um solo reforçado com fibras em carregamento estático e cíclico, de muito pequenas a grandes deformações

A utilização de fibras como solução de reforço de solos é reconhecida actualmente como uma técnica eficaz na melhoria das características de resistência e rigidez. Ao longo dos anos, os estudos realizados permitiram compreender a relação solo/fibras na melhoria do comportamento mecânico para gamas de deformação próximas da rotura. Porém, tem sido dispensada pouca atenção no que diz respeito à avaliação do comportamento mecânico e à determinação da rigidez no âmbito das muito pequenas deformações. Assim, este estudo visa identificar a influência de diferentes percentagens de fibras, bem como do uso de malhas de fibras orientadas, na resposta mecânica de um solo reforçado com fibras, numa gama variada de deformações. Para o efeito, foram realizados ensaios de compressão uniaxial e cíclica num solo residual granítico reforçado com fibras, com medições da velocidade das ondas sísmicas com recurso a bender elements e acelerómetros. Foi ainda realizado um estudo comparativo entre o uso de fibras orientadas aleatoriamente e em malha quadrada entre 0⁰ e 90⁰.The use of fibres for soil reinforcement is currently recognised as an effective technique in the improvement of the strength and stiffness properties of soils. Along the years, several studies have focused on the soil/fiber ratio for the improvement of the mechanical behavior of the soil for large strains, near failure. However, little attention has been given to the assessment of the mechanical behaviour and stiffness of the reinforced soil at very small strains. This paper aims to address this issue, by investigating the influence of different fiber percentages, as well as the use of oriented fiber meshes on the mechanical response of the reinforced soil for a wide range of strains. For this purpose, uniaxial static and cyclic compression tests were performed on a granitic residual soil, reinforced with fibers, together with measurements of seismic wave velocities by means of bender elements and accelerometers. A comparative study was also performed between randomly oriented fibers and square 0º to 90º oriented fiber meshes.Os autores gostariam de agradecer o apoio dado pela Fundação para a Ciência e Tecnologia (FCT) através do projeto de investigação WaveSoil (PTDC/ECM/122751/2010) do projeto FCOMOP-01-0124-FEDER020365 no âmbito da qual este trabalho foi desenvolvido

Measurements and interpretation of small strain siffness of a sand

Este trabalho apresenta a medição e interpretação de velocidades de ondas sísmicas em ensaios realizados numa areia através do uso combinado de bender elements (BE) e acelerómetros (AC). A amostra foi preparada para um determinado índice de vazios e ensaiada em ensaio monotónico de compressão isotrópica até 400 kPa. A técnica dos BE foi utilizada com vista à determinação do módulo de distorção (G0) no âmbito das muito pequenas deformações. Para melhorar a consistência das medições, dois AC foram utilizados em conjunto com os BE. Na determinação de G0 foram utilizados, simultaneamente, análises no domínio dos tempos e das frequências. São apresentadas considerações relativas aos diferentes valores de G0obtidos nas distintas análises. A relação de G0 com a tensão normal média efetiva é avaliada para a areia de estudo e comparada com expressões empíricas.This paper presents measurement and interpretation of seismic wave velocities from tests conducted on a sand, based on the combined use of bender elements (BE) with accelerometers (AC). The specimen was prepared at certain initial void ratio and monotonic-isotropically compressed up to 400 kPa. The BE technique was used to determine the sand shear modulus (G0) at very small strains. In order to increase the reliability of the measurements, two AC were jointly used with BE. The G0 stiffness was determined using time and frequency-domain methods. The systematic differences observed between the G0 values, calculated using the different methods are discussed. The relationship between G0 and the effective mean normal stress was evaluated for the studied sand and compared with empirical expressions.Fundação para a Ciência e Tecnologia (FCT), projeto WaveSoil (PTDC/ECM/122751/ 2010), FCOMOP-01-0124-FEDER-02036

Measurement of shear modulus using bender elements and resonant-column

In recent times, new demands in geotechnical engineering, mainly in transportation geotechnics, require the use of advanced characterization techniques in order to accurately assess soil stiffness parameters. From this perspective, seismic wave-based techniques have received significant attention, since these allow performing the same basic measurement in the laboratory and field. With an enormous potential, bender elements are currently one of the most popular techniques used to measure reference soil properties in the very small strain range, namely the shear modulus. Bench and triaxial tests conducted on a wide range of geomaterials already demonstrated the applicability of this technique. However, the combined use of bender elements with other testing techniques, as the resonant column, is quite important in order to compare and validate some of the procedures used. In this context, bench bender elements tests were carried out on stiff sandy silt/silty sand specimens and the interpretation of seismic wave velocities was performed using time domain methods under a variety of excitations. Resonant column tests were also conducted on the same material to validate the obtained results with the bench bender elements setup. A critical discussion is made on the advantages and limitations of bender elements usage in contrast with the resonant-column for the assessment of the shear modulus, as well as some insights regarding damping. Additional tests were carried out in two distinct BE setups, one of which installed in the resonant column device, as well as ultrasonic measurements, with the purpose of validating the BE procedure and results interpretation. From this research, it was possible to compare and analyze the results obtained with the three different bender element setups and derive recommendations towards achieving reliable measurements.This work was developed with the financial support provided by FCT (Portuguese Foundation for Science and Technology) under the research project WaveSoil - PTDC/ECM/122751/2010 from FCOMOP-01-0124-FEDER-020365 project

S100A6 Amyloid Fibril Formation Is Calcium-modulated and Enhances Superoxide Dismutase-1 (SOD1) Aggregation

S100A6 is a small EF-hand calcium- and zinc-binding protein involved in the regulation of cell proliferation and cytoskeletal dynamics. It is overexpressed in neurodegenerative disorders and a proposed marker for Amyotrophic Lateral Sclerosis (ALS). Following recent reports of amyloid formation by S100 proteins, we investigated the aggregation properties of S100A6. Computational analysis using aggregation predictors Waltz and Zyggregator revealed increased propensity within S100A6 helices HI and HIV. Subsequent analysis of Thioflavin-T binding kinetics under acidic conditions elicited a very fast process with no lag phase and extensive formation of aggregates and stacked fibrils as observed by electron microscopy. Ca2+ exerted an inhibitory effect on the aggregation kinetics, which could be reverted upon chelation. An FT-IR investigation of the early conformational changes occurring under these conditions showed that Ca2+ promotes anti-parallel β-sheet conformations that repress fibrillation. At pH 7, Ca2+ rendered the fibril formation kinetics slower: time-resolved imaging showed that fibril formation is highly suppressed, with aggregates forming instead. In the absence of metals an extensive network of fibrils is formed. S100A6 oligomers, but not fibrils, were found to be cytotoxic, decreasing cell viability by up to 40%. This effect was not observed when the aggregates were formed in the presence of Ca2+. Interestingly, native S1006 seeds SOD1 aggregation, shortening its nucleation process. This suggests a cross-talk between these two proteins involved in ALS. Overall, these results put forward novel roles for S100 proteins, whose metal-modulated aggregation propensity may be a key aspect in their physiology and function