An Overview

This work was financed by national funds from FCT—Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication—i3N. European Cooperation in Science & Technology (COST) Action European Topology Interdisciplinary Action (PhoBioS CA21159). Publisher Copyright: © 2023 by the authors.Catastrophic oil spill accidents, oily industrial wastewater, and other types of uncontrolled release of oils into the environment are major global issues since they threaten marine ecosystems and lead to a big economic impact. It can also affect the public health of communities near the polluted area. This review addresses the different types of oil collecting methods. The focus of this work will be on the different approaches to materials and technologies for oil/water separation, with a special focus on water/oil emulsion separation. Emulsified oil/water mixtures are extremely stable dispersions being, therefore, more difficult to separate as the size of the droplets in the emulsion decreases. Oil-absorbent materials, such as sponges, foams, nanoparticles, and aerogels, can be adjusted to have both hydrophobic and oleophilic wettability while displaying a porous structure. This can be advantageous for targeting oil spills in large-scale environmental and catastrophic sets since these materials can easily absorb oil. Oil adsorbent materials, for example, meshes, textiles, membranes, and clays, involve the capture of the oily material to the surface of the adsorbent material, additionally attracting more attention than other technologies by being low-cost and easy to manufacture.publishersversionpublishe

Tropisms of the dowser texture

UID/CTM/50025/2019 M-ERA-NET2/0007/2016 Action EUTOPIA CA17139Due to its low symmetry C2υ, the dowser texture is characterised by a 2D unitary vector field or alternatively by a unitary complex field. For the same symmetry reasons, the dowser texture is sensitive, in first order, to perturbations such as thickness gradients, electric fields or flows. We will focus on corresponding properties called respectively: Cuneitropism, electrotropism and rheotropism. In particular we will show that topological defects, known as dowsons or monopoles, can be manipulated by means of these tropisms.publishersversionpublishe

On Generation, Motions, and Collisions of Dowsons

PTDC/CTM-BIO/6178/2014. M-ERA-NET2/0007/2016 (CellColor).Dowsons are ±2π point singularities of the unitary complex order parameter eiφ characterizing the so-called dowser texture in a thin nematic layer with homeotropic boundary conditions. Dowsons are therefore similar to disclinations in freely-standing smectic C films or to vortices in two-dimensional superfluids or superconductors. Using especially tailored setups called dowsons' colliders, pairs of dowsons of opposite signs are generated and set into motion on counter-rotating trajectories leading to collisions. In a first approximation, the velocity of dowsons is orthogonal and proportional to the local phase gradient (Formula presented.). The outcome of collisions, i.e., either annihilation or bypass, depends on the distance of trajectories Δφ in terms of the phase: for Δφ π the dowsons are passing by. This rule is valid only for quasi-static stationary wound up textures and can be easily broken by application of a Poiseuille flow in an appropriate direction.publishersversionpublishe

Divulgação de acervos documentais: as exposições como ferramenta privilegiada

A divulgação documental é uma das funções estruturantes das instituições de arquivo e tem subjacente um conjunto de tarefas fundamentais: a organização, o tratamento, a preservação e a recuperação documental. Todas estas tarefas têm o objetivo comum de dar a conhecer os acervos documentais, quer para fins educativos, quer para fins culturais. As exposições constituem uma ferramenta privilegiada para a divulgação documental, pois permitem o acesso à documentação de uma forma estruturada e apelativa.A exposição Memórias em Arquivo pretendeu desvelar alguns dos tesouros municipais e fixar parte da memória sobre o passado do concelho. Com uma linha cronológica que se inicia ainda antes da fundação do concelho, a Exposição segue a evolução do espaço, das pessoas e das suas vidas até à atualidade. Apresentada pela primeira vez em 2014 a exposição Memórias em Arquivo tem circulado por diversos espaços graças à sua estrutura modular

A identidade e a imagem das organizações

Lusíada. Economia & Empresa. - ISSN 1645-6750. - S. 2, n. 2-3 (2003). - p. 71-88.O desenvolvimento da identidade e a expressão da missão da empresa e cultura, incluindo as suas responsabilidades sociais, em termos de modificação e melhoramento das próprias mentalidades das pessoas e entidades que com classe relacionam. Para enfrentar com êxito as mutações em curso, as empresas necessitam de modificar a forma como são percebidas pelos seus públicos-chave (internos e externos) dando a conhecer de forma clara, coerente e eficaz o que e que fazem, como o fazem e como o pretendem fazer e qual a sua finalidade, os seus objectivos e a sua estratégia. A identidade da organização não e apenas desenho gráfico mas também a forma como a empresa esta organizada e funciona, quais são os objectivos, quais são as suas marcas e como são geridos. A comunicação empresarial e o processo que vai converter a identidade organizacional em imagem organizacional. A imagem da empresa, ao contrário da identidade, e uma concepção ou realidade do domínio público ou do cliente a que respeita o interesse relacionado com a empresa. A comunicabilidade e um dos caracteres essenciais de qualquer empresa porque, obviamente, as operações que realiza tem de ser projectadas sobre o mundo exterior e nele produzir efeitos conducentes ou condicionantes de relações económicas

Light shutters from nanocrystalline cellulose rods in a nematic liquid crystal

This work reports a recently developed electro-optical (EO) device that can potentially be used as a light shutter or a privacy window. By using nanocrystalline cellulose rods, we were able to improve some of the most relevant parameters characterising the EO behaviour. A brief description of the proposed working mechanism for these devices is presented, and numerical simulations based on this mechanism of both the optical transmission and the cells' electrical capacitance are compared with the obtained results, validating the underlying working model considered

Light shutters from nanocrystalline cellulose rods in a nematic liquid crystal

This work reports a recently developed electro-optical (EO) device that can potentially be used as a light shutter or a privacy window. By using nanocrystalline cellulose rods, we were able to improve some of the most relevant parameters characterising the EO behaviour. A brief description of the proposed working mechanism for these devices is presented, and numerical simulations based on this mechanism of both the optical transmission and the cells' electrical capacitance are compared with the obtained results, validating the underlying working model considered

Liquid crystal beads constrained on thin cellulosic fibers: Electric field induced microrotors and N-I transition

We directly visualize the response of nematic liquid crystal drops of toroidal topology threaded in cellulosic fibers, suspended in air, to an AC electric field and at different temperatures over the N-I transition. This new liquid crystal system can exhibit non-trivial point defects, which can be energetically unstable against expanding into ring defects depending on the fiber constraining geometries. The director anchoring tangentially near the fiber surface and homeotropically at the air interface makes a hybrid shell distribution that in turn causes a ring disclination line around the main axis of the fiber at the center of the droplet. Upon application of an electric field, E, the disclination ring first expands and moves along the fiber main axis, followed by the appearance of a stable "spherical particle" object orbiting around the fiber at the center of the liquid crystal drop. The rotation speed of this particle was found to vary linearly with the applied voltage. This constrained liquid crystal geometry seems to meet the essential requirements in which soliton-like deformations can develop and exhibit stable orbiting in three dimensions upon application of an external electric field. On changing the temperature the system remains stable and allows the study of the defect evolution near the nematic-isotropic transition, showing qualitatively different behaviour on cooling and heating processes. The necklaces of such liquid crystal drops constitute excellent systems for the study of topological defects and their evolution and open new perspectives for application in microelectronics and photonics

Hierarchical wrinkling on elastometric Janus spheres

Hierarchical wrinkling on elastomeric Janus spheres is permanently imprinted by swelling, for different lengths of time, followed by drying the particles in an appropriate solvent. First-order buckling with a spatial periodicity (lambda(11)) of the order of a few microns and hierarchical structures comprising of 2nd order buckling with a spatial periodicity (lambda(12)) of the order of hundreds of nanometers have been obtained. The 2nd order buckling features result from a Grinfeld surface instability due to the diffusion of the solvent and the presence of sol molecules