Solid flow drives surface nanopatterning by ion-beam irradiation

Ion Beam Sputtering (IBS) is known to produce surface nanopatterns over macroscopic areas on a wide range of materials. However, in spite of the technological potential of this route to nanostructuring, the physical process by which these surfaces self-organize remains poorly under- stood. We have performed detailed experiments of IBS on Si substrates that validate dynamical and morphological predictions from a hydrodynamic description of the phenomenon. Our results elucidate flow of a nanoscopically thin and highly viscous surface layer, driven by the stress created by the ion-beam, as a description of the system. This type of slow relaxation is akin to flow of macroscopic solids like glaciers or lead pipes, that is driven by defect dynamics.Comment: 12 pages, 4 figure

Parque de Campismo da Torreira: Novos Desafios para a Competitividade e Sustentabilidade do Negócio

O estudo aqui apresentado, procura debruçar-se, essencialmente, no campismo e caravanismo, enquanto atividades de lazer, económica, ecológica e ambientalmente sustentáveis, tendo como objetivo alcançar o novo modelo de campismo denominado de glamping, vocacionado para o ecoturismo, focando-nos nos segmentos de mercado júnior, sénior, familiar e desportivo. Assim sendo, considera-se pertinente o reconhecimento destas dimensões, de modo a construir aplicações práticas sustentáveis, relativamente ao Parque de Campismo da Torreira, contribuindo para um desenvolvimento da região e da população local, a nível económico, psicossocial e cultural, recorrendo as estratégias de marketing de curto-médio prazo. A metodologia praticada foi a recolha de informação bibliográfica, infográfica, estatística e a observação direta no decorrer de um estágio curricular. Os resultados obtidos, resultam de uma visão holística das diversas partes deste documento, a sustentabilidade ambiental e o marketing, determinando, assim, a criação de um plano para melhorar a qualidade e os serviços do Parque de Campismo da Torreira, reforçando o seu posicionamento, como parque com boas práticas ambientais e como referência ao nível da região norte e centro de Portugal

Contamination des moules (Mytilus galloprovincialis) des côtes de la région de Dakar par les Hydrocarbures Aromatiques Polycycliques (HAPs)

Dans ce travail, nous avons etudie la contamination par les Hydrocarbures Aromatiques Polycycliques des moules recoltees au niveau des cotes de la region de Dakar. Les sites ont ete choisis en fonction des activites qui y sont developpees. Lfextraction des HAPs a ete faite au moyen dfun extracteur Soxhlet avec un melange hexane/acetone et la purification est realisee avec lfoxyde dfaluminium. Nous avons analyse lfextraitpar un chromatographe de gaz couple a un spectrographe de masse (GC/MS). Les resultats montrent que les teneurs en hydrocarbures evoluent de facon croissante en fonction du temps. Au port de Dakar, lesconcentrations passent de 5308,67 en 2007 a 17973,37 ƒÊg/kg de poids sec, en 2008. Lfevolution des hydrocarbures suit la meme tendance dans les differents sites. Ainsi, le Port concentre la plus forte teneur, ensuite suivent les sites de Mbao et de Hann. Au niveau du port, la contamination proviendrait des depots de stockages des hydrocarbures mais egalement des operations de transbordement du petrole. La zone de Mbao estpolluee par la presence de nombreuses usines dont une raffinerie qui a ces canaux directement ouvert sur la plage. Le site de Hann abrite un canal qui draine les eaux usees domestiques mais aussi les huiles de rejet des stations services. Ainsi, les moules deviennent un bon indicateur de la qualite des eaux mais egalement un danger pour la population, grande consommatrice de cette espece. Ces etudes qui constituent un etat de lieu doivent etre poursuivies afin de fournir des donnees scientifiques de base aux decideurs politiques pour la recherche de solutions durables a la pollution de notre environnement

A Nexafs Study of Nitric Oxide Layers Adsorbed from a nitrite Solution onto a Pt(111) Surface

NO molecules adsorbed on a Pt(111) surface from dipping in an acidic nitrite solution are studied by near edge X-ray absorption fine structure spectroscopy (NEXAFS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) techniques. LEED patterns and STM images show that no long range ordered structures are formed after NO adsorption on a Pt(111) surface. Although the total NO coverage is very low, spectroscopic features in N K-edge and O K-edge absorption spectra have been singled out and related to the different species induced by this preparation method. From these measurements it is concluded that the NO molecule is adsorbed trough the N atom in an upright conformation. The maximum saturation coverage is about 0.3 monolayers, and although nitric oxide is the major component, nitrite and nitrogen species are slightly co-adsorbed on the surface. The results obtained from this study are compared with those previously reported in the literature for NO adsorbed on Pt(111) under UHV conditions