Results of geoelectrical surveys in the area of Crater 70, Deception Island, Maritime Antarctica

Deception Island is horse-shoe shaped stratovolcano with 15 km diameter and a large caldera that opens towards the southeast, forming a bay about 7 km wide. The maximum altitude is at Mount Pond (539 m a.s.l.). About 57% of the island area is covered by glaciers. In geological terms Deception Island is composed of volcano-sedimentary deposits, including pyroclastic flows and deposits, strombolian scoriae and lava, volcanic and hypo-volcanic indurated ashes, and phreatomagmatic deposits. Recent eruptions took place in the interior of the island in 1967, 1969, and 1970. Permafrost is widespread in the island but its characteristics are still poorly studied. In this study we present geoelectrical data collected in the Crater 70 area of Deception Island which was formed during the eruptions of 1970. The study area is located in the southern slope of a volcanic cone and the objective of the geoelectrical survey was to determine if there were any permafrost aggradation after the eruptive event and to assess the thickness of the frozen body. Two electrical resistivity tomography (ERT) profiles and a vertical electrical sounding (VES) were done (Fig. 1). Geoelectrical methods are particularly well adapted to study the spatial distribution of permafrost because of its high electrical resistivities in comparison with the electrical resistivities of soil and rocks with water and above 0 oC

O Horizonte do Mar Português

O texto procura dar uma visão ampla da importância actual do mar para o País. Defende que o mar é para Portugal um espaço de vocação que, se devidamente aproveitado, pode contrabalançar o seu reduzido peso no contexto regional. De facto, o mar tem enorme potencial por explorar nos campos económico, da investigação científica e da segurança e defesa capaz de constituir não só fonte de bem estar, como elemento de prestígio e de afirmação do País. Depois de identificar os factores relevantes de cada uma dessas áreas, o artigo conclui que o mar é vital para Portugal e que a economia, a investigação científica e a segurança e defesa deverão formar os vértices de uma nova estratégia assente sobre o mar

Leverage instability and persistence: evidence from the United States and Europe

We find that leverage behavior both in level and time-series variation is very similar between the United States and Europe throughout the 1990-2013 period. Leverage regimes are simultaneously unstable and persistent for both regions. We define instability as the extent to which firms largely deviate from their long-term leverage mean, while persistence as the extent to which today’s leverage influences its future levels. We then show that this simultaneous evidence imply a mean-reversion behavior of leverage and discuss some of its implications for future research on this field

Guiding legacy systems for evolution. PmatE: a case study of maintenance and engineering

Even though software change is inevitable, accurate maintenance can extend software lifespan in a subtle way when both budget and time constraints get in the way of software replacement. In the University of Aveiro, the project PmatE – a quiz web platform created to encourage students to like Math – emerged in the early 1990’s and stacked several applications over the decades without major planning, cleaning or upgrade. This resulted in a huge-sized framework that was crucial to be always available and online and had high operational cost, leading to an increasing amount of technical debt. After 3 decades, the project was studied, refactored and refurbished, leading to a stable consistent framework ready for evolution and software spinouts. This work shows how to manage and engineer solutions to maintain a legacy system and evolve it even when tied up to heavy constraints.info:eu-repo/semantics/publishedVersio

UAVs for Science in Antarctica

Remote sensing is a very powerful tool that has been used to identify, map and monitor Antarctic features and processes for nearly one century. Satellite remote sensing plays the main role for about the last five decades, as it is the only way to provide multitemporal views at continental scale. But the emergence of small consumer-grade unoccupied aerial vehicles (UAVs) over the past two decades has paved the way for data in unprecedented detail. This has been also verified by an increasing noticeable interest in Antarctica by the incorporation of UAVs in the field activities in diversified research topics. This paper presents a comprehensive review about the use of UAVs in scientific activities in Antarctica. It is based on the analysis of 190 scientific publications published in peer-reviewed journals and proceedings of conferences which are organised into six main application topics: Terrestrial, Ice and Snow, Fauna, Technology, Atmosphere and Others. The analysis encompasses a detailed overview of the activities, identifying advantages and difficulties, also evaluating future possibilities and challenges for expanding the use of UAV in the field activities. The relevance of using UAVs to support numerous and diverse scientific activities in Antarctica becomes very clear after analysing this set of scientific publications, as it is revolutionising the remote acquisition of new data with much higher detail, from inaccessible or difficult to access regions, in faster and cheaper ways. Many of the advances can be seen in the terrestrial areas (detailed 3D mapping; vegetation mapping, discrimination and health assessment; periglacial forms characterisation), ice and snow (more detailed topography, depth and features of ice-sheets, glaciers and sea-ice), fauna (counting penguins, seals and flying birds and detailed morphometrics) and in atmosphere studies (more detailed meteorological measurements and air-surface couplings). This review has also shown that despite the low environmental impact of UAV-based surveys, the increasing number of applications and use, may lead to impacts in the most sensitive Antarctic ecosystems. Hence, we call for an internationally coordinated effort to for planning and sharing UAV data in Antarctica, which would reduce environmental impacts, while extending research outcomes.info:eu-repo/semantics/publishedVersio

Shoreline change rates and land to sea sediment and soil organic carbon transfer in eastern Parry Peninsula from 1965 to 2020 (Amundsen Gulf, Canada)

As the Arctic is warming, permafrost coasts are eroding faster, threatening coastal communities, habitats, and altering sediment and nutrient budgets. The western Canadian Arctic is eroding at a rapid pace; however, little is known on changes occurring in the Amundsen Gulf area. This study was conducted in the eastern coast of Parry Peninsula, a neglected rock dominated coastal area. We used orthorectified aerial photos of 1965 and 1993 and very high-resolution satellite imagery of 2020 to manually delineate the shoreline according to backshore and foreshore centered approaches. Shoreline change rates were calculated and sediment and organic carbon transfer from land to sea estimated using digital elevation model, the Northern Circumpolar Soil Carbon Database, and ground ice content. The results show a mean erosion rate of 0.12 m/yr for the backshore zone and 0.16 m/yr for the foreshore zone, with increasing erosion in the Paulatuk Peninsula in recent decades. The average sediment transfer from land to sea was 20 m3/m/yr and the soil organic carbon (SOC) flux was 7 kg C/m/yr. We highlight the importance of using the cliff-top as shoreline reference to accurately estimate sediment and SOC transfers, an approach neglected in automatic shoreline delineation techniques based on remote sensing imagery using the waterline.Natural Resources Canada; Canadian Forest Service; Climate Change Geoscience Program, Crown-Indigenous Relations and Northern Affairs Canada (CIRNAC) through the Beaufort Sea; Regional Strategic Environment and Research Assessment (BRSEA); European Union's Horizon 2020 Research and Innovation Program; Community of Paulatukinfo:eu-repo/semantics/publishedVersio

Produção de extratos bioativos a partir de resíduos de Quercus cerris por extração supercrítica com solventes verdes

Esta dissertação teve como objetivo estudar a produção e caracterização de extratos ricos em compostos bioativos (nomeadamente fridelina) a partir de cortiça de Quercus cerris. Realizaram-se extrações Soxhlet e extrações sólido-líquido (SLE) em descontínuo com metanol, etanol, diclorometano e éter de petróleo, assim como extração supercrítica (SFE) com dióxido de carbono modificado (por adição de etanol). Os extratos produzidos foram caracterizados por FTIR-ATR e GC-MS e o método de escalonamento multidimensional (MDS) foi aplicado para comparação dos mesmos. Realizou-se uma otimização experimental de SFE, usando um desenho fatorial de experiências do tipo Box-Behnken e a metodologia de superfícies de resposta. O rendimento total de extração (Total) máximo foi obtido para o ensaio Soxhlet com metanol (Total = 13.8 wt.%) e o rendimento mínimo foi obtido para extração sólido-líquido em descontínuo com éter de petróleo (Total = 0.35 wt.%). Registou-se uma variabilidade significativa dos valores de Total, marcada pelos rendimentos superiores para extração com solventes polares, nomeadamente metanol e etanol. No caso da extração supercrítica, Total variou de 1.2 wt.% no ensaio SFE3 (50 ℃, 2.5 wt.% EtOH, 5 g min−1) até 1.7 wt.% no ensaio SFE4 (60 ℃, 2.5 wt.% EtOH, 8 g min−1). Em termos de concentração em fridelina (Friedelin), os resultados oscilaram entre 41.3 wt. % (Soxhlet com diclorometano) e 5.4 wt. % (SLE em descontínuo com éter de petróleo). Os melhores resultados em termos de Friedelin foram os que envolveram solventes pouco polares/apolares. Os ensaios SFE atingiram resultados de Friedelin melhores do que a maioria dos ensaios de extração Soxhlet e sólido-líquido em descontínuo, o que confirma a interessante seletividade do processo para a fridelina. A análise MDS destacou a maior proximidade química entre os extratos alcoólicos e a biomassa, e entre os extratos de solventes apolares ou pouco polares e a fridelina pura. Para a otimização experimental de SFE da cortiça Q. cerris, as condições que maximizam Total (2.2 wt.%) e F,nF (3.3 para t = 8.0 h) são valores máximos de (60 ℃), teor de etanol (5 wt.%) e de caudal de CO2 (11 g min−1). De registar os valores de seletividade superior a 1.0 no espaço experimental estudado, o que confirma que a fridelina é removida seletivamente por SFE. No caso de Friedelin, o valor máximo (38.2 wt.%) foi obtido para a combinação de baixa temperatura (40 ℃), ausência de cossolvente (0 wt.% EtOH) e menor caudal (5 g min−1). Em definitivo, as condições ótimas dependerão de qual o principal objetivo da extração: um extrato rico numa maior diversidade de compostos (maior Total) ou em compostos alvo como a fridelina (maior Friedelin). No geral, este trabalho fornece argumentos importantes para a produção de extratos ricos em fridelina a partir da cortiça de Quercus cerris, através da tecnologia SFE no âmbito do conceito de biorrefinariaThe present work studied the production and characterization of extracts rich in bioactive compounds (namely friedelin) from Quercus cerris cork. Soxhlet and batch solid-liquid extraction (SLE) with methanol, ethanol, dichloromethane and petroleum ether were carried out, as well as supercritical fluid extraction (SFE) using modified carbon dioxide (by addition of ethanol). The produced extracts were characterized by FTIR-ATR and GC-MS, and multidimensional scaling (MDS) was applied to compare them. The optimization of SFE was performed using Box-Behnken design of experiments and response surface methodology. The maximum total extraction yield (Total) was attained for the Soxhlet extraction with methanol (Total = 13.8 wt.%) and the minimum was attained in batch SLE with petroleum ether (Total = 0.35 wt.%). A significant variability of Total values was evident, marked by the higher yields obtained with polar solvents, namely methanol and ethanol. For the supercritical fluid extractions, Total ranged from 1.2 wt.% for run SFE3 (50 ℃, 2.5 wt.% EtOH, 5 g min−1) to 1.7 wt.% for run SFE4 (60 ℃, 2.5 wt.% EtOH, 8 g min−1). For friedelin concentration (Friedelin), the results ranged from 41.3 wt.% (Soxhlet with dichloromethane) to 5.4 wt.% (batch SLE with methanol). The best performing assays on Friedelin were those involving weakly polar/non-polar solvents. The SFE assays provided Friedelin results better than most Soxhlet and batch SLE experiments, which confirms the interesting selectivity to friedelin (F,nF). MDS analysis highlighted the chemical proximity between the alcoholic extracts and the biomass, and between the weakly or non-polar solvent extracts and pure friedelin. For the experimental optimization of SFE of Q. cerris cork, the conditions that maximize Total (2.2 wt.%) and F,nF (3.3 at t = 8.0 h) were the maximum values of (60 ℃), ethanol content (5 wt.%) and CO2 flow rate (11 g min−1). In fact, the selectivity values were higher than 1.0 anywhere within the studied experimental space, which shows that friedelin can be removed selectively over all the other compounds by SFE. For friedelin concentration, the maximum (Friedelin= 38.2 wt.%) was attained for the combination of a lower temperature (40 ℃), no cosolvent (0 wt.% EtOH) and lower CO2 flow rate (5 g min−1). The optimal conditions depend on what is the main goal of extraction: an extract enriched in a higher diversity of compounds (higher Total) or in a target compound like friedelin (higher Friedelin). On the whole, this work provides strong arguments towards the production of friedelin enriched extracts from Quercus cerris cork through SFE technology, under the biorefinery conceptMestrado em Engenharia Químic

Deception Island 1967–1970 volcano eruptions from historical aerial frames and satellite imagery (Antarctic Peninsula)

Aerial frames and satellite imagery are widely recognized data sources from which to produce maps. For volcanoes, maps enable the quantification of erupted ash and the destruction caused. The last eruptive sequence on Deception Island was endured from 1967 to 1970. Analogue maps were produced via classical photogrammetric methods with a high degree of human intervention mainly to analyse the volcanic-centres areas only. However, historical aerial frames cover the whole of Deception Island. Structure from motion photogrammetry, a near-automated compilation of digital image processing strategies, minimizes the degree of human intervention to produce orthographic mosaics and digital elevation models from digital aerial frames. Orthographic mosaics were produced from historical aerial frames of 1956 and 1968, and a Kompsat-3 image of 2020. Their shared rootmean-square deviation was 1.8 m and 1.7 m in easting and northing, respectively, at ground control points measured with phase-differential global navigation satellite systems. The digital elevation models were processed with a root-mean-square deviation of 2.3 m and 3.6 m from 1956 and 1968 aerial frames, respectively. As the first application, erupted ashfall and the subsequent destruction, mainly at the former Chilean and British bases, were identified, and the volume of erupted ash was assessed to be over 0.16 km3 within the area mapped by these new digital cartographic products.info:eu-repo/semantics/publishedVersio