Minerals and vitamin B9 in dried plants vs. infusions: assessing absorption dynamics of minerals by membrane dialysis tandem in vitro digestion

Vitamins and mineral elements are among the most important phytochemicals due to their important role in the maintenance of human health. Despite these components had already been studied in different plant species, their full characterization in several wild species is still scarce. In addition, the knowledge regarding the in vivo effects of phytochemicals, particularly their bioaccessibility, is still scarce. Accordingly, a membrane dialysis process was used to simulate gastrointestinal conditions in order to assess the potential bioaccessibility of mineral elements in different preparations of Achillea millefolium (yarrow), Laurus nobilis (laurel) and Taraxacum sect. Ruderalia (dandelion). The retention/passage dynamics was evaluated using a cellulose membrane with 34 mm pore. Dandelion showed the highest levels of all studied mineral elements (except zinc) independently of the used formulations (dried plant or infusion), but yarrow was the only species yielding minerals after the dialysis step, either in dried form, or as infusion. In fact, the ability of each evaluated element to cross the dialysis membrane showed significant differences, being also highly dependent on the plant species. Regarding the potential use of these plants as complementary vitamin B9 sources, the detected values were much lower in the infusions, most likely due to the thermolability effect.

PHYTOPLANKTON AND NUTRIENT DYNAMICS WITH A FOCUS ON NITROGEN FORM IN THE ANACOSTIA RIVER, IN WASHINGTON, D.C. AND WEST LAKE, IN HANGZHOU, CHINA

Nutrient loading has been linked with severe water quality impairment, ranging from hypoxia to increased frequency of harmful algal blooms (HABs), loss of fisheries, and changes in biodiversity. Waters around the globe are experiencing deleterious effects of eutrophication; however, the relative amount of nitrogen (N) and phosphorus (P) reaching these waters is not changing proportionately, with high N loads increasingly enriched in chemically-reduced N forms. Research involving two urban freshwater and nutrient enriched systems, the Anacostia River, USA, a tributary of the Potomac River feeding into the Chesapeake Bay, and West Lake, Hangzhou, Zhejiang Province, China, was conducted to assess the response of phytoplankton communities to changing N-form and N/P-ratios. Field observations involving the characterization of ambient phytoplankton communities and N-forms, as well as experimental (nutrient enrichment) manipulations were used to understand shifts in phytoplankton community composition with increasing NH4+ loads. In both locations, a >2-fold increase in ambient NH4+:NO3- ratios was followed by a shift in the phytoplankton community, with diatoms giving way to chlorophytes and cyanobacteria. Enrichment experiments mirrored this, in that samples enriched with NH4+ lead to increased abundance of chlorophytes and cyanobacteria. This work shows that in both of these systems experiencing nutrient enrichment that NH4+ supports communities dominated by more chlorophytes and cyanobacteria than other phytoplankton groups.

Innovation dynamics in rural areas: contributions to capture and measure innovation, valuing territorial specificities

Doutoramento em Gestão Interdisciplinar da Paisagem - Instituto Superior de Agronomia / Universidade dos Açores / Universidade de Évora

Factors affecting current and future treeline locations and dynamics in the Peruvian Andes

The elevational distributions of tropical treelines are thought to be determined by temperature, and are predicted to shift upslope in response to global warming. In contrast to this hypothesis, global-scale studies have shown that only half of all studied treelines are shifting upslope. Understanding how treelines will respond to climate change has important implications for global biodiversity, especially in the tropics, because tropical treelines generally represent the upper-elevation distribution limit of the hyper-diverse cloudforest ecosystem. In Chapter 1, I introduce the idea that grasslands found above tropical treelines may represent a potential grass ceiling which forest species cannot cross or invade. I use an extensive literature review to outline potential mechanisms which may be acting to stabilize treeline and prevent forest expansion into high-elevation grasslands. In Chapters 2-4, I begin to explore these potential mechanisms through the use of observational and experimental methods. In Chapter 2, I show that there are significant numbers of seedlings occurring just outside of the treeline in the open grasslands and that seed rain is unlikely to limit seedling recruitment above treeline. I also show that microclimates outside of the closed-canopy cloudforest are highly variable and that mean temperatures are likely a poor explanation of tropical treeline elevations. In Chapter 3, I show that juvenile trees maintain freezing resistances similar to adults, but nighttime radiative cooling near the ground in the open grassland results in lower cold temperatures relative to the free atmosphere, exposing seedlings of some species growing above treeline to lethal frost events. In Chapter 4, I use a large-scale seedling transplant experiment to test the effects of mean temperature, absolute low temperature and shade on transplanted seedling survival. I find that increasing mean temperature negatively affects seedling survival of two treeline species while benefiting another. In addition, low temperature extremes and the presence of shade also appear to be important factors affecting seedling survival above tropical treelines. This work demonstrates that mean temperature is a poor predictor of tropical treelines and that temperature extremes, especially low temperatures, and non-climatic variables should be included in predictions of current and future tropical treeline dynamics.^

Particle dynamics and airflow patterns in a ventilated two-zone enclosure

Understanding the transport mechanisms of aerosol particles in enclosures has broad ramifications in the context of cleaning strategies, and health risk assessment (e. g., occupational exposure). This paper addresses airflow pattern and aerosol transport mechanism in a ventilated two-zone enclosure with the outlet (exhaust location) situated at different locations. A numerical approach that combines a Eulerian simulation of turbulent flow with a Lagrangian particle-tracking algorithm is used. Simulations are carried out using solid suspensions with different sizes (1 to 100 micron) and densities (240 and 2300 kg/m3). The effect of location of the outlet (exhaust) on airflow patterns and aerosol dynamics is analyzed and quantified.