Sorption of mercury (II) in Amazon soils from column studies

The sorption of Hg (II) onto four different types of Amazon soils from the A-horizon was investigated by means of column experiments under saturation conditions and controlled metal load. Higher organic matter contents in the soil resulted in higher Hg (II) adsorptions, reaching values as high as 3.8 mg Hg g⁻¹ soil. The amount of mercury adsorbed on a soil column (Q) shows a very poor correlation with soil clay content (r² = 0.2527), indicating that Hg sorption in these topsoil samples is chiefly governed by the organic matter content. Desorption experiments using Negro River (Amazon) waters were conducted using soil saturated with Hg (II) in order to better understand the metal leaching mechanism. The amount of Hg (II) released from soils was around 30% of the total sorbed mercury upon saturation, suggesting that mercury sorption in the soils present in the catchment area of the Negro River basin is not a reversible process.     

Effects of parental acclimation temperature and egg-incubation temperature on egg-hatching time in Acartia tonsa (Copepoda: Calanoida)

Experimental results indicate that both parental acclimation temperature and egg-incubation temperature have significant effects on the egg-hatching time of Acartia tonsa Dana between 15° and 25°C. Effects of parental acclimation temperature and egg-incubation temperature are additive if the long-term parental acclimation temperature is constant. A. tonsa are sensitive to temperature and changes of temperature during development (in vivo) and after they are laid (in vitro), up to the time of hatching. A temperature change of the parent culture for time periods of 86 h to 8 d is sufficient to change egg-hatching times. The time required for a temperature change to affect egg-hatching times depends on the magnitude and direction of the temperature change. Field collected A. tonsa demonstrate that changes in egg-hatching times occur in the field populations and can be predicted by mean weekly water temperature.     

Mechanosensitivity in the model sea anemone <Emphasis Type="Italic">Nematostella vectensis</Emphasis>

Tentacles of the sea anemone, Nematostella vectensis, are covered with hair bundles. Hair bundles were deflected by water jets to test whether they are mechanoreceptors. Electrophysiological recordings confirm that deflections of hair bundles induce transients in membrane current. In a different species of anemone, hair bundle mechanoreceptors are known to change shape and responsiveness according to the activity of chemoreceptors that bind prey-derived compounds including N-acetylated sugars. In Nematostella, hair bundles significantly elongate upon exposure to NANA, an N-acetylated sugar. Based on a bioassay in which discharged nematocysts are counted in gelatin-coated test probes touched to tentacles, we find that NANA shifts vibration dependent discharge of basitrich nematocysts to lower frequencies overlapping those produced during swimming by known prey including planktonic crustaceans. Furthermore, we find for the first time that vibration detection extends at least 2.5 cm beyond the tentacle tips. Thus, Nematostella likely employs its hair bundles to detect swimming movements of nearby prey.     

Identification of Enteric Viruses in Foods from Mexico City

Foodborne viruses are a common and, probably, the most under-recognized cause of outbreaks of gastroenteritis. Among the main foods involved in the transmission of human enteric viruses are mollusks, and fruits and vegetables irrigated with wastewater and/or washed with non-potable water or contaminated by contact with surfaces or hands of the infected personnel during its preparation. In this study, 134 food samples were analyzed for the detection of Norovirus, Rotavirus, and Hepatitis A virus (HAV) by amplification of conserved regions of these viruses. From the 134 analyzed samples, 14 were positive for HAV, 6 for Norovirus, and 11 for Rotavirus. This is the first report in Mexico where emphasis is given to the presence of HAV and Norovirus on perishable foods and food from fisheries, as well as Rotavirus on frozen vegetables, confirming the role of vegetables and bivalve mollusks as transmitting vehicles of enteric viruses.     

Factors affecting adolescents’ use of urban public spaces in their leisure time: an exploratory study from the city of Vienna

Urban public spaces are important areas for leisure, recreation and physical activity and therefore contribute to the quality of life in cities. In particular, for adolescents they provide important spaces to meet with their peers, away from parental or school control. In many cities worldwide, public spaces have undergone severe developmental processes, and often a withdrawal from public space is noted. With regard to the opportunities those spaces provide for adolescents, it is necessary to investigate their current meaning for adolescents in a leisure context. In this article, qualitative research methods were used to investigate factors affecting adolescents’ use of public spaces in Vienna, Austria. In total 45 adolescents were interviewed. Results show that public open spaces are not regarded as important leisure spaces, and data reveal a strong retreat to private areas for leisure purposes. Perceived insecurities and fears support these processes and often result in avoidance of public spaces but also the wish for more control by authorities.     

Neoliberalism and the making of food politics in Eastern Ontario

Despite their opposition to the dominant agri-food system, alternative agri-food initiatives may unwittingly reproduce central features of neoliberalism. Julie Guthman has been a particularly strong proponent of this view, arguing that food activism and neoliberalism have shaped one another dialectically in California in recent decades. This paper responds to her argument, with a view to distinguishing between what it reveals and what it may conceal about the transformative potential of alternative agri-food initiatives in North America. Drawing on primary research on a variety of community-based food initiatives in Eastern Ontario, Canada, we show how a neoliberal lens does help to illuminate some problematic characteristics of these initiatives, including assumptions about market-based solutions and focus on self-improvement at the expense of state involvement. However, this lens underestimates those aspects of community-based food initiatives that may appear commensurate with neoliberal rationalities but which also push in more progressive directions.