Fishes from Lachuá Lake, Upper Usumacinta Basin, Guatemala

Guatemala’s Maya Lowlands constitute one of the most biodiverse regions in Mesoamerica and include 35% of the total number of continental fish species estimated for the nation. From May 2000 through February 2001, we conducted the first long-term ichthyological survey of Lachuá Lake, a 4 km2, 195 m deep, karstic sinkhole located in the middle of Guatemala’s Laguna Lachuá National Park (LLNP), southern Maya Lowlands. Thirty-six native fish species were identified and Gobiomorus dormitor Lacepède, 1800 was collected for the first time in northern Guatemala. Greater number of species occurred in the rocky shore of the lake’s littoral zone, especially around the mouths of Lachuá’s tributary and effluent rivers, and close to the visitor center of LLNP. A hierarchical cluster analysis for classifying ichthyogeographically regional fish assemblages placed Lachuá Lake in the upper Usumacinta River drainage basin shared by Guatemala and Mexico, stressing the need for regional conservation and management strategies

Temporal evolution of the transpolar potential after a sharp enhancement in solar wind dynamic pressure

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95384/1/grl23891.pd

Attribution and contestation: Relations between elites and other social groups

In this article we explore the often ambiguous relations between elites and other social groups, both subordinate and of relatively equal standing. The article draws on two distinctive ethnographic cases: the white Franco-Mauritian elite, and the expert elite of management consultants in a Western European context. Our analysis of the two cases provides insights into how the power and status of elites is both contested and attributed by the people they interact with and relate to in concrete, yet substantially different contexts and situations. The aim is to show how the position and power of different kinds of elites is relationally negotiated and achieved. As we argue, a better understanding of the role of other social groups in the attribution, maintenance and contestation of status is relevant for understanding both more traditional economic elites and expert elites without tight networks

Applications of yeast flocculation in biotechnological processes

A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects – the basics of yeast flocculation, the development of “new” flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer’s yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous β-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculation bioreactors and discussing potential new uses of these systems.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI - BD11306/97

Measurement of potential activity of fixed nitrifying bacteria in biological filters used in drinking water production

Nitrification during biological filtration is being used more and more in drinking water production to remove ammonia, which can be the source of several water quality problems during distribution. In this process, ammonia is converted into nitrite and then into nitrate by fixed autotrophic nitrifying bacteria. The purpose of this work was to develop a technique to estimate fixed nitrifying biomass (sum of ammonia- and nitrite-oxidizing populations). The quantification of autotrophic nitrifying biomass was determined by potential nitrifying activity measurement. The production of oxidized forms of inorganic nitrogen (nitrates and nitrites) was measured after an incubation of 2 cm3 of colonized solid support in the presence of a 5-ml nitrifier medium containing 10 mg N-NH4 L−1 for 30 min at 32°C. The production rate of oxidized nitrogen in optimal conditions was measured and converted into nitrifying biomass by using the maximum specific oxidizing activity. This technique was shown to be appropriate for conditions encountered in the biological filters used in drinking water production and sufficiently simple to be used for routine measurementsinfo:eu-repo/semantics/publishe

Fishes from Lachuá Lake, Upper Usumacinta Basin, Guatemala

Guatemala’s Maya Lowlands constitute one of the most biodiverse regions in Mesoamerica and include 35% of the total number of continental fish species estimated for the nation. From May 2000 through February 2001, we conducted the first long-term ichthyological survey of Lachuá Lake, a 4 km2, 195 m deep, karstic sinkhole located in the middle of Guatemala’s Laguna Lachuá National Park (LLNP), southern Maya Lowlands. Thirty-six native fish species were identified and Gobiomorus dormitor Lacepède, 1800 was collected for the first time in northern Guatemala. Greater number of species occurred in the rocky shore of the lake’s littoral zone, especially around the mouths of Lachuá’s tributary and effluent rivers, and close to the visitor center of LLNP. A hierarchical cluster analysis for classifying ichthyogeographically regional fish assemblages placed Lachuá Lake in the upper Usumacinta River drainage basin shared by Guatemala and Mexico, stressing the need for regional conservation and management strategies