ERP evidence suggests executive dysfunction in ecstasy polydrug users

Background: Deficits in executive functions such as access to semantic/long-term memory have been shown in ecstasy users in previous research. Equally, there have been many reports of equivocal findings in this area. The current study sought to further investigate behavioural and electro-physiological measures of this executive function in ecstasy users. Method: Twenty ecstasy–polydrug users, 20 non-ecstasy–polydrug users and 20 drug-naïve controls were recruited. Participants completed background questionnaires about their drug use, sleep quality, fluid intelligence and mood state. Each individual also completed a semantic retrieval task whilst 64 channel Electroencephalography (EEG) measures were recorded. Results: Analysis of Variance (ANOVA) revealed no between-group differences in behavioural performance on the task. Mixed ANOVA on event-related potential (ERP) components P2, N2 and P3 revealed significant between-group differences in the N2 component. Subsequent exploratory univariate ANOVAs on the N2 component revealed marginally significant between-group differences, generally showing greater negativity at occipito-parietal electrodes in ecstasy users compared to drug-naïve controls. Despite absence of behavioural differences, differences in N2 magnitude are evidence of abnormal executive functioning in ecstasy–polydrug users

Abundance and diversity of phytoplankton in the Paran\ue1 River (Argentina) 220 km downstream of the Yacyret\ue1 reservoir

Patterns in the temporal composition, abundance and diversity of the phytoplankton community of the Paraná river prior to and after the initial filling phase of the Yacyretá reservoir are analyzed. The study site is located 220 km downstream from the Yacyretá reservoir and 30 km downstream from the confluence with the Paraguay river. Because both rivers remain separate and unmixed at the study site, we compared the possible effects of the impoundment on both river banks (left and right banks) in hydrological periods with similar duration and magnitude of the low and high water phases. Physical and chemical conditions measured on the right bank (water from the Paraguay river) were similar at both periods (pre and post-impoundment) whereas conductivity, pH and orthophosphate concentration increased on the left bank (water from the High Paraná river and Yacyretá reservoir) after the impoundment. Changes in phytoplankton density and diversity were observed only in samples collected from water flowing from the reservoir (left bank). The density of Chlorophyceae (Chloromonas acidophila, Chlamydomonas leptobasis, Choricystis minor, Chlorella vulgaris, Scenedesmus ecornis, Monoraphidium minutum, M. contortum and M. pusillum) and Cryptophyceae (Rhodomonas minuta, Cryptomonas marssonii and C. ovata) increased while Cyanophyceae (Cylindrospermopsis raciborskii, Raphidiopsis mediterranea and Planktolyngbya subtilis) and Bacillariophyceae (Aulacoseira granulata and its bioforms) decreased compared to previous studies conducted on the left bank of the Paraná river. Phytoplankton collected from the right bank of the river did not differ in pre and post- impoundment samples because they originate from the Paraguay river, which remains relatively unaffected by human activities

Eight years of monitoring aquatic Oligochaeta from the Baía and Ivinhema Rivers

The aim of this study was to analyze the factors that influence spatial and temporal variations of the Oligochaeta assemblage in the Baía and Ivinhema Rivers, located in the Upper Paraná River floodplain (Mato Grosso do Sul State, Brazil). Samples of Oligochaeta were collected between February 2000 and November 2007. A total of 27 Oligochaeta species were identified. A Principal Component Analysis (PCA) of the physical and chemical variables was used to summarize the total variation in the data and to identify major environmental gradients. Detrended Correspondence Analysis (DCA) was conducted to verify possible spatial and temporal gradients in the Oligochaeta species distribution. The highest Oligochaeta species densities and richness values were recorded during limnophases. The intensity and amplitude of the potamophase influenced the density, richness and composition of Oligochaeta since many species were transported by high water current velocities and/or died due to the low oxygen levels that are characteristic of this phase. L. hoffmeisteri, P. descolei and A. pigueti were recorded in the potamophase and in the limnophase and we concluded that they are adapted to different conditions of rivers (lotic and lentic) due to the presence of these species during the entire study period in both rivers. Nevertheless, these species were dominant in the potamophase periods of these rivers as they have body adaptations to survive in these conditions

Arc–continent collision : the making of an orogen

There is no one model, no paradigm, that uniquely defines arc–continent collision. Natural examples and modelling of arc–continent collision show that there is a large degree of, and variation in, complexity that depend on a number of key first-order parameters and the nature of the main players; the continental margin and the arc–trench complex (the arc–trench complex includes the arc and the subduction zone). Although modelling techniques can be used to gain insights into these, they cannot and do not aim at reproducing the messiness of nature. In natural examples, identifying the nature of the main players involved, such as the age, physical properties, and pre-existing structure of the margin and the arc is just a beginning. Once this is done, parameters such as time, convergence velocity and vector need to be taken into account when determining the tectonic processes that were operative in any one arc–continent collision. In active examples, such as those in the southwest Pacific, some of these first-order parameters can be readily determined, and the nature of the main players easily assessed. Fossil arc–continent collisions, however, have commonly undergone post-collision deformation, erosion, and possibly partial dispersion to be left outcropping in the middle of a forest, with many of the key ingredients missing or hidden. This leaves the geologist to resort to comparison with other natural examples and with models that are mechanically constrained and simplified reproductions of the process to reconstruct and explain what may have been there and, importantly, what processes may have been operating and when. We attempt to show that this is not an easy task that can be put into one simple model. In this chapter we do not present a model for arc–continent collision. Instead, we begin with the main players involved, highlighting the characteristics of each that likely have a major influence on an arc–continent collision. Then, we investigate a range of possible processes that could take place once an intra-oceanic volcanic arc collides with a continental margin.17 page(s

Tropical Ungulates of Argentina

Argentina has an extensive and diverse terrain classified into 11 ecoregions. Seven of these ecoregions, occupying the north and north-central parts of the country, house the 11 tropical ungulate species found here. The ecoregions are lowland and subtropical, some beginning in the tropics, some extending to temperate climates. The principal topographical characteristics, hydrology, climate, vegetation and fauna are described for these seven ecoregions. Each of the 11 species is then treated in detail with respect to its ecology and conservation. Emphasis is placed on distribution, habitat and density, feeding ecology, threats and conservation in Argentina, based on the most recent studies. Data on reproductive biology and behaviour are included where information is relatively recent and unlikely to be covered elsewhere. The species include the following: the Brazilian tapir (Tapirus terrestris), found in northern subtropical ecoregions, three species of peccary (Tayassu pecari, Pecari tajacu and Parachoerus wagneri) from northern subtropical and drier regions, of which the Chacoan peccary (P. wagneri) is endemic while the other two species have more extensive distributions. The guanaco (Lama guanicoe) occurs only in relict populations in the ecoregions considered. The taruca (Hippocamelus antisensis) occupies the eastern boundary between the Yungas and drier, high altitude ecoregions. Three species of brocket deer (Mazama americana, M. gouazoubira and M. nana) occupy the northern tropical, subtropical and Chacoan areas. The marsh deer (Blastocerus dichotomus), the largest South American deer, has small populations occupying wetlands from the northern border to the Parana delta, while the pampas deer (Ozotocerus bezoaticus) is found in four isolated populations from Ibera to Buenos Aires province. Argentina represents the southern limit to the distribution of all these species and thus threats are often magnified. Ongoing conservation activities include the maintenance of protected areas, promotion (difusion, education, sensitization), investigation and the reintroduction of some species of formerly extinct ungulates into the Ibera wetlands area.Fil: Black Decima, Patricia. Universidad Nacional de Tucumán; ArgentinaFil: Camino, Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Cirignoli, Sebastian. Centro de Investigaciones del Bosque Atlántico; ArgentinaFil: de Bustos, Soledad. Fundación Biodiversidad; ArgentinaFil: Matteucci, Silvia Diana. Universidad de Buenos Aires. Facultad de Arquitectura y Urbanismo. Grupo de Ecología del Paisaje y Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Perez Carusi, Lorena Cynthia. Administración de Parques Nacionales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Varela, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Universidad Nacional de Misiones. Instituto de Biología Subtropical; Argentina. Centro de Investigaciones del Bosque Atlántico; Argentin