1,720,967 research outputs found
Iron demand by thermophilic and mesophilic bacteria isolated from an Antarctic geothermal soil
No full textThe thermophilic bacterial strain MP4 assigned to a new species, likely of the genus Alicyclobacillus, was isolated from geothermal soils on the NW slope of Mount Melbourne, Antarctica. These soils have high iron concentrations and the strain MP4 requires iron additions for growth. Four mesophilic bacterial strains Paenibacillus validus MP5, MP8, and MP10, and P. apiarius MP7, isolated from the same site, need iron supply for growth depending on the medium. Growth temperature of thermophilic strain ranges from 42 to 70 degrees C, and that one of mesophiles from 25 to 44 degrees C. Thermophilic and mesophilic strains shared microenvironments with temperature of 42-44 degrees C and showed optima of pH values ranging from 5.5 to 6.0. The thermophilic strain MP4 reached values of 10(6) CFU ml(-1) in aqueous soil extract from the NW slope of Mt. Melbourne, and 10(5) CFU ml(-1) in water extracts from other geothermal Antarctic areas ( Mt. Rittmann and Cryptogam Ridge). Growth of thermophilic bacteria in aqueous extracts of the NW slope of Mount Melbourne soils caused a reduction of 50% of soluble iron content, which was recovered in bacterial biomass. These results suggest a possible involvement of the thermophilic strain MP4 in iron bioavailability in these geothermal soils
A coastal polynya enhances mercury bioaccumulation in terrestrial ecosystems around the Nansen Ice-Sheet (Victoria Land Antarctica)
No full textEnhanced deposition and bioaccumulation of mercury in Antarctic terrestrial ecosystems facing a coastal polynya
No full textMercury emitted by anthropogenic and natural sources occurs in the atmosphere mostly in the gaseous elemental form, which has a long lifetime in tropical and temperate regions. Once deposited in terrestrial and aquatic ecosystems the metal is partly re-emitted into the air, thus assuming the characteristics of global pollutants such as persistent volatile chemicals. In polar regions, during and after the sunrise, the photochemically driven oxidation of gaseous Hg by reactive halogens may result in areas of greatly enhanced Hg deposition. Mercury concentrations in soils, lichens, and mosses collected in a stretch between 74 degrees 30' S and 76 degrees 00' S, in ice-free coastal areas of Victoria Land facing the Terra Nova Bay coastal polynya, were higher than typical Antarctic baselines. The finding of enhanced Hg bioaccumulation in Antarctic terrestrial ecosystems facing a coastal polynya strongly supports recent speculations on the role of ice crystals ("frost flowers") growing in polynyas as a dominant source of sea salt aerosols and bromine compounds, which are involved in springtime mercury depletion events (MDEs). These results raise concern about the possible environmental effects of changes in regional climate and sea ice coverage, and on the possible role of Antarctica as a sink in the mercury cycle
Oak leaves as accumulators of airborne elements in an area with geochemical and geothermal anomalies
No full textThe Colline Metallifere (Tuscany) was a major Italian mining district (FeS2, Ag, Cu, Pb, Zn) for centuries, and in the last fifty years it has become the most important area for the exploitation of geothermal resources. Leaves of the widespread oak Quercus pubescens and surface soils were collected from 90 sampling sites in the area and their elemental composition was compared. The results showed that the composition of oak leaves was not significantly affected by the presence of mineral deposits (metal sulphide ores) or soils with high concentrations of Cr, Mg, and Ni (ultramafic). Arsenic was the only element showing higher concentrations in leaves from sites with deposits of metal sulphide ores or As-polluted soils around abandoned smelting plants. Compared to the composition of epiphytic lichens and epigeic mosses from the same sites in the Colline Metallifere, the elemental composition of Q. pubescens leaves was less affected by element contributions from adsorbed soil particles. It was thus easier to evaluate atmospheric inputs of elements in oak leaves than in cryptogams. © 2003 Elsevier Science Ltd. All rights reserved
Il biomonitoraggio delle deposizioni atmosferiche di elementi in tracce mediante muschi
No full textIl muschio Hypnum cupressiforme è stato raccolto in 94 stazioni nelle Colline Metallifere (Toscana meridionale), per valutare la contaminazione ambientale dovuta agli elementi in tracce. Poiché i muschi epigei possono intrappolare le particelle di suolo, le concentrazioni degli elementi litofili sono state normalizzate utilizzando rAl ed il Ti come indicatori della contaminazione da suolo. Elevate concentrazioni di As, B, Cr, Ni e di altri elementi in alcuni campioni riflettono le caratteristiche geochimiche, le attività minerarie pregresse e le emissioni geotermiche della regione. Vengono discussi dei possibili approcci per rendere più affidabile il biomonitoraggio degli elementi in tracce mediante muschi
Mosses and lichens as biomonitors of trace metals. A comparison study on Hypnum cupressiforme and Parmelia caperata in a former mining district in Italy
No full textSamples of the moss Hypnum cupressiforme and the epiphytic lichen Parmelia caperata were collected during the summer of 1999 in an area (Colline Metallifere, central Italy) intensively exploited in the past for metals (Cu, Fe, Pb, Zn) and currently for geothermal resources. Lichens were more sensitive than mosses to emissions of S compounds near geothermal fields and abandoned sulphide ore smelting plants. Comparison of elemental compositions of the two cryptogamic species from the same sampling sites showed significantly higher concentrations of lithophile elements (Al, Cr, Fe, Mn, Ni, Ti) in the moss and atmophile elements (Hg, Cd, Pb, Cu, V, Zn) in the lichen. Patterns of bioaccumulation of elements throughout the study area were quite similar for widespread pollutants such as S, B, As, Zn, Cr and Ni, but the lichen and the moss showed different distribution patterns of Hg, Cd and other elements subject to long-range atmospheric transport. These results are due to differences in the morphology and ecophysiology of mosses and lichens and indicate that these organisms cannot be used interchangeably as biomonitors of metals in areas with mineral deposits. © 2001 Elsevier Science Ltd. All rights reserved
New record of moss and thermophilic bacteria species and physico-chemical properties of geothermal soils on the northwest slope of Mt. Melbourne (Antarctica)
No full textFour samples of surface soils, one with shoots of an unidentified moss species, were collected from a geothermal site on the northwest slope of volcanic Mt. Melbourne (northern Victoria Land, continental Antarctica) to determine physico-chemical properties, isolate existing strains of heterotrophic microorganisms, and identify the moss species through molecular genetic techniques. Surface soil features such as temperature, grain-size, pH, moisture content, and isolated genera of bacteria, generally corresponded to those previously reported for other geothermal sites in Victoria Land. However, when compared with chemical characteristics of warm substrata from these sites, soils from the northwest slope of Mt. Melbourne showed lower contents of total N and water-extractable PO43- and K+, and relatively higher concentrations of Na, Fe, Mn, and of potentially toxic elements such as Cd and Pb. Preliminary results indicate that a new species of thermophilic bacteria growing in Fe-enriched medium was isolated. Although the study area lay only about 1.5 km from "Cryptogam Ridge", a geothermal site in the rim of the Mt. Melbourne summit crater with a well-developed population of the moss Campylopus pyriformis, molecular genetic analyses showed that the moss on the volcano slope is Pohlia nutans, a species closely related to populations some 110 km to the north in the Mt. Rittmann fumaroles. It was concluded that physico-chemical features of geothermal grounds may affect the colonisation history and dispersal of microorganisms and mosses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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