Climate change,ecosystems and smallholder agriculture in Central America: an introduction to the special issue     

Pablo Imbach  Megan Beardsley  Claudia Bouroncle  Claudia Medellin  Peter Läderach  Hugo Hidalgo  Eric Alfaro  Jacob Van Etten  Robert Allan  Debbie Hemming  Roger Stone  Lee Hannah  Camila I. Donatti 《Climatic change》2017,140(1):1-4

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Analyses of the Relationship Between Mucous Aggregates and Phytoplankton Communities in the Gulf of Trieste (Northern Adriatic Sea) by Multivariate Techniques     

Bruno  Cataletto  Enrico  Feoli  Serena Fonda  Umani  Marina  Monti Irene  Pecchiar 《Marine Ecology》1996,17(1-3):291-307

Abstract. Multivariate techniques (cluster analysis and Principal Component Analysis) applied on phytoplankton data collected in June, July, August, and September 1990, 1991, 1992, and 1993 in the Gulf of Trieste (Northern Adriatic Sea) highlighted a clear temporal pattern from 1990 to 1993. In the summer of 1991, phytoplankton communities showed a dramatic increase in the dinoflagellatddiatom ratio. In particular, during June and July 1991 only few specimens of diatoms ( Cylindrorhecu closreriurn. Probosciu alata, Nirzschio longissimu , and Nitzschiu spp.) were collected; this confirmed the diatom scarcity in the phytoplankton communities before and during the appearance of large mucous aggregates (mucilage) in July 1991 in the Gulf of Trieste. The differences observed between the structure of the phytoplankton communities inside the aggregates and in the ambient waters suggested two hypotheses: 1) the aggregates were not produced in the gulf, but were carried ints the gulf by the eastern bordering current; 2) the aggregates were produced by a few, scarce species with a high exudate production that are capable of quickly reaching a high reproductive rate within the aggregates.  相似文献   

Secondary phase formation on UO₂ in phosphate media     

A. Rey  J. Gimnez  I. Casas  F. Clarens  J. de Pablo 《Applied Geochemistry》2008,23(8):2249-2255

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Differential Late Paleozoic active margin evolution in South-Central Chile (37°S–40°S) – the Lanalhue Fault Zone     

Johannes Glodny  Helmut Echtler  Santiago Collao  Mary Ardiles  Pablo Burn  Oscar Figueroa 《Journal of South American Earth Sciences》2008,26(4):397-411

The N–S oriented Coastal Cordillera of South Central Chile shows marked lithological contrasts along strike at 38°S. Here, the sinistral NW–SE-striking Lanalhue Fault Zone (nomen novum) juxtaposes Permo-Carboniferous magmatic arc granitoids and associated, frontally accreted metasediments (Eastern Series) in the northeast with a Late Carboniferous to Triassic basal-accretionary forearc wedge complex (Western Series) in the southwest. The fault is interpreted as an initially ductile deformation zone with divergent character, located in the eastern flank of the basally growing, upwarping, and exhuming Western Series. It was later transformed and reactivated as a semiductile to brittle sinistral transform fault. Rb–Sr data and fluid inclusion studies of late-stage fault-related mineralizations revealed Early Permian ages between 280 and 270 Ma for fault activity, with subsequent minor erosion. Regionally, crystallization of arc intrusives and related metamorphism occurred between 306 and 286 Ma, preceded by early increments of convergence-related deformation. Basal Western Series accretion started at >290 Ma and lasted to 250 Ma. North of the Lanalhue fault, Late Paleozoic magmatic arc granitoids are nearly 100 km closer to the present day Andean trench than further south. We hypothesize that this marked difference in paleo-forearc width is due to an Early Permian period of subduction erosion north of 38°S, contrasting with ongoing accretion further south, which kinematically triggered the evolution of the Lanalhue Fault Zone. Permo-Triassic margin segmentation was due to differential forearc accretion and denudation characteristics, and is now expressed in contrasting lithologies and metamorphic signatures in todays Andean forearc region north and south of the Lanalhue Fault Zone.  相似文献   

Molecular and cultivation-dependent analysis of metal-reducing bacteria implicated in arsenic mobilisation in south-east asian aquifers     

Marina Héry  Andrew G. GaultJonathan R. Lloyd 《Applied Geochemistry》2008

The reduction of sorbed As(V) to the potentially more mobile As(III) by As-respiring anaerobic bacteria has been implicated in the mobilisation of the toxic metalloid in aquifer sediments in SE Asia. However, there is currently only a limited amount of information on the identity of the organisms that can respire As(V) in these sediment systems. Here experiments are described that have targeted As(V)-respiring bacteria using cultivation-independent molecular techniques, and also more traditional microbiological approaches that have used growth media highly selective for organisms that can grow using arsenate as the sole electron acceptor supplied for anaerobic growth. The molecular techniques used have initially targeted DNA from microcosms displaying maximal rates of arsenate reduction, both with and without added electron donor. More recent studies from the authors’ laboratory have used stable isotope probing techniques, targeting DNA from the active microbial fraction in microcosms labelled with [¹³C]acetate supplied as an electron donor for arsenate reduction. Phylogenetic analyses using a highly conserved genetic marker (the 16S rRNA gene) have suggested the involvement of Sulfurospirillum and Geobacter species in arsenate-respiration, and this has been supported further by complimentary experiments using more traditional microbiological techniques. Additional research required to clarify the role of these organisms in the mobilisation of As in situ are discussed.  相似文献   

Taphonomy and zooarchaeology in the Neotropics: A view from northwestern Patagonian forest and steppe     

Pablo Marcelo Fernndez 《Quaternary International》2008,180(1):63

Modes of faunal exploitation in NW Chubut Province (Patagonia, Argentina) during the last 3500 calibrated years BP are discussed, based on taphonomic and zooarchaeological analyses. Bone assemblages were recovered from archaeological sites of the Sub-Antarctic forests and the extra-Andean Patagonian steppe, where huemul (Hippocamelus bisulcus) and guanaco (Lama guanicoe) were, respectively, the main staple. In the steppe, lesser rhea (Pterocnemia pennata), a medium-sized flightless bird, also was integrated into the hunter-gatherer diet. Rodents, carnivores, flying birds, and fishes also were recovered. Different processes and agents were involved in the accumulation of small vertebrates bone assemblages (e.g. birds of prey, foxes, and small carnivores). In the steppe, only two taxa of small vertebrates—birds and mountain viscacha (Lagidium viscacia)—can be related with human subsistence activities. These two taxa and all large vertebrates reveal fat-oriented carcass processing.Guanaco bone assemblages associated both with ceramic and non-ceramic technologies do not show changes in carcass processing. Moreover, the similarities in bone grease exploitation suggest boiling prior to the appearance of pottery.  相似文献   

Large-scale moraine deformation at the Athabasca Glacier,Jasper National Park,Alberta, Canada     

Chris H. Hugenholtz  Brian J. Moorman  John Barlow  Pablo A. Wainstein 《Landslides》2008,5(3):251-260

In this paper the development of a large-scale gravitational deformation involving the eastern lateral moraine of the Athabasca Glacier in Jasper National Park, Alberta, Canada, is described. Interpretation and analysis of sequential aerial photographs indicates that a 540-m-wide segment of the eastern lateral moraine began to deform in the early 1950s; however, significant movement only began in the late 1960s. Since then, the moraine has undergone progressive gravitational deformation leading to a network of fractures, bulging, and the development of a large gap in the moraine crest. Geographic information system analysis of topographic changes between 1967 and 2006 indicates that the displaced volume of the moraine is approximately 9.0 × 10⁵ m³. In the last 39 years, the moraine crest has displaced 55 m (1.4 m yr⁻¹) down towards the glacier. The development of slope instability is linked to a combination of debuttressing from recent glacier recession, deformation of the moraine, as well as the movement of a large, mobile, debris-mantled slope impinging the upslope margin of the lateral moraine. This case study illustrates the importance of glacial conditioning and local geomorphological factors in creating conditions for large-scale moraine instability in recently deglacierized alpine basins.  相似文献   

Optimizing the Determination of Roughness Parameters for Model Urban Canopies     

Pablo Huq  Auvi Rahman 《Boundary-Layer Meteorology》2018,168(3):497-515

We present an objective optimization procedure to determine the roughness parameters for very rough boundary-layer flow over model urban canopies. For neutral stratification the mean velocity profile above a model urban canopy is described by the logarithmic law together with the set of roughness parameters of displacement height d, roughness length \(z_0\), and friction velocity \(u_*\). Traditionally, values of these roughness parameters are obtained by fitting the logarithmic law through (all) the data points comprising the velocity profile. The new procedure generates unique velocity profiles from subsets or combinations of the data points of the original velocity profile, after which all possible profiles are examined. Each of the generated profiles is fitted to the logarithmic law for a sequence of values of d, with the representative value of d obtained from the minima of the summed least-squares errors for all the generated profiles. The representative values of \(z_0\) and \(u_*\) are identified by the peak in the bivariate histogram of \(z_0\) and \(u_*\). The methodology has been verified against laboratory datasets of flow above model urban canopies.  相似文献   

Comparison of spatial interpolation methods for the estimation of precipitation distribution in Distrito Federal,Brazil     

Pablo de Amorim Borges  Johannes Franke  Yumiko Marina Tanaka da Anunciação  Holger Weiss  Christian Bernhofer 《Theoretical and Applied Climatology》2016,123(1-2):335-348

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Environmental aspects and potential impacts of proposed water transfer scheme on sustainable water management in eastern Herzegovina     

Marina Čokorilo Ilić  Zoran Stevanović  Vesna Ristić Vakanjac 《Environmental Earth Sciences》2016,75(6):521

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