Search results for "Antarctica"
showing 10 items of 38 documents
Bulk carbonate isotope stratigraphy from CRP-3 core (Victoria Land Basin, Antarctica): evidence for Eocene–Oligocene palaeoclimatic evolution
2005
Bulk carbonate isotope compositions and carbonate petrography from upper Eocene and lower Oligocene siliciclastic sediments of the CRP-3 sediment core (Victoria Land Basin, Antarctica) have been investigated with the aim of contributing to reconstruction of the Antarctic Cenozoic palaeoclimate. Most of the carbonate is calcite cement occurring as patches, nodules and horizons and consisting of equant and/or drusy sparry calcite, pervasive blocky calcite and rare poikilotopic calcite spar. 18O-depleted values (from −17 to −8 δ‰) of the CRP-3 carbonates suggest that the precipitating fluids were a mixing between marine and meteoric waters from melting glaciers. The δ18O record exhibits a numb…
Theoretical Study of Primary Reaction of Pseudozyma antarctica Lipase B as the Starting Point To Understand Its Promiscuity
2014
Pseudozyma antarctica lipase B (PALB) is a serine hydrolase that catalyzes the hydrolysis of carboxylic acid esters in aqueous medium but it has also shown catalytic activity for a plethora of reactions. This promiscuous activity has found widespread applications. In the present paper, the primary reaction of PALB, its native hydrolytic activity, has been studied using hybrid quantum mechanical/molecular mechanical (QM/MM) potentials. Free energy surfaces, obtained from QM/MM Molecular Dynamics (MD) simulations, show that the reaction takes place by means of a multi-step mechanism where the first step, the activation of the carbonyl group of the substrate and the nucleophilic attack of Ser1…
Improved synthesis of Bn5CpRu(CO)2Cl and its application as racemization catalyst in preparative-scale metalloenzymatic dynamic kinetic resolution of…
2010
An improved gram-scale synthesis of Bn5CpRu(CO)2Cl is reported based on heating of pentabenzylcyclopentadiene with Ru3(CO)12 at 160 °C under argon atmosphere in mesitylene followed by addition of chloroform, continued heating, and evaporation of the solvents. Subsequent washing of unreacted ligand precursor with hexane provided pure title compound in 77 % yield. In combination with Candida antarctica lipase B (CAL-B) (Novozym 435), this complex forms a highly active racemization catalyst for metallo-enzymatic dynamic kinetic resolution (DKR) of secondary alcohols as demonstrated in the present work by converting 100 g of racemic 1-phenylethanol to (R)-1-phenylethanol in >99 % ee and 93 %…
Southern Ocean areas of endemism: a reanalysis using benthic hydroids (Cnidaria, Hydrozoa)
2013
The biogeographic history of the Southern Ocean (SO) fauna is complex and poorly studied, especially the areas of endemism. We reanalyzed the data of Marques & Peña Cantero (2010), along with other geographical records of endemic benthic hydroids below 45°S. A Parsimony Analysis of Endemicity (PAE) based on 5° latitude by 5° longitude matrix with 61 species resulted in eight areas of endemism. We discuss these results in the context of different hypotheses of the evolution of the SO fauna and previously proposed biogeography patterns.
South Pole glacial climate reconstruction from multi-borehole laser particulate stratigraphy
2013
AbstractThe IceCube Neutrino Observatory and its prototype, AMANDA, were built in South Pole ice, using powerful hot-water drills to cleanly bore>100 holes to depths up to 2500 m. The construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques. We made high-resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010. The South Pole laser logs are among the most clearly resolved measurements of Antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail. Here we use…
Solar UV-B radiation affects leaf quality and insect herbivory in the southern beech tree Nothofagus antarctica
2004
We examined the effects of solar ultraviolet-B (UV-B) radiation on plant-insect interactions in Tierra del Fuego (55°S), Argentina, an area strongly affected by ozone depletion because of its proximity to Antarctica. Solar UV-B under Nothofagus antarctica branches was manipulated using a polyester plastic film to attenuate UV-B (uvb-) and an Aclar film to provide near-ambient UV-B (uvb+). The plastic films were placed on both north-facing (i.e., high solar radiation in the Southern Hemisphere) and south-facing branches. Insects consumed 40% less leaf area from north- than from south-facing branches, and at least 30% less area from uvb+ branches than from uvb-branches. The reduced herbivory …
Monitoring of persistent organic pollutants in the polar regions: knowledge gaps & gluts through evidence mapping
2017
Persistent organic pollutants (POPs) are widespread compounds that accumulating in polar regions canalise through trophic webs. Although several dozens of studies have been carried out in the last decades, the information is generally scattered across a large number of literature sources. This does not allow an efficient synthesis and constraints our understanding on how address future monitoring plans and environmental conservation strategies on the Polar Regions with respect to POPs. Thus, here, we present the outcome of a systematic map (SM) to scope, screen and chart evidences from literature dealing with POPs in Polar regions. The SMs strive to produce rigorous guidelines and have rece…
Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the Southern Ocean: the role of the l…
2018
22 pages; International audience; One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus…
Phylogeography and demographic inference in Nacella (Patinigera) concinna (Strebel, 1908) in the western Antarctic Peninsula
2011
10 pages; International audience; Endemic to Antarctic ecosystems, the limpet Nacella (Patinigera) concinna (Strebel, 1908) is an abundant and dominant marine benthic invertebrate of the intertidal and shallow subtidal zone. In order to examine the phylogeographic pattern and historical demography of the species along the western Antarctic Peninsula, we amplified 663 bp of the mitochondrial DNA cytochrome oxidase subunit I of 161 N. concinna specimens from five localities, as well as two specimens from South Georgia and Sub-Antarctic Marion Island. As two different morphotypes, one characterized by an elevated shell in the intertidal and the other by a flat one in the subtidal, have been re…
The design and performance of IceCube DeepCore
2011
The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector a…