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Search Results: 1 - 10 of 219331 matches for " C. Barbante "
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Fire and climate: Biomass burning recorded in ice and lake cores
Kehrwald N.,Zangrando R.,Gambaro A.,Barbante C.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/201009008
Abstract: Human activities including fossil fuel burning are currently altering the global climate system at rates faster than ever recorded in geologic time. Biomass burning causes carbon dioxide emissions equal to 50% of those from fossil-fuel combustion and so are highly likely to influence future climate change. However, aerosols continue to be one of the least understood aspects of the modern climate system and even less is known about their past influence. Ice and lake core proxy records provide quantifiable data on past fire regimes across most spatial and temporal scales. Some monosaccharide anhydrides such as levoglucosan, mannosan and galactosan are used as specific molecular markers for biomass burning as they can only be produced by combustion processes at temperatures greater than 300 °C and are present in both ice and lake cores. Other paleofire tracers such as microcharcoal, polycyclic aromatic hydrocarbons, and pollen records augment the fire history derived at single sites or across regions. As both pyrochemical and climate parameters are determined from the same depth and time within the ice or sediment matrix, the multi-proxy nature of ice and lake cores presents an ideal material to investigate the links between fires and climate change.
Greenland ice core evidence of the 79 AD Vesuvius eruption
C. Barbante,N. M. Kehrwald,P. Marianelli,B. M. Vinther
Climate of the Past Discussions , 2012, DOI: 10.5194/cpd-8-5429-2012
Abstract: Volcanic tephra are indepenent age horizons and can synchronize strata of various paleoclimate records including ice and sediment cores. Before such paleoclimate records can be synchronized, it is essential to first confidently identify individual independent marker horizons. The Greenland Ice Core Project (GRIP) ice core from Central Greenland is often used as a "golden spike" to synchronize Northern Hemisphere paleoclimte records. The Holocene section of the GRIP ice core is dated by multi-parameter annual layer counting, and contains peaks in acidity, SO42 and microparticle concentrations at a depth of 428.4 to 429.6 m, which have not previously been definitively ascribed to a volcanic eruption. Here, we identify tephra particles and determine that volcanic shards extracted from a depth of 429.2 m in the GRIP ice core are likely due to the 79 AD Vesuvius eruption. The chemical compositon of the tephra particles is consistent with the K-phonolitic composition of the Vesuvius juvinile ejecta and differs from the chemical composition of other major eruptions (≥VEI 4) between 50–100 AD.
Iron fluxes to Talos Dome, Antarctica, over the past 200 kyr
P. Vallelonga,C. Barbante,G. Cozzi,J. Gabrieli
Climate of the Past Discussions , 2012, DOI: 10.5194/cpd-8-6093-2012
Abstract: Atmospheric fluxes of iron (Fe) over the past 200 kyr are reported for the coastal Antarctic Talos Dome ice core, based on acid leachable Fe concentrations. Fluxes of Fe to Talos Dome were consistently greater than those at Dome C, with the greatest difference observed during interglacial climates. We observe different Fe flux trends at Dome C and Talos Dome during the deglaciation and early Holocene, attributed to a combination of deglacial activation of dust sources local to Talos Dome and reorganization of atmospheric transport pathways with the retreat of the Ross Sea ice shelf. This supports similar findings based on dust particle sizes and fluxes and Rare Earth Element fluxes. We show that Ca and Fe should not be used as quantitative proxies for mineral dust, as they all demonstrate different deglacial trends at Talos Dome and Dome C. Considering that a 20 ppmv decrease in atmospheric CO2 at the coldest part of the last glacial maximum occurs contemporaneously with the period of greatest Fe and dust flux to Antarctica, we conclude that the maximum contribution of aeolian dust deposition to Southern Ocean sequestration of atmospheric CO2 is approximately 20 ppmv.
Iron fluxes to Talos Dome, Antarctica, over the past 200 kyr
P. Vallelonga, C. Barbante, G. Cozzi, J. Gabrieli, S. Schüpbach, A. Spolaor,C. Turetta
Climate of the Past (CP) & Discussions (CPD) , 2013,
Abstract: Atmospheric fluxes of iron (Fe) over the past 200 kyr are reported for the coastal Antarctic Talos Dome ice core, based on acid leachable Fe concentrations. Fluxes of Fe to Talos Dome were consistently greater than those at Dome C, with the greatest difference observed during interglacial climates. We observe different Fe flux trends at Dome C and Talos Dome during the deglaciation and early Holocene, attributed to a combination of deglacial activation of dust sources local to Talos Dome and the reorganisation of atmospheric transport pathways with the retreat of the Ross Sea ice shelf. This supports similar findings based on dust particle sizes and fluxes and Rare Earth Element fluxes. We show that Ca and Fe should not be used as quantitative proxies for mineral dust, as they all demonstrate different deglacial trends at Talos Dome and Dome C. Considering that a 20 ppmv decrease in atmospheric CO2 at the coldest part of the last glacial maximum occurs contemporaneously with the period of greatest Fe and dust flux to Antarctica, we confirm that the maximum contribution of aeolian dust deposition to Southern Ocean sequestration of atmospheric CO2 is approximately 20 ppmv.
Amino acids in Arctic aerosols
E. Scalabrin, R. Zangrando, E. Barbaro, N. M. Kehrwald, J. Gabrieli, C. Barbante,A. Gambaro
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Amino acids are significant components of atmospheric aerosols, affecting organic nitrogen input to marine ecosystems, atmospheric radiation balance, and the global water cycle. The wide range of amino acid reactivities suggest that amino acids may serve as markers of atmospheric transport and deposition of particles. Despite this potential, few measurements have been conducted in remote areas to assess amino acid concentrations and potential sources. Polar regions offer a unique opportunity to investigate atmospheric processes and to conduct source apportionment studies of such compounds. In order to better understand the importance of amino acid compounds in the global atmosphere, we determined free amino acids (FAAs) in seventeen size-segregated aerosol samples collected in a polar station in the Svalbard Islands from 19 April until 14 September 2010. We used an HPLC coupled with a tandem mass spectrometer (ESI-MS/MS) to analyze 20 amino acids and quantify compounds at fmol m 3 levels. Mean total FAA concentration was 1070 fmol m 3 where serine and glycine were the most abundant compounds in almost all samples and accounted for 45–60% of the total amino acid relative abundance. The other eighteen compounds had average concentrations between 0.3 and 98 fmol m 3. The higher amino acid concentrations were present in the ultrafine aerosol fraction (< 0.49 μm) and accounted for the majority of the total amino acid content. Local marine sources dominate the boreal summer amino acid concentrations, with the exception of the regional input from Icelandic volcanic emissions.
Mercury in the snow and firn at Summit Station, Central Greenland, and implications for the study of past atmospheric mercury levels
X. Fa n, C. P. Ferrari, A. Dommergue, M. Albert, M. Battle, L. Arnaud, J.-M. Barnola, W. Cairns, C. Barbante,C. Boutron
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Gaseous Elemental Mercury (Hg° or GEM) was investigated at Summit Station, Greenland, in the interstitial air extracted from the perennial snowpack (firn) at depths ranging from the surface to 30 m, during summer 2005 and spring 2006. Photolytic production and destruction of Hg° were observed close to the snow surface during summer 2005 and spring 2006, and we observed dark oxidation of GEM up to 270 cm depth in June 2006. Photochemical transformation of gaseous elemental mercury resulted in diel variations in the concentrations of this gas in the near-surface interstitial air, but destruction of Hg° was predominant in June, and production was the main process in July. This seasonal evolution of the chemical mechanisms involving gaseous elemental mercury produces a signal that propagates downward through the firn air, but is unobservably small below 15 m in depth. As a consequence, multi-annual averaged records of GEM concentration should be well preserved in deep firn air at depths below 15 m, and available for the reconstruction of the past atmospheric history of GEM over the last decades.
Impact of Po Valley emissions on the highest glacier of the Eastern European Alps
J. Gabrieli, L. Carturan, P. Gabrielli, N. Kehrwald, C. Turetta, G. Cozzi, A. Spolaor, R. Dinale, H. Staffler, R. Seppi, G. dalla Fontana, L. Thompson,C. Barbante
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2011,
Abstract: In June 2009, we conducted the first extensive glaciological survey of Alto dell'Ortles, the uppermost glacier of Mt. Ortles (3905 m a.s.l.), the highest summit of the Eastern European Alps. This section of the Alps is located in a rain shadow and is characterized by the lowest precipitation rate in the entire Alpine arc. Mt. Ortles offers a unique opportunity to test deposition mechanisms of chemical species that until now were studied only in the climatically-different western sector. We analyzed snow samples collected on Alto dell'Ortles from a 4.5 m snow-pit at 3830 m a.s.l., and we determined a large suite of trace elements and ionic compounds that comprise the atmospheric deposition over the past two years. Trace element concentrations measured in snow samples are extremely low with mean concentrations at pg g 1 levels. Only Al and Fe present median values of 1.8 and 3.3 ng g 1, with maximum concentrations of 21 and 25 ng g 1. The median crustal enrichment factor (EFc) values for Be, Rb, Sr, Ba, U, Li, Al, Ca, Cr, Mn, Fe, Co, Ga and V are lower than 10 suggesting that these elements originated mainly from soil and mineral aerosol. EFc higher than 100 are reported for Zn (118), Ag (135), Bi (185), Sb (401) and Cd (514), demonstrating the predominance of non-crustal depositions and suggesting an anthropogenic origin. Our data show that the physical stratigraphy and the chemical signals of several species were well preserved in the uppermost snow of the Alto dell'Ortles glacier. A clear seasonality emerges from the data as the summer snow is more affected by anthropogenic and marine contributions while the winter aerosol flux is dominated by crustal sources. For trace elements, the largest mean EFc seasonal variations are displayed by V (with a factor of 3.8), Sb (3.3), Cu (3.3), Pb (2.9), Bi (2.8), Cd (2.1), Zn (1.9), Ni (1.8), Ag (1.8), As (1.7) and Co (1.6). When trace species ratios in local and Po Valley emissions are compared with those in Alto dell'Ortles snow, the deposition on Mt. Ortles is clearly linked with Po Valley summer emissions. Despite climatic differences between the Eastern and Western Alps, trace element ratios from Alto dell'Ortles are comparable with those obtained from high-altitude glaciers in the Western Alps, suggesting similar sources and transport processes at seasonal time scales in these two distinct areas. In particular, the large changes in trace element concentrations both in the Eastern and Western Alps appear to be more related to the regional vertical structure of the troposphere rather than the synoptic weather patterns.
Reaction time assessment in children with ADHD
Bolfer, Cristiana;Casella, Erasmo Barbante;Baldo, Marcus Vinícius Chrysóstomo;Mota, Amanda Manzini;Tsunemi, Miriam Harumi;Pacheco, Sandra Pasquali;Reed, Umbertina C.;
Arquivos de Neuro-Psiquiatria , 2010, DOI: 10.1590/S0004-282X2010000200025
Abstract: attention deficit, impulsivity and hyperactivity are the cardinal features of attention deficit hyperactivity disorder (adhd) but executive function (ef) disorders, as problems with inhibitory control, working memory and reaction time, besides others efs, may underlie many of the disturbs associated with the disorder. objective: to examine the reaction time in a computerized test in children with adhd and normal controls. method: twenty-three boys (aged 9 to 12) with adhd diagnosis according to diagnostic and statistical manual of mental disorders, fourth edition, 2000 (dsm-iv) criteria clinical, without comorbidities, intelligence quotient (iq) >89, never treated with stimulant and fifteen normal controls, age matched were investigated during performance on a voluntary attention psychophysical test. results: children with adhd showed reaction time higher than normal controls. conclusion: a slower reaction time occurred in our patients with adhd. this findings may be related to problems with the attentional system, that could not maintain an adequate capacity of perceptual input processes and/or in motor output processes, to respond consistently during continuous or repetitive activity.
Change in dust variability in the Atlantic sector of Antarctica at the end of the last deglaciation
A. Wegner, P. Gabrielli, D. Wilhelms-Dick, U. Ruth, M. Kriews, P. De Deckker, C. Barbante, G. Cozzi, B. Delmonte,H. Fischer
Climate of the Past (CP) & Discussions (CPD) , 2012,
Abstract: We present a Rare Earth Elements (REE) record determined on the EPICA ice core drilled at Dronning Maud Land (EDML) in the Atlantic sector of the East Antarctic Plateau. The record covers the transition from the last glacial stage (LGS) to the early Holocene (26 600–7500 yr BP) at decadal to centennial resolution. Additionally, samples from potential source areas (PSAs) for Antarctic dust were analyzed for their REE characteristics. The dust provenance is discussed by comparing the REE fingerprints in the ice core and the PSA samples. We find a shift in variability in REE composition at ~15 000 yr BP in the ice core samples. Before 15 000 yr BP, the dust composition is very uniform and its provenance was most certainly dominated by a South American source. After 15 000 yr BP, multiple sources such as Australia and New Zealand become relatively more important, although South America remains the major dust source. A similar change in the dust characteristics was observed in the EPICA Dome C ice core at around ~15 000 yr BP, accompanied by a shift in the REE composition, thus suggesting a change of atmospheric circulation in the Southern Hemisphere.
Anomalous somatic embryos in Acca sellowiana (O. Berg) Burret (Myrtaceae)
Pescador, Rosete;Kerbauy, Gilberto Barbante;Viviani, Daniela;Kraus, Jane Elizabeth;
Brazilian Journal of Botany , 2008, DOI: 10.1590/S0100-84042008000100014
Abstract: somatic embryogenesis represents a valuable tool for the studies on the basic aspects of plant embryo development. today this process is used as a potencial technique for large-scale plant micropropagation although, so far, it has been applied to only a small number of species. however, when somatic embryos are malformed they are considered economically useless. in acca sellowiana (o. berg) burret, an important fruit-producing crop, large amounts of anomalous somatic embryos (76.3%) were found just after 40 days of culture of explants in a 2,4-d containing medium. among the anomalous forms found in the cotiledonary stage, 12.2% consisted of fused embryos, 40.4% displayed fused cotyledons, 13.0% presented supernumerary cotyledons, and 10.7% showed absence or poorly developed cotyledons, including those without the shoot apical meristem. histological analyses indicated that the altered embryos were formed either directly from cotyledons, hypocotyl and radicle of the zygotic embryos used as explants, or indirectly from calli formed from these tissue parts. it is suggested that the formation of anomalous somatic embryos, as well as a low frequency of conversion into emblings reflect physiological and/or genetic disturbances triggered by the presence of 2,4-d in the medium. in vitro experimental alternative approaches are discussed in order to lessen the occurrence of malformed somatic embryos.
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