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  • 1
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    Specific frontal neural dynamics contribute to decisions to check (2016)
    Springer Nature
    Details
    Publication Date: 2016-06-22
    Description: Article Information seeking is thought to rely on the brain's frontal cortex but which regions specifically control this drive remains unknown. Here the authors show that monkeys deciding to seek information on the current state of the environment showed specific neural dynamics in the lateral prefrontal cortex and midcingulate cortex. Nature Communications doi: 10.1038/ncomms11990 Authors: Frederic M. Stoll, Vincent Fontanier, Emmanuel Procyk
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 2
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    Determination of low B/Ca ratios in carbonates using ICP-QQQ (2015)
    Wiley
    Details
    Publication Date: 2015-05-16
    Description: The very low B/Ca ratios characteristic of some natural biogenic carbonates, are of interest for research in ocean acidification but represent an analytical challenge. We describe a method using a novel instrument configuration (ICP-QQQ), for which we are not aware of any previously published geological applications, and for coccoliths, a sample type unique in its low B content and organic phases. Detection limits as low as 0.41 µmol/mol were achieved. Isobaric interferences, out of the reach even for SF-ICP-MS, can be solved using this instrument, which permits the safe measurement of the lowest abundance Ca isotope ( 46 Ca). This allows maximizing the B concentration measured (matrix concentration up to 800 ppm Ca) while maintaining both B and Ca signals in counting mode. More significantly for low B samples, the ICP-QQQ is also able to overcome the interference of the ubiquitous 12 C tail on the 11 B mass, which otherwise leads to significant overestimates at very low B concentrations. This could be a reason for the significantly lower B/Ca ratios observed for the low B content interlaboratory calibration standards (Carrara and OKA), while matching for the high B content standards was good. Finally, results obtained in the analysis of coccoliths grown in laboratory culture seems to corroborate that SIMS analysis of the samples mounted in Indium leads also to B/Ca overestimates due to porosity effects, as previously observed using LA-ICP-MS. This approach also permits the interference-free measurement of P/Ca and S/Ca ratios, which could be used as indicators of the complete removal of the organic matter from the samples. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Vital effects in coccolith calcite: Cenozoic climate-pCO2 drove the diversity of carbon acquisition strategies in coccolithophores? (2012)
    Wiley
    Details
    Publication Date: 2012-11-03
    Description: Coccoliths, calcite plates produced by the marine phytoplankton coccolithophores, have previously shown a large array of carbon and oxygen stable isotope fractionations (termed “vital effects”), correlated to cell size and hypothesized to reflect the varying importance of active carbon acquisition strategies. Culture studies show a reduced range of vital effects between large and small coccolithophores under high CO2, consistent with previous observations of a smaller range of interspecific vital effects in Paleocene coccoliths. We present new fossil data examining coccolithophore vital effects over three key Cenozoic intervals reflecting changing climate and atmospheric partial pressure of CO2 (pCO2). Oxygen and carbon stable isotopes of size-separated coccolith fractions dominated by different species from well preserved Paleocene-Eocene thermal maximum (PETM, ∼56 Ma) samples show reduced interspecific differences within the greenhouse boundary conditions of the PETM. Conversely, isotope data from the Plio-Pleistocene transition (PPT; 3.5–2 Ma) and the last glacial maximum (LGM; ∼22 ka) show persistent vital effects of ∼2‰. PPT and LGM data show a clear positive trend between coccolith (cell) size and isotopic enrichment in coccolith carbonate, as seen in laboratory cultures. On geological timescales, the degree of expression of vital effects in coccoliths appears to be insensitive to pCO2 changes over the range ∼350 ppm (Pliocene) to ∼180 ppm (LGM). The modern array of coccolith vital effects arose after the PETM but before the late Pliocene and may reflect the operation of more diverse carbon acquisition strategies in coccolithophores in response to decreasing Cenozoic pCO2.
    Print ISSN: 0883-8305
    Electronic ISSN: 1944-9186
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Palaeoclimate: Aptian mystery solved (2016)
    Springer Nature
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    Publication Date: 2016-02-03
    Description: Nature Geoscience 9, 95 (2016). doi:10.1038/ngeo2634 Author: Heather M. Stoll The volcanic eruption that created the Ontong Java Plateau released large quantities of carbon dioxide. A reconstruction of CO2 concentrations suggests that the eruption promoted climate change and the expansion of ocean anoxia.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 5
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    I-STAL, a model for interpretation of Mg/Ca, Sr/Ca and Ba/Ca variations in speleothems and its forward and inverse application on seasonal to millennial scales (2012)
    Wiley
    Details
    Publication Date: 2012-09-11
    Description: Trace element ratios Mg/Ca, Sr/Ca, and Ba/Ca are readily measured in speleothems and may be closely related to hydrological balance, enhancing paleoclimate information inferred from stable isotope measurements. We develop a model which simulates the variation in dripwater chemistry resulting from variable degree of water-rock interaction and prior calcite precipitation (PCP), with the latter process depending both on drip interval and drip oversaturation with respect to CaCO3. Partition coefficients between speleothem and dripwater are dependent on temperature for Mg and on speleothem growth rate for Sr and Ba, as observed in laboratory experiments. The drip oversaturation state, regulated both by cave pCO2 and the dilution and soil karst dissolution processes, strongly affects stalagmite trace element concentrations by modulating the extent of PCP and speleothem growth rates. Application of an inverse model confirms that seasonal CO2 cycles can explain the uncorrelated seasonal cycles in Mg/Ca and Sr/Ca observed in our speleothem records from NW Spain for which high CO2 coincides with dry season. In absence of seasonal variations in drip interval, cycles in cave pCO2 can produce seasonal covariation in Sr/Ca, Mg/Ca and Ba/Ca. In long time series (104 yr) where seasonal sampling resolution is not obtained in stalagmites, a change from dominance of summer to winter rainfall can shift the season of strongest stalagmite deposition to one of lower mean CO2 and hence greater PCP and higher Mg/Ca, Sr/Ca and Ba/Ca ratios. Caves best suited to record a dominantly water balance signal, such as mean drip intervals, are those with minimal seasonal variation in cave pCO2.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Mid‐latitude temperature variations in the Oligocene to Early Miocene (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Antarctic ice sheet margin extent and the sensitivity of benthic δ18O to orbital forcing have varied on million‐year timescales during the Oligocene to Early Miocene. However, few Sea Surface Temperature (SST) records for this time interval exist to evaluate links between polar processes and mean temperature outside polar regions. Here, we present a new record of SST for the time interval 30 to 17 Ma derived from the long‐chain alkenone unsaturation ratio ( ) at IODP Site 1406A in the mid‐latitude North Atlantic. Results confirm that warm temperatures from 24°C to over 30°C prevailed in mid‐latitudes in this time and suggest a transition from colder early‐middle Oligocene to warmer average conditions after 24.5 Ma. The global significance of this transition is highlighted by the coincidence with changes in the dominance from marine‐ to terrestrial‐terminating ice sheets in the Ross Sea around Antarctica. The longest continuous section of the record (20.6 to 26.6 Ma), contains multiple 2 million‐year cycles in SST, potentially paced by long obliquity modulation. Complex and temporally varying relationships are observed between North Atlantic SST and benthic δ18O in paired samples; significant covariation is only observed around the Oligocene‐Miocene transition, coincident with a lower average marine ice extent. These North Atlantic temperature records provide a new context in which to examine the stability of climate and the Antarctic ice sheet during the Oligocene and early Miocene.
    Print ISSN: 0883-8305
    Electronic ISSN: 2572-4525
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    A genomic-systems biology map for cardiovascular function (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-11-27
    Description: With the draft sequence of the human genome available, there is a need to better define gene function in the context of systems biology. We studied 239 cardiovascular and renal phenotypes in 113 male rats derived from an F2 intercross and mapped 81 of these traits onto the genome. Aggregates of traits were identified on chromosomes 1, 2, 7, and 18. Systems biology was assessed by examining patterns of correlations ("physiological profiles") that can be used for gene hunting, mechanism-based physiological studies, and, with comparative genomics, translating these data to the human genome.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stoll, M -- Cowley, A W Jr -- Tonellato, P J -- Greene, A S -- Kaldunski, M L -- Roman, R J -- Dumas, P -- Schork, N J -- Wang, Z -- Jacob, H J -- 1P50-HL-54998/HL/NHLBI NIH HHS/ -- R01 HL064541/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 2001 Nov 23;294(5547):1723-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology, Bioinformatics Research Center, and, Human and Molecular Genetics Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226-0509, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11721057" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blood Pressure/drug effects/genetics ; *Cardiovascular Physiological Phenomena/drug effects ; Chromosome Mapping/*methods ; Chromosomes/genetics ; Crosses, Genetic ; Female ; Genomics/*methods ; Humans ; Kidney/physiology ; Lod Score ; Male ; Nitric Oxide Synthase/genetics ; Norepinephrine/pharmacology ; Phenotype ; Quantitative Trait, Heritable ; Rats ; Vasodilation/genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Late Miocene threshold response of marine algae to carbon dioxide limitation (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-08-30
    Description: Coccolithophores are marine algae that use carbon for calcification and photosynthesis. The long-term adaptation of these and other marine algae to decreasing carbon dioxide levels during the Cenozoic era has resulted in modern algae capable of actively enhancing carbon dioxide at the site of photosynthesis. This enhancement occurs through the transport of dissolved bicarbonate (HCO3(-)) and with the help of enzymes whose expression can be modulated by variable aqueous carbon dioxide concentration, [CO2], in laboratory cultures. Coccolithophores preserve the geological history of this adaptation because the stable carbon and oxygen isotopic compositions of their calcite plates (coccoliths), which are preserved in the fossil record, are sensitive to active carbon uptake and transport by the cell. Here we use a model of cellular carbon fluxes and show that at low [CO2] the increased demand for HCO3(-) at the site of photosynthesis results in a diminished allocation of HCO3(-) to calcification, which is most pronounced in larger cells. This results in a large divergence between the carbon isotopic compositions of small versus large coccoliths only at low [CO2]. Our evaluation of the oxygen and carbon isotope record of size-separated fossil coccoliths reveals that this isotopic divergence first arose during the late Miocene to the earliest Pliocene epoch (about 7-5 million years ago). We interpret this to be a threshold response of the cells' carbon acquisition strategies to decreasing [CO2]. The documented coccolithophore response is synchronous with a global shift in terrestrial vegetation distribution between 8 and 5 Myr ago, which has been interpreted by some studies as a floral response to decreasing partial pressures of carbon dioxide () in the atmosphere. We infer a global decrease in carbon dioxide levels for this time interval that has not yet been identified in the sparse proxy record but is synchronous with global cooling and progressive glaciations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bolton, Clara T -- Stoll, Heather M -- England -- Nature. 2013 Aug 29;500(7464):558-62. doi: 10.1038/nature12448.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Geology Department, University of Oviedo, Jesus Arias de Velasco S/N, 33005, Oviedo, Asturias, Spain. cbolton@geol.uniovi.es〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23985873" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/*metabolism ; Atmosphere/chemistry ; Bicarbonates/metabolism ; Calcification, Physiologic ; Calcium Carbonate/chemistry/metabolism ; Carbon/metabolism ; Carbon Dioxide/analysis/*metabolism ; Carbon Isotopes ; Chloroplasts/metabolism ; Climate ; Fossils ; History, Ancient ; Oxygen Isotopes ; Partial Pressure ; Photosynthesis ; Phytoplankton/*metabolism ; Temperature
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 9
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    Evidence for Glacial Control of Rapid Sea Level Changes in the Early Cretaceous (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-06-21
    Description: Lower Cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves. Strontium data from an interval spanning 7 million years in the Berriasian-Valanginian imply that global sea level fluctuated about 50 meters over time scales of 200,000 to 500,000 years, which is in agreement with the Exxon sea level curve. Oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes. If glaciation caused all the rapid sea level changes in the Cretaceous that are indicated by the Exxon curve, then an Antarctic ice sheet may have existed despite overall climatic warmth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stoll -- Schrag -- New York, N.Y. -- Science. 1996 Jun 21;272(5269):1771-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological and Geophysical Sciences, Princeton University, Princeton, NJ 08544-1003, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662480" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Vital effects in coccolith calcite: Cenozoic climate-pCO2 drove the diversity of carbon acquisition strategies in coccolithophores? (2013)
    Wiley
    Details
    Publication Date: 2013-01-03
    Description: [1]  Coccoliths, calcite plates produced by the marine phytoplankton coccolithophores, have previously shown a large array of carbon and oxygen stable isotope fractionations (termed “vital effects”), correlated to cell size and hypothesized to reflect the varying importance of active carbon acquisition strategies. Culture studies show a reduced range of vital effects between large and small coccolithophores under high CO 2 , consistent with previous observations of a smaller range of interspecific vital effects in Paleocene coccoliths. We present new fossil data examining coccolithophore vital effects over three key Cenozoic intervals reflecting changing climate and atmospheric partial pressure of CO 2 ( p CO 2 ). Oxygen and carbon stable isotopes of size-separated coccolith fractions dominated by different species from well preserved Paleocene-Eocene thermal maximum (PETM, ∼56 Ma) samples show reduced interspecific differences within the greenhouse boundary conditions of the PETM. Conversely, isotope data from the Plio-Pleistocene transition (PPT; 3.5–2 Ma) and the last glacial maximum (LGM; ∼22 ka) show persistent vital effects of ∼2‰. PPT and LGM data show a clear positive trend between coccolith (cell) size and isotopic enrichment in coccolith carbonate, as seen in laboratory cultures. On geological timescales, the degree of expression of vital effects in coccoliths appears to be insensitive to p CO 2 changes over the range ∼350 ppm (Pliocene) to ∼180 ppm (LGM). The modern array of coccolith vital effects arose after the PETM but before the late Pliocene and may reflect the operation of more diverse carbon acquisition strategies in coccolithophores in response to decreasing Cenozoic p CO 2 .
    Print ISSN: 0883-8305
    Electronic ISSN: 1944-9186
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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