"Les frères Limbourg : Le Mois de Mars des Très Riches Heures du Duc de Berry" (n. 5) ; "Léonard de Vinci : Paysage, 5 août 1473" (n. 15) ; "El Greco : Vue et Plan de Tolède" (n. 47)

Commentaires sur une sélection d’œuvres illustrant l'histoire de la représentation du paysage dans la peinture occidentale.

Lliçó inaugural: "Ensenyar a pensar històricament. El llegat de Pierre Vilar"

Rosa Congost recupera l'expressió 'pensar històricament' per començar la lliçó inaugural del curs 2003-2004, i que resumeix el pensament i les preocupacions no solament de l'historiador sinó també de l'ensenyant Pierre Vilar

Genetical and comparative genomics of Brassica under altered Ca supply identifies Arabidopsis Ca-transporter orthologs

Although Ca transport in plants is highly complex, the overexpression of vacuolar Ca2+ transporters in crops is a promising new technology to improve dietary Ca supplies through biofortification. Here, we sought to identify novel targets for increasing plant Ca accumulation using genetical and comparative genomics. Expression quantitative trait locus (eQTL) mapping to 1895 cis- and 8015 trans-loci were identified in shoots of an inbred mapping population of Brassica rapa (IMB211 × R500); 23 cis- and 948 trans-eQTLs responded specifically to altered Ca supply. eQTLs were screened for functional significance using a large database of shoot Ca concentration phenotypes of Arabidopsis thaliana. From 31 Arabidopsis gene identifiers tagged to robust shoot Ca concentration phenotypes, 21 mapped to 27 B. rapa eQTLs, including orthologs of the Ca2+ transporters At-CAX1 and At-ACA8. Two of three independent missense mutants of BraA.cax1a, isolated previously by targeting induced local lesions in genomes, have allele-specific shoot Ca concentration phenotypes compared with their segregating wild types. BraA.CAX1a is a promising target for altering the Ca composition of Brassica, consistent with prior knowledge from Arabidopsis. We conclude that multiple-environment eQTL analysis of complex crop genomes combined with comparative genomics is a powerful technique for novel gene identification/prioritization.

Stable oxygen isotope record and Sr/Ca ratios of corals from IODP Holes M0009D and M0023A

We present monthly resolved records of strontium/calcium (Sr/Ca) and oxygen isotope (d18O) ratios from well-preserved fossil corals drilled during the Integrated Ocean Drilling Program (IODP) Expedition 310 'Tahiti Sea Level' and reconstruct sea surface conditions in the central tropical South Pacific Ocean during two time windows of the last deglaciation. The two Tahiti corals examined here are uranium/thorium (U/Th)-dated at 12.4 and 14.2 ka, which correspond to the Younger Dryas (YD) cold reversal and the Bølling-Allerød (B-A) warming of the Northern Hemisphere, respectively. The coral Sr/Ca records indicate that annual average sea surface temperature (SST) was 2.6-3.1 °C lower at 12.4 ka and 1.0-1.6 °C lower at 14.2 ka relative to the present, with no significant changes in the amplitude of the seasonal SST cycle. These cooler conditions were accompanied by seawater d18O (d18Osw) values higher by ~0.8 per mill and ~0.6 per mill relative to the present at 12.4 and 14.2 ka, respectively, implying more saline conditions in the surface waters. Along with previously published coral Sr/Ca records from the island [Cohen and Hart (2004), Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral. Paleoceanography 19, PA4031, doi:10.1029/2004PA001084], our new Tahiti coral records suggest that a shift toward lower SST by ~1.5 °C occurred from 13.1 to 12.4 ka, which was probably associated with a shift toward higher d18Osw by ~0.2 per mill. Along with a previously published coral Sr/Ca record from Vanuatu [Corrège et al. (2004), Interdecadal variation in the extent of South Pacific tropical waters during the Younger Dyras event. Nature 428, 927-929], the Tahiti coral records provide new evidence for a pronounced cooling of the western to central tropical South Pacific during the Northern Hemisphere YD event.

Monthly Tahiti coral Sr/Ca and oxygen isotope data from IODP Hole 310-M0024A

The early last glacial termination was characterized by intense North Atlantic cooling and weak overturning circulation. This interval between ~18,000 and 14,600 years ago, known as Heinrich Stadial 1, was accompanied by a disruption of global climate and has been suggested as a key factor for the termination. However, the response of interannual climate variability in the tropical Pacific (El Niño-Southern Oscillation) to Heinrich Stadial 1 is poorly understood. Here we use Sr/Ca in a fossil Tahiti coral to reconstruct tropical South Pacific sea surface temperature around 15,000 years ago at monthly resolution. Unlike today, interannual South Pacific sea surface temperature variability at typical El Niño-Southern Oscillation periods was pronounced at Tahiti. Our results indicate that the El Niño-Southern Oscillation was active during Heinrich Stadial 1, consistent with climate model simulations of enhanced El Niño-Southern Oscillation variability at that time. Furthermore, a greater El Niño-Southern Oscillation influence in the South Pacific during Heinrich Stadial 1 is suggested, resulting from a southward expansion or shift of El Niño-Southern Oscillation sea surface temperature anomalies.

Element ratio (Sr/Ca, Ba/Ca, B/Ca, and Mg/Ca) profiles throughout the larval life stage of Mytilus edulis, 2011

Rising anthropogenic CO2 in the surface ocean has raised serious concerns for the ability of calcifying organisms to secrete their shells and skeletons. Previous mollusc carbonate perturbation experiments report deleterious effects at lowered pH (7.8-7.4 pH units), including reduced shell length and thickness and deformed shell morphology. It is not clear whether the reduced shell growth results from a decrease in calcification rate due to lowered aragonite saturation or from an indirect effect on mollusc metabolism. We take a novel approach to discerning between these two processes by examining the impact of lowered pH on the 'vital-effect' associated with element ratios. Reported herein are the first element ratio (Sr/Ca, Ba/Ca, B/Ca, Mg/Ca and Mn/Ca) profiles throughout the larval life stage of Mytilus edulis. Element ratio data for individuals reared in ambient conditions provide new insights into biomineralization during larval development. Sr/Ca ratios are consistent with Sr incorporation in the mineral phase. Mg and Mn are likely hosted in an organic phase. The Ba partition coefficient of early larval shells is one of the highest reported in biogenic aragonite. The reason for the high Ba concentrations is unknown, but may reflect the assimilation of Ba from food and/or Ba concentration in an organic or amorphous carbonate phase. There is no observable difference in the way the studied elements are incorporated into the shells of individuals reared in ambient and lowered pH conditions. The reduced growth rate at lower pH may be a consequence of a disruption to the larval mollusc metabolism.

The influence of seawater pH on U/ Ca ratios in the scleractinian cold-water coral Lophelia pertusa

The increasing pCO2 in seawater is a serious threat for marine calcifiers and alters the biogeochemistry of the ocean. Therefore, the reconstruction of past-seawater properties and their impact on marine ecosystems is an important way to investigate the underlying mechanisms and to better constrain the effects of possible changes in the future ocean. Cold-water coral (CWC) ecosystems are biodiversity hotspots. Living close to aragonite undersaturation, these corals serve as living laboratories as well as archives to reconstruct the boundary conditions of their calcification under the carbonate system of the ocean. We investigated the reef-building CWC Lophelia pertusa as a recorder of intermediate ocean seawater pH. This species-specific field calibration is based on a unique sample set of live in situ collected L. pertusa and corresponding seawater samples. These data demonstrate that uranium speciation and skeletal incorporation for azooxanthellate scleractinian CWCs is pH dependent and can be reconstructed with an uncertainty of ±0.15. Our Lophelia U / Ca-pH calibration appears to be controlled by the high pH values and thus highlighting the need for future coral and seawater sampling to refine this relationship. However, this study recommends L. pertusa as a new archive for the reconstruction of intermediate water mass pH and hence may help to constrain tipping points for ecosystem dynamics and evolutionary characteristics in a changing ocean.

Catalogus haereticorum, omnium pene, qui ad haec vsque tempora passim literarum monumentis proditi sunt, illorum nomina, errores, & te[m]pora quibus vixerunt oste[n]dens / a F. Bernardo Lutzenburgo ... Ordinis Pr[a]edicatorii, co[n]scriptus, in cuius calc

Marca tip. en port. (Renouard, 893)