SPECTRAL ANALYSIS OF TOARCIAN SEDIMENTS FROM THE VALDORBIA SECTION (UMBRIA-MARCHE APENNINES): THE ASTRONOMICAL INPUT IN THE FORAMINIFERAL RECORD

Toarcian sections studied mainly in Europe have revealed the incidence of Milankovitch forcing with a well-developed, highly stable, 405 ky component of eccentricity, a short-term eccentricity of ~100 kyr, the cycle of obliquity ~36 kyr, and the precession signal at ~21 kyr. Cyclostratigraphic analysis of the Toarcian succession at the Valdorbia section (Umbria-Marche Apennines) was conducted based on time-series of foraminiferal assemblages. Well-developed cyclic patterns were obtained, with several significant cycles corresponding to thicknesses of 3.8-4.1 m / 5.8-6.3 m / 8.2 m / 10.4 m. Comparison with previous studies at the Valdorbia section led us to interpret the cycle of ~4 m as directly related with the short-term eccentricity (95-105 kyr). The rest of the cycles could be assigned to a periodicity of ~140-160 kyr, ~200 kyr and ~250 kyr, and interpreted as indirect signals of the long-term eccentricity, obliquity and precession, whose record would be impeded by the incompleteness of the studied succession and the sampling interval. Studied components in the foraminiferal assemblage show variable cyclostratigraphic patterns, allowing for a differentiation of groups based on similar registered cycles. These groups reveal different responses by the foraminiferal assemblage, associated with particular requirements, to the palaeoenvironmental changes of Milankovitch origin

Nitrogen isotope record of a perturbed paleoecosystem in the aftermath of the end-Triassic crisis, Doniford section, SW England

International audience[1] The Triassic-Jurassic transition (TJ) is characterized by successive perturbations of the carbon cycle during a time of biotic disruption as recorded by the carbon isotopic composition of organic matter (δ13Corg). The nitrogen isotopic composition of sedimentary organic matter (δ15Norg) constitutes a key parameter to explore the functioning of the ecosystem during carbon cycle perturbations and biological crises, because it provide information on seawater redox conditions and/or nutrient cycling. Here we report the first continuous δ15Norg record across the TJ transition at the Doniford Bay section (Bristol Channel Basin, UK), combined with δ13Corg, kerogen typology and carbon (δ13Cmin) and oxygen (δ18Omin) isotopic composition of bulk carbonates. The end Triassic is characterized by a major negative excursion both in δ13Corg and δ13Cmin, very low TOC (Total Organic Carbon, wt%) and high δ15Norg values, associated with a sea level lowstand. A second δ13Corg negative excursion occurs during the lower Hettangian. This interval is characterized by phases of carbonate production increase alternated with phases of exceptional accumulations of type I organic matter (up to 12%) associated with lower δ15Norg and δ13Corg. This alternation likely reflects a succession of nutrient input increase to the basin leading to enhanced productivity and eutrophication, which promoted a primary production driven by organic-walled prokaryotic organisms. The following OM export increase generates anaerobic conditions within the basin. These events occur between periods of relatively good seawater column ventilation and nutrient recycling boosting the carbonate producer recovery. Ecosystems remain perturbed in the Bristol Channel Basin during the aftermath of the end-Triassic crisis

Discovery of Dual Aβ/Tau Inhibitors and Evaluation of Their Therapeutic Effect on a Drosophila Model of Alzheimer's Disease

Alzheimer's disease (AD), the most common type of dementia, currently represents an extremely challenging and unmet medical need worldwide. Amyloid-β (Aβ) and Tau proteins are prototypical AD hallmarks, as well as validated drug targets. Accumulating evidence now suggests that they synergistically contribute to disease pathogenesis. This could not only help explain negative results from anti-Aβ clinical trials but also indicate that therapies solely directed at one of them may have to be reconsidered. Based on this, herein, we describe the development of a focused library of 2,4-thiazolidinedione (TZD)-based bivalent derivatives as dual Aβ and Tau aggregation inhibitors. The aggregating activity of the 24 synthesized derivatives was tested in intact Escherichia coli cells overexpressing Aβ42 and Tau proteins. We then evaluated their neuronal toxicity and ability to cross the blood−brain barrier (BBB), together with the in vitro interaction with the two isolated proteins. Finally, the most promising (most active, nontoxic, and BBB-permeable) compounds 22 and 23 were tested in vivo, in a Drosophila melanogaster model of AD. The carbazole derivative 22 (20 μM) showed extremely encouraging results, being able to improve both the lifespan and the climbing abilities of Aβ42 expressing flies and generating a better outcome than doxycycline (50 μM). Moreover, 22 proved to be able to decrease Aβ42 aggregates in the brains of the flies. We conclude that bivalent small molecules based on 22 deserve further attention as hits for dual Aβ/Tau aggregation inhibition in A

La teoria dei numeri transfiniti nei suoi aspetti matematici e filosofici

La presente tesi si occupa, da un punto di vista matematico e filosofico, dello studio dei numeri transfiniti introdotti da Georg Cantor. Vengono introdotti i concetti di numero cardinale ed ordinale, la loro aritmetica ed i principali risultati riguardo al concetto di insieme numerabile. Si discutono le nozioni di infinito potenziale ed attuale e quella di esistenza secondo la concezione di Cantor. Viene infine presentata l'induzione transfinita, una generalizzazione al caso transfinito del principio di induzione matematica

High trophic levels of the Pacific surface waters related to Upper Valanginian carbon cycle perturbation (Site 1149, ODP LEG 185)

Bartolini Annachiara, Erba Elisabetta. High trophic levels of the Pacific surface waters related to Upper Valanginian carbon cycle perturbation (Site 1149, ODP LEG 185). In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. p. 27

Ocean Cores, Climate Archives

International audienceThe study of ocean sediment cores has made it possible to document past climate variability beyond the instrumental period, that is, since direct measurements of climate variables such as water or atmospheric temperature are available. In paleoclimatology, or the study of past climates, scientists use indirect methods, called “proxies”, to reconstruct past climate conditions. This chapter attempts to cover first a brief history of the MNHN oceanic collection, second, the development of coring techniques and, finally, the types of proxies currently used to reconstruct sea temperature, salinity and CO 2 concentration, three parameters that are very sensitive to climate change. There are several coring techniques, but most of the cores in the oceanic collection are from “calypso” type piston corers, derived from the Kullenberg corer, invented in 1947. Although knowledge of foraminiferal biology and geochemistry has made significant progress in recent years, much work remains to be done to make these new proxies more robust

Ocean Cores, Climate Archives

International audienceThe study of ocean sediment cores has made it possible to document past climate variability beyond the instrumental period, that is, since direct measurements of climate variables such as water or atmospheric temperature are available. In paleoclimatology, or the study of past climates, scientists use indirect methods, called “proxies”, to reconstruct past climate conditions. This chapter attempts to cover first a brief history of the MNHN oceanic collection, second, the development of coring techniques and, finally, the types of proxies currently used to reconstruct sea temperature, salinity and CO 2 concentration, three parameters that are very sensitive to climate change. There are several coring techniques, but most of the cores in the oceanic collection are from “calypso” type piston corers, derived from the Kullenberg corer, invented in 1947. Although knowledge of foraminiferal biology and geochemistry has made significant progress in recent years, much work remains to be done to make these new proxies more robust

Ocean Cores, Climate Archives

International audienceThe study of ocean sediment cores has made it possible to document past climate variability beyond the instrumental period, that is, since direct measurements of climate variables such as water or atmospheric temperature are available. In paleoclimatology, or the study of past climates, scientists use indirect methods, called “proxies”, to reconstruct past climate conditions. This chapter attempts to cover first a brief history of the MNHN oceanic collection, second, the development of coring techniques and, finally, the types of proxies currently used to reconstruct sea temperature, salinity and CO 2 concentration, three parameters that are very sensitive to climate change. There are several coring techniques, but most of the cores in the oceanic collection are from “calypso” type piston corers, derived from the Kullenberg corer, invented in 1947. Although knowledge of foraminiferal biology and geochemistry has made significant progress in recent years, much work remains to be done to make these new proxies more robust

Étude stratigraphique du Rosso Ammonitico du Monte Inici (domaine Trapanais, Sicile occidentale) : événements biosédimentaires au Jurassique moyen-Crétacé inférieur

Les successions pélagiques jurassiques de la Sicile occidentale sont essentiellement caractérisées par le Rosso Ammonitico. Dans le secteur Est du Monte Inici ce lithofaciès est représenté du Callovien au Berriasien supérieur, tandis que dans les secteurs SW et NW il se termine à l\u27Oxfordien moyen et il est surmonté de calcaires à silex corrélables aux radiolarites téthysiennes. La base de la succession pélagique étudiée révèle que les sédiments du Callovien étaient soumis à un fort hydrodynamisme. Il s\u27ensuit une période plus calme puis l\u27intervalle Kimméridgien supérieur-Berriasien est à nouveau soumis à un hydrodynamisme intense et cyclique. Le milieu devient plus calme à la fin du Berriasien. À l\u27Oxfordien moyen-supérieur la diversité squelettique maximale, l\u27apparition du faciès noduleux à Monte Inici Est et la mise en place de calcaires silicifiés dans le secteur sud sont corrélées à un pic positif du d 13 C (d 13 C = + 3 [[perthousand]]) qui indiquerait une productivité biologique accrue. En revanche, dans la Zone à Planula (Oxfordien supérieur), un minimum relatif de la courbe du d 13 C (+ 2,3 [[perthousand]]) coïncide avec une baisse de la biodiversité et la disparition locale des protoglobigérinidés. Les fluctuations de la courbe du d 13 C seraient dues à des variations de conditions paléoenvironnementales globales. L\u27hétéropie Rosso Ammonitico/radiolarites s.l. est contrôlée par des gradients paléotopographiques locaux.The pelagic Jurassic successions of Western Sicily are dominated by the Tethyan Rosso Ammonitico. In the eastern sector of Monte Inici this lithofacies has been deposited during the Callovian-upper Berriasian interval. In the southwestern and northwestern sectors, it reached the middle Oxfordian and was followed by the deposition of silicified limestones which form a lateral equivalent of Tethyan radiolarites. The base of the studied pelagic succession reveals a high energy environment during the Callovian. It is followed by a low energy period until the upper Kimmeridgian-Berriasian interval, characterised by an intense and cyclic hydrodynamism. This energy decreases during the end of the Berriasian time. During the middle-upper Oxfordian a positive d 13 C peak (d 13 C = + 3 [[perthousand]]) coincides with the highest skeletal diversity, the appearance of the nodular facies in Monte Inici East and the deposition of the silicified limestones in the southern zone. This peak indicates a high biological productivity. On the other hand, the Planula Zone (upper Oxfordian) is characterised by a relative negative excursion of the d 13 C curve (+ 2.3 [[perthousand]]), a decrease of the biodiversity and the local disappearance of protoglobigerinids. The fluctuations of the d 13 C curve are interpreted as variations of global palaeoenvironmental conditions. The heteropy Rosso Ammonitico/radiolarites s.l. is controlled by local palaeotopographic gradients.</p