154 research outputs found
Application du microscope électronique à balayage (MEB) à la paléontologie et à la sédimentologie
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Anthelmintic activity of trans-cinnamaldehyde and A- and B-type proanthocyanidins derived from cinnamon (Cinnamomum verum)
Cinnamon (Cinnamomum verum) has been shown to have anti-inflammatory and antimicrobial properties, but effects on parasitic worms of the intestine have not been investigated. Here, extracts of cinnamon bark were shown to have potent in vitro anthelmintic properties against the swine nematode Ascaris suum. Analysis of the extract revealed high concentrations of proanthocyanidins (PAC) and trans-cinnamaldehyde (CA). The PAC were subjected to thiolysis and HPLC-MS analysis which demonstrated that they were exclusively procyanidins, had a mean degree of polymerization of 5.2 and 21% of their inter-flavan-3-ol links were A-type linkages. Purification of the PAC revealed that whilst they had activity against A. suum, most of the potency of the extract derived from CA. Trichuris suis and Oesophagostomum dentatum larvae were similarly susceptible to CA. To test whether CA could reduce A. suum infection in pigs in vivo, CA was administered daily in the diet or as a targeted, encapsulated dose. However, infection was not significantly reduced. It is proposed that the rapid absorption or metabolism of CA in vivo may prevent it from being present in sufficient concentrations in situ to exert efficacy. Therefore, further work should focus on whether formulation of CA can enhance its activity against internal parasites
Mesozoic biostratigraphic, paleoenvironmental, and paleobiogeographic synthesis, equatorial Atlantic
Cretaceous sediments from Ocean Drilling Program Leg 159 on the Côte d’Ivoire-Ghana Marginal Ridge (CIGMR), eastern equatorial Atlantic, are characterized by distinct stratigraphic changes in sedimentary facies associated with changes in the composition of the clayey and organic fractions, as well as of the calcareous nannofossil, radiolarian, foraminiferal, and palynomorph assemblages. In the absence of reliable magnetostratigraphic information, an integrated biostratigraphy provides the only means used to calibrate the geologic history of the Leg 159 area.
The existence of marine depositional environments as early as the late Aptian to early Albian close to the Leg 159 drill sites puts constraints on the timing of the opening of the equatorial Atlantic gateway. Marine sedimentation on the ridge suggests that the West African and South American cratons were largely detached at this segment of the margin by the middle to late Albian. During the Cenomanian to Coniacian the ridge appears to have remained in an elevated position with concurrent low deposition or condensation (Site 959), high carbonate debris accumulation (Site 960), and even erosion (Site 962). Total organic Carbon measurements and microfaunal data lead us to suggest that, following the early opening of the seaway during the Albian, circulation remained restricted in the fragmented sub-basins of the CIGMR. It probably was not until the Santonian that a deep-water connection and circulation system became established between the Central and the South Atlantic. The sedimentary and faunal record at Site 959 show that a rapid subsidence occurred during the Santonian, with sub-calcite compensation depth conditions maintained until and beyond the Cretaceous/Tertiary boundary
Direct Visualization of Protease Action on Collagen Triple Helical Structure
Enzymatic processing of extracellular matrix (ECM) macromolecules by matrix metalloproteases (MMPs) is crucial in mediating physiological and pathological cell processes. However, the molecular mechanisms leading to effective physiological enzyme-ECM interactions remain elusive. Only scant information is available on the mode by which matrix proteases degrade ECM substrates. An example is the enzymatic degradation of triple helical collagen II fragments, generated by the collagenase MMP-8 cleavage, during the course of acute inflammatory conditions by gelatinase B/MMP-9. As is the case for many other matrix proteases, it is not clear how MMP-9 recognizes, binds and digests collagen in this important physiological process. We used single molecule imaging to directly visualize this protease during its interaction with collagen fragments. We show that the initial binding is mediated by the diffusion of the protease along the ordered helix on the collagen Âľ fragment, with preferential binding of the collagen tail. As the reaction progressed and prior to collagen degradation, gelatin-like morphologies resulting from the denaturation of the triple helical collagen were observed. Remarkably, this activity was independent of enzyme proteolysis and was accompanied by significant conformational changes of the working protease. Here we provide the first direct visualization of highly complex mechanisms of macromolecular interactions governing the enzymatic processing of ECM substrates by physiological protease
Deep Neural Network Attribution Methods for Leakage Analysis and Symmetric Key Recovery
Deep Neural Networks (DNNs) have recently received significant attention
in the side-channel community due to their state-of-the-art
performance in security testing of embedded systems. However,
research on the subject mostly focused on techniques to improve the
attack efficiency in terms of the number of traces required to extract secret
parameters. What has not been investigated in detail is a constructive
approach of DNNs as a tool to evaluate and improve the effectiveness
of countermeasures against side-channel attacks. In this work, we try to
close this gap by applying attribution methods that aim for interpreting
DNN decisions, in order to identify leaking operations in cryptographic
implementations. In particular, we investigate three different approaches
that have been proposed for feature visualization in image classification
tasks and compare them regarding their suitability to reveal Points of
Interests (POIs) in side-channel traces. We show by experiments with
three separate data sets that Layer-wise Relevance Propagation (LRP)
proposed by Bach et al. provides the best result in most cases. Finally, we
demonstrate that attribution can also serve as a powerful side-channel
distinguisher in DNN-based attack setups
The dinoflagellate cyst genera <i>Achomosphaera</i> Evitt 1963 and <i>Spiniferites</i> Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions
We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by workshop participants. In addition, several holotypes and topotypes are reillustrated. Three species previously assigned to Spiniferites are here considered/accepted as belonging to other genera: Impagidinium inaequalis (Wall and Dale in Wall et al. 1973) Londeix et al. 2009, Spiniferites rubinus (Rossignol 1962 ex Rossignol 1964) Sarjeant 1970, and Thalassiphora balcanica Baltes & 1971. This summary forms the basis for a set of papers that follows, where points raised during the workshops are explored in greater detail
Analyse palynologique de l'argile lignitifère à ambre de l'Albian terminal d'Archingeay (Charente Maritime, France).
Un niveau d’argile lignitifère à ambre, provenant de l’Albien terminal affleurant dans une carrière située sur la commune d’Archingeay (Charente-Maritime, France), a livré une association palynologique bien conservée, riche et diversifiée, d’origine mixte, continentale et marine. Son étude détaillée, en microscopie optique et électronique, permet d’en dresser l’inventaire, puis de proposer une reconstitution du paléoenvironnement et de déduire le paléoclimat qui régnait sur cette région : un milieu estuarien sous un climat plutôt humide, tempéré à chaud. Le paysage du rivage et de l’arrière-pays devait être essentiellement composé de fougères variées, d’autres ptéridophytes et de conifères producteurs de la résine ayant évolué en ambre ; l’affinité angiospermienne est remarquable, bien qu’encore modeste sur le plan de la diversification. Des « algues » filamenteuses peuplaient les cours d’eau. La microflore d’origine marine, de diversité modérée, comprend des « basales » chitineuses de foraminifères, des acritarches et des kystes de dinoflagellés, parmi lesquels figurent les taxons repères de l’Albien terminal ; la dominance des espèces néritiques reste cependant mesurée
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