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The Hall response function of symmetric and asymmetric planar Hall effect devices is investigated by scanning a magnetized tip above a sensor surface while simultaneously recording the topography and the Hall voltage. Hall sensor geometries are tailored using a focused ion beam, in standard symmetric and asymmetric geometries. With this technique we are able to reduce a single voltage probe to a narrow constriction 20 times smaller than the other device dimensions. We show that the response function is peaked above the constriction, in agreement with numerical simulations. The results suggest a way to pattern Hall sensors for enhanced spatial resolution. [ABSTRACT FROM AUTHOR]

Looks at a study which examined the impact of probe geometry on the classical Hall response of a perpendicular inhomogeneous magnetic field. Details on an electric equation which was based on a classical model of the two-dimensional Hall effect; Information on the probe geometry; Methodology used to conduct the study; Results of the study.

A coupled paleomagnetic/dating investigation has been conducted on a sequence of 25 successive lava flows, emplaced during the upper transition of the Jaramillo subchron in Tenerife, Canary Islands. This sequence is located along the western wall of the Güímar collapse scar, in the south central part of the island. Nine flows distributed throughout this sequence were dated using unspiked K/Ar and 40 Ar/ 39 Ar methods. They bracket the section between 1009 ± 22 ka and 971 ± 21 ka (2 σ ). A first group of 8 flows at the bottom of the sequence is characterized by normal polarity with paleointensity values of the order of present-day field intensity in the Canary Islands. The virtual geomagnetic poles (VGP) of these 8 flows describe a short loop at high latitudes. Seven overlying flows are transitional in directions and dated between 991 ± 14 ka and 1002 ± 11 ka consistently with published ages of the upper Jaramillo reversal. This second group of flows is characterized by low paleointensity values (around 8–12 μT) that are less than 30% of the present dipole value in Tenerife. The VGPs of the first two transitional flows lie over northeastern Pacific whereas the five following transitional flows have all negative inclinations and their VGPs lie initially over East Antarctica, then describe a northward loop almost reaching New Zealand. The final group of ten flows yield intensities varying between 20 and 35 μT and VGPs close to the southern pole with two of them describing a small amplitude second loop to southeastern Pacific. Assuming a constant extrusion rate as a very first approximation, the distribution of the obtained ages suggests a duration of 7.6 ± 5.6 ka for the transitional interval. The obtained transitional positions of VGPs are consistent with the path reported for the same reversal from North Atlantic sediments but are different from the only other volcanic record from Tahiti. The intensity low characterizing the transitional interval remains the best tie point, centered at 996 ± 7 ka (2 σ ) relative to 28.02 Ma FC sanidine. [ABSTRACT FROM AUTHOR]

Abstract: We present a coupled paleomagnetic/dating investigation conducted on three different lava flows from the island of Tenerife (Canary Islands; Spain) erupted during the Mono Lake excursion (MLE). Paleomagnetic analyses consist in zero field demagnetizations (AF and/or thermal) and of Thellier and Thellier experiments using the PICRIT-03 set of criteria to select reliable intensity determinations. One of the flows is characterized by a direction largely deviated from the one expected from an axial geocentric dipole (GAD) field. Its paleointensity value is very low (7.8μT). The two other sites are characterized by inclinations slightly shallower than the GAD value and by low intensity values (about 12 and 21μT; present value: 38μT). The three K/Ar ages combined with two 40Ar/39Ar ages range from 32.0 to 33.2ka and they are not statistically distinguishable from one another. It therefore appears that these lavas have recorded the MLE (the only excursion in this time interval) confirming its brief duration (shorter than the minimum age uncertainties available). The mean age is younger but, within the uncertainties, consistent with the age of the 10Be peak and of the marine intensity low when reported in the most recent ice age model. These new results are the first ones with radiometric dating produced from the northern hemisphere. Combined with existing cosmogenic, marine and volcanic paleomagnetic data, these results are discussed in terms of dating, and geometry of the earth magnetic field during the excursion. [Copyright &y& Elsevier]

Abstract: Membrane based nanocalorimeters have been developed for ac-calorimetry experiments. It has allowed highly sensitive measurements of heat capacity from solid state physics to complex systems like polymers and proteins. In this article we review what has been developed in ac-calorimetry toward the measurement of very small systems. Firstly, at low temperature ac-calorimetry using silicon membrane permits the measurement of superconducting sample having geometry down to the nanometer scale. New phase transitions have been found in these nanosystems illustrated by heat capacity jumps versus the applied magnetic field. Secondly, a sensor based on ultra-thin polymer membrane will be presented. It has been devoted to thermal measurements of nanomagnetic systems at intermediate temperature (20–300K). Thirdly, three specific polyimide membrane based sensors have been designed for room temperature measurements. One is devoted to phase transitions detection in polymer, the second one to protein folding/unfolding studies and the third one will be used for the study of heat release in living cells. The possibility of measuring systems out of equilibrium will be emphasized. [Copyright &y& Elsevier]

Although considerable studies have been carried out, the true nature of high-Tc superconductors (HTSC) is still not clear. Pseudogap phase at high temperature as well as possible time reversal symmetry breaking at low temperature need further investigations. The need of carefully made samples showing the intrinsic properties of superconductivity is essential to test new theoretical developments. We present in this paper how to control crystallographic orientation in the junction and a technique developed to determine the quality of the interface barrier between a gold electrode and a HTSC: YBa2Cu3O7−δ. This potentially allows us to perform Andreev spectroscopy in the CuO2 planes of cuprate superconductors as a function of temperature, crystallographic orientation and doping. [Copyright &y& Elsevier]

The thermodynamic treatment of the glass transition remains an issue of intense debate. When associated with the formalism of non-equilibrium thermodynamics, the lattice-hole theory of liquids can provide new insight in this direction, as has been shown by Schmelzer and Gutzow [J. Chem. Phys. 125, 184511 (2006)], by Möller et al. [J. Chem. Phys. 125, 094505 (2006)], and more recently by Tropin et al. [J. Non-Cryst. Solids 357, 1291 (2011); ibid. 357, 1303 (2011)]. Here, we employ a similar approach. We include pressure as an additional variable, in order to account for the freezing-in of structural degrees of freedom upon pressure increase. Second, we demonstrate that important terms concerning first order derivatives of the affinity-driving-force with respect to temperature and pressure have been previously neglected. We show that these are of crucial importance in the approach. Macroscopic non-equilibrium thermodynamics is used to enlighten these contributions in the derivation of Cp,κT, and αp. The coefficients are calculated as a function of pressure and temperature following different theoretical protocols, revealing classical aspects of vitrification and structural recovery processes. Finally, we demonstrate that a simple minimalist model such as the lattice-hole theory of liquids, when being associated with rigorous use of macroscopic non-equilibrium thermodynamics, is able to account for the primary features of the glass transition phenomenology. Notwithstanding its simplicity and its limits, this approach can be used as a very pedagogical tool to provide a physical understanding on the underlying thermodynamics which governs the glass transition process. [ABSTRACT FROM AUTHOR]

Scanning Thermal Microscopy (SThM) has become an important measurement technique for characterizing the thermal properties of materials at the nanometer scale. This technique requires a SThM probe that combines an Atomic Force Microscopy (AFM) probe and a very sensitive resistive thermometer; the thermometer being located at the apex of the probe tip allows for the mapping of temperature or thermal properties of nanostructured materials with very high spatial resolution. The high interest of the SThM technique in the field of thermal nanoscience currently suffers from a low temperature sensitivity despite its high spatial resolution. To address this challenge, we developed a high vacuum-based AFM system hosting a highly sensitive niobium nitride (NbN) SThM probe to demonstrate its unique performance. As a proof of concept, we utilized this custom-built system to carry out thermal measurements using the 3ω method. By measuring the V3ω voltage on the NbN resistive thermometer under vacuum conditions, we were able to determine the SThM probe's thermal conductance and thermal time constant. The performance of the probe is demonstrated by performing thermal measurements in-contact with a sapphire sample. [ABSTRACT FROM AUTHOR]

Two phenomenological approaches are currently used in the study of the vitreous state. One is based on the concept of fictive temperature introduced by Tool [J. Res. Natl. Bur. Stand. 34, 199 (1945)] and recently revisited by Nieuwenhuizen [Phys. Rev. Lett. 80, 5580 (1998)]. The other is based on the thermodynamics of irreversible processes initiated by De Donder at the beginning of the last century [L’Affinité (Gauthier-Villars, Paris, 1927)] and recently used by Möller et al. for a thorough study of the glass transition [J. Chem. Phys. 125, 094505 (2006)]. This latter approach leads to the possibility of describing the glass transition by means of the freezing-in of one or more order parameters connected to the internal structural degrees of freedom involved in the vitrification process. In this paper, the equivalence of the two preceding approaches is demonstrated, not only for glasses but in a very general way for any system undergoing an irreversible transformation. This equivalence allows the definition of an effective temperature for all systems departed from equilibrium generating a positive amount of entropy. In fact, the initial fictive temperature concept of Tool leads to the generalization of the notion of temperature for systems out of thermodynamic equilibrium, for which glasses are just particular cases. [ABSTRACT FROM AUTHOR]

This review aims to provide an update on our current knowledge of the various effects of pesticide cocktails. We have collected data from studies conducted in mammalian models in vitro and in vivo that was published between 2000 and 2014. All ecotoxicological studies were voluntarily excluded. Cocktail effects were classified according to how they had been classified by each author. The frequency of the various cocktail effects and the classes and chemical families of pesticides involved in the observed effects were assessed. When focusing on the function of pesticides (i.e. herbicide, insecticide or fungicide), 46% of the mixtures contained insecticides alone, 15% fungicides alone, and 4.5% herbicides alone. Mixtures with effects associated with neurotoxicity were mainly composed of insecticides, and most studies on the effects of fungicide mixtures (90%) were associated with effects on endocrine regulation and/or reproduction. Dose addition was observed with each kind of mixture except herbicide combinations. In contrast, synergic interactions or greater-than-additive effects were mainly reported for insecticide mixtures. There were few examples of potentiating and antagonistic interactions. We have identified chemical families of compounds specifically involved in synergy, addition, potentiation and antagonism, and those that do not interact when combined. The chemical families identified as being involved in synergy are in agreement with data from another recently published compilation of ecotoxicological studies. For most mixtures investigated, further validation data is still needed from experiments using other compounds and other experimental models but this update provides useful information to help in human health risk assessments. [ABSTRACT FROM AUTHOR]

The Samtskhe-Javakheti volcanic plateau (Republic of Georgia) is the northernmost and youngest expression of the magmatism following the Arabia-Eurasia collision. Here, we present whole rock elemental and twenty-one new unspiked K/Ar and 40 Ar/ 39 Ar ages for the volcanic sequence well exposed east of the plateau. Based on our new radio-isotopic ages, we have identified three magmatic episodes. The oldest one (2.84–1.08 Ma), corresponding to the “Javakheti plateau s.s. ”, is mainly constituted of medium-K alkaline mafic lavas (basalt, basaltic trachyandesite) and of intermediate composition domes (dacite). The more recent volcanic activity has constructed an impressive N–S trending volcanic ridge (Samsari s.s. ) composed of evolved rocks (medium-K dacite to rhyolite). Within this ridge, two main periods of activity could be depicted: Middle Pleistocene (439–189 ka) and Late Pleistocene (90–13 ka). The youngest activity is restricted to the northern edge of this prominent magmatic structure and linked to the Tavkvetili volcano activity. According to these young ages, this area can be considered as a potential zone of volcanic hazards. The oldest volcanic activity shaping the Javakheti plateau is distributed between major strike slip faults in pull-apart position. The emplacement of the volcanism is controlled by a localized upper crustal extension. This is particularly outlined by the N–S linear array of domes that constitutes the Samsari ridge. This volcanic structure emplaced indeed on top of two major N–S faults that have probably played a key role to control the Middle to Late Pleistocene volcanism. The new 40 Ar/ 39 Ar ages date between 2.32 and 1.54 Ma the fauna assemblage of the Tsalka paleontological site. Rocks from the Samtskhe-Javakheti volcanic plateau derived from a low degree of melting of a metasomatized lithospheric mantle source (spinel facies). Except the obsidians from the Chickiani dome, they all derived from this source and evolved following a crystallization sequence involving mainly clinopyroxene, garnet, and/or amphibole. A crustal contamination component modified the composition of the youngest products (Samsari ridge rocks). According to the geochemical signature of these rocks, it seems that the magmatism does not fit with models involving asthenospheric upwelling in this region. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study is to identify the hierarchy of importance amongst pathways involved in fatty acid (FA) metabolism and their regulators in the control of hepatic FA composition. A modeling approach was applied to experimental data obtained during fasting in knockout (KO) mice and wild-type mice. A step-by-step procedure was used in which a very simple model was completed by additional pathways until the model fitted correctly the measured quantities of FA in the liver. The resulting model included FA uptake by the liver, FA oxidation, elongation and desaturation of FA, which were found active in both genotypes during fasting. From the model analysis we concluded that had a strong effect on FA oxidation. There were no indications that this effect changes during the fasting period, and it was thus considered to be constant. In KO mice, FA uptake was identified as the main pathway responsible for FA variation in the liver. The models showed that FA were oxidized at a constant and small rate, whereas desaturation of FA also occurred during fasting. The latter observation was rather unexpected, but was confirmed experimentally by the measurement of delta-6-desaturase mRNA using real-time quantitative PCR (QPCR). These results confirm that mathematical models can be a useful tool in identifying new biological hypotheses and nutritional routes in metabolism. [Copyright &y& Elsevier]

Abstract: Polytetrafluoroethylene can be considered as a model for calorimetric studies of complex systems with thermodynamics transitions at ambient temperature. This polymer exhibits two phase transitions of different nature at 292K and 303K. We show that sensitive ac-calorimetry measurements allow us to study the thermodynamic behaviour of polytetrafluoroethylene when it is brought out of thermodynamic equilibrium. Thanks to the thermal modelization of our calorimetric device, the frequency-dependent complex heat capacity of this polymer is extracted. The temperature and frequency variations of the real and imaginary parts of the complex heat capacity are obtained when polytetrafluoroethylene undergoes its first-order structural phase transition at 292K. [Copyright &y& Elsevier]

The Teide and Pico Viejo stratocones and the Northwest and Northeast Rifts are products of the latest eruptive phase of the island of Tenerife, initiated with the lateral collapse of its northern flank that formed the Las Cañadas Caldera and the Icod--La Guancha Valley ca. 200 ka. The eruptive and structural evolution of this volcanic complex has been reconstructed after detailed geological mapping and radioisotopic dating of the significant eruptive events. A set of 54 new 14C and K/Ar ages provides precise age control of the recent eruptive history of Tenerife, particularly Teide Volcano, the third-highest volcanic feature on Earth (3718 m above sea level, >7 km high), and unique in terms of its intraplate setting. The development of the Teide--Pico Viejo Volcanoes may be related to the activity of the Northwest and Northeast Rifts. Volcanic and intrusive activity along both rift zones may have played an important role in activating the gravitational landslide and in the subsequent growth, nested within the collapse embayment, of an increasingly higher central volcano with progressively differentiated magmas. The coeval growth of the central volcano with sustained activity along the rifts led to a clear bimodal distribution in composition of eruptive products, with the basaltic eruptions in the distal part of the rifts and phonolitic and more explosive eruptions in the central area, where the differentiated stratocones developed. Current volcanic hazard in Tenerife is considered to be moderate, because eruptive frequency is low, explosivity is modest, and the eruptive activity of the Teide stratocone seems to have declined over the past 30 k.y., with only one eruption in this period (1150 yr B.P.). [ABSTRACT FROM AUTHOR]

A correction to the article "Temperature of systems out of thermodynamic equilibrium" that was published online on 2008 is presented.

Marine and subaerial erosion of volcanic ocean islands form coastal cliffs and shore platforms, particularly during stable sea levels. Posterosional lava flows can spill over these coastal cliffs and fill the platforms, leading to the progradation of lava deltas. This work aims to analyze this volcanic rocky coast setting at the island scale and to assess the volcanic constructional and erosive degradational effects on the coast at the scale of one volcanic edifice. El Hierro Island, Canary Islands, exemplifies a rocky coast with an active sea-cliff profile, reflecting its early evolutionary stage as a young ocean volcanic island with no fringing reef. The occurrence of a contemporary insular shelf formed during the Holocene sea-level highstand (<7 ka) allows constraining the ages of those eruptions forming lava deltas affecting this geomorphological landform. A detailed bathymetry around the island allowed us to distinguish 17 eruptions fulfilling this criterion. The Montaña del Tesoro, which occurred about 1050 years BP, is one of these eruptions and was selected as a case study for morphometric modeling integrating subaerial and submarine data at the scale of a volcanic edifice. This eruption was a Strombolian basaltic volcanic event that produced a scoria cone, pyroclastic fall deposits, and lava flows that reached the ocean in the eastern rift zone of El Hierro island. We combine field-based observations with topographic and bathymetric data analysis to reconstruct the pre- and post-eruption Digital Elevation Models (DEMs) and, comparing with present-day DEM, to analyze morphometrically the influence of volcanism on the coastal landscape's development. The resulting landform complexity required the discretization of the lava field according to the coastline evolution and lava front sectors, and the subaerial or submarine lava placement. The pyroclastic materials' total erupted bulk volume (12,829,578 m3) corresponds to a volcanic eruption index (VEI) of 3. This event was primarily effusive. From a dense rock equivalent (DRE) volume of 25,615,424 m3, 87 % flowed as lava, 10 % formed the cinder cone, and 3 % the tephra fall deposits. We quantitatively demonstrate that dominant degradation occurs in the lava field, mainly disturbed by marine erosion. Marine erosion removed 9 % of the erupted volume of lava flows against 1 % by fluvial erosion. This work provides methods and results of great interest with different implications in oceanic volcanic islands, among which we can mention coastal planning (e.g., rock coast evolution) and volcanic risk assessment (e.g., the importance of Holocene sea-level rise on the development of shore platforms facilitating the progradation of lava deltas). [Display omitted] • The Canary Islands are a natural laboratory for subaerial-submarine volcanic systems. • Detailed bathymetry discovers coastline evolution affected by recent volcanism. • Contemporary shore platforms in El Hierro allow relative dating of volcanism. • Submarine lava deltas identify volcanoes erupting in the last 7000 years. • The Montaña del Tesoro eruption produced a lava delta ca. 1050 years BP. [ABSTRACT FROM AUTHOR]

We report on new paleomagnetic directions obtained from 38 lava flows located at Tenerife and Gran Canaria (Canary Islands, Spain). One flow is a historical one (1706 AD) and 28 other flows are dated by radiocarbon between 1550 AD and about 13 200 BC. Nine other flows are not dated but they have stratigraphic links with the other flows. Thermomagnetic curves, unblocking temperatures and coercivities suggest that the main carrier of the remanent magnetization is titanomagnetite with various titanium contents in the pseudo-single domain range. Paleodirections were obtained by thermal and alternating field demagnetization on more than 400 specimens. The two youngest flows yield directions well consistent with the data previously published from the Canary Islands but only covering the last 500 yr. Comparison with model predictions indicates that the models account on the long-term for most of the data. However, on short-term scale, a better agreement is observed with the archeomagnetic-based model predictions (ARCH3K and SHA.DIF.14k). Two time intervals (between 25 BC and 85 AD and around 600–700 BC), however, are characterized by more variable paleomagnetic directions, suggesting that the variability of the earth magnetic field was faster than predicted by the models. On a wider geographical scale, a rather good consistency is observed between the Canarian dataset and those from Northern Africa, Spain and Azores. Field information is well consistent with paleomagnetic information for the undated sites and they both confirm that the eruption rate of the Gran Canaria volcanic system was high around 600 BC, 1000 BC and 4650 BC. Refined ages could be obtained for two of the undated sites using archeomagnetic dating. Combined with the data previously published for the last 500 yr, this new dataset is the first long PSV record available for the Canary Islands, significantly contributing to the archeomagnetic/paleomagnetic database at latitudes lower than 30°N. Improvement in the time resolution of model predictions is now needed to allow more detailed data-model comparisons on short time scale. [ABSTRACT FROM AUTHOR]

Background and Purpose: Long-term intake of dietary fatty acids is known to predispose to chronic inflammation, but their effects on acute intestinal ischaemia/reperfusion (I/R) injury is unknown. The aim of this study was to determine the consequences of a diet rich in n-3 or n-6 polyunsaturated fatty acids (PUFA) on intestinal I/R-induced damage.Experimental Approach: Mice were fed three different isocaloric diets: a balanced diet used as a control and two different PUFA-enriched diets, providing either high levels of n-3 or of n-6 PUFA. Intestinal injury was evaluated after intestinal I/R. PUFA metabolites were quantitated in intestinal tissues by LC-MS/MS.Key Results: In control diet-fed mice, intestinal I/R caused inflammation and increased COX and lipoxygenase-derived metabolites compared with sham-operated animals. Lipoxin A4 (LxA4 ) was significantly and selectively increased after ischaemia. Animals fed a high n-3 diet did not display a different inflammatory profile following intestinal I/R compared with control diet-fed animals. In contrast, intestinal inflammation was decreased in the I/R group fed with high n-6 diet and level of LxA4 was increased post-ischaemia compared with control diet-fed mice. Blockade of the LxA4 receptor (Fpr2), prevented the anti-inflammatory effects associated with the n-6 rich diet.Conclusions and Implications: This study indicates that high levels of dietary n-6, but not n-3, PUFAs provides significant protection against intestinal I/R-induced damage and demonstrates that the endogenous production of LxA4 can be influenced by diet. [ABSTRACT FROM AUTHOR]

Background and Purpose Long-term intake of dietary fatty acids is known to predispose to chronic inflammation, but their effects on acute intestinal ischaemia/reperfusion ( I/R) injury is unknown. The aim of this study was to determine the consequences of a diet rich in n-3 or n-6 polyunsaturated fatty acids ( PUFA) on intestinal I/R-induced damage. Experimental Approach Mice were fed three different isocaloric diets: a balanced diet used as a control and two different PUFA-enriched diets, providing either high levels of n-3 or of n-6 PUFA. Intestinal injury was evaluated after intestinal I/R. PUFA metabolites were quantitated in intestinal tissues by LC-MS/MS. Key Results In control diet-fed mice, intestinal I/R caused inflammation and increased COX and lipoxygenase-derived metabolites compared with sham-operated animals. Lipoxin A4 ( LxA4) was significantly and selectively increased after ischaemia. Animals fed a high n-3 diet did not display a different inflammatory profile following intestinal I/R compared with control diet-fed animals. In contrast, intestinal inflammation was decreased in the I/R group fed with high n-6 diet and level of LxA4 was increased post-ischaemia compared with control diet-fed mice. Blockade of the LxA4 receptor ( Fpr2), prevented the anti-inflammatory effects associated with the n-6 rich diet. Conclusions and Implications This study indicates that high levels of dietary n-6, but not n-3, PUFAs provides significant protection against intestinal I/R-induced damage and demonstrates that the endogenous production of LxA4 can be influenced by diet. [ABSTRACT FROM AUTHOR]

Eight volcanic ash layers, linked to large explosive events caused by subduction-related volcanism from the Vardar Ocean back-arc, interbedded with marine limestones and cherts, have been identified in the Rosso Ammonitico Veronese Formation (northeastern Italy). The thickest ash layer, attributed to the Gregoryceras transversarium ammonite Biozone (Oxfordian Stage), yields a precise and reliable 40Ar–39Ar date of 156.1 ± 0.89 Ma, which is in better agreement with GTS2004 boundaries than with the current GTS2012. This first biostratigraphically well-constrained Oxfordian date is proposed as a new radiometric tie-point to improve the Geologic Time Scale for the Late Jurassic, where ammonite-calibrated radiometric dates are particularly scarce. [ABSTRACT FROM PUBLISHER]

Abstract: Quaternary active Nemrut volcano is situated 12km north of the Bitlis–Zagros suture zone, southern margin of continental collision between Arabian and Anatolian plates. The latest activity of the volcano dates back to historic times. Volcanic evolution of the volcano is investigated under two main stages: Pre-caldera and post-caldera separated by paroxysmal caldera forming eruptions not older than 90ka. The majority of the products are silica oversaturated peralkaline {([Na2O+K2O]/Al2O3)>1} felsic rocks with rare transitional-to-mildly alkaline basalts and mugearites. A compositional gap (Daly Gap) between 53% and 59% SiO2 is partly filled with benmoreitic enclaves in peralkaline rhyolites. Benmoreitic enclaves display evidence of interminglement between mafic and felsic magmas. Observed mineral assemblages represent typical peralkaline mineralogy with aenigmatite, arfvedsonite-riebeckite, aegirine, fayalite and chevkinite. Geochemical evolution trends and modelling depict that protracted crystal fractionation dominated by feldspar, clinopyroxene, olivine and Fe-Ti oxides and crustal contamination would produce peralkaline rhyolites from the actual mafic compositions taken as parents. Mineralogical and petrographical observations indicate that the magma chamber is zoned compositionally having a crystal rich density layer between mafic and felsic melts. The genesis of Nemrut peralkaline magmatism has been ascribed to the ascension of slightly subduction modified asthenospheric melts into upper crustal high level reservoirs in localized extension in Muş ramp basin. [Copyright &y& Elsevier]

Abstract: Modeling of volcanic morphometry provides reliable measurements of parameters that assist in the determination of volcanic landform degradation. Variations of the original morphology enable the understanding of patterns affecting erosion and their development, facilitating the assessment of associated hazards. A total of 24 volcanic Holocene eruptions were identified in the island of Gran Canaria (Canary Islands, Spain). 87% of these eruptions occurred in a wet environment while the rest happened in a dry environment. 45% of Holocene eruptions are located along short barrancos (S-type, less than 10km in length), 20% along large barrancos (L-type, 10–17km in length) and 35% along extra-large barrancos (XL-type, more than 17km in length). The erosional history of Holocene volcanic edifices is in the first stage of degradation, with a geomorphic signature characterized by a fresh, young cone with a sharp profile and a pristine lava flow. After intensive field work, a careful palaeo-geomorphological reconstruction of the 24 Holocene eruptions of Gran Canaria was conducted in order to obtain the Digital Terrain Models (DTMs) of the pre- and post-eruption terrains. From the difference between these DTMs, the degradation volume and the incision rate were obtained. The denudation of volcanic cones and lava flows is relatively independent both their geographical location and the climatic environment. However, local factors, such as pre-eruption topography and ravine type, have the greatest influence on the erosion of Holocene volcanic materials in Gran Canaria. Although age is a key factor to help understand the morphological evolution of monogenetic volcanic fields, the Gran Canaria Holocene volcanism presented in this paper demonstrates that local and regional factors may determine the lack of correlation between morphometric parameters and age. Consequently, the degree of transformation of the volcanic edifices evolves, in many cases, independently of their age. [Copyright &y& Elsevier]

Abstract: The Kvemo-Orozmani locality contains a 15 m thick Early Pleistocene fluvio-lacustrine sequence bracketed by two lava flows. Located 13 km up the Masavera River Valley (west) from the Dmanisi Site, Kvemo-Orozmani is therefore of prime interest to improve the paleoecological framework as well as dating Dmanisi. 40Ar/39Ar ages obtained on the two lava flows indicate that Kvemo-Orozmani sequence brackets the Dmanisi sediments between 1.825 ± 0.021 Ma and 1.765 ± 0.021 Ma. Phytolith assemblages found at the bottom of the sequence indicate a warm and humid climate while the assemblages found at the top suggest dryer-colder climatic conditions. The shift in phytolith assemblages observed at Kvemo-Orozmani is similar to the one already described in Dmanisi and occurs near the end of the Oluduvai subchron. The new palaeoecological and chronological data confirm the hypothesis made in Dmanisi about the palaeoenvironmental context during the hominin occupation that suggests a temperate climate becoming drier. The age we obtained on the overlying lava flow establishes a minimum age for the climatic transition at both Kvemo-Orozmani and the Dmanisi Site of 1.765 ± 0.021 Ma. [Copyright &y& Elsevier]

Abstract: De novo fatty acid biosynthesis is also called lipogenesis. It is a metabolic pathway that provides the cells with fatty acids required for major cellular processes such as energy storage, membrane structures and lipid signaling. In this article we will review the role of the Liver X Receptors (LXRs), nuclear receptors that sense oxysterols, in the transcriptional regulation of genes involved in lipogenesis. [Copyright &y& Elsevier]

Abstract: In this work we analyzed the transcriptome profiles of chicken hepatoma cells (LMH) in response to T0901317, a pharmacological agonist of the liver X receptor (LXR). Through an in silico search for LXRE (LXR response element) consensus sequences in the promoter of genes whose expression was shown to be sensitive to TO901317, we identified a LXRE in the promoter of the LPCAT3 (lysophosphatidylcholine acyltransferase 3). This motif is highly conserved between species. We further investigated the regulation of this gene and showed that the expression of LPCAT3 was induced both in chicken and human hepatoma cells (LMH and HuH-7, respectively) in response to T0901317. Transactivation and electrophoretic mobility shift assays allowed us to locate a functional LXRE in the chicken LPCAT3 promoter. Altogether these data evidence for the first time that the chicken LPCAT3 gene is a direct target of LXR and therefore suggest a new role for LXR in phospholipid homeostasis. [ABSTRACT FROM AUTHOR]

Abstract: The northern part of the N–S-trending basin of the Limagne graben, located in the northern part of the Massif Central (France), contains Oligocene and Miocene calcareous lacustrine deposits. The area is known for its stromatolite reefs surrounded by marl, clay and uncemented carbonate sand with oncolites. Because the origin of the carbonate accumulated by cyanobacteria has long been debated, the clayey deposits associated with the stromatolites were analysed using XRD, SEM and K–Ar dating methods. The results show a monotonous assemblage of carbonates, dioctahedral smectite, illite–smectite (Reichweite) R=0, glauconitic illite and abundant orthoclase. Detrital minerals such as quartz and detrital illite are found near the basin''s borders but are very scarce in its central part, indicating a lack of detrital input from the regional basement. Hence, the abundant orthoclase found in all the clayey deposits of the Limagne Basin cannot be linked to erosion of the surrounding Hercynian basement. The SEM analysis showed the orthoclase crystals to have a tabular morphology with sharp boundaries and to be embedded within a clay matrix, whilst the K–Ar dating of the orthoclase and glauconitic illite yielded ages ranging from 90 to 66±2Ma, i.e. Turonian to Maastrichtian. These two results clearly indicate that the fill of the Limagne Basin, composed mainly of carbonate, clay and orthoclase, must have been partly due to the erosion of an Upper Cretaceous sedimentary blanket once covering the Massif Central basement. This cover was probably constituted of chalk, dioctahedral smectite, I/S and glauconitic illite, associated with authigenic orthoclase and flint. Flints are found reworked in the alluvial formations of the Late Pliocene Lower Bourbonnais sands and clays (‘Sables et argiles du Bourbonnais’) and in the Pleistocene terraces. Moreover, relicts of the Upper Cretaceous cover were preserved during the sedimentary filling of the Cenozoic Limagne Basin. Authigenic orthoclase of similar shape has been described in the Chalk Group of the Paris Basin and from localities in northern France and Belgium. The mineral is rare in the Turonian chalk but increases rapidly at the base of the Coniacian to Campanian chalk; it has also been noted that the number of orthoclase crystals increases as the quantity of clastic components decreases. Similar orthoclase crystals were found associated with dioctahedral smectite in the decarbonated residues of the Coniacian to Santonian chalk from Fécamp and Etretat (northern France). Moreover, our results are consistent with other data from within and around the Paris Basin, such as the palaeogeography and facies distribution of the Chalk formations, the residual flints in the clay-with-flints of the southern Paris Basin and around the Morvan, and apatite fission-track thermochronology data from the Hercynian basement of the Massif Central and the Morvan. All these data indicate a major connection between the Paris Basin and the Tethys, and an extensive palaeocover on the Massif Central and Morvan basement. [Copyright &y& Elsevier]

Abstract: The morphogenetic evolution of the Lesser Caucasus has been strongly influenced by Plio-Quaternary volcanic and tectonic events and Pleistocene glaciations. Fluvio-lacustrine environments, indicated by diatomaceous deposits, prevailed in the Syunik region of southern Armenia during the Pliocene and Pleistocene. The Pleistocene diatomaceous deposits studied contain leaf impressions and pollen, allowing local palaeoclimatic reconstructions. The chronology of morphogenetic events has been determined by 17 radiometric dates (K/Ar, Ar/Ar, U/Th), palaeomagnetic investigations and is placed in a spatial context by a detailed geomorphological map and a 24-km geological transect of the Vorotan valley, the main area studied. Before 1.21Ma, tectonic movements (antecedents of the lower part of the Vorotan valley) generated extensive lake formations with diatomaceous deposits. From 993ka, volcanic eruptions produced lava flows that covered the fluvio-lacustrine accumulations. During Marine Isotopic Stages 12, 6 and 4, glaciers and fluvio-glacial deposits were probably present overall the principal uplands and valleys of southern Armenia. At 53.68ka (MIS 3), 12.6ka, 10.78ka and 4.14ka (MIS 1), the development of travertines on some slopes and in some valleys highlights temperate and humid climatic phases. Palaeobotanical studies of leaf and pollen floras show that the vegetation changed several times from forested to steppic phases in response to the climate oscillations of the Lower Pleistocene. This work proposes a first morphogenic and palaeoclimatic reconstruction from the lower Pleistocene to the Postglacial period, when the first settlements of the population in the Lesser Caucasus were influenced by tectono-volcanic events, lake level changes and glacial–interglacial oscillations forced by the obliquity orbital parameter (41ky cycles). [ABSTRACT FROM AUTHOR]

Errors in the interpretation of clouds, fumarolic activity and forest fires as volcanic eruptions in Tenerife, mainly in relation with Teide volcano, are common in references by passing navigators and other eyewitness accounts from the fifteenth and sixteenth centuries. In the case of the most common, historical, multiple-vent fissure eruptions in the Canaries, vent locations provided by these accounts are frequently uncertain or are clearly erroneous and often conflict with geological evidence. Significant examples are the general association of the latest eruption of Teide volcano, dated at 1150 ± 140bp, with the reference made by Christopher Columbus in 1492 to an eruption ‘on the flanks of Teide’, which actually corresponds to an eruptive vent (Boca Cangrejo volcano) situated in the NW Rift, dated at 400 ± 110bp. Similar conflicting vent locations occurred in the 1730–36 eruption of Lanzarote and the 1677 eruption of La Palma. This article considers the volcanic cones located in the Orotava Valley, erroneously assigned by Chevalier de Borda and Alexander von Humboldt to a 1430ad eruption. Geological evidence and radiocarbon dating of charcoal underlying the lapilli, and 40Ar/39Ar dating of one of the lava flows, show that these volcanic cones and lavas correspond to an eruption that took place about 30 000 yrbp. Analysis of the influence of these erroneous ages for the recent volcanism of Tenerife shows an overestimation of eruptive hazards of this island. [ABSTRACT FROM AUTHOR]

Abstract: The anisotropy of magnetic susceptibility (AMS), coupled with mineral magnetic identification, has been investigated in about 640 samples from 27 basaltic dikes of Tertiary age in Eastern Iceland. The dikes are a few meters thick and they have been sampled all across. Three types of magnetic fabrics with well-defined mean principal axes of anisotropy are recognized. In the first one the maximum axis is vertical and the minimum axis coincides with the pole of the dike plan (“geometrically normal” fabric). The second fabric shows opposite orientation (“geometrically inverse” fabric). The third type is when these two fabrics coexist with the “normal” one at the margins and the “inverse” one in the center of the dike (“mixed” fabric). No relationship is observed between the type of fabric and the width of the dikes. Each fabric is carried by clear magnetic assemblages made of low (x ∼0.15) Ti-content fine-grained magnetites for the “normal” one and high Ti-content (around TM60) coarse magnetite grains for the “inverse” fabric. Upon heating, the magnetic properties and the orientation of the anisotropy ellipsoid characterizing the “inverse” fabric in the mixed dikes change and evolve toward the “normal” type. These two geometrically “normal” and “inverse” fabrics are interpreted as primary ones, representing different physico-chemical conditions during the emplacement of the magma. The AMS results indicate that, during the volcanic events occurring about 10Myr ago, the extrusion of the magma was vertical at the depth of the studied sites in eastern Iceland. [Copyright &y& Elsevier]

Liver X receptor α (LXRα), also referred to as nuclear receptor subfamily 1, group H, member 3 is a member of the nuclear hormone receptor superfamily, and has recently been shown to act as a master transcription factor governing hepatic lipogenesis in mammals. Liver X receptor a directly regulates both the expression of other lipogenic transcription factors and the expression of lipogenic enzymes, thereby enhancing hepatic fatty acid synthesis (FASN). In birds, like in humans, fatty acid synthesis primarily occurs in the liver. Whether LXRα is involved in hepatic regulation of lipogenic genes remained to be investigated in this species. Here we show that fatty acid synthase and the expression of other lipogenic genes (sterol regulatory element binding protein 1 and steroyl coenzyrne A desaturase 1) are induced in chicken hepatoma cells in response to a pharmacological liver X receptor agonist, T0901317. A detailed analysis of the chicken FASN promoter revealed a functional liver X response element. These data define the chicken FASN gene as a direct target of LXRα and further expand the role of LXRα as a regulator of lipid metabolism in this species. [ABSTRACT FROM AUTHOR]

The lavas of the Mount Cameroon, a Plio-Quaternary stratovolcano and the most important volcano along the Cameroon Volcanic Line (CVL), constitute a weakly differentiated alkaline series: mainly comprising basanites as well as alkaline basalts, hawaiites and mugearites. Ultramafic xenoliths (1–5 × 0.5–4 cm) of dunites, wehrlites and clinopyroxenites have been discovered in the basanites of a strombolian cone, located near Batoke on the South flank of the massif at an elevation of 500 m. K-Ar whole rock dating of the basanitic host rock has yielded an age of 0.73 ± 0.08 Ma. This result falls within the range of the seven new K-Ar age determinations of mafic lavas, between 2.83 Ma and the Present. These are the first K-Ar data on this massif. The 87Sr/86Sr ratios of basic lavas are low (0.703198–0.703344), and 143Nd/144Nd ratios are intermediate (0.512851–0.512773). These ratios are typical of a mantle origin. The main characteristics of the xenoliths are: (a) total FeO contents are 15.1 to 19.1 wt.% in olivines (chrysolite, Mg# ranging from 79 to 84) of xenoliths, and 4.7 to 6.9 wt.% in diopsides of xenoliths, (b) diopsides of the clinopyroxenites have up to 7.2 wt.% Al2O3 and 2.3 wt.% TiO2, (c) spinels occur as interstitial grains between chrysolite and diopside grains, i.e. Cr2O3-rich magnetites (19 to 21 wt.% Cr2O3) in the dunites as well as (22 to 25 wt.% Cr2O3) in the wehrlites and titanomagnetites (14 to 15 wt.% TiO2) in the clinopyroxenites. Mineralogical analyses show an important re-equilibration between the chrysolite xenocrysts and the host basanitic magma. We observed a decrease in Mg and Ni towards the rim, and an enrichment in all others cations like Fe, Mn, Ca, Si. The changes of Fe2+ / Mg2+ are the most important. The xenoliths are interpreted as cumulates: clinopyroxenite xenoliths have probably crystallized and fractionated at an early stage from the mafic (host basanitic) magma, while dunite and wehrlite xenoliths seem to have crystallized from a previous more primitive batch of magma. These alkaline liquids could have been derived from partial melting of a garnet- rich lherzolite in the upper mantle beneath the Cameroon Volcanic Line. The AlIV/AlVI ratios remain high (1.2 to 4.9) in the clinopyroxenes of the xenoliths. This suggests crystallization under a lower pressure than that of equilibration of the clinopyroxenes (ratios 0.6 to 0.8) found in typical mantle xenoliths from the CVL. [ABSTRACT FROM AUTHOR]

The Miocene Las Burras--Almagro--El Toro magmatic complex lies ~300 km to the east of the Central Andes volcanic arc, in the easternmost sector of the transverse Calama--Olacapato--El Toro fault zone. The magmatic rocks of the Las Burras--Almagro--El Toro complex comprise a monzogabbro to monzogranite laccolith like intrusion and basaltic andesite to dacite volcanic rocks that include seven lithostratigraphic members. New Rb-Sr dates indicate that the intrusive rocks are ca. 14 Ma, and K-Ar dates suggest emplacement ages of ca. 12.8--6.4 Ma for the volcanic rocks. The emplacement of the intrusion was controlled by N-S--striking strike-slip faults in a context of oblique convergence; the volcanism, which occurred along WNW-ESE--and N-S--striking extensional faults, relates to the Calama--Olacapato--El Toro fault zone. Two magmatic phases were recognized. Intrusive and volcanic rocks of the older magmatic phase (ca. 14--13 Ma) are characterized by Ba/Nb (7--14), La/Ta (11--18), and isotopic ratios (87Sr/86Sr: 0.704339--0.705281, 143Nd/144Nd: 0.512713--0.512598), which are intraplate characteristics. The source of the older magmas was isotopically depleted lithospheric mantle rich in K, Rb, and Th. Energy constrained--assimilation and fractional crystallization (EC-AFC) modeling indicates that fractional crystallization and crustal assimilation moderately modified magma composition during its residence in the crust. The products of the younger magmatic phase (ca. 11--6 Ma) have higher Ba/Nb (24--42) and La/Ta (24--30) and 87Sr/86Sr (0.706738--0.708729) and lower 143Nd/144Nd (0.512433--0.512360). The results of EC-AFC modeling exclude a significant role for the upper crust in the generation of the most primitive magmas of this phase. Their compositions can be explained by (1) contamination of the primary magmas having originated in a depleted mantle with a mafic crust, or (2) the contribution of isotopically enriched mantle zones. Shallow differentiation and moderate contamination by continental crust can explain the composition of the intermediate and evolved products of the younger phase. The variation of the magma source characteristics at 11 Ma is discussed in the frame of the complex geodynamical setting in this region. [ABSTRACT FROM AUTHOR]

Abstract: A revised kinematic model is proposed for the Neogene tectono-magmatic development of the North Tanzanian Divergence where the axial valley in S Kenya splits southwards into a wide diverging pattern of block faulting in association with the disappearance of volcanism. Propagation of rifting along the S Kenya proto-rift during the last 8 Ma is first assumed to have operated by linkage of discrete magmatic cells as far S as the Ngorongoro–Kilimanjaro transverse volcanic belt that follows the margin of cratonic blocks in N Tanzania. Strain is believed to have nucleated throughout the thermally-weakened lithosphere in the transverse volcanic belt that might have later linked the S Kenya and N Tanzania rift segments with marked structural changes along-strike. The North Tanzanian Divergence is now regarded as a two-armed rift pattern involving: (1) a wide domain of tilted fault blocks to the W (Mbulu) that encompasses the Eyasi and Manyara fault systems, in direct continuation with the Natron northern trough. The reactivation of basement fabrics in the cold and intact Precambrian lithosphere in the Mbulu domain resulted in an oblique rift pattern that contrasts with the orthogonal extension that prevailed in the Magadi–Natron trough above a more attenuated lithosphere. (2) To the E, the Pangani horst-like range is thought to be a younger (<1 Ma) structure that formed in response to the relocation of extension S of the Kilimanjaro magmatic center. A significant contrast in the mechanical behaviour of the stretched lithosphere in the North Tanzanian diverging rift is assumed to have occurred on both sides of the Masai cratonic block with a mid-crustal decoupling level to the W where asymmetrical fault-basin patterns are dominant (Magadi–Natron and Mbulu), whereas a component of dynamical uplift is suspected to have caused the topographic elevation of the Pangani range in relation with possible far-travelled mantle melts produced at depth further N. [Copyright &y& Elsevier]

On the basis of the first systematic mapping of Ua Pou, long known for its exceptionally abundant phonolites, we estimate that these rocks cover 65% of the surface of the island whereas mafic lavas cover 27% and intermediate ones 8%. The silica-undersaturated suite was erupted in a restricted time span (2·9–2·35 Myr), following the emplacement of tholeiites derived from a young HIMU-type source at c. 4 Ma. Primitive basanites, derived from a heterogeneous mantle source with a dominant EM II + HIMU signature, represent likely parental magmas. The series is characterized by a Daly gap defined by a lack of phonotephrites. We consider that the most likely model for the origin of evolved lavas is partial melting at depth of primitive basanites, leaving an amphibole-rich residuum and producing tephriphonolitic magmas. These tephriphonolitic magmas may have evolved by closed-system fractional crystallization towards Group A phonolites. Three other groups of phonolites could have been derived from tephriphonolitic magmas by open-system fractional crystallization processes, characterized respectively by seawater contamination (Group B), assimilation of nepheline syenite-type materials (Group C) and extreme fractionation coupled with assimilation of the underlying oceanic crust (Group D). The prominence of evolved lavas is a consequence of their origin from partial melting of mafic precursors followed by crustal contamination. [ABSTRACT FROM AUTHOR]

Le glyphosate est l'herbicide le plus vendu en France. Son usage intensif est associé à l'exposition chronique de l'homme via l'eau et l'alimentation. La molécule agit en inhibant l'EPSPS, une enzyme indispensable aux plantes mais aussi à de nombreuses bactéries pour la synthèse d'acides aminés. Cette enzyme est retrouvée dans la majorité des bactéries présentes dans notre microbiote et différentes études ont démontré des effets off-target du glyphosate sur le microbiote du sol, des volailles et des abeilles. Le microbiote intestinal joue un rôle clé dans le métabolisme énergétique et l'immunité. En effet, les dysbioses sont associées à des maladies métaboliques telles que l'obésité, le diabète ou la stéatose hépatique non-alcoolique. Nous émettons l'hypothèse qu'une exposition chronique au glyphosate peut impacter la composition et/ou l'activité du microbiote intestinal et que cela pourrait perturber ses fonctions physiologiques. Nous avons donc étudié l'impact d'une exposition chronique au glyphosate à des doses de référence réglementaires sur le microbiote intestinal et le métabolisme énergétique de la souris. Des souris femelles C57Bl6/J ont été exposées à des régimes contrôle ou enrichis en glyphosate à 2 doses de référence, la DJA et la NOAEL, pendant les périodes de gestation et lactation. Leurs descendants (F1) mâles et femelles ont ensuite été exposés au même régime que leur mère pendant 10 semaines. Des paramètres métaboliques (poids, consommation alimentaire et hydrique, tolérance au glucose) ont été évalués et les urines récoltées, dans lesquelles la mesure du glyphosate a été effectuée. Le métabolisme et l'activité du microbiote intestinal ont été évalués par différentes approches (séquençage 16S, métabolomique, analyses biochimique, transcriptomique et histologique). L'exposition des animaux aux 2 doses de glyphosate a été confirmée par LC/MS urinaire. Les F1 mâles et femelles exposés au glyphosate ont montré une augmentation du poids des cæcums et des changements de la composition du microbiote intestinal par rapport aux animaux contrôles. L'exposition des animaux a induit une perturbation des profils métaboliques urinaires chez les 2 sexes ainsi qu'une diminution des taux circulants d'acides gras libres et de triglycérides. Dans le foie, les analyses transcriptomiques ont montré des perturbations d'un grand nombre de gènes impliqués dans la lipogenèse de novo dans les 2 sexes et aux 2 doses d'exposition, sans changement des niveaux de lipides neutres. Des analyses complémentaires sont en cours. Ces études apportent des éléments nouveaux à prendre en considération lors des études réglementaires sur ce pesticide largement utilisé dans le monde. [ABSTRACT FROM AUTHOR]

Tchabal Mbabo massif within the Cameroon Volcanic Line (CVL) at the junction with Adamawa line in Central Africa is a huge (55 × 30km × 2340 m) Eocene-Oligocene volcano composed of frankly alkali lavas of basanites and basalts, trachybasalts, basaltic trachyandesites, trachyandesites, peralkaline trachytes and rhyolites. Lavas show flows and domes shape features and crop up along N160E, N135E and N70E Panafrican cracks. They have microlitic porphyritic textures and are composed of euhedral and subhedral phenocrysts and microcrysts of olivine, clinopyroxene, Ti-magnetite, ilmenite, amphibole (in basanite, basalt and trachybasalt as well as in peralkaline trachyte), plagioclase (in trachybasalt and basaltic trachyandesite), biotite and orthoclase (in trachyte and rhyolite). Same minerals occur in the matrices of the lavas (and moreover plagioclase in basalt). Spinel, olivine and diopside xenocrysts of mantle origin are present in some lavas. ICP-MS and ICP-AES geochemical analyses show that the basanites mostly contain one pyroxene (diopside), with abundant nepheline and olivine in their norms, linked to strong silica undersaturation. Trace element concentrations and ratios (Zr, Nb, Y) witness of alkali affinities, in intra-continental/within-plate anorogenic setting. Increased (Na 2 O, K 2 O, Ta, a.s.o.) or decreased (MgO, Fe 2 O 3 , TiO 2 , CaO, a.s.o.) compositional variations of majors and trace elements from basaltic lavas (dated at 28.6–28.9 Ma) to felsic lavas deal to a differentiated through fractional crystallization process. Trachyandesite lavas dated at 38.2 Ma do not belong to this series. Tchabal Mbabo basalts are the result of low partial melting rate of a lherzolite mantle source containing residual phlogopite + garnet, similar to those of the continental and oceanic sectors of the CVL. Melting of mantle source took place just at the base of the lithospheric mantle. Sr, Nd and Pb isotopic ratios of Tchabal Mbabo basaltic lavas are closed to the FOZO reservoir with (206Pb/204 Pb)i: 17.869407 to 19.747896. Tchabal Mbabo mafic and felsic lavas display variable but moderate (87Sr/86Sr)i ratios (0.703481–0.705053) and similar range of Ndi and Pbi isotopic ratios: 0.512526 < (143Nd/144Nd)i < 0.512771, 15.568709 < (207Pb/204 Pb)i < 15.735532 and 37.905174 < (208Pb/204 Pb)i < 39.579573. Values for trachyandesite and peralkaline trachyte are close to OIB rather than FOZO reservoir. Low (87Sr/86Sr)i ratios (0.703481) and positive εNd (+2.59) of basalt preclude any important crustal contamination. Meanwhile, magma mixing, fluid-rocks interaction and selective crustal contamination of felsic lava by underline Pan-African crust might have occurred later, during the differentiation of Tchabal Mbabo lavas series. Image 1 • Tchabal Mbabo displays a complete alkaline series from basanite until rhyolite. • Low partial melting of a lherzolite mantle containing residual phlogopite + garnet. • Trachyte, that contains sodium and sodium-calcium amphibole, evidences peralkaline affinities. • Low (87Sr/86Sr)i ratios and positive εNd of basalt preclude any important crustal contamination. [ABSTRACT FROM AUTHOR]

Introduction et but de l’étude La fumonisine B1 est une mycotoxine produite par plusieurs espèces de moisissures du genre Fusarium , retrouvées principalement dans le maïs et dans le blé. À forte dose, elle entraîne une hépatotoxicité et des œdèmes pulmonaires chez les animaux. La fumonisine B1 est connue pour être un inhibiteur pharmacologique de la voie de biosynthèse des céramides, au cœur du métabolisme complexe des sphingolipides. La fumonisine B1 influence l’homéostasie du cholestérol par des mécanismes qui restent à définir. L’objectif de cette étude était d’évaluer la contribution du liver X receptor (LXR), un récepteur nucléaire qui contrôle l’élimination du cholestérol par les voies biliaires, dans les effets hépatiques de la fumonisine B1. Matériel et méthodes Des souris LXR α/β +/+ et LXR α/β –/– ont reçu quotidiennement durant 28 jours différentes doses de fumonisine B1 (0 ; 0,1 ; 1,0 ; 10 mg/kg p.c) dans l’eau de boisson. Les foies ont été prélevés et analysés par des approches biochimiques, histologiques et moléculaires. Résultats En premier lieu, nos résultats montrent que selon la dose administrée, la fumonisine B1 avait des effets inverses sur le métabolisme des céramides. La synthèse de céramide était augmentée par l’administration d’une faible dose de fumonisine B1 (1 mg/kg/j) alors qu’elle était diminuée en présence d’une forte dose (10 mg/kg/j). Ces résultats ont été confirmés par le rapport sphinganine/sphingonine qui diminue à faible dose et qui augmente à forte dose. En second lieu, nos résultats ont démontré que la toxicité hépatique induite par la fumonisine était sensible à LXR. En effet, à forte dose, la fumonisine B1 entraînait une augmentation des taux plasmatiques d’ASAT, ALAT chez les souris LXR α/β –/– . Histologiquement, les foies de ces mêmes souris présentaient de nombreux foci inflammatoires à l’inverse des souris WT contaminées avec 10 mg/kg de fumonisine. À forte dose, la fumonisine B1 s’accumulait anormalement dans le plasma des souris LXR α/β –/– . Parallèlement, la fumonisine B1 induisait une augmentation significative des différents taux de cholestérols plasmatiques chez les souris LXR α/β –/– . Une analyse par microarray réalisée sur les foies de souris LXR α/β +/+ et LXR α/β –/– exposées ou non à la fumonisine B1 a permis de confirmer les effets spécifiques de la fumonisine B1 en absence de LXR. En outre, l’analyse des données a confirmé aussi qu’en absence de LXR, la fumonisine B1 induisait une réponse inflammatoire hépatique. Enfin, nous avons mis en évidence un groupe de gènes dont l’expression était réprimée uniquement chez les souris LXR α/β –/– exposées avec une forte dose de fumonisine B1. C’est le cas de nombreux gènes de détoxification ( Fmo3 , Sult3a1 , Cyp2b10 ) et du métabolisme du cholestérol et des acides biliaires ( Abcg8 , Cyp7a1, Cyp8b1 ). Conclusion L’ensemble de ces résultats suggèrent que le récepteur nucléaire LXR soit important dans les mécanismes de détoxification hépatique de la fumonisine B1 et que cette détoxification implique une modulation de la synthèse et de la dégradation du cholestérol en acides biliaires. [ABSTRACT FROM AUTHOR]

Introduction et but de l’étude La régulation du métabolisme hépatique des acides gras obéit à de nombreux mécanismes transcriptionnels. Les récepteurs activés par les proliférateurs de peroxysomes (PPARs) dont il existe trois isotypes, sont des facteurs de transcription de la famille des récepteurs nucléaires activés par des acides gras et leurs dérivés. Ils coexistent dans les hépatocytes. PPARa contrôle l’expression d’enzymes impliquées dans le catabolisme des acides gras hépatiques en réponse au jeûne notamment et PPARg est exprimé dans les situations de surcharge des hépatocytes en lipides ce qui suggère un rôle dans l’étiologie des stéatoses hépatiques. PPARb est l’isotype dont la fonction hépatique est la moins connue. Afin d’étudier son rôle dans les hépatocytes, nous avons créé un nouveau modèle murin de délétion hépato-spécifique du récepteur par le système Albumine-Cre/Lox ( Pparb hep–/– ) et une approche de biologie intégrative in vivo. Matériel et méthodes Nous avons tout d’abord déterminé l’activité circadienne du récepteur par une approche transcriptomique. Après avoir défini la fenêtre d’activité circadienne du récepteur, nous avons analysé sa réponse à un stimulus pharmacologique (traitement avec un agoniste spécifique de PPARb), métabolique (régime obésogène), pathologique (injection de LPS, régime déficient en méthionine et choline favorisant la stéatohépatite) et nutritionnel (régimes apportant différents types d’acides gras de l’alimentation). Nous avons utilisé des approches combinant exploration fonctionnelle in vivo (tolérance au glucose, sensibilité à l’insuline), biochimie (lipidomique et RMN), histologie et analyses du transcriptome. Résultats Nos résultats ont prouvé que, dans les hépatocytes, PPARb obéit in vivo à une régulation circadienne dépendante de la prise alimentaire. En outre, nous avons montré que l’activité du récepteur est uniquement détectable en fin de phase nocturne, coïncidant avec la forte activité glycolytique et lipogénique du foie. Le récepteur contrôle l’expression de gènes impliqués dans l’homéostasie des acides gras en réponse à une activation pharmacologique. L’activité du récepteur est inhibée en réponse à une inflammation aiguë (choc septique) et chronique (stéatohépatite). Il est également inhibé lors de la stéatose induite par un régime obésogène. Enfin, PPARb est inhibé par un régime riche en polyinsaturés alimentaires (huile de poisson) mais activé par un régime déficient en acides gras essentiels (huile de coco hydrogéné). L’absence de PPARb dans les hépatocytes inhibe la capacité du foie à réguler la biosynthèse des acides gras insaturés via la voie des désaturases (Scd1, Fads2) et élongases (Elovl6, Elovl5) qui est stimulée lors d’une carence alimentaire. Conclusion En conclusion, notre étude permet de mieux connaître les fonctions hépatocytaires de PPARb dans des conditions physiologiques et physiopathologiques. De plus, nos travaux identifient PPARb comme le premier récepteur aux acides gras agissant comme régulateur circadien de l’homéostasie des lipides en réponse aux variations qualitatives des apports alimentaires. [ABSTRACT FROM AUTHOR]

Introduction et but de l’étude Lors du jeûne, l’organisme tire en grande partie son énergie de la lipolyse du tissu adipeux blanc. Les acides gras libérés sont métabolisés par le foie où la disponibilité des protéines nécessaires à leur catabolisme passe par des régulations transcriptionnelles induites par des hormones et des nutriments. L’un des facteurs de transcription nécessaires à ces régulations au niveau hépatique est le récepteur nucléaire PPARα, dont le domaine de liaison aux ligands présente une grande affinité pour de nombreux acides gras. Une fois activée, cette protéine induit la transcription de très nombreux gènes impliqués dans le catabolisme des lipides hépatiques. Les travaux ici présentés testent l’hypothèse selon laquelle la nature des acides gras apportés préalablement par l’alimentation influence l’activité hépatique du récepteur PPARα lors d’une période de jeûne. Matériel et méthodes Des souris C57bl6/J déficientes ou non pour le récepteur PPARα au niveau systémique ont été mises pendant 10 semaines sous des régimes à composition en acides gras variable (REF : référence, FISH : huile de poisson, EFAD : déficient en acides gras essentiels, FF : régime sans graisse, n = 6 à 8 par lot). En fin d’étude, les animaux ont été mis à jeun ou non pendant 24 h et euthanasiés à l’heure où le récepteur est à son maximum d’activité dans le foie. Des analyses d’expression de gènes par qPCR, de la composition en acides gras par GC-MS et des approches histologiques ont été réalisées sur le foie des souris. Divers paramètres biochimiques plasmatiques (glycémie, HDL et LDL cholestérol, acides gras libres, ALAT et ASAT) ont été mesurés. Résultats Les profils d’acides gras hépatiques des souris sous régimes EFAD et FF indiquent des carences en acides gras polyinsaturés des séries n-3 et n-6, au contraire des souris sous régime REF et FISH, validant notre modèle expérimental. La mise à jeun provoque une hypoglycémie qui est plus importante en l’absence de PPARα. Les souris déficientes pour PPARα présentent une hausse des marqueurs de dommages hépatiques, particulièrement marquée sous régime EFAD et FF, et ces résultats sont corrélés avec le score histologique de stéatose. Le classement des profils d’expression de 32 gènes impliqués dans le métabolisme des acides gras sépare les individus en deux grandes populations selon leur mise à jeun ou non, puis en fonction de leur génotype. Si l’enrichissement en acides gras essentiel semblait favoriser modérément l’activité du récepteur PPARα à l’état nourri chez les souris sauvages C57bl6/J, il n’influençait pas l’activité du récepteur à jeun. Conclusion Ces résultats montrent que le jeûne plus que la nature des acides gras apportés par l’alimentation induit une activité intense de PPARα dans le foie. Cela implique que la voie de signalisation prépondérante pour l’activation de PPARα lors du jeûne ne dépend pas de la nature des acides gras tissulaires. En outre, il semble que la lipolyse induite par le jeûne soit hépatotoxique pour le foie lorsque PPARα est inactif et que l’animal est carencé en acides gras essentiels. [ABSTRACT FROM AUTHOR]