Thermal model of successive dike injections and implications for the development of intraplate volcanoes

Temperatures in the root zones of volcanoes play a critical role in the development and persistence of shallow-level magmatic reservoirs in the crust. Here, we present a 1D thermal model allowing evaluation of the thermal impact of magma travelling in conduits to the surface on the root zone of a volcano. This thermal model has been developed to better understand the formation of a vertical intrusion located in the root zone of a dismembered Miocene volcano on Fuerteventura, Canary Archipelago. This intrusion, named PX1, constitutes an almost pure amalgamation of dikes of either clinopyroxenitic or gabbroic composition. Both types of dikes display cumulate textures and are interpreted as resulting from the protracted crystallization of a mafic magma. The formation of clinopyroxenitic, in contrast to gabbroic dikes, requires that the residual melt was extracted at high temperature (N1050°) to avoid plagioclase crystallization. Simulations of multiple dike injections show that the temperature in the root zone increases significantly with the addition of dikes, but the maximum temperature reached in the system depends on the duration of magma flow in the conduits and the time interval between dike injections (i.e., repose period). Active flow is the critical parameter that distinguishes instantaneous dike injection from a magmatic conduit. Without significant magma flow (N1 month), high-temperature conditions (N1000 °C) cannot be maintained in the pluton unless dikes are very thick and the repose period is extremely small. On the other hand,magma flow times of one to several months, combined with short time intervals between dike injections (b25 years), which are conditions comparable to those recorded for historical eruptions of oceanic island volcanoes, allowthe production and preservation of temperatures above the plagioclase liquidus for significant durations, as required to generate clinopyroxenitic dikes such as those observed in the PX1 pluton. Persistent high temperature in the vicinity of magma conduits limits the differentiation of melts in transit to the surface, providing a potential explanation forwhy lavas ofmafic to intermediate composition predominate in intraplate volcanoes such as Fuerteventura or Fogo Island (Cape Verde Archipelago). In extreme cases, when temperatures over 1000–1050 °C in the central part of the feeding zone are maintained for years, the remaining magma in the conduit does not solidify but is preserved in a mushy state. New pulses of magma would not be able to cross this zone butwould rather amalgamate in the incipientmagma reservoir. The present model differs from previous models of sill intrusion in that magmas do not need to pond at depth to create a reservoir but merely supply heat while travelling to the surface. Depending on the time interval between dike injections and the duration ofmagma flow through the crust, magma rising in vertical conduits could directly feed the volcanic edifice or could lead to the formation of magma reservoirs. This process may explain why some volcanoes erupt mafic or differentiated magmas during distinct periods of activity

EVALUATION OF THE NEWLY FORMED BONE IN IRRADIATED AREAS BY ADDITION OF MESENCHYMAL STEM CELLS TO THE ASSOCIATION OF BIPHASIC CALCIUM PHOSPHATE AND TOTAL BONE MARROW

Oral Communication presented at the ";Forum des Jeunes Chercheurs";, Brest (France) 2011

Model-free Consensus Maximization for Non-Rigid Shapes

Many computer vision methods use consensus maximization to relate measurements containing outliers with the correct transformation model. In the context of rigid shapes, this is typically done using Random Sampling and Consensus (RANSAC) by estimating an analytical model that agrees with the largest number of measurements (inliers). However, small parameter models may not be always available. In this paper, we formulate the model-free consensus maximization as an Integer Program in a graph using `rules' on measurements. We then provide a method to solve it optimally using the Branch and Bound (BnB) paradigm. We focus its application on non-rigid shapes, where we apply the method to remove outlier 3D correspondences and achieve performance superior to the state of the art. Our method works with outlier ratio as high as 80\%. We further derive a similar formulation for 3D template to image matching, achieving similar or better performance compared to the state of the art.Comment: ECCV1

The activation of the cannabinoid receptor type 2 reduces neutrophilic protease-mediated vulnerability in atherosclerotic plaques

Aims The activation of cannabinoid receptor type 2 (CB2)-mediated pathways might represent a promising anti-atherosclerotic treatment. Here, we investigated the expression of the endocannabinoid system in human carotid plaques and the impact of CB2 pharmacological activation on markers of plaque vulnerability in vivo and in vitro. Methods and results The study was conducted using all available residual human carotid tissues (upstream and downstream the blood flow) from our cohort of patients symptomatic (n = 13) or asymptomatic (n = 27) for ischaemic stroke. Intraplaque levels of 2-arachidonoylglycerol, anandamide N-arachidonoylethanolamine, N-palmitoylethanolamine, N-oleoylethanolamine, and their degrading enzymes (fatty acid amide hydrolase and monoacylglycerol lipase) were not different in human plaque portions. In the majority of human samples, CB1 (both mRNA and protein levels) was undetectable. In downstream symptomatic plaques, CB2 protein expression was reduced when compared with asymptomatic patients. In these portions, CB2 levels were inversely correlated (r = −0.4008, P = 0.0170) with matrix metalloprotease (MMP)-9 content and positively (r = 0.3997, P = 0.0174) with collagen. In mouse plaques, CB2 co-localized with neutrophils and MMP-9. Treatment with the selective CB2 agonist JWH-133 was associated with the reduction in MMP-9 content in aortic root and carotid plaques. In vitro, pre-incubation with JWH-133 reduced tumour necrosis factor (TNF)-α-mediated release of MMP-9. This effect was associated with the reduction in TNF-α-induced ERK1/2 phosphorylation in human neutrophils. Conclusion Cannabinoid receptor type 2 receptor is down-regulated in unstable human carotid plaques. Since CB2 activation prevents neutrophil release of MMP-9 in vivo and in vitro, this treatment strategy might selectively reduce carotid vulnerability in human

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Cytochrome bd is a tri-heme (b558, b595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in oneelectron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (t,1.5 ms) electron transfer from heme d to heme b595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b558 (t,16 ms). It returns from the b-hemes to heme d with t,180 ms. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (t,16 ms) yielding a transient hexacoordinate state (CO-Fe2+ -L). Then the ligand slowly (t,30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (t,20 ms), some heme b558 (t,0.2–3 ms), and finally migrates from heme d to heme b595 (t,24 ms) in ,5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions

Identification of a major QTL for Xanthomonas arboricola pv. pruni resistance in apricot

Xanthomonas arboricola pv. pruni causes bacterial spot of stone fruit resulting in severe yield losses in apricot production systems. Present on all continents, the pathogen is regulated in Europe as a quarantine organism. Host resistance is an important component of integrated pest management; however, little work has been done describing resistance against X. arboricola pv. pruni. In this study, an apricot population derived from the cross “Harostar” × “Rouge de Mauves” was used to construct two parental genetic maps and to perform a quantitative trait locus analysis of resistance to X. arboricola pv. pruni. A population of 101 F1 individuals was inoculated twice for two consecutive years in a quarantine greenhouse with a mixture of bacterial strains, and disease incidence and resistance index data were collected. A major QTL for disease incidence and resistance index accounting respectively for 53 % (LOD score of 15.43) and 46 % (LOD score of 12.26) of the phenotypic variation was identified at the same position on linkage group 5 of “Rouge de Mauves.” Microsatellite marker UDAp-452 co-segregated with the resistance, and two flanking microsatellites, namely BPPCT037 and BPPCT038A, were identified. When dividing the population according to the alleles of UDAp-452, the subgroup with unfavorable allele had a disease incidence of 32.6 % whereas the group with favorable allele had a disease incidence of 21 %, leading to a reduction of 35.6 % in disease incidence. This study is a first step towards the marker-assisted breeding of new apricot varieties with an increased tolerance to X. arboricola pv. pruni