Counter-propagating radiative shock experiments on the Orion laser and the formation of radiative precursors

We present results from new experiments to study the dynamics of radiative shocks, reverse shocks and radiative precursors. Laser ablation of a solid piston by the Orion high-power laser at AWE Aldermaston UK was used to drive radiative shocks into a gas cell initially pressurised between $0.1$ and $1.0 \ bar with different noble gases. Shocks propagated at {80 \pm 10 \ km/s} and experienced strong radiative cooling resulting in post-shock compressions of { \times 25 \pm 2}. A combination of X-ray backlighting, optical self-emission streak imaging and interferometry (multi-frame and streak imaging) were used to simultaneously study both the shock front and the radiative precursor. These experiments present a new configuration to produce counter-propagating radiative shocks, allowing for the study of reverse shocks and providing a unique platform for numerical validation. In addition, the radiative shocks were able to expand freely into a large gas volume without being confined by the walls of the gas cell. This allows for 3-D effects of the shocks to be studied which, in principle, could lead to a more direct comparison to astrophysical phenomena. By maintaining a constant mass density between different gas fills the shocks evolved with similar hydrodynamics but the radiative precursor was found to extend significantly further in higher atomic number gases (\sim$$4$ times further in xenon than neon). Finally, 1-D and 2-D radiative-hydrodynamic simulations are presented showing good agreement with the experimental data.Comment: HEDLA 2016 conference proceeding

Magnetic reconnection driven by electron dynamics

Magnetic reconnections play essential roles in space, astrophysical, and laboratory plasmas, where the anti-parallel magnetic field components re-connect and the magnetic energy is converted to the plasma energy as Alfvénic out flows. Although the electron dynamics is considered to be essential, it is highly challenging to observe electron scale reconnections. Here we show the experimental results on an electron scale reconnection driven by the electron dynamics in laser-produced plasmas. We apply a weak-external magnetic field in the direction perpendicular to the plasma propagation, where the magnetic field is directly coupled with only the electrons but not for the ions. Since the kinetic pressure of plasma is much larger than the magnetic pressure, the magnetic field is distorted and locally anti-parallel. We observe plasma collimations, cusp and plasmoid like features with optical diagnostics. The plasmoid propagates at the electron Alfvén velocity, indicating a reconnection driven by the electron dynamics

Astrophysique de laboratoire avec les lasers de haute énergie et de haute puissance : des chocs radiatifs aux jets d'étoiles jeunes

Laboratory astrophysics are a rapidly developing domain of the High Energy Density Physics. It aims to recreate at smaller scales physical processes that astronomical telescopes have difficulties observing. We shall approach, in this thesis, three major subjects : 1) Jets ejected from young stars, characterized by an important collimation degree and ending with a bow shock; 2) Radiative shocks in which radiation emitted by the shock front itself plays a dominant role in its structure and 3) Accretion shocks in magnetic cataclysmic variables whose important cooling factor allows them to reach stationarity. From the conception to experimental realization, we shall attempt to reproduce in laboratory each of these processes by respecting the scaling laws linking both situations (experimental and astrophysical) established beforehand. The implementation of a large array of visible and X-ray diagnostics will finally allow to completely characterize them and calculate the dimensionless numbers that validate the astrophysical relevance.L'astrophysique de laboratoire est un domaine de la Physique des Hautes Densités d'Énergie en plein essor. Elle vise à recréer en laboratoire des processus physiques difficilement accessibles avec les diagnostics astronomiques. Nous aborderons, dans cette thèse, trois sujets majeurs: 1) les jets issus d'étoiles jeunes caractérisés par une collimation importante et se terminant par un choc d'étrave; 2) les chocs radiatifs pour lesquels le rayonnement propre du choc joue une rôle prépondérant dans sa structure et 3) les chocs d'accrétion dans le cas des variables cataclysmiques magnétiques dont l'important facteur de refroidissement permet d'atteindre la stationnarité. De la conception à la réalisation expérimentale, nous nous attacherons à reproduire en laboratoire chacun de ces processus en respectant les lois d'échelle liant les deux situations (expérimentale et astrophysique) précédemment établies. L'implémentation d'un grand nombre de diagnostics visibles et X nous permettra enfin de les caractériser complètement et de calculer les nombres sans dimension assurant la pertinence astrophysique

A new simple method for the synthesis of 1-alkynylphosphonates using (EtO)2P(O)CCl3 as precursor

International audience1-Alkynylphosphonates 4 were obtained from (EtO) 2 P(O)CCl 3 1 and aldehydes in a one-pot procedure. It involves the formation of α-chlorovinyl phosphonate intermediates 3 by a Peterson olefination reaction followed by dehydrochlorination with LiHMDS

Invariance concepts and scalability of two-temperature astrophysical radiating fluids

International audienceIn this work, we present a classification of laboratory astrophysics experiments. We introduce different invariance concepts in order to build scaling laws and to determine the astrophysical relevant of laboratory experiments. Finally we present an analysis of the two-temperature radiating fluid scalability

New route to 1-formylalkylphosphonates using diethyl trichloromethylphosphonate as a precursor

International audienceDiethyl trichloromethylphosphonate 1 and chlorotrimethylsilane were converted in a threestep sequence by BuLi into α−phosphorylated α−silylated α−substituted carbanions 4. On reaction with ethyl formate in the presence of chlorotrimethylsilane they give transient silylated acetals 8 which are readily hydrolysed in acid medium into 1formylalkylphosphonates 7 which are isolated in good yields

New route to amino[ 2 H 2 ]methylphosphonic acid via bis(trifluoroethyl) phosphonate transesterification

International audienceTransesterification of bis(trifluoroethyl) chloromethyl- and azidomethyl-phosphonates with alcohols in the presence of catalytic quantities of alcoholates gives dialkyl chloromethyl- and azidomethyl-phosphonates in good yield. This process has been used for the synthesis of dibenzyl azido[2H2]methylphosphonate which has been reduced and hydrogenolised to amino[2H2]methylphosphonic acid under neutral conditions

Gender-specific association of FABP2 and MTP variants with response to dietary lipid changes in the 3-mo Medi-RIVAGE primary intervention study

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Sex-specific association of fatty acid binding protein 2 and microsomal triacylglycerol transfer protein variants with response to dietary lipid changes in the 3-mo Medi-RIVAGE primary intervention study

International audienceBackground: The dietary guidelines targeted at reducing cardiovascular risk lead to largely heterogeneous responses in which genetic determinants are largely involved. Objectives: We evaluated the effect of fatty acid binding protein 2 (FABP2) Ala54Thr and microsomal triacylglycerol transfer protein (MTTP) –493G/T allelic variations on plasma lipid markers, at baseline and on the response to the 3-mo Medi-RIVAGE primary prevention study. Design: Subjects with moderate cardiovascular disease risk (n = 169) were advised to reduce total and saturated dietary fats and to increase intake of monounsaturated and polyunsaturated fats. They were genotyped for FABP2 Ala54Thr and MTTP –493G/T allelic variations, and plasma was processed for cardiovascular risk marker analyses. Results: At baseline, men and women homozygous for Thr54 presented a significant opposite profile for plasma oleic acid (18:1), triacylglycerol-rich lipoprotein (TRL) cholesterol, and TRL phospholipids. In addition, all Thr/Thr men presented higher 18:1 values than did women. For the MTTP –493G/T polymorphism, although all TT subjects presented high apolipoprotein B-48, a genotype x sex interaction was present for palmitic acid, linolenic acid, eicosatrienoic acid, and insulin. The prudent diet clearly improved plasma lipid markers. FABP2 genotype did not interact much with the amplitude of the response. However, for MTTP polymorphism, men homozygous for the T allele displayed a significantly more pronounced response than did men carrying the G allele, which is particularly evident by their larger decrease in the Framingham score. Conclusions: These 2 polymorphic loci are thus differently associated with the baseline lipid markers as well as with the response to nutritional recommendations, but both presented a marked sex-specific profile, with the response to diet being particularly efficient in men homozygous for the MTTP –493T allel

Gender-specific association of FABP2 and MTP variants with response to dietary lipid changes in the 3-mo Medi-RIVAGE primary intervention study

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