Description of an aerodynamic levitation apparatus with applications in Earth sciences

<p>Abstract</p> <p>Background</p> <p>In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO₂-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments.</p> <p>Results</p> <p>Liquid silicate droplets (~2 mm) were maintained stable in levitation using a nozzle with a 0.8 mm bore and an opening angle of 60°. The gas flow was ~250 ml min^-1. Rock powders were melted and homogenized for microchemcial analyses. Laser melting produced chemically homogeneous glass spheres. Only highly (e.g. H₂O) and moderately volatile components (Na, K) were partially lost. The composition of evaporated materials was determined by directly combining levitation and inductively coupled plasma mass spectrometry. It is shown that the evaporated material is composed of Na > K >> Si. Levitation of metal oxide-rich material in a mixture of H₂and Ar resulted in the exsolution of liquid metal.</p> <p>Conclusions</p> <p>Levitation melting is a rapid technique or for the preparation of bulk rock powders for major, minor and trace element analysis. With exception of moderately volatile elements Na and K, bulk rock analyses can be performed with an uncertainty of ± 5% relative. The technique has great potential for the quantitative determination of evaporated materials from silicate melts. Reduction of oxides to metal is a means for the extraction and analysis of siderophile elements from silicates and can be used to better understand the origin of chondritic metal.</p

Quantification and characterisation of porosity in selectively laser melted Al–Si10–Mg using x-ray computed tomography

We used X-ray computed tomography (CT), microscopy and hardness measurements to study Al–Si10–Mg produced by selective laser melting (SLM). Specimens were subject to a series of heat treatments including annealing and precipitation hardening. The specimen interiors were imaged with X-ray CT, allowing the non-destructive quantification and characterisation of pores, including their spatial distribution. The specimens had porosities less than 0.1%, but included some pores with effective cross-sectional diameters up to 260 μm. The largest pores were highly anisotropic, being flat and lying in the plane normal to the build direction. Annealing cycles caused significant coarsening of the microstructure and a reduction of the hardness from (114 ± 3) HV, in the as-built state, to (45 ± 1) HV, while precipitation hardening increased this to a final hardness of (59 ± 1) HV. The pore size and shape distributions were unaffected by the heat treatments. We demonstrate the applicability of CT measurements and quantitative defect analysis for the purposes of SLM process monitoring and refinement

Frequency Conversion Activation on the Mercury Laser

High efficiency frequency conversion while operating at average power is critical for the Mercury laser. We will demonstrate average power frequency conversion of face-cooled DKDP and YCOB crystals using a sapphire heat spreader approach

HIBISCUS: Hydroxychloroquine for the secondary prevention of thrombotic and obstetrical events in primary antiphospholipid syndrome

The relapse rate in antiphospholipid syndrome (APS) remains high, i.e. around 20%-21% at 5 years in thrombotic APS and 20-28% in obstetrical APS [2, 3]. Hydroxychloroquine (HCQ) appears as an additional therapy, as it possesses immunomodulatory and anti-thrombotic various effects [4-16]. Our group recently obtained the orphan designation of HCQ in antiphospholipid syndrome by the European Medicine Agency. Furthermore, the leaders of the project made the proposal of an international project, HIBISCUS, about the use of Hydroxychloroquine in secondary prevention of obstetrical and thrombotic events in primary APS. This study has been launched in several countries and at now, 53 centers from 16 countries participate to this international trial. This trial consists in two parts: a retrospective and a prospective study. The French part of the trial in thrombosis has been granted by the French Minister of Health in December 2015 (the academic trial independent of the pharmaceutical industry PHRC N PAPIRUS) and is coordinated by one of the members of the leading consortium of HIBISCUS

MICROANALYSE EN INCIDENCE RASANTE

L'utilisation d'une microsonde électronique en incidence rasante pour la caractérisation des couches minces est décrite. La simulation des trajectoires électroniques par la méthode de Monte-Carlo montre que les calculs de correction effectués en microanalyse ne dépendent pas de la composition de la couche mince sauf pour l'absorption et la fluorescence dont les effets sont faibles dans ce cas. On note un bon accord entre les résultats théoriques et expérimentaux.A simple method is presented wherby an electron probe can be used at grazing incidence for supported thin film characterization. Monte carlo calculations show that a part from X-Ray absorption and fluorescence which are weak in this particular case, microanalysis correction calculations do not depend on the film composition. Fair agreement between the experimental results and theoretical calculations are obtained

Time Projection Compton Spectrometer (TPCS). User`s guide

The Time Projection Compton Spectrometer (TPCS) is a radiation diagnostic designed to determine the time-integrated energy spectrum between 100 keV -- 2 MeV of flash x-ray sources. This guide is intended as a reference for the routine operator of the TPCS. Contents include a brief overview of the principle of operation, detailed component descriptions, detailed assembly and disassembly procedures, guide to routine operations, and troubleshooting flowcharts. Detailed principle of operation, signal analysis and spectrum unfold algorithms are beyond the scope of this guide; however, the guide makes reference to sources containing this information

Characterization and modeling of void nucleation by interface decohesion in dual phase steels

International audienceIn situ tensile tests have been carried out during X-ray microtomography imaging of dual phase steels. Void nucleation has been quantified as a function of strain and triaxiality using the obtained three-dimensional images. The Argon criterion of decohesion has been used in a model for nucleation in the case where martensite plays the role of inclusions. This criterion has been modified to include the local stress field and the effect of kinematic hardening present in such a heterogeneous material

Apport de l’EXAFS à l’étude de l’effet alcalin mixte dans les verres silicates

Nous avons enregistré des spectres de photoabsorption sur des verres appartenant au système ternaire SIO2 - Cs2O - Rb2O au voisinage des seuils de la raie LIII du césium (5012 eV) et de la rale K du rubidium (15200 eV). La comparaison des spectres EXAFS décrit la variation de l’environnement de l’ion alcalin lorsqu’on remplace progressivement un Ion alcalin par un autre

Study of Crystallisation of Yttrium Garnets Y3R5O12 (R = Al, Ga) by High Temperature EXAFS

In this paper, we present a new high temperature EXAFS device using a laser heating system and aerodynamic levitation for experiments up to 2300°C. We report here the first spectra of Y K-edge for YAG at room temperature and in the liquid