Silicon electrodeposition in molten fluorides

Silicon nucleation process was investigated in molten NaF-KF (40-60 mol%) on silver electrodes in the 820-950°C temperature range in order to optimize silicon coating operating conditions. Chronoamperometric measurements evidenced that silicon electrodeposition process involved an instantaneous nucleation with diffusion-controlled nuclei growth whatever temperature and Si(IV) ions concentration in the mixture. The overpotential and temperature influence on nucleation sites number was also studied. Silicon deposits were obtained using the same temperature range as nucleation study, for different current densities on substrates: Ni, Ag, Cgraphite and Cvitreous. A sensitive influence of the cathodic substrate on the deposit adherence and roughness was observed and discussed

Silicon recovery from silicon-iron alloys by electrorefining in molten fluorides

Electrorefining of a silicon-iron material (Si-4.7at%Fe) in molten NaF-KF at 850°C has been investigated in view of recovering pure Si, using electrochemical techniques, SEM-EDS and ICP-AES analyses. The selective electrochemical dissolution of Si was evidenced. Electrorefining runs led to a maximum Si recovery of 80% of the initial Si contained in the material, in the form of a dense deposit at the cathode, with very high current efficiencies. The Si purity has been examined and no Fe was detected by ICP-AES analysis: the recovered Si purity is thus assumed to be higher than 99.99%

Fluoroacidity evaluation in molten salts

The fluoroacidity of several alkaline fluoride media was studied by monitoring the concentration of electroactive species which is decreasing versus time due to a gas species release, such as silicon fluorides, as indicated by the reaction: SiF(4+x)x- = SiF4(g) + x F- This article relates the Si(IV) reaction study to define a relative fluoroacidity scale by studying the silicon ions stability in different melts. Electrochemical techniques allow the measurement of SiF4+xx- concentration evolution and thus the reaction rate constant to be calculated at different temperatures and for several fluoride media. The article shows that the free F- content depends on the fluoride mixture and that the rate values are correlated with the fluoroacidity allowing a qualitative estimation. Then a fluoride solvents fluoroacidity scale was proposed, scaling the different eutectic melts from basic melt to acidic one: NaF-KF < LiF-KF < NaF-MgF2 < NaF-CaF2 < LiF-NaF < LiF < LiF-CaF2

Transforming Growth Factor-β1 Regulates the Expression of the High-Affinity Receptor for IgE on CD34+ Stem Cell-Derived CD1a+ Dendritic Cells In Vitro

It has been reported that monocytes, Langerhans cells (LC) and other dendritic cells (DC) express the high-affinity receptor for IgE (FcεRI) in patients with atopic diseases. These cells may be instrumental in the control of the immune response and the allergic inflammation. In this context, transforming growth factor beta 1 (TGF-β1) has been highlighted as a key cytokine involved in the mechanisms aimed to orchestrate tolerance and has been suggested as a candidate gene in atopic diseases. In this report, we investigate the putative role of TGF-β1 in the regulation of FcεRI on cord blood CD34+ stem cell-derived CD1a+ DC (CD34-derived CD1a+ DC). Kinetic experiments show that FcεRI spontaneously appears on the surface of CD1a+ DC, but decreases when exogenous TGF-β1 is added at high doses (10 ng per mL) or when endogenous TGF-β1 is neutralized in the culture conditions. In contrast, low-dose TGF-β1 (0.5 ng per mL) stabilizes surface FcεRI expression on DC. Increasing TGF-β1 concentrations leads to the generation of LC-like DC showing an augmentation in stimulatory capacity towards allogeneic T cells. In view of these data, a picture emerges that FcεRI+ on DC is finely modified by the TGF-β1 concentration in the microenvironment and could be of primary relevance in the context of atopic diseases

Model Based Risk Assessment of Procedures and Systems for Aircraft Trajectory Management

International audienceModern Air Traffic Management (ATM) concepts of operation require a strong interaction between agents such as human operators (pilots, air traffic controllers) and information technology systems (either on-ground or on-board). Although risks shall jointly be managed by all these agents, current risk assessment techniques are usually dedicated to only one class ofagents (either human operators or IT systems). This paper addresses this issue. It proposes to extend Model Based Safety Assessment (MBSA) techniques originally developed to assess complex systems. This MBSA extension enables to assess how risk can be jointly managed by procedures and systems. The paper shows the methodology used and it presents lessons learnt from an aircraft trajectory management case study

Similarities and dissimilarities between safety levels and security levels

International audienceThe paper proposes a comparative analysis of the notions of Safety Levels and Security Levels as defined (under various names) by the relevant standards. This comparison is a basis for the elaboration of a harmonised process to develop and validate embedded systems having to comply with both safety and security requirements (including related certification requirements when applicable), which is the objective of the French collaborative project SEISES. An important case corresponds to systems for which security requirements come from safety needs i.e., the necessity to preserve safety properties even in case of security threats. In such a case it is necessary to identify clearly the dependencies between the Safety and the Security Levels of the system

Security and Safety Assurance for Aerospace Embedded Systems

International audienceThe paper starts with the list of basic principles that guided the development of the SEISES security and safety assurance framework. Then we present the SEISES structure and we provide some examples of assurance objectives and related assurance activities. We detail the convergence between safety and security assurance activities that we have identified. Finally, we introduce the three demonstrators and we summarize the main lessons learnt from these experimentations. We conclude the paper by summarizing the results of the SEISES project, by comparing these results with other approaches dealing with joint safety and security assurance and by listing promising directions for further research

Reconfigurable IMA platform: from safety assessment to test scenarios on the SCARLETT demonstrator

International audienceThe next generation of IMA platforms should include reconfiguration capabilities in order to limit the effect of some hardware failures on aircraft operational reliability. The contribution of this paper is to describe the safety assessment process from the safety assessment on the preliminary design of a reconfigurable IMA architecture to the execution of the failure scenarios on the SCARLETT demonstrator

Antideuterons as a Signature of Supersymmetric Dark Matter

Once the energy spectrum of the secondary component is well understood, measurements of the antiproton cosmic-ray flux at the Earth will be a powerful way to indirectly probe for the existence of supersymmetric relics in the galactic halo. Unfortunately, it is still spoilt by considerable theoretical uncertainties. As shown in this work, searches for low-energy antideuterons appear in the mean time as a plausible alternative, worth being explored. Above a few GeV/n, a dozen spallation antideuterons should be collected by the future AMS experiment on board ISSA. For energies less than about 3 GeV/n, the antideuteron spallation component becomes negligible and may be supplanted by a potential supersymmetric signal. If a few low-energy antideuterons are discovered, this should be seriously taken as a clue for the existence of massive neutralinos in the Milky Way.Comment: 16 pages, 9 figure