Finite Volume Time Domain modelling of microwave breakdown and plasma formation in a metallic aperture

The modelling of plasma formation during microwave breakdown is a difficult task because of the strong non-linear coupling between Maxwell?s equations and plasma equations, and of the large plasma density gradients that form during breakdown. An original Finite Volume Time Domain (FVTD) method has been developed to solve Maxwell?s equations coupled with a simplified fluid plasma model and is described in this paper. This method is illustrated with the study of the shielding of a metallic aperture by the plasma generated by an incident high power electromagnetic wave. Typical results obtained with the FVTD method for this shielding problem are shown.     

Predictive neuro-control of uncertain systems: design and use of a neuro-optimizer

We consider the problem of predictive control of uncertain stochastic discrete I/O systems. Given a model identification procedure able to give accurate output system estimates, e.g. a neural network approximation, we use another feedforward neural network to generate at each time step a constrained optimal control. Dynamic backpropagation is used to improve when necessary the controller network parameters. Both system and controller neural structures are first selected off-line by a statistical Bayesian procedure in order to make the predictive control minimizing process more efficient. The issue of stochastic stability of the closed-loop is considered. We developed this approach for the tracking control of such uncertain systems as biotechnological processes. Actual and simulated predictive neuro-control case studies in this field of application are proposed as illustrations. A comparison with a more classic quasi-Newton-based approach is also proposed, showing the interest of this neuro-control approach.     

Personality Organizations, Psychiatric Severity, and Self and Object Representations.

This study examined the hypothesis that psychotic, borderline, and neurotic personality organizations (POs) present a progressive differentiation between self and object representations and an increasing integration of their bad and good aspects. Fifty patients participated in the study. Measures included scales of self and object representations (S. J. Blatt, S. A. Bers, & C. E. Schaffer, 1993; S. J. Blatt, H. Wiseman, E. Prince-Gibson, & C. Gatt, 1991), as well as the Personality Organization Diagnostic Form (L. Diguer & L. Normandin, 1997) and estimations of psychiatric severity. Results showed that PO groups differed in terms of the integration of the object and its valence. It was also observed that although object and self representations were closely intertwined, the latter showed more discrimination between POs than the former. Psychiatric severity was shown to correlate more with object representations than self representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Back and forth between continuous and discrete for the working computer scientist

This paper gives a perfect, ideal, discretization of continuous notions. This is a very convenient frame to treat continuous problems or theories with the help of a computer. This is illustrated by the conversion of algorithms using real numbers into algorithms using integers only and the founding of discrete geometry.     

Selective Laser Melting process optimization of Ti–Mo–TiC metal matrix composites

Selective Laser Melting (SLM) was used to process a powder mixture of CP Ti, 6.5 wt% Mo and 3.5 wt% Mo₂C. The process parameters were optimized to obtain full-density, crack free parts. After the in situ decomposition of Mo₂C in favor of the formation of TiC, the material consisted of a homogeneous dispersion of submicrometer sized TiC platelets in a β-(Ti,Mo) matrix exhibiting a high hardness up to 550 HV and compressive yield stress of 1164 ± 37 MPa. The microstructure and mechanical properties could be tailored by variation of the process parameters within the high-density processing window, as well as through post-process heat treatments.     

Tribological behavior of composites fabricated by reactive SPS sintering in Ti-Si-C system

In this study, wear and friction behavior of two based-composites from the Ti-Si-C system, (40 wt% TiC; 28 wt% Ti₅Si₃; 17 wt% Ti₃SiC₂) and (18 wt% TiC; 26 wt% Ti₅Si₃; 41 wt% Ti₃SiC₂) reinforced by 15 wt% of large size SiC (100-150 µm) particles were investigated. The four-phase composites exhibited approximatively the same friction coefficient (µ ~ 0.9) under high loads (10 N and 7 N). The composite with high Ti₃SiC₂ showed higher wear rate values by one order of magnitude. However, under 1 N, the composite with high TiC content showed a higher running-in period and a lower steady state µ value (0.37 after 1000 m sliding distance). Scanning electron microscopy, Energy Dispersive X-Ray and Raman spectroscopy analysis of the worn surfaces of the two composites revealed that oxidation was the dominant wear mechanism. The oxidation process and the removal kinetics of the oxides during sliding controlled the tribological behavior of the composites. The influence of processing variables on microstructures development and wear mechanisms of the composites is discussed.     

Engineered Neutral Phosphorous Dendrimers Protect Mouse Cortical Neurons and Brain Organoids from Excitotoxic Death

Nanoparticles are playing an increasing role in biomedical applications. Excitotoxicity plays a significant role in the pathophysiology of neurodegenerative diseases, such as Alzheimer’s or Parkinson’s disease. Glutamate ionotropic receptors, mainly those activated by N-methyl-D-aspartate (NMDA), play a key role in excitotoxic death by increasing intraneuronal calcium levels; triggering mitochondrial potential collapse; increasing free radicals; activating caspases 3, 9, and 12; and inducing endoplasmic reticulum stress. Neutral phosphorous dendrimers, acting intracellularly, have neuroprotective actions by interfering with NMDA-mediated excitotoxic mechanisms in rat cortical neurons. In addition, phosphorous dendrimers can access neurons inside human brain organoids, complex tridimensional structures that replicate a significant number of properties of the human brain, to interfere with NMDA-induced mechanisms of neuronal death. Phosphorous dendrimers are one of the few nanoparticles able to gain access to the inside of neurons, both in primary cultures and in brain organoids, and to exert pharmacological actions by themselves.     

Centrifugal partition chromatography applied to the isolation of oak wood aroma precursors

Flavours extracted from oak wood during barrel ageing contribute to the organoleptic character of wines and spirits. The aim of this work was to identify the glycosidic precursors of the key volatile compounds responsible for oak wood aroma. Oak extract is a very complex matrix and, furthermore, precursors are present in very small quantities. Preparative centrifugal partition chromatography (CPC) is a promising solution for purifying the oak extract. The solvent system was selected on the basis of the partition coefficient of glycosidase enzyme activity (K_ca). Thanks to the efficacy of CPC separation, three glucoside gallates were subsequently isolated by HPLC chromatography. Vanillin-(6′-O-galloyl)-O-β-d-glucopyranoside, 3,4,5-trimethoxyphenyl-(6′-O-galloyl)-O-β-d-glucopyranoside, and (6R,9R)-3-oxo-α-ionol-9-O-(6′-O-galloyl)-β-glucopyranoside (macarangioside E) were isolated and identified. This was the first time that vanillin-(6′-O-galloyl)-O-β-d-glucopyranoside was identified and the first time that macarangioside E was isolated from oak wood. Heating macarangioside E resulted in the formation of megastigmatrienone, which has an aroma reminiscent of tobacco.     

Formation of the Perovskite Phase in the PbMg1/3Nb2/3O3─PbTiO3 System

The reaction sequences during calcination of oxide mixtures were studied for the PbMg_1/3Nb_2/3O₃─PbTiO₃ (PMN-PT) system. The effect of reactivity and composition of the starting mixtures was investigated. In the present study, a B-site-deficient, cubic pyrochlore phase in the PbO-Nb₂O₅ system was formed at 500°C. The perovskite phase of PMN was formed at 7007deg;C through the diffusion of MgO into the pyrochlore phase. The lattice parameter of the pyrochlore phase decreased as this transformation to perovskite progressed.     

Contribution to DEMO reactor RH maintenance assessment

The scope of this paper is a preliminary assessment of the maintenance scheme in support of the European study for the next generation of fusion reactor: DEMO. Despite other fusion machine requiring remote handling maintenance operations, DEMO is supposed to work under steady state operational conditions. Therefore, requirement on the maintenance scheme is stronger. To target a good availability of the machine along machine operation plan, it is necessary to draw an adequate maintenance scheme. Indeed, due to the high fluxes generated by the plasma in the vacuum vessel, the first wall lifetime is limited, so the frequent replacement is necessary. On current fusion experimental machine, as first wall load conditions are less severe, DEMO condition implies high level of requirement on maintenance time. During DEMO lifetime, several full first wall replacements are expected. To provide access to the vacuum vessel machine for first wall removal, preparatory work is required to set the machine to adequate maintenance conditions and to open the machine properly, the same situation at the end of the maintenance period. Shutdown duration for first wall replacement should be as short as possible to reach the availability target of the machine. From this statement, the maintenance duration should not exceed 20% of the total lifetime of the reactor operation. First wall segmentation (i.e. total number of component to replace) has a high impact onto the replacement time. Considering the number of feasible designs for the first wall segmentation, we concentrate remote handling concept assessments one type of segmentation, the one minimizing the numbers of modules to replace [4], [5], [6]. Assumption on Divertor segmentation for these DEMO studies have similarities with Divertor ITER design; therefore ITER design output is relevant [1], [2]. We assume divertor removal performed in shadow time, while removing the other first wall modules.