Determination of the pure silicon monocarbide content of silicon carbide and products based on silicon carbide

Experience has shown that different methods of analysis of SiC products give different results. Methods identified as AFNOR, FEPA, and manufacturer P, currently used to detect SiC, free C, free Si, free Fe, and SiO2 are reviewed. The AFNOR method gives lower SiC content, attributed to destruction of SiC by grinding. Two products sent to independent labs for analysis by the AFNOR and FEPA methods showed somewhat different results, especially for SiC, SiO2, and Al2O3 content, whereas an X-ray analysis showed a SiC content approximately 10 points lower than by chemical methods

Adaptation des fiches HT des Septa électrostatiques du SPS pour les Septa du PS en vue d’utiliser le câble EPR

Suite à de nombreux problèmes de destruction de câbles PB300b d’alimentation des Septa électrostatiques de l’accélérateur PS, il a été choisi de les remplacer par un câble de type EPR. En effet ces câbles haute tension PB300b devenus trop vieux et installés en milieu radioactif ne tiennent plus la tension nominale requise pour les Septa. De plus ceux-ci ne sont plus fabriqués dans l’industrie ce qui empêche tout échange avec un câble similaire. Le câble type EPR est basé sur une technologie plus récente et est aussi plus résistant à la radiation. Il a fait ses preuves dans le passé étant utilisé pour l’alimentation des Septa électrostatiques ZS situés sans le SPS. Étant donné que le câble PB300b 300 kV n’a pas les mêmes dimensions que le câble EPR, il a été nécessaire d’adapter une fiche compatible avec ce nouveau câble et la traversée utilisée sur les Septa électrostatiques du PS. L’ancien câble PB330b est utilisé avec de l’huile comme liquide diélectrique dans la traversée. Tenant compte, en cas de fuite de la traversée des risques de pollution du vide du septum, et de l’accélérateur PS, il a été décidé de remplacer l’huile comme liquide diélectrique par du Fluorinert non polluant si une fuite apparait dans l’enceinte à vide. L‘adaptation des fiches HT pour le câble EPR en tient compte également

Casimir stresses in active nematic films

We calculate the Casimir stresses in a thin layer of active fluid with nematic order. By using a stochastic hydrodynamic approach for an active fluid layer of finite thickness L, we generalize the Casimir stress for nematic liquid crystals in thermal equilibrium to active systems. We show that the active Casimir stress differs significantly from its equilibrium counterpart. For contractile activity, the active Casimir stress, although attractive like its equilibrium counterpart, diverges logarithmically as L approaches a threshold of the spontaneous flow instability from below. In contrast, for small extensile activity, it is repulsive, has no divergence at any L and has a scaling with L different from its equilibrium counterpart

Soft Listeria: actin-based propulsion of liquid drops

We study the motion of oil drops propelled by actin polymerization in cell extracts. Drops deform and acquire a pear-like shape under the action of the elastic stresses exerted by the actin comet. We solve this free boundary problem and calculate the drop shape taking into account the elasticity of the actin gel and the variation of the polymerization velocity with normal stress. The pressure balance on the liquid drop imposes a zero propulsive force if gradients in surface tension or internal pressure are not taken into account. Quantitative parameters of actin polymerization are obtained by fitting theory to experiment.Comment: 5 pages, 4 figure

Boundaries of solidarity: a meta-ethnography of mask use during past epidemics to inform SARS-CoV-2 suppression

Background: Many countries aiming to suppress SARS-CoV-2 recommend the use of face masks by the general public. The social meanings attached to masks may influence their use, but remain underinvestigated. / Methods: We systematically searched eight databases for studies containing qualitative data on public mask use during past epidemics, and used meta-ethnography to explore their social meanings. We compared key concepts within and across studies, then jointly wrote a critical synthesis. / Results: We found nine studies from China (n=5), Japan (n=1), Mexico (n=1), South Africa (n=1) and the USA (n=1). All studies describing routine mask use during epidemics were from East Asia. Participants identified masks as symbols of solidarity, civic responsibility and an allegiance to science. This effect was amplified by heightened risk perception (eg, during SARS in 2003), and by seeing masks on political leaders and in outdoor public spaces. Masks also acted as containment devices to manage threats to identity at personal and collective levels. In China and Japan, public and corporate campaigns framed routine mask use as individual responsibility for disease prevention in return for state- or corporate-sponsored healthcare access. In most studies, mask use waned as risk perception fell. In contexts where masks were mostly worn by patients with specific diseases (eg, for patients with tuberculosis in South Africa), or when trust in government was low (eg, during H1N1 in Mexico), participants described masks as stigmatising, uncomfortable or oppressive. / Conclusion: Face masks can take on positive social meanings linked to solidarity and altruism during epidemics. Unfortunately, these positive meanings can fail to take hold when risk perception falls, rules are seen as complex or unfair, and trust in government is low. At such times, ensuring continued use is likely to require additional efforts to promote locally appropriate positive social meanings, simplifying rules for use and ensuring fair enforcement