Current-driven filamentation upstream of magnetized relativistic collisionless shocks

The physics of instabilities in the precursor of relativistic collisionless shocks is of broad importance in high energy astrophysics, because these instabilities build up the shock, control the particle acceleration process and generate the magnetic fields in which the accelerated particles radiate. Two crucial parameters control the micro-physics of these shocks: the magnetization of the ambient medium and the Lorentz factor of the shock front; as of today, much of this parameter space remains to be explored. In the present paper, we report on a new instability upstream of electron-positron relativistic shocks and we argue that this instability shapes the micro-physics at moderate magnetization levels and/or large Lorentz factors. This instability is seeded by the electric current carried by the accelerated particles in the shock precursor as they gyrate around the background magnetic field. The compensation current induced in the background plasma leads to an unstable configuration, with the appearance of charge neutral filaments carrying a current of the same polarity, oriented along the perpendicular current. This ``current-driven filamentation'' instability grows faster than any other instability studied so far upstream of relativistic shocks, with a growth rate comparable to the plasma frequency. Furthermore, the compensation of the current is associated with a slow-down of the ambient plasma as it penetrates the shock precursor (as viewed in the shock rest frame). This slow-down of the plasma implies that the ``current driven filamentation'' instability can grow for any value of the shock Lorentz factor, provided the magnetization \sigma <~ 10^{-2}. We argue that this instability explains the results of recent particle-in-cell simulations in the mildly magnetized regime.Comment: 14 pages, 8 figures; to appear in MNRA

Projet de développement de la culture du maïs dans la zone de Mweka (Zaire) : conservation, conditionnement et commercialisation du maïs

L'objectif principal du présent rapport est d'étudier dans la zone de "Mweka" où se poursuit le projet de développement de maïs, les problèmes posés pour la conservation, le conditionnement et la commercialisation du maïs compte tenu des conditions de culture et des contraintes climatiques et techniques locales, proposer éventuellement des solutions aux problèmes posé

A multi-flow model for microquasars

We present a new picture for the central regions of Black Hole X-ray Binaries. In our view, these central regions have a multi-flow configuration which consists in (1) an outer standard accretion disc down to a transition radius r_J, (2) an inner magnetized accretion disc below r_J driving (3) a non relativistic self-collimated electron-proton jet surrounding, when adequate conditions for pair creation are met, (4) a ultra relativistic electron-positron beam. This accretion-ejection paradigm provides a simple explanation to the canonical spectral states, from radio to X/gamma-rays, by varying the transition radius r_J and disc accretion rate independently. Large values of r_J and low accretion rate correspond to Quiescent and Hard states. These states are characterized by the presence of a steady electron-proton MHD jet emitted by the disc below r_J. The hard X-ray component is expect to form at the jet basis. When r_J becomes smaller than the marginally stable orbit r_i, the whole disc resembles a standard accretion disc with no jet, characteristic of the Soft state. Intermediate states correspond to situations where r_J ~ r_i. At large accretion rate, an unsteady pair cascade process is triggered within the jet axis, giving birth to flares and ejection of relativistic pair blobs. This would correspond to the luminous intermediate state, with its associated superluminal motions.Comment: 12 pages, 3 figures. Proceedings of ``High Energies in the Highlands'', Fort-William, 27 June-1 July 200

Alien Registration- Pelletier, Marie L. (Sanford, York County)

https://digitalmaine.com/alien_docs/2679/thumbnail.jp

Conceptualising digital transformation in SMEs: an ecosystemic perspective

Purpose: Supported by a service ecosystem that is increasingly immersed into digital transformation, small- and medium-sized enterprises (SMEs) have access to turnkey information technology (IT) applications, which may come free of charge but not free of concerns. The purpose of this paper is to explore a group conceptualisation and associated perceptions of IT issues within an ecosystem that includes three subgroup profiles: entrepreneurs, IT professionals and socioeconomic support professionals. Design/methodology/approach: Using group concept mapping, a bottom-up and participatory mixed methods-based approach, a concept map was estimated, based on a list of items, to define seven clusters pertaining to issues and challenges of adoption and use of turnkey IT applications in SMEs of less than 20 employees. Perceptions measures of relative importance and feasibility were obtained by subgroup profiles. Findings: The relative importance and relative feasibility measures for the seven clusters indicate significant statistical differences in ratings among the subgroup profiles. A discussion on the importance of relational capital in addressing challenges of digital transformation in SMEs is developed. Originality/value: Results highlight signifiant differences concerning key dimensions in the adoption and use of IT from the perspective of three subgroup profiles of actors within the ecosystem. First, the results stress the need to develop a shared understanding of IT challenges. Second, they suggest policymakers could use these conceptual representations to further develop and strengthen the IT-related support agenda for SMEs, especially the smaller ones (e.g. training programs, business support and coaching initiatives, etc.). © 2019, Emerald Publishing Limited

Inhibition of Tendon Cell Proliferation and Matrix Glycosaminoglycan Synthesis by Non-Steroidal Anti-Inflammatory Drugs in vitro

The purpose of this study was to investigate the effects of some commonly used non-steroidal anti-inflammatory drugs (NSAIDs) on human tendon. Explants of human digital flexor and patella tendons were cultured in medium containing pharmacological concentrations of NSAIDs. Cell proliferation was measured by incorporation of 3H-thymidine and glycosaminoglycan synthesis was measured by incorporation of 35S-Sulphate. Diclofenac and aceclofenac had no significant effect either on tendon cell proliferation or glycosaminoglycan synthesis. Indomethacin and naproxen inhibited cell proliferation in patella tendons and inhibited glycosaminoglycan synthesis in both digital flexor and patella tendons. If applicable to the in vivo situation, these NSAIDs should be used with caution in the treatment of pain after tendon injury and surgery