Interstellar MHD Turbulence and Star Formation

This chapter reviews the nature of turbulence in the Galactic interstellar medium (ISM) and its connections to the star formation (SF) process. The ISM is turbulent, magnetized, self-gravitating, and is subject to heating and cooling processes that control its thermodynamic behavior. The turbulence in the warm and hot ionized components of the ISM appears to be trans- or subsonic, and thus to behave nearly incompressibly. However, the neutral warm and cold components are highly compressible, as a consequence of both thermal instability in the atomic gas and of moderately-to-strongly supersonic motions in the roughly isothermal cold atomic and molecular components. Within this context, we discuss: i) the production and statistical distribution of turbulent density fluctuations in both isothermal and polytropic media; ii) the nature of the clumps produced by thermal instability, noting that, contrary to classical ideas, they in general accrete mass from their environment; iii) the density-magnetic field correlation (or lack thereof) in turbulent density fluctuations, as a consequence of the superposition of the different wave modes in the turbulent flow; iv) the evolution of the mass-to-magnetic flux ratio (MFR) in density fluctuations as they are built up by dynamic compressions; v) the formation of cold, dense clouds aided by thermal instability; vi) the expectation that star-forming molecular clouds are likely to be undergoing global gravitational contraction, rather than being near equilibrium, and vii) the regulation of the star formation rate (SFR) in such gravitationally contracting clouds by stellar feedback which, rather than keeping the clouds from collapsing, evaporates and diperses them while they collapse.Comment: 43 pages. Invited chapter for the book "Magnetic Fields in Diffuse Media", edited by Elisabete de Gouveia dal Pino and Alex Lazarian. Revised as per referee's recommendation

Trade shows and the creation of market and industry

This study addresses the question of the constitution of markets in advanced societies.Specifically, the article studies the role of the traveling trade show in creatingthe real time computing market, which is part of the US electronics sector, duringthe mid-1990’s. Real time computing products assist the transfer, storage and processingof digital signals in real time and support many of the internet applicationswe use today.By applying ethnographic methods,we explore the general question ofhow economic actors cope with uncertainty in the phase of market-making and atthe cutting edge of technology. The paper makes two contributions to the existingliterature. First, it shows that the attempt to organize a trade show in real timecomputing was triggered by the uncertainty experienced by sellers regarding theidentity of prospective buyers and about the exact use to which they would put theemergent technology which is offered for sale. Secondly, we trace the history of anemergent market.We claim that trade shows for innovative products are importantvenues at which markets coalesce.The identification and ordering of market actors,the institutionalization of a distinct business culture and the social networks developedamong market actors and across the subsidiary markets provided the basicsocial infrastructure for what later became known as the real time computingindustry.M2007-0244:1-PKEuropean Research Council ERC-2010- StG 263699-CEVVR 2009–195