29 research outputs found
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