A model for collimated outflows in molecular clouds and the case of HH 7–11
Collimated outflows of high-velocity gas, with typical scale lengths of 0.01–0.2 pc, are often observed to be associated with linear chains of optical emission knots1, sometimes connected by faint nebulosities. The flows have been ascribed to the interaction between an energetic wind ejected by a young stellar object and circumstellar material. However, none of the acceleration and collimation mechanisms proposed so far can easily account for the most peculiar properties of the outflows, namely the almost constant spacing between the knots, their radial motion and the abrupt velocity changes along the flow, well illustrated by the prototype we use for our modelling, HH 7–11. We suggest here a new interpretation of the phenomenon, based on flows in a channel of variable cross-sectional area due to Kelvin–Helmholtz instabilities between the flow and the ambient medium; and present solutions of the Mach number equation for such a channel, which possess multiple critical points and shocks identified with the observed optical knots.
Effects of rapidly diverging flow, heat addition, and momentum addition in the solar wind and stellar winds
The roles of rapid flow tube divergence and heat and momentum addition in one-fluid models of the solar wind and stellar winds and the role of heat addition in two-fluid models of the solar wind ae explored. It is found that under certain circumstances heat addition, momentum addition, or the rapid divergence of a flow tube can produce more than one critical point in the solution topologies of the solar and stellar wind equations. For the solar wind, additional critical points associated with rapid flow tube divergence (e.g., in coronal holes) and/or with momentum addition can lead to high expansion speeds near the coronal base, and these high speeds, in conjuction with a rapid flow tube divergence, may in certain cases produce an increased conductive energy supply to the solar wind. If such an increased conductive energy supply is produced, the need for energy addition above the coronal base is correspondingly reduced. In addition, the high flow speeds at low altitudes make it possible for any required energy addition to occur relatively near the coronal base, so that the need for extended heating of the solar wind may be substantially less than has been suggested in the past. For radiation-drivenmore » stellar winds the additional critical points associated with rapid flow tube divergence can lead to supersonic flow much deeper in the stellar atmosphere than is predicted by radial, spherically symmetric flow models, and this might resolve the apparent conflict between radiation-driven wind models and certain observations of Of stars. In two-fluid solar wind models including proton heat addition it is shown that the radial electron temperature profile has a sufficiently important dynamical influence that the accurate treatment of electron energy transport is a primary prerequisite to obtaining quantitatively significant results. (AIP)« less
The Bastille: A History of a Symbol of Despotism and Freedom
This book is both an analysis of the Bastille as cultural paradigm and a case study on the history of French political culture. It examines in particular the storming and subsequent fall of the Bastille in Paris on July 14, 1789 and how it came to represent the cornerstone of the French Revolution, becoming a symbol of the repression of the Old Regime. Lusebrink and Reichardt use this semiotic reading of the Bastille to reveal how historical symbols are generated; what these symbols’ functions are in the collective memory of societies; and how they are used by social, political, and ideological groups.

To facilitate the symbolic nature of the investigation, this analysis of the evolving signification of the Bastille moves from the French Revolution to the nineteenth century to contemporary history. The narrative also shifts from France to other cultural arenas, like the modern European colonial sphere, where the overthrow of the Bastille acquired radical new signification in the decolonization period of the 1940s and 1950s. The Bastille demonstrates the potency of the interdisciplinary historical research that has characterized the end of this century, combining quantitative and qualitative approaches, and taking its methodological tools from history, sociology, linguistics, and cultural and literary studies.