20,419 research outputs found

    Kolmogorov-Burgers Model for Star Forming Turbulence

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    The process of star formation in interstellar molecular clouds is believed to be controlled by driven supersonic magnetohydrodynamic turbulence. We suggest that in the inertial range such turbulence obeys the Kolmogorov law, while in the dissipative range it behaves as Burgers turbulence developing shock singularities. On the base of the She-Leveque analytical model we then predict the velocity power spectrum in the inertial range to be E_k ~ k^{-1.74}. This result reproduces the observational Larson law, ~ l^{0.74...0.76}, [Larson, MNRAS 194 (1981) 809] and agrees well with recent numerical findings by Padoan and Nordlund [astro-ph/0011465]. The application of the model to more general dissipative structures, with higher fractal dimensionality, leads to better agreement with recent observational results.Comment: revised, new material added, 8 page

    Hayashi and the Thermal Physics of Star-Forming Clouds

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    This brief historical review highlights the early work of Hayashi and his associates on the thermal physics of star-forming clouds, as summarized in the temperature-density diagrams first presented by this group. Some of the more recent developments in this subject, including its application to understanding stellar masses and to understanding the formation of the first stars, are also briefly reviewed.Comment: Presented at the meeting on "First Stars IV" in Kyoto, Japan, May 21-25, 2012, honoring Chushiro Hayash

    Adapting Human Rights

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    Governmental leaders, scholars, and activists have advocated for human rights to food, water, education, health care, and energy. Such rights, also called positive rights, place an affirmative duty upon the state to provide a minimum quantity and quality of these goods and services to all citizens. But food, education, water, and health care are so different–in how they are produced, consumed, and financed–that the implementation of a positive right must be adapted to the distinctive characteristics of the good or service it guarantees. The primary aims of this adaptive implementation are transparency, enforceability and sustainability in the provision of positive rights. Only by adapting a positive right to its policy environment can such a right function as a viable means of protecting disadvantaged members of society. This article uses the example of positive rights to public utilities, such as water and energy, to illustrate adaptive implementation of positive rights. In doing so, this article explains why and how a positive right must be adapted to the unique policy environment of a given public utility
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