This paper re-examines the problem of ambipolar diffusion as a mechanism for the production and runaway evolution of centrally condensed molecular cloud cores, a process that has been termed the gravomagneto catastrophe. Our calculation applies in the geometric limit of a highly flattened core and allows for a semi-analytic treatment of the full problem, although physical fixes are required to ...

In a weakly ionized plasma, the evolution of the magnetic field is described by a “generalized Ohm’s law” that includes the Hall effect and the ambipolar diffusion terms. These terms introduce additional spatial and time scales which play a decisive role in the cascading and the dissipation mechanisms in magnetohydrodynamic turbulence. We determine the Kolmogorov dissipation scales for the visc...

Until recently, many of the dozens of quantitative predictions of the ambipolar-diffusion theory of gravitational fragmentation (or core formation) of molecular clouds have been confirmed by observations and, just as importantly, no prediction has been contradicted by any observation. A recent paper, however, claims that measurements of the variation of the mass-to-flux ratio from envelopes to ...

Although thermal pressure is unimportant dynamically in most molecular gas, the temperature is an important diagnostic of dynamical processes and physical conditions. This is the first of two papers on thermal equilibrium in molecular clouds. We present calculations of frictional heating by ion-neutral (or ambipolar) drift in three–dimensional simulations of turbulent, magnetized molecular clou...

Charge transport in carbon nanotube network transistors strongly depends on the properties of the gate dielectric that is in direct contact with the semiconducting carbon nanotubes. In this work, we investigate the dielectric effects on charge transport in polymer-sorted semiconducting single-walled carbon nanotube field-effect transistors (s-SWNT-FETs) by using three different polymer insulato...

The heating of the ion-neutral (or ambipolar) diffusion may affect the thermal phases of the molecular clouds. We present an investigation on the effect of this heating mechanism in the thermal instability of the molecular clouds. A weakly ionized one dimensional slab geometry, which is allowed for self-gravity and ambipolar diffusion, is chosen to study its thermal phases. We use the thermodyn...

We investigate numerically the combined effects of supersonic turbulence, strong magnetic fields and ambipolar diffusion on cloud evolution leading to star formation. We find that, in clouds that are initially magnetically subcritical, supersonic turbulence can speed up star formation, through enhanced ambipolar diffusion in shocks. The speedup overcomes a major objection to the standard scenar...

8:20 AM Invited M1, Material and Electronic Properties of CVD Graphene Grown on Ni and Cu then Transferred to Insulators: Helin Cao1; Qingkai Yu2; Luis Jauregui1; Deepak Pandey1; Robert Colby1; Jifa Tian1; Nathan Guisinger3; Eric Stach1; Steven Pei2; Yong Chen1; 1Purdue Univ; 2University of Houston; 3Argonne Nat Lab We have synthesized large scale (up to several inches) graphitic and graphene t...