Protostellar Disk Evolution Over Million-Year Timescales with a Prescription for Magnetized Turbulence

Magnetorotational instability (MRI) is the most promising mechanism behind accretion in low-mass protostellar disks. Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulence activity criteria to determine thermal structure and accretion rate without resorting to a 3-D magnetohydrodynamical (MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times the minimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositional gradients. Second, the surface density of the active layer is nearly constant in time at roughly 10 g/cm2, which we use to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHD computations. Furthermore, unlike a standard disk with constant-alpha viscosity, the disk midplane does not cool off over time, though the surface cools as the star evolves along the Hayashi track. The ice line is firmly in the terrestrial planet-forming region throughout disk evolution and can move either inward or outward with time, depending on whether pileups form near the star. Finally, steady-state mass transport is a poor description of flow through an MRI-active disk. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grain size, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameter study here.Comment: Accepted for publication in Astrophysical Journal. 19 pages, including 8 figure

Alien Registration- Landry, Patrick J. (Westbrook, Cumberland County)

https://digitalmaine.com/alien_docs/20750/thumbnail.jp

Alien Registration- Landry, Gerard J. (Auburn, Androscoggin County)

https://digitalmaine.com/alien_docs/31168/thumbnail.jp

Kasky v. Nike: Lurking First Amendment Time Bomb for Marketers?

While attention has focused on the U. S. Supreme Court protecting corporate political speech, the Court has left untouched a California Supreme Court ruling of significance to marketers in their efforts to use advertising and public relations to offset what they view as unfair criticism. The case, Kasky v. Nike, stems from 1995 accusations that athletic footwear and apparel manufacturer Nike exploited and abused employees in Asian sweatshops. Through advertising and public relations efforts, Nike denied the claims. In 1998, Californian Mark Kasky sued, claiming Nike’s denials violated laws regarding unfair competition and false advertising and, because the denials were “commercial speech,” they were not protected by the First Amendment. California Superior Court dismissed the case and Kasky also lost in the state Court of Appeal, but won at the California Supreme Court. The U.S. Supreme Court ultimately declined to hear an appeal from Nike. As a result, companies doing business in California, including online, risk being charged with false advertising when attempting to defend themselves against accusations of unfair, illegal, or unethical corporate practices