Convection-Dominated Accretion Flows

Non-radiating, advection-dominated, accretion flows are convectively unstable. We calculate the two-dimensional (r-theta) structure of such flows assuming that (1) convection transports angular momentum inwards, opposite to normal viscosity and (2) viscous transport by other mechanisms (e.g., magnetic fields) is weak (alpha << 1). Under such conditions convection dominates the dynamics of the accretion flow and leads to a steady state structure that is marginally stable to convection. We show that the marginally stable flow has a constant temperature and rotational velocity on spherical shells, a net flux of energy from small to large radii, zero net accretion rate, and a radial density profile proportional to r^{-1/2}, flatter than the r^{-3/2} profile characteristic of spherical accretion flows. This solution accurately describes the full two-dimensional structure of recent axisymmetric numerical simulations of advection-dominated accretion flows.Comment: final version accepted by ApJ; discussion expanded, references adde

Potential Treatments for Epileptiform Activity in Microgyral Cortex

In this study, the effects of several drug treatments on epileptiform activity in the freeze lesion (FL) mouse model of epilepsy have been evaluated and compared. The FL model replicates the histopathology and epileptiform activity that occurs in humans with the developmental cortical malformation of polymicrogyria (PMG). While Gabapentin is already used in a clinical setting to treat seizures, there are other alternatives that have not been fully tested. Rapamycin, for instance, has been shown to reduce seizures in other models of epilepsy. It is an inhibitor of the mammalian target of rapamycin (mTOR) pathway, which regulates the function of many organs of the body. MTEP has also been shown to have an anticonvulsant effect in certain forms of epilepsy. MTEP is an mGlu5 receptor antagonist. These drugs were delivered in a frame of time that is specific to this study and medically relevant. The age of the mouse at the time of injection corresponded in cortical development with a term human infant, which is the earliest age at which assessment and treatment of PMG would be likely to occur. To compare the effectiveness of these drugs, local field potential recordings were made using brain slices collected from the somatosensory cortex of FL and Sham lesioned mice with and without the specific drug treatments. It was hypothesized that the incidence of epileptiform activity in the rapamycin, MTEP, and gabapentin treated FL mice will be significantly reduced compared to the FL mice without drug treatment

Interview with Eliot Cutler by Mike Hastings

Biographical NoteEliot Raphael Cutler was born in 1946 in Bangor, Maine. His mother was an economist and his father, a physician, was responsible for the reorganization of the Maine university system; the Cutler Health Center in Orono, Maine, is named in his honor. As a sophomore in high school, Eliot transferred from Bangor High School to Deerfield Academy. He attended Harvard University and Georgetown Law School. While at Harvard he was involved with the Harvard Lampoon. He worked as a legislative assistant and clerk for Senator Muskie from 1967 to 1972 and was a senior staff person at the OMB during the Carter administration. He has served on the Board of Visitors of the Muskie School for Public Service at University of Southern Maine in Portland, Maine. At the time of this Interview, he was a member of the law firm of Akin, Gump, Strauss, Hauer & Feld, LLP. SummaryInterview includes discussion of: Cutler’s candidacy for governor; campaigns Cutler has worked on, including those for Muskie, Carter, and Mondale; Cutler’s connection to China; Cutler’s role as chairman of the Board of Visitors at the Muskie School; political attention to energy issues under Carter and today; Cutler\u27s meeting George Mitchell as an intern in Muskie’s office; how Mitchell’s operating style differed from Muskie’s; Cutler’s role as press secretary in 1968 and contact with the media; Mitchell’s role in Muskie’s fund-raising in 1968 and 1972; the 1972 campaign; Muskie as a negotiator; Mitchell’s role in Ireland and the Middle East; and Marshall Stern

Nonthermal THz to TeV Emission from Stellar Wind Shocks in the Galactic Center

The central parsec of the Galaxy contains dozens of massive stars with a cumulative mass loss rate of ~ 10^{-3} solar masses per year. Shocks among these stellar winds produce the hot plasma that pervades the central part of the galaxy. We argue that these stellar wind shocks also efficiently accelerate electrons and protons to relativistic energies. The relativistic electrons inverse Compton scatter the ambient ultraviolet and far infrared radiation field, producing high energy gamma-rays with a roughly constant luminosity from \~ GeV to ~ 10 TeV. This can account for the TeV source seen by HESS in the Galactic Center. Our model predicts a GLAST counterpart to the HESS source with a luminosity of ~ 10^{35} ergs/s and cooling break at ~ 4 GeV. Synchrotron radiation from the same relativistic electrons should produce detectable emission at lower energies, with a surface brightness ~ 10^{32} B^2_{-3} ergs/s/arcsec^2 from ~ THz to ~ keV, where B_{-3} is the magnetic field strength in units of mG. The observed level of diffuse thermal X-ray emission in the central parsec requires B < 300 micro-G in our models. Future detection of the diffuse synchrotron background in the central parsec can directly constrain the magnetic field strength, providing an important boundary condition for models of accretion onto Sgr A*.Comment: submitted to ApJ Letter