Large scale simulations of the jet-IGM interaction

In a parameter study extending to jet densities of $10^{-5}$ times the ambient one, I have recently shown that light large scale jets start their lives in a spherical bow shock phase. This allows an easy description of the sideways bow shock propagation in that phase. Here, I present new, bipolar, simulations of very light jets in 2.5D and 3D, reaching the observationally relevant scale of $>200$ jet radii. Deviations from the early bow shock propagation law are expected because of various effects. The net effect is, however, shown to remain small. I calculate the X-ray appearance of the shocked cluster gas and compare it to Cygnus A and 3C 317. Rings, bright spots and enhancements inside the radio cocoon may be explained.Comment: 8 pages, 5 figures, ApSS accepted, proceedings of the virtual jets 2003 conference in Dogliani/Italy, v3: funny and unimportant bug corrected, one reference adde

Theory of a refined earth model

Refined equations are derived relating the variations of the earths gravity and radius as functions of longitude and latitude. They particularly relate the oblateness coefficients of the old harmonics and the difference of the polar radii /respectively, ellipticities and polar gravity accelerations/ in the Northern and Southern Hemispheres

Transport coefficients for the shear dynamo problem at small Reynolds numbers

We build on the formulation developed in Sridhar & Singh (JFM, 664, 265, 2010), and present a theory of the \emph{shear dynamo problem} for small magnetic and fluid Reynolds numbers, but for arbitrary values of the shear parameter. Specializing to the case of a mean magnetic field that is slowly varying in time, explicit expressions for the transport coefficients, $\alpha_{il}$ and $\eta_{iml}$, are derived. We prove that, when the velocity field is non helical, the transport coefficient $\alpha_{il}$ vanishes. We then consider forced, stochastic dynamics for the incompressible velocity field at low Reynolds number. An exact, explicit solution for the velocity field is derived, and the velocity spectrum tensor is calculated in terms of the Galilean--invariant forcing statistics. We consider forcing statistics that is non helical, isotropic and delta-correlated-in-time, and specialize to the case when the mean-field is a function only of the spatial coordinate $X_3$ and time $\tau\,$; this reduction is necessary for comparison with the numerical experiments of Brandenburg, R{\"a}dler, Rheinhardt & K\"apyl\"a (ApJ, 676, 740, 2008). Explicit expressions are derived for all four components of the magnetic diffusivity tensor, $\eta_{ij}(\tau)\,$. These are used to prove that the shear-current effect cannot be responsible for dynamo action at small \re and \rem, but for all values of the shear parameter.Comment: 27 pages, 5 figures, Published in Physical Review

Fraud in Universal Coverage: The Usual Suspects (and then Some)

This is the published version

Off-Label Drug Promotion and the Ephemeral Line Between Marketing and Education

Fueled by massive settlements and concerns about pharmaceutical company influence over medical practice, the fight over off-label promotion has become a rancorous one with little middle ground. For some, off-label restrictions are both bad law and bad medicine, violating the First Amendment while denying physicians access to crucial information. For others, the battle pits the very soul of the FDA against the excesses of a profit-driven marketplace. Far from ameliorating concerns over manufacturer influence, the New Model proposed by Bennett et al. would exacerbate them. The Model would limit FDA authority to core communications proposing immediate commercial transactions, giving manufacturers unfettered discretion over scientific exchanges and nearly free rein over truthful quasi-commercial communications. Most problematically, the New Model relies on the longstanding assumption that truly educational and scientific activities can be distinguished from simple product promotion – a dichotomy that exists not only in federal law and professional association codes, but also underlies the jurisdiction of the federal agencies overseeing the pharmaceutical sector. Experience invites skepticism that these activities can be cleanly separated, suggesting that the New Model may simply perpetuate abusive behaviors without offering concomitant benefits to physicians or patients