Allogeneic grafts of spontaneous canine melanomas and their cell culture strains in neonatal immunosuppressed dogs.

Canine melanoma has been transplanted to allogeneic neonatal recipients receiving continuous immunosuppression with anti-lymphocyte serum. One spontaneous melanoma was directly transplanted into 8 recipients, 6 of which developed tumours. 5/5 melanoma cell cultures were transplantable, with 19 tumour takes in 31 allogeneic recipients. Serial passage was performed in the case of two melanomas. Tumour development required continuous immunosuppression and the site was dependent upon the route of inoculation and other factors. Transplanted cell cultures were all amelanotic in vitro and in vivo, except in the case of one melanoma which reverted to a melanotic morphology after in vivo growth

A Magnetically-Switched, Rotating Black Hole Model For the Production of Extragalactic Radio Jets and the Fanaroff and Riley Class Division

A model is presented in which both Fanaroff and Riley class I and II extragalactic jets are produced by magnetized accretion disk coronae in the ergospheres of rotating black holes. While the jets are produced in the accretion disk itself, the output power still is an increasing function of the black hole angular momentum. For high enough spin, the black hole triggers the magnetic switch, producing highly-relativistic, kinetic-energy-dominated jets instead of Poynting-flux-dominated ones for lower spin. The coronal mass densities needed to trigger the switch at the observed FR break power are quite small ($\sim 10^{-15} g cm^{-3}$), implying that the source of the jet material may be either a pair plasma or very tenuous electron-proton corona, not the main accretion disk itself. The model explains the differences in morphology and Mach number between FR I and II sources and the observed trend for massive galaxies to undergo the FR I/II transition at higher radio power. It also is consistent with the energy content of extended radio lobes and explains why, because of black hole spindown, the space density of FR II sources should evolve more rapidly than that of FR I sources. If the present model is correct, then the ensemble average speed of parsec-scale jets in sources distinguished by their FR I morphology (not luminosity) should be distinctly slower than that for sources with FR II morphology. The model also suggests the existence of a population of high-redshift, sub-mJy FR I and II radio sources associated with spiral or pre-spiral galaxies that flared once when their black holes were formed but were never again re-kindled by mergers.Comment: 14 pages, 2 figures, final version to appear in Sept Ap

Animal movement modelling: Independent or dependent models?

Hidden Markov models have become a popular time series method for the analysis of GPS tracked animals. Their advantage for identifying latent behavioural states compared with Independent Mixture models is that they take into account the time series dependency of successive displacement distances by the tracked animals. However, little is known about how the analysis results may differ depending on which of these approaches is used. We compared the results and interpretations obtained from fitting Hidden Markov and Independent Mixture models to simulated movement data as well as to field data recording the hourly movements of sable antelope and buffalo within the Kruger National Park, South Africa. Hidden Markov models consistently yielded narrower confidence intervals around parameters and smaller standard errors than simpler time independent mixture models, but for some data the improvement was marginal and the Independent Mixture model provided an adequate alternative for identifying the latent behavioural states of the animal. In general, it is expected Hidden Markov models will provide the better balance between model complexity and extensibility for animal movement modelling from a statistical perspective. However, in some cases, Independent Mixture models could provide an adequate alternative method and might be more faithful biologically