Proxy Functions and Inscrutability of Reference

Objection to Quine's argument for the inscrutability of reference. The proxy functions don't preserve the relations to experience, contrary to Quine's claims

Accretional heating of the satellites of Saturn and Uranus

Voyager images of the satellites of Saturn and Uranus have shown that these bodies are characterized by remarkable diversity and surprisingly complex geologic histories. Despite their small sizes, a number of the satellites show unambiguous evidence for resurfacing. The goal was to develop a detailed model for heating of these small satellites, and then to explore the consequences of variations in the free parameters in the model. Specifically an attempt was made to determine for what range of conditions melting will occur in these satellites. Along with varying a number of model parameters, the important effects of inclusion of small amounts of ammonia and methane in the system were considered

Why We Should Prefer Knowledge

This chapter contains sections titled: References

Solvation of Ions. II. Use of a Variable Solvation Number for K+

Gibbs free energies of transfer of K(I) ion from water to water-dimethyl sulfoxide mixtures corrected to zero ionic strength have been used to deduce information concerning states of solvation of K+ ion in the purely aqueous phase and in the mixed solvent phase. It was found that the largest number of water molecules which needed to be assigned to the solvent cage of K+ was 11 in either phase. The partition equilibrium constant, /?0, for the distribution of K(H20)H+ between the two phases was found as a function of the mole fraction of dimethyl sulfoxide in the mixed solvent phase. The largest number of dimethyl sulfoxide molecules which needed to be assigned to the solvent cage was 10. The number of solvent molecules in the solvent cage was allowed to be variable and the overall formation constants of all K(H20)j((CH3)2S0)k+ ions contributing to the free energy of transfer were determined. The results are compared with the results from molecular dynamics computer simulations for K+ where possible

Constraining the Nature of X-ray Cavities in Clusters and Galaxies

We present results from an extensive survey of 64 cavities in the X-ray halos of clusters, groups and normal elliptical galaxies. We show that the evolution of the size of the cavities as they rise in the X-ray atmosphere is inconsistent with the standard model of adiabatic expansion of purely hydrodynamic models. We also note that the majority of the observed bubbles should have already been shredded apart by Rayleigh-Taylor and Richtmyer-Meshkov instabilities if they were of purely hydrodynamic nature. Instead we find that the data agrees much better with a model where the cavities are magnetically dominated and inflated by a current-dominated magneto-hydrodynamic jet model, recently developed by Li et al. (2006) and Nakamura et al. (2006). We conduct complex Monte-Carlo simulations of the cavity detection process including incompleteness effects to reproduce the cavity sample's characteristics. We find that the current-dominated model agrees within 1sigma, whereas the other models can be excluded at >5sigma confidence. To bring hydrodynamic models into better agreement, cavities would have to be continuously inflated. However, these assessments are dependent on our correct understanding of the detectability of cavities in X-ray atmospheres, and will await confirmation when automated cavity detection tools become available in the future. Our results have considerable impact on the energy budget associated with active galactic nucleus feedback.Comment: 21 pages, 12 figures, emulateapj, accepted for publication in ApJ, responded to referee's comments and added a new model, conclusions unchange

Solvation of Ions. V. Silver(I) Ion in Water-Dimethyl Sulfoxide Mixtures

The Gibbs\u27 free energies of transfer of silver(I) ion, AtG° (Ag+), from water to water-dimethyl sulfoxide (W/D) binary mixtures have been used to obtain the distribution of solvated ions, [AgW/Dfc]+, present over the mole fraction range from 0.05 to 0.95 for dimethyl sulfoxide. Major species were [AgWsD]+, [AgW1gD]+, [AgW3D2]+, [AgWD3]+, [AgDg]+, [AgWD9]+, [AgD14]+. The water-rich solvated ions were present only at small dimethyl sulfoxide concentrations

Accretion onto the Supermassive Black Hole in M87

Chandra X-ray observations of the giant elliptical galaxy M87 resolve the thermal state of the hot interstellar medium into the accretion (Bondi) radius of its central 3 10^9 Msun black hole. We measure the X-ray gas temperature and density profiles and calculate the Bondi accretion rate, Mdot_Bondi \sim 0.1 Msun/yr. The X-ray luminosity of the active nucleus of M87 observed with Chandra is L_{x, 0.5-7 \keV} \sim 7 \times 10^{40}erg/s. This value is much less than the predicted nuclear luminosity, L_{Bondi} \sim 5 \times 10^{44} erg/s, for accretion at the Bondi rate with a canonical accretion radiative efficiency of 10%. If the black hole in M87 accretes at this rate it must do so at a much lower radiative efficiency than the canonical value. The multiwavelength spectrum of the nucleus is consistent with that predicted by an advection-dominated flow. However, as is likely, the X-ray nucleus is dominated by jet emission then the properties of flow must be modified, possibly by outflows. We show that the overall energetics of the system are just consistent with the predicted Bondi nuclear power. This suggests that either most of the accretion energy is released in the relativistic jet or that the central engine of M87 undergoes on-off activity cycles. We show that, at present, the energy dumped into the ISM by the jet may reduce the accretion rate onto the black hole by a factor \propto (v_j/c_s)^{-2}, where v_j is the jet velocity and c_s the ISM sound speed, and that this is sufficient to account for the low nuclear luminosity.Comment: emulateapj.sty, revised version, accepted by Ap