Different convection models in ATLAS

Convection is an important phenomenon in the atmospheres of A-type and cooler stars. A description of convection in ATLAS models is presented, together with details of how it is specified in model calculations. The effects of changing the treatment of convection on model structures and how this affects observable quantities are discussed. The role of microturbulence is examined, and its link to velocity fields within the atmosphere. Far from being free parameters, mixing-length and microturbulence should be constrained in model calculations.Comment: 7 pages, 6 figures. To appear in the proceedings of the Workshop "ATLAS 12 and related codes", Trieste, July 11-15, 200

Observations of convection in A-type stars

Convection and turbulence in stellar atmospheres have a significant effect on the emergent flux from A-type stars. The recent theoretical advancements in convection modelling have proved a challenge to the observers to obtain measurements with sufficient precision and accuracy to allow discrimination between the various predictions. A discussion of the current observational techniques used to evaluate the various convection theories is presented. These include filter photometry, spectrophotometry, hydrogen lines, and metal lines. The results from these techniques are given, along with the successes and limitations.Comment: 8 pages, 4 figures, Invited Lecture at IAU Symposium 224 "The A Star Puzzle", 7-13 July 2004, Poprad, Slovaki

Fine structure of the zeros of orthogonal polynomials, I. A tale of two pictures

Mhaskar-Saff found a kind of universal behavior for the bulk structure of the zeros of orthogonal polynomials for large n. Motivated by two plots, we look at the finer structure for the case of the Verblunsky coefficients and for what we call the BLS condition: αn = Cb^n + O ((bΔ)^n). In the former case, we describe the results of Stoiciu. In the latter case, we prove asymptotically equal spacing for the bulk of zeros

Spinoza and the problem of other substances

ABSTRACTMost of Spinoza’s arguments for God’s existence do not rely on any special feature of God, but instead on merely general features of substance. This raises the following worry: those arguments prove the existence of non-divine substances just as much as they prove God’s existence, and yet there is not enough room in Spinoza’s system for all these substances. I argue that Spinoza attempts to solve this problem by using a principle of plenitude to rule out the existence of other substances and that the principle cannot be derived from the PSR, as many claim.Abbreviation: PSR: Principle of Sufficient Reason

Towards an ontology of common sense

Philosophers from Plotinus to Paul Churchland have yielded to the temptation to embrace doctrines which contradict the core beliefs of common sense. Philosophical realists have on the other hand sought to counter this temptation and to vindicate those core beliefs. The remarks which follow are to be understood as a further twist of the wheel in this never-ending battle. They pertain to the core beliefs of common sense concerning the external reality that is given in everyday experience -the beliefs of folk physics, as we might call them. Just as critics of Churchland et al. have argued that the folk-psychological ontology of beliefs, desires, etc. yields the best explanation we can have of the order of cognitive phenomena conceived from the perspective of first-person experience, so we shall argue that (1) the commonsensical ontology of folk physics yields the best explanation we can have of our externally directed cognitive experience and that (2) an ontology of mesoscopic things, events and processes must play a role, in particular, in our best scientific theory of human action

New desiderata for biomedical terminologies

It is only by fixing on agreed meanings of terms in biomedical terminologies that we will be in a position to achieve that accumulation and integration of knowledge that is indispensable to progress at the frontiers of biomedicine. Standardly, the goal of fixing meanings is seen as being realized through the alignment of terms on what are called ‘concepts’. Part I addresses three versions of the concept-based approach – by Cimino, by Wüster, and by Campbell and associates – and surveys some of the problems to which they give rise, all of which have to do with a failure to anchor the terms in terminologies to corresponding referents in reality. Part II outlines a new, realist solution to this anchorage problem, which sees terminology construction as being motivated by the goal of alignment not on concepts but on the universals (kinds, types) in reality and thereby also on the corresponding instances (individuals, tokens). We outline the realist approach, and show how on its basis we can provide a benchmark of correctness for terminologies which will at the same time allow a new type of integration of terminologies and electronic health records. We conclude by outlining ways in which the framework thus defined might be exploited for purposes of diagnostic decision-support

On Tractarian law

"'It is clear", wrote Wittgenstein in the Tractatus, "that ethics has nothing to do with punishment and reward in the usual sense of the terms" (6.422). But he insisted also that there must be some kind of ethical punishment and reward; "the reward", he tells us, "must be something pleasant, and the punishment something unpleasant" (ibid.). I argue that we can understand what Wittgenstein meant by "reward" and "punishment" by conceiving these notions as elements in a system of interrelated concepts connected with the idea of law