The influence of sediment oxygen heterogeneity, due to bioturbation, on diffusive oxygen flux was investigated. Laboratory experiments were carried out with 3 macrobenthic species presenting different bioturbation behaviour patterns: the polychaetes Nereis diversicolor and Nereis virens, both constructing ventilated galleries in the sediment column, and the gastropod Cyclope neritea, a burrowing species which does not build any structure. Oxygen two-dimensional distribution in sediments was quantified by means of the optical planar optode technique. Diffusive oxygen fluxes and a variability index were (...) calculated on the captured oxygen images. All species increased sediment oxygen heterogeneity compared to the controls without animals. This was particularly noticeable with the polychaetes because of the construction of more or less complex burrows. Integrated diffusive oxygen flux increased with oxygen heterogeneity due to the production of interface available for solute exchanges between overlying water and sediments. This work shows that sediment heterogeneity is an important feature of the control of oxygen exchanges at the sediment–water interface. (shrink)

Writing in the late 1990s about the tendency of encyclopedists to designate existentialism a finished project, Thomas W. Busch cautions that such hasty periodization risks distorting our understanding of the contemporary philosophical scene and of depriving ourselves of vital resources for critiquing contemporary forms of oppression, what Garbriel Marcel referred to as processes of dehumanization. We should recall that "existentialism made possible present forms of Continental philosophy, all of which assume the existentialist critique of dualism, essentialism, and totality in modern (...) philosophy," and we should acknowledge that "existentialism remains capable of haunting today's scene as an important and relevant critic." Offered in honor of Thomas W. Busch after his more than fifty years of work in philosophy, the essays in this volume attest to existentialism as a living project. The essays are written by scholars who championed existentialism in America and by scholars who now seek to extend existentialist insights into new territory, including into research in cognitive science. The essays range from studies of key figures and texts to explorations of urgent topics such as the nature of freedom and the possibility of what Busch calls "incorporation," a sense of communicative solidarity that respects difference and disagreement. (shrink)

We study logical systems for reasoning about equations involving recursive definitions. In particular, we are interested in "propositional" fragments of the functional language of recursion FLR [18, 17], i.e., without the value passing or abstraction allowed in FLR. The "pure," propositional fragment FLR 0 turns out to coincide with the iteration theories of [1]. Our main focus here concerns the sharp contrast between the simple class of valid identities and the very complex consequence relation over several natural classes of models.

The traditional view was that a concept must be immediate if anything is, i.e., it must be something possessed directly by my mind. To deny this seems to be saying "I think but I don't have ideas." This is of course what the proponents of the linguistic philosophy are in effect saying, and perhaps for them it is all right. Professor Price has argued ingeniously against the whole linguistic position: against the possibility of a purely linguistic solution to the problem. (...) Yet whether we follow Price or the language philosophers we are forced into a rather puzzling situation. One likes to say that one has ideas, thoughts, concepts, but there is a serious question as to whether we can ever actually cognize such entities. Indeed Price introspects and does not find them. Most of us--including our linguistic colleagues--would be quick to agree. A thought cannot be introspected like an image. There just does not seem to be anything there. As thinkers of thoughts, we are looking inward toward nothing; we are indeed living examples of "hollow men." So it is that we are faced with a dilemma. Either we say we think but do not really have ideas, or we must somehow show that such concepts are actually immediate after all. Neither alternative seems the least bit welcome. The latter seems utterly impossible. (shrink)