Hedgehog proteins are of pivotal importance for development and maintenance of tissue patterns in adult organisms. Despite the role of Hedgehogs in differentiation and tumorigenesis, signal transduction of Hedgehog remains a relatively uncharted area of signalling biochemistry. For proper Hedgehog distribution into tissues, two highly unusual covalent modifications are necessary, palmitoylation of a secreted protein and the attachment of a cholesterol group, making Hedgehog the only established sterolated protein in nature. Hedgehog exerts its function via two membrane‐bound receptors, Patched and (...) Smoothened; presumably, Patched transports a cholesterol derivate out of cells which inhibits Smoothened. Binding of Hedgehog to Patched impedes this proposed pump function and thus Inhibition of Smoothened, which leads to expression of genetic Hedgehog targets via relief of transcriptional repression. These atypical features make Hedgehog physiology unique in biology and may explain why this field has attracted such significant attention. BioEssays 26:387–394, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

This collection of new essays locates Boethius' Consolatio Philosophiae in the medieval context of Latin learning and vernacular translations. The first part is devoted to the Latin commentary tradition, while the other parts explore the vernacular traditions.

This article provides a historico-philosophical profile of late-medieval nominalism. It shows how nominalism placed limitations on the use of logic and natural reason in academic theology. In the first part, the historical meaning and use of the notions ‘moderni’ and ‘nominales’ are explored. In the second part, the methodology of the ‘moderni’ and ‘nominales’ is investigated, showing how nominalist understanding of logic and natural reason led to a separation of philosophy and theology. Three examples are discussed, taken from commentaries on (...) the Sentences. As these examples show, according to a number of ‘moderni’ and ‘nominales’ , logic and natural reason are not able to exclude all ambiguities and heresies from theological discourse. Thus logic loses its privileged function in theology as arbiter of true reasoning, clearing the way for the rules of traditional and ordinary speech, the ‘vulgus modus loquendi’. Only when logic and reason deal with the natural aspects of creation, do they remain authoritative. When applied to the divine, however, they may easily lead to heresy and error. (shrink)

This collection of essays delineates the history of the rather disparate intellectual tradition usually labeled as "Platonic" or "Neoplatonic". In chronological order, the book covers the most eminent philosophic schools of thought within that tradition. The most important terms of the Platonic tradition are studied together with a discussion of their semantic implications, the philosophical and theological claims associated with the terms, the sources that furnish the terms, and the intellectual traditions aligned with or opposed to them. The contributors thereby (...) provide a vivid intellectual map of the Middle Ages and the Early Modern period. Contributions are written in English or German. (shrink)

The commentary of the Italian physician and philosopher Pietro d'Abano on Bartholomew of Messina's Latin translation of Pseudo-Aristotle's 'Problemata Physica', published in 1310, constitutes an important historical source. In a section of the corpus Aristotelicum that was not part of the standard curriculum at the medieval university, the commentary of Pietro d'Abano investigates the complex relationship between text, translation, and commentary. The eight articles in this volume provide valuable insights into the manner in which Pietro d'Abano deals with the problems (...) of a translated text. They emphasize the idiosyncrasy of his approach in comparison to his contemporaries and successors, the particularities of his commentary in light of the habitual exegetical practices applied in the teaching of curricular texts, as well as the influence of philosophical traditions outside the strict framework of the medieval arts faculty. (shrink)

Colour has been shown to facilitate the recognition of scene images, but only when these images contain natural scenes, for which colour is ‘diagnostic’. Here we investigate whether colour can also facilitate memory for scene images, and whether this would hold for natural scenes in particular. In the first experiment participants first studied a set of colour and greyscale natural and man-made scene images. Next, the same images were presented, randomly mixed with a different set. Participants were asked to indicate (...) whether they had seen the images during the study phase. Surprisingly, performance was better for greyscale than for coloured images, and this difference is due to the higher false alarm rate for both natural and man-made coloured scenes. We hypothesized that this increase in false alarm rate was due to a shift from scrutinizing details of the image to recognition of the gist of the image. A second experiment, utilizing images without a nameable gist, confirmed this hypothesis as participants now performed equally on greyscale and coloured images. In the final experiment we specifically targeted the more detail-based perception and recognition for greyscale images versus the more gist-based perception and recognition for coloured images with a change detection paradigm. The results show that changes to images are detected faster when image-pairs were presented in greyscale than in colour. This counterintuitive result held for both natural and man-made scenes and thus corroborates the shift from more detailed processing of images in greyscale to more gist-based processing of coloured images. (shrink)

C.F Gauss’s computational work in number theory attracted renewed interest in the twentieth century due to, on the one hand, the edition of Gauss’s Werke, and, on the other hand, the birth of the digital electronic computer. The involvement of the U.S. American mathematicians Derrick Henry Lehmer and Daniel Shanks with Gauss’s work is analysed, especially their continuation of work on topics as arccotangents, factors of n2 + a2, composition of binary quadratic forms. In general, this strand in Gauss’s reception (...) is part of a more general phenomenon, i.e. the influence of the computer on mathematics and one of its effects, the reappraisal of mathematical exploration. (shrink)

This collection of 17 articles offers an overview of the philosophical activities of a group of philosophers (who have been) working at the Groningen University. The meta-methodological assumption which unifies the research of this group, holds that there is a way to do philosophy which is a middle course between abstract normative philosophy of science and descriptive social studies of science. On the one hand it is argued with social studies of science that philosophy should take notice of what scientists (...) actually do. On the other hand, however, it is claimed that philosophy can and should aim to reveal cognitive patterns in the processes and products of scientific and common sense knowledge. Since it is thought that those patterns can function as guidelines in new research and/or in research in other disciplines, philosophy can nevertheless hold on to the normative aim which is characteristic of 'classical' philosophy of science. Compared to this common assumption, there is a diversity of subjects. Some papers deal with general problems of science, knowledge, cognition and argumentation, others with topics relating to foundational problems of particular sciences. Therefore this volume is of interest to philosophers of science, to philosophers of knowledge and argumentation in general, to philosophers of mind, as well as for scientists working in the physical and applied sciences, biology, psychology and economy who are interested in the foundations of their disciplines. After a foreword by Leszek Nowak and a general introduction by the editors, the book is divided into four parts, with special introductions. - I: Conceptual Analysis in Service of Various Research Programmes (Henk Zandvoort, Rein Vos, Rick Looijen, Gerben Stavenga, Renée Dalitz); - II: The Logic of the Evaluation of Arguments, Hypotheses, Default Rules, and Interesting Theorems (Erik Krabbe, Theo Kuipers, Alfons Keupink, Maarten Janssen/Yao-Hua Tan, Bert Hamminga); - III: Three Challenges to the Truth Approximation Programme (Sjoerd Zwart, Hinne Hettema/Theo Kuipers, Roberto Festa); - IV: Explicating Psychological Intuitions (Anne-Ruth Mackor, Jeanne Peijnenburg, Lex Guichard, Michel ter Hark). The Groningen research group was recently qualified, by an official international assessment committee, as one of the best philosophy research groups in the Netherlands. (shrink)

Introduction. Bert HAMMINGA and Neil DE MARCHI: Préface. Bert HAMMINGA and Neil DE MARCHI: Idealization and the Defence of Economics: Notes Toward a History. Part I: General Observations on Idealization in Economics. Kevin D. HOOVER: Six Queries about Idealization in an Empirical Context. Bernard WALLISER: Three Generalization Processes for Economic Models. Steven COOK and David HENDRY: The Theory of Reduction in Econometrics. Maarten C.W. JANSSEN: Economic Models and Their Applications. Adolfo GARCÍA DE LA SIENRA: Idealization and Empirical Adequacy in (...) Economic Theory. Izabella NOWAKOWA and Leszek NOWAK: On Correspondence between Economic Theories. Uskali MÄKI: Isolation, Idealization and Truth in Economics. Part II: Case Studies of Idealization in Economics. Nancy CARTWRIGHT: Mill and Menger: Ideal Elements and Stable Tendencies. Wolfgang BALZER: Exchange Versus Influence: A Case of Idealization. Kees COOLS, Bert HAMMINGA, Theo A.F. KUIPERS: Truth Approximation by Concretization in Capital Structure Theory. Daniel M. HAUSMAN: Paul Samuelson as Dr. Frankenstein: When an Idealization Runs Amuck. Hugo A. KEUZENKAMP: What if an Idealization is Problematic? The Case of the Homogeneity Condition in Consumer Demand. Werner DIEDERICH: Nowak on Explanation and Idealization in Marx's 'Capital'. Gérard JORLAND: Idealization and Transformation. Jack BIRNER: Idealizations and Theory Development in Economics. Some History and Logic of the Logic Discovery. Discussions. Leszek NOWAK: The Idealizational Methodology and Economics. Replies to Diederich, Hoover, Janssen, Jorland and Mäki. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Journal of the History of Philosophy 39.4 (2001) 587-589 [Access article in PDF] Maarten J. F. M. Hoenen and Paul J. J. M. Bakker, editors. Philosophie und Theologie des ausgehenden Mittelalters: Marsilius von Inghen und das Denken seiner Zeit. Leiden: Brill, 2000. Pp. x + 322. Cloth, $98.00. Albert of Saxony, Nicholas Oresme, and Marsilius of Inghen were among the fourteenth-century Parisian masters of arts who were influenced (...) by Buridan's philosophy and, while continuing as master of arts, simultaneously pursued a degree in theology. Marsilius, born around 1340, was a very popular master in Paris from 1362. In 1366 he began the study of theology. He did not finish his theological studies in Paris, but later at the new university of Heidelberg (1393-4), where he held a chair of theology until his death in 1396.Marsilius wrote a number of treatises on logic, commentaries on Aristotle's works, commentaries on the Bible, a commentary on the Sentences and some tracts on ecclesiastical politics. His works were widely read and he was regarded as a representative of the via moderna and nominalist philosophy in the fifteenth century. Several scholars are currently studying and editing Marsilius's works. The collection of essays Philosophy and Theology in late Middle Ages, edited by Hoenen and Bakker, is a report on this ongoing work. It has been preceded by two similar research reports, Marsilius of Inghen, edited by H. Braakhuis and M. Hoenen (1992), and Marsilius von Inghen, Werk und Wirkung, edited by S. Wielgus (1993). Most of the articles in the present volume deal with special historical and doxographical questions. In this sense the title of the book is somewhat misleading, though the contributions themselves are of high scholarly quality and contain lots of interesting historical details and new research results.The first part involves four papers on late medieval conceptions of the relationship between philosophy and theology. Hoenen describes the increasing separation of theology from logic and philosophy as the context of Marsilius's theological work, using as examples his treatment of the doctrines of divine foreknowledge and creation from nothing. Sigrid Müller argues that those fourteenth-century theologians who were called representatives of nominalistic theology in the fifteenth century, such as William [End Page 587] of Ockham, Gregory of Rimini, and Marsilius Inghen, had a similar view of the relationship between language and reality, though their theological sources and solutions to particular questions varied. Manfred Schulze sheds light on Marsilius's theology by comparing his views on predestination, grace, and the freedom of the will with those of Gregory of Rimini and Gabriel Biel. These papers are preceded by William Courtenay's historically illuminating study of the teachers of theology in Paris during 1362-77.The papers on the relationship between philosophy and theology are learned and useful but somewhat general. What does it mean that philosophy and theology were increasingly separated by authors who after all were keen to make logical and semantic distinctions? Further light might have been shed on this question by concentrating more on the widely discussed controversies about logic and the Trinity which have recently been considered by many scholars. One position was to criticize the special logic of faith and to show that the alleged logical problems in theological doctrines are mainly based on incorrect interpretations of revealed truths. Showing this demanded discussions of logic and semantics in theology, as can also be seen in question nine of the first book of Marsilius of Inghen's Questions on the Sentences.The second part involves papers on specific themes in the works of Marsilius and attempts to identify some anonymous works. Henk Braakhuis deals with Marsilius's view on the question of the different senses of a proposition, which was mentioned in the famous prohibition statute of the Faculty of Arts in Paris in 1340 and was found interesting in many contexts, one of them being Aristotle's theory of sophistic refutations. Braakhuis's paper, which is a valuable contribution to the history of logic, contains... (shrink)

The issue of whether the writings of Thomas Aquinas show internal contradictions has not only stirred readers from his earliest, often critical, reception, but also led to the emergence of a literary genre that has crucial relevance to the history of medieval Thomism. Concordances were drawn up which listed Thomas' contradictory statements and, in most cases, tried to disguise the appearance of contradiction by exegesis. But what was at stake in this interpretive endeavor? What role did the concordances play in (...) shaping Thomism? What tensions did they reveal in the works of Thomas? The book aims to investigate these questions and puts the concordance of Peter of Bergamo (1482), which represents the most important example of this type of text, at the center of the investigation. Contributors are Marieke Abram, Kent Emery, Jr., Maarten J.F.M. Hoenen, Isabel Iribarren, Thomas Jeschke, Catherine König-Pralong, Mario Meliadò, Silvia Negri, Zornitsa Radeva, and Peter Walter. (shrink)

Hybrid languages are expansions of propositional modal languages which can refer to worlds. The use of strong hybrid languages dates back to at least [Pri67], but recent work has focussed on a more constrained system called $\mathscr{H}$. We show in detail that $\mathscr{H}$ is modally natural. We begin by studying its expressivity, and provide model theoretic characterizations and a syntactic characterization. The key result to emerge is that $\mathscr{H}$ corresponds to the fragment of first-order logic which is invariant for generated (...) submodels. We then show that $\mathscr{H}$ enjoys interpolation, provide counterexamples for its finite variable fragments, and show that weak interpolation holds for the sublanguage $\mathscr{H}$. Finally, we provide complexity results for $\mathscr{H}$ and other fragments and variants, and sharpen known undecidability results for $\mathscr{H}$. (shrink)

The globalization in business and tourism becomes crucial more and more for the economical sustainability of local communities. In the presence of an epidemic outbreak, there must be such a decision on the policy by the host community as whether to accept visitors or not, the number of acceptable visitors, or the condition for acceptable visitors. Making use of an SIRI type of mathematical model, we consider the influence of visitors on the spread of a reinfectious disease in a community, (...) especially assuming that a certain proportion of accepted visitors are immune. The reinfectivity of disease here means that the immunity gained by either vaccination or recovery is imperfect. With the mathematical results obtained by our analysis on the model for such an epidemic dynamics of resident and visitor populations, we find that the acceptance of visitors could have a significant influence on the disease’s endemicity in the community, either suppressive or supportive. (shrink)

Quantified hybrid logic is quantified modal logic extended with apparatus for naming states and asserting that a formula is true at a named state. While interpolation and Beth's definability theorem fail in a number of well-known quantified modal logics , their counterparts in quantified hybrid logic have these properties. These are special cases of the main result of the paper: the quantified hybrid logic of any class of frames definable in the bounded fragment of first-order logic has the interpolation property, (...) irrespective of whether varying, constant, expanding, or contracting domains are assumed. (shrink)