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First we give an overview about variants of visibility and related problems. Then we prove that some guarding and covering problems are NP-hard for ortho-polygons with holes, using a so-called vertex cover technique.

D. T. Lee and A. K. Lin [2] proved that VERTEX-GUARDING and POINT-GUARDING are NP-hard for simple polygons. We prove that those problems are NP-hard for ortho-polygons, too.

We show that given a simple Polygon P it is NP-hard to determine the smallest α ∈ [0, π] such that P can be illuminated by α-vertexlights, if we place exactly one α-vertexlight in each vertex of P.

We consider the problem of quadrilaterizing an orthogonal polygon P, that is to decompose P into nonoverlapping convex quadrangles without adding new vertices. In this paper we present a CREW-algorithm for this problem which runs in O time using Θ processors if the rectangle decomposition of P is given, and Θ processors if not. Furthermore we will show that the latter result is optimal if the polygon is allowed to contain holes.

For each vertex of a simple polygon P an integer valued weight is given. We consider the path p1, p2, ..., pk in P which is created according to the following strategy: p1 is a designated start vertex s and pi+1 is obtained by choosing the vertex with smallest weight among all vertices visible from pi and different from p1, p2, ..., pi. If there is no such vertex the path is finished. This path is called geometric lexicographic dead end (...) path. We shall prove the problem of determining whether a distinguished vertex t of P is on the geometric lexicographic dead end path or not to be P-complete. (shrink)

Summary A large survey of German and Israeli younger and older adolescents was conducted to reveal their opinions and attitudes towards violence and aggression, their personal engagement in aggressive and violent behaviors in and outside the school environment, their attitudes toward physical activity, their engagement in physical activity, and the linkage between physical activity engagement and conductance of violence and aggression. The findings point out that there are more similarities than differences between German and Israeli adolescents concerning violence and aggression (...) in and outside schools. No linkage between physical activity involvement and the extent of violent and/or aggressive acts is found. The findings pertaining adolescents’ opinions and attitudes toward aggression and violence and their behaviors in and outside school are encouraging. (shrink)

Advancements in biological ageing research have shown that age-related diseases may be fought more effectively in the future by directly intervening into the ageing process. This prospect is associated with hopes for solving problems of demographic change. It also addresses raising awareness for complex ethical, legal and social issues that have hardly been a topic of discussion to date. Therefore, as the objective of our project, an interdisciplinary discourse module entitled “Ethics of Biogerontology” was developed to initiate a social debate (...) on the ethical, legal, and societal implications of biogerontology. The discourse module focuses on competences and argumentation skills and was developed with experts from relevant disciplines, e.g. biogerontology, social gerontology, philosophy, geriatrics, and medical ethics. Concepts of age and ageing are tightly interlinked with biogerontology and are as such relevant as teaching contents of the discourse module. The course module was tested in eight discourse teaching projects in research, medicine, and education in various partner institutions and evaluated based on an ethical competence model. This article describes the conception, including the learning objectives, of such a teaching course and the associated teaching contents. It also gives a justification for their selection. Finally, we summarize the results of the evaluation. (shrink)

The present study examines the work of a group of medical scientists as they identify interpretative ‘pitfalls’ – recurrent sources of error – in the use of a new radiographic technique, formulate suggestions on how these pitfalls can be avoided and communicate their findings in the form of a scientific publication. The analysis focuses on a session in which previously diagnosed cases are discussed, and demonstrates the ways in which a certain source of diagnostic error gradually emerges as a taken-for-granted (...) in the interaction. An increased sense of recognition, recurrence and typicality is discernible in the treatment of the cases. Talk characterized by expansions and elaborations, displays of understanding in the form of reformulations, understanding checks, and so on, leave room for brief typifications and reifications of interpretative difficulties in characteristics of the imaging technique. Topical treatment of perception and interpretation, as well as embodied engagement, become decreasingly salient. It is argued that the abstracted formulations in the published text rely on the case-by-case working up of generality from particularity; from individualized accounts of why ‘I’ interpreted the image in a certain way to proffered generalizations achieved through articulated perceptions of a generalized ‘one’. If these proffers are ratified, a potential ground is established for the consensual formulation of a pitfall. The formulation of novel instructions is consequently made relevant, projecting a re-instructed diagnostic practice. (shrink)

Hans Drieschs "Wirklichkeitslehre".--Emanuel Laskers "Philosophie des Unvollendbar".--Carl Ludwig Schleich und die "neue Epoche der Weltanschauung".--Fr. J. Kurt Geisslers "System der Seinsgebiete".--Graf Hermann Keyserlings "Gefüge der Welt", "Reisetagebuch eines Philosophen", "Unsterblichkeit", "Prolegomena zur Naturphilosophie".--Henri Bergsons "Schöpferische Entwicklung".--L. William Sterns "Person und Sache".--G. Heymans "psychischer monismus".--Wilhelm Wundts "Sinnliche und übersinnliche Welt".--Emil Boutroux und die "Kontingenz der Naturgesetze".--Rudolf Otto, Christof Schrempf, Romain Rolland und die intuitive Methode des Welterkenens.--Rudolf Steiners "Philosophie der Freiheit".--Erich Becher und die fremddienliche Zweckmässigkeit.--Edmund Husserl, Heinrich Rickert, Emil Lask, (...) Leonard Nelson und der methodologische Gott.--Anhang: Eucken, Dessoir, Scheler, Heiler, James, Bo Yin Ra, Oesterreich, Schneider. (shrink)

Transcendental Pragmatics and Discourse Ethics. Elements and Perspectives of Apel's Discourse-Philosophy. The author follows Apel's intellectual biography and shows the conception of a critique of meaning qua ‘reflection upon the discourse within the discourse’ to be the centre of Apel's language-pragmatic ‘Transformation of Philosophy’. Beginning with an explication of the situation of a speaker/thinker, especially of the situation of a philosophising speaker/thinker, Apel reconstructs a two fold apriori of communication: Every thought is situated within the context of a particular, historically (...) evolved, community of language and interaction. At the same time, however, the validity-claims of thoughts transcend the context of their origin towards an unlimited community of argumentation. On the basis of the first apriori Apel criticises the methodical solipsism as well as the objectivism of modern philosophy and theory of science. Drawing upon the second apriori he develops a universalist critique of meaning of relativism and contextualism. In the sixties and seventies Apel worked out a differentiated theory of the – more or less – communicatively cognizing humanities and set it apart from the theory of the causal-explanatory natural sciences, thus challenging the objectivism of a Theory of Unified Science. Building upon this work Transcendental Pragmatics, as developed by Apel and others, sets philosophy primarily two tasks: firstly, a internal reconstruction of argumentative discourse as the situation of speech and thought which seeks to elucidate the conditions of the meaningfulness, i. e. the presuppositions, of discourse. These presuppositions comprise, thus Apel with Habermas, the four validity-claims to intelligibility, sincerety/credibility, truth and normative rightness/legitimacy. Their moral content consists, thus Apel, not only in the recognition of the equality of all beings capable of discursive reasoning but also in their recognition of a co-responsibility for the realizability of discourses and of responsibility. The author argues that the existence of a co-responsibility of this kind is indisputable because the discursive claims to validity are intertwined with a set of ‘primordial promises of dialogue’. Only with the elucidation and explication of these promises can the reconstruction of the internal conditions of discourse be completed.The second task of a pragmatics of argumentation isthe strict resp. actual reflection of the thinker upon the presuppositions of the discourse in which he currently engages. This reflection has a Socratic character and can only be done in the form of discussion and debate with critics of the reconstruction. In this context, the author proposes a method of Socratic reflection upon the presuppositions of dialogue which suspends the usual, theoretically oriented, attitude of the scientist and the philosopher in favour of an actual reflective attitude. Within a dialogue with a sceptic who doubts one of the results of the internal reconstruction of dialogical presuppositions, say X, it is tested whether his doubt as to the unrestricted validity of X can be understood as a sincere contribution to the current dialogue or whether this particular sceptical thesis does not make sense, because it is incompatible with the role of a sincere participant of argumentation which, after all, the sceptic cannot refuse to claim for himself.Finally the author explains Apel's characterization of the tension between “Discourse and Responsibility”. In the course of discussions with Max Weber, Lawrence Kohlberg, Hans Jonas et al., Apel formulates and justifies an ethics of responsibility and gives an affirmative answer to the crucial question of whether the fulfilment of the moral obligations connected with the recognition of co-responsibility can be demanded within the non-dialogical circumstances of social reality. Apel's answer employs the idea of counter-strategies which are morally legitimate in virtue of their being worthy of argumentative consensus. (shrink)

Nach drei Semestern war ich 1951 von München nach Köln umgezogen, weil ich mit Wirtschaftswissenschaft Ernst machen wollte. Im wirtschaftswissenschaftlichen Seminar traf ich zum ersten Mal auf Hans Albert. Obwohl er ein halbes Jahrzehnt älter war als ich, arbeitete er als studentischer Amanuensis in der ökonomischen Bibliothek.