Feedback control in neural systems is ubiquitous. Here we study the mathematics of nonlinear feedback control. We compare models in which the input is multiplied by a dynamic gain (multiplicative control) with models in which the input is divided by a dynamic attenuation (divisive control). The gain signal (resp. the attenuation signal) is obtained through a concatenation of an instantaneous nonlinearity and a linear low-pass filter operating on the output of the feedback loop. For input steps, the dynamics of gain (...) and attenuation can be very different, depending on the mathematical form of the nonlinearity and the ordering of the nonlinearity and the filtering in the feedback loop. Further, the dynamics of feedback control can be strongly asymmetrical for increment versus decrement steps of the input. Nevertheless, for each of the models studied, the nonlinearity in the feedback loop can be chosen such that immediately after an input step, the dynamics of feedback control is symmetric with respect to increments versus decrements. Finally, we study the dynamics of the output of the control loops and find conditions under which overshoots and undershoots of the output relative to the steady-state output occur when the models are stimulated with low-pass filtered steps. For small steps at the input, overshoots and undershoots of the output do not occur when the filtering in the control path is faster than the low-pass filtering at the input. For large steps at the input, however, results depend on the model, and for some of the models, multiple overshoots and undershoots can occur even with a fast control path. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Kinship:The Relationship Between Johnstone's Ideas about Philosophical Argument and the Pragma-Dialectical Theory of ArgumentationFrans H. van Eemeren and Peter Houtlosser1. Johnstone on the Nature of Philosophical ArgumentAs he himself declared in Validity and Rhetoric in Philosophical Argument (1978, 1), the late philosopher Henry W. Johnstone Jr. devoted a long period of his professional life to clarifying the nature of philosophical argument. His well-known view was that philosophical arguments are (...) sui generis, i.e., not to be judged by the standards of argumentation in science or everyday discourse. Philosophical arguments are not ad rem, but are based on premises that are expressed or implied commitments of a party in dialogue. This is why philosophical argumentation is, according to Johnstone, always ad hominem. In philosophical argumentation, every ad rem argument begs the question.Usually, ad hominem argumentation is dismissed as invalid. Johnstone, however, maintains that making use of argumentum ad hominem is the only way to establish a philosophical conclusion. In an argumentum ad hominem, inferences are drawn from propositions stated or implied by the other party and critical questions are raised about the conclusions that were drawn, so that it can be used to refute a philosophical position by showing that this position is inconsistent. As Walton (2001) rightly observes, this type of ad hominem argumentation boils down to arguing from commitments of the other party, i.e., ex concessis.The use of ad hominem argumentation as the criticism of a position in terms of its own presuppositions is, in Johnstone's view, the only valid argument in philosophy, if any philosophical argument is indeed valid. All philosophical polemic is in this perspective in fact addressed ad hominem. This applies not only to philosophical argumentation that concerns self-referential refutation but also to other ad hominem types of philosophical argumentation, including the tu quoque argument (1978, 11–12).According to Johnstone, there is no objective criterion for determining the validity of ad hominem argumentation. Validity must, says Johnstone in the [End Page 51] epilogue of his collected essays on philosophical argument, be viewed as "a regulative ideal" (135). Much earlier, Johnstone had already come to the conclusion that "the valid argument is the one that maintains philosophical discussion" (38). It is this self-perpetuating feature that is the distinctive rationality of philosophy. By forcing the interlocutor to elaborate his philosophical position rather than just repeat it, the gap between the interlocutors is bridged.In order to distinguish between constructive persuasive argumentation and mere repetition or other forms of paralyzing the discourse, the line must be drawn between responsible and irresponsible persuasion. This is a problem for Johnstone. Where the Ancients solved the problem by insisting that the persuader be virtuous, Johnstone proposed to base the distinction between responsible and irresponsible persuasion on the attitude of the philosopher and his interest in maintaining the philosophical enterprise. The philosopher is a critic who criticizes con amore. His intention to do so, however, is revealed "only in the way he goes about his work" (84).A more down to earth criterion for responsible persuasion that Johnstone proposed is that the discourse should not tend to degenerate. Logic, as the discipline concerned with reason, serves to prevent the discussion from degenerating, but it can do so only if the parties concerned have jointly committed themselves to certain logical principles. If in philosophical argument a defendant is under no obligation to acknowledge an inconsistency when the other party points out an inconsistency in his position, then the other party's criticism cannot count as valid. According to Johnstone, however, it will depend on the parties' presuppositions whether or not they consider two statements as being inconsistent. In other words, what is inconsistent for the one party may not be inconsistent for the other party.Few obligations are imposed on everyone; most obligations arise from commitments made by specific individuals or groups of individuals. As Johnstone says, "Even the cogent philosophical argument is not, of course, absolutely cogent; it is cogent only relatively to interlocutors who maintain the premises on which it depends" (27). Once we abandon the search for objective conditions under which philosophical arguments can be valid, according... (shrink)

This systematic review aimed to provide an overview of earlier research on the relationships between age conceptualizations and indicators of employability. We have conducted a systematic literature search using PsycINFO, Academic Search Premier, Business Source Complete, CINAHL, ERIC, MEDLINE, and Science Direct. Two raters evaluated the articles and subsequently distinguished k = 41 studies that met the inclusion criteria for this systematic review. Our review revealed that many researchers adopted different operationalizations to measure employability. Moreover, most studies included calendar age (...) as indicator of aging at work, and were based on a cross-sectional design. Based on the Standardized Index of Convergence method, different types of evidence were found for the relationships between age and the employability measures. For relationships between psychosocial age and lifespan age, on the one hand, and employability measures, on the other hand, too few studies were found to draw conclusions. Yet, for relationships between calendar age and labor market-based measures strong consistent negative relationships were found across the studies, and moderately strong positive relationships were found for functional age and labor market- based measures. For organizational age and both competence-based as well as labor market-based measures moderately strong negative relationships were found. We discuss the implications of these results and propose a research agenda for future studies. (shrink)

Despite the proliferation of research on ethical leadership, there remains a limited understanding of how specifically the assumingly moral component of this leadership style affects employee behavior. Taking an identity perspective, we integrate the ethical leadership literature with research on the dynamics of the moral self-concept to posit that ethical leadership will foster a sense of moral identity among employees, which then inspires followers to adopt more ethical actions, such as increased organization citizenship behavior. We further argue that these identity (...) effects should be more pronounced when leaders are perceived to be group prototypical, as their actions then speak louder to followers’ sense of identity. Two studies—a scenario experiment with 138 participants and a field study with 225 employees—provided support for our hypothesized moderated mediation model. Perceived ethical leadership positively affected OCB via followers’ moral identity but only under conditions of high perceived leader group prototypicality. We discuss how the identity pathway of ethical leadership can facilitate novel theorizing about moral transference. Our findings also suggest that, when hiring external ethical leaders or training internal managers, practitioners are well advised to consider that these individuals may only be effective in morally transforming followers when they are perceived as prototypical for the group. (shrink)

Lysophosphatidic acid (LPA) is a lipid mediator with a wide variety of biological actions, particularly as an inducer of cell proliferation, migration and survival. LPA binds to specific G‐protein‐coupled receptors and thereby activates multiple signal transduction pathways, including those initiated by the small GTPases Ras, Rho, and Rac. LPA signaling has been implicated in such diverse processes as wound healing, brain development, vascular remodeling and tumor progression. Knowledge of precisely how and where LPA is produced has long proved elusive. Excitingly, (...) it has recently been discovered that LPA is generated from precursors by ‘autotaxin’, a once enigmatic exo‐phosphodiesterase implicated in tumor cell motility. Exogenous phospholipases D can also produce LPA, which may contribute to their toxicity. Here we review recent progress in our understanding of LPA bioactivity, signaling and synthesis. BioEssays 26:870–881, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

In ‘The making of argumentation theory’ van Eemeren and van Haaften describe the contributions made to the five components of a full-fledged research program of argumentation theory by four prominent approaches to the discipline: formal dialectics, rhetoric/pragmalinguistics, informal logic, and pragma-dialectics. Most of these approaches do not contribute to all components, but to some in particular. Starting from the pragma-dialectical view of the relationship between dialectical reasonableness and rhetorical effectiveness – the crucial issue in argumentation theory – van Eemeren and (...) van Haaften explain the positions taken by representatives from the approaches discussed and indicate where they differ from the pragma-dialectical approach. It transpires that approaches focusing on dialectical reasonableness are, next to pragma-dialectics, formal dialectics and informal logic; approaches focusing on rhetorical effectiveness are, next to pragma-dialectics, rhetoric and pragmalinguistics, and the informal logician Tindale. When it comes to the relationship between dialectical reasonableness and rhetorical effectiveness, some interest in it is shown in rhetoric and pragmalinguistics, but only in pragma-dialectics and in Tindale’s work is it a real focus. The main difference between Tindale’s view and the pragma-dialectical view is that in pragma-dialectics the decisive role in deciding about reasonableness is assigned to a code of conduct for reasonable argumentative discourse and in Tindale’s approach this role is assigned to Tindale’s interpretation of the Perelmanian universal audience. (shrink)

This article examines the effects of strategic and substantive news on political cynicism, turnout intention and voter uncertainty, drawing on two experiments. We found that among less politically knowledgeable citizens, all news mobilizes, but strategic news also induces cynicism. For the more knowledgeable citizens, we found that the combination of strategic and substantive news yields slightly less cynicism and that substantive news makes these citizens reconsider their voting choice. Overall, we only found favorable or neutral effects among the more knowledgeable, (...) while we found both favorable and unfavorable effects among the less knowledgeable. The implications for news effects research are discussed. (shrink)

Pragmatics and dialectics are two disciplines which have been amongst the first and most important partners for argument studies in the exploration of the complex realm of communication. Treating argumentation as a construct consisting of premises and conclusion allows for investigating some interesting properties of the phenomenon of reasoning, but does not capture a variety of aspects related to the usage of natural language and dialogical context in which real-life argumentation is typically embedded. This special issue explores some of the (...) fascinating research questions which emerge when we move beyond logic into the territory of the pragmatics and dialectics of argument. (shrink)

In this book two of the leading figures in argumentation theory present a view of argumentation as a means of resolving differences of opinion by testing the acceptability of the disputed positions. Their model of a 'critical discussion' serves as a theoretical tool for analysing, evaluating and producing argumentative discourse. They develop a method for the reconstruction of argumentative discourse that takes into account all aspects that are relevant to a critical assessment. They also propose a practical code of behaviour (...) for discussants who want to resolve their differences in a reasonable way. This is a major contribution to the study of argumentation and will be of particular value to professionals and graduate students in speech communication, informal logic, rhetoric, critical thinking, linguistics, and philosophy. (shrink)

The objective of the new series, "Molecular Biology, Biochemistry and Biophysics", of which this brochure forms the first volume, is to produce more than another compilation of data. It is hoped that the new series will help the individual "specialist" keep abreast of important developments in the natural sciences at the molecular and subcellular level in fields complementary to his own. The predominant aim is not so much to increase the ever-growing body of information in an encyclopedic fashion but rather (...) to give, in addition to a well rounded factual presentation of subjects which have reached a degree of maturation, a leitmotiv developed by the individual authors from a more personal point of view. The reader should thus be able to use these mono graphs not only for acquisition of knowledge but as a source of further motiva tion in his own work. This latter and more consequential aim of the monograph series is one of the reasons for presenting here a most unusual talk which should enable the reader to sit back and view his own efforts in the context of science and creative attempts as a whole. The lecture is the virtually unknown inaugural address of the Dutch physical chemist JACOBUS HENRICUS VAN'T HOFF. As is shown in his short biography presented on pages 3 and 4 the principal thoughts of the molecular biologist of today are akin to his own and he clearly recognized the universality of molecular life processes. (shrink)

This article explores the role of surface ambiguities in referring expressions, and how the risk of such ambiguities should be taken into account by an algorithm that generates referring expressions, if these expressions are to be optimally effective for a hearer. We focus on the ambiguities that arise when adjectives occur in coordinated structures. The central idea is to use statistical information about lexical co-occurrence to estimate which interpretation of a phrase is most likely for human readers, and to avoid (...) generating phrases where misunderstandings are likely. Various aspects of the problem were explored in three experiments in which responses by human participants provided evidence about which reading was most likely for certain phrases, which phrases were deemed most suitable for particular referents, and the speed at which various phrases were read. We found a preference for ‘‘clear’’ expressions to ‘‘unclear’’ ones, but if several of the expressions are ‘‘clear,’’ then brief expressions are preferred over non-brief ones even though the brief ones are syntactically ambiguous and the non-brief ones are not; the notion of clarity was made precise using Kilgarriff's Word Sketches. We outline an implemented algorithm that generates noun phrases conforming to our hypotheses. (shrink)

Results of two survey studies are presented. It is shown that attitudes of the public about "technology in general" are not stable and can easily be affected by how the subject is introduced. Eight areas of technology are compared on the basis of empirical relations in attitudinal judgments, in attribute ratings, in self- assigned importance weights of attributes, and in importance of reference groups and persons. On the basis of similarities in these four kinds of judgments, three clusters of technology (...) areas were identified: a cluster of modern reproductive technologies, an information cluster containing automation, computer, and communication technologies, and a cluster containing nuclear energy and military technology. The attitude toward "technology in general" can not be considered as an aggregation of attitudes toward these areas of technology: The relations between general attitude and specific attitudes are only moderate to negligible. (shrink)