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)

INTRODUCTION TO ASPECTS OF FACE PROCESSING: TEN QUESTIONS IN NEED OF ANSWERS. HD Ellis 1. INTRODUCTION These proceedings of the first international ...

On Islamic practices, doctrines and on Islamic ethics.

Guidelines for a model bride in Islam based on Islamic teachings; includes stories of six exemplary Muslim wives during Prophet Muhammad's time.

The present volume contains the lectures and papers given at the 1994 international conference on hermeneutics in Halle (Germany). The conference aimed at a state of the art in the light of recent developments in science and humanities. The place in which the conference was held is renowned for its centuries-old tradition in hermeneutics and among the lectures there are indeed some devoted to this history. For the most part, however, the papers concentrate on present-day problems in fields as different (...) as comparative literature, religious studies, bible exegesis, esthetics, social sciences, intercultural dialogue. The theme of the conference, "strangeness and familiarity", reflects the tension in which any interpretation process is situated and that any theory of interpretation has to account for. The contributions to the volume are in German and French. (shrink)

SUFFERING HUMAN AND DIVINE INTRODUCTION I KNEW when I asked Dr. H. Wheeler Robinson to write this volume on Suffering that I was giving him the most difficult ...

The doctrine of the Trinity developed in response to a range of theological interests, among them the project of reconciling claims about the divinity of Christ with monotheism and massaging Christian doctrine into the ambient (largely Platonic) philosophical framework of the period. More recently the Trinity doctrine has been deployed to promote normative claims concerning human nature, human relationships and social justice. During the past two decades analytic philosophers of religion have increasingly engaged with the doctrine. There are, however, a (...) number of foundational questions that have not been addressed in the philosophical literature. The Trinity: A Philosophical Investigation considers the competing accounts of the Trinity doctrine, whether orthodox or heterodox, and aims to respond to objections and explicate their motivations and entailments. (shrink)

Receptor‐mediated stimulation induces massive actin polymerization and cyto‐skeletal reorganization. The activity of a potent actin‐modulating protein, gelsolin, is regulated both by Ca2+ and polyphos‐phoinositides, and it may have a pivotal role in restructuring the actin cytoskeleton in response to agonist stimulation. Structure‐function analysis of gelsolin has (1) indicated that its NH2‐terminal half is primarily responsible for modulating actin filament length and polymerization; and (2) elucidated mechanisms by which Ca2+ and phospholipids may regulate such functions. Gelsolin is functionally and structurally similar (...) to villin, another Ca2+‐activated actin‐severing protein found in microvilli, suggesting that gelsolin may be a prototype of this family of actin‐modulating proteins. A molecular variant of gelsolin is secreted and may be involved in the clearance of actin filaments released during tissue damage. The two forms of gelsolin are encoded by a single gene, and distinct messages are derived by alternative message splicing. (shrink)