The aim of this work was to compare experimental investigations on effects of lidocaine, calcium and, BRL 34915 on reentries to simulated data obtained by use of a model of propagation based on the Huygens' constriction method already described in previous works. Calcium and lidocaine effects are investigated on anisotropic conduction conditions. In both cases, reduction in conduction velocities are observed. In lidocaine case, a refractory area is located along the longitudinal axis. In agreement with experimental electrical mapping, the simulations (...) show that the stabilization of reentrant excitation is mainly due to the existence of this refractory area around which the reentrant circuit can develop. The experimental study shows that BRL 34915 has both arrhythmogenic and antiarrhythmic effects. A detailed electrophysiological analysis has shown that drug infusion act on normal cardiac cells by decreasing the relative and absolute refractory period. BRL 34915 action is simulated by a decrease in the refractory period showing that the time frequency of the reentrant activity is increased and that the spatial size where the reentry is developing is becoming smaller. These two effects are arrhythmogenic, the simulated data being so in good agreement with the experimental ones. (shrink)

We generally agree with Burt's thesis. However, we note that the author did not discuss epigenetics, the study of how the environment can alter gene structure and function. Given epigenetic mechanisms, the utility of polygenic risk scores (PRS) is limited in studies of development and mental illness. Finally, in this commentary we expand upon the risks of reliance upon PRSs.

This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is (...) assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities. (shrink)

Spatial and temporal heterogeneity are often described as important factors having a strong impact on biodiversity. The effect of heterogeneity is in most cases analyzed by the response of biotic interactions such as competition of predation. It may also modify intrinsic population properties such as growth rate. Most of the studies are theoretic since it is often difficult to manipulate spatial heterogeneity in practice. Despite the large number of studies dealing with this topics, it is still difficult to understand how (...) the heterogeneity affects populations dynamics. On the basis of a very simple model, this paper aims to explicitly provide a simple mechanism which can explain why spatial heterogeneity may be a favorable factor for production. We consider a two patch model and a logistic growth is assumed on each patch. A general condition on the migration rates and the local subpopulation growth rates is provided under which the total carrying capacity is higher than the sum of the local carrying capacities, which is not intuitive. As we illustrate, this result is robust under stochastic perturbations. (shrink)

The excessive and unsustainable exploitation of our marine resources has led to the promotion of marine reserves as a fisheries management tool. Marine reserves, areas in which fishing is restricted or prohibited, can offer opportunities for the recovery of exploited stock and fishery enhancement. This study examines the impact of the creation of marine protected areas, from both economic and biological perspectives. The consequences of reserve establishment on the long-run equilibrium fish biomass and fishery catch levels are evaluated. We include (...) reserve size as control variable to maximize catch at equilibrium. A continuous time model is used to simulate the effects of reserve size on fishing catch. Fish movements between the sites is assumed to take place at a faster time scale than the variation of the stock and the change of the fleet size. We take advantage of these two time scales to derive a reduced model governing the dynamics of the total fish stock and the fishing effort. Simulation results suggest that the establishment of a protected marine reserve will always lead to an increase in total fish biomass, an optimal size of a marine reserve can achieve to maximize the catch at equilibrium. (shrink)

The balance between births and deaths in an age-structured population is strongly influenced by the spatial distribution of sub-populations. Our aim was to describe the demographic process of a fish population in an hierarchical dendritic river network, by taking into account the possible movements of individuals. We tried also to quantify the effect of river network changes (damming or channelling) on the global fish population dynamics. The Salmo trutta life pattern was taken as an example for.We proposed a model which (...) includes the demographic and the migration processes, considering migration fast compared to demography. The population was divided into three age-classes and subdivided into fifteen spatial patches, thus having 45 state variables. Both processes were described by means of constant transfer coefficients, so we were dealing with a linear system of difference equations. The discrete case of the variable aggregation method allowed the study of the system through the dominant elements of a much simpler linear system with only three global variables: the total number of individuals in each age-class. (shrink)

Ventricular Fibrillation is responsible for a majority of sudden cardiac death, but little is known about how ventricular tachycardia (VT) degenerates into ventricular fibrillation. Several clinical studies focused only on preventing VT with a class III antiarrhythmic drug resulted in many deaths. Our simulations investigate the interactions between an antiarrhythmic drug likely to suppress a VT and a Figure 8 reentry. A parameter AAR is introduced to increase the action potential duration and therefore simulate various Class III drugs. Simulations are (...) ran under several conditions (phases of the reentry, values of AAR, durations). They show that a VT can be suppressed whatever the phase of the reentry but it strongly depends on the duration of the effect. It confirms that a drug which can suppress a reentry can also worsen it. It also shows a great variety of activation patterns and thus the complexity of antiarrhythmic drugs effects. Simulations also demonstrate that suppressing VT is an increasing function of AAR. (shrink)

In this work we deal with a general class of spatially distributed periodic SIS epidemic models with two time scales. We let susceptible and infected individuals migrate between patches with periodic time dependent migration rates. The existence of two time scales in the system allows to describe certain features of the asymptotic behavior of its solutions with the help of a less dimensional, aggregated, system. We derive global reproduction numbers governing the general spatially distributed nonautonomous system through the aggregated system. (...) We apply this result when the mass action law and the frequency dependent transmission law are considered. Comparing these global reproductive numbers to their non spatially distributed counterparts yields the following: adequate periodic migration rates allow global persistence or eradication of epidemics where locally, in absence of migrations, the contrary is expected. (shrink)

We used computer simulations to study the possible role of the dispersion of cellular coupling, refractoriness or both, in the mechanisms underlying cardiac arrhythmias. Local ischemia was first assumed to induce cell to cell dispersion of the coupling resistance (Case 1), refractory period (Case 2), or both of them (Case 3). Our numerical experiments based on the van Capelle and Durrer model showed that vortices could not be induced by cell to cell variations. With cellular properties dispersed in a patchy (...) way within the ischemic zone, a single activation wave could give rise to abnormal activities. This demonstrates the stability of the wave front under small inhomogeneities. Probabilities of reentry, estimated for the three cases cited above showed that a severe alteration of the coupling resistance may be an important factor in the genesis of reentry. Moreover, use of isochronal maps revealed that vortices were both stable and sustained with an alteration of the coupling alone or combined with a reduction of the action potential duration. Conversely, simulations with reduction of the refractoriness alone, inducing only transient patterns, could exhibit functionally determined reentries. (shrink)

We consider a two-patch epidemiological system where individuals can move from one patch to another, and local interactions between the individuals within a patch are governed by the classical SIRS model. When the time-scale associated with migration is much smaller than the time-scale associated with infection, aggregation methods can be used to simplify the initial complete model formulated as a system of ordinary differential equations. Analysis of the aggregated model then shows that the two-patch basic reproduction rate is smaller than (...) the 1 patch one. We extend this result to a linear chain of P patches . These results are illustrated by some examples for which numerical integration of the system of ordinary differential equations is performed. Simulations of an individual based model implemented with a multi-agent system are also carried out. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Vetera Novis Augere et Perficere:Thomas Aquinas and Christian-Muslim DialogueJoseph Ellul, O.P.Pope Leo XIII's encyclical letter Aeterni Patris, issued on August 4, 1879, sought to address many issues that were challenging nineteenth-century Catholic scholarship and academic life. In proposing the thought of Thomas Aquinas as a model of Catholic teaching, the Pope intended, in his own words, "to strengthen and complete the old by aid of the new,"1 not only (...) by reviving the study of the works and teachings of the Angelic Doctor, especially in the realm of philosophy, but also to uphold as perennial his method of engaging with his contemporaries within and without the Catholic faith.2 It is within this context that we are called upon to reflect upon this appeal: "vetera novis augere et perficere."The thirteenth century was indeed a time of intellectual upheaval, following the introduction of Aristotle and, later on, the translations into Latin of the Arabic commentaries on Aristotle by Ibn Rušd (Lat. Averröes; d. 1198). This event was met within the ecclesiastical world with apprehension, if not outright fear. Neo-Platonic philosophy and its interpretation by Ibn Sina (Lat. Avicenna; d. 1037) was already perfectly acceptable to Mediaeval Christian scholars. The latter was in fact considered an essential tool for understanding the illuminationist thought of St. Augustine. Étienne Gilson even spoke of Augustinisme avicennisant (Avicennized [End Page 1231] Augustinianism).3 The problem was Aristotle and his renowned commentator Ibn Rušd: a pagan commented on by an infidel.One must also note, however, that mediaeval Western intellectuals and institutions were able to encounter and adapt the Islamic legacy, because they already possessed a sufficient scientific base (with of course the contribution of translations of Greek together with Latin works) with which to understand, assimilate, and build upon this new knowledge that appeared from the East. In sum, mediaeval Christendom created living, vibrant societies, constantly searching, always discovering something new.In dealing with the specific (and delicate) subject of Aquinas's dialogue with Islamic thought, it would be necessary to reflect in particular upon two key works of his: the Liber de Veritate Catholicae Fidei contra Errores Infidelium (A Book on the Truth of the Catholic Faith against the Errors of Unbelievers),4 popularly known as the Summa contra gentiles [SCG], together with his De rationibus fidei contra Saracenos, Gnæcos et Armenos ad Cantorem Antiochenum, better known simply as De rationibus fidei.At this point it would be necessary to articulate the term "Islamic thought." Of itself it should not be identified with Islam as a religion. Rather, it should be considered as embracing classical Greek philosophy as interpreted by the Neo-Platonic movement and disseminated through Oriental Christian and Jewish schools of thought. Islamic civilization absorbed these teachings and built its own proper ediice upon these foundations.A Model for Interreligious Dialogue?Proposing Thomas Aquinas as a model for engagement with Islamic thought may also raise a few eyebrows. Hence, it would be appropriate to pose an essential question: "What type of dialogue existed in mediaeval times?" One should begin with an a priori exclusion of dialogue as it is understood today, given the fact that there existed neither the motive nor the means to implement it.In fact mediaeval society was aware of only three religions: the pagan, which had been replaced by Christianity; the Jewish, founded upon the precepts of the First Covenant which "Christ fulilled by his actions and [End Page 1232] by his teaching"5 and which was also believed to prefigure the everlasting New Covenant sealed by Jesus on the Cross; and finally, the Christian, which believed in Jesus as the final revelation of God to humanity.6 With such a vision in mind it is obvious that any doctrine that is not situated within these parameters, or which proposes some form of belief or conduct which was different from, if not contrary to, the Christian vision of God, the cosmos, and society, would be considered as heretical and its promoter an impostor.7When Islam made its appearance in the Christian world, it carried with it a book that it considered of divine provenance, and... (shrink)

The book deals with the notion of Downward Causation from a wide array of perspectives, including physics, biology, psychology, social science, communication studies, text theory, and philosophy. The book includes proponents as well as opponents discussing the validity of the notion.

Unlike many major figures in Western intellectual history, Hobbes has refused to become dated and quietly take his appointed place in the museum of historical scholarship. Whether by way of adoption or reaction, his ideas have remained vibrant forces in mankind's attempts to understand the problems and dilemmas of living peaceably with one another. As Richard Ashcraft said a few years ago: One of the standards by which the greatness of political theorists is measured, is their ability to evoke in (...) us new insights into 'the human condition'. Only a few political writers have risen Dionysus-like from the titanic assaults of their critics to become even more formidable forces in the shaping of our destiny. One of these giants is surely the irascible l and irrepressible Thomas Hobbes . Given the power of Hobbes's thought, it is not then perhaps surprising to find that his writings have generated seemingly endless scholarly controversy and an astonishing range of imcompatible interpretations. Among other things, he has been interpreted as a theist and an atheist, as a utilitarian and a deontologist, a humanist and a scientist, as a traditional natural law theorist and a legal positivist, a contractualist and an absolutist - indeed, as Professor Morris notes in his contribution to the present volume, 'as almost any kind of philosophical 'ist except Platonist or Aristotelist'. (shrink)

A continuoxis t- norm is a continuous map * from [0, 1]² into [0,1] such that is a commutative totally ordered monoid. Since the natural ordering on [0,1] is a complete lattice ordering, each continuous t-norm induces naturally a residuation → and becomes a commutative naturally ordered residuated monoid, also called a hoop. The variety of basic hoops is precisely the variety generated by all algebras, where * is a continuous t-norm. In this paper we investigate the structure of the (...) variety of basic hoops and some of its subvarieties. In particular we provide a complete description of the finite subdirectly irreducible basic hoops, and we show that the variety of basic hoops is generated as a quasivariety by its finite algebras. We extend these results to Hájek's BL-algebras, and we give an alternative proof of the fact that the variety of BL-algebras is generated by all algebras arising from continuous t-norms on [ 0,1] and their residua. The last part of the paper is devoted to the investigation of the subreducts of BL- algebras, of Gödel algebras and of product algebras. (shrink)

A continuoxis t- norm is a continuous map * from [0, 1]² into [0,1] such that ([ 0,1], *, 1) is a commutative totally ordered monoid. Since the natural ordering on [0,1] is a complete lattice ordering, each continuous t-norm induces naturally a residuation → and ([ 0,1], *, →, 1) becomes a commutative naturally ordered residuated monoid, also called a hoop. The variety of basic hoops is precisely the variety generated by all algebras ([ 0,1], *, →, 1), where (...) * is a continuous t-norm. In this paper we investigate the structure of the variety of basic hoops and some of its subvarieties. In particular we provide a complete description of the finite subdirectly irreducible basic hoops, and we show that the variety of basic hoops is generated as a quasivariety by its finite algebras. We extend these results to Hájek's BL-algebras, and we give an alternative proof of the fact that the variety of BL-algebras is generated by all algebras arising from continuous t-norms on [ 0,1] and their residua. The last part of the paper is devoted to the investigation of the subreducts of BL- algebras, of Gödel algebras and of product algebras. (shrink)

Distributive, procedural, and interactional justice are constructs that are increasingly being recognized as important factors that affect individual perceptions in the workplace environment. This paper presents a theoretical perspective that suggests that justice is perceived through a subjective lens that consists of individualized beliefs and proposes that cultural attributes and demographic characteristics play an integral part in determining the perception of justice. The distinctions between these three constructs are presented in context with the core beliefs of individual employees – affected (...) by a multitude of perceptual and demographic factors that we briefly identify herein. Based on the theoretical perspective, an instrument that measures the constructs of justice as perceived by individuals was developed. With a focus on justice within the business setting, hypotheses about attitudes related to justice were tested. Survey results confirm that the three constructs of justice are distinct but correlated. Significant differences were found in the perceptions of African-American respondents with regard to procedural justice. Although the empirical findings do not support all the hypotheses, this research highlights the need for further development of measures to assess the perception of justice in business settings and at an applied level, underscores the importance of recognizing cultural attributes and demographic characteristics in understanding how justice is perceived. (shrink)

When I offered this title, I was engaging myself to investigate an apparent difference between two kinds of intentionality, in the hope that I should be able to find some firm logical criterion to distinguish them. I was less successful in this than I had hoped. I think I have gained a certain amount of insight into the logic and semantics of one kind of intentional context, largely due to the work I was doing while visiting the University of Pennsylvania (...) on Frege and on Michael Dummett’s monumental commentary on Frege. But as regards the other variety of intentionality I am still very much in the dark; so I am giving you thus far merely a progress report on that. (shrink)

One diagnosis of what is wrong with the Knowledge Argument rests on the Ability Hypothesis. This couples an ability analysis of knowing what an experience is like together with a denial that phenomenal propositions exist. I argue against both components. I consider three arguments against the existence of phenomenal propositions and find them wanting. Nevertheless I deny that knowing phenomenal propositions is part of knowing what an experience is like. I provide a hybrid account of knowing what an experience is (...) like which is the coherent expression of a single idea: knowing what an experience is like is knowing what it would be like to have the phenomenal content of the experience as the content of an experience one is currently having. I explain how my conclusions indicate that the focus of discussion should be on the alleged explanatory gap between phenomenal facts and physical facts and not on the Knowledge Argument. The latter is a poor expression of the difficulty Physicalists face. (shrink)

The conception of “prospective potency” was defined by its author H.Driesch as “the sum of the possible modes of development of a given part of the embryo”. However, in the language of science the word “potency” usually means “power”, not “possibility”. Therefore this conception from the beginning possessed a certain ambiguity, that it retained up to the present. The distinction of “active” and “passive” potency, introduced by Roux, has found no general acceptance. It appeared necessary to submit the conception of (...) “potency” to a profound analysis. In the first place it is shown, that the ambiguity of this conception vanishes, if we understand by the word “potency” those fundamental properties of the embryonic material, that are responsible for its various developmental possibilities. We can distinguish among these properties the “reactive powers”, by which the embryonic material reacts to inductive stimulations, and its own “developmental tendencies”. These faculties only differ by their strength; a “reactive power” may change into a “tendency”, when its intensity increases during development; conversely, a “tendency” may change into a mere “reactive power” by a decrease of its strength. The determination of the material results from the conflict of its tendencies. The inductive actions interfere by strengthening or weakening different tendencies, and by activating new tendencies by reinforcement of the “reactive powers” of the embryonic material.La conception de „prospektive Potenz” fut définie par son auteur H.Driesch comme „l'ensemble des modes de développement possibles d'une certaine partie de l'embryon”. Cependant, le, mot „Potenz” dans le langage de la science répond plutôt à la „puissance” qu'à la „possibilité”. De là résulte, que cette conception dès son origine avait une certaine ambiguïté, qui se fait sentir jusqu'à présent. La distinction entre „potentialité active” et „potentialité passive”, proposée par Roux, n'est pas acceptée généralement. Il se trouvait nécessaire, que la conception de „Potenz” fût soumise à une. analyse profonde. D'abord il est démontré, que l'ambiguïté de cette conception disparaît, si on entend par le mot „Potenz” les propriétés fondamentales du matériel embryonnaire, qui sont à la base de ses diverses possibilités de développement. On peut distinguer parmi ces propriétés les „pouvoirs réactifs”, en vertu desquels le matériel embryonnaire répond à des inductions morphogénétiques, et les „tendances propres” du matériel. Ils ne diffèrent que par leur intensité; un „pouvoir réactif” peut se changer en „tendance” par suite d'un renforcement au cours du développement, une „tendance” peut se changer en „pouvoir réactif” par une diminution d'intensité. La détermination du matériel se réalise par une „lutte” entre les tendances. Les actions inductives influent sur cette lutte en renforçant ou en diminuant l'intensité des diverses tendances, et en activant de nouvelles tendances par le renforcement de „pouvoirs réactifs”. (shrink)

It has been argued that the fundamental laws of physics are deceitful in that they give the impression of greater unity and coherence in our theories than is actually found to be the case. Causal stories and phenomenological relationships are claimed to provide a more acceptable account of the world, and only theoretical entities — not laws — are considered as perhaps corresponding to real features of the world.This paper examines these claims in the light of the author's own field (...) of research: high energy physics. Some of the distinctions upon which the above conclusions are based are found not to be tenable in practice. Examples from experimental particle physics are presented which suggest an important role of the underlying theoretical structure which cannot be overlooked. It is argued that the fundamental theories must, in fact, be treated as being as worthy or unworthy of ontological commitment as the entities they postulate or the phenomenological relationships they inspire. Whilst it is conceded that aspects of the current theoretical formalism belie literal interpretation, it is maintained that revision in these particular areas need not affect the symmetry principles, particle spectra, or coupling strengths that largely determine the empirical content of the theory. (shrink)