Cardiovascular modelling has been a major research subject for the last decade. Different cardiac models have been developed at a cellular level as well as at the whole organ level. Most of these models are defined by a comprehensive cellular modelling using continuous formalisms or by a tissue-level modelling often based on discrete formalisms. Nevertheless, both views still suffer from difficulties that reduce their clinical applications: the first approach requires heavy computational resources while the second one is not able to (...) reproduce certain pathologies.This paper presents an original methodology trying to gather advantages from both approaches, by means of a hybrid model mixing discrete and continuous formalisms. This method has been applied to define a hybrid model of cardiac action potential propagation on a 2D grid of endocardial cells, combining cellular automata and a set of cells defined by the Beeler-Reuter model. For simulations under physiological and ischemic conditions, results show that the action potential propagation as well as electrogram reconstructions are consistent with clinical diagnosis. Finally, the advantage of the proposed approach is discussed within the frame of cardiac modelling and simulation. (shrink)

This paper presents research regarding the monitoring of the brain and the adequacy of anesthesia during surgery. Particular variables are derived from EEG and ECG signals and are correlated to anesthetic gas (sevoflurane) concentration, in pediatric anesthesia. The methods used for parameter extraction are based on change detection theory and time-frequency representation. Preliminary results show that the expired anesthetic gas concentration modulates both the heart rate variability and the duration of the burst suppression. Monitors of the central nervous system and (...) autonomic nervous system activities can be expected to be based on these variables. (shrink)

Much research effort has been directed in different physiological contexts towards describing realistic behaviors with differential equations. One observes obviously that more state-variables give the model more accuracy. Unfortunately, the computational cost involved is higher. A new algorithm is presented for simulating a model described by a system of differential equations in which efficiency may not be altered by its size. In order to do this, the method is based on a polynomial description of the state-variables' evolution and on a (...) computation distributed control. Evaluations and results performed with classical models like Fitzhugh Nagumo or Hodgkin Huxley, allow validation of the method and exhibits its potential to decrease the computational costs. (shrink)

Different approaches have been proposed in order to achieve knowledge integration for coronary care monitoring applications, usually in the form of expert systems. The clinical impact of these expert systems, which are based only on "shallow" knowledge, has not been remarkable due to the difficulties associated with the construction and maintenance of a complete knowledge base. Model-based systems represent an alternative to these problems because they allow efficient integration of the "deep" knowledge on the underlying physiological phenomena being monitored. In (...) this work, a brief review of existing model-based systems for cardiac rhythm interpretation is presented, followed by the description of a new system forCardiac Arrhythmia Recognition by Model-Based ECG Matching (CARMEM). Fundamental characteristics of CARMEM are presented; in particular, its ability to provide on-line parameter adaptation to simulate complex rhythms and to match observed ECG signals. The proposed model can be useful for the explanation of the origin of cardiac arrhythmias and contribute towards their robust characterization in the context of coronary care units. (shrink)

The study of the autonomic nervous system (ANS) function has shown to provide useful indicators for risk stratification and early detection on a variety of cardiovascular pathologies. However, data gathered during different tests of the ANS are difficult to analyse, mainly due to the complex mechanisms involved in the autonomic regulation of the cardiovascular system (CVS). Although model-based analysis of ANS data has been already proposed as a way to cope with this complexity, only a few models coupling the main (...) elements involved have been presented in the literature. In this paper, a new model of the CVS, representing the ventricles, the circulatory system and the regulation of the CVS activity by the ANS, is presented. The models of the vascular system and the ventricular activity have been developed using the Bond Graph formalism, as it proposes a unified representation for all energetic domains, facilitating the integration of mechanic and hydraulic phenomena. In order to take into account the electro-mechanical behaviour of both ventricles, an electrophysiologic model of the cardiac action potential, represented by a set of ordinary differential equations, has been integrated. The short-term ANS regulation of heart rate, cardiac contractility and peripheral vasoconstriction is represented by means of continuous transfer functions. These models, represented in different continuous formalisms, are coupled by using a multi-formalism simulation library. Results are presented for two different autonomic tests, namely the Tilt Test and the Valsalva Manoeuvre, by comparing real and simulated signals. (shrink)

The study of the autonomic nervous system (ANS) function has shown to provide useful indicators for risk stratification and early detection on a variety of cardiovascular pathologies. However, data gathered during different tests of the ANS are difficult to analyse, mainly due to the complex mechanisms involved in the autonomic regulation of the cardiovascular system (CVS). Although model-based analysis of ANS data has been already proposed as a way to cope with this complexity, only a few models coupling the main (...) elements involved have been presented in the literature. In this paper, a new model of the CVS, representing the ventricles, the circulatory system and the regulation of the CVS activity by the ANS, is presented. The models of the vascular system and the ventricular activity have been developed using the Bond Graph formalism, as it proposes a unified representation for all energetic domains, facilitating the integration of mechanic and hydraulic phenomena. In order to take into account the electro-mechanical behaviour of both ventricles, an electrophysiologic model of the cardiac action potential, represented by a set of ordinary differential equations, has been integrated. The short-term ANS regulation of heart rate, cardiac contractility and peripheral vasoconstriction is represented by means of continuous transfer functions. These models, represented in different continuous formalisms, are coupled by using a multi-formalism simulation library. Results are presented for two different autonomic tests, namely the Tilt Test and the Valsalva Manoeuvre, by comparing real and simulated signals. (shrink)

The study of the autonomic nervous system (ANS) function has shown to provide useful indicators for risk stratification and early detection on a variety of cardiovascular pathologies. However, data gathered during different tests of the ANS are difficult to analyse, mainly due to the complex mechanisms involved in the autonomic regulation of the cardiovascular system (CVS). Although model-based analysis of ANS data has been already proposed as a way to cope with this complexity, only a few models coupling the main (...) elements involved have been presented in the literature. In this paper, a new model of the CVS, representing the ventricles, the circulatory system and the regulation of the CVS activity by the ANS, is presented. The models of the vascular system and the ventricular activity have been developed using the Bond Graph formalism, as it proposes a unified representation for all energetic domains, facilitating the integration of mechanic and hydraulic phenomena. In order to take into account the electro-mechanical behaviour of both ventricles, an electrophysiologic model of the cardiac action potential, represented by a set of ordinary differential equations, has been integrated. The short-term ANS regulation of heart rate, cardiac contractility and peripheral vasoconstriction is represented by means of continuous transfer functions. These models, represented in different continuous formalisms, are coupled by using a multi-formalism simulation library. Results are presented for two different autonomic tests, namely the Tilt Test and the Valsalva Manoeuvre, by comparing real and simulated signals. (shrink)

The ventricular pressure profile is characteristic of the cardiac contraction progress and is useful to evaluate the cardiac performance. In this contribution, a tissue-level electromechanical model of the left ventricle is proposed, to assist the interpretation of left ventricular pressure waveforms. The left ventricle has been modeled as an ellipsoid composed of twelve mechano-hydraulic sub-systems. The asynchronous contraction of these twelve myocardial segments has been represented in order to reproduce a realistic pressure profiles. To take into account the different energy (...) domains involved, the tissue-level scale and to facilitate the building of a modular model, multiple formalisms have been used: Bond Graph formalism for the mechano-hydraulic aspects and cellular automata for the electrical activation. An experimental protocol has been defined to acquire ventricular pressure signals from three pigs, with different afterload conditions. Evolutionary Algorithms have been used to identify the model parameters in order to minimize the error between experimental and simulated ventricular pressure signals. Simulation results show that the model is able to reproduce experimental ventricular pressure. In addition, electro-mechanical activation times have been determined in the identification process. For example, the maximum electrical activation time is reached, respectively, 96.5, 139.3 and 131.5 ms for the first, second, and third pigs. These preliminary results are encouraging for the application of the model on non-invasive data like ECG, arterial pressure or myocardial strain. (shrink)

The ventricular pressure profile is characteristic of the cardiac contraction progress and is useful to evaluate the cardiac performance. In this contribution, a tissue-level electromechanical model of the left ventricle is proposed, to assist the interpretation of left ventricular pressure waveforms. The left ventricle has been modeled as an ellipsoid composed of twelve mechano-hydraulic sub-systems. The asynchronous contraction of these twelve myocardial segments has been represented in order to reproduce a realistic pressure profiles. To take into account the different energy (...) domains involved, the tissue-level scale and to facilitate the building of a modular model, multiple formalisms have been used: Bond Graph formalism for the mechano-hydraulic aspects and cellular automata for the electrical activation. An experimental protocol has been defined to acquire ventricular pressure signals from three pigs, with different afterload conditions. Evolutionary Algorithms have been used to identify the model parameters in order to minimize the error between experimental and simulated ventricular pressure signals. Simulation results show that the model is able to reproduce experimental ventricular pressure. In addition, electro-mechanical activation times have been determined in the identification process. For example, the maximum electrical activation time is reached, respectively, 96.5, 139.3 and 131.5 ms for the first, second, and third pigs. These preliminary results are encouraging for the application of the model on non-invasive data like ECG, arterial pressure or myocardial strain. (shrink)

Hume's Reception in Early America: Expanded Edition brings together the original American responses to one of Britain's greatest men of letters, David Hume. Now available as a single volume paperback, this new edition includes updated further readings suggestions and dozens of additional primary sources gathered together in a completely new concluding section. From complete pamphlets and booklets, to poems, reviews, and letters, to extracts from newspapers, religious magazines and literary and political journals, this book's contents come from a wide variety (...) of sources published in colonial America and the early United States between 1758 and 1850. As well as classics by Thomas Jefferson, John Adams and Alexander Hamilton, it contains scores of unknown and hard-to-locate items, many of which have not been reprinted since their original publication. These responses are divided into four parts covering Hume's Essays; his Philosophical Writings; his History of England; and his Character and Death. Each of those parts has a separate introductory essay, and every selection is introduced by a short headnote that sets the piece in its historical context and provides bibliographical references. Packed with new insights into Hume and American thought and culture, Hume's Reception in Early America reveals the relevance and impact of Hume on American political, philosophical, historical, religious, and aesthetic debates. (shrink)

This is a welcome reprint of a book that continues to grow in importance.

Editor James Fetzer presents an analytical and historical introduction and a comprehensive bibliography together with selections of many of Carl G. Hempel's most important studies to give students and scholars an ideal opportunity to appreciate the enduring contributions of one of the most influential philosophers of science of the 20th century.

There is a strong need to connect agricultural research to social movements and community-based food system reform efforts. Participatory research methods are a powerful tool, increasingly used to give voice to communities overlooked by academia or marginalized in the broader food system. Plant breeding, as a field of research and practice, is uniquely well-suited to participatory project designs, since the basic process of observing and selecting plants for desirable traits is accessible to participants without formal plant breeding training. The challenge (...) for plant breeders engaged in participatory research is to consider not only how their work incorporates farmer input in developing new varieties, but also how it interacts with broader questions of food sovereignty, food justice, diversity and democratization in the food system. This article examines these issues in the context of the Seed to Kitchen Collaborative, a participatory variety evaluation and breeding project at the University of Wisconsin-Madison. (shrink)

O texto busca refletir criticamente sobre alguns fenômenos sociais contemporâneos, fortemente imbricados, notadamente as tendências contemporâneas de entrincheiramento e achatamento do eu; o reforço da iconomania e da compulsiva produção de avatares de si, em meio a bolhas narcísicas digitais, franqueadas pelas recentes tecnologias de informação e comunicação; e a virtual destruição da intimidade e da privacidade, diante da emergência de panópticos digitais e da vigilância algorítmica. Para tanto, toma-se como ponto de partida proposições apresentadas por Christopher Lasch em sua (...) obra _The Minimal Self: Psychic Survival in Troubled Times_, publicada originalmente em 1984, em particular a própria noção de mínimo eu, as quais são, então, entretecidas com argumentos de Christophe Dejours, Günther Anders, Theodor Adorno, Hebert Marcuse, Jonathan Crary, entre outros. Em acréscimo, busca-se salientar a ancoragem desses processos à hodierna dinâmica de acumulação de capital, a partir da crítica da economia política, perspectiva que atravessa todo o texto, bem como assinalar a atualidade do pensamento de Lasch. (shrink)

We examine the role of religious identity in promoting strategic renewal in privately held founder family firms. Religious identity in these firms refers to their collective sense of being that reflects their founders’ and owner family members’ espoused religious values and beliefs, thereby distinguishing themselves from others in what is central, distinct, and enduring about their organization. We propose that such a religious identity determines family firms’ spiritual capital, which influences strategic renewal activities such as conflict resolution and resource allocation. (...) Specifically, we argue that spiritual capital can be a double-edged sword when family firms pursue strategic renewal. We discuss the implications of our work for future research. (shrink)

We examine the role of religious identity in promoting strategic renewal in privately held founder family firms. Religious identity in these firms refers to their collective sense of being that reflects their founders’ and owner family members’ espoused religious values and beliefs, thereby distinguishing themselves from others in what is central, distinct, and enduring about their organization. We propose that such a religious identity determines family firms’ spiritual capital, which influences strategic renewal activities such as conflict resolution and resource allocation. (...) Specifically, we argue that spiritual capital can be a double-edged sword when family firms pursue strategic renewal. We discuss the implications of our work for future research. (shrink)