654 research outputs found
"Cic. Inv. 1.27 and Rhet. Her. 1.12 f.: the question of the tertium genus narrationis"
No full textSince the birth of rhetorical handbooks narration has been considered an important part of the speech and therefore taken into account in detail. We find precepts about its virtues (narratio lucida, brevis, verisimilis), about its use and position inside the speech (narra-tion can be longer, shorter, cut into flashes or, when contrary to the speaker’s interest, even absent), about its different genres (main or accessory narration). Its difference from the digression is agreed. Nowhere, on the contrary, we find mentioned a tertium genus narrationis split into a kind of narration based in negotiis and a kind of narration based in personis as offered in Cicero’s De inven-tione and in the Rhetorica ad Herennium. The question is of the greatest interest because the source of this doctrine is unknown. Two details, however, bring us back to the dihvghma dealt with in the Progumnavsmata, the open allusion to the usefulness of this narratio for practice (quod delectationis causa non inutili cum exercitatione dicitur et scribitur) and the threefold nature of the negotia (fabula, historia, argumentum). Extremely unclear, however, is the reference to the personae. Against Barwick’s opinion that we have here to do with personae loquentes, i.e. with the well known formal criterion according to which a narration can be monologi-cal, dialogical or mixed, I want to argue in this paper that the personae referred to by the two authors are either agentes or patientes. In other words I do not think that the question of the distinction of this narratio into two kinds, in negotiis and in personis, can be solved interpreting negotia and personae as content and form of the narration itself. My argument will be therefore that this distinc-tion was born inside the doctrine of the peristavsei~ or stoicei`a of the narration, among which pravgmata (negotia) and provswpa (personae) were considered the most important. Hence the attention to the quality of the negotium (true, invented but probable, in-vented and impossible) and to the feelings or the speeches of the personae
Reverse Engineering Biological Interaction Networks by Exploiting Prior Knowledge and Topological Features
No full text
Reverse Engineering Biological Interaction Networks by Exploiting Prior Knowledge and Topological Features
No full textCORE-Net: exploiting prior knowledge and preferential attachment to infer biological interaction networks
No full textThe problem of reverse engineering in the topology of functional interaction networks from time-course experimental data has received considerable attention in literature, due to the potential applications in the most diverse fields, comprising engineering, biology, economics and social sciences. The present work introduces a novel technique, CORE-Net, which addresses this problem focusing on the case of biological interaction networks. The method is based on the representation of the network in the form of a dynamical system and on an iterative convex optimisation procedure. A first advantage of the proposed approach is that it allows to exploit qualitative prior knowledge about the network interactions, of the same kind as typically available from biological literature and databases. A second novel contribution consists of exploiting the growth and preferential attachment mechanisms to improve the inference performances when dealing with networks which exhibit a scale-free topology. The technique is first assessed through numerical tests on in silico random networks, subsequently it is applied to reverse engineering a cell cycle regulatory subnetwork in Saccharomyces cerevisiae from experimental microarray data. These tests show that the combined exploitation of prior knowledge and preferential attachment significantly improves the predictions with respect to other approaches
Inferring scale-free networks via multiple linear regression and preferential attachment2008 16th Mediterranean Conference on Control and Automation
No full textThe problem of reverse-engineering the topology of interaction networks from time-course experimental data has been the subject of a considerable research effort in the last years, due to the potential applications in the most diverse fields, comprising engineering, biology, economics and social sciences. An important insight into such topic was brought by the introduction of the concept of scale-free topology, whose implications have been widely discussed in literature over the last decade. The aim of this work is to investigate whether it is possible to improve the performances of an inference technique, based on dynamical linear systems and multiple linear regression, by exploiting the same mechanisms that underpin scale-free networks generation, i.e. growth and preferential attachment (PA). The work is prominently concerned with applications in the biological domain, though the algorithm can be in principle adapted also to other frameworks. A statistical evaluation is performed, by using numerically simulated networks, showing that the growth and PA mechanisms actually improve the inference power of the considered technique. Finally the method has been applied to a biological case-study, validating the results against experimental data available in literature
Geometric slow-fast analysis of a hybrid pituitary cell model with stochastic ion channel dynamics
No full textTo obtain explicit understanding of the behavior of dynamical systems, geometrical methods and slow-fast analysis have proved to be highly useful. Such methods are standard for smooth dynamical systems and increasingly used for continuous, non-smooth dynamical systems. However, they are much less used for random dynamical systems, in particular for hybrid models with discrete, random dynamics. Here we propose a geometrical method that works directly with the hybrid system. We illustrate our approach through an application to a hybrid pituitary cell model in which the stochastic dynamics of very few active large-conductance potassium (BK) channels is coupled to a deterministic model of the other ion channels and calcium dynamics. To employ our geometric approach, we exploit the slow-fast structure of the model. The random fast subsystem is analyzed by considering discrete phase planes, corresponding to the discrete number of open BK channels, and stochastic events correspond to jumps between these planes. The evolution within each plane can be understood from nullclines and limit cycles, and the overall dynamics, e.g., whether the model produces a spike or a burst, is determined by the location at which the system jumps from one plane to another. Our approach is generally applicable to other scenarios to study discrete random dynamical systems defined by hybrid stochastic-deterministic models
From local to global modeling for characterizing calcium dynamics and their effects on electrical activity and exocytosis in excitable cells
No full textElectrical activity in neurons and other excitable cells is a result of complex interactions between the system of ion channels, involving both global coupling (e.g., via voltage or bulk cytosolic Ca2+concentration) of the channels, and local coupling in ion channel complexes (e.g., via local Ca2+ concentration surrounding Ca2+ channels (CaVs), the so-called Ca2+ nanodomains). We recently devised a model of large-conductance BKCapotassium currents, and hence BKCa–CaV complexes controlled locally by CaVs via Ca2+ nanodomains. We showed how different CaV types and BKCa–CaV stoichiometries affect whole-cell electrical behavior. Ca2+ nanodomains are also important for triggering exocytosis of hormone-containing granules, and in this regard, we implemented a strategy to characterize the local interactions between granules and CaVs. In this study, we coupled electrical and exocytosis models respecting the local effects via Ca2+ nanodomains. By simulating scenarios with BKCa–CaV complexes with different stoichiometries in pituitary cells, we achieved two main electrophysiological responses (continuous spiking or bursting) and investigated their effects on the downstream exocytosis process. By varying the number and distance of CaVs coupled with the granules, we found that bursting promotes exocytosis with faster rates than spiking. However, by normalizing to Ca2+ influx, we found that bursting is only slightly more efficient than spiking when CaVs are far away from granules, whereas no difference in efficiency between bursting and spiking is observed with close granule-CaV coupling
Exploiting prior knowledge and preferential attachment to infer biological interaction networks2009 17th Mediterranean Conference on Control and Automation
No full text- …
