1,690 research outputs found
"Bene agere et laetari". Paolo Cristofolini, Spinoza e la gioia
No full textConcepito nell’ambito di una raccolta di scritti dedicati a Paolo Cristofolini in occasione del suo settantesimo compleanno, lo studio prende in esame alcuni elementi chiave della sua interpretazione di Spinoza: la questione della “continuità e tensione” di alcuni tratti del pensiero del filosofo di Amsterdam rispetto al cartesianesimo, il netto differenziarsi della sua etica (incentrata sulla meditatio vitae) dai tratti più salienti dell’etica stoica, gli elementi di “dilemma e dinamismo” riscontrabili all’interno della teoria spinoziana dell’immaginazione, cui viene dato significativo risalto in relazione alla sua virtus o potentia . Attraverso l’analisi di questioni terminologiche (dalla doppia valenza di affectus, alla traduzione di laetitia con “gioia” e alla resa efficace di transitio con “passaggio” a connotare il carattere dinamico e trasformativo degli affetti) si riscontra infatti nelle pagine di Cristofolini una feconda prospettiva di lettura dell’Etica e degli scritti politici del filosofo di Amsterdam sulla quale è da allora avviato un proficuo e fertile confronto. Di comune interesse teorico sono, infatti, la questione dell’immaginazione, non disgiunta da quello della socialità e della gioia, dell’individuo plurimo e senziente, dell’uomo libero e del saggio nel contesto della civitas o respublica, alla luce della centrale questione del nos, ovvero della possibilità di individuare effetti ‘sociali’ e ‘socializzanti’ non solo della ragione e delle nozioni comuni, ma anche dell’immaginazione e delle nostre passioni, cui sempre siamo “sottoposti”, sino alle più recenti questioni della “moltititudine” e del “popolo”, passando attraverso la saggezza delle donne e la questione dell’oggetto della scienza intuitiva intesa come scienza delle res singulares
Il "Systema Naturae": la classificazione e la nomenclatura dei viventi
No full textThe Linnean “systema naturae”: classifying and naming all living beings.
Linnaeus introduced into biological systematics two main ideas: the sexual classification system, and the binomial nomenclature. Both classification and nomenclature were aimed at the same scope: to provide botany with an effective information storage and retrieval system. Linnaeus main concern was not as much to describe plants, as to deal with their diversity.
The sexual system is basically a way of ordering plants into classes and orders, characterised by the number of stamens and the number of pistils respectively. Although quite artificial in its nature, this system is highly practical and unambiguous.
The binomial system of nomenclature is a straightforward hierarchical method, where all species are named after the genus to which they are attributed (generic name) followed by a specific epithet.
The Linnaean nomenclature was immediately and widely accepted, while the classification system was the object of discussion and polemics throughout the second half of the eighteenth century. Some scientists hold that the very attempt to classify the living diversity was an unrealistic task, due to the unlimited variety of life. An outstanding representative of this way of thinking was J. W. von Goethe. Other scholars, mainly belonging to the French scientific world, judged it unnatural to classify plants just based on the number of stamens and pistils. This school had in J.-L. Buffon its main leader and in M. Adanson the one who tried to practically develop a classification system shaped after this views. Finally, to some authors the very fact of seeing sex in flowers was scientifically unconvincing as well as morally unacceptable. In spite of so many different objections, the Linnaean system rapidly overcame all competing systems and, by the end of the Century was largely adopted in all Europe.
New views developed during the Nineteenth Century drew systematists to explore other taxonomic criteria. From the beginning of the Century, the development of biogeography first, and the evolutionary interpretation of biodiversity later, resulted in a deep reformation of systematic biology. Nevertheless, the Linnean legacy still survives, not only in the nomenclature system, which is still in use, but even more in the basic principle that dealing with plant and animal diversity requires an homogeneous, coherent, rigorous classification system
A new subspecies of Pulmonaria officinalis (Boraginaceae) from the southern Alps
No full textAstuti, Giovanni, Cristofolini, Giovanni, Peruzzi, Lorenzo, Pupillo, Paolo (2014): A new subspecies of Pulmonaria officinalis (Boraginaceae) from the southern Alps. Phytotaxa 186 (3): 148-157, DOI: 10.11646/phytotaxa.186.3.3, URL: http://dx.doi.org/10.11646/phytotaxa.186.3.
Magnetohydrodynamics equations
No full textMagnetohydrodynamics (MHD) is a branch of physics and engineering that investigates the effects of a magnetic field on the motion of an electrically conducting fluid. The term ‘magnetohydrodynamics’ and its acronym MHD may be somewhat misleading, it is often used to designate physical phenomena in which the conducting fluid is not a liquid, but rather a compressible ionized gas or a plasma. Same authors prefer more specific terms as magneto-fluid-dynamics or magneto-gas-dynamics.
Since the pioneering experiment of Michael Faraday in 1832, MHD has appeared as an appealing way to manipulate a fluid without the intervention of mechanical means. Faraday failed his attempt to measure the electric current produced by the MHD interaction taking place in the water of the river Thames flowing through the Earth’s magnetic field. However, his experimental activities opened the way to the study of a mechanism which has fundamental implications in plasma physics, astrophysics, and engineering.
The MHD interaction principles have been proposed for a number of technological applications. A first example can be found in MHD generators, in which the MHD interaction is used for the direct conversion of the working fluid energy into electrical energy. MHD generators have been intensively investigated as a means to increase the efficiency of electrical power plants and as a viable alternative to gas turbines. MHD electric generators has also been proposed in nuclear-powered spacecraft for deep space missions
A multi-stage approach for DBD modelling
No full textA multi-stage numerical technique for the assessment of Dielectric Barrier Discharge (DBD) in atmospheric pressure air is presented. The model is conceived to work on the characteristic times of heavy species. The dynamics of the heavy species are computed with a 2D drift-drift diffusion model, based on a Finite Volume approach. A non-linear Poisson solver is employed for the calculation of the electric field produced by the heavy species and electrons distributions. This latter is assumed to instantly follow the Boltzmann distribution, allowing limiting the transport model to the heavy species. The main chemical reactions taking place during the discharge process between the air chemical constituents are included in the model, whereas the effects of the impact ionization are accounted by means of a simplified 1D streamer model
A reassessment of the sections of the genus Cytisus (Cytiseae, Leguminosae)
No full textRecent morphological and molecular research on Cytisus and allied genera has produced a great deal of new
data relevant to systematics, which have not yet been incorporated into a consistent classification system of the
genus. We have compared and evaluated recently published cladograms and phenograms based on morphological
and molecular (nuclear and plastid DNA) characters. The genus Cytisus sensu lato, including Calicotome,
Chamaecytisus, Chronanthus, and Lembotropis, appears to be monophyletic. A subdivision of the genus
Cytisus in 13 sections is presented; one species, C. tribracteolatus, remains incertae sedis. A new section (C.
sect. Dendrocytisus) and two new combinations for taxa in C. sect. Calicotome are proposed.
KEYWORDS: Calicotome, Chamaecytisus, Chronanthus, Lembotropis, nomenclature, sections, taxonomy
Megnetohydrodynamics equations
No full textPlasma Modeling: Methods and Applications presents and discusses the different approaches that can be adopted for plasma modeling, giving details about theoretical and numerical methods. The book is intended to assist and direct students and researchers, who want to develop research activity in the field of plasma physics, in the choice of the best model for the problem of interest. The book is organised in three parts. The first describes kinetic models used in plasma investigations, consisting of the solution of the Boltzmann equation using different approaches. The second part develops the theory of fluid equations and of hybrid models, and the third part is devoted to applications, considering some practical problems of interest in different fields
The inexact Newton method applied for the solution of a magnetostatic problem
No full textInexact Newton solvers can offer many attractive features for the solution of non linear problem in the field of electromagnetics. A critical point for the optimal set up of the solver is the choice of the best algorithm for the evaluation of the approximate solutions of the linear systems at each Newton step, and the most effective preconditioning strategy. In this paper, the NITSOL method is proposed for the solution of a non linear linear magnetostatic problem. The problem has been discretized by means of a finite element approach. The GMRES method has been adopted as linear solver, and four preconditioners have been tested. The performance of the procedure are evaluated for different meshes with increasing number of discretization points
Airborne bioparticles and speleotherapy: a case study in a disused mine of siderite (Brescia, Italy)
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