8,317 research outputs found
Principios y definiciones de rontgengrafía
No full textCaracterísticas y propiedades del procedimiento radiográfico en odontología.Fil: Barbero, Luis M. A. Academia Argentina de Odontología. Buenos Aires, Argentina
One sign ion mobile approximation
No full textThe electrical response of an electrolytic cell to an external excitation is discussed in the simple case where only one group of positive and negative ions is present. The particular case where the diffusion coefficients of the negative ions, D-m, is very small with respect to that of the positive ions, D-p, is considered. In this framework, it is discussed under what conditions the one mobile approximation, in which the negative ions are assumed fixed, works well. The analysis is performed by assuming that the external excitation is sinusoidal with circular frequency omega, as that used in the impedance spectroscopy technique. In this framework, we show that there exists a circular frequency, omega*, such that for omega > omega*, the one mobile ion approximation works well. We also show that for D-m << D-p, omega* is independent of D-m. (C) 2011 American Institute of Physic
Domenico Barbero e le universalità patrimoniali
No full textIl saggio costituisce una rilettura della monografia di Domenico Barbero sulle universalità patrimoniali. Si tratta di un “classico” del diritto che, come tale, conserva un significato attuale in relazione al metodo seguito dall’autore e alle soluzioni giuridiche in essa proposte.
Sotto il primo profilo l’autore avverte che lo studio del diritto non può appiattirsi nella «prospettiva analitica», ma deve cogliere anche la «dimensione empirica» della scienza giuridica. In questo senso il metodo argomentativo di Barbero, pur presentando elementi propri del formalismo concettuale, non prescinde dal confronto costruttivo con la realtà. Da tale prospettiva Barbero ricostruisce l’universalità di beni come categoria unitaria non dal punto di vista ontologico, ma logico, osservando che essa rimane identica pur quando cambino le cose che ontologicamente ne costituiscono parte integrante.
Altro aspetto di modernità dell’opera di Barbero è il convincimento che le norme giuridiche sono frutto di precise scelte politiche e non già mera sovrastruttura di fenomeni economici. L’impostazione positivistica di Barbero non domina tuttavia incontrastata, ma è controbilanciata dalla consapevolezza che la regola applicata, lungi dal risolversi in una manifestazione arbitraria di volontà del legislatore, debba essere espressione della naturale razionalità del diritto.Universality of Assets
The essay revisits Domenico Barbero's monograph on universality of assests . It is a "classic" of law, which, as such, retains a contemporary relevance both in relation to the method followed by the author and the legal solutions proposed in it.
Regarding the first aspect, the author notes that the study of law cannot be reduced to an "analytical perspective," but must also capture the "empirical dimension" of legal science. In this sense, Barbero's argumentative method, while presenting elements typical of conceptual formalism, does not disregard a constructive dialogue with reality. On this basis, Barbero reconstructs the universality of assets as a unified category, not from an ontological point of view but a logical one, observing that it remains identical even when the individual things change.
Another modern aspect of Barbero's work is the conviction that legal rules are the result of precise political choices and not merely a superstructure of economic phenomena. However, Barbero's positivist approach does not prevail unchallenged, but is counterbalanced by the awareness that the applied rule, far from being an arbitrary manifestation of the legislator's will, must be an expression of the natural rationality of law
Do Barbero-Immirzi connections exist in different dimensions and signatures?
No full textsummary:We shall show that no reductive splitting of the spin group exists in dimension other than in dimension . In dimension there are reductive splittings in any signature. Euclidean and Lorentzian signatures are reviewed in particular and signature is investigated explicitly in detail. Reductive splittings allow to define a global \mbox{SU} (2)-connection over spacetime which encodes in an weird way the holonomy of the standard spin connection. The standard Barbero-Immirzi (BI) connection used in LQG is then obtained by restriction to a spacelike slice. This mechanism provides a good control on globality and covariance of BI connection showing that in dimension other than one needs to provide some other mechanism to define the analogous of BI connection and control its globality
The structure of the distortion free-energy density in nematics: second-order elasticity and surface terms
No full textPrólogo Introducción. Contra Viento y Marea: Historias de Pequeñas y Medianas Empresas Argentinas
No full textEste libro reconstruye, a lo largo de sus capitulos, la historia de veinticinco PyME industriales pertenecientes a diversos sectores de la actividad manufacturera, localizadas en distintas provincias del país (Buenos Aires, Rio Negro, Mendoza, San Juan, La Rioja, Córdoba, Santa Fe, Chaco, Misiones y Formosa, además de la Ciudad Autónoma de Buenos Aires).
En sus páginas pueden apreciarse los rasgos particulares de cada una de las firmas, pero también un denominador común: la capacidad que han tenido los empresarios a cargo de cada una de ellas de hacer frente a los desafíos y de resistir, adaptarse y responder a la volatilidad macroeconómica y a la inestabilidad institucional que han caracterizado a la Argentina a lo largo de las últimas décadas.
Desde el punto de vista académico este volumen representa un aporte significativo a la historia de empresas, disciplina que ha experimentado un fuerte dinamismo en la Argentina de los últimos años, y en la cual los estudios sobre pequeñas y medianas empresas recién comienzan a despuntar. Constituye también una contribución relevante al estudio de las economías de aglomeración. El análisis de la trayectoria de la veinticinco empresas, que se encuentran ubicadas dentro de áreas geográficas especializadas desde el punto de vista sectorial, permite reflexionar acerca de las muy diversas realidades territoriales argentinas y de cómo operan, en cada una de ellas, las redes que vinculan a las firmas entre sí y con las comunidades y las organizaciones públicas y privadas de las áreas en las cuales despliegan su actividad
Influence of the flexoelectricity on the stable configuration of a nematic layer with opposite boundary conditions
No full textWe discuss the influence of flexoelectricity on the critical thickness of a hybrid aligned nematic liquid crystal cell. We show that the critical thickness is independent of the flexoelectrical properties of the nematic only under the hypothesis that the distorted-undistorted transition is of second order. Afterall, the only effect of flexoelectricity is to introduce a very large elastic anisotropy. On the other hand, if first order transitions are considered, the flexoelectricity may play an important role. We also consider the surface polarization which can be different from zero for symmetry considerations. The analysis shows that its influence on the critical thickness or on the order of the transitions is negligible when there is no applied electric field. Some considerations on the terms connected with the surface polarization are also reported. The analysis is performed by supposing the nematic material a perfect insulator.Nous discutons l'influence de la flexoélectricité sur l'épaisseur critique d'une cellule hybride nématique. Nous montrons que cette épaisseur critique est indépendante des propriétés flexoélectriques du nématique dans un cas seulement : celui où la transition distordu/non distordu est du 2e ordre. Dans ce cas, la flexoélectricité ne fait qu'introduire une très grande anisotropie élastique. Par contre, si on considère le cas de transitions du 1er ordre, la flexoélectricité peut jouer un rôle important. Nous considérons aussi la polarisation de surface, qui peut être non nulle à cause de la symétrie du système. L'analyse montre que son influence sur l'épaisseur critique ou sur l'ordre des transitions est négligeable quand il n'y a pas de champ électrique appliqué; les termes qui sont reliés à la polarisation de surface sont également discutés. L'analyse est faite en supposant que le matériau nématique est un isolant parfait
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