87,680 research outputs found
Introduzione
No full textIntroduzione al volume: Processi di vittimizzazione e reti di sostegno alle vittime / a cura di Augusto Balloni, Roberta Bisi. Milano : F. Angeli, [2008
On proper polynomial maps of C 2
No full textTwo proper polynomial maps f 1,f 2 :C 2→C 2 are said to be equivalent if there exist Φ 1,∈Φ 2 Aut(C 2) such that f 2=Φ 2 o f 1 o Φ 1. We investigate proper polynomial maps of topological degree d ≥2 up to equivalence. Under the further assumption that the maps are Galois coverings, we also provide the complete description of equivalence classes. This widely extends previous results obtained by Lamy in the case d=2. © 2009 Mathematica Josephina, Inc
Excluded-volume potential for rigid molecules endowed with symmetry
No full textThe excluded volume of a pair of molecules is proportional to the second virial coefficient in hard-core models that represent, for instance, the reference model in perturbation approaches to statistical theories of fluids [see, e.g. Chap. 5 of Kalikmanov, V. (2001), Statistical Physics of Fluids. Texts and Monograph in Physics, Springer, Berlin]. In three space dimensions, there exist exact results for convex molecules and in fact lack of convexity has been a major obstacle in applying the mathematical techniques employed in the convex case. In this paper, we illustrate how a mixed—analytical and numerical—method can be used to obtain exact expressions of the excluded volume for a pair of non-convex molecules conceived as aggregates of hard spheres; these can model van der Waals regions associated to the atoms forming each molecule. To compute the excluded volume for molecules endowed with C2v symmetry, modelled as chains of tangent hard spheres, we adapt a numerical code available to the scientific community. Because the result is a rather cumbersome expression in term of the relative orientation of the interacting molecules, we expand it over a suitable set of symmetry adapted Wigner functions to build up approximate, but faithful expressions, and we also prove analytical results announced elsewhere [Bisi, F., Durand, G., Rosso, R. & Virga, E. (2008), Polar steric interactions for v-shaped molecules. Phys. Rev. E, 78, 011705]
Il broglio metafisico: lacci del pensiero, urgenze della volontà nella città invisibile del Cottolengo
No full textIn questo lungo racconto che segna una svolta anche nella sua stessa produzione Calvino mette a tema non tanto la disabilità in sé, quanto il rapporto nel quale essa inevitabilmente coinvolge l’altro da sé, quell’‘altro’ dalla cui straniata prospettiva si leggono i fatti del racconto. L’autore guida, così, il lettore a una meditazione sull’inalienabilità, sulla tenuta dell’essenza umana, sulla natura umana come fatto che, nelle sue molteplici forme, si impone, oltre che all’esperienza, alle considerazioni dell’intelletto ma soprattutto alle risposte della volontà. I confini dell’umano, che fino a un certo punto, nel racconto, sembrano oggetto di discernimento razionale, si rivelano nella loro problematicità ineludibile, che esige continui riorientamenti, correzioni di rotta da parte di una volontà chiamata allora non più a delimitare, ma ad allargare tali confini, anche oltre lo spazio di manovra dell’intelletto e in sofferta dialettica rispetto alla prospettiva culturale marxista. Si tratta di una volontà da trasfigurare, che sia espressione non solo del sé, ma anche, e soprattutto, della rinuncia all’affermazione di sé di fronte all’intuizione di vedersi altro rispetto a qualcuno che si fa presente e interpella. Lo stile interrogativo, l’attitudine al progressivo approssimarsi al cuore delle questioni, le forme espressive attraverso le quali l’autore sospinge il lettore ad un capovolgimento di sguardo sui confini dell’idea di disabilità sono oggetto privilegiato di queste analisi, in quanto strumenti performativi di una poetica tesa a far maturare nei lettori coscienza delle cose del mondo, a far esplodere, come diceva Calvino, la «carica morale dei fatti».In this long story that marks a turning point also in his own production, Calvino focuses not so much on disability in itself, but on the relationship in which it inevitably involves the other from himself, that other from whose alienated perspective we read the facts of the tale. Thus, the author guides the reader to a meditation on inalienability, on the sealing of human essence, on human nature as a fact that, in its many forms, imposes itself on the considerations of the intellect but especially to the responses of the will. It is a will that must transfigured, which is an expression not only of the self, but also, and above all, of the renunciation of self-affirmation. The interrogative style, the attitude to progressively approach the heart of the issues, the expressive forms through which the author pushes the reader to a reversal of the gaze on the boundaries of the idea of disability are the privileged object of these analyze
«Legne al bosco e gocciole al mare»: la retorica dell’«Agnesa da Faenza» di G.C. Becelli
No full textThe contribution tries to show the effectiveness of combining the two levels of the language of use and of the literary language in the "Agnesa da Faenza" of Becelli. The aim is to highlight the peculiar way in which the author sets up the performance of the word, because this is mainly the characteristic feature of its comedies. its originality lies not so much in the choice of themes, nor in the way of representing them, but rather in the ability to shed new light on trite ways of saying and foreseeable dialogical or structural paradigms that are here highlighted
Amplitude Noise and Linewidth Reduction of an Ar+ Laser
No full textFrequency modulation spectroscopy is used to frequency stabilize an Ar+ laser at 515 nm with respect to a commercial passive cavity. Two transducers, a slow and a fast one, are used. The fast transducer is also used to perform amplitude
stabilization of a laser beam. Measured amplitude and frequency spectral noise densities are reported. A simplified scheme of
the circuitry used to reduce amplitude noise is shown. Noise characteristics of the realized system are adequate to perform spectroscopy of hyperfine-structure transitions of molecular iodine
X-ray absorption and emission from different atoms of the same compound: success and failure of the single-particle picture
No full textTheoretical x-ray absorption and emission spectra of crystalline CoSi2 and NiSi2 have been computed considering the single-particle matrix elements between one-electron states. The effect of the core hole has been considered. The validity of the proposed models of absorption and emission processes, based on single-particle calculations and the density of state information that can be obtained from the experimental data is investigated. The comparison with the experimental results shows a different behavior for different atoms: a single-particle approach, namely, the final-state rule, describes the process occurring on a Si atom rather well, but no one-electron calculation is able to interpret transitions involving a Co or Ni atom
Steric Effects in Polar Nematic Liquid Crystals
No full textRecent measurements in a nematic liquid crystal formed by polyester compounds have given evidence of spontaneous macroscopic polar ordering. A mean-field theory for liquid crystals is built combining short-range, repulsive, steric forces with the average electric dipolar energy exchanged between molecules sharing the same excluded region. Such model is capable of identifying both uniaxial and biaxial polar phases. Under the assumption of a spheroidal shape for the molecules, and through a numerical bifurcation analysis, we assess the stability of phases upon two interaction parameters: the degree of intrinsic biaxiality, and the relative orientation of the permanent electric dipoles
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