Displaying similar documents to “Alcune questioni sulla conduzione del calore in mezzi compositi”

Alcune questioni sulla conduzione del calore in mezzi compositi

Vincenzo De Rienzo, Angelo Messina (1982)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

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The so-called diffraction problem for the heat equation is considered in a semi-infinite medium consisting of a sequence of different layers. Existence and uniqueness of the solution for the problem with no initial condition is proved and it is shown that periodic solutions are generated by periodic data on the boundary. A general method for calculating periodic solutions is discussed, taking into account possible thermal resistances between the layers.

Onde di calore e onde di densità di vortici nella turbolenza superfluida

Michele Sciacca, Maria Stella Mongiovì, David Jou (2008)

Bollettino dell'Unione Matematica Italiana

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The main topic of this paper is the interaction between vortex density waves and high-frequency second sound in counterflow superfluid turbulence. To this end a thermodynamical model including vortex flux as independent variable is considered. This choice is crucial for the study of the transition of the behavior of the vortex-density perturbations from diffusive to propagative, which is necessary to interpret the details of the high-frequency second sound waves.

Osservazioni sulla cinetica della transizione acido-alcalina nella metamioglobina di Aplisia

Giorgio Maria Giacometti, Alvaro Da Ros, Maurizio Brunori (1973)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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The paper reports a study on the kinetics of the transition between acid and alkaline Aplysia myoglobin. The results, obtained with the temperature-jump method, show that the observed relaxation effect corresponds to a perturbation of the equilibrium between the protonated and deprotonated forms of the protein. The pH dependence of the data and their analysis suggest that the process involves a proton-linked conformational change of the protein, in agreement with independent experiments....

Alcune considerazioni su una classe di sistemi del primo ordine quasi-lineari conservativi ed iperbolici di due equazioni in due variabili indipendenti

Domenico Fusco (1980)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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In this paper we determine a class of first order quasi-linear hyperbolic systems in conservative form involving two independent and two dependent variables which are not deducible, in general, from a variational principle but can be reduced to a Godunov’s symmetric form [5], [6] where the coefficient of the field spatial derivative is a constant matrix. That enables us to extend to these systems several results obtained by G. Boillat in [8], [9] and concerning with shocks in quasi-linear...

Ulteriori osservazioni sulla rigenerazione del mesencefalo in Xenopus laevis (Daudin). Istologia del tetto ottico normale e rigenerato

Sergio Filoni, Vito Margotta, Giancarlo Gibertini (1971)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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The histology of normal and regenerated optic lobes was examined in young specimens of Xenopus laevis by applying the Golgi-Cox method. In the operated animals the unilateral ablation of the optic lobe has been performed at the early larval stages (48-51) and at the later larval stages (55-56), according to Nieuwkoop and Faber. From our observations we drew the following conclusions: 1) The histological features of the optic tectum of Xenopus laevis are essentially similar to those of...

Discretizzazione di domini infiniti (elementi infiniti). Nota I

Gianmaria Donida, Luisa Tabusso (1980)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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A new technique for analysing problems which extend to infinity using elements is presented. A typical situation is that of the unbounded surface wave problems, either in two or three dimensions. The strategy is to discretize the inner domain in the standard finite element manner and to discretize the outer domain which extends to infinity with special infinite elements, for these elements are here suggested a series of shape functions analogous to Lagrange polynomials, but including...

Discretizzazione di domini infiniti (elementi infiniti). Nota II

Gianmaria Donida, Luisa Tabusso (1980)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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A new technique for analysing problems which extend to infinity using elements is presented. A typical situation is that of the unbounded surface wave problems, either in two or three dimensions. The strategy is to discretize the inner domain in the standard finite element manner and to discretize the outer domain which extends to infinity with special infinite elements, for these elements are here suggested a series of shape functions analogous to Lagrange polynomials, but including...

Proprietà e possibile ruolo regolativo della N—formil—tetraidrofolato: metionil-tRNA transformilasi in Euglena gracilis

Annastella Gambini, Paolo Crosti, Paolo Tortora, Giovanni Lucchini, Renato Bianchetti (1974)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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The properties of N-formyl-tetrahydrofolate: methionyl-tRNA transformylase from Euglena gracilis were studied and compared with those of the E. coli enzyme. The Euglena enzyme, functioning in formylation of met-tRNA initiator of organellar protein synthesis, shows a partial requirement of Mg, with an optimum of 5 mM, stimulation by K, Km for N-formyl-THFA 2.5 x 10 M. These properties are different from those of the bacterial enzyme. For example the affinity for the substrate N-formyl-THFA...

Assenza di nucleoside fosfondasi purinica e deficit selettivo grave dei linfociti T

Rosa Maria Corbo (1979)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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We studied a 22 months-old girl with severe selective T-cell deficiency and no measurable purine nucleoside phosphorylase activity in the RBC and granulocytes. No inhibitor was found in the patient's erythrocytes. Her parents are second cousins and their red cells exhibited about half the normal level of NP activity. The identification of heterozygotes within a three generation pedigree confirms that PNP deficiency is inherited as a mendelian autosomal trait and that erythrocytes can...

Sul collasso di un ammasso di materia disgregata. Nota I

Dionigi Galletto, Bruno Barberis (1985)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Starting from the considerations developed in [4], it is shown that the only forces at a distance exerted among the elements of an isolated spherical cluster of incoherent matter which, preserving homogeneity, is collapsing are those expressed by Newton's law of gravitation and those of the elastic type. Furthermore the reverse is shown, that is if the forces at a distance are of these two types during the collapse the homogeneity is preserved.

Sul collasso di un ammasso di materia disgregata. Nota I

Dionigi Galletto, Bruno Barberis (1985)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

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Starting from the considerations developed in [4], it is shown that the only forces at a distance exerted among the elements of an isolated spherical cluster of incoherent matter which, preserving homogeneity, is collapsing are those expressed by Newton's law of gravitation and those of the elastic type. Furthermore the reverse is shown, that is if the forces at a distance are of these two types during the collapse the homogeneity is preserved.

Sintesi di acidi ribonucleici e di proteine nelle diverse regioni dell'embrione di Xenopus laevis

Marisa Leonardi Cigada, Fiorenza Laria De Bernardi, Anna Maria Scarpetti Bolzern (1975)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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An analysis of RNA and protein synthesis has been carried out on Xenopus laevis embryos, cut into two portions, during the early stages of their development. Actinomycin D was employed to inhibit the synthesis. The action of actinomycin on synthesis is stronger during gastrulation than during neurulation. In each stage a correlation between RNA synthesis inhibition and protein synthesis inhibition has been observed. In the ventral fragments of the neurula the ratio between the two inhibitions...

Simmetria delle soluzioni di equazioni ellittiche semilineari in R N

Alberto Farina (1999)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

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Nella prima parte di questa Nota si dimostrano dei risultati di simmetria unidimensionale e radiale per le soluzioni di Δ ⁢ u + f ⁢ u = 0 in R N . Questi risultati sono legati a due congetture (De Giorgi, 1978 e Gibbons, 1994) riguardanti la classificazione delle soluzioni dell’equazione Δ ⁢ u + u ⁢ 1 - u 2 = 0 in R N . Si dimostra, in particolare, la seguente generalizzazione della congettura di Gibbons: se N > 1 e se l’insieme degli zeri di u è limitato nella direzione ν , allora u ⁢ x = u 0 ⁢ ν ⋅ x , ovvero, u è unidimensionale. Nella seconda parte...