High repetition rate effects in XeCl tea lasers

The high repetition rate capability of a discharge pumped XeCl laser with static fill has been studied by double pulse experiments. By suitably selecting the laser parameters (energy deposition, gas mixture composition, filling pressure), following an analytical model of the discharge induced thermal effects, laser action from the second pulse for delays as short as 5 ms with an energy of 12.5 mJ has been achieved.     

Ab initio calculations including solvent effects of the structure of pyrazine, 4-nitropyridine and dicyanobenzenes ion pairs

The potential surfaces of pyrazine, 4-nitropyridine, 1,2-, 1,3-, 1,4- dicyanobenzene radical anions have been calculated within theab initio and electrostatic molecular potential formalism, including the effect of the solvent. These potential surfaces suggest models of ion pairs with alkali cations, which are in agreement with those deduced from related ESR spectra.     

Two-group kinetic theory of vehicular traffic

Summary We study a two-group model of vebicular traffic oli a highway which generalizes the Prigogine-Herman model. According to the two-group theory, drivers are divided into “slow” and “fast”. Correspondingly, we introduce a slow and a fast desired distribution representing the program that drivers of each of the two groups wish to follow. We first prove the existence and the uniqueness of a solution belonging to a suitable Banach space by using the theory of semigroups. Then, we indicate some sufficient conditions for the stability of an x and t independent solution.

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Sommario Si generalizza il modello di Prigogine-Herman del traffico automobilistico su un'autostrada, introducendo due gruppi di guidatori: i “lenti” ed i “veloci”. Ognuno dei due gruppi riene caratterizzato da un'opportuna funzione “desiderio”, che traduce i programmi che i guidatori intendono seguire nel corso del loro viaggio. Facendo poi uso della teoria dei semigruppi, si prova l'esistenza e l'unicità di una soluzione appartenente ad un opportuno spazio di Banach e si danno condizioni sufficienti per la stabilità.

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Work performed under the auspices of the National Research Council (C.N.R., Gruppo Nazionale per la Fisica Matematica).As the choice of the appropriate model for these problems is still a controversial matter, the Editorial Board welcomes any comment or discussion from the readers.     

Geometrical substituent parameters for benzene derivatives: inductive and resonance effects

A full set of geometrical parameters describing the effect of 21 substituents on the internal angles of the benzene ring has been derived by linear regression from many structural results. The parameters are shown to reflect the inductive and resonance effects of the substituents.     

Separation of human fibrinopeptides by capillary zone electrophoresis

We describe a method for the simultaneous determination of the five fibrinopeptide forms derived from the thrombin-promoted activation of human fibrinogen by capillary zone electrophoresis (CZE). The fibrinopeptide mixture was first desalted by a solid-phase extraction (SPE) step. The analysis was performed in reversed polarity in a highly cross-linked polyethylene glycol (PEG)-coated capillary with UV-light absorption detection at 200 nm. Several parameters including buffer concentration and pH, presence of an organic modifier, temperature, and applied voltage, have been tested. The best separations were obtained within 20 min, utilizing a 20 mM sodium phosphate buffer without organic modifier, in the narrow 6.1-6.2 pH range, at 25 degrees C, with an applied voltage of 20 kV. Quantitative analysis is made possible by the use of sheep fibrinopeptide A as an internal standard to correct for both extraction and injection errors.     

Boundary value problems and Mayer-Vietoris sequence

Milan Journal of Mathematics - We define formally non characteristic hypersurfaces for a complex of differential operators and we establish a Mayer-Vietoris sequence. We give applications to...     

Discontinuità e ipersuperfici caratteristiche in magnetofluidodinamica relativistica

Sunto L'A., dopo aver mostrato come si riduce il numero delle equazioni della m.f.d. in relatività generale quando la conducibilità elettrica è infinita, esamina le ipersuperfici di discontinuità nelle derivate delle funzioni incognite e ricerca le soluzioni proprie dei sistemi di equazioni lineari omogenee nei parametri di discontinuità. In primo luogo viene esaminato il sistema, indeterminato, che si deduce dalla solenoidalità del tensore energetico e dalle equazioni di Maxwell; successivamente si esaminano i sistemi determinati o associandovi l'ipotesi che il fluido sia barotropico, comprimibile o incomprimibile, o che valga un'equazione termica di stato e il principio di conservazione della densità numerica delle particelle. Si distingue tra ipersuperfici che siano luogo di linee di corrente e di linee di forza per il campo magnetico, e ipersuperfici che siano in vari modi intersecate da linee di corrente e da linee di forza, ottenendone le equazioni differenziali, nonchè i legami tra i parametri di discontinuità.

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Summary The A., after having shown how the number of the equations of magnetofluid-dynamics in general relativity is reduced when the electrical conductivity is infinite, studies the discontinuity manifolds of the derivatives of the unknown functions and looks for the eigensolutions of the linear homogeneous equations in the jumps of the derivatives. Firstly the A. studies the indeterminate system derived from the equations which state that the divergence of the energy-tensor is null and from the Maxwell equations; successively, he studies the systems which are determined by the hypothesis that either the fluid is incompressible, or is compressible and barotropic, or by a caloric state equation and by the conservation law of the numerical density of the particles. A distinction is made form manyfolds locus of path lines and locus of lines of force for the magnetic field and manyfolds which are variously crossed by path lines and by lines of force. The differential equations of the manyfolds and the relations from the jumps are found.

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Lavoro eseguito nell'ambito dell'attività dei Gruppi di ricerca Matematici del C.N.R.