Stress,body force,and momentum balance in mixture theory

Summary A general momentum balance for a mixture constituent is motivated from corpuscular considerations. The interpretations of stress and internal body force in the separate cases of ionic and non-ionic species are indicated. The Gurtin-Oliver-Williams paradox concerning the interpretation of partial stress is resolved, and relations between total and inner stress shown to be more complex than usually assumed. Comparison is made with kinetic theory.

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Sommario Una relazione generale di bilancio della quantità di moto per un costituente di una mistura è ricavata sulla base di considerazioni particellari. Interpretazioni di stress e forza interna di volume sono fornite per costituenti sia carichi sia neutri. In tal modo il paradosso di Gurtin, Oliver e Williams sull'interpretazione degli stress parziali viene risolto e, inoltre, le relazioni tra stress totali e parziali risultano in generale più complesse di quanto si assuma solitamente. Infine si effettua un confronto con la teoria cinetica.

     

Spatial interaction in magneto-micropolar continua

Summary We consider a micropolar continuum, whose material points are endowed with magnetic moment, in the presence of a magnetic field within the approximation of the quasimagnetostatics. We deduce the balance equations by a suitable averaging technique and then we examine the compatibility of spatial interaction effects with thermodynamics. As a result, we show that such effects are confined to the constitutive equations for the dissipative stress_DT, the dissipative couple stress_Dm and the heat flux q. Moreover, as a consequence of the reduced dissipation inequality, a linear theory would account only for a dependence of_DT,_Dm, and q on the velocity gradient, the angular velocity, the gradient of the angular velocity, and on the temperature gradient.

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Sommario Si considera un continuo micropolarc, i cui punti materiali sono dotati di momento magnetico, in presenza di un campo magnetico nell'approssimazione della quasimagnetostatica. Dopo aver dedotto le equazioni di bilancio mediante un opportuno procedimento di media, si esamina la compatibilità tra effetti di interazione spaziale e seconda legge della termodinamica e si mostra che tali effetti possono essere presenti solo nelle equazioni costitutive per lo stress dissipativo (di Cauchy)_DT.lo stress dissipativo delle coppie_Dm e il flusso di calore q. Inoltre, in conseguenza della disuguaglianza di dissipazione ridotta, si osserva che una teoria lineare permetterebbe solo una dipendenza di_DT,_Dm, q dal gradiente di velocità, dalla velocità angolare, dal gradiente della velocità angolare e dal gradiente di temperatura.

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This work was supported by the «Gruppo Nazionale per la Fisica Matematica» of CNR.     

Solid phase synthesis of a molecular library of pyrimidines, pyrazoles, and isoxazoles with biological potential

A small molecular library of 40 pyrimidine, pyrazole, and isoxazole derivatives, bearing structural features for a promising binding of therapeutically interesting enzymes, was designed and prepared. An efficient and straightforward solid phase synthesis was envisaged and carried out on a Rink amide resin. The assistance of microwave heating in any step reduced the reaction time, increased the reaction yields, and allowed an easy work-up and purification of the targeted compounds.     

Parametric, external and self-excitation of a tower under turbulent wind flow

In this paper the analysis of a self-excited tower under turbulent wind flow is carried out. The structure is considered as a one dof nonlinear system, and the implications of this modeling are deeply discussed. The stationary wind is responsible for self-excitation, while the turbulent part provides both parametric and external excitations. The simultaneous presence of those excitations is taken into account in a specific resonance condition. The periodic and quasi-periodic solutions are studied by means of a perturbation method and the effects of the turbulence on the dynamics of the structure are analyzed.     

Fast perturbation Monte Carlo method for photon migration in heterogeneous turbid media

We present a two-step Monte Carlo (MC) method that is used to solve the radiative transfer equation in heterogeneous turbid media. The method exploits the one-to-one correspondence between the seed value of a random number generator and the sequence of random numbers. In the first step, a full MC simulation is run for the initial distribution of the optical properties and the "good" seeds (the ones leading to detected photons) are stored in an array. In the second step, we run a new MC simulation with only the good seeds stored in the first step, i.e., we propagate only detected photons. The effect of a change in the optical properties is calculated in a short time by using two scaling relationships. By this method we can increase the speed of a simulation up to a factor of 1300 in typical situations found in near-IR tissue spectroscopy and diffuse optical tomography, with a minimal requirement for hard disk space. Potential applications of this method for imaging of turbid media and the inverse problem are discussed.     

Configuration interactions constrained by energy density functionals

A new method for constructing a Hamiltonian for configuration interaction calculations with constraints to energies of spherical configurations obtained with energy-density-functional (EDF) methods is presented. This results in a unified model that reproduced the EDF binding-energy in the limit of single-Slater determinants, but can also be used for obtaining energy spectra and correlation energies with renormalized nucleon–nucleon interactions. The three-body and/or density-dependent terms that are necessary for good nuclear saturation properties are contained in the EDF. Applications to binding-energies and spectra of nuclei in the region above ²⁰⁸Pb are given.     

Gold-catalyzed intramolecular hydroamination of α-amino allenamides as a route to enantiopure 2-vinylimidazolidinones

An efficient gold-catalyzed procedure for the preparation of 2-vinylimidazolidinones has been developed. The starting materials for the synthesis of these compounds are α-amino allenamides which undergo heterocyclization by means of nucleophilic attack of the amino group on the inside double bond of the 1,2-diene moiety. This is the first example of a gold-catalyzed cyclization on allene substrates bearing an amido group which, however, resulted inactive.     

Well-posed elliptic Neumann problems involving irregular data and domains

Non-linear elliptic Neumann problems, possibly in irregular domains and with data affected by low integrability properties, are taken into account. Existence, uniqueness and continuous dependence on the data of generalized solutions are established under a suitable balance between the integrability of the datum and the (ir)regularity of the domain. The latter is described in terms of isocapacitary inequalities. Applications to various classes of domains are also presented.