Optical characterization of pigments by reflectance spectroscopy in support of UV laser cleaning treatments

The study of optical properties of artwork materials is of fundamental importance for laser-based restoration techniques. In this work, reflectance spectroscopic measurements and colorimetric analyses of painted wooden models were performed to discriminate between pigments on the basis of their spectral features. In particular, the spectral reflection factors of different white pigments were recorded with a fibre optics reflectance spectroscopy module, both before and after excimer laser (248 nm) irradiation. Colour data were obtained and monitored with an integrating sphere spectrophotometer and expressed with the CIE L^*a^*b^* colour coordinates. Moreover, the laser-induced morphological changes of the samples were investigated by scanning electron microscopy. PACS  42.62-b; 61.80.Ba; 07.60.Dq     

A measurement of the azimuthal angle dependence of the process ep → enπ+ near threshold

The azimuthal angle dependence of the process ep → enπ⁺ has been measured by detecting the electron and neutron in coincidence. Data are presented for momentum transfers (?k²) between 0.08 and 0.32 $\text{(}\text{GeV}\text{c}\text{)}{}^2$ and at energies close to threshold. Fixed-t dispersion relation models give predictionsin good qualitative agreement with the data.     

Sul primo principio della termodinamica per I materiali semplici

It is known that the correct formulation of rational thermodynamics for mixtures requires an inequality more general than the Clausius-Duhem principle. On the other hand, in a recent paper on the thermodynamics of “interstitial working”[2] it was pointed out the need to correct the classical balance law of internal energy. There is no good reason for modifying both, however. It is worth to derive, hence, the most general expression of the Second Law by keeping the First in its classical form, as shown in a previous paper [4], or, what is the object of this article, to look for the most general formulation of the First Law assuming the Clausius-Duhem inequality as the Second. As a consequence of results obtained here, the statement of the First Principle needs not to be changed in the class of “simple material”. Thus, it is worth noting that a generalized expression of the First Law applies only non-simple materials, like as Korteweg fluids.

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Lavoro eseguito nell'ambito delle attività del G.N.F.M. del C.N.R. e dei progetti di ricerca ministeriali 40% e 60%.     

Su una teoria generale della misura (r − 1)-dimensionale in uno spazio adr dimensioni

Sunto In questo lavoro do una definizione della misura (r − 1)-dimensionale della frontiera orientata di un insieme diBorel contenuto in uno spazio euclideo ad r dimensioni e dimostro alcune fra le più notevoli proprietà di tale misura. Lavoro eseguito nell'Istituto Nazionale per le Applicazioni del Calcolo.     

The specific heat of two cubic laves compounds: TiBe2 and ThMg2

The low temperature specific heats of two isomorphous Laves compounds, TiBe₂ and ThMg₂, have been measured. The shape of the transition for the itinerant antiferromagnet TiBe₂ is characteristic of magnetic ordering; the entropy of this transition is quite small, approximately 107 mJ/mole-K, a further indication of itinerancy. The γ, proportional to the density of states, is 42 mJ/mole-K² for TiBe₂, and the Debye temperature, θ_D, is 650 K. These numbers are compared to those for the itinerant ferromagnet, ZrZn₂. The results for ThMg₂ are γ=9.2 mJ/ mole-K² and θ_D = 217 K. Results for both compounds are discussed in regards to the theory of Enz and Matthias.     

The total cross section for π+ electroproduction on hydrogen near threshold

The total cross section for the reaction ep → enπ⁺ at momentum transfers |k²| between 0.08 and 0.32 ($\text{GeV}\text{c}$)² and for centre of mass energies between threshold, at W = 1.078 GeV, and W = 1.106 GeV has been measured by detecting the electron and neutron in coincidence. Comparisons are made with both current algebra and dispersion relation theoretical models.     

Polarization in π+p → K+Σ+ backward scattering at 3.5 GeV/c

In a counter and wire spark chamber experiment with a polarized target, backward kaons were detected, and the Σ⁺'s identified by a missing-mass technique. An average polarization of ?0.08 ± 0.05 was found for ?0.2 < u < 0.1 GeV².     

Pump polarization effect in a superradiant NH3 and CH3F FIR Raman laser

The pump polarization has an evident effect on a superradiant FIR Raman laser both in NH₃ and CH₃F gases when the pump detuning from the resonant line is larger than the Raby frequency. In particular for R resonant lines the circular polarization shows a spontaneous gain about 1.5 times greater than the linear polarization as expected from the theory.