Cosmological string models from Milne spaces and SL(2,Z) orbifold

The $n+1$-dimensional Milne Universe with extra free directions is used to construct simple FRW cosmological string models in four dimensions, describing expansion in the presence of matter with $p=k \rho$, $k=(4-n)/3n$. We then consider the n=2 case and make SL(2,Z) orbifold identifications. The model is surprisingly related to the null orbifold with an extra reflection generator. The study of the string spectrum involves the theory of harmonic functions in the fundamental domain of SL(2,Z). In particular, from this theory one can deduce a bound for the energy gap and the fact that there are an infinite number of excitations with a finite degeneracy. We discuss the structure of wave functions and give examples of physical winding states becoming light near the singularity.Comment: 14 pages, harvma

Drying kinetics and physico-chemical quality of mango slices

Mango (Mangifera indica L.) is an important tropical fruit consumed worldwide and grown in Italy only in Sicily, where the areas of the Tyrrhenian coast have proved to be suitable to produce valuable fruits. Mango fruit has a pleasant aroma and taste, which are important qualities for consumer’s sensorial acceptance. However, they are highly perishable, prone to progressive undesired changes if stored untreated, resulting in around 25% postharvest losses, which is further increased during storage and transportation. An alternative for reducing the above-mentioned undesired changes is the dehydration of the cut fruit, which reduce the fruit water activity, thereby avoiding the deteriorative process and extending the shelf-life. This study investigates the effect of dehydration at different temperatures (50, 60 and 70°C) on drying kinetics and volatile compounds of two cultivars (Keitt and Osteen) of mango fruits cultivated in Sicily. Significant losses of volatile constituents of fresh mango occurred at higher temperature, especially for the Osteen cultivar. A diffusion model including the effect of shrinkage is also proposed, which may be used to describe drying behaviour of fruits and to define the optimal drying conditions.. Experimental data of the moisture ratio during drying were well predicted by the model

Thermomechanical properties of amorphous metallic tungsten-oxygen and tungsten-oxide coatings

In this work, we investigate the correlation between morphology, composition, and the mechanical properties of metallic amorphous tungsten-oxygen and amorphous tungsten-oxide films deposited by Pulsed Laser Deposition. This correlation is investigated by the combined use of Brillouin Spectroscopy and the substrate curvature method. The stiffness of the films is strongly affected by both the oxygen content and the mass density. The elastic moduli show a decreasing trend as the mass density decreases and the oxygen-tungsten ratio increases. A plateaux region is detected in correspondence of the transition between metallic and oxide films. The compressive residual stresses, moderate stiffness and high local ductility that characterize compact amorphous tungsten-oxide films make them promising for applications involving thermal or mechanical loads. The coefficient of thermal expansion is quite high (i.e. 8.9 $\cdot$ 10$^{-6}$ K$^{-1}$), being strictly correlated to the amorphous structure and stoichiometry of the films. Under thermal treatments they show a quite low relaxation temperature (i.e. 450 K). They crystallize into the $\gamma$ monoclinic phase of WO$_3$ starting from 670 K, inducing an increase by about 70\% of material stiffness.Comment: The research leading to these results has also received funding from the European Research Council Consolidator Grant ENSURE (ERC-2014-CoG No. 647554). The views and opinions expressed herein do not necessarily reflect those of the European Commissio

Role of antiviral therapy in the natural history of hepatitis B virus-related chronic liver disease

Hepatitis B virus (HBV) infection is a dynamic state of interactions among HBV, hepatocytes, and the host immune system. Natural history studies of chronic hepatitis B (CHB) infection have shown an association between active viral replication and adverse clinical outcomes such as cirrhosis and hepatocellular carcinoma. The goal of therapy for CHB is to improve quality of life and survival by preventing progression of the disease to cirrhosis, decompensation, end-stage liver disease, hepatocellular carcinoma (HCC) and death. This goal can be achieved if HBV replication is suppressed in a sustained manner. The accompanying reduction in histological activity of CHB lessens the risk of cirrhosis and of HCC, particularly in non-cirrhotic patients. However, CHB infection cannot be completely eradicated, due to the persistence of covalently closed circular DNA in the nucleus of infected hepatocytes, which may explain HBV reactivation. Moreover, the integration of the HBV genome into the host genome may favour oncogenesis, development of HCC and may also contribute to HBV reactivation

Dilaton Gravity with a Non-minmally Coupled Scalar Field

We discuss the two-dimensional dilaton gravity with a scalar field as the source matter. The coupling between the gravity and the scalar, massless, field is presented in an unusual form. We work out two examples of these couplings and solutions with black-hole behaviour are discussed and compared with those found in the literature