Termodinamica di assorbimento di acqua in polimeri termoplastici vetrosi ad elevate prestazioni

Sorption thermodynamics of water in polymers is a subject of primary interest both from a fundamental point of view and for its practical implications. In fact, several polymer matrices, when exposed to a humid environment, absorb significant amounts of water which adversely affect most physical- mechanical properties. In this thesis, modelling of water sorption thermodynamics in high performance glassy thermoplastic matrices of polyetheretherketone (PEEK) and polyetherimide (PEI) and equilibrium water sorption in miscible PEEK/PEI blends as a function of blend ratio, has been investigated. Equation of state theories originally developed to interpret thermodynamics of mixtures at equilibrium, namely Sanchez-Lacombe Hydrogen Bonding (SLHB) and Non Random Hydrogen Bonding (NRHB), have been extended to the case of glassy polymer- low molecular weight penetrant mixtures, displaying possible hydrogen bonding interactions (HB). To this aim, the approach developed by Doghieri and Sarti in deriving the Non Equilibrium Theory for Glassy Polymers (NETGP), which is based on thermodynamics of internal state variables, has been adopted to extend the equilibrium models to out-of-equilibrium glassy systems, resulting in NETGP-SLHB and NETGP-NRHB theories. Making reasonable choices about the selected internal state variables and based on critical assumptions concerning the rate of evolution of these variables, it has been possible to obtain workable equations which have been used to interpret water sorption isotherms in PEEK and PEI, determined at temperatures ranging from 30 to 70 C°. For comparative purposes the Non-Equilibrium Lattice Fluid theory (NELF), which does not account for possible interactions between the components, has been also employed. The NELF model provided an unsatisfactory prediction of sorption isotherms, in view of its inability to reproduce the upward concavity exhibited at high vapor water activities, which is related to clustering of absorbed water molecules. Conversely, NETGP-SLHB and NETGP-NRHB models provided a good fitting of equilibrium sorption isotherms in the whole activity range investigated. In particular, differently from the NELF theory, the models displayed the same upward concavity as the experimental data. This improvement is to be ascribed to the HB contributions to the Gibbs energy. Once the best fitting parameters have been determined from experimental sorption isotherms, the developed models have been used to predict the amount of self-HB and cross-HB interactions occurring at equilibrium in the mixtures as a function of water mass fraction absorbed within polymers. At low water concentration cross-HB interactions prevailed while the water self-HB interactions increased their importance as total water concentration increased. For the PEI/water system the theoretical predictions were in good agreement with the experimental results obtained from FTIR spectroscopy. Differential scanning calorimetry measurements of PEEK/PEI mixtures showed a single glass transition temperature that increased with enhancing PEI content, confirming the complete miscibility in the amorphous state of components. The equilibrium water sorption in the blends decreased with increasing PEEK content and the sorption isotherms showed trends similar to those of neat components. At high activities the isotherms exhibited an upward concavity due to clustering of water molecules and not to plasticization effects in view of the low amount of water absorbed and of the very high glass transition temperature of the mixtures. On PEEK/PEI blends a study to evaluate their chemical resistance in Skydrol, Jet-fuel and methyl-ethyl-ketone (MEK) has been also performed. These solvents were chosen to represent a range of chemically aggressive environments that high performance polymers may encounter in aeronautic applications. Sorption kinetics showed modest absorptions of Skydrol and low absorptions of Jet-fuel for PEEK and PEI, while the blends exhibited a small weight lost, which decreased with enhancing the amount of PEEK. Conversely, higher absorptions were recorded with MEK, mainly for PEI and for blends rich in PEI

Integrated Indicators for the Estimation of Vulnerability to Land Degradation

In this chapter we approach the assessment of the vulnerability to land degradation of a typical Mediterranean environment using a modified version of the ESA model. This approach combines analyses of the socio-economic component with analyses of the vegetation trends. According to the standard ESA strategy, different indicators representing the impact of agricultural and grazing activities are used. The main feature of these indicators is that they are census-based and consequently suitable only for the analysis at municipal scale. Therefore we have also elaborated a mechanization index (proxy for soil compaction induced by agricultural machineries) that uses land cover and morphological data [36], enabling high spatial resolution and faster rate of update. The indicators related to the anthropic impact are integrated into an overall Land Management Index (LMI) and in each area it is possible to enhance the main contributing factors to highlight the prevailing forces that drive human-induced degradation processes. In order to include vegetation in the vulnerability map we analyze satellite vegetation index NDVI (Normalized Difference Vegetation Index) which is recognized as ideal tool for monitoring long term trends of degradation phenomena and assessing different values of severity of the concerned processes [37,38]. The final result of our analyses is an integrated vulnerability map of the investigated region, accounting for management and vegetation factors, which allows us to identify priority sites where restoration/rehabilitation interventions are urgent. The adopted procedure can be easily applied to geographic contexts characterized by high complexity in terms of land cover type and economic vocation (intensive agriculture, grazing, industrial activities) thus enabling an early detection of the areas most vulnerable to land degradation

Investigating climate variability and long-term vegetation activity across heterogeneous Basilicata agroecosystems

The Basilicata region summarizes many basic features of the biogeographic complexity characterizing Mediterranean countries. The intricate geomorphology and the long history of human management generated the current landscapes, which include both high-value ecosystems and areas prone to desertification. Preserving goods and services provided by such composite land cover mosaics poses many problems due to the interference/overlap of diverse natural and anthropic factors which make the correct selection of relevant parameters and the interpretation of observational data rather difficult. Here, we study interconnections between local climate and vegetation activity by correlating parameters characterizing the interannual statistics of the NDVI (Normalized Difference Vegetation Index), derived from satellite data, with a recently devised multivariate statistical index of meteoclimatic variability. We used a 15-year sequence of remote images concerning a set of plots located around meteorological ground stations of the central-eastern part of the region to pick up spatial structures in the vegetation–climate relationships. Our analyses were able to correlate spatial heterogeneity to variations in water exchanges between vegetation and atmosphere. This study represents a first step to improve the description of relevant processes to protect natural habitats and quality agriculture, therefore combating land degradation and climate change detrimental effects

Wavelet analysis as a tool to characteriseand remove environmental noisefrom self-potential time series

Multiresolution wavelet analysis of self-potential signals and rainfall levels is performed for extracting fluctuations in electrical signals, which might be addressed to meteorological variability. In the time-scale domain of the wavelet transform, rain data are used as markers to single out those wavelet coefficients of the electric signal which can be considered relevant to the environmental disturbance. Then these coefficients are filtered out and the signal is recovered by anti-transforming the retained coefficients. Such methodological approach might be applied to characterise unwanted environmental noise. It also can be considered as a practical technique to remove noise that can hamper the correct assessment and use of electrical techniques for the monitoring of geophysical phenomena

The VMC Survey -- XXXV. Model fitting of LMC Cepheid light curves

We present the results of the light curve model fitting technique applied to optical and near-infrared photometric data for a sample of 18 Classical Cepheids (11 fundamentals and 7 first overtones) in the Large Magellanic Cloud (LMC). We use optical photometry from the OGLE III database and near--infrared photometry obtained by the European Southern bservatory public survey "VISTA near--infrared survey of the Magellanic Clouds system". Iso--periodic nonlinear convective model sequences have been computed for each selected Cepheid in order to reproduce the multi--filter light curve amplitudes and shape details. The inferred individual distances provide an intrinsic weighted mean value for the LMC distance modulus of $\mu_0=18.56$ mag with a standard deviation of 0.13 mag. We derive also the Period--Radius, the Period--Luminosity and the Period--Wesenheit relations that are consistent with similar relations in the literature. The intrinsic masses and luminosities of the best--fitting models show that all the investigated pulsators are brighter than the redictions of the canonical evolutionary mass--luminosity relation, suggesting a significant efficiency of non--canonical phenomena, such as overshooting, mass loss and/or rotation.Comment: 14 pages, 10 figures, MNRAS accepte

Heavy Metal Concentrations in Dairy Products from Sheep Milk Collected in Two Regions of Southern Italy

The aim of this work was to detect the concentrations of some heavy metals in milk collected from ewes in 8 farms located in Calabria and Campania and to evaluate to what extent these metals may be present in dairy products for human consumption. The analysis of chromium, cadmium, lead and mercury was performed in a atomic absorption spectrophotometer equipped with a graphite furnace. The determination of Hg content in dry samples was carried out by means of an automatic Mercury analyser. Chromium was the metal detected at highest levels in milk and lead was highest in fresh, mature cheese and in ricotta. In Italy, human consumption of sheep milk is very limited and addressed to milk products. In our study the levels of some metals were higher than those reported in literature. However, the results indicate that sheep milk and milk products from the two regions of Italy investigated in this study are safe for consumers

The VMC survey – XXIII. Model fitting of light and radial velocity curves of Small Magellanic Cloud classical Cepheids

We present the results of the χ2 minimization model fitting technique applied to optical and near-infrared photometric and radial velocity data for a sample of nine fundamental and three first overtone classical Cepheids in the Small Magellanic Cloud (SMC). The near-infrared photometry (JK filters) was obtained by the European Southern Observatory (ESO) public survey ‘VISTA near-infrared Y, J, Ks survey of the Magellanic Clouds system’ (VMC). For each pulsator, isoperiodic model sequences have been computed by adopting a non-linear convective hydrodynamical code in order to reproduce the multifilter light and (when available) radial velocity curve amplitudes and morphological details. The inferred individual distances provide an intrinsic mean value for the SMC distance modulus of 19.01 mag and a standard deviation of 0.08 mag, in agreement with the literature. Moreover, the intrinsic masses and luminosities of the best-fitting model show that all these pulsators are brighter than the canonical evolutionary mass–luminosity relation (MLR), suggesting a significant efficiency of core overshooting and/or mass-loss. Assuming that the inferred deviation from the canonical MLR is only due to mass-loss, we derive the expected distribution of percentage mass-loss as a function of both the pulsation period and the canonical stellar mass. Finally, a good agreement is found between the predicted mean radii and current period–radius (PR) relations in the SMC available in the literature. The results of this investigation support the predictive capabilities of the adopted theoretical scenario and pave the way for the application to other extensive data bases at various chemical compositions, including the VMC Large Magellanic Cloud pulsators and Galactic Cepheids with Gaia parallaxe

Il progetto Lab2Go per la diffusione della pratica laboratoriale nelle Scuole Secondarie di II grado

Even if laboratory practice is essential for all scientific branches of knowledge, it is often neglected at High School, due to lack of time and/or resources. To establish a closer contact between school and experimental sciences, Sapienza Università di Roma and the Istituto Nazionale di Fisica Nucleare (INFN) launched the Lab2Go project, with the goal of spreading laboratory practice among students and teachers in high schools