Performance assessment and LCA of a PCM-based coating for residential buildings of the north-west Mediterranean region

The paper focuses on the thermo-economic and life cycle assessment of three different Phase-Change Materials (PCM) for use in residential buildings on the North-West Italian coast. For the purpose of this work, we considered the climatic conditions of the city of Genoa, Italy, and used publicly available weather data from year 2020. We numerically assessed three PCMs against conventional thermal insulating materials, on three different flat wall geometries, using a one-dimensional heat transfer model, implemented in MATLAB. The most relevant characteristic of PCMs is their phase transition condition. Our model is based on the assumption that PCMs transition occur in a specific temperature range, and this yields to an instantaneous increase of their specific heat. Subsequently, based on a 25-year PCM life cycle assumption, we carried out a thermo-economic analysis based on the Net Present Value (NVP) index, a life cycle assessment (LCA) and a carbon dioxide (CO2) saving estimation. Linear regression was used to predict the future economic and environmental scenarios. Simulation results showed that PCM performance is not as high as expected when benchmarked against a conventional insulating material. Specifically, PCMs do not reduce winter thermal demand and CO2 emissions over their life cycle are twice those of the classical insulator taken as a reference. We then numerically evaluated their performance in a warmer climate, corresponding to a South Mediterranean region, and under these conditions PCMs outperformed against conventional insulators, thus justifying their current higher cost

Synchronization Gauges and the Principles of Special Relativity

The axiomatic bases of Special Relativity Theory (SRT) are thoroughly re-examined from an operational point of view, with particular emphasis on the status of Einstein synchronization in the light of the possibility of arbitrary synchronization procedures in inertial reference frames. Once correctly and explicitly phrased, the principles of SRT allow for a wide range of `theories' that differ from the standard SRT only for the difference in the chosen synchronization procedures, but are wholly equivalent to SRT in predicting empirical facts. This results in the introduction, in the full background of SRT, of a suitable synchronization gauge. A complete hierarchy of synchronization gauges is introduced and elucidated, ranging from the useful Selleri synchronization gauge (which should lead, according to Selleri, to a multiplicity of theories alternative to SRT) to the more general Mansouri-Sexl synchronization gauge and, finally, to the even more general Anderson-Vetharaniam-Stedman's synchronization gauge. It is showed that all these gauges do not challenge the SRT, as claimed by Selleri, but simply lead to a number of formalisms which leave the geometrical structure of Minkowski spacetime unchanged. Several aspects of fundamental and applied interest related to the conventional aspect of the synchronization choice are discussed, encompassing the issue of the one-way velocity of light on inertial and rotating reference frames, the GPS's working, and the recasting of Maxwell equations in generic synchronizations. Finally, it is showed how the gauge freedom introduced in SRT can be exploited in order to give a clear explanation of the Sagnac effect for counter-propagating matter beams.Comment: 56 pages, 3 eps figures, invited paper; to appear in Foundations of Physics (Special Issue to honor Prof. Franco Selleri on his 70th birthday

A direct kinematical derivation of the relativistic Sagnac effect for light or matter beams

The Sagnac time delay and the corresponding Sagnac phase shift, for relativistic matter and electromagnetic beams counter-propagating in a rotating interferometer, are deduced on the ground of relativistic kinematics. This purely kinematical approach allows to explain the ''universality'' of the effect, namely the fact that the Sagnac time difference does not depend on the physical nature of the interfering beams. The only prime requirement is that the counter-propagating beams have the same velocity with respect to any Einstein synchronized local co-moving inertial frame.Comment: 10 pages, 1 EPS figure, to appear in General Relativity and Gravitatio

The Sagnac Phase Shift suggested by the Aharonov-Bohm effect for relativistic matter beams

The phase shift due to the Sagnac Effect, for relativistic matter beams counter-propagating in a rotating interferometer, is deduced on the bases of a a formal analogy with the the Aharonov-Bohm effect. A procedure outlined by Sakurai, in which non relativistic quantum mechanics and newtonian physics appear together with some intrinsically relativistic elements, is generalized to a fully relativistic context, using the Cattaneo's splitting technique. This approach leads to an exact derivation, in a self-consistently relativistic way, of the Sagnac effect. Sakurai's result is recovered in the first order approximation.Comment: 18 pages, LaTeX, 2 EPS figures. To appear in General Relativity and Gravitatio

Performance Assessment and LCA of a PCMBased Coating for Residential Buildings of the North-West Mediterranean Region

The paper focuses on the thermo-economic and life cycle assessment of three different Phase-Change Materials (PCM) for use in residential buildings on the North-West Italian coast. For the purpose of this work, we considered the climatic conditions of the city of Genoa, Italy, and used publicly available weather data from year 2020. We numerically assessed three PCMs against conventional thermal insulating materials, on three different flat wall geometries, using a one-dimensional heat transfer model, implemented in MATLAB. The most relevant characteristic of PCMs is their phase transition condition. Our model is based on the assumption that PCM transitions occur in a specific temperature range, and this yields to an instantaneous increase of their specific heat. Subsequently, based on a 25-year PCM life cycle assumption, we carried out a thermo-economic analysis based on the Net Present Value (NVP) index, a Life Cycle Assessment (LCA) and a carbon dioxide (CO2) saving estimation. Linear regression was used to predict the future economic and environmental scenarios. Simulation results showed that PCM performance is not as high as expected when benchmarked against a conventional insulating material. Specifically, PCMs do not reduce winter thermal demand and CO2 emissions over their life cycle are twice those of the classical insulator taken as a reference. We then numerically evaluated their performance in a warmer climate, corresponding to a South Mediterranean region, and under these conditions PCMs outperformed against conventional insulators, thus justifying their current higher cost

Tonsillectomy in a European Cohort of 1,147 Patients with IgA Nephropathy

Background: Tonsillectomy has been considered a treatment for IgA nephropathy (IgAN). It is aimed at removing a source of pathogens, reducing mucosa-associated lymphoid tissue and decreasing polymeric IgA synthesis. However, its beneficial effect is still controversial. In Asia, favorable outcomes have been claimed mostly in association with corticosteroids. In Europe, small, single-center uncontrolled studies have failed to show benefits. Methods: The European validation study of the Oxford classification of IgAN (VALIGA) collected data from 1,147 patients with IgAN over a follow-up of 4.7 years. We investigated the outcome of progression to end-stage renal disease (ESRD) and/or 50% loss of estimated glomerular filtration rate (eGFR) and the annual loss of eGFR in 61 patients who had had tonsillectomy. Results: Using the propensity score, which is a logistic regression model, we paired 41 patients with tonsillectomy and 41 without tonsillectomy with similar risk of progression (gender, age, race, mean blood pressure, proteinuria, eGFR at renal biopsy, previous treatments and Oxford MEST scores). No significant difference was found in the outcome. Moreover, we performed an additional propensity score pairing 17 patients who underwent tonsillectomy after the diagnosis of IgAN and 51 without tonsillectomy with similar risk of progression at renal biopsy and subsequent treatments. No significant difference was found in changes in proteinuria, or in the renal end point of 50% reduction in GFR and/or ESRD, or in the annual loss of eGFR. Conclusion: In the large VALIGA cohort of European subjects with IgAN, no significant correlation was found between tonsillectomy and renal function decline