476 research outputs found
Percorsi di lettura urbanistica
No full textIl contributo scientifico analizza il tessuto urbanistico in cui sono presenti alcune delle nuove stazioni della metropolitana collinare di Napoli, in particolar modo quelle di Salvator Rosa, Materdei, Museo e Piazza Dante. Il lavoro svolto è stato finalizzato alla comprensione e diffusione dei valori culturali e ambientali presenti e soprattutto a mettere in evidenza la compiuta reciprocità tra arte e vita cittadina, in linea con le scelte educative delle grandi metropoli europee tese alla riscoperta delle città come "grandi musei all'aperto". Il saggio approfondisce la conoscenza del tessuto urbanistico prossimo alle stazioni al fine di leggerne la composizione, la storia e le risorse culturali in esso insistenti
Cold-Curing Epoxy Resins: Aging and Environmental Effects. I – Thermal Properties
No full textThe effects of physical and chemical aging have been investigated on two cold-curing epoxy adhesives.
One of the two has been physically aged at different temperatures below its glass transition (i.e. 10, 23, 30 and 40°C) and then subjected to enthalpy relaxation measurements in a differential scanning calorimeter (DSC). According to recent literature, DSC studies have suggested that enthalpy relaxation gradually increases with aging time to a limiting value, depending on the temperature, until structural equilibrium is reached.
Specimens of both adhesives, previously cured at room temperature for 10 days, have been aged in dry-dark atmosphere or in a freezer (–20°C) for a prolonged time, measuring Tg and enthalpy relaxation at different time spans. When the structural equilibrium is reached, the samples aged in the dark-dry atmosphere exhibit Tg and relaxation peak values similar to those found in the earlier analysis for samples isothermally cured at 23°C. Samples aged at –20°C, the curing time suggested by suppliers which was not sufficient to cure the adhesives completely, have glass transition temperatures that are always lower.
The cured adhesives have also been exposed to natural weather for up to 36 months. Some samples, taken at different periods of time, have been analyzed in DSC. Other samples have been subjected to a de-aging procedure (24 hours at 50°C) before the thermal analysis. The natural exposition, regarded as chemical aging, determines a cycling change of Tg of both adhesives around average values slightly lower than the initial ones. This behavior cannot be erased by the de-aging procedure, which is able to delete only the effects due to physical aging. Enthalpy relaxation peaks, characteristics of physical aging, are observed only for exposed samples not subjected to de-aging procedure. These samples, finally, are subjected during the natural exposition to aging and de-aging processes taking place in non-isothermal conditions and, therefore, not predictable
Epoxy resins employed in civil engineering applications: effects of exposure to mild temperatures
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Chronic hepatitis C infection induces cardiovascular disease and type 2 diabetes: mechanisms and management
No full textDespite the availability of effective treatments, hepatitis C virus (HCV) still remains a threat to public health. HCV is capable to trigger, behind liver damage, extrahepatic manifestations, including cardiovascular disease and type 2 diabetes (T2DM). A close association has been reported between HCV infection and cardiovascular disease due to imbalances in metabolic pathways and chronic inflammation. HCV through both direct and indirect mechanisms causes a higher incidence of ischemic stroke, acute coronary syndrome, heart failure and peripheral arterial disease. In addition, a higher risk of death from cardiovascular events has been showed in HCV patients. Insulin resistance is a hallmark of HCV infection and represents the link between HCV and T2DM, which is one of the most frequent HCV-associated extrahepatic manifestations. The pathological basis of the increased risk of T2DM in HCV infection is provided by the alterations of the molecular mechanisms of IR induced both by the direct effects of the HCV proteins, and by the indirect effects mediated by chronic inflammation, oxidative stress and hepatic steatosis. T2DM increases the risk of compensated and decompensate cirrhosis and hepatocellular carcinoma as well as increases the risk of cardiovascular disease, lower limb amputation and end stage renal disease. Current evidence suggests that HCV eradication reduces the incidence and mortality of cardiovascular disease and T2DM, further underling the importance of public health strategies for eradication the infection. Aim of this review is to update evidence and management of interaction between HCV, cardiovascular disease, and T2DM in the era of DAA treatmen
Role of high-temperature Equal-Channel Angular Pressing strain path on secondary-phase precipitation in a T6-Al-Cu-Li-Mg-Ag-Zr-Sc alloy
No full textEqual-channel angular pressing (ECAP) is known to induce significant grain refinement and formation of tangled dislocations
within the grains. These are induced to evolve to form low-angle boundaries (i.e., cell boundaries) and eventually
high-angle boundaries (i.e., grain boundaries). On the other hand, precipitation sequence of age hardening aluminum alloys
can be significantly affected by pre-straining, and severe plastic deformation. Thus, ECAP is expected to influence the T6
response of aluminum alloys. In this study, a complex Al-Cu-Mg-Li-Ag-Zr-Sc alloy was subjected to ECAP following different
straining paths. The alloy was ECAP at 460K via route A, C, and by forward-backward route A up to 4 passes. The alloy
was also aged at 460K for different durations after ECAP. It resulted that T1-Al2CuLi phase was the one that mostly showed a
precipitation sequence speed up induced by the tangled dislocations formed during ECAP. The T1 phase was found to grow
with aging time according to Lifshitz-Slyozov-Wagner power-low regime
Cold-curing epoxy resins: Aging and environmental effects. II - Mechanical properties
No full textThermosetting adhesives, suitable to join different materials in structural applications, are influenced during their service life by various effects which might cause them damage and that are not deeply experienced. They can be, in fact, exposed to atmospheric influences as well as subjected to physical aging as a consequence of their glassy non-equilibrium nature.
In the first part of this study, the influences of natural exposure and physical aging, occurring separately or concurrently, on thermal properties of cold-curing epoxy adhesives have been examined. This second part analyzes weathering influences on the mechanical properties of the same adhesives. For this purpose, the different aging processes have been first separated, in order to investigate any single effect, and then their simultaneous influences have been evaluated.
The specimens only physically aged exhibit the highest values of static modulus and yield strength, in accordance with current literature. The exposure to natural weathering (i.e. to chemical and physical agings) determines a fluctuation of mechanical properties, whose average values, however, remain close to the initial ones. The effects of chemical aging have been found particularly severe on the filled adhesive. A de-aging treatment, able to erase only physical aging and to remove a limited amount of sorbed water, results in an incomplete recovery in modulus and strength. This effect is partially due to the crosslinking reactions taking place in the cold-cured adhesives.
It is thought that the results of this qualitative study can be extended to longer periods of natural exposure, even in the absence of any critical external agent, and that the behavior observed for the selected adhesives can be considered comparable to that of other cold-curing epoxy adhesives
Insight of thermo-meccanical and fire properties of an aerospace epoxy matrix loaded with micro and nanofillers
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