Studio del processo CVI/CVD per lo sviluppo di compositi ceramici rinforzati a fibra lunga

The most relevant thermo-mechanical properties of SiC or C based CFCCs are high strength, high toughness, low weight, high reliability, thermal shock and fatigue resistance. Thanks to these special characteristics, the CFCCs are the best candidates to substitute metals and monolithic ceramics, traditionally employed to realize components in energy, aeronautic and nuclear fields. Among the commonly techniques for the CFCCs production, CVI still represents the most significant one. Its main advantages are the versatility, the high quality deposits and the fact that it is conducted under mild temperature conditions. On the other hand, this technique is quite complex, therefore the set up of all process parameters needs long development time. The main purpose of the present study was to analyze the parameters controlling the CVD and CVI processes. Specifically, deposition and infiltration of SiC and Py-C tests were conducted on non-porous and porous substrates. The experiments were performed with a pilot size Isothermal/Isobaric CVI plant, designed and developed by ENEA. To guarantee the control of the process parameters, a previously optimization of the plant was needed. Changing temperature, pressure, flow rates and methane/hydrogen ratio, the Py-C deposition rate value, for an optimal fibre/matrix interphase thickness, was determined. It was also underlined the hydrogen inhibiting effect over the Py-C deposition rate. Regarding SiC morphologies, a difference between the inner and outer substrate surfaces was observed, as a consequence of a flow rate non-uniformity. In the case of the Cf/C composites development, the key parameter of the CVI process was the gas residence time. In fact, the hydrogen inhibiting effect was evident only with high value of residence time. Furthermore, lower the residence time more homogeneous the Py-C deposition rate was obtained along the reaction chamber axis. Finally, a CVD and CVI theoretical modelling was performed.

Identificazione di profili di rischio cardiovascolare nel trapianto di rene: polimorfismi di geni coinvolti nei processi di infiammazione e di apoptosi

Introduction. Cardiovascular disease (CVD) represents the main cause of morbidity and mortality in kidney recipients. This study was undertaken to assess the impact of functional polymorphisms located in cytokine and apoptosis genes on CVD after kidney transplantation. Cytokine polymorphisms, generally located in gene regulatory regions, are associated with high and low cytokine production and are likely to modulate the magnitude of inflammatory responses following transplantation, depending on the balance between the levels of pro-inflammatory and antiinflammatory cytokines. The role of apoptosis in atherosclerosis has not been completely elucidated, and here we explored the hypothesis that the heterogeneity in cardiovascular risk in kidney recipients may also be linked to functional polymorphisms involved in apoptosis induction. Purpose. In the search for relevant genetic markers of predisposition to CVD after renal transplant, the present investigation was undertaken to identify the clinical impact of polymorphisms of cytokines TNF-α, TGF-β, IL-10, IL-6, IFN-γ and IL-8 and of apoptosis genes Fas and Caspase 9 in a population of kidney transplant recipients. Materials and methods. The study involved 167 patients who received cadaveric kidney transplantation at our centre between 1997 and 2005 (minimum follow-up of 12 months); 35 of them had experienced cardiovascular events (CVD group) and 132 had no cardiovascular complications (non-CVD group). Genotyping was performed using RFLP (Restriction Fragment Length Polymorphism) for RFLP per IL-8/T-251A, Fas/G-670A e Casp9/R221Q polymorphism and SSP (Sequence Specific Primer) for TNF-α/G-308A, TGF-β/L10P, TGF-β/R25P, IL-10/G-1082A, IL- 10/C-819T, IL-10/C-592A, IL-6/G-174C, IFN-γ/T+874A polymorphisms.Results. We found a significant difference in TNF-α and IL-10 genotype frequencies between the patients who had suffered cardiovascular events and those with no CVD history. The high producer genotype for proflogistic cytokine TNF-α appeared to have a significantly superior prevalence in the CVD group compared to the non-CVD group (40.0% vs 21.2%) and it resulted in a 2.4-fold increased cardiovascular risk (OR=2.361; p=0.0289). On the other hand, the high producer genotype for the antiinflammatory cytokine IL-10 was found in 2.8% of the CVD group and in 16.7% of non-CVD group; logistic regression showed a 0.3-fold reduced risk of CVD associated with genetically determined high IL-10 production (OR=0.278; p<0.0001). The other polymorphisms did not prove to have any impact on CVD. Conclusions. TNF-α and IL-10 gene polymorphisms might represent cardiovascular risk markers in renal transplant recipients.

Studio della funzione cardiaca e della massa ventricolare sinistra mediante ecocardiografia convenzionale e tissue doppler imaging in una popolazione pediatrica con malattia renale cronica in terapia conservativa e sostitutiva

Background: Cardiovascular disease (CVD) is a common cause of morbidity and mortality in childhood chronic kidney disease (CKD). Left ventricular hypertrophy (LVH) is known to be one of the earliest events in CVD development. Left ventricular diastolic function (DF) is thought to be also impaired in children with CKD. Tissue Doppler imaging (TDI) provide an accurate measure of DF and is less load dependent than conventional ECHO. Aim: To evaluate the LV mass and the DF in a population of children with CKD. Methods: 37 patients, median age: 10.4 (3.3-19.8); underlying renal disease: hypo/dysplasia (N=28), nephronophthisis (N=4), Alport (N=2), ARPKD (N=3), were analyzed. Thirty-eight percent of the patients were on stage 1-2 of CKD, 38% on stage 3, 16% on stage 4. Three patients were on dialysis. The most frequent factors related to CVD in CKD have been studied. LVH has been defined as a left ventricular mass index (LVMI) more than 35.7 g/h2,7. Results: Twenty-five patients (81%) had a LVH. LVMI and diastolic function index (E’/A’) were significantly related to the glomerular filtration rate (p<0.003 and p<0.004). Moreover the LVMI was correlated with the phosphorus and the hemoglobin level (p<0.0001 and p<0.004). LVH was present since the first stages of CKD (58% of patients were on stages 1-2). Early-diastolic myocardial velocity was reduced in 73% of our patients. We didn’t find any correlation between LVH and systemic hypertension. Conclusion: ECHO evaluation with TDI is suggested also in children prior to dialysis and with a normal blood pressure. If LVH is diagnosed, a periodic follow-up is necessary with the treatment of the modifiable risk factors (hypertension, disturbances of calcium, phosphorus and PTH, anemia ).

Chemical Production and Microelectronic Applications of Graphene and Nano-Graphene Derivatives

Graphene and graphenic derivatives have rapidly emerged as an extremely promising system for electronic, optical, thermal, and electromechanical applications. Several approaches have been developed to produce these materials (i.e. scotch tape, CVD, chemical and solvent exfoliation). In this work we report a chemical approach to produce graphene by reducing graphene oxide (GO) via thermal or electrical methods. A morphological and electrical characterization of these systems has been performed using different techniques such as SPM, SEM, TEM, Raman and XPS. Moreover, we studied the interaction between graphene derivates and organic molecules focusing on the following aspects: - improvement of optical contrast of graphene on different substrates for rapid monolayer identification1 - supramolecular interaction with organic molecules (i.e. thiophene, pyrene etc.)4 - covalent functionalization with optically active molecules2 - preparation and characterization of organic/graphene Field Effect Transistors3-5 Graphene chemistry can potentially allow seamless integration of graphene technology in organic electronics devices to improve device performance and develop new applications for graphene-based materials. [1] E. Treossi, M. Melucci, A. Liscio, M. Gazzano, P. Samorì, and V. Palermo, J. Am. Chem. Soc., 2009, 131, 15576. [2] M. Melucci, E. Treossi, L. Ortolani, G. Giambastiani, V. Morandi, P. Klar, C. Casiraghi, P. Samorì, and V. Palermo, J. Mater. Chem., 2010, 20, 9052. [3] J.M. Mativetsky, E. Treossi, E. Orgiu, M. Melucci, G.P. Veronese, P. Samorì, and V. Palermo, J. Am. Chem. Soc., 2010, 132, 14130. [4] A. Liscio, G.P. Veronese, E. Treossi, F. Suriano, F. Rossella, V. Bellani, R. Rizzoli, P. Samorì and V. Palermo, J. Mater. Chem., 2011, 21, 2924. [5] J.M. Mativetsky, A. Liscio, E. Treossi, E. Orgiu, A. Zanelli, P. Samorì , V. Palermo, J. Am. Chem. Soc., 2011, 133, 14320

Hypertension, hypercholesterolemia, hyperaldosteronism: a genetic perspective for personalized therapy.

Essential, primary, or idiopathic hypertension is defined as high BP in which secondary causes such as renovascular disease, renal failure, pheochromocytoma, hyperaldosteronism, or other causes of secondary hypertension are not present. Essential hypertension accounts for 80-90% of all cases of hypertension; it is a heterogeneous disorder, with different patients having different causal factors that may lead to high BP. Life-style, diet, race, physical activity, smoke, cultural level, environmental factors, age, sex and genetic characteristics play a key role in the increasing risk. Conversely to the essential hypertension, secondary hypertension is often associated with the presence of other pathological conditions such as dyslipidaemia, hypercholesterolemia, diabetes mellitus, obesity and primary aldosteronism. Amongst them, primary aldosteronism represents one of the most common cause of secondary hypertension, with a prevalence of 5-15% depending on the severity of blood pressure. Besides high blood pressure values, a principal feature of primary aldosteronism is the hypersecretion of mineralcorticoid hormone, aldosterone, in a manner that is fairly autonomous of the renin-angiotensin system. Primary aldosteronism is a heterogeneous pathology that may be divided essentially in two groups, idiopathic and familial form. Despite all this knowledge, there are so many hypertensive cases that cannot be explained. These individuals apparently seem to be healthy, but they have a great risk to develop CVD. The lack of known risk factors makes difficult their classification in a scale of risk. Over the last three decades a good help has been given by the pharmacogenetics/pharmacogenomics, a new area of the traditional pharmacology that try to explain and find correlations between genetic variation, (rare variations, SNPs, mutations), and the risk to develop a particular disease.

Electrochemical surface modification of Single walled carbon nanotubes and graphene-based electrodes for (bio)sensing applications

Sensors are devices that have shown widespread use, from the detection of gas molecules to the tracking of chemical signals in biological cells. Single walled carbon nanotube (SWCNT) and graphene based electrodes have demonstrated to be an excellent material for the development of electrochemical biosensors as they display remarkable electronic properties and the ability to act as individual nanoelectrodes, display an excellent low-dimensional charge carrier transport, and promote surface electrocatalysis. The present work aims at the preparation and investigation of electrochemically modified SWCNT and graphene-based electrodes for applications in the field of biosensors. We initially studied SWCNT films and focused on their topography and surface composition, electrical and optical properties. Parallel to SWCNTs, graphene films were investigated. Higher resistance values were obtained in comparison with nanotubes films. The electrochemical surface modification of both electrodes was investigated following two routes (i) the electrografting of aryl diazonium salts, and (ii) the electrophylic addition of 1, 3-benzodithiolylium tetrafluoroborate (BDYT). Both the qualitative and quantitative characteristics of the modified electrode surfaces were studied such as the degree of functionalization and their surface composition. The combination of Raman, X-ray photoelectron spectroscopy, atomic force microscopy, electrochemistry and other techniques, has demonstrated that selected precursors could be covalently anchored to the nanotubes and graphene-based electrode surfaces through novel carbon-carbon formation.