Evaluation of In-Batch and In-Flow Synthetic Strategies towards the Stereoselective Synthesis of a Fluorinated Analogue of Retro-Thiorphan

A stereoselective synthetic strategy for the preparation of trifluoromethylamine mimics of retro-thiorphan, involving a diastereoselective, metal-free catalytic step, has been studied in batch and afforded the target molecule in good yields and high diastereoselectivity. A crucial point of the synthetic sequence was the catalytic reduction of a fluorinated enamine with trichlorosilane as reducing agent in the presence of a chiral Lewis base. The absolute configuration of the key intermediate was unambiguously assigned by X-ray analysis. The synthesis was also investigated exploiting continuous flow reactions; that is, an advanced intermediate of the target molecule was synthesized in only two in-flow synthetic modules, avoiding isolation and purifications of intermediates, leading to the isolation of the target chiral fluorinated amine in up to an 87:13 diastereoisomeric ratio

Aortic haemodynamics and wall stress analysis following arch aneurysm repair using a single-branched endograft

Introduction: Thoracic endovascular aortic repair (TEVAR) of the arch is challenging given its complex geometry and the involvement of supra-aortic arteries. Different branched endografts have been designed for use in this region, but their haemodynamic performance and the risk for post-intervention complications are not yet clear. This study aims to examine aortic haemodynamics and biomechanical conditions following TVAR treatment of an aortic arch aneurysm with a two-component single-branched endograft. Methods: Computational fluid dynamics and finite element analysis were applied to a patient-specific case at different stages: pre-intervention, post-intervention and follow-up. Physiologically accurate boundary conditions were used based on available clinical information. Results: Computational results obtained from the post-intervention model confirmed technical success of the procedure in restoring normal flow to the arch. Simulations of the follow-up model, where boundary conditions were modified to reflect change in supra-aortic vessel perfusion observed on the follow-up scan, predicted normal flow patterns but high levels of wall stress (up to 1.3M MPa) and increased displacement forces in regions at risk of compromising device stability. This might have contributed to the suspected endoleaks or device migration identified at the final follow up. Discussion: Our study demonstrated that detailed haemodynamic and biomechanical analysis can help identify possible causes for post-TEVAR complications in a patient-specific setting. Further refinement and validation of the computational workflow will allow personalised assessment to aid in surgical planning and clinical decision making

Combustion analysis of a light duty diesel engine using oxygen-enriched and humidified combustion air

The present work presents the results of 3D CFD combustion simulations of a current production 4-cylinder turbocharged Diesel engine using oxygen-enriched and humidified combustion air. Enriched Air (EA) is supposed to be produced by desorption from water, exploiting the different Henry constants of N2 and O2. Simulation results show that EA permits to increase the engine thermal efficiency (up to 10%) and drastically reduces soot emissions but increases in-cylinder peak pressure and NOx emissions. Combustion air humidification helps to reduce NOx increment, without losing the advantage in terms of thermal efficiency and in soot reduction, even if NOx emissions cannot be reported to the base case values

A Case of Concurrent Riedel's, Hashimoto's and Acute Suppurative Thyroiditis

Riedel's thyroiditis (RT) is a rare form of infiltrative and inflammatory disease of the thyroid, first described by Bernard Riedel in 1896. The concurrent presence of RT and other thyroid diseases has been reported, but, the association of RT with Hashimoto's thyroiditis and acute thyroiditis has not yet been reported. We present a case of concurrent Riedel's, Hashimoto's and acute thyroiditis that occurred in a 45-year-old patient

Effect of Carbon Support, Capping Agent Amount, and Pd NPs Size for Bio-Adipic Acid Production from Muconic Acid and Sodium Muconate

The effect of support, stabilizing agent, and Pd nanoparticles (NPs) size was studied for sodium muconate and t,t-muconic acid hydrogenation to bio-adipic acid. Three different activated carbons (AC) were used (Norit, KB, and G60) and carbon morphology did not affect the substrate conversion, but it greatly influenced the adipic acid yield. 1% Pd/KB Darco catalyst, which has the highest surface area and Pd surface exposure, and the smallest NPs size displayed the highest activity. Furthermore, the effect of the amount of the protective agent was studied varying metal/protective agent weight ratios in the range of 1/0.00-1/1.20, using KB as the chosen support. For sodium muconate reduction 1% Pd/KB_1.2 catalyst gave the best results in terms of activity (0.73 s-1), conversion, and adipic acid yield (94.8%), while for t,t-muconic acid hydrogenation the best activity result (0.85 s-1) was obtained with 1% Pd/KB_0.0 catalyst. Correlating the results obtained from XPS and TEM analyses with catalytic results, we found that the amount of PVA (polyvinyl alcohol) influences mean Pd NPs size, Pd(0)/Pd(II) ratio, and Pd surface exposure. Pd(0)/Pd(II) ratio and Pd NPs size affected adipic acid yield and activity during sodium muconate hydrogenation, respectively, while adipic acid yield was related by exposed Pd amount during t,t-muconic acid hydrogenation. The synthesized catalysts showed higher activity than commercial 5% Pd/AC

Effect of Metal Cocatalysts and Operating Conditions on the Product Distribution and the Productivity of the CO2 Photoreduction

open7The CO2 photoreduction is a promising way to convert one of the most abundant greenhouse gases to valuable chemicals. The photoreduction in the liquid phase is limited by the low solubility of CO2 in water, but this point is overcome here by using an innovative photoreactor, which allows one to work up to pressures of 20 bar, improving the overall productivity. The photoreduction was performed in the presence of Na2SO3 and using in primis commercial titanium dioxide (P25) and a set of titania catalysts functionalized by surface deposition of either monometallic or bimetallic cocatalysts. The gaseous products were hydrogen and traces of CO, while, in the liquid phase, formic acid/formate, formaldehyde and methanol were quantitatively detected. The pH was observed to shift the products distribution. A neutral environment led mainly to hydrogen and methanol, while, at pH 14, formate was the most abundant compound. The trend for monometallic cocatalysts showed enhanced productivity when using noble metals (i.e., gold and platinum). In order to limit the cost of the catalytic material, bimetallic cocatalysts were explored, adding titania with Au+Ag or Au+Pt. This may open to the possibility of performing the reaction with a smaller amount of the most expensive metals. In the end, we have expressed some conclusions on the cost of the photocatalysts here employed, to support the overall feasibility assessment of the process.openConte F.; Villa A.; Prati L.; Pirola C.; Bennici S.; Ramis G.; Rossetti I.Conte, F.; Villa, A.; Prati, L.; Pirola, C.; Bennici, S.; Ramis, G.; Rossetti, I