Experimental and numerical characterization of a positive displacement vane expander with an auxiliary injection port for an ORC-based power unit

Abstract In the present work a novel technology based on a dual injection vane expander has been introduced. The component works on a power unit fed by the exhaust gases of 3L turbocharged diesel engine. The new device was tested in a wide range of operating conditions and its numerical model was validated on the experimental data. The performances of the new machine were compared to those of the original one. The results showed that the dual injection expander provided an increase of the indicated and mechanical power up to 50% and 30%. Mass flow rate can be increased by 30% and this widens the performances of the power unit; this aspect is particularly suitable for a recovery unit fed by the widely changing exhaust gases flow rates in ICEs

charge air subcooling in a diesel engine via refrigeration unit effects on the turbocharger equilibrium

Abstract The stringent regulations on fuel saving and emissions reduction in the transportation sector have become game-raisers in the development of present internal combustion engines for road applications, even if under-the-hood space constraints, downsizing and down-weighting prevent from adopting radical changes in the engine layout. Charge air cooling is the standard in present turbocharged diesel engines, to the point that a dedicated heat exchanger, fed by environmental air, is located downstream the compressor. The paper proves the option of an additional cooling through the cabin-heating unit - usually over-sized with respect to normal operation - very effective to increase charge air density and improve cylinder filling. The intercooler downstream the compressor would be provided with a lower thermal load, hence calling for smaller heat exchange surfaces, leading to reduced weight, space saving and no increased layout complexity. By pushing this idea forward, a properly sized cabin-heating unit could even supply enough air cooling to replace the intercooler instead of just assisting it, further raising the weight/space/layout advantages. In presence of an additional heat exchanger, the cooling efficiency would be no longer related to the vehicle speed and the benefit in terms of cylinder filling could be kept to the desired value on a wider operating range for the engine. Plus, the lower combustion temperatures associated with both a colder air and a more diluted charge approaching the chamber would also result in a more regular combustion process, in spite of a moderate penalty on the thermodynamic efficiency. The additional fuel consumption to compress the cooling fluid is always offset by the fuel saving with respect to normal operation and a beneficial effect is appreciated on emissions. Nonetheless, major variables to account for when evaluating the feasibility of such a layout are (i) the impact it has on the equilibrium of the turbocharger, i.e. on the efficiency at each operating point, (ii) to what extent the presence of a colder air affects the turbine/compressor matching and (iii) the rack position the ECU fixes at the VGT, to face both pressure losses at the additional evaporator and the different enthalpy content for both the air at the compressor outlet and the exhaust gases at the turbine inlet. A comprehensive experimental activity supported by a detailed 1D model of the engine unit, aimed at assessing the benefits of the air under-cooling, allowed to select the most appropriate cooling layout and, once validated based on the experimental evidence, to investigate the equilibrium at the turbocharger

Ruptured middle cerebral artery aneurysms. retrospective study and multivariate analysis of 105 patients treated by surgical clipping

Objective of the study: We analyze in this study only patients with surgically treated ruptured aneurysms in order to identify statistical significance of each predictive factor in terms of outcome of patients with ruptured MCAAs. Materials and methods: In this retrospective study, we analyzed 105 cases of ruptured MCAAs, admitted from January 2001 to December 2015 at Neurosurgical Department of Umberto I University Hospital of Rome, Italy. Predictive factors evaluated are: Patient’s features (age, sex, co-morbidities), aneurysmal location (proximal, bifurcation or distal) and size of aneurysmal dome (small, large or giant); surgical timing (ultra-early, early, delayed), and Intracerebral Hemorrhage (ICH) volume. For each parameter we calculated mean and standard deviation, covariance and relation coefficient (through the linear regression model). Results: The clinical evaluation of patients assessed through the World Federation of Neurological Surgeons (WFSN) grading scale, that is 5 for 37 patients (35.3%), 4 for 28 patients. In 40% of cases the maximum sac diameter was between 7 mm and 12 mm, while in 67% of the cases the aneurysms concerned the bifurcation of the middle cerebral artery. ICH was associated in 57 cases (54.3%). As far as outcome is concerned, at 3 months, 32 patients (30.47%) had a favourable outcome, while 73 (69.52%) patients had not favourable outcome. To one year, 46 patients (43.8%) had favourable outcomes, while 59 patients (56.19%) had not favourable outcome. The mean outcomes as mean mRS are significantly less favourable in patients with ICH. Conclusion: In MCAAs patients, the presence of ICH strongly affects the outcome with a marked increase in mortality and morbidity. Surgical timing significantly influences the outcomes and ultra-early surgery should always be taken into account

Antegrade selective cerebral perfusion and moderate hypothermia in aortic arch surgery: clinical outcomes in elderly patients†

OBJECTIVES To evaluate the outcome in elderly patients (≥75 years) undergoing elective aortic arch surgery with the aid of selective antegrade cerebral perfusion (SACP) and moderate hypothermic circulatory arrest (HCA). METHODS A series of 95 patients ≥75 years (median age 77 years, median EuroSCORE 28) undergoing elective aortic arch surgery with SACP and moderate HCA were analysed with regard to clinical outcome. Risk factors for serious adverse events (mortality, neurological injury) were determined. RESULTS Sixty-three patients (66%) underwent ascending aorta and hemiarch replacement, whereas 32 patients (34%) underwent ascending aorta and total arch replacement. Isolated arch replacement was rare. Additionally, 27% of patients underwent aortic valve replacement and 26% underwent root replacement. In-hospital mortality was 7%. Permanent neurological deficits occurred in 5%, transient neurological deficits occurred in 2%. Median SACP time was 24min. Univariate analysis revealed femoral cannulation site (OR: 3.4; CI: 1.25-9.22, P=0.016) as well as HCA ≥40min (OR: 4.21; CI: 1.83-12.58, P=0.001) as predictors of serious adverse events (mortality, neurological injury). CONCLUSIONS Summarizing, elective aortic arch surgery in elderly patients using SACP and moderate HCA provides excellent results regarding mortality and postoperative neurological outcome. Prolonged HCA time and femoral cannulation were the only predictors of serious adverse events (mortality, neurological injury

Traumatic rupture of the thoracic aorta: Ten years of delayed management

ObjectiveTraumatic rupture of the thoracic aorta is a highly fatal condition in which patient outcome is strongly conditioned by other associated injuries. Delayed aortic treatment has been proposed to improve results.MethodsThe charts of 69 patients with traumatic rupture of the thoracic aorta observed between 1980 and 2003 were reviewed. Patients were grouped according the timing of repair: group I, immediate repair (21 patients); and group II, delayed repair (48 patients). In group II, 45 patients were treated surgically or by endovascular procedure.ResultsIn-hospital mortalities were 4 of 21 patients (19%) in group I and 2 of 48 patients (4.2%) in group II. There were 3 cases of paraplegia in group I and none in group II.ConclusionImprovement of patient outcome with traumatic rupture of the thoracic aorta can be achieved by delaying surgical repair until after management of major associated injuries if there are no signs of impending rupture. Endovascular treatment is feasible and safe and may represent a valid alternative to open surgery in selected cases

Minimally Invasive Aortic Valve Replacement with Sutureless Valves:Results From an International Prospective Registry

Objective: To report the early and mid-term results of patients who underwent minimally invasive aortic valve replacement (MI-AVR) with a sutureless prosthesis from an international prospective registry. Methods: Between March 2011 and September 2018, among 957 patients included in the prospective observational SURE-AVR (Sorin Universal REgistry on Aortic Valve Replacement) registry, 480 patients underwent MI-AVR with self-expandable Perceval aortic bioprosthesis (LivaNova PLC, London, UK) in 29 international institutions through either minithoracotomy (n = 266) or ministernotomy (n = 214). Postoperative, follow-up, and echocardiographic outcomes were analyzed for all patients. Results: Patient age was 76.1 ± 7.1 years; 64.4% were female. Median EuroSCORE I was 7.9% (interquartile range [IQR], 4.8 to 10.9). Median cardiopulmonary bypass and cross-clamp times were 81 minutes (IQR 64 to 100) and 51 minutes (IQR 40 to 63). First successful implantation was achieved in 97.9% of cases. Two in-hospital deaths occurred, 1 for noncardiovascular causes and 1 following a disabling stroke. In the early (≤30 days) period, stroke rate was 1.4%. Three early explants were reported: 2 due to nonstructural valve dysfunction (NSVD) and 1 for malpositioning. One mild and 1 moderate paravalvular leak were reported. In 16 patients (3.3%) pacemaker implantation was needed. Mean follow-up was 2.4 years (maximum = 7 years). During follow-up 5 explants were reported, 3 due to endocarditis and 2 due to NSVD. Follow-up stroke rate was 2.5%. Three structural valve deteriorations not requiring reintervention were reported. Five-year survival was 91.45%. Conclusions: In this large prospective international registry, MI-AVR with Perceval valve confirmed to be safe, reproducible, and effective in an intermediate-risk population, providing excellent clinical recovery both in early and mid-term follow-up

Aortic Root Replacement With Biological Valved Conduits

none9The execution of Bentall procedures using biological valved conduits is expanding owing to the increased incidence of aortic valve and root diseases in the aging population. To review the available data, a systematic search identified 29 studies with a total of 3,298 patients. Although evidence on short-term results suggested favorable outcomes after biological Bentall operations, data beyond 5 years are limited and highlight the urgent need for further investigations with longer follow-up.openCastrovinci, Sebastiano; Tian, David H; Murana, Giacomo; Cefarelli, Mariano; Berretta, Paolo; Alfonsi, Jacopo; Yan, Tristan D; Di Bartolomeo, Roberto; Di Eusanio, MarcoCastrovinci, Sebastiano; Tian, David H; Murana, Giacomo; Cefarelli, Mariano; Berretta, Paolo; Alfonsi, Jacopo; Yan, Tristan D; Di Bartolomeo, Roberto; Di Eusanio, Marc

Light-activated porphyrinoid-capped nanoparticles for gas sensing

The coupling of semiconductors with organic molecules results in a class of sensors whose chemoresistive properties are dictated by the nature of dyes. Organic molecules generally reduce conductivity, but in the case of optically active dyes, such as porphyrinoids, the conductivity is restored by illumination with visible light. In this paper, we investigated the gas sensing properties of ZnO nanoparticles coated with porphyrins and corroles. Under light illumination, the resistance of these materials increases with the adsorption of volatile compounds but decreases when these are strong electron donors. The behavior of these sensors can be explicated on the basis of the structural difference between free-base porphyrin and corrole, the influence of coordinated metal, and the corresponding electronic structures. These sensors are promising electronic noses that combine the selectivity to strong electron donors with the broad selectivity toward the other classes of chemicals. An efficient representation of the data of this peculiar array can be obtained by replacing the Euclidean distance with the angular distance. To this end, a recently introduced spherical principal component analysis algorithm is applied for the first time to gas sensor array data. Results show that a minimal gas sensor array (four elements) can produce a sort of chemotopic map, which enables us to cluster a very large class of pure chemical vapors. Furthermore, this map provides information about the composition of complex odor matrices, such as the headspaces of beef meat and their evolution over the time

Chiral selectivity of porphyrin-ZnO nanoparticle conjugates

Recognition of enantiomers is one of the most arduous challenges in chemical sensor development. Although several chiral systems exist, their effective exploitation as the sensitive layer in chemical sensors is hampered by several practical implications that hinder stereoselective recognition in solid state. In this paper, we report a new methodology to efficiently prepare chiral solid films, by using a hybrid material approach where chiral porphyrin derivatives are grafted onto zinc oxide nanoparticles. Circular dichroism (CD) evidences that the solid-state film of the material retains supramolecular chirality due to porphyrin interactions, besides an additional CD feature in correspondence of the absorbance of ZnO (375 nm), suggesting the induction of chirality in the underlying zinc oxide nanoparticles. The capability of hybrid material to detect and recognize vapors of enantiomer pairs was evaluated by fabricating gas sensors based on quartz microbalances. Chiral films of porphyrin on its own were used for comparison. The sensor based on functionalized nanostructures presented a remarkable stereoselectivity in the recognition of limonene enantiomers, whose ability to intercalate in the porphyrin layers makes this terpene an optimal chiral probe. The chiroptical and stereoselective properties of the hybrid material confirm that the use of porphyrin-capped ZnO nanostructures is a viable route for the formation of chiral selective surfaces. © 2019 American Chemical Society

Cryopreservation protocol for human biliary tree stem/progenitors, hepatic and pancreatic precursors

Human biliary tree stem/progenitor cells (hBTSCs) are being used for cell therapies of patients with liver cirrhosis. A cryopreservation method was established to optimize sourcing of hBTSCs for these clinical programs and that comprises serum-free Kubota's Medium (KM) supplemented with 10% dimethyl sulfoxide (DMSO), 15% human serum albumin (HSA) and 0.1% hyaluronans. Cryopreserved versus freshly isolated hBTSCs were similar in vitro with respect to self-replication, stemness traits, and multipotency. They were able to differentiate to functional hepatocytes,cholangiocytes or pancreatic islets, yielding similar levels of secretion of albumin or of glucose-inducible levels of insulin. Cryopreserved versus freshly isolated hBTSCs were equally able to engraft into immunocompromised mice yielding cells with human-specific gene expression and human albumin levels in murine serum that were higher for cryopreserved than for freshly isolated hBTSCs. The successful cryopreservation of hBTSCs facilitates establishment of hBTSCs cell banking offering logistical advantages for clinical programs for treatment of liver diseases