Numerical Characterisation of a HP Compressor Stage Equipped with a Closed Shrouded Stator Cavity

In axial compressors, shrouded stator cavity flows are responsible for performance degradation due to their interaction with the power stream. The present paper aims at exploring the possibility of employing a single stage high pressure axial compressor as a test vehicle for cavity flows investigations. In a first step, the robustness of the adopted RANS approach is tested against experimental data on the closed-cavity baseline configuration (i.e. no downstream-to-upstream recirculation). In a second phase, the effect of different hub cavities layouts of different levels of realism is numerically investigated. The focus is set on the representativeness of a closed cavity configuration with injection. The cavity flow topology and impact on the overall performance are considered in the analysis. At its final extent, this paper provides numerical and experimental guidelines for the robust assessment of cavity flows topology and performance effects.

Numerical Characterization of a HP Compressor Stage Equipped With a Closed Shrouded Stator Cavity

In axial compressors, shrouded stator cavity flows are responsible for performance degradation due to their interaction with the power stream. The present paper aims at exploring the possibility of employing a single stage high pressure axial compressor as a test vehicle for cavity flows investigations. In a first step, the robustness of the adopted RANS approach is tested against experimental data on the closed-cavity baseline configuration (i.e. no downstream-to-upstream recirculation). In a second phase, the effect of different hub cavities layouts of different levels of realism is numerically investigated. The focus is set on the representativeness of a closed cavity configuration with injection. The cavity flow topology and impact on the overall performance are considered in the analysis. At its final extent, this paper provides numerical and experimental guidelines for the robust assessment of cavity flows topology and performance effects.

Cooled Pressure Probes Design Methodology for Harsh Environment Applications

The present paper discusses in detail the methodology adopted for the cooling layout design of a water-cooled fast-response wall-static pressure probe intended for measurements in the combustion chamber of gas turbines. The proposed design approach is structured upon three main steps. In the first step, different reduced order correlations for convective and radiative heat transfer are used to derive the heat load at which the measurement device is submitted. In the second part, a quasi-2D conjugate heat transfer model is developed and operated through the application of the boundary conditions computed in the previous step. The model is based on empirical correlations and computes representative global cooling performance parameters for different cooling layouts and coolant mass flow rates. In the final step, the obtained design candidate is further validated by means of state-of-the-art fully 3D conjugate heat transfer numerical simulations performed on a probe geometry characterized by an increased degree of complexity. At its final extent, the present paper describes and validates a complete and robust methodology for the design of a cooling layout for cooled fast-response pressure probes.

The clinically effective use of cardiac markers by restructuring laboratory profiles at Cardiology wards

BackgroundLaboratory overutilization is associated with diagnostic error and potential patient risk. We applied a demand management strategy in collaboration with the local Department of Cardiology to reduce the cardiac markers high-sensitive troponin T (hsTropT) and N-terminal pro brain natriuretic peptide (NTproBNP) in laboratory ordering profiles (LOPs). The present study aimed to retrospectively evaluate the implemented strategies.MethodsStrategies included educational measures and evidence-guided, active test de-selection from all cardiology ward LOPs, and/or permanent removal from LOPs. Tests remained available at all times. We evaluated overutilization by reductions in monthly orders, and assessed differences in 30-day all-cause readmission rate and length of patients’ hospital stay.ResultsOverall, we observed a mean reduction of 66.1% ± 7.6% (n = 277 ± 31) in hsTropT tests. Educational measures effectively reduced NTproBNP orders by 52.8% ± 17.7% (n = 60 ± 20). Permanent removal of tests from LOPs additionally decreased orders to a final extent of 75.8% ± 8.0% (n = 322 ± 31) in NTproBNP tests. The 30-day readmission rate and overall length of hospital stay did not increase.ConclusionsOur results indicate that cardiac markers in routine care are subject to extensive overutilization when used within LOPs. Educational measures are an effective strategy to overcome the overutilization of cardiac markers but may be more effective when combined with the removal of cardiac markers from LOPs.

Advanced therapies to treat cardiovascular diseases: controversies and perspectives

There is a pressing need to develop novel therapies for myocardial infarction and heart failure, two conditions that affect over 20% of the world population. Despite important advances in achieving revascularization of the ischaemic myocardium and the usefulness of devices in assisting failing hearts, therapy for these conditions remains poor. The final extent of myocardial tissue loss after infarction is a major determinant of post-infarction mortality due to heart failure. In this chapter we review the current strategies aimed at counteracting injury due to acute myocardial ischaemia–reperfusion and the experimental approaches to achieve cardiac and vascular regeneration once damage has occurred. We critically discuss the possibility of inducing tissue restoration by gene transfer or exogenous cell implantation, and report on the exciting possibility of stimulating the endogenous capacity of cardiac regeneration using growth factors and small regulatory RNAs.

Modeling Jet Erosion of Particle Beds

Here we present and benchmark an analytical model to describe the radial extent of erosion of settled particle beds by radial wall jets as a function of time. The extent of erosion is an essential measure of the performance of vessels mixed by arrays of radial wall jets because portions of vessel floors not cleared of settled particles may accumulate undesirable constituents. We derive a model of the cleared radius as a function of time scaled so that fits may be described using only two free parameters. We find remarkably good agreement between experimental data and the model upon fitting. Extracted fitting parameters are shown to be reasonable. The influence of nozzle transience on erosion transience has also been evaluated. We find that nozzle transience explains the initially slower rate of erosion and decreases the final extent of erosion by one to three nozzle diameters for the cases considered. Future work remains to evaluate the dimensionless groups from conservation laws and account for vessel curvature.

Traumatic spinal cord injury: current concepts and treatment update

ABSTRACT Spinal cord injury (SCI) affects 1.3 million North Americans, with more than half occurring after trauma. In Brazil, few studies have evaluated the epidemiology of SCI with an estimated incidence of 16 to 26 per million per year. The final extent of the spinal cord damage results from primary and secondary mechanisms that start at the moment of the injury and go on for days, and even weeks, after the event. There is convincing evidence that hypotension contributes to secondary injury after acute SCI. Surgical decompression aims at relieving mechanical pressure on the microvascular circulation, therefore reducing hypoxia and ischemia. The role of methylprednisolone as a therapeutic option is still a matter of debate, however most guidelines do not recommend its regular use. Neuroprotective therapies aiming to reduce further injury have been studied and many others are underway. Neuroregenerative therapies are being extensively investigated, with cell based therapy being very promising.

Antiplatelet effect of ticagrelor compared to tirofiban in non-ST-segment elevation ACS patients undergoing PCI

SummaryAddition of a potent P2Y12 inhibitor to aspirin is the standard therapy for non-ST-segment elevation acute coronary syndrome (NSTE-ACS) patients undergoing percutaneous coronary intervention (PCI). Glyco-protein IIb/IIIa inhibitor, together with antiplatelet therapy, may be considered as part of initial therapy in NSTE-ACS patients with high-risk features. This study investigated the antiplatelet effect of ticagrelor loading dose (LD) versus tirofiban bolus injection with a post-bolus infusion on top of aspirin among NSTE-ACS patients planned to PCI. NSTE-ACS patients were randomised to receive either ticagrelor (n = 47) or tirofiban (n = 48). Platelet reactivity was assessed by light transmittance aggregometry at 0, 2, 8, and 24 hours (h) after treatment initiation. Primary endpoint was inhibition of platelet aggregation (IPA, 20 µM ADP, final extent) at 2 h after LD therapy, with a non-inferiority margin of 10 %. The prevalence of high on-treatment platelet reactivity (HPR) was also compared at 0, 2, 8, and 24 h. The mean difference in IPA between ticagrelor and tirofiban was -9.9 % (95 % confidence interval: –25.7 % to 5.9 %) at 2 h, –1.6 % (-8.0 % to 4.8 %) at 8 h, and –3.3 % (-18.4 % to 12.0 %) at 24 h. The prevalence of HPR did not differ between the two groups at any time point (all p values ≥ 0.059), which was almost abolished by 8 h post-LD (< 5 %). In conclusion, the antiplatelet effect during the early phase (~2 h) after ticagrelor LD appeared to be relatively strong, but it did not reach that of tirofiban in NSTE-ACS patients.