An adaptable parallel algorithm for the direct numerical simulation of incompressible turbulent flows using a Fourier spectral/hp element method and MPI virtual topologies.

A hybrid parallelisation technique for distributed memory systems is investigated for a coupled Fourier-spectral/hp element discretisation of domains characterised by geometric homogeneity in one or more directions. The performance of the approach is mathematically modelled in terms of operation count and communication costs for identifying the most efficient parameter choices. The model is calibrated to target a specific hardware platform after which it is shown to accurately predict the performance in the hybrid regime. The method is applied to modelling turbulent flow using the incompressible Navier-Stokes equations in an axisymmetric pipe and square channel. The hybrid method extends the practical limitations of the discretisation, allowing greater parallelism and reduced wall times. Performance is shown to continue to scale when both parallelisation strategies are used.

High-density lipoprotein oxidation in type 2 diabetic patients and young patients with premature myocardial infarction.

BACKGROUND AND AIMS: ApoA-I can undergo oxidative changes that reduce anti-atherogenic role of HDL. The aim of this study was to seek any significant differences in methionine sulfoxide (MetO) content in the ApoA-I of HDL isolated from young patients with coronary heart disease (CHD), type 2 diabetics and healthy subjects. METHODS AND RESULTS: We evaluated the lipid profile of 21 type 2 diabetic patients, 23 young patients with premature MI and 21 healthy volunteers; we determined in all patients the MetO content of ApoA-I in by MALDI/TOF/TOF technique. The typical MALDI spectra of the tryptic digest obtained from HDL plasma fractions all patients showed a relative abundance of peptides containing Met(112)O in ApoA-I in type 2 diabetic and CHD patients. This relative abundance is given as percentages of oxidized ApoA-I (OxApoA-I). OxApoA-I showed no significant correlations with lipoproteins in all patients studied, while a strong correlation emerged between the duration of diabetic disease and OxApoA-I levels in type 2 diabetic patients. CONCLUSIONS: The most remarkable finding of our study lies in the evidence it produced of an increased HDL oxidation in patients highly susceptible to CHD. Levels of MetO residues in plasma ApoA-I, measured using an accurate, specific method, should be investigated and considered in prospective future studies to assess their role in CHD.

From h to p efficiently: optimal implementation strategies for explicit time-dependent problems using the spectral/hp element method.

We investigate the relative performance of a second-order Adams-Bashforth scheme and second-order and fourth-order Runge-Kutta schemes when time stepping a 2D linear advection problem discretised using a spectral/hp element technique for a range of different mesh sizes and polynomial orders. Numerical experiments explore the effects of short (two wavelengths) and long (32 wavelengths) time integration for sets of uniform and non-uniform meshes. The choice of time-integration scheme and discretisation together fixes a CFL limit that imposes a restriction on the maximum time step, which can be taken to ensure numerical stability. The number of steps, together with the order of the scheme, affects not only the runtime but also the accuracy of the solution. Through numerical experiments, we systematically highlight the relative effects of spatial resolution and choice of time integration on performance and provide general guidelines on how best to achieve the minimal execution time in order to obtain a prescribed solution accuracy. The significant role played by higher polynomial orders in reducing CPU time while preserving accuracy becomes more evident, especially for uniform meshes, compared with what has been typically considered when studying this type of problem.© 2014. The Authors. International Journal for Numerical Methods in Fluids published by John Wiley & Sons, Ltd.

[Evaluation of diosmectite in acute diarrhea in children]. / Valutazione della diosmectite nella diarrea acuta in età pediatrica.

The aim of this case-control study, was to estimate clinical effects, safety and parents' assessment of Diosmectite, in acute infantile diarrhoea. Thirty-five children aged 0-5 years, with acute diarrhoea from at least 5 days received alternatively oral rehydration solution (ORS) and Diosmectite (3 g/day for 3 days in children aged under 3 years and 6 g/day for 3 days in children aged over 3 years) (16 cases) or ORS only (19 cases). At discharge, parents' opinion concerning satisfaction for treatment received was evaluated through a questionnaire. Differences in the amount of liquid intake, weigh recovery, resolution of fever, resolution of vomiting and number of loose stools in the first 48 hours of hospitalization were not significant. Diosmectite was well tolerated and no major side effects were found. Parents' satisfaction for therapy resulted higher in the treated group than in the control group, even if differences were not significant. Treatment with ORS and Diosmectite allowed to shorten the mean duration of hospitalization by 0.4 days/children in the treatment group compared to the control group. Further studies with more cases and with higher does of the drug are necessary to confirm our results.