Dynamic MR of the pelvic floor. Influence of alternative methods to draw the pubococcygeal line (PCL) on the grading of pelvic floor descent

Objective: To evaluate the impact of the pubococcygeal line (PCL) position on hiatal descent grading, comparing the method recommended by the official guidelines with the other two most common methods reported in literature. Methods: Female patients prospectively included performed dynamic-MR (1,5 T) in supine position. Rectum and vagina were filled with ultrasound gel. MR protocol included TSE T2 weighted sequences on axial/sagittal/coronal planes and steady-state sequences (FIESTA) on midsagittal plane during three phases (rest, strain and defecation). On each phase, the posterior point of PCL was traced in the region recommended by the official guidelines (last coccygeal joint or PCLcc) and in the other two regions: coccyx's tip (PCLtip) and sacrococcygeal joint (PCLsc). The resulting grades of pelvic floor descent (according to HMO-System) were compared. Inter-reader and intra-reader agreement were evaluated. Results: The final population consisted of 60 patients (56yy±10). No significant differences in grading were observed using PCLtip and PCLcc in all phases (p = 0.3016/0.0719/0.0719 during rest/strain/defecation). Using PCLsc, the grading was significantly overestimated compared to PCLcc in all phases (p = 0.0041/0.0001/0.0001 during rest/strain/defecation). Inter-reader and intra-reader agreement were significantly higher using PCLtip (p < 0.05). Conclusions: PCLtip is a reliable and highly reproducible option to the official PCLcc to correctly grade the pelvic floor descent and could be used when the PCLcc is not clearly visible. The use of PCLsc overestimates the grading compared to the official PCLcc and should not be used to avoid wrong patients’ management

Unsteady Simulation of CO/H2/N2/air Turbulent Non-Premixed Flame

The Sandia/ETH-Zurich CO/H2/N2 non-premixed unconfined turbulent jet flame (named ‘Flame A’) is numerically simulated by solving the unsteady compressible reactive Navier– Stokes equations in a three-dimensional axisymmetric formulation, hence, in a formally twodimensional domain. The turbulent combustion closure model adopted is the Fractal Model, FM, developed as a subgrid scale model for Large Eddy Simulation. The fuel is injected from a straight circular tube and the corresponding Reynolds number is 16 700, while the air coflows. Since the thickness of the nozzle is 0.88 mm, and the injection velocity high, ?104ms?1, capturing the stabilization mechanism of the actual flame requires high spatial resolution close to the injector. Results are first obtained on a coarse grid assuming a fast-chemistry approach for hydrogen oxidation and a single step mechanism for carbon monoxide oxidation.With this approach the flame is inevitably anchored. Then, to understand the actual flame stabilization a more complex chemical mechanism, including main radical species, is adopted. Since using this chemistry and the coarse grid of previous simulation the flame blows off numerically, attention is focused on understanding the actual flame stabilization mechanism by simulating a small spatial region close to the injection with a very fine grid. Then, analysing these results, an artificial anchoring mechanism is developed to be used in simulations of the whole flame with a coarse grid. Unsteady characteristics are shown and some averaged radial profiles for temperature and species are compared with experimental data

A non-adiabatic flamelet progress-variable approach for LES of turbulent premixed flames

A progress variable/flame surface density/probability density function method has been employed for a Large Eddy Simulation of a CH4/Air turbulent premixed bluff body flame. In particular, both mean and variance of the progress variable are transported and subgrid spatially filtered gradient contributes to model the flame surface density (that introduces the effect of the subgrid flame reaction zone) and to presume a probability density function (that introduces the effect of subgrid fluctuations on chemistry). Chemistry is preliminarly tabulated in terms of laminar premixed flames and enthalpy is included as a new coordinate in their tabulation to take into account heat losses in the flowfield. Then, the PDF is used to build a turbulent flamelet library. The filtered mass, momentum, enthalpy and scalar equations mentioned above are integrated by an explicit scheme using finite differences, 2nd–order accurate in space and third order in time, over a cylindrical non-uniform grid using a staggered mesh. The bluff-body geometry is modelled by using the Immersed Boundary Method. The numerical predictions are compared with the available experimental data

Indications, limitations and complications of operative hysteroscopy: a retrospective study of an 8-year experience

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