Characterization of Flow Dynamics in the Pulmonary Bifurcation of Patients With Repaired Tetralogy of Fallot: A Computational Approach

The hemodynamic environment of the pulmonary bifurcation is of great importance for adult patients with repaired tetralogy of Fallot (rTOF) due to possible complications in the pulmonary valve and narrowing of the left pulmonary artery (LPA). The aim of this study was to computationally investigate the effect of geometrical variability and flow split on blood flow characteristics in the pulmonary trunk of patient-specific models. Data from a cohort of seven patients was used retrospectively and the pulmonary hemodynamics was investigated using averaged and MRI-derived patient-specific boundary conditions on the individualized models, as well as a statistical mean geometry. Geometrical analysis showed that curvature and tortuosity are higher in the LPA branch, compared to the right pulmonary artery (RPA), resulting in complex flow patterns in the LPA. The computational analysis also demonstrated high time-averaged wall shear stress (TAWSS) at the outer wall of the LPA and the wall of the RPA proximal to the junction. Similar TAWSS patterns were observed for averaged boundary conditions, except for a significantly modified flow split assigned at the outlets. Overall, this study enhances our understanding about the flow development in the pulmonary bifurcation of rTOF patients and associates some morphological characteristics with hemodynamic parameters, highlighting the importance of patient-specificity in the models. To confirm these findings, further studies are required with a bigger cohort of patients

Sensing and control of segmented mirrors with a pyramid wavefront sensor in the presence of spiders

The segmentation of the telescope pupil (by spiders & the segmented M4) create areas of phase isolated by the width of the spiders on the wavefront sensor (WFS), breaking the spatial continuity of the wavefront. The poor sensitivity of the Pyramid WFS (PWFS) to differential piston leads to badly seen and therefore uncontrollable differential pistons. In close loop operation, differential pistons between segments will settle around integer values of the average sensing wavelength. The differential pistons typically range from one to ten times the sensing wavelength and vary rapidly over time, leading to extremely poor performance. In addition, aberrations created by atmospheric turbulence will contain large amounts of differential piston between the segments. Removing piston contribution over each of the DM segments leads to poor performance. In an attempt to reduce the impact of unwanted differential pistons that are injected by the AO correction, we compare three different approaches. We first limit ourselves to only use the information measured by the PWFS, in particular by reducing the modulation. We show that using this information sensibly is important but will not be sufficient. We discuss possible ways of improvement by using prior information. A second approach is based on phase closure of the DM commands and assumes the continuity of the correction wavefront over the entire unsegmented pupil. The last approach is based on the pair-wise slaving of edge actuators and shows the best results. We compare the performance of these methods using realistic end-to-end simulations. We find that pair-wise slaving leads to a small increase of the total wavefront error, only adding between 20-45 nm RMS in quadrature for seeing conditions between 0.45-0.85 arcsec. Finally, we discuss the possibility of combining the different proposed solutions to increase robustness.Comment: 12 pages, 15 figures, AO4ELT5 Proceedings, Adaptive Optics for Extremely Large Telescopes 5, Conference Proceeding, Tenerife, Canary Islands, Spain, June 25-30, 201

k.p theory beyond standard 8-band theory parametrization strategies and its applicability in electronic and optoelectronic devices design

International audienc

Solving thermal issues in tensile-strained Ge microdisks

International audienceWe propose to use a Ge-dielectric-metal stacking to allow one to address both thermal management with the metal as an efficient heat sink and tensile strain engineering with the buried dielectric as a stressor layer. This scheme is particularly useful for the development of Ge-based optical sources. We demonstrate experimentally the relevance of this approach by comparing the optical response of tensile-strained Ge microdisks with an Al heat sink or an oxide pedestal. Photoluminescence indicates a much reduced temperature rise in the microdisk (16 K with Al pedestal against 200 K with SiO 2 pedestal under a 9 mW continuous wave optical pumping). An excellent agreement is found with finite element modeling of the temperature rise. This original stacking combining metal and dielectrics is promising for integrated photonics where thermal management is an issue

Food insecurity in adults with severe mental illness living in Northern England: A co-produced cross-sectional study

\ua9 2024 The Authors. Nutrition & Dietetics published by John Wiley & Sons Australia, Ltd on behalf of Dietitians Australia.Aim: This study aimed to explore food insecurity prevalence and experiences of adults with severe mental illness living in Northern England. Methods: This mixed-methods cross-sectional study took place between March and October 2022. Participants were adults with self-reported severe mental illness living in Northern England. The survey included demographic, health, and financial questions. Food insecurity was measured using the US Department of Agriculture Adult Food Security measure. Quantitative data were analysed using descriptive statistics and binary logistic regression; and qualitative data using content analysis. Results: In total, 135 participants completed the survey, with a mean age of 44.7 years (SD: 14.1, range: 18–75 years). Participants were predominantly male (53.3%), white (88%) and from Yorkshire (50.4%). The food insecurity prevalence was 50.4% (n = 68). There was statistical significance in food insecurity status by region (p = 0.001); impacts of severe mental illness on activities of daily living (p = 0.02); and the Covid pandemic on food access (p < 0.001). The North West had the highest prevalence of food insecurity (73.3%); followed by the Humber and North East regions (66.7%); and Yorkshire (33.8%). In multivariable binary logistic regression, severe mental illness\u27 impact on daily living was the only predictive variable for food insecurity (odds ratio = 4.618, 95% confidence interval: 1.071–19.924, p = 0.04). Conclusion: The prevalence of food insecurity in this study is higher than is reported in similar studies (41%). Mental health practitioners should routinely assess and monitor food insecurity in people living with severe mental illness. Further research should focus on food insecurity interventions in this population

Ultra-Low Threshold cw Lasing in Tensile Strained GeSn Microdisk Cavities

GeSn is proven as a good candidate to achieve CMOS-compatible laser sources on silicon. Lasing demonstrations in this alloy were based on directness of the band structure, this directness being increased with increasing the Sn content above 8 at.%. These past few years the research were consequently focused on incorporating the highest Sn content as possible to achieve high directness and high temperature laser operation. This unfortunately results is increased threshold. In this contribution we discuss the advantages in combining tensile strain engineering with lower Sn content alloys. This approach is motivated by the higher material quality in lower Sn content. The case with Sn content as small as 5.4 at.% Sn will be discussed. The alloy is initially compressively strained, and exhibits an indirect band gap that is turned to direct by applying tensile strain. A specific technology based on transfer On Insulator stressor layer on metal was developed to address strain engineering, thermal cooling and defective interface with the Ge-VS. This led to lasing in Ge0.95Sn0.05 microdisk cavities with dramatically reduced thresholds, by two order of magnitude, as compared to the case with high Sn alloys and as consequence enables cw operation