Modeling momentum and scalar transport in a wall-bounded turbulent flow

A mildly-heated turbulent boundary layer was studied to characterize the relationship between velocity structures and the scalar field. Particle image velocimetry (PIV) and a Malley probe (Malley et al., 1992) were used to simultaneously measure the velocity field and the streamwise gradients of the scalar field (Gordeyev et al., 2014) respectively. Two distinct velocity scales were identified to be correlated to scalar mixing by conditionally averaging the velocity field on the existence of a scalar gradient. Resolvent analysis was used to create simple models of these velocity scales (McKeon and Sharma, 2010) and to probe their interaction. Using a combination of structural conditional averaging and conditional averaging on the scalar gradient, significant interaction was observed between the two scales of interest, with behavior consistent with the general scale interaction described by amplitude modulation (Hutchins and Marusic, 2007). The study constructed a model of the velocity field that was correlated to streamwise scalar gradients in the outer boundary layer

Studies of the large-scale structure in adiabatic and moderately-wall-heated subsonic boundary layers

Simultaneous velocity-optical measurements in subsonic boundary layers were conducted in order to investigate the relationship between the instantaneous 2-D wavefronts, measured by different optical sensors, the Malley probe and 2-D Shack-Hartmann sensors, and the instantaneous large-scale structure along a wall-normal plane, using PIV in both incompressible and compressible subsonic boundary layers. These systematic studies of the instantaneous relation between the large-scale boundary layer structure and its aero-optical signature provide additional understanding of the instantaneous dynamics of the large-scale structure at subsonic and transonic speeds

Modeling momentum and scalar transport in a wall-bounded turbulent flow

A mildly-heated turbulent boundary layer was studied to characterize the relationship between velocity structures and the scalar field. Particle image velocimetry (PIV) and a Malley probe (Malley et al., 1992) were used to simultaneously measure the velocity field and the streamwise gradients of the scalar field (Gordeyev et al., 2014) respectively. Two distinct velocity scales were identified to be correlated to scalar mixing by conditionally averaging the velocity field on the existence of a scalar gradient. Resolvent analysis was used to create simple models of these velocity scales (McKeon and Sharma, 2010) and to probe their interaction. Using a combination of structural conditional averaging and conditional averaging on the scalar gradient, significant interaction was observed between the two scales of interest, with behavior consistent with the general scale interaction described by amplitude modulation (Hutchins and Marusic, 2007). The study constructed a model of the velocity field that was correlated to streamwise scalar gradients in the outer boundary layer

Scale interactions and 3D critical layers in wall-bounded turbulent flows

Phenomena related to scale interaction in wall-bounded turbulent flows were considered through the lens of critical layer analysis. A 3D critical layer formulation was used, with the 3D critical layer associated with a particular structure defined as the height where the instantaneous velocity field composed of the large scales and the mean velocity matched the convection velocity of that structure. Characterization of the velocity field surrounding the 3D critical layer in wall-bounded turbulent flows led to conclusions consistent with previously observed phenomena including the shape of the interface defining uniform momentum zones (UMZs) [1] [2] and amplitude modulation of the small scales by the large scales [5]. The use of a 3D critical layer formulation in wall-bounded turbulent flows may lead to improved modeling of small scale activity in reduced order models and LES

Studies of the large-scale structure in adiabatic and moderately-wall-heated subsonic boundary layers

Simultaneous velocity-optical measurements in subsonic boundary layers were conducted in order to investigate the relationship between the instantaneous 2-D wavefronts, measured by different optical sensors, the Malley probe and 2-D Shack-Hartmann sensors, and the instantaneous large-scale structure along a wall-normal plane, using PIV in both incompressible and compressible subsonic boundary layers. These systematic studies of the instantaneous relation between the large-scale boundary layer structure and its aero-optical signature provide additional understanding of the instantaneous dynamics of the large-scale structure at subsonic and transonic speeds

Plasmapheresis to remove amyloid fibrin(ogen) particles for treating the post‐COVID‐19 condition

Background The post‐COVID‐19 condition (PCC) consists of a wide array of symptoms including fatigue and impaired daily living. People seek a wide variety of approaches to help them recover. A new belief, arising from a few laboratory studies, is that 'microclots' cause the symptoms of PCC. This belief has been extended outside these studies, suggesting that to recover people need plasmapheresis (an expensive process where blood is filtered outside the body). We appraised the laboratory studies, and it was clear that the term 'microclots' is incorrect to describe the phenomenon being described. The particles are amyloid and include fibrin(ogen); amyloid is not a part of a thrombus which is a mix of fibrin mesh and platelets. Initial acute COVID‐19 infection is associated with clotting abnormalities; this review concerns amyloid fibrin(ogen) particles in PCC only. We have reported here our appraisal of laboratory studies investigating the presence of amyloid fibrin(ogen) particles in PCC, and of evidence that plasmapheresis may be an effective therapy to remove amyloid fibrin(ogen) particles for treating PCC. Objectives Laboratory studies review To summarize and appraise the research reports on amyloid fibrin(ogen) particles related to PCC. Randomized controlled trials review To assess the evidence of the safety and efficacy of plasmapheresis to remove amyloid fibrin(ogen) particles in individuals with PCC from randomized controlled trials. Search methods Laboratory studies review We searched for all relevant laboratory studies up to 27 October 2022 using a comprehensive search strategy which included the search terms ‘COVID’, ‘amyloid’, ‘fibrin’, ‘fibrinogen’. Randomized controlled trials review We searched the following databases on 21 October 2022: Cochrane COVID‐19 Study Register; MEDLINE (Ovid); Embase (Ovid); and BIOSIS Previews (Web of Science). We also searched the WHO International Clinical Trials Registry Platform and ClinicalTrials.gov for trials in progress. Selection criteria Laboratory studies review Laboratory studies that investigate the presence of amyloid fibrin(ogen) particles in plasma samples from patients with PCC were eligible. This included studies with or without controls. Randomized controlled trials review Studies were eligible if they were of randomized controlled design and investigated the effectiveness or safety of plasmapheresis for removing amyloid fibrin(ogen) particles for treating PCC. Data collection and analysis Two review authors applied study inclusion criteria to identify eligible studies and extracted data. Laboratory studies review We assessed the risk of bias of included studies using pre‐developed methods for laboratory studies. We planned to perform synthesis without meta‐analysis (SWiM) as described in our protocol. Randomized controlled trials review We planned that if we identified any eligible studies, we would assess risk of bias and report results with 95% confidence intervals. The primary outcome was recovery, measured using the Post‐COVID‐19 Functional Status Scale (absence of symptoms related to the illness, ability to do usual daily activities, and a return to a previous state of health and mind). Main results Laboratory studies review We identified five laboratory studies. Amyloid fibrin(ogen) particles were identified in participants across all studies, including those with PCC, healthy individuals, and those with diabetes. The results of three studies were based on visual images of amyloid fibrin(ogen) particles, which did not quantify the amount or size of the particles identified. Formal risk of bias assessment showed concerns in how the studies were conducted and reported. This means the results were insufficient to support the belief that amyloid fibrin(ogen) particles are associated with PCC, or to determine whether there is a difference in the amount or size of amyloid fibrin(ogen) particles in the plasma of people with PCC compared to healthy controls. Randomized controlled trials review We identified no trials meeting our inclusion criteria. Authors' conclusions In the absence of reliable research showing that amyloid fibrin(ogen) particles contribute to the pathophysiology of PCC, there is no rationale for plasmapheresis to remove amyloid fibrin(ogen) particles in PCC. Plasmapheresis for this indication should not be used outside the context of a well‐conducted randomized controlled trial

Protein-coding variants implicate novel genes related to lipid homeostasis contributing to body-fat distribution.

Body-fat distribution is a risk factor for adverse cardiovascular health consequences. We analyzed the association of body-fat distribution, assessed by waist-to-hip ratio adjusted for body mass index, with 228,985 predicted coding and splice site variants available on exome arrays in up to 344,369 individuals from five major ancestries (discovery) and 132,177 European-ancestry individuals (validation). We identified 15 common (minor allele frequency, MAF ≥5%) and nine low-frequency or rare (MAF <5%) coding novel variants. Pathway/gene set enrichment analyses identified lipid particle, adiponectin, abnormal white adipose tissue physiology and bone development and morphology as important contributors to fat distribution, while cross-trait associations highlight cardiometabolic traits. In functional follow-up analyses, specifically in Drosophila RNAi-knockdowns, we observed a significant increase in the total body triglyceride levels for two genes (DNAH10 and PLXND1). We implicate novel genes in fat distribution, stressing the importance of interrogating low-frequency and protein-coding variants

Genome-wide trans-ancestry meta-analysis provides insight into the genetic architecture of type 2 diabetes susceptibility.

To further understanding of the genetic basis of type 2 diabetes (T2D) susceptibility, we aggregated published meta-analyses of genome-wide association studies (GWAS), including 26,488 cases and 83,964 controls of European, east Asian, south Asian and Mexican and Mexican American ancestry. We observed a significant excess in the directional consistency of T2D risk alleles across ancestry groups, even at SNPs demonstrating only weak evidence of association. By following up the strongest signals of association from the trans-ethnic meta-analysis in an additional 21,491 cases and 55,647 controls of European ancestry, we identified seven new T2D susceptibility loci. Furthermore, we observed considerable improvements in the fine-mapping resolution of common variant association signals at several T2D susceptibility loci. These observations highlight the benefits of trans-ethnic GWAS for the discovery and characterization of complex trait loci and emphasize an exciting opportunity to extend insight into the genetic architecture and pathogenesis of human diseases across populations of diverse ancestry