Experimental Investigation of Turbulence Diffusion — A Factor in Transportation of Sediment in Open-Channel Flow

Turbulence diffusion in open-channel flow was investigated experimentally by photographing the spread of globules formed by the injection of an immiscible fluid into water. The mean-square transverse deviations of the globules at various distances downstream from the source were computed and analyzed in an effort to determine the shape of the velocity-correlation curve. Comparison was made between two types of curve which fitted the deviation data, one corresponding to a power-correlation law and the other to an exponential-correlation law

Anomalous relaxation kinetics of biological lattice-ligand binding models

We discuss theoretical models for the cooperative binding dynamics of ligands to substrates, such as dimeric motor proteins to microtubules or more extended macromolecules like tropomyosin to actin filaments. We study the effects of steric constraints, size of ligands, binding rates and interaction between neighboring proteins on the binding dynamics and binding stoichiometry. Starting from an empty lattice the binding dynamics goes, quite generally, through several stages. The first stage represents fast initial binding closely resembling the physics of random sequential adsorption processes. Typically this initial process leaves the system in a metastable locked state with many small gaps between blocks of bound molecules. In a second stage the gaps annihilate slowly as the ligands detach and reattach. This results in an algebraic decay of the gap concentration and interesting scaling behavior. Upon identifying the gaps with particles we show that the dynamics in this regime can be explained by mapping it onto various reaction-diffusion models. The final approach to equilibrium shows some interesting dynamic scaling properties. We also discuss the effect of cooperativity on the equilibrium stoichiometry, and their consequences for the interpretation of biochemical and image reconstruction results.Comment: REVTeX, 20 pages, 17 figures; review, to appear in Chemical Physics; v2: minor correction

Drag estimation on wedge-shaped protuberances in high-speed flows

A semi-empirical method is developed to estimate drag on wedge-shaped projections in hypersonic flow. Force balance measurements from gun tunnel tests directly measure total drag on blunt wedges, where the boundary layer and the entropy layer are weakly coupled. Detailed flowfield analysis from numerical simulations provides estimated locations of peak pressure ratio and skin friction. Schlieren images are used for detecting incipient separation in incoming flows with laminar and turbulent boundary layers. Test results indicate the presence of local hotspots at reattachment points of strong detached shocks on the wedge compression ramp, and of primary and secondary vortical structures around lateral faces. Total drag is found to decrease with decreasing bluntness but increasing slenderness in wedges tend to increase skin friction drag

Reference enthalpy method developed from solutions of the boundary-layer equations

A simple average of local enthalpy over the velocity profile is proposed as the proper definition of reference enthalpy for the purpose of quasi-one-dimensional treatment of compressible boundary layers. Use of Van Driest's nearly exact solutions of the laminar boundary-layer equations shows that this definition produces Eckert's reference enthalpy formulation for the special case of an adiabatic wall. For surfaces other than adiabatic, either Eckert's form should be replaced by that of Young and Janssen, or the coefficient in Eckert's viscous heating term should be slightly modified. A similar analysis was conducted for turbulent flows using Whitfield and High's simplified solutions of the turbulent boundary-layer equations. Dorrance's derivation of reference quantities is also addressed. This work provides a theoretical basis for the empirical reference enthalpy formulas of Eckert and others and supplies practical expressions for the reference enthalpy of both laminar and turbulent compressible boundary layers

Etude DNS de la transition déclenchée par rugosité à Mach 6

International audienceIn hypersonic flows, it is useful to be able to trip the transition to turbulence upstream of air intakes for example. In the present work, direct numerical simulations have been performed of the flow past an isolated roughness element at Mach 6. First, the capability of two solvers to compute laminar and transitional flow involving freestream disturbances was demonstrated. A series of simulations was then carried out without acoustic perturbation of the freestream. The Reynolds number was increased from 14,000, to 28,000 and then to 40,000. The first two cases remain laminar within the computational domain, whereas the last case undergoes a self-sustained transition to turbulence. A response to a perturbation impulse shows the presence of a varicose mode at the intermediate Reynolds number and a sinuous mode at the largest Reynolds number.Dans les écoulements hypersoniques, il est nécessaire de pouvoir déclencher la transition vers la turbulence en amont des prises d'air par exemple. Dans cette étude, des simulations numériques directes de l'écoulement autour d'une rugosité isolée à Mach 6 ont été réalisées Dans un premier temps la capacité de deux solveurs à prédire l'écoulement laminaire ainsi que transitionnel impliquant des perturbations acoustiques a été démontrée. Une série de simulations a ensuite été réalisée à Mach 6 avec perturbations acoustiques. Le nombre de Reynolds a été augmenté de 14,000 à 28,000 puis à 40,000. Les deux premiers cas demeurent laminaires, alors que le dernier cas expérience une transition auto-entretenue vers la turbulence.Une étude de la réponse à une perturbation impulsionnelle montre la présence d'une instabilité variqueuse au nombre de Reynolds intermédiaire, et une instabilité sinueuse au plus fort nombre de Reynolds

The prevalence, incidence and management of low back pain with radiating leg pain in Dutch general practice:A population-based cohort study in the Rijnmond Primary Care Database

BACKGROUND: Radiating leg pain is common in patients with low back pain (LBP). In this study, we aimed to determine the prevalence and incidence of LBP with radiating leg pain in Dutch general practice, and to describe the prescribed medications and requested imaging diagnostics.METHODS: The Rijnmond Primary Care Database containing over 500,000 primary care patients was used to select patients ≥18 years with LBP with radiating leg pain between 2013 and 2021. Data on patient characteristics, LBP episodes, prescribed medication and requested imaging in the first 3 months of an episode was extracted. Descriptive statistics were used to present patient characteristics and diagnostic/therapeutic interventions.RESULTS: A total of 27,695 patients were included. The total number of LBP with radiating leg pain episodes in these patients was 36,268. In 2021, the incidence and prevalence were 19.1 and 25.7 per 1000 patient years, respectively. In 60% of patients, the episode duration was shorter than 1 month. In 62% of the episodes, patients visited the general practitioner (GP) one to two times. In 59% of the episodes, at least one medication was prescribed, non-steroidal anti-inflammatory drugs (NSAIDs) being the most common one (45%). In approximately 11% of the episodes, additional diagnostic imaging was requested.CONCLUSION: LBP with radiating leg pain is common in Dutch general practice patients. About 2/3rd were prescribed pain medications. Dutch request few to none diagnostic imaging for these patients which is in line with clinical practice guidelines.SIGNIFICANCE: In this new study, we have gained insights into the incidence and prevalence of LBP with radiating leg pain in Dutch general practice. Both remained fairly stable over the study period of 9 years (2013-2021). Overall, the care burden regarding seeking contact with the GPs and the requested diagnostics seem not to be that high. In 62% of the care episodes, there were one or two consultations with the GP, and in 11% of the episodes a diagnostic imaging was requested. Pain medications frequently prescribed (i.e. 2/3rd of the episodes), with NSAIDs being the most common ones.</p

No Added Value of Duloxetine in Patients With Chronic Pain due to Hip or Knee Osteoarthritis:A Cluster-Randomized Trial

OBJECTIVE: To assess the effectiveness of duloxetine in addition to usual care in patients with chronic osteoarthritis (OA) pain. The cost‐effectiveness and whether the presence of symptoms of centralized pain alters the response to duloxetine were secondary objectives. METHODS: We conducted an open‐label, cluster‐randomized trial. Patients with chronic hip or knee OA pain who had an insufficient response to acetaminophen and nonsteroidal antiinflammatory drugs were included. Randomization took place at the general practice level, and patients received duloxetine (60 mg/day) in addition to usual care or usual care alone. The presence of centralized pain was defined as a modified PainDETECT Questionnaire score >12. The primary outcome measure was Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scores (scale 0–20) at 3 months after the initiation of treatment. Our aim was to detect a difference between the groups of a clinically relevant effect of 1.9 points (effect size 0.4). We used a linear mixed model with repeated measurements to analyze the data. RESULTS: In total, 133 patients were included, and 132 patients were randomized into treatment groups. A total of 66 patients (at 31 practices) were randomized to receive duloxetine in addition to usual care, and 66 patients (at 35 practices) were randomized to receive usual care alone. We found no differences in WOMAC pain scores between the groups at 3 months (adjusted difference –0.58 [95% confidence interval (95% CI) –1.80, 0.63]) or at 12 months (adjusted difference –0.26 [95% CI –1.86, 1.34]). In the subgroup of patients with centralized pain symptoms, we also found no effect of duloxetine compared to usual care alone (adjusted difference –0.32 [95% CI –2.32, 1.67]). CONCLUSION: We found no effect of duloxetine added to usual care compared to usual care alone in patients with chronic knee or hip OA pain. Another trial including patients with centralized pain symptoms should be conducted to validate our results

The prevalence, incidence and management of low back pain with radiating leg pain in Dutch general practice:A population-based cohort study in the Rijnmond Primary Care Database

BACKGROUND: Radiating leg pain is common in patients with low back pain (LBP). In this study, we aimed to determine the prevalence and incidence of LBP with radiating leg pain in Dutch general practice, and to describe the prescribed medications and requested imaging diagnostics.METHODS: The Rijnmond Primary Care Database containing over 500,000 primary care patients was used to select patients ≥18 years with LBP with radiating leg pain between 2013 and 2021. Data on patient characteristics, LBP episodes, prescribed medication and requested imaging in the first 3 months of an episode was extracted. Descriptive statistics were used to present patient characteristics and diagnostic/therapeutic interventions.RESULTS: A total of 27,695 patients were included. The total number of LBP with radiating leg pain episodes in these patients was 36,268. In 2021, the incidence and prevalence were 19.1 and 25.7 per 1000 patient years, respectively. In 60% of patients, the episode duration was shorter than 1 month. In 62% of the episodes, patients visited the general practitioner (GP) one to two times. In 59% of the episodes, at least one medication was prescribed, non-steroidal anti-inflammatory drugs (NSAIDs) being the most common one (45%). In approximately 11% of the episodes, additional diagnostic imaging was requested.CONCLUSION: LBP with radiating leg pain is common in Dutch general practice patients. About 2/3rd were prescribed pain medications. Dutch request few to none diagnostic imaging for these patients which is in line with clinical practice guidelines.SIGNIFICANCE: In this new study, we have gained insights into the incidence and prevalence of LBP with radiating leg pain in Dutch general practice. Both remained fairly stable over the study period of 9 years (2013-2021). Overall, the care burden regarding seeking contact with the GPs and the requested diagnostics seem not to be that high. In 62% of the care episodes, there were one or two consultations with the GP, and in 11% of the episodes a diagnostic imaging was requested. Pain medications frequently prescribed (i.e. 2/3rd of the episodes), with NSAIDs being the most common ones.</p

Screening mutations in myosin binding protein C3 gene in a cohort of patients with Hypertrophic Cardiomyopathy

<p>Abstract</p> <p>Background</p> <p><it>MyBPC3 </it>mutations are amongst the most frequent causes of hypertrophic cardiomyopathy, however, its prevalence varies between populations. They have been associated with mild and late onset disease expression. Our objectives were to establish the prevalence of <it>MyBPC3 </it>mutations and determine their associated clinical characteristics in our patients.</p> <p>Methods</p> <p>Screening by Single Strand Conformation Polymorphisms (SSCP) and sequencing of the fragments with abnormal motility of the <it>MyBPC3 </it>gene in 130 unrelated consecutive HCM index cases. Genotype-Phenotype correlation studies were done in positive families.</p> <p>Results</p> <p>16 mutations were found in 20 index cases (15%): 5 novel [D75N, V471E, Q327fs, IVS6+5G>A (homozygous), and IVS11-9G>A] and 11 previously described [A216T, R495W, R502Q (2 families), E542Q (3 families), T957S, R1022P (2 families), E1179K, K504del, K600fs, P955fs and IVS29+5G>A]. Maximum wall thickness and age at time of diagnosis were similar to patients with <it>MYH7 </it>mutations [25(7) vs. 27(8), p = 0.16], [46(16) vs. 44(19), p = 0.9].</p> <p>Conclusions</p> <p>Mutations in <it>MyBPC3 </it>are present in 15% of our hypertrophic cardiomyopathy families. Severe hypertrophy and early expression are compatible with the presence of <it>MyBPC3 </it>mutations. The genetic diagnosis not only allows avoiding clinical follow up of non carriers but it opens new possibilities that includes: to take preventive clinical decisions in mutation carriers than have not developed the disease yet, the establishment of genotype-phenotype relationship, and to establish a genetic diagnosis routine in patients with familial HCM.</p