Effects of plan area densities of cubical roughness elements on turbulent boundary layers

During the past few years, large-scale motions (LSM) in turbulent boundary layers over smooth-walls have received renewed attention from the research community. Common features of the LSMs found in wall-bounded flows are that they consist in elongated low- and high-speed regions, the length of which scale with the boundary-layer depth (?) and can reach several times ?, they populate the log- and outer layer, they are animated by a meandering motion in the horizontal plane (Hutchins & Marusic, JFM, 2007) and interact with near-wall turbulence through an amplitude-modulation mechanism (Mathis et al, JFM, 2009). At the same time, attention has been devoted to the structure of boundary layer flows developing over rough walls, at laboratory scales or in the framework of atmospheric flows over urban or vegetation canopies, demonstrating similarities between flows over smooth and rough wall. In particular, the presence of streaky patterns of low- and high-speed regions, of ejection and sweep motions associated to the hairpin model and the organization of hairpin vortices in packets have been evidenced (Jimenez, Ann Rev Fluid Mech, 2004; Finnigan et al, JFM, 2009; Inagaki & Kanda, BLM, 2010; Takimoto et al, BLM, 2011). The results obtained in flows over rough-walls suggest that, in spite of the strong disturbance of the flow at the wall, LSMs exist and interact with the canopy flow in a similar manner as in smooth wall boundary layers. However, in configurations representative of flows over urban canopies, it is likely that the arrangement, the shape and plan density of the roughness elements have a strong influence on the flow dynamics in the lower part of the boundary layer. Building upon these recent results, the aim of the present work is to analyze the statistical and spectral characteristics of turbulent boundary layer developing over cubical roughness arrays of different plan densities, at high Reynolds number, which has never been fully properly documented. This study, conducted in an atmospheric wind tunnel, is based on single hot-wire measurements performed along a vertical profile across the boundary layer, in a flow configuration representative of the atmospheric boundary layer (ABL) developing over an urban canopy. Three different rough walls of plan area density (i.e the ratio between the area of the surface occupied by the roughness elements and that of the total surface) of 6,25%, 25% and 44% are studied. Each roughness configuration is composed of a staggered array of cubes of height of h = 50 mm distributed on the wind tunnel floor over a total length of 22 m and a width of 2 m. The experiments have been performed with two free-stream velocities Ue = 5.8 and 9.1 m/s corresponding to Reynolds numbers h+ = h.u-/? ~ 1300, 2000 and Re? = ?.u-/? ~ 27000, 42000, respectively (where u- is the friction velocity). One-point statistics up to the fourth order are computed using hot-wire data acquired at 10000 kHz over a period corresponding to about 27000 turnover times, ?/Ue, to ensure proper statistical convergence of both large- and small-scale contents. It should me emphasized that the large-scales convergence criterion requires one hour and twenty minutes of acquisition per measured point. Besides the computation of mean velocity, standard deviation, skewness and kurtosis, this unprecedented database is also used to investigate the evolution of the spectral density content of the streamwise velocity component as a function of the wall-distance, the roughness element distribution and the Reynolds number. The ultimate goal of this ongoing study is to identify the mechanisms of interaction between the ABL and the canopy flow in order to contribute to the development of wall and/or canopy model

Pharmaceutics

The purpose of this study is to evaluate the visual acuity (VA) gain profiles between patients with drug-naive diabetic macular edema (DME) treated by dexamethasone implant (DEX-implant) and assess the baseline anatomical and functional factors that could influence the response to the treatment in real-life conditions. A retrospective, multi-center observational study included 129 eyes with drug-naive DME treated by DEX-implant. The Median follow-up was 13 months. Two groups of VA gain trajectories were identified-Group A, with 71% (n = 96) of patients whose average VA gain was less than five letters and Group B, with 29% (n = 33) of patients with an average gain of 20 letters. The probability of belonging to Group B was significantly higher in patients with baseline VA \textbackslashtextless 37 letters (p = 0.001). Ellipsoid zone alterations (EZAs) or disorganization of retinal inner layers (DRILs) were associated with a lower final VA (53.0 letters versus 66.4, p = 0.002) but without a significant difference in VA gain (4.9 letters versus 6.8, p = 0.582). Despite a low baseline VA, this subgroup of patients tends to have greater visual gain, encouraging treatment with DEX-implant in such advanced-stage disease. However, some baseline anatomic parameters, such as the presence of EZAs or DRILs, negatively influenced final vision

The atmospheric boundary layer over urban-like terrain: influence of the plan density on roughness sublayer dynamics

We investigate the effect of the packing density of cubical roughness elements on the characteristics of both the roughness sublayer and the overlying turbulent boundary layer, in the context of atmospheric flow over urban areas. This is based on detailed wind-tunnel hot-wire measurements of the streamwise velocity component with three wall-roughness configurations and two freestream flow speeds. The packing densities are chosen so as to obtain the three near-wall flow regimes observed in urban canopy flows, namely isolated-wake, wake-interference and skimming-flow regimes. Investigation of the wall-normal profiles of the one-point statistics up to third order demonstrates the impossibility of finding a unique set of parameters enabling the collapse of all configurations, except for the mean streamwise velocity component. However, spectral analysis of the streamwise velocity component provides insightful information. Using the temporal frequency corresponding to the peak in the pre-multiplied energy spectrum as an indicator of the most energetic flow structures at each wall-normal location, it is shown that three main regions exist, in which different scaling applies. Finally, scale decomposition reveals that the flow in the roughness sublayer results from a large-scale intrinsic component of the boundary layer combined with canopy-induced dynamics. Their relative importance plays a key role in the energy distribution and influences the near-canopy flow regime and its dynamics, therefore suggesting complex interactions between the near-wall scales and those from the overlying boundary layer

Parkinson disease and AMD : is there a link?

La dégénérescence liée à l’âge (DMLA) néovasculaire est l’une des causes majeures de perte de vision, malgré une thérapie répétée par injection intravitréenne d’anti-VEGF qui constitue un fardeau considérable pour les patients, les ophtalmologistes et le système de santé. Une étude de cohorte rétrospective sur plusieurs millions de patients aux États-Unis a retrouvé que les patients parkinsoniens, traités par la L-DOPA avaient un âge de diagnostic de DMLA néovasculaire significativement plus tardif que les patients non traités. Grâce à l’utilisation d’un modèle murin de Parkinson par intoxication au MPTP, et d’un modèle murin de DMLA néovasculaire induite par phototraumatisme laser, en association avec le traitement standard de la maladie de Parkinson, nous avons montré qu’un traitement par L-DOPA induit une augmentation de la signalisation du récepteur à la dopamine D2, responsable d’une inhibition de la néovascularisation choroïdienne. Ces résultats apportent une explication à une épidémiologie intrigante. Poursuivant les travaux sur les récepteurs de la dopamine dans nos modèles murins, nous avons montré que des agonistes systémiques du récepteur D2 provoquaient une diminution de la néovascularisation. Ce comportement pourrait constituer une thérapie efficace pour réduire le besoin d’injections d’anti-VEGF chez les patients atteints de DMLA néovasculaire.Neovascular age-related macular degeneration (nAMD) remains a major cause of visual impairment, despite the continuous repeated intravitreal administration of anti-VEGF therapies that puts a considerable burden on patients, ophthalmologists and health care systems. A retrospective cohort of several million of patients in US found that L-DOPA treated parkinsons disease (PD) patients have a significantly delayed age of onset for nAMD. Using MPTP-induced PD- and laser-induced nAMD- mouse models in combination with the standard PD treatment of L-DOPA / DOPA-decarboxylase inhibitor, we here demonstrate that an L-DOPA treatment-induced increase of dopamine receptor 2 (DR2) signaling, and not the PD itself, is likely responsible for the inhibition of choroidal neovascularization. While explaining an intriguing epidemiological observation, our findings show that systemic DR2 agonists might constitute a much sought after therapy to reduce the need for anti-VEGF therapy in nAMD patients

Maladie de Parkinson et DMLA : y a-t-il un lien ?

Neovascular age-related macular degeneration (nAMD) remains a major cause of visual impairment, despite the continuous repeated intravitreal administration of anti-VEGF therapies that puts a considerable burden on patients, ophthalmologists and health care systems. A retrospective cohort of several million of patients in US found that L-DOPA treated parkinsons disease (PD) patients have a significantly delayed age of onset for nAMD. Using MPTP-induced PD- and laser-induced nAMD- mouse models in combination with the standard PD treatment of L-DOPA / DOPA-decarboxylase inhibitor, we here demonstrate that an L-DOPA treatment-induced increase of dopamine receptor 2 (DR2) signaling, and not the PD itself, is likely responsible for the inhibition of choroidal neovascularization. While explaining an intriguing epidemiological observation, our findings show that systemic DR2 agonists might constitute a much sought after therapy to reduce the need for anti-VEGF therapy in nAMD patients.La dégénérescence liée à l’âge (DMLA) néovasculaire est l’une des causes majeures de perte de vision, malgré une thérapie répétée par injection intravitréenne d’anti-VEGF qui constitue un fardeau considérable pour les patients, les ophtalmologistes et le système de santé. Une étude de cohorte rétrospective sur plusieurs millions de patients aux États-Unis a retrouvé que les patients parkinsoniens, traités par la L-DOPA avaient un âge de diagnostic de DMLA néovasculaire significativement plus tardif que les patients non traités. Grâce à l’utilisation d’un modèle murin de Parkinson par intoxication au MPTP, et d’un modèle murin de DMLA néovasculaire induite par phototraumatisme laser, en association avec le traitement standard de la maladie de Parkinson, nous avons montré qu’un traitement par L-DOPA induit une augmentation de la signalisation du récepteur à la dopamine D2, responsable d’une inhibition de la néovascularisation choroïdienne. Ces résultats apportent une explication à une épidémiologie intrigante. Poursuivant les travaux sur les récepteurs de la dopamine dans nos modèles murins, nous avons montré que des agonistes systémiques du récepteur D2 provoquaient une diminution de la néovascularisation. Ce comportement pourrait constituer une thérapie efficace pour réduire le besoin d’injections d’anti-VEGF chez les patients atteints de DMLA néovasculaire

Age-Related Macular Degeneration: New Insights in Diagnosis, Treatment, and Prevention

Age-related macular degeneration (AMD) is an aging-related ocular disease that can be responsible for severe loss of visual acuity and loss of autonomy in patients [...

Do new drugs for diabetic macular edema offer a safer option?

International audienc

Pharmacological Management of Diabetic Macular Edema in Real-Life Observational Studies

Objectives of the Study. Summary of observational studies concerning the pharmacological management of diabetic macular edema (DME). Methods. A literature review was conducted using the PubMed database on 1 February 2018 to identify studies evaluating the efficacy of anti-VEGF and dexamethasone (DEX) implants for DME. Studies with more than 10 patients and follow-up of more than 6 months were selected. Analyses were carried out on the overall population and on subgroups defined according to baseline visual acuity (BVA) and the patients’ naïve or non-naïve status. Results. Thirty-two studies evaluating the efficacy of anti-VEGF and 31 studies evaluating the efficacy of DEX-implants were retained, concerning 6,842 and 1,703 eyes, respectively. A mean gain of +4.7 letters for a mean of 5.8 injections (mean follow-up: 15.6 months) and +9.6 letters for a mean of 1.6 injections (10.3 months) was found in the anti-VEGF and DEX-implant studies, respectively. Final VA appears to be similar for both treatment (62 letters for anti-VEGF, 61.2 letters for DEX-implant), and BVA appears lower for DEX-implant, which may partially explain the greater visual gain. The DEX-implant studies show greater gains in VA compared to the anti-VEGF studies, especially for higher BVA. Indeed, mean gains for the subgroups of patients with BVA60 letters are +4.3, +5.8, and +3.1 letters, respectively, in the anti-VEGF studies and +10.5, +9.3, and +8.8 letters, respectively, in the DEX-implant studies. Regarding the patient’s initial status, only naïve status appears to confer the best functional response in DEX-implant studies. Conclusion. Observational studies investigating DEX-implant report clinically similar final VA when compared to anti-VEGF, but superior visual gains in real-life practice. This latter difference could be due to the better BVA, but also to the fact that less injections were administered in the anti-VEGF observational studies than in the interventional studies