Wind turbine wake characterization in complex terrain via integrated Doppler lidar data from the Perdigão experiment

During the intensive period (May-June 2017) of the Perdigäo experiment, three sets of Doppler lidar were operated to scan the wake of the wind turbine (WT) on the southwest ridge. CU operated a Doppler scanning lidar in the valley bottom approximately 1 km northeast of the WT and conducted multiple arc scans and two RHI scans every 10-minutes centred on the WT. DTU used a dual Doppler lidar system scanning almost horizontally from the northeast ridge. Two of the three DLR lidars were in-plane with the WT for the main wind direction, one in the valley and one on the distant mountain ridge. The third DLR lidar was on the southwest ridge. All three systems (CU, DTU and DLR) were operated such that in data processing vertical and/or horizontal profiles of the wake can be derived at different distances from the WT. The paper describes the strategies used to scan the wake by the three groups and compares wake characteristics derived from the different systems

Evidence for excess pore pressures in southwest Indian Ocean sediments

Brown clay cores from the Madagascar and Crozet basins show the following evidence of excess pore pressures: large amounts of flow-in, increasing average sedimentation rate with age, and nonlinear temperature gradients. Additionally, many hilltops in these basins have no visible sediment cover. The bare hilltops may result from periodic slumping caused by excess pore pressures. Calculated excess pore pressures which equal or exceed the overburden pressure were inferred from water fluxes predicted by nonlinear temperature gradients and laboratory permeability measurements by using Darcy's law. Since pore pressures which exceed the overburden pressure are unreasonable, we attribute this discrepancy to laboratory measurements which underestimate the in situ permeability. The widespread presence of overpressured sediments in areas of irregular topography provides a process for resuspension of clay-sized particles. This mechanism does not require high current velocities for the erosion of clay and therefore can be applied to many areas where no strong currents are evident. Carbonate-rich sediments from the Madagascar Ridge, the Mozambique Ridge, and the Agulhas Plateau had almost no flow-in and occurred in areas where all topography was thickly draped with sediment. Since the age and tectonic location of the ridges and plateaus preclude water circulation in the basement, we attribute these differences between the brown clay and the carbonate-rich material to an absence of significant excess pore pressures in the plateau and ridge sediments

Reproducibility of Nerve Fiber Layer Thickness Measurements Using 3D Fourier-Domain OCT

PURPOSE. Conventional time-domain optical coherence tomography (OCT) has been shown to provide reproducible retinal nerve fiber layer (RNFL) measurements. Recently, high-speed, high-resolution Fourier-domain 3D-OCT has been introduced to improve OCT quality. It can provide 6-mm 2 high-density scans to provide RNFL thickness measurements. The purpose of this study was to test the reproducibility of 3D-OCT RNFL thickness measurements in healthy volunteers. METHODS. Thirty-eight eyes were included in the study. Highdensity 6-mm 2 3D scans were registered by two independent operators. RNFL thickness was calculated for eight areas corresponding to the ETDRS areas and for two ring areas. The ETDRS grid was centered on the optic disc. Intraclass correlation coefficients (ICC) and coefficients of variation (COV) were calculated. Interobserver reproducibility was visualized by using Bland-Altman analysis. RESULTS. Intrasession reproducibility was good with a mean ICC of 0.90. The mean COV for operator 1 and 2 was 4.2% and 4%, respectively (range, 1.9%-6.7%). Highest reproducibility was found for the two ring areas and the superior and inferior quadrants. Mean differences in RNFL thickness measurements for ring 1 and 2 between operator 1 and 2 were 0.9 m (limits of agreement, Ϫ11.4 to ϩ9.6 m) and 0.1 m (limits of agreement Ϫ4.1 to ϩ3.9 m), respectively. CONCLUSIONS. 3D-OCT RNFL thickness measurements in healthy volunteers showed good intra-and interobserver reproducibility. 3D-OCT provides more RNFL thickness information compared to conventional time-domain OCT measurements and may be useful for the management of glaucoma and other optic neuropathies. (Invest Ophthalmol Vis Sci. 2008;49:5386 -5391) DOI:10.1167/iovs.07-1435 E valuation of the retinal nerve fiber layer (RNFL) is fundamental for diagnosing and managing glaucoma and other optic neuropathies. In the past, RNFL could be assessed subjectively only by slit lamp examination. This method requires clinical experience and offers only qualitative data. In addition, comparisons over time are almost impossible. Successively, other techniques such as color photographs of the optic disc or red-free photographs of the RNFL have become available and have facilitated comparisons over time. Scanning laser ophthalmoscopy and scanning laser polarimetry were the first instruments to allow objective and quantitative evaluation of the RNFL and the optic disc. Studies have been conducted to investigate the reproducibility of OCT RNFL thickness measurements, to assess the value of OCT as a clinical tool for distinguishing between healthy and glaucomatous eyes. Recently, improvements in OCT technology have been introduced. 10 -11 Fourier-domain (FD)-OCT provides increased resolution and scanning speed by recording the interferometric information with a Fourier-domain spectrometric method instead of adjusting the position of a reference mirror. Resolution is up to five times higher, and imaging speed is 60 times faster than in conventional time-domain OCT. 12-13 In addition to high image quality, it is important to have reliable and reproducible software programs to analyze the data acquired by FD-OCT. Previous versions of OCT (Stratus OCT3; Carl Zeiss Meditec, GmbH, Oberkochen, Germany) mostly used a 3.4-mm diameter circle scan centered on the optic disc to generate 512 A-scans. The RNFL thickness profile showed a characteristic curve with two peaks, one in the superior and one in the inferior quadrant. FD-OCT can perform a high-density raster-scan (512 ϫ 128 axial B-scans in a 6 mm 2 area). Recently, the peripapillary nerve fiber layer thickness profile was determined with FD-OCT by using high-density scanning. 14 These raster scans provide considerably more data for RNFL thickness analysis. The purpose of this study was to test the reproducibility of RNFL thickness measurements in healthy subjects by using FD-OCT high-density raster scans (3D OCT1000; Topcon, Tokyo, Japan). METHODS Thirty-eight eyes of 19 healthy subjects (10 women) with a mean age of 26 Ϯ 3 years were included in the study. Exclusion criteria were history of glaucoma, history of any other ocular disease, intraocular pressure greater than 21 mm Hg, or a refractive error of more than Ϫ5 or ϩ5 D. FD-OCT high-density scans were performed with the 3D OCT1000 system. The 3D OCT1000 is an FD-OCT device providing OCT images up to 50 times faster than time-domain OCTs with a sweep-scan technique. The device has a field angle of 45°with a color fundus camera included. The scanning range of the device is from 3 to 6 mm 2 . Horizontal resolution is Յ20 m and depth resolution is up to 5 m. As a light source, the system uses superluminescent diodes with a wavelength of 840 nm. Pupil diameter had to be at least 4 mm for scanning. High-density raster scans (512 ϫ 128 B-scans in a 6 mm 2 area) were centered on the From th

Correlated sediment thickness, temperature gradient and excess pore pressure in a marine fault block basin

Measurements of temperature gradient and excess pore pressure in the surficial sediment of a fault block basin in the Guatemala Basin correlate with sediment thickness. The temperature gradient is smaller and the excess pore pressure gradient is more negative in areas of thinner sediment. This correlation is explained by postulating downward pore water advection within the sediments, with flow velocities on the order of 10−9 to 10−8 m/s in the thinnest sediments and much less flow in the thickest sediments. Sediment physical properties and pore water chemistry also support this interpretation. Since the conductive heat flow of the basin as a whole is less than one third that predicted by sea floor spreading models, the oceanic basement may be the site of a vigorous hydrothermal circulation system. The pore water advection in the sediments may be driven by this larger scale circulation

Breakdown of scale-invariance in the coarsening of phase-separating binary fluids

We present evidence, based on lattice Boltzmann simulations, to show that the coarsening of the domains in phase separating binary fluids is not a scale-invariant process. Moreover we emphasise that the pathway by which phase separation occurs depends strongly on the relation between diffusive and hydrodynamic time scales.Comment: 4 pages, Latex, 4 eps Figures included. (higher quality Figures can be obtained from [email protected]

The Role of Intravitreal Corticosteroids in the Treatment of DME: Predictive OCT Biomarkers

Abstract: This work aims to summarize predictive biomarkers to guide treatment choice in DME. Intravitreal anti-VEGF is considered the gold standard treatment for centers involving DME, while intravitreal steroid treatment has been established as a second-line treatment in DME. However, more than 1/3 of the patients do not adequately respond to anti-VEGF treatment despite up to 4-weekly injections. Not surprisingly, insufficient response to anti-VEGF therapy has been linked to low-normal VEGF levels in the serum and aqueous humor. These patients may well benefit from an early switch to intravitreal steroid treatment. In these patients, morphological biomarkers visible in OCT may predict treatment response and guide treatment decisions. Namely, the presence of a large amount of retinal and choroidal hyperreflective foci, disruption of the outer retinal layers and other signs of chronicity such as intraretinal cysts extending into the outer retina and a lower choroidal vascular index are all signs suggestive of a favorable treatment response of steroids compared to anti-VEGF. This paper summarizes predictive biomarkers in DME in order to assist individual treatment decisions in DME. These markers will help to identify DME patients who may benefit from primary dexamethasone treatment or an early switc

Measurement of parton shower observables with OPAL

A study of QCD coherence is presented based on a sample of about 397,000 e+e- hadronic annihilation events collected at √s = 91 GeV with the OPAL detector at LEP. The study is based on four recently proposed observables that are sensitive to coherence effects in the perturbative regime. The measurement of these observables is presented, along with a comparison with the predictions of different parton shower models. The models include both conventional parton shower models and dipole antenna models. Different ordering variables are used to investigate their influence on the predictions

Lattice-Boltzmann hydrodynamics of anisotropic active matter

A plethora of active matter models exist that describe the behavior of self-propelled particles (or swimmers), both with and without hydrodynamics. However, there are few studies that consider shape-anisotropic swimmers and include hydrodynamic interactions. Here, we introduce a simple method to simulate self-propelled colloids interacting hydrodynamically in a viscous medium using the lattice-Boltzmann technique. Our model is based on raspberry-type viscous coupling and a force/counter-force formalism which ensures that the system is force free. We consider several anisotropic shapes and characterize their hydrodynamic multipolar flow field. We demonstrate that shape-anisotropy can lead to the presence of a strong quadrupole and octupole moments, in addition to the principle dipole moment. The ability to simulate and characterize these higher-order moments will prove crucial for understanding the behavior of model swimmers in confining geometries.Comment: 11 pages, 3 figures, 3 table

Volume-rendered optical coherence tomography angiography during ocular interventions: Advocating for noninvasive intraoperative retinal perfusion monitoring.

We aimed to test for feasibility of volume-rendered optical coherence tomography angiography (OCTA) as a novel method for assessing/quantifying retinal vasculature during ocular procedures and to explore the potential for intraoperative use. Thirty patients undergoing periocular anaesthesia were enrolled, since published evidence suggests a reduction in ocular blood flow. Retinal perfusion was monitored based on planar OCTA image-derived data provided by a standard quantification algorithm and postprocessed/volume-rendered OCTA data using a custom software script. Overall, imaging procedures were successful, yet imaging artifacts occurred frequently. In interventional eyes, perfusion parameters decreased during anaesthesia. Planar image-derived and volume rendering-derived parameters were correlated. No correlation was found between perfusion parameters and a motion artifact score developed for this study, yet all perfusion parameters correlated with signal strength as displayed by the device. Concluding, volume-rendered OCTA allows for noninvasive three-dimensional retinal vasculature assessment/quantification in challenging surgical settings and appears generally feasible for intraoperative use