Quantification of retinal layer thickness changes in acute macular neuroretinopathy.

PURPOSE To quantitatively evaluate retinal layer thickness changes in acute macular neuroretinopathy (AMN). METHODS AMN areas were identified using near-infrared reflectance (NIR) images. Intraretinal layer segmentation using Heidelberg software was performed. The inbuilt ETDRS -grid was moved onto the AMN lesion and the mean retinal layer thicknesses of the central grid were recorded and compared with the corresponding area of the fellow eye at initial presentation and during follow-up. RESULTS Eleven patients were included (mean age 26±6 years). AMN lesions at baseline had a significantly thinner outer nuclear layer (ONL) (51±21 µm vs 73±17 µm, p=0.002). The other layers, including inner nuclear layer (37±8 µm vs 38±6 µm, p=0.9) and outer plexiform layer (OPL) (45±19 µm vs 33±16 µm, p=0.1) did not show significant differences between the study eyes and fellow eyes. Adjacent to NIR image lesions, areas of OPL thickening were identified (study eye: 50±14 µm vs fellow eye: 39±16 µm, p=0.005) with corresponding thinning of ONL (study eye: 52±16 µm vs fellow eye: 69±16 µm, p=0.002). CONCLUSIONS AMN presents with characteristic quantitative retinal changes and the extent of the lesion may be more extensive than initially presumed from NIR image lesions.

Irrigation regime affected SOC content rather than plow layer thickness of rice paddies : A county level survey from a river basin in lower Yangtze valley, China

Acknowledgements This work was funded by Natural Science Foundation of China under grant numbers of 41071337 and 40830528 and jointly by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China.

(Table 1) Active-layer thickness as measured by the Biocomplexity Experiment (BE) for the flooded, drained and control sections in Barrow, Alaska

A continuous time series of annual soil thaw records, extending from 1994 to 2009, is available for comparison with the records of thaw obtained from the Biocomplexity Experiment (BE) for the period 2006-2009. Discontinuous records of thaw at Barrow from wet tundra sites date back to the 1960s. Comparisons between the longer records with the BE observations reveal strong similarities. Records of permafrost temperature, reflecting changes in the annual surface energy exchange, are available from the 1950s for comparison with results from measurement programs begun in 2002. The long-term systematic geocryological investigations at Barrow indicate an increase in permafrost temperature, especially during the last several years. The increase in near-surface permafrost temperature is most pronounced in winter. Marked trends are not apparent in the active-layer record, although subsidence measurements on the North Slope indicate that penetration into the ice-rich layer at the top of permafrost has occurred over the past decade. Active-layer thickness values from the 1960s are generally higher than those from the 1990s, and are very similar to those of the 2000s. Analysis of spatial active-layer observations at representative locations demonstrates significant variations in active-layer thickness between different landscape types, reflecting the influence of vegetation, substrate, microtopography, and, especially, soil moisture. Landscape-specific differences exist in the response of active-layer thickness to climatic forcing. These differences are attributable to the existence of localized controls related to combinations of surface and subsurface characteristics. The geocryological records at Barrow illustrate the importance and effectiveness of sustained, well organized monitoring efforts to document long-term trends.

Detrital layer thickness in 12 varved sediment cores in Lake Mondsee and related flood events AD1976-2005

A succession of 23 sub-millimetre to maximum 12-mm-thick, mostly flood-triggered detrital layers, deposited between 1976 and 2005, was analysed in 12 varved surface sediment cores from meso-scale peri-alpine Lake Mondsee applying microfacies and high-resolution micro X-ray fluorescence analyses. Detailed intrabasin comparison of these layers enabled identification of (i) different source areas of detrital sediments, (ii) flood-triggered sediment flux and local erosion events, and (iii) seasonal differences of suspended flood sediment distribution within the lake basin. Additional calibration of the detrital layer record with river discharge and precipitation data reveals different empirical thresholds for flood layer deposition for different parts of the basin. At proximal locations detrital layer deposition requires floods exceeding a daily discharge of 40 m**3/s, whereas at a location 2 km more distal an hourly discharge of 80 m**3/s and at least 2 days of discharge above 40 m**3/s are necessary. Furthermore, we observe a better correlation between layer thickness and flood amplitude in the depocentre than in distal and proximal areas of the basin. Although our results are partly site-specific, the applied dual calibration approach is suitable to precisely decipher flood layer formation processes and, thereby, improve the interpretation of long flood time series from lake sediments.

Scaling for the Prandtl number of the natural convection boundary layer of an inclined flat plate under uniform surface heat flux

An improved scaling analysis and direct numerical simulations are performed for the unsteady natural convection boundary layer adjacent to a downward facing inclined plate with uniform heat flux. The development of the thermal or viscous boundary layers may be classified into three distinct stages: a start-up stage, a transitional stage and a steady stage, which can be clearly identified in the analytical as well as the numerical results. Previous scaling shows that the existing scaling laws of the boundary layer thickness, velocity and steady state time scale for the natural convection flow on a heated plate of uniform heat flux provide a very poor prediction of the Prandtl number dependency of the flow. However, those scalings perform very well with Rayleigh number and aspect ratio dependency. In this study, a modified Prandtl number scaling is developed using a triple layer integral approach for Pr > 1. It is seen that in comparison to the direct numerical simulations, the modified scaling performs considerably better than the previous scaling.

Diurnal Variation of Retinal Thickness with Spectral Domain OCT

Purpose. To investigate whether diurnal variation occurs in retinal thickness measures derived from spectral domain optical coherence tomography (SD-OCT). Methods. Twelve healthy adult subjects had retinal thickness measured with SD-OCT every 2 h over a 10 h period. At each measurement session, three average B-scan images were derived from a series of multiple B-scans (each from a 5 mm horizontal raster scan along the fovea, containing 1500 A-scans/B-scan) and analyzed to determine the thickness of the total retina, as well as the thickness of the outer retinal layers. Average thickness values were calculated at the foveal center, at the 0.5 mm diameter foveal region, and for the temporal parafovea (1.5 mm from foveal center) and nasal parafovea (1.5 mm from foveal center). Results. Total retinal thickness did not exhibit significant diurnal variation in any of the considered retinal regions (p > 0.05). Evidence of significant diurnal variation was found in the thickness of the outer retinal layers (p < 0.05), with the most prominent changes observed in the photoreceptor layers at the foveal center. The photoreceptor inner and outer segment layer thickness exhibited mean amplitude (peak to trough) of daily change of 7 ± 3 μm at the foveal center. The peak in thickness was typically observed at the third measurement session (mean measurement time, 13:06). Conclusions. The total retinal thickness measured with SD-OCT does not exhibit evidence of significant variation over the course of the day. However, small but significant diurnal variation occurs in the thickness of the foveal outer retinal layers.

Prandtl number scaling of the unsteady natural convection boundary layer adjacent to a vertical flat plate for Pr > 1 subject to ramp surface heat flux

It is found in the literature that the existing scaling results for the boundary layer thickness, velocity and steady state time for the natural convection flow over an evenly heated plate provide a very poor prediction of the Prandtl number dependency of the flow. However, those scalings provide a good prediction of two other governing parameters’ dependency, the Rayleigh number and the aspect ratio. Therefore, an improved scaling analysis using a triple-layer integral approach and direct numerical simulations have been performed for the natural convection boundary layer along a semi-infinite flat plate with uniform surface heat flux. This heat flux is a ramp function of time, where the temperature gradient on the surface increases with time up to some specific time and then remains constant. The growth of the boundary layer strongly depends on the ramp time. If the ramp time is sufficiently long, the boundary layer reaches a quasi steady mode before the growth of the temperature gradient is completed. In this mode, the thermal boundary layer at first grows in thickness and then contracts with increasing time. However, if the ramp time is sufficiently short, the boundary layer develops differently, but after the wall temperature gradient growth is completed, the boundary layer develops as though the startup had been instantaneous.