Association of drusen deposition with choroidal intercapillary pillars in the aging human eye

PURPOSE. To determine the pattern of drusen accumulation with age and to investigate the initial sites of deposition and their relationship to choroidal capillaries in human donor eyes from the eye bank of Moorfields Eye Hospital.METHODS. Wholemounted, hydrated preparations of the choriocapillaris and Bruch's membrane from donor eyes ranging from 42 to 95 years, with or without retinal pigment epithelium (RPE), were examined by conventional and confocal microscopy. Drusen were visualized by their autofluorescence.RESULTS. In all age groups studied autofluorescent drusen were present at the equator but were not found centrally where the vascular architecture is different, being tubular rather than a honeycomb pattern. Autofluorescing drusen were strongly associated with the lateral walls of the choriocapillaris (an area commonly known as the intercapillary pillars of the choriocapillaris (P = 0.028; Wilcoxon signed ranks test). Nonfluorescing drusen were occasionally seen centrally, but were not easily identified, and because of their large size, their localization with respect to capillary walls was not possible.CONCLUSIONS. These results strongly support the notion that autofluorescent drusen are not randomly distributed and have a specific spatial relationship to choroidal vessel walls. That equatorial drusen fluoresce, whereas central drusen do not, suggests that they may have different chemical compositions at the two sites and possibly different significance in age-related macular disease

An analysis of ultraviolet spectra of Extreme Helium Stars and new clues to their origins

Abundances of about 18 elements including the heavy elements Y and Zr are determined from Hubble Space Telescope Space Telescope Imaging Spectrograph ultraviolet spectra of seven extreme helium stars (EHes): LSE 78, BD+10 2179, V1920 Cyg, HD 124448, PV Tel, LS IV -1 2, and FQ Aqr. New optical spectra of the three stars -- BD+10 2179, V1920 Cyg, and HD 124448 were analysed. The abundance analyses is done using LTE line formation and LTE model atmospheres especially constructed for these EHe stars. The stellar parameters derived from an EHe's UV spectrum are in satisfactory agreement with those derived from its optical spectrum. Adopted abundances for the seven EHes are from a combination of the UV and optical analyses. Published results for an additional ten EHes provide abundances obtained in a nearly uniform manner for a total of 17 EHes, the largest sample on record. The initial metallicity of an EHe is indicated by the abundance of elements from Al to Ni; Fe is adopted to be the representative of initial metallicity. Iron abundances range from approximately solar to about one-hundredth of solar. Clues to EHe evolution are contained within the H, He, C, N, O, Y, and Zr abundances. Two novel results are (i) the O abundance for some stars is close to the predicted initial abundance yet the N abundance indicates almost complete conversion of initial C, N, and O to N by the CNO-cycles; (ii) three of the seven stars with UV spectra show a strong enhancement of Y and Zr attributable to an s-process. The observed compositions are discussed in light of expectations from accretion of a He white dwarf by a CO white dwarf.Comment: 126 pages, 15 figures, 20 Tables, accepted for publication in the Ap

KIC 10449976: discovery of an extreme-helium subdwarf in the Kepler field

Optical spectroscopy of the blue star KIC 10449976 shows that it is an extremely helium-rich subdwarf with effective temperature T=40000+/-300 K and surface gravity log g=5.3+/-0.1. Radial-velocity measurements over a five-day timescale show an upper variability limit of ~50+/-20 km/s. Kepler photometry of KIC 10449976 in both long and short cadence modes shows evidence for a periodic modulation on a timescale of ~3.9 days. We have examined the possibility that this modulation is not astrophysical but conclude it is most likely real. We discuss whether the modulation could be caused by a low-mass companion, by stellar pulsations, or by spots. The identification of any one of these as cause has important consequences for understanding the origin of helium-rich subdwarfs.Comment: Accepted by MNRA

Topical cyclodextrin reduces amyloid beta and inflammation improving retinal function in ageing mice

Retinal ageing results in chronic inflammation, extracellular deposition, including that of amyloid beta (Aβ) and declining visual function. In humans this can progress into age-related macular degeneration (AMD), which is without cure. Therapeutic approaches have focused on systemic immunotherapies without clinical resolution. Here, we show using aged mice that 2-Hydroxypropyl-β-cyclodextrin, a sugar molecule given as eye drops over 3 months results in significant reductions in Aβ by 65% and inflammation by 75% in the aged mouse retina. It also elevates retinal pigment epithelium specific protein 65 (RPE65), a key molecule in the visual cycle, in aged retina. These changes are accompanied by a significant improvement in retinal function measured physiologically. 2-Hydroxypropyl-β-cyclodextrin is as effective in reducing Aβ and inflammation in the complement factor H knockout (Cfh(-/-)) mouse that shows advanced ageing and has been proposed as an AMD model. β-cyclodextrin is economic, safe and may provide an efficient route to reducing the impact of retinal ageing

Total Thickness of the Amburgy Coal in Eastern Kentucky

This map showing the regional characteristics of the Amburgy coal bed was prepared as part of the U.S. Geological Survey\u27s National Coal Assessment program, which compiles regional maps and databases that provide a comprehensive assessment of the most important coal beds in the nation. The Amburgy coal zone is composed of a number of distinct coal beds that merge in some areas to form mineable coal bodies. For the purpose of this assessment, the zone has been divided into two beds; the Lower Amburgy (A) and Upper Ambury (B). The lower bed is of greatest economic significance and is the subject of this publication. The map shows the total coal thickness, minus partings, of the lower or main Amburgy bed for the eastern Kentucky region. It is not a traditional isopach map, because the mineable bed is not composed of the same benches in all areas (Figs. 1-3). Discontinuities, delineated by facies boundaries on the map, indicate abrupt changes in thickness caused by splitting. Discontinuities were classified on the basis of the nature, as well as the confidence in location, of the discontinuity (Fig. 1). The Lower Amburgy bed is the main bed north of the Pine Mountain Overthrust Fault, where it is also known as the Williamson, Gun Creek, and Cannel City coal. South of the Pine Mountain Overthrust Fault, the lower bed has complex bench architecture, and is known locally as the Creech coal

Ultraviolet Vision May Enhance the Ability of Reindeer to Discriminate Plants in Snow

In reindeer/caribou (Rangifer tarandus), the lens and cornea of the eye transmit ultraviolet (UV) light, and the retinae respond to it electro-physiologically. Here we tie this finding to the unusual visual environment experienced by these animals and propose that their sensitivity to UV light enhances vision at the low luminance characteristic of the polar winter. For such visual enhancement to occur, it is essential that functional components of the environment, such as forage plants, be visually salient under natural UV luminance. However, it is not self-evident that this is the case. Although organic material generally absorbs UV radiation, powerful scattering of UV light by snow crystals may reduce the contrast with the background. We therefore recorded UV images of vegetation in situ on snow-covered pasture under natural winter (March) luminance in northern Norway. For each vegetation scene, we made three monochrome digital images, at 350 – 390 nm (UV-Only), 400 – 750 nm (No-UV), and 350 – 750 nm (control), respectively. Plants at the snow surface appeared in high achromatic contrast against snow in UV-Only images. The contrast was substantially greater in the UV-Only images than in corresponding images in which UV was blocked. We conclude that plants are visually salient under natural UV luminance at wavelengths to which Rangifer are sensitive. This sensitivity is likely to improve the animals’ ability to discriminate forage in snow, particularly at low but relatively UV-enriched twilight luminance.Le cristallin et la cornée de l’oeil du caribou (aussi connu sous le nom de renne) (Rangifer tarandus) transmettent une lumière ultraviolette (UV), à laquelle la rétine envoie une réponse électrophysiologique. Ici, nous faisons le lien entre cette observation et l’environnement visuel inhabituel de ces animaux, puis nous proposons que leur sensibilité à la lumière UV enrichit leur vision dans la faible luminance de l’hiver polaire. Pour que cet enrichissement ait lieu, il est essentiel que les composantes fonctionnelles de l’environnement, comme les plantes fourragères, soient visuellement saillantes sous la luminance UV naturelle. Il ne va cependant pas de soi que c’est le cas. Bien que la matière organique absorbe généralement le rayonnement ultraviolet, la diffusion puissante de la lumière UV découlant de la présence des cristaux de neige peut avoir pour effet de réduire le contraste avec l’arrière-plan. Par conséquent, nous avons enregistré des images ultraviolettes de la végétation in situ dans des pâturages couverts de neige sous la luminance naturelle de l’hiver (en mars), dans le nord de la Norvège. Pour chacune des scènes de végétation, nous avons fait trois images monochromes numériques, soit 350 à 390 nm (UV seulement), 400 à 750 nm (sans UV) et 350 à 750 nm (contrôlé), respectivement. Les plantes à la surface de la neige apparaissaient en fort contraste achromatique contre la neige dans le cas des images en UV seulement. Le contraste était beaucoup plus grand dans les images en UV seulement que dans les images correspondantes pour lesquelles l’UV était bloqué. Nous concluons que les plantes sont visuellement saillantes sous la luminance UV naturelle aux longueurs d’onde auxquelles le Rangifer est sensible. Cette sensibilité est susceptible d’améliorer l’aptitude de cet animal à distinguer le fourrage dans la neige, particulièrement en situation de faible luminance relativement enrichie en UV, au crépuscule

Diffusiophoretic Behavior of Polyelectrolyte-Coated Particles

Diffusiophoresis, the movement of particles under a solute concentration gradient, has practical implications in a number of applications, such as particle sorting, focusing, and sensing. For diffusiophoresis in an electrolyte solution, the particle velocity is described by the electrolyte relative concentration gradient and the diffusiophoretic mobility of the particle. The electrolyte concentration, which typically varies throughout the system in space and time, can also influence the zeta potential of particles in space and time. This variation affects the diffusiophoretic behavior, especially when the zeta potential is highly dependent on the electrolyte concentration. In this work, we show that adsorbing a single bilayer (or 4 bilayers) of a polyelectrolyte pair (PDADMAC/PSS) on the surface of microparticles resulted in effectively constant zeta potential values with respect to salt concentration throughout the experimental range of salt concentrations. This allowed a constant potential model for diffusiophoretic transport to describe the experimental observations, which was not the case for uncoated particles in the same electrolyte system. This work highlights the use of simple polyelectrolyte pairs to tune the zeta potential and maintain constant values for precise control of diffusiophoretic transport