Enhanced structure-function relationship in glaucoma with an anatomically and geometrically accurate neuroretinal rim measurement

yesPurpose: To evaluate the structure–function relationship between disc margin–based rim area (DM-RA) obtained with confocal scanning laser tomography (CSLT), Bruch's membrane opening–based horizontal rim width (BMO-HRW), minimum rim width (BMO-MRW), peripapillary retinal nerve fiber layer thickness (RNFLT) obtained with spectral-domain optical coherence tomography (SD-OCT), and visual field sensitivity. Methods: We examined 151 glaucoma patients with CSLT, SD-OCT, and standard automated perimetry on the same day. Optic nerve head (ONH) and RNFL with SD-OCT were acquired relative to a fixed coordinate system (acquired image frame [AIF]) and to the eye-specific fovea-BMO center (FoBMO) axis. Visual field locations were mapped to ONH and RNFL sectors with fixed Garway-Heath (VFGH) and patient-specific (VFPS) maps customized for various biometric parameters. Results: Globally and sectorally, the structure–function relationships between DM-RA and VFGH, BMO-HRWAIF and VFGH, and BMO-HRWFoBMO and VFPS were equally weak. The R2 for the relationship between DM-RA and VFGH ranged from 0.1% (inferonasal) to 11% (superotemporal) whereas that between BMO-HRWAIF and VFGH ranged from 0.1% (nasal) to 10% (superotemporal). Relatively stronger global and sectoral structure–function relationships with BMO-MRWAIF and with BMO-MRWFoBMO were obtained. The R2 between BMO-MRWAIF and VFGH ranged from 5% (nasal) to 30% (superotemporal), whereas that between BMO-MRWFoBMO and VFPS ranged from 5% (nasal) to 25% (inferotemporal). The structure–function relationship with RNFLT was not significantly different from that with BMO-MRW, regardless of image acquisition method. Conclusions: The structure–function relationship was enhanced with BMO-MRW compared with the other neuroretinal rim measurements, due mainly to its geometrically accurate properties

Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly

The Lifecycle of Caldera-Forming Volcanoes in the Main Ethiopian Rift: Insights from Aluto Volcano

The silicic peralkaline volcanoes of the East African Rift are some of the least studied and yet potentially most dangerous volcanoes in the world. We present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in the Main Ethiopian Rift, using newconstraints from fieldwork, remote sensing, 40Ar/39Ar geochronology and geochemistry. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at ca. 300 ka developing a ~42 km2 collapse structure. After a hiatus of ~250 kyr, a phase of post-caldera volcanism began.Since ca. 60 ka, highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. The age of the youngest volcanism is not well known. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (>80 %) of typical rift basalt. Based on the field stratigraphy and the number, style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement oflocalised pumice cones and effusive obsidian coulees of volumes between 1100 106 m3. Comparisons with other caldera volcanoes in this section of the rift suggest that there may be parallels between Alutos behaviour and that of other volcanic centres, both in terms of the volcanic lifecycle, and broad timings of caldera collapse events

The Lifecycle of Caldera-Forming Volcanoes in the Main Ethiopian Rift: Insights from Aluto Volcano

The silicic peralkaline volcanoes of the East African Rift are some of the least studied and yet potentially most dangerous volcanoes in the world. We present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in the Main Ethiopian Rift, using newconstraints from fieldwork, remote sensing, 40Ar/39Ar geochronology and geochemistry. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at ca. 300 ka developing a ~42 km2 collapse structure. After a hiatus of ~250 kyr, a phase of post-caldera volcanism began.Since ca. 60 ka, highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. The age of the youngest volcanism is not well known. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (>80 %) of typical rift basalt. Based on the field stratigraphy and the number, style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement oflocalised pumice cones and effusive obsidian coulees of volumes between 1100 106 m3. Comparisons with other caldera volcanoes in this section of the rift suggest that there may be parallels between Alutos behaviour and that of other volcanic centres, both in terms of the volcanic lifecycle, and broad timings of caldera collapse events