THE INCLINATION OF THE SOFT X-RAY TRANSIENT A0620–00 AND THE MASS OF ITS BLACK HOLE

We analyze photometry of the soft X-ray transient A0620 – 00 spanning nearly 30 years, including previously published and previously unpublished data. Previous attempts to determine the inclination of A0620 using subsets of these data have yielded a wide range of measured values of i. Differences in the measured value of i have been due to changes in the shape of the light curve and uncertainty regarding the contamination from the disk. We give a new technique for estimating the disk fraction and find that disk light is significant in all light curves, even in the infrared. We also find that all changes in the shape and normalization of the light curve originate in a variable disk component. After accounting for this disk component, we find that all the data, including light curves of significantly different shapes, point to a consistent value of i. Combining results from many separate data sets, we find i = 51fdg0 ± 0fdg9, implying M = 6.6 ± 0.25 M ☉. Using our dynamical model and zero-disk stellar VIH magnitudes, we find d = 1.06 ± 0.12 kpc. Understanding the disk origin of nonellipsoidal variability may assist with making reliable determinations of i in other systems, and the fluctuations in disk light may provide a new observational tool for understanding the three-dimensional structure of the accretion disk.National Science Foundation (U.S.) (NSF Graduate Research Fellowship DGE-0202738)National Science Foundation (U.S.) (NSF/AST grant 0407063)National Science Foundation (U.S.) (NSF/AST grant 0707627

Predicting the immediate impact of national lockdown on neovascular age-related macular degeneration and associated visual morbidity: an INSIGHT Health Data Research Hub for Eye Health report

OBJECTIVE: Predicting the impact of neovascular age-related macular degeneration (nAMD) service disruption on visual outcomes following national lockdown in the UK to contain SARS-CoV-2. METHODS AND ANALYSIS: This retrospective cohort study includes deidentified data from 2229 UK patients from the INSIGHT Health Data Research digital hub. We forecasted the number of treatment-naïve nAMD patients requiring anti-vascular endothelial growth factor (anti-VEGF) initiation during UK lockdown (16 March 2020 through 31 July 2020) at Moorfields Eye Hospital (MEH) and University Hospitals Birmingham (UHB). Best-measured visual acuity (VA) changes without anti-VEGF therapy were predicted using post hoc analysis of Minimally Classic/Occult Trial of the Anti-VEGF Antibody Ranibizumab in the Treatment of Neovascular AMD trial sham-control arm data (n=238). RESULTS: At our centres, 376 patients were predicted to require anti-VEGF initiation during lockdown (MEH: 325; UHB: 51). Without treatment, mean VA was projected to decline after 12 months. The proportion of eyes in the MEH cohort predicted to maintain the key positive visual outcome of ≥70 ETDRS letters (Snellen equivalent 6/12) fell from 25.5% at baseline to 5.8% at 12 months (UHB: 9.8%-7.8%). Similarly, eyes with VA <25 ETDRS letters (6/96) were predicted to increase from 4.3% to 14.2% at MEH (UHB: 5.9%-7.8%) after 12 months without treatment. CONCLUSIONS: Here, we demonstrate how combining data from a recently founded national digital health data repository with historical industry-funded clinical trial data can enhance predictive modelling in nAMD. The demonstrated detrimental effects of prolonged treatment delay should incentivise healthcare providers to support nAMD patients accessing care in safe environments. TRIAL REGISTRATION NUMBER: NCT00056836

A Cluster Randomized Trial of Routine HIV-1 Viral Load Monitoring in Zambia: Study Design, Implementation, and Baseline Cohort Characteristics

The benefit of routine HIV-1 viral load (VL) monitoring of patients on antiretroviral therapy (ART) in resource-constrained settings is uncertain because of the high costs associated with the test and the limited treatment options. We designed a cluster randomized controlled trial to compare the use of routine VL testing at ART-initiation and at 3, 6, 12, and 18 months, versus our local standard of care (which uses immunological and clinical criteria to diagnose treatment failure, with discretionary VL testing when the two do not agree).Dedicated study personnel were integrated into public-sector ART clinics. We collected participant information in a dedicated research database. Twelve ART clinics in Lusaka, Zambia constituted the units of randomization. Study clinics were stratified into pairs according to matching criteria (historical mortality rate, size, and duration of operation) to limit the effect of clustering, and independently randomized to the intervention and control arms. The study was powered to detect a 36% reduction in mortality at 18 months.From December 2006 to May 2008, we completed enrollment of 1973 participants. Measured baseline characteristics did not differ significantly between the study arms. Enrollment was staggered by clinic pair and truncated at two matched sites.A large clinical trial of routing VL monitoring was successfully implemented in a dynamic and rapidly growing national ART program. Close collaboration with local health authorities and adequate reserve staff were critical to success. Randomized controlled trials such as this will likely prove valuable in determining long-term outcomes in resource-constrained settings.Clinicaltrials.gov NCT00929604

An Improved Dynamical Model for the Microquasar XTE J1550-564

We present an improved dynamical model of the X-ray binary and microquasar XTE J1550-564 based on new moderate-resolution optical spectroscopy and near-infrared photometry. By combining our new radial velocity measurements with previous measurements obtained 2001 May at the 8.2m VLT and with light curves, we find an orbital period of P=1.5420333 +/- 0.0000024 days and a radial velocity semiamplitude of K_2=363.14 +/- 5.97$ km/sec, which together imply an optical mass function of f(M)=7.65 +/- 0.38 solar masses. We find that the projected rotational velocity of the secondary star is 55 +/- 5 km/sec, which implies a very extreme mass ratio of Q=M/M_2=30. Using a model of a Roche lobe-filling star and an azimuthally symmetric accretion disk, we fit simultaneously optical light curves from 2001, near-infrared light curves from 2008 and all of the radial velocity measurements to derive system parameters. We find an inclination of 74.7 +/- 3.8 deg and component masses of M_2=0.30 +/- 0.07 solar masses and M=9.10 +/- 0.61 solar masses for the secondary star and black hole, respectively. The radius of the secondary star for the adopted model is 1.75 +/- 0.12 solar radii. Using this radius, the average K_S magnitude, and an extinction of A_K=0.507 +/- 0.050 mag, we find a distance of 4.38^{+0.58}_{-0.41} kpc, which is in good agreement with a recent distance estimate based on HI absorption lines (abstract shortened).Comment: 29 pages, 11 figures, to appear in ApJ, figures 1 and 2 are compresse

Ozone depletion events observed in the high latitude surface layer during the TOPSE aircraft program

During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) aircraft program, ozone depletion events (ODEs) in the high latitude surface layer were investigated using lidar and in situ instruments. Flight legs of 100 km or longer distance were flown 32 times at 30 m altitude over a variety of regions north of 58° between early February and late May 2000. ODEs were found on each flight over the Arctic Ocean but their occurrence was rare at more southern latitudes. However, large area events with depletion to over 2 km altitude in one case were found as far south as Baffin Bay and Hudson Bay and as late as 22 May. There is good evidence that these more southern events did not form in situ but were the result of export of ozone-depleted air from the surface layer of the Arctic Ocean. Surprisingly, relatively intact transport of ODEs occurred over distances of 900–2000 km and in some cases over rough terrain. Accumulation of constituents in the frozen surface over the dark winter period cannot be a strong prerequisite of ozone depletion since latitudes south of the Arctic Ocean would also experience a long dark period. Some process unique to the Arctic Ocean surface or its coastal regions remains unidentified for the release of ozone-depleting halogens. There was no correspondence between coarse surface features such as solid ice/snow, open leads, or polynyas with the occurrence of or intensity of ozone depletion over the Arctic or subarctic regions. Depletion events also occurred in the absence of long-range transport of relatively fresh “pollution” within the high latitude surface layer, at least in spring 2000. Direct measurements of halogen radicals were not made. However, the flights do provide detailed information on the vertical structure of the surface layer and, during the constant 30 m altitude legs, measurements of a variety of constituents including hydroxyl and peroxy radicals. A summary of the behavior of these constituents is made. The measurements were consistent with a source of formaldehyde from the snow/ice surface. Median NOx in the surface layer was 15 pptv or less, suggesting that surface emissions were substantially converted to reservoir constituents by 30 m altitude and that ozone production rates were small (0.15–1.5 ppbv/d) at this altitude. Peroxyacetylnitrate (PAN) was by far the major constituent of NOy in the surface layer independent of the ozone mixing ratio

Natural History of Geographic Atrophy Secondary to Age-Related Macular Degeneration: Results from the Prospective Proxima A and B Clinical Trials.

Abstract Purpose To better characterize visual function decline and geographic atrophy (GA) progression secondary to age-related macular degeneration (AMD). Design Proxima A (NCT02479386) and Proxima B (NCT02399072) were global, prospective, non-interventional, observational clinical trials. Participants Eligible patients were aged ≥50 years. Patients in Proxima A had bilateral GA without choroidal neovascularization (CNV) in either eye (N=295). Patients in Proxima B had GA with no CNV in the study eye and CNV±GA in the fellow eye (fellow eye CNV cohort, n=168); or GA with no CNV in the study eye, without CNV/GA in the fellow eye (fellow eye intermediate AMD cohort, n=32). Methods Changes in visual function and imaging/anatomic parameters were evaluated over time using a Mixed Model for Repeated Measurement (MMRM) accounting for key baseline characteristics. Main Outcome Measures Pre-specified endpoints included change in GA area from baseline, best corrected visual acuity (BCVA) score assessed by ETDRS, and BCVA under low-luminance conditions (LLVA). Results At 24 months, the adjusted mean (standard error; SE) change in GA lesion area from baseline was 3.87 (0.15) mm2 in participants with bilateral GA (Proxima A), 3.55 (0.16) mm2 in the fellow eye CNV cohort (Proxima B), and 2.96 (0.25) mm2 in the fellow eye intermediate AMD cohort (Proxima B). GA progression was greater in patients with baseline non-subfoveal (vs. subfoveal) GA lesions, and tended to increase as baseline low-luminance deficit increased (Proxima A; Proxima B, all patients). Conversion to GA or CNV in the fellow eye occurred in 30% and 6.7% of participants, respectively, in the Proxima B intermediate AMD cohort at month 12. Adjusted mean (SE) changes in BCVA and LLVA (ETDRS letters) in the study eye from baseline to 24 months: −13.88 (1.40) and −7.64 (1.20) in Proxima A, −9.49 (1.29) and −7.57 (1.26) in the Proxima B fellow eye CNV cohort, −11.48 (3.39) and −8.37 (3.02) in the Proxima B fellow eye intermediate AMD cohort, respectively. Conclusions The prospective Proxima A and B studies highlight the severe functional impact of GA and the rapid rate of GA lesion progression over a 2-year period, including in patients with unilateral GA at baseline

Direct Ophthalmic Healthcare Resource Use among Geographic Atrophy Patients in a Large Cohort from the United Kingdom

Objective To estimate the direct ophthalmic health care resource use in patients with geographic atrophy (GA) secondary to age-related macular degeneration (AMD). Design Retrospective analysis of anonymized data derived from electronic medical records acquired at 10 clinical sites in the United Kingdom. Participants Patients aged ≥50 years with ≥1 eye with a clinical record of GA or, for comparison, bilateral early/intermediate AMD. Four subgroups were identified: GA in both eyes (GA : GA); GA in 1 eye, choroidal neovascularization (CNV) in the fellow eye (GA : CNV); GA in 1 eye with early or intermediate AMD in the fellow eye (GA : E); and early/intermediate AMD in both eyes (E : E). Methods Electronic medical records were analyzed to derive the median number of visits over the first 2 years following diagnosis of GA or early/intermediate AMD. Clinical tests recorded at visits were used to calculate estimated costs (payer perspective) of monitoring. Analyses were restricted to patients with an initial diagnosis on or after January 1, 2011 to represent present day monitoring and costs associated with AMD. Main Outcome Measures Median number of visits and estimated monitoring costs per patient (in £) over the first 2 years among patients with ≥2 years of follow-up and in the individual subgroups. Intravitreal treatment costs in the GA : CNV group were excluded. Results For all 3 GA subgroups (n = 1080), the median number of visits over the first 2 years was 5 and monitoring costs were £460.80 per patient. The GA : CNV subgroup (n = 355) had the highest number of visits (median, 15), with a cost of £1581, compared with the GA : E subgroup (n = 283; median 4 visits; cost ∼£369) and the GA : GA subgroup (n = 442; median 3 visits; cost ∼£277). Ophthalmic tests were conducted most frequently in the GA : CNV subgroup. Visits and costs in the E : E subgroup (n = 6079) were lower. Conclusions Resource use in patients with GA varies considerably and is strongly influenced by the concomitant presence of CNV and lack of monitoring strategies for GA

Continuum-continuum population trapping

We consider the problem of coherent population trapping in a model quantum system consisting of two (and briefly three) coupled continua of energy levels. While an earlier study [Z. Deng and J. H. Eberly, Phys. Rev. A 34, 2492 (198611 has demonstrated population trapping in a closely related system, it has done so only for the case of a broad featureless continuum. We will demonstrate, on the other hand, that the time evolution of the continuum is qualitatively very different when different types of continua are allowed, and that population trapping is not likely to occur except in the broad featureless continuum. We do show, however, that in some cases other counterintuitive results surface