Utility for Uncorrected Refractive Errors in Adolescent Schoolchildren in Kakamega County, Kenya.

SIGNIFICANCE: Uncorrected refractive errors (UREs) present an enormous lifetime burden in children. Despite this, there is a dearth of knowledge on URE-related preference-based quality of life (QoL) in East Africa. This study demonstrates the positive impact of interventions on UREs; hence, it provides an empirical justification for advocacy to improve the QoL of children with URE. PURPOSE: This study investigated the preference-based QoL (utility) for URE in school-going adolescents of Kakamega County, in Kenya. METHODS: An observational cross-sectional study with multistage sampling was conducted on randomly selected secondary school adolescents. School-going adolescents in Forms 1 to 4 were clinically examined for the presence of URE and classified according to their URE types. Pre-screened students who met the selection criteria were classified into two groups: URE and normal sight. Participants in the normal-sight group were randomly selected from among screened students without URE. Selected participants were administered a previously validated adolescent-specific utility weighting instrument-Assessment of Quality of Life-Six Dimensions. RESULTS: A total of 330 participants aged 17.32 ± 1.60 years (URE, 17.50 ± 1.58 years; normal-sight, 17.15 ± 1.61 years) were included in the study. The mean utility score, as elicited by the Assessment of Quality of Life-Six Dimensions scoring algorithm, was better in the normal-sight group (URE, 0.496 ± 0.22; normal sight, 0.567 ± 0.25) at baseline, whereas the reverse was true at follow-up (URE, 0.655 ± 0.20; normal sight, 0.603 ± 0.25). In all cases, the differences were significant ( P < .05); however, there was no significantly better ( P > .05) utility elicited by any URE subtype at any given time point. Nonetheless, the URE group showed significantly better utility ( P < .05) after spectacle correction. CONCLUSIONS: Uncorrected refractive errors are associated with reduced utility in school-going adolescents, regardless of URE subtype. Spectacle correction resulted in a significantly improved utility for those with URE. Thus, this study recommends early public health strategies and spectacle interventions in schools for adolescents with URE.

Author Correction: Discrepancy in scientific authority and media visibility of climate change scientists and contrarians.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Discrepancy in scientific authority and media visibility of climate change scientists and contrarians.

We juxtapose 386 prominent contrarians with 386 expert scientists by tracking their digital footprints across ∼200,000 research publications and ∼100,000 English-language digital and print media articles on climate change. Projecting these individuals across the same backdrop facilitates quantifying disparities in media visibility and scientific authority, and identifying organization patterns within their association networks. Here we show via direct comparison that contrarians are featured in 49% more media articles than scientists. Yet when comparing visibility in mainstream media sources only, we observe just a 1% excess visibility, which objectively demonstrates the crowding out of professional mainstream sources by the proliferation of new media sources, many of which contribute to the production and consumption of climate change disinformation at scale. These results demonstrate why climate scientists should increasingly exert their authority in scientific and public discourse, and why professional journalists and editors should adjust the disproportionate attention given to contrarians.

More extreme swings of the South Pacific convergence zone due to greenhouse warming.

The South Pacific convergence zone (SPCZ) is the Southern Hemisphere's most expansive and persistent rain band, extending from the equatorial western Pacific Ocean southeastward towards French Polynesia. Owing to its strong rainfall gradient, a small displacement in the position of the SPCZ causes drastic changes to hydroclimatic conditions and the frequency of extreme weather events--such as droughts, floods and tropical cyclones--experienced by vulnerable island countries in the region. The SPCZ position varies from its climatological mean location with the El Niño/Southern Oscillation (ENSO), moving a few degrees northward during moderate El Niño events and southward during La Niña events. During strong El Niño events, however, the SPCZ undergoes an extreme swing--by up to ten degrees of latitude toward the Equator--and collapses to a more zonally oriented structure with commensurately severe weather impacts. Understanding changes in the characteristics of the SPCZ in a changing climate is therefore of broad scientific and socioeconomic interest. Here we present climate modelling evidence for a near doubling in the occurrences of zonal SPCZ events between the periods 1891-1990 and 1991-2090 in response to greenhouse warming, even in the absence of a consensus on how ENSO will change. We estimate the increase in zonal SPCZ events from an aggregation of the climate models in the Coupled Model Intercomparison Project phases 3 and 5 (CMIP3 and CMIP5) multi-model database that are able to simulate such events. The change is caused by a projected enhanced equatorial warming in the Pacific and may lead to more frequent occurrences of extreme events across the Pacific island nations most affected by zonal SPCZ events.

Stability analysis of multiplicative update algorithms and application to nonnegative matrix factorization.

Multiplicative update algorithms have proved to be a great success in solving optimization problems with nonnegativity constraints, such as the famous nonnegative matrix factorization (NMF) and its many variants. However, despite several years of research on the topic, the understanding of their convergence properties is still to be improved. In this paper, we show that Lyapunov's stability theory provides a very enlightening viewpoint on the problem. We prove the exponential or asymptotic stability of the solutions to general optimization problems with nonnegative constraints, including the particular case of supervised NMF, and finally study the more difficult case of unsupervised NMF. The theoretical results presented in this paper are confirmed by numerical simulations involving both supervised and unsupervised NMF, and the convergence speed of NMF multiplicative updates is investigated.