IMPORTANCE Time spent in outdoor activities has decreased owing to home confinement for the coronavirus disease 2019 (COVID-19) pandemic. Concerns have been raised about whether home confinement may have worsened the burden of myopia owing to substantially decreased time spent outdoors and increased screen time at home. OBJECTIVE To investigate the refractive changes and prevalence of myopia in school-aged children during the COVID-19 home confinement. DESIGN, SETTING, AND PARTICIPANTSA prospective cross-sectional study using school-based photoscreenings in 123 535 children aged 6 to 13 years from 10 elementary schools in Feicheng, China, was conducted. The study was performed during 6 consecutive years (2015-2020). Data were analyzed in July 2020.EXPOSURES Noncycloplegic photorefraction was examined using a photoscreener device. MAIN OUTCOMES AND MEASURESThe spherical equivalent refraction was recorded for each child and the prevalence of myopia for each age group during each year was calculated. The mean spherical equivalent refraction and prevalence of myopia were compared between 2020 (after home confinement) and the previous 5 years for each age group. RESULTSOf the 123 535 children included in the study, 64 335 (52.1%) were boys. A total of 194 904 test results (389 808 eyes) were included in the analysis. A substantial myopic shift (approximately −0.3 diopters [D]) was found in the 2020 school-based photoscreenings compared with previous years (2015-2019) for younger children aged 6 (−0.32 D), 7 (−0.28 D), and 8 (−0.29 D) years. The prevalence of myopia in the 2020 photoscreenings was higher than the highest prevalence of myopia within 2015-2019 for children aged 6 (21.5% vs 5.7%), 7 (26.2% vs 16.2%), and 8 (37.2% vs 27.7%) years. The differences in spherical equivalent refraction and the prevalence of myopia between 2020 and previous years were minimal in children aged 9 to 13 years.CONCLUSIONS AND RELEVANCE Home confinement during the COVID-19 pandemic appeared to be associated with a significant myopic shift for children aged 6 to 8 years according to 2020 school-based photoscreenings. However, numerous limitations warrant caution in the interpretation of these associations, including use of noncycloplegic refractions and lack of orthokeratology history or ocular biometry data. Younger children's refractive status may be more sensitive to environmental changes than older ages, given the younger children are in a critical period for the development of myopia.

This paper is concerned with the properties of L 2 -normalized minimizers of the Gross-Pitaevskii (GP) functional for a two-dimensional Bose-Einstein condensate with attractive interaction and ring-shaped potential. By establishing some delicate estimates on the least energy of the GP functional, we prove that symmetry breaking occurs for the minimizers of the GP functional as the interaction strength a > 0 approaches a critical value a * , each minimizer of the GP functional concentrates to a point on the circular bottom of the potential well and then is non-radially symmetric as a ր a * . However, when a > 0 is suitably small we prove that the minimizers of the GP functional are unique, and this unique minimizer is radially symmetric.

We are interested in the attractive Gross-Pitaevskii (GP) equation in R 2 , where the external potential V (x) vanishes on m disjoint bounded domains Ω i ⊂ R 2 (i = 1, 2, · · · , m) and V (x) → ∞ as |x| → ∞, that is, the union of these Ω i is the bottom of the potential well. By making some delicate estimates on the energy functional of the GP equation, we prove that when the interaction strength a approaches some critical value a * the ground states concentrate and blow up at the center of the incircle of some Ω j which has the largest inradius. Moreover, under some further conditions on V (x) we show that the ground states of GP equations are unique and radially symmetric at leat for almost every a ∈ (0, a * ).

Half-Heusler alloys (MgAgSb structure) are promising thermoelectric materials. RNiSn halfHeusler phases (R=Hf, Zr, Ti) are the most studied in view of thermal stability. The highest dimensionless figure of merit (ZT) obtained is ~1 in the temperature range ~450-900 o C, primarily achieved in nanostructured alloys. Through proper annealing, ZT~1.2 has been obtained in a previous ZT~1 n-type (Hf,Zr)NiSn phase without the nanostructure. There is an appreciable increase in power factor, decrease in charge carrier density, and increase in carrier mobility. The findings are attributed to improved structural order. Present approach may be applied to optimize the functional properties of Heusler-type alloys. a)