Macular choroidal thickness in Chinese preschool children: decrease with axial length but no evident change with age

AIM: To explore the distribution pattern of macular choroidal thickness(ChT) and its association with age as well as refractive status in Chinese preschoolers.METHODS: School-based, cross-sectional study. A total of 550 healthy preschool children aged 3 to 6 years old from 6 kindergartens were enrolled. Comprehensive ocular examinations, including measurement of visual acuity, axial length, intraocular pressure and slit-lamp examination before cycloplegia, as well as refraction measurement and sweptsource optical coherence tomography(SS-OCT) examination after cycloplegia, were performed. The macular ChT in each sector of the ETDRS grid was measured by the builtin software of SS-OCT.RESULTS: The mean central ChT of the participants was 312±59 μm. The mean axial length and spherical equivalent refraction were 22.36±0.72 mm and 1.51±0.83 D, respectively. Axial length increased with age(P<0.001), while the spherical equivalent refraction was similar among different age groups. Similarly, no significant difference was observed in ChT in all sectors among different age groups(all P>0.05). The central ChT of 3-4, 5 and 6 years old children was 314±59 μm, 312±60 μm and 312±59 μm, respectively(P=0.920). No difference was observed in ChT in most of the sectors between genders. No statistical significant difference was observed among different refractive groups(all P>0.05), though the ChT of each sector seemed to be smaller in myopic children. Axial length and weight were the independent factors of central Ch T. Children with longer axial length(β=-21.184, P<0.001) and smaller weight(β=1.502, P=0.041) tended to have thinner choroid.CONCLUSION: In preschool children, the ChT remains relatively stable with age, while a negative association between ChT and axial length existed. This will be helpful to elucidate the characteristics of ChT during the early refractive development.

Realizing high thermoelectric performance of Cu and Ce co-doped p-type polycrystalline SnSe via inducing nanoprecipitation arrays

Thermoelectric(TE)performance of polycrystalline stannous selenide(SnSe)has been remarkably promoted by the strategies of energy band,defect engineering,etc.However,due to the intrinsic insufficiencies of phonon scattering and carrier concentration,it is hard to simultaneously realize the regulations of electrical and thermal transport properties by one simple approach.Herein,we develop Cu and Ce co-doping strategy that can not only greatly reduce lattice thermal conductivity but also improve the electrical transport properties.In this strategy,the incorporated Cu and Ce atoms could induce high-density SnSe_(2) nanoprecipitation arrays on the surface of SnSe microplate,and produce dopant atom point defects and dislocations in its interior,which form multi-scale phonon scattering synergy,thereby presenting an ultralow thermal conductivity of 0.275 W·m^(−1)·K^(−1) at 786 K.Meanwhile,density functional theory(DFT)calculations,carrier concentration,and mobility testing reveal that more extra hole carriers and lower conducting carrier scattering generate after Cu and Ce co-doping,thereby improving the electrical conductivity.The co-doped Sn_(0.98)Cu_(0.01)Ce_(0.01)Se bulk exhibits an excellent ZT value up to~1.2 at 786 K and a high average ZT value of 0.67 from 300 to 786 K.This work provides a simple and convenient strategy of enhancing the TE performance of polycrystalline SnSe.

Improved performances of lithium disilicate glass-ceramics by seed induced crystallization

Self-reinforced lithium disilicate(Li_(2)Si_(2)O_(5),LD)glass-ceramics were hot pressing sintered by introducing 5 wt%Li_(2)Si_(2)O_(5)crystal seeds into two different glass compositions of SiO_(2)-Li_(2)O-P2O_(5)-ZrO_(2)-Al_(2)O_(3)-K_(2)O-La_(2)O_(3)(7C LD)and SiO_(2)-Li_(2)O-K_(2)O-La_(2)O_(3)(4C LD).The results show that the seeds play an important role in the crystallization inducement,and microstructural and property improvement of the glass,especially for the glass powder without the nucleating agent of P_(2)O_(5).The microstructure features a wider bimodal grain size distribution with large rod-like crystals epitaxially grown along the seeds and small crystals nucleated from the glass powder itself,contributing to the improvement of the performance especially the fracture toughness.The specimen of 4C LD glass with the addition of 5 wt%Li_(2)Si_(2)O_(5) seeds exhibited the best comprehensive properties with a good flexural strength(396±7 MPa),improved fracture toughness(3.31±0.19 MPa·m^(1/2)),and comparable translucency as IPS e.max.This research provides a new idea and method for the improvement of the fracture toughness of lithium disilicate glass-ceramics without affecting its aesthetic appearance,and lays the foundation for its clinical applications.

Hydrogen peroxide enabled two-dimensional molybdenum trioxide nanosheet clusters for enhanced surface Li-ion storage

Molybdenum trioxide(MoO3)is regarded as a promising electrode material for lithium(Li)-ion batteries because of its unique layered structure with a high theoretical capacity(~1117 mAh·g-1).Till now,numerous researches have focused on tuning MoO3 morphology to improve its electrochemical performance.However,the fabrication of MoO3 with a two-dimensional(2D)nanosheet clusters structure has yet been achieved.Here,we report a facile one-step solvothermal method to prepare MoO3 nanosheets,of which the morphology can be facilely tuned via the dose of hydrogen peroxide.Both the experimental results and theoretical calculation suggest that the resultant 2D nanosheets structure could reduce the diffusion paths,which is beneficial for the intercalation of Li-ion.As a result,the nanosheets assembled Li-ion battery has a reversible specific capacity of 756.1 mAh·g-1 at 0.5·g-1,and maintained at 214.7 mAh·g-1 after 600 cycles at a current density of 1 A·g-1with the Coulombic efficiency as high as 97.17%.

Causes of Severe Visual Impairment and Blindness in Schools for the Blind

To the Editor： Reduced vision impacts not only the individual but also the family, community, and public health. It leads to a significant economic burden, including increased education cost, reduced personal income, and loss of productivity for caregivers, and numerous intangible consequences, such as loss of independence, reduced quality of life, and excess morbidity for individuals. An estimated 19 million of the world＇s children are visually impaired, while 1.4 million are blind, according to the World Health Organization （WHO） criteria. Therefore, the control of visual impairment or blindness （VI/BL） in children is still one of the priority areas of the WHO＇s ＂Vision 2020： the Right to Sight＂ program.