[The prevalence of retinopathy of prematurity in the mainland of China from 2008 to 2018].

With improved neonatal care, the survival rate of premature infants has been greatly increased, and retinopathy of prematurity (ROP) has already been the leading cause of blindness in children. Thereupon screening and treatment of ROP have been deeply performed in China. However, the implementation and the detection rate vary greatly in different regions. In this article, based on the 20-year prevalence data of ROP in all parts of the country before 2010, we review and summarize the literatures from 2008 to 2018, in order to track and update the screening data of ROP in the mainland of China and to find the incidence trend during the decade. The evidence of the changing prevalence of ROP would benefit further prevention of this serious eye disease. (Chin J Ophthalmol, 2021, 57: 379-385).

Resonantly Enhanced Betatron Hard X-rays from Ionization Injected Electrons in a Laser Plasma Accelerator.

Ultrafast betatron x-ray emission from electron oscillations in laser wakefield acceleration (LWFA) has been widely investigated as a promising source. Betatron x-rays are usually produced via self-injected electron beams, which are not controllable and are not optimized for x-ray yields. Here, we present a new method for bright hard x-ray emission via ionization injection from the K-shell electrons of nitrogen into the accelerating bucket. A total photon yield of 8 × 10(8)/shot and 10(8 )photons with energy greater than 110 keV is obtained. The yield is 10 times higher than that achieved with self-injection mode in helium under similar laser parameters. The simulation suggests that ionization-injected electrons are quickly accelerated to the driving laser region and are subsequently driven into betatron resonance. The present scheme enables the single-stage betatron radiation from LWFA to be extended to bright γ-ray radiation, which is beyond the capability of 3(rd) generation synchrotrons.

A novel laser-collider used to produce monoenergetic 13.3 MeV (7)Li (d, n) neutrons.

Neutron energy is directly correlated with the energy of the incident ions in experiments involving laser-driven nuclear reactions. Using high-energy incident ions reduces the energy concentration of the generated neutrons. A novel "laser-collider" method was used at the Shenguang II laser facility to produce monoenergetic neutrons via (7)Li (d, n) nuclear reactions. The specially designed K-shaped target significantly increased the numbers of incident d and Li ions at the keV level. Ultimately, 13.3 MeV neutrons were obtained. Considering the time resolution of the neutron detector, we demonstrated that the produced neutrons were monoenergetic. Interferometry and a Multi hydro-dynamics simulation confirmed the monoenergetic nature of these neutrons.