Characteristics of Korean Children and Adolescents Who Die by Suicide Based on Teachers' Reports.

We analyzed the clinical characteristics and suicide-related factors of students who died by suicide in Korea in 2016-2020, based on teachers' reports. Using data on total suicide deaths (N = 654, mean age = 16.0, 52.6% boys) collected by the Ministry of Education of Korea, we investigated the demographic and clinical characteristics and suicide-related factors of suicide deaths in students aged 9-18 years. Considering gender, more boys (52.6%, N = 344) died by suicide than girls (47.4%, N = 310). About 425 (65.0%) of the suicides were among high school students. The most common suicide method was jumping from a high place (70.6%, N = 454), followed by hanging (25.7%, N = 165). Additionally, 9.4% (N = 48) of the students who died by suicide had a history of attempted suicide, 13.4% (N = 73) had attempted self-harm, and 12.8% (N = 48) were acquainted with someone who had died by suicide. Teachers observed 20.6% (N = 120) of the suicide warning signs at school. Girls tended to have higher rates of attempted suicide, emotional problems, and psychiatric disorders than boys. This study was conducted with the largest sample of Korean suicide students observed at school. Effective suicide-related mental health training for teachers could contribute to suicide prevention in students.

Broadband antireflective silicon nanostructures produced by spin-coated Ag nanoparticles.

We report the fabrication of broadband antireflective silicon (Si) nanostructures fabricated using spin-coated silver (Ag) nanoparticles as an etch mask followed by inductively coupled plasma (ICP) etching process. This fabrication technique is a simple, fast, cost-effective, and high-throughput method, making it highly suitable for mass production. Prior to the fabrication of Si nanostructures, theoretical investigations were carried out using a rigorous coupled-wave analysis method in order to determine the effects of variations in the geometrical features of Si nanostructures to obtain antireflection over a broad wavelength range. The Ag ink ratio and ICP etching conditions, which can affect the distribution, distance between the adjacent nanostructures, and height of the resulting Si nanostructures, were carefully adjusted to determine the optimal experimental conditions for obtaining desirable Si nanostructures for practical applications. The Si nanostructures fabricated using the optimal experimental conditions showed a very low average reflectance of 8.3%, which is much lower than that of bulk Si (36.8%), as well as a very low reflectance for a wide range of incident angles and different polarizations over a broad wavelength range of 300 to 1,100 nm. These results indicate that the fabrication technique is highly beneficial to produce antireflective structures for Si-based device applications requiring low light reflection.

Antireflective silicon nanostructures with hydrophobicity by metal-assisted chemical etching for solar cell applications.

We present broadband antireflective silicon (Si) nanostructures with hydrophobicity using a spin-coated Ag ink and by subsequent metal-assisted chemical etching (MaCE). Improved understanding of MaCE, by conducting parametric studies on optical properties, reveals a design guideline to achieve considerably low solar-weighted reflectance (SWR) in the desired wavelength ranges. The resulting Si nanostructures show extremely low SWR (1.96%) and angle-dependent SWR (<4.0% in the range of 0° to 60°) compared to that of bulk Si (SWR, 35.91%; angle-dependent SWR, 37.11%) in the wavelength range of 300 to 1,100 nm. Relatively large contact angle (approximately 102°) provides a self-cleaning capability on the solar cell surface.