Fast and rigorous optical simulation of periodically corrugated light-emitting diodes based on a diffraction matrix method.

Increasing the light extraction efficiency has been widely studied for highly efficient organic light-emitting diodes (OLEDs). Among many light-extraction approaches proposed so far, adding a corrugation layer has been considered a promising solution for its simplicity and high effectiveness. While the working principle of periodically corrugated OLEDs can be qualitatively explained by the diffraction theory, dipolar emission inside the OLED structure makes its quantitative analysis challenging, making one rely on finite-element electromagnetic simulations that could require huge computing resources. Here, we demonstrate a new simulation method, named the diffraction matrix method (DMM), that can accurately predict the optical characteristics of periodically corrugated OLEDs while achieving calculation speed that is a few orders of magnitude faster. Our method decomposes the light emitted by a dipolar emitter into plane waves with different wavevectors and tracks the diffraction behavior of waves using diffraction matrices. Calculated optical parameters show a quantitative agreement with those predicted by finite-difference time-domain (FDTD) method. Furthermore, the developed method possesses a unique advantage over the conventional approaches that it naturally evaluates the wavevector-dependent power dissipation of a dipole and is thus capable of identifying the loss channels inside OLEDs in a quantitative manner.

Electrically focus-tuneable ultrathin lens for high-resolution square subpixels.

Owing to the tremendous demands for high-resolution pixel-scale thin lenses in displays, we developed a graphene-based ultrathin square subpixel lens (USSL) capable of electrically tuneable focusing (ETF) with a performance competitive with that of a typical mechanical refractive lens. The fringe field due to a voltage bias in the graphene proves that our ETF-USSL can focus light onto a single point regardless of the wavelength of the visible light-by controlling the carriers at the Dirac point using radially patterned graphene layers, the focal length of the planar structure can be adjusted without changing the curvature or position of the lens. A high focusing efficiency of over 60% at a visible wavelength of 405 nm was achieved with a lens thickness of <13 nm, and a change of 19.42% in the focal length with a 9% increase in transmission was exhibited under a driving voltage. This design is first presented as an ETF-USSL that can be controlled in pixel units of flat panel displays for visible light. It can be easily applied as an add-on to high resolution, slim displays and provides a new direction for the application of multifunctional autostereoscopic displays.

Atmospheric Pressure Pulsed Plasma Induces Cell Death in Photosynthetic Organs via Intracellularly Generated ROS.

The toxicity of atmospheric-pressure pulsed plasma on plant leaf tissues is studied. A nanosecond-pulsed plasma jet is applied to Arabidopsis thaliana leaves. In case of cotyledon, cell death is induced by treatment of only a few seconds. Cell death is also induced in the adult leaf by only 5 seconds of plasma treatment. Plasma induced reactive oxygen species (ROS) accumulation across the tissues within plasma-treated area. Plasma also induced direct physical damage to epidermis tissue of treated area but merely no damage to mesophyll. Thus, we propose direct physical damage in epidermis and ROS accumulation across the treated area induced cell death by plasma treatment. Plasma treatment with same duration in different organ also induced ROS accumulation but not plant death, suggests damage on photosynthetic organ by oxidative stress might be direct reason to induce cell death. We could also observe similar plasma induced death in Solanum esculentum, Petunia axillaris, and Nicotiana benthamiana but death is induced only in treated area. Thus, we propose atmospheric plasma induce oxidative stress in photosynthetic organ to induce cell death in plants.

[The life of Dr. RO Kishun, a reflection of modern Korean medical history of the borders].

RO Kishun was born on February 2, 1893 in Ongjin County, Hwanghae Province of Joseon Korea. He graduated from the Medical Training Center, a campus associated with the Joseon Government-General Hospital, in 1915, and from Kyushu Imperial University School of Medicine in 1917. He continued his medical study at the university in 1929, majoring in biochemistry, and earned a doctorate in medicine in 1932. Dr. RO, one of the earliest pioneers in Korean biochemistry, was active in his research, publishing four studies in the Japanese Journal of Biochemistry between 1931 and 1932. After returning from Japan in 1932, Dr. RO opened a medical practice in Mokpo and Busan, port cities situated on the southern tip of Korea. Later in 1936, he moved north to Manchuria (northeast China) to practice medicine at the International Hospital in Mukden (present-day Shenyang). He also served as president of Tumen Public Hospital between 1942 and 1946. When Japan signed unconditional surrender bringing World War II to an end, Dr. RO relocated to Yanbian and began providing medical training to ethnic Koreans. In October 1946, he was appointed dean of the First Branch School of China Medical University in Longjing, and in October 1948 the first dean of Yanbian Medical School, the predecessor of Yanbian University College of Medicine. Dr. RO dedicated his life to medical practice, teaching and training students, and mentoring younger faculty. A brilliant clinician, he also inspired and helped his colleagues with his outstanding ability to diagnose and treat patients. He was one of the founding members of Yanbian University College of Medicine. RO Kishun died on June 7, 1957 at age 64. Ethnic Koreans hailed him as Sinui (literally, the physician of God), and a bronze statue of himself was erected in front of the medical college in 1988. Dr. RO's life brings modern historians' attention to the issue of determining geographical territories and nationality, in that his life unfolded at the borderlands or frontiers of Joseon Korea, China, and Japan, where the history of the three nations met and intermingled with one another. He was a biochemist and researcher, practicing physician and medical professor of the era under Japanese Rule and the one following it. In modern Korean medicine, his life is viewed as a history of the borders, or a transnational legacy going beyond individual history of Korea, China, and Japan.