Development and Verification of a 480 nm Blue Light Enhanced/Reduced Human-Centric LED for Light-Induced Melatonin Concentration Control.

With the inherent sleep and wake cycle regulated by natural sunlight, the human body has evolved over millennia to be active during the day and to rest at night. However, maintaining an optimal 24 h cycle has become increasingly problematic in modern society as more people spend the majority of the day indoors. Many research groups have reported that inadequate artificial lighting interferes with melatonin production and disrupts the circadian rhythm. This study considered biological functions for light-emitting diodes (LEDs) of next-generation illumination, and LED packages and spectra suitable for both daytime and nighttime applications were designed. The prepared daytime human-centric (HC)-LEDs had a melanopic/photopic (M/P) ratio that was up to 26% higher than that of conventional (c)-LEDs, whereas the nighttime HC-LEDs exhibited up to a 26% lower M/P ratio compared to the c-LEDs. Nevertheless, because the HC-LED is designed to have almost the same color coordinates as the c-LED having the same correlated-color temperature (CCT), there is no change in the perceived color. To substantiate the biological effect, melatonin level data were obtained from 22 voluntary participants in c- and HC-LED lighting environments. In the HC-LED lighting environment, melatonin was suppressed by 21.9% after waking, and nocturnal melatonin secretion was increased by up to 12.2%. As human-centric lighting, our HC-LEDs are expected to become an essential element for modern life, where people spend most of their time indoors.

Protective effects of TES trioleate, an inhibitor of phospholipase A2, on reactive oxygen species and UVA-induced cell damage.

2-[Tris(oleoyloxymethyl)methylamino]-1-ethane sulfonic acid (TES trioleate) is an inhibitor of phospholipase A2 (PLA2), which hydrolyzes cell membrane phospholipids to produce arachidonic acid (AA) and lysophospholipids (LysoPLs). Here, we investigated the protective effects of TES trioleate on cell damage caused by ultraviolet A (UVA) light and reactive oxygen species (ROS). Pre-incubation with 250-1000µM TES trioleate resulted in concentration-dependent protection from UVA-induced damage in HaCaT cells. Additionally, 25-1000µM TES trioleate provided protection against H2O2 in a concentration-dependent manner. In human erythrocytes treated with 1O2, 10-100µM TES trioleate showed concentration-dependent protective effects, similar to but stronger than the controls, 4-BPB and lipophilic antioxidant (+)-α-tocopherol at 100µM. TES trioleate did not have detectable radical scavenging activity. Moreover, compared with (+)-α-tocopherol and rutin, TES trioleate showed low ROS scavenging activity. Thus, although TES trioleate showed cell protective effects against UVA, H2O2, and 1O2-induced damages, these effects were not caused by the scavenging ability of the radical or ROS. Finally, pretreatment of HaCaT cells and human erythrocytes with l-α-lysophosphatidylcholine produced by PLA2 promoted increased cell damage at low concentrations. Thus, the protective effects of TES trioleate on cellular damage by UVA and ROS may be associated with inhibition of PLA2-dependent cell damage rather than ROS scavenging.

Highly improved reliability of amber light emitting diode with Ca -α-SiAlON phosphor in glass formed by gas pressure sintering for automotive applications.

Phosphor in glass (PiG) with 40 wt% of Ca-α-SiAlON phosphor and 60 wt% of Pb-free silicate glass was synthesized and mounted on a high-power blue LED to make an amber LED for automotive applications. Gas pressure sintering was applied after the conventional sintering process was used to achieve fully dense PiG plates. Changes in photoluminescence spectra and color coordination were inspected by varying the thickness of the plates that were mounted after optical polishing and machining. A trade-off between luminous flux and color purity was observed. The commercial feasibility of amber PiG packaged LED, which can satisfy international regulations for automotive components, was successfully demonstrated by examining the practical reliability under 85% humidity at an 85°C condition.

The Composite Structure and Two-Peak Emission Behavior of a Ca1.5Ba0.5Si5O3N6:Eu(2+) Phosphor.

A Ca1.5Ba0.5Si5O3N6:Eu(2+) phosphor with a monoclinic lattice in the Cm space group exhibiting a composite structure consisting of CaSi2O2N2-like and BaSi6N8O-like structures was examined in terms of structure and luminescence. The luminescent properties of the Ca1.5Ba0.5Si5O3N6:Eu(2+) phosphor could be suitable for light-emitting diode applications since it exhibited a promising yellow (or amber) emission peaking at ∼ 570-590 nm at excitations of 450-460 nm. The present investigation was focused on verifying the composite structure by employing quantum mechanical calculations such as the Hartree-Fock ab initio calculation and a density functional theory calculation along with precise structural and compositional analyses. The two-peak emission behavior ascribed to the composite structure was also examined in terms of continuous wave and time-resolved photoluminescence. In addition, the energy transfer between two activator sites ascribed to the composite structure was examined in detail.