Research Update: Recent progress in the development of effective dielectrics for high-output triboelectric nanogenerator

A new energy generating device, triboelectric nanogenerator (TENG), was discovered in 2012 and thereafter, many applications such as portable power sources and self-powered, appropriate for portable electronic devices. So far, rapid development of device fabrication technologies and mechanical system designs significantly increased the instantaneous output power up to several tens of mW/cm2. This article provides a comprehensive review of effective dielectrics used so far in TENGs for further enhancement in output power, as well as the fundamental issues regarding the materials. Finally, we show some strategies for obtaining the properties that the materials should have as effective dielectrics.ope

High-Performance PVC Gel for Adaptive Micro-Lenses with Variable Focal Length.

This paper presents a bio-inspired adaptive micro-lens with electrically tunable focus made of non-ionic high-molecular-weight polyvinyl chloride (PVC) gel. The optical device mimics the design of the crystalline lens and ciliary muscle of the human eye. It consists of a plano-convex PVC gel micro-lens on Indium Tin Oxide (ITO) glass, confined with an annular electrode operating as an artificial ciliary muscle. Upon electrical activation, the electroactive adhesive force of the PVC gel is exerted on the annular anode electrode, which reduces the sagittal height of the plano-convex PVC gel lens, resulting in focal length variation of the micro-lens. The focal length increases from 3.8 mm to 22.3 mm as the applied field is varied from 200 V/mm to 800 V/mm, comparable to that of the human lens. The device combines excellent optical characteristics with structural simplicity, fast response speed, silent operation, and low power consumption. The results show the PVC gel micro-lens is expected to open up new perspectives on practical tunable optics

Tip-Enhanced Raman Scattering Imaging of Two-Dimensional Tungsten Disulfide with Optimized Tip Fabrication Process

We successfully achieve the tip-enhanced nano Raman scattering images of a tungsten disulfide monolayer with optimizing a fabrication method of gold nanotip by controlling the concentration of etchant in an electrochemical etching process. By applying a square-wave voltage supplied from an arbitrary waveform generator to a gold wire, which is immersed in a hydrochloric acid solution diluted with ethanol at various ratios, we find that both the conical angle and radius of curvature of the tip apex can be varied by changing the ratio of hydrochloric acid and ethanol. We also suggest a model to explain the origin of these variations in the tip shape. From the systematic study, we find an optimal condition for achieving the yield of similar to 60% with the radius of similar to 34 nm and the cone angle of similar to 35 degrees. Using representative tips fabricated under the optimal etching condition, we demonstrate the tip-enhanced Raman scattering experiment of tungsten disulfide monolayer grown by a chemical vapor deposition method with a spatial resolution of similar to 40 nm and a Raman enhancement factor of similar to 4,760. © The Author(s) 2017

O-GlcNAcylation in health and neurodegenerative diseases

O-GlcNAcylation is a posttranslational modification that adds O-linked ??-N-acetylglucosamine (O-GlcNAc) to serine or threonine residues of many proteins. This protein modification interacts with key cellular pathways involved in transcription, translation, and proteostasis. Although ubiquitous throughout the body, O-GlcNAc is particularly abundant in the brain, and various proteins commonly found at synapses are O-GlcNAcylated. Recent studies have demonstrated that the modulation of O-GlcNAc in the brain alters synaptic and neuronal functions. Furthermore, altered brain O-GlcNAcylation is associated with either the etiology or pathology of numerous neurodegenerative diseases, while the manipulation of O-GlcNAc exerts neuroprotective effects against these diseases. Although the detailed molecular mechanisms underlying the functional roles of O-GlcNAcylation in the brain remain unclear, O-GlcNAcylation is critical for regulating diverse neural functions, and its levels change during normal and pathological aging. In this review, we will highlight the functional importance of O-GlcNAcylation in the brain and neurodegenerative diseases

Replenishment of selenium deficient rats with selenium results in redistribution of the selenocysteine tRNA population in a tissue specific manner

AbstractWe reported previously that the selenium status of rats influences both the steady-state levels and distributions of two selenocysteine tRNA isoacceptors and that these isoacceptors differ by a single methyl group attached to the ribosyl moiety at position 34. In this study, we demonstrate that repletion of selenium-deficient rats results in a gradual, tissue-dependent shift in the distribution of these isoacceptors. Rats fed a selenium-deficient diet possess a greater abundance of the species unmethylated on the ribosyl moiety at position 34 compared to the form methylated at this position. A redistribution of the Sec–tRNA isoacceptors occurred in tissues of selenium-supplemented rats whereby the unmethylated form gradually shifted toward the methylated form. This was true in each of four tissues examined, muscle, kidney, liver and heart, although the rate of redistribution was tissue-specific. Muscle manifested a predominance of two minor serine isoacceptors under conditions of extreme selenium-deficiency which also appeared to respond to selenium. Ribosomal binding studies revealed that one of the two additional isoacceptors decodes the serine codeword, AGU, and the second decodes the serine codeword, UCU. Interestingly, muscle and heart were the slower tissues to return to a `selenium adequate' tRNA distribution pattern

A search for exoplanets around north circumpolar stars. VII. Detection of planetary companion orbiting the largest host star HD 18438

We have been conducting a exoplanet search survey using Bohyunsan Observatory Echelle Spectrograph (BOES) for the last 18 years. We present the detection of exoplanet candidate in orbit around HD 18438 from high-precision radial velocity (RV) mesurements. The target was already reported in 2018 (Bang et al. 2018). They conclude that the RV variations with a period of 719 days are likely to be caused by the pulsations because the Lomb-Scargle periodogram of HIPPARCOS photometric and Ha EW variations for HD 18438 show peaks with periods close to that of RV variations and there were no correlations between bisectors and RV measurements. However, the data were not sufficient to reach a firm conclusion. We obtained more RV data for four years. The longer time baseline yields a more accurate determination with a revised period of 803 +/- 5 days and the planetary origin of RV variations with a minimum planetary companion mass of 21 +/- 1 MJup. Our current estimate of the stellar parameters for HD 18438 makes it currently the largest star with a planetary companion.Comment: 6 pages, 4 figures, Accept to the Journal of the Korean Astronomical Societ