Characteristics of dusk-side IHFAC polarity during storm and quiet time

第150回地球電磁気・地球惑星圏学会（SGEPSS）総会および講演会, 2021年10月31日-11月4

Seasonal variation of inter-hemispheric field-aligned currents deduced from time-series analysis of the equatorial geomagnetic field data during solar cycle 23-24

The east–west component of magnetic field variation (∆D-component) at Davao station (Philippines, geomagnetic latitude: – 2.22˚N) are used to investigate the characteristics of the long-term Inter-Hemispheric Field-Aligned Currents (IHFACs) based on the time-series analysis from August 1998 to July 2020. Recent in situ satellite and ground-based observations have reported that dusk-side current polarity of IHFAC is often opposite to that of the noon IHFAC, being inconsistent with Fukushima\u27s IHFACs model. We investigated the consistency of the dusk-side IHFAC polarity derived from the observations with the polarity expected from Fukushima’s IHFACs model and examined the solar cycle dependence of IHFACs. It was confirmed that the dusk-side IHFACs during June and December solstices flow in the same direction of the noontime IHFACs, which was consistent with the IHFAC polarities suggested by the Fukushima model. The dusk-side IHFACs around March and September–November months disagreed with the Fukushima model. The ∆D variations clearly showed seasonal asymmetry in the dawn and noon sectors, whereas the ∆D variations in the dusk sector demonstrated seasonal symmetry. Solar cycle dependence of IHFACs was exhibited in the dusk sector. For the dawn and noon sectors, the yearly peak-to-peak ∆D amplitude in the later solar cycle SC24 decreased by about 35% in comparison with the earlier solar cycle SC23. In contrast, the dusk-side yearly peak-to-peak ∆D amplitude increased by about 200%. The dusk-side IHFAC yearly amplitude tended to be in inverse proportion to solar activity

Lifestyle and occupation risk factors for poor semen quality: a cross sectional study in Sri Lanka

Background: Infertility is a major problem all around the world. According to WHO, the rate of infertility is approximately 15% worldwide and it differ from geographical location, ethnicity and social status. Lifestyle habits, environmental and occupational hazards, physical parameters can be recognized as major risk factors which may affect male infertility. The objective of this study was to determine factors associated with male infertility in Sri Lankan context.Methods: A cross-sectional study was conducted on 299 individuals participated for an infertility clinic at Castle Street Teaching Hospital, Colombo, Sri Lanka. Socio-demographic, occupational and environmental characteristics were collected using interviewer administered questionnaire. Semen samples were collected from each participant for laboratory investigations. Sperm concentration and motility were measured.Results: Out of total participants, 30.1% of participants had a sperm concentration of <15×10⁶ and the sperm motility was <32% in 34.7% participants.  Older age, tobacco smokers, using tight under wears and individuals exposed to either heat or chemical hazards were identified as risk groups with low sperm concentration and low semen volume. In addition, older age, individuals using tight under wears and individuals exposed to either heat or chemical hazards were significantly associated with low or abnormal sperm mortality. Individuals having diabetes showed a significantly higher non-motility rate of sperms. Alcohol usage, betel chewing, mumps, special radiation exposure, body mass index and waist circumference were not significantly associated with semen parameters in study population.Conclusions: Older age, tobacco smoking, wearing tight underwear, occupational exposures, and diabetes mellitus has shown a risk for the generation of poor semen parameters, which can lead to male infertility. Furthermore, it is very important to carry out extended studies regarding this problem to establish the effect of above factors

Inkjet‐Printed Self‐Hosted TADF Polymer Light‐Emitting Diodes

Thermally activated delayed fluorescent (TADF) materials are extensively investigated as organic light-emitting diodes (OLEDs) with TADF emitting layers demonstrating high efficiency without the use of heavy metal complexes. Therefore, solution-processable and printable TADF emitters are highly desirable, moving away from expensive vacuum deposition techniques. In addition, using emissive materials not requiring an external host simplifies the fabrication process significantly. Herein, OLEDs using a solution-processable TADF polymer that do not need an external host are introduced. The non-conjugated TADF polymer features a TADF emitter (4-(9H-carbazol-9-yl)-2-(3′-hydroxy-[1,1′-biphenyl]-3-yl)-isoindoline-1,3-dione) as a side chain, as well as a hole-transporting side chain and an electron-transporting side chain on an inactive polymer backbone. All organic layers of the OLEDs are fabricated using solution processing methods. The OLEDs with inkjet-printed emissive layers have comparable maximum current and external quantum efficiency as their spin-coated counterparts, exceeding luminance of 2000 cd m$^{-2}$. The herein-explored strategy is a viable route toward self-hosted printable TADF OLEDs

Structural changes of water molecules during photoelectrochemical water oxidation on TiO2 thin film electrodes

Behaviors of photogenerated charge carriers and structural changes of water molecules on TiO2 photoelectrodes were investigated by using time-resolved visible to mid-IR absorption spectroscopy. From the spectra measured in the visible to NIR region, it was shown that the lifetime of trapped electrons and holes becomes longer upon applying more positive potentials. This result was reasonably explained by the enhancement of the upward band bending at the water/TiO2 interface. On the other hand, from the spectra measured in the mid-IR region, structural changes of the water molecules were observed. When a TiO2 electrode was photoexcited at the potential where the water oxidation starts, a new absorption peak appeared at 3620 cm−1 with a slight decrease in the intensity of hydrogen-bonded water. This new peak was assigned to the isolated O–H band of water molecules. Usually, TiO2 surfaces exhibit super-hydrophilic properties with strong hydrogen-bonding; however, the obtained result was opposite. Therefore, the appearance of this isolated O–H band was ascribed to the cleavage of the hydrogen-bonding networks resulting from the production of reaction intermediates such as OH radicals or H2O2. The intensity of the isolated O–H decreases when applying more positive potentials, where the O2 evolution proceeds more efficiently. This could be ascribed to the rapid consumption of the reaction intermediates. At these potentials, the intensity of hydrogen-bonded water was also further decreased

Fabrication of robust TiO2 thin films by atomized spray pyrolysis deposition for photoelectrochemical water oxidation

Photoelectrodes are highly essential for the photoelectrochemical water splitting process and development of novel fabrication techniques is vital for further enhancement of activity. In this study, we successfully fabricated highly active TiO2 thin films by using novel atomized spray pyrolysis deposition (ASPD) technique. The ASPD technique utilizes a unique atomization process to produce highly fine aerosols which resulted in a highly crystalline TiO2 nanostructure. The deposition process was optimized by controlling deposition temperatures and precursor amounts. XRD and SEM studies confirmed the formation of anatase TiO2 phase and a highly interconnected nano-flakes on FM substrate at 550 degrees C. The photoelectrochemical activity of the optimized thin films showed a photocurrent density of similar to 5 mA cm(-2) at 1.0 V (vs. Ag/AgCl) in 0.1 M Na2SO4 (aq) under 375 nm (150 mW cm(-2)) illumination. This photocurrent was much higher than the two other anatases TiO2 thin films fabricated by conventional spray pyrolysis deposition (SPD) using the same precursor and anatase TiO2 powder (particle size similar to 21 nm). Transient IR absorption study revealed that the SPD powder based thin films have deeply trapped electrons, whereas ASPD thin films consisted with only free and/or shallowly trapped electrons. Higher crystallinity and enhanced electron conductivity of the TiO2 thin films fabricated by ASPD are responsible for this stable and high photoelectrochemical activity. (C) 2017 Elsevier B.V. All rights reserved