Effect of lattice distortions on the electron and thermal transport properties of transparent oxide semiconductor Ba1-xSrxSnO3 solid solution films

La-doped ASnO3 (A = Ba, Sr) have great potential as advanced transparent oxide semiconductors due to their large optical bandgap and relatively high electron mobility. The bandgap of Ba1-xSrxSnO3 solid solution increases from 3.2 eV (BaSnO3) to 4.6 eV (SrSnO3) with x. However, the increase in the bandgap is accompanied by reductions in the electrical conductivity. The versatility in the changes in the electrical properties are not trivial, and the property optimization has been challenging. Here we propose a simple metric for quantifying the transport properties of ASnO3. We investigated the electron/thermal transport properties of Ba1-xSrxSnO3 solid solution films and their relationship with the lattice distortion. The results suggest that the all transport properties of Ba1-xSrxSnO3 are dominated by the lattice distortion. This phenomenon is attributed to the distortions in the SnO6 octahedron, which consists the conduction band

Measurement of the Background Activities of a 100Mo-enriched powder sample for AMoRE crystal material using a single high purity germanium detector

The Advanced Molybdenum-based Rare process Experiment (AMoRE) searches for neutrino-less double-beta (0{\nu}\b{eta}\b{eta}) decay of 100Mo in enriched molybdate crystals. The AMoRE crystals must have low levels of radioactive contamination to achieve low background signals with energies near the Q-value of the 100Mo 0{\nu}\b{eta}\b{eta} decay. To produce low-activity crystals, radioactive contaminants in the raw materials used to form the crystals must be controlled and quantified. 100EnrMoO3 powder, which is enriched in the 100Mo isotope, is of particular interest as it is the source of 100Mo in the crystals. A high-purity germanium detector having 100% relative efficiency, named CC1, is being operated in the Yangyang underground laboratory. Using CC1, we collected a gamma spectrum from a 1.6-kg 100EnrMoO3 powder sample enriched to 96.4% in 100Mo. Activities were analyzed for the isotopes 228Ac, 228Th, 226Ra, and 40K. They are long-lived naturally occurring isotopes that can produce background signals in the region of interest for AMoRE. Activities of both 228Ac and 228Th were < 1.0 mBq/kg at 90% confidence level (C.L.). The activity of 226Ra was measured to be 5.1 \pm 0.4 (stat) \pm 2.2 (syst) mBq/kg. The 40K activity was found as < 16.4 mBq/kg at 90% C.L.Comment: 20 pages, 6 figures, 5 table

Trait-based evaluation of plant assemblages in traditional farm ponds in Korea: Ecological and management implications

The Korean traditional farm pond called dumbeong is an important rural landscape element that supports local biodiversity and is useful in irrigating agricultural fields during dry periods. This study assesses how plant communities in dumbeongs respond to adjacent land use, water depth, open-water surface, and nutrient levels and irrigation usage. Plant functional and species groups, based on trait and species data respectively from 20 dumbeongs in Seocheon-gun, South Korea, were classified by hierarchical analysis and non-metric multidimensional scaling. Relationships between the plant community composition and explanatory variables at both the species and functional group levels were tested through redundancy analysis. The results showed that irrigation usage prevented nutrient accumulation and water depth reduction of the ponds, and we found water depth was the only significant factor that determined plant composition at both species and functional group levels. The plant functional groups were more useful than plant species in predicting plant composition in dumbeongs, owing to their collective response to water depth and open-water surface. Our results demonstrate that management practices of dumbeong, such as periodic drainage, sediment removal and control of dominant plant species, alter its plant communities and thus need to be considered for biodiversity conservation in agricultural landscapes.

Large thickness dependence of the carrier mobility in a transparent oxide semiconductor, La-doped BaSnO3

We report herein that the carrier mobility of the 2%-La-doped BaSnO3 (LBSO) films on (001) SrTiO3 and (001) MgO substrates strongly depends on the thickness whereas it is unrelated to the lattice mismatch (+5.4% for SrTiO3, -2.3% for MgO). Although we observed large differences in the lattice parameters, the lateral grain size (~85 nm for SrTiO3, ~20 nm for MgO), the surface morphology and the density of misfit dislocations, the mobility increased almost simultaneously with the thickness in both cases and saturated at ~100 cm2 V-1 s-1, together with the approaching to the nominal carrier concentration (=[2% La3+]), clearly indicating that the behavior of mobility depends on the film thickness. The present results would be beneficial to understand the behavior of mobility and fruitful to further enhance the mobility of LBSO films.Comment: 15 pages, including 4 figure

Measurement of the Background Activities of a 100Mo-enriched Powder Sample for an AMoRE Crystal Material by using Fourteen High-Purity Germanium Detectors

The Advanced Molybdenum-based Rare process Experiment in its second phase (AMoRE-II) will search for neutrinoless double-beta (0{\nu}\b{eta}\b{eta}) decay of 100Mo in 200 kg of molybdate crystals. To achieve the zero-background level in the energy range of the double-beta decay Q-value of 100Mo, the radioactive contamination levels in AMoRE crystals should be low. 100EnrMoO3 powder, which is enriched in the 100Mo isotope, is used to grow the AMoRE crystals. A shielded array of fourteen high-purity germanium detectors with 70% relative efficiency each was used for the measurement of background activities in a sample of 9.6-kg powder. The detector system named CAGe located at the Yangyang underground laboratory was designed for measuring low levels of radioactivity from natural radioisotopes or cosmogenic nuclides such as 228Ac, 228Th, 226Ra, 88Y, and 40K. The activities of 228Ac and 228Th in the powder sample were 0.88 \pm 0.12 mBq/kg and 0.669 \pm 0.087 mBq/kg, respectively. The activity of 226Ra was measured to be 1.50 \pm 0.23 mBq/kg. The activity of 88Y was 0.101 \pm 0.016 mBq/kg. The activity of 40K was found as 36.0 \pm 4.1 mBq/kg.Comment: 24 pages, 10 figures, 5 table

Buffer layer-less fabrication of high-mobility transparent oxide semiconductor, La-doped BaSnO3

Transparent oxide semiconductors (TOSs) showing both high visible transparency and high electron mobility have attracted great attention towards the realization of advanced optoelectronic devices. La-doped BaSnO3 (LBSO) is one of the most promising TOSs because its single crystal exhibits a high electron mobility. However, in the LBSO films, it is very hard to obtain high mobility due to the threading dislocations, which are originated from the lattice mismatch between the film and the substrate. Therefore, many researchers have tried to improve the mobility by inserting a buffer layer. While the buffer layers increased the electron mobilities, this approach leaves much to be desired since it involves a two-step film fabrication process and the enhanced mobility values are still significantly lower than single crystal values. We show herein that the electron mobility of LBSO films can be improved without inserting any buffer layers if the films are grown under highly oxidative ozone (O3) atmospheres. The O3 environments relaxed the LBSO lattice and reduced the formation of Sn2+ states, which are known to suppress the electron mobility in LBSO. The resultant O3-LBSO films showed improved mobility values up to 115 cm2 V-1 s-1, which is among the highest in LBSO films on SrTiO3 substrates and comparable to LBSO films with buffer layers.Comment: 16 pages including 5 figure

Unveiling the Electronic Structure of Grain Boundaries in Anatase with Electron Microscopy and First-Principles Modeling

Polycrystalline anatase titanium dioxide has drawn great interest, because of its potential applications in high-efficiency photovoltaics and photocatalysts. There has been speculation on the electronic properties of grain boundaries but little direct evidence, because grain boundaries in anatase are challenging to probe experimentally and to model. We present a combined experimental and theoretical study of anatase grain boundaries that have been fabricated by epitaxial growth on a bicrystalline substrate, allowing accurate atomic-scale models to be determined. The electronic structure in the vicinity of stoichiometric grain boundaries is relatively benign to device performance but segregation of oxygen vacancies introduces barriers to electron transport, because of the development of a space charge region. An intrinsically oxygen-deficient boundary exhibits charge trapping consistent with electron energy loss spectroscopy measurements. We discuss strategies for the synthesis of polycrystalline anatase in order to minimize the formation of such deleterious grain boundaries

Refined prefrontal working memory network as a neuromarker for Alzheimer’s disease

Detecting Alzheimer’s disease (AD) is an important step in preventing pathological brain damage. Working memory (WM)-related network modulation can be a pathological feature of AD, but is usually modulated by untargeted cognitive processes and individual variance, resulting in the concealment of this key information. Therefore, in this study, we comprehensively investigated a new neuromarker, named “refined network,” in a prefrontal cortex (PFC) that revealed the pathological features of AD. A refined network was acquired by removing unnecessary variance from the WM-related network. By using a functional near-infrared spectroscopy (fNIRS) device, we evaluated the reliability of the refined network, which was identified from the three groups classified by AD progression: healthy people (N=31), mild cognitive impairment (N=11), and patients with AD (N=18). As a result, we identified edges with significant correlations between cognitive functions and groups in the dorsolateral PFC. Moreover, the refined network achieved a significantly correlating metric with neuropsychological test scores, and a remarkable three-class classification accuracy (95.0%). These results implicate the refined PFC WM-related network as a powerful neuromarker for AD screening. © 2021 Optical Society of America1

The erythropoietin-derived peptide MK-X and erythropoietin have neuroprotective effects against ischemic brain damage

Erythropoietin (EPO) has been well known as a hematopoietic cytokine over the past decades. However, recent reports have demonstrated that EPO plays a neuroprotective role in the central nervous system, and EPO has been considered as a therapeutic target in neurodegenerative diseases such as ischemic stroke. Despite the neuroprotective effect of EPO, clinical trials have shown its unexpected side effects, including undesirable proliferative effects such as erythropoiesis and tumor growth. Therefore, the development of EPO analogs that would confer neuroprotection without adverse effects has been attempted. In this study, we examined the potential of a novel EPO-based short peptide, MK-X, as a novel drug for stroke treatment in comparison with EPO. We found that MK-X administration with reperfusion dramatically reduced brain injury in an in vivo mouse model of ischemic stroke induced by middle cerebral artery occlusion, whereas EPO had little effect. Similar to EPO, MK-X efficiently ameliorated mitochondrial dysfunction followed by neuronal death caused by glutamate-induced oxidative stress in cultured neurons. Consistent with this effect, MK-X significantly decreased caspase-3 cleavage and nuclear translocation of apoptosis-inducing factor induced by glutamate. MK-X completely mimicked the effect of EPO on multiple activation of JAK2 and its downstream PI3K/AKT and ERK1/2 signaling pathways, and this signaling process was involved in the neuroprotective effect of MK-X. Furthermore, MK-X and EPO induced similar changes in the gene expression patterns under glutamate-induced excitotoxicity. Interestingly, the most significant difference between MK-X and EPO was that MK-X better penetrated into the brain across the brain-blood barrier than did EPO. In conclusion, we suggest that MK-X might be used as a novel drug for protection from brain injury caused by ischemic stroke, which penetrates into the brain faster in comparison with EPO, even though MK-X and EPO have similar protective effects against excitotoxicity.1

Inhibition of multidrug-resistant foodborne Staphylococcus aureus biofilms by a natural terpenoid (+)-nootkatone and related molecular mechanism

CITATION: Farha, A. K. et al. 2020. Inhibition of multidrug-resistant foodborne Staphylococcus aureus biofilms by a natural terpenoid (+)-nootkatone and related molecular mechanism. Food Control, 112. doi:10.1016/j.foodcont.2020.107154.The original publication is available at http://www.journals.elsevier.com/food-control/Staphylococcus aureus, a foodborne pathogen, poses serious problems to the food industries owing to biofilm formation, and over 25% of the foodborne illnesses in China have been attributed to S. aureus only. Phytochemicals are widely used as anti-biofilm agents with promising efficacy, and most of them are widely available and safe. This study reported the anti-biofilm efficacy of (+)-nootkatone, a sesquiterpene ketone found in a common fruit grapefruit, against multidrug-resistant S. aureus and its potential molecular mechanism. (+)-Nootkatone exhibited bacteriostatic and bactericidal effects at 200 and 400 μg/mL, respectively, against S. aureus SJTUF 20758 and S. aureus ATCC 25923. Crystal violet staining indicated that (+)-nootkatone inhibited S. aureus biofilm formation (p < 0.05) at a sub-MIC of 50 μg/mL and reduced exopolysaccharide production. The thickness of biofilms was significantly reduced by (+)-nootkatone, which was supported by the light microscopy and confocal laser scanning microscopy. Growth curve of bacteria showed that the antibacerial activity of (+)-nootkatone was dose-dependent, and the sub-MIC concentrations did not affect the bacterial growth of planktonic cells. Besides, (+)-nootkatone affected the sliding motility of S. aureus. At 200 μg/mL, (+)-nootkatone led to the reduction of preformed biofilm mass by 50% and bacterial cell death of 79%, accompanied with a reduction of exopolysaccharide. The expression of biofilm-related genes, including sarA, icaA, agrA, RNAIII, and spa, was suppressed by (+)-nootkatone, as revealed by the transcriptional analysis. Additionally, MTT assay revealed that there was no toxicity of (+)-nootkatone to the human foreskin fibroblasts (HFF) cells. Therefore, (+)-nootkatone is a promising phytochemical against S. aureus biofilms, and has the potential to be used in food industry to fight against S. aureus-induced safety issues.https://www.sciencedirect.com/science/article/pii/S0956713520300700?via%3DihubPublishers versio