Controlled Crystallinity of a Sn-Doped α-Ga2O3 Epilayer Using Rapidly Annealed Double Buffer Layers.

Double buffer layers composed of (AlxGa1-x)2O3/Ga2O3 structures were employed to grow a Sn-doped α-Ga2O3 epitaxial thin film on a sapphire substrate using mist chemical vapor deposition. The insertion of double buffer layers improved the crystal quality of the upper-grown Sn-doped α-Ga2O3 thin films by blocking dislocation generated by the substrates. Rapid thermal annealing was conducted for the double buffer layers at phase transition temperatures of 700-800 °C. The slight mixing of κ and ß phases further improved the crystallinity of the grown Sn-Ga2O3 thin film through local lateral overgrowth. The electron mobility of the Sn-Ga2O3 thin films was also significantly improved due to the smoothened interface and the diffusion of Al. Therefore, rapid thermal annealing with the double buffer layer proved advantageous in achieving strong electrical properties for Ga2O3 semiconductor devices within a shorter processing time.

Protocatechuic acid prevents isoproterenol-induced heart failure in mice by downregulating kynurenine-3-monooxygenase.

Protocatechuic acid (3,4-dihydroxybenzoic acid) prevents oxidative stress, inflammation and cardiac hypertrophy. This study aimed to investigate the therapeutic effects of protocatechuic acid in an isoproterenol-induced heart failure mouse model and to identify the underlying mechanisms. To establish the heart failure model, C57BL/6NTac mice were given high-dose isoproterenol (80 mg/kg body weight) for 14 days. Echocardiography revealed that protocatechuic acid reversed the isoproterenol-induced downregulation of fractional shortening and ejection fraction. Protocatechuic acid attenuated cardiac hypertrophy as evidenced by the decreased heart-weight-to-body-weight ratio and the expression of Nppb. RNA sequencing analysis identified kynurenine-3-monooxygenase (Kmo) as a potential target of protocatechuic acid. Protocatechuic acid treatment or transfection with short-interfering RNA against Kmo ameliorated transforming growth factor ß1-induced upregulation of Kmo, Col1a1, Col1a2 and Fn1 in vivo or in neonatal rat cardiac fibroblasts. Kmo knockdown attenuated the isoproterenol-induced increase in cardiomyocyte size, as well as Nppb and Col1a1 expression in H9c2 cells or primary neonatal rat cardiomyocytes. Moreover, protocatechuic acid attenuated Kmo overexpression-induced increases in Nppb mRNA levels. Protocatechuic acid or Kmo knockdown decreased isoproterenol-induced ROS generation in vivo and in vitro. Thus, protocatechuic acid prevents heart failure by downregulating Kmo. Therefore, protocatechuic acid and Kmo constitute a potential novel therapeutic agent and target, respectively, against heart failure.

Microstructural Gradational Properties of Sn-Doped Gallium Oxide Heteroepitaxial Layers Grown Using Mist Chemical Vapor Deposition.

This study examined the microstructural gradation in Sn-doped, n-type Ga2O3 epitaxial layers grown on a two-inch sapphire substrate using horizontal hot-wall mist chemical vapor deposition (mist CVD). The results revealed that, compared to a single Ga2O3 layer grown using a conventional single-step growth, the double Ga2O3 layers grown using a two-step growth process exhibited excellent thickness uniformity, surface roughness, and crystal quality. In addition, the spatial gradient of carrier concentration in the upper layer of the double layers was significantly affected by the mist flow velocity at the surface, regardless of the dopant concentration distribution of the underlying layer. Furthermore, the electrical properties of the single Ga2O3 layer could be attributed to various scattering mechanisms, whereas the carrier mobility of the double Ga2O3 layers could be attributed to Coulomb scattering owing to the heavily doped condition. It strongly suggests the two-step-grown, lightly-Sn-doped Ga2O3 layer is feasible for high power electronic devices.

Is Rheumatoid Arthritis Related to Coffee Consumption in Korea? A Nationwide Cross-Sectional Observational Study.

Coffee consumption is gradually increasing in Korea. As a result, interest in the relationship between coffee consumption and various diseases is growing. Several factors affect the development of rheumatoid arthritis (RA), and coffee consumption may be related. We conducted a nationwide cross-sectional study using data from the Korea National Health and Nutrition Examination Survey (2012-2016). A total of 12,465 eligible participants (4819 men and 7646 women) were included in the study. Participants with RA were defined as those who were diagnosed and currently being treated by physicians. Daily coffee consumption amounts were categorized as none, <1 cup, 1-2 cups, 2-3 cups, and ≥3 cups a day based on a self-report. A multivariable logistic regression model was employed, and we calculated the odds ratios (ORs) and 95% confidence intervals (CIs) for the odds of participants having RA with respect to coffee consumption. Compared to the no-coffee group, the ORs for RA in the <1 cup and 1-2 cups groups were 2.99 (95% CI 0.33-27.28) and 2.63 (95% CI 0.31-22.63) in men, respectively, and the ORs for RA for women in the <1 cup, 1-2 cups, 2-3 cups, and ≥3 cups groups were 0.62 (95% CI 0.31-1.26), 0.67 (95% CI 0.33-1.37), 1.08 (95% CI 0.35-3.36), and 1.43 (95% CI 0.25-8.36), respectively. Our study concludes, therefore, that daily coffee consumption is not related to the prevalence of RA in the general Korean population.

A New Fracture Detection Algorithm of Low Amplitude Acoustic Emission Signal Based on Kalman Filter-Ripple Voltage.

In this study, an acoustic emission (AE) sensor was utilized to predict fractures that occur in a product during the sheet metal forming process. An AE activity was analyzed, presuming that AE occurs when plastic deformation and fracturing of metallic materials occur. For the analysis, a threshold voltage is set to distinguish the AE signal from the ripple voltage signal and noise. If the amplitude of the AE signal is small, it is difficult to distinguish the AE signal from the ripple voltage signal and the noise signal. Hence, there is a limitation in predicting fractures using the AE sensor. To overcome this limitation, the Kalman filter was used in this study to remove the ripple voltage signal and noise signal and then analyze the activity. However, it was difficult to filter out the ripple voltage signal using a conventional low-pass filter or Kalman filter because the ripple voltage signal is a high-frequency component governed by the switch-mode of the power supply. Therefore, a Kalman filter that has a low Kalman gain was designed to extract only the ripple voltage signal. Based on the KF-RV algorithm, the measured ripple voltage and noise signal were reduced by 97.3% on average. Subsequently, the AE signal was extracted appropriately using the difference between the measured value and the extracted ripple voltage signal. The activity of the extracted AE signal was analyzed using the ring-down count among various AE parameters to determine if there was a fracture in the test specimen.

Toward Large-Scale Ga2O3 Membranes via Quasi-Van Der Waals Epitaxy on Epitaxial Graphene Layers.

Epitaxial growth using graphene (GR), weakly bonded by van der Waals force, is a subject of interest for fabricating technologically important semiconductor membranes. Such membranes can potentially offer effective cooling and dimensional scale-down for high voltage power devices and deep ultraviolet optoelectronics at a fraction of the bulk-device cost. Here, we report on a large-area ß-Ga2O3 nanomembrane spontaneous-exfoliation (1 cm × 1 cm) from layers of compressive-strained epitaxial graphene (EG) grown on SiC, and demonstrated high-responsivity flexible solar-blind photodetectors. The EG was favorably influenced by lattice arrangement of SiC, and thus enabled ß-Ga2O3 direct-epitaxy on the EG. The ß-Ga2O3 layer was spontaneously exfoliated at the interface of GR owing to its low interfacial toughness by controlling the energy release rate through electroplated Ni layers. The use of GR templates contributes to the seamless exfoliation of the nanomembranes, and the technique is relevant to eventual nanomembrane-based integrated device technology.

Improvement of SiC Crystal Growth Rate and Uniformity via Top-Seeded Solution Growth under External Static Magnetic Field: A Numerical Investigation.

Silicon carbide (SiC) is an ideal material for highpower and highperformance electronic applications. Topseeded solution growth (TSSG) is considered as a potential method for bulk growth of highquality SiC single crystals from the liquid phase source material. The crystal growth performance, such as growth rate and uniformity, is driven by the fluid flow and constitutional flux in the solution. In this study, we numerically investigate the contribution of the external static magnetic field generated by Helmholtz coils to the fluid flow in the silicon melt. Depending on the setup of the Helmholtz coils, four static magnetic field distributions are available, namely, uniform vertical upward/downward and vertical/horizontal cusp. Based on the calculated carbon flux coming to the crystal surface, the vertical downward magnetic field proved its ability to enhance the growth rate as well as the uniformity of the grown crystal.

The Effect of Co-Doping at the A-Site on the Structure and Oxide Ion Conductivity in (Ba0.5-xSrx)La0.5InO3-δ: A Molecular Dynamics Study.

A molecular dynamics simulation was used to investigate the structural and transport properties of a (Ba0.5-xSrx)La0.5InO3-δ (x = 0, 0.1, 0.2) oxygen ion conductor. Previous studies reported that the ionic conductivity of Ba-doped LaInO3 decreases because Ba dopant forms a narrow oxygen path in the lattice, which could hinder the diffusion of oxygen ions. In this study, we reveal the mechanism to improve ionic conductivity by Ba and Sr co-doping on an La site in LaInO3 perovskite oxide. The results show that the ionic conductivity of (Ba0.5-xSrx)La0.5InO3-δ increases with an increasing number of Sr ions because oxygen diffusion paths which contain Sr ions have a larger critical radius than those containing Ba ions. The radial distribution function (RDF) calculations show that the peak heights in compositions including Sr ions were lower and broadened, meaning that the oxygen ions moved easily into other oxygen sites.

Hypersensitive electrochemical immunoassays based on highly N-doped silicon carbide (SiC) electrode.

Highly N-doped SiC was presented as an optimal electrode for electrochemical immunoassays with a far higher sensitivity than chemiluminescence detection. As the first step, the electrochemical properties of highly N-doped SiC, such as the double-layer capacitance (Cdl), rate constant for electron transfer (kapp) and ideal polarizable potential range (electrochemical window) were analyzed and compared with those of Au, Pt, and graphite electrodes. The highly N-doped SiC electrode was used for the quantification of oxidized 3,3',5,5'-tetramethylbenzidine (TMB) which was widely used as chromogenic substrate for commercialized immunoassay kits. In order to enhance the sensitivity for the quantification of the oxidized TMB the chronoamperometry was applied to avoid the background current of i-V measurement. Finally, the chronoamperometry based on the highly N-doped SiC electrode was applied to commercial immunoassay kits for the medical diagnosis of the human immunodeficiency virus (HIV) and the human hepatitis B surface antigen (hHBsAg). The chronoamperometric measurement based on the highly N-doped SiC electrode was proved to detect at far lower limits in comparison with the conventional optical density measurement as well as the chemiluminescence assay based on luminol as a chemiluminescent probe.

Flow modification enhancing the growth rate in top seeded solution growth of SiC crystals.

In this study, multiphysics simulations were carried out to understand the convection mechanisms of the top seeded solution growth (TSSG) of SiC. Experimental melting tests and crystal growth were conducted to verify the simulation results in the growing temperatures between 1700 and 1900 °C with rf induction heating furnace. From the solidified melt of Si-Cr solution after the melting test, the melt flow in the simulation was successfully verified. In the given experimental conditions, the electromagnetic convection was found to govern the global fluid flow, while other mechanisms including the Marangoni convection, the buoyancy convection and the centrifugal forced convection influence the fluid flow near the crystal. Based on an understanding of the fluid flow obtained with the simulations, a structural flow modifier (FM) was applied to enhance the growth rate of the SiC crystal. The growth rates of SiC with/without FM were successfully estimated from simulations showing good agreements with the experimental values. After the experimental crystal growth using FM, a remarkable enhancement in the growth rate was found in an FM configuration, which suggests a way to improve the growth rate by the TSSG method based on the efficient use of the dissolved C in the melt.

One-step growth of multilayer-graphene hollow nanospheres via the self-elimination of SiC nuclei templates.

We introduce a one-step growth method for producing multilayer-graphene hollow nanospheres via a high-temperature chemical vapor deposition process using tetramethylsilane as an organic precursor. When the SiC nuclei were grown under an excess carbon atmosphere, they were surrounded via desorption of the hydrocarbon gas species, and graphene layers formed on the surface of the SiC nuclei via the rearrangement of solid carbon during the heating and cooling. The core SiC nuclei were spontaneously removed by the subsequent thermal decomposition, which also supplied the carbon for the graphene layers. Hence, multilayer-graphene hollow nanospheres were acquired via a one-step process, which was simply controlled by the growth temperature. In this growth process, the SiC nuclei acted as both the template and carbon source for the formation of multilayer-graphene hollow nanospheres.

How early must an acute Achilles tendon rupture be repaired?

An acute Achilles tendon rupture is the most common tendon rupture of the lower extremities, yet the optimal timing for an early surgical repair is unclear. To identify the optimal time for an early surgical repair with favorable results, we evaluated the isokinetic muscle strength and clinical outcomes of early surgical repairs of acute Achilles tendon ruptures performed at different time points after injury. Between January 2011 and July 2015, a total of 65 patients underwent an acute Achilles tendon rupture repair within 1 week after injury. To compare the outcomes at different time points post-injury, we divided patients into 3 groups: group 1, surgical treatment at ≤24h; group 2, surgery at ≥24h and ≤48h; and group 3, surgery at ≥48 hours and ≤1 week. The isokinetic muscle strength in both ankles were measured using a Cybex dynamometer, and the Achilles tendon total rupture score, the modified Tegner scoring system, the visual analog scale was used to assess clinical outcomes. Kruskal-Wallis and Fisher's exact tests were used to compare multiple results in the 3 groups. No significant differences were found among the groups in terms of ankle isokinetic muscle strength or clinical outcome scores (P>0.05). The complication rate was low in all groups. There were no significant differences in isokinetic muscle strength or clinical outcomes following acute Achilles tendon rupture repairs performed within 1 week after injury.

Associations of smoking with overall obesity, and central obesity: a cross-sectional study from the Korea National Health and Nutrition Examination Survey (2010-2013).

OBJECTIVES: The association between smoking and obesity is a significant public health concern. Both are preventable risk factors of cardiovascular disease and a range of other conditions. However, despite numerous previous studies, no consensus has emerged regarding the effect of smoking on obesity. We therefore carried out a novel study evaluating the relationship between smoking and obesity. METHODS: A total of 5,254 subjects aged 19 years or older drawn from the 2010-2013 Korea National Health and Nutrition Examination Survey were included in this cross-sectional study. Smoking was examined both in terms of smoking status and the quantity of cigarettes smoked by current smokers. Multiple logistic regression analysis was used to assess the association between smoking and obesity. Overall obesity was defined as a body mass index (BMI) ≥25 kg/m(2), and central obesity was defined as a waist circumference ≥90 cm for males and ≥85 cm for females. We adjusted for the possible confounding effects of age, sex, physical activity, alcohol consumption, and the presence of hypertension or diabetes. RESULTS: A statistically significant difference in central obesity according to smoking status was identified. Current smokers were more likely to be centrally obese than never-smokers (adjusted odds ratio,1.30; 95% confidence interval, 1.02 to 1.67). However, no significant association was found between smoking and obesity defined by BMI. Moreover, among current smokers, no statistically significant association was found between the daily amount of smoking and obesity or central obesity. CONCLUSIONS: Smoking was positively associated with central obesity. Current smokers should be acquainted that they may be more prone to central obesity.

Spontaneous Growth of Ultra-Long SiO(x) Nanowires from SiC Thin Films by Thermal Annealing.

The use of a simple thermal treatment for growing ultra-long SiO(x) nanowires on silicon carbide (SiC) thin films is reported for the first time. SiC thin films with a thickness of 100 nm were prepared by sputtering at room temperature followed by annealing in an Ar/H2 gas atmosphere. The growth of SiO(x) nanowires started when the annealing temperature was at 1200 degrees C, and was rapidly and spontaneously grown at temperatures above 1250 degrees C. The diameters of as-grown SiO(x) nanowires with lengths up to several hundred micrometers were determined to be -1 µm.

Molecular Dynamics Simulation of Oxygen Ion Conduction in Orthorhombic Perovskite Ba-Doped LaInO3 Using Cubic and Orthorhombic Model.

The oxygen ion conduction behavior of an orthorhombic perovskite oxide Ba-doped LaInO3 was evaluated by molecular dynamics simulation. Comparative calculations for cubic and the orthorhombic models show that the orthorhombic model was in better agreement with the experimental results with respect to both ionic conductivity and activation energy. The results of the radial distribution function for O-O pair provided and explanation for why the ionic conductivity of cubic perovskite is higher than that of orthorhombic perovskite. The orthorhombic model has a higher peak intensity of O-O pair than the cubic model, it means that the orthorhombic model has a smaller number of oxygen-vacancy pairs in the lattice structure. Consequently, the ionic conductivity of orthorhombic perovskite is lower than that of cubic perovskite due to less conduction path.

Effects of in vitro and in vivo Qi-therapy on neutrophil superoxide generation in healthy male subjects.

The present study investigated the effects of in vitro and in vivo Korean ChunSoo Qi-Energy Healing on neutrophil superoxide generation. Neutrophil superoxide generation was measured by a chemiluminescence assay. Superoxide generation was significantly increased in vitro by emitted Qi-therapy (QT) of 60-second duration and 150-second duration compared to control (1.59-fold for 60 seconds, p < 0.05; 1.50-fold for 150 seconds, p < 0.05). Neutrophil superoxide generation increased significantly immediately after 5 minutes of QT in vivo (1.42-fold, p < 0.05). These results show that QT in vivo and in vitro has an acute stimulatory effect on neutrophil superoxide generation. This study provides direct scientific support that Qi as such may positively affect human innate immunity.

Effects of Qigong on immune cells.

The aim of this study was to investigate the influence of two acute Qigong interventions (Qi-training and Qi-therapy) on immune cells. The Qigong interventions were compared with placebo training and placebo therapy in which no attempt was made to gather or move Qi. Immune cell numbers were measured pre-intervention, immediately post-intervention and 1 or 2 hours post-intervention. White blood cells increased significantly 2 hours after actual Qi-training (p < 0.05) but not sham training compared with pre-intervention There were significant increases in lymphocytes 2 hours after actual but not sham Qi-training (p < 0.05) and monocyte numbers were significantly increased immediately after both actual Qi-training (p < 0.01) and sham training (p < 0.05). NK cell numbers decreased significantly both immediately after Qi-training and after sham movements done without concomitant Qi-training (p < 0.01). There were no significant effects on neutrophils. Actual Qi-therapy but not sham therapy increased monocyte numbers immediately after Qi-therapy, and lymphocytes increased more after real than after sham therapy. Neutrophils were again little changed The data indicate that a single Qigong intervention can increase the monocyte and lymphocyte numbers.

Qi-training enhances respiratory burst function and adhesive capacity of neutrophils in young adults: a preliminary study.

The main objective of this study is to examine the effect of Qi-training on the immune system, especially neutrophil bactericidal function. Nine healthy male subjects were studied for the effects of one bout of ChunDoSunBup (CDSB) Qi-training on superoxide (O2- production and adhesion capacity of neutrophils at times immediately after (Post I) and 2 hours after the Qi-training (Post II). The Qi-training enhanced O2- production, reaction velocity and neutrophil adhesion capacity and there were significant differences at Post I compared to before Qi-training (Pre). In addition, the number of white blood cells (WBC), monocytes and lymphocytes were changed significantly through Qi-training.Therefore, it seems that CDSB Qi-training may increase the resistance of trained individuals against common infection and inflammation.