Machine-learning-assisted analysis of transition metal dichalcogenide thin-film growth

In situ reflective high-energy electron diffraction (RHEED) is widely used to monitor the surface crystalline state during thin-film growth by molecular beam epitaxy (MBE) and pulsed laser deposition. With the recent development of machine learning (ML), ML-assisted analysis of RHEED videos aids in interpreting the complete RHEED data of oxide thin films. The quantitative analysis of RHEED data allows us to characterize and categorize the growth modes step by step, and extract hidden knowledge of the epitaxial film growth process. In this study, we employed the ML-assisted RHEED analysis method to investigate the growth of 2D thin films of transition metal dichalcogenides (ReSe2) on graphene substrates by MBE. Principal component analysis (PCA) and K-means clustering were used to separate statistically important patterns and visualize the trend of pattern evolution without any notable loss of information. Using the modified PCA, we could monitor the diffraction intensity of solely the ReSe2 layers by filtering out the substrate contribution. These findings demonstrate that ML analysis can be successfully employed to examine and understand the film-growth dynamics of 2D materials. Further, the ML-based method can pave the way for the development of advanced real-time monitoring and autonomous material synthesis techniques.Comment: 21 pages, 4 figure

Synergetic strengthening of layered steel sheet investigated using an in situ neutron diffraction tensile test

Synergetic strengthening induced by plastic strain incompatibility at the interface, and the resulting extra geometrically necessary dislocations (GNDs) generated during plastic deformation, were investigated to understand the origin of extra strength in heterogeneous structured (HS) materials. The mechanism of extra GND generation in twinning-induced plasticity (TWIP)-interstitial free (IF) steel layered sheet was quantitatively analyzed by conducting in situ neutron scattering tensile test. Load partitioning due to the different mechanical properties between the TWIP-steel core and IF-steel sheath at the TWIP/IF interface was observed during the in situ tensile testing. Because of the plastic strain incompatibility from load partitioning, extra GNDs are generated and saturate during tensile deformation. The extra GNDs can be correlated with the back-stress evolution of the HS materials, which contributes to the strength of layered materials. Because of the back-stress evolution caused by load partitioning, the strength of TWIP-IF layered steel is higher than the strength estimated by the rule-of-mixtures. This finding offers a mechanism by which extra GNDs are generated during load partitioning and shows how they contribute to the mechanical properties of HS materials.11Ysciescopu

A DNA barcode library of the beetle reference collection (Insecta: Coleoptera) in the National Science Museum, Korea

AbstractColeoptera is a group of insects that are most diverse among insect resources. Although used as indicator species and applied in developing new drugs, it is difficult to identify them quickly. Since the development of a method using mitochondrial DNA information for identification, studies have been conducted in Korea to swiftly and accurately identify species. The National Science Museum of Korea (NSMK) has been collecting and morphologically identifying domestic reference insects since 2013, and building a database of DNA barcodes with digital images. The NSMK completed construction of a database of digital images and DNA barcodes of 60 beetle species in the Korean National Research Information System. A total of 179 specimens and 60 species were used for the analysis, and the averages of intraspecific and interspecific variations were 0.70±0.45% and 26.34±6.01%, respectively, with variation rates ranging from 0% to 1.45% and 9.83% to 56.23%, respectively

Association between Choroidal Thickness and Ocular Perfusion Pressure in Young, Healthy Subjects: Enhanced Depth Imaging Optical Coherence Tomography Study

PURPOSE. To investigate the correlation of choroidal thickness (CT) with ocular perfusion pressure (OPP) in young, healthy subjects using enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS. A single horizontal section and a single vertical section of EDI-OCT scans in each eye of 69 young, healthy subjects were obtained at the macula. CT was measured at the fovea, and up to 3 mm, at intervals of 0.5 mm, away from the fovea in the superior, inferior, nasal, and temporal choroid. Univariable and multivariable analyses were performed to assess the association of CT with OPP while axial length (AL), refractive error (RE), sex, and/or body mass index (BMI), were taken into consideration. RESULTS. Mean subfoveal CT was 307.03 6 91.27 lm (mean age, 22.3 6 3 years; mean axial length, 25.35 6 1.14 mm; mean refractive error, À3.89 6 2.02 diopters; mean OPP, 44.18 6 5.49 mm Hg). Multivariable regression analysis showed that in eyes with <6 diopters of myopia, subfoveal CT (325.92 6 88.46 lm) changed most significantly in association with RE and mean OPP (b ¼ 25.941, P < 0.001; b ¼À3.551, P ¼ 0.042, respectively; adjusted R 2 ¼ 0.249). In subjects with myopia of >6 diopters, subfoveal CT (225.17 6 49.37 lm) was significantly thinner (P < 0.0001), and a significant correlation with OPP was not observed (P > 0.05). CONCLUSIONS. In vivo subfoveal CT as measured by EDI-OCT was significantly associated with OPP in young, healthy subjects when adjusted for RE, suggesting that subfoveal CT may be indirectly indicative of subfoveal ocular perfusion status. This association was not observed in subjects with high myopia. (Invest Ophthalmol Vis Sci. 2012;53:7710-7717

Premixed Calcium Silicate-Based Root Canal Sealer Reinforced with Bioactive Glass Nanoparticles to Improve Biological Properties

Recently, bioactive glass nanoparticles (BGns) have been acknowledged for their ability to promote interactions with the periapical tissue and enhance tissue regeneration by releasing therapeutic ions. However, there have been no studies on calcium silicate sealers with bioactive glass nanoparticle (BGn) additives. In the present study, a premixed calcium silicate root canal sealer reinforced with BGn (pre-mixed-RCS@BGn) was developed and its physicochemical features and biological effects were analyzed. Three specimens were in the trial: 0%, 0.5%, and 1% bioactive glass nanoparticles (BGns) were gradually added to the premixed type of calcium silicate-based sealer (pre-mixed-RCS). To elucidate the surface properties, scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy were used and flowability, setting time, solubility, and radiopacity were analyzed to evaluate the physical properties. Chemical properties were investigated by water contact angle, pH change, and ion release measurements. The antibacterial effects of the bioactive set sealers were tested with Enterococcus faecalis and the viability of human bone marrow-derived mesenchymal stem cells (hMSCs) with this biomaterial was examined. In addition, osteogenic differentiation was highly stimulated, which was confirmed by ALP (Alkaline phosphatase) activity and the ARS (Alizarin red S) staining of hMSCs. The pre-mixed-RCS@BGn satisfied the ISO standards for root canal sealers and maintained antimicrobial activity. Moreover, pre-mixed-RCS@BGn with more BGns turned out to have less cytotoxicity than pre-mixed-RCS without BGns while promoting osteogenic differentiation, mainly due to calcium and silicon ion release. Our results suggest that BGns enhance the biological properties of this calcium silicate-based sealer and that the newly introduced pre-mixed-RCS@BGn has the capability to be applied in dental procedures as a root canal sealer. Further studies focusing more on the biocompatibility of pre-mixed-RCS@BGn should be performed to investigate in vivo systems, including pulp tissue

Permanent Pacemaker for Syncope after Heart Transplantation with Bicaval Technique

Sinus node dysfunction occurs occasionally after heart transplantation and may be caused by surgical trauma, ischemia to the sinus node, rejection, drug therapy, and increasing donor age. However, the timing and indication of permanent pacemaker insertion due to sinus node dysfunction following heart transplantation is contentious. Here, we report a case of a permanent pacemaker insertion for syncope due to sinus arrest after heart transplantation, even with a bicaval technique, which has been known to associate with few incidences of sinus node dysfunction