56016 research outputs found
Sort by
?????? ????????? ?????? ??????????????? ????????? MXene ????????? ?????? ?????? ??????
Get PDFDepartment of Materials Science and EngineeringTwo-dimensional (2D) materials, including graphene, transition metal dichalcogenides (TMDs), and transition metal carbides, nitrides, and carbonitrides (MXenes), have drawn a lot of attention due to the combination of thinness with several extraordinary properties including high mechanical strength, optical transparency, electrical and thermal conductivity, leading to the numerous potential applications. However, the synthesis of 2D materials that combine the solution processability with excellent mechanical, optical, electrical, and thermal properties remains challenging. Therefore, many attempts have been made to achieve the synthesis and design of MXenes, especially transition metal carbides (Ti3C2Tx), owing to the easy solution processability, hydrophilicity, high mechanical strength, oxidation stability, metallic conductivity, excellent printing processability, and tunable properties, originating from the various surface terminations, such as -F, -O, -OH. This study presents the solution-processable production of site-selectively coated Ti3C2Tx MXene films via blade coating and substrate engineering for transparent electronic devices. Unlike other methods, such as patterning and etching, spraying, 3D printing, imprinting, laser engraving, we fabricated Ti3C2Tx MXene mesh by depositing Al2O3 on SiO2 or glass substrates via atomic layer deposition (ALD), followed by photolithography, blade coating, and sonication as the fabrication of Ti3C2Tx MXene mesh is affected by four key factors: i) Al2O3 thickness, ii) synthesis process and condition of Ti3C2Tx MXene, iii) pattern size, iv) Ti3C2Tx MXene concentration, where Al2O3, most importantly, must be used for the fabrication of Ti3C2Tx MXene mesh, leading to the strong adhesion between Al2O3 and Ti3C2Tx MXene mesh. The fabricated Ti3C2Tx MXene mesh was transferred onto pressure sensitive adhesive film (PSAF). However, several cracks were generated owing to the unrelease of stress caused by the strong interaction between Al2O3 and Ti3C2Tx MXene mesh. Thus, Ti3C2Tx MXene mesh was directly fabricated on ALD-deposited Al2O3 / glass substrates, exhibiting high performances: high transmittance (77.70 - 86.23 %), low sheet resistance (111.34 ?? 5.26 ??/sq), and high HER performance with low overpotential (0.56 V), outperforming the reported Ti3C2Tx MXene mesh. Furthermore, drying decreased the sheet resistance of as-fabricated Ti3C2Tx MXene mesh to 66.83 ?? 0.05 ??/sq, which is 1.67 times lower than that of pristine Ti3C2Tx MXene mesh. Consequently, our Ti3C2Tx MXene mesh in this study has great potentials for various applications.ope
??????????????? ????????? ??? ????????? ??????????????????????????? ???????????? ????????? ????????? ??? 2??? ?????? ??????
Get PDFDepartment of Urban and Environmental Engineering (Environmental Science and Engineering)Total of 24 atmospheric volatile organic compounds (VOCs) including both anthropogenic VOCs (AVOCs) and biogenic VOCs (BVOCs) were investigated in highly industrialized city Ulsan by active (AAS) and passive air sampling (PAS) to confirm the effect of anthropogenic and biogenic sources for secondary formation. Samples were automatically sampled using a sequential tube sampler every 3 hours for a week in urban site and passively sampled at 6 industrial, 10 urban, and 5 rural sites in Ulsan from the summer of 2021 to the winter of 2022. From AAS and PAS, AVOCs concentration was dominant in all seasons, and concentrations of BVOCs were high in summer. For diurnal variation, AVOCs were high in the daytime (05:00-17:00) than nighttime (17:00-05:00) with sea-breeze through the industrial facilities. Regarding BVOCs, the concentration of isoprene was high in the daytime with easterly wind and emission characteristics, and that of monoterpenes was high in the nighttime. With the diagnostic ratios and principal component (PCA) analysis, industrial sites and urban sites were affected by local emission of AVOCs. However, rural sites and urban sites near forests were affected by BVOCs. From the CBPF analysis, urban was dominantly affected by industrial facilities and broad-leaves forests with southeasterly wind and sea-breeze in summer and daytime. On the other hand, the effect of vehicle exhaust gas in the downtown and highway was more dominant with the northwesterly seasonal wind in autumn and winter. By applying the Propylene-Equivalent method, there was high ozone formation potential (OFP) in summer daytime (08:00~17:00) for both AVOCs and BVOCs. OFPs of AVOCs and BVOCs were high in most sampling sites in summer with the influence of seasonal wind and sea-land breeze with high reactivity of BVOCs. On the other hand, regarding secondary organic aerosol formation potential (SOAFP), there was a dominant contribution of AVOCs in all seasons. Also, the SOAFP contribution of BVOCs by season was relatively low compared to the OFP contribution, and the contribution of SOAFP was more influenced by AVOCs than that of OFP. There was dominant AVOCs pollution in Ulsan during all seasons with the strong effect of secondary formation potential from BVOCs in summer. With the BVOCs emitted from trees and AVOCs transported from industrial facilities, secondary formation in Ulsan needs to be controlled with the monitoring of high reactive AVOCs and BVOCs concentration and pollution characteristics.ope
?????? ????????? ????????? ????????? ????????? DNA ?????? ?????? ?????? ??????
Get PDFDepartment of Biological SciencesDNA molecules are damaged by malfunctioning metabolism and bulky adducts, inducing genetic instability and passing it on to the next generation. DNA damage repair processes should be conducted properly. Thus, understanding the detail molecular mechanism of DNA damage repair process is important. My research focuses on DNA damage repair at the single molecular level, especially the dynamics of DNA damage recognition proteins on DNA.
Chapter 1
Global genome nucleotide excision repair (GG-NER) eliminates chemical bulky adducts and UV-induced thymine dimers. This process is initiated by Xeroderma pigmentosum complementation group C protein (XPC), which detects DNA lesions by recognizing structural distortions. However, the exact mechanism for this detection and the factors affecting it are unclear.
The detailed mechanism of XPC-RAD23B was revealed by DNA curtain assay, a single-molecule imaging technique that unidirectionally aligns DNA strands. The assay uses the fluidity of the lipid bilayer to track the movement of a single protein molecule on DNA in real time. I observed XPC-RAD23B (Red) jump over the protein obstacles (EcoRI^E111Q, Green) at specific sites while diffusing. Its diffusion coefficient increases in direct proportion to the ionic strength of the environment.
These results indicate that human XPC-RAD23B uses diffusion along the DNA, especially via hopping, as a proxy for DNA lesions. This process allows it to bypass protein obstacles. Moreover, XPC-RAD23B moves along DNA strands in a heterogeneous fashion ??? at times immobile, diffusive, or constrained state, depending on the stability of DNA duplexes.
Taken together, these results provide insight into how hXPC-Rad23B can rapidly find DNA defects, preventing mutations and ultimately cancer in human cells.
Chapter 2
R-loops ??? three-stranded nucleotide structures consisting of an RNA-DNA hybrid and a displaced ssDNA structure ??? serve as signaling molecules in various cellular processes, but they also act as DNA lesions when improperly regulated. These molecules can be recognized and eliminated by Tonicity enhancer-binding protein (TonEBP), a transcription factor for immune response and tonicity regulation. Using a DNA curtain with purified TonEBP and R-loop-containing lambda DNA, I demonstrated that TonEBP identifies R-loops via both 1D diffusion and 3D collision. In addition, TonEBP preferentially binds the displaced ssDNA in the R-loop structure, as I confirmed using electrophoretic mobility shift assay with diverse types of DNA constructs.
This study reveals that TonEBP recognizes R-loops on DNA and recruits R-loop elimination proteins such as METTL3-METTL14 to resolve the R-loops by RNase H1.
Chapter 3
Although DNA curtain is a well-established single-molecule imaging technique, it???s imaging quality and experimental efficiency is compromised by two factors. First, on the chromium nano-barrier slide, the remaining materials for the DNA curtain assembly on the surface can induce protein aggregation, degrading the barriers in the harsh chemical and physical cleaning method. Second, in the DNA curtain, the aligned DNA molecules are visualized using YOYO-1, which causes rapid photocleavage of DNA under continuous laser illumination.
We developed nano-trench, a novel type of DNA curtain barrier featuring an engraved zigzag pattern on the fused silica surface. Nano-trench is more durable and then conventional imaging techniques under harsh chemical treatment and causes less laser scattering. These features increase the quality of DNA curtain imaging.
We also developed the FP-DBP, a chimeric construct of fluorescent protein (FP) and DNA binding peptide (DBP) that is less phototoxic than YOYO-1.ope
Real-Time External Compensation System With Error Correction Algorithm for High-Resolution Mobile Displays
No full textpaper presents an external compensation system for QHD+ (3040 x 1224) mobile active-matrix organic light emitting diode (AMOLED) displays at a frame rate of 60 Hz. During vertical blank periods, current sensing AFE (CS-AFE) measures OLED currents to calculate threshold voltage (VT H) of driving thin-film transistors (TFTs). For precise VT H calculation against panel ground noise, a differential sensing scheme with 5-bit programmable capacitor array (PCA) is employed. In addition, digital correlated double sampling (CDS) removes an offset of the CS-AFE. However, recent advances in high efficiency OLED technology have led to increase in pixel density as well as the driving TFTs to operate close to subthreshold region. Therefore, the V-TH calculation based on the quadratic model yields inaccurate results. To compensate for the modeling error, we propose an error correction algorithm, which establishes an error function using a relationship between the modeling error and calculated threshold voltage during the manufacturing process. The proposed external compensation system was verified using CMOS-modeled three transistors and one capacitor (3T1C) pixel circuit. The test chip, fabricated in a 0.18 mu m BCD process, comprises 26 channels. Each channel consumes 78 mu W and occupies 1350 x 50 mu m(2). Measurement results show that current error at 64th gray level is reduced from 35.56 LSB to 6.03 LSB after error correction and four frames average
Predictors of Upcycling in the Highly Industrialised West: A Survey across Three Continents of Australia, Europe, and North America
No full textUpcycling, as a way to reutilise resources, offers a promising alternative to production and consumption based on virgin materials. Despite the growing academic and industrial interest in recent years, there is a lack of large-scale cross-country or cross-regional studies that systematically investigate influencing factors for consumer upcycling behaviour. By drawing on social psychological theories of interpersonal behaviour and planned behaviour, this study investigated predictors of upcycling behaviour in five highly industrialised countries of three continents: Australia, Canada, Germany, UK, and USA. Results showed that intention and perceived behavioural control (confidence in abilities) were the most important factors for upcycling. Theoretical and practical implications from this study are discussed in the context of efforts to scale up global upcycling
Momentum and reversal: information from prior returns
No full textThis paper studies the joint dynamics of momentum and reversal strategies. Momentum investors face uncertainty about whether past patterns of price movements will continue (momentum) or turn over (reversal), thereby increasing volatility of momentum returns and occasionally leading to momentum crashes. We argue that the forces driving reversal over momentum tend to be strong if losers??? past returns are extremely low (in the time-series) or if losers are small and illiquid (in the cross-section). We subsequently propose new risk-managed momentum strategies by taking into account behavioural divergence between momentum and reversal in an effort to boost momentum profits and reduce volatility. Empirical tests for the U.S. stock market in the sample period of 1947 to 2015 document that momentum strategies in which investors implement stop-trading rules if losers??? past returns are extremely low as well as buy-small-loser rules substantially outperform traditional momentum strategies. International stock markets and robustness checks confirm our U.S. tests. Importantly, we find that outperformance is mainly attributable to the increase in abnormal returns (i.e. alpha) from various factor models
Conjugated Polymer Nanoparticles: Photothermal and Photodynamic Capabilities According to Molecular Ordering in Their Assembly Structures
No full textWe report that conjugated polymer nanoparticles (CPNs) coated with polyethylene glycols (PEGs) exhibit photothermal and photodynamic capabilities according to molecular ordering in their assembly structures. CPN-PEGs were made using three different methods: a dispersion process of phase-separated film assemblies of a conjugated polymer and a phospholipid-conjugated PEG (CPN-I), a dispersion process of a conjugated polymer and a phospholipid followed by surface conjugation with PEGs (CPN-II), and a miniemulsification of the conjugated polymer and the phospholipid-conjugated PEG. Our findings revealed that the ordered molecular assembly structures in CPN-I and CPN-II increased intermolecular interactions and decreased the optical band gap, promoting nonradiative exciton relaxation via the energy-gap law's internal conversion mechanism and rationalizing CPN-I's shorter singlet exciton lifetime (13 ps). Meanwhile, CPN-III with a disordered structure generated more singlet oxygen than CPN-I and CPN-II, indicating increased triplet exciton generation upon the polaron recombination. Our findings present that the photothermal and photodynamic properties of CPNs are obviously dependent on the assembly structure order and that CPNs with an ordered assembly of conjugated backbones have a stronger photothermal effect, whereas those with a disordered structure have a better photodynamic effect
Multiferroicity of 2H-BaMnO3 Single Crystal
No full textGeometric ferroelectrics are called as improper ferroelectrics where geometric structural constraints, rather than typical cation-anion pairing, induce proper ferroelectric polarization. Trimerization of MnO5 bipyramids, a kind of geometric structural distortions, is observed in RMnO3 (R = Ho, Er, Yb, Lu, Y), which share same symmetric group with 2H-BaMnO3. And the distortion induces intriguing multiferroicity such as topological vortex-antivortex, angle dependent conducting domain walls, enhanced magnetoelectric coupling at domain walls, etc. In hexagonal RMnO3, it has been unavailable to study thermodynamic behavior of trimerization and polarization because of high ferroelectric transition temperature (1120-1435??C). But it was reported that polycrystalline 2H-BaMnO3 exhibits antiferromagnetic order at 59 K [1], and ferroelectric transition at 130 K [2]. Here, we present ferroelectric and magnetic properties of single crystalline 2H-BaMnO3.
[1] E. J. Cussen and P. D. Battle, Chem. Mater. 12, 831-838 (2000)
[2] Stanislav Kamba et al, Physical Review B 95, 174103 (2017
Accelerated Design of High-Efficiency Lead-Free Tin Perovskite Solar Cells via Machine Learning
No full textTin (Sn) perovskite solar cells (PSCs) are the most promising alternatives to lead (Pb) PSCs, which pose a theoretical limitation on efficiency and an environmental threat. However, Sn PSCs are still in the early stage of development in comparison with the conventional Pb PSCs, and still require a considerable amount of time and effort to obtain an optimum structure via manual trial-and-error methods. Herein, we propose a machine learning (ML) approach to accelerate the design of the optimized structure of Sn PSCs with high efficiency. The proposed method uses K-fold cross-validation-based deep neural networks, thus maximizing the prediction and recommendation accuracy with a limited amount of experimental data recorded for the Sn PSCs. Our approach establishes a new appropriate Sn-PSC design based on an ML recommendation algorithm. The validation experiment reveals a three times higher efficiency of the ML-designed Sn PSCs (5.57%) than that of those designed through unguided fabrication trials (avg. 1.72%)
