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356 result(s) for "Jun-Hyuk, Kim"
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The efficacy of CRISPR-mediated cytosine base editing with the RPS5a promoter in Arabidopsis thaliana
CRISPR/Cas9-mediated genome editing is an important and versatile technology in modern biological research. Recent advancements include base-editing CRISPR tools that enable targeted nucleotide substitutions using a fusion protein comprising a nickase variant of Cas9 and a base deaminase. Improvements in base editing efficiencies and inheritable of edited loci need to be made to make CRISPR a viable system in plants. Here, we report efficiency of cytosine base editors (CBEs) in Arabidopsis thaliana by applying the strong endogenous RPS5a promoter to drive the expression of nickase Cas9 and either rAPOBEC1 from rat (BE3) or the PmCDA1 activation-induced cytidine deaminase from sea lamprey (AIDv2). Compared with the strong heterologous CaMV35S promoter of viral origin, the RPS5a promoter improved CBE efficiency by 32% points with the number of T 1 plants showing over 50% conversion ratio when the LFY gene was targeted. CBE induced nonsense mutations in LFY via C-to-T conversion, which resulted in loss-of-function lfy phenotypes; defects in LFY function were associated with the targeted base substitutions. Our data suggest that optimal promoter choice for CBE expression may affect base-editing efficiencies in plants. The results provide a strategy to optimize low-efficiency base editors and demonstrate their applicability for functional assays and trait development in crop research.
Selective electrocatalysis imparted by metal–insulator transition for durability enhancement of automotive fuel cells
Repetitive start-up and shut-down events in polymer electrolyte membrane fuel cells for automotive applications lead to serious corrosion of the cathode due to an instantaneous potential jump that results from unintended air leakage into the anodic flow field followed by a parasitic oxygen reduction reaction (ORR) on the anode. Here we report a solution to the cathode corrosion issue during the start-up/shut-down events whereby intelligent catalyst design is used to selectively promote the hydrogen oxidation reaction (HOR) while concomitantly suppressing the ORR on the anode. Platinum thin layers supported on hydrogen tungsten bronze (Pt/H x WO 3 ) suppressed the ORR by converting themselves into an insulator following exposure to oxygen, while selectively promoting the HOR by regaining metallic conductivity following subsequent exposure to hydrogen. The HOR-selective electrocatalysis imparted by a metal–insulator transition in Pt/H x WO 3 demonstrated a remarkably enhanced durability of membrane electrode assemblies compared to those with commercial Pt/C catalysts. The stability of polymer electrolyte membrane fuel cells is limited by the degradation of the cathode catalyst during repetitive start-up/shut-down events — a parasitic oxygen reduction reaction on the anode causes an instantaneous potential jump at the cathode. The issue is now addressed by selectively suppressing the oxygen reduction reaction on the anode by exploiting the metal–insulator transition behaviour of Pt/H x WO 3 catalysts.
Shape and Composition Control of Monodisperse Hybrid Pt-CoO Nanocrystals by Controlling the Reaction Kinetics with Additives
Here, we report the effect of Fe(CO) 5 additives in the synthesis of branched Pt-CoO nanowires (NWs) and core@shell concave nanocubes (NCs), in a one-pot system. Key to the success of this synthesis is control over the shape of the Pt seeds by controlling the quantity of Fe(CO) 5 additive. In the absence of Fe(CO) 5 , branched Pt-CoO NWs were synthesized through the attachment of small Pt seed particles, followed by the growth of CoO by deposition. On the other hand, Pt@CoO concave NCs were obtained in the presence of Fe(CO) 5 because of the stronger adsorption of Co on the Pt (100) surfaces than on the closely packed (111) surfaces. Also, various other conditions including the control of reducing agents, precursor concentrations, and stabilizing agents, were used to verify the effects of reaction kinetics on the synthesis of Pt-CoO nanoparticles. Compared to Pt/graphene oxide (GO) catalyst, branched Pt-CoO NWs supported on GO showed enhanced specific activity toward the oxygen reduction reaction (ORR).
Facile CuFeO2 microcrystal synthesis for lithium ion battery anodes via microwave heating
This paper reports a facile synthetic method to synthesize delafossite CuFeO 2 for the use of lithium ion battery (LIB) anodes. We obtained 0.7–2.5 μm CuFeO 2 microcrystals with rhombohedral morphology by microwave heating, with a significantly reduced heating time compared to creating the crystals using solid-state reaction or hydrothermal methods. The resultant CuFeO 2 electrode exhibits enhanced battery performance with high reversible capacity of 555 mAhg −1 at 0.2 C after 200 cycles than the performances of the previous CuFeO 2- based electrodes. Thus, CuFeO 2 microcrystals prepared via the proposed method offer a practical alternative for lithium ion battery anodes.
Tongue-in-Groove: A Novel Implant Design for a Blow-Out Fracture
Background: During blow-out fracture surgery, restoration of the orbital volume and rigid implant fixation are essential. The migration of an implant is a concern of most surgeons. The purpose of this study was to introduce a simple idea of molding and fixing an orbital implant. Methods: In the tongue-in-groove method, an incision of about 2 mm was made on the edge of the implant and it was bent to form a slot. A hole was made in the center of the implant for fitting a bone hook, and the implant was firmly fit into the remaining intact bone. Before and after surgery, computed tomography (CT) was used to evaluate changes in the orbital volume and the location of the implant. Statistically significant restoration of the orbital volume was confirmed on postoperative CT. Results: Compared with the unaffected orbital volume, the affected orbital volume was increased from 87.06 ± 7.92% before surgery to 96.14 ± 6.11% after surgery (p < 0.001). There was one case of implant migration during follow-up. However, the degree of movement was not severe, and there were no events during the follow-up period. Conclusions: The tongue-in-groove technique offers advantages, such as easy fixation of the implant, with minimal trauma to the surrounding tissues. In addition, the method offers advantages, such as being easy to learn, requiring little time for trimming the implant, and being relatively low cost. Therefore, it can be one of the options for implant fixation.
A robust fuel cell operated on nearly dry methane at 500 °C enabled by synergistic thermal catalysis and electrocatalysis
Solid oxide fuel cells (SOFCs) are potentially the most efficient technology for direct conversion of hydrocarbons to electricity. While their commercial viability is greatest at operating temperatures of 300–500 °C, it is extremely difficult to run SOFCs on methane at these temperatures, where oxygen reduction and C–H activation are notoriously sluggish. Here we report a robust SOFC that enabled direct utilization of nearly dry methane (with ~3.5% H 2 O) at 500 °C (achieving a peak power density of 0.37 W cm −2 ) with no evidence of coking after ~550 h operation. The cell consists of a PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ nanofibre-based cathode and a BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3–δ -based multifunctional anode coated with Ce 0.90 Ni 0.05 Ru 0.05 O 2 (CNR) catalyst for reforming of CH 4 to H 2 and CO. The high activity and coking resistance of the CNR is attributed to a synergistic effect of cationic Ni and Ru sites anchored on the CNR surface, as confirmed by in situ/operando experiments and computations. Solid oxide fuel cells are most commercially viable when run at low temperatures, but this makes it challenging to achieve high performance with hydrocarbon fuels. Here the authors report a fuel cell running at 500 °C on nearly dry methane that incorporates a Ni–Ru–CeO 2 -based reforming catalyst, achieving high power densities and coking resistance.
An Experimental and Clinical Study of Flap Monitoring with an Analysis of the Clinical Course of the Flap Using an Infrared Thermal Camera
Flap surgery is a common method used to cover defects following tumor ablation, trauma, or infection. However, insufficient vascularity in the transferred flap can lead to flap necrosis and failure. Proper postoperative monitoring is essential to prevent these complications. Recently, research has explored the use of infrared thermal imaging in plastic surgery, leading to its clinical application. This study comprises two separate parts: an in vivo experimental study and a clinical study. In this study, 28 rats underwent reverse McFarlane flap surgery, and their flaps were analyzed using a FLIR thermal imaging camera seven days post-surgery. Additionally, thermal images of flaps were taken on postoperative days 0, 1, 2, 3, and 7 in 22 patients. This study focused on temperature differences between normal skin and the perforator compared to the average flap temperature. Results showed that the temperature difference was higher in the necrosis group and increased over time in cases of total necrosis. A lower perforator temperature compared to the flap’s average indicated vascular compromise, potentially leading to flap failure. The FLIR camera, being contact-free and convenient, shows promise for understanding and inferring the clinical progression of flaps in postoperative monitoring.
Advanced Secondary Intention Healing for Complex Soft-Tissue Defects Using Reprocessed Micronized Acellular Dermal Matrix
Secondary intention healing offers an alternative when surgical options are infeasible. This study analyzed the effect of micronized acellular dermal matrices (mADMs; CGderm Matrix®, CG Bio, Seoul, Republic of Korea) on secondary intention healing in patients with complex soft-tissue defects and assessed mADMs’ efficacy in promoting secondary healing and improving clinical outcomes in these challenging cases. This retrospective study included 26 patients treated with sheet-type reprocessed mADMs between August 2022 and December 2022 at Soonchunhyang University Cheonan Hospital. Patients with full-thickness skin defects classified as complex wounds were included. Data on demographics, wound characteristics, and treatment outcomes were collected and analyzed. Wound area was measured using ImageJ software, and statistical analyses were conducted using SPSS. The application of mADMs resulted in a median wound area reduction of 81.35%, demonstrating its significant efficacy in wound healing. Most patients presented with compromised vascular supply, significant tissue loss, or infections that precluded conventional surgical interventions. No significant correlations were observed between patient variables and wound-healing outcomes, indicating the complex nature of wound healing. mADMs effectively promote secondary intention healing by providing a supportive extracellular matrix scaffold that enhances epithelialization and angiogenesis. Their rapid absorption, ease of handling, and ability to improve wound tensile strength make them particularly suitable for complex wounds.
Recent breakthroughs in cathode of protonic ceramic fuel cells: Materials, functionalization, and future perspectives
Hydrogen stands as a promising energy carrier that plays a pivotal role in addressing global sustainability and achieving carbon neutrality. The conversion of hydrogen energy through fuel cells has emerged as a central technology in this pursuit. Notably, protonic ceramic fuel cells (PCFCs) hold potential for the future hydrogen energy ecosystem, owing to their impressive energy conversion efficiencies at low‐to‐intermediate temperatures (300–750°C). It is becoming increasingly evident that the development of PCFC technology relies on advancements in the cathode, as oxygen‐involved reactions often exhibit sluggish kinetics. In this comprehensive review, we aim to provide an overview of the current state of knowledge concerning the design of advanced cathodes for PCFCs. This includes discussing key descriptors for cathodes, methods for characterizing material properties, and functionalization techniques to enhance electrode performance. Finally, we present insights into future research directions. Hydrogen is a promising energy source, and protonic ceramic fuel cells (PCFCs) offer high efficiency at moderate temperatures. However, improving the cathode is essential due to slow oxygen reaction kinetics. This review discusses advanced cathode designs, characterization methods, and future research directions.
PLLA Composites Combined with Delivery System of Bioactive Agents for Anti-Inflammation and Re-Endothelialization
The development of a biodegradable vascular scaffold (BVS) for the treatment of cardiovascular diseases (CVDs) still requires some improvement. Among them, re-endothelialization and anti-inflammation are clinically important to restore vascular function. In this study, we proposed a coating system to deliver hydrophilic bioactive agents to BVS using nanoemulsion and drop-casting methods. The poly(L-lactide) (PLLA) scaffold containing magnesium hydroxide (MH) was coated on the surface with bioactive molecules such as polydeoxyribonucleotide (PDRN), L-arginine (Arg, R), and mesenchymal stem cell-derived extracellular vesicles (EVs). PDRN upregulates the expression of VEGF as one of the A2A receptor agonists; and Arg, synthesized into nitric oxide by intracellular eNOS, induces endothelialization. In particular, EVs, which are composed of a lipid bilayer and transfer bioactive materials such as protein and nucleic acid, regulate homeostasis in blood vessels. Such a bioactive agent coating system and its PLLA composite suggest a new platform for the treatment of cardiovascular dysfunction.