Korea University
  • Seoul, South Korea
Recent publications
Two-dimensional (2D) MXenes are promising as electrode materials for energy storage, owing to their high electronic conductivity and low diffusion barrier. Unfortunately, similar to most 2D materials, MXene nanosheets easily restack during the electrode preparation, which degrades the electrochemical performance of MXene-based materials. A novel synthetic strategy is proposed for converting MXene into restacking-inhibited three-dimensional (3D) balls coated with iron selenides and carbon. This strategy involves the preparation of Fe 2 O 3 @carbon/MXene microspheres via a facile ultrasonic spray pyrolysis and subsequent selenization process. Such 3D structuring effectively prevents interlayer restacking, increases the surface area, and accelerates ion transport, while maintaining the attractive properties of MXene. Furthermore, combining iron selenides and carbon with 3D MXene balls offers many more sites for ion storage and enhances the structural robustness of the composite balls. The resultant 3D structured microspheres exhibit a high reversible capacity of 410 mAh g ⁻¹ after 200 cycles at 0.1 A g ⁻¹ in potassium-ion batteries, corresponding to the capacity retention of 97% as calculated based on 100 cycles. Even at a high current density of 5.0 A g ⁻¹ , the composite exhibits a discharge capacity of 169 mAh g ⁻¹ .
Background A favorable neurological outcome is closely related to patient characteristics and total cardiopulmonary resuscitation (CPR) duration. The total CPR duration consists of pre-hospital and in-hospital durations. To date, consensus is lacking on the optimal total CPR duration. Therefore, this study aimed to determine the upper limit of total CPR duration, the optimal cut-off time at the pre-hospital level, and the time to switch from conventional CPR to alternative CPR such as extracorporeal CPR. Methods We conducted a retrospective observational study using prospective, multi-center registry of out-of-hospital cardiac arrest (OHCA) patients between October 2015 and June 2019. Emergency medical service–assessed adult patients (aged ≥ 18 years) with non-traumatic OHCA were included. The primary endpoint was a favorable neurological outcome at hospital discharge. Results Among 7914 patients with OHCA, 577 had favorable neurological outcomes. The optimal cut-off for pre-hospital CPR duration in patients with OHCA was 12 min regardless of the initial rhythm. The optimal cut-offs for total CPR duration that transitioned from conventional CPR to an alternative CPR method were 25 and 21 min in patients with initial shockable and non-shockable rhythms, respectively. In the two groups, the upper limits of total CPR duration for achieving a probability of favorable neurological outcomes < 1% were 55–62 and 24–34 min, respectively, while those for a cumulative proportion of favorable neurological outcome > 99% were 43–53 and 45–71 min, respectively. Conclusions Herein, we identified the optimal cut-off time for transitioning from pre-hospital to in-hospital settings and from conventional CPR to alternative resuscitation. Although there is an upper limit of CPR duration, favorable neurological outcomes can be expected according to each patient’s resuscitation-related factors, despite prolonged CPR duration.
Resistive strain sensors (RSS) with ultrasensitivity have attracted much attention as multifunctional sensors. However, since most ultrasensitive RSS are designed by cracked conductive metals, the sensing performance is severely degraded due to accumulated structural deformation with consecutive cycles. To overcome such limitation, newly designed structures have been suggested, but the development of mechanosensors exhibiting superior stability and ultrasensitivity still remains a challenge. Here, we demonstrate that vertical graphene (VG) RSS with high sensitivity (gauge factor greater than 5000), remarkable durability (>10,000 cycles), and extraordinary resilience can serve multifunctional applications. We find that well-defined cracks on tufted network structure result in highly reversible resistance variation, especially revivable status even after broken current path, confirmed by microscopic in situ monitoring. The VG integrated with a wireless sensing system exhibits excellent timbre recognition performance. Our findings provide inspirable insights for mechanosensing system, making VG a promising component for future practicable flexible sensor technologies.
Two-dimensional (2D) transition metal chalcogenides (TMC) and their heterostructures are appealing as building blocks in a wide range of electronic and optoelectronic devices, particularly futuristic memristive and synaptic devices for brain-inspired neuromorphic computing systems. The distinct properties such as high durability, electrical and optical tunability, clean surface, flexibility, and LEGO-staking capability enable simple fabrication with high integration density, energy-efficient operation, and high scalability. This review provides a thorough examination of high-performance memristors based on 2D TMCs for neuromorphic computing applications, including the promise of 2D TMC materials and heterostructures, as well as the state-of-the-art demonstration of memristive devices. The challenges and future prospects for the development of these emerging materials and devices are also discussed. The purpose of this review is to provide an outlook on the fabrication and characterization of neuromorphic memristors based on 2D TMCs.
A novel device structure for thermally activated delayed fluorescence (TADF) top emission organic light-emitting diodes (TEOLEDs) that improves the viewing angle characteristics and reduces the efficiency roll-off is presented. Furthermore, we describe the design and fabrication of a cavity-suppressing electrode (CSE), Ag (12 nm)/WO 3 (65 nm)/Ag (12 nm) that can be used as a transparent cathode. While the TADF-TEOLED fabricated using the CSE exhibits higher external quantum efficiency (EQE) and improved angular dependency than the device fabricated using the microcavity-based Ag electrode, it suffers from low color purity and severe efficiency roll-off. These drawbacks can be reduced by using an optimized multi-quantum well emissive layer (MQW EML). The CSE-based TADF-TEOLED with an MQW EML fabricated herein exhibits a high EQE (18.05%), high color purity (full width at half maximum ~ 59 nm), reduced efficiency roll-off (~ 46% at 1000 cd m ⁻² ), and low angular dependence. These improvements can be attributed to the synergistic effect of the CSE and MQW EML. An optimized transparent CSE improves charge injection and light outcoupling with low angular dependence, and the MQW EML effectively confines charges and excitons, thereby improving the color purity and EQE significantly. The proposed approach facilitates the optimization of multiple output characteristics of TEOLEDs for future display applications.
The multifunctional soft sensor developed here is capable of simultaneously sensing six stimuli, including pressure, bending strain, temperature, proximity, UV light, and humidity, with high accuracy and without interference among the respective built-in components. The sensor is fabricated via a facile, scalable, and cost-effective supersonic cold-spraying method using silver nanowires (AgNWs), carbon nanotubes (CNTs), zinc oxide (ZnO), and conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). A mask and laser cutter are used in conjunction with the supersonic cold-spraying method to produce miniaturized multifunctional sensors that can be readily installed on various substrates; for example, the production of gloves capable of multifunctional sensing. In particular, the proximity sensor of the multifunctional glove sensor can produce a three-dimensional (3D) image of a scanned object, showing high potential for use in military, medical, and industrial applications.
Collembola are soil-dwelling arthropods that play a key role in the soil ecosystem. Allonychiurus kimi (Lee) (Collembola: Onychiuridae) was isolated from the natural environment and has been maintained for 20 years under laboratory conditions. Though the morphological and physiological features of A. kimi are being widely used to evaluate the impact of pesticides and heavy metals on the soil ecosystem, variations observed in these features might be on account of its microbiota. However, the microbiota composition of the laboratory-maintained A. kimi is undetermined and how the community structure is changing in response to soil environments or interacting with the soil microbiota are still unknown. In this study, we determined the microbiota of laboratory-maintained A. kimi at both adult and juvenile stages and examined how the microbiota of A. kimi is affected by the microbial community in the soil environments. Chryseobacterium , Pandoraea, Sphingomonas, Escherichia–Shigella, and Acinetobacter were the core microbiota of A. kimi. Exposure of the laboratory-maintained A. kimi to different soil microbial communities drove dynamic shifts in the composition of A. kimi microbiota. Microbial association network analysis suggested that gut microbiota of lab-grown A. kimi was affected by exposing to soil microbial community. This study implies that shifts in the bacterial community of adult A. kimi can be utilized as an indicator to evaluate the soil ecosystem.
Prime editing can induce a desired base substitution, insertion, or deletion in a target gene using reverse transcriptase after nick formation by CRISPR nickase. In this study, we develop a technology that can be used to insert or replace external bases in the target DNA sequence by linking reverse transcriptase to the Francisella novicida Cas9, which is a CRISPR-Cas9 ortholog. Using FnCas9(H969A) nickase, the targeting limitation of existing Streptococcus pyogenes Cas9 nickase [SpCas9(H840A)]-based prime editing is dramatically extended, and accurate prime editing is induced specifically for the target genes in human cell lines.
Although the potential role of superior longitudinal fasciculus (SLF) in intellectual deficits and treatment response (TR) in patients with schizophrenia (SZ) has been previously described, little is known about the white-matter (WM) integrity of SLF subcomponents (SLF I, II, III, and arcuate fasciculus) and their particular relationships with the clinical presentations of the illness. This study examined the associations between fractional anisotropy (FA) of SLF subcomponents and intelligence level and 6-month treatment response (TR) of negative symptoms (NS) in patients with SZ. At baseline, 101 patients with SZ and 101 healthy controls (HCs) underwent structural magnetic resonance imaging. Voxel-wise group comparison analysis showed significant SLF FA reductions in patients with SZ compared with HCs. Voxel-wise correlation analyses revealed significant positive correlations of FAs of right SLF II with Korean–Wechsler Adult Intelligence Scale at baseline and the percentage reduction of negative syndrome subscale of the Positive and Negative Syndrome Scales at 6 months. These findings suggest that aberrance in WM microstructure in SLF II may be associated with intellectual deficits in patients with SZ and TR of NS, which may support the potential role of SLF II as a novel neuroimaging biomarker for clinical outcomes of the illness.
The quality factor (Q), describing the rate of energy loss from a resonator, is a defining performance metric for nanophotonic devices. Suppressing cavity radiative losses enables strong nonlinear optical responses or low-power operation to be achieved. Exploiting long-lived, spatially-confined bound states in the continuum (BICs) has emerged from the numerous approaches considered as a promising route to boost nanophotonic Q factors. Initial research explored the formation mechanisms of various types of BICs, drawing parallels to topological physics. With these fundamentals now established, we review the recent application of BICs in passive and active nanophotonic devices.
Background C–C motif chemokine receptor 2 (CCR2), the main receptor for monocyte chemoattractant protein-1 (MCP-1), is expressed on immune cells, including monocytes, macrophages, and activated T cells, and mediates cell migration toward MCP-1 in inflammation-related diseases. The CCR2 gene encodes two isoforms: CCR2A and CCR2B. The CCR2B open reading frame is localized in a single exon, similar to other chemokine receptors, and CCR2A and CCR2B feature different amino acid sequences in their C-terminal intracellular loops due to alternative splicing. Most biochemical studies on CCR2-related cellular responses in the immune system have focused on CCR2B, with few reports focused on CCR2A. Understanding the functional properties of CCR2A in cellular responses may elucidate the roles played by MCP-1 and CCR2 in pathophysiological responses. Results CCR2 gene expression analysis in several cell types revealed that most adherent cells only expressed CCR2A, whereas CCR2B expression was dominant in monocytic cells. The C-terminal Helix 8 region of CCR2A contains few basic amino acids, which may be unfavorable for cell surface localization, as confirmed with the HiBiT assay. CCR2B contains many C-terminal Ser/Thr residues, similar to other chemokine receptors, which may be phosphorylated by G protein–coupled receptor kinases (GRKs) to promote β-arrestin recruitment and subsequent endocytosis. By contrast, CCR2A contains few C-terminal Ser/Thr residues, which are unlikely to be phosphorylated by GRKs. CCR2A localized on the cell surface is resistant to internalization, despite the interaction between Gβ and GRKs induced by ligand binding with CCR2A. CCR2A induced cellular responses at a relatively higher degree than CCR2B, although both receptors mediated signaling events through Gαq and Gαi. HeLa cells lacking CCR2A showed slowed growth compared with parent cells, regardless of MCP-1 stimulation, and their chemotactic activity toward MCP-1, in addition to basal motility, was significantly impaired. Conclusion MCP-1 and CCR2 may play pivotal roles in cancer progression by recruiting macrophages into cancer tissue. This study demonstrates that CCR2A but not CCR2B is expressed in solid cancer–derived cells. CCR2A is resistant to internalization by β-arrestin due to a distinct C-terminal region from CCR2B, which enhances MCP-1-stimulated responses, indicating that CCR2A may play essential roles in solid cancer progression.
Isoacteoside is a caffeoyl phenylethanoide glycoside found in various plant parts, such as the flower of Magnolia denudata . In particular, magnolia has been studied for its anti-obesity, anticancer, and anti-inflammatory effects. However, isoacteoside has not been extensively studied, except for its anti-inflammatory effects. In this study, the anti-obesity effects of isoacteoside were investigated in 3T3-L1 mouse pre-adipocytes. Isoacteoside treatment did not induce cytotoxicity in 3T3-L1 cells up to a concentration of 1000 μM. The anti-obesity effects on 3T3-L1 cells were confirmed using oil red O staining. In addition, the expression of obesity-related proteins and genes, such as peroxisome proliferator-activated acceptor gamma ( PPARγ ), CCAAT/enhancer-binding protein alpha ( C/EBPα ), and perilipin ( PLIN1 ), was determined by western blotting and qRT-PCR assays to confirm the anti-obesity effects of isoacteoside. The results of this study suggest that isoacteoside, a natural substance isolated from plant extracts, is not highly toxic to normal cells, such as pre-adipocytes, and displays anti-obesity effects in vitro.
The habenula (Hb) is an epithalamic structure that links multiple forebrain areas with the mid/hindbrain monoaminergic systems. As an anti-reward center, it has been implicated in the etiology of various neuropsychiatric disorders, particularly those associated with dysregulated reward circuitry. In this regard, Hb has been proposed as a therapeutic target for treatment-resistant depression associated with a higher risk of suicide. Therefore, we aimed to gain insight into the molecular signatures of the Hb in association with suicide in individuals with major depression. Postmortem gene expression analysis identified 251 differentially expressed genes (DEGs) in the Hb tissue of suicides in comparison with Hb tissues from neurotypical individuals. Subsequent bioinformatic analyses using single-cell transcriptome data from the mouse Hb showed that the levels of a subset of endothelial cell-enriched genes encoding cell–cell junctional complex and plasma membrane-associated proteins, as well as the levels of their putative upstream transcriptional regulators, were significantly affected in suicides. Although our findings are based on a limited number of samples, the present study suggests a potential association of endothelial dysfunction in the Hb with depression and suicidal behavior.
The automatic generation control (AGC) system is a crucial control system based on information and communication technology in interconnected power systems. However, the dependence on cyber systems has increased the risk of false data injection attacks (FDIAs) against AGC systems. Furthermore, as the penetration level of wind power increases, an AGC dynamic framework incorporating wind stochastic modeling should be developed, and the impact of FDIAs on AGC considering wind power penetrations should also be evaluated. This paper proposes an evaluation method of the impact of FDIAs on AGC considering wind power penetrations. First, a linearized analysis framework is developed, in which the network model is considered due to its geographical smoothing effects. Then, stochastic differential equations (SDEs) are employed to model wind power and load temporal uncertain behaviors, and the overall system dynamics under different FDIA types are also proposed. Finally, the proposed methodology is illustrated via a 4-area practical AGC system. The simulation results show the effects of different types of attacks on the AGC system considering wind power penetrations and demonstrate that the existing evaluation frameworks may overestimate FDIA effects and wind power fluctuation and corresponding system inertia reduction may help the attacker to cause system instability.
A graph is intrinsically knotted if every embedding contains a nontrivially knotted cycle. It is known that intrinsically knotted graphs have at least 21 edges and that there are exactly 14 intrinsically knotted graphs with 21 edges, in which the Heawood graph is the only bipartite graph. The authors showed that there are exactly two graphs with at most 22 edges that are minor minimal bipartite intrinsically knotted: the Heawood graph and Cousin 110 of the E9+e family. In this paper we show that there are exactly six bipartite intrinsically knotted graphs with 23 edges so that every vertex has degree 3 or more. Four among them contain the Heawood graph and the other two contain Cousin 110 of the E9+e family. Consequently, there is no minor minimal intrinsically knotted graph with 23 edges that is bipartite.
A spatial susceptible–infected–susceptible epidemic model with a free boundary, where infected individuals disperse non-uniformly, is investigated in this study. Spatial heterogeneity and movement of individuals are essential factors that affect pandemics and the eradication of infectious diseases. Our goal is to investigate the effect of a dispersal strategy for infected individuals, known as risk-induced dispersal (RID), which represents the motility of infected individuals induced by risk depending on whether they are in a high- or a low-risk region. We first construct the basic reproduction number and then understand the manner in which a nonuniform movement of infected individuals affects the spreading–vanishing dichotomy of a disease in a one-dimensional domain. We conclude that even though the infected individuals reside in a high-risk initial domain, the disease can be eradicated from the region if the infected individuals move with a high sensitivity of RID as they disperse. Finally, we demonstrate our results via simulations for a one-dimensional case.
Aqueous zinc-ion batteries (ZIBs) are receiving considerable research highlights owing to their high safety and environment-friendliness. To implement this promising technology for grid-scale energy storage, effective cathode materials with high capacity, cycle stability, and electrochemical kinetics should be developed. Herein, the synthesis of uniquely structured porous VN-reduced graphene oxide composite (VN-rGO) microspheres through a facile spray pyrolysis process and their application as cathodes for ZIBs are introduced. The electrochemical reaction mechanism of VN-rGO microspheres with zinc ions is investigated through various in situ and ex situ analyses. During the initial charge process, VN phase transforms into the Zn3(OH)2V2O7·2H2O (ZVOH) phase. From the second cycle and on, the ZVOH phase undergoes zinc-ion ingress and egress processes. VN-rGO microspheres exhibit an unprecedented high capacity (809 mA h g⁻¹ at 0.1 A g⁻¹), high energy density (613 W h kg⁻¹), and good rate capability (467 mA h g⁻¹ at 2.0 A g⁻¹). The cathode delivers a reversible capacity of 445 mA h g⁻¹ after 400 cycles at 1.0 A g⁻¹, which ascertains the robustness of the structure. The 3D porous rGO matrix to which VN nanocrystals are homogenously anchored accelerates the zinc-ion storage kinetics and endows the cathode with structural robustness.
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9,941 members
Tai Hyun Yoon
  • Department of Physics
Inamul Hasan Madar
  • Center for Cancer ProteoGenome Research (CPGR), College of Science
Seong Hwan Park
  • College of Medicine
June Kang
  • Department of Brain and Cognitive Engineering
Moon Ho Park
  • Department of Neurology
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http://www.korea.ac.kr