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result(s) for
"Kim, Hyewon"
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High-speed, cortex-wide volumetric recording of neuroactivity at cellular resolution using light beads microscopy
2021
Two-photon microscopy has enabled high-resolution imaging of neuroactivity at depth within scattering brain tissue. However, its various realizations have not overcome the tradeoffs between speed and spatiotemporal sampling that would be necessary to enable mesoscale volumetric recording of neuroactivity at cellular resolution and speed compatible with resolving calcium transients. Here, we introduce light beads microscopy (LBM), a scalable and spatiotemporally optimal acquisition approach limited only by fluorescence lifetime, where a set of axially separated and temporally distinct foci record the entire axial imaging range near-simultaneously, enabling volumetric recording at 1.41 × 108 voxels per second. Using LBM, we demonstrate mesoscopic and volumetric imaging at multiple scales in the mouse cortex, including cellular-resolution recordings within ~3 × 5 × 0.5 mm volumes containing >200,000 neurons at ~5 Hz and recordings of populations of ~1 million neurons within ~5.4 × 6 × 0.5 mm volumes at ~2 Hz, as well as higher speed (9.6 Hz) subcellular-resolution volumetric recordings. LBM provides an opportunity for discovering the neurocomputations underlying cortex-wide encoding and processing of information in the mammalian brain.Light beads microscopy is a two-photon microscopy approach that allows high-speed volumetric imaging of neuronal activity at the mesoscale.
Journal Article
Determination of monolayer-protected gold nanoparticle ligand–shell morphology using NMR
by
Stellacci, Francesco
,
Liu, Xiang
,
Mameli, Marta
in
639/638/440/527/878
,
639/925/357/354
,
Humanities and Social Sciences
2012
It is accepted that the ligand shell morphology of nanoparticles coated with a monolayer of molecules can be partly responsible for important properties such as cell membrane penetration and wetting. When binary mixtures of molecules coat a nanoparticle, they can arrange randomly or separate into domains, for example, forming Janus, patchy or striped particles. To date, there is no straightforward method for the determination of such structures. Here we show that a combination of one-dimensional and two-dimensional NMR can be used to determine the ligand shell structure of a series of particles covered with aliphatic and aromatic ligands of varying composition. This approach is a powerful way to determine the ligand shell structure of patchy particles; it has the limitation of needing a whole series of compositions and ligands' combinations with NMR peaks well separated and whose shifts due to the surrounding environment can be large enough.
Binary mixtures of molecules on the surface of nanoparticles can arrange randomly or into different domains to form Janus, patchy or striped particles. Liu
et al.
show that NMR can be used to determine the ligand-shell morphology of particles coated with aliphatic and aromatic ligands.
Journal Article
Clinical predictors of cybersickness in virtual reality (VR) among highly stressed people
2021
The use of virtual reality (VR) in the treatment of psychiatric disorders is increasing, and cybersickness has emerged as an important obstacle to overcome. However, the clinical factors affecting cybersickness are still not well understood. In this study, we investigated clinical predictors and adaptation effect of cybersickness during VR application in highly stressed people. Eighty-three healthy adult participants with high stress level were recruited. At baseline, we conducted psychiatric, ophthalmologic, and otologic evaluations and extracted physiological parameters. We divided the participants into two groups according to the order of exposure to VR videos with different degrees of shaking and repetitively administered the Simulator Sickness Questionnaire (SSQ) and the Fast Motion sickness Scale (FMS). There was no significant difference in changes in the SSQ or the FMS between groups. The 40–59 years age group showed a greater increase in FMS compared to the 19–39 years age group. Smoking was negatively associated with cybersickness, and a high Positive Affect and Negative Affect Schedule score was positively associated with cybersickness. In conclusion, changing the intensity of shaking in VR did not affect cybersickness. While smoking was a protective factor, more expression of affect was a risk factor for cybersickness.
Journal Article
Optimal Vehicle-to-Grid Charge Scheduling for Electric Vehicles Based on Dynamic Programming
by
Kim, Hyunjoong
,
Kim, Hyewon
,
Kim, Hyunsup
in
Algorithms
,
Automobiles, Electric
,
Dynamic programming
2025
Recently, as the market share of electric vehicles (EVs) has increased, how to handle the increased electricity demand for EV charging in the power grid and how to use EV batteries from a grid-operating aspect have become more important. Also, from the perspective of individual EVs, Vehicle-to-Grid (V2G) technologies that reduce the cost for each vehicle’s charging in conjunction with the power grid are significant. In this paper, the V2G control problem at the individual vehicle level is studied using a Dynamic Programming (DP) algorithm that considers EVs’ charging efficiency. The DP algorithm is developed to generate an optimized charging/discharging power profile that minimizes electricity costs, while satisfying the constraints of the initial and final battery states of charge, for given a time-of-use electricity price. To show the effectiveness of the proposed algorithm, simulation is conducted for three different charging scenarios (unidirectional charging, bidirectional charging, and unidirectional charging with cost variations based on electricity usage), and the results showed that DP can achieve significant cost savings of about 30% compared to the normal charging method. Also, the result of DP is compared with that of Linear Programming, demonstrating that DP outperforms Linear Programming in cost savings for the V2G control problem.
Journal Article
Static analysis-based rapid fire-following earthquake risk assessment method using simple building and GIS information
2024
After the occurrences of large-scale earthquakes, secondary damage (e.g., fire following earthquake) can result in tremendous losses of life, properties, and buildings. To reduce these disaster risks, fire following earthquake assessment methods composed of ignition and fire-burned rate estimation models have been utilized. However, previous methods required for large amounts of building and GIS information, and complex modeling and analysis processes, leading to significant time consumption. This paper proposed a static analysis-based rapid fire following earthquake assessment method using simple information and implemented it in Pohang City, South Korea. Based on previous studies, the best-fit model for the ignition rate estimation was selected, and a cluster-based fire-burned rate estimation model was developed using simple building information (e.g., construction year, building occupancy, story, and total floor area) from the public building database (e.g., building registration data). For the fire-burned rate estimation model, fire-resistant structure types were defined using simple building information, and this was utilized to generate clusters of buildings at a regional level by comparing fire-spread distances for each fire-resistant structure type with adjacent distances among the buildings. This proposed method was applied to Pohang City, South Korea, and validated as follows: (1) the selected ignition rate model predicted similar ignition numbers to the actual reported number (actual number of ignitions = 4 vs. predicted number of ignitions = 3), and (2) the fire-burned rate model estimated fire-burned areas with a marginal difference compared to the fire spread simulation (fire-burned area using the proposed model = 13,703.6 m
2
vs. results of fire spread simulation = 16,800.0 m
2
, with an error of approximately 18%).
Journal Article
Impact of environmental changes on the dynamics of temporal networks
by
Jeong, Hawoong
,
Jo, Hang-Hyun
,
Kim, Hyewon
in
Analysis
,
Biology and Life Sciences
,
Changing environments
2021
Dynamics of complex social systems has often been described in the framework of temporal networks, where links are considered to exist only at the moment of interaction between nodes. Such interaction patterns are not only driven by internal interaction mechanisms, but also affected by environmental changes. To investigate the impact of the environmental changes on the dynamics of temporal networks, we analyze several face-to-face interaction datasets using the multiscale entropy (MSE) method to find that the observed temporal correlations can be categorized according to the environmental similarity of datasets such as classes and break times in schools. By devising and studying a temporal network model considering a periodically changing environment as well as a preferential activation mechanism, we numerically show that our model could successfully reproduce various empirical results by the MSE method in terms of multiscale temporal correlations. Our results demonstrate that the environmental changes can play an important role in shaping the dynamics of temporal networks when the interactions between nodes are influenced by the environment of the systems.
Journal Article
Exposure assessment and carcinogenic risk characterization of industrial chemical emissions in incheon, South Korea
2025
Rapid industrialization has intensified chemical emissions, raising urgent concerns about carcinogenic risks to surrounding communities. This study assessed the spatial distribution of industrial facilities emitting chemicals in Incheon Metropolitan City, South Korea, with a particular focus on Group 1 carcinogens. Using Geographic Information System (GIS) and multimedia exposure model (SimpleBox), we estimated exposure levels and cancer risks for residents within a 1-km radius of industrial facilities. The results demonstrated that approximately 22% of the region’s population resides near chemical emission sources, with vulnerable facilities, including kindergartens, elementary schools, and medical institutions, located in these affected areas. Of particular concern, 9.4% of residents are potentially exposed to Group 1 carcinogens, including formaldehyde, benzene, chromium compounds, trichloroethylene, and cadmium compounds. Cancer risk assessments for chromium and cadmium compounds exceeded EPA management standards. This research underscores the urgent need for enhanced emission management policies at industrial facilities, the establishment of protective buffer zones, and strengthened collaboration between local communities and industries to mitigate these significant health risks.
Journal Article
A Rho Kinase (ROCK) Inhibitor, Y-27632, Inhibits the Dissociation-Induced Cell Death of Salivary Gland Stem Cells
2021
Salivary gland stem cells (SGSCs) are potential cell sources for the treatment of salivary gland diseases. The control of cell survival is an essential factor for applying stem cells to regenerative medicine or stem cell-based research. The purpose of this study was to investigate the effects of the ROCK inhibitor Y-27632 on the survival of SGSCs and its underlying mechanisms. SGSCs were isolated from mouse submandibular glands and cultured in suspension. Treatment with Y-27632 restored the viability of SGSCs that was significantly decreased during isolation and the subsequent culture. Y-27632 upregulated the expression of anti-apoptotic protein BCL-2 in SGSCs and, in the apoptosis assay, significantly reduced apoptotic and necrotic cell populations. Matrigel was used to mimic the extracellular environment of an intact salivary gland. The expression of genes regulating apoptosis and the ROCK signaling pathway was significantly reduced when SGSCs were embedded in Matrigel. SGSCs cultured in Matrigel and treated with Y-27632 showed no difference in the total numbers of spheroids and expression levels of apoptosis-regulating genes. Matrigel-embedded SGSCs treated with Y-27632 increased the number of spheroids with budding structures and the expression of acinar cell-specific marker AQP5. We demonstrate the protective effects of Y-27632 against dissociation-induced apoptosis of SGSCs during their culture in vitro.
Journal Article
Effects of metformin and phenformin on apoptosis and epithelial‐mesenchymal transition in chemoresistant rectal cancer
2019
Recurrence and chemoresistance in colorectal cancer remain important issues for patients treated with conventional therapeutics. Metformin and phenformin, previously used in the treatment of diabetes, have been shown to have anticancer effects in various cancers, including breast, lung and prostate cancers. However, their molecular mechanisms are still unclear. In this study, we examined the effects of these drugs in chemoresistant rectal cancer cell lines. We found that SW837 and SW1463 rectal cancer cells were more resistant to ionizing radiation and 5‐fluorouracil than HCT116 and LS513 colon cancer cells. In addition, metformin and phenformin increased the sensitivity of these cell lines by inhibiting cell proliferation, suppressing clonogenic ability and increasing apoptotic cell death in rectal cancer cells. Signal transducer and activator of transcription 3 and transforming growth factor‐β/Smad signaling pathways were more activated in rectal cancer cells, and inhibition of signal transducer and activator of transcription 3 expression using an inhibitor or siRNA sensitized rectal cancer cells to chemoresistant by inhibition of the expression of antiapoptotic proteins, such as X‐linked inhibitor of apoptosis, survivin and cellular inhibitor of apoptosis protein 1. Moreover, metformin and phenformin inhibited cell migration and invasion by suppression of transforming growth factor β receptor 2‐mediated Snail and Twist expression in rectal cancer cells. Therefore, metformin and phenformin may represent a novel strategy for the treatment of chemoresistant rectal cancer by targeting signal transducer and activator of transcription 3 and transforming growth factor‐β/Smad signaling.
Metformin and phenformin decreased the expression of pro‐apoptotic proteins by inhibiting STAT3 phosphorylation at Ser‐727 and suppressed invasion and migration by inhibiting TGFBR2‐mediated signaling
Journal Article
HDAC inhibitors restore osteoimmune balance and bone regeneration via selective MAPK modulation in inflammatory bone disease
by
Kim, Hyewon
,
Kang, Leewoo
,
Park, Shin-Young
in
Analysis
,
Animals
,
Biomedical and Life Sciences
2025
Background
Inflammatory bone diseases are characterized by persistent immune activation and progressive bone destruction, posing significant barriers to spontaneous repair. Current treatments for inflammatory bone diseases seldom achieve both inflammation control and bone regeneration, underscoring the need for dual-action strategies. Epigenetic regulation via histone deacetylases (HDACs) has emerged as a pivotal mechanism linking immune responses to osteogenesis. In this study, we evaluated the therapeutic potential of the HDAC inhibitors Trichostatin A (TSA), PXD-101 (PXD), and MGCD-0103 (MGCD) to suppress inflammation, promote bone regeneration, and elucidate the underlying molecular mechanisms.
Methods
The osteoimmunomodulatory effects of three HDAC inhibitors, Trichostatin A(TSA), PXD-101 (PXD), and MGCD-0103 (MGCD), were investigated under lipopolysaccharide (LPS)-induced inflammatory conditions. RAW264.7 and MC3T3-E1 cells were co-cultured under LPS stimulation and osteogenic differentiation was induced. Macrophage polarization, cytokine secretion, osteogenic differentiation, and MAPK signaling were analyzed by qPCR, ELISA, western blotting, alkaline phosphatase and Alizarin Red S staining. In vivo, an LPS-induced calvarial osteolysis model was established in male C57BL/6 mice, and TSA, PXD, or MGCD was locally administered after significant bone erosion. Bone resorption, new bone formation, and macrophage polarization were evaluated by micro-computed tomography and immunohistochemistry.
Results
TSA, PXD, and MGCD promoted M2 macrophage polarization, suppressed pro-inflammatory cytokine production, and restored osteogenic differentiation under inflammatory conditions. These effects were mediated by selective modulation of the MAPK pathway, whereby inhibition of LPS-induced NF-κB/p38/JNK phosphorylation and enhancement of ERK activation generated a pro-regenerative osteoimmune microenvironment. In vivo, HDAC inhibitor treatment significantly shifted macrophage polarization toward M2 dominance, reduced bone resorption, and promoted new bone formation.
Conclusions
TSA, PXD, and MGCD function as dual-action therapeutics by regulating macrophage polarization and enhancing osteogenesis, thereby establishing a pro-regenerative microenvironment and reversing inflammatory bone loss. These findings provide mechanistic insight into the epigenetic control of immune-bone crosstalk and support a drug-repurposing strategy that utilizes clinically available HDAC inhibitors to accelerate the development of osteoimmunomodulatory therapies.
Journal Article