Catalogue Search | MBRL
Search Results Heading
Explore the vast range of titles available.
MBRLSearchResults
-
DisciplineDiscipline
-
Is Peer ReviewedIs Peer Reviewed
-
Item TypeItem Type
-
SubjectSubject
-
YearFrom:-To:
-
More FiltersMore FiltersSourceLanguage
Done
Filters
Reset
274
result(s) for
"Lee, Sangjun"
Sort by:
Ethnic-specific associations between body mass index and gastric cancer: a Mendelian randomization study in European and Korean populations
2024
Given the uncertainties surrounding the associations in previous epidemiological studies, we conducted linear and nonlinear Mendelian randomization (MR) studies to evaluate whether body mass index (BMI) associated with gastric cancer (GC) risk in European and Korean.
Genome-wide association study-summary statistics were used from the Pan-UK Biobank, the Genetic Investigation of Anthropometric Traits consortium, the K-CHIP consortium, and BioBank Japan. BMI-associated single nucleotide polymorphisms (SNPs) were used as instrumental variables (IVs) in MR to identify the association between BMI and GC. Both linear and nonlinear MR analyses were performed. Sensitivity analyses were also conducted for individuals below or above a BMI of 24 kg/m
.
The study used 22 and 55 SNPs as IVs for BMI in European and Korean populations, respectively. Genetically predicted BMI was positively associated with GC risk in the European population (Odds ratio per 1 kg/m
increase; 95% CI = 1.17; 1.01-1.36 using simple median method), but no significant association was observed in the Korean population. However, the nonlinear MR identified a U-shaped association between BMI and GC in the Korean population, with both low and high BMIs associated with increased GC risk. A BMI of 24 kg/m
presented the lowest risk. Sensitivity analyses did not yield any genome-wide significant SNPs.
While MR analysis suggests a linear association between BMI and GC in those of European ancestry, nonlinear MR hints at a U-shaped association in Koreans. This suggests the association between BMI and GC risk may vary according to ethnic ancestry.
Journal Article
Chemosensory modulation of neural circuits for sodium appetite
2019
Sodium is the main cation in the extracellular fluid and it regulates various physiological functions. Depletion of sodium in the body increases the hedonic value of sodium taste, which drives animals towards sodium consumption
1
,
2
. By contrast, oral sodium detection rapidly quenches sodium appetite
3
,
4
, suggesting that taste signals have a central role in sodium appetite and its satiation. Nevertheless, the neural mechanisms of chemosensory-based appetite regulation remain poorly understood. Here we identify genetically defined neural circuits in mice that control sodium intake by integrating chemosensory and internal depletion signals. We show that a subset of excitatory neurons in the pre-locus coeruleus express prodynorphin, and that these neurons are a critical neural substrate for sodium-intake behaviour. Acute stimulation of this population triggered robust ingestion of sodium even from rock salt, while evoking aversive signals. Inhibition of the same neurons reduced sodium consumption selectively. We further demonstrate that the oral detection of sodium rapidly suppresses these sodium-appetite neurons. Simultaneous in vivo optical recording and gastric infusion revealed that sodium taste—but not sodium ingestion per se—is required for the acute modulation of neurons in the pre-locus coeruleus that express prodynorphin, and for satiation of sodium appetite. Moreover, retrograde-virus tracing showed that sensory modulation is in part mediated by specific GABA (γ-aminobutyric acid)-producing neurons in the bed nucleus of the stria terminalis. This inhibitory neural population is activated by sodium ingestion, and sends rapid inhibitory signals to sodium-appetite neurons. Together, this study reveals a neural architecture that integrates chemosensory signals and the internal need to maintain sodium balance.
Sodium appetite in mice is driven by a neural circuit that is focused on neurons of the pre-locus coeruleus and integrates the sensory detection of sodium and internal signals.
Journal Article
Azide-functionalized ligand enabling organic–inorganic hybrid dielectric for high-performance solution-processed oxide transistors
2022
We propose a highly efficient crosslinking strategy for organic–inorganic hybrid dielectric layers using azide-functionalized acetylacetonate, which covalently connect inorganic particles to polymers, enabling highly efficient inter- and intra-crosslinking of organic and inorganic inclusions, resulting in a dense and defect-free thin-film morphology. From the optimized processing conditions, we obtained an excellent dielectric strength of over 4.0 MV cm
−1
, a high dielectric constant of ~14, and a low surface energy of 38 mN m
−1
. We demonstrated the fabrication of exceptionally high-performance, hysteresis-free n-type solution-processed oxide transistors comprising an In
2
O
3
/ZnO double layer as an active channel with an electron mobility of over 50 cm
2
V
−1
s
−1
, on/off ratio of ~10
7
, subthreshold swing of 108 mV dec
−1
, and high bias-stress stability. From temperature-dependent
I–V
analyses combined with charge transport mechanism analyses, we demonstrated that the proposed hybrid dielectric layer provides percolation-limited charge transport for the In
2
O
3
/ZnO double layer under field-effect conditions.
Low cost and low power consumption of transistors are needed for the development of internet of things. Here Chung et al. develop a high performance n-type oxide thin film transistor by introducing a ligand for crosslinking nanoparticles and polymers, obtaining a near-ideal hybrid dielectric layer.
Journal Article
Graphene perfect absorber with loss adaptive Q-factor control function enabled by quasi-bound states in the continuum
2021
Numerous device structures have been proposed for perfect absorption in monolayer graphene under single-sided illumination, all of which requires the critical coupling condition, i.e., the balance between the loss of graphene and the leakage rate of the device. However, due to the difficulty of the precise control of the quality of synthesized graphene and unwanted doping in graphene transferred to the substrate, the loss of graphene is rather unpredictable, so that the perfect absorption is quite difficult to achieve in practice. To solve this problem, we designed a novel perfect absorber structure with a loss adaptive leakage rate control function enabled by the quasi-bound states in the continuum (BIC) and numerically demonstrated its performance. Our designed device is based on a slab-waveguide grating supporting both the quasi-BIC and the guided-mode resonance (GMR); the quasi-BIC with an adjustable leakage rate controlled by an incident angle is responsible for absorption, while the GMR works as an internal mirror. Since the proposed device scheme can have an arbitrarily small leakage rate, it can be used to implement a perfect absorber for any kind of ultrathin absorbing media. Due to the simple structure avoiding an external reflector, the device is easy to fabricate.
Journal Article
The cellular basis of distinct thirst modalities
2020
Fluid intake is an essential innate behaviour that is mainly caused by two distinct types of thirst
1
–
3
. Increased blood osmolality induces osmotic thirst that drives animals to consume pure water. Conversely, the loss of body fluid induces hypovolaemic thirst, in which animals seek both water and minerals (salts) to recover blood volume. Circumventricular organs in the lamina terminalis are critical sites for sensing both types of thirst-inducing stimulus
4
–
6
. However, how different thirst modalities are encoded in the brain remains unknown. Here we employed stimulus-to-cell-type mapping using single-cell RNA sequencing to identify the cellular substrates that underlie distinct types of thirst. These studies revealed diverse types of excitatory and inhibitory neuron in each circumventricular organ structure. We show that unique combinations of these neuron types are activated under osmotic and hypovolaemic stresses. These results elucidate the cellular logic that underlies distinct thirst modalities. Furthermore, optogenetic gain of function in thirst-modality-specific cell types recapitulated water-specific and non-specific fluid appetite caused by the two distinct dipsogenic stimuli. Together, these results show that thirst is a multimodal physiological state, and that different thirst states are mediated by specific neuron types in the mammalian brain.
The authors uncover the diverse transcriptomic cell types of thirst-driving neurons in the lamina terminalis and show that unique combinations of neuron types respond to and mediate distinct thirst states.
Journal Article
Autonomous multi-joint soft exosuit with augmentation-power-based control parameter tuning reduces energy cost of loaded walking
2018
Background
Soft exosuits are a recent approach for assisting human locomotion, which apply assistive torques to the wearer through functional apparel. Over the past few years, there has been growing recognition of the importance of control individualization for such gait assistive devices to maximize benefit to the wearer. In this paper, we present an updated version of autonomous multi-joint soft exosuit, including an online parameter tuning method that customizes control parameters for each individual based on positive ankle augmentation power.
Methods
The soft exosuit is designed to assist with plantarflexion, hip flexion, and hip extension while walking. A mobile actuation system is mounted on a military rucksack, and forces generated by the actuation system are transmitted via Bowden cables to the exosuit. The controller performs an iterative force-based position control of the Bowden cables on a step-by-step basis, delivering multi-articular (plantarflexion and hip flexion) assistance during push-off and hip extension assistance in early stance. To individualize the multi-articular assistance, an online parameter tuning method was developed that customizes two control parameters to maximize the positive augmentation power delivered to the ankle. To investigate the metabolic efficacy of the exosuit with wearer-specific parameters, human subject testing was conducted involving walking on a treadmill at 1.50 m s
− 1
carrying a 6.8-kg loaded rucksack. Seven participants underwent the tuning process, and the metabolic cost of loaded walking was measured with and without wearing the exosuit using the individualized control parameters.
Results
The online parameter tuning method was capable of customizing the control parameters, creating a positive ankle augmentation power map for each individual. The subject-specific control parameters and resultant assistance profile shapes varied across the study participants. The exosuit with the wearer-specific parameters significantly reduced the metabolic cost of load carriage by 14.88 ± 1.09% (
P
= 5 × 10
− 5
) compared to walking without wearing the device and by 22.03 ± 2.23% (
P
= 2 × 10
− 5
) compared to walking with the device unpowered.
Conclusion
The autonomous multi-joint soft exosuit with subject-specific control parameters tuned based on positive ankle augmentation power demonstrated the ability to improve human walking economy. Future studies will further investigate the effect of the augmentation-power-based control parameter tuning on wearer biomechanics and energetics.
Journal Article
Point Cloud Wall Projection for Realistic Road Data Augmentation
2024
Several approaches have been developed to generate synthetic object points using real LiDAR point cloud data for advanced driver-assistance system (ADAS) applications. The synthetic object points generated from a scene (both the near and distant objects) are essential for several ADAS tasks. However, generating points from distant objects using sparse LiDAR data with precision is still a challenging task. Although there are a few state-of-the-art techniques to generate points from synthetic objects using LiDAR point clouds, limitations such as the need for intense compute power still persist in most cases. This paper suggests a new framework to address these limitations in the existing literature. The proposed framework contains three major modules, namely position determination, object generation, and synthetic annotation. The proposed framework uses a spherical point-tracing method that augments 3D LiDAR distant objects using point cloud object projection with point-wall generation. Also, the pose determination module facilitates scenarios such as platooning carried out by the synthetic object points. Furthermore, the proposed framework improves the ability to describe distant points from synthetic object points using multiple LiDAR systems. The performance of the proposed framework is evaluated on various 3D detection models such as PointPillars, PV-RCNN, and Voxel R-CNN for the KITTI dataset. The results indicate an increase in mAP (mean average precision) by 1.97%, 1.3%, and 0.46% from the original dataset values of 82.23%, 86.72%, and 87.05%, respectively.
Journal Article
Mechanism of stable lithium plating and stripping in a metal-interlayer-inserted anode-less solid-state lithium metal battery
2025
To reliably operate anode-less solid-state Li metal batteries, wherein precipitated Li acts as the anode, stabilizing the interface between the solid electrolyte and electrode is crucial. The interface can be controlled by a metal interlayer on the electrolyte to form a Li alloy buffer that facilitates stable Li plating/stripping, thereby mitigating the loss of physical contact and preventing short circuits. However, the mechanism governing stable Li plating/stripping in the metal interlayer without degrading battery materials remains unclear owing to an incomplete understanding of the dynamic and complex electrochemical reactions in the solid state. Through multiple
operando
and
post-mortem
analyses of the Li deposition behavior in the morphology, chemistry and microstructure, a close correlation is found between the Li-metal alloying process with the microstructural evolution and electrochemical performance when Ag, Au, Zn, and Cu interlayers were adopted on the garnet-type solid electrolyte Li
6.5
La
3
Zr
1.5
Ta
0.5
O
12
. The Ag interlayer improved the interfacial stability enabled by Ag-dissolved Li, which inhibited dendritic growth, passing through the phase-separated Li-Ag alloy microstructure, while the other metals did not because of the Li plating at the Li-metal alloy/solid electrolyte interface. This work provides fundamental guidance for material selection and interface design, advancing the development of anode-less solid-state batteries.
To ensure the reliable operation of anode-less solid-state lithium metal battery, herein, the authors report the role of metal interlayer as the interface control strategy for achieving the stable lithium plating and stripping using the multiple operando and in-situ analysis.
Journal Article
Towards Mirror-Less Graphene-Based Perfect Absorbers
2023
Owing to its exceptional electronic and optical properties, graphene has attracted extensive attention among researchers in the development of high-performance optoelectronic devices. However, the light absorption of pure graphene is very poor, limiting its development in practical application. In this review, as a solution for this issue, various types of graphene-based perfect absorbers are addressed in terms of their operation principles and design requirements. Their recent progress and potential applications such as photodetectors and modulators are also discussed. In particular, we emphasize the importance of mirror-less (in particular, one-port mimicking) perfect absorber design due to simplified fabrication processes or enhanced tolerance for fabrication error.
Journal Article
Temporal Association Between ChatGPT-Generated Diarrhea Synonyms in Internet Search Queries and Emergency Department Visits for Diarrhea-Related Symptoms in South Korea: Exploratory Study
2025
Diarrhea, a common symptom of gastrointestinal infections, can lead to severe complications and is a major cause of emergency department (ED) visits.
This study explored the temporal association between internet search queries for diarrhea and its synonyms and ED visits for diarrhea-related symptoms.
We used data from the National Emergency Department Information System (NEDIS) and NAVER (Naver Corporation), South Korea's leading search engine, from January 2017 to December 2021. After identifying diarrhea synonyms using ChatGPT, we compared weekly trends in relative search volumes (RSVs) for diarrhea, including its synonyms and weekly ED visits. Pearson correlation analysis and Granger causality tests were used to evaluate the relationship between RSVs and ED visits. We developed an Autoregressive Integrated Moving Average with Exogenous Variables (ARIMAX) model to further predict these associations. This study also examined the age-based distribution of search behaviors and ED visits.
A significant correlation was observed between the weekly RSV for diarrhea and its synonyms and weekly ED visits for diarrhea-related symptoms (ranging from 0.14 to 0.51, P<.05). Weekly RSVs for diarrhea synonyms, such as \"upset stomach,\" \"watery diarrhea,\" and \"acute enteritis,\" showed stronger correlations with weekly ED visits than weekly RSVs for the general term \"diarrhea\" (ranging from 0.20 to 0.41, P<.05). This may be because these synonyms better reflect layperson terminology. Notably, weekly RSV for \"upset stomach\" was significantly correlated with weekly ED visits for diarrhea and acute diarrhea at 1 and 2 weeks before the visit (P<.05). An ARIMAX model was developed to predict weekly ED visits based on weekly RSVs for diarrhea synonyms with lagged effects to capture their temporal influence. The age group of <50 years showed the highest activity in both web-based searches and ED visits for diarrhea-related symptoms.
This study demonstrates that weekly RSVs for diarrhea synonyms are associated with weekly ED visits for diarrhea-related symptoms. By encompassing a nationwide scope, this study broadens the existing methodology for syndromic surveillance using ED data and provides valuable insights for clinicians.
Journal Article