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"Lee, Yu Seon"
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V2O5-Assisted Low-Temperature Sintering and Microwave Dielectric Properties of (1 − x)Li2.08TiO3–xLi2ZnTi3O8 (x = 0.3−0.7) Ceramics for LTCC Applications
2025
A new composite microwave–dielectric system, (1 − x)Li2.08TiO3-xLi2ZnTi3O8 (x = 0.3–0.7), was systematically investigated to identify the optimal composition for low-temperature co-fired ceramic (LTCC) applications by correlating sintering behavior, microstructural evolution, and microwave–dielectric properties. Although the undoped compositions exhibited excellent intrinsic dielectric performance, they required sintering at 1100 °C, making them incompatible with Ag-based LTCC processing. Among the investigated formulations, 0.6Li2.08TiO3–0.4Li2ZnTi3O8 was identified as the most suitable base composition. To reduce the sintering temperature, 0.3–1.0 wt.% V2O5 was introduced as a sintering aid, enabling densification at 900 °C for 30 min (97.0% relative density) while preserving the coexistence of Li2.08TiO3 and Li2ZnTi3O8 without XRD-detectable secondary phases. Microstructural observations indicated that V2O5 promoted liquid-phase sintering, leading to enhanced densification and Li2.08TiO3-selective abnormal grain coarsening without altering the intrinsic permittivity. Complementary dilatometry provided process-level evidence for this liquid-phase sintering mechanism: large total shrinkage at 900 °C (∆L/Lo≈ −17–19%), earlier Tonset/Tpeak with Tpeak lowered by ~250 °C, and an increased Rpeak, collectively supporting 900 °C/30 min as the practical firing window. The optimized 0.6Li2.08TiO3–0.4Li2ZnTi3O8 composition containing 0.3 wt.% V2O5 exhibits excellent microwave–dielectric properties (εr = 23.32, Q × f = 68,400 GHz, and τf = −1.55 ppm/°C). Higher V2O5 contents (>0.3 wt.%) caused a gradual reduction in Q × f due to increasing microstructural non-uniformity. Ag co-firing tests confirmed electrode stability with no interfacial reactions at 900 °C for 30 min. Overall, 0.3 wt.% V2O5-assisted 0.6Li2.08TiO3–0.4Li2ZnTi3O8 provides a practical sub-950 °C processing window that satisfies key LTCC requirements, including moderate permittivity, high Q × f, near-zero τf, and compatibility with Ag electrodes.
Journal Article
Longitudinal long term follow up investigation on the carcinogenic impact of polyhexamethylene guanidine phosphate in rat models
2024
Polyhexamethylene guanidine phosphate (PHMG-p) is a major component in humidifier disinfectants, which cause life-threatening lung injuries. However, to our knowledge, no published studies have investigated associations between PHMG-p dose and lung damage severity with long-term follow-up. Therefore, we evaluated longitudinal dose-dependent changes in lung injuries using repeated chest computed tomography (CT). Rats were exposed to low (0.2 mg/kg, n = 10), intermediate (1.0 mg/kg, n = 10), and high (5.0 mg/kg, n = 10) doses of PHMG-p. All rats underwent repeated CT scans after 10 and 40 weeks following the first exposure. All CT images were quantitatively analyzed using commercial software. Inflammation/fibrosis and tumor counts underwent histopathological evaluation. In both radiological and histopathologic results, the lung damage severity increased as the PHMG-p dose increased. Moreover, the number, size, and malignancy of the lung tumors increased as the dose increased. Bronchiolar–alveolar hyperplasia developed in all groups. During follow-up, there was intergroup variation in bronchiolar–alveolar hyperplasia progression, although bronchiolar–alveolar adenomas or carcinomas usually increase in size over time. Thirty-three carcinomas were detected in the high-dose group in two rats. Overall, lung damage from PHMG-p and the number and malignancy of lung tumors were shown to be dose-dependent in a rat model using repeated chest CT scans during a long-term follow-up.
Journal Article
Long-Term Alterations of Renal Microvasculature in Rats Following Maternal PM2.5 Exposure: Vitamin D Effects
by
Park, Eujin
,
Lee, Ju-Han
,
Yim, Hyung-Eun
in
ambient particulate matter
,
angiogenesis
,
Angiopoietin
2025
Background: This study aimed to investigate the long-term effects of maternal exposure to fine particulate matter (PM2.5) with or without vitamin D supplementation on the renal microvasculature in adult rat offspring. Methods: Pregnant Sprague–Dawley rats were exposed to normal saline, PM2.5, and PM2.5 with vitamin D for one month during nephrogenesis. Male offspring kidneys were taken for analyses on postnatal day 56. Results: Adult offspring rats exposed to maternal PM2.5 exhibited lower body weights and greater glomerular and tubular injury scores compared to control rats. Semi-quantitative analysis revealed a significant reduction in glomerular and peritubular capillary endothelial cells, along with a decrease in the number of glomeruli in the PM2.5 group. Maternal vitamin D supplementation reduced these changes. In offspring rats exposed to maternal PM2.5, intrarenal expression of renin, angiotensin-converting enzyme (ACE), cytochrome P450 27B1, and vascular endothelial growth factor-A (VEGF-A) increased, while expression of the vitamin D receptor, Klotho, VEGF receptor 2, angiopoietin-1, and Tie-2 decreased. Maternal vitamin D supplementation restored VEGF receptor 2 and angiopoietin-1 activities and reduced ACE and VEGF-A protein expression in adult offspring kidneys. Conclusions: Early-life exposure to PM2.5 may lead to long-term alterations in renal microvasculature and nephron loss. Maternal vitamin D supplementation during renal development can ameliorate PM2.5-induced capillary rarefaction and nephron loss in the kidneys of adult offspring.
Journal Article
Enhancing Lesion Detection in Rat CT Images: A Deep Learning-Based Super-Resolution Study
2025
Background/Objectives: Preclinical chest computed tomography (CT) imaging in small animals is often limited by low resolution due to scan time and dose constraints, which hinders accurate detection of subtle lesions. Traditional super-resolution (SR) metrics, such as peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM), may not adequately reflect clinical interpretability. We aimed to evaluate whether deep learning-based SR models could enhance image quality and lesion detectability in rat chest CT, balancing quantitative metrics with radiologist assessment. Methods: We retrospectively analyzed 222 chest CT scans acquired from polyhexamethylene guanidine phosphate (PHMG-p) exposure studies in Sprague Dawley rats. Three SR models were implemented and compared: single-image SR (SinSR), segmentation-guided SinSR with lung cropping (SinSR3), and omni-super-resolution (OmniSR). Models were trained on rat CT data and evaluated using PSNR and SSIM. Two board-certified thoracic radiologists independently performed blinded evaluations of lesion margin clarity, nodule detectability, image noise, artifacts, and overall image quality. Results: SinSR1 achieved the highest PSNR (33.64 ± 1.30 dB), while SinSR3 showed the highest SSIM (0.72 ± 0.08). Despite lower PSNR (29.21 ± 1.46 dB), OmniSR received the highest radiologist ratings for lesion margin clarity, nodule detectability, and overall image quality (mean score 4.32 ± 0.41, κ = 0.74). Reader assessments diverged from PSNR and SSIM, highlighting the limited correlation between conventional metrics and clinical interpretability. Conclusions: Deep learning-based SR improved visualization of rat chest CT images, with OmniSR providing the most clinically interpretable results despite modest numerical scores. These findings underscore the need for reader-centered evaluation when applying SR techniques to preclinical imaging.
Journal Article
Polyhexamethylene Guanidine Phosphate Induces Restrictive Ventilation Defect and Alters Lung Resistance and Compliance in Mice
2024
Polyhexamethylene guanidine phosphate (PHMG-p), a major ingredient of humidifier disinfectants, is known to induce inflammation, interstitial pneumonitis, and fibrosis in the lungs. While its histopathologic toxicities have been studied in rodents, research on pulmonary function test (PFT) changes following PHMG-p exposure is limited. This study aimed to investigate the acute and chronic effects, as well as the dose and time response, of PHMG-p on the lungs in mice using PFT and histopathologic examinations. In the single instillation model, mice received PHMG-p and were sacrificed at 2, 4, and 8 weeks. In the five-time instillation model, PHMG-p was administered five times at one-week intervals, and mice were sacrificed 10 weeks after the first instillation. Results showed that PHMG-p exposure reduced lung volume, increased resistance, and decreased compliance, indicating a restrictive ventilation defect. Histopathologic examination showed increases in lung inflammation and fibrosis scores. Changes in several lung volume and compliance parameters, as well as histopathology, were dose-dependent. Lung resistance and compliance parameters had significant correlations with lung inflammation and fibrosis scores. PHMG-p exposure in mice resulted in a restrictive ventilation defect with altered lung resistance and compliance, along with histopathologic lung inflammation and fibrosis.
Journal Article
Roles of eIF4E-binding protein Caf20 in Ste12 translation and P-body formation in yeast
by
Jung, Daehee
,
Park, Kiyoung
,
Lee, Yu-Seon
in
Baking yeast
,
Binding Sites
,
Biomedical and Life Sciences
2018
Translation initiation factor eIF4E forms eIF4E-eIF4G complex at the 5’ cap of mRNA. This interaction can be inhibited by the family of 4E-binding proteins (4E-BP). In yeast
Saccharomyces cerevisiae
, two 4E-BPs, Caf20 and Eap1, compete with eIF4G for binding to eIF4E via the shared conserved interaction motif. In order to investigate the roles of Caf20 in gene-specific translational regulation and the formation of mRNA granules (P-bodies), we introduced substitution mutations,
caf20-Y4A
or
caf20-L9A
, in the eIF4E-binding motif for
CAF20
. Overexpression of the wild-type
CAF20
showed an increased protein level of Ste12 transcription factor as well as highly developed P-body formation. However, 4E-binding site mutations of
CAF20
led to a reduced number of P-body foci and decreased levels of Ste12 protein. The phenotypes of the
caf20
deletion mutation were also analyzed, and we suggest that
Caf20
plays a critical role in Ste12 protein expression and in the control of P-body formation.
Journal Article
Disentangling variation patterns and partitioning strategies of net primary productivity: insights from cool-temperate forests in South Korea
2026
Background
Understanding the processes underlying carbon storage and balance is critical for equipping the terrestrial biosphere to respond to contemporary climatic challenges. However, ecosystem-level estimates and distribution of net primary productivity (NPP), a metric for evaluating forest carbon cycling patterns and dynamics, remain constrained by uneven empirical observations between above- and belowground fractions. We herein quantified the rate and composition of NPP for four stands characteristic of the cool-temperate deciduous (
Larix kaempferi
, LK;
Quercus mongolica
, QM) and evergreen (
Pinus densiflora
, PD;
Pinus koraiensis
, PK) forests of South Korea over a complete annual cycle (2022–2023). Variations in dynamic NPP compartments, particularly (1) canopy litterfall by stand and season and (2) fine root production by stand, diameter class, and depth interval, were further characterized using litter traps and ingrowth cores, respectively.
Results
Total NPP varied from 1226 ± 101 to 1796 ± 154 g m
−2
yr
−1
, with 78–84% allocated aboveground and 16–22% belowground. LK and QM exhibited total NPP up to 46% higher than PD and PK. Both litterfall and fine root production differed considerably across stands, decreasing in the order of QM > PK > PD > LK for litterfall and QM & PD > LK & PK for fine root production. Litterfall peaked in autumn, similar to the leaf phenological rhythm of many temperate deciduous species. In contrast, fine root production showed a negative vertical distribution with depth, which is consistent with decreasing nutrient availability and increasing mechanical impedance along the soil profile.
Conclusions
By disentangling the contribution levels and dynamic patterns of each NPP compartment, our findings demonstrate a strong inclination toward aboveground NPP investment when belowground resources are not limiting. In other words, an adequate nutrient supply enables plants to modify their priority allocation from fine root maintenance to internal resource transport, leaf production, canopy expansion, reproduction, and other critical aboveground functions. Such information underscores the necessity for forest management strategies that target soil fertility to strengthen not only canopy productivity and CO
2
sequestration but also ecosystem resilience by reinforcing allocation patterns that sustain high NPP and safeguard forests against shifting climate conditions.
Journal Article
Hematotoxic Effect of Respiratory Exposure to PHMG-p and Its Integrated Genetic Analysis
2022
Polyhexamethylene guanidine phosphate (PHMG-p), the main ingredient of humidifier disinfectants, circulates systemically through the lungs; however, its toxicological assessment has been primarily limited to pulmonary disease. Herein, we investigated the possible abnormalities in hematopoietic function 20 weeks after intratracheal instillation of PHMG-p in a rat model. Notable abnormalities were found out in the peripheral blood cell count and bone marrow (BM) biopsy, while RNA sequencing of BM tissue revealed markedly altered gene expression. Furthermore, signaling involved in hematopoietic dysfunction was predicted by analyzing candidate genes through Ingenuity Pathway Analysis (IPA) program. Respiratory PHMG-p exposure significantly decreased monocyte and platelet (PLT) counts and total protein, while significantly increasing hemoglobin and hematocrit levels in peripheral blood. Histopathological analysis of the BM revealed a reduced number of megakaryocytes, with no significant differences in spleen and liver weight to body weight. Moreover, PHMG-p exposure significantly activated estrogen receptor signaling and RHOA signaling, and inhibited RHOGDI signaling. In IPA analysis, candidate genes were found to be strongly related to ‘hematological system development and function’ and ‘hematological disease.’ Accordingly, our results suggest that PHMG-p could affect hematopoiesis, which participates in monocyte differentiation and PLT production, and may induce hematologic diseases via the respiratory tract.
Journal Article
Vsub.2Osub.5-Assisted Low-Temperature Sintering and Microwave Dielectric Properties of Ceramics for LTCC Applications
2026
A new composite microwave–dielectric system, (1 − x)Li[sub.2.08]TiO[sub.3]-xLi[sub.2]ZnTi[sub.3]O[sub.8] (x = 0.3–0.7), was systematically investigated to identify the optimal composition for low-temperature co-fired ceramic (LTCC) applications by correlating sintering behavior, microstructural evolution, and microwave–dielectric properties. Although the undoped compositions exhibited excellent intrinsic dielectric performance, they required sintering at 1100 °C, making them incompatible with Ag-based LTCC processing. Among the investigated formulations, 0.6Li[sub.2.08]TiO[sub.3]–0.4Li[sub.2]ZnTi[sub.3]O[sub.8] was identified as the most suitable base composition. To reduce the sintering temperature, 0.3–1.0 wt.% V[sub.2]O[sub.5] was introduced as a sintering aid, enabling densification at 900 °C for 30 min (97.0% relative density) while preserving the coexistence of Li[sub.2.08]TiO[sub.3] and Li[sub.2]ZnTi[sub.3]O[sub.8] without XRD-detectable secondary phases. Microstructural observations indicated that V[sub.2]O[sub.5] promoted liquid-phase sintering, leading to enhanced densification and Li[sub.2.08]TiO[sub.3]-selective abnormal grain coarsening without altering the intrinsic permittivity. Complementary dilatometry provided process-level evidence for this liquid-phase sintering mechanism: large total shrinkage at 900 °C (∆L/L[sub.o]≈ −17–19%), earlier T[sub.onset]/T[sub.peak] with T[sub.peak] lowered by ~250 °C, and an increased R[sub.peak], collectively supporting 900 °C/30 min as the practical firing window. The optimized 0.6Li[sub.2.08]TiO[sub.3]–0.4Li[sub.2]ZnTi[sub.3]O[sub.8] composition containing 0.3 wt.% V[sub.2]O[sub.5] exhibits excellent microwave–dielectric properties (ε[sub.r] = 23.32, Q × f = 68,400 GHz, and τ[sub.f] = −1.55 ppm/°C). Higher V[sub.2]O[sub.5] contents (>0.3 wt.%) caused a gradual reduction in Q × f due to increasing microstructural non-uniformity. Ag co-firing tests confirmed electrode stability with no interfacial reactions at 900 °C for 30 min. Overall, 0.3 wt.% V[sub.2]O[sub.5]-assisted 0.6Li[sub.2.08]TiO[sub.3]–0.4Li[sub.2]ZnTi[sub.3]O[sub.8] provides a practical sub-950 °C processing window that satisfies key LTCC requirements, including moderate permittivity, high Q × f, near-zero τ[sub.f], and compatibility with Ag electrodes.
Journal Article
V 2 O 5 -Assisted Low-Temperature Sintering and Microwave Dielectric Properties of (1 - x)Li 2.08 TiO 3 -xLi 2 ZnTi 3 O 8 (x = 0.3-0.7) Ceramics for LTCC Applications
2025
A new composite microwave-dielectric system, (1 - x)Li
TiO
-xLi
ZnTi
O
(x = 0.3-0.7), was systematically investigated to identify the optimal composition for low-temperature co-fired ceramic (LTCC) applications by correlating sintering behavior, microstructural evolution, and microwave-dielectric properties. Although the undoped compositions exhibited excellent intrinsic dielectric performance, they required sintering at 1100 °C, making them incompatible with Ag-based LTCC processing. Among the investigated formulations, 0.6Li
TiO
-0.4Li
ZnTi
O
was identified as the most suitable base composition. To reduce the sintering temperature, 0.3-1.0 wt.% V
O
was introduced as a sintering aid, enabling densification at 900 °C for 30 min (97.0% relative density) while preserving the coexistence of Li
TiO
and Li
ZnTi
O
without XRD-detectable secondary phases. Microstructural observations indicated that V
O
promoted liquid-phase sintering, leading to enhanced densification and Li
TiO
-selective abnormal grain coarsening without altering the intrinsic permittivity. Complementary dilatometry provided process-level evidence for this liquid-phase sintering mechanism: large total shrinkage at 900 °C (∆L/Lo≈ -17-19%), earlier Tonset/Tpeak with Tpeak lowered by ~250 °C, and an increased Rpeak, collectively supporting 900 °C/30 min as the practical firing window. The optimized 0.6Li
TiO
-0.4Li
ZnTi
O
composition containing 0.3 wt.% V
O
exhibits excellent microwave-dielectric properties (εr = 23.32,
= 68,400 GHz, and τf = -1.55 ppm/°C). Higher V
O
contents (>0.3 wt.%) caused a gradual reduction in
due to increasing microstructural non-uniformity. Ag co-firing tests confirmed electrode stability with no interfacial reactions at 900 °C for 30 min. Overall, 0.3 wt.% V
O
-assisted 0.6Li
TiO
-0.4Li
ZnTi
O
provides a practical sub-950 °C processing window that satisfies key LTCC requirements, including moderate permittivity, high
, near-zero τf, and compatibility with Ag electrodes.
Journal Article