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result(s) for
"Lee, Kwan Bok"
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First Detection of Influenza D Virus Infection in Cattle and Pigs in the Republic of Korea
2023
Influenza D virus (IDV) belongs to the Orthomyxoviridae family, which also include the influenza A, B and C virus genera. IDV was first detected and isolated in 2011 in the United States from pigs with respiratory illness. IDV circulates in mammals, including pigs, cattle, camelids, horses and small ruminants. Despite the broad host range, cattle are thought to be the natural reservoir of IDV. This virus plays a role as a causative agent of the bovine respiratory disease complex (BRDC). IDV has been identified in North America, Europe, Asia and Africa. However, there has been no information on the presence of IDV in the Republic of Korea (ROK). In this study, we investigated the presence of viral RNA and seroprevalence to IDV among cattle and pigs in the ROK in 2022. Viral RNA was surveyed by the collection and testing of 999 cattle and 2391 pig nasal swabs and lung tissues using a real-time RT-PCR assay. IDV seroprevalence was investigated by testing 742 cattle and 1627 pig sera using a hemagglutination inhibition (HI) assay. The viral RNA positive rate was 1.4% in cattle, but no viral RNA was detected in pigs. Phylogenetic analysis of the hemagglutinin-esterase-fusion (HEF) gene was further conducted for a selection of samples. All sequences belonged to the D/Yamagata/2019 lineage. The seropositivity rates were 54.7% in cattle and 1.4% in pigs. The geometric mean of the antibody titer (GMT) was 68.3 in cattle and 48.5 in pigs. This is the first report on the detection of viral RNA and antibodies to IDV in the ROK.
Journal Article
A deep learning model for the detection of both advanced and early glaucoma using fundus photography
by
Kim, Sangsoo
,
Lee, Kwan Bok
,
Cho, Sung-Hoon
in
Analysis
,
Artificial neural networks
,
Biology and Life Sciences
2018
To build a deep learning model to diagnose glaucoma using fundus photography.
Cross sectional case study Subjects, Participants and Controls: A total of 1,542 photos (786 normal controls, 467 advanced glaucoma and 289 early glaucoma patients) were obtained by fundus photography.
The whole dataset of 1,542 images were split into 754 training, 324 validation and 464 test datasets. These datasets were used to construct simple logistic classification and convolutional neural network using Tensorflow. The same datasets were used to fine tune pre-trained GoogleNet Inception v3 model.
The simple logistic classification model showed a training accuracy of 82.9%, validation accuracy of 79.9% and test accuracy of 77.2%. Convolutional neural network achieved accuracy and area under the receiver operating characteristic curve (AUROC) of 92.2% and 0.98 on the training data, 88.6% and 0.95 on the validation data, and 87.9% and 0.94 on the test data. Transfer-learned GoogleNet Inception v3 model achieved accuracy and AUROC of 99.7% and 0.99 on training data, 87.7% and 0.95 on validation data, and 84.5% and 0.93 on test data.
Both advanced and early glaucoma could be correctly detected via machine learning, using only fundus photographs. Our new model that is trained using convolutional neural network is more efficient for the diagnosis of early glaucoma than previously published models.
Journal Article
Correction: A deep learning model for the detection of both advanced and early glaucoma using fundus photography
2019
[This corrects the article DOI: 10.1371/journal.pone.0207982.].
Journal Article
Clusterin mRNA expression in apoptotic and activated rat thymocytes
2003
Clusterin is a 75-80 kDa heterodimeric glycoprotein,that is produced in most tissues but which exact biological role is still not clear.Pwarticularly,its role in protection or promotion of apoptosis is heavily disputed,since data supporting both views have been reported in several independent sutdies.To clarify this issue,and also to determine whether clusterin expression itself might be affected by apoptosis,in the present study,rat thymocytes were treated with dexamethasone,-a synthetic glucocorticoid that elicits apoptosis in thymocytes-,and clusterin mRNA expression was analyzed by semi-quantitative RT-PCR before and after induction of apoptosis.Interestingly,neither the treatment with dexamethasone in vitro nor triggering of apoptosis in vivo up-regulated clusterin expression,opposing the view that clusterin is involved in apoptotic processes.On the other hand,a new clusterin mRNA isoform was detected and isolated,whose expression ws restricted to freshly isolated thymocytes.This novel isoform lacks the post-translational proteolytic cleavage site and is therefore predicted to encode a monomeric protein.The biological function under normal circumstances,however,will nedd further investigations for clarification.While apoptosis could not modulate clusterin expression,activation of thymocytes with concanavalin A and interleukin-2 resulted in up-regulation of clusterin mRNA level,indicating that clusterin expression is rather under the control of cell activation-mediated rather than apoptosis-induced signals.
Journal Article
Clusterin mRNA expression in apoptotic and activated rat thymocytes
by
PARK, Yoo-Kyoung
,
KANG, Myung-Hee
,
JU, Sung-Kyu
in
Biomedical and Life Sciences
,
Cell Biology
,
Life Sciences
2003
ABSTRACT
Clusterin is a 75-80 kDa heterodimeric glycoprotein, that is produced in most tissues but which exact biological role is still not clear. Particularly, its role in protection or promotion of apoptosis is heavily disputed, since data supporting both views have been reported in several independent studies. To clarify this issue, and also to determine whether clusterin expression itself might be affected by apoptosis, in the present study, rat thymocytes were treated with dexamethasone, -a synthetic glucocorticoid that elicits apoptosis in thymocytes-, and clusterin mRNA expression was analyzed by semi-quantitative RT-PCR before and after induction of apoptosis. Interestingly, neither the treatment with dexamethasone in vitro nor triggering of apoptosis in vivo up- regulated clusterin expression, opposing the view that clusterin is involved in apoptotic processes. On the other hand, a new clusterin mRNA isoform was detected and isolated, whose expression was restricted to freshly isolated thymocytes. This novel isoform lacks the post-translational proteolytic cleavage site and is therefore predicted to encode a monomeric protein. The biological function under normal circumstances, however, will need further investigations for clarification. While apoptosis could not modulate clusterin expression, activation of thymocytes with concanavalin A and interleukin-2 resulted in up-regulation of clusterin mRNA level, indicating that clusterin expression is rather under the control of cell activation-mediated rather than apoptosis- induced signals.
Journal Article
High Temperature Mechanical Properties and Wear Performance of B4C/Al7075 Metal Matrix Composites
by
Lee, Sang-Bok
,
Lee, Yeong-Hwan
,
Lee, Sang-Kwan
in
al matrix composites (amcs)
,
Aluminum base alloys
,
Aluminum matrix composites
2019
In this study, high volume fraction B4C reinforced Al matrix composites were fabricated with a liquid pressing process. Microstructural analysis by scanning electron microscope and a transmission electron microscopy shows a uniform distribution of the B4C reinforcement in the matrix, without any defects such as pore and unwanted reaction products. The compressive strength and wear properties of the Al7075 matrix and the composite were compared at room temperature, 100, 200, and 300 °C, respectively. The B4C reinforced composite showed a very high ultimate compression strength (UCS) over 1.4 GPa at room temperature. The UCS gradually decreased as the temperature was increased, and the UCS of the composite at 300 °C was about one third of the UCS of the composite at room temperature. The fractography of the compressive test specimen revealed that the fracture mechanism of the composites was the brittle fracture mode at room temperature during the compression test. However, at the elevated temperature, AMCs had a mixed mode of a brittle and ductile fracture mechanism under the compressive load. The composite produced by a liquid pressing process also showed superior wear resistance compared with the Al matrix. The result of the wear test indicates that the wear loss of the Al matrix at 300 °C was two times higher than that of the AMCs, which is attributed to the formation of a mechanically mixed layer (MML) in the composites at the high temperature.
Journal Article
Effect of Boron Carbide Addition on Wear Resistance of Aluminum Matrix Composites Fabricated by Stir Casting and Hot Rolling Processes
2021
In this study, to evaluate the effect of boron carbide (B4C) addition on the wear performance of aluminum (Al), Al6061 and 5, 10, and 20 vol.% B4C/Al6061 composites were manufactured using the stir casting and hot rolling processes. B4C particles were randomly dispersed during the stir casting process; then, B4C particles were arranged in the rolling direction using a hot rolling process to further improve the B4C dispersion and wear resistance of the composites. Furthermore, a continuous interfacial layer between B4C and the Al6061 matrix was generated by diffusion of titanium (Ti) and chromium (Cr) atoms contained in the Al6061 alloy. Wear depth and width of the composites decreased with increasing B4C content. Furthermore, with B4C addition, coefficient of friction (COF) improved as compared with that of Al6061. The results indicate that interface-controlled, well-aligned B4C particles in the friction direction can effectively increase the wear properties of Al alloys and improve their hardness.
Journal Article
Chromium carbide/Carbon Nanotube Hybrid Structure Assisted Copper Composites with Low Temperature Coefficient of Resistance
2017
In order to explore the possibility of using carbon nanotube (CNT) to introduce and control the temperature coefficient of resistance (TCR) of metal matrix composite, relatively thick and short multi-walled CNTs (MWCNTs) were introduced in the metal matrix with
in-situ
formation of chromium carbide (Cr
7
C
3
) at the CNT/copper (Cu) interface. We demonstrate that incompatible properties such as electrical conductivity and TCR can be achieved simultaneously by introducing MWCNTs in the Cu matrix, with control of the interfacial resistivity using the MWCNT/Cr
7
C
3
–Cu system. High electrical conductivity of 94.66 IACS and low TCR of 1,451 10
–6
°C
−1
are achieved in the 5 vol.% MWCNT–CuCr composite.
In-situ
formation of Cr
7
C
3
nanostructures at the MWCNT/Cu interface by reaction of diffused Cr atoms and amorphous carbon of MWCNTs would assist in improving the electrical properties of the MWCNT–CuCr composites.
Journal Article
A Comparison of Two LDL Cholesterol Targets after Ischemic Stroke
by
Meseguer, Elena
,
Lee, Byung-Chul
,
Charles, Hugo
in
Adult
,
Aged
,
Anticholesteremic Agents - adverse effects
2020
In this trial, patients with stroke or TIA and atherosclerosis who received a statin with or without ezetimibe were randomly assigned to an LDL cholesterol target of less than 70 mg per deciliter or to a target range of 90 to 110 mg per deciliter. At a median follow-up of 3.5 years, the incidence of a composite cardiovascular end point was 12% lower in the lower-target group than in the higher-target group. The incidence of cerebral hemorrhage did not differ significantly between the two groups.
Journal Article
Dispersion Mechanism and Mechanical Properties of SiC Reinforcement in Aluminum Matrix Composite through Stir- and Die-Casting Processes
by
Lee, Sang-Bok
,
Lee, Sang-Kwan
,
Park, Byeongjin
in
Al matrix composites (AMCs)
,
Alloys
,
Aluminum composites
2021
In this study, different volume fractions of silicon-carbide-reinforced AA2024 matrix composites were successfully fabricated using stir-casting (SC) and die-casting (DC) processes. The microstructural difference and physical properties of the composites during the manufacturing process were investigated in detail. The microstructural analysis found that the composite produced by the SC process had some reinforcement clusters and pores; however, defects and clusters significantly decreased after the DC process. In particular, the degree of reinforcement dispersion was quantitatively analyzed and compared before and after the DC process using the dispersion-analysis method. As a result of quantitative evaluation, the degree of dispersion was improved 2.5, 4.6, and 4.0 times with 3 vol.%, 6 vol.%, and 9 vol.% SiC-reinforced composite after the DC process, respectively. The electron backscatter diffraction (EBSD) analysis showed that the grain size of the 9 vol.% SiC-reinforced DC composite (17.67 μm) was 75% smaller than that of the SC composite (68.06 μm). The average tensile strength and hardness of the 9 vol.% SiC-reinforced DC composite were 2 times higher than those of the AA2024 matrix. The superior mechanical properties of the DC-processed composite can be attributed to the increase in dispersivity of the SiC particles and to decreases in defects and grain size during the DC process.
Journal Article