Publications by authors named "Ki Sang Lee"

7 Publications

  • Page 1 of 1

Optomechanical engineering of quasi-continuous-wave background in mode-locked fiber laser.

Opt Express 2021 May;29(10):14452-14466

Noise-like quasi-continuous-wave background (qCWB) in a mode-locked fiber laser mediates various multi-pulse dynamics via long-range inter-pulse interactions. This raises a possibility to control multi-pulse phenomena through manipulation of the qCWB, while it has been rarely studied yet. Here, we investigate the qCWB engineering by imposing optomechanically induced impulsive intensity modulations on the qCWB. The mode-locked pulses excite electrostrictively several transverse acoustic resonance modes inside the fiber cavity, which eventually leads to the formation of sharp qCWB modulations regularly spaced in the time domain. In particular, we experimentally demonstrate that the characteristics of the optomechanical qCWB modulations can be adjusted by controlling the in-fiber optomechanical interactions via changing the structure of the fiber core, cladding, and coating. Our observations are supported by directly measured forward stimulated Brillouin scattering spectra of the intracavity fibers.
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May 2021

Combined use of basal insulin analog and acarbose reduces postprandial glucose in patients with uncontrolled type 2 diabetes.

J Diabetes Investig 2015 Mar 6;6(2):219-26. Epub 2014 Aug 6.

Kang Cheolmin Internal Medicine Clinic Suncheon, Korea.

Aims/introduction: Early initiation of basal insulin therapy is recommended for normalizing fasting blood glucose in type 2 diabetes mellitus. However, basal insulin treatment might not adequately control postprandial glucose levels. The present study evaluated whether the combination of the α-glucosidase inhibitor, acarbose, and basal insulin improved blood glucose control under daily-life treatment conditions in a large sample of Korean patients.

Materials And Methods: The present study was a multicenter, prospective, observational study under daily-life treatment conditions. A total of 539 patients with type 2 diabetes who were treated with basal insulin and additional acarbose were enrolled and followed up for 20 weeks. Changes in hemoglobin A1c, fasting and postprandial blood glucose were evaluated at baseline and at the end of the observation period. The physician and patient satisfaction of the combination treatment and safety were assessed.

Results: Hemoglobin A1c decreased by 0.55 ± 1.05% from baseline (P < 0.0001). Fasting and postprandial blood glucose levels were reduced by 0.89 ± 3.79 and 2.59 ± 4.77 mmol/L (both P < 0.0001). The most frequently reported adverse drug reactions were flatulence (0.37%) and abnormal gastrointestinal sounds (0.37%), and all were mild in intensity and transient. In the satisfaction evaluation, 79.0% of physicians and 77.3% of patients were 'very satisfied' or 'satisfied' with the combined basal insulin and acarbose therapy.

Conclusions: Combination therapy of basal insulin and acarbose in patients with type 2 diabetes improved glucose control, and had no drug-specific safety concerns, suggesting that the treatment might benefit individuals who cannot control blood glucose with basal insulin alone.
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March 2015

Usefulness of plasma epigenetic changes of five major genes involved in the pathogenesis of colorectal cancer.

Int J Colorectal Dis 2013 Jan 19;28(1):139-47. Epub 2012 Sep 19.

Department of Internal Medicine, Seonam University Namgwang Hospital, Gwang-ju, South Korea.

Purpose: The purpose of present study was to investigate the methylation status of the promoter region in five genes (mothers against decapentaplegic homolog 4, fragile histidine triad protein, death-associated protein kinase 1, adenomatous polyposis coli (APC), and E-cadherin), which are known to be involved in the pathogenesis of colorectal cancer (CRC) and its clinicopathological significance.

Methods: The study subjects were 60 CRC patients, 40 patients with adenomatous colorectal polyp and 60 healthy control individuals. We further enrolled a total of 16 patients (two patients with Crohn's disease, two patients with ulcerative colitis, one patient with serrated adenoma, and 11 patients with colorectal cancer). The methylation states of the five genes were determined in peripheral blood plasma using methylation-specific polymerase chain reaction single-strand conformation polymorphism analysis.

Results: This study showed the most sensitive epigenetic markers, E-cadherin (60 %), followed by APC (57 %), for detecting CRC. E-cadherin and APC had similar specificities and amplified 84 and 86 %, respectively, of CRC patients compared to non-CRC patients. Additionally, APC was the only marker to be significantly increased (OR = 6.67, 95 % CI = 1.19-23.4, P = 0.045) and the most sensitive (57 %) and specific (89 %) marker in stage I CRC. Though we have not examined the paired cancer tissues and plasma, there was relatively high concordant rate (60-80 %) in our limited number of colorectal cancer patients.

Conclusions: Five genes, promoter methylation, in plasma were statistically significant risk factors in CRC patients. In this study, E-cad and APC genes may be particularly useful epigenetic biomarkers in plasma for the detection of CRC. Additionally, APC may able to identify early potential CRC.
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January 2013

Frequent occurrence of mitochondrial DNA mutations in Barrett's metaplasia without the presence of dysplasia.

PLoS One 2012 22;7(5):e37571. Epub 2012 May 22.

Department of Internal Medicine, College of Medicine, Seonam University, Namwon, Korea.

Background: Barrett's esophagus (BE) is one of the most common premalignant lesions and can progress to esophageal adenocarcinoma (EA). The numerous molecular events may play a role in the neoplastic transformation of Barrett's mucosa such as the change of DNA ploidy, p53 mutation and alteration of adhesion molecules. However, the molecular mechanism of the progression of BE to EA remains unclear and most studies of mitochondrial DNA (mtDNA) mutations in BE have performed on BE with the presence of dysplasia.

Methods/findings: Thus, the current study is to investigate new molecular events (Barrett's esophageal tissue-specific-mtDNA alterations/instabilities) in mitochondrial genome and causative factors for their alterations using the corresponding adjacent normal mucosal tissue (NT) and tissue (BT) from 34 patients having Barrett's metaplasia without the presence of dysplasia. Eighteen patients (53%) exhibited mtDNA mutations which were not found in adjacent NT. mtDNA copy number was about 3 times higher in BT than in adjacent NT. The activity of the mitochondrial respiratory chain enzyme complexes in tissues from Barrett's metaplasia without the presence of dysplasia was impaired. Reactive oxygen species (ROS) level in BT was significantly higher than those in corresponding samples.

Conclusion/significance: High ROS level in BT may contribute to the development of mtDNA mutations, which may play a crucial role in disease progression and tumorigenesis in BE.
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December 2012

A case of duodenal anisakiasis with duodenal ulcer.

Chonnam Med J 2012 Apr 26;48(1):73-5. Epub 2012 Apr 26.

Department of Internal Medicine, Seonam University College of Medicine, Seonam University Namkwang Hospital, Gwangju, Korea.

Humans can be incidentally parasitized by third-stage larvae of Anisakis species following the ingestion of raw or undercooked seafood. Acute gastric anisakiasis is one of the most frequently encountered complaints in Korea. However, duodenal anisakiasis with duodenal ulcer had not been reported in Korea, despite the habit of eating raw fish. In this case, a 47-year-old man was hospitalized because of sharp epigastric pain and repeated vomiting after eating raw fish 3 days previously. On admission, esophagogastroduodenoscopic examination revealed an active duodenal bulb ulcer. At 5 mm away from the ulcer margin, a whitish linear worm was found with half of its body penetrating the duodenal mucosa. Herein, we report this case of duodenal anisakiasis accompanied by duodenal ulcer.
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April 2012

Bacterial diversity and structural changes of oyster shell during 1-year storage.

Microb Ecol 2009 Feb 2;57(2):221-8. Epub 2008 Sep 2.

Division of Applied Life Science (BK21 Program), Gyeongsang National University, Chinju, 660-701, Republic of Korea.

We examined the biodiversity of bacteria associated with oyster-shell waste during a 1-year storage period using 16S ribosomal DNA analysis. Temperature variation and structural changes of oyster shell were observed during storage. Initial and final temperatures were at 16-17 degrees C, but a high temperature of about 60 degrees C was recorded after approximately 6 months of storage. The crystal structure and nanograin of the oyster shell surface were sharp and large in size initially and became gradually blunter and smaller over time. Phylogenetic analysis revealed that Firmicutes were dominant in the oyster-shell waste initially, during the high-temperature stage, and after 1 year of storage (making up >65% of the biodiversity at all three sampling times). Bacillus licheniformis was presumed as the predominate Firmicutes present. These bacteria are likely to have important roles in the biodegradation of oyster shell.
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February 2009

Determination of metallic impurities in a silicon wafer by local etching and electrothermal atomic absorption spectrometry.

Anal Sci 2003 Jul;19(7):1051-4

R & D Center, LG Siltron Inc., 283 Imsoo-dong, Gumi, 730-350, Korea.

An etching technique for the determination of the metallic impurities distribution in silicon wafers has been developed. An area of 10 mmphi and 10 microm depth was etched by 100 microL of an etching solution with a HF and HNO3 mixture. The acid matrix was evaporated on the wafer surface by IR lamp illumination and vacuum exhaust. Metallic impurities remaining on the wafer surface were redissolved into the collection solution, which was measured by electrothermal atomic absorption spectrometry (ET-AAS). The recovery invested by local etching/ET-AAS was within 95 - 112% for Fe, Cu and Ni. The detection limit (3sigma) for Fe, Cu and Ni in silicon was 1 x 10(13) atoms/cm3. To confirm the applicability, local etching was applied to evaluate the effects of metallic impurities in a gettering study and the electronic properties of semiconductor devices. It was found that local etching is a useful sample preparation technique for the analysis of metallic impurities in a specific area on a silicon wafer.
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July 2003