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RISS 인기검색어
- 검색키워드
- 저자 : Samjin Choi (검색결과 32 건)
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Short-term nanostructural effects of high radiofrequency treatment on the skin tissues of rabbits.
Choi, Samjin,Cheong, Youjin,Shin, Jae-Ho,Lee, Hui-Jae,Lee, Gi-Ja,Choi, Seok Keun,Jin, Kyung-Hyun,Park, Hun-Kuk Baillière Tindall ; Springer London 2012 Lasers in medical science Vol.27 No.5
<P>The aim of this study is to quantitatively investigate the short-term effects of RF tissue-tightening treatment in in vivo rabbit dermal collagen fibrils. These effects were measured at different energy levels and at varying pass procedures on the nanostructural response level using histology and AFM analysis. Each rabbit was divided into one of seven experimental groups, which included the following: control group, and six RF group according to RF energy (20?W and 40?W) and three RF pass procedures. The progressive changes in the diameter and D-periodicity of rabbit dermal collagen fibrils were investigated in detail over a 7-day post-treatment period. The dermal tissues treated with the RF tissue-tightening device showed more prominent inflammatory responses with inflammatory cell ingrowth compared to the control. This effect showed more prominent with the passage of day after treatment. Although an increase in the diameter and D-periodicity of dermal collagen fibrils was identified immediately after the RF treatment, a decrease in the morphology of dermal collagen fibrils continued until post-operative day 7. Furthermore, RF treatment led to the loss of distinct borders. Increases in RF energy with the same pass procedure, as well as an increase in the number of RF passes, increased the occurrence of irreversible collagen fibril injury. A multiple-pass treatment at low energy rather than a single-pass treatment at high energy showed a large amount of collagen fibrils contraction at the nanostructural level.</P>
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Choi, Samjin,Cheong, Youjin,Shin, Jae-Ho,Kim, Kyung A,Bang, Jae Beum,Jin, Kyung-Hyun,Park, Hun-Kuk Cambridge University Press 2013 Microscopy and microanalysis Vol.19 No.1
<B>Abstract</B><P>This study investigated the inflammatory effect of intraoperative mitomycin C (MMC) on adhesion reformation in human rectus muscles. Ten consecutive patients who underwent medial rectus resection had their postoperative rectus muscles divided into two groups: control group (<I>n</I> = 10) and MMC group (<I>n</I> = 10). In the MMC group, the muscle was soaked for 2 min with MMC, prepared as a 0.2 mg/mL (0.02%) solution. The 0.02% MMC reactions were examined using histological analysis with hematoxylin-eosin (inflammatory response) and Masson's trichrome (collagen fibrils), immunoreactivities of cyclooxygenase-II (inflammatory response), and collagen type I and III, scanning electron microscopy analysis to quantify the diameter and D-periodicity of collagen fibrils, and atomic force microscopy analysis to quantify the diameter, D-periodicity, and adhesion force of collagen fibrils. The rectus muscles treated with 0.02% MMC showed a significantly increased inflammatory response (<I>p</I> < 0.05), increased collagen density (<I>p</I> < 0.0001), increased fibril diameter (<I>p</I> < 0.001 or <I>p</I> < 0.05), and decreased fibril adhesion force (<I>p</I> < 0.005) compared to the rectus muscles in the control group. MMC simultaneously caused an inflammatory response as well as nanostructural and biomechanical property changes in the collagen fibril network.</P>
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Choi, Samjin,Shin, Jae-Ho,Cheong, Youjin,Jin, Kyung-Hyun,Park, Hun-Kuk Cambridge University Press 2013 Microscopy and microanalysis Vol.19 No.5
<B>Abstract</B><P>This study quantitatively investigated the immediate effects of a photooxidative collagen cross-linking treatment with photosensitizer riboflavin (RF) and 370 nm UVA light in <I>in vitro</I> human corneoscleral collagen fibrils using histology, thickness, scanning electron microscopy, and atomic force microscopy analyses. Twenty 8 × 2 mm corneoscleral strips were dissected sagittally from donor tissue using a scalpel. Four parameters were investigated, including the density, thickness, adhesion force, and stiffness of corneoscleral tissues before and after the collagen cross-linking treatment. The RFUVA-catalyzed collagen cross-linking treatment led to an increase in the density of both corneal (8%) and scleral (23%) stromal collagens. However, there was no difference in corneoscleral thickness. Furthermore, RFUVA-catalyzed collagen cross-linking treatment led to an increased biomechanical response of corneosclera: 25 and 8% increases in corneoscleral stiffness, and 24 and 22% increases in corneoscleral adhesion force. The collagen cross-linking treatment through RF-sensitized photoreaction may cause structural and biomechanical changes in the collagen fibril network of the cornea and the sclera. This is due to narrowing of the interfibrillar spacing and the stromal edema.</P>
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Wavelet Packet Based Features for Insufficient Murmur Identification
Samjin Choi,Young-Kyun Shin,Youjin Cheong,Gi-Ja Lee,Hun-Kuk Park 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
This paper presents a new analysis method for aortic and mitral insufficient murmurs using wavelet packet decomposition. We proposed four diagnostic features including the maximum peak frequency, the position index of the wavelet packet coefficient corresponding to the maximum peak frequency, and the ratios of the wavelet energy and entropy information to achieve greater accuracy for detection of heart murmurs. The proposed wavelet packet based insufficient murmur analysis method was validated by some case studies. We employed a thresholding scheme to discriminate between insufficient murmurs and control sounds. Three hundred 32 heart sounds with 126 control and 206 murmur cases were acquired from four healthy volunteers and 47 patients who suffered from heart defects. Control sounds were recorded by applying a wireless electric stethoscope system to subjects with no history of other heart complications. Insufficient murmurs were grouped into two valvular heart defect categories, aortic and mitral. These murmur subjects had no other coexistent valvular defects. The proposed insufficient murmur detection method yielded a high classification efficiency of 99.78% specificity and 99.43% sensitivity.
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Cheong, Youjin,Choi, Samjin,Kim, So Jung,Park, Hun-Kuk Elsevier 2012 Materials Science and Engineering C Vol.32 No.5
<P><B>Abstract</B></P><P>This study examined the nanostructural effects of fluoride application and the acid-etching time with respect to the time elapsed after fluoride application on the primary and permanent tooth enamel layers using atomic force microscopy (AFM) and scanning electron microscopy (SEM). 192 non-carious teeth were assigned to sixteen experimental groups (n=12) including primary (1 to 8) and permanent (9 to 16) teeth, based on the timing of acid-etching with 37% phosphoric acid after an acidulated phosphate fluoride (APF) pre-treatment. The APF pre-treatment led to a decrease in surface roughness in both the primary and permanent teeth. After the APF treatment, the roughness in both primary and permanent teeth increased with the time elapsed. An acid-etching time of 40s led to increased nanostructural changes in the enamel surfaces compared to the conventional acid-etching time of 20s. This acid-etching process led to a higher roughness changes in the primary teeth than in the permanent teeth. To obtain proper enamel adhesion of a sealant after APF pre-treatment, it is important to apply acid-etching two weeks after pre-treatment. In addition, the acid-etching time should be prolonged to apply etching more quickly than two weeks, regardless of the primary and permanent teeth.</P> <P><B>Graphical abstract</B></P><P><ce:figure id='f0005'></ce:figure></P><P><B>Highlights</B></P><P>► APF pre-treatment led to decreased surface roughness in the enamel. ► After APF treatment, the more roughness increased with increasing time elapsed. ► Acid-etching should be performed two weeks after fluoride application.</P>
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인공 치아우식 발생 모델에서 디지털 방사선 공제술을 이용한 인접면 치아우식증의 진단
박정훈,최용석,황의환,이기자,최삼진,박영호,김경숙,진현석,홍경원,오범석,박헌국 대한구강악안면방사선학회 2009 Imaging Science in Dentistry Vol.39 No.1
Purpose : The purpose of the experiment was to evaluating the diagnostic ability of dental caries detection using digital subtraction in the artificial caries activity model. Materials and Methods : Digital radiographies of five teeth with 8 proximal surfaces were obtained by CCD sensor (Kodak RVG 6100 using a size #2). The digital radiographic images and subtraction images from artificial proximal caries were examined and interpreted. In this study, we proposed novel caries detection method which could diagnose the dental proximal caries from single digital radiographic image. Results : In artificial caries activity model, the range of lesional depth was 572-1,374 μm and the range of lesional area was 36.95-138.52mm². The lesional depth and the area were significantly increased with demineralization time (p<0.001). Furthermore, the proximal caries detection using digital subtraction radiography showed high detection rate compared to the proximal caries examination using simple digital radiograph. Conclusion : The results demonstrated that the digital subtraction radiography from single radiographic image of artificial caries was highly efficient in the detection of dental caries compared to the data from simple digital radiograph.
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Biomechanical Analysis of Dynamic Behavior in Human Postural Control
Youngkyun Shin,Samjin Choi 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
The functional behaviors of human standing postural control investigated when they were exposed to the long-term horizontal vibration in the sagittal plane. For complexity of human postural control, a useful alternative method which has been based on a black-box approach was taken, that is, where the feedback mechanism were lumped into a single element. The motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced continuous anterior/posterior (AP) motion. The data was analyzed, both in the time domain and in the frequency domain. The cross-correlation and the coherency function were estimated. Subjects behaved as a non-rigid pendulum with a mass and a spring throughout the whole period of the platform motion. It is consistent with the scheme that we adopted in this study.
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Kwoni, Eri,Choi, Samjin,Cheong, Youjin,Park, Ki-Ho,Park, Hun-Kuk American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7
<P>Scanning electron microscopy (SEM) was used to examine the abrasive and erosive potential of the brushing time on the dentin surface eroded by acidic soft drinks to suggest an optimized toothbrushing start time after the consumption of cola (pH 2.52) in children. Thirty-six non-carious primary central incisors were assigned to 12 experimental groups (n = 3) based on the erosive and abrasive treatment protocols. Cola exposure was used as the erosive treatment. Three brushing durations (5, 15, and 30 sec) and four brushing start times (immediately, 30 min, 60 min, and 120 min) after an erosive pre-treatment were used for the abrasive treatment. Toothbrushing after exposure to acidic soft drinks led to an increase in the open-tubule fraction and microstructural changes. Toothbrushing immediately after the erosive pre-treatment showed the largest abrasive and erosive potential on the dentin whereas that 60 and 120 min after the pre-treatment showed the least abrasive and erosive potential on the dentin. Toothbrushing for both 60 and 120 min after the pre-treatment showed similar erosive and abrasive potentials on the dentin. The brushing duration showed no effect on the erosive and abrasive potential on the dentin. Therefore, to achieve the desired tooth surface cleaning and less surface lesion on the dentin surface, toothbrushing should be performed at least 1 hour after cola consumption. Three-minute brushing after cola consumption is sufficient to prevent dental lesions, and prolonged brushing can irritate the gingival tissues.</P>
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