• 한국임상수의학회지
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• 제33권1호
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• pp.10-15
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• 2016

The purpose of this study was to establish reproducible ischemic infarction model using allogenic blood clot in beagle dogs and identify induced ischemic lesion after middle cerebral artery occlusion using magnetic resonance imaging (MRI) and histopathologic findings. Twenty eight male beagle dogs with no evidence of neurologic disease were experimented. Allogenic embolus was made using a healthy beagle dog. After internal carotid artery (ICA) was exposure, 16G catheter was introduced through the ICA. The dog was administered 0.3 ml blood clot for 15 seconds followed by 3 ml of saline for 15 seconds. MRI scans were performed with 1.5T to evaluate ischemic lesion at 7 days after middle cerebral artery occlusion procedure. Evaluation parameters of MRI include location, distribution, infarction type, margin, shape, mass effect and intensity of T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), fluid attenuated inversion recovery (FLAIR) sequence, diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC). On MRI, all dogs (28/28) showed focal or multifocal lesion including telencephalon and thalamus lesions, especially caudate nucleus (24/28). These lesions had well-defined margin from adjacent brain parenchyma, none or mild mass effect and various shape. Most of dogs appeared hyperintensity on T1WI, T2WI, FLAIR, and DWI/ADC, corresponding to chronic infarction. These lesions were histopathologically confirmed atrophic changes and unstained lesion. In conclusion, MRI is the useful method to provide information about ischemic infarction in dogs and the best reproducible ischemic infarction model was developed by using allogenic blood clot.

• 지구물리와물리탐사
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• 제16권2호
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• pp.97-105
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• 2013

자기공명검층은 수소와 자기장의 상호작용을 측정, 분석하는 물리검층 방법으로 이는 저류층 평가를 위한 중요한 물리검층 방법 중 하나이다. 측정된 감쇠 신호 즉, 이완은 측정지역 내 수소의 밀도에 대한 정보와 유체의 종류에 따른 감쇠속도에 대한 정보를 포함하고 있으며, 이를 바탕으로 공극률, 투과도와 습윤도 등을 예측할 수 있다. 1950년대 초반 랜덤워크로 자기공명의 이완감쇠를 시뮬레이션한 것을 시작으로 자기공명반응에 대한 연구가 급격히 발전되었다. 이 논문에서는 자기공명 시뮬레이션의 연구 동향을 먼저 살펴 보고, 자기공명반응인 이완을 발생시키는 이완메커니즘에 대해 간단히 알아본다. 이에 기초하여 자기공명검층에서 주로 측정하는 횡축이완곡선을 자기장구배를 고려하는 경우와 고려하지 않는 시뮬레이션 방법에 대해 비교분석하고 자기장구배가 이완메커니즘 및 횡축이완곡선에 미치는 영향에 대해 분석한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.76-76
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• 2008

The resonance properties due to the surface plasmon(SP) excitation of metal nanoparticles make the nanocomposite films promising for various applications such as optical switching devices. In spite of the well-known ultra-sensitive operation of optical switches based on a guided wave, the application of nanocomposite film(NC) has inherent limitation originating from the excessive optical loss related with the surface plasmon resonance(SPR). In this study, we addressed this problem and present the experimental and theoretical analysis on the pump-probe optical switching in prism-coupled Au(1 vol.%):$SiO_2$ nanocomposite waveguide film. The guided mode was successfully generated using a near infrared probe beam of 1550 nm and modulated with an external pump beam of 532 nm close to the SPR wavelength. We extend our approach to ultra-fast operation using a pulsed laser with 5 ns pulse width. To improve the switching speed through the reduction in thermal loading effect accompanied by the resonant absorption of pump beam light, we adopted a metallic film as a coupling layer instead of low-index dielectric layer between the high-index SF10 prism and NC slab waveguide. We observed great enhancement in switching speed for the case of using metallic coupling layer, and founded a distinct difference in origin of optical nonlinearities induced during switching operation using cw and ns laser.

• 한국전자파학회논문지
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• 제25권10호
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• pp.959-965
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• 2014

본 논문에서는 그 동안 서울대학교에서 수행된 무선 전력 전송 관련 몇 가지 기본적인 연구 결과를 요약 정리하였다. 첫 번째 고찰은 무선전력 전송의 물리적인 한계에 대한 것으로, 주어진 안테나(공진기)를 이용하여 주어진 거리에서 얻을 수 있는 전송효율의 한계를 구면파 모드 이론을 이용하여 구하는 것이다. 두 번째로, 무선 전력 전송에서 사용되는 전력원의 종류에 따른 무선 전력 전송 특성 변화를 연구한 것이다. 더불어, 무선 전력 전송 안테나 사이의 거리가 변할 때 효율적인 전력전송이 가능한 방법을 제안하는 것이다. 마지막으로, 그 동안 무선 전력 전송에서 불분명하게 사용된 자기 유도방식과 자기 공명 방식의 차이를 분명히 하고자 하였으며, 결합 모드 이론을 이용하여 정량적인 구별 기준을 제시하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.261-261
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• 2007

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to- electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen. Under an external vibration acceleration of 0.1G at 120 Hz, the device exhibited a peak-to-peak voltage of 2.8 V and a power of 0.5 mw in resonance mode.

• 폴리머
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• 제37권6호
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• pp.777-783
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• 2013

본 연구에서는 실리카 나노입자를 dipodal 형태의 bis[3-(trimethoxysilyl)propyl]amine(BTMA) 실란 커플링제로 실리카 표면을 개질한 후, glycidyl methacrylate(GMA)로 표면 처리를 하여 실리카에 결합된 BTMA의 N-H기와 GMA의 epoxide기의 개환 반응에 의하여 실리카 표면에 중합용 methacrylate기를 도입하는 연구를 수행하였다. 반응시간, 반응온도 및 투입하는 GMA의 농도 변화가 BTMA의 N-H기와 GMA의 epoxide기 사이의 반응에 미치는 영향을 Fourier transform infrared spectroscopy(FTIR), elemental analysis(EA) 및 고체상태 $^{13}C$ cross-polarization magic angle spinning(CP/MAS), nuclear magnetic resonance spectroscopy(NMR)법을 사용하여 분석하였다. BTMA로 개질된 실리카를 GMA로 처리하면 실리카 입자에 결합되어 있는 BTMA의 N-H기와 GMA의 epoxide기가 열리면서 상호 반응이 일어났으며, 실험한 조건에서는 반응시간, 반응온도 및 투입하는 GMA 농도가 증가할수록 실리카 표면에 도입되는 methacrylate기가 증가함을 확인하였다.

• Journal of Korean Neurosurgical Society
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• 제39권3호
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• pp.210-214
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• 2006

Objective : We investigate risk factors of cerebral microbleeds[MBs] and their relation to concomitant magnetic resonance[MR] findings in intracerebral hemorrhages[ICHs] patients. Methods : We studied 100 consecutive patients with primary ICH over a 1-year period. These patients underwent brain MR images using 3.0-T scanners within the first week of the hemorrhage. MBs and old hematomas were located and counted by using $T2^*-weighted$ gradient-echo MR imaging. We also counted lacunes and graded white matter and periventricular hyperintensity on T1- and T2-weighted spin-echo sequences. The association between MBs and vascular risk factors and MR abnormalities were analyzed. Results : MBs were seen in 77 of ICH patients, and their number ranged from 1 to 65 lesions [mean 11, median 6]. The locations of MBs were subcortex-cortex [40.6%], basal ganglia [26.7%], thalamus [14.1 %], brain stem [12.5%], and cerebellum [9.1 %]. Analysis of clinical data revealed that age, hypertension, history of stroke, and duration of hypertension were frequently associated with MBs. The incidence of lacunes, old hematomas, and advanced leukoaraiosis was significantly higher in the MBs group, compared with the patients without MBs. Conclusion : MBs are frequently observed in ICH patients with advancing age, chronic hypertension, and previous hemorrhagic stroke, and are also closely related with morphological signs of occlusive type microangiopathy, such as lacunar infarct and severe leukoaraiosis.

• Clinical and Experimental Pediatrics
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• 제62권4호
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• pp.131-137
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• 2019

Purpose: Respiratory syncytial virus (RSV) infection can cause various neurological complications. This study aimed to investigate the RSV-associated neurologic manifestations that present with seizures. Methods: We retrospectively reviewed the medical records of patients aged less than 15 years with laboratory-confirmed RSV infections and seizures between January 2011 and December 2016 in a regional hospital in South Korea. Results: During this period, 1,193 patients with laboratory-confirmed RSV infection were identified. Of these, 35 (35 of 1,193, 2.93%; boys, 19; girls, 16; mean age: $20.8{\pm}16.6months$) presented with seizure. Febrile seizure was the most common diagnosis (27 of 35, 77.1%); simple febrile seizures in 13 patients (13 of 27, 48.1%) and complex febrile seizures in 14 (14 of 27, 51.9%). Afebrile seizures without meningitis or encephalopathy were observed in 5 patients (5 of 35, 14.3%), seizures with meningitis in 2 (2 of 35, 5.7%), and seizure with encephalopathy in 1 (1 of 35, 2.9%) patient. Lower respiratory symptoms were not observed in 8 patients. In a patient with encephalopathy, brain diffusion-weighted magnetic resonance imaging revealed transient changes in white matter, suggesting cytotoxic edema as the mechanism underlying encephalopathy. Most patients recovered with general management, and progression to epilepsy was noted in only 1 patient. Conclusion: Although febrile seizures are the most common type of seizure associated with RSV infection, the proportion of patients with complex febrile seizures was higher than that of those with general febrile seizures. Transient cytotoxic edema may be a pathogenic mechanism in RSV-related encephalopathy with seizures.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제24권2호
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• pp.154-163
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• 2021

Purpose: In children overlap of autoimmune hepatitis (AIH) and primary sclerosing cholangitis is labelled as autoimmune sclerosing cholangitis (ASC). The only prospective pediatric study showed a high prevalence of ASC by using endoscopic retrograde cholangiopancreatography. Aims of our study were to find the prevalence of ASC by using magnetic resonance cholangiography (MRC) in AIH and in non-AIH cirrhosis and to compare clinical presentation and outcome of AIH and ASC. Methods: Prospectively we did MRC in 38 children with AIH (cases) and 19 disease controls (Wilson disease). Multiple biliary strictures with proximal dilatation on MRC were taken as definitive changes of ASC. Detail clinical, laboratory parameters, liver histopathology and treatment outcome were recorded. Results: The median age of cases was 11.5 (3-18) years, 22 (57.9%) were girls and 28 (73.7%) were diagnosed as type 1 AIH. MRC was done in 11 children (28.9%) at the time of diagnosis and in 27 (71.1%) after a median follow-up of 2.5 (0.3-10) years. Abnormal MRC changes were seen in 14/38 (36.8%) of AIH and 8/19 (42.1%) of controls. However, definite changes of ASC were present in four (10.5%) children in AIH and none in controls. None of the clinical, laboratory, histological parameters and treatment response were significantly different between ASC and AIH groups. Conclusion: The prevalence of ASC in children with AIH was just 10.5%. We suggest MRC in select group with cholestatic features, inflammatory bowel disease and in those who showed poor response to immunosuppression instead of all children with AIH.

• 한국임상수의학회지
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• 제39권6호
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• pp.334-341
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• 2022

A decrease in the paraspinal muscle cross-sectional area (CSA) and functional cross-sectional area (FCSA) are associated with low back pain and disc herniation in humans. This study examined whether chronicity or lateralization of disc herniation affects the CSA and FCSA of the paraspinal muscles. The CSA and FCSA of the paraspinal muscles between the 12th and 13th thoracic vertebrae were measured in 31 dogs with intervertebral disc herniation (IVDH). The muscle CSA and FCSA were evaluated by dividing the values of the body weight, spinal disc CSA, and spinal canal CSA to offset the differences in body type between subjects. In the chronic IVDH group, the ratio of the paraspinal muscle CSA divided by the body weight was significantly lower, and fat infiltration in the paraspinal muscle was significantly higher than in the acute group. The lateralization of the disc herniation was significantly related to the changes in the paraspinal muscle CSA. In the right-sided disc herniation group, right epaxial muscle CSA was significantly reduced compared to the left-sided disc herniation group. The change in the paraspinal muscle might be a helpful indicator to localize less obvious disc pathologies and target the search for the pathology responsible for disc-related symptoms in dogs.