• 한국자기공명학회논문지
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• 제13권2호
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• pp.108-116
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• 2009

The HP0902, a homodimeric 22.1 kDa protein, has been suggested as a putative secretory protein from Helicobacter pylori, although the protein possesses no signal peptide for secretion. Since it may be associated with the virulence of the bacterium, NMR study has been initiated in terms of structural genomics. In our previous effort to assign the backbone NMR resonances, using 800MHz NMR machine at pH 7.8, the resonances from eight of the 99 residues could not be assined due to missing of the signals. In this work, to enhance the extent of assignments, a 900 MHz machine was employed and the sample pH was reduced down to 6.5. Finally, almost all signals, except for those from G9 and S24, could be clearly assigned. The determined secondary structure using the assined chemical shifts indicated that the HP0902 consists of 11 ${\beta}$-strands with no helices. In our database search result, HP0902 was predicted to interact with VacA (Vacuolating cytotoxin A), which is a representative virulence factor secreted from Helicobacter pylori. Thus, molecular interaction between HP0902 and VacA would be worthy of investigation, on the basis of the present results of NMR assignments.

• Journal of Korean Neurosurgical Society
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• 제59권1호
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• pp.58-61
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• 2016

Choroid plexus papillomas (CPPs) are relatively rare neuroectodermal tumors that develop from choroid plexus epithelial cells and are usually restricted to the ventricles. Extraventricular CPPs are very unusual and can be difficult to diagnose and treat. A 50-year-old male patient was admitted to our clinic complaining of headache and visual deterioration. Neurological examination found no abnormalities except decreased light perception and secondary optic atrophy in the left eye. Endocrine testing revealed normal levels of hormones produced by the pituitary and target glands. Magnetic resonance imaging of the brain revealed a huge regular-shaped lesion in the sellar-suprasellar region occupying the sella turcica and extending into the suprasellar cistern and planum sphenoidale. The lesion was completely excised by microsurgery via an ordinary left-sided pterional approach. Histopathology identified the lesion as a choroid plexus papilloma. Following the case report, literature on the origin, differential diagnosis, and treatment of this rare tumor is reviewed.

• Korean Journal of Radiology
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• 제24권12호
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• pp.1260-1283
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• 2023

Magnetic resonance imaging (MRI) has been extensively applied in the study of multiple sclerosis (MS), substantially contributing to diagnosis, differential diagnosis, and disease monitoring. MRI studies have significantly contributed to the understanding of MS through the characterization of typical radiological features and their clinical or prognostic implications using conventional MRI pulse sequences and further with the application of advanced imaging techniques sensitive to microstructural damage. Interpretation of results has often been validated by MRI-pathology studies. However, the application of MRI techniques in the study of neuromyelitis optica spectrum disorders (NMOSD) remains an emerging field, and MRI studies have focused on radiological correlates of NMOSD and its pathophysiology to aid in diagnosis, improve monitoring, and identify relevant prognostic factors. In this review, we discuss the main contributions of MRI to the understanding of MS and NMOSD, focusing on the most novel discoveries to clarify differences in the pathophysiology of focal inflammation initiation and perpetuation, involvement of normal-appearing tissue, potential entry routes of pathogenic elements into the CNS, and existence of primary or secondary mechanisms of neurodegeneration.

• Journal of Periodontal and Implant Science
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• 제48권6호
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• pp.360-372
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• 2018

Purpose: It has been suggested that resonance frequency analysis (RFA) can measure changes in the stability of dental implants during osseointegration. This retrospective study aimed to evaluate dental implant stability at the time of surgery (primary stability; PS) and secondary stability (SS) after ossseointegration using RFA, and to investigate the relationship between implant stability and cortical bone thickness. Methods: In total, 113 patients who attended the Tohoku University Hospital Dental Implant Center were included in this study. A total of 229 implants were placed in either the mandibular region (n=118) or the maxilla region (n=111), with bone augmentation procedures used in some cases. RFA was performed in 3 directions, and the lowest value was recorded. The preoperative thickness of cortical bone at the site of implant insertion was measured digitally using computed tomography, excluding cases of bone grafts and immediate implant placements. Results: The mean implant stability quotient (ISQ) was $69.34{\pm}9.43$ for PS and $75.99{\pm}6.23$ for SS. The mandibular group had significantly higher mean ISQ values than the maxillary group for both PS and SS (P<0.01). A significant difference was found in the mean ISQ values for PS between 1-stage and 2-stage surgery (P<0.5). The mean ISQ values in the non-augmentation group were higher than in the augmentation group for both PS and SS (P<0.01). A weak positive correlation was observed between cortical bone thickness and implant stability for both PS and SS in all cases (P<0.01). Conclusions: Based on the present study, the ISQ may be affected by implant position site, the use of a bone graft, and cortical bone thickness before implant therapy.

• 전력전자학회논문지
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• 제18권3호
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• pp.247-255
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• 2013

In this paper, a soft switching DC-DC converter for AC module type photovoltaic (PV) module integrated converter is proposed. A push-pull converter is suitable for a low voltage PV AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. However, the conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZCS) condition and turned off at zero current switching (ZVS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

• 조명전기설비학회논문지
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• 제19권6호
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• pp.16-21
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• 2005

본 논문에서는 고주파 트랜스의 여자 전류를 이용하지 않고, 인덕턴스를 이용한 새로운 부분공진 영전압 스위칭 PWM제어 고주파 절연형 풀-브리지 DC/DC 컨버터의 회로를 제안하여 그 동작 원리를 기존 방식과 특성을 비교하였다. 또한 고주파 절연 트랜스 2차측에 동기 정류용 전력용 MOSFET에 새로운 기능을 부가한 온-오프 제어방식을 이용하여 넓은 부하 범위에 걸쳐 안정된 영전압 스위칭(ZVS)동작을 실현하였다. 또한 제안한 DC-DC 컨버터의 실험장치에 의해서 실측 효율을 97[%]이상 달성하였고 직류 무정전전원의 PWM 정류기의 출력단에 이용되는 새로운 방식이 스위칭 전원으로서 유효성을 증명하였다.

• 한국생물정보학회:학술대회논문집
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• 한국생물정보시스템생물학회 2003년도 제2차 연례학술대회 발표논문집
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• pp.268-274
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• 2003

Most currently known molecular structures were determined by X-ray crystallography or Nuclear Magnetic Resonance (NMR). These methods generate a large amount of structure data, even far small molecules, and consist mainly of three-dimensional atomic coordinates. These are useful for analyzing molecular structure, but structure elements at higher level are also needed for a complete understanding of structure, and especially for structure prediction. Computational approaches exist for identifying secondary structural elements in proteins from atomic coordinates. However, similar methods have not been developed for RNA due in part to the very small amount of structure data so far available, and extracting the structural elements of RNA requires substantial manual work. Since the number of three-dimensional RNA structures is increasing, a more systematic and automated method is needed. We have developed a set of algorithms for recognizing secondary and tertiary structural elements in RNA molecules and in the protein-RNA structures in protein data banks (PDB). The present work represents the first attempt at extracting RNA structure elements from atomic coordinates in structure databases. The regularities in the structure elements revealed by the algorithms should provide useful information for predicting the structure of RNA molecules bound to proteins.

• 전기학회논문지
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• 제65권9호
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• pp.1571-1576
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• 2016

A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla in 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity. Tesla coil can generate a long streamer with several million volts of electricity as a high voltage device. It is basically consists of a voltage transformer, high voltage capacitor, spark gap, primary coil, secondary coil and toroid. It is difficult to appear in the output size of the streamer is controlled by the spark gap. The general decision method of the length of streamer is to display the electric output in accordance with the design specifications in initial development plan. Design specifications and the electric output is determined by the application of facilities. In this paper the spark gap is replaced with periodic switching semiconductor device to control output voltage easily in order to apply overvoltage protective circuit due to a secondary coil and a performance test. In these days, their main use is for entertainment and educational displays of the museum, although small coils are still used as leak detectors for high vacuum systems.

• 전기학회논문지
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• 제59권5호
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• pp.939-944
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• 2010

A high voltage air-cored helical strip/wire type pulse transformer has been fabricated for charging of a high voltage pulse forming line. As a primary coil, copper strip of 25mm width was wound helically around a MC nylon cylinder. For a secondary coil, copper enameled wire of 1mm diameter was wound around conical cylinder in order to provide insulation between two windings. The coupling coefficient of 0.53 was obtained when two coils were combined coaxially in the insulation oil filled chamber. Voltage gain and energy transfer efficiency were investigated by varying the parameters of primary and secondary circuit. Test results shows that the voltage gain increases up to 17 with increasing the primary capacitance up to 200nF. And highest energy transfer efficiency of 44% was obtained when the dual resonant operation condition was nearly satisfied. The pulse transformer developed in this study can be used for charging the middle conductor of a Blumlein pulse forming line.

• 전자공학회논문지SC
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• 제45권3호
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• pp.80-85
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• 2008

기존의 캡슐형 내시경은 공간적 제약으로 인해 약 30mW 용량의 1차 전지를 사용한다. 그러나 1차 전지를 사용하는 방식은 배터리 용량의 한계와 1회용 소모품으로 가격이 비싸다. 이러한 문제를 해결하기 위해 신체 외부에서 캡슐형 내시경에 무선으로 에너지를 전송 방식을 제안하였다. 제안된 방식은 송 수신측 양단에 LC공진 회로를 이용하여 $10{\sim}20cm$의 공극을 통해 송신측 코일에서 캡슐형 내시경으로 에너지를 전달하는 방식이다. 위치와 방향성에 상관없이 에너지 효율의 증가를 위해 수신측 코일은 페라이트 코어를 이용한 3축 권선 방식을 이용하였다. 실험에 의한 측정 결과 제안된 방식은 수신측 회로에 안정적으로 30mW의 전력을 공급할 수 있음을 확인하였다.