• Toxicological Research
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• v.6 no.2
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• pp.167-182
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• 1990

Dietary restriction (caloric restriction) is the only intervention which has been reliably shown to extend the maximum life span of warm-blooded animals and delay the many phenomena associated with aging. It is also one of the most effective modulators of toxicity, especially cancer endpoints. In spite of the known modulator effects of caloric restriction, the biological mechanisms responsible for these effects had not been in vestigated until recently. The National Center for Toxicological Research (NCTR), in a collaborative effort with the National Institute of Aging (NIA), initiated a project whereby nine (9) combinations of rodent species/strains and diets were fed both restricted and ad libitum. The NIA's initiative was to identify biomarkers of aging whereas NCTR's initiative was to identify the biological effects associated with the profound effects caloric restriction has in protecting against both spontaneous (age-related) and chemically-induced toxic endpoints. Independent of sex or species, caloric restriction has similar effects on body temperature, oxygen consumption and $CO_2$production. Caloric restriction also decreased lipid glycolysis and metabolism in rats and mice, which suggest decreased production of metabolites which could lead to fatty acid epoxide formation. The age-associated loss of ciradian regulation of intermediate enzymes is also significantly reduced. Moreover, caloric restriction reduced the age-associated feminization of sexually dimorphic liver isozymes, increased several glucocorticoid responsive isozymes, elevated glucagon/insulin ratios, produced less microsomal superoxide and enhanced the capacity for utilzing detoxicating metabolic pathways. Calorically restricted rats have less than half the number of aflatoxin ($AFB_1$)-DNA adducts than ad libitum animals and urinary excretion of $AFB_1$ was increased significantly. Finally, DNA repair mechanisms are enhanced and oncogene expression is decreased in calorically restricted animals.

• Korean Journal of Veterinary Research
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• v.39 no.3
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• pp.665-671
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• 1999

The aim of this study was to establish selective hepatic artery catheterization technique through percutaneous femoral artery puncture and to offer digital subtraction angiography (DSA) of hepatic artery in beagle dogs. Percutaneous femoral artery puncture was performed with Sheldinger's method. Microferret$^{TM}$-18 Infusion catheter(William, Cook, Europe) was introduced into abdominal aorta. Then, under fluoroscopy, iopamidol 370(Bracco, Italy) was injected to identify celiac artery and 'J' shaped guide wire was introduced into celiac artery. Catheter could be introduced into celiac artery through guide wire. In this manner, catheter was located at the insertion of hepatic artery and DSA was performed. In DSA of beagle dogs, hepatic artery which was divided into lateral branch, right-medial branch, right-lateral branch of hepatic artery, cystic artery and gastroduodenal artery was opacified without superimposition of any other body structure and so was the parenchyme of liver afterward. In autopsy angiographic finding of resected liver, cystic artery, caudate branch, lateral branch, right-medial branch, right-lateral branch and quadrate branch of hepatic artery were identified. It was concluded that selective hepatic artery catheterization technique was a minimally invasive method that facillitated the approach of hepatic artery and DSA was an excellent tool to visualize the vessle of liver in dogs.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.155-161
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• 1999

The land reclamation area of Saemangeum(Kunsan) is located between 126$^{\circ}$10' E~126$^{\circ}$50' E and 35$^{\circ}$35' N~356$^{\circ}$05'N at the western coast of the Korean peninsula. The are many small islands including extensive areas of semi-diurnally flooded and dewatered tidal flats. The reclamation area of Saemangeum has a range of 5.6m spring tide and the maximum tidal current speed is about 1.41m s-1 in ordinary spring tide. Most of the sediments deposited on the tidal flats are transported from the Geum river, the Manjyung river and The Dongjin river. The soil in this area consists of silty sand with the depth of 10m to 30m . The wind in winter is strong from the direction of northwest. In the past twenty years, land reclamation projects for agricutural purpose or industrial cocmplex have been mostly implemented along the western coast of Korea. Saemangeum coastal area is being constructed the33km sea dike and 40, 100ha reclamation area. The purpose of this study is to find the residual circulations in four seasons after the dike construction by a robust diagnostic and prognostic numerical model. Heat flux at the sea surface in January ,May , August , October was asopted on the basis on the daily inflow of solar radiation at the earth surface, assuming an average atomospheric transmission and no clouds , as a function of latitude and time of year(George L.P.J.E William, 1990). The discharge from the Geum , the Mankyung and the Dongjin rivers was adopted on the basis of experience formula of river flow in January , May ,August, October (The M. of C.Korea, 1993) . Water temperature and salinity along the open boundaries are obtained from the results of field observation s.

• Korean Journal of Remote Sensing
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• v.20 no.3
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• pp.175-188
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• 2004

The objectives of this study were to estimate leaf area index (LAI) as a function of image-derived vegetation indices, and to compare measured and estimated LAI to the results of crop model simulation. Soil moisture, crop phenology, and LAI data were obtained several times during the 2001 growing season at monitoring sites established in two central Missouri experimental fields, one planted to com (Zea mays L.) and the other planted to soybean (Glycine max L.). Hyper- and multi-spectral images at varying spatial. and spectral resolutions were acquired from both airborne and satellite platforms, and data were extracted to calculate standard vegetative indices (normalized difference vegetative index, NDVI; ratio vegetative index, RVI; and soil-adjusted vegetative index, SAVI). When comparing these three indices, regressions for measured LAI were of similar quality $(r^2$ =0.59 to 0.61 for com; $r^2$ =0.66 to 0.68 for soybean) in this single-year dataset. CERES(Crop Environment Resource Synthesis)-Maize and CROPGRO-Soybean models were calibrated to measured soil moisture and yield data and used to simulate LAI over the growing season. The CERES-Maize model over-predicted LAI at all corn monitoring sites. Simulated LAI from CROPGRO-Soybean was similar to observed and image-estimated LA! for most soybean monitoring sites. These results suggest crop growth model predictions might be improved by incorporating image-estimated LAI. Greater improvements might be expected with com than with soybean.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.1-7
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• 2021

Purpose: The aim of this study was to assess artifacts generated in cone-beam computed tomography (CBCT) of 3 types of dental implants using 3 metal artifact reduction (MAR) algorithm conditions (pre-acquisition MAR, post-acquisition MAR, and no MAR), and 2 peak kilovoltage (kVp) settings. Materials and Methods: Titanium-zirconium, titanium, and zirconium alloy implants were placed in a dry mandible. CBCT images were acquired using 84 and 90 kVp and at normal resolution for all 3 MAR conditions. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the intensity of artifacts for each combination of material and settings. A 3-factor analysis of variance model with up to 3-way interactions was used to determine whether there was a statistically significant difference in the mean intensity of artifacts associated with each factor. Results: The analysis of all 3 MAR conditions showed that using no MAR resulted in substantially more severe artifacts than either of the 2 MAR algorithms for the 3 implant materials; however, there were no significant differences between pre- and post-acquisition MAR. The 90 kVp setting generated less intense artifacts on average than the 84 kVp setting. The titanium-zirconium alloy generated significantly less intense artifacts than zirconium. Titanium generated artifacts at an intermediate level relative to the other 2 implant materials, but was not statistically significantly different from either. Conclusion: This in vitro study suggests that artifacts can be minimized by using a titanium-zirconium alloy at the 90 kVp setting, with either MAR setting.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2334-2340
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• 2021

Radioactive particle tracking (RPT) is a minimally invasive nuclear technique that tracks a radioactive particle inside a volume of interest by means of a mathematical location algorithm. During the past decades, many algorithms have been developed including ones based on artificial intelligence techniques. In this study, RPT technique is applied in a simulated test section that employs a simplified mixer filled with concrete, six scintillator detectors and a¹³⁷Cs radioactive particle emitting gamma rays of 662 keV. The test section was developed using MCNPX code, which is a mathematical code based on Monte Carlo simulation, and 3516 different radioactive particle positions (x,y,z) were simulated. Novelty of this paper is the use of a location algorithm based on a deep learning model, more specifically a 6-layers deep rectifier neural network (DRNN), in which hyperparameters were defined using a Bayesian optimization method. DRNN is a type of deep feedforward neural network that substitutes the usual sigmoid based activation functions, traditionally used in vanilla Multilayer Perceptron Networks, for rectified activation functions. Results show the great accuracy of the DRNN in a RPT tracking system. Root mean squared error for x, y and coordinates of the radioactive particle is, respectively, 0.03064, 0.02523 and 0.07653.

• Journal of Veterinary Science
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• v.25 no.5
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• pp.60.1-60.6
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• 2024

Importance: Alzheimer's disease (AD) is the most common cause of dementia in the elderly with the incidence rising exponentially after the age of 65 years. Unfortunately, effective treatments are extremely limited and definite diagnosis can only be made at autopsy. This is in part due to our limited understanding of the complex pathophysiology, including the various genetic, environmental, and metabolic contributing factors. In an effort to better understand this complex disease, researchers have employed nonhuman primates as translational models. Case Presentation: This report aims to describe the AD-like neuropathology in the brain of a 37-year-old female baboon (Papio hamadryas), which at the time of her death made her the oldest hamadryas baboon at any member institution of the Association of Zoos and Aquariums. A diagnostic necropsy was performed, and the brain was evaluated for neurodegenerative disease. Frequent amyloid-β deposits were identified, consistent with what has been described in other geriatric nonhuman primates. Phospho-tau pathology, including neurofibrillary tangles, a feature not well-described in other primate models, was also abundant. Conclusions and Relevance: Our results suggest that more detailed, prospective, longitudinal studies are warranted utilizing this particular species to see if they represent a viable model for human brain aging.

• Korea journal of population studies
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• v.33 no.2
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• pp.33-59
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• 2010

This paper intends to find the determinants of the occupational aspirations of college students in Korea. According to Wisconsin model, the occupational aspiration of youth has a statistically significant influence on his or her actual education level and occupation choice implying that the more motivated with high-level occupational aspiration will obtain the higher level of occupation. The analysis for this study is based on the survey of undergraduate students' perception, attitude and lifestyle in Korea 2004, which was conducted against 1,947 respondents, and multiple regression model was utilized. The dependent variable for occupational aspirations was measured by the Standard International Occupational Prestige Scale (SIOPS) of Donald J. Treiman. Independent variables include social capital and cultural capital as well as demographic variables, socio-economic status, and human capital variables. Social capital variable was measured by the position generator scale of Nan Lin and Mary Dumin, and cultural capital variable was done to our original index. This study shows that social and cultural capitals are factors having significant influence on occupational aspiration, in addition to the well-known factors such as gender, human capital and the occupation of father.

• The Magazine of the IEIE
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• v.29 no.6
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• pp.76-80
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• 2002

'Liquid Crystal의 상전이(相轉移)와 광학적 이방성(異方性)이 1888년과 1889년 F. Reinitzer와 O. Lehmann에 의해 Monatsch Chem.과 Z.Physikal.Chem.에 각각 보고된 후 부터 제2차 세계대전이 끝난 뒤인 1950년대 까지는 Liquid Crystal을 단지실험실에서의 기초학문 차원의 연구 대상으로만 다루어 왔다. 1963년 Williams가 Liquid Crystal Device로는 최초로 특허 출원을 하였으며, 1968년 RCA사의 Heilmeier등은 Nematic 액정(液晶)에 저주파(低周波) 전압(電壓)을 인가하면 투명한 액정이 혼탁(混濁)상태로 변화하는 '동적산란(動的散亂)'(Dynamic Scattering) 현상을 이용하여 최초의 DSM(Dynamic Scattering Mode) LCD(Liquid Crystal Display)를 발명하였다. 비록 150V 이상의 높은 구동전압과 과소비전력의 특성 때문에 실용화에는 실패하였지만 Guest-Host효과와 Memory효과 등을 발견하였다. 1970년대에 이르러 실온에서 안정되게 사용 가능한 액정물질들이 합성되고(H. Kelker에 의해 MBBA, G. Gray에 의한 Cyano-Biphenyl 액정의 합성), CMOS 트랜지스터의 발명, 투명도전막(ITO), 수은전지등의 주변기술들의 발전으로 인하여 LCD의 상품화가 본격적으로 이루어지게 되었다. 1971년에는 M. Shadt, W. Helfrich, J.L. Fergason등이 TN(Twisted Nematic) LCD를 발명하여 전자 계산기와 손목시계에 응용되었고, 1970년대 말에는 Sharp에서 Dot Matrix형의 휴대형 컴퓨터를 발매하였다. 이러한 단순 구동형의 TN LCD는 그래픽 정보를 표시하는 데에는 품질의 한계가 있어 1979년 영국의 Le Comber에 의해 a-Si TFT(amorphous Silicon Thin Film Transistor) LCD의 연구가 시작되었고, 1983년 T.J. Scheffer, J. Nehring, G. Waters에 의해 STN(Super Twisted Nematic) LCD가 창안되었고, 1980년 N. Clark, S. Lagerwall 및 1983년 K.Yossino에 의해 Ferroelectric LCD가 등장하여 LCD의 정보 표시량 증대에 크게 기여하였다. Color화의 진전은 1972년 A.G. Ficher의 셀 외부에 RGB(Red, Green, Blue) filter를 부착하는 방안과, 1981년 T. Uchida 등에 의한 셀 내부에 RGB filter를 부착하는 방법에 의해 상품화가 되었다. 1985년에는 J.L. Fergason에 의해 Polymer Dispersed LCD가 발명되었고, 1980년대 중반에 이르러 동화상(動畵像) 표시가 가능한 a-Si TFT LCD의 시제품(試製品) 개발이 이루어지고 1990년부터는 본격적인 양산 시대에 접어들게 되었다. 1990년대 초에는 STN LCD의 Color화 및 대형화(大型化) 고(高)품위화에 힘입어 Note-Book PC에 LCD가 본격적으로 적용이 되었고, 1990년대 후반에는TFT LCD의 표시품질 대비 가격경쟁력 확보로 인하여 Note-Book PC 시장을 독점하기에 이르렀다. 이후로는 TFT LCD의 대형화가 중요한 쟁점으로 부각되고 있고, 1995년 삼성전자는 당시 세계최대 크기의 22' TFT LCD를 개발하였다. 또한 LCD의 고정세(高情細)화를 위해 Poly Si TFT LCD의 개발이 이루어졌고, 디지타이져 일체형 LCD의 상품화가 그 응용의 폭을 넓혔으며, LCD의 대형화를 위해 1994년 Canon에 의해 14.8', 21' 등의 FLCD가 개발되었다. 대형화 방안으로 Tiled LCD 기술이 개발되고 있으며, 1995년에 Sharp에 의해 21' 두장의 Panel을 이어 붙인 28' TFT LCD가 전시되었고 1996년에는 21' 4장의 Panel을 이어 붙인 40'급 까지의 개발이 시도 되었으며 현재는 LCD의 특성향상과 생산설비의 성능개선과 안정적인 공정관리기술을 바탕으로 삼성전자에서 단패널 40' TFT LCD가 최근에 개발되었다. Projection용 디스플레이로는 Poly-Si TFT LCD를 이용하여 $25'{\sim}100'$사이의 배면투사형과 전면투사형 까지 개발되어 대형 TV시장을 주도하고 있다. 21세기 디지털방송 시대를 맞아 플라즈마디스플레이패널(PDP) TV, 액정표시장치 (LCD)TV, 강유전성액정(FLCD) TV 등 2005년에 약 1500만대 규모의 거대 시장을 형성할 것으로 예상되는 이른바 '벽걸이TV'로 불리는 차세대 초박형 TV 시장을 선점하기 위하여 세계 가전업계들이 양산에 총력을 기울이고 있다. 벽걸이TV 시장이 본격적으로 형성되더라도 PDP TV와 LCD TV가 직접적으로 시장에서 경쟁을 벌이는 일은 별로 없을 것으로 보인다. 향후 디지털TV 시장이 본격적으로 열리면 40인치 이하의 중대형 시장은 LCD TV가 주도하고 40인치 이상 대화면 시장은 PDP TV가 주도할 것으로 보는 시각이 지배적이기 때문이다. 그러나 이러한 직시형 중대형(重大型)디스플레이는 그 가격이 너무 높아서 현재의 브라운관 TV를 대체(代替)하기에는 시일이 많이 소요될 것으로 추정되고 있다. 그 대안(代案)으로는 비교적 저가격(低價格)이면서도 고품질의 디지털 화상구현이 가능한 고해상도 프로젝션 TV가 유력시되고 있다. 이러한 고해상도 프로젝션 TV용으로 DMD(Digital Micro-mirror Display), Poly-Si TFT LCD와 LCOS(Liquid Crystals on Silicon) 등의 상품화가 진행되고 있다. 인터넷과 정보통신 기술의 발달로 휴대형 디스플레이의 시장이 예상 외로 급성장하고 있으며, 요구되는 디스플레이의 품질도 단순한 문자표시에서 그치지 않고 고해상도의 그래픽 동화상 표시와 칼라 표시 및 3차원 화상표시까지 점차로 그 영역이 넓어지고 있다. <표 1>에서 보여주는 바와 같이 LCD의 시장규모는 적용분야 별로 지속적인 성장이 예상되며, 새로운 응용분야의 시장도 성장성을 어느 정도 예측할 수 있다. 따라서 LCD기술의 연구개발 방향은 크게 두가지로 분류할 수 있으며 첫째로는, 현재 양산되고 있는 LCD 상품의 경쟁력강화를 위하여 원가(原價) 절감(節減)과 표시품질을 향상시키는 것이며 둘째로는, 새로운 타입의 LCD를 개발하여 기존 상품을 대체하거나 새로운 시장을 창출하는 분야로 나눌 수 있다. 이와 같은 관점에서 현재 진행되고 있는 LCD기술개발은 다음과 같이 분류할 수 있다. 1) 원가 절감 2) 특성 향상 3) New Type LCD 개발.

• Journal of the Korean earth science society
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• v.28 no.4
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• pp.497-540
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• 2007

Late Tremadocian radiolarian faunas were first recovered from the Cow Head Group, Newfoundland, Canada. Three faunal assemblages were recognized, one from Martin Point and two from Western Brook Pond in Gros Morne National Park. These radiolarian faunas include six families, 11 genera, and 26 species. In these faunas, six genera (Archeoproventocitum, Cowheadia, Neopalaeospiculum, Protospongentactinia, Protoproventocitum and Westernbrookia) and 17 species (Archeoproventocitum nudiformum, A. retiformum, Aspiculum densum, A. jamesi, A. multistratum, A. gigantium, Cowheadia duplextesta, Neopalaeospiculum densum, N. laxum, N. transformum, Pararcheoentactinia stilla, Protospongentactinia spongiosa, Protoproventocium nazarovii, P. aitchisoni, Westernbrookia cancella, W. diversa, and W. ovata) are new. Late Tremadocian faunas are characterized by the appearance of proventocitiids and diversification of aspiculumids and reduction of protoentactiniids and echidniniids that had flourished in the early Tremadocian faunas. An examination of the biostratigraphic range of co-occurring conodonts indicates that the radiolarian faunas described here belong to the late Tremadocian, from the Lower Diversity Interval through the M. dianae Zone to the lower P. proteus Zone. With the recovery of conodonts of the R. manitouensis Zone from other localities in the study area, the correlation among Martin Point, Western Brook Pond, Broom Point, and St. Paul's Inlet strata has became more precise. Also, the middle and late Tremadocian Cow Head Group can be subdivided into the R. manitouensis Zone, the Low Diversity Interval, and the M. dianae Zone of North America. The lower P. proteus Zone of the latest Tremadocian for northern Europe is recognized in the Western Brook Pond South section.