Showing papers by "Korea University published in 1987"

The Rise of Bureaucratic Authoritarianism in South Korea

Abstract: In this paper, I investigate why a bureaucratic-authoritarian (hereafter BA) regime emerged in South Korea during the early 1970s. The regime transition was the outcome of conflict among key political actors who were constrained, although not in a deterministic way, by the change in the Korean economic structure. It can be understood as the outcome of strategic choices made by key political actors among alternatives that satisfied structural constraints.

Coherent States for the Damped Harmonic Oscillator.

Abstract: Using the Caldirola-Kanai Hamiltonian for the damped harmonic oscillator, exact coherent states are constructed. These new coherent states satisfy the properties which coherent states should generally have.

Coherent states for the damped harmonic oscillator

Abstract: Using the Caldirola-Kanai Hamiltonian for the damped harmonic oscillator, exact coherent states are constructed. These new coherent states satisfy the properties which coherent states should generally have.

A study on the effect of garlic to the heavy metal poisoning of rat

Abstract: When garlic (Allium sativum) was administered to rat per os simultaneously with cadmium, methylmercury and phenylmercury to detect the protective effect against the heavy metal poisoning, accumulation of heavy metals in liver, kidneys, bone and testes were decreased, and histopathological damages and the inhibition of serum alkaline phosphatase activities by heavy metals were reduced. Such effect of garlic was not shown in the 1.7% garlic treated group and most remarkable in the 6.7% garlic treated group. The protective effect of garlic was superior to those of 2,3 dimercapto-1-propanol (BAL) and D-penicillamine (PEN), and nearly similar to those of 2,3-dimercaptosuccinic acid (DMSA) and N-acetyl-DL-penicillamine (APEN), the current remedies, while garlic was not effective as a curative agent for heavy metal poisoning. The excretion of cadmium was enhanced, more through feces than urine by garlic but the effect to the urinary excretion of cadmium was not significant comparing with DMSA or APEN when cadmium was ip injected in the first 3 days during the 12 days of oral administration of DMSA, APEN or garlic.

Stable isotope studies of the Dae Hwa tungsten-molybdenum mine, Republic of Korea; evidence of progressive meteoric water interaction in a tungsten-bearing hydrothermal system

Abstract: The Dae Hwa W-Mo mine is located approximately 100 km southeast of Seoul within the Precambrian metamorphic belt of the southern Korean peninsula. The major ore minerals, wolframite, scheelite, and molybdenite, together with minor cassiterite, chalcopyrite, and bismuthinite, occur within fissure-filling quartz veins contained within Precambrian granitic gneiss adjacent to a granitic stock of Cretaceous age. K-Ar dates of 88 + or - 2 m.y. for vein muscovite suggest a Late Cretaceous age for W-Mo mineralization.The ore mineral paragenesis can be divided into three distinct stages: a molybdenite-wolframite stage (400 degrees -315 degrees C), an iron sulfide-scheelite stage (315 degrees -230 degrees C), and a late carbonate stage (230 degrees -150 degrees C). The delta 18 O values of vein minerals are: quartz, 10.6 to 11.4 per mil; muscovite, 8.2 per mil; cassiterite, 2.9 per mil; wolframite, 4.0 to 4.3 per mil; color-zoned scheelite, -7.3 to 2.2 per mil (cores = -0.8-+2.2ppm, edges = -7.3 - -2.7ppm); siderite, 11.8 per mil; dolomite, 7.7 to 10.0 per mil; calcite, 5.7 to 9.3 per mil. There is a nearly monotonic decrease in calculated delta 18 O values of hydrothermal waters with decreasing temperature in the Dae Hwa hydrothermal system, from values of approximately 6 per mil for quartz-muscovite-molybdenite-cassiterite-wolframite deposition, to approximately 3.5 to 0.0 per mil for iron sulfide-early scheelite mineralization, to -3.5 to -7.0 per mil for late scheelite-carbonate deposition. We believe the decrease of delta 18 O water values with paragenetic time and decreasing temperature represents the progressively increasing importance of meteoric water interaction in the Dae Hwa tungsten-molybdenum hydrothermal system.The measured and calculated ranges of delta D values of inclusion fluids and hydrous minerals are: -48 to -78 per mil for quartz-muscovite-molybdenite-wolframite deposition, -60 to -67 per mil for early scheelite deposition, and -71 to -101 per mil for late scheelite-carbonate deposition. The hydrogen and oxygen isotope compositions of hydrothermal fluids at Dae Hwa are consistent with progressive mixing of a magmatic or highly exchanged meteoric water (exchanged with granitic rocks over a series of temperatures at variable, but low water to rock ratios) with an unexchanged meteoric water (delta D = -140ppm). The stable isotope composition of the tungsten-molybdenum-mineralizing fluid is controlled predominately by the host granitic rocks.Sulfur isotope analyses of sulfide vein minerals suggest an igneous source of sulfur with a delta 34 S (sub Sigma S) value near 3.0 per mil. Together with the hydrogen and oxygen isotope data, they indicate that deposition of molybdenite, wolframite, and scheelite occurred during a period of declining temperatures from 400 degrees to 230 degrees C in response to inundation of an original magmatic system with low-temperature waters of meteoric origin.Differences in mineralogy, paragenesis, and delta 18 O values of hydrothermal fluids between W-Mo (scheelite rich) and W-base metal (wolframite rich) vein-type deposits may reflect differences in their postwolframite deposition interactions with meteoric waters. The hydrothermal system at Dae Hwa may have experienced more pervasive fracturing and a higher degree of meteoric water interaction, resulting in remobilization of tungsten and a higher scheelite to wolframite ratio than lower water to rock ratio systems such as Pasto Bueno and San Cristobal, Peru, and Panasqueira, Portugal.

Stable isotope and fluid inclusion studies of gold- and silver-bearing hydrothermal vein deposits, Cheonan-Cheongyang-Nonsan mining district, Republic of Korea; Cheonan area

Abstract: The Cheonan gold-silver-mineralized area is located approximately 80 km south-southeast of Seoul within the Precambrian Gyeonggi metamorphic belt of the Korean peninsula. The Cheonbo, Ilbo, Seonggeo, Daeheung, and Chungnam mines which comprise the area are each located along gold-bearing hydrothermal quartz veins that crosscut early Proterozoic gneiss and Jurassic and Cretaceous granites. Mineralization can be separated into three distinct stages (I, II, and III) which fill preexisting fault breccia zones. Stages I and II are terminated by the onset of fracturing and brecciation events. Fluid inclusion data suggest that quartz-sulfide-bearing stages I and II each evolved from initial high temperatures (near 400 degrees C) to later lower temperatures (near 200 degrees C). Each of these stages represents a separate mineralizing system which cooled and largely abated prior to the onset of the next stage. Fluid inclusion data from stage III, a postore carbonate stage of mineralization, indicate a much cooler (240 degrees - 115 degrees C), more dilute (3-4 equiv wt % NaCl) hydrothermal system which was the result of increasing influx of meteoric waters.Sulfur isotope and fluid inclusion evidence suggests electrum-sphalerite-galena ore mineralization was deposited during stage I at temperatures between 170 degrees and 255 degrees C from fluids with salinities between 3 and 9 equiv wt percent NaCl. Fluid inclusion evidence of boiling suggests pressures of less than 100 to 300 bars. This range of pressure is consistent with a depth of mineralization near 1 km under pressure conditions that alternated between hydrostatic and lithostatic. Sulfur isotope compositions of sulfide minerals are consistent with an igneous source of sulfur with a delta 34 S (sub Sigma S) value near 5.0 per mil.Measured and calculated delta D and delta 18 O values of hydrothermal fluids in the Cheonan area ore deposits are: stage I, -122 to -127 and 6.2 to 5.9 per mil; stage II, -135 to -143 and 3.6 to 3.2 per mil; stage III, -134 to -137 and 3.4 to -7.4 per mil, respectively. These values are consistent with progressive meteoric water involvement (increasing water/rock ratios) with increasing paragenetic time. Comparison of these values with those of a deeper (2-3 km) Jurassic gold deposit (delta D = -78--102; delta 18 O = 7.7-3.8ppm) suggests a relationship between depth and water/rock ratio in Korean Au-Ag-bearing vein deposits: the Jurassic Au system has ratios of 0.001 to 0.01; the Cretaceous Au-Ag system, 0.02 to 0.5. The relationships among depth, metal contents, and water/rock ratios in these Korean Au-Ag deposits suggest differences in the hydrodynamics and postmagmatic evolutions of granitic hydrothermal systems and may be indicative of the manner in which gold and silver are scavenged from cooling plutons.

Pb and Cd levels among Korean populations.

Abstract: World-wide monitoring has been conducted on the exposure of humans to heavy metals such as lead (Pb) and cadmium (Cd). The background exposure to Cd appears to be higher among Japanese than among Americans and Europeans, while the exposure of Japanese to Pb appears to be lower than that of Americans and Europeans. Reports are, however, rather scarce on the people in other Asian countries. Surveys of the background exposure to Pb and Cd were conducted in the urban and rural areas in Korea as a joint study of two institutions, one each in Korea and Japan, in a manner so that the data should be comparable to that of a nation-wide survey in Japan. The results are described in the present report.

Geographic Variation of Esterase Isozymes in Populations of Alternaria mali on Apple Leaves

Abstract: The 500 monoconidial isolates of Alternaria mali occurring in different locations, Suweon, Cheongju, Kochang, Daegu and Jinju, Korea, in 1983 were used to examine geographic variation of esterase isozymes. The electrophoretic patterns of esterases were qualitatively and quantitatively different between isolates. The 14 different bands were detected on the basis of the decreasing electrophoretical mobility, although all bands were not present in any of the isolates. A comparison of the frequency of esterase isozymes at different bands showed marked variations among the geographic locations. The geographic distance between A. mali populations did not correlate strongly with divergence in esterase isozymes, whereas A. mali populations within a geographic feature were more closely related than populations separated by a mountain range. Zusammenfassung Geographische Veranderungen der Esteraseisoenzyme in Altemaria mali-Populationen an Apfelblattern Die 500 Einzelsporisolate von Altemaria mali, die in Suweon, Cheongju, Kochang, Daegu und Jinju, Korea, im Jahr 1983 vorgekommen waren, wurden auf die geographische Variabilitat der Esteraseisozyme gepruft. Die elektrophoretischen Muster der Esterasen waren zwischen den Isolaten qualitativ und quantitativ verschieden. In bezug auf abnehmende elektrophoretische Mobilitat wurden 14 verschiedene Banden festgestellt, die aber in keinem Isolat alle gefunden wurden. Die Haufigkeiten der Esteraseisozyme waren zwischen den geographischen Standorten deutlich variabel. Die geographischen Abstande zwischen den A. mali-Populationen korrelierten nicht stark mit der Divergenz in Esteraseisozymen, aber A. mali-Populationen innerhalb einer geographischen Lage standen in engerer Beziehung als die durch ein Gebirge getrennten Populationen.

Fluid inclusion and stable isotope studies of gold-silver-bearing hydrothermal vein deposits, Yeoju mining district, Republic of Korea

Abstract: The Yeoju gold-silver mineralized district is located approximately 60 km southeast of Seoul within the Precambrian Gyeonggi metamorphic belt of the Korean peninsula. Mines of the district are located along gold-bearing hydrothermal quartz veins that crosscut early Proterozoic augen gneiss and Mesozoic granites. Mineralization occurs in three stages (I, II, and carbonate) which fill preexisting fault breccia zones. Fluid inclusion data suggest that quartz sulfide-bearing stages I and II evolved from initial high temperatures (near 350 degrees C) to later lower temperatures (near 180 degrees C). Fluid inclusion data from the postore carbonate stage reflect much cooler (220 degrees -190 degrees C), more dilute (4-5 equiv wt % NaCl) hydrothermal fluids.Fluid inclusion and stable isotope evidence show that electrum, jalpaite, argentite, galena, and sphalerite were deposited at temperatures between 285 degrees and 185 degrees C from fluids with salinities between 14.0 and 2.6 equiv wt percent NaCl. Fluid inclusion evidence of boiling suggests pressures of less than 100 bars during portions of stage I and II mineralization, corresponding to depths between 500 and 1,250 m, assuming lithostatic and hydrostatic loads.Sulfur isotope compositions of stage I sulfide minerals decrease systematically with paragenetic time from calculated delta 34 S (sub H 2 S) values of 7.7 to 0.7 per mil. A gradual increase in the sulfate/sulfide ratio of the fluid, likely due to H 2 S loss during boiling coupled with declining temperatures, not only resulted in the systematic decrease of delta 34 S (sub H 2 S) values with time but may also have caused gold deposition by the breakdown of Au(HS) (super -) 2 .The H and O isotope values of hydrothermal fluids in the Yeoju district are consistent with meteoric water dominance approaching unexchanged meteoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship between depth and water to rock ratios: Jurassic Au systems are mesothermal and have ratios of 0.001 to 0.01 whereas Cretaceous Au-Ag systems are epithermal with ratios of 0.02 to 0.5.

Detection of hantaviruses with RNA probes generated from recombinant DNA.

Abstract: Radiolabeled RNA probes generated from cDNA clones of the M and S genome segments of Hantaan virus readily detected Hantaan virus and two isolates from Korean hemorrhagic fever patients but were less effective in detecting four other hantaviruses.

Thermotropic polyesters with main chain isomeric naphthylene, trans‐1,4‐cyclohexylene, and 2,5‐pyridinediyl units: The importance of the order of ester linkages in the mesogenic units

Abstract: Two new series of thermotropic polyesters were prepared and their mesomorphic properties were investigated. The polymers consist of triad aromatic ester-type mesogenic units with decamethylene spacers. The mesogenic units of the first series are composed of isomeric dihydroxynaphthalene moieties as the central structure flanked by two p-oxybenzoyl groups. In the second series the mesogenic units were of reversed ester linkages: the central moieties, derived from 1,4-naphthalene dicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, or 2,5-pyridinedicarboxylic acid, are connected on both sides to p-phenylene structures. Two low molecular weight model compounds with 1,4-naphthylene unit at the center of the mesogenic unit were synthesized and their mesomorphic properties were compared with those of corresponding polymers. It was observed both for the model compounds and the polymers containing 1,4-naphthylene units that the linking order of the ester group in the mesogenic unit exerted a decisive influence on the capability for the formation of a mesophase. Thermal and mesomorphic properties were investigated by DSC, on a polarizing microscope equipped with a hot-stage, and by visual observation of stir-opalescence of the melts.

The Jeoneui Gold-Silver Mine, Republic of Korea: A Geochemical Study

Abstract: Electrum-galena-sphalerite mineralization of the Jeoneui Au-Ag mine was deposited in three stages of quartz and calcite veins at temperatures between 350•Kand 180•Ž from moderate salinity fluids (4 to 14 wt%NaCI eq). Evidence of boiling indicates pressures of <150 bars, corresponding to depths of 700 and 1,800m assuming lithostatic and hydrostatic loads. Au-Ag deposition was likely a result of boiling, coupled with declining temperatures. Sulfur isotope compositions of sulfides indicate an igneous source with a ƒÂ34S value near 4•ñ. Measured and calculated hydrogen and oxygen isotope values of ore-forming fluids suggest significant meteoric water involvement. Comparison of the Jeoneui Au-Ag deposits to similar shallow Cretaceous Au-Ag deposits and a deeper Jurassic Au system reveals an inverse relationship between depth and water-to-rock ratios in Korean Au-Ag vein deposits. This indicates significant differences in the postmagmatic evolutions of these granite-related gold-bearing hydrothermal systems and may be indicative of the manner in which Au and Ag are scavenged from cooling

Reactions of N-(chlorobenzyl)alkylamines with sodium methoxide in methanol. Steric effects in elimination reactions

Abstract: Les eliminations sont quantitatives et regiospecifiques, conduisant uniquement aux alkylimines du benzaldehyde

Evaluation of rice cultivars under greenhouse conditions for adult-plant resistance to Pyricularia oryzae

Abstract: Six rice cultivars showing various types of resistance or susceptibility to Pyricularia oryzae in the field were compared under controlled environmental conditions. The resistance of the cultivars with adult-plant resistance was race-specificat early growth stage. On all cultivars tested, blast infection became increasingly reduced on either leaves of adult plants or older leaves, as observed in rice plants of different leaf stages infected with different individual races. Their increase inhost resistance was marked by an apparent transition in infection type and reduced blast severity depending on leaf age and developmental stage of plants. The ranking of disease severity of the adult-plantresistant cultivars to different races was constant during plant development, whereas that of the susceptible cultivars was differential. It is suggested that different degrees of resistance in rice cultivars may exist in seedlings and be consistently maintained during plant development, probably becoming more distinct as rice plants mature.

Serological evidence of Hantaan-related viruses in Hong Kong.

Abstract: Sera from rats (Rattus norvegicus), domestic animals and man in Hong Kong were studied by immunofluorescent antibody assay and plaque reduction neutralization tests for evidence of infection by Hantaan-related viruses. Antibody probably arising from infection by Seoul or a Seoul-like virus was detected in rat and human sera (and one pig serum), highlighting the potential public health importance of this group of viruses in Hong Kong, and in the region.

Ion channeling study of damage in neutron irradiated GaAs

Abstract: The lattice disorder in GaAs produced by fast neutrons with a fluence of 7 × 10 17 n cm −2 has been investigated with 1.5-MeV 4 He + channeling and electron spin resonance (ESR) measurements. The slight change in the 〈100〉-aligned yield for irradiated crystals indicates that each primary knock-on (PKO) produces approximately 10 3 displaced atoms. Detailed angular scans suggest a spread distribution of randomly-located defects imbedded in the lattice structure. On the other hand, As Ga 4 antisite defects per PKO estimated from ESR measurements are ~ 100. It is suggested that neighboring atoms of As Ga 4+ antisite defects are slightly distorted after the PKO event.

X-ray diffraction studies of amorphous (Fe1 − xNix)77Si10B13 alloys

Abstract: The atomic structures of single roll-quenched amorphous (Fe 1 − x Ni x ) 77 Si 10 B 13 (atomic fraction, 0 ≤ x ≤ 1 alloys have been studied by X-ray diffraction. Interference functions, atomic distribution functions, and radial distribution functions were calculated from the data. We find that the nearest neighbor distance decreases from (2.540 ± 0.005) A for x = 0 (Fe 77 Bi 10 B 13 ) to (2.490 ± 0.005) A for x =1 (Ni 77 Si 10 B 13 ), while the average coordination number of (12.53 ± 0.09) is independent of x . These results are consistent with the measured densities of the samples, which are found to increase with increasing Ni content.

Reactions of N-halogenobenzylmethylamines with triethylamine in acetonitrile. Effect of leaving group upon the imine-forming transition state

Abstract: Reactions of N-halogenobenzylmethylamines (1) and (2) with Et3N–MeCN have been investigated kinetically. Eliminations from (1) and (2) were quantitative and regiospecific, producing only benzylidenemethylamines. For the elimination reaction of (1) with Et3N, kH/kD 5.7, p 0.88, ΔH‡ 9.1 kcal mol–1, and ΔS‡–42.4 cal mol–1K–1 were determined. The transition-state structure is assessed as being highly symmetric with similar extents of Cβ–H and Nα–Cl bond cleavage, little carbanionic character, and significant π-bond formation. The structure of the transition state changes only slightly with the change in the leaving group from Cl to Br.