UBVVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group     

Sang Chul Kim  Hwankyung Sung  Hong Soo Park  Eon-Chang Sung 《中国天文和天体物理学报》2004,(4)

We present UBVI surface photometry over a 20.5' × 20.5' area of the late-type spiral galaxy NGC 300. We have derived isophotal maps, surface brightness profiles, ellipticity profiles, position angle profiles, and color profiles. By merging our I-band measurements with those of Boker et al. based on Hubble Space Telescope observations, we have obtained combined I-band surface brightness profiles for the region 0.02" < r < 500" and have decomposed the profiles into three components: a nucleus, a bulge, and an exponential disk.  相似文献   

Distinction between sortable silts and aggregated particles in muddy intertidal sediments of the East Frisian Wadden Sea, southern North Sea     

Tae Soo Chang  Burghard W. Flemming 《Sedimentary Geology》2007,202(3):453-463

In muddy sediments, the distinction between sortable silt and aggregated silty clay is important for the understanding of fine particle dynamics because both have different hydraulic properties. The Wadden Sea of the southern North Sea is severely depleted in fine-grained sediments mainly due to high energy levels along the diked coastline. As a result, muddy sediments are restricted to a narrow belt along the diked mainland shore. In the present study, the mechanism by which this mud is deposited and how floc deposition and break-up are reflected in the size distribution, has been investigated. For this purpose, surficial sediments from four intertidal nearshore transects were monitored and repeatedly sampled in the course of two years. High-resolution grain-size analyses were performed by an automated settling tube and a Sedigraph particle analyser for the sand and mud fractions, respectively.The grain size frequency distributions of the fine fractions demonstrate that the Wadden Sea muds are composed of two subpopulations, a well-sorted coarse silt and an unsorted silty clay population. A depletion of grain size around 8 μm (7 phi) demarcates the grain-size boundary between the two populations, suggesting that the finer mud population (< 8 μm) is deposited in the form of flocs and aggregates which are hydraulically equivalent to the local sands and coarser silts. Floc break-up and reconstitution in response to seasonally changing energy regimes lead to apparent seasonal sedimentation patterns in the back-barrier tidal basins. Furthermore, in the course of sample preparation, the flocs and aggregates are broken down into their constituent particles. This mechanical artefact in the size distributions produces an artificial seasonal fining/coarsening pattern. It was found that the comparison of clay/silt and < 8 μm/63 − 8 μm particle ratios are good indicators of floc behaviour. Higher ratios are found in mixed flats which are relatively protected from wave action, thereby promoting deposition of flocs. In addition, progressive size sorting and mixing processes along the transects are recognized in the frequency distributions of sands. The skewness pattern shows a landward decrease in positive values, which is exactly opposite to previously reported patterns, suggesting progressive winnowing of fine particles caused by increased wave action over the last decade. This effect of climate change further promotes depletion of fine-grained sediments in the basin.  相似文献   

Granitoids and Their Magnetic Susceptibility in South Korea   总被引：1，自引：0，他引：1  

Myung–Shik JIN  Youn Soo LEE  Shunso ISHIHARA 《Resource Geology》2001,51(3):189-203

Abstract: Magnetic susceptibility (MS) measurements were carried out for 1,120 samples in the Middle Proterozoic to Early Tertiary granitoids so far recognized in South Korea, and the lateral and spatial variation of their magnetic susceptibility, i.e., content of magnetite, is studied. The Middle Proterozoic two mica granitoids related to cassiterite (Sn) deposits in northeastern part of the Sobaegsan Massif show very low MS (less than 0.3 A‐ 10^‐3 SI unit), and the Permo‐Triassic tonalitic to granodioritic and monzonitic rocks which are barren in mineralization, distributed in the middle part of South Korea also show low MS (less than 1 A‐ 10^‐3 SI unit). On the contrary the Late Triassic to Jurassic granitoids (= Daebo granitoids) which were evolved from tonalite through granodiorite to granite, and are most widely distributed in South Korea, show a wide variation on MS. Particularly in the Andong, Igsan, Gimcheon and Geochang areas, the granitoids which are barren in mineralization, are characterized by high MS (more than 10 A‐ 10^‐3 SI unit). The Chuncheon, Jecheon, Namyang and Geumsan plutons related to molybdenite (Mo) and/or wolframite or scheelite (W), and fluorite (F) mineralizations show a little high MS (more than 3 A‐ 10^‐3 SI unit). However, more than 60% of the Daebo granitoids show low MS (less than 3 A‐ 10^‐3 SI unit) and the rest show a little high MS (more than 3 A‐ 10^‐3 SI unit). Heterogeneous distribution of magnetite content in the Daebo granitoids is considered to reflect heterogeneity of redox state of the source materials for these granitoids. The Cretaceous to Early Tertiary granitoids (= Bulgugsa granitoids) in the Gyeongsang Basin had been generally evolved in the order of tonalite, diorite, granodiorite, granite and alkali‐feldspar granites, which are closely related to base metal ore deposits, and mostly show higher MS (more than 3 A‐ 10^‐3 SI unit) than other granitoids mentioned above, although some exceptions are recognized in highly evolved alkali‐feldspar granites (SiO₂ > 76%). In contrast, as most of the highly oxidized or evolved Cretaceous granitoids distributed in areas other than the Gyeongsang Basin show lower MS than those of the Gyeongsang Basin, and appear to be magnetite free, ilmenite‐series granites, but they might be hematite bearing magnetite‐series granitoids. Highly oxidized nature of the Bulgugsa granitoids may be due to high Fe₂O₃/FeO ratio of the source materials and also high level intrusion style of the granitic magma activities. Most of the granitic rocks of the Middle Proterozoic, Permo‐Triassic and more than 60% of the Late Triassic to Jurassic (Daebo granitoids) belong to ilmenite–series, however less than 40% of the Daebo granitoids and most Cretaceous ones are magnetite–series. Thus, the granitic magma intruded in Korean Peninsula became oxidized while the intrusive ages become younger.  相似文献   

Palustrine calcretes of the Cretaceous Gyeongsang Supergroup, Korea: Variation and paleoenvironmental implications   总被引：2，自引：0，他引：2  

In Sung Paik  Hyun Joo Kim 《Island Arc》2003,12(2):110-124

Abstract Mostly siliciclastic lacustrine deposits from five stratigraphically different formations (Jinju Formation, Jindong Formation, Geoncheonri and correlative Hwasan Formations and Dadaepo Formation, in ascending order) in the Cretaceous Gyeongsang Basin, Korea, were examined for aspects of lithofacies and pedogenesis to evaluate the relative influence of geological controls on the development of palustrine calcretes (calcretes formed from palustrine deposits). The pedogenic carbonate development of palustrine deposits in the Gyeongsang Supergroup varies from formation to formation. The highest development is in the Dadaepo Formation and the second is in the Jindong Formation. The lowest development of palustrine calcretes is in the Geoncheonri and Hwasan Formations and the Jinju Formation shows intermediate development. The more negative d¹³C values and the less negative d¹⁸O values of the Dadaepo palustrine calcretes confirm greater pedogenic development in the Dadaepo Formation. That the highest development was in the Dadaepo Formation was attributed to it having the smallest lake size, indicating that lake size is critical to palustrine calcrete development in non‐carbonate lakes under semi‐arid climate. In spite of having the largest lake size, the higher development in the Jindong Formation could have resulted from its lowest lake gradient and most arid paleoclimate. The higher development of palustrine calcretes in the Late Cretaceous deposits (Jindong Formation) than the Early Cretaceous deposits (Jinju Formation) reflect overall increase in aridity throughout the period during the deposition of the Gyeongsang Supergroup. Consequently, the diverse development of the palustrine calcretes in the Gyeongsang Supergroup indicates that the lacustrine settings varied in time and space throughout the evolution of the Cretaceous Gyeongsang Basin. Such variation in palustrine calcrete development according to the change in paleoenvironments may provide a basis to interpret the relative paleoenvironmental condition of lacustrine deposits including paleoclimate, lake size and gradient.  相似文献   

Metal and transuranic records in mussel shells, byssal threads and tissues     

Minoru Koide  Dong Soo Lee  Edward D. Goldberg 《Estuarine, Coastal and Shelf Science》1982,15(6)

Bivalve shells offer several advantages over tissues for the monitoring of heavy metal pollutants in the marine environment. They are easier to handle and to store. The problem of whether to depurate the animals before analyses is avoided. The shells appear to be more sensitive to environmental heavy metals levels over the long term than do the soft parts. Of the substances examined (Cd, Cu, Zn, Pb, Ag, Ni, ²³⁸Pu and ^{239 + 240}Pu) only Pb and Pu displayed a strong covariance between soft tissue and shell concentrations. There were strong correlations between metals in the shell but not in the soft tissues in general. The byssal threads, because of their enrichment of transuranic elements and of their ease in handling, may be useful in monitoring these metals. A very weak discharge of ²³⁸Pu to marine waters adjacent to a nuclear reactor was detected in the byssal threads of mussels.  相似文献   

Accumulation and biological mixing of Peru margin sediments     

Kee Hyun Kim  William C Burnett 《Marine Geology》1988,80(3-4):181-194

Rates of sediment accumulation and biological particle mixing in eight cores from the Peru shelf have been estimated by application of uranium-series disequilibrium techniques and radiocarbon dating. Activities of ²¹⁰Pb, ²²⁶Ra, ²³⁴Th and ²³⁸U have been determined in closely spaced intervals in each sediment core. Biological particle mixing coefficients were determined via a two-box advection-diffusion steady-state mixing model based on the distribution profiles of excess ²¹⁰Pb and, in some cases, excess ²³⁴Th activities.

The sedimentation rates estimated were in the order of a few millimeters/yr except for cores enriched in phosphatic components which displayed rates a few orders of magnitude slower. Bioturbation was significant in most cores studied with the exception of one core collected from within the middle of the oxygen-minimum zone. Estimated biological mixing coefficients were in the order of 10⁰–10¹ cm² yr⁻¹ for the surface mixed layer and 10⁻¹–10⁰ cm² yr⁻¹ for the layer below. Sediment slumping appears to have affected the ²¹⁰Pb distribution of two or three of our cores.  相似文献   

Redescription of free-living marine nematode, dracograllus filipjevi allen and noffsinger, 1978 (nematoda: draconematidae) from korea     

Hyun Soo Rho  Dong-Sung Kim  Won Kim 《Ocean Science Journal》2006,41(3):163-173

A draconematid nematode species,Dracograllus filipjevi Allen and Noffsinger, 1978, is described from the washings of shallow littoral coralline algae at Guryongpo in the eastern coast of Korea. This species is recognized by the following characteristics: larger body size, number of posterior sublateral adhesion tubes (9 in male and 12-13 in female) and subventral adhesion tubes (8-9 in male and 9-10 in female), the absence of cephalic acanthiform setae on rostrum, the presence of longitudinally areolated body cuticle with dot-like punctations, the presence of some cuticular collar in swollen pharyngeal region, the shape of amphidial fovea (large, elongate, and loop-shaped in both sexes), the absence of preanal corniform setae, and the absence of lateral differentiation on narrow body region. Morphological features of the species using differential interference contrast photomicrographs are described in detail in the present work. This is the first report ofD. filipjevi in Korea.  相似文献   

Effects of several salt marsh plants on mouse spleen and thymus cell proliferation using mtt assay     

Youngwan Seo  Hee-Jung Lee  You Ah Kim  Hyun Joo Youn  Burm-Jong Lee 《Ocean Science Journal》2005,40(4):209-212

In the present study, we have tested the effects of 21 salt marsh plants on cell proliferation of mouse immune cells (spleen and thymus) using MTT assay in culture. The methanolic extracts of six salt marsh plants (Rosa rugosa, Ixeris tamagawaensis, Artemisia capillaris, Tetragonia tetragonoides, Erigeron annus, and Glehnia littoralis) showed very powerful suppressive effects of mouse immune cell death and significant activities of cell proliferationin vitro. Especially, the methanolic extract ofRosa rugosa was found to have fifteen times compared to the control treatment, demonstrating that Rosa rugosa may have a potent stimulation effect on immune cell proliferation. These results suggest that several salt marsh plants includingRosa rugosa could be useful for further study as an immunomodulating agent.  相似文献   

Numerical modeling of tide and tidal current in the kangjin bay,south sea,Korea     

Young Jae Ro  Kwang Young Jung  Woong Sik Jun  Hyun Min Eom 《Ocean Science Journal》2007,42(3):153-163

This study is based on a series of numerical modeling experiments to understand the tidal circulation in the Kangjin Bay (KB). The tidal circulation in the KB is mostly controlled by the inflow from two channels, Noryang and Daebang which introduce the open ocean water into the northern part of the KB with relatively strong tidal current, while in the southern part of the KB, shallowest region of the entire study area, weak tidal current prevails. The model prediction of the sea level agrees with observed records at skill scores exceeding 90 % in terms of the four major tidal constituents (M2, S2, K1, O1). However, the skill scores for the tidal current show relatively lower values of 87, 99, 59, 23 for the semi-major axes of the constituents, respectively. The tidal ellipse parameters in the KB are such that the semi-major axes of the ellipse for M2 range from 1.7 to 38.5 cm/s and those for S2 range from 0.5 to 14.4 cm/s. The orientations of the major-axes show parallel with the local isobath. The eccentricity values at various grid points of ellipses for M2 and S2 are very low with 0.2 and 0.06 on the average, respectively illustrating that the tidal current in the KB is strongly recti-linear. The magnitude of the tidal residual current speed in the KB is on the order of a few cm/s and its distribution pattern is very complex. One of the most prominent features is found to be the counter-clockwise eddy recirculation cell at the mouth of the Daebang Channel.  相似文献   

226Ra in phosphate nodules from the Peru/Chile seafloor     

Kee Hyun Kim  William C. Burnett 《Geochimica et cosmochimica acta》1985,49(4):1073-1081

²²⁶Ra and other uranium-series radionuclides have been measured in a suite of marine phosphorite samples from the upwelling area off Peru/Chile by gamma-ray spectrometry and radiochemical techniques. Our results lead to the following conclusions: (1) phosphorite nodules typically show unidirectional growth at rates of 1 to 10 mm/Kyr; (2) very young samples (less than a few thousand years) contain slight excess amounts of ²²⁶Ra probably derived from pore fluids; and (3) slow but persistent leakage of ²²⁶Ra out of phosphate nodules occurs resulting in systematically lower ²²⁶Ra ages compared to ²³⁰Th ages for samples older than about twenty thousand years. Radium fluxes from these phosphate nodules appear to be 1 to 3 orders of magnitude less than those calculated for deep-sea sediments and ferromanganese nodules.  相似文献