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  • Author: H.G. Park, x
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Summary

We have investigated freshwater cyprinid fish for its current infection status with plerocercoid of ligulid tapeworm in the Republic of Korea. A total of 6,049 (517 Euiam Lake and 4,071 Hoengseong Lake in Gangweon-do and 1,461 Chungju Lake in Chungcheongbuk-do) fish were examined by dissecting the peritonial cavity between March 2015 and December 2016. Totally 45 (0.74 %) fish in of 5 (26.3 %) species (8 Squalidus japonicus coreanus, 6 Squalidus gracilis majimae, 7 Opsariichthys uncirostris amurensis, 15 Zacco platypus and 9 Erythroculter erythropterus) were infected with plerocercoids of ligulid tapeworm. The infection density with plerocercoids in Erythroculter erythropterus was 12 – 26 per fish infected in Erythroculter erythropterus, and 1 – 2 in other 4 fish species. The plerocercoid was ivory-white and 26.2 – 57.8 cm long. The prevalence value in this survey was 0.9 % (45/6,049). The genetic analysis in this study was conducted to identify plerocercoid species. Based on genetic analysis with data in GenBank, these plerocercoids were identified as the L. intestinalis.

Abstract

Particulates exhausted from diesel engine are imperfectly burned carbons of oil and are difficult to re­move. Oil is organic compounds composed of hydrogen and carbon and has relatively long chain that the numbers of carbons are from 10 to 18. When a short chain oil is used in diesel engine, the combustion efficiency could be better than that used a long chain oil, and then particulates could be reduced. In this paper, in order to increase combustion efficiency and reduce particle materials exhausted from diesel engine, an experimental works to crack the long chain oil to short chain oil by streamer plasma induced in oil is conducted. The discharge electrode geometries of a needle and a plate are tested. AC high voltage with 60 Hz of frequency is supplied for electrical discharge in oil. Fresh oil and cracked oil are analyzed with GC-MS (Gas Chromatograph-Mass). From the results, Oil cracking is observed at 14 kV, however, it can not observed below 14 kV in two reactor tested. Operating time is not significantly influence to oil cracking. With derived by the results by GC/MS, it is confirmed that a long chain oil with a heavy molecule weight was changed to a short chain oil with a light molecule weight.

Abstract

A twelve-month field survey of the genus Pseudo-nitzschia was carried out in Chinhae Bay, an area of commercial culturing and harvesting of oysters. The study used molecular DNA probes and WGA lectins to determine monthly species abundance and relate this to environmental conditions and nutrients. Ten species of Pseudo-nitzschia were identified during the study: Pseudo-nitzschia multiseries, P. pungens, P. multistriata, P. delicatissima, P. cuspidata, P. subfraudulenta, P. granii, P. fraudulenta, P. subpacifica, and an unidentified Pseudo- nitzschia sp. Of the Pseudo-nitzschia species, Pseudo-nitzschia pungens had the highest cell abundance, followed by P. delicatissima and P. multistriata. The presence of Pseudo-nitzschia multiseries was correlated with domoic acid (DA) contamination of shellfish, for example at Stations (Stn) P2, P3 and P4. Where Pseudo-nitzschia multiseries was recorded, trace levels of DA were detected, but at Stn P1 neither Pseudo-nitzschia multiseries nor DA were detected during the period of this study. Pseudo-nitzschia multiseries is regarded as the most toxic of the DA-producing species known in Korea. Korean isolates of Pseudo-nitzschia multiseries were strongly labeled by WGA lectin and the Pseudo-nitzschia multiseries species-specific DNA probe, and were distributed in seawater of lower temperature (≤ 15 °C) and linked with lower nutrient concentrations, although cell numbers were significantly lower than for Pseudo-nitzschia pungens. The use of the probes puD1, deD1 and frD1 led to the recognition of Pseudo-nitzschia pungens, P. delicatissima and P. fraudulenta, respectively. Although Pseudo-nitzschia species varied depending on month and sampling site, most were present at higher cell densities in lower temperature waters except for Pseudo-nitzschia multistriata. It was demonstrated that these methods provide a simple and rapid technique for the identification of a variety of Pseudo-nitzschia in Korean waters, and offer the opportunity for a series of real-time species detection in the future.

Abstract

Quercus acutissima is a large deciduous tree of hillsides ranging from South Korea to Japan. It occurs in many plant communities, often as a pioneer species in monospecific stands which colonized gaps after gap formation. This study used multilocus allozyme genotypes mapped from two disturbed populations near farm houses in southern Korea to compare our results with previous studies conducted on undisturbed populations of trees in southern Korea. Coancestry measures (fij), RIPLEY’s L-statistics, and WRIGHT’s F-statistics were then calculated to examine the distribution of individuals and spatial genetic structure both within and between populations. RIPLEY’s Lstatistics indicated significant aggregation of individuals at interplant distances. A weak but significant positive fine-scale genetic structure at 10 m distance was detected in the two disturbed populations, which is consistent with the structure found in an inland, disturbed population in southern Korea. Estimates of near-distance fij in the two populations (0.020 and 0.036) were considerably lower than that expected for half-sibs (0.125) under random mating, suggesting secondary seed dispersal and substantial overlap of seed shadows. The levels of genetic diversity within the two disturbed populations of Q. acutissima were found to be comparable to the within-mean for populations of other oak species. Significant deficits of heterozygosity were detected in both populations, probably due to several parent-offspring and sib matings. Finally, a significant but low differentiation between the two disturbed populations of Q. acutissima was found, which is likely to be attributable to long-distance pollen movement by wind, which should enhance homogeneity of allele frequencies between adjacent local oak populations.