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81.
Gi-Tak Chae Seong-Taek Yun Bernhard Mayer Kyoung-Ho Kim Soon-Young Yu 《Agricultural Water Management》2009,96(12):1819-1827
Major ions and stable isotopic (δDwater, δ18Owater, δ15Nnitrate, δ18Onitrate) measurements in concert with hydrochemical modeling were used in order to elucidate the sources and geochemical processes controlling nitrate contamination of shallow alluvial groundwater underneath a riverside agricultural field in the Buyeo area, Korea. Beneath vegetable fields in the sandy soil, the mean nitrate concentration of groundwater was 148.6 mg/L, which is significantly higher than in groundwater (mean 28.8 mg/L) beneath silty soils underneath rice paddy fields. Nitrogen isotope data indicate that synthetic fertilizers are the predominant source of groundwater nitrate in the study area. Denitrification during recharge through rice paddy soils appears to be responsible for the lower nitrate concentrations in groundwater beneath the silty soil zone. The relationship between nitrogen and oxygen isotope data of nitrate also suggests mixing of two different groundwater bodies with nitrates from the silt zone and the sand zone. Geochemical mass balance modeling on hydrochemical data indicates that various agricultural chemicals such as urea, lime, magnesium sulfate and potassium chloride dissolve in vegetable fields of the sandy zone, resulting in significant enrichment of various solutes such as K+, Ca2+, Mg2+, NO3−, SO42− and Cl−. As a consequence of over-utilization of synthetic nitrogen fertilizers, the sand zone is characterized by very high nitrate concentrations in the groundwater. This study suggests that a reduction of over-fertilization especially on vegetable fields in the riverside sand zone is required to minimize the nitrate contamination of groundwater. This study also shows that combination of geochemical and isotopic techniques with simple mass balance modeling provides information about the causes and processes of nitrate contamination of groundwater underneath a riverside agricultural field. The study also provides sustainable measures to optimize fertilization rate as an important basis of eco-friendly agriculture. 相似文献
82.
Jho Eun Hea Yun Seong Ho Lee Sung Jong Kim Hongseok Chae Heehun Kim Kangsuk 《Journal of Soils and Sediments》2020,20(4):2306-2315
Journal of Soils and Sediments - Contaminated marine sediment can be treated to satisfy the concentration-based chemical criteria, but the treated sediment could still not be appropriate for reuse.... 相似文献
83.
D S Cheon C Chae 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(5):567-571
Polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) analysis was developed for directly typing porcine reproductive and respiratory syndrome virus (PRRSV) from lung specimens without virus isolation. Twenty nine lung specimens collected from postweaning pigs were isolated for PRRSV. When the PCR products from the 29 lung specimens were digested by the restriction enzymes MluI, HincII, SacII and HaeIII, the RFLP patterns from the 29 lung specimens matched with those from the corresponding PRRSV isolates from each pig. The results suggest that the PCR-based RFLP analysis method may be useful to distinguish PRRSV isolates directly from lung specimens without virus isolation. 相似文献
84.
Hepatitis E virus (HEV) infections have been reported in pigs throughout the world but have only recently been recorded in Korean pigs. The aim of this study was to investigate whether HEV was present in archived porcine hepatic tissues collected between 1995 and 2004 using RT-PCR and immunohistochemistry and, if so, to determine the genotype of the isolates. Swine HEV was identified in the liver tissue of 42 pigs of 388 submissions (four pigs every year on average). The isolates showed genetic homology with swine and human HEV isolates identified in the United States and Japan (92.5-97%) and phylogenetic tree analysis indicated they belonged to genotype III. The study indicates that HEV is not a newly emerging virus in Korean pigs, but a pathogen that has existed in the country since at least 1995. 相似文献
85.
86.
Chan Sol Kang Chae Won Park Min Ho Jee Min Jung Paik Doo Hyun Baik 《Fibers and Polymers》2016,17(5):657-662
We synthesized a polyhydroxyamide (PHA) copolymer via low-temperature solution polymerization of 3,3'-dihydroxybenzidine with terephthaloyl chloride (80.0 mol%) and isophthaloyl chloride (20.0 mol%) in N,Ndimethylacetamide with the aid of LiCl. We prepared the PHA copolymer derivatives containing the fluorine-based substituents and investigated their solubility, cyclization behavior, and thermal properties using a differential scanning calorimeter (DSC), a thermogravimetric analyzer (TGA), and the simultaneous thermogravimetric analyzer coupled with a mass spectrometer (STA-MS). The chemical structures of the PHA copolymer and its derivatives, as well as the polybenzoxazoles (PBOs) obtained through thermal cyclization of the copolymer and derivatives, were determined by a fourier transform infrared (FT-IR) spectroscopic analysis. The PHA copolymer could be dissolved in organic solvents only with the aid of LiCl, while its derivatives were readily soluble in DMAc and NMP without LiCl at room temperature. The DSC and TGA results demonstrated that the PHA copolymer derivatives could be converted to PBOs at a lower temperature than the PHA copolymer. 相似文献
87.
Little is known of the association of enterohemorrhagic Escherichia coli O157:H7/NM (EHEC O157) with disease in naturally infected calves, although cattle have been known as a major source for EHEC O157 outbreaks in humans. In this study, we investigated the occurrence of EHEC O157 in calves associated with/without diarrhoea to examine if EHEC O157 is involved in calf diarrhoea and to characterize the isolates. Four hundred and ninety eight diarrhoeic and non-diarrhoeic young calves from 115 different farms were examined. Of 244 diarrhoeic calves, 24 (9.8%) were positive for EHEC O157, and of 254 non-diarrhoeic calves, 7 (2.8%) were positive. EHEC O157 was recovered from 12/76 (15.79%) of diarrhoeic calves less than 2-week-old, and no EHEC O157 was detected in this age group of non-diarrhoeic calves. This implicates EHEC O157 as a possible cause of the disease in naturally infected neonatal calves. The occurrence of EHEC O157 was relatively lower in the older calves (aged older than 8 weeks) and no significant difference was found in the occurrence rates between these diarrhoeic and non-diarrhoeic calves. PCR analysis of virulence markers revealed that the isolates carried various virulence genes such as Ehly, eae, stx1 and stx2, which underlines the potential importance of these attributes for the infection, colonization and possible pathogenesis of calf diarrhoea. 相似文献
88.
Hai Thi Hong Truong Jeong Ho Kim Myoung Cheoul Cho Soo Young Chae Hye Eun Lee 《European journal of plant pathology / European Foundation for Plant Pathology》2013,135(2):289-297
Phytopthora root rot in pepper (C. annuum) is caused by Phytophthora capsici L., which exhibits a high level of pathogenic diversity. Resistance to this disease is conditioned by a number of quantitative trait loci. Pyramiding resistance alleles is desirable and could be simplified by the use of molecular markers tightly linked to the resistance genes. The purpose of this study was development of molecular markers linked to Phytophthora root rot resistance. An F8 recombinant inbred line (RIL) population derived from a cross between YCM334 and a susceptible cultivar ‘Tean’ was used in combination with bulk segregant analysis utilizing RAPD and conversion of AFLP markers linked to Phytophtora root rot resistance into sequence-characterized amplified region (SCAR) markers. In conversion: one marker was successfully converted into a co-dominant SCAR marker SA133_4 linked to the trait. In bulked segregant analysis (BSA): three RAPD primers (UBC484, 504, and 553) produced polymorphisms between DNA pools among 400 primers screened. Genetic linkage analysis showed that the SCAR and RAPD markers were located on chromosome 5 of pepper. Quantitative trait locus (QTL) analysis showed that the SA133_4 and UBC553 were linked to Phytophtora root rot resistance. These markers were correctly identified as resistant or susceptible in nine promising commercial pepper varieties. These markers will be beneficial for marker-assisted selection in pepper breeding. 相似文献
89.
We have prepared the blends of poly(pentamethylene 2,6-naphthalate) (PPN) with poly(heptamethylene 2,6-naphthalate) (PHepN)
by solution blending method and investigated their glass transition behaviour, melting behaviour, and tensile properties.
It was observed that the blends of PPN/PHepN(9/1) and PPN/PHepN(1/9) have a single glass transition, reflecting a homogeneous
phase, whereas those of PPN/PHepN(7/3), PPN/PHepN(5/5), and PPN/PHepN(3/7) exhibit double glass transitions, representing
the existence of two phases. The PPN homopolymer annealed below 90 °C shows triple melting peaks (T
m1, T
m2, and T
m3). It was proved that T
m1 is attributed to melting of thin lamellar formed during secondary crystallization process, T
m2 to melting of thick lamellar created during primary crystallization, and T
m3 to melting of crystals recrystallized after melting the primary crystals at T
m2. For the annealed PHepN homopolymer, double melting endotherms (T
m1 and T
m2) were observed, caused by dual lamellar population with different thickness, i.e. T
m1 corresponding to the melting of secondary crystal and T
m2 to primary one. The Hoffman-Weeks plots, applied to the melting of primary crystals (T
m2s), indicate that the equilibrium melting temperatures of PPN homopolymer, PPN/PHepN(9/1), and PPN/PHepN(7/3) blends are same
to be 147 °C, and those of PHepN homopolymer, PPN/PHepN(1/9), and PPN/PHepN(3/7) blends to be 145 °C. Both the glass transition
and melting behaviours demonstrate that the PPN/PHepN blend system is partially miscible. In addition, both the modulus and
strength for the blends almost follow additive rule against blend composition, indicating that the PPN/PHepN blends are mechanically
compatible over all blend compositions. 相似文献
90.
Guishan Cui Hanbin Kwak Sungho Choi Moonil Kim Chul-Hee Lim Woo-Kyun Lee Joon-Soon Kim Yeora Chae 《林业研究》2016,27(3):489-503
This study demonstrated a framework to assess vulnerability of forests to climate change. We focused on how alterations of temperature and precipitation might affect forest type distributions and carbon-related functions. In particular, our framework considered three sectors of forest type distribution, net primary production, and soil carbon storage. Future projections were derived from mechanistic models for South Korean forests under the A1B scenarios of the intergovernmental panel on climate change. Forest type distributions were simulated by the Hydrological and thermal analogy group model, while the MAPSS and CENTURY1 models estimated forest carbon flux/storage. We quantified normalized vulnerability indices for each sector. Our results indicate that the overall vulnerability of forest type distribution is greater in the west central regions and southeastern inlands. The vulnerabilities of carbon flux/storage show that net primary production of South Korean forests is relatively less susceptible to climate change, but a highly vulnerable area of soil carbon storage mainly spreads from the west central to the south east region. The spatio-temporal vulnerability map with a synoptic overview from this study might be useful for policy makers in preparing adaptive measures and identifying management priorities. 相似文献