• Bulletin of the Korean Mathematical Society
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• v.59 no.5
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• pp.1167-1176
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• 2022

In this paper, we study Einstein-type manifolds generalizing static spaces and V-static spaces. We prove that if an Einstein-type manifold has non-positive complete divergence of its Weyl tensor and non-negative complete divergence of Bach tensor, then M has harmonic Weyl curvature. Also similar results on an Einstein-type manifold with complete divergence of Riemann tensor are proved.

• Communications of the Korean Mathematical Society
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• v.34 no.3
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• pp.863-879
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• 2019

In this paper we study the Myers' theorem for orientable Riemannian hypersurfaces under some restrictions on the mean curvature, the second-order mean curvature, or the divergence of the shape operator and give some estimates for the diameter of such hypersurfaces.

• Korean Journal of Mathematics
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• v.16 no.2
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• pp.157-163
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• 2008

Using informations of subsets of divergence points and the relation between members of spectral classes, we give another complete decomposition of spectral classes generated by lower(upper) local dimensions of a self-similar measure on a self-similar Cantor set with full information of their dimensions. We note that it is a complete refinement of the earlier complete decomposition of the spectral classes. Further we study the packing dimension of some uncountable union of distribution sets.

• Bulletin of the Korean Mathematical Society
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• v.54 no.3
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• pp.817-824
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• 2017

In this paper, we prove that a gradient shrinking Ricci soliton is rigid if the radial curvature vanishes and the second order divergence of Bach tensor is non-positive. Moreover, we show that a complete non-compact gradient expanding Ricci soliton is rigid if the radial curvature vanishes, the Ricci curvature is nonnegative and the second order divergence of Bach tensor is nonnegative.

• The Korean Journal of Applied Statistics
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• v.18 no.2
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• pp.395-410
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• 2005

For the analysis of large tables formed by many categorical variables, we suggest a method to group the variables into several disjoint groups in which the variables are completely associated within the groups. We use a simple function of Kullback-Leibler divergence as a similarity measure to find the groups. Since the groups are complete hierarchical sets, we can identify the association structure of the large tables by the marginal log-linear models. Examples are introduced to illustrate the suggested method.

• Parasites, Hosts and Diseases
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• v.57 no.1
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• pp.55-60
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• 2019

This study was undertaken to determine the complete mitochondrial DNA sequence and structure of the mitochondrial genome of Spirometra ranarum, and to compare it with those of S. erinaceieuropaei and S. decipiens. The aim of this study was to provide information of the species level taxonomy of Spirometra spp. using the mitochondrial genomes of 3 Spirometra tapeworms. The S. ranarum isolate originated from Myanmar. The mitochondrial genome sequence of S. ranarum was compared with that of S. erinaceieuropaei (GenBank no. KJ599680) and S. decipiens (GenBank no. KJ599679). The complete mtDNA sequence of S. ranarum comprised 13,644 bp. The S. ranarum mt genome contained 36 genes comprising 12 protein-coding genes, 22 tRNAs and 2 rRNAs. The mt genome lacked the atp8 gene, as found for other cestodes. All genes in the S. ranarum mitochondrial genome are transcribed in the same direction and arranged in the same relative position with respect to gene loci as found for S. erinaceieuropaei and S. decipiens mt genomes. The overall nucleotide sequence divergence of 12 protein-coding genes between S. ranarum and S. decipiens differed by 1.5%, and 100% sequence similarity was found in the cox2 and nad6 genes, while the DNA sequence divergence of the cox1, nad1, and nad4 genes of S. ranarum and S. decipiens was 2.2%, 2.1%, and 2.6%, respectively.

• International Journal of Industrial Entomology and Biomaterials
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• v.44 no.2
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• pp.55-64
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• 2022

Bombyx shini Park & Sohn, 2002 (Lepidoptera: Bombycidae), which was listed as an endemic species in South Korea has recently been renamed as the East Asian silk moth Rotunda rotundapex Miyata & Kishida, 1990 (Lepidoptera: Bombycidae). In this study, we sequenced the complete mitochondrial genome (mitogenome) of the R. rotundapex to announce genomic characteristics and to clarify its validity with a new name. The 15,294-bp long complete mitogenome comprises a typical set of genes [13 protein-coding genes (PCGs), 2 rRNA genes, and 22 tRNA genes] and one major noncoding, A + T-rich region, with an arrangement identical to that observed in most lepidopteran mitogenomes. The A/T content of the whole mitogenome was 79.22%; however, it varied among the regions/genes as follows: A + T-rich region, 91.62%; srRNA, 84.67%; lrRNA, 83.01%; tRNAs, 81.43%; and PCGs, 77.46%. Phylogenetic analyses of 35 species in the Bombycoidea superfamily showed the sister relationship between the families Sphingidae and Bombycidae s. str., with the higher nodal support [bootstrap support (BS) = 78%]. The Saturniidae was placed as the sister to the two families, but the nodal support for this relationship was low (BS = 53%). Current R. rotundapex was placed together with previously reported con-species with the highest nodal support, forming a separate clade from Bombyx, validating that B. shini can have a new genus name, Rotunda. However, the Korean R. rotundapex showed a substantial sequence divergence at 5.28% to that originated from an individual of type locality Taiwan in 1,459-bp of COI sequences. Considering such a high sequence divergence an additional study, which includes morphological and DNA barcoding data from further extensive distributional range maybe is needed for further robust taxonomic conclusion.

• International Journal of Industrial Entomology and Biomaterials
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• v.27 no.1
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• pp.142-158
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• 2013

The bumblebee, Bombus ignitus (Hymenoptera: Apidae), is a valuable natural resource that is widely utilized for greenhouse pollination in South Korea. Understanding the magnitude of genetic diversity and geographic relationships is of fundamental importance for long term preservation and utilization. As a first step, we sequenced a partial COI gene of mitochondrial DNA (mtDNA) corresponding to the "DNA barcode" region and the complete internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA from 88 individuals collected in nine South Korean localities. The complete ITS2 sequences were longest among known insects, ranging in size from 2,034 bp ~ 2,052 bp, harboring two duplicated 112-bp long repeats. The 658-bp long mtDNA sequences provided only six haplotypes with a maximum sequence divergence of 0.61% (4 bp), whereas the ITS sequences provided 84 sequence types with a maximum sequence divergence of 1.02% (21 sites). The combination of the current COI data with those of published data suggest that the B. ignitus in South Korea and China are genetically a large group, but those in Japan can be roughly separated into another group. Overall, a very high per generation migration ratio, a very low level of genetic fixation, and no discernable hierarchical population were found to exist among the South Korean populations of B. ignitus, which suggests panmixia. This finding is consistent with our understanding of the dispersal capability of the species.

• The Plant Pathology Journal
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• v.25 no.2
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• pp.142-150
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• 2009

The complete genome sequences of RNA3 and RNA4 of the 13 different Rice stripe virus (RSV) isolates were determined and characterized in this study to address the possible causes of the recent re-emergence of RSV that affected many rice fields in Korea. The genome size of each RNA segment varied among isolates and significant differences were observed in the intergenic region. There was up to 4% average divergence in the RNA4 nucleotide sequence among 13 Korean isolates and only 1.4% in the RNA3. Phylogenetic relationships among different Korean isolates revealed that there were at least 2 types of RNA3 and 4 distinct types of RNA4 genomes present in Korea. However, Korean isolates with one type of RNA3 predominate over the other while the occurrences of the RSV Korean isolates with the 4 types of RNA4 genome were not correlated to specific geographical areas. Results further indicate that RNA4 had diverged more than RNA3 and these differences in accumulation of mutations in the individual RNA segments indicate that genetic reassortment were likely to contribute to the genetic divergence in the 13 Korean isolates. All of the Korean-RNA3 sequences except for one isolate grouped with Chinese isolates (JY and Z). In contrast, the RNA 4 sequences segregated together with either Chinese (JY and Z) and Japanese (M and T) isolates but genetic relationships of Korean isolates- RNAs 3 and 4 segments to Chinese-Y isolate were low. Altogether, these results suggest that the occurrence of mixtures of RNAs 3 and 4 genotypes in the natural population of RSV may have contributed to the sudden outbreak in Korea.

• The Plant Pathology Journal
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• v.28 no.4
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• pp.428-432
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• 2012

We determined the complete genome sequence of a Vietnamese isolate of Southern rice black-streaked dwarf virus (SRBSDV). Whole genome comparisons and phylogenetic analysis showed that the genome of the Vietnamese isolate shared high nucleotide sequence identities of over 97.5% with those of the reported Chinese isolates, confirming a common origin of them. Moreover, the greatest divergence between different SRBSDV isolates was found in the segments S1, S3, S4 and S6, which differs from the sequence alignment results between SRBSDV and Rice black streaked dwarf virus (RBSDV), implying that SRBSDV evolved in a unique way independent of RBSDV. This is the first report of a complete nucleotide sequence of SRBSDV from Vietnam and our data provides new clues for further understanding of molecular variation and epidemiology of SRBSDV in Southeast Asia.