Solenopsis invicta, known as the red imported fire ant, is an insect native to South America. This species was unintentionally introduced into Australia, New Zealand, several Asian countries, Caribbean countries, and the United States. It shows a high survival rate and settlement potential in human-habitable and non-living areas such as tropical rainforests, disturbed areas, deserts, grasslands, and roads. In Korea, invasions of red fire ants have been reported every year since 2017, and two invasions were discovered in 2023. Quarantine agency analyzing the haplotype and colony social type of S. invicta for surveillance and control. Population genetic analysis using Microsatellite Alleleic data of 66 loci to trace the origin of the invasion. Through research cooperation with the United States Department of Agriculture (USDA), we have received samples and expanded our genetic information database. This study analyzed genetic differences between 15 invasive populations and 44 reference groups. As a result of microsatellite analysis, the domestic invasive population showed a genetic structure similar to those in Guangzhou, China, and Florida, USA.

Epoxy-based composites find extensive application in electronic packaging due to their excellent processability and insulation properties. However, conventional epoxy-based polymers exhibit limitations in terms of thermal properties and insulation performance. In this study, we develop epoxy-based siloxane/silica composites that enhance the thermal, mechanical, and insulating properties of epoxy resins. This is achieved by employing a sol–gelsynthesized siloxane hybrid and spherical fused silica particles. Herein, we fabricate two types of epoxy-based siloxane/ silica composites with different siloxane molecular structures (branched and linear siloxane networks) and investigate the changes in their properties for different compositions (with or without silica particles) and siloxane structures. The presence of a branched siloxane structure results in hardness and low insulating properties, while a linear siloxane structure yields softness and highly insulating properties. Both types of epoxy-based siloxane/silica composites exhibit high thermal stability and low thermal expansion. These properties are considerably improved by incorporating silica particles. We expect that our developed epoxy-based composites to hold significant potential as advanced electronic packaging materials, offering high-performance and robustness.

An estuary is a water ecosystem with a high abundance of the species diversity, due to a variety of complex physicochemical factors of the area where freshwater and ocean mixed. The identification of Corbicula species in the estuary environments is difficult because of various morphological characteristics. In this study, we provide taxonomic information on Corbicula species with taxonomic difficulties using morphological and genetic analysis. This study was conducted on clams from the Seomjin River-Gwangyang Bay, one of the major production area of marsh clam in Korea. As a result, we characterized Cytocrome C Oxidase subunit I (COI) sequences of the Corbicula. The 636 bp nucleotide sequences of COI have 98% homology among Corbicula species collected from 2 sites of Seomjin River-Gwangyang Bay. The phylogenetic analysis with 17 species of Corbicula indicated that most of the species collected from Seomjin River-Gwangyang Bay were brackish water clam (Corbicula japonica), and only one Asian clam (Corbicula fluminea). The evolutionary distance between C. japonica and C. fluminea was less than 0.003. Therefore, it was confirmed that C. japonica is phylogenetically closely related to C. fluminea. In 9 species of Cyrenidae, phylogenetic tree was classified into three lineages. These results will be used as an important data for an identification of clam species by providing genetic information for Corbicula species with a morphological diversity. Key words: Corbicula japonica, cytochrome c oxidase subunit I (

Two tree frogs, Dryophytes suweonensis and Dryophytes japonicus, inhabiting Korea, are morphologically similar and share the same habitats. Therefore, they are identified mainly through their calls, especially for males. Dryophytes suweonensis is registered as an endangered (IUCN: EN grade) and protected species in South Korea. Thus, it is necessary to develop a method to rapidly identify and discriminate the two species and establish efficient protection and restoration plans. We identified significant genetic variation between them by sequencing a maternallyinherited mitochondrial 12S ribosomal DNA region. Based on the sequence data, we designed a pair of primers containing 7 bp differences for high resolution melting (HRM) analysis to rapidly and accurately characterize their genotypes. The HRM analysis using genomic DNA showed that the melting peak for D. suweonensis was 76.4±0.06°C, whereas that of D. japonicus was 75.0±0.05°C. The differential melt curve plot further showed a distinct difference between them. We also carried out a pilot test for the application of HRM analysis based on immersing D. suweonensis in distilled water for 30 min to generate artificial environmental DNA (eDNA). The results showed 1.10-1.31°C differences in the melting peaks between the two tree frog samples. Therefore, this HRM analysis is rapid and accurate in identifying two tree frogs not only using their genomic DNA but also using highly non-invasive eDNA.

Namnabat et al. (cf., [Carbon Letters, https://doi.org/10.1007/s42823-020-00194-2]) employ the classical approach of Li and Chou (cf., [Int J Solids Struct 40: 2487–2499]) to the implementation of the molecular structural mechanics method using the Bernoulli–Euler beam elements for nonlinear buckling analysis of double-layered graphene nanoribbons. However, more recent studies by Eberhardt and Wallmersperger (cf., [Carbon 95: 166–180]) and others (see, e.g., [Int J Eng Sci 133: 109–131]) have shown that the classical approach of Li and Chou poorly reproduces both in-plane and out-of-plane mechanical moduli of graphene. We have shown that the 2D beam-based hexagonal material used by Namnabat et al. poorly simulates the mechanical moduli of graphene, especially the bending rigidity modulus, and this material cannot be used for the buckling simulation of graphene sheets (or nanoribbons). In addition, it is noted that in Int J Eng Sci 133: 109–131, a modification of the classical approach of Li and Chou is given which exactly reproduces both in-plane (2D Young’s modulus and Poisson’s ratio) and out-of-plane (bending rigidity modulus) mechanical moduli of graphene using beam elements.

Double-layer graphene nanoribbons promise potential application in nanoelectromechanical systems and optoelectronic devices, and knowledge about mechanical stability is a crucial parameter to flourish the application of these materials at the next generation of nanodevices. In this paper, molecular mechanics is utilized to investigate nonlinear buckling behavior, critical buckling stress, and lateral deflection of double-layered graphene nanoribbons under various configurations of stacking mode and chirality. The implicit arc-length iterative method (modified Riks method) with Ramm’s algorithm is utilized to analyze the nonlinear structural stability problem. The covalent bonds are modeled using three-dimensional beam elements in which elastic moduli are calculated based on molecular structural mechanics technique, and the interlayer van der Waals (vdW) interactions are modeled with nonlinear truss elements. An analytical expression for Young’s modulus of nonlinear truss elements is derived based on the Lennard–Jones potential function and implemented in numerical simulation with a UMAT subroutine based on FORTRAN code to capture the nonlinearity of the vdW interactions during the buckling analysis. The results indicate that the highest critical buckling stress and the minimum lateral deflection occur for armchair and zigzag chirality, both with AB stacking mode, respectively. Moreover, the critical buckling stress is found to be directly dependent on the mode shape number regardless of in-phase or anti-phase deflection direction of layers. Lateral deflection exhibits a similar trend with mode shape in anti-phase mode; however, it is decreasing by increasing mode shape number in in-phase mode.

이취미 물질인 2-MIB를 합성하는 원인종에 대한 정보는 담수생태계에서 이와 관련된 환경 및 경제적 문제를 해결하는 데 필수적이다. 본 연구는 북한강 수계에서 출현하는 Pseudanabaena strain을 분리·배양하고, 16S rDNA 염기서열을 이용하여 종 수준의 동정과 2-MIB 합성 유전자 탐색을 통해 이취미 물질 발생 잠재성을 분석하였다. 북한강 본류 지역 (삼봉리, 조암면, 의암호 지역)에서 분리한 Pseudanabaena strain은 총 11개로서 NHUA201911과 NHPD201909 strain을 제외하고 단일세포의 크기는 서로 유사하였다. 그러나 16S rDNA 계통분석을 통한 유전자 염기서 열의 유연관계를 분석한 결과, 분리된 strain들은 총 5개 종 (P. cinerea, P. yagii, P. mucicola, P. galeata, P. redekei)으 로 분류되었다 (40~55% 유사도). 2-MIB를 합성하는 mibC 유전자는 P. cinerea 07 strain (NHUA202007-07)와 P. yagii (NHUA202007-08), P. redekei (NHUA201911)에서만 발견 되었으며, 가스크로마토그래피 분석에 따라 실질적인 2-MIB 합성은 P. cinerea와 P. redekei 종에서 확인되었다. 본 연구 결과는 분자생물학적 수준에서 북한강 수역에서 발생하는 Pseudanabaena속 남조류의 다양도에 대한 증거를 제공하는 연구로서 북한강 수계에서 2-MIB 생산 원인종에 대한 중요한 정보를 제공한다.