PURPOSES : Thermal cracking (also called low-temperature cracking) is a serious stress for asphalt pavement, especially in eastern South Korea, the northern USA, and Canada. Thermal cracking occurs when the level of thermal stress exceeds the corresponding level of low temperature strength of the given asphalt materials. Therefore, computation of thermal stress is a key factor for understanding, quantifying, and evaluating the level of low-temperature cracking resistance of asphalt pavement. In this paper, two different approaches for computing thermal stress on asphalt binder were introduced: Hopkins and Hamming’s algorithm (1967) and the application of a simple power-law function. All the computed results were compared visually; then the findings and recommendations were discussed. METHODS: Thermal stress of the tested asphalt binder was computed based on the methodology introduced in previous literatures related to viscoelastic theory. To perform the numerical analysis, MATLABTM 2D matrix-correlation and Microsoft Excel visual basic code were developed and used for the function fitting and value-minimization processes, respectively. RESULTS : Different results from thermal stress were observed with application of different computation approaches. This variation of the data trends could be recognized not only visually but also statistically. CONCLUSIONS: It can be concluded that these two different computation approaches can successfully provide upper and lower limits (i.e. boundaries) for thermal stress prediction of a given asphalt binder. Based on these findings, more reliable and reasonable thermal stress results could be provided and finally, better pavement performance predictions could also be expected.

The eggs of Asian tiger mosquito, Aedes albopictus, possess high desiccation resistance, which contribute the rapid spread of this mosquito across the world. Melanization of eggshell appear to play a role in the resistance to desiccation. Dopachrome-conversion enzyme (DCE, Yellow) significantly accelerates the melanization of the eggshell. In this study, we demonstrated functional importance of two yellow genes, AalY-g and AalY-g2, in the chorion formation. Both genes were highly induced in the ovary at 48 h after blood meal. Injection of dsRNA for AalY-g or AalY-g2 into adult females had no effect on fecundity. However, the outermost colorless exochorion of the eggs obtained from both dsRNA-treated females was fragile and peeled off in places, and melanization of the endochorion was obviously delayed by several hours. In addition, unlike eggs from control females which acquired high desiccation resistance between 18 and 24 h after oviposition (HAO), 60-70% 24 HAO eggs from either AalY-g- or AalY-g2-deficient females were collapsed when they were moved to an air-dry condition, and the desiccation resistance was not increased in later stages of embryonic development analyzed. TEM analysis revealed that abnormal morphology and ultrastructure of the endochorion, particularly outer-endochorion, in the 24 HAO and older eggs from either AalY-g-and AalY-g2-deficient females. These results indicate that AalY-g and AalY-g2 are required for morphology and formation of the endochorion (outer-endochorion), a structure that appears to be critical for desiccation resistance of the Ae. albopictus eggs. This work was supported by NRFs (NRF-2015R1A6A3A04060323 and NRF-2018R1A2B6005106)

Insect cuticle or exoskeleton is an extracellular matrix consisting of three major morphologically distinct layers, the water-proofing envelope, the protein-rich epicuticle and the chitin/protein-rich procuticle. To accommodate growth, insects must periodically replace their cuticles in a process called “molting or ecdysis”. During each molt cycle a new cuticle is deposited simultaneously with degradation of the inner part of the chitinous procuticle of the old one by molting fluid enzymes including epidermal chitinases. In this study, we show a novel role for an epidermal endochitinase containing two catalytic domains, TcCHT7, from the red flour beetle, Tribolium castaneum, belonging to a subfamily (group III) of insect chitinases in organizing chitin in the newly forming cuticle rather than in degrading chitin present in the prior one. RNAi of TcCHT7 reveals that this enzyme is nonessential for any type of molt or degradation of the chitinous matrix in the old cuticle. In contrast, TcCHT7 is required for formation of properly oriented long chitin fibers inside pore canals that are vertically oriented columnar structures, which contribute to maintain the integrity and the mechanical strength of a light-weight, yet rigid, adult cuticle. Because group III chitinases are highly conserved among insect and other arthropod species, these enzymes have a critical role in the higher ordered organization of chitin fibers for development of the structural integrity of many invertebrate cuticular extracellular matrices. This work was supported by NRFs (NRF-2015R1A2A2A01006614 and NRF-2018R1A2B6005106)

Chitin deacetylases (CDAs) are extracellular-modifying enzymes that deacetylate chitin to produce chitosan. In insects, this modification may contribute to the affinity and/or cross-linking of chitin/chitosan-like polysaccharides for a variety of structural proteins, which may lead to diverse mechanical properties of the cuticle. We previously reported the functional importance of Group I CDAs, TcCDA1 and TcCDA2, as well as the two alternative spliced isoforms of the latter, TcCDA2a and TcCDA2b from the red flour beetle, Tribolium castaneum in molting, morphology of cuticle and movement of legs. In this study, we further analyzed protein localization, ultrastructural defects of the cuticles and leg joints after RNAi of those genes. Both proteins are mainly present in the innermost procuticle region called the “assembly zone”. Loss of function of either TcCDA1 or TcCDA2 caused disorganized chitinous horizontal laminae and vertical pore canals in both the rigid and soft cuticles. RNAi of TcCDA2b affects cuticle integrity similar to that seen in RNAi of the two alternatively spliced forms of TcCDA2. In contrast, TcCDA2a-deficient adult, like that seen in the hypomorphic phenotype produced by RNAi of TcCDA1, exhibited ruptured tendons between femur and tibia, resulting in loss of locomotion ability. These results suggest that Group I CDAs play critical roles in molting, morphology, ultrastructure and mobility in T. castaneum. This work was supported by NRFs (NRF-2015R1A6A3A04060323 and NRF-2018R1A2B6005106).

최근 기온이 높아지면서 강원도 대관령 감자 재배지로 날아오는 진딧물 발생이 늘어나고 있다. 그 중 복숭아혹진딧물(Myzus persicae)은 전 세계적으로 분포하고 경제적으로 중요한 해충으로, 감자, 고추 등 노지작물에 흡즙을 통한 바이러스 매개하고 생육저하를 일으키는 피해를 주고 있다. 본 연구는 복숭아혹진딧물의 지리적 차이에 따른 집단의 유전적 관계 규명을 통해 기주식물, 메타집단 등의 군집구조 및 발생패턴을 분석하고, 이러한 요인으로 인한 진딧물 집단의 분산 및 이주 관계를 추정하였다. 최종적으로 개체들 간의 집단유전학적 관계규명을 통해 이들의 확산과 비래 양상을 규명하고자 한다.