Pyrethroid resistance in cockroach populations has been a public health challenge since the 1950s. The pyrethroid resistance in the German cockroach, Blattella germanica, is primarily attributed to knockdown resistance (kdr) mutations (E434K, C764R, and L993F) in the voltage-sensitive sodium channel gene (vssc). In this study, the pyrethroid resistance state of the German cockroach in the Republic of Korea (ROK) was assessed by analyzing the frequencies of kdr mutations using one-step PCR with total RNA. The results revealed that among the 25 populations examined, 14 populations exhibited the L993F kdr mutation, while no other mutations were detected. Since other cockroach species are also commonly found in human dwellings in ROK, the vssc genes were cloned from four other species, including Blattella nipponica, Periplaneta americana, Periplaneta japonica, and Periplaneta fuliginosa. Based on the genomic DNA (gDNA) sequences obtained from the vssc cloning, primer sets were designed to amplify the vssc fragment spanning the L993F mutation for each species and used to monitor the development of pyrethroid resistance in cockroach populations in the ROK. The study will facilitate the implementation of a nationwide monitoring program to assess cockroach resistance and select suitable alternatives.

Radioactive waste is typically disposed of using standard 200 and 320 L drums based on acceptance criteria. However, there have been no cases evaluating the disposal and suitability of 200 L steel drums for RI waste disposal. There has been a lack of prior assessments regarding the disposal and suitability of 200 L steel drums for the disposal of RI waste. Radioactive waste is transported to disposal facilities after disposal in containers, where the drums are loaded and temporarily stored. Subsequently, after repackaging the disposal drums, the repackaged drums are transported to disposal facilities by vehicle or ship for permanent disposal. Disposal containers can be susceptible to damage due to impacts during transportation, handling, and loading, leading to potential damage to the radiation primer coating during loading. Additionally, disposal containers may be subject to damage from electrochemical corrosion, necessitating the enhancement of corrosion resistance. Metal composite coatings can be employed to enhance both abrasion resistance and corrosion resistance. The application of metal composite coatings to disposal containers can improve the durability and radiation shielding performance of radioactive waste disposal containers. The thickness of radioactive waste disposal containers is determined through radioactive shielding analysis during the design process. The designed disposal containers undergo structural analysis, considering loading conditions based on the disposal environment. This paper focuses on evaluating the structural improvements achieved through the implementation of metal composite coatings with the goal of enhancing corrosion and abrasion resistance.

We study galaxies undergoing ram pressure stripping in the Virgo cluster to examine whether we can identify any discernible trend in their star formation activity. We first use 48 galaxies undergoing different stages of stripping based on Hi morphology, Hi deficiency, and relative extent to the stellar disk, from the VIVA survey. We then employ a new scheme for galaxy classification which combines Hi mass fractions and locations in projected phase space, resulting in a new sample of 365 galaxies. We utilize a variety of star formation tracers, which include g - r, WISE [3.4]-[12] colors, and starburstiness that are defined by stellar mass and star formation rates to compare the star formation activity of galaxies at different stripping stages. We find no clear evidence for enhancement in the integrated star formation activity of galaxies undergoing early to active stripping. We are instead able to capture the overall quenching of star formation activity with increasing degree of ram pressure stripping, in agreement with previous studies. Our results suggest that if there is any ram pressure stripping induced enhancement, it is at best locally modest, and galaxies undergoing enhancement make up a small fraction of the total sample. Our results also indicate that it is possible to trace galaxies at different stages of stripping with the combination of Hi gas content and location in projected phase space, which can be extended to other galaxy clusters that lack high-resolution Hi imaging.

Abstract1)Recent scandals of milk additives in several developing countries provoked controversy about quality issue of dairy products, grapping academic attention to the dairy supply chain. In this paper, we first focus on moral hazard problem of self-interested entities about the quality across the dairy supply chain, due to unobservable and unverifiable quality management efforts of all entities – including dairy producers, stations, and a final producer – and high inspection cost for the quality. Based on the identified moral hazard problem, we understand why the adoption of IoT-based tracking systems about quality produced from each entity is a must, different from RFID-based tracking systems.

Ochratoxin A, which is frequently detected in cereals and infant diets worldwidely, is a mycotoxin to damage mainly the kidney and liver. Because ochratoxin A is highly thermostable compound. it is necessary to study ways of reducing level of ochratoxin A by controling processing steps. However, food processes, including extrusion, expansion, roasting, and steam cooking, which are used in order to mitigate the contents of ochratoxin A, are known to produce polycyclic aromatic hydrocarbons, which are generated from radicals decomposed by pyrolysis. Therefore, this study analyzed the levels of 4 polycyclic aromatic hydrocarbons, benz (a) anthracene, chrysene, benzo (b) fluoranthene and benzo (a) pyrene in rice-based products made in high pressure and heating process. Rice samples were finely ground, and homogenized samples were alkaline treatement with 1 M KOH/EtOH and extracted with liquid-liquid extraction method using n-hexane. The extracted solution was pretreated with a silica cartridge. The purified solution was dried with nitrogen gas and dissolved in 1 mL of dichloromethane and injected into GC/MSD. We had overall recoveries for 4 polycyclic aromatic hydrocarbons spiked into rice samples ranging from 92.8 to 110.2%. The limit of quantitations of benz (a) anthracene, chrysene, benzo (b) fluoranthene and benzo (a) pyrene in rice-based product were 0.19 ng/g, 0.38 ng/g, 0.51 ng/g, and 0.31 ng/g, respectively. However, these 4 polycyclic aromatic hydrocarbons in all processed rice samples were not detected.

We present analyses of 1250 variable sources identied in a 20 square degree eld toward NGC 2784 by the KMTNet Supernova Program. We categorize the variable sources into three groups based on their B-band variability. The rst group consists of 31 high variability sources with their B- band RMS variability greater than 0.3 magnitudes. The second group of medium variability contains 265 sources with RMS variability between 0.05 and 0.3 magnitudes. The remaining 951 sources belong to the third group of low variability with an RMS variability smaller than 0.05 magnitudes. Of the entire 1250 sources, 4 clearly show periods of variability greater than 100 days, while the rest have periods shorter than 51 days or no reliable periods. The majority of the sources show either rather irregular variability or short periods faster than 2 days. Most of the sources with reliable period determination between 2 and 51 days belong to the low-variability group, although a few belong to the medium-variability group. All the variable sources with periods longer than 35 days appear to be very red with B􀀀V > 1.5 and V 􀀀I > 2.1 magnitudes. We classify candidates of 51 Cepheids, 17 semi-regular variables, 3 Mira types, 2 RV(B) Tauri stars, 26 eclipsing binary systems and 1 active galactic nucleus. The majority of long-term variables in our sample belong to either Mira or semi-regular types, indicating that long-term variability may be more prominent in post-main sequence phases of late-type stars. The depth of the eclipsing dips of the 26 candidates for eclipsing binaries is equivalent to 0.61 as the average relative size of the two stars in the binary system. Our results illustrate the power of the KMTNet Supernova Program for future studies of variable objects.

Isotropic pitch fibers were stabilized and carbonized for preparing carbon fibers. To optimize the duration and temperature during the stabilization process, a thermogravimetric analysis was conducted. Stabilized fibers were carbonized at 1000, 1500, and 2000℃ in a furnace under a nitrogen atmosphere. An elemental analysis confirmed that the carbon content increased with an increase in the carbonization temperature. Although short graphitic-like layers were observed with carbon fibers heat-treated at 1500 and 2000℃, Raman spectroscopy and X-ray diffraction revealed no significant effect of the carbonization temperature on the crystalline structure of the carbon fibers, indicating the limit of developing an ordered structure of isotropic pitch-based carbon fibers. The electrical conductivity of the carbonized fiber reached 3.9×10⁴S/m with the carbonization temperature increasing to 2000℃ using a four-point method.

In this study, reduced graphene oxide/polyimide (r-GO/PI) composite films, which showed significant enhancement in their electrical conductivity, were successfully fabricated. GO was prepared from graphite using a modified Hummers method. The GO was used as a nanofiller material for the preparation of r-GO/PI composites by in-situ polymerization. An addition of 20 wt% of GO led to a significant decrease in the volume resistivity of composite films by less than nine orders of magnitude compared to that of pure PI films due to the electrical percolation networks of reduced GO created during imidization within the films. A tensile test indicated that the Young's modulus of the r-GO/PI composite film containing 20 wt% GO increased drastically from 2.3 GPa to 4.4 GPa, which was an improvement of approximately 84% compared to that of pure PI film. In addition, the corresponding tensile strength was found to have decreased only by 12%, from 113 MPa to 99 MPa.