As social media penetrates more deeply into people’s everyday lives, social commerce (a type of commerce that combines SNS features and possibility for commercial transactions) has enjoyed unprecedented growth. Shopping on Facebook is a representative example of social commerce platform that allows consumers to interact with other users, exchange information and purchase products without leaving a Facebook page. Social commerce presents great opportunities for marketers in terms of leveraging social aspects of shopping experience. It also offers a large potential for Korean companies to reach various target markets, as well as establish their presence abroad. Yet, acceptance of social commerce as a legitimate shopping channel has been slow, and consumers are still hesitant to shop via Facebook. This study draws on uses and gratification theory and the concept of perceived risk to examine how different motives for SNS use and the associated types of perceived risks can affect the purchase intention on the platform. Empirical data from 288 young users of Facebook were analyzed. Findings identified two main motives for SNS use: information-related motive and communication-related motive. Information-related motive significantly affected the intention to shop on Facebook, whereas communication- related motive did not have any significant influence. Risks associated with shopping via Facebook included delivery risk, security risk, social risk and economic risk. Overall, consumers perceived a higher level of security and social risk associated with shopping on Facebook. However, only social risk had a significant negative influence on the purchase intention. Awareness and previous experience of buying via social commerce platform positively affected consumers’ purchase intention.
As a key element in the RED process, the membrane influences the overall power output of the RED stack. Especially, the membrane resistance is one of important properties of the membrane. In this study, CEM(cation exchange membrane) and AEM(anion exchange membrane) consisting of cross-linked polymers in a porous polyolefin substrate were developed to simultaneously satisfy high performance and cost-down of the applied RED system. Physico-chemically stable and ultrathin ion exchange pore filling membranes (cation exchange membranes and anion exchange membranes) with high ion transfer coefficients have been developed for reverse electrodialysis as an energy conversion system. The polymer electrolytes in both cases of cation exchangeable and anion exchangeable ones consisting of the whole hydrocarbon materials were introduced into porous hydrocarbon substrates and crosslinked by radical polymerization in this work. The thickness of the prepared pore filling membranes was controlled between 16 and 23 micrometers to extremely lower membrane resistance and to increase ion transfer. All the properties of the prepared membranes were compared with commercial membranes obtained from Tokuyama, Fuji, and Fuma-Tech. Furthermore, RED cell performance and energy efficiency using the prepared pore filling membranes were also evaluated.
La1-xBaxMnO3 (x = 0.30, 0.35 and 0.40) samples have been prepared by solid-state reaction method. The X-ray diffraction (XRD) study showed that all the samples crystallized in a rhombohedral structure with an R-3c space group. Variation of the magnetization as a function of the temperature and applied magnetic field was carried out. All the samples revealed ferromagnetic to paramagnetic (FM-PM) phase transition at the Curie temperature TC ~ 342 K. The magnetic entropy change was also studied through examination of the measured magnetic isotherms M(H, T) near TC. The magnetocaloric effect was calculated in terms of the isothermal magnetic entropy change. The maximum entropy change reaches a value of 1.192 J/ kgK under a magnetic field change of 2.5T for the La0.6Ba0.4MnO3 composition. The relative cooling power (RCP) is 79.31 J/ kg for the same applied magnetic field.
Withthe increasing trend of global trades and protection of agro-ecosystem in importing and exporting countries against quarantine pest, quarantine and pre-shipment(QPS) fumigation in perishable commodities is now more important to maintain postharvest quality until delivering to end user not just eradiation of quarantine pest. However, there are limited use of MB fumigation on export fruits and vegetables due to phytotoxic damages of fumigated one.
VapormateTM, alternative to methyl bromide(MB), a gas formulation of ethyl formate(EF) with carbon dioxide, is commercially in use for imported fruits fumigation such as bananas and lemon. Herein, based on previous preliminary studies, scale-up and commercial scale fumigation of ethyl formate is presented for promising export paprika and tomato. Efficacy of ethyl formate was described in terms of concentration × time (CT) products to Myzus persicae for paprika and Bemisia tabaci for tomato.
Since Montreal protocol in1989 designated MB(methyl bromide) as ozone depleting chemicals, IPPC(International Plant Protection Convention) has adopted replacing the MB with alternative chemical and reducing the rate of MB use in plant quarantine in 2008. Pineapples are one of the most frequently fumigated imported fruit with MB in Korea. However, there was no technically available replacement. Therefore, we evaluated phosphine(PH3) fumigation as alternative to MB in applying pineapples.
In the preliminary test, PH3 gas in 12L desicators to calculate ranged to 0.1 from 2g/m3 was tested at 2 and 24hr exposure to target pest, citrus mealy bug(CMB, Planococcus citri). All different of stage of CMB was shown 100% mortality when 2g/m3 of PH3 applied for 24hrs at 8℃. To confirm studies designed in 0.5m3 fumigation chamber, all egg, nymph and adult stages of CMB was killed completely and there wasn’t any phytotoxic and quality damages on pineapples for 2 weeks post-fumigation periods at 8℃. In terms of commercial use, further commercial research will need to be carry out in cooperation with importers and fumigators.
Chrysanthemum stunt viroid (CSVd) is a serious pathogen affecting chrysanthemum that has caused significant economic losses to Chrysanthemum flower production worldwide. Control of CSVd disease is difficult due to its contagious nature and long latent period in the field. As chrysanthemum is most often produced by implanting seedlings, it is necessary to diagnose CSVd infection before cultivation. In this study, we screened CSVd infection in seedlings from 30 varieties including 5 domestic, 6 Japanese, and 19 European varieties. Molecular diagnosis of the combination of RT-PCR and nested PCR showed that CSVd was not detected by the first RT-PCR but detected by the second nested PCR analysis in 10 varieties, including 1 domestic, 2 Japanese, and 7 European varieties. Further comparison of 10 identified CSVd nucleotide sequences showed that those are highly conserved (99-100%) and the most similar to an isolate (AB006737) identified in Hokkaido, Japan. Our study suggests that the combination of RT-PCR and nested PCR analysis is successful for the CSVd diagnosis of seedlings and the molecular diagnosis is necessary to prevent the introduction and propagation of viroid disease into the fields.
Vector-borne plant virus transmission is a complex mechanism involving various interactions of viruses, vectors and plants. Plant viruses modify, either directly or indirectly, the rates of development, reproduction and behavior of vector insects in a positive, negative, or neutral manner. The sweetpotato whitefly, Bemisia tabaci, is the only known vector of Tomato Yellow Leaf Curl Virus (TYLCV) which is a virus that seriously damaged tomato cultivars all around the world. Acquisition of TYLCV influences on various developmental, physiological and molecular mechanisms of Q1 biotype B. tabaci. We compared several behavioral and physiological characteristics between non-viruliferous (NV) and TYLCV-viruliferous (V) of Q1 biotype whiteflies. When B. tabaci acquired TYLCV, total life span was shorter and fecundity was lower than NV ones. V whiteflies were more susceptible to thermal stress by increasing hsp mRNA levels but higher in mortality by either heat or cold shocks. Furthermore, V whiteflies increased the rates of plant sap probing and light attraction behaviors than NV ones. All together, our results show that TYLCV acquisition regulates B. tabaci to enhance the rates of development and environmental susceptibility. Our results provide insights to understand vector’s role in relation to the acquisition and transmission of plant viruses.
겨울철 해표면 수온 및 한국 주변역 생태계의 장기 변화 특성 및 상관관계를 분석하였다. 기후 및 해양환경의 변화와 동반된 어획강도의 변화는 1970 년대 이후 어획량 증가의 주요 원인으로 나타났다. 한국 주변역의 겨울철 SST는 1980년대 후반 기후체제변환 시점을 중심으로 상대적으로 저수온에서 고수온으로 변화되었다. 평균영양단계(MTL)는 1970년대 중반 이후 지속적으로 감소하기 시작하였으며, 하위영양단계 어류의 어획량 증가가 중요 변수로 작용하였다. 통합생태계 기반 자원평가 방법중 한가지인 FIB 지수는 1970년 초부터 1970년 후반까지 증가하였으며, 이후 일정 수준을 유지하였다. 특히, 중간영양단계에 위치하는 멸치와 정어리의 개체수 변화는 1970년대 초 이후 MTL 변화의 주요 인자로 작용하였다.
The sweetpotato whitefly, Bemisia tabaci, acts as a vector of more than 100 plant viruses. B. tabaci is known to harbor a primary endosymbiont (Portiera) and 6 secondary endosymbionts (Arsenophonus, Cardinium, Fritschea, Hamiltonella, Rickettsia and Wolbachia). These endosymbionts play important roles in the acquisition and transmission of plant viruses. Using PCR analysis, we identified endosymbiotic bacteria in various B. tabaci populations collected from different places of Korea. Distribution of endosymbionts was different according to the biotype of B. tabaci. Subsequently, their relative densities of endosymbionts were compared between TYLCV-viruliferous and non-viruliferous populations of the Q biotype using quantitative realtime PCR. We found that the densities of Portiera, Cardinium and Hamiltonella are higher in viruliferous than non-viruliferous whiteflies. Our results suggest the role of endosymbiont for the TYLCV transmission of whiteflies.
The sweetpotato whitefly, Bemisia tabaci, is a vector of more than 100 plantdiseased viruses as well as a serious pest to various horticultural crops. Virus acquisition affects the vector’s development and reproduction, but its mechanism is largely unknown. Here we compared the temperature responses between non-viruliferous and TYLCV-viruliferous Q biotype of B. tabaci. When both non-viruliferous and viruliferous whiteflies were exposed for 1 and 3 h at 4, 25, and 35°C, the mortality rate of viruliferous whiteflies is higher than nonviruliferous after exposure at 4°C and 35°C, but no differences at 25°C between them. Analysis of the expression levels of heat shock protein (hsp) genes using the quantitative realtime PCR showed that viruliferous whiteflies has higher expression in hsp70, and hsp90 at both 4°C and 35°C, but no differences at 25°C. The results suggest that vector insects may not be durable to unfavorable temperature conditions when they acquisite plant viruses.
The sweetpotato whitefly, Bemisia tabaci, is a vector insect of more than 100 plant-diseased viruses as well as a serious pest of various horticultural crops. B. tabaci is a species-complex that consists of at least 24 biotypes, which show different biological characteristics including host range, fecundity, insecticide resistance and virus transmission. Here we identified biotype, endosymbiotic bacteria, and tomato yellow leaf curl virus (TYLCV) acquisition of various B. tabaci populations collected in Korea. In addition, we compared those profiles with B. tabaci collected from Bangladesh and Myanmar, and the greenhouse whitefly, Trialeurodes vaporariorum. PCR diagnosis of cytochrome oxidase I (COI) showed that all B. tabaci populations of Korea were Q-biotype and closely related with a subgroup I (MedBasin 1), which is indigenous to the Western Mediterranean area. Ribosomal DNA analysis of 5 endosymbionts showed that both Cardinium and Hamiltonella were detected in most tested populations while the presence of Arsenophonus, Fritschea and Wolbachia dependent on populations. Our results suggest that the acquisition of TYLCV do not related with the endosymbiont profile of B. tabaci.