University dropout is a serious problem. It affects not only the individual who drops out but also the university and society. However, most previous studies have focused only on the ...subjective/individual level. University dropout is a very important issue in South Korea, but it has not received much research attention so far. This study examined the possible causes of university dropout in South Korea at the aggregate level, focusing on four fundamental categories: students, resources, faculty, and university characteristics. Three-year balanced panel data from 2013 to 2015 were constructed and estimated by using nonlinear panel data models. The findings show that cost and burden for students, financial resources, qualitative and quantitative features of faculty, and type/size of the university have significant effects on university dropout.
Our study aims to explore new directions for researches on government’s role in enhancing quality of life (QOL). Although government can influence, to the greatest extent, people’s happiness, very ...few studies have systemically examined the quantitative or qualitative attributes of government in happiness enhancement, compared with the large volume of studies on economic, political, and cultural factors’ impact on QOL. Related to government’s role in happiness, we suggest ‘nine new research directions,’ all of which can generally be related with its’ quantitative and qualitative attributes. Even though much existing researches have focused on a part of quantitative sides of government, there are still many remaining attributes to be highlighted. Moreover, we expect that new, composite and nonlinear quality attributes of government will provide bountiful research topics in the future. Also, cross-boundary comparisons and mixtures between quality and quantity, as well as the conditional macro-context for government’s role, suggest new ideas for QOL studies.
Nematode-trapping fungi develop trap and consume nematodes are an important part of the subsoil ecosystem and they share a special predator-prey relationship. Four nematode-trapping species, there ...with adhesive network, Arthrobotrys oligospora, A. sinensis, A. thaumasia and one with constricting ring, Drechslerella brochopaga were collected from soils in Korea and tested their predacity against 12 different nematode species. They were three feeding groups, plant-parasitic (Meloidogyne incognita and Pratylenchus penetrans), fungivorous (Aphelenchus avenae), bacteriovorous (Betlerius sp. and Diplogasteritus sp. in diplogasterid, Panagrolaimus labiatus, P. multidentatus in panagrolaimid, Mesorhabditis irregularis, Pelodera strongyloides and Rhabditis sp., in rhabditid, and Acrobeloides sp. in cephalobid). Results showed that nematode-trapping fungi successfully captured most of nematodes in Petri dish in the group of plant-parasitic nematodes and rhabditids, moderately and variably in other nematodes in 15 days. But it didn't captured A. avenae and Acrobeloides sp. both belongs to c-p group 2. Numbers of Acrobeloides sp. and A. avenae even increased during the test period. The results of this study indicated that nematode-trapping fungi may have specificity among nematode species. 선충 포식성곰팡이는 유기물에서 번식하다가 양분이 부족해지면 특수 기관을 형성하여 선충을 포획하고 선충으로부터 양분을 섭취하기 때문에 토양 내 동물계와 먹이사슬을 이루며 생태계에서 중요한 부분을 차지한다. 본 연구에서는 끈끈이그물형 포식기관을 가진 3종, Arthrobotrys oligospora, A. sinensis, A. thaumasia과 수축성올가미형 포식기관을 가진 Drechslerella brochopaga 1종 등 4종의 선충 포식성곰팡이의 식세균성선충 9종, 식균성선충 1종, 식물기생성선충 2종 등 총 12종의 선충류에 대한 포식력을 검정하였다. 4종의 포식성곰팡이에 모두 감수성인 선충은 식물기생성선충 2종류(Meloidogyne incognita, Pratylenchus penetrans), Rhabditidae에 속하는 P. strongyloides, Mesorhabditis irregularis이었고 접종 4일 후부터 선충을 포식하였으며, 선충 내부로 곰팡이가 번식하여 15일째에는 거의 선충의 형태를 알아볼 수 없을 정도였다. 반면, Cephlobidae에 속하는 Acrobeloides spp., A. avenae는 4종의 포식성곰팡이에 모두 저항성을 보였으며 15일 후 관찰하였을 때, 접종배지 내에 선충 수가 초기접종 밀도와 같거나 오히려 2-3배 정도까지 번식되었다. 나머지 선충 종들은 포식성곰팡이 종류에 따라 감수성에 다소간 차이가 있었다. 본 연구결과, 선충 포식성곰팡이가 선충 종에 따라 특이적으로 반응하였으며 이러한 기주특이성을 이용하여 식물기생성선충의 친환경적 방제를 위한 하나의 수단으로 이용될 수 있다.
We study the impact of tacit collusion on price dispersion in the U.S. airline industry. We find that tacit collusion driven by multimarket contact has a positive effect on prices, but a negative ...effect on price dispersion. Our empirical results suggest that airfares throughout the price distribution increases, yet the price distribution becomes more compressed since 10th percentile airfares increase by a larger amount than 90th percentile airfares. Moreover, we also find that this pricing phenomenon does not exist if Southwest Airlines is present on the route. Thus, route‐level price competition is softened when the same airlines directly compete more frequently, except when Southwest Airlines services that route. As such, our empirical analysis provides evidence that the presence of Southwest Airlines exhibits an anti‐collusive effect.
This study compares the impacts of economic incentives on attitudes related to the acceptance of fossil fuels, renewable, and nuclear energies. Linear and nonlinear regression models are applied for ...the robust estimation results. Empirical findings based upon these regression models are summarized as follows: First, when people belong to the upper social class, reside in metropolitan area, and have more trust in the government’s energy policy, they tend to accept the construction of specific energy-related facilities in a neighborhood and raise the probability of attitude change and stability. Second, those who have more perceived risk and negative image are less likely to accept any types of energies and tend to lower the probability of attitude change toward positive direction or stability. Third, those who have more knowledge are less likely to accept some energy sources such as fossil fuels and there exists a trade-off relationship between knowledge and trust. Finally, the structural changes between acceptance of all energy sources with and without economic incentives imply that economic incentives play a significant role in determining acceptance of energies.
Intelligent information technology (IIT) based on AI and intelligent network communication technology is rapidly changing the social structure and the personal lives. However, IIT acceptancefrom ...various perspectives still requires extensive research. The research question in this paper examines how five factors—psychological, technological, resource, risk perception, and value factors—influence IIT acceptance. Based on an analysis of survey data, it was first found that the acceptance rate of IIT itself was generally very high. Second, in terms of IIT acceptance, among twenty-five predictors, voluntariness (+), positive image of technology (+), performance expectancy (+), relative advantage (+), radical innovation (+), and experience of use (+) were found to have significant effects on the IIT acceptance. Third, in addition to technological factors, psychological factors and risk perception factors also played an important role in individuals’ decisions regarding IIT acceptance.
This article examines US airline mergers between 1993 and 2018 and studies their impact on the labor market. Our difference‐in‐differences estimates indicate a significant reduction in the merging ...airlines' long‐term wage and fringe benefits following the mergers. The effect is particularly salient among large‐scale mergers involving major airlines and low cost carriers. The results also suggest a negative short‐term employment impact of mergers that varies by occupation types. Our findings are consistent with the impact of merger‐induced monopsony power discussed in recent literature and offer important policy implications regarding how to account for employer monopsony power during mergers and acquisitions.
As tree rings can reveal various information regarding climate and environmental factors, increasing research is being conducted on them. Although tree ring analysis software such as Windendro has ...been applied, research on the development of analysis software using image preprocessing algorithms and deep learning is recently being attempted as computer vision technology. In this study, Mask R-CNN and linear interpolation were applied from images collected using a smartphone (SM-G973, Samsung, Suwon) and a scanner (CanoScan 9000F, Canon, Otaku) to propose an effective method for detecting tree ring boundaries. Pitch pine (Pinus rigida), Korean pine (Pinus koraiensis), white birch (Betula platyphylla), and cork oak (Quercus variabilis) were selected as tree species. Of the 300 images, 240 were classified as training data and 60 as validation data. As a result of learning, smartphones detected 86.0 % (381 ring boundaries) of the rings in pitch pine, 82.1 % (367 ring boundaries) in Korean pine, 84.7 % (309 ring boundaries) in white birch, and 78.7 % (318 ring boundaries) in cork oak. The scanner detected 93.2 % (413 ring boundaries) of the rings in pitch pine, 90.8 % (405 ring boundaries) in Korean pine, 88.2 % (322 ring boundaries) in white birch, and 89.4 % (361 ring boundaries) in cork oak. In particular, the smartphone showed satisfactory results of 84.7 % and 78.7 % for detecting tree ring boundaries of white birch and cork oak, where the boundaries of the rings were unclear. In the annual growth analysis results, both smartphones and scanners were statistically insignificant, and there was no difference compared with those of Windendro. Therefore, Mask R-CNN might be an effective approach for tree ring boundary detection as it showed satisfactory results, even with smartphones. In addition, although there was distortion in cases where images were acquired with a circular lens, there was no statistically significant difference from Windendro results. Thus, Mask R-CNN and linear interpolation can be used for tree ring boundary detection and growth measurement.
Biofilms are microbial communities that inhabit various surfaces and are surrounded by extracellular matrices (ECMs). Clinical microbiologists have shown that the majority of chronic infections are ...caused by biofilms, following the introduction of the first biofilm infection model by J. W. Costerton and colleagues (J. Lam, R. Chan, K. Lam, and J. W. Costerton, Infect Immun 28:546-556, 1980). However, treatments for chronic biofilm infections are still limited to surgical removal of the infected sites.
and
are two frequently identified bacterial species in biofilm infections; nevertheless, the interactions between these two species, especially during biofilm growth, are not clearly understood. In this study, we observed phenotypic changes in a dual-species biofilm of
and
, including a dramatic increase in biofilm matrix thickness. For clear elucidation of the spatial distribution of the dual-species biofilm,
and
were labeled with red and green fluorescence, respectively.
was located at the lower part of the dual-species biofilm, while
developed a structured biofilm on the upper part. Mutants with altered exopolysaccharide (EPS) productions were constructed in order to determine the molecular basis for the synergistic effect of the dual-species biofilm. Increased biofilm matrix thickness was associated with EPSs, not extracellular DNA. In particular, Pel and Psl contributed to interspecies and intraspecies interactions, respectively, in the dual-species
and
biofilm. Accordingly, targeting Pel and Psl might be an effective part of eradicating
polymicrobial biofilms.
Chronic infection is a serious problem in the medical field. Scientists have observed that chronic infections are closely associated with biofilms, and the vast majority of infection-causing biofilms are polymicrobial. Many studies have reported that microbes in polymicrobial biofilms interact with each other and that the bacterial interactions result in elevated virulence, in terms of factors, such as infectivity and antibiotic resistance.
and
are frequently isolated pathogens in chronic biofilm infections. Nevertheless, while both bacteria are known to be agents of numerous nosocomial infections and can cause serious diseases, interactions between the bacteria in biofilms have rarely been examined. In this investigation, we aimed to characterize
and
dual-species biofilms and to determine the molecular factors that cause synergistic effects, especially on the matrix thickening of the biofilm. We suspect that our findings will contribute to the development of more efficient methods for eradicating polymicrobial biofilm infections.
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