• Toxicological Research
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• 제35권1호
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• pp.1-7
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• 2019

Mycotoxin contamination is a global phenomenon and causes a wide array of negative effects and other complications. This study focused on commonly found mycotoxins in Africa and the possible means of prevention or reduction of their contaminating effects. Mycotoxins are secondary metabolites of mold and fungi; they are generally toxic to living organisms. Hundreds of mycotoxins have been identified thus far, with some, such as aflatoxins, ochratoxins, trichothecenes, zearalenone, fumonisins, and patulin, considered agro-economically important. Several factors contribute to the presence of mycotoxins in food, such as climatic conditions, pest infestation, and poor harvest and storage practices. Exposure to mycotoxins, which occurs mostly by ingestion, leads to various diseases, such as mycotoxicoses and mycoses that may eventually result in death. In light of this, this review of relevant literature focuses on mycotoxin contamination, as well as various methods for the prevention and control of their prevalence, to avert its debilitating consequences on human health. Clear evidence of mycotoxin contamination is present in Africa, and it was therefore recommended that adequate prevention and control of these toxic substances in our food system should be encouraged and that appropriate measures must be taken to ensure food safety as well as the enhanced or long-lifespan of the African populace. Governments, research institutions, and non-governmental organizations should tailor the limited resources available to tackle mycotoxin prevalence, as these will offer the best prospects for successful development of a sustainable food system in Africa.

• International Journal of Oral Biology
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• 제44권3호
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• pp.115-123
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• 2019

Among the environmental chemicals that may be able to disrupt the endocrine systems of animals and humans are polychlorinated biphenyls (PCBs), a chemical class of considerable concern. PCB consists of two six-carbon rings linked by a single carbon bond, and theoretically, 209 congeners can form, depending on the number of chlorines and their location on the biphenyl rings. Furthermore, 3,3',4,4',5-pentachlorobiphenyl (PCB126) exposure also increases nitric oxide production and nuclear factor kappa-light-chain-enhancer of activated B cells binding activity in chondrocytes, thus contributing as an initiator of chondrocyte apoptosis and resulting in thymic atrophy and immunosuppression. This study identified whether cardiac and immune abnormalities from PCB126 were caused by the Kv1.3 and Kv1.5 channels. PCB126 did not affect either the steady-state current or peak current of the Kv1.3 and Kv1.5 channels. However, PCB126 right-shifted the steady-state activation curves of human Kv1.3 channels. These results suggest that PCBs can affect the heart in a way that does not block voltage-dependent potassium channels including Kv1.3 and Kv1.5 directly.

• Restorative Dentistry and Endodontics
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• 제44권2호
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• pp.20.1-20.8
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• 2019

Objectives: To achieve pulp-dentin complex regeneration with tissue engineering, treatment efficacies and safeties should be evaluated using in vivo orthotopic transplantation in a sufficient number of animals. Mice have been a species of choice in which to study stem cell biology in mammals. However, most pulp-dentin complex regeneration studies have used large animals because the mouse tooth is too small. The purpose of this study was to demonstrate the utility of the mouse tooth as a transplantation model for pulp-dentin complex regeneration research. Materials and Methods: Experiments were performed using 7-week-old male Institute of Cancer Research (ICR) mice; a total of 35 mice had their pulp exposed, and 5 mice each were sacrificed at 1, 2, 4, 7, 9, 12 and 14 days after pulp exposure. After decalcification in 5% ethylenediaminetetraacetic acid, the samples were embedded and cut with a microtome and then stained with hematoxylin and eosin. Slides were observed under a high-magnification light microscope. Results: Until 1 week postoperatively, the tissue below the pulp chamber orifice appeared normal. The remaining coronal portion of the pulp tissue was inflammatory and necrotic. After 1 week postoperatively, inflammation and necrosis were apparent in the root canals inferior to the orifices. The specimens obtained after experimental day 14 showed necrosis of all tissue in the root canals. Conclusions: This study could provide opportunities for researchers performing in vivo orthotopic transplantation experiments with mice.

• 환경영향평가
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• 제28권1호
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• pp.1-22
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• 2019

본 연구에서는 국가 생태분야 기후변화 리스크 평가와 연계한 적응 정책 및 연구의 방향성에 대한 시사점을 마련하고자 하였다. 본 논문에서 검토한 적응 정책과 연구에 대한 해외 모범사례의 공통점은 국가 적응정책 수립 시 과학적 근거기반 구축 및 불확실성 저감을 목표로 국가단위에서 기후변화가 생물다양성과 생태계에 미치는 영향 연구를 강조한다는 점이다. 이에 비추어 추후 국가 정책 마련 시 기후변화 협약과 생물다양성 협약 등 효율적 통합적 준수를 위한 적응체계를 유도하고, 적응의 경제적 가치평가를 통한 정책 반영, 과학적 연구 프로그램 강화 및 기술 개발의 측면을 보강하여 보다 성공적인 국가적응 정책 구조를 정착해 갈 수 있어야 할 것이다. 특히 생태계 분야 적응방안이 보다 실효성 있게 실행되기 위해서는 우리나라 서식지 및 종의 기후변화 리스크 요소(위해, 노출, 취약성)에 대한 과학적 진단과 분석을 바탕으로 리스크를 평가하고 이에 대한 적응방안을 통합하여 고민하는 노력이 필요할 것이다.

• 한국환경과학회지
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• 제30권1호
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• pp.77-85
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• 2021

This study was carried out to establish optimal conditions for breaking dormancy of Agastache rugosa O. Kuntze seeds. A series of experiments according to seed maturity and treatment with plant growth regulators were performed to improve germination percentage and synchronize germination of the seeds. In addition, it was conducted to test whether the useful effect of seed treatment before sowing leads to healthy seedling and early vigorous growth. The average seed size was 1.85 mm (length) × 0.82 mm(width). The seed size was much smaller than other vegetable seeds. Seeds colorappeared dark brown, the shape of the seeds was oval and the weight of 1,000seeds was 352.8 mg. The optimum germination temperature was 22℃. Light exposure during germination did not affect germination promotion, suggesting that A. rugosa seeds are a kind of dark germinating seeds. Seed dormancy lasted for 40 days after harvesting, and GA3 treatment of dormant seeds could break dormancy. There were significant differences in germination percentage and rate according to the maturity of seeds. The germination percentage of mature seeds was 10 - 18% higher than that of immature seeds, and germination rate was 2 days faster. GA3 treatment during growth regulator treatment improved germinability, but BAP or ethephone treatment did not. The optimal growth regulator concentration of for germination was the combination treatment of 100 mM GA3 ＋ 100 mM BAP.

• Journal of Korean Dental Science
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• 제15권1호
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• pp.9-18
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• 2022

Purpose: The purpose of this study was to evaluate whether three-dimensional (3D)-printed flexible denture resin has suitable mechanical properties for use as a thermoplastic denture base resin material. Materials and Methods: A total of 96 specimens were prepared using the 3D printed flexible denture resin (Flexible Denture). Specimens were designed in CAD software (Tinkercad) and printed through a digital light-processing 3D printer (Asiga MAX UV). Post-polymerization process was conducted according to air exposure or glycerin immersion at 35℃ or 60℃ and for 30 or 60 minutes. The maximum flexural strength, elastic modulus, 0.2% offset yield strength, and Vickers hardness of 3D-printed flexible denture resin were assessed. Result: The maximum flexural strength ranged from 64.46±2.03 to 84.25±4.32 MPa, the 0.2% offset yield strength ranged from 35.28±1.05 to 46.13±2.33 MPa, the elastic modulus ranged from 1,764.70±64.66 to 2,179.16±140.01 MPa, and the Vickers hardness ranged from 7.01±0.40 to 11.45±0.69 kg/mm². Conclusion: Within the limits of the present study, the maximum flexural strength, 0.2% offset yield strength, elastic modulus, and Vickers hardness are sufficient for clinical use under the post-polymerization conditions of 60℃ at 60 minutes with or without glycerin precipitation.

• 분석과학
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• 제35권5호
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• pp.212-217
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• 2022

In this study, ozone (O₃) samples were prepared for investigating the heterogeneous reactions between O₃ and tropospheric aerosols and were characterized by spectroscopic methods. O₃ generated from an ozone generator was purified by selective adsorption on refrigerated silica gel, followed by transfer to a sample bulb. The amount of UV light (λ = 256 nm) absorbed by O₃ was measured as a function of time at two different temperatures (room temperature and 50 ℃) and under different irradiation conditions. A correlation plot of 1/[O₃] versus time showed that O₃ decomposition follows the 2^nd order reaction rate under a steady-state approximation. The initial concentration of O₃, observed rate constants (k_obs), and the half-life of O₃ in the sample stored at room temperature were determined to be 2.74 [±0.14] × 10¹⁶ molecules·cm^-3, 4.47 [±0.64] × 10^-23 molecules^-1·cm³·s^-1, and 9.5 [±1.4] days, respectively. The evaluation of O₃ stability under various conditions indicated that special care should be taken to prevent the exposure of the O₃ samples to hightemperature environment and/or UV radiation. This study established a protocol for the preparation of highly purified O₃ samples and confirmed that the O₃ samples can be stored for a day after preparation for further experiments.

• 한국환경보건학회지
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• 제48권5호
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• pp.255-265
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• 2022

Background: Research in environmental health (EH) is of crucial strategic importance for contemporary society. It is becoming even more critical in light of the increasingly rapid pace of environmental changes, opportunities, and threats. Objectives: This study aimed to identify trends and the prospective of environmental health research using SWOT analysis. Methods: The trends in environmental health research were reviewed in previous studies and reports. Reviewed manuscripts were searched for using the keywords of 'environmental health' and 'environmental hygiene' in the KCI (Korean Journal of Citation Index), KISS (Korean Academic Information), PubMed, and Google Scholar. Results: It is essential to center the EH research agenda around key priorities focusing on technological innovation, job creation, and the increasingly prominent role of the private sector. Given the rapidly evolving global sustainability agenda, greater clarity on the ever-increasing sources of complexity and growing expectations of the public might be needed. This requires the identification of criteria to identify EH research priorities with the ultimate goal of maximizing societal benefit. Public health relevance, such as extent and severity of health impact, level of exposure, and inequalities of effects, could be included. Conclusions: Considering the recent interest in and importance of environmental health, a comprehensive approach to environmental health research should be required through the application of the latest science and technology, citizen participation, and environmental health surveillance systems.

• International Journal of Computer Science & Network Security
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• 제21권12호
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• pp.335-343
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• 2021

The study aimed to elucidate how to design a learning environment on the premise of micro-learning (ML) and investigate its impact on website designing skills and achievement motivation among secondary school students. Adopting the experimental approach, data were collected through an achievement test, a product evaluation form, and a test to gauge motivation for achievement. The sample was divided into two experimental groups. Results revealed statistically significant differences at 0.05≥α between the mean scores of the two groups that experienced ML, irrespective of the two modes of presenting the video in the pre-test and post-test, as for the test of websites design skills, product evaluation form, and achievement motivation test. Besides, there have been statistically significant differences at 0.05≥α between the mean scores of the first experimental group that had exposure to ML using the split-video presentation style and the scores of the second experimental group that underwent ML using continuous video presentation style in the post cognitive test of website design and management skills in favor of the group that had segmented-video-presentation ML. Another salient finding is the nonexistence of significant differences at 0.05≥α between the mean scores of the first experimental group that underwent segmented-video-presentation ML and the grades of the second experimental group that received ML with continuous video presentation style in the post-application of the product scorecard of websites designing skills and the motivation test. In light of these salient findings, the study recommended using ML in teaching computer courses at different educational stages in Saudi Arabia, training computer and information technology teachers to harness ML in their teaching and using ML in designing courses at all levels of education.

• 대한임베디드공학회논문지
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• 제17권1호
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• pp.9-17
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• 2022

As the COVID-19 pandemic situation worsens, the time spent indoors increases, and the exposure to indoor environmental pollution such as indoor air pollution and noise also increases, causing problems such as deterioration of human health, stress, and discord between neighbors. This paper designs and implements a system that measures and monitors indoor air quality and noise, which are representative evaluation criteria of the indoor environment. The system proposed in this paper consists of a particulate matter measurement subsystem that measures and corrects the concentration of particulate matters to monitor indoor air quality, and a noise measurement subsystem that detects changes in sound and converts it to a sound pressure level. The concentration of indoor particulate matters is measured using a laser-based light scattering method, and an error caused by temperature and humidity is compensated in this paper. For indoor noise measurement, the voltage measured through a microphone is basically measured, Fourier transform is performed to classify it by frequency, and then A-weighting is performed to correct loudness equality. Then, the RMS value is obtained, high-frequency noise is removed by performing time-weighting, and then SPL is obtained. Finally, the equivalent noise level for 1 minute and 5 minutes are calculated to show the indoor noise level. In order to classify noise into direct impact sound and air transmission noise, a piezo vibration sensors is mounted to determine the presence or absence of direct impact transmitted through the wall. For performance evaluation, the error of particulate matter measurement is analyzed through TSI's AM510 instrument. and compare the noise error with CEM's noise measurement system.