• Restorative Dentistry and Endodontics
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• v.46 no.1
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• pp.6.1-6.10
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• 2021

Objectives: The aim of this study was to evaluate the corrosion resistance of heat-treated (Reciproc and WaveOne) and non-heat-treated (ProTaper and Mtwo) superelastic nickel-titanium endodontic files when immersed in a 5.25% sodium hypochlorite solution. Materials and Methods: Anodic polarization curves were obtained with potential sweeps that began at the open circuit potential or corrosion potential (E_corr). The pitting potential (E_pit) was identified on the anodic polarization curve as the potential at which a sudden increase in current was observed. The micromorphology of the 28 tested files was analyzed before and after the electrochemical assay using scanning electron microscope (SEM). The data were analyzed using 1-way analysis of variance with the post hoc Bonferroni test (for E_corr) and the Student t-test for independent samples (for E_pit). Results: The mean E_corr values were 0.506 V for ProTaper, 0.348 V for Mtwo, 0.542 V for Reciproc, and 0.321 V for WaveOne files. Only WaveOne and Protaper files exhibited pitting corrosion, with E_pit values of 0.879 V and 0.904 V, respectively. On the SEM images of the ProTaper and WaveOne files, cavities suggestive of pitting corrosion were detected. Conclusions: Signs of corrosion were observed in both heat-treated and non-heat-treated files. Of the evaluated files, WaveOne (a heat-treated file) and ProTaper (a non-heat-treated file) exhibited the lowest corrosion resistance.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.125-137
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• 2024

In paste backfill mining, cemented coal gangue-fly ash backfill (CGFB) can effectively utilize coal-based solid waste, such as gangue, to control surface subsidence. However, given the pressurized water accumulation environment in goafs, CGFB is subject to coupling effects from water pressure and chloride ions. Therefore, studying the influence of pressurized water on the chlorine salt erosion of CGFB to ensure green mining safety is important. In this study, CGFB samples were soaked in a chloride salt solution at different pressures (0, 0.5, 1.5, and 3.0 MPa) to investigate the chloride ion transport characteristics, hydration products, micromorphology, pore characteristics, and mechanical properties of CGFB. Water pressure was found to promote chloride ion transfer to the CGFB interior and the material hydration reaction; enhance the internal CGFB pore structure, penetration depth, and chloride ion content; and fill the pores between the material to reduce its porosity. Furthermore, the CGFB peak uniaxial compression strain gradually decreased with increasing soaking pressure, whereas the uniaxial compressive strength first increased and then decreased. The resulting effects on the stability of the CGFB solid-phase hydration products can change the overall CGFB mechanical properties. These findings are significant for further improving the adaptability of CGFB for coal mine engineering.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.3
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• pp.289-297
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• 2017

Local and general factors have been attributed to root resorption occurred by injuries such as trauma and dental caries that affect periodontal ligament or dental pulp tissue. Pathologic root resorption is different from physiologic root resorption in terms of resorption pattern such as micromorphology of resorption fossae and types of observed cells. Microscopic morphologies and histologic features of physiologic and pathologic root resorption surface of maxillary primary central incisors resulting from trauma and periapical inflammation were observed by scanning electron microscope and light microscope. The morphology of physiologic resorption lacunae was small and oval or circular shape with regularities. The morphology of pathologic resorption lacunae was large and polygonal shape with irregularities compared with the physiologic resorption lacunae. Multinucleated giant cells and mononuclear cells were closely attached to the physiologic and pathologic resorption lacunae, whereas several kinds of mesenchymal cells with numerous inflammatory cells were found in the areas adjacent to the pathologic resorption surface. Compensating cementum formation took place along some of the areas of physiologic and pathologic resorption area resulting from trauma, but could not be observed on pathologic resorption area resulting from periapical inflammation.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.524-534
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• 2000

Deciduous teeth can be extracted for two reasons, one due to the physiologic resorption and the other by the inflammation at the apex after traumatic injury. Physiologic resorption may be different from pathologic resorption in timing and mechanism. Therefore we resumed the different features of physiologic and pathologic resorption root surfaces. Many previous studies showed micromorphology of resorbed surface of roots of deciduous teeth. But, few studies compared physiological and pathological root resorption surfaces. In this study, we carefully observed microscopic morphologies of those two different root surfaces by scanning electron microscope and histologic features by light microscope. The resultant differences between physiologic and pathologic resorption surfaces of deciduous teeth were as follows: 1. The morphology of pathologic resorption lacunae due to inflammation varied in size and shape with irregular boundaries compared with the physiologic areas from scanning electron microscope observations. 2. From light microscope observations, several large resorption fossae containing numerous resorption lacunae were found, whereas the resorption lacunae were irregular in shape with pathologic resorption surface. 3. Numerous multinucleated giant cells were closely attached to the physiologic resorption lacunae, whereas several kinds of mesenchymal cells with numerous inflammatory cells were found in the areas adjacent to the pathologic resorption surface. 4. Light microscope findings showed that compensating cementum formation took place along some of the areas of inflammatory dentinal resorption. In conclusion, several morphological differences were present between physiologic and pathologic root resorption surfaces of human deciduous teeth. The future studies should include cytochemistry to clarify the cellular roles in resorption process observations of pulpal surfaces of coronal and radicular dentin to and the changes that occur in each phase of human deciduous tooth resorption.

• Korean Journal of Plant Taxonomy
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• v.38 no.4
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• pp.509-522
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• 2008

한국산 가막사리속(Bidens L.)에 포함된 10분류군(8종 2변종)의 수과형태를 연구하기 위하여 입체현미경과 주사전자현미경을 이용하여 관찰하였다. 연구된 가막사리속에서 까끄라기를 제외한 수과의 크기는 $3.0-19.5{\times}0.7-2.6 mm$이다. 관모는2-4개의 까끄라기로 구성되어 있고, 까끄라기의 길이는 2.2-5.6 mm이다. 강모의 배열은 1-3열이었다. 수과의 다형화가 6개의 분류군(B. bipinnata, B. biternata, B. frondosa, B. parviflora, B. pilosa var. pilosa, B. tripartita var. tripartita)에서 확인되었다. 수과의 형태와 까끄라기의 수에 의해 4가지 유형으로 구분되었다. - Type A: 장타원형이고, 까끄라기 수는 2개(B. parviflora); Type B: 장타원형이고, 까끄라기 수는 3개 이상(B. bipinnata, B. biternata, B. pilosa var. pilosa, B. pilosa var. minor) Type C: 도란형이고, 까끄라기의 수는 2개(B. frondosa, B. radiata var. radiata, B. radiata var. pinnatifida, B. tripartita var. tripartita); Type D: 도란형이고, 까끄라기의 수는 3개 이상(B. cernua). 까끄라기의 강모 표면무늬는 3가지 즉 나선상, 평활상, 불규칙한 직선형으로 나타났다. 수과의 표면은 각피층이 발달한 다각형, 평활상 그리고 굴곡형으로 나타났다. 수과형질의 분류학적 적용에 대하여 간략하게 토의하였다. 수과형질을 바탕으로 한국산 가막사리속 분류군에 대한 검색표를 제시하였다.

• Korean Journal of Plant Taxonomy
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• v.46 no.2
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• pp.199-212
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• 2016

A comparative study of leaf epidermal microstructures in the tribe Sorbarieae (Adenostoma: 3 spp., Chamaebatiaria: 1 sp., Sorbaria: 11 spp., Spiraeanthus: 1 sp.) including related genera Gillenia (2 spp.) and Lyonothamnus (2 spp.) was carried out using scanning electron microscopy (SEM) in order to evaluate their significance in taxonomy. The leaves of Adenostoma, Chamaebatiaria, and Spiraeanthus were amphistomatic, whereas Gillenia, Lyonothamnus, and Sorbaria were hypostomatic. The size range of the guard cells is $7.84-48.7{\times}5.86-38.6{\mu}m$; the smallest one was found in Sorbaria tomentosa var. tomentosa ($7.84-11.8{\times}6.84-10.5{\mu}m$), while the largest measured example was Adenostoma fasciculatum var. obtusifolium ($30.3-48.7{\times}18.8-38.6{\mu}m$). Anomocytic stomata complex were the most frequent type (rarely cyclocytic), with usually both anomocytic and actinocytic types occurring in one leaf. On the surfaces, both the adaxial and abaxial anticlinal walls of the subsidiary cells vary (e.g., straight/curved, undulate, sinuate). Four types (unicellular non-glandular trichome, stellate, glandular trichome, pustular glandular trichome) of trichomes are found in the leaves. The epicuticular wax can be divided two types: membraneous platelets (Lyonothamnus) and platelets (Sorbaria arborea var. arborea, S. arborea var. subtomentosa, S. kirilowii, S. tomentosa var. tomentosa, Spiraeanthus schrenkianus). The trichome diversity (in particular, stellate, gland) and the existence of epicuticular wax may have taxonomic significance, although the leaf epidermal micromorphological characteristics do not provide synapomorphy in this tribe. These leaf micromorphological features are most likely better understood in the Sorbarieae when used in conjunction with external morphological characters.

• Korean Journal of Plant Taxonomy
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• v.47 no.3
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• pp.222-235
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• 2017

A comparative study of the leaf epidermal micromorphology in the tribe Neillieae (Neillia: 4 species, 4 varieties; Physocarpus: 5 species; Stephanandra: 2 species) was carried out using scanning electron microscopy in order to evaluate the taxonomic and systematic implications of these characteristics. The leaves of the genera Neillia and Stephanandra were hypostomatic, whereas those of P. monogynus, P. opulifolius were amphistomatic. The range of the size of the stomata is $12.02-34.39{\times}10.76-27.13{\mu}m$; the smallest was found in N. thyrsiflora (average $13.98{\times}12.43{\mu}m$; $L{\times}W$), while the largest was measured in N. gracilis (average $26.82{\times}20.67{\mu}m$; $L{\times}W$). Paracytic stomata complexes are only found in N. affinis, and the anomocytic type was most commonly found. The papillate epidermal cell type was only observed on the abaxial surfaces of P. insularis. Platelet epicuticular waxes were found on the adaxial surfaces of N. affinis and S. tanakae. Four types (unicellular non-glandular, two- to five-armed, stellate, and glandular) of trichomes were found on the leaves. Stellates were observed in all species of Physocarpus except for P. insularis. Consequently, leaf epidermal micromorphological characteristics (e.g., the presence of papillate epidermal cells and stellate, and stomata complexes) may have high taxonomic and systematic value in Neillieae. Our results strongly support previous molecular phylogenetic and palynological hypotheses that Stephanandra and Neillia are a single genus and that Physocarpus insularis should be considered as a member of Spiraea.