• Journal of Periodontal and Implant Science
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• 제29권3호
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• pp.553-560
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• 1999

The aim of the present study was to evaluate the effect of the expanded polytetrafluoroethylene (e-PTFE) membrane exposure on the initial healing of the periodontal tissue in guided tissue regeneration (GTR) procedure. 90 sites selected from 90 patients were treated with gingival flap surgery supported by an e-PTFE membrane. The material included angular bony defects with probing attachment loss of > 5mm or degree II furcation involvement. Treated sites were classified with membrane exposure group and non-exposure group at membrane removal and evaluated healing type. The results were obtained as follows. 1. e-PTFE membrane was exposed at 61 sites (67.8%) among 90 sites. 2. Thirteen sites (14.4%) depicted rapid healing type, 65 sites (72.2%) depicted typical healing type, 9 sites (10%) showed delayed healing type and 3 sites (3.3%) were categorized as adversed healing type. 3. In e-PTFE membrane exposure group, 1 site (1.6%), 51 sites (83.6%), 6 sites (9.8%) and 3 sites (4.9%) showed rapid healing type, typical healing type, delayed healing type and adverse healing type respectively. 4. In e-PTFE membrane non-exposure group, 12 sites (41.3%), 14 sites (48.3%) and 3 sites (10.3%) showed rapid healing type, typical healing type and delayed healing type respectively. Adverse healing type was not observed. 5. The rate of favourable healing between e-PTFE membrane exposure group and non-exposure group was not statistically significant(p=0.56). These results suggest that the prevention of membrane exposure may be important to obtain rapid healing type. However favourable healing could be obtained with stringent infection control program even if membrane was exposed.

• 상하수도학회지
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• 제38권4호
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• pp.223-232
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• 2024

This study was conducted to simulate the lifetime of the membrane by analyzing the performance of the membrane degraded by chlorine. Chlorine exposure under several conditions caused the degradation of the membrane, resulting in the absence of any salts and an extreme increase in permeability. When the n value was calculated and compared through CⁿT analysis and CTⁿ analysis, the p values were all less than 0.005, but CTⁿ analysis, which had a higher R² value, was adopted to simulate the membrane lifetime. Power coefficients take on values higher than 1, indicating that the exposure time to chlorine has a greater influence on membrane deterioration than the chlorine exposure concentration at 20℃ and 30℃. In particular, the process should be operated at less than 0.5 ppm at 30℃, and the chlorine exposure time of 1 cycle should be set to within 15 hours. In addition, the sensitivity to chlorine increased by 10.5 to 12.2 times when the chlorine exposure temperature increased by 10℃ through the correlation between the chlorine exposure cycle and membrane lifetime. The membrane lifetime investigated in this study is only an estimated value, entirely because of chlorine membrane deterioration, excluding raw water characteristics and the type of detergent. Accordingly, it is considered that the membrane lifetime simulation can be applied by comparing the membrane performance with the actual process based on the filtration performance of membrane deterioration by chlorine.

• Journal of Periodontal and Implant Science
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• 제37권2호
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• pp.237-249
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• 2007

This study was performed to evaluate the effect of membrane exposure on new bone formation when guided bone regeneration with perforated titanium membrane on atrophic alveolar ridge. The present study attempted to establish a GBR model for four adult beagle dog premolar. Intra-marrow penetration defects were created on the alveolar ridge(twelve weeks after extraction) on the mandibular premolar teeth in the beagle dogs. Space providing perforated titanium membrane with various graft material were implanted to provide for GBR. The graft material were demineralized bovine bone(DBB), Irradiated cancellous bone(ICB) and demineralized human bone powder(DFDB). The gingival flap were advanced to cover the membranes and sutured. Seven sites experienced wound failure within 2-3weeks postsurgery resulting in membrane exposure. The animals were euthanized at 4 weeks postsurgery for histologic and histometric analysis. The results of this study were as follows: 1. There was little new bone formation at 4 weeks postsurgery. irrespectively of membrane exposure. 2. There was significant relationship between membrane exposure and bone graft resorption(P<0.05), but no relation between membrane exposure and infiltrated connective tissue. 3. There was much bone graft resorption on DFDB than ICB and DBB. 4. The less exposure was on the perforated titanium membrane, the more dense infiltrated connective tissue was filled under the membrane when grafted with ICB and DBB. but there was no relationship between the rate of membrane exposure and the percentage of infiltrated connective tissue area and no relationship between the percentage of the area in the infiltrated connective tissue and in the residual bone graft. Within the above results, bone formation may be inhibited when membrane was exposed and ICB and DBB were more effective than DFDB as a bone graft material when guided bone regeneration.

• Journal of Periodontal and Implant Science
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• 제26권1호
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• pp.103-116
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• 1996

This study was performed to observe the bacterial adhesion and penetration to e-PTFE membrane following guided tissue regeneration(GTR) procedure and to evaluate the association of the membrane exposure and bacterial contamination with the clinical outcome. For the study, ten infrabony defects in 9 patient were treated by mucoperiosteal flap operation including placement of the e-PTFE membrane. The treated teeth were monitored weekly for the membrane exposure, gingival recession and gingival inflammation. The membranes were retrieved after 4 to 6 weeks, examined by SEM for bacterial contamination and adherent connective tisue elements, and observed under LM for the bacterial penetration into membrane. Three months postsurgery, the defect sites were clinically reexamined for the changes in attachment level and probing depth. Comparison of the ultrastuctural findings and clinical outcome revealed that extent of membrane exposure and bacterial contamination of the membrane was inversely associated with clinical attachment gain. From this finding, the extent of membrane exposure and the bacterial contamination on the apical portion of the e-PTFE membrane at the time of removal seemed to be a critical determinant on the clinical outcome of GTR and the membrane exposure needs to be controlled for optimal results.

• Membrane and Water Treatment
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• 제8권3호
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• pp.211-223
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• 2017

In this work, an attempt was made to compare the effects of UV irradiation on the intrinsic and separation properties of membranes made of two different polymeric materials, i.e., polyvinylidene fluoride (PVDF) and polyetherimide (PEI). The changes on membrane structural morphologies and chemical characteristics upon UV-A exposure (up to 60 h) were studied by FESEM and FTIR, respectively. It was found that cracks and fractures were detected on the PVDF-based membrane surface when the membrane was exposed directly to UV light for up to 60 h. Furthermore, the mechanical strength and thermal stability of irradiated PVDF-based membrane was reported to decrease with increasing UV exposure time. The PEI membrane surface meanwhile remained almost intact throughout the entire UV irradiation process. Filtration experiments showed that the permeate flux of UV-irradiated PVDF membrane was significantly increased from approximately 11 to $16L/m^2.h$ with increasing UV exposure time from zero to 60 h. Oil rejection meanwhile was decreased from 98 to 85%. For the PEI-based membrane, oil rejection of >97% was recorded and its overall structural integrity was marginally affected throughout the entire UV irradiation process. The findings of this work showed that the PEI-based membrane should be considered as the host for photocatalyts incorporation if the membrane was to be used for UV-assisted wastewater treatment process.

• 한국표면공학회지
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• 제47권2호
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• pp.57-62
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• 2014

The biogas holder is composed of an outer membrane and an inner membrane which are subject to outdoor exposure and gas exposure respectively. The influence of weathering conditions on the photo-degradation of a biogas holder was investigated. Tests were performed under three different methods - outdoor exposure tests (Seosan, Arizona), accelerated tests (Xenon-are lamp) with the outer-membrane of biogas. Moreover, the changes in the aging process were monitored using color difference, gloss, the contact angle and an optical microscope. Changes in physical properties, such as decrease reduction in gloss, decrease in the contact angle, increase in color difference were observed in the aging process. The comparison between membrane 3B, 4B and membrane 5B under xenon-arc were discussed. Membrane 5B was very sensitive to ultraviolet (UV) ray. There were many difficulties in the outdoor exposure test due to acid rain, dust, and stain resistance.

• 공업화학
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• 제26권3호
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• pp.326-330
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• 2015

고분자 막은 다양한 응용분야에 적용되고 있다. 기존에 고분자 막은 옥외환경에 노출되지 않는 형태로 적용되어 왔으나 최근 대기환경 측정용도, 해수에서 유용금속 추출용 등의 옥외에 적용되는 고분자 막 시스템들이 보고되고 있다. 이에 옥외환경에서의 고분자 막의 특성 연구가 필요하게 되었으며 이러한 측면에서 촉진 자외선 노출 실험 및 이에 대한 영향 연구는 고분자 막의 내후성을 예측할 수 있는 정보를 제공할 수 있다. 본 연구에서는 폴리설폰 비대칭성 막과 폴리프로필렌 부직포 형태의 막에 대해 촉진 자외선 노출을 실시하고 이에 대한 열적, 기계적 특성, 몰폴로지, 그리고 색차변화 특성에 대한 영향을 보고한다. 실험 결과를 통해서 고분자 막의 자외선 노출에 대한 효과는 막 제조시 사용한 고분자 종류 뿐 만 아니라 막의 형태에도 영향을 받는다는 것을 확인하였다. 본 연구는 옥외용도에 적용하는 고분자막에 대한 중요한 정보를 제공할 수 있을 것으로 기대한다.

• Journal of Plant Biology
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• 제38권3호
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• pp.275-280
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• 1995

The formation of osmiophilic globules related to the granal lysis has been investigated with a shade plant ginseng (Panax ginseng C. A. Meyer) exposed to full sunlight. The changes of chloroplast were examined as a function of time over 9 days under full sunlight exposure. The ultrastructure of ginseng leaf showed swelling of the granal thylakoid during an early stage of the light exposure. The thylakoid membrane faded and small electron-opaque dots were aggregated on the edges of the granal thylakoid membrane when the exposure time was increased over 1 day. Then, the sahpe of the grana changed into round. After the exposure over 3 days, there appeared many osmiophilic globules with multi-lamellated concentric structure. The globules at this stage were partly accumulated with osmiophilic substances. The outermost membrane of these multi-lamellated osmiophilic globules was attached to the stromal thylakoid membrane connecting to the deforming grana. The osmiophilic globules were elongated after 9 days. In this stage, the multi-lamellated structure was difficult to identify due to severe accumulation of osmiophilic substances. The number of the osmiophilic globules also increased along with the full sunlight exposure time. This observation leads us to believe that the multi-lamellated osmiophilic globules came from the deformation of grana.

• Membrane and Water Treatment
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• 제5권4호
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• pp.235-250
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• 2014

The impacts of membrane degradation due to chlorine attack on the rejection of inorganic salts and trace organic contaminants by nanofiltration (NF) and reverse osmosis (RO) membranes were investigated in this study. The rejection of trace contaminants was examined at environmentally relevant concentrations. Changes in the membrane surface morphology were observed as a result of chlorine exposure. A small increase in rejection was consistently observed with all four membranes selected in this study after being exposed to a low concentration of hypochlorite (100 ppm). In contrast, a higher concentration of hypochlorite (i.e., 2000 ppm) could be detrimental to the membrane separation capacity. Membranes with severe chlorine impact showed a considerable decrease in rejection over filtration time, possibly due to rearrangement of the polyamide chains under the influence of chlorine degradation and filtration pressure. The reported results indicate that loose NF membranes are more sensitive to chlorine exposure than RO membranes. The impact of hypochlorite exposure (both positive and negative) on rejection is dependent on the strength of the hypochlorite solution and is more significant for the neutral carbamazepine compound than the negatively charged sulfamethoxazole.

• Environmental Analysis Health and Toxicology
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• 제24권1호
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• pp.33-41
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• 2009

Among the toxicants in the environment dioxin-like compounds, including TCDD(2,3,7,8-Tetrachlorodibenzo-p-Dioxin), are well known as carcinogen and teratogen. TCDD the most toxic of these compounds, may result in a wide variety of adverse health effects in humans and environment, including carconogenesis, hepatotoxicity, teratogenesis, and immunotoxicity. Also TCDD increases superoxide, peroxide radicals and induces oxidative stress that leads to breakage of DNA single-strand and mitochondrial dysfunction. Recently, there have been reports that persistent organic pollutants(POPs) may be causing metabolic disease through mitochondrial toxicity. In order to examine if dioxin brings about toxicity on mitochondria directly, we measured the change of the mitochondrial membrane potential after exposure to TCDD using JC-1 dye. After short time exposure of dioxin, mitochondrial depolarization was observed but it recovered to the control level immediately. This TCDD effect on mitochondrial membrane potential was not correlated either to the production of reactive oxygen species(ROS) or extracellular $Ca^{2+}$ by TCDD. Less than 2 hours exposure of TCDD did not show any change in ROS production but 0.25 nM TCDD for 48 hours or 0.5 nM TCDD for 12 hours exposure did increase in ROS production. Under these conditions of ROS production by TCDD, no changes in the mitochondrial membrane potential by TCDD was observed.