• 제목/요약/키워드: irreversible change

검색결과 107건 처리시간 0.227초

세라믹 막여과의 성능향상을 위한 응집 전처리의 적용 (Application of coagulation pretreatment for enhancing the performance of ceramic membrane filtration)

  • 강준석;송지영;박서경;정아영;이정준;서인석;채선하;김성수;김한승
    • 상하수도학회지
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    • 제31권6호
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    • pp.501-510
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    • 2017
  • In this study, it is estimated that ceramic membrane process which can operate stably in harsh conditions replacing existing organic membrane connected with coagulation, sedimentation etc.. Jar-test was conducted by using artificial raw water containing kaolin and humic acid. It was observed that coagulant (A-PAC, 10.6%) 4mg/l is the optimal dose. As a results of evaluation of membrane single filtration process (A), coagulation-membrane filtration process (B) and coagulation-sedimentation-membrane filtration process (C), TMP variation is stable regardless of in Flux $2m^3/m^2{\cdot}day$. But in Flux $5m^3/m^2{\cdot}day$, it show change of 1-89.3 kpa by process. TMP of process (B) and (C) is increased 11.8, 0.6 kpa each. But, the (A) showed the greatest change of TMP. When evaluate (A) and (C) in Flux $10m^3/m^2{\cdot}day$, TMP of (A) stopped operation being exceeded 120 kpa in 20 minutes. On the other hand, TMP of (C) is increased only 3 kpa in 120 minutes. Through this, membrane filtration process can be operated stably by using the linkage between the pretreatment process and the ceramic membrane filtration process. Turbidity of treated water remained under 0.1 NTU regardless of flux condition and DOC and $UV_{254}$ showed a removal rate of 65-85%, 95% more each at process connected with pretreatment. Physical cleaning was carried out using water and air of 500kpa to show the recovery of pollutants formed on membrane surface by filtration. In (A) process, TMP has increased rapidly and decreased the recovery by physical cleaning as the flux rises. This means that contamination on membrane surface is irreversible fouling difficult to recover by using physical cleaning. Process (B) and (C) are observed high recovery rate of 60% more in high flux and especially recovery rate of process (B) is the highest at 95.8%. This can be judged that the coagulation flocs in the raw water formed cake layer with irreversible fouling and are favorable to physical cleaning. As a result of estimation, observe that ceramic membrane filtration connected with pretreatment improves efficiency of filtration and recovery rate of physical cleaning. And ceramic membrane which is possible to operate in the higher flux than organic membrane can be reduce the area of water purification facilities and secure a stable quantity of water by connecting the ceramic membrane with pretreatment process.

항콜린에스테라제 약물의 소화관 운동성에 대한 영향 (The Effects of Anticholinesterase Drugs on Gastric Motility)

  • 최형철;김종호;하정희;이광윤;김원준;곽동석;김성희;송필현;여지현
    • Journal of Yeungnam Medical Science
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    • 제16권2호
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    • pp.318-325
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    • 1999
  • 항콜린에스테라제 약물은 AChE를 억제하여 ACh을 콜린성 수용체에 축적시켜 지속적인 ACh 자극을 유도하는 약물이다. 이러한 특성이 적출한 위장의 운동성에 미치는 영향과 콜린에스테라제 활성화 약물의 영향을 조사하고, 에탄올이 AChE의 활성도를 감소시키는 보고를 바탕으로 항콜린에스테라제와 에탄올의 동시 투여시 나타나는 위장관의 수축운동의 변화를 규명하고자 다음과 같은 실험을 수행하였다. 흰쥐의 위장을 적출하여 $2{\times}10mm$ 환상근 절편을 만들어 적출근편 실험조에 고정하고 등척성 장력측정기를 이용하여 약물 처치에 따른 위장 절편의 수축 변화를 측정하였다. 비가역성 항콜린에스테라제인 fenthion은 ACh 유발 위장 절편의 수축을 증가시켰으며 콜린에스테라제 활성화 약물인 PAM은 이 작용을 길항하였다. 가역성 항콜린에스테라제인 physostigmine은 그 자체로 인해 위장 절편의 수축이 증가하였는데, 이는 비극성을 나타내어 위장 절편 조직으로의 흡수가 빠르기 때문이라고 생각되고, ACh에 의한 반응성 또한 현저히 증가하였다. PAM에 의한 반응성 감소효과도 대조군과 통계적으로 유의한 차이를 보였다. 최근 평활근 이완을 유도한다고 알려진 에탄올은 fenthion 처치에 의한 수축운동 증가를 억제하였고 이러한 결과로 볼 때 항콜린에스테라제와 에탄올의 동시 투여시에는 콜린에스테라제 활성도 감소보다 에탄올에 의한 위장관 운동성 감소가 많이 작용함을 의미하였다. 이상의 결론은 가역성 및 비가역성 항콜린에스테라제에 의해서 위장관 운동성 항진이 나타나고 이는 콜린에스테라제의 활성화 약물로서 길항되었다. 그리고 에탄올과 항콜린에스테라제에 동시에 노출된 경우는 에탄올의 평활근 이완 효과에 의해 위장관 운동성 감소가 나타남을 알 수 있었다.

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볼밀링법으로 제조된 흑연-실리콘 복합체의 리튬전지 음전극 특성 (Lithium Battery Anode Properties of Ball-Milled Graphite-Silicon Composites)

  • 강근영;신동옥;이영기;김광만
    • Korean Chemical Engineering Research
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    • 제51권4호
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    • pp.411-417
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    • 2013
  • 리튬 2차전지 음전극 활물질로 사용하기 위해, 실리콘(Si) 나노입자(평균입경 100 nm, 0~50 wt%)와 흑연 분말(평균입경 $15{\mu}m$)을 사용하여 볼밀링법으로 흑연-실리콘 복합체 분말을 제조하고 그 전기화학적 특성을 조사하였다. 실리콘 함량이 증가할수록 흑연은 볼밀링에 의해 입경이 작아지고 무정형 특성을 보이는 반면, 실리콘 입자는 나노결정성의 변화 없이 무정형 흑연 내에 싸여진 형태로 유지되었다. 저속 사이클릭 볼타메트리 특성상 0.2~0.35 V와 0.55~0.6 V에서 각각 흑연과 실리콘의 전형적 산화피크가 검출되었고 가역성도 우수(첫 사이클 제외)한 반면, 고속 거동에서는 사이클 반복에 따른 비가역성이 현저하게 나타났다. 또한 충방전 초기에는 큰 비가역 용량이 나타나지만 사이클 경과에 따라 감소하였으며, 특히 실리콘을 20 wt% 정도 포함하는 복합체가 50 사이클에서 약 485 mAh $g^{-1}$의 포화된 방전용량을 나타내었다. 이것은 실리콘을 싸고 있는 흑연의 무정형 상이 실리콘-리튬의 합금/탈합금에 따른 체적 변화를 안정적으로 완충할 수 있는 모폴로지가 재료의 적정 조성(흑연:실리콘=8:2 w/w)에 의해 형성되었기 때문이다.

수정진동자를 이용한 프탈로시아닌 LB박막의 $NO_2$ 감지 특성 (The Application of Octa-Substituted Metallophthalocyanine Langmuir-Blodgett films for $NO_2$ Measurement)

  • 권현정;이영진;장용근;김종득
    • 센서학회지
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    • 제7권4호
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    • pp.254-262
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    • 1998
  • 수정진동자(QCM)위에 네 종류의 프탈로시아닌($MPc(OEH)_8$, M ${\equiv}$ Cu, Co, Sn, $H_2$) LB박막을 여러 층 적층시킨 후 순수한 질소 분위기 하에서 $NO_2$에 노출시켜 그 농도를 정량화 하였다. 사용한 네 종류의 프탈로시아닌 중에서 중심위치에 금속 이온이 자리하지 않은 $H_2Pc(OEH)_8$ 감응막이 $NO_2$에 대하여 가장 민감한 것으로 나타났다. 그러나 이 박막은 $NO_2$에 노출된 후 질소로 퍼지해도 처음의 주파수를 회복하지 못하는 비가역적인 흡착 양상을 보였다. NMR과 FTIR 스펙트럼 조사 결과 비가역적인 흡착은 빙고링과 프탈로시아닌 곁가지의 결합부위인 ether 그룹에서 일어나는 것으로 판명되었다. 따라서 비가역적으로 흡착이 일어나는 부분을 미리 고농도에서 포화시키는 방법으로 박막을 전처리 한 후 반복실험에 사용하였다. $CuPc(OEH)_8$박막 사용 시 수십 ppm 수준부터 4 ppm의 $NO_2$ 농도까지 정량화가 가능하였고 $H_2Pc(OEH)_8$ 박막의 경우에는 수 ppm부터 35 ppb까지의 낮은 농도까지 정량화가 가능하였다. 또한, 실제 대기 조건을 모사하기 위하여 운반기체를 순수한 질소 대신 공기로 교체하여 $H_2Pc(OEH)_8$ 감응막의 성능을 실험한 결과 산소의 영향으로 센싱 가능 한계가 수백 ppb 수준으로 증가하였다. 습기가 운반기체에 포함된 경우 감지 성능에 매우 큰 영향을 미쳤다.

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Pulsed Nd:YAG 레이저 조사거리에 따른 상아질의 온도변화 (Temperature Changes in Dentin upon Pulsed Nd:YAG Lasing Distance)

  • Jae-Hyung Kim;Woo-Cheon Kee
    • Journal of Oral Medicine and Pain
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    • 제20권2호
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    • pp.327-334
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    • 1995
  • In order to observe the influence of pulsed Nd:YAG laser at its out-of-contact with dentin on tooth temperature, we have applied pulsed Nd:YAG laser to 2mm thick dentin sample at a point of contact and from a distance of 1mm, 2mm, 3mm and 4mm with an energy of 0.3W, 0.5W, 0.8W, 1.5W and 2.0W. They were exposed to periods of 3 seconds, 6 seconds, 9 seconds and 15 seconds respectively and measured temperature changes. The results as follows : 1. When the time ad intensity of power were constant, the temperature changes on dentin of tooth depended on the distance. The temperature increased when the laser intensity increased bu two other conditions were contact. 2. At the point of contact, the temperature has risen over $5^{\circ}C$ regrdless of intensity of the power or the time. However, there was $5^{\circ}C$ fluctuation with 0.3 W for 3 seconds treatment. 3. The temperature change was less than $5^{\circ}C$ thermal change at the distance of 1mm and 2mm respectively when lased for 3 seconds, 6 seconds, 12 seconds and 15 seconds with 0.3 W. Similar results were observed at 3 and 6 seconds treatment with 0.5 W and at 3 seconds treatment with 0.8 and 1.0W respectively. 4. It showed less than 5(C thermal change when lased for 3 seconds, 6 seconds, 9 seconds, 12 seconds and 15 seconds with 0.3W at the distance of 3mm and 4mm. The same results were seen in 3 seconds, 6 seconds and 9 seconds treatment with 0.5W and in 3 seconds with 0.8W and 1.0W respectively. As we have seen the above, the results has indicated that pulsed Nd:YAG lasing at its off contact on dentin of 2mm thickness will not cause irreversible changes if lasing intensity, lasing distance and lasing time are appropriate.

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The Singapore Field Epidemiology Service: Insights Into Outbreak Management

  • Ooi, Peng-Lim;Seetoh, Theresa;Cutter, Jeffery
    • Journal of Preventive Medicine and Public Health
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    • 제45권5호
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    • pp.277-282
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    • 2012
  • Field epidemiology involves the implementation of quick and targeted public health interventions with the aid of epidemiological methods. In this article, we share our practical experiences in outbreak management and in safeguarding the population against novel diseases. Given that cities represent the financial nexuses of the global economy, global health security necessitates the safeguard of cities against epidemic diseases. Singapore's public health landscape has undergone a systemic and irreversible shift with global connectivity, rapid urbanization, ecological change, increased affluence, as well as shifting demographic patterns over the past two decades. Concomitantly, the threat of epidemics, ranging from severe acute respiratory syndrome and influenza A (H1N1) to the resurgence of vector-borne diseases as well as the rise of modern lifestyle-related outbreaks, have worsened difficulties in safeguarding public health amidst much elusiveness and unpredictability. One critical factor that has helped the country overcome these innate and man-made public health vulnerabilities is the development of a resilient field epidemiology service, which includes our enhancement of surveillance and response capacities for outbreak management, and investment in public health leadership. We offer herein the Singapore story as a case study in meeting the challenges of disease control in our modern built environment.

투과전자현미경을 이용한 수종의 수복재가 L292세포의 미세구조 변화에 미치는 영향 (EFFECT OF SEVERAL RESTORATIVE MATERIALS ON ULRASTRUCTURAL CHANGES OF L929 CELLS USING TRANSMISSION ELECTRON MICROSCOPE)

  • 임미경
    • Restorative Dentistry and Endodontics
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    • 제21권1호
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    • pp.385-402
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    • 1996
  • Cytotoxicity of dental restorative materials using cell culture technique has been extensively studied by various quantitative assays. The aim of this study was to investigate the microstructural change of damaged L292 cells which could not observed with light microscope. Cytotoxic effect of ZOE, Prisma APH (Densply International Inc., U.S.A.), Clearfil FII(Kuraray Co., Japan), Fuji II(GC Co., Japan) and Fuji II LC(GC Co., Japan) on cultured L292 cells were observed. Irreversible cell damage and cytolysis were found in ZOE and Fuji II groups. In Clearfil FII, mild to moderate cell damage was observed. APH group showed variable cytotoxicity. Moderate cell damage was found in Fuji II LC group. Cytotoxic effect were as follows : A condensation of the chromatin occureds along or adjacent to the inner membrane of the nuclear envelops. The nuclear envelope remained resonably intact but the contents were partially or completely lost. The cell nucleus contains clusters of markedly electron-dense interchromatin granules. The rough endoplasmic reticulum were dilated. In some mitochondira, matrix was disoriented and fused cristae were discernible. Mitochondiral swelling and woolly appearance were recognized. Large vacuoles and autolysosmes were found in cytoplasm. Some breaks of the cytoplasmic membrane and even cytolysis could be seen in dying cells.

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Coumarin 유도체들의 전기화학적 환원과 형광성의 증강 (Enhancement of Fluorescent Properties and Electrochemical Reduction of Coumarin Derivatives)

  • 천현자;김성현;정은주;이혜숙;김일광
    • 분석과학
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    • 제18권1호
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    • pp.89-95
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    • 2005
  • Studies on the electrochemical reduction of 7-acetoxy-4-bromomethyl-coumarin (ABMC), 7-acetoxymethyl coumarin (AMC), and coumarin in 0.1 M tetraethyl ammonium perchlorate acetonitrile solution were carried out with direct current, differential pulse polarography, cyclic voltammetry, and controlled potential coulometry. The electrochemical reduction of ABMC was proceeded through three irreversible steps coupled with the chemical reactions. The solution color was changed to yellow when the carbonyl group was reduced during second step and the color change was independent with bromo group of ABMC. Fluorescent intensity was highest when the electrochemical reduction was controlled at near the overpotential of supporting electrolyte (-2.3 volts).

반사상 교감 신경 위축 증후군에 대한 교감신경 차단효과 -증례 보고- (Effects of Repeated Sympathetic Blocks for Reflex Sympathetic Dystrophy Syndrome -A Case Report-)

  • 배운호;노선주;고준석;민병우
    • The Korean Journal of Pain
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    • 제3권2호
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    • pp.165-171
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    • 1990
  • The reflex sympathetic dystrophy syndrome (RSDS) consists of sustained burning pain and tenderness, vasomotor instabilitiy, swelling, occasional functional instability, trophic skin change and edema of extremity following trauma, peripheral nerve injury, spinal cord injury, infection, burn and other etiologic factors. The most important thing in RSDS is to start the treatment as soon as the disease was diagnosed. Most patients with RSDS respond dramatically and permanently to sympathetic blocks if treatment is instituted before irreversible trophic changes. The characteristic radiological finding in RSDS is a patchy osteoporosis in the cancellous bone. Periarticular hyperactivity is seen in RSDS by Tc99m bone scan. We have managed 4 cases of RSDS. The methods of management and effects are as follows: 1) In case 1, 28 lumbar sympathetic blocks in both sides were performed. The patient did not complain of pain or tenderness and the limping improved. 2) In case 2, 7 lumbar sympathetic blocks were performed, but we could find only a slight improvement in the symptoms. 3) In case 3, 8 stellate ganglion blocks were carried out. The patient refused the treatment of RSDS because of the lack of rapid improvement. 4) In case 4, total 64 stellate ganglion blocks were carried out; the patient was permanently improved.

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Adsorption of chlorhexidine digluconate on acid modified fly ash: Kinetics, isotherms and influencing factors

  • Singh, Astha;Sonal, Sonalika;Kumar, Rohit;Mishra, Brijesh Kumar
    • Environmental Engineering Research
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    • 제25권2호
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    • pp.205-211
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    • 2020
  • Chlorhexidine digluconate (CHD) in the aquatic environment causes irreversible change to microbes, making them resistant to biodegradation, which needs remediation other than biological process. Adsorption study was performed for the removal of CHD on fly ash (FA) as a function of pH and ionic strength. Experimental result has been validated by characterization using Scanning electron microscopy, Fourier Transform-Infrared Spectroscopy and Brunauer-Emmett-Teller. CHD adsorption with FA showed an increasing trend with an increase in pH. Variation in pH proved to be an influential parameter for the surface charge of adsorbent and the degree of ionization of the CHD molecules. The adsorption capacity of CHD decreased from 23.60 mg g-1 to 1.13 mg g-1, when ionic strength increased from to M. The adsorption isotherms were simulated well by the Freundlich isotherm model having R2 = 0.98. The Lagergren's model was incorporated to predict the system kinetics, while the mechanistic study was better explained by pseudo-second order for FA. On the basis of operational conditions and cost-effectiveness FA was found to be more economical as an adsorbent for the adsorption of CHD.