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정지헌,우윤주,이미현,Muhammad R. Haque,안철희,이해신,변영로 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.57 No.-
Porcine islets are an alternative cell source for cell replacement therapy in diabetes. However, porcineislets are very fragile, and isolated islets are easily damaged during culture. Therefore, the purpose of thisstudy was to incorporate a tissue-adhesive chitosan derivative on the surface of porcine islets to preventthe dissociation of porcine islet clusters into single cells. Chitosan-catechol was evenly covered on thesurface of islets without any toxicity. In addition, the tissue-adhesive chitosan catechol was effective inpreventing cell dissociation. Therefore, tissue adhesive chitosan-catechol conjugation onto the porcineislet surface is a promising technique to stabilize islets after isolation.
정지헌,육심명,변영로 한국고분자학회 2016 Macromolecular Research Vol.24 No.11
Improvements in preventing pancreatic islet rejection are needed for successful treatment of type 1 diabetes. Our objective was to develop an optimized protocol combining modification of islets with polyethyleneglycol (PEG) chains and administration of tacrolimus (FK506, Prograf), an immunosuppressive drug for preventing rejection following transplantation. Freshly isolated islets were incubated with different concentrations (0.25, 1.00, 10.00, and 25.00%) of FITC-labeled mPEG-SCM (MW. 20 KDa) for various incubation times. 1% mPEG-SCM incubated with islets for 1 h is optimized surface coverage condition without cell toxicity. In addition, in order to optimize the concentration of tacrolimus (FK506, Prograf), different concentrations (0.1, 0.5 or 2.0 mg/kg) were injected into the diabetic mice following transplantation of PEGylated islets. The PEGylated islet survival time in mice injected daily with 0.1 mg/kg and 0.5 mg/kg of tacrolimus was significantly better than in the group without tacrolimus injection. The graft survival time in mice injected daily with 2.00 mg/kg of exhibited no prolonged survival time. Finally, immunohistochemical staining of left kidney containing PEGylated islets (injected with 0.1 mg/kg of tacrolimus) demonstrated strong staining for insulin, glucagon, and somatostatin but very weak CD20 staining was observed in the islet transplanted area. In conclusion, 1% mPEG-SCM incubated with islets for 1 h was the optimal condition for PEGylation without affecting the cell viability. A dose of tacrolimus between 0.1-0.5 mg/kg was highly effective for inhibiting immune cell activation. These results are promising for their application in developing a novel immunosuppressive protocol for successful pancreatic islet transplantation in the treatment of type 1 diabetes.
Development of Inverse Model for Reservoir Characterization Using SA Algorithm
정지헌,권순일,이정환 한국자원공학회 2011 Geosystem engineering Vol.14 No.3
This paper presents the development and application of the inverse model that can generate the optimum distribution of permeability and porosity by matching the production data (bottomhole pressure) applying the Simulated Annealing algorithm. From the results of the feasibility study and the sensitivity analysis, if the maximum perturbation value was large, the fitness was improved highly at early stage of the optimization, but its improvement was smaller and smaller after middle stage. It was found that the appropriate size of the maximum perturbation value is required to escape from the local optimum. In the case of the maximum perturbation value for permeability of 1% and porosity of 2%, the maximum fitness was calculated to 0.00449 and the optimum distribution of porosity and permeability were generated. The pressure matching result showed the RMS error of pressure was 0.74psi and the average relative error was 0.036% at all producer,which means the developed model was quite valid. Finally, the comparison of the result performed by GA with this research showed that SA was similar to GA.
정지헌,한동권,김상호,유인항,권순일 한국가스학회 2020 한국가스학회지 Vol.24 No.1
Drilling operation is the most important and costly essential work in oil and gas exploration and development. Therefore, the studies about rate of penetration have been carried out continuously to improve drilling efficiency. In recent years, data-driven models have been developed by various researchers to overcome disadvantages of traditional mathematical models. For the data-driven models, selecting proper algorithms and parameters is very important. In addition, data-driven models should be retrained in real-time during continuous drilling operations in order to improve the model performance. In this paper, the latest studies are investigated to provide information about algorithms, drilling parameters and model retraining intervals that used in drilling optimization. 시추는 석유자원 탐사와 개발에서 가장 중요하며 많은 비용이 소요되는 필수 작업이다. 그래서 시추의 효율 향상을 위한 굴진율 연구가 지속적으로 진행되어왔다. 근래에는 전통적인 수학적 모델의 단점을 극복하기 위하여 새로운 방식의 자료기반 모델이 다양한 연구자들에 의해 개발되고 있다. 자료기반 모델은 알고리즘과 매개변수의 선택이 매우 중요하다. 또한 개발된 모델의 성능향상을 위하여 실시간으로 모델을 재훈련하여 연속적인 시추작업을실현해야한다. 이 논문에서는 최신 연구들을 조사하여 시추 최적화에서 사용된 알고리즘, 시추 매개변수, 모델 재훈련 간격에 대한 정보를 제공하고자 한다.
정지헌 대한약학회 2015 Archives of Pharmacal Research Vol.38 No.5
It is important to chase the function of isletafter transplantation. Thus, we examined the correlationbetween grafted islets function and molecular imagingintensity using Cy5.5 labeled islet. The ability of Cy5.5-PEG-NHS to chemically bind on the surface of islets wasdetermined by confocal laser scanning microscope. Then,fluorescence intensity of different number of Cy5.5 labeledislets was determined using optical imaging system. Wehave found out the intensity of fluorescence increased withincreasing the total number of islet in each well. In addition,different number of Cy5.5-labeled islet has beentransplanted into the athymic mice for in vivo imaging. Theintensity emitted from Cy5.5-labeled islets augmentedproportionally with increased number of transplanted islets. To understand the correlation between the function ofgrafted islet and the fluorescence intensity emitted opticalimaging system, Cy5.5-labeled islets have been transplantedinto F344 rats. The results revealed that there was acorrelation between the fluorescence intensity and the nonfastingblood glucose (NBG) levels of islets received rats. Strong fluorescence intensity corresponded to low NBGwhereas low signal was associated to high NBG. In conclusion,the fluorescence intensity emitted from Cy5.5-labeled islets can be used as a marker of cells viability andfunctionality after transplantation.
정지헌,백형환,김태운,고일규,지은상,신말순,김보균,서진희,김동희,진영호,백성수 대한스트레스학회 2010 스트레스硏究 Vol.18 No.4
Physical exercise enhances cell proliferation and/or neurogenesis in the hippocampal dentate gyrus. Brain-derived neurotrophic factor (BDNF) is implicated in the modulation of neurotransmitters turnover, neurite genesis, and neuronal survival. BDNF binds to the tyrosine kinas B (TrK). In this study, we compared the effects of the one bout of long-duration treadmill exercise and the repeated short-duration treadmill exercise on cell proliferation and expressions of BDNF and TrKB in the hippocampus. Adult male Sprague-Dawley rats, weighing 200±5 g, were randomly divided into three groups (n=8 in each group): control group, one hour-one bout-treadmill exercise group, and ten minutes-six bouts-treadmill exercise group. The rats in the one hour-one bout-treadmill exercise group were forced to run on a motorized treadmill for 60 min once a day (at 16:00). The rats in the ten minutes-six bouts-treadmill exercise group were forced to run on a treadmill once 10 minutes per six times for a day (at 10:00, 11:00, 14:00, 15:00, 19:00, 20:00). Treadmill exercise was continued for 7 consecutive days. The rats in the control group were left without running. Both types of treadmill exercise increased cell proliferation and enhanced expressions of BDNF and TrkB in the hippocampus. Cell proliferation and BDNF expression was more potently increased by the ten minutes-six bouts treadmill exercise than the one hour-one bout treadmill exercise. These results showed that repeated bouts of short-duration treadmill exercise may achieve more useful results for the brain functions than one-bout long-duration treadmill exercise. (Korean J Str Res 2010;18:295∼303) 운동은 해마 치상회에서 신경세포의 생성을 증가시킨다. 뇌 유래 신경영양 인자(brain-derived neurotrophic factor, BDNF)는 신경전달 물질의 분비, 신경 성장, 그리고 신경의 생존 등에 관여하며, tyrosine kinas B (TrK)에 결합하게 된다. 본 연구에서, 일회의 긴 시간 운동과 여러 번의 짧은 시간의 운동이 해마에서 신경세포 생성과 뇌 유래 신경영양 인자와 TrKB의 발현에 미치는 영향을 비교하였다. 무게 200±5 g의 Sprague-Dawley계 흰쥐를 대조군, 하루 1시간 1회 운동군, 하루 10분씩 6회 운동군의 세 군으로 분류하였다(각 군=8마리). 하루 1시간 1회 운동군은 16시에 매일 한 시간씩 트레드밀 운동을 시행하였다. 하루 10분씩 6회 운동군은 10시, 11시, 14시, 15시, 19시, 20시에 각 10분씩 하루 6번 트레드밀 운동을 시행하였다. 이러한 운동은 7일간 지속하였다. 실험결과, 두 가지 형태의 트레드밀 운동 모두 해마에서 신경세포 생성과 뇌 유래 신경영양 인자, 그리고 TrkB의 발현을 증가시켰다 신경세포 생성과 뇌 유래 신경영양 인자는 하루 10분씩 6회 운동군에서 더욱 증가되었다. 본 실험을 통하여 긴 시간의 일회 운동보다 짧은 시간 여러 번 운동이 뇌기능의 향상에 좋은 결과를 미침을 알 수 있었다.
디지털시대의 영상과 그 사회적 의미에 관하여 : 영상매체의 발달과 관련해서
정지헌 한국일러스트레이션학회 2007 일러스트레이션 포럼 Vol.15 No.-
영상이 아날로그에서 디지털로 바뀌면서 영상산업 전반뿐만 아니라 사회적으로도 많은 영향을 미치고 있다. 디지털 영상의 특징은 기저의 의미는 나타나지 않고, 의미 없는 외형적인 이미지들만 난무하여 기존의 근대적 사고방식으로는 이해하기 어려울 뿐만 아니라 근대성의 사고와 가치는 붕괴되기 때문에 새로운 접근방식이 필요한 것이다. 그러나 디지털 시대의 영상은 우리의 삶을 아름답고, 편하고, 자유롭게 만들어야함에도 불구하고, 다국적 기업들 또는 정치적 목적의 수단으로 그 미래가 불투명할 뿐만 아니라 오히려 우리의 인간성 말살을 조장하기도 한다. 과학이 변하지 않는 진실을 사용해 이데올로기로부터 자유로워야 함에도 불구하고 오히려 이데올로기에 의해서 이용되고 변질되었던 것처럼, 디지털영상은 자유로움의 추구보다는 문화제국주의적(cultural imperialism) 이데올로기가, 정치, 삶의 방식 등이 새로운 매체를 통하여 전 세계적으로 퍼지고 있다. 하지만 오늘날 디지털시대에 영상의 지향점은 인간성 회복과 삶의 질 향상에 초점을 맞춰야한다. 누구나 영상에 접할 수 있고, 누구나 촬영과 편집, 배포를 할 수 있으며, 원활한 소통을 통한 자유로움의 추구와 개인의 존중을 실현시킬 수 있는 장이다. 디지털 영상에 의해서 휘둘리기 시작하면 이것은 큰 역효과를 내게 되며 우리는 더 이상 헤어 나올 수 없는 암울한 세계로 빠져들게 될 것이다. 이렇듯 디지털 시대의 영상은 철저한 양면성과 다원성을 동시에 가지고 있으며, 역동적이고 무한한 잠재력을 구현할 수 있다고 볼 수 있다. The images are changing from analog to digital and the social influence of images is bigger than ever before. The uniqueness of digital images is that they don't show the connotative meanings but mainly show the denotative meanings, therefore, we need to have a new way to understand the digital images. The images in digital era, should help for our better life, but because of the multinational corporations' profits and returns, the digital images are somewhat used in wrong ways.However, in digital era, the intention of the images should recover humanity and improve the quality of our life. People shouldn't be controled by manipulated digital images. Nowadays, anybody can make digital images and give out the images what they made, and also people pursue communication with each other by digital images. The digital images are very close to our lives and people should grasp the digital images' real nature. As described before, The images in digital era, have two different faces which are positive way and wrong way. We will have to try to understand the real connotative meanings of digital images and those effort should make our lives better.