Liquid Crystal Elastomers: Dynamic, Shape-Changing Materials

Suk-Kyun Ahn(안석균) 한국고분자학회 2019 한국고분자학회 학술대회 연구논문 초록집 Vol.44 No.1

Liquid Crystal Elastomer-based Shape Transformable Materials

Suk-Kyun Ahn(안석균) 한국고분자학회 2022 한국고분자학회 학술대회 연구논문 초록집 Vol.47 No.2

Embedding Intelligence in Polymers via Liquid Crystal Units

Suk-Kyun Ahn(안석균) 한국고분자학회 2022 한국고분자학회 학술대회 연구논문 초록집 Vol.47 No.1

Programmable and Reconfigurable Liquid Crystal Elastomers: Synthesis, Alignment and Actuation

Suk-Kyun Ahn(안석균) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1

Liquid crystal elastomers (LCEs) are emerging smart materials featured by reversible and programmable actuation. To enable such actuating property, a proper chemistry that can couple with LCE alignment process is essential. Here, the preparation of macroscopically aligned LCE monoliths through various synthetic strategies (e.g., Michael-addition and photopolymerization) and alignment methods (e.g., surface, mechanical and shear alignment) will be presented. With these strategies, we successfully demonstrate various programmable (and reprogrammable) actuation of LCEs commanded by heat as well as humidity. Our work can expand opportunities for structural design and functionality of LCEs, and expedite their potential applications for soft-robotics, adaptive textiles, and responsive surfaces.

쥐의 좌심방에서 세포막을 통한 $Ca^{2+}\;Flux$에 영향을 주는 약물이 자극빈도-장력 곡선에 미치는 영향

김찬윤,안석균,서창국,강두희,Kim, Chan-Yun,Ahn, Sok-Kyun,Suh, Chang-Kook,Kang, Doo-Hee 대한생리학회 1989 대한생리학회지 Vol.23 No.2

Cardiac muscles show stimulation frequency-dependent tension changes i.e. Bowditch phenomenon and Woodworth phenomenon, the former is an increase of tension with the increase of stimulation frequency, whereas the latter is an increase of tension with a decrease of stimulation frequency. Bowditch phenomenon is seen in the range of frequency 1.0 cps and above, and Woodworth phenomenon below the frequency 1.0 cps in the most of mammalian cardiac atrium. To throw some light on the possible mechanism of both phenomena in rat atrium, influences of drugs affecting $Ca^{2+}$ influx through the plasma membrane $(verapamil,\;La^{3+},\;norepinephrine)$ and $Ca^{2+}$ release from sarcoplasmic reticulum (SR) on frequency-tension curve were studied. The results obtained are summarized as follows: 1) At low temperature $(27.5^{\circ}C)$, both Bowditch and Woodworth phenomenon were demonstrated. But Bowditch phenomenon disappeared at the temperature above $(32.5^{\circ}C)$. 2) At $(27.5^{\circ}C)$, in the presence of verapamil, a $Ca^{2+}$ channel blocker, a time course of change in the frequency-tension was studied. It was found that Bowditch phenomenon was affected before the Woodworth phenomenon, then the former was completely disappeared. At $(32.5^{\circ}C)$, where no Bow-ditch is seen in normal atrial muscle, Bowditch phenomenon was reappeared by an administration of norepinephrine suggesting again that slow inward current of such as $Ca^{2+}$ channel is closely related to Bowditch phenomenon. 3) At $27.5^{\circ}C$, in the presence of $La^{3+}$, although tensions were decreased at all stimulation frequencies, Bowditch and Woodworth phenomenon were still demonstrated. However in the presence of both $La^{3+}$ and verapamil, Bowditch phenomena was disappeared suggesting that $La^{3+}$ is less effective in blocking $Ca^{2+}$ channel than verapamil. 4) At $27.5^{\circ}C$, in the presence of ryanodine, an inhibitor of calcium release from SR, Woodworth phenomenon was disappeared, which was consistent with previous reports of others, suggesting that $Ca^{2+}$ release from SR is closely related to Woodworth phenomenon. From the above findings, it may be concluded that Bowditch phenomenon is dependent on the magnitude of $Ca^{2+}$ influx through slow channel and Woodworth phenomenon is dependent on the amount of $Ca^{2+}$ stored in SR.

쥐의 좌심방에서 세포막을 통한 Ca²⁺ Flux에 영향을 주는 약물이 자극빈도-장력 곡선에 미치는 영향

김찬윤(Kim, Chan-Yun),안석균(Ahn, Sok-Kyun),서창국(Suh, Chang-Kook),강두희(Kang, Doo-Hee) 대한생리학회 1989 대한생리학회지 Vol.23 No.2

Cardiac muscles show stimulation frequency-dependent tension changes i.e. Bowditch phenomenon and Woodworth phenomenon, the former is an increase of tension with the increase of stimulation frequency, whereas the latter is an increase of tension with a decrease of stimulation frequency. Bowditch phenomenon is seen in the range of frequency 1.0 cps and above, and Woodworth phenomenon below the frequency 1.0 cps in the most of mammalian cardiac atrium. To throw some light on the possible mechanism of both phenomena in rat atrium, influences of drugs affecting Ca²⁺ influx through the plasma membrane (verapamil, La³⁺, norepinephrine) and Ca²⁺ release from sarcoplasmic reticulum (SR) on frequency-tension curve were studied. The results obtained are summarized as follows: 1) At low temperature (27.5℃), both Bowditch and Woodworth phenomenon were demonstrated. But Bowditch phenomenon disappeared at the temperature above (32.5℃). 2) At (27.5℃), in the presence of verapamil, a Ca²⁺ channel blocker, a time course of change in the frequency-tension was studied. It was found that Bowditch phenomenon was affected before the Woodworth phenomenon, then the former was completely disappeared. At (32.5℃), where no Bow-ditch is seen in normal atrial muscle, Bowditch phenomenon was reappeared by an administration of norepinephrine suggesting again that slow inward current of such as Ca²⁺ channel is closely related to Bowditch phenomenon. 3) At 27.5℃, in the presence of La³⁺, although tensions were decreased at all stimulation frequencies, Bowditch and Woodworth phenomenon were still demonstrated. However in the presence of both La³⁺ and verapamil, Bowditch phenomena was disappeared suggesting that La³⁺ is less effective in blocking Ca²⁺ channel than verapamil. 4) At 27.5℃, in the presence of ryanodine, an inhibitor of calcium release from SR, Woodworth phenomenon was disappeared, which was consistent with previous reports of others, suggesting that Ca²⁺ release from SR is closely related to Woodworth phenomenon. From the above findings, it may be concluded that Bowditch phenomenon is dependent on the magnitude of Ca²⁺ influx through slow channel and Woodworth phenomenon is dependent on the amount of Ca²⁺ stored in SR.

액정 엘라스토머 기반 소프트 액추에이터

배재희 ( Jaehee Bae ),김금비 ( Keumbee Kim ),최수비 ( Subi Choi ),안석균 ( Suk-kyun Ahn ) 한국공업화학회 2021 공업화학전망 Vol.24 No.6

자극응답성 액정 엘라스토머(liquid crystal elastomer)는 하이드로겔(hydrogel), 형상 기억 고분자(shape memory polymer)와 더불어 생체 특성을 모방한 인공 근육, 소프트 액추에이터 및 소프트 로봇을 위한 스마트 소재로 최근 높은 관심을 받고 있다. 특히, 액정 엘라스토머는 고무 탄성과 액정 이방성이 결합된 비등방성 탄성 고분자로, 열, 빛, 전기 및 수분과 같은 외부자극에 반응하여 가역적이며, 액정 분자들의 배향조절을 통한 프로그램된 변형이 가능하다. 액정 엘라스토머가 개념 증명을 하는 수준을 넘어 실제로 유용한 소프트 액추에이터 및 로봇 시스템에 적용되기 위해서는 우수한 구동력 및 작업 용량, 높은 구동 변형률, 빠른 응답 시간, 낮은 구동 온도, 다양한 외부 자극반응성 및 높은 에너지 전환 효율 등을 확보하는 것이 중요하다. 본 기고문에서는 액정 엘라스토머의 개념에 대해 소개하고, 이러한 소재가 소프트 액추에이터로써 광범위하게 활용될 수 있도록 다양한 성능들을 향상시킬 수 있는 방법에 대해 소개하고자 한다.

정신분열병 환자에서 Haloperidol이 99m-Tc-ECD SPECT로 측정한 국소뇌혈류량에 미치는 영향

천근아,이종두,민성길,김세주,안석균 大韓神經精神醫學會 1999 신경정신의학 Vol.38 No.4

연구목적 : 정신분열병 환자에서의 뇌혈류량은 약리학적 상태를 포함한 다양한 요소들에 의하여 영향을 받는다. 항정신병약물이 국소뇌혈류량에 미치는 영향에 관한 많은 연구가 행해져 왔으나 항정신병약물의 종류와 노출기간, 약물용량의 차이로 인해 다양하고도 상반된 결과를 보여왔다. 따라서 본 연구에서는 정신분열병 환자에서 항정신병약물의 종류와 노출기간을 통제한 상태에서 약물 투여시 국소뇌혈류량의 변화를 관찰하고자 하였다. 방 법 : 항정신병약물 비노출(antipsychotic drug-naive) 정신분열병 환자 18명과 haloperidol을 투여받은 환자 19명을 대상으로 안정 상태(resting state)에서 SPECT를 촬영하여 국소뇌혈류량을 측정한 후 두군 사이의 상대적 뇌혈류량을 비교하였다. Haloperidol은 D2 수용체에 비교적 선택적으로 작용하고 활성대사산물이 적기 때문에 실험약물로 선택되었고 약물노출기간은 1∼3주동안으로 제한하였다. 결 과 : 우측 저측두엽, 좌측 저전두엽, 좌·우측 기저신경절, 좌측 시상에서의 상대적 평균 혈류지표는 halo-peridol 투여군에서 비노출군에 비해 유의하게 증가되어 있었다. 또한 좌·우측 두정-후두엽과 우측 두정엽에서의 상대적 평균 혈류지표도 haloperidol 투여군에서 비노출군에 비해 유의하게 증가되어 있었다. 반면 좌측 저측두엽의 상대적 평균 혈류지표는 haloperidol 투여군에서 항정신병약물 비노출군에 비해 유의하게 감소되어 있었다. 그러나 우측 저전두엽, 우측 시상, 좌·우측 고측두엽, 좌·우측 고전두엽, 좌측 두정엽에서 두 군 사이의 상대적 평균 혈류지표는 유의한 차이를 보이지 않았다. 결 론 : 정신분열병 환자에서 항정신병약물이 국소뇌혈류량에 영향을 미치며, 항정신병약물 투여상태가 뇌혈류량 측정시 고려되어야할 중요한 변수임을 시사한다. Objectives : Regional cerebral blood flow(rCBF) in schizophrenics is confounded by various factors including medication status. Previously, there have been numerous studies regarding the effects of antipsychotics on rCBF. However, these works have shown contradictory and inconsistent findings due to the different of type, dose and exposed duration of antipsychotics. The aim of this study was to observe the effect of antipsychotic medication on rCBF and exposed duration of antipsychotics under control. Methods : Eighteen drug-naive schizophrenics and 19 schizophrenics medicated with halo-peridol were included in the study. Regional cerebral blood flow was assessed with single-photon emission computed tomography(SPECT) under a resting state. Relative rCBF was compared between two groups. Haloperidol was selected as the antipsychotic drug as it has relatively selective action at the D2 receptor and less active metabolites. Exposed duration was limited from one to three weeks. Results : Haloperidol-medicated schizophrenic patients had a significantly greater increase of relative cerebral perfusion in the right inferior temporal lobe, left inferior frontal lobe, both basal ganglia, left thalamus, both parieto-occipital lobes, and right parietal lobe than drug-naive schizophrenic patients. Haloperidol-medicated schizophrenic patients had a significant decrease of relative cerebral perfusion in left inferior temporal lobe. However, no significant differences in relative rCBF were found between drug-naive and haloperidol-medicated schizophrenic patients in right inferior frontal lobe, right thalamus, both superior temporal lobes, both superior frontal lobes, and left parietal lobe. Conclusion : These findings suggest that antipsychotics affect regional cerebral blood flow, and antipsychotic medication status must be considered in the relative rCBF studies of schizophrenic patients.

항정신병약물 비노출과 비투여 정신분열증 환자의 99m-Tc-ECD SPECT로 측정한 상대적 뇌혈류량 차이

김세주,안석균,전덕인,이종두,민성길 大韓神經精神醫學會 1998 신경정신의학 Vol.37 No.6

연구 목적: 정신분열중 환자에서 뇌 혈류량은 나이. 성별, 이환기간, 임상양상 등에 영향을 받는다. 또한 약리학적 상태도 고려해야 할 중요한 요소이다. 그러나 항정신병약물 비투여 (drug-free) 정신분열증 환자군과 전혀 약물을 복용하지 않은 환자군(drug-naive)사이의 상대적 뇌혈류량에 대한 유용한 자료는 거의 없다. 이런 상태에서 많은 연구들이 '항정신병약물 비노출군과 비 투여군의 상대적 뇌혈류량 양상이 동일할 것이다.'라는 가정에서 두 군 모두를 '현재 약물을 복용하고 있지 않은(unmedicated)'정신분열증 환자에 포함시켜 연구하고 있다. 따라서 본 연구에서는 뇌혈류량에 영향을 미칠 것으로 생각되는 나이, 성별. 이환기간, 임상중상(양성증상 및 음성증상) 등의 혼란변수를 통제한 상태에서 항정신병약물 비노출 정신분열증 환자화 비투여 정신분열증 환자의 뇌혈류량이 동일한지 여부를 알아보고자 하였다. 연구방법 : 항정신병약물 비노출(antipsychotic drug-rlaive) 정신분열증 환자 18명과 비투여(drug-free) 환자 15명을 대상으로 안정 상태에서 SPECT를 촬영하여 국소 뇌혈류량을 폭정하였고, 두 군 사이의 상대적 뇌혈류량을 비교하였다. 결 과: 좌측 저측두엽, 우측 저전두엽. 좌 · 우측 기저신경절, 좌 · 우측 시상. 좌 · 우측 고측두엽. 우측 두정-후두염 및 좌 · 우측 고전두엽에서 두 군 사이의 상대적 평균 혈류지표는 유의한 차이를 보이지 않았다. 그러나 우측 저측두엽과 좌측 저전두엽에서의 상대적 평균 혈류지표는 항정신병약물 비투여군에서 비노 출군에 빅해 유의하게 증가되어 있었다. 또한,좌측 두정∼후두엽과 좌·우측 두장엽에서의 상대적 평균 혈류지표는 항정신병약물 비노출군에서 비투여에 비해 유의하게 증가되어 있었다. 결 론; 항정신병약물 비노출 정신분열증 환자군과 비투여 환자군의 상대적 뇌 혈류량은 서로 다름을 알 수 있었다. 그러므로 이전의 항정신병약물 노출여부는 정신분열증 환자의 뇌혈류량 연구에서 반드시 고려되어야 할 중요 요소로 시사된다. 0bjectives : In schizophrenics, regional cerebral blood flow(rCBF) are affected by various confounding variables, i.e., age, sex, duration of illness, and clinical status. The pharmacological condition of patients is also a particular important variable to be taken into consideration. However, few data are available regarding the differences between the relative rCBF findings in drug-free and drug-naive schizophrenic patients. Currently, numerous studies have included drug-free and drug-naive schizophrenic patients in the same'unmedicated'group under the assumption that the rCBF is identical between drug-free and drug-naive cases. Therefore, the aim of this study was to compare the rCBF between a group of drug-free schizophrenic patients and a group of drug-naive schizophrenic patients about the effects of age, sex, duration of illness, and clinical status(positive and negative symptoms) under control. Methods : Eighteen drug-naive schizophrenics and fifteen drug-free schizophrenics were included in the study. Regional cerebral blood flow was studied with the single-photon emission computed tomography(SPECT) under resting state. Symptoms were assessed with Positive and Negative Syndrome Scale(PANSS). Regions of interest were both inferior temporal lobe, inferior frontal lobe, superior temporal lobe, thalamus, basal ganglia, parieto-occipital lobe, superior frontal lobe, and parietal lobe. Results: No significant differences of relative rCBF were found between drug-free and drug-naive schizophrenic patients in left inferior temporal lobe, right inferior frontal lobe, both superior temporal lobe, both thalamus, both basal ganglia, right parieto-occipital lobe, and both superior frontal lobe. But, drug-free schizophrenic patients had a significant increase of perfusion in the right inferior temporal lobe and left inferior frontal lobe and a significant decrease of perfusion in both parietal lobes and left parieto-occipital lobe. Conclusions : Relative rCBF in drug-free schizophrenic patients is different from that in drug-naive schizophrenic patients. So, in the relative rCBF studies of schizophrenic patients, it must be considered whether the patients were previously medicated or not.

정신분열병 환자에 대한 통합심리치료의 효과

이만홍,이희상,조현상,현명호,안석균,유상우,박지환,한승진,현용호,구민성,손석한,김세주,이현주,박소라,송선미,안혜리,최정아,남궁기,유계준 大韓神經精神醫學會 1998 신경정신의학 Vol.37 No.6

목 적: 본 연구는 인지재활이 강화된 통합심리치료를 정 신분열병 환자에게 시행하여 그 결과를 평가하고 행상의 문제점을 분석하여 정신분열병 환자의 재활을 위한 한국형 통합심치료를 개발하기 위한 목적으로 실시되었다 . 방 법. 정신분열병으로 입원한 환자에게 인지분화,사회지각, 언어소통,사회기술, 문제해결기술의 5단계 구성된 통합심리치료를 12주간 주3회 실시하였고 치료 전후에 저자들이 개발한 인지분화평가척도, 사회기술평가척로,문제해결기술척도와Positive And Negative Syndrome Scale로 치료효과를 평가하였다. 집단내의 상호작용과 사회적 관심과 같은 비특이적인 간섭변인을 배제하기 위하여 정신건강교육에 의한 관심 -위약 대조군을 설정하여 비교하였다. 결 과: 통합심리치료를 시행한 군은 대조군에 비해 일반정신병리점수와 임상중상 총점수의 유의미한 호전이 있었고 인지기능의 호전은 인지분화 소프로그램후에서만 관찰되었으며 사회기술 소프로그램후의 사회기술기능은 제한적 효과만 있었다. 그러나 통합심리치료 시행군내에서는 12주후 양성증상. 음성증상. 일반 정신병리 모두에서 호전되었다. 결 론: 본 결과는 통할심리치료가 정신분열병 환자에게 임상 중상 영역의 치료효과가 있음을 지지하지만 인지 영역 훈련이 갖는 특정 효과는 보여주지 않았다 한편으로는 치료 프로그램의 사회문화적이고도 언어적인 배경의 차이. 치료기간, 집단구성원의 기능 동질화, 정서 처리, 인지영역 훈련에 대한 치료자의 숙련도 등의 시행상의 문제가 있어 우리나라 환자에의 적용을 위해서는 통합심리치료 원저의 수정이 요구된다. 0bjectives : This study, as a preliminary one attempting to develop the Korean version of Integrated Therapy for the rehabilitation of schizophrenic patients, was designed to investigate the results of Integrated Psychological Therapy(IPT) and review the problems during the program application. Methods : Cognitive Differentiation Scale, problem-Solving Scale, and PANSS(Positive And Negative Syndrome ScalE) were administered to schizophrenic inpatients before and after IPT incorporating cognitive diffirentiation, social perception, verbal communication, social skill and interpersonal Problem-solving skill subprograms. The therapy groups were offered activities three times per week during the 12-week program. The control groups were attention-placebo groups for control ling factors such as group interaction and social attention, and were offered psychoeducation. Results : The 12-week IPT groups, compared with the control groups, demonstrated sign-nificant improvements in the general psychopathology and the total symptoms of PANSS, but did not in cognitive functions and problem-solving skill. Significant improvements in cognitive functions were found only artier cognitive differentiation subprogram and social skill subprogram had limited effects on social skills. But within 12-week IPT groups significant improvements in the positive symptoms, negative symptoms and general psychopathology werc found. Conclusion : These findings support some effectiveness of IPT, but do not address the unique contribution by cognitive components. Applied to schizophrenic patients in this country, this modality had the problems such as differences in sociocultural and lingual background, duration of treatment, homogeneity in the level of the functioning among group members, management of emotions in activities, and the therapists'skill in the training of cognitive components. So the modification of this modality will be required.