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Synthesis and Properties of Highly Ordered Mesoporous Materials with Spinel Structure
박희연,김경호,김지만 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Mixed Oxides with spinel structure have received great attention for decades in the field of electrolytes, refractories, and catalytic material due to their optical, electrical, and catalytic properties. Highly ordered mesoporous AB<sub>2</sub>O<sub>4</sub> (A=Mn, Co, Ni, and Zn, B=Mn, Fe, Co) spinel materials have been synthesized through nanocasting method, using KIT-6 silica as a hard template. From low-angle X-ray diffraction (XRD) patterns of highly ordered mesoporous of AB<sub>2</sub>O<sub>4</sub> (A=Mn, Co, Ni, and Zn, B=Mn, Fe, Co) spinel materials, a new (110) peak was observed before 2θ=1°. It indicates the meso-structure transformation from cubic to tetragonal or the lower space group after the silica template etching process. N<sub>2</sub> adsorption-desorption isotherms exhibit the obtained replicas have high specific surface areas (92-125 ㎡/g), and large pore volumes (0.11-0.26 ㎤/g).
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부인과 수술을 위한 Sevoflurane-Remifentanil 또는 Sevoflurane- Nitrous Oxide 전신마취에서 혈역학적 반응과 회복 양상의 비교
박희연 대한마취통증의학회 2008 Anesthesia and pain medicine Vol.3 No.3
Background: This study was designed to compare hemodynamic responses and postoperative courses between sevoflurane-remifentanil and sevoflurane-nitrous oxide anesthesia. Methods: Forty ASA I or II patients undergoing gynecologic surgery were randomly assigned to receive sevoflurane-remifentanil (group R) or sevoflurane-nitrous oxide group (group N). In group R, remifentanil was continuously infused by using target-controlled infusion pump from anesthetic induction (effect-site target concentration: 4 ng/ml) to the end of surgery (1−5 ng/ml). In group N, fentanyl (2μg/kg) was administered before tracheal intubation and 50% N2O was used during anesthesia. In both groups, 2 vol% sevoflurane was used during anesthetic induction and then end-tidal sevoflurane concentrations were controlled between 1 to 3 vol% according to systolic blood pressure. We compared blood pressure (BP) and heart rate (HR) before and after tracheal intubation and frequencies of hemodynamic aberrations between the two groups. Postoperative nausea/vomiting, sedation, pain scores at 2 and 24 hours after operation were also compared. Results: Changes of BP and HR after tracheal intubation were similar in group R and group N, but MAP at 1 and 2 min after intubation was significantly decreased versus baseline MAP in group N. Intraoperative hypertensive episodes (systolic BP > 140 mmHg) were more frequent in group N compared to group R, and hypotensive episodes (SBP < 90 mm Hg) were similar in both groups. There were no differences in postoperative nausea/vomiting, sedation and pain scores. Conclusions: Sevoflurane/remifentanil anesthesia provided more stable intraoperative hemodynamic status than sevoflurane/N2O and postoperative adverse effects were similar in both groups.
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Insecticidal and Repellent Activities of Crude Saponin from the Starfish Asterias Amurensis
박희연,김지영,김현주,이건휘,박진일,임치원,김연계,윤호동 한국수산과학회 2009 Fisheries and Aquatic Sciences Vol.12 No.1
Crude saponin, extracted from the starfish Asterias amurensis, was assessed for its capacity as a biological pesticide. As part of this analysis, its insecticidal and repellent activities, in addition to its acute and chronic toxicities were tested. In comparison with the control group, insecticidal activity of saponin against tobacco cutworm, Spodoptera litura, in kale, Brassica loeracea was low at 36.4%. Repellent activities of the extracted saponin against green peach aphid, Myzus persicae, and S. litura, on soybean leaf, Glycine max and kale were 65.6% and 35.0% at 1st day, and 54.5% and 30.0% at 3rd day, respectively. Acute and chronic toxicity analysis was carried out using acute immobilizatioin test and reproduction impairment test, respectively. The saponin had 48 h-EC50 of 65.21 μg/mL. Twenty-one day accumulative reproduction after treatment was lower in Daphnia magna at 7 μg/mL saponin (78 youngs), compared with the control group (129 youngs). These results indicate that the extracted saponin exhibited some toxicity and has potential as a repellent against insects.
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YBCO 초전도 선재를 이용한 단일 브릿지 및 이중 브릿지 형태로의 변형에 따른 국소적 영역에서의 물리적 특성 비교 분석
박희연,박상국,이형철 한국물리학회 2013 새물리 Vol.63 No.2
Measuring and visualizing the local transition critical temperature and critical current density of a YBCO-coated conductor, rather than just a rough average value, through a nondestructive way is significant. In particular, in this study, we transformed the shape of a sample with striation and compared a single-bridge-type sample with a two-bridge-type sample. The samples were examined under a low-temperature scanning-laser Hall-probe microscope (LTSLHPM) at temperatures near the transition temperature. The result showed no differences in the superconducting properties within the margin of error. Thus, the ac loss is expected to be reduced by patterning the sample. 본 연구에서는 기하학적인 구조의 변형이 미시적 영역에서의 물리적특성에 미치는 영향을 분석하기 위해 YBCO 초전도 선재 시료를 단일브릿지 형태와 단일 브릿지를 평행하게 배열한 이중 브릿지의 형태로제작하였다. 액체질소를 주입한 저온의 진공 용기 내에서 저온 주사레이저 및 홀 소자 현미경을 이용하여 국소적인 영역에서의 임계온도 및전류밀도를 측정하여 시료의 형태에 따라 어떻게 달라지는 가를 보았다. 그 결과 단일 브릿지와 이중 브릿지의 국소적 영역에서의 초전도 특성은실험 오차범위 내에서 차이가 없었으며, 특히 단일브릿지 형태의 GdBCO 시료와 비교하여 보았을 때 차이가 극명하게 드러남을 알 수 있었다. 따라서 시료를 패터닝 함으로써 초전도 특성에 손실 없이 교류 손실을저감할 수 있을 것으로 기대된다.
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단일 세포 변형 및 점탄성 특성 정량화를 위한 고주파 음향 핀셋 시스템
박희연,윤상연,황재윤 한국비파괴검사학회 2022 한국비파괴검사학회지 Vol.42 No.6
High-frequency acoustic tweezers have been used as noncontact biophysical tools for various biomedical applications. Cell mechanics are an important indicator for representing the pathological properties of cells. Acoustic tweezers have shown their potential as a non-contact method for measuring the mechanics of a single cell through the quantification of cell deformation during acoustic trapping. In this study, we developed an ultra-fast acoustic tweezer system that can measure both cell deformation and viscoelasticity and then examined its potential for measuring cell viscoelasticity. To develop the acoustic tweezer system for measuring cell viscoelasticity, a 27.8 MHz highly focused lithium niobate (LiNbO3) single-element ultrasound transducer was developed. An ultra high-speed camera was integrated with the acoustic tweezer system to measure the cell deformation over time. To evaluate its potential for measuring cell viscoelasticity, cell deformation variations over time under different types of acoustic trapping forces were monitored. The system was also applied to measure the mechanics of breast cancer cells with different degrees of invasiveness. The phase delay between the applied amplitude-modulated force and cell deformation was found to change during acoustic trapping. Moreover, the deformation rates of breast cancer cells were found to differ for different degrees of invasiveness. These results indicate that the viscoelasticity of cells can be quantified by analyzing the cell deformation phase delay by using the developed ultrafast ultrasound tweezer system. 고주파 음향 핀셋은 비접촉 생물 물리학적 도구로써 생물학적 기전 연구를 포함한 다양한 생물학 의학 분야에서 유용하게 사용되어왔다. 세포의 기계적 특성은 세포의 병리학적 특성을 나타내기 위한 핵심 지표 중 하나이다. 이 음향 핀셋은 세포 포획 시 세포 변형 정량화를 통해 단일 세포의 기계적 특성을 측정하는 데 있어서 비접촉 방식으로써 그 유용성을 보여 왔다. 본 논문에서는 세포의 변형뿐만 아니라, 세포의 점탄성도 측정 가능한 음향 핀셋 시스템을 개발하고, 개발한 음향 핀셋 시스템이 세포 점탄성 및 변형 측정에서의 그 가능성을 조사한다. 점탄성 측정이 가능한 음향 핀셋 시스템을 개발하기 위해서 27.8 MHz LiNbO3 단일소자 초음파 변환자를 개발하고, 세포 포획 시 시간에 따른 세포 변형률을 초고속으로 측정하기 위해 초고속 카메라를 음향 핀셋 시스템에 결합하였다. 그 개발한 시스템의 세포 점탄성 측정 가능성을 평가하기 위해서 다른 형태의 포획 힘에 따른 세포 변형의 위상 변화를 확인하였다. 이와 더불어 이 시스템을 이용해 전이성이 상이 한 유방암 세포의 기계적 특성을 측정하였다. 상기 실험을 통해 진폭 변조된 포획력 아래에서 세포가 포획된 동안 가해진 힘과 세포의 변형 사이 위상 지연이 초래됨을 확인하였고, 전이성이 다른 유방암 세포의 변형률에서 차이가 나는 것을 확인하였다. 이 결과는 개발한 초고속 초음파 핀셋 시스템을 이용해 포획된 세포 변형 위상 지연을 분석함으로써 세포의 점탄성을 정량화할 수 있음을 시사한다.
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