Structural and Spectroscopic Investigation of Ceria Nanofibers Fabricated by Electrospinning Process

Ah Reum Hwang,Juyun Park,강용철 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.9

We fabricated ceria (CeO_2) nanofibers by applying a mixed solution of polyvinylpyrrolidone (PVP) and various concentrations of cerium nitrate hydrate (Ce(NO_3)_3) ranging from 15.0 to 26.0 wt % by the electrospinning process. Ceria nanofibers were obtained after calcining PVP/Ce(NO_3)_3 nanofiber composites at 873 and 1173 K. The SEM images indicated that the diameters of CeO_2 nanofibers calcined at 873 and 1173K were smaller than those of nanofibers obtained at RT. As the amount of cerium increased, the diameter of CeO_2 nanofibers increased. XRD analysis revealed that the ceria nanofibers were in cubic form. TEM results revealed that the ceria nanofibers were formed by the interconnection of Ce oxide nanoparticles. The ceria nanofibers obtained at low concentrations of Ce (CeL) showed spotty ring patterns indicated that the ceria nanofibers were polycrystalline structure. And the ceria nanofibers obtained at high concentration of Ce (CeH)showed fcc (001) diffraction pattern. XPS study indicated that the oxidation of Ce shifted from Ce^3+ to Ce^4+ as the calcination temperature increased.

Structural and Spectroscopic Investigation of Ceria Nanofibers Fabricated by Electrospinning Process

Hwang, Ah-Reum,Park, Ju-Yun,Kang, Yong-Cheol Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.9

We fabricated ceria ($CeO_2$) nanofibers by applying a mixed solution of polyvinylpyrrolidone (PVP) and various concentrations of cerium nitrate hydrate ($Ce(NO_3)_3$) ranging from 15.0 to 26.0 wt % by the electrospinning process. Ceria nanofibers were obtained after calcining PVP/$Ce(NO_3)_3$ nanofiber composites at 873 and 1173 K. The SEM images indicated that the diameters of $CeO_2$ nanofibers calcined at 873 and 1173 K were smaller than those of nanofibers obtained at RT. As the amount of cerium increased, the diameter of $CeO_2$ nanofibers increased. XRD analysis revealed that the ceria nanofibers were in cubic form. TEM results revealed that the ceria nanofibers were formed by the interconnection of Ce oxide nanoparticles. The ceria nanofibers obtained at low concentrations of Ce (CeL) showed spotty ring patterns indicated that the ceria nanofibers were polycrystalline structure. And the ceria nanofibers obtained at high concentration of Ce (CeH) showed fcc (001) diffraction pattern. XPS study indicated that the oxidation of Ce shifted from $Ce^{3+}$ to $Ce^{4+}$ as the calcination temperature increased.

Photodynamic Behavior of Heteroleptic Ir(III) Complexes with Carbazole-Functionalized Dendrons Associated with Efficient Electron Transfer Processes

Hwang, Ah-Reum,Han, Won-Sik,Wee, Kyung-Ryang,Kim, Hyun Young,Cho, Dae Won,Min, Byoung Koun,Nam, Suk Woo,Pac, Chyongjin,Kang, Sang Ook American Chemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.2

<P>We prepared dendrimers of heteroleptic iridium(III) complexes, [(dfppy–Cz<SUB>1</SUB>)<SUB>2</SUB>Ir(dpq)]<SUP>+</SUP> (<B>G1</B>) and [(dfppy–Cz<SUB>2</SUB>)<SUB>2</SUB>Ir(dpq)]<SUP>+</SUP> (<B>G2</B>), which have the dfppy ligand connected to carbazole-functionalized dendron Cz<SUB><I>n</I></SUB> (<I>n</I> = 1, 2) [dfppy–Cz<I><SUB>n</SUB></I> = 5-Cz<I><SUB>n</SUB></I>-2-(4,6-difluorophenyl)pyridine, dpq = 2,3-bis-(2-pyridyl)-qinoxaline, Cz<SUB>1</SUB> = 4-(9-carbazolyl)benzyloxymethyl, and Cz<SUB>2</SUB> = 4-[1,3-bis(9-carbazolyl)benzyloxy]benzyloxymethyl]. While parent complex [(dfppy)<SUB>2</SUB>Ir(dpq)]<SUP>+</SUP> (<B>G0</B>) shows an intense emission at ∼635 nm with a lifetime of 1 μs assigned to dpq-based metal-to-ligand charge-transfer (MLCT) phosphorescence, excitation of the dendrimers at either carbazole (309 nm) or MLCT band (355 nm) resulted in markedly weaker and much shorter-lived MLCT emission (τ<SUB>p</SUB> = 44 ns for <B>G1</B> and 115 ns for <B>G2</B>) at room temperature. Upon exciting the carbazole chromophore of <B>G1</B> and <B>G2</B> at 309 nm, furthermore, both the carbazole fluorescence and the MLCT emission were very weak at room temperature. It was found that the lifetime of carbazole fluorescence is 20 ps for <B>G1</B> and 62 ps for <B>G2</B>, shorter by 2-orders of magnitude than that of free carbazole dendron Cz<SUB><I>n</I></SUB>′–OH (τ<SUB>F</SUB> = 6.1 ns). These observations demonstrate that both the excited-singlet state of carbazole and the triplet MLCT state of the Ir(dpq) core are efficiently quenched in the dendrimers. At 77 K, however, the MLCT emission lifetime for both <B>G1</B> and <B>G2</B> is ∼7 μs that is nearly identical to that of <B>G0</B> (6.8 μs), and the carbazole fluorescence lifetime is ∼11.5 ± 0.5 ns, which is again almost the same as that of Cz<SUB><I>n</I></SUB>′–OH (11.5 ns). Since the apparent quenching of either carbazole fluorescence or MLCT emission observed at room temperature does not occur at 77 K, the temperature-dependent emission behavior of <B>G1</B> and <B>G2</B> for both the carbazole fluorescence and the MLCT phosphorescence was attributed to the participation of activated processes, that is, electron transfer from excited-singlet carbazole to the Ir(dpq) core as well as from the ground-state carbazole unit to the triplet MLCT Ir(dpq) core. This mechanism was supported by transient-absorption spectroscopic experiments that demonstrate the generation of the carbazole radical cation after exciting <B>G1</B> and <B>G2</B> by laser pulses.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-2/jp2093077/production/images/medium/jp-2011-093077_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp2093077'>ACS Electronic Supporting Info</A></P>

Extraction of Canola Oil Using Ultrasound-Assisted Supercritical Fluid

Ah-Reum Hwang,Byung-Hyun Won,In-Il Jung,Gio-Bin Lim,Jong-Hoon Ryu 한국생물공학회 2008 한국생물공학회 학술대회 Vol.2008 No.10

Chemical syntheses of autoinducer produced by Pseudomonas syringae pv. tabaci

Ah Reum Hwang,Ji Young Cha,So Young Park,Hyun Ju Yang,Hyung Suk Baik 한국생명과학회 2004 한국생명과학회 심포지움 Vol.41 No.-

Detection and identification of genes regulated by quorum sensing of Pseudomonas syringae pv. tabaci

Ah Reum Hwang,Ji Young Cha,So Young Park,Hyun Ju Yang,Hyung Suk Baik 한국생명과학회 2004 한국생명과학회 심포지움 Vol.43 No.-

Effect of Ultrasonic Power and Flow Direction on the Extraction of Canola Oil

Ah-Reum HWANG,In-Il JUNG,Gio-Bin LIM,Jong-Hoon RYU 한국생물공학회 2009 한국생물공학회 학술대회 Vol.2009 No.4

초임계 이산화탄소를 이용한 캐놀라 오일 추출

황아름(Ah-Reum Hwang),정인일(In-Il Jung),임교빈(Gio-Bin Lim),유종훈(Jong-Hoon Ryu) 한국생물공학회 2009 KSBB Journal Vol.24 No.4

본 연구에서는 초임계 이산화탄소 추출기술의 scale-up 을 위한 기초 연구로서 추출 용량이 다른 두 종류의 초임계 추출장치를 사용하여 추출기 용량, 초임계 이산화탄소의 흐름방향, 캐놀라 씨앗 입자의 크기, 온도, 압력 등의 공정변수가 캐놀라 오일의 추출 속도와 수율에 미치는 영향을 조사하였다. 분쇄된 씨앗의 입자 크기가 작을수록 추출 효율이 증가하였으며, 약 330 bar 이하의 압력에서는 온도가 증가함에 따라 추출 효율이 감소하고, 330 bar 이상의 압력 범위에서는 온도 증가와 함께 추출 효율이 증가하는 crossover 지점이 나타나는 것을 확인하였다. 추출기의 용량을 10배 증가시킨 경우 추출용량이 추출 수율에 거의 영향을 미치지 않는 다는 것을 알 수 있었으며, 초임계 이산화탄소가 추출기 아래에서 위로 흐르는 경우 반대 방향에 비해 추출 속도가 훨씬 더 높다는 사실을 확인하였다. 또한, 초임계 이산화탄소로 추출된 캐놀라 오일의 트리글리세라이드와 지방산의 조성은 유기용매 추출에 의해 얻은 오일의 조성과 비슷하였으며, 추출 시간이나 초임계 유체의 흐름 방향에 따라서도 오일 조성에 큰 변화가 없음을 확인하였다. In this study, two supercritical extraction systems of different scale, analytical-scale and lab-scale, were employed to investigate the extraction efficiency of canola oil from canola seeds using supercritical carbon dioxide (SCCO2) as an extraction solvent. The effects of various parameters such as extraction temperature (40~80℃), pressure (200~500 bar), particle size, and SCCO2 flow direction on the extraction rate and yield were examined in detail. Triglycerides and fatty acids in the extracted canola oil were analyzed quantitatively by high-performance liquid chromatography and gas chromatography. The solubility values of canola oil in SCCO2 could be calculated from the experimental results. Similar extraction yields were obtained from both analytical-scale and lab-scale extraction systems. The extraction rates obtained under solvent SCCO2) upflow conditions were found to be higher than those of solvent downflow extraction. However, the effect of SCCO2 flow direction on the extraction yield was observed to be relatively insignificant.

초음파가 적용된 초임계 유체 공정을 이용한 캐놀라오일 추출

황아름(Ah-Reum Hwang),임교빈(Giobin Lim),유종훈(Jong-Hoon Ryu) 한국생물공학회 2010 KSBB Journal Vol.25 No.5

본 연구에서는 초임계 이산화탄소의 추출기술에 초음파 적용을 위한 기초 연구로서 캐놀라 씨앗의 입자의 크기, CO₂ 유속, 추출기의 종횡비, 초음파 파워 등의 공정변수가 캐놀라 오일의 추출 속도와 수율에 미치는 영향에 대하여 조사하였다. 초임계 이산화탄소 추출에 있어 씨앗을 더 작게 분쇄할수록 더 빠른 추출속도를 보였으며, 추출기의 종횡비가 감소할수록, CO₂의 유속이 증가할수록 추출 속도는 증가하였다. 그러나 초음파가 적용된 초임계 이산화탄소 추출의 경우 0.6 mm 이하로 분쇄된 씨앗의 입자 크기 분포가 가장 큰 시료 C의 경우 입자들의 뭉침 현상 증가로 인해 오히려 초음파의 적용이 추출속도와 수율을 크게 감소시켰으며, 12.0 L/min의 CO₂ 유속에서도 추출 속도와 수율이 감소하는 것을 확인하였다. 초음파의 적용은 초기 추출시간 50-70분동안 추출속도 증가에 거의 영향을 미치지 않았으며, 초음파 파워 또한 추출 속도와 수율의 증가에 큰 영향을 미치지 않음을 확인할 수 있었다. The objective of this study was to investigate the effect of ultrasound on the extraction of oil from canola seeds when supercritical carbon dioxide (SCCO₂) was used as an extraction solvent. The ultrasound-assisted SCCO₂ extraction were carried out while varying such operating parameters as particle size of crushed canola seed, flow rate of SCCO₂, aspect ratio of the extraction vessel, and ultrasound power. The extraction rate decreased with increasing particle size of samples, showing a maximun at a CO₂ flow rate of 6.2 L/min. Both the extraction rate and extraction yield increased with a decrease in the aspect ratio of the extraction vessel. For the ultrasoundassisted SCCO₂ extraction, the extraction yield was slightly increased when the CO₂ flow rate was below 6 mL/min with sample A and B.

Assessment of Abdominal Organs Movement by Respiration Using Computed Tomography in Dogs: A Pitfall for Radiation Therapy

Ah Reum Kim,Soyon An,Gunha Hwang,Moonyeong Choi,황태성,이희천 한국임상수의학회 2023 한국임상수의학회지 Vol.40 No.2

The change in the position of the abdominal organs due to movement by respiration is one of the reasons behind inaccurate irradiation of organs during radiotherapy (RT). Although studies in human medicine have revealed on the respiratory movements of abdominal organs, there is little information and no reference data for dogs. The purpose of this study was to establish the reference values of abdominal organs movement in various postures using computed tomography (CT), and to compare the movements of organs between dorsal recumbency and ventral, right and left lateral recumbency during respiration. CT images for kidney, adrenal gland, medial iliac lymph node, urinary bladder, gallbladder, liver, stomach, and thoracic and lumbar vertebral body of five beagle dogs were acquired. The movements of organs were evaluated by comparing the end-expiratory and end-inspiratory images. Movements of the organs were evaluated by dividing it into right-to-left, dorsal-to-ventral, and cranial-to-caudal directions. The movements of abdominal organs according to the change in postures and respiration were establish. The movement of the bilateral organs was the least when the organs were in the downward position (p < 0.017). The movement of cranial-to-caudal direction was greater than the movement of the other directions in most of the organs. Data obtained in this study may be useful in selecting the appropriate posture that can reduce the movements of organs to be treated with RT, and the data could be useful for setting the planning target volume to consider the movements of the abdominal organs by respiration.