http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Neutron Diffraction and Mössbauer Studies of LiFePO_4
이찬혁,김철성,이인규,문승제,김삼진 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.3
The crystal structure of LiFePO_4 has been determined to be orthorhombic (Pnma) from neutron diffraction measuerment. The temperature dependence of the magnetization was measured by using a SQUID magnetometer. The microscopic interaction was investigated with ^57Fe Mössbauer spectroscopy. At temperature below T_N = 51 K, LiFePO_4 exhibited an anti-ferromagnetic behavior while at temperature below 23 K, we observed abrupt increase in magnetization and magnetic hyperfine field (H_(hf)). The electric quadrupole splitting (ΔE_Q) reached its maximum value at 23 K and decreases steadily with decreasing temperature below 23 K. This indicated that the orbital angular momentum L was quenched by strong crystalline field in the asymmetric octahedral structure at temperature above 23 K. ΔE_Q decreased due to spin-orbit coupling, and the orbital angular moment contribution enhances H_(hf) at temperatures below 23 K.
Crystallographic and Magnetic Properties of LiCoPO4 at Low Temperature
이찬혁,김삼진,김철성 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.2
Polycrystalline LiCoPO4 powder was synthesized by using a solid-state reaction method. The temperature dependences of the crystallographic characteristics were analyzed by using highresolution powder neutron diffraction at various temperatures. We found that the octahedron formed with one cobalt and six oxygen ions was distorted in one direction at low temperature. Above 23 K, the distances between cobalt and each of two oxygen ions were about 2.11 °A; however at temperatures below 23 K, the distances changed to about 2.05 and 2.15 °A, respectively. The temperature dependence of the magnetization was also measured by using a superconducting quantum interference device magnetometer at temperatures ranging from 5 to 100 K. Although LiCoPO4showed an anti-ferromagnetic behavior, a rapid increase in magnetization was observed at temperatures below 8 K and a large coercivity of 335 Oe was observed at 5 K. The N´eel temperature (TN)of LiCoPO4 was determined to be 23 K.
Neutron Diffraction and Magnetic Properties of Ba2Co2Fe12O22: Co2Y
이찬혁,임정태,김철성,김성백 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
Polycrystalline Y-type barium cobalt ferrite (Ba2Co2Fe12O22; Co2Y) was synthesized using bythe conventional ceramic method. At temperatures below 260 K, the crystal structure of Co2Y wasdetermined to be hexagonal with the space group R¯3m. It showed a soft ferrimagnetic behaviorwith Hc = 113 Oe at 297 K and the N´eel temperature (TN) was determined to be 615 K. Most of thesuper-lattice peaks of Co2Y coming from the spin structure decreased with increasing temperature. However, the super-lattice peak at 21.8 increased with increasing temperature at temperaturesabove 200 K. In addition, we observed a change in the slope of the zero-field cooled magnetizationunder a low field of 0.01 T at 215 K due to a magnetic structure transition from a helical to aferrimagnetic spin structure.
생후 6일째(P6) 쥐와 성체 쥐의 해마체에서 시냅스의 발달과 프로테아좀 활성에 관한 연구
이찬혁,김형태,서혜명 한양대학교 이학기술연구소 2005 이학기술연구지 Vol.8 No.-
유비퀴틴-프로테아좀 시스템(ubiquitin-proteasome system: UPS) 은 세포내에서 비정상적인 단백질을 분해하는 기능을 담당하며, 그기능의 상실은 생체의 비정상적인 발달단계나 여러 퇴행성 신경질환의 병리학적 진행을 이해하는데 중요한 것으로 생각된다, 본 연구에서는 생후 6일째의 쥐(P6) 와 성체 쥐 뇌의 해마체에서 시냅스의 발달을 대표할수 있는 nerve growth factor(NGF)와 synaptophysin 의 발현 정도를 측정하고 더불어 프로테아조 활성의 차이를 알아보고자 하였다, 먼저 우리는 P6쥐 의 해마체에서 성체 쥐에 비하여 NGF의 발현이 1.3배 증가된 것을 확인하였고, 또한synaptophysin의 양이 특이적으로 감소된 것을 볼수 있었다, 흥미롭게도 P6쥐의 해마체에서 성체 쥐와 비교하여 유의성 있게 높은 프로테아좀 활성을 관찰 할수 있었다, 이와 같은 연구를 통하여 쥐 뇌의 발달 과정에 있어서 프로테아좀 활성의 조절은 시냅스의 발달과 밀접하게 연관되어 있다고 추정된다. Dysfunction of ubiquitin-proteasome system (UPS)has been proposed or implicated in the pathological processing of several neurodegenerative diseases and abnormalities in development . To address th differences of UPS in the sysnaptic development we determined the proteasome activities in the hippocampus of postnatal day 6 (P6) and adult rats. Using ELISA and western blot we found that the hippocampal NGF expression level is 1.3 times higher and synaptophysin level is significantly lower in P6 compared to adult Interestingly P6 rats in development showed 3~5 times higher hippocampal proteasome activities compared to adults. These results suggest that ubiquitin-proteasome are potentially related to synaptic divelopment.