• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.94-94
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• 2003

목적： 기능적 자기공명영상과 확산텐서영상기법을 이용하여 전음성 난청과 감각신경성 난청에서의 뇌활성화 양상 그리고 청신경경로상의 차이점을 비교 연구하고자 하였다. 대상 및 방법： 전음성 난청군 (n=4)과 감각신경성 난청군(n=5) 그리고 정상군(n=5)에서의 기능적 자기 공명영상과 확산텐서영상을 획득하였다. 기능적 자기공명영상의 경우 1.5T Siemens MR scanner에서 BOLD 기법을 이용하여 500 Hz 순음 청각자극에 대한 뇌활성화 영역을 검출하였고 영상촬영시 발생하는 기계적 소음을 차폐하기 위한 청각자극기를 특별히 제작하여 사용하였다. 뇌백질신경로를 영상화하는 확산텐서영상은 3.0T GE whole body MR scanner를 사용하였으며 미세한 확산운동을 검출하기 위해 초고속 영상기법인 EPI 기법을 사용하였다. 영상의 화질을 높이기 위해 공간적으로 25개의 다른 방향으로 확산경사자장을 가하였다. 청신경로의 비등방성 영상, 신경로 방향 영상등을 구현하기 위해 획득한 확산영상들에 대한 영상 후처리과정을 시행하였다.

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.313-325
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• 2007

In order to have better insights into adsorption of organic molecules on kaolinite surfaces, we performed quantum chemical calculations of interaction between three different model clusters of kaolinite siloxane surfaces and benzyl alcohol, with emphasis on the effect of size and lattice topology of the cluster on the variation of electron density and magnetic shielding tensor. Model cluster 1 is an ideal silicate tetrahedral surface that consists of 7 hexagonal rings, and model cluster 2 is composed of 7 ditrigonal siloxane rings with crystallographically distinct basal oxygen atoms in the cluster, and finally model cluster 3 has both tetrahedral and octahedral layers. The Mulliken charge analysis shows that siloxane surface of model cluster 3 undergoes the largest electron density transfer after the benzyl alcohol adsorption and that of model cluster 1 is apparently larger than that of model cluster 2. The difference of Mulliken charges of basal oxygen atoms before and after the adsorption is positively correlated with hydrogen bond strength. NMR chemical shielding tensor calculation of clusters without benryl alcohol shows that three different basal oxygen atoms (O3, O4, and O5) in model cluster 2 have the isotropic magnetic shielding tensor as $228.2{\pm}3.9,\;228.9{\pm}3.4,\;and\;222.3{\pm}3.0ppm$, respectively. After the adsorption, the difference of isotropic chemical shift varies from 1 to 5.5 ppm fer model cluster 1 and 2 while model cluster 2 apparently shows larger changes in isotropic chemical shift. The chemical shift of oxygen atoms is also positively correlated with electron density transfer. The current results show that the adsorption of benzyl alcohol on the kaolinite siloxane surfaces can largely be dominated by a weak hydrogen bonding and electrostatic force (charge-charge interaction) and demonstrate the importance of the cluster site and the lattice topology of surfaces on the adsorption behavior of the organic molecules on clay surfaces.

• Proceedings of the Petrological Society of Korea Conference
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• 2009.05a
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• pp.32-34
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• 2009