Study on the effect of Mytilopsis sallei on ecological environment in Yundang Lagoon, Xiamen

外来物种沙筛贝（Mytilopsissallei）原产于中美洲热带水域，随着航运的发展入侵世界上许多国家和地区，对入侵地造成巨大的经济损失。筼筜湖位于厦门岛西南部，旧称筼筜港，原是一片天然的港湾。20世纪70年代初，为围海造田，修建了西堤，使筼筜港变成一座基本封闭的人工泻湖，水体污染较为严重，水交换能力大大减弱，改称筼筜湖。筼筜湖水体呈富营养化状态，湖内属重污染水体。海洋入侵种是生态变化的主要驱动者，它们适应当地栖息环境，与本地种竞争，还可能是带菌者，对生物多样性造成严重的危害。因此，只有研究沙筛贝与其他生物和非生物因子的相关关系，才能正确地判断沙筛贝的利弊及其对生态环境的影响程度。 本研究...The normal distribution of alien species Mytilopsis sallei is in tropic water area in Central America. It has been introduced into many countries and areas by attached to hulls of ship. Mytilopsis sallei made a great economic lose in the invasive areas. Yundang Lagoon, which lies in the western part of Xiamen Island, used to be a natural bay called Yundang Harbor. In the early 1970s, a great numbe...学位：理学硕士院系专业：海洋与环境学院环境科学与工程系_环境科学学号：2262006115234

Field map-based rectification of susceptibility distortion and signal compensation in diffusion tensor imaging

目的采用基于体素的场图对磁共振弥散张量成像(diffusion-tensor; imaging,DTI)进行几何变形矫正及信号补偿研究,扩大DTI临床研究及应用价值。材料与方法获取29名健康人脑场图,分别对其DTI进行相位反; 卷积计算及信号校准补偿,将结果配准到3D结构图像。选择对磁场敏感的双侧颅底额叶和颞叶作为观察脑区,对磁场不敏感的丘脑作为对照脑区,对部分各向异性; (fractional; anisotropy,FA)值及信号的差异及其与结构像的形态差异进行统计分析。结果在颅底额叶和颞叶,DTI的磁敏感变形得到了矫正,因场不均性导致; 的信号损失得到了补偿。结论高场中DTI的畸变及体素信号丢失可应用场图的校准得到明显矫正,有利于进一步扩大高场DTI在临床中的应用价值。Objective: This study was designed to employ the voxel-based field map; to rectify the geometric deformation and compensate the signal loss of; diffusion tensor imaging (DTI), and thus facilitate the studies and; clinical applications of DTI. Materials and Methods: Brain field maps; from 29 healthy persons were first used to get B1 field heterogeneous; signals, and then the compensation and phase disconsolation of signals; were performed. Finally, the geometry deformations of DTI were rectified; and registered to 3D images. Magnetic sensitive bilateral temporal lobes; and frontal lobes were selected as regions of interesting and meanwhile,; magnetic insensitive thalamus was selected as control area. Results:; Geometry deformations of DTI produced by different susceptibilities; between specific tissues were completely rectified, and thus the signal; loss was compensated and the accuracy of DTI was significantly enhanced.; Conclusion: Signal compensations and deformation rectifications can be; well achieved using field map, which may improve the applications of DTI; in neurosurgery.国家自然科学基金面上项