Accurate 3D reconstruction of underwater infrastructure using stereo vision

University of Technology Sydney. Faculty of Engineering and Information Technology.Modern vehicle and pedestrian bridges over water are built on concrete piles; foundations that penetrate the soft soil of the bed of the body of water to sit on the solid rock below. Like all built structures these concrete piles require regular inspection to determine if any preventative maintenance is needed. Stereo vision and Structure from Motion techniques offer a cost effective method of creating a 3D reconstructions of a scene, but the underwater environment around a bridge pile has unique challenges. Poor visibility, strong and varying sunlight, and floating material in the water create difficulties for computer vision. This thesis evaluates exposure control, image enhancement, and feature detection and description algorithms, for the purpose of localising images captured around a bridge pile. Stereo correspondence algorithms are evaluated and used to create a single viewpoint 3D reconstruction of a scene, then a visual SLAM system is used to localise the single viewpoint reconstructions, so that they can be merged together to create a 3D reconstruction of a bridge pile. Visual odometry, using KAZE with CLAHE image enhancement for feature detection, was successfully performed in the underwater environment. ORB-SLAM2 can also perform well, and 3D reconstructions from a single viewpoint (created with block matching, semi-global matching, or ELAS) were merged to create 3D reconstructions of submerged bridge piles

Regulatory Mechanisms at the Mouse Igf2/H19 Locus

The closely linked H19 and Igf2 genes show highly similar patterns of gene expression but are reciprocally imprinted. H19 is expressed almost exclusively from the maternally inherited chromosome, while Igf2 expression is mostly from the paternal chromosome. In humans, loss of imprinting at this locus is associated with tumors and with developmental disorders. Monoallelic expression at the imprinted Igf2/H19 locus occurs by at least two distinct mechanisms: a developmentally regulated silencing of the paternal H19 promoter, and transcriptional insulation of the maternal Igf2 promoters. Both mechanisms of allele-specific silencing are ultimately dependent on a common cis-acting element located just upstream of the H19 promoter. The coordinated expression patterns and some experimental data support the idea that positive regulatory elements are also shared by the two genes. To clarify the organization and function of positive and negative regulatory elements at the H19/Igf2 locus, we analyzed two mouse mutations. First, we generated a deletion allele to localize enhancers used in vivo for expression of both H19 and Igf2 in mesodermal tissues to sequences downstream of the H19 gene. Coincidentally, we demonstrated that some expression of Igf2 is independent of the shared enhancer element. Second, we used this new information to further characterize an ectopic H19 differentially regulated region and the associated insulator. We demonstrated that its activity is parent-of-origin dependent. In contrast to recent results from Drosophila model systems; we showed that this duplication of a mammalian insulator does not interfere with its normal function. Implications of these findings for current models for monoallelic gene expression at this locus are discussed