37 research outputs found

    Structure-from-Motion on shallow reefs and beaches: potential and limitations of consumer-grade drones to reconstruct topography and bathymetry

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    Reconstructing the topography of shallow underwater environments using Structure-from-Motion—Multi View Stereo (SfM-MVS) techniques applied to aerial imagery from Unmanned Aerial Vehicles (UAVs) is challenging, as it involves nonlinear distortions caused by water refraction. This study presents an experiment with aerial photographs collected with a consumer-grade UAV on the shallow-water reef of Fuvahmulah, the Maldives. Under conditions of rising tide, we surveyed the same portion of the reef in ten successive flights. For each flight, we used SfM-MVS to reconstruct the Digital Elevation Model (DEM) of the reef and used the flight at low tide (where the reef is almost entirely dry) to compare the performance of DEM reconstruction under increasing water levels. Our results show that differences with the reference DEM increase with increasing depth, but are substantially larger if no underwater ground control points are taken into account in the processing. Correcting our imagery with algorithms that account for refraction did not improve the overall accuracy of reconstruction. We conclude that reconstructing shallow-water reefs (less than 1 m depth) with consumer-grade UAVs and SfM-MVS is possible, but its precision is limited and strongly correlated with water depth. In our case, the best results are achieved when ground control points were placed underwater and no refraction correction is used

    TAC102 is a novel component of the mitochondrial genome segregation machinery in trypanosomes

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    Trypanosomes show an intriguing organization of their mitochondrial DNA into a catenated network, the kinetoplast DNA (kDNA). While more than 30 proteins involved in kDNA replication have been described, only few components of kDNA segregation machinery are currently known. Electron microscopy studies identified a high-order structure, the tripartite attachment complex (TAC), linking the basal body of the flagellum via the mitochondrial membranes to the kDNA. Here we describe TAC102, a novel core component of the TAC, which is essential for proper kDNA segregation during cell division. Loss of TAC102 leads to mitochondrial genome missegregation but has no impact on proper organelle biogenesis and segregation. The protein is present throughout the cell cycle and is assembled into the newly developing TAC only after the pro-basal body has matured indicating a hierarchy in the assembly process. Furthermore, we provide evidence that the TAC is replicated de novo rather than using a semi-conservative mechanism. Lastly, we demonstrate that TAC102 lacks an N-terminal mitochondrial targeting sequence and requires sequences in the C-terminal part of the protein for its proper localization

    "Integrating CUMULVS into AVS/Express”

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    Abstract. This paper discusses the development of a CUMULVS interface for runtime data visualization using the AVS/Express commercial visualization environment. The CUMULVS (Collaborative, User Migration, User Library for Visualization and Steering) system, developed at Oak Ridge National Laboratory, is an essential platform for interacting with high-performance scientific simulation programs on-the-fly. It provides run-time visualization of data while they are being computed, as well as coordinated computational steering, application-directed checkpointing and fault recovery mechanisms, and rudimentary model coupling functions. CUMULVS primarily consists of two distinct but cooperative libraries- an application library and a viewer library. The application library allows instrumentation of scientific simulations to describe distributed data fields, and the viewer library interacts with this application side to dynamically attach and then extract and assemble sequences of data snapshots for use in front-end visualization tools. A development strategy will be presented for integrating and using CUMULVS in AVS/Express, including discussion of the various objects, modules, macros and user interfaces. 1

    Activity-state profile of tau kinases in hibernating animals

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    A variety of neurological disorders including Alzheimer's disease are associated with the formation of neurofibrillary tangles, made up by intraneuronal paired helical filaments (PHFs) that are composed of hyperphosphorylated tau protein. The phosphorylation of tau is assumed to be crucial for aggregation; however, the underlying mechanisms are not well understood. Several kinases have been identified as potential candidates for the abnormal phosphorylation under pathological conditions. Nevertheless, based on the lack of appropriate models the actual relevance of these enzymes could not be studied concertedly under physiological conditions. Recently, we described the reversible formation of highly phosphorylated tau protein in hibernating animals under physiological conditions. Using hibernation as a model we determined the activity profile of four major tau kinases in three different species to analyse the state-dependent regulation of these enzymes and reveal the importance of each kinase for tau phosphorylation

    Constraint Programming Based Column Generation for Crew Assignment

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    Airline crew assignment problems are large-scale optimization problems which can be adequately solved by column generation. The subproblem is typically a so-called constrained shortest path problem and solved by dynamic programming. However, complex airline regulations arising frequently in European airlines cannot be expressed entirely in this framework and limit the use of pure column generation. In this paper, we formulate the subproblem as a constraint satisfaction problem, thus gaining high expressiveness
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