Impact of distance determinations on Galactic structure. II. Old tracers

Here we review the efforts of a number of recent results that use old tracers to understand the build up of the Galaxy. Details that lead directly to using these old tracers to measure distances are discussed. We concentrate on the following: (1) the structure and evolution of the Galactic bulge and inner Galaxy constrained from the dynamics of individual stars residing therein; (2) the spatial structure of the old Galactic bulge through photometric observations of RR Lyrae-type stars; (3) the three\--dimensional structure, stellar density, mass, chemical composition, and age of the Milky Way bulge as traced by its old stellar populations; (4) an overview of RR Lyrae stars known in the ultra-faint dwarfs and their relation to the Galactic halo; and (5) different approaches for estimating absolute and relative cluster ages.Comment: Review article, 80 pages (25 figures); Space Science Reviews, in press (chapter of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

The Giraffe Inner Bulge Survey (GIBS) II. Metallicity distributions and alpha element abundances at fixed Galactic latitude

High resolution (R$\sim$22,500) spectra for 400 red clump giants, in four fields within $\rm -4.8^{\circ} \lesssim b \lesssim -3.4^{\circ}$ and $\rm -10^{\circ} \lesssim l \lesssim +10^{\circ}$, were obtained within the GIRAFFE Inner Bulge Survey (GIBS) project. To this sample we added another $\sim$ 400 stars in Baade's Window, observed with the identical instrumental configuration. We constructed the metallicity distributions for the entire sample, as well as for each field individually, in order to investigate the presence of gradients or field-to-field variations in the shape of the distributions. The metallicity distributions in the five fields are consistent with being drawn from a single parent population, indicating the absence of a gradient along the major axis of the Galactic bar. The global metallicity distribution is well fitted by two Gaussians. The metal poor component is rather broad, with a mean at $\rm =-0.31$ dex and $\sigma=0.31$ dex. The metal-rich one is narrower, with mean $\rm =+0.26$ and $\sigma=0.2$ dex. The [Mg/Fe] ratio follows a tight trend with [Fe/H], with enhancement with respect to solar in the metal-poor regime, similar to the one observed for giant stars in the local thick disc. [Ca/Fe] abundances follow a similar trend, but with a considerably larger scatter than [Mg/Fe]. A decrease in [Mg/Fe] is observed at $\rm [Fe/H]=-0.44$ dex. This \textit{knee} is in agreement with our previous bulge study of K-giants along the minor axis, but is 0.1 dex lower in metallicity than the one reported for the Bulge micro lensed dwarf and sub-giant stars. We found no variation in $\alpha$-element abundance distributions between different fields.Comment: Accepted for publication in A&

Seaglider observations of biogeochemical variability in the Iberian upwelling system.

Seasonal upwelling events along the Galician coastline of the North Atlantic furnish the upper watercolumn with nutrients, resulting in strong summer phytoplankton blooms and the sustenance of one of Europe’s largest fisheries. The episodic nature of these upwelling events result in considerable challenges studying the region using traditional shipboard observations. This thesis demonstrates an alternative sampling technique, providing high spatial and temporal resolution biogeochemical data through the use of an autonomous underwater gliderthe Seaglider. SG510 “Orca” was outfitted with sensors to measure dissolved oxygen, temperature, salinity, chlorophyll a (chl a), coloured dissolved organic material (CDOM) and optical backscatter. Deployed for 113 days over summer 2010, Orca completed 17 zonal transects across the shelf, continental slope and open ocean at 42.1° N. Data collected during the campaign was used to assess both the physics of the watercolumn, and the effect these physical processes have on the region’s biogeochemistry. As part of this biogeochemical study, a novel attempt at calculating net community production (NCP) was completed using an oxygen inventory technique. Two major phytoplankton bloom events occurred during the deployment period, with respective peak Chl a concentrations of 9.65 and 11.23 mg m3. During these bloom events, NCP varied between (net autotrophic) values of 25 and 123 (±17 ) mmol m2. d1. Negative values of NCP were only observed twice for 24 and 60 hours respectively, with a maximum heterotrophy of 44 (±17) mmol m2 d1. Overall, the summer season featured a net autotrophic metabolic balance of +27 mmol m2 d1 .thus highlighting the importance of the region for net carbon sequestration. Finally, this thesis also demonstrates the success of using autonomous glider platforms for sustained biogeochemical and physical observations within a highly dynamic and challenging operational environment with strong currents and considerable shipping traffic

Design synthesis & prototype implementation of parallel orientation manipulators for optomechatronic applications

This thesis documents a research endeavor undertaken to develop high-performing designs for parallel orientation manipulators (POM) capable of delivering the speed and the accuracy requirements of a typical optomechatronic application. In the course of the research, the state of the art was reviewed, and the areas in the existing design methodologies that can be potentially improved were identified, which included actuator design, dimensional synthesis of POMs, control system design, and kinematic calibration. The gaps in the current art of designing each of these POM system components were addressed individually. The outcomes of the corresponding development activities include a novel design of a highly integrated voice coil actuator (VCA) possessing the speed, the size, and the accuracy requirements of small-scale parallel robotics. Furthermore, a method for synthesizing the geometric dimensions of a POM was developed by adopting response surface methodology (RSM) as the optimization tool. It was also experimentally shown how conveniently RSM can be utilized to develop an empirical quantification of the actual kinematic structure of a POM prototype. In addition, a motion controller was formulated by adopting the active disturbance rejection control (ADRC) technology. The classic formulation of the ADRC algorithm was modified to develop a resource-optimized implementation on control hardware based on field programmable gate arrays (FPGA). The practicality and the effectiveness of the synthesized designs were ultimately demonstrated by performance benchmarking experiments conducted on POM prototypes constructed from these components. In specific terms, it was experimentally shown that the moving platforms of the prototyped manipulators can achieve highspeed motions that can exceed 2000 degrees/s in angular velocity, and 5×105 degrees/s2 in angular acceleration

Kinematic Calibration of Parallel Kinematic Machines on the Example of the Hexapod of Simple Design

The aim of using parallel kinematic motion systems as an alternative of conventional machine tools for precision machining has raised the demands made on the accuracy of identification of the geometric parameters that are necessary for the kinematic transformation of the motion variables. The accuracy of a parallel manipulator is not only dependent upon an accurate control of its actuators but also upon a good knowledge of its geometrical characteristics. As the platform's controller determines the length of the actuators according to the nominal model, the resulted pose of the platform is inaccurate. One way to enhance platform accuracy is by kinematic calibration, a process by which the actual kinematic parameters are identified and then implemented to modify the kinematic model used by the controller. The first and most general valuation criterion for the actual calibration approaches is the relative improvement of the motion accuracy, eclipsing the other aspects to pay for it. The calibration outlay has been underestimated or even neglected for a long time. The scientific value of the calibration procedure is not only in direct proportion to the achieved accuracy, but also to the calibration effort. These demands become particularly stringent in case of the calibration of hexapods of the so-called simple design. The objectives of the here proposed new calibration procedure are based on the deficits mentioned above under the special requirements due to the circumstances of the simple design-concept. The main goals of the procedure can be summarized in obtaining the basics for an automated kinematic calibration procedure which works efficiently, quickly, effectively and possibly low-cost, all-in-one economically applied to the parallel kinematic machines. The problem will be approached systematically and taking step by step the necessary conclu-sions and measurements through: Systematical analysis of the workspace to determine the optimal measuring procedure, measurements with automated data acquisition and evaluation, simulated measurements based on the kinematic model of the structure and identifying the kinematic parameters using efficient optimization algorithms. The presented calibration has been successfully implemented and tested on the hexapod of simple design `Felix' available at the IWM, TU Dresden. The obtained results encourage the application of the procedure to other hexapod structures

Design of a Robotic Inspection Platform for Structural Health Monitoring

Actively monitoring infrastructure is key to detecting and correcting problems before they become costly. The vast scale of modern infrastructure poses a challenge to monitoring due to insufficient personnel. Certain structures, such as refineries, pose additional challenges and can be expensive, time-consuming, and hazardous to inspect. This thesis outlines the development of an autonomous robot for structural-health-monitoring. The robot is capable of operating autonomously in level indoor environments and can be controlled manually to traverse difficult terrain. Both visual and lidar SLAM, along with a procedural-mapping technique, allow the robot to capture colored-point-clouds. The robot is successfully able to automate the point cloud collection of straightforward environments such as hallways and empty rooms. While it performs well in these situations, its accuracy suffers in complex environments with variable lighting. More work is needed to create a robust system, but the potential time savings and upgrades make the concept promising

Systematic literature review of realistic simulators applied in educational robotics context

This paper presents a systematic literature review (SLR) about realistic simulators that can be applied in an educational robotics context. These simulators must include the simulation of actuators and sensors, the ability to simulate robots and their environment. During this systematic review of the literature, 559 articles were extracted from six different databases using the Population, Intervention, Comparison, Outcomes, Context (PICOC) method. After the selection process, 50 selected articles were included in this review. Several simulators were found and their features were also analyzed. As a result of this process, four realistic simulators were applied in the review’s referred context for two main reasons. The first reason is that these simulators have high fidelity in the robots’ visual modeling due to the 3D rendering engines and the second reason is because they apply physics engines, allowing the robot’s interaction with the environment.info:eu-repo/semantics/publishedVersio

Transcriptional and post-transcriptional regulation of leaf development in Arabidopsis thaliana

Plant growth follows a strict developmental program but needs to incorporate also environmental cues to adapt to the encountered conditions. This requires a complex regulatory network to ensure an appropriate response to changing conditions. We used the first leaf pair of Arabidopsis thaliana as a model system to study the regulation of organ development. Leaf growth can be divided in subsequent phases according to the major process driving it. In a young leaf primordium cells divide continuously and cell size homeostasis is ensured by matching rates of cell expansion. Next, cell division ceases and cell expansion becomes the driving force for growth. When the leaf has attained its final size, maturity is reached. In this thesis, I studied the regulation of leaf development at two regulatory levels. At the gene level, we analyzed the function of the CYCA2 core cell cycle regulatory gene family. We also studied the function of two new proliferation specific gene families putatively involved in cell cycle regulation. On the other hand, we profiled small RNA sequences during development and linked this with the occurrence of DNA methylation. The core machinery of the cell cycle in plants has been thoroughly studied, but our knowledge on how developmental and environmental signals impinge on cell division is still limited. CYCA2s are known core cell cycle regulators, involved in G2-to-M transition. Here, we studied the functional requirement of this gene family and showed that transcriptional repression is required for specific differentiation processes. Members of the CYCA2 protein family function in vascular development and differentiation of guard cells. For the latter process, we demonstrated that FOUR LIPS and MYB88, two transcription factors involved in stomatal development, directly repress CYCA2;3 expression, thus ensuring correct guard cell differentiation. Next to known ‘core’ cell cycle regulating genes, we also selected proliferation specific genes with unknown function, assuming them to be involved in the cell division process. We focused on two small gene families: three genes with four transmembrane domains (4TMs) and two genes containing three High Mobility Group (HMG) domains (3xHMG-box). Expression analysis and localization of transcriptional fusions with a fluorescent marker confirmed for both gene families the highly proliferation-specific expression pattern. Moreover, both families are highly induced in the M-phase of the cell cycle in synchronized cell cultures. The 4TMs localize to the cell plate during mitosis and we observed defects in cell plate formax tion upon overexpression and depletion of these genes. Therefore, we hypothesize that the 4TM genes are involved in formation of the cell plate. Profiling of small RNAs (sRNAs) in plants has thusfar mainly been focused on inflorescence tissue or whole seedlings. Here, we studied sRNAs during the different phases of development. Early in development, microRNAs implicated in nutrient stress response are upregulated, suggesting that at this phase nutrient availability is limiting for growth. We showed that specifically 24-nt sRNAs increase in expression during development. This class of sRNAs is known to be involved in RNA-dependent DNA methylation (RdDM) and can thus silence both transposons and genes. In general, the expression of sRNAs matching the coding sequences of protein-coding genes is positively correlated to the mRNA expression of this gene. We specifically selected genes that do not show this correlation, which were highly enriched in two categories: targets of microRNAs and trans-acting siRNAs, which generate phased sRNAs upon cleavage, and genes for which the sRNA profile is enriched for 24-nt sRNAs. This latter category is likely regulated through RdDM as this subset of genes shows increased DNA methylation in the gene body. This suggests that sRNA regulation could play an important role in regulating the leaf developmental process not only by preserving genome integrity by repressing transposon activity but also through silencing of protein-coding genes