Evidence on Night Movements of Macroinvertebrates to Macrophytes in a Pampean Stream

Nocturnal invertebrate abundance peaks in lotic systems are usually associated to drift, however, diel migrations other than drift may be important in slow-flowing systems. Then, macroinvertebrate distribution on macrophytes may change along the day as result of vertical or horizontal migration from sediments or the water column. My objective was to determine whether macroinvertebrate abundance on macrophytes changes along 24 h. Three Ceratophyllum demersum patches were sampled in late spring from the Las Flores stream (Central Argentina) at 11:20 h, 17:10 h, 23:00 h and 5:00 h. Macroinvertebrates were counted and identified, and relative abundances were estimated for each sampling time. The dominant groups of macroinvertebrates sampled were Oligochaeta, Amphipoda and Cladocera. The relative abundance of macroinvertebrates on macrophytes was the highest at 5:00 h, when dissolved oxygen in water reached its minimum. In conclusion, the abundance of macroinvertebrates on macrophytes in Pampean streams may increase at night, probably as result of nocturnal migration driven by changes in predation risk or dissolved oxygen.Fil: Ferreiro, Nicolas Andres. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The relationship between the intergalactic medium and galaxies

In this thesis we study the relationship between the intergalactic medium (IGM) and galaxies at z<1, in a statistical manner. Galaxies are mostly surveyed in emission using optical spectroscopy, while the IGM is mostly surveyed in absorption in the ultra-violet (UV) spectra of background quasi-stellar objects (QSOs). We present observational results investigating the connection between the IGM and galaxies using two complementary methods: • We use galaxy voids as tracers of both underdense and overdense regions. We use archival data to study the properties of H I absorption line systems within and around galaxy voids at z<0.1. Typical galaxy voids have sizes 10 Mpc and so our results constrain the very large-scale association. This sample contains 106 H I absorption systems and 1054 galaxy voids. • We use a sample of H I absorption line systems and galaxies from pencil beam surveys to measure the H I–galaxy cross-correlation at z<1. Our sample is composed of a combination of archival and new data taken by the author and collaborators. This survey covers transverse separations between H I and galaxies from ∼ 100 kpc (proper) up to ∼ 10 Mpc, filling the gap between the very large scales and those associated with the so-called circumgalactic medium (CGM). This sample contains 654 H I absorption systems and 17509 galaxies. Our results hint towards a picture in which there are at least three types of association between the diffuse gas in the Universe and galaxies at z 1: • One-to-one direct association because galaxies do contain diffuse gas. • Indirect association because both the IGM and galaxies trace the same over-dense underlying dark matter distribution. We provide quantitative evidence for this association. Moreover, we show that not all galaxies are related to the diffuse gas in the same way. In particular, a non negligible fraction of ‘non-star-forming’ galaxies might reside in environments devoid of diffuse H I. • No association because there are regions in the Universe that contain a significant amount of diffuse gas but that are devoid of galaxies. In these regions, only the IGM follows the underdense underlying dark matter distribution because galaxies are not present. We provide quantitative evidence for this scenario

Bildverarbeitungskarte CubeSat: Diplom 2015

L'objectif du travail de bachelor est de développer une carte électronique qui peut prendre des photos d'une caméra, les traiter et transmettre les données résultantes à la carte processeur principale du satellite.Das Ziel der Bachelorarbeit ist es, eine elektronische Karte zu entwickeln, welche Bilder einer Kamera aufnehmen kann, diese verarbeitet und die resultierenden Daten an die Hauptprozessorkarte des Satelliten weiterleitet

Rethinking Streets: a study of streetspace allocation metrics and street networks in London

This research investigates streetspace allocation metrics for all streets in London providing quantitative evidence about a key parameter of street design citywide. A new methodology to quantify streetspace allocation is introduced using a geocomputational approach that allows both the processing of high-resolution topographic data over a large geographic extent and enables replicability for other cities. The correlation between streetspace allocation metrics and street network centrality at distinct scales is investigated across different geographic areas. These variables are then examined using cluster analysis to identify a typology of streets based on streetspace allocation and centrality. The results provide the framework for a design scenario study of inner London applying shortest-path analysis under an active travel prioritisation perspective. Streetspace statistics for London confirm the predominance of space allocated for vehicular transport over pedestrian uses. Most streets display standard "residential" street metrics, coinciding with traditional street classification schemes. Also, this serves to demonstrate quantitatively the spatially efficient organisation of the London street system with few wider distributors and many narrower local streets. In addition, through the combined examination of the streets' allocation and configurational metrics, it is possible to identify a new sub-type of local streets. The spatial arrangement of the streets segments types follows a centre-periphery pattern: wider and higher centrality streets are clustered at the city centre and show relative larger streetspace designated to pedestrians, corresponding with higher levels of estimated activity. On a prescriptive streetspace model of Inner London, the streetspace allocation of critical pathways is modified to illustrate how strategic scale street properties affect and are affected by design scale street parameters. The fine-grain physical metrics analysed here, not only can be useful to tackle a wide range of contemporary street related questions from urban environmental quality to the adoption of new technologies but also offer alternative analytical methods for street research, planning and design

Understanding Grafted Cations in Controlled Environments for Heterogeneous Catalysis

Catalytic processes occurring on the surfaces of heterogeneous catalysts are controlled by the molecular structures of active sites where these reactions occur. These active sites can be broadly thought to consist of an active center, where bond making and breaking events occur, surrounding by the surface of the support. These are the inner-sphere (i.e. active center) and outer-sphere (i.e. surface) environments of the active site. Catalyst design typically focuses on the choice of the optimal inner-sphere environment, while surfaces are often regarded as inert oxide supports onto which active sites are dispersed to facilitate catalyst recovery. In this thesis, I demonstrate that the outer-sphere surface environment is, in fact, an essential element for controlling the structure and reactivity of active sites supported on silicates.The theoretical concepts, silicate supports, and synthetic approaches that are used in this thesis are introduced in Chapter 1. Given the importance of silanol groups as grafting sites in synthetic approaches used in this thesis, I begin by providing a detailed study of silanol speciation across zeotypes and amorphous supports, in Chapter 2. Subsequently, I provide an example of how silanol environments control grafting processes and how crystalline silicates provide stable support environments for FeIII cations, in Chapter 3. I then introduce an approach to synthesizing well-defined active sites by controlling the structure of a grafted cation using an organic ligand, applied to calix[4]arene-TiIV complexes grafted on amorphous SiO2 as epoxidation catalysts, in Chapter 4. Having established the structure of silicates and approaches to synthesize well-defined active sites on their surface, I present three studies where this enables the study of structure and catalytic properties. In Chapter 5, I demonstrate how this approach enables the unambiguous deconvolution of the effect of support outer-sphere on epoxidation catalysis. In Chapter 6, I investigate how the support outer-sphere can also control the conformation and structure of grafted complexes, while providing insight into adsorption processes occurring on surfaces. Finally, in Chapter 7, I provide a detailed mechanistic study of how partially confining outer-sphere environments impact catalytic reactivity for olefin epoxidation. Taken together, this work provides fresh insights into the structure of silicate supports and their ability to control catalysis, providing an additional and important avenue to the design of heterogeneous catalysts

Efficient Decomposition of Image and Mesh Graphs by Lifted Multicuts

Formulations of the Image Decomposition Problem as a Multicut Problem (MP) w.r.t. a superpixel graph have received considerable attention. In contrast, instances of the MP w.r.t. a pixel grid graph have received little attention, firstly, because the MP is NP-hard and instances w.r.t. a pixel grid graph are hard to solve in practice, and, secondly, due to the lack of long-range terms in the objective function of the MP. We propose a generalization of the MP with long-range terms (LMP). We design and implement two efficient algorithms (primal feasible heuristics) for the MP and LMP which allow us to study instances of both problems w.r.t. the pixel grid graphs of the images in the BSDS-500 benchmark. The decompositions we obtain do not differ significantly from the state of the art, suggesting that the LMP is a competitive formulation of the Image Decomposition Problem. To demonstrate the generality of the LMP, we apply it also to the Mesh Decomposition Problem posed by the Princeton benchmark, obtaining state-of-the-art decompositions