Improved simulation of naturally fractured reservoirs using unstructured grids and multi-rate dual-porosity models

Naturally Fractured Reservoirs (NFR) hold about half of the world’s remaining oil reserves and are typically very heterogeneous. NFR are also important for many other subsurface engineering applications including (nuclear) waste storage, CO2 sequestration, groundwater aquifers, and geothermal energy extraction. They contain faults, fracture corridors, large fractures but also many small-scale fractures as well as a heterogeneous rock matrix. Multi-phase flow in NFR is strongly influenced by this multi-scale heterogeneity. Therefore, accurate conceptual models that reliably quantify fluid flow in NFR are needed. In this thesis, three important contributions are made towards an improved simulation of multi-phase flow processes in NFR. First, the Implicit Pressure Implicit Saturation (IMPIS) method using unstructured grids was implemented to numerically simulate two-phase flow in a Discrete Fracture and Matrix (DFM) model. Second, a Multi-Rate Dual-Porosity (MRDP) model was developed including fracture-matrix transfer functions that are based on analytical solutions for spontaneous imbibition and gravity drainage. Finally, the two approaches were combined to a DFM-MRDP model. This model represents the multi-scale heterogeneity inherent to NFR more accurately by resolving fluid-flow processes in large-scale fractures directly using the DFM model while accounting for complex matrix heterogeneities when modelling fluid exchange between small-scale fractures and rock matrix using the MRDP model

Cavity-Controlled Collective Scattering at the Recoil Limit

We study collective scattering with Bose-Einstein condensates interacting with a high-finesse ring cavity. The condensate scatters the light of a transverse pump beam superradiantly into modes which, in contrast to previous experiments, are not determined by the geometrical shape of the condensate, but specified by a resonant cavity mode. Moreover, since the recoil-shifted frequency of the scattered light depends on the initial momentum of the scattered fraction of the condensate, we show that it is possible to employ the good resolution of the cavity as a filter selecting particular quantized momentum states.Comment: 4 pages, 4 figure

Das Online-Tutorial der USB Köln

Darstellung der Konzeptionierung und Fertigstellung eines Online-Tutorials auf Grundlage von ILIAS (Integriertes Lern-, Informations- und Arbeitskooperationssystem), das an der Univrsität zu Köln entwickelt wurde. Das Online-Tutorial bietet dem Nutzer Materialien zum Aufbau von Informtionskompetenz an, die ihm helfen sollen, sich bestimmte Themen selbst zu erarbeiten. Gedacht nicht als Ersatz sondern als Ergänzung des Schulungsangebots der USB Köln soll es alle Benutzer der Bibliothek ansprechen, insbesondere aber die Studierenden. Die Module wurden durch Tests und weitere interaktive Module ergänzt, und es ist gewünscht auch die Institutsbibliotheken in dieses Projekt einzubeziehen

Fit für die Facharbeit. Ein neuer Kurs im Angebot der Universitäts- und Stadtbibliothek Köln

In dem Aufsatz, der in der Zeitschrift ProLibris (Heft 2/2008) erschienen ist, wird die Entwicklung eines neuen Schülerkurses an der USB Köln beschrieben - von der Konzipierung über die Vorbereitung und die Durchführung bis hin zur Evaluation. Um eine konzentrierte und effektive Planung durchführen zu können, wurde das "Projekt zur Förderung von Informationskompetenz für Oberstufenschüler" im Frühjahr 2007 ins Leben gerufen. Dieser Kurs ist speziell auf Schülerinnen und Schüler zugeschnitten, die in der Jahrgangsstufe 12 die Facharbeit schreiben. Auf ca. 10-15 Seiten sollen die Schülerinnen und Schüler ein individuelles Thema abhandeln, etwa einer Seminararbeit an der Universität entsprechend. Es gilt, Informationsbedarf zu erkennen, kompetent und effizient zu recherchieren und das richtige herauszufiltern und in die eigene Arbeit bedarfsgerecht zu integrieren. Daran anknüpfend ergibt sich eine gute Gelegenheit, den Schülerinnen und Schülern eine große wissenschaftliche Bibliothek zu zeigen und auf die formale und sachliche Literaturrecherche einzugehen. Das Neue an dem Kurs ist, dass die Schülerinnen und Schüler entsprechend des Prinzips der "learning library" zunächst ohne vorherige Erklärungen im Online-Katalog der USB Köln recherchieren und dann feststellen, dass Erklärungen nötig sind, um effektiv bessere Ergebnisse zu erzielen. Die Erläuterungen zu den Recherchetechniken und zum Online-Katalog der USB erfolgen also erst nach der selbständigen Suche. Dadurch wird ein größeres Interesse und höhere Konzentration bei den Teilnehmern erreicht. Im Anschluss an die Recherche findet ein Rundgang durch die Bibliothek statt, bei dem die Schülerinnen und Schüler die Gelegenheit haben, die recherchierten Bücher auch am Standort zu finden und in die Hand zu nehmen. Die Schülerinnen und Schüler lernen die Räume kennen und erhalten Erklärungen zu den Ausleihmodalitäten. Der Kurs dauert 90 Minuten und wird von zwei Diplom-Bibliothekarinnen durchgeführt. Ergänzend zur Beschreibung des Kurses werden die Erfahrungen eines Lehrers mit der Vermittlung von Informationskompetenz dargestellt, und in einem Interview sind die Meinungen einer Lehrerin und einiger Schüler zu dem Kurs "Fit für die Facharbeit" abgedruckt

Engineers are using social media for work purposes

Given the nowadays often distributed nature of product development and the tendency of engineers to rely on their colleagues and people they can easily reach, social media may offer solutions to support information seeking and efficient and effective knowledge sharing. This paper explores the use of social media in the Danish engineering industry. Results from over 130 survey participants show that 88% report to actually use social media for work purposes. The most addressed purposes are to search for information, knowledge and solutions, together with networking

Environment-assisted quantum transport in a 10-qubit network

The way in which energy is transported through an interacting system governs fundamental properties in many areas of physics, chemistry, and biology. Remarkably, environmental noise can enhance the transport, an effect known as environment-assisted quantum transport (ENAQT). In this paper, we study ENAQT in a network of coupled spins subject to engineered static disorder and temporally varying dephasing noise. The interacting spin network is realized in a chain of trapped atomic ions and energy transport is represented by the transfer of electronic excitation between ions. With increasing noise strength, we observe a crossover from coherent dynamics and Anderson localization to ENAQT and finally a suppression of transport due to the quantum Zeno effect. We found that in the regime where ENAQT is most effective the transport is mainly diffusive, displaying coherences only at very short times. Further, we show that dephasing characterized by non-Markovian noise can maintain coherences longer than white noise dephasing, with a strong influence of the spectral structure on the transport effciency. Our approach represents a controlled and scalable way to investigate quantum transport in many-body networks under static disorder and dynamic noise.Comment: Mai

Binding of coatomer by the PEX11 C-terminus is not required for function

AbstractMicrobodies are single membrane-bound organelles found in eukaryotes from trypanosomes to man. Although they have diverse roles in metabolism, the mechanisms and molecules involved in membrane biogenesis and matrix protein import are conserved. Similarly, the basic mechanisms and structures involved in vesicular transport are similar throughout eukaryotic evolution. The PEX11 proteins are required for the division of microbodies in trypanosomes, yeast and mammals, and a role of coatomer in this process has been suggested. We show here that the binding of trypanosome, yeast and bovine coatomers to selected peptides is identical. Coatomer binds to the C-termini of trypanosome PEX11 and rat Pex11α, but not yeast Pex11p or human Pex11β. Mutations of the C-terminus of trypanosome PEX11 that eliminated coatomer binding did not affect function in yeast or trypanosomes. Thus binding of coatomer to the C-terminus of PEX11 is not required for PEX11 function

Nitrogen fixation in eukaryotes – New models for symbiosis

BACKGROUND: Nitrogen, a component of many bio-molecules, is essential for growth and development of all organisms. Most nitrogen exists in the atmosphere, and utilisation of this source is important as a means of avoiding nitrogen starvation. However, the ability to fix atmospheric nitrogen via the nitrogenase enzyme complex is restricted to some bacteria. Eukaryotic organisms are only able to obtain fixed nitrogen through their symbiotic interactions with nitrogen-fixing prokaryotes. These symbioses involve a variety of host organisms, including animals, plants, fungi and protists. RESULTS: We have compared the morphological, physiological and molecular characteristics of nitrogen fixing symbiotic associations of bacteria and their diverse hosts. Special features of the interaction, e.g. vertical transmission of symbionts, grade of dependency of partners and physiological modifications have been considered in terms of extent of co-evolution and adaptation. Our findings are that, despite many adaptations enabling a beneficial partnership, most symbioses for molecular nitrogen fixation involve facultative interactions. However, some interactions, among them endosymbioses between cyanobacteria and diatoms, show characteristics that reveal a more obligate status of co-evolution. CONCLUSION: Our review emphasises that molecular nitrogen fixation, a driving force for interactions and co-evolution of different species, is a widespread phenomenon involving many different organisms and ecosystems. The diverse grades of symbioses, ranging from loose associations to highly specific intracellular interactions, might themselves reflect the range of potential evolutionary fates for symbiotic partnerships. These include the extreme evolutionary modifications and adaptations that have accompanied the formation of organelles in eukaryotic cells: plastids and mitochondria. However, age and extensive adaptation of plastids and mitochondria complicate the investigation of processes involved in the transition of symbionts to organelles. Extant lineages of symbiotic associations for nitrogen fixation show diverse grades of adaptation and co-evolution, thereby representing different stages of symbiont-host interaction. In particular cyanobacterial associations with protists, like the Rhopalodia gibba-spheroid body symbiosis, could serve as important model systems for the investigation of the complex mechanisms underlying organelle evolution