Digital fabrication of custom interactive objects with rich materials

As ubiquitous computing is becoming reality, people interact with an increasing number of computer interfaces embedded in physical objects. Today, interaction with those objects largely relies on integrated touchscreens. In contrast, humans are capable of rich interaction with physical objects and their materials through sensory feedback and dexterous manipulation skills. However, developing physical user interfaces that offer versatile interaction and leverage these capabilities is challenging. It requires novel technologies for prototyping interfaces with custom interactivity that support rich materials of everyday objects. Moreover, such technologies need to be accessible to empower a wide audience of researchers, makers, and users. This thesis investigates digital fabrication as a key technology to address these challenges. It contributes four novel design and fabrication approaches for interactive objects with rich materials. The contributions enable easy, accessible, and versatile design and fabrication of interactive objects with custom stretchability, input and output on complex geometries and diverse materials, tactile output on 3D-object geometries, and capabilities of changing their shape and material properties. Together, the contributions of this thesis advance the fields of digital fabrication, rapid prototyping, and ubiquitous computing towards the bigger goal of exploring interactive objects with rich materials as a new generation of physical interfaces.Computer werden zunehmend in Geräten integriert, mit welchen Menschen im Alltag interagieren. Heutzutage basiert diese Interaktion weitgehend auf Touchscreens. Im Kontrast dazu steht die reichhaltige Interaktion mit physischen Objekten und Materialien durch sensorisches Feedback und geschickte Manipulation. Interfaces zu entwerfen, die diese Fähigkeiten nutzen, ist allerdings problematisch. Hierfür sind Technologien zum Prototyping neuer Interfaces mit benutzerdefinierter Interaktivität und Kompatibilität mit vielfältigen Materialien erforderlich. Zudem sollten solche Technologien zugänglich sein, um ein breites Publikum zu erreichen. Diese Dissertation erforscht die digitale Fabrikation als Schlüsseltechnologie, um diese Probleme zu adressieren. Sie trägt vier neue Design- und Fabrikationsansätze für das Prototyping interaktiver Objekte mit reichhaltigen Materialien bei. Diese ermöglichen einfaches, zugängliches und vielseitiges Design und Fabrikation von interaktiven Objekten mit individueller Dehnbarkeit, Ein- und Ausgabe auf komplexen Geometrien und vielfältigen Materialien, taktiler Ausgabe auf 3D-Objektgeometrien und der Fähigkeit ihre Form und Materialeigenschaften zu ändern. Insgesamt trägt diese Dissertation zum Fortschritt der Bereiche der digitalen Fabrikation, des Rapid Prototyping und des Ubiquitous Computing in Richtung des größeren Ziels, der Exploration interaktiver Objekte mit reichhaltigen Materialien als eine neue Generation von physischen Interfaces, bei

Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth

In this study, we investigated pre-structured (100) GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination

Power estimation for non-standardized multisite studies

AbstractA concern for researchers planning multisite studies is that scanner and T1-weighted sequence-related biases on regional volumes could overshadow true effects, especially for studies with a heterogeneous set of scanners and sequences. Current approaches attempt to harmonize data by standardizing hardware, pulse sequences, and protocols, or by calibrating across sites using phantom-based corrections to ensure the same raw image intensities. We propose to avoid harmonization and phantom-based correction entirely. We hypothesized that the bias of estimated regional volumes is scaled between sites due to the contrast and gradient distortion differences between scanners and sequences. Given this assumption, we provide a new statistical framework and derive a power equation to define inclusion criteria for a set of sites based on the variability of their scaling factors. We estimated the scaling factors of 20 scanners with heterogeneous hardware and sequence parameters by scanning a single set of 12 subjects at sites across the United States and Europe. Regional volumes and their scaling factors were estimated for each site using Freesurfer's segmentation algorithm and ordinary least squares, respectively. The scaling factors were validated by comparing the theoretical and simulated power curves, performing a leave-one-out calibration of regional volumes, and evaluating the absolute agreement of all regional volumes between sites before and after calibration. Using our derived power equation, we were able to define the conditions under which harmonization is not necessary to achieve 80% power. This approach can inform choice of processing pipelines and outcome metrics for multisite studies based on scaling factor variability across sites, enabling collaboration between clinical and research institutions

Ebene Homogenisierung des periodisch zellularen Verbundmaterials Geozelle-Boden

Die Anwendungsgebiete von Geokunststoffen sind vielfältig. Dementsprechend existieren eine Vielzahl unterschiedlicher Geokunststoffarten, um die an diese gestellten Anforderungen optimal zu erfüllen. Geozellen stellen hierbei eine Besonderheit dar. Bedingt durch die dreidimensionale, periodische und zellulare Struktur weisen diese ein komplexes Interaktionsverhalten mit dem Füllmaterial aus Boden auf und die Höhe der bewehrten Schicht besitzt einen entscheidenden Einfluss auf die Wirkungsweise. Werden die Geozellen und das Füllmaterial zusammengefasst betrachtet, ergibt sich ein heterogenes und richtungsabhängiges Verbundmaterial mit verbesserten Materialeigenschaften. Die vorliegende Arbeit behandelt die ebene Homogenisierung und die Abbildung des Verbundmaterials Geozelle-Boden über das mechanische Modell einer Platte und/oder Scheibe. Die Abbildbarkeit als Platte liegt dabei in einer aus der Höhe folgenden Biegesteifigkeit der bewehrten Schicht begründet. Unter Berücksichtigung der strukturellen Materialsymmetrie weist das Verbundmaterial ein orthotropes Materialverhalten auf, zu dessen homogener Beschreibung äquivalente Materialkennwerte notwendig sind. Die Herleitung dieser Kennwerte erfolgt ausgehend von einem flächenbasierten Homogenisierungsverfahren für hexagonale Wabenkerne in Sandwichwerkstoffen. Neben Bestimmungsgleichungen zur Ermittlung der äquivalenten Materialkennwerte werden Anwendungsgrenzen und über Grenzwertbetrachtungen vereinfachte Formulierungen abgeleitet sowie die Plausibilität der Lösung überprüft. Ein Vergleich mit Finite-Elemente-Berechnungen bestätigt die Gültigkeit der abgeleiteten Bestimmungsgleichungen. Im allgemeinen Fall erfüllen die äquivalenten Materialkennwerte des homogenen Verbundmaterials Geozelle-Boden die aus der Materialtheorie folgenden Bedingungen nur für bestimmte Lastkombinationen. Im Rahmen einer Parameterstudie werden zusätzlich Gültigkeitsgrenzen für die vereinfachten Bestimmungsgleichungen aufgestellt sowie die wesentlichen Einflussgrößen erläutert. Der Zellwinkel, die Schlankheit der Zellwände und das Steifigkeitsverhältnis des Füllmaterials zu den Wandsteifigkeiten stellen dabei die maßgebenden Einflussfaktoren dar. Zudem werden die grundlegenden Zusammenhänge zwischen den äquivalenten Materialkennwerten, insbesondere die Sonderfälle einer Richtungsunabhängigkeit des Materialverhaltens in der Aufspannebene, aufgezeigt. Abschließend werden unter Berücksichtigung der Abhängigkeit von den jeweiligen Randbedingungen die äquivalenten Materialkennwerte auf das mechanische Tragwerksmodell einer Scheibe und Platte übertragen. Zur Abbildung als homogene Platte werden ergänzend Gleichungen zu äquivalenten Plattensteifigkeiten hergeleitet sowie deren Anwendung an Zahlenbeispielen verdeutlicht. Die Betrachtung des Verbundmaterials Geozelle-Boden als homogenes Material über das mechanische Modell einer Platte und/oder Scheibe ist somit möglich.There are a large number of geosynthetics available to meet the requirements in various kinds of application. Usually geosynthetics are flat and their height is very small in comparison with the horizontal dimension. However, geocells with their three-dimensional, periodic and cellular features are a very special type of geosynthetic. The height dimension of geocells cannot be ignored but has a decisive impact on the reinforcement effect. In combination with an infill material, which usually is some type of coarse grained soil without tensile strength, it results in a heterogeneous and anisotropic composite material showing improved material properties. Due to the missing tensile strength of the infill material the in-plane behaviour of the composite material geocell-soil varies when loaded axially in compression or tension. This thesis presents an in-plane homogenization of the composite material geocell-soil and its application to classical plate as well as shell theory. Test results from literature and the ones presented hereafter indicate that the height of a geocell-reinforced layer causes a plate-like reinforcement effect due to bending stiffness. Taking into account the planes of symmetry the composite material shows an orthotropic material behaviour, which requires equivalent material properties for a homogeneous description. These material properties are derived from a surface-based homogenization technique originally developed for hexagonal honeycombs in sandwich materials. In order to apply this homogenization technique to geocells it is modified and the influence of the infill material is added. An additional limit analysis yields simplified solution for the equivalent material properties and their application limits. A comparison of the analytical solution with the results of a Finite-Element-Analysis shows very good agreement and proves its validity. In general the equivalent material properties only meet the conditions of orthotropic material theory for certain load combinations. Validity limits for the simplified solution are defined and the main factors influencing the equivalent material properties of the composite material are highlighted in a parameter study. The cell angle, the slenderness of the cell walls and the ratio of the infill material stiffness to the cell wall stiffness depict the most relevant influence factors. In addition, basic relationships between the different equivalent material properties, in particular directional independency of the material behaviour for certain cell geometries, are presented. The application of the equivalent material properties to classical plate and shell theory is illustrated by several examples. Since the composite material behaves differently when loaded in compression or tension additional equations are developed to calculate equivalent bending stiffnesses for the homogeneous plate approach. As a result of this thesis, it is possible to describe the reinforcement effect of the discrete composite material geocell-soil by a homogeneous model of a plate and/or shell

The structure of mean equicontinuous group actions

We study mean equicontinuous actions of locally compact σ-compact amenable groups on compact metric spaces. In this setting, we establish the equivalence of mean equicontinuity and topo-isomorphy to the maximal equicontinuous factor and provide a characterization of mean equicontinuity of an action via properties of its product. This characterization enables us to show the equivalence of mean equicontinuity and the weaker notion of Besicovitch-mean equicontinuity in fairly high generality, including actions of abelian groups as well as minimal actions of general groups. In the minimal case, we further conclude that mean equicontinuity is equivalent to discrete spectrum with continuous eigenfunctions. Applications of our results yield a new class of non-abelian mean equicontinuous examples as well as a characterization of those extensions of mean equicontinuous actions which are still mean equicontinuous

Design of recombinant whole-cell catalysts for double reduction of C=C and C=O bonds in enals and application in the synthesis of Guerbet alcohols as industrial bulk chemicals for lubricants

Biermann M, Bakonyi D, Hummel W, Gröger H. Design of recombinant whole-cell catalysts for double reduction of C=C and C=O bonds in enals and application in the synthesis of Guerbet alcohols as industrial bulk chemicals for lubricants. GREEN CHEMISTRY. 2017;19(2):405-410.Whole-cell catalysts overexpressing two enzymes for a double reduction cascade in which aliphatic alpha-branched alpha,beta-unsaturated aldehydes are converted into Guerbet alcohols as a highly demanded class of lubricants were constructed and characterized. The reaction conditions were optimized to suppress by-product formation, achieving high conversion and selectivity. Application of methanol as a co-solvent on a 500 mL scale enabled a substrate concentration of 18.5 g L-1 obtaining 97% yield and 88% purity without further distillation. Addressing the needs of industrial processes, substrate loading was increased up to 94 g L-1 and the E-factor (environmental factor) was significantly improved compared to the original process with isolated enzymes

The function of the oxylipin 12-oxophytodienoic acid in cell signaling, stress acclimation, and development

Maynard D, Gröger H, Dierks T, Dietz K-J. The function of the oxylipin 12-oxophytodienoic acid in cell signaling, stress acclimation, and development. Journal of Experimental Botany . 2018;69(22):5341-5354.Forty years ago, 12-oxophytodienoic acid (12-OPDA) was reported as a prostaglandin (PG)-like metabolite of linolenic acid found in extracts of flaxseed. Since then, numerous studies have determined the role of 12-OPDA in regulating plant immunity, seed dormancy, and germination. This review summarizes our current knowledge of the regulation of 12-OPDA synthesis in the chloroplast and 12-OPDA-dependent signaling in gene expression and targeting protein functions. We describe the properties of OPDA that are linked to the activities of PGs, which are derived from arachidonic acid and act as tissue hormones in animals, including humans. The similarity of OPDA with bioactive PGs is particularly evident for the most-studied cyclopentenone, PG 15-dPGJ(2). In addition to chemical approaches towards 12-OPDA synthesis, bio-organic synthesis strategies for 12-OPDA and analogous substances have recently been established. The resulting availability of OPDA will aid the identification of additional effector proteins, help in elucidating the mechanisms of OPDA sensing and transmission, and will foster the analysis of the physiological responses to OPDA in plants. There is a need to determine the compartmentation and transport of 12-OPDA and its conjugates, over long distances as well as short. It will be important to further study OPDA in animal and human cells, for example with respect to beneficial anti-inflammatory and anti-cancer activities

Two-wavelength digital holography through fog

Interferometric detection enables the acquisition of the amplitude and phase of the optical field. By making use of the synthetic wavelength as a computational construct arising from digital processing of two off-axis digital holograms, it is possible to identify the shape of an object obscured by fog and further increase the imaging range due to the increased sensitivity in coherent detection. Experiments have been conducted inside a 27 m long fog tube filled with ultrasonically generated fog. We show the improved capabilities of synthetic phase imaging through fog and compare this technique with conventional active laser illumination imaging