374 Works

Development of an in situ extraction process of fatty acids from microalgae cultures

Philipp Glembin
In this work micellar extraction was investigated in order to develop an alternative process for the in situ extraction of hydrophobic substances from microalgae cultures. The main requirements for an in situ extraction process such as biocompatibility, phase separation behavior and partitioning of the hydrophobic target substance between micellar- and aqueous phases were studied for a number of surfactants. The cloud point temperatures (CPT) as well as the biocompatibility of the nonionic surfactants with the...

Assembly force and taper angle difference influence the relative motion at the stem-neck interface of bi-modular hip prostheses

Henning Haschke, Sabrina Y. Jauch-Matt, Kay Sellenschloh, Gerd Huber & Michael Morlock
Bi-modular hip arthroplasty prostheses allow adaptation to the individual patient anatomy and the combination of different materials but introduce an additional interface, which was related lately to current clinical issues. Relative motion at the additional taper interface might increase the overall risk of fretting, corrosion, metallic debris and early failure. The aim of this study was to investigate whether the assembly force influences the relative motion and seating behaviour at the stem-neck interface of a...

Weblog campaigning in the German Bundestag election 2005

Steffen Albrecht, Maren Lübcke & Rasco Hartig-Perschke
Election campaigns are catalysts for new forms of political communication. They are a field of experimentation for new techniques and technologies to reach target groups and influence voters. This article explores how weblogs were used in the 2005 Bundestag election campaign in Germany, examining their effect on the mediatized political field. It is based on an empirical analysis of 317 campaign weblogs.

Influence of cooling on curing temperature distribution during cementing of modular cobalt-chromium and monoblock polyethylene acetabular cups

Stephan Rothstock, Mahnaz Saadatmand, Matthias Vollmer, Andreas Paech, Christian Jürgens, Roman Nassutt & Michael Morlock
Total hip replacements for older patients are usually cemented to ensure high postoperative primary stability. Curing temperatures vary with implant material and cement thickness (30°C to 70°C), whereas limits for the initiation of thermal bone damage are reported at 45°C to 55°C. Thus, optimizing surgical treatment and the implant material are possible approaches to lower the temperature. The aim of this study was to investigate the influence of water cooling on the temperature magnitude at...

Fabrication of composites via spouted bed granulation process and simulation of their micromechanical properties

Eduard Eichner, Maksym Dosta, Stefan Heinrich & Gerold A. Schneider
In this contribution numerical simulation of Young’s modulus of copper-polymer composites is presented. For the simulation of the composites the Bonded-Particle-Model was applied. The model allows representing of the structure of composite materials realistically. The polymer matrix, which surrounds the particles, was represented as network of solid bonds connecting copper particles. Simulation results were validated based on mechanical determination of modulus of elasticity. The modulus of elasticity was approximated in experiments as well as in...

What pathways lead to frugal innovation? : Some insights on modes & routines of frugal, technical inventions based on an analysis of patent data in German auto components industry

Rajnish Tiwari & Stephan Bergmann
Frugal innovations, i.e. affordable products and services with appropriately good quality, are getting increasingly important for securing long-term competitiveness in both, the developing world and in industry nations. Nevertheless, ensuring actual implementation of technology-driven frugal inventions remains an under-researched area. This study investigates modes and routines employed by techno-entrepreneurs from industry nations when innovating frugally. The study is based on the patent data of seven auto component sector firms from Germany with a documented history...

Jahresbericht des Präsidiums 2017

& Garabed Antranikian
Jahresbericht des Präsidiums der TU Hamburg 2017

The influence of pressure on crude oil biodegradation in shallow and deep Gulf of Mexico sediments

Uyen T. Nguyen, Sara A. Lincoln, Ana Gabriela Valladares Juárez, Martina Schedler, Jennifer L. Macalady, Rudolf Müller & Katherine H. Freeman
A significant portion of oil released during the Deepwater Horizon disaster reached the Gulf of Mexico (GOM) seafloor. Predicting the long-term fate of this oil is hindered by a lack of data about the combined influences of pressure, temperature, and sediment composition on microbial hydrocarbon remineralization in deep-sea sediments. To investigate crude oil biodegradation by native GOM microbial communities, we incubated core-top sediments from 13 GOM sites at water depths from 60-1500 m with crude...

Electro-conductive composite gold-polyethersulfone-ultrafiltration-membrane : characterization of membrane and natural organic matter (NOM) filtration performance at different in-stiu applied surface potentials

Tomi Mantel, Paul Benne, Stanislav Parsin & Mathias Ernst
Next to the pore size distribution, surface charge is considered to be one main factor in the separation performance of ultrafiltration (UF) membranes. By applying an external surface potential onto an electro-conductive UF membrane, electrostatic induced rejection was investigated. This study introduces in a first part a relatively simple but yet not reported technology of membrane modification with direct current sputter deposition of ultrathin (15 nm) highly conductive gold layers. In a second part, characterization...

Compiler-based extraction of event arrival functions for real-time systems analysis

Dominic Oehlert, Selma Saidi & Heiko Falk
Event arrival functions are commonly required in real-time systems analysis. Yet, event arrival functions are often either modeled based on specifications or generated by using potentially unsafe captured traces. To overcome this shortcoming, we present a compiler-based approach to safely extract event arrival functions. The extraction takes place at the code-level considering a complete coverage of all possible paths in the program and resulting in a cycle accurate event arrival curve. In order to reduce...

Modeling chemistry and flow in catalytic fixed-bed reactors with detailed geometry

Ying Dong
In der vorliegenden Arbeit wurden 3D-CFD-Modelle entwickelt und angewandt, um Festbettreaktoren mit verschiedenartigen Festbettkonfigurationen und Reaktionen zu modellieren. Die Ergebnisse wurde durch Vergleich mit ortsaufgelösten Reaktorprofilen der Reaktantenkonzentrationen und Reaktortemperatur kritisch validiert. Die experimentellen Daten wurden auch zur Kalibrierung wichtiger Modellparameter verwendet. Der in dieser Arbeit gewählte Ansatz ist ein wertvolles Werkzeug für ein tieferes Verständnis des Zusammenspiels von Fluiddynamik, Wärme- und Stofftransport und der katalytischen Reaktion in Festbettreaktoren, und stellt einen Schritt in Richtung...

Surface excess elasticity of gold: ab initio coefficients and impact on the effective elastic response of nanowires

Beatrix A. M. Elsner, Stefan Müller, Swantje Bargmann & Jörg Weissmüller
Predicting the influence of the surface on the effective elastic properties of nanoscale structures and nanomaterials remains a challenge, which we here address on both levels, continuum and atomic. Density Functional Theory (DFT) computation at the atomic level yields the first reliable surface excess elastic parameters for the (111) and (001) surfaces of gold. At the continuum level, we derive closed-form expressions for the effective elastic behavior that can be combined with the DFT-derived excess...

A ferroelectric liquid crystal confined in cylindrical nanopores : reversible smectic layer buckling, enhanced light rotation and extremely fast electro-optically active Goldstone excitations

Mark Busch, Andriy V. Kityk, Wiktor Piecek, Tommy Hofmann, Dirk Wallacher, Sylwia Calus, Przemyslaw Kula, Martin Steinhart, Manfred Eich & Patrick Huber
The orientational and translational order of a thermotropic ferroelectric liquid crystal (2MBOCBC) imbibed in self-organized, parallel, cylindrical pores with radii of 10, 15, or 20 nm in anodic aluminium oxide monoliths (AAO) are explored by high-resolution linear and circular optical birefringence as well as neutron diffraction texture analysis. The results are compared to experiments on the bulk system. The native oxidic pore walls do not provide a stable smectogen wall anchoring. By contrast, a polymeric...

Wie kommt das Repositorium in die Suchmaschine?

Beate Rajski
Beantwortung einer ABI Technik Frage: Publikations-Repositorien bedienen eine spezielle Schnittstelle für die Bereitstellung ihrer Metadaten: OAI-PMH („Protocol for Metadata Harvesting“ der Open Archive Initiative). Da diese von Suchmaschinen wie Google Scholar nicht genutzt wird, werden Metadaten zusätzlich im maschinenlesbaren HTML-Header zu einer Publikation bereitgestellt.

The cultural economy of cities : a comparative study of the audiovisual sector in Hamburg and Lisbon

Eduardo Brito-Henriques & Joachim Thiel
This article examines the role that big cities play in an ongoing change towards a ‘global cultural economy’. Starting from Allen Scott’s argument that a handful of urban flagships may benefit from this shift, it looks for an alternative approach to the territorial dimension of the ‘culture–economy nexus’ based on a more complex understanding of urban culture. A broad theoretical discussion of Scott’s ideas, as well as on the key concepts of culture, economy and...

Die Architektur von Offenheit - Überlegungen zur Gestaltung der digitalen Transformation

Axel Dürkop
Vortragstext der Nachwuchskeynote auf dem Jungen Forum für Medien und Hochschulentwicklung 2017 an der Uni Hamburg. Die Potenziale der Gestaltung von Offenheit sozio-technischer Systeme bilden sich in der Architektur ab. Entscheidungen im Entwicklungsprozess dieser Systeme sind nicht nur gestalterischer, sondern auch politischer Art. Am Ende des Beitrags werden Beispiele für dezentrale und föderierte Architekturen entfaltet.

The measurement of the Young's modulus of ice with ultrasonic waves

Kulbir Singh Randhawa
Many techniques have been used to measure the Young’s modulus of ice. The purpose of this bachelor thesis is to develop a more effective and precise technique. The impulse-echo method has been used to measure the longitudinal ultrasonic velocities of three different types of specimens. From this, the Young’s modulus has been calculated. The specimens included homogeneous, inhomogeneous and a cracked polycrystalline ice Ih sample. The homogenous samples studied were found to be elastic isotropic,...

Untersuchung des Einflusses der Struktursteifigkeit auf Eislasten

Maximilian Miotke
Diese Arbeit beschäftigt sich mit Eis-Struktur-Interaktionsversuchen mit Hilfe derer der Einfluss der Struktursteifigkeit auf Eislasten experimentell untersucht wird. Hierbei werden sowohl physikalische (Dicke, Temperatur) als auch mechanische (Druckfestigkeit, Biegesteifigkeit, relative/ absolute Durchbiegung, Reibungsverluste, Reaktionskräfte, Kontaktflächenentwicklung) Aspekte betrachtet. Es werden bisherige Erkenntnisse und Wissen aufgegriffen und zusammen mit den neuen Erkenntnissen Rückschlüsse auf das Eis-Stahl-Verhalten geschlossen.

From the World Brain to the first transatlantic information dialogue : activities in information and documentation in Germany in the first half of the 20th Century

Thomas Hapke
It is not enough to found libraries. It is necessary, by means of lectures and bibliographic. lists, to instruct those eager for knowledge in the best methods of utilizing their treasures. And this is by no means so easy as it sounds!

Silver-rich clusters in nanoporous gold

Tobias Krekeler, Anastasia V. Straßer, Matthias Graf, Ke Wang, Christian Hartig, Martin Ritter & Jörg Weissmüller
Herein we report on how to render Ti3C2Tx (MXene) monolayers deposited on SiO2/Si wafers, with different SiO2 thicknesses, visible. Inputting the effective thickness of a Ti3C2Tx monolayer (1 ± 0.2 nm) measured by atomic force microscopy, and its refractive index into a Fresnel-law-based simulation software, we show that the optical contrast of Ti3C2Tx monolayers deposited on SiO2/Si wafers depends on the SiO2 thickness, number of MXene layers, and the light’s wavelength. The highest contrast was...

Elastic behaviour at the nanoscale of innovative composites of nanoporous gold and polymer

Emma Griffiths, Swantje Bargmann & B. Dayanand Reddy
Nanoporous gold is a material with unique properties that make it attractive for use in multiple areas. It has an extremely high compressive strain capability but is very brittle in tension which limits its usage. One means of addressing this limitation is to fill the voids of the nanoporous material with a polymer, resulting in a more ductile and stronger material. In this work, the mechanical properties of a nanocomposite representative sample are studied numerically....

Elastic and plastic poisson’s ratios of nanoporous gold

Lukas Lührs, Celal Soyarslan, Jürgen Markmann, Swantje Bargmann & Jörg Weissmüller
We explore the elastic and plastic Poisson’s ratios, mE and mP, of nanoporous gold, using digital image correlation during compression experiments including load/unload segments. The two coefficients differ significantly, with mE independent of the ligament size, L, and with a trend for mP / L at not too large L. Disorder in the network of ligaments may explain why mE is smaller than predicted by lattice-based models. Finite element simulations, based on the Deshpande–Fleck constitutive...

Hydrogen bonding and thermoplastic elastomers - a nice couple with temperature-adjustable mechanical properties

Elisabeth Wittenberg, Andreas Meyer, Steffen Eggers & Volker Abetz
Styrene-butadiene copolymers are modified with varying fractions of benzoic acid moieties being able to perform hydrogen bonding. This is done by using a simple synthetic approach which utilizes click hemistry. Temperature-dependent dynamic mechanical properties are studied, and it turns out that even the apparently rather simple ydrogen bonding motif has a marked impact on the material properties due to the fact that it facilitates the formation of a supramolecular polymer network. Besides a glass transition,...

Nanoporous gold : testing macro-scale samples to probe small-scale mechanical behavior

Nadiia Mameka, Ke Wang, Jürgen Markmann, Erica Lilleodden & Jörg Weißmüller
Nanoporous gold made by dealloying exemplifies how the exciting mechanical properties of nanoscale objects can be exploited in designing materials from which macroscopic things can be formed. The homogeneous microstructure and the possibility of adjusting the ligament size, L, between few and few hundred nm, along with the high deformability and reproducible mechanical behavior predestine the material for model studies of small-scale plasticity using reliable macroscopic testing schemes on mm- or cm-size samples. Such experiments...

Automatic three-dimensional geometry and mesh generation of periodic representative volume elements for matrix-inclusion composites

Konrad Schneider, Benjamin Klusemann & Swantje Bargmann
This paper introduces an efficient method to automatically generate and mesh a periodic three- dimensional microstructure for matrix-inclusion composites. Such models are of major importance in the field of computational micromechanics for homogenization purposes utilizing unit cell models. The main focus of this contribution is on the creation of cubic representative volume elements (RVEs) featuring a periodic geometry and a periodic mesh topology suitable for the application of periodic boundary condi- tions in the framework...

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