373 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...

Structural and differential analysis for program comprehension of executables

Arne Wichmann
Wir führen eine strukturelle Analyse (StA), die Schlüsselstellen für das Programmverständnis von ausführbaren Programmen identifiziert, und eine differenzielle Analyse (DiA), die Ähnlichkeiten zwischen solchen ausführbaren Programmen identifiziert, ein. Unsere StA basiert auf einer neuen Abstraktion von Kontrollflussinformationen auf Statementebene zu einer Repräsentation mit einer graphischen Ansicht, die eine intuitive Identifizierung von mitgelieferten Mustern ermöglicht. Unsere DiA basiert auf Sequenzalignments und benötigt nur die Position und Größe der Funktionen. Wir validieren die StA manuell mit einer...

A statistical study of scattering in periodic and random helix layers

Christian Meiners & Arne F. Jacob
This paper aims at providing information on scattering in layers composed of periodic and non-periodic arrangements of small metal helices. Metal helices exhibit a pronounced resonance and are thus very effective scatterers.

On the effects of the external surface on the equilibrium transport in zeolite crystals

Nils E. R. Zimmermann, Berend Smit & Frerich Keil
With the aid of molecular simulation techniques (molecular dynamics [MD], Grand-Canonical Monte Carlo [GCMC], and reactive flux correlation function [RFCF]), the influence of the external surface on the equilibrium permeation of methane and ethane into and out of an AFI-type zeolite crystal has been studied. In particular, “extended dynamically corrected transition state theory”, that has been proven to describe the transport of tracers in periodic crystals correctly, has been applied to surface problems. The results...

A three-component model of the control error in manual tracking of continuous random signals

Hans Gerisch, Gerhard Staude, Werner Wolf & Gerhard Bauch
The performance of human operators acting within closed-loop control systems is investigated in a classic tracking task. The dependence of the control error (tracking error) on the parameters display gain, k(display), and input signal frequency bandwidth, f(g), which alter task difficulty and presumably the control delay, is studied with the aim of functionally specifying it via a model.

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...

Biomechanical, morphological, and histological analysis of early failures in hip resurfacing arthroplasty

Michael Morlock, Nicholas Bishop, Wolfgang Rüther, Günter Delling & Michael Hahn
The present revival of hip resurfacing arthroplasty may be related to an increase in early failures owing to the challenging technique of the procedure. Fifty-five retrieved implants were analysed with respect to wear, cement mantle and cement penetration, fracture and head morphology, as well as standard histology. Femoral neck fractures occurred in median after 102 days. The time to failure was shorter for older women. Major deviations from the suggested cement mantle thickness and cement...

Biomechanical evaluation of 3 stabilization methods on acromioclavicular joint dislocations

Jakob V. Nüchtern, Kay Sellenschloh, Nick Bishop, Sabrina Jauch, Daniel Briem, Michael Hoffmann, Wolfgang Lehmann, Klaus Pueschel, Michael Morlock, Johannes M. Rueger & Lars G. Großterlinden
Traumatic acromioclavicular (AC) joint dislocations can be addressed with several surgical stabilization techniques. The aim of this in vitro study was to evaluate biomechanical features of the native joint compared with 3 different stabilization methods: locking hook plate (HP), TightRope (TR), and bone anchor system (AS).

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...

Modelling of ballistic impact over a ceramic-metal protection system

Leandro Neckel, Dachamir Hotza, Daniel Stainer, Rolf Janßen & Hazim Ali Al-Qureshi
The behavior of ceramic-metal protection against a projectile impact is modeled. The model takes into account the mass and velocity for each stage of the phenomenon. A former model was modified considering more realistic parameters such as geometries and deformation profile. To analyze the model, simulations on different parameters have been run. The impact results of different ballistic projectiles were simulated, and the movement was plotted. In addition, a deterministic simulation on the mechanical properties...

Development of cube texture in coarse grained copper

M. Sindel, G. D. Köhlhoff, K. Lücke & B. J. Duggan
Cube oriented deformed material has been detected in the rolling texture measured on edge sectionsof heavily rolled coarse grained copper. The level of intensity is low, and seems to be independent ofrolling reduction over the range 93–98%. Recrystallization textures show an increasing strength ofCube with rolling reduction. The evidence is consistent with the idea that Cube nuclei are created bya mechanism similar to that proposed by Dillamore and Katoh, and the strength of the recrystallizedCube...

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...

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!

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.

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...

To live in the city centre : housing and tenants in central neighbourhoods of Latin American cities

Hans Harms
After reviewing structural changes in metropolitan areas of Latin America and the implications for housing, this paper describes five central neighbourhoods with a predominance of rental housing: three in Lima and one each in Havana and Rio de Janeiro. This includes the types of buildings, how, when and why they were built, who occupies them and who owns them. It also describes what influence government policy has had on them and what measures (if any)...

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...

Strain-gauge-based measurements of ice loads on ships

Till Zorn
Design loads are a central element of ship construction, because they influence plate and frame thickness. For the construction of ships that are destined to navigate in cold areas, it is extremely important to take into account the loads of ice impacts and their location on the hull. But ice is a particularly inconsistent material. To measure ice-induced loads, a lot of measurement has been undertaken, many of them used strain gauges. However, long-term strain...

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.

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...

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.

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...

Three-dimensional Aerographite-GaN hybrid networks: single step fabrication of porous and mechanically flexible materials for multifunctional applications

Arnim Schuchardt, Tudor Braniste, Yogendra Kumar Mishra, Mao Deng, Matthias Mecklenburg, Marion A. Stevens-Kalceff, Simion Raevschi, Karl Schulte, Lorenz Kienle, Rainer Adelung & Ion Tiginyanu
Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes. In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite material as...

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