1,863 Works

Hybrid system calibration for multidimensional magnetic particle imaging

Anselm Von Gladiß, Matthias Gräser, Patryk Szwargulski, Tobias Knopp & Thorsten M. Buzug
Magnetic particle imaging visualizes the spatial distribution of superparamagnetic nanoparticles. Because of its key features of excellent sensitivity, high temporal and spatial resolution and biocompatibility of the tracer material it can be used in multiple medical imaging applications. The common reconstruction technique for Lissajous-type trajectories uses a system matrix that has to be previously acquired in a time-consuming calibration scan, leading to long downtimes of the scanning device. In this work, the system matrix is...

Molecular simulations of thermodynamic properties for the system α-cyclodextrin/alcohol in aqueous solution

Daniel Markthaler, Julia Gebhardt, Sven Jakobtorweihen & Niels Hansen
Free-energy calculations based on molecular simulations provide access to a wide range of thermodynamic properties such as the solubility and partitioning of a molecule in and between various phases. It is demonstrated how molecular dynamics free-energy simulations may be used to obtain the solubilities of primary alcohols and n-alkanes in water and binding affinities of primary alcohols to α-cyclodextrin. The equivalence of two distinct routes to calculate binding free energies is shown leading to the...

2-phase dynamic simulation of deep sand compaction to reduce liquefaction

Sparsha Sinduri Nagula & Jürgen Grabe
A numerical model of a shallow foundation resting on sand is set up to simulate the liquefaction of partially saturated sand subjected to a confined transient loading. The foundation is observed to undergo large settlements due to liquefaction of sand. In order to analyze the feasibility of deep vibration compaction in liquefaction mitigation, saturated sand was subjected to compaction and later the same compacted sand with foundation was subjected to a confined transient loading. It...

Surface modification of alumina nanoparticles with silane coupling agents

Luís Antônio Sanchez De Almeida Prado, Montira Sriyai, Marcos Ghislandi, Ana Barros-Timmons & Karl Schulte
In the present paper we describe the surface modification of alumina nanoparticles using epoxy-containing alkoxysilanes (silane coupling agents, SCA). The materials were characterized using infrared spectroscopy and solid-state nuclear magnetic resonance. Whereas, neat alumina nanoparticles could be expectedly modified with the afore mentioned SCA, as evidenced by 13C CPMAS NMR, the presence of arylsulphonates at the surface of alumina caused the ringopening polymerization of the epoxide. This polymerization reaction facilitated the surface modification of alumina...

Occurrence of micropollutants in the wastewater streams of cruise ships

Lena Westhof, Stephan Köster & Margrit Reich
Nowadays the protection of the marine environment raises increasing academic and public attention. The issue of organic micropollutants is of equally high importance for the marine ecosystems. Maritime vessels are considered to significant sources of micropollutants especially if the ship carries many passengers, which is often true for cruise ships which frequent attractive and sensitive sea areas. The emission pathways for micropollutants include wastewater discharges and sewage sludge disposal. The findings of the German research...

Inteins, valuable genetic elements in molecular biology and biotechnology

Skander Elleuche & Stefanie Pöggeler
Inteins are internal protein elements that self-excise from their host protein and catalyze ligation of the flanking sequences (exteins) with a peptide bond. They are found in organisms in all three domains of life, and in viral proteins. Intein excision is a posttranslational process that does not require auxiliary enzymes or cofactors. This self-excision process is called protein splicing, by analogy to the splicing of RNA introns from pre-mRNA. Protein splicing involves only four intramolecular...

Influence of laser cutting parameters on CFRP part quality

André Goeke & Claus Emmelmann
Material processing of Carbon Fibre Reinforced Plastics (CFRP) parts by means of shape-cutting or jet-cutting technologies is state of the art today. These processes still perform in some applications with lack of part quality such as delamination and low productivity. Therefore, laser cutting processes have a great potential in material processing of CFRP. Laser process parameters have to be adjusted carefully in order to reduce the heat affected zone at cutting edge and influence on...

Multifunctional fibre metal laminates with improved load bearing capability

Björn Bosbach
Zur Steigerung der mechanischen Eigenschaften sowie der Lebensdauer einer Bolzenverbindung im Vergleich zu herkömmlichen glasfaserverstärkten Kunststoffen (GFK) werden im Rahmen dieser Arbeit multifunktionelle Fasermetalllaminate (FML) mit permeablen und oberflächenbehandelten Metallschichten untersucht. Darüber hinaus wird ein neuer Ansatz zur Schadensdetektion in FML entwickelt. Die Laminate werden im Harzinjektionsverfahren hergestellt.

Reaction engineering in biocatalytic reactive distillation

Steffen Kühn
Reactive distillation is a well-established unit operation in chemical industry incorporating reaction and separation in one device. In this study, practicability of Candida antarctica lipase B is evaluated for biocatalytic kinetic resolution of either secondary alcohols or chiral esters to broaden the scope of feasible reactions in reactive distillation. In fact, successful operation of an integrated batch biocatalytic reactive distillation column is approved by in situ isolation of the chiral target compound (S)-2-pentanol with high...

Analyse von Arbeitsabläufen mit 3D-Kameras

Martin Benter
Productivity analyses are important tools to control labour costs in industrial companies. This work presents a consistent method for determining times and analysing productivity. To achieve this goal, the method accesses motion tracking data acquired by 3D cameras. The method derives worker states and determines relevant state data. By systematically analysing this data, it is capable to provide meaningful results.

High-precision calibration of a weld-on-the-fly-system

Claus Emmelmann, Kerstin Schenk, Jörg Wollnack & Marc Kirchhoff
Since 20 years the importance of laser based material processing increases constantly due to its significant higher process speed in comparison to conventional processing technologies. A scanner system for laser-remote-welding mounted on a robot hand to achieve more freedom in positioning the laser spot has been investigated. Additionally the scanner head contains two fixed cameras for measurements and process monitoring. To perform required measurements with maximum accuracy the allover system has to be calibrated precise....

Draft genome sequence of the piezotolerant and crude oil-degrading bacterium rhodococcus qingshengii strain TUHH-12

Sara A. Lincoln, Trinity L. Hamilton, Ana Gabriela Valladares Juárez, Martina Schedler, Jennifer L. Macalady, Rudolf Müller & Katherine H. Freeman
We report here the draft genome sequence of Rhodococcus qingshengii strain TUHH-12. The ability of this piezotolerant bacterium to grow on crude oil and tetracosane as sole carbon sources at 150 × 10(5) Pa makes it useful in studies of hydrocarbon degradation under simulated deep-sea conditions.

Synthesis of heat exchanger networks taking into account cost and dynamic considerations

Matthias Rathjens, Timo Bohnenstädt, Georg Fieg & Ole Engel
In this work an approach is presented for the synthesis of near cost optimal heat exchanger networks with a high controllability. The presented methodology is based on a sequential approach utilizing different algorithms and mathematical models. The procedure is carried out in three steps. A genetic algorithm is used to produce a high diversity of promising structures that suffice the needs for cost reduction and controllability characteristics. For selected structures controllability evaluations are carried out,...

IR-thermography for quality prediction in selective laser deburring

Mauritz Möller, Christian Conrad, Walter Haimerl & Claus Emmelmann
Selective Laser Deburring (SLD) is an innovative edge-refinement process being developed at the Laser Zentrum Nord (LZN) in Hamburg. It offers a wear-free processing of defined radii and bevels at the edges as well as the possibility to deburr several materials with the same laser source. Sheet metal parts of various applications need to be post-processed to remove sharp edges and burrs remaining from the initial production process. Thus, SLD will provide an extended degree...

Influence of an angular hatching exposure strategy on the surface roughness during picosecond laser ablation of hard materials

Christian Daniel, Jannik Manderla, Sina Hallmann & Claus Emmelmann
Innovative chip breakers for cutting tools made of very hard materials require laser ablation and demand a high quality regarding the manufactured surface. When processing materials such as polycrystalline cubic boron-nitride or tungsten carbide the surface roughness by laser ablation reaches Sa= 1,0-2,9 μm compared to Sa= 0,42 μm achieved by grinding. Therefore in the presented research the influence of the hatching exposure strategy on surface roughness during picosecond laser ablation of tungsten carbide is...

Prozessentwicklung einer linearen Reaktionskaskade zur biotechnologischen Herstellung von epsilon-Caprolacton

Christian Scherkus
In der vorliegenden Arbeit wurde die enzymatische Synthese von ε-Caprolacton mittels einer Alkohol-Dehydrogenase und einer sauerstoffabhängigen Baeyer-Villiger-Monooxygenase ausgehend von Cyclohexanol untersucht. Zusätzlich ist eine Lipase zur Hydrolyse sowie zur Polymerisation von ε-Caprolacton eingesetzt worden. Im Rahmen der Prozessentwicklung wurden die einzelnen Reaktionsschritte und Enzyme kinetisch charakterisiert, um ein Prozessdesign mit optimalen Reaktionsbedingungen festzulegen. Hierfür wurden insbesondere Ergebnisse im Satzbetrieb und im Zulaufverfahren gegenübergestellt. Auf der Basis eines kinetischen Modells sind zusätzlich Simulationen durchgeführt und mit...

University-industry knowledge transfer: an empirical analysis of channels, motives and distances

Jan Willem Reerink
The present thesis investigates several technology transfer channels in the context of university-industry knowledge transfer. Both traditional channels such as collaborative research or academic patenting and innovative alternatives such as broadcast search are considered. Theoretical advances and implications for policy can be derived by implementing novel methods from the field of Data Science.

Towards a standardization of biomethane potential tests

Christof Holliger, Madalena Alves, Diana Andrade, Irini Angelidaki, Sergi Astals, Urs Baier, Claire Bougrier, Pierre Buffière, Marta Carballa, Vinnie De Wilde, Florian Ebertseder, Belén Fernández, Elena Ficara, Ioannis A. Fotidis, Jean-Claude Frigon, Hélène Fruteau De Laclos, Dara S. M. Ghasimi, Gabrielle Hack, Mathias Hartel, Jörn Heerenklage, Ilona Sárvári Horváth, Pavel Jeníček, Konrad Koch, Judith Krautwald, Javier Lizasoain … & Isabella Wierinck
Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the...

Sediments and the "system" : from site-specific to regional-scale research : a story of joy in researching dirt

Wim Salomons & Ulrich Förstner
For both of us, it has been a struggle on how to write a kind of official “Farewell address” to our colleagues. After all, we do it only once in our lifetime. The result is twofold; we will have one editorial with a broad and short (admittedly very biased) history and outlook of our experience, and a second, more scientific editorial, which covers the first 10 years of our Journal of Soils and Sediments.

Process types of customisation and personalisation in design for additive manufacturing applied to vascular models

Johanna Spallek & Dieter Krause
Manufacturing companies face high demand for products that fulfil individual customer desires. Recent improvements in additive manufacturing (AM) enable the fabrication of customer-specific components of a product. This paper presents a categorisation of design processes for customised and personalised products through the use of AM in three process types: special design, specific adaptation, and standardised individualisation. The characteristics of design processes are examined in medical development of vascular models integrated into a modular neurovascular training...

New biocatalytic approaches for lactonization and lactamization

Lei Huang
Lactones and lactams are cyclic esters and amides, respectively. They are the monomers of polyesters and polyamides, such as polycaprolactone and polycaprolactam, which are the commonly used polymer materials in our daily life and in industry. Apart from that, lactones and lactams are also widely used as raw materials in the pharmaceutical industry and as flavors and fragrances or laundry detergents for bleaching. Up to date, the industrial synthesis of most of the lactones and...

Comparison of natural gas combined cycle power plants with post combustion and oxyfuel technology at different CO2 capture rates

Jan Mletzko, Sören Ehlers & Alfons Kather
Within this work a natural gas-fired combined cycle plant is investigated with post-combustion CO2 capture (PCC) and as a semi-closed oxyfuel combustion combined cycle (SCOC-CC) using process simulation tools. In most studies the CO2 capture rate of PCC units is set to 90% while the SCOC-CC is often considered for zero emission plants. To allow a comparison between the processes the capture rate needs to be taken into account. If a certain CO2 emission value...

Metabolic engineering von Clostridium pasteurianum zur Optimierung der Biobutanolproduktion

Rebekka Schmitz
Clostridium pasteurianum is of great industrial interest regarding its substrate utilization and product spectrum. In this study, methods for metabolic engineering of C. pasteurianum, especially transformation and gene deletion, were analyzed and optimized. Optimized strains were generated by overexpression of pyruvate carboxylase and glycerol dehydratase deletion. Butanol production was selectively increased. Furthermore, our results indicate a novel mechanism of redox regulation in C. pasteurianum.

Factors influencing taper failure of modular revision hip stems

Annika Krull, Michael Morlock & Nicholas Bishop
Stem modularity of revision hip implant systems offers the advantage of the restoration of individual patient geometry but introduces additional interfaces, which are subjected to repetitive bending loading and have a propensity for fretting corrosion. The male stem taper is the weakest part of the modular junction due to its reduced cross section compared to the outside diameter of the stem. Taper fractures can be the consequence of overloading in combination with corrosion. The purpose...

Head taper corrosion causing head bottoming out and consecutive gross stem taper failure in total hip arthroplasty

Michael Morlock, Emilie C. Dickinson, Klaus-Peter Günther, Dennis Bünte & Valerie Polster
Taper corrosion in total hip arthroplasty for bearings with metal heads against polyethylene has developed from an anecdotal observation to a clinical problem. Increased taper wear and even gross taper failure have been reported for one particular design. It is hypothesized that corrosion of the female head taper results in taper widening, allowing the cobalt-chromium head to turn on the stem and wear down the softer titanium alloy by abrasive wear, ultimately causing failure. The...

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