464 Works

Bio-inspired solution for optimal adhesive performance

Antonio Papangelo
In recent years there has been a growing interest into high performance bioinspired adhesives. This communication focuses on the adhesive behavior of a rigid cylinder that indents an elastic layer coated on a rigid substrate. With the assumption of short range adhesive interactions (JKR type) the adhesive solution is obtained very easily starting from the adhesiveless one. We show that ultrastrong adhesion (up to theoretical material strength) can be reached in line contact by reducing...

Influence of application parameters of ultrasonic-assisted bone instruments on the tear force of a substitute material for spinal dura mater

Marie C. Foelkel, Vitali Herzog, Markus Meier & Michael Morlock
An ultrasonic-assisted bone instrument can be used for the dissection of bone in spinal surgery. During surgery, the tip of such a bone instrument can touch spinal dura mater. Especially during critical re-operations, high forces can be unintentionally applied on spinal dura mater. To prevent dural tears, the influence of application parameters on the tear force shall be analyzed. Collagen foil is used as a substitute material for spinal dura mater because of its similar...

Thy-1 deficiency augments bone loss in obesity by affecting bone formation and resorption

Ann-Kristin Picke, Graeme Michael Campbell, Felix N. Schmidt, Björn Busse, Martina Rauner, Jan C. Simon, Ulf Anderegg, Lorenz C. Hofbauer & Anja Saalbach
Healthy bone remodeling results from a balanced bone formation and bone resorption realized by bone-forming osteoblasts and bone-resorbing osteoclasts, respectively. Recently, Thy-1 (CD90) was identified as positive regulator of osteoblast differentiation and activation, thus, promoting bone formation while concurrently inhibiting adipogenesis and obesity in mice. Additionally, Thy-1 did not affect bone resorption. An obesity-related co-morbidity that is increasing in prevalence is a disturbed bone formation resulting in an increased fracture risk. The underlying mechanisms of...

Backscattering design for a focusing grating coupler with fully etched slots for transverse magnetic modes

Jahn Hoffmann, Kai Marvin Schulz, Giampaolo Pitruzzello, Lena Simone Fohrmann, Alexander Yu Petrov & Manfred Eich
Grating couplers are a fundamental building block of integrated optics as they allow light to be coupled from free-space to on-chip components and vice versa. A challenging task in designing any grating coupler is represented by the need for reducing back reflections at the waveguide-grating interface, which introduce additional losses and undesirable interference fringes. Here, we present a design approach for focusing TM grating couplers that minimizes these unwanted reflections by introducing a modified slot...

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Brett D. Crist, Ferris M. Pfeiffer, Michael S. Khazzam, Rebecca A. Kueny, Gregory J. Della Rocca & William L. Carson
Background: Pelvic ringecomminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. Objective: Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of boneeimplant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods: 3D relative motion across sacralerami fractures and screws relative to bone was measured with...

Optimization of solvent-free enzymatic esterification in eutectic substrate reaction mixture

Magdalena Pätzold, Anna Weimer, Andreas Liese & Dirk Holtmann
The Candida rugosa lipase catalyzed esterification of (-)-menthol and lauric acid (LA) was studied in a eutectic mixture formed by both substrates((-)-menthol:LA 3:1, mol/mol). No additional reaction solvent was necessary, since the (-)-menthol:LA deep eutectic solvent (DES) acts as combined reaction medium and substrate pool. Therefore, the esterification is conducted under solvent-free conditions. The thermodynamic water activity (aw) was identified as a key parameter affecting the esterification performance in the (-)-menthol:LA DES. A response surface...

Drift stability of HyStOH semi-submersible supported by airfoil shaped structures

Andreas Manjock & Stefan Netzband
This study presents the results of the German research project HyStOH funded by German Federal Ministry of Economic Affairs and Energy (BMWi). The project consortium of German universities, wind turbine designers, wind farm developers and certification bodies design a novel semi-submersible steel structure with a single point mooring and self-aligning capabilities. The tower, which carries a 6 MW two-bladed downwind turbine, has an airfoil shaped cover, which supports the self-alignment of the full structure towards...

Fracture toughness of porous materials – Experimental methods and data

Hans Jelitto & Gerold A. Schneider
We provide numerical experimental data and detailed information about the sample preparation and the experimental methods, used by different research groups for measuring the fracture toughness of porous materials. These data are supplemental information to the publication “A Geometric Model for the Fracture Toughness of Porous Materials,” [1], which is based on experimental data of ceramic and polymer materials. For the sake of completeness, we provide here also data from fracturing metallic foams. The corresponding...

Influence of flexural rigidity on micromotion at the head-stem taper interface of modular hip prostheses

Henning Haschke, Tobias Konow, Gerd Huber & Michael Morlock
Fretting corrosion as one reason for failure of modular hip prostheses has been associated with micromotion at the head taper junction. Historically the taper diameter was reduced to improve the range of motion of the hip joint. In combination with other developments, this was accompanied by increased observations of taper fretting, possibly due to the reduced flexural rigidity of smaller tapers. The aim of the study was to investigate how the flexural rigidity of tapers...

Protein-protein-interaction network organization of the hypusine modification system

Henning Sievert, Simone Venz, Oscar Platas Barradas, Vishnu Mukund Dhople, Martin Schaletzky, Claus-Henning Nagel, Melanie Braig, Michael Preukschas, Nora Pällmann, Carsten Bokemeyer, Tim H. Brümmendorf, Ralf Pörtner, Reinhard Walther, Kent E. Duncan, Joachim Hauber & Stefan Balabanov
Hypusine modification of eukaryotic initiation factor 5A (eIF-5A) represents a unique and highly specific post-translational modification with regulatory functions in cancer, diabetes, and infectious diseases. However, the specific cellular pathways that are influenced by the hypusine modification remain largely unknown. To globally characterize eIF-5A and hypusine-dependent pathways, we used an approach that combines large-scale bioreactor cell culture with tandem affinity purification and mass spectrometry: "bioreactor-TAP-MS/MS." By applying this approach systematically to all four components of...

Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets

Mehmet Ali Kücüker, Nils Wieczorek, Kerstin Kuchta & Nadim K. Copty
In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the...

Measurement of local crystal lattice strain variations in dealloyed nanoporous gold

Christoph Mahr, Knut Müller-Caspary, Matthias Graf, Anastasia Lackmann, Tim Grieb, Marco Schowalter, Florian Fritz Krause, Thorsten Mehrtens, Arne Wittstock, Jörg Weissmüller & Andreas Rosenauer
Reversible macroscopic length changes in nanoporous structures can be achieved by applying electric potentials or by exposing them to different gases or liquids. Thus, these materials are interesting candidates for applications as sensors or actuators. Macroscopic length changes originate from microscopic changes of crystal lattice parameters. In this report, we show spatially resolved measurements of crystal lattice strain in dealloyed nanoporous gold. The results confirm theory by indicating a compression of the lattice along the...

The temperatures distributions of a single-disc clutches using heat partitioning and total heat generated approaches

Oday Ibraheem Abdullah, Josef Schlattmann, Mahir H. Majeed & Laith Abed Sabri
An accurate estimation of temperature distribution is considered necessary to avoid the premature failure of friction clutches. In this work, different approaches were used to compute the surface temperatures of the friction clutch disc. The results presented the maximum surface temperature when the contact occurs between the rubbing surfaces during a single engagement and repeated engagements. Two approaches were used to simulate the thermal models of the automotive clutches to obtain the temperature field are...

Zero stress aging of glass and carbon fibers in water and oil : strength reduction explained by dissolution kinetics

Andreas T. Echtermeyer, Andrey E. Krauklis, Abedin I. Gagani & Erik Sæter
Understanding the strength degradation of glass and carbon fibers due to exposure to liquids over time is important for structural applications. A model has been developed for glass fibers that links the strength reduction in water to the increase of the Griffith flaw size of the fibers. The speed of the increase is determined by regular chemical dissolution kinetics of glass in water. Crack growth and strength reduction can be predicted for several water temperatures...

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  • 2019
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