661 Works

In vivo testing of a bioabsorbable magnesium alloy serving as total ossicular replacement prostheses

Rebecca Lensing, Peter Behrens, Peter Paul Müller, Thomas Lenarz & Martin Stieve
Magnesium alloys have been investigated in different fields of medicine and represent a promising biomaterial for implants due to characteristics like bioabsorbability and osteoinduction. The objective of this study was to evaluate the usability of magnesium as implant material in middle ear surgery. Magnesium implants were placed into the right middle ear of eighteen New Zealand White rabbits. Nine animals were euthanized after four weeks and nine animals after three month. The petrous bones were...

Investment under company-level pacts before and during the Great Recession

Lutz Bellmann, Hans-Dieter Gerner & Olaf Hübler
Company-level pacts between the management and the works council are often preferred in comparison to agreements between employers’ association and unions because the former negotiating partners are better informed about the economic situation of a company and have fewer goal conflicts than the latter. Moreover, these company-level pacts might reduce the ‘hold-up’ problems which arise once specialized investment is made. Therefore, this article investigates whether such agreements affect firm-level investment. Based on the IAB Establishment...

Non-negative global weak solutions for a degenerate parabolic system modelling thin films driven by capillarity

Bogdan-Vasile Matioc
We prove the global existence of non-negative weak solutions for a strongly coupled, fourth-order degenerate parabolic system governing the motion of two thin fluid layers in a porous medium when capillarity is the sole driving mechanism. © 2012 Royal Society of Edinburgh.

Full-scale experiences with mechanical-biological pretreatment of municipal solid waste and landfilling

Dierk Von Felde & Heiko Doedens
In Lower Saxony three full-scale plants for the mechanical-biological pretreatment (MBP) of residual municipal solid waste (RMSW) prior to landfilling are now in operation. The three plants support a wide range of mechanical and encapsulated biological process techniques. In addition to biological degradation, pretreatment allows mechanical separation of iron fractions and refuse derived fuel (RDF). This causes a strong reduction in the need for landfill sites and hence lowers landfill emissions. To describe the efficiency...

Efficient magneto-optical trapping of a metastable helium gas

F. Pereira Dos Santos, F. Perales, J. Léonard, A. Sinatra, J. Wang, F.S. Pavone, E. Rasel, C.S. Unnikrishnan & M. Leduc
This article presents a new experiment aiming at BEC of metastable helium atoms. It describes the design of a high flux discharge source of atoms and a robust laser system using a DBR diode coupled with a high power Yb doped fiber amplifier for manipulating the beam of metastable atoms. The atoms are trapped in a small quartz cell in an extreme high vacuum. The trapping design uses an additional laser (repumper) and allows the...

Estimating Beta

Fabian Hollstein & Marcel Prokopczuk
We conduct a comprehensive comparison of market beta estimation techniques. We study the performance of several historical, time-series model, and option-implied estimators for estimating realized market beta. Thereby, we find the hybrid methodology of Buss and Vilkov to consistently outperform all other approaches. In addition, all other approaches, including fully implied and dynamic conditional beta, based on generalized autoregressive conditional heteroskedasticity (GARCH) models, are dominated by a simple beta estimate based on historical (co-)variances and...

Fabrication of polymer based integrated photonic devices by maskless lithography

Maik Rahlves
We present our recent results on the fabrication of photonic devices such as single-mode and few-mode waveguides, Ycouplers as well as integrated interferometric sensor devices. The devices were created by means of a fabrication method based on maskless lithography, which allows for fabricating embedded integrated polymer elements on a scale of several square centimeters with a resolution down to one micron. We demonstrate the versatility of our approach by presenting first results on photonic structures...

Process regulation in the problem-solving processes of fifth graders [Usmerjanje procesov resevanja problemov petosolcev]

Benjamin Rott
It is well known that the regulation of processes is an important factor in problem solving from Grade 7 to university level (cf. Mevarech & Kramarski, 1997; Schoenfeld, 1985). We do not, however, know much about the problem-solving competencies of younger children (cf. Heinze, 2007, p. 15). Do the results of studies also hold true for students below Grade 7? The study presented here strongly suggests that metacognition and process regulation is important in Grade...

Hydraulic performance of elastomeric bonded permeable revetments and subsoil response to wave loads

Hocine Oumeraci, T. Staal, S. Pförtner, M. Kudella, Stefan Schimmels & H.J. Verhagen
Elastomeric bonded permeable revetments, also called PBA (Polyurethane bonded aggregate) revetments, are highly porous structures made of mineral aggregates (e.g. crushed stones) which are durably and elastically bonded by polyurethane (PU). Despite their numerous advantages as compared to conventional revetments and the large experience available from more than 25 pilot projects, physically-based design formulae to predict their hydraulic performance, wave loading and response are still lacking. Therefore, the present study aims at improving the understanding...

Impact of different polyimide-based substrates on the soft magnetic properties of NiFe thin films

Johannes Rittinger, Piriya Taptimthong, Lisa Jogschies, Marc Christopher Wurz & Lutz Rissing
We investigated the impact of polymer substrates on the magnetic properties of soft magnetic thin films. Experiments were carried out to evaluate the performance of AMR (anisotropic magnetoresistive) sensors deposited on polymeric substrates and to give indications for the design of future sensors on flexible substrates. Sputtered permalloy (NiFe 81/19) was used as a soft magnetic thin film layer. As substrate materials, liquid polyimide precursors and DuPont Kapton® HN foil were examined. Surface roughness was...

Manufacturing of polymer optical waveguides using self-assembly effect on pre-conditioned 3D-thermoformed flexible substrates

Gerd-Albert Hoffmann, Tim Wolfer, Jochen Zeitler, Jörg Franke, Oliver Suttmann & Ludger Overmeyer
Optical data communication is increasingly interesting for many applications in industrial processes. Therefore mass production is required to meet the requested price and lot sizes. Polymer optical waveguides show great promises to comply with price requirements while providing sufficient optical quality for short range data transmission. A high efficient fabrication technology using polymer materials could be able to create the essential backbone for 3D-optical data transmission in the future. The approach for high efficient fabrication...

Optodic bonding of optoelectronic components in transparent polymer substrates-based flexible circuit systems

Yixiao Wang, Meriem Akin, Lisa Jogschies, Ludger Overmeyer & Lutz Rissing
In the field of modern information technology, optoelectronics are being widely used, and play an increasingly important role. Meanwhile, the demand for more flexible circuit carriers is rapidly growing, since flexibility facilitates the realization of diverse functions and applications. As a potential candidate, transparent polymer substrates with a thickness of about a hundred micrometers by virtue of their low cost and sufficient flexibility are getting more attention. Thus, accomplishing an integration of optoelectronic components into...

Printing polymer optical waveguides on conditioned transparent flexible foils by using the aerosol jet technology

Thomas Reitberger, Gerd-Albert Hoffmann, Tim Wolfer, Ludger Overmeyer & Jörg Franke
The optical data transfer is considered as the future of signal transfer due to its various advantages compared to conventional copper-based technologies. The Aerosol Jet Printing (AJP) technology offers the opportunity to print materials with high viscosities, such as liquid transparent polymer adhesives (epoxy resins), on almost any possible substrate material and even in third dimension. This paper introduces a new flexible and comparatively cost-effective way of generating polymer optical waveguides through AJP. Furthermore, the...

Flexible registration method for light-stripe sensors considering sensor misalignments

W. Gorschenew, M. Kaestner & Eduard Reithmeier
In many application areas such as object reconstruction or quality assurance, it is required to completely or partly measure the shape of an object or at least the cross section of the required object region. For complex geometries, therefore, multiple views are needed to bypass undercuts respectively occlusions. Hence, a multi-sensor measuring system for complex geometries has to consist of multiple light-stripe sensors that are surrounding the measuring object in order to complete the measurements...

Parametric amplification of matter waves in dipolar spinor Bose-Einstein condensates

Frank Deuretzbacher, Garu Gebreyesus, Oliver Topic, Manuel Scherer, Bernd Lücke, Wolfgang Ertmer, Jan J. Arlt, Carsten Klempt & Luis Santos
Spin-changing collisions may lead under proper conditions to the parametric amplification of matter waves in spinor Bose-Einstein condensates. Magnetic dipole-dipole interactions, although typically very weak in alkalimetal atoms, are shown to play a very relevant role in the amplification process. We show that these interactions may lead to a strong dependence of the amplification dynamics on the angle between the trap axis and the magnetic-field orientation. We analyze as well the important role played by...

Quantum magnetism without lattices in strongly interacting one-dimensional spinor gases

Frank Deuretzbacher, D. Becker, J. Bjerlin, S.M. Reimann & Luis Santos
We show that strongly interacting multicomponent gases in one dimension realize an effective spin chain, offering an alternative simple scenario for the study of one-dimensional (1D) quantum magnetism in cold gases in the absence of an optical lattice. The spin-chain model allows for an intuitive understanding of recent experiments and for a simple calculation of relevant observables. We analyze the adiabatic preparation of antiferromagnetic and ferromagnetic ground states, and show that many-body spin states may...

Momentum distributions and numerical methods for strongly interacting one-dimensional spinor gases

Frank Deuretzbacher, D. Becker & Luis Santos
One-dimensional spinor gases with strong δ interaction fermionize and form a spin chain. The spatial degrees of freedom of this atom chain can be described by a mapping to spinless noninteracting fermions and the spin degrees of freedom are described by a spin-chain model with nearest-neighbor interactions. Here, we compute momentum and occupation-number distributions of up to 16 strongly interacting spinor fermions and bosons as a function of their spin imbalance, the strength of an...

Engineering interactions and anyon statistics by multicolor lattice-depth modulations

Lorenzo Cardarelli, Sebastian Greschner & Luis Santos
We show that a multicolor modulation of the depth of an optical lattice allows for a flexible independent control of correlated hopping, occupation-dependent gauge fields, effective on-site interactions without Feshbach resonances, and nearest-neighbor interactions. As a result, the lattice-depth modulation opens the possibility of engineering with minimal experimental complexity a broad class of lattice models in current experiments with ultracold atoms, including Hubbard models with correlated hopping, peculiar extended models, and two-component anyon-Hubbard models. ©...

Polar molecules in frustrated triangular ladders

Tapan Mishra, Sebastian Greschner & Luis Santos
Polar molecules in geometrically frustrated lattices may result in a very rich landscape of quantum phases, due to the nontrivial interplay between frustration, and two- and possibly three-body intersite interactions. In this paper we illustrate this intriguing physics for the case of hard-core polar molecules in frustrated triangular ladders. Whereas commensurate lattice fillings result in gapped phases with bond order and/or density-wave order, at incommensurate fillings we find chiral, two-component, and pair superfluids. We show...

Exploring unconventional hubbard models with doubly modulated lattice gases

Sebastian Greschner, Luis Santos & D. Poletti
Recent experiments show that periodic modulations of cold atoms in optical lattices may be used to engineer and explore interesting models. We show that double modulation combining lattice shaking and modulated interactions allows for the engineering of a much broader class of lattice with correlated hopping, which we study for the particular case of one-dimensional systems. We show, in particular, that by using this double modulation it is possible to study Hubbard models with asymmetric...

First all-sky search for continuous gravitational waves from unknown sources in binary systems

J. Aasi, Bruce Allen, Stefan Ast, Peter Aufmuth, Karsten Danzmann, S. Kaufer, Harald Lück, Tobias Meier, R. Schnabel, H. Vahlbruch, Benno Willke, , & Virgo Collaboration
We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from...

Plasmons in Pb nanowire arrays on Si(557): Between one and two dimensions

Tammo Block, Christoph Tegenkamp, Jens Baringhaus, Herbert Pfnür & T. Inaoka
The plasmon dispersion in arrays of nanowires of Pb close to an average Pb coverage of one monolayer was determined on the Si(557) surface using electron energy loss spectroscopy with both high energy and momentum resolution. While we find purely one-dimensional (1D) plasmon losses at a Pb concentration of 1.31 monolayers (ML), measured with respect to the Si(111) surface concentration, the 1.2 and 1.4 ML coverages exhibit wavelength-dependent transitions from 1D to anisotropic 2D properties....

Observing gravitational-wave transient GW150914 with minimal assumptions

B.P. Abbott, Bruce Allen, Peter Aufmuth, A. Bisht, Karsten Danzmann, T. Denker, M. Heurs, S. Kaufer, C. Krueger, J.D. Lough, Harald Lück, A. Sawadsky, D. Schütte, D. Steinmeyer, H. Vahlbruch, Benno Willke, M.H. Wimmer, H. Wittel, , & Virgo Collaboration
The gravitational-wave signal GW150914 was first identified on September 14, 2015, by searches for short-duration gravitational-wave transients. These searches identify time-correlated transients in multiple detectors with minimal assumptions about the signal morphology, allowing them to be sensitive to gravitational waves emitted by a wide range of sources including binary black hole mergers. Over the observational period from September 12 to October 20, 2015, these transient searches were sensitive to binary black hole mergers similar to...

Light driven reactions of single physisorbed azobenzenes

Maciej Bazarnik, Jörg Henzl, Ryszard Czajka & Karina Morgenstern
We present a successful attempt of decoupling a dye molecule from a metallic surface via physisorption for enabling direct photoisomerization. Effective switching between the isomers is possible by exposure to UV light via the rotation pathway. © 2011 The Royal Society of Chemistry.

On the mechanisms of ionic conductivity in BaLiF3: A molecular dynamics study

Dirk Zahn, Sven Herrmann & Paul Heitjans
The mechanisms of ionic conductivity in BaLiF3 are investigated using molecular simulations. Direct molecular dynamics simulations of (quasi) single crystalline super cell models hint at the preferred mobility mechanism which is based on fluoride interstitial (and to a smaller extent F- vacancy) migration. Analogous to previous modeling studies, the energy related to Frenkel defect formation in the ideal BaLiF3 crystal was found as 4-5 eV which is in serious controversy to the experimentally observed activation...

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