1,274 Works

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...

Directly comparing GW150914 with numerical solutions of Einstein's equations for binary black hole coalescence

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
We compare GW150914 directly to simulations of coalescing binary black holes in full general relativity, including several performed specifically to reproduce this event. Our calculations go beyond existing semianalytic models, because for all simulations—including sources with two independent, precessing spins—we perform comparisons which account for all the spin-weighted quadrupolar modes, and separately which account for all the quadrupolar and octopolar modes. Consistent with the posterior distributions reported by Abbott et al. [Phys. Rev. Lett. 116,...

A calibration strategy for LA-ICP-MS using isotope dilution for solid reference materials

J. P. Thieleke & C. Vogt
An isotope dilution method for the quantitative analysis of trace elements in biological samples and for the characterization of reference materials for the analysis of biological samples by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-ID-MS) has been tested. Polymeric thin layers with 5–10 μm thickness containing the ID-spike and the correction standard were produced by knife application onto polyester substrates. For the ID experiments 204Pb enriched lead was used, and bismuth served as the internal standard....

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...

Understanding charge transfer processes on metal oxides - A laser-flash-photolysis study

Fabian Sieland, Jenny Schneider, Thorsten Lippmann & Detlef W. Bahnemann
In the focus of this study, mixtures of commercially available TiO2 powders were created and their photocatalytic activity concerning the acetaldehyde degradation in the gas phase was tested. Further, the lifetime of the photogenerated charge carriers was analyzed by Laser-Flash-Photolysis-Spectroscopy. The acetaldehyde degradation experiments of the mixed powders lead to positive and negative deviations from the expected weighted mean. Nevertheless, their photocatalytic activity could be correlated with the lifetime of the charge carriers. A longer...

What makes student entrepreneurs? On the relevance (and irrelevance) of the university and the regional context for student start-ups

Heiko Bergmann, Christian Hundt & Rolf Sternberg
Student start-ups are a significant part of overall university entrepreneurship. Yet, we know little about the determinants of this type of start-ups and, specifically, the relevance of context effects. Drawing on organizational and regional context literature, we develop and test a model that aims to explain student entrepreneurship in a contextual perspective. Based on unique micro-data and using multi-level techniques, we analyse nascent and new entrepreneurial activities of business and economics students at 41 European...

Direct hot embossing of microelements by means of photostructurable polyimide

Meriem Akin, Maher Rezem, Maik Rahlves, Kevin Cromwell, Bernhard Roth, Eduard Reithmeier, Marc Christopher Wurz, Lutz Rissing & Hans Jürgen Maier
While automatic hot embossing systems are available for large- and small-scale productions of polymeric devices, one of the process challenges remains to be the manufacturing of precise, durable, and yet inexpensive hot embossing stamps. The use of metallic stamps manufactured by electroplating a photoresist pattern or by precision milling and their replication into silicone molds with UV-lithography, electroplating, and molding techniques is state of the art. Yet, there have been few, if any, thriving attempts...

Direct in situ GDD measurement in optical coating process

S. Schlichting, Thomas Willemsen, H. Ehlers, Uwe Morgner & Detlev Ristau
In the presented work a fast frequency domain measurement system to determine group delay (GD) and group delay dispersion (GDD) of optical coatings is proposed. The measurements are performed in situ directly on moving substrates during the thin film coating process. The method is based on a Michelson interferometer, which is equipped with a high power broad band light source and a fast spectrometer. Especially for the production of chirped mirrors it is advantageous to...

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...

Diffusing magnetic Tb impurities and magnetotransport in strongly spin-polarized Bi films

Sergii Sologub, Daniel Lükermann, Herbert Pfnür & Christoph Tegenkamp
As a contribution to electronic transport within strongly spin-polarized surface states and its modification by adsorption of magnetic impurities we studied the adsorption of Tb (atomic magnetic moment 10 μB) on epitaxial Bi(111) films by means of surface sensitive (magneto)conductance and low-energy electron diffraction. Surface diffusion turned out to be non-negligible even at substrate temperatures of 10 K. The Tb adatoms finally nucleate at intrinsic defects of the Bi(111) surface, where the Tb impurities act...

Barrier-free subsurface incorporation of 3d metal atoms into Bi(111) films

C. Klein, N.J. Vollmers, U. Gerstmann, P. Zahl, Daniel Lükermann, G. Jnawali, Herbert Pfnür, Christoph Tegenkamp, P. Sutter, W.G. Schmidt & Michael Horn-Von Hoegen
By combining scanning tunneling microscopy with density functional theory it is shown that the Bi(111) surface provides a well-defined incorporation site in the first bilayer that traps highly coordinating atoms such as transition metals (TMs) or noble metals. All deposited atoms assume exactly the same specific sevenfold coordinated subsurface interstitial site while the surface topography remains nearly unchanged. Notably, 3d TMs show a barrier-free incorporation. The observed surface modification by barrier-free subsorption helps to suppress...

Coupled Pb chains on Si(557): Origin of one-dimensional conductance

Christoph Tegenkamp, T. Ohta, J.L. McChesney, H. Dil, E. Rotenberg, Herbert Pfnür & K. Horn
The Pb/Si(557) system exhibits a strong anisotropy in conductance below 78 K, with the evolution of a characteristic chain structure. Here we show, using angle-resolved photoemission, that chain ordering results in complete Fermi-like nesting in the direction normal to the chains; in addition, the domain structure along the chains forms split-off valence bands with mesoscopic Fermi wavelengths which induce the 1D conductance without further instabilities at low temperatures. © 2008 The American Physical Society.

Antiferromagnetic heisenberg spin chain of a few cold atoms in a one-dimensional trap

S. Murmann, Frank Deuretzbacher, G. Zürn, J. Bjerlin, S.M. Reimann, Luis Santos, T. Lompe & S. Jochim
We report on the deterministic preparation of antiferromagnetic Heisenberg spin chains consisting of up to four fermionic atoms in a one-dimensional trap. These chains are stabilized by strong repulsive interactions between the two spin components without the need for an external periodic potential. We independently characterize the spin configuration of the chains by measuring the spin orientation of the outermost particle in the trap and by projecting the spatial wave function of one spin component...

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...

Spin dynamics in a two-dimensional quantum gas

P.L. Pedersen, M. Gajdacz, Frank Deuretzbacher, Luis Santos, Carsten Klempt, J.F. Sherson, A.J. Hilliard & Jan J. Arlt
We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimposed angular density modulations. The density distributions depend on the applied magnetic field and are well explained by a simple Bogoliubov model. We show that the two clouds are anticorrelated in momentum space. The observed momentum correlations pave the...

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...

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....

Subaquatisch-gravitativ umgelagerte Sedimente des Devons und Karbons um Bad Lauterberg (SW-Harz)

Sabine Hahlbeck
Aus dem SW-Harz werden Ton-/SiItsteine mit Einlagerungen aus verschiedenartigen und -alten Gesteinen beschrieben. Die Sedimentkörper werden aufgrund eindeutig submarin-gravitativer Umlagerungsgefüge als Olisthostrome eingestuft. Andere Strukturen innerhalb der Olisthostrome können auch diagenetisch oder tektonisch bedingt sein. Es werden drei verschiedene Olisthostromkomplexe ausgegliedert, die voneinander durch unterschiedliche Klastenführung abgegrenzt werden. Neben Olisthostromen stehen im Untersuchungsgebiet auch slumps und Steinschlagsedimente an.

Influence of Heat Treatment on the Degradation Behaviour of Degradable Magnesium Based Implants

Katja Bracht, Nina Angrisani, J. Seitz, S. Besdo & Janin Reifenrath
Aim of the study was to characterise the influence of heat treatment on the degradation behaviour and stability of degradable magnesium based implants. For this purpose two groups (untreated/ heat treated) of LAE442 pins were separately analysed in an in vitro and in vivo study. The corrosion behaviour was evaluated during 8 weeks degradation in SBF (in vitro) and 48 weeks degradation intramedullary in the rabbit tibia (in vivo). The analyses were made by using...

[Review untitled to: Leon de Stadler and Christoph Eyrich (eds.): Issues in Cognitive Linguistics. 1993 Proceedings of the International Cognitive Linguistics Conference]

Rainer Schulze
Review to: Leon de Stadler and Christoph Eyrich (eds.): Issues in Cognitive Linguistics. 1993 Proceedings of the International Cognitive Linguistics Conference. - Berlin : Walter de Gruyter, 1999. ISBN 978-3-11-015219-7

Well-posedness, blow-up phenomena, and global solutions for the b-equation

Joachim Escher & Zhaoyang Yin
In the paper we first establish the local well-posedness for a family of nonlinear dispersive equations, the so called b-equation. Then we describe the precise blow-up scenario. Moreover, we prove that for the b-equation we do have the coexistence of global in time solutions and blow-up phenomena: Depending on the initial data solutions may exist for ever, while other data force the solution to produce a singularity in finite time. Finally, we prove the uniqueness...

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