@article{59695, abstract = {{We demonstrate electrical spin injection from ferromagnetic Fe/Tb multilayer structures with remanent perpendicular magnetization into GaAs-based light-emitting diodes at room temperature. Using a reverse-biased Schottky contact and a MgO tunnel contact, respectively, we achieve spin injection at remanence. The maximum degree of circular polarization of the emitted light is 3% at room temperature.}}, author = {{Hövel, S. and Gerhardt, N. C. and Hofmann, M. R. and Lo, F.-Y. and Ludwig, A. and Reuter, D. and Wieck, A. D. and Schuster, E. and Wende, H. and Keune, W. and Petracic, O. and Westerholt, K.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{2}}, publisher = {{AIP Publishing}}, title = {{{Room temperature electrical spin injection in remanence}}}, doi = {{10.1063/1.2957469}}, volume = {{93}}, year = {{2008}}, } @article{64685, author = {{Glöckner, Helge}}, issn = {{0017-0895}}, journal = {{Glasgow Mathematical Journal}}, keywords = {{26E15, 26E20, 26E30, 46A16, 46S10}}, number = {{2}}, pages = {{271–288}}, title = {{{Ultrametric and non-locally convex analogues of the general curve Lemma of convenient differential calculus}}}, doi = {{10.1017/S0017089508004199}}, volume = {{50}}, year = {{2008}}, } @article{64684, author = {{Glöckner, Helge}}, issn = {{0046-5755}}, journal = {{Geometriae Dedicata}}, keywords = {{22E65}}, pages = {{71–86}}, title = {{{Solutions to open problems in Neeb’s recent survey on infinite-dimensional Lie groups}}}, doi = {{10.1007/s10711-008-9263-z}}, volume = {{135}}, year = {{2008}}, } @article{64683, author = {{Glöckner, Helge}}, issn = {{0025-5874}}, journal = {{Mathematische Zeitschrift}}, keywords = {{22E20, 22E60}}, number = {{4}}, pages = {{889–904}}, title = {{{Contractible Lie groups over local fields}}}, doi = {{10.1007/s00209-008-0305-x}}, volume = {{260}}, year = {{2008}}, } @inproceedings{63082, author = {{Fechner, Sabine and Sumfleth, Elke}}, booktitle = {{Concept Mapping: Connecting Educators. Proceedings of the Third International Conference on Concept Mapping, Tallinn, Estonia & Helsinki, Finland}}, editor = {{Canas, A. J. and Reiska, P. and Ahlberg, M. and Novak, J.}}, title = {{{Collaborative concept mapping in context-oriented chemistry learning}}}, year = {{2008}}, } @inproceedings{63081, author = {{Fechner, Sabine and Haugwitz, Marion and Sandmann, Angela and Sumfleth, Elke}}, booktitle = {{Proceedings of the NARST 2008 Annual Meeting, Baltimore, MD, USA}}, title = {{{Context-oriented learning and its effects on students' achievement levels in chemistry education}}}, year = {{2008}}, } @article{18564, abstract = {{In the context of photoelectron spectroscopy, the GW approach has developed into the method of choice for computing excitation spectra of weakly correlated bulk systems and their surfaces. To employ the established computational schemes that have been developed for three-dimensional crystals, two-dimensional systems are typically treated in the repeated-slab approach. In this work we critically examine this approach and identify three important aspects for which the treatment of long-range screening in two dimensions differs from the bulk: (1) anisotropy of the macroscopic screening, (2) k-point sampling parallel to the surface, (3) periodic repetition and slab-slab interaction. For prototypical semiconductor (silicon) and ionic (NaCl) thin films we quantify the individual contributions of points (1) to (3) and develop robust and efficient correction schemes derived from the classic theory of dielectric screening.}}, author = {{Freysoldt, Christoph and Eggert, Philipp and Rinke, Patrick and Schindlmayr, Arno and Scheffler, Matthias}}, issn = {{1550-235X}}, journal = {{Physical Review B}}, number = {{23}}, publisher = {{American Physical Society}}, title = {{{Screening in two dimensions: GW calculations for surfaces and thin films using the repeated-slab approach}}}, doi = {{10.1103/PhysRevB.77.235428}}, volume = {{77}}, year = {{2008}}, } @misc{9199, booktitle = {{Partial Answers}}, editor = {{Hyvärinen, Matti and Mikkonen, Kai and Mildorf, Jarmila}}, issn = {{1565-3668}}, number = {{2}}, pages = {{225--231}}, publisher = {{Johns Hopkins University Press}}, title = {{{Narrative: Knowing, Living, Telling}}}, volume = {{6}}, year = {{2008}}, } @article{66782, abstract = {{The link between formal education and the formation of national attachment is widely acknowledged. Yet, research on teachers’ national attachment is still relatively rare. Based on a comparative analysis of survey data obtained from 281 Berlin and London state secondary school head teachers, this paper proposes a multivariate model in which notions of national identity, levels of national pride and levels of supranational attachment represent predictors of national attachment. The respective statistical analyses reveal striking cross‐national similarities in terms of the individual and joint explanatory impact of these predictors. Other findings concern correlations between different notions of Britishness/Germanness and levels of national attachment, the relationship between national and supranational attachment, and associations between national pride and national attachment.}}, author = {{Pöllmann, Andreas}}, issn = {{0305-5698}}, journal = {{Educational Studies}}, number = {{1}}, pages = {{45--53}}, publisher = {{Informa UK Limited}}, title = {{{National attachment among Berlin and London head teachers: The explanatory impact of national identity, national pride and supranational attachment}}}, doi = {{10.1080/03055690701785277}}, volume = {{34}}, year = {{2008}}, } @article{31026, abstract = {{Am Beispiel der naturwissenschaftlichen Fächer untersucht die Studie den einzelschulischen Gesamtzusammenhang, in dem sich Fachunterricht am Gymnasium vollzieht. Dazu werden die Schulkultur als auch die fachspezifische Kultur mit einem umfangreichen Indikatorensatz operationalisiert und anschließend aufeinander bezogen sowie in Bezug zur fachspezifischen Schuleffektivität gesetzt. Es ergeben sich deutliche Hinweise auf eine Autonomie fachspezifischer Subkulturen sowie auf einen Zusammenhang zwischen dem Stellenwert naturwissenschaftlicher Fächer und den betreffenden Leistungsergebnissen.}}, author = {{van Ackeren, Isabell and Block, Rainer and Kullmann, Harry and Sprütten, Frank and Klemm, Klaus}}, issn = {{0044-3247}}, journal = {{Zeitschrift für Pädagogik}}, keywords = {{Lernen, Schulkultur}}, number = {{3}}, pages = {{341–360}}, title = {{{Schulkultur als Kontext naturwissenschaftlichen Lernens. Allgemeine und fachspezifische explorative Analysen}}}, doi = {{10.25656/01:4355}}, volume = {{54}}, year = {{2008}}, } @inproceedings{1107, abstract = {{Dieser Beitrag beschäftigt sich mit der Informationsextraktion aus Stellenanzeigen im französischsprachigen Web. Ziel dieser Arbeit ist es, unstrukturierte Dokumente in Repräasentationsvektoren anhand lokaler Grammatiken zu transformieren. Auf diese Weise wird es möglich, den Stellenmarkt für Jobsuchmaschinen transparenter zu gestalten, indem nur auf dem Inhalt der Anzeige in Form von Darstellungsvektoren anstatt auf unübersichtlichem Fließtext gesucht werden muss.}}, author = {{Bsiri, Sandra and Geierhos, Michaela}}, booktitle = {{LWA 2007: Lernen - Wissen - Adaption, Halle, September 2007, Workshop Proceedings}}, editor = {{Hinneburg, Alexander }}, isbn = {{978-3-86010-907-6}}, location = {{Halle (Saale), Germany}}, pages = {{229--236}}, publisher = {{Martin-Luther-University}}, title = {{{Informationsextraktion aus Stellenanzeigen im Internet}}}, year = {{2007}}, } @article{18589, abstract = {{For the calculation of neutral excitations, time-dependent density functional theory (TDDFT) is an exact reformulation of the many-body time-dependent Schrödinger equation, based on knowledge of the density instead of the many-body wavefunction. The density can be determined in an efficient scheme by solving one-particle non-interacting Schrödinger equations—the Kohn–Sham equations. The complication of the problem is hidden in the—unknown—time-dependent exchange and correlation potential that appears in the Kohn–Sham equations and for which it is essential to find good approximations. Many approximations have been suggested and tested for finite systems, where even the very simple adiabatic local-density approximation (ALDA) has often proved to be successful. In the case of solids, ALDA fails to reproduce optical absorption spectra, which are instead well described by solving the Bethe–Salpeter equation of many-body perturbation theory (MBPT). On the other hand, ALDA can lead to excellent results for loss functions (at vanishing and finite momentum transfer). In view of this and thanks to recent successful developments of improved linear-response kernels derived from MBPT, TDDFT is today considered a promising alternative to MBPT for the calculation of electronic spectra, even for solids. After reviewing the fundamentals of TDDFT within linear response, we discuss different approaches and a variety of applications to extended systems.}}, author = {{Botti, Silvana and Schindlmayr, Arno and Del Sole, Rodolfo and Reining, Lucia}}, issn = {{1361-6633}}, journal = {{Reports on Progress in Physics}}, number = {{3}}, pages = {{357--407}}, publisher = {{IOP Publishing}}, title = {{{Time-dependent density-functional theory for extended systems}}}, doi = {{10.1088/0034-4885/70/3/r02}}, volume = {{70}}, year = {{2007}}, } @article{18591, abstract = {{Using density-functional theory, we investigate the stability of the half-metallic ground state of magnetite under different strain conditions. The effects of volume relaxation and internal degrees of freedom are fully taken into account. For hydrostatic compression, planar strain in the (001) plane and uniaxial strain along the [001] direction, we derive quantitative limits beyond which magnetite becomes metallic. As a major new result, we identify the bond length between the octahedrally coordinated iron atoms and their neighbouring oxygen atoms as the main characteristic parameter, and we show that the transition occurs if external strain reduces this interatomic distance from 2.06 Å in equilibrium to below a critical value of 1.99 Å. Based on this criterion, we also argue that planar strain due to epitaxial growth does not lead to a metallic state for magnetite films grown on (111)-oriented substrates.}}, author = {{Friák, Martin and Schindlmayr, Arno and Scheffler, Matthias}}, issn = {{1361-6633}}, journal = {{New Journal of Physics}}, number = {{1}}, publisher = {{IOP Publishing and Deutsche Physikalische Gesellschaft}}, title = {{{Ab initio study of the half-metal to metal transition in strained magnetite}}}, doi = {{10.1088/1367-2630/9/1/005}}, volume = {{9}}, year = {{2007}}, } @inbook{18593, abstract = {{We present a quantitative parameter-free method for calculating defect states and charge-transition levels of point defects in semiconductors. It combines the strength of density-functional theory for ground-state total energies with quasiparticle corrections to the excitation spectrum obtained from many-body perturbation theory. The latter is implemented within the G0W0 approximation, in which the electronic self-energy is constructed non-self-consistently from the Green’s function of the underlying Kohn–Sham system. The method is general and applicable to arbitrary bulk or surface defects. As an example we consider anion vacancies at the (110) surfaces of III–V semiconductors. Relative to the Kohn–Sham eigenvalues in the local-density approximation, the quasiparticle corrections open the fundamental band gap and raise the position of defect states inside the gap. As a consequence, the charge-transition levels are also pushed to higher energies, leading to close agreement with the available experimental data.}}, author = {{Schindlmayr, Arno and Scheffler, Matthias}}, booktitle = {{Theory of Defects in Semiconductors}}, editor = {{Drabold, David A. and Estreicher, Stefan K.}}, isbn = {{978-3-540-33400-2}}, issn = {{1437-0859}}, pages = {{165--192}}, publisher = {{Springer}}, title = {{{Quasiparticle calculations for point defects at semiconductor surfaces}}}, doi = {{10.1007/11690320_8}}, volume = {{104}}, year = {{2007}}, } @inproceedings{9562, abstract = {{Penetration tests (Magness-Taylor, force/deformation, Kramer multiblade shear) applied directly over the peel of the fruit are the most acceptable methods for measuring firmness and turgidity of fruits and vegetables [1, 2]. To replace these destructive and mechanical penetration methods by non-destructive ultrasonic measurements implies a great advance in order to obtain fast studies about the state of the fruit at the time of harvest, during storage, and in the distribution points. Moreover, there are other advantages since this technique can be fast, non-destructive, fully automated, and performed on-line [1]. Within this context, the objective of this study was to examine the relationship between physico-mechanical characteristics (oil-gland break stress, thickness and dehydration) and ultrasonic characteristics in the ``Salustiana'' orange peel during the complete dehydration process of the orange at ambient conditions. After a description of the measurement system [3], the fruit selection procedure and the measurement protocol, we analyze the results of the change of physico-mechanical and ultrasonic properties in the orange peel and their change with storage time.}}, author = {{Camarena Gandia, Francisco and Hemsel, Tobias and Espinosa, Victor and Twiefel, Jens and Ardid, Miquel and Martinez-Mora, Joan and Gandia, Joan Babtiste}}, booktitle = {{Proceedings of 19th international congress on Acoustics, Madrid}}, title = {{{Non-destructive ultrasonic test of orange dehydration}}}, year = {{2007}}, } @article{9564, abstract = {{Surgical resection of brain tumours is a difficult task. To enhance surgery results, a tactile sensor is wanted that gives better resolution and sensitivity than the human tactile sense. The characteristics of resonant vibrating piezoelectric elements change with varying load. This allows for calculation of mechanical load parameters by measuring electrical quantities. Different setups of piezoelectric sensors have been used to investigate soft materials. Finally, a piezoelectric bimorph sensor gave good results for distinguishing tissue mimicking gel-phantoms with different gelatine concentrations. }}, author = {{Hemsel, Tobias and Stroop, Ralf and Oliva Uribe, David and Wallaschek, Jörg}}, issn = {{0022-460X}}, journal = {{Journal of Sound and Vibration}}, pages = {{441 -- 446}}, title = {{{Resonant vibrating sensors for tactile tissue differentiation}}}, doi = {{10.1016/j.jsv.2007.03.063}}, volume = {{308}}, year = {{2007}}, } @inproceedings{9565, author = {{Lierke, Ernst-Günter and Hemsel, Tobias}}, booktitle = {{Proceedings of 19th international congress on Acoustics, Madrid}}, title = {{{Perspectives of Tumour Therapy by Local Ultrasonic Hyperthermia and Thermal Ablation}}}, year = {{2007}}, } @article{9566, author = {{Shigematsu , Takashi and Morita, Takeshi and Hemsel, Tobias}}, journal = {{Proceedings of Symposium on Ultrasonic Electronics}}, pages = {{439 -- 440}}, title = {{{Fundamental Study on A Thickness-Shear Transformer using X-Cut Lithium Niobate}}}, volume = {{28}}, year = {{2007}}, } @article{9567, abstract = {{Numerical predictions of the forced vibration of a disk assembly including frictional effects between the shrouds are presented concerning engineering needs for the blade design process. Assuming a tuned disk assembly, numerical static, free, and then forced vibration analyses of a shrouded turbine blade measured in the spin pit are performed systematically. For the excitation forces of an air jet evaluated from the fairly linear behavior of the experimental blade resonance peaks, the reliability of the proposed approach is validated through the very close agreement of the computed and measured resonant peaks. These resonant peaks demonstrate either a fairly linear behavior or a nonlinear one like the jump effect of blade resonance amplitudes, or elastic impacts between the shrouds. Also, the damping performance for different contact configurations between the shrouds is numerically analyzed. These numerical results indicate that the shrouds generate higher frictional damping for small angles (0{\^a}30deg) between the circumferential direction and the normal vector to the contact surface.}}, author = {{Szwedowicz, J and Visser, R and Sextro, Walter and Masserey, P. A}}, issn = {{0889-504X}}, journal = {{Journal of Turbomachinery}}, number = {{1}}, pages = {{011002--011002}}, title = {{{On Nonlinear Forced Vibration of Shrouded Turbine Blades}}}, volume = {{130}}, year = {{2007}}, } @article{18595, abstract = {{Excited-state calculations, notably for quasiparticle band structures, are nowadays routinely performed within the GW approximation for the electronic self-energy. Nevertheless, certain numerical approximations and simplifications are still employed in practice to make the computations feasible. An important aspect for periodic systems is the proper treatment of the singularity of the screened Coulomb interaction in reciprocal space, which results from the slow 1/r decay in real space. This must be done without introducing artificial interactions between the quasiparticles and their periodic images in repeated cells, which occur when integrals of the screened Coulomb interaction are discretised in reciprocal space. An adequate treatment of both aspects is crucial for a numerically stable computation of the self-energy. In this article we build on existing schemes for isotropic screening and present an extension for anisotropic systems. We also show how the contributions to the dielectric function arising from the non-local part of the pseudopotentials can be computed efficiently. These improvements are crucial for obtaining a fast convergence with respect to the number of points used for the Brillouin zone integration and prove to be essential to make GW calculations for strongly anisotropic systems, such as slabs or multilayers, efficient.}}, author = {{Freysoldt, Christoph and Eggert, Philipp and Rinke, Patrick and Schindlmayr, Arno and Godby, Rex W. and Scheffler, Matthias}}, issn = {{0010-4655}}, journal = {{Computer Physics Communications}}, number = {{1}}, pages = {{1--13}}, publisher = {{Elsevier}}, title = {{{Dielectric anisotropy in the GW space–time method}}}, doi = {{10.1016/j.cpc.2006.07.018}}, volume = {{176}}, year = {{2007}}, }