Die Einbettung von Käfern in Polyester-Gießharz : eine Methode zur Typenkonservation?

Die wohlbekannte Methode der Einbettung von Insekten in Polyester-Gießharz wird am Beispiel von Käfern sowohl beschrieben als auch bewertet und die Frage zur Diskussion gestellt: Sollten alle Typen oder wenigstens Paratypen neu beschriebener Arten in Gießharz eingeschlossen werden?The well-known method of embedding insects (example: beetles) in polyester resin is as well described as evaluated and the question is raised: Schould all Types or at least Paratypes of newly described species be embedded in resin

Percolation threshold and mean grain size in AlxSi1-x thin films

Reiss G, Vancea J, Hoffmann H. Percolation threshold and mean grain size in AlxSi1-x thin films. Journal of Physics, C: Solid State Physics. 1985;18(21):L657-L660.We determined the critical composition xc of the percolation threshold in polycrystalline AIxSi1-x thin films with a new method, using structural arguments only. The result xc = (0.55 + - 0.05) agrees with the results of the commonly used methods. Moreover, our model explains the wide spread of experimental values of xc as reported in the literature

Kurslehrpläne für die gymnasiale Oberstufe – geschlossene Konzeption oder Kompromiss?

Dies ist kein akademischer Aufsatz über die theoretisch fundierte Entwicklung einer Konzeption und ihre detaillierte Umsetzung in praktikable Unterrichtsgliederungen. Hier soll nicht von Planungen und Entscheidungen "am grünen Tisch" und auch nicht von der wissenschaftlich begründeten Arbeit in einem Didaktik-Institut die Rede sein, sondern von dem Versuch, über Jahre hinweg bei häufig wechselnden Vorgaben und Auflagen immer wieder neue, einigermaßen vertretbare Kompromisse zu schließen und dabei doch eine gewisse Grundeinstellung durchzuhalten, so gut es eben ging. Im Mittelpunkt soll dabei die Arbeit an den Grundkursen in Geographie für die neugestaltete gymnasiale Oberstufe (NGO) im Lande Bremen stehen, an deren Erstellung der Verfasser wesentlichen Anteil hatte

Visual servoing with moments of SIFT features

Robotic manipulation of daily-life objects is an essential requirement in service robotic applications. In that context image based visual servoing is a means to position the end-effector in order to manipulate objects of unknown pose. This contribution proposes a 6 DOF visual servoing scheme that relies on the pixel coordinates, scale and orientation of SIFT features. The control is based on geometric moments computed over an alterable set of redundant SIFT feature correspondences between the current and the reference view. The method is generic as it does not depend on a geometric object model but automatically extracts SIFT features from images of the object. The foundation of visual servoing on generic SIFT features renders the method robust with respect to loss of redundant features caused by occlusion or changes in view point.The moment based representation establishes an approximate one-to-one relationship between visual features and degrees of motion. This property is exploited in the design of a decoupled controller that demonstrates superior performance in terms of convergence and robustness compared with an inverse image Jacobian controller. Several experiments with a robotic arm equipped with a monocular eye-in-hand camera demonstrate that the approach is efficient and reliable

Emergence of thermodynamic behavior within composite quantum systems

Entanglement within a given device provides a potential resource for quantum information processing. Entanglement between system and environment leads to decoherence (thus suppressing non-classical features within the system) but also opens up a route to robust and universal control. The latter is related to thermodynamic equilibrium, a generic behavior of bi-partite quantum systems. Fingerprints of this equilibrium behavior (including relaxation and stability) show up already far from the thermodynamic limit, where a complete solution of the underlying Schroedinger dynamics of the total system is still feasible.Comment: 12 pages, 12 figures, accepted for publication in Physica

Two-way shape memory effect in (?+?) two-phase Co38Ni33Al29 single crystals

In the present study, it is shown that the aging in martensite under load is the effective way to create two-way shape memory effect at the martensite start temperature Ms=311 K with the reversible strain of 5 % along the [001]B2-direction in Co38Ni33Al29 single crystals with the minimum volume fraction fγ~1 % of large γ- phase precipitations. The increase of volume fraction up to fγ~5 % leads to the suppression of two-way shape memory effect, the reversible strain is less than 1 %

Growth and structure of polycrystalline Cr/Au multilayered thin films

Brückl H, Vancea J, Lecheler R, Reiss G, Hoffmann H. Growth and structure of polycrystalline Cr/Au multilayered thin films. Thin solid films. 1994;250(1-2):56-60.Metallic multilayered thin films have recently been investigated due to their new magnetic and transport properties. The interest here is focussed on the characterization of the interfaces between the layers. The analysis of growth and structure of polycrystalline Cr/Au multilayers is accomplished by two complementary techniques: in situ ultrahigh vacuum scanning tunnelling microscopy and ex situ transmission electron microscopy. The combination of these powerful methods provides detailed information about structural characteristics such as crystallite size, surface roughness and crystallographic orientation. Moreover, conclusions can be drawn on the atomic arrangement and growth mechanism at the Cr-Au interface. The results are supported by semiempirical and theoretical expectations

Resistivity and the Hall effect in polycrystalline Ni-Cu and Ta-Cu multi-layered thin films

Reiss G, Vancea J, Kapfberger K, Meier G, Hoffmann H. Resistivity and the Hall effect in polycrystalline Ni-Cu and Ta-Cu multi-layered thin films. Journal of Physics, Condensed Matter. 1989;1(7):1275-1283.In the present paper the dependences of the resistivity p and the Hall voltage UH of polycrystalline Ni-Cu and Ta-Cu multi-layered thin films on the layer thickness dr are discussed. The thickness dependence of p and UH can be well understood using a simple model in which the layers are considered as parallel resistors, whereby the resistivity of a single layer is enhanced via surface scattering described by the well known Fuchs-Namba size theory. The Hall coefficients are independent of the layer thickness, although the measured Hall voltage varies with dr owing to the enhancement of the individual layer resistivities. For very thin layers, i.e. if the layer thickness becomes smaller than the layer roughness, the experimental data on both p and UH indicate a breakdown of the multi-layered structure to an island-like clustered film structure. For Ni-Cu a crossover from ferroparamagnetic to superparamagnetic behaviour was observed at this critical thickness

Substrate effects on the surface topography of evaporated gold films: a scanning tunnelling microscopy investigation

Vancea J, Reiss G, Schneider F, Bauer K, Hoffmann H. Substrate effects on the surface topography of evaporated gold films: a scanning tunnelling microscopy investigation. Surface science. 1989;218(1):108-126.Direct observation of surface roughness on metal films is a longstanding problem in thin film characterization. In this work the high quality of scanning tunnelling microscopy (STM) was used for investigation of evaporated gold films. A scanning tunnelling microscope able to scan areas up to 0.8 × 0.8 micro m with high reproducibility is presented. The topography of 80 nm thick gold films grown under identical evaporation conditions was investigated as a function of the selected substrate material (Corning glass, silicon, NaCl, mica and highly oriented pyrolitic graphite (HOPG)). The incipient growth mechanism on the substrate is the primary reason for the surface roughness. The real space images of the surface topography correlate very well with knowledge achieved from former growth experiments given in the literature. Moreover, very flat gold surfaces on HOPG allowed the observation of atomic corrugations in air environments

Bluetongue Virus Serotype 8 Reemergence in Germany, 2007 and 2008

Reemerging bluetongue virus serotype 8 (BTV-8) in Germany was detected first in May 2007 in a sentinel cow and in February 2008 in an export heifer. Reemergence was confirmed by retesting the samples, experimental inoculation, fingerprinting analysis, and virus isolation. Overwintering of BTV-8 and continuous low-level infections are assumed