Simulation based case studies for management training in the fields of production and supply chain Management

It is well known that interactive learning is much more efficient than classical learning with textbooks. With the broad propagation of computers, new opportunities for computer-based interactive learning are available. In particular, simulation based learning allows the student to learn based on experience. In economic and technical environments, where complex systems comprise numerous decision variables, conducting experiments can provide a deeper insights and an intuitive understanding to the student. In the present paper, a newly developed environment for computer-based interactive learning in the fields of production and supply chain training is described. The different steps from the evaluation of an appropriate electronic platform to the development of eight different case studies for the students are explained. The environment now provides an easily applicable and ready-to-use solution for university teachers and their students

Assembly, trafficking and function of gamma-secretase

gamma-Secretase catalyzes the final cleavage of the beta-amyloid precursor protein to generate amyloid-beta peptide, the principal component of amyloid plaques in the brains of patients suffering from Alzheimer's disease. Here, we review the identification of gamma-secretase as a protease complex and its assembly and trafficking to its site(s) of cellular function. In reconstitution experiments, gamma-secretase was found to be composed of four integral membrane proteins, presenilin (PS), nicastrin (NCT), PEN-2 and APH-1 that are essential and sufficient for gamma-secretase activity. PS, which serves as a catalytic subunit of gamma-secretase, was identified as a prototypic member of novel aspartyl proteases of the GxGD type. In human cells, gamma-secretase could be further defined as a heterogeneous activity consisting of distinct complexes that are composed of PS1 or PS2 and APH-1a or APH-1b homologues together with NCT and PEN-2. Using green fluorescent protein as a reporter we localized PS and gamma-secretase activity at the plasma membrane and endosomes. Investigation of gamma-secretase complex assembly in knockdown and knockout cells of the individual subunits allowed us to develop a model of complex assembly in which NCT and APH-1 first stabilize PS before PEN-2 assembles as the last component. Furthermore, we could map domains in PS and PEN-2 that govern assembly and trafficking of the complex. Finally, Rer1 was identified as a PEN-2-binding protein that serves a role as an auxiliary factor for gamma-secretase complex assembly. Copyright (c) 2006 S. Karger AG, Basel

Laser spectroscopy and cooling of Yb+ ions on a deep-UV transition

We perform laser spectroscopy of Yb+ ions on the 4f14 6s 2S_{1/2} - 4f13 5d 6s 3D[3/2]_{1/2} transition at 297 nm. The frequency measurements for 170Yb+, 172Yb+, 174Yb+, and 176Yb+ reveal the specific mass shift as well as the field shifts. In addition, we demonstrate laser cooling of Yb+ ions using this transition and show that light at 297 nm can be used as the second step in the photoionization of neutral Yb atoms

Coloring Drawings of Graphs

We consider face-colorings of drawings of graphs in the plane. Given a multi-graph $G$ together with a drawing $\Gamma(G)$ in the plane with only finitely many crossings, we define a face-$k$-coloring of $\Gamma(G)$ to be a coloring of the maximal connected regions of the drawing, the faces, with $k$ colors such that adjacent faces have different colors. By the $4$-color theorem, every drawing of a bridgeless graph has a face-$4$-coloring. A drawing of a graph is facially $2$-colorable if and only if the underlying graph is Eulerian. We show that every graph without degree 1 vertices admits a $3$-colorable drawing. This leads to the natural question which graphs $G$ have the property that each of its drawings has a $3$-coloring. We say that such a graph $G$ is facially $3$-colorable. We derive several sufficient and necessary conditions for this property: we show that every $4$-edge-connected graph and every graph admitting a nowhere-zero $3$-flow is facially $3$-colorable. We also discuss circumstances under which facial $3$-colorability guarantees the existence of a nowhere-zero $3$-flow. On the negative side, we present an infinite family of facially $3$-colorable graphs without a nowhere-zero $3$-flow. On the positive side, we formulate a conjecture which has a surprising relation to a famous open problem by Tutte known as the $3$-flow-conjecture. We prove our conjecture for subcubic and for $K_{3,3}$-minor-free graphs.Comment: 24 pages, 17 figure

Fast and Reliable Assessment of a Reservoir Model Quality on the Basis of Dynamic Behaviour

The article presents the first successful industrial application of the Target Pressure and Phase Method (TPPM) on a reservoir with secondary gas cap and a compositional fluid model. The method can provide correct in- and outflow at the boundaries and at the well locations over the entire calculated time interval of reservoir operations, without modification of the static parameters, relative permeabilities or endpoint saturations. For 13 out of 21 wells of the field example a perfect match of three-phase rates was achieved. The TPPM helped to identify immediately and clearly static model-regions, which do not fulfil dynamic requirements and need modifications before a history matching process could start

Synthesis and Structural Investigation of Protonated Haloacetyl Fluorides

Herein, we report the O-monoprotonated species of chloroacetyl fluoride and fluoroacetyl fluoride in the binary superacidic systems HF/MF5 and DF/MF5 (M=As, Sb) as hexafluoridoarsenates and hexafluoridostibates. The colorless salts were characterized by low temperature vibrational spectroscopy, low temperature NMR spectroscopy and single-crystal X-ray diffraction. [CCIH2C(OH)F][SbF6] crystallizes in the monoclinic space group P2(1)/c with four formula units per unit cell and [CIH2FC-(OD)F][SbF6] in the triclinic space group P (1) over bar with two formula units per cell. The experimental data are discussed together with quantum chemical calculations at the omega B97XD/aug-cc-pVTZ-level of theory. Protonation leads to significant shortening of the C F bond due to back-donation of fluorine lone-pair electrons

Exponential Decay Lifetimes of Excitons in Individual Single-Walled Carbon Nanotubes

The dynamics of excitons in individual semiconducting single-walled carbon nanotubes was studied using time-resolved photoluminescence (PL) spectroscopy. The PL decay from tubes of the same (n,m) type was found to be monoexponential, however, with lifetimes varying between less than 20 and 200 ps from tube to tube. Competition of nonradiative decay of excitons is facilitated by a thermally activated process, most likely a transition to a low-lying optically inactive trap state that is promoted by a low-frequency phonon mode