Shifted Landau levels in curved graphene sheets

We study the Landau levels in curved graphene sheets by measuring the discrete energy spectrum in the presence of a magnetic field. We observe that in rippled graphene sheets, the Landau energy levels satisfy the same square root dependence on the energy quantum number as in flat sheets, $E_n \sim \sqrt{n}$. Though, we find that the Landau levels in curved sheets are shifted towards lower energies by an amount proportional to the average spatial deformation of the sheet. Our findings are relevant for the quantum Hall effect in curved graphene sheets, which is directly related to Landau quantization. For the purpose of this study, we develop a new numerical method, based on the quantum lattice Boltzmann method, to solve the Dirac equation on curved manifolds, describing the low-energetic states in strained graphene sheets

Dynamical universality of the contact process

The dynamical relaxation and scaling properties of three different variants of the contact process in two spatial dimensions are analysed. Dynamical contact processes capture a variety of contagious processes such as the spreading of diseases or opinions. The universality of both local and global two-time correlators of the particle-density and the associated linear responses are tested through several scaling relations of the non-equilibrium exponents and the shape of the associated scaling functions. In addition, the dynamical scaling of two-time global correlators can be used as a tool to improve on the determination of the location of critical points.Comment: 20 pages, 8 figure

Electrochemical determination of the oxygen activity in tin melts by means of the solid electrolyte method

The measurements of oxygen activity in the tin melt were carried out under inert (light oxidizing) as well as under reducing (N2 with 2 vol.% H2 and 10 vol% H2, respectively) conditions. As solid electrolyte (SE) material Y2O3-, CaO- and MgO-stabilized zirconia was used in the form of a long tube closed at one end. Α short SE tube closed at one end within an alumina tube was applied as industrial probe. The galvanic cells worked with a Pt/air and Me/MeO reference electrode and with electrical leads of steel, tantalum as well as rhenium wires. Under inert conditions (argon with 30 vol.ppm O2) a saturation of the tin with oxygen is always obtained and SnO2 is formed. Under reducing conditions the saturation of the melt with oxygen does not take place and no SnO2 is formed. An equilibrium is adjusted between oxygen in the atmosphere and solute oxygen in the melt. At extremely low oxygen contents no equilibrium will be achieved. The lower operating temperatures of the probes were between 500 and 700 °C. The data taken from the literature were confirmed by EMF measurements (solubility of oxygen in liquid tin, molar free solution enthalpy of oxygen in tin, molar free standard enthalpy of formation of SnO2). This kind of investigations is new as to the behaviour of the tin melt under forming gas and the defined addition of elements and compounds to the tin melt (Na2SnO3, Na2O, Na, Fe2O3, Fe, MgO, Mg). Under reducing conditions and the addition of sodium or magnesium to the tin melt a quick decline of the oxygen activity can be recognized at the moment of addition. The melt becomes strongly deoxidized by the addition of these metals. The subsequent processes of deoxidation, which are different from metal to metal, have still to be investigated. No change of the oxygen activity in the melt was observed by addition of iron in the ppm range to the tin melt. For the measurements alumina and a fireclay brick were used as crucible materials. The tin surface was either in immediate contact with the gas phase or was covered with a float glass melt. The oxygen activity of the tin melt was influenced by the crucible material and the float glass melt, too

Intensivierung und Differenzierung des Leguminosen-Anbaus unter Berücksichtigung der Nematoden

Zusammenfassung Um Empfehlungen für eine Erhöhung des Anteils der Leguminosen in Ökologischen Anbausystemen bei gleichzeitiger Erweiterung des Artenspektrums zu erarbeiten, wurden die Arten Trifolium subterraneum (Erdklee), Trifolium campestre (Feldklee), Medicago orbicularis (Schneckenklee), Medicago minima (Zwergschneckenklee) und Medicago truncatula (Einjährige Luzerne) in Verfahren des Lebendmulches und der Gründüngung untersucht. Besonders interessant für Mischkulturen hat sich der Erdklee erwiesen, für kurzzeitige Gründüngung die Einjährige Luzerne. Die enge Abfolge von Leguminosen birgt die Gefahr der Unverträglichkeit durch Nematodenbefall speziell mit Meloidogyne und Paratylenchus. In einem Gefäßversuch zeigte sich, dass die Arten der Gattungen Pisum, Vicia und Trifolium eine höhere Vermehrungsrate für Meloidogyne hapla hatten als Kopfsalat. Medicago und Melilotus waren dagegen weniger anfällig. Daraus ergibt sich, dass beim Fruchtfolgemanagement die unterschiedliche Nematodenanfälligkeit durch die Wahl der Arten und die Anbauzeiten berücksichtigt werden sollte

Simulierte Welten – die Zukunft im Rechner

Wie kommen die „Kachelmänner“ dieser Welt eigentlich zu ihren detaillierten Vorhersagen? Und warum liegen sie manchmal trotzdem so daneben? Was veranlasst Automobilhersteller, das Ende der Ära des Prototypen anzukündigen? Liegt die wiedergekehrte Ruhe im Mururoa-Atoll wirklich darin begründet, dass man im fernen Paris zur Einsicht gelangt ist? Und wer gibt der Voyager-Sonde ihren merkwürdig anmutenden Weg vor, der sie – obwohl schnurstracks unterwegs in Regionen, die nie ein Mensch zuvor gesehen hat – doch wieder an die Erde heranführt? Das Zauberwort heißt numerische Simulation. Auf leistungsfähigen Großrechnern – seien es klassische Supercomputer oder Cluster aus vernetzten PCs – nachgestellte oder vorausberechnete Phänomene und Prozesse aus Natur-, Ingenieur- oder Wirtschaftswissenschaften spielen in Forschung und Entwicklung eine immer wichtigere Rolle. Dies gilt für die eingangs genannten Beispiele ebenso wie für zahlreiche Anwendungen in der Astrophysik, Halbleiter- und Biotechnologie oder in der Systemdynamik sowie – ganz konkret und für alle T-Geplagten relevant – für Aktienkursprognosen

A modeling approach to study the effect of cell polarization on keratinocyte migration

The skin forms an efficient barrier against the environment, and rapid cutaneous wound healing after injury is therefore essential. Healing of the uppermost layer of the skin, the epidermis, involves collective migration of keratinocytes, which requires coordinated polarization of the cells. To study this process, we developed a model that allows analysis of live-cell images of migrating keratinocytes in culture based on a small number of parameters, including the radius of the cells, their mass and their polarization. This computational approach allowed the analysis of cell migration at the front of the wound and a reliable identification and quantification of the impaired polarization and migration of keratinocytes from mice lacking fibroblast growth factors 1 and 2 an established model of impaired healing. Therefore, our modeling approach is suitable for large-scale analysis of migration phenotypes of cells with specific genetic defects or upon treatment with different pharmacological agents.Comment: 27 pages, 3 figure

SyProLei - A systematic product development process to exploit lightweight potentials while considering costs and CO2 emissions

In lightweight design, developers are used to face the conflicting objectives of functional fulfillment, economic performance, and sustainability. Against this background, however, a clearly structured approach for the satisfied use of specific lightweight engineering methods within the product development is still missing. Thus, this contribution deals with the fundamental conception and first implementation of a systematic development methodology covering the disciplines of mechanics, electrics/electronics and software just like the focus on an integrated view on product, production and material aspects. To ensure an application-specific manifestation of the product development process for three exemplary use cases from small and medium-sized enterprises but also large corporations in the area of prosthetics, bike construction and plant engineering, the individually developed methods and tools are first generalized in order to make them adaptable to a wide variety of industries. As a result, one lightweight-specific method or tool (e.g., function mass analysis, “PPM solution correlator“ or “2D layout & weight drafting”) is introduced in more detail for all stages of the technically extended RFL(T)P approach derived from model-based systems engineering (MBSE)