Der Einfluss von Methylalkohol auf die Lumineszenzeigenschaften in Szintillationszählern verwendeter Lösungen

Zusammenfassung Bei einigen Aufgaben, z. B. bei der Untersuchung des Alters organischer Überreste, ist es zweckmässig, diese Überreste in solche Stoffe umzuwandeln, die sich in Szintillationszählern verwenden lassen. Eine der Möglichkeiten der Durchführung dieser Aufgabe besteht in der Umwandlung dieser organischen Überreste in einen organischen Stoff, der den Lumineszenzlösungen zugesetzt wird [3, 4].Den einfachsten Stoff dieser Art stellt Methylalkohol dar.Die Aufgabe der vorliegenden Arbeit bestand in der Feststellung des wesentlichen Einflusses von Methylalkohol auf die Wirksamkeit der Lumineszenzlösungen unter verschiedenen Bedingungen.     

Quantum beat of two single photons

The interference of two single photons impinging on a beam splitter is measured in a time-resolved manner. Using long photons of different frequencies emitted from an atom-cavity system, a quantum beat with a visibility close to 100% is observed in the correlation between the photodetections at the output ports of the beam splitter. The time dependence of the beat amplitude reflects the coherence properties of the photons. Most remarkably, simultaneous photodetections are never observed, so that a temporal filter allows one to obtain perfect two-photon coalescence even for nonperfect photons.     

Complex shape evolution of electromigration-driven single-layer islands

The shape evolution of two-dimensional islands through periphery diffusion biased by an electromigration force is studied numerically using a continuum approach. We show that the introduction of crystal anisotropy in the mobility of edge atoms induces a rich variety of migration modes, which include oscillatory and irregular behavior. A phase diagram in the plane of anisotropy strength and island size is constructed. The oscillatory motion can be understood in terms of stable facets that develop on one side of the island, and which the island then slides past. The facet orientations are determined analytically.     

Localization of matter waves in two-dimensional disordered optical potentials

We consider ultracold atoms in 2D disordered optical potentials and calculate microscopic quantities characterizing matter wave quantum transport in the noninteracting regime. We derive the diffusion constant as a function of all relevant microscopic parameters and show that coherent multiple scattering induces significant weak localization effects. In particular, we find that even the strong localization regime is accessible with current experimental techniques and calculate the corresponding localization length.     

Canonical Semigroups of States and Cocycles for the Group of Automorphisms of a Homogeneous Tree

Let G=A ut(T) be the group of automorphisms of a homogeneous tree and let d(v,gv) denote the natural tree distance. Fix a base vertex e in T. The function (g)=exp(–d(e,ge)), being positive definte on G, gives rise to a semigroup of states on G whose infinitesimal generator d/d|₌₀=log() is conditionally positive definite but not positive definite. Hence, log() corresponds to a nontrivial cocycle (g): GH in some representation space H . In contrast with the case of PGL(2,), the representation is not irreducible.Let _o (g) be the derivative of the spherical function corresponding to the complementary series of A ut(T). We show that –d(e,ge) and _o (g) come from cohomologous cocycles. Moreover, _o is associated to one of the two (irreducible) special representations of A ut(T).     

Modeling High-Resolution Broadband Discourse in Complex Adaptive Systems

Numerous researchers and practitioners have turned to complexity science to better understand human systems. Simulation can be used to observe how the microlevel actions of many human agents create emergent structures and novel behavior in complex adaptive systems. In such simulations, communication between human agents is often modeled simply as message passing, where a message or text may transfer data, trigger action, or inform context. Human communication involves more than the transmission of texts and messages, however. Such a perspective is likely to limit the effectiveness and insight that we can gain from simulations, and complexity science itself. In this paper, we propose a model of how close analysis of discursive processes between individuals (high-resolution), which occur simultaneously across a human system (broadband), dynamically evolve. We propose six different processes that describe how evolutionary variation can occur in texts—recontextualization, pruning, chunking, merging, appropriation, and mutation. These process models can facilitate the simulation of high-resolution, broadband discourse processes, and can aid in the analysis of data from such processes. Examples are used to illustrate each process. We make the tentative suggestion that discourse may evolve to the edge of chaos. We conclude with a discussion concerning how high-resolution, broadband discourse data could actually be collected.     

Ein elementarer Beweis des Weierstraßschen Approximationssatzes

Ohne Zusammenfassung