Deterministic Autopoietic Automata

This paper studies two issues related to the paper on Computing by Self-reproduction: Autopoietic Automata by Jiri Wiedermann. It is shown that all results presented there extend to deterministic computations. In particular, nondeterminism is not needed for a lineage to generate all autopoietic automata

The complexity of presburger arithmetic with bounded quantifier alternation depth

AbstractIt is shown how the method of Fischer and Rabin can be extended to get good lower bounds for Presburger arithmetic with a bounded number of quantifier alternations. In this case, the complexity is one exponential lower than in the unbounded case. This situation is typical for first order theories

The application of Cu(I) phenanthroline dyes in DSCs with optimized I⁻/I₃⁻ and Co(II/III) electrolytes

The world faces an energy and climate crisis. After an unprecedented worldwide increase in energy consumption, which has largely been based on the use of fossil fuels, mankind is challenged by global warming and its consequences. The demand for renewable energy has focused our attention on capturing the inexhaustible solar energy. Photovoltaic (PV) devices based on silicon have been and remain the most popular choice. However, the high purity demands of this technique are a drawback for cheap energy production from solar power. Dye sensitized solar cells (DSCs) are a valuable alternative for low-cost PVs since the separation of light-harvesting and charge transport implicates less stringent purity demands of the built-in compositions. Replacing rare ruthenium used in Grätzel-type n-type DSCs by more Earthabundant and sustainable metals is a goal of our research group. This thesis describes the use of heteroleptic Cu(I) dyes using phenanthroline ancillary ligands to harvest light. Chapter 1 gives a short overview of the current energy problems and outlines the current status of the literature relevant to this thesis. Chapter 2 describes the methods for the characterization of the investigated dyes and their application in dye sensitized solar cells (DSCs). Chapter 3 shows the synthesis and characterization of ligands and of copper(I) complexes designed for application in DSCs. Chapter 4 compares the performances of DSCs containing heteroleptic Cu(I) complexes made from [Cu(13)2][PF6] (ligand 13 contains a peripheral hole-transporting NPh2 group) and four different anchoring ligands with carboxylic acid (ALC1) or phosphonic acid (ALP, ALP1 and ALP1 TBA) anchors. Chapter 5 investigates the differences between heteroleptic Cu(I) dyes from several phenanthroline based ancillary ligands in combination with anchoring ligand ALP1. Chapter 6 deals with the optimization of I−/I3− electrolytes for [Cu(15)(ALP1)]+ sensitized solar cells (ligand 15 contains a peripheral hole-transporting domain related to that in ligand 13). Chapter 7 shows the incorporation of [Co(bpy)3][PF6]2/3 electrolyte in DSCs using [Cu(13)(ALP1)]+ and [Cu(15)(ALP1)]+ sensitizers. Chapter 8 lists the experimental details. Chapter 9 concludes the work and gives an outlook for future work

Modeling, scaling and sequencing writing phases of Swiss television journalists

Writing phases – defined as identifiable temporal procedural units with typical dominant writing actions such as formulating or source reading – have long been conceived fundamental for the success of writing processes. However, the methodology for an objectively verifiable analysis of the nature and interplay of writing phases has not yet been developed. Also, most of the current scientific concepts of writing phases are based on introspection, single case studies or experimental research designs. This thesis drew on one of the most extensive data collections of writing processes in natural settings: Over 120 multimodal writing processes of Swiss television journalists were recorded, annotated and merged into one dataset. Since the data was collected in an ethnographic research framework, writing activities such as insertions or deletions could be related to background conditions such as the writing environment, the writing task and the experience of the writers. In a first methodological step, the writing processes were coded qualitatively, and writing phases on different scales and timeframes were identified. Based on the time series format of the data, statistical models of scalable writing phases were developed in a second step, which enabled automated detection of writing phases in the corpus in a third step. In a fourth step, the effect of sequences of writing phases on writing processes and products was investigated. As a result, phases and their sequence in natural writing processes were described and explained, which contributes to both theoretical and practical endeavors of applied linguistics. From a theoretical perspective, the concept of the writing phase and its relation to writing practices were clarified and refined on a strong empirical basis. From a practical perspective, the thesis provides tools for the process oriented, domain specific teaching of writing

An Improvement of Reed's Treewidth Approximation

We present a new approximation algorithm for the treewidth problem which constructs a corresponding tree decomposition as well. Our algorithm is a faster variation of Reed's classical algorithm. For the benefit of the reader, and to be able to compare these two algorithms, we start with a detailed time analysis for Reed's algorithm. We fill in many details that have been omitted in Reed's paper. Computing tree decompositions parameterized by the treewidth $k$ is fixed parameter tractable (FPT), meaning that there are algorithms running in time $O(f(k) g(n))$ where $f$ is a computable function, $g$ is a polynomial function, and $n$ is the number of vertices. An analysis of Reed's algorithm shows $f(k) = 2^{O(k \log k)}$ and $g(n) = n \log n$ for a 5-approximation. Reed simply claims time $O(n \log n)$ for bounded $k$ for his constant factor approximation algorithm, but the bound of $2^{\Omega(k \log k)} n \log n$ is well known. From a practical point of view, we notice that the time of Reed's algorithm also contains a term of $O(k^2 2^{24k} n \log n)$, which for small $k$ is much worse than the asymptotically leading term of $2^{O(k \log k)} n \log n$. We analyze $f(k)$ more precisely, because the purpose of this paper is to improve the running times for all reasonably small values of $k$. Our algorithm runs in $\mathcal{O}(f(k)n\log{n})$ too, but with a much smaller dependence on $k$. In our case, $f(k) = 2^{\mathcal{O}(k)}$. This algorithm is simple and fast, especially for small values of $k$. We should mention that Bodlaender et al.\ [2016] have an asymptotically faster algorithm running in time $2^{\mathcal{O}(k)} n$. It relies on a very sophisticated data structure and does not claim to be useful for small values of $k$

Approximately Counting Embeddings into Random Graphs

Let H be a graph, and let C_H(G) be the number of (subgraph isomorphic) copies of H contained in a graph G. We investigate the fundamental problem of estimating C_H(G). Previous results cover only a few specific instances of this general problem, for example, the case when H has degree at most one (monomer-dimer problem). In this paper, we present the first general subcase of the subgraph isomorphism counting problem which is almost always efficiently approximable. The results rely on a new graph decomposition technique. Informally, the decomposition is a labeling of the vertices such that every edge is between vertices with different labels and for every vertex all neighbors with a higher label have identical labels. The labeling implicitly generates a sequence of bipartite graphs which permits us to break the problem of counting embeddings of large subgraphs into that of counting embeddings of small subgraphs. Using this method, we present a simple randomized algorithm for the counting problem. For all decomposable graphs H and all graphs G, the algorithm is an unbiased estimator. Furthermore, for all graphs H having a decomposition where each of the bipartite graphs generated is small and almost all graphs G, the algorithm is a fully polynomial randomized approximation scheme. We show that the graph classes of H for which we obtain a fully polynomial randomized approximation scheme for almost all G includes graphs of degree at most two, bounded-degree forests, bounded-length grid graphs, subdivision of bounded-degree graphs, and major subclasses of outerplanar graphs, series-parallel graphs and planar graphs, whereas unbounded-length grid graphs are excluded.Comment: Earlier version appeared in Random 2008. Fixed an typo in Definition 3.