Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.Comment: 10 pages, 5 figure

Intensity Thresholds and the Statistics of the Temporal Occurrence of Solar Flares

Introducing thresholds to analyze time series of emission from the Sun enables a new and simple definition of solar flare events, and their interoccurrence times. Rescaling time by the rate of events, the waiting and quiet time distributions both conform to scaling functions that are independent of the intensity threshold over a wide range. The scaling functions are well described by a two parameter function, with parameters that depend on the phase of the solar cycle. For flares identified according to the current, standard definition, similar behavior is found.Comment: 5 pages, 4 figures, revtex

Beyond Games: A Systematic Review of Neural Monte Carlo Tree Search Applications

The advent of AlphaGo and its successors marked the beginning of a new paradigm in playing games using artificial intelligence. This was achieved by combining Monte Carlo tree search, a planning procedure, and deep learning. While the impact on the domain of games has been undeniable, it is less clear how useful similar approaches are in applications beyond games and how they need to be adapted from the original methodology. We review 129 peer-reviewed articles detailing the application of neural Monte Carlo tree search methods in domains other than games. Our goal is to systematically assess how such methods are structured in practice and if their success can be extended to other domains. We find applications in a variety of domains, many distinct ways of guiding the tree search using learned policy and value functions, and various training methods. Our review maps the current landscape of algorithms in the family of neural monte carlo tree search as they are applied to practical problems, which is a first step towards a more principled way of designing such algorithms for specific problems and their requirements.Comment: 38 pages, 14 figures, submitted to Springer Applied Intelligenc

Communication Between Process and Structure: Modelling and Simulating Message Reference Networks with COM/TE

Focusing on observable message signs and referencing structures, communication processes can be described and analysed as message reference networks which are characterized by dynamic pattern evolution. Computational simulation provides a way of obtaining insights into the factors driving such processes. Our paper describes a theoretical framework for communication-oriented modelling — the COM approach — that is centred around the notion of social visibility as a reputation mechanism. The approach contrasts with agent-based social networks on the one hand, and with bibliometric document networks on the other. In introducing our simulation environment COM/TE, typical properties of message reference networks are discussed in terms of a case study which deals with the impact of different media and styles of communication on emergent patterns of social visibility.Communication, Communication-Oriented Modelling, Message Sign, Dynamic Networks, Bottom-up Approach, Temporality, Social Visibility, Reputation, Socionics

Mimesis, Widerstand, Subversion : Bettina von Arnims Briefroman Die Günderode als Ansatz diskursiver Entgrenzung

Bibliography: pages 166-171.Bettina von Arnims novel Die Günderode was written during the period of early German romanticism. The novel consists of an exchange of letters between the literary figure Bettine and an opposite, Gunderode. This exchange takes place in the light of the philosophical discourse of German idealism, mainly represented by Johann Gottlieb Fichte, which excludes women as independent subjects. The novel reveals Bettine's dissatisfaction about her exclusion as a woman within the discourse of idealism. As Bettine realizes her non-representation in the existing discourse of her time she develops distinct writing techniques in order to discover her own subjectivity. She comes to the conclusion, however, that as a woman she can neither be represented in the prevailing discourse nor in another alternative "female" discourse. Using the feminist theoretical framework of Luce lrigaray, in particular her book Das Geschlecht, das nicht eins ist, the author investigates the discursive nature of German idealism and comes to the conclusion that it is essentially a male discourse. The author then analyses Bettine's attempts to liberate herself from male discourse using lrigaray. The author concludes that Bettine's writing technique corresponds to a great extent with the concepts formulated by Irigaray. While Bettine is able to undermine and subvert male discourse, she is aware that she cannot establish a new alternative discourse in which her subjectivity is fully represented

Wie sich die Kommunikation ordnet. Anmerkungen zur kommunikationsorientierten Modellierung sozialer Sicht­barkeit

Ordnungsbildung und Erkenntnis bedingen einander. Erkenntnis setzt die Beobachtung von Ordnungsstrukturen voraus oder deren Schöpfung durch Abstraktion und Modellbildung. Beiträge aus unterschiedlichen Bereichen universitärer Forschung untersuchen Strukturen, die einen Bezug haben zu (partiell) autonomen Akteuren (beziehungsweise Agierenden, Agenten) und den dynamischen Prozessen, in denen sie entwickelt werden. Dabei ablaufende Erkenntnisprozesse erfordern interobjektiv erfahrbare, teilweise auch in Symbolik und Ritualen fassbare Ordnungsstrukturen, auch wenn diese erst simultan mit Handlungs- oder Erkenntnisprozessen entstehen. Rekursive Bezüge können zu Formen der Selbstorganisation führen. Bei höher entwickelten Strukturen können Aspekte des Wissens, Lernens (und Vergessens) einbezogen werden und zusätzlich durch emotionale Zustände verstärkt oder abgeschwächt werden. • Wie entstehen Struktur und Ordnung? • Wie werden sie stabilisiert, modifiziert, revolutioniert, restabilisiert? • Wie werden sie zerstört und aufgelöst? • Wie lässt sich das Verhältnis von Ordnung/Struktur und Wandel/Prozess fassen und (gegebenenfalls formal oder im Rechner) modellieren? • Welche institutionalisierten Mechanismen spielen dabei welche Rolle? • Wie prägen diese Mechanismen die Auseinandersetzungen zwischen Akteuren um "richtiges" und "falsches" Handeln und " richtiges" und "falsches" Wissen von diesem Handeln (Realitätsdefinitionen, Ordnungs- und Zielvorstellungen, Legitimationen)? • Welche Wechselwirkungen bestehen zwischen "stummen" Verhaltensordnungen (Handeln) und "beredter" symbolvermittelter Reflexion eben dieser Verhaltensordnungen (Reden und Wissen)? Wissenschaftlerinnen und Wissenschaftler hatten sich am 5.9.2005 an der Universität Hamburg zu einem Workshop über "Ordnungsbildung und Erkenntnisprozesse" zusammengefunden. In diesem Band sind zahlreiche der gehaltenen Beiträge gesammeltFormation of order and cognition are interdependent. Knowledge presupposes the observation of order structures or their creation through abstraction and modelling. Contributions from different areas of university research examine structures that relate to (partially) autonomous actors (or agents) and the dynamic processes in which they are developed. Processes of knowledge that take place in this context require structures of order that can be experienced interobjectively, and in some cases can also be grasped in symbolism and rituals, even if these structures are created simultaneously with processes of action or knowledge. Recursive references can lead to forms of self-organization. In more highly developed structures, aspects of knowledge, learning (and forgetting) can be included and additionally strengthened or weakened by emotional states. On November 5, 2005, scientists came together for a workshop on "Formation of Order and Knowledge Processes" at the University of Hamburg. In this volume, numerous of the given talks and articles are collected

Artificial quantum confinement in LAO3/STO heterostructure

Heterostructures of transition metal oxides (TMO) perovskites represent an ideal platform to explore exotic phenomena involving the complex interplay between the spin, charge, orbital and lattice degrees of freedom available in these compounds. At the interface between such materials, this interplay can lead to phenomena that are present in none of the original constituents such as the formation of the interfacial 2D electron system (2DES) discovered at the LAO3/STO3 (LAO/STO) interface. In samples prepared by growing a LAO layer onto a STO substrate, the 2DES is confined in a band bending potential well, whose width is set by the interface charge density and the STO dielectric properties, and determines the electronic band structure. Growing LAO (2 nm) /STO (x nm)/LAO (2 nm) heterostructures on STO substrates allows us to control the extension of the confining potential of the top 2DES via the thickness of the STO layer. In such samples, we explore the dependence of the electronic structure on the width of the confining potential using soft X-ray ARPES combined with ab-initio calculations. The results indicate that varying the thickness of the STO film modifies the quantization of the 3d t2g bands and, interestingly, redistributes the charge between the dxy and dxz/dyz bands