Exchange effects in spin polarized transport through carbon nanotube quantum dots

We investigate linear and nonlinear transport across single-walled carbon nanotube quantum dots weakly coupled to spin-polarized leads. We consider tubes of finite length and small diameter, where not only forward scattering contributions of the Coulomb potential, but also short-ranged processes play an important role. In particular, they induce exchange effects leading for electron fillings 4n+2 either to a non-degenerate groundstate of spin S=0 or to a triplet groundstate. In the linear regime we present analytical results for the conductance - for both the S=0 and the triplet groundstate - and demonstrate that an external magnetic field is crucial to reveal the spin nature of the groundstates. In the nonlinear regime we show stability diagrams that clearly distinguish between the different groundstates. We observe a negative differential conductance (NDC) effect in the S=0 groundstate for antiparallel lead magnetization. In presence of an external magnetic field spin blockade effects can be detected, again leading to NDC effects for both groundstates.Comment: 13 pages, 15 figures, 2 tables; revised published versio

Bericht über das vom DGfE-Vorstand veranstaltete Roundtable-Gespräch \u27Digitales Publizieren und neues Urheberrecht\u27 am 24.10.2008 in Berlin

Die Diskussion des Roundtable-Gesprächs konzentrierte sich vor allem auf drei Fragenkomplexe, die hier zusammengefasst werden: 1) die absehbaren bzw. zu erwartenden Veränderungen des wissenschaftlichen Publizierens, 2) die Besonderheiten, die dabei im Blick auf die Erziehungswissenschaft als spezifische scientific community zu berücksichtigen sind, und 3) die Aufgaben, die auf die verschiedenen Akteure wie Verlage, Bibliotheken, WissenschaftlerInnen, Fachgesellschaften etc. zukommen. (DIPF/Orig.

Dealing with Discrimination and the Struggle for Social Advancement in Migrant Families: Theoretical and Methodo - logical Aspects of a Study on Adolescent Generational Dynamics in Turkish Migrant Families Subjected to Marginalization

What are the effects of experiences of discrimination on the adolescent process of detachment from the family? What strategies and forms do migrant families develop to deal with discrimination and how do parents’ ways of contending with discrimination affect those of their sons? Those are the central questions addressed by this study of the educational careers and adolescent detachment processes of sons from Turkish migrant families. Foregrounding the theoretical and methodological approaches, the study examines how the strategies handed specifically to sons influence their personal and educational histories. One of our findings is that the ways adolescents are able to address experiences of discrimination are heavily influenced by intergenerational communication processes

ZEBISTIS tools and technologies for energy : energy toolbox

One target of the ZEBISTIS-project was to find frame values for the planning of Zero Emission Buildings (ZEB) in the contributing countries (Germany, Switzerland, Korea, and Turkey). According to this separate toolboxes for energy, water, and biomass were defined. The energy toolbox refers to the “backbone” of every ZEB, which should lead to a massive reduction of the energy consumption

"Veränderungen von Leuten, die etwas verändern wollen": über symbolische Gewalt und Bildungsprozesse in Emine Sevgi Özdamars Roman "Die Brücke vom Goldenen Horn"

'Ausgehend von einem Bildungsbegriff, der Bildung als Transformation grundlegender Figuren des Welt- und Selbstverhältnisses in Auseinandersetzung mit neuartigen Herausforderungen versteht, wird danach gefragt, wie solche Bildungsprozesse trotz der relativen Stabilität gesellschaftlicher Machtstrukturen und trotz der subtilen Wirkungsweisen symbolischer Gewalt im Sinne Bourdieus möglich sind. Özdamars Roman wird dabei einerseits interpretiert als eindringliche Darstellung der Mechanismen symbolischer Gewalt am Arbeitsplatz, in der politischen Öffentlichkeit und in der Familie, und andererseits als gelungene Inszenierung einer subversiven Infragestellung dieser Gewalt, die ihren Rückhalt findet in kommunikativen Orten einer Art Gegenöffentlichkeit und im verfremdenden Gebrauch vorherrschender Sprachmuster.' (Autorenreferat)'Conceiving of individual development as of change occurring in the patterns of a subject's relations to the world and to his or herself and brought about by coping with novel challenges, the paper addresses the issue of how - in spite of the relative stability of power structures and notwithstanding the subtle modes of action of symbolic violence as described by Bourdieu - such processes of individual development are at all possible. Özdamar's novel is interpreted, on the one hand, as a vivid description of the mechanisms of symbolic violence operating at the workplace, in the political public and in the family and, on the other hand, as a successful enactment of subversive forms of challenging this violence, which find their support in the communicational sites of a kind of counter public and in the defamiliarizing use of hegemonic speech patterns.' (author's abstract)

Energy toolbox : framework for the development of a tool for the primary design of zero emission buildings in european and asian cities

This paper discusses the framework for the development of an Energy Toolbox (ETB). The aim of the ETB is to support the design of domestic Zero Emission Buildings (ZEBs), according to the concept of net zero-energy buildings during the early architectural design and planning phases. The ETB concept is based on the calculation of the energy demand for heating, cooling, lighting, and appliances. Based on a building’s energy demand, technologies for the onsite conversion and production of the specific forms and quantities of final and primary energy by means of renewable energy carriers can be identified. The calculations of the ETB are based on the building envelope properties of a primary building design, as well as the physical and climate parameters required for the calculation of heat transfer coefficients, heat gains, and heat losses. The ETB enables the selection and rough dimensioning of technologies and systems to meet, and, wherever possible, reduce the thermal and electric energy demand of a building. The technologies included comprise green facades, adaptable dynamic lighting, shading devices, heat pumps, photovoltaic generators, solar thermal collectors, adiabatic cooling, and thermal storage. The ETB facilitates the balancing of the energy consumption and the production of renewable energies of a primary building design

Towards Label Embedding -- Measuring classification difficulty

Uncertainty quantification in machine learning is a timely and vast field of research. In supervised learning, uncertainty can already occur in the very first stage of the training process, the labelling step. In particular, this is the case when not every instance can be unambiguously classified. The problem occurs for classifying instances, where classes may overlap or instances can not be clearly categorised. In other words, there is inevitable ambiguity in the annotation step and not necessarily a 'ground truth'. We look exemplary at the classification of satellite images. Each image is annotated independently by multiple labellers and classified into local climate zones (LCZs). For each instance we have multiple votes, leading to a distribution of labels rather than a single value. The main idea of this work is that we do not assume a ground truth label but embed the votes into a K-dimensional space, with K as the number of possible categories. The embedding is derived from the voting distribution in a Bayesian setup, modelled via a Dirichlet-Multinomial model. We estimate the model and posteriors using a stochastic Expectation Maximisation algorithm with Markov Chain Monte Carlo steps. While we focus on the particular example of LCZ classification, the methods developed in this paper readily extend to other situations where multiple annotators independently label texts or images. We also apply our approach to two other benchmark datasets for image classification to demonstrate this. Besides the embeddings themselves, we can investigate the resulting correlation matrices, which can be seen as generalised confusion matrices and reflect the semantic similarities of the original classes very well for all three exemplary datasets. The insights gained are valuable and can serve as general label embedding if a single ground truth per observation cannot be guaranteed