Technical University of Berlin

About: Technical University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Laser & Catalysis. The organization has 27292 authors who have published 59342 publications receiving 1414623 citations. The organization is also known as: Technische Universität Berlin & TU Berlin.

Emergent behavior in active colloids

Abstract: Active colloids are microscopic particles, which self-propel through viscous fluids by converting energy extracted from their environment into directed motion. We first explain how artificial microswimmers move forward by generating near-surface flow fields via self-phoresis or the self-induced Marangoni effect. We then discuss generic features of the dynamics of single active colloids in bulk and in confinement, as well as in the presence of gravity, field gradients, and fluid flow. In the third section, we review the emergent collective behavior of active colloidal suspensions, focusing on their structural and dynamic properties. After summarizing experimental observations, we give an overview of the progress in modeling collectively moving active colloids. While active Brownian particles are heavily used to study collective dynamics on large scales, more advanced methods are necessary to explore the importance of hydrodynamic and phoretic particle interactions. Finally, the relevant physical approaches to quantify the emergent collective behavior are presented.

Zinc Oxide Nanoparticles with Defects

Abstract: Zinc oxide in the form of nanoscale materials can be regarded as one of the most important semiconductor oxides at present. However, the question of how chemical defects influence the properties of nanoscale zinc oxide materials has seldom been addressed. In this paper, we report on the introduction of defects into nanoscale ZnO, their comprehensive analysis using a combination of techniques (powder X-ray diffraction (PXRD), X-ray absorption spectroscopy/extended X-ray absorption fine structure (XAS/EXAFS), electron paramagnetic resonance (EPR), magic-angle spinning nuclear magnetic resonance (MAS-NMR), Fourier-transform infrared (FTIR), UV-vis, and photoluminescence (PL) spectroscopies coupled with ab-initio calculations), and the investigation of correlations between the different types of defects. It is seen that defect-rich zinc oxide can be obtained under kinetically controlled conditions of ZnO formation. This is realized by the thermolysis of molecular, organometallic precursors in which ZnO is pre-organized on a molecular scale. It is seen that these precursors form ZnO at low temperatures far from thermodynamic equilibrium. The resulting nanocrystalline ZnO is rich in defects. Depending on conditions, ZnO of high microstructural strain, high content of oxygen vacancies, and particular content of heteroatom impurities can be obtained. It is shown how the mentioned defects influence the electronic properties of the semiconductor nanoparticles.

Usability, aesthetics and emotions in human–technology interaction

Abstract: In the past, research on human–technology interaction has almost exclusively concentrated on aspects of usefulness and usability. Despite the success of this line of research, its narrow perspective has recently become a target for criticism. To explain why people prefer some systems over others, factors such as aesthetic qualities and emotional experiences play an important role in addition to instrumental aspects. In the following, we report three experiments that illustrate the importance of such factors. In the first experiment, we study the role of emotions in human–technology interaction by using Scherer's (1984) component theory of emotions as a theoretical foundation. A combination of methods is derived from that theory and employed to measure subjective feelings, motor expressions, physiological reactions, cognitive appraisals, and behaviour. The results demonstrate that the manipulation of selected system properties may lead to differences in usability that affect emotional user reactions. The s...