Explanatory and illustrative visualization of special and general relativity

This paper describes methods for explanatory and illustrative visualizations used to communicate aspects of Einstein's theories of special and general relativity, their geometric structure, and of the related fields of cosmology and astrophysics. Our illustrations target a general audience of laypersons interested in relativity. We discuss visualization strategies, motivated by physics education and the didactics of mathematics, and describe what kind of visualization methods have proven to be useful for different types of media, such as still images in popular science magazines, film contributions to TV shows, oral presentations, or interactive museum installations. Our primary approach is to adopt an egocentric point of view: the recipients of a visualization participate in a visually enriched thought experiment that allows them to experience or explore a relativistic scenario. In addition, we often combine egocentric visualizations with more abstract illustrations based on an outside view in order to provide several presentations of the same phenomenon. Although our visualization tools often build upon existing methods and implementations, the underlying techniques have been improved by several novel technical contributions like image-based special relativistic rendering on GPUs, special relativistic 4D ray tracing for accelerating scene objects, an extension of general relativistic ray tracing to manifolds described by multiple charts, GPU-based interactive visualization of gravitational light deflection, as well as planetary terrain rendering. The usefulness and effectiveness of our visualizations are demonstrated by reporting on experiences with, and feedback from, recipients of visualizations and collaborators.     

Rational design of highly active and selective ligands for the alpha5beta1 integrin receptor

The inhibition of integrin function is a major challenge in medicinal chemistry. Potent ligands are currently in different stages of clinical trials for the antiangiogenic therapy of cancer and age-related macula degeneration (AMD). The subtype alpha5beta1 has recently been drawn into the focus of research because of its genuine role in angiogenesis. In our previous work we could demonstrate that the lack of structural information about the receptor could be overcome by a homology model based on the X-ray structure of the alphavbeta3 integrin subtype and the sequence similarities between both receptors. In this work, we describe the rational design and synthesis of high affinity alpha5beta1 binders, and the optimisation of selectivity against alphavbeta3 by means of extensive SAR studies and docking experiments. A first series of compounds based on the tyrosine scaffold resulted in affinities in the low and even subnanomolar range and selectivities of 400-fold against alphavbeta3. The insights about the structure-activity relationship gained from tyrosine-based ligands could be successfully transferred to ligands that bear an aza-glycine scaffold to yield alpha5beta1 ligands with affinities of approximately 1 nm and selectivities that exceed 10(4)-fold. The ligands have already been successfully employed as selective alpha5beta1 ligands in biological research and might serve as lead structures for antiangiogenic cancer therapy.     

Size effects on Raman spectra of small CdSe nanoparticles in polymer films

The results of a resonant Raman scattering (RRS) study of polymer-stabilized colloidal CdSe nanoparticles (NPs) are reported. The size-selective nature of the RRS is demonstrated by analysing the NP ensembles with different average size [Formula: see text] and size distribution Δd using a set of excitation wavelengths. The effect of size selection on the estimation of [Formula: see text] and Δd values from the RRS spectra is discussed, as well as some peculiarities of RRS on surface optical phonons. From the experimentally observed small variation of the I(2LO)/I(LO) ratio for 2-5?nm NPs a minor effect of [Formula: see text] on the electron-phonon coupling strength in this [Formula: see text] range is supposed.     

Natural graphite filled polyolefins — electrical and electrochemical behavior

Composite materials with 80 wt.-% natural graphite and 20 wt.-% polyolefins have been characterized for their application as positive electrodes in batteries. With respect to graphite, resistivity is enhanced by a factor of 10⁴ (ρ = 1–10 Ωcm), and the anisotropy factor is lowered to 10. A thin polymer film barrier and/or a thin bilayer of graphite surface groups between the graphite flakes, crossed by electron tunneling, is responsible for this and for a pronounced field effect of resistivity. The presence of a polymer binder is also indicated by a formation effect in the course of the first anion intercalation cycles performed by electrochemical experiments. Long term cycling of a model cell reveals a strong influence of the mechanical properties of the polyolefin binders. Those with high tensile strength lead to a much poorer cycle life than those with low tensile strength, where cycle numbers up to 5000 (one hour charge) have been obtained. The latter material has an improved compatibility to the periodical volume alterations in the course of electrochemical cycling.     

Optimization of multi-wavelength interdigital dielectrometryinstrumentation and algorithms

Interdigital frequency-wavelength dielectrometry can be used to measure the dielectric permittivity and conductivity of insulating materials. The complex dielectric permittivity is directly related to other material properties, such as moisture content, temperature, concentration of impurities and additives, density, aging status, etc. The analysis of spatial and temporal variations of these properties lends valuable insights into physical phenomena which take place in electrical equipment, provides instrumentation for system monitoring and diagnostics, and can be used for optimization of design and performance of electrical apparatus. The optimization of various aspects of this technology is described in this paper. Improvement of performance is achieved through variation of geometrical design, materials, manufacturing processes, and electronic circuitry. Accumulated effects of non-ideal geometry of the experimental setup and the sensor itself are accounted for through empirical measurements, calibration, and use of finite-element calculations. Three distinct operating modes are developed: floating voltage with grounded backplane, floating voltage with guarded backplane, and short circuit current. Measurements reveal that the interfacial contact quality has a strong influence on the sensor's response. Gain/phase measurements over the frequency range 5 mHz to 10 kHz agree well with theoretical calculations on the interfacial contact quality. Full-frequency measurements for several liquid and solid dielectrics are shown to have a good match with theoretical predictions     

Detection and resolution of normative conflicts in multi-agent systems: a literature survey

Multi-agents systems are composed of autonomous and possibly heterogeneous software agents that act according to their own interests. Some coordination mechanism must be adopted to ensure a proper functioning of the whole system. Norms can be viewed as a powerful means to regulate and influence the behaviour of the agents by specifying, for instance, obligations, permissions, or prohibitions in a given context. A critical issue that must be considered in a system governed by multiple norms is the possible existence of normative conflicts. A conflict between norms is a situation in which the fulfilment of a norm causes a violation of another one. In this paper, we present several techniques that have been proposed to detect and resolve normative conflicts in multi-agent systems. Our aim is to organize the literature, present a classification of the techniques found, and provide a means to compare alternative approaches dealing with normative conflicts.     

Impact of Excitation and Material Parameters on the Efficiency of Ultrasonic Cutting of Bakery Products

ABSTRACT: Cutting with tools excited by ultrasound is increasingly applied in the food industry, especially for cheese, confectionary, and bakery products. Due to the lack of a thorough understanding of the separation process, most of the ultrasonic cutting systems are designed and applied on the basis of empirical knowledge. The aim of the study was to elaborate the impact of ultrasonic parameters, that is, amplitude and frequency, on the cutting process, and special emphasis was placed on resulting effects in the close vicinity of the cutting edge, which are reflected by the separation forces. To allow a direct investigation of the mechanical separation without artifacts due to secondary effects such as melting and cavitation, the crumb of different bakery products (for example, dark and white bread, yeast dumplings, and cake) were analyzed. The results show that the influence of ultrasonic amplitude and frequency can be expressed by the maximum vibration speed on the cutting edge. For each product, an increasing maximum vibration speed results in a particular reduction of the cutting force and an increased quality of the cut. The magnitude of the cutting force reduction is inversely related to a material-specific parameter c_x, which was calculated from the mechanical properties according to the speed-of-sound concept. Therefore, the determination of c_x allows a specific adjustment of ultrasonic amplitude and frequency to achieve optimum cutting quality.     

Alternative Anschlußbewehrung für im Fundament eingespannte Stützen und Wände

Alternative Detail of the Connection Reinforcement for Columns and Walls fixed at the Footing The paper suggests an alternative detail for the connection reinforcement transferring the bending moments at the base of fixed columns and walls to their foundation. In contrast to the typically used interlocking L‐shaped starter bars, the suggested connection reinforcement is in the form of U‐bars, thus greatly improving the constructability. The performance of U‐shaped starter bars was experimentally investigated in two test series and by comparative parameter studies using nonlinear finite element analyses. The results of these investigations are presented and discussed herein.