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Iron complexes that model the structural and functional properties of the active iron site in rabbit lipoxygenase are described. The ligand sphere of the mononuclear pseudo-octahedral cis-(carboxylato)(hydroxo)iron(III) complex, which is completed by a tetraazamacrocyclic ligand, reproduces the first coordination shell of the active site in the enzyme. In addition, two corresponding iron(II) complexes are presented that differ in the coordination of a water molecule. In their structural and electronic properties, both the (hydroxo)iron(III) and the (aqua)iron(II) complex reflect well the only two essential states found in the enzymatic mechanism of peroxidation of polyunsaturated fatty acids. Furthermore, the ferric complex is shown to undergo hydrogen atom abstraction reactions with O-H and C-H bonds of suitable substrates, and the bond dissociation free energy of the coordinated water ligand of the ferrous complex is determined to be 72.4 kcal·mol-1. Theoretical investigations of the reactivity support a concerted proton-coupled electron transfer mechanism in close analogy to the initial step in the enzymatic mechanism. The propensity of the (hydroxo)iron(III) complex to undergo H atom abstraction reactions is the basis for its catalytic function in the aerobic peroxidation of 2,4,6-tri(tert-butyl)phenol and its role as a radical initiator in the reaction of dihydroanthracene with oxygen.

The science of the total environment 769, 144324 (2021). doi:10.1016/j.scitotenv.2020.144324, Published by Elsevier Science, Amsterdam [u.a.]

Robotic systems in additive manufacturing (AM) processes offer new possibilities to meet constantly growing requirements for product individualization and small batch sizes. Solids are produced by the layered addition of material, which represents a benefit compared to conventional processes, especially in the production of complex geometries with cavities and undercuts. Recently, research into the entire process of AM from CAD models to the execution of an optimized trajectory has moved into focus. This is motivated by the use of Multidirectional Additive Manufacturing (MDAM) for Wire Arc Additive Manufacturing (WAAM). Since the material is fed eccentrically, the freedom of movement of the welding torch is strongly restricted. The novel procedure of pure manipulation of the component (with six degrees of freedom) can therefore avoid this problem and obtains optimization potentials. This paper gives an overview of the characteristics of MDAM for WAAM processes. Besides an introduction to the extended MDAM process chain, a method for optimizing trajectories is presented and analyzed. To improve the welding result, orientation tolerances are applied to the unique path supporting poses along the welding path. Additionally, implementing a custom cost function for the trajectory optimization has a positive impact on the acceleration and jerk levels. The generated trajectories thus follow the specified welding path with reduced acceleration and jerk.

Understanding internal dose metrics is integral to adequately assess effects environmental contaminants might have on aquatic wildlife, including fish. In silico toxicokinetic (TK) models are a leading approach for quantifying internal exposure metrics for fishes; however, they often do not adequately consider chemicals that are actively biotransformed and have not been validated against early-life stages (ELS) that are often considered the most sensitive to the exposure to contaminants. To address these uncertainties, TK models were parameterized for the rapidly biotransformed chemical benzo[a]pyrene (B[a]P) in embryo-larval and adult life stages of fathead minnows. Biotransformation of B[a]P was determined through measurements of in vitro clearance. Using in vitro-in vivo extrapolation, in vitro clearance was integrated into a multi-compartment TK model for adult fish and a one-compartment model for ELS. Model predictions were validated using measurements of B[a]P metabolites from in vivo flow-through exposures to graded concentrations of water-borne B[a]P. Significantly greater amounts of B[a]P metabolites were observed with exposure to greater concentrations of parent compound in both life stages. However, when assessing biotransformation capacity, no differences in phase I or phase II biotransformation were observed with greater exposures to B[a]P. Results of modelling suggested that biotransformation of B[a]P can be successfully implemented into in silico models to accurately predict life stage-specific abundances of B[a]P metabolites in either whole-body larvae or the bile of adult fish. Models developed increase the scope of applications in which TK models can be used to support environmental risk assessments.

The assessment of the exposure of aquatic wildlife to complex environmental mixtures of chemicals originating from both point and diffuse sources and evaluating the potential impact thereof constitutes a significant step towards mitigating toxic pressure and the improvement of ecological status. In the current proof-of-concept study, we demonstrate the potential of a novel Aggregated Biomarker Response (ABR) approach involving a comprehensive set of biomarkers to identify complex exposure and impacts on wild brown trout (Salmo trutta fario). Our scenario used a small lowland river in Germany (Holtemme river in the Elbe river catchment) impacted by two wastewater treatment plants (WWTP) and diffuse agricultural runoff as a case study. The trout were collected along a pollution gradient (characterised in a parallel study) in the river. Compared to fish from the reference site upstream of the first WWTP, the trout collected downstream of the WWTPs showed a significant increase in micronucleus formation, phase I and II enzyme activities, and oxidative stress parameters in agreement with increasing exposure to various chemicals. By integrating single biomarker responses into an aggregated biomarker response, the two WWTPs' contribution to the observed toxicity could be clearly differentiated. The ABR results were supported by chemical analyses and whole transcriptome data, which revealed alterations of steroid biosynthesis and associated pathways, including an anti-androgenic effect, as some of the key drivers of the observed toxicity. Overall, this combined approach of in situ biomarker responses complemented with molecular pathway analysis allowed for a comprehensive ecotoxicological assessment of fish along the river. This study provides evidence for specific hazard potentials caused by mixtures of agricultural and WWTP derived chemicals at sublethal concentrations. Using aggregated biomarker responses combined with chemical analyses enabled an evidence-based ranking of sites with different degrees of pollution according to toxic stress and observed effects.

Journal of physics / Condensed matter Condensed matter 32(16), 165801 - (2020). doi:10.1088/1361-648X/ab678c, Published by IOP Publ., Bristol

Moderne Robotersysteme sind ein Kernelement der Industrie 4.0, um die Flexibilisierung und Individualisierung der Produktion bis zur Losgrose Eins bei hoher Ressourceneffizienz umzusetzen. Ein Ziel, das nur mit umfassender Automatisierung und Digitalisierung der gesamten Wertschopfungskette zu erreichen sein wird. Innerhalb dieser Wertschopfungskette gilt es die richtigen Roboter mit den richtigen Fahigkeiten, zur richtigen Zeit am richtigen Ort verfugbar zu haben.

This paper gives an overview of current research topics at the Institute of Mechanism Theory, Machine Dynamics and Robotics of RWTH Aachen University. A variety of application areas is introduced, including robotic reconstruction, agile production, additive manufacturing and human-robot collaboration. Each topic offers novel and unique contributions to its field of robotics.

The manipulation of the magnetism of self-assembled iron oxide nanoparticle (NP) monolayers on top of BaTiO3 (BTO) single crystals is reported. We observe strain induced magnetoelectric coupling (MEC) as shown by measurements of both the magnetization and magneto-electric AC susceptibility (MEACS). The magnetization, coercivity, remanent magnetization and MEACS signal as a function of temperature show abrupt jumps at the BTO phase transition temperatures. Hereby the jump values are opposite for in-plane and out-of-plane measurements. Grazing incidence small angle X-ray scattering (GISAXS) and scanning electron microscopy (SEM) confirm a hexagonal close-packed supercrystalline order of the NP monolayers. Cross-sectional scanning transmission electron microscopy (STEM) experiments provide information about the layer structure of the sample. This work opens up viable possibilities for fabricating energy-efficient electronic devices by self-assembly techniques.

Motivated by the new master program Robotic Systems Engineering at RWTH Aachen University, the existing robotic education at the Institute of Mechanism Theory, Machine Dynamics and Robotics (IGMR) was updated. The new modules Robotic Systems and Advanced Robotic Kinematics and Dynamics cover multiple core areas of robotics. Robotic Systems focuses on robotic application, manipulator and process structures, while Advanced Robotic Kinematics and Dynamics teaches all kinematic, dynamic and control computations needed for accurate robotic motion and trajectory planning. To complete the round off the teaching, both modules are accompanied by practical exercises. A Robot Education Cell in conjunction with the Roboguide software offers students the opportunity to expand their theoretical knowledge of industrial robots and processes independently within the framework of projects. In order to consolidate theoretical knowledge on robotic computations, a MATLAB environment is provided, which enables students to solve tasks independently. This environment is characterized by the automated evaluation of the submitted solutions.