Bose-Einstein condensation of alkaline earth atoms: 40^{40}{Ca}

We have achieved Bose-Einstein condensation of $^{40}$Ca, the first for an alkaline earth element. The influence of elastic and inelastic collisions associated with the large ground state s-wave scattering length of $^{40}$Ca was measured. From these findings, an optimized loading and cooling scheme was developed that allowed us to condense about $2 \cdot 10^4$ atoms after laser cooling in a two-stage magneto-optical trap and subsequent forced evaporation in a crossed dipole trap within less than 3 s. The condensation of an alkaline earth element opens novel opportunities for precision measurements on the narrow intercombination lines as well as investigations of molecular states at the $^1$S--$^3$P asymptotes

Entwicklung, Produktion und Qualitätssicherung urgeformter Mikrobauteile aus metallischen und keramischen Werkstoffen : Abschlussbericht Sonderforschungsbereich 499 (KIT Scientific Reports ; 7607)

Im Sonderforschungsbereich 499 wird die gesamte Prozesskette für die urformen­den Fertigungsverfahren Pulverspritzgießen und Mikrogießen von mechanisch hoch beanspruchbaren Mikrobauteilen aus Keramik und Metalllegierungen entwickelt. Um die Umsetzung der Forschungsergebnisse in die industrielle Anwendung gewährleisten zu können, wird die Produktentstehungskette von der Konstruktion und Simulation über die Prozessvorbereitung, die Produktionsverfahren einschließlich der Qualitätssicherung bis zur Ermittlung geometrischer, mechanischer und tribologischer Bauteileigenschaften durchdrungen

Towards Semantic Integration of Federated Research Data

Digitization of the research (data) lifecycle has created a galaxy of data nodes that are often characterized by sparse interoperability. With the start of the European Open Science Cloud in November 2018 and facing the upcoming call for the creation of the National Research Data Infrastructure (NFDI), researchers and infrastructure providers will need to harmonize their data efforts. In this article, we propose a recently initiated proof-of-concept towards a network of semantically harmonized Research Data Management (RDM) systems. This includes a network of research data management and publication systems with semantic integration at three levels, namely, data, metadata, and schema. As such, an ecosystem for agile, evolutionary ontology development, and the community-driven definition of quality criteria and classification schemes for scientific domains will be created. In contrast to the classical data repository approach, this process will allow for cross-repository as well as cross-domain data discovery, integration, and collaboration and will lead to open and interoperable data portals throughout the scientific domains. At the joint lab of L3S research center and TIB Leibniz Information Center for Science and Technology in Hanover, we are developing a solution based on a customized distribution of CKAN called the Leibniz Data Manager (LDM). LDM utilizes the CKAN’s harvesting functionality to exchange metadata using the DCAT vocabulary. By adding the concept of semantic schema to LDM, it will contribute to realizing the FAIR paradigm. Variables, their attributes and relationships of a dataset will improve findability and accessibility and can be processed by humans or machines across scientific domains. We argue that it is crucial for the RDM development in Germany that domain-specific data silos should be the exception, and that a semantically-linked network of generic and domain-specific research data systems and services at national, regional, and organization levels should be promoted within the NFDI initiative

Instrumented indentation at elevated temperatures for determination of material properties of fusion relevant materials

The testing of small sized samples is an important advantage of the instrumented indentation with re- spect to the investigation of materials for fusion application. A continuous recording of the indentation depth and force enables a determination of mechanical properties of the tested material. In this study, the results of the high temperature experiments with a custom made indentation device are presented. The reduced activation ferritic martensitic steel EUROFER is investigated in an unirradiated state with spherical tips and for the first time Vickers tips at increasing temperatures up to 500 °C. The indentation procedure is numerically simulated at different temperatures and the corresponding load-displacement-data are compared with the experimental results. A quantification of the influence of variations of the indentation tip radius is presented as well. Finally, the operation of the indentation device with respect to the restrictions of the Hot Cell envi- ronment is discussed

Vibrant times for mechanical metamaterials

Metamaterials are man-made designer matter that obtains its unusual effective properties by structure rather than chemistry. Building upon the success of electromagnetic and acoustic metamaterials, researchers working on mechanical metamaterials strive at obtaining extraordinary or extreme elasticity tensors and mass-density tensors to thereby mold static stress fields or the flow of longitudinal/transverse elastic vibrations in unprecedented ways. In this prospective paper, we focus on recent advances and remaining challenges in this emerging field. Examples are ultralight-weight, negative mass density, negative modulus, pentamode, anisotropic mass density, Origami, nonlinear, bistable, and reprogrammable mechanical metamaterials

Electromigration failure by shape change of voids in bamboo lines

The behavior of electromigration-induced voids in narrow, unpassivated aluminum interconnects is examined, using scanning electron microscopy. Some electromigration tests were interrupted several times in order to observe void nucleation, void growth, and finally the failure of the conductor line. It is found that voids which opened the line have a specific asymmetric shape with respect to the electron flow direction. Besides void nucleation and void growth, void shape changes can consume a major part of the lifetime of the conductor line. A first attempt to model these processes on the basis of diffusion along the void surface shows that voids with a noncircular initial shape tend to produce the fatal asymmetry due to electron wind effects, with the anisotropy of surface energy possibly playing only a minor role

Mechanical assessment of ultrafine-grained nickel by microcompression experiment and finite element simulation

Over the past two decades, nanoindentation has been the most versatile method for mechanical testing at small length scales. Because of large strain gradients, it does not allow for a straightforward identification of material parameters such as yield and tensile strength, though. This represents a major drawback and has led to the development of alternative microscale testing techniques with microcompression as one of the most popular ones today. In this research, the influence of the realistic sample configuration and unavoidable variations in the experimental conditions is studied systematically by combing in-situ microcompression experiments on ultrafine-grained nickel and finite element simulations. It will be demonstrated that neither qualitative let alone quantitative analyses are as straightforward as they may appear, which diminishes the apparent advantages of microcompression testin

Motion compensation with a scanned ion beam: a technical feasibility study

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Mechanical behavior and size effects of polymer/amorphous NiB composites with 3D micro‐ architectures

Micro-architectured materials are a new class of hierarchical cellular material with outstanding properties. By designing advantageous cellular geometries and combining the material size effects at the nanometer scale, lightweight hybrid micro-architectured materials with hierarchical cellular structures and tailored structural properties are achieved. Previous papers have reported the mechanical properties of ceramic/polymer composites but few studies have examined the properties of similar structures with metal coatings instead of ceramic. To estimate the mechanical performance of polymer cellular structure reinforced with a metal coating, we combined 3D laser lithography and electroless deposition of an amorphous layer of NiB to produce metal/polymer hybrid structures. In this poster, the fabrication of 3D hybrid structures by electroless deposition aiming at achieving high and yet low density material will be presented. We also studied the mechanical response of micro-architectured structures as a function of the architecture design and the thickness of the amorphous NiB layer on their deformation mechanisms. In situ SEM microcompression experiments revealed a change in the deformation behavior with the NiB layer thickness, suggesting that the deformation mechanism and the buckling behavior are controlled by the size induced brittle-to-ductile transition in the NiB layer. In addition, the energy absorption properties demonstrate the possibility of tuning the energy absorption efficiency with adequate designs. Please click Additional Files below to see the full abstract