Synthesis and crystal structure of the inter-alkali-metal chloride RbLiCl2

The crystal structure of RbLiCl₂ [a= 1441.3(3), b= 412.57(8), c= 720.9(1) pm, Guinier-Simon data, orthorhombic, Ccmm, No. 63, Z= 4] was determined and refined from single crystal data, R= 0.074, R_W= 0.062. The coordination polyhedron of Rb⁺ is a bicapped trigonal prism, Li⁺ is tetrahedrally coordinated. [LiCl₄] tetrahedra are connected via common corners to undulated layers $\text{∞}\text{2}\text{[}\text{LiCl}{}^{\mathrm{c}}{}_{\mathrm{<mtext>4</mtext><mtext>2</mtext>}}\text{]}{}^{\mathrm{?}}$ parallel to (100). The structure is closely related to that of SrZnO₂.     

Untersuchungen zum Anschlagtiefziehen von vergütetem Stahlblech

Versuche zum Anschlagtiefziehen runder zylindrischer Teile mit einem vergütbaren Stahlband bei unterschiedlich hoher Vergütung. Ermittlung der maximalen Ziehkräfte und Grenzziehverhältnisse. Methode zur näherungsweisen Berechnung der maximalen Ziehkraft. Beurteilung und Eigenschaften der tiefgezogenen Näpfe.     

Imaging performance of A-PET: a small animal PET camera

The evolution of positron emission tomography (PET) imaging for small animals has led to the development of dedicated PET scanner designs with high resolution and sensitivity. The animal PET scanner achieves these goals for imaging small animals such as mice and rats. The scanner uses a pixelated Anger-logic detector for discriminating 2 x 2 x 10 mm3 crystals with 19-mm-diameter photomultiplier tubes. With a 19.7-cm ring diameter, the scanner has an axial length of 11.9 cm and operates exclusively in three-dimensional imaging mode, leading to very high sensitivity. Measurements show that the scanner design achieves a spatial resolution of 1.9 mm at the center of the field-of-view. Initially designed with gadolinium orthosilicate but changed to lutetium- yttrium orthosilicate, the scanner now achieves a sensitivity of 3.6% for a point source at the center of the field-of-view with an energy window of 250-665 keV. Iterative image reconstruction, together with accurate data corrections for scatter, random, and attenuation, are incorporated to achieve high-quality images and quantitative data. These results are demonstrated through our contrast recovery measurements as well as sample animal studies.     

Chemical vapor synthesis of size-selected zinc oxide nanoparticles

ZnO can be regarded as one of the most important metal oxide semiconductors for future applications. Similar to silicon in microelectronics, it is not only important to obtain nanoscale building blocks of ZnO, but also extraordinary purity has to be ensured. A new gas-phase approach to obtain size-selected, nanocrystalline ZnO particles is presented. The tetrameric alkyl-alkoxy zinc compound [CH(3)ZnOCH(CH(3))(2)](4) is chemically transformed into ZnO, and the mechanism of gas-phase transformation is studied in detail. Furthermore, the morphological genesis of particles via gas-phase sintering is investigated, and for the first time a detailed model of the gas-phase sintering processes of ZnO is presented. Various analytical techniques (powder XRD, TEM/energy-dispersive X-ray spectroscopy, magic-angle spinning NMR spectroscopy, FTIR spectroscopy, etc.) are used to investigate the structure and purity of the samples. In particular, the defect structure of the ZnO was studied by photoluminescence spectroscopy.     

Zusammenhang zwischen dem Feuchtigkeitsgehalt basischer Schweißpulver und dem Gehalt an diffusiblem Wasserstoff im Schweißgut

Untersuchung des Wasserabgabe- und Wasseraufnahmeverhaltens an fünf Schweißpulvern – agglomerierte und erschmolzene – für das Verbindungsschweißen hochfester niedriglegierter Stähle. Kontinuierliche Erfassung des Wasserabgabeverhaltens bei Temperaturen von 150 bis 450°C. Klimaschrank mit kontinuierlicher Wägevorrichtung. Eindeutiger Zusammenhang zwischen dem Feuchtigkeitsgehalt und dem Gehalt an diffusiblem Wasserstoff im Schweißgut nur unter Berücksichtigung der Wasserbindungsart.     

Kohärente Ausscheidung in Substitutionsmischkristallen des α-Eisens

Bildungsbedingungen, Merkmale und Formen kohärenter Ausscheidungen in Nichteisen- und Eisenmetallegierungen. Beispiele für die kohärente Ausscheidung vor allem in den Systemen des α-Eisens mit Kupfer, Gold, Aluminium, ferner mit Beryllium, Chrom, Molybdän und Wolfram. Änderung von mechanischen und physikalischen Eigenschaften (vor allem Härte, Kennwerte im Zugversuch; elektrischer Widerstand, Koerzitivfeidstärke) in Abhängigkeit vom Ausscheidungszustand.     

Energy resolution of an Omega-type monochromator and imaging properties of the MANDOLINE filter

We report on the energy resolution properties of an Omega-type monochromator. In a TEM/STEM setup with a MANDOLINE filter and extreme stability of the high voltage and the filter current, an energy resolution of 43 meV for 0.1 s exposure time and 87 meV for 100 s exposure time was measured at 200 kV with 40 meV monochromator slit width. The monochromized zero-loss peaks are additionally characterized by their edge steepness. Moreover a drop in the monochromized zero-loss peak by 10³ after 260 meV can be obtained even without deconvolution. For small fields of view, the energy resolution mostly does not depend on the MANDOLINE filter. With the Corrected OMEGA filter an energy resolution of 41 meV was measured for 0.03 s exposure time at 200 kV with 30 meV monochromator slit width and 77 meV for 50 s exposure time at 80 kV with 40 meV monochromator slit width. Furthermore, the MANDOLINE filter’s setup and imaging properties are presented such as isochromaticity (<5 meV) and transmissivity (T_(1 eV)=17,400 nm²), which set a new standard for imaging energy filters and allow EFTEM spectrum imaging with energy windows ≤200 meV and reasonable fields of view.     

Zur sinnvollen Anwendung ganzheitlicher Gebäudemodelle in der Tragwerksplanung von Hochbauten

Ausgehend von den kritischen Randbedingungen der Berechnung mit ganzheitlichen Gebäudemodellen werden typische und häufig anzutreffende Konstruktionsfälle diskutiert, bei denen Gesamtmodelle Vorteile für den Entwurf aufzeigen. Hier sind räumliche Tragwirkungen zu nennen, die Erfassung von Zwangsbeanspruchungen bei komplexen Grundrissen mit vielfältigen Festhaltungen sowie die Beanspruchung schlanker Gebäudestrukturen aus Windlasten und seismischen Einwirkungen. Für die genannten sinnvollen Anwendungsfälle werden die notwendigen Randbedingungen diskutiert. Die jeweiligen Anwendungsfälle werden anhand konkreter Gebäudebeispiele vorgestellt. On the reasonable use of total building models in the design of building structures Coming from the critical boundary conditions of the calculation with total building models, typical and prevalent constructions, where total models show advantages for the design, will be discussed. Here, spatial load‐bearing impact, the registration of unforced interactions of complex ground plans with various supports as well as the stressing of slender building structures resulting from wind loads and seismic impacts have to be mentioned. For the stated reasonable use cases the necessary boundary conditions will be discussed. The respective use cases will be presented by means of concrete building examples.