Muon-oxygen bonding in V2O3

A muon site search using calculated internal fields has been performed for V₂O₃, where purely dipolar fields allow a site determination free from covalent complications. The obtained sites are a subset of the Rodriguez and Bates sites found in α-Fe₂O₃ and indicate muon oxygen bond formation. The sites missing at low temperatures are consistent with the vanadium pairing mechanism for the metal-to-insulator (corundum-to-monoclinic) phase transition.     

Influence of variable selection on partial least squares discriminant analysis models for explosive residue classification

Using a series of thirteen organic materials that includes novel high-nitrogen energetic materials, conventional organic military explosives, and benign organic materials, we have demonstrated the importance of variable selection for maximizing residue discrimination with partial least squares discriminant analysis (PLS-DA). We built several PLS-DA models using different variable sets based on laser induced breakdown spectroscopy (LIBS) spectra of the organic residues on an aluminum substrate under an argon atmosphere. The model classification results for each sample are presented and the influence of the variables on these results is discussed. We found that using the whole spectra as the data input for the PLS-DA model gave the best results. However, variables due to the surrounding atmosphere and the substrate contribute to discrimination when the whole spectra are used, indicating this may not be the most robust model. Further iterative testing with additional validation data sets is necessary to determine the most robust model.     

Erweiterung von Linearfunktionen in linearen Räumen

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Die Quotientenräume eines linearen vollkommenen Raumes

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Structural Basis for (2R,3R)-Taxifolin Binding and Reaction Products to the Bacterial Chalcone Isomerase of Eubacterium ramulus

The bacterial chalcone isomerase (CHI) from Eubacterium ramulus catalyses the first step in a flavanone-degradation pathway by a reverse Michael addition. The overall fold and the constitution of the active site of the enzyme completely differ from the well-characterised chalcone isomerase of plants. For (+)-taxifolin, CHI catalyses the intramolecular ring contraction to alphitonin. In this study, Fwe perform crystal structure analyses of CHI and its active site mutant His33Ala in the presence of the substrate taxifolin at 2.15 and 2.8 Å resolution, respectively. The inactive enzyme binds the substrate (+)-taxifolin as well defined, whereas the electron density maps of the native CHI show a superposition of substrate, product alphitonin, and most probably also the reaction intermediate taxifolin chalcone. Evidently, His33 mediates the stereospecific acid-base reaction by abstracting a proton from the flavonoid scaffold. The stereospecificity of the product is discussed.     

Jodometrische Bestimmung des Natriums als Natriumzinkuranylacetat

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Die Sulfide des Galliums

Zusammenfassung 1. Es wurde erstmalig das Gallium-3-sulfid hergestellt und seine Eigenschaften beschrieben. 2. Durch Reduktion desselben wurde das Gallium-2-sulfid erhalten. 3. Im Hochvakuum zerlegt sich das Zweisulfid in das grauschwarze Gallium-1-sulfid und gelbe Trisulfid. 4. Durch R?ntgenogramme wurde die Existenz des ein-, zwei- und dreiwertigen Sulfides nachgewiesen.