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- Mobile Radiographie (2)
- Archäologischer Nassholzfund (1)
- Automated analysis (1)
- Bacterial adhesion (1)
- Biofilm (1)
- Biofilm quantification (1)
- Built environment (1)
- Ce complexes (1)
- Construction products (1)
- Crystal structure (1)
Organisationseinheit der BAM
Die radiologische Untersuchung von Holz ist hinsichtlich der Durchführung
und Auswertung komplex. Im Gegensatz zu künstlich hergestellten Materialien zeichnet
sich Holz besonders durch seine Heterogenität und Individualität aus, kein Stück ist wie das
andere. Dies erschwert bei der radiologischen Inspektion die Fehlerdetektion, da diese teilweise
schwer von natürlichen Wachstumsmerkmalen zu unterscheiden sind. Insektenfraßgänge
und Hohlräume durch biologischen Abbau sind deutlich erkennbar, schwieriger
wird es bei feinen Rissen und Anzeichen für Fäulnis. Metallische Einbauten wie Nägel und
Bolzen sind natürlich gut zu erkennen, großflächigere Platten können jedoch den Einblick
in die benachbarten Gebiete versperren. Klebstoffschichten sind im Röntgenbild nur dann
sichtbar, wenn sie exakt parallel zum Strahlengang getroffen werden. Verschiedene
Strukturmerkmale treten also radiologisch recht unterschiedlich in Erscheinung, deshalb
liegt es nahe, zu deren Erkennung mehr als nur eine Durchstrahlungstechnologie
anzuwenden. Während bei immobilen Objekten, d.h. Bauwerken und Bäumen, mobile
Durchstrahlungstechniken mit Röntgen- oder Gammastrahlen (Se-75) in Frage kommen,
stehen im Labor auch (schnelle) Neutronen alternativ zur Verfügung. Die verschiedenen
Techniken, einschließlich der Tomographie mit Neutronen, werden an zwei größeren Prüfteilen
demonstriert, einer Brettschichtholzprobe und einem Knotenpunkt aus einer Holzbrücke
mit eingebauter Stahlplatte. Neutronen lassen Materialunterschiede differenzierter hervortreten
und durchdringen sperrige Metallteile besser, trotz verringerter Bildqualität. An
Verbesserungen wird derzeit gearbeitet.
A European round robin test according to ISO 5725-2 was conceptually prepared, realised, and evaluated. The aim was to determine the inter-laboratory variability of the overall process for the ecotoxicological characterization of construction products in eluates and bioassays. To this end, two construction products BAM-G1 (granulate) and HSR-2 (roof sealing sheet), both made of EPDM polymers (rubber), were selected. The granular construction product was eluted in a one stage batch test, the planar product in the Dynamic Surface Leaching test (DSLT). A total of 17 laboratories from 5 countries participated in the round robin test: Germany (12), Austria (2), Belgium (1), Czech Republic (1) and France (1). A test battery of four standardised ecotoxicity tests with algae, daphnia, luminescent bacteria and zebrafish eggs was used. As toxicity measures, EC50 and LID values were calculated. All tests, except the fish egg test, were basically able to demonstrate toxic effects and the level of toxicity. The reproducibility of test results depended on the test specimens and the test organisms. Generally, the variability of the EC50 or LID values increased with the overall level of toxicity. For the very toxic BAM-G1 eluate a relative high variability of CV ¼ 73%e110% was observed for EC50 in all biotests, while for the less toxic HSR-2 eluate the reproducibility of EC50 varied with sensitivity: it was very good (CV ¼ 9.3%) for the daphnia test with the lowest sensitivity, followed by the algae test (CV ¼ 36.4%). The luminescent bacteria test, being the most sensitive bioassay for HSR-2 Eluate, showed the highest variability (CV ¼ 74.8%). When considering the complex overall process the reproducibility of bioassays with eluates from construction products was acceptable.
Cerium(III) and cerium(IV) both form formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy. Ce(III) formate shows only mononuclear complexes, which is in agreement with the predicted mononuclear species of Ce(HCOO)2+ and Ce(HCOO)2+. In contrast, Ce(IV) formate forms in aqueous solution a stable hexanuclear complex of [Ce6(µ3-O)4(µ3-OH)4(HCOO)x(NO3)y]12x-y. The structural differences reflect the different influence of hydrolysis, which is weak for Ce(III) and strong for Ce(IV). Hydrolysis of Ce(IV) ions causes initial polymerization while complexation through HCOO– results in 12 chelate rings stabilizing the hexanuclear Ce(IV) complex. Crystals were grown from the above-mentioned solutions. Two crystal structures of Ce(IV) formate were determined. Both form a hexanuclear complex with a [Ce6(µ3-O)4(µ3-OH)4]12+ core in aqueous HNO3/HCOOH solution. The pH titration with NaOH resulted in a structure with the composition [Ce6(µ3-O)4(µ3-OH)4(HCOO)10(NO3)2(H2O)3]·(H2O)9.5, while the pH adjustment with NH3 resulted in [Ce6(µ3-O)4(µ3-OH)4(HCOO)10(NO3)4]·(NO3)3(NH4)5(H2O)5. Furthermore, the crystal structure of Ce(III) formate, Ce(HCOO)3, was determined. The coordination polyhedron is a tricapped trigonal prism which is formed exclusively by nine HCOO– ligands. The hexanuclear Ce(IV) formate species from aqueous solution is widely preserved in the crystal structure, whereas the mononuclear solution species of Ce(III) formate undergoes a polymerization during the crystallization process.
Recent DNA-based studies have shown that the built environment is surprisingly rich in fungi. These indoor fungi – whether transient visitors or more persistent residents – may hold clues to the rising levels of human allergies and other medical and building-related health problems observed globally. The taxo¬nomic identity of these fungi is crucial in such pursuits. Molecular identification of the built mycobiome is no trivial undertaking, however, given the large number of unidentified, misidentified, and technically compromised fungal sequences in public sequence databases. In addition, the sequence metadata required to make informed taxonomic decisions – such as country and host/substrate of collection – are often lacking even from reference and ex-type sequences. Here we report on a taxonomic annotation workshop (April 10–11, 2017) organized at the James Hutton Institute/University of Aberdeen (UK) to facilitate reproducible studies of the built mycobiome. The 32 participants went through public fungal ITS bar¬code sequences related to the built mycobiome for taxonomic and nomenclatural correctness, technical quality, and metadata availability. A total of 19,508 changes – including 4,783 name changes, 14,121 metadata annotations, and the removal of 99 technically compromised sequences – were implemented in the UNITE database for molecular identification of fungi (https://unite.ut.ee/) and shared with a range of other databases and downstream resources. Among the genera that saw the largest number of changes were Penicillium, Talaromyces, Cladosporium, Acremonium, and Alternaria, all of them of significant importance in both culture-based and culture-independent surveys of the built environment.
Low-temperature electron-paramagnetic-resonance study of extrinsic and intrinsic defects in CuGaSe2
(1999)
Biofilms cause complications and high costs in both industry and medicine. Of particular interest are bacterial infections of prosthetic materials, which usually cannot be eliminated due to the high antibiotic resistance known for bacteria forming biofilms. The search for new materials and coatings with lower colonization potential and antibacterial activity is of great importance to reduce biofilm formation. However, there is no standardized procedure to examine the colonization characteristics of bacteria in the Biofilm state in situ. Here, we describe an automated epifluorescence microscopy system for the semi-quantitative analysis of three-dimensional (3D) biofilms on various surfaces. To analyze adherent bacteria, three materials (glass, steel and titanium) were incubated with bacteria in a flow chamber system. After fluorescence staining of the bacteria, automated image capturing, quantification of the bacteria, measurement of the colonized area and determination of the 3D biofilm height were carried out by using novel software.
Furthermore, the materials were examined for their surface topography using white light scanning interferometry. Titanium compared to glass showed a significantly higher number of adherent bacteria.
We argue that this was due to the higher microroughness of titanium. The colonized area was in accordance with the number of adherent bacteria and was also significantly larger on titanium coupons compared to glass. Maximum 3D biofilm height on glass coupons was significantly lower compared to the ones on steel and titanium. This novel method enables the standardized, automated investigation of the colonization with bacteria on different materials. This approach can considerably support the characterization of new material surfaces and their innovative coatings by analyzing the amount of attached Bacteria and thickness of biofilms in situ and eliminates the need of conventional cultivation.