TY - JOUR A1 - Valentin, Jules D. P. A1 - Altenried, Stefanie A1 - Varadarajan, Adithi R. A1 - Ahrens, Christian H. A1 - Schreiber, Frank A1 - Webb, Jeremy S. A1 - van der Mei, Henny C. A1 - Ren, Qun T1 - Identification of Potential Antimicrobial Targets of Pseudomonas aeruginosa Biofilms through a Novel Screening Approach N2 - Pseudomonas aeruginosa is an opportunistic pathogen of considerable medical importance, owing to its pronounced antibiotic tolerance and association with cystic fibrosis and other life-threatening diseases. The aim of this study was to highlight the genes responsible for P. aeruginosa biofilm tolerance to antibiotics and thereby identify potential new targets for the development of drugs against biofilm-related infections. By developing a novel screening approach and utilizing a public P. aeruginosa transposon insertion library, several biofilm-relevant genes were identified. The Pf phage gene (PA0720) and flagellin gene (fliC) conferred biofilm-specific tolerance to gentamicin. Compared with the reference biofilms, the biofilms formed by PA0720 and fliC mutants were completely eliminated with a 4-fold-lower gentamicin concentration. Furthermore, the mreC, pprB, coxC, and PA3785 genes were demonstrated to play major roles in enhancing biofilm tolerance to gentamicin. The analysis of biofilm-relevant genes performed in this study provides important novel insights into the understanding of P. aeruginosa antibiotic tolerance, which will facilitate the detection of antibiotic resistance and the development of antibiofilm strategies against P. aeruginosa. KW - Antimicrobial resistance KW - Bacteria KW - Biofilms KW - Pseudomonas aeruginosa PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-570205 DO - https://doi.org/10.1128/spectrum.03099-22 SP - 1 EP - 5 PB - ASM Journals AN - OPUS4-57020 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bui, M. A1 - Hoffmann, K. F. A1 - Braun, T. A1 - Riedel, S. A1 - Heinekamp, Christian A1 - Scheurell, K. A1 - Scholz, G. A1 - Stawski, Tomasz A1 - Emmerling, Franziska T1 - An Amorphous Teflate Doped Aluminium Chlorofluoride: A Solid Lewis-Superacid for the Dehydrofluorination of Fluoroalkanes N2 - Ananion-dopedaluminiumchlorofluoride AlCl0.1F2.8(OTeF5)0.1(ACF-teflate) was synthesized.The material contains pentafluor-oorthotellurate(teflate)groups, which mimic fluoride ions electronically, but are sterically more demanding. They are embedded into the amorphous structure. The latter was studied by PDF analysis, EXAFS data and MAS NMR spectroscopy. The mesoporous powder is a Lewis superacid, and ATR-IR spectra of adsorbed CD3CN reveal a blue-shift of the adsorption band by73 cm-1, which is larger than the shift for SbF5. Remarkably,ACF-teflate catalyzes dehydrofluorination reactions of mono-fluoroalkanes to yield olefins in C6D6. In these cases,no Friedel-Crafts products were formed. KW - Aluminium fluorides KW - Aluminium teflates KW - C-F bond activation KW - Lewis superacids KW - Silanes PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572290 DO - https://doi.org/10.1002/cctc.202300350 SN - 1867-3880 SP - 1 EP - 7 PB - Wiley VHC-Verlag AN - OPUS4-57229 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dhamo, Lorena A1 - Carulli, F. A1 - Nickl, Philip A1 - Wegner, Karl David A1 - Hodoroaba, Vasile-Dan A1 - Würth, Christian A1 - Brovelli, S. A1 - Resch-Genger, Ute T1 - Efficient luminescent solar concentrators based on environmentally friendly Cd-free ternary AIS/ZnS quantum dots N2 - Luminescent solar concentrators (LSC) allow to obtain renewable energy from building integrated photovoltaic systems. As promising efficient and long-term stable LSC fluorophores semiconductor nanocrystals like Quantum dots (QDs) with size and composition tunable optoelectronic properties have recently emerged. The most popular II/VI or IV/VI semiconductor QDs contain, however, potentially hazardous cadmium or lead ions, which is a bottleneck for commercial applications. A simple aqueous based, microwaveassisted synthesis for environmentally friendly and highly emissive AgInS2/ ZnS QDs is developed using 3-mercaptopropionic acid (MPA) and glutathione (GSH) and their incorporation into polylaurylmethacrylate (PLMA) polymer slabs integrable in LSC devices (10.4 × 10.4 × 0.2 cm3, G = 12.98). With this simple approach, optical power efficiencies (OPE) of 3.8% and 3.6% and optical quantum efficiencies (OQE) of 24.1% and 27.4% are obtained, which are among the highest values yet reported. KW - Solar energy KW - Solar concentrator KW - Quantum dots KW - Advanced material KW - Quantum yield PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-529735 DO - https://doi.org/10.1002/adom.202100587 SN - 2195-1071 SN - 0935-9648 VL - 9 IS - 17 SP - 1 EP - 8 PB - Wiley-VCH CY - Weinheim AN - OPUS4-52973 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Würth, Christian A1 - Fischer, S. A1 - Grauel, Bettina A1 - Alivisatos, A. P. A1 - Resch-Genger, Ute T1 - Quantum Yields, Surface Quenching, and Passivation Efficiency for Ultrasmall Core/Shell Upconverting Nanoparticles N2 - We synthesized and characterized a set of ultrasmall hexagonal-phase NaGdF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles with core diameters of 3.7 ± 0.5 nm. In order to assess passivation effects and the influence of possible core−shell intermixing and to identify optimum particle structures for combined imaging in the visible and near-infrared (vis−NIR: 410−850 nm) and short-wave infrared (SWIR: 1520 nm), NaYF4 shells of varying thicknesses (monolayer to 10 nm) were introduced and the influence of this parameter on the upconversion and downshifting photoluminescence of these particles was studied at different excitation power densities. This included excitation power-dependent emission spectra, slope factors, quantum yields, and excited state decay kinetics. These measurements revealed enhancement factors of the upconversion quantum yield of >10 000 in the low power region and an excitation power density-independent quantum yield of the downshifted emission at 1520 nm between 0.1 and 14%. The optimized shell thickness for combined vis and SWIR imaging was identified as 5 nm. Moreover, lifetimes and quantum yields can be continuously tuned by shell thickness which can be exploited for lifetime multiplexing and encoding. The fact that we did not observe a saturation of the upconversion quantum yield or the excited state decay kinetics with increasing shell thickness is ascribed to a strong intermixing of the active core with the inert shell during the shelling procedure. This indicates the potential of spectroscopic tools to detect cation intermixing. KW - Nanoparticle KW - Upconversion KW - Quenching PY - 2018 DO - https://doi.org/10.1021/jacs.8b01458 IS - 140 SP - 4922 EP - 4928 PB - American Chemical Society AN - OPUS4-45378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Völzke, Holger A1 - Herold, Christian A1 - Wolff, Dietmar A1 - Orellana Pérez, Teresa A1 - Bollingerfehr, W. A1 - Prignitz, S. A1 - Wunderlich, A. T1 - Abschlussbericht zum FuE-Verbundvorhaben KoBrA: Anforderungen und Konzepte für Behälter zur Endlagerung von Wärme entwickelnden radioaktiven Abfällen und ausgedienten Brennelementen in Steinsalz, Tonstein und Kristallingestein N2 - Im Forschungsvorhaben KoBrA werden Anforderungen an Endlagerbehälter für hochradioaktive Abfälle erstmals systematisch und unter Berücksichtigung des internationalen Standes von Wissenschaft und Technik hergeleitet. Parallel werden die behälterrelevanten Randbedingungen und Beanspruchungsgrößen für Endlagerbehälter in den drei potenziellen Wirtsgesteinen Steinsalz, Tonstein und Kristallingestein ermittelt. Darauf aufbauend werden die zur Erfüllung der Anforderungen unter den gegebenen Einwirkungen und Beanspruchungen notwendigen Behälterfunktionen bestimmt und erste Konzeptideen für zukünftige Endlagerbehälter diskutiert bzw. entwickelt. KW - Endlager KW - Behälter KW - Anforderungen KW - Hochradioaktive Abfälle KW - Wirtsgestein PY - 2020 DO - https://doi.org/10.2314/KXP:1750909669 N1 - Auftraggeber: Bundesministerium für Wirtschaft und Energie (BMWi), Förderkennzeichen: 02E11527 und 02E11537. SP - 1 EP - 110 PB - BGE Technology CY - Peine AN - OPUS4-52289 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wanner, C. A1 - Poethig, R. A1 - Carrero, S. A1 - Fernandez-Martinez, A. A1 - Jäger, Christian A1 - Furrer, G. T1 - Natural occurrence of nanocrystalline Al-hydroxysulfates: Insights on formation, Al solubility control and As retention N2 - Nanocrystalline basaluminite [Al4OH10(SO4)(H2O)3–5] and Aggregation of the e-Keggin polyoxocation [Al12(AlO4)(OH)24(H2O)12]7+, referred to as Al13, have both been described to form in acid mine Drainage environments. Although the chemical composition is quite similar, their crystalline varieties significantly differ, demonstrating that various types of Al-hydroxysulfates can form under similar conditions and that their respective formation is not fully understood yet. Here, we report the occurrence of nanocrystalline precipitates that form naturally in a small alpine catchment in Switzerland where an acidic mountainous stream (pH 4) is neutralized successively after mixing with several neutral tributaries. The stepwise neutralization in conjunction with the large amount of precipitates provide an ideal setting for obtaining new insights into (i) the structure of naturally forming Al-hydroxysulfates, (ii) their formation mechanism, (iii) their role in controlling the solubility of Al, and (iv) their ability to lower the mobility of As. Synchrotron-based high-energy X-ray diffraction and subsequent pair distribution function analyses demonstrate that these precipitates are structurally identical to basaluminite samples obtained from acid mine drainage sites. In contrast, only minor amounts of tetrahedrally coordinated Al, as present in Al13, were identified by nuclear magnetic resonance spectroscopy. The precipitates are further characterized by elevated As concentrations up to 600 lg/g, whereas other heavy metals are at background concentrations only. Given the low As concentrations in the stream from which precipitation occurs (<0.03 mg/L), high As concentrations confirm that basaluminite serves as a highly efficient As sink, which is attributed to its high anion-exchange capacity. Chemical analysis of streamwater samples in combination with geochemical modeling show that precipitation occurs instantaneously upon mixing with neutral streams. Moreover, our data reveal that the precipitation of basaluminite exerts a strong solubility control on dissolved Al concentrations as manifested by the quasi-constant basaluminite ion activity product observed during neutralization from pH 5 to pH 5.9. We hypothesize that in our field system, high fluoride and sulfate concentrations on the order of 100 and 1–2 mg/L, KW - Basaluminite KW - Al13 KW - Acid rock drainage KW - Arsenic retention KW - Aluminum KW - Anion exchange PY - 2018 DO - https://doi.org/10.1016/j.gca.2018.06.031 SN - 0016-7037 SN - 1872-9533 VL - 238 SP - 252 EP - 269 PB - Elsevier Ltd. AN - OPUS4-46164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chaves Spoglianti de Souza, Roberto A1 - Andreini, M. A1 - La Mendola, S. A1 - Zehfuß, J. A1 - Knaust, Christian T1 - Probabilistic thermo-mechanical finite element analysis for the fire resistance of reinforced concrete structures N2 - This paper presents a probabilistic methodology based on the thermo-mechanical finite elements analysis to investigate the impact of the variability of the thermal properties of the concrete in the fire safety of structures. This is meant to evaluate if characteristic values or safety factors for the conductivity and specific heat are required during the semi-probabilistic structural fire safety assessment. To illustrate the use of the proposed methodology, this work includes a case-study with a tunnel lining which considers the uncertainties related to the thermal and mechanical properties of the concrete, the soil load, and the temperatures described by the standard temperature-time curve. Two failure criteria are considered: one was the maximum temperature of 300 °C at the reinforcement and the other based on the temperature-dependent strength as provided in the Eurocode EN 1992-1-2. Several finite element analyses are performed. The design of experiments is executed by a Correlation Latin Hypercube Sampling. The calculated probability of failure has different values depending on the adopted failure criteria. A sensitivity analysis using the Spearman's rank correlation coefficient was carried out and demonstrates that the uncertainty related to the specific heat has the greatest impact on the results. KW - Thermo-mechanical PY - 2019 DO - https://doi.org/10.1016/j.firesaf.2018.12.005 SN - 0379-7112 SN - 1873-7226 VL - 104 SP - 22 EP - 33 PB - Elsevier AN - OPUS4-48583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chaves Spoglianti de Souza, Roberto A1 - Andreini, M. A1 - La Mendola, S. A1 - Zehfuß, J. A1 - Knaust, Christian T1 - Probabilistic thermo-mechanical finite element analysis for the fire resistance of reinforced concrete structures N2 - This paper presents a probabilistic methodology based on the thermo-mechanical finite elements analysis to investigate the impact of the variability of the thermal properties of the concrete in the fire safety of structures. This is meant to evaluate if characteristic values or safety factors for the conductivity and specific heat are required during the semi-probabilistic structural fire safety assessment. To illustrate the use of the proposed methodology, this work includes a case-study with a tunnel lining which considers the uncertainties related to the thermal and mechanical properties of the concrete, the soil load, and the temperatures described by the standard temperature-time curve. Two failure criteria are considered: one was the maximum temperature of 300 °C at the reinforcement and the other based on the temperature-dependent strength as provided in the Eurocode EN 1992-1-2. Several finite element analyses are performed. The design of experiments is executed by a Correlation Latin Hypercube Sampling. The calculated probability of failure has different values depending on the adopted failure criteria. A sensitivity analysis using the Spearman's rank correlation coefficient was carried out and demonstrates that the uncertainty related to the specific heat has the greatest impact on the results. KW - Fire Safety KW - Concrete KW - Probabilistic KW - Finite Elements PY - 2018 DO - https://doi.org/10.1016/j.firesaf.2018.12.005 SN - 0379-7112 VL - 104 SP - 22 EP - 33 PB - Elsevier AN - OPUS4-47422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Maierhofer, Christiane A1 - Köpp, Christian A1 - Binda, L. A1 - Zanzi, L. A1 - Santiago, J.R. A1 - Knupfer, B. A1 - Johansson, B. A1 - Modena, C. A1 - da Porto, F. A1 - Marchisio, M. A1 - Gravina, F. A1 - Falci, M. A1 - Ruiz, J.C.G. A1 - Tomazevic, M. A1 - Bosiljkov, V. A1 - Hennen, C. A1 - Toledo, D.E.L. A1 - Zajc, A. A1 - delli Paoli, S. A1 - Drdácký, M. A1 - Válek, J. T1 - On-site investigation techniques for the structural evaluation of historic masonry buildings, Community research, Project Report EUR 21696 EN, Onsiteformasonry project KW - Non-destructive testing in civil engineering KW - Historic masonry KW - Damage KW - Cultural heritage KW - Complementary methods KW - Structural modelling KW - Guidelines and recommendations PY - 2006 SN - 92-894-9601-0 SP - 1 EP - 141 PB - Office for Official Publications of the European Communities CY - Luxembourg AN - OPUS4-14168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seto, J. A1 - Ma, Y. A1 - Davis, S.A. A1 - Meldrum, F. A1 - Gourrier, A. A1 - Kim, Y.-Y. A1 - Schilde, U. A1 - Sztucki, M. A1 - Burghammer, M. A1 - Maltsev, Sergey A1 - Jäger, Christian A1 - Cölfen, H. T1 - Structure-property relationships of a biological mesocrystal in the adult sea urchin spine N2 - Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials. KW - Calcium carbonate biomineralization KW - Echinoderm skeleton KW - Hierarchical structuring KW - Mesocrystal KW - Skeletal elements PY - 2012 DO - https://doi.org/10.1073/pnas.1109243109 SN - 0027-8424 SN - 1091-6490 VL - 109 IS - 10 SP - 3699 EP - 3704 PB - National Academy of Sciences CY - Washington, DC AN - OPUS4-27726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -