TY - CONF A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, I. L. A1 - Mbugua, R. A1 - Olonade, K. A. ED - Greim, M. ED - Kusterle, W. ED - Teubert, O. T1 - Natural rheology modifying admixtures for concrete N2 - The possibility to tailor the rheology of concrete eventually opened up the path to new technologies, where design criteria are no longer limited to the compressive strength. Thus, it can be concluded that the capability to control the rheology of concrete can be considered as catalyst for many of today’s concrete innovations. In the same way rheology modifying admixtures will be key to mastering the challenges of the next decades. In many regions of the Southern hemisphere, the effective use of chemical admixtures would significantly contribute to solve problems induced by the challenging climate, but particularly in Africa there is often a lack of local supply and supply infrastructure. In Africa, concrete admixtures are largely shipped or transported from outside the continent. The long distance transportation of chemicals is not very environmentally friendly and the economic consequences are dramatic: the agents are difficult to purchase, expensive, and there is no large variety of products available in the market. Due to the enormous relevance of rheology modifying admixtures, it is worthwhile to recollect that nature provides an enormous variety of chemicals that can be used readily or with low processing and without enormous transportation distances, since these plants are typically regionally abundantly available, cheap, and they are environmental friendly. The paper presents an overview of various options for rheology modifying admixtures, that can be found in Africa, and that may become a real alternative, once their interaction within the complex cementitious system is well understood. T2 - 26. Workshop und Kolloquium "Rheologische Messungen an Baustoffen" CY - Regensburg, Germany DA - 21.02.2017 KW - Concrete KW - Rheology PY - 2017 SN - 978-3-7439-0171-1 SP - 75 EP - 87 PB - tredition GmbH CY - Hamburg AN - OPUS4-40599 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Harald A1 - Hodoroaba, Vasile-Dan A1 - Schmidt, Alexandra A1 - Rasmussen, K. A1 - Rauscher, H. T1 - Counting Small Particles in Electron Microscopy Images — Proposal for Rules and Their Application in Practice N2 - Electron microscopy (EM) is the gold standard for the characterisation of the morphology (size and shape) of nanoparticles. Visual observation of objects under examination is always a necessary first step in the characterisation process. Several questions arise when undertaking to identify and count particles to measure their size and shape distribution. In addition to challenges with the dispersion and identification of the particles, more than one protocol for counting particles is in use. This paper focuses on precise rules for the counting of particles in EM micrographs, as this influences the measurement accuracy of the number of particles, thus implicitly affecting the size values of the counted particles. We review and compare four different, commonly used methods for counting, which we then apply in case studies. The impact of the selected counting rule on the obtained final particle size distribution is highlighted. One main aim of this analysis is to support the application of a specific, well-defined counting approach in accordance with regulatory requirements to contribute to achieving more reliable and reproducible results. It is also useful for the new harmonised measurement procedures for determining the particle size and particle size distribution of nanomaterials. KW - Nano KW - Particle size distribution KW - Nanoparticle KW - Nanomaterial KW - OECD PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-551891 DO - https://doi.org/10.3390/nano12132238 SN - 2079-4991 VL - 12 IS - 13 SP - 2238 PB - MDPI CY - Basel AN - OPUS4-55189 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lüth, Peter A1 - Frost, K. A1 - Kurth, Lutz A1 - Malow, Marcus A1 - Schmidt, Martin A1 - Michael-Schulz, Heike A1 - Uhlig, S. A1 - Zakel, S. T1 - CEQAT-DGHS Ringversuchsprogramm für die Chemikaliensicherheit - Schlussfolgerungen N2 - Die Ursachen für Chemikalienunfälle können vielfältig sein. Prävention beginnt bereits im Prüflabor, wenn Chemikalien auf ihre gefährlichen Eigenschaften getestet werden. Dazu sind Prüfmethoden entwickelt und veröffentlicht worden, die heute weltweit Anwendung finden. Auf die Validität der Prüfmethode und richtige Durchführung der Prüfung im Laboratorium müssen sich Sicherheitsfachkräfte, Transporteure oder Händler verlassen können. Anhand der in den letzten 10 Jahren im Rahmen des CEQAT-DGHS von BAM und PTB durchgeführten Ringversuche (RV) wird gezeigt, dass bei allen bisher untersuchten Prüfmethoden ein Verbesserungsbedarf besteht. Die RV müssen daher zunächst auf die Methodenverbesserung und -validierung abzielen und nicht auf Leistungstests. Das Labormanagement und die praktische Durchführung der Prüfung sind in vielen Laboratorien verbesserungsbedürftig. Der Begriff „Erfahrung der Prüfer“ ist kritisch zu sehen: Eine „lange Erfahrung mit vielen Prüfungen“ ist nicht unbedingt ein Garant für richtige Ergebnisse. T2 - 15. BAM-PTB-Kolloquium zur chemischen und physikalischen Sicherheitstechnik CY - Braunschweig, Germany DA - 21.05.2019 KW - Gefahrgut KW - Gefahrstoff KW - Ringversuch KW - Prüfmethode KW - Validierung KW - Qualitätssicherung PY - 2019 UR - https://www.ptb.de/cms/index.php?id=18763 DO - https://doi.org/10.7795/210.20190521M SP - 1 EP - 8 PB - Physikalisch-Technische Bundesanstalt (PTB) CY - Braunschweig AN - OPUS4-49489 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lüth, Peter A1 - Frost, K. A1 - Kurth, Lutz A1 - Malow, Marcus A1 - Schmidt, Martin A1 - Michael-Schulz, Heike A1 - Uhlig, S. A1 - Zakel, S. T1 - CEQAT-DGHS Ringversuchsprogramm für die Chemikaliensicherheit – Entwicklung von Verfahren zur Verifizierung der Prüfapparatur am Beispiel der Prüfmethode UN Test N.5 N2 - Prävention beginnt im Prüflabor, wenn Chemikalien auf ihre gefährlichen Eigenschaften getestet werden. Dazu sind Prüfmethoden entwickelt und veröffentlicht worden, die heute weltweit Anwendung finden. Auf die Validität der Prüfmethode und richtige Durchführung der Prüfung im Laboratorium müssen sich Sicherheitsfachkräfte, Transporteure oder Händler verlassen können. Anhand der in den letzten 10 Jahren im Rahmen des CEQAT-DGHS von BAM und PTB durchgeführten Ringversuche (RV) wird gezeigt, dass bei allen bisher untersuchten Prüfmethoden ein Verbesserungsbedarf besteht. Die RV müssen daher zunächst auf die Methodenverbesserung und -validierung abzielen und nicht auf Leistungstests. Das Labormanagement und die praktische Durchführung der Prüfung sind in vielen Laboratorien verbesserungsbedürftig. Der Begriff „Erfahrung der Prüfer“ ist kritisch zu sehen: Eine „lange Erfahrung mit vielen Prüfungen“ ist nicht unbedingt ein Garant für richtige Ergebnisse. Bei der Prüfung der gefährlichen Eigenschaften von Chemikalien sind Referenzmaterialen auf Grund der Instabilität in der Regel nicht verfügbar. Für Prüflaboratorien sind RV daher eine Alternative bei der Qualitätssicherung. RV sind jedoch aufwendig und können nur in relativ großen Zeitabständen durchgeführt werden. Es sind deshalb Verfahren zur Verifizierung z. B. der in den Laboratorien verwendeten Prüfapparaturen zu entwickeln. Die Entwicklung von Verifizierungsverfahren wird am Bespiel der Prüfmethode UN Test N.5 demonstriert. T2 - 15. BAM-PTB-Kolloquium zur chemischen und physikalischen Sicherheitstechnik CY - Braunschweig, Germany DA - 21.05.2019 KW - Gefahrgut KW - Gefahrstoff KW - Ringversuch KW - Prüfmethode KW - Validierung KW - Qualitätssicherung KW - Verifizierung PY - 2019 UR - https://www.ptb.de/cms/index.php?id=18763 DO - https://doi.org/10.7795/210.20190521E SP - 1 EP - 10 CY - Braunschweig AN - OPUS4-49495 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lüth, Peter A1 - Frost, K. A1 - Kurth, Lutz A1 - Malow, Marcus A1 - Michael-Schulz, Heike A1 - Schmidt, Martin A1 - Schulte, Petra A1 - Uhlig, S. A1 - Zakel, S. T1 - CEQAT-DGHS Interlaboratory Test Programme for Chemical Safety - Need of Test Methods Validation N2 - Safety experts, manufacturers, suppliers, importers, employers or consumers must be able to rely on the validity of safety-related test methods and on correct test results and assessments in the laboratory. Via the eChemPortal lots of data from the REACH registration dossiers are available. However, the quality and correctness of the information remains in the responsibility of the data submitter. Unfortunately, we found more or less appropriate information on physicochemical properties and concluded that more quality or adequacy of any data submitted will be needed. Interlaboratory tests play a decisive role in assessing the reliability of test results. Interlaboratory tests on different test methods have been performed by Bundesanstalt für Materialforschung und –prüfung (BAM) and Physikalisch-Technische Bundesanstalt (PTB) in collaboration with the QuoData GmbH during the last 10 years. Significant differences between the results of the participating laboratories were observed in all interlaboratory tests. The deviations of the test results were not caused only by laboratory faults but also by deficiencies of the test method. In view of the interlaboratory test results the following conclusions can be drawn: • To avoid any discrepancy on classification and labelling of chemicals it should become state of the art to use validated test methods and the results accompanied by the measurement uncertainty. • A need for improvement is demonstrated for all examined test methods. Thus, interlaboratory tests shall initially aim at the development, improvement and validation of the test methods and not on proficiency tests. • The laboratory management and the practical execution of the tests need to be improved in many laboratories. • The term "experience of the examiner" must be seen critically: A "long experience with many tests" is not necessarily a guarantee for correct results. T2 - 16th International Symposium on Loss Prevention and Safety Promotion in the Process Industries and accompanying exhibition. Loss prevention 2019 CY - Delft, The Netherlands DA - 16.06.2019 KW - Dangerous goods KW - Hazardous substances KW - Round robin test KW - Interlaboratory comparison KW - Test method KW - Validation KW - Quality assurance PY - 2019 UR - https://www.aidic.it/cet/19/77/001.pdf SN - 978-88-95608-74-7 DO - https://doi.org/10.3303/CET1977001 SN - 2283-9216 VL - 77 SP - 1 EP - 6 PB - Italian Association of Chemical Engineering AN - OPUS4-49496 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiedensohler, A. A1 - Wiesner, A. A1 - Weinhold, K. A1 - Birmili, W. A1 - Herrmann, M. A1 - Merkel, M. A1 - Müller, T. A1 - Pfeifer, S. A1 - Schmidt, A. A1 - Tuch, T. A1 - Velarde, F. A1 - Quincey, P. A1 - Seeger, Stefan A1 - Nowak, A. T1 - Mobility particle size spectrometers: Calibration procedures and measurement uncertainties N2 - Mobility particle size spectrometers (MPSS) belong to the essential instruments in aerosol science that determine the particle number size distribution (PNSD)in the submicrometer size range. Following calibration procedures and target uncertainties against standards and reference instruments are suggested for a complete MPSS quality assurance program: a) calibration of the CPC counting efficiency curve (within 5% for the plateau counting efficiency; within 1 nm for the 50% detection efficiency diameter), b) sizing calibration of the MPSS, using a certified polystyrene latex (PSL) particle size standard at 203 nm (within 3%), c) intercomparison of the PNSD of the MPSS (within 10% and 20% of the dN/dlogDP concentration for the particle size range 20 – 200 nm and 200 to 800 nm, respectively), and d) intercomparison of the integral PNC of the MPSS (within 10%). Furthermore, following measurement uncertainties have been investigated: a) PSL particle size standards in the range from 100-500nm match within 1% after sizing calibration at 203 nm. b) Bipolar diffusion chargers based on the radioactive nuclides Kr85, Am241 and Ni63 and a new ionizer based on corona discharge follow the recommended bipolar charge distribution, while soft X-ray-based charges may alter faster than expected. c) The use of a positive high voltage supply show a 10% better performance than a negative one. d) The intercomparison of the integral PNC of an MPSS against the total number concentration is still within the target uncertainty at an ambient pressure of approximately 500 hPa. KW - Measurement uncertainties KW - Mobility particle size spectrometer (MPPS) KW - Condensation particle counter (CPC) KW - Calibration PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-425060 DO - https://doi.org/10.1080/02786826.2017.1387229 SN - 1521-7388 VL - 52 IS - 2 SP - 146 EP - 164 PB - Tailor & Francis CY - USA AN - OPUS4-42506 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Poyraz, Ö. A1 - Schmidt, H. A1 - Seidel, K. A1 - Delißen, Friedmar A1 - Ader, C. A1 - Tenenboim, H. A1 - Goosmann, C. A1 - Laube, B. A1 - Thünemann, Andreas A1 - Zychlinsky, A. A1 - Baldus, M. A1 - Lange, A. A1 - Griesinger, C. A1 - Kolbe, M. T1 - Protein refolding is required for assembly of the type three secretion needle N2 - Pathogenic Gram-negative bacteria use a type three secretion system (TTSS) to deliver virulence factors into host cells. Although the order in which proteins incorporate into the growing TTSS is well described, the underlying assembly mechanisms are still unclear. Here we show that the TTSS needle protomer refolds spontaneously to extend the needle from the distal end. We developed a functional mutant of the needle protomer from Shigella flexneri and Salmonella typhimurium to study its assembly in vitro. We show that the protomer partially refolds from α-helix into β-strand conformation to form the TTSS needle. Reconstitution experiments show that needle growth does not require ATP. Thus, like the structurally related flagellar systems, the needle elongates by subunit polymerization at the distal end but requires protomer refolding. Our studies provide a starting point to understand the molecular assembly mechanisms and the structure of the TTSS at atomic level. PY - 2010 DO - https://doi.org/10.1038/nsmb.1822 SN - 1545-9993 SN - 1545-9985 VL - 17 SP - 788 EP - 792 PB - Nature Publ. Comp. CY - New York, NY, USA AN - OPUS4-21726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chowdhary, S. A1 - Schmidt, R. F. A1 - Sahoo, A. K. A1 - tom Dieck, T. A1 - Hohmann, T. A1 - Schade, B. A1 - Brademann-Jock, Kerstin A1 - Thünemann, Andreas A1 - Netz, R. R. A1 - Gradzielski, M. A1 - Koksch, B. T1 - Rational design of amphiphilic fluorinated peptides: Evaluation of self-assembly properties and hydrogel formation N2 - Advanced peptide-based nanomaterials composed of self-assembling peptides (SAPs) are of emerging interest in pharmaceutical and biomedical applications. The introduction of fluorine into peptides, in fact, offers unique opportunities to tune their biophysical properties and intermolecular interactions. In particular, the degree of fluorination plays a crucial role in peptide engineering as it can be used to control the characteristics of fluorine-specific interactions and, thus, peptide conformation and self-assembly. Here, we designed and explored a series of amphipathic peptides by incorporating the fluorinated amino acids (2S)-4-monofluoroethylglycine (MfeGly), (2S)-4,4-difluoroethylglycine (DfeGly) and (2S)-4,4,4-trifluoroethylglycine (TfeGly) as hydrophobic components. This approach enabled studying the impact of fluorination on secondary structure formation and peptide self-assembly on a systematic basis. We show that the interplay between polarity and hydrophobicity, both induced differentially by varying degrees of side chain fluorination, does affect peptide folding significantly. A greater degree of fluorination promotes peptide fibrillation and subsequent formation of physical hydrogels in physiological conditions. Molecular simulations revealed the key role played by electrostatically driven intra-chain and inter-chain contact pairs that are modulated by side chain fluorination and give insights into the different self-organization behaviour of selected peptides. Our study provides a systematic report about the distinct features of fluorinated oligomeric peptides with potential applications as peptide-based biomaterials. KW - Small-angle X-ray scattering KW - SAXS KW - Amyloid PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-553504 DO - https://doi.org/10.1039/D2NR01648F SN - 2040-3364 VL - 14 IS - 28 SP - 10176 EP - 10189 PB - Royal Society of Chemistry AN - OPUS4-55350 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schulz, K. A1 - Schmack, R. A1 - Klemm, H. W. A1 - Kabelitz, Anke A1 - Schmidt, T. A1 - Emmerling, Franziska A1 - Kraehnert, R. T1 - Mechanism and kinetics of hematite crystallization in air: Linking bulk and surface models via mesoporous films with defined nanostructure N2 - Iron can form numerous oxides, hydroxides, and oxide−hydroxides. Despite their relevance, many of the transformation processes between these phases are still poorly understood. In particular the crystallization of quasi-amorphous hydroxides and oxide−hydroxides is difficult to assess, since typical diffraction and scattering methods provide only sampleaveraged information about the crystallized phases. We report a new approach for the investigation of the crystallization of oxide−hydroxides. The approach relies on model-type films that comprise a defined homogeneous nanostructure. The nanostructure allows quantitative linking of Information obtained by bulk-averaging diffraction techniques (XRD, SAXS) with locally resolved information, i.e., Domain sizes (SEM, TEM, LEEM) and phase composition (SAED). Using time-resolved imaging and diffraction we deduce mechanism and kinetics for the crystallization of ferrihydrite into hematite. Hematite forms via nucleation of hematite domains and subsequent Domain growth that terminates only upon complete transformation. A Johnson−Mehl−Avrami−Kolmogorov model describes the kinetics over a wide temperature range. The derived understanding enables the first synthesis of ferrihydrite films with ordered mesoporosity and quantitative control over the films’ hematite and ferrihydrite content. KW - Iron oxide KW - Crystallization KW - Mesoporous films KW - Nanostructure PY - 2017 DO - https://doi.org/10.1021/acs.chemmater.6b05185 SN - 0897-4756 SN - 1520-5002 VL - 29 IS - 4 SP - 1724 EP - 1734 AN - OPUS4-39690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Wilrich, Cordula A1 - Schröder, Volkmar A1 - Brandes, E. A1 - Schmidt, Martin A1 - Wandrey, Peter-Andreas A1 - Mix, K.-H. A1 - Wehrstedt, Klaus-Dieter A1 - Bender, H. A1 - Stephan, U. A1 - Eberz, A. A1 - Steinbach, J. A1 - Stoessel, F. T1 - Plant and process safety - 2. Hazardous materials and process conditions N2 - "Ullmann's Encyclopedia of Industrial Chemistry" is the benchmark reference in chemistry and chemical and life science engineering, covering inorganic and organic chemicals, advanced materials, pharmaceuticals, polymers and plastics, metals and alloys, biotechnology and biotechnological products, food chemistry, process engineering and unit operations, analytical methods, environmental protection, and much more. The present article is part of the topic collection "Environmental Protection and Industrial Safety". It covers plant and process safety, focusing on hazardous materials and process conditions. KW - Flammable gases and vapors KW - Combustibility of liquids KW - Dust explosions KW - Explosive condensed substances KW - Harmful effects of substances KW - Exothermic and pressure-inducing chemical reactions PY - 2012 SN - 978-3-527-30673-2 DO - https://doi.org/10.1002/14356007.q20_q01 SP - 1 EP - 50 PB - Wiley-VCH CY - Weinheim AN - OPUS4-58108 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Everard, C.D. A1 - Schmidt, Martin A1 - McDonnell, K.P. A1 - Finnan, J. T1 - Heating processes during storage of Miscanthus chip piles and numerical simulations to predict self-ignition N2 - Miscanthus x Giganteus (Miscanthus) energy crop was examined at laboratory scale to assess its self-heating and self-ignition risks during storage. Chipped Miscanthus (18 mm) from February and March harvests, in 2012, were assessed as well as ground Miscanthus (3 mm) from the March harvest. February and March crops had moisture contents of 41.6 and 20.2%, respectively. Self-ignition temperatures were independent of moisture although moisture did affect the time from the beginning of storage until storage temperature was reached. Ground Miscanthus had lower self-ignition temperatures than chipped Miscanthus. Isothermal respirometric tests carried out showed increase risk of self-heating in the February crop compared to the March crop due to increased microbial activity. Numerical simulations were used to determine critical enhanced start temperatures, e.g. caused by microbial decomposition, of the stored Miscanthus. Safe storage conditions have been derived from the investigations. The numerical simulations demonstrated that self-ignition was possible in Miscanthus chip piles with a height greater than 6 m if there was significant heat release from microbiological activity. Reliable assessment of self-heating and self-ignition risks in large scale Miscanthus energy crop clamps or piles are required to prevent losses due to decomposition and fire damage. KW - Miscanthus x Giganteus KW - Hot storage test KW - Respirometric rates KW - Self-heating KW - Self-ignition KW - Numerical simulations KW - Biomass storage PY - 2014 DO - https://doi.org/10.1016/j.jlp.2014.06.003 SN - 0950-4230 SN - 1873-3352 VL - 30 SP - 188 EP - 196 PB - Butterworth CY - Guildford, Surrey AN - OPUS4-31149 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -