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E5 Tribologie
(2018)
The ultrasonic echo technique is frequently used in non-destructive testing (NDT) of concrete structures for thickness measurements, geometry determinations as well as localization of built-in components. To improve ultrasonic imaging of complex structures in concrete, we transferred a geophysical imaging technique, the reverse time migration (RTM), to NDT in civil engineering. In contrast to the conventionally used synthetic aperture focusing technique (SAFT) algorithms, RTM is a wavefield continuation method in time and uses the full wave equation. Thus, RTM can handle complicated wave propagations in any direction without dip limitation. In this paper, we focused on the application and evaluation of a two-dimensional (2D) elastic RTM algorithm considering compressional waves, vertically polarized shear waves, and Rayleigh waves. We tested the elastic RTM routine on synthetic ultrasonic echo data generated with a 2D concrete model consisting of several steps and circular air inclusions. As these complex structures can often be found in real-world NDT use cases, their imaging is especially important. By using elastic RTM, we were able to clearly reproduce vertical reflectors and lower edges of circular air voids inside our numerical concrete model. Such structures cannot be imaged with conventional SAFT algorithms. Furthermore, the used elastic RTM approach also yielded a better reconstruction of a horizontal reflector and upper boundaries of circular air inclusions. Our encouraging results demonstrate that elastic RTM has the potential to significantly improve the imaging of complex concrete structures and, thus, is a step forward for detailed, high-quality ultrasonic NDT in civil engineering.
The ultrasonic echo technique is a frequently used method in non destructive testing for geometry Determination of concrete building elements. Important tasks are thickness measurements as well as the localization and characterization of built-in components and inhomogeneities.
Currently mainly the synthetic aperture focusing family of techniques (SAFT) is used for imaging. These algorithms have difficulties in imaging steeply dipping interfaces and complicated structures such as steps and lower boundaries of voids. As an alternative two geophysical migration methods, pre-stack Kirchhoff depth migration and pre-stack Reversetimemigration (RTM)were tested in this paper at a reinforced concrete foundation slab. The slab consists of various reinforcement contents, different thicknesses and two pile heads.
In a first step, both methods were evaluated with synthetic 2D data. In the second step, ultrasonic measurement data recorded with shear wave transducers on a line profile on the foundation slab were processed. The use of an automatic scanner simplified the measurements. A comparison of the geophysical migration results with those of SAFT shows, in particular for RTM, a significant improvement in the Imaging of the geometry of the foundation slab. Vertical borders were reconstructed and the location and structure of the lower boundary of the foundation slab were reproduced better. Limitations still exist in imaging the piles below the slab.
Metakaolin-based alkali activated mortars (AAM) - with and without CuSO4·5H2O and ZnO addition (mass ratio Mn+/solid binder 0.08% to 1.7%) - were casted and exposed within an extensive long-term field campaign over the period of 20 months to a sewer basin, strongly affected by biogenic acid corrosion. (Un-)exposed AAM were tested regarding their physicochemical and microstructural properties, bioreceptivity and overall durability. Metal addition led to a retarding effect during alkali-activation reaction, as well as to an increase in open porosity of up to 3.0% and corresponding lower compressive strength of up to 10.9%. Reduced microbial colonization and diversity were observed on AAM with Cu, while Zn addition led to increased biodiversity. We propose that the observed higher durability of Cu-doped AAM is due to antibacterial effects and associated reduction of biogenic acid production, superseding overall negative effects of metal-dosage on physical material properties. Observed lower durability of Zn-doped AAM was related to combined negative physicochemical and microbial effects.
In this study, a multi-proxy approach combining 29Si, 27Al and 1H MAS-NMR, FEG-EPMA, XANES at the Cu K-edge and XRD analytics with hydrochemical tools such as ICP-OES analyses, oxygen-isotope signatures, and thermodynamic modelling was applied to K-silicate-activated metakaolin specimens - with and without CuSO4·5H2O addition - exposed to sulfuric acid at pH = 2 for 35 days. The results revealed a multistage deterioration mechanism governed by (i) acid diffusion, (ii) leaching of K-A-S-H, (iii) microstructural damage related to precipitation of expansive (K,Ca,Al)-sulfate-hydrate phases (iv) complete dissolution of the K-A-S-H framework, (v) and formation of silica gel in the outermost corroded regions. Copper ions were mainly located in layered spertiniite-chrysocolla-like phases in the as-cured materials. The results demonstrate an overall negative effect of Cu addition on chemical material durability, implying that the reported higher durability of Cu-doped AAM in biocorrosion environments can be best explained by bacteriostatic effects.
This chapter aims to give a brief introduction into the field of alkali activated materials (AAM) and their physicochemical material behavior when exposed to sulfuric acid and in biochemically aggressive sewer environments. Additionally, the differences in material behavior within chemical (abiotic) and microbially induced acid environments are highlighted. Finally, existing data on overall performance of AAM, compared to conventional concrete-based building materials in sewer systems will be discussed.
Die größten Rotorblätter von Windenergieanlagen erreichen heutzutage Längen von über 75 m. Die Durchführung von Betriebsfestigkeitsuntersuchungen an Rotorblättern im Original-Maßstab ist aufwendig hinsichtlich der Größe der Bauteile und der komplexen Lastsituation. Für die Zulassung werden in der Regel nur statische Sicherheitsnachweise gefordert, dynamische Untersuchungen am Gesamtbauteil sind hingegen nicht erforderlich. Aus diesem Grund wurde ein Stellvertreter-Prüfstand zur Untersuchung von Rotorblättern im verkleinerten Maßstab entwickelt. Darüber hinaus erfolgte durch systematische Dauerschwingversuche die Validierung und Bewertung eines Condition Monitoring Systems. Für die Berechnung eines Versuchsrotorblattes werden die äußeren auf das Blatt wirkenden Lasten unter Berücksichtigung des Eigengewichts und der aerodynamischen Umströmung analysiert. Die Ergebnisse belegen eine dominierende Belastung in Schlaglast-Richtung und eine deutlich geringere Belastung in Schwenklast-Richtung. Auf den Lastannahmen basierend erfolgt die Bestimmung des inneren Spannungs- und Verzerrungszustandes für die einzelnen Strukturbauteile, wobei als Grundlage die Geometriedaten, die Materialdaten und der Laminataufbau des Originalrotorblattes herangezogen werden. Für den Aufbau des Versuchsrotorblattes kommen ausschließlich Original-Halbzeuge zum Einsatz. Die durch den Prüfstand in das Versuchsrotorblatt eingeleiteten Lasten werden derart dimensioniert, dass sich der erforderliche Spannungs- und Verzerrungszustand im Laminat einstellt. Der innere Aufbau des Versuchsrotorblattes mit zwei Stegen und vier Gurten entspricht dem des Originalrotorblattes. Die Lasteinleitung in das Versuchsrotorblatt erfolgt simultan und unabhängig für die Schlaglast- und Schwenklast-Richtung. Der Biegegemomentenverlauf des Originalrotorblattes wird bei Einleitung von jeweils drei Einzellasten pro Lastrichtung in Kombination mit der Erzeugung eines freien Momentes zur Erzeugung eines Sprungs im Querkraftverlauf sehr gut nachgebildet. Für die Realisierung eines Condition Monitoring Systems werden FBG-Sensoren verwendet, da sowohl die Möglichkeit zur Strukturintegration mit nur minimal-invasiven Störstellen als auch eine einfache Verlegung mit einer Vielzahl an FBG-Sensoren in einer einzelnen Sensorfaser gegeben ist. Die im Vergleich zu FBG-Patches durchgeführten Dauerfestigkeits-untersuchungen belegen für die strukturintegrierten Sensoren eine signifikant höhere Lebensdauer. Die Betriebsfestigkeitsuntersuchungen werden sowohl als Einstufenversuche bei Nennlast und 50a- Böenlast als auch in Lastkollektivanregung bei unabhängiger Regelung der Schlag- und Schwenklast durchgeführt. Zusätzlich erfolgt mehrfach eine Modalanalyse bei frei aufgehängtem Versuchsrotorblatt in verschiedenen Stadien des Versuchsprogramms. Da bei Einstufenbelastung mit 50a-Böenlast auf natürliche Weise keine sichtbaren Schäden entstanden sind, werden künstliche Bauteilschäden in Form eines Längsrisses an der Blatthinterkante und eines Querrisses zwischen den lasttragenden Gurten eingebracht. Diese Schäden verursachen bei 50a-Böenlast lokale Dehnungsüberhöhungen, die mit dem gewählten Condition Monitoring System gut detektierbar sind. Die lokal begrenzte Dehnungszunahme korreliert sehr gut mit den Ergebnissen der FEM-Berechnungen des Versuchsrotorblattes. Der Vergleich der berechneten und gemessenen Eigenfrequenzen weist eine hohe Übereinstimmung auf. Bei der Eigenfrequenzanalyse macht sich die Verringerung der Steifigkeit aufgrund des Querrisses in der Blattschale durch eine signifikante Verringerung der Eigenfrequenzen bemerkbar. Für einen Vergleich der numerisch berechneten und mittels Geophonen gemessenen Eigenformen wird das MAC-Kriterium herangezogen, welches für die ersten Eigenformen sowohl des ungeschädigten als auch des geschädigten Versuchsrotorblattes sehr gute Übereinstimmungen belegt.
Molybdenum disulfide (MoS₂) is a well-known solid lubricant for tribosystems running in vacuum or dry gases. Problems arise due to its sensitivity to humidity, which is a drawback for its application under ambient conditions. However, by using a physical vapor deposition (PVD) process, deposition parameters can be optimized not only to gain a coatings structure with favorable frictional properties but also to minimize the sensitivity to attack by water molecules. Therefore, an improved tribological behavior even under moist conditions can be achieved. MoS₂coatings are also candidates for being applied at cryogenic temperatures. They already have proven their suitability, e.g., for sliding support elements between superconducting magnets of the nuclear fusion-experiment Wendelstein 7-X. However, these coatings were exclusively produced for this particular application and the utilization for more common tribosystems may be precluded due to cost considerations. In view of a wider range of applications, pure and Cr containing PVD-MoS₂ coatings with an optimized structure were tested under varying environments including hydrogen gas and cryogenic temperatures. Results of the most promising variant are presented in this paper.
Schnelle ortsaufgelöste Chloridbestimmung mit der laserinduzierten Plasmaspektroskopie (LIBS)
(2020)
Im Zuge der Ist-Zustandserfassung von Stahl- und Spannbetonbauwerken spielt die chemische Analyse von Beton eine zentrale Rolle. Durch den externen Eintrag von schädigenden Substanzen wie Chlorid oder Alkalien aus Tausalzen oder Meerwasser, kann u.U. der Beton und/oder die Stahlbewehrung angegriffen werden. Bei Überschreitung kritischer korrosionsauslösender Chloridgehalte, z.B. bei Stahlbeton 0,4 M.-% (bzw. 0,5 M.-%) und Spannbeton 0,2 M.-% bezogen auf den Zement, erhöht sich das Risiko für eine Chlorid-induzierte Korrosion. Für die Beurteilung eines Instandsetzungsbedarfs und, sofern notwendig, der Erarbeitung eines Instandsetzungskonzeptes muss nach der Rili-SIB1 ein sachkundiger Planer herangezogen werden. Standardmäßig werden für die chemische Analyse Bohrkerne bzw. Bohrmehlproben aus dem zu untersuchenden Bauwerk entnommen und nach aufwendiger Probenvorbereitung nasschemisch analysiert (nach DAfStb Heft 401 oder DIN 14629). Dabei wird der Gesamtchloridgehalt bezogen auf die Einwaage angegeben. Eine Umrechnung auf den Zementgehalt erfolgt i.d.R. durch Schätzwerte. Der Einsatz der laserinduzierten Plasmaspektroskopie (LIBS) wird seit Mitte der 90er Jahren an der Bundesanstalt für Materialforschung und -prüfung erforscht, um den Chloridgehalt durch eine ortsaufgelöste Elementanalyse an einer Betonprobe möglichst genau zu ermitteln. Die zweidimensionale LIBS-Messung mit einer lateralen Auflösung von 100 µm x 100 µm erlaubt die Berücksichtigung der Heterogenität von Beton. Dabei lassen sich die Bindemittelmatrix und die Gesteinskörnung separat betrachten, wodurch sich die Aussagekraft der Ergebnisse und somit die Sicherheit der chemischen Zustandserfassung erhöht. Durch die stetige Weiterentwicklung von Komponenten wie Laser, Spektrometer und analytischer Auswerteroutinen sind mittlerweile automatisierte Systeme für die schnelle LIBS-Analyse auf dem Markt verfügbar. In diesem Vortrag wird der aktuelle Stand der Technik anhand von Praxisbeispielen präsentiert und entscheidende Vorteile gegenüber dem Standardverfahren herausgestellt. Aufgrund der Möglichkeit für eine simultane Multielementanalyse mit LIBS werden weitere Anwendungen, wie z.B. die Ermittlung der Karbonatisierungstiefe, Untersuchungen von Transportprozessen, Chlorideintrag entlang von Rissen oder Untersuchungen von Elementverteilungen im Kontext einer AKR vorgestellt.
The fluorescence properties of three molecular rotors, related to 4-dimethylamino-4-nitrostilbene (4-DNS), are studied versus different diesel/kerosene blends. In nonviscous solvents, these compounds can populate a twisted intramolecular charge transfer state which deactivates nonradiatively, successfully suppressing fluorescence emission. Solution experiments with diesel/kerosene blends showed a good linear correlation between the fluorescence intensity of the probe molecules and the diesel fraction of the blend. The dyes have been immobilized on paper, retaining their fluorescence behavior, i.e., negligible emission in the presence of nonviscous organic solvents and increasing fluorescence when the environment is increasingly viscous. When the impregnated paper is devised as a test strip, the latter is compatible with a newly designed smartphone reader system, which allows in-the-field measurements. The method can safely detect the presence of kerosene in diesel at ≥7%, which competes favorably with current standard methods for the detection of diesel adulteration.
In the modern world there is an increased understanding that design and performance monitoring of materials have to be tested in connection to chemical, physical and (micro)biological challenges. A systematic study on how biofilms interact with materials and what could be done to engineer biofilms and/or materials in order to maximize the resistance of the material (surface) or the resistance the biofilm-modified material (bulk) is in strong need. In the Department “Materials and the Environment” of the BAM new experimental platform is being developed. With the help of different type of device for high throughput and microbiologically-controlled environment simulation we establish a new approach to clarify the mechanisms of biofilm/material interactions. Despite the focus on fundamental research, the main results of this project proposal will be transferable into material technology and construction chemistry and will influence the development of standardization in this topic. As the interactions of biofilms and materials have implications for most constructions as well as climate change, the results of the research generates additional value.
Human-made systems, also called “build environment” or “technosphere”, sustain human comfort as well as our industrial activities. These systems have become particularly widespread since the Industrial Revolution, i.e., since the 17th century. At the same time, these technical systems – buildings, monuments, energy production, transformation and transmission, water purification and supply systems - serve as new habitats for living organisms.
Life is ubiquitously present on our planet since a very long time: the Earth is 4.54 billion years old and microbial communities have played a key role on our planet for 3.7 billion years. Once human-made system appeared, microorganisms became an integral part of all types of technosphere infrastructure as well.
Here we will illustrate biosphere-technosphere interactions using a specific example of the black fungi and their impact on the efficiency of solar (photovoltaic) panels. This expanding renewable infrastructure for electricity generation is growing on all continents - and create a specific, arid habitat for stress-tolerant black fungi.
Black fungi were once discovered in hot and cold natural deserts – and now belong to the persistent colonisers of human-made deserts of solar parks. This new niche is evolving an impressive biodiversity. So far more than 60 isolates of black fungi belonging to Arthoniomycetes, Eurotiomycetes and Dothideomycetes were obtained from solar panels in Europe and Americas. Here we will present the analysis of this emerging anthropogenic biodiversity.
Opportunities for future research in the field include quantification of the microbial load on technosphere surfaces – along with characterisation of the corresponding microbial diversity. The strategy of precise measurement and characterisation will enable us to reliably determine the beneficial and harmful functions that living microorganisms play in the functioning of energy-generating systems – and technosphere in general.
Cementitious materials are frequently applied in environments in which they are exposed to acid attack, e.g., in sewer systems, biogas plants, and agricultural/food-related industries. Alkali-activated materials (AAMs) have repeatedly been shown to exhibit a remarkably high resistance against attack by organic and inorganic acids and, thus, are promising candidates for the construction and the repair of acid-exposed structures. However, the reaction mechanisms and processes affecting the acid resistance of AAMs have just recently begun to be understood in more detail. The present contribution synthesises these advances and outlines potentially fruitful avenues of research. The interaction between AAMs and acids proceeds in a multistep process wherein different aspects of deterioration extend to different depths, complicating the overall determination of acid resistance. Partly due to this indistinct definition of the ‘depth of corrosion’, the effects of the composition of AAMs on their acid resistance cannot be unambiguously identified to date. Important parallels exist between the deterioration of low-Ca AAMs and the weathering/corrosion of minerals and glasses (dissolution-reprecipitation mechanism). Additional research requirements relate to the deterioration mechanism of high-Ca AAMs; how the character of the corroded layer influences the rate of deterioration; the effects of shrinkage and the bond between AAMs and substrates.
Materials with a high acid resistance are required in different important infrastructures. Examples include repair systems for sewer structures, where biogenic sulfuric acid corrosion is the major degradation mechanism. Low-calcium alkali-activated materials (AAMs) have been repeatedly observed to exhibit high acid resistance. However, the reasons for the high acid resistance of these materials were not fully under¬stood until recently, and the use of highly alkaline activator solutions to produce AAMs appears to hamper their commercial uptake. These issues have been tackled by characterising one-part AAMs and studying their alteration when exposed to sulfuric acid.
One-part AAMs were synthesized by mixing blends of solid silica and sodium aluminate with water, and subsequent curing at 60–80 °C. Acid resistance testing was performed according to DIN 19573, i.e. exposure to sulfuric acid at pH = 1 for 70 days. Characterisation of the cured and the acid-exposed materials was done by XRD, ATR-FTIR, SEM as well as 29Si, 27Al and 1H MAS NMR spectroscopy, including cross-polarisation and double-resonance methods.
Materials synthesized from industrial silicas were gel-zeolite composites, containing a substantial amount of unreacted ‘excess’ silica, while materials synthesized from rice husk ash were fully amorphous, containing ‘excess’ hydrous alumina. The sulfuric acid resistance of mortars based on these binders conformed to the requirements of DIN 19573 for sewer repair applications. The high acid resistance was caused by precipitation of silica gel at the mortar–solution interface, inhibiting further degradation. The presence of alumina gel may inhibit bacterial activity, potentially further improving performance in sewer environments.
The phase assemblage of silica/sodium aluminate-based one-part AAMs can be adjusted via choice of the silica starting material. Properly designed materials exhibit excellent acid resistance, caused by precipi¬tation of silica gel which protects subjacent regions, and they may also inhibit bacterial activity.
Alkali-activated materials have been repeatedly reported to exhibit high acid resistance, but no generally accepted hypothesis regarding the underlying mechanisms has emerged yet. To contribute to this issue, K-waterglass-activated metakaolin specimens, with and without the addition of CuSO4·5H2O in the starting mix, were exposed to either a chemically aggressive sewer environment (mortars) or sulfuric acid (pastes). The mode of copper incorporation in the materials and the formation of copper phases in the corroded layers were studied by XANES at the Cu K-edge, and 29Si, 27Al and 1H MAS NMR was employed to understand the processes during acid attack. Copper was found as a spertiniite-like phase in the as-cured materials, while in the deterioration layers of the pastes it was present as copper sulfate. In the corroded regions of the mortars, unequivocal identification of Cu phases was not possible, but the results were reconcilable with the presence of copper carbonate hydroxide. The solid-state NMR results revealed virtually complete dissolution of the K-A-S-H gel and the formation of silica gel, interpreted to be a central mechanism determining the acid resistance. No significant differences between the microstructural alterations of the pastes with and without Cu addition on (chemical) sulfuric acid attack were observed.
The present paper aims to re-examine the validity of the linear correlation found between AFTLOC, the adiabatic flame temperature at the apex of the flammability range of fuel-air-inert mixtures (where LOC, the Limiting Oxygen Concentration, is measured) and AFTLFL, the adiabatic flame temperature at the lower flammability limit of fuel-air mixtures (LFL). New sets of experimental measurements of LFL and LOC referring to fuel-air mixtures diluted with N2, CO2 and H2O(vap) from trusted literature sources form a comprehensive database for such evaluation. Both the slope and intercept of correlations AFTLOC = a + b*AFTLFL are dependent on the nature of inert gas and on initial temperature. Based on the linear correlation between AFTLOC and AFTLFL, a procedure for calculation of LOC and MIC (Minimum Inert Concentration) of fuel-air-inert mixtures is presented, using measured or calculated LFL of fuel-air mixtures and their corresponding AFT. The method predicts with reasonable accuracy LOC and MIC of fuel-air-inert mixtures (relative deviations ranging between -14 and +17% when calculated and measured LOC and MIC for fuelair-nitrogen and fuel-air-carbon dioxide at ambient initial conditions are examined).
Future lunar exploration will be based on in-situ resource utilization (ISRU) techniques. The most abundant raw material on the Moon is lunar regolith, which, however, is very scarce on Earth, making the study of simulants a necessity. The objective of this study is to characterize and investigate the sintering behavior of EAC-1A lunar regolith simulant. The characterization of the simulant included the determination of the phase assemblage, characteristic temperatures determination and water content analysis. The results are discussed in the context of sintering experiments of EAC-1A simulant, which showed that the material can be sintered to a relative density close to 90%, but only within a very narrow range of temperatures (20–30 °C). Sintering experiments were performed for sieved and unsieved, as well as for dried and non-dried specimens of EAC-1A. In addition, an analysis of the densification and mechanical properties of the sintered specimens was done. The sintering experiments at different temperatures showed that the finest fraction of sieved simulant can reach a higher maximum sintering temperature, and consequently a higher densification and biaxial strength. The non-dried powder exhibited higher densification and biaxial strength after sintering compared to the dried specimen. This difference was explained with a higher green density of the non-dried powder during pressing, rather than due to an actual influence on the sintering mechanism. Nevertheless, drying the powder prior to sintering is important to avoid the overestimation of the strength of specimens to be fabricated on the Moon.
Melanins are organic pigments produced by most fungi. These organisms either fix these pigments in their cell wall or secrete them into their extracellular environment to protect themselves against an array of physicochemical stresses (e.g., UV irradiation, desiccation, ...). Melanin can adsorb metals like Fe. How this affects fungal uptake of Fe and deterioration of Fe-containing minerals and metals is however less known. To study this, we use the model fungi Knufia petricola A95, a rock-inhabiting fungus known to deteriorate minerals and have melanised cell walls, and Amorphotheca resinae, able to contaminate fuel tanks, secrete melanin and corrode metals. In K. petricola, we have deleted genes involved in melanin production and Fe uptake using CRISPR/Cas. Through comparison of the geochemical signatures of these gene deletion mutants with those of the wild type (WT), we explore the specific mineral/metal deterioration mechanisms of melanised fungi.
Fe isotope signatures of the biomass of melanin- and Fe uptake-deficient mutants of K. petricola revealed that Fe adsorbed either directly onto melanin or after being reduced by Fe reductases. Importantly, once adsorbed to melanin, Fe could not be mobilised and taken up into the cell: both the WT and its melanin-deficient mutant, previously grown at Fe replete conditions, showed similar growth at Fe deficient conditions.
Olivine dissolution experiments revealed that Fe oxidation inhibits dissolution. K. petricola was able to enhance dissolution when this inhibition is strongest (at pH 6) and prevented dissolution when this inhibition is weakest (at pH 4). The fungus therefore dissolves olivine by interacting with the oxidised Fe at the olivine surface. However, Fe uptake did not seem to be involved: mutants deficient in various Fe uptake mechanism dissolved olivine at the same rate as the WT. This indicates that Fe adsorption onto melanin might play a key role. This is also shown by K. petricola’s ability to enhance olivine dissolution even further if secreting a melanin precursor and A. resinae’s corrosion of carbon steel whilst secreting melanin. Combined, our results imply that the Fe adsorbed to melanin cannot be taken up but enables fungi to deteriorate Fe-containing substrates at a higher rate.
Nanomaterials are used in many different applications in the material and life sciences. Examples are optical reporters, barcodes, and nanosensors, magnetic and optical contrast agents, and catalysts. Due to their small size and large surface area, there are also concerns about their interaction with and uptake by biological systems. This has initiated an ever increasing number of cyctoxicity studies of nanomaterials of different chemical composition and surface chemistry, but until now, the toxicological results presented by different research groups often do not address or differ regarding a potential genotoxicity of these nanomaterials. This underlines the need for a standardized test procedure to detect genotoxicity.1,2
Aiming at the development of fast, easy to use, and automatable microscopic methods for the determination of the genotoxicity of different types of nanoparticles, we assess the potential of the fluorometric γH2AX assay for this purpose. This assay, which can be run on an automated microscopic detection system, relies on the determination of DNA double strand breaks as a sign for genotoxicity.3 Here, we present first results obtained with broadly used nanomaterials like CdSe/CdS and InP/ZnS quantum dots as well as iron oxide, gold, and polymer particles of different surface chemistry with previously tested colloidal stability. These studies will be also used to establish nanomaterials as positive and negative genotoxicity controls or standards for assay performance validation for users of this fluorometric genotoxicity assay. In the future, after proper validation, this microscopic platform technology will be expanded to other typical toxicity assays.
References. (1) Landsiedel, R.; Kapp, M. D.; Schulz, M.; Wiench, K.; Oesch, F., Reviews in Mutation Research 2009, 681, 241-258. (2) Henriksen-Lacey, M.; Carregal-Romero, S.; Liz-Marzán, L. M., Bioconjugate Chem. 2016, 28, 212-221. (3) Willitzki, A.; Lorenz, S.; Hiemann, R.; Guttek, K.; Goihl, A.; Hartig, R.; Conrad, K.; Feist, E.; Sack, U.; Schierack, P., Cytometry Part A 2013, 83, 1017-1026.
An ideal sensor system is a combination of a selective receptor, an effective transducer, and a sensitive detector. To utilize molecularly imprinted polymers (MIPs) as responsive recognition phases in sensors, the employment of fluorescent molecules or nanoparticles (NPs) that show prominent changes in their spectroscopic properties after binding of the target molecule in the MIP’s cavity is particularly attractive. Such fluorescent MIPs (fMIPs) act through target-induced quenching, enhancement, or spectral shifts of the fluorescence. This contribution introduces different strategies of incorporation of fluorescent dyes, probes, and NPs into fMIPs. In addition, various sensing mechanisms are reviewed, and depending on the application of the sensor, the different deployable formats, their advantages, drawbacks, and impact will be presented and discussed.
Sealing and strengthening of the subsoil by grout injection is a major issue in the field of geotechnical engineering. One commonly applied method is jet grouting, which allows creating columns of grouted soil by eroding and mixing the in-situ soil with a thin cement suspension. A general difficulty linked with this method is in predicting the resulting column diameter and its material strength. In this paper, we illustrate the application of a newly developed non-destructive quality assurance tool used to determine the diameter of jet grout columns. This approach incorporates standard crosshole and downhole seismic measurements. To demonstrate its effectiveness, we tested the new approach within two-dimensional finite-difference numerical simulations. Additional field tests showed that this tool is also applicable in real site conditions. For this purpose, three jet grout columns were produced with different process parameters in a depth between 3 and 10 m. The evaluated diameters were within 1 and 1.5 m, slightly deviating from the previously predicted range by the jet grouting contractor. Moreover, we were able to detect the base of the columns at a 10-m depth with no significant difficulties. On the other hand, unsaturated, less compacted sands between the groundwater level and surface considerably affected the seismic data, hence complicating the detection of the top of the columns.
Novel approaches of tunable devices for millimeter wave applications based on liquid crystal (LC) are presented. In the first part of the paper, a novel concept of a tunable LC phase shifter realized in Low Temperature Cofired Ceramics technology is shown while the second part of the paper deals with a tunable high-gain antenna based on an LC tunable reflectarray. The reflectarray features continuously beam scanning in between ±25°. Also first investigations on radiation hardness of LCs are carried out, indicating that LCs might be suitable for space applications.
This paper presents the results concerning monotropic nematic liquid crystals 4-pentylphenyl 40-alkyl benzoate (5PnB) (n = 3 or 5 carbon atoms in the alkyl chain). Their mesophase properties were supported by images of the polarized optical microscopy. Molecular dynamics in the bulk samples or in the composites prepared with aerosil A380 was investigated by broadband dielectric spectroscopy in a large temperature range, appropriately chosen. Thermo gravimetric and infrared investigations were additionally performed. The data were compared with those of structurally related nematics like cyanophenyl pentyl benzoates, which have a cyan group instead of the pentyl chain. The dielectric spectra of the bulk 3P5B and 5P5B demonstrate a dielectric behavior with several relaxation processes as expected for nematic liquid crystals. The temperature dependence of the relaxation rates (and of the dielectric strength) seems to have two distinguished regimes. Thus, in the isotropic state, at higher temperatures the data obey the Vogel–Fulcher–Tammann law, whereas an Arrhenius law is fitted at lower temperature, in a close similarity to the behavior of a constrained dynamic glass transition. Samples with a high density of silica (larger than 7 g aerosil/1 g of 5PnB) were prepared to observe a thin layer adsorbed on the particle surface; it was estimated that almost each guest 5PnB molecule interacts with the aerosil surface. For the composites only one main relaxation process is observed at frequencies much lower than those for the corresponding bulk, which was assigned to the dynamics of the molecules in the surface layer. Infrared spectroscopy shows that these molecules interact with the surface by the ester carbonyl group leading to the monolayer self-assembly at liquid–solid interface. We note once more the importance of the functional unit(s) for the interaction with the hydroxyl groups on the aerosil surface.
Antimicrobials can exert specific physiological effects when used in combination that are different from those when applied alone. While combination effects have been extensively mapped for antibiotic-antibiotic combinations, the combination effects of antibiotics with antimicrobials used as biocides or antiseptics have not been systematically investigated. Here, we investigated the effects of combinations of antibiotics (meropenem, gentamicin, and ciprofloxacin) and substances used as biocides or antiseptics [octenidine, benzalkonium chloride, cetrimonium bromide, chlorhexidine, Povidone-iodine, silver nitrate (AgNO3), and Ag-nanoparticles] on the planktonic growth rate of Pseudomonas aeruginosa. Combination effects were investigated in growth experiments in microtiter plates at different concentrations and the Bliss interaction scores were calculated. Among the 21 screened combinations, we find prevalent combination effects with synergy occurring six times and antagonism occurring 10 times. The effects are specific to the antibiotic-biocide combination with meropenem showing a tendency for antagonism with biocides (6 of 7), while gentamicin has a tendency for synergy (5 of 7). In conclusion, antibiotics and biocides or antiseptics exert physiological combination effects on the pathogen P. aeruginosa. These effects have consequences for the efficacy of both types of substances and potentially for the selection of antimicrobial resistant strains in clinical applications with combined exposure (e.g., wound care and coated biomaterials).
Hochgeschwindigkeitsbeanspruchungen metallischer Bauteile sind bei einer Vielzahl ingenieurtechnischer Anwendungsbereiche, beispielsweise bei Crash- oder Falltests, bei Umform- oder Spanprozessen mit hohen Belastungsgeschwindigkeiten oder bei Aufprallproblemen von Komponenten schnell rotierender Bauteile auf das umgebende Gehäuse, z. B. bei Flugzeugturbinen, relevant. Dabei treten in dem beanspruchten Bauteil typischerweise Zonen mit großen, lokalisierten Deformationen auf, die auf die Entfestigung des Werkstoffs durch die Entwicklung von Schädigung und durch die Temperaturerhöhung infolge plastischer Dissipation zurückzuführen sind. Die Ausbildung von Scherbändern stellt dabei eine typische Form der Deformationslokalisierung dar. Die kontinuumsmechanische Modellierung solcher Vorgänge erfordert im Allgemeinen die Berücksichtigung einer Vielzahl von Faktoren und Effekten, wie beispielsweise dehnraten- abhängiges Materialverhalten, mit adiabatischer Erhitzung einhergehende thermische Entfestigung, Reibung und Kontakt sowie Schädigung. Darüber hinaus sind die genannten Effekte in dem Rahmen der Theorie großer Deformationen zu betrachten. Dehnratenabhängige ”lokale“ Modelle resultieren dabei nicht zwangsläufig in einer physikalisch sinnvollen Scherbandabbildung, d. h. in einer endlichen Scherbandbreite. Die innere Länge, die eine Begrenzung des Lokalisierungsvolumens darstellt, strebt für verschiedene im Rahmen der Simulation von Hochgeschwindigkeitsbelastungen eingesetzte, nichtlinear dehnratenabhängige Modelle, wie z.B. Potenzgesetz-Modelle oder dem Modell nach JOHNSON&COOK, mit infolge von Entfestigung abnehmender Spannung sowie zunehmender plastischer Dehnrate sehr stark gegen null. Dadurch tritt ein Verlust der lokalisierungsbegrenzenden Wirkung dieser ratenabhängigen Modelle ein, so dass insbesondere jedes, auf diesen Modellen aufbauende Finiten-Element Verfahren eine pathologische Netzabhängigkeit der Ergebnisse aufweist. ”Nicht-lokale“ Gradientenmodelle der Plastizität sind dazu geeignet, die beschriebenen Nachteile zu vermeiden. Die innere Länge dieser Modelle weist eine im Vergleich zu lokalen Modellen deutlich reduzierte Abhängigkeit von dem vorherrschenden Spannungszustand sowie der plastischen Dehnrate auf und wird darüber hinaus wesentlich durch den Wert des nichtlokalen Modellparameters beeinflusst. Die Größenordnung der inneren Länge bleibt dabei selbst für kleine Werte dieses Parameters auch mit Einsetzen von Lokalisierungseffekten zunächst erhalten. Infolge der numerischen Umsetzung nicht-lokaler Modelle mittels der Methode der Finiten- Elemente zeigt sich, dass im Gegensatz zu den auf lokalen Modellen basierenden Verfahren das Volumen der Lokalisierungszone bei stetiger Netzverfeinerung gegen einen endlichen Wert konvergiert. Damit gelingt es durch die Verwendung nicht-lokaler Modelle, die Ausbildung endlicher Scherbanddicken diskretisierungsunabhängig zu simulieren und im Rahmen der Kontinuumsmechanik eine sinnvolle Lösung des zugrunde liegenden physikalischen Problems zu gewährleisten.
For the first time, structure−electrochemical relationships of thin films of a plasma-polymerized acrylic acid/carbon dioxide AA/CO2 (75/25%) copolymer modified by implanted silver nanoparticles are discussed. The pulsed plasma polymerization of AA/CO2 was utilized and adjusted to obtain a maximal amount of COOH Groups forming an almost uncross-linked polymer structure. The prepared polymer layer is rinsed by a silver nitrate solution to impregnate Ag+ ions. This step is followed by its reduction of Ag+ with NaBH4 as a chemical route in comparison to the reduction by sunlight as an ecofriendly photoreduction method. The chemical composition and morphology of the topmost surface layer of the AA/CO2 polymer thin film were investigated by X-ray photoelectron spectroscopy and atomic force microscopy. Moreover, the molecular mobility, conductivity, and thermal stability of the polymer layer were analyzed using broadband dielectric spectroscopy. The dielectric properties of the AA/
CO2 polymer thin film were studied in the presence of Ag+ ions or Ag0. It was found that a cross-linked polymer layer with a smooth surface and high conductivity was obtained in the presence of Ag+/ Ag0.
A series of Mg₁₋ₓZnₓTiO₃, x = 0–0.5 (MZT0–MZT0.5) ceramics was synthesised and characterised. The dielectric properties of the samples in the frequency range of
1 Hz – 7.7 GHz were explored using three different methods:
a contacting electrode method, a parallel-plate method and a perturbed resonator method. The electrical properties in the space charge and dipolar polarisation frequency ranges are discussed in relation to the phase composition and microstructure data. Differences in the zinc Substitution divided the dielectrics into two groups, namely MZT0-MZT0.2 and MZT0.3–MZT0.5, each with different amount of a main Mg₁₋ₓZnₓTiO₃ solid solution phase and a secondary solid solution phase. Zinc substitution promoted the density of the ceramics, improved the purity of the main phase and increased the permittivity for frequencies up to 10⁸ Hz, but reduced the permittivity in the microwave range. In the MZT0.3–MZT0.5 samples, for frequencies less than 1 MHz the quality (Q x ƒ) factors were lower and log σ ₐ.c, the AC conductivity, was higher than for the MZT0–MZT0.2 samples. Above 10 MHz, the (Q x ƒ) factors and log σ ₐ.c of the two groups were similar.
For decades, the low-strain impact integrity testing using a hammer blow is well established as a method of quality assurance for various pile types. However, this method has its limitations. Our research and development focuses on improving the excitation signal using a shaker system in contrast to the standard hammer method. Another approach is to increase the amount of sensors used during testing. The purpose is to identify the direction of wave propagation which gives advantages under difficult conditions, such as piles below structures.
Pile integrity testing (PIT) using a shaker system was performed on two 11 m long piles of 90 cm in diameter. While one pile was intact, the other one showed a flaw at approx. 3.5 m below pile top, which was confirmed by standard PIT in 2012. A logarithmic sweep between 500 Hz and 1 KHz of 0.1 s was used as the input signal, being vertically injected into the pile. Prior to that, simulations on similar pile geometries showed that the depth of the pile toe as well as flaws within the pile can be extracted by applying regularized deconvolution. The result is the impulse response in the time domain.
The application of deconvolution on the measured signals shows that it is possible to identify the pile length but it is more difficult to clearly extract the flaw’s position in the pile. Additional digital signal processing techniques and the improvement of the regularized deconvolution method as well as the experimental setup need to be investigated.
Another way to improve the PIT method is to use a multichannel sensor arrangement. By arranging several accelerometers vertically along the accessible part of the pile shaft, it is possible to distinguish between downward and upward traveling waves. Furthermore, it is possible to estimate the unknown wave speed, which gives the possibility of more accurate pile length calculations. The method was evaluated successfully during a measurement campaign of a slab foundation with subjacent piles. In 20 of 28 cases the pile length could be detected accurately.
The impact fracture behavior of two common high-density polyethylene grades for container applications were intensively studied by the instrumented Charpy impact test after well-defined exposure to UV-irradiation. Individual stages of the impact event, such as crack initiation and crack propagation energy as well as maximum impact load, were investigated from the recorded load–deflection curves. UV-induced material property changes were further investigated by infrared spectroscopy, differential scanning calorimetry, and dynamic-mechanical analysis as well as density measurements. Based on the results of the Charpy impact test, three indicators were identified to describe the extend of photooxidation on high-density polyethylene: (a) a reduced Charpy impact strength—at least to half of its initial value for a distinctly brittle impact fracture, (b) a marked decrease in the crack propagation contribution to the impact strength, and (c) an increase of the brittle features of the fracture surface.
In the present study, a simple approach was used to investigate the effect of UV-exposure on two high density Polyethylene materials (PE-HD), commonly used for storage tanks, on fuel sorption behavior and colonization by microorganisms. The aim was to investigate whether the sorption behavior of the fuels (diesel/biodiesel) and the colonization by microorganisms, frequently occurring in the fuel, is affected and may lead to undesirable or safety-relevant material changes. We showed that the UV-irradiation leads to significant changes of the sorption behavior due to chemi-crystallization and crosslinking. The fuel Sorption is affected by the UV-induced formation of polar carbonyl and hydroxyl groups predominantly occurring at the surface. With respect to microbial colonization behavior for Bacillus subtilis and Pseudomonas aeruginosa, isolated from a contaminated diesel sample, differences of the initial adhesion could be shown depending on the initial type of polyethylene as well as on the degree of UV-induced degradation.
Renewable resources become more and more relevant to maintain energy demands for an increasing global population. Biosynthetic fuels like biodiesel might replace conventional petrochemical fuels. In this study the influence of microbial growth on biodiesel and diesel on the storage tank systems were investigated. Polymeric fuel storage tanks for diesel and biodiesel provide suitable environmental conditions for a broad spectrum of fungi and various bacteria, including cyanobacteria and aerobic heterotrophic, and even anaerobic, fermentative Bacteria. However, the questions whether and how ageing of the materials is affected by biofouling processes have not been answered so far. Therefore, a model system for biofilm formation was established to study the initial attachment phase of bacteria in dependency of ageing, quality and surface modification of thermoplastic polymers used for storage tank systems. The microbial survey is closely connected with a detailed characterization of the material’s properties and its ageing processes.
A widely applied plastic used for fuel storage tanks is high-density polyethylene (PE-HD), which is available with various additives to increase UV-light stability and even for the storage of biodiesel. These materials were aged under UV-light and temperature using a defined climate chamber set-up. Further, the repeated filling of fuels was mimicked for such storage tanks, as this has an important impact on the life-cycle length for the storage Container. The aged polymers showed a significant change in the material’s characteristics, including surface characteristics (e.g. hydrophobicity) and carbonyl groups. The effect of the changed material properties on the biofilm formation are studied using bacterial isolates, previously obtained from a “dieselpest”, and as a model-reference E. coli. The unaged polymers showed already some significant differences for the initial attachment of E. coli K12. Polyethylene with additives was colonized faster than the reference material (without additives) although the final biofilm coverage was not impaired. Likewise, the settlement of a kerosene-isolated Bacillus species on the unaged materials independently of additives was only minor interfered.
In future, our results should give stakeholders in industry and public authorities a better estimation of the life-cycle security for fuel storage tank systems and on the fuel quality. Further, our results could help to test and develop new materials or additives to prevent biofouling processes.
Biofilm formation poses high risks in multiple industrial and medical settings. However, the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization.
Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e. a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten dentical samples were laser-processed.
These samples were subjected to microbial adhesion tests, investigating bacterial adhesion behavior on the laser structures in comparison to polished reference surfaces. Short term experiments (<24h) were carried out to determine initial biofilm development. E. coli as a typical bacterium representing pathogenic bacteria and Shewanella putrefaciens as metal corrosive bacterium were used for biofilm development analyses. Bacterial cell adhesion was determined microscopically after DAPI cell staining (DNA staining). Comparison of the coverage areas between nanostructured and polished surfaces revealed differences in cell adhesion behavior and biofilm structure.
An analytical model for forecasting the temperature dependence of γ/γ' misfit in heat-resistant nickel alloys is proposed. The model accounts for the concentration dependences of the periods of crystalline lattices of the γ and γ' phases (Vegard law), thermal expansion of the γ and γ' lattices, and dissolution of the γ' phase at high temperatures. Adequacy of calculations of misfit is confirmed by comparison with the results of measurements using methods of X-ray and neutron diffraction. The model is applied for development of a nickel alloy with positive misfit.
Der Vortrag beschreibt den Entwicklungsprozess des Analysenverfahrens TED-GC-MS zur Bestimmung von Mikroplastikgehalten in Umweltproben im Rahmen des BMBF-Projektes MiWa. Die Funktionsweise, die Automatisierung und die Optimierung einzelner Geräteparameter und Leistungsdaten werden gezeigt. Untersuchungen des Einflusses von Probenmatrices werden dargestellt und die Ergebnisse einiger Messkampagnen und Ringversuche vorgestellt, die die Routinefähigkeit des Verfahrens dokumentieren.
Fichtenholz wird häufig als energieabsorbierendes Material in Stoßdämpfern von Transportbehältern für radioaktive Stoffe eingesetzt. Bei der vorgeschriebenen Fallprüfung aus 9 m Höhe auf ein unnachgiebiges Fundament erfährt das Fichtenholz im Stoßdämpfer eine dynamische Druckbelastung, wobei die seitliche Ausdehnung durch eine Blechkapselung eingeschränkt ist. Das Ziel dieser Arbeit war es, auf der Grundlage einer experimentellen Charakterisierung ein Materialmodell für Fichtenholz zur Berechnung solcher Lastfälle zur Verfügung zu stellen. Die experimentellen Untersuchungen zur Charakterisierung von Fichtenholz bestanden aus ca. 600 Druckversuchen an würfelförmigen Fichtenholzproben mit einem Stauchgrad von bis zu 70 %. Das Material wurde dabei als transversal isotrop angenommen. Insbesondere die Querdehnungsbehinderung konnte als ein relevanter Einflussfaktor auf die Materialcharakteristik identifiziert werden: Ohne Querdehnungsbehinderung dehnt sich das Material sowohl bei Last parallel als auch senkrecht zur Faser stark seitlich aus. Die Druckkraft- Verformungs-Verläufe weisen ein vergleichsweise geringes Kraftniveau und keine bzw. eine kaum ausgeprägte Verfestigung auf. Parallel zur Faser findet außerdem nach dem linear-elastischen Bereich eine starke Entfestigung statt. Eine Behinderung der Querdehnung führt zu einem deutlichen Anstieg des Druckkraftniveaus, einer stark ausgeprägten Verfestigung und lateral wirkenden Kräften. Die Entfestigung bei Last parallel zur Faser ist vergleichsweise gering ausgeprägt. Dehnrate und Temperatur haben festigkeitssteigernde bzw. festigkeitsverringernde Einflüsse, die im für Stoßdämpfer relevanten Bereich quantifiziert wurden. Anhand der experimentellen Erkenntnisse wurde die Hypothese der entkoppelten Fließflächenevolution aufgestellt, die von einer unabhängigen Festigkeitsentwicklung bei deviatorischer und volumetrischer Verformung ausgeht. Die Hypothese konnte mit einer Modifikation des Materialmodells MAT_075 aus dem FE-Code LS-DYNA bestätigt werden. Auf dieser Basis wurde anschließend ein transversal isotropes Materialmodell für Fichtenholz neu entwickelt und in LS-DYNA implementiert. Die Charakteristika von Fichtenholz unter Druckbelastung wurden in einer 15-flächigen Fließbedingung und einer nicht-assoziierten Fließregel umgesetzt. Die Fließbedingung berücksichtigt Mehrachsigkeiten des Druckspannungszustands durch eine lineare Interpolation der aus den Druckversuchen mit und ohne Querdehnungsbehinderung abgeleiteten Festigkeiten. Nachrechnungen der Druckversuche zeigten eine gute Abbildung der grundsätzlichen Festigkeitscharakteristik von Fichtenholz durch das Modell. Der für blechgekapselte Stoßdämpfer sehr bedeutsame Einfluss der Querdehnungsbehinderung kann durch die entkoppelte Evolution der Fließfläche angemessen wiedergegeben werden. Bei Last unter spitzen Faserwinkeln werden die Festigkeiten vom Modell jedoch überschätzt, was durch eine Anpassung der Druckfließflächen verhindert werden könnte. Die Einflüsse von Dehnrate und Temperatur können grundsätzlich nachgebildet werden, die verwendeten Skalierungsfaktoren sollten aber überarbeitet werden. Die Nachrechnung eines Behälterfallversuchs mit holzgefüllten Stoßdämpfern bestätigte die grundsätzliche Anwendbarkeit des Modells und zeigte plausible Rechenergebnisse. Für ein verifiziertes Stoßdämpfermodell sind weitere experimentelle und numerische Arbeiten erforderlich, wie z. B. die Untersuchung von Reibkoefizienten und Versagensparametern. Die Arbeit leistet mit dem transversal isotropen Materialmodell einen wichtigen Beitrag für die numerische Beanspruchungsanalyse bei der sicherheitstechnischen Begutachtung von Transportbehältern für radioaktive Stoffe.
Based on methane from renewable resources, LNG is an alternative fuel for heavy and long-distance traffic in land transport. Contrary to its positive properties, the fuel contains risks from an explosion and extremely low temperatures for personal and infrastructure safety. CFD-models are suitable for doing risk analyses for arbitrary scenarios. For examining how to model for risk research the dispersion of LNG-vapor, this paper contains a model variant study, with an evaluation by experiments.
This paper describes the use of the CFD-code ANSYS Fluent for simulating experiments of the ‘LNG Safety Program Phase II‘. The content of the well-documented experiments was the research of the vaporization rate of LNG on land and the dispersion of LNG-vapor in the air. Based on the comparison to two experiments, overall 12 CFD-model variants with varying thermal and turbulence parameters were examined how they affect the transient LNG-vapor dispersion in air.
The definition of turbulence-boundary-condition at the domain borders had the biggest impact on modeling, followed by the turbulence model. The most accurate model variant had been applied for observing the spreading behavior of LNG-vapor in the air after evaporation on land and analyzing the influence of the LNG-composition to the dispersion. The results show that the mixture of LNG-vapor and the air in the free field is cooler than the ambient air and spreads like a heavy gas on the ground.
Fungal pigments such as melanin and carotenoids are distinctive markers of animal and plant pathogenic fungi as well as their environmental relatives. These complex pigments play important roles in pathogenicity and stress tolerance while also being useful as biomarkers. Accordingly, it is important to be able to identify in situ the pigments in black fungi, a group of clinical and environmental importance. In this study, wild-type and genetically modified strains of Knufia petricola A95 and wild fungal cells attached to ancient rock were investigated for their spectroscopic and microscopic Raman features and morphological appearance. Knockout mutants of melanin synthesis genes pks1 (polyketide synthase), sdh1 (scytalone dehydratase), and both pks1 and the carotenoid synthesis gene phd1 (phytoene desaturase) were studied We applied two different Raman microscopes using two lasers, with 633 nm and 488 nm wavelengths. We analyzed and compared Raman spectra between the measured reference substances and the mutant and wild-type strains. In the wild strain WT:A95, the peaks close to melanin peals were found at 1353 cm−1 and 1611 cm−1. There are no characteristic melanin peaks at 1580–1600 cm−1 and around 1350 cm−1 at the spectrum of the Δpks1/Δphd1 mutant and the Δsdh1 mutant. The Δpks1 mutant spectrum has the peaks at the beta-carotene v2 C-C in-plane stretch at 1155 cm−1 and v3 C-CH3 deformation at 1005 cm−1. The peaks of carotenoids and melanin were found in all mutants and the wild strain, except the Δpks1/Δphd1 mutant. Raman spectra allow for discrimination between the various pigments. Hence, interactions between natural fungal melanin, as well as other protective pigments, and complex environmental matrices can be characterized on a range of spatial and temporal scales.
With the latest ICP-MS technology - ICP-ToF (time of flight)-MS - it is possible to analyze the multi-element fingerprint of individual cells. The interface between material and environmental analysis thus receives special attention, e.g. when considering corrosion processes. Microbiologically influenced corrosion (MIC) is highly unpredictable due to the diversity of microbial communities involved. The development of the MIC-specific ICP-ToF-MS analytical method presented here at the single cell level, in combination with the investigation of steel-MIC interactions, contributes significantly to progress in instrumental MIC analysis and will enable clarification of the processes taking place.
The supplied document shows the basis of a four minutes lightning talk.
ICP-ToF (Flugzeitanalysator, engl. time of flight)-MS ermöglicht den Multielement Fingerabdruck einzelner Zellen (single cell) zu analysieren. Die single cell-ICP-ToF-MS kommt bei dem vorgestellten Poster bei der Analyse von Archaeen, die an mikrobiell beeinflusster Korrosion (engl. microbiologically influenced corrosion, MIC) von Stahl eine Rolle spielen, zum Einsatz. Mittels sc-ICP-ToF-MS wird die mögliche Aufnahme von einzelnen Elementen aus dem jeweiligen Stahl untersucht – die erhaltenen Informationen fließen zukünftig in die Aufklärung zugrunde liegender Mechanismen sowie Entwicklung möglicher Materialschutzkonzepte ein. Die Arbeiten Verknüpfen moderne Methoden der Analytical Sciences mit Materialien.
ICP-ToF (time of flight) MS enables the analysis of the multi-element fingerprint of single cells. The single cell ICP-ToF-MS is used in the presented poster for the analysis of archaea involved in microbiologically influenced corrosion (MIC) of steel. By means of sc-ICP-ToF-MS, the possible uptake of individual elements from the respective steel is investigated - the information obtained will be used in the future to elucidate underlying mechanisms and develop possible material protection concepts. The work combines modern methods of analytical sciences with materials.
The latest ICP-MS technology - ICP-ToF (time of flight)-MS – enables the analysis of the multi-element fingerprint of individual cells. The interface between material and environmental analysis thus receives special attention, e.g., when considering corrosion processes. Microbiologically influenced corrosion (MIC) is a highly unpredictable phenomenon due to the influence of the environment, microbial communities involved and the respective electron source. However, the interaction pathway between cells and the metal surface remains unclear. The development of the MIC-specific ICP-ToF-MS analytical method presented here at the single cell level, in combination with the investigation of steel-MIC interactions, contributes significantly to progress in instrumental MIC analysis and will enable clarification of the processes taking place. For this, a MIC-specific staining procedure was developed. It allows the analysis of archaea at a single cell level and provides information about the interaction of the cells with the staining agent which is extremely scarce compared to other well characterized organisms. Additionally, the single cell ICP-ToF-MS is used for the analysis of archaea involved in MIC of steel. Hence, the possible uptake of individual elements from different steel samples is investigated - the information obtained will be used in the future to elucidate underlying mechanisms and develop possible material protection concepts, thus combining modern methods of analytical sciences with materials.
Up to now, different analytical methods for single cell analysis exist focusing on key features such as size, shape, morphology and elemental composition. The combination of the latest ICP-MS techniques - ICP-ToF-MS - together with the latest developments in the field of sample delivery - micro droplet generator (MDG) – will allow a Deep insight into the composition and size of cells.
Microbiologically influenced corrosion (MIC) is an oxidation of metals affected by the presence or activity (or both) of microorganisms e.g. Shewanella Putrefaciens in biofilms on the surface of the corroding material. As this can happen for example in the soil on iron pipes of water pipes, in oil tanks or on steel sheet piling, there is great interest in MIC research, not only from various industrial sectors, but also from the environmental aspect.
The role of methanogens in microbiologically influenced corrosion (Mi-MIC) is often neglected, due to 1) low reported corrosion rates and 2) the suspected corrosion product siderite, which is electrically non-conductive. Typically, MIC corrosion studies are carried out using batch cultures, which did not represent the dynamic conditions, i.e. pipeline and provide insufficient information on the overall corrosion potential.
We established a unique approach, a multiport flow column (MFC), to simulate pipeline conditions and obtained 10-times higher corrosion rates than previously published. Our result showed that testing procedures have a large impact on the corrosive potential of methanogens. We found strong indications with a combination of ToF-SIMS, SEM-EDS and FIB-SEM analyses that siderite is not the sole corrosion product. The corrosion layers contain phosphorus, oxygen, magnesium, calcium and iron. To verify and deepen our understanding of Mi-MIC, we are currently studying the influence of other environmental parameters (e.g. pH) on Mi-MIC.
Corrosion is a very expensive and serious problem in the different industry sectors, eg. Petroleum-, On- and off-shore, infrastructure. It is estimated that 20% of all corrosion damage is caused by microorganisms or microbiologically influenced corrosion (MIC). Several microorganisms are known to cause corrosion, including sulfate-reducing bacteria, nitrate-reducing bacteria, methanogens etc. For several years, methanogens were regarded as a mild corroder (~0.065 mm/yr), largely due to a lack of detailed investigation on the corrosion mechanism under real-environment simulated conditions. Resulting in the common belief that siderite, a non-conductive compound, is the sole corrosion product (CP) of methanogen-induced MIC (Mi-MIC).
To simulate natural environmental conditions, we developed and introduced the multiport flow column system (MFC), a multi-sectional corrosion flow-cell. Using the MFC, we obtained ten times higher corrosion rates than previously reported. With a combination of several analytical techniques, such as ToF-SIMS, SEM-EDS and FIB-SEM, we found strong indication that siderite is not the sole corrosion product of Mi-MIC. The corrosion layers contained phosphorus, oxygen, magnesium, calcium and iron. The differences in the CP between static and dynamic environments demonstrated the impact of testing procedures on the corrosive potential of methanogens. To further verify and deepen our understanding of Mi-MIC, we are currently studying the influence of additional environmental parameters (e.g. pH, salinity, flow rate) on Mi-MIC.
Overall, results of this study will expand the current understanding of MIC from both analytical and mechanistic points of view, thus aiding the development of different mitigation strategies for various industry sectors.
Microbiologically influenced corrosion (MIC) is a now well-known challenge and affects industry, society and infrastructure. For a long time, the impact of methanogen-induced MIC (Mi-MIC) was underestimated. This was mainly due to the rather low published corrosion rates and the presumed corrosion product siderite, which is not electrically conductive. In our laboratory, we were able to show that this trivialization or underestimation of Mi-MIC was due to the nature of the testing. The static systems used so far do not provide environmentally relevant information about the corrosion rate and the corrosion product, especially for methanogens
To further illustrate the importance of the environment on the MIC process, we established a multiport flow column (MFC), to simulate the natural environment. With this method, and in contrast to published results using the static conditions, we obtained ten times higher corrosion rates. We analyzed the corrosion products with a combination of techniques, like ToF-SIMS, SEM-EDS and FIB-SEM, and found strong evidence that siderite is not the sole corrosion product of Mi-MIC. The corrosion layers contain phosphorus, oxygen, magnesium, calcium and iron and lacked on carbon-related species. It is hypothesized that methanogens may have influenced the nucleation process of siderite, converting bicarbonate into carbon dioxide for methanogenesis. This results in increased localized corrosion and reduced siderite formation. To verify and deepen our understanding of Mi-MIC, we are currently studying the influence of additional environmental parameters (e.g. pH, salinity, flow rate etc.) on Mi-MIC and the subsequent impacts on corrosion rates and the corrosion products.
Overall, results of this study will expand the current understanding of MIC from both analytical and mechanistic points of view, thus aiding the development of different mitigation strategies for various industry sectors.
We invented the first non-metallic, self-adhesive and dry biosignalling electrode. The PEDOT polymer electrode changes its aggregate state and conductivity by a light curing procedure. The electrode can be applied as a gel underneath hair without shaving. With the aid of blue light, the electrode can be hardened within a few seconds at the desired location on the scalp. The cured polymer electrode is highly conductive and can be applied on a very small location. Unlike other EEG electrodes, our electrode does not lose conductivity upon drying. Furthermore, our electrode strongly bonds to Skin and does not require any additional adhesive. Short circuits due to an outflow of gel are prevented with this technique. Therefore, the PEDOT polymer electrode is extremely well suited for applications that, up to now, have been challenging, such as non-invasive EEG recordings from awake and freely moving animals, EEG recordings from preterm babies in the neonatal intensive care unit or long-term recordings in the case of sleep monitoring or epilepsy diagnostics. We addressed two technical questions in this work. First, is the EEG recorded with polymer electrodes comparable to a standard EEG? Second, is it possible to record full-band EEGs with our electrodes?
Implant-associated infections present severe and difficult-to-treat complications after surgery, related to implant biofilm colonization. Systemic administration of antibiotics cannot reach sufficient concentrations at the infected site and may be toxic. Here we describe how mussel-inspired dendritic material coated on a titanium surface can locally activate a prodrug of daptomycin (pro-dapto) to treat methicillin-resistant Staphylococcus aureus. The mechanism of the prodrug activation is based on bio-orthogonal click chemistry between a tetrazine (Tz) and trans-cyclooctene (TCO). The former is attached to the dendritic polymer, while the later converts daptomycin into a prodrug. Characterization of the material's properties revealed that it is hydrophobic, non-toxic, and stable for a prolonged period of time. We envision that the titanium coated dendritic material will be able to improve the treatment of implant-associated infections by concentrating systemically administered antibiotic prodrugs, thus converting them into active localized medicines.
The synthesis, characterization, and application of mesoporous materials containing boron–dipyrromethene (BODIPY) moieties that allow the sensitive and selective detection of HgII in aqueous environments by fluorescence enhancement is reported. For this purpose, BODIPY dye I containing a thia‐aza crown ether receptor as the fluorescent probe for the detection of HgII in aqueous environments is encapsulated into mesoporous materials to avoid self‐quenching or aggregation in water. Determination of HgII is accomplished within a few seconds with high selectivity and sensitivity, reaching a limit of detection of 12 ppt. The determination of trace amounts of HgII in natural waters and in fish extracts is demonstrated by using our sensing material. The incorporation of the material into several μ‐PAD strips yields a portable, cheap, quick, and easy‐to‐handle tool for trace HgII analysis in water.
Silver nanoparticles (AgNPs) nowadays appear in close to 24% of consumer products that contain engineered nanomaterials. Thus, they are expected to be released into the environment, where their fate and effect are still undetermined. Considering the evidenced efficacy of the single particle Inductively Coupled Plasma – Mass Spectrometry (sp ICP-MS) technique in the study of nanomaterials, this work reports on the use of sp ICP-MS along with an online dilution sample introduction system for the direct analysis of untreated and spiked seawater samples, as part of a larger scale experiment studying the fate of Ag (ionic and nanoparticles) in seawater mesocosm systems. Silver nanoparticles coated with branched polyethyleneimine (BPEI@AgNPs) or ionic silver (Ag+) were introduced gradually into the seawater mesocosm tanks at very low, environmentally relevant concentrations (50 ng Ag L− 1 per day, for 10 consecutive days, up to a total of 500 ng Ag L− 1 ), and samples were collected and analyzed daily, within a consistent time window. Using very low detector dwell time (75 μs) and specialized data treatment, information was obtained on the nanoparticles’ size distribution and particle number concentration, as well as the ionic silver content, of both the AgNPs and the Ag+ treated seawater mesocosm tanks. The results for the AgNP treated samples indicated the rapid degradation of the added silver particles, and the subsequent increase of ionic silver, with recoveries close to 100% for the first days of the experiment. On the other hand, particle formation was observed in the Ag+ treated seawater tanks, and even though the number concentration of silver-containing nanoparticles increased throughout the experiment, the amount of silver per particle remained relatively constant from the early days of the experiment. In addition, the online dilution sample introduction system for the ICP-MS proved capable of handling the untreated seawater matrix without significant contamination issues and downtime, while the low dwell time and data treatment procedure developed were shown to be suitable for the analysis of nanomaterials at the low nm-scale, despite the complex and heavy matrix introduced into the ICP-MS.
Excessive discharge of quaternary ammoniumdisinfectants such as benzalkonium chloride (BAC) into aquatic systems can trigger several physiological responses in environmental microorganisms. In this study, we isolated a less-susceptible strain of Aeromonas hydrophila to BAC, designated as INISA09, froma wastewater treatment plant in Costa Rica. We characterized its phenotypic response upon exposure to three dierent concentrations of BAC and characterizedmechanisms related to its resistance using genomic and proteomic approaches. The genome of the strain, mapped against 52 dierent sequenced A. hydrophila strains, consists of approximately 4.6Mb with 4,273 genes. We found a massive genome rearrangement and thousands of missense mutations compared to the reference strain A. hydrophila ATCC 7966.
We identified 15,762 missense mutations mainly associated with transport, antimicrobial resistance, and outer membrane proteins.
In addition, a quantitative proteomic analysis revealed a significant upregulation of several efflux pumps and the downregulation of porins when the strain was exposed to three BAC concentrations.Other genes related tomembrane fatty acid metabolism and redox metabolic reactions also showed an altered expression.
Our findings indicate that the response of A. hydrophila INISA09 to BAC primarily occurs at the envelop level, which is the primary target of BAC. Our study elucidates the mechanisms of antimicrobial susceptibility in aquatic environments against a widely used disinfectant and will help better understand howbacteria can adapt to biocide pollution. To our knowledge, this is the first study addressing the resistance to BAC in an environmental A. hydrophila isolate. We propose that this bacterial species could also serve as a new model to study antimicrobial pollution in aquatic environments.
The demands for the assessment of water quality are increasing steadily, making it necessary to routinely monitor multiple contaminants in water samples. For this application a hapten microarray was developed. In order to reach the required low detection limits a design of experiments (DoE) approach was used to optimize the assay performance. Here we show that a Box-Behnken design plan is an adequate choice for the straightforward exploration of hapten microarray assay parameters. For both read-out systems studied (fluorophore-labelled detection antibodies or enzymatic signal development followed by reflectometric scan, respectively), it was possible to significantly extend the measurement ranges. Furthermore, it could be shown that multivariate data analysis, here partial least squares regression (PLS), can improve the prediction accuracy of 'unknown' samples when used as calibration model, compared to classical, univariate data evaluation methods.
In the framework of non-destructive-testing advanced seismic imaging techniques have been applied to ultrasonic echo data in order to examine the integrity of an engineered test-barrier designed to be used for sealing an underground nuclear waste disposal site. Synthetic data as well as real multi-receiver ultrasonic data acquired at the test site were processed and imaged using Kirchhoff prestack depth migration reverse time migration (RTM). In general, both methods provide a good Image quality as demonstrated by various case studies, however deeper parts within the test barrier containing inclined reflectors were reconstructed more accurately by RTM. In particular, the image quality of a specific target reflector at a depth of 8 m in the test-barrier has been significantly improved compared to previous investigations using synthetic aperture Focusing technique, which justifies the considerable computing time of this method.
Das Kapitel beginnt mit einer kurzen Einführung über die Korrosion (Wechselwirkung zwischen einem Metall, einer korrosiven Umgebung und der der jeweiligen Konstruktion). Im zweiten Abschnitt werden die wichtigsten Formen der wässrigen elektrochemischen Korrosion (Flächenkorrosion, galvanische, selektive und interkristalline Korrosion sowie Loch- und Spaltkorrosion) betrachtet. Darüber hinaus wird die elektrochemische Korrosion unter mechanischer Belastung betrachtet (Spannungsrisskorrosion, wasserstoffunterstützte Rissbildung, Korrosionsermüdung), sowie Sonderformen der Korrosion (Erosion, Fretting und mikrobiologisch induzierte Korrosion). Der dritte Abschnitt befasst sich mit der chemischen und Hochtemperaturkorrosion (Oxidation, Aufkohlung, Hochtemperatur-Wasserstoffangriff, Aufschwefelung, Nitrierung, Halogenierung). Zusätzlich enthält das Kapitel Maßnahmen zur Vermeidung der Korrosion.
The chapter starts with a brief introduction about corrosion, which is defined as the interdependency between a metal, a corrosive environment, and the respective component design. The second section introduces the most important forms of aqueous electrochemical corrosion (uniform corrosion, galvanic corrosion, selective and intergranular corrosion, and finally pitting and crevice corrosion in the case of passive layer forming metals). In addition, electrochemical corrosion under applied mechanical load is introduced (stress corrosion cracking, hydrogen-assisted cracking, corrosion fatigue), as well as special forms of corrosion (erosion, fretting, and microbiologically induced corrosion). The third section of this chapter introduces (mostly dry) chemical corrosion and high-temperature corrosion (oxidation, carburization, high-temperature hydrogen attack, sulfurization, nitriding, halogenation). As in the case of electrochemical corrosion, chemical corrosion can also be superimposed by mechanical loads. Finally, general facts on the testing of corrosion are introduced.
Für Anwender nichtrostender Stähle wird im neu überarbeiteten Merkbaltt 833 eine Planungshilfe für Anwendungen nichtrostender Stähle in Erdböden gegeben. Hinweise und Empfehlungen zur Werkstoffauswahl sowie allgemeine Hinweise zum Einsatz nichtrostender Stähle und auch Anwendungsbeispiele sind im neu überarbeitetn Merkblatt enthalten.
Zu Sicherstellung der Korrosionsbeständigkeit sind zu beachten: geeignete Werkstoffauswahl und Legierungszusammensetzung; fehlerfreie, ggf. zertifizierte Halbzeuge; eine gleichmäßige Elementverteilung; die Vermeidung von Ausscheidungen; eine geeignete Umformung; möglichst wenig Wärmeeinbringung; eine möglichst glatte Oberflächenausführung, eine gute schweißtechnische Verarbeitung und die nachträgliche Entfernung von Anlauffarben, eine geeignete mechanische Bearbeitung (Schleifen, Strahlen); ggf. eine chemische Nachbehandlung wie Beizen, Passivieren) sowie eine ausreichende Grundreinigung und eine angepasste Unterhaltsreinigung.
Eine zentrale Aufgabe der zerstörungsfreien Prüfung und der Strukturüberwachung (engl. Structural Health Monitoring - SHM) mit Ultraschallwellen ist die Bewertung von Schäden in Bauteilen. In vielen Bauteilen, wie zum Beispiel platten- und schalenförmigen Strukturen, Rohrleitungen oder Laminaten, breitet sich der Ultraschall in Form geführter Wellen aus. Zwar haben geführte Wellen eine relativ große Reichweite innerhalb des Bauteils und ermöglichen so eine großflächige Prüfung, ihre multimodalen und dispersiven Eigenschaften erschweren jedoch die Analyse der vom Schaden kommenden Reflexionen. Eine Möglichkeit, die Messsignale zu interpretieren und die Schäden zu charakterisieren, ist deren Vergleich mit der Wellenausbreitung in einem digitalen Modell. Hierbei stellt sich die Aufgabe, den Schaden im digitalen Modell anhand der Messdaten zu rekonstruieren. Diese Rekonstruktion beschreibt ein inverses Problem, das mehrere Vorwärtsrechnungen braucht, um das Schadensmodell an die Messdaten anzupassen. Durch die kleine Wellenlänge von Ultraschallwellen sind klassische Vorwärtsmethoden wie die Finte Elemente Methode rechenintensiv, weshalb die Autoren die semi-analytische Scaled Boundary Finite Element Method (SBFEM) benutzen, um den Rechenaufwand zu verringern. Im Beitrag wird ein inverses Verfahren basierend auf dem Automatischen Differenzieren in Kombination mit der SBFEM vorgestellt und an verschiedenen Schadenstypen in 2D-Querschnittmodellen von Wellenleitern getestet. In der präsentierten Vorstudie werden dafür „Messdaten“ aus unabhängigen Simulationen verwendet.
ln den letzten Jahren wurden diverse Prüfverfahren und Methoden entwickelt, um die Leistungsfähigkeit von Beton bzw. Bindemittel hinsichtlich des Widerstands gegenüber betonaggressiven Einwirkungen beurteilen zu können. Ein wesentliches Ziel von Prüfverfahren zur Beurteilung der Dauerhaftigkeit von Baustoffen ist, die im Laufe der Nutzungsdauer zu erwartenden Einwirkungen auf den Baustoff realitätsnah abzubilden. Dazu sind die Prüfparameter auf die im jeweiligen Anwendungsbereich vorherrschenden Umgebungs- und Randbedingungen anzupassen. Daneben sind auch die Bewertungskriterien individuell unter Berücksichtigung der im Einzelfall geforderten Nutzungsdauer eines Bauwerks festzulegen. Eine systematische Zuordnung von adäquaten Prüfverfahren bzw. Prüfparametem und Bewertungskriterien für die verschiedenen Anwendungsbereiche im Betonbau, in denen betonaggressive Einwirkungen auftreten, ist mit Ausnahme von Einzelfällen bislang nicht vorhanden. Daneben stellt sich in der Praxis immer wieder das Problem, das Angriffspotenzial der Umgebung eines Bauwerks (prüftechnisch) zu erfassen und zu bewerten.
Der Hauptausschuss Baustofftechnik des DBV hat daher den Arbeitskreis „Chemischer Angriff auf Beton“ beauftragt, dieses Merkblatt zu erarbeiten, das auf Basis von einschlägigen Erfahrungen der Baupraxis und wissenschaftlichen Erkenntnissen Grundsätze und bewährte Methoden zur Beurteilung der Einwirkungs- und Widerstandsseite beim chemischen Angriff auf Beton aufzeigt und diesbezüglich Hinweise für verschiedene Anwendungsbereiche im Betonbau liefert.
Microstructure-property connections for porous ceramics: The possibilities offered by micromechanics
(2016)
Microstructure of porous ceramics is highly “irregular”: it comprises pores and microcracks of diverse shapes and orientations.
This makes their quantitative modeling challenging, and one
often resorts to empirical relations containing Fitting Parameters and having somewhat uncertain range of applicability. We review the substantial progress made in modeling of “irregular” microstructures that does not seem to have been sufficiently utilized in the context of ceramics. We discuss the possibilities offered by micromechanics in developing microstructure–property relations for porous microcracked ceramics. After an overview of relevant micromechanics topics, we focus on several issues of specific interest for ceramics: nonlinear stress–strain behavior, effective elastic properties, and thermally induced microcracking. We discuss extraction of microscale Parameters (such as strength of the intergranular cohesion, density of cracks and pores, etc.) from macroscopic data and identify the extent of uncertainty in this process. We also argue that there is no quantitative correlation between fracturing process and the loss of elastic stiffness.
Assessment of international reference materials for isotope-ratio analysis (IUPAC Technical report)
(2014)
Phase-segregated PEU exhibits two-way shape changes under various constant stresses. Most distinct actuation (expansion on cooling and contraction on heating) can be detected between +60 and -20 °C when the maximum stress applied during a thermo-mechanical pretreatment approached the point where deformation-induced crystallization of the PBA soft segment sets in. The driving forces for the strain-related two-way shape changes consist of PBA crystallization and PBA melting-induced entropy elasticity. At low constant stresses (<1.5 MPa), entropy elasticity also contributes to specimen expansion on cooling. The results of multiple- cycling experiments imply that PEU is an appropriate candidate for the fabrication of thermoresponsive actuators working under constant stress conditions.
Shape memory polymers (SMPs) can change their shape on application of a suitable stimulus. To enable such behavior, a ‘programming’ procedure fixes a deformation, yielding a stable temporary shape. In thermoresponsive SMPs, subsequent heating triggers entropy-elastic recovery of the initial shape. An additional shape change on cooling, i.e. thermoreversible two-way actuation, can be stimulated by a crystallization phenomenon. In this thesis, cyclic thermomechanical measurements systematically determined (1) the shape memory and (2) the actuation behavior under constant load as well as under stress-free conditions. Chemically cross-linked, star-shaped polyhedral oligomeric silsesquioxane polyurethane (SPOSS-PU) hybrid polymer networks and physically cross-linked poly(ester urethane) (PEU) block copolymers were investigated around the melting and crystallization temperatures of their polyester soft segments. (1) The SPOSS-PUs showed excellent shape fixities and recoverabilities of almost 100% at high cross-linking density, while PEUs exhibited pronounced shape memory properties at increased soft segment content. Furthermore, two-fold programmed SPOSS-PU specimens were able to recover their initial shape in two thermally separated events. Even a neck, which formed during deformation of SPOSS-PUs with high soft segment content, was reversed. (2) In PEUs, globally oriented crystallization on cooling drove expansion of the sample, in particular at high soft segment content and after application of a strong deformation. Melting reversed that orientation; the PEU sample contracted and thereby completed the thermoreversible actuation cycle. Under load, multiple polymorphic phase transitions enabled two successive expansion and contraction steps, while under stress-free conditions various geometric shape changes, including the increase and decrease of PEU sample length and thickness as well as twisting and untwisting could be experimentally witnessed. Such actuation technology allows for entirely new applications, enabling mimicry of reversible, bidirectional and repeated organic movements.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the picosecond to femtosecond range. During the past few years significantly increasing research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical or chemical properties. In this contribution current applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting, the tailoring of surface colonization by bacterial biofilms, and the improvement of the tribological performance of nanostructured metal surfaces.
Reinigung wird in der Lebensmittel- und Pharmaindustrie aufgrund des stetig steigenden Kosten- und Zeitdrucks sowie der hohen Verbrauchererwartungen hinsichtlich Produktsicherheit und -haltbarkeit ein immer zentraleres Thema. Eine verbesserte Reinigbarkeit bedeutet für die produzierende Industrie eine Steigerung der Effizienz der Produktionsanlage. Besonders in der heutigen medienintensiven Zeit kommt ein "Lebensmittelskandal" durch ein unsicheres Produkt einem finanziellen Desaster und immensem Imageverlust gleich. Aus diesem Grund ist die Reinigbarkeit der produktberührenden Oberflächen stets ein wichtiges Kriterium für die Werkstoffauswahl.
Basierend auf den Theorien zu Schmutzhaftung und -entfernung wurde im Rahmen dieser Arbeit überprüft, ob und wie die theoretisch relevanten Parameter auch in den Experimenten den Reinigungserfolg beeinflussen. Der Schwerpunkt wurde auf die Einflussgrößen des Werkstoffes gelegt, um herauszufinden, wie stark eine Oberfläche selbst zu ihrer Reinigbarkeit beitragen kann (self-cleaning).
In den durchgeführten Versuchen hat sich gezeigt, dass die Oberflächenrauheit lediglich bei der Reinigung von kohäsiven Schmutzfilmen eine entscheidende Rolle gespielt hat. Hingegen ist ihr Einfluss auf das Reinigungsergebnis von sich auflösenden Schmutzfilmen und Partikeln nur begrenzt bis gar nicht zur Geltung gekommen. Das Oberflächenmaterial hatte keinen starken, aber dennoch signifikanten Einfluss auf die Reinigbarkeit der untersuchten Oberflächen. Dass die Reinigbarkeit einer Oberfläche keine Materialkonstante sein kann, wurde unter Verwendung spezieller Oberflächen mit definiert geätzten Rauheitsstrukturen nachgewiesen. Der Reinigungserfolg hängt immer auch von der Verunreinigungsart ab, was sich auch in vergleichbaren Versuchen der Einzelpartikelablösung mittels AFM in dem Einfluss der Elastizität bzw. Plastizität der Partikeln geäußert hat.
Praxistaugliche Empfehlungen gehören mit zu den wichtigsten Zielen dieser Arbeit gewesen. Mit Fokus auf die Oberflächenparameter und auf Basis der durchgeführten Untersuchungen wurde zur Optimierung der Reinigung produktberührender Oberflächen für bekannte Kontaminationen eine Checkliste als Orientierungshilfe erarbeitet. Ist die Verunreinigungsart dennoch unbekannt, so sollte der "Grenzwert" von Ra = 1 µm unterschritten werden, um bei Vorhandensein filmartiger Verschmutzungen keine negativen Auswirkungen auf die Reinigbarkeit zu haben. Die Notwendigkeit nach hochpolierten Oberflächen (Ra < 0,3 µm) aus Reinigbarkeitsgründen kann aufgrund der Untersuchungen nicht nachvollzogen werden.
Das Ziel des Vorhabens wurde erreicht.
Mechanically flexible single crystals of molecular materials offer potential for a multitude of new directions in advanced materials design. Before the full potential of such materials can be exploited, insight into their mechanisms of action must be better understood. Such insight can be only obtained through synergistic use of advanced experimentation and simulation. We herein report the first detailed mechanistic study of elasto-plastic flexibility in a molecular solid. An atomistic origin for this mechanical behaviour is proposed through a combination of atomic force microscopy, μ-focus synchrotron X-ray diffraction, Raman spectroscopy, ab initio simulation, and computed elastic tensors. Our findings suggest that elastic and plastic bending are intimately linked and result from extensions of the same molecular deformations. The proposed mechanism bridges the gap between contested mechanisms, suggesting its applicability as a general mechanism for elastic and plastic bending in organic molecular crystals.
While noncovalent interactions between graphene derivatives and biosystems are extensively studied, less knowledge about their covalent multivalent interactions at biointerfaces is available. Due to the affinity of boronic acids towards cis-diol bearing biosystems, graphene sheets with this functionality were synthesized and their covalent interactions with the bacteria and nematode were investigated. As expected, graphene platforms with boronic acid functionality were able to wrap bacteria and destroy it in a short time. Surprisingly, body of nematodes was ruptured and their viability decreased to 30% after 24 h incubation with the functionalized graphene sheets. Because of their antibacterial and antiparasitic activities as well as their ability for wound dressing, graphene platforms with the boronic acid functionality were further investigated for diabetic wound healing. In vivo experiments showed that graphene platforms are more efficient than the commercially available drug, phenytoin, and restore both infected and non-infected diabetic wounds in ten days. Taking advantage of their straightforward synthesis, strong interactions with different biosystems as well as their ability to heal diabetic wounds, the boronic Acid functionalized graphene sheets are promising candidates for a broad range of future biomedical applications.
Polylactide (PLA) and poly(methyl methacrylate) (PMMA) constitute, already for several decades, the gold standards for various biomedical applications due to their biocompatibility/inertness. Moreover, they have an additional property: they can form stereocomplexes (SCs) that have a more compact crystalline structure than the individual components. As a result, polymer SCs display improved thermal and mechanical properties, as well as delayed drug release and biodegradation rate in the case of drug delivery systems and biomaterials based on PLA, which is of prime importance in the biomedical field. In this article, the potential of SCs for biomedical applications in the areas of drug delivery, tissue engineering, and nanostructured surfaces is highlighted.
Modelling becomes more and more important in modern NDE. It is increasingly used to optimize techniques for complex applications, to support the preparation of written procedures, and for education purposes. To describe the complete chain of RT, the model includes simulating all necessary properties of X- or Gamma-ray sources, the interaction of photons with material with special attention to scattered radiation, the detection process, and the complete geometrical RT setup handling arbitrary parts or constructions. Depending on the given inspection problem and the influencing factors that should be addressed by the simulation, an appropriate physical model has to be chosen to describe the underlying interaction mechanisms. The simulator aRTist combines analytical and Monte Carlo methods to efficiently model the radiation transport such that transmission as well as scatter techniques can be modelled. In this contribution we focus on Monte Carlo simulation of scatter contribution within aRTist. Examples for RT/tomographic applications and back-scatter techniques are presented to demonstrate the usability of the presented simulation tool for a broad range of radiological applications.
In order to develop simple and versatile procedures for the preparation of red emissive particles, various one-step swelling procedures for the loading of fluorophores into nanometer- and micrometer-sized polystyrene particles were systematically assessed. Parameters studied for model dyes from common dye classes include the composition of the swelling medium, dye charge and polarity, dye concentration, and particle surface chemistry. The dye loading procedures were compared based upon the efficiency of dye incorporation, fluorescence intensity, and colloidal stability of the resulting particles as well as the absence of dye leaking as determined by absorption and fluorescence spectroscopy, flow cytometry, and measurements of zeta potentials. In addition, for the first time, the influence of the amount of incorporated dye on the absolute fluorescence quantum yield and brightness of the fluorescent particles was investigated for selected chromophores in differently sized particles using a custom-made calibrated integrating sphere setup. Our results demonstrate the general suitability of these one-step loading procedures for efficient particle staining with neutral, zwitterionic, and charged fluorophores like oxazines, coumarines, squaraines, xanthenes, and cyanines emitting in the visible and near infrared. Dye polarity was identified as a suitable tool to estimate the loading efficiency of fluorophores into these polymer particles.
Ablation experiments with ultrashort laser pulses (pulse duration 150 fs, wavelength 800 nm) on polymers (PC, PMMA) relevant for biomedical technology have been performed in air. The lateral and vertical machining precision was evaluated by optical, atomic force and scanning electron microscopy. The ablation threshold reaches values in the range of 0.52.5 J/cm2 and depends significantly on the number of laser pulses applied to the same spot. The hole diameters are influenced by the laser fluence and the number of laser pulses. The relation between the ablation threshold and the number of laser pulses applied to the same spot is described in accordance with an incubation model.
Flammschutz von polymeren Baustoffen: Bewertung von Konzepten auf der Basis von small- scale Cone Calorimeter Untersuchungen. In der Arbeit wurden zwei unterschiedliche Flammschutzkonzepte polymerer Baustoffe mit Hilfe des Cone Calorimeter untersucht und bewertet. Polymer-Schicht-Nanocomposites sind ein neues Konzept für flammgeschützte Werkstoffe, die aus einer Polymermatrix und der Zugabe eines nanoskaligen Schichtsilikat- Additivs von ca. 5 Gew.-% bestehen. Im Brandfall bilden die Schichtsilikate eine Barriere, die den Wärmetransport in das Material bzw. den Stofftransport der Pyrolysegase aus dem Material hemmt. Mit einem Modellsystem wurde gezeigt, dass dieser Barriereeffekt das Brandverhalten hinsichtlich der Flammenausbreitung verbessert, in anderen Brandszenarien aber wirkungslos bleibt. Die Ergebnisse der Cone Calorimeter Untersuchungen wurden mit denen der Entflammbarkeitstests UL 94 und LOI verglichen. Eine Korrelation in Richtung kleiner Probendimensionen (downscale) und in Richtung Phase der Brandentstehung wurde aufgezeigt. Die Anwendung intumeszierender Beschichtungen auf Bauteile verschiedener Art, wie z. B. tragende Stahlkonstruktionen, ist ein etabliertes Brandschutzkonzept. Das intumeszierende Polymermaterial schäumt unter Wärmeeinwirkung auf und bildet eine wärmeisolierende Schicht. Zur Bewertung der Wirkungsweise dieses Polymermaterials wurde ein auf Temperaturmessungen basierendes Verfahren mit dem Cone Calorimeter und für Simulationsrechnung entwickelt. Die Ergebnisse wurden mit denen aus Kleinprüfstanduntersuchungen verglichen. Eine Korrelation in Richtung großer Probendimensionen (upscale) und in Richtung der Phase des voll entwickelten Brandes konnte bis zu einer Temperaturgrenze gezeigt werden.
Vorstellung der Korrosionsuntersuchungen im Rahmen des Themenfeldprojektes LeBeWind an der BAM
(2017)
Im Vortrag wird das Teilprojekt Korrosion des Themenfeldprojektes LeBeWind vorgestellt. Dabei werden mit Blick auf die geltenden Regelwerke und Normen die Unterschiede verschiedener Prüfmethoden zur kathodischen Enthaftung bei organischen Beschichtungen vorgestellt und deren Aussagekraft kritisch betrachtet. Am Beispiel von systematischen Versuchsreihen an einem Kurzzeittest werden die Grenzen einiger Methoden herausgearbeitet und die Anwendbarkeit für Reparaturbeschichtungen in Offshore-Bereich hinterfragt. Zusätzlich werden die Problemstellungen bei der Versalzung von metallischen Oberflächen im maritimen und Offshore-Bereich betrachtet.
Das Ziel des Verbundforschungsvorhabens KKS-Gründung war die Entwicklung eines Monitoringsystems zur Erfassung von Korrosion an Gründungsstrukturen im Labormaßstab. Dafür war eine umfassende Bewertung und Beschreibung korrosionsbeeinflussender Faktoren und der Korrosionssysteme notwendig. Im Vorhaben KKS-Gründung wurde die Gründungsstruktur unterhalb der Wasserlinie betrachtet bis hin zum anaeroben Bereich im Sediment. Insbesondere der Sedimentbereich wurde bisher nur unzureichend betrachtet. Da die komplexen Mechanismen in der Sedimentzone noch nicht ausreichend wissenschaftlich untersucht wurden, mussten Möglichkeiten entwickelt werden, um diese zu bewerten.
Im Verbundforschungsvorhaben KKS-Gründung agierte die Bundesanstalt für Materialforschung und -prüfung (BAM) als Forschungsstelle. Die Hauptziele des Teilvorhabens der BAM waren die Bereitstellung einer Messumgebung für das von den Partnern entwickelte Monitoringsystem, die umfassende wissenschaftliche Beschreibung der Korrosionssysteme im Unterwasserbereich und Sediment sowie die Gewinnung von Messdaten zur Verifizierung und Überführung in die Simulation. Als Forschungsstelle war die BAM der Ansprechpartner für die Verbundpartner bei wissenschaftlichen Fragestellungen.
Die Hauptziele des Vorhabens wurden erreicht und es wurden grundlegende Erkenntnisse zum Korrosionsverhalten von Offshore-Stahl im Unterwasser und Sedimentbereich gewonnen. Darüber hinaus wurden wichtige Erkenntnisse zum Betrieb eines Laborcontainers und zur Nachstellung von Korrosionssystemen in Meerwasserbecken bei Verwendung von künstlichem Meerwasser und Sand als Sediment gewonnen. Eine Beschreibung und Bewertung der Korrosivität und ablaufender Reaktionen in den einzelnen Belastungszonen wurde mittels elektrochemischer und gravimetrischer Verfahren vorgenommen.
En este artículo se presentan 2 metodologías basadas en las formulaciones del Método de los Elementos de Contorno y del Método de los Elementos Finitos para estudiar el efecto de la interacción suelo-estructura en el comportamiento dinámico de edificaciones. Se ha estudiado la respuesta de un edificio de 3 plantas producida por un campo de ondas incidente con los 2 métodos propuestos. Los resultados obtenidos presentan un buen grado de acuerdo entre ellos. A partir de estos resultados se ha validado un modelo aproximado para estudiar este tipo de problemas y se han examinado diferentes tipologías de edificaciones. Las conclusiones alcanzadas muestran que la respuesta global de las estructuras se debe a la deformación de los forjados y depende de su superficie, de las condiciones de apoyo y del acoplamiento con los forjados de la misma planta. Del mismo modo, se ha observado un acoplamiento del comportamiento de pilares y forjados cuando las rigideces de ambos son similares.----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- This paper presents 2 methodologies based on the Boundary Element Method and the Finite Element Method to study soil-structure interaction effect on building behaviour. A 3-story building response induced by an incident wave field is studied using both methods. The results obtained show a good agreement. Then, a simplified model is validated from these methods and several buildings are analysed. Conclusions show that structural responses are due to floor deformation, and depend on their area, support conditions and coupling. A coupling between floors and columns when both elements have similar stiffness is also observed.
Treatment and reusing of hazardous wastes have become significant issues of modern societies. Blast furnace sludge (BFS) and electric arc furnace dust (EAFD) are such typical wastes, because they usually contain high amounts of undesirable elements such as zinc (Zn) and lead (Pb).
These elements can cause operational problems in reusing of BFS and EAFD. In this study, the Ferro Duo GmbH and the Federal Institute for Materials Research and Testing have investigated a novel approach for eliminating and/or recovering Zn and Pb from both wastes. Applied was a selective chlorination and volatilization of Zn and Pb as chlorides at temperatures between 500 °C and 1100 °C. Both product obtained, Zn and Pb in the form of ZnCl2 and PbCl2 and the purified solid mineral compound are attractive materials for further use. Hydrochloric acid and iron(II) chloride were used as chlorination agents. Exceptionally high Zn and Pb removal efficiencies of >99.5 % could be achieved with both chlorination agents, whereby iron(II) chloride exhibited better performance.
Im Zuge der Energiewende finden Wasserstofftechnologien in der industriellen Praxis und im öffentlichen Raum immer mehr Anwendung. Beim Einsatz von Wasserstoff als Ersatz für andere fossile Energieträger wie Erdgas müssen u.a. Explosionsschutzmaßnahmen überprüft und angepasst werden. Eine Art von Explosionsschutzmaßnahmen ist die Vermeidung von Zündquellen. Gemäß den einschlägigen Regelwerken ist die Bildung von Funken oder heißen Aufschlagstellen beim mechanischen Schlag eine mögliche Zündquelle, die vor allem beim Wasserstoff berücksichtigt werden muss. Die Zündwirksamkeit ist dabei u.a. stark von der Werkstoffpaarung und der kinetischen Schlagenergie abhängig. Der Einsatz von funkenarmen Werkzeugen aus schwer oxidierbaren Nicht-Eisen-Metallen in explosionsgefährdeten Bereichen kann z.B. eine Maßnahme sein, um diese Zündquelle zu vermeiden und wird als solche in den Regelwerken benannt. Es gibt aber kaum Quellen, die dabei helfen die Zündwirksamkeit bei Schlägen mit heterogenen Materialpaarungen einzuschätzen. In dieser Arbeit wurde zu diesem Zweck die Zündwirksamkeit von mechanischen Schlägen mit unterschiedlichen, auch nicht-metallischen Schlagpartnern in wasserstoffhaltigen Atmosphären systematisch untersucht.
Im Projekt HySpark wird die Wirksamkeit mechanischer Schlagvorgänge beim Aufprall von unterschiedlichen Werkstoffen als Zündquelle für wasserstoffhaltige Atmosphären experimentell untersucht. Zum Einen wird die Zündwirksamkeit bei Wasserstoff/Luft-Gemischen in Abhängigkeit der Werkstoffpaarung untersucht. Dabei konnte v.a. festgestellt werden, dass bei Schlagvorgängen von Nicht-Eisen-Metallen mit verschiedenen Stahlsorten die wirksame Zündung vermieden werden kann. Jedoch können bei Schlagvorgängen mit Estrichbeton hohe Zündwahrscheinlichkeiten beobachtet werden. Zum anderen wird der Einfluss von Wasserstoffbeimischungen im Erdgasnetz auf die Zündwirksamkeit von mechanischen Schlägen untersucht. Bei Anteilen bis 25% Wasserstoff konnte bei den Versuchen kein Erhöhung der Zündwahrscheinlichkeit festgestellt werden.
In this lecture the safety related properties og hydrogen compared to other fuel gases and the explosion protection measures of avoiding flammable mixtures, avoiding ignition sources and mitigating the consequences of explosions when handling hydrogen and hydrogen mixtures are presented.
The Joint European Summer School JESS 2021 addresses these issues by offering high quality graduate level courses on selected topics of vehicle technology, innovation & business development, safe handling of hydrogen, and modelling. The course content is tailored to the needs of a diverse audience: newcomers to the field, experienced students, and young professionals working at the forefront of fuel cell and hydrogen applications.
Hinsichtlich ihrer sicherheitstechnischen Kenngrößen (STK) unterscheiden sich Wasserstoff und Erdgas zum Teil stark. Im Vortrag werden verschiedene STK von Erdgas/Wasserstoff-Gemischen im Abhängigkeit des Wasserstoffanteils vorgestellt und die Auswirkung der Beimischung von Wasserstoff zum Erdgas auf die Wirksamkeit von Explosionsschutzmaßnahmen erläutert.
In this lecture the safety related properties of hydrogen and hydrogen mixtures and explosion protection measures are shown and compared with other fuel gases. Measures for primary explosion protection (avoiding flammable mixtures), secondary explosion protection (avoiding ignition sources) and constructive explosion protection (mitigating the consequences of explosions) when handling hydrogen and hydrogen mixtures are presented.
The Joint European Summer School JESS 2022 addresses these issues by offering high quality graduate level courses on selected topics of vehicle technology, innovation & business development, safe handling of hydrogen, and modelling. The course content is tailored to the needs of a diverse audience: newcomers to the field, experienced students, and young professionals working at the forefront of fuel cell and hydrogen applications.
In this presentation the results of the Project HySpark are shown. Mechanical impacts are among the important possible ignition sources to be considered in explosion protection. Hydrogen is particularly prone to be ignited by mechanical impacts compared to natural gas. The effectivity of mechanical impacts as ignition source is dependent from different parameters. In this work the effectivity of impacts as an ignition source for hydrogen containing atmospheres was studied experimentally depending on the inhomogeneous material pairing of the impact. Moreover it was studied, how the effectivity of mechanical impacts as ignition source changes when hydrogen is added to natural gas.
This is a digital lecture on Explosion Protection for Hydrogen Applications. It was designed in context with the project "KICstartH2 Accelerating Sustainable Hydrogen Uptake Through Innovation and Education" and integrated in a teaching module of the University of Birmingham. It is divided in five parts: Introduction, Avoiding Explosive Mixtures, Avoiding Ignition Sources, Mitigation of Consequences and Summary & Comparison.
In dem hier vorgestellten Projekt wurde die Wirksamkeit mechanischer Schläge als Zündquelle für wasserstoffhaltige Atmosphären in Abhängigkeit von der inhomogenen Materialpaarung systematisch untersucht. Dabei wurden praxisrelevante Materialien wie Edelstahl, niedrig legierter Stahl, Beton und Nichteisenmetalle betrachtet. Es wurde festgestellt, dass eine Zündung vermieden werden kann, wenn Nichteisenmetalle in Kombination mit verschiedenen metallischen Werkstoffen verwendet werden. In Kombination mit Beton muss die kinetische Schlagenergie auch mit Nichteisenmetallen weiter begrenzt werden, um eine wirksame Entzündung zu vermeiden. Außerdem wurde untersucht, wie sich die Beimischung von Wasserstoff zu Erdgas auf die Wirksamkeit mechanischer Stöße als Zündquelle auswirkt. Bei Beimischungen von bis zu 25 % Wasserstoff und sogar mehr konnte kein Einfluss festgestellt werden. Die Ergebnisse sind vor allem relevant im Zusammenhang mit der Umwidmung des Erdgasnetzes oder der Beimischung von Wasserstoff im Erdgasnetzes.
Research software has become a central asset in academic research. It optimizes existing and enables new research methods, implements and embeds research knowledge, and constitutes an essential research product in itself. Research software must be sustainable in order to understand, replicate, reproduce, and build upon existing research or conduct new research effectively. In other words, software must be available, discoverable, usable, and adaptable to new needs, both now and in the future. Research software therefore requires an environment that supports sustainability.
Hence, a change is needed in the way research software development and maintenance are currently motivated, incentivized, funded, structurally and infrastructurally supported, and legally treated. Failing to do so will threaten the quality and validity of research. In this paper, we identify challenges for research software sustainability in Germany and beyond, in terms of motivation, selection, research software engineering personnel, funding, infrastructure, and legal aspects. Besides researchers, we specifically address political and academic decision-makers to increase awareness of the importance and needs of sustainable research software practices. In particular, we recommend strategies and measures to create an environment for sustainable research software, with the ultimate goal to ensure that software-driven research is valid, reproducible and sustainable, and that software is recognized as a first class citizen in research. This paper is the outcome of two workshops run in Germany in 2019, at deRSE19 - the first International Conference of Research Software Engineers in Germany - and a dedicated DFG-supported follow-up workshop in Berlin.
Flow-back and produced waters from shale gas and shale oil fields contain high ammonium, which can be formed by methanogenic degradation of methylamines into methane and ammonium. Methylamines are added to fracturing fluid to prevent clay swelling or can originate from metabolism of the osmolyte triglycinebetaine (GB).
We analyzed field samples from a shale gas reservoir in the Duvernay Formation and from a shale oil reservoir in the Bakken formation in Canada to determine the origin of high ammonium. Fresh waters used to make fracturing fluid, early flow-back waters, and late flow back waters from the shale gas reservoir had increasing salinity of 0.01, 0.58, and 2.66 Meq of NaCl, respectively. Microbial community analyses reflected this fresh water to saline transition with halophilic taxa including Halomonas, Halanaerobium, and Methanohalophilus being increasingly present. Early and late flow-back waters had high ammonium concentrations of 32 and 15 mM, respectively.
Such high concentrations had also been found in the Bakken produced waters.
Enrichment cultures of Bakken produced waters in medium containing mono, di-, or trimethylamine, or triglycinebetaine (GB) converted these substrates into ammonium (up to 20 mM) and methane. The methylotrophic methanogen Methanohalophilus, which uses methylamines for its energy metabolism and uses GB as an osmolyte, was a dominant community member in these enrichments. Halanaerobium was also a dominant community member that metabolizes GB into trimethylamine, which is then metabolized further by Methanohalophilus. However, the micromolar concentrations of GB measured in shale reservoirs make them an unlikely source for the 1,000-fold higher ammonium concentrations in flow-back waters. This ammonium either originates directly from the reservoir or is formed from methylamines, which originate from the reservoir, or are added during the hydraulic fracturing process. These methylamines are then converted into ammonium and methane by halophilic methylotrophic methanogens, such as Methanohalophilus, present in flow-back waters.
The survey of Canadian shale sites showed a dominance of halophilic microorganisms, including Halomonas (HA). Nitrate-amended incubations of the field samples under high salinity (14.6% NaCl), revealed a dominance of HA (>72%) and an accumulation of nitrite. Nitrite accumulation directly inhibited the growth of SRB, thereby decreasing their souring and corrosion risks. However, accumulated nitrite may also contribute to iron corrosion, which will be tested by using different concentrations of nitrate as an electron acceptor to HA. Different salinities are further tested on HA strains supplemented with iron coupons to determine their effects on iron corrosion rates. HA incubated with separate cultures of corrosive methanogen and SRB were tested to determine whether a positive or adverse effect will occur between them. Lastly, analyses of iron coupons will be conducted using TOF-SIMS, FIB-SEM and EDS for corrosion product characterization
Microbiologically influenced corrosion (MIC) is an expensive but unpredictable problem for the industries. The most well-known culprit for MIC is the sulfate-reducing microorganisms (SRM), such as members from the genus Desulfovibrio. It has been widely accepted that SRM can contribute significantly to MIC through the production of hydrogen sulfide (HS-) or in some cases a direct electron uptake from the metal surface. However, in a real environmental system, SRM is not exclusive and often involved with other microorganisms that may also contribute to MIC, such as methanogens.
Methanogenic archaea can produce methane (CH4) using H2+CO2, formate, methylated amines or acetate. Methanogens are highly abundant in the environment and many are found in very extreme conditions, such as high temperature and high salinity. Previous researches have demonstrated that methanogens are capable of MIC, though the specific mechanisms are still under investigation. In the oil and gas industry, methanogens are not considered as the main contributor for MIC since the corrosion rates are often too low. However, the tests for methanogen-induced MIC are usually performed at static conditions, which cannot represent the system accurately. Here, we developed a novel anaerobic system to evaluate the corrosion potential of methanogens under flow conditions. We will use the Methanococcus maripaludis KA1 strain, which was isolated from a crude oil tank, as the organism of interest. A separate system for Desulfovibrio alaskensis will be established for corrosion rate comparisons. Furthermore, we will study the synergistic effects of M. maripaludis and D. alaskensis on MIC under flow.
Currently, sulfate-reducing bacteria (SRB) is regarded as the main culprit of microbiologically influenced corrosion (MIC), mainly due to the low reported corrosion rates of other microorganisms. For example, the highest reported corrosion rate for methanogens is 0.065 mm/yr. However, by investigating methanogen-induced microbiologically influenced corrosion (Mi-MIC) using an in-house developed versatile multiport flow test column, extremely high corrosion rates were observed. We analyzed a large set of carbon steel beads, which were sectionally embedded into the test columns as substrates for iron-utilizing methanogen Methanobacterium IM1. After 14 days of operation using glass beads as fillers for section separation, the highest average corrosion rate of Methanobacterium IM1 was 0.2 mm/yr, which doubled that of Desulfovibrio ferrophilus IS5 and Desulfovibrio alaskensis 16109 investigated at the same conditions. At the most corroded region, nearly 80% of the beads lost 1% of their initial weight (fast-corrosion), resulting in an average corrosion rate of 0.2 mm/yr for Methanobacterium IM1-treated columns. When sand was used as filler material to mimic sediment conditions, average corrosion rates for Methanobacterium IM1 increased to 0.3 mm/yr (maximum 0.52 mm/yr) with over 83% of the beads having corrosion rates above 0.3 mm/yr. Scanning electron images of metal coupons extracted from the column showed methanogenic cells were clustered close to the metal surface. Methanobacterium IM1 is a hydrogenotrophic methanogen with higher affinity to metal than H2. Unlike SRB, Methanobacterium IM1 is not restricted to the availability of sulfate concentration in the environment. Thus, the use of the multiport flow column provided a new insight on the corrosion potential of methanogens, particularly in dynamic conditions, that offers new opportunities for monitoring and development of mitigation strategies. Overall, this study shows under certain conditions methanogenic archaea can cause higher corrosion than SRB, specific quantifications, i.e., maximum, average, and minimum corrosion rates can be determined, and that spatial statistical evaluations of MIC can be carried out.