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Paper des Monats
- ja (68)
Geosynthetics are planar polymeric products, which are used in connection with soil, rock or other soil-like materials to fulfill various functions in geoenvironmental engineering. Geosynthetics are of ever-growing importance in the construction industry. Sealing of waste storage facilities to safely prevent the emission of wastewater, landfill gas and contaminated dust as well as the diffusion of pollutants into the environment and coastal protection against storms and floods and reconstruction after natural disaster are important fields of application. We will give an overview of the various geosynthetic products. Two examples of the material problems related to geosynthetics are discussed in detail: the effect of creep on the long-term performance of geocomposite drains and the numerical simulation of the interaction of soil with geogrids. Both issues are of importance for the use of these products in landfill capping systems. The various functions, which geosynthetics may fulfill in the protection of coastal lines, are illustrated by case studies. The geosynthetic market is evaluated and economical and environmental benefits, as well as environmental side effects related to the use of geosynthetics, are discussed.
Online-Strukturüberwachungssysteme sind eine Möglichkeit, den Anforderungen hinsichtlich Leichtbau und Zuverlässigkeit gleichzeitig gerecht zu werden. Die Integration solcher Systeme liefert aktuelle Informationen über die Integrität der sicherheitsrelevanten Struktur, wodurch sich Aussagen über notwendige Instandhaltungsarbeiten und möglicherweise über die zu erwartende Restlebensdauer ableiten lassen. Der zielgerichtete Einsatz der Überwachungssysteme ermöglicht es somit, die benötigten Sicherheitsfaktoren bei der Auslegung der Bauteile zu reduzieren und Wartungsintervalle zu verlängern. Dadurch können Kosten gesenkt werden, ohne die Zuverlässigkeit zu verringern. Im Rahmen einer Studie zur Machbarkeit eines Online-Überwachungssystems für Eisenbahn-Radsatzwellen wurde der Einsatz geführter Ultraschallwellen, die von Sensoren an einer Stirnseite der Wellen angeregt werden, demonstriert. Aufgrund der Bauteilgeometrie und der dispersiven, multimodalen Wellenausbreitung stellt die Interpretation der Echosignale eine wesentliche Herausforderung dar. Basierend auf dem a-priori-Wissen über die Wellenausbreitung wurden in der Studie klassifizierende Auswertealgorithmen entwickelt und erfolgreich an maßstabsgetreuen Labormodellen getestet.
Durch den Einsatz von faserverstärkten Kunststoffen und Multi-Material-Konstruktionen zur Gewichtsreduzierung erlangen Klebeverbindungen immer stärkere Bedeutung. Die Prüfung dieser Fügeverbindungen stellt neue Anforderungen an die zerstörungsfreie Prüfung. Hinzu kommt, dass die Zugänglichkeit häufig eingeschränkt und die Verwendung flüssiger Koppelmittel aufgrund konstruktiver oder fertigungstechnischer Gegebenheiten ausgeschlossen ist. Unter Berücksichtigung dieser Beschränkungen wurde ein Prüfverfahren entwickelt, das eine luftgekoppelte Anregung geführter Ultraschallwellen mit einer laserbasierten Detektion kombiniert. Nachdem das Prüfverfahren zunächst mit einer einfachen Signalauswertung im Zeitbereich getestet wurde, konnte in nachfolgenden Untersuchungen die örtliche Auflösung durch die Implementierung von Filteralgorithmen im Frequenz-Wellenzahl-Bereich und zusätzlich durch direktionale Filter erhöht werden. Das resultierende bildgebende Prüfverfahren wurde an realitätsnahen Klebeproben mit künstlichen Fehlern getestet. Die Zuverlässigkeit und Ortsauflösung des Verfahrens wurde im Vergleich mit herkömmlichen Prüfverfahren validiert. Mithilfe des Verfahrens können Poren, Einschlüsse und Bereiche mit ungenügender Verklebung detektiert werden.
Synthesis, structure determination, and formation of a theobromine: oxalic acid 2:1 cocrystal
(2015)
The structure and the formation pathway of a new theobromine : oxalic acid (2 : 1) cocrystal are presented. The cocrystal was synthesised mechanochemically and its structure was solved based on the powder X-ray data. The mechanochemical synthesis of this model compound was studied in situ using synchrotron XRD. Based on the XRD data details of the formation mechanism were obtained. The formation can be described as a self-accelerated ('liquid like') process from a highly activated species.
In carrier gas hot extraction the calibration of low amounts of non-metals with masses of a few micrograms with small uncertainty remains a challenge. To achieve high flexibility a high precision gas mixture pump was combined with an automated syringe drive. The gas mixing pump allows filling the syringe with different gas compositions; the automated syringe drive allows matching to modulate the signal profiles to those of real samples. The system was designed and its experimental potential explored. The resulting calibration curves were comparable to those obtained by calibration using solid materials of sufficient purity and stoichiometry. However smaller uncertainties and lower limits of quantification (i.e. 0.5 µg and 0.6 µg for O and N, respectively) were found using the gas calibration device.
Für den stetigen Einsatz und die erhöhten Anforderungen bei der mechanisierten Prüfung sowie in der Handprüfung ist notwendig, einen möglichst genauen Eindruck bzgl. Funktionsweise und Zuverlässigkeit der eingesetzten Prüfmittel zu besitzen. Prüfköpfe weisen, wie jedes andere technische Erzeugnis gewisse Toleranzen hinsichtlich Fertigungs- und Alterungsprozessen auf, welche sich speziell bei Winkelprüfköpfen durch eine Verschiebung des Nominalwinkels äußern können. Die Definition der Parameter von Prüfköpfen und entsprechende Methoden zu deren Überprüfung sind in der DIN EN 12668-2 geregelt.
Von der BAM werden für diese Aufgaben Richtcharakteristikmessplätze eingesetzt. Um auf die gestiegenen Anforderungen hochauflösender Prüfungen zu reagieren wurde der Richtcharakteristikmessplatz modernisiert. Dabei wurde für die teil-automatisierte Untersuchung der akustischen Parameter (z.B. Einschallwinkel) unter Verwendung digitaler Messdatenverarbeitung - ein neuer Messplatz für die Überprüfung sowie Untersuchung von Prüfkopftoleranzen und Alterungsprozessen realisiert. Der Messplatz verfügt über eine hochauflösende Messdatenerfassung sowie einer automatisierten Protokollierung der erhobenen Messdaten.
Für eine hochauflösende Untersuchung von sicherheitsrelevanten Bauteilen innerhalb der Tauchtechnik haben fokussierende Prüfköpfe eine hohe Verbreitung erlangt. Für den Einsatz moderner und komplexer Rekonstruktionsverfahren bildet jedoch die Kenntnis über Schallfeldgeometrie, insbesondere die Lage und Ausdehnung der Fokusbereichs und die Empfindlichkeit des verwendeten Prüfkopfs in Abhängigkeit zum Schallweg, eine entscheidende Rolle für die Datenrekonstruktion und die abschließende Bauteildiagnose.
Für die automatisierte Bestimmung der wichtigsten Kenngrößen (bspw. Lage und Länge des Fokuspunkts bzw. Fokusschlauchs, sowie des Schallbündel-durchmessers) wurde die Schalldruckverteilung mechanisiert, vierdimensional (x,y,z,t) vermessen und unter Einsatz der digitalen Signal- und Bildverarbeitung, ein vollautomatisches Analysewerkzeug erarbeitet. Weiterhin konnte anhand des Messdatensatzes und unter Einsatz von dreidimensionalen Rekonstruktions- und Visualisierungstechniken das Schallfeld bzw. die Schalldruckverteilung dreidimensional abgebildet werden und für etwaige Nachuntersuchungen von Simulationsergebnissen oder allein zur Visualisierung eingesetzt werden.
Temperature-memory polymers are able to generate a substantial mechanical response when heated above the temperature, at which a preceding deformation was carried out. Here we show how to design the temperature-memory effect (TME) by thermomechanical treatment. As a model polymer, phase segregated poly(ester urethane) (PEU) containing crystallizable segments of poly(1,4-butylene adipate) (PBA) was used. For programming, strain elongation was applied at temperatures within the PBA melting transition area, before temperature holding, unloading and cooling were carried out. Upon heating under stress-free or constant strain recovery conditions, precisely set temperature-memory onsets could be witnessed. Most importantly, strain fixities and recoverabilities the same as maximum recovery stresses turned out to be controllable by strain rate and temperature holding time after deformation, while transition temperatures remained largely unaffected. The tailoring of thermoresponsiveness was structurally enabled by different PBA crystallinities in the programmed state as verified by wide-angle X-ray scattering (WAXS). The reported studies intend to design TMEs in semicrystalline polyurethanes according to user-defined needs to make this technology broadly applicable.
Für die Durchführung einer Dichtheitsprüfung und für die Bewertung des Ergebnisses ist es wichtig, den sich unter Betriebsbedingungen im Prüfobjekt einstellenden Überdruck zu kennen. Entspricht der Prüfüberdruck nicht dem Betriebsüberdruck, so ist es oft erforderlich, die unter Prüfbedingungen gemessenen Leckageraten auf den realen Betriebsüberdruck umzurechnen. Im Bereich der Gefahrgutverpackungen ist jedoch der spätere maximale Betriebsüberdruck nicht genau bekannt. Er hängt für jede einzelne Verpackungsbauart von dem eingefüllten Füllmedium mit seinen spezifischen Stoffeigenschaften, dem Füllgrad sowie den Beförderungsbedingungen, insbesondere der mittleren Transporttemperatur, ab. Es werden Berechnungsansätze vorgestellt, mit denen sich der Überdruck in Gefahrgutverpackungen unter Beförderungsbedingungen rechnerisch ermitteln lässt. Die theoretisch berechneten Überdrücke werden mit Überdruck-Messwerten verglichen, die mit verschiedenen Füllmedien in unterschiedlichen Verpackungsbauarten ermittelt wurden.
We present a systematic study on the effect of surface ligands on the luminescence properties and colloidal stability of β-NaYF4:Yb3+,Er3+ upconversion nanoparticles (UCNPs), comparing nine different surface coatings to render these UCNPs water-dispersible and bioconjugatable. A prerequisite for this study was a large-scale synthetic method that yields ~2 g per batch of monodisperse oleate-capped UCNPs providing identical core particles. These ~23 nm sized UCNPs display an upconversion quantum yield of ~0.35% when dispersed in cyclohexane and excited with a power density of 150 W cm-2, underlining their high quality. A comparison of the colloidal stability and luminescence properties of these UCNPs, subsequently surface modified with ligand exchange or encapsulation protocols, revealed that the ratio of the green (545 nm) and red (658 nm) emission bands determined at a constant excitation power density clearly depends on the surface chemistry. Modifications relying on the deposition of additional (amphiphilic) layer coatings, where the initial oleate coating is retained, show reduced non-radiative quenching by water as compared to UCNPs that are rendered water-dispersible via ligand exchange. Moreover, we could demonstrate that the brightness of the upconversion luminescence of the UCNPs is strongly affected by the type of surface modification, i.e., ligand exchange or encapsulation, yet hardly by the chemical nature of the ligand.
Solgel prepared ternary FeF3–MgF2 materials have become promising heterogeneous catalysts due to their porosity and surface Lewis/Brønsted acidity (bi-acidity). Despite the good catalytic performance, nanoscopic characterisations of this type of material are still missing and the key factors controlling the surface properties have not yet been identified, impeding both a better understanding and further development of ternary fluoride catalysts. In this study, we characterised the interaction between the bi-acidic component (FeF3) and the matrix (MgF2) on the nano-scale. For the first time, the formation pathway of FeF3–MgF2 was profiled and the template effect of MgF2 during the synthesis process was discovered. Based on these new insights two novel materials, FeF3–CaF2 and FeF3–SrF2, were established, revealing that with decreasing the atomic numbers (from Sr to Mg), the ternary fluorides exhibited increasing surface acidity and surface area but decreasing pore size. These systematic changes gave rise to a panel of catalysts with tuneable surface and bulk properties either by changing the matrix alkaline earth metal fluoride or by adjusting their ratios to Fe or both. The template effect of the alkaline earth metal fluoride matrix was identified as the most probable key factor determining the surface properties and further influencing the catalytic performance in ternary fluoride based catalysts, and paves the way to targeted design of next-generation catalysts with tunable properties.
Polyglycerol (PG) coated polypropylene (PP) films were synthesized in a two-step approach that involved plasma bromination and subsequently grafting hyperbranched polyglycerols with very few amino functionalities. The influence of different molecular weights and density of reactive linkers were investigated for the grafted PGs. Longer bromination times and higher amounts of linkers on the surface afforded long-term stability. The protein adsorption and bacteria attachment of the PP-PG films were studied. Their extremely low amine content proved to be beneficial for preventing bacteria attachment.
In order to assess the anisotropy-related uncertainties of relatively determined photoluminescence quantum yields (ΦPL) of molecular emitters and luminescent nanomaterials, we compared ΦPL values measured without and with polarizers using magic angle conditions and studied systematically the dependence of the detected emission intensity on the polarizer settings for samples of varying anisotropy. This includes a dispersion of a spherical quantum dot (QD) with an ideally isotropic emission, a solution of a common small organic dye in a fluid solvent as well as dispersions of elongated quantum dot rods (QDR) with an anisotropic luminescence and a small organic dye in a rigid polymeric matrix, as ideally anisotropic emitter. Our results show that for instruments lacking polarizers, anisotropy-related measurement uncertainties of relative photoluminescence quantum yields can amount to more than 40%, with the size of these systematic errors depending on the difference in emission anisotropy between the sample and the standard.
In- and quasielastic neutron scattering is employed to investigate both the vibrational density of states and the molecular dynamics of two homologous discotic liquid crystals (DLC) with different length of the alkyl side chain based on a triphenylene derivate. For both compounds characteristic low frequency excess contributions to the vibrational density of states are found. Therefore it is concluded that these liquid crystals show a glass-like behaviour. Elastic scans further show that in these materials a rich molecular dynamics takes place.
This paper reflects recent progress in the field of fluorescent polymer optical fiber sensors (F-POF) for partial discharge (PD) detection in high voltage (HV) cable accessories using optical-only PD detection by coincidence single photon counting. In experiments with artificial PD sources these sensors show the ability to detect optical emissions from picocoulomb-level PDs in a real-scale model of a translucent high voltage cable accessory. False positives (caused by detector noise) are efficiently suppressedwhile maintaining sufficient sensitivity,even when the sensor is located in an unfavorable position.
This report is the result of a comprehensive study on the available CMs which come potentially in question for the reliable analysis of the number based size distribution of a nanomaterial according to the EC recommendation for a definition of nanomaterial. Based on the performance criteria already established in NanoDefine the potential CMs are evaluated according to studies available in the literature as well as following the expertise of the NanoDefine consortium partners. The specific advantages and disadvantages of each method with respect to its applicability to the scope of NanoDefine are particularly highlighted. An CM evaluation table is produced so that the mostly suited CMs with respect to the EC definition can be grouped and recommended to the corresponding NanoDefine work packages for further specific development (improvement and adaption), or for direct validation and standardisation, respectively. The actual evaluation report including the recommended CMs will be revised and, if necessary, eventually updated at the mid time of the project. The update will be jointly discussed in the NanoDefine consortium on the basis of the results of testing the methods on the NanoDefine real world materials.
Pigments and dyes
(2015)
The present volume is the main achievement of the Research Networking Programme ‘Comparative Oriental Manuscript Studies’, funded by the European Science Foundation in the years 2009–2014. It is the first attempt to introduce a wide audience to the entirety of the manuscript cultures of the Mediterranean East.
The chapters reflect the state of the art in such fields as codicology, palaeography, textual criticism and text editing, cataloguing, and manuscript conservation as applied to a wide array of language traditions including Arabic, Armenian, Avestan, Caucasian Albanian, Christian Palestinian Aramaic, Coptic, Ethiopic, Georgian, Greek, Hebrew, Persian, Slavonic, Syriac, and Turkish.
Seventy-seven scholars from twenty-one countries joined their efforts to produce the handbook. The resulting reference work can be recommended both to scholars and students of classical and oriental studies and to all those involved in manuscript research, digital humanities, and preservation of cultural heritage.
The volume includes maps, illustrations, indexes, and an extensive bibliography.
Dietary supplements high in isolated isoflavones are commercially available for human consumption primarily to alleviate menopausal symptoms in women. The isoflavone composition, quantity and importantly their estrogenic potency are poorly standardised and can vary considerably between different products. The aim of this study was to analyse the isoflavone composition of 11 dietary supplements based on soy or red clover using the HPLC/MS/MS technique. Furthermore, we investigated the transactivational potential of the supplements on the estrogen receptors (ER), ERα and ERβ, performing luciferase reporter gene assays. As expected, we found that the isoflavone composition varies between different products. The measured total isoflavone contents in various supplements were mostly comparable to those claimed by the manufacturers in their product information. However expressing the isoflavone content as isoflavone aglycone equivalents, soy-based supplements had a clearly lower quantity compared to the manufacturer information. All supplements transactivated more or less ERα and ERβ with a preference for ERβ. The transactivational efficiency exceeded partly the maximal 17β-estradiol induced ER activation. While the different soy-based supplements revealed similar transactivation potential to both ERs, red clover-based supplements differed considerably. We conclude that different commercial dietary supplements based on soy or red clover vary in their isoflavone composition and quantity. They are estrogenically active, although especially the red clover-based supplements show considerable differences in their estrogenic potential to ERα and ERβ. Thus, different isoflavone-rich products cannot be necessarily compared regarding possible biological effects.
Introducing fluorine into molecules has a wide range of effects on their physicochemical properties, often desirable but in most cases unpredictable. The fluorine atom imparts the C–F bond with low polarizability and high polarity, and significantly affects the behavior of neighboring functional groups, in a covalent or noncovalent manner. Here, we report that fluorine, present in the form of a single fluoroalkyl amino acid side chain in the P1 position of the well-characterized serine-protease inhibitor BPTI, can fully restore inhibitor activity to a mutant that contains the corresponding hydrocarbon side chain at the same site. High resolution crystal structures were obtained for four BPTI variants in complex with bovine b-trypsin, revealing changes in the stoichiometry and dynamics of water molecules in the S1 subsite. These results demonstrate that the introduction of fluorine into a protein environment can result in “chemical complementation” that has a significantly favorable impact on protein–protein interactions.
The adsorption of porphyrin derivatives on a Au(111) surface was studied by scanning tunneling microscopy and spectroscopy at low temperatures in combination with density functional theory calculations. Different molecular appearances were found and could be assigned to the presence of single gold adatoms bonded by a coordination bond underneath the molecular monolayer, causing a characteristic change of the electronic structure of the molecules. Moreover, this interpretation could be confirmed by manipulation experiments of individual molecules on and off a single gold atom. This study provides a detailed understanding of the role of metal adatoms in surface–molecule bonding and anchoring and of the appearance of single molecules, and it should prove relevant for the imaging of related molecule–metal systems.
The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the International Measurement Evaluation Program (IMEP). IMEP organises inter-laboratory comparisons in support of European Union policies. This paper presents the results of two proficiency tests (PTs): IMEP-116 and IMEP-39, organised for the determination of total Cd, Pb, As, Hg and inorganic As (iAs) in mushrooms. Participation in IMEP-116 was restricted to National Reference Laboratories (NRLs) officially appointed by national authorities in European Union member states. IMEP-39 was open to all other laboratories wishing to participate. Thirty-seven participants from 25 countries reported results in IMEP-116, and 62 laboratories from 36 countries reported for the IMEP-39 study. Both PTs were organised in support to Regulation (EC) No. 1881/2006, which sets the maximum levels for certain contaminants in food. The test item used in both PTs was a blend of mushrooms of the variety shiitake (Lentinula edodes). Five laboratories, with demonstrated measurement capability in the field, provided results to establish the assigned values (Xref). The standard uncertainties associated to the assigned values (uref) were calculated by combining the uncertainty of the characterisation (uchar) with a contribution for homogeneity (ubb) and for stability (ust), whilst uchar was calculated following ISO 13528. Laboratory results were rated with z- and zeta (ζ)-scores in accordance with ISO 13528. The standard deviation for proficiency assessment, σp, ranged from 10% to 20% depending on the analyte. The percentage of satisfactory z-scores ranged from 81% (iAs) to 97% (total Cd) in IMEP-116 and from 64% (iAs) to 84% (total Hg) in IMEP-39.
The color X-ray camera SLcam® is a full-field, single photon detector providing scanning-free, energy and spatially resolved X-ray imaging. Spatial resolution is achieved with the use of polycapillary optics guiding X-ray photons from small regions on a sample to distinct energy dispersive pixels on a charged-coupled device detector. Applying sub-pixel resolution, signals from individual capillary channels can be distinguished. Therefore, the SLcam® spatial resolution, which is normally limited to the pixel size of the charge-coupled device, can be improved to the size of individual polycapillary channels. In this work a new approach to a sub-pixel resolution algorithm comprising photon events also from the pixel centers is proposed. The details of the employed numerical method and several sub-pixel resolution examples are presented and discussed.
Micro structured reactors are attractive candidates for further process intensification in heterogeneous catalysis. However, they require catalytic coatings with significantly improved space-time yields compared to traditional supported catalysts. We report the facile synthesis of homogeneous nanocrystalline Pt coatings with hierarchical pore structure by electrochemical dealloying of amorphous sputter-deposited platinum silicide layers. Thickness, porosity and surface composition of the catalysts can be controlled by the dealloying procedure. XPS analysis indicates that the catalyst surface is primarily composed of metallic Pt. Catalytic tests in gas-phase hydrogenation of butadiene reveal the typical activity, selectivity and activation energy of nanocrystalline platinum. However, space time yields are about 13 to 200 times higher than values reported for Pt-based catalysts in literature. The highly open metallic pore structure prevents heat and mass transport limitations allowing for very fast reactions and reasonable stability at elevated temperatures.
Lewis and Brønsted sites were quantified in a series of weak acidic hydroxylated magnesium fluorides by Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance spectroscopy (NMR) with pyridine as probe molecule. Molar extinction coefficients, which are necessary for quantitative FTIR measurements, were calculated by an easy approach. It utilizes the fact that both signals, used for the quantification by FTIR, are caused by the same deformation vibration mode of pyridine. Comparison of quantitative FTIR experiments and quantification by NMR shows that concentrations of acidic sites determined by FTIR spectroscopy have to be interpreted with caution. Furthermore, it is shown that the transfer of molar extinction coefficients from one catalyst to another may lead to wrong results. Molar extinction coefficients and concentrations of acidic sites determined by FTIR spectroscopy are affected by grinding and probably the particle size of the sample. High temperature during FTIR experiments has further impact on the quantification results.
While polymorphism is a common phenomenon in the crystallization processes of organic compounds, polyamorphism has gained importance only recently. Using sophisticated sample environments and applying in situ scattering methods and vibrational spectroscopy, the complete crystallization process of organic compounds from solution can be traced and characterized. Diffuse scattering from amorphous intermediates can be investigated by analyzing the atomic pair distribution function (PDF) to gain further insights into molecular pre-orientation. The crystallization behavior of paracetamol was studied exemplarily under defined, surface-free conditions. Based on the choice of the solvent, the formation of different polymorphs is promoted. The thermodynamically stable form I and the metastable orthorhombic form II could be isolated in pure form directly from solution. For both polymorphs, the crystallization from solution proceeds via a distinct amorphous precursor phase. PDF analyses of these different amorphous states indicate a specific pre-orientation of the analyte molecules introduced by the solvent. The resulting crystalline polymorph is already imprinted in these proto-crystalline precursors. Direct experimental evidence for the polyamorphism of paracetamol is provided.
The reaction of iron chlorides with an alkaline reagent is one of the most prominent methods for the synthesis of iron oxide nanoparticles. We studied the particle formation mechanism using triethanolamine as reactant and stabilizing agent. In situ fast-X-ray absorption near edge spectroscopy and small-angle X-ray scattering provide information on the oxidation state and the structural information at the same time. In situ data were complemented by ex situ transmission electron microscopy, wide-angle X-ray scattering and Raman analysis of the formed nanoparticles. The formation of maghemite nanoparticles (γ-Fe2O3) from ferric and ferrous chloride was investigated. Prior to the formation of these nanoparticles, the formation and conversion of intermediate phases (akaganeite, iron(II, III) hydroxides) was observed which undergoes a morphological and structural collapse. The thus formed small magnetite nanoparticles (Fe3O4) grow further and convert to maghemite with increasing reaction time.
The need for technological progress in bio-diagnostic assays of high complexity requires both fundamental research and constructing efforts on nano-scaled assay recognition elements that can provide unique selectivity and design-enhanced sensitivity features. Nanoparticle induced sensitivity enhancement and its application related to multiplexed capability Surface-Enhanced InfraRed Absorption (SEIRA) assay formats are well suitable for these purposes. The potential of diverse fluorophore–antibody conjugates, being chemisorbed onto low-cost gold nanoparticulate SEIRA substrates, has been explored with respect to their spectral discriminability. These novel biolabels deliver molecular SEIRA fingerprints that have been successfully analyzed by both uni- and multivariate analyzing tools, to discriminate their multiplexing capabilities. We show that this robust spectral encoding via SEIRA fingerprints opens up new opportunities for a fast, reliable and multiplexed high-end screening in biodiagnostics.
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.
A novel synthetic strategy toward highly fluorinated BODIPY dyes with exceptional photostabilities relying on sustainable gold catalysis has been developed. A key to the tailored pyrrole precursors is the gold catalysis performed in ionic liquids as the reaction medium, allowing a facile recycling of the catalysts. The dyes prepared are well-matching with the spectral windows of popular rhodamine dyes and possess high brightness while showing a distinctly higher photostability than the rhodamines especially in aprotic solvents.
Magneto-resistive (MR) sensor arrays are suited for high resolution eddy current testing (ET) of aerospace components due to two significant advantages compared to conventional coil systems. First, to obtain high spatial resolution they can be manufactured down to the µm-regime without losing their outstanding field sensitivity. Secondly, MR technology has a relatively frequency-independent sensitivity in the range of common ET-frequencies thus providing a benefit for low frequency applications.
This paper presents measurements using MR array probes consisting of 32 TMR-elements (tunnel magneto resistance), an ASIC, and subsequent readout components. A source for generating the eddy currents inside the material under test is also implemented onboard of the PCB. These probes were developed in the IMAGIC-project* for detection and imaging of surface breaking defects.
The performance of the new sensor system has been investigated for several mock-ups, Aluminum and Titanium plate specimens having small adjacent boreholes with diameter of 0.44 mm and micro notches in the µm-range, respectively. To compare our results we used conventional eddy current probes. The MR sensor elements have a length of around 60 µm leading to a nearly 'point like' measurement. Neighbouring boreholes (depth 0.25 mm) with a separation of 0.6 mm between their centres could be resolved with a good SNR, and more important, the boreholes could be confidently distinguished using the TMR-probes. In case of conventional probes a reliable separation was not possible. In this paper we present the MR-ET-probes of the IMAGIC consortium and a comparison with conventional techniques.
*The IMAGIC-project ('Integrated Magnetic imagery based on spIntronics Components', 2011 – 2014, project reference: 288381) was funded by the European Commission, Seventh Framework Programme. Further partners involved in the consortium beside BAM and CEA were INESC-ID and INESC-MN (Portugal), Sensitec GmbH (Germany), Tecnatom S.A. (Spain), and Airbus Group (France).
Defect detection in concrete pile using impulse response measurements with sine sweep excitations
(2015)
For pile integrity inspection, a low cost and portable shaker was used to create the sine sweep signal for pile excitation. The impulse response function, calculated by the deconvolution of pile response from the sine sweep excitation, was proposed to identify the echoes in the piles due to the pile’s impedance changes. The proposed methodology has been evaluated and validated both numerically and experimentally. Based on the results from the simulations and experiments, it was found that the impulse response measurement with sine sweep excitation could be an effective tool to detect the echoes of the pile toe and the defects in the pile.
This paper describes the production and characteristics of the nanoparticle test materials prepared for common use in the collaborative research project NanoChOp (Chemical and optical characterization of nanomaterials in biological systems), in casu suspensions of silica nanoparticles and CdSe/CdS/ZnS quantum dots (QDs). This paper is the first to illustrate how to assess whether nanoparticle test materials meet the requirements of a "reference material" (ISO Guide 30, 2015) or rather those of the recently defined category of "representative test material (RTM)" (ISO/TS 16195, 2013). The NanoChOp test materials were investigated with small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and centrifugal liquid sedimentation (CLS) to establish whether they complied with the required monomodal particle size distribution. The presence of impurities, aggregates, agglomerates, and viable microorganisms in the suspensions was investigated with DLS, CLS, optical and electron microscopy and via plating on nutrient agar. Suitability of surface functionalization was investigated with attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and via the capacity of the nanoparticles to be fluorescently labeled or to bind antibodies. Between-unit homogeneity and stability were investigated in terms of particle size and zeta potential. This paper shows that only based on the outcome of a detailed characterization process one can raise the status of a test material to RTM or reference material, and how this status depends on its intended use.
Effect of fluorescent staining on size measurements of polymeric nanoparticles using DLS and SAXS
(2015)
The influence of fluorescence on nanoparticle size measurements using dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) was investigated. For this purpose, two series of 100 nm-sized polymer nanoparticles stained with different concentrations of the fluorescent dyes DY555 and DY680 were prepared, absorbing/emitting at around 560 nm/590 nm and 695 nm/715 nm, respectively. SAXS measurements of these particle series and a corresponding blank control (without dye) revealed similar sizes of all particles within an uncertainty of 1 nm. DLS measurements carried out at three different laboratories using four different DLS instruments and two different laser wavelengths, i.e., 532 nm and 633 nm, revealed also no significant changes in size (intensity-weighted harmonic mean diameter, ZAverage) and size distribution (polydispersity index, PI) within and between the two dye-stained particle series and the blank sample. Nevertheless, a significant decrease of the detected correlation coefficients was observed with increasing dye concentration, due to the increased absorption of the incident light and thus, less coherent light scattering. This effect was wavelength dependent, i.e. only measurable for the dye-stained particles that absorb at the laser wavelength used for the DLS measurements.
Für die Prüfung von Leichtbaustrukturen ist in den letzten Jahren ein vermehrter Einsatz der Luftultraschallprüfung zu verzeichnen. Insbesondere eignet sich Luftultraschall für die Prüfung von Faserkunststoffverbunden und hybrider Werkstoffverbunde, die ihre Anwendung in der Automobilindustrie und Luftfahrt finden. Für den Bau von marktüblichen Luftultraschall-Wandlern werden Piezokomposite mit Anpassschichten versehen. Ihre Herstellung ist allerdings sehr anspruchsvoll und die erreichbaren Signal-Rausch-Abstände sind für viele Prüfprobleme als noch nicht ausreichend einzustufen. Zwecks gesteigerter Effizienz beim Schallübertrag in die Luft wurden Luftultraschall-Sender und -Empfänger aus zellulärem Polypropylen entwickelt. Dieses piezoelektrische Material ist aufgrund seiner geringer Dichte und seiner sehr geringen Schallgeschwindigkeit an die niedrige akustische Impedanz der Luft deutlich besser angepasst, als die üblicherweise verwendeten Anpassschichten. Letztere können bei Polypropylen-Wandlern daher gänzlich vermieden werden.
In diesem Beitrag wird Luftultraschall-Prüfung an zwei verschiedenen CFK-Testkörpern vorgestellt: an einer Platte mit T-Stringern aus dem Seitenleitwerk eines Flugzeugs und an einer Platte mit künstlich eingebrachten Fehlern. Es wurde mit unterschiedlichen planaren und fokussierenden Wandlern geprüft. Marktübliche Wandler mit Anpassschichten wurden mit den selbstentwickelten Wandlern aus zellulärem Polypropylen verglichen. Der Signal-Rausch-Abstand und die laterale Auflösung wurden sowohl im Prüfaufbau mit senkrechter Einschallung als auch mit Schrägeinschallung gemessen. Die Ergebnisse zeigen, dass die Schrägeinschallung zwar den Signal-Rauschabstand erhöht, aber die laterale Auflösung verschlechtern kann.
Recommendations on a Revision of the EC Definition of Nanomaterial Based on Analytical Possibilities
(2015)
In October 2011 the European Commission (EC) published a "Recommendation on the definition of nanomaterial" (2011/696/EU), to promote consistency in the interpretation of the term "nanomaterial" for legislative and policy purposes in the EU. The EC NM Definition includes a commitment to its review in the light of experience and of scientific and technological developments. This review is ongoing in 2015 and as a contribution to the review the Joint Research Centre of the European Commission (JRC) has already developed a series of three scientific-technical reports with the title: “Towards a review of the EC Recommendation for a definition of the term nanomaterial” which provides to the EC policy services science-based options on how the definition could be revised or supported with additional guidance.
The overarching nature and wide scope of the EC NM Definition, as it does not exclude a priori any particulate material regardless the state, form and size, creates many analytical challenges in its imple-mentation for all stakeholders, including enterprises and regulators.
The NanoDefine project has as core objective to support the implementation of the EC NM Definition. In this report key aspects of the EC NM Definition are addressed, with the goal to improve the implement-ability of the EC NM Definition. These aspects are presented and discussed based on the results of two years of research performed within the framework of the project. As a result this report assesses how well the requirements of the EC NM Definition can be fulfilled with currently available analytical possi-bilities. It presents recommendations and options on a revision of the EC NM Definition to improve the implementability of the definition based on currently available analytical possibilities, according to the state of the art of mid-2015.
Of the technical issues considered in this report, the following seem to deserve the most attention in terms of clarification of the definition and/or provision of additional implementation guidance:
The term ‘external dimension’.
A clear definition of 'External dimension' should be included in the text of the EC NM definition and more precise guidance on what is considered as an external dimension and how to properly character-ise it should be provided.
The ‘number based particle size distribution‘.
The EC NM Definition uses a threshold related to the number based size distribution of particles. Yet most of the easily available techniques provide a mass-, volume- or scattered light intensity-based size distribution which needs to be converted into a number based distribution to be used for regulatory pur-poses. A specific guidance on the conditions under which these methods can be used to identify a na-nomaterial by employing appropriate quantity or metrics conversion should be provided.
The ‘polydispersity‘ and ‘upper size limit‘
Polydispersity is a challenge for the measurement of particle size distribution for the EC NM definition, specifically for materials with high polydispersity index and broad size distribution especially when the volume or mass of the fraction containing particles below 100 nm is very small. Therefore a dedicated guidance should be provided that allows applying an upper size limit in measurements and particle statistics.
Selective Electron Beam Melting (SEBM) is a promising powder bed Additive Manufacturing technique for near-net-shape manufacture of high-value titanium components. However without post-manufacture HIPing the fatigue life of SEBM parts is currently dominated by the presence of porosity. In this study, the size, volume fraction, and spatial distribution of the pores in model samples have been characterised in 3D, using X-ray Computed Tomography, and correlated to the process variables. The average volume fraction of the pores (b0.2%) was measured to be lower than that usually observed in competing processes, such as selective laser melting, but a strong relationship was found with the differentbeamstrategies used to contour ,and infill by hatching, a part section. The majority of pores were found to be small spherical gas pores, concentrated in the infill hatched region; this was attributed to the lower energy density and less focused beam used in the infill strategy allowing less opportunity for gas bubbles to escape the melt pool. Overall, increasing the energy density or focus of the beam was found to correlate strongly to a reduction in the level of gas porosity. Rarer irregular shaped pores were mostly located in the contour region and have been attributed to a lack of fusion between powder particles.
Sealing and strengthening of the subsoil by 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 to predict the resulting column diameter and its material strength. In this paper we illustrate the application of a newly developed non-destructive quality assurance testing 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 3.0 and 10 m. The evaluated diameters were within 1.0 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 10 m depth with no significant difficulties. On the other hand, unsaturated, partly unconsolidated sands between ground water level and surface considerably affected the seismic data, hence complicating the detection of the top of the columns.
Challenging new constructions and ageing infrastructure are increasing the demand for permanent monitoring of loads and condition. Various methods and sensors are used for this purpose. But the technologies available today have difficulties in detecting slowly progressing locally confined damages. Extensive investigations or instrumentations are required so far for this purpose. In this study we present new sensors and data processing methods for ultrasonic transmission, which can be used for non-destructive long term monitoring of concrete. They can be mounted during construction or thereafter. Larger volumes can be monitored by a limited number of sensors for changes of material properties. The principles of ultrasonic transmission and influencing factors are presented. This latter include load, damages as well as environmental parameters as temperature or moisture. Various methods for data processing, e. g. coda wave interferometry are introduced. They allow the detection of very small changes in the medium. The embedded sensors are shown including mounting and operation. Application examples so far include small scale laboratory freeze-thaw experiments, localizing loads in larger concrete models, monitoring load effects on real structures as well as detecting acoustic events. Some sensors are operating already for several years. The sensors can be used as transmitter or receivers or switched between both roles. While most of the previous experiments have been active (at least one sensor serving as transmitter), new studies show that the sensors are useful as well for passive measurements, e. g. in acoustic emission or time reversal experiments. Besides application in civil engineering our setups can also be used for model studies in geosciences.
Elastic wave propagation of ultrasound in bituminous road surfaces - simulations and measurements
(2015)
Maintenance costs of road infrastructure are increasing steadily. The main cause of this is the nearly exponential increase of traffic during the last decades. Adverse environmental impacts on infrastructure get more and more important as well. Therefore, it is important to determine how limited financial resources can be directed with an optimum pay-out. Often a decision has to be made whether existing structures have to be rebuilt or repaired based on the condition of the structures. The present study takes first steps towards the usage of low-frequency ultrasound as a tool to evaluate the road condition. The overall aim is to derive a prediction model for future road conditions. In order to better understand and interpret recorded wave fields simulations of elastic wave propagation in layered and scattering road models have been performed. The study combined investigations in the laboratory with field measurements. In a series of extensive laboratory tests with different asphalt mixtures characteristic wave properties have been derived. Travel time (resp. velocity) as important material parameter has been investigated for different wave types, different centre frequencies and at various temperatures. An investigation of the directivity of wave radiation in the heterogeneous asphalt bodies led to an estimate of the related disturbing influences. Based on the laboratory results field measurements were performed on a real road and the records were processed to identify layers, propagation speeds and attenuation. The results were verified by a series of simulations.
Recently developed new transducers for ultrasonic transmission, which can be embedded right into concrete, are now used for non-destructive permanent monitoring of concrete. They can be installed during construction or thereafter. Large volumes of concrete can be monitored for changes of material properties by a limited number of transducers. The transducer design, the main properties as well as installation procedures are presented. It is shown that compressional waves with a central frequency of 62 kHz are mainly generated around the transducer's axis. The transducer can be used as a transmitter or receiver. Application examples demonstrate that the transducers can be used to monitor concrete conditions parameters (stress, temperature,
) as well as damages in an early state or the detection of acoustic events (e.g., crack opening). Besides application in civil engineering our setups can also be used for model studies in geosciences.
Ultrasonic echo testing is widely used in non-destructive testing in civil engineering to investigate concrete structures, to measure thickness, and to locate and characterise built-in components or inhomogeneities. Currently, synthetic aperture focusing techniques are mostly used for imaging. These algorithms are highly developed but have some limitations. For example, it is not possible to image the lower boundary of built-in components like tendon ducts or vertical reflectors. We adopted reverse time migration for non-destructive testing in civil engineering in order to improve the imaging of complicated structures in concrete. By using the entire wavefield, including waves reflected more than once, there are fewer limitations compared to synthetic aperture focusing technique algorithms. As a drawback, the required computation is significantly higher than that for the techniques currently used. Simulations for polyamide and concrete structures showed the potential for non-destructive testing. The simulations were followed by experiments at a polyamide specimen. Here, having acquired almost noise-free measurement data to test the algorithm, we were able to determine the shape and size of boreholes with sufficient accuracy. After these successful tests, we performed experiments at a reinforced concrete foundation slab. We obtained information from the data by reverse time migration, which was not accessible by traditional imaging. The imaging of the location and structure of the lower boundary of the concrete foundation slab was improved. Furthermore, vertical reflectors inside the slab were imaged clearly, and more flaws were found. It has been shown that reverse time migration is a step forward in ultrasonic testing in civil engineering.
Geophysical methods have been used in civil engineering for decades. The main field of application is - to no surprise – in geotechnical projects from site characterization to foundation quality assurance. For more than 25 years, ground penetrating radar (GPR) and seismic methods have found applications in structural engineering. Recently introduced geophysical methods have been adopted to ultrasonic investigations in various fields. They help to improve the quality of structural imaging and to detect small changes in concrete. An overview of the history and current use of geophysics in civil engineering is given. Selected examples of new concepts include advances in wave based imaging, quality assurance for foundations, detecting small changes in concrete as well as moisture and corrosion detection are discussed.
Various plant compartments of a single bell pepper plant were studied to verify the variability of boron isotope composition in plants and to identify possible intra-plant isotope fractionation. Boron mass fractions varied from 9.8 mg/kg in the fruits to 70.0 mg/kg in the leaves. Boron (B) isotope ratios reported as δ11B ranged from -11.0 to +16.0 (U ≤ 1.9, k=2) and showed a distinct trend to heavier δ11B values the higher the plant compartments were located in the plant. A fractionation of Δ11Bleaf-roots = 27 existed in the studied bell pepper plant, which represents about about 1/3 of the overall natural boron isotope variation (ca. 80). Two simultaneous operating processes are a possible explanation for the observed systematic intra-plant δ11B variation: 1) B is fixed in cell walls in its tetrahedral form (borate), which preferentially incorporates the light B isotope and the remaining xylem sap gets enriched in the heavy B isotope and 2) certain transporter preferentially transport the trigonal 11B-enriched boric acid molecule and thereby the heavy 11B towards young plant compartments which were situated distal of the roots and typically high in the plant. Consequently, an enrichment of the heavy 11B isotope in the upper young plant parts located at the top of the plant could explain the observed isotope systematic. The identification and understanding of the processes generating systematic intra-plant δ11B variations will potentially enable the use of B isotope for plant metabolism studies.
Sicherheitsrelevante und zyklisch hoch belastete Bauteile erfordern zur Vermeidung von kostenintensiven Ausfällen besonders stabile Prozessparameter. Bereits sehr kleine Randzonenfehler können unter zyklischer Bauteilbelastung zu Risswachstum und letztendlich zum Bauteilversagen führen. Die frühzeitige Erkennung von Randzonenfehler in Hochleistungsbauteilen wie z.B. Zahnräder, Ritzelwellen und Kurbelwellen erfordert daher eine leistungsfähige zerstörungsfreie Oberflächenrissprüfung, die es ermöglicht in den hochbeanspruchten Funktionsflächen auch Härterisse, Schleifrisse oder Zundereinschlüsse zu detektieren.
Hierzu sind in den letzten Jahren einige neue, innovative Oberflächenprüfverfahren wie die laserangeregte Thermografie und die Streuflussprüfung mit hochauflösenden GMR-Sensoren oder magnetooptischen Verfahren entwickelt worden. Zusätzlich zur hohen Empfindlichkeit zeichnen sich diese innovativen Verfahren durch einen schnellen und teils auch berührungslosen Einsatz aus. Da die noch relativ neu-en Verfahren naturgemäß noch nicht normativ verankert sind, wurden auch bereits erste Validierungen durchgeführt. Um die Leistungsfähigkeit der Verfahren eingehend zu untersuchen, erfolgten Testreihen an verschiedenen Testkörpern in Bezug auf Ortsauflösung, Empfindlichkeit, Automatisierung und Bewertung der Messsig-nale.
Neben den neuen Verfahren und ihren ersten Schritten hin zur Validierung kamen als Referenz auch die „klassischen“ Verfahren der Magnetpulver- und Wirbelstromprüfung zum Einsatz, deren Leistungsfähigkeit durch angepasste Sondenentwicklung auch für sehr kleine Oberflächendefekte nochmals unter Beweis gestellt wurde. Zusätzlich wurde an einigen Testkörpern eine hochauflösende CT durchgeführt. Die Ergebnisse dieses Vergleiches werden vorgestellt und Möglichkeiten sowie Grenzen der einzelnen Verfahren herausgearbeitet.
Characterization of silver nanoparticles in cell culture medium containing fetal bovine serum
(2015)
Nanoparticles are being increasingly used in consumer products worldwide, and their toxicological effects are currently being intensely debated. In vitro tests play a significant role in nanoparticle risk assessment, but reliable particle characterization in the cell culture medium with added fetal bovine serum (CCM) used in these tests is not available. As a step toward filling this gap, we report on silver ion release by silver nanoparticles and on changes in the particle radii and in their protein corona when incubated in CCM. Particles of a certified reference material, p1, and particles of a commercial silver nanoparticle material, p2, were investigated. The colloidal stability of p1 is provided by the surfactants polyethylene glycol-25 glyceryl trioleate and polyethylene glycol-20 sorbitan monolaurate, whereas p2 is stabilized by polyvinylpyrrolidone. Dialyses of p1 and p2 reveal that their silver ion release rates in CCM are much larger than in water. Particle characterization was performed with asymmetrical flow field-flow fractionation, small-angle X-ray scattering, dynamic light scattering, and electron microscopy. p1 and p2 have similar hydrodynamic radii of 15 and 16 nm, respectively. The silver core radii are 9.2 and 10.2 nm. Gel electrophoresis and subsequent peptide identification reveal that albumin is the main corona component of p1 and p2 after incubation in CCM that consists of Dulbecco's modified Eagle medium with 10% fetal bovine serum added.
SASfit: a tool for small-angle scattering data analysis using a library of analytical expressions
(2015)
SASfit is one of the mature programs for small-angle scattering data analysis and has been available for many years. This article describes the basic data processing and analysis workflow along with recent developments in the SASfit program package (version 0.94.6). They include (i) advanced algorithms for reduction of oversampled data sets, (ii) improved confidence assessment in the optimized model parameters and (iii) a flexible plug-in system for custom user-provided models. A scattering function of a mass fractal model of branched polymers in solution is provided as an example for implementing a plug-in. The new SASfit release is available for major platforms such as Windows, Linux and MacOS. To facilitate usage, it includes comprehensive indexed documentation as well as a web-based wiki for peer collaboration and online videos demonstrating basic usage. The use of SASfit is illustrated by interpretation of the small-angle X-ray scattering curves of monomodal gold nanoparticles (NIST reference material 8011) and bimodal silica nanoparticles (EU reference material ERM-FD-102).
A user-friendly open-source Monte Carlo regression package (McSAS) is presented, which structures the analysis of small-angle scattering (SAS) using uncorrelated shape-similar particles (or scattering contributions). The underdetermined problem is solvable, provided that sufficient external information is available. Based on this, the user picks a scatterer contribution model (or 'shape') from a comprehensive library and defines variation intervals of its model parameters. A multitude of scattering contribution models are included, including prolate and oblate nanoparticles, core-shell objects, several polymer models, and a model for densely packed spheres. Most importantly, the form-free Monte Carlo nature of McSAS means it is not necessary to provide further restrictions on the mathematical form of the parameter distribution; without prior knowledge, McSAS is able to extract complex multimodal or odd-shaped parameter distributions from SAS data. When provided with data on an absolute scale with reasonable uncertainty estimates, the software outputs model parameter distributions in absolute volume fraction, and provides the modes of the distribution (e.g. mean, variance etc.). In addition to facilitating the evaluation of (series of) SAS curves, McSAS also helps in assessing the significance of the results through the addition of uncertainty estimates to the result. The McSAS software can be integrated as part of an automated reduction and analysis procedure in laboratory instruments or at synchrotron beamlines.
Online monitoring and process control requires fast and noninvasive analytical methods, which are able to monitor the concentration of reactants in multicomponent mixtures with parts-per-million resolution. Online NMR spectros-copy can meet these demands when flow probes are directly coupled to reactors, since this method features a high linearity between absolute signal area and sample concentration, which makes it an absolute analytical com-parison method being independent on the matrix. Due to improved magnet design and field shimming strategies portable and robust instruments have been introduced to the market by several manufacturers during the last few years. First studies with this technology showed promising results to monitor chemical reaction in the laboratory.
Hochduktiler Beton eröffnet neue Möglichkeiten bei der Instandsetzung von Bauwerken, der Herstellung dünnwandiger Bauelemente oder dem Einsatz von Dämpfungselementen in stoßartig beanspruchten Bauwerken (z.B. in Erdbebengebieten).
Die Steigerung der Duktilität kann durch die Zugabe von Kurzfasern erreicht werden. Im Falle einer Rissbildung in der Zementsteinmatrix überbrücken die Fasern den Riss, nehmen die Spannung vollständig auf und stoppen lokal das Risswachstum. Bei weiterer Steigerung der Last reißt die Matrix an anderer Stelle. Auf diese Weise wird die Rissbildung fein verteilt und es werden große Dehnungen erreicht, bevor das Bauteil versagt. Zur Optimierung der Festbetoneigenschaften müssen die Matrixfestigkeit und die Faserart sowie deren Gehalt aufeinander abgestimmt werden. Dabei sind auch die Verarbeitungseigenschaften des Frischbetons zu berücksichtigen.
Anhand der Schallemissionen kann die Rissbildung in der Matrix und die Interaktion mit den Fasern analysiert werden. So konnte in ersten Zugversuchen gezeigt werden, dass sich Schallereignisse dem Versagen der Zementsteinmatrix bzw. dem Auszug der Fasern aus der Matrix zuordnen lassen. Damit steht zur Beurteilung des mechanischen Verhaltens von hochduktilem Beton neben der Spannungs-Dehnungs-Linie ein weiteres Verfahren zur Verfügung.
Melt flow and dripping of the pyrolysing polymer melt can be both a benefit and a detriment during a fire. In several small-scale fire tests addressing the ignition of a defined specimen with a small ignition source, well-adjusted melt flow and dripping are usually beneficial to pass the test. The presence of flame retardants often changes the melt viscosity crucially. The influence of certain flame retardants on the dripping behaviour of four commercial polymers, poly(butylene terephthalate) (PBT), polypropylene (PP), polypropylene modified with ethylene-propylene rubber (PP-EP) and polyamide 6 (PA 6), is analysed based on an experimental monitoring of the mass loss due to melt dripping, drop size and drop temperature as a function of the furnace temperature applied to a rod-shaped specimen. Investigating the thermal transition (DSC), thermal and thermo-oxidative decomposition, as well as the viscosity of the polymer and collected drops completes the investigation. Different mechanisms of the flame retardants are associated with their influence on the dripping behaviour in the UL 94 test. Reduction in decomposition temperature and changed viscosity play a major role. A flow limit in flame-retarded PBT, enhanced decomposition of flame-retarded PP and PP-EP and the promotion of dripping in PA 6 are the salient features discussed.
N-Hydroxysuccinimide (NHS) esters are the most important activated esters used in many different bioconjugation techniques, such as protein labelling by fluorescent dyes and enzymes, surface activation of chromatographic supports, microbeads, nanoparticles, and microarray slides, and also in the chemical synthesis of peptides. Usually, reactions with NHS esters are very reliable and of high yield, however, the compounds are sensitive to air moisture and water traces in solvents. Therefore, the quantification of NHS would be a very helpful approach to identify reagent impurities or degradation of stored NHS esters. No robust and sensitive method for the detection of NHS (or the more hydrophilic sulfo-NHS) has been reported yet. Here, a chromatographic method based on HILIC conditions and UV detection is presented, reaching a detection limit of about 1 mg L-1, which should be sensitive enough for most of the applications mentioned above. Exemplarily, the hydrolytic degradation of a biotin-NHS ester and a purity check of a fluorescent dye NHS ester are shown. An important advantage of this approach is its universality, since not the structurally variable ester compound is monitored, but the constant degradation product NHS or sulfo-NHS, which avoids the necessity to optimize the separation conditions and facilitates calibration considerably.
In this work, sample losses of silver nanoparticles (Ag NPs) in asymmetrical flow field-flow fractionation (AF4) have been systematically investigated with the main focus on instrumental conditions like focusing and cross-flow parameters as well as sample concentration and buffer composition. Special attention was drawn to the AF4 membrane. For monitoring possible silver depositions on the membrane, imaging laser ablation coupled to inductively coupled plasma mass spectrometry (LA-ICP-MS) was used. Our results show that the sample residue on the membrane was below 0.6% of the total injected amount and therefore could be almost completely avoided at low sample concentrations and optimized conditions. By investigation of the AF4 flows using inductively coupled plasma mass spectrometry (ICP-MS), we found the recovery rate in the detector flow under optimized conditions to be nearly 90%, while the cross-flow, slot-outlet flow and purge flow showed negligible amounts of under 0.5%. The analysis of an aqueous ionic Ag standard solution resulted in recovery rates of over 6% and the ionic Ag content in the sample was found to be nearly 8%. Therefore, we were able to indicate the ionic Ag content as the most important source of sample loss in this study.
Bottom ash from municipal solid waste incineration (MSWI) consists of eiemental metals in considerable amounts. The fine fraction < 4 mm additionally contains chemically bound metals (oxides, carbonates, Silicates). Separation prospects with techniques as in ore processing (flotation, density separation, bioleaching, hydrothermal solution) are discussed. During alteration after wet extraction mineral material with hydraulic properties form coatings on almost all particles of the bottom ash and complicate separation procedures. ln addition bottom ash from MSWI is a heterogeneaus material. For sufficient enrichment different concerted treatment steps seemed to be essential associated with an uncertainty of economic viability. The utilisation of metal compounds present in bottom ash as secondary raw material depends on the energy- and resource-efficiency of the enrichment processes. Therefore energy and material flow considerations are presented.
In this paper, we identify the strategic motives of German manufacturing companies in the electrical engineering and machinery industry to be involved in standards development organizations. First, we present the general motives for the formation of strategic alliances and relate them to specific standardization motives. Then, we identify pursuing specific company interests, solving technical problems, knowledge seeking, influencing regulation, and facilitating market access as motives to standardize by means of factor analysis. In a second step, we test hypotheses on the relationship between the importance of strategic motives and firm level variables, e.g. R&D intensity, innovation activities, and firm size. The results reveal that firms in electric engineering and machinery have a particularly strong interest in ensuring industry-friendly design of regulations, which can be achieved by standards. Moreover, the results confirm that small firms also from these two sectors are active in standardization alliances to access knowledge from other involved stakeholders.
Characterization of multiphase metal matrix composites by means of CT and neutron diffraction
(2016)
The present study examines the relationship between the microstructure of multiphase metal matrix composites and their damage mechanisms. The matrix AlSi12CuMgNi was combined with 15% vol. Al₂O₃ (short fibers), and with 7% vol. Al₂O₃ + 15% vol. SiC (short fibers and whiskers, respectively). The experimental approach encompasses 3D microstructure characterization by means of computed tomography of samples (a) as-cast, (b) after heat treatment, and (c) after compression tests at room temperature. The volume fraction of different phases, their distribution, their orientation, and the presence of defects and damage are studied.
The influence of the addition of SiC particles on mechanical properties of composite was investigated. Phase-specific load partition analysis for samples with fiber plane parallel to load was performed by using neutron diffraction (ND) during in-situ compression. ND results show damage in the Si phase, while Al₂O₃ short fibers carry load without damage until failure. The computed tomography observations confirm the load partition analysis.
Column percolation tests may be suitable for prediction of chemical leaching from soil and soil materials. However, compared with batch leaching tests, they are time-consuming. It is therefore important to investigate ways to shorten the tests without affecting the quality of results. In this study, we evaluate the feasibility of decreasing testing time by increasing flow rate and decreasing equilibration time compared to the conditions specified in ISO/TS 21268-3, with equilibration periods of 48 h and flow rate of 12 mL/h. We tested three equilibration periods (0, 12–16, and 48 h) and two flow rates (12 and 36 mL/h)on four different soils and compared the inorganic constituent releases. For soils A and D, we observed similar values for all conditions except for the 0 h–36 mL/h case. For soil B, we observed no appreciable differences between the tested conditions, while for soil C there were no consistent trends probably due to the difference in ongoing oxidation reactions between soil samples. These results suggest that column percolation tests can be shortened from 20 to 30 days to 7–9 days by decreasing the equilibration time to 12–16 h and increasing the flow rate to 36 mL/h for inorganic substances.
Multifunctional composite nanoprobes consisting of iron oxide nanoparticles linked to silver and gold nanoparticles, Ag–Magnetite and Au–Magnetite, respectively, were introduced by endocytic uptake into cultured fibroblast cells. The cells containing the non-toxic nanoprobes were shown to be displaceable in an external magnetic field and can be manipulated in microfluidic channels. The distribution of the composite nanostructures that are contained in the endosomal system is discussed on the basis of surfaceenhanced Raman scattering (SERS) mapping, quantitative laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) micromapping, and cryo soft X-ray tomography (cryo soft-XRT). Cryo soft-XRT of intact, vitrified cells reveals that the composite nanoprobes form intra-endosomal aggregates. The nanoprobes provide SERS signals from the biomolecular composition of their surface in the endosomal environment. The SERS data indicate the high stability of the nanoprobes and of their plasmonic properties in the harsh environment of endosomes and lysosomes. The spectra point at the molecular composition at the surface of the Ag–Magnetite and Au–Magnetite nanostructures that is very similar to that of other Composite structures, but different from the composition of pure silver and gold SERS nanoprobes used for intracellular investigations. As shown by the LA-ICP-MS data, the uptake efficiency of the magnetite composites is approximately two to three times higher than that of the pure gold and silver nanoparticles.
Safety assessment of nanoparticles (NPs) requires techniques that are suitable to quantify tissue and cellular uptake of NPs. The most commonly applied techniques for this purpose are based on inductively coupled plasma mass spectrometry (ICP-MS). Here we apply and compare three different ICP-MS methods to investigate the cellular uptake of TiO2 (diameter 7 or 20 nm, respectively) and Ag (diameter 50 or 75 nm, respectively) NPs into differentiated mouse neuroblastoma cells (Neuro-2a cells). Cells were incubated with different amounts of the NPs. Thereafter they were either directly analyzed by laser ablation ICP-MS (LA-ICP-MS) or were lysed and lysates were analyzed by ICP-MS and by single particle ICP-MS (SP-ICP-MS).
A new cocrystal of pyrazinamide with oxalic acid was prepared mechanochemically and characterized by PXRD, Raman spectroscopy, solid-state NMR spectroscopy, DTA-TG, and SEM. Based on powder X-ray diffraction data the structure was solved. The formation pathway of the reaction was studied in situ using combined synchrotron PXRD and Raman spectroscopy. Using oxalic acid dihydrate the initially neat grinding turned into a rapid self-accelerated liquid-assisted grinding process by the release of crystallization water. Under these conditions, the cocrystal was formed directly within two minutes.
The International Dangerous Goods Regulations prescribe the immersion under water method (“bubble test”) as standard method for the leakproofness test of dangerous goods packagings. But this test procedure acts as a test method for leak localisation, not for quantitative leakage rates measurement. Additionally, the sensitivity in detecting leaks of small diameters is restricted, depending on the test liquid and the test pressure. The bubble test is not suitable for a comparison with quantitative limit leakage rates based on realistic transport conditions. This is especially important when estimating the risk of the formation of an explosive atmosphere during the intercontinental carriage of dangerous goods packagings in freight containers. To compare measured leakage rates with limit leakage rates, a quantitative leak testing procedure is required. Therefore a new approach for dangerous goods packagings is implemented: The pressure technique by accumulation using Helium as a tracer gas. This work presents the test equipment necessary for the quantitative measurement of Helium leakage rates through closures of different kinds of dangerous goods packagings. The essential steps to achieve good repeatable results are: A controlled Helium filling process to reach a defined test pressure in the test sample, a sufficient homogenisation of the Helium-air-mixture inside the test sample and the ensuring of a constant pressure level of the test sample during the test. The Helium loss rate of the accumulation chamber has to be measured separately to receive a correction factor for the measured leakage rates. Different constructional measures are introduced to prevent a disturbing influence of the Helium leakage rate of the filling valves on the measurement results. Methods to estimate the disturbing effect of Helium permeation through permeable parts of the test sample are also presented. As a supporting method for the experimental investigations the Helium sniffer test can be applied. This practical application-oriented advice can enable other users to establish a pressure technique by accumulation for their own technical field.
In respect of modern approaches in material sciences and highly increased
requirements on materials on safety relevant components, quality management
and non-destructive testing reclaims a steadily increased meaning. The
destructive meaning of measuring the degree of purity is defined in DIN EN 10247
through metallurgical investigations, especially microsections.
For and comparable, but non-destructive testing due ultrasonic testing, the material
the SEP 1927 is a well-defined industry standard. A novel and alternative way
of reference block construction was focused by this work. The proposed amendments,
regarding the manufacturing and machining, are less time and cost consuming.
Verified by measurements the presented reference block fits the same acoustical
characteristics and the requirements of the guideline.
Determination of the elastic behavior of silicon nanowires within a scanning electron microscope
(2016)
Three-point bending tests were performed on double-anchored, <110> silicon nanowire samples inside a scanning electron microscope (SEM) via a micromanipulator equipped with a piezo-resistive force sensor. Representing the upper and lower boundaries achievable in a consistent manner, silicon nanowires with widths of 35 nm and 74 nm and a height of 168 nm were fabricated. The nanowires were obtained monolithically along with their 10-m-tall supports through a top-down fabrication approach involving a series of etching processes. Hence, no interface compliance was introduced between supports and nanowires. Exact nanowire dimensions and cross-sectional features were determined by transmission electron microscopy (TEM) following sample preparation through focused ion beam (FIB) machining. Conducting the experiments inside an SEM chamber further raised the opportunity of the direct observation of any deviation from ideal loading conditions such as twisting, which was taken into consideration in simulations. Measured force-displacement behavior was observed to exhibit close resemblance to simulation results obtained by finite element modeling, when the bulk value of 169 GPa was taken as the modulus of elasticity for <110> silicon. Hence, test results show neither any size effect nor evidence of residual stresses for the considered nanoscale objects. The increased effect of the native oxide with reduced nanowire dimensions was captured as well. Thus this very simple in-situ testing method was found to be an alternative to elaborate AFM measurements on geometrically formidable nanostructures. The results demonstrate the applicability of the developed fabrication approach to the incorporation of silicon nanowires in functional micromechanical devices.
A new concept that comprises both time- and lateral-resolved X-ray absorption fine-structure information simultaneously in a single shot is presented. This uncomplicated set-up was tested at the BAMline at BESSY-II (Berlin, Germany). The primary broadband beam was generated by a double multilayer monochromator. The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by either an energy-sensitive area detector, the so-called color X-ray camera, or by an area-sensitive detector based on a CCD camera, in θ-2θ geometry. The first tests were performed with thin metal foils and some iron oxide mixtures. A time resolution of lower than 1 s together with a spatial resolution in one dimension of at least 50 µm is achieved.
The optical properties of semiconductor nanocrystals (SC NCs) are largely controlled by their size and surface chemistry, i.e., the chemical composition and thickness of inorganic passivation shells and the chemical nature and number of surface ligands as well as the strength of their bonds to surface atoms.
The latter is particularly important for CdTe NCs, which – together with alloyed CdₓHg₁₋ₓTe – are the only SC NCs that can be prepared in water in high quality without the need for an additional inorganic passivation shell. Aiming at a better understanding of the role of stabilizing ligands for the control of the application-relevant fluorescence features of SC NCs, we assessed the influence of two of the most commonly used monodentate thiol ligands, thioglycolic acid (TGA) and mercaptopropionic acid (MPA),
on the colloidal stability, photoluminescence (PL) quantum yield (QY), and PL decay behavior of a set of CdTe NC colloids. As an indirect measure for the strength of the coordinative bond of the ligands to SC NC surface atoms, the influence of the pH (pD) and the concentration on the PL properties of these colloids was examined in water and D₂O and compared to the results from previous dilution studies with a set of thiol-capped Cd₁₋ₓHgₓTe SC NCs in D₂O. As a prerequisite for these studies, the number of surface ligands was determined photometrically at different steps of purification after SC NC synthesis with Ellman’s test.
Our results demonstrate ligand control of the pH-dependent PL of these SC NCs, with MPA-stabilized CdTe NCs being less prone to luminescence quenching than TGA-capped ones. For both types of CdTe colloids, ligand desorption is more pronounced in H₂O compared to D₂O, underlining also the role of hydrogen bonding and solvent molecules.
Amongst various other NDT methods, within the EMRP-project
‘VITCEA’ active thermography is validated for testing of CFRP and
GFRP structures constructed for energy application. In this
contribution, the optical and thermal properties of CFRP and GFRP
reference defect artefact (RDA) and natural defects artefact (NDA)
test specimens are characterized. Different excitation techniques
and techniques for data analysis are compared for optimizing the
number of detected defects.
This article reports a comprehensive investigation of the average and local structure of La5.6WO12-δ, which has excellent mixed proton, electron and oxide ion conduction suitable for device applications. Synchrotron X-ray and neutron powder diffraction show that a cubic fluorite supercell describes the average structure, with highly disordered lanthanum and oxide positions. On average, the tungsten sites are sixfold coordinated and a trace [3.7 (1.3)%] of anti-site disorder is detected. In addition to sharp Bragg reflections, strong diffuse neutron scattering is observed, which hints at short-range order. Plausible local configurations are considered and it is shown that the defect chemistry implies a simple 'chemical exchange' interaction that favours ordered WO6 octahedra. The local model is confirmed by synchrotron X-ray pair distribution function analysis and EXAFS experiments performed at the La K and W L-3 edges. It is shown that ordered domains of similar to 3.5 nm are found, implying that mixed conduction in La5.6WO12-δ is associated with a defective glassy-like anion sublattice. The origins of this ground state are proposed to lie in the nonbipartite nature of the face-centred cubic lattice and the pairwise interactions which link the orientation of neighbouring octahedral WO6 sites. This 'function through frustration' could provide a means of designing new mixed conductors.
In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification.
The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly Brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst.
In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC₁im]⁺[NTf₂]⁻ and [C₄C₁im]⁺[I]⁻). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
A combined experimental numerical approach is applied to determine the transformation induced plasticity (TRIP)-parameter K for different strength low-alloy steels of grade S355J2+N and S960QL as well as the super martensitic filler CN13-4-IG containing 13 wt% chromium and 4 wt% nickel. The thermo-physical analyses were conducted using a Gleeble® 3500 facility. The thermal histories of the specimens to be tested were extracted from corresponding simulations of a real gas metal arc weldment. In contrast to common TRIP-experiments which are based on complex specimens a simple flat specimen was utilized together with an engineering evaluation method. The evaluation method was validated with literature values for the TRIP-parameter. It could be shown that the proposed approach enables a correct description of the TRIP behavior.
Active thermography is well suited for the detection of delaminations and cracks in façade elements like plaster and tiles. Not only artificial heating but also solar heating can be used if the adjustment of the façade and the weather conditions are suitable. Optical methods like laser scanners, photogrammetric methods and crack tracking sensors are providing geometrical 3D data which can be used for a 3D mapping of thermograms and for providing data with higher geometrical resolution. Thus, by the combination and fusion of these data, a comprehensive mapping and monitoring of damages of façade systems is possible.
A round robin test on flash thermography was organized within the scope of a standardization research project. This test gives information on reliability, comparability and efficiency of different testing situations. Data recorded on metal and CFRP test specimens with flat bottom holes (FBH) were analysed by evaluating the detectability and by calculating the signal-to-noise ratio (SNR) of the defect signatures as a function of defect parameters. For the investigation of the influence of material properties on the spatial resolution as well as on penetration depth, test specimens made of steel and copper with crossed notches and a notch ramp were constructed and investigated. Here, the minimum resolvable notch distance and the maximum detectable depth of the ramp were analysed.
The corrosion resistance of martensitic stainless steels (MSS) depends strongly on the chemical composition and the applied heat treatment. Both determines the distribution of the alloying elements in the microstructure and the resulting material properties. The addition of nitrogen is known to be beneficial for the pitting corrosion resistance of stainless steels. In case of MSS this effect is not only connected to nitrogen itself because nitrogen can be used to substitute carbon which also influences the result of the heat treatment process. This paper shows the effect of nitrogen on the corrosion resistance in relation to the hardening process of MSS. Therefore the effects of austenitization duration, austenitization temperature and cooling rate on microstructure, hardness and corrosion resistance were studied on the MSS X30CrMoN15 1 and X50CrMoV15. The effect of different cooling rates was studied in the range of > 100 K/s down to 1 K/s using the jominy end quench test. The changes in corrosion resistance were detected with electrochemical potentiodynamic reactivation (EPR) and by the determination of critical pitting potentials. Besides this experimental approach thermodynamic calculations with the software thermocalc will be presented and used for the interpretation of the effect of nitrogen on the corrosion resistance of MSS.
The canister for the permanent storage of spent nuclear fuel used by SKB in Sweden consists of a cast iron insert surrounded by a five centimetre thick shell of copper. It is a safety critical component and in order to secure long-term structural integrity non-destructive methods are used to inspect 100% of the volume of each canister, before it is disposed of in the repository. One of the critical components that requires inspection is a sealing weld, joining the copper tube and the lid. The friction stir weld is inspected using an ultrasonic phased array system. The area of the weld is inspected with several inspection channels with different angles and varying coverage. To make sure that no defects that might occur in the weld are overseen, the reliability of the inspection must be quantified. The reliability of NDT is usually quantified with the probability of detection curves. The influence of the parameters that might influence the POD of the flaws in the weld is investigated analysing the experimental results, as well as with a help of a numerical simulation of the inspection.
Reliability analysis of the ultrasonic inspection system for the inspection of hollow railway axles
(2016)
Axles are safety critical train components that are subjected to significant cyclic loading during operation. If the crack is initiated in the axle, cyclic loading will lead to crack propagation. To maintain structural integrity, axles must be periodically inspected for fatigue cracks in the material. Deutsche Bahn uses mechanized ultrasonic inspection system to inspect hollow railway axles. The inspections are performed from the bore surface, using several conventional transducers with different incident angles, inspecting the axle along the entire length. As with the every safety critical system, the reliability of these inspections must be determined with regard to their flaw detection capabilities. Traditionally this is done according to the relevant standards for railway vehicles. To investigate the capability of the NDT system more thoroughly, we want to evaluate the capability of the inspection system to detect flaws by means of probability of detection (POD) curves. It will be shown that other parameters, beside the size of the crack, for example crack position in the axle, influence the detection of the crack. The influence of these parameters was evaluated using ultrasonic simulation. The evaluation served as an input for the manufacturing of the flaws in the real scale axle. Once these axles are inspected and the data evaluated, using data from both measurement and simulation, we will express the POD of the crack as function of influencing parameters using the multiparameter POD model.
Novel air-coupled ultrasonic transducer combining the thermoacoustic with the piezoelectric effect
(2016)
In recent years, there has been an increasing industrial demand for one-sided inspection of various structures by means of air-coupled ultrasonic technique. Lightweight structures based on carbon-fibre-reinforced polymers may have very complex shapes, making air-coupled transmission difficult or even impossible. The inspection of concrete structures is another example where one-sided inspection is required.
To address these challenges a new type of transducer for air-coupled pulse-echo inspection was developed, which unites two principles: thermoacoustic emission and piezoelectric reception. The thermoacoustic emitter is a titanium electrode with a thickness of several tens of nanometer. This electrode was deposited onto charged cellular polypropylene, which serves as a piezoelectric receiver. The thermoacoustic transmission is based on a transformation of the thermal energy of an electrically heated electrode into the acoustic energy of an ultrasonic wave. Thermoacoustic emitters provide resonance-free behaviour and thus extremely broadband pulses. Charged cellular polypropylene is piezoelectric due to the polarization of its cells and it is well matched to air, with a Young modulus in the order of magnitude of MPa. In this contribution we present some pulse-echo measurements with the first prototypes of the combined thermoacoustic-piezoelectric transducer.
Sub-aerial biofilms (SAB) are ubiquitous, self-sufficient microbial ecosystems found on mineral surfaces at all altitudes and latitudes. SABs, which are the principal causes of weathering on exposed terrestrial surfaces, are characterized by patchy growth dominated by associations of algae, cyanobacteria, fungi and heterotrophic bacteria. A recently developed in vitro system to study colonization of rocks exposed to air included two key SAB participants - the rock-inhabiting ascomycete Knufia petricola (CBS 123872) and the phototrophic cyanobacterium Nostoc punctiforme ATCC29133. Both partners are genetically tractable and we used them here to study weathering of granite, K-feldspar and plagioclase. Small fragments of the various rocks or minerals (1–6 mm) were packed into flow-through columns and incubated with 0.1% glucose and 10 μM thiamine-hydrochloride (90 μL min−1) to compare weathering with and without biofilms. Dissolution of the minerals was followed by: (i) analysing the degradation products in the effluent from the columns via Inductively Coupled Plasma Spectroscopy and (ii) by studying polished sections of the incubated mineral fragments/grains using scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analyses. K. petricola/N. punctiforme stimulated release of Ca, Na, Mg and Mn. Analyses of the polished sections confirmed depletion of Ca, Na and K near the surface of the fragments. The abrupt decrease in Ca concentration observed in peripheral areas of plagioclase fragments favored a dissolution-reprecipitation mechanism. Percolation columns in combination with a model biofilm can thus be used to study weathering in closed systems. Columns can easily be filled with different minerals and biofilms, the effluent as well as grains can be collected after long-term exposure under axenic conditions and easily analyzed.
Biological erosion is a key process for the recycling of carbonate and the formation of calcareous sediments in the oceans. Experimental studies showed that bioerosion is subject to distinct temporal variability, but previous long-term studies were restricted to tropical waters. Here, we present results from a 14-year bioerosion experiment that was carried out along the rocky limestone coast of the island of Rhodes, Greece, in the Eastern Mediterranean Sea, in order to monitor the pace at which bioerosion affects carbonate substrate and the sequence of colonisation by bioeroding organisms. Internal macrobioerosion was visualised and quantified by micro-computed tomography and computer-algorithm-based segmentation procedures. Analysis of internal macrobioerosion traces revealed a dominance of bioeroding sponges producing eight types of characteristic Entobia cavity networks, which were matched to five different clionaid sponges by spicule identification in extracted tissue. The morphology of the entobians strongly varied depending on the species of the producing sponge, its ontogenetic stage, available space, and competition by other bioeroders. An early community developed during the first 5 years of exposure with initially very low macrobioerosion rates and was followed by an intermediate stage when sponges formed large and more diverse entobians and bioerosion rates in-creased. After 14 years, 30 % of the block volumes were occupied by boring sponges, yielding maximum bioerosion rates of 900 g m.
Bei der Power-to-Gas-Technologie wird überschüssiger Strom aus erneuerbaren Ener-gien durch Elektrolyse von Wasser in Wasserstoff umgewandelt. Dieser Wasserstoff kann als „chemischer Energiespeicher“ dienen und rückverstromt werden oder aber in das Erdgasnetz eingespeist werden. Die BAM hat die Auswirkungen von Wasserstoffzu-sätzen zum Erdgas im Hinblick auf den Explosionsschutz untersucht und sicherheitstechnische Kenngrößen für Erdgas-Wasserstoff-Gemische bestimmt.
Von besonderem Interesse waren dabei die Explosionsgrenzen, die Sauerstoffgrenzkonzentration, die maximalen Explosionsdrücke, die KG-Werte und die Normspaltweiten. Für die Messungen sind zwei Modellgase eingesetzt worden, reines Methan und ein Modell-Erdgas mit Anteilen höherer Kohlenwasserstoffe. Sie repräsentieren die Bandbreite der in Deutschland eingesetzten Erdgase.
Die Untersuchungen ergaben, dass bei einem Zusatz von bis zu 10 Mol-% Wasserstoff keine der untersuchten Kenngrößen signifikant beeinflusst wird. Die Gemische haben nur geringfügig erweiterte Explosionsbereiche und bleiben, wie die reinen Erdgase, in der Explosionsgruppe IIA. Auch die maximalen Explosionsdrücke und die zeitlichen Druckanstiege bei den Gasexplosionen werden nur wenig beeinflusst.
The successful mechanochemical syntheses of three cadmium phenylphosphonates indicates that mechanochemistry is ideally suited for synthesizing metal phosphonates. With this powerful synthesis tool it is possible to synthesize rapidly and efficiently both known and novel phosphonates. The Crystal structures of the two new compounds, and, were solved from PXRD data. They contain monodeprotonated phenylphosphonate and neutral phenylphosphonic acid ligands. The synthesis pathways of all three compounds were investigated in situ. A diffusion mechanism is corroborated by our findings.
Intermediates could be detected and identified. The kinetically favored product (3) could always be detected during the syntheses. The thermodynamic stability of the compounds and the stoichiometric ratio of the starting materials are the two directing factors for the synthesis of the final products.
The folding of single-stranded telomeric DNA into guanine (G) quadruplexes is a conformational change that plays a major role in sensing and drug targeting. The telomeric DNA can be placed on DNA origami nanostructures to make the folding process extremely selective for K+ ions even in the presence of high Na+ concentrations. Here, we demonstrate that the K+-selective G-quadruplex formation is reversible when using a cryptand to remove K+ from the G-quadruplex. We present a full characterization of the reversible switching between single-stranded telomeric DNA and G-quadruplex structures using Förster resonance energy transfer (FRET) between the dyes fluorescein (FAM) and cyanine3 (Cy3). When attached to the DNA origami platform, the G-quadruplex switch can be incorporated into more complex photonic networks, which is demonstrated for a three-color and a four-color FRET cascade from FAM over Cy3 and Cy5 to IRDye700 with G-quadruplex-Cy3 acting as a switchable transmitter.
Emerging infectious diseases (EIDs) have contributed significantly to the current biodiversity crisis, leading to widespread epidemics and population loss. Owing to genetic variation in pathogen virulence, a complete understanding of species decline requires the accurate identification and characterization of EIDs. We explore this issue in the Western honeybee, where increasing mortality of populations in the Northern Hemisphere has caused major concern. Specifically, we investigate the importance of genetic identity of the main suspect in mortality, deformed wing virus (DWV), in driving honeybee loss. Using laboratory experiments and a systematic field survey, we demonstrate that an emerging DWV genotype (DWV-B) is more virulent than the established DWV genotype (DWV-A) and is widespread in the landscape. Furthermore, we show in a simple model that colonies infected with DWV-B collapse sooner than colonies infected with DWV-A. We also identify potential for rapid DWV evolution by revealing extensive genome-wide recombination in vivo. The emergence of DWV-B in naive honeybee populations, including via recombination with DWV-A, could be of significant ecological and economic importance. Our findings emphasize that knowledge of pathogen genetic identity and diversity is critical to understanding drivers of species decline.
Currently established and projected regulatory frameworks require the classification of materials (whether nano or non-nano) as specified by respective definitions, most of which are based on the size of the constituent particles. This brings up the question if currently available techniques for particle size determination are capable of reliably classifying materials that potentially fall under these definitions.
In this study, a wide variety of characterisation techniques, including counting, fractionating, and spectroscopic techniques, has been applied to the same set of materials under harmonised conditions.
The selected materials comprised well-defined Quality control materials (spherical, monodisperse) as well as industrial materials of complex shapes and considerable polydispersity. As a result, each technique could be evaluated with respect to the determination of the number-weighted median size. Recommendations on the most appropriate and efficient use of techniques for different types of material are given.
Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the “outer shape” of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials.
A combined analysis of EXAFS and Raman spectra is applied for the study of
InxGa1-xN alloys with 0.3<x<0.5. Alloying causes relaxation of the selection rules resulting in
Raman spectra that resemble the vibrational density of states. On the other hand, theoretical
simulation of the Raman spectra using the Equation of Motion routine of FEFF8 provides the
vibrational component of the Debye-Waller factor (DWF). The static disorder component of
the DWFs was obtained by fitting the Ga and In K-edge EXAFS spectra. The analysis revealed
that the nearest neighbor distances of the 1st and 2nd shell deviate from the values predicted by
the law of Vegard and the virtual crystal approximation. The static disorder in the first nearest
neighboring shell (In-N and Ga-N) is null whereas in the cation-cation neighboring shells the
static component is generally smaller than the vibrational.
We describe a fast and effective synthesis for molecular metal phosphonates. Isomorphic compounds [M(II)(HO₃PPh)₂(H₂O₃PPh)₂(H₂O)₂] (M = Mn (1), Co (2), Ni (3); Ph = C₆H₅) were obtained by grinding. The complexes are mononuclear compounds containing neutral and monodeprotonated phenylphosphonic acid and water as ligands. The crystal structures were determined using powder X-ray diffraction (PXRD) data and validated by extended X-ray absorption fine structure (EXAFS) data. Combined synchrotron XRD measurements and Raman spectroscopy were conducted for investigating the reactions in situ. Based on these data, the intermediates were characterized and the formation mechanism was derived.
Titanium dioxide (TiO₂) nanoparticles (NPs) are one of the main sources of the nanoparticulate matter to which humans are directly exposed and several studies have demonstrated their potential toxic effects. The in vivo detailed spatial distribution of TiO₂ NPs is investigated herein for the first time, using a 2D chemical imaging analysis based on confocal Raman spectroscopy. The invertebrate nematode C. elegans was employed as a prototypical model of living organisms. Rod, bipyramidal and quasispherical engineered TiO₂ NPs with different primary particle sizes and agglomeration states were prepared, characterized and then administered to nematodes. Exploiting the typical fingerprint of TiO₂ in the Raman spectrum, we monitored the biodistribution of NPs inside the worm using a non-invasive, label-free method. The high spatial resolution chemical imaging and the specificity of the Raman technique in the localization of TiO₂ NPs helped in the design of behavioral C. elegans studies aimed at elucidating the relationship among the size, shape, and agglomeration state of NPs and their ability to induce specific toxic effects. Rod-shaped NPs were the most toxic, greatly impairing pharyngeal function, reproduction and larval growth; this indicates that the rod shape, more than the bipyramidal and spherical shapes, enables NPs to interact with biological systems. These findings indicate that this Raman-nematode combined approach represents a step forward in the field of detection of NPs in living organisms, and being rapid and inexpensive enough, it can be applied as the first screening for the ability of NPs to biodistribute and exert toxicological properties in vivo.
Currently at Deutsche Bahn (DB) ultrasonic inspections in maintenance procedures for wheelset axles with a bore hole are, to the greatest possible extent, carried out using automated ultrasonic inspection system. Although the acceptance levels are in accordance with DIN 27201 part 7, the testing results have shown in recent years that in the case of true indications, the effective defect sizes were far below the level of acceptance. Due to this experience it can be assumed that the automated ultrasonic inspection systems are testing substantially more sensitively than required. This increased sensitivity leads to an increase in false indications, generally resulting in the unnecessary demounting of wheelsets. In Research cooperation between Federal Institute for Materials Research and Testing (BAM) and DB the effective flaw detection sensitivity of existing automated ultrasonic inspection system will be determined and the true/false indication ratio optimised. Through systematic investigations with the Probability of Detection method on the existing automated ultrasonic inspection system the results could be directly applied to the optimisation of existing ultrasonic inspections of wheelset axles with a bore hole in maintenance procedures and the level of reliability can be considerably increased.
The sliding behaviors of two simplified tribofilms with amorphous structure consisting either of SiO₂ molecules or C atoms were simulated by molecular dynamics modeling. The objective was to identify mechanisms explaining the experimentally observed lubricating properties of the two amorphous films. The impacts of layer thickness, normal pressure, temperature and different substrate materials were studied systematically, while the sliding velocity was kept constant at 30 m/s. While the layer thickness was not critical, all the other parameters showed special effects under certain conditions. Normal pressure impeded void formation and could even eliminate voids if applied at high temperature. Stick-slip sliding was changed to smooth sliding at high temperature due to void healing. Considering the carbon film, high friction forces and shearing of the entire film was observed with diamond substrates, whereas interface sliding at low friction forces and an amorphous layer of iron mixed with carbon was observed if the supporting substrates consisted of α-Fe. Both films show a decrease of friction forces and smooth sliding behavior at elevated temperature, corresponding well to the tribological behavior of and advanced nanocomposite sliding against a steel disc under severe stressing conditions when high flash temperatures can be expected.
Maintenance and renewal costs of a typical railway, track and substructure represents 50–60% of the total costs of such infrastructure over its entire service life. Innovations in track and substructure are therefore fundamental to achieve a significant
impact on the overall cost reduction for the railways. Therefore new solutions for track improvements that are effective and that can minimize the interruption of traffic are needed. Moreover, failures of railway embankments happened recently in different regions of the world. Such events, such as the one happened in UK in February 2013 (http://www.bbc.co.uk/news/uk-england-south-yorkshire-21441070), are showing the importance of monitoring track and infrastructure coupled with the use of numerical models for the localization of the critical areas and the design of appropriate countermeasures. Indeed embankment failures, landslides and uneven settlements and similar events are becoming much more common than in the past due to climate changes, and this requires the infrastructure managers to look from a different perspective infrastructure maintenance issues. What was previously consider as “extreme” is now “common” and thus actions need to be taken to be ready when such events will happen. The aim is to mitigate their effects on the infrastructure and to minimize disruptions to train services and reduce maintenance costs to restore the normal service conditions. If this mental change happens, then the need for solutions and techniques for global asset monitoring and ground stabilization will probably increase. Among the others, geotextiles and geogrids for soil reinforcement used in combination with condition monitoring techniques have the potential for minimizing catastrophic events, whilst at the same time providing a good balance among costs and benefits (i.e. sustainability).
The paper describe a case study where the use of multifunctional geotextiles, able to provide both strengthening and monitoring functions, has been tested along a railroad near the city of Chemnitz (Germany). The results are here reported to show the potential use and the innovative aspect of this solution.
The maximum magnetisation (saturation magnetisation) obtainable for iron oxide nanoparticles can be increased by doping the nanocrystals with non-magnetic elements such as zinc. Herein, we closely study how only slightly different synthesis approaches towards such doped nanoparticles strongly influence the resulting sub-nano/atomic structure. We compare two co-precipitation approaches, where we only vary the base (NaOH versus NH3), and a thermal decomposition route. These methods are the most commonly applied ones for synthesising doped iron oxide nanoparticles. The measurable magnetisation change upon zinc doping is about the same for all systems. However, the sub-nano structure, which we studied with Mössbauer and X-ray absorption near edge spectroscopy, differs tremendously. We found evidence that a much more complex picture has to be drawn regarding what happens upon Zn doping compared to what textbooks tell us about the mechanism. Our work demonstrates that it is crucial to study the obtained structures very precisely when “playing” with the atomic order in iron oxide nanocrystals.
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial colonization. Standardized tests relying on statistical evidence are indispensable to evaluate the quality and safety of these new materials. We describe here a flow chamber system for biofilm cultivation under controlled conditions with a total capacity for testing up to 32 samples in parallel. In order to quantify the surface colonization, bacterial cells were DAPI (4‘,6-diamidino-2-phenylindole)-stained and examined with epifluorescence microscopy. More than 100 images of each sample were automatically taken and the surface coverage was estimated using the free open source software g’mic, followed by a precise statistical evaluation. Overview images of all gathered pictures were generated to dissect the colonization characteristics of the selected model organism Escherichia coli W3310 on different materials (glass and implant steel). With our approach, differences in bacterial colonization on different materials can be quantified in a statistically validated manner. This reliable test procedure will support the design of improved materials for medical, industrial, and environmental (subaquatic or subaerial) applications.
With increased usage of highly demanded, modern materials on safety
relevant parts (e.g. railway wheel sets, generator shafts, turbine disks, medical
implants, etc.) comprehensive analyses regarding the quality of the material are
requested. This gives a focus to non-destructive methods using ultrasound immersion
tank testing for classifying the degree of purity. Two autonomous standards,
ASTM E588 and SEP 1927, have been established for the definition, execution and
evaluation for this high resolution ultrasonic measurements on steel products.
The propagation of ultrasonic waves and the resulting sound field are strongly
dependent on the acoustical properties of the inspected material and the geometry
of probes and specimen. The definition of the measurement setup and the evaluation
methods appear to differ significantly in the given standards. ASTM E588 and
SEP 1927 prescribe the requirement for surface roughness and probe selection, are
using threshold based methods for cleanliness detection, but differ in computation
for the degree of purity. This has been the motivation for a comparison between
both standards with the main focus on amplitude depth dependency and overall spatial
resolution taking the influence of different material characteristics, geometry of
the specimen and sound fields into account.
A performance comparison between the use of non-focusing and focusing probes
respective to the threshold based detection will be presented in this contribution. In
addition, the usage of complex reconstruction algorithms (e.g. SAFT, echo tomography)
is compared with the traditional approaches of inclusion detection and
estimation of the degree of purity
Grating interferometric set-ups have been established in the last decade. They are promising candidates to obtain enhanced image contrast from weakly absorbing micro and nano structures. They are based on X-ray refraction and near-field diffraction using the Talbot effect.
At the expense of taking multiple images, Talbot-Lau grating interferometry allows separating the absorption, refraction, and scattering contributions by analysing the disturbances of a phase grating interference pattern. Contrary to other refraction enhanced methods, this technique can be applied using conventional X-ray tubes (divergent, polychromatic source). This makes it attractive to solve typical non-destructive testing problems.
We investigated the efficiency of phase gratings, i.e. the visibility (the amplitude of oscillations) upon variation of propagation distance and phase grating rotation around an axis parallel to the grid lines. This grating rotation changes the grating shape (i.e. the distributions of phase shifts). This can yield higher visibilities than derived from rectangular shapes.
Our study includes experimental results obtained from synchrotron radiation, as well as simulations for monochromatic radiation. The advantages of Talbot-Lau interferometry are demonstrated at the example of glass capillaries.
A high-performance fiber Bragg grating-based (FBG) sensor device has been developed for the detection of small magnetic fields. Based on a smart multilayer jacket around the fibre over the physical length of the FBG, magnetic fields generated by rotating machine parts, power generators or power cable can be easily detected, analysed and evaluated. Consequently, this innovative, on-line and non-contact inspection method results in an increase in quality and reliability of high-performing machine parts, devices and cables. The basic physical principle is based on a magnetostrictive multilayer system that strains the high-resolution FBG element in presence of magnetic fields. Subsequently, a fixed relationship between induced magnetic field and wavelength change of the FBG element describes the characteristic sensitivity curve. Intensive tests regarding characterisation of this magnetic field FBG sensor have been carried out and its performance has been evaluated.
Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-up rate for changing wall thicknesses over the manufacturing process. Spot diameter, powder feed rate, welding velocity and laser power were changed as main parameters for a different track size. An optimal overlap rate for a constant layer height was used to calculate the best track size for a fitting layer width similar to the part dimension. Deviations in width and height over the whole build-up process were detected and customized build-up strategies for the 3D sequences were designed. The results show the possibility of a near net shape repair by using different track geometries with laser metal deposition.
Mechanochemical reactions often result in 100% yields of single products, making purifying procedures obsolete. Mechanochemistry is also a sustainable and eco-friendly method. The ever increasing interest in this method is contrasted by a lack in mechanistic understanding of the mechanochemical reactivity and selectivity. Recent in situ investigations provided direct insight into formation pathways. However, the currently available theories do not predict temperature T as an influential factor. Here, we report the first determination of an apparent activation energy for a mechanochemical reaction. In a temperaturedependent in situ study the cocrystallisation of ibuprofen and nicotinamide was investigated as a model system. These experiments provide a pivotal step towards a comprehensive understanding of milling reaction mechanisms.
High-power laser beam welding became new stimuli within the last 10 years due to the availability of a new generation of high brightness multi kilowatt solid state lasers. In the welding research new approaches have been developed to establish reliable and praxis oriented welding processes meeting the demands of modern industrial applications during this time. The paper focuses on some of the current scientific and technological aspects in this research field like hybrid laser arc welding, simulation techniques, utilization of electromagnetic fields or reduced pressure environment for laser beam welding processes, which contributed to the further development of this technology or will play a crucial role in its further industrial implementation.
Since decades the evaluation of flaw indications on radiographs from welds or castings are based on well accepted reference film catalogues from organizations like IIW (weldments), ASTM (castings) or DGZfP (D5 recommendation on heavy steel castings). Today, the transformation of classical film radiography to the digital world is in full progress. Some ASTM standards do not permit the evaluation of digital radiographs in reference to film catalogues. Therefore, these reference film catalogues have to be converted into the digital age too. BAM is supporting this transition by high definition film scanning. The result is a corresponding reference image catalogue. The different standard organizations selected different ways to distribute the digital data. ASTM used high definition film scanning at 10 μm pixel size and distribution of a huge amount of high-res data via DVD. The user sub-samples these high-res data during catalogue import to the resolution of his system. The comparison is done by synchronized image viewing on the computer work station. IIW recently decided to distribute their ISO 5817 reference images installed on tablets, which are used for image viewing too. The tablet image has to be compared with the digital image on the system monitor. DGZfP transformed their D5 reference radiographs into a PDF for monitor viewing. This is the simplest and cheapest solution, but still allows the full usage of the catalogue in the digital era. The status of ongoing work in progress will be discussed.
Analyzing the reliability of non-destructive tests using the modular modell - a practical approach
(2016)
Non-destructive testing is an important tool to guarantee the safety of railway traffic.
The infrastructure with tracks, switches and sleepers is regularly tested, the
locomotives and wagons with their wheels, bogies and axles as well. Many years of experience and some events lead in Germany to a good practice in testing the railway components. Now, European authorities are drafting a system of common requirements and standards for the European Railway Market. The German practice combines an intensive training of the NDT-personnel including sufficient time for practical exercises with organizational measures of the companies, responsible for rolling stock and infrastructure. Through the example of UT-testing of railway axles it will be shown, how training and organizational measures influence the reliability of such testing.