Wissenschaftliche Artikel der BAM
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We report on calibration standards of nanoparticles meeting the definition of a nanomaterial given by the European Commission (EU 2011) which are relevant for the characterisation methods applied in the NanoDefine project. We found that the Impact of nanoparticles is outstanding in the scientific literature. A number of 270.000 paper titles on nanoparticles are listed in the Web of Science data base. But surprisingly, the availability of suitable certified standard reference materials is scarce. Only a few sources were found. For example, BAM provides the database Nanoscaled Reference Materials at http://www.nano-refmat.bam.de/en/ in cooperation with the ISO/TC 229 Nanotechnologies. In addition, two publications from 2013 on nanoscale reference materials are available. Candidates of nano-(certified) reference materials from other ongoing or just finished FP6 and FP7 nano-metrology projects have been extracted from the Compendium of Projects in the European NanoSafety Cluster (Compendium NSC, 2013). Recommendations for selection of representative test materials and calibration standards for NanoDefine internal tasks, respectively, are also given.
The EU FP7 NanoDefine project was launched in November 2013 and will run until October 2017. The Project is dedicated to support the implementation of the EU Recommendation on the Definition of Nanomaterial
by the provision of the required analytical tools and respective guidance. Main goal is to develop a novel
tiered approach consisting of (i) rapid and cost-efficient screening methods and (ii) confirmatory measurement
methods. The "NanoDefiner" eTool will guide potential end-users, such as concerned industries and regulatory bodies as well as enforcement and contract laboratories, to reliably classify if a material is nano or not. To achieve this objective, a comprehensive inter-laboratory evaluation of the performance of current
characterisation techniques, instruments and software is performed. Instruments, software and methods are
further developed. Their capacity to reliably measure the size of particulates in the size range 1-100 nm and
above (according to the EU definition) is validated. Technical reports on project results are published to
reach out to relevant stakeholders, such as policy makers, regulators, industries and the wider scientific community, to present and discuss our goals and results, to ensure a continuous exchange of views,
needs and experiences obtained from different fields of expertise and application, and to finally integrate the resulting feedback into our ongoing work on the size-related classification of nanomaterials.
Industrial production of the cell protectant ectoine: protection mechanisms, processes, and products
(2014)
Bacteria, Archaea and Eukarya can adapt to Saline environments by accumulating compatible solutes in order to maintain an osmotic equilibrium. Compatible solutes are of diverse chemical structure (sugars, polyols, amino acid derivatives) and are beneficial for bacterial cells not only as osmoregulatory solutes, but also as protectants of proteins by mitigating detrimental effects of freezing, drying and high temperatures. The aspartate derivative ectoine is a wide spread compatible solute in Bacteria and possesses additional protective properties compared with other compatible solutes, and stabilizes even whole cells against stresses such as UV radiation or cytotoxins. The protective properties of ectoine for proteins can be explained by its strong (kosmotropic) interaction with water and subsequent exclusion from Protein surface, the decrease of the solubility of the peptide backbone and the strengthening of intramolecular hydrogen bonds (secondary structures). The stabilizing and UV-protective properties of ectoine attracted industry, which saw the potential to market ectoine as a novel active component in health care products and cosmetics. In joint efforts of industry and research large-scale fermentation procedures have been developed with the halophilic bacterium Halomonas elongata used as a producer strain. The two key technologies that allow for the annual production of ectoine on a scale of tons are the bacterial milking procedure and the development and application of ectoine-excreting mutants (“leaky” mutant). The details of these two procedures including the strain development and Fermentation processes will be introduced and current and future applications of ectoine will be discussed.
This survey will discuss current and emerging isothermal and rapid polymerase chain reaction (PCR) based nucleic acid amplification methods for patient near diagnostics. To assess the clinical need of rapid diagnostics for infectious diseases based on nucleic acid tests (NATs) we performed and analysed a questionnaire among laboratories participating in corresponding INSTAND ring trials for external quality assurance. The questions concerning new amplification technologies like isothermal nucleic acid amplification, potentially suited to significantly decrease turnaround times, were complemented by questions to evaluate the present status of NATs. Besides end-users, companies were also addressed by sending out a manufacturer specific questionnaire. Analysis of the answers from 48 laboratories in 14 European countries revealed that a much shorter turnaround time is requested for selected pathogens compared to about 2 h or longer when applying temperature cycling amplification, i.e. PCR. In this context, most frequently mentioned were MRSA, norovirus, influenza A and B viruses, cytomegalovirus (CMV) as well as hepatitis B virus (HBV) and hepatitis C virus (HCV). At present, 8% of the laboratories having participated in this survey apply isothermal amplification of nucleic acid to identify infectious pathogens.
Starch is one of the most common and easily obtained natural polymers, making it attractive as a potential bio-based alternative to synthetic polymers. This study shows that a simple quaternary ammonium salt combined with urea or glycols forms effective modifiers that produce flexible plastics with good mechanical properties that are comparable to some polyolefin plastics. The processing conditions are shown to significantly affect the structure of the polymer which has a concomitant effect upon the mechanical and physical properties of the resulting plastic. Using a glycerol based modifier results in a totally sustainable and biodegradable material which can be injection moulded.
Die Ortung von schlaffer Bewehrung in Beton erfolgt routinemäßig mit bildgebenden Radar- oder Wirbelstromverfahren. Die Anwendung dieser Verfahren ist aber begrenzt, wenn es sich um die Ortung tiefliegender Bewehrung (ab ca. 30 cm) oder um jungen Beton handelt. Grund ist die Schwächung der Radarpulse durch oberflächennahe Bewehrung oder durch die Betonfeuchte. Das bildgebende Ultraschallechoverfahren bietet den Vorteil, dass die Ultraschallpulse in diesen Fällen eine wesentlich höhere Eindringtiefe erreichen.
Im vorliegenden Beitrag wird eine Fallstudie vorgestellt, bei der mehrlagig eingebrachte Bewehrungseisen in einer nur einseitig zugänglichen 60 cm dicken Betonplatte geortet werden sollten, um eine Kernbohrung ohne Verkanten der Bohrkrone durchzuführen.
Zur Ortung der Bewehrung wurde das Ultraschallechoverfahren mitScherwellen der Mittenfrequenz 50 kHz mit einem automatisch arbeitenden Bauwerksscanner eingesetzt. Aus den flächig aufgenommenen Messdaten wurde mit der Rekonstruktionsrechnung nach dem Prinzip der synthetischen Apertur (SAFT, Synthetic Aperture Focusing Technique) die Position der Bewehrungseisen bildhaft ortsgenau dargestellt. Dies gelingt mit einer Auswertungsoption, bei der die Phase der reflektierten Ultraschallpulse ermittelt und farbcodiert dargestellt wird (Phasenauswertung). Damit lassen sich Reflexionen der Bewehrung eindeutig von eventuellen Fehlstellen oder Rückwandechos unterscheiden.
Klebverbindungen im modernen Hochbau können helfen, innovative ästhetische Bedürfnisse im Fassadenbau umzusetzen, technologische Verbesserungen zu erreichen, aber auch die Wechselwirkung von Gebäuden mit der Umwelt unter energetischen Aspekten zu optimieren. Aufgrund der hohen sicherheitstechnischen Bedeutung gibt es hohe Anforderungen an die Leistungsfähigkeit, Dauerhaftigkeit und die Gütesicherheit.
Mit einer zerstörungsfreien praxistauglichen Prüftechnik, die eine sichere Überprüfung der Integrität von Glas-Metall Klebverbindungen im Ingenieurhochbau gewährleistet, kann sowohl ein wichtiger Beitrag zur Qualitätssicherung bei der Herstellung von Fassadenelementen aber auch bei der späteren Bauwerksüberwachung im Verlauf der Nutzungsdauer geleistet werden. Für eine Beurteilung der Qualität der Verbundfuge (z.B. bezgl. Standsicherheit) sind dabei Aussagen zur Homogenität der Verbundfuge, zum adhäsiven und kohäsiven Verbundverhalten gefordert. Hierzu besteht aktuell insbesondere Bedarf an zerstörungsfreien praxisgerechten, hoch ortsauflösenden und möglichst bildgebenden Untersuchungsverfahren.
Es wird mit einem Matrixarray und mit konventionellen Winkelprüfköpfen eine Prüftechnik vorgestellt, mit der die Wechselwirkung zwischen Ultraschallwelle und Fehlstelle in der Klebefuge untersucht wird. Hierbei ist das erste Untersuchungsziel, mit einer angepassten Ultraschall-Prüftechnik mögliche Inhomogenitäten oder Schädigungsstellen in der geklebten Glas-Metall Verbindung zu detektieren.
Über diese qualitativen Aussagen hinaus werden weiterführende Informationen über die flächenhafte Ausdehnung und den Ort einer mangelnden Klebung ermittelt. Dazu werden die Messwerte zusammen mit den Positionen des Ultraschallprüfkopfs aufgezeichnet. Mit Hilfe einer bildhaften Auswertung der gemessenen Ultraschallechos in Abhängigkeit vom Prüfkopfort werden die Möglichkeiten einer detaillierten Integritätsanalyse der Glas-Metall Klebschicht dargestellt. In diesem Beitrag werden experimentelle Prüfergebnisse vorgestellt, die im Sinne einer Verfahrensvalidierung an einem speziellen Beispielprobekörper zur Nachstellung einer SSG-Verglasung (ermittelt wurden und die Detektion fehlerhafter Klebestellen in einer Glas-Metall-Klebverbindung zum Ziel haben.
The objective of the report is to present the state-of-the art of non-destructive testing methods and technologies for the inspection of thick, heavily-reinforced structures, (e.g. found in nuclear power plants). Wall thicknesses can be in excess of one meter and the structures often have increased steel reinforcement density. The accessibility for any testing method may be limited due to the presence of liners and other components such as cast-in-place items. Testing methods have to provide solutions for tasks such as locating failure (inclusions, corrosion, voids, delaminations) in the structures or the assessment of the condition of the structure in general.
Measurement of spontaneous magnetic stray field signals has been reported to be a promising tool for capturing macro-scale information of deformation states, defects and stress concentration zones in a material structure. This paper offers a new method for self-magnetic leakage field detection using a magneto-optical (MO) hand-held microscope. Its sensor has a dynamic field range between ±0.05 and ±2 kA/m and a lateral optical resolution of approx. 10 µm. We examined flat tensile test specimens of metastable austenitic steel AISI 304. Static tensile tests were repeatedly interrupted at various predetermined states of strain and the magnetic information was measured by the MO system. Comparative measurements using a high-precision magnetic field GMR-sensor, verify the outstanding capability of the MO microscope regarding spatial resolution of magnetic fields.
Ergopeptides, like ergocornine and a-ergocryptine, exist in an S- and in an R-configuration. Kinetic experiments imply that certain configurations are preferred depending on the solvent. The experimental methods are explained in this article. Furthermore, computational methods are used to understand this configurational preference. Standard quantum chemical methods can predict the favored configurations by using minimum energy calculations on the potential energy landscape. However, the explicit role of the solvent is not revealed by this type of methods. In order to better understand its influence, classical mechanical molecular simulations are applied. It appears from our research that 'folding' the ergopeptide molecules into an intermediate state (between the S- and the R-configuration) is mechanically hindered for the preferred configurations.
Slicing - a new method for non destructive 3D elemental sensitive characterization of materials
(2014)
Recent advances in synchrotron sources and detector technology have led to substantial improvements in spatial resolution and detection limits for X-ray fluorescence analysis (XRF). However, the non-destructive three-dimensional elemental sensitive characterization of samples remains a challenge. We demonstrate the use of the so-called 'Color X-ray Camera' (CXC) for 3D measurements for the first time. The excitation of the sample is realized with a thin sheet-beam. The stepwise movement of the sample allows getting the elemental distribution for each layer with one measurement. These layers can be combined to a full 3D dataset for each element afterwards. Since the information is collected layer by layer, there is no need to apply reconstruction techniques, which quite often are the reason for artifacts in the results achieved by computed tomography (CT). The field of applications is wide, as the 3D elemental distribution of a material contains clues to processes inside the samples from a variety of origins. The technique is of special interest and well suited for biological specimens, because their light matrix minimizes restricting absorption effects. Measurement examples of a hornet and the teeth of a Sorex araneus are shown.
In this work an air-based sensor network for the localization of persons at extensive areas is presented. The developed network consists of a localization device which the person is wearing (BodyGuard-System), a mobile relay station in the air, and a base station. All three parts communicate with the same radio chip. The BodyGuard-System is an inertial navigation system which was developed for localization in difficult environments with high accuracy and low measurement uncertainty. To increase the range of the system, a multi-hop network was built up. The measured data of the BodyGuard-System and the mobile relay station is visualized on a PC in the base station. This multi-hop network is necessary for example for fire department missions.
Bei der Abschätzung der Beständigkeit von Kunststoffen gegenüber niedermolekularen Flüssigkeiten ist die Kohäsionsenergiedichte CED ein wichtiger Parameter auf molekularer Ebene. Die Vernetzungsdichte ν eines polymeren Festkörpers bildet hierbei einen bedeutsamen Kennwert, der darüber hinaus neben der Löslichkeit wichtige Eigenschaften wie thermische Stabilität und Steifigkeit des Materials charakterisiert. Für die experimentelle Bestimmung von CED und ν eignet sich die Untersuchung des Quellverhaltens in unterschiedlichen Lösungsmitteln. Es werden zwei Messmethoden miteinander verglichen und die Ergebnisse unter Berücksichtigung des molekularen Aufbaus von Proben aus Polyurethan (PU) und hochmolekularem – (HMWPE) und ultrahochmolekularem Polyethylen (UHMWPE) diskutiert. Zum Verständnis des Quellverhaltens dieser Polymerproben in niedermolekularen Lösungsmitteln werden neben den Messergebnissen Literaturdaten zu Grunde gelegt.
Quantitative determination of acidic surface sites is highly important for the characterization of solid acids because the activity of a catalyst is often related to the concentration of these sites. A recently developed method using 15N Nuclear Magnetic Resonance spectroscopy (NMR) for the quantification of acidic Lewis and Brønsted sites has been tested for a series of nanoscopic aluminum hydroxide fluorides. Comparison with other methods for the quantitative determination of acidic sites shows that this 15N NMR quantification method is a promising technique for the comprehensive investigation of acidic sites. Three different acidic sites, one Brønsted and two Lewis sites, can be distinguished by their 15N chemical shifts of pyridine and simultaneously quantified under conditions corresponding to catalytic reaction conditions. Determination of the individual concentrations of acidic sites allows further insight into the catalytic process. It was found that the concentration of Brønsted sites correlates with catalyzed conversion of citronellal to isopulegol in the investigated series of catalysts. Additionally, investigations indicate that one of the Lewis sites become blocked during the reaction of citronellal.
The digital photography has almost completely substituted the film photography. The film replacement is also fast progressing in medical X-ray radiography. This process is slower in NDT and especially in Europe. Reasons for the hesitating change to digital radiography (RT-D) in NDT are the necessary time for adoption of standards and the conservative request for film RT by auditors and NDT managers for applications in large plants and at construction areas. The fast serial inspection for small castings is already almost completely dominated by RT-D due to the cost effective short exposure and interpretation times. Standards were developed in parallel at CEN, ISO, ASTM and ASME. Unfortunately, the standard practices are different and the requirements on image quality and useable hardware are different too. The first standard series on Computed Radiography were developed and published by CEN and ASTM in 2005. Harmonized classification and qualification standards are available but the published practices are different. ASTM has developed the first standards for application of Digital Detector Arrays (DDA) in 2010. The first digital RT ISO standard practice is ISO 17636-2 (2013), which describes the practice for application of DDAs and Imaging Plates for weld inspection. At the first time this standard provides requirements for the selection of suitable hardware. Minimum image quality requirements are specified in analogy to film radiography and 3 Compensation Principles are defined to enable the application of a wider range of digital detectors. A comparison of the different international digital RT standards is given and first experiences with ISO 17636-2 are discussed. New standards on RT wall thickness and corrosion measurements (EN 16407, film and digital) have been developed recently.
A comparative study on the performance of digital detector systems for high energy applications
(2014)
For cast components reaching or exceeding total material thicknesses of 150mm, high energy sources such as linear accelerators or Betatrons are required in order to obtain reasonable exposure times. In this study, the performance of digital detector systems, involving imaging plates (IP) and digital detector arrays (DDA), was evaluated with respect to the testing class B requirements as formulated in the standard EN ISO 17636-2. As a reference, traditional radiographic film and a Cobalt-60 source was used. With film exposures, testing class B was achieved with Co-60 and Betatron (7.5 MV) at longer exposure times. The preliminary results show that the testing class B was not obtained with the examined digital detector arrays (DDA) and the high resolution imaging plates (IP) , even at 40, 60 and 80 minutes exposure time with a 7.5 MV Betatron. Class A was achieved using high resolution imaging plates with optimized metal filters between object and IPs and a high resolution DDA with intermediate Cu filters. Class A was also achieved applying a DDA with lower basic spatial resolution than required by Table B.13 of EN ISO 17636-2, but using the compensation principle as described in this standard. The next generation of digital detector arrays might potentially be able to obtain class B performance with the expected spatial resolution and sensitivity improvements.
The progress in X-ray detector electronics (sensitivity and speed) allows meanwhile fast single photon detection by a matrix detector. Combined photon counting and energy discrimination is implemented in the electronic circuit of each detector pixel. The company XCounter developed detectors based on CdTe single crystals, which can be tiled to larger areas and have a pixel size of 100ìm. The largest area available in beginning of 2014 is 50x75 mm². These detectors have very promising properties, which make them very suitable for NDT applications:
1. A CdTe attenuation layer of 750 µm thickness allows efficient X-ray detection up to ca. 300 keV. In counting mode only photon noise is important; no other detector noise sources need to be considered. There is no Offset signal without radiation.
2. Each of the detector pixels has two energy thresholds. These can be used for dual energy imaging for materials separation. Also the suppression of scattered radiation by energy thresholding will improve the image contrast sensitivity. First experiments will be presented which demonstrate the advantages of this new detector technology over the conventional charge integrating detectors.
A challenge is the development of a modified detector calibration procedure, which becomes critical at longer exposure times.
Using ultrafast X-ray diffraction, we study the coherent picosecond lattice dynamics of photoexcited thin films in the two limiting cases, where the photoinduced stress profile decays on a length scale larger and smaller than the film thickness. We solve a unifying analytical model of the strain propagation for acoustic impedance-matched opaque films on a semi-infinite transparent substrate, showing that the lattice dynamics essentially depend on two parameters: One for the spatial profile and one for the amplitude of the strain. We illustrate the results by comparison with high-quality ultrafast X-ray diffraction data of SrRuO3 films on SrTiO3 substrates.
Innovative X-ray backscatter technique for security applications: Detection of dangerous materials
(2014)
Radiological inspections, in general, are NDT&E methods to detect the bulk of explosives without invasion into the object of analysis. In contrast to personal luggage, cargo or structural components constitute a complexity that may significantly hamper the detection of a threat by conventional transmission radiography. A novel approach of interrogating a large object to a certain depth only with a single sided access will be presented. It consists of an X-ray backscatter camera with a special twisted slit collimator for imaging backscattered objects. The new X-ray backscatter camera is not only imaging the objects due to their densities but also by taking into account the influences of surrounding objects. Additionally, it does not only image illuminated features but also depicts shadows from absorbing materials. This is a unique characteristic of the developed X-ray backscatter camera. Experimental mock-ups are conducted imitating container with threats among a complex packing as they may be encountered in reality. At the end, the significant advantages of the presented X-ray backscatter camera in the context of aviation and port security will be discussed.
In this contribution, we present a dual high-energy X-ray imaging technique for cargo container inspection using the 'spectral high-energy X-ray attenuation method'. This method is based on attenuation of continuous highenergy spectra. The developed experimental technique consists of a betatron as high-energy (up to 7.5 MeV) X-ray source and a matrix detector with high spatial resolution (400 ìm) for digital X-ray imaging. In order to evaluate the material discrimination capability using dual high-energy X-ray imaging, a test specimen is proposed, comprising step wedges of different low and high atomic number (Z) materials. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the betatron. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the 'analytical Radiographic Testing inspection simulation tool' (aRTist) developed at BAM. The simulated effective attenuation coefficients are compared with corresponding experimental results in order to establish a method for identification of low- and high-Z materials in the container. Finally, important applications of the proposed technique in the context of aviation security are discussed.