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Eingeladener Vortrag
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One of the important analytical challenges is the fast and reliable trace detection of explosives in the context of security issues, ammunition disposal, and environmental pollution. Antibodies (Ab) are a promising tool for this purpose and the combination with a
surface acoustic wave (SAW) sensor opens the opportunity of highly selective and fast, label-free detection. A robust and sensitive method for the detection of the explosive trinitrotoluene (TNT) was developed. The detection limit was determined to be around 0.5 μg/L. The fast signal response of less than 1 minute shows that this approach is suitable for security and other time-critical applications. In addition, the very low crossreactivity highly reduces the number of false-positives in relation to competing techniques, including sniffer dogs. Due to the multianalyte ability of the SAW system, several explosives might be detected in parallel. Terminal amino groups were functionalized with trinitrophenyl (TNP) groups by reaction with trinitrobenzene sulfonic acid (TNBS). In less than 1 minute, a good signal response was obtained. 50 μL of sample was used. No non-specific interaction with the SAM surface was observed. A complete measuring cycle needed 19 minutes including a surface regeneration step with 50 μL of acetonitrile/water/propionic acid (50:50:1) and 150 μL of SDS solution (0.1 %, pH 1 with 100 mM glycine and 100 mM NaCl). A good long-term stability could be shown for at least 6 hours. Two polyclonal antibodies (R1, R2, affinity purified with Protein A) and a monoclonal antibody (A1.1.1) were tested successfully. A commercially available SAW sensor (sam5 blue, SAW Instruments) was used for liquid handling and detection. Self-assembled monolayers (SAM) of alkanethiol derivatives were
prepared on gold surfaces leading to non-fouling and hydrophilic properties, due to attached polyethylene glycol (PEG) residues. A continuous flow of buffer (phosphate-buffered saline, PBS plus Tween 20) of 100 μL/min was applied to the sensor system. TNT antibodies were pre-incubated with the samples containing traces of explosives. Polyclonal and monoclonal antibodies were tested.
The limit of detection (LOD) was determined to 0.5 μg/L for all three antibodies (3s from 12 replicates).
Nuclear Power Plants have been in operation for ca. 50 years. Based on this experience, non-destructive testing tasks specific to thick and highly reinforced nuclear containment structures have materialized. The performance based Service life extension of existing NPPs also needs a measurement based decision to support continuing the service of the concrete part of the installations.
By nature, concrete is a very durable material and any natural Deterioration processes may take a long time to become critical to the structure. The experience of more than 50 years of service limits the testing tasks to a few ones which are not yet solved.
Research in NDT of concrete structures is performed by many research institutions all over the world with different technical and systematic approaches. Results are mainly obtained on laboratory specimens, sometimes additional field studies are reported. This research takes place independently without coordination and as a result, the outcomes mostly lack full comparability.
Software for data analysis has become indispensable and very powerful. This part of testing needs more attention when it comes to evaluate test results. Validation of NDE solutions is becoming a critical part in concrete structure testing.
Validation is by definition the proof that a customer´s requirements in the test are being met by the testing solution. This includes equipment, personnel qualification and data analysis. In the following tables, the research recommendation Validation is used in the sense, that proof of the performance of existing solutions needs to be adressed. In general, a validation methodology for NDE solutions for concrete testing in itself needs to be researched and established.
Comparability of research also needs an accepted and easily accessible reference. From experience, it is almost impossible to manufacture exact copies of test specimens at different locations. Round Robin tests are therefore needed to evaluate the performance of a test.
Data evaluation is generally done using dedicated software, sometimes Hardware dependant and not interchangeable between systems. Software is ever more increasingly becoming more powerful and sophisticated. An in-depth evaluation needs to address the comparability and validation of Software used for data analysis and evaluation. The vision of a unified software pool for NDE investigations would undoubtedly support research tremendously.
Quantitative NDE is mostly recommended to assess the condition of a structure. However, qualitative data can be very useful, especially for processes which change the material properties or deteriorate the structure (e.g. corrosion of reinforcement). The need for reliable baseline data is a key factor for such monitoring tasks.
Experiments in this study reveal that the initiating capability of commonly used squibs is not high enough to initiate PETN in all cases. The fulfilment of the ‘new’ essential safety requirement 4 as set out in the European directive 2013/29/EU and the categorization of squibs as theatrical pyrotechnic articles (T2) can therefore be justified, as the explosive investigated belongs to quite a sensitive type (Initiation with low impulse energies possible). Underwater initiating capability tests according to EN 13763-15 led to meaningful results, showing that squibs are usually unable to initiate a secondary explosive. For a general assessment of the initiating capability of squibs and comparable (theatrical) pyrotechnic articles a threshold range of an equivalent initiation capability in grams of PETN on the basis of the performed underwater initiating capability tests was determined. It was found that squibs are generally not capable of initiating secondary explosives if the underwater initiating capability test showed an equivalent Initiation capability below 0.25 g PETN. As a consequence of this result, the underwater initiating capability test gives an effective and safer alternative to the experimental confirmation of the ‘new’ ESR 4 by direct contact of the article with the secondary explosive and should then be preferred to it.
The potentialities of a thin layer of steel-fiber reinforced self-compacting concrete (SFRSCC) for the flexural strengthening of handmade brick structural elements are investigated. For this purpose, an experimental program was carried out covering the relevant phenomena that can influence the effectiveness of this technique. The SFRSCC has a post-cracking residual tensile strength capable of improving the flexural stiffness, flexural resistance and ductility of prototypes representatives of ancient handmade brick based structures that fail in bending. To appraise the flexural strengthening effectiveness of this technique, straight beams composed of handmade bricks, low-strength mortar (LSM) and SFRSCC were tested. The obtained results have shown that this technique can increase significantly the flexural stiffness and resistance, and the ductility performance of this type of structures. The strengthening effectiveness depends on the post-cracking residual strength of the SFRSCC, its layer thickness and on the possibility of replacing part of the LSM by SFRSCC. Based on the experimental results for the characterization of the intervening materials, and adopting a cross section layer model capable of predicting the moment-curvature relationship for the distinct types of cross sections of this structural system, the maximum load registered in the tested prototypes was predicted with good accuracy.
SMP Tagnologies
(2013)
Automated MFL inspection
(2013)
The materials making up wind power plants or railways undergo high stresses. Greatly stressed components of technical systems must be inspected regularly, as production or material defects can lead to high costs. In a joint project with several partners, scientists at BAM recently developed new sensors - GMR sensors - enabling automation of MFL inspections (Magnetic flux leakage, MFL).
Mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes are capable of mechanical motion on the nanoscale and are therefore promising prototypes for molecular machines in recent nanotechnology. However, most of the existing examples are isotropically distributed in solution, which prohibits concerted movement and with it the generation of macroscopic effects. Thus, arranging them in ordered arrays is of huge interest in recent research. We report the deposition of quite densely packed multilayers of tetralactam macrocycles on gold surfaces by metal-coordinated layer-by-layer self-assembly. Linear dichroism effects in angle-resolved NEXAFS spectra indicate a preferential orientation of the macrocycles. The sequence of the metal ions can be programmed by the use of different transition metal ions at each deposition step. Additionally, reversible on-surface pseudorotaxane formation was successfully realized by repeated uptake and release of axle molecules inside the macrocycles cavities.
Ultrasonic vibration enhanced friction stir welding (UVeFSW) is a recent modification of conventional friction stir welding (FSW), which transmits ultrasonic vibration directly into the localized area of the workpiece near and ahead of the rotating tool. In this study, a high strength aluminium alloy (2024-T4) was welded by this process and conventional FSW, respectively. Then tensile tests, microhardness tests and fracture surface analysis were performed successively on the welding samples. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints. The microhardness of the stir zone also increases.
The study of protein corona formation on nanoparticles (NPs) represents an actual main issue in colloidal, biomedical and toxicological sciences. However, little is known about the influence of polymer shells on the formation and time evolution of protein corona onto functionalized NPs. Therefore, silicapoly(ethylene glycol) core–shell nanohybrids (SNPs@PEG) with different polymer molecular weights (MW) were synthesized and exhaustively characterized. Bovine serum albumin (BSA) at different concentrations (0.1–6 wt%) was used as model protein to study protein corona formation and time evolution. For pristine SNPs and SNPs@PEG (MW = 350 g/mol), zeta potential at different incubation times show a dynamical evolution of the nanoparticle–protein corona. Oppositely, for SNPs@PEG with MW ≥2000 g/mol a significant suppression of corona formation and time evolution was observed.
Furthermore, AFM investigations suggest a different orientation (side-chain or perpendicular) and Penetration depth of BSA toward PEGylated surfaces depending on the polymer length which may explain differences in protein corona evolution.
Applications of X-ray refraction to non-destructive characterization of ceramics and composites
(2013)
X-ray refraction is analogous to visible light deflection by matter, with two main differences: 1- convex objects cause divergence (i.e., the refraction index n is smaller than 1), and 2- deflection angles are very small, from a few seconds to a few minutes of arc (i.e., n is near to 1). Trivially but importantly, deflection of X-rays is also sensitive to the orientation of the object boundaries. These features make X-ray refraction techniques extremely suitable to a) detect defects such as pores and microcracks, and quantify their densities in bulk (light) materials, and b) evaluate porosity and particle properties such as orientation, size, and spatial distribution (by mapping). While X-ray refraction techniques cannot in general image single defects, their detectability is simply limited by the wavelength of the radiation.
We will thereby show the application of X-ray refraction 2D mapping (topography) and tomography to different sorts of problems in ceramic science and technology: 1) Sintering of SiC green bodies; 2) Porosity analysis in diesel particulate filter silicates; 3) fiber de-bonding in metal and polymer matrix composites; 4) micro-cracking of glass-precursor -eucryptite. We will see that the use of X-ray refraction analysis yields quantitative results, also directly usable in available models.