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Organisationseinheit der BAM
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- 1.2 Biophotonik (1)
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Poly(butadiene)-b-poly(ethylene oxide) vesicles were successfully loaded with hydrophilic dye Phloxine B. Dye addition during vesicle formation leads to Phloxine B encapsulated inside the water filled vesicle core as well as to freely diffusing dye molecules. The removal of uncapsulated substrate involves time consuming methods like dialysis or harsher methods like ultra filtration or selective precipitation, posing the risk of irreversible sample manipulation. Here used Phloxine B as pH sensitive fluorescence indicator allows the characterization of hydrophilic loading without separation procedure by adjusting the pH value. Additionally membrane blocking efficiency can be studied by time dependent fluorescence measurements. Cryogenic TEM studies showed that the self-assembled structure remained unchanged when the hydrophilic dye was incorporated within the vesicles. Fluorescence microscopy imaging proved the encapsulation of the hydrophilic dye inside the core volume. The combination of fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS) measurements as ensemble methods confirmed those results additionally.
While structural ceramics usually display a brittle mechanical behavior, their composites may show nonlinearities, mostly due to microcracking. Herein, the stiffness evolution of a sandwich-like laminate of an Al2O3 15%vol. ZrO2 matrix reinforced with Nextel 610 fibers is studied as a function of number of cycles N in tension. The stiffness of the composite degrades with increasing N, indicating microcracking. However, synchrotron X-ray refraction radiography shows that the internal specific surface of such cracks varies differently. A modeling strategy is developed for the calculation of the equivalent stiffness of mixtures (first the matrix and then the sandwich), based on the Voigt and Reuß schemes. The Bruno–Kachanov model is then used to estimate the initial microcrack density in the matrix (due to the thermal expansion mismatch) and the amount of microcracking increase upon cyclic loading. The stiffness in the composite degrades dramatically already after 20 000 cycles but then remains nearly constant. The combination of mechanical testing, quantitative imaging analysis, and modeling provides insights into the damage mechanisms acting: microcrack propagation is more active than microcrack initiation upon cyclic loading, but the second also occurs. This scenario is similar but not equal to previous results on porous and microcracked ceramics.
Superficial white matter (SWM) contains the most cortico-cortical white matter connections in the human brain encompassing the short U-shaped association fibers. Despite its importance for brain connectivity, very little is known about SWM in humans, mainly due to the lack of noninvasive imaging methods. Here, we lay the groundwork for systematic in vivo SWM mapping using ultrahigh resolution 7 T magnetic resonance imaging. Using biophysical modeling informed by quantitative ion beam microscopy on postmortem brain tissue, we demonstrate that MR contrast in SWM is driven by iron and can be linked to the microscopic iron distribution. Higher SWM iron concentrations were observed in U-fiber–rich frontal, temporal, and parietal areas, potentially reflecting high fiber density or late myelination in these areas. Our SWM mapping approach provides the foundation for systematic studies of interindividual differences, plasticity, and pathologies of this crucial structure for cortico-cortical connectivity in humans.
Two fluorescent dyes were incorporated into sol-gel derived SiO2 matrices. The dye was added to SiO2 precursors of different degrees of pre-condensation and the spectroscopic properties of the immobilized dye were measured at various aging and drying stages of the resulting gels. The significant influence of the processing parameters on the spectroscopic properties is manifested in the relative intensity of a second red shifted emission band (550560 nm), which was observed besides the typical coumarin emission band (495 nm). The appearance of this long wavelength emission might be attributed to dye aggregation or to other reactions with the ambient matrix forced by micro porosity phenomena.
Long-term behaviour of geosynthetic drains - excavations on landfills after up to 12 years service
(2002)
Micro-computed tomography (µCT) provides quantitative three-dimensional information of bone around titanium implants similar to classical histology. The study, based on an animal model, using cuboid-shaped biofunctionalised Ti6Al4V implants with surrounding bone after 4 weeks, is performed using 3 µCT-systems with X-ray tubes, one synchrotron-radiation-based µCT-system (SRµCT), and classical histology. Although the spatial resolution of the µCTsystems is comparable, only the results of SRµCT agree with results of classical histology. The X-ray tube sources give rise to huge artefacts in the tomograms (interface scattering, beam hardening), which impaired the quantitative analysis of bone up to about 200 µm from the implant surface. Due to the non-destructive character of µCT the specimens can be subsequently examined by classical histology
without restriction. The quantitative comparison of bone formation uncovers the strong dependence of the detected amount of newly formed bone from the selected slice. This
implies the necessity of 3D analysis. SRµCT and classical histology prove that surface modifications of the titanium implant significantly influence the bone formation. Using SRµCT, the preparation artefacts due to cutting and polishing are excluded.
Archaeological bone, ivory and antler, as well as objects manufactured from them, are largely studied to extract as much information as possible from these materials. Among others, one key question in archaeology is the exact identification of the material. Even if the identification of different kinds of osseous material seems to be trivial in many cases, it can be a difficult issue when small, heavily carved and more or less altered ancient objects are concerned. This study was focused on the determination of parameters allowing the distinction of archaeological ivory, bone and antler in order to identify the raw material used for the manufacture of prehistoric objects. The high performance of synchrotron radiation (SR) and laboratory-based micro X-ray computed tomography (microCT), providing highly resolved three-dimensional information on the micromorphology, permitted the establishment of such distinctive features of modern references of ivory, antler, land mammal and whale bones: ivory shows characteristic tubular pores with a diameter of about 1 to 2 µm, bone and antler show typical osteon structures. In our measured references, antler shows on average larger and more elongated shaped pores of the osteons compared to terrestrial mammal bone. This feature however depends very much on the original localization of the studied sample within the antler. Whale bones can be distinguished from the other osseous materials by a cancellous, osteoporotic-like structure with irregularly distributed rounded porosities with diameters reaching up to 500 µm. These characteristics have also been tested on determined Palaeolithic fragments, as diagenetic changes during burial have to be considered and may lead to the modification of the parameters established on the basis of modern bone references. In general, the chemical composition of bone objects can change drastically over time while micromorphological features, as evidenced by microCT, seem to be less susceptible to such alterations. In addition, microCT enables the comparison of inner and possibly less altered parts of the objects, and can be considered as completely non-destructive for small mineralised prehistoric objects. In this study, specific morphological features allowing the distinction of ivory and of whale bone from other bone and antler material were determined, even for altered materials dating back to Palaeolithic periods. Thus, we provide, in addition to archaeozoological, chemical and isotopic markers, a new non-destructive tool to identify some raw materials used for the fabrication of osseous objects ranging from recent to prehistoric periods.
Crystallization behavior in different atmospheres (air, Ar, and 7% H2/Ar) of lithium iron phosphate glass (33Li2O33Fe2O31Nb2O5–33P2O5 (LFNP)) powders with different sizes of 2–1000 µm was examined. The crystallization peak temperature (Tp) in Ar and 7% H2/Ar decreased with decreasing the particle size of glass powders, but the value of Tp in air was independent of particle size. The crystallized glass obtained by heating to Tp showed the formation of the α-Li3Fe2(PO4)3 and LiFePO4 crystalline phases. Fe2O3 crystals were formed only in the inside of crystallized glass plates in the heating in air. The crystallization of LiFePO4 was largely enhanced in the particle size of <2 µm during the heating in Ar and 7% H2/Ar atmospheres. The main crystallization mechanism in LFNP glass was found to be surface crystallization. Significant shrinkages were observed for glass compacts (pellets) in the heating in 7% H2/Ar. These results suggest that controlling particle sizes and atmospheres enables the design the morphology of LiFePO4 crystals in LFNP glass.
The Final Gravettian level (level 2) of the abri Pataud (Dordogne, France) yielded a large assemblage of body ornaments that consists essentially of 85 quite standardized rectangular beads. Some uncertainty remained about the raw material in which these small beads were made: mammoth ivory, reindeer antler or bone? Non-invasive methods were employed in order to determine the raw material. First chemical analyses using microbeam Proton Induced X-ray Emission analysis (microPIXE) did not enable us to conclude definitively. Therefore, synchrotron and laboratory X-ray microtomography (microCT) were applied on eight beads and allowed us to identify ivory for all of them except for one, which shows slightly different morphological features.
To properly understand and assess the long-term behaviour of geosynthetic materials it is necessary to investigate the various types of possible degradation mechanims. This includes both chemical and mechanical behaviour, and sometimes even their interactions with one another. Clearly, chemical degradation of geosynthetics depends on the polymer type. For example, polyolefins are vulnerable to oxidation; polyesters are susceptible to hydrolysis; and plasticizers can leach from polyvinyl chloride. This paper describes the concept of these three types of degradation, but focuses on the oxidation of polyolefins since the majority of the geosynthetics is made from this type of polymer. The methods used to predict the lifetime of antioxidants and service life of the geosynthetic material will be illustrated. Furthermore, the influence of temperature, pressure, and ultraviolet light on the service life are also demonstrated. Finally, the current specifications targeting the longevity of different geosynthetics are presented.
Regarding mechanical degradation, the paper mainly focuses upon the creep deformation of geogrids and stress crack resistance (SCR) of polyethylene geomembranes and geopipe. The method to assess stress crack resistance is described, and the microscopic mechanisms that lead to such failure are explained. For creep evaluation, different acceleration tests are presented and their applicability with respect to the different types of polymers is illustrated. In addition, the long-term shear behaviour of geocomposites and geosynthetic clay liners is presented.
The paper will give an overview of new methodology for evaluating the
reliability of NDE systems accurately, reliably and efficiently in accordance with the
specific requirements of industrial application. After a review of the substantive
issues from the previous workshops, the go forward guidance from these
interactions is considered.
At the beginning of the reliability analysis, the actual safety demands have to
be defined in order to fit the investigation to the level of risk when the component
would fail. Next, all the essential influencing parameters need to be documented and
transferred to an appropriate design of experiments (DOE) to determine the
reliability in terms of a qualitative assessment for lower risk or in terms of a
quantitative probability of detection (POD) or ROC (Receiver Operating
Characteristics) curves for higher safety demands. A new paradigm is offered to
consider the POD or reliability of the system as a function of the configuration of
input variables and use it for optimisation rather than for a final judgement. An
advantage for the end user is also to sample all single PODs to an integral 'Volume
POD' of a part.
Among the influencing parameters, the human factor is the most important one.
A systematic psychological approach shall help to find out where the bottlenecks are
but most importantly to provide best possible working conditions for the human
inspectors.
This report describes the methodology of the reliability investigation performed on the ultrasonic
phased array NDT system, developed by SKB in collaboration with Posiva, for inspection of the
canisters for permanent storage of nuclear spent fuel.
The canister is composed of a cast iron insert surrounded by a copper shell. The shell is composed
of the tube and the lid/base which are welded to the tube after the fuel has been place, in the
tube. The manufacturing process of the canister parts and the welding process are described.
Possible defects, which might arise in the canister components during the manufacturing
or in the weld during the welding, are indentified.
The number of real defects in manufactured components have been limited. Therefore the reliability
of the NDT system has been determined using a number of test objects with artifical defects.
The reliability analysis is based on the signal response analysis. The conventional signal response
analysis is adopted and further developed before applied on the modern ultrasonic phased-array
NDT system. The concept of multi-parameter a, where the response of the NDT system is dependent
on more than just one parameter, is introduced. The weakness of use of the peak signal response
in the analysis is demonstrated and integration of the amplitudes in the C-scan is proposed as an
alternative. The calculation of the volume POD, when the part is inspected with more configurations,
is also presented. The reliability analysis is supported by the ultrasonic simulation based on the
point source synthesis method.
The paper presents technical details of the drop test performance as well as some experimental results of tests carried out with the Japanese 'Yoyushindo-disposal' waste container for intermediate depth disposal. The tests were accompanied by various metrology to collect data as basis for safety assessment.
Background - It is known that dietary intake of polyunsaturated fatty acids may improve cardiac function. However, relatively high daily doses are required to achieve sufficient cardiac concentrations of beneficial omega‐3 fatty acids. The liver X receptor (LXR) is a nuclear hormone receptor and a crucial regulator of lipid homeostasis in mammals. LXR activation has been shown to endogenously reprogram cellular lipid profiles toward increased polyunsaturated fatty acids levels. Here we studied whether LXR lipid reprogramming occurs in cardiac tissue and exerts cardioprotective actions.
Methods and Results - Male 129SV mice were treated with the LXR agonist AZ876 (20 µmol/kg per day) for 11 days. From day 6, the mice were injected with the nonselective β‐agonist isoproterenol for 4 consecutive days to induce diastolic dysfunction and subendocardial fibrosis while maintaining systolic function. Treatment with isoproterenol led to a marked impairment of global longitudinal strain and the E/e' ratio of transmitral flow to mitral annular velocity, which were both significantly improved by the LXR agonist. Histological examination showed a significant reduction in isoproterenol‐induced subendocardial fibrosis by AZ876. Analysis of the cardiac lipid composition by liquid chromatography‐high resolution mass spectrometry revealed a significant increase in cardiac polyunsaturated fatty acids levels and a significant reduction in saturated fatty acids by AZ876.
Conclusions - The present study provides evidence that the LXR agonist AZ876 prevents subendocardial damage, improves global longitudinal strain and E/e' in a mouse model of isoproterenol‐induced cardiac damage, accompanied by an upregulation of cardiac polyunsaturated fatty acids levels. Cardiac LXR activation and beneficial endogenous cardiac lipid reprogramming may provide a new therapeutic strategy in cardiac disease with diastolic dysfunction.
In many industrial sectors, Structural Health Monitoring (SHM) is considered as an addition to Non-Destructive Testing (NDT) that can reduce maintenance effort during lifetime of a technical facility, structural component or vehicle. A large number of SHM methods is based on ultrasonic waves, whose properties change depending on structural health. However, the wide application of SHM systems is limited due to the lack of suitable methods to assess their reliability. The evaluation of the system performance usually refers to the determination of the Probability of Detection (POD) of a test procedure. Up to now, only few limited methods exist to evaluate the POD of SHM systems, which prevent them from being standardised and widely accepted in industry. The biggest hurdle concerning the POD calculation is the large amount of samples needed. A POD analysis requires data from numerous identical structures with integrated SHM systems. Each structure is then damaged at different locations and with various degrees of severity. All of this is connected to high costs. Therefore, one possible way to tackle this problem is to perform computer-aided investigations. In this work, the POD assessment procedure established in NDT according to the Berens model is adapted to guided wave-based SHM systems. The approach implemented here is based on solely computer-aided investigations. After efficient modelling of wave propagation phenomena across an automotive component made of a carbon fibre-reinforced composite, the POD curves are extracted. Finally, the novel concept of a POD map is introduced to look into the effect of damage position on system reliability.
Traditional earthen structures of cultural value are often damaged by static or dynamic loads. This is usually manifested by the appearance of cracks. All too often these cracks are insufficiently or inappropriately repaired if at all because of lack of knowledge and/or technology. In particular, the behavior of crack repair by grouting poses a challenge in earthen materials and demands specific requirements for the grouting mortar, such as low water content, good water retention, low shrinkage, etc. If dynamic loads, e.g. induced by earthquakes, are expected, the grouting material requires additional specifications such as a compatible strength and modulus of elasticity as well as good adhesion to the earthen materials. The study presents results from the development of a grouting material based on hydraulic lime mortar suitable for the repair of cracks in a variety of earthen building techniques. The goal was to develop a material also compatible with earthen structures exposed to dynamic load. The grouting mortar was designed to be adaptable in strength properties and at the same time to have sufficient robustness for the use on the construction site. First results show a satisfactory performance of the grout concerning fresh and hardened mortar properties as well as injectability. The study is part of our work in the framework of the ongoing project NIKER, funded by the European Commission dealing with improving imovable Cultural Heritage assets against the risk of earthquakes.