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Eingeladener Vortrag
- nein (1024)
Biofilms living on gold (Au) grains play a key role in the biogeochemical cycle of Au by promoting the dispersion of Au via the formation of Au nanoparticles as well as the formation of secondary biomorphic Au. Gold grains from Queensland, Australia, are covered by a polymorphic, organic-inorganic layer that is up to 40 μm thick. It consists of a bacterial biofilm containing Au nanoparticles associated with extracellular polymeric substances as well as bacterioform Au. Focused ion beam (FIB) sectioning through the biofilm revealed that aggregates of nanoparticulate Au line open spaces beneath the active biofilm layer. These aggregates (bacterioform Au type 1) resulted from the reprecipitation of dissolved Au, and their internal growth structures provide direct evidence for coarsening of the Au grains. At the contact between the polymorphic layer and the primary Au, bacterioform Au type 2 is present. It consists of solid rounded forms into which crystal boundaries of underlying primary Au extend, and is the result of dealloying and Ag dissolution from the primary Au. This study demonstrates that (1) microbially driven dissolution, precipitation, and aggregation lead to the formation of bacterioform Au and contribute to the growth of Au grains under supergene conditions, and (2) the microbially driven mobilization of coarse Au into nanoparticles plays a key role in mediating the mobility of Au in surface environments, because the release of nanoparticulate Au upon biofilm disintegration greatly enhances environmental mobility compared to Au complexes only.
EBSD is nowadays a common technique for the characterization of crystalline microstructures in scanning electron microscopy. The diffraction patterns are often interpreted by superimposing individual Kikuchi bands which are geometrically described by band edges derived from Braggs law. For the typically very simple crystal structures of technically applied materials, such a simplification of the Kikuchi pattern interpretation works sufficiently well, especially for orientation determinations as a main application of EBSD. The more complex crystal structures, however, are a challenge for EBSD indexing routines which in such cases often fail unpredictably. The use of only the intensities of single reflectors for a description of the Kikuchi band intensity and as a cut-off criterion for a pre-selection of the strongest bands are not satisfactory. Often the result will match too many phases, or there are certain deviations in the intensity prediction which must be adapted manually. This is already problematic if one is absolutely sure that the patterns are originating from the expected phase and it becomes a very questionable procedure for an unknown phase.
Modern EBSD systems perform diffraction pattern “quality” (PQ) calculations, essentially measurements of the contrast of the brighter bands in the pattern above background, for every pattern analyzed. Since the calculations are independent of EBSD indexing, data are generated from all points on the analyzed sample surface, regardless of indexability or the state of the material beneath. EBSD maps generated from PQ data are like microstructurally sensitive SEM images, collected at EBSD speeds and grid resolutions, with contrast arising from phase density, crystal structure, crystallographic orientation, grain boundary location, near-surface plastic strain, coating density/thickness, and to some extent topography. Grain boundaries and other aspects of sample microstructure are readily revealed, so the PQ map is a very useful characterization tool in its own right, and serves as a reference for EBSD maps generated from indexing-derived data, such as orientation, grain boundary character, phase distribution and strain maps.
The halophilic bacterium Halomonas elongata takes up the compatible solute ectoine via the osmoregulated TRAP transporter TeaABC. A fourth orf (teaD) is located adjacent to the teaABC locus that encodes a putative universal stress protein (USP). By RT-PCR experiments we proved a cotranscription of teaD along with teaABC. Deletion of teaD resulted in an enhanced uptake for ectoine by the Transporter TeaABC and hence a negative activity regulation of TeaABC by TeaD. Atranscriptional regulation viaDNA binding could be excluded. ATP binding to native TeaD was shown by HPLC, and the Crystal structure of TeaD was solved in complex with ATP to a resolution of 1.9 A ° by molecular replacement. TeaD forms a dimer-dimer complex with one ATP molecule bound to each monomer, which has a Rossmann-like R/β overall fold. Our results reveal an ATP-dependent oligomerization of TeaD, which might have a functional role in the regulatory mechanism of TeaD. USP-encoding orfs, which are located adjacent to genes Encoding for TeaABC homologues, could be identified in several other organisms, and their physiological role in balancing the internal cellular ectoine pool is discussed.
For the characterization of disperse and porous solids, usually single gas adsorption(GA) is employed. In the case of liquid adsorption (LA), the extraction of information on solids immediately becomes a more sophisticated matter since information on geometric as well energetic parameters of the solids is both superposed by liquid-mixture effects and displayed in excess terms. We have to ask if reliable solid parameters can be also obtained from LA isotherms. The enlarged data bank of gas and liquid adsorption measurements enables us to change systematically solid parameters (e.g., the pore width of MCM-41, the pore entrances of SBA-16, chemical heterogeneity) and to study in this way the influence of solid parameters on LA.
Certification report for the reference materials ERM-AE102a, -AE104a, -AE120, -AE121 and -AE122
(2010)
Isotope reference materials are essential to enable reliable and comparable isotope data. Besides the correction of mass fractionation or mass discrimination isotope reference materials are indispensible for validation and quality control of analytical procedures. This article describes the production and certification of a set of five isotope reference materials ERM-AE102a, 104a, AE120, 121 and 122, for boron isotope analysis. The isotopic composition of all materials has been adjusted by mixing boron mother solutions enriched in 10B or 11B with a boron mother solution having natural-like isotopic composition under full gravimetric control. All mother solutions have been analysed for their boron mass fraction as well as their boron isotopic composition by TIMS using IDMS as calibration technique. For all five reference materials the isotopic composition obtained on the basis of the gravimetric data agrees very well with the isotopic composition obtained from different TIMS techniques. Performed stability and homogeneity studies show no significant influence on the isotopic composition as well as on the related uncertainties.
The certified isotope abundances for 10B are 0.29995 (27) for ERM-AE102a and 0.31488 (28) for ERM-AE104a. The certified δ11B values are -20.2 (6) ‰ for ERM-AE120, 19.9(6) ‰ for ERM-AE121 and 39.7 (6) ‰ for ERM-AE122.
Together with the formerly certified ERM-AE101 and -AE103 a unique set of seven certified reference materials (CRM) for boron isotope analysis is now available from BAM.
Hochtemperaturtribologie
(2010)
Die Temperatur ist eine fundamentale Beanspruchungs- bzw. Einflussgröße für alle tribologischen Systeme. Für die in zahlreichen tribologischen Systemen benötigten Schmierstoffe liegen die thermischen Stabilitätsgrenzen bei etwa 400?°C. Es wird die tribologische Prüftechnik für Tribomaterialien beschrieben, die für den Einsatz in tribologischen Systemen bei hohen Betriebstemperaturen verwendbar sind. Ausgehend von metallurgischen Lösungsansätzen aus der Tribologieforschung werden Anwendungsmöglichkeiten hochtemperaturbeständiger Ingenieurwerkstoffe mit Beispielen aus der Automobiltechnik (Luftlagerung von Turboladern, Leistungssteigerung von Bremsmaterialien), der Fertigungstechnik (Standzeitverlängerung von Werkzeugen) und dem chemischen Anlagenbau (Effizienzsteigerung von Kühlkreisläufen) dargestellt.
Verification of activity release cpmpliance with regulatory limits within spent fuel transport casks
(2010)
Verification of activity release compliance with regulatory limits within spent fuel transport casks
(2010)
The Witness - Screen Test
(2010)
IAPRI World conference on packaging - Proceedings of the 17th IAPRI world conference on packaging
(2010)
Subjecting a thin NiTi specimen to uniaxial tension often leads to a localized martensitic transformation: macroscopic transformation bands form and propagate through the specimen, separating it into regions of fully transformed martensite and original austenite. In the present study, the alternating current potential drop (ACPD) technique is used to analyze the change in electrical resistance of ultra-fine grained NiTi wires subjected to a broad range of thermo-mechanical load cases: (i) uniaxial tensile straining at constant temperatures (pseudoelastic deformation); (ii) cooling and heating through the transformation range at constant load (actuator load case); (iii) a combination of mechanical and thermal loading. We monitor the ACPD signals in several zones along the gauge length of specimens, and we demonstrate that a localized type of transformation is a generic feature of pseudoelastic as well as of shape memory deformation. Moreover, the ACPD signals allow to differentiate between temperature-induced martensite (formed during cooling at no or relatively small loads), stress-induced martensite, and reoriented martensite (formed under load at low temperatures).
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.
This paper presents three examples of applied
numerical modeling and inverse profiling in electromagnetic
non-destructive testing. In the first example, we discuss
numerical modeling and optimization of eddy current sensors for
in-line inspection of hot wire steel. To detect longitudinal cracks
a series of new sensors are modelled and optimized by numerical
modeling and is successfully tested. The second example presents
the application of a time-domain technique to reconstruct the
unknown permittivity and electric conductivity profile of a onedimensional
slab of finite length. The inverse scattering problem
is solved by an Invariant Embedding Method which requires a
finite time trace of reflection data and therefore is suitable for
reconstructing the material parameters in real-time. The
implemented method is validated against synthetic and measured
Time Domain Reflectometry data. The third example
demonstrates the application of the Contrast Source Inversion
method to reconstruct the 2-D permittivity profile of a beech
tree. Thus, the discussed applications present an identified need
of numerical modeling and inverse profiling in electromagnetic
non-destructive evaluation.
Lamb waves travel in plates and hollow cylinders over large distances and propagate with multiple mode shapes. Therefore the waves can be used for integrity tests of large scale structures. Each propagating wave mode has a unique dispersive character and a frequency dependent vibration pattern. Therefore, by interacting with flaws each mode is assumed to generate an individual reflection pattern depending on the flaw type, flaw orientation and size. To extract this information a frequency as well as wave number dependent mode excitation is required ensuring a single mode excitation. The challenge, however, is to control the selective mode excitation electronically to allow a sequence of consecutive tests with different wave modes to collect the data. A method is proposed using phased array wedge transducers with fluid coupling for normal force excitation of Lamb wave modes. The excitation principle is investigated analytically on plates by modelling the wave generation in the wedge and the coupling between wedge and structure. The analytical results of the excitation principle are validated by corresponding experiments where the field patterns on the wedge surface and on the plate were scanned using a laser vibrometer. The directivity of the radiated field is investigated together with the direction dependent analysis of the mode content.
In this contribution a simulation tool is developed to compute the energy skewing angles and energy coefficients
for the reflected and refracted plane waves in following general cases: (1) reflection and refraction
of plane elastic waves at an interface between isotropic and transversely isotropic solid, (2) reflection
and refraction of plane elastic waves at an interface between transversely isotropic and isotropic solid, (3)
reflection and refraction of plane elastic waves at an interface between two general transversely isotropic
solid and (4) reflection of plane elastic waves from a stress free boundary of a transversely isotropic solid.
Computational results for analytically evaluated acoustic wave energy skewing angles and energy reflection
and transmission coefficients in acoustically anisotropic materials such as austenitic steel materials
exhibiting columnar grain orientation are presented. The obtained results show that the acoustic energy
skewing angles and coefficients in austenitic steel materials strongly depend upon the columnar grain
orientation and are less influenced by the grain orientations which are parallel and perpendicular to the
interface.
When dealing in ultrasonic testing with inhomogeneous and anisotropic material structure such as
diverse types of components made from austenitic or nickel based cast, which are currently used
for modern power plant concepts, data interpretation is quite difficult. For better understanding of
the complex interaction between the sound field and the component under test, the mathematical
modeling of sound propagation in solids is a substantial task to increase the probability of
detection of relevant defects.
First we present a mathematical approach for modeling the three dimensional transient
particle displacement as a function of time in each point in a half space excited by an impulsive
point load at the surface. The transient ultrasonic field of a rectangular array element is calculated
with this approach by a point source synthesis. Based on this solution we model the wave
propagation of a phased array transducer by time delayed superposition of the wave field of the
transducer elements.
Next we use an electrodynamic technique to visualize the grazing sound field at the surface
of a test block radiated by a phased array probe. By detecting the grazing beam at the samples
surface with a small electrodynamic probe, we measured the particle displacement as a function of
time. It allows for measuring the displacement in all three spatial directions. This comprises the
detection of the horizontal and vertical particle displacement with respect to the surface and thus
also the detection of longitudinal and shear waves is possible.
The calculated and measured wave fields will be compared for different delay laws in
isotropic and transversely isotropic media. The results support the theoretical activities to model
the wave propagation and to find optimal testing parameters for different components and
configurations.
The classification of solid oxidizers according to the GHS (Globally Harmonized System of Classifica-tion and Labelling of Chemicals) and according to regulations on the transport of dangerous goods (based on the UN Recommendations/Model Regulations and implemented in all carrier domains as transport by road, railway, sea, air) is performed on the basis of the results of the UN test O.1 (―Test for oxidizing solids‖ described in chapter 34.4.1 in the Recommendations on the Transport of Danger-ous Goods, Manual of Tests and Criteria, Fifth revised edition, United Nations, New York and Geneva, 2009). This test was introduced into the UN Test Manual in 1995 as a replacement for a similar test from 1986. Even though the O.1 test is much better than the previous one there are still many prob-lems with this test. For this reason the IGUS-EOS working group (international group of experts on the explosion risks of unstable substances – working group: energetic and oxidizing substances) installed an ad-hoc working group in 2002 assigned with the task of proposing solutions for the existing prob-lems. The adequacy of such proposals has to be proven preferably by interlaboratory comparison (interlaboratory test) before they are presented to the UN Sub Committee for adoption into the UN Test Manual. The present report is the evaluation of an interlaboratory test which was designed by the Ad-hoc working group in order to find out whether the current method of comparing combustion times of test mixtures with those of reference mixtures is suitable in principle and whether some approaches for improvement of the method can be identified.
Die Ressourcenverknappung und steigende Preise rücken nachhaltiges Wirtschaften und die Wiederverwertung von Abfällen in den Blickpunkt der Forschung. Bauabfälle sind in Deutschland – mit 72,4 Mio.t im Jahr 2004 – der größte Abfallstrom. Es wird ein Überblick über den Stand der Technik zur Aufarbeitung und Verwertung von Bauabfällen gegeben und die Anforderungen an Bauabfälle, die als Sekundärrohstoff eingesetzt werden sollen, diskutiert. Die Forschung im Baustoffrecycling bezieht sich sowohl auf neue Aufbereitungstechniken als auch auf die Charakterisierung der Recyclingmaterialien sowie auf deren Einfluss auf die Betonqualität. Die Eignung und Verwertung von Bauabfällen als Sekundärrohstoffe für Baustoffe wird anhand ihrer chemischen Zusammensetzungen mit Hilfe von ternären Diagrammen diskutiert.----------------------------------------------------------------------
An overview about quantity of construction and demolition waste (CDW) and a state of the art of the reuse is given. The technology is described, which is applied for the processing of CDW in a stationary plant. The requirements on recycled aggregates, which shall be used in road construction or in manufacturing of concrete, can be divided in such related to the material and physical properties and such related to the environmental properties. The rules give guidance on the composition with the aim of excluding the constituents with unfavourable features. The environmental standards which yet in discussion are give threshold of the leachable components in recycled aggregates. The material potential of building waste is discussed. Information on the chemical composition of recycled materials is compared with the composition of pure materials. With the aid of ternary charts such building materials are identified, in which the recycled materials can be used as recycled feedstock.