Analytische Chemie
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The vulnerability of low-quality concrete of some bridges to ageing and deterioration while they are exposed to environmental conditions during their service life, influence of growing population and climate changes, is a well-known effect and requires survey. For survey, the development of a low cost, cost-efficient sensor network to be embedded for continuous or attached to the surface for periodic monitoring is essential.
Changing ground water conditions, flood or even leakage in fresh or disposal of waste water can lead to in-creased moisture content in building materials and structural elements as walls or floors. Moisture allows the transport of other adverse chemicals that might reduce the durability of structures. The paper presents a feasibility study about the capability of microwave modules as bluetooth® or ZigBee with frequency range at 2,4 GHz to create advanced Wireless Sensor Networks (WSN) for estimation and visualization of moisture distribution in infrastructure assets. It was found that the value of the received signal strength indication (RSSI) depends on the moisture content and can be the basis for the moisture distribution inside a massive structure.
The microwave modules may be used to compose networks outside and inside of building materials or structural elements. The higher the number of connections between BLE modules, the more precise and the more distant information can be obtained from the network. Mesh networking was applied to increase the quantitative information.
A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12–43 nm is presented utilizing steady-state and time-resolved fluorometry.
Special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by highenergy O–H and C–H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated Population pathways of the 4F9/2 energy level of Er3+ were examined. Our results highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Er3+ emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. Because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the 4F9/2 energy level of Er3+, which correlate with the size-, environment-, and P-dependent quenching states of the higher Er3+ energy levels.
Cerro do Jarau is a conspicuous, circular morpho‐structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat “Pampas” terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30o12′S and 56o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná‐Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low‐pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks.
The stabilization of crystal phases and nanostructured morphologies is an essential topic in application-driven design of mesoporous materials. Many applications, e.g. catalysis, require high temperature and humidity. Typical metal oxides transform under such conditions from a metastable, low crystal-line material into a thermodynamically more favorable form, i.e. from ferrihy-drite into hematite in the case of iron oxide. The harsh conditions induce also
a growth of the crystallites constituting pore walls, which results in sintering and finally collapse of the porous network. Herein, a new method to stabi-lize mesoporous templated metal oxides against sintering and pore collapse is reported. The method employs atomic layer deposition (ALD) to coat the internal mesopore surface with thin layers of either alumina or silica. The authors demonstrate that silica exerts a very strong influence: It shifts hematite formation from 400 to 600 °C and sintering of hematite from 600 to 900 °C.
Differences between the stabilization via alumina and silica are rationalized by a different interaction strength between the ALD material and the ferrihydrite film.
The presented approach allows to stabilize mesoporous thin films that require a high crystallization temperature, with submonolayer quantity of an ALD material, and to apply mesoporous materials for high temperature applications.
Structural design and application have always been linked to the compressive strength of concrete as the main relevant criterion. This was justifiable in the past, where concrete consisted of water, ordinary Portland cement and aggregates, but this concept is no longer relevant for modern and more sustainable cement and concrete.
Despite these new developments, existing standards, guidelines and academic curricula have not been much updated and are still used worldwide. There is a need to change this situation by proper education of the users.
This overview describes the challenges that arise at a user Level from the higher complexity of modern concrete, and defines needs and requirements for enhanced applicability of sustainable concrete concepts.
Furthermore, recommendations are given on how better concrete practice can be communicated to all the involved parties, from civil and design engineers to constructors and site-appliers on the construction site.
Many ambient desorption/ionization mass spectrometry (ADI-MS) techniques rely critically on thermal desorption. Meanwhile, the analyte classes that are successfully studied by any particular ADI-MS methods are strongly dependent on the type of ionization source. Generally, spraybased ionization sources favor polar analytes, whereas plasmabased sources can be used for more hydrophobic analytes and are more suitable for molecules with small molar masses. In the present work, classic atmospheric-pressure chemical ionization (APCI) is used. To provide improved desorption performance for APCI, a surface acoustic wave nebulization (SAWN) device was implemented to convert liquid analytes into fine airborne particles. Compared to conventional SAWN that is used solely as an ionization source for liquid samples, the coupling of SAWN and APCI significantly improves ion signal by up to 4 orders of magnitude, reaching comparable ion abundances to those of electrospray ionization (ESI). Additionally, this coupling also extends the applicable mass range of an APCI source, conventionally known for the ionization of small molecules <500 Da. Herein, we discuss cursory evidence of this applicability to a variety of analytes including both polar and nonpolar small molecules and novel peptides that mimic biomolecules upward of 1000 Da. Observed species are similar to ESI-derived ions including doubly charged analyte ions despite presumably different charging mechanisms. SAWN−APCI coupling may thus involve more nuanced ionization pathways in comparison to other ADI approaches.
Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus, using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues.
Investigation on Wall Thickness Ranges Using Digital Radiography for Tangential Projection Technique
(2018)
X-ray testing is based on the attenuation of X-rays when passing through matter. Image detectors acquire the X-ray information which is defined by the local penetrated wall thickness of the tested sample. By X-ray absorption in the detector and following read-out and digitization steps a digital image is generated. As detectors a radiographic film and film digitization, a storage phosphor imaging plate and a special Laser scanner (Computer Radiography - CR) or a digital detector array (DDA) can be used. The digital image in the computer can then be further analyzed using many types of image processing. In the presented work the automated evaluation of wall thickness profiles are investigated using a test steel pipe with 9 different wall thicknesses and various X-ray voltages and different filter materials at the tube port and intermediate between object and detector. In this way the influence of different radiation qualities on the accuracy of the automated wall thickness evaluation depending on the penetrated wall thickness of the steel pipe was investigated.
We describe a lattice-based crystallographic approximation for the analysis of distorted crystal structures via Electron Backscatter Diffraction (EBSD) in the scanning electron microscope. EBSD patterns are closely linked to local lattice parameter ratios via Kikuchi bands that indicate geometrical lattice plane projections. Based on the transformation properties of points and lines in the real projective plane, we can obtain continuous estimations of the local lattice distortion based on projectively transformed Kikuchi diffraction simulations for a reference structure. By quantitative image matching to a projective transformation model of the lattice distortion in the full solid angle of possible scattering directions, we enforce a crystallographically consistent approximation in the fitting procedure of distorted simulations to the experimentally observed diffraction patterns. As an application example, we map the locally varying tetragonality in martensite grains of steel.
Increased speed, heavier loads, altered material and modern drive systems result in an increasing number of rail flaws. The appearance of these flaws also changes continually due to the rapid change in damage mechanisms of modern rolling stock. Hence, interpretation has become difficult when evaluating non-destructive rail testing results. Due to the changed interplay between detection methods and flaws, the recorded signals may result in unclassified types of rail flaws. Methods for automatic rail inspection (according to defect detection and classification) undergo continual development. Signal processing is a key technology to master the challenge of classification and maintain resolution and detection quality, independent of operation speed. The basic ideas of signal processing, based on the Glassy-Rail-Diagram for classification purposes, are presented herein. Examples for the detection of damages caused by rolling contact fatigue also are given, and synergetic effects of combined evaluation of diverse inspection methods are shown.