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The importance of microRNA (miRNA) dysregulation for the development and progression of diseases and the discovery of stable miRNAs in peripheral blood have made these short-sequence nucleic acids next-generation biomarkers. Here we present a fully homogeneous multiplexed miRNA FRET assay that combines careful biophotonic design with various RNA hybridization and ligation steps. The single-step, single-temperature, and amplification-free assay provides a unique combination of performance parameters compared to state-of-the-art miRNA detection technologies. Precise multiplexed quantification of miRNA-20a, -20b, and -21 at concentrations between 0.05 and 0.5 nm in a single 150 mL sample and detection limits between 0.2 and 0.9 nm in 7.5 mL serum samples demonstrate the feasibility of both highthroughput and point-of-care clinical diagnostics.
Selective Electron Beam Melting (SEBM) is a promising powder bed Additive Manufacturing technique for near-net-shape manufacture of high-value titanium components. However without post-manufacture HIPing the fatigue life of SEBM parts is currently dominated by the presence of porosity. In this study, the size, volume fraction, and spatial distribution of the pores in model samples have been characterised in 3D, using X-ray Computed Tomography, and correlated to the process variables. The average volume fraction of the pores (b0.2%) was measured to be lower than that usually observed in competing processes, such as selective laser melting, but a strong relationship was found with the differentbeamstrategies used to contour ,and infill by hatching, a part section. The majority of pores were found to be small spherical gas pores, concentrated in the infill hatched region; this was attributed to the lower energy density and less focused beam used in the infill strategy allowing less opportunity for gas bubbles to escape the melt pool. Overall, increasing the energy density or focus of the beam was found to correlate strongly to a reduction in the level of gas porosity. Rarer irregular shaped pores were mostly located in the contour region and have been attributed to a lack of fusion between powder particles.
Green Fenton-like magnetic nanocatalysts: Synthesis, characterization and catalytic application
(2015)
Five iron oxalate core–shell magnetite nanoparticles catalysts are evaluated as magnetic heterogeneous materials. Simple and efficient procedures for the preparation of magnetic iron oxalate coated nanoparticles are presented. The catalysts are fully characterized using various investigation techniques. Additionally, the formation of photo-sensitized oxygen by spin-trapping using electron spin resonance is investigated. The catalytic activity of two model substrates (carbamazepine and bisphenol A) is also evaluated. The effect of operational parameters (catalyst and H2O2 concentration, UVA light) on the degradation performance of the oxidation process is investigated. The obtained reaction rates depend on the nature of the compound and increase with iron oxide shell thickness of the catalyst. Moreover, these materials show a significant activity during two consecutive tests. The optimum experimental parameters are found to be 1.0 g L−1 of catalysts, 10 mM H2O2, under UVA irradiation. More than 99% of both substrates are removed after 30 min of reaction time under the experimental conditions given above. The results obtained show that the catalysts are suitable candidates for the removal of pollutants in wastewaters by means of the Fenton heterogeneous reaction.
This paper deals with the system identification of a mechanical structure supported by nonlinear springs subjected to an external load. If all mechanical parameters of the system were known, the displacement of the system subjected to this load could be easily calculated. However, the monitoring applications often deal with the inverse problem. The loads and displacements of the system are known and certain mechanical Parameters of the system are sought. The solution of such inverse problems can be difficult, especially when they have a nonlinear and multimodal character, which often makes them appear intractable at first sight. However, evolutionary computing can be applied to solve this inverse, nonlinear and multimodal problem. Sometimes a prior knowledge exists on certain system properties, which is difficult to implement into analytical or numerical solvers. This knowledge can play a decisive role in identifying the System properties and it can be easily included as a boundary condition when applying evolutionary algorithms.
This article discusses how and under what conditions the unknown spring resistances can be identified. The practical application of this procedure is exemplified here with the mechanical system of a pile foundation.
Simple models describing the relationship between basic mechanical properties and the relative density of various types of porous metals (such as foams, sponges and lattice structures) are well established. Carefully evaluating these relationships experimentally is challenging, however, because of the stochastic structure of foams and the fact that it is difficult to systematically isolate density changes from variations in other factors, such as pore size and pore distribution. Here a new method for producing systematic sets of stochastic foams is employed based on electron beam melting (EBM) additive manufacturing (AM). To create idealised structures, structural blueprints were reverse-engineered by inverting X-ray computed tomographs of a randomly packed bed of glass beads. This three-dimensional structure was then modified by computer to create five foams of different relative density ρr, but otherwise consistent structure. Yield strength and Young’s modulus have been evaluated in compression tests and compared to existing models for foams. A power of 3 rather than a squared dependence of stiffness on relative density is found, which agrees with a recent model derived for replicated foams. A similar power of 3 relation was found for yield strength. Further analysis of the strength of nominally fully dense rods of different diameters built by EBM AM suggest that surface defects mean that the minimum size of features that can be created by EBM with similar strengths to machined samples is ∼1 mm.
Polyurethane foam used as impact limiter material undergoes high plastic deformations, whereat the resulting stress-strain relations strongly depend on loading speed and temperature. This paper discusses the efforts necessary to develop a reliable numerical foam simulation model focussing on generation and implementation of temperature- dependent yield curves
The catalytic efficiency of two magnetically responsive nanocatalysts was evaluated for the Degradation of Reactive Black 5 (RB5) and Reactive Yellow 84 (RY84) azo dyes using hydrogen peroxide as oxidant undervery mild conditions (atmospheric pressure, room temperature). In order to obtain the nanocatalysts, thesurface of magnetite (Fe3O4) nanoparticles, prepared by a co-precipitation method, was further modified with ferrous oxalate, a highly sensitive non-hazardous reducing agent. The sensitized nanomaterials were characterized by X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy and vibrating sample magnetometry, and used in the catalytic wet hydrogen peroxideoxidation (CWHPO) of RB5 and RY84, in laboratory-scale experiments. The effect of important variables such as catalyst dosage, H2O2 concentration, and contact time was studied in the dye Degradation kinetics. The results showed that it was possible to remove up to 99.7% dye in the presence of 20 mM H2O2 after 240 min of oxidation for a catalyst concentration of 10 g L−1at 25◦C and initial pH value of 9.0.CWHPO of reactive dyes using sensitized magnetic nanocatalysts can be a suitable pre-treatment methodfor complete decolorization of effluents from textile dyeing and finishing processes, once the Optimum operating conditions are established.
The use of magnetic materials as heterogeneous catalysts has attracted increasing attention in the last years since they proved to be promising candidates for water treatment. In the present study, two types of surface-modified magnetite (Fe3O4) nanoparticles, coated with non-hazardous naturally occurring agents—either tannic acid (TA) or dissolved natural organic matter—were evaluated as magnetic heterogeneous catalysts. Chemical synthesis (co-precipitation) was chosen to yield the nanocatalysts due to its well-established simplicity and efficiency. Subsequently, the properties of the final products were fully assessed by various characterization techniques. The catalytic activity in heterogeneous oxidation of aqueous solutions containing a model pollutant, Bisphenol A (BPA), was comparatively studied. The effect of operational parameters (catalyst loading, H2O2 dosage, and UV light irradiation) on the Degradation performance of the oxidation process was investigated. The optimum experimental parameters were found to be 1.0 g/L of catalysts and 10 mM H2O2, under UV irradiation. The highest mineralization rates were observed for Fe3O4-TA catalyst. More than 80 % of BPA was removed after 30 min of reaction time under the specified experimental conditions. The obtained results showed that the two catalysts studied here are suitable candidates for the removal of pollutants in wastewaters by means of heterogeneous reaction using a green sustainable treatment method.
Numerical simulation of ultrasonic wave propagation using higher order methods in space and time
(2015)
The paper discusses the efficient simulation of ultrasonic wave propagation.
It is demonstrated that a combination of higher methods in space and time leads to a significant performance boost. Higher order spectral elements are used for the spatial
discretization. A comparison with standard finite elements shows the advantages when using explicit time integration schemes. For the temporal discretization, an efficient explicit fourth order Nyström method is presented. Its computational efficiency for wave propagation problems is compared to a second order Velocity Verlet integration.
In this paper, we present a new dataset consisting of 19,407 X-ray images. The images are organized in a public database called GDXray that can be used free of charge, but for research and educational purposes only. The database includes five groups of X-ray images: castings, welds, baggage, natural objects and settings. Each group has several series, and each series several X-ray images. Most of the series are annotated or labeled. In such cases, the coordinates of the bounding boxes of the objects of interest or the labels of the images are available in standard text files. The size of GDXray is 3.5 GB and it can be downloaded from our website. We believe that GDXray represents a relevant contribution to the X-ray testing community. On the one hand, students, researchers and engineers can use these X-ray images to develop, test and evaluate image analysis and computer vision algorithms without purchasing expensive X-ray equipment. On the other hand, these images can be used as a benchmark in order to test and compare the performance of different approaches on the same data. Moreover, the database can be used in the training programs of human inspectors.
Sealing and strengthening of the subsoil by injection is a major issue in the field of geotechnical engineering. This involves also jet grouting, which allows creating columns of grouted soil by eroding and mixing the in-situ soil with a thin cement suspension. A general difficulty of this method is to predict the column diameter and its material strength. Here, we present two-dimensional finite-difference numerical simulation results of a promising non-destructive quality assurance testing tool to evaluate the diameter of jet grout columns. This approach incorporates crosshole and downhole seismic measurements. Preliminary tests showed that this tool is applicable under real site conditions.
In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (CNTs) embedded in metal matrices. We conducted experimental pull-out tests of CNTs embedded in Pd or Au and found Maximum forces in the range 10 - 102 nN. These values are in good agreement with forces obtained from molecular Dynamics simulations taking into account surface functional Groups (SFGs) covalently linked to the CNT material. The dominant failure mode in experiment is a CNT rupture, which can be explained with the presence of SFGs. To qualify the existence of SFGs on our used CNT material, we pursue investigations by means of fluorescence labeling of surface species in combination with Raman imaging. We also report of a tensile test system to perform pull-out tests inside a transmission electron microscope to obtain in situ images of CNT-metal interfaces under mechanical loads at the atomic scale.
The intention of this compilation of articles was to introduce brand-new developments in the field of chemical imaging which have not been discussed in previous review articles. These include the design of new sensor nanomaterials based on photon uponversion crystals which convert near-infrared excitation light into sensor signals in the visible wavelength range highlighted by Christ and Schäferling. Sun, Ungerböck and Mayr describe the state of the art in oxygen imaging in microreactors and microfluidic devices. Miniaturized sensors for the imaging of oxygen, pH and temperature in microchips, microfluidic platforms and microbioreactors are reviewed by Pfeiffer and Nagl. Furthermore, Dmitriev and Papkovsky present a critical assessment of the applicability of probes for intracellular oxygen sensing.
I hope these articles provide an interesting insight into advanced luminescent sensor materials and the applications of optical micro- and nanosensors in fluorescence imaging today and will be inspiring for the reader. Finally, I would like to thank all authors and referees for spending their time to enable this collection of articles.
The NanoMag project brings together various leading experts in magnetic nanoparticle synthesis as well as nanoparticle analysis and characterization from research institutes, companies, universities and metrology institutes that will perform cutting-edge research and develop applications in the field of magnetic particles. This work is supported by the European Commission Framework Programme7 under the NanoMag project [grant agreement no 604448].
CONRAD-2 is an imaging instrument using low-energy (cold) neutrons. The instrument is installed at the end of a curved neutron guide which avoids the direct line of sight towards the reactor core. This ensures a very low background of high-energy neutrons and. photons at the sample position. The cold neutron beam provides a wavelength range which is suitable for phase-and diffraction-contrast imaging such as grating interferometry and Bragg edge mapping. The instrument is well suited for high resolution imaging due to the high efficiency of the very thin scintillators that can be used for the detection of cold neutrons. An instrument upgrade was performed recently as a part of an upgrade program for the cold neutron instrumentation at HZB. The parameters of the instrument as well as some research highlights will be presented.
Several ultrasonic approaches for material determination are formulated in terms of an (nonlinear) inverse problem, e.g. immersion technique (Castaings et al. (2000)) or plate-waveguide techniques (Marzani et al. (2012)). In this contribution we focus on cylindrical waveguides for ultrasonic material determination and especially on the sensitivity of recorded transmission signals to the material properties. We utilize composite scaled sensitivities to determine the information content that can be achieved by the setup to certain parameters and discuss the limitations of the approach.
Many industrial processes are run at non-atmospheric conditions (elevated temperatures and pressures, other oxidizers than air). To judge whether and if yes to what extent explosive gas(vapor)/air mixtures will occur or may be generated during malfunction it is necessary to know the safety characteristic data at the respective conditions. Safety characteristic data like Explosion limits, are depending on pressure, temperature and the oxidizer. Most of the determination methods are standardized for ambient conditions.
In order to obtain determination methods for non-atmospheric conditions, particularly for higher initial pressures, reliable ignition criteria were investigated. Ignition tests at the explosion Limits were carried out for mixtures of methane, propane, n-butane, n-hexane, hydrogen, ammonia and acetone in air at initial pressures up to 20 bar. The tests have been evaluated according to different ignition criteria: visual flame propagation, temperature and pressure rising. It could be shown that flame propagation and occasionally self-sustained combustion for several seconds occurred together with remarkable temperature rise, although the pressure rise was below 3%. The results showed that the combination of a pressure rise criterion of 2% and a temperature rise criterion of 100 K seems to be a suitable ignition criterion for the determination of explosion limits and limiting oxidizer concentration at higher initial pressures and elevated temperatures. The tests were carried out within the framework of a R&D project founded by the German Ministry of Economics and Technology.
Spatial light modulators (SLM) can be used for many applications, including imaging and beam steering. With the emergence of THz SLMs being able to control thousands of pixels, the aforementioned applications become feasible for the THz region. The degree of control that can be exerted with a SLM and in turn its usefulness directly depends on the light pattern it creates. The resulting light patterns can be quite different from the intended light patterns, due to systematic and random non-uniformities, especially for large THz wavelengths. Here we present results on the performance of a Germanium based THz SLM. These results enable the efficient application of Compressed Sensing techniques in THz SLM imaging settings.
An experimental investigation has been carried out to characterize and discriminate seven saffron samples and to verify their declared geographical origin using a voltammetric electronic tongue (VE-tongue). The ability of multivariable analysis methods such as Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) to classify the saffron samples according to their geographical origin have been investigated. A good discrimination has reached using PCA and HCA in the VE-tongue characterization case. Furthermore, cross validation and Partial Least Square (PLS) techniques were applied in order to build suitable management and prediction models for the determination of safranal concentration in saffron samples based on SPME-GC-MS and UV-Vis Spectrophotometry. The obtained results reveals that some relationships were established between the VE-tongue signal, SPMEGC-MS and UV-Vis spectrophotometry methods to predict safranal concentration levels in saffron samples by using the PLS model. In the light of these results, we can say that the proposed electronic system offer a fast, simple and efficient tool to recognize the declared geographical origin of the saffron samples.
Microorganisms accumulate molar concentrations of compatible solutes like ectoine to prevent proteins from denaturation. Direct structural or spectroscopic information on the mechanism and about the hydration shell around ectoine are scarce. We combined surface plasmon resonance (SPR), confocal Raman spectroscopy, molecular dynamics simulations, and density functional theory (DFT) calculations to study the local hydration shell around ectoine and its influence on the binding of a gene-S-protein (G5P) to a single-stranded DNA (dT(25)). Due to the very high hygroscopicity of ectoine, it was possible to analyze the highly stable hydration shell by confocal Raman spectroscopy. Corresponding molecular dynamics simulation results revealed a significant change of the water dielectric constant in the presence of a high molar ectoine concentration as compared to pure water. The SPR data showed that the amount of protein bound to DNA decreases in the presence of ectoine, and hence, the protein-DNA dissociation constant increases in a concentration-dependent manner. Concomitantly, the Raman spectra in terms of the amide I region revealed large changes in the protein secondary structure. Our results indicate that ectoine strongly affects the molecular recognition between the protein and the oligonudeotide, which has important consequences for osmotic regulation mechanisms.
A pilot study for the quantitative surface analysis of multi-element alloy films has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study is to ensure the equivalency in the measurement capability of national metrology institutes for the quantification of multi-element alloy films. A Cu(In,Ga)Se2 (CIGS) film with non-uniform depth distribution was chosen as a representative multi-element alloy film. The atomic fractions of the reference and the test CIGS films were certified by isotope dilution - inductively coupled plasma/mass spectrometry. A total number counting (TNC) method was used as a method to determine the signal intensities of the constituent elements, which are compared with their certified atomic fractions. The atomic fractions of the CIGS films were measured by various methods, such as Secondary Ion Mass Spectrometry (SIMS), Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-Ray Fluorescence (XRF) analysis and Electron Probe Micro Analysis (EPMA) with Energy Dispersive X-ray Spectrometry (EDX). Fifteen laboratories from eight National Metrology Institutes (NMIs), one Designated Institute (DI) and six non-NMIs participated in this pilot study. Although the average atomic fractions of 18 data sets showed rather poor relative standard deviations of about 5.5 % to 6.8 %, they were greatly improved to about 1.5 % to 2.2 % by excluding 5 strongly deviating data sets from the average atomic fractions. In this pilot study, the average expanded uncertainties of SIMS, XPS, AES, XRF and EPMA were 3.84%, 3.68%, 3.81%, 2.88% and 2.90%, respectively. These values are much better than those in the key comparison K-67 for composition of a Fe-Ni alloy film. As a result, the quantification of CIGS films using the TNC method was found to be a good candidate as a subject for a CCQM key comparison.
Endosulfan – an agricultural insecticide and banned by Stockholm Convention – is produced as a 2:1 to 7:3 mixture of isomers endosulfan I (ESI) and endosulfan II (ESII). Endosulfan is transformed under aerobic conditions into endosulfan sulfate (ESS). The study shows for 76 sampling locations in German forests that endosulfan is abundant in all samples with an opposite ratio between the ESI and ESII than the technical product, where the main metabolite ESS is found with even higher abundance. The ratio between ESI/ESII and ESS show clear dependence on the type of stands (coniferous vs. deciduous) and humus type and increases from deciduous via mixed to coniferous forest stands. The study argues for a systematic monitoring of ESI, ESII, and ESS and underlines the need for further research, specifically on the fate of endosulfan including biomagnifications and bioaccumulation in soil.
Molecular imaging of inflammatory lung diseases, such as asthma, has been limited to date. The recruitment of innate immune cells to the airways is central to the inflammation process. This study exploits these cells for imaging purposes within the lung, using inhaled polystyrene nanoparticles loaded with the near-infrared fluorescence dye Itrybe (Itrybe-NPs). By means of in vivo and ex vivo fluorescence reflectance imaging of an ovalbumin-based allergic airway inflammation (AAI) model in hairless SKH-1 mice, we show that subsequent to intranasal application of Itrybe-NPs, AAI lungs display fluorescence intensities significantly higher than those in lungs of control mice for at least 24 h. Ex vivo immunofluorescence analysis of lung tissue demonstrates the uptake of Itrybe-NPs predominantly by CD68+CD11c+ECF-L+MHCIIlow cells, identifying them as alveolar M2 macrophages in the peribronchial and alveolar areas. The in vivo results were validated by confocal microscopy, overlapping tile analysis, and flow cytometry, showing an amount of Itrybe-NP-containing macrophages in lungs of AAI mice significantly larger than that in controls. A small percentage of NP-containing cells were identified as dendritic cells. Flow cytometry of tracheobronchial lymph nodes showed that Itrybe-NPs were negligible in lung draining lymph nodes 24 h after inhalation. This imaging approach may advance preclinical monitoring of AAI in vivo over time and aid the investigation of the role that macrophages play during lung inflammation. Furthermore, it allows for tracking of inhaled nanoparticles and can hence be utilized for studies of the fate of potential new nanotherapeutics.
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been suggested as a promising tool for the investigation of pollen, but the usefulness of this approach for classification and identification of pollen species has to be proven by an application to samples of varying taxonomic relations.
The analytical utility of a new and simple to use ionization method, matrix-assisted ionization (MAI), coupled with ion mobility spectrometry (IMS) and mass spectrometry (MS) is used to characterize a 2-armed europium(III)-containing poly(ethylene glycol) (Eu-PEG) complex directly from a crude sample. MAI was used with the matrix 1,2-dicyanobenzene, which affords low chemical background relative to matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI). MAI provides high ion abundance of desired products in comparison to ESI and MALDI. Inductively coupled plasma-MS measurements were used to estimate a maximum of 10% of the crude sample by mass was the 2-arm Eu-PEG complex, supporting evidence of selective ionization of Eu-PEG complexes using the new MAI matrix, 1,2-dicyanobenzene. Multiply charged ions formed in MAI enhance the IMS gas-phase separation, especially relative to the singly charged ions observed with MALDI. Individual components are cleanly separated and readily identified, allowing characterization of the 2-arm Eu-PEG conjugate from a mixture of the 1-arm Eu-PEG complex and unreacted starting materials. Size-exclusion chromatography, liquid chromatography at critical conditions, MALDI-MS, ESI-MS, and ESI-IMS-MS had difficulties with this analysis, or failed.
Trimesoyl chloride is polycondensed with various alpha,omega'-alkanediols in dichloromethane at different concentrations using equifunctional feed ratios. As evidenced by MALDI-TOF (matrix assisted laser desorption/ionization-time of flight) mass spectrometry the soluble reaction products mainly consist of perfect multicyclic oligomers and polymers. The solphase extracted from the gels also consists of perfect multicycles. SEC (size exclusion chromatography) measurements show that both soluble reaction products and extracted solphases also contain a high molar mass fraction of perfect and nonperfect multicycles extending up to masses beyond 10 5 g mol-1. When the polycondensation is stopped after a few minutes perfect multicycles are already detectable in the reaction mixture along with functional (multi)cyclic oligomers. These results prove that at initial monomer concentrations < 0.2 mol L-1 networks and large multicyclic polymers are synthesized from functional cyclic oligomers formed in early stages of the polycondensation and not from hyperbranched polymers. This interpretation is presented as 'egg-first theory' and compared with the 'hen-first theory' of Stockmayer and Flory.
Coatings deposited by magnetron co-sputtering from a single RF magnetron with a ceramic SnO2 target with iron inset in argon plasma were studied. The mass spectra of the process identified Sn+ and SnO+ species as the dominant species sputtered from the target, but no SnO2+ species were detected. The dominant positive ions in argon plasma are Ar+ species. The only detected negative ions were O-. Sputtered neutral tin related species were not detected. Iron related species were also not detected because their concentration is below the detection limit.
The concentration of iron dopant in the tin oxide coatings was controlled by the RF bias applied on the substrate holder while the discharge pressure also has some influence. The iron concentration was in the range from 0.9 at.% up to 19 at.% increasing with the substrate bias while the sheet resistivity decreases. The stoichiometry ratio of O/(Sn + Fe) in the coatings increased from 1.7 up to 2 in dependence on the substrate bias from floating bias (- 5 V) up to - 120 V of RF self-bias, respectively. The tin in the coatings was mainly bonded in Sn4 + state and iron was mainly in Fe2 + state when other tin bonding states were detected only in a small amounts. Iron bonding states in contrary to elemental compositions of the coatings were not influenced by the RF bias applied on the substrate.
The coatings showed high transparency in the visible spectral range. However, an increased metallic behavior could be detected by using a higher RF bias for the deposition. The X-ray diffraction patterns and electron microscopy pictures made on the coatings confirmed the presence of an amorphous phase.
Continuously tuneable liquid crystal based stripline phase shifter realised in LTCC technology
(2015)
This work presents the design, fabrication and measurements of a low temperature cofired ceramic (LTCC) integrated liquid crystal (LC) phase shifter. The effective permittivity of the phase shifter and therefore its differential phase shift can be tuned continuously by orienting the LC directors with electric fields. The phase-shift demonstrator is designed for Ka-band frequencies around 30 GHz and represents a stripline filled with LC, embedded inside an LTCC multilayer structure, which provides a space-qualified and hermetically-sealed LC cavity within an RF-capable material system. The total length of the device is 37 mm while the phase shifting LC section has a length of 14.6 mm. At 30 GHz it exhibits a differential phase shift of 60° with an insertion loss around 6 dB, resulting in a figure of merit around 10°/dB. An advantage is that the insertion loss is nearly independent of the tuning state of the LC. The response time of the phase shifter, depending on the desired LC orientation, is between 62 ms and 37 s.
As polypeptoids become increasingly popular, they present a more soluble and processable alternative to natural and synthetic polypeptides; the breadth of their potential functionality slowly comes into focus. This report analyzes the ability of an alkyne-functionalized polypeptoid, poly(N-propargyl glycine), to crosslink upon heating. The crosslinking process is analyzed by thermal analysis (differential scanning calorimetry and thermogravimetric analysis), Fourier-transform infrared, electron paramagnetic resonance, and solid-state NMR spectroscopy. While a precise mechanism cannot be confidently assigned, it is clear that the reaction proceeds by a radical mechanism that exclusively involves the alkyne functionality, which, upon crosslinking, yields alkene and aromatic products.
Various plant compartments of a single bell pepper plant were studied to verify the variability of boron isotope composition in plants and to identify possible intra-plant isotope fractionation. Boron mass fractions varied from 9.8 mg/kg in the fruits to 70.0 mg/kg in the leaves. Boron (B) isotope ratios reported as δ11B ranged from -11.0 to +16.0 (U ≤ 1.9, k=2) and showed a distinct trend to heavier δ11B values the higher the plant compartments were located in the plant. A fractionation of Δ11Bleaf-roots = 27 existed in the studied bell pepper plant, which represents about about 1/3 of the overall natural boron isotope variation (ca. 80). Two simultaneous operating processes are a possible explanation for the observed systematic intra-plant δ11B variation: 1) B is fixed in cell walls in its tetrahedral form (borate), which preferentially incorporates the light B isotope and the remaining xylem sap gets enriched in the heavy B isotope and 2) certain transporter preferentially transport the trigonal 11B-enriched boric acid molecule and thereby the heavy 11B towards young plant compartments which were situated distal of the roots and typically high in the plant. Consequently, an enrichment of the heavy 11B isotope in the upper young plant parts located at the top of the plant could explain the observed isotope systematic. The identification and understanding of the processes generating systematic intra-plant δ11B variations will potentially enable the use of B isotope for plant metabolism studies.
The expression of cell surface glycans terminating with sialic acid (SA) residues has been found to correlate with various disease states there among cancer. We here report a novel strategy for specific fluorescence labeling of such motifs. This is based on sialic acid-imprinted core–shell nanoparticles equipped with nitrobenzoxadiazole (NBD) fluorescent reporter groups allowing environmentally sensitive fluorescence detection at convenient excitation and emission wavelengths. Imprinting was achieved exploiting a hybrid approach combining reversible boronate ester formation between p-vinylphenylboronic acid and SA, the introduction of cationic amine functionalities, and the use of an NBD-appended urea-monomer as a binary hydrogen-bond donor targeting the SA carboxylic acid and OH functionalities. The monomers were grafted from 200 nm RAFT-modified silica core particles using ethylene glycol dimethacrylate (EGDMA) as cross-linker resulting in a shell thickness of ca. 10 nm. The particles displayed strong affinity for SA in methanol/water mixtures (K = 6.6 × 105 M-1 in 2% water, 5.9 × 103 M-1 in 98% water, Bmax ≈ 10 µmol g-1), whereas binding of the competitor glucuronic acid (GA) and other monosaccharides was considerably weaker (K (GA) = 1.8 × 103 M-1 in 98% water). In cell imaging experiments, the particles selectively stained different cell lines in correlation with the SA expression level. This was further verified by enzymatic cleavage of SA and by staining using a FITC labeled SA selective lectin.
Recently, the detection of molecular species in laser-induced breakdown spectroscopy (LIBS) has gained increasing interest, particularly for isotopic analysis. In LIBS of organic materials, it is predominantly CN and C2 species that are formed, and multiple mechanisms may contribute to their formation. To gain deeper insight into the formation of these species, laser-induced plasma of 13C and 15N labeled organic materials was investigated in a temporally and spatially resolved manner. LIBS on fumaric acid with a 13C labeled double bond allowed the formation mechanism of C2 to be investigated by analyzing relative signal intensities of 12C2, 12C13C, and 13C2 molecules. In the early plasma (<5 µs), the majority of C2 originates from association of completely atomized target molecules, whereas in the late plasma, the increased concentration of 13C2 is due to incomplete dissociation of the carbon double bond. The degree of this fragmentation was found to be up to 80% and to depend on the type of the atmospheric gas. Spatial distributions of C2 revealed distinct differences for plasma generated in nitrogen and argon. A study of the interaction of ablated organics with ambient nitrogen showed that the ambient nitrogen contributed mainly to CN formation. The pronounced anisotropy of the C15N to C14N ratio across the diameter of the plasma was observed in the early plasma, indicating poor initial mixing of the plasma with the ambient gas. Overall, for accurate isotope analysis of organics, LIBS in argon with relatively short integration times (<10 µs) provides the most robust results. On the other hand, if information about the original molecular structure is of interest, then experiments in nitrogen (or air) with long integration times appear to be the most promising.
Under the assumption of local thermal equilibrium, a numerical algorithm is proposed to find the equation of state for laser-induced plasmas (LIPs) in which chemical reactions are permitted in addition to ionization processes. The Coulomb interaction in plasma is accounted for by the DebyeHückel method. The algorithm is used to calculate the equation of state for LIPs containing carbon, silicon, nitrogen, and argon. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules N2 ,C2 ,Si2 ,CN,SiN,SiC and their ions. The algorithm is incorporated into a fluid dynamic numerical model based on the NavierStokes equations describing an expansion of LIP plumes into an ambient gas. The dynamics of LIP plumes obtained by the ablation of SiC, solid silicon, or solid carbon in an ambient gas containing N2 and Ar is simulated to study formation of molecules and molecular ions.
Raman microspectroscopy provides the means to obtain local orientations on polycrystalline materials at the submicrometer level. The present work demonstrates how orientation-distribution maps composed of Raman intensity distributions can be acquired on large areas of several hundreds of square micrometers. A polycrystalline CuInSe2 thin film was used as a model system. The orientation distributions are evidenced by corresponding measurements using electron backscatter diffraction (EBSD) on the same identical specimen positions. The quantitative, local orientation information obtained by means of EBSD was used to calculate the theoretical Raman intensities for specific grain orientations, which agree well with the experimental values. The presented approach establishes new horizons for Raman microspectroscopy as a tool for quantitative, microstructural analysis at submicrometer resolution.
New V-shaped non-centrosymmetric dyes, possessing a strongly electron-deficient azacyanine core, have been synthesized based on a straightforward two-step approach. The key step in this synthesis involves palladium-catalysed cross-coupling of dibromo-N,N'-methylene-2,2'-azapyridinocyanines with arylacetylenes. The resulting strongly polarized π-expanded heterocycles exhibit green to orange fluorescence and they strongly respond to changes in solvent polarity. We demonstrate that differently electron-donating peripheral groups have a significant influence on the internal charge transfer, hence on the solvent effect and fluorescence quantum yield. TD-DFT calculations confirm that, in contrast to the previously studied bis(styryl)azacyanines, the proximity of S1 and T2 states calculated for compounds bearing two 4-N,N-dimethylaminophenylethynyl moieties establishes good conditions for efficient intersystem crossing and is responsible for its low fluorescence quantum yield. Non-linear properties have also been determined for new azacyanines and the results show that depending on peripheral groups, the synthesized dyes exhibit small to large two-photon absorption cross sections reaching 4000 GM.
Gradient porous silicon nitride (Si3N4) was fabricated by a novel vacuum foaming and freeze drying process. Aqueous Si3N4 slurries were foamed at vacuum pressure of 50–90 kPa, the green body was obtained by the freeze drying process, a gradient pore structure with porosities of 72–90% was achieved after pressureless sintering at 1680 °C. The porosity was increased with decreasing vacuum pressure. The pore structure consists of large pores (~100 μm) on top, medium pores (~45 μm) on the wall of the large pores, and small pores (~0.7 μm) in the matrix. Such gradient porous Si3N4 with macro- and micro-pores has potential application as high temperature filters.
Room temperature mechanical behavior of extruded Mg–Y–Zn alloys with varying fractions of LPSO phase was studied in tension and compression along the extrusion direction. The microstructure is characterised by elongated LPSO fibers along the extrusion direction within the magnesium matrix. Moreover, the magnesium matrix presents a bimodal grain structure with dynamically-recrystallized grains and deformed, elongated grains with the basal plane parallel to the extrusion direction. The beginning of plasticity depends on the volume fraction of deformed and DRX grains. Alloys with low volume fraction of LPSO phase (<10 vol%), with a high volume fraction of deformed grains, show the typical behavior of extruded magnesium alloys where yield stress in tension is higher than in compression. This effect is, however, reversed as the volume fraction of the LPSO phase increases since DRX grains are majority.
Different electronic sensor systems coupled with multivariate data analysis were applied to characterize and classify seven saffron samples and to verify their declared geographical origin. The proposed electronic sensing consists of a low-cost electronic nose (E-nose) based on metal oxide semiconductor sensors and a voltammetric electronic tongue (VE-tongue) based on voltammetric sensors. The ability of multivariable analysis methods such as Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Support Vector Machines (SVMs) to classify the saffron samples according to their geographical origin have been investigated. Both PCA and HCA have shown an overlapping of E-nose responses. Moreover, the SVM analysis of the E-nose database reached a 66.07% success rate in the recognition of the saffron sample odour. On the other hand, good discrimination has been reached using PCA and HCA in the VE-tongue characterization case, besides a 100% accuracy in the saffron flavour recognition was attained. To validate the proposed electronic sensing systems, analytical chemical methods such as SPME-GC-MS and UV-Vis spectrophotometry were used. These analytical methods could be helpful tools to identify the composition of volatile compounds of the analysed saffron samples. Moreover, UV-Vis spectrophotometry was also used to determine the non-volatile profile of the samples from different geographic origins. It is demonstrated that the electronic sensing systems' findings are in a satisfactory correlation with the analytical methods. In the light of these results, we might say that the electronic systems offer a fast, simple and efficient tool to recognize the declared geographical origin of the saffron samples.
Fiber optic sensors have gained increasing importance in recent years and are well established in many areas of industrial applications. In this paper, we introduce a concept of a self-diagnostic fiber optic sensor. The presented sensor is to resolve the problems of embedded fiber optic sensors in complex structures and to enable the validation under operational conditions. For this purpose, different magnetostrictive coated fiber optic sensors were developed and various experiments were performed to verify their mode of operation and to determine the respective reproducibility. The measuring principle is illustrated by obtained experimental results, which showed a change in wavelength from 1 pm at a magnetic field strength change of 0.25 mT. In addition, the temperature characteristics of the implemented magnetostrictive sensor were analyzed and an experimental factor of 1.5 compared to a reference fiber optic sensor was determined.
Lewis and Brønsted sites were quantified in a series of weak acidic hydroxylated magnesium fluorides by Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance spectroscopy (NMR) with pyridine as probe molecule. Molar extinction coefficients, which are necessary for quantitative FTIR measurements, were calculated by an easy approach. It utilizes the fact that both signals, used for the quantification by FTIR, are caused by the same deformation vibration mode of pyridine. Comparison of quantitative FTIR experiments and quantification by NMR shows that concentrations of acidic sites determined by FTIR spectroscopy have to be interpreted with caution. Furthermore, it is shown that the transfer of molar extinction coefficients from one catalyst to another may lead to wrong results. Molar extinction coefficients and concentrations of acidic sites determined by FTIR spectroscopy are affected by grinding and probably the particle size of the sample. High temperature during FTIR experiments has further impact on the quantification results.
Micro structured reactors are attractive candidates for further process intensification in heterogeneous catalysis. However, they require catalytic coatings with significantly improved space-time yields compared to traditional supported catalysts. We report the facile synthesis of homogeneous nanocrystalline Pt coatings with hierarchical pore structure by electrochemical dealloying of amorphous sputter-deposited platinum silicide layers. Thickness, porosity and surface composition of the catalysts can be controlled by the dealloying procedure. XPS analysis indicates that the catalyst surface is primarily composed of metallic Pt. Catalytic tests in gas-phase hydrogenation of butadiene reveal the typical activity, selectivity and activation energy of nanocrystalline platinum. However, space time yields are about 13 to 200 times higher than values reported for Pt-based catalysts in literature. The highly open metallic pore structure prevents heat and mass transport limitations allowing for very fast reactions and reasonable stability at elevated temperatures.
The need for technological progress in bio-diagnostic assays of high complexity requires both fundamental research and constructing efforts on nano-scaled assay recognition elements that can provide unique selectivity and design-enhanced sensitivity features. Nanoparticle induced sensitivity enhancement and its application related to multiplexed capability Surface-Enhanced InfraRed Absorption (SEIRA) assay formats are well suitable for these purposes. The potential of diverse fluorophore–antibody conjugates, being chemisorbed onto low-cost gold nanoparticulate SEIRA substrates, has been explored with respect to their spectral discriminability. These novel biolabels deliver molecular SEIRA fingerprints that have been successfully analyzed by both uni- and multivariate analyzing tools, to discriminate their multiplexing capabilities. We show that this robust spectral encoding via SEIRA fingerprints opens up new opportunities for a fast, reliable and multiplexed high-end screening in biodiagnostics.
The reaction of iron chlorides with an alkaline reagent is one of the most prominent methods for the synthesis of iron oxide nanoparticles. We studied the particle formation mechanism using triethanolamine as reactant and stabilizing agent. In situ fast-X-ray absorption near edge spectroscopy and small-angle X-ray scattering provide information on the oxidation state and the structural information at the same time. In situ data were complemented by ex situ transmission electron microscopy, wide-angle X-ray scattering and Raman analysis of the formed nanoparticles. The formation of maghemite nanoparticles (γ-Fe2O3) from ferric and ferrous chloride was investigated. Prior to the formation of these nanoparticles, the formation and conversion of intermediate phases (akaganeite, iron(II, III) hydroxides) was observed which undergoes a morphological and structural collapse. The thus formed small magnetite nanoparticles (Fe3O4) grow further and convert to maghemite with increasing reaction time.
While polymorphism is a common phenomenon in the crystallization processes of organic compounds, polyamorphism has gained importance only recently. Using sophisticated sample environments and applying in situ scattering methods and vibrational spectroscopy, the complete crystallization process of organic compounds from solution can be traced and characterized. Diffuse scattering from amorphous intermediates can be investigated by analyzing the atomic pair distribution function (PDF) to gain further insights into molecular pre-orientation. The crystallization behavior of paracetamol was studied exemplarily under defined, surface-free conditions. Based on the choice of the solvent, the formation of different polymorphs is promoted. The thermodynamically stable form I and the metastable orthorhombic form II could be isolated in pure form directly from solution. For both polymorphs, the crystallization from solution proceeds via a distinct amorphous precursor phase. PDF analyses of these different amorphous states indicate a specific pre-orientation of the analyte molecules introduced by the solvent. The resulting crystalline polymorph is already imprinted in these proto-crystalline precursors. Direct experimental evidence for the polyamorphism of paracetamol is provided.
Porous polymer membranes made via electrostatic complexation are fabricated from a water-soluble poly(ionic liquid) (PIL) for the first time. The porous structure is formed as a consequence of simultaneous phase separation of the PIL and ionic complexation with an acid, which occurred in a basic solution of a nonsolvent for the PIL. These membranes have a stimuli-responsive porosity, with open and closed pores in isopropanol and in water, respectively. This property is quantitatively demonstrated in filtration experiments, where water is passing much slower through the membranes than isopropanol.
An ionization scheme for fast online mass spectrometric interrogation of levitated droplets is presented. That renewed method comprises the output of an a Er:YAG laser at λ = 2.94 µm which is in resonance with the OH stretch vibration band of solvents like water and alcohols. A temporal pulse width larger than the time needed for pressure redistribution and also above the temperature redistribution time constant was found to lead to soft evaporation/ionization. Despite these mild desorption conditions, no additional postionization is found to be needed. Accordingly, the ionization is found to be very soft resulting in entirely intact analyte ions and concentration dependent cluster ions. Resulting mass spectra of small amino acids and large antibiotics are presented showing the versatility of the introduced technique. Above a critical mass of m ≈ 1 kDa, the formed ions carry multiple charges as it is typical for thermospray or electrospray ionization. The detection technique enables fast contactless analysis of the chemical composition of levitated microreactors and, thus, paves the way for future contactless reaction monitoring.
Metal organic vapor phase epitaxy (MOVPE) of Mn-rich (Mn,Ga)As on (001) oriented GaAs wafers resulted in atomically ordered (Mn,Ga)As crystallites of two morphological kinds, partially embedded on the wafer surface and fully embedded within the single crystalline matrix. While the former were apparently free of defects (other than unavoidable point defects), the latter contained two domains separated by a grain boundary. Since atomic ordering can be modeled by space group symmetry descent considerations (Bärnighausen trees) that start with the space group of the known crystallographic phases of random (Mn,Ga)As alloys with specified chemical compositions, reasonable structure hypotheses have been derived for two atomically ordered Mn0.75Ga0.25As phases that we call the trigonal α' and the monoclinic β' phases. The implications of these structure hypotheses are in agreement with the results of a range of scanning transmission electron microscopy (STEM) and parallel illumination electron diffraction (ED) studies that include quantitative energy dispersive X-ray spectroscopy, X-ray spectroscopic imaging, as well nanobeam diffraction and high angle precession ED. The coexistence of two domains within the fully embedded crystallites is predicted by the corresponding Bärnighausen tree and observed experimentally for the fully embedded crystallites.
Partial penetration welding with a fiber laser at a 9-kW laser power was carried out on 20-mm-thick plates at different positions and analyzed by both experimental and numerical methods. Experiments were carried out for four different angular positions at 1.5 m/min welding speed. All four cases showed a tail-like structure of molten pool on the top surface. The in-depth mechanisms of the energy input characteristics in fiber laser position welding for eight different positions were studied by numerical simulation using the volume-of-fluid (VOF) method. Experimental and numerical results were compared for four cases and showed fair agreement. Observation of flow pattern and bead shape revealed that gravity had little influence on bead shape and flow structure, but changed the pore structure considerably. Flow structure showed a periodic behavior which probably nullified the effect of gravity in position welding. Most of the laser rays reached the bottom of the keyhole without interruption and then multiple reflections started within the keyhole. The first five reflections inside the keyhole delivered around 70 % of the total energy.
The fire behaviour of light-weight material used in structural applications is regarded as the main challenge to be solved for mass transportation. The task is to perform realistic experiments, including a mechanical test scenario under fully developed fires, to improve the material's reliability in structural applications. Our approach utilises an intermediate-scale test set-up (specimen size 500 × 500 mm) to apply realistic compressive loads and fully developed fires directly to one side of a carbon-fibre-reinforced sandwich composite. Three different intumescent coatings were applied to sandwich structures and compared to a bench-scale study. The results emphasise intumescent coatings as a promising method to sustain fire resistance, multiplying the time to failure. Nevertheless, the realistic intermediate-scale test using severe direct flame application underlines the extremely short failure times when the actual composite components are tested without any additional insulation.
Location estimation and navigation, especially on smartphones has shown great progress in the past decade due to its low cost and ability to work without additional infrastructure. However, a challenge is the positioning, both in terms of step detection, step length approximation as well as heading estimation, which must be accurate and robust, even when the use of the device is varied in terms of placement or orientation. In this paper, we propose a scheme for retrieving relevant information to detect steps and to estimate the correct step length from raw inertial measurement unit (IMU) data. This approach uses Bidirectional Long Short-Term Memory Recurrent Neural Networks (BLSTM-RNNs). Designed to take contextual information into account, the network can process data gathered from different positions, resulting in a system, which is invariant with respect to transformation and distortions of the input patterns. An experimental evaluation on a dataset produced from 10 individuals demonstrates that this new approach achieves significant improvements over previous attempts and increase the current state-of-the-art results even in the presence of variations and degradations. We achieved a mean classification rate of 98.5% and a standard deviation of 0.70 for 10000 different test sequences and an average error of 1.45% regarding the step length. Thus is the best result on the task gathered in the experiments compared with competing techniques.
Nitrogen- and oxygen-based plasma polymer films are materials with a complex and partially elusive surface chemistry. We present an overview of innovative and established X-ray photoelectron spectroscopy (XPS)-based analysis strategies developed to elucidate the surface chemistry of such films. We focus on both experimental methods and data analysis strategies and include the following topics: high-resolution spectra curve fitting, aging, chemical derivatization, and depth profiling by angle- and energy-resolved XPS.
The safety of components or constructions is of great importance in the manufacturing and processing of metallic materials. Solidification cracking as well as the weldability of materials remain still for many years a highly contentious issues, particularly with regard to the causes of the hot crack formation. Many of studies have been conducted to determine the critical condition of occurrence of the solidification cracking. In this study different digital image correlation measuring techniques in conjunction with laser diodes as the illuminating source have been employed to measure the arising strain field during the laser welding process at the surface of the workpiece directed to the laser beam in the close vicinity of the weld pool. The Controlled Tensile Weldability test (CTW) was used to apply an external tensile load during the laser beam welding in order to generate the solidification cracks. The results showed that by means of those techniques it is possible to measure the strain field without any disturbances from the intense welding light or the smoke. Additionally, the strain and the strain rate as a critical factor determining solidification crack formation can be measured and analyzed.
Probing local pH-based precipitation processes in self-assembled silica-carbonate hybrid materials
(2015)
Crystallisation of barium carbonate in the presence of silica can lead to the spontaneous assembly of highly complex superstructures, consisting of uniform and largely co-oriented BaCO3 nanocrystals that are interspersed by a matrix of amorphous silica. The formation of these biomimetic architectures (so-called silica biomorphs) is thought to be driven by a dynamic interplay between the components, in which subtle changes of conditions trigger ordered mineralisation at the nanoscale. In particular, it has been proposed that local pH gradients at growing fronts play a crucial role in the process of morphogenesis. In the present work, we have used a special pH-sensitive fluorescent dye to directly trace these presumed local fluctuations by means of confocal laser scanning microscopy. Our data demonstrate the existence of an active region near the growth front, where the pH is locally decreased with respect to the alkaline bulk solution on a length scale of few microns. This observation provides fundamental and, for the first time, direct experimental support for the current picture of the mechanism underlying the formation of these peculiar materials. On the other hand, the absence of any temporal oscillations in the local pH another key feature of the envisaged mechanism challenges the notion of autocatalytic phenomena in such systems and raises new questions about the actual role of silica as an additive in the crystallisation process.
Among the large number of new ambient ionization schemes in the last few years, dielectric barrier discharge (DBD) has witnessed special attention. In this contribution a versatile dual mode DBD is introduced and characterized by means of optical emission spectroscopy and time-of-flight mass spectrometry. A direct comparison of the individual results from spectroscopy, spectrometry and transient current/voltage consumption gives evidence for the existence of two individual operational mechanisms. The first is driven by rapid transient changes in the potential difference between the two electrodes over time (usually denoted as the homogeneous mode), while the second is caused at high static potential differences (leading to filamentary discharges). The transient versus steady-state characteristics of the individual discharge origin suggest the driving force for the current flow to be inductive and capacitive, respectively. In most cases of dielectric barrier plasmas both discharge types coexist as competitive ion formation channels, however, detailed plasma characteristics of DBDs operated under different conditions allow for a clear distinction of the individual contributions. In this way, two characteristic product channels for the ionization of ambient water could be observed resulting in the generation of either preferentially protonated water clusters or ammonium water clusters. Careful tuning of the operation parameters of the discharge device allows an operation predominated by either of the two modes. As a consequence, facile switching into the desired operational mode results in either protonated molecules or ammoniated molecules of the analyte. Plasma characteristics for both moieties were evaluated and cross-correlated on the basis of several factors including: the production of reagent ions, the individual appearance of current/voltage profiles, UV/Vis spectroscopy, voltage and flux dependence and the individual response to test compounds. Although the filamentary mode has been already discussed in the literature to induce fragmentation processes, no experimental evidence for analyte dissociation could be found in the case of the test compounds used
Bright, long-lived emission from first-row transition-metal complexes is very challenging to achieve. Herein, we present a new strategy relying on the rational tuning of energy levels. With the aid of the large N-Cr-N bite angle of the tridentate ligand ddpd (N,N′-dimethyl-N,N′-dipyridine-2-ylpyridine-2,6-diamine) and its strong σ-donating capabilities, a very large ligand-field splitting could be introduced in the chromium(III) complex [Cr(ddpd)2]3+, that shifts the deactivating and photoreactive 4T2 state well above the emitting 2E state. Prevention of back-intersystem crossing from the 2E to the 4T2 state enables exceptionally high near-infrared phosphorescence quantum yields and lifetimes for this 3d metal complex. The complex [Cr(ddpd)2](BF4)3 is highly water-soluble and very stable towards thermal and photo-induced substitution reactions and can be used for fluorescence intensity- and lifetime-based oxygen sensing in the NIR.
A novel method for the determination of phomopsin A (1) in lupin flour, pea flour, and bean flour as well as whole lupin plants was established based on stable isotope dilution assay (SIDA) LC-MS/MS using 15N6-1 as an isotopically labeled internal standard. Artificially infected samples were used to develop an optimized extraction procedure and sample pretreatment. The limits of detection were 0.5–1 µg/kg for all matrices. The limits of quantitation were 2–4 µg/kg. The method was used to analyze flour samples generated from selected legume seeds and lupin plant samples that had been inoculated with Diaporthe toxica and two further fungal strains. Finally, growing lupin plants infected with D. toxica were investigated to simulate a naturally in-field mycotoxicosis. Toxin levels of up to 10.1 µg/kg of 1 were found in the pods and 7.2 µg/kg in the stems and leaves.
Specific drug formulation additives: Revealing the impact of architecture and block length ratio
(2015)
Combining poly(ethylene glycol) (PEG) with sequence-defined peptides in PEG–peptide conjugates offers opportunities to realize next-generation drug formulation additives for overcoming undesired pharmacological profiles of difficult small molecule drugs. The tailored peptide segments provide sequence-specific, noncovalent drug binding, and the hydrophilic PEG block renders the complexes water soluble. On the basis of a peptide sequence known to bind the photosensitizer m-tetra(hydroxyphenyl)chlorin (m-THPC) for photodynamic cancer therapy, a set of different conjugate architectures is synthesized and studied. Variations in PEG block length and amplification of the peptidic binding domain of PEG–peptide conjugates are used to fine tune critical parameters for hosting m-THPC, such as drug payload capacities, aggregation sizes, and drug release and activation kinetics.
Thermal decomposition of AIBN Part A: Decomposition in real scale packages and SADT determination
(2015)
In this paper the thermal decomposition of 2,2′-azobisisobutyronitrile (AIBN) was investigated in real scale packages of different sizes and in 500 mL Dewar vessels. Packages containing 5 kg, 20 kg and 50 kg of AIBN have been investigated according to the UN test H.1 method and the 500 mL Dewar experiments were performed according to the UN test H.4 method. The self-accelerating decomposition temperature (SADT) was determined for the different masses and for the 500 mL Dewar vessel. Additionally, DSC curves have been recorded in closed crucibles. All these experimental data are the basis of a series of forthcoming papers dealing with the simulation of the SADT for different masses using reliable kinetic data.
Three strategies to sample volatile organic compounds (VOC) from lung cancer cell lines cultured in vitro were compared. Headspace solid phase microextraction was applied in situ to culture flasks and alternatively to subsamples of headspace gas or to nutrient solution subsamples followed by gas chromatography–mass spectrometry. The direct quantification of 55 VOC in the headspace of cell cultures was validated and is discussed with respect to reproducibility and system-related interferences. The role of the VOC background from culture media and usually employed polystyrene culture vessels is examined and was seen to invoke potentially misleading conclusions. The commercial A549 and two further adenocarcinoma cell lines displayed largely similar VOC profiles with distinct differences regarding certain individual substances. There is evidence for the inappropriateness of the standard cell culturing methods in the search for volatile cancer markers.
Residual stresses are often the cause for cracks in weld constructions. That is why the residual stress level, induced by manufacturing process, plays a crucial role. The present study aims on the effect of multiple repair weld procedures on a high-strength structural steel S690QL. The widespread technology of carbon arc-air gouging was applied. The weld zone and the heat-affected zone (HAZ) were subjected to multiple thermal cycles by gouging and subsequent repair welding. The investigations were focused on the change of the residuals stresses, the impact on the microstructure and the changes for the mechanical properties of the repair welded joint. The residual stresses were determined by X-ray diffraction. The results have shown a significant dependence for the residual stress levels from the repair cycle. In addition, distinctive changes in microstructures and hence mechanical properties occurred. The fusion line of the repair weld and the adjacent HAZ are the most critical areas. This is where the loss of ductility is most pronounced.
Stir bar sorptive extraction (SBSE) and solid phase microextraction (SPME) are well-established sample preparation methods for the analysis of polycyclic aromatic hydrocarbons in aqueous samples. However, complex matrices especially characterized by slurry particles and dissolved organic matter (DOM) can hamper the extraction of PAH with both SBSE and SPME and lead to different results. Thus, we produced aqueous eluates from PAH-contaminated soils differing in particle size distribution and organic matter content and determined the PAH concentration in the eluates with both SBSE and SPME. Furthermore, we tested the influence of filtration on the PAH analysis. The excess finding of PAH with SBSE compared to SPME ranged from −16.6 to 24.5 %. The differences increased after filtration. We found a strong positive correlation of the excess finding to the total organic carbon content (TOC) and a negative one to the pH value. The results indicate that SBSE is less affected by complex matrices than SPME.
Life Cycle Assessment (LCA) is applied in evaluating environmental impacts of state-of-the-art welding technologies. Manual Metal Arc Welding (MMAW), Laser Arc-Hybrid Welding (LAHW) and two Gas Metal Arc Welding (GMAW) variants are used to join a plate of 20 mm thick structural steel. The LCA results indicate that for 1 m weld seam, MMAW causes the highest environmental impacts in global warming potential (GWP), eutrophication potential (EP), acidification potential (AP), and photochemical ozone creation potential (POCP) among the selected processes, and the LAHW variant performances the least. Filler material and electricity consumptions generally dominate the impacts and reach shares of up to 80% and 61% in the respective impact categories. However, electrode coating consumption in MMAW remarkably contributes impacts on AP and EP, for instance 52% of AP and 76% of EP. Strategies for improvement of the applied welding technologies are discussed.
Effect of fluorescent staining on size measurements of polymeric nanoparticles using DLS and SAXS
(2015)
The influence of fluorescence on nanoparticle size measurements using dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) was investigated. For this purpose, two series of 100 nm-sized polymer nanoparticles stained with different concentrations of the fluorescent dyes DY555 and DY680 were prepared, absorbing/emitting at around 560 nm/590 nm and 695 nm/715 nm, respectively. SAXS measurements of these particle series and a corresponding blank control (without dye) revealed similar sizes of all particles within an uncertainty of 1 nm. DLS measurements carried out at three different laboratories using four different DLS instruments and two different laser wavelengths, i.e., 532 nm and 633 nm, revealed also no significant changes in size (intensity-weighted harmonic mean diameter, ZAverage) and size distribution (polydispersity index, PI) within and between the two dye-stained particle series and the blank sample. Nevertheless, a significant decrease of the detected correlation coefficients was observed with increasing dye concentration, due to the increased absorption of the incident light and thus, less coherent light scattering. This effect was wavelength dependent, i.e. only measurable for the dye-stained particles that absorb at the laser wavelength used for the DLS measurements.
The objective was to find out whether an explosive atmosphere can be created in a freight container by gaseous leakage flow of vapour-air-mixture through leaks in the closures of dangerous goods packagings filled with hazardous liquids. Because of high temperatures during intercontinental carriage, there is a gauge pressure in the free vapour phase inside the packagings which can cause a gaseous leakage flow. Two different methods were applied:
Helium limit leakage rates for 23 quantitatively important hazardous liquids concerning their lower explosion limit (LEL) were calculated for a worst case transport scenario (Method 1).
Helium leakage rates of five closure types of dangerous goods packagings with volumes of approximately 6 l were measured using the pressure technique by accumulation (Method 2).
All types of closures of steel packagings were uncritical. The maximum measured leakage was 33% of the limit leakage rate. The leakage rates of screw closures of plastic jerricans can exceed the LEL if there are production-related patterns such as non-concentricity of the closures and flashes on the neck. Especially for plastic packagings it is important to minimize gaseous leakage flow, because an explosive atmosphere can also be reached by permeation of the individual filling substance or by a combination of both effects. For the assessment of potentially explosive mixtures in freight containers, both mass transfer mechanisms have to be taken into account.
The surface charge density of nanoparticles plays an important role in the way they interact with biological systems. The ability to measure the surface charge density of nanoparticles in biological media is therefore of importance in understanding the magnitude of such interactions. There are a number of methods which may be used to assess surface charge density through the measurement of electrophoretic mobility. In order to better understand the comparability of these methods, the ζ-potential of silica nanoparticles in water, buffer and serum-based biological medium was measured by one ensemble and two particle-by-particle techniques: electrophoretic light scattering (ELS), tunable resistive pulse sensing (TRPS) and zeta particle tracking analysis (z-PTA). To allow the comparability of results from different techniques, test samples were prepared according to an established protocol, although some variations were necessary to meet specific instrument requirements. Here we compare, for the first time, measurement results from the different techniques and discuss how modifications related to parameters such as environmental pH, dilution factor and presence of biomolecules influence the charge measurements.
This paper describes the production and characteristics of the nanoparticle test materials prepared for common use in the collaborative research project NanoChOp (Chemical and optical characterization of nanomaterials in biological systems), in casu suspensions of silica nanoparticles and CdSe/CdS/ZnS quantum dots (QDs). This paper is the first to illustrate how to assess whether nanoparticle test materials meet the requirements of a "reference material" (ISO Guide 30, 2015) or rather those of the recently defined category of "representative test material (RTM)" (ISO/TS 16195, 2013). The NanoChOp test materials were investigated with small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and centrifugal liquid sedimentation (CLS) to establish whether they complied with the required monomodal particle size distribution. The presence of impurities, aggregates, agglomerates, and viable microorganisms in the suspensions was investigated with DLS, CLS, optical and electron microscopy and via plating on nutrient agar. Suitability of surface functionalization was investigated with attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and via the capacity of the nanoparticles to be fluorescently labeled or to bind antibodies. Between-unit homogeneity and stability were investigated in terms of particle size and zeta potential. This paper shows that only based on the outcome of a detailed characterization process one can raise the status of a test material to RTM or reference material, and how this status depends on its intended use.
The potentials of incoherent X-ray scattering (Compton) computed tomography (CT) are investigated. The imaging of materials of very different atomic number or density at once is generally a perpetual challenge for X-ray tomography or radiography. In a basic laboratory set-up for simultaneous perpendicular Compton scattering and direct beam attenuation tomography are conducted by single channel photon counting line scans. This results in asymmetric distortions of the projection profiles of the scattering CT data set. In a first approach, corrections of Compton scattering data by taking advantage of rotational symmetry yield tomograms without major geometric artefacts. A cylindrical sample composed of PE, PA, PVC, glass and wood demonstrates similar Compton contrast for all the substances, while the conventional absorption tomogram only reveals the two high order materials. Comparison to neutron tomography
reveals astonishing similarities except for the glass component (without hydrogen). Therefore, Compton CT offers the potential to replace neutron tomography, which requires much more efforts.
Selective laser sintering of ceramic powders is a promising technique for the additive manufacturing of complex- and delicate-shaped ceramic parts. Most techniques have in common that the powder to be sintered is spread to a thin layer as a dry powder by means of a roller or shaker system. These layers have a relatively low density. On the other hand, appreciable densities can be reached with the use of ceramic slurries as the starting material. Therefore, the layer-wise slurry deposition (LSD) process has been developed. Layer stacks, i.e. powder beds, built up by employing the LSD technology exhibit a density comparable to ceramic powder compacts processed by means of conventional forming technologies. Writing the layer information with a focused laser beam in these dense ceramic powder compacts enables the manufacture of ceramic bodies with a high density and precision in contour.
Additive manufacturing (AM) is a technology which has the potential not only to change the way of conventional industrial manufacturing processes, adding material instead of subtracting, but also to create entirely new production and business strategies. Since about three decades, AM technologies have been used to fabricate prototypes or models mostly from polymeric or metallic materials. Recently, products have been introduced into the market that cannot be produced in another way than additively. Ceramic materials are, however, not easy to process by AM technologies, as their processing requirements (in terms of feedstock and/or sintering) are very challenging. On the other hand, it can be expected that AM technologies, once successful, will have an extraordinary impact on the industrial production of ceramic components and, moreover, will open for ceramics new uses and new markets.
Porous Al2O3 with high porosity (~45%), remarkable flexural strength (~70 MPa), and low dimensional change (~1–2%), was produced by indirect 3D printing and reaction bonding. Coarse Al with good flowability was carried out printing green body. The green body was heat treated to get fully oxidized, volume expansion during oxidation simultaneously formed strong neck bonding, not only brought good strength, but also restricted shrinkage. Porous Al2O3 with architecture of macro pores designed by 3D printing and micro pores in the strut formed by packing of particles was obtained. The near zero shrinkage can facilitate precise design of product with complex shape.
Laser-fused K0.5Na0.5NbO3 (KNN) powder of 75% transparent fraction has been sintered by pressureless sintering, spark plasma sintering (SPS), and hot isostatic pressing (HIP). The laser-fused KNN has a fictive temperature of 503 °C and an onset crystallization temperature of around 529 °C. The results have shown that sintering of the laser-fused KNN powder utilizing the viscous flow of the transparent microspheres (amorphous content)–at the kinetic window (26 °C)–is possible. The highest yield relative density is around 83% at a sintering temperature of 525 °C and at a sintering pressure of 280 MPa. Limited density has been reached because of formation of crystalline surface layers around the amorphous areas. The samples hipped at 525 °C have low piezoelectric coefficient d33 of 5 pC/N because of the residual porosity that led to early dielectric breakdown during the polarization. The sintering behavior, the resulting microstructure as well as the measured properties will be discussed.
Silicate bioceramics possess an excellent bioactivity; however, shaping them into complex geometries is still challenging. Therefore, this paper aims to present a new strategy for the shaping of a bioglass-ceramic with controlled geometry and properties starting from a glass powder combined with a preceramic polymer, i.e. a silicon resin, and reactive fillers. The powder-based three-dimensional (3D)-printing of wollastonite (CaSiO3)-based silicate bioceramic parts was demonstrated in this work. The resin plays a dual role, as it not only acts as a non-sacrificial binder for the filler powders in the printing process but it also reacts with the fillers to generate the desired bioceramic phases. The mechanical and physical properties, i.e. ball-on-three-balls test, density, porosity and morphology, were evaluated in 3D-printed discs. These samples possessed a total porosity around 64 vol% and a biaxial flexural strength around 6 MPa. The raw materials used in this work also enabled the 3D-printing of scaffolds possessing a designed multi-scale porosity, suitable bioceramic phase assemblage and a compressive strength of 1 MPa (for cylindrical scaffolds with total porosity ~80 vol%). Solubility in TRIS/HCl and in vitro assays, i.e. viability, cytotoxicity and apoptosis assays, were also performed. In vitro tests indicated good cell viability and no cytotoxicity effect on the cells.
Porous Si3N4/SiC ceramics were prepared with Si and SiC as raw materials, Y2O3 as sintering additive and ZrO2 as nitrided catalyst through a rapid nitration process. The nitriding rate as a function of temperature and duration was investigated. The porous Si3N4/SiC ceramics with 8 wt% monoclinic ZrO2 addition that was nitrided at 1400 °C for 2 h exhibited the highest nitridation degree of 95%. The experimental results also demonstrated that the reciprocal formation of ZrO2 and ZrN can effectively enhance the level of nitridation by suppressing the melting of silicon in micro-regions. The effects of nitriding time on the mechanical properties of the specimens with ZrO2 as a catalyst was also studied. After nitrided at 1400 °C for various durations from 2 to 8 h, the porous Si3N4/SiC ceramics with the properties of a porosity over 39.8%, a flexural strength over 88.9 MPa and a linear shrinkage lower than 0.6% were achieved. The systematic investigation reveals the catalytic mechanism of ZrO2 in the synthesis of Si3N4/SiC ceramics.
2014AbstractWollastonite/apatite glass-ceramics have been successfully prepared by a novel approach, consisting of the heat treatment of a silicone resinembedding micro-sized CaCO3particles, that act as reactive fillers, and bioactive glass powder in the SiO2–CaO–P2O5–K2O–Na2O–MgO–CaF2system. Zn-containing silicates, such as hardystonite (Ca2ZnSi2O7) and willemite (Zn2SiO4), were also developed either by directly mixing ZnOpowders with the glass, or by embedding them in the preceramic polymer, as additional fillers.
Dampening of energetic properties and the effects of blending proportions of isododecane on the diffusive burning behaviour of peroxy-fuels are experimentally studied. Blended peorxy-fuels are obtained by adding isododecane in the proportions of 25 wt.%, 50 wt.% and 75 wt.%, respectively, in technical pure peroxy-fuels. The fuels were burned in form of pool fires with diameters 0.02 m ≤ d ≤ 1 m. The mass burning rates and relative flame lengths are found to be weakened with increasing diluent proportions. By measuring the mass burning rates and visible flame lengths of pool fires of different samples of fuel blends an optimum blending criterion is developed. Furthermore, it is shown that the dilution proportions and flame characteristics can be correlated by empirical equations.
Certified water reference materials are currently not available for most of the hydrophobic organic pollutants listed in the EU Water Framework Directive. To find the most suitable container type for subsequent reference material productions, feasibility studies for the preparation of waters with polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs) and tributyltin (TBT) close to environmental quality standards in water have been performed. Due to the hydrophobic nature of these compounds and their tendency to adsorb onto container walls, an adequate selection of the most appropriate material for containment, storage and transport of water reference materials is crucial. Three different materials (aluminium, amber glass and fluorinated polyethylene, FPE) and three volumes (500/600 mL, 1000/1200 mL and 2000/3000 mL, depending on commercial availability) were tested at ng L-1 level of the target compounds. FPE shows by far the highest loss of analytes due to adsorption onto the container walls for all compounds studied. Aluminium and glass are equally suited for PAHs and PBDEs, but aluminium is unsuitable as container material for TBT due to acid cleaning requirements. The volume of the containers had no dramatic effect on the adsorption behaviour of target compounds for the different volumes tested.
Two different hair reference materials, one produced from authentic hair displaying an ethyl glucuronide (EtG) content of about 25 pg/mg and one obtained by fortification of blank hair to an EtG level of 85 pg/mg were submitted to accelerated aging between 4 degrees C and 60 degrees C for periods between one and 24 months. Subsequently, the EtG content was determined in the aged samples and untreated reference samples stored at -22 degrees C under repeatability conditions following the so-called isochronous approach. The EtG content remained stable even at 40 degrees C for 24 months and at 60 degrees C over six months. This is in contrast to many organic analytes contained in trace concentrations in diverse matrices. A slight but significant increase of the recovered EtG in case of authentic hair samples having been exposed for 24 months between 4 degrees C and 60 degrees C may be due to a temperature-driven process that allows increased recoveries of the physiologically embedded EtG.
The safety assessment of casks for radioactive material at interim storage facilities or in final repositories includes the investigation of possible handling accidents if clearly defined test conditions are not available from the regulations. Specific handling accidents usually are the drop of a cask onto the transport vehicle or the floor as well as the collision with the wall of the storage building or another cask. For such load cases an experimental demonstration of cask safety would be difficult. Therefore, numerical analyses of the entire load scenario are preferred. The lessons learnt from dynamic finite element analyses of accident scenarios with thick-walled cubical containers or cylindrical casks are presented. The dependency of calculation results on initial and boundary conditions, material models, and contact conditions is discussed. Parameter sets used should be verified by numerical simulation of experimentally investigated similar test scenarios. On the other hand, decisions have to be made whether a parameter or property is modeled in a realistic or conservative manner. For example, a very small variation of the initial impact angle of a container can cause significantly different stresses and strains. In sophisticated cases an investigation of simpler limit load scenarios could be advantageous instead of analyzing a very complicated load scenario.
Die Zahl der industriellen Anwendungen mit Einsatz von Faserverbundwerkstoffen wächst kontinuierlich vor allem wegen der exzellenten Materialeigenschaften und des geringen Gewichtes dieses Werkstoffes. Entsprechend steigen die Anforderungen an zerstörungsfreie Prüfsysteme zur Gewährleistung des sicheren Betriebes von Komponenten und Strukturen bestehend aus Verbundwerkstoffen.
Im Rahmen des EU-Projekes VITCEA (Validated Inspection Techniques for Composites in Energy Applications) wird das Ziel verfolgt, neue Prüfverfahren für moderne Verbundwerkstoffe zu entwickeln und zu validieren. Im Vordergrund steht hierbei als Applikation im Industriesektor Energieversorgung die Prüfung von sicherheitsrelevanten Komponenten von onshore und offshore Windkraftanlagen, wie z.B. deren Rotorblätter und tragende Strukturen.
Eine Teilaufgabe innerhalb des Projektes stellen der Vergleich und die Validierung verschiedener Ultraschallprüfmethoden bezüglich ihrer Fähigkeit zum Nachweis der typischen Herstellungs- und betriebsbedingten Materialschädigungen von CFK und GFK dar.
Neben verschiedenen konventionellen Ultraschall-Prüftechniken, werden die Phased-Array-Prüfung, insbesondere die Prüfung mit Matrixarrays, sowie die Untersuchung mit berührüngsloser Luftultraschalltechnik bezüglich ihrer Nachweisgrenzen und der Möglichkeiten zur Fehlercharakterisierung an Faserverbundwerkstoffen untersucht. Die Ergebnisse werden mit Untersuchungen mit thermographischen Methoden und Mikrowellentechnik verglichen.
The interest in nanoparticles remains at a high level in fundamental research since many years and increasingly, nanoparticles are incorporated into consumer products to enhance their performance. Consequently, the accurate and rapid characterization of nanoparticles is more and more demanded. Electron microscopy (SEM, TSEM and TEM) is one of the few techniques which are able to image individual nanoparticles. It was demonstrated recently that the transmission electron microscopy at a SEM can successfully be applied as a standard method to characterize accurately the size (distribution) and shape of nanoparticles down to less than 10 nm.
While nano-scaled intermediate and consumer products are omnipresent in many industries, one challenge consists in the development of methods that reliably identify, characterize and quantify nanomaterials both as a substance and in various matrices. For product registration purposes, the European Commission proposed a definition for nanomaterial which requires a quantitative size determination of the primary particles in a sample down to sizes of 1 nm. According to a material is defined as nano if 50% of the primary particles are observed to comprise a smallest dimension <100 nm. The NanoDefine project was set up to develop and validate a robust, readily implementable and cost-effective measurement approach to obtain a quantitative particle size distribution and to distinguish between nano and non-nano materials according to the definition Among the available particle sizing techniques, electron microscopy was found to be one option meeting most of the requirements of the regulation. However, the use of electron microscopy for particle sizing is often limited by cost per sample, availability in industry, particle agglomeration/aggregation, extremely broad size distributions, 2D materials and operator bias in case of manual evaluation.
Tribological properties of neat polyetherimide (PEI), glass, carbon fiber, and solid lubricants filled PEI composites are presented in this article. The aim of this study was to investigate the friction and wear properties of these composites under dry oscillating sliding condition at room temperature (RT) as well as at elevated temperature (120 °C). The polymer specimens were made to oscillate against steel cylinder as a counterpart. The friction and wear properties of PEI and composites were strongly influenced by the temperature. Incorporation of carbon fiber in the PEI matrix has increased the wear rate at RT, while at elevated temperature this trend was opposite. Abrasive action of carbon fibers has severely damaged the counterpart and resulted in accelerated wear of the composite at RT. Solid lubricants filled (PTFE, MoS2, graphite) along with glass fiber is beneficial in improving the friction and wear performance of the PEI composite at RT, whereas at elevated temperature wear performance was deteriorated. Tribological performance of neat PEI and glass fiber composite was similar with each other at RT. Scanning electron micrographs and optical micrographs of the worn polymer specimens and the steel cylinders was used to study the possible wear mechanisms. The present test results were also compared with data available on the reciprocating wear of PEI and composites in the literature and trends have been reported.
The plasmon resonance of metal nanoparticles determines their optical response in the visible spectral range. Many details such as the electronic properties of gold near the particle surface and the local environment of the particles influence the spectra. We show how the cheap but highly precise fabrication of composite nanolayers by spin-assisted layer-by-layer deposition of polyelectrolytes can be used to investigate the spectral response of gold nanospheres (GNS) and gold nanorods (GNR) in a self-consistent way, using the established Maxwell–Garnett effective medium (MGEM) theory beyond the limit of homogeneous media. We show that the dielectric function of gold nanoparticles differs from the bulk value and experimentally characterize the shape and the surrounding of the particles thoroughly by SEM, AFM and ellipsometry. Averaging the dielectric functions of the layered surrounding by an appropriate weighting with the electric field intensity yields excellent agreement for the spectra of several nanoparticles and nanorods with various cover-layer thicknesses.
Because of the rising application of nanoparticles in food and food-related products, we investigated the influence of the digestion process on the toxicity and cellular uptake of silver nanoparticles for intestinal cells. The main food components – carbohydrates, proteins and fatty acids – were implemented in an in vitro digestion process to simulate realistic conditions. Digested and undigested silver nanoparticle suspensions were used for uptake studies in the well-established Caco-2 model. Small-angle X-ray scattering was used to estimate particle core size, size distribution and stability in cell culture medium. Particles proved to be stable and showed radii from 3.6 to 16.0 nm. Undigested particles and particles digested in the presence of food components were comparably taken up by Caco-2 cells, whereas the uptake of particles digested without food components was decreased by 60%. Overall, these findings suggest that in vivo ingested poly (acrylic acid)-coated silver nanoparticles may reach the intestine in a nanoscaled form even if enclosed in a food matrix. While appropriate for studies on the uptake into intestinal cells, the Caco-2 model might be less suited for translocation studies. Moreover, we show that nanoparticle digestion protocols lacking food components may lead to misinterpretation of uptake studies and inconclusive results.
The driving forces triggering the formation of co-crystals under milling conditions were investigated by using a set of multicomponent competitive milling reactions. In these reactions, different active pharmaceutical ingredients were ground together with a further compound acting as coformer. The study was based on new co-crystals including the coformer anthranilic acid. The results of the competitive milling reactions indicate that the formation of co-crystals driven by intermolecular recognition are influenced and inhibited by kinetic aspects including the formation of intermediates and the stability of the reactants.
Klärschlammaschen weisen hohe Gehalte an Phosphor auf, dieser ist allerdings schlecht für Pflanzen verfügbar. Des Weiteren enthalten sie Schwermetalle die vor dem Einsatz als Düngemittel entfernt werden müssen. Vor diesem Hintergrund wurden in den letzten Jahren nasschemische und thermochemische Verfahren entwickelt und zum Teil bereits in Demonstrationsanlagen getestet. Ein thermochemischer Verfahrensansatz wird in diesem Beitrag näher vorgestellt. Klärschlammaschen werden mit Klärschlamm als Reduktionsmittel und Natriumsulfat als Aufschlussmittel im Drehrohrofen thermisch behandelt. Bei diesem Prozess wird pflanzenverfügbares NaCaPÜ4 gebildet, unerwünschte Elemente wie As, Cd, Hg und Pb werden zum Teil über die Gasphase separiert. Die Ergebnisse eines Demonstrationsversuchs werden vorgestellt.
The industrial demand for flexible and innovative manufacturing technologies is continuously increasing. These technologies have to be sustainable and resource-efficient, and have to allow the production of long-life capital goods. Consequently, the additive processes gain in importance as they offer an enormous potential of application, especially for the turbomachinery industry.
In order to use additive manufacturing technologies in industrial applications, it is necessary to consider the complete process chain, including all necessary pre- and postprocessing. Although additive manufacturing is increasingly covered in scientific research, the linking between this technology and conventional industrial processes is rarely described.
A monitoring method is introduced that creates, in near real-time, two-dimensional (2D) maps of the soil gas distribution. The method combines linear gas sensing technology for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct spatial and temporal resolved gas distribution maps. A weighted iterative algebraic reconstruction method based on Maximum Likelihood with Expectation Maximization (MLEM) in combination with a source-by-source reconstruction approach is introduced that works with a sparse setup of orthogonally-aligned linear gas sensors. The reconstruction method successfully reduces artifact production, especially when multiple gas sources are present, allowing the discrimination between true and non-existing so-called ghost source locations. A first experimental test indicates the high potential of the proposed method for, e.g., rapid gas leak localization.
This work addresses the fatigue strength of friction-welded joints for the drive pinion in heavy-duty trucks. Three different friction welding (FW) variants were tested for the joint between the pinion and the bevel of the shaft: (1) conventional FW using series materials, (2) conventional FW from dissimilar materials for every part, and (3) dissimilar joints by applying joint-site structure of FW. Each joint variant was compared to the series production part using a 4-point bending test. Results showed that the higher strength material slightly improved the fatigue strength of the conventional friction-welded joints. Despite the light weight of the component joined structurally at the site, the joint revealed a lower endurance limit compared to other variants. However, there has been little discussion on the weld zone position. The applied equivalent stresses on the weld zone of the joint-site structure are less similar to the position for the conventional FW. Characterization of the failure explains the extraordinary behaviors in relation to S-N curves.
Grain refinement is an important opportunity to improve mechanical properties of fusion welds and the weldability (susceptibility to solidification cracking) of the base metal. In this study, grain refinement was achieved in aluminium welds through additions of grain refiner to the weld metal. Increasing grain refiner additions led to a decrease of the weld metal mean grain size (down to −86 %). The grain refinement efficiency was the highest in commercial pure Al (Alloy 1050A, Al 99.5), followed by Alloy 6082 (Al Si1MgMn) and Alloy 5083 (Al Mg4.5Mn0.7). To investigate this clear influence of alloy content on grain size, the undercooling parameters P and Q were calculated. Temperature measurements revealed that solidification parameters such as solidification growth rate or cooling rate vary significantly along the solidification front, dependent upon torch speed and alloy. On the basis of this comparison, an analytical approach was used to model the columnar to equiaxed transition (CET). Moreover, wavelength dispersive X-ray spectroscopy (WDS) and transmission electron microscopy (TEM) analyses revealed particles rich in Ti and B that are probably TiB2 particles coated by Al3Ti nucleating Al grains during solidification. Also, Ti/B contents needed in commercial filler wires to allow optimum weld metal grain refinement were calculated dependent upon base alloy and welding process.
Polypropylen (PP) ist als Niedrigenergie-Polymer ohne nass- und plasmachemische Vorbehandlung weder haftfest zu beschichten noch verbundfest zu kleben. Typische Haft- bzw. Klebfestigkeiten liegen für die unbehandelte Polymeroberfläche bei maximal 0,5 MPa. Hinzu kommt, dass bei der Bestimmung von Haft- und Klebfestigkeiten der unmodifizierten Oberfläche mit großen Streuungen zu rechnen ist, die bezogen auf die Spannweite durchaus einem Faktor 5 entsprechen können. Generell besteht bei Prüfung der Haftfestigkeit mittels Stirnabzugsversuch und bei der Prüfung der Klebfestigkeit die Notwendigkeit eines statistisch validierten Herangehens. Hierzu sind zeitaufwändige Ein-Proben-Klebungen und -Prüfungen nur eingeschränkt geeignet. Zudem ist, insbesondere für geringe Haft- bzw. Klebfestigkeiten, ein querkraftfreies Prüfen Grundvoraussetzung. Im vorliegenden Beitrag werden verschiedenartige plasmagestützte Oberflächenfunktionalisierungen von PP sowie das Mehr-Proben-Konzept zur Klebung/Prüfung von bis zu acht Proben vorgestellt. Dazu werden ein BAM-Funktionsmuster einer Mehr-Proben-Kleb-Vorrichtung und eine kommerzielle analytische Zentrifuge zum Prüfen verwendet.
Composite materials show a degradation of properties depending on Service life. This creates the necessity to find tailored methods to determine strength and residual strength of composite cylinders. The determination can be done e.g. by load cycles tests. The result needs a Statistical assessment for the precise description of strength. Especially the Statistical assessment of load cycle strength properties has a high uncertainty. It is unclear if a Log-Normal distribution, a WEIBULL distribution or others, describe the scatter behaviour of residual strength properties correctly. Distribution functions aim at approximating the frequency of occurrence of residual load cycle strength for high survival rates. An assumption has to be found and confirmed to prevent overestimation of reliability.
In this work, a routinely applicable approach is presented to characterize metal NPs. Individual droplets generated from a microdroplet generator (MDG) were merged into an aerosol generated by a pneumatic nebulizer (PN) and introduced into an ICPMS. The MDG offers high transport efficiency of individual and discrete droplets and was therefore used to establish a calibration function for mass quantification of NPs which were introduced through the PN following the single particle procedure as described elsewhere. The major advantages of such a combined configuration include fast processing of large sample volumes, fast exchanges of different sample matrixes, and the calibration of the NP signal using traceable elemental standards, thus avoiding the need to use NP reference materials or other, not always thoroughly characterized, commercially available NPs. The transport efficiency of the sample introduction is calculated based on the fact that 100% of the calibrant reaches the plasma through the MDG, whereas for the PN a NP suspension containing a known number concentration is used. Alternatively, bulk analysis of the NP material allows transport efficiency determination without any additional information from reference NPs. With this method, we could determine the size of standard silver NPs at 60.4 ± 1.0 nm and 80.0 ± 1.4 nm, respectively, which agrees with the size ranges given by the supplier (60.8 ± 6.6 nm and 79.8 ± 5.4 nm). Furthermore, we were also able to determine the NPs number concentration of the sample (Ag/Au) with a deviation of 3.2% the expected value.
Neutron tomography has been applied to investigate the mechanism of hydrogen assisted cracking in technical iron and supermartensitic steel. Rectangular technical iron block samples showed blistering due to intense hydrogen charging and the tomographic method revealed in situ the spatial distribution of hydrogen and cracks. Hydrogen accumulated in a small region around cracks and the cracks are filled with hydrogen gas. Cracks close to the surface contained no hydrogen. Hydrogenous tensile test samples of supermartensitic steel were pulled until rupture and showed hydrogen accumulations at the notch base and in the plastically deformed region around the fracture surface.
Organosilanes are used routinely to functionalize various support materials for further modifications. Nevertheless, reliable quantitative information about surface functional group densities after layer formation is rarely available. Here, we present the analysis of thin organic nanolayers made from nitrogen containing silane molecules on naturally oxidized silicon wafers with reference-free total reflection X-ray fluorescence (TXRF) and X-ray photoelectron spectroscopy (XPS). An areic density of 2−4 silane molecules per nm2 was calculated from the layer’s nitrogen mass deposition per area unit obtained by reference-free TXRF. Complementary energy and angle-resolved XPS (ER/ARXPS) in the Si 2p core-level region was used to analyze the outermost surface region of the organic (silane layer)−inorganic (silicon wafer) interface. Different coexisting silicon species as silicon, native silicon oxide, and silane were identified and quantified. As a result of the presented proof-of-concept, absolute and traceable values for the areic density of silanes containing nitrogen as intrinsic marker are obtained by calibration of the XPS methods with reference-free TXRF. Furthermore, ER/AR-XPS is shown to facilitate the determination of areic densities in (mono)layers made from silanes having no heteroatomic marker other than silicon. After calibration with reference-free TXRF, these areic densities of silane molecules can be determined when using the XPS component intensity of the silane’s silicon atom.
Pressure-assisted sintering (PAS) is an established procedure for the production of low-temperature cofired ceramics (LTCC) without lateral shrinkage and minimal shrinkage tolerances for automotive and high-frequency applications. To develop a feasible model for the prediction of densification during that process, master sintering curves (MSCs) for the commercial LTCC DP951 were generated from thermomechanical analysis (TMA) data in the pressure regime from 2 to 500 kPa. Strain mainly related to creep deformation of the LTCC was identified by evaluation of the strain rate and was discarded for the determination of MSC parameters. It was found that no creep occurred at any pressure up to a relative density of 0.9. Different pressure levels can be modeled with the same activation energy of 400 kJ/mol. Densification curves predicted by the model were in good agreement with experimental data. Based on MSCs, the pressure-assisted master sintering surface was compiled to illustrate the influence of pressure on densification. The results show that the MSC approach is a suitable method to feasibly predict the densification of LTCC during PAS.
Samples of 474 forest stands in Germany were analysed for concentrations of polycyclic aromatic hydrocarbons (PAHs) in three sampling depths. Enhanced concentrations were mainly found at spots relatively close to densely industrialized and urbanized regions and at some topographically elevated areas. Average enrichment factors between mineral soil and humic layer depend on humus type i.e. decrease from mull via moder to mor. Based on their compound-patterns, the observed samples could be assigned to three main clusters. For some parts of our study area a uniform assignment of samples to clusters over larger regions could be identified. For instance, samples taken at vicinity to brown-coal strip-mining districts are characterized by high relative abundances of low-molecular-weight PAHs. These results suggest that PAHs are more likely originated from local and regional emitters rather than from long-range transport and that specific source-regions can be identified based on PAH fingerprints.