Application of Time-Resolved Fluorescence Spectroscopy on the Analysis of PAH-Coated Aerosols

A fiberoptic sensor system was developed for the detection of PAH-coated aerosols. It incorporates a pulsed nitrogen laser for excitation and a monochromator, a photomultiplier and a digital storage oscilloscope for recording of fluorescence decay curves. With a software-realized photon counting technique detection limits less than 100 ng/m³ for most of the PAHs investigated were achieved with NaCl as a substrate (e.g., 20 ng/m³ for benzo(e)pyrene on NaCl). The sensitivity of the system decreased dramatically when PAH adsorbed on carbon aerosol were analyzed. With pyrene on polydisperse NaCl aerosol the formation of excimers was observed and the formation kinetic could be analyzed. With benzo(e)pyrene on NaCl under similar conditions excimer fluorescence was observed but not the formation kinetic. This indicates the formation of micro-crystals of PAHs on aerosol surfaces even at surface coverages Θ ?1. Due to the observed matrix effects experiments were carried out, at which the PAHs were thermally desorbed in advance of the analysis. By this PAH fluorescence was measurable with carbon as matrix.     

Development of a class-specific ELISA for sulfonylurea herbicides (sulfuron screen)

The development of a direct competitive ELISA for the detection of a broad range of sulfonylurea herbicides (SUs) is described. Polyclonal antibodies were generated in rabbits using three different immunizing haptens. Antiserum with the broadest specificity was obtained with a mesosulfuronbenzylamine derivative which was coupled via a succinic acid spacer to keyhole limpet hemocyanine. A heterologous enzyme tracer which did not contain the succinic acid bridge was prepared using activated horseradish peroxidase. The direct competitive ELISA was optimized and applied for spiked tap and surface water samples. From 30 SUs, 8 compounds showed a molar cross-reactivity (CR) higher than 100% (this value was set for the hapten) and 11 compounds CRs between 10% and 100%. The ELISA can detect 16 SUs at a concentration of 0.1 microg/L or lower. Different surface and tap water samples were spiked with chlorimuron ethyl, metsulfuron methyl, or primisulfuron methyl at concentrations of 100, 200, or 500 ng/L and subsequently analyzed by both ELISA and HPLC-UV. Correlation analysis revealed good agreement between both methods (r2 = 0.983/0.948/0.982; n = 21 for each analyte). Using ELISA, no sample pretreatment other than filtration was necessary.     

Microanalysis by laser-induced plasma spectroscopy in the vacuum ultraviolet

A new setup for microanalysis by laser-induced plasma spectroscopy in the VUV range is presented and described in detail. The system features an integrated ablation and detection module with a newly designed VUV echelle system. The echelle permits a full spectral coverage between 150 and 300 nm with a resolving power lambda/Deltalambda between 11,000 and 15,000. At present, the ablation module permits a microanalysis with a crater size of 25 microm and a nominal depth resolution with an ablation rate of 150 nm/pulse. The VUV performance was demonstrated for bulk analysis of steel; detection limits for sulfur, carbon, and phosphorus were in the lower milligram per kilogram range. The VUV scanning and mapping performance for heterogeneous matrixes was illustrated for mineral bottom ash samples from a waste incineration process.     

Oxygen determination in oxygen-supersaturated drinking waters by NMR relaxometry

In recent years, a rising number of different table waters supersaturated with oxygen have hit the market with claims of both positive health effects and an increase in athletic performance. In addition to research on the correctness of these claims and their possible physiological reasons, the appearance of oxygen supersaturation as a marketing promise also creates a need for appropriate analytical techniques allowing a rapid and reliable determination of oxygen contents in such waters. Here, we present NMR relaxometry as a possible analytical tool for such studies. NMR relaxation in oxygen supersaturated water is not only of interest in the context of monitoring the oxygen content in such drinking water products, but also might offer some interesting possibilities in medical and environmental science MRI applications. As a contact-less measuring method, NMR relaxometry avoids disturbance of the measurement due to outgassing. The method was applied in the concentration range from 10 mg l(-1) to over 100 mg l(-1) dissolved oxygen. In addition to freshly sampled drinking waters, also oxygen losses during storage of the water in open drinking vials was studied.     

Microarrays for the screening of allergen-specific IgE in human serum

The described in vitro test system for allergy diagnosis is based on microscope glass slides activated with (3-glycidyloxypropyl)trimethoxysilane. Allergen solutions are immobilized as small droplets (approximately 10 nL) on the activated glass slides with a piezoelectric arrayer. In contrast to other tests for specific IgE, such as Pharmacia CAP FEIA, AlaSTAT, or FAST, only a 25-microL serum sample is needed for the screening of allergen-specific IgE against a multitude of allergens and the test can be performed in less than 1 h. Compared with multiallergen dipstick screening tests (e.g., IgEquick, CMG Immunodot) based on multiallergen-coated nitrocellulose strips, the measurement of the microarray-based system can be performed automatically. The chemiluminescence intensities are detected with a sensitive CCD camera. Allergen extracts and recombinant/purified allergens (24 preparations) have been used on the same modified surface for the screening of allergen-specific IgE. With these disposable microarray slides, it is possible to distinguish between patients with and without elevated levels of allergen-specific IgE. Repeated measurements of serum samples demonstrated a sufficient reproducibility. Detection limits (microg/L) of 0.35 (r Betvl), 0.16 (PLA2), and 1.9 (Der p1) were achieved.     

Monitoring polycyclic aromatic hydrocarbon metabolites in human urine: extraction and purification with a sol-gel glass immunosorbent.

A new, rapid method for selective extraction of hydroxylated polycyclic aromatic hydrocarbons metabolites (OH-PAHs) in human urine was developed using an immunosorbent of anti-pyrene antibodies which were encapsulated in a sol-gel glass (SGG) matrix. Resulting chromatograms after immunoextraction of urine samples and HPLC analysis of the extracts were free from matrix interferences. The LODs for the determination of OH-PAHs in these difficult samples were in the low-ppt range (1-16 ng/L). In addition to its high selectivity, the immunosorbent proved to be robust and reusable. Obtained recoveries in spiked urine samples ranged from 83 to 107% for the hydroxyphenanthrene and hydroxypyrene compounds under investigation, while recovery for 3-hydroxybenzo[a]pyrene was only 45-62%. In a biomonitoring study, the SGG immunosorbent was successfully used for trace-level analysis of OH-PAHs in 20 human urine samples. Results were compared to data obtained by an independent reference analysis method and revealed good correlation between both methods.     

Air filtration performance of nanofiber membranes with different morphologies produced by green electrospinning

To further target product development with low environmental impact, an integral green electrospinning (G-ES) approach has been adopted through the simultaneous application of various strategies, such as the use of biopolymers, reduction of energy use to avoid melting temperatures, and selection of non-toxic solvents and surfactants. Green solubility spinnability maps for cellulose acetate (CA), poly ε-caprolactone (PCL), and polyvinyl alcohol (PVA) are presented. Green electrospinning (G-ES) allows the production of new morphologies for CA and PCL nanofiber membranes. In this work, CA exhibits a ribbon-like morphology, PCL shows a honeycomb-like morphology and PVA cylindrical fibers. Membrane morphologies are compared with filtration efficiency (FE) for particle size of 1.0 μm and quality factor (Q_F) at a volumetric flux of 27.63 cm⁻¹. For CA is between 83% and 96% and high Q_F = 0.31–0.38 Pa⁻¹, PCL is 92% and 99% and high Q_F = 0.28–0.21 Pa⁻¹ and for PVA between 96% and 99% and high Q_F = 0.14–0.08 Pa⁻¹. These results suggest that the hierarchical nanofiber structure improves filtration performance because of the reduction in pressure drop and increase in PM interception. CA ribbon-like fibers favored air filtration performance, followed by PCL honeycomb-like fibers.     

Multiwavelength Raman microspectroscopy for rapid prediction of soot oxidation reactivity

Multiwavelength Raman microspectroscopy (MWRM) analysis for characterization of soot structure and reactivity was developed. This new method is based on the dispersive character of carbon D mode in Raman spectra (i.e., red shift and increase in intensity at higher excitation wavelength, λ(0)). The approach was proven by investigating various diesel soot samples and related carbonaceous materials at different λ(0) (785, 633, 532, and 514 nm). In order to compare the behavior of the D mode for various samples and to derive a single parameter characterizing the soot structure, the difference of integrals for pairs of spectra collected at different λ(0) was calculated. MWRM analysis revealed substantial differences in the structural ordering which decreases from graphite, over Printex XE2 and various diesel soot samples, to spark discharge soot. To obtain the relation between structure and reactivity of soot, MWRM analysis was combined with temperature-programmed oxidation (TPO). TPO allowed us to characterize the oxidation behavior of soot in terms of the maximum emission (CO + CO(2)) temperature and reactivity index. The latter was calculated by introducing the reactivity limits: spark discharge soot containing a large amount of disorder represents the upper limit, whereas the lower limit is given by graphite powder with high structural order. The comparison of MWRM (viz., the observed Raman difference integrals) and TPO data revealed a linear correlation between soot structure and oxidation reactivity. Thus, we demonstrated for the first time the potential of MWRM for a robust and rapid prediction of diesel soot reactivity based on the structure-reactivity correlation.     

Festigkeitsberechnung scharf gekerbter Bauteile

Strength calculation of sharp notched components In this report the strength calculation of sharp notched components under static and cyclic loading is investigated and compared to the FKM code “Analytical strength assessment for machine components”. The calculation of the strength of sharp notched components according to the guideline does not lead to satisfying solutions. Therefore different concepts of strength calculation with consideration of scale and notch effects are examined e.g. the gradient concept of Siebel/Stieler. This concept is implemented in the FKM code for the calculation of the notch sensitivity factor. In order to evaluate the numerical results, experimental tests with various sharp notched specimens under static and cyclic loading were carried out. Based on these experimental results the FKM code is extended to sharp notched components.     

QuadriFlow: A Scalable and Robust Method for Quadrangulation

QuadriFlow is a scalable algorithm for generating quadrilateral surface meshes based on the Instant Field‐Aligned Meshes of Jakob et al. (ACM Trans. Graph. 34(6):189, 2015). We modify the original algorithm such that it efficiently produces meshes with many fewer singularities. Singularities in quadrilateral meshes cause problems for many applications, including parametrization and rendering with Catmull‐Clark subdivision surfaces. Singularities can rarely be entirely eliminated, but it is possible to keep their number small. Local optimization algorithms usually produce meshes with many singularities, whereas the best algorithms tend to require non‐local optimization, and therefore are slow. We propose an efficient method to minimize singularities by combining the Instant Meshes objective with a system of linear and quadratic constraints. These constraints are enforced by solving a global minimum‐cost network flow problem and local boolean satisfiability problems. We have verified the robustness and efficiency of our method on a subset of ShapeNet comprising 17,791 3D objects in the wild. Our evaluation shows that the quality of the quadrangulations generated by our method is as good as, if not better than, those from other methods, achieving about four times fewer singularities than Instant Meshes. Other algorithms that produce similarly few singularities are much slower; we take less than ten seconds to process each model. Our source code is publicly available.