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Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces
(2016)
Bacterial biofilms are considered one of the salient contributing factors to the deterioration of metals and their alloys, occurring in virtually all environments and across various industrial systems. Considering the sheer magnitude of detrimental effects, it is of pertinent interest to elucidate the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces to facilitate the development of efficient antifouling strategies. A common constituent of microbial communities within aquatic and sedimentary settings, the Shewanella genus consists of facultatively aerobic, Gram-negative bacterium which exhibit exceptional plasticity in respiratory capacities. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor; conversely, under anaerobic conditions, it is able to undertake respiration by reducing alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms not yet thoroughly discerned.
The aim of this work is to explicate the mechanisms governing the initial bacterial adhesion and subsequent biofilm formation on metallic surfaces. To investigate this dynamic interplay, a combined approach has been followed which couples surface enhanced Raman spectroscopy (SERS) with electrochemical techniques using Shewanella sp. model biofilms. Gold nano-islands deposited on thin glass slides have been chosen as inert model substrates with good uniformity and high surface enhancement factor. Furthermore, the utilization of gold as substrate material not only allowed the differentiation of the sole effect of substrate polarization on bacterial attachment but also enabled a precise adjustment of the surface chemistry and surface energy by means of surface functionalization with organothiol self-assembled monolayers.
The results present the correlation of the primary settlement rate of bacteria on metallic substrates with the environmental parameters such as electrolyte composition and pH as well as surface-related properties like hydrophobicity/hydrophilicity and polarization. With the overall strategic goal of transferring this methodology to technical systems the results provide the fundamental basis for the bottom-up design of anti-fouling surfaces.
Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces
(2016)
Bacterial biofilms are considered one of the salient contributing factors to the deterioration of metals and their alloys, occurring in virtually all environments and across various industrial systems. Considering the sheer magnitude of detrimental effects, it is of pertinent interest to elucidate the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces to facilitate the development of efficient antifouling strategies. A common constituent of microbial communities within aquatic and sedimentary settings, the Shewanella genus consists of facultatively aerobic, Gram-negative bacterium which exhibit exceptional plasticity in respiratory capacities. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor; conversely, under anaerobic conditions, it is able to undertake respiration by reducing alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms not yet thoroughly discerned.
The aim of this work is to explicate the mechanisms governing the initial bacterial adhesion and subsequent biofilm formation on metallic surfaces. To investigate this dynamic interplay, a combined approach has been followed which couples surface enhanced Raman spectroscopy (SERS) with electrochemical techniques using Shewanella sp. model biofilms. Gold nano-islands deposited on thin glass slides have been chosen as inert model substrates with good uniformity and high surface enhancement factor. Furthermore, the utilization of gold as substrate material not only allowed the differentiation of the sole effect of substrate polarization on bacterial attachment but also enabled a precise adjustment of the surface chemistry and surface energy by means of surface functionalization with organothiol self-assembled monolayers.
The results present the correlation of the primary settlement rate of bacteria on metallic substrates with the environmental parameters such as electrolyte composition and pH as well as surface-related properties like hydrophobicity/hydrophilicity and polarization. With the overall strategic goal of transferring this methodology to technical systems the results provide the fundamental basis for the bottom-up design of anti-fouling surfaces.
Worldwide BAM Certification of Radigraphic Image Detectors for the NDT Market – Status of 2016
(2016)
The Poster shows the status of 2016 in BAM certification of radiographic image detectors for industrial radiology for nondestructive testing. BAM was generating first the basis by worldwide standardization activities and released later certificates on request of the device manufacturers using these Standards a base for certification.
The development of innovative medium resolution NMR spectrometers (MR-NMR) is remarkable due to their possible applications in quality control, education, or process monitoring.
The use of compact permanent magnets allows to employ NMR devices in an industrial environment without high maintenance requirements and without the need for cryogenic liquids.
A benchtop 43 MHz MR-NMR spectrometer was used for reaction monitoring. Quasi-simultaneous proton and fluorine NMR spectra were acquired. Automatic data pretreatment and evaluation methods were applied and compared to quantitative 500 MHz HR-NMR spectroscopy
Optical lock-in thermography is a completely contactless and very sensitive NDT technique. As an optical source of energy, incandescent (i.e. halogen) lamps are most commonly used because they are relatively inexpensive and offer high irradiances at the test site. However, they are strongly restricted by their low modulation bandwidth with a maximum modulation frequency of only about 1 Hz. The use of high-power kilowatt-class laser sources, e.g. diode laser arrays, pushes this constraint beyond 100 Hz, see Fig.1. This allows for the exploration of the near-surface region of metals and layer systems with better and more accurate penetration depth and depth resolution. Moreover, these lasers are virtually free of any additional thermal radiation that could interfere with the “true” thermal response emitted from the heated sample. In turn, they can be easily used in a one-sided test configuration.
Using the one-dimensional solution to the thermal heat diffusion equation together with the absorptance of the material which is illuminated with a harmonically modulated light source, we can calculate the temperature oscillation at the surface of a solid. As a second step, we calculate the corresponding oscillation of the total thermal emission using Stefan-Boltzmann law as a first order approximation and taking into account the emissivity of the material. Within this framework we can calculate the minimal irradiance of a light source necessary to provoke a measurable signal within a thermographic camera at a noise equivalent temperature difference (NETD) of 30 mK. In Fig. 2 this relationship is displayed for a wide spectrum of modulation frequencies and for a number of different light sources scaled to the same electrical input power and illumination area. Using this figure, it is now easily possible to analyze the range of materials to be tested using lock-in thermography, since only the materials (dotted lines) below the irradiance-vs-frequency curves (solid lines) are heated in excess of the camera’s NETD. This figure clearly shows that laser sources considerably increase the application range of lock-in thermography, since especially for metals with a high reflectance and high thermal diffusivity a high irradiance is vitally important to allow for lock-in texting.
We present current activities with kilowatt-class high-power laser sources for advanced lock-in thermography and focus on the application of laser arrays that offer a very high irradiation strength over a large sample area beyond the mentioned advantages.
Optical lock-in thermography is a completely contactless and very sensitive NDE technique. As an optical source of energy, incandescent (i.e. halogen) lamps are most commonly used because they are relatively inexpensive, do not need any work safety measures and offer high irradiances at the test site. However, they are strongly restricted by their low modulation bandwidth with a maximum modulation frequency of only about 1 Hz. The use of high-power kilowatt-class laser sources, e.g. diode laser arrays, pushes this constraint beyond 100 Hz. This allows for the exploration of the near-surface region of metals and layer systems with better and more accurate penetration depth and depth resolution. Moreover, these lasers are virtually free of any additional thermal radiation that could interfere with the “true” thermal response emitted from the heated sample. In turn, they can be easily used in a one-sided test configuration. Altogether using lasers considerably increases the application range of lock-in thermography, since especially for metals with a high reflectance and high thermal diffusivity a high irradiance is vitally important to allow for lock-in testing [1, 2]. We report on the mentioned benefits of using such high-power lasers and analyze the range of materials to be tested using lock-in thermography in dependence on the laser irradiance, the modulation frequency, the infrared camera as well as the optical and thermal material parameters. In this context, we also address a number of systematic errors caused by the use of ideal and non-ideal heat sources. For example, the measured phase angle in lock-in thermography depends on the irradiance and the modulation bandwidth of the source. This in turn has a decisive influence on the uncertainty in the quantification of, e.g. layer thicknesses.
Die Thermografie ist trotz ihrer ausgereiften wissenschaftlichen und technologischen Grundlagen ein noch relativ junges Mitglied in der Familie der zerstörungsfreien Prüfverfahren. Sie erschließt sich aufgrund einer Reihe von Vorzügen eine wachsende Anwendungsgemeinde. Für eine weitere Verbreitung insbesondere im industriellen Kontext spielen Normen, Standards und technische Regeln eine wichtige Rolle. In diesem Beitrag wird der aktuelle Stand der Normung in Deutschland vorgestellt. Wir zeigen, welche Normen und technischen Regeln es für die Thermografie in Deutschland und international gibt und wir wagen einen Blick in die Zukunft. Darüber hinaus lebt auch die Normierungsarbeit von der Beteiligung durch interessierte Kreise. Dies können industrielle und akademische Anwender*innen, Hersteller*innen von Geräten, Forschungseinrichtungen oder Dienstleistungsunternehmen sein. Sie können gern Ihre Bedarfe bezüglich Normierungsprojekten mitbringen und/oder direkt an die Autoren senden.
Thermographic non-destructive testing is based on the interaction of thermal waves with inhomogeneities. The propagation of thermal waves from the heat source to the inhomogeneity and to the detection surface according to the thermal diffusion equation leads to the fact that two closely spaced defects can be incorrectly detected as one defect in the measured thermogram. In order to break this spatial resolution limit (super resolution), the combination of spatially structured heating and numerical methods of compressed sensing can be used. The improvement of the spatial resolution for defect detection then depends in the classical sense directly on the number of measurements. Current practical implementations of this super resolution detection still suffer from long measurement times, since not only the achievable resolution depends on performing multiple measurements, but due to the use of single spot laser sources or laser arrays with low pixel count, also the scanning process itself is quite slow. With the application of most recent high-power digital micromirror device (DMD) based laser projector technology this issue can now be overcome.
Cancer is the second leading cause of death globally according to the WHO 2018. Lung, prostate, colorectal, stomach and liver cancer are the most common types of cancer in men, while breast, colorectal, lung, cervix and thyroid cancer are the most common among women. Sialic acid (SA) plays an important role in a variety of biological processes in cells. Tumor cells express high levels of SA, which is often associated with poor prognosis due to increased invasive potential. In this study, we have performed a screening of SA-MIPs binding to different cancer cell lines. The overall aim is to use the SA-MIPs for detection of tumor cells, analyzed by flow cytometry and fluorescence microscopy. To confirm the levels of SA expression on the investigated cell lines, we started out by analyzing the binding of the lectins MAL I and SNA. The staining pattern of the two lectins binding to either α-2,3 or α-2,6 linkage SA, respectively, was compared with the staining pattern of the SA-MIPs. We show that the different cell types analyzed have a varying pattern of SA-MIP binding. The comparison with lectin binding will be further evaluated.
Polymers, such as polystyrene, have been successfully analyzed with matrix-assisted laser desorption/ionization (MALDI) through the addition of e.g. copper or silver salts. This method is often used to establish the polydispersity index of polymer blends.
However, the mechanism of cation addition and the possible interactions between the added salts and the chosen target material are still points of interest. Therefore, the addition of several trifluoroacetate salts to a mixture of polystyrene and matrix
on a range of different target plate materials was systematically investigated, revealing several new interesting aspects of MALDI.
Polystyrene (Mw 1,920 Da) was mixed with a range of trifluoroacetate salts (Li, Na, K, Cs, Ba, Cr, Pd, Cu, Ag, Zn, Al and In, as well as
trifluoroacetic acid) and analyzed with MALDI using 2
-[2E-3-4-tert-butylphenyl)-
2-
methylprop-2-enylidene]ma
lononitrile DCTB) as matrix on different target plate materials (chrome, copper, silver, gold, Ti90/Al6/V4, Inconel® 625, Zinc and stain
less steel) to evaluate the occurrence of redox-reactions.
Polystyrene/salt/matrix solutions were deposited through pneumatic-assisted spraying on microscope slide
-shaped target plate insets of varying material, which, secured with copper tape, fitted a milled out structure from the original target plate. Spectra, obtained on a Bruker Autoflex I MALDI-Time
-of-Flight mass spectrometer, were processed with MATLAB to obtain polystyrene-and matrix
-adduct ion signal intensities for direct comparison between chosen conditions.
The resulting spectra shed light on the MALDI adduct formation process and the cation-polystyrene interactions. It was found
that the following cation
-polystyrene adducts were formed on stainless steel: Al, Li, Na, Cu and Ag, where the yield was found to depend on the sample layer thickness and possibly the cation’s ability to form a complex with either one or two of polystyrene’s phenyl rings, based on the ligand-field and the valence bond theory. With the exception of Al, these salts also formed adducts
and in case of Cu and Ag also sandwich adducts with DCTB. Some alkali salts (e.g. potassium) formed clusters rather than interacting with polystyrene or DCTB, which can be explained with the HSAB theory. Application of TFA salts on a copper surface
led to copper cation formation, resulting in DCTB and polystyrene copper-adduct formation. The same effect occurred for silver substrate. In the absence of copper or silver salts, it is therefore still possible to form their respective adducts by choosing the proper alternative salt (e.g. Li, Cs, Ba, Cr) in combination with either a silver or a copper substrate surface. Incubation tests with copper beads in various salt solutions, before matrix and polystyrene addition, support that copper ions are not generated during the deposition process before the MALDI experiment is carried out, except when trifluoroacetic acid, indium and aluminium
trifluoroacetate are used. For all other salts used on a copper plate, it can therefore be concluded that these copper cation forming redox-reactions are enabled by the input of laser photon energy. Furthermore, it was discovered that copper beads can successfully sequester polystyrene from the sample mixture, indicating the strong bonding of polystyrene to the copper surface.
These findings support that the redox-reactions occur (almost) instantaneously with laser pulse impact at the sample-coated substrate surface.