Analytische Chemie
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- Ground penetrating radar (4)
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- Online NMR spectroscopy (4)
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Eingeladener Vortrag
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Derzeit finden gravierende Veränderungen im Umfeld der Informations- und Kommunikationstechnik statt, die eine große Chance für die optimierte Prozessführung und Wertschöpfung mit darauf abgestimmten vernetzt kommunizierenden Sensoren bieten. Diese Art „smarter“ Sensoren stellen Dienste innerhalb eines Netzwerks bereit und nutzen Informationen daraus. Dadurch ergibt sich aktuell die Notwendigkeit, die Anforderungen an Prozess-Sensoren sowie an deren Kommunikationsfähigkeiten detaillierter zu beschreiben – vom einfachen Temperatursensor bis über heute in Entwicklung befindlichen Mess-Systemen hinaus – da diese Technologieentwicklungen rasant voranschreiten. Vernetzte Sensoren sind die Voraussetzung für die Realisierung von Cyber-physischen Produktionssystemen (CPPS) und zukünftiger Automatisierungskonzepte für die Prozessindustrie, wie sie auch durch das Zukunftsprojekt „Industrie 4.0“ adressiert werden.
Polysaccharides modify the rheological properties of cement based systems. Depending upon their chemistry, molecular architecture, and adsorption tendency, they have different modes of action. Some polysaccharides like diutan gum have strong effect on the fluid phase; others like starch strongly interact with particles. This paper presents effects of diutan gum and starches in presence of polycarboxylates. Rheometric investigations with varied particle volume fractions and increasing coarse aggregate diameters were conducted. The results show that starches have stronger influence on the rheology at high particle volume fractions than diutan gum. At lower particle volume fractions this trend is inverted. Experiments with aggregates sizes up to 16 mm (0.63 in.) indicate that stabilizing agent influences on the effects of aggregates on yield stress were small; however up to 1.0 mm (0.04 in.), a significant effect on the plastic viscosity could be observed, which levelled off at larger diameters.
Die Blitzthermografie weist eine Reihe von Vorteilen gegenüber anderen Verfahren der aktiven Thermografie auf und hat daher eine relativ große Verbreitung in Forschung und Industrie gefunden. Ein wesentlicher Nachteil ist jedoch die begrenzte Energie, die pro Blitz genutzt werden kann. Es stellt sich die Frage, ob sich durch mehrere kurz hintereinander ausgeführte Blitze eine Verbesserung des Energieeintrags erreichen lässt. Zur experimentellen Untersuchung dieser Frage wurde ein Versuchsstand mit vier Blitzlampen so umgerüstet, dass die Blitzlampen zeitgleich oder nacheinander mit einer regelbaren Verzögerung ausgelöst werden können („Multiblitz“). Als Probekörper dienten Platten aus CFK, an deren Rückseite Flachbodenbohrungen (FBB) eingebracht worden waren. Betrachtet wurde jedoch nur der absolute Temperaturhub am ungestörten Material. Die Experimente zeigen relativ geringe Effekte im Prozentbereich, wie sie auch gemäß einer quantitativen Abschätzung zu erwarten sind. Interessanterweise vergrößerte sich der Einfluss der Multiblitzanregung auf die Energieeinkopplung deutlich bei einem etwas vergrößerten Abstand zwischen Blitzlampen und untersuchter Oberfläche. Die Ursache für diesen Effekt ist derzeit unklar, vermutet werden eine Temperaturabhängigkeit und/oder eine Abstandsabhängigkeit des Wärmübergangskoeffizienten im Konvektionsterm.
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 kinetic energy of keV electrons backscattered from a rutile (TiO2) surface depends measurably on the mass of the scattering atom. This makes it possible to determine separately the angular distribution of electrons backscattered elastically from either Ti or O. Diffraction effects of these backscattered electrons inside the rutile crystal lead to the formation of Kikuchi patterns. The element-resolved Kikuchi patterns of Ti and O differ characteristically, but each can be described fairly well in terms of the dynamical theory of diffraction. Qualitatively, much of the differences can be understood by considering the relative arrangement of the Ti and O atoms with respect to planes defined by the crystal lattice.
In the near future, it will be important to adopt innovative approaches and technologies in order to further guarantee the reliability and availability of the highway network. New tools are therefore needed in order to obtain in-depth information about the condition of bridges and its development early enough before significant, precarious damage cases occur. In 2011, the research program “Intelligente Brücken (Smart Bridges)” was launched by the BASt together with the BMVI to evolve systems for information and holistic evaluation for Bridge structures as a supplement to the current inspection-based maintenance management. Several projects dealt with the topic in the last few years and provided guidelines and a solid basis to move towards a first implementation considering the input of all research projects carried out so far.
Recently developed new transducers for ultrasonic transmission, which can be embedded right into concrete, are now used for non-destructive permanent monitoring of concrete. They can be installed during construction or thereafter. Large volumes of concrete can be monitored for changes of material properties by a limited number of transducers. The transducer design, the main properties as well as installation procedures are presented. It is shown that compressional waves with a central frequency of 62 kHz are mainly generated around the transducer's axis. The transducer can be used as a transmitter or receiver. Application examples demonstrate that the transducers can be used to monitor concrete conditions parameters (stress, temperature,
) as well as damages in an early state or the detection of acoustic events (e.g., crack opening). Besides application in civil engineering our setups can also be used for model studies in geosciences.
Ziel dieser Arbeit war die Entwicklung einer Methode zur Hochdurchsatzanalyse von partikelgebundenen Split-and-Mix-Peptidbibliotheken. Dabei wurde ein System entwickelt, das Partikelbibliotheken in kurzer Zeit auf ihre Bindung zu einem Zielmolekül hin untersucht und im nächsten Schritt eine direkte „Ein-Partikel“-Sequenzierung der Peptide von der festen Phase ermöglicht. Die Analyse der Bindung eines Zielmoleküls an ein selektiv bindendes Peptid wurde dabei in einem Modellsystem simuliert. Dazu wurde FITC-markiertes Neutravidin 3 mit festphasengebundenen biotinylierten und nicht-biotinylierten Peptiden inkubiert. Die Bindung von Neutravidin-FITC an die biotinylierten Peptide konnte erfolgreich mittels eines Fluoreszenzmikroskops nachgewiesen werden, wobei diese Methode für eine Hochdurchsatzanalyse ungeeignet war. So wurde die Analyse des Fluoreszenzassays auf einen Microarrayscanner übertragen (siehe Abbildung 33). Dies gelang erfolgreich wobei die hohe Eigenfluoreszenz des Tentagel-Harzes zu falsch positiven Ergebnissen führte. Mit einem Wechsel zum längerwelligen Fluoreszenzfarbstoff ATTO-633 konnten falsch positive Ergebnisse vermieden werden. Somit wurde die zeitintensive Fluoreszenzanalyse von einem Fluoreszenzmikroskop erfolgreich auf einen Microarrayscanner übertragen, welcher in kurzer Zeit (ca. 5 min pro Objektträger) eine Vielzahl an peptidbeladenen Partikeln gleichzeitig analysieren kann.
Titanium dioxide is one of the most studied metal oxides due to its interesting chemical, surface, electronic and (photo)catalytic properties. These properties provide this material of multisectorial applications, ranging from healthcare, photocatalysis, smart materials with self cleaning and self sterilizing properties and solar energy harvesting (photovoltaics and water photosplitting). However it is difficult to correlate the functional properties of TiO₂ nanomaterials to the properties at single nanoparticle level due to the high polydispersity in shape, size and surface properties of the currently available TiO₂ nanoparticles (NPs) Although intensive experimental and theoretical studies have been conducted on the reactivity of different surfaces of metal oxides such as TiO₂ [1,2] much less attention is paid on the dependence of functional properties, like photocatalytic activity, dye adsorption, open circuit potential and fill factor in dye sensitized solar cells, on crystal facets in different orientations [3]. One of the goal of SETNanoMetro is the development of design rules to tune crystal facets of TiO₂ NPs in order to optimize and control functional properties. By tuning the ratio of different facets, the functional properties would be correspondingly changed. In the present work we have developed a series of design rules in order to obtain sets of anatase TiO₂ NPs with low polydispersity and to tune their shape and their size though hydrothermal processing of Ti(IV)-Triethanolamine complex in presence of different shape controllers (OH-, triethanolamine, fluoride). Through a careful experimental design the influence of many process parameters (pH, temperature, shape controller type and concentration) on the synthesis outcome (size, shape and polydispersity), a predictive soft model was developed. The model is able to predict reasonably well the synthesis outcome allowing to tune the shape factor from 5 (prisms) to 1.5 (bipyramids) to 0.2 (platelets). This allows to control the main crystal facets exposed ranging from (100) to (001).
Online monitoring and process control requires fast and noninvasive analytical methods, which are able to monitor the concentration of reactants in multicomponent mixtures with parts-per-million resolution. Online NMR spectros-copy can meet these demands when flow probes are directly coupled to reactors, since this method features a high linearity between absolute signal area and sample concentration, which makes it an absolute analytical com-parison method being independent on the matrix. Due to improved magnet design and field shimming strategies portable and robust instruments have been introduced to the market by several manufacturers during the last few years. First studies with this technology showed promising results to monitor chemical reaction in the laboratory.
Introducing fluorine into molecules has a wide range of effects on their physicochemical properties, often desirable but in most cases unpredictable. The fluorine atom imparts the C–F bond with low polarizability and high polarity, and significantly affects the behavior of neighboring functional groups, in a covalent or noncovalent manner. Here, we report that fluorine, present in the form of a single fluoroalkyl amino acid side chain in the P1 position of the well-characterized serine-protease inhibitor BPTI, can fully restore inhibitor activity to a mutant that contains the corresponding hydrocarbon side chain at the same site. High resolution crystal structures were obtained for four BPTI variants in complex with bovine b-trypsin, revealing changes in the stoichiometry and dynamics of water molecules in the S1 subsite. These results demonstrate that the introduction of fluorine into a protein environment can result in “chemical complementation” that has a significantly favorable impact on protein–protein interactions.
Air-coupled ultrasound has been applied increasingly as a non-destructive testing method for lightweight construction in recent years. It is particularly appropriate for composite materials being used in automotive and aviation industry. Air-coupled ultrasound transducers mostly consist of piezoelectric materials and matching layers. However, their fabrication is challenging and their signal-to-noise ratio often not sufficient for many testing requirements. To enhance the efficiency, air-coupled ultrasound transducers made of cellular polypropylene have been developed. Because of its small density and sound velocity, this piezoelectric ferroelectret matches the small acoustic impedance of air much better than matching layers applied in conventional transducers. In our contribution, we present two different methods of spherical focusing of ferroelectret transducers for the further enhancement of their performance in NDT applications. Measurements on carbon-fiber-reinforced polymer (CFRP) samples and on metal adhesive joints performed with commercially available focused air-coupled ultrasound transducers are compared to measurements executed with self-developed focused ferroelectret transducers.
Globalisierung und die beschleunigte technologische Entwicklung bringen heute für die Industrieländer Herausforderungen im Hinblick auf Wachstum, Beschäftigung und Strukturwandel mit sich, denen nur mit einer entsprechenden Innovationsdynamik und -dichte begegnet werden kann. Grundvoraussetzung hierfür ist eine leistungsfähige Forschung und Entwicklung ebenso wie Wissens- und Technologietransfer zur Umsetzung von Forschungsergebnissen in marktfähige Produkte und Dienstleistungen. Europa hat sich im Rahmen des Lissabon-Prozesses zum Ziel gesetzt, den Anteil der Forschungsausgaben am Bruttoinlandsprodukt auf 3 % zu steigern. Um die Forschungsinfrastruktur in der Bundesrepublik zu stärken und global wettbewerbsfähig zu bleiben, hat die Bundesregierung mit der Hightech-Strategie einen weiteren wichtigen Schritt zur Förderung des wissenschaftlich-technischen Fortschritts in Deutschland getan.
Forschungsprogramme sind sowohl für Forschungseinrichtungen als auch für Mittelgeber ein wichtiges Instrument für die Darstellung und Steuerung ihrer Aktivitäten. Dies gilt auch für die Bundeseinrichtungen mit Forschungs- und Entwicklungsaufgaben, zu denen die Bundesanstalt für Materialforschung und -prüfung (BAM) zählt. Die BAM verfügt über einen klaren gesetzlichen Auftrag für die Sicherheit in Technik und Chemie. Ihre Forschung ist mit der Wahrnehmung öffentlicher Aufgaben verbunden. Das Forschungsprogramm zeigt Perspektiven im Bereich ihres Aufgabenfeldes sowie ihrer damit verbundenen Forschungsaktivitäten transparent und politisch nutzbar auf und dient darüber hinaus der Koordinierung der Ressortforschung. Das Forschungsprogramm der BAM wird alle zwei Jahre aktualisiert. Es gibt einen Überblick über die aktuellen und zukünftigen Forschungsthemen und die hierfür erforderlichen Rahmenbedingungen.
Fraunhofer Life Science Day
(2015)
Their high affinity, selectivity and specificity make monoclonal antibodies (mAbs) very important tools in research, diagnostics and therapy. The production of mAbs is routinely performed by hybridoma technique. Hybridomas are generated by fusing antibody-producing B cells with indefinitely proliferating myeloma cells. Both, cell fusion and the indispensable identification and isolation of the desired antibody-producing hybridoma clone is still far from being trivial.
We describe a novel method that should help to optimize the cell fusion, and the screening for antibody-secreting hapten-specific hybridoma cells by using fluorescence activated cell sorting and single-cell fusion. Hybridoma cells specific for a hapten were incubated with a hapten-peroxidase conjugate (hapten-HRP), which was subsequently incubated with a fluorophore-labeled polyclonal anti-peroxidase antibody (anti-HRP-Alexa Fluor® 488). To characterize the expression of membrane-bound immunoglobulin G (IgG) a fluorophore-labeled anti-mouse IgG antibody (anti-IgG-Alexa Fluor® 647) was used. Successful staining was verified by confocal laser scanning microscopy (CLSM). We show that it is possible to specifically label hapten-specific hybridoma cells. It should also be possible to use this labelling approach for the isolation of hapten-specific B cells from the spleen and use these cells for single-cell fusion. Parallelized cell fusion chips were developed to increase fusion efficiencies.
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.
Geophysical methods have been used in civil engineering for decades. The main field of application is - to no surprise – in geotechnical projects from site characterization to foundation quality assurance. For more than 25 years, ground penetrating radar (GPR) and seismic methods have found applications in structural engineering. Recently introduced geophysical methods have been adopted to ultrasonic investigations in various fields. They help to improve the quality of structural imaging and to detect small changes in concrete. An overview of the history and current use of geophysics in civil engineering is given. Selected examples of new concepts include advances in wave based imaging, quality assurance for foundations, detecting small changes in concrete as well as moisture and corrosion detection are discussed.
The synthesis of water-soluble dyes, which absorb and emit in the range between 650 and 950 nm and display high extinction coefficients (ε) as well as high fluorescence quantum yields (Φf), is still a demand for optical imaging. We now present a synthetic route for the preparation of a new group of glycerol-substituted cyanine dyes from dendronized indole precursors that have been functionalized as Nhydroxysuccinimide (NHS) esters. High Φf values of up to 0.15 and extinction coefficients of up to 189 000 L mol−1 cm−1 were obtained for the pure dyes. Furthermore, conjugates of the new dendronized dyes with the antibody cetuximab (ctx) that were directed against the epidermal growth factor receptor (EGFR) of tumor cells could be prepared with dye to protein ratios between 0.3 and 2.2 to assess their potential as imaging probes. For the first time, ctx conjugates could be achieved without showing a decrease in Φf and with an increasing labeling degree that exceeded the value of the pure dye even at a labeling degree above 2. The incorporation of hydrophilically and sterically demanding dendrimers into cyanines prevented dimer formation after covalent conjugation to the antibody. The binding functionality of the resulting ctx conjugates to the EGFR was successfully demonstrated by cell microscopy studies using EGFR expressing cell lines. In summary, the combination of hydrophilic glycerol dendrons with reactive dye labels has been established for the first time and is a promising Approach toward more powerful fluorescent labels with less dimerization.
Surface-enhanced Raman scattering (SERS) exploits the enhancement of electromagnetic fields in close vicinity of plasmonic nanostructures, enabling characterization of analytes at the single-molecule level. The nanometer-scale spatial arrangement of plasmonic metal nanoparticles and analyte molecules has a significant effect on the observed signal enhancements and represents a great challenge in this technique.
In our work, DNA origami is used as platform for precise positioning of gold nanoparticles (AuNPs). Especially high sensitivities are expected for gold nanolenses (AuNLs), consisting of rows of three or more differently-sized AuNPs. We assembled different AuNL designs and determined respective SERS enhancement factors by collecting Raman spectra from single AuNLs. Finite difference time domain calculations estimate attainable electromagnetic field enhancements. Ultimately, we aim to develop a versatile platform for various SERS applications.