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- Traceability (2)
- 3R concept (1)
- AIE (1)
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- Animal welfare (1)
- Brake dust (1)
- Bremse (1)
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- Coproantibodies (1)
Organisationseinheit der BAM
The inter-instrument, inter-laboratory, and long-term comparability of fluorescence data requires the correction of the measured emission and excitation spectra for the wavelength- and polarization-dependent spectral irradiance of the excitation channel at the sample position and the spectral responsivity of the emission channel employing procedures that guarantee traceability to the respective primary standards. In this respect the traceability chain of fluorometry is discussed from a radiometrists point of view. This involves, in a first step, the realization of the spectral radiance scale, based on the blackbody radiator and electron storage ring, and the spectral responsivity scale, based on the cryogenic radiometer and their control via key comparisons of the national metrology institutes. In a second step, the characterization including state-of-the art uncertainties of the respective source and detector transfer standards such as tungsten strip lamps, integrating sphere radiators, and trap detectors used to disseminate these radiometric quantities to users of spectroscopic techniques is presented.
Aggregation-induced emission (AIE) has been meanwhile observed for many dye classes and particularly for fluorophores containing propeller-like groups. Herein, we report on the AIE characteristics of a series of four hydrophobic pyrrolidinylvinylquinoxaline (PVQ) derivatives with phenyl, pyrrolyl, indolyl, and methoxythienyl substituents used to systematically vary the torsion angle between this substituent at the quinoxaline C2 position and the planar PVQ moiety. These molecules, which are accessible via four- or five-component one-pot syntheses, were spectroscopically studied in organic solvents and solvent−water mixtures, as dye aggregates, solids, and entrapped in polystyrene particles (PSP). Steady-state and time-resolved fluorescence measurements revealed a strong fluorescence enhancement for all dyes in ethanol−water mixtures of high water content, accompanying the formation of dye aggregates with sizes of a few hundred nm, overcoming polarity and H-bonding-induced fluorescence quenching of the chargetransfer-type emission of these PVQ dyes. The size and shape of these dye aggregates and the size of the AIE effect are controlled by the water content and the substituent-dependent torsion angle that influences the nucleation process and the packing of the molecules during aggregation. Staining of 1 μm-sized carboxy-functionalized PSP with the PVQ dyes resulted also in a considerable increase in the fluorescence quantum yield and lifetime, reflecting the combined influence of the restricted molecular motion and the reduced polarity of the dye microenvironment.
Starting from trivalent 10-alkoxy-10H-9-oxa-10-phosphaphenanthrenes, a broad range of DOPO derivatives was synthesized via transesterification with aliphatic alcohols and subsequent Michaelis-Arbuzov rearrangement using catalytic amounts of p-toluenesulfonic acid methylester. Due to the considerable differences in the nature of the alcohols employed, several procedures for processing them are presented.
10-Ethyl-9-oxa-10-phosphaphenanthrene-10-oxide (1) can be nitrated using acetic anhydride and fuming nitric acid. The nitro group is reduced using palladium on charcoal and hydrogen. These reaction conditions are used for the synthesis of an analogous DOPO-based diaminic hardener (7). An evaluation of the curing behavior, mechanical properties and flammability of a neat resin made of DGEBA and 7 (DGEBA + 7) and of a carbon fiber-reinforced resin made of DGEBA, 4,4-diaminodiphenylsulfon (DDS) and 7 (DGEBA + DDS + 7) shows the potential of this hardener to lead to flame-retardant systems while keeping relevant properties on a high level; especially when compared to a similar system (DGEBA + DDS + 1).
The need for the traceable characterization of fluorescence instruments is emphasized from a chemists point of view, focusing on spectral fluorescence standards for the determination of the wavelength- and polarization-dependent relative spectral responsivity and relative spectral irradiance of fluorescence measuring systems, respectively. In a first step, major sources of error of fluorescence measurements and instrument calibration are revealed to underline the importance of this issue and to illustrate advantages and disadvantages of physical and chemical transfer standards for generation of spectral correction curves. Secondly, examples for sets of traceable chemical emission and excitation standards are shown that cover a broad spectral region and simple procedures for the determination of corrected emission spectra with acceptable uncertainties are presented. With proper consideration of the respective measurement principle and geometry, these dye-based characterization procedures can be not only applied to spectrofluorometers but also to other types of fluorescence measuring systems and even to Raman spectrometers.
Die Ultraschallmikroskopie von kleinen Bauteilen mit fokussierenden Prüfköpfen
ist seit Jahren gängige Praxis. Leider Ist sie für den Einsatz in der On-Line-
Qualitätskontrolle zu zeitaufwändig. Deshalb wurde an der Bundesanstalt für
Materialforschung und -prüfung (BAM) auf der Basis von Polyvinyliden-Fluorid
(PVDF) wurde eine fokussierende Wandlerzeile entwickelt Sie ist Teil eines Prüfgerätes,
das durch die Verbindung von mechanischer und elektronischer Steuerung
des Ultraschallfeldes hohe Abtastgeschwindigkeiten erreicht. Dadurch, können
die Prüfzeiten so stark reduziert werden, dass eine On-line-Nutzung möglich
wird.
Das Ultraschallfeld der Wandlerzeile wurde dreidimensional ausgemessen und
das Ergebnis mit einem numerischen Modell /1/ verglichen. Die Übereinstimmung
zwischen berechnetem und gemessenem Schallfeld war sehr gut. Eine
Optimierung der elektronischen Ansteuerung führte darüberhinaus zu einer
erheblichen Reduzierung der störenden Nebenmaxima. Die Mittenfrequenz der
Prüfimpulse liegt über 15 MHz und der Fokus des Prüfkopfes beträgt weniger als
0,5 mm im Durchmesser.
Mit dieser Wandlerzeile und der entsprechenden elektronischen Steuerung
wurde eine Aluminium-Schweißnaht untersucht, die vorher mit einem konventionellen
fokussierenden Prüfkopf abgetastet worden war. Beide Prüfergebnisse
zeigen die gleiche Strukturauflösung, so dass der Zeitgewinn uneingeschränkt
als Vorteil für die Wandlerzeile zu Buche schlägt.
A non-invasive method to monitor the humoral immune response in mice after immunization is described. From fecal pellets of an individual mouse, a sufficient amount of active immunoglobulins or their fragments can be extracted to perform a regular examination of the status of the immune response by immunoassay. Hapten-specific antibodies from the feces of mice from three immunization trials showed very similar characteristics to those obtained from serum at a given date. Therefore, it can be suspected that some serum IgG enters the intestinal lumen and ends up in the feces, where they appear to be considerably stable. Hapten-specific IgAs were not found in the feces. Being able to analyze antibody titers in feces could be an interesting animal welfare refinement to standard practice that does not entail repeated blood sampling.