Mechanistische Untersuchung der in Acrylsäure ablaufenden Prozesse

Acrylsäure besitzt eine hohe Reaktivität, welche sich zur Herstellung von einer Vielzahl an Produkten eignet, jedoch Probleme beim Transport und bei der Lagerung verursacht. Hierbei tritt durch die Alterung ein Qualitätsverlust ein, weshalb in dieser Arbeit zunächst die Nebenproduktbildung in reiner Acrylsäure und in wässrigen Acrylsäuremischungen untersucht wird. Hierzu werden die Konzentrationsverläufe der Komponenten Acrylsäure (AA), Diacrylsäure (DiAA), Triacrylsäure (TriAA), 3-Hydroxypropionsäure (3-HPA) und 3-Hydroxydiacrylsäure (3-HDiAA) ermittelt. Diese Konzentrationsverläufe werden mit den vorgestellten Reaktionswegen modelliert. Weiterhin ist die Neigung zur unerwünschten Polymerisation von Acrylsäure ein erhebliches Problem bei falscher Lagerung, welche zu einem Runaway führen kann. Deshalb wird in dieser Arbeit die Effektivität und Wirkungsweise eines Restabilisator-Gemisches untersucht. Hierzu werden unterschiedliche Szenarien der Restabilisierung durchgeführt und dabei die eingesetzte Menge an Restabilisator variiert. Aus den Ergebnissen werden Sicherheitsdiagramme erstellt, mit deren Hilfe die zur Restabilisierung benötigte Menge ermittelt werden kann

How to Measure the Mental Health of Teachers? Psychometric Properties of the GHQ-12 in a Large Sample of German Teachers.

To improve the health status of teachers, there is a need for good and reliable instruments to continuously assess their mental health. The current study proposed the GHQ-12 questionnaire as an appropriate instrument for measuring the mental health of teachers. The GHQ-12 is a well-established screening instrument that has mostly been applied in non-teaching samples. In the current study, the psychometric properties of the questionnaire were analyzed using a large sample of German teachers (N = 3996). The data was collected yearly over an extended period of time (2012-2020). Results showed good to very good reliability, as well as high correspondence to burnout and life satisfaction scales. Principal axis factor analysis supported a two-factor structure: Factor 1 represents "depression/stress" and Factor 2 represents "loss of confidence". However, the mental health of the investigated teachers was worse than that of a representative sample in Germany. Consequently, this study highlighted the fact that the teaching profession is vulnerable to mental strain and underlined the importance of promoting prevention programs that could help to sustain and foster the mental health of teachers. In this context, the GHQ-12 could be proposed as a good and economic tool to assess and analyze mental health in German teachers. The presented norm could help practitioners and teachers to compare individual scores within a larger peer group

Direct laser-written optomechanical membranes in fiber Fabry-Perot cavities

Integrated micro and nanophotonic optomechanical experiments enable the manipulation of mechanical resonators on the single phonon level. Interfacing these structures requires elaborate techniques limited in tunability, flexibility, and scaling towards multi-mode systems. Here, we demonstrate a cavity optomechanical experiment using 3D-laser-written polymer membranes inside fiber Fabry-Perot cavities. Vacuum coupling strengths of ~ 30 kHz to the fundamental megahertz mechanical mode are reached. We observe optomechanical spring tuning of the mechanical resonator by tens of kHz exceeding its linewidth at cryogenic temperatures. The extreme flexibility of the laser writing process allows for a direct integration of the membrane into the microscopic cavity. The direct fiber coupling, its scaling capabilities to coupled resonator systems, and the potential implementation of dissipation dilution structures and integration of electrodes make it a promising platform for fiber-tip integrated accelerometers, optomechanically tunable multi-mode mechanical systems, or directly fiber-coupled systems for microwave to optics conversion.Comment: 10 pages, 5 figure

Flexible experimental platform for dispersion-free temporal characterization of ultrashort pulses

The precise temporal characterization of laser pulses is crucial for ultrashort applications in biology, chemistry, and physics. Especially in femto- and attosecond science, diverse laser pulse sources in different spectral regimes from the visible to the short-wavelength infrared as well as pulse durations ranging from picoseconds to few femtoseconds are employed. In this article, we present a versatile temporal-characterization apparatus that can access these different temporal and spectral regions in a dispersion-free manner and without phase-matching constraints. The design combines transient-grating and surface third-harmonic-generation frequency-resolved optical gating in one device with optimized alignment capabilities based on a noncollinear geometry