Browsing by Subject "Identification"

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Career adaptability and vocational identity of commercial apprentices in the German dual system
(2020) Kirchknopf, Sebastian
The construct of career adaptability has recently gained importance in research on vocational development and has led to a variety of theoretical and empirical approaches. Alongside with vocational identity it has been theorised as the crucial meta-competency of modern career construction. Due to its roots in adolescent career development, career adaptability is not limited to the vocational adjustments of working adults, but is also highly relevant for the pre-occupational orientation processes of adolescents initially developing a vocational identity. Despite the recent increase in empirical research on career adaptability, the field of vocational education has been largely neglected so far. Therefore, a quantitative survey among nearly N = 400 commercial apprentices within the German dual system of VET has been conducted. This study focuses on the replication of the Career Adapt-Abilities Scale (CAAS) among commercial apprentices within the German dual system, and its discrimination against alternative operationalisations of career adaptability. Furthermore, the relationship between career adaptability and vocational identity (operationalised as occupational and organisational identification) was explored. Results showed that the four-dimensional structure of career adaptability covered by the CAAS could be largely replicated in the dual system. In addition, it was found that the CAAS can in part be separated from alternative operationalisations. Finally, the results confirmed career adaptability positively predicts both foci of identification in a cognitive and affective manner. This indicates that career adaptability can be seen as a beneficial factor for vocational education and training as it fosters the vocational ties of apprentices in terms of their identity.
Development of strategies for the prioritization of organic trace substances in water by effect-directed analysis
(2020) Stütz, Lena; Schwack, Wolfgang
The protection of the aquatic environment and the supply of clean drinking water to people all over the world are central challenges of our time. Monitoring of the aquatic environment and the input of anthropogenic trace substances into it is therefore very important. However, since aquatic environmental samples often consist of complex substance mixtures, their characterization and evaluation is very demanding. By using generic target analysis methods, selected known anthropogenic trace substances can be detected and quantified very sensitively. For the detection of previously unknown substances, non-target analysis methods have been increasingly used in recent years. However, these methods do not provide information on the relevance of the anthropogenic trace substances occurring in water. In this context, especially all those trace substances are regarded as relevant from which a harmful effect on humans or water organisms is to be expected. For the detection of such effective substances, effect-directed analysis (EDA) can be used. In EDA, a bioassay is combined with a fractionation method and subsequent chemical analysis, the aim being to identify the bioactive substance. The separation method used in this work is high-performance thin-layer chromatography (HPTLC). After chromatography, the bioassay is performed directly on the HPTLC plate. If an effective zone appears in the bioassay, a prioritization strategy is used to clarify the identity of the substance. Due to the complex aquatic samples, a large number of different substances in a zone must still be expected despite the applied HPTLC separation, which makes it difficult to identify the effective substance. Therefore, a strategy to simplify the identification of effective substances should be developed. The aim was to reduce the complexity by multidimensional separation in such a way that chemical analysis can be used to prioritize to a few candidates in the effective fraction. In the first part of the work, a selective two-dimensional HPTLC separation was developed to reduce the number of substances in a bioactive zone. After the first separation dimension (1D) the acetylcholinesterase inhibition assay (AChE assay) was performed and afterwards only the effective zones were extracted from the HPTLC plate. The selected effective zones were separated in a second separation dimension (2D) and the bioassay was performed again. With this 2D separation, the peak capacity could be increased by a factor of 7 compared to a 1D HPTLC gradient development. If real water samples are examined for their effects, an additional structural elucidation must be carried out to clearly identify the unknown bioactive substances. In this work, the developed 2D EDA was therefore connected to a high-performance liquid chromatography (HPLC) with high-resolution mass spectrometry (HRMS) and a non-target screening (NTS) was performed. Using three water samples(drinking water, surface water and purified sewage water) spiked with six effective substances, it was shown that the developed strategy is suitable for the identification of effective substances and that these can be recovered despite repeated extraction. When applying the developed methodology to real samples, it was also possible to assign and quantify the detected effect in several waters to the substance lumichrome and to linear alkylbenzene sulfonates. Genotoxicity is a crucial endpoint for the effect assessment of water samples. However, this endpoint with metabolic activation cannot yet be performed directly on the HPTLC plate. Since many of the genotoxic substances have an indirect genotoxic effect, i.e. they only acquire their activity after metabolic activation; this endpoint was investigated in the present work with the umu assay in the microtiter plate. However, separation with HPTLC, subsequent extraction of effective zones and non-target analysis of the extracts, should also be performed for this assay. Therefore the umu assay in the microtiter plate was integrated into the existing EDA-with-HPTLC concept. In laboratory experiments, sodium hypochlorite was added to the drug metformin in order to simulate the behavior of the substance during water treatment (chlorination). The metformin sample treated with hypochlorite was examined with the umu assay and a genotoxic effect was detected. After HPTLC separation of the chlorinated sample, zones were extracted over the entire retardation range. When the extracted zones were examined with the umu assay, the genotoxic effect could be clearly assigned to one fraction. Using high-resolution mass spectrometry, the genotoxic effect could be assigned to an already known transformation product of metformin. The HPTLC separation and extraction of the zones from the plate led to a reduction of the possible effective candidate masses by a factor of 10 and thus to a clear prioritization in HRMS analysis.