Knowledge of the time of deposition is pivotal in forensic investigations. Recent studies show that changes in intrinsic fluorescence over time can be used to estimate the age of body fluids. These changes have been attributed to oxidative modifications caused by protein–lipid interactions. This pilot study aims to explore the impact of these modifications on body fluid fluorescence, enhancing the protein–lipid model system for age estimation. Lipid and protein oxidation markers, including protein carbonyls, dityrosine, advanced glycation end-products (AGEs), malondialdehyde (MDA), and 4-hydroxynonenal (HNE), were studied in aging semen, urine, and saliva over 21 days. Surface plasmon resonance imaging (SPRi), enzyme-linked immunosorbent assay (ELISA), and fluorescence spectroscopy were applied. Successful detection of AGE, dityrosine, MDA, and HNE occurred in semen and saliva via SPRi, while only dityrosine was detected in urine. Protein carbonyls were measured in all body fluids, but only in saliva was a significant increase observed over time. Additionally, protein fluorescence loss and fluorescent oxidation product formation were assessed, showing significant decreases in semen and saliva, but not in urine. Although optimization is needed for accurate quantification, this study reveals detectable markers for protein and lipid oxidation in aging body fluids, warranting further investigation.
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The research in this dissertation aims to investigate the acquisition of students’ science skills in grades 5 and 6 of primary education in the Netherlands. In most primary science classes, science skills are mainly taught by way of conducting investigations. However, prior research indicates that explicit instruction and separate skills training may be more effective. In this dissertation, four studies are discussed. In the first study, an instructional framework was developed based on a categorization of science skills into thinking skills, science-specific skills and metacognitive skills. This instructional framework was used to develop lessons using systematic instruction aimed at the development of these different skills. The second study describes the development and psychometric quality of the measurement instruments in order to examine the acquisition and transfer of science skills. Two paper-and-pencil tests, three performance assessments and two questionnaires were used for this purpose. In a third study, the effects of two experimental conditions were evaluated, following an experimental pretest-posttest design: a condition with explicit instruction and a condition in which all aspects of explicit instruction were absent. Students in both conditions received an 8-week intervention and were compared to students in a baseline condition who followed their regular science curriculum. The fourth study addresses the use of performance assessments as a diagnostic tool for science teachers. In general, the results indicate that the measurement instruments can be used to reliably measure science skills. Findings also show that explicit instruction facilitates acquisition and transfer of science skills.
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