The age estimation of biological traces is one of the holy grails in forensic investigations. We developed a method for the age estimation of semen stains using fluorescence spectroscopy in conjunction with a stoichiometric ageing model. The model describes the degradation and generation rate of proteins and fluorescent oxidation products (FOX) over time. The previously used fluorimeter is a large benchtop device and requires system optimization for forensic applications. In situ applications have the advantage that measurements can be performed directly at the crime scene, without additional sampling or storage steps. Therefore, a portable fiber-based fluorimeter was developed, consisting of two optimized light-emitting diodes (LEDs) and two spectrometers to allow the fluorescence protein and FOX measurements. The handheld fiber can be used without touching the traces, avoiding the destruction or contamination of the trace. In this study, we have measured the ageing kinetics of semen stains over time using both our portable fluorimeter and a laboratory benchtop fluorimeter and compared their accuracies for the age estimation of semen stains. Successful age estimation was possible up to 11 days, with a mean absolute error of 1.0 days and 0.9 days for the portable and the benchtop fluorimeters, respectively. These results demonstrate the potential of using the portable fluorimeter for in situ applications.
Many citizens experience ambivalence – having simultaneously positive and negative evaluations – about changing their behaviour towards a more environmentally friendly lifestyle. Based on 36 studies, this study identifies and synthesises the current evidence on how ambivalence impacts environmental behaviours. In most studies, ambivalence is shown to be directly and negatively associated with environmental behaviours, i.e., higher levels of ambivalence are linked to lower levels of environmentally friendly and unfriendly behaviours. This applies to both types of ambivalence: objective (OA) and subjective (SA). Mediator analyses show, in line with the theory, that SA, not OA, drives behavioural change. In addition, results indicate that ambivalence moderates the relationship between independent–dependent variables mainly negatively, for example, by weakening attitude–behaviour relationships. This review shows the potential of ambivalence to facilitate behaviour change: SA about environmentally friendly behaviour can hinder, whereas SA about environmentally unfriendly behaviour can motivate, behaviour change. In addition, this review highlights some significant knowledge gaps in this body of research. A lack of validated standardised measurements of ambivalence makes it challenging to compare studies and reach conclusions about underlying theoretical constructs. Methods, research designs, and theoretical underpinnings need improvement to fully understand ambivalence and progress towards the transition of environmentally friendly behaviours.
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