Recent and ongoing curriculum innovations in Dutch secondary chemistry education have led to questions about which concepts should be central in the programme and which contexts should be used to embed these concepts into. Another important question is in the discussions about these innovations is: how do students learn chemistry? This thesis examines the relations between students' metacognitive beliefs, their learning outcomes, and the learning activities they conduct in the domain of chemistry. In studying these relations, a useful framework is provided bij Novak's educational theory on 'meaningful learning' as is described in chapter 2. In chapter 3, the development of an instrument for assessing students' metacognitive beliefs regarding chemistry is described. More specifically, this instrument, a questionnaire, consists of items that can be used to determine the nature of students' epistemological beliefs, learning conceptions, and goal orientations concerning chemistry. Using this instrument, it was found that the students' aforementioned metacognitive beliefs were highly interrelated. By means of the data produced in this study, an improved version of the instrument was constructed. We used this version of the instrument in a follow-up study and identified a set of items to assess a student's 'competence mindedness'. 'Competence mindedness' is defined as the extent to which students are oriented towards coming to understand subject matter in the chemical domain. This orientation is for instance inferred from students' beliefs about chemistry as a coherent body of knowledge and about chemistry learning as a process in which knowledge is actively constructed. We describe a student's score on this scale as the extent to which he is oriented towards developing chemical competence, or, in short, the student's 'competence mindedness'. As an indicator of students' chemical competence we used the so-called 'macro-micro concept'. The macro-micro concept consists of the ability to use the macro perspective (focusing on chemical phenomena on a substance level) and micro perspective on chemistry (focusing on the structure and behavior of subatomic particles) interchangeably. Although the macro-micro concept is considered to be a central chemical competence by many experts in the field of chemistry education, the concept itself is not mentioned explicitely in any Dutch chemistry textbook used in secondary education. Using the final version of the instrument described in chapter 3, relations between the competence mindedness of students and a central chemical competency were assessed in chapter 4. Consequently, an explorative study was conducted in which a small number of chemistry teachers was questioned on the extent to which they paid attention to the macro-micro concept in their own teaching. Five out of nine teachers interviewed, held the opinion that the macro-micro concept should be a part of chemistry teaching and consequently dedicated time in class to this concept. The other teachers that were interviewed, did not mention the macro-micro concept as a central chemical concept in the interviews. In another study, students' use of the macro-micro concept when answering regular chemistry test questions, was examined. From this study, it can be concluded that there are large differences in the students' use of this concept. However, from answers given by the students involved, it can be concluded that they use the macro-micro concept. Following from the last two studies mentioned, two more studies were conducted that focused on the use of the macro-micro concept by students. In particular we were interested in the way students use this concept differently than is to be expected from the sequencing of learning contents in chemistry textbooks. More specifically, we conducted two studies to determine if students' competence mindedness and the way they use the macro-micro concept (i.e. starting from the micro aspect or not) are related. In the first, small-scale, study, we concluded that senior students that are more competence minded, more often take the micro aspect of chemistry as a starting point when relating the micro and macro aspects of chemistry. In a follow-up study, a standardized instrument was used to assess students' use of the macro-micro concept. This instrument made it possible to include a larger sample of students in the study. This study confirmed the results found in the small-scale study: more competence minded students were found to prefer relations between the macro and micro aspects of chemistry that started from the micro aspect. Chapter 5 consists of several studies concerning students' notions about how the chemical domain can be described: their chemical domain beliefs. The development of these notions are considered an important indicator of chemical competence. Relations between students' competence mindedness and aspects of their chemical domain beliefs were examined through a repertory test procedure. More specifically, the students involved in this study were asked to compare the subject of chemistry with several other subjects. Thereby, data were gathered on constructs these students' used to describe the subject of chemistry and how they contrasted with the other subjects or resembled them. In another study, relations between students' chemical domain beliefs and the extent to which these students are competence minded were examined. The results show a number of relations between students' competence mindedness and selections of their chemical domain beliefs: in general, more competence minded students more often use concepts like 'chemistry as a science', 'properties of substances', and 'chemical reactions' to typify chemistry. Having found indications that students' competence mindedness regarding chemistry is related to their learning outcomes, the question arises how students' competence mindedness can be enhanced. Moreover, relations between students' competence mindedness and the learning strategies they deploy, have not been taken into consideration up to this point. In chapter 6, a learning environment was redesigned in the form of a student study guide, that is used as a supplement to the chemistry textbook students were used working with. The main purpose of the study guide was to change the type of learning activities students use. The two quasi-experimental studies in which the study guide was used as an intervention, did not lead to significant changes in students' learning activities. However, relations were found between students' learning activities and the extent to which students were competence minded. We conclude therefore, that the learning strategies used by the students involved in the study are in particular a consequence of their metacognitive beliefs, i.e. their competence mindedness, and not of the learning environment concerned.
Background: Adverse outcome pathway (AOP) networks are versatile tools in toxicology and risk assessment that capture and visualize mechanisms driving toxicity originating from various data sources. They share a common structure consisting of a set of molecular initiating events and key events, connected by key event relationships, leading to the actual adverse outcome. AOP networks are to be considered living documents that should be frequently updated by feeding in new data. Such iterative optimization exercises are typically done manually, which not only is a time-consuming effort, but also bears the risk of overlooking critical data. The present study introduces a novel approach for AOP network optimization of a previously published AOP network on chemical-induced cholestasis using artificial intelligence to facilitate automated data collection followed by subsequent quantitative confidence assessment of molecular initiating events, key events, and key event relationships. Methods: Artificial intelligence-assisted data collection was performed by means of the free web platform Sysrev. Confidence levels of the tailored Bradford-Hill criteria were quantified for the purpose of weight-of-evidence assessment of the optimized AOP network. Scores were calculated for biological plausibility, empirical evidence, and essentiality, and were integrated into a total key event relationship confidence value. The optimized AOP network was visualized using Cytoscape with the node size representing the incidence of the key event and the edge size indicating the total confidence in the key event relationship. Results: This resulted in the identification of 38 and 135 unique key events and key event relationships, respectively. Transporter changes was the key event with the highest incidence, and formed the most confident key event relationship with the adverse outcome, cholestasis. Other important key events present in the AOP network include: nuclear receptor changes, intracellular bile acid accumulation, bile acid synthesis changes, oxidative stress, inflammation and apoptosis. Conclusions: This process led to the creation of an extensively informative AOP network focused on chemical-induced cholestasis. This optimized AOP network may serve as a mechanistic compass for the development of a battery of in vitro assays to reliably predict chemical-induced cholestatic injury.
Lignocellulose biorefining is a promising technologyfor the sustainable production of chemicals and biopolymers.Usually, when one component is focused on, the chemical natureand yield of the others are compromised. Thus, one of thebottlenecks in biomass biorefining is harnessing the maximumvalue from all of the lignocellulosic components. Here, we describea mild stepwise process in a flow-through setup leading to separateflow-out streams containing cinnamic acid derivatives, glucose,xylose, and lignin as the main components from differentherbaceous sources. The proposed process shows that minimaldegradation of the individual components and conservation oftheir natural structure are possible. Under optimized conditions,the following fractions are produced from wheat straw based ontheir respective contents in the feed by the ALkaline ACid ENzyme process: (i) 78% ferulic acid from a mild ALkali step, (ii) 51%monomeric xylose free of fermentation inhibitors by mild ACidic treatment, (iii) 82% glucose from ENzymatic degradation ofcellulose, and (iv) 55% native-like lignin. The benefits of using the flow-through setup are demonstrated. The retention of the ligninaryl ether structure was confirmed by HSQC NMR, and this allowed monomers to form from hydrogenolysis. More importantly, thecrude xylose-rich fraction was shown to be suitable for producing polyhydroxybutyrate bioplastics. The direct use of the xylose-richfraction by means of the thermophilic bacteria Schlegelella thermodepolymerans matched 91% of the PHA produced with commercialpure xylose, achieving 138.6 mgPHA/gxylose. Overall, the ALACEN fractionation method allows for a holistic valorization of theprincipal components of herbaceous biomasses.
