Epistemic Network Analyses of Economics Students' Graph Understanding: An Eye-Tracking Study.

Learning to solve graph tasks is one of the key prerequisites of acquiring domain-specific knowledge in most study domains. Analyses of graph understanding often use eye-tracking and focus on analyzing how much time students spend gazing at particular areas of a graph-Areas of Interest (AOIs). To gain a deeper insight into students' task-solving process, we argue that the gaze shifts between students' fixations on different AOIs (so-termed transitions) also need to be included in holistic analyses of graph understanding that consider the importance of transitions for the task-solving process. Thus, we introduced Epistemic Network Analysis (ENA) as a novel approach to analyze eye-tracking data of 23 university students who solved eight multiple-choice graph tasks in physics and economics. ENA is a method for quantifying, visualizing, and interpreting network data allowing a weighted analysis of the gaze patterns of both correct and incorrect graph task solvers considering the interrelations between fixations and transitions. After an analysis of the differences in the number of fixations and the number of single transitions between correct and incorrect solvers, we conducted an ENA for each task. We demonstrate that an isolated analysis of fixations and transitions provides only a limited insight into graph solving behavior. In contrast, ENA identifies differences between the gaze patterns of students who solved the graph tasks correctly and incorrectly across the multiple graph tasks. For instance, incorrect solvers shifted their gaze from the graph to the x-axis and from the question to the graph comparatively more often than correct solvers. The results indicate that incorrect solvers often have problems transferring textual information into graphical information and rely more on partly irrelevant parts of a graph. Finally, we discuss how the findings can be used to design experimental studies and for innovative instructional procedures in higher education.

Changes in Students' Understanding of and Visual Attention on Digitally Represented Graphs Across Two Domains in Higher Education: A Postreplication Study.

Domain-specific understanding of digitally represented graphs is necessary for successful learning within and across domains in higher education. Two recent studies conducted a cross-sectional analysis of graph understanding in different contexts (physics and finance), task concepts, and question types among students of physics, psychology, and economics. However, neither changes in graph processing nor changes in test scores over the course of one semester have been sufficiently researched so far. This eye-tracking replication study with a pretest-posttest design examines and contrasts changes in physics and economics students' understanding of linear physics and finance graphs. It analyzes the relations between changes in students' gaze behavior regarding relevant graph areas, scores, and self-reported task-related confidence. The results indicate domain-specific, context- and concept-related differences in the development of graph understanding over the first semester, as well as its successful transferability across the different contexts and concepts. Specifically, we discovered a tendency of physics students to develop a task-independent overconfidence in the graph understanding during the first semester.

Undergraduate Students' Critical Online Reasoning-Process Mining Analysis.

To successfully learn using open Internet resources, students must be able to critically search, evaluate and select online information, and verify sources. Defined as critical online reasoning (COR), this construct is operationalized on two levels in our study: (1) the student level using the newly developed Critical Online Reasoning Assessment (CORA), and (2) the online information processing level using event log data, including gaze durations and fixations. The written responses of 32 students for one CORA task were scored by three independent raters. The resulting score was operationalized as "task performance," whereas the gaze fixations and durations were defined as indicators of "process performance." Following a person-oriented approach, we conducted a process mining (PM) analysis, as well as a latent class analysis (LCA) to test whether-following the dual-process theory-the undergraduates could be distinguished into two groups based on both their process and task performance. Using PM, the process performance of all 32 students was visualized and compared, indicating two distinct response process patterns. One group of students (11), defined as "strategic information processers," processed online information more comprehensively, as well as more efficiently, which was also reflected in their higher task scores. In contrast, the distributions of the process performance variables for the other group (21), defined as "avoidance information processers," indicated a poorer process performance, which was also reflected in their lower task scores. In the LCA, where two student groups were empirically distinguished by combining the process performance indicators and the task score as a joint discriminant criterion, we confirmed these two COR profiles, which were reflected in high vs. low process and task performances. The estimated parameters indicated that high-performing students were significantly more efficient at conducting strategic information processing, as reflected in their higher process performance. These findings are so far based on quantitative analyses using event log data. To enable a more differentiated analysis of students' visual attention dynamics, more in-depth qualitative research of the identified student profiles in terms of COR will be required.

Synthesis of the Entomopathogenic Fungus Metabolites Militarinone C and Fumosorinone A.

Militarinone C and fumosorinone A, 3-oligoenoyltetramic acids produced by insect pathogenic fungi, were synthesized for the first time. The pyrrolidine-2,4-dione ring was closed through a late-stage Dieckmann condensation of N-(ß-ketoacyl) derivatives of tyrosine, obtained by its acylation with either thioesters or Meldrum's acid derivatives bearing the all- trans-polyene side chain. The latter was built up from ( S)-citronellol via an Evans methylation and Wittig or HWE olefinations.

A Synthetic Route to ß-Hydroxytyrosine-Derived Tetramic Acids: Total Synthesis of the Fungal Metabolite F-14329.

3-Acyltetramic acids derived from ß-hydroxytyrosine are synthetically challenging. The first route to this structural motif, based upon a condensation between a Meldrum's acid conjugate bearing the acyl side chain, and a ß-hydroxytyrosinate, N-protected by an ortho-nitrobenzyl group is presented. This group enables the Dieckmann cyclization of the resulting N-(ß-ketoacyl)amino ester, after which it can be removed photolytically without compromising the delicate 3'-hydroxy group. This strategy was applied to the first total synthesis of the fungal metabolite F-14329 (1).

Synthesis and Antibacterial Activity of Four Stereoisomers of the Spider-Pathogenic Fungus Metabolite Torrubiellone D.

Four stereoisomers of the spider-pathogenic fungus metabolite torrubiellone D were synthesized for the first time in 10% overall yield starting from L-tyrosine or D-tyrosine. The 3-decatrienoyl side chain was assembled and attached via (E)-selective HWE and Wittig olefinations. Their antibiotic activities against drug-susceptible Escherichia coli strains differed considerably.

Time-Resolved In Situ Spectroscopy During Formation of the GaP/Si(100) Heterointerface.

Though III-V/Si(100) heterointerfaces are essential for future epitaxial high-performance devices, their atomic structure is an open historical question. Benchmarking of transient optical in situ spectroscopy during chemical vapor deposition to chemical analysis by X-ray photoelectron spectroscopy enables us to distinguish between formation of surfaces and of the heterointerface. A terrace-related optical anisotropy signal evolves during pulsed GaP nucleation on single-domain Si(100) surfaces. This dielectric anisotropy agrees well with the one calculated for buried GaP/Si(100) interfaces from differently thick GaP epilayers. X-ray photoelectron spectroscopy reveals a chemically shifted contribution of the P and Si emission lines, which quantitatively corresponds to one monolayer and establishes simultaneously with the nucleation-related optical in situ signal. We attribute that contribution to the existence of Si-P bonds at the buried heterointerface. During further pulsing and annealing in phosphorus ambient, dielectric anisotropies known from atomically well-ordered GaP(100) surfaces superimpose the nucleation-related optical in situ spectra.

Formation of GaP/Si(100) Heterointerfaces in the Presence of Inherent Reactor Residuals.

Adequate silicon preparation is a prerequisite for defect-free III-V growth on Si. We transfer the silicon processing from clean to GaP containing metalorganic vapor phase epitaxy reactors, where we monitor the entire process in situ with reflection anisotropy spectroscopy and analyze the chemical composition of the surface with X-ray photoelectron spectroscopy. Beyond a certain submonolayer threshold value of (Ga,P) residuals found on the Si(100) surface, GaP grows with an inverted majority sublattice. Analogously to III-V growth on two-domain substrates, the coexistence of Si-Ga and Si-P interfacial bonds at terraces of the same type causes antiphase disorder in GaP epilayers.