Bridging over p-wave pi-production and weak processes in few-nucleon systems with chiral perturbation theory

I study an aspect of chiral perturbation theory (\chi PT) which enables one to ``bridge'' different reactions. That is, an operator fixed in one of the reactions can then be used to predict the other. For this purpose, I calculate the partial wave amplitude for the p-wave pion production (pp\to pn\pi^+) using the pion production operator from the lowest and the next nonvanishing orders. The operator includes a contact operator whose coupling has been fixed using a matrix element of a low-energy weak process (pp\to de^+\nu_e). I find that this operator does not reproduce the partial wave amplitude extracted from experimental data, showing that the bridging over the reactions with significantly different kinematics is not necessarily successful. I study the dependence of the amplitude on the various inputs such as the NN potential, the \pi N\Delta coupling, and the cutoff. I argue the importance of a higher order calculation. In order to gain an insight into a higher order calculation, I add a higher order counter term to the operator used above, and fit the couplings to both the low-energy weak process and the pion production. The energy dependence of the partial wave amplitude for the pion production is described by the operator consistently with the data. However, I find a result which tells us to be careful about the convergence of the chiral expansion for the pp\to pn\pi^+ reaction.Comment: 30 pages, 13 figures, figures changed, compacted tex

Self-Generated or Cue-Induced—Different Kinds of Expectations to Be Considered

Peer Reviewe

Eye Tracking Indicators of Reading Approaches in Text-Picture Comprehension

Despite numerous researches on reading as well as multimedia comprehension, reading approaches in text-picture comprehension have become a focus of research only rarely. The current experiment aims at exploring text-picture comprehension in different reading approaches with item solving. In a within subjects design using eye tracking, seventeen secondary school students processed our blended text and picture materials in three different ways. (1) Unguided processing with text and picture and without the question. (2) Information gathering to answer the question after the prior experience with text and pictures. (3) Comprehending text and pictures to solve the task with the prior information of the question. Eye tracking data showed that text and picture play different roles in comprehension in different reading approaches. The data suggest that (1) text plays the main role to construct the mental model in unguided spontaneous processing of text and picture. (2) Students seem to mainly rely on the picture as an external representation when trying to answer a question after the prior experience with the material. (3)Text and picture are both used heavily when students work out an answer with the prior experience with the question presented. The text likely plays a major part in guiding the processing of meaning, whereas the picture is used as an external representation for information retrieval. Our work provides a first step towards an Item Solving Model in Text-Picture Comprehension. It also provides pedagogical implications for learning in secondary school

Regulating distance to the screen while engaging in difficult tasks

Regulation of distance to the screen (i.e., head-to-screen distance, fluctuation of head-to-screen distance) has been proved to reflect the cognitive engagement of the reader. However, it is still not clear (a) whether regulation of distance to the screen can be a potential parameter to infer high cognitive load and (b) whether it can predict the upcoming answer accuracy. Configuring tablets or other learning devices in a way that distance to the screen can be analyzed by the learning software is in close reach. The software might use the measure as a person-specific indicator of need for extra scaffolding. In order to better gauge this potential, we analyzed eye-tracking data of children (N = 144, Mage = 13 years, SD = 3.2 years) engaging in multimedia learning, as distance to the screen is estimated as a by-product of eye tracking. Children were told to maintain a still seated posture while reading and answering questions at three difficulty levels (i.e., easy vs. medium vs. difficult). Results yielded that task difficulty influences how well the distance to the screen can be regulated, supporting that regulation of distance to the screen is a promising measure. Closer head-to-screen distance and larger fluctuation of head-to-screen distance can reflect that participants are engaging in a challenging task. Only large fluctuation of head-to-screen distance can predict the future incorrect answers. The link between distance to the screen and processing of cognitive task can obtrusively embody reader’s cognitive states during system usage, which can support adaptive learning and testing

Strategic influences on implementing instructions for future actions

Temporal and strategic factors that might influence the transformation of verbal task rules into functional stimulus–response associations were investigated in three experiments. In a dual task paradigm of the ABBA type participants were presented new S–R instructions for the A-task at the beginning of each trial. On varying proportions of trials No-go signals rendered the instructed A-task mappings irrelevant before instruction implementation was assessed during performance of an unrelated B-task. Our results indicate that participants refrain from implementing the mappings during instruction presentation when No-go signals appear frequently and late (Exp. 2), and that they can interrupt implementing instructed S–R mappings when frequent No-go signals appear early enough during implementation (Exp. 3). When No-go signals are rare and late, however (Exp. 1), the instructed stimulus features always activate their associated responses during performance of the embedded B-task in an automatic manner. Together, these findings suggest that participants strategically control whether or not they implement verbal instructions. Once implemented, however, instructed S–R associations influence behaviour even when the instructed mappings are no longer task relevant

Molecular Design as a Tool to Understand and Manipulate Cell Death

Phenotypic screening is a powerful technique for discovering small organic molecules with the ability to effect a desired change in biological systems. Yet, because of the diversity of ways that a small molecule can alter a biological system, phenotypic screens provide little to no insight into how a hit molecule elicits such a change. Understanding a molecule’s mechanism of action—which proteins it engages, where it localizes, and its reactivity—is critical to fully developing a hit molecule into a research tool or a therapeutic. In this dissertation, strategic, hypothesis-driven molecular design is used as a cornerstone technique to understand the mechanism of action of molecules that regulate cell death. In the first part, we examine the structural requirements for ferroptotic death induction by the 1,2-dioxolane FINO2. Next, we create a panel of ferroptosis inhibiting molecules that are targeted to specific organelles and used as imaging agents in order to examine the contribution of different organelles to ferroptosis. I then apply molecular design in a target-based context to discover which molecular features of LOC14 promote association with its receptor protein. Finally, I discuss a computational approach to developing a ligand that inhibits protein-protein interactions mediated by the small GTPase Rheb