Search

This work presents a detailed case study on using Generative AI (GenAI) to develop AI surrogates for simulation models in fusion energy research. The scope includes the methodology, implementation, and results of using GenAI to assist in model development and optimization, comparing these results with previous manually developed models.

An applied field can modulate optical signals by resonance shifting via the Stark effect. The optical Stark effect (OSE) uses ultrafast light in the transparency region of a material to shift resonances with speeds limited by the pulse duration or system coherence. In this Letter we investigate the OSE in resonant optical harmonic generation (OHG) using the ground state exciton transition of WS2 with a variety of morphologies. Multidimensional pump-harmonic-probe measurements, in which the probe is second- or third-harmonic emission, reveal not only large Stark shifts that are commensurate with the large optical susceptibilities common to WS2 excitons, but also behaviors more complex than simple OSE treatments predict. We show how a new manifestation of the Stark Effect, brought forth by coherent photon exchange between the pump and OHG fundamental fields, can strongly enhance or suppress OHG.

Triple sum-frequency (TSF) spectroscopy measures multidimensional spectra by resonantly exciting multiple quantum coherences of vibrational and electronic states. In this work we demonstrate pump-TSF-probe spectroscopy in which a pump excites a sample and some time later three additional electric fields generate a probe field which is measured. We demonstrate pump-TSF-probe spectroscopy on polycrystalline, smooth, thin films and spiral nanostructures of both MoS2 and WS2. The pump-TSF-probe spectra are qualitatively similar to the more conventional transient-reflectance spectra. While transient-reflectance sensitivity suffers under low surface coverage, pump-TSF-probe sensitivity is independent of the sample coverage and nanostructure morphologies. Our results demonstrate that pump-TSF-probe is a valuable methodology for studying microscopic material systems.

Triple sum-frequency (TSF) spectroscopy is a recently-developed methodology that enables collection of multidimensional spectra by resonantly exciting multiple quantum coherences of vibrational and electronic states. This work reports the first application of TSF to the electronic states of semiconductors. Two independently tunable ultrafast pulses excite the A, B, and C features of a MoS2 thin film. The measured TSF spectrum differs markedly from absorption and second harmonic generation spectra. The differences arise because of the relative importance of transition moments and the joint density of states. We develop a simple model and globally fit the absorption and harmonic generation spectra to extract the joint density of states and the transition moments from these spectra. Our results validate previous assignments of the C feature to a large joint density of states created by band nesting.

The effects of group and phase velocity mismatch are well-known in optical harmonic generation, but the non-degenerate cases remain unexplored. In this work we develop an analytic model which predicts velocity mismatch effects in non-degenerate triple sum-frequency mixing, TSF. We verify this model experimentally using two tunable, ultrafast, short-wave-IR lasers to demonstrate spectral fringes in the TSF output from a 500 $\mu$m thick sapphire plate. We find the spectral dependence of the TSF depends strongly on both the phase velocity and the group velocity differences between the input and output fields. We define practical strategies for mitigating the impact of velocity mismatches.

This paper reports on a study of a structured active learning approach to an analytical chemistry course. The purpose of the study was to assess the longitudinal outcomes of this approach and to provide feedback to curriculum developers about the effects of the changes being made in the chemistry curriculum. The data, collected from a cohort of students in 1995, consists of open-ended interviews with students, open-ended student survey questions, Likert scale student survey items, and faculty and teaching assistant interviews. The results indicate that there is a number of longitudinal effects of structured active learning and although it is possible to assert that the comparison group does not report the kinds of learning outcomes that the structured active learning students report, further study is needed to be sure that the findings are reliable. Contains 11 references. (DDR)

This paper reports on a unique assessment of a structured active learning approach to a freshman chemistry course. Faculty members (N=25) from 11 departments outside the chemistry department served as assessors interviewing approximately 200 students from the experimental and a comparison version of the course. The experimental section of the course, characterized by a structured active learning approach, includes specific strategies such as an absolute grading scale, open-ended laboratory projects, and a variety of interactive lecture techniques. Two specific conclusions can be drawn from this study: (1) there are a number of longitudinal effects of structured active learning; and (2) although it is possible to assert that the comparison group does not report the kinds of learning outcomes that the structured active learning students report, further study is needed to be sure that the findings are reliable. (DDR)

Describes the evolution of a primary, community-based drug prevention program and the challenges associated with becoming established within a particular community. Addresses the use of consortium to implement program goals and objectives; parental involvement and home visitation; developing and maintaining a positive relationship with the host organization; developing a curriculum for effective execution of program interventions; and the evaluation process. (Contains 27 references.) (GCP)

Children's attention to and comprehension of television programs were studied by comparing the effects of viewing continuous stories (i.e., those with meaningful plots brought to resolution) and magazine-format programs containing unrelated bits of entertainment. Effects of program pacing were also studied. Multiple programs, differing in content, were developed for each of four design cells (high/low pace by high/low continuity). Participants were 160 children divided into two age groups (kindergarten/first and third/fourth grades). Visual fixation of the television monitor was recorded during viewing of two programs in same-sex pairs, and children were then tested individually for comprehension and recall of both programs, using a non-verbal procedure requiring the child to order five still photographs from the program and five from a single segment. Control scores were obtained by having children order photos from one program which they had not viewed. Results indicated that the integrated stories can be effectively used to promote both attention and comprehension at an early age, because children clearly responded to and used the organizational structure provided by television stories even when the stories were low pace. Twelve references, and tables showing study design and attention and comprehension data are included. (LMM)

This study investigated two methods for establishing a systematic, selective, attending strategy in a memory task for children. One method was direct training of a specific strategy, employing instructions, fading, modeling, and prompts to direct the child's attention to the relevant features and to organize systematic looking behavior. The second method involved the design of the stimuli, making relevant features perceptually more (or less) salient. Observing behavior and short-term recognition were studied. Sixty 3 1/2-to-5 1/2-year-old children matched pictures from memory with either strategy training for systematic scanning or placebo practice followed by transfer. One-third of the subjects in each condition saw stimuli with relevant portions made perceptually salient, another third with irrelevant portions salient, and the rest with no portions salient. Strategy training enhanced systematic relevant observing behavior and facilitated recognition in both training and transfer. Stimulus saliency, when irrelevant, interfered in training for placebo subjects. Saliency directly influenced looking behavior only for young subjects in the early part of each trial. (Author/SB)

Examined whether children's schemata for occupations they observe in real life differ from schemata for occupations portrayed on television. Found that children do form separate schemata for television and real life. Compared to subjects' schemata of real life occupations, those for television versions entailed more glamour, higher income, more stereotypes, and more dramatic events without negative consequences. (HTH)

Five and seven year olds were able to correctly distinguish between factual and fictional television programs and test clips, based upon genre of program, production features, content. Age and vocabulary scores predicted accuracy of factuality judgments, but television viewing history did not. Older children understood better than younger ones that fictional characters do not retain roles in real life. (MDM)