First Light for the BYU 0.9-m Telescope

Preservice elementary teachers enter their science methods courses with a range of prior experience with science practice. Those prior experiences likely inform much of their science pedagogy and goals. In this study, the authors examine how a cohort of preservice elementary teachers engaged in science practice as they learned content in a physics course. Drawing on course documents, videorecords, and artifacts from in-class lab work and interviews with nine participants, the authors used an asset-based, mixed methods approach. The authors developed rubrics to assess the level of sophistication the participants used while engaging in science practice on a scale of 1 (pre-novice) to 4 (experienced). They used descriptive statistics and ANOVA's to interpret the performance of the participants in addition to grounded theory open coding of interviews to determine the participants' level of prior experience with science practice. The findings suggest that these preservice teachers primarily engaged in science practices at a novice level. In general, their sophistication scores on the rubric aligned with their prior experience. The findings suggest that while one content course steeped in science practice was not enough to significantly change preservice teachers' engagement, it can provide a needed starting place and that it likely takes time to develop these skills. The findings have implications for both teacher educators and researchers who hope to increase the use of science practice as a method of learning science content.

The ubiquity of particulate contamination requires dust mitigation techniques to provide low scatter surfaces and edges on sensitive optical devices in space. Poly(olefin sulfone)s have been shown to photodegrade with the assistance of a photobase generator when exposed to UV light (254 nm) and heat (120 °C). These may be applicable in minimizing dust on optical surfaces for space applications. However, their behavior in vacuum has not been fully characterized. We synthesized poly(2-methyl-1-pentene sulfone) (PMPS) and poly(1-hexene sulfone) (PHS) with and without a photobase generator. We studied the photodegradation (172 nm or 254 nm) of thin films in vacuum. Spectroscopic ellipsometry was used to quantify film thickness over time. The PMPS and PHS films both degraded when exposed to UV light in vacuum, though PHS to a lesser degree. We found that heat was not required to cause degradation, and that degradation occurred with UV irradiation even without a photobase generator. This investigation shows that poly(olefin sulfone)s could be used to protect optical surfaces until their deployment in space.

Focusing waves with a spatial extent smaller than a half wavelength (i.e., super resolution or sub diffraction limit) is possible using resonators placed in the near field of time reversal (TR) focusing. While a two-dimensional (2D) Helmholtz resonator array in a three-dimensional reverberant environment has limited ability to produce a high-resolution spatial focus in the TR focusing of audible sound, it is shown that acoustic waves propagating out-of-plane with the resonator array are not as strongly affected by the smaller effective wavelength induced by the resonator array, partially negating the effect of the resonators. A physical 2D waveguide is shown to limit the out-of-plane propagation, leading to improved resolution. It is also shown that post processing using an orthogonal particle velocity decomposition of a spatial scan of the focusing can filter out-of-plane particle motion in the near field of the array, which bypasses the effect of the unwanted third spatial dimension of propagation. The spatial resolution in a reverberant environment is shown to improve in the presence of a 2D Helmholtz resonator array and then further improve by adding a 2D waveguide. The resolution among the resonator array is better still without using a waveguide and instead using the partial-pressure reconstruction.

An ocean acoustics experiment in 2017 near a shipping lane on the New England continental shelf in about 75 m of water provided an opportunity to evaluate a methodology to extract source signatures of merchant ships in a bottom-limited environment. The data of interest are the received acoustic levels during approximately 20 min time intervals centered at the closest position of approach (CPA) time for each channel on two 16-element vertical line arrays. At the CPA ranges, the received levels exhibit a frequency-dependent peak and null structure, which possesses information about the geophysical properties of the seabed, such as the porosity and sediment thickness, and the characterization of the source, such as an effective source depth. The modeled seabed is represented by two sediment layers, parameterized with the viscous grain shearing (VGS) model, which satisfies causality, over a fixed deep layered structure. Inferred estimates of the implicit source levels require averaging an error function over the full 20 min time intervals. Within the 200-700 Hz band, the Wales-Heitmeyer model captures the inferred frequency dependence of the source levels.

We fit various color-magnitude diagrams (CMDs) of the high-latitude Galactic globular clusters NGC 5024 (M53), NGC 5053, NGC 5272 (M3), NGC 5466, and NGC 7099 (M30) by isochrones from the Dartmouth Stellar Evolution Database and Bag of Stellar Tracks and Isochrones for alpha-enrichment [alpha/Fe] = +0.4. For the CMDs, we use data sets from Hubble Space Telescope, Gaia, and other sources utilizing, at least, 25 photometric filters for each cluster. We obtain the following characteristics with their statistical uncertainties for NGC 5024, NGC 5053, NGC 5272, NGC 5466, and NGC 7099, respectively: metallicities [Fe/H] = -1.93 +/- 0.02, -2.08 +/- 0.03, -1.60 +/- 0.02, -1.95 +/- 0.02, and -2.07 +/- 0.04 dex with their systematic uncertainty 0.1 dex; ages 13.00 +/- 0.11, 12.70 +/- 0.11, 11.63 +/- 0.07, 12.15 +/- 0.11, and 12.80 +/- 0.17 Gyr with their systematic uncertainty 0.8 Gyr; distances (systematic uncertainty added) 18.22 +/- 0.06 +/- 0.60, 16.99 +/- 0.06 +/- 0.56, 10.08 +/- 0.04 +/- 0.33, 15.59 +/- 0.03 +/- 0.51, and 8.29 +/- 0.03 +/- 0.27 kpc; reddenings E(B - V) = 0.023 +/- 0.004, 0.017 +/- 0.004, 0.023 +/- 0.004, 0.023 +/- 0.003, and 0.045 +/- 0.002 mag with their systematic uncertainty 0.01 mag; extinctions A(V) = 0.08 +/- 0.01, 0.06 +/- 0.01, 0.08 +/- 0.01, 0.08 +/- 0.01, and 0.16 +/- 0.01 mag with their systematic uncertainty 0.03 mag, which suggest the total Galactic extinction A(V) = 0.08 across the whole Galactic dust to extragalactic objects at the North Galactic Pole. The horizontal branch morphology difference of these clusters is explained by their different metallicity, age, mass-loss efficiency, and loss of low-mass members in the evolution of the core-collapse cluster NGC 7099 and loose clusters NGC 5053 and NGC 5466.

The coherent recombination of a direct and seabed reflected path is sensitive to the geophysical properties of the seabed. The concept of feature-based inversion is used in the analysis of acoustic data collected on a vertical line array (VLA) on the New England continental shelf break in about 200 m of water. The analysis approach for the measurements is based on a ray approach in which a direct and bottom reflected path is recombined, resulting in constructive and destructive interference of the acoustic amplitudes with frequency. The acoustic features have the form of prominent nulls of the measured received levels as a function of frequency as a broadband (500–4500 Hz) source passes the closest point of approach to the VLA. The viscous grain shearing (VGS) model is employed to parameterize a two-layer seabed model. The most likely seabed is a sand sediment with a porosity of about 0.42. There is a possibility of a thin (less than 0.5 m) surface layer having a slightly higher porosity between 0.45 and 0.50. Using the estimates for the VGS parameters inferred from the short-range frequency features, a normal mode model is used to predict the received acoustic levels over larger range scales.