635 research outputs found

    Infusing Problem-Based Learning (PBL) Into Science Methods Courses Across Virginia

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    This article outlines the results of a collaborative study of the effects of infusing problem-based learning (PBL) into K-12 science methods courses across four universities in Virginia. Changes in pre-service teachers\u27 attitudes surrounding science teaching were measured before and after completing a science methods course in which they experienced PBL first-hand as participants, and then practiced designing their own PBL units for use in their future classrooms. The results indicate that exposure to PBL enhances pre-service teachers\u27 knowledge of inquiry methods and self-efficacy in teaching science

    Phosphonate production by marine microbes: exploring new sources and potential function

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    © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Acker, M., Hogle, S. L., Berube, P. M., Hackl, T., Coe, A., Stepanauskas, R., Chisholm, S. W., & Repeta, D. J. Phosphonate production by marine microbes: exploring new sources and potential function. Proceedings of the National Academy of Sciences of the United States of America, 119(11), (2022): e2113386119, https://doi.org/10.1073/pnas.2113386119.Phosphonates are organophosphorus metabolites with a characteristic C-P bond. They are ubiquitous in the marine environment, their degradation broadly supports ecosystem productivity, and they are key components of the marine phosphorus (P) cycle. However, the microbial producers that sustain the large oceanic inventory of phosphonates as well as the physiological and ecological roles of phosphonates are enigmatic. Here, we show that phosphonate synthesis genes are rare but widely distributed among diverse bacteria and archaea, including Prochlorococcus and SAR11, the two major groups of bacteria in the ocean. In addition, we show that Prochlorococcus can allocate over 40% of its total cellular P-quota toward phosphonate production. However, we find no evidence that Prochlorococcus uses phosphonates for surplus P storage, and nearly all producer genomes lack the genes necessary to degrade and assimilate phosphonates. Instead, we postulate that phosphonates are associated with cell-surface glycoproteins, suggesting that phosphonates mediate ecological interactions between the cell and its surrounding environment. Our findings indicate that the oligotrophic surface ocean phosphonate pool is sustained by a relatively small fraction of the bacterioplankton cells allocating a significant portion of their P quotas toward secondary metabolism and away from growth and reproduction.This work was supported in part by grants from the NSF (OCE-1153588 and DBI-0424599 to S.W.C.; OCE-1335810 and OIA-1826734 to R.S.; and OCE-1634080 to D.J.R.), the Gordon and Betty Moore Foundation (no. 6000 to D.J.R.), and the Simons Foundation (Life Sciences Project Award IDs 337262 and 647135 to S.W.C.; 510023 to R.S.; and Simons Collaboration on Ocean Processes and Ecology [SCOPE] Award ID 329108 to S.W.C. and D.J.R.)

    Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope

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    We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HAT-P-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b, XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system and variations in planetary radius with wavelength can help constrain the properties of the exoplanet's atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths that may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2-4.6σ\sigma, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for 5 of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b, WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.Comment: 18 pages, 7 figures, 9 Tables. Light Curves available online. Accepted to MNRAS (2017 August 25
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