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Abstract Labile dissolved organic carbon in the surface oceans accounts for ~¼ of carbon produced through photosynthesis and turns over on average every three days, fueling one of the largest engines of microbial heterotrophic production on the planet. Volatile organic compounds are poorly constrained components of dissolved organic carbon. Here, we detected 72 m/z signals, corresponding to unique volatile organic compounds, including petroleum hydrocarbons, totaling approximately 18.5 nM in the culture medium of a model diatom. In five cocultures with bacteria adapted to grow with this diatom, 1 to 59 m/z signals were depleted. Two of the most active volatile organic compound consumers, Marinobacter and Roseibium, contained more genes encoding volatile organic compound oxidation proteins, and attached to the diatom, suggesting volatile organic compound specialism. With nanoscale secondary ion mass spectrometry and stable isotope labeling, we confirmed that Marinobacter incorporated carbon from benzene, one of the depleted m/z signals detected in the co-culture. Diatom gross carbon production increased by up to 29% in the presence of volatile organic compound consumers, indicating that volatile organic compound consumption by heterotrophic bacteria in the phycosphere – a region of rapid organic carbon oxidation that surrounds phytoplankton cells – could impact global rates of gross primary production. 

3D printing (3DP) has been becoming pervasive in the K-16 education system. However, in many schools, new 3D printers arrive, work for a certain period, and before long break down due to lack of maintenance and support. It is therefore imperative for teachers to develop a deeper understanding of 3D printing in order to fully release its potential in engineering design. In this project, the course of engineering design for preservice teachers (PST, current undergraduate students) is developed and implemented with mechanical components from dissected 3D printers. The approach is to dissect a 3D printer’s hardware, explain each component’s function, introduce each component’s manufacturing methods, describe possible defects, and elucidate what works and what does not. This allows the PSTs to develop a better understanding of 3D printing process, have a better idea on how to fix a 3D printer when it breaks down, and design components that are compatible with 3D printing. The evaluation results show that the course was well received by the PSTs who have improved their knowledge in 3D printing. In the future course offering, both knowledge gain and efficacy will be evaluated to help us better understand the impact of the course. 

Free viruses are the most abundant type of biological particles in the biosphere, but the lack of quantitative knowledge about their consumption by heterotrophic protists and bacterial degradation has hindered the inclusion of virovory in biogeochemical models. Using isotope-labeled viruses added to three independent microcosm experiments with natural microbial communities followed by isotope measurements with single-cell resolution and flow cytometry, we quantified the flux of viral C and N into virovorous protists and bacteria and compared the loss of viruses due to abiotic vs biotic factors. We found that some protists can obtain most of their C and N requirements from viral particles and that viral C and N get incorporated into bacterial biomass. We found that bacteria and protists were responsible for increasing the daily removal rate of viruses by 33% to 85%, respectively, compared to abiotic processes alone. Our laboratory incubation experiments showed that abiotic processes removed roughly 50% of the viruses within a week, and adding biotic processes led to a removal of 83% to 91%. Our data provide direct evidence for the transfer of viral C and N back into the microbial loop through protist grazing and bacterial breakdown, representing a globally significant flux that needs to be investigated further to better understand and predictably model the C and N cycles of the hydrosphere. 

X-ray and electron scattering from free gas-phase molecules is examined using the independent atom model (IAM) andab initioelectronic structure calculations. The IAM describes the effect of the molecular geometry on the scattering, but does not account for the redistribution of valence electrons due to, for instance, chemical bonding. By examining the total,i.e.energy-integrated, scattering from three molecules, fluoroform (CHF₃), 1,3-cyclohexadiene (C₆H₈) and naphthalene (C₁₀H₈), the effect of electron redistribution is found to predominantly reside at small-to-medium values of the momentum transfer (q≤ 8 Å⁻¹) in the scattering signal, with a maximum percent difference contribution at 2 ≤q≤ 3 Å⁻¹. A procedure to determine the molecular geometry from the large-qscattering is demonstrated, making it possible to more clearly identify the deviation of the scattering from the IAM approximation at small and intermediateqand to provide a measure of the effect of valence electronic structure on the scattering signal. 

Disulfide bonds are ubiquitous molecular motifs that influence the tertiary structure and biological functions of many proteins. Yet, it is well known that the disulfide bond is photolabile when exposed to ultraviolet C (UVC) radiation. The deep-UV–induced S─S bond fragmentation kinetics on very fast timescales are especially pivotal to fully understand the photostability and photodamage repair mechanisms in proteins. In 1,2-dithiane, the smallest saturated cyclic molecule that mimics biologically active species with S─S bonds, we investigate the photochemistry upon 200-nm excitation by femtosecond time-resolved x-ray scattering in the gas phase using an x-ray free electron laser. In the femtosecond time domain, we find a very fast reaction that generates molecular fragments with one and two sulfur atoms. On picosecond and nanosecond timescales, a complex network of reactions unfolds that, ultimately, completes the sulfur dissociation from the parent molecule. 

In 2019, University of Houston (UH) at Houston, Texas was awarded an NSF Research Experience for Teachers (RET) site grant titled “RET Site: High School Teacher Experience in Engineering Design and Manufacturing.” The goal of the project is to host 12 high school teachers each summer to participate in engineering design and manufacturing research and then convert their experience into high school curriculum. Given the experience from the first year’s operation and assessment, it was noted that the extant teacher self-efficacy surveys need to be further improved according to the specific needs of RET site. As such, an updated set of assessment tools was developed to evaluate the impact of RET site on high school teacher participants. In particular, a new teacher self-efficacy survey was created from synthesizing multiple sources including Bandura’s Instrument Teacher Self-Efficacy Scale, Collective Teacher Beliefs, and Teachers’ Sense of Efficacy Scale (Ohio State Teacher Efficacy Scale). Besides the new self-efficacy survey, more specific questions were added to pre- and post-summer self-reported questionnaires to better understand the teachers’ perception and receptance of the summer experience. Interviews were conducted individually instead of using a focus group. This allows the interviewee to be more vocal during the interview, allowing more in-depth understanding of their perception for future improvement. The new assessment tools were applied to the second cohort of 12 teachers in summer 2022. The assessment results show that the assessment tools were able to effectively capture teachers’ change in perception and evaluate the affective impact of the RET site. In the future, the tools may be improved and used in similar teacher professional development activities. 

Abstract Advances in x-ray free electron lasers have made ultrafast scattering a powerful method for investigating molecular reaction kinetics and dynamics. Accurate measurement of the ground-state, static scattering signals of the reacting molecules is pivotal for these pump-probe x-ray scattering experiments as they are the cornerstone for interpreting the observed structural dynamics. This article presents a data calibration procedure, designed for gas-phase x-ray scattering experiments conducted at the Linac Coherent Light Source x-ray Free-Electron Laser at SLAC National Accelerator Laboratory, that makes it possible to derive a quantitative dependence of the scattering signal on the scattering vector. A self-calibration algorithm that optimizes the detector position without reference to a computed pattern is introduced. Angle-of-scattering corrections that account for several small experimental non-idealities are reported. Their implementation leads to near quantitative agreement with theoretical scattering patterns calculated withab-initiomethods as illustrated for two x-ray photon energies and several molecular test systems.