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Succinic acid, a four-carbon (C4) dicarboxylic acid, was previously identified by the U.S. Department of Energy as a ‘Top Value-Added Chemical from Biomass’ due to its ability to be converted to numerous other high-value chemicals and materials2, including food additives, resins, biodegradable plastics and polymers, pharmaceutical formulations, and cosmetics3. As an alternative to its petroleum-based synthesis, succinic acid can instead be produced from biomass-derived sugars by metabolically engineered E. coli during anaerobic fermentation primarily by two different pathways: the reductive branch of the tricarboxylic acid (rTCA) cycle, a carbon-negative process, and the tricarboxylic acid (TCA) cycle, a carbon-positive process. During glucose fermentation to succinate, specifically in strains relying exclusively on glucokinase for glucose uptake (i.e. E. coli KJ122), a max theoretical yield of 1.71 mol mol-1 glucose is achievable, where 2 units of phosphoenolpyruvate (PEP) are generated in which 71.4% of PEP is directed through the rTCA cycle (requiring 2 units of NADH and 1 unit of CO2 per unit of succinic acid produced), and 28.6% of PEP is directed through the TCA cycle (generating up to 2 units of NADH and CO2 per unit of PEP). The purpose for E. coli KJ122 partially redirecting carbon through the TCA cycle is to satisfy a redox imbalance (i.e. a deficit in reducing cofactor NADH required for the rTCA cycle) when and if, theoretically, 100% of carbon is directed through the rTCA cycle. Comparatively, malic acid producing strains (i.e. E. coli MO128), generate 2 units of NADH per unit of glucose consumed, and subsequently requires 1 units of NADH per unit of malic acid produced, which ultimately creates a balanced redox condition and results in a maximum theoretical malic acid yield of 2 mol mol-1 glucose. 

Value-added chemicals produced from biomass remain of great interest as renewable and sustainable alternatives to conventional petrochemicals. In particular, four-carbon (C4) dicarboxylic acids, which includes both succinic and malic acid, were previously identified by the U.S. Department of Energy as ‘Top Value-Added Chemicals from Biomass’ due to their ability to be converted to numerous other high-value chemicals and materials. As an alternative to their petroleum-based synthesis, succinic and malic acid can instead be produced from biomass-derived sugars under anaerobic fermentation conditions by metabolically engineered Escherichia coli via the reductive branch of the tricarboxylic acid (rTCA) cycle. In this carbon-negative process, phosphoenolpyruvate carboxylase and/or carboxykinase fix inorganic carbon which must in turn be supplied to the process as an essential co-substrate. Although (bi)carbonate salts (i.e., HCO3 - and/or CO3 2-) are typically used during conventional fermentations, their production remains thermodynamically unfavorable (ΔG = +54.9 kJ/mol) and thus extremely energy intensive (e.g., 9.7-13.6 GJ/ton NaHCO3), making it unsustainable. Meanwhile, as global annual CO2 emissions have now reached 37.6 Gt, the alternative ability to directly use CO2 as feedstock in these and other bioprocesses would be highly advantageous for enhancing sustainability, improving the circular CO2 economy, and curbing the e\ects of climate change. That said, e\icient supply of CO2 to aqueous fermentation broths remains a significant bottleneck as conventional delivery mechanisms (i.e., spargers, bubblers, porous di\users) display relatively poor gas-liquid mass transfer. We have been exploring how such limitations can be addressed during E. coli succinic and malic acid using hollow fiber membranes (HFMs) to achieve direct and e\icient CO2 delivery in a bubbleless and on-demand manner. For example, as guided by a CO2 mass transfer model which predicts CO2 dissolution rates in a novel HFM bioreactor as a function of relevant process variables, CO2 delivery pressure (2.5 psig) and HFM specific surface area (7.4 m-1) were readily tuned to maximize malic acid titer (38.2 g/L) and yield (0.94 g/g); performance comparable to conventional fermentations with directly supplied (bi)carbonate salts. Meanwhile, by performing a total carbon balance on the system, it was further determined that the HFM bioreactor also enabled a ~50% reduced in carbon waste due to o\-gassing. Lastly, to further address the challenge of enhancing overall carbon conservation during biochemical production, a novel, integrated bioprocess was also developed that incorporates HFM-mediated CO2 recycling between upstream CO2-emitting and downstream CO2-fixing fermentation processes. Using an initial model system comprised of ethanol-producing E. coli LY180 (CO2 emitter) and succinate-producing E. coli KJ122 (CO2 fixer), we have thus far demonstrated that at least 78% of the total CO2 gas emitted during ethanol production can recycled and reutilized in support of co-producing succinate. Process conditions supporting maximal product titers, yields, and level of CO2 recycling/reutilization have also been identified. Moreover, since the upstream and downstream bioreactors can be operated under dissimilar environmental conditions, this facilitates the mixing and matching of di\erent CO2-emitting vs. CO2-fixing strain pairs. For instance, we have so far also studied the alternative pairing of ethanol-producing E. coli LY180 with malate-producing Aspergillus oryzae DSM 1863 – a strictly aerobic, filamentous fungi; a combination that would be wholly incompatible as a single pot coculture. Overall, HFM bioreactors represent promising designs for enhancing the rates and e\iciency of CO2 transfer during microbial biochemical production as well as increasing overall carbon conservation in such processes. 

The present study examines the assistance dilemma of providing combinations of perceptual supports in math education by fitting a Bayesian knowledge tracing model (BKT) to an open-source, online order-of-operations intervention dataset. This online intervention dataset contained 688 U.S. middle schoolers’ accuracy data who solved order-of-operations problems in pre-test, intervention, post-test, and delayed post-test sessions. Combinations of spacing and color cues were embedded in intervention materials, alongside immediate correctness feedback and worked examples, creating nine between-subject cue conditions (congruent, incongruent, or neutral spacing and/or color). To examine the effect of perceptual cues on immediate performance and long term learning, we trained a BKT variant, conditioning guess, slip, learn, and forget parameters on perceptual cue conditions. The estimated cue-specific BKT parameters suggest two main findings. First, the presence of congruent perceptual cues (color and/or spacing, e.g., 2 − 8 + 3×11) increased guessing rate and reduced slipping rate, suggesting that visually highlighting high-order suboperations facilitated students’ immediate problem solving. Second, students who underwent intervention with incongruent color cues (e.g., 2 − 8 + 3 × 11) showed reduced guessing rate but exhibited the highest learning rate and the lowest forgetting rate. These results imply that providing misleading visual highlights may hinder immediate performance but can be beneficial for long term learning. Furthermore, the impact of perceptual cues on immediate performance and long term learning indicated by BKT parameters approximately aligned with the patterns revealed by behavioral measures (i.e., intervention, post-test, and delayed post-test accuracy). Such consistencies demonstrate the feasibility of using the BKT framework to understand the assistance dilemma of perceptual supports. The code and data are available at: osf.io/q8kn6. 

Teacher self-efficacy—an individual’s belief in their ability to achieve desired outcomes—is critical for effective science and engineering instruction. However, studies report elementary teachers’ low confidence in teaching science and engineering, which may limit student outcomes and classroom innovation. Although professional learning (PL) has shown promise in fostering self-efficacy, most research relies on single-time measurements and single data sources, either surveys or interviews, restricting insights into how efficacy develops over time. This study addresses these gaps through a two-year longitudinal, multi-method design examining elementary teachers’ professional growth in teaching NGSS-aligned science and engineering. Four teachers’ professional growth was traced using repeated T-STEM surveys (pre-, post-, and end-of-year), end-of-program interviews, and teacher-created confidence graphs. Data were analyzed using framework-based thematic analysis (Braun & Clarke, 2012; Ritchie & Spencer, 1994), guided by Clarke and Hollingsworth’s (2002) Interconnected Model of Teacher Professional Growth (IMTPG). Findings reaffirm that professional growth is a complex and individualized process, highlighting the importance of diverse stimuli within PL to support teacher development. Despite its small sample, the study contributes to theoretical understandings of the IMTPG and teacher self-efficacy, emphasizing the value of longitudinal, multi-source research for capturing the evolving nature of teacher growth. 

Rural teachers often experience professional isolation, limiting access to collaborative pedagogical growth. This mixed-methods study examines how a large-scale, online professional learning program supported collaboration among 150 rural science teachers across two academic years. Grounded in Social Network Theory and Collaborative Professionalism, we analyzed survey (n=149) and interview (n=38) data to explore how rural educators built community, exchanged resources, and engaged in joint planning. Results highlight key supports, structures, and strategic facilitation that enabled teachers to overcome geographic isolation and develop sustained, trust-based ties. By centering rural voices and digitally bridging dispersed educators, this study contributes to “unforgetting histories” and reimagining rural professional learning as a space of solidarity, equity, and collective transformation. 

In this study, we used the construct of relevance to investigate the ways elementary teachers designed and implemented engineering lessons that supported students’ engagement, interest, and values. Participants in this study included eight teachers who were part of a larger professional learning community focused on community-relevant engineering instruction. Data were collected from teachers’ lesson plans, teaching videos, and exit interviews. Data were analyzed using a multilayered coding approach. Results indicated that teachers asked open-ended questions, allowed students to make meaningful choices, and continuously made connections to students’ lives to support relevance in engineering lessons. The implications of this study will be of interest to STEM teacher educators, researchers, and educational psychology researchers. 

Bimanual coordination, fundamental to human motor control, typically involves the execution of different functions by the two limbs (e.g., opening a jar). Previous research has largely investigated bimanual control through simple coordination tasks in which the limbs perform similar movements (e.g., finger tapping); however, few studies have specifically examined coordination when the two limbs perform different yet complementary functions. In the current study, participants performed point-to-point movements of a rectangular cursor, where one limb controlled cursor trajectory and the other rotated a knob to match a target orientation. Participants (N = 116, 76 female, 1 nonbinary; 92% right-handed) were divided into four groups and completed the task with a visual feedback gain perturbation (an increase or decrease) applied either to the cursor trajectory or orientation. Our results showed rapid adaptation to perturbations of visual feedback of the movement trajectory, affecting both the perturbed limb controlling the trajectory and the unperturbed limb controlling the orientation. Conversely, perturbation to the visual orientation feedback primarily only influenced the perturbed limb controlling orientation, with minimal impact on movement trajectory metrics. Importantly, these results were independent of reaching amplitude, duration, and limb dominance. In addition, we assessed the temporal coordination between the two limbs and found that perturbations in visual trajectory feedback led to significant changes in limb coordination, whereas no notable difference was observed for perturbations of orientation. These findings indicate asymmetries in bimanual motor recalibration dependent on the perturbed aspect of visual feedback (orientation vs trajectory), suggesting differences in underlying neural mechanisms and interhemispheric communication. 

Abstract Upper limb based neuromuscular interfaces aim to provide a seamless way for humans to interact with technology. Among noninvasive interfaces, surface electromyogram (EMG) signals hold significant promise. However, their sensitivity to physiological and anatomical factors remains poorly understood, raising questions about how these factors influence gesture decoding across individuals or groups. To facilitate the study of signal distribution shifts across individuals or groups of individuals, we present a dataset of upper limb EMG signals and physiological measures from 91 demographically diverse adults. Participants were selected to represent a range of ages (18 to 92 years) and body mass indices (healthy, overweight, and obese). The dataset also includes measures such as skin hydration and elasticity, which may affect EMG signals. This dataset provides a basis to study demographic confounds in EMG signals and serves as a benchmark to test the development of fair and unbiased algorithms that enable accurate hand gesture decoding across demographically diverse subjects. Additionally, we validate the quality of the collected data using state-of-the-art gesture decoding techniques.