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Abstract PurposeThis study aims to characterize the dependence of measured retinal arterial and venous saturation on vessel diameter and central reflex in retinal oximetry, with an ultimate goal of identifying potential causes and suggesting approaches to improve measurement accuracy. MethodsIn 10 subjects, oxygen saturation, vessel diameter and optical density are obtained using Oxymap Analyzer software without diameter correction. Diameter dependence of saturation is characterized using linear regression between measured values of saturation and diameter. Occurrences of negative values of vessel optical densities (ODs) associated with central vessel reflex are acquired from Oxymap Analyzer. A conceptual model is used to calculate the ratio of optical densities (ODRs) according to retinal reflectance properties and single and double‐pass light transmission across fixed path lengths. Model‐predicted values are compared with measured oximetry values at different vessel diameters. ResultsVenous saturation shows an inverse relationship with vessel diameter (D) across subjects, with a mean slope of −0.180 (SE = 0.022) %/μm (20 < D < 180 μm) and a more rapid saturation increase at small vessel diameters reaching to over 80%. Arterial saturation yields smaller positive and negative slopes in individual subjects, with an average of −0.007 (SE = 0.021) %/μm (20 < D < 200 μm) across all subjects. Measurements where vessel brightness exceeds that of the retinal background result in negative values of optical density, causing an artifactual increase in saturation. Optimization of model reflectance values produces a good fit of the conceptual model to measured ODRs. ConclusionMeasurement artefacts in retinal oximetry are caused by strong central vessel reflections, and apparent diameter sensitivity may result from single and double‐pass transmission in vessels. Improvement in correction for vessel diameter is indicated for arteries however further study is necessary for venous corrections. 

Writing is generally recognized as fundamental to the formation and communication of scientific and technical knowledge to peer groups and general audiences. Often, persuasive writing is an essential attribute emphasized by industries and businesses for a successful career in STEM fields. Nevertheless, the current scenario is that students in STEM fields, with their increased demand for more specialized skills in fewer credit hours combined with a lack of emphasis on writing from engineering faculty members, make addressing this need difficult. In addition, students in engineering fields often do not value writing skills and underestimate the amount of writing they will do in their careers. Hence, it is essential to understand and quantify the level of writing skills STEM students exhibit in their technical courses so that mitigation efforts can be designed using commonly available resources to enhance this important skillset among the students, including university writing centers. A research question was posed to study this aspect of technical writing: How do STEM students at institutions conceive of writing and its role in classroom laboratories? This research was conducted at three different universities with students of varied demographics, including one which is designated as a Hispanic-serving institution, via a sequential mixed-methods design. The demography variation among the institutions includes the level of college preparation among students and the mix of ethnicity to see if there are variations among certain groups. Although the sample size is small, the goal was to establish a methodology and a preliminary outcome set that could be used in further research with larger populations. Research data in the form of reports and surveys, were collected from groups of students from four distinct campuses to ascertain the technical writing capability of each group and provide a comparison to better understand the level of intervention required. The quantitative data was collected throughout the academic year through Likert scale surveys as well as rubric-based evaluation of reports. The research design, methodology, and results of the research findings and the proposed mitigation efforts to improve student writing in STEM fields are presented in the paper. The above research was sponsored by the National Science Foundation grant: Collaborative: Research: Writing Assignment Tutor Training in STEM (WATTS), an Interdisciplinary Approach for the Enhancement of Student Writing in STEM fields. 

Abstract Solar‐induced chlorophyll fluorescence (SIF) is a remotely sensed optical signal emitted during the light reactions of photosynthesis. The past two decades have witnessed an explosion in availability of SIF data at increasingly higher spatial and temporal resolutions, sparking applications in diverse research sectors (e.g., ecology, agriculture, hydrology, climate, and socioeconomics). These applications must deal with complexities caused by tremendous variations in scale and the impacts of interacting and superimposing plant physiology and three‐dimensional vegetation structure on the emission and scattering of SIF. At present, these complexities have not been overcome. To advance future research, the two companion reviews aim to (1) develop an analytical framework for inferring terrestrial vegetation structures and function that are tied to SIF emission, (2) synthesize progress and identify challenges in SIF research via the lens of multi‐sector applications, and (3) map out actionable solutions to tackle these challenges and offer our vision for research priorities over the next 5–10 years based on the proposed analytical framework. This paper is the first of the two companion reviews, and theory oriented. It introduces a theoretically rigorous yet practically applicable analytical framework. Guided by this framework, we offer theoretical perspectives on three overarching questions: (1)The forward (mechanism) question—How are the dynamics of SIF affected by terrestrial ecosystem structure and function? (2)The inference question: What aspects of terrestrial ecosystem structure, function, and service can be reliably inferred from remotely sensed SIF and how? (3)The innovation question: What innovations are needed to realize the full potential of SIF remote sensing for real‐world applications under climate change? The analytical framework elucidates that process complexity must be appreciated in inferring ecosystem structure and function from the observed SIF; this framework can serve as a diagnosis and inference tool for versatile applications across diverse spatial and temporal scales. 

Abstract Although our observing capabilities of solar‐induced chlorophyll fluorescence (SIF) have been growing rapidly, the quality and consistency of SIF datasets are still in an active stage of research and development. As a result, there are considerable inconsistencies among diverse SIF datasets at all scales and the widespread applications of them have led to contradictory findings. The present review is the second of the two companion reviews, and data oriented. It aims to (1) synthesize the variety, scale, and uncertainty of existing SIF datasets, (2) synthesize the diverse applications in the sector of ecology, agriculture, hydrology, climate, and socioeconomics, and (3) clarify how such data inconsistency superimposed with the theoretical complexities laid out in (Sun et al., 2023) may impact process interpretation of various applications and contribute to inconsistent findings. We emphasize that accurate interpretation of the functional relationships between SIF and other ecological indicators is contingent upon complete understanding of SIF data quality and uncertainty. Biases and uncertainties in SIF observations can significantly confound interpretation of their relationships and how such relationships respond to environmental variations. Built upon our syntheses, we summarize existing gaps and uncertainties in current SIF observations. Further, we offer our perspectives on innovations needed to help improve informing ecosystem structure, function, and service under climate change, including enhancing in‐situ SIF observing capability especially in “data desert” regions, improving cross‐instrument data standardization and network coordination, and advancing applications by fully harnessing theory and data. 

Abstract Plants with crassulacean acid metabolism (CAM) are increasing in distribution and abundance in drylands worldwide, but the underlying drivers remain unknown. We investigate the impacts of extreme drought and CO₂enrichment on the competitive relationships between seedlings ofCylindropuntia imbricata(CAM species) andBouteloua eriopoda(C₄grass), which coexist in semiarid ecosystems across the Southwestern United States. Our experiments under altered water and CO₂water conditions show thatC. imbricatapositively responded to CO₂enrichment under extreme drought conditions, whileB. eriopodadeclined from drought stress and did not recover after the drought ended. Conversely, in well‐watered conditionsB. eriopodahad a strong competitive advantage onC. imbricatasuch that the photosynthetic rate and biomass (per individual) ofC. imbricatagrown withB. eriopodawere lower relative to when growing alone. A meta‐analysis examining multiple plant families across global drylands shows a positive response of CAM photosynthesis and productivity to CO₂enrichment. Collectively, our results suggest that under drought and elevated CO₂concentrations, projected with climate change, the competitive advantage of plant functional groups may shift and the dominance of CAM plants may increase in semiarid ecosystems.