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  1. Particulate inorganic carbon (PIC) plays a major role in the ocean carbon cycle impacting pH, dissolved inorganic carbon, and alkalinity, as well as particulate organic carbon (POC) export and transfer efficiency to the deep sea. Remote sensing retrievals of PIC in surface waters span two decades, yet knowledge of PIC concentration variability in the water column is temporally and spatially limited due to a reliance on ship sampling. To overcome the space–time gap in observations, we have developed optical sensors for PIC concentration and flux that exploit the high mineral birefringence of CaCO 3 minerals, and thus enable real-time datamore »when deployed operationally from ship CTDs and ARGO-style Carbon Flux Explorer floats. For PIC concentrations, we describe a fast (10 Hz) digital low-power (∼0.5 W) sensor that utilizes cross-polarized transmitted light to detect the photon yield from suspended birefringent particles in the water column. This sensor has been CTD-deployed to depths as great as 6,000 m and cross-calibrated against particulates sampled by large volume in situ filtration and CTD/rosettes. We report data from the September–November 2018 GEOTRACES GP15 meridional transect from the Aleutian Islands to Tahiti along 152°W where we validated two prototype sensors deployed on separate CTD systems surface to bottom at 39 stations, many of which were taken in nearly particle-free waters. We compare sensor results with major particle phase composition (particularly PIC and particulate aluminum) from simultaneously collected size-fractionated particulate samples collected by large volume in situ filtration. We also report results from the June 2017 California Current Ecosystem-Long Term Ecological Research (CCE-LTER) process study in California coastal waters where high PIC levels were found. We demonstrate that the PIC concentration sensor can detect PIC concentration variability from 0.01 to >1 μM in the water column (except in nepheloid layers) and outline engineering needs and progress on its integration with the Carbon Flux Explorer, an autonomous float.« less
    Free, publicly-accessible full text available March 8, 2023
  2. Free, publicly-accessible full text available January 1, 2023
  3. Shea ; Joan-Emma (Ed.)
    Proton transfer reactions are ubiquitous in chemistry, especially in aqueous solutions. We investigate photo-induced proton transfer between the photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) and water using fast fluorescence spectroscopy and ab initio molecular dynamics simulations. Photo-excitation causes rapid proton release from the HPTS hydroxyl. Previous experiments on HPTS/water described the progress from photoexcitation to proton diffusion using kinetic equations with two time constants. The shortest time constant has been interpreted as protonated and photoexcited HPTS evolving into an “associated” state, where the proton is “shared” between the HPTS hydroxyl and an originally hydrogen bonded water. The longer time constant has been interpretedmore »as indicating evolution to a “solvent separated” state where the shared proton undergoes long distance diffusion. In this work, we refine the previous experimental results using very pure HPTS. We then use excited state ab initio molecular dynamics to elucidate the detailed molecular mechanism of aqueous excited state proton transfer in HPTS. We find that the initial excitation results in rapid rearrangement of water, forming a strong hydrogen bonded network (a “water wire”) around HPTS. HPTS then deprotonates in ≤3 ps, resulting in a proton that migrates back and forth along the wire before localizing on a single water molecule. We find a near linear relationship between emission wavelength and proton-HPTS distance over the simulations’ time scale, suggesting that emission wavelength can be used as a ruler for proton distance. Our simulations reveal that the “associated” state corresponds to a water wire with a mobile proton and that the diffusion of the proton away from this water wire (to a generalized “solvent-separated” state) corresponds to the longest experimental time constant.« less
    Free, publicly-accessible full text available November 7, 2022
  4. Free, publicly-accessible full text available November 9, 2022
  5. Free, publicly-accessible full text available October 1, 2022
  6. Abstract Helmet continuous positive applied pressure is a form of noninvasive ventilation (NIV) that has been used to provide respiratory support to COVID-19 patients. Helmet NIV is low-cost, readily available, provides viral filters between the patient and clinician, and may reduce the need for invasive ventilation. Its widespread adoption has been limited, however, by the lack of a respiratory monitoring system needed to address known safety vulnerabilities and to monitor patients. To address these safety and clinical needs, we developed an inexpensive respiratory monitoring system based on readily available components suitable for local manufacture. Open-source design and manufacturing documents aremore »provided. The monitoring system comprises flow, pressure, and CO2 sensors on the expiratory path of the helmet circuit and a central remote station to monitor up to 20 patients. The system is validated in bench tests, in human-subject tests on healthy volunteers, and in experiments that compare respiratory features obtained at the expiratory path to simultaneous ground-truth measurements from proximal sensors. Measurements of flow and pressure at the expiratory path are shown to deviate at high flow rates, and the tidal volumes reported via the expiratory path are systematically underestimated. Helmet monitoring systems exhibit high-flow rate, nonlinear effects from flow and helmet dynamics. These deviations are found to be within a reasonable margin and should, in principle, allow for calibration, correction, and deployment of clinically accurate derived quantities.« less
    Free, publicly-accessible full text available March 1, 2023
  7. Free, publicly-accessible full text available October 4, 2022
  8. Abstract In Fall 2020, universities saw extensive transmission of SARS-CoV-2 among their populations, threatening health of the university and surrounding communities, and viability of in-person instruction. Here we report a case study at the University of Illinois at Urbana-Champaign, where a multimodal “SHIELD: Target, Test, and Tell” program, with other non-pharmaceutical interventions, was employed to keep classrooms and laboratories open. The program included epidemiological modeling and surveillance, fast/frequent testing using a novel low-cost and scalable saliva-based RT-qPCR assay for SARS-CoV-2 that bypasses RNA extraction, called covidSHIELD, and digital tools for communication and compliance. In Fall 2020, we performed >1,000,000 covidSHIELDmore »tests, positivity rates remained low, we had zero COVID-19-related hospitalizations or deaths amongst our university community, and mortality in the surrounding Champaign County was reduced more than 4-fold relative to expected. This case study shows that fast/frequent testing and other interventions mitigated transmission of SARS-CoV-2 at a large public university.« less
    Free, publicly-accessible full text available December 1, 2023