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1. Testing of a custom, portable drill press to minimize probe misalignment in sap flow sensors

   https://doi.org/10.1093/treephys/tpad049  

   Beslity, Justin; Shaw, Stephen B.; Pfautsch, ed., Sebastian (April 2023, Tree Physiology)

   Abstract The accurate estimation of plant transpiration is critical to the fields of hydrology, plant physiology and ecology. Among the various methods of measuring transpiration in the field, the sap flow methods based on head pulses offers a cost-effective and energy-efficient option to directly measure the plant-level movement of water through the hydraulically active tissue. While authors have identified several possible sources of error in these measurements, one of the most common sources is misalignment of the sap flow probes due to user error. Though the effects of probe misalignment are well documented, no device or technique has been universally adopted to ensure the proper installation of sap flow probes. In this paper we compare the magnitude of misalignment errors among a 5 mm thick drilling template (DT), a 10 mm thick DT, and a custom designed, field-portable drill press. The different techniques were evaluated in the laboratory using a 7.5 cm wood block and in the field, comparing differences in measured sap flow. Based on analysis of holes drilled in the wood block, we found that the portable drill press was most effective in assuring that drill holes remained parallel, even at 7.5 cm depth. In field installations, nearly 50% of holes drilled with a 5 mm template needed to be redrilled while none needed to be when drilled with the drill press. Widespread use of a portable drill press when implementing the heat pulse method would minimize alignment uncertainty and allow a clearer understanding of other sources of uncertainty due to variability in tree species, age, or external drivers or transpiration. 

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2. A double-ratio method to measure fast, slow and reverse sap flows

   https://doi.org/10.1093/treephys/tpab081  

   Deng, Zijuan; Vice, Heather K; Gilbert, Matthew E; Adams, Mark A; Buckley, Thomas N (June 2021, Tree Physiology)

   Steppe, Kathy (Ed.)

   Abstract Sap velocity measurements are useful in fields ranging from plant water relations to hydrology at a variety of scales. Techniques based on pulses of heat are among the most common methods to measure sap velocity, but most lack ability to measure velocities across a wide range, including very high, very low and negative velocities (reverse flow). We propose a new method, the double-ratio method (DRM), which is robust across an unprecedented range of sap velocities and provides real-time estimates of the thermal diffusivity of wood. The DRM employs one temperature sensor upstream (proximal) and two sensors downstream (distal) to the source of heat. This facilitates several theoretical, heat-based approaches to quantifying sap velocity. We tested the DRM using whole-tree lysimetry in Eucalyptus cypellocarpa L.A.S. Johnson and found strong agreement across a wide range of velocities. 

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3. Quantifying the Global Power Needed for Sap Ascent in Plants

   https://doi.org/10.1029/2022JG006922  

   Quetin, Gregory R.; Anderegg, Leander D. L.; Konings, Alexandra G.; Trugman, Anna T. (August 2022, Journal of Geophysical Research: Biogeosciences)

   Abstract Terrestrial photosynthesis requires the evaporation of water (transpiration) in exchange for CO₂needed to form sugars. The water for transpiration is drawn up through plant roots, stem, and branches via a water potential gradient. However, this flow of water—or sap ascent—requires energy to lift the water to the canopy and to overcome the resistance of the plant’s water transporting xylem. Here, we use a combination of field measurements of plant physiology (hydraulic conductivity) and state‐of‐the‐science global estimates of transpiration to calculate how much energy is passively harvested by plants to power the sap ascent pump across the world’s terrestrial vegetation. Globally, we find that 0.06 W/m²is consumed in sap ascent over forest dominated ecosystems or 9.4 PWh/yr (equal to global hydropower energy production). Though small in comparison to other components of the Earth’s surface energy budget, sap ascent work in forests represents 14.2% of the energy compared to the energy consumed to create sugars through photosynthesis, with values up to 18% in temperate rainforests. The power needed for sap ascent generally increases with photosynthesis, but is moderated by both climate and plant physiology, as the most work is consumed in regions with large transpiration fluxes (such as the moist tropics) and in areas where vegetation has low conductivity (such as temperate rainforests dominated by conifer trees). Here, we present a bottom‐up analysis of sap ascent work that demonstrates its significant role in plant function across the globe. 

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4. Zero- to Ultralow-Field NMR Spectroscopy of Small Biomolecules

   Put, Piotr; Pustelny, Szymon; Budker, Dmitry; Druga, Emmanuel; Sjolander, Tobias; Pines, Alexander; Barskiy, Danila (November 2020, ChemRxiv)

   null (Ed.)

   Nuclear magnetic resonance (NMR) spectroscopy is a well-established analytical technique used to study chemicals and their transformations. However, high-eld NMR spectroscopy necessitates advanced infrastructure and even cryogen-free benchtop NMR spectrometers cannot be readily assembled from commercially available components. We demonstrate the construction of a portable zero-field NMR spectrometer employing a commercially available magnetometer and investigate its applications in analytical chemistry. In particular, J-spectra of small representative biomolecules [13C]-formic acid, [1-13C]-glycine, [2,3-13C]-fumarate, and [1-13C]-D-glucose were acquired and an approach relying on the presence of a transverse magnetic eld during the detection was investigated for relaxometry purposes. We found that water relaxation time strongly depends on the concentration of dissolved D-glucose in the range of 1-10 mM suggesting opportunities for indirect assessment of glucose concentration in aqueous solutions. Extending analytical capabilities of zero-field NMR to aqueous solutions of simple biomolecules (aminoacids, sugars and metabolites) and relaxation studies of aqueous solutions of glucose highlight the analytical potential of non-invasive and portable ZULF NMR sensors for applications outside of research laboratories. 

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5. On Design Challenges of Portable Nuclear Magnetic Resonance System

   https://doi.org/10.3390/jne4020025  

   Mohsen Hosseinzadehtaher; Silvanus D'silva; Matthew Baker; Ritesh Kumar; Nathan Hein; Mohammad B. Shadmand; S.V. Krishna Jagadish; Behzad Ghanbarian (April 2023, Journal of nuclear engineering)

   This article studies the optimal design approach for a portable nuclear magnetic resonance (NMR) system for use in non-destructive flow measurement applications. The mechanical and electromagnetic design procedures were carried out using the Ansys Maxwell finite-element analysis (FEA) software tool. The proposed procedure considered homogeneity and strength constraints while ensuring the desired functionality of the intended device for a given application. A modified particle swarm optimization (MPSO) algorithm was proposed as a reference design framework for optimization stages. The optimally designed NMR tool was prototyped, and its functionality was validated via several case studies. To assess the functionality of the prototyped device, Larmor frequency for hydrogen atom was captured and compared with theoretical results. Furthermore, the functionality and accuracy of the prototyped NMR tool is compared to the off-the-shelf NMR tool. Results demonstrated the feasibility and accuracy of the prototyped NMR tool constrained by factors, such as being lightweight and compact. 

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