More Like this

1. Comparison of triple quantum (TQ) TPPI and inversion recovery TQ TPPI pulse sequences at 9.4 and 21.1 T

   https://doi.org/10.1002/nbm.5106  

   Reichert, Simon ; Schepkin, Victor ; Kleimaier, Dennis ; Zöllner, Frank G. ; Schad, Lothar R. ( January 2024 , NMR in Biomedicine)

   Both sodiumT₁triple quantum (TQ) signal andT₁relaxation pathways have a unique sensitivity to the sodium molecular environment. In this study an inversion recovery time proportional phase increment (IRTQTPPI) pulse sequence was investigated for simultaneous and reliable quantification of sodium TQ signal and bi‐exponentialT₁relaxation times.

   The IRTQTPPI sequence combines inversion recovery TQ filtering and time proportional phase increment. The reliable and reproducible results were achieved by the pulse sequence optimized in three ways: (1) optimization of the nonlinear fit for the determination of bothT₁‐TQ signal andT₁relaxation times; (2) suppression of unwanted signals by assessment of four different phase cycles; (3) nonlinear sampling during evolution time for optimal scan time without any compromises in fit accuracy. The relaxation timesT₁andT₂and the TQ signals from IRTQTPPI and TQTPPI were compared between 9.4 and 21.1 T. The motional environment of the sodium nuclei was evaluated by calculation of correlation times and nuclear quadrupole interaction strengths.

   Reliable measurements of theT₁‐TQ signals andT₁bi‐exponential relaxation times were demonstrated. The fit parameters for all four phase cycles were in good agreement with one another, with a negligible influence of unwanted signals. The agar samples yielded normalizedT₁‐TQ signals from 3% to 16% relative to single quantum (SQ) signals at magnetic fields of both 9.4 and 21.1 T. In comparison, the normalizedT₂‐TQ signal was in the range 15%–35%. The TQ/SQ signal ratio was decreased at 21.1 T as compared with 9.4 T for bothT₁andT₂relaxation pathways. The bi‐exponentialT₁relaxation time separation ranged from 15 to 18 ms at 9.4 T and 15 to 21 ms at 21.1 T. TheT₂relaxation time separation was larger, ranging from 28 to 35 ms at 9.4 T and 37 to 40 ms at 21.1 T.

   The IRTQTPPI sequence, while providing a less intensive TQ signal than TQTPPI, allows a simultaneous and reliable quantification of both theT₁‐TQ signal andT₁relaxation times. The unique sensitivities of theT₁andT₂relaxation pathways to different types of molecular motion provide a deeper understanding of the sodium MR environment.

    

   more » « less
2. How and why do species break a developmental trade‐off? Elucidating the association of trichomes and stomata across species

   https://doi.org/10.1002/ajb2.16328  

   Baird, Alec S ; Medeiros, Camila D ; Caringella, Marissa A ; Bowers, Julia ; Hii, Michelle ; Liang, John ; Matsuda, Joshua ; Pisipati, Kirthana ; Pohl, Caroline ; Simon, Benjamin ; et al ( May 2024 , American Journal of Botany)

   Previous studies have suggested a trade‐off between trichome density (D_t) and stomatal density (D_s) due to shared cell precursors. We clarified how, when, and why this developmental trade‐off may be overcome across species.

   We derived equations to determine the developmental basis forD_tandD_sin trichome and stomatal indices (i_tandi_s) and the sizes of epidermal pavement cells (e), trichome bases (t), and stomata (s) and quantified the importance of these determinants ofD_tandD_sfor 78 California species. We compiled 17 previous studies ofD_t–D_srelationships to determine the commonness ofD_t–D_sassociations. We modeled the consequences of differentD_t–D_sassociations for plant carbon balance.

   Our analyses showed that higherD_twas determined by higheri_tand lowere, and higherD_sby higheri_sand lowere. Across California species, positiveD_t–D_scoordination arose due toi_t–i_scoordination and impacts of the variation ine. AD_t–D_strade‐off was found in only 30% of studies. Heuristic modeling showed that species sets would have the highest carbon balance with a positive or negative relationship or decoupling ofD_tandD_s, depending on environmental conditions.

   Shared precursor cells of trichomes and stomata do not limit higher numbers of both cell types or drive a generalD_t–D_strade‐off across species. This developmental flexibility across diverse species enables differentD_t–D_sassociations according to environmental pressures. Developmental trait analysis can clarify how contrasting trait associations would arise within and across species.

    

   more » « less
3. Does plant ecosystem thermoregulation occur? An extratropical assessment at different spatial and temporal scales

   https://doi.org/10.1111/nph.18632  

   Guo, Zhengfei ; Still, Christopher J. ; Lee, Calvin K. F. ; Ryu, Youngryel ; Blonder, Benjamin ; Wang, Jing ; Bonebrake, Timothy C. ; Hughes, Alice ; Li, Yan ; Yeung, Henry C. H. ; et al ( December 2022 , New Phytologist)

   To what degree plant ecosystems thermoregulate their canopy temperature (T_c) is critical to assess ecosystems' metabolisms and resilience with climate change, but remains controversial, with opinions from no to moderate thermoregulation capability.

   With global datasets ofT_c, air temperature (T_a), and other environmental and biotic variables from FLUXNET and satellites, we tested the ‘limited homeothermy’ hypothesis (indicated byT_c&T_aregression slope < 1 orT_c < T_aaround midday) across global extratropics, including temporal and spatial dimensions.

   Across daily to weekly and monthly timescales, over 80% of sites/ecosystems have slopes ≥1 orT_c > T_aaround midday, rejecting the above hypothesis. For those sites unsupporting the hypothesis, theirT_c–T_adifference (ΔT) exhibits considerable seasonality that shows negative, partial correlations with leaf area index, implying a certain degree of thermoregulation capability. Spatially, site‐mean ΔTexhibits larger variations than the slope indicator, suggesting ΔTis a more sensitive indicator for detecting thermoregulatory differences across biomes. Furthermore, this large spatial‐wide ΔTvariation (0–6°C) is primarily explained by environmental variables (38%) and secondarily by biotic factors (15%).

   These results demonstrate diverse thermoregulation patterns across global extratropics, with most ecosystems negating the ‘limited homeothermy’ hypothesis, but their thermoregulation still occurs, implying that slope < 1 orT_c < T_aare not necessary conditions for plant thermoregulation.

    

   more » « less
4. A Closer Look at the Evolution of Supercooled Cloud Droplet Temperature and Lifetime in Different Environmental Conditions with Implications for Ice Nucleation in the Evaporating Regions of Clouds

   https://doi.org/10.1175/JAS-D-22-0239.1  

   Roy, Puja ; Rauber, Robert_M ; Di_Girolamo, Larry ( October 2023 , Journal of the Atmospheric Sciences)

   This study investigates the evolution of temperature and lifetime of evaporating, supercooled cloud droplets considering initial droplet radius (r₀) and temperature (), and environmental relative humidity (RH), temperature (T_∞), and pressure (P). The time (t_ss) required by droplets to reach a lower steady-state temperature (T_ss) after sudden introduction into a new subsaturated environment, the magnitude of ΔT=T_∞−T_ss, and droplet survival time (t_st) atT_ssare calculated. The temperature difference (ΔT) is found to increase withT_∞, and decrease with RH andP. ΔTwas typically 1–5 K lower thanT_∞, with highest values (∼10.3 K) for very low RH, lowP, andT_∞closer to 0°C. Results show thatt_ssis <0.5 s over the range of initial droplet and environmental conditions considered. Larger droplets (r₀= 30–50μm) can survive atT_ssfor about 5 s to over 10 min, depending on the subsaturation of the environment. For higher RH and larger droplets, droplet lifetimes can increase by more than 100 s compared to those with droplet cooling ignored.T_ssof the evaporating droplets can be approximated by the environmental thermodynamic wet-bulb temperature. Radiation was found to play a minor role in influencing droplet temperatures, except for larger droplets in environments close to saturation. The implications for ice nucleation in cloud-top generating cells and near cloud edges are discussed. UsingT_ssinstead ofT_∞in widely used parameterization schemes could lead to enhanced number concentrations of activated ice-nucleating particles (INPs), by a typical factor of 2–30, with the greatest increases (≥100) coincident with low RH, lowP, andT_∞closer to 0°C.

   Cloud droplet temperature plays an important role in fundamental cloud processes like droplet growth and decay, activation of ice-nucleating particles, and determination of radiative parameters like refractive indices of water droplets. Near cloud boundaries such as cloud tops, dry air mixes with cloudy air exposing droplets to environments with low relative humidities. This study examines how the temperature of a cloud droplet that is supercooled (i.e., has an initial temperature < 0°C) evolves in these subsaturated environments. Results show that when supercooled cloud droplets evaporate near cloud boundaries, their temperatures can be several degrees Celsius lower than the surrounding drier environment. The implications of this additional cooling of droplets near cloud edges on ice particle formation are discussed.

    

   more » « less
5. ReversePetrogen : A Multiphase Dry Reverse Fractional Crystallization‐Mantle Melting Thermobarometer Applied to 13,589 Mid‐Ocean Ridge Basalt Glasses

   https://doi.org/10.1029/2020JB021292  

   Brown Krein, S. ; Molitor, Z. J. ; Grove, T. L. ( July 2021 , Journal of Geophysical Research: Solid Earth)

   We present a new algorithm,ReversePetrogen (RevPet), to infer mantle melting conditions (pressure, temperature, source composition) using evolved basalts that have experienced multiphase fractional crystallization.RevPetmeasures and minimizes the compositional distance between experimentally predicted phase saturation boundaries and an erupted basalt and the more primitive liquids that return it to a primary melt. We useRevPetto investigate mantle melting conditions at mid‐ocean ridges (MORs) using a global data set of 13,589 basaltic glasses. We find that their average apparent mantle potential temperature (T_P*) is 1322°C ± 56°C with melting pressures of 13.0 ± 5 kbars. Inferring the true initial (pre‐melted)T_PfromT_P* requires knowing the style and degree of melting of the input basalts. If MORB glasses were entirely produced by near‐fractional melting of a homogenous source, they would record the cooling of the mantle during melting from an initialT_P = ∼1380°C (ΔT_P = 0°C) down toT_P = ∼1270°C. If, instead, they were all fully pooled near‐fractional melts of the same source, they would record variations in ambient MORT_Pfrom ∼1300°C to 1450°C (ΔT_P = 150°C). However, because MOR basalts are thought to be both near‐fractional and variably pooled melts of variable sources, MORT_Pmust be intermediate between these two extremes. Our best estimate, consistent with MOR crustal thickness, is that ambient MORT_Pis homogenous (∼1350°C–1400°C) except near hotspots whereT_Preaches ∼1600°C. Some primitive glasses found near slow‐spreading ridges and back‐arcs record very low temperatures (T_P* < 1250°C) and pressures of melting (<10 kbar) and reflect mantle cooling during melting and melt equilibration in the mantle lithosphere.

    

   more » « less