34 Search Results

Agriculture depletes soil organic carbon (SOC), partly due to the exclusion of deep-rooted perennials. Reintroducing deep-rooted perennials to cultivated land may help to mitigate SOC loss. We quantified the effect of deep roots on SOC by comparing 8 to 30 year-old stands of switchgrass (Panicum virgatum L.) with paired annual row crop fields at 12 sites across the central and eastern USA. We hypothesized that switchgrass would store more root C and SOC than neighboring shallow-rooted annual crops, and that these effects would extend deeper than 30 cm. We also evaluated whether switchgrass stimulates decomposition of SOC at depth usingmore » radiocarbon (¹⁴C). Finally, we explored whether the effect of switchgrass on SOC is moderated by soil chemical and physical properties. While the effect of switchgrass on SOC in the surface 100 cm was positive at most sites, the average effect was not statistically significant (difference in SOC = 0.6 kg C m⁻² [95% CI −0.8 to +1.9 kg C m⁻²]). By contrast, we found that root C was consistently more abundant under switchgrass, yielding an estimated additional 0.6 kg C m⁻² in the surface 100 cm of soil [95% CI +0.5 to +0.7 kg C m⁻²]. ¹⁴C measurements suggested that root C inputs were adding to existing SOC without stimulating decomposition. The effect of switchgrass on belowground C was not strongly related to any of the soil properties that we evaluated. Our observations show that root C can contribute substantially to belowground C stocks when deep-rooted perennials replace shallow-rooted crops.« less

The electrochemical conversion of biomass-derived 5-hydroxymethylfurfural (HMF) represents a promising, economically viable, and environmentally sustainable approach for producing value-added chemicals using renewable energy and in situ hydrogen generated through water electrolysis. However, the electrochemical hydrogenation (ECH) of HMF remains challenging due to the inherently low catalytic activity and selectivity of the electrodes, compounded by competition with the kinetically favored hydrogen evolution reaction (HER) in aqueous electrolytes. In this work, we demonstrate that Cu_xNi_100−x heteroatomic thin films, fabricated via direct current (DC) magnetron co-sputtering, achieve a more than one order of magnitude increase in the HMF to 2,5-Bis-hydroxymethylfuran (BHMF) conversion rate,more » with nearly 50% faradic efficiency (FE) for BHMF, when compared to pure Cu and Ni electrodes (~ 10% BHMF FE). Our results suggest that the synergistic interaction between Cu and Ni creates an optimal catalytic environment for both HMF and adsorbed hydrogen (H_ads) species, thereby enhancing BHMF formation through the ECH pathway.« less

Recent simulation studies using the RAM-SCB model showed that proton precipitation contributes significantly to the total energy flux deposited into the subauroral ionosphere thereby affecting the magnetosphere-ionosphere coupling. Here, in this study, we use the BATS-R-US + RAM-SCB model to understand the evolution of ElectroMagnetic Ion Cyclotron (EMIC) waves in the inner magnetosphere, their correspondence to the proton precipitation into the subauroral ionosphere, and to assess the performance of the model in reproducing the EMIC wave-particle interactions. During the 27 May 2017 storm, Arase and RBSP-A satellites observed typical signatures of EMIC waves in the inner magnetosphere. Within this interval, Defense Meteorologicalmore » Satellite Program (DMSP) and National Oceanic and Atmospheric Administration (NOAA)/MetOp satellites observed significant proton precipitation in the dusk-midnight sector. Simulation results show that H- and He-band EMIC waves are excited within regions of strong temperature anisotropy near the plasmapause. The simulated growth rates of EMIC waves show a similar trend to that of the EMIC wave power observed by the Arase and RBSP-A satellites, suggesting that the model can reproduce the EMIC wave activity qualitatively. The simulated H-band waves in the dusk sector are stronger than He-band waves possibly due to the presence of excess protons in the boundary conditions obtained from the BATS-R-US code. The precipitating proton fluxes reproduced by the simulation with EMIC waves are found to agree reasonably well with the DMSP and NOAA/MetOp satellite observations. It is suggested that EMIC wave scattering of ring current ions can account for proton precipitation observed by the DMSP and MetOp satellites during the 27 May 2017 storm.« less

We present a study on the transport and material properties of aluminum spanning from ambient to warm dense matter conditions using a machine-learned interatomic potential (ML-IAP). Prior research has utilized ML-IAPs to simulate phenomena in warm dense matter, but these potentials have often been calibrated for a narrow range of temperatures and pressures. In contrast, we train a single ML-IAP over a wide range of temperatures, using density functional theory molecular dynamics (DFT-MD) data. Our approach overcomes the computational limitations of DFT-MD simulations, enabling us to study the transport and material properties of matter at higher temperatures and longer timemore » scales. We demonstrate the ML-IAP transferability across a wide range of temperatures using molecular dynamics by examining the ionic part of thermal conductivity, shear viscosity, self-diffusion coefficient, sound velocity, and structure factor of aluminum up to about 60000 K, where we find good agreement with previous theoretical data.« less

Monoterpenoid indole alkaloids (MIAs) represent a large class of plant natural products with marketed pharmaceutical activities against a wide range of indications, including cancer, malaria and hypertension. Halogenated MIAs have shown improved pharmaceutical properties; however, synthesis of new-to-nature halogenated MIAs remains a challenge. Here we demonstrate a platform for de novo biosynthesis of two MIAs, serpentine and alstonine, in baker’s yeast Saccharomyces cerevisiae and deploy it to systematically explore the biocatalytic potential of refactored MIA pathways for the production of halogenated MIAs. From this, we demonstrate conversion of individual haloindole derivatives to a total of 19 different new-to-nature haloserpentine andmore » haloalstonine analogs. Furthermore, by process optimization and heterologous expression of a modified halogenase in the microbial MIA platform, we document de novo halogenation and biosynthesis of chloroalstonine. Together, this study highlights a microbial platform for enzymatic exploration and production of complex natural and new-to-nature MIAs with therapeutic potential.« less

Here, using Arase observations of the inner magnetosphere during 26 CIR-driven geomagnetic storms with minimum Sym-H between –33 and –86 nT, we investigated ring current pressure development of ions (H⁺, He⁺, O⁺) and electron during prestorm, main, early recovery and late recovery phases as a function of L-shell and magnetic local time. It is found that during the main and early recovery phase of the storms the ion pressure is asymmetric in the inner magnetosphere, leading to a strong partial ring current. The ion pressure becomes symmetric during the late recovery phase. H⁺ ions with energies of ~20–50 keV andmore » ~50–100 keV contribute more to the ring current pressure during the main phase and early/late recovery phase, respectively. O⁺ ions with energies of ~10–20 keV contribute significantly during main and early recovery phase. These are consistent with previous studies. The electron pressure was found to be asymmetric during the main, early recovery and late recovery phase. The electron pressure peaks from midnight to the dawn sector. Electrons with energy of <50 keV contribute to the ring current pressure during the main and early recovery phase of the storms. Overall, the electron contribution to the total ring current is found to be ~11% during the main and early recovery phases. However, the electron contribution is found to be significant (~22%) in the 03–09 MLT sector during the main and early recovery phase. The results indicate an important role of electrons in the ring current build up.« less

Selective electrochemical hydrogenation (ECH) of biomass-derived unsaturated organic molecules has enormous potential for sustainable chemical production. However, an efficient catalyst is essential to perform an ECH reaction consisting of superior product selectivity and a higher conversion rate. Here, we examined the ECH performance of reduced metal nanostructures, i.e., reduced Ag (rAg) and reduced copper (rCu) prepared via electrochemical or thermal oxidation and electrochemical reduction process, respectively. Surface morphological analysis suggests the formation of nanocoral and entangled nanowire structure formation for rAg and rCu catalysts. rCu exhibits a slight enhancement in ECH reaction performance in comparison to the pristine Cu. However,more » the rAg exhibits more than two times higher ECH performance without compromising the selectivity for 5-(HydroxyMethyl) Furfural (HMF) to 2,5-bis(HydroxyMethyl)-Furan (BHMF) formation in comparison to the Ag film. Moreover, a similar ECH current density was recorded at a reduced working potential of 220 mV for rAg. This high performance of rAg is attributed to the formation of new catalytically active sites during the Ag oxidation and reduction processes. This study demonstrates that rAg can potentially be used for the ECH process with minimum energy consumption and a higher production rate.« less

Soil carbon dioxide (CO₂) emissions from the field of corn (Zea mays L.) play an important role in global warming. This study investigated temporal variability of soil CO₂ fluxes (R_s) with soil temperature (T_s) and moisture (θ) and built DAYCENT models for predicting future impacts of climate changes on R_s using the measured high-frequency data. R_s trend was tested by Mann–Kendall and Sen Estimator. Predicted R_ss under different climate scenarios were compared using Parallel-line Analysis. Herein, the findings indicated that daily R_s exponentially increased with T_s constrained by θ. During the θ of 27–31%, there was a strong exponential relationshipmore » between R_s and T_s, but the relationship was weaker for the θ of 38–41% and 22–26%. Soil environmental index (SEI, T_s × θ) significantly impacted R_s with linear regression R_s^0.5 = 0.4599 + 0.002059 × SEI in 2008, 2009 and 2011. At the diurnal scale, there were different trends in R_ss and relationships among R_s and T_s and θ in different years. Predicted yearly R_ss, root R_ss and corn yield in 2014–2049 increased with an increase in temperature scenarios, but the R_ss significantly increased as temperature rose by 1°C or higher. Predicted yearly R_ss, root R_ss and yield reduced with precipitation scenario increase, and the root R_ss and yield significantly diminished as precipitation increased by 15 and 30%. Predicted yearly R_s from cornfields had a significantly increasing trend. Future research is needed to explore methods for mitigating cornfield R_s and evaluating sensitivities of different cropland R_ss to temperature changes.« less

Background: Biochar ozonization was previously shown to dramatically increase its cation exchange capacity, thus improving its nutrient retention capacity. The potential soil application of ozonized biochar warrants the need for a toxicity study that investigates its effects on microorganisms. Results: In the study presented here, we found that the filtrates collected from ozonized pine 400 biochar and ozonized rogue biochar did not have any inhibitory effects on the soil environmental bacteria Pseudomonas putida, even at high dissolved organic carbon (DOC) concentrations of 300 ppm. However, the growth of Synechococcus elongatus PCC 7942 was inhibited by the ozonized biochar filtrates atmore » DOC concentrations greater than 75 ppm. Further tests showed the presence of some potential inhibitory compounds (terephthalic acid and p-toluic acid) in the filtrate of non-ozonized pine 400 biochar; these compounds were greatly reduced upon wet-ozonization of the biochar material. Nutrient detection tests also showed that dry-ozonization of rogue biochar enhanced the availability of nitrate and phosphate in its filtrate, a property that may be desirable for soil application. Conclusion: Ozonized biochar substances can support soil environmental bacterium Pseudomonas putida growth, since ozonization detoxifies the potential inhibitory aromatic molecules.« less