bluuebunny/crossref_metadata_2025_split huggingface dataset:
Planktonic Metabolism and Microbial Carbon Substrate Utilization in Response to Inundation in Semi‐Arid Floodplain Wetlands
Authors: Rana A. , Kobayashi T. , Ralph T. J. 
Published: March 2021

AbstractIn semi‐arid floodplain wetlands, planktonic metabolism, a balance of gross primary productivity of phytoplankton (GPP) and planktonic respiration (PR), may be affected by hydrology, geomorphology, carbon, and microbial communities. Understanding relationships between these factors helps develop effective water and land management plans for these wetlands. In this study, variations in planktonic metabolism and microbial carbon substrate utilization were investigated in the semi‐arid floodplain wetlands of the Macquarie Marshes, south‐eastern Australia, by comparing three geomorphologically distinct zones with different historical inundation frequencies (zones 1: moderate, 2: low, and 3: very low). Floodplain soil samples collected from each zone were inundated artificially in controlled laboratory conditions. GPP and PR were determined using biological oxygen demand methods. Biolog EcoPlates™ were used to assess microbial utilization of carbon substrate. Among the zones examined, zone 1 had the highest GPP and lowest PR, while zone 3 had the lowest GPP and highest PR. GPP/PR showed zones 1 and 2 autotrophic, and zone 3 heterotrophic. EcoPlates showed the highest and lowest microbial activity in zone 3 and zone 1 respectively, indicating a strong link between microbial carbon substrate utilization and PR for heterotrophy in the rarely inundated zone. Inundation of drier wetland zones may lead to a large pulse in PR, at least for a short period of time, potentially leading to anoxic water events. When making decisions for environmental water allocations, the antecedent hydro‐geomorphological and microbial condition of the targeted wetlands should be considered to help predict expected aquatic ecosystem responses.
Climatic and Geochemical Controls on Soil Carbon at the Continental Scale: Interactions and Thresholds
Authors: Yu Wenjuan , Weintraub Samantha R. , Hall Steven J. 
Published: March 2021

AbstractPrevious studies found conflicting results on the importance of temperature and precipitation versus geochemical variables for predicting soil organic carbon (SOC) concentrations and trends with depth, and most utilized linear statistical models. To reconcile the controversy, we used data from 2574 mineral horizons from 675 pits from National Ecological Observatory Network sites across North America, typically collected to 1 m depth. Climate was a fundamental predictor of SOC and played similarly important roles as some geochemical predictors. Yet, this only emerged in the generalized additive mixed model and random forest model and was obscured in the linear mixed model. Relationships between water availability and SOC were strongest in very dry ecosystems and SOC increased most strongly at mean annual temperature < 0°C. In all models, depth, oxalate‐extractable Al (Alox), pH, and exchangeable calcium plus exchangeable magnesium were important while silt + clay, oxalate‐extractable Fe (Feox), and vegetation type were weaker predictors. Climate and pH were independently related to SOC and also interacted with geochemical composition: Feox and Alox related more strongly to SOC in wet or cold climates. Most predictors had nonlinear threshold relationships with SOC, and a saturating response to increasing reactive metals indicates soils where SOC might be limited by C inputs. We observed a mostly constant relative importance of geochemical and climate predictors of SOC with increasing depth, challenging previous statements. Overall, our findings challenge the notion that climate is redundant after accounting for geochemistry and demonstrate that considering their nonlinearities and interactions improves spatial predictions of SOC.
Investigation of the Variability of Night‐Time Equatorial Thermospheric Winds Over Nigeria, West Africa
Authors: Rabiu A. B. , Okoh D. I. , Wu Q. , Bolaji O. S. , Abdulrahim R. B. , Dare‐Idowu O. E. , Obafaye A. A. 
Published: March 2021

AbstractThis study examined the variability of the night‐time equatorial thermospheric meridional and zonal wind speeds using an optical Fabry‐Perot interferometer (FPI) located in Abuja, Nigeria (Geographic: 8.99°N, 7.39°E; Geomagnetic latitude: −1.60). The study period covered 9 months with useable data of 139 nights between March 2016 and January 2018. The hourly zonal wind speed is between −124 and 163 ms−1 and that of the meridional wind ranged between −70 and 95 ms−1. Comparison of FPI ground‐based measurements with estimates from the Horizontal Wind Model (HWM‐14) accurately reproduced the post‐midnight meridional component, but for some departure of ∼50 ms−1 during pre‐midnight. A very good agreement is observed between the predicted and measured zonal winds speed in the month of January 2018. However, the HWM‐14 more often underestimated the zonal wind speeds in the months of 2016. Hence, this necessitates a call for improvement of the HWM‐14 by using newly observed data in order to better characterize the West African sector. The varying zonal winds showed modal periods of 25.9 and 133.5 days, which are quasi 27 days and quasiterannual periodic variations, respectively. On the meridional wind, oscillatory periods of 133.5 and 23.1 days are seen in year 2016 and 2017, respectively.
Seasonal Variations in Flocculation and Erosion Affecting the Large‐Scale Suspended Sediment Distribution in the Scheldt Estuary: The Importance of Biotic Effects
Authors: Horemans Dante M. L. , Dijkstra Yoeri M. , Schuttelaars Henk M. , Sabbe Koen , Vyverman Wim , Meire Patrick , Cox Tom J. S. 
Published: March 2021

AbstractMany estuaries exhibit seasonality in the estuary‐scale distribution of suspended particulate matter (SPM). This SPM distribution depends on various factors, including freshwater discharge, salinity intrusion, erodibility, and the ability of cohesive SPM to flocculate into larger aggregates. Various authors indicate that biotic factors, such as the presence of algae and their excretion of sticky transparent exopolymer particles (TEP), affect the flocculation and erosion processes. Consequently, seasonality in these biotic factors may play a role in the observed seasonality in SPM. Whereas the impact of abiotic factors on seasonality in SPM is well studied, the relative contribution of biotically induced seasonality is largely unknown. In this study, we employ two approaches to assess the aggregated importance of biotically induced seasonality in flocculation and erosion on seasonality in SPM in the Scheldt estuary. In the first approach, we focus on seasonality of in situ observations in the Scheldt estuary of turbidity, floc size, Chlorophyll‐a, and TEP, showing that the abiotic parameters show seasonality, while seasonality in TEP is ambiguous. The second approach concerns a reverse engineering method to calibrate biotically affected parameters of a coupled sediment transport‐flocculation model to turbidity observations, allowing us to compare the modeled SPM concentrations to the observations. Driven by seasonality in freshwater discharge, the model captures the observed seasonality in SPM without requiring biotically induced seasonality in flocculation and erosion, which is supported by the absence of seasonality in TEP.
Stirring of Sea‐Ice Meltwater Enhances Submesoscale Fronts in the Southern Ocean
Authors: Giddy I. , Swart S. , du Plessis M. , Thompson A. F. , Nicholson S.‐A. 
Published: March 2021

AbstractIn the sea‐ice‐impacted Southern Ocean, the spring sea‐ice melt and its impact on physical processes set the rate of surface water mass modification. These modified waters will eventually subduct near the polar front and enter the global overturning circulation. Submesoscale processes modulate the stratification of the mixed layer (ML) and ML properties. Sparse observations in polar regions mean that the role of submesoscale motions in the exchange of properties across the base of the ML is not well understood. The goal of this study is to determine the interplay between sea‐ice melt, surface boundary layer forcing, and submesoscale flows in setting properties of the surface ML in the Antarctic marginal ice zone. High‐resolution observations suggest that fine‐scale lateral fronts arise from either/both mesoscale and submesoscale stirring of sea‐ice meltwater anomalies. The strong salinity‐driven stratification at the base of the ML confines these fronts to the upper ocean, limiting submesoscale vertical fluxes across the ML base. This strong stratification prevents the local subduction of modified waters by submesoscale flows, suggesting that the subduction site that links to the global overturning circulation does not correspond with the location of sea‐ice melt. However, surface‐enhanced fronts increase the potential for Ekman‐driven cross‐frontal flow to modulate the stability of the ML and ML properties. The parameterization of submesoscale processes in coupled‐climate models, particularly those contributing to the Ekman buoyancy flux, may improve the representation of ML heat and freshwater transport in the ice‐impacted Southern Ocean during summer.
Forest Greening Increases Land Surface Albedo During the Main Growing Period Between 2002 and 2019 in China
Authors: Yan Hao , Wang Shaoqiang , Dai Junhu , Wang Junbang , Chen Jin , Shugart Herman H. 
Published: March 2021

AbstractThis study is the first to find the unexpected increases in albedo due to forest greening, which has important implications in research of land‐surface energy‐balance and the forest‐climate feedback. We investigated interannual changes of vegetation and albedo for forests and grassland during the main growing period, May to September, between 2002 and 2019 in China using the MODIS‐satellite vegetation index and albedo products. These results indicate significant greening (PMK < 0.01) in all types of forests as well as grasslands in China. However, forests had an increasing trend of shortwave albedo (PMK < 0.01) for evergreen forests, deciduous broadleaf forests, and mixed forests. Grasslands showed a decreasing albedo trend (PMK < 0.01) over the same period. Corroborating statistical analyses revealed a positive correlation (P < 0.01) between Moderate Resolution Imaging Spectroradiometer (MODIS) enhanced vegetation index (EVI) and albedo for forests on interannual scales. However, EVI and albedo for grasslands had a negative correlation. Forest greening increased the albedo during the main growing period. This contrasts previous results indicating that albedo decreases as annual forest‐cover increases. Developing and analyzing a simple vegetation‐coverage‐based albedo model showed that increasing forest coverage (i.e., forest greening) had increased area of more brightly leafy canopy and decreased area of darker gaps in the forest canopy. In conjunction, these produced the increased overall albedo observed by satellite. Contrastingly, grassland greening and more precipitation produced decreased albedo. Hence, the greening of forests and grasslands, representing dense and scarce vegetation respectively, has contrasting albedo responses.
Influence of Volatiles on Mass Wasting Processes on Vesta and Ceres
Authors: Parekh R. , Otto K. A. , Jaumann R. , Matz K. D. , Roatsch T. , Kersten E. , Elgner S. , Raymond C. 
Published: March 2021

AbstractWe have analyzed mass wasting features, their distribution and deposit geometry on the two largest main asteroid belt objects—protoplanet Vesta and dwarf planet Ceres—and compared their geomorphology and mobility. Both asteroids have similar surface accelerations, but different surface compositions. Based on our observations and previous studies, we categorized three distinct morphological mass wasting classes: slumps, slides, and flow‐like movements. We conclude that Ceres has abundant features of flow‐like mass movements. Further, sliding and flow‐like characteristics are identified in craters within mid‐latitudes which supports the possibility of the presence of water ice in the near subsurface of Ceres. Vesta predominantly shows characteristics of dry granular‐like slide features which are distributed homogenously across the surface. By plotting the ratio between fall height (H) and run‐out length (L) (effective coefficient of friction, H/L) against the run‐out length and spreading width (W), we demonstrate that deposits on Vesta terminate on shorter distances, whereas on Ceres they travel longer distances. The deposit geometry and the similar surface gravity on both asteroids suggest that the material composition and volatile component have a significant effect on deposit emplacement. However, both bodies’ mass movements have similar effective coefficients of friction, even though Vesta's regolith is comparatively dry, whereas Ceres is rich in water ice. This leads to the conclusion that volatile content alone cannot be responsible for low effective coefficients of friction, and that more than one geological process is needed to explain the mass motion behavior and morphology.
An Integrative Conceptualization of Floodplain Storage
Authors: Wohl Ellen 
Published: March 2021

AbstractFloodplains perform diverse functions, including attenuation of fluxes of water, solutes, and particulate material. Critical details of floodplain storage including magnitude, duration, and spatial distribution are strongly influenced by floodplain biogeochemical processes and biotic communities. Floodplain storage of diverse materials can be conceptualized in the form of a budget that quantifies inputs, outputs, and storage within the floodplain control volume. The floodplain control volume is here defined as bounded on the inner edges by the banks of the active channel(s), on the outer edges by the limit of periodic flooding and the deposition of fluvially transported sediment, on the underside by the extent of hyporheic exchange flows and the floodplain aquifer, and on the upper side by the upper elevation of living vegetation. Fluxes within the floodplain control volume can also change the location, characteristics, and residence time of material in storage. Fluxes, residence time, and quantities of material stored in floodplains can be measured directly; inferred from diverse types of remotely sensed data; or quantitatively estimated using numerical models. Human activities can modify floodplain storage by: hydrologically and/or geomorphically disconnecting channels and floodplains; altering fluxes of water and sediment to the river corridor; and obliterating floodplains through alluvial mining or urbanization. Floodplain restoration can focus on enlarging the functional floodplain, reconnecting the channel and floodplain, restoring natural regimes of water, sediment, and/or large wood, or enhancing the spatial heterogeneity of the channel and floodplain. Each form of floodplain restoration can increase floodplain storage and resilience to disturbances.
Application of a Multi‐Layer Artificial Neural Network in a 3‐D Global Electron Density Model Using the Long‐Term Observations of COSMIC, Fengyun‐3C, and Digisonde
Authors: Li Wang , Zhao Dongsheng , He Changyong , Shen Yi , Hu Andong , Zhang Kefei 
Published: March 2021

AbstractThe ionosphere plays an important role in satellite navigation, radio communication, and space weather prediction. However, it is still a challenging mission to develop a model with high predictability that captures the horizontal‐vertical features of ionospheric electrodynamics. In this study, multiple observations during 2005–2019 from space‐borne global navigation satellite system (GNSS) radio occultation (RO) systems (COSMIC and FY‐3C) and the Digisonde Global Ionosphere Radio Observatory are utilized to develop a completely global ionospheric three‐dimensional electron density model based on an artificial neural network, namely ANN‐TDD. The correlation coefficients of the predicted profiles all exceed 0.96 for the training, validation and test datasets, and the minimum root‐mean‐square error of the predicted residuals is 7.8 × 104 el/cm3. Under quiet space weather, the predicted accuracy of the ANN‐TDD is 30%–60% higher than the IRI‐2016 at the Millstone Hill and Jicamarca incoherent scatter radars. However, the ANN‐TDD is less capable of predicting ionospheric dynamic evolution under severe geomagnetic storms compared to the IRI‐2016 with the STORM option activated. Additionally, the ANN‐TDD successfully reproduces the large‐scale horizontal‐vertical ionospheric electrodynamic features, including seasonal variation and hemispheric asymmetries. These features agree well with the structure revealed by the RO profiles derived from the FORMOSAT/COSMIC‐2 mission. Furthermore, the ANN‐TDD successfully captures the prominent regional ionospheric patterns, including the equatorial ionization anomaly, Weddell Sea anomaly and mid‐latitude summer nighttime anomaly. The new model is expected to play an important role in the application of GNSS navigation and in the explanation of the physical mechanisms involved.
Triassic–Jurassic Accretionary History and Tectonic Origin of Stikinia From U‐Pb Geochronology and Lu‐Hf Isotope Analysis, British Columbia
Authors: George S. W. M. , Nelson J. L. , Alberts D. , Greig C. J. , Gehrels G. E. 
Published: March 2021

AbstractThe timing of assembly and tectonic origins of terranes in the northern Cordillera of Alaska, British Columbia, and the Pacific Northwest are debated. Stikinia, a long‐lived arc terrane, has an enigmatic regional Mesozoic accretionary history and its tectonic origins remain unconstrained. Zircon U‐Pb geochronology and Lu‐Hf isotopic data on Triassic–Jurassic sedimentary and igneous rocks from central Stikinia shed light on the terrane‐scale effects of a latest Triassic–Early Jurassic collision between Stikinia and pericratonic Yukon‐Tanana terrane. Main age peaks from central Stikinia are 250–160 Ma, reflecting ongoing Mesozoic arc‐related igneous activity within Stikinia. Comparison of isotopic evolution and unconformity development between central Stikinia and northern Stikinia (Whitehorse trough) provide new constraints on regional latest Triassic–earliest Jurassic deformation. We attribute the shortening‐related deformation to variable along‐strike interactions during end‐on collision with the Yukon‐Tanana terrane, with significant crustal thickening at the northern apex of Stikinia that did not persist farther south. A small pre‐Devonian zircon population is significant, as the oldest exposed rocks in Stikinia are Early Devonian. Pre‐Devonian age peaks differ from those of the northern Yukon‐Tanana terrane, but resemble zircons from southern Wrangellia. These zircons are likely multi‐cyclic, derived from crust that originated in the Arctic region near the northern end of the Caledonide orogeny. We suggest that Stikinia was an independent crustal block prior to latest Triassic onset of collision with Yukon‐Tanana terrane. The ongoing, end‐on collision in turn promoted oroclinal assembly of the peri‐Laurentian terranes.
LGK974 suppresses lipopolysaccharide-induced endotoxemia in mice by modulating the crosstalk between the Wnt/β-catenin and NF-κB pathways
Authors: Jang Jaewoong , Song Jaewon , Lee Hyunji , Sim Inae , Kwon Young V. , Jho Eek-hoon , Yoon Yoosik 
Published: March 2021

AbstractEndotoxemia, a type of sepsis caused by gram-negative bacterial endotoxin [i.e., lipopolysaccharide (LPS)], is associated with manifestations such as cytokine storm; failure of multiple organs, including the liver; and a high mortality rate. We investigated the effect and mechanism of action of LGK974, a Wnt signaling inhibitor, in mice with LPS-induced endotoxemia, an animal model of sepsis. LGK974 significantly and dose-dependently increased the survival rate and reduced plasma cytokine levels in mice with LPS-induced endotoxemia. Transcriptome analysis of liver tissues revealed significant changes in the expression of genes associated with the Wnt pathway as well as cytokine and NF-κB signaling during endotoxemia. LGK974 treatment suppressed the activation of NF-κB signaling and cytokine expression as well as the Wnt/β-catenin pathway in the livers of endotoxemic mice. Coimmunoprecipitation of phospho-IκB and β-transducin repeat-containing protein (β-TrCP) was increased in the livers of endotoxemic mice but was reduced by LGK974 treatment. Moreover, LGK974 treatment decreased the coimmunoprecipitation and colocalization of β-catenin and NF-κB, which were elevated in the livers of endotoxemic mice. Our results reveal crosstalk between the Wnt/β-catenin and NF-κB pathways via interactions between β-TrCP and phospho-IκB and between β-catenin and NF-κB during endotoxemia. The results of this study strongly suggest that the crosstalk between the Wnt/β-catenin and NF-κB pathways contributes to the mutual activation of these two pathways during endotoxemia, which results in amplified cytokine production, liver damage and death, and that LGK974 suppresses this vicious amplification cycle by reducing the crosstalk between these two pathways.
Solitary beam propagation in periodic layered Kerr media enables high-efficiency pulse compression and mode self-cleaning
Authors: Zhang Sheng , Fu Zongyuan , Zhu Bingbing , Fan Guangyu , Chen Yudong , Wang Shunjia , Liu Yaxin , Baltuska Andrius , Jin Cheng , Tian Chuanshan , Tao Zhensheng 
Published: March 2021

AbstractGenerating intense ultrashort pulses with high-quality spatial modes is crucial for ultrafast and strong-field science and can be achieved by nonlinear supercontinuum generation (SCG) and pulse compression. In this work, we propose that the generation of quasi-stationary solitons in periodic layered Kerr media can greatly enhance the nonlinear light-matter interaction and fundamentally improve the performance of SCG and pulse compression in condensed media. With both experimental and theoretical studies, we successfully identify these solitary modes and reveal their unified condition for stability. Space-time coupling is shown to strongly influence the stability of solitons, leading to variations in the spectral, spatial and temporal profiles of femtosecond pulses. Taking advantage of the unique characteristics of these solitary modes, we first demonstrate single-stage SCG and the compression of femtosecond pulses from 170 to 22 fs with an efficiency >85%. The high spatiotemporal quality of the compressed pulses is further confirmed by high-harmonic generation. We also provide evidence of efficient mode self-cleaning, which suggests rich spatiotemporal self-organization of the laser beams in a nonlinear resonator. This work offers a route towards highly efficient, simple, stable and highly flexible SCG and pulse compression solutions for state-of-the-art ytterbium laser technology.
The effect of Quorum sensing inhibitors on the evolution of CRISPR-based phage immunity in Pseudomonas aeruginosa
Authors: Broniewski Jenny M , Chisnall Matthew A W , Høyland-Kroghsbo Nina Molin , Buckling Angus , Westra Edze R 
Published: March 2021

Abstract
Quorum sensing controls the expression of a wide range of important traits in the opportunistic pathogen Pseudomonas aeruginosa, including the expression of virulence genes and its CRISPR-cas immune system, which protects from bacteriophage (phage) infection. This finding has led to the speculation that synthetic quorum sensing inhibitors could be used to limit the evolution of CRISPR immunity during phage therapy. Here we use experimental evolution to explore if and how a quorum sensing inhibitor influences the population and evolutionary dynamics of P. aeruginosa upon phage DMS3vir infection. We find that chemical inhibition of quorum sensing decreases phage adsorption rates due to downregulation of the Type IV pilus, which causes delayed lysis of bacterial cultures and favours the evolution of CRISPR immunity. Our data therefore suggest that inhibiting quorum sensing may reduce rather than improve the therapeutic efficacy of pilus-specific phage, and this is likely a general feature when phage receptors are positively regulated by quorum sensing.