Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling

The objectives of the overall collaborative EMSP effort (with which this project is associated) were to characterize sorption and desorption processes of U(VI) on pristine and contaminated Hanford sediments over a range of sediment facies and materials properties and to relate such characterization both to fundamental molecular-scale understanding and field-scale models of geochemistry and mass transfer. The research was intended to provide new insights on the mechanisms of U(VI) retardation at Hanford, and to allow the development of approaches by which laboratory-developed geochemical models could be upscaled for defensible field-scale predictions of uranium transport in the environment. Within this broader context, objectives of the JHU-based project were to test hypotheses regarding the coupled roles of adsorption and impermeable-zone diffusion in controlling the fate and transport of U(VI) species under conditions of comparatively short-term exposure. In particular, this work tested the following hypotheses: (1) the primary adsorption processes in the Hanford sediment over the pH range of 7 to 10 are surface complexation reactions of aqueous U(VI) hydroxycarbonate and carbonate complexes with amphoteric edge sites on detrital phyllosilicates in the silt/clay size fraction; (2) macroscopic adsorption intensity (at given aqueous conditions) is a function of mineral composition and aquatic chemistry; and (3) equilibrium sorption and desorption to apply in short-term, laboratory-spiked pristine sediments; and (4) interparticle diffusion can be fully understood in terms of a model that couples molecular diffusion of uranium species in the porewater with equilibrium sorption under the relevant aqueous conditions. The primary focus of the work was on developing and applying both models and experiments to test the applicability of "local equilibrium" assumptions in the modeling interpretation of sorption retarded interparticle diffusion, as relevant to processes of U(VI) diffusion in silt/clay layers. Batch isotherm experiments were first used to confirm sorption isotherms under the intended test conditions and diffusion cell experiments were then conducted to explore the diffusion hypotheses. Important new information was obtained about the role of aqueous calcium and solid calcium carbonate in controlling sorption equilibrium with Hanford sediments. The retarded interparticle diffusion model with local sorption equilibrium was shown to very successfully simulate diffusion at high aqueous concentration of U(VI). By contrast, however, diffusion data obtained at low concentration suggested nonequilibrium of sorption even at diffusion time scales. Such nonequilibrium effects at low concentration are likely to be the result of sorption retarded intraparticle diffusion, and strong U(VI) sorption in the low concentration range

Nonlinear dynamic characteristics of a large-scale tilting pad journal bearing-rotor system

In this work, the nonlinear dynamic characteristics of a large-scale tilting pad journal bearings-rotor system with oil-film force model are investigated. The oil-film force of the 4-tilting-pad journal bearings considering oil cavitation is studied, and it is indicated that preload coefficient, wrapping and swing angle of pad have effects on the force. The system state trajectory, Poincaré maps, frequency spectra and bifurcation diagram are constructed to analyse the nonlinear dynamic characteristics of the double cantilever rotor supported by the tilting pad journal bearings in a large-scale turbo expander. The result from the numerical analysis is in agreement with behaviors of the turbo expander, and it is shown that the tilting pad journal bearings are more stable because of better oil-film distribution and larger oil-film force than that of the conventional plain bearing. Oil whirl and oil whip have an important influence on vibration of the rotor system. The study makes sense to improvement of the turbo expander and may contribute to a further understanding of its nonlinear dynamics

Single-cell sequencing analysis related to sphingolipid metabolism guides immunotherapy and prognosis of skin cutaneous melanoma

BackgroundWe explore sphingolipid-related genes (SRGs) in skin melanoma (SKCM) to develop a prognostic indicator for patient outcomes. Dysregulated lipid metabolism is linked to aggressive behavior in various cancers, including SKCM. However, the exact role and mechanism of sphingolipid metabolism in melanoma remain partially understood.MethodsWe integrated scRNA-seq data from melanoma patients sourced from the GEO database. Through the utilization of the Seurat R package, we successfully identified distinct gene clusters associated with patient survival in the scRNA-seq data. Key prognostic genes were identified through single-factor Cox analysis and used to develop a prognostic model using LASSO and stepwise regression algorithms. Additionally, we evaluated the predictive potential of these genes within the immune microenvironment and their relevance to immunotherapy. Finally, we validated the functional significance of the high-risk gene IRX3 through in vitro experiments.ResultsAnalysis of scRNA-seq data identified distinct expression patterns of 4 specific genes (SRGs) in diverse cell subpopulations. Re-clustering cells based on increased SRG expression revealed 7 subgroups with significant prognostic implications. Using marker genes, lasso, and Cox regression, we selected 11 genes to construct a risk signature. This signature demonstrated a strong correlation with immune cell infiltration and stromal scores, highlighting its relevance in the tumor microenvironment. Functional studies involving IRX3 knockdown in A375 and WM-115 cells showed significant reductions in cell viability, proliferation, and invasiveness.ConclusionSRG-based risk signature holds promise for precise melanoma prognosis. An in-depth exploration of SRG characteristics offers insights into immunotherapy response. Therapeutic targeting of the IRX3 gene may benefit melanoma patients

Preliminary Evidence of Sex Differences in Cortical Thickness Following Acute Mild Traumatic Brain Injury

The main objective of this study was to evaluate sex differences in cortical thickness after acute mild traumatic brain injury (mTBI) and its associations with clinical outcomes. Thirty-two patients with mTBI at acute phase (2.4 ± 1.3 days post-injury) and 30 healthy controls were enrolled. All the participants underwent comprehensive neurocognitive assessments and MRI to assess cortical thickness. Significant sex differences were determined by using variance analysis of factorial design. Relations between the cortical thickness and clinical assessments were measured with the Spearman Correlation. Results revealed that patients with mTBI had significantly reduced cortical thickness in the left entorhinal cortex while increased cortical thickness in the left precuneus cortex and right lateral occipital cortex, compared with healthy controls. The interaction effect of the group × sex on cortical thickness was significant. Female patients had significant thicker cortical thickness in the left caudal anterior cingulate cortex (ACC) than male patients and had higher scores on Posttraumatic stress disorder Checklist—Civilian Version (PCL-C). Spearman correlational analysis showed a significantly positive correlations between the cortical thickness of the left caudal ACC and PCL-C ratings in female patients. Sex differences in cortical thickness support its potential as a neuroimaging phenotype for investigating the differences in clinical profiles of mild TBI between women and men

Rhizome Severing Increases Root Lifespan of Leymus chinensis in a Typical Steppe of Inner Mongolia

Root lifespan is an important trait that determines plants' ability to acquire and conserve soil resources. There have been several studies investigating characteristics of root lifespan of both woody and herbaceous species. However, most of the studies have focused on non-clonal plants, and there have been little data on root lifespan for clonal plants that occur widely in temperate grasslands.We investigated the effects of rhizome severing on overall root lifespan of Leymus chinensis, a clonal, dominant grass species in the temperate steppe in northern China, in a 2-year field study using modified rhizotron technique. More specifically, we investigated the effects of rhizome severing on root lifespan of roots born in different seasons and distributed at different soil depths. Rhizome severing led to an increase in the overall root lifespan from 81 to 103 days. The increase in root lifespan exhibited spatial and temporal characteristics such that it increased lifespan for roots distributed in the top two soil layers and for roots born in summer and spring, but it had no effect on lifespan of roots in the deep soil layer and born in autumn. We also examined the effect of rhizome severing on carbohydrate and N contents in roots, and found that root carbohydrate and N contents were not affected by rhizome severing. Further, we found that root lifespan of Stipa krylovii and Artemisia frigida, two dominant, non-clonal species in the temperate steppe, was significantly longer (118 d) than that of L. chinensis (81 d), and this value became comparable to that of L. chinensis under rhizome severing (103 d).We found that root lifespan in dominant, clonal L. chinensis was shorter than for the dominant, non-clonal species of S. krylovii and A. frigida. There was a substantial increase in the root lifespan of L. chinensis in response to severing their rhizomes, and this increase in root lifespan exhibited temporal and spatial characteristics. These findings suggest that the presence of rhizomes is likely to account for the observed short lifespan of clonal plant species in the temperate steppe

Clonality-dependent dynamic change of plant community in temperate grasslands under nitrogen enrichment

Clonal plants with diverse growth forms are dominant in plant community of temperate grasslands and sensitive to enhanced atmospheric nitrogen (N) deposition. However, whether and how clonal plants with different growth forms differ in their responses to N deposition remains unclear. We investigated the long-term (14-year) and short-term (4-year) effects of N addition on clonal plants of three growth forms (clumper, stoloniferous and rhizomatous clonal plants) in temperate grasslands of northern China by monitoring the clonal traits and belowground meristems. We found that, for the first time, the effects of N addition on clonal plants were dependent on N-addition duration and growth forms of clonal plants. Short-term N addition enhanced growth of clumper clonal plants, while long-term N addition favored growth of rhizomatous clonal plants and suppressed growth of stoloniferous clonal plants. We further revealed that clumper clonal plants can preempt space by tillering rapidly, thus conferring their dominance in the community and suppressing vegetative reproduction of stoloniferous clonal plants upon exposure to short-term N enhancement. In contrast, long-term N addition depressed initiation of buds and tillering of clumper clonal plants. Moreover, long-term N addition shortened rhizome internode and enhanced vegetative reproduction of rhizomatous clonal plants, leading to their ultimate dominance in the steppe community. Our results highlight the important roles of belowground meristems and clonal traits in control of dynamic changes of plant community in response to N enrichment. These findings provide a new perspective to understand N-induced changes in plant community of temperate grasslands

Root trait-mediated belowground competition and community composition of a temperate steppe under nitrogen enrichment

AimsShifts of plant community composition with enhanced atmospheric nitrogen (N) deposition in grasslands have occurred globally. Despite extensive studies on the effects of enhanced N deposition on plant species composition of grassland community, few studies have focused on belowground ecological processes and duration of N addition.MethodsIn situ long-term (14-year: 2004-2017) and short-term (4-year: 2014-2017) N-addition experiments in the same sites were conducted in a temperate steppe of northern China. We investigated the effects of N-addition on plant community composition and root traits by comparing results of short-term and long-term N addition.ResultsNitrogen-evoked changes in plant community composition were primarily dependent on N-addition duration and functional groups. Short-term N addition favored growth of grasses, and depressed growth of forbs, while long-term N addition favored growth of sedges, and concurrently depressed growth of grasses and forbs, ultimately leading to a time-dependent shift of plant community composition from co-dominance by grasses and forbs to dominance by grasses, then to dominance by sedges. Similar to the observed aboveground biomass, short-term N addition led to an increase in the relative belowground biomass (the proportion of belowground biomass of individual plant to community belowground biomass) of the grass Stipa krylovii and a decrease in the relative belowground biomass of the forb Artemisia frigida, respectively. In contrast, long-term N addition enhanced the relative belowground biomass of the sedge Carex korshinskyi, and reduced the relative belowground biomass of the grass S. krylovii and the forb A. frigida. Moreover, traits of absorptive fine roots (first-two orders) in the three species (grass: S. krylovii; forb: A. frigida; sedge: C. korshinskyi) that are representatives of three functional groups differed in their responses to short-term and long-term N addition, thus rendering them differentially competitive for acquisition of belowground resource. The changes in root traits of the three species in responses to N addition of varying duration were associated with their relative aboveground biomass.ConclusionsRoot traits play important roles in mediating the competition for belowground resource and changes in plant community composition of temperate grasslands under N enrichment. Our findings provide novel insights into N-deposition-induced changes in steppe community composition by linking root traits of functional groups and duration of N addition