Monte Carlo Simulation for Polychromatic X-ray Fluorescence Computed Tomography with Sheet-Beam Geometry

X-ray fluorescence computed tomography based on sheet-beam can save a huge amount of time to obtain a whole set of projections using synchrotron. However, it is clearly unpractical for most biomedical research laboratories. In this paper, polychromatic X-ray fluorescence computed tomography with sheet-beam geometry is tested by Monte Carlo simulation. First, two phantoms (A and B) filled with PMMA are used to simulate imaging process through GEANT 4. Phantom A contains several GNP-loaded regions with the same size (10 mm) in height and diameter but different Au weight concentration ranging from 0.3% to 1.8%. Phantom B contains twelve GNP-loaded regions with the same Au weight concentration (1.6%) but different diameter ranging from 1mm to 9mm. Second, discretized presentation of imaging model is established to reconstruct more accurate XFCT images. Third, XFCT images of phantom A and B are reconstructed by fliter backprojection (FBP) and maximum likelihood expectation maximization (MLEM) with and without correction, respectively. Contrast to noise ratio (CNR) is calculated to evaluate all the reconstructed images. Our results show that it is feasible for sheet-beam XFCT system based on polychromatic X-ray source and the discretized imaging model can be used to reconstruct more accurate images

Human activities accelerated the degradation of saline seepweed red beaches by amplifying top‐down and bottom‐up forces

Salt marshes dominated by saline seepweed (Suaeda heteroptera) provide important ecosystem services such as sequestering carbon (blue carbon), maintaining healthy fisheries, and protecting shorelines. These salt marshes also constitute stunning red beach landscapes, and the resulting tourism significantly contributes to the local economy. However, land use change and degradation have led to a substantial loss of the red beach area. It remains unclear how human activities influence the top‐down and bottom‐up forces that regulate the distribution and succession of these salt marshes and lead to the degradation of the red beaches. We examined how bottom‐up forces influenced the germination, emergence, and colonization of saline seepweed with field measurements and a laboratory experiment. We also examined whether top‐down forces affected the red beach distribution by conducting a field survey for crab burrows and density, laboratory feeding trials, and waterbird investigations. The higher sediment accretion rate induced by human activities limited the establishment of new red beaches. The construction of tourism facilities and the frequent presence of tourists reduced the density of waterbirds, which in turn increased the density of crabs, intensifying the top‐down forces such as predators and herbivores that drive the degradation of the coastal red beaches. Our results show that sediment accretion and plant–herbivory changes induced by human activities were likely the two primary ecological processes leading to the degradation of the red beaches. Human activities significantly shaped the abundance and distribution of the red beaches by altering both top‐down and bottom‐up ecological processes. Our findings can help us better understand the dynamics of salt marshes and have implications for the management and restoration of coastal wetlands

AGL61/80 regulates BGAL9, which participates in early somatic embryogenesis and increases longan resistance to heat stress

β-galactosidase (BGAL) is a glycosyl hydrolase that participates in cell wall modification, playing an essential role in plant growth, development and environmental stress adaptation. However, the function of BGALs in longan remains unclear. In this study, a total of 20 BGAL genes were identified from the longan (Dimocarpus longan Lour.) genome, which were distributed to eight chromosomes. Transcript profiles revealed that the majority of 11 detected DlBGAL genes were highly expressed in the embryogenic callus (EC) (four) and globular embryos (GE) (six), and responsive to heat stress. Combined with RNA-seq, ATAC-seq, and ChIP-seq results, most DlBGAL genes differentially expressed during early somatic embryogenesis (SE) were related with chromatin accessibility and high levels of H3K4me1. DlBGAL9 was selected for further analysis. Dual-luciferase assays and transient transformation indicated that the transcription factor (TF) DlAGL61 and DlAGL80 might bind to the DlBGAL9 promoters to activate DlBGAL9 transcription. Overexpression of DlBGAL9 and TF DlAGL80 induces longan hairy roots β-GAL activity and thickening of cell walls. The expression levels of DlBGAL9 and TF DlAGL80 in longan hairy roots were significantly increased under heat stress, and ROS scavengers related genes were significantly upregulated in overexpressing DlBGAL9 and TF DlAGL80 hairy roots. This study proposes the significance of the regulatory network composed of DlBGAL9 and TF DlAGL80 in regulating the early longan SE and heat stress response

An Integrative Salt Marsh Conceptual Framework for Global Comparisons

Salt marshes occur globally across climatic and coastal settings, providing key linkages between terrestrial and marine ecosystems. However, salt marsh science lacks a unifying conceptual framework; consequently, historically well-studied locations have been used as normative benchmarks. To allow for more effective comparisons across the diversity of salt marshes, we developed an integrative salt marsh conceptual framework. We review ecosystem-relevant drivers from global to local spatial scales, integrate these multi-scale settings into a framework, and provide guidance on applying the framework using specific variables on 11 global examples. Overall, this framework allows for appropriate comparison of study sites by accounting for global, coastal, inter-, and intra-system spatial settings unique to each salt marsh. We anticipate that incorporating this framework into salt marsh science will provide a mechanism to critically evaluate research questions and a foundation for effective quantitative studies that deepen our understanding of salt marsh function across spatial scales

Predicting the invasive potential of a non-native mangrove reforested plant ( Laguncularia racemosa ) in China

Abstract(#br)Mangroves are critical inter-tidal ecosystems with high productivity and ecological significance. Afforestation was regarded as one of the key projects worldwide in recovering mangrove ecosystem function. Laguncularia racemosa, a non-native mangroves species in China has been used in mangrove afforestation, while its invasiveness is widely concerned. Understanding how it tolerates shade and salinity stresses is crucial as these factors can affect its invasive potential. However, the effects of soil salinity and light on mangroves (especially on non-native species) are ambiguous. We examined the combined effects of salinity and light on the growth and physiological responses of L. racemosa and predicted an extensive range of dispersal habitats for L. racemosa in a typical estuary using Kriging model. The field surveys showed that the seedling density and seedling height were positively correlated with light availability but negatively correlated with salinity. Our greenhouse experiment also demonstrated that moderate shading (60–80% PAR) and low salinity treatments (0–10 psu) enhanced the survival and growth of seedlings, whereas high salinity limited their assimilation rates ( A ), independent of the light levels. Under high salinity (30 psu) and low light level (20%), L. racemosa seedlings employed a water-saving strategy (248.96 ± 24.27 µmol·mmol −1 in instantaneous water use efficiency), which helped them to improve their adaptability to stressful environmental conditions and maintain their growth. Our findings indicate the combined effects of salinity and light on the growth strategies of L. racemosa as well as its environmental tolerance to high salinity which limits its growth and survival in coastal ecosystems. These results can provide a reference for the management of non-native mangrove species in China and worldwide

An integrative salt marsh conceptual framework for global comparisons

Salt marshes occur globally across climatic and coastal settings, providing key linkages between terrestrial and marine ecosystems. However, salt marsh science lacks a unifying conceptual framework; consequently, historically well-studied locations have been used as normative benchmarks. To allow for more effective comparisons across the diversity of salt marshes, we developed an integrative salt marsh conceptual framework. We review ecosystem-relevant drivers from global to local spatial scales, integrate these multi-scale settings into a framework, and provide guidance on applying the framework using specific variables on 11 global examples. Overall, this framework allows for appropriate comparison of study sites by accounting for global, coastal, inter-, and intra-system spatial settings unique to each salt marsh. We anticipate that incorporating this framework into salt marsh science will provide a mechanism to critically evaluate research questions and a foundation for effective quantitative studies that deepen our understanding of salt marsh function across spatial scales

An Experimental Investigation for Seepage-Induced Instability of Confined Broken Mudstones with Consideration of Mass Loss

To study and prevent water-mud-outburst disasters of tectonic fracture zones in geotechnical engineering, we tested seepage stability of confined broken mudstones with consideration of mass loss using syringe seepage method and a self-designed seepage testing system, obtained the variation laws of seepage instable duration, total mass loss, and mass loss rate of broken mudstones under different pressure gradients and Talbol power exponents (simplified as Talbol hereafter), and explained their instable seepage behaviors. The results showed that the mass loss is the internal cause of seepage-induced instability of broken rocks and pressure gradient is the external cause, and the persistent migration and loss of particles result in progressive failure process, while the large enough pressure gradient causes sudden overall instability. The seepage instable duration shortens with pressure gradient increasing, with the longest and shortest duration at Talbol of 0.5 and 0.1, respectively. In general, mass loss increases with pressure gradient increasing and with Talbol decreasing. Mass loss rate increases with pressure gradient increasing but shows no monotonic changes with Talbol. Their expressions can be used to establish dynamic model in the further seepage stability researches

Nocturnal sap flow as compensation for water deficits: an implicit water-saving strategy used by mangroves in stressful environments

As part of the plant water-use process, plant nocturnal sap flow (Qn) has been demonstrated to have important ecophysiological significance to compensate for water loss. The purpose of this study was to explore nocturnal water-use strategies to fill the knowledge gap in mangroves, by measuring three species co-occurring in a subtropical estuary. Sap flow was monitored over an entire year using thermal diffusive probes. Stem diameter and leaf-level gas exchange were measured in summer. The data were used to explore the different nocturnal water balance maintaining mechanisms among species. The Qn existed persistently and contributed markedly over 5.5%~24.0% of the daily sap flow (Q) across species, which was associated with two processes, nocturnal transpiration (En) and nocturnal stem water refilling (Rn). We found that the stem recharge of the Kandelia obovata and Aegiceras corniculatum occurred mainly after sunset and that the high salinity environment drove higher Qn while stem recharge of the Avicennia marina mainly occurred in the daytime and the high salinity environment inhibited the Qn. The diversity of stem recharge patterns and response to sap flow to high salinity conditions were the main reasons for the differences in Qn/Q among species. For Kandelia obovata and Aegiceras corniculatum, Rn was the main contributor to Qn, which was driven by the demands of stem water refilling after diurnal water depletion and high salt environment. Both of the species have a strict control over the stomata to reduce water loss at night. In contrast, Avicennia marina maintained a low Qn, driven by vapor pressure deficit, and the Qn mainly used for En, which adapts to high salinity conditions by limiting water dissipation at night. We conclude that the diverse ways Qn properties act as water-compensating strategies among the co-occurring mangrove species might help the trees to overcoming water scarcity