We studied the formation and evolution mechanism of polygonal cracks on rock surfaces under cooling by modelling meso-damage mechanics, continuum mechanics and thermodynamics. Factors that affect ...rock surface damage include ambient temperature, lithology difference and boundary restrictions. We established and simulated a heterogeneous model with a surface weak layer for three types of boundaries. These were biaxial constraint, uniaxial constraint and free boundary. The initiation and propagation of polygonal cracks were reproduced for varying thickness and homogeneity of the weak layer. The results show that the boundary constraints strongly influence the polygonal cracking. Many polygonal or parallel cracks are generated on the rock surface under biaxial or uniaxial constraint. The unconstrained rock surface displays polygonal cracks at the center and parallel cracks in the surrounding areas. The thicker the surface weak layer, the larger the average area of formed blocks. Small blocks and short cracks are more numerous than large blocks and long cracks. As the heterogeneity index increases, the rock layer is more likely to produce blocks with relatively regular shapes. Quadrilateral, pentagonal and hexagonal blocks dominate regardless of changes in layer thickness and heterogeneity. However, the number of edges of the polygonal blocks is sensitive to rock heterogeneity. The polygons tend to become more complex with increasing inhomogeneity. This study contributes to understanding the complex formation mechanisms of polygonal cracks on rock surfaces in nature. Additionally, the simulations of three-dimensional fracture geometry provide a basis for developing algorithms to generate discrete fractures and blocks in discrete fracture network (DFN) analyses.
•New cracks occur in polygon areas and expand outwards until crack saturation.•The probability density of crack length and intersection angle is affected by upper layer thickness.•The formation mechanisms of typical 90° and 120° intersecting angles differ.•The complexity of surface cracking is sensitive to rock heterogeneity.
•A Bayesian belief network (BBN) model is developed to determine the driving factors regarding trade-off changes.•The multi-scenario scheme of ES optimization is obtained by visualizing the key state ...of key variables.•Suggestions for ecological restoration were given, and a good way is to adjust the combination of the key state of key variables.
The relationships between trade-off and synergy in ecosystem services (ESs) is essential for eco-environmental management and restoration in Karst regions, and many researchers have focused heavily on this. However, to date, and to the best of our knowledge, we still lack an adequate understanding of the driving factors of relationship changes and the optimization of the spatial pattern of ESs in this region. In this study, a Bayesian belief network (BBN) model was developed to link three major ESs—net primary productivity (NPP), water yield (WY), and soil conservation (SC)—and determine the driving factors regarding trade-off changes. Furthermore, the multi-scenario scheme of ES optimization was obtained and suggestions are provided in this paper for ecological restoration and decision-making in Guizhou Province, China. The results revealed that the relationships of regional ESs were mainly synergistic, but the synergistic relationship was weakening, accompanied by a trade-off trend during the study period. The area ratios with an enhancement of trade-offs in NPP and SC, SC and WY, and NPP and WY were 17.9%, 28.6%, and 26.6%, respectively, which indicates a significant uncoordinated changes between WY and the two other ESs. The ES relationships in this region are underpinned by multiple factors. Among them, water resources are the primary natural factor that restricts the concerted development of ESs, and the afforestation area (AA) is the main human factor that lowers the trade-offs among ESs. The superiority and distribution scope of ecological restoration were recognized through a multi-scenario analysis of the BBN model. In terms of the superiority of ecological restoration, it was concluded that scenario 3 > scenario 2 > scenario 1; in terms of the restoration area, it was scenario 1 > scenario 2 > scenario 3. Duyun City, in the south of Guizhou Province, as well as surrounding counties, were regions with a high probability of trade-off occurrences, and they could be regions for future ES optimization. Based on the driving factors and the occurrence probability of trade-offs, the ecological restoration area was identified, and it was found the ESs trade-off in this region can be decreased by adjusting a combination of the key variables’ key states. This study provides insight towards achieving a mechanistic understanding and spatial expression of the driving forces underpinning trade-offs/synergies, in turn ensuring the accurate implementation of ecological restoration and the effective management of karst ecosystems.
The Humber zone's Paleozoic sedimentary rocks, located on the rocky beaches of the Saint-Lawrence River in Quebec, Canada, exhibit interlayered calcareous greywacke beds and ductile shale. Fractures ...within these layers are characterized by either carbonate veins or barren joints, which are parallel arrays of planar fractures aligned in similar orientations. Fracture initiation occurred at either lithological interfaces or within brittle layers. The thickness of carbonate veins increases linearly with either bed thickness or layer-parallel extension strain, and carbonate precipitation occurred either simultaneously or ephemerally after the fracture opened. For a given bed thickness, veins are more closely and regularly spaced than joints, a feature that was successfully modeled using 2D finite element modeling. Both veins and joints follow a power-law relation between fracture spacing (s) and bed thickness (t), yielding a Weibull modulus of ∼2.5, a tensile strength of ∼9 MPa for the greywacke, and a shear flow strength of ∼1 MPa for the shale at the time of fracture formation. The different s-t relationships observed between joints and veins indicate that carbonate cementation results in 60% strength recovery for greywacke layers in the study area. This approach provides a new constraint on the degree of rock strength recovery due to mineral precipitation into opening fractures under natural conditions. The cementation-induced strength recovery inhibits stress axis permutation, and consequently, suppresses the formation of orthogonal veins.
•Veins are more closely spaced than barren joints in the same lithology.•Cementation-induced rock strength recovery can be inferred from field data.•Cementation inhibits stress swap and suppresses formation of orthogonal veins.•Thickness of veins increases with bed thickness and layer-parallel extension strain.•Mechanical properties of graywacke and shale at natural conditions are assessed.
Abstract Extensive studies have demonstrated the spatiotemporal changes in carbon use efficiency (CUE) and its driving factors over the past three decades. However, how the global CUE will change and ...to what extent the CUE is affected by the dominant factor in this century is still unclear. Herein, based on CMIP6 model outputs, we estimated the situation and change trends of CUE in baseline (1982–2014) and future (2015–2100), and identified the controlling factor of CUE variation by boosted regression tree. Further, we predicted the CUE-controlling factor sensitivity ( S value , referring to higher/lower controlling factor producing more/less CUE) and its variation under four representative pathways, and revealed the relationship between S value and social economy. Results showed decreased CUE at the end of the 21st century, especially in the SSP5-8.5, its decline rate of CUE is 1.2 × 10 −2 ± 5.2 × 10 −4 /decade, which is 10 times higher than that in the SSP1-2.6. Spatially, 56.9%, 74.5%, 83.1%, and 88.6% of the global land will exhibit a decreased CUE under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, and primarily concentrates at the middle-high latitudes of the Northern Hemisphere (30°–60° N). Except in Africa, temperature is the controlling factor for CUE variation, and the S value decreases over time, indicating an enhanced inhibitory effect of temperature on CUE. The turning time of S value change will advance with increases in CO 2 emission, presenting prolonged high-temperature stress of vegetation ecosystem under high-emission scenarios. A threshold effect can be found between S value change and precipitation, and the precipitation threshold is higher under the SSP5-8.5 scenario. The negative effect of temperature on CUE is attenuated by economic development and population control but this effect diminishes with rising CO 2 concentrations; in the future, developing clean energy and formulating population management policies can be used to enhance the carbon sink ability of the global ecosystem.
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•Anaerobic digestion of fracturing wastewater was impacted when salinity exceed 15 g/L.•High salinity decreased granular size and the activity of granular sludge.•Percentage of ...damaged cell in granular sludge increased with increase of salinity.•High salinity reduced the diversity and the abundance of methanogens.
The effects of salinity shock on the anaerobic treatment of fracturing wastewater regarding chemical oxygen demand (COD) removal performance, sludge characteristics and microbial community were investigated. Results showed COD removal efficiency decreased from 76.0% to 69.1%, 65.6%, 33.7% and 21.9% with the increase of salinity from 2.5 g/L to 10, 15, 25 and 45 g/L, respectively. The cumulative biogas production decreased by 13.8%–81.1% when salinity increased to 15–85 g/L. The increase of salinity led to the decline in particle size of granular sludge, and the activity of granular sludge, including SMA, coenzyme F420 and dehydrogenase, was inhibited significantly. Flow cytometry indicated the percentage of damaged cells in granular sludge gradually increased with the increase of salinity. Sequence analysis illustrated that microbial community structure in anaerobic digestion reactor was influenced by the salinity, high salinity reduced the diversity of archaea and decreased the abundance of methanogens, especially Methanosaeta.
Tensile fractures and resultant microboudinage structures of brittle fiber inclusions (e.g., tourmaline, piedmontite and amphibole) in the soft matrix of deforming minerals are of great significance ...for determining the finite strains and paleostresses of naturally deformed rocks. Using statistical strength theory, damage mechanics, and continuum mechanics, we have reproduced in a series of numerical models the sequential fractures of either homogeneous or heterogeneous fiber inclusions under axial tension in an elastoplastic matrix. The results clarify that: (1) The spacing between fractures in fibers is inversely proportional to the applied strain. As the applied strain increases, the fracture spacing systematically decreases as sequential fractures fill in until fracture saturation is reached. (2) As fiber length increases, the critical tensile strain for fracture saturation rises. For the same fiber diameter, saturation fracture spacing increases slightly with rising fiber length. For the same fiber length, however, saturation fracture spacing decreases significantly with lessening fiber diameter. Hence, fracture spacing at the saturation state depends on the volume fraction of fiber. (3) The rupture mode of fibers strongly depends on the non-uniform distribution of mechanical properties, which provides an effective approach for estimating the inhomogeneity of fibers by analyzing the formation of fractures. Furthermore, due to material heterogeneity, new fractures are unlikely to occur in the middle of existing adjacent fractures.
•Microboudinage structures of fiber inclusions are of great geological significance.•Sequential fractures of elastic-brittle fibers in elastoplastic matrix are reproduced.•Fractures hardly appear in the middle of segments due to material heterogeneity.•Fracture spacing decreases with rising the applied strain prior to saturation.•Aspect ratio and volume fraction of fiber affects saturation fracture spacing.
•A new benzothiazole-based sensing system was provided for detection of Zn2+ and Cd2+ by employing cysteine as an auxiliary regent.•A new verification method of aggregation by fluorescence polarized ...emission was developed.•The sensing system can detect Zn2+ and Cd2+ with the level of nanomole and micromole detection limit, respectively.
This paper describes the design and synthesis of a benzothiazole-based fluorescent probe (H1) for zinc and cadmium ion detection and discrimination, using cysteine as an auxiliary reagent. Among the various metal ions tested, zinc and cadmium ions induced blue-shifted emissions of probe H1 from 573 nm to 520 nm and 540 nm, respectively. The addition of cysteine caused the emission of H1-Cd2+ to red-shift back to 573 nm. In contrast, the emission of H1-Zn2+ with the addition of cysteine only decreased without any red-shift of wavelength. Furthermore, confocal laser scanning micrographs of HeLa cells demonstrated satisfactory cell permeability of H1 and selectivity toward zinc and cadmium ions in living cells. Test strip experiments suggest that probe H1 can recognise zinc and cadmium ions together by a remarkable fluorescence change, thus providing a convenient method for tracking zinc and cadmium ions in biological systems.
Aluminum is the third (after O and Si) most abundant metal in the earth’s crust and associates with neurological diseases when abnormal level of Al3+ occurs in nervous center. Developing highly ...sensitive and selective methods for Al3+ detection is of significant interest. In this work, we developed an excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) active fluorescent probe for ratiometric detection of Al3+ in aqueous medium and living cells. The BTZ-SF can detect Al3+ with high selectivity and a good linear relationship (R 2 = 0.9911) between fluorescence intensity ratio (I 476 nm/I 568 nm) and Al3+ concentration (0–100 μM). In addition, the detection limit was calculated as low as 2.2 μM. The single crystal structure of BTZ-SF–Al clearly exhibited the interaction between BTZ-SF and Al3+ with a hexa-coordinated structure. Furthermore, confocal fluorescence images of HeLa cell indicated that BTZ-SF could be used for monitoring Al3+ in living cells. Finally, a test strips experiment suggests that the BTZ-SF can recognize the Al3+ selectively accompanied by remarkable color change.
Summary
Artemisinin, isolated from Artemisia annua, is recommended as the preferred drug to fight malaria. Previous research showed that jasmonate (JA)‐mediated promotion of artemisinin accumulation ...depended on light. However, the mechanism underlying the interaction of light and JA in regulating artemisinin accumulation is still unknown.
We identified a WRKY transcription factor, AaWRKY9, using transcriptome analysis. The glandular trichome‐specific AaWRKY9 positively regulates artemisinin biosynthesis by directly binding to the promoters of AaDBR2 and AaGSW1.
The key regulator in the light pathway AaHY5 activates the expression of AaWRKY9 by binding to its promoter. In addition, AaWRKY9 interacts with AaJAZ9, a repressor in the JA signalling pathway. AaJAZ9 represses the transcriptional activation activity of AaWRKY9 in the absence of methyl jasmonate. Notably, in the presence of methyl jasmonate, the transcriptional activation activity of AaWRKY9 is increased.
Taken together, our results reveal a novel molecular mechanism underlying AaWRKY9 contributes to light‐mediated and jasmonate‐mediated to regulate the biosynthesis of artemisinin in A. annua. Our study provides new insights into integrating the two signalling pathways to regulate terpene biosynthesis in plants.
Curcumin (Cur) has been widely used in medicine, due to its antibacterial, anti-inflammatory, antioxidant, and antitumor effects. However, its clinic application is limited by its instability and ...poor solubility. In the present wok, curcumin was loaded into solid lipid nanoparticles (SLNs), in order to improve the therapeutic efficacy for breast cancer. The results measured using transmission electron microscopy (TEM) indicated that Cur-SLNs have a well-defined spherical shape; the size was about 40 nm with a negative surface charge. The drug loading and encapsulation efficiency in SLNs reached 23.38% and 72.47%, respectively. The Cur-SLNs showed a stronger cytotoxicity against SKBR3 cells. In vitro cellular uptake study demonstrated a high uptake efficiency of the Cur-SLNs by SKBR3 cells. Moreover, Cur-SLNs induced higher apoptosis in SKBR3 cells, compared to cells treated by free drug. In addition, Western blot analysis revealed that Cur-SLNs could promote the ratio of
, but decreased the expression of
and
. These results suggested that Cur-SLNs could be a potential useful chemotherapeutic formulation for breast cancer therapy.
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