Consider a double degenerate parabolic equation arising from the electrorheological fluids theory and many other diffusion problems. Let
v
ε
be the viscous solution of the equation. By showing that
|
...∇
v
ε
|
∈
L
∞
(
0
,
T
;
L
loc
p
(
x
)
(
Ω
)
)
and
∇
v
ε
→
∇
v
almost everywhere, the existence of weak solutions is proved by the viscous solution method. By imposing some restriction on the nonlinear damping terms, the stability of weak solutions is established. The innovation lies in that the homogeneous boundary value condition is substituted by the condition
a
(
x
)
|
x
∈
∂
Ω
=
0
, where
a
(
x
)
is the diffusion coefficient. The difficulties come from the nonlinearity of
|
∇
v
|
p
(
x
)
−
2
as well as the nonlinearity of
|
v
|
α
(
x
)
.
The May 22nd, 2021, Mw ${\mathrm{M}}_{\mathrm{w}}$ 7.4 Maduo earthquake occurred on an intraplate fault of Bayan‐Har block in the Tibet Plateau. Here, we derive the coseismic and early postseismic ...surface deformations from the Sentinel‐1 (S1) interferometric synthetic aperture radar (InSAR) data. We use the subpixel offsets of SAR and Sentinel‐2 (S2) optical images to determine the surface rupture traces. The fault geometry and coseismic fault slip distribution of multi‐segmented ruptures are estimated by inverting InSAR interferograms and SAR pixel offsets. We show that at least five fault segments with curved geometry are activated, with a peak coseismic slip of about 5 m. The geodetic data inversion suggests that an NW‐striking blind segment near the Eling Lake may have ruptured during the 2021 event. Postseismic slip inversion with the 60‐day cumulative line‐of‐sight deformations, shows that the early afterslip of 0.1 ∼ 0.3 m occurred mostly toward the downdip direction of the main coseismic slip asperities. The afterslip geodetic moment accounts for approximately 15.3% of the coseismic one. Coulomb stress analysis shows that the nucleation of the Maduo earthquake is partially facilitated by the 1947 M7.7 Dari earthquake.
Plain Language Summary
We derive the co‐ and postseismic deformations and fault‐slip distributions of the 2021 Maduo earthquake from the space‐based geodetic data. We find that the pattern of eastward and upward postseismic deformations is similar to that of the coseismic left‐lateral motions, and the 60‐day early afterslip of 0.1∼0.3 m occurrs mostly toward the down‐dip of the main coseismic slip asperities. We propose a six‐segment geological structure model with varied dips and orientations to better recover the actual surface deformations. We find that at least five fault segments are activated from west to east. We examine the stress loading induced by the 1947 M7.7 Dari and the 2021 Maduo earthquakes. We find that nucleation of the 2021 event is partially facilitated by the 1947 event, and the 2021 event increases the potential seismic risk on the Tuosuo Lake and Maqin segments of the East Kunlun fault.
Key Points
Co‐ and post‐seismic deformations and fault‐slip distributions of the 2021 Maduo earthquake are derived from space‐based geodetic data
A six‐segment geological structure model with varied dips and orientations is proposed for interpretation of the Maduo event
The 1947 Dari earthquake increases stress in the western rupture zones and partially promotes the fault failure of the Maduo event
Alkaline zinc-based flow batteries are regarded to be among the best choices for electric energy storage. Nevertheless, application is challenged by the issue of zinc dendrite/accumulation. Here, we ...report a negatively charged nanoporous membrane for a dendrite-free alkaline zinc-based flow battery with long cycle life. Free of zinc dendrite/accumulation, stable performance is afforded for ∼240 cycles at current densities ranging from 80 to 160 mA cm
using the negatively charged nanoporous membrane. Furthermore, 8 h and 7 h plating/stripping processes at 40 mA cm
yield an average energy efficiency of 91.92% and an areal discharge capacity above 130 mAh cm
. A peak power density of 1056 mW cm
is achieved at 1040 mA cm
. This study may provide an effective way to address the issue of zinc dendrite/accumulation for zinc-based batteries and accelerate the advancement of these batteries.
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•OPTSI is an optical image matching time series selection and inversion algorithm.•OPTSI enables decreasing the uncertainty and enhancing the spatial coverage.•The annual dune ...migration rates are extracted in NSS from Landsat 8 and Sentinel-2.•The migration directions from optical images agree with RDD from the wind data.
Sand dune migration poses a potential threat to desert infrastructure, vegetation, and atmospheric conditions. Capturing the patterns of long-term dune migration is useful for predicting probable desertification issues and wind conditions across vast desert areas. In this study, we employed optical image matching and a singular value decomposition approach to estimate the rates of dune migration in the North Sinai Sand Sea using the free Landsat 8 and Sentinel-2 archives. Our optical image matching time-series selection and inversion (OPTSI) algorithm limited the difference in the solar illumination of correlated pairs to decrease shadows and seasonal variability. We found that the maximum annual dune migration rates were 9.4 m/a and 15.9 m/a for Landsat 8 and Sentinel-2 data, respectively, and the results of time-series analysis revealed the existence of seasonal variations in dune migration controlled by wind regimes. The directions of sand movement extracted from the mean velocity solution agreed strongly with each other and with the drift directions estimated using wind data from meteorological stations. We assessed the uncertainty of each solution based on the variance of stable areas. Our results showed that the proposed inversion decreased uncertainty by up to 25% and increased the spatial coverage by up to 20%. This algorithm is also promising for the retrieval of historical time series on the ground displacements of glaciers and slow-moving landslides employing free archives that provide high-frequency images.
Wetland vegetation aboveground biomass (AGB) directly indicates wetland ecosystem health and is critical for water purification, carbon cycle, and biodiversity conservation. Accurate AGB estimation ...is essential for the monitoring and supervision of ecosystems, especially in seasonal floodplain wetlands. This paper explored the capability of spectral and texture features from the Sentinel-2 Multispectral Instrument (MSI) for modeling grassland AGB using random forest (RF) and extreme gradient boosting (XGBoost) algorithms in Shengjin Lake wetland (a Ramsar site). We use five-fold cross-validation to verify the model effectiveness. The results indicated that the RF and XGBoost models had a robust and efficient performance (with root mean square error (RMSE) of 126.571 g·m−2 and R2 of 0.844 for RF, RMSE of 112.425 g·m−2 and R2 of 0.869 for XGBoost), and the XGBoost models, by contrast, performed better. Both traditional and red-edge vegetation indices (VIs) obtained satisfactory results of AGB estimation (RMSE = 127.936 g·m−2, RMSE = 125.879 g·m−2 in XGBoost models, respectively), with the red-edge VIs contributed more to the AGB models. Moreover, we selected eight gray-level co-occurrence matrix (GLCM) textures calculated by four processing window sizes using the mean value of four offsets, and further analyzed the results of three analysis sets. Textures derived from traditional and red-edge bands using a 7 × 7 window size performed better in biomass estimation. This finding suggested that textures derived from the traditional bands were as important as the red-edge bands. The introduction of textures moderately improved the accuracy of modeling AGB, whereas the use of textures alo ne was not satisfactory. This research demonstrated that using the Sentinel-2 MSI and the two ensemble algorithms is an effective method for long-term dynamic monitoring and assessment of grass AGB in seasonal floodplain wetlands, which can support sustainable management and carbon accounting of wetland ecosystems.
Metformin is a commonly used drug for the treatment of diabetes. Accumulating evidence suggests that it exerts anti-tumor effects in many cancers, including multiple myeloma (MM); however, the ...underlying molecular mechanisms have not been clearly elucidated.
The anti-myeloma effects of metformin were evaluated using human MM cell lines (RPMI8226 and U266) in vitro and in vivo NOD-SCID murine xenograft MM model. Cell viability was assessed with CCK8 and cell proliferation was measured by EdU incorporation assay. Cell cycle distribution and apoptosis were examined by flow cytometry. Transmission electron microscopy was used to visualized autophagosomes. Activation of AMPK and inhibition of mTORC1/C2 pathways was assessed by Western blot analysis. RPMI8226 cells and U266 cell lines with AMPK knockdown were generated by transfection with small interfering RNA targeting the AMPK-α1 and α2 subunits using Lipofectamine 2000 reagent.
Metformin effectively inhibited the proliferation of MM cell lines, an effect that was associated with the induction of autophagy and G0/G1 cell cycle arrest, but not apoptosis. Metformin activated AMPK and repressed both mTORC1 and mTORC2 signaling pathways in myeloma cells as well as downstream molecular signaling pathways, such as p-4EBP1 and p-AKT. AMPK activation resulted in direct phosphorylation and activation of tuberous sclerosis complex 2 (TSC2), leading to inhibition of the mammalian target of rapamycin (mTOR). In addition, metformin inhibited myeloma cell growth in an AMPK-dependent manner. The xenograft mouse model further confirmed that metformin inhibited tumor growth by upregulation of AMPK and downregulation of mTOR.
Metformin inhibits the proliferation of myeloma cells by inducing autophagy and cell-cycle arrest. Our results suggest that the molecular mechanism involves dual repression of mTORC1 and mTORC2 pathways via AMPK activation. Our study provides a theoretical basis for the development of novel strategies for the treatment of MM using metformin as an already approved and safe drug.
Understanding the magmatic systems beneath rift volcanoes provides insights into the deeper processes associated with rift architecture and development. At the slow spreading Erta Ale segment (Afar, ...Ethiopia) transition from continental rifting to seafloor spreading is ongoing on land. A lava lake has been documented since the twentieth century at the summit of the Erta Ale volcano and acts as an indicator of the pressure of its magma reservoir. However, the structure of the plumbing system of the volcano feeding such persistent active lava lake and the mechanisms controlling the architecture of magma storage remain unclear. Here, we combine high-resolution satellite optical imagery and radar interferometry (InSAR) to infer the shape, location and orientation of the conduits feeding the 2017 Erta Ale eruption. We show that the lava lake was rooted in a vertical dike-shaped reservoir that had been inflating prior to the eruption. The magma was subsequently transferred into a shallower feeder dike. We also find a shallow, horizontal magma lens elongated along axis inflating beneath the volcano during the later period of the eruption. Edifice stress modeling suggests the hydraulically connected system of horizontal and vertical thin magmatic bodies able to open and close are arranged spatially according to stresses induced by loading and unloading due to topographic changes. Our combined approach may provide new constraints on the organization of magma plumbing systems beneath volcanoes in continental and marine settings.
•Slow accumulation in a dike-shaped reservoir is observed beneath Erta Ale volcano prior to the eruption.•Co-eruption deformation is explained with hydraulically connected shallow dikes and a horizontal axial sill.•The shallow magma bodies at Erta Ale are oriented according to stresses induced by edifice loading.
Soil contamination by heavy metals threatens the quality of agricultural products and human health, so it is necessary to choose certain economic and effective remediation techniques to control the ...continuous deterioration of land quality. This paper is intended to present an overview on the application of biochar as an addition to the remediation of heavy-metal-contaminated soil, in terms of its preparation technologies and performance characteristics, remediation mechanisms and effects, and impacts on heavy metal bioavailability. Biochar is a carbon-neutral or carbon-negative product produced by the thermochemical transformation of plant- and animal-based biomass. Biochar shows numerous advantages in increasing soil pH value and organic carbon content, improving soil water-holding capacity, reducing the available fraction of heavy metals, increasing agricultural crop yield and inhibiting the uptake and accumulation of heavy metals. Different conditions, such as biomass type, pyrolysis temperature, heating rate and residence time are the pivotal factors governing the performance characteristics of biochar. Affected by the pH value and dissolved organic carbon and ash content of biochar, the interaction mechanisms between biochar and heavy metals mainly includes complexation, reduction, cation exchange, electrostatic attraction and precipitation. Finally, the potential risks of in-situ remediation strategy of biochar are expounded upon, which provides the directions for future research to ensure the safe production and sustainable utilization of biochar.
Electrochemical reduction of CO2 to value‐added products is an important and challenging reaction for sustainable energy study. Herein, bismuth nanosheets with thickness of around 10 nm were prepared ...through the electrochemical reduction of Bi3+. Ultrathin Bi nanosheets with numerous low‐coordination sites can efficiently reduce CO2 to formate in aqueous solution. Within the potential range of −0.9 to −1.2 V vs. reversible hydrogen electrode (RHE), the faradaic efficiency of formate is over 90 %, outperforming many Bi catalysts. At −0.7 V, the Bi nanosheets exhibit much higher current for formate generation than that of bulk Bi, attributed to a high surface area and also modified intrinsic electronic properties brought about by the ultrathin structure. DFT calculations demonstrate that Bi nanosheets have much higher density of states at the Fermi level compared to bulk Bi, favoring improved CO2 reduction on Bi nanosheets. At −1.0 V, Bi nanosheets exhibit high selectivity for formate and excellent stability during 5 h of electrolysis.
It′s bismuth time: Bismuth nanosheets with thickness of approximately 10 nm were fabricated through the electrochemical reduction of Bi3+. As a CO2 reduction electrocatalyst, ultrathin Bi nanosheets exhibit high selectivity for formate generation owing to a high density of states near the Fermi level, as verified by DFT calculations.
In the past 30 years, the small baseline subset (SBAS) InSAR time-series technique has emerged as an essential tool for measuring slow surface displacement and estimating geophysical parameters. ...Because of its ability to monitor large-scale deformation with millimeter accuracy, the SBAS method has been widely used in various geodetic fields, such as ground subsidence, landslides, and seismic activity. The obtained long-term time-series cumulative deformation is vital for studying the deformation mechanism. This article reviews the algorithms, applications, and challenges of the SBAS method. First, we recall the fundamental principle and analyze the shortcomings of the traditional SBAS algorithm, which provides a basic framework for the following improved time series methods. Second, we classify the current improved SBAS techniques from different perspectives: solving the ill-posed equation, increasing the density of high-coherence points, improving the accuracy of monitoring deformation and measuring the multi-dimensional deformation. Third, we summarize the application of the SBAS method in monitoring ground subsidence, permafrost degradation, glacier movement, volcanic activity, landslides, and seismic activity. Finally, we discuss the difficulties faced by the SBAS method and explore its future development direction.
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