•A model is proposed to describe the water-heat coupling process during freezing.•Unfrozen water function for saline soil is determined and applied in modeling.•Frozen depth of the saline region is ...predicted based on the coupling analysis.•Finale ice formation and water dynamics are simulated and validated.•Temperature variation hysteresis in soil profile is proved and analysed.
Frozen depth has a great significance for the foundation engineering in cold regions, always showing a high correlation with some attendant engineering phenomena, including water aggregation, frost heave, and salt accumulation. To study the heat-water dynamics and frozen depth characteristics during the freezing process, soils in western Jilin Province of China, a typical seasonal frozen region, were selected for investigation. A coupled heat and water model was proposed to describe the water-heat coupling process during freezing, with full consideration of the unfrozen water variation, the ice layer formation, and the interaction among different elements. Then, the dynamics of the heat-water and frozen depth were simulated based on the boundary conditions of temperature variation with reference to the meteorological data. The in- situ monitoring data from the whole winter were used to analyse the model performance. The results show that water content and temperature data match the test data, and the Root Mean Square Error (RMSE) values of the temperatures (within 2 °C) at different depths were acceptable, indicating that the water-heat dynamics can predict the maximum frozen depth well. In addition, the temperature of the soil profile varies rapidly in the first 60 days of winter, and the frozen depth continues to increase even though the temperature starts to rise after freezing for 80 days. The moisture transfers upwards with the effect of heat flow, and the formation of ice occurred mainly at a depth of 1.5 m. Heat conduction plays an important role in modelling, predominantly leading to the hysteresis in the frozen depth variation during freezing. This new method can provide a reference for water-heat movement and the prediction of the frozen depth during freezing in the saline soil regions.
A photoinduced SET process enables the direct B−H bond activation of NHC–boranes. In contrast to common hydrogen atom transfer (HAT) strategies, this photoinduced reaction simply takes advantage of ...the beneficial redox potentials of NHC–boranes, thus obviating the need for extra radical initiators. The resulting NHC–boryl radical was used for the borylation of a wide range of α‐trifluoromethylalkenes and alkenes with diverse electronic and structural features, providing facile access to highly functionalized borylated molecules. Labeling and photoquenching experiments provide insight into the mechanism of this photoinduced SET pathway.
A photoinduced SET process enables the direct B−H bond activation of NHC–boranes. The resulting NHC–boryl radical was used for the borylation of a wide range of α‐trifluoromethylalkenes and alkenes with diverse electronic and structural features, providing facile access to highly functionalized borylated molecules.
The goal of no-reference objective image quality assessment (NR-IQA) is to develop a computational model that can predict the human-perceived quality of distorted images accurately and automatically ...without any prior knowledge of reference images. Most existing NR-IQA approaches are distortion specific and are typically limited to one or two specific types of distortions. In most practical applications, however, information about the distortion type is not really available. In this paper, we propose a general-purpose NR-IQA approach based on visual codebooks. A visual codebook consisting of Gabor-filter-based local features extracted from local image patches is used to capture complex statistics of a natural image. The codebook encodes statistics by quantizing the feature space and accumulating histograms of patch appearances. This method does not assume any specific types of distortions; however, when evaluating images with a particular type of distortion, it does require examples with the same or similar distortion for training. Experimental results demonstrate that the predicted quality score using our method is consistent with human-perceived image quality. The proposed method is comparable to state-of-the-art general-purpose NR-IQA methods and outperforms the full-reference image quality metrics, peak signal-to-noise ratio and structural similarity index on the Laboratory for Image and Video Engineering IQA database.
Herein, we report a photochemical synthesis of 1,4‐dicarbonyl containing quinoxalin‐2(1H)‐ones through consecutive photoredox catalysed reactions. A wide range of C3‐modified quinoxalin‐2(1H)‐ones ...were obtained in 53–91% yields by this approach. Mechanistic studies including radical trapping, EPR studies, D‐labelling investigations, and many other control experiments well explained the proposed consecutive photoredox mechanism.
The accumulation of lipid peroxides is recognized as a determinant of the occurrence of ferroptosis. However, the sensors and amplifying process of lipid peroxidation linked to ferroptosis remain ...obscure. Here we identify PKCβII as a critical contributor of ferroptosis through independent genome-wide CRISPR-Cas9 and kinase inhibitor library screening. Our results show that PKCβII senses the initial lipid peroxides and amplifies lipid peroxidation linked to ferroptosis through phosphorylation and activation of ACSL4. Lipidomics analysis shows that activated ACSL4 catalyses polyunsaturated fatty acid-containing lipid biosynthesis and promotes the accumulation of lipid peroxidation products, leading to ferroptosis. Attenuation of the PKCβII-ACSL4 pathway effectively blocks ferroptosis in vitro and impairs ferroptosis-associated cancer immunotherapy in vivo. Our results identify PKCβII as a sensor of lipid peroxidation, and the lipid peroxidation-PKCβII-ACSL4 positive-feedback axis may provide potential targets for ferroptosis-associated disease treatment.
Blind image quality assessment (BIQA) research aims to develop a perceptual model to evaluate the quality of distorted images automatically and accurately without access to the non-distorted ...reference images. The state-of-the-art general purpose BIQA methods can be classified into two categories according to the types of features used. The first includes handcrafted features which rely on the statistical regularities of natural images. These, however, are not suitable for images containing text and artificial graphics. The second includes learning-based features which invariably require large codebook or supervised codebook updating procedures to obtain satisfactory performance. These are time-consuming and not applicable in practice. In this paper, we propose a novel general purpose BIQA method based on high order statistics aggregation (HOSA), requiring only a small codebook. HOSA consists of three steps. First, local normalized image patches are extracted as local features through a regular grid, and a codebook containing 100 codewords is constructed by K-means clustering. In addition to the mean of each cluster, the diagonal covariance and coskewness (i.e., dimension-wise variance and skewness) of clusters are also calculated. Second, each local feature is softly assigned to several nearest clusters and the differences of high order statistics (mean, variance and skewness) between local features and corresponding clusters are softly aggregated to build the global quality aware image representation. Finally, support vector regression is adopted to learn the mapping between perceptual features and subjective opinion scores. The proposed method has been extensively evaluated on ten image databases with both simulated and realistic image distortions, and shows highly competitive performance to the state-of-the-art BIQA methods.
Current protocols for synthesizing monodisperse platinum (Pt) nanoparticles typically involve the use of hydrocarbon molecules as surface‐capping ligands. Using Pt nanoparticles as catalysts for the ...oxygen reduction reaction (ORR), however, these ligands must be removed to expose surface sites. Here, highly durable ORR catalysts are realized without ligand removal; instead, the native ligands are converted into ultrathin, conformal graphitic shells by simple thermal annealing. Strikingly, the annealing temperature is a critical factor dictating the ORR performance of Pt catalysts. Pt nanoparticles treated at 500 °C show a very poor ORR activity, whereas those annealed at 700 °C become highly active along with exceptional stability. In‐depth characterization reveals that thermal treatment from 500 to 700 °C gradually opens up the porosity in carbon shells through graphitization. Importantly, such graphitic‐shell‐coated Pt catalysts exhibit a superior ORR stability, largely retaining the activity after 20 000 cycles in a membrane electrode assembly. Moreover, this ligand carbonization strategy can be extended to modify commercial Pt/C catalysts with substantially enhanced stability. This work demonstrates the feasibility of boosting the ORR performance of common Pt nanoparticles by harnessing the native surface ligands, offering a robust approach of designing highly durable catalysts for proton‐exchange‐membrane fuel cells.
Native surface ligands (e.g., oleylamine and oleic acid) attached to Pt nanoparticles during synthesis can be directly converted into ultrathin, conformal graphitic shells upon thermal annealing, rendering common Pt particles highly stable catalysts for the oxygen reduction reaction. This in situ ligand carbonization strategy is general and can also be applied to improve the stability of commercial Pt/C catalysts.
Kinesin dimer walks processively along a microtubule (MT) protofilament in a hand‐over‐hand manner, transiting alternately between one‐head‐bound (1HB) and two‐heads‐bound (2HB) states. In 1HB state, ...one head bound by adenosine diphosphate (ADP) is detached from MT and the other head is bound to MT. Here, using all‐atom molecular dynamics simulations we determined the position and orientation of the detached ADP‐head relative to the MT‐bound head in 1HB state. We showed that in 1HB state when the MT‐bound head is in ADP or nucleotide‐free state, with its neck linker being undocked, the detached ADP‐head and the MT‐bound head have the high binding energy, and after adenosine triphosphate (ATP) binds to the MT‐bound head, with its neck linker being docked, the binding energy between the two heads is reduced greatly. These results reveal how the kinesin dimer retains 1HB state before ATP binding and how the dimer transits from 1HB to 2HB state after ATP binding. Key residues involved in the head‐head interaction in 1HB state were identified.
vitexin, an apigenin-8-C-glucoside, is widely present in numerous edible and medicinal plants. vitexin possesses a variety of bioactive properties, including antioxidation, anti-inflammation, ...anti-cancer, neuron-protection, and cardio-protection. Other beneficial health effects, such as fat reduction, glucose metabolism, and hepatoprotection, have also been reported in recent studies. This review briefly discusses the absorption and metabolism of vitexin, as well as its influence on gut microbiota. Recent advances in understanding the pharmacological and biological effects of vitexin are then reviewed. Improved knowledge of the absorption, metabolism, bioactivity, and molecular targets of vitexin is crucial for the better utilization of this emerging nutraceutical as a chemopreventive and chemotherapeutic agent.
Velocity and density jumps across the 410-km seismic discontinuity generally indicate olivine contents of ∼30 to 50 vol.% on the basis of the elastic properties of anhydrous olivine and wadsleyite, ...which is considerably less than the ∼60% olivine in the widely accepted pyrolite model for the upper mantle. A possible explanation for this discrepancy is that water dissolved in olivine and wadsleyite affects their elastic properties in ways that can reconcile the pyrolitic model with seismic observations. In order to more fully constrain the olivine content of the upper mantle near the 410-km discontinuity, and to place constraints on the mantle water content at this depth, we determined the full elasticity of hydrous wadsleyite at the P-T conditions of the discontinuity based on density functional theory calculations. Together with previous determinations for the effect of water on olivine elasticity, we simultaneously modeled the density and seismic velocity jumps (Δρ, ΔVP, ΔVS) across the olivine-wadsleyite transition. Our models allow for several scenarios that can well reproduce the density and seismic velocity jumps across the 410-km discontinuity when compared to globally averaged seismic models. When the water content of olivine and wadsleyite is assumed to be equal as in a simple binary system, our modeling indicates a best fit for low water contents (<0.1 wt.%) with an olivine proportion of ∼50%, suggesting a relatively dry, non-pyrolitic mantle at depths of the 410-km discontinuity. However, our modeling can be reconciled with a pyrolitic mantle if the water content in wadsleyite is ∼0.9 wt.% and that in olivine is at its storage capacity of ∼500-1500 ppm. The result would be consistent with a hydrous melt phase produced at depths just above the phase transition.
•Elasticity of hydrous wadsleyite at high P-T were obtained from ab initio method.•High-precision data was used to model 410-km discontinuity without extrapolation.•Hydrous MTZ can reconcile the long-standing discrepancy on olivine content.•Pyrolitic MTZ is globally hydrous at least at its top.
