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Magnesium hydroxide (Mg(OH)2), magnesium fluoride (MgF2), and hydroxyapatite (HA) films on Mg are widely studied owing to their easy preparation and favorable corrosion protection. Nevertheless, the most suitable film with the best performance for biomedical applications between the three films remains unknown. Therefore, the performance of the three coatings from in vitroto in vivomust be systematically investigated. In this study, Mg(OH)2, MgF2, and HA films were fabricated on pure Mg. Electrochemical analysis and the hydrogen evolution test suggested that the HA film showed the best in vitrocorrosion resistance, followed by MgF2and Mg(OH)2films. In vitrocell culture indicated that the extract of the MgF2-coated sample was most beneficial for the osteogenic differentiation of MC3T3-E1 cells and the vascularization of human umbilical vein endothelial cells (HUVECs), which might be ascribed to the existence of the F element in the film. The result of this subcutaneous implantation showed that the HA film exhibited the best in vivocorrosion resistance and induced the lightest inflammatory response. Femoral implantation data revealed that the HA film exhibited the best osseointegration. Furthermore, the major organs and blood indicators of all of the tested rats were normal in 8 weeks. In summary, though the in vitrobiological performance of the MgF2film was the best among the three films, the HA film showed the best in vivoperformance, suggesting that it is a more promising modification method for orthopedic applications.

After volume fracture, the permeability field is found to be varying with space. This is not only a commonly-occurring production effect, but has also become a hot research topic in the field of tight gas reservoirs. However, different flow velocities and temporal scales controlled by varying permeability field are often neglected. In this study, the temporal scale analysis for two-dimensional (2D) inhomogeneous permeability field is introduced to explain the inhomogeneity and different flow velocities in the stimulated-reservoir-volume (SRV). Firstly, a new mathematical approach for temporal scale analysis to the well response has been provided. According to the proposed approach, the solution is obtained by using finite element method in the Laplace domain. The well performance is then speared into the temporal scales, which are derived from the analytical Laplace inversion of the solution. Based on this, the temporal scale diagrams are provided for production performance analysis and comparison. Secondly, the significant differences in the well response and its temporal scale analysis from one-dimensional (1D) field have been highlighted. The results showed that the varying permeability is observed to be properly represented by two-dimensional field. In general, the shape of the temporal scale distribution stripe is different with varying pattern of the permeability, and its width and density are enhanced by the rapid variation of the permeability. The temporal scales are enhanced at higher permeability area, while their contributions are reduced by the permeability, though these are enhanced by the initial energy of their corresponding area. By analyzing the initial energy, the propagation of the pressure and the exploited area are presented in a better way. Furthermore, the exponential and power fields explain the permeability inhomogeneity better than the linear field. In spite of this, the linear field is described better by the temporal scale analysis, while multiple temporal scale is the result of permeability inhomogeneity. Last but not the least, the effect of the less permeable outer boundary is eliminated by decelerating the decline in permeability in the whole SRV. The temporal scales fail to couple in terms of both mass and energy, and their corresponding processes fail to influence each other. Finally, practical guidelines for the volume fracture techniques are derived based upon the proposed model.

Catalytic efficiency in synthesis of vitamin E succinate was dramatically increased via the preparation of robust catalyst and the improvement of reaction system. 4-dimethylaminopyridine (DMAP) was covalently immobilized on nano-SiO2to avoid the catalyst contamination of the product and permit the easy recycling of DMAP. Then, a hexane-acetone mixed solvent system was firstly introduced to replace the traditional single-solvent system, which was employed to improve the activity of immobilized DMAP derivative and the substrate solubility of the reaction system. The highest vitamin E succinate yield of 94% was achieved. In addition, the recyclability and stability of the immobilized DMAP derivative was excellent, the yield of vitamin E succinate had no obvious loss and remained 90% after recycling 20 times. The excellent results make this technology be a promising candidate for the industrial production of vitamin E succinate.

Calcined sodium silicate could serve as an efficient and benign heterogeneous catalyst for the production of L-α-glycerophosphocholine from natural lecithin. The catalytic transesterification of natural lecithin by calcined sodium silicate proceeded to almost 100% conversion under the following conditions: sodium silicate amount of 6 wt%, reaction temperature of 65°C, lecithin concentration of 10.5 mmol/l, stirring intensity of 300 rpm, reaction time of 120 min. In addition, this catalyst could be separated completely by simple centrifugation and retained high activity after three re-uses. Compared to the previously reported catalysts, calcined sodium silicate, with the significantly important characteristics of non-toxicity and easy excretion from the human body, was beneficial to the benign production of L-α-glycerophosphocholine and its security as well as application in food and medicine fields.

In this paper, we deal with Gaussian graphical classifiaction problem. We aim to provide a systematic study of the relationship between Chernoff information and topological, as well as algebraic properties of the corresponding Gaussian graphs for the underlying graphical testing problems. We first show the relationship between Chernoff information and generalized eigenvalues of the associated covariance matrices. It is then proved that Chernoff information between two Gaussian trees sharing certain local subtree structures can be transformed into that of two smaller trees. In this way, we provide a sequence of equivalent Gaussian tree pairs in terms of Chernoff Information. Under our proposed grafting operations, bottleneck Gaussian trees, namely, Gaussian trees connected by one such operation, can thus be simplified into two 3-node Gaussian trees. Thereafter, we provide a thorough study about how Chernoff information changes when small differences are accumulated into bigger ones via concatenated grafting operations, as well as partial ordering. In the end, we propose an optimal linear dimension reduction method based on generalized eigenvalues for the purpose of classification, which is proved to achieve maximum Chernoff information among all linear transformations. [ABSTRACT FROM AUTHOR]

During the fracturing operations for oils and gases, not only the oil and gas reservoirs, but also the nearby civil aquifers are often polluted by the invasion of fracturing fluid filtrates. In this study, we investigated the potential of silica nanoparticles as a high-performance filtrate reducer for a foam fluid in a porous media. First, the three factors affecting filtration reduction using nanoparticles, i.e., surface rheology, foam slipping, and foam stability, were described. Then, the foam filtration through a porous media in the core was measured using a dynamic fluid-loss device, and the effects of foam quality, pressure drop, and core permeability on the performance of the filtrate reducer were evaluated. The difficulty of bubbles flowing from a throat to a pore in a porous media was described by resistance gradient coefficient C f , which is a combination of surface tension and viscoelastic modulus and increases by adding nanoparticles. Nanoparticles improve the roughness of the SiO 2 /sodium dodecyl benzene sulfonate foam film surface, thus increasing the slipping resistance F slip when foams flow on the wall of a throat in a porous media. For the foams in a porous media, the diffusion of bubbles decreased in the presence of nanoparticles, and the growth rate of gas bubble size also decreased, thus increasing the foam resistance to gas channeling. The results of core filtration tests indicate that the fluid-loss-control properties increased with foam quality ranging from 0 to 85%, and the negative effects of pressure drop and permeability increase to foam filtration were weakened by adding SiO 2 nanoparticles. Thus, silica nanoparticles can be used as a high-performance filtrate reducer for a foam fluid in a porous media. [ABSTRACT FROM AUTHOR]

A new super-resolution model, namely the turbulence volumetric super-resolution (TVSR) model, is developed based on convolutional neural network (CNN) to reconstruct three-dimensional high-resolution turbulent flow field data from low-resolution data. Direct numerical simulation (DNS) and corresponding filtered DNS (FDNS) data of homogeneous isotropic turbulence at various Reynolds numbers are used to train the TVSR model. The proposed model is a modification of Liu et al. (2020), aiming to provide an improved generalization capability of the super-resolution model. For this purpose, we propose a patchwise training strategy in consideration of the property of turbulence that the velocity correlation between two points diminishes as the separation becomes sufficiently large. Furthermore, data at various Reynolds numbers are combined together to train the model. In comparison with existing models, the present TVSR model shows a better generalization capability in two aspects. First, the TVSR model trained using data at low Reynolds numbers is found robust and accurate in the super-resolution reconstructions of flow fields at higher Reynolds numbers. Second, although only DNS data are used for training, the TVSR model is also robust in reconstructing high-resolution flow fields from low-resolution data obtained from large-eddy simulation (LES). This feature of the TVSR model provides a new access to obtain turbulent motions at unresolved scales in LES studies of turbulent flows. • A new model proposed for super-resolution reconstruction of 3D turbulent fields. • Model trained using a combination of DNS data at different Reynolds numbers. • A patchwise reconstruction strategy proposed to provide generalization capability. • Model performance evaluated in both a priori and a posteriori LES tests. [ABSTRACT FROM AUTHOR]