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This article considers the problem of event-triggered optimal control for discrete-time switched nonlinear systems with constrained control input. First, an event-triggered condition is given to make the closed-loop switched system asymptotically stable. Second, a novel method, event-triggered heuristic dynamic programming (ETHDP), is applied to derive the optimal control policy. Two neural networks (NNs) are utilized to approximate the value function and control law, respectively. When the event-triggered condition is violated, the weights of the two NNs are updated, which can decrease the networks calculation and transmission load notably. A proof of the convergence of the ETHDP is also carried out. Finally, the effectiveness of the proposed method is verified by an example.

The ultrafine Mo-Y2O3 composite powders were successfully synthesized by innovative freeze-drying method. Consequently, the freeze-dried Mo-Y2O3 composite powders with high sintering activities possess an average grain size of 54 nm. After low temperature sintering at 1600 °C, the Mo-Y2O3 alloys maintaining a high density (99.6 %) have the finest grain size (620 nm) comparing with available literature about oxide dispersion strengthened molybdenum alloy (ODS-Mo). The oxide particles remain their small size (mainly

A fully discrete ADI scheme is proposed for solving the two-dimensional time-fractional diffusion equation with weakly singular solutions, where L1 scheme on graded mesh is adopted to tackle the initial singularity. An improved discrete fractional Gronwall inequality is employed to give an α-robust H 1 -norm convergence analysis of the fully discrete ADI scheme, where the error bound does not blow up when the order of fractional derivative α → 1 − . Numerical results show that the theoretical analysis is sharp.

The fluorescence quenching effect of polymeric carbon nitride-based materials can be efficiently applied to the rapid detection of Hg2+. Herein, we chose dicyandiamide and sodium hypophosphite as precursors to prepare bulk phosphorous-doped polymeric carbon nitride through thermal polycondensation, and then a one-step hydrothermal treatment caused the depolymerization of the bulk products and the formation of the nanorod-like structures. The depolymerization resulted in the good aqueous colloidal stability of the polymeric carbon nitride-based derivative, and phosphorus-doping significantly improved its fluorescence. More terminal amino and abundant surface hydroxyl groups led to the enhanced selective fluorescence quenching of Hg2+ by the depolymerized products. Therefore, the depolymerized phosphorous-doped polymeric carbon nitride with a fluorescence quantum yield of 23.2% showed excellent Hg2+ detection capability. The limit of detection of the depolymerized polymeric carbon nitride to Hg2+ can reach 0.74 nmol L−1. And the depolymerized products also showed good accuracy in the Hg2+ detection of shrimp samples. This work broadens the scope of polymeric carbon nitride-based heavy metal ion fluorescent probes, and provides a new roadmap for the highly selective determination of Hg2+.

In this work, the (1-x)CaWO4-xNa2WO4 (x = 0.1, 0.2, denoted as 0.9CW-0.1NW and 0.8CW-0.2NW, respectively) ultralow-loss microwave dielectric ceramics were prepared via solid-state reaction method. Using low melting-point Na2WO4 as sintering aid to prepare CaWO4 Na2WO4 composite ceramics, the sintering temperature of CaWO4 was successfully reduced while maintaining excellent microwave performance. The optimal microwave dielectric properties have been achieved at 900 °C for 0.9CW-0.1NW ceramic: er = 9.0, Q × f = 105660 GHz, tanδ = 1.1 × 10−4 and τf = −35.4 ppm/°C at a frequency of 12.0 GHz. For the 0.8CW-0.2NW ceramic, the optimal microwave dielectric properties have been obtained at 740 °C, with er = 8.5, Q × f = 97014 GHz, tanδ = 1.2 × 10−4 and τf = −37.4 ppm/°C at a frequency of 11.8 GHz. In summary, both composite ceramics exhibit low sintering temperatures, excellent dielectric properties and chemical compatibility with the Ag electrode. The findings of this study provide an effective approach to prepare novel composite ceramics as promising candidates for LTCC applications.

The machinability of hard brittle polycrystalline ceramic has a strong correlation with internal microstructures and their accommodated deformation behavior. In the present work, we investigate the mechanisms governing the brittle-to-ductile transition behavior of polycrystalline 3C–SiC in diamond cutting by means of molecular dynamics simulations. Simulation results reveal the co-existence of dislocation slip and amorphization-dominated ductile deformation and cracking along grain boundaries-mediated brittle fracture, as well as the correlation of individual deformation modes with machining force variation and machined surface morphology. In addition, inter-granular fracture, grain boundary sliding and grain pull-up are also operating brittle deformation modes of polycrystalline 3C–SiC. The strong competition between above heterogeneous deformation modes determines the brittle-to-ductile transition behavior in grooving of polycrystalline 3C–SiC. Simulation results also demonstrate that grain size has a strong impact on the brittle-to-ductile transition and material deformation behavior of polycrystalline 3C–SiC under diamond cutting.

β-tricalcium phosphate (β-TCP) is an ideal biomaterial for the bone repair because of its biocompatibility and biodegradability. In this study, 0 mol%, 5 mol%, 15 mol% and 30%mol bivalent manganese ion (Mn2+) doped β-TCP (Mn-TCP) powders were synthesized by a sol-gel method. The amount of the dopants significantly influences the crystallinity and the parameters related with structure of β-TCP, such as the lattice parameters and crystallite dimensions. The particle size and the particle distribution of doped β-TCP powers were evaluated as well. Meanwhile, the as-synthesized powders were consolidated by sintering at 1000 °C in muffle furnace for 5 h to get Mn-TCP porous material and the degradation experiment was carried out in Simulated Body Fluid (SBF) solution for 28 days. Then, Mn-TCP porous material were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Significantly, there were bone-like apatite materials deposited on the surface of bone-like porous materials. With the increasing doping amount of Mn2+, the newly formed apatite-like materials decreased, while the crystallinity increased significantly. Besides, pH results showed that alkaline environment was more favorable for the formation of sedimentary materials.

Determination and conceptualization of atomic structures of metallic glasses or amorphous alloys remain a grand challenge. Structural models proposed for bulk metallic glasses are still controversial owing to experimental difficulties in directly imaging the atom positions in three-dimensional structures. With the advanced atomic-resolution imaging, here we directly observed the atomic arrangements in atomically thin metallic glassy membranes obtained by vapor deposition. The atomic packing in the amorphous membrane is shown to have a fractal characteristic, with the fractal dimension depending on the atomic density. Locally, the atomic configuration for the metallic glass membrane is composed of many types of polygons with the bonding angles concentrated on 45°–55°. The fractal atomic structure is consistent with the analysis by the percolation theory, and may account for the enhanced relaxation dynamics and the easiness of glass transition as reported for the thin metallic glassy films or glassy surface.

The notions ofos{o}_{s}-convergence andS∗{S}^{\ast }-doubly quasicontinuous posets are introduced, which can be viewed as common generalizations of Birkhoff’s order-convergence andS∗{S}^{\ast }-doubly continuous posets, respectively. We first consider the relationship betweenos{o}_{s}-convergence and B-topology and show that the topology induced byos{o}_{s}-convergence according to the standard topological approach is the B-topology precisely. Then, the topological characterization for theS∗{S}^{\ast }-doubly quasicontinuity is presented. It is proved that a poset isS∗{S}^{\ast }-doubly quasicontinuous iff the poset equipped with the B-topology is locally hyperclosed iff the lattice of all B-open subsets of the poset is hypercontinuous. Finally, the order theoretical condition for theos{o}_{s}-convergence being topological is given and the complete regularity of B-topology onS∗{S}^{\ast }-doubly quasicontinuous posets is explored.

The coordination between a ligand and a metal is a spontaneous and uncontrollable process. In this Article, we successfully observe the formation of metal coordination in a triphenylamine-functionalized salicylaldehyde Schiff base with a copper(II) ion. The ligand TPA-Py first reacts with Cu2+ in a stepwise process to afford the dynamic complex TPA-Py@Cu2+ ([ligand]:[Cu2+] = 1:1), which further reacts with an extra copper(II) ion to afford 2TPA-Py@4Cu2+ with the following stepwise (or cumulative) stability constants: K1 = 4.0694 × 103 and K2 = 1.0761 × 106, respectively. The entire metal coordination process can be visualized, and the coordination mode of the probe toward copper was further evaluated by ultraviolet-visible/fluorescence spectra, single-crystal X-ray diffraction, density functional theory calculations, high-resolution mass spectra, and nuclear magnetic resonance spectroscopic titrations. Compound TPA-Py exhibited excellent sensitivity and specificity toward copper(II) ions in THF/water media with a low limit of detection of 2.687 × 10-7 mol L-1. In addition, TPI-An-Py can be applied to the detection of Cu2+ in real samples with satisfactory recoveries in the range of 100-112% in lake water and 98-101% in tap water. This Article not only reports an excellent fluorescence probe for copper(II) ion detection but also presents an instance for more fully understanding the metal coordination process.

Understanding the physics of droplet collisions is of crucial importance in many industrial processes such as inkjet printing, spray cooling, and spray combustion. In this paper, a modified multiple-relaxation-time pseudopotential multiphase lattice Boltzmann model is proposed to investigate binary droplet collision with different collision angles. The surface tension can be adjusted independently under the condition of high Reynolds number and large density ratio using this model. Then the model validation is performed by simulating three benchmark cases including stationary droplet, oscillating droplet, and capillary wave instability, respectively. Finally, different regimes of binary droplet collision are presented, and collision features such as liquid filament and satellite droplet are investigated at collision angles of 30°, 60°, 90°, 120°, and 150°. The results show that there is no liquid filament or satellite droplet at the collision angle of 30°, yet both of them appear as the angle increases. When the collision angle is 60°, the percentage of satellite droplet to liquid phase reaches 30%, while the proportions are less than 10% at collision angles of 90°, 120°, and 150°. Besides, two break-up mechanisms of “end-pinching” and capillary wave instability are inspected. It is found out that the back-flow phenomena at the joints of droplets and the liquid filament are caused by the “end-pinching” mechanism, which further leads to the capillary wave instability of the liquid filament.

A highly sensitive refractive index (RI) sensor based on the surface plasmon resonance (SPR) phenomenon is proposed and demonstrated. The sensor is composed of a quasi D-shape ten-fold photonic qua...

In order to prepare high-performance tungsten alloys, surface modification of tungsten nanopowders prepared by a wet chemical method was carried out by acid pickling at room temperature. The low-te...

Use of data assimilation to initialize hydrometeors plays a vital role in numerical weather prediction (NWP). To directly analyze hydrometeors in data assimilation systems from cloud-sensitive observations, hydrometeor control variables are necessary. Common data assimilation systems theoretically require that the probability density functions (PDFs) of analysis, background, and observation errors should satisfy the Gaussian unbiased assumptions. In this study, a Gaussian transform method is proposed to transform hydrometeors to more Gaussian variables, which is modified from the Softmax function and renamed as Quasi-Softmax transform. The Quasi-Softmax transform method then is compared to the original hydrometeor mixing ratios and their logarithmic transform and Softmax transform. The spatial distribution, the non-Gaussian nature of the background errors, and the characteristics of the background errors of hydrometeors in each method are studied. Compared to the logarithmic and Softmax transform, the Quasi-Softmax method keeps the vertical distribution of the original hydrometeor mixing ratios to the greatest extent. The results of the D’Agostino test show that the hydrometeors transformed by the Quasi-Softmax method are more Gaussian when compared to the other methods. The Gaussian transform has been added to the control variable transform to estimate the background error covariances. Results show that the characteristics of the hydrometeor background errors are reasonable for the Quasi-Softmax method. The transformed hydrometeors using the Quasi-Softmax transform meet the Gaussian unbiased assumptions of the data assimilation system, and are promising control variables for data assimilation systems.

Ulcerative colitis (UC) is a relapsing disorder characterized by chronic inflammation of the intestinal tract. However, the home care of UC based on remote monitoring, due to the operational complexity and time-consuming procedure, restrain its widespread applications. Here we constructed an optotheranostic nanosystem for self-diagnosis and long-acting mitigations of UC at home. The system included two major modules: (i) A disease prescreening module mediated by smartphone optical sensing. (ii) Disease real-time intervention module mediated by an optogenetic engineered bacteria system. Recombinant Escherichia coli Nissle 1917 (EcN) secreted interleukin-10 (IL-10) could downregulate inflammatory cascades and matrix metalloproteinases; it is a candidate for use in the therapeutic intervention of UC. The results showed that the Detector was able to analyze, report, and share the detection results in less than 1 min, and the limit of detection was 15 ng·mL-1. Besides, the IL-10-secreting EcN treatment suppressed the intestinal inflammatory response in UC mice and protected the intestinal mucosa against injury. The optotheranostic nanosystems enabled solutions to diagnose and treat disease at home, which promotes a mobile health service development.

The mechanical response of a bi-crystal model with a 90° grain boundary under external compressive and tensile loading parallel to the boundary plane normal was investigated with molecular dynamics simulations. The grain boundary was found to migrate along two opposite directions upon compressive and tensile straining, with the formation of inter-connected coherent twin boundary and basal/prismatic boundary. The atomic details of such grain boundary migration were unraveled, which indicated the role of interface dislocations. The temperature effect was also discussed.

The synthesis of highly luminescent colloidal CsSnX3 (X = halogen) perovskite nanocrystals (NCs) remains a long-standing challenge due to the lack of a fundamental understanding of how to rationally suppress the formation of structural defects that significantly influence the radiative carrier recombination processes. Here, we develop a theory-guided, general synthetic concept for highly luminescent CsSnX3 NCs. Guided by density functional theory calculations and molecular dynamics simulations, we predict that, although there is an opposing trend in the chemical potential-dependent formation energies of various defects, highly luminescent CsSnI3 NCs with narrow emission could be obtained through decreasing the density of tin vacancies. We then develop a colloidal synthesis strategy that allows for rational fine-tuning of the reactant ratio in a wide range but still leads to the formation of CsSnI3 NCs. By judiciously adopting a tin-rich reaction condition, we obtain narrow-band-emissive CsSnI3 NCs with a record emission quantum yield of 18.4%, which is over 50 times larger than those previously reported. Systematic surface-state characterizations reveal that these NCs possess a Cs/I-lean surface and are capped with a low density of organic ligands, making them an excellent candidate for optoelectronic devices without any postsynthesis ligand management. We showcase the generalizability of our concept by further demonstrating the synthesis of highly luminescent CsSnI2.5Br0.5 and CsSnI2.25Br0.75 NCs. Our findings not only highlight the value of computation in guiding the synthesis of high-quality colloidal perovskite NCs but also could stimulate intense efforts on tin-based perovskite NCs and accelerate their potential applications in a range of high-performance optoelectronic devices.

An inorganic anticorrosive coating, merging wollastonite into Chemically Bonded Phosphate Ceramic (CBPC) binders, was prepared to protect rebar from corrosion. In order to evaluate the corrosion resistance behavior of Wollastonite-based Chemically Bonded Phosphate Ceramic (WoCBPC) coatings, the electrochemical measurements were applied. The experiment results showed that the value of corrosion potential (Ecorr) and polarization resistance (Rp) is the largest and the value of corrosion current density (Icorr) is the smallest among all WoCBPC coatings, when the content of wollastonite reaches 20% of the ceramic filler (WoCBPC20). Moreover, the resistance of WoCBPC20 coating (Rc) value was much higher than that of other WoCBPC coatings, which means the best anticorrosion properties. The structure formation of WoCBPC coatings was identified by using XRD as well as SEM/EDS techniques. The intensity of berlinite phase reaches the maximum with the introduction of wollastonite in WoCBPC20 coatings. Meanwhile, the fibrous wollastonite particles with high modulus can inhibit the spread of cracks in CBPC matrix. Therefore, the WoCBPC coatings show a barrier effect to prevent aggressive substances from contacting the rebar effectively.

In cyanobacteria, photomixotrophic growth is considered as a promising strategy to achieve both high cell density and product accumulation. However, the conversion of glucose to acetyl coenzyme A (acetyl-CoA) in the native glycolytic pathway is insufficient, which decreases the carbon utilization and productivity of engineered cyanobacteria under photomixotrophic conditions. To increase the carbon flux from glucose to key intracellular precursor acetyl-CoA in Synechocystis sp. PCC 6803 (hereafter, Synechocystis 6803) under photomixotrophic conditions, a synthetic nonoxidative cyclic glycolysis (NOG) pathway was introduced into the wild type strain, which successfully increased the intracellular pool of acetyl-CoA by approximately 1-fold. To minimize the competition for glucose, the native Embden-Meyerhof-Parnas (EMP) and Entner-Doudoroff (ED) pathways were knocked out, respectively. Notably, eliminating the native ED pathway in the engineered strain carrying the NOG pathway further increased the intracellular pool of acetyl-CoA up to 2.8-fold. Another carbon consuming pathway in Synechocystis 6803, the glycogen biosynthesis pathway, was additionally knocked out in the above-mentioned engineered strain, which enabled an increase of the intracellular acetyl-CoA pool by up to 3.5-fold when compared with the wild type strain. Finally, the content of intracellular lipids was analyzed as an index of the productive capacity of the engineered Synechocystis 6803 cell factory under photomixotrophic conditions. The results showed the total lipids yield increased about 26% compared to the wild type (from 15.71% to 34.12%, g/g glucose), demonstrating that this integrated approach could represent a general strategy not only for the improvement of the intracellular concentration of acetyl-CoA, but also for the production of value-added chemicals that require acetyl-CoA as a key precursor in cyanobacteria.

The coordination environment of single-atom catalysts (SACs) plays a crucial role in determining the energy conversion efficiency of related electrochemical devices. Herein, the coordination enviro...

Aiming at the problems of complex structure, fault prone and low accuracy of fault identification of asynchronous motor, this paper proposed a fault location recognition model of asynchronous motor based on AB-CNN (AdaBelief-CNN) intelligent algorithm. Taking asynchronous motor as the application background, an experimental platform is built to collect different types of fault data of asynchronous motor. Firstly, the dimension of the data is reduced by principal component analysis, the convolutional neural network (CNN) is used to carry out forward propagation fault recognition training for asynchronous motor fault data, and output the trained data prediction value. Secondly, through the loss function and AdaBelief optimization algorithm, the asynchronous motor fault location recognition model is optimized. Finally, the accuracy of the fault location identification model is tested with the test data. Comparing with the original CNN network identification model and Adam optimized CNN network (AD-CNN), the proposed solution outperforms other schemes by about 10%.

Bismuth ion-doped phosphate crystals have shown rich luminescence phenomena. However, the complexity and variety of Bi3+-related transitions bring great challenges to the understanding of the under...

Liang Zhang, Shilin Xiao, Xun Kang, Tao Sun, Chunyu Zhou, Zhongsheng Xu, Mengmeng Du, Ya Zhang, Guangxian Wang, Yun Liu, Dong Zhang, Mingfu Gong Department of Radiology, Xinqiao Hospital, Army Medical University, Chongqing, People’s Republic of ChinaCorrespondence: Dong Zhang; Mingfu GongDepartment of Radiology, Xinqiao Hospital, Army Medical University, No. 183, Xinqiao Street, Shapingba District, Chongqing, People’s Republic of ChinaTel +86 2368763843Fax +86 2368755306Email hszhangd@163.com; hummer198625@163.comBackground: Manganese Ferrite Nanoparticles (Mn-IONPs) are widely used in biomedical field and their cytotoxicity has been initially explored, but the mechanism remains obscure. The nano-bio interactions are believed to be crucial for cytotoxicity mechanism, while little data have been acquired.Methods: Mn-IONPs were synthesized by thermal decomposition of acetylacetonate precursor. After physicochemical characterization, we analyzed the metabolic conversion and removal of Mn-IONPs in RAW264.7 cells by Prussian blue staining, TEM, HRTEM and elemental quantitative analysis, followed by gene expression evaluation using quantitative RT-PCR.Results: Mn-IONPs were successfully synthesized. Both the uptake and cytotoxicity of Mn-IONPs on RAW264.7 cells were time- and dose-dependent. After internalized, Mn-IONPs were passed to daughter cells with passages on. Meanwhile, Mn-IONPs were exocytosed and digested to metal ions and further excreted out, resulted in the labeling rate and ions contents decreased gradually. As ion influx related genes, the expressions of ZIP14, IRP2, FtH and DMT1 were suppressed within 24 hours but overexpressed to a plateau at the 48th hour in a dose-dependent manner. At the 72nd hour, ZIP14 and DMT1 mRNA levels decreased toward normal, while IRP2 and FtH kept up-regulated. As efflux related genes, FPN, SLC30A10 and Hamp2 genes were up-regulated within 24– 72 hours; SPCA1 was suppressed at the 24th and 72nd hour, while overexpressed at the 48th hour. All the efflux related genes’ mRNA had a dose-dependent increasing manner at the corresponding time points.Conclusion: Mn-IONPs showed time- and dose-dependent cytotoxicity and cell labeling rate in RAW264.7 cells. Accompanying with the intracellular catabolic breakdown and exocytosis of Mn-IONPs, RAW264.7 cells also secreted and re-uptook manganese and iron ions to maintain intracellular homeostasis in the succeeding passages. And the metabolic conversion of Mn-IONPs in RAW264.7 cells can affect the expression of ZIP14, DMT1, FPN, SLC30A10, IRP2, FtH, Hamp2 and SPCA1 genes.Keywords: manganese ferrite nanoparticles, cytotoxicity, metabolism, metal transporter genes, RAW264.7 macrophage cells

China has experienced an unprecedented rate of urbanization in recent decades. As a city with strong political and economic influences in the southwest of China, Chongqing is a typical example of rapidurban development in this period of time. To study the land cover changes and urban expansion of Chongqing, Landsat images from 1999 to 2018 were selected, processed, and quantitatively analysed The results showed that the built-up area of the city had increased tremendously during these years, yet vegetation still accounted for the vast majority of the city’s land area. Restricted by the local topography including mountains and hills and infrastructure constructions, the urbanization process that occurred in central Chongqing actually showed a dominant expansion direction, an obvious spatial clustering tendency, and significant spatio-temporal differences among various regions.

In this work, a novel calix[4]resorcinarene-based ionic liquid (C4RA-2IL) was synthesized, structurally characterized, and statically coated on capillary column as stationary phase for capillary gas chromatography (GC). The column efficiency of the C4RA-2IL column is 3345 plates m−1, which are determined by n-dodecane at 120 °C. Based on its McReynolds constants, the C4RA-2IL column showed moderate polarity. Particularly, the C4RA-2IL column show high separation performance for a wide range of analytes and some difficult separation of meta/para-isomers. Moreover, it exhibited excellent selectivity for critical aromatic isomers of chloroaniline, bromaniline, iodoaniline, toluidine and xylidine isomers and shows advantageous separation capability over the commercial polysiloxane stationary phase. This work presents a promising future of calixarene-based ionic liquid as a new type of stationary phase in GC separations.

Synthesizing highly luminescent active iondoped phosphors is desirable for many related applications but, remains challenging when a conventional solid-state reaction method is used for this purpos...

Determination of Cabernet Sauvignon grapes quality plays an important role in commercial processing. In this research, a rapid approach based on near infrared spectroscopy was proposed to the determination of soluble solids content (SSC), pH, and total phenol content (TPC) in entire bunches of Cabernet Sauvignon grapes. Standardized normal variate (SNV) and competitive adaptive weighted sampling (CARS), genetic algorithm (GA), and synergy interval partial least squares (si-PLS) were used to optimize the spectral data. With optimal combination input, the prediction accuracy of partial least squares regression (PLSR) and support vector regression (SVR) models was compared. The results showed that these models based on variable optimization method could predict well the SSC, pH, and TPC of Cabernet Sauvignon grapes. The correlation coefficient of prediction for SSC, pH, and TPC had reached more than 0.85. This work provides an alternative to analyze the chemical parameters in whole bunch of Cabernet Sauvignon grape.

In this paper, (1-x)Li2MoO4(LMO)-xNi0.2Cu0.2Zn0.6Fe2O4 (NCZO) ceramic composites were consolidated using cold sintering method at a temperature of 150 °C, which is far below the sintering temperature of NZFO ceramic-based systems via conventional ceramic preparation method. The phase composition, microstructure, dielectric properties and magnetic properties of the as-cold-sintered LMO-NCZO ceramic composites were studied. The relative density of all composites is larger than 95 % at a cold sintering temperature of 150 °C for 30 min under a uniaxial pressure of 200 MPa. XRD results showed that the composites were only composed of two phases. SEM revealed that the NCZO particles were enwrapped by the LMO phase. The 0.46LMO-0.54NCZO ceramic composite exhibited excellent magnetodielectric properties with an effective permittivity of about 8.3, a dielectric loss of 0.003, a permeability of 7 and a magnetic loss of 0.024 (@10 MHz), which make it potentially applicable in the miniaturization of electronic devices.

High-speed penetration into carbon fiber composites is of fundamental importance to materials science and impact engineering, but research along this line suffers considerably from the lack of direct experimental observations. Here we investigate such penetration dynamics of a unidirectional carbon fiber reinforced epoxy (UCFRE) composite, with a combination of in situ, ultrafast, synchrotron phase contrast imaging and finite element (FE) analysis. The experiments yield the first direct observation on projectile trajectories and fiber-scale deformation and damage in the UCFRE composites during supersonic microprojectile penetration, for different fiber orientations ( 0 ∘ − 90 ∘ from the impact direction) and projectile velocities 600 − 850 m.s - 1 , at unprecedented temporal ( ∼ 100 ps) and spatial (5 μm) resolutions. The maximum penetration depth decreases with increasing fiber orientation angles, as a result of anisotropic damage evolution in the composite sample. Strain localizations are prone to develop along a direction perpendicular to the fiber orientation, while the damage or cavity region, along the fiber direction. FE modeling with a three-dimensional Hashin criterion yields consistent projectile trajectory and cavity morphology with the experimental results. With increasing fiber orientation angles, damage analyses show a transition in the damage mode from fiber compression to matrix compression damage, in line with the increasing maximum penetration depth.

The present article was to investigate the mechanical design, efficiency, and performance of a new type of cylindrical vane pump. The configuration is proposed on the traditional working principle of the hydraulic pump. The stator surface equations are driven by using the geometric theory of applied spatial triangulation function. The three-dimensional model of the cylindrical vane pump is established with the help of MATLAB, and Pro/E.A displacement formula is derived, which depends upon the design structure of the cylindrical vane pump. The flow output characteristics of the pump are analyzed. According to the kinematic analysis of the stator-cylindrical vane by Pro/Mechanism, the kinematic equation of the cylindrical vane is established and the kinematic analysis proves the effectiveness of structural design of vane pump. The CFD software COMSOL is used to simulate the force of the main parts under the different dynamic conditions, and the discharge flow of the pump are monitored. The result shows that the hermetic space is formed by the cylindrical vane, driving plate and the surface of the stator, and the size of the hermetic space is charged by the rotation of the cylindrical vane. The cylindrical vane pump satisfies the three elements design of positive displacement pump. The angle at the arc transition of stator surfaces is 5°–10°, when the number of cylindrical vanes increased, the flow pulsation of cylindrical vanes decreased and vice versa. There is a 3.6% error between theoretical and simulation results. The simulation result shows that the internal flow of the flow field is regular, the deformation is small, and the stress distribution of the main components is regular.

The sequence convergence of inexact nonconvex and nonsmooth algorithms is proved with an unrealistic assumption on the noise. In this paper, we focus on removing the assumption. Without the assumpt...

Real-time imaging of multiple low-abundance microRNAs (miRNAs) simultaneously in living cells with high sensitivity is of vital importance for accurate cancer clinical diagnosis and prognosis studies. Maintaining stability of nanoprobes resistant to enzyme degradation and enabling effective signal amplification is highly needed for in vivo imaging studies. Herein, a rationally designed one-pot assembled multicolor tetrahedral DNA frameworks (TDFs) by encoding multicomponent nucleic acid enzymes (MNAzymes) was developed for signal-amplified multiple miRNAs imaging in living cells with high sensitivity and selectivity. TDFs could enter cells via self-delivery with good biocompatibility and stability. Two kinds of MNAzymes specific for miRNA-21 and miRNA-155 with fluorescein labeling were encoded in the structure of TDFs respectively through one-step thermal annealing. In the intracellular environment, the TDFs could be specifically bound with its specific miRNA target and form an active DNAzyme structure. The cleavage of the active site would trigger the release of target miRNA and circular fluorescence signal amplification, which enabled accurate diagnosis on miRNA identifications of different cell lines with high sensitivity. Meanwhile, with the specific AS1411 aptamer targeting for nucleolin overexpressed on the surface of the carcinoma cells, this well-designed TDFs nanoprobe exhibited good discrimination between cancer cells and normal cells. The strategy provides an efficient tool for understanding the biological function of miRNAs in cancer pathogenesis and therapeutic applications.

Due to severe speckle noise in synthetic aperture radar (SAR) images and the large nonlinear intensity differences between SAR and optical images, the registration of SAR and optical images is a challenging problem that remains to be solved. In this paper, an improved nonlinear scale-invariant feature transform (SIFT)-framework-based algorithm that combines spatial feature detection with local frequency-domain description for the registration of SAR and optical images is proposed. First, multiscale representations of the SAR and optical images are constructed based on nonlinear diffusion to better preserve edges and obtain consistent edge information. The ratio of exponentially weighted averages (ROEWA) operator and the Sobel operator are utilized in the process of scale space construction to calculate consistent gradient information. Then, a new feature detection strategy based on the Harris–Laplace ROEWA and Harris–Laplace Sobel techniques is proposed to detect stable and repeatable keypoints in the scale space. Finally, a novel descriptor, called the rotation-invariant amplitudes of log-Gabor orientation histograms (RI-ALGH), and a simplified version, ALGH, are proposed. The proposed descriptors are built based on the amplitudes of multiscale and multiorientation log-Gabor responses and utilize an improved spatial structure of the gradient location and orientation histogram (GLOH) descriptor, which is robust to local distortions. The experimental results on both simulated and real images demonstrate that the proposed method can achieve better results than other state-of-the-art methods in terms of registration accuracy.

Two carbazole sulfonamide-based macrocycles 1 and 2 were facilely synthesized and carefully evaluated for their anion recognition properties. The obtained results revealed that macrocycle 1 with a 1,3-xylyl linker was able to bind fluoride ion more strongly and selectively in acetonitrile medium than its strong competitors (like acetate and dihydrogen phosphate anions), with a large binding constant (Ka) of 50 878 M−1. More importantly, an exclusive fluoride recognition was achieved for macrocycle 1 in the more polar DMSO-d6 solution, albeit with a moderate affinity of Ka = 147 M−1. Compared with macrocycle 1, macrocycle 2 bearing a 2,6-lutidinyl linkage exhibited a remarkable change not only in the anion affinity but also in the anion selectivity, although with only a slight difference in their molecular structures.

Context Glucagon-like peptide 1 (GLP-1) and α-tocopheryl quinone can promote the growth of intestinal flora and affect the pathogenesis of non-alcoholic steatohepatitis (NASH). Objective This study determines the molecular mechanism of the effect of tocopheryl quinone in the treatment of high cholesterol and cholate diet (HFCC)-induced NASH. Materials and methods Thirty-two male Sprague Dawley (SD) rats grouped as lean control (LC), LC + tocopheryl quinone (1 mL of 3 × 106 dpm tocopheryl quinone via i.p. injection), HFCC (5.1 kcal/g of fat diet), and HFCC + tocopheryl quinone. Profiles of intestinal flora were assessed by 16S ribosomal ribonucleic acid–based analysis. Levels and activity of GLP-1, interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α) in intestinal tissues were detected by immunohistochemistry (IHC), Western blot and enzyme-linked immunosorbent assay (ELISA). Results HFCC rats presented higher levels of cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL), while tocopheryl quinone reversed the effects of HFCC. HFCC dysregulated malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), Vitamin E, 12-hydroxyeicosatetraenoic acid (12-HETE), 13-hydroxyoctadecadienoic acid (13-HODE) and nuclear factor kappa B (NF-κB), and the effects of HFCC were reversed by the treatment of tocopheryl quinone. Also, GLP-1 in the HFCC group was down-regulated while the IL-6 and TNF-α activity and endotoxins were all up-regulated. HFCC significantly decreased the number and diversity of bacteria, whereas tocopheryl quinone substantially restored the balance of intestinal flora and promoted the growth of both Bacteroides and Lactobacilli in vitro. Discussion and conclusions α-Tocopheryl quinone relieves HFCC-induced NASH via regulating oxidative stress, GLP-1 expression, intestinal flora imbalance, and the metabolism of glucose and lipids.

Generic submodularity ratio γ is a general measurement to characterize how close a nonnegative monotone set function is to be submodular. In this paper, we make a systematic analysis of greedy algorithms for maximizing a monotone and normalized set function with a generic submodularity ratio γ under Cardinality constraints, Knapsack constraints, Matroid constraints and K-intersection constraints.

In this paper, the stability problem for a class of switched dynamic systems with logic switching signals is investigated. Emphasis is placed on the stability of logically switched dynamic systems ...

Bond cleavage bioorthogonal chemistry has been widely employed to restore or activate proteins or prodrugs. Nitric oxide (NO), as a free radical molecule, has joined the clinical arena of cancer therapy, since high levels of NO could produce a cancer cell growth inhibitory effect. However, the spatiotemporal controlled release of NO remains a great challenge, and bioorthogonal chemistry may open a new window. Herein, we described a class of O2-3-isocyanopropyl diazeniumdiolates 3a-f as new bioorthogonal NO precursors, which can be effectively uncaged via tetrazine-mediated bond cleavage reactions to liberate NO and acrolein in living cancer cells, exhibiting potent antiproliferative activity. Furthermore, 3a and tetrazine BTZ were respectively encapsulated into two liposomes. It was found that simultaneous administrations of the two liposomes could specifically release large amounts of NO in the implanted cancer cells in zebrafish, thus generating potent tumor suppression activity in vivo. Our findings indicate that the TZ-labile NO precursors could serve to expand the NO-based smart therapeutics and the scope of bioorthogonal chemistry utility in vivo in the near future.

Magnetic pulse welding (MPW) exhibits an enormous advantage on welded joints of dissimilar metals. Various process parameters (discharge energy and standoff distance) were considered to weld aluminum alloys and galvanized steels by MPW. Mechanical behavior and interfacial morphology of MPW joints between galvanized steels and aluminum alloys were investigated systematically. Results indicated that the weldable standoff distance range of the MPW joints was enhanced with ascending discharge energy. The change of weld dimension (width and gap of the effective weld) was the main reason for the difference in joint performance at the various welding process parameters. With enhancing discharge energy, both the length of zinc-free zone and the size of interfacial waves increased, which contributed to the enhancement of the mechanical strength of the MPW joint. With increasing standoff distance, the strength of MPW joints appeared to increase first and then decrease. This was owing to the change of interfacial wave size and zinc-free zone length.

As a rapid proliferating tissue, tumor cells have to optimize nutrient utilization to withstand harsh conditions. Several approaches have been explored to inhibit the growth and metastasis of tumor by disrupting the reprogrammed tumor metabolism. However, nutrient limitations within solid tumors may induce the metabolic flexibility of malignant cells to sustain growth and survival using one nutrient to fill metabolite pools normally supplied by the other. To overcome this predicament, a promising click-nucleic-acid-containing platform for codelivery of rapamycin, anti-PFKFB4 siRNA, and targeting ligand aptamer AS1411 was applied. PFKFB4 could act as a promising target for tumor therapy for being a molecular fulcrum that could couple glycolysis to autophagy by promoting aggressive metastatic tumors. The downregulation of PFKFB4 can help inhibit the SRC3/Akt/mTOR pathway, leading autophagy to the direction of promoting apoptosis of tumor cells, which is induced by the collapse of tumor cellular homeostasis, while low dosages of rapamycin could decrease surgery-induced immune dysfunction. Enhanced tumor autophagy, favorable in vivo antitumor efficacy, and effective systematic immune activation are observed after treatment, suggesting that autophagy and glycolysis can serve as an integrated target for tumor treatment.

Driving the pores away The formation of “keyholes” (vapor-filled depressions) during additive manufacturing leads to porosity, which degrades alloy performance, especially fracture properties, and remains a big challenge for the 3D printing of metals. Zhao et al. used high-speed x-ray imaging to take a detailed look at how keyhole formation connects to porosity in a titanium alloy. They found that instability at the keyhole tip drives pores away to get trapped in the solidification front. Understanding this process and the operating parameters under which it occurs provides a roadmap for avoiding porosity and building high-quality metal parts. Science , this issue p. 1080

Bioorthogonal decaging reactions for controllable drug activation within complex biological systems are highly desirable yet extremely challenging. Herein, we find a new class of Pt(II)-triggered bioorthogonal cleavage reactions in which Pt(II) but not Pt(IV) complexes effectively trigger the cleavage of O/N-propargyl in a variety of ranges of caged molecules under biocompatible conditions. Based on these findings, we propose a general strategy for integrated bioorthogonal prodrugs and accordingly design a prodrug 16, in which a Pt(IV) moiety is covalently connected with an O2-propargyl diazeniumdiolate moiety. It is found that 16 can be specifically reduced by cytoplasmic reductants in human ovarian cancer cells to liberate cisplatin, which subsequently stimulates the cleavage of O2-propargyl to release large amounts of NO in situ, thus generating synergistic and potent tumor suppression activity in vivo. Therefore, Pt(II)-triggered depropargylation and the integration concept might provide a general strategy for broad applicability of bioorthogonal cleavage chemistry in vivo.

In this paper, we develop a spectral method with essential imposition of nonhomogeneous Neumann boundary condition on quadrilaterals. Results on irrational orthogonal approximation are established, which facilitate the numerical solutions of partial differential equations of the sort. As applications, we provide spectral schemes for two model problems, and prove their spectral accuracy. Efficient numerical implementations are described. Numerical results demonstrate high efficiency of the suggested algorithms.

The free-flying space manipulators present challenges in controlling the motions of both the spacecraft bus and the manipulator, because of the highly-coupling system dynamics and the unknown space environment disturbances. Although the sliding mode controllers are robust to the unknown disturbances and system uncertainties, the chattering effect could affect the pointing accuracy and the lifetime of the actuators. This paper first introduces the dynamics of a CuBot, which is a 3-rigid-link manipulator based on the CubeSat platform. To maintain the robustness while decreasing the chattering effect, an innovative reinforcement learning based fuzzy adaptive sliding mode controller is proposed. To maintain the robustness while reducing the chattering effect, an innovative reinforcement learning based fuzzy adaptive sliding mode controller is proposed. The switching gain is updated to estimate the lumped upper bound of the system uncertainties and the unknown disturbances, and then a new fuzzy logic adaptive law is applied on the switching gain to decrease the chattering effects. On top of that, the fuzzy logic rules are tuned by an innovative modified reinforcement learning mechanism to achieve the better tracking performance. The uniformly ultimately bounded tracking errors are guaranteed by the proposed control scheme, and the effectiveness is validated by the simulation results.

Additive manufacturing (AM) comprises a group of transformative technologies that are likely to revolutionize manufacturing. In particular, laser-based metal AM techniques can not only fabricate parts with extreme complexity, but also provide innovative means for designing and processing new metallic systems. However, there are still several technical barriers that constrain metal AM. Overcoming these barriers requires a better understanding of the physics underlying the complex and dynamic laser–metal interaction at the heart of many AM processes. This article briefly describes the state of the art of in situ/operando synchrotron x-ray imaging and diffraction for studying metal AM, mostly the laser powder-bed fusion process. It highlights the immediate impact of operando synchrotron studies on the advancement of AM technologies, and presents future research challenges and opportunities.

Informative and accurate survival prediction with individualized dynamic risk profiles over time is critical for personalized disease prevention and clinical management. The massive genetic data, such as SNPs from genome-wide association studies (GWAS), together with well-characterized time-to-event phenotypes provide unprecedented opportunities for developing effective survival prediction models. Recent advances in deep learning have made extraordinary achievements in establishing powerful prediction models in the biomedical field. However, the applications of deep learning approaches in survival prediction are limited, especially with utilizing the wealthy GWAS data. Motivated by developing powerful prediction models for the progression of an eye disease, age-related macular degeneration (AMD), we develop and implement a multilayer deep neural network (DNN) survival model to effectively extract features and make accurate and interpretable predictions. Various simulation studies are performed to compare the prediction performance of the DNN survival model with several other machine learning-based survival models. Finally, using the GWAS data from two large-scale randomized clinical trials in AMD with over 7800 observations, we show that the DNN survival model not only outperforms several existing survival prediction models in terms of prediction accuracy (eg, c-index =0.76), but also successfully detects clinically meaningful risk subgroups by effectively learning the complex structures among genetic variants. Moreover, we obtain a subject-specific importance measure for each predictor from the DNN survival model, which provides valuable insights into the personalized early prevention and clinical management for this disease.

Two-dimensional transition-metal-containing polyphthalocyanine conjugated porous frameworks are synthesized, and transition-metal (TM) ions ranging from Fe, Co, Ni, Cu to In are chosen to combine in phthalocyanine centers to tune their delocalized electronic structure. The fully closed planar delocalized π-conjugated frameworks exhibit efficient nonlinear optical absorption and excellent optical limiting performance under ns pulsed laser. The metal ion (Co, Ni) with ferromagnetism in phthalocyanine center manifests its contribution in enhanced nonlinear optical response through resonance enhancement of the nonlinear excited-state absorption.

Controlling the atomic configurations of structural defects in graphene nanostructures is crucial for achieving desired functionalities. Here, we report the controlled fabrication of high-quality single-crystal and bicrystal graphene nanoislands (GNI) through a unique top-down etching and post-annealing procedure on a graphite surface. Low-temperature scanning tunneling microscopy (STM) combined with density functional theory calculations reveal that most of grain boundaries (GBs) formed on the bicrystal GNIs are 5-7-5-7 GBs. Two nanodomains separated by a 5-7-5-7 GB are AB stacking and twisted stacking with respect to the underlying graphite substrate and exhibit distinct electronic properties, forming a graphene homojunction. In addition, we construct homojunctions with alternative AB/twisted stacking nanodomains separated by parallel 5-7-5-7 GBs. Remarkably, the stacking orders of homojunctions are manipulated from AB/twist into twist/twist type through a STM tip. The controllable fabrication and manipulation of graphene homojunctions with 5-7-5-7 GBs and distinct stacking orders open an avenue for the construction of GBs-based devices in valleytronics and twistronics.

For the successful application of boundary lubrication, detailed investigations about the influence of preparation process on molecular films are needed. In this paper, a specially designed device was used for the film preparation. The scanning electron microscope (SEM) combined with atomic force microscope (AFM) was employed to characterize the surface morphology and nanotribological behavior of molecular films. After the liquid phase deposition, molecular films are randomly and densely distributed over Ti-doped diamond-like carbon (Ti-DLC) substrates. Through rigorous surface treatments, island-like molecular films were finally achieved on substrate surfaces. The surface friction of molecular films is obviously lower than that of Ti-DLC surfaces. Then, pin-on-disk tribotests were performed to study the macrofriction behavior of molecular films under different preparation parameters. Based on the orthogonal experiment, the effect of five preparation parameters (solution weight percent, smearing force and processing time of three smearing steps) on initial friction coefficient of molecular films was investigated. The results indicated that the order of significance levels is as follows: processing time of the second smearing step > solution weight percent > processing time of step 1 > processing time of step 3 > smearing force. For the purpose of friction reduction, the appropriate level ranges are 0.75% (Solution), 2.5 N–15 N (Force), 1 min–10 min (Step 1), 1 min–2 min (Step 2) and 1 min, 2 min, 5 min and 15 min (Step 3). The initial friction coefficient under the optimized conditions is around 0.112, and the equilibrium friction coefficient is around 0.162, which is lower than that of unlubricated Ti-DLC substrates.