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This paper aims to the investigation of the global threshold dynamics of an infection age-space structured HIV infection model. The model is formulated in a bounded domain involving two infection routes (virus-to-cell and cell-to-cell) and Neumann boundary conditions. We first transform the original model to a hybrid system containing two partial differential equations and a Volterra integral equation. By appealing to the theory of fixed point problem together with Picard sequences, the well-posedness of the model is shown by verifying that the solution exists globally and the solution is ultimately bounded. Under the Neumann boundary condition, we establish the explicit expression of the basic reproduction number. By analyzing the distribution of characteristic roots of the associated characteristic equation in terms of the basic reproduction number, we achieve the local asymptotic stability of the steady states. The global asymptotic stability of the steady states is established by the technique of Lyapunov functionals, respectively. Numerical simulations are performed to validate our theoretical results. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the effect of chromium content on the microstructure and corrosion resistance of Ni-Cr coating. Design/methodology/approach: Ni-Cr coating was prepared by pulse current electrodeposition with trivalent chromium. On the basis of studying effect of electroplating parameters on composition and morphology, Ni-Cr alloy coatings with various chromium contents were obtained. The microstructure was characterized by scanning electron microscopy, X-ray diffractometer and transmission electron microscopy. Corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Findings: Electrodeposited chromium was solidly dissolved in nickel and refined the grain of the coating. With the increase of Cr content, the corrosion resistance of Ni-Cr coating was enhanced, which is due to the formation of continuous nickel hydroxide and compact chromium oxide passive films. Originality/value: Ni-Cr alloy coating without penetration crack was prepared in trivalent chromium electrolyte, and the mechanism of its excellent corrosion resistance was proposed. [ABSTRACT FROM AUTHOR]

Irinotecan is an anticancer topoisomerase I inhibitor that acts as a prodrug of the active metabolite, SN-38. Unfortunately, the limited utility of irinotecan is attributed to its pH-dependent stability, short half-life and dose-limiting toxicity. To address this problem, a novel trivalent PEGylated prodrug (PEG-[Irinotecan] 3) has been synthesized and its full-profile pharmacokinetics, antitumor activity and toxicity compared with those of irinotecan. The results show that after intravenous administration to rats, PEG-[Irinotecan] 3 undergoes stepwise loss of irinotecan to form PEG-[Irinotecan] 3‒ x (x = 1,2) and PEG-[linker] during which time the released irinotecan undergoes conversion to SN-38. As compared with conventional irinotecan, PEG-[Irinotecan] 3 displays extended release of irinotecan and efficient formation of SN-38 with significantly improved AUC and half-life. In a colorectal cancer-bearing model in nude mice, the tumor concentrations of irinotecan and SN-38 produced by PEG-[Irinotecan] 3 were respectively 86.2 and 2293 times higher at 48 h than produced by irinotecan. In summary, PEG-[Irinotecan] 3 displays superior pharmacokinetic characteristics and antitumor activity with lower toxicity than irinotecan. This supports the view that PEG-[Irinotecan] 3 is a superior anticancer drug to irinotecan and it has entered the phase II trial stage. PEG-[Irinotecan] 3 prodrug acts as an extended-release form of irinotecan and prolongs the half-life and tumor exposure time of SN-38 to improve the anticancer activity and lower toxicity compared to irinotecan. [Display omitted] [ABSTRACT FROM AUTHOR]

Rapidly increasing numbers of the plastic-covered greenhouse (PCG) worldwide ensure food security but threaten environmental security; thus, accurate monitoring of the spatiotemporal pattern in plastic-covered greenhouses (PCGs) is necessary for modern agricultural management and environmental protection. However, many urgent issues still exist in PCG mapping, such as multi-source data combination, classification accuracy improvement, spatiotemporal scale expansion, and dynamic trend quantification. To address these problems, this study proposed a new framework that progressed layer by layer from multi-feature scenario construction, classifier and feature scenario preliminary screening, feature optimization, and spatiotemporal mapping, to rapidly identify large-scale PCGs by integrating multi-source data using Google Earth Engine (GEE), and the framework was first applied to Central Yunnan Province (CYP), where PCGs are concentrated but no relevant research exists. The results suggested that: (1) combining the random forest (RF) classifier and spectrum (S) + backscatter (B) + index (I) + texture (T) + terrain (Tr) feature scenario produced the highest F-score (95.60%) and overall accuracy (88.04%). (2) The feature optimization for the S + I + T + B + Tr scenario positively impacted PCG recognition, increasing the average F-score by 1.03% (96.63% vs. 95.60%). (3) The 6-year average F-score of the PCGs extracted by the combined RF algorithm and the optimal feature subset exceeded 95.00%, and its spatiotemporal mapping results indicated that PCGs were prominently agglomerated in the central CYP and continuously expanded by an average of 65.45 km2/yr from 2016 to 2021. The research reveals that based on the GEE platform, multi-source data can be integrated through a feature optimization algorithm to more efficiently map PCG spatiotemporal information in complex regions. [ABSTRACT FROM AUTHOR]