The mean orbital pseudo-metric and the space of invariant measures

We study the mean orbital pseudo-metric for Polish dynamical systems and its connections with properties of the space of invariant measures. We give equivalent conditions for when the set of invariant measures generated by periodic points is dense in the set of ergodic measures and the space of invariant measures. We also introduce the concept of asymptotic orbital average shadowing property and show that it implies that every non-empty compact connected subset of the space of invariant measures has a generic point.Comment: 20 pages. To appear in Acta Mathematica Sinica, English Serie

pH-Sensitive Peptide Hydrogels as a Combination Drug Delivery System for Cancer Treatment

Conventional antitumor chemotherapeutics generally have shortcomings in terms of dissolubility, selectivity and drug action time, and it has been difficult to achieve high antitumor efficacy with single-drug therapy. At present, combination therapy with two or more drugs is widely used in the treatment of cancer, but a shortcoming is that the drugs do not reach the target at the same time, resulting in a reduction in efficacy. Therefore, it is necessary to design a carrier that can release two drugs at the same site. We designed an injectable pH-responsive OE peptide hydrogel as a carrier material for the antitumor drugs gemcitabine (GEM) and paclitaxel (PTX) that can release drugs at the tumor site simultaneously to achieve the antitumor effect. After determining the optimal gelation concentration of the OE polypeptide, we conducted an in vitro release study to prove its pH sensitivity. The release of PTX from the OE hydrogel in the medium at pH 5.8 and pH 7.4 was 96.90% and 38.98% in 7 days. The release of GEM from the OE hydrogel in media with pH of 5.8 and 7.4 was 99.99% and 99.63% in 3 days. Transmission electron microscopy (TEM) and circular dichroism (CD) experiments were used to observe the microstructure of the peptides. The circular dichroism of OE showed a single negative peak shape when under neutral conditions, indicating a β-folded structure, while under acidic conditions, it presented characteristics of a random coil. Rheological experiments were used to investigate the mechanical strength of this peptide hydrogel. Furthermore, the treatment effect of the drug-loaded peptide hydrogel was demonstrated through in vitro and in vivo experiments. The results show that the peptide hydrogels have different structures at different pH values and are highly sensitive to pH. They can reach the tumor site by injection and are induced by the tumor microenvironment to release antitumor drugs slowly and continuously. This biologically functional material has a promising future in drug delivery for combination drugs

Effect of Watering down Environmental Regulation on Residents’ Health in China: A Quasi-Natural Experiment of Local Officials’ Promotion Motivation

Environmental performance is increasingly important in promoting officials, whose pursuit of promotions and related behavior may affect the health of residents in their jurisdictions. In this study, we spatially matched Chinese river water quality monitoring station data, enterprise pollution emission data, and resident health data and quantified how Chinese officials pursuing promotions based on environmental performance affected resident health using a regression discontinuity design and difference-in-difference with interaction terms design strategy. The results show that the upstream–downstream disparity of environmental governance and pollutant emissions affects the residents’ health, medical treatment behavior, and medical expenditure. Furthermore, we identified the causal relationship between official promotion and upstream–downstream disparity and estimated the marginal effect of promotion on residents’ health. The study suggests that local officials limit the pollution emissions of enterprises in the upstream river to achieve environmental performance and relax the pollution restrictions of firms in the downstream river to achieve economic performance, such that the health of residents near the river is differentially affected

Effects of Decentralized Water Regulation on Agriculture in China: A Quasi-Natural Experiment Based on Incentives for Promoting Officials

Environmental performance is becoming increasingly essential for promoting local officials in China; thus, their pursuit of promotion may affect agricultural output. This study spatially matched Chinese local official promotion data, regional agricultural output, river-water-quality-monitoring stations, and riverside enterprise discharge data. Based on the difference-in-difference model, the exogenous impact of the natural experiment based on the promotion of officials is quantified as how the promotion behavior of local officials in pursuit of environmental achievements affects agricultural output. This was examined under the decentralization system of China’s environmental governance. The results show that local officials improve agricultural production by controlling environmental pollution through promotion incentives. However, since the central government can observe the regulatory effect of upstream officials through the readings of water monitoring stations, upstream officials strictly enforce the central environmental regulations due to promotion motivation, while downstream officials do not strictly enforce their counterparts. This can result in differentiated impacts on agriculture in upstream and downstream regions. We also carried out a parallel test, placebo test, and measurement error test for the quasi-natural experiment, and the conclusions derived from the analysis remained robust. Our study has important implications for designing compatible environmental governance contracts and incentive policies for promoting agricultural production

Development of Abiraterone Acetate Nanocrystal Tablets to Enhance Oral Bioavailability: Formulation Optimization, Characterization, In Vitro Dissolution and Pharmacokinetic Evaluation

Abiraterone acetate is a prodrug of abiraterone used in combination with prednisone as a standard therapeutic strategy for hormone-resistant prostate cancer (mCRPC). Due to the poor solubility and permeability, the release and absorption of abiraterone acetate are low and reduce its bioavailability. In this project, abiraterone acetate tablets prepared using nanocrystal technology were developed to overcome the drawbacks of normal tablets by enhancing in vitro dissolution rate and oral bioavailability. The abiraterone acetate nanocrystal suspensions were prepared by top-down wet milling method using a planetary ball mill with the mixture of Poloxamer 407 and Poloxamer 188 as the optimized stabilizer at a ratio of 7:1. The optimized nanocrystals were freeze-dried and characterized using DLS, TEM, DSC, and XRD. The abiraterone acetate nanocrystal tablets significantly improve the in vitro dissolution rate of abiraterone acetate compared to raw materials. Although exhibiting a similar dissolution rate compared to the Zytiga® tablets, the nanocrystal tablets significantly improve the oral bioavailability with Cmax and AUC0–t being 3.51-fold and 2.80-fold higher, respectively, in the pharmacokinetic study. The present data indicate that nanocrystal is a promising strategy for improving the dissolution and bioavailability of abiraterone acetate

Hydrogel Patch with Biomimetic Tree Frog Micropillars for Enhanced Adhesion and Perspiration Wicking

Hydrogels with superior adhesion in both wet and dry interfaces, excellent biocompatibility, and electrical conductivity are highly essential for biomedical engineering and wearable electronics. Although a variety of artificial adhesives have been developed to enhance adhesion in a wet interface, a single adhesion strategy has limitations in complex adhesion environments. Inspired by the ortho-hexagonal toe pads of the tree frog, we present a microstructured hydrogel adhesive (MS-HAD) that combines chemical adhesive and perspiration wicking introduced by a biomimetic microstructure. This MS-HAD is made by a biocompatible PDA/PAM hydrogel featuring ortho-hexagonal micropillars on the surface. The PDA/PAM hydrogel composition was optimized, balancing the hydrogel adhesive and mechanical strength to match the micropillar fabrication process. By studying the adhesion behavior of micropillar structures of various sizes, it is found that the liquid self-splitting and liquid self-sucking introduced by the microstructure were the synergistic mechanism of adhesion strength enhancement in the wet interface. The adhesion of MS-HAD in the wet interface is enhanced by 47% in comparison to a flat hydrogel adhesive (F-HAD). Finally, the application of the MS-HAD patches for ECG signal monitoring under dry and wet skins is demonstrated. For both dry and wet skins, the ECG signal measured by the MS-HAD is more stable and accurate compared to those measured by commercial gel electrodes and F-HAD. The MS-HAD reported here provides a potential adhesive electrode that could perform well in both wet and dry interfaces for future portable health monitoring devices

Hydrogel Patch with Biomimetic Tree Frog Micropillars for Enhanced Adhesion and Perspiration Wicking

Hydrogels with superior adhesion in both wet and dry interfaces, excellent biocompatibility, and electrical conductivity are highly essential for biomedical engineering and wearable electronics. Although a variety of artificial adhesives have been developed to enhance adhesion in a wet interface, a single adhesion strategy has limitations in complex adhesion environments. Inspired by the ortho-hexagonal toe pads of the tree frog, we present a microstructured hydrogel adhesive (MS-HAD) that combines chemical adhesive and perspiration wicking introduced by a biomimetic microstructure. This MS-HAD is made by a biocompatible PDA/PAM hydrogel featuring ortho-hexagonal micropillars on the surface. The PDA/PAM hydrogel composition was optimized, balancing the hydrogel adhesive and mechanical strength to match the micropillar fabrication process. By studying the adhesion behavior of micropillar structures of various sizes, it is found that the liquid self-splitting and liquid self-sucking introduced by the microstructure were the synergistic mechanism of adhesion strength enhancement in the wet interface. The adhesion of MS-HAD in the wet interface is enhanced by 47% in comparison to a flat hydrogel adhesive (F-HAD). Finally, the application of the MS-HAD patches for ECG signal monitoring under dry and wet skins is demonstrated. For both dry and wet skins, the ECG signal measured by the MS-HAD is more stable and accurate compared to those measured by commercial gel electrodes and F-HAD. The MS-HAD reported here provides a potential adhesive electrode that could perform well in both wet and dry interfaces for future portable health monitoring devices