This paper presents a detailed study on the dynamics of a three‐species food chain system with memory‐based delay under weak Allee effect and middle predator refuge. The local stability analyses of the non‐diffusive and memory‐based diffusion systems are investigated. Moreover, we give a priori estimates and obtain the existence of the positive constant steady state by applying the comparison theorem. Sufficient conditions for the global stability are established by Barbǎlat lemma and the Lyapunov function. The theoretical results suggest the joint effect of cross‐diffusion and memory‐based delay can lead to Hopf bifurcation, which cannot appear in the system with self‐diffusion or a small cross‐diffusion coefficient. Numerical results verify the validity of the theoretical analysis.
Extracting gold from wastes of electronic equipment (e-waste) is a sustainable strategy for the recovery of the precious metal, reducing environmental pollution, and addressing the growing demands for gold resources. In this work, we synthesized a thiourea-modified porous aromatic framework (PAF-1-thiourea) with exceptional gold-extraction ability. The optimum adsorption capacity for PAF-1-thiourea to gold reaches up to 2629.87 mg g-1. The adsorption process can be well fitted according to the pseudo-second-order kinetic model and Langmuir model, featuring strong affinity caused by strong soft-soft interactions between Au(III) and the S and N donor atoms of the modified PAF and the electrostatic interactions between protonated amino groups and AuCl4-. PAF-1-thiourea was especially capable of extracting gold rapidly and efficiently (capturing 98.73% of gold within 5 min) from a central processing unit (CPU) in extremely acidic conditions. It is found that PAF-1-thiourea captures gold ions and simultaneously converts it to a Au(0) solid, obtaining gold with purity up to 23.5 karat. PAF-1-thiourea with its high acid resistance and anti-interference against cheap metals in the recovery process presents a practical means to extract gold from e-waste.
The biomass of thinned unripe grape (TUR) was investigated and estimated in China and the world. In addition, the physicochemical parameters, nutritional and functional components and antioxidant activity of nine TUR and ripe grape fruit (RGF) samples were determined and analyzed. The results showed that about 1695.75 kt TUR was produced in China and as much as 14436.16 kt worldwide, which was closely related to the fruit thinning time. The total sugar and protein contents of TUR were significantly lower than those of RGF (p < 0.05), while the organic acids (especially tartaric acid and malic acid) and crude fiber of TUR were significantly higher than those of RGF (p < 0.05). Moreover, the total polyphenol, flavonoid, tannin and flavan-3-ols contents of TUR were 4.2-13.5, 3.6-12.3, 4.3-62.8 and 1.5-7.6 times those of RGF, respectively. Meanwhile, the antioxidant capacity of TUR was significantly higher than that of RGF, as well (p < 0.05). This study aimed to conduct in-depth research into the nutritional characteristics of TUR, propose the targeted direction for their further investigation and then lay a theoretical foundation from which the research findings could be applied in practice.
How to restrain the recombination of photogenerated electrons and holes is still very important for photocatalytic hydrogen production. Herein, Z-scheme ZnWO4/Mn0.5Cd0.5S (ZWMCS) nanocomposites are prepared and are applied as visible-light driven precious metal cocatalyst free photocatalyst for hydrogen generation. The ZnWO4/Mn0.5Cd0.5S nanocomposites with 30 wt% ZnWO4 (ZWMCS-2) can reach a photocatalytic hydrogen evolution rate of 3.36 mmol g−1 h−1, which is much higher than that of single ZnWO4 (trace) and Mn0.5Cd0.5S (1.96 mmol g−1 h−1). Cycling test reveals that the ZMWCS-2 nanocomposite can maintain stable photocatalytic hydrogen evolution for seven cycles (21 h). The type of heterojunction in the ZWMCS-2 nanocomposite can be identified as Z-scheme heterojunction. The Z-scheme heterojunction can effectively separate the electrons and holes, so that the hydrogen generation activity and stability of the ZWMCS-2 nanocomposite can be enhanced. This work provides a highly efficient and stable Z-scheme heterojunction photocatalyst for hydrogen generation.
One of the factors that inhibits the development of the Chinese wine industry is that the sugar content ofthe grape feedstock is insufficient. In order to produce wine with better qualities using these materials,concentrating the grape juice could be a good alternative to adding sugars. In this study, suspension freezeconcentrationtechnology was applied to concentrating grape juice with a low sugar content. The freezeconcentratedgrape juice was made into red and white wines separately. In the control group, red andwhite wines were made from chaptalized (sugar-enriched) grape juice. The physical and chemical indexes,sensory evaluation results and polyphenolic content of the wine were analysed to evaluate the practicalityof applying the freeze-concentration technology in the wine industry. The results show that, after removingice every 30 min for approximately 14 h with a -18°C coolant, grape juice with an initial sugar content of14°Brix reached 23°Brix. Both the red wines and white wines made from freeze-concentrated grape juicewere of a higher quality than the wines made from chaptalised grape juice. Moreover, the phenolic contentwas concentrated, which may provide health benefits. Thus, suspension freeze-concentration technology isa promising alternative to traditional chaptalisation technology.
Highly sensitive detection of Fe<sup>3+</sup> was achieved using a fluorescein-based fluorescent porous aromatic framework.
Abstract In response to the shortcomings of magnesium oxychloride cement (MOC), which has excellent with outstanding mechanical properties and favorable bioactivity but poor water resistance, strontium hydrogen phosphate (SrHPO 4 ) was used as a water resistance modifier for MOC in the paper, and the effects of SrHPO 4 on the strength, water resistance, in vitro degradation and bioactivity of MOC were investigated; the results showed that SrHPO 4 could enhance the water resistance of MOC, in which the initial strength of MOC containing 4.0 wt% SrHPO 4 was 92.3 ± 2.5 MPa, and the strength was still 8.2 ± 0.9 MPa after 84 d of immersion in SBF solution; the degradation experiments of the samples in SBF solution showed that the degradation of SrHPO 4 -MOC was controlled, and the low alkaline environment created by the degradation promoted the deposition of hydroxyapatite on the cement surface, it indicated that SrHPO 4 -MOC material had good degradation properties and bioactivity; cell experiments showed that compared with MOC, SrHPO 4 -MOC was noncytotoxic and could promote cell proliferation, which was expected to be a new material for bone repair.
Abstract Purpose: This paper explores the effect of active break on the distinguishability of autonomic nervous patterns of learning states through machine learning. Method: First, we collected electrocardiogram (ECG) data of 77 subjects before and after active break, and accurately located the R-wave peaks from the ECG signal to calculate the RR interval series. Second, the RR interval samples were segmented according to the inclusion criteria of certain learning states. The initial 39 ECG features were empirically calculated, and the optimal feature combination for learning states recognition was selected through sequential backward selection and leave-one-subject-out cross test. Finally, we established binary-classification models of pairs of learning states and compared their performance of learning states recognition before and after active break. Discussion: Active break can promote or inhibit the students’ academic performance. Besides statistical analysis shows the stability of the cognitive ability. What’s more active break increases the physiological response to fatigue Conclusion: (1) The autonomic nervous patterns of knowledge input-processing and retrieval-processing and those of cognitive load matching and mismatching in knowledge retrieval processing became less distinguishable with the effect of active break. (2) The autonomic nervous patterns of mental fatigue and no fatigue states became more distinguishable with the effect of active break. (3) Stronger parasympathetic nervous activities make students achieve better academic performance during using new knowledge to solve problem stage.
