Two-photon polymerization (TPP) is a powerful and potential technology to fabricate true three-dimensional (3D) micro/nanostructures of various materials with subdiffraction-limit resolution. And it ...has been applied to microoptics, electronics, communications, biomedicine, microfluidic devices, MEMS and metamaterials. These applications, such as microoptics and photon crystals, put forward rigorous requirements on the processing accuracy of TPP, including the dimensional accuracy, shape accuracy and surface roughness and the processing accuracy influences their performance, even invalidate them. In order to fabricate precise 3D micro/nanostructures, the factors influencing the processing accuracy need to be considered comprehensively and systematically. In this paper, we review the basis of TPP micro/nanofabrication, including mechanism of TPP, experimental set-up for TPP and scaling laws of resolution of TPP. Then, we discuss the factors influencing the processing accuracy. Finally, we summarize the methods reported lately to improve the processing accuracy from improving the resolution and changing spatial arrangement of voxels.
In nature, land plants as sessile organisms are faced with multiple nutrient stresses that often occur simultaneously in soil. Nitrogen (N), phosphorus (P), sulfur (S), zinc (Zn), and iron (Fe) are ...five of the essential nutrients that affect plant growth and health. Although these minerals are relatively inaccessible to plants due to their low solubility and relative immobilization, plants have adopted coping mechanisms for survival under multiple nutrient stress conditions. The double interactions between N, Pi, S, Zn, and Fe have long been recognized in plants at the physiological level. However, the molecular mechanisms and signaling pathways underlying these cross-talks in plants remain poorly understood. This review preliminarily examined recent progress and current knowledge of the biochemical and physiological interactions between macro- and micro-mineral nutrients in plants and aimed to focus on the cross-talks between N, Pi, S, Zn, and Fe uptake and homeostasis in plants. More importantly, we further reviewed current studies on the molecular mechanisms underlying the cross-talks between N, Pi, S, Zn, and Fe homeostasis to better understand how these nutrient interactions affect the mineral uptake and signaling in plants. This review serves as a basis for further studies on multiple nutrient stress signaling in plants. Overall, the development of an integrative study of multiple nutrient signaling cross-talks in plants will be of important biological significance and crucial to sustainable agriculture.
A piezoelectric actuator based on parasitic motion principle is proposed and tested. The piezoelectric actuator is explored to simultaneously realize coarse (long stroke) and fine (high accuracy) ...motions using dual-servo control method. The working principle of the proposed piezoelectric actuator is discussed, and finite-element method is adopted. A dynamic model of parasitic motion based on the LuGre friction model is simulated using matlab/Simulink. A prototype is manufactured to investigate working performance. Experimental results indicate that the maximum speed of the presented parasitic-type piezoelectric actuator is 7.95 mm/s and the resolution is 10 nm. These findings confirm the feasibility of the dual-servo nanopositioning system using piezoelectric stacks and flexure hinges.
This paper presents the classical Preisach hysteresis modeling and tracking control of a curved pre-stressed piezoceramic patch actuator system with severe hysteresis. The actuator is also flexible ...with very small inherent damping. It has potential applications in active antennas. A series of tests are conducted to study the hysteresis properties of the piezoceramic actuator system. The numerical expressions of the classical Preisach model for different input variations are presented. The classical Preisach model is applied to simulate the static hysteresis behavior of the system. Higher order hysteresis reversal curves predicted by the classical Preisach model are verified experimentally. The good agreement found between the measured and predicted curves showed that the classical Preisach model is an effective mean for modeling the hysteresis of the piezoceramic actuator system. Subsequently, the inverse classical Preisach model is established and applied to cancel the hysteresis the piezoceramic actuator system for the real-time microposition tracking control. In order to improve the control accuracy and to increase damping of the actuator system, a cascaded PD/lead-lag feedback controller is designed with consideration of the dynamics of the actuator. In the experiments, two cases are considered, control with major loop hysteresis compensation, and control with minor loop hysteresis compensation. Experimental results show that RMS tracking errors are reduced by 50% to 70% if the hysteresis compensation is added in the feedforward path in both cases. Therefore, hysteresis compensation with the feedback controller greatly improves the tracking control accuracy of the piezoceramic actuator.
With the rapid aging of the domestic population, China has a strong incentive to increase the statutory retirement age. How retirement affects the health of the elderly is crucial to this ...policymaking. The health consequences of retirement have been debated greatly. This study aims to investigate the effects of retirement on physical and mental health among Chinese elderly people.
The data we use in this study comes from four waves (2011, 2013, 2015, and 2018) of the Harmonized China Health and Retirement Longitudinal Study (Harmonized CHARLS), a prospective cohort. We use the nonparametric fuzzy regression discontinuity design to estimate the effects of retirement on physical and mental health. We test the robustness of our results with respect to different bandwidths, kernel functions, and polynomial orders. We also explore the heterogeneity across gender and education.
Results show that retirement has an insignificant effect on a series of physical and mental health outcomes, with and without adjusting several sociodemographic variables. Heterogeneity exists regarding gender and education. Although stratified analyses indicate that the transition from working to retirement leaves minimal effects on males and females, the effects go in the opposite direction. This finding holds for low-educated and high-educated groups for health outcomes including depression and cognitive function. Most of the results are stable with respect to different bandwidths, kernel functions, and polynomial orders.
Our results suggest that it is possible to delay the statutory retirement age in China as retirement has insignificant effects on physical and mental health. However, further research is needed to assess the long-term effect of retirement on health.
•The new concept of available carbon was introduced in anaerobic co-digestion.•The available carbon released rate of FVW was high and that of straw was low.•Available carbon quickly released ...substrate could improve the hydrolysis process.•The methane yield of anaerobic co-digestion of cow manure and corn straw increased.•The microbes changed and FVW enhanced the variation of the bacterial communities.
Based on continuous anaerobic co-digestion of cow manure with available carbon slowly released corn straw, the effect of adding available carbon quickly released fruit and vegetable waste (FVW) was explored, meanwhile microbial community variation was studied in this study. When the FVW added was 5% and 1%, the methane production of the cow manure and corn straw was improved, and the start-up process was shortened. With higher proportion of FVW to 5%, the performance was superior with a mean methane yield increase of 22.4%, and a greater variation of bacterial communities was observed. FVW enhanced the variation of the bacterial communities. The microbial community structure changed during fermentation and showed a trend toward a diverse and balance system. Therefore, the available carbon quickly released FVW was helpful to improve the anaerobic co-digestion of the cow manure and available carbon slowly released corn straw.
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•20 randomly real urine samples were collected and analyzed.•Totally 30 antibiotics in the fresh real urine were identified.•Representative antibiotic resistance bacteria and its gene ...were identified.•Changes of antibiotics, antibiotic resistance bacteria and gens of urine were monitored.
Human urine is a source of fertilizer and, with proper management, it can be reused in agriculture. Determining the contamination issue of antibiotics in source-separated urine is important because the majority of antibiotics are excreted with urine. In this study, source-separated urine samples were randomly collected from a male toilet in a university building and analyzed in terms of 30 typical antibiotics (including 14 sulfonamides, 4 tetracyclines, and 12 fluoroquinolones) and tetracycline-resistant Escherichia coli, as well as its antibiotic-resistant genes to determine the contamination characteristics of antibiotic-related pollution in fresh and stored urine. Results showed that 18 out of 30 typical antibiotics were detected in fresh source-separated human urine. The dominant antibiotic was oxytetracycline with a frequency of 100%, followed by tetracycline, sparfloxacin, enrofloxacin, and ofloxacin, which demonstrated a detection frequency of 55%. Among the detected values, sulfonamides (2 antibiotics), tetracyclines (4 antibiotics), and fluoroquinolones (12 antibiotics) had a concentration range of 0.25–2.94, 0.94–41.2, and 0.06–163.16 ng/mL, respectively. Furthermore, tetracycline-resistant Escherichia coli, which was measured using plate count method, and its related gene, tet M, exhibited a maximum cell density of (200,000 ± 5000) CFU/100 mL and (2.73 ± 0.261) × 107 copies/mL, respectively. When the fresh urine was stored in an ambient environment for 30 days to simulate the real circumstances of urine management, a significant reduction in antibiotics and antibiotic-resistant bacteria was observed, while the change in antibiotic-resistant genes was insignificant. The results of this study suggest that risks associated with antibiotics and their antibiotic-resistant bacteria and genes are retained during collection and storage. Hence, these kinds of microcontaminants must be considered in further urine utilization.
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•The g-C3N4 was prepared by using a mixture of urea and melamine.•AgBr can easily drop on the g-C3N4 with thermal and ultrasonic exfoliation.•h+ plays dominate role in the ...disinfection process.•The disinfection effect to cell destroy mainly resulted in lipid peroxidation and ATP change.
In this study, novel AgBr-modified g-C3N4 (AgBr/g-C3N4) photocatalysts were prepared by an adsorption–deposition method and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and ultraviolet–visible spectroscopy (UV–vis). Furthermore, the photocatalytic disinfection performance on Escherichia coli (ATCC 15597) was investigated. The as-prepared photocatalysts exhibited well crystalline structures and morphologies with C3N4 and exhibited a stronger bacterial inactivation than that of pristine g-C3N4. The disinfection efficiency reached up to 4.80 log under 150 min of visible light irradiation when AgBr-modified g-C3N4 was prepared at a molar ratio of 1:5 (AgBr: g-C3N4), which was a 4.2 log increase compared with that of pristine g-C3N4 under the same experimental conditions. The enhancement of the photocatalytic activity of AgBr/g-C3N4 was attributed to the effective production and transfer of the photo-induced electrons under visible light irradiation, since the AgBr modification reduced the bandgap energy and boarded the visible light area. Furthermore, h+ was found to be the dominant contributor for bacterial inactivation. The h+ and photo-generated reactive oxygen species (ROSs) damaged the cell membranes and destroyed metabolic processes, resulting in leakage of potassium ions and proteins, lipid peroxidation, degradation of intracellular protein, and a reduction of the ATP levels, which finally lead to bacterial death. These results provide a theoretical basis for the development of low-cost, high-efficiency photocatalysts for green/sustainable water disinfection.
In the newly proposed rotary spatial vibration (RSV)-assisted diamond cutting system, a piezoelectrically actuated monolithic compliant spatial vibrator (CSV), generating three decoupled ...translational vibrations with high working bandwidth, is deliberately designed to work on the rotating spindle of a machine. Using a matrix-based compliance modeling method and the Lagrangian principle, the complete compliance and system dynamics models of the CSV are formulated. The analytical modeling results are further validated by comparison with results obtained through finite-element analysis. Offline experimental tests were conducted to investigate the actual strokes, parasitic motions, as well as the natural frequencies of the CSV along its three working directions. A preliminary performance assessment of the developed RSV-assisted diamond cutting system for the generation of complex multitier micro-/nanostructures was conducted to demonstrate the feasibility and efficiency of the RSV system for mechanical micro-/nanomachining.
Due to world population growth, global climate change and the deteriorated quality of water, water supply struggles to keep up the clean water demand to meet human needs. Ultraviolet (UV) technology ...holds a great potential in advancing water and wastewater treatment to improve the efficiency of safe treatment. Over the last 20 years, the UV light disinfection industry has shown a tremendous growth. Therefore, reuse of wastewater contributes significantly to an efficient and sustainable water usage. Disinfection is a requirement for wastewater reuse due to the presence of a swarm of pathogens (e.g. bacteria, viruses, worms and protozoa) in secondary effluents. UV technology is widely favoured due to its environmentally friendly, chemical-free ability to provide high-log reductions of all known microorganisms, including chlorine-resistant strains such as
. The UV disinfection process does not create disinfection by-products and unlike the chlorine UV disinfection process, it is not reliant on water temperature and pH. UV disinfection can eliminate the need to generate, handle, transport or store toxic/hazardous or corrosive chemicals and requires less space than other methods. As UV does not leave any residual effect that can be harmful to humans or aquatic life, it is safer for plant operators.
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