Ecological security assessment of China based on the Pressure-State-Response framework

As the largest developing country and a country facing enormous pollution pressure, China's ecosystem has been the object of wide concern among researchers. As governments around the world accelerate the process of ecological protection, assessing the state of regional ecological security is extremely important for the formulation of ecological protection policies. However, previous studies on ecological security assessment in China have often assessed the ecosystem in a small area only and have not carried out an overall review of China's environmental security. Therefore, it is urgent to establish a comprehensive index system to assess the ecological security status of China. Based on the Pressure-State-Response framework, this study constructs an assessment index system. Taking the 31 provinces in China as the research objects, this study combines China's yearbook data and the entropy method to calculate an ecological security index for China. Then, this study combines analyzes the ecological security index in a temporal and spatial scale. The study found that from 2009 to 2018, China's ecological security index showed an approximately “U”-shaped change trend. Specifically, in 2009, China's ESI was 0.52, which was classified as Ordinary status. By 2014, China's ESI had dropped to its lowest value in 2010–2019, at 0.35, in a relatively weak state. However, from 2015 onwards, China's ESI began to rise steadily, reaching 0.56 in 2018, which was considered an ordinary state. Among the assessment indices, the pressure index was the highest, and the status index was the lowest. The index system constructed based on the PSR framework makes the assessment tool of this study more systematic and scientific, and the ecological security index calculated using the entropy weighting method comprehensively reflects the ecological status of China and more accurately identifies the ecological problems of each region in China

Experimental Study on a Novel Dry Connection for a Precast Concrete Beam-To-Column Joint

At present, precast buildings have become the focus of the building industrialization, and the precast concrete frame structure has been widely used in the construction industry. On this background, a novel precast concrete frame with a bolt connection joint was proposed in this paper. The novel connections include connection steel plates, bolts and rubber layers. To investigate the seismic performance of the precast structure, two full-scale, precast, cruciform, reinforced concrete specimens, and a monolithic counterpart, are tested under reversed cyclic loading. For the precast specimens, two different thickness rubber layers are applied in the connection region, respectively. Seismic behavior was evaluated based on failure mode, hysteretic behavior, stiffness degeneration, ductility and energy dissipation. The results indicated that precast specimens had almost the same ultimate bearing capacity as the cast-in-place ones, and the failure mode is also the same. The precast specimens satisfied the strong column-weak beam design concept. Additionally, the initial stiffness is obviously decreased by adding rubber washers at the joint region, showing a semi-rigid characteristic. At the end of this paper, an equivalent stiffness computation method of the precast joint is discussed

Agarose-Based Microfluidic Device for Point-of-Care Concentration and Detection of Pathogen

Preconcentration of pathogens from patient samples represents a great challenge in point-of-care (POC) diagnostics. Here, a low-cost, rapid, and portable agarose-based microfluidic device was developed to concentrate biological fluid from micro- to picoliter volume. The microfluidic concentrator consisted of a glass slide simply covered by an agarose layer with a binary tree-shaped microchannel, in which pathogens could be concentrated at the end of the microchannel due to the capillary effect and the strong water permeability of the agarose gel. The fluorescent <i>Escherichia coli</i> strain OP50 was used to demonstrate the capacity of the agarose-based device. Results showed that 90% recovery efficiency could be achieved with a million-fold volume reduction from 400 μL to 400 pL. For concentration of 1 × 10³ cells mL^–1 bacteria, approximately ten million-fold enrichment in cell density was realized with volume reduction from 100 μL to 1.6 pL. Urine and blood plasma samples were further tested to validate the developed method. In conjugation with fluorescence immunoassay, we successfully applied the method to the concentration and detection of infectious <i>Staphylococcus aureus</i> in clinics. The agarose-based microfluidic concentrator provided an efficient approach for POC detection of pathogens

Agarose-Based Microfluidic Device for Point-of-Care Concentration and Detection of Pathogen

Preconcentration of pathogens from patient samples represents a great challenge in point-of-care (POC) diagnostics. Here, a low-cost, rapid, and portable agarose-based microfluidic device was developed to concentrate biological fluid from micro- to picoliter volume. The microfluidic concentrator consisted of a glass slide simply covered by an agarose layer with a binary tree-shaped microchannel, in which pathogens could be concentrated at the end of the microchannel due to the capillary effect and the strong water permeability of the agarose gel. The fluorescent <i>Escherichia coli</i> strain OP50 was used to demonstrate the capacity of the agarose-based device. Results showed that 90% recovery efficiency could be achieved with a million-fold volume reduction from 400 μL to 400 pL. For concentration of 1 × 10³ cells mL^–1 bacteria, approximately ten million-fold enrichment in cell density was realized with volume reduction from 100 μL to 1.6 pL. Urine and blood plasma samples were further tested to validate the developed method. In conjugation with fluorescence immunoassay, we successfully applied the method to the concentration and detection of infectious <i>Staphylococcus aureus</i> in clinics. The agarose-based microfluidic concentrator provided an efficient approach for POC detection of pathogens