Symbiotic integration of waste disposal capability within a city cluster: The case of the Yangtze River Delta.

With the ongoing urbanization in developing regions, integrating regional waste disposal capability is challenging due to unbalanced economic development and rising environmental issues. This research proposed a multi-dimensional symbiotic integration of waste disposal capability. Applying data from the Yangtze River Delta (YRD) in China, we first explore the waste flows and interactions between cities to identify the possibility of inter-municipal collaboration based on the augmented gravity model. We then employ social network analysis to categorize the cities in the collaborative network of waste disposal into subgroups by functionalities. Finally, we proposed the top-down framework of symbiotic networks for waste disposal. Our findings indicate that YRD cities can be classified into four types according to their waste density and disposal efficiency: High-High, Low-High, Low-Low, and High-Low. We also identify three types of inter-municipal collaborative relationships: between high-density and high-efficiency cities, between high-density cities, and between high-efficiency cities. The city subgroups can be categorized into "high-efficiency clusters," "high-density clusters," and "hub clusters," which pave the way for a shared or complementary urban symbiosis in the waste recycling industry. The division of roles among subgroups enables symbiotic activities within the city cluster. This paper extends the spatial scope of industrial symbiosis literature and has practical implications for transitioning to a circular economy in waste management of developing countries.

Three-Mediator Enhanced Collisions on an Ultramicroelectrode for Selective Identification of Single Saccharomyces cerevisiae.

Selective detection of colliding entities, especially cells and microbes, is of great challenge in single-entity electrochemistry. Herein, based on the different cellular electron transport pathways between microbes and mediators, we report a three-mediator system [K3Fe(CN)6, K4Fe(CN)6, and menadione] to achieve redox activity analysis and selective identification of single Saccharomyces cerevisiae without the usage of antibodies. K4Fe(CN)6 in the three-mediator system will oxidize near the electrode surface and increase the local concentration of K3Fe(CN)6, which will promote the redox reaction of S. cerevisiae. The hydrophobic mediator─menadione─can selectively penetrate through the S. cerevisiae membrane and get access to its intracellular redox center and can further react with K3Fe(CN)6 in the bulk solution. In contrast, the mediator can only get access to the bacterial membranes of Escherichia coli and Staphylococcus aureus, which results in different electrochemical collision signals between the above microbes. In the three-mediator system, upward step-like collision signals were observed in S. cerevisiae suspension, which are related to their microbial redox activity. In comparison, E. coli or S. aureus only generated downward current steps because the blockage effect of mediator diffusion suppresses their redox activities. When S. cerevisiae co-existed with E. coli or S. aureus, transients generated by both blockage and redox activity were observed. The approach enables us to trace the collision behaviors of different microbes and distinguish their simultaneous collisions, which is the foundation for further application of electrochemical collision technique in the specific identification of single biological entities.

Universal probe-based intermediate primer-triggered qPCR (UPIP-qPCR) for SNP genotyping.

BACKGROUND: The detection and identification of single nucleotide polymorphism (SNP) is essential for determining patient disease susceptibility and the delivery of medicines targeted to the individual. At present, SNP genotyping technology includes Sanger sequencing, TaqMan-probe quantitative polymerase chain reaction (qPCR), amplification-refractory mutation system (ARMS)-PCR, and Kompetitive Allele-Specific PCR (KASP). However, these technologies have some disadvantages: the high cost of development and detection, long and time consuming protocols, and high false positive rates. Focusing on these limitations, we proposed a new SNP detection method named universal probe-based intermediate primer-triggered qPCR (UPIP-qPCR). In this method, only two types of fluorescence-labeled probes were used for SNP genotyping, thus greatly reducing the cost of development and detection for SNP genotyping. RESULTS: In the amplification process of UPIP-qPCR, unlabeled intermediate primers with template-specific recognition functions could trigger probe hydrolysis and specific signal release. UPIP-qPCR can be used successfully and widely for SNP genotyping. The sensitivity of UPIP-qPCR in SNP genotyping was 0.01 ng, the call rate was more than 99.1%, and the accuracy was more than 99.9%. High-throughput DNA microarrays based on intermediate primers can be used for SNP genotyping. CONCLUSION: This novel approach is both cost effective and highly accurate; it is a reliable SNP genotyping method that would serve the needs of the clinician in the provision of targeted medicine.

Tailored negative/positive photoresponse of BP via doping.

Black phosphorus (BP) is a promising material for photodetectors due to its excellent and broadband photoresponse. To realize a wide application of BP in photodetection, there is a continuous eagerness for new approaches to tailor photoresponse of BP for a specific purpose, such as high sensitivity and switching of negative/positive responses. Here, we demonstrate that the ion irradiation with controllable conditions can enhance the photoresponsivity of BP for two orders compared to the pristine one, and can select the positive/negative photoresponse of the BP. The range of the tailored photoresponse covers the whole optical spectrum, ranging from the visible (532 nm) to the mid-infrared (10 µm). This work shows a pathway to modulate the photoresponse of BP, which opens new possibilities for potential photonic applications.

Feasibility investigation and development of microbial electrochemical biosensors for marine pollution monitoring.

Electrochemical biosensor, as a real-time and rapid detection method, has rarely been explored in marine monitoring. In present work, microbial electrochemical biosensors based on two design strategies: disperse system and integrated microbial electrode, were systematically discussed and their feasibility in marine biotoxicity assessment were investigated. An isolation method was initially investigated to eliminate the potential interference and detect the biological response accurately. The influence of water salinity on the current response was eliminated by adopting the salt-tolerant bacteria Staphylococcus aureus as test microorganism and buffer solution with sufficient ionic strength. The biotoxicity of heavy metal ions and pesticides were sensitively determined. Furthermore, a novel integrated microbial biosensor was designed by immobilizing S. aureus with a redox-active gel that consists of chitosan and poly (diallyl dimethyl ammonium chloride) mixture and confined potassium ferricyanide via electrostatic interaction. The IC50 values for Cu2+, Zn2+, Cr2O72- and Ni2+ were 3.01 mg/L, 1.34 mg/L, 7.64 mg/L and 9.41 mg/L, respectively. This work not only verified the feasibility of electrochemical biosensor in marine pollution monitoring, but also compared the pros and cons of two biosensor design strategies, which provide a guidance for the future development and application of marine monitoring devices based on electrochemical method.

Oxygen-enriched lignin-derived porous carbon nanosheets promote Zn2+ storage.

Carbon-based zinc-ion capacitors (ZICs) have sparked intense research enthusiasm because of large power density, good rate capability and cycling stability. However, there is still a long way to go before they achieve commercial applications. Herein, oxygen-enriched lignin-derived porous carbon nanosheets (OLCKs) were prepared by one-step carbonization-activation method, and more O-containing functional groups were generated on the surface of the porous carbon by post-surface functionalization strategy. The self-doped N can change the electron distribution of carbon skeleton and decrease energy barrier of chemical absorption of Zn2+/H+. Meanwhile, the carbonyl group can significantly enhance the wettability of OLCKs. Furthermore, the diffusion-controlled reactions mainly exist at high and low potential ranges in CV curves, which demonstrates the occurred Faradaic reaction. Consequently, the assembled aqueous ZICs based on OLCKs demonstrate a capacity of 121.7 mAh/g at 0.3 A/g, energy density of 94.3 Wh kg-1 and good cyclic stability. Besides, the assembled Zn//PVA/LiCl/ZnCl2(gel)//OLCK4 ZIC can also achieve energy density of 134.4 Wh kg-1 at 0.1 A/g. This work provides a novel design strategy by incorporating abundant O and N-containing functional groups to enhance energy density.

Effect of cell settlement on the electrochemical collision behaviors of single microbes.

Electrochemical collision technique has emerged as a powerful approach to detect the intrinsic properties of single entities. The diffusion model, together with migration and convection processes are generally used to describe the transport and collision processes of single entities. However, things become more complicated concerning microbes because of their relatively large size, inherent motility and biological activities. In this work, the electrochemical collision behaviors of four different microorganisms: Escherichia coli (Gram-negative bacteria), Staphylococcus aureus, Bacillus subtilis (Gram-positive bacteria) and Saccharomyces cerevisiae (fungus) were systematically detected and compared using a blocking strategy. By using K4Fe(CN)6 as redox probe, the downwards step-like signals were recorded in the collision process of all the three bacteria, whereas the collision of S. cerevisiae was rarely detected. To further investigate the underlying reason for the abnormal collision behavior of S. cerevisiae, the effect of cell settlement was discussed. The results indicated that ellipsoidal S. cerevisiae with a cell size larger than 2 µm exhibited a cell sedimentation rate of 261.759 nm s-1, which is dozens of times higher than the other three bacteria. By further enhanced convection near the microelectrode or positioned the microelectrode at the bottom of electrochemical cell, the collision signals of S. cerevisiae were successfully detected, indicating cell sedimentation is a nonnegligible force in large cell transport. This study fully addressed the effect of cell settlement on the transport of microbial cells and provided two strategies to counteract this effect, which benefit for the deeper understanding and further application of electrochemical collision technique in single-cell detection.

Multifunctional Magnetic Oxide-MoS2 Heterostructures on Silicon.

Correlated oxides and related heterostructures are intriguing for developing future multifunctional devices by exploiting their exotic properties, but their integration with other materials, especially on Si-based platforms, is challenging. Here, van der Waals heterostructures of La0.7 Sr0.3 MnO3 (LSMO) , a correlated manganite perovskite, and MoS2 are demonstrated on Si substrates with multiple functions. To overcome the problems due to the incompatible growth process, technologies involving freestanding LSMO membranes and van der Waals force-mediated transfer are used to fabricate the LSMO-MoS2 heterostructures. The LSMO-MoS2 heterostructures exhibit a gate-tunable rectifying behavior, based on which metal-semiconductor field-effect transistors (MESFETs) with on-off ratios of over 104 can be achieved. The LSMO-MoS2 heterostructures can function as photodiodes displaying considerable open-circuit voltages and photocurrents. In addition, the colossal magnetoresistance of LSMO endows the LSMO-MoS2 heterostructures with an electrically tunable magnetoresponse at room temperature. This work not only proves the applicability of the LSMO-MoS2 heterostructure devices on Si-based platform but also demonstrates a paradigm to create multifunctional heterostructures from materials with disparate properties.

Carbon Dioxide Emissions Reduction through Technological Innovation: Empirical Evidence from Chinese Provinces.

Energy consumption and industrial activities are the primary sources of carbon emissions. As the "world's factory" and the largest carbon emitter, China has been emphasizing the core role of technological innovation in promoting industrial structure upgrades (ISU) and energy efficiency (EE) to reduce carbon emissions from industrial production and energy consumption. This study investigated the mechanism (through ISU and EE) and spillover effect of technological innovation on carbon emission reduction using the panel dataset of 30 Chinese provinces from 2008 to 2019 and spatial econometrics models. The study concluded that (1) technological innovation had a negative direct effect on provincial carbon emissions, while it also showed a spatial spillover effect on neighboring provinces; (2) technological innovation had an indirect effect on provincial carbon emissions reduction through the mediation of energy efficiency improvement, while the mediation effect of industrial structure upgrading is not yet significant; and (3) the effect of technological innovation on carbon emission reduction showed heterogeneity in the eastern, central, and western regions of China. This study provided empirical and theoretical references to decision-makers in China and other developing countries in promoting technological and carbon control policies. More specifically, direct technology investment and indirect investment in industrial structure upgrades and energy efficiency could help with regional carbon emissions reduction.

Oxygen-Deficient α-MnO2 Nanotube/Graphene/N, P Codoped Porous Carbon Composite Cathode To Achieve High-Performing Zinc-Ion Batteries.

A major drawback of α-MnO2-based zinc-ion batteries (ZIBs) is the poor rate performance and short cycle life. Herein, an oxygen-deficient α-MnO2 nanotube (VO-α-MnO2)-integrated graphene (G) and N, P codoped cross-linked porous carbon nanosheet (CNPK) composite (VO-α-MnO2/CNPK/G) has been prepared for advanced ZIBs. The introduction of VO in MnO2 can decrease the value of the Gibbs free energy of Zn2+ adsorption near VO (ca. -0.73 eV) to the thermal neutral value. The thermal neutral value demonstrates that the Zn2+ adsorption/desorption process on VO-α-MnO2 is more reversible than that on α-MnO2. The as-made Zn/VO-α-MnO2 battery is able to deliver a large capacity of 305.0 mAh g-1 and high energy density up to 408.5 Wh kg-1. The good energy storage properties can be attributed to VO. Additionally, the VO-α-MnO2/CNPK/G composite possesses the structure of nanotube arrays, which results from the vertical growth of α-MnO2 nanotubes on CNPK. This unique array structure helps to realize fast ion/electron transfer and stable microstructure. The electrochemical performance of VO-α-MnO2 has been comprehensively improved by compositing with G and CNPK. The VO-α-MnO2/CNPK/G can achieve capacity up to 405.2 mAh g-1, energy density of 542.2 Wh kg-1, and long cycle life (80% capacity retention after 2000 cycles).

Redox activity of single bacteria revealed by electrochemical collision technique.

This paper reports on an innovative strategy based on the electrochemical collision technique to quantify the redox activity of two bacterial species: the Gram-negative Escherichia coli and the Gram-positive Bacillus subtilis. Thionine (TH), as a redox mediator, was electrostatically adsorbed on bacterial surface and formed the bacterium-TH complexes. TH can receive electrons from bacterial metabolic pathways and be reduced. When a single bacterium-TH complex collides on the ultramicroelectrode, the reduced TH will be re-oxidized at certain potential and generate current spike. The frequency of the spikes is linearly proportional to the living bacteria concentration, and the redox activity of individual bacterium can be quantified by the charges enclosed in the current spike. The redox ability of Gram-negative E.coli to the TH mediator was 6.79 ± 0.26 × 10-18 mol per bacterial cell in 30 min, which is relatively more reactive than B. subtilis (3.52 ± 0.31 × 10-18 mol per cell). The spike signals, fitted by 3D COMSOL Multiphysics simulation, revealed that there is inherent redox ability difference of two bacterial strains besides the difference in bacterial size and collision position. This work successfully quantified the bacterial redox activity to mediator in single cells level, which is of great significance to improve understanding of heterogeneous electron transfer process and build foundations to the microorganism selection in the design of microbial electrochemical devices.

Highly efficient ratiometric nanothermometers based on colloidal carbon quantum dots.

Optical nanothermometers have attracted much attention due to their non-contact and precise measurement with high spatial resolution at the micro- and nanoscales. They can be applied in various fields such as micro-opto-electronics, photonics, and biomedical thermal and pH sensing, while most thermal sensors reported so far contain heavy metals or have low sensitivity. Herein, we demonstrate a highly sensitive ratiometric thermal sensor based on colloidal C-dots. C-dots exhibit dual emission originating from the band gap emission and surface-dominant emission, which show a different temperature-dependent photoluminescence (PL) response. Among different surface-functionalized C-dots, C-dots@OH exhibit an absolute thermal sensitivity of -0.082 °C-1, which is the highest among various types of ratiometric thermosensors, making it a very promising candidate for high-sensitivity, self-calibrated nanoscale thermometry. As a proof-of-concept, C-dots@OH were employed to monitor the intracellular temperature (32-42 °C), showing a clear trend for temperature variation in a single cell, indicating that C-dots could offer a powerful tool for a potential precise measurement of the intracellular temperature. They could also be used as thermal sensors for nano-electronic and optoelectronic devices.

Defect Engineering of Out-of-Plane Charge Transport in van der Waals Heterostructures for Bi-Direction Photoresponse.

Defects are ubiquitous in two-dimensional (2D) transition-metal dichalcogenides (TMDs), generated by the initial growth- or the postprocessing. However, the defects may play negative roles in the photoelectronic properties of TMDs due to the reduction of in-plane transport of carriers. In this work, we demonstrate that the Se-vacancy defects in MoSe2 side of the van der Waal heterostructure is able to switch direction of out-of-plane charge transport. Photoresponse spectra showed defect density enable modified surface potential of MoSe2-x, leading to the barrier reverse between graphene and MoSe2-x and switches of the photoresponse from the negative to the positive. This unexpected property stemmed from appearance of midgap states by defects at heterostructure, as demonstrated by the density functional theory calculation and scanning tunneling microscope results. MoSe2-0.2/graphene heterostructure has a broadband response ranging from 450 to 1064 nm and exhibits comparable or higher positive responsivity (5.4 × 103 A/W to -15.3 × 103 A/W at 632.8 and 5.7 × 103 A/W to -1.2 × 103 A/W at 1064 nm) to the negative one of the pristine MoSe2/graphene. Based on defect-engineered heterostructures, we construct optoelectronic OR and AND logic devices with a broadband operation. Our work elucidates an alternative avenue to tailor the out-of-plane charge transport in TMD-based heterostructure through defects, and potentially invokes applicable utilization for 2D photodetectors and optoelectronic logic gates.

A portable instrument for monitoring acute water toxicity based on mediated electrochemical biosensor: Design, testing and evaluation.

A water quality early-warning instrument for evaluating acute water toxicity based on the electrochemical biosensor, Model ETOX18-01, was developed and manufactured with the features of low current detection (0.1 nA), precise thermostatic control, self-cleaning as well as remote data transmission. A sensitive integrated microbial electrode, made up of a glass carbon electrode that was modified by an active biofilm consisting of Escherichia coli, thionine, carbon nanodots and chitosan, has been fabricated as the biosensor. To validate the performance, multiple real water samples and artificial water samples were tested by Model ETOX18-01, and compared with ISO standardized luminescent bacterial test simultaneously. The correlation between the Model ETOX18-01 and luminescent bacterial test for these water samples showed good determination coefficient (R2 = 0.9827). In addition, Model ETOX18-01 is more sensitive to colored metal ionic samples. With its characteristics of high sensitivity, excellent repeatability and easy operation, the instrument Model ETOX18-01 provides a promising tool for large-scale water environmental assessment, and has a potential application in evaluating the water quality and early risk warning.

A novel c.2179T>C mutation blocked the intracellular transport of PHEX protein and caused X-linked hypophosphatemic rickets in a Chinese family.

BACKGROUND: X-linked hypophosphatemic rickets (XLH) is a heterogeneous genetic phosphate wasting disorder that occupies the majority of inheritable hypophosphatemic rickets (HR). XLH is caused by loss-of-function mutations in the phosphate-regulating endopeptidase gene (PHEX) located on the X chromosome. METHOD: In this study, we performed whole-exome sequencing (WES) on the proband to identify the causative gene. The mutations were analyzed by predictive online software, such as PolyPhen-2. Plasmids containing the wild-type (WT) and mutant cDNA of the candidate gene were transfected into HEK293, then, the expression, cellular localization, and glycosylation state of the candidate proteins were detected by western blot, immunostaining, and endoglycosidase H digestion. The expression and concentration of related factor were measured by RT-PCR and ELISA. RESULTS: We identified a novel missense mutation c.2179T>C in the PHEX that results in the substitution of p.Phe727Leu (F727L). This mutation was predicted to be disease-causing by all four predictive online software. In vitro studies demonstrated that the F727L substitution hindered the intracellular trafficking of the mutant PHEX, with ~59% of mutant PHEX protein retained in the endoplasmic reticulum (ER) and only ~16% of the mutant protein localized on the cell surface. Endoglycosidase H digestion assay showed that the mutant F727L PHEX protein was not fully glycosylated. The concentration of intact FGF23 in hFOB1.19 cell culture medium collected from the mutant PHEX group was the highest (62.9 pg/ml) compared to the WT group (32.1 pg/ml) and control group (23.5 pg/ml). CONCLUSION: Our results confirmed that the mutant PHEX protein was lowly glycosylated and retarded within the ER, the intact FGF23 level in cell culture media caused by the mutant PHEX protein was significantly elevated compared to that of the WT group, which may explain why the single base mutation in the PHEX led to XLH syndrome in this family.

A Novel Bat Coronavirus Closely Related to SARS-CoV-2 Contains Natural Insertions at the S1/S2 Cleavage Site of the Spike Protein.

The unprecedented pandemic of pneumonia caused by a novel coronavirus, SARS-CoV-2, in China and beyond has had major public health impacts on a global scale [1, 2]. Although bats are regarded as the most likely natural hosts for SARS-CoV-2 [3], the origins of the virus remain unclear. Here, we report a novel bat-derived coronavirus, denoted RmYN02, identified from a metagenomic analysis of samples from 227 bats collected from Yunnan Province in China between May and October 2019. Notably, RmYN02 shares 93.3% nucleotide identity with SARS-CoV-2 at the scale of the complete virus genome and 97.2% identity in the 1ab gene, in which it is the closest relative of SARS-CoV-2 reported to date. In contrast, RmYN02 showed low sequence identity (61.3%) to SARS-CoV-2 in the receptor-binding domain (RBD) and might not bind to angiotensin-converting enzyme 2 (ACE2). Critically, and in a similar manner to SARS-CoV-2, RmYN02 was characterized by the insertion of multiple amino acids at the junction site of the S1 and S2 subunits of the spike (S) protein. This provides strong evidence that such insertion events can occur naturally in animal betacoronaviruses.

Enhancement of Out-of-Plane Charge Transport in a Vertically Stacked Two-Dimensional Heterostructure Using Point Defects.

Point defects in 2D materials block in-plane charge transport, which incurs negative effects on the photoresponse of 2D monolayer materials. In contrast to in-plane charge transport, we show that out-of-plane charge transport in 2D materials can be enhanced through controllable formation of point defects, thus enhancing the photoresponse of a vertical heterostructure. Graphene and WSe2 monolayers were stacked together to construct a vertical heterostructure (W/G). Se point defects were artificially formed on the top atomic layer of WSe2 with controllable density via Ga ion irradiation. The interlayer charge transport in the W/G heterostructure was detected with femtosecond optical probe-pump measurements and photoelectric detection. Our experiments show that point defects can be used to provide higher transfer rate for out-of-plane charge transport and more electronic states for photoexcitation, leading to enhanced photoinduced interlayer charge transfer from WSe2 to graphene. Based on this feature, a photodetector based on W/G modified by point defects is proposed and implemented, exhibiting a fast photoresponsivity (∼0.6 ms) (2 orders of magnitude larger than the photoresponse in pristine W/G). This work demonstrates that out-of-plane charge transport is enhanced by the presence of point defects and illustrates an efficient method to optimize the performance of photoelectric devices based on vertical heterostructures.

Problems analysis and new fabrication strategies of mediated electrochemical biosensors for wastewater toxicity assessment.

Conventional mediated electrochemical biosensors for toxicity assessment were almost based on 'one-pot' principle, i.e., mediators and the under-test chemicals were mixed together in the same vessel. In this process, the electron mediator is assumed to be merely an electron acceptor and cannot react with under-test toxicants. Actually，some under-test pollutants (such as metal ions) could react with the electron mediators, thus affecting the detection accuracy and sensitivity of the sensors. It was also found that at least two other interference factors have been ignored in present'one-pot' mediated electrochemical biosensor systems, i.e., (1) the electrochemical sensitivity of mediators to pH; and (2) the potential reactions between under-test chemicals and buffers and the consequent pH changes. In this study, the three ignored interference factors have been investigated systematically and demonstrated by significance tests. Moreover, a solving strategy, an isolation method, is proposed for fabrication of novel mediated electrochemical biosensor to avoid the interference factors existing at present mediated electrochemical biosensor. According to the testing results obtained from the isolation method, IC50 values of Cu2+, Cd2+, Zn2+, Fe3+, Ni2+ and Cr3+ were 21.3 mg/L, 3.7 mg/L, 26.7 mg/L, 4.4 mg/L and 10.7 mg/L, respectively. The detection results of four real water samples also suggested this method could be applied for the practical and complex samples.

Effect of fiber orientation on the stress distribution within a leaflet of a polymer composite heart valve in the closed position.

Polymer trileaflet valves offer natural hemodynamics with the potential for better durability than commercially available tissue valves. Strength and durability of polymer-based valves may be increased through fiber reinforcement. A finite element analysis of the mechanics of a statically loaded polymer trileaflet aortic heart valve has been conducted. A parametric analysis was performed to determine the effects of fiber orientation and volume density in a single and double ply model. A maximum stress value of 1.02MPa was obtained in the non-reinforced model for a transvalvular load (downstream-upstream) of 120mmHg. The maximum stress on the downstream side of the leaflet was approximately twice the maximum stress on the upstream side, and always occurred on the interface with the valve stent. The single ply model reduced the stress on the polymer matrix, with the maximum reduction of at least 64% occurring when the fiber orientation was such that the fibers ran perpendicular to the stent edge. The double ply model further reduced the stress on the polymer matrix, with the maximum reduction of greater than 86% now occurring when the fibers are oriented most perpendicular to one another.