Construction of Frustrated Lewis Pairs in Poly(heptazine imide) Nanosheets via Hydrogen Bonds for Boosting CO2 Photoreduction.

The creation of frustrated Lewis pairs on catalyst surface is an effective strategy for tuning CO2 activation. The critical step in the formation of frustrated Lewis pairs is the spatial effect of proximal Lewis acid-Lewis base pairs. Here, we demonstrate a facile surface functionalization methodology that enables hydrogen bonding between N and H atoms to mediate the construction of frustrated Lewis pairs in poly(heptazine imide), thereby increasing the propensity to activate CO2 molecules. Experimental and theoretical results show that the construction of active hydrogen bonding regions can facilitate the bending of CO2 molecules. Furthermore, the delocalization of electron clouds induced by the hydrogen bonding-mediated frustrated Lewis pairs can promote the heterolytic cleavage and photocatalytic conversion of CO2. This work highlights the potential of utilizing hydrogen bonding-mediated strategy in heterogeneously photocatalytic activation of CO2 over polymer materials.

The design of a linear voltage divider based on metal oxide arresters.

In recent years, linearization technology for nonlinear devices has become a hot topic in many fields. In this study, a linear voltage divider based on metal oxide arresters was designed by combining linearization technology and electrical measurement technology to solve the objective problems of online voltage monitoring. These problems include high difficulty in equipment installation, low measurement accuracy, and poor economic benefits. Based on a summary of linearization theory, the sufficient and necessary conditions for the linearization of the voltage divider were deduced in detail. The relevant circuit simulations were conducted, along with voltage divider experiments under power frequency AC voltage, operating overvoltage, and lightning overvoltage. The results revealed that the voltage divider was able to realize linearized measurements and meet the relevant standards of online voltage monitoring. The measurement errors were concentrated in the transition region between the pre-breakdown region (small current region) and the breakdown region (nonlinear region) in the volt-ampere characteristic curve. The main influencing factor of errors was the consistency of the nonlinear characteristics of the high- and low-voltage arms of the voltage divider. The voltage divider designed in this study can be applied in many scenarios, such as power plants, substations, high-voltage electrical equipment manufacturing plants, and high-voltage laboratories.

Rapid sand filtration for <10 µm-sized microplastic removal in tap water treatment: Efficiency and adsorption mechanisms.

The omnipresence of microplastics (MPs) in potable water has become a major concern due to their potential disruptive effect on human health. Therefore, the effective removal of MPs in drinking water is essential for life preservation. In this study, tap water containing microplastic <10 µm in size was treated using constructed pilot-scale rapid sand filtration (RSF) system to investigate the removal efficiency and the mechanisms involved. The results show that the RSF provides significant capacity for the removal and immobilization of MPs < 10 µm diameter (achieving 98 %). Results showed that silicate sand reacted with MPs through a cooperative assembly process, which mainly involved interception, trapping, entanglement, and adsorption. The MPs were quantified by Flow cytometry instrument. A kinetics study underlined the pivotal role of physio-chemisorption in the removal process. MP particles smaller than absorbents, saturation of adsorbents, and reactor hydrodynamics were identified as limiting factors, which were alleviated by backwashing. Backwashing promoted the desorption of up to 97 % MPs, conducive for adsorbent active site regeneration. These findings revealed the critical role of RSF and the importance of backwashing in removing MPs. Understanding the mechanisms involved in removing microplastics from drinking water is crucial in developing more efficient strategies to eliminate them.

Hidden risks: Simulated leakage of domestic sewage to secondary water supply systems poses serious microbiological risks.

There are continuous reports about the pollution of the secondary water supply systems (SWSSs), among which domestic sewage leakage is the most serious. In this study, a pilot experiment lasting 70 days was conducted to explore the changes in physicochemical water quality and the microbial profiles in SWSSs polluted by different doses of domestic sewage through qPCR and high-throughput sequencing methods. The results showed that when domestic sewage entered the simulated water storage tank, a large amount of organic matter brought by domestic sewage quickly consumed chlorine disinfectants. High pollution levels (pollution index ≥ 1/1000) were accompanied by significant increases in turbidity and ammonia nitrogen concentration (p < 0.05) and by abnormal changes in sensory properties. Although different microbial community structures were found only at high pollution levels, qPCR results showed that the abundance of the bacterial 16S rRNA gene and some pathogenic gene markers in the polluted tank increased with the pollution level, and the specific gene marker of pathogens could be detected even at imperceptible pollution levels. In particular, the high detection frequency and abundance of Escherichia coli and Enterococcus faecails in polluted tank water samples demonstrated that they can be used for early warning. Moreover, it seems that the microorganisms that came with the domestic sewage lost their cultivability soon after entering SWSSs but could recover their activities during stagnation. In addition, the biofilm biomass in the polluted tank with high pollution levels increased faster at the initial stage, while after a longer contact time, it tended to remain at the same level as the control tank. This study emphasized the high microbial risk introduced by sewage water leakage even at imperceptible levels and could provide scientific suggestions for early warning and prevention of pollution to SWSSs.

Dynamic characteristics of total and microcystin-producing Microcystis in a large deep reservoir.

Microcystis, one of the common cyanobacteria, often causes blooms in reservoirs, which has seriously threatened the safety of drinking water worldwide. To identify the growth characteristic of total and microcystin-producing Microcystis in large deep reservoirs, we used Quantitative PCR (qPCR) to measure the cell density of total and microcystin-producing Microcystis and monitored water quality in the water samples collected in Dongzhang Reservoir once a month. Microcystis blooms occurred in Dongzhang Reservoir in April 2017, which was composed of microcystin-producing and non-microcystin-producing Microcystis. Water temperature, dissolved oxygen, pH, and chlorophyll-a showed significant vertical stratification during Microcystis blooms. Total and microcystin-producing Microcystis grew rapidly under the high concentration of total phosphorus and rising water temperatures. Nitrate-nitrogen had a significant linear correlation with the abundance of microcystin-producing Microcystis. Our results indicated that nutrients and water temperature could be key triggers of Microcystis blooms and nitrate-nitrogen potentially regulates the competition between microcystin-producing and non-microcystin-producing Microcystis. This study improves our understanding of the characteristics of Microcystis blooms and the competition between microcystin-producing and non-microcystin-producing Microcystis in large deep reservoirs.

Microbiological quality of roof tank water in an urban village in southeastern China.

Urban villages are unique residential neighborhoods in urban areas in China. Roof tanks are their main form of water supply, and water quality deterioration might occur in this system because of poor hygienic conditions and maintenance. In this study, water samples were seasonally collected from an urban village to investigate the influence of roof tanks as an additional water storage device on the variation in the microbial community structure and pathogenic gene markers. Water stagnation in the roof tank induced significant decreases in chlorine (p < 0.05), residual chlorine was as low as 0.02 mg/L in spring. Propidium monoazide (PMA)-qPCR revealed a one-magnitude higher level of total viable bacterial concentration in roof tank water samples (2.14 ± 1.81 × 105 gene copies/mL) than that in input water samples (3.57 ± 2.90 × 104 gene copies/mL, p < 0.05), especially in spring and summer. In addition, pathogenic fungi, Mycobacterium spp., and Legionella spp. were frequently detected in the roof tanks. Terminal users might be exposed to higher microbial risk induced by high abundance of Legionella gene marker. Spearman's rank correlation and redundancy analysis showed that residual chlorine was the driving force that promoted bacterial colonization and shaped the microbial community. It is worth noted that the sediment in the pipe will be agitated when the water supply is restored after the water outages, which can trigger an increase in turbidity and bacterial biomass. Overall, the findings provide practical suggestions for controlling microbiological health risks in roof tanks in urban villages.

In situ synthesis of novel type II BiOCl/CAU-17 2D/2D heterostructures with enhanced photocatalytic activity.

A novel type II BiOCl/CAU-17 2D/2D heterostructure photocatalyst was synthesized by in situ growth of ultrathin BiOCl on the surface of CAU-17 nanorods through a solvothermal process. The 2D/2D heterostructures endow the BiOCl/CAU-17 heterojunction with a large specific surface area and tight interfacial contact, which can provide sufficient channels for carrier migration. The introduction of CAU-17 can enhance the light absorption ability of BiOCl/CAU-17 photocatalysts. Furthermore, the staggered type II heterostructure energy band alignment formed between BiOCl and CAU-17 can promote the separation of photoexcited carriers. The improved performance for carrier migration and light absorption was evaluated by SEM, TEM, BET, EIS, and DRS tests. Transient photocurrent response and photoluminescence tests confirmed the improvement in separating photoexcited carriers. The optimal 70% BiOCl/CAU-17 sample exhibited the highest photocatalytic degradation efficiency of 96.3% for RhB and 85.5% for TC, under 90 min of simulated solar light irradiation. Its apparent first-order rate constant k values are 0.02947 and 0.01955 min-1, respectively, being 48.31 and 19.75 fold higher than those of CAU-17, and 7.61 and 1.84 fold higher than those of BiOCl. The free radical scavenging experiment results showed that h+ and ˙O2- are the prime active species during the photodegradation process. Hence, a possible photocatalytic mechanism of the type II BiOCl/CAU-17 heterojunction was proposed.

A survey on heavy metal concentrations in residential neighborhoods: The influence of secondary water supply systems.

Water quality deterioration often occurs in secondary water supply systems (SWSSs), and increased heavy metal concentrations can be a serious problem. In this survey, twelve residential neighborhoods were selected to investigate the influence of SWSSs on the seasonal changes in heavy metal concentrations from input water to tank and tap water. The concentrations of nine evaluated heavy metals in all groups of water samples were found to be far below the specified standard levels in China. The concentrations of Fe, Mn, and Zn increased significantly from the input water samples to the tank and tap water samples in spring and summer (p < 0.05), especially for the water samples that had been stagnant for a long time. Negative correlations were found between most of the heavy metals and residual chlorine (Fe, Cu, Zn, and As, r = -0.186 to -0.519, p < 0.05). In particular, a high negative correlation was observed between Fe and residual chlorine (r = -0.489 to -0.519, p < 0.01) in spring and summer. Fe and Mn displayed positive correlations with turbidity (r = 0.672 and 0.328, respectively; p < 0.05). In addition, Cr and As were found to be positively associated with some nutrients (NO3-, TN, and SO42-; r = 0.420-0.786, p < 0.01). The material of the storage tanks had little influence on the difference in heavy metal concentrations. Overall, this survey illustrated that SWSSs may pose a chronic threat to water quality and could provide useful information for practitioners.

One-pot hydrothermal fabrication of 2D/2D BiOIO3/BiOBr Z-scheme heterostructure with enhanced photocatalytic activity.

A 2D/2D BiOIO3/BiOBr Z-scheme heterostructure was firstly synthesized by a simple one-pot hydrothermal process and it was used to effectively remove rhodamine B under irradiation of Xe and LED light. The BB-15 heterostructure has an optimal apparent rate constant k of 0.046 min-1 (0.17 min-1), which is ∼6.2 (89.7) and 3.5 (3.5) times that of BiOIO3 and BiOBr under the irradiation of Xe light (LED light). The enhanced photocatalytic activity can be attributed to the following points: (1) the face-to-face and tight contact in 2D/2D BiOIO3/BiOBr heterostructures provides more migration channels for photogenerated carriers which facilitates the transfer and separation of photogenerated carriers; (2) the Z-scheme photocarrier transport path not only hastens the separation and transfer efficiency of photocarriers in space but also maintains a robust redox capacity; (3) the presence of IO3-/I- redox couple and built-in electric field further encourage the separation and transfer of photocarriers and enhance the photocatalytic activity of the composite. And the O2-, h+, and OH are active species, which are responsible for the photodegrade process of RhB under irradiation of Xe light. This study provided an easy and reliable strategy to design and prepare an efficient bismuth-containing heterojunction, the characterization and evaluation experiment results proved its effectiveness for solar utilization and environmental purification.

A novel qPCR-based method to quantify seven phyla of common algae in freshwater and its application in water sources.

The light microscope is widely used to count algae, however, there are some disadvantages associated with this method, such as time consuming and laborious. In this study, a qPCR-based method was established for quantifying seven phyla of common algae in freshwater, including Cyanophyta, Chlorophyta, Euglenophyta, Bacillariophyta, Dinophyta, Cryptophyta, and Chrysophyta. The accuracy of qPCR in estimating algal cells was confirmed by comparing it with the microscopic counting. The qPCR was used to detect the cell concentration of seven phyla of algae in Longhu Reservoir, showing that green algal blooms occurred during the monitoring period. The intensity of algal blooms was further evaluated according to the classification standard, which suggested that the grade of this bloom was mild. An early warning system was proposed to early warn the occurrence of algal blooms in two water sources, Longhu Reservoir and Dongzhang Reservoir. The qPCR method developed in this study could be a useful tool in the monitoring of algae. The early warning system reported here will have important implications for the effective warning of algal blooms.

Radiotherapy for head and neck tumours using an oral fixation and parameter acquisition device and TOMO technology: a randomised controlled study.

INTRODUCTION: Radiotherapy has become one of the main methods used for the treatment of malignant tumours of the head and neck. Spiral tomographic intensity-modulated radiotherapy has the many advantages of precision radiotherapy, which puts forward high requirements for postural reproducibility and accuracy. We will aim to ensure that the accurate positioning of the tumour will reduce the side effects of radiotherapy caused by positioning errors. We will design and implement this clinical trial using the patent of 'a radiotherapy oral fixation and parameter acquisition device (patent number: ZL201921877986.5)'. METHODS AND ANALYSIS: This will be a randomised, controlled, prospective study with 120 patients with head and neck tumours. Using the random number table method, a random number sequence will be generated, and the patients will be enrolled in the experimental group (oral fixation device) and the control group (conventional fixation) in a 2:1 ratio. The primary outcome will be the progression-free survival time after the treatment. Secondary outcomes will include the oral mucosal reaction and the quality of life. Follow-ups will be carried out according to the plan. This is V.1.0 of protocol on 1 April 2021. The recruitment process for this clinical trial commenced on 1 May 2021, and will end on 1 October 2022. ETHICS AND DISSEMINATION: The trial received ethical approval from Medical Ethics Committee of Liaoning Provincial Cancer Hospital (number 20210131X). The final results will be presented at a scientific conference and published in a peer-reviewed journal in accordance with the journal's guidelines. TRIAL REGISTRATION NUMBER: ChiCTR2100045096.

A Promising Alternative for Sustainable and Highly Efficient Solar-Driven Deuterium Evolution at Room Temperature by Photocatalytic D2 O Splitting.

Motivated by energy shortages and in view of current efforts to develop clean, renewable energy sources based on fusion, a solar-driven strategy has been developed for deuterium evolution. Deuterium is a critical resource for many aspects. However, the limited natural abundance of deuterium and the complexity of established technologies, such as quantum sieving (QS) for deuterium production under extreme conditions, pose challenges. The new method has the potential for robust and sustainable deuterium evolution, enabling deuterium production at a high rate of 9.745 mmol g-1 h-1 . The activity, thermodynamic, and kinetic characteristics are also investigated and compared between photocatalytic heavy water (D2 O) splitting and water (H2 O) splitting. This study opens a new avenue to discover promising photocatalytic deuterium generation systems for advanced solar energy utilization and deuterium enrichment.

Understanding the effects of co-exposed facets on photocatalytic activities and fuel desulfurization performance in BiOCl singlet-crystalline sheets.

Two kinds of well-crystallized BiOCl singlet-crystalline sheets (BOC-01 with twin-facet co-exposure of {001} and {110} and BOC-02 with tri-facet co-exposure of {001}, {110}, and {010}) were prepared and characterized. The photocatalytic desulfurization performance of BOC-01 and BOC-02 was tested by using n-decane and tetradecane as model oil containing heterocyclic sulfur-containing compounds (benzothiophene, or dibenzothiophene, or 4,6-dimethyldibenzothiophene). The desulfurization performance showed that twin-facet co-exposed BOC-01 had a slightly higher photocatalytic activity than tri-facet co-exposed BOC-02. The differences of photocatalytic activity between BOC-01 and BOC-02 were further explored by paramagnetic resonance spectroscopy, ultraviolet diffuse reflectance spectroscopy, steady-state and time-resolved prompt fluorescencespectra. The results disclosed that the exciton effect in BOC-01 played a key role in photocatalytic activation of molecular oxygen, while BOC-02 mainly produced reactive oxygen species by charge transfer. Theoretical calculations further indicated that the photogenerated electrons are mainly distributed on the {110} facets and the photogenerated holes are mainly distributed on the {001} facets in BOC-01 and BOC-02. This work provides a useful clue for an in-depth understanding of the effects of co-exposed facets in BiOCl on photocatalytic performance.

DNA-Binding, Photocleavage, and Photodynamic Anti-cancer Activities of Pyridyl Corroles.

The DNA-binding, photocleavage, and antitumor activity of three free base pyridyl corroles 1, 2, and 3 have been investigated. The binding affinity toward CT-DNA decreases with increasing number of pentafluorophenyl, whereas the photocleavage activity toward pBR322 DNA becomes more efficient. Singlet oxygen was demonstrated as active species responsible for DNA cleavage. These corroles exhibited high cytotoxicity against three tested cancer cells (Hela, HapG2, and A549) and the cytotoxicity could be further enhanced under irradiation. Intracellular reactive oxygen species level was also monitored using HeLa Cells upon the combined treatment of corroles and light. These corroles could be absorbed by HeLa cells at low concentration. They can induce the decrease of mitochondrial membrane potential and apoptosis of tumor cells under irradiation.