Electrochemical sensors have the advantage of fast analysis, low cost, high sensitivity, flexible and diverse technique, and excellent adaptability for in-situ analysis. This review introduces the ...recent advances in the field of electrochemical sensing of heavy metal ions (HMIs) based on polymers modified electrodes. In particular, the unique properties of polymers, excellent bridging ability, absorbing ability for HMIs, different conducting polymers and composites, and highly selectively ions imprinted polymers used for the detection of HMIs are highlighted.
Three-dimensional nickel oxide nanoparticles was synthesized by electrochemical method on the glassy carbon electrode previously modified with graphene oxide, which was applied for supercapacitor and ...nonenzymatic glucose sensor.
Based on the extraordinarily properties of graphene oxide (GO), nickel oxide nanoparticles (NiONPs)/GO/glassy carbon (GC) modified electrode was prepared by electrodeposition of NiONPs on the GC surface previously modified with GO, which was characterized by scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results showed that GO was partially reduced and three-dimensional NiONPs were electrochemically synthesized on the surface of GO. Compared with NiONPs/GC electrode, NiONPs/GO/GC modified electrode exhibited more excellent conductivity, more superior electrochemical capacitive behavior (16-folds) and better electro-catalytic oxidation of glucose, applying for the electrochemical detection of glucose. The linear range for glucose is from 3.13μM to 3.05mM with the detection limit of 1μM. In addition, the effects of common interfering species, including ascorbic acid (AA), uric acid (UA), and NaCl were investigated in detail. The result indicated that these foreign substances did not interfere significantly on the determination of glucose.
Agricultural non-point contaminants are the main source of groundwater nitrate in China. The source and transformation of groundwater nitrate in the intensive agricultural region must be understood. ...To elucidate the overall groundwater nitrate situation in Weifang (a typical representative intensive planting area), groundwater was sampled in 2009 and 2019, respectively. The hydrochemical compositions, nitrogen, and oxygen isotopes were measured to trace the source and transformation of the nitrate and quantify the proportional contribution of nitrate sources of groundwater (including sewage and manure (M&S), soil nitrogen (SN), chemical fertilizer (CF), and atmospheric deposition (AD)) in Weifang, China. The concentration of nitrates in groundwater generally decreased, and the groundwater quality improved significantly. The reasons for the variation of nitrate sources between 2009 and 2019 were likely due to the reduction in the amount of fertilizer, the number of livestock and the area of agricultural land. Land-use affected the concentration of nitrates in groundwater, which ranked as follows: vegetable greenhouse (VG) > winter wheat (WW) > drinking and domestic water (DW). Nitrification was the main process in the study area, and the effect of denitrification was weak. The study area was affected by mixed CF, SN, and M&S contaminants. According to the Bayesian isotope mixing model (SIAR), the proportional contribution of each source was ranked as follows: M&S (65.09%) > SN (17.97%) > AD (9.32%) > CF (7.63%). M&S is the main source of NO3−. In this research, identifying the source of nitrate pollution can cut off the source of pollution in a targeted way, ensure the safety of groundwater in Weifang and protect the agricultural environment of intensive agricultural area, which has significance for nitrate prevention and control in other places.
•The nitrate concentration in groundwater decreased in 2019 compare to 2009.•Using δ15N–NO3− and δ18O–NO3− isotopes to trace the nitrate sources in groundwater.•Contributions of sources rank as follows: manure > soil > rainfall > chemical fertilizer.•Reducing use of manure is critical to control nitrate contaminants.
Nonuniform sampling with equal arc length intervals can be found in shape measurements with contact sensor arrays. In this study, the conditions of nonuniform spatial sampling with an equal arc ...length interval are derived from two frame theorems. First, for general nonuniform sampling, the condition is that the equal arc length interval of the sensors should be less than
1
4
Ω
. Second, for strictly increasing sampling (the sampling point set is strictly increasing), the condition is that the equal arc length interval of the sensors should be less than
1
2
Ω
. The
Ω
is the maximum frequency of the detected object. For the latter, if the sampling frequency is more than twice the sampling frequency required, the reconstruction error (RRMSE and MRE) is less than 5%. If the sampling frequency is more than 2.5 times, the reconstruction error is less than 3%. The simulation and the application test are carried out, and the results show that a sensor array with equal arc length interval can reconstruct the detected object with high accuracy.
•This article presents an FBG-based method for submarine cable shape monitoring.•The Frenet framework is used in the paper to achieve the continuity of discrete curvature.•When the monitoring system ...from the article was used on the undersea landing cable, it discovered potential dangers.
Submarine cables are crucial in the transmission of electricity between coastal islands. Compared with terrestrial cables, submarine cables operate under harsher environments and thus their probability of failure is higher. Therefore, the effective monitoring of submarine cables is necessary to prevent related accidents. Quasi-distributed sensing technology based on fiber Bragg gratings converts the sensing information into discrete curvature information according to the pure bending theory and subsequently reconstructs the shape of the submarine cable using discrete curvature interpolation and curve reconstruction algorithms. The fiber Bragg grating sensor is placed on the landing cable section to analyze the reconstruction effect and error, demonstrating the feasibility of the method for submarine cable monitoring. Finally, the monitoring results in extreme weather reveal potential safety hazards in the submarine landing cable.
To systematically explore the influence of aromatic polycarboxylate coligands on building high-dimensional Cd(II)-bmb (1,4-bis(2-methylbenzimidazol-1-ylmethyl) benzene) coordination polymers, we ...synthesized six coordination polymers, namely {Cd(bmb)(o-phda)·H2O} n (1), Cd(bmb)0.5(m-phda) n (2), Cd(bmb)(p-phda) n (3), Cd(bmb)0.5(oba) n (4), Cd(bmb)(bpdc) n (5), Cd2(bmb)(bta)(mta)0.5 n (6), (H2phda = phenylenediacetic acid, H2oba =4,4′-oxybis(benzoic acid), H2bpdc = biphenyl-4,4′-dicarboxylic acid, H3bta =1,2,4-benzenetricarboxylic acid, and H2mta = 2-(methoxycabonyl)terephthalic acid) by varying aromatic polycarboxylate coligands. Structural analyses reveal that polymers 1–6 display diverse 3D frameworks and topologies, in which all of the N-donor ligands bmb exhibit trans-conformation but with different Ndonor···N–Csp3···Csp3 torsion angles. Polymer 1 shows a 3-fold interpenetrating dia array with a 4-connected 66 topology. Polymer 2 features a (3,4)-connected pillar-layered structure with (63)(65·8)-ins topology. Polymer 3 is a 4-connected framework with 66-dia topology and two types of meso-helical chains. Polymer 4 possesses a 2-fold interpenetrating 6-connected framework with (412·63)-pcu topology. The structure of polymer 5 is a 4-connected 5-fold interpenetrating architecture with 66-dia topology. Interestingly, in 6, part of bta3- anions are converted into a new ligand mta2- via in situ esterification reaction under solvothermal conditions. As a result, polymer 6 exhibits a scarce mixed-ligands framework with two O-donor and one N-donor ligands based on tetranuclear Cd(II) clusters. It is an 8-connected (36·418·53·6)-hex topology. A systematically structural comparison of these polymers indicates that the coordination modes of aromatic polycarboxylates along with the structural characteristics of the semirigid N-donor ligand bmb simultaneously play an important role in constructing the high-dimensional frameworks. Moreover, polymers 1–6 indicate high thermal stabilities and different photoluminescence behaviors in the solid state.
Ankle joint flexion and extension movements play an important role in the rehabilitation training of patients who have been injured or bedridden for a long time before and after surgery. Accurately ...guiding patients to perform ankle flexion and extension movements can significantly reduce deep vein thromboembolism. Currently, most ankle rehabilitation devices focus on assisting patients with ankle flexion and extension movements, and there is a lack of devices for effectively monitoring these movements. In this study, we designed an ankle joint flexion and extension movement-monitoring device based on a pressure sensor. It was composed of an STM32 microcontroller, a pressure sensor, an HX711A/D conversion chip, and an ESP8266 WiFi communication module. The value of the force and the effective number of ankle joint flexion and extension movements were obtained. An experimental device was designed to verify the accuracy of the system. The maximum average error was 0.068 N; the maximum average relative error was 1.7%; the maximum mean-squared error was 0.00464 N. The results indicated that the monitoring device had a high accuracy and could effectively monitor the force of ankle flexion and extension movements, ultimately ensuring that the patient could effectively monitor and grasp the active ankle pump movement.
Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this ...study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures δ(15)N(bulk), δ(18)O, and SP (intramolecular (15)N site preference) that emitted from vegetable soil after the addition of NH4(+) fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ(15)N(bulk) and δ(18)O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4(+) fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification.
•Novel β-nickel molybdate (β-NiMoO4) nanosheets were synthesized by a microwave-assisted solvothermal method.•The as-prepared NiMoO4 nanosheets exhibited strong absorption property for electroactive ...ferricyanide ion and graphite.•NiMoO4 nanosheets provided a potential catalytic platform for NADH and ethanol sensing.
Novel β-nickel molybdate (β-NiMoO4) nanosheets were synthesized by a microwave-assisted solvothermal method, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), and energy dispersive spectrum (EDS). The as-prepared NiMoO4 nanosheets exhibited strong absorption property for electroactive ferricyanide ion (Fe(CN)63−) and graphite, allowing their easy and stable modification on carbon paste electrode (CPE), which was demonstrated good electrocatalytic activity toward the oxidation of β-nicotinamide adenine dinucleotide (NADH). In addition, a nonenzymatic ethanol sensor based on NiMoO4 nanosheets was also first presented in this work.
To evaluate the effects of application of biochar and straw return for consecutive years on N2O emissions and crop yields in North China, a three-year field experiment of applying biochar and straw ...following a ten-year application was conducted in a wheat–maize rotation system. Four treatments were set up, including F (NPK fertilizer only); FB (NPK fertilizer + 9.0 t·ha−1 biochar); FS (NPK fertilizer + straw); and FSB ((NPK fertilizer + 9.0 t·ha−1 biochar combined with straw). The results showed that compared with the F treatment, the FB treatment significantly reduced soil N2O emissions by 20.2%, while the FS and FSB treatments increased it by 23.7% and 41.4%, respectively. The FB treatment reduced soil N2O emissions by 15.1% in the wheat season and 23.2% in the maize season, respectively. The FS and FSB treatments increased the N2O emissions by 20.7% and 36.7% in the wheat season, respectively, and by 25.5% and 44.2% in the maize season, respectively. In the wheat season, the soil water content (SWC), NO3−-N content and pH were the main influencing factors of the soil N2O emissions. In the maize season, SWC and NO3−-N content were the main influencing factors. In addition, the FB, FS and FSB treatments increased the crop yield by 4.99%, 8.40% and 10.25% compared with the F treatment, respectively. In conclusion, consecutive application of biochar can significantly reduce N2O emissions and improve crop yield. Although FS and FSB treatments can also improve the crop yield, they are not beneficial to suppressing N2O emissions. Therefore, the successive application of biochar is an effective measure to reduce N2O emissions and maintain crop yield.
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