Antibiotic pollution is becoming an increasingly serious threat in different regions of China. The distribution of antibiotics in water sources varies significantly in time and space, corresponding ...to the amount of antibiotics used locally. The main source of this contamination in the aquatic environment is wastewater from antibiotic manufacturers, large scale animal farming, and hospitals. In response to the excessive antibiotic contamination in the water environment globally, environmentally friendly alternatives to antibiotics are being developed to reduce their use. Furthermore, researchers have developed various antibiotic treatment techniques for the degradation of antibiotics, such as physical adsorption, chemical oxidation, photodegradation, and biodegradation. Among them, biodegradation is receiving increasing attention because of its low cost, ease of operation, and lack of secondary pollution. Antibiotic degradation by enzymes could become the key strategy of management of antibiotics pollution in the environment in future. This review summarizes research on the distribution of antibiotics in China’s aquatic environments and different techniques for the degradation of antibiotics. Special attention is paid to their degradation by various enzymes. The adverse effects of the pollutants and need for more effective monitoring and mitigating pollution are also highlighted.
Atomically thin two-dimensional (2D) layered materials, including graphene, boron nitride, and transition metal dichalcogenides (TMDs), can exhibit novel phenomena distinct from their bulk ...counterparts and hold great promise for novel electronic and optoelectronic applications. Controlled growth of such 2D materials with different thickness, composition, and symmetry are of central importance to realize their potential. In particular, the ability to control the symmetry of TMD layers is highly desirable because breaking the inversion symmetry can lead to intriguing valley physics, nonlinear optical properties, and piezoelectric responses. Here we report the first chemical vapor deposition (CVD) growth of spirals of layered MoS2 with atomically thin helical periodicity, which exhibits a chiral structure and breaks the three-dimensional (3D) inversion symmetry explicitly. The spirals composed of tens of connected MoS2 layers with decreasing areas: each basal plane has a triangular shape and shrinks gradually to the summit when spiraling up. All the layers in the spiral assume an AA lattice stacking, which is in contrast to the centrosymmetric AB stacking in natural MoS2 crystals. We show that the noncentrosymmetric MoS2 spiral leads to a strong bulk second-order optical nonlinearity. In addition, we found that the growth of spirals involves a dislocation mechanism, which can be generally applicable to other 2D TMD materials.
A highly efficient method for the synthesis of versatile cyclopentenones from readily available enynyl acetates via tandem Au(I)-catalyzed 3,3-rearrangement and the Nazarov reaction is developed. ...Significant substrate flexibility and excellent control of the double bond position in the cyclopentenone ring render this an attractive method for cyclopentenone synthesis.
Data-driven mechanical fault diagnosis has been successfully developed in recent years, and the task of training and testing data from the same distribution has been well-solved. However, for some ...large machines with complex mechanical structures, such as reciprocating pumps, it is often not possible to obtain data from specific sensor locations. When the sensor position is changed, the distribution of the features of the signal data also changes and the fault diagnosis problem becomes more complicated. In this paper, a cross-sensor transfer diagnosis method is proposed, which utilizes the sharing of information collected by sensors between different locations of the machine to complete a more accurate and comprehensive fault diagnosis. To enhance the model’s perception ability towards the critical part of the fault signal, the local attention mechanism is embedded into the proposed method. Finally, the proposed method is validated by applying it to experimentally acquired vibration signal data of reciprocating pumps. Excellent performance is demonstrated in terms of fault diagnosis accuracy and sensor generalization capability. The transferability of practical industrial faults among different sensors is confirmed.
An efficient, formal 4 + 2 synthesis of synthetically valuable piperidin-4-ones from secondary amines in two steps has been achieved via a key gold catalysis without the purification of tertiary ...amine intermediates. This reaction is selective toward the less-substituted alkyl group and shows moderate to excellent diastereoselectivities. Its synthetic potential in alkaloid synthesis is demonstrated in a highly diastereoselective synthesis of (±)-cermizine C.
A novel approach to generate Au-containing all-carbon 1,3-dipoles is developed via an unprecedented migration−fragmentation of ketals/acetals. These in situ generated dipoles undergo rapid 3+2 ...cycloaddition under mild conditions with various enones/enals, electron-rich aromatic aldehydes, and N-benzylindole, leading to flexible formation of highly functionalized dihydrofurans and cyclopentenes.
MicroRNAs（miRNAs）are small noncoding RNAs,which play a central role in gene expression regulation and have been considered as excellent biomarker candidates for clinical diagnosis and prognosis.So ...far,many miRNAs detection methods require polymerase chain reaction（PCR）amplification following reverse transcription of miRNAs.These processes are complicated and time-consuming.In this work,we have developed a simpler method for miRNA detection based on base stacking hybridization happening on the surface of NaYF_4：Yb,Er upconversion nanoparticles.In this method,the fluorescence of NaYF_4：Yb,Er upconversion nanoparticles were functionalized as a reference standard,which can improve the accuracy of miRNA detection.On the basis of these findings,we suggest this novel approach for miRNA detection could be applied as an accurate and specific technique for miRNAs detection.
In recent years, the sweet potato cultivar Jishu 25 has exhibited good characteristics for starch processing in northern China. The storage root dry matter yields of this cultivar can exceed one ton ...per mu (1/15 of a hectare) at nitrogen (N) rates of 60-90 kg ha-1 based on soil nutrient content. However, the effect of N fertilizer on the physicochemical properties of starches isolated from this cultivar has not been reported. In order to evaluate these effects, three different N rates, 0 (control, N0), 75 (N1), and 150 kg ha-1 (N2), were selected for a field experiment in 2017. The results showed that N1 exhibited the highest storage root yield and starch yield. Compared to the control group, N fertilizer significantly increased the total starch content while no significant difference was found in these between the N1 and N2 groups. The amylose (AM) content was highest in the N2 group and lowest in the N0 group. In addition, N fertilizer exhibited no significant effects on the values of D(v, 0.9), D 4, 3 and D 3, 2. Compared to the control group, N1 demonstrated significantly higher setback viscosity (SV), while N2 showed significantly higher peak viscosity (PV), cold paste viscosity (CPV) and SV. However, there were no significant differences in the hot paste viscosity (HPV), peak time and pasting temperature between the N1 and N2 groups. For the thermal properties of starch, there were no significant differences in peak temperature (Tp), conclusion temperature (Tc) or gelatinization enthalpy (ΔH) between the N1 and N2 groups. Overall, for the starch samples of cultivar Jishu 25, N fertilizer exerts significant effects on the starch content, AM content and viscosity properties but little effect on the particle size distribution and ΔH. 75 kg N ha-1 can easily lead to substantial planting benefits from the high storage root yield, dry matter yield and total starch content of this cultivar.
Electrophilic indole? Indoles, which are typically nucleophilic, can be made electrophilic through gold catalysis. By using an ortho‐azido group to deliver a nitrene intramolecularly, an arylalkyne ...is converted into a gold carbene intermediate containing an indole skeleton that is highly electrophilic at the 3‐position. A range of functionalized indoles is readily accessed by utilizing this strategy.
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