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Abstract Fluoro‐ and chlorofluorocabons (FC/CFCs) are important refrigerants, solvents, and fluoropolymers in industry while being toxic and carrying high global warming potential. Detection and reclamation of FC/CFCs based on adsorption technology with highly selective adsorbents is important to labor safety and environmental protection. Herein, the study reports an integrated method to combine capture, separation, enrichment, and analysis of representative FC/CFCs (chlorodifluoromethane(R22) and 1,1,1,2‐tetrafluoroethane (R134a)) by using the highly stable and porous Zr‐MOF, DUT‐67. Gas adsorption and breakthrough experiments demonstrate that DUT‐67 has high R22/R134a uptake (124/116 cm3 g−1) and excellent R22/R134a/CO2 separation performance (IAST selectivities of R22/CO2 and R134a/CO2 ranging from 51.4 to 33.3, and 31.1 to 25.8), even in rather low concentration and humid conditions. A semi‐quantitative analysis protocol is set up to analyze the low concentrations of R22/R134a based on the high selective R22/R134a adsorption ability, fast adsorption kinetics, water‐resistant utility, facile regeneration, and excellent recyclability of DUT‐67. In situ single‐crystal X‐ray diffraction, theoretical calculations, and in situ diffuse reflectance infrared Fourier transform spectra have been employed to understand the adsorption mechanism. This work may provide a potential adsorbent for purge and trap technique under room temperature, thus promoting the application of MOFs for VOCs sampling and quantitative analysis.

Objective To compare the tooth drift differences between different types of patients after orthodontic extraction for 1.5 months (45 days) without return to the clinic on time for some reasons. Methods This study has been reviewed and approved by the Ethics Committee, and informed consent has been obtained from patients. A total of 84 patients had bilateral premolars extracted but were not bonded the bracket for some reasons. The upper and lower jaw dental models were cast, scanned, and reconstructed in 3D. Patients were divided into 12 groups based on extraction positions (first premolar or second premolar), jaw types (maxilla or mandible) and vertical facial types (average angle, high angle, or low angle). Multivariate analysis of variance was used to analyze the changes in the following five indicators in different types of patients who were interrupted for 1.5 months after extraction: anterior tooth crowding, width between canines, width between first molars, tooth extraction space, and overbite of anterior teeth. Results The tooth extraction position, jaw type and vertical facial type had an effect on the reduction in tooth extraction space and anterior tooth crowding before and after the sudden emergent state (1.5 months after tooth extraction) (P

A kind of fourth-order boundary value problem with eigenparameter-dependent boundary and transmission conditions is investigated. By constructing the characteristic function, we prove that the problems consist of a finite number of eigenvalues. We obtain that the number of eigenvalues of the problems not only depend on the order of the equation but also depend on the partition of the domain interval, the boundary conditions, and the eigenparameter-dependent transmission conditions.

A highly efficient separation method for trace plutonium from high uranium plutonium ratio samples was established by combining two Reillex anion exchange chromatographic columns. The effects of resin type, wash condition, valence state adjustment on plutonium separation were investigated, and the conditions of separation process were determined. When the mass ratio of uranium to plutonium in the feed liquid is 106, after two-stage Reillex column separation, the average yield of plutonium is 99.35% and the decontamination factor of uranium is greater than 107. Using this process, high purity trace 239Pu is separated from irradiated uranium target, and the atomic ratio of (238U+238Pu)/239Pu is (3.60±1.15)×10-5(n=6).

In the future, high-speed vehicles will develop towards the integration of aviation and aerospace technologies, such as longer range and faster speed, and constantly break through the boundary of flight speed and cruising space. With the continuous increase of flight speed, the thermal load is becoming more and more severe. Meanwhile, the requirements of multi-function integrated design of thermal protection structures and strong constraints on structural quality have put forward new requirements and challenges for thermal protection. In response to these, new features and needs of thermal protection are emerged, and the demand for thermal protection has undergone significant changes. There are obvious gaps in existing technologies, design methods, and recognition of relevant scientific issues, so revolutionary technologies are urgently needed. Therefore, the concept of new thermal barrier was proposed in this paper. It analysed the research status of long time heating, non-ablative heat protection and refined thermal environment prediction, pointed out the specific connotation and important development direction of new thermal barrier, reviewed the new direction and new methods being explored in thermal protection technology, including low ablative/non-ablative technology, system genome material design method, channel-based innovative thermal protection technology, etc. It is believed that solving the new thermal barrier is a scientific and technological problem to break through the limit of existing thermal protection technology, and it is necessary to break through the bottleneck problem of thermal protection of high-speed aircraft with multi-approach combination, multi-method synthesis and multidiscipline crossing. It explores innovative solutions to the problem of new thermal barrier from the aspects of refined thermal environment prediction and control, multi-scale performance prediction of thermal protection materials, new design approach of thermal protection materials, innovative thermal structure, etc. The progress of related research was summarized.

Abstract The spin degree of freedom is an important and intrinsic parameter in boosting carrier dynamics and surface reaction kinetics of photocatalysis. Here we show that chiral structure in ZnO can induce spin selectivity effect to promote photocatalytic performance. The ZnO crystals synthesized using chiral methionine molecules as symmetry-breaking agents show hierarchical chirality. Magnetic circular dichroism spectroscopic and magnetic conductive-probe atomic force microscopic measurements demonstrate that chiral structure acts as spin filters and induces spin polarization in photoinduced carriers. The polarized carriers not only possess the prolonged carrier lifetime, but also increase the triplet species instead of singlet byproducts during reaction. Accordingly, the left- and right-hand chiral ZnO exhibit 2.0- and 1.9-times higher activity in photocatalytic O2 production and 2.5- and 2.0-times higher activities in contaminant photodegradation, respectively, compared with achiral ZnO. This work provides a feasible strategy to manipulate the spin properties in metal oxides for electron spin-related redox catalysis.

Abstract Surface reconstruction generates real active species in electrochemical conditions; rational regulating reconstruction in a targeted manner is the key for constructing highly active catalyst. Herein, we use the high-valence Mo modulated orthorhombic Pr3Ir1−x Mo x O7 as model to activate lattice oxygen and cations, achieving directional and accelerated surface reconstruction to produce self-terminated Ir‒Obri‒Mo (Obri represents the bridge oxygen) active species that is highly active for acidic water oxidation. The doped Mo not only contributes to accelerated surface reconstruction due to optimized Ir‒O covalency and more prone dissolution of Pr, but also affords the improved durability resulted from Mo-buffered charge compensation, thereby preventing fierce Ir dissolution and excessive lattice oxygen loss. As such, Ir‒Obri‒Mo species could be directionally generated, in which the strong Brønsted acidity of Obri induced by remaining Mo assists with the facilitated deprotonation of oxo intermediates, following bridging-oxygen-assisted deprotonation pathway. Consequently, the optimal catalyst exhibits the best activity with an overpotential of 259 mV to reach 10 mA cmgeo −2, 50 mV lower than undoped counterpart, and shows improved stability for over 200 h. This work provides a strategy of directional surface reconstruction to constructing strong Brønsted acid sites in IrOx species, demonstrating the perspective of targeted electrocatalyst fabrication under in situ realistic reaction conditions.