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Electron adsorption ionization ion mobility spectrometry can be used to detect halogen-containing volatile organic compounds with high sensitivity. However, this traditional electron attachment detection method cannot distinguish between volatile organic compounds containing the same halogen. For different organic compounds containing the same halogen, the product ions formed by the dissociation electron attachment process are the same. In this article, we propose a novel negative corona discharge ion mobility spectrometry method to distinguish between and detect halogenated alkanes containing the same halogen according to the different electron attachment rates and reaction kinetic parameters of the different halogenated alkanes. Although these halogenated alkanes, which contain the same halogen, produce the same type of ions through the electron attachment process, their electron attachment rates are different from each other. In this work, the kinetic information is used as the fingerprint information for the tested samples to distinguish different halogenated alkanes. Five halogenated alkanes were successfully detected using this method. The results show that the method based on the electron attachment rate constant is feasible for the determination of halogenated alkanes containing the same halogen.

We searched the lowest-energy structures of hydrated calcium ion clusters Ca2+(H2O)n (n = 10–18) in the whole potential energy surface by the comprehensive genetic algorithm (CGA). The lowest-energy structures of Ca2+(H2O)10–12 clusters show that Ca2+ is always surrounded by six H2O molecules in the first shell. The number of first-shell water molecules changes from six to eight at n = 12. In the range of n = 12–18, the number of first-shell water molecules fluctuates between seven and eight, meaning that the cluster could pack the water molecules in the outer shell even though the inner shell is not full. Meanwhile, the number of water molecules in the second shell and the total hydrogen bonds increase with an increase in the cluster size. The distance between Ca2+ and the adjacent water molecules increases, while the average adjacent O-O distance decreases as the cluster size increases, indicating that the interaction between Ca2+ and the adjacent water molecules becomes weaker and the interaction between water molecules becomes stronger. The interaction energy and natural bond orbital results show that the interaction between Ca2+ and the water molecules is mainly derived from the interaction between Ca2+ and the adjacent water molecules. The charge transfer from the lone pair electron orbital of adjacent oxygen atoms to the empty orbital of Ca2+ plays a leading role in the interaction between Ca2+ and water molecules.

Veronicastrum latifolium (V. latifolium) is rich in biologically active flavonoids, and is widely used in folk medicine. The purpose of this study was to investigate flavonoids of V. latifolium, and evaluate its antioxidant, antimicrobial, and anti-inflammatory activities. Eight flavonoids including vitexin, luteolin, wogonoside, apigenin, hispidulin, chrysoeriol, acacetin, and pectolinarigenin were identified by LC–MS/MS. The purified extract was obtained by enriching crude extract of V. latifolium through macroporous adsorption resins (MARs). The antioxidant activity of the crude extract and purified extract was evaluated by (1,1-diphenyl-2-picrylhydrazyl) DPPH, (Ferric ion reducing antioxidant power) FRAP, and (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) ABTS assay. This study found that the crude extract and purified extract exhibited ability to scavenge free radicals, and the ability of the purified extract to scavenge free radicals was stronger than the crude extract in DPPH, ABTS, and FRAP assay. In addition, the antimicrobial activity of the crude extract and purified extract against five bacterial strains (Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), and Acinetobacter baumannii (A. baumannii)), and yeast (Candida albicans (C. albicans)) was investigated. The crude extract and purified extract displayed bacteriostatic effects against both gram-positive bacteria and yeast, and the bacteriostatic effects of the purified extract was stronger compared with the crude extract. The vitro cytotoxicity of the crude extract and purified extract against isolated rat peritoneal macrophages (RAW264.7) cells was considered that it was not toxic to RAW264.7 cells at the concentration of 25–300 μg/mL. Anti-inflammatory activity of the crude extract and purified extract was evaluated by their effects on nitric oxide (NO) production in lipopolysaccharide (LPS) induced RAW264.7 cells. The crude extract and purified extract significantly inhibited NO production in RAW264.7 cells at the concentration of 200 μg/mL and 300 μg/mL. This study indicated that V. latifolium has good antioxidant, antimicrobial, and anti-inflammatory effect.

A structure with new meta-atom is proposed. The meta-atom with C3 rotational symmetry consists of three slits. The slits are drilled in the metal. Based on this meta-atom, metasurface lenses with different functions are designed. It is based on the phase and amplitude modulation by tuning the rotational angle of the meta-atom. The rotational angle of each meta-atom is achieved by simulated annealing algorithm. Three kinds of focal lenses, which can realize one or two focus points on the left and right sides, have been designed in terahertz frequency. The finite-difference time-domain method is employed to verify and appraise the properties of the designed lenses. Simulation results show that the designed lenses can perform the preset functions well. It demonstrates that such meta-atom is more suitable for focusing metasurface in different directions. It will promote the lightness, miniaturization and integration of optical components. And it is more suitable for microwave and terahertz wavefront modulation.

Deoxyribozymes can catalyze various types of reactions mostly with metal ions as their cofactors. Here we demonstrate that three copper compounds with thiosemicarbazide or semicarbazide ligands, are highly active cofactors of Cu2+-dependent deoxyribozymes without any additional reagents. The maximum catalytic rate constant of the deoxyribozyme with dichloro(di-thiosemicarbazide)copper as a cofactor is ∼25-fold faster than Cu2+ cofactor under the same reaction condition. Using a variety of spectroscopies, electrochemistry, and mutagenesis, we demonstrate that both the three-dimensional structure and redox potential of the copper center of the cofactors are essential to the catalysis of deoxyribozymes. The cofactor interacts with the enzyme-substrate complex forming a ternary enzyme-substrate-cofactor complex, which is confirmed by changing the structure of the enzyme-substrate complex through varying the temperature, or mutating the active site of the enzyme and conserved site of the substrate. The result suggests that Cu2+-dependent deoxyribozyme requires a well-defined active site to carry out the catalysis proficiently.

The knowledge of the behavior of Te in nickel grain boundaries (GB) is of significant importance for the application of nickel alloys in molten salt reactors. The atomic structures, stabilities, segregation behaviors and diffusion barriers of Te are studied for the bulk, surfaces and four kinds of GBs of nickel. Our first-principles calculations indicate the segregation of Te is most favorable at Σ = 5 (021) GB and the weakest at Σ = 3 (111) GB. The diffusion barriers of Te increase in sequence: Σ = 11 (11), Σ = 9 (221), Σ = 3 (111) and Σ = 5 (021). The calculated diffusion barrier of Te on Σ = 11 (11) is 0.35 eV lower than in the bulk, indicating a fast diffusion of Te along this GB. We also consider the effect of strain on the diffusion and find it to be sensitive to the different GB types. When the tensile strain is up to 4%, the diffusion barriers of Te are lowered by 0.51 eV and 0.15 eV for Σ = 5 (021) and Σ = 11 (11), respectively. In contrast, this effect for Σ = 3 (111) is negligible.

A novel method is proposed to detect chloroform concentrations based on the kinetic parameters using ion mobility spectrometer with a negative corona discharge ion source operating at atmospheric pressure. Unlike conventional sample introduction mode, in this technique, CHCl3 enters into the drift tube from the end of drift region carried by the drift gas. There are two tails before Cl− and (CHCl3)·Cl− ion peaks, which fit to the ions formed in the drift region. Utilizing the kinetic parameters, concentration for CHCl3 can be calculated. This method not only offers a new way to get concentrations of CHCl3 under atmospheric pressure.

The mass-selected infrared photodissociation (IRPD) spectroscopy combined with quantum chemical calculations was utilized to study the interactions between niobium dioxide cation and carbon dioxide molecules. Experimental and calculated results indicate that the CO2 molecules are weakly bound to the NbO2+ cation in an end-on configuration via a charge-quadrupole electrostatic interaction. For n ≥ 6, CO2 molecules in the second shell no longer have contribution to CO2 activation. The similarity of experimental spectra for n ≥ 7 also indicates that ion cores of NbO2+(CO2)n cluster have not changed. Compared with the congeneric YO+ complexes (Phys. Chem. Chem. Phys., 2018, 20, 19314–19320), NbO2+ is found to be thermodynamically and kinetically more difficult to react with CO2.

The Biome-BGC (biome biogeochemical cycles) model is widely used for modeling the net primary productivity (NPP) of ecosystems. However, this model ignores soil water changes during the freeze-thaw process in permafrost regions, which may lead to considerable errors in the NPP estimations. In this study, we proposed a numerical simulation method for improving soil water during the freeze-thaw process based on the field observation data of soil water and temperature. This approach does not require new parameters and has no impact on other modules. The improvement of soil water content during the freeze-thaw process was then incorporated in the Biome-BGC model for NPP in an alpine meadow in the central Qinghai-Tibetan Plateau (QTP). The results indicated that this method effectively reduced the RMSEs (root mean square errors) of the simulated soil moisture, leaf area index, and NPP, indicating that this approach performs well in the Biome-BGC model. This study suggested that the improvement of soil water content during the freeze-thaw process is also applicable to other models and, thus, could be a useful method to reduce the uncertainty of NPP estimations in permafrost regions.

It is well observed that some infectious diseases show a feature of periodicity; that is, the disease may prevail during a certain season and vanish afterwards. In the effort of understanding this specific phenomenon, in this paper, we propose a spreading model with a time-variant infectivity function considering both the features of periodicity and agent variability. We apply the modified model to a scale-free network frame with tunable power-law coefficient to find out the characteristics of periodic spreading dynamics. Our work consists of both theoretical derivation and a series of corresponding numerical simulations in order to find out the influence of the parameters of both network topology and the modified model on spreading dynamics in the underlined networks. The experiments prove the success of our model in producing a periodic behavior of spreading, and the results agree well with theoretical calculations.