[en] We investigate the collective synchronization of cicada chirping. Using both experimental and phenomenological numerical techniques, here we show that the onset of a periodic two-state acoustic synchronous behavior in cicada chorus depends on a critical size of population N_c = 21, above which a typical chorus state appears periodically with a 30 second-silence state in between, and further clarify its possibility concerning a new class of phase transition, which is unusually driven by population. This work has relevance to acoustic synchronization and to general physics of phase transition. (general)

[en] It has been emphasized that the temporal occurrence of earthquakes in various spatial areas and over ranges of magnitude may be described by a unique distribution of inter-earthquake intervals under suitable rescaling, implying the presence of a universal mechanism governing seismicity. Nevertheless, it is possible that some features in the fine temporal patterns of event occurrences differ between spatial regions, reflecting different conditions that cause earthquakes, such as relative motion of tectonic plates sharing a boundary. By abstracting the non-Poissonian feature from non-stationary sequences using a metric of local variation of event intervals Lv, we find a wide range of non-Poissonian burstiness present in the temporal event occurrences in different spatial areas. Firstly, the degree of bursty features in the occurrence of earthquakes depends on spatial location; earthquakes tend to be bursty in areas where they are less frequent. Secondly, systematic regional differences remain even if the overall correlation between burstiness and the rate of event occurrence is eliminated. Thirdly, the degree of burstiness is particularly high on divergent tectonic boundaries compared to convergent and transform boundaries. In this way, temporal patterns of event occurrences bear witness to the circumstances underlying event generation.

[en] A new program is developed to compute the beta delayed fission gamma spectrum, and applied to compute the spectra of n+²³⁵U, ²³⁹Pu and ²⁴¹Pu fissions wherein the recent nuclear database is adopted. The results show that most spectra are well in agreement with the data from ENDF/B-VII.0 library, and some are quite different, which should be caused by the improvement of the nuclear database.

[en] Highlights: • MoS₂ flakes are close loaded on CNTs, and further immobilized by a outer elastic protective layer of PPy. • Double electron channels are provided by tubular CNTs and PPy coating layers. • The composite electrode maintained a highly stable electrode structure during electrochemical reactions. • CNT/MoS₂@PPy anode material has excellent high-rate lithium storage performance. • The charge transfer characteristics are studied in detail by via various techniques. Molybdenum disulfide (MoS₂) has received extensive attention as a potential material for lithium-ion battery anodes, but its low electrical conductivity and poor cycle stability need to be overcome. This work uses carbon nanotubes (CNTs) to provide basic framework for the close attachment of MoS₂ flakes on it, and employs a outer elastic protective layer of polypyrrole (PPy) to further immobilize MoS₂. The combination of conductive CNTs and PPy provides efficient ionic/electronic channels for MoS₂ and helps to maintain high structure stability of the composite. The resultant CNT/MoS₂@PPy anode exhibit a capacity of 1220 mAh g⁻¹ at 200 mA g⁻¹ and a reversible high-rate capacity of 736.9 mAh g⁻¹ after 400 elongated cycles at 1000 mA g⁻¹. The origin of the excellent performance in the CNT/MoS₂@PPy composite is studied from the aspects of electrochemical reaction dynamics, electrochemical impedance and lithiation/delithiation mechanism. It is concluded that the CNT/PPy double electron channels bring reduced charge transfer resistance, accelerated Li⁺ diffusion and enhanced structure/performance reversibility during cycling. The composite also demonstrates capacitive-controlled process at high-rates, which further assures its excellent high-rate performance as anodes. All of the above factors are important internal reasons for the Li-storage performance of the CNT/MoS₂@PPy composite.

[en] Highlights: • The Pt@Ce₂/3DCN photocatalyst was successfully synthesized. • Pt@Ce₂/3DCN exhibit best ability of CO₂ photoreduction under UV light. • The synergy of CeO₂ and 3DCN improves the photocatalytic performance. The conversion of CO₂ into high value-added carbon-based compounds through photocatalytic reduction technology is considered as one of the more promising strategies to solve the greenhouse effect. And construction of heterojunction photocatalysts can promote the separation of photoelectron-hole pairs, so as to achieve higher activity of photocatalytic CO₂ reduction. Hence, Pt@Ce₂/3DCN heterojunction are prepared by calcination method and photoreduction technology. The photocatalytic results revealed that Pt@Ce₂/3DCN show better photocatalytic activity for reducing CO₂ into CO and CH₄, compared with 3DCN. Especially, Pt@Ce₂/3DCN shows the maximum photocatalytic activity of 4.69 and 3.03 μmol·h⁻¹·g⁻¹ for CO and CH₄ under UV light irradiation, respectively, and the reduction activity did not decrease significantly after five cycles. The enhanced photoreduction of CO₂ performance can be ascribed to the synergistic effects of the oxygen vacancies in CeO₂ for CO₂ activation and heterojunction for electron separation. Besides, Pt nanoparticles (NPs) on CeO₂/3DCN can further promote the transfer of electrons, resulting in higher photocatalytic activity.

[en] Soil contamination with heavy metals is a worldwide problem especially in China. The interrelation of soil bacterial community structure, antibiotic resistance genes, and heavy metal contamination in soil is still unclear. Here, seven agricultural areas (G1–G7) with heavy metal contamination were sampled with different distances (741 to 2556 m) to the factory. Denaturing gradient gel electrophoresis (DGGE) and Shannon index were used to analyze bacterial community diversity. Real-time fluorescence quantitative PCR was used to detect the relative abundance of ARGs sul1, sul2, tetA, tetM, tetW, one mobile genetic elements (MGE) inti1. Results showed that all samples were polluted by Cadmium (Cd), and some of them were polluted by lead (Pb), mercury (Hg), arsenic (As), copper (Cu), and zinc (Zn). DGGE showed that the most abundant bacterial species were found in G7 with the lightest heavy metal contamination. The results of the principal component analysis and clustering analysis both showed that G7 could not be classified with other samples. The relative abundance of sul1 was correlated with Cu, Zn concentration. Gene sul2 are positively related with total phosphorus, and tetM was associated with organic matter. Total gene abundances and relative abundance of inti1 both correlated with organic matter. Redundancy analysis showed that Zn and sul2 were significantly related with bacterial community structure. Together, our results indicate a complex linkage between soil heavy metal concentration, bacterial community composition, and some global disseminated ARG abundance.

[en] Highlights: • Phase-pure double perovskite La2Fe2-xCoxO6 was prepared. • Orthorhombic and trigonal structures were obtained depending on the ratio of Fe to Co. • La2Fe2-xCoxO6 is a new high Tc ferromagnetic semiconductor with tunable magnetic properties. • Theoretical ab initio calculations further support our experimental results. - Abstract: Double perovskite La₂Fe_2-xCo_xO₆ was prepared and studied. Orthorhombic and trigonal structures were obtained depend on the molar ratio of Fe to Co. Fe-rich sample demonstrate ferrimagnetic properties; with increasing content of Co, trigonal structure is favored and the net magnetic moment of sample decrease gradually to zero. Our experimental results were further supported by first-principle theoretical calculations and demonstrate that La₂Fe_2-xCo_xO₆ is a new high T_c ferromagnetic semiconductor with tunable magnetic properties and is thus a promising material for spintronics devices.