Testing Seven Hypotheses to Determine What Explains the Current Planthopper (Fulgoridae) Geographical and Species Richness Patterns in China.

Although many hypotheses have been proposed to understand the mechanisms underlying large-scale richness patterns, the environmental determinants are still poorly understood, particularly in insects. Here, we tested the relative contributions of seven hypotheses previously proposed to explain planthopper richness patterns in China. The richness patterns were visualized at a 1° × 1° grid size, using 14,722 distribution records for 1335 planthoppers. We used ordinary least squares and spatial error simultaneous autoregressive models to examine the relationships between richness and single environmental variables and employed model averaging to assess the environmental variable relative roles. Species richness was unevenly distributed, with high species numbers occurring in the central and southern mountainous areas. The mean annual temperature change since the Last Glacial Maximum was the most important factor for richness patterns, followed by mean annual temperature and net primary productivity. Therefore, historical climate stability, ambient energy, and productivity hypotheses were supported strongly, but orogenic processes and geological isolation may also play a vital role.

Effects of Deformation Texture and Grain Size on Corrosion Behavior of Mg-3Al-1Zn Alloy Sheets.

Effects of deformation texture and grain size on mechanical properties and corrosion behavior of the Mg-3Al-1Zn (AZ31) alloys were systematically investigated. The results revealed that the ultimate tensile strength (UTS) and fracture elongation (FE) significantly increased from 232 to 273 MPa and 12.5 to 26.4%, respectively. According to the immersion and electrochemical measurements, the results indicated that the corrosion resistance of the alloy was improved obviously. Via electron backscattered diffraction (EBSD), corrosion morphology showed that the propagation of local pitting corrosion was suppressed, which is ascribed to grain refinement, higher texture intensity, and lower dislocation density after rolling and subsequent annealing.

Effect of Sn Content on the Microstructure, Mechanical Properties and Corrosion Behavior of Biodegradable Mg⁻x (1, 3 and 5 wt.%) Sn⁻1Zn⁻0.5Ca Alloys.

The microstructure, mechanical properties and corrosion behavior of hot⁻rolled Mg⁻xSn⁻1Zn⁻0.5Ca (x = 1, 3 and 5 wt.%) alloys were investigated for possible application as biodegradable implants. The hot⁻rolled Mg⁻xSn⁻1Zn⁻0.5Ca alloys consisted of α-Mg matrix and Mg2Sn phase. The number of the Mg2Sn particles significantly increased and the grains were gradually refined (14.2 ± 1.5, ~10.7 ± 0.7 and ~6.6 ± 1.1 µm), while the recrystallized fraction significantly decreased with the increase in the Sn content, the Mg⁻1Sn⁻1Zn⁻0.5Ca alloy was almost completely recrystallized. Ultimate tensile strength (UTS) and tensile yield strength (TYS) increased slightly, reaching maximum values of 247 MPa and 116 MPa, respectively, for the Mg⁻5Sn⁻1Zn⁻0.5Ca alloy, and the elongation decreased with the increase in the Sn content; the Mg⁻1Sn⁻1Zn⁻0.5Ca alloy showed the highest elongation (15.3%). In addition, immersion tests and electrochemical measurements in Hank's solution revealed that the corrosion rates of Mg⁻xSn⁻1Zn⁻0.5Ca alloys increased with the increase in the Sn content. A model of the corrosion behavior was discussed for hot⁻rolled Mg⁻xSn⁻1Zn⁻0.5Ca alloys in Hank's solution. Among the Mg⁻xSn⁻1Zn⁻0.5Ca (x = 1, 3 and 5 wt.%) alloys, Mg⁻1Sn⁻1Zn⁻0.5Ca alloy exhibits optimal corrosion resistance and appropriate mechanical properties.