[Responses of tree growth and intrinsic water-use efficiency of Robinia pseudoacacia to climate factors]. / åˆºæ§ç”Ÿé•¿å’Œå† åœ¨æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡å¯¹æ°”å€™å› å­çš„å“åº”.

We investigated tree growth in Robinia pseudoacacia plantations at Ansai in Shaanxi Province and at Ji-xian in Shanxi Province by comparing the tree-ring width, basal area increase (BAI), δ13C value, intrinsic water-use efficiency (iWUE), and stomatal regulation. We quantified the responses of tree growth and iWUE to climatic factors at each site. The tree-ring width at Ansai and Jixian decreased with stand age, whereas the BAI at Ansai increased, and that at Jixian decreased after the BAI peaked. The δ13C value and iWUE of trees at Jixian were higher than those at Ansai. The iWUE of trees at both sites was similar to the constant intercellular CO2 concentration/atmospheric CO2 concentration (Ci/Ca) scenario, indicating that the Ci of trees was elevated with increasing Ca, while the stomata remained open. The BAI at Ansai was significantly positively correlated with highest temperature in May, relative humidity in June, precipitation in August, relative humidity in September, and standardized precipitation evapotranspiration index (SPEI) in September and October of current year, but negatively correlated with temperature in June. The BAI at Jixian was significantly positively correlated with SPEI in June and July, and lowest temperature in October of current year. The iWUE of trees at Ansai was significantly positively correlated with relative humidity and precipitation in June of the current year, but negatively correlated with minimum temperature in May, relative humidity in June, and temperature and maximum temperature in July of current year. A significant positive correlation between iWUE of trees at Jixian and lowest temperature in June of current year was detected. At the annual scale, the BAI of trees at Ansai was positively correlated with precipitation and SPEI, but no significant relationship was observed for trees at Jixian. However, the iWUE of trees at both sites was significantly affected by precipitation. Path analysis showed that SPEI and minimum temperature had a direct effect on BAI and iWUE of trees at Ansai, whereas precipitation and average temperature indirectly affected BAI and iWUE through SPEI. The highest temperature had a direct effect on tree growth at Jixian, whereas precipitation, minimum temperature, and average temperature had direct effects on iWUE. These results suggested that SPEI was the main climatic factor that affected the growth of R. pseudoacacia, while Ci was an important physiological factor. Our results could provide reference for the protection and management of R. pseudoacacia plantations under climate change.

Size-controllable synthesis of Bi/Bi2O3 heterojunction nanoparticles using pulsed Nd:YAG laser deposition and metal-semiconductor-heterojunction-assisted photoluminescence.

We synthesized Bi/Bi2O3 heterojunction nanoparticles at various substrate temperatures using the pulsed laser deposition (PLD) technique with a pulsed Nd:YAG laser. The Bi/Bi2O3 heterojunction nanoparticles consisted of Bi nanoparticles and Bi2O3 surface layers. The average diameter of the Bi nanoparticles and the thickness of the Bi2O3 surface layer are linearly proportional to the substrate temperature. The heterojunctions between the Bi nanoparticles and Bi2O3 surface layers, which are the metal-semiconductor heterojunctions, can strongly enhance the photoluminescence (PL) of the Bi/Bi2O3 nanoparticles, because the metallic Bi nanoparticles can provide massive free Fermi-level electrons for the electron transitions in the Bi2O3 surface layers. The enhancement of PL emission at room temperature by metal-semiconductor-heterojunctions make the Bi/Bi2O3 heterojunction nanoparticles potential candidates for use in optoelectronic nanodevices, such as light-emitting diodes (LEDs) and laser diodes (LDs).

Toward single-mode active crystal fibers for next-generation high-power fiber devices.

We report what we believe to be the first demonstration of a facile approach with controlled geometry for the production of crystal-core ceramic-clad hybrid fibers for scaling fiber devices to high average powers. The process consists of dip coating a solution of polycrystalline alumina onto a high-crystallinity 40-µm-diameter Ti:sapphire single-crystalline core followed by thermal treatments. Comparison of the measured refractive index with high-resolution transmission electron microscopy reveals that a Ca/Si-rich intragranular layer is precipitated at grain boundaries by impurity segregation and liquid-phase formation due to the relief of misfit strain energy in the Al2O3 matrix, slightly perturbing the refractive index and hence the optical properties. Additionally, electron backscatter diffractions supply further evidence that the Ti:sapphire single-crystalline core provides the template for growth into a sacrificial polycrystalline cladding, bringing the core and cladding into a direct bond. The thus-prepared doped crystal core with the undoped crystal cladding was achieved through the abnormal grain-growth process. The presented results provide a general guideline both for controlling crystal growth and for the performance of hybrid materials and provides insights into how one might design single-mode high-power crystal fiber devices.