Effect of ZnO nanoparticles on anti-aging properties of polyurethane coating

Polyurethane nano-coatings were prepared by adding nano-concentrates with nanometer zinc oxide （nano-ZnO） to polyurethane coating. The dispersion state of nanoparticles was observed by TEM images. SEM observation and FT-IR analysis indicate that the nano-coating with 1% ZnO nanoparticles can retain better morphological structure than the nano-coating with 5% ZnO nanoparticles after 500 h accelerated aging. It is known from XPS analysis that the anti-oxidation properties of polyurethane coating are enhanced by 1% ZnO nanoparticles through the nano-network and destroyed by 5% ZnO nanoparticles due to the strong light catalysis. A small change in capacitances of nano-coatings with 1% ZnO nanoparticles before and after accelerated aging indicates that 1% ZnO nanoparticles improve the corrosion resistance of coating, while a large increase in capacitances of nano-coating with 5% ZnO nanoparticles before and after accelerated aging demonstrates that 5% ZnO nanoparticles damage the corrosion resistance of coating.     

Activation of northern margin of the North China Craton in Late Paleozoic: Evidence from U-Pb dating and Hf isotopes of detrital zircons from the Upper Carboniferous Taiyuan Formation in the Ningwu-Jingle basin

LA-MC-ICPMS U-Pb dating has been performed on detrital zircons from the Upper Carboniferous Tai-yuan Formation (N-8) in the Ningwu-Jingle Basin, west of the North China Craton (NCC). The ages of 72 detrital zircon grains are divided into three groups: 303―320 Ma (6 grains), 1631―2194 Ma (37 grains, peaked at 1850 Ma), 2318―2646 Ma (29 grains, peaked at 2500 Ma). Detrital zircons of Group 2 and Group 3 were likely derived from the basement of the NCC. Group 1 zircons exhibit 176Hf/177Hf ratios ranging from 0...     

Spatial analysis of intra-site use at a Late Paleolithic site at Shuidonggou,Northwest China

Intra-site spatial analysis provides an alternative perspective for understanding the functions of a site, and the occupational organization of early human living and activities associated with it. We examined features and cultural remains recovered from Locality 2 at Shuidonggou, a Late Paleolithic site, focusing on early occupants’ survival behaviors and settlement patterns, as indicated by evidence regarding the functional organization of the site. Three-dimensional data from unearthed remains (including lithic assemblages, faunal remains, ornaments, etc) were used to reconstruct intra-site use patterns of Cultural Layer 2, which yielded seven earth-pit hearths and tens of thousands of artifacts and bones. We discuss the population size and group composition, as well as the functions of the living spaces, based on the analysis of the hearth patterns and the ostrich eggshell ornaments surround the hearths. In conclusion, Cultural Layer 2 of SDG Locality 2 appears to have functioned as a base camp for ancient foragers, where occupants produced tools, as well as preparing and consuming food.     

Global warming accelerates the upfreezing of permafrost in arid middle Tianshan Mountains

Upfreezing is an important geomorphic process in the periglacial environment. It is a product of cold climate and thus an important part of the cryospheric processes. Based on the long-term positioning observations in the source area of the Urumqi River, this article represents an in-depth discussion of the characteristics of sorted circles and upfreezing mechanisms in the Tianshan Mountains. In the source area of the Urumqi River, the intensity of upfreezing is the highest within the top 25 cm near the surface, while targets with a diameter of 3 cm are least affected by upfreezing. There is no distinct difference between the centre with fine grains and the margin with coarse debris within the same sorted circle in terms of the intensity of upfreezing. The correlation analysis demonstrates that temperature plays an important role in upfreezing and the development of sorted circles. A long-time positioning observation of sorted circles reveals that periglacial landforms are sensitive to regional climate change and respond quickly to the temperature increase of the recent two decades. Enhanced upfreezing was found to be due to increased soil moisture content.     

Identification of a novel tillering dwarf mutant and fine mapping of the TDDL（T） gene in rice （Oryza sativa L.）

Rice plant architecture is an important agronomic trait that affects the grain yield. To understand the molecular mechanism that controls plant architecture, a tillering dwarf mutant with darker-green leaves derived from an indica cultivar IR64 treated with EMS is characterized. The mutant, designated as tddl（t）, is nonallelic to the known tiilering dwarf mutants. It is controlled by one recessive nuclear gene, TDDL（T）, and grouped into the dn-type dwarfism according to Takeda＇s definition. The dwarfism of the mutant is independent of gibberellic acid based on the analyses of two GA-mediated processes. The independence of brassinosteroid （BR） and naphthal-3-acetic acid （NAA） of the tddl（t） mutant, together with the decreased size of parenchyma cells in the vascular bundle, indicates that the TDDL（7） gene might participate in another hormone pathway. TDDL（T） is fine mapped within an 85.51 kb region on the long arm of rice chromosome 4, where 20 ORFs are predicted by RiceGAAS （http：//ricegaas.dna.affrc. go.jp/rgadb/）. Further cloning of TDDL（T） will benefit both marker assisted selection （MAS） of plant architecture and dissection of the molecular mechanism underlying tillering dwarf in rice.     

液相有机氢载体的催化研究与应用

氢能清洁高效、能量密度高，是理想的能源载体，也是公认的未来能源发展方向之一。氢气的存储是氢能利用的关键环节，目前仍没有完美适配所有场景的储氢材料，储氢技术的选择势必要以使用场景为导向。液相有机氢载体（liquid organic hydrogen carriers，LOHCs）作为一种液相储氢材料，在运输方面具有独特的应用优势。本文介绍了常见的液相有机储氢材料，重点探讨了适用于运输工具（车、船、航空器等）的LOHCs，综述其加氢/脱氢的催化研究进展、应用技术难点，并展望了其应用前景。     

Study of low-pressure premixed laminar n-heptane+propane/oxygen/nitrogen flames

Low-pressure premixed laminar n-heptane+propane/oxygen/nitrogen flames were investigated with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Three flames with different mass percentage of propane in the fuel blends of 0%, 10%, and 20% were studied. The combustion intermediates were identified by comparing the measured IEs with those values in literatures. Mole fraction profiles of the main species were compared among the three flames. The experimental results provide detailed data in understanding the combustion of n-heptane and n-heptane/propane blends in engine. They are also helpful in establishing and verifying the kinetic models. Supported by the National Natural Science Foundation of China (Grant Nos. 50636040 and 50521604)     

Optical limiting of niobic tellurite glass induced by self-trapped exciton absorption of the AgCl nanocrystal dopant

Niobic tellurite glass doped by silver chloride nanocrystal was prepared with the melting-quenching and heat treatment method, and the self-trapped exciton absorption band of the silver chloride nanocrystal was observed at 532 nm in the UV-visible absorption spectrum. The glass structure characteristics were investigated by Raman spectroscopy, and the mechanism of self-trapped exciton was analyzed by Jahn-Teller model. Its optical limiting was measured with 532 nm picosecond laser pulses, and the corresponding nonlinear absorption coefficient was measured with open-aperture Z-scan. The experimental results showed that optical limiting at 532 nm was attributed to free carrier absorption between the self-trapped state and the continuum band. Supported by Shanghai Leading Academic Discipline Project (Grant No. B408), National Basic Research Program of China (Grant Nos. 2006CB806006, 2006CB921105), Program for Changjiang Scholars and Innovative Research Team in University, Doctoral Program of High Education (Grant No. 20050269011) and Project sponsored by Shanghai Science and Technology Committee (Grant Nos. 06DJ14008, 07dz22025, 06QH14003)     

Density functional study on mechanism of CO oxidation with activated water on O/Au （1 1 1 ） surface

With density functional theory, the mechanism of water-enhanced CO oxidation on oxygen pre-covered Au （111） surface is theoretically studied. First, water is activated by the pre-covered oxygen atom and dissociates to OHads group. Then, OHads reacts with COads to form chemisorbed HOCOads, Finally, with the aid of water, HOCOads dissociates to CO2. The whole process can be described as 1/2H2Oads ＋ H2Oads ＋ 1/2Oads＋ COads→H3Osds ＋ CO2, gas. One CO2 is formed with only 1/2 pre-covered oxygen atom. That is why more CO2 is observed when water is present on oxygen pre-covered Au （111） surface. Activation energy of each elementary step is low enough to allow the reaction to proceed at low temperature.     

Tribological properties of La2O3 and CeO2 doped CoCrW coatings deposited by supersonic plasma spraying

A novel supersonic plasma spraying was used to prepare rare earth oxides doped CoCrW coatings. X-ray diffractometer, contact surface profiler, hardness tester, micro-friction and -wear tester and en- vironmental scanning electron microscope equipped with energy dispersive X-ray spectroscopy were employed to investigate the phase structure, surface morphology, microhardness, friction and wear properties of the sprayed coatings. The results show that rare earth oxide doped coatings have high microhardness and excellent tribological properties. Furthermore, the friction and wear mechanisms of sprayed coatings are also discussed.