Youming Chen

The preparation and mechanical properties of Al-containing a-C : H thin films

Al-containing hydrogenated amorphous carbon (Al?C?:?H) films were deposited on silicon substrates using a mid frequency magnetron sputtering Al target in an argon and methane gas mixture. The composition, surface morphology, hardness and friction coefficient of the films were characterized using x-ray photoelectron spectroscopy, atomic force microscopy, nanoindentation and tribological tester. The Al?C?:?H films deposited at low CH4 content show high surface roughness, low hardness and high friction coefficient, similar to metallic Al films; in contrast, the Al?C?:?H films prepared under high CH4 content indicate low surface roughness, high hardness and low friction coefficient, close to that of hard a-C?:?H films as wear-resistance films.

Is photosynthetic acclimation to free-air CO2 enrichment (FACE) related to a strong competition for the assimilatory power between carbon assimilation and nitrogen assimilation in rice leaf?

Net photosynthetic rate (PN) of leaves grown under free-air CO2 enriched condition (FACE, about 200 µmol mol−1 above ambient air) was significantly lower than PN of leaves grown at ambient CO2 concentration (AC) when measured at CO2 concentration of 580 µmol mol−1. This difference was found in rice plants grown at normal nitrogen supply (25 g m−2; NN-plants) but not in plants grown at low nitrogen supply (15 g m−2; LN-plants). Namely, photosynthetic acclimation to FACE was observed in NN-plants but not in LN-plants. Different from the above results measured in a period of continuous sunny days, such photosynthetic acclimation occurred in NN-plants, however, it was also observed in LN-plants when PN was measured before noon of the first sunny day after rain. Hence strong competition for the assimilatory power between nitrogen (N) and carbon (C) assimilations induced by an excessive N supply may lead to the photosynthetic acclimation to FACE in NN-plants. The hypothesis is supported by the following facts: FACE induced significant decrease in both apparent photosynthetic quantum yield (Φc) and ribulose-1,5-bisphosphate (RuBP) content in NN-plants but not in LN-plants.

Determinant of photosynthetic capacity in rice leaves under ambient air conditions

At the grain-filling stage, net photosynthetic rate (PN), stomatal conductance (gs), and ribulose-1,5-bisphosphate carboxylation efficiency (CE) were correlated in order to find the determinant of photosynthetic capacity in rice leaves. For a flag leaf, PN in leaf middle region was higher than in its upper region, and leaf basal region had the lowest PN value. The differences in gs and CE were similar. PN, gs, and CE gradually declined from upper to basal leaves, showing a leaf position gradient. The correlation coefficient between PN and CE was much higher than that between PN and gs in both cases, and PN was negatively correlated with intercellular CO2 concentration (Ci). Hence the carboxylation activity or activated amount of ribulose-1,5-bisphosphate carboxylase/oxygenase rather than gs was the determinant of the photosynthetic capacity in rice leaves. In addition, in flag leaves of different tillers PN was positively correlated with gs, but negatively correlated with Ci. Thus gs is not the determinant of the photosynthetic capacity in rice leaves.

Changes in leaf photosynthesis of transgenic rice with silenced OsBP-73 gene

In comparison with its wild type (WT), the transgenic (TG) rice with silenced OsBP-73 gene had significantly lower plant height, grain number per panicle, and leaf net photosynthetic rate (PN). Also, the TG rice showed significantly lower chlorophyll (Chl), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO), RuBPCO activase, and RuBP contents, photosystem 2 (PS2) photochemical efficiency (Fv/Fm and ΔF/Fm′), apparent quantum yield of carbon assimilation (Φc), carboxylation efficiency (CE), photosynthetic electron transport and photophosphorylation rates as well as sucrose phosphate synthase activity, but higher intercellular CO2 concentration, sucrose, fructose, and glycerate 3-phosphate contents, and non-photochemical quenching of Chl fluorescence (NPQ). Thus the decreased PN in the TG rice leaves is related to both RuBP carboxylation and RuBP regeneration limitations, and the latter is a predominant limitation to photosynthesis.

Tribological Behavior of Sputtered Boron Carbon Nitride Coatings and the Influence of Processing Gas

This work describes the composition and bonding structure of boron carbon nitride (BCxNy) films synthesized by medium frequency magnetron sputtering from a boron target in a N2+CH4+Ar gas mixture. Varying the flow rate of methane in the applied gas mixture was used. The three elements of B, C and N were bonded each other and an atomic-level hybridized B-C-N had been formed in the films. The chemical bonds with carbon (B-C and C=N) were enhanced as carbon content in the films increased. The tribological behavior of BCN thin films was investigated using ball-on-disc tests and 100Cr6 balls as counter-faces. The coefficient of friction was reduced approximately from 0.8 to 0.18, and wear resistance was considerably improved by increasing the ratio of CH4 gas component from 0 to 40 sccm. By adding amount of CH4 (∼ 40sccm) in the deposition process the boron carbon nitride coating exhibited the lowest friction and highest wear resistance.