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Warming strongly stimulates soil nitrous oxide (N(2)O) emission, contributing to the global warming trend. Submerged paddy soils exhibit huge N(2)O emission potential; however, the N(2)O emission pathway and underlying mechanisms for warming are not clearly understood. We conducted an incubation experiment using (15)N to investigate the dynamics of N(2)O emission at controlled temperatures (5, 15, 25, and 35°C) in 125% water-filled pore space. The community structures of nitrifiers and denitrifiers were determined via high-throughput sequencing of functional genes. Our results showed that elevated temperature sharply enhanced soil N(2)O emission from submerged paddy soil. Denitrification was the main contributor, accounting for more than 90% of total N(2)O emission at all treatment temperatures. N(2)O flux was coordinatively regulated by nirK-, nirS-, and nosZ-containing denitrifiers but not ammonia-oxidizing archaea or ammonia-oxidizing bacteria. The nirS-containing denitrifiers were more sensitive to temperature shifts, especially at a lower temperature range (5 to 25°C), and showed a stronger correlation with N(2)O flux than that of nirK-containing denitrifiers. In contrast, nosZ-containing denitrifiers exhibited substantial variation at higher temperatures (15 to 35°C), thereby playing an important role in N(2)O consumption. Certain taxa of nirS- and nosZ-containing denitrifiers regulated N(2)O flux, including nirS-containing denitrifiers affiliated with Rhodanobacter and Cupriavidus as well as nosZ-containing denitrifiers affiliated with Azoarcus and Azospirillum. Together, these findings suggest that elevated temperature can significantly increase N(2)O emission from denitrification in submerged paddy soils by shifting the overall community structures and enriching some indigenous taxa of nirS- and nosZ-containing denitrifiers. IMPORTANCE The interdependence between global warming and greenhouse gas N(2)O has always been the hot spot. However, information on factors contributing to N(2)O and temperature-dependent community structure changes is scarce. This study demonstrated high-temperature-induced N(2)O emission from submerged paddy soils, mainly via stimulating denitrification. Further, we speculate that key functional denitrifiers drive N(2)O emission. This study showed that denitrifiers were more sensitive to temperature rise than nitrifiers, and the temperature sensitivity differed among denitrifier communities. N(2)O-consuming denitrifiers (nosZ-containing denitrifiers) were more sensitive at a higher temperature range than N(2)O-producing denitrifiers (nirS-containing denitrifiers). This study’s findings help predict N(2)O fluxes under different degrees of warming and develop strategies to mitigate N(2)O emissions from paddy fields based on microbial community regulation.

Phosphorus is an essential life element, which can affect the activities and functions of denitrifiers. Both

Fertilizer applications have important effects on soil microbial abundance and community structure. In this study, total soil microbial DNA and RNA were directly extracted from paddy soils of N0 (control treatment, no nitrogen fertilizer), NPK (balanced fertilization), NPK+LS (balanced fertilization with additional 3.0 t·hm

A large number of researches showed that the N

The emissions of greenhouse gas in winter are often neglected, and the latest research results showed that N

A new polymer alloy has been developed by blending powder of UHMWPE and graphite into nitrile rubber for marine stern tube bearings. It has good self-lubrication performance, which decreases the friction coefficient under low speed conditions and the critical speed at which bearing vibration and noise occur. Experimental investigations have been completed to examine its physical properties, integrated bearing friction as well as dynamic characteristics of the system in vibration and noise environments. The results show that mechanical and physical properties of new alloy meet the requirements of ship standard CB/T769-2008. Stick-slip occurs at the critical speed of 0.27 m/s. The friction coefficient is only about 50% of the restricted value in USA millitary specification MIL-DTL-17901C(SH)(2005) at or less than the speed of 0.18 m/s, and reached a minimum value at the speed of 0.54 m/s. The permissible maximum value of local projected pressure is 0.7 MPa. The experimental results have confirmed the excellent low-speed performance and comprehensive function of the new Rubber/UHMWPE alloy which may be a good type of water-lubricated materials for marine stem tube bearings.

Poly (vinyl alcohol)/Hydroxyapatite (PVA-H/HA) composite prepared from aqueous solution of the polymer and dimethylsulfoxide (DMSO) by freezing and thawing method are developing to repair or replace articular cartilage. In the present study, the tribological behaviors of this composite were investigated in a three-factor, three-level designed experiment using an improved four-ball tester. Factors include sliding velocity, applied load and HA content of composite. Friction coefficient of the PVA-H/HA was found to depend significantly on load and sliding velocity, while HA content had small effects on the friction coefficient of PVA-HA composite in our investigation. We also found that wear loss of PVA-H/HA increased sharply with the increasing loads and HA content of specimen.

Using the basic principle of heat transfer, tribology and numerical simulation, a two-dimensional heat transfer model of the three-layer composite brake pair materials were established. The temperature fields of brake pairs during the process of friction were analyzed. Applied given heat loads at different time node on the brake pair model, the temperatures of different bicycle brake pairs were compared and analyzed. Results show that the improved surface structures of brake pair have positive effect on decreasing the temperature of contact areas than that of ordinary surface structure.

Porous UHMWPE with different character were prepared by hot press molding in Metallographic Sample Mounting. Friction and wear loss of porous UHMWPE samples were studied under different loads and lubricant on an improved tribological tester. The friction coefficient and wear loss of samples with porosity of 5.44% are lower than that of samples with porosity of 10.17%, which attribute to the better porous structure and extrusion effect of lubricant in testing. Among the increasing of loads, friction and wear loss of porous samples are enhance rapidly. It is also found that the thickness of porous layer has little effect on the tribological properties of porous UHMWPE.

Porous UHMWPE were prepared by hot press molding in Metallographic Sample Mounting. The tribological properties of normal UHMWPE and porous UHMWPE were studied under different loads and lubricant on an improved tribological tester. The friction coefficient and wear loss of porous UHMWPE are steady and low under low loads, which attribute to the porous structure and extrusion effect of lubricant in testing. The results also show that the lubricant of BSA is better than that of water by its high viscosity. Among the increasing of loads, friction coefficient and wear loss are enhance rapidly. Serious cutting is the wear mechanism for porous UHMWPE under high loads.

Porous ultra high molecular weight polyethylene (UHMWPE) materials have been developed by Hot Press molding technique in this investigation. The tribological behaviors of porous UHMWPE with different initial NaCl content were studied. The worn surfaces of UHMWPE and porous UHMWPE samples were examined using a Scanning Electron Microscope (SEM). It was found that the porous structure improved the wear resistance of porous UHMWPE with the proper initial NaCl content under water lubrication condition. The minimal wear loss was about 10.6mg in the case of the UHMWPE filled by 50% initial NaCl content, 43% less than that of pure UHMWPE sample.

Since electro-hydraulic servo system has fast response and highest control accuracy, it has been widely used in industrial application, including aircraft, mining, manufacturing, and agriculture, etc. With the fast development of computer science, it is feasible and available to evaluate the performance of the designed control system via virtual simulation before the practical usage of the system. In order to optimize the design procedure of the electro-hydraulic proportional controller, the co-simulation design method based on AMESim-Matlab is presented for the electro-hydraulic servo system in this paper. High accuracy of the mathematical model of electro-hydraulic servo system was full-fitted by the use of AMESim, and the advantage of high solving precision for large amount of calculation was full played using Matlab. The PID controller was employed to realize the efficient control of the motion of the hydraulic cylinder. The united simulation technique was adopted to verify the good performance of the designed control system. The simulation results suggest that the proposed method is effective for the design of electro-hydraulic servo systems and thus has application importance.

A field experiment was carried out to study the effects of combined applications of pig manure and chemical fertilizers on CH4 and N2O emissions, which were measured using the static chamber/gas chromatography method, and their global warming potentials in typical paddy fields with double-rice cropping in Hunan province. The results showed that the combined applications of pig manure and chemical fertilizers did not change the seasonal patterns of CH4 and N2O emissions from paddy soils, but significantly changed the magnitudes of CH4 and N2O fluxes in rice growing seasons as compared with sole application of chemical fertilizers. During the two rice growing seasons, the cumulative CH4 emissions for the pig manure and chemical nitrogen (N) fertilizer each contributing to 50% of the total applied N (1/2N + PM) treatment were higher than those for the treatments of no N fertilizer (ON), half amount of chemical N fertilizer (1/2N) and 100% chemical N fertilizer (N) by 54.83%, 33.85% and 43.30%, respectively (P0.05), whilst the cumulative N2O emissions for the 1/2N + PM treatment were decreased by 67.50% compared with N treatment, but increased by 129.43% and 119.23% compared with ON and 1/2N treatments, respectively (P0.05). CH4 was the dominant contributor to the global warming potential (GWP) in both rice growing seasons, which contributed more than 99% to the integrated GWP of CH4 and N2O emissions for all the four treatments. Both GWP and yield-scaled GWP for the treatment of 1/2N + PM were significantly higher than the other three treatments. The yield-scaled GWP for the treatment of 1/2N + PM was higher than those for the N, 1/2N and ON treatments by 58.21%, 26.82% and 20. 63%, respectively. Therefore, combined applications of pig manure and chemical fertilizers in paddy fields would increase the GWP of CH4 and N2O emissions during rice growing seasons and this effect should be considered in regional greenhouse gases emissions inventory.

Taking a long-term fertilization experiment in Taoyuan Agro-ecosystem Research Station under Chinese Academy of Sciences as the platform, and selecting four treatments (no fertilization, CK; rice straw returning, C; nitrogen, phosphorus and potassium fertilization, NPK; and NPK+C) as the objects, soil samples were collected at the tillering, booting and maturing stages of rice, and the abundance, composition and diversity of nifH-containing bacterial community were measured by real-time quantitative PCR and terminal restriction fragment length polymorphism (T-RFLP), aimed to understand the effects of rice straw returning on the nifH-containing bacterial community in paddy soil. Compared with CK, treatments NPK+C and NPK increased the abundance of nifH-containing microorganisms significantly (except at tillering stage), and NPK+C had the highest abundance of nifH-containing microorganisms. Under the effects of long-term fertilization, the composition of nifH gene community in CK differed obviously from that in the other three treatments. The nifH composition had definite difference between C and NPK, but less difference between NPK and NPK+C. Long-term fertilization did not induce significant changes in nifH diversity. Therefore, long-term rice straw returning not only induced the changes of nifH gene community composition, but also resulted in a significant increase in the abundance of nifH-containing community, and hence, the increase of soil nitrogen fixing capacity.

Due to the low temperature in winter, the emissions of greenhouse gas are often neglected. And the latest research results showed that there is continuous N2O emission in winter, therefore, research on understanding the No2O flux regulation is important for evaluating agricultural soil N2O emission. By using static chamber techniques, the N2O emission from soils under different land use patterns including fallow paddy field, rape cropping, honey pomelo orchard and abandon land in Taoyuan agricultural ecological experimental station of Chinese Academy of Sciences was measured. The results showed that fallow paddy field and rape cropping N2O emissions were obviously higher than those of the honey pomelo orchard and abandon land, and the total N2O flux in winter decreased in the order of rape croppingfallow paddy fieldhoney pomelo orchardabandon land. Cumulative N2O emission was 0.502, 0.392, 0.162 and 0.075 kg x hm(-2), respectively. Fallow paddy field and rape cropping N2O emissions accounted for large proportions of the annual N2O emissions, while honey pomelo orchard and abandon land had small contribution to the annual N2O emissions. The correlation analysis results showed that for different land use patterns, when the soil temperature5 degrees C, N2O emissions in winter and soil temperature had significant positive exponential correlation, and had little to do with moisture. This research showed that: when the soil temperature5 degrees C, the soil temperature was the leading factor in N2O emissions in winter under different land patterns; When the soil temperature5 degrees C, other environmental factors had comprehensive influences on the N2O emissions.

Investigations were conducted on the effects of intensive application of chemical fertilizers in crop production on soil nitrifier communities and the relationship between nitrifier communities and soil nitrification ability. Two series of vegetable soils were selected from Huangxing, Changsha, reflecting continuous vegetable cropping with about 20 years and new vegetable field with only about 2 years vegetable growing history. In each series five independent topsoils (0-20 cm) were sampled and each soil was a mixture of 10 cores randomly taken in the same field. Terminal restriction fragment length polymorphism (T-RFLP) and quantity PCR (Q-PCR) were used to determine the composition and abundance of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities. Results indicated that long-term and continuous vegetable cropping obviously changed the compositions of both AOB and AOA amoA gene, soil pH and Olsen-P content were the dominant factors affecting the composition of AOB amoA. In the vegetable soils, although the copy number of AOA amoA gene was about 5 times higher than AOB amoA gene, no significant correlation was detected between AOA amoA gene abundance and soil nitrification rate. It was not sure whether long-term and continuous vegetable cropping could shift the abundance of AOB and AOA, but it resulted in the enrichment of some dominant AOB species and increase of soil nitrification potential (PNF).

Soil samples were collected from three vegetable fields under different years of cultivation in Changsha suburbs of Hunan Province, South-central China to study the accumulation characteristics, risks, and sources of soil available nitrogen and phosphorus and heavy metals in the fields. With the increasing year of vegetable cultivation, the soil NO3(-)-N, Olsen-P, and heavy metals contents in the fields increased significantly. The average contents of soil NO3(-)-N, Olsen-P, and Cd in the vegetable fields having been cultivated for 1-2 years in Ningxiang County, 10-15 years in Changsha County, and 30 years in Kaifu District were 21.1, 31.9 and 0.33 mg x kg(-1), 42.0, 146.9 and 0.52 mg x kg(-1), and 49.5, 219.9 and 1.40 mg x kg(-1), respectively. The cumulative index (CI) of soil heavy metals generally followed the sequence of CdCuPbNiZn. Principal component analysis and cluster analysis showed that compared with soil NH4 OAc-extracted potassium, pH, organic matter and NH4(+)-N, that were dominated by natural factors, the soil Olsen-P and NO3(-)-N had the similar accumulation characteristics with the soil heavy metals, being mainly controlled by fertilization. It was considered that the soil environment and health quality of the vegetable fields in Changsha suburbs were not optimistic. The longer the cultivation year of vegetables, the more the soil NO3(-)-N, Olsen-P, and heavy metals accumulated in the fields. The accumulation of these elements in the fields could be primarily due to the long-term fertilization.

The effects of long-term (16 years) fertilization on the diversity and community structure of soil ammonia-oxidizing gene (amoA) and hydroxylamine-oxidizing gene (hao) in paddy soil were evaluated using the methods of polymerase chain reaction, cloning and sequencing. The soil samples were collected from the treatments of NPK (CK) and NPK plus rice straw (SR) of the long-term field fertilization experiment in Taoyuan Agro-ecological Experimental Station. The Shannon Indices showed that the diversity of amoA and hao in SR treatment was lower than that in CK, and LUBSHUFF statistical analyses demonstrated that the sequence compositions of both amoA and huo libraries were significantly different between CK and SR. The phylogenetic trees indicated that some clusters appeared in SR treatment but were not detected in CK treatment. As to amoA, only Nitrosospira besides the uncultured amoA sequences were cloned from the two treatments, while no Nitrosomonas species were detected. As to hao, the strains from Silicibacter and Methylococcus were dominant in CK, while in SR the strains from Nitrosospira and Nitrosomonas were dominant. Sum up, the long-term rice straw application has caused a remarkable impact on the diversity and community structure on Nitrosobacteria.

In order to investigate the effects of long-term application of nitrogen fertilizer on soil denitrifying communities, the diversities of nir genes (nirK and nirS) were studied using molecular approaches in the long-term paddy field experiment (started in 1990) located in Taoyuan. Analysis of clone sequences indicated that the nirK fragments from paddy soil showed close similarity (90.7%) to the nirK sequences registered in GenBank database, but were not related to any known strain. Whereas, most of the airS clones showed low similarity (74.7%) to the nirS gene fragments registered in GenBank. The Chao1 estimates showed that the diversity of nirK gene 13) OTUs] than in N treatment [(49 +/- 9) OTUs], but the difference was not significant. However, application of nitrogen fertilizer resulted in significant difference of nirS-community compared to CK. Nitrogen fertilizer had obvious effect on tbe community structure of nirK-denitrifiers (p0.022), but the nirS-containing community was not affected. Based on phylogenetic analysis, nirK clones grouped into three clusters with aggregations of some OTUs cloned from N treatment. Although nirS clones grouped into four clusters, the majority of the clones were attributed in one cluster. The results suggested that application of nitrogen fertilizer had a greater influence on the diversity of nirS-containing bacterial community than that of the nirK. However, the community structure of nirK-containing denitrifiers was more sensitive to nitrogen fertilization than that of the mrS.