Correlation between the topologically close-packed structure and the deformation behavior of metallic Cu64.5Zr35.5.

The topologically close-packed (TCP) structural characteristics in a model metallic glass (MG) of Cu64.5Zr35.5 have been investigated by molecular dynamics simulations. A group of structural indicators based on the largest standard cluster (LaSC) have been correlated with the non-affine displacement (D2) of atoms, so as to reveal the hidden correlation between local structures and deformation behavior of Cu64.5Zr35.5 during compression. It was found that the 15 types of Top-10 LaSCs are all TCP-like ones, among which the most numerous icosahedron (Z12 and 1-Z12) decreases in population sharply and moderately during respectively the elastic and yield region of compression; while in the fluid-flow region, the number of all Top-10 LaSCs tends to be almost constant. Low-D2 atoms prefer to link with each other; while medium-D2 atoms act as transition structures between backbone areas and deformation areas. Most interestingly, the deformation response of TCP-like atoms is not only determined by its nearest neighbor characteristics, but also depends on the linkage with other atoms. In addition, icosahedral atoms with a higher degree of medium range five-fold symmetry (MRFFS) are more resistant to the stress-induced deformation. Therefore, the TCP characteristics, including its nearest neighbor feature and the inter-connection between TCP LaSCs, are closely related with the deformation behavior of atoms, especially the MRFFS (up to 5 layers) of icosahedral atoms. These findings shed new light on the understanding of the relationship between microstructure and deformation response of MGs, which will promote the development of deformation theory of MGs.

Structural evolutions and hereditary characteristics of icosahedral nano-clusters formed in Mg70Zn30 alloys during rapid solidification processes.

To investigate the structural evolution and hereditary mechanism of icosahedral nano-clusters formed during rapid solidification, a molecular dynamics (MD) simulation study has been performed for a system consisting of 107 atoms of liquid Mg70Zn30 alloy. Adopting Honeycutt-Anderson (HA) bond-type index method and cluster type index method (CTIM-3) to analyse the microstructures in the system it is found that for all the nano-clusters including 2~8 icosahedral clusters in the system, there are 62 kinds of geometrical structures, and those can be classified, by the configurations of the central atoms of basic clusters they contained, into four types: chain-like, triangle-tailed, quadrilateral-tailed and pyramidal-tailed. The evolution of icosahedral nano-clusters can be conducted by perfect heredity and replacement heredity, and the perfect heredity emerges when temperature is slightly less than Tm then increase rapidly and far exceeds the replacement heredity at Tg; while for the replacement heredity, there are three major modes: replaced by triangle (3-atoms), quadrangle (4-atoms) and pentagonal pyramid (6-atoms), rather than by single atom step by step during rapid solidification processes.

[Effects of different long-term fertilization on the activities of enzymes related to carbon, nitrogen, and phosphorus cycles in a red soil].

Using a microplate fluorimetric assay method, five fertilization treatments, i.e. no-fertilizer control (CK) , sole application of nitrogen (N), balanced application of nitrogen, phosphorus, and potassium fertilizer (NPK), application of pig manure (M), and combination of pig manure with balanced chemical fertilizer (MNPK) were selected to investigate the effects of different long-term fertilization regimes on the activity of five enzymes (ß-1, 4-glucosidase, ßG; cellobiohydrolase, CBH; ß-1, 4-xylosidase, ßX; ß-1, 4-N-acetylglucosaminidase, NAG; acid phosphatase, AP) in a red soil sampled from Qiyang, Hunnan Province. The results showed that compared with CK treatment, N treatment had no impact on ßG, ßX, CBH, and NAG activities but reduced AP activity, while NPK, M and MNPK treatments increased the activities of all the five enzymes. Correlation analysis indicated that all the five enzyme activities were positively correlated with the content of nitrate (r=0.465-0.733) , the content of available phosphorus (r=0.612-0.947) , soil respiration (r=0.781-0.949) and crop yield (r=0.735-0.960), while ßG, CBH and AP were positively correlated with pH (r= 0.707-0.809), only AP was significantly correlated with dissolvable organic carbon (r = -0.480). These results suggested that the activities of the measured enzymes could be used as indicators of red soil fertility under different fertilization regimes, but the five enzymes tested provided limited information on the degree of acidification induced by application of mineral nitrogen.

[Degradation of oxytetracycline in chicken feces aerobic-composting and its effects on their related parameters].

In order to illustrate the degradation of tetracyclines (TCs) and their influences on process parameters during the period of chicken feces aerobic-composting, the degradation of oxytetracycline (OTC), a kind of TCs and its effects on parameters during the period of chick feces aerobic-composting including temperature, pH, and germination index were investigated using the method of aerobic-composting. The contents of OTC decreased gradually with composting time. The degradation rate was high before 10 d, and then decreased gradually. The differences in OTC degradation among the OTC treatments were also found. The degradation rate of OTC was higher at the level of 25 mg.kg-1, than that of other levels. The degradation curve of OTC could be described by the first-order kinetic model, and the correlation coefficients ranged from 0. 911 1 to 0. 9913. The impacts of OTC on chick feces composting were found. OTC could decrease the rising rate of composting temperature and make the high temperature (> or =50 degrees C) period shorter than that of the control. The values of pH, TN, WSC, and the content of NH: -N of composting were 4.58%, 12.62%, 49.06%, and 35.30% higher than those of the control. The impacts of OTC on maturity of chicken feces composting was not found when the OTC addition contents were lower than 50 mg.kg-1. However, the strong impacts of OTC on maturity of chicken feces composting were found when the OTC addition contents were higher than 50 mg.kg-1. The rates of NH+4 -N to NO-3 -N, and GI were much higher than 0. 5 and lower than 80% , respectively. Theses results suggest that OTC have strong impacts on chicken feces composting when the contents of TOC was higher than 50 mg.kg-1, although OTC have the short half-life period ranged from 1.79-4.88 d.

[Influences of long-term application of organic and inorganic fertilizers on the composition and abundance of nirS-type denitrifiers in black soil].

The objectives of this study were to explore the effects of long-term organic and inorganic fertilizations on the composition and abundance of nirS-type denitrifiers in black soil. Soil samples were collected from 4 treatments (i. e. no fertilizer treatment, CK; organic manure treatment, OM; chemical fertilizer treatment (NPK) and combination of organic and chemical fertilizers treatment (MNPK)) in Gongzhuling Long-term Fertilization Experiment Station. Composition and abundance of nirS-type denitrifiers were analyzed with terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR (Q-PCR), respectively. Denitrification enzyme activity (DEA) and soil properties were also measured. Application of organic fertilizers (OM and MNPK) significantly increased the DEAs of black soil, with the DEAs in OM and MNPK being 5.92 and 6.03 times higher than that in CK treatment, respectively, whereas there was no significant difference between NPK and CK. OM and MNPK treatments increased the abundances of nirS-type denitrifiers by 2.73 and 3.83 times relative to that of CK treatment, respectively. The abundance of nirS-type denitrifiers in NPK treatment was not significantly different from that of CK. The T-RFLP analysis of nirS genes showed significant differences in community composition between organic and inorganic treatments, with the emergence of a 79 bp T-RF, a significant decrease in relative abundance of the 84 bp T-RF and a loss of the 99 bp T-RF in all organic treatments. Phylogenetic analysis indicated that the airS-type denitrifiers in the black soil were mainly composed of alpha, beta and gamma-Proteobacteria. The 79 bp-type denitrifiers inhabiting exclusively in organic treatments (OM and MNPK) were affiliated to Pseudomonadaceae in gamma-Proteobacteria and Burkholderiales in beta-Proteobacteria. The 84 bp-types were related to Burkholderiales and Rhodocyclales. Correlation analysis indicated that pH, concentrations of total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), nitrate (NO3(-) -N) and ammonia (NH4(+) -N) were significantly related to abundances of nirS-denitrifers (r = 0.724-0.922, P < 0.05) and the DEA (r = 0.453-0.938, P < 0.01). In addition, the DEAs were linearly and positively correlated with the abundances of nirS-type denitrifers (r = 0.85, P < 0.01). Redundancy analysis showed that except moisture, pH and concentrations of TP, TP, TOC, NH4(+) -N and NO3(-) -N were significantly correlated with the community structure of nirS-type denirifiers (r = 0.440-0.862, P < 0.01). Furthermore, the DEAs were significantly correlated with the compositions of nirS-denirifiers (r = 0.863, P < 0.01). In conclusion, the airS-type denitrifiers in the black soil are more responsive to the organic treatments than to the inorganic treatments in terms of community composition and abundance, both of which are correlated with the changes of DEAs.

[Altered microbial communities change soil respiration rates and their temperature sensitivity].

Inoculating common sterilized soil with different non-sterilized soils was used to investigate the potentials of altered microbial communities to change rate and temperature sensitivity of soil microbial respiration. Results showed that accumulative CO2 emission of sterilized Hailun black soils inoculated with non-sterilized Harbin black soil, Fengqiu fluvo-aquic soil and Qiyang red soil were 684.25, 753.97 and 644.91 microg, respectively, at 15 degrees C; were 963.06, 1 015.44 and 852.31 microg, respectively, at 25 degrees C; and were 1 252.55, 380.36 and 1 177.88 microg, respectively, at 35 degrees C. The soil accumulative CO2 emissions increased with pH of inoculant soils, but did not relate to organic content of and geographical distance from inoculant soils. Difference of microbial respiration rates among the three inoculant soils kept for 104, 277 and 1 177 h at 15 degrees C, 25 degrees C and 35 degrees C, respectively. Temperature sensitivity quotients (Q10) of microbial respiration of sterilized Hailun black soils inoculated with non-sterilized Harbin black soil, Fengqiu fluvo-aquic soil and Qiyang red soil were 1.63, 1.49 and 1.80, respectively, during 0-104 h; were 1.43, 1.39 and 1.46, respectively, during 0-277 h and were 1.35, 1.35 and 1.35, respectively, during 0-1 609 h. The Q10 decreased with pH of inoculant soils and incubation time. The results suggest that altered microbial community would change rate and temperature sensitivity of soil microbial respiration.

[Effects of soil trituration size on adsorption of oxytetracycline on soils].

In order to understand the effects of soil trituration size on adsorption of oxytetracycline (OTC) on soils, two contrasting soils including moisture soil and purplish soil were selected to investigate adsorption of OTC on these soils, at the scales of no more than 0.20 mm, 0.84 mm, 0.25 mm and 0.15 mm, using the method of batch equilibrium experiments respectively. The results presented as the following: (1) Adsorption amount of OTC on moisture soil and purplish soil increased with the sampling time, and reached to equilibration at 24 h. First-order kinetic model, second-order kinetic model, parabolic-diffusion kinetic model, Elovich kinetic model, and two-constant kinetic model could be used to fit the changes in adsorption on soils with sampling time. Adsorption of OTC on two soils consisted of two processes such as quick adsorption and slow adsorption. Quick adsorption process happened during the period of 0-0.5 h. The adsorption rates of OTC on soils were higher at the small trituration size than those at the large trituration size, and at the same trituration size, the k(f) of purplish soil was about two times higher than those of moisture soil. (2) Adsorption isotherms of OTC on two soils with different trituration sizes were deviated from the linear model. The data were fitted well to Freundlich and Langmuir models, with the correlation coefficients between 0.956 and 0.999. The values of k(f) and q(m) for purplish soil were higher than those for moisture soil. At the same soil, adsorption amount of OTC increased with the decreases of soil trituration size. The results suggested that it is important to select the appropriate trituration size, based on the physical and chemical properties such as soil particle composition and so on, when the fate of antibiotics on soils was investigated.

[Effects of different long-term fertilizations on community properties and functions of methanotrophs in dark brown soil].

The microbial mechanisms of how different long-term fertilizations change methane oxidation of Chinese upland arable soil is unclear so far. In the present study, we attempted to investigate the "soil properties-community properties of methanotrophs-methane oxidation" relation of dark brown soil in Northeastern China under different long-term fertilization regimes. Community structure and abundance were monitored with PCR-DGGE and real time PCR, respectively. Methane oxidizing rate and soil properties were measured as well. The results show that combined use of mineral fertilizer and compost (MNP) reduce soil methane oxidation by 61.2%, whereas either mineral fertilizer (NP) or compost (M) shows no effect. Comparing with no fertilizer (CK), M and MNP increase the Shannon index of methanotrophs by 91.9% and 102.5%, respectively, whereas NP has no effect. Similarly, M ( M or MNP) significantly increases pmoA gene abundance by up to 12.7 folds compared with no M addition (CK or NP). Methane oxidizing rates are significantly correlated with community structure and specific activity of methanotrophs, with correlation coefficients of 0.363 and 0.684, respectively. However, methane oxidizing rates do not correlate with abundance and diversity of methanotrophs. In addition, community structures and specific activity of methanotrophs are significantly correlated with soil pH and content of total nitrogen and organic matter. Our results suggest that long-term different fertilizations may change soil properties (such as pH and content of total nitrogen and organic matter) and thereafter the community structure and specific activity of soil methanotrophs, by which long-term different fertilizations influence soil methane oxidizing rate. The opposite change of methane oxidation to methanotrophs diversity and abundance in MNP suggests that only parts of the methanotrophs are active, which needs further research.

[Effect of application of silicon on arsenic uptake by rice seedlings in soil].

The objective of study was to investigate effect of silicon on arsenic uptake by rice seedlings in two soils with different arsenic concentrations. The results show that the addition of silicon has little effect on shoot and root dry weights of rice seedlings. The addition of silicon did not affect shoot and root P concentrations of rice seedlings grown in low arsenic soil, but significantly increased shoot P concentrations on rice grown in high arsenic soil. Irrespective of the initial pH of K2SiO3 solution, the addition of silicon significantly decreased shoot and root As concentrations of rice seedlings compared with the control. For seedlings grown in low As-contaminated soil, As concentrations in shoot and root were reduced by 36%-59% and 15%-37% with the application of silicon, respectively. For seedlings grown in high As-contaminated soil, As concentrations in shoot and root were reduced by 42%-58% and 70%-82% with the application of silicon, respectively. These results are in agreement with our previous reports based on a solution culture experiment. Possible mechanisms of the effect of Si on As uptake was also discussed.