Fe(III) oxyhydroxides play critical roles in arsenic immobilization due to their strong surface affinity for arsenic. However, the role of bacteria in Fe(II) oxidation and the subsequent ...immobilization of arsenic has not been thoroughly investigated to date, especially under the micro-oxic conditions present in soils and sediments where these microorganisms thrive. In the present study, we used gel-stabilized gradient systems to investigate arsenic immobilization during microaerophilic microbial Fe(II) oxidation and Fe(III) oxyhydroxide formation. The removal and immobilization of dissolved As(III) and As(V) proceeded via the formation of biogenic Fe(III) oxyhydroxides through microbial Fe(II) oxidation. After 30 days of incubation, the concentration of dissolved arsenic decreased from 600 to 4.8 μg L−1. When an Fe(III) oxyhydroxide formed in the presence of As(III), most of the arsenic ultimately was found as As(V), indicating that As(III) oxidation accompanied arsenic immobilization. The structure of the microbial community in As(III) incubations was highly differentiated with respect to the As(V)-bearing ending incubations. The As(III)-containing incubations contained the arsenite oxidase gene, suggesting the potential for microbially mediated As(III) oxidation. The findings of the present study suggest that As(III) immobilization can occur in micro-oxic environments after microbial Fe(II) oxidation and biogenic Fe(III) oxyhydroxide formation via the direct microbial oxidation of As(III) to As(V). This study demonstrates that microbial Fe(II) and As(III) oxidation are important geochemical processes for arsenic immobilization in micro-oxic soils and sediments.
In the engineering and economic management fields, optimisation models frequently involve different decision-making levels. These are known as multi-level optimisation problems. Because the ...decision-making process of such problems are hierarchical, they are also called a hierarchical optimisation problems. When the problem involves only two-level decision-making, the corresponding optimisation model is referred to as a bilevel programming problem(BLPP). To address the complex nonlinear bilevel programming problem, in this study, we design an evolutionary algorithm embedded with a surrogate model-that it is a approximation method and correlation coefficients. First, the isodata method is used to group the initial population, and the correlation coefficients of the individuals in each group are determined based on the rank of the leader and follower objective functions. Second, for the offspring individuals produced by the evolutionary operator, the surrogate model is used to approximate the solution of the follower’s programming problem, during which the points in the population are screened by combining the correlation coefficients. Finally, a new crossover operator is designed by the spherical search method, which diversifies the generated offspring. The simulation experimental results demonstrate that the proposed algorithm can effectively obtain an optimal solution.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Successive rotation and monoculture, as common silvicultural practices, are extensively applied worldwide, particularly in subtropical Chinese fir (
) plantations in southern China. Although ...regeneration failure and productivity decline are frequently observed in continuous monoculture plantations, the potential mechanisms are still unclear. In this study, high-throughput sequencing was used to compare the diversity and composition of bacterial and fungal communities among different generations of Chinese fir plantation (first rotation, FRP; second rotation, SRP; third rotation, TRP) and natural forest (NF) in December and June. Our results showed significant declines in richness and diversity of bacterial and fungal communities in TRP compared with FRP and SRP, but no significant difference between FRP and SRP. The fungal phyla with high relative abundance were
(12.9-76.9%) and
(14.3-52.8%), while the bacterial phyla with high relative abundance were
(39.1-57.7%) and
(21.2-39.5%) in all treatments at both sampling months. On average, the relative abundance of
in TRP increased by 53.4%, while that of
decreased by 37.1% compared with FRP and SRP. Moreover, soil NH
-N, pH, and DOC appear to be the key factors in shaping the fungal communities, while soil NH
-N, DOCN, and AP primarily drive the changes in bacterial communities. Collectively, our findings highlighted the alteration of soil bacterial and fungal communities induced by changes in soil nutrient environment in different generations of continuously cultivated Chinese fir plantation.
Comparison of the climate, especially extreme climate changes between the Little Ice Age (LIA) and the present, could provide important information for the predication of extreme climate change in ...the future. Based on a laminated stalagmite from the middle reaches of the Yangtze River, Central China, an annually resolved stalagmite record of growth rate has been produced dating from 1640 AD. An 11-year running variance sequence of the growth rate shows a positive correlation with a local historical flooding frequency record from 1640 to 1920 AD, suggesting that the stalagmite growth rate variance could be used as a local flooding frequency indicator. In the middle Yangtze catchment, the flooding frequency during the late LIA (1750–1900 AD) is much higher than during the middle LIA (1640–1750 AD) and the early twentieth century (1900–1920 AD). The discrepancy between the stalagmite growth rate variance and the flooding frequency after 1920s AD suggests that the scale of modern flooding is possibly larger than during the earlier periods. Spectral power analysis on growth rate variance of the stalagmite suggests that the flooding cycles around the middle Yangtze River catchment may relate to El Niño/Southern Oscillation (ENSO). The comparison between the stalagmite growth rate variance and reconstructed ENSO records further suggests a link between strong ENSO and high flooding frequency in the middle Yangtze catchment.
The evolutionary conserved WD-40 protein PRL1 plays important roles in immunity and development. Here we show that PRL1 is required for the accumulation of microRNAs (miRNAs) and small interfering ...RNAs (siRNAs). PRL1 positively influences the processing of miRNA primary transcripts (pri-miRNAs) and double-stranded RNAs (dsRNAs). Furthermore, PRL1 interacts with the pri-miRNA processor, DCL1, and the dsRNA processors (DCL3 and DCL4). These results suggest that PRL1 may function as a general factor to promote the production of miRNAs and siRNAs. We also show that PRL1 is an RNA-binding protein and associates with pri-miRNAs in vivo. In addition, prl1 reduces pri-miRNA levels without affecting pri-miRNA transcription. These results suggest that PRL1 may stabilize pri-miRNAs and function as a co-factor to enhance DCL1 activity. We further reveal the genetic interaction of PRL1 with CDC5, which interacts with PRL1 and regulates transcription and processing of pri-miRNAs. Both miRNA and pri-miRNA levels are lower in cdc5 prl1 than those in either cdc5 or prl1. However, the processing efficiency of pri-miRNAs in cdc5 prl1 is similar to that in cdc5 and slightly lower than that in prl1. Based on these results, we propose that CDC5 and PRL1 cooperatively regulate pri-miRNA levels, which results in their synergistic effects on miRNA accumulation, while they function together as a complex to enhance DCL1 activity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study was conducted to explore the changes in soil microbial populations, enzyme activity, and tuber yield under the rotation sequences of Potato-Common vetch (P-C), Potato-Black medic (P-B) and ...Potato-Longdong alfalfa (P-L) in a semi-arid area of China. The study also determined the effects of continuous potato cropping (without legumes) on the above mentioned soil properties and yield. The number of bacteria increased significantly (p < 0.05) under P-B rotation by 78%, 85% and 83% in the 2, 4 and 7-year continuous cropping soils, respectively compared to P-C rotation. The highest fungi/bacteria ratio was found in P-C (0.218), followed by P-L (0.184) and then P-B (0.137) rotation over the different cropping years. In the continuous potato cropping soils, the greatest fungi/bacteria ratio was recorded in the 4-year (0.4067) and 7-year (0.4238) cropping soils and these were significantly higher than 1-year (0.3041), 2-year (0.2545) and 3-year (0.3030) cropping soils. Generally, actinomycetes numbers followed the trend P-L>P-C>P-B. The P-L rotation increased aerobic azotobacters in 2-year (by 26% and 18%) and 4-year (40% and 21%) continuous cropping soils compared to P-C and P-B rotation, respectively. Generally, the highest urease and alkaline phosphate activity, respectively, were observed in P-C (55.77 mg g-1) and (27.71 mg g-1), followed by P-B (50.72 mg mg-1) and (25.64 mg g-1) and then P-L (41.61 mg g-1) and (23.26 mg g-1) rotation. Soil urease, alkaline phosphatase and hydrogen peroxidase activities decreased with increasing years of continuous potato cropping. On average, the P-B rotation significantly increased (p <0.05) tuber yield by 19% and 18%, compared to P-C and P-L rotation respectively. P-L rotation also increased potato tuber yield compared to P-C, but the effect was lesser relative to P-B rotation. These results suggest that adopting potato-legume rotation system has the potential to improve soil biology environment, alleviate continuous cropping obstacle and increase potato tuber yield in semi-arid region.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Let $P_r$ denote an almost-prime with at most $r$ prime factors, counted according to multiplicity. In this paper, it is proved that for every sufficiently large even integer $N$, the equation ...\begin{gather*} N=x^2+p_1^2+p_2^3+p_3^3+p_4^4+p_5^4 \end{gather*} is solvable with $x$ being an almost-prime $P_{4}$ and the other variables primes. This result constitutes an improvement upon that of L\"{u} \cite{7}. KCI Citation Count: 2
The heavy metal pollution, mainly caused by mining-related activities over extended period of time, is imposing a severe threat to environments and human health. Environmental systems, including ...rivers and paddy soils, have been widely established as one of the key sinks of potentially harmful metals. Aiming to understand contamination sources and pathways of Zn in karst area, we studied the Zn concentration and isotope composition of river waters, sediments, mine tailings, paddy soils, dust and three soil profiles with different levels of Zn-pollution around a Zn-mine, southwestern China. The distinct Zn isotope compositions among tailing (−0.42 ± 0.02‰), dust (−0.24 ± 0.02‰), and geogenic soil (−0.16 ± 0.03‰) allowed for separation of anthropogenic-Zn from native Zn. In the plot of δ66Zn value and 1/Zn, all samples can be explained by the mixing of three components: mining-input, agricultural input, and background. Evolution of these three components helps produce direct sources: dust and geogenic soil. Under this framework, the Zn pollution in paddy soil and sediment can be explained by mixing of mine-tailing, dust, and geogenic soil. Our study shows that the contamination of mine drainage is limited in the area due to the relatively high pH buffered by carbonate in karst area. While the dust contributes most of the anthropogenic Zn with an average value of 19.5%. The dominant pathway of anthropogenic Zn from dust to paddy soil or sediment is through the long-term wind dispersion of fine-grained material from the tailing and the physical transmission. Under the special hydrogeological conditions of karst, mining activities will increase the migration of heavy metals. The Fe-Al oxides control the migration of Zn in soil profile, but probably do not lead to significantly Zn isotopes fractionation. This further enhances the reliability of Zn isotopes as a “fingerprint” in karst area.
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•Tailings, rivers, sediments, dusts and soils were analyzed for Zn isotope ratios.•Anthropogenic Zn in karst area was mainly from dust through physical transmission.•Zn in paddy soil was imported by long-term wind dispersion of fine-grained material.•Pollution sources and pathways of heavy metals can be traced using Zn isotopes in karst area.
High temperatures are known to reduce anthocyanin accumulation in a number of diverse plant species. In potato (Solanum tuberosum L.), high temperature significantly reduces tuber anthocyanin pigment ...content. However, the mechanism of anthocyanin biosynthesis in potato tuber under heat stress remains unknown. Here we show that high temperature causes reduction of anthocyanin biosynthesis in both potato tuber skin and flesh, with white areas forming between the vasculature and periderm. Heat stress reduced the expression of the R2R3 MYB transcription factors (TFs) StAN1 and StbHLH1, members of the transcriptional complex responsible for coordinated regulation of the skin and flesh pigmentation, as well as anthocyanin biosynthetic pathway genes in white regions. However, the core phenylpropanoid pathway, lignin, and chlorogenic acid (CGA) pathway genes were up-regulated in white areas, suggesting that suppression of the anthocyanin branch may result in re-routing phenylpropanoid flux into the CGA or lignin biosynthesis branches. Two R2R3 MYB TFs, StMYB44-1 and StMYB44-2, were highly expressed in white regions under high temperature. In transient assays, StMYB44 represses anthocyanin accumulation in leaves of Nicotiana tabacum and N. benthamiana by directly suppressing the activity of the dihydroflavonol reductase (DFR) promoter. StMYB44-1 showed stronger repressive capacity than StMYB44-2, with both predicted proteins containing the repression-associated EAR motif with some variation. StMYB44-1 conferred repression without a requirement for a basic helix-loop-helix (bHLH) partner, suggesting a different repression mechanism from that of reported anthocyanin repressors. We propose that temperature-induced reduction of anthocyanin accumulation in potato flesh is caused by down-regulation of the activating anthocyanin regulatory complex, by enhancing the expression of flesh-specific StMYB44 and alteration of phenylpropanoid flux.
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