Search

Abstract: In this paper we study the projective vector field of a three-dimensional quasi-homogeneous system with weight and degree , . Projective vector fields of this kind are classified into two types. For one type, has no closed orbit and at most eight singularities, which lead to a global topology of the three-dimensional system. For the other type, has at most ten singularities. In addition, we show a relationship between and a Lienard system of this type. For both of them we obtain some conditions for the existence of limit cycles. [Copyright &y& Elsevier]

Combining phytoremediation plants and microorganisms is a promising method of remediating heavy metal contaminated soil. In this study, two manganese-tolerant strains were isolated from Mn slag and identified as Bacillus cereus HM5 and Bacillus thuringiensis HM7. These two Bacillus spp. have the ability to dissolve phosphorus, produce IAA and iron carrier. A pot experiment of Broussonetia papyrifera was conducted to explore potential of B. cereus HM5 and B. thuringiensis HM7 to improve effect of remedying Mn pollution by B. papyrifera. The strains were inoculated under different Mn treated (5 mmol/L, 50 mmol/L, Mn slag) respectively and the growth, root structure, root activity, physiological and biochemical characteristics of the leaves and accumulation of Mn for B. papyrifera were determinated. The effects of the soil environment to remediation were observed, the results showed that the biomass, total root length, surface area, crossings, tips, forks and root activity of B. papyrifera with inoculated strain were higher than those of the control group. The inoculation of these two Bacillus spp. increased the absorption of Mn by B. papyrifera and the concentration of Mn in the aerial parts of plants, indicating that the two strains could promote the growth of B. papyrifera and the accumulation of Mn. In addition, microbes reduced malonaldehyde content and the activities of antioxidant enzymes in leaves, suggesting that the two Bacillus spp. reduced Mn-induced oxidative stress. The principal component analysis showed that the added Bacillus strain prefer to promote plant root function maintenance and improve soil environment, rather than direct adsorption of heavy metals. These observations indicated that B. cereus HM5 and B. thuringiensis HM7 were valuable microorganisms, which could improve the remediating efficiency of B. papyrifera under Mn-contaminated soil. • B. cereus HM5/ B. thuringiensis HM7 improved the accumulation of Mn by B. papyrifera. • B. cereus HM5 and B. thuringiensis HM7 could reduce oxidative stress induced by Mn. • The strains promoted the growth of plant root system and improved soil environment. [ABSTRACT FROM AUTHOR]

Heavy metal pollution has become increasingly prominent, and bioremediation of heavy metal polluted areas is urgently needed. Broussonetia papyrifera is a pioneer tree species for vegetation restoration in the tailings area, while its molecular mechanism of heavy metal adaptation is not clear. Here, we report that a R2R3 MYB from B. papyrifera (BpMYB1) is involved in Cd accumulation by controlling the down-stream genes and mineral accumulation. Overexpression of BpMYB1 in B. papyrifera resulted in a significant increase in Cd accumulation and multiple gene transcription. Among the up-regulated genes, BpMYB1 could bind to ferrochelatase (BpFC2), basic helix-loop-helix transcription factor bHLH93 (BpbHLH93), and basic leucine zipper transcription factor bZIPs (BpbZIP1 , BpbZIP-CPC1) by recognizing TATCCAOSAMY (TATCCA) motif and related promoter segments. Further investigations revealed that overexpression of BpbZIP1 promotes the absorption of Cd, BpMYB1 regulate Cd uptake in plant relating to Fe accumulation without Fe-deficiency pathway via recognizing the downstream BpbHLH93 and involving in PCs biosynthetic pathway via recognizing the target BpFC2. Moreover, the Cd response effect mediated by BpMYB1 was boosted by interacting with a DELLA protein BpGAI1, a vital member of GA signaling. These results provide new insights into the molecular feedback mechanisms underlying BpMYB1-BpGAI1 controlled Cd uptake in plants, which will benefit for phytoremediation of Cd polluted soil. [Display omitted] • BpMYB1 overexpression benefits for Cd enrichment and tolerance of B. papyrifera. • BpMYB1 could regulate the transcription of multiple genes in Cd stress response. • The Cd stress response of BpMYB1 involves in the gibberellin-dependant signaling. • BpMYB1 could recognize downstream genes of BpFC2 , BpbHLH93 , BpbZIP1 , BpbZIP-CPC1. • BpFC2 , BpbHLH93 , BpbZIP1 , BpbZIP-CPC1 overexpression improves plant Cd uptake. [ABSTRACT FROM AUTHOR]

Abstract A novel ternary composite of graphitic carbon nitride (g-C 3 N 4)/graphene oxide (GO) sheets/BiFeO 3 (CNGB) with highly enhanced visible-light photocatalytic activity toward Cr(VI) photoreduction is prepared and characterized. The characterization and photocatalysis experiments corroborate its reasonable band gap, efficient charge separation and transfer, widened visible-light adsorption, easy solid-liquid separation, good stability and superior catalytic activity of CNGB. Three CNGB samples with different ratios of g-C 3 N 4 and BiFeO 3 (CNGB-1, -2, -3 with 2:4, 3:3, and 4:2, respectively), though possessing different adsorption ability, eventually remove all Cr(VI) ions via photocatalysis within 90 min. The catalytic efficiency of the composite is the highest at pH 2; increases in pH decrease the catalytic ability. The inorganic anions such as SO 4 −, Cl−, and NO 3 − only slightly affects the photocatalytic process. The matching of the band structure between BiFeO 3 and g-C 3 N 4 generates efficient photogenerated electron migration from the conduction band of g-C 3 N 4 to that of BiFeO 3 , which is also facilitated by the electron bridging and collecting effects of GO, and holes transfer from the valence band of BiFeO 3 to that of g-C 3 N 4 , yielding the efficient separation of photogenerated electron-hole pairs and the subsequent enhancement of photocatalytic activity. The research provides a theoretical basis and technical support for the development of photocatalytic technologies for effective application in wastewater treatment and Cr-contaminated water restoration. Highlights • g-C 3 N 4 /graphene oxide/BiFeO 3 (CNGB) ternary assembly is easily prepared. • CNGB shows excellent photocatalysis of Cr (Ⅵ) reduction and easy removal from water. • CNGB shows maximized efficiency at low pH. • CNGB have little chance of electron-hole recombination. • CNGB shows great visible-light response. [ABSTRACT FROM AUTHOR]

Abstract A novel aptamer sensor for ratiometric ochratoxin A (OTA) detection was constructed based on the host-guest competition mode. Firstly, the aptamer modified with methylene blue (MB) at its terminal was fixed on the surface of the gold electrode via the host-guest recognition with β-cyclodextrin (β-CD). Then the MoS 2 nanosheets/Au NPs nanocomposites were used for the signal amplification. When OTA was present, the configuration of MB-aptamer transformed from vertical linear to G-quadruplex, thus making itself unable to get close to the electrode surface and causing a decrease in the redox current of the MB-aptamer. Whereas the free ferrocenecarboxylic acid could recognize and occupy the vacant site and produce signals in the current, resulting in the “ratiometric” effect. Consequently, on the basis of the “dual-signal” principle, a highly sensitive detection of OTA was made, indicating that the OTA concentration had a linear response to the signal of sensor between 0.1 nM and 50 nM, and as low as 0.06 nM OTA had been detected. Overall, this method for OTA detection was constructed easily with high sensitivity and specificity, providing a significant platform for highly efficient detection of OTA in biological samples. Graphical abstract Image 1 Highlights • A novel electrochemical sensor for ochratoxin A detection was developed. • MoS 2 nanosheets-Au NPs nanocomposites were used for the signal amplification. • OTA aptamer ensures the specificity of detection. • The merit of β-CD with superior recognition capability was employed. • The ratiometric strategy could avoid the majority of the interferences and maintain higher precision. [ABSTRACT FROM AUTHOR]

The protective role of spermidine addition in media to Salix matsudana exposed to Pb was investigated by a hydroponic experiment in this study. The application of spermidine enhanced the biomass of S. matsudana exposed to Pb. Pb induced an increase in Pb levels in all organs of S. matsudana with the order of roots (maximum of 27616.0 mg/kg DW) > cuttings > twigs > leaves. Exogenous spermidine promoted the accumulation of Pb in the roots, but inhibited the Pb translocation to the shoots and thus the Pb content in the twigs and leaves. The Pb-induced decrease in the concentrations of spermidine, soluble protein, and nitric oxide was elevated by the application of spermidine in the leaves of S. matsudana . Exogenous spermidine could also effectively up-regulate the antioxidative capacity and reduced the accumulation of superoxide anion, hydrogen peroxide, malondialdehyde, and putrescine. The results suggested that S. matsudana could accumulate a high level of Pb in the roots, and exogenous spermidine could enhance S. matsudana tolerance to Pb by the synergistic promotion of Pb accumulation in the roots and the levels of spermidine, nitric oxide, and antioxidants in the leaves. [ABSTRACT FROM AUTHOR]

Modifying energy band structure and increasing absorption are two efficient strategies to improve the photocatalytic performance of semiconductor photocatalysts. In this study, a novel biochar (BC) based photocatalyst, nitrogen-doped (N-doped) BC based PbMoO 4 (NPBC) was developed by combining both strategies. After loading PbMoO 4 on poplar sawdust via in situ method, the composites were pyrolyzed in the presence of a certain amount of urea. Nitrogen doping successfully increased the specific surface area and narrowed the bandgap of the composite of PbMoO 4 @BC (PBC) to improve its adsorption-photocatalytic performance. NPBC-2, in which the ratio of PbMoO 4 : poplar sawdust was 3:1.6, exhibited excellent adsorption-photocatalytic removal for 40 mg L−1 tetracycline (TC) under visible light and the total removal rate was 88.25%, which was 1.60 and 3.46 folds of that for PBC and PbMoO 4, respectively. The adsorption kinetic of TC removal by NPBC-2 fitted well with pseudo fist order models, and the adsorption was dominated by the physical process. Vacancies (h+) and superoxide radicals (•O 2 −) were the main active species for TC photodegradation. In addition, after 5 cycles, the composite still exhibited high ability for TC removal. Therefore, N-doped BC based photocatalysts provided a feasible and effective way for the remediation of organism-contaminated water. • A novel PbMoO 4 @NBC catalyst was synthetic by combing precipitation and calcination. • The N doping shorten the band gap of the PBC. • The N-doped on PBC enhanced separation efficiency of electron-hole pairs. • The N-doped on PBC improved the adsorption capacity and removal efficiency of TC. [ABSTRACT FROM AUTHOR]

Developing broad-spectrum light reactions, effective charge separation, and easily recoverable photocatalysts were considered cost-effective pollution remediation methods. The ZnFe 2 O 4 /BC/ZnO composite was prepared to achieve these objectives, where biochar (BC) was used as a conductive channel and ZnFe 2 O 4 as a magnetic substance. Among them, the 0.6-ZBO composite performed the best, with photocatalytic removal of tetracycline (TC) reaching 85.6%. The photocatalytic degradation rated constant of 0.6-ZBO composite was 23.36 × 10−3 min−1, which was 7.6, 4.1, and 2.5 times higher than that of ZnFe 2 O 4 /BC, ZnO, and ZnFe 2 O 4 /ZnO samples, respectively. According to several characterization data, it was demonstrated that successful Z-scheme heterojunctions were constructed between ZnFe 2 O 4 and ZnO. The 0.6-ZBO complex increased the range of light absorption and strengthened the separation of electron-hole pairs, thus improving the redox ability of the complex. In the different water matrices, the stability of 0.6-ZBO was excellent and its ability to remove TC decreased slightly to about 11% after 5 cycles. This work provided a valuable approach to design a novel and efficient system for degrading organic pollutants in wastewater using magnetic biochar. [Display omitted] • A novel ZnFe 2 O 4 /BC/ZnO (ZBO) Z-scheme heterojunction was successfully constructed. • The ZBO heterojunction promotes the separation of electron-hole pairs. • BC as a conductive channel of ZnO and ZnFe 2 O 4. • The ZBO composite was relatively effective to remove TC from the wastewater. [ABSTRACT FROM AUTHOR]

Developing efficient and economical photocatalysts was considered as an efficient and economical strategy for pollution remediation. Herein, magnetically separable ZnFe 2 O 4 /CuWO 4 composites (ZW) had been developed via combining ZnFe 2 O 4 with CuWO 4. The composite with a mass ratio of 40% CuWO 4 (ZW-40) performed best, and the tetracycline hydrochloride (TC) removal by adsorption-photocatalysis of ZW-40 reached 86.5%. The photocatalytic degradation rated constant of it was 9.44 × 10−3 min−1, which was approximately 5.04 and 3.28 times compared to the ZnFe 2 O 4 and CuWO 4 samples, respectively. Pseudo-second-order kinetic models could describe well the TC adsorption process, in which chemisorption was the major driving factor, with the maximum adsorption at 23.56 mg g−1. The improved photo-catalytic capability owed to the formation of Z-scheme heterojunctions with ZnFe 2 O 4 and CuWO 4 , which improved the intensity of visible light absorption and enhanced the separation electron-hole pairs as well as the redox capability of the composite. ZW-40 was high stability as its removal ability of TC in different water conditions slightly dropped about 15% after 5 cycles. ZW-40 could effectively remove TC in different water matrix, its removal ability for 40 mg/L was as follows: super-pure water> municipal wastewater> swine farm wastewater. Hence, the complexation of ZnFe 2 O 4 with CuWO 4 provides a valuable strategy to improve the photocatalytic potential for ZnFe 2 O 4 -based catalysts as well as providing a promising pathway for water clarification. • A novel ZnFe 2 O 4 /CuWO 4 (ZW) Z-scheme heterojunction was successfully constructed. • Heterojunction between ZnFe 2 O 4 and CuWO 4 promotes the electron-hole pair separation. • Synergistic adsorption-photocatalysis could more effectively remove tetracycline. • The ZW composite was relatively effective to remove TC from the wastewater. [ABSTRACT FROM AUTHOR]

For highly efficient photocatalytic remediation of organic pollutants, broad-spectrum light response and effective charge separation are two key goals. To achieve these goals, a novel biochar (BC) modified PbMoO 4 composite catalyst was successfully synthesized in situ by combining coprecipitation with pyrolysis treatment of poplar sawdust and the technical feasibility of degradation of tetracycline (TC) with compound photocatalyst prepared from recovered agricultural and forestry residues was preliminarily demonstrated. The characterization demonstrated that the presence of BC narrowed the bandgap, enhanced visible light absorption as well as facilitated charge separation. Three composites (with the mass ratio of PbMoO 4 to BC = 1:4; 1:1; and 4:1, respectively) displayed higher activity than pure PbMoO 4. The results showed that the composite with the PbMoO 4 to BC ratio of 1:4 exhibited the best photocatalytic activity, for 150 mg L−1 TC the removal rate was 61.0%, and the rate constant was 8.1 × 10−3 min−1, while the photocatalytic activity of PbMoO 4 was 26.0% and 3.9 × 10−3 min−1. The reactions in the presence of radical quenchers indicated that holes (h+) and superoxide radicals (O 2 −) were the dominant active species for photodegradation. In different water matrices, for 150 mg L−1 TC solution the photocatalytic activity of optimal photocatalyst decreased as follows: ultrapure water > artificial sewage > farm sewage > municipal sewage. Moreover, the catalyst exhibited good stability over five cycles. Therefore, BC doped PbMoO 4 provides a useful strategy for improving the photocatalytic ability of PbMoO 4 -based photocatalysts and offers a promising method for water purification. [Display omitted] • Using poplar sawdust as biochar source realized the rational application of waste. • In situ synthesis enhanced the adsorption and photocatalytic activity of PbMoO 4. • Superior electrical conductivity of BC helps transport of photogenerated carrier. • BC strengthened the visible light response of PbMoO 4 @BC-1. • PbMoO 4 @BC-1 showed promising visible-light photodegradation for TC degradation. [ABSTRACT FROM AUTHOR]