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Surface modification techniques with plasma are widely investigated to improve the surface insulation capability of polymers under dry conditions, while the relationship between treatment method, surface physical and chemical properties, and wet flashover voltage is still unclear for inorganic ceramics. In this paper, the surface insulation properties of ceramics under wet conditions are improved using nanosecond-pulsed dielectric barrier discharge with PDMS as the precursor. The relationships between PDMS concentration and the water contact angle, dry and wet flashover voltages are obtained to acquire the optimal concentration. The surface charge dissipation test and surface physio-chemical property measurement with SEM, AFM, XPS are carried out to further explore the mechanism of surface insulation enhancement. The results show that film deposition with micron thickness and superhydrophobicity occurs at the PDMS concentration of 1.5%. The dry flashover voltage is increased by 9.6% due to the induction of deep traps, while the wet flashover voltage is increased by 66.7%. The gap between dry-wet flashover voltage is decreased by 97.4% compared with the untreated one due to the self-cleaning effect.

In recent years, improving the surface properties of large-scale insulation by plasma modification has attracted extensive attention with the development of power systems and high-tech industries. However, routine evaluations of the modification effect and uniformity require complicated tests after the plasma is powered off, which waste a lot of time and cannot regulate the modification effect online. In this study, a novel fluorescence-assisted dielectric barrier discharge (DBD) for fabricating a functional film is developed, and a rapid evaluation method of the modification effect and uniformity is proposed based on fluorescence coloring and image processing technologies. The results show that the addition of an organic fluorescent agent in the DBD with hexamethyldisiloxane (HMDSO) has no negative effect on the plasma discharge and modification effect, and the fluorescence-assisted DBD successfully fabricates the functional films with typical chromogenic groups (N-H and S═O) that exhibit typical fluorescence under an UV lamp. According to image processing and parameter extraction, the plasma-assisted fluorescent film is converted into a two-dimensional (2D) color map with nine color levels, and three characteristic parameters are proposed to evaluate the modification effect rapidly and directly. It shows that the warmer the color of the treated sample, the better the hydrophobicity and electrical insulating properties, where the red region represents the optimally modified surface, while the blue region represents the worst one. The area, shape, and integrity of the plasma modification are clarified quantificationally, which provides the possibility of further online evaluation of the modification effect and uniformity by the plasma treatment.

Soil mesofauna plays an important role in decomposing organic matter, recycling nutrients, and increasing nutrient availability. The effects of nitrogen (N) deposition and reduced precipitation on the litter-dwelling mesofaunal community and how this process affects litter decomposition remain poorly understood. Herein, a two-year simulated N deposition and throughfall reduction experiment was carried out in a natural evergreen broad-leaved subtropical forest to examine the effects of N deposition and reduced precipitation on soil mesofauna during litter decomposition. Four treatments were established: control (CK), N deposition (N), reduced precipitation (RP), and combined N deposition and reduced precipitation (N + RP). We collected and identified 19,782 individuals of mesofauna in litterbags during the whole experiment. Mites (Prostigmata, Mesostigmata, and Oribatida) and Collembola comprised almost 90% of the total number of individuals collected and dominated the soil mesofauna in our study. Our results revealed the negative effects of N deposition on the density of Oribatida mites and Collembola and the total density of soil mesofauna. Reduced precipitation significantly increased the density of Collembola and Oribatida mites and the total density of mesofauna and marginally significantly increased the density of Mesostigmata mites but decreased the diversity of mesofauna. The interaction effects of N deposition and reduced precipitation significantly affected the density of Prostigmata mites, Oribatida mites, Collembola, and the diversity of mesofauna. N deposition combined with reduced precipitation significantly inhibited litter decomposition, whereas no significant interaction effects were observed. Furthermore, correlation analysis indicated that litter mass loss was significantly positively correlated with the density of Prostigmata, Mesostigmata, and Oribatida, as well as the diversity of mesofauna. Overall, during the two-year decomposition process, our results suggest that N deposition and reduced precipitation interactively affected mesofaunal diversity and that N deposition adversely affected the mesofaunal community, while reduced precipitation increased the density of some groups but decreased mesofaunal diversity, consequently cascading on the decomposition of leaf litter.

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus. Increasing evidence suggests that microRNA-30c-5p (miR-30c-5p) participates in the pathogenesis of DN, but the mechanism has not been clearly understood. Therefore, this study aimed to investigate the biological role of miR-30c-5p in human DN progression in vitro. Compared with the controls, DN tissues and high glucose-induced HK-2 cells had significantly reduced miR-30c-5p levels, while ROCK2 expression was prominently elevated. Additionally, the miR-30c-5p mimic distinctly facilitated cell proliferation and blocked cell apoptosis and epithelial–mesenchymal transition (EMT). However, ROCK2 was a target gene of miR-30c-5p, and the effects of miR-30c-5p mimic on cell proliferation, apoptosis and EMT were reversed by ROCK2 upregulation in vitro. Furthermore, the pathogenesis of DN was regulated by the miR-30c-5p/ROCK2 axis via the PI3K/AKT pathway. MiR-30c-5p regulating cell proliferation, apoptosis and EMT through targeting ROCK2 via the PI3K/AKT pathway provides the novel potential target for clinical treatment of DN.

Terrestrial plants and fire have interacted for at least 420 million years1. Whether recurrent fire drives plants to evolve higher flammability and what the evolutionary pattern of plant flammability is remain unclear2–7. Here, we show that phylogeny, the susceptibility of a habitat to have recurrent fires (that is, fire-proneness) and growth form are important predictors of the shoot flammability of 194 indigenous and introduced vascular plant species (Tracheophyta) from New Zealand. The phylogenetic signal of the flammability components and the variation in flammability among phylogenetic groups (families and higher taxonomic level clades) demonstrate that shoot flammability is phylogenetically conserved. Some closely related species, such as in Dracophyllum (Ericaceae), vary in flammability, indicating that flammability exhibits evolutionary flexibility. Species in fire-prone ecosystems tend to be more flammable than species from non-fire-prone ecosystems, suggesting that fire may have an important role in the evolution of plant flammability. Growth form also influenced flammability—forbs were less flammable than grasses, trees and shrubs; by contrast, grasses had higher biomass consumption by fire than other groups. The results show that shoot flammability of plants is largely correlated with phylogenetic relatedness, and high flammability may result in parallel evolution driven by environmental factors, such as fire regime. Fire has shaped plant life for millions of years, but flammability as an inherited trait has been difficult to discern. This Letter reveals several predictors in the evolution of plant flammability.

Litter decomposition is a vital link between material circulation and energy flow in forest ecosystems and is intensely affected by global change factors, such as increased nitrogen (N) deposition and altered precipitation regimes. As essential nutrients, calcium (Ca), magnesium (Mg), and manganese (Mn) play crucial roles in plant energy metabolism, photosynthesis, and membrane transport of plants, and the major source of these nutrients is litter decomposition. However, the dynamics of Ca, Mg, and Mn during decomposition have been largely ignored. Thus, to better understand Ca, Mg, and Mn dynamics during leaf litter decomposition in the scenario of increasing N deposition and decreasing precipitation, we carried out a two-year field litterbag experiment in a natural evergreen broad-leaved forest in the central area of the rainy area of Western China. Two levels of N deposition (ambient N deposition and 150 kg·N·ha−1·y−1) and precipitation reduction (no throughfall reduction and 10% throughfall reduction) were set, i.e., control (Ctr: without nitrogen deposition or throughfall reduction), N deposition (N, 150 kg·N·ha−1·y−1), throughfall reduction (T, 10% throughfall reduction), and N deposition and throughfall reduction (NT, 150 kg·N·ha−1·y−1 and 10% throughfall reduction). We found that leaf litter Ca concentration increased in the early decomposition stage and then decreased, while Mg and Mn concentrations generally decreased during the whole period of decomposition. The amount of Ca showed an accumulation pattern, while Mg and Mn generally showed a release pattern. N deposition and throughfall reduction affected the Ca, Mg, and Mn dynamics, varying with different decomposition stages, i.e., N deposition significantly affected the concentration and amount of Ca, regardless of the decomposition stages, while throughfall reduction significantly affected the Ca concentration in the whole and early decomposition stages. N deposition significantly affected the concentration and amount of Mg in the whole and early decomposition stages, while throughfall reduction had no significant effects. Throughfall reduction significantly affected the concentration and amount of Mn in the whole and late decomposition stages, while N deposition had no significant effects. Ca concentration generally showed a significant positive linear relationship with mass loss in the early decomposition stage, Mg concentration showed a significant positive linear relationship with mass loss in the Ctr and N treatments in the early and late decomposition stages, Mn generally showed a significant negative linear relationship with mass loss, regardless of the decomposition stage. Overall, the results suggest that Ca accumulation is more likely affected by N deposition, while Mg and Mn releases are more likely affected by N deposition combined with throughfall reduction, particularly in the early decomposition stage.

Atmospheric pressure low-temperature plasma jet technology is widely used in biomedical field, but the diameter of plasma jet is only millimeter level, which constricts its applications for large-scale treatment, as the efficiency is relatively low. Even though the plasma jet array can broaden the treatment area, the performance is not uniform due to the gap between plasma plumes. Therefore, a uniform large-scale plasma jet which can be contacted by human body has great research prospects in biomedical field. In this paper, a plasma brush of 15mm width is produced using single-barrier dielectric barrier discharge structure and argon as discharge gas under the excitation of high-frequency AC power supply. By means of voltage-current waveforms, luminescence images, emission spectra and temperature nephogram, the optimal discharge conditions, active particle generation and plasma plume temperature of the plasma brush are analyzed. The results show that the length of the plasma brush increases with the increase of the amplitude of the excitation power supply voltage and the volume flow rate of argon gas. When the amplitude of the excitation power supply voltage is 18.0kV, and the volume flow rate of argon gas is 8.0L/min, the shape of the plasma brush is the best, and the U- shaped brush plasma with a length of 15.0mm can be formed. The maximum peak discharge current is less than 10.0mA, and the average discharge power is 3.9W. The emission spectra and temperature nephogram show that there are a lot of active particles such as OH, nitrogen and argon particles in the plasma brush, and the temperature of the plasma brush discharge plume is close to room temperature, which has a good prospect for biomedical applications. The safety of human contact is analyzed with the human equivalent impedance model, and verified with experiments.

Epoxy resin is widely used in insulating mediums in power system for their excellent electrical and mechanical properties. The improvement of the surface hydrophobicity of epoxy resin is key important to further enhance the insulating performance of epoxy resin. In this paper, the super-hydrophobic film is deposited on the surface of epoxy resin by a one dimensional Ar jet array driven by nanosecond pulse with hexamethyldisiloxane (HMDSO) addition. The influences of the plasma treatment time and the HMDSO content ratio on discharge characteristic and surface hydrophobicity of the deposited film are investigated by electrical and optical diagnoses, and surface physical and chemical measurements. With the optimized experimental conditions (60 s plasma treatment with 0.04 % HMDSO), the surface of the treated epoxy is found to be covered with dense coral like nano-particles with the scanning electron microscope (SEM) measurement. The Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyze the chemical changes of the surface of epoxy resin. And it is found that the original C=O, C-H and other organic functional groups were replaced by Si-O-Si, Si-(CH 3 ) and other Silicon-containing functional groups and the element ratio of Si was increased from 0.4% to 28.0%. The water contact angle increased from 60.3° of the untreated surface to 150.0° after plasma treated.

Ceramic material is widely used in power system as insulation devices, but wet flashover phenomenon always happens under rainy weather and humid environment. Its resistance to wet flash is quite important to the normal work of power system. In recent years, plasma material modification technology is used to improve the dry flashover of polymer materials, while the research on improving the wet flashover of inorganic ceramic needs to be further studied. In this paper, dielectric barrier discharge driven by nanosecond pulse power supply is used to treat ceramic with PDMS added in Ar. The relationship between PDMS concentration and wet flashover voltage of ceramics is obtained to achieve the optimal parameter. The experimental results show that with the increasing of the concentration of PDMS, the wet flashover voltage after the treatment first increases and then decreases. When the concentration of PDMS is 1.5%, the wet flashover voltage of the ceramic surface reaches the maximum, which increases by more than 50%. On this basis, in order to further explore the mechanism of ceramic modification, the physical and chemical properties of ceramic surface are characterized and analyzed. When the concentration of PDMS reached 1.5%, the ceramic surface is covered by silicon-containing film, and the surface roughness reached the maximum, resulting in the "lotus leaf effect" and the formation of superhydrophobic surface.

Wildfire is a widespread natural hazard that is expected to increase in areal extent, severity and frequency with ongoing changes in climate and land-use. One tool that has been used in an effort to reduce the damage caused by wildfires is green firebreaks: strips of low-flammability vegetation grown at strategic locations in the landscape. Green firebreaks are increasingly being recommended for wildfire management and have been implemented in many countries. The approach is particularly widely used in China, where more than 364,000 km of green firebreaks have been planted and a further 167,000 km are planned for construction before 2025. China is not only a world leader in the implementation of green firebreaks but has also led the way in testing the effectiveness of green firebreaks and in providing guidelines for green firebreak construction. However, most of this research has been reported in the non-English literature, and so is inaccessible to many readers. Here we review the extensive research on the construction and effectiveness of green firebreaks in China and examine how the lessons learned from this research could contribute to the effective implementation of green firebreaks globally. Chinese studies suggest that the ideal species for green firebreaks should meet trait requirements from three perspectives: ecological, silvicultural and economic. Green firebreaks with a multi-layered structure and a closed canopy have the potential to be an effective, long-term, biodiversity-friendly and low-cost tool for fire suppression, although they complement rather than replace other more traditional fire suppression approaches.

Background and Aims Human activities-mediated input of nitrogen (N) and phosphorus (P) to ecosystem may significantly affect soil hydrolyzing enzyme activities (Hy-EAs). However, the mechanisms underlying the responses of soil Hy-EAs to change in N and P availability remains unclear. Methods Here, a two-year field N and P addition experiment was conducted in a subtropical evergreen broad-leaved forest to elucidate the effects of N addition, P addition, and NP co-additions on soil Hy-EAs and biochemistry properties. Results The invertase, cellulase, and acid phosphatase activities were increased in N treatment but reduced in P treatment. The urease activity was reduced in N treatment but did not alter in P treatment. NP treatment significantly increased the invertase and cellulase activities. Furthermore, the cellulase activity was positively correlated with soil organic carbon concentration. The acid phosphatase activity was negatively correlated with microbial biomass carbon (MBC), total P, and available P concentrations. Whereas the urease activity was not strongly dependent on total N concentrations, but positively correlated with soil pH and MBC. These Hy-EAs were significantly correlated with C-to-P and N-to-P ratios, while no significantly correlation with C-to-N ratio. Conclusions Overall, our results indicated that N and P addition significantly affected the soil C-, N-, and P-hydrolyzing enzyme activities. With ongoing imbalanced N and P input in our studied subtropical evergreen broad-leaved forest, N addition may exacerbate the limitation of soil C and P availability, while the exogenous P addition may improve the soil C and P availability.

Plant flammability varies across species, but the evolutionary basis for this variation is not well understood. Phylogenetic analysis of interspecific variation in flammability can provide insights into the evolution of plant flammability. We measured four components of flammability (ignitability, sustainability, combustibility and consumability) to assess the shoot-level flammability of 21 species of Dracophyllum (Ericaceae). Using a macroevolutionary approach, we explored phylogenetic patterns of variation in shoot-level flammability. Shoot-level flammability varied widely in Dracophyllum. Species in the subgenus Oreothamnus had higher flammability and smaller leaves than those in the subgenus Dracophyllum. Shoot flammability (ignitability, combustibility and consumability) and leaf length showed phylogenetic conservatism across genus Dracophyllum, but exhibited lability among some closely related species, such as D. menziesii and D. fiordense. Shoot flammability of Dracophyllum species was negatively correlated with leaf length and shoot moisture content, but had no relationship with the geographic distribution of Dracophyllum species. Shoot-level flammability varied widely in the genus Dracophyllum, but showed phylogenetic conservatism. The higher flammability of the subgenus Oreothamnus may be an incidental or emergent property as a result of the evolution of flammability-related traits, such as smaller leaves, which were selected for other functions and incidentally changed flammability.

The atmospheric pressure plasma jet (APPJ) in Ar/TMS (Trimethysilanol) is used to improve the surface hydrophobicity of glass, and a jet array composed of three linear connected jets is generated to increase the treatment scale and area. The discharge characteristics of the jet array are studied to determinate the treatment parameters, and the surface properties of the glass are studied through water contact angle (WCA), AFM, SEM, FTIR and XPS. The effects of TMS content and treatment time on WCA are investigated, and the optimum treatment conditions for hydrophobicity modification are obtained. Results show that jet array plasma with good uniformity can be obtained at certain applied voltage. The WCA increases from 60° to its maximum value of 110° after treatments at treatment time of 240 s and TMS content of 0.04%. The plasma treatment can induce the incorporation of hydrophobic bonds such as Si-C, Si-O onto the surface and the changing of surface topography, and the replacement of hydrophilic bonds on the glass surface by active Si containing species produced in the plasma is the main reason accounting for the improvement of surface hydrophobicity. The variation of the intensities of Si species is found to agree well with those of the measured WCA values on the surface.

Electrical lifespan prediction is one of the key problems for the designers of switching apparatus. It is of great necessity to develop empirical correlations between the design parameters and the electrical lifespan. In this paper, a novel method using the arc erosion mass as the prediction variable is proposed to predict the electrical lifespan of high-voltage direct-current (HVDC) relays. The arc current waveforms are measured, and the arc erosion mass during each breaking operation is calculated based on the relationship between the arc current and the arc erosion rate. The arc erosion mass is accumulated until it reaches a threshold value, which is determined by the electrical lifespan experimental results using HVDC products. It is found that the arc erosion mass linearly accumulates with the lifespan, which is very convenient in the electrical lifespan prediction. Experiments are carried out with a parameter-adjustable device similar to the actual HVDC relay structure. Effects of two key design parameters, the arc-blowing magnetic field flux density and the contact breaking speed, of the electrical lifespan are investigated. The magnetic field flux density is changed in the range from 40 to 80 mT, and the breaking speed is varied from 0.85 to 1.3 m/s. The relationships between the lifespan and the magnetic field flux density as well as the breaking speed are regressively constructed. It is shown that the developed relationships can be used for HVDC relay electrical lifespan prediction.

Terrestrial plants and fire have interacted for at least 420 million years

Two mass erosion mechanisms or mass loss modes for electrodes during the repetitive arcing processes should be responsible for the failure of electromagnetic relays, and there are evaporation erosion and sputter erosion. Of these two, the evaporation erosion is believed to be the main failure mechanism for the electrodes used in low-current relays. Unfortunately, there is still no straight-forward model to predict the characteristics of the evaporation process on the electrodes. In this paper, heat transfer and fluid dynamics in the molten pool in silver contacts are coupled with the gas dynamics in the vicinity of arc spot to determine the evaporation rate due to static arc. The influences of input parameters, such as arc current and material properties, on the evaporation rate are analyzed. Of all those parameters, boiling point and thermal conductivity of the electrode are found to be the most significant influences on the evaporation rate. The transfer direction of mass due to electrode evaporation is discussed on the assumption of zero net material loss, and it is found to be directly related to the current and heat flux from the arc to the electrodes. The method used in this paper to evaluate the evaporation erosion characteristics can serve for strategies to alleviate evaporation erosion for relay electrodes.

Background Fluorescence in situ hybridization (FISH) is an efficient cytogenetic technology to study chromosome structure. Transposable element (TE) is an important component in eukaryotic genomes and can provide insights in the structure and evolution of eukaryotic genomes. Results A FISH probe derived from bacterial artificial chromosome (BAC) clone 299N22 generated striking signals on all 26 chromosomes of the cotton diploid A genome (AA, 2x=26) but very few on the diploid D genome (DD, 2x=26). All 26 chromosomes of the A sub genome (At) of tetraploid cotton (AADD, 2n=4x=52) also gave positive signals with this FISH probe, whereas very few signals were observed on the D sub genome (Dt). Sequencing and annotation of BAC clone 299N22, revealed a novel Ty3/gypsy transposon family, which was named as ‘CICR’. This family is a significant contributor to size expansion in the A (sub) genome but not in the D (sub) genome. Further FISH analysis with the LTR of CICR as a probe revealed that CICR is lineage-specific, since massive repeats were found in A and B genomic groups, but not in C–G genomic groups within the Gossypium genus. Molecular evolutionary analysis of CICR suggested that tetraploid cottons evolved after silence of the transposon family 1–1.5 million years ago (Mya). Furthermore, A genomes are more homologous with B genomes, and the C, E, F, and G genomes likely diverged from a common ancestor prior to 3.5–4 Mya, the time when CICR appeared. The genomic variation caused by the insertion of CICR in the A (sub) genome may have played an important role in the speciation of organisms with A genomes. Conclusions The CICR family is highly repetitive in A and B genomes of Gossypium, but not amplified in the C–G genomes. The differential amount of CICR family in At and Dt will aid in partitioning sub genome sequences for chromosome assemblies during tetraploid genome sequencing and will act as a method for assessing the accuracy of tetraploid genomes by looking at the proportion of CICR elements in resulting pseudochromosome sequences. The timeline of the expansion of CICR family provides a new reference for cotton evolutionary analysis, while the impact on gene function caused by the insertion of CICR elements will be a target for further analysis of investigating phenotypic differences between A genome and D genome species. Electronic supplementary material The online version of this article (10.1186/s12870-018-1519-7) contains supplementary material, which is available to authorized users.

Table S3. The genes inserted with CICR-LTR in GhAt and their homologous in GhDt. (DOCX 19 kb)

Table S1. Major BLASTN results of Scaf 02 with D5 and A2 genome. (DOCX 19 kb)

Background Dissecting genome organization is indispensable for further functional and applied studies. As genome sequences data shown, cotton genomes contain more than 60 % repetitive sequences, so study on repetitive sequences composition, structure, and distribution is the key step to dissect cotton genome. Results In this study, a bacterial artificial chromosome (BAC) clone enriched in repetitive sequences, was discovered initiatively by fluorescence in situ hybridization (FISH). FISHing with allotetraploidy cotton as target DNA, dispersed signals on most regions of all A sub-genome chromosomes, and only middle regions of all D sub-genome chromosomes were detected. Further FISHing with other cotton species bearing A or D genome as target DNA, specific signals were viewed. After BAC sequencing and bioinformational analysis, 129 repeat elements, size about 57,172 bp were found, accounting for more than 62 % of the BAC sequence (91,238 bp). Among them, a type of long terminal repeat-retrotransposon (LTR-RT), LTR/Gypsy was the key element causing the specific FISH results. Using the fragments of BAC matching with the identified Gypsy-like LTR as probes, the BAC-57I23-like FISH signals were reappeared. Running BLASTN, the fragments had good match with all chromosomes of G. arboreum (A2) genome and A sub-genome of G. hirsutum (AD1), and had relatively inferior match with all chromosomes of D sub-genome of AD1, but had little match with the chromosomes of G. raimondii (D5) genome, which was consistent with the FISH results. Conclusion A repeats-enriched cytogenetic marker to identify A and D sub-genomes of Gossypium was discovered by FISH. Combined sequences analysis with FISH verification, the assembly quality of repetitive sequences in the allotetraploidy cotton draft genome was assessed, and better chromosome belonging was verified. We also found the genomic distribution of the identified Gypsy-LTR-RT was similar to the distribution of heterochromatin. The expansion of this type of Gypsy-LTR-RT in heterochromatic regions may be one of the major reasons for the size gap between A and D genome. The findings showed here will help to understand the composition, structure, and evolution of cotton genome, and contribute to the further perfection of the draft genomes of cotton.

Axial and transverse magnetic fields are widely used in many kinds of switches to decrease the arc erosion. In this paper, the influence of these two kinds of magnetic fields on the arc phase transition was studied particularly for AgSnO2 contacts breaking a 28V/25A circuit. The experiments were carried out under resistive and inductive loads in an atmospheric environment. The relationships between flux densities ranging from 0 to 200mT and the arc duration were obtained. It was found that the transverse magnetic field was more efficient in balancing the arc phases and decreasing the arc erosion. The results can be used to guide the design of arc extinguishment systems in DC high power relays.