Ant–plant–herbivore interactions in the neotropical cerrado savanna

The Brazilian cerrado savanna covers nearly 2 million km² and has a high incidence on foliage of various liquid food sources such as extrafloral nectar and insect exudates. These liquid rewards generate intense ant activity on cerrado foliage, making ant–plant–herbivore interactions especially prevalent in this biome. We present data on the distribution and abundance of extrafloral nectaries in the woody flora of cerrado communities and in the flora of other habitats worldwide, and stress the relevance of liquid food sources (including hemipteran honeydew) for the ant fauna. Consumption by ants of plant and insect exudates significantly affects the activity of the associated herbivores of cerrado plant species, with varying impacts on the reproductive output of the plants. Experiments with an ant–plant–butterfly system unequivocally demonstrate that the behavior of both immature and adult lepidopterans is closely related to the use of a risky host plant, where intensive visitation by ants can have a severe impact on caterpillar survival. We discuss recent evidence suggesting that the occurrence of liquid rewards on leaves plays a key role in mediating the foraging ecology of foliage-dwelling ants, and that facultative ant–plant mutualisms are important in structuring the community of canopy arthropods. Ant-mediated effects on cerrado herbivore communities can be revealed by experiments performed on wide spatial scales, including many environmental factors such as soil fertility and vegetation structure. We also present some research questions that could be rewarding to investigate in this major neotropical savanna.     

Environmentally friendly bagasse pulping with NH4OH–KOH–AQ

Bagasse pulping trials were carried out with NH₄OH–KOH in the presence of anthraquinone for the purpose of reducing or eliminating the black liquor problem in pulping processes. The operating conditions, such as the composition of the cooking liquor, the liquid to bagasse ratio, the maximum cooking temperature and the cooking time at the maximum temperature during the pulping process were investigated systematically to establish optimal pulping conditions. The experimental results indicated that this pulping process is particularly well suited for the pulping of bagasse, where the bagasse was delignified to a low Kappa number value of 11.3, the percentage delignification was 80%, and the pulp yield was 65%. This newly developed pulping process provided a high tensile index of 51.6 N.m/g. The laboratory-scale experimental results were replicated on a pilot-scale process successfully, demonstrating the initial stages of scale-up and also demonstrating a degree of repeatability. There is a good prospect that this process can utilize black liquor, which contains nitrogen, phosphorus, potassium and ammoniacal lignin, as a fertilizer for agricultural production. Hence the black liquor problem associated with the pulping industry can potentially be turned into a benefit through this environmentally friendly bagasse pulping process.     

Cu–Mn–Ce ternary mixed-oxide catalysts for catalytic combustion of toluene

Cu–Mn, Cu–Mn–Ce, and Cu–Ce mixed-oxide catalysts were prepared by a citric acid sol–gel method and then characterized by XRD, BET, H₂-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu–Mn–Ce ternary mixed-oxide catalyst with 1:2:4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu–Mn–Ce catalyst, a portion of Cu and Mn species entered into the CeO₂ fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu–Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu–Mn and Cu–Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.     

Effect of mechanical surface treatments on Ti–6Al–4V direct metal deposition parts

The effect of surface treatments, including aggressive milling, rotational burnishing, and nonrotational burnishing, on Ti–6Al–4V DMD (direct metal deposition) parts was investigated. Particular emphasis is on the question of whether these surface treatments could induce the plastically deformed and work-hardened layer that was proven to enhance the fatigue resistance of titanium alloys and was a key step for recrystallization. Through the microhardness examination and microstructure analysis, it was found that the rotational burnishing process was able to work harden the material deeper than 1000 μm, while the work-hardened layer generated by the nonrotational process was ∼600 μm and that for aggressive milling was less than 10 μm. Because surface finish is another critical factor for the resistance of fatigue crack initiation, it was also evaluated for these treatments.     

Reduction of NO by CO using Pd–CeTb and Pd–CeZr catalysts supported on SiO_2 and La_2O_3–Al_2O_3

The catalytic activity of Pd catalysts supported on Ce0.73Tb0.27 O x/Si O2, Ce0.6Zr0.4O x/Si O2,Ce0.73Tb0.27 O x/La2O3–Al2O3and Ce0.6Zr0.4O x/La2O3–Al2O3was studied using the reduction of NO by CO. The catalysts were characterized by X-ray fluorescence, surface area, X-ray diffraction, temperature-programmed reduction, CO chemisorption and oxygen storage capacity. Temperature-programmed reduction results indicated that Tb or Zr incorporation improves the reducibility and oxygen storage capacity. CO chemisorption data suggested the presence of large Pd O particles due to the low CO/Pd ratio. No significant differences were obtained in light off temperatures(T Light off) for all Pd catalysts and the most active was1.5%Pd/Ce0.6Zr0.4O x/Si O2.     

Promoting effect of vanadium on catalytic activity of Pt/Ce–Zr–O diesel oxidation catalysts

A series of Pt–V/Ce–Zr–O diesel oxidation catalysts was prepared using the impregnation method. The catalytic activity and sulfur resistance of Pt–V/Ce–Zr–O were investigated in the presence of simulated diesel exhaust. The effect of vanadium on the structure and redox properties of the catalysts was also investigated using the Brunauer–Emmett–Teller method,X-ray diffraction, H2temperature-programmed reduction, CO temperature-programmed desorption, X-ray photoelectron spectroscopy, and Energy Dispersive Spectroscopy. Results showed that the Pt particles were well dispersed on the Ce–Zr–O carrier through the vanadium isolation effect, which significantly improved the oxidation activity toward CO and hydrocarbons. An electron-withdrawing phenomenon occurred from V to Pt, resulting in an increase in the metallic nature of platinum, which was beneficial to hydrocarbon molecular activation.     

基于发射环境炮–弹–引耦合仿真的中大口径加榴炮机械触发引信失效分析

目的 研究高动态发射环境中大口径加榴炮机械触发引信及其内部典型机构的响应特性和底层失效原因。方法 建立炮–弹–引耦合数值模型,开展0号装药、1号装药、0.4''装填角和身管中等程度磨损等4种工况下的动力学仿真,对比不同工况下引信典型部位的响应特性。结果 装药量和火炮身管磨损量是引信典型部位载荷响应的主要影响因素,身管磨损量是弹丸出炮口姿态角的主要影响因素。身管中期磨损条件下,引信夹板部位膛内径向过载响应峰值达2 498.4g,为初始状态的6.1倍;回转体轴响应峰值达4 296.1g,为初始状态的1.5倍;弹丸出炮口俯仰角达0.4°,为初始状态的4.4倍。试验验证结果表明,典型特征参量的仿真模拟误差不大于5%。结论 弹丸发射过程中,远离弹轴的引信安全系统轴类零件会承受更大的轴向载荷冲击和径向多维度载荷冲击,更容易导致与夹板配合的轴孔结合处发生失效。火炮身管磨损会导致榴弹配用引信在内弹道和出炮口承受更高的径向过载,以更大的姿态角进入外弹道飞行,是中大口径加榴炮机械触发引信外弹道飞行章动角增大的主要因素之一。     

Twin-roll casting of aluminum–steel clad strips

The results of experiments on twin-roll casting of aluminum–steel clad strips are presented. For the first time this energy-saving production technology for a clad material of this metals combination was implemented. Besides the experimental equipment and processing details, the results of metallographic, electron microprobe and transmission electron microscopy analysis of the aluminum–steel interface are shown. The pack rolling and deep-drawing tests of the twin-roll cast clad strips were performed to check their applicability for a further processing using plastic deformation. In addition adhesive strength of the bond was tested. The performed analysis have shown the formation of a continuous, thin and uniform layer of intermetallic phases on the materials interface of approx. 3 μm thickness having an adhesive strength over 70 MPa.     

Detoxification of ferrocyanide in asoil–plant system

The detoxification of iron cyanide in a soil–plant system was investigated to assess the total cyanide extracted from contaminated soil and allocated in the leaf tissue of willow trees(Salix caprea). They were grown in soil containing up to 1000 mg/kg dry weight(dw) of cyanide(CN),added as ~(15)N-labeled potassium ferrocyanide and prepared with a new method for synthesis of labeled iron cyanides. CN content and ~(15)N enrichment were monitored weekly over the exposure in leaf tissue of different age. The ~(15)N enrichment in the young and old leaf tissue reached up to 15.197‰ and 9063‰, respectively; it increased significantly over the exposure and with increasing exposure concentrations(p 0.05). Although the CN accumulation in the old leaf tissue was higher, compared to the young leaf tissue(p 0.05), the ~(15)N enrichment in the two tissue types did not differ statistically. This indicates a non-uniform CN accumulation but a uniform ~(15)N allocation throughout the leaf mass. Significant differences were detected between the measured CN content and the C~(15)N content, calculated from the ~(15)N enrichment(p 0.05), revealing a significant CN fraction within the leaf tissue, which could not be detected as ionic CN. The application of labeled iron CN clearly shows that CN is detoxified during uptake by the willows. However, these results do not exclude other detoxification pathways, not related to the trees. Still, they are strongly indicative of the central role the trees played in CN removal and detoxification under the experimental conditions.     

Determination of hexabromocyclododecanes in sediments from the Haihe River in China by an optimized HPLC–MS–MS method

Hexabromocyclododecanes(HBCDs),a new type of persistent organic pollutants widely used as brominated flame retardants,have attracted wide attention due to their increasing level and toxicity. A method based on high-performance liquid chromatography mass spectrometry(HPLC–MS–MS)in electrospray ionization mode has been developed by optimization of various parameters,which effectively improved the separation degree and responsive intensity of α-,β-and γ-HBCD isomers. The concentrations and distribution profiles of three HBCD isomers were investigated in sediments from the Haihe River in China.It was observed that the concentrations of HBCDs varied in the range of 0.4–58.82 ng/g,showing a decreasing trend along the flow direction,possibly due to attenuation and biodegradation along the flow direction of the Haihe River. The distribution profile of α-,β-,γ-HBCD was 7.91%–88.6%,0–91.47%,and 0.62%–42.83%,respectively. Interestingly,α-HBCD dominated in most sample sites. This was different from the distribution profile in commercial industrial products,which might be attributed to the inter-transformation and different degradation rates of the three HBCD isomers. The potential ecological risk of HBCDs in sediment was characterized under the two-tiered procedure of the European Medicines Evaluation Agency for environmental risk assessment. Although the HBCDs in the selected section of the Haihe River presented "no risk" in the sediment compartment,its risk in sediment cannot be neglected since sediment is one of the important sinks and reservoirs of pollutants.     

Effect of post-fire resprouting on leaf fluctuating asymmetry, extrafloral nectar quality, and ant–plant–herbivore interactions

Fires in the Cerrado savanna are a severe form of disturbance, but some species are capable of resprouting afterwards. It is unknown, however, how and whether post-fire resprouting represents a stressful condition to plants and how their rapid re-growth influences both the production of biochemical compounds, and interactions with mutualistic ants. In this study, we examined the influence of post-fire resprouting on biotic interactions (ant–plant–herbivore relationships) and on plant stress. The study was performed on two groups of the extrafloral nectaried shrub Banisteriopsis campestris (Malpighiaceae); one group was recovering from fire while the other acted as control. With respect to biotic interactions, we examined whether resprouting influenced extrafloral nectar concentration (milligrams per microliter), the abundance of the ant Camponotus crassus and leaf herbivory rates. Plant stress was assessed via fluctuating asymmetry (FA) analysis, which refers to deviations from perfect symmetry in bilaterally symmetrical traits (e.g., leaves) and indicates whether species are under stress. Results revealed that FA, sugar concentration, and ant abundance were 51.7 %, 35.7 % and 21.7 % higher in resprouting plants. Furthermore, C. crassus was significantly associated with low herbivory rates, but only in resprouting plants. This study showed that post-fire resprouting induced high levels of plant stress and influenced extrafloral nectar quality and ant-herbivore relationships in B. campestris. Therefore, despite being a stressful condition to the plant, post-fire resprouting individuals had concentrated extrafloral nectar and sustained more ants, thus strengthening the outcomes of ant–plant mutualism.     

Analysis of air quality characteristics of Beijing–Tianjin–Hebei and its surrounding air pollution transport channel cities in China

Beijing–Tianjin–Hebei(BTH) and its surrounding areas are very important to air pollution control in China.To analyze the characteristics of BTH and its surrounding areas of China,we collected 5,641,440 air quality data from 161 air monitoring stations and 37,123,000 continuous monitoring data from air polluting enterprises in BTH and surrounding cities to establish an indicator system for urban air quality portraits.The results showed that particulate matter with aerodynamic diameters of 2.5 μm(PM_(2.5)),particulate matter with aerodynamic diameters of 10 μm(PM_(10)) and SO_2 improved significantly in 31 cities from2015 to 2018,but ozone deteriorated.Air quality in BTH and the surrounding areas showed obvious seasonal characteristics,among which PM_(2.5),PM_(10),SO_2,and NO_2 showed a "U" type distribution from January to December,while O_3 had an "inverted U" distribution.The hourly changes in air quality revealed that peaks of PM_(2.5),PM_(10) and NO_2 appeared from 8:00 to 10:00,while those for O_3 appeared at 15:00–16:00.The exposure characteristics of the 31 cities showed that six districts in Beijing had the highest air quality population exposure,and that exposure levels in Zhengzhou,Puyang,Anyang,Jincheng were higher than the average of the 31 investigated cities.Additionally,multiple linear regression revealed a negative correlation between meteorological factors(especially wind and precipitation) and air quality,while a positive correlation existed between industrial pollution emissions and air quality in most of BTH and its surrounding cities.     

Battersea Power Station and environmental issues 1929–1989

From inception (1920s) to partial demolition (1980s) London's Battersea Power Station provoked public concern over environmental impacts. Adverse reaction during the early stages concerned siting and the effects of air pollutants on the urban surroundings. Potential air pollution problems resulted in a restrictive ‘condition’ being inserted in the consent for Battersea which required smoke and sulphur dioxide to be controlled. The ‘condition’ did not reassure either the public or special interest groups who campaigned against the construction of the station. However plans were too advanced to be halted and the official response focused on ensuring successful implementation of flue gas desulphurization. Though the subsequent effectiveness of emission control during the station's working life is arguable, the building itself rapidly became a popular London landmark and an architectural symbol of the fascination that surrounds technology. Objections to its decommissioning and demolition in the 1980s once again placed Battersea Power Station at the centre of public protest. Reactions to the station illustrate the rapidity with which our perception of environmental threats may change.     

Microbial spheres: a novel cyanobacterial–diatom symbiosis

Cyanobacteria, algae and bacteria are widespread inhabitants of North Sea microbial mats. Our studies of these populations showed uncommon modes of living and extraordinary structures, which have not been described before. The structures are spherical objects covering a community of cyanobacteria, diatoms and bacteria. The cultivation of these communities in the laboratory and intensive observations of their exceptional movement has led to some spectacular findings. The sphere formations go through different phases with variation in the dominance of different microorganisms. The role of the bacteria is the most important in the first phase, and can be increased by the addition of signal substances. Spheres surrounded by envelopes of unknown composition and permeability appear, with numerous bacteria and sporadic diatoms inside. Then the cyanobacteria penetrate the spheres and arrange themselves at the surface. The communities proliferate over some weeks and are finally released. Laboratory expositions of the microbial communities to different parameters pinpoint the limits of sphere formation. The metabolic products of the sphere communities are concentrated in the spheres and lead to a different kind of compound compared with the surrounding environment. In this way, the microbial communities strongly influence the structure of the sediments. Uncommon circular structures, which develop into spheres between 0.08 and 3 mm in size were found in subcultures of non-axenic filamentous cyanobacteria enrichments from North Sea microbial mats. These filamentous cyanobacteria (Phormidium sp.) together with associated benthic diatoms of the genus Navicula and associated heterotrophic bacteria were held as reproducible synergistic cultures. Phormidium sp. filaments tightly intertwined with each other, formed the surface of the spheres, trapping diatoms inside. The formation of "spheres" was the result of radial and synchronous movements of the cyanobacteria. In old cultures, the direction of the cyanobacterial movement has turned in the opposite direction, away from the sphere. The integrity of large "spheres" was influenced by chemotactic phenomena and maintained by some type of trichome-trichome interaction. This suggests the presence of metabolic secondary products, which attract cyanobacteria and influence their movement in a form of chemotactic response.