An all-optical scheme is proposed for studying laser plasma based incoherent photon emission from inverse Compton scattering in the quantum electrodynamic regime. A theoretical model is presented to explain the coupling effects among radiation reaction trapping, the self-generated magnetic field and the spiral attractor in phase space, which guarantees the transfer of energy and angular momentum from electromagnetic fields to particles. Taking advantage of a prospective ∼ 10 23 W cm −2 laser facility, 3D particle-in-cell simulations show a gamma-ray flash with unprecedented multi-petawatt power and brightness of 1.7 × 10 23 photons s −1 mm −2 mrad −2 /0.1% bandwidth (at 1 GeV). These results bode well for new research directions in particle physics and laboratory astrophysics exploring laser plasma interactions.
The activation of C-H bonds in terminal alkynyl groups at room temperature was achieved in the reaction of 2,5-diethynyl-1,4-bis(4-bromophenylethynyl) benzene on Ag(111). Scanning tunneling microscopy studies showed the formation of organometallic species, whose stabilization was confirmed by density functional theory calculations, at room temperature as the product of C-H bond activation. The partial conversion of organometallic structures into covalent products of the homocoupling between the terminal alkynes was achieved by further annealing the sample at 420 K. Detached Br adatoms were suggested to play a key role in promoting the C-H bond activation. This proposal was supported by the theoretical study based on a simplified model of the system, showing the weakening of the C-H bond in the alkynyl group by an approaching Br atom. The results provide a new strategy for on-surface C-H bond activation under mild conditions, which register great potential applications in on-surface synthesis and bottom-up preparation of functional nanomaterials.
Background: More than 90% of the world's population lives in areas where outdoor air pollution levels exceed health-based limits. In these areas, individuals may use indoor air filtration, often on a sporadic basis, in their residences to reduce exposure to respirable particles (PM2.5). Whether this intervention can lead to improvements in health outcomes has not been evaluated.Methods: Seventy non-smoking healthy adults, aged 19 to 26 years, received both true and sham indoor air filtration in a double-blinded randomized crossover study. Each filtration session was approximately 13 h long. True and sham filtration sessions were separated by a two-week washout interval. The study was carried out in a suburb of Shanghai.Results: During the study period, outdoor PM2.5 concentrations ranged from 18.6 to 106.9 mu g/m(3), which overlapped with levels measured in Western Europe and North America. Compared to sham filtration, true filtration on average decreased indoor PM2.5 concentration by 72.4% to 10.0 mu g/m(3) and particle number concentration by 59.2% to 2316/cm(3). For lung function measured immediately after the end of filtration, true filtration significantly lowered airway impedance at 5 Hz (Z(5)) by 7.1% [95% CI: 2.4%, 11.9%], airway resistance at 5 Hz (R-5) by 7.4% [95% CI: 2.4%, 12.5%], and small airway resistance (R-5-R-20) by 20.3% [95% CI: 0.1%, 40.5%], reflecting improved airway mechanics especially for the small airways. However, no significant improvements for spirometry indicators (FEV1, FVC) were observed. True filtration also significantly lowered von Willebrand factor (VWF) by 26.9% [95% CI: 7.3%, 46.4%] 24 h after the end of filtration, indicating reduced risk for thrombosis. Stratified analysis in male and female participants showed that true filtration significantly decreased pulse pressure by 3.3% [95% CI: 0.8%, 7.4%] in females, and significantly reduced VWF by 42.4% [95% CI: 17.4%, 67.4%] and interleukin-6 by 22.6% [95% CI: 0.4%, 44.9%] in males. Effect modification analyses indicated that filtration effects in male and female participants were not significantly different.Conclusion: A single overnight residential air filtration, capable of reducing indoor particle concentrations substantially, can lead to improved airway mechanics and reduced thrombosis risk.
Language users need to interpret others’ subjective opinions in communication. In causal relations, subjectivity is defined as the involvement of a speaker who is responsible for the causal reasoning. Subjectivity can be expressed by various linguistic cues such as perspective markers (e.g. I think, it is said) and modal verbs (e.g. may, must). Some connectives encode subjectivity as well – the Chinese connective kejian ‘so/therefore’ and the Dutch connective dus ‘so’ indicate that a causal relation is based on the subjective reasoning of the speaker. These linguistic cues function as instructions for comprehenders in on-line language processing. This dissertation explores the use of linguistic markers expressing subjectivity in discourse and how these markers influence the representation and processing of discourse. Three different methods were applied to Mandarin Chinese: a collocational analysis, an on- line reading study and a visual world paradigm eye-tracking study. The results show that linguistic cues such as perspective markers and modal verbs are used in combination with connectives to express subjectivity in causal relations. In on-line reading, these linguistic cues function as processing instructions to readers – helping them track the source of information and interpret subjectivity. Moreover, this process is highly incremental. An eye-tracking study using the visual world paradigm provided evidence about how subjectivity influences processing: the processing of subjectivity involves activating the source of information in the mental representation of the linguistic input. Combining these three methods has proved to be a fruitful way of gaining more insight into the phenomenon of subjectivity.
The ozone layer depletion and its recovery, as well as the climate influence of ozone-depleting substances (ODSs) and their substitutes that influence climate, are of interest to both the scientific community and the public. Here we report on the emissions of ODSs and their substitute from China, which is currently the largest consumer (and emitter) of these substances. We provide, for the first time, a comprehensive information on ODSs and replacement Hydrofluorocarbon (HFC) emissions in China starting from 1980 based on reported production and usage. We also assess the impacts (and costs) of controls on ODS consumption and emissions on the ozone layer (in terms of CFC-11-equivalent) and climate (in CO2-equivalent). In addition, we show that while China’s future ODS emissions are likely to be defined as long as there is full compliance with the Montreal Protocol, its HFC emissions through 2050 are very uncertain. Our findings imply that HFC controls over the next decades that are more stringent than those under the Kigali Amendment to the Montreal Protocol would be beneficial in mitigating global climate change.
Recent studies on biochars confirmed their potential benefits in improving soil fertility and sequestrating contaminants. However, little information on the changes in structural characteristics and metal speciation of biochars after exposure to soils is currently available. The aim of this study was to use double experimental bags to study the transformation of ozonized biochars derived from poultry manure and drying sludge (denoted PB and SB, respectively) in typic udic ferrisols. The carbon and sulfur functional groups and chemical characteristics of the biochars were determined using spectroscopic techniques, such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy spectroscopy, combined with chemical extractions. Metal species were characterized using Cu K-edge X-ray absorption near-edge structure and chemical sequential fractionation schemes. The results showed that the potential changes in structural characteristics and metal species of biochars in soil were highly dependent on the composition of the biochars. PB comprised highly aromatic and chemically stable C, whereas SB contained a substantial amount of easily degradable C. Oxygen-containing groups slightly increased after incubation in the soil with either 60% water holding capacity (WHC) or flooding for 3 months. Sulfur in the biochars was predominantly inorganic S. Minerals such as K, Na, Mg, and S were mobilized from the biochars, accounting for 5-55% depending on the properties and sources of the element. Both PB and SB contained high concentrations of Cu and Zn. CuO in PB dissolved within 3 months, whereas CuS in both PB and SB was partly oxidized in the soil with 60% WHC for 9 months and adsorbed to the organic phase. Zn had relatively high mobility in both biochars, resulting in its vertical migration into soils.
Trace elements in atmospheric particular matter play a significant role in controlling aerosolbehavior, and can thereby endanger air quality. Here, the comprehensive investigation on the elemental characteristics and sources in fine and coarse particles at Chifeng was presented. The daily samples of particular matter (PM2.5 and PM10) were collected at six sites for a one-year period, and concentrations of 19 elements were analyzed. Results showed that Al, K, Ca, Fe were the most concentrated elements, in both PM2.5 and PM10. The crustal elements mainly in coarse particles (PM2.5–10) presented higher levels during March to May, due to the increased dust suspension in springtime. The highly enriched elements as Pb, Cd mainly in fine particles (PM2.5) presented elevated levels in cold seasons, related to the increased emissions of coal combustion for heating. Site Songshan had significantly higher Pb, As, Cd levels, ascribing to the influence of coal mining. The influences of metallurgy industries on Fe, Cu, Zn levels in both size fractions were also observed. Positive matrix factorization (PMF) identified four common sources for trace elements in both fine and coarse fractions, namely fugitive dust, coal mining, a mixed industrial factor with iron and zinc, and copper smelting. The factors of coal combustion, biomass burning, oil combustion, vehicle emission and fireworks were merely obtained for fine particles. The crustal elements were mainly related to the impact of fugitive dust, while the notable impacts of coal combustion and iron/steel production were also confirmed. Cu was attributed to copper smelting in both sizes, while the major sources of Zn varied from vehicle emission (44.3%), coal combustion (32.1%) in PM2.5 to mixed industrial factor (89.3%) in PM2.5–10. Although coal combustion, coal mining and copper smelting contributed <20% of the total elemental concentrations, they were responsible for >80% of the toxic elements Pb, As, Cd.
Chengdu is a megacity in the southwest of China with high ozone (O3) mixing ratio. Observation of volatile organic compounds (VOCs), NO2 and O3 with high temporal resolution was conducted in Chengdu to investigate the chemical processes and causes of high O3 levels. The hourly mixing ratios of VOCs, NO2, and O3 were monitored by an online system from 28 August to 7 October, 2016. According to meteorological conditions, Chengdu, with relative warm weather and low wind speed, is favorable to O3 formation. Part of the O3 in Chengdu may be transported from the downtown area. In O3 episodes, the average mixing ratios of NO2 and O3 were 20.20 ppbv and 47.95 ppbv, respectively. In non-O3 episodes, the average mixing ratios of NO2 and O3 were 16.38 ppbv and 35.15 ppbv, respectively. The average mixing ratio of total VOCs (TVOCs) was 40.29 ppbv in non-O3episodes, which was lower than that in O3 episodes (53.19 ppbv). Alkenes comprised 51.7% of the total O3 formation potential (OFP) in Chengdu, followed by aromatics which accounted for 24.2%. Ethylene, trans-pentene, propene, and BTEX (benzene, ethylbenzene, toluene, m/p-xylene, o-xylene) were also major contributors to the OFP in Chengdu. In O3 episodes, intensive secondary formations were observed during the campaign. Oxygenated VOCs (OVOCs), such as acetone, Methylethylketone (MEK), and Methylvinylketone (MVK) were abundant. Isoprene rapidly converted to MVK and Methacrolein (MACR) during O3 episodes. Acetone was mainly the oxidant of C3-C5 hydrocarbons.
