One challenge in merging community and ecosystem ecology is to integrate the complexity of natural multitrophic communities into concepts of ecosystem functioning. Here, we combine food‐web and allometry theories to demonstrate that primary production, as measured by the total nutrient uptake of the multitrophic community, is determined by vertical diversity (i.e. food web's maximum trophic level) and structure (i.e. distributions of species and their abundances and metabolic rates across trophic levels). In natural ecosystems, the community size distribution determines all these vertical patterns and thus the total nutrient uptake. Our model suggests a vertical diversity hypothesis (VDH) for ecosystem functioning in complex food webs. It predicts that, under a given nutrient supply, the total nutrient uptake increases exponentially with the maximum trophic level in the food web and it increases with its maximum body size according to a power law. The VDH highlights the effect of top–down regulation on plant nutrient uptake, which complements traditional paradigms that emphasised the bottom–up effect of nutrient supply on vertical diversity. We conclude that the VDH contributes to a synthetic framework for understanding the relationship between vertical diversity and ecosystem functioning in food webs and predicting the impacts of global changes on multitrophic ecosystems.
Chromium contamination can be remediated by catalytic reduction with precious metal palladium (Pd). Thus, enhancing Pd catalytic performance is of strong interest. An environmentally friendly and nontoxic approach for production of palladium nanoparticles (Pd-NPs) is to use microorganisms. Herein, the biosynthesis of Pd-NPs by Shewanella loihica PV-4 is reported for the first time. Both extracellular and intracellular bioreduction of Pd(II) has contributed this bio-fabrication, with the production of Pd0 particles in the size range of 4-10 nm. It was found that several factors including a higher initial Pd(II) concentration, weak acid medium condition, and a lager dosage of sodium formate and biomass amount could facilitate this synthesis process. The biosynthesized Pd-NPs exhibited excellent catalytic activities for chromium (VI) reduction, with complete removal of Cr(VI) after 3-h operation with a catalyst amount of 0.5 mg/mL, an initial Cr(VI) concentration of 0.5 mM, and formic acid as electron donor; these are significant advantages to chemically prepared Pd0. Cr(VI) reduction catalyzed by biosynthesized Pd-NPs was promoted with factors such as a higher dosage of formic acid, lower pH, and a lower initial Cr(VI) concentration. Density functional theory calculations of formic acid decomposition on Pd-NPs revealed that Pd-NPs facilitated formic acid to decompose into CO2 and H2. These results have collectively demonstrated the feasibility of the biosynthesis of Pd-NPs by Shewanella loihica PV-4 and its potential application as a promising catalyst for remediation of chromium contamination.
BACKGROUND/OBJECTIVES: Prenatal growth, which is widely marked by birthweight, may have a pivotal role in affecting the lifelong risk of cardiometabolic disorders; however, comprehensive evaluation of its relations with childhood cardiometabolic risk patterns and the ethnic and gender disparities in national representative populations is still lacking. The aim of this study was to evaluate the associations between birthweight and comprehensive patterns of cardiometabolic risk in a nationally representative sample of children and adolescents. SUBJECTS/METHODS: Prospective analyses were performed using data from 28 153 children 0 to 15 years in the National Health and Nutrition Examination Survey from 1999 through 2014. We defined childhood cardiometabolic disorders using standard definitions for obesity, high blood pressure, hyperglycemia and dyslipidemia. RESULTS: Five birthweight categories <2.5, 2.5-3.0, 3.0-3.5, 3.5-4.2 and 4.2 kg accounted for 8.2%, 17.9%, 35.7%, 27.9% and 10.4% of the population, respectively. In all children, with increasing birthweight, we observed significantly increasing trends of the risk of general and central obesity (P for trend <0.01) and significantly decreasing trends of the risk of high systolic blood pressure (SBP), high HbA1c and low high-density lipoprotein cholesterol (HDL-C) (P for trend <0.05). The associations were independent of current body mass index (BMI). In addition, we found that the relations of birthweight with high waist circumference in Black children showed U-shape, as well as high SBP in Mexican and Hispanic children. Moreover, we found that the associations of low birthweight with high SBP and low HDL-C appeared to more prominent significant in boys, whereas the inverse association with high HbA1c was more evident in girls. CONCLUSIONS: Our data indicate that birthweight is significantly related to childhood cardiometabolic risk, independent of current BMI, and the associations exhibit race and gender-specific patterns.
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.