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Widespread mortality of eastern hemlock (Tsuga canadensis [L.] Carr.) has been occurring due to the introduction of hemlock woolly adelgid (Adelges tsugae Annand) (HWA), threatening millions of hectares of hemlock-dominated forests in the eastern United States. HWA feeds at the base of needles and removes stored carbohydrates, which can impact leaf-level physiology, contributing to the decline of the tree. However, these physiological mechanisms in HWA-infested hemlocks are still not clearly understood. We investigated hemlock leaf physiology year-round at three forested sites with various degrees of infestation. At each site, half the trees were treated with imidacloprid (Merit® 2 F, Bayer, Kansas City, MO, USA) while the rest were left untreated. Imidacloprid is widely used to control HWA but can itself have phytotoxic effects. After one growing season, there was an increase in photosynthetic rates (7.5%, p = 0.0163) and stomatal conductance (7.1%, p = 0.0163) across sites in the trees treated with imidacloprid. After two years, the imidacloprid treatment also increased bud break from 22.5% to 88.7% at Fishburn (the most severely impacted site) and from 22.7% to 58.9% at Mountain Lake (the least impacted site), and slightly increased chlorophyll fluorescence for treated trees at Fishburn. Chemical treatment also slightly increased water use efficiency at Mountain Lake. These results suggest that HWA is causing tree mortality largely through a reduction in leaf area caused by decreasing bud break and also by a slight, but significant, reduction in leaf-level photosynthesis and stomatal conductance.

Aerobic exercise is the predecessor of aerobics. Aerobics is a kind of young and energetic sports, although it is only is popular in recent years, but because of its strong ornamental, very beautiful, so many people like it. Now, the characteristic of sports development is to integrate competitive sports into schools, and the establishment of high-level sports teams in Chinese colleges and universities is the need of the current development trend and adapts to the trend of the times. Many colleges and universities have invested a lot of time, money, and energy. It is to set up a high-level sports team. It has provided great help to physical education and athletes. Therefore, it is very beneficial to the sustainable development of aerobics of high-level sports teams in colleges and universities to compare, analyze, and study the aerobic training methods of high-level sports teams in colleges and universities, and find out the existing problems in current training, correct them in time, and find out more suitable training methods.

Soil nitrification driven by ammonia-oxidizing microorganisms is the most important source of nitrous oxide (N

Super-resolution ultrasound (SRUS) imaging through localising and tracking sparse microbubbles has been shown to reveal microvascular structure and flow beyond the wave diffraction limit. Most SRUS studies use standard delay and sum (DAS) beamforming, where large main lobe and significant side lobes make separation and localisation of densely distributed bubbles challenging, particularly in 3D due to the typically small aperture of matrix array probes. This study aims to improve 3D SRUS by implementing a low-cost 3D coherence beamformer based on channel signal variance, as well as two other adaptive weight-based coherence beamformers: nonlinear beamforming with p-th root compression and coherence factor. The 3D coherence beamformers, together with DAS, are compared in computer simulation, on a microflow phantom, and in vivo. Simulation results demonstrate that the adaptive weight-based beamformers can significantly narrow the main lobe and suppress the side lobes for modest computational cost. Significantly improved 3D SR images of microflow phantom and a rabbit kidney are obtained through the adaptive weight-based beamformers. The proposed variance-based beamformer performs best in simulations and experiments., Ultrasound localisation microscopy (ULM), super-resolution, contrast-enhanced ultrasound, 3D beamforming

International audience; Temperature response of gross primary productivity (GPP) is a well-known property of ecosystem, but GPP at the optimum temperature (GPP_Topt) has not been fully discussed. Our understanding of how GPP_Topt responds to warming and water availability is highly limited. In this study, we analyzed data at 326 globally distributed eddy covariance sites (79oN-37oS), to identify controlling factors of GPP_Topt. Although GPP_Topt was significantly influenced by soil moisture, global solar radiation, mean annual temperature, and vapor pressure deficit in a non-linear pattern (R2 = 0.47), the direction and magnitude of these climate variables’ effects on GPP_Topt depend on the dryness index (DI), a ratio of potential evapotranspiration to precipitation. The spatial pattern showed that soil moisture did not affect GPP_Topt across energy-limited sites with DI < 1 while dominated GPP_Topt across water-limited sites with DI >1. The temporal pattern showed that GPP_Topt was lowered by warming or low precipitation in water-limited sites while energy-limited sites tended to maintain a stable GPP_Topt regardless of changes in air temperature. Vegetation types in humid climates tended to have higher GPP_Topt and were more likely to benefit from a warmer climate since it was not restricted by water conditions. This study highlights that the response of GPP_Topt to global warming depends on the dryness conditions, which explains the nonlinear control of water and temperature over GPP_Topt. Our finding is essential to realistic prediction of terrestrial carbon uptake under future climate and vegetation conditions.

Super-Resolution (SR) Ultrasound imaging overcomes the wave diffraction limit and can reveal microvasculature by localizing spatially isolated contrast agents. Volumetric SR ultrasound imaging, however, is limited by both the fabrication and computational complexity associated with 2D matrix array probes. The most used diagnostic imaging modality, X-ray radiography, requires much simpler hardware than X-ray CT and can present volumetric information in a single projection image. Inspired by X-ray radiography, this study aims to investigate the feasibility of volumetric image projection super-resolution (VIP-SR) ultrasound using a 1D transducer array probe in simulation. Results show that, without a focusing lens, the capability of capturing volumetric information for a 1D array probe is significantly improved over that of a focused 1D array probe and is comparable to that of a 1.75D array probe with the same aperture size. Here we demonstrated the potential of VIP-SR as a high-resolution microvascular imaging technique with volumetric information and significantly reduced cost.

Achieving highly selective acetylene semi-hydrogenation in an ethylene-rich gas stream is of great industrial importance. Herein, we construct isolated single Pd atom in a polyoxometalate-based metal-organic framework (POMOF). The unique internal environment allows this POMOF to separate acetylene from acetylene/ethylene gas mixtures and confine it close to the single Pd atom. After semi-hydrogenation, the resulting ethylene is preferentially discharged from the pores, achieving a selectivity of 92.6 %. First-principles simulations reveal that the adsorbed acetylene/ethylene molecules form hydrogen bond networks with oxygen atoms of SiW12 O404- and create dynamic confinement regions, which preferentially release the produced ethylene. Besides, at the Pd site, the over-hydrogenation of ethylene exhibits a higher reaction energy barrier than the semi-hydrogenation of acetylene. The combined advantages of POMOF and single Pd atom provides an effective approach for the regulation of semi-hydrogenation selectivity.

Disentangling the relative response sensitivity of soil autotrophic (Rₐ) and heterotrophic respiration (Rₕ) to nitrogen (N) enrichment is pivotal for evaluating soil carbon (C) storage and stability in the scenario of intensified N deposition. However, the mechanisms underlying differential sensitivities of Rₐ and Rₕ and relative contribution of Rₕ to soil respiration (Rₛ) with increasing N deposition remain elusive. A manipulative field experiment with multi‐level N addition rates was conducted over 3 years (2015–2017) in an alpine meadow to explore the relative impact of N enrichment on Rₐ and Rₕ and the response of Rₕ/Rₛ ratio to the gradient of N addition. Soil respiration components had different sensitivities to N enrichment, with Rₐ decreasing more than Rₕ, leading to a higher Rₕ/Rₛ ratio as a function of increasing N addition rates. Rₐ and Rₕ decreased nonlinearly as N addition rates increased, with a critical load of 8 g N m⁻² year⁻¹ above which N enrichment significantly inhibited them. Rₐ and Rₕ were controlled by different abiotic and biotic factors, and the regulation of controlling factors on soil respiration components varied over time. N‐induced reduction in the relative abundance of forb significantly affected Rₐ, and this effect was mainly evident in the second and third years. Nitrogen enrichment significantly changed Rₕ in the third year, and the decreased Rₕ under high doses of N addition could be attributed to the changes in microbial biomass C, soil substrate quality and microbial composition. Our study highlights the leading role of Rₐ in regulating Rₛ responses to N enrichment and the enhancement of Rₕ/Rₛ ratio with increasing N addition. We also emphasize that N‐induced shifts in plant community composition play a vital role in regulating Rₐ instead of Rₕ. The changing drivers of Rₐ and Rₕ with time suggests that long‐term experiments with multiple levels of N addition are further needed to test the nonlinear responses and underlying mechanisms of soil respiration components in face to aggravating N deposition. A free Plain Language Summary can be found within the Supporting Information of this article.

The microstructure evolution and creep property degradation of the Ni-based superalloy K417 were studied at different high-temperature thermal exposure conditions. The results showed that the equivalent radius of γ′ precipitates increased with the exposure time at all the temperatures and displayed spherical morphologies. Moreover, small blocky-type Cr-rich M23C6 carbides were observed due to the decomposition of the primary MC after exposure to 950 °C for 200 h and 50 h both at 1000 °C and 1050 °C. The creep-rupture lifetimes deteriorated with increased exposure time and temperature due to γ′ precipitates coarsening and the decomposition of the primary carbides. Furthermore, a physically based analytical model was developed to describe the influence of the microstructural evolution of the γ′ precipitates on the residual creep lifetime.

Transgenic Bacillus thuringiensis (Bt) crops have been widely planted, and the resulting environmental risks have attracted extensive attention. To foresee the impacts of Bt crops on soil quality, it is essential to understand how Bt crops alter the soil enzymatic activities and what the important influencing factors are. We compiled data from 41 published papers that studied soil enzymatic activities with Bt crops and their non-Bt counterparts. The results showed that dehydrogenase and urease significantly increased, but neutral phosphatase significantly decreased under Bt crop cultivations without Bt residues incorporation. The activities of dehydrogenase, β-glucosidase, urease, nitrate reductase, alkaline phosphatase, and aryl sulfatase significantly increased under Bt crop cultivation with Bt residues incorporation. The response ratios of other enzymes were not significantly changed. Generally, the response ratios of soil enzymes were greater with Bt residues incorporation than those of Bt crop cultivations without Bt residues incorporation. Further, the response ratios of soil enzymes varied with Bt crop types and growth periods. It was the strongest under Bt cotton among Bt crops, and the significant responses usually appeared in the middle growth stages. The responses of soil enzymes ascribed more to the properties of Bt crops than to soil properties across sites. Given - significant responses of some soil enzymes to Bt crops, we recommended that soil environmental risks should be carefully evaluated over the transgenic crops.

AIM: Root turnover is an important process determining carbon and nutrient cycling in terrestrial ecosystems. It is an established fact that root turnover is jointly regulated by climatic, edaphic and biotic factors. However, the relative importance of these forces in determining the global patterns of root turnover time is far from clear. LOCATION: Global. TIME PERIOD: 1946–2017. MAJOR TAXA STUDIED: Grasslands. METHODS: We compiled a database of 141 sites with 433 observations on root turnover time and applied structural equation modelling (SEM) to investigate the relative contribution of climate, soil properties and vegetation type to the observed variations in root turnover time. RESULTS: Root turnover time was 3.1 years on average across the global grasslands and differed significantly among grassland types (tropical grassland and savanna, temperate grassland and meadow, alpine grassland and meadow, tundra and desert). It decreased with mean annual temperature, mean annual precipitation and Palmer drought severity index but increased with soil organic carbon content, total nitrogen content and carbon : nitrogen ratio. Soil bulk density and soil texture also significantly affected root turnover time, with clay content negatively correlating to root turnover time and explaining more variations than bulk density and sand content. The SEM showed that climatic factors had dominant effects on root turnover time when vegetation type was not considered. Vegetation type became the primary driver when it was included in the SEM. MAIN CONCLUSIONS: Our results indicate that the influences of climatic and edaphic factors on root turnover time are predominantly manifested through vegetation type. The critical role of precipitation as revealed for the first time in this study challenges our current understanding of climate impacts on root turnover time. The findings necessitate accurate representation of vegetation type in Earth system models to predict root function dynamics under global change.

Prussian blue analogues (PBA) possess a high theoretical specific capacity for sodium ion batteries. However, cycling PBA to a high current density causes severe capacity fading. Here, we develop a selective edge-etching approach to tackle this long-standing issue of poor rate capability. Well-crystallized PBA particles were produced by hydrothermal treatment of a sodium hexacyanoferrate precursor dissolved in muriatic acid solution, which were then eroded in hydrochloric acid solution to promote selective etching along the edges of the PBA crystals. The defect concentration ([Fe(CN)6]4−) on the edge is denser than that at the face or corner, which stimulates the preferred etching of edges via the defect-induced heterogeneous mechanism. Due to the increasing exposed surface area and active sites, the etched PBA display much improved electrochemical performance with a capacity of 167 mA h g−1 at a current density of 5 mA g−1 and a capacity retention of 82.7% when the current density was increased to 40 mA g−1, demonstrating fast sodium ion transfer and high rate capability.

It seems that understanding how individuals make decision within a group is an attractive and difficult challenge for economists, managerialists and researchers in human and social sciences for a long time, which is closely related to the theoretical development of economics. The rational assumptions of traditional economic theory, which are highly simplified and cannot manifestly illustrate the inherent mechanism for complexities of economic or financial phenomena (from behavioural perspectives). This paper devoted to seek a reasonable theoretical foundation under the framework of game theory and complex network, based on behavioral big data and the establishment of integrated model, to analyze the behavioral compatibility between individuals and collective deeply, which includes their static consistency and dynamic interactive adaptability. In addition, the paper built relevant computational experiment models to further understand the complex macro-phenomena based on real and heterogeneous investor’s behaviors with more extensive applications. Specifically, the paper contains three sections. Firstly, some typical types of relationship are listed for decision-making behaviors between individual and collective; Then, it is discussed to establish more coordinating consistent institutions and rules for understanding the independence between individual and collective decision-making behaviors through introducing virtual public player(s) into collective decision games; At last, by building the integrated ACE/F model of Chinese stock market, we try to clarify the inner relationship between the real investors’ behaviors with heterogeneity, interactions at micro-level and stylized facts at macro-level. Consequently, our theoretic viewpoint, to some extent, is positively supported by empirical evidence.

Grazing has been reported to significantly affect the flux of three greenhouse gases (GHGs: CO2, CH4 and N2O) in grasslands, but its effect on total global warming potential (GWP) is still unclear. To assess the effect of grazing on GWP, we simultaneously measured the flux of these three GHGs using static chambers in meadow, typical, and desert steppes under no grazing (NG) and summer grazing (SG) conditions during the 2012-14 growing seasons. We aimed to examine the impact of grazing on total GWP across different steppes and to assess the relative contribution of different environmental factors to changes in GWP. Our results showed that total GWP values were almost entirely negative in all steppe environments and displayed high spatio-temporal variability. Net ecosystem exchange was the most important predictor of total GWP in all three steppes, and the positive GWP induced by N2O emission was approximately equal to the negative GWP induced by CH4 uptake. Steppe type and sampling year—but not grazing treatment—were found to affect GWP. Air temperature and precipitation were the major factors driving total GWP change under the no grazing treatment. In contrast, soil temperature, soil moisture, and precipitation explained a significant percentage of variation in total GWP under the summer grazing treatment. Our study suggests that moderate grazing does not change the role of temperate steppe's function in mitigating climate change; however, multi-year GWP data are necessary for extrapolation to a regional scale.

Preventing soil biological degradation under the cultivation of Bacillus thuringiensis (Bt) crops is crucial to soil health. Despite studies concerning environmental risks of Bt crops, we surprisingly know little about whether soil biological degradation occurs under Bt crop cultivations. To fill this gap, we calculated the index of resistance (IR) and resilience (IR′) of 13 soil properties (the activities of enzymes, the rates of ecosystem processes, soil microbial biomass, and soil carbon and nutrients) using soil samples collected from an 8‐year Bt rice cultivation experiment, including three treatments, that is, continual cultivation of Bt rice (GM) and non‐Bt rice (non‐GM), and rotation between Bt and non‐Bt rice every 2 years (GM/non‐GM rotation). In GM and GM/non‐GM rotation, the IR of the activities of dehydrogenase, acid phosphatase, methane production rates was significantly greater than that in non‐GM. Further, the IR of denitrification, methane oxidation, microbial carbon, and microbial nitrogen was significantly lowered in GM, and the IR of microbial carbon in GM/non‐GM rotation was significantly decreased compared with that in non‐GM. However, the results of IR′ showed no significant differences in these soil properties between treatments, except for methane oxidation and urease in GM and microbial nitrogen in GM/non‐GM rotation. Taking into consideration of soil resistance and resilience, the most soil properties remained relatively stable. These findings suggest that the Bt rice cultivations have not significantly resulted in soil biological degradation.

Autophagy is a conserved cellular process playing a role in maintenance of cellular homeostasis and response to changing nutrient conditions via degradation and recirculation of cellular redundant components. Autophagy-related proteins (Atg) play important function in autophagy pathway. Aedes albopictus mosquito is an effective vector transmitting multiple viruses which cause serious human diseases. Moreover, Aedes albopictus mosquito is becoming a serious threat to human health due to its widening distribution in recent years and thus worth of more research attention. It was reported that autophagy might play a role in viral infection in Aedes mosquito. To better understand the interaction between autophagy and arbovirus infection in mosquito system, it is necessary to identify autophagy pathway in the system. However, autophagy in Aedes albopictus mosquito is still poorly understood so far. We recently identified AaAtg8, the first Atg protein reported in Aedes albopictus mosquito. This work further identified twelve atg genes in Aedes albopictus mosquito. Sequence and phylogenetic analysis of the twelve atg genes were performed. Expression profiles of all the twelve Aaatg genes in different developmental stages and genders of Aedes albopictus mosquito were conducted. Effects of chemicals inhibiting or inducing autophagy on the levels of eight identified AaAtg proteins were examined. The function of two identified AaAtg proteins AaAtg6 and AaAtg16 and their response to arbovirus SINV infection were studied preliminarily. Taken together, this work systematically identified Aedes albopictus atg genes and provided basic information which might help to elucidate the autophagy pathway and the role of autophagy in arbovirus infection in Aedes mosquito system.

In summer 2018, Europe experienced a record drought, but it remains unknown how the drought affected ecosystem carbon dynamics. Using observations from 34 eddy covariance sites in different biomes across Europe, we studied the sensitivity of gross primary productivity (GPP) to environmental drivers during the summer drought of 2018 versus the reference summer of 2016. We found a greater drought-induced decline of summer GPP in grasslands (−38%) than in forests (−10%), which coincided with reduced evapotranspiration and soil water content (SWC). As compared to the ‘normal year’ of 2016, GPP in different ecosystems exhibited more negative sensitivity to summer air temperature (Ta) but stronger positive sensitivity to SWC during summer drought in 2018, that is, a stronger reduction of GPP with soil moisture deficit. We found larger negative effects of Ta and vapour pressure deficit (VPD) but a lower positive effect of photosynthetic photon flux density on GPP in 2018 compared to 2016, which contributed to reduced summer GPP in 2018. Our results demonstrate that high temperature-induced increases in VPD and decreases in SWC aggravated drought impacts on GPP. This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’., Philosophical Transactions of the Royal Society B: Biological Sciences, 375 (1810), ISSN:0962-8436, ISSN:1471-2970, ISSN:0080-4622

Current localization-based super-resolution ultrasound imaging requires a low concentration of flowing microbubbles to visualize microvasculature beyond the diffraction limit and acquisition is slow. Recent studies have shown that Acoustic Wave Sparsely Activated Localization Microscopy (AWSALM) using phase change nanodroplets can generate fast or even real-time super-resolution imaging. However, the optimal experimental conditions to activate the droplets for generating the super-resolution images are still unknown, especially the activation ultrasound amplitude or mechanical index (MI). The aim of this study is to investigate the effect of the activation MI on the repeated activation of decafluorobutane nanodroplets in vivo . Noninvasive ultrasound data acquisition on a rabbit kidney using the AWSALM pulse sequence was repeated for different activation MIs. It was found that the droplet activation was not observed in the rabbit kidney at an MI of 1.1. The activation of droplet started at an activation MI of 1.3. The contrast of activated droplet signals is maximized at an MI of 1.5 and decreased when the activation MI was increased above 1.5. Such understanding of the effects of activation MI could help improve droplet-base fast super-resolution imaging.

While control over chemical reactions is largely achieved by altering the intrinsic properties of catalysts, novel strategies are constantly being proposed to improve the catalytic performance in an extrinsic way. Since the fundamental chemical behavior of molecules can remarkably change when their molecular scale is comparable to the size of the space where they are located, creating spatially confined environments around the active sites offers new means of regulating the catalytic processes. We demonstrate through first-principles calculations that acetylene hydrogenation can exhibit significantly improved selectivity within the confined sub-nanospace between two-dimensional (2D) monolayers and the Pd(111) substrate. Upon intercalation of molecules, the lifting and undulation of a 2D monolayer on Pd(111) influence the adsorption energies of intermediates to varying extents, which, in turn, changes the energy profiles of the hydrogenation reactions. Within the confined sub-nanospace, the formation of ethane is always unfavorable, demonstrating effective suppression of the unwanted overhydrogenation. Moreover, the catalytic properties can be further tuned by altering the coverage of the adsorbates as well as strains within the 2D monolayer. Our results also indicate that for improving the selectivity, the strategy of spatial confinement could not be combined with that of single-atom catalysis, since the reactant molecules cannot enter the sub-nanospace due to the too weak adsorbate-substrate interaction. This work sheds new light on designing novel catalysts with extraordinary performance for the selective hydrogenation of acetylene.

Atomically monodispersed heterogeneous catalysts with uniform active sites and high atom utilization efficiency are ideal heterogeneous catalytic materials. Designing such type of catalysts, however, remains a formidable challenge. Herein, using a wet-chemical method, we successfully achieved a mesoporous graphitic carbon nitride (mpg-C3N4) supported dual-atom Pt2 catalyst, which exhibited excellent catalytic performance for the highly selective hydrogenation of nitrobenzene to aniline. The conversion of ˃99% is significantly superior to the corresponding values of mpg-C3N4-supported single Pt atoms and ultra-small Pt nanoparticles (~2 nm). First-principles calculations revealed that the excellent and unique catalytic performance of the Pt2 species originates from the facile H2 dissociation induced by the diatomic characteristics of Pt and the easy desorption of the aniline product. The produced Pt2/mpg-C3N4 samples are versatile and can be applied in catalyzing other important reactions, such as the selective hydrogenation of benzaldehyde and the epoxidation of styrene., Designing atomically monodispersed heterogeneous catalysts with uniform active sites and high atom utilization efficiency is of fundamental and practical interest. Here, the authors report a Pt2/mpg-C3N4 catalyst showing enhanced catalytic performance toward the selective hydrogenation and epoxidation

Figures. S1-S3 and Table S1