AIMS: The response of microbial metagenome to polycyclic aromatic hydrocarbons (PAHs) degradation in the rice rhizosphere remains poorly understood. We investigated the spatial and temporal ...variations of microbial communities and reconstructed metagenomes along the rice rhizosphere gradient during PAHs degradation. METHODS AND RESULTS: The experiment was performed in rhizoboxes, in which the rhizosphere region was divided into five 1‐mm thick layers. Based on denaturant gradient gel electrophoresis profiling and sequencing of bacterial and archaeal 16S rRNA genes, predicted metagenomes were reconstructed. The microbial communities in the rice rhizosphere were influenced by the PAHs concentration and distance from the root surface during PAHs degradation. Correlation network analysis showed that archaea played an important role in PAHs degradation. Predicted metagenomes can be clustered into two groups with high and low PAHs degrading potential, respectively. The relative abundance of genes for defense mechanisms, replication, recombination and reparation was significantly higher in samples with high PAHs degrading potentials. The relative abundance of the dioxygenase gene was greater near the root surface of the rice. However, the abundance of aldolase and dehydrogenase was constant in rhizosphere soils at different distances from the root surface. CONCLUSIONS: Distance from root surface and PAH concentrations affected the microbial communities and metagenomes in rice rhizosphere. The abundance of dioxygenase genes relating to PAH degradation in metagenomes mirrored the PAH degradation potential in rice rhizosphere. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings suggested that the predicted metagenomes reconstructed from 16S rRNA marker gene sequences provide further insights into the spatial variation and dynamics of microbial functioning that occur during bioremediation.
Adolescent myopia has become one of the researchers' focuses among visual problems around the world. Carrying out a scientific and efficient epidemiological study on myopia is an essential basis for ...discovering the rules of the occurrence and the development of myopia, exploring related influencing factors and identifying the mechanisms, which are critical for the policy-making for myopia control. The epidemiological studies of myopia at home and abroad have a long history of exploration, standardization and unification, and are enriched by new technologies and up-to-date discoveries. Based on the characteristics of social development and the prevalence of adolescent myopia in the past six decades, the epidemiological studies on myopia are divided into four stages in this article. Each stage is specified and analyzed to identify the difference in research methods and strategies. The main scientific issues and research elements in the current epidemiology of myopia in adolescents are put forward. (
.
We present the results of a search for heavy QCD axions performed by the ArgoNeuT experiment at Fermilab. We search for heavy axions produced in the NuMI neutrino beam target and absorber decaying ...into dimuon pairs, which can be identified using the unique capabilities of ArgoNeuT and the MINOS near detector. This decay channel is motivated by a broad class of heavy QCD axion models that address the strong CP and axion quality problems with axion masses above the dimuon threshold. We obtain new constraints at a 95% confidence level for heavy axions in the previously unexplored mass range of 0.2-0.9 GeV, for axion decay constants around tens of TeV.
Abstract
Exploring an efficient and photostable heterostructured photocatalyst is a pivotal scientific topic for worldwide energy and environmental concerns. Herein, we reported that Pt decorated g-C
...3
N
4
/Bi
2
MoO
6
heterostructured composites with enhanced photocatalytic performance under visible light were simply synthesized by one-step hydrothermal method for methylene blue (MB) dye degradation. Results revealed that the synthetic Pt decorated g-C
3
N
4
/Bi
2
MoO
6
composites with Bi
2
MoO
6
contents of 20 wt.% (Pt@CN/20%BMO) presented the highest photocatalytic activity, exhibiting 7 and 18 times higher reactivity than the pure g-C
3
N
4
and Bi
2
MoO
6
, respectively. Structural analyses showed that Bi
2
MoO
6
microplates were anchored on the wrinkled flower-like g-C
3
N
4
matrix with Pt decoration, leading to a large expansion of specific surface area from 10.79 m
2
/g for pure Bi
2
MoO
6
to 46.09 m
2
/g for Pt@CN/20%BMO. In addition, the Pt@CN/20%BMO composites exhibited an improved absorption ability in the visible light region, presenting a promoted photocatalytic MB degradation. Quenching experiments were also conducted to provide solid evidences for the production of hydroxyl radicals (
•
OH), electrons (e
−
), holes (h
+
) and superoxide radicals (
•
O
2−
) during dye degradation. The findings in this critical work provide insights into the synthesis of heterostructured photocatalysts with the optimization of band gaps, light response and photocatalytic performance in wastewater remediation.
ABSTRACT
GW190814 was reported during LIGO’s and Virgo’s third observing run with the most asymmetric component masses (an ∼23 M⊙ black hole and an ∼2.6 M⊙ compact object). Under the assumption that ...this event is a binary black hole (BBH) merger formed through the isolated binary evolution channel, we reanalyse the publicly released data of GW190814 with the modified astrophysical priors on the effective spin χeff, and further explore its formation history using detailed binary modelling. We show that GW190814 is likely to have been formed through the classical common envelope channel. Our findings show that the properties inferred using the modified astrophysical priors are consistent with those inferred by the uniform priors. With the newly inferred properties of GW190814, we perform detailed binary evolution of the immediate progenitor of the BBH (namely a close binary system composed of a BH and a helium star) in a large parameter space, taking into account mass-loss, internal differential rotation, supernova kicks, and tidal interactions between the helium star and the BH companion. Our findings show that GW190814-like events could be formed in limited initial conditions just after the common envelope phase: an ∼23 M⊙ BH and a helium star of MZamsHe ∼ 8.5 M⊙ at solar metallicity (∼ 7.5 M⊙ at 10 per cent solar metallicity) with an initial orbital period at around 1.0 d. Additionally, the inferred low spin of the secondary indicates that the required metallicity for reproducing GW190814-like events should not be too low (e.g. Z ≳ 0.1 Z⊙).
Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) is a space‐borne instrument dedicated to monitoring high‐energy transients, including Terrestrial Gamma‐ray Flashes ...(TGFs) and Terrestrial Electron Beams (TEBs). We implemented a TGF/TEB search algorithm for GECAM, with which 147 bright TGFs, 2 typical TEBs and 2 special TEB‐like events are identified during an effective observation time of ∼9 months. We show that, with gamma‐ray and charged particle detectors, GECAM can effectively identify and distinguish TGFs and TEBs, and measure their temporal and spectral properties in detail. A very high TGF‐lightning association rate of ∼80% is obtained between GECAM and GLD360 in east Asia region.
Plain Language Summary
Terrestrial gamma‐ray flashes (TGFs) and Terrestrial Electron Beams (TEBs) represent the most energetic radioactive phenomena in the atmosphere of the Earth. They reflect a natural particle accelerator that can boost electrons up to at least several tens of mega electron volts and produce gamma‐ray radiation. With novel detection technologies, Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) is a new powerful instrument to observe TGFs and TEBs, as well as study their properties. For example, it is difficult for most space‐borne high‐energy instruments to distinguish between TGFs and TEBs. However, we show here that, with the joint observation of gamma‐ray and charged particle detectors, GECAM can effectively identify TGFs and TEBs. GECAM can also reveal their fine features in the light curves and spectra.
Key Points
During 9‐month observation, Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) has detected 147 bright Terrestrial Gamma‐ray Flashes (TGFs), 2 typical Terrestrial Electron Beams (TEBs), and 2 special TEB‐like events
With novel detector design, GECAM can effectively classify TGFs and TEBs, and reveal their fine temporal features
We obtained a very high TGF‐lightning association rate (∼80%) between GECAM and GLD360 in east Asia region
ABSTRACT
On 2019 April 25, the LIGO/Virgo Scientific Collaboration detected a compact binary coalescence, GW190425. Under the assumption of the binary neutron star (BNS), the total mass of ...$3.4^{+0.3}_{-0.1}\, \mathrm{M}_\odot$ lies five standard deviations away from the known Galactic population mean. In the standard common envelope scenario, the immediate progenitor of GW190425 is a close binary system composed of an NS and a He-rich star. With the detailed binary evolutionary modelling, we find that in order to reproduce GW190425-like events, super-Eddington accretion (e.g. $1,000\, \dot{M}_{\rm Edd}$) from a He-rich star onto the first-born NS with a typical mass of 1.33 M⊙ via stable Case BB mass transfer (MT) is necessarily required. Furthermore, the immediate progenitors should potentially have an initial mass of MZamsHe in a range of 3.0–3.5 M⊙ and an initial orbital period of Pinit from 0.08 d to 0.12 d, respectively. The corresponding mass accreted onto NSs via stable Case BB MT phase varies from $0.70\, \mathrm{M}_\odot$ to $0.77\, \mathrm{M}_\odot$. After the formation of the second-born NS, the BNSs are expected to be merged due to gravitational wave emission from ∼11 Myr to ∼190 Myr.
We report a study of scattering dynamics in crystals employing momentum-resolved scanning transmission electron microscopy under varying illumination conditions. As we perform successive changes of ...the probe focus, multiple real-space signals are obtained in dependence of the shape of the incident electron wave. With support from extensive simulations, each signal is shown to be characterised by an optimum focus for which the contrast is maximum and which differs among different signals. For instance, a systematic focus mismatch is found between images formed by high-angle scattering, being sensitive to thickness and chemical composition, and the first moment in diffraction space, being sensitive to electric fields. It follows that a single recording at one specific probe focus is usually insufficient to characterise materials comprehensively. Most importantly, we demonstrate in experiment and simulation that the second moment μ20+μ02=〈p2〉 of the diffracted intensity exhibits a contrast maximum when the electron probe is focused at the top and bottom faces of the specimen, making the presented concept attractive for measuring local topography. Given the versatility of 〈p2〉, we furthermore present a detailed study of its large-angle convergence both analytically using the Mott scattering approach, and by dynamical simulations using the multislice algorithm including thermal diffuse scattering. Both approaches are in very good agreement and yield logarithmic divergence with increasing scattering angle.
•Different STEM signals are found to be affected in specific ways by the probe focus.•Highest sensitivity to different material parameters requires specific conditions.•Specific STEM signals, e.g. the second moment, show sensitivity to the surfaces.•The high-angle behaviour of the second moment follow a simple Mott scattering model.
Although metallic glasses (MGs) with unique disordered atomic structure have increasingly attracted great research interest as one of the most innovative heterogeneous catalysts in water remediation, ...few works focused on the synergistic role of different elemental constituents to well understand their superb catalytic performance. Herein, Co atoms were selected to partially substitute for the Fe elements in Fe-based MGs to study the corresponding synergistic catalytic function in dye degradation. Experimental results demonstrated that the Fe36Co36Si4.8B19.2Nb4 MG with a kinetic rate constant of k = 0.06 min−1 degrades rhodamine B (RhB) dye 20 times faster than the Fe73.5Si13.5B9Cu1Nb3 MGs with k = 0.003 min−1. Three types of dye including RhB, methylene blue (MB) and malachite green were investigated to draw attention to the broad, practical applications. Various chemical parameters, such as catalyst dosage, persulfate concentration, and dye concentration, were also studied. Quenching experiments indicated that the highly active hydroxyl (⋅OH) and sulfate (SO4⋅−) radicals are largely produced from persulfate by the activation of the Fe36Co36Si4.8B19.2Nb4 MG catalyst. This critical work uncovers a new paradigm to establish an effective approach for alloy design in widespread catalytic applications.
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•Co atoms were selected to partially substitute for the Fe elements in Fe-based MGs.•Catalytic activity was greatly enhanced by synergistic function of iron and cobalt.•Increasing boron contents could promote dye degradation efficiency.•⋅OH and SO4⋅− were found to be the primary radicals for dye degradation.
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