China's Loess Plateau is both the largest and deepest loess deposit in the world, and it has long been one of the most severely eroded areas on Earth. Since the 1970s, numerous soil- and ...water-conservation practices have been implemented: terracing, planting of vegetation, natural vegetation rehabilitation, and check-dam construction. With the implementation of the Grain-for-Green Project in 1999, the Loess Plateau has become the most successful ecological restoration zone in China. However, these large-scale restoration measures and drought have significantly reduced both runoff and sediment from the Loess Plateau. This situation has both advantages and disadvantages for the lower Yellow River. Some local soil erosion has been successfully controlled, but the whole regional ecosystem remains very fragile. Therefore, it is necessary to balance each ecosystem service, for example, by determining the region's vegetation capacity and its spatial distribution for the sustainable development of the socioecological system of the Loess Plateau.
The new decade of the 21
century (2020) started with the emergence of a novel coronavirus known as SARS-CoV-2 that caused an epidemic of coronavirus disease (COVID-19) in Wuhan, China. It is the ...third highly pathogenic and transmissible coronavirus after severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) emerged in humans. The source of origin, transmission to humans, and mechanisms associated with the pathogenicity of SARS-CoV-2 are not yet clear, however, its resemblance to SARS-CoV and several other bat coronaviruses was recently confirmed through genome sequencing-related studies. The development of therapeutic strategies is necessary in order to prevent further epidemics and cure infections. In this review, we summarize current information about the emergence, origin, diversity, and epidemiology of three pathogenic coronaviruses with a specific focus on the current outbreak in Wuhan, China. Furthermore, we discuss the clinical features and potential therapeutic options that may be effective against SARS-CoV-2.
Coralomorph-lithistid demosponge-microbial reefs are developed in deep subtidal settings of the lower part of the Zhangxia Formation (Crepicephalina Zone: Drumian of Cambrian Series 3) in the ...Jiulongshan section of the Laiwu area of Shandong Province, North China. These reefs are several tens of centimeters thick and formed upon stabilized substrates of microbial origin. The coralomorph-bearing reefs are clearly distinguishable from demosponge-calcimicrobial reefs and Epiphyton bioherms by the development of dendritic thrombolites and the immediately overlying columnar-layered stromatolites. The microbial degradation of sponges facilitated the precipitation of micritic, peloidal, and clotted carbonates, leading to the formation of coralomorph-bearing thrombolitic cores. In contrast, Epiphyton preferentially grew upward, and the accumulation of Epiphyton clumps formed the dendritic thrombolites and the overlying columnar frameworks of the stromatolites. Marked changes in the microbialite texture are considered to reflect some kind of ecological succession, possibly changing environmental conditions. Therefore, the reefs originated from both heterotrophic and photoautotrophic microbial activities. Concave-upward infillings and lateral bridges are common in the interthrombolite and intercolumnar spaces, suggesting episodic sedimentation on the lateral outgrowths of biofilms and highlighting the columnar-layered structures. The coralomorph-lithistid demosponge-microbial reefs are characteristic of the pioneering, stabilizing, and climax stages of a microbial succession. They are age-specific features of microbial-dominated reefs from deep subtidal settings in the Drumian Stage, when skeletal-dominated reefs were inhibited globally, long before the regime shift in reef construction around the Early Ordovician.
In contrast to their spontaneous deprotonation in aqueous solution, reactions of guanine and guanosine radical cations with water in the gas phase are exclusively initiated by hydration of the ...radical cations as reported in recent work (Y. Sun
,
, 2018,
, 27510). As gas-phase hydration reactions closely mimic the actual scenario for guanine radical cations in double-stranded DNA, exploration of subsequent reactions within their water complexes can provide an insight into the resulting oxidative damage to nucleosides. Herein guided-ion beam mass spectrometry experiment and direct dynamics trajectory simulations were carried out to examine prototype complexes of the 9-methylguanine radical cation with one and two water ligands (
, 9MG˙
·(H
O)
) in the gas phase, wherein the complexes were activated by collisional activation in the experiment and by thermal excitation at high temperatures in the simulations. Guided by mass spectroscopic measurements, trajectory results and reaction potential energy surface, three reaction pathways were identified. The first two reaction pathways start with H-atom abstraction from water by the O6 and N7 atoms in 9MG˙
and are referred to as HA
and HA
, respectively. The primary products of HA
and HA
reactions, including 9MG + H
/9MG + H
and ˙OH, react further to either form 8OH-9MG + H
˙
and 8OH-9MG + H
˙
C8-hydroxylation or form radical cations of 6-
-guanine (6-
-G˙
) and 7H-guanine (7HG˙
)
S
2-type methanol elimination. The third reaction pathway corresponds to the formation of 8OH-9MG
by H elimination from the complex, referred to as HE. Among these product channels, 8OH-9MG + H
˙
has the most favorable formation probability, especially in the presence of additional water molecules. This product may serve as a preceding structure to the 8-oxo-7,8-dihydroguanine lesion in DNA and has implications for health effects of radiation exposure and radiation therapy.
Coacervate microdroplets, formed
via
liquid-liquid phase separation, have been extensively explored as a compartment model for the construction of artificial cells or organelles. In this study, ...coacervate-in-coacervate multi-compartment protocells were constructed using four polyelectrolytes, in which carboxymethyl-dextran and diethylaminoethyl-dextran were deposited on the surface of as-prepared polydiallyldimethyl ammonium/deoxyribonucleic acid coacervate microdroplets through layer-by-layer assembly. The resulting multi-compartment protocells were composed from two immiscible coacervate phases with distinct physical and chemical properties. Molecule transport experiments indicated that small molecules could diffuse between two coacervate phases and that macromolecular enzymes could be retained. Furthermore, a competitive cascade enzymatic reaction of glucose oxidase/horseradish peroxidase-catalase was performed in the multi-compartment protocells. The different enzyme organization and productions of H
2
O
2
led to a distinct polymerization of dopamine. The spatial organization of different enzymes in immiscible coacervate phases, the distinct reaction fluxes between coacervate phases, and the enzymatic cascade network led to distinguishable signal generation and product outputs. The development of this multi-compartment structure could pave the way toward the spatial organization of multi-enzyme cascades and provide new ideas for the design of organelle-containing artificial cells.
A coacervate-in-coacervate micro-architecture is constructed as a multi-compartment protocell model, in which a multi-enzyme cascade is spatially organized for competitive enzymatic reactions.
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•CNT worsened ammonia inhibition when TAN was above 2500 mg N/L.•Potassium transport was interrupted by the interactive effects of CNT and ammonia.•CNT formed potassium channel and ...dispatched proton motivate force.•CNT affected intercellular ATP level and reduced microbial detoxification activity.•Enhanced secretion of bound EPS was related to the presence of ammonia and CNT.
Carbon-based materials are promising in improving the performance and stability of anaerobic digestion (AD). However, it is not clear if carbon-based materials would have any interaction with ammonia on AD performance, especially when ammonia is above inhibition level. This study aims to explore the effects of ammonia on carbon nanotube assisted AD reactors. Methanogenic performance, intracellular energy production, potassium transport activity as well as extracellular polymeric substance (EPS) changes were investigated. The results show that the presence of CNT may mitigate or worsen the ammonia inhibition depending on the total ammonia nitrogen (TAN) concentration. Further investigation found that potassium transportation process of the culture was disturbed with the presence of CNT, which dispatched the proton motive force. As a result, the intracellular energy level reduced, and the microbial detoxification capability decreased. TAN exhibited a strong positive correlation with microbes’ detoxification activity, and CNT concentration was positively correlated with polysaccharide which created a physical structure to protect cell membrane.
Here, we have developed a localized catalytic hairpin assembly (LCHA) strategy for intracellular miR-21 imaging by using DNA nanowires confining both hairpin probes in a compact space. The LCHA is ...constructed by interval hybridization of DNA hairpin probe pairs to a DNA nanowire with multiplex footholds generated by alternating chain hybridization. Compared to the conventional catalytic hairpin assembly (CHA) strategy, the LCHA significantly shortens the reaction time and enhances the sensitivity. Moreover, the proposed LCHA can serve as a carrier for delivery of probes into live cells as well as protect the probes from nuclease degradation and enhances the stability. We anticipate that this design can be widely applied in facilitating basic biomedical research and disease diagnosis.
•A probabilistic evaluation method for corrosion risk of steel reinforcement was proposed.•A probabilistic prediction model of concrete resistivity was developed.•Relationship between concrete ...resistivity and corrosion rate of steel reinforcement was calibrated.•Evaluation criterion for corrosion risk of steel reinforcement based on concrete resistivity was proposed.
In order to overcome the disadvantages of traditional deterministic methods, a probabilistic evaluation method to assess the corrosion risk of steel reinforcement in concrete was proposed based on the probabilistic prediction model of concrete resistivity. The influences of major influential factors including water-to-cement ratio, chloride content, ambient temperature and ambient relative humidity on concrete resistivity were investigated first. Then a probabilistic prediction model of concrete resistivity in terms of the above major influential factors was developed by using the Bayesian theory and the Markov Chain Monte Carlo (MCMC) method. Meanwhile, the evaluation criterion for corrosion risk of steel reinforcement based on concrete resistivity was proposed according to the relationship between concrete resistivity and corrosion rate of steel reinforcement. Finally, a probabilistic evaluation method for corrosion risk of steel reinforcement in concrete was developed by means of the proposed probabilistic prediction model of concrete resistivity. Analysis results show that the proposed probabilistic evaluation method can not only identify the dominant risk of reinforcement corrosion, but also determine the probabilities of steel reinforcement under different corrosion risk levels (e.g. negligible, low, moderate, and high), which could avoid the misjudgment of corrosion risk of steel reinforcement often encountered by the traditional deterministic evaluation methods.
Stromatolites just after the end-Permian extinction are exceptionally well developed in the Chongyang area of Hubei Province, South China. The stromatolites include endolithic coccoidal microbes and ...exhibit three growth forms: columnar-layered, pseudo-columnar, and columnar, each located in different stratigraphic horizons. The columnar type is the most conspicuous and provides key information on the mode of their construction. In this paper, we describe the mega- to microscopic features of these stromatolites together with interpretations of their construction. The columnar type typically comprises alternations of lighter and darker laminae with intercalations of dense micritic laminae. The lighter laminae are composed of fine to coarse calcite cement and fine dolomite, whereas the darker laminae are composed of micrite and microspar. Endolithic coccoids are sporadic in these laminae. In contrast, the dense micritic laminae consist of micrite with abundant endolithic coccoids, accentuating the laminae of stromatolites. The columnar stromatolites were formed under deteriorating conditions after the end-Permian mass extinction as follows: (1) the alternating development of lighter and darker laminae due to the colonization of different microbial communities in lower-energy, shallow- to deep-subtidal settings; (2) carbonate precipitation within each microbial community through microbial metabolic activity and degradation of extracellular polymeric substances (EPS), leading to the alternations of lighter and darker laminae; (3) episodic interruption of the growth of the lighter and darker laminae by endolithic coccoidal activity; and (4) high levels of endolithic activity, accompanied by the precipitation of carbonate within boreholes to produce the dense micritic laminae. In contrast, the columnar-layered and pseudo-columnar types comprise alternations of lighter and darker laminae, composed mainly of fine to coarse calcite cement, fine dolomite, micrite, peloids, and microspar with sporadic endolithic coccoids. The dense micritic laminae are absent or rare in these stromatolites. These types were essentially produced by the repetition of processes (1) and (2) documented in the columnar type. The finely alternating laminae of these stromatolites are therefore the product of the repeated initiation and cessation of growth of relevant microbial communities in response to changing environmental conditions. The stromatolites were formed immediately after the end-Permian extinction and persisted intermittently throughout the Early Triassic. The Chongyang stromatolites are undoubtedly some of the best-developed stromatolites near the Permian–Triassic boundary and retain a high-resolution record of microbial successions and palaeo-oceanic perturbations immediately following the end-Permian extinction.
•PTB stromatolites exceptionally occur in the Chongyang area of Hubei Province, South China.•The columnar type consists of alternations of lighter and darker laminae with intercalations of dense micritic laminae.•The lighter laminae were produced as a result of microbial metabolic and degradation activity.•The darker laminae were produced by extensive endolithic coccoid microbial activity.•The stromatolites record valuable information about microbial successions and environmental changes after the extinction.
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