First‐order organic matter decomposition models are used within most Earth System Models (ESMs) to project future global carbon cycling; these models have been criticized for not accurately ...representing mechanisms of soil organic carbon (SOC) stabilization and SOC response to climate change. New soil biogeochemical models have been developed, but their evaluation is limited to observations from laboratory incubations or few field experiments. Given the global scope of ESMs, a comprehensive evaluation of such models is essential using in situ observations of a wide range of SOC stocks over large spatial scales before their introduction to ESMs. In this study, we collected a set of in situ observations of SOC, litterfall and soil properties from 206 sites covering different forest and soil types in Europe and China. These data were used to calibrate the model MIMICS (The MIcrobial‐MIneral Carbon Stabilization model), which we compared to the widely used first‐order model CENTURY. We show that, compared to CENTURY, MIMICS more accurately estimates forest SOC concentrations and the sensitivities of SOC to variation in soil temperature, clay content and litter input. The ratios of microbial biomass to total SOC predicted by MIMICS agree well with independent observations from globally distributed forest sites. By testing different hypotheses regarding (using alternative process representations) the physicochemical constraints on SOC deprotection and microbial turnover in MIMICS, the errors of simulated SOC concentrations across sites were further decreased. We show that MIMICS can resolve the dominant mechanisms of SOC decomposition and stabilization and that it can be a reliable tool for predictions of terrestrial SOC dynamics under future climate change. It also allows us to evaluate at large scale the rapidly evolving understanding of SOC formation and stabilization based on laboratory and limited filed observation.
Microbial explicit decomposition models have been developed to replace the conventional first‐order model used in most Earth System Models, but their evaluation was limited to observations from laboratory incubations or few field experiments. A comprehensive evaluation of these models is essential using large‐scale in situ observations. We found that, compared to first‐order decomposition model, microbial explicit model more accurately estimates SOC concentrations, microbe/SOC ratio, SOC composition and the sensitivities of SOC stock to changed climate, litter input and soil properties. We support to replace the first‐order decomposition model used in existing Earth System Models with microbial explicit model.
Carbon-supported first-row transition metal complexes drive electroreduction of CO2 to CO in aqueous medium with remarkable activity and selectivity. However, their durability under negative ...potentials is quite low and the deactivation mechanisms are still not clear. Herein, we present an in-depth mechanistic study on the stability of Co porphyrin-based catalysts during CO2 reduction in an aqueous electrolyte. The mechanisms of the degradation reactions were evaluated for Co tetraphenylporphyrin (CoTPP) using a combination of spectral, electrochemical, and theoretical methods. Our evidence shows that two major pathways contribute to the gradual activity loss. The first route is oxidative and yields the catalytically inactive complex CoIIITPPOH. The second pathway is based on reductive carboxylation of the porphyrin ring via transient formation of Co0TPP2– and Co0TPP-CO2–. The latter reaction disrupts the π-system of the porphyrin structure and leads to the complete disintegration of the macrocyclic core. In contrast to the earlier reports, we found that the direct poisoning by CO, demetallation, and reduction to chlorins play no significant role in the deactivation process. It was further determined that the bulky donating functional groups disfavor the formation of dianionic species and restrict access of CO2 to the vulnerable meso-position of the porphyrin ligand, thus improving the catalyst stability. The effect was found to be especially strong for the −OMe-substituted complex CoTPP-(OMe)8 that shows excellent reusability under overpotentials below 500 mV. In turn, electronegative substituents such as fluorine suppress the activity of the catalyst and provide no advantages in terms of durability.
•A hybrid hydrogel (ADPH) composed of ε-Polylysine, polydopamine and agarose was synthesized.•ADPH showed stable photothermal functionality and desirable physicochemical properties.•ADPH possessed ...excellent biocompatibility and photothermal sterilization efficiency.•ADPH significantly promoted wound healing by regulating bacteria-induced inflammation.
Polydopamine (PDA) is emerging as an attractive photothermal agent due to its good photothermal performance and excellent biocompatibility. However, without chemical modification, PDA is normally unstable and usually leached out from the constructed biomaterials, realistically limiting its application space. Here, we constructed a new hydrogel dressing with robust and stable photothermal performance by introduction of ε-Polylysine (ε-PL) into agarose/PDA matrix to efficiently lock PDA. By optimizing PDA/ε-PL rational dose in agarose network structure, a hybrid agarose/PDA/ε-PL hydrogel (ADPH) with stable photothermal functionality and desirable physicochemical properties could be achieved. ADPH possessed satisfactory microbicidal efficacy in vivo, which enabled the bacteria-infected skin wound to be cured quickly by successful suppressing inflammation, accelerating collagen deposition and promoting angiogenesis in a bacterial-infected wound model. Collectively, this study illustrates a simple, convenient but powerful strategy to design functionally stable ADPH dressing for treating dermal wounds, which could open vistas in clinical wound management.
Traditional macroeconomic stabilization policies seek to moderate swings in economic activity through measures that primarily augment aggregate demand. Such measures are, however, inadequate in ...mitigating the comprehensive effects of crisis such as the COVID-19, which affects both the demand and supply sides of the economy. Moreover, monetary policies are presently close to a liquidity trap combined with weakened transmission links to the real economy. Fiscal policies have been reactivated, albeit in an ad hoc and experimental manner. Based on a literature review and the policy responses following the COVID-19 crisis, the objective is to present a modified and extended framework for stabilization policies. In particular, the importance of microeconomic supply-side measures that promote entrepreneurial processes and knowledge-upgrading efforts are emphasized. Furthermore, a coherent realigning of policies at the micro- and macro-levels is argued to enhance the potential for long-term growth and to facilitate the restructuring of an economy that normally follows a crisis.
Plain English Summary
The COVID-19 crisis makes traditional stabilization policies obsolete. Reinstate the market and redirect policy from interest rates and unconditional state support toward providing employees and firms with adequate knowledge for future challenges. Traditional crises policies seek to moderate swings in economic activity by primarily lowering interest rates and increase governmental expenditure to stimulate demand and economic activity. However, the effectiveness of both of these measures has been questioned, in particular, further reductions in already extremely low-interest rates. The present COVID-19 crisis has highlighted the importance of taking firms, entrepreneurs, trade, etc., into account, i.e., the supply side of the economy. It is argued that traditional policies should partly be replaced by measures targeting entrepreneurial processes, firm growth, innovation, and knowledge upgrading. Corporate taxes should be used to increase firms’ crisis resilience, increase investment, and encourage start-ups, while state support should be conditioned on employees engaging in knowledge upgrading. Hence, the main conclusion of this study is that such redirection of policies will more effectively level out swings in the business cycle, increase the potential for long-term growth, and make it easier for employees and firms to adjust to new economic conditions.
Polyacrylonitrile (PAN) is a versatile man-made polymer and has been used in a large array of products since its first mass production in the mid 40s. Among all applications of PAN the widely used ...application is in manufacture of precursor fiber for fabrication of carbon fibers. The process of PAN-based carbon fiber production comprises fiber spinning, thermal stabilization and carbonization stages. Carbon fiber properties are significantly dependent on the quality of PAN precursor fiber and in particular the process parameters involved in thermal stabilization. This paper is the first comprehensive review that provides a general understanding of the links between PAN fiber structure, properties, and its stabilization process along with the use of mathematical modelling as a powerful tool in prediction and optimization of the processes involved. Since the promise of the mathematical modelling is to predict the future behaviour of the system and the value of the variables for the unseen or unmeasured domain of variables; and in the era of industry 4.0 rise, this review will be valuable in further understanding of the intricate processes of carbon fiber manufacture and utilising the advanced mathematical modelling using machine learning techniques to predict and optimize a range of critical factors that control the quality of PAN and resultant carbon fibers.
•Humic acid residue (HAS) is currently a wasted resource.•We modified HAS with NH4H2PO4 to improve its heavy metal stabilization capacity.•N-HAS reduces the mobility of Hg and Pb in soils.•Addition ...of N-HAS alters soil physicochemical properties.•N-HAS was an industrially produced heavy metal passivator.
Humic acid residue (HAS), as a waste product from the extraction of humic acid from low-rank coal such as weathered coal and lignite, is characterized by its abundant yield and low price. However, the low efficiency and high pH value of HAS in passivating heavy metals limit their application in the passivation of heavy metals in soils. To improve the passivation efficiency of humic acid residues against heavy metals, in this study, modified humic acid residues (N-HAS) were prepared by pretreatment with HNO3 and modification with NH4H2PO4. The results showed that the passivation efficiency of N-HAS was up to 87.75% and 57.07% for Hg and Pb in the effective state, and the adsorption kinetics were under the pseudo-second-order model. The addition of N-HAS to the soil resulted in a change in the morphology of the heavy metals, with the acid extractable state of Hg and Pb reduced by 66.92% and 30.44% respectively, and the results of the Toxicity Leaching Test (TCLP) showed that the addition of N-HAS significantly reduced the leaching toxicity and potential ecological risk index (RI). The soil physicochemical properties changed after the addition of N-HAS and there was a correlation between the soil physicochemical properties and the effective state of Hg and Pb content. In conclusion, N-HAS has a positive effect on the remediation of heavy metal-contaminated soil and has a broad application prospect.
This article addresses the event-triggered stabilization for continuous-time stochastic systems. Due to stochastic effects, the system state is hard to predict and dominate, and the system behavior ...would vary with every trial (i.e., sample path) even for the same initial condition. This gives rise to substantial challenges, especially, in determining the execution/sampling times and assessing the closed-loop performance, which urges us to develop powerful and sophisticated tools/methods for the analysis and design of stochastic event-triggered control. In this article, basic theorems, particularly a stochastic convergence theorem, are first proposed for stochastic event-triggered controlled systems. Then, a framework of event-triggered stabilization is established for the stochastic systems without applying the well-known Lyapunov theorems. Specifically, we present conditions under which event-triggered stabilization is feasible for the systems. Accordingly, static and dynamic event-triggering mechanisms are proposed with enforcing a fixed positive lower bound for the interexecution times. While avoiding infinitely fast execution/sampling, both asymptotic stabilization and exponential stabilization are achieved for the systems by the proposed stochastic convergence theorem. The involved analysis is helpful to form a pattern for stochastic event-triggered controlled systems. As the direct application of the established framework, the constructive design of event-triggered controller is realized, respectively, for two representative classes of stochastic systems.
The paper provides a comparative investigation on accuracy and conservation properties of two particle regularization schemes, namely, the Dynamic Stabilization (DS) 1 and generalized Particle ...Shifting (PS) 2 schemes in simulations of both internal and free-surface flows in ISPH (Incompressible SPH) context. The paper also presents an Optimized PS (OPS) scheme for accurate and consistent implementation of particle shifting for free-surface flows. In contrast to PS, the OPS does not contain any tuning parameters for free-surface, consistently resulting in perfect elimination of shifting normal to an interface and resolves the unphysical discontinuity beneath the interface, seen in PS results.
•Accuracy and conservation properties of two particle regularization schemes are comparatively investigated.•The considered particle regularization schemes are dynamic stabilization and particle shifting.•An optimized particle shifting is proposed for free-surface flows.•The optimized particle shifting is free of tuning parameters and eliminates shifting normal to an interface.•The optimized particle shifting outperforms dynamic stabilization in terms of accuracy and energy conservation.
This paper considers the problem of sampled-data adaptive output feedback fuzzy stabilization for switched uncertain nonlinear systems associated with asynchronous switching. A state observer is ...designed to estimate the unmeasured states and fuzzy logic systems are employed to deal with the unknown nonlinear terms. Sampled-data controller and novel switched adaptive laws are constructed based on the recursive design method and an average dwell time constraint is given to ensure that the closed-loop system is stable. The proposed scheme is employed in a mass-spring-damper system to demonstrate its effectiveness.
Aqueous dispersions of graphene oxide are inherently unstable in the presence of electrolytes, which screen the electrostatic surface charge on these nanosheets and induce irreversible aggregation. ...Two complementary strategies, utilizing either electrostatic or steric stabilization, have been developed to enhance the stability of graphene oxide in electrolyte solutions, allowing it to stay dispersed in cell culture media and serum. The electrostatic stabilization approach entails further oxidation of graphene oxide to low C/O ratio (∼1.1) and increases ionic tolerance of these nanosheets. The steric stabilization technique employs an amphiphilic block copolymer that serves as a noncovalently bound surfactant to minimize the aggregate-inducing nanosheet–nanosheet interactions. Both strategies can stabilize graphene oxide nanosheets with large dimensions (>300 nm) in biological media, allowing for an enhancement of >250% in the bioconjugation efficiency of streptavidin in comparison to untreated nanosheets. Notably, both strategies allow the stabilized nanosheets to be readily taken up by cells, demonstrating their excellent performance as potential drug-delivery vehicles.
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