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The influence on the loss of energetic passing ions by the n = 4 resonant magnetic perturbation (RMP) is investigated through numerical simulations (here, n is the toroidal mode number of the RMP field). Dedicated efforts have been made to uncover how the plasma response modifies the loss fractions and underlying mechanisms. The stochastization of the drift surfaces and the particle loss fractions increase significantly under the response field, in which the resonant component is significantly shielded. In order to better understand how the response field contributes a considerable drift island width, the respective effect of each poloidal component $m_\mathrm{b}$ on the outermost drift island $m_\mathrm{p}/n = 9/4$ are compared (here, $m_\mathrm{b}$ and $m_\mathrm{p}$ are poloidal mode numbers of the RMP components and drift island, respectively). Contrary to the intuition that the components with $m_\mathrm{b} = m_\mathrm{p} \pm 1$ should dominate the sideband resonance, some of the components which fulfill $|m_\mathrm{p}-m_\mathrm{b}|\gg 1$ have the dominant contributions under the response field. There are mainly two reasons accounting for this phenomenon, i.e. the drift motion of particles and the enhancement of amplitudes of non-resonant high- m components by the plasma response near the edge due to the resonant field amplification (RFA) effect. The former made it possible for particles to resonate with the far non-resonant components, and the latter significantly enhanced the perturbation field experienced by particles. The above results imply that the RFA effect is more critical than the stochastization of magnetic topology in the fast ion losses under RMP.

Abstract Atom-transfer radical polymerization (ATRP) is a well-known technique for controlled polymer synthesis. However, the ATRP usually employed toxic heavy metal ionas as the catalyst and was susceptible to molecular oxygen, which made it should be conducted under strictly anoxic condition. Conducting ATRP under ambient and biocompatible conditions is the major challenge. In this study, cytochrome C was explored as an efficient biocatalyst for ATRP under biocompatible conditions. The cytochrome C catalyzed ATRP showed a relatively low polymer dispersity index of 1.19. More interestingly, the cytochrome C catalyzed ATRP showed superior oxygen resistance as it could be performed under aerobic conditions with high dissolved oxygen level. Further analysis suggested that the Fe(II) embed in the cytochrome C might serve as the catalytic center and methyl radical was responsible for the ATRP catalysis. This work explored new biocompatible catalyst for aerobic ATRP, which might open new dimension for practical ATRP and application of cytochrome C protein. Graphical Abstract

An experiment was conducted to study the mode penetration of $n = 1$ resonant magnetic perturbation (RMP) in EAST under low neutral beam injection torque in the co-current direction (Co-NBI). The experimental results indicate that the threshold current ${I_{{\text{RMP,th}}}}$ for field penetration decreases with higher input torque ${T_{{\text{NBI}}}}$ . Furthermore, it is observed that the plasma mode frequency $| {{f_{{\text{MHD}}}}} |$ at counter-current direction is greatly reduced when the plasma toroidal rotation frequency ${f_\phi }$ increases. The theoretical scaling of mode frequency $( {{I_{{\text{RMP,th}}}} \propto {{| {{f_{{\text{MHD}}}}} |}^{0.70}}} )$ predicted by the field penetration theory is in good agreement with the experimental observation ( ${I_{{\text{RMP,th}}}} \propto {| {{f_{{\text{MHD}}}}} |^{0.53}}$ ). The role of $| {{f_{{\text{MHD}}}}} |$ and ${f_\phi }$ on the mode onset threshold was separately investigated using the full toroidal geometry initial value code MARS-Q (Liu et al 2013 Phys. Plasmas 20 042503). The numerical scaling based on the experimental mode frequency is consistent with the experimental and theoretical ones. Numerical results suggest that evaluating the total mode frequency $| {{f_{{\text{MHD}}}}} |$ is crucial in field penetration analysis, in contrast to toroidal rotation frequency ${f_\phi }$ . With the increase of ${T_{{\text{NBI}}}}$ , the decreasing $| {{f_{{\text{MHD}}}}} |$ leads to a reduction in the field penetration threshold. This suggests that more attention should be paid to error field tolerance in low Co-NBI torque scenarios, where the electron diamagnetic frequency may be canceled out by NBI-driven toroidal plasma rotation.

The plasma-beta effect on the n = 1 resonant magnetic perturbation (RMP) field penetration in purely radio-frequency (RF) wave heated discharges has been investigated in EAST. The experimental results show that the dependence of the threshold RMP coil current for field penetration, $I_{\textrm {RMP,th}}$ , on the total absorbed power P _tot scales as approximately $I_{\textrm {RMP,th}} \propto P_{\textrm {tot}}^{0.30}$ , indicating that the error-field tolerance is improved with increasing RF power. This is benefited by the increased electron perpendicular flow dominated by a counter-current electron diamagnetic flow with increasing RF power. However, theoretical scaling in cylindrical geometry overestimates the power index. Assuming an additional term $\beta_\textrm N^{\alpha_{\beta_\textrm N}}$ for the normalized beta in the scaling, it is shown that the fitted $\alpha_{\beta_\textrm N}$ from the experimental observation is around −1, indicating a degradation effect of plasma beta. To clarify the underlying physics of the plasma-beta effect that was not included in the theoretical scaling in cylindrical geometry, the MARS-Q code with full toroidal geometry is employed for simulation of nonlinear field penetration (Liu et al 2013 Phys. Plasmas 20 042503). The MARS-Q simulation results reproduce the $\beta_\textrm N$ dependence well, and hence the P _tot scaling of the threshold current in experimental observations. The main reason for this is that the net total torque, which is mainly contributed by the neoclassical toroidal viscosity (NTV), increases with increasing plasma $\beta_\textrm N$ . The results demonstrate that the nonlinear toroidal coupling effect via NTV torque plays an important role in determining field penetration, even in cases with relatively low $\beta_\textrm N \in [0.3,0.6]$ , which is far less than the no-wall beta limit.

The aim of this paper is to summarize the research progress on the application of biochar in the remediation of heavy metals in tailings soil. Through combing and analyzing the related literature, this paper summarizes the preparation and influencing factors of biochar, its main properties, the effect of remediation of soil heavy metal pollution and the remediation mechanism, as well as the application of biochar in the remediation of heavy metals in tailings soil. The study shows that biochar has good adsorption and passivation of heavy metals, which can significantly reduce the content of heavy metals in the soil and thus improve the soil environment. However, there are certain shortcomings in the study, such as the aging, regeneration and economy of biochar need to be further investigated. Therefore, future studies should deeply investigate the optimal conditions, economic feasibility and technical application of biochar in soil heavy metal remediation, with a view to providing new ideas and methods for the remediation of heavy metal pollution in tailings soil. [ABSTRACT FROM AUTHOR]