Evidence of a nonlinear transition from mitigation to suppression of the edge localized mode (ELM) by using resonant magnetic perturbations (RMPs) in the EAST tokamak is presented. This is the first demonstration of ELM suppression with RMPs in slowly rotating plasmas with dominant radio-frequency wave heating. Changes of edge magnetic topology after the transition are indicated by a gradual phase shift in the plasma response field from a linear magneto hydro dynamics modeling result to a vacuum one and a sudden increase of three-dimensional particle flux to the divertor. The transition threshold depends on the spectrum of RMPs and plasma rotation as well as perturbation amplitude. This means that edge topological changes resulting from nonlinear plasma response plays a key role in the suppression of ELM with RMPs. DOI: 10.1103/PhysRevLett.117.115001 Magnetic reconnection and the resultant topological change play an important role in plasma dynamics in both laboratory and space plasma physics research. The formation of an edge stochastic magnetic field caused by resonant magnetic perturbations (RMPs) is believed to be the reason for the suppression of periodic crash events near the plasma edge known as the edge localized mode (ELM) observed in the DIII-D tokamak [1]. The ELM causes transient heat loads to the plasma facing components and may degrade them on the next generation fusion device like ITER [2]. The reduction of free energy in the edge pressure gradient and current because of field stochasticity moves the plasma into a stable regime against the ELM [3]. This successful experiment motivated ELM control using RMPs in many other tokamaks [4][5][6][7]. However, the plasma response effect usually shields the external applied RMPs and may significantly reduce the magnetic field stochasticity [8][9][10][11], which makes this mechanism questionable. Different from topological change, the linear peelinglike magneto hydro dynamics (MHD) response has been found to play an important role in ELM control [12][13][14]. Nonlinear plasma response has been observed in the JET totamak [15]. The possible formation of a magnetic island near the plasma edge [16] with a toroidal Fourier mode number n ¼ 1 during ELM suppression by using n ¼ 2 RMP has been recently observed on DIII-D [17]. However, the key difference between ELM suppression and mitigation and the different roles of linear and nonlinear plasma response on ELM suppression are still not clear.In this Letter, we report the first observation of full ELM suppression using low n RMPs in slowly rotating plasmas with dominant radio-frequency (rf) wave heating, which is potentially important for the application of this method for a future fusion device. This is the first observation of full ELM suppression using RMPs in the medium plasma collisionality regime in EAST, and it expands beyond the previous observations of ELM suppression on DIII-D [1,3] and KSTAR [7]. It is found that not only the formation of a magnetic island near the edge [17] but also a critical leve...

Photodissociation dynamics of H 2 O at 121.6 nm have been studied using the H atom Rydberg ''tagging'' time-of-flight technique and by quasiclassical trajectory ͑QCT͒ calculations. Product kinetic energy distributions and angular distributions have been measured. From these distributions, rovibronic distributions of the OH radical product as well as the state resolved angular anisotropy parameters were determined. The dissociation energy D 0 0 ͑H-OH͒ is determined to be 41151 Ϯ5 cm Ϫ1 . Two clear alternations in the OH(X,vϭ0) rotational distribution have been observed, with each alternation corresponding to an oscillation in the anisotropy distribution. These oscillations had been attributed to the dynamical interference between the two conical intersection pathways. Further theoretical modeling in this work strongly supports this argument. Very highly vibrationally excited OH(X) products ͑up to vϭ9͒ have also been observed. These are ascribed to interconversion of H-O-H bending ͑H-H vibration͒ and O-H vibration in O-H-H geometries. The effect of parent rotational excitation on the OH(A) product state distribution and anisotropy distribution was observed for the first time. Experimental results also show clear evidence for the triple dissociation channel, O( 3 P)ϩ2H. Accurate branching ratios of different product channels have been determined. Results of detailed QCT calculations agree well with the experimental results in this work.

To face the increasing demand of self-healing hydrogels with biocompatibility and high performances, a new class of cellulose-based self-healing hydrogels are constructed through dynamic covalent acylhydrazone linkages. The carboxyethyl cellulose-graft-dithiodipropionate dihydrazide and dibenzaldehyde-terminated poly(ethylene glycol) are synthesized, and then the hydrogels are formed from their mixed solutions under 4-amino-DL-phenylalanine (4a-Phe) catalysis. The chemical structure, as well as microscopic morphologies, gelation times, mechanical and self-healing performances of the hydrogels are investigated with 1 H NMR, Fourier transform infrared spectroscopy, atomic force microscopy, rheological and compression measurements. Their gelation times can be controlled by varying the total polymer concentration or 4a-Phe content. The resulted hydrogels exhibit excellent self-healing ability with a high healing efficiency (≈96%) and good mechanical properties. Moreover, the hydrogels display pH/redox dual responsive sol-gel transition behaviors, and are applied successfully to the controlled release of doxorubicin. Importantly, benefitting from the excellent biocompatibility and the reversibly cross-linked networks, the hydrogels can function as suitable 3D culture scaffolds for L929 cells, leading to the encapsulated cells maintaining a high viability and proliferative capacity. Therefore, the cellulose-based self-healing hydrogels show potential applications in drug delivery and 3D cell culture for tissue engineering.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201703174.For this purpose, intensive efforts have been made so far to design and fabricate self-healing hydrogels by incorporating dynamic covalent and noncovalent bonds into the hydrogel networks. [2] Since dynamic covalent bonds, such as Schiff bases, [3] disulfide bonds, [4] Diels-Alder reactions, [5] and phenylboronate complexations, [6] can integrate both the stability of covalent bonds and the reversibility of noncovalent bonds, [2a] they have been employed to prepare the self-healing hydrogels with diverse functions. In particular, chitosan-based self-healing hydrogels constructed via Schiff bases have been widely explored as biomaterials for hemostasis, [7] drug delivery, [8] cell therapy, and 3D cell culture, [3a,9] due to their good biocompatibility and automatic repair ability under physiological conditions. [3b] However, the relatively fast hydrolytic degradation rate, [2a] poor structural integrity, and weak mechanical properties [3b] of those hydrogels impede their biomedical applications for achieving longer-lasting functions. Acylhydrazone bonds, which formed via the condensation of hydrazides with carbonyl groups, are very close relatives to Schiff bases, but are much more stable. Thus, the acylhydrazone bonds have been utilized to construct the selfhealing hydrogels with robust mechanical properties. [4b,10] For instance, a strong self-healing hydrogel that...

Achieving rapid and effective hemostasis on irregularly shaped, non‐compressible visceral, and high‐pressure arterial bleeding wounds remains a critical clinical challenge. Herein, an ultrafast self‐gelling and wet adhesive polyethyleneimine/polyacrylic acid/quaternized chitosan (PEI/PAA/QCS) powder is reported as the hemostatic material and wound dressing. PEI/PAA/QCS powder deposited on bleeding wounds can rapidly absorb a large amount of blood to concentrate coagulation factors. Meanwhile, the powder can form an adhesive hydrogel in situ within 4 s upon hydration to form a pressure‐resistant physical barrier. Furthermore, PEI/PAA/QCS hydrogels can aggregate blood cells and platelets to enhance hemostasis. Depositing PEI/PAA/QCS powder on various bleeding wounds, including at the liver and heart, high‐pressure femoral artery and tail vein of rats, arrests the bleeding around 10 s with no rebleeding after ten minutes. Excellent hemostasis of PEI/PAA/QCS powder is further demonstrated against massive hemorrhage in porcine spleen and liver in vivo, which are non‐compressible organs with abundant blood supply. In addition, the powder can be used as a wound dressing to promote the healing of the full‐thickness skin wounds. The advantages of PEI/PAA/QCS powder including rapid and effective hemostasis, effective wound healing, easy usage, low cost, and adaptability to fit complex target sites make it a promising biomaterial for surgical applications.