Kinking-facilitated nano-crystallization in a shock compressed Mg-1Zn alloy

The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM.Since dislocation slipping and twinning were locally suppressed during high strain-rate deformation,a more flexible kinking deformation was activated to adjusted local orientation and facilitate slipping and twinning within the kinks.Meanwhile,due to the slow heat dissipation that resulted in a local temperature elevating,the kink bands were evolved into deformation bands with recrystallized nano-grains.Such a finding provides a new perspective for kinking-facilitated nanocrystallization in Mg alloys and other anisotropic metallic materials.

Twin recrystallization mechanisms in a high strain rate compressed Mg-Zn alloy

Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which showed a{1012}-{1012}double twin relationship with the matrix.When the as-deformed alloy was annealed at 200°C,the{1011}compression twins and{1011}-{1012}double twins showed a higher priority to recrystallize.In addition,the coarse{1012}tension twins and their inner double twins were preferentially to recrystallize,while the lenticular tension twins had little impact on the recrystallization.Therefore,obtaining more compression twins or coarse twins instead of lenticular tension twins can be an effective approach to manipulate recrystallization process in deformed Mg alloys.

Effective femtosecond laser shock peening on a Mg-3Gd alloy at low pulse energy 430 μJ of 1 kHz

In this paper,microstructure evolution and hardness of Mg-3 Gd alloy treated by femtosecond(fs)laser shock peening(LSP)with direct and confined ablation m odes were investigated in detail.Under a relatively low pulse energy of 430μJ with a repetition of 1 kHz,the surface hardness of sample has been enhanced by 70%effectively.Comp a r e d with ns-LSP with pulse fluence of 71.7J/cm2,fs-LSP with pulse fluence of 34.2 J/cm2 is superior in the hardness increment,both of which are in the same order of magnitude.A distinct grain refinement of surface layer has been discovered and results in the increase of hardness.Nonuse of absorption and confining layers and the employment of the industry commercial fs laser with high repetition can inspire big potential L S P application in special metal material.©2019 Published by Elsevier B.V.on behalf of Chongqing University.

Enhancing strength-ductility synergy in a Mg-Gd-Y-Zr alloy at sub-zero temperatures via high dislocation density and shearable precipitates

The strength-ductility trade-offdilemma is hard to be evaded in high-strength Mg alloys at sub-zero temperatures,especially in the Mg alloys containing a high volume fraction of precipitates.In this paper,we report an enhanced strength-ductility synergy at sub-zero temperatures in an aged Mg-7.37Gd-3.1Y-0.27Zr alloy.The tensile stress-strain curves at room temperature(RT),−70℃ and−196℃ show that the strength increases monotonically with decreasing temperature,but the elongation increases first from RT to−70℃ then declines from−70℃ to−196℃.After systematic investigation of the microstructure evolutions at different deformation temperatures via synchrotron X-ray diffraction,electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM),it is found that a high dislocation density with sufficient<c+a>dislocations promotes good tensile ductility at−70℃,which is attributed to the minimized critical resolved shear stress(CRSS)ratio of non-basal<c+a>to basaldislocations.In ad-dition,more shearable precipitates can further improve the ductility via lengthening the mean free path of dislocation glide.The present work demonstrates that an excellent strength-ductility synergy at sub-zero temperatures can be achieved by introducing a high dislocation density and shearable precipitates in high-strength Mg alloys.

Phase equilibria of long-period stacking ordered phase in the ternary Mg-Y-Al alloys

Phase equilibria focusing on the long-period stacking ordered(LPSO)phases have been experimentally in-vestigated in the Mg-Y-Al alloys.The microstructures of the eleven representative alloys annealed at 450,500 and 550°C were systematically investigated using X-ray diffraction(XRD),scanning electron mi-croscopy(SEM)and transmission electron microscopy(TEM).Two thermodynamically stable LPSO poly-types were identified,including 18R and 10H structures.Meanwhile,the transformation of 18R→10H was detected in Mg-9.0Y-1.7Al(at.%)alloy,while the coexistence of 18R and 10H was observed in Mg-14.2Y-12.8Al(at.%)alloy.It was found that the LPSO phases were non-stoichiometric compounds with ternary solubilities.The 18R can dissolve up to 7.21 at.%-8.37 at.%Al and 10.75 at.%-12.01 at.%Y,while the 10H can dissolve up to 9.35 at.%-10.37 at.%Al and 14.50 at.%-14.94 at.%Y.All of the experimental re-sults were used to construct the isothermal sections,which is conducive to the design of Mg-Y-Al alloys.

Ribosome biogenesis in disease:new players and therapeutic targets

The ribosome is a multi-unit complex that translates mRNA into protein.Ribosome biogenesis is the process that generates ribosomes and plays an essential role in cell proliferation,differentiation,apoptosis,development,and transformation.The mTORC1,Myc,and noncoding RNA signaling pathways are the primary mediators that work jointly with RNA polymerases and ribosome proteins to control ribosome biogenesis and protein synthesis.Activation of mTORC1 is required for normal fetal growth and development and tissue regeneration after birth.Myc is implicated in cancer development by enhancing RNA Pol II activity,leading to uncontrolled cancer cell growth.The deregulation of noncoding RNAs such as microRNAs,long noncoding RNAs,and circular RNAs is involved in developing blood,neurodegenerative diseases,and atherosclerosis.We review the similarities and differences between eukaryotic and bacterial ribosomes and the molecular mechanism of ribosome-targeting antibiotics and bacterial resistance.We also review the most recent findings of ribosome dysfunction in COVID-19 and other conditions and discuss the consequences of ribosome frameshifting,ribosome-stalling,and ribosome-collision.We summarize the role of ribosome biogenesis in the development of various diseases.Furthermore,we review the current clinical trials,prospective vaccines for COVID-19,and therapies targeting ribosome biogenesis in cancer,cardiovascular disease,aging,and neurodegenerative disease.

Inflammasomes as therapeutic targets in human diseases

Inflammasomes are protein complexes of the innate immune system that initiate inflammation in response to either exogenous pathogens or endogenous danger signals.Inflammasome multiprotein complexes are composed of three parts:a sensor protein,an adaptor,and pro-caspase-1.Activation of the inflammasome leads to the activation of caspase-1,which cleaves pro-inflammatory cytokines such as IL-ip and IL-18,leading to pyroptosis.Effectors of the inflammasome not only provide protection against infectious pathogens,but also mediate control over sterile insults.Aberrant inflammasome signaling has been implicated in the development of cardiovascular and metabolic diseases,cancer,and neurodegenerative disorders.Here,we review the role of the inflammasome as a double-edged sword in various diseases,and the outcomes can be either good or bad depending on the disease,as well as the genetic background.We highlight inflammasome memory and the two-shot activation process.We also propose the M-and N-type inflammation model,and discuss how the inflammasome pathway may be targeted for the development of novel therapy.

The effect of basal dislocation on {11■1} twin boundary evolution in a Mg-Gd-Y-Zr alloy

This study aims to understand the features of{11■1}twin boundaries in a high strain rate compressed Mg-10 Gd-3Y-0.4Zr using electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM).Based on the Schmid factor calculations,the basal dislocations are easily activated within the{11■1}twin and suppressed in the surrounding matrix.The consequent basal dislocation-twin interaction during deformation can lead to the misorentiation deviation of{11■1}twin boundaries,accompanying with the formation of a step at the twin boundary.Such a{11■1}twin boundary evolution mechanism provides a new vision of twinning behavior in Mg alloys.

Stem cell-derived exosomes repair ischemic muscle injury by inhibiting the tumor suppressor Rbl-mediated NLRP3 inflammasome pathway

Dear Editor,Lower-limb ischemia is a serious clinical condition affecting many patients world-wide and there is no effective therapy.Ischemia activates the NLRP3 inflammasome,which triggers tissue damage by releasing inflammatory cytokines including IL-1β and IL-18.1 However,the molecular mechanisms underlying activation of the NLRP3 inflammasome remain largely unknown.

Deformation mechanism and dynamic precipitation in a Mg-7Al-2Sn alloy processed by surface mechanical attrition treatment

The effect of second phases on the deformation mechanism of as-cast, solution-treated and aged Mg-7Al-2Sn (AT72) alloys during surface mechanical attrition treatment (SMAT) was investigated. Twinning was suppressed in the alloys containing second phases, which can provide nonuniform microstructures and phase boundaries as dislocation sources. Dynamic precipitation in AT72 alloys was studied during SMAT deformation as well.Mg2Sn particles can dynamically precipitate on the surface of all AT72 alloys during SMAT process. The quantity of Mg2Sn particles in the as-cast alloy, which is determined by the initial quantity of second phases, is larger than that of T4 and T6 alloys after the SMAT process.