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Effect of refinement of grains and icosahedral phase on hot compressive deformation and processing maps of Mg-Zn-Y magnesium alloys with different volume fractions of icosahedral phase

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journal of Materials Science & Technology 2019年第1期35卷 181-191页

作者： T.Y.kwak w.j.Kim Department of Materials Science and Engineering Hongik University

The effect of the volume fraction of I-phase on the hot compressive behavior and processing maps of the extruded Mg-Zn-Y alloys was examined, and the obtained results were compared with those of the cast alloys in a previous work. The average grain sizes, fractions of dynamically recrystallized(DRXed) grains,and sizes of DRXed grains of the extruded alloys after compressive deformation were significantly smaller,higher and smaller, respectively, than those of the cast alloys after compressive deformation under the same experimental conditions. This was because the microstructures of the extruded alloys, having much more grain boundaries and more refined I-phase particles than the cast alloys, provided a larger number of nucleation sites for dynamic recrystallization than those of the cast alloys. The constitutive equations for high-temperature deformation of the extruded and cast alloys could be derived using the same activation energy for plastic flow, which was close to the activation energy for lattice diffusion in *** with the cast alloys, the onset of the power law breakdown(PLB) occurred at larger ZenerHolloman(Z) parameter values in the extruded alloys. This was because the extruded alloys had finer initial grain sizes and higher fractions of finer DRXed grains compared to the cast alloys, such that the onset of PLB caused by creation of excessive concentrations of deformation-induced vacancies was delayed to a higher strain rate and a lower temperature. The flow-stress difference between the extruded alloys and the cast alloys could be attributed to the difference in the fraction of DRXed grains. According to the processing maps, the extruded alloys exhibited higher power dissipation efficiency and flow stability than the cast alloys. This agreed with the microstructural observations.

关键词： Hot compression Magnesium alloy Processing map Grain refinement Dynamic recrystallization

Superplastic behavior of an ultrafine-grained Mg-13Zn-1.55Y alloy with a high volume fraction of icosahedral phases prepared by high-ratio differential speed rolling

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journal of Materials Science & Technology 2017年第9期33卷 919-925页

作者： T.Y.kwak w.j.Kim Rare Metal R&BD Group Korea Institute of Industrial Technology Department of Materials Science and Engineering Hongik University

An ultrafine-grained（UFG） Mg-13Zn-1.55 Y alloy（Zw132） with a high volume fraction（7.4%） of icosahedral phase（I-phase, Mg;Zn;Y） particles was prepared by applying high-ratio differential speed rolling（HRDSR） on the cast microstructure following homogenization. The alloy exhibited excellent superplasticity at low temperatures(tensile elongations of 455% and 1021% 473 K-10;s;and 523 K-10;s;,respectively). Compared with UFG Mg-9.25Zn-1.66 Y alloy（Zw92） with a lower volume fraction of I-phase particles（4.1%）, which was prepared using the same processing routes, the UFG Zw132 alloy exhibited a higher thermal stability of grain size. Rapid grain coarsening, however, occurred at temperatures beyond523 K, leading to a loss of superplasticity. The high-temperature deformation behavior of the HRDSRprocessed Zw132 alloy could be well described assuming that the mechanisms of grain boundary sliding and dislocation climb creep competed with each other and considering that the grain-size was largely increased by accelerated grain growth at the temperatures beyond 523 K.

关键词： Magnesium alloy Superplastic deformation Ultrafine grain Icosahedral quasicrystal Grain growth

A functional tacrolimus-releasing nerve wrap for enhancing nerve regeneration following surgical nerve repair

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Neural Regeneration Research 2025年第1期20卷 291-304页

作者： Simeon C.Daeschler Katelyn j.w.So Konstantin Feinberg Marina Manoraj jenny Cheung jennifer Zhang Kaveh Mirmoeini jPaul Santerre Tessa Gordon Gregory HBorschel SickKids Research Institute Neuroscience and Mental Health ProgramTorontoONCanada Institute of Biomaterials and Biomedical Engineering University of TorontoTorontoONCanada Indiana University School of Medicine IndianapolisINUSA Division of Plastic and Reconstructive Surgery the Hospital for Sick ChildrenTorontoONCanada Translational Biology and Engineering Program Ted Rogers Centre for Heart ResearchInstitute of Biomedical EngineeringFaculty of DentistryUniversity of TorontoTorontoONCanada

Axonal regeneration following surgical nerve repair is slow and often incomplete,resulting in poor functional recovery which sometimes contributes to lifelong ***,there are no FDA-approved therapies available to promote nerve *** accelerates axonal regeneration,but systemic side effects presently outweigh its potential benefits for peripheral nerve *** authors describe herein a biodegradable polyurethane-based drug delivery system for the sustained local release of tacrolimus at the nerve repair site,with suitable properties for scalable production and clinical application,aiming to promote nerve regeneration and functional recovery with minimal systemic drug *** is encapsulated into co-axially electrospun polycarbonate-urethane nanofibers to generate an implantable nerve wrap that releases therapeutic doses of bioactive tacrolimus over 31 *** and drug loading are adjustable for applications in small and large caliber nerves,and the wrap degrades within 120 days into biocompatible *** released from the nerve wrap promotes axon elongation in vitro and accelerates nerve regeneration and functional recovery in preclinical nerve repair models while off-target systemic drug exposure is reduced by 80%compared with systemic *** its surgical suitability and preclinical efficacy and safety,this system may provide a readily translatable approach to support axonal regeneration and recovery in patients undergoing nerve surgery.

关键词： biodegradable local drug delivery nerve injury nerve regeneration nerve wrap tacrolimus

s-REGULAR DIHEDRAL COVERINGS OF THE COMPLETE GRAPH OF ORDER 4

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Chinese Annals of Mathematics,Series B 2004年第1期25卷 57-64页

作者： FENGYANQUAN j.H.kwak DepartmentofMathematics NorthernJiaotongUniversityBeijing100044China CombinatorialandComputationalMathematicsCenter PohangUniversityofScienceandTechnologyPohang790-784Korea.

A graph is s-regular if its automorphism group acts regularly on the set of its s-arcs. An infinite family of cubic 1-regular graphs was constructed in [7] as cyclic coverings of the three-dimensional Hypercube, and a classification of all s-regular cyclic coverings of the complete bipartite graph of order 6 was given in [8] for each s ≥ 1, whose fibre-preserving automorphism subgroups act arc-transitively. In this paper, the authors classify all s-regular dihedral coverings of the complete graph of order 4 for each s ≥ 1, whose fibre-preserving automorphism subgroups act arc-transitively. As a result, a new infinite family of cubic 1-regular graphs is constructed.

关键词： s-regular graphs s-arc-transitive graphs Regular coverings

Treating amyotrophic lateral sclerosis with allogeneic Schwann cell-derived exosomal vesicles: a case report

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Neural Regeneration Research 2025年第4期20卷 1207-1216页

作者： Pascal j.Goldschmidt-Clermont Aisha Khan George jimsheleishvili Patricia Graham Adriana Brooks Risset Silvera Alexander j.P.Goldschmidt Damien D.Pearse w.Dalton Dietrich Allan D.Levi james D.Guest Miller School of Medicine University of MiamiMiamiFLUSA Stem Cell Institute Miller School of MedicineUniversity of MiamiMiamiFLUSA The Miami Project to Cure Paralysis Miller School of MedicineUniversity of MiamiMiamiFLUSA Alzady International LLC MiamiFLUSA Neurological Surgery Miller School of MedicineUniversity of MiamiMiamiFLUSA

Schwann cells are essential for the maintenance and function of motor neurons,axonal networks,and the neuromuscular *** amyotrophic lateral sclerosis,where motor neuron function is progressively lost,Schwann cell function may also be ***,important signaling and potential trophic activities of Schwann cell-derived exosomal vesicles have been *** case report describes the treatment of a patient with advanced amyotrophic lateral sclerosis using serial intravenous infusions of allogeneic Schwann cell-derived exosomal vesicles,marking,to our knowledge,the first instance of such *** 81-year-old male patient presented with a 1.5-year history of rapidly progressive amyotrophic lateral *** initial diagnosis,the patient underwent a combination of generic riluzole,sodium phenylbutyrate for the treatment of amyotrophic lateral sclerosis,and *** patient volunteered to participate in an FDA-approved single-patient expanded access treatment and received weekly intravenous infusions of allogeneic Schwann cell-derived exosomal vesicles to potentially restore impaired Schwann cell and motor neuron *** confirmed that cultured Schwann cells obtained from the amyotrophic lateral sclerosis patient via sural nerve biopsy appeared impaired(senescent)and that exposure of the patient’s Schwann cells to allogeneic Schwann cell-derived exosomal vesicles,cultured expanded from a cadaver donor improved their growth capacity in *** a period of observation lasting 10 weeks,during which amyotrophic lateral sclerosis Functional Rating Scale-Revised and pulmonary function were regularly monitored,the patient received weekly consecutive infusions of 1.54×1012(×2),and then consecutive infusions of 7.5×1012(×6)allogeneic Schwann cell-derived exosomal vesicles diluted in 40 mL of Dulbecco’s phosphate-buffered *** of the infusions were associated with adverse events such as infusion reactions(allergic or otherwise)or

关键词： allogeneic amyotrophic lateral sclerosis exosomes infusion neuromuscular junction Schwann cell

Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy

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中国有色金属学会会刊：英文版 2008年第A1期18卷 369-373页

作者： S.O.KIM j.S.kwak Graduate School of Mechanical Engineering Pukyong National UniversitySouth Korea School of Mechanical Engineering Pukyong National UniversitySouth Korea

The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing *** in a case of polishing nonferrous materials,the strength of magnetic force is very low and it leads lower polishing *** magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength is one of the most famous nonferrous *** improving strategy of the magnetic force for the AZ31 magnesium alloy installed with a permanent magnet was proposed and experimental verification was carried *** the proposed strategy,the effect of process parameters on the surface roughness of the AZ31 magnesium alloy was evaluated by a design of experimental method.

关键词：镁合金物理性能磁力最优化设计磁性

Study of residual stresses in tailor rolled blanked Al5j32-T4 sheets

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Rare Metals 2006年第Z2期25卷 111-117页

作者： KIM Dongok KIM jinpyeong LEE Yong kwak Heeman RYU Yongmun HAN Beomsuck Materials & Processing Research Center Korea Automotive Technology Institute (KATECH) 74 Yongjung Ri PungseMyun Chonan Chungnam 330-912 Korea

Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5j32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.

关键词： tailor rolled blanks residual stresses deformation microstructure

Apples to oranges:environmentally derived,dynamic regulation of serotonin neuron subpopulations in adulthood?

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Neural Regeneration Research 2025年第9期20卷 2596-2597页

作者： Christopher j.O’Connell Matthew j.Robson Department of Genetics College of MedicineHarvard UniversityBostonMAUSA james L.winkle College of Pharmacy Division of Pharmaceutical SciencesUniversity of CincinnatiCincinnatiOHUSA Neuroscience Graduate Program College of MedicineUniversity of CincinnatiCincinnatiOHUSA

Traumatic brain injury(TBI)is a public health problem with an undue economic burden that impacts nearly every age,ethnic,and gender group across the globe(Capizzi et al.,2020).TBIs are often sustained during a dynamic range of exposures to energetic environmental forces and as such outcomes are typically heterogeneous regarding severity and pathology(Capizzi et al.,2020).

关键词： sustained orange dynamic

Temporal dynamics of neonatal hypoxic-ischemic encephalopathy injuries on magnetic resonance imaging

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Neural Regeneration Research 2025年第11期20卷 3144-3150页

作者： Holly Flyger Samantha j.Holdsworth Alistair j.Gunn Laura Bennet Hamid Abbasi Mātai Medical Research Institute Tairāwhiti GisborneNew Zealand Department of Anatomy&Medical Imaging Faculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand Center for Brain Research The University of AucklandAucklandNew Zealand Auckland Bioengineering Institute The University of AucklandAucklandNew Zealand

Moderate to severe perinatal hypoxic-ischemic encephalopathy occurs in~1 to 3/1000 live births in high-income countries and is associated with a significant risk of death or neurodevelopmental *** assessment is important to help identify highrisk infants,to help families,and to support appropriate interventions.A wide range of monitoring tools is available to assess changes over time,including urine and blood biomarkers,neurological examination,and *** present,magnetic resonance imaging is unique as although it is expensive and not suited to monitoring the early evolution of hypoxic-ischemic encephalopathy by a week of life it can provide direct insight into the anatomical changes in the brain after hypoxic-ischemic encephalopathy and so offers strong prognostic information on the long-term outcome after hypoxic-ischemic *** review investigated the temporal dynamics of neonatal hypoxic-ischemic encephalopathy injuries,with a particular emphasis on exploring the correlation between the prognostic implications of magnetic resonance imaging scans in the first week of life and their relationship to long-term outcome prediction,particularly for infants treated with therapeutic hypothermia.A comprehensive literature search,from 2016 to 2024,identified 20 pertinent *** review highlights that while the optimal timing of magnetic resonance imaging scans is not clear,overall,it suggests that magnetic resonance imaging within the first week of life provides strong prognostic *** challenges limit the timing consistency,particularly the need for intensive care and clinical ***,although most reports examined the prognostic value of scans taken between 4 and 10 days after birth,there is evidence from small numbers of cases that,at times,brain injury may continue to evolve for weeks after *** suggests that in the future it will be important to explore a wider range of times after hypo

关键词： magnetic resonance imaging neonatal hypoxic-ischemic encephalopathy neurodevelopmental outcomes prognostic biomarkers in neuroimaging scan timing therapeutic hypothermia