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Mechanical and corrosion properties of full liquid phase sintered WE43 magnesium alloy specimens fabricated via binder jetting additive manufacturing

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journal of Magnesium and Alloys 2024年第7期12卷 2711-2724页

作者： Dae hyun Cho David Dean Alan A.Luo Department of Materials Science and Engineering The Ohio State UniversityColumbusOH 43210USA Department of Plastic and Reconstructive Surgery The Ohio State UniversityColumbusOH 43210USA Department of Integrated Systems Engineering The Ohio State UniversityColumbusOH 43210USA

This study investigates full liquid phase sintering as a process of fabrication parts from WE43(Mg-4wt.%y-3wt.%RE-0.7wt.%Zr)alloy using binder jetting additive manufacturing(BjAM).This fabrication process is being developed for use in producing structural or biomedical ***,this study focused on achieving a near-dense microstructure with WE43 Mg alloy while substantially reducing the duration of sintering post-processing after BjAM part *** optimal process resulted in microstructure with 2.5%porosity and significantly reduced sintering *** improved sintering can be explained by the presence of y_(2)O_(3)and Nd_(2)O_(3)oxide layers,which form spontaneously on the surface of WE43 powder used in *** layers appear to be crucial in preventing shape distortion of the resulting samples and in enabling the development of sintering necks,particularly under sintering conditions exceeding the liquidus temperature of WE43 *** WE43 specimens rendered by BjAM achieved significant improvement in both corrosion resistance and mechanical properties through reduced porosity levels related to the sintering time.

关键词： Magnesium alloy Liquid phase sintering Additive manufacturing Binder jetting process Biodegradation

Copper telluride with manipulated carrier concentrations for high-performance solid-state thermoelectrics

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journal of Materials Science & Technology 2022年第34期129卷 190-195页

作者： hyun ju Dabin Park Minsu Kim jooheon Kim G.W.Woodruff School of Mechanical Engineering Georgia Institute of TechnologyAtlantaGA 30332USA School of Chemical Engineering&Materials Science Chung-Ang UniversitySeoul 06974Republic of Korea Department of Intelligent Energy and Industry Graduate SchoolChung-Ang UniversitySeoul 06974Republic of Korea Department of Advance Materials Engineering Chung-Ang UniversityAnseong 17546Republic of Korea

This study proposed a strategy for effectively diminishing the carrier concentration in Cu_(2)Te by introducing graphene sheets,Based on thermoelectric property measurements and single parabolic band modeling,the incorporated graphene effectively reduced the carrier concentration,not only enhancing the thermoelectric performance of the Cu_(2)Te/graphene composite but also substantially improving its figure of merit up to ~1.47 at 1000 K,which is 268% higher than that of pristine Cu_(2)Te,This study gives an insight into the control of carrier concentration and thermoelectric properties in Cu_(2)Te,and it could be extended to other copper chalcogenides for excellent thermoelectrics.

关键词： Thermoelectric Copper telluride Graphene Carrier concentration Single parabolic band model

Mo and Ta addition in NbTiZr medium entropy alloy to overcome tensile yield strength-ductility trade-off

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journal of Materials Science & Technology 2022年第14期109卷 176-185页

作者： Muhammad Akmal hyun Woo Seong Ho jin Ryu Department of Materials Science and Engineering KAISTDaejeonYuseong-gu 34141South Korea Department of Nuclear and Quantum Engineering KAISTDaejeonYuseong-gu 34141South Korea

In this study,single-phase NbTiZr and NbTiZr(MoTa)_(0.1) medium-entropy alloys(MEAs)were investigated for their use in biomedical *** alloys were prepared by arc melting,and were then cold-rolled,annealed,and characterized in terms of phase analysis,mechanical properties,fractography,and wear *** alloys showed a single body-centered cubic phase with superior mechanical,and tribological properties compared to commercially available biomedical *** and Ta-containing MEAs showed higher tensile yield strength(1060±18 MPa)and higher tensile ductility(~20%),thus overcoming the strength-ductility trade-off with no signs of transformation-induced plasticity,twinning,or *** generalized stacking fault energy(GSFE)calculations on the{112}slip system by the first-principles calculations based on density functional theory showed that the addition of less than0.2 molar fraction of Mo and Ta lowers the GSFE *** behavior posits the increase in ductility of the alloy by facilitating slips although strength is also increased by solid solution *** wear resistance of both alloys against hardened steel surfaces was superior to that of commercial biomedical ***,we concluded that NbTiZr(MoTa)_(0.1)MEA with good tensile ductility is a potential candidate for biomedical implants.

关键词： Medium-entropy alloys Wear-resistant Biomedical implants Solid solution hardening Staking fault energy

Effect of the protection layer formed by cross-linked gelatin on the stability and performance of glucose and oxygen fuel cells

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journal of Energy Chemistry 2021年第10期30卷 155-162,I0005页

作者： Kyuhwan hyun joonyoung Lee Suhyeon Kang yongchai Kwon Graduate School of Energy and Environment Seoul National University of Science and Technology232 Gongneung-roNowon-guSeoul 01811Republic of Korea Department of Chemical and Biomolecular Engineering Seoul National University of Science and Technology232 Gongneung-roNowon-guSeoul 01811Republic of Korea

A glucose oxidation catalyst comprising carbon nanotube,tetrathiafulvalene(TTF),gelatin,glutaraldehyde(GA)and glucose oxidase(GOx)(CNT/[TTF-GOx]/Gelatin+GA)is suggested to enhance the reactivity of glucose oxidation reaction(GOR),and the performance and stability of enzymatic biofuel cells(EBCs)using this *** this catalyst,TTF is used as mediator to transfer electron effectively,while GA is crosslinked to gelatin to form non-soluble *** structure prevents the dissolution of gelatin from aqueous electrolyte and reduces the leaching-out of GOx and TTF *** confirm the crosslinking effect of GA and gelatin,Fourier-transform infrared spectroscopy(FT-IR)and electrochemical evaluations are *** to FT-IR analysis,it was observed that the amide I peak shifted after *** is evidence showing the appropriate network formation and the reactivity of CNT/[TTFGOx]/Gelatin+GA is well preserved even after multiple potential *** addition,its GOx activity is regularly monitored for one month and the measurements prove that the structure prevents the leaching out of GOx *** on that,EBC using the anodic catalyst shows excellent performances,such as open circuit voltage of 0.75 V and maximum power density of 184μW/cm^(2).

关键词： Enzymatic biofuel cell Tetrathiafulvalene Crosslinking of glutaraldehyde and gelatin Hemi-acetal bond group

Local dose-dense chemotherapy for triple-negative breast cancer via minimally invasive implantation of 3D printed devices

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Asian journal of Pharmaceutical Sciences 2024年第1期19卷 69-85页

作者： Noehyun Myung hyun-Wook Kang Department of Biomedical Engineering Ulsan National Institute of Science and Technology(UNIST)Ulju-gun 44919South Korea

Dose-dense chemotherapy is the preferred first-line therapy for triple-negative breast cancer(TNBC),a highly aggressive disease with a poor *** treatment uses the same drug doses as conventional chemotherapy but with shorter dosing intervals,allowing for promising clinical outcomes with intensive ***,the frequent systemic administration used for this treatment results in systemic toxicity and low patient compliance,limiting therapeutic efficacy and clinical ***,we report local dose-dense chemotherapy to treat TNBC by implanting 3D printed devices with timeprogrammed pulsatile release *** implantable device can control the time between drug releases based on its internal microstructure design,which can be used to control dose *** device is made of biodegradable materials for clinical convenience and designed for minimally invasive implantation via a *** density variation of local chemotherapy using programmable release enhances anti-cancer effects in vitro and in *** the same dose density conditions,device-based chemotherapy shows a higher anticancer effect and less toxic response than intratumoral *** demonstrate local chemotherapy utilizing the implantable device that simulates the drug dose,number of releases,and treatment duration of the dose-dense AC(doxorubicin and cyclophosphamide)regimen preferred for TNBC *** density modulation inhibits tumor growth,metastasis,and the expression of drug resistance-related proteins,including p-glycoprotein and breast cancer resistance *** the best of our knowledge,local dose-dense chemotherapy has not been reported,and our strategy can be expected to be utilized as a novel alternative to conventional therapies and improve anti-cancer efficiency.

关键词： Dose-dense chemotherapy Triple-negative breast cancer 3D printing Pulsatile release Local drug delivery systems

Brazilin and Caesalpinia sappan L. extract protect epidermal keratinocytes from oxidative stress by inducing the expression of GPX7

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Chinese journal of Natural Medicines 2018年第3期16卷 203-209页

作者： hyung Seo Hwang joong hyun Shim Department of Oriental Cosmetic Science Semyung University

Caesalpinia sappan L., belonging to the family Leguminosae, is a medicinal plant that is distributed in Southeast Asia. The dried heartwood of this plant is used as a traditional ingredient of food, red dyes, and folk medicines in the treatment of diarrhea, dysentery, tuberculosis, skin infections, and inflammation. Brazilin is the major active compound, which has exhibited various phar- macological effects, including anti-platelet activity, anti-hepatotoxicity, induction of immunological tolerance, and anti-inflammatory and antioxidant activities. The present study aimed to evaluate the antioxidant activity and expression of antioxidant enzymes of C. sappan L. extract and its major compound, brazilin, in human epidermal keratinocytes exposed to UVA irradiation. Our results indi- cated that C. sappan L. extract reduced UVA-induced H202 production via GPX7 activation. Moreover, brazilin exhibited anfioxidant effects that were similar to those of C. sappan L. via glutathione peroxidase 7 （GPX7）, suggesting that C. sappan L. extract and its natural compound represent potential treatments for oxidative stress-induced photoaging of skin.

关键词： Caesalpinia sappan L. Brazilin Ultraviolet GPX7 Antioxidative

Improved photocatalytic activity of surface charge functionalized ZnO nanoparticles using aniline

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journal of Materials Science & Technology 2021年第17期76卷 1-10页

作者： Chatchai Rodwihok Korakot Charoensri Duangmanee Wongratanaphisan Won Mook Choi Seung hyun Hur hyun jin Park jin Suk Chung School of Chemical Engineering University of Ulsan680-749.South ICorea Department of Biotechnology College of Life Sciences andBiotechnologyKorea University145 Anam-roSeongbuk-guSeoul02841South Korea Research Center in Physics andAstronomy Faculty of ScienceChiang Mai UniversityChiang Mai50200Thailand

Functionalization of aniline molecules on zinc oxide(ZnO)nanoparticles is reported using a simple impregnation *** ZnO samples were systematically characterized based on morphology,surface and optical properties,and photocatalytic performance towards methyl orange(MO).Aniline functionalization increased the surface charge of the modified *** to pristine ZnO,the aniline-functionalized ZnO yielded faster photodegradation of MO,degrading 98.29%of MO in 60 min and superoxide radicals were the major species during the MO photodegradation *** results indicate that the improvement of photocatalytic degradation could be attributed to opposite charge-induced surface ***,protonated amine as a positively charged molecule was expected to increase the surface adsorption of MO(as an anionic dye)on ZnO nanoparticles surfaces,thereby increasing their photocatalytic degradation performance.

关键词： Photocatalysts Surface charge ZnO Aniline Methyl orange

Nrf2 is required for normal postnatal bone acquisition in mice

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Bone Research 2014年第4期2卷 231-240页

作者： jung-hyun Kim Vandana Singhal Shyam Biswal Rajesh K Thimmulappa Douglas j Di Girolamo Department of Environmental Health Sciences Johns Hopkins Bloomberg School of Public HealthBaltimoreMDUSA Department of Orthopaedic Surgery Johns Hopkins University School of MedicineBaltimoreMDUSA

A large body of literature suggests that bone metabolism is susceptible to the ill effects of reactive species that accumulate in the body and cause cellular dysfunction. One of the body＇s front lines in defense against such damage is the transcription factor, Nrf2. This transcription factor regulates a plethora of antioxidant and cellular defense pathways to protect cells from such damage. Despite the breadth of knowledge of both the function of Nrf2 and the effects of reactive species in bone metabolism, the direct role of Nrf2 in skeletal biology has yet to be thoroughly examined. Thus, in the current study, we have examined the role of Nrf2 in postnatal bone metabolism in mice. Mice lacking Nrf2 （Nrf2-/-） exhibited a marked deficit in postnatal bone acquisition, which was most severe at 3 weeks of age when osteoblast numbers were 12-fold less than observed in control animals. While primary osteoblasts from Nrf2-/- mice functioned normally in vitro, the colony forming capacity of bone marrow stromal cells （BMSCs） from these mice was significantly reduced compared to controls. This defect could be rescued through treatment with the radical scavenger N-acetyl cysteine （NAC）, suggesting that increased reactive species stress might impair early osteoblastogenesis in BMSCs and lead to the failure of bone acquisition observed in Nrf2-/- animals. Taken together, these studies suggest Nrf2 represents a key pathway in regulating bone metabolism, which may provide future therapeutic targets to treat osteoporosis.

关键词： bone Nrf2 is required for normal postnatal bone acquisition in mice

Airborne bioaerosols and their impact on human health

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journal of Environmental Sciences 2018年第5期30卷 23-35页

作者： Ki-hyun Kim Ehsanul Kabir Shamin Ara jahan Department of Civil and Environmental Engineering Hanyang UniversitySeoul 04763Republic of Korea Department of Farm Power&MachineryBangladesh Agricultural UniversityMymensinghBangladesh BRAC Clinic DhakaBangladesh

Bioaerosols consist of aerosols originated biologically such as metabolites, toxins, or fragments of microorganisms that are present ubiquitously in the environment. International interests in bioaerosols have increased rapidly to broaden the pool of knowledge on their identification,quantification, distribution, and health impacts（e.g., infectious and respiratory diseases,allergies, and cancer）. However, risk assessment of bioaerosols based on conventional culture methods has been hampered further by several factors such as：（1） the complexity of microorganisms or derivatives to be investigated;（2） the purpose, techniques, and locations of sampling; and（3） the lack of valid quantitative criteria（e.g., exposure standards and dose/effect relationships）. Although exposure to some microbes is considered to be beneficial for health,more research is needed to properly assess their potential health hazards including inter-individual susceptibility, interactions with non-biological agents, and many proven/unproven health effects（e.g., atopy and atopic diseases）.

关键词： Health effect Exposure Infectious diseases Respiratory diseases Cancer Guideline