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Frictional shear stress of ZnO nanowires on natural and pyrolytic graphite substrates

Friction 2022年第12期10卷 2059-2068页

作者： Lizhen HOU Maofen HOU Tursunay YIBIBULLA james lee MEAD Sergej FATIKOW Shiliang WANG Han HUANG Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education School of Physics and Electronic ScienceHunan Normal UniversityChangsha 410081China School of Physics and Electronics Central South UniversityChangsha 410083China Division Microrobotics and Control Engineering Department of Computing ScienceUniversity of OldenburgOldenburg D-26129Germany School of Mechanical and Mining Engineering The University of QueenslandBrisbaneQLD 4072Australia

The friction behaviour of ZnO nanowires on natural graphite(NG)and highly oriented pyrolytic graphite(HOPG)substrates was tested in ambient conditions by use of optical microscopy based *** on the step-free and waviness-free NG substrate exhibit a diameter-independent nominal frictional shear stress of 0.48 MPa,and this provides a benchmark for studying how the surface topography of graphite influences nanowire *** on the HOPG substrate present a significant diameter-dependent frictional shear stress,increasing from 0.25 to 2.78 MPa with the decrease of nanowire diameter from 485 to 142 *** waviness of HOPG has a limited effect on the nanowire friction,as a nanowire can fully conform to the *** surface steps on the HOPG can significantly enhance the nanowire friction and lead to a much higher frictional shear stress than that on NG due to mechanical blocking and the presence of a Schwoebel barrier at step *** surface steps,however,can also generate small wedge-shaped gaps between a nanowire and substrate,and thus reduce the nanowire *** the decrease in nanowire diameter,the capacity for the nanowire to better conform to the substrate reduces the length of the wedge-shaped gaps,leading to the observed increase in nanowire *** results have improved our understanding of the unique friction behaviour of *** an improved understanding is expected to benefit the design and operation of nanowire-friction-based devices,including bio-inspired fibrillar adhesives,soft grippers,rotary nanomotors,and triboelectric nanogenerators.

关键词： frictional shear stress nanowires graphite surface step waviness

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Tissue-specific Tregs in cancer metastasis:opportunities for precision immunotherapy

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Cellular & Molecular Immunology 2022年第1期19卷 33-45页

作者： Laura A.Huppert Michael D.Green Luke Kim Christine Chow Yan Leyfman Adil I.Daud james C.lee Division of Hematology/Oncology Department of MedicineUniversity of CaliforniaSan FranciscoSan FranciscoCAUSA Department of Radiation Oncology University of Michigan School of MedicineAnn ArborMIUSA Veterans Affairs Ann Arbor Healthcare System Ann ArborMIUSA University of California San Francisco School of MedicineSan FranciscoCAUSA Penn State College of Medicine HersheyPAUSA Parker Institute for Cancer Immunotherapy San FranciscoCAUSA

Decades of advancements in immuno-oncology have enabled the development of current immunotherapies,which provide longterm treatment responses in certain metastatic cancer ***,cures remain infrequent,and most patients ultimately succumb to treatment-refractory metastatic *** insights suggest that tumors at certain organ sites exhibit distinctive response patterns to immunotherapy and can even reduce antitumor immunity within anatomically distant tumors,suggesting the activation of tissue-specific immune tolerogenic mechanisms in some cases of therapy *** immune cells known as regulatory T cells(Tregs)are present within all tissues in the body and coordinate the suppression of excessive immune activation to curb autoimmunity and maintain immune *** the high volume of research on Tregs,the findings have failed to reconcile tissue-specific Treg functions in organs,such as tolerance,tissue repair,and regeneration,with their suppression of local and systemic tumor immunity in the context of immunotherapy *** improve the understanding of how the tissue-specific functions of Tregs impact cancer immunotherapy,we review the specialized role of Tregs in clinically common and challenging organ sites of cancer metastasis,highlight research that describes Treg impacts on tissue-specific and systemic immune regulation in the context of immunotherapy,and summarize ongoing work reporting clinically feasible strategies that combine the specific targeting of Tregs with systemic cancer *** knowledge of Tregs in the framework of their tissue-specific biology and clinical sites of organ metastasis will enable more precise targeting of immunotherapy and have profound implications for treating patients with metastatic cancer.

关键词： Tissue Tregs Immunotherapy Organ-specific tolerance Metastasis Cancer

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CD69 expression on airway eosinophils and airway inflammation in a murine model of asthma

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Chinese Medical Journal 2006年第23期119卷 1983-1990页

作者： WANG Hui-ying SHEN Hua-hao james J lee Nancy A lee Department of Respiratory Medicine Second Affiliated Hospital ofZhejiang University Medical College Institute of RespiratoryDiseases of Zhejiang University Hangzhou 310009 China Department of Biochemistry and Molecular Biology Mayo ClinicScottsdale Scottsdale Arizona 85259 USA

Background Asthma is a chronic airway disease with inflammation characterized by physiological changes （airway hyper-responsiveness, AHR） and pathological changes （inflammatory cells infiltration and mucus production）. Eosinophils play a key role in the allergic inflammation. But the causative relationship between eosinophils and airway inflammation is hard to prove. One of the reasons is lack of activation marker of murine eosinophils. We investigated the expression of CD69 on murine eosinophils in vitro, the relationship between the expression of CD69 on eosinophils from peripheral blood and bronchoalveolar lavage fluid and on airway inflammation in asthmatic mice. Methods Eosinophils from peripheral blood of IL-5 transgenic mice （NJ.1638） were purified. Mice were divided into five groups： wild type mice sensitized and challenged with saline （WS group）, wild type mice sensitized and challenged with ovalbumin （WO group）, IL-5^-/- mice sensitized and challenged with saline and transferred with purified eosinophils （ISE group）, IL-5^-/- mice sensitized and challenged with OVA and transferred with purified eosinophils （IOE group）, IL-5^-/- mice sensitized and challenged with OVA and transferred with purified eosinophils, pretreated with anti CD4 monoclonal antibody （IOE＋antiCD4mAb group）. IL-5^-/- mice were sensitized with OVA at day 0 and day 14, then challenged with OVA aerosol. On days 24, 25, 26 and 27 purified eosinophils were transferred intratracheally to IL-5^-/- mice. On day 28, blood and BALF were collected and CD69 expression on eosinophils measured by flowcytometry. Results Purified eosinophils did not express CD69. But eosinophils cultured with PMA＋MA, IFN- T, IL-5 or GM-CSF expressed CD69 strongly. Eosinophils from blood of WO, WS group did not express CD69 at all. The numbers of eosinophils in BALF of WO group, IOE group, ISE group and IOE＋antiCD4mAb group were significantly higher than in mice of WS group which did not have eosinophils at all. CD69

关键词： asthma eosinophils CD69 airway inflammation murine model

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Micromorphic theory:a gateway to nano world

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International Journal of Smart and Nano Materials 2010年第2期1卷 115-135页

作者： Xianqiao Wang james D.lee Department of Mechanical and Aerospace Engineering The George Washington UniversityWashingtonDC 20052USA

Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner *** is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner *** this work,the kinematics including the objective Eringen tensors is *** laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean *** concept of material force and the balance law of pseudomomentum are generalized for *** axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic *** of MMT in micro/nanoscale are discussed.

关键词： micromorphic theory Eringen tensors constitutive theory generalized micromorphic solid/fluid electromagnetic-thermoelastic coupling micro/nanomechanics

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Work conjugate strain of virial stress

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International Journal of Smart and Nano Materials 2016年第1期7卷 39-51页

作者： Leyu Wang Jiaoyan Li james D.lee Center for Collision Safety and Analysis College of ScienceGeorge Mason UniversityFairfaxVAUSA School of Engineering Brown UniversityProvidenceRIUSA Department of Mechanical and Aerospace Engineering The George Washington UniversityWashingtonDCUSA

Certain stress tensor and strain tensor form a conjugate pair if there exists a scalar valued strain energy function such that the stress tensor is equal to the derivative of strain energy function with respect to the strain *** stress is widely accepted as the stress measurement in molecular dynamics(MD).However,its conjugate strain is not yet *** atomic logarithmic strain is proposed and numerically verified as the conjugate strain of virial stress at 0 K *** strain energy is calculated by virial stress and the proposed atomic logarithmic strain equals to the interatomic potential energy *** conclusion is numerically verified with(1)Coulomb-Buckingham potential,Lenard-Jones potential,or arbitrary nonlinear pair potential and(2)randomly generated atomic configurations and deformation *** are given in determining the stress–strain relation for magnesium oxide with MD *** result shows that the atomic logarithmic strain is identical to engineer-ing strain when deformation is small.

关键词： Thermodynamic pair conjugacy virial stress atomic logarithmic strain molecular dynamics interatomic potential strain energy magnesium oxide

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Work conjugate pair of stress and strain in molecular dynamics

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International Journal of Smart and Nano Materials 2016年第3期7卷 144-178页

作者： Leyu Wang james D.lee Cing-Dao Kan Center for Collision Safety and Analysis College of ScienceGeorge Mason UniversityFairfaxVAUSA Department of Mechanical and Aerospace Engineering the George Washington UniversityWashingtonDC 20052USA

Certain stress and strain form a thermodynamic conjugate pair such that their strain energy equals to a scalar-valued potential *** atomistic stresses and strains are analytically derived based on the work conjugate *** is numerically verified with both two-body and three-body potentials that the atomistic Kirchhoff stress,first-order Piola–Kirchhoff stress and second-order Piola–Kirchhoff stress are conjugates to atomistic logarithmic strain,deformation gradient and Lagrangian strain,*** stress at 0 K based on original volume is the special form of atomistic Kirchhoff stress for pair *** is numerically verified that Hencky strain is not conjugate to any stress.

关键词： Thermodynamic conjugacy logarithmic strain atomistic stress deformation gradient strain energy interatomic potential Tersoff potential atomistic first-order Piola-Kirchhoff stress atomistic second-order Piola-Kirchhoff stress atomistic Kirchhoff stress virial stress

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Catalyst-free synthesis and mechanical characterization of TaC nanowires

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Science China(Physics,Mechanics & Astronomy) 2021年第5期64卷 43-53页

作者： Shiliang Wang Liang Ma james lee Mead Shin-Pon Jui Guodong Li Han Huang School of Physics and Electronics Central South University Changsha 410083China School of Mechanical and Mining Engineering.The University of Queensland Brisbane QLD 4072Australia Deparment of Computing Science University of OldenburgOldenburg D-26129Germany Deparment of Mechanical and Electro-Mechanical Engineering Sun Yat-sen UniversiyKaohsiung 804China Deparment of Medicinal and Applied Chemistry Kaohsiung Medical UniversityKaohsiung 807China State Key Laboratory of Powder Metallurgw Central South UniversityChangsha 410083China

TaC nanowires are expected to be an ideal reinforcing material in ultra-high-temperature ceramics. However, their growth mechanisms and mechanical properties remain unclear, and low-cost large-scale synthesis has not been realised. In this study,bulk synthesis of [100]-oriented TaC nanowires is accomplished by carbothermal synthesis through a direct vapor-solid mechanism. Thermal resonance test results show that the synthesized square TaC nanowires with cross-sectional side-lengths of 65 to 497 nm have a size-independent Young’s modulus of(510.6±12.6) GPa;very close to the corresponding values of their bulk counterparts, but differing considerably from previously published measurements. Molecular dynamics(MD) simulations show that TaC nanowires with side-lengths of above 15 nm have a constant Young’s modulus of 517 GPa, and size effects on the modulus values should only occur at side-lengths below 15 nm. During bending tests, the TaC nanowires fracture into several segments in a brittle mode, and exhibit an increasing fracture strain from 1.88% to 4.28% as their side-length decreases from 489 to 90 nm. Weibull statistics analyses and TEM observations indicate that the failure of the nanowires should be primarily dependent on the number and size of surface defects. MD simulations further reveal that the defect-free TaC nanowires fail brittlely at a theoretical strain up to 5.76%.

关键词： tantalum carbide nanowires carbothermal synthesis vapor-solid mechanism mechanical properties

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超越传统NO_(x)和VOCs控制的臭氧污染防治新思路

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科学通报:英文版 2023年第18期68卷 1989-1992页

作者：陆克定周厚华 james lee Beth Nelson 张远航 State Environmental Protection Key Laboratory of Atmospheric Ozone Pollution Control State Key Joint Laboratory of Environmental Simulation and Pollution ControlCollege of Environmental Sciences and EngineeringPeking UniversityBeijing 100871China National Centre for Atmospheric Science Department of ChemistryUniversity of YorkYork YO105DDUK

Ambient ozone(O3)was first identified as a key harmful air pollutant in the study of photochemical smog during the 1950s in Los *** studies uncovered that surface O3 was not emitted directly,but formed from the reactions of nitrogen oxides(NO_(x))and volatile organic compounds(VOCs)in *** the relationship between O3 and its two main precursors,NOx and VOCs,is considered to be the cornerstone for enabling successful mitigation of *** the past,a central area for the study and practice of O3 pollution control was Los Angeles and the surrounding *** ambient O3 concentrations in the area were successfully and continuously reduced from 400 ppb(1 ppb=109 m^(3)/m^(3))to ca.120 ppb due to the joint mitigation of VOC and NOx emissions from 1960 to 2010[1].Nevertheless,O3 pollution still represents one of the most pervasive and stubborn environmental problems in megacities worldwide,with many populous centres regularly breaching WHO 8-hour Interim Targets-1 levels(160 lg/m^(3)),not to mention the updated air quality guideline value of 100 lg/m^(3).The difficulty of O3 pollution control is due to a number of factors,including its non-linear relationship with NOx[2],the difficulty of anthropogenic VOC control[3]and the contributions of biogenic VOCs.

关键词： pollution difficulty corners

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Multiscale analysis of composite material reinforced by randomly-dispersed particles

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International Journal of Smart and Nano Materials 2012年第1期3卷 2-13页

作者： Jiaoyan Li james D.lee Ken P.Chong The George Washington University WashingtonDC 20052USA National Institute of Standards and Technology GaithersburgMD 20899USA

A multiscale analysis method is presented in which detailed information on the microscopic level is incorporated into macroscopic models capable of simulating damage evolution and ultimate *** composite considered is reinforced by randomly-dispersed particles,which reflects the statistical characteristics of real materials,such as cement-based ***,a three-dimensional material body is decomposed into many unit *** unit cell is reinforced by a cylindrical particle,the orientation of which is characterized by three Euler angles generated by the random number *** on a detailed finite element analysis,the material properties of the representative volume element are *** verification,the properties of the cylindrical particles are set equal to those of the matrix and the computed‘composite’properties reduce exactly to those of the‘isotropic’material,as *** coordinate transformation,the effective material properties of each unit cell are *** assembly of stiffness matrices of all unit cells leads to the stiffness matrix of the whole *** the simple tension loading condition,the initial damaged unit cell can be identified according to the vonMises yield *** stiffness of the damaged unit cell will then be reduced to zero and it will cause stress redistribution and trigger further *** was found that the reinforcement is effective to mitigate and arrest the damage propagation,and therefore prolongs the material’s *** results suggest that the hierarchical coupling approaches used here may be useful for material design and failure protection in composites.

关键词： multiscale analysis random response finite element method representative volume element Euler angle damage propagation

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Pneumocystis jiroveci pneumonia and pneumomediastinum in an anti-TNFαnaive patient with ulcerative colitis

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World Journal of Gastroenterology 2009年第15期15卷 1897-1900页

作者： james C lee Deborah C Bell Richard M Guinness Tariq Ahmad Department of Gastroenterology Royal Devon and Exeter Hospital

We report the case of a 21-year-old man who was noted to have pneumomedi astinum during an admission for an acute flare of ulcerative *** that time,he was on maintenance treatment with azathioprine at a dose of 1.25 mg/kg per day,and had not received supplementary steroids for 9 mo. He had never received anti-tumor necrosis factor (TNF)α*** after apparently effective treatment with intravenous steroids and an increased dose of azathioprine,he developed worsening colitic and new respiratory symptoms,and was diagnosed with Pneumocystis jiroveci(carinii)pneumonia(PCP). Pneumomediastinum is rare in immunocompetent hosts,but is a recognized complication of PCP in human immunodeficiency virus(HIV)patients, although our patient’s HIV test was negative. Treatment of PCP with co-trimoxazole resulted in resolution of both respiratory and gastrointestinal symptoms,without the need to increase the steroid *** is increasing vigilance for opportunistic infections in patients with inflammatory bowel disease following the advent of anti-TNFαtherapy. This case emphasizes the importance of considering the possibility of such infections in all patients with inflammatory bowel disease,irrespective of the immunosuppressants they receive,and highlights the potential of steroid-responsive opportunistic infections to mimic worsening colitic symptoms in patients with ulcerative colitis.

关键词：溃疡性结肠炎纵隔气肿肺炎维持治疗剂量人类免疫缺陷病毒抗肿瘤坏死因子呼吸道症状炎症性肠病

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