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Characterization of the tribologically relevant cover layers formed on copper in oxygen and oxygen-free conditions

Friction 2023年第8期11卷 1505-1521页

作者： Selina RAUMEL Khemais BARIENtI Hoang-thien LUU Nina MERKERt Folke DENCKER Florian NÜRNBERGER Hans Jürgen MAIER Marc christopher WURZ Institute of Micro Production technology Leibniz Universität HannoverGarbsen 30823Germany Institut für Werkstoffkunde(Materials Science) Leibniz Universität HannoverGarbsen 30823Germany Institute of Applied Mechanics Clausthal University of TechnologyClausthal-Zellerfeld 38678Germany

Engineering in vacuum or under a protective atmosphere permits the production of materials, wherever the absence of oxygen is an essential demand for a successful processing. However, very few studies have provided quantitative evidence of the effect of oxidized surfaces to tribological properties. In the current study on 99.99% pure copper, it is revealed that tribo-oxidation and the resulting increased abrasive wear can be suppressed by processing in an extreme high vacuum (XHV) adequate environment. the XHV adequate atmosphere was realized by using a silane-doped shielding gas (1.5 vol% SiH4 in argon). to analyse the influence of the ambient atmosphere on the tribological and mechanical properties, a ball–disk tribometer and a nanoindenter were used in air, argon, and silane-doped argon atmosphere for temperatures up to 800 ℃. Resistance measurements of the resulting coatings were carried out. to characterize the microstructures and the chemical compositions of the samples, the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used. the investigations have revealed a formation of η-Cu3Si in silane-doped atmosphere at 300 ℃, as well as various intermediate stages of copper silicides. At temperatures above 300 ℃, the formation of γ-Cu5Si were detected. the formation was linked to an increase in hardness from 1.95 to 5.44 GPa, while the Young’s modulus increased by 46% to 178 GPa, with the significant reduction of the wear volume by a factor of 4.5 and the suppression of further oxidation and susceptibility of chemical wear. In addition, the relevant diffusion processes were identified using molecular dynamics (MD) simulations.

关键词： wear behavior tribochemical reaction oxidation behavior surface analysis molecular dynamics(MD)simulation

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Computational synthesis of substrates by crystal cleavage

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npj Computational Materials 2021年第1期7卷 1336-1341页

作者： Joshua t.Paul Alice Galdi christopher Parzyck Kyle M.Shen Jared Maxson Richard G.Hennig Department of Materials Science and Engineering University of FloridaGainesvilleFLUSA Quantum theory Project University of FloridaGainesvilleFLUSA Department of Physics Cornell UniversityIthacaNYUSA Cornell Laboratory for Accelerator-Based Sciences and Education Cornell UniversityIthacaNYUSA

the discovery of substrate materials has been dominated by trial and error,opening the opportunity for a systematic *** generate bonding networks for materials from the Materials Project and systematically break up to three bonds in the networks for three-dimensional *** cleavage reduces the bonding network to two periodic *** identify 4693 symmetrically unique cleavage surfaces across 2133 bulk crystals,4626 of which have a maximum Miller index of *** characterize the likelihood of cleavage by creating monolayers of these surfaces and calculating their thermodynamic stability using density functional theory to discover 3991 potential ***,we identify distinct trends in the work of cleavage and relate them to bonding in the three-dimensional *** illustrate the potential impact of the substrate database by identifying several improved epitaxial substrates for the transparent conductor *** open-source databases of predicted and commercial substrates are available at ***.

关键词： cleavage bonding synthesis

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Deep learning ferroelectric polarization distributions from StEM data via with and without atom finding

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npj Computational Materials 2021年第1期7卷 1342-1352页

作者： christopher t.Nelson Ayana Ghosh Mark Oxley Xiaohang Zhang Maxim Ziatdinov Ichiro takeuchi Sergei V.Kalinin Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTNUSA Computational Sciences and Engineering Division Oak Ridge National LaboratoryOak RidgeTNUSA Department of Materials Science and Engineering University of MarylandCollege ParkMDUSA

Over the last decade,scanning transmission electron microscopy(StEM)has emerged as a powerful tool for probing atomic structures of complex materials with picometer precision,opening the pathway toward exploring ferroelectric,ferroelastic,and chemical phenomena on the atomic *** to date extracting a polarization signal from lattice coupled distortions in StEM imaging rely on discovery of atomic positions from intensity maxima/minima and subsequent calculation of polarization and other order parameter fields from the atomic ***,we explore the feasibility of polarization mapping directly from the analysis of StEM images using deep convolutional neural networks(DCNNs).In this approach,the DCNN is trained on the labeled part of the image(i.e.,for human labelling),and the trained network is subsequently applied to other *** explore the effects of the choice of the descriptors(centered on atomic columns and grid-based),the effects of observational bias,and whether the network trained on one composition can be applied to a different *** analysis demonstrates the tremendous potential of the DCNN for the analysis of high-resolution StEM imaging and spectral data and highlights the associated limitations.

关键词： Deep network ferroelectric

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2219-t87铝合金的中心表面裂纹拉伸试样的断裂强度(英文)

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transactions of Nonferrous Metals Society of China 2011年第12期21卷 2568-2575页

作者： S. RAJAKUMAR t. christopher thanthai Periyar Government Institute of technology Vellore-632002 India Government College of Engineering Perumalpuram Tirunelveli-627007 India

将2219-t87铝合金板材进行低温拉伸试验,用改进的固有缺陷模型分析铝合金基材和焊接接头金属表面裂纹试样的断裂强度数据,通过构成的失效评估图来确定材料的断裂参数。通过考虑材料的极限拉伸强度、铝基材及焊接接头金属的断裂强度数据... 详细信息

将2219-t87铝合金板材进行低温拉伸试验,用改进的固有缺陷模型分析铝合金基材和焊接接头金属表面裂纹试样的断裂强度数据,通过构成的失效评估图来确定材料的断裂参数。通过考虑材料的极限拉伸强度、铝基材及焊接接头金属的断裂强度数据,对具有不同厚度的中心表面裂纹拉伸试样进行断裂分析。由拉伸断裂板材所得到的失效评估图能够应用到由相同材料构成的任何开裂组件的失效压力估计。

关键词：中心穿透裂纹拉伸试样失效评估图断裂强度固有缺陷模型 2219-t87铝合金

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MtBStFA derivatization-LC-MS/MS approach for the quantitative analysis of endogenous nucleotides in human colorectal carcinoma cells

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Journal of Pharmaceutical Analysis 2022年第1期12卷 77-86页

作者： Huixia Zhang Yan Li Zheng Li christopher Wai-Kei Lam Peng Zhu Caiyun Wang Hua Zhou Wei Zhang State Key Laboratory of Quality Research in Chinese Medicines Macao Institute for Applied Research in Medicine and HealthMacao University of Science and TechnologyTaipaMacaoChina

Endogenous ribonucleotides(RNs)and deoxyribonucleotides(dRNs)are important metabolites related to the pathogenesis of many *** light of their physiological and pathological significances,a novel and sensitive pre-column derivatization method with N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide(MtBStFA)was developed to determine RNs and dRNs in human cells using high-performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS).A one-step extraction of cells with 85%methanol followed by a simple derivatization reaction within 5 min at room temperature contributed to shortened analysis *** derivatives of 22 nucleoside mono-,di-and tri-phosphates were retained on the typical C;column and eluted by ammonium acetate and acetonitrile in 9 *** these optimal conditions,good linearity was achieved in the tested calibration *** lower limit of quantitation(LLOQ)was determined to be 0.1-0.4μM for the tested RNs and 0.001-0.1μM for *** addition,the precision(CV)wasthe RSD of stability was lower than 10.4%.Furthermore,this method was applied to quantify the endogenous nucleotides in human colorectal carcinoma cell lines HCt 116 exposed to *** conclusion,our method has proven to be simple,rapid,sensitive,and *** may be used for specific expanded studies on intracellular pharmacology in vitro.

关键词： Ribonucleotides Deoxyribonucleotides Derivatization N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide High-performance liquid chromatography tandem mass spectrometry

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the Representation of Soil Moisture−Atmosphere Feedbacks across the tibetan Plateau in CMIP6

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Advances in Atmospheric Sciences 2023年第11期40卷 2063-2081页

作者： Joshua tALIB Omar V.MÜLLER Emma J.BARtON christopher M.tAYLOR Pier Luigi VIDALE U.K.Centre of Ecology and Hydrology WallingfordOX108BBU.K. National Centre for Atmospheric Science ReadingRG66BBU.K. Consejo Nacional de Investigaciones Científicas y técnicas(CONICEt) Centro de Estudios de Variabilidad y Cambio Climático(CEVARCAM)Facultad de Ingeniería y Ciencias HídricasUniversidad Nacional del LitoralSanta FeArgentina National Centre for Earth Observation WallingfordOX108BBU.K. Department of Meteorology University of ReadingReadingRG66BBU.K.

thermal processes on the tibetan Plateau(tP)influence atmospheric conditions on regional and global *** this,previous work has shown that soil moisture−driven surface flux variations feed back onto the *** soil moisture is a source of atmospheric predictability,no study has evaluated soil moisture−atmosphere coupling on the tP in general circulation models(GCMs).In this study,we use several analysis techniques to assess soil moisture−atmosphere coupling in CMIP6 simulations including:instantaneous coupling indices;analysis of flux and atmospheric behaviour during dry spells;and a quantification of the preference for convection over drier *** these metrics we partition feedbacks into their atmospheric and terrestrial *** with previous global studies,we conclude substantial inter-model differences in the representation of soil moisture−atmosphere coupling,and that most models underestimate such *** on dry spell analysis,most models underestimate increased sensible heat during periods of rainfall *** example,the model-mean bias in anomalous sensible heat flux is 10 W m−2(≈25%)smaller compared to *** dry-spell sensible heat fluxes lead to a weaker atmospheric *** also find that most GCMs fail to capture the negative feedback between soil moisture and deep *** poor simulation of feedbacks in CMIP6 experiments suggests that forecast models also struggle to exploit soil moisture−driven *** improve the representation of land−atmosphere feedbacks requires developments in not only atmospheric modelling,but also surface processes,as we find weak relationships between rainfall biases and coupling indexes.

关键词： model evaluation land-atmosphere feedbacks tibetan Plateau precipitation surface energy balance

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A modular microfluidic system based on a multilayered configuration to generate large-scale perfusable microvascular networks

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Microsystems & Nanoengineering 2021年第1期7卷 63-75页

作者： tao Yue Da Zhao Duc t.t.Phan Xiaolin Wang Joshua Jonghyun Park Zayn Biviji christopher C.W.Hughes Abraham P.Lee Department of Biomedical Engineering University of CaliforniaIrvineCAUSA School of Mechatronic Engineering and Automation Shanghai UniversityShanghaiChina Department of Molecular Biology and Biochemistry University of CaliforniaIrvineCAUSA Department of Micro/Nano Electronics Shanghai Jiao Tong UniversityShanghaiChina National Key Laboratory of Science and technology for Micro/Nano Fabrication Shanghai Jiao Tong UniversityShanghaiChina Key Laboratory for thin Film and Micro Fabrication of the Ministry of Education Shanghai Jiao Tong UniversityShanghaiChina Department of Electrical Engineering and Computer Science University of CaliforniaIrvineCAUSA. Department of Applied Mathematics-Biology Brown UniversityProvidenceRIUSA. Department of Mechanical and Aerospace Engineering University of CaliforniaIrvineCAUSA

the vascular network of the circulatory system plays a vital role in maintaining homeostasis in the human *** this paper,a novel modular microfluidic system with a vertical two-layered configuration is developed to generate largescale perfused microvascular networks in *** two-layer polydimethylsiloxane(PDMS)configuration allows the tissue chambers and medium channels not only to be designed and fabricated independently but also to be aligned and bonded *** method can produce a modular microfluidic system that has high flexibility and scalability to design an integrated platform with multiple perfused vascularized tissues with high *** medium channel was designed with a rhombic shape and fabricated to be semiclosed to form a capillary burst valve in the vertical direction,serving as the interface between the medium channels and tissue *** and anastomosis at the vertical interface were successfully achieved by using different combinations of tissue chambers and medium *** large-scale microvascular networks were generated and quantified in terms of vessel length and *** leakage of the perfused 70-kDa FItC-dextran confirmed the lumenization of the microvascular networks and the formation of tight vertical interconnections between the microvascular networks and medium channels in different structural *** platform enables the culturing of interconnected,large-scale perfused vascularized tissue networks with high density and scalability for a wide range of multiorgan-on-a-chip applications,including basic biological studies and drug screening.

关键词： interconnection networks configuration

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Wildfire effects on permafrost and soil moisture in spruce forests of Interior Alaska

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Journal of Forestry Research 2020年第2期31卷 553-563页

作者： christopher Potter Charles Hugny NASA Ames Research Center Moffett FieldCA 94035USA Interior Alaska Wilderness Consultants NenanaAKUSA

In the summer of 2015,hundreds of forest fires burned across the state of *** uncontrolled wildfires near the town of tanana on the Yukon River were responsible for the largest portion of the area burned *** July 2017,field measurements were carried out in both unburned and burned forested areas nearly adjacent to one another,all within 15 miles of the village of *** surveys were used to first visually verify locations of different burn severity classes,(low,moderate,or high),estimated in 2016 from Landsat images(collected before and after the 2015 tanana-area wildfires).Surface and soil profile measurements to 30-cm depth at these same locations were collected for evidence of moss layer and forest biomass *** temperature and moisture content were measured to 30-cm depth,and depth to permafrost was estimated by excavation wherever *** thermal infra-red images of the soil profiles were taken at each site location,and root-zone organic layer samples were extracted for further chemical *** supported the hypothesis that the loss of surface organic layers is a major factor determining post-fire soil water and temperature changes and the depth of permafrost *** the most severely burned forest sites,complete consumption of the living moss organic layer was strongly associated with both warming at the surface layer and increases in soil water content,relative to unburned forest *** temperatures at both 10-cm and 30-cm depths at burned forest sites were higher by 8-10C compared to unburned *** 15 cm,temperatures of unburned sites dropped gradually to frozen levels by 30 cm,while soil temperatures at burned sites remained above 5C to 30-cm *** water content measured at 3 cm at burned sites was commonly in excess of 30%by volume,compared to unburned *** strong correlation between burn index values and depth to permafrost measured across all sites sampled in July 2017 showed tha

关键词： Alaska Landsat Permafrost RdNBR Soil temperature Soil water Wildfire

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Comparison of Flux-Switching Machines With and Without Permanent Magnets

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Chinese Journal of Electrical Engineering 2015年第1期1卷 78-84页

作者： christopher H.t.Lee K.t.Chau C.C.Chan Department of Electrical and Electronic Engineering The University of Hong KongHong KongChina

In this paper,three advanced flux-switching(FS)machines,namely the radial-field flux-switching permanent-magnet(RF-FSPM)machine,the radial-field flux-switching DC-field(RF-FSDC)machine,and the axial-field FSDC(AF-FSDC)machine are quantitatively *** the installation of the high-energy-density PM materials,the RF-FSPM machine can definitely provide the superior torque performances as compared to its magnetless ***,the PM machines suffer from two major fundamental problems,namely the high material costs,and the uncontrollable flux *** utilizing the concept of axial-field structure,the AF-FSDC machine can offer comparable torque performance as the RF-FSPM ***,with the consideration of the cost-effectiveness and the control flexibility,the magnetless AF-FSDC machine has exhibited promising potential in various applications.

关键词： Flux-switching magnetless radial-field axial-field cost-effectiveness

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Safety and immunogenicity of a third dose of mRNA-1273 vaccine among cancer patients

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Cancer Communications 2023年第7期43卷 749-764页

作者： Anna Giuliano Barbara Kuter Shari Pilon-thomas Junmin Whiting Qianxing Mo Brett Leav Bradley Sirak christopher Cubitt christopher Dukes Kimberly Isaacs-Soriano Kayoko Kennedy Somedeb Ball Ning Dong Akriti Jain Patrick Hwu Jeffrey Lancet Department of Cancer Epidemiology Moffitt Cancer CenterTampaFloridaUSA Moderna CambridgeMassachusettsUSA Department of Immunology Moffitt Cancer CenterTampaFloridaUSA Department of Biostatistics and Bioinformatics Moffitt Cancer CenterTampaFloridaUSA Immune Monitoring Core Moffitt Cancer CenterTampaFloridaUSA Non-therapeutic Research Office(NtRO) Moffitt Cancer CenterTampaFloridaUSA Department of Malignant Hematology Moffitt Cancer CenterTampaFloridaUSA

Background:Compared to the general population,cancer patients are at higher risk of morbidity and mortality following SARS-CoV-2 *** immune response to a two-dose regimen ofmRNA vaccines in cancer patients is generally lower than in immunocompetent *** doses may meaningfully augment immune response in this *** conducted an observational study with the primary objective of determining the immunogenicity of vaccine dose three(100μg)of mRNA-1273 among cancer patients and a secondary objective of evaluating safety at 14 and 28 ***:the mRNA-1273 vaccine was administered~7 to 9 months after administering two vaccine doses(i.e.,the primary series).Immune responses(enzyme-linked immunosorbent assay[ELISA])were assessed 28 days post-dose *** events were collected at days 14(±5)and 28(+5)post-dose *** exact or X^(2)tests were used to compare SARS-CoV-2 antibody positivity rates,and paired t-tests were used to compare SARS-CoV-2 antibody geometric mean titers(GMts)across different time ***:Among 284 adults diagnosed with solid tumors or hematologic malignancies,dose three of mRNA-1273 increased the percentage of patients seropositive for SARS-CoV-2 antibody from 81.7%pre-dose three to 94.4%28 days post-dose *** increased 19.0-fold(15.8-22.8).Patients with lymphoid cancers or solid tumors had the lowest and highest antibody titers post-dose three,*** responses after dose three were reduced among those who received anti-CD20 antibody treatment,had lower total lymphocyte counts and received anticancer therapy within 3 *** patients seronegative for SARS-CoV-2 antibody pre-dose three,69.2%seroconverted after dose three.A majority(70.4%)experienced mostly mild,transient adverse reactions within 14 days of dose three,whereas severe treatment-emergent events within 28 days were very rare(three of the mRNA-1273 vaccine was well-tolerated and augmented SAR

关键词： Cancer Coronavirus disease 2019 Immunogenicity Observational study Vaccination

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