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Fabrication of ultrafine-grained Ti-15Zr-xCu alloys through martensite decompositions under thermomechanical coupling conditions

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Journal of Materials Science & Technology 2022年第32期127卷 19-28页

作者： Wenwei Gao Hai Wang konrad Koenigsmann Shuyuan Zhang Ling Ren Ke Yang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China University of Chicago ChicagoIL 60637USA

Grain refinement is a well-recognized method to simultaneously increase the strength and ductility of metallic *** of ultrafine-grained metals in bulk using a simple low-cost approach is a long-term goal for material *** this work,based on the chemical composition of a biomedical Ti-15Zr alloy,a series of novel Ti-15Zr-xCu(x=0,3,5,7 wt.%)alloys were designed and *** alloys were quenched in the singleβphase region to obtain a martensitic microstructure and deformed in the temperature range of 710–750℃to obtain an ultrafine-grained microstructure through martensite decomposition under thermomechanical coupling *** results showed that Cu alloying could increase the dynamic recrystallization(DRX)nucleation rate due to its role in both refining martensitic lath width and increasing dislocation *** alloying could also suppress grain growth due to the precipitated Ti_(2)Cu particles exerting pinning forces on the grain *** optimal Cu content in the Ti-15Zr-xCu alloy was determined to be 5 wt.%.After being subjected to a compression leading to a 70%height reduction at 730℃and 1 s^(–1),the grain size of the Ti-15Zr-5Cu alloy was only 180±70 *** tensile strength of the as-prepared alloy reached 975±10 MPa,which was 45%higher than that of the conventional Ti-15Zr alloy(673±16 MPa).This increase in strength was achieved without any reduction in *** comprehensive mechanical properties of the ultrafinegrained Ti-15Zr-5Cu alloy are better than that of the Roxolid Ti–Zr alloy currently used for dental implants.

关键词： Titanium alloy Dynamic recrystallization Hot deformation Nucleation

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Applying Methods from Differential Geometry to Devise Stable and Persistent Air Layers Attached to Objects Immersed in Water

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Journal of Bionic Engineering 2009年第4期6卷 350-356页

作者： Wilfried konrad Christian Apeltauer Jrg Frauendiener Wilhelm Barthlott Anita Roth-Nebelsick Institute for Geosciences University of Tubingen D-72016 Tubingen Germany Department of Mathematics and Statistics University of Otago Dunedin 9054 New Zealand Centre of Mathematics for Applications University of Oslo NO-0317 Oslo Norway Nees Institute for Biodiversity of Plants University of Bonn D-53115 Bonn Germany State Museum of Natural History Stuttgart Rosenstein 1 D-70191 Stuttgart Germany

We describe a few mathematical tools which allow to investigate whether air-water interfaces exist(under prescribed conditions)and are mechanically stable and temporally *** terms of physics,air-water interfaces are governed by the Young-Laplace *** they are surfaces of constant mean curvature which represent solutions of a nonlinear elliptic partial differential *** explicit solutions of this equation can be obtained only in very special cases,it is -under moderately special circumstances-possible to establish the existence of a solution without actually solving the differential *** also derive criteria for mechanical stability and temporal persistence of an air *** we calculate the lifetime of a non-persistent air ***,we apply these tools to two examples which exhibit the symmetries of 2D *** examples can be viewed as abstractions of the biological model represented by the aquatic fern Salvinia.

关键词： interfaces air layers differential geometry stability persistence Salvinia

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High-performance oxygen permeation membranes:Cobalt-free Ba_(0.975)La_(0.025)Fe_(1-x)Cu_(x)O_(3)-δceramics

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Journal of Materiomics 2019年第2期5卷 264-272页

作者： Zilu Liu Kui Li Hailei Zhao konrad Swierczek School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Beijing Municipal Key Lab for Advanced Energy Materials and Technologies Beijing 100083China AGH University of Science and Technology Faculty of Energy and Fuelsal.A.Mickiewicza 3030-059 KrakowPoland AGH Centre of Energy AGH University of Science and Technologyul.Czarnowiejska 3630-054 KrakowPoland

A new group of cobalt-free perovskite oxides,Ba_(0.975)La_(0.025)Fe_(1-x)Cu_(x)O_(3-δ)(BLFC,x=0.05-0.15),was designed,characterized and applied as oxygen permeation *** was found that BLFC oxides with Cu doping range of 0.075-0.15 maintain cubic perovskite phase in a wide range of *** Cu introduced at the B-site results in a gradual increase of the electrical conductivity,which is attributed to the denser overlapping of electron clouds of CueO *** increasing Cu content,the oxygen vacancy concentration increases and the oxygen ion migration energy decreases,leading to the highest oxygen permeation flux of 1.59 mL cm^(-2)min^(-1)recorded for Ba_(0.975)La_(0.025)Fe_(0.9)Cu_(0.1)O_(3-δ)1mm thick membrane at 950℃.However,the oxygen permeability decreases with further Cu doping,which may be correspond to a presence of defect ***_(0.975)La_(0.025)Fe_(0.9)Cu_(0.10)O_(3-δ)membrane with 0.7mm thickness delivers stable oxygen permeation flux of 1.57 mL cm^(-2)min^(-1)for 200 h at 900℃.All of the obtained results indicate that the developed BLFC with optimized Cu content(i.e.x=0.1)is a very promising material for usage in oxygen separation applications.

关键词： Perovskite Oxygen permeability Structure stability Oxygen ion migration

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Laser additive manufactured high-performance Fe-based composites with unique strengthening structure

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Journal of Materials Science & Technology 2021年第30期89卷 242-252页

作者： Hongyu Chen Dongdong Gu Liang Deng Tiwen Lu Uta Kühn konrad Kosiba College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China Jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic Components Nanjing University of Aeronautics and AstronauticsNanjing 210016China Leibniz IFW Dresden Institute for Complex MaterialsP.O.Box 270116D-01069 DresdenGermany

Steel matrix composites(SMCs),reinforced by ceramic particles,have received a consistent attention in recent *** conventional methods to prepare SMCs is generally challenging,and the mechanical properties of conventionally fabricated SMCs are *** this study,we successfully fabricated highperformance SMCs by laser powder bed fusion(LPBF)of a composite powder consisting of Fe-based alloy powder and submicron-sized WC *** effect of laser energy density on the phase formation,microstructural evolution,overall density and resulting mechanical properties of LPBF-fabricated composites was *** present results show that a novel Fe_(2)W_(4)C carbidic network precipitates in the solidified microstructure entailing segregations along the boundaries of cellular *** presence of this carbidic network hampers the growth of sub-grains even at elevated temperatures,and hence,stabilizes the grain size though prepared at a broad range of different energy *** exact distribution of the Fe_(2)W_(4)C carbides depends on the employed laser energy densities,as for instance they are more uniformly distributed at higher energy *** density of LPBF samples reaches the maximum value of 99.4%at 150 J/mm^(3).In this parameter set,high microhardness of~753 HV,compression strength of~3350 MPa and fracture strain of~24.4%are *** enhanced mechanical properties are ascribed to less metallurgical defects,higher volume fraction of the martensitic phase and increasing pile-up dislocations resulting from the pinning effect by Fe_(2)W_(4)C carbide.

关键词： Laser additive manufacturing Laser powder bed fusion Steel matrix composite Microstructures Mechanical properties

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Mitochondrial transport of catalytic RNAs and targeting of the organellar transcriptome in human cells

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Journal of Molecular Cell Biology 2023年第8期15卷 40-53页

作者： PawełGłodowicz konrad Kuczynski Romain Val AndréDietrich Katarzyna Rolle Department of Molecular Neurooncology Institute of Bioorganic ChemistryPolish Academy of Sciencesul.Z.Noskowskiego 12/1461-704 PoznanPoland Institute of Plant Molecular Biology French National Center for Scientific Research(CNRS)and University of Strasbourg12 rue du Général Zimmer67084 StrasbourgFrance

Mutations in the small genome present in mitochondria often result in severe *** genetic strategies have been explored,aiming to rescue such mutations.A number of these strategies were based on the capacity of human mitochondria to import RNAs from the cytosol and designed to repress the replication of the mutated genomes or to provide the organelles with wild-type versions of mutant ***,the mutant RNAs present in mitochondria turned out to be an obstacle to therapy and little attention has been devoted so far to their ***,we present the development of a strategy to knockdown mitochondrial RNAs in human cells using the transfer RNA-like structure of Brome mosaic virus or Tobacco mosaic virus as a shuttle to drive trans-cleaving ribozymes into the organelles in human cell *** obtained a specific knockdown of the targeted mitochondrial ATP6 mRNA,followed by a deep drop in ATP6 protein and a functional impairment of the oxidative phosphorylation *** strategy provides a powerful approach to eliminate mutant organellar transcripts and to analyse the control and communication of the human organellar genetic system.

关键词： human cells mitochondria ribozyme RNA trafficking transcriptome manipulation tRNA-like structure

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Accuracy and Consistency of Respiratory Inductive Plethysmography for Overnight Tidal Volume Measurement

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Journal of Huazhong University of Science and Technology(Medical Sciences) 2001年第1期21卷 35-37,58页

作者：张劲农 Eric W Ruch konrad E Bloch Respiratory Disease Research Laboratory Xiehe Hospital Tongji Medical College Huazhong University of Science and Technology Abteilung Pneumologie Unisipital Zuerich

To validate the accuracy and consistency of respiratory inductive plethysmography (RIP) in measuring tidal volume after an overnight sleep, tidal volumes of 18 patients with suspected sleep disordered breathing and 8 normal volunteers were measured simultaneously with RIP (V TRIP ) and with an ultrasonic airflow meter (V TUFM ) before and after an unstrained overnight sleep on supine and lateral decubitus. The bias of the V TRIP was expressed as (V TRIP V TUFM )/ V TUFM ·100 %, limits of agreement between V TRIP and V TUFM was measured by averaged bias ±2 s . Results showed that in normal subjects, the bias of RIP before and after overnight sleep was precise and consistent in both supine (0.7 % and -1.6 %) and lateral decubitus (3.7 % and -0.56 %). In these patients, the bias of RIP before and after sleep in supine also remained small (1.9 % and 1.7 %), but it became larger in lateral decubitus (24.5 % and 20.4 %) and 11.5 % exceeded the limits of agreement observed in the evening. The patients′ body mass indices (BMI) were higher than those of normal subjects (median 34.2 vs. 27.8 kg/m 2). Pooled data showed that the bias of V TRIP in the morning on lateral decubitus but not on supine was correlated to BMI (Spearman R=0.32, n =52, P =0.02). Thus, we were led to conclude that the accuracy of V TRIP overnight was precise and consistent in normal subjects, but the deviation of V TRIP measured on lateral decubitus in patients especially in those with excessive obesity was greater, thus, the method should not be used for quantitative determination.

关键词： sleep study respiratory inductive plethysmography (RIP) tidal volume

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Working models for the gravitational field of Phobos

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Science China(Physics,Mechanics & Astronomy) 2012年第2期55卷 358-364页

作者： SHI Xian WILLNER konrad OBERST Jürgen PING JinSong YE ShuHua Shanghai Astronomical Observatory Chinese Academy ofSciencesShanghai 200030China Departmentfor Geodesy and Geoinformation Science Technical University BerlinBerlin 10623Germany Institute of Planetary Research Planetary GeodesyGerman Aerospace CenterBerlin 12489Germany

Models for the gravitational field of Mars moon Phobos were developed using the latest shape model and assuming homogeneous density *** methods were applied in our *** were made between these methods and all were shown to yield consistent ***,the most accurate shape model of Phobos to date,complete up to degree and order 17 was used for the first time in our analysis.A set of spherical harmonic coefficients up to degree and order 17 were derived for the gravitational field of *** considered was the gravitational field on the surface of *** characteristics as well as some pronounced surface features of this irregular-shaped small body could be conveniently *** results are readily applicable for such purposes as spacecraft orbit analysis and assessing the dynamical environment of Phobos.

关键词： Phobos gravitational field forward modeling

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Ultrafine-grained Ti6Al7Nb-xCu alloy with ultrahigh strength and exceptional biomedical properties

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Journal of Materials Science & Technology 2023年第33期164卷 68-78页

作者： Yi Li Hai Wang konrad Koenigsmann Hui Liu Shuyuan Zhang Ling Ren Ke Yang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China University of Chicago ChicagoIL 60637USA Binzhou Institute of Technology Shandong Key Laboratory of Advanced Aluminum Materials and TechnologyBinzhou 256606China

Grain refinement has been found to be able to improve the strength of metals without reducing their plasticity or *** this work,ultrafine-grained Ti6Al7Nb-xCu(x=0,3 wt%,6 wt%,9 wt%)alloys were fabricated based on the clinically used Ti6Al7Nb alloy via Cu alloying fabrication strategy combined with dynamic recrystallization(DRX)from martensite during hot *** results indicate that Cu alloying is not only effective in reducing the width of martensite laths after quenching in theβphase region but also increases the nucleation rate of DRX during the high-temperature ***,the Ti2Cu phase that precipitates from the matrix can pin the grain boundaries and inhibit their growth during the high-temperature *** optimal Cu concentration of Ti6Al7Nb-xCu alloy is determined to be 6 wt%,and the optimal deformation temperature is determined to be 750°*** this Cu content and deformation temperature,the grain size is only 270 nm,the tensile strength is up to 1266±10 MPa,and the elongation is 17%.Compared with the commercial Ti6Al7Nb alloy,the ultrafine-grained Ti6Al7Nb-6Cu alloy has better overall mechanical properties,good biocompatibility,and unique antibacterial *** work provides a theoretical basis for fabricating the new antibacterial titanium-based alloys with high strength.

关键词： High strength titanium alloy Ultrafine grain Antibacterial Dynamic recrystallization

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Biogeography and Evolutionary Factors Determine Genetic Differentiation of Pinus mugo(Turra) in the Tatra Mountains(Central Europe)

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Journal of Mountain Science 2015年第3期12卷 549-557页

作者： CELINSKI konrad ZBRáNKOVá Veronika WOJNICKA-PóLTORAK Aleksandra CHUDZINSKA Ewa Department of Genetics Adam Mickiewicz University in Poznań Department of Biology and Ecology University of Ostrava

Inter Simple Sequence Repeats （ISSR） markers were used to assess genetic diversity within and among populations of dwarf mountain pine （Pinus rnugo Turra） growing in the Tatra National Park （UNESCO Biosphere Reserve） in Southern Poland （Central Europe）. The analyzed population belongs to two different geobotanical sub-districts： the Western and High Tatras. The level of genetic diversity assessed in this study for P. mugo is generally comparable to that reported for the other pine species in the Pinaceae family assessed by ISSR markers, especially with respect to Nei＇s genetic diversity and the percentage of polymorphic bands. Bayesian analysis clustered the analyzed populations into two groups, corresponding to their geobotanical locations in the Tatras. Significant divergence between the two genetical clusters was supported by the results of Analysis of Molecular Variance （AMOVA）. According to the Mantel test, there was no correlation between the genetic distance and the geographical distance. The present study confirms the existence of two genetically distinct dusters of P. mugo populations in the Tatra Mountains. The observed high population-genetic differentiation of *** in the Tatras could be attributed to several genetic, environmental and historical factors occurring in this mountain area.

关键词： Biogeography Conservation genetics The Tatra Mountains Pinus mugo

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Natural variation in social conditions affects male mate choosiness in the amphipod Gammarus roeselii

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Current Zoology 2022年第4期68卷 459-467页

作者： konrad Lipkowski Sophie Steigerwald Lisa M Schulte Carolin Sommer-Trembo Jonas Jourdan Department of Wildlife/Zoo-Animal-Biology and Systematics Institute for EcologyEvolution and Diversity Goethe University FrankfurtMaxvon-Laue-Straße 13Frankfurt am MainD-60438Germany Department of Environmental Science Stockholm UniversitySvante Arrheniusväg 8StockholmSE-11418Sweden Zoological Institute University of BaselVesalgasse 1BaselCH-4051Switzerland Department of Aquatic Ecotoxicology Institute for EcologyEvolution and DiversityGoethe University Frankfurt am MainFrankfurt am MainGermany

The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition,quality assessment and opportunity *** knowledge about natural variation in male mate choosiness across different populations of the same species,however,remains *** this study,we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii(Gervais 1835),a species with overall high male mating investments,and evaluated the relative influence of population density and sex ratio(both affecting mate availability)on male mate *** investigated amplexus establishment after separating mating pairs and presenting focal males with a novel,size-matched female from the same *** analysis revealed considerable effects of sex ratio and(to a lesser extent)population density on time until amplexus establishment(choosiness).Male amphipods are able to perceive variable social conditions(e.g.,sex ratio)and modify their mating strategy accordingly:We found choosiness to be reduced in increasingly male-biased populations,whereas selectivity increases when sex ratio becomes female *** this,our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio(i.e.,level of competition)for male mating decisions in natural *** for variation in sex ratios,therefore,allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies.

关键词： amplexus Crustacea local adaptation mate choice population density sex ratio

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