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991.
Gaëtan Mary Aurore Van de Walle Jose Efrain Perez Tomofumi Ukai Toru Maekawa Nathalie Luciani Claire Wilhelm 《Advanced functional materials》2020,30(25)
Pluripotent stem cells are central tools to many regenerative medicine strategies due to their ability to differentiate toward the three embryonic germ layers. One challenge remains in providing control over their differentiation into specific lineages, such as cardiac commitment. Here, the possibility of directing cardiomyogenesis of embryonic stem cells using a microfabricated magnetic pattern is demonstrated. The stem cells are labeled with magnetic nanoparticles, aggregated into embryoid bodies (EBs) onto the pattern, and stimulated with a local magnetic force applied via the pattern. The EBs formed on this magnetic device experience the same differentiation profile as the ones created by the common hanging drop approach, while it allows high‐throughput production of hundreds of EBs. Further on/off cyclic magnetic force stimulation mediated by the same device is sufficient to enhance cardiomyogenesis in a way that almost all EBs develop spontaneous beating, confirmed by the overexpression of α‐actin and troponin proteins, and by the upregulation (twofold to fivefold) of genes involved in mesoderm differentiation (Nkx2.5, Gata4, and Gata6), and more specifically cardiac lineage (Tnnt2, Myh6, and Myl‐2). Beyond holding high application‐level potential, this work confirms that physical forces, and specifically on/off dynamic ones can be sufficient to govern cell function. 相似文献
992.
Armel Elysée Yapo Caroline Strub Noël Durand Angora Rémi Constant Ahoua Sabine Schorr-Galindo Bassirou Bonfoh 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2020,37(9):1564-1578
ABSTRACT ‘Kankankan’ is a popular spice powder used to season roasted meat in Côte d’Ivoire. However, produced in a traditional way, the conditions of production and storage of kankankan favour the proliferation of mycotoxin-producing fungal strains. The aim of this study was to carry out an inventory of mycotoxin contamination of this spice powder and to assess risk exposure to consumers. In total, 75 samples of kankankan were collected from wholesalers (6), sellers of kankankan in the markets (35) and sellers of roasted meat (34) across three municipalities of Abidjan, the economic capital of Côte d’Ivoire. Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used to detect and quantify nine different mycotoxins. Dietary exposure was calculated by using estimated daily intake (EDI), whereas risk characterisation was assessed using the margin of exposure (MOE) approach. Aflatoxins and fumonisins were found in 99% of samples assessed, while contamination with beauvericin was proportionally lowest (28%). At all the three types of actors within the food production chain (wholesalers, kankankan sellers and roasted meat sellers) the mean concentrations of aflatoxin B1 (AFB1) in samples exceeded the European standard for spice mixtures, with concentrations reaching up to 502 µg/kg. The estimated daily intakes of aflatoxins observed in the different populations were above the recommended level of 0.017 ng kg?1 b.w. day?1. The MOES values for adolescents and adults were 8.10 and 12.78, respectively, well below the safe margin of 10,000. The co-occurrence of mycotoxins in kankankan samples together with high aflatoxin exposure to consumers represent a potential risk to public health, calling for immediate risk management and education of kankankan producers and consumers. 相似文献
993.
Nadia Morin-Crini Jean-Noël Staelens Sonia Loiacono Bernard Martel Gilles Chanet Grégorio Crini 《应用聚合物科学杂志》2020,137(24):48823
Two hemp-based materials were used as nonconventional adsorbents for the final treatment of industrial discharge waters (DWs) from a metal-finishing plant. The first adsorbent, referred as HEMP, was a felt made of 100% hemp fiber. The second was the same felt coated with a maltodextrin-1,2,3,4-butanetetracarboxylic crosslinked polymer (HEMPM) in order to provide ion-exchange properties to the material by introducing carboxylic groups. The batch experiments showed that both materials exhibited high adsorption capacities toward metal ions present in 12 DWs, leading to concentrations well below those allowed by the French regulation. Measurements of the germination rate of Lactuca sativa seeds and of mobility inhibition of Daphnia magna, used as ecotoxicological tests, were carried out on DWs before and after hemp treatment. The average germination rate before and after treatment were 47.2 ± 4.1 for untreated DWs, 71.2 ± 6.3 for DWs treated by HEMP, and 89.3 ± 4.7 for DWs treated by HEMPM. The EC50 values for four DWs were between 2.1 and 10.4% of DW, indicating high toxicity. After HEMPM treatment, exposure to the DW for 24 h did not cause immobilization (EC50 > 90%). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48823. 相似文献
994.
Prof. Dr.-Ing. František Wald Dr.-Ing. Martin Vild Dr.-Ing. Marta Kuříková Dr.-Ing. Jaromír Kabeláč David Sekal Ing. Nadine Maier Dr.-Ing. Laura Da Silva Seco Dr.-Ing. Maël Couchaux 《Stahlbau》2020,89(5):482-495
Component based finite element design of steel joints This paper describes the principles of multi-level finite element modelling for design of structural steel joints. The internal part of the design by finite elements is the validation and verification of the model and its results. For models by shell and solid elements is mesh sensitivity study. In component bases finite element design (CBFEB) are the steel plates considered by geometrically and materially non-linear analysis (GMNA). Its resistance in elastoplastic stage is limited by strains. The behaviour of components, e. g. of bolts, anchor bolts, welds etc., is treated by introducing nonlinear springs representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of finite element analyses (FEA) in structural steel connections. This paper shows differences of the research-oriented and design-oriented models and the currents trends in modelling of connection components. Both have their roles in advanced analyses. The validation and verification is demonstrated on model of block shear during potential failure mode for gusset plate connection and for the base plates loaded by bending moments to both axes. The summary shows the potential in design of elements including its connection. 相似文献
995.
996.
997.
Ricardo Costa João M. Nóbrega Stéphane Clain Gaspar J. Machado Raphaël Loubère 《International journal for numerical methods in engineering》2019,117(2):188-220
Obtaining very high-order accurate solutions in curved domains is a challenging task as the accuracy of discretization methods may dramatically reduce without an appropriate treatment of boundary conditions. The classical techniques to preserve the nominal convergence order of accuracy, proposed in the context of finite element and finite volume methods, rely on curved mesh elements, which fit curved boundaries. Such techniques often demand sophisticated meshing algorithms, cumbersome quadrature rules for integration, and complex nonlinear transformations to map the curved mesh elements onto the reference polygonal ones. In this regard, the reconstruction for off-site data method, proposed in the work of Costa et al, provides very high-order accurate polynomial reconstructions on arbitrary smooth curved boundaries, enabling integration of the governing equations on polygonal mesh elements, and therefore, avoiding the use of complex integration quadrature rules or nonlinear transformations. The method was introduced for Dirichlet boundary conditions and the present article proposes an extension for general boundary conditions, which represents an important advance for real context applications. A generic framework to compute polynomial reconstructions is also developed based on the least-squares method, which handles general constraints and further improves the algorithm. The proposed methods are applied to solve the convection-diffusion equation with a finite volume discretization in unstructured meshes. A comprehensive numerical benchmark test suite is provided to verify and assess the accuracy, convergence orders, robustness, and efficiency, which proves that boundary conditions on arbitrary smooth curved boundaries are properly fulfilled and the nominal very high-order convergence orders are effectively achieved. 相似文献
998.
Andreas Hutzler Birk Fritsch Michael P. M. Jank Robert Branscheid R. Christian Martens Erdmann Spiecker Martin Mrz 《Advanced Materials Interfaces》2019,6(20)
Etching and growth of gold nanoparticles at a solid–liquid–gas interface are investigated via in situ liquid cell transmission electron microscopy. For this purpose, the gold precursor tetrachloroauric acid is enclosed in the wells of a free‐standing, locally thinned silicon nitride film covered by few‐layer graphene. Etching of gold is attributed to hydroxide radicals generated by radiolysis and gaseous species which are located within a gas bubble. The etching mechanism comprises two distinct cases. In one case, the gas bubble is in direct contact with the gold particle, separated only by a thin liquid membrane. In the other case, the gold particle is thoroughly immersed in liquid in the vicinity of the particle. In the latter, etching molecules diffuse from the bubble through the liquid toward the surface of the nanoparticle and subsequently etch the gold platelet. During the particle etching process, concurrent nucleation and ripening of gold nanoparticles are observed. This growth is induced by local supersaturation of the solution with gold ions. Experimental results show that the growth process is limited by diffusion, even though the diffusivity of reactants is very low due to narrow‐channel effects compared against the diffusivity of solvated ions in bulk liquids. 相似文献
999.
This systematic literature review paper investigates the key techniques employed to identify smells in different paradigms of software engineering from object-oriented (OO) to service-oriented (SO). In this review, we want to identify commonalities and differences in the identification of smells in OO and SO systems. Our research method relies on an automatic search from the relevant digital libraries to find the studies published since January 2000 on smells until December 2017. We have conducted a pilot and author-based search that allows us to select the 78 most relevant studies after applying inclusion and exclusion criteria. We evaluated the studies based on the smell detection techniques and the evolution of different methodologies in OO and SO. Among the 78 relevant studies selected, we have identified six different studies in which linguistic source code analysis received less attention from the researchers as compared to the static source code analysis. Smells like the yo-yo problem, unnamed coupling, intensive coupling, and interface bloat received considerably less attention in the literature. We also identified a catalog of 30 smells infrequently reported for SO systems and that require further attention. Moreover, a suite of 20 smells reported for SO systems can also be detected using static source code metrics in OO. Finally, our review highlighted three major research trends that are further subdivided into 20 research patterns initiating the detection of smells toward their correction. 相似文献
1000.
Jacob L. Meyer Mete Bakir Pixiang Lan James Economy Iwona Jasiuk Gaëtan Bonhomme Andreas A. Polycarpou 《大分子材料与工程》2019,304(4)
Reversible bonding is an attractive option for assembly and disassembly of reconfigurable space structures due to the simplicity of the fastening concept. Interchain transesterifications reaction [ITR—a type of dynamic covalent exchange reactions afforded by aromatic thermosetting copolyesters (ATSP)] between two ATSP coatings can successfully be used as a reversible bonding concept, provided that the mode of debonding is completely cohesive (rather than adhesive or delaminatory from metal substrate). An optimization study is carried out on the ITR bonding for which ATSP coating is applied on 7075 aluminum substrates and bond/debond experiments are carried out using a custom‐built tool kit. The toolkit enables precise control over bonding pressure, temperature, and contact time. Bonding conditions are optimized to produce complete cohesive failure with maximized bonding strength. Optimized bonding parameters are successfully implemented to realize 50 cycles of bond/debond process without compromising adhesive strength. Experiments show a debonding strength of 28.7 MPa for the 51st cycle at room temperature—significantly in excess of prior highest reversible bonding strength results found in the literature. These results, in addition to the high thermal stability and glass transition temperature of the base polymer, indicate viability of this reversible bonding concept for in‐space assembly. 相似文献