Metal additive manufacturing: process, conception and post-treatments

This research project is a global study of the metal additive manufacturing from the optimization of the design phase to the improvement of the final state of the parts with finishing treatments and passing by the adjustment of the production process. It starts with a state of art of the technologies, materials and industrial projects leading to focus on the laser melting of a metallic powder bed. The study of the manufacturing process has been realised focusing on the laser’s parameters: its speed and power. The optimization has been made with the objective of improving the surface state of the parts as long as the production was concerning dental implants in Cobalt-Chromium alloy. The design phase has been focused on with the topological optimization method applied to a suspension’s triangle in stainless steel. This method leading to a reduction of the mass and/or gain of stiffness of the part is used a lot with the additive manufacturing as long as it permits complex geometries. It although has to be linked to real tests to get information like the mechanical characteristics necessary for the simulation and to validate or not the resistance of the new geometry. The improvement of the final state of the parts can be related to the surface aspect with the shot peening process but although to the internal state of the part with post heat treatments. Here various heat treatments have been realised on a stainless steel, an aluminium alloy and a Nickel based superalloy to reduce the internal residual stresses and improve the homogeneity of the parts. Different macro and microscopic characterisations have been realised to validate or not the effect of the treatments on the quality of the samples to avoid their deformation and break and to try to approach the characteristics of a part issued from a more classical metal manufacturing proces

Selective Aerobic Oxidation of Cumene to Cumene Hydroperoxide over Mono- and Bimetallic Trimesate Metal Organic Frameworks Prepared by a Facile Green Aqueous Synthesis

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acssuschemeng.8b06472"[EN] Co-Ni and Mn-Ni bimetallic trimesate MOFs prepared by a fast aqueous synthesis method are excellent and reusable catalysts for the selective aerobic oxidation of cumene to cumene hydroperoxide (CHP). Isolation of Co2+ (or Mn2+) in an inert Ni-BTC framework is a good strategy to optimize CHP selectivity above 90%: since only Co2+ sites catalyze CHP decomposition, a drop of the CHP selectivity is observed as the cobalt content in the bimetallic MOF increases. The statistical probability of having isolated Co2+ sites is calculated as a function of the total cobalt content of the bimetallic compound, assuming homogeneous distribution of Co2+ ions in the Ni-BTC framework and preferential occupation of terminal sites. Thus, in our best sample, with a Co:Ni ratio of 5:95, 73% of the total Co2+ ions are isolated so that CHP decomposition/overoxidation processes at the surface of the catalyst are not likely to occur before CHP desorption. This can explain the excellent CHP selectivity (91%) attained over this material. This "site isolation" effect is further supported by similar findings on Mn-Ni bimetallic compounds.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641887 (project acronym: DEFNET) and the Spanish Government through projects MAT2017-82288-C2-1-P and Severo Ochoa (SEV-2016-0683).Nowacka, AE.; Briantais, P.; Prestipino, C.; Llabrés I Xamena, FX. (2019). Selective Aerobic Oxidation of Cumene to Cumene Hydroperoxide over Mono- and Bimetallic Trimesate Metal Organic Frameworks Prepared by a Facile Green Aqueous Synthesis. ACS Sustainable Chemistry & Engineering. 7(8):7708-7715. https://doi.org/10.1021/acssuschemeng.8b06472S770877157

Facile "Green" Aqueous Synthesis of Mono- and Bimetallic Trimesate Metal-Organic Frameworks

[EN] Various isoreticular monometallic (Co2+, Ni2+, Cu2+, and Zn2+) and bimetallic (Co-Ni, Co-Zn, Mn-Ni) trimesate MOFs have been prepared by a fast (10 min) and green synthesis method from aqueous solutions, at room temperature and ambient pressure. A combined XRD and SEM/EDX analysis clearly revealed bimetallic compounds form true solid solutions rather than a simple physical mixture of pure-phase monometallic compounds. Moreover, a detailed evaluation of the evolution of cell parameters with the composition provides strong evidence indicating a preferential occupation of one crystallographic position (bidentate terminal sites) by Co2+ (or Mn2+) ions. This leads to a precise and predictable array of metal ions in the framework, which can be finely tuned by changing the overall composition of the bimetallic MOF. Implications are envisaged in the design and catalytic properties of well-defined single-site catalysts.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641887 (project acronym: DEFNET) and the Spanish Government through projects MAT2017-82288-C2-1-P and Severo Ochoa (SEV-2016-0683). The Microscopy Service of the Universitat Politecnica de Valencia is gratefully acknowledged for the electron microscopy measurements.Nowacka, AE.; Briantais, P.; Prestipino, C.; Llabrés I Xamena, FX. (2019). Facile "Green" Aqueous Synthesis of Mono- and Bimetallic Trimesate Metal-Organic Frameworks. Crystal Growth & Design. 19(9):4981-4989. https://doi.org/10.1021/acs.cgd.9b00237S4981498919

Photoprotection in Plants Involves a Change in Lutein 1 Binding Domain in the Major Light-harvesting Complex of Photosystem II

Nonphotochemical quenching (NPQ) is the fundamental process by which plants exposed to high light intensities dissipate the potentially harmful excess energy as heat. Recently, it has been shown that efficient energy dissipation can be induced in the major light-harvesting complexes of photosystem II (LHCII) in the absence of protein-protein interactions. Spectroscopic measurements on these samples (LHCII gels) in the quenched state revealed specific alterations in the absorption and circular dichroism bands assigned to neoxanthin and lutein 1 molecules. In this work, we investigate the changes in conformation of the pigments involved in NPQ using resonance Raman spectroscopy. By selective excitation we show that, as well as the twisting of neoxanthin that has been reported previously, the lutein 1 pigment also undergoes a significant change in conformation when LHCII switches to the energy dissipative state. Selective two-photon excitation of carotenoid (Car) dark states (Car

Origin of Chlorophyll Fluorescence in Plants at 55–75°C ¶

The origin of heat-induced chlorophyll fluorescence rise that appears at about 55–60°C during linear heating of leaves, chloroplasts or thylakoids (especially with a reduced content of grana thylakoids) was studied. This fluorescence rise was earlier attributed to photosystem I (PSI) emission. Our data show that the fluorescence rise originates from chlorophyll a (Chl a ) molecules released from chlorophyll-containing protein complexes denaturing at 55–60°C. This conclusion results mainly from Chl a fluorescence lifetime measurements with barley leaves of different Chl a content and absorption and emission spectra measurements with barley leaves preheated to selected temperatures. These data, supported by measurements of liposomes with different Chl a /lipid ratios, suggest that the released Chl a is dissolved in lipids of thylakoid membranes and that with increasing Chl a content in the lipid phase, the released Chl a tends to form low-fluorescing aggregates. This is probably the reason for the suppressed fluorescence rise at 55–60°C and the decreasing fluorescence course at 60–75°C, which are observable during linear heating of plant material with a high Chl a /lipid ratio ( e.g. green leaves, grana thylakoids, isolated PSII particles).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74574/1/0031-8655_2003_0770068OOCFIP2.0.CO2.pd

Excitation energy transfer in native and unstacked thylakoid membranes studied by low temperature and ultrafast fluorescence spectroscopy

In this work, the transfer of excitation energy was studied in native and cation-depletion induced, unstacked thylakoid membranes of spinach by steady-state and time-resolved fluorescence spectroscopy. Fluorescence emission spectra at 5 K show an increase in photosystem I (PSI) emission upon unstacking, which suggests an increase of its antenna size. Fluorescence excitation measurements at 77 K indicate that the increase of PSI emission upon unstacking is caused both by a direct spillover from the photosystem II (PSII) core antenna and by a functional association of light-harvesting complex II (LHCII) to PSI, which is most likely caused by the formation of LHCII-LHCI-PSI supercomplexes. Time-resolved fluorescence measurements, both at room temperature and at 77 K, reveal differences in the fluorescence decay kinetics of stacked and unstacked membranes. Energy transfer between LHCII and PSI is observed to take place within 25 ps at room temperature and within 38 ps at 77 K, consistent with the formation of LHCII-LHCI-PSI supercomplexes. At the 150-160 ps timescale, both energy transfer from LHCII to PSI as well as spillover from the core antenna of PSII to PSI is shown to occur at 77 K. At room temperature the spillover and energy transfer to PSI is less clear at the 150 ps timescale, because these processes compete with charge separation in the PSII reaction center, which also takes place at a timescale of about 150 ps. © 2007 Springer Science+Business Media B.V

Mutations in Arabidopsis YCF20-like genes affect thermal dissipation of excess absorbed light energy

Plants dissipate excess absorbed light energy as heat to protect themselves from photo-oxidative stress. The Arabidopsis thaliananpq6 mutant affected in thermal dissipation was identified by its partial defect in the induction of nonphotochemical quenching of chlorophyll fluorescence (NPQ) by excess light. Positional cloning revealed that npq6 contains a frameshift mutation caused by a single base-pair deletion in the At5g43050 gene, which encodes a member of the hypothetical chloroplast open reading frame 20 (YCF20) family of proteins with unknown function(s). The YCF20 protein family is mostly conserved in oxygenic photosynthetic organisms including cyanobacteria, eukaryotic algae, and plants. Amino acid sequence comparison identified two other genes in Arabidopsis that encode similar proteins to NPQ6: At1g65420 and At3g56830. These three Arabidopsis proteins have functional chloroplast-targeting transit peptides. Using reverse genetics, a mutant with a T-DNA insertion within the At1g65420 gene was identified and shown to exhibit a low NPQ phenotype similar to that of npq6; therefore, At1g65420 was named NPQ7. In contrast, a knockdown mutant in the At3g56830 gene with lower transcript levels showed wild-type levels of NPQ. The npq6 npq7 double mutant had an additive NPQ defect, indicating that the YCF20 family members in Arabidopsis have overlapping functions affecting thermal dissipation

A Massive Open Online Course on Particle Accelerators

International audienceThe TIARA (Test Infrastructure and Accelerator Research Area) project funded by the European Union 7th framework programme made a survey of provision of education and training in accelerator science in Europe. This survey highlighted the need for more training opportunities targeting undergraduate-level students. This need is now being addressed by the European Union H2020 project ARIES (Accelerator Research and Innovation for European Science and Society) via the preparation of a Massive Online Open Course (MOOC) on particle accelerator science and engineering. We present here the current status of this project, the main elements of the syllabus, how it will be delivered, and the schedule for providing the course