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  • Open Access
    Authors: 
    Massimo Nespolo; Bernd Souvignier;
    Countries: Netherlands, France

    International audience; Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr. For further information see http://journals.iucr.org/services/authorrights.html Many research topics in condensed matter research, materials science and the life sciences make use of crystallographic methods to study crystalline and non-crystalline matter with neutrons, X-rays and electrons. Articles published in the Journal of Applied Crystallography focus on these methods and their use in identifying structural and diffusion-controlled phase transformations, structure–property relationships, structural changes of defects, interfaces and surfaces, etc. Developments of instrumentation and crystallographic apparatus, theory and interpretation, numerical analysis and other related subjects are also covered. The journal is the primary place where crystallographic computer program information is published.

  • Open Access English
    Authors: 
    Hicham Jabraoui; Etienne Paul Hessou; Siwar Chibani; Laurent Cantrel; Sébastien Lebègue; Michael Badawi;
    Publisher: HAL CCSD
    Country: France

    International audience; The ability of Ag-exchanged mordenite (Ag-MOR)to capture iodine species such as I2 and CH3I as released for instance during a nuclear accident could be severely limited by the presence of volatile organic compounds (VOCs)that can disrupt their adsorption in the zeolite. Here, using density functional theory (DFT), we investigate in detail the adsorption process of several hydrocarbons (methane, cyclohexane, benzene, and 1,3-dimethylbenzene)and oxygenated compounds (methanol, ethanol, propan-2-ol and propanone)and compare it with the adsorption of I2 and CH3I for different values of the Si/Al ratio of the Ag-exchanged mordenite. It is found that the adsorption process of the iodine species becomes favorable as the Si/Al ratio is decreased. Indeed at high Si/Al ratio, some VOCs such as benzene, 1, 3-dimethylbenzene and propan-2-ol exhibit strong inhibiting effects, while at low Si/Al ratio, only the adsorption of CH3I is limited by the presence of aromatic hydrocarbons. Also, in addition to the elongation of the I[sbnd]I bond upon the adsorption of the iodine molecule in Ag-MOR with a high silver content, we found that there is a significant electron transfer between the Ag and I atoms. Thus, our results indicate that the I[sbnd]I bond becomes weaker during the adsorption and therefore the formation of AgI precipitates is favored. © 2019 Elsevier B.V.

  • Closed Access English
    Authors: 
    Nadège Arnal; Claude Alban; Martine Quadrado; Olivier Grandjean; Hakim Mireau;
    Publisher: HAL CCSD
    Country: France

    Mitochondria are involved in the production of various vitamins, such as biotin, in plants. It is unclear why these biosynthetic pathways have been maintained partly or entirely within the mitochondria throughout evolution. The last step in biotin biosynthesis occurs within the mitochondria and is catalyzed by the biotin synthase complex containing the BIO2 gene product. We investigated whether the Arabidopsis Bio2 enzyme could function outside mitochondria, by trying to complement a bio2 mutant with a truncated version of BIO2 lacking the region encoding the mitochondrial targeting sequence. We describe the characterization of a new T-DNA allele of bio2, with the sole phenotype of an absence of biotin production, in contrast to the previously characterized EMS bio2 allele (Patton et al. 1998, Plant Physiol 116(3):935–946). We found that a cytosolic version of the Bio2 protein could not complement this mutant. Supplementation with the substrate dethiobiotin (DTB) also failed to rescue the mutant phenotype. Thus, the lack of availability of DTB in the cytosol is not the only factor preventing this reaction from occurring outside mitochondria. Bio2 requires mitochondrial targeting for activity, enabling it to fulfill its role in biotin synthesis. The reaction catalyzed by Bio2 may be subject to biochemical constraints, and the apparent close connection with the mitochondrial Fe-S machinery may account for the reaction being retained within the organelle.

  • Closed Access English
    Authors: 
    Nesrine Ben Yahmed; Hélène Carrère; M. Nejib Marzouki; Issam Smaali;
    Publisher: HAL CCSD
    Country: France

    Abstract The green macroalgal biomass corresponds to an emerging and promising biofuel feedstock. Their biological pretreatment and energetic conversion to biomethane were investigated and the enhancement of biogas production using the solid-state fermentation (SSF) as an eco-friendly innovative pretreatment of Ulva sp. was precisely assessed. Compared to conventional acid and alkali pretreatments, the highest methane potential of 153 ± 3 mL CH 4 g − 1 VS with an anaerobic biodegradability of 57% was obtained using SSF pretreatment with a locally isolated Aspergillus fumigatus SL1 strain. It was 132 ± 2 mL CH 4 g − 1 VS for raw Ulva sp. with biodegradability of 49%. Acid pretreatment with 4% HCl at 150 °C had a negative effect on Ulva sp.'s methane potential while alkali pretreatment with 4% NaOH at 20 °C showed a significant effect. The proposed SSF-based pretreatment enhanced therefore biogas production of 21% and permitted an eco-friendly valorization of large amounts of abundant macroalgae.

  • Open Access English
    Authors: 
    Emmanuelle Bignon; Tomáš Dršata; Christophe Morell; Filip Lankaš; Elise Dumont;
    Publisher: HAL CCSD
    Country: France
    Project: ANR | PRIMES (ANR-11-LABX-0063), ANR | Avenir L.S.E. (ANR-11-IDEX-0007)

    International audience; Oxidatively-generated interstrand cross-links rank among the most deleterious DNA lesions. They originate from abasic sites, whose aldehyde group can form a covalent adduct after condensation with the exocyclic amino group of purines, sometimes with remarkably high yields. We use explicit solvent molecular dynamics simulations to unravel the structures and mechanical properties of two DNA sequences containing an interstrand cross-link. Our simulations palliate the absence of experimental structural and stiffness information for such DNA lesions and provide an unprecedented insight into the DNA embedding of lesions that represent a major challenge for DNA replication, transcription and gene regulation by preventing strand separation. Our results based on quantum chemical calculations also suggest that the embedding of the ICL within the duplex can tune the reaction profile, and hence can be responsible for the high difference in yields of formation.

  • Open Access English
    Authors: 
    Yulong Fan; Benoit Cluzel; Marlène Petit; Xavier Le Roux; Anatole Lupu; André de Lustrac;
    Publisher: HAL CCSD
    Country: France
    Project: ANR | EIPHI (ANR-17-EURE-0002)

    International audience; Near-field imaging of the propagation of a diffraction-free Bessel-type beam in a guided wave configuration generated by means of a metasurface-based axicon lens integrated on a silicon waveguide is reported. The operation of the axicon lens with a footprint as small as 11 μm2 is based on local engineering of the effective index of the silicon waveguide with plasmonic nanoresonators. This generic approach, which can be adapted to different types of planar lightwave circuit platforms, offers the possibility to design nano-engineered optical devicesbased on the use of plasmonic resonators to control light at the nanoscale.

  • Open Access
    Authors: 
    Julien Toulouse; Wuming Zhu; János G. Ángyán; Andreas Savin;
    Publisher: American Physical Society (APS)
    Country: France

    Using Green-function many-body theory, we present the details of a formally exact adiabatic-connection fluctuation-dissipation density-functional theory based on range separation, which was sketched in Toulouse, Gerber, Jansen, Savin and Angyan, Phys. Rev. Lett. 102, 096404 (2009). Range-separated density-functional theory approaches combining short-range density functional approximations with long-range random phase approximations (RPA) are then obtained as well-identified approximations on the long-range Green-function self-energy. Range-separated RPA-type schemes with or without long-range Hartree-Fock exchange response kernel are assessed on rare-gas and alkaline-earth dimers, and compared to range-separated second-order perturbation theory and range-separated coupled-cluster theory. Comment: 15 pages, 3 figures, 2 tables

  • Publication . Preprint . Article . 2016
    Open Access English
    Authors: 
    Jonathan Chappelon; Luis Pedro Montejano; Jorge Luis Ramírez Alfonsín;
    Publisher: HAL CCSD
    Country: France

    Let $r(G,H)$ be the smallest integer $N$ such that for any $2$-coloring (say, red and blue) of the edges of $K\_n$, $n\geqslant N$, there is either a red copy of $G$ or a blue copy of $H$. Let $K\_n-K\_{1,s}$ be the complete graph on $n$ vertices from which the edges of $K\_{1,s}$ are dropped. In this note we present exact values for $r(K\_m-K\_{1,1},K\_n-K\_{1,s})$ and new upper bounds for $r(K\_m,K\_n-K\_{1,s})$ in numerous cases. We also present some results for the Ramsey number of Wheels versus $K\_n-K\_{1,s}$. Comment: 9 pages ; 1 table in Discrete Applied Mathematics, Elsevier, 2016

  • Open Access English
    Authors: 
    A. P. S. Baghel; B. Sai Ram; Krzysztof Chwastek; Laurent Daniel; S.V. Kulkarni;
    Publisher: HAL CCSD
    Country: France

    The anisotropy of magnetic properties in grain-oriented steels is related to their microstructure. It results from the anisotropy of the single crystal properties combined to crystallographic texture. The magnetization process along arbitrary directions can be explained using phase equilibrium for domain patterns, which can be described using Neel's phase theory. According to the theory the fractions of 180 degrees and 90 degrees domain walls depend on the direction of magnetization. This paper presents an approach to model hysteresis loops of grain-oriented steels along arbitrary in-plane directions. The considered description is based on a modification of the Jiles-Atherton model. It includes a modified expression for the anhysteretic magnetization which takes into account contributions of two types of domain walls. The computed hysteresis curves for different directions are in good agreement with experimental results. (C) 2016 Elsevier B.V. All rights reserved.

  • Open Access English
    Authors: 
    Ulysse Chabaud; Giulia Ferrini; Frédéric Grosshans; Damian Markham;
    Publisher: HAL CCSD
    Country: France
    Project: ANR | VanQuTe (ANR-17-CE24-0035)

    We consider Gaussian quantum circuits supplemented with non-Gaussian input states and derive sufficient conditions for efficient classical strong simulation of these circuits. In particular, we generalise the stellar representation of continuous-variable quantum states to the multimode setting and relate the stellar rank of the input non-Gaussian states, a recently introduced measure of non-Gaussianity, to the cost of evaluating classically the output probability densities of these circuits. Our results have consequences for the strong simulability of a large class of near-term continuous-variable quantum circuits. Comment: 8+6 pages, 3 figures. Comments welcome!

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