Connectivity, habitat heterogeneity, and population persistence in Ranunculus nodiflorus, an endangered species in France

International audience• Here, we explore the role of habitat spatial structure in the maintenance of metapopulations of Ranunculus nodiflorus. This rare species grows in puddles that can be connected occasionally by flooded corridors. • We monitored five locations in the Fontainebleau forest, France, since 2002 and recorded the presence of corridors among puddles and evaluated their impact on puddle demography and plant fitness. • We showed that connections increased population size, by increasing both the number of puddles occupied by the species and the density of individuals within puddles, but seemed to have no direct influence on plant fitness. We found no evidence of a large persistent soil seed bank. • Natural corridors are likely to decrease the extinction probability of the populations , most probably by allowing recolonization of empty puddles after extinctions. Therefore, the preservation of corridors appears crucial for the conservation of R. nodiflorus in its natural habitat

Diffusion Of Indigo Molecules Inside The Palygorskite Clay Channels

The search for durable dyes led several past civilizations to develop artificial pigments. Maya Blue (MB), manufactured in pre-Columbian Mesoamerica, is one of the best known examples of an organic-inorganic hybrid material. Its durability is due to the unique association of indigo molecule and palygorskite, a particular fibrous clay occurring in Yucatan. Despite 50 years of sustained interest, the microscopic structure of MB and its relation to the durability remain open questions. Combining new thermogravimetric and synchrotron X-ray diffraction analyses, we show that indigo molecules can diffuse into the channel of the palygorskite during the heating process, replacing zeolitic water and stabilizing the room temperature phases of the clay

Monitoring by in situ neutron diffraction of simultaneous dehydration and Ni2+ mobility in partially exchanged NaY zeolites

International audiencePowder neutron diffraction is used to follow structural changes occurring during heat and vacuum assisted dehydration of 3 wt% nickel exchanged NaY. The structures determined from Rietveld refinement confirm the nickel ion displacement from the supercages and sodalite cages towards hexagonal prisms upon water removal. Not only this mobility but also its relationship with the dehydration level is demonstrated, owing to real time quantification of dehydration through changes in the intensity of the incoherent neutron scattering signal. Comparison with TGA data proves that this signal is fully attributable to water molecules adsorbed in the zeolite. STEM/EDX and in situ heating TEM studies provide complementary information on homogeneous Ni distribution (initial state) and on reductive sintering in vacuum at a high temperature

Systematical, experimental investigations on LiMgZ (Z= P, As, Sb) wide band gap semiconductors

This work reports on the experimental investigation of the wide band gap compounds LiMgZ (Z = P, As, Sb), which are promising candidates for opto-electronics and anode materials for Lithium batteries. The compounds crystallize in the cubic (C1_b) MgAgAs structure (space group F-43m). The polycrystalline samples were synthesized by solid state reaction methods. X-ray and neutron diffraction measurements show a homogeneous, single-phased samples. The electronic properties were studied using the direct current (DC) method. Additionally UV-VIS diffuse reflectance spectra were recorded in order to investigate the band gap nature. The measurements show that all compounds exhibit semiconducting behavior with direct band gaps of 1.0 eV to 2.3 eV depending on the Z element. A decrease of the peak widths in the static 7Li nuclear magnetic resonance (NMR) spectra with increasing temperature was observed, which can directly be related to an increase of Li ion mobility.Comment: 8 page

Dynamic Study of N'N-dimethylparanitroaniline encapsulated in Silicalite-1 matrix using neutron spin-echo spectroscopy

International audienceThe present work focuses on the dynamic studies of N'N-dimethyl- paranitroaniline (dmpNA) encapsulated in silicalite zeolite. Quasielastic neutron scattering (QENS) experiments are carried out using neutron spin-echo technique. Polarisation of the scattered neutron beam is measured at carefully chosen values of Q=0.35, 0.9, 1.1 and 1.45 A -1 at xed T=298 K and at xed Q=0.9 A -1 at 150, 200, 250 and 298 K. This gives insight into the motion and the related activation energy of the guest dmpNA molecule. The quasielastic signal observed in the present system within the time range considered is due to fast local rotational motions of protons of the end methyl groups. The results are in good agreement with the dynamics of methyl group rotations reported in the literature by back- scattering QENS technique

Association of indigo with zeolites for improved colour stabilization

International audienceThe durability of an organic colour and its resistance against external chemical agents and exposure to light can be significantly enhanced by hybridizing the natural dye with a mineral. In search for stable natural pigments, the present work focuses on the association of indigo blue with several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The manufacturing of the hybrid pigment is tested under varying oxidising conditions, using Raman and UV-visible spectrometric techniques. Blending indigo with MFI is shown to yield the most stable composite in all of our artificial indigo pigments. In absence of defects and substituted cations such as aluminum in the framework of the MFI zeolite matrix, we show that matching the pore size with the dimensions of the guest indigo molecule is the key factor. The evidence for the high colour stability of indigo@MFI opens a new path for modeling the stability of indigo in various alumino-silicate substrates such as in the historical Maya Blue pigment

The A-cation deficient perovskite series La_2-xCoTiO_6-δ (0 ≤ x ≤ 0.20): new components for potential SOFC composite cathodes

The best performances are obtained for low x due to a compromise between sufficiently high amount of defects, but not so high to induce defect clustering.</p

Revisiting Maya Blue and Designing Hybrid Pigments by Archaeomimetism

Maya Blue is actually one of the best known examples of an organic-inorganic hybrid material. Yet despite 50 years of sustained interest, its microscopic structure and its relation to durability remain open questions. We address the issue by archaeomimetism: engineering an archaeoinspired pigment, satisfactorily reproducing the colour and chemical stability of Maya Blue. By comparing and contrasting ancient pigment and the new analogue, we deduce a new explanation for this durability

The origin of the dual ferroic properties in quasi-centrosymmetrical SrFe12−xInxO19 hexaferrites

The local crystal/magnetic structures of the SrFe12−xInxO19 solid solutions (x = 0.1; 0.3; 0.6 and 1.2) were investigated using neutron powder diffraction. The measurements of the electric polarization for all investigated samples were carried out as a function of the external electric field. The presence of the ferroelectric and ferromagnetic ordering (dual ferroic ordering) in the SrFe12−xInxO19 hexaferrites at 300 K was found. This appearance contradicts to the conventional opinion describing their crystal structure (centrosymmetric space group P63/mmc (No. 194)). The reason for the existence of a spontaneous polarization (nonzero dipole moment) in the SrFe12−xInxO19 hexaferrites continues controversial. The crystal structure of the hexaferrites was considered both the centrosymmetric P63/mmc and non-centrosymmetric P63mc space groups. This fact made it possible to find a connection between the emerging dipole moment and not equal distortions of the neighbor oxygen polyhedral. The nature description of the nonzero dipole moment formation in a quasi-centrosymmetrical system of the In-substituted SrFe12−xInxO19 hexaferrites was presented based on the neutron diffraction data.This work was supported by the Russian Science Foundation (Agreement no. 19-19-00694 of 06 May 2019).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe