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Jul 31, 2020
La recherche de l'origine de la vie demande d'identifier chaque étape élémentaire d'une longue chaine de processus pouvant, à partir des atomes issus de la nucléosynthèse au cœur des étoiles (essentiellement de l'hydrogène au fer) ou sous l'effet de l'explosion finale des supernovæ (éléments lourds au-delà du fer), conduire à la formation des générations successives de molécules de plus en plus complexes, pour aboutir aux molécules constitutives du vivant telles qu'elles sont présentes sur Terre.
Jul 21, 2020
Premakumar Yanda, I. V. Golosovsky, I. Mirebeau, N. V. Ter-Oganessian, Juan Rodríguez-Carvajal and A. Sundaresan In most of the spin-induced multiferroics, the ferroelectricity is caused by inversion symmetry breaking by complex spin structures of the transition-metal ions. Here, we report the importance of interplay of 4 f -3d magnetic interactions in inducing ferroelectricity in the centrosymmetric (Pnma) green phase compound Gd2BaCuO5.
Jul 09, 2020
Contact SPEC: Yannick Dappe
Dans ce travail publié dans  Appl. Phys. Lett. 116, 141605 (2020), nous présentons l’exploration de la surface d’énergie potentielle de la face carbone du SiC. Depuis la première observation expérimentale en 1997 d’une reconstruction 3 × 3 sur cette surface, le modèle atomique sous-jacent reste l’objet de débat.
Jul 08, 2020
Contacts SPEC : Dana Stanescu, Helene Magnan, Jean-Baptiste Moussy, Cindy Rountree, Antoine Barbier
Les matériaux ferroélectriques ont connu un essor considérable en raison de leurs applications potentielles dans des domaines comme la spintronique ou la conversion de l’énergie solaire1–3. Au SPEC nous avons étudié le rôle des interfaces, du substrat et des couches d’oxyde supérieures sur les propriétés ferroélectriques des hétérostructures à base des couches minces de BaTiO34.
Jun 23, 2020
We show by X-ray and neutron small-angle scattering that gold nanoparticles with controlled sizes and morphologies can be obtained by the metallic reduction of AuCl4– ions trapped in 3D organic molds by X-ray radiolysis. The molds are spherical frozen micelles of polystyrene-b-poly(dimethylaminoethyl methacrylate) (PS-b-PDMAEMA) block copolymer in acidic aqueous solution with a PS spherical core surrounded by a corona of PDMAEMA chains in good solvent.
Jun 01, 2020
Editors : Véronique Arluison and Frank Wien This volume looks at the different spectroscopic and biophysical methods used by researchers to study the structure and folding of RNA, and to follow their interactions with proteins.
May 23, 2020
Au sein d'un échantillon solide, réduire la température des spins est une bonne méthode pour améliorer le signal de RMN ou de RPE, puisque cela favorise leur polarisation selon la direction imposée par le champ externe appliqué.
May 09, 2020
Andrew M. Jimenez, Dan Zhao, Kyle Misquitta, Jacques Jestin and Sanat K. Kumar Understanding the structure and dynamics of the bound polymer layer (BL) that forms on favorably interacting nanoparticles (NPs) is critical to revealing the mechanisms responsible for material property enhancements in polymer nanocomposites (PNCs).
Apr 28, 2020
Black phosphorus (BP) is a stack of monoatomic layers of phosphorus, bound together by Van der Waals forces. This 2d material is today attracting a great interest due to its widely tunable band gap, depending on the thickness of the material, the very high mobility of its carriers, for its application in field effect transistors (FETs), and the possible emergence of topologically protected states.
Apr 09, 2020
  Dans une nanostructure ferromagnétique, la dynamique de l’aimantation peut rester cohérente à des angles de précession remarquablement élevés, ce qui constitue un élément important pour un contrôle fiable des dispositifs nanomagnétiques.
Apr 08, 2020
Aline Maire du Poset, Mikaela Börjesson, Céline Rameau, Claire Madeleine-Perdrillat, Adrien Lerbret, Camille Loupiac, Fabrice Cousin, Ali Assifaoui We show here how the structure of polygalacturonate (polyGalA) hydrogels cross-linked by Ca2+ cations via external gelation controls the loading and release rate of beta-lactoglobulin (BLG), a globular protein.
Mar 17, 2020
A. C. Ferreira, S. Paofai, A. Létoublon, J. Ollivier, S. Raymond, B. Hehlen, B. Rufflé, S. Cordier, C. Katan, J. Even & P. Bourges   Hybrid organolead perovskites (HOP) have started to establish themselves in the field of photovoltaics, mainly due to their great optoelectronic properties and steadily improving solar cell efficiency. Study of the lattice dynamics is key in understanding the electron-phonon interactions at play, responsible for such properties.
Feb 13, 2020
de Oliveira-Silva, Rodrigo; Bélime, Agathe; Le Coeur, Clémence; Chennevière, Alexis; Helary, Arnaud; Cousin, Fabrice; Judeinstein, Patrick; Sakellariou, Dimitrios; Zanotti, Jean-Marc In soft condensed matter, Small Angle Neutron Scattering (SANS) is a central tool to probe structures with characteristic sizes ranging from 1 to 100 nm. However, when used as a standalone technique, the dynamic properties of the sample are not accessible.
Jan 14, 2020
N. Martin, M. Deutsch, T. C. Hansen, M. T. Fernandez-Diaz, L. N. Fomicheva, A. V. Tsvyashchenko, and I. Mirebeau In the MnGe chiral magnet, the helimagnetic order and local moment collapse in two steps, showing the succession of high spin (HS) and low spin (LS) states as pressure increases. Here, we use high-pressure neutron diffraction to study the doped compounds Mn0.86Co0.14Ge and Mn0.9Rh0.1Ge, and show that the evolution of their microscopic magnetic properties is instead continuous.
Dec 21, 2019
M. Ruminy, S. Guitteny, J. Robert, L.-P. Regnault, M. Boehm, P. Steffens, H. Mutka, J. Ollivier, U. Stuhr, J. S. White, B. Roessli, L. Bovo, C. Decorse, M. K. Haas, R. J. Cava, I. Mirebeau, M. Kenzelmann, S. Petit, and T. Fennell Tb2Ti2O7 presents an ongoing conundrum in the study of rare-earth pyrochlores.
Dec 13, 2019
La ténacité d’un matériau définit sa résistance à rupture. Si on sait la mesurer expérimentalement de manière précise, on ne sait pas, à l’heure actuelle, prévoir sa valeur à partir de la structure atomistique du matériau considéré, même dans les cas les plus simples.
Nov 25, 2019
A. S. Sukhanov, Praveen Vir, A. S. Cameron, H. C. Wu, N. Martin, S. Mühlbauer, A. Heinemann, H. D. Yang, C. Felser, and D. S. Inosov The cubic chiral helimagnets with the P213 space group represent a group of compounds in which the stable skyrmion-lattice state is experimentally observed. The key parameter that controls the energy landscape of such systems and determines the emergence of a topologically nontrivial magnetic structure is the Dzyaloshinskii-Moriya interaction (DMI).
Oct 23, 2019
N. Martin, I. Mirebeau, C. Franz, G. Chaboussant, L. N. Fomicheva, and A. V. Tsvyashchenko We study the helimagnetic ground state of the MnGe cubic alloy using small-angle neutron scattering and a high-resolution method, the so-called MIEZE spectroscopy. Upon cooling below the Néel temperature TN = 170(5) K, we observe the proliferation of long-wavelength gapless spin fluctuations, concomitant with a continuous evolution of the helical correlation length.
Sep 22, 2019
Daniela Russo, Maya Dimova Lambreva, Christiane Alba Simionesco, Pierre Sebban,and Giuseppina Rea Studies on the dynamical properties of photosynthetic membranes of land plants and purple bacteria have been previously performed by neutron spectroscopy, revealing a tight coupling between specific photochemical reactions and macromolecular dynamics.
Sep 11, 2019
La réduction catalytique de composés organiques comportant des liaisons C=O suscite de nombreuses études en chimie fine pour former des molécules d’intérêt (éthers, alcools…), mais l’obtention sélective d’un produit de réaction est parfois difficile. Le choix du catalyseur et du réducteur joue ici un rôle essentiel.
Aug 27, 2019
D. Russo, A. De Angelis, A. Paciaroni, B. Frick, N. de Sousa, F. R. Wurm, and J. Teixeira We investigate the relaxation dynamics of protein−polymer conjugates by neutron scattering spectroscopy to understand to which extent the coating of a protein by a polymer can replace water in promoting thermal structural fluctuations.
Jul 19, 2019
The response of a position-sensitive Li-glass scintillator detector to alpha-particles from a collimated 241Am source scanned across the face of the detector has been measured. Scintillation light was read out by an 8x8 pixel multi-anode photomultiplier and the signal amplitude for each pixel has been recorded for every position on a scan. The pixel signal is strongly dependent on position and in general several pixels will register a signal (a hit) above a given threshold.
Jul 11, 2019
La métrologie (spectroscopie, mesures de temps ou de distances) ou encore la réalisation de réseaux optiques quantiques nécessitent des sources de photons uniques efficaces. Une équipe du SPEC à Saclay, en collaboration avec l'IQST d'Ulm en Allemagne, propose une voie originale pour obtenir une source de photons microondes uniques, simple, efficace et brillante.
Jun 20, 2019
A. Theodoratou, L.-T. Lee, J. Oberdisse and A. Aubert-Pouëssel, Langmuir 35(20) (2019) 6620. Abstract : Nanofilms of about 2 nm thickness have been formed at the air–water interface using functionalized castor oil (ICO) with cross-linkable silylated groups.
May 30, 2019
"Dynamics properties of photosynthetic microorganisms probed by incoherent neutron scattering" Daniela Russo, Maya Dimova Lambreva, Christiane Alba Simionesco, Pierre Sebban, and Giuseppina Rea Biophysical Journal, 116 (9) (2019) 1759-1768 Studies on the dynamical properties of photosynthetic membranes of land plants and purple bacteria have been previously performed by neutron spectroscopy, revealing a tight coupling between specific photochemical reactions and macromolecular dynamics.
May 04, 2019
B. Annighöfer , A. Hélary, A. Brulet, A. Colas de la Noue, C. Loupiac and S. Combet Review of Scientific Instruments 90 (2019) 025106 Abstract : We report on a high pressure (HP) cell designed for the determination of the structure of molecular solutions by small-angle neutron scattering (SANS). The HP cell is fitted up with two thick metallic windows that make the device very resistant under hydrostatic pressures up to 600 MPa (or 6 kbar).
Apr 01, 2019
Andrés Marcoleta, Frank Wien, Véronique Arluison, Rosalba Lagos, Rafael Giraldo Bacterial Amyloids (2019) Amyloids are supramolecular protein assemblies based on fibrillar arrangements of β‐sheets that were first found as linked to neurodegenerative and systemic human diseases. However, there is now overwhelming evidence on alternative roles of amyloids as functional assemblies and as epigenetic determinants of beneficial traits, both in Fungi and Metazoa.
Mar 11, 2019
La métrologie (spectroscopie, mesures de temps ou de distances) ou encore la réalisation de réseaux optiques quantiques nécessitent des sources de photons uniques efficaces. Une équipe du SPEC à Saclay, en collaboration avec l'IQST d'Ulm en Allemagne, démontre expérimentalement une voie originale pour obtenir une source de photons microonde uniques, simple, efficace et brillante.
Mar 05, 2019
Annelies Sels, Giovanni Salassa, Fabrice Cousin, Lay-Theng Lee, Thomas Bürgi, Nanoscale 26 (2018) 12754. Aromatic dithiol linkers were used to prepare aggregates of Au25(SR)18 clusters (SR: thiolate) via ligand exchange reactions. Fractions of different aggregate sizes were separated by size exclusion chromatography (SEC).
Mar 04, 2019
Marguerite Léang, Didier Lairez, Fabrice Cousin, Frédérique Giorgiutti-Dauphiné, Ludovic Pauchard, Lay-Theng Lee During evaporative drying of a colloidal dispersion, the structural behavior at the air-dispersion interface is of particular relevance to the understanding of the consolidation mechanism and the final structural and mechanical properties of the porous media.

 

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