Charge-Density-Waves Tuned by Crystal Symmetry

The electronic orders appearing in condensed matter systems are originating from the precise arrangement of atoms constituting the crystal as well as their nature. This teneous relationship can lead to highly different phases in condensed matter, and drive electronic phase transitions. Here, we show that a very slight deformation of the crystal structure of TbTe$_3$ can have a dramatic influence on the electronic order that is stabilized. In particular, we show that the Charge Density Wave (CDW) developping along the $\vec{c}$ axis in the pristine state, switches to an orientation along $\vec{a}$ when the naturally orthorhombic system is turned into a tetragonal system. This is achieved by performing true biaxial mechanical deformation of a TbTe$_3$ sample from 250K to 375K, and by measuring both structural and electronic parameters with x-ray diffraction and transport measurements. We show that this switching transition is driven by the tetragonality parameter $a/c$, and that the transition occurs for $a=c$, with a coexistence region for $0.9985< a/c < 1.002$. The CDW transition temperature $T_c$ is found to have a linear dependence with $a/c$, with no saturation in the deformed states investigated here, while the gap saturates out of the coexistence region. The linear dependence of $T_c$ is accounted for within a tight-binding model. Our results question the relationship between the gap and $T_c$ in RTe$_3$ systems. More generally, our method of applying true biaxial deformation at cryogenic temperatures can be applied to many systems displaying electronic phase transitions, and opens a new route towards the study of coexisting or competing electronic orders in condensed matter

Biophysical Characterization and Membrane Interaction of the Two Fusion Loops of Glycoprotein B from Herpes Simplex Type I Virus

The molecular mechanism of entry of herpesviruses requires a multicomponent fusion system. Cell invasion by Herpes simplex virus (HSV) requires four virally encoded glycoproteins: namely gD, gB and gH/gL. The role of gB has remained elusive until recently when the crystal structure of HSV-1 gB became available and the fusion potential of gB was clearly demonstrated. Although much information on gB structure/function relationship has been gathered in recent years, the elucidation of the nature of the fine interactions between gB fusion loops and the membrane bilayer may help to understand the precise molecular mechanism behind herpesvirus-host cell membrane fusion. Here, we report the first biophysical study on the two fusion peptides of gB, with a particular focus on the effects determined by both peptides on lipid bilayers of various compositions. The two fusion loops constitute a structural subdomain wherein key hydrophobic amino acids form a ridge that is supported on both sides by charged residues. When used together the two fusion loops have the ability to significantly destabilize the target membrane bilayer, notwithstanding their low bilayer penetration when used separately. These data support the model of gB fusion loops insertion into cholesterol enriched membranes

Diffraction techniques and vibrational spectroscopy opportunities to characterise bones

From a histological point of view, bones that allow body mobility and protection of internal organs consist not only of different organic and inorganic tissues but include vascular and nervous elements as well. Moreover, due to its ability to host different ions and cations, its mineral part represents an important reservoir, playing a key role in the metabolic activity of the organism. From a structural point of view, bones can be considered as a composite material displaying a hierarchical structure at different scales. At the nanometre scale, an organic part, i.e. collagen fibrils and an inorganic part, i.e. calcium phosphate nanocrystals are intimately mixed to assure particular mechanical properties

Effect of fatty acid infusion on muscle glycogen resynthesis after exercise in healthy subjects: 13C NMR study

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In situ monitoring of X-ray strain pole figures of a biaxially deformed ultra-thin film on a flexible substrate

International audienceX-ray strain pole figures (SPFs) have been captured in situ during biaxial deformation of a gold ultra-thin film (thickness = 40 nm) deposited on a polymer substrate. An area detector was used to extract one line in the reciprocal space while the strained sample was rotated azimuthally step by step to produce the SPF. Such SPFs have been obtained for a textured anisotropic ultra-thin film under controlled non-equibiaxial loading using the SOLEIL synchrotron DIFFABS tensile device. The experimental setup allows the pole figure measurements of \111\ and \200\ reflections to be performed simultaneously. Interestingly, those two crystallographic directions are related to the two-extreme elastic mechanical behaviour. The full directional lattice strain dependence (SPF) is obtained within 15 min and can be monitored step by step upon loading. This procedure gives an insight into ultra-thin film mechanical response under complex biaxial loading

Sin(2) psi analysis in thin films using 2D detectors: Non-linearity due to set-up, stress state and microstructure

International audienceTwo synchrotron set-ups have been used to carry out in situ strain measurements on systems constituted by Au films on polyimide substrates. These film/substrate composites have been submitted to either uniaxial or equibiaxial loadings. For the two configurations, an area detector (2D) was employed to extract the so-called epsilon-sin(2) psi curves. These latter are shown to be affected by geometrical effect unless equibiaxial loading is employed. Moreover, non-linearity of these curves can occur, even in the case of equibiaxial loading, when the film is thin (120 nm). This last phenomenon is explained by surface anisotropy

Mastering the biaxial stress state in nanometric thin films on flexible substrates

International audienceBiaxial stress state of thin films deposited on flexible substrate can be mastered thanks to a new biaxial device. This tensile machine allows applying in-plane loads F-x and F-y in the two principal directions x and y of a cruciform-shaped polymer substrate. The transmission of the deformation at film/substrate interface allows controlling the stress and strain field in the thin films. We show in this paper a few illustrations dealing with strain measurements in polycrystalline thin films deposited on flexible substrate. The potentialities of the biaxial device located at Soleil synchrotron are also discussed