The effect of compressive strain on the Raman modes of the dry and hydrated BaCe0.8Y0.2O3 proton conductor

The BaCe0.8Y0.2O3-{\delta} proton conductor under hydration and under compressive strain has been analyzed with high pressure Raman spectroscopy and high pressure x-ray diffraction. The pressure dependent variation of the Ag and B2g bending modes from the O-Ce-O unit is suppressed when the proton conductor is hydrated, affecting directly the proton transfer by locally changing the electron density of the oxygen ions. Compressive strain causes a hardening of the Ce-O stretching bond. The activation barrier for proton conductivity is raised, in line with recent findings using high pressure and high temperature impedance spectroscopy. The increasing Raman frequency of the B1g and B3g modes thus implies that the phonons become hardened and increase the vibration energy in the a-c crystal plane upon compressive strain, whereas phonons are relaxed in the b-axis, and thus reveal softening of the Ag and B2g modes. Lattice toughening in the a-c crystal plane raises therefore a higher activation barrier for proton transfer and thus anisotropic conductivity. The experimental findings of the interaction of protons with the ceramic host lattice under external strain may provide a general guideline for yet to develop epitaxial strained proton conducting thin film systems with high proton mobility and low activation energy

The experimental power of FR900359 to study Gq-regulated biological processes.

Despite the discovery of heterotrimeric αβγ G proteins ∼25 years ago, their selective perturbation by cell-permeable inhibitors remains a fundamental challenge. Here we report that the plant-derived depsipeptide FR900359 (FR) is ideally suited to this task. Using a multifaceted approach we systematically characterize FR as a selective inhibitor of Gq/11/14 over all other mammalian Gα isoforms and elaborate its molecular mechanism of action. We also use FR to investigate whether inhibition of Gq proteins is an effective post-receptor strategy to target oncogenic signalling, using melanoma as a model system. FR suppresses many of the hallmark features that are central to the malignancy of melanoma cells, thereby providing new opportunities for therapeutic intervention. Just as pertussis toxin is used extensively to probe and inhibit the signalling of Gi/o proteins, we anticipate that FR will at least be its equivalent for investigating the biological relevance of Gq

The structural and dynamics neutron study of proton conductors: Difficulties and improvement procedures in protonated perovskite

With the expected development of Hydrogen as energy vector, there is a great impetus on the study of thermally stable proton conductors, the core of fuel cells, electrolysers and potential CO2 converters. Prior to a successful industrial application one should first well determine their extremely complex physical and chemical behaviour related to the unique character of the proton. The difficulties in comprehension of the nature of mobile protonic species, their location (especially the differentiation between bulk and surface species) as well as local and long range dynamics are different as a function of the hydration level: i) in hydrates the number of protons not really involved in the conduction is much larger than that of protonic conducting species, ii) in non-hydrated materials, the total amount of conducting protons can be very small, as dopants in semiconductors, and similar to that arising from surface water and physisorbed protonic moieties. The attempts and difficulties to locate and identify the protonic species and their dynamics using the neutron techniques are discussed in the light of representative examples, with emphasis on proton conducting perovskites

Raman Intensity: An Important Tool in the Study οf Nanomaterials and Nanostructures

Analysis of the relative and absolute Raman intensity is very important and powerful tool which allows to understand and characterize the modifications of the crystal/amorphous structure due to: (i) changes of the symmetry, e.g. substitution of the B site ion by the rare earth/lanthanide one and incorporation of mobile species in the case of high temperature protonic conducting perovskites; (ii) changes of the short/long range order, e.g. existence/disappearance of the nanoregions in the case of $PbMg_{1/3}Nb_{2/3}O_{3-x}PbTiO_3$ (PMN-PT) relaxor ferroelectric perovskites; (iii) changes of the nanostructure, e.g. depolymerisation of the Si-O network due to the substitution of the $Si^{4+}$ ions (and associated covalent bonds) by the $M^+$ cations (forming ionic bonds) or by the incorporation of the metal nanoprecipitates in the case of glasses, glazes and enamels

Raman Intensity: An Important Tool in the Study οf Nanomaterials and Nanostructures

Analysis of the relative and absolute Raman intensity is very important and powerful tool which allows to understand and characterize the modifications of the crystal/amorphous structure due to: (i) changes of the symmetry, e.g. substitution of the B site ion by the rare earth/lanthanide one and incorporation of mobile species in the case of high temperature protonic conducting perovskites; (ii) changes of the short/long range order, e.g. existence/disappearance of the nanoregions in the case of $PbMg_{1/3}Nb_{2/3}O_{3-x}PbTiO_3$ (PMN-PT) relaxor ferroelectric perovskites; (iii) changes of the nanostructure, e.g. depolymerisation of the Si-O network due to the substitution of the $Si^{4+}$ ions (and associated covalent bonds) by the $M^+$ cations (forming ionic bonds) or by the incorporation of the metal nanoprecipitates in the case of glasses, glazes and enamels

Distribution of relaxation times in PMN single crystal

The dielectric permittivity of PMN single crystal was measured in the frequency range from 20 Hz to 3 GHz. Dielectric dispersion was observed in all investigated frequency range. From the frequency dependence of the real and imaginary parts of dielectric permittvity, the distribution of relaxation times was calculated. The low frequency limit of the distribution of the relaxation times diverge according to the Vogel – Fulcher law with the freezing temperature T$_{0}$ = 228 K, which is in good agreement with mean relaxation time temperature dependence obtained from Cole – Cole equation. Broadening of the relaxation time distribution function at low temperatures indicates the existence of two different components making contribution to the total dielectric spectrum of PMN

Enhanced Performance of Gadolinia-Doped Ceria Diffusion Barrier Layers Fabricated by Pulsed Laser Deposition for Large-Area Solid Oxide Fuel Cells

Diffusion barrier layers are typically introduced in solid oxide fuel cells (SOFCs) to avoid reaction between state-of-the-art cathode and electrolyte materials, La 1-x Sr x Co 1-y Fe y O 3-\u3b4 and yttria-stabilized zirconia (YSZ), respectively. However, commonly used layers of gadolinia-doped ceria (CGO) introduce overpotentials that significantly reduce the cell performance. This performance decrease is mainly due to the low density achievable with traditional deposition techniques, such as screen printing, at acceptable fabrication temperatures. In this work, perfectly dense and reproducible barrier layers for state-of-the-art cells ( 3c80 cm 2 ) were implemented, for the first time, using large-area pulsed laser deposition (LA-PLD). In order to minimize cation interdiffusion, the low-temperature deposited barrier layers were thermally stabilized in the range between 1100 and 1400 \ub0C. Significant enhanced performance is reported for cells stabilized at 1150 \ub0C showing excellent power densities of 1.25 W\ub7cm -2 at 0.7 V and at a operation temperature of 750 \ub0C. Improved cells were finally included in a stack and operated in realistic conditions for 4500 h revealing low degradation rates (0.5%/1000 h) comparable to reference cells. This approach opens new perspectives in manufacturing highly reproducible and stable barrier layers for a new generation of SOFCs