Activity of iron pyrite towards low-temperature ammonia production

© 2016 In this work we report the characteristics of iron pyrite toward the production of ammonia at low temperatures under ultra-high vacuum conditions. We review (with additional unpublished details) our previous systematic study of nitrogen and hydrogen adsorption on single-crystal iron pyrite (FeS 2 ) and summarise our earlier findings regarding the possibility of ammonia synthesis on this material. We also present new results concerning the adsorption of nitrogen and hydrogen on two related materials, namely molybdenum-treated iron pyrite surfaces and iron pyrite nanostructures deposited on a gold single-crystal. On the bare iron pyrite samples, ammonia is produced upon hydrogenation of preadsorbed N species at 230 K, demonstrating that all hydrogenation steps are possible at low pressures and temperatures. Nitrogen adsorbs molecularly on FeS 2 {100} at low temperatures, desorbing at 130 K, but does not adsorb dissociatively even at pressures up to 1 bar. Adsorbed nitrogen species can, however, be obtained through exposure to excited nitrogen species. Hydrogen adsorbs on FeS 2 {100}, but only in the presence of an incandescent Ta filament. Recombinative desorption of H 2 occurs at 225 K and is accompanied by desorption of H 2 S at 260 K. On the molybdenum-treated iron-pyrite, no appreciable N ads species were detected under the experimental conditions studied, and the same is true for iron pyrite nanostructures on Au{111}. We also provide further details of our efficient and reproducible method for preparing well-ordered stoichiometrically pure FeS 2 {100} suitable for surface science studies

The barocaloric effect: A Spin-off of the Discovery of High-Temperature Superconductivity

Some key results obtained in joint research projects with Alex M\"uller are summarized, concentrating on the invention of the barocaloric effect and its application for cooling as well as on important findings in the field of high-temperature superconductivity resulting from neutron scattering experiments.Comment: 26 pages, 9 figure

Effects of spin-phonon interaction on the properties of in high-TC_C superconductors

The mechanism of spin-phonon coupling in high-T$_C$ copper oxides is explored from band calculations on La$_{(2-x)}$Sr$_x$CuO$_4$ and HgBa$_2$CuO$_4$ systems. The LMTO band calculations, based on the local density approximation, are made for cells containing frozen phonon displacements and/or spin waves within the CuO plane. The virtual crystal approximation is used for studies of hole doped systems. The main result is that phonons are favorable for spin waves and vice-versa, and that pseudogaps appear naturally in the band structures of striped materials with strong SPC. The qualitative results are compatible with many observations showing that the properties of high-T$_C$ superconductors depend both on lattice interactions and magnetic fluctuations. The band results are used to model various properties, mainly of the normal state, such as isotope effects, pseudogaps, Fermi surface broadening, T-dependence of the pseudogap, phonon softening and some aspects of superconductivity. The possibility of perpendicular SPC is investigated, partly by the use of a nearly free electron model.Comment: 12 pages, 12 figure

Epitaxial growth of few-layer MoS2(0001) on FeS2{100}.

Physical vapour deposition of Mo on an FeS2{100} surface was performed at 170 K. Near-epitaxial growth of MoS2(0001) overlayers of the order of 1 nm thickness was observed when the Mo-covered substrate was subsequently heated to 600 K.The authors thank the EPSRC (grant ref. EP/E039782/1) for funding.This is the final published version. It first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CC/c4cc06628f#!divAbstract

Liberación de la patela en las artroplastias totales de rodilla: estudio gammagráfico

Se han realizado estudios gammagráficos en 20 pacientes intervenidos de artroplastia total cementada de rodilla. En 10 casos fue necesaria la liberación del alerón rotuliano externo y en otros 10 no se había indicado dicho gesto quirúrgico. En ningún paciente existía alteración evolutiva del aparato extensor. Los estudios gammagráficos se practicaron a los 12 meses del implante con el objeto de valorar la situación vascular de la rótula en ese momento. Se comparó, en la proyección lateral, la captación de la rótula en relación a la metáfisis distal del fémur homolateral. No hemos encontrado diferencias entre ambos grupos por lo que consideramos que la liberación patelar no produce un déficit vascular rotuliano a los 12 meses de la cirugía.Scintigraphic studies were performed in 20 patients with cemented total prosthesis of the knee. The patellar release was necessary in 10 cases. None of the patients developed knee extension deficits. Scintigraphic studies were performed 12 months after surgery in order to know the patellar blood supply at that moment. Patellar isotopic uptake was compared with the uptake at the distal metaphysis of the homolateral femur, at lateral projection. We haven't found any differences between both groups, so we consider that the patellar release doesn't make a less blood supply twelve months after surgery

Pipeline for recording datasets and running neural networks on the Bela embedded hardware platform

Deploying deep learning models on embedded devices is an arduous task: oftentimes, there exist no platform-specific instructions, and compilation times can be considerably large due to the limited computational resources available on-device. Moreover, many music-making applications de- mand real-time inference. Embedded hardware platforms for audio, such as Bela, offer an entry point for beginners into physical audio computing; however, the need for cross- compilation environments and low-level software develop- ment tools for deploying embedded deep learning models imposes high entry barriers on non-expert users. We present a pipeline for deploying neural networks in the Bela embedded hardware platform. In our pipeline, we include a tool to record a multichannel dataset of sen- sor signals. Additionally, we provide a dockerised cross- compilation environment for faster compilation. With this pipeline, we aim to provide a template for programmers and makers to prototype and experiment with neural networks for real-time embedded musical applications

Spin-phonon interaction and band effects in the high-T_C superconductor HgBa_2CuO_4

Band calculations show that a stripe-like anti-ferromagnetic spin wave is enforced by a 'half-breathing' phonon distortion within the CuO plane of HgBa_2CuO_4. This spin-phonon coupling is increased further by shear distortion and by increased distance between Cu and apical oxygens. The effects from spin-phonon coupling are consistent with many observations in high-T_C materials. Spin-phonon coupling can be important for the mechanism of spin fluctuations and superconductivity, although the effects are quantitatively weak when using the local density potential.Comment: 4 pages, 1 figur

Dynamical charge inhomogeneity and crystal-field fluctuations for 4f ions in high-Tc cuprates

The main relaxation mechanism of crystal-field excitations in rare-earth ions in cuprates is believed to be provided by the fluctuations of crystalline electric field induced by a dynamic charge inhomogeneity generic for the doped cuprates. We address the generalized granular model as one of the model scenario for such an ingomogeneity where the cuprate charge subsystem remind that of Wigner crystal with the melting transition and phonon-like positional excitation modes. Formal description of R-ion relaxation coincides with that of recently suggested magnetoelastic mechanism.Comment: 4 page

Pseudogap behavior of nuclear spin relaxation in high Tc superconductors in terms of phase separation

We analyze anew experiments on the NMR in cuprates and find an important information on their phase separation and its stripe character hidden in the dependence of $1/^{63}T_{1}$ on degree of doping. In a broad class of materials $1/^{63}T_{1}$ is the sum of two terms: the temperature independent one attributed to ``incommensurate'' stripes that occur at external doping, and an ``universal'' temperature dependent term ascribed to moving metallic and AF sub-phases. We argue that the frustrated first order phase transition in a broad temperature interval bears a dynamical character.Comment: 5 pages, 3 figures; some comments and references added; accepted for publication in JETP Letter