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Non-stoichiometric 214-nickelates with Ruddlesden-Popper (RP) type frameworks emerged as potential candidates for mixed electronic/ionic conductors in the intermediate temperature range. In this work we investigated structural aspects of the oxygen ion mobility diffusion mechanisms in non-stoichiometric Nd 2 NiO 4+ δ nickelates by X-ray (laboratory and synchrotron) as well by neutron diffraction. Temperature dependent synchrotron powder diffraction revealed a phase diagram of unprecedented complexity, involving a series of highly organized, 3D modulated phases related to oxygen ordering below 800 K. All phase transitionsimply translational periodicities exceeding 100 Å, and are found to be of 1 st order, together with fast ordering kinetics. These surprising structural correlations, induced by the presence of interstitial oxygen atoms, suggest a collective phason-like oxygen diffusion mechanism together with dynamical contributions from the aperiodical lattice creating shallow diffusion pathways down to room temperature., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The support material can play an important role in oxidation catalysis, notably for CO oxidation. Here, we study two materials of the Brownmillerite family, CaFeO 2.5 and SrFeO 2.5 , as one example of a stoichiometric phase (CaFeO 2.5, CFO) and one existing in different modifications (SrFeO 2.75 , SrFeO 2.875 and SrFeO 3 , SFO). The two materials are synthesized using two synthesis methods, one bottom-up approach via a complexation route and one top-down method (electric arc fusion), allowing to study the impact of the specific surface area on the oxygen mobility and catalytic performance. CO oxidation on 18 O-exchanged materials shows that oxygen from SFO participates in the reaction as soon as the reaction starts, while for CFO, this onset takes place 185 °C after reaction onset. This indicates that the structure of the support material has an impact on the catalytic performance. We report here on significant differences in the catalytic activity linked to long-term stability of CFO and SFO, which is an important parameter not only for possible applications, but equally to better understand the mechanism of the catalytic activity itself.

High resolution and high intensity neutron powder diffraction are used to determine the temperature dependence of the crystallographic and magnetic structure of the orthoferrite CeFeO 3 . The high temperature G x -type magnetic coupling of the Fe-sublattice described by the Γ 4 ( G x A y F z ) irreducible representation changes at the spin reorientation temperature T SR = 228 K to a G y -type coupling of Γ 1 ( A x G y C z ). The spin reorientation is of first order and sees a hysteresis of about 2.5 K at T SR . Below 35 K faint magnetic peaks reflecting C z type magnetic coupling appear and are argued to be related to the Ce-sublattice. Magnetic moments at 2 K amount to μ Fe = 4.15  μ B and μ Ce = 0.11  μ B . CeFeO 3 is only the second R FeO 3 compound after DyFeO 3 showing this ground state magnetic structure of the Fe-sublattice. The orthorhombic structure Pbnm is kept over the whole temperature range., (© 2021 IOP Publishing Ltd.)

Depending on the synthesis route, the oxygen ion electrolyte Sr 2 ScGaO 5 shows two polymorphs, a brownmillerite and a cubic perovskite framework. In order to better explore oxygen diffusion pathways and mechanisms, we report here on a multitechnical approach to characterize local structural changes for Sr 2 ScGaO 5 polymorphs as a function of temperature, using a neutron pair distribution function (PDF) analysis together with an extended X-ray absorption fine structure (EXAFS) analysis. While for the brownmillerite type structure PDF and Rietveld refinements yield identical structural descriptions, considerable differences are found for the cubic oxygen-deficient polymorph. On a local scale a brownmillerite type vacancy structure could be evidenced for the cubic phase, suggesting a complex short-range ordering and respective microstructure. Both PDF and EXAFS data confirm an octahedral and tetrahedral coordination for Sc and Ga, respectively, at a local scale for both polymorphs. Related changes in the bond distances and oxygen vacancy ordering are discussed.

Oxygen intercalation/deintercalation in Pr 2 NiO 4+δ and Nd 2 NiO 4+δ was followed by in situ neutron powder diffraction during electrochemical oxidation/reduction, in a dedicated reaction cell at room temperature. For both systems three phases, all showing the same line width, were identified. The starting phases Pr 2 NiO 4.23 and Nd 2 NiO 4.24 , considered with an average orthorhombic Fmmm symmetry, although both show a slight monoclinic distortion, get reduced in a two-phase reaction step to tetragonal intermediate phases with 0.07 ≤ δ ≤ 0.10 and P4 2 / ncm space group, which on further reduction transform, again in a two-phase reaction step, toward the respective stoichiometric (Pr/Nd) 2 NiO 4.0 phases, with Bmab space group. Electrochemical oxidation does, however, not proceed fully reversibly for both cases: while the reoxidation of Nd 2 NiO 4+δ is limited to the tetragonal intermediate phase with δ = 0.10, the homologous Pr 2 NiO 4+δ can be reoxidized up to δ = 0.17, showing orthorhombic symmetry. For the intermediate tetragonal phase, we were able to establish for Pr 2 NiO 4.09 a complex anharmonic displacement behavior of the apical oxygen atoms, as analyzed by single-crystal neutron diffraction and maximum entropy analysis, in agreement with a low- T diffusion pathway for oxygen ions, activated by lattice dynamics.

Oxygen-deficient Sr 2 ScGaO 5 single crystals with a cubic perovskite structure were grown by the floating-zone technique. The transparent crystals of this pure 3D oxygen electrolyte are metastable at ambient temperature, showing one-sixth of all oxygen positions vacant. While neutron single-crystal diffraction, followed by maximum entropy analysis, revealed a strong anharmonic displacements for the oxygen atoms, a predominant formation of ScO 6 octahedra and GaO 4 tetrahedra is indicated by Raman spectroscopic studies, resulting in a complex oxygen defect structure with short-range order. Temperature-dependent X-ray powder diffraction (XPD) and neutron powder diffraction (NPD) studies reveal the cubic Sr 2 ScGaO 5 to be thermodynamically stable only above 1400 °C, while the stable modification below this temperature shows the brownmillerite framework with orthorhombic symmetry. Cubic Sr 2 ScGaO 5 remains surprisingly kinetically stable upon heating from ambient temperature to 1300 °C, indicating a huge inertia for the retransformation toward the thermodynamically stable brownmillerite phase. Ionic conductivity investigated by impedance spectroscopy was found to be 10 -4 S/cm at 600 °C, while oxygen 18 O/ 16 O isotope exchange indicates a free oxygen mobility to set in at around 500 °C.

Modular neck hip prosthesis born in the 1990 with the aim of allowing the surgeon to modify CCD angle, offset and femoral anteversion intra-operatively restoring patient's original biomechanics. In order to achieve the best biomechanics of the reconstructed hip, preoperative planning is essential. In the last few years modularity has been questioned and an argument made for the return to mono block stems due to events of breakage or disconnection of modular components. Fretting or crevice corrosion may lead to failure of such modular device due to the contamination inside the modular coupling or to high loads. We present a case of repetitive modular femoral neck prosthesis fracture.

Periodic DFT calculations allow an understanding of the strong orientation-dependent Raman spectra of oriented CaFeO2.5 single crystals. Modes involving the oscillation of the apical oxygen (O(ap)) atoms perturb the induced electric dipoles. These are formed by anisotropy in the charge distribution and are found to be strongly enhanced when the electric field of the linearly polarized laser line is parallel to the b axis. For the CaFeO2.5 ordered system, strong polarizability of these modes corresponds to strong Raman intensities. Conversely, the apical oxygen disorder observed in low-temperature oxygen-conducting SrFeO2.5 destroys the long-range coherence of the respective Raman modes, which consequently show a strongly reduced intensity. This study provides a vibrational tool to discriminate between ordered and disordered isomorporphous ABO2.5 Brownmillerite frameworks. Furthermore, in combination with DFT calculations, we have found that the weakening of the interlayer interactions is responsible for the loss of ordering in Brownmillerite compounds.

Purpose: Bone stock reconstruction in TKR surgery is one of the biggest challenges for the surgeon. According to some, authors causes of bone stock loosening are multiple, including stress shielding, osteolysis from wear, septic or aseptic loosening, and bone loss caused by a poorly balanced implant. Moreover, bone loss may be iatrogenic at the time of implant removal, indicating that bone preservation during implant removal is critical., Methods: Defect localization and extension affect the surgeon's decisions about the choice of the surgical technique and the type of plant to be taken. Today there are several options available for bone deficiency treatment. The treatment choice is undoubtedly linked to the cause of revision, experience and personal philosophy, but it is necessary to consider also the patient's age, expectations of life, functional requirements and bone quality. Many authors prefer bone stock reconstruction techniques in patients with high bone quality and a better quality of life with more prospects. In patients with lower lease on life and lower bone quality the best bone replacement techniques are of modular systems, wedges, and augments. In cases with septic bone loss, more or less extended, different authors recommend reducing bone grafts in favor of modular prostheses to reduce the risk of graft contamination., Results: All of these techniques have been shown to be durable in midterm outcomes, but concerns exist for a number of reasons, including disease transmission, resorption, fracture, immune reaction to allograft, the cost of custom prostheses, the inability to modify the construct intraoperatively and the overall technical challenge of applying these techniques., Conclusions: The choice between different surgical options depends on bone defect dimension and characteristics but are also patient-related. Reestablishment of well-aligned and stable implants is necessary for successful reconstruction, but this can't be accomplished without a sufficient restoration of an eventual bone loss.

The acetabular shell mobilization is the main long-term complication in total hip replacement. Metal-back fracture has also to be considered among the possible causes of shell mobilization. A case is presented of bilateral acetabular shell mobilization due to the trabecular covering de-soldering from the metal-back in a 43 year-old patient, 13-14 years after the first surgery., (Copyright © 2013 SECOT. Published by Elsevier Espana. All rights reserved.)

In this report we analyse a case of ischiatic tuberosity avulsion. A 15-year-old patient who came to our first aid department two days after a football match accident was treated conservatively and examined at month 1-4, 6 and 12. In order to examine patient condition, a new index was formulated: the inability score index (ISI), which is based on hip range of motion and scales for rest, walking, running pain and compared to other parameters such as oedema area, fragment diastasis evaluated by X-ray and CT accordingly. ISI defines the inability as severe, moderate and mild. It guides the rehabilitative program in the right way. In this case, the patient was able to run softly after 35 days and to go back to the full agonist activity after 4 months. At the end of treatment the patient referred to the complete pain remission, full range of motion recovery and a good fracture consolidation. After 1 year we discuss about therapeutic strategies used and results obtained.

Posterior shoulder dislocation is a rare event that may occur after a direct trauma, an epileptic seizure, electric shock or electroconvulsive therapy. In more than 50% of the cases, posterior dislocations are missed on initial evaluation and often misdiagnosed as frozen shoulders with unfortunate consequences. We present the case of a missed posterior subluxation and reverse Hill Sachs lesion (McLaughlin lesion) in a 40-year-old woman caused by anelectric shock of 240 V. The patient underwent surgery in our institute two weeks after the injury. The humeral head was reduced and the reverse Hill Sachs lesion was filled by demineralized bone matrix allograft with osteoinductive factors. Tendons were repaired and a temporaneous artrodesis was performed. At the final follow up of 12 months, we obtained a Costant Score of 93 and the patient returned to her previous daily activities.

This work summarises the results of a series of experiences made on Panasonic UD-802AS, a multi-element dosemeter that is currently used in Caorso Nuclear Power Plant for personnel external monitoring. Two main topics have been considered: energy response and the influence of working place dose rate on relative readings of the elements at the end of the monitoring period. The presence of four elements of different materials and filtrations gives the possibility of evaluating radiation energy by a simple algorithm, so that an accurate estimate of the personal dose equivalent can be provided; the good results of the participation of Caorso Individual Monitoring Service (IMS) to 'EURADOS 2008 intercomparison on whole-body dosemeters' account for the reliability of the method. A study on the response in low-dose rate fields is also reported, giving in practice interesting information about operational conditions.

SrFeO(2.5) and SrCoO(2.5) are able to intercalate oxygen in a reversible topotactic redox reaction already at room temperature to form the cubic perovskites Sr(Fe,Co)O(3), while CaFeO(2.5) can only be oxidized under extreme conditions. To explain this significant difference in low temperature oxygen mobility, we investigated the homologous SrFeO(2.5) and CaFeO(2.5) by temperature dependent oxygen isotope exchange as well as by inelastic neutron scattering (INS) studies, combined with ab initio (DFT) molecular dynamical calculations. From (18)O/(16)O isotope exchange experiments we proved free oxygen mobility to be realized in SrFeO(x) already below 600 K. We have also evidence that low temperature oxygen mobility relies on the existence of specific, low energy lattice modes, which trigger and amplify oxygen mobility in solids. We interpret the INS data together with the DFT-based molecular dynamical simulation results on SrFeO(2.5) and CaFeO(2.5) in terms of an enhanced, phonon-assisted, low temperature oxygen diffusion for SrFeO(3-x) as a result of the strongly reduced Fe-O-Fe bond strength of the apical oxygen atoms in the FeO(6) octahedra along the stacking axis. This dynamically triggered phenomenon leads to an easy migration of the oxide ions into the open vacancy channels and vice versa. The decisive impact of lattice dynamics, giving rise to structural instabilities in oxygen deficient perovskites, especially with brownmillerite-type structure, is demonstrated, opening new concepts for the design and tailoring of low temperature oxygen ion conductors.

Conventional high-temperature reactions limit the control of coordination polyhedra in transition-metal oxides to those obtainable within the bounds of known coordination geometries for a given transition metal. For example, iron atoms are almost exclusively coordinated by three-dimensional polyhedra such as tetrahedra and octahedra. However, recent works have shown that binary metal hydrides act as reducing agents at low temperatures, allowing access to unprecedented structures. Here we show the reaction of a perovskite SrFeO3 with CaH2 to yield SrFeO2, a new compound bearing a square-planar oxygen coordination around Fe2+. SrFeO2 is isostructural with 'infinite layer' cupric oxides, and exhibits a magnetic order far above room temperature in spite of the two-dimensional structure, indicating strong in-layer magnetic interactions due to strong Fe d to O p hybridization. Surprisingly, SrFeO2 remains free from the structural instability that might well be expected at low temperatures owing to twofold orbital degeneracy in the Fe2+ ground state with D(4h) point symmetry. The reduction and the oxidation between SrFeO2 and SrFeO3 proceed via the brownmillerite-type intermediate SrFeO2.5, and start at the relatively low temperature of approximately 400 K, making the material appealing for a variety of applications, including oxygen ion conduction, oxygen gas absorption and catalysis.

Guanosine derivatives, dissolved in water, can form cholesteric and hexagonal mesophases. The common structural unit is a chiral rod-shaped aggregate consisting of a stack of Hoogsten-bonded guanosine tetrameric disks. In order to elucidate the self-association process, we decided to investigate, by small-angle neutron scattering, the structural properties of d(pG), d(GpG), d(GpGpG), d(GpGpGpG) and d(GpGpGpG pGpG) derivatives in very dilute solutions. Under our experimental conditions only d(pG) seems not to form detectable particles. On the other hand, the results for the other derivatives indicate that cylindrical aggregates, having a 10 A cross-section gyration radius and a length of about 70 A, exist in the isotropic phase. According to the structure of the hexagonal and cholesteric phases, we fitted the experimental data by using a model of rod-shaped aggregates formed by stacking about 18 to 20 guanosine tetramers. Moreover, from the measurement of the concentration of scattering particles, we deduced that guanosine derivatives are only partially aggregated, depending on their ability to form mesophases.