Effect of doping and oxygen vacancies on the octahedral tilt transitions in the BaCeO3 perovskite

We present a systematic study of the effect of Y doping and hydration level on the structural transformations of BaCeO3 based on anelastic spectroscopy experiments. The temperature of the intermediate transformation between rhombohedral and orthorhombic Imma phases rises with increasing the molar fraction x of Y roughly as (500 K)x in the hydrated state, and is depressed of more than twice that amount after complete dehydration. This is explained in terms of the effect of doping on the average (Ce/Y)-O and Ba-O bond lengths, and of lattice relaxation from O vacancies. The different behavior of the transition to the lower temperature Pnma orthorhombic phase is tentatively explained in terms of progressive flattening of the effective shape of the OH ion and ordering of the O vacancies during cooling.Comment: 8 pages, 5 figure

Sustainable Recycling of Insoluble Rust Waste for the Synthesis of Iron-Containing Perovskite-Type Catalysts

Insoluble rust waste from the scraping of rusted iron-containing materials represents a cheap, eco-friendly, and available source of iron. LaFeO3 perovskite-type powders were successfully prepared by solution combustion synthesis using rust waste from an electricity transmission tower manufacturer. Solution combustion synthesis enabled introduction of this insoluble iron precursor directly into the final product, bypassing complex extraction procedures. Catalytic activity in the propylene oxidation of the waste-derived LaFeO3 with stoichiometric Fe/La ratio was almost identical to the commercial iron nitrate-derived LaFeO3 , thus demonstrating the viability of this recycling solution. The amount of waste iron precursor was varied and its effect on the powder properties was investigated. A lesser stoichiometric amount of precursor produced a LaFeO3 -La2O3 binary system, whereas a higher stoichiometric amount led to a LaFeO3 -Fe2O3 binary system. Catalytic activity of iron-rich compositions in the propylene oxidation was only slightly lower than the stoichiometric one, whereas iron-poor compositions were much less active. This eco-friendly methodology can be easily extended to other iron perovskites with different chemical compositions and to other iron-containing compounds

Hydrogen tunneling in the perovskite ionic conductor BaCe(1-x)Y(x)O(3-d)

We present low-temperature anelastic and dielectric spectroscopy measurements on the perovskite ionic conductor BaCe(1-x)Y(x)O(3-x/2) in the protonated, deuterated and outgassed states. Three main relaxation processes are ascribed to proton migration, reorientation about an Y dopant and tunneling around a same O atom. An additional relaxation maximum appears only in the dielectric spectrum around 60 K, and does not involve H motion, but may be of electronic origin, e.g. small polaron hopping. The peak at the lowest temperature, assigned to H tunneling, has been fitted with a relaxation rate presenting crossovers from one-phonon transitions, nearly independent of temperature, to two-phonon processes, varying as T^7, to Arrhenius-like. Substituting H with D lowers the overall rate by 8 times. The corresponding peak in the dielectric loss has an intensity nearly 40 times smaller than expected from the classical reorientation of the electric dipole associated with the OH complex. This fact is discussed in terms of coherent tunneling states of H in a cubic and orthorhombically distorted lattice, possibly indicating that only H in the symmetric regions of twin boundaries exhibit tunneling, and in terms of reduction of the effective dipole due to lattice polarization.Comment: submitted to Phys. Rev.

Direct nucleation of calcium oxalate dihydrate crystals onto the surface of living renal epithelial cells in culture

Direct nucleation of calcium oxalate dihydrate crystals onto the surface of living renal epithelial cells in culture.BackgroundThe interaction of the most common crystal in human urine, calcium oxalate dihydrate (COD), with the surface of monkey renal epithelial cells (BSC-1 line) was studied to identify initiating events in kidney stone formation.MethodsTo determine if COD crystals could nucleate directly onto the apical cell surface, a novel technique utilizing vapor diffusion of oxalic acid was employed. Cells were grown to confluence in the inner four wells of 24-well plates. At the start of each experiment, diethyloxalate in water was placed into eight adjacent wells, and the plates were sealed tightly with tape so that oxalic acid vapor diffused into a calcium-containing buffer overlying the cells.ResultsSmall crystals were visualized on the cell surface after two hours, and by six hours the unambiguous habitus of COD was confirmed. Nucleation onto cells occurred almost exclusively via the (001) face, one that is only rarely observed when COD crystals nucleate onto inanimate surfaces. Similar results were obtained when canine renal epithelial cells (MDCK line) were used as a substrate for nucleation. Initially, COD crystals were internalized almost as quickly as they formed on the apical cell surface.ConclusionsFace-specific COD crystal nucleation onto the apical surface of living renal epithelial cells followed by internalization is a heretofore unrecognized physiological event, suggesting a new mechanism to explain crystal retention within the nephron, and perhaps kidney stone formation when this process is dysregulated or overwhelmed

Strontium and iron-doped barium cobaltite prepared by solution combustion synthesis: exploring a mixed-fuel approach for tailored intermediate temperature solid oxide fuel cell cathode materials

Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF) powders were prepared by solution combustion synthesis using single and double fuels. The effect of the fuel mixture on the main properties of this well-known solid oxide fuel cell cathode material with high oxygen ion and electronic conduction was investigated in detail. Results showed that the fuel mixture significantly affected the area-specific resistance of the BSCF cathode materials, by controlling the oxygen deficiency and stabilizing the Co2+ oxidation state. It was demonstrated that high fuel-to-metal cations molar ratios and high reducing power of the combustion fuel mixture are mainly responsible for the decreasing of the area-specific resistance of BSCF cathode materials. Moreover, a new metastable monoclinic phase with Ba0.5Sr0.5CO3 composition was discovered in the as-burned BSCF powders, enlarging the existing information on the BSCF phase formation mechanis

Palliative combined treatment for unresectable cutaneous basosquamous cell carcinoma of the head and neck.

A case is presented of a patient with a skin basosquamous cell carcinoma of the frontal region infiltrating the cerebral tissue and with a widespread unresectable regional metastatic ulceration of the left parotid region. The patient underwent combined palliative treatment: surgical coverage of the ulceration by means of a pectoralis mayor flap transposition and radiotherapy. After 18 months of follow-up, no signs of tumour progression were noted, the patient is currently free from pain, no increase in trismus was seen, and a slight gain in weight was recorded. Unresectable cancer is mainly treated by concurrent chemoradiation; radiotherapy, however, is contraindicated in deep neoplastic ulcerations with exposure of large vessels. The data reported suggest that surgical coverage of an unresectable neoplastic ulcer is feasible, and combined with early administration of radiation permits a palliative approach in an otherwise untreatable condition.Abstract available from the publisher

Subtotal supracricoid laryngectomy: changing in indications, surgical techniques and use of new surgical devices.

The aim of this study is to evaluate the evolution of supracricoid partial laryngectomy (SCPL) in indications, surgical techniques and outcomes through last decades.A retrospective analysis of 146 patients affected by laryngeal cancer treated with SCPL was carried on. We defined: (1) group A, 100 patients treated by cold instruments between 1995 and 2004; (2) group B, 46 patients treated by harmonic scalpel between 2005 and 2010. Complications rate, and functional and oncological results were documented and a comparison between the two groups was made; histopathological analysis of surgical margins was evaluated and correlated with local incidence of recurrence.Significant differences in age mean-value (p=0.02), T classification (p=0.007), and in indication for more advanced-staged patients were found in group B (p=0.001). Surgical procedure was shorter in group B (p<0.001), with shorter swallowing recovery (p=0.003). Oncological outcomes did not report any significant differences. Group B showed a higher incidence of post- operative arytenoid edema (p=0.03) associated with a lower rate of pneumonia (p=0.038). Despite a higher rate of close or positive-margins found in group B no higher incidence of local-recurrence was reported (p=0.02) compared to group A.We documented changing in indications and surgical technique for SCPL because of the development of modern diagnostic techniques and the introduction of low-thermal injury device allowing a more challenging tumor excision as well as with a shorter swallowing recovery in our series

Tobacco exposure and complications in conservative laryngeal surgery.

Smoking is an important risk factor in the development of head and neck cancer. However, little is known about its effects on postoperative complications in head and neck cancer surgery. We performed a retrospective analysis on 535 consecutive laryngeal cancer patients submitted to open partial laryngectomy at the Otolaryngology-Head and Neck Surgery Department of Florence University to evaluate a possible correlation between smoking and surgical complications. Patients were grouped in non smokers and smokers and evaluated for airway, swallowing, local and fistula complications by multivariate analysis: 507 (95\%) patients were smokers, 69\% presented supraglottic, 30\% glottic and 1\% transglottic cancer. The most common operation was supraglottic horizontal laryngectomy in 58\%, followed by supracricoid partial laryngectomy in 27\% and frontolateral hemilaryngectomy in 15\% of cases. The incidence of overall complications was 30\%, airway complications representing the most frequent (14\%), followed by swallowing (7\%), local (6\%) and fistula complications (3\%). Smokers developed more local complications (p = 0.05, univariate, p = 0.04, multivariate analysis) and pharyngocutaneous fistula (p = 0.01, univariate, p = 0.03, multivariate analysis)

Is open tracheotomy performed by residents in otorhinolaryngology a safe procedure? a retrospective cohort study.

Surgical or percutaneous tracheotomy is one of the commonest operations in the ENT practice and one of the first procedures to be taught to residents. No study exists that demonstrates the safety of this surgical procedure performed by unexperienced surgeons. The purpose was to compare outcomes of tracheotomies performed by supervised residents and surgeons in terms of postoperative complications and mortality, and identify risk factors for the onset of complications. Retrospective cohort study. Otolaryngology-Head and Neck Surgery Department, University of Florence, Italy. We included all patients undergoing tracheotomy from July 2008 to January 2013 and compared tracheotomies performed by supervised residents or surgeons. During the study period, 304 patients were submitted to tracheotomy. Patients operated by surgeons had a significantly higher number of tracheal rings fracture (p = 0.05), subcutaneous emphysema (p = 0.003) and tracheostomy tube displacement (p = 0.003), while supervised residents had a higher number of tracheitis/pneumonia (p = 0.04) as early complications. Patients operated by supervised residents had a significantly higher number of tube obstructions as late complication (p = 0.04). Using multivariate model, risk factors for early postoperative complications were male sex (p = 0.04) and delayed time to substitution with cuffless tube (p = 0.01), while only a trend to statistical significance was observed for urgent tracheotomies concerning the risk for late postoperative complications (p = 0.08). The current practice where residents perform tracheotomies supervised by a surgeon should not be disheartened. Our study demonstrates that it is safe and does not lead to higher risk of complications nor negatively affects the quality of care