621 research outputs found
The effect of water in the low-temperature catalytic oxidation of hydrogen sulfide to sulfur over activated carbon
No full textThis study investigates the use of law-temperature catalytic oxidation for the removal of H2S from tail gases originating from geothermal plants, with special focus on the effect of water on the overall performance of the activated carbon catalyst. It is shown that water strongly influences the reaction rate and the total amount of sulfur that can be adsorbed on the catalyst prior to regeneration. It is suggested that the reaction takes place in a thin water layer, inside the carbon pores, from the reaction of dissolved H2S with chemisorbed oxygen
Catalysis by Ceria and Related Materials, 2nd Edition: Volume 12
No full textThis book follows the 2002 edition of Catalysis by Ceria and Related Materials, which was the first book entirely devoted to ceria and its catalytic properties. In the ten years since the first edition a massive amount of work has been carried out in the field, and ceria has gained a prominent position in catalysis as one of the most valuable material for several applications. This second edition covers fundamental and applied aspects of the latest advances in ceria-based materials with a special focus on structural, redox and catalytic features. Special emphasis is given to nano-engineered and nano-shaped systems which are a key factor in the predictive and rational design of ceria with novel properties. In addition, the book presents recent advances in emerging and traditional large-scale applications of ceria in catalysis, such as the treatment of emissions from mobile sources (including diesel and gasoline engines). The primary readership includes catalysis and material science researchers from academy and industry and postdoctorate and graduate students in chemistry, chemical engineering and physics
Investigation of the redox behavior of double perovskite PrBaMn2O5+δ
No full textA multi analytical approach (in situ X-ray diffractometry, XRD, temperature programmed reduction TPR, thermogravimetry TGA) was used to deeply study the phase transition between the Pr0.5Ba0.5MnO3-δ (m-PBM) and the double layered perovskite PrBaMn2O5+δ (l-PBM). m-PBM sample was prepared by an autocombustion based citrate procedure and exposed to consecutive reduction and oxidation cycles at high temperature to understand the effect of oxidizing and reducing atmospheres on structural changes and stabilization of the layered double perovskite. XRD analysis showed the existence of a pseudo cubic structure (c-PBM), which is formed from the direct oxidation of l-PBM. TPR results confirmed the c-PBM to l-PBM reversibility to the redox processes, and the TGA characterization showed a fast transition between l-PBM to c- PBM. The oxidation of l-PBM to c-PBM seems pivotal for the stabilization of the layered reduced structure. The results are discussed in the perspective to develop versatile electrodes for SOEC/SOFC applications
Is there a role for knee arthrodesis with modular endoprostheses for tumor and revision of failed endoprostheses?
No full textAbstract
BACKGROUND: Knee arthrodeses are performed to treat infection after arthroplasty and tumors requiring extensive soft tissue resection. Many techniques have been described, but most have important disadvantages. Currently, endoprosthetic arthrodesis implants are available, but little is known about them.
QUESTIONS/PURPOSES: Our objective was to analyze a series of knee arthrodeses with a modular prosthetic system to evaluate (1) survivorship of the implant, (2) complications, (3) whether survivorship differed between arthrodeses done for primary tumor resection and revision reconstructions, and (4) whether survivorship differed based on the presence of previous infection or the use of a gastrocnemius flap.
METHODS: We present 32 patients with modular knee arthrodeses; arthrodeses were performed in 25 patients with tumors and in seven patients without tumors. There were 14 implants done at the time of tumor resection and 18 for revision of failed implants. Survivorship and complications were analyzed with Kaplan-Meier curves. Log-rank test was used for comparison between primary and revision implants, not infected and previously infected implants, and use or nonuse of a gastrocnemius flap.
RESULTS: Survivorship of arthrodeses with modular endoprostheses was 50% and 25% at 5 and 10 years, respectively. There were nine infections (29%) and one implant fracture (3%). Amputation as final surgery was required in 8 patients (six owing to infection and two to oncologic failures). There was no significant difference in survivorship between arthrodeses done for primary tumor resection and as a salvage procedure for failed implants. No differences were found between patients with and without prior infection or with and without a gastrocnemius flap.
CONCLUSIONS: Survivorship of a modular arthrodesis implant was 50% at 5 years owing to a high complication rate. Infection is the most common cause of failure of oncologic and revision implants. Implant fracture is a rare occurrence. Modular segmental arthrodesis provides a stable construct for patients in whom limb preservation is possible but a hinged device is contraindicated as a result of major muscle resection.
LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence
Proximal femoral reconstructions: A European "italian" experience. A case series
No full textBackground: The aim of the study was to analyze our experience with a single system of modular proximal femoral replacement, evaluating oncologic results, complications, and functional results. Methods: We reviewed data on 38 patients (21 men and 17 women; mean age 59 y) treated with proximal femoral reconstructions by two orthopaedic surgeons. Reconstruction was performed in all patients using a MUTARS® modular proximal femoral prosthesis, and an acetabular reconstruction in eight patients. Diagnoses included primary bone sarcomas (21), bone metastases (15), and radioinduced osteonecrosis (2). The stem was press fit in 11 patients and cemented in 27. Results: At a mean follow-up of 1.9 yr, 12 patients were alive with no evidence of disease, three have no evidence of disease after treatment of a recurrence or metastasis, 12 were alive with disease, and nine had died. The two with osteonecrosis were not included in this analysis. Complications occurred in seven patients: four type I (wound dehiscence in one and dislocation in three), one type II, one type IV, and one type V failures, while type III failures did not occur. At last follow-up, 89% of patients (34/38) had retained their implant. The mean Musculoskeletal Tumor Society (MSTS) score was 24.7 (14-30), with excellent or good results in all patients except one. Conclusion: The overall survival of this prosthesis was satisfactory with good implant survival in proximal femoral reconstruction. The most frequent cause of failure was dislocation. The incidence of infection was low. Functional results were good or excellent. Level of Evidence: IV; case series
Approaching risk management from a new integrated perspective
No full textIn recent years, risk management has acquired increasing relevance within the organizational realm. Although the Integrated Reporting Framework includes 'risk' as one of the content elements of the Integrated Report, its main purpose does not specifically relate to risk management. Drawing on the evolving academic debate, this chapter aims to provide an overview of the different approaches to risk management and to highlight the need for a broader and integrated perspective. The chapter ends by highlighting the potential contribution of this perspective to the Integrated Reporting Framework
Nanophased Iron Carbides as Catalysts for Carbon Dioxide Hydrogenation
No full textNanophase carbides obtained by ball milling elemental iron and carbon powders at room temperature (mechanochemical synthesis or mechanosynthesis) are shown to be more active and selective in the hydrogenation of carbon dioxide than Fe/C mixtures and coarse-grained conventionally synthesized carbides; a positive effect is also observed for a ball-milled commercial cementite powder
Structure-activity relationship in Pd/CeO2 methane oxidation catalysts
No full textPalladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness with a strong impact on their overall performances. Among the several combinations of supports and promoters that have been utilized, Pd/CeO2 has attracted a great attention due to its activity and durability coupled with the unusually high degree of interaction between Pd/PdO and the support. This allows the creation of specific structural arrangements which profoundly impact on methane activation characteristics. Here we want to review the latest findings in this area, and particularly to envisage how the control (when possible) of Pd-CeO2 interaction at nanoscale can help in designing more robust methane oxidation catalysts
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