The ability of Ce-containing bioactive glasses to inhibit oxidative stress in terms of reduction of hydrogen peroxide, by mimicking the catalase enzyme activity is demonstrated here for the first ...time. The antioxidant properties of three bioactive glasses containing an increasing amount of CeO2 have been evaluated by following the degradation of hydrogen peroxide with time after immersion in H2O2 aqueous solutions with different concentration. XPS and UV–vis measurements allowed us to determine the Ce3+/Ce4+ ratio in the bulk and on the glass surface, and to correlate it with the ability of the samples to show catalase mimetic activity. Interestingly, we have found that the bioactive glass with composition 23.2Na2O–25.7CaO–43.4SiO2–2.4P2O5–5.3CeO2 immersed in 0.1 M H2O2 aqueous solution is able to degrade 90% of it in 1 week. The reduction in bioactivity of the glasses with increasing CeO2 content is here rationalized in terms of a lower amount of phosphate groups available for the hydroxyapatite layer formation, after binding with cerium ions. In fact, classical molecular dynamics simulations revealed that the addition of CeO2 leads to the formation of cerium phosphate rich regions. The formation of an insoluble CePO4 crystalline phase is also observed by XRD analysis after thermal treatment of the glass samples.
Cerium oxide is a very interesting material that finds applications in many different fields, such as catalysis, energy conversion, and biomedicine. An interesting approach to unravel the complexity ...of real systems and obtain an improved understanding of cerium oxide-based materials is represented by the study of model systems in the form of epitaxial ultrathin films or nanostructures supported on single crystalline substrates. These materials often show interesting novel properties, induced by spatial confinement and by the interaction with the supporting substrate, and their understanding requires the use of advanced experimental techniques combined with computational modeling. Recent experimental and theoretical studies performed within this field are examined and discussed here, with emphasis on the new perspectives introduced in view of the optimization of cerium oxide-based materials for application in different fields.
The structure of Ag nanoparticles of different size, supported on the cerium oxide (111) surface, was investigated by X-ray absorption fine structure at the Ag K-edge. The results of the data ...analysis in the near and extended energy range are interpreted with the help of the results obtained by X-ray photoelectron spectroscopy and scanning tunneling microscopy measurements and allow to obtain a detailed atomic scale description of the model system investigated. The Ag nanoparticles have an average size of a few tens of angstroms, which increases with increasing deposited Ag amount. The nanoparticles show a slight tendency to nucleate at the step edges between different cerium oxide layers and they have a face centered cubic structure with an Ag–Ag interatomic distance contracted by 3–4% with respect to the bulk value. The interatomic distance contraction is mainly ascribed to dimensionality induced effects, while epitaxial effects have a minor role. The presence of Ag–O bonds at the interface between the nanoparticles and the supporting oxide is also detected. The Ag–O interatomic distance decreases with decreasing nanoparticle size.
The inertial sliding of physisorbed submonolayer islands on crystal surfaces contains unexpected information on the exceptionally smooth sliding state associated with incommensurate superlubricity ...and on the mechanisms of its disappearance. Here, in a joint quartz crystal microbalance and molecular dynamics simulation case study of Xe on Cu(111), we show how superlubricity emerges in the large size limit of naturally incommensurate Xe islands. As coverage approaches a full monolayer, theory also predicts an abrupt adhesion-driven two-dimensional density compression on the order of several per cent, implying a hysteretic jump from superlubric free islands to a pressurized commensurate immobile monolayer. This scenario is fully supported by the quartz crystal microbalance data, which show remarkably large slip times with increasing submonolayer coverage, signalling superlubricity, followed by a dramatic drop to zero for the dense commensurate monolayer. Careful analysis of this variety of island sliding phenomena will be essential in future applications of friction at crystal/adsorbate interfaces.
Background
Multi-visceral resection often is used in the treatment of retroperitoneal sarcoma (RPS). The morbidity after distal pancreatectomy for primary pancreatic cancer is well-documented, but ...the outcomes after distal pancreatectomy for primary RPS are not. This study aimed to evaluate morbidity and oncologic outcomes after distal pancreatectomy for primary RPS.
Methods
In this study, 26 sarcoma centers that are members of the Trans-Atlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG) retrospectively identified consecutive patients who underwent distal pancreatectomy for primary RPS from 2008 to 2017. The outcomes measured were 90-day severe complications (Clavien-Dindo ≥ 3), postoperative pancreatic fistula (POPF) rate, and oncologic outcomes.
Results
Between 2008 and 2017, 280 patients underwent distal pancreatectomy for primary RPS. The median tumor size was 25 cm, and the median number of organs resected, including the pancreas, was three. In 96% of the operations, R0/R1 resection was achieved. The 90-day severe complication rate was 40 %. The grades B and C POPF complication rates were respectively 19% and 5% and not associated with worse overall survival. Administration of preoperative radiation and factors to mitigate POPF did not have an impact on the risk for the development of a POPF. The RPS invaded the pancreas in 38% of the patients, and local recurrence was doubled for the patients who had a microscopic, positive pancreas margin (hazard ratio, 2.0;
p
= 0.042).
Conclusion
Distal pancreatectomy for primary RPS has acceptable morbidity and oncologic outcomes and is a reasonable approach to facilitate complete tumor resection.
In this work, an analysis of the tribological performance of laser-induced periodic surface structures (LIPSS) treated X5CrNi1810 stainless steel was conducted. The approach followed by authors was ...to generate LIPSS-patterned circular tracks, composed of radial straight grooves with uniform angular periodicity. This permitted to measure the tribological properties in a pin-on-flat configuration, keeping fixed the orientation between the grooves and the sliding direction. A Stribeck curve was measured, as well as the consequent wear. A deep analysis of the sub-surface conditions after LIPSS generation was moreover performed using Focused Ion Beam (FIB) cross-section.
Films of magnetic Ni@NiO core-shell nanoparticles (NPs, core diameter d ≅ 12 nm, nominal shell thickness variable between 0 and 6.5 nm) obtained with sequential layer deposition were investigated, to ...gain insight into the relationships between shell thickness morphology, core-shell interface, and magnetic properties. Different values of NiO shell thickness ts could be obtained while keeping the Ni core size fixed, at variance with conventional oxidation procedures where the oxide shell is grown at the expense of the core. Chemical composition, morphology of the as-produced samples and structural features of the Ni NiO interface were investigated with x-ray photoelectron spectroscopy and microscopy (scanning electron microscopy, transmission electron microscopy) techniques, and related with results from magnetic measurements obtained with a superconducting quantum interference device. The effect of the shell thickness on the magnetic properties could be studied. The exchange bias (EB) field Hbias is small and almost constant for ts up to 1.6 nm; then it rapidly grows, with no sign of saturation. This behavior is clearly related to the morphology of the top NiO layer, and is mostly due to the thickness dependence of the NiO anisotropy constant. The ability to tune the EB effect by varying the thickness of the last NiO layer represents a step towards the rational design and synthesis of core-shell NPs with desired magnetic properties.
Diamond-like carbon is one of the most studied and used solid lubricants on the market. Despite this large use and its outstanding mechanical and tribological properties, there are still some unclear ...aspects related to its self-lubricant properties, and some drawbacks in the deposition methods. We deposited “soft” DLC films on Si(100), iron, and stainless steel substrates by PVD magnetron sputtering technique with a Cr/CrN adhesive interlayer. The DLC films were characterized from a chemical, mechanical, and tribological point of view. Our aim was to connect the coating chemical and mechanical characteristics to the different conditions used for the deposition, such as discharge power and substrate–target distance. We found a stronger sp3 dependence on the discharge power for DLC deposited closer to the target. The tribological results did not depend on the chosen substrate–target distance, but rather on the hardness of the substrate. This could be ascribed to the better mechanical coupling of soft DLC films on harder substrates.
Background Laser ablation with a neodymium:yttrium aluminum garnet (Nd:YAG) laser can achieve a high rate of complete tissue necrosis and has been applied as a minimally invasive, palliative option ...in hepatocellular carcinoma, liver metastasis in colorectal cancer, and malignant thyroid nodules. Objective To assess the in vivo feasibility of EUS-guided laser ablation with an Nd:YAG laser of normal pancreatic tissue of a porcine model. Design Prospective investigation. Setting Hospital animal laboratory. Subjects Eight pigs. Interventions EUS-guided puncture of the pancreatic tail with a laser-beam fiber. An Nd:YAG laser (1.064 nm) was used, with an output power of 2 and 3 W and a total delivered energy of 500 and 1000 J in continuous mode. Main Outcome Measurements The 24-hour follow-up of the pigs was focused on clinical and laboratory aspects. Results of histological studies of the pancreas were obtained 24 hours after the procedure on necroscopy tissue. Results There were no technical limitations to the performance of the procedure. Tissue necrosis, localized in the pancreatic parenchyma, was observed in all animals on histological examination. The volume of ablation tissue ranged from a mean of 314 mm3 to 483 mm3 . The ablation area ranged from a mean of 49 mm2 to 80 mm2 . No major postprocedure complications were recorded, and all the pigs survived at 24 hours. Limitation Animal study. Conclusions EUS-guided laser ablation of the pancreas with an Nd:YAG laser is feasible in a porcine model.
The work is focused on understanding the dynamics of the processes which occur at the interface between ceria and platinum during redox processes, by investigating an inverse catalytic model system ...made of ceria epitaxial islands and ultrathin films supported on Pt(111). The evolution of the morphology, structure and electronic properties is analyzed in real-time during reduction and oxidation, using low-energy electron microscopy and spatially resolved low-energy electron diffraction. The reduction is induced using different methods, namely thermal treatments in ultra-high vacuum and in H
as well as deposition of Ce on the oxide surface, while re-oxidation is obtained by exposure to oxygen at elevated temperature. The use of two different epitaxial systems, continuous films and nanostructures, allows determining the influence of platinum proximity on the stabilization of the specific phases observed. The factors that limit the reversibility of the observed modifications with the different oxidation treatments are also discussed. The obtained results highlight important aspects of the cerium oxide/Pt interaction that are relevant for a complete understanding of the behavior of Pt/CeO
catalysts.
PDF
