A fixed-time second order sliding mode observer for a class of nonlinear systems

This paper presents a second order fixed time sliding mode observer based on an extension of the super-twisting algorithm. This observer can be applied to a class of nonlinear system with a block-wise representation. The block structure provides a straightforward form to the application of the proposed second order sliding mode algorithm, yielding to finite-time convergence with a settling time independent to the system initial conditions. Finally, as numerical simulation example, the case of a linear induction motor is studied, exposing the efficiency and feasibility of the proposal

Identification of the safe(r) by design alternatives for nanosilver-enabled wound dressings

The use of silver nanoparticles (NPs) in medical devices is constantly increasing due to their excellent antimicrobial properties. In wound dressings, Ag NPs are commonly added in large excess to exert a long-term and constant antimicrobial effect, provoking an instantaneous release of Ag ions during their use or the persistence of unused NPs in the wound dressing that can cause a release of Ag during the end-of-life of the product. For this reason, a Safe-by-Design procedure has been developed to reduce potential environmental risks while optimizing functionality and costs of wound dressings containing Ag NPs. The SbD procedure is based on ad-hoc criteria (e.g., mechanical strength, antibacterial effect, leaching of Ag from the product immersed in environmental media) and permits to identify the best one among five pre-market alternatives. A ranking of the SbD alternatives was obtained and the safer solution was selected based on the selected SbD criteria. The SbD framework was also applied to commercial wound dressings to compare the SbD alternatives with products already on the market. The iterative procedure permitted to exclude one of the alternatives (based on its low mechanical strength) and proved to be an effective approach that can be replicated to support the ranking, prioritisation, and selection of the most promising options early in the innovation process of nano-enabled medical devices as well as to encourage the production of medical devices safer for the environment

Occupational risk of nano-biomaterials: Assessment of nano-enabled magnetite contrast agent using the BIORIMA Decision Support System

The assessment of the safety of nano-biomedical products for patients is an essential prerequisite for their market authorization. However, it is also required to ensure the safety of the workers who may be unintentionally exposed to the nano-biomaterials (NBMs) in these medical applications during their synthesis, formulation into products and end-of-life processing and also of the medical professionals (e.g., nurses, doctors, dentists) using the products for treating patients. There is only a handful of workplace risk assessments focussing on NBMs used in medical applications. Our goal is to contribute to increasing the knowledge in this area by assessing the occupational risks of magnetite (Fe3O4) nanoparticles coated with PLGA-b-PEG-COOH used as contrast agent in magnetic resonance imaging (MRI) by applying the software-based Decision Support System (DSS) which was developed in the EU H2020 project BIORIMA. The occupational risk assessment was performed according to regulatory requirements and using state-of-the-art models for hazard and exposure assessment, which are part of the DSS. Exposure scenarios for each life cycle stage were developed using data from literature, inputs from partnering industries and results of a questionnaire distributed to healthcare professionals, i.e., physicians, nurses, technicians working with contrast agents for MRI. Exposure concentrations were obtained either from predictive exposure models or monitoring campaigns designed specifically for this study. Derived No-Effect Levels (DNELs) were calculated by means of the APROBA tool starting from in vivo hazard data from literature. The exposure estimates/measurements and the DNELs were used to perform probabilistic risk characterisation for the formulated exposure scenarios, including uncertainty analysis. The obtained results revealed negligible risks for workers along the life cycle of magnetite NBMs used as contrast agent for the diagnosis of tumour cells in all exposure scenarios except in one when risk is considered acceptable after the adoption of specific risk management measures. The study also demonstrated the added value of using the BIORIMA DSS for quantification and communication of occupational risks of nano-biomedical applications and the associated uncertainties

Microwave-assisted polyol synthesis of Cu nanoparticles

Microwave heating was applied to synthesize copper colloidal nanoparticles by a polyol method that exploits the chelating and reducing power of a polidentate alcohol (diethylenglycol). The synthesis was carried out in the presence of eco-friendly additives such as ascorbic acid (reducing agent) and polyvinylpirrolidone (chelating polymer) to improve the reduction kinetics and sols stability. Prepared suspensions, obtained with very high reaction yield, were stable for months in spite of the high metal concentration. In order to optimize suspensions, synthesis parameters were modified and the effects on particle size, optical properties, and reaction yield were investigated. XRD analysis, scanning transmission electron microscopy (STEM), and DLS measurements confirmed that prepared sols consist of crystalline metallic copper with a diameter ranging from 45 to 130 nm. Surface plasmon resonance (SPR) of Cu nanoparticles was monitored by UV\u2013Vis spectroscopy and showed both a red shift and a band weakening due to nanoparticle diameter increase. Microwave use provides rapid, uniform heating of reagents and solvent, while accelerating the reduction of metal precursors and the nucleation of metal clusters, resulting in monodispersed nanostructures. The proposed microwave-assisted synthesis, also usable in largescale continuous production, makes process intensification possible

“Microwave-Assisted Synthesis of Noble Metal Nanoparticles”

Selección de obras de arte visual de Luis Arellano y Fernando Chacón Meza.Selección de obras de arte visual de Luis Arellano y Fernando Chacón Meza

Au-Ag nanoparticles as red pigment in ceramic inks for digital decoration

Novel pigments, consisting of Au-Ag mixed nanoparticles, were developed for digital decoration by ink-jet printing of ceramic wares. Special attention was paid to set up a microwave assisted synthesis route, with a low environmental impact, easily transferable to large-scale production. Several suspensions, based on Au, Ag and Au-Ag mixed nanoparticles were prepared, trying to get a core-shell assemblage, and the synthesis parameters like metal concentration, Ag/Au ratio, time, temperature and chelating agent amount were optimized. The suspensions are stable over many months and a total reaction yield, assessed by ICP-AES analysis, was achieved. Particle size, shape, composition and optical properties were measured by DLS, TEM-EDS, XRD and UV-VIS spectroscopy. The so-prepared inks were applied on ceramic tiles simulating the ceramic process and the colour performance, assessed by colourimetry, were expressed in the CIELab parameters

Easily scalable synthesis of Ni nanosols suitable for the hydrogenation of 4-nitrophenol to p-aminophenol under mild condition

Ni nanoparticles with a dimension ranging between 80 and 200 nm were synthesized by a microwaveassisted polyol route. The reaction was carried out at 200 C in diethylenglycol (DEG) in the presence of a binary chelating agent system (polyvinylpyrrolidone PVP and dodecylamine DDA), in order to obtain stable and highly concentrated nanosols whose ratio was carefully optimized. Stable suspensions were produced with the future prospect of improving the performance of the anodic layer in solid oxide fuel cells (SOFCs), in which the metal is employed as catalyst. Studying the influence of different reaction times on the final product, it was possible to identify the reaction path that goes through the formation, after 10 min, of crystalline Ni-glycolate that turns completely into crystalline Ni metal after 20 min. The as obtained Ni nanoparticles were characterized by XRD, TG\u2013DTA, FT-IR, TEM. Preliminary tests on their catalytic and electrochemical activities were carried out by studying the hydrogenation of 4-nitrophenol (4-NP) to p-aminophenol (4-AP) in the presence of NaBH4 as probe reaction and by calculating the electrochemically active surface area (AECSA) with cyclic voltammetry

\u201cProcesso per la preparazione di sospensioni stabili di nanoparticelle metalliche e sospensioni colloidali stabili cos\uec ottenute\u201d

Grazie alla loro versatilit\ue0 e ai molteplici settori dove trovano applicazione, le sospensioni di nanoparticelle metalliche sono oggetto di grande interesse per l\u2019industria. In particolare le nano particelle di metallo, grazie alle loro caratteristiche chimico fisiche hanno importanti applicazioni in diversi campi: biomedicale, dispositivi ottici ed elettronici e catalizzatori. In questo brevetto sono descritti processi per la preparazione di sospensioni stabili di nanoparticelle metalliche in cui si opera in ambiente acquoso a bassa temperatura e a pressione ed atmosfera ambiente riscaldando con un apparecchio a microonde e le sospensioni stabili di nanoparticelle cos\uec ottenute