Experimental Identification of Induction Machine Flux Maps for Traction Applications

Nowadays the permanent magnet machines are a widespread solution in the automotive field. However, the induction machine (IM) represents a valid solution as it is rare-earth free and does not have induced stator back-emf in case of inverter turn-off. Regardless of the machine type, identification procedures are needed for torque control calibration and for optimal machine utilization in terms of efficiency and maximum torque production under inverter current and voltage constraints. For synchronous machines, a common and consolidated practice is to obtain the machine flux maps (current-to-flux relationship) in the rotor (d,q) frame using calibrated Finite Element Analysis (FEA) or experimental procedures. However, to the best of the authors' knowledge, the literature does not report an experimental approach able to obtain the flux maps for IMs. Therefore, this paper proposes an experimental procedure to obtain the IM flux maps in (d,q) rotor flux frame for inverter supply and real operating conditions. In addition, the proposed procedure is able to obtain the parameters of the IM equivalent circuit with no need of additional tests. Experimental validation is provided for a 4-poles IM rated 10 kW, 200 Hz

Effect of silver ion incorporation into a bioactive glass surface on the adsorption of albumin

Introduction Nowadays, bacterial infection is one of the major causes for orthopedic implants failure. While it is well known how to manufacture materials that are able to stimulate osseointegration and to firmly bond with the bone, the fight against pathogenic microorganisms is carried on mainly by antibiotics, with consequent problems of poorly localized actions and antibiotic-resistance. Therefore, novel antibacterial strategies have been deeply researched. Among those, incorporation of silver in biomaterials, such as bioactive glasses, is acknowledged as an effective way to reduce bacteria proliferation. Osseointegration of biomaterials is dependent on the surface properties of the implants and on the interactions with the biological environment. In particular, a protein layer is formed on the surface within minutes after the contact between the surface and the biological fluids and it will dictate how the cells will respond to the implanted foreign body. As consequence, it is important to understand how antibacterial modifications of bioactive materials affect their interactions with proteins. In this work, the adsorption of albumin was investigated onto a silica-based bioactive glass where silver ions were incorporated through ionic exchange (Ag-SBA2) in order to understand eventual differences with the untreated surface (SBA2)[1]. Experimental Methods SBA2 bioactive glass (mol %: 48% SiO2, 18% Na2O, 30% CaO, 3% P2O5, 0.43% B2O3, 0.57% Al2O3) was prepared via precursors melting and casting, cut into disks and grinded (up to 1000 grit). Ag-SBA2 was prepared by soaking glass slices for 1h in 0.03M AgNO3 solution. Protein adsorption was obtained by soaking the samples for 2h at 37°C in albumin solution in PBS, in near physiological conditions (20 mg/ml, pH 7.4). The glass substrates were characterized in terms of topography and roughness (SEM, AFM and confocal microscopy), chemical composition (EDS and XPS), surface charge and potential (solid surface zeta potential, Kelvin Probe Force Microscopy (KPFM)) and surface energy (contact angle, Owens-Wendt method). The adsorbed proteins were quantified by using different methods (BCA assay, fluorescent proteins and XPS) and the BSA layer was also imaged (fluorescent microscopy and KPFM). Substrate-protein interactions and albumin conformation were investigated, too (solid surface zeta potential and ATR-FTIR). Results and Discussion After silver incorporation, confirmed by chemical analysis, the surface properties of Ag-SBA2 were mostly similar to the undoped glass. In particular, topography and roughness were unchanged during soaking in the silver solution, as expected. Wettability and surface free energy, both the dispersive and polar components, were also similar between the two substrates. Instead, zeta potential titration curve showed that the incorporation of Ag3+ ions increased the surface potential, in particular around physiological pH (7.4). Quantification of adsorbed BSA showed that both surfaces adsorb a similar amount of albumin, with a little higher amount on Ag-SBA2. This can be possibly related to a couple of different factors: the high affinity of silver for proteins and the presence of a more positive charge on the surface, which is able to attract the negatively charged albumin. On both surfaces, albumin forms a complete and homogeneous layer, as detected by imaging techniques. Adsorption of proteins was confirmed also by zeta potential measurement on the surfaces, with a shift of the IEP of both glassestowards the IEP of albumin. Thanks to ATR-FTIR measurement, it was found that albumin retains more its native conformation on the undoped glass with respect to the silver containing glass, where a more disordered structure was found. This fact can be ascribed to a greater interaction between the proteins and the doped surface, due to the presence of metal ions and more positive charges. Conclusion In conclusion, even though the incorporation of silver ions in a bioactive glass surface does not affect surface properties that are usually addressed as pivotal in protein adsorption, such as roughness and surface energy, the presence of a more positive charge on the surface of the glass and affinity of proteins towards metallic ions seems to be enough to increase adsorption of albumin and strength of the protein-biomaterial interaction. The increased interaction with proteins may be beneficial for the cells response to antibacterial silver containing materials

Hyperspectral Chemical Imaging of Single Bacterial Cell Structure by Raman Spectroscopy and Machine Learning

6openopenBarzan, Giulia; Sacco, Alessio; Mandrile, Luisa; Giovannozzi, Andrea Mario; Portesi, Chiara; Rossi, Andrea MarioBarzan, Giulia; Sacco, Alessio; Mandrile, Luisa; Giovannozzi, Andrea Mario; Portesi, Chiara; Rossi, Andrea Mari

Advanced characterization of albumin adsorption on a chemically treated surface for osseointegration: An innovative experimental approach

Surface chemistry, charge, wettability, and roughness affect the adsorbed protein layer, influencing biocompatibility and functionality of implants. Material engineering seeks innovative, sensitive, and reliable characterization techniques for study the adsorbed proteins. These techniques must be suitable to be directly used on the surfaces of clinical interest. In this paper, the characterization of surfaces with topography and chemistry developed for osseointegration is performed by innovative surface analysis techniques to investigate the properties of adsorbed bovine serum albumin. Ti6Al4V alloy chemically treated with an oxidative process to obtain peculiar surface features (roughness and surface hydroxylation) was tested and compared with mirror-polished titanium. Albumin forms a continuous layer on both Ti surfaces when adsorbed from near physiological concentrations, as proved by Kelvin force probe microscopy. It was observed that the hydroxylation degree plays a pivotal role in determining the conformation of proteins after adsorption, where it strongly drives protein unfolding, as confirmed by Surface Enhanced Raman scattering, and in influencing the mechanism and chemical stability of protein-surface interactions, which was highlighted by zeta potential titration curves.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Effect on albumin and fibronectin adsorption of silver doping via ionic exchange of a silica-based bioactive glass

Protein adsorption is a crucial step in the life of biomaterials for bone application, such as bioactive glasses. The investigation of adsorption mechanisms is a difficult task per se, which is even more complex on bioactive glasses due to surface reactivity. Here, the effect of silver doping by ionic exchange on the interaction of a silica-based bioactive glass with albumin and fibronectin, serum proteins related to osseointegration, is reported. The presence of silver does not change relevant surface properties such as topography, surface energy, wettability, or surface ζ potential. Nevertheless, the interactions with proteins are much different. The presence of silver significantly increases the adsorption of albumin and fibronectin and leads to a higher loss of secondary structure compared to the undoped surface, as a consequence of the interactions and bonding between silver and thiols in the cysteine residues. Selectivity of silver-doped glass is discovered: Ag enhances more adsorption and dena- turation of albumin since it has more cysteines than fibronectin. It is also here observed that due to the formation of a hydrated silica gel layer during adsorption, proteins are not only present on the surface of the bioactive glasses, but also embedded inside the surface reaction laye

Influence of the long-range ordering of gold-coated Si nanowires on SERS

Controlling the location and the distribution of hot spots is a crucial aspect in the fabrication of surface-enhanced Raman spectroscopy (SERS) substrates for bio-analytical applications. The choice of a suitable method to tailor the dimensions and the position of plasmonic nanostructures becomes fundamental to provide SERS substrates with significant signal enhancement, homogeneity and reproducibility. In the present work, we studied the influence of the long-range ordering of different flexible gold-coated Si nanowires arrays on the SERS activity. The substrates are made by nanosphere lithography and metal-assisted chemical etching. The degree of order is quantitatively evaluated through the correlation length (ξ) as a function of the nanosphere spin-coating speed. Our findings showed a linear increase of the SERS signal for increasing values of ξ, coherently with a more ordered and dense distribution of hot spots on the surface. The substrate with the largest ξ of 1100 nm showed an enhancement factor of 2.6 · 103 and remarkable homogeneity over square-millimetres area. The variability of the signal across the substrate was also investigated by means of a 2D chemical imaging approach and a standard methodology for its practical calculation is proposed for a coherent comparison among the data reported in literature