Avda University 30

Leganés, Spain

Avda University 30

Leganés, Spain
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Sierra-Fernandez A.,Complutense University of Madrid | Sierra-Fernandez A.,Charles III University of Madrid | De La Rosa-Garcia S.C.,Juarez Autonomous University of Tabasco | Gomez-Villalba L.S.,Complutense University of Madrid | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2017

More recently, the biological colonization of stone heritage and consequently its biodeterioration has become the focus of numerous studies. Among all microorganisms, fungi are considered to be one of the most important colonizers and biodegraders on stone materials. This is why the development of new antifungal materials requires immediate action. ZnMgO nanoparticles (NPs) have several exciting applications in different areas, highlighting as an efficient antimicrobial agent for medical application. In this research, the application of Zn-doped MgO (Mg1-xZnxO, x = 0.096) NPs obtained by sol-gel method as antifungal coatings on dolomitic and calcitic stones has been explored as a means to develop effective protective coatings for stone heritage. Moreover, the photocatalytic and antifungal activity of Mg1-xZnxO NPs were comparatively studied with single ZnO and MgO NPs. Thus, compared to the MgO and ZnO nanomaterials, the Mg1-xZnxO NPs exhibited an enhanced photocatalytic activity. After UV irradiation for 60 min, 87% methylene blue was degraded over Zn-doped MgO NPs, whereas only 58% and 38% of MB was degraded over ZnO and MgO NPs, respectively. These nanoparticles also displayed a better antifungal activity than that of single pure MgO or ZnO NPs, inhibiting the growth of fungi Aspergillus Niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans, which are especially active in the bioweathering of stone. The improved photocatalytic and antifungal properties detected in the Mg1-xZnxO NPs was attributed to the formation of crystal defects by the incorporation of Zn into MgO. The application of the MgO- and Zn-doped MgO NPs as protective coatings on calcareous stones showed important antifungal properties, inhibiting successfully the epilithic and endolithic colonization of A. Niger and P. oxalicum in both lithotypes, and indicating a greater antifungal effectiveness on Zn-doped MgO NPs. The use of Zn-doped MgO NPs may thus represent a highly efficient antifungal protection for calcareous stone heritage. © 2017 American Chemical Society.

del Campo R.,Charles III University of Madrid | Savoini B.,Charles III University of Madrid | Savoini B.,Avda University 30 | Jordao L.,Instituto Nacional Of Saude Dr Ricardo Jorge | And 4 more authors.
Materials Science and Engineering C | Year: 2017

In this work the cytocompatibility of pure magnesium and Mg-xHAP composites (x = 5, 10 and 15 wt%) fabricated by powder metallurgy routes has been investigated. The materials were produced from raw HAP powders with particle mean sizes of 6 μm (S-xHAP) or 25 μm (L-xHAP). The biocompatibility study has been performed for MC3T3 cells (osteoblasts/osteoclasts) and L929 fibroblasts. The results indicate that S-Mg (pure magnesium), S-10HAP and L-10HAP composites are the materials with the best biocompatibility. The ability of S. aureus bacteria to assemble biofilms was also evaluated. Biofilm formation assays showed that these materials are not particular prone to colonization and biofilm assembly is strain dependent. The corrosion resistance of S-Mg, S-10HAP and L-10HAP materials immersed in the media used for the cells culture has also been analyzed. Different trends in the corrosion resistance have been found: S-Mg and S-10HAP show a very high resistance to corrosion whereas the corrosion of L-10HAP steadily increases with time. © 2017 Elsevier B.V.

Sierra-Fernandez A.,Complutense University of Madrid | Sierra-Fernandez A.,Charles III University of Madrid | Gomez-Villalba L.S.,Complutense University of Madrid | Rabanal M.E.,Charles III University of Madrid | And 3 more authors.
RSC Advances | Year: 2016

Paper aging and protection are of crucial interest for improving the preservations of library collections and archives. Highly aging-resistant cellulose fiber sheets were obtained by treatment with magnesium hydroxide nanoparticles (Mg(OH)2). The procedure was tested on the sheets made of bleached (B) and refined unbleached (UB) pine cellulose fibers as well as their 50%/50% mixture (M). The mor and structural properties of the obtained sheets were studied by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) methods. Stress-strain, smoothness and pH measurements were employed to determine the changes in physical-chemical characteristics of the sheets after mixing two types of the fibers and subsequent treatment with Mg(OH)2. It has been shown that the sheets made of the fiber mixture show a higher tensile index and smoothness. The modification with Mg(OH)2 nanoparticles induces an increase in the pH of the sheets to slightly basic values (around pH 8), facilitates the inter-fiber bonding and additionally enhances the smoothness of the sheets. Finally, by exposing the sheets to thermo-hygrometric accelerated artificial ageing, it was found that the physical properties of the treated sheets were not significantly dependent on the environmental factors. © 2016 The Royal Society of Chemistry.

Gomez-Villalba L.S.,Complutense University of Madrid | Sierra-Fernandez A.,Complutense University of Madrid | Sierra-Fernandez A.,Charles III University of Madrid | Rabanal M.E.,Charles III University of Madrid | And 2 more authors.
Ceramics International | Year: 2016

The dehydration process from Mg0.97Ca0.03 (OH)2 nanoparticles (brucite type hexagonal structure) to Mg0.97Ca0.03O (periclase type cubic structure) was studied by Transmission Electron Microscopy (TEM-HRTEM), Electron Diffraction (SAED), Electron Energy Loss Spectroscopy (EELS) and image analysis. The transformation process was monitored in function of the reaction time applying 200 and 300 KV. Changes in porosity were possible to observe only during the irradiation with 200KV. Depending on the irradiation time, the changes were gradual, producing an increase from the particle's edge towards the inner region. Different stages were observed, corresponding to the amount of water extracted from the particle, until finally a decrease in porosity and particle shrinkage occurs, coinciding with the formation of the Mg-Ca oxide. However, when samples were exposed to 300KV, the dehydration process was much faster, and the pores structure was destroyed in a shorter time in comparison with lower doses of radiation. High resolution electron microscopy (HRTEM) applying 300kV allowed identifying the progressive changes from brucite to periclase, including the formation of an intermediate dehydrated phase. The transformation along [0001]brucite and [101-0] brucite orientations was monitored determining differences in the kinetic of reaction related to the presence of point defects affecting the atomic lattice. © 2016.

Castrillo P.D.,Avda University 30 | Olmos D.,Avda University 30 | Sue H.-J.,Texas A&M University | Gonzalez-Benito J.,Avda University 30
Composite Structures | Year: 2015

In this work the mechanical behavior of composite materials formed by a diepoxy-diamine (epoxy) thermosetting matrix filled with kaolin intercalated with ethylenediamine (K-EDA) was studied. Fracture toughness experiments showed that an addition of 2. wt% K-EDA to the epoxy matrix causes an approximately 24% increase in the critical stress intensity factor (KIC). The study of fracture mechanisms was completed using the double-notch four-point-bending test. The presence of kaolin particles in the matrix induces crack branching and deflection mechanisms. Furthermore, observation of the fracture surface revealed the presence of tails near kaolin particles, which is consistent with crack-pinning. The present study indicates that kaolin clay can be effective in toughening epoxy at small quantities if it is reasonably well dispersed. © 2015 Elsevier Ltd.

Sanchez R.,Charles III University of Madrid | Sanchez R.,Avda University 30 | Hernandez J.A.,Charles III University of Madrid | Hernandez J.A.,Avda University 30 | And 2 more authors.
International Conference on Transparent Optical Networks | Year: 2013

OpenFlow is a protocol that enables networks to evolve and change flexibly, by giving a remote controller the capability of modifying the behavior of network devices. In an OpenFlow network, each device needs to maintain a dedicated and separated connection with a remote controller. All these connections can be described as the OpenFlow control network, that is the data network which transports control plane information, and can be deployed together with the data infrastructure plane (in-band) or separated (out-of-band), with advantages and disadvantages in both cases. The control network is a critical subsystem since the communication with the controller must be reliable and ideally should be protected against failures. This paper proposes a novel ring architecture to efficiently transport both the data plane and an out-of-band control network. © 2013 IEEE.

Valdivia V.,Charles III University of Madrid | Lazaro A.,Charles III University of Madrid | Barrado A.,Charles III University of Madrid | Barrado A.,Avda University 30 | And 3 more authors.
SAE Technical Papers | Year: 2011

Modeling and simulation are powerful tools to design power distribution systems made up by multiple converters and loads, such as the system of the more-electric-aircraft. However, the system designer usually has no access to detailed data of the power converters, due to confidentiality of manufacturers. Therefore, a behavioral black-box modeling approach is necessary. These models can be used to evaluate the response of power electronics systems which are composed of commercial converters, since they can be fully parameterized from the actual converter response and only reproduce the signals required for a system-level analysis: input-output voltage and currents. In this paper a behavioral black-box modeling method of three-phase DC-AC converters is proposed. The identification of the model is based on the analysis of the converter transient response, which is obtained by means of a set of simple experiments and easily usable fitting algorithms. An experimental validation of the proposed method has been carried out on a 5 kVA three-phase DC-AC converter implemented in an aircraft power system test bench. Copyright © 2011 SAE International.

Parra-Cerrada A.,Technical University of Madrid | Jimenez-Martin J.L.,Technical University of Madrid | Segovia-Vargas D.,Avda University 30 | Gonzalez-Posadas V.,Technical University of Madrid
Journal of Electromagnetic Waves and Applications | Year: 2016

This paper shows one active patch antenna with a Negative Impedance Converters (NIC) and other one without it. The NIC works as negative admittance to increase the Q of the antenna. These circuits can be analysed using classic methods, but classic methods require the verification of the appropriated provisos. The chosen classic method depends on the oscillator topology, while the Normalized Determinant Function (NDF) is independent of topologies and it does not require any provisos. The NDF is suitable for Q estimation and noise optimization during linear analysis of any topology. The oscillators are designed using the NDF and the Admittance; then the phase noise is evaluated using the NDF. The Harmonic Balance (HB) analysis and the measurements of the prototypes confirm, in favour of NDF, the stability discrepancies between classic methods and NDF. The linear approximation of the improvements introduced by a NIC is questioned by the risk of instabilities and the introduction of new noise sources. © 2015 Taylor and Francis.

Nieto A.B.,Avda University 30 | Garcia J.L.S.R.,Avda University 30 | Lopez V.D.,Avda University 30 | Babe A.G.,Avda University 30
International Journal of Heavy Vehicle Systems | Year: 2015

Vehicle brake efficiency, for a fully loaded vehicle scenario, is computed by means of Directive 2010/48/EU. According to this Directive, brake efficiency must be calculated using vehicle's maximum authorised mass (MAM) value instead of the real weight measured during the inspection. However, vehicles, such as buses and those assigned for transportation of hazardous merchandise, cannot be tested under fully loaded conditions. Directive 2010/48/EU allows obtaining the braking forces that develop fully loaded vehicles using the extrapolation method proposed by the ISO 21069. However, this method is only applicable for vehicles with purely pneumatic brakes and equipped with standard pressure taps. This paper presents a novel simulation model, which extrapolates maximum braking forces measured in the periodic technical inspection (PTI) stations regardless of the type of brake system and regardless of vehicle loading condition during which brake force is measured on the brake roller tester of the PTI station. © Copyright 2015 Inderscience Enterprises Ltd.

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