Magnetic nanostructures at IMN: multilayers, patterned elements and antidots

Trabajo presentado en el Workshop 2020 de la Red Española de Espintrónica, celebrado el 18 de noviembre de 202

Building initial models of rotating white dwarfs with SPH

A general procedure to build self-gravitational, rotating equilibrium structures with the Smoothed Particle Hydrodynamics (SPH) technique does not exist. In particular, obtaining stable rotating configurations for white dwarf (WD) stars is currently a major drawback of many astrophysical simulations. Rotating WDs with low internal temperatures are connected with both, explosive and implosive scenarios such as type Ia supernova explosions or neutron stars formation. Simulations of these events with SPH codes demand stable enough particle configurations as initial models. In this work we have developed and tested a relaxation method to obtain equilibrium configurations of rotating WDs. This method is straightforward and takes advantage of the excellent mass and angular momentum conservation properties of the SPH technique. Although we focus on rigid rotation and its potential applications to several Type Ia supernova scenarios, we also show that our proposal is also able to provide good initial models in differential rotation, which has the potential to benefit many other types of simulations where rotation plays a capital role, like disk evolution and stellar formation.Peer ReviewedPostprint (published version

Development of Magnetostrictive Transducer Prototype for Blockage Detection on Molten Salt Pipes

In solar thermal power plants molten salt is often used to store and transport the energy that is collected during the day. The external pipe temperature is measured to activate an electric heating system if the temperature approaches the melting point. However, salt solidification cannot be completely excluded from the plant management. Once occurred, the location of a salt blockage is very complex due to the high temperature of the pipe. Therefore, when this problem arises, power plants have to stop production with the consequences in time and cost that this entails. Electro-magnetic acoustic transducers can be used as non-destructive testing systems for this application. A method for salt blockage detection is proposed that is applicable in straight sections of pipes by employing torsional guided waves that are generated with magnetostrictive transducers. The present paper deals with the transducer conception and the design of the power supply to activate it. Two alternatives are proposed and compared to determine the improvement in the amplitude/noise ratio. Finally, the experimental results show the performance of the equipment in a small prototype, thus validating the technique presented

Intertwined magnetooptical and plasmonic properties in magnetoplasmonic multilayers

Comunicación presentada en el 2nd Early Stage Researchers Workshop in Nanoscience, celebrado en Madrid el 28 y 29 de junio de 2012.This work deals with metal and metal-dielectric magnetoplasmonic (MP) multilayers, which combine noble metals and ferromagnetic ones and exhibit interrelated effects between the excitation of Surface Plasmon-Polaritons (SPPs) and their magnetooptical (MO) activity. We have studied the effect of the SPP resonances for the enhancement of the MO activity and the magnetic modulation of the SPP wavevector.Peer Reviewe

Optical and magneto-optical properties of Au:Conanoparticles and Co:Aunanoparticles doped magnetoplasmonic systems

© 2015 AIP Publishing LLC. We report a study of Au:CoNPs and Co:AuNPs doped magnetoplasmonic systems. In particular, we analyze the effect of adding different concentrations of Co (or Au) nanoparticles (NPs) in a Au (or Co) matrix on both the optical and magneto-optical constants. Through the use of a simple effective medium model, relevant changes in the optical properties of the Au NPs compared to those of bulk material have been identified. Such effects are not observed in the Co NPs system. However, in both systems, there is an increase of the effective diameter of the NPs as compared to the real diameter that can be due to interface effects surrounding the NPs. Moreover, the magneto-optical constants values of both systems are smaller (in absolute values) than expected, which could also be attributed to interface effects such as hybridization between Au and Co.This work was supported by the Spanish MINECO under Project Nos. MAT2011-29194-C02 (MAPS), CSD2007-00041 (NANOSELECT), and CSD2008-00023 (FUNCOAT). http://dx.doi.org/10.1063/1.4906946Peer Reviewe

Transparent nanocellular PMMA: Characterization and modeling of the optical properties

In this work, the optical properties of transparent nanocellular polymethylmethacrylate (PMMA) have been studied, experimental and theoretically. Transmittance measurements of samples presenting different cell sizes (14, 24, 39 and 225 nm) and a constant relative density of around 0.45 have been carried out obtaining values as high as 0.94 for the sample with the smaller cell size and a thickness of 0.05 mm. In addition, the light absorption coefficient has been measured as a function of cell size and wavelength. It has been found that the transmittance has a strong dependence with the wavelength, presenting these transparent materials Rayleigh scattering. On the other hand, the transmission of visible light through these nanocellular materials has been modelled for the first time. The developed model reproduces with good accuracy the trends observed in the experimental results and provides remarkable insights into the physics mechanisms controlling the optical behavior of these materials

Rearrangement of the near-field landscape in heterogeneous nanoparticle arrays

Comunicación presentada en la Conferencia Española de Nanofotónica (CEN2012), celebrada en Carmona (Sevilla) del 1 al 4 de octubre de 2012.Geometric resonances in nanostructure arrays sustaining localized surface plasmons have received increasing attention in the last few years. These geometric resonances exhibit narrower peaks than the purely plasmonic ones, therefore these systems are promising candidates for sensing applications. Moreover, they provide new features in the near-field distribution patterns. Heterogeneous nanoparticle arrays offer a way to tune both the near and far-field response by using nanoparticles of different sizes, shapes or materials, but there is a lack of experimental studies in this context.Peer Reviewe

Use of statistical design of experiments in the optimization of Ar–O2 low-pressure plasma treatment conditions of polydimethylsiloxane (PDMS) for increasing polarity and adhesion, and inhibiting hydrophobic recovery

Polydimethylsiloxane (PDMS) film was treated with RF low-pressure plasmas (LPPs) made of mixtures of oxygen and argon for increasing surface polarity, minimizing hydrophobic recovery (i.e. retard ageing) and increasing adhesion to acrylic adhesive tape for medical use. Statistical design of experiments has been used for determining the most influencing experimental parameters of the LPP treatment of PDMS. Water contact angle values (measured 24 h after treatment) and the O/C ratio obtained from XPS experiments were used as response variables. Working pressure was the most influencing parameter in LPP treatment of PDMS, and the duration of the treatment, the power and the oxygen–argon mixture composition determined noticeably its effectiveness. The optimal surface properties in PDMS and inhibited hydrophobic recovery were achieved by treatment with 93 vol% oxygen + 7 vol% argon LLP at low working pressure (300 mTorr), low power (25 W) and long duration of treatment (120 s).This study was carried out in the framework of COST MP1101project

Sigillata africana con tema bíblico encontrada en la provincia de Salamanca

We present here several fragments from a single pot of African red slip ware with relief decoration. They were found at a settlement in the territory limits o f Huerta (Salamanca). The decorative motives are of a religous carácter, corresponding with two specific biblical episodes: «Abraham sacrificing Isaac» and «The three hebrews saved from the fournace».Se presentan aquí varios fragmentos de un único recipiente de sigillata africana con decoración aplicada a molde, encontrados en un yacimiento situado en el término municipal de Huerta (Salamanca). La temática decorativa es de carácter religioso, correspondiendo a dos episodios bíblicos concretos: El sacrificio de Isaac y los tres hebreos salvados del horno

Langmuir and Langmuir–Blodgett technologies as nanoarchitectonic tools for the incorporation of curcumin in membrane systems

Curcumin (CCM) is a molecule of particular interest in health applications due to its wide spectrum of benefits for humans. However, its water-insoluble character and low bioavailability have so far prevented its extended use as a therapeutic agent. Incorporation of CCM in drug delivery vehicles (liposomes, vesicles, exosomes, etc.) is expected to contribute to increasing its bioavailability. Studies of the affinity of CCM with the components of the membrane systems of such vehicles and determination of factors that may enhance curcumin entrapment in biological membranes are of fundamental importance. To that end, here we take advantage of the nanoarchitectonic capabilities of the Langmuir technique for the construction of model cell membranes and determination of thermodynamic properties in mixed films. The obtained results may serve to: (i) provide some light on the miscibility of CCM with the components in the cell membrane and (ii) determine the optimal conditions for the fabrication of membrane systems incorporating CCM. For that, binary and ternary mixed Langmuir films of CCM, DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and CHOL (cholesterol) have been prepared. Whilst binary mixtures of DPPC and CCM exhibit poor miscibility and even phase segregation, CHOL has shown itself as a key element to promote the incorporation of CCM in the phospholipidic membrane containing DPPC. Both the thermodynamic studies of the ternary Langmuir films and the Atomic Force Microscopy (AFM) images of Langmuir–Blodgett films have shown that ternary mixed films with a molar fraction composition of xDPPC/xCHOL/xCCM = 0.4/0.4/0.2 exhibit good miscibility, stability, and result in monolayers with a very homogeneous topography