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Caceres, C., Moczko, E., Basozabal, I., Guerreiro, A., & Piletsky, S. (2021). Molecularly Imprinted Nanoparticles (NanoMIPs) Selective for Proteins: Optimization of a Protocol for Solid-Phase Synthesis Using Automatic Chemical Reactor. Polymers, 13(3), 314.
Abstract: Molecularly imprinted polymer nanoparticles (nanoMIPs) are receiving broad interest as robust and highly selective synthetic receptors for a variety of molecules. Due to their stability, inexpensive synthesis and easy implementation, they are considered a promising alternative to antibodies in sensors, diagnostics and separation applications. The most challenging targets for the production of synthetic receptors are proteins due to their fragile nature and the multitude of possible binding sites in their structure. Herein, we describe the modification and optimization of the protocol for synthesis of nanoMIPs with specificity for proteins using the prototype of an automated solid-phase synthesizer. Using an automated system gives an advantage for the simple, fast and fully controlled, reproducible production of nanoMIPs. The molecular imprinting in the reactor is performed using a template covalently immobilized on a solid support, in mild conditions suitable for preserving protein native structure. The validation of the protocol was made by assessing the ability to regenerate a solid-phase, and by measuring affinity and specificity of nanoparticles. As a model protein, we have chosen trypsin since its enzymatic activity can be easily monitored by using a commercial colorimetric assay. Different protocols were tested for their ability to improve the yield of high affinity nanoparticles in the final elution.
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Fullenkamp, K., Montane, M., Caceres, G., & Araya-Letelier, G. (2019). Review and selection of EPCM as TES materials for building applications. Int. J. Sustain. Energy, 38(6), 561–582.
Abstract: In order to improve the thermal efficiency of building thermal energy storage (TES) systems, the feasibility of using encapsulated phase change materials (EPCMs) as heat storage media is analysed in this work. Specifically, the finite element method is used to perform thermal behaviour analyses of several EPCMs. These analyses include technical and economic assessments in order to identify the best combination of PCM and shell material, using as main parameters: thermal energy storage, heat transfer rate, materials cost, among others. The results show that EPCMs composed by Na2SO4 center dot 6H(2)O as PCM and covered by stainless steel highlight as TES materials.
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Garces, H. O., Fuentes, A., Reszka, P., & Carvajal, G. (2018). Analysis of Soot Propensity in Combustion Processes Using Optical Sensors and Video Magnification. Sensors, 18(5), 18 pp.
Abstract: Industrial combustion processes are an important source of particulate matter, causing significant pollution problems that affect human health, and are a major contributor to global warming. The most common method for analyzing the soot emission propensity in flames is the Smoke Point Height (SPH) analysis, which relates the fuel flow rate to a critical flame height at which soot particles begin to leave the reactive zone through the tip of the flame. The SPH and is marked by morphological changes on the flame tip. SPH analysis is normally done through flame observations with the naked eye, leading to high bias. Other techniques are more accurate, but are not practical to implement in industrial settings, such as the Line Of Sight Attenuation (LOSA), which obtains soot volume fractions within the flame from the attenuation of a laser beam. We propose the use of Video Magnification techniques to detect the flame morphological changes and thus determine the SPH minimizing observation bias. We have applied for the first time Eulerian Video Magnification (EVM) and Phase-based Video Magnification (PVM) on an ethylene laminar diffusion flame. The results were compared with LOSA measurements, and indicate that EVM is the most accurate method for SPH determination.
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Kumar, M. P., Sasikumar, M., Arulraj, A., Rajasudha, V., Murugadoss, G., Kumar, M. R., et al. (2022). NiFe Layered Double Hydroxide Electrocatalyst Prepared via an Electrochemical Deposition Method for the Oxygen Evolution Reaction. Catalysts, 12(11), 1470.
Abstract: Herein, we aimed to obtain NiFe layered double hydroxide (LDH) with a controlled phase and surface morphology as a highly active and stable oxygen evolution catalyst via the electrochemical deposition method, which was thermodynamically stable for the oxygen evolution reaction (OER) in an alkaline medium. The NiFe-LDH sample was analyzed by sophisticated instruments and tested as an electrocatalyst on Toray carbon (TC). The NiFe-LDH electrocatalyst showed an excellent performance with lower overpotential of 0.27 V at 35 mA cm(-2) and higher density of 125 mA cm(-2) for OER in the 1 M KOH electrolyte solution. Moreover, the prepared catalyst exhibited unpredictable long-time stability for 700 h. From our knowledge, NiFe-LDH is a robust highly stable electrocatalyst compared to the recent reports.
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Mellado, P. (2020). Timescales in the thermal dynamics of magnetic dipolar clusters. Phys. Rev. B, 102(21), 214442.
Abstract: The collective behavior of thermally active structures offers clues on the emergent degrees of freedom and the physical mechanisms that determine the low-energy state of a variety of systems. Here, the thermally active dynamics of magnetic dipoles at square plaquettes is modeled in terms of Brownian oscillators in contact with a heat bath. Solution of the Langevin equation for a set of interacting x-y dipoles allows the identification of the timescales and correlation length that reveal how interactions, temperature, damping, and inertia may determine the frequency modes of edge and bulk magnetic mesospins in artificial dipolar systems.
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Mellado, P. (2022). Intrinsic topological magnons in arrays of magnetic dipoles. Sci. Rep., 12(1), 1420.
Abstract: We study a simple magnetic system composed of periodically modulated magnetic dipoles with an easy axis. Upon adjusting the geometric modulation amplitude alone, chains and two-dimensional stacked chains exhibit a rich magnon spectrum where frequency gaps and magnon speeds are easily manipulable. The blend of anisotropy due to dipolar interactions between magnets and geometrical modulation induces a magnetic phase with fractional Zak number in infinite chains and end states in open one-dimensional systems. In two dimensions it gives rise to topological modes at the edges of stripes. Tuning the amplitude in two-dimensional lattices causes a band touching, which triggers the exchange of the Chern numbers of the volume bands and switches the sign of the thermal conductivity.
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Moya-Cessa, H. M., Hojman, S. A., Asenjo, F. A., & Soto-Eguibar, F. (2022). Bohm approach to the Gouy phase shift. Optik, 252, 168468.
Abstract: By adapting the Madelung-Bohm formalism to paraxial wave propagation we show, by using Ermakov-Lewis techniques, that the Gouy phase is related to the form of the phase chosen in order to produce a Gaussian function as a propagated field. For this, we introduce a quantum mechanical invariant, that it is explicitly time dependent. We finally show that the effective Bohm index of refraction generates a GRIN medium that produces the focusing needed for the Gouy phase.
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Parrado, C., Caceres, G., Bize, F., Bubnovich, V., Baeyens, J., Degreve, J., et al. (2015). Thermo-mechanical analysis of copper-encapsulated NaNO3-KNO3. Chem. Eng. Res. Des., 93, 224–231.
Abstract: The present paper presents a numerical study to investigate and assess the heat transfer behavior of a copper and salt composite. A mixture of nitrates, KNO3-NaNO3, within a deformable spherical shell coating of copper will be used as an encapsulated phase change material, E-PCM. In the context of a thermo-mechanical analysis of this E-PCM, a simulation is proposed to determine its storage capacity and properties The melting, or solidification of the encapsulated PCM particles do not provoke cracking of the deformable shell. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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Sepúlveda, E., Sanhueza, F., Cobo, R., Jiménez, J., & Mangalaraja, R. V. (2024). Relationship among the powder mass, press charge, and final properties of an LSGM electrolyte for solid oxide cells. MRS Adv., Early Access.
Abstract: In this work, La0.85Sr0.15Ga0.85Mg0.15O3-delta (LSGM) was prepared as an electrolyte for solid oxide cell (SOC) applications. A fast combustion method was used, starting with nitrate salts and citric acid as fuel. Different parameters, such as mass and pressing load, in the pre-sintering step were used to obtain a highly ionic conductive material at intermediate temperatures. The aim is to find optimal processing conditions for energy savings. SEM analysis showed similar grain sizes and distributions for all samples. The XRD spectra showed two main phases corresponding to LSGM orthorhombic (space group Imma) and LSGM cubic (space group Pm-3m). LaSrGaO4 appeared in lighter samples. The EIS revealed that heavier samples present high conductivity, showing a clear relationship between conductivity, sample mass (during the pre-sintering step), and the LSGM phase amount. The effect of pressure was less evident. The highest conductivity was 0.013 and 0.063 S cm-1 at 600 and 800 degrees C, respectively.
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Simon, F., Ruiz-Valero, L., Girard, A., & Galleguillos, H. (2023). Experimental and Numerical Analysis of a PCM-Integrated Roof for Higher Thermal Performance of Buildings. J. Therm. Sci., Early Access.
Abstract: Phase change materials (PCMs) designate materials able to store latent heat. PCMs change state from solid to liquid over a defined temperature range. This process is reversible and can be used for thermo-technical purposes. The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management. The experiment is conducted in two test rooms in Antofagasta (Chile) during summer, fall, and winter. The PCM is integrated into the rooftop of the first test room, while the roof panel of the second room is a sealed air cavity. The work introduces a numerical model, which is built using the finite difference method and used to simulate the rooms' thermal behavior. Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates. Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1 degrees C +/- 10.6 degrees C, while the one of the air-panel room varies 28.3 degrees C +/- 18.5 degrees C. Under the experiment's conditions, the PCM room's indoor temperature observes smoother diurnal fluctuations, with lower maximum and higher minimum indoor temperatures than that of the air-panel room. Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter, as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures. This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs, and improve indoor thermal comfort in different climates of Chile.
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Tierra, G., Pavissich, J. P., Nerenberg, R., Xu, Z. L., & Alber, M. S. (2015). Multicomponent model of deformation and detachment of a biofilm under fluid flow. J. R. Soc. Interface, 12(106), 13 pp.
Abstract: A novel biofilm model is described which systemically couples bacteria, extracellular polymeric substances (EPS) and solvent phases in biofilm. This enables the study of contributions of rheology of individual phases to deformation of biofilm in response to fluid flow as well as interactions between different phases. The model, which is based on first and second laws of thermodynamics, is derived using an energetic variational approach and phase-field method. Phase-field coupling is used to model structural changes of a biofilm. A newly developed unconditionally energy-stable numerical splitting scheme is implemented for computing the numerical solution of the model efficiently. Model simulations predict biofilm cohesive failure for the flow velocity between O(10(-3)) and O(10(-2))ms(-1) which is consistent with experiments. Simulations predict biofilm deformation resulting in the formation of streamers for EPS exhibiting a viscous-dominated mechanical response and the viscosity of EPS being less than O(10) kgm(-1) s(-1). Higher EPS viscosity provides biofilm with greater resistance to deformation and to removal by the flow. Moreover, simulations show that higher EPS elasticity yields the formation of streamers with complex geometries that are more prone to detachment. These model predictions are shown to be in qualitative agreement with experimental observations.
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Zhang, H. L., Baeyens, J., Degreve, J., Caceres, G., Segal, R., & Pitie, F. (2014). Latent heat storage with tubular-encapsulated phase change materials (PCMs). Energy, 76, 66–72.
Abstract: Heat capture and storage is important in both solar energy projects and in the recovery of waste heat from industrial processes. Whereas heat capture will mostly rely on the use of a heat carrier, the high efficiency heat storage needs to combine sensible and latent heat storage with phase change materials (PCMs) to provide a high energy density storage. The present paper briefly reviews energy developments and storage techniques, with special emphasis on thermal energy storage and the use of PCM. It thereafter illustrates first results obtained when encapsulating NaNO3/KNO3-PCM in an AISI 321 tube, as example of a storage application using a multi-tubular exchanger filled with PCM. To increase the effective thermal conductivity of the PCM, 2 inserts i.e. metallic foam and metallic sponge are also tested. Experimental discharging (cooling) rates are interpreted by both solving the unsteady-state conduction equation, and by using Comsol Multiphysics. Predictions and experimental temperature evolutions are in fair agreement, and the effect of the inserts is clearly reflected by the increased effective thermal conductivity of the insert-PCM composite. Application of Comsol to predict the mechanical behavior of the system, when melting and associated expansion increase the internal pressure, demonstrates that the pressure build-up is far below the Young's modulus of the AISI 321 encapsulation and that this shell will not crack (C) 2014 Elsevier Ltd. All rights reserved.
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