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The melting of a phase change material (PCM) in a cuboidal domain under microgravity conditions is investigated numerically. The upper surface of the PCM is free (in contact with air, for example) and variations in its surface tension drive thermocapillary convection in the liquid phase, which significantly enhances heat transfer and accelerates melting. Furthermore, the change in liquid fraction during melting is associated with transitions among various modes of thermocapillary dynamics, including an oscillatory instability to hydrothermal waves. While the characteristics of PCM melting and thermocapillary dynamics have previously been investigated in this system using a two-dimensional model, the current work examines the important question of transverse dynamics and their effect on the melting process. Careful quantitative comparisons are made between the three- and two-dimensional models in terms of melting times, solid/liquid interface evolution, thermal fields, and spectrograms. The results show that transverse modes are often, but not always, reflection symmetric about the midplane and that their influence on melting and PCM performance is relatively minor in most cases. Thus, two-dimensional models may be used to reduce computational costs while still providing a reasonable approximation of the melting process for high Prandtl number materials, especially when compared to the midplane of the full cuboidal domain.

The melting of a phase change material (PCM) in a cuboidal domain under microgravity conditions is investigated numerically. The upper surface of the PCM is free (in contact with air, for example) and variations in its surface tension drive thermocapillary convection in the liquid phase, which significantly enhances heat transfer and accelerates melting. Furthermore, the change in liquid fraction during melting is associated with transitions among various modes of thermocapillary dynamics, including an oscillatory instability to hydrothermal waves. While the characteristics of PCM melting and thermocapillary dynamics have previously been investigated in this system using a two-dimensional model, the current work examines the important question of transverse dynamics and their effect on the melting process. Careful quantitative comparisons are made between the three- and two-dimensional models in terms of melting times, solid/liquid interface evolution, thermal fields, and spectrograms. The results show that transverse modes are often, but not always, reflection symmetric about the midplane and that their influence on melting and PCM performance is relatively minor in most cases. Thus, two-dimensional models may be used to reduce computational costs while still providing a reasonable approximation of the melting process for high Prandtl number materials, especially when compared to the midplane of the full cuboidal domain.

Present as well as future challenges of space exploration point to the need for improved thermal control systems. The “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” experiment, which is approved by ESA for execution on board the International Space Station, aims to contribute directly to current knowledge and basic understanding of heat and mass transport in phase change materials (PCMs) that incorporate a free surface in reduced gravity. The experiment will apply fixed temperatures to opposite ends of PCM samples held in cuboidal and cylindrical containers in order to drive controlled melting and solidification cycles that will be observed by means of optical cameras. The recorded images will be complemented by thermal measurements at key positions along the samples, which will allow different thermocapillary flow regimes to be distinguished according to their temporal dynamics. It is anticipated that thermal Marangoni (thermocapillary) convection will increase the heat transfer rate in these PCM devices by a significant factor (on the order of two or more) compared to melting governed by thermal diffusion (conduction). If the PCM designs prove robust, the experiment results can be expected to lead to substantial improvements in future designs for passive PCM applications in space missions.

Present as well as future challenges of space exploration point to the need for improved thermal control systems. The “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” experiment, which is approved by ESA for execution on board the International Space Station, aims to contribute directly to current knowledge and basic understanding of heat and mass transport in phase change materials (PCMs) that incorporate a free surface in reduced gravity. The experiment will apply fixed temperatures to opposite ends of PCM samples held in cuboidal and cylindrical containers in order to drive controlled melting and solidification cycles that will be observed by means of optical cameras. The recorded images will be complemented by thermal measurements at key positions along the samples, which will allow different thermocapillary flow regimes to be distinguished according to their temporal dynamics. It is anticipated that thermal Marangoni (thermocapillary) convection will increase the heat transfer rate in these PCM devices by a significant factor (on the order of two or more) compared to melting governed by thermal diffusion (conduction). If the PCM designs prove robust, the experiment results can be expected to lead to substantial improvements in future designs for passive PCM applications in space missions.

© 2019 by the authors Inertial focusing conditions of fluorescent polystyrene spherical particles are studied at the pointwise level along their pathlines. This is accomplished by an algorithm that calculates a degree of spreading function of the particles’ trajectories taking streaklines images as raw data. Different confinement ratios of the particles and flow rates are studied and the results are presented in state diagrams showing the focusing degree of the particles in terms of their position within a curve of an asymmetric serpentine and the applied flow rate. In addition, together with numerical simulation results, we present empirical evidence that the preferred trajectories of inertially focused spheres are contained within Dean vortices’ centerlines. We speculate about the existence of a new force, never postulated before, to explain this fact.

This work presents the preliminary characterization of the vibrational environment of the DCMIX4 thermodiffusion experiment conducted onboard the ISS from December 2018 to March 2019. Given the long duration of each one of the 58 runs of the campaign and to ensure a correct interpretation of the results, an accurate analysis of acceleration levels all along the experiment is advisable. Digital signals coming from the nearest sensor, es09006, located in the Microgravity Science Glovebox (Destiny module) were downloaded from the PIMS NASA website. The techniques used to identify the main disturbances during the experiments were defined both in time and frequency domains. It is expected that the results obtained can help the experimentalist to have an overview of the possible sources of disturbances that may affect their experiments. To visualize the possible impact of the accelerometric environment on the experiment a numerical simulation has been performed. Four signals have been chosen, one considering the ideal case g = 0, one coming from the OSS raw sensor (outside the Microgravity Science Glovebox) and the other two, coming from the es09006 sensor that needed to be mathematical manipulated for considering only the low frequency range. Independent of the location of the sensor, numerical simulations do not detect, in any case, appreciable flow disturbances if quiescent periods are considered. Therefore, in case the reference sensor is not available one can use other sensors placed in the same module.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). The dynamics of a spherical particle in an asymmetric serpentine is studied by finite element method (FEM) simulations in a physically unconstrained system. The two-way coupled time dependent solutions illustrate the path of the particle along a curve where a secondary flow (Dean flow) has developed. The simulated conditions were adjusted to match those of an experiment for which particles were focused under inertial focusing conditions in a microfluidic device. The obtained rotational modes inferred the influence of the local flow around the particle. We propose a new approach to find the decoupled secondary flow contribution employing a quasi-Stokes flow.

An optofluidic device for cell discrimination with two independent interrogation regions is presented. Pumping light coupling to the device and cells’ fluorescence extraction from the two interrogation zones is accomplished employing optical fibers embedded in said optofluidic chip. To test the reliability of this device AU-565 cells -expressing EpCAM and HER2 receptors- and RAMOS cells were mixed in a controlled manner, confined inside an hydrodynamic focused flow in the microfluidic chip and detected individually to be later discriminated as positive (signal re- ception from fluorescently labeled antibodies from the AU-565 cells) or negative events (RAMOS cells). A correlation analysis is performed over the two intensity versus time signals obtained at each of the two interrogation zones. A post-processing analysis permits a peak-to-peak pairing between the two output signals, being the detected peaks at each channel events related to the passing of a single cell through an interrogation region. Said method reduces the influence of noise on the overall data and allows to better discern actual cells’ characteristic intensity bursts from noise without the need of digitally aided signal processing.

DOI: 10.1038/s41598-017-04033-9 https://www.nature.com/articles/s41598-017-04033-9 Filiació URV: SI, Metastatic cancer patients require a continuous monitoring during the sequential treatment cycles to carefully evaluate their disease evolution. Repetition of biopsies is very invasive and not always feasible. Herein, we design and demonstrate a 3D-flow focusing microfluidic device, where all optics are integrated into the chip, for the fluorescence quantification of CTCs in real samples. To test the chip performance, two cell membrane targets, the epithelial cell adhesion molecule, EpCAM, and the receptor tyrosine-protein kinase, HER2, are selected. The efficiency of the platform is demonstrated on cell lines and in a variety of healthy donors and metastatic-breast cancer patients.

© 2017 Elsevier B.V. Macrodefect-free samples of Yb3+:KLu(WO4)2, Yb3+:Nb:RbTiOPO4 and Yb3+:KGd(PO3)4 laser crystals were grown using the Top Seeded Solution Growth – Slow Cooling technique. Structural and morphological studies related with the three materials were carried out and discussed. The dispersion of the refractive indices was measured and Sellmeier equations were constructed which are valid in the UV-Vis-IR range. The Stark splitting of the two electronic states of trivalent ytterbium was determined and the CW laser generation was demonstrated in these hosts. This paper shows a review of the main results achieved in FiCMA-FiCNA-URV laboratories in relation with these laser materials in the last years.

We developed a new compact, low-cost and non-invasive temperature sensor based on a ratiometric luminescence technique. The setup included a commercial digital color sensor, which collects simultaneously signals in the blue, green and red regions of the electromagnetic spectrum, usually used to assess the quality of computer screens and used for the first time here as a sensor for luminescent thermometry, coupled to an optical system that focuses an excitation laser beam onto luminescent nanoparticles emitting at least in two of these electromagnetic regions, which simplifies considerably the design, alignment and measurement procedures of setups used up to now for the same purpose. The same optical system collects the emission arising from the luminescent nanoparticles and directs it towards the digital color sensor through a dichroic mirror. We probed the potentiality of this setup for luminescence thermometry in the biological range of temperatures using Er,Yb:NaYF, and up to 673 K for microelectronic applications using Tm,Yb:GdVO up-converting nanoparticles. The thermal sensitivity obtained in both cases is similar to that previously reported for the same kinds of nanoparticles using conventional systems. This validates our setup for temperature measurements. Also, we developed new flexible and transparent polymer composites, in which we embedded upconversion luminescent nanoparticles of Er,Yb:NaYF in PDMS, a standard polymer for microfluidic devices used for biomedical studies, which allow fabricating thermometric microfluidic chips in which temperature can be determined using our setup. The thermal sensitivity for these composites is slightly smaller than that of the bare nanoparticles, bur still allowing for precise and fast temperature measurements.

We present our recent achievements in the growth and spectroscopic characterization of (formula presented) crystals doped with erbium ions (hereafter KYbW:Er). We grew single crystals of KYbW:Er at several erbium concentrations with optimal crystalline quality by the top-seeded-solution growth (TSSG) slow-cooling method. We carried out spectroscopic measurements related to the polarized optical absorption and optical emission at room temperature (RT) and low temperature (6 K). The splitting of the excited energy levels and the ground energy level of erbium in KYbW were determined, derived from the absorption and emission measurements at 6 K, respectively. We determined the near infrared, around (formula presented) (formula presented) emission channels from the emission spectrum, and used the reciprocity method to calculate a maximum emission cross section of (formula presented) for the polarization parallel to the (formula presented) principal optical direction for the (formula presented) (formula presented) infrared emission. We measured the lifetime of the (formula presented) transition of ytterbium and the (formula presented) transition of erbium at RT for several erbium concentrations. Finally, we present the Judd-Ofelt calculations for the KYbW:Er system. © 2002 The American Physical Society.

A cloud-detection method was used to retrieve cloudy pixels from Meteosat images. High spatial resolution (one pixel), monthly averaged cloud-cover distribution was obtained for a 1-year period. The seasonal cycle of cloud amount was analyzed. Cloud parameters obtained include the total cloud amount and the percentage of occurrence of clouds at three altitudes. Hourly variations of cloud cover are also analyzed. Cloud properties determined are coherent with those obtained in previous studies.

A three-dimensional meteorological model and a Lagrangian particle dispersion model are used to study the effects of a uniform large-scale wind on the dispersion of a non-reactive pollutant in a coastal region with complex terrain. Simulations are carried out both with and without a background wind. A comparison between model results and measured data (wind and pollutant concentrations) indicates that the coupled model system provides a useful mechanism for analyzing pollutant dispersion in coastal regions.