Composite polymer membranes for laserinduced fluorescence thermometry

We demonstrate a modified version of laser-induced fluorescence thermometry (LIFT) for mapping temperature gradients in the vicinity of small photothermal devices. Our approach is based on temperature sensitive fluorescent membranes fabricated with rhodamine B and polydimethylsiloxane (PDMS). Relevant membrane features for LIFT, such as temperature sensitivity, thermal quenching and photobleaching are presented for a range of 25 °C to 90 °C, and their performance is evaluated upon obtaining the temperature gradients produced in the proximity of optical fiber micro-heaters. Our results show that temperature measurements in regions as small as 750 μm x 650 μm, with a temperature resolution of 1 °C, can be readily obtained

Charge control in laterally coupled double quantum dots

We investigate the electronic and optical properties of InAs double quantum dots grown on GaAs (001) and laterally aligned along the [110] crystal direction. The emission spectrum has been investigated as a function of a lateral electric field applied along the quantum dot pair mutual axis. The number of confined electrons can be controlled with the external bias leading to sharp energy shifts which we use to identify the emission from neutral and charged exciton complexes. Quantum tunnelling of these electrons is proposed to explain the reversed ordering of the trion emission lines as compared to that of excitons in our system.Comment: 4 pages, 4 figures submitted to PRB Rapid Com

A search for magnetic fields on central stars in planetary nebulae

One of the possible mechanisms responsible for the panoply of shapes in planetary nebulae is the presence of magnetic fields that drive the ejection of ionized material during the proto-planetary nebula phase. Therefore, detecting magnetic fields in such objects is of key importance for understanding their dynamics. Still, magnetic fields have not been detected using polarimetry in the central stars of planetary nebulae. Circularly polarized light spectra have been obtained with the Focal Reducer and Low Dispersion Spectrograph at the Very Large Telescope of the European Southern Observatory and the Intermediate dispersion Spectrograph and Imaging System at the William Herschel Telescope. Nineteen planetary nebulae spanning very different morphology and evolutionary stages have been selected. Most of central stars have been observed at different rotation phases to point out evidence of magnetic variability. In this paper, we present the result of two observational campaigns aimed to detect and measure the magnetic field in the central stars of planetary nebulae on the basis of low resolution spectropolarimetry. In the limit of the adopted method, we can state that large scale fields of kG order are not hosted on the central star of planetary nebulae.Comment: Paper accepted to be published in Astronomy and Astrophysics on 20/01/201

Cortante-fricción de los hormigones reciclados

The aim of this research was to determine the behavior of recycled concrete in response to the phenomenon of shear transfer. To perform it, a conventional control concrete and a concrete with 50% recycled coarse aggregate were designed. An additional goal was to shed light on how this behavior is modified with a pozzolanic addition, silica fume. Therefore, two types of concrete were designed, a conventional and a recycled concrete, both made with 8% of silica fume. In conclusion, a reduction of shear friction capacity was observed in recycled concretes, considerably higher in the case of the specimen without reinforcement. The addition of silica fume improved the behavior of recycled concretes. The results obtained were compared with the formulations of the different authors. In all cases, these were found to be conservative. However, the safety margins offered by recycled concretes are lower than those obtained with conventional concretes.En esta investigación se estudió el comportamiento de los hormigones reciclados frente al fenómeno de transmisión de cortante. Para ello se diseñó un hormigón convencional de control y un hormigón con el 50% del árido grueso reciclado. Adicionalmente, para determinar cómo este comportamiento se ve modificado con la incorporación de una adición puzolánica (humo de sílice), se procedió al diseño de un hormigón convencional y su correspondiente reciclado con un 8% de humo de sílice. Los resultados indicaron una disminución de la capacidad frente a este fenómeno en los hormigones reciclados, más acusada en ausencia de armadura pasante. La adición de humo de sílice mejora el comportamiento de este material. Los resultados experimentales obtenidos se compararon con formulaciones teóricas de diversos autores, concluyéndose que éstas son, en todos los casos, conservadoras, aunque reducen el margen de seguridad en los hormigones reciclados

Physiology\u27s influence on the thermal comfort of the occupants: A study in Ensenada, Baja California

INTRODUCTION: Thermal environment\u27s adverse conditions can significantly affect the performance, comfort and well-being of people, so this study aims to estimate the thermal comfort range from the cold period in Ensenada city, Baja California: February month, from different levels of metabolic activity: passive, moderate and intense. PURPOSE: This study seeks to identify the relationship between the people thermal perception, their metabolic activity and the physical or psychological sensations involved in the process of adaptation indoors. Thermal sensations are caused by several factors: 1) Physical stimuli of the thermal environment, 2) Activity metabolic, as well as the intensity with which it is performed, 3) Clothing, 4) Experience and 5) Human expectation. METHODS: Data collection was based on the application of questionnaires, which considered physiological, perceptual and environmental characteristics measurements. The study case is located in Ensenada city (temperate-dry bioclimate); with a target population that is within the range of 15-19 years old and 20-24 years old. It was decided to apply the assessments to university students of the Autonomous University of Baja California, who represent 60 % of the statewide student community. RESULTS: Estimated thermal comfort during the cold period resulted from 16.9 °C to 23.9 °C for occupants that exercising passive activity (0.8 met to 1.2 met), from 16.6 °C to 23.9 °C for moderate activity (1.2 met to 1.6 met); and 17.1 °C to 23.2 °C for those who exercised intense activity (2.0 met to 2.4 met). CONCLUSION: According to the aforementioned, it is possible to inform that occupants metabolic activity and, thereby the production of generated internal heat, exerts an influence in the thermal sensation that they perceive from immediate environment

Improvement of scanning tunneling microscopy resolution with H-sensitized tips

Recent scanning tunneling hydrogen microscopy (STHM) experiments on PTCDA (perylene-3,4,9,10- tetracarboxylic-3,4,9,10-dianhydride)/Au(111) have shown unprecedented intramolecular and intermolecular spatial resolution. The origin of this resolution is studied using an accurate STHM theoretical simulation technique that includes a detailed description of the electronic structure of both the tip and sample. Our results show that H2 molecules are dissociated on the Au tip; the adsorbed H atoms change the density of states at the Fermi level (EF) of the tip, increasing its p-orbital character and reducing the s-orbital contribution. Also, due to the interaction with the H-decorated tip, EF is shifted to the middle of the PTCDA lowest unoccupied molecular orbital peak, increasing dramatically the density of states of the sample at EF. These effects give rise to the enhanced STHM resolutionThis work is supported by Spanish MICIIN under Contract No. FIS2010-16046, the CAM under Contract No. S2009/MAT-1467, and the European Project MINOTOR (Grant No. FP7-NMP-228424). J. I. M. acknowledges funding from Spanish MICINN through Juan de la Cierva Program, E. A. the financial support by Consejería de Educación de la CAM, FSE, and European Project MINOTOR, and C. G. the CSIC JA

Development of a calibration satellite for a CMB telescope flying in formation about L2 libration point

Trabajo presentado a la 8th European Conference for aeronautics and aerospace sciences (EUCASS), celebrada en Madrid (España) del 1 al 4 de julio de 2019.The new generation of cosmic microwave background (CMB) telescopes have reached unprecedented levels of sensitivity. These telescopes measure several cosmological parameters with different levels of accuracy. In particular, considerable effort has been made to measure the B-mode polarization, which is related to the inflationary process of the universe. The power spectrum of this signal is about four orders of magnitude fainter than the CMB temperature power spectrum. Due to the signal weakness, the instruments must be subjected to calibration processes before and after launching. Additionally, data from the same sky area is gathered repeatedly to mitigate during data analysis the systematic errors induced by instruments. Celestial sources are often used as an external reference for calibration after launch, but these sources are not perfectly characterized. In this paper we study the concept of using a calibration satellite (CalSat) flying in formation with a CMB telescope in an orbit located at the second Lagrange point (L2). The CalSat is conceived as a micro satellite (10-100 kg) and serves as a perfectly known source of a reference signal to reduce the polarization angle measurement uncertainty. According to the scanning law followed by the telescope, the influence of the relative position between the spacecrafts in the calibration process is studied. The relative motion of the spacecrafts is considered with a simplified dynamic model. Based on the mission requirements, the different subsystems are sized and a preliminary design to evaluate the feasibility is obtained. The design has been carried out under the principle of reducing at minimum the impact on the telescope architecture. It would require to be launched along with the telescope to reach L2 at the same time and being able to communicate with the telescope. This new calibration element could have a huge impact on the performance of this kind of missions, providing a significant improvement in the measurements accuracy without requiring new and costly technological developments.The authors would like to thank Spanish Ministry for Economy and Competitiveness (currently Ministry of Science,innovation and Universities) for the financial support provided under the projects with references ESP2017-92135-EXP all co-financed with EU FEDER funds