Third-Harmonic and intermodulation distortion in bulk acoustic-wave resonators

This article discusses on the measured third-order intermodulation (IMD3) products and third harmonics (H3) appearing in a set of six different solidly mounted resonators (SMR) and bulk acoustic-wave (BAW) resonators with different shapes and stack configurations. The discussion is supported by a comprehensive nonlinear distributed circuit model that considers the nonlinear effects potentially occurring in any layer of the resonator stack. The aluminum-nitride (AlN) and silicon-dioxide (SiO2) layers are identified as the most significant contributors to the IMD3 and H3. The frequency profile of the third-order spurious signals also reveals that, in temperature-compensated resonators, where the SiO2 layers are usually thicker, the remixing effects from the second-order nonlinear terms are the major contributors to the IMD3 and H3. These second-order terms are those that explain the second-harmonic (H2) generation, whose measurements are also reported in this article. Unique values of the nonlinear material constants can explain all the measurements despite the resonators have different shapes, resonance frequencies, and stack configurations.Peer ReviewedPostprint (author's final draft

A new synthetic approach to the lactol moiety of halichoblelide

A stereoselective approach to the γ-lactol moiety of halichoblelide is described starting from commercially available (R)-1-butyn-3-ol. The key step is the hydroboration of a chiral protected 1,2-butadien-3-ol and its addition to furfural

Nanocàpsules polimèriques per a l'alliberament controlat de fàrmacs

El càncer és una de les malalties que causa més morts als països desenvolupats. En aquest article s'ofereix un resum dels diferents tractaments d'aquesta malaltia, els quals han anat evolucionant cap a teràpies cada vegada més dirigides. Les innovacions en quimioteràpia, i més específicament les relacionades amb els nanomaterials, tenen com a objectiu modificar les propietats dels fàrmacs per tal d'incrementar-ne l'índex terapèutic, reduir-ne els efectes secundaris i millorar la qualitat de vida del pacient. Dins d'aquest context es presenta el treball que s'està desenvolupant a l'empresa Ecopol Tech, SL, en col·labo- ració amb la Universitat de Barcelona, basat en la preparació de nanocàpsules polimèriques com a materials intel·ligents per a l'alliberament controlat de molècules citotòxiques

Stereoselective Acetate Aldol Reactions From Metal Enolates

This review deals with metal enolate-mediated stereoselective acetate aldol reactions. It summarizes recent advances on aldol additions of unsubstituted metal enolates from chiral auxiliaries, stoichiometric and catalytic Lewis acids, or acting in substrate- controlled reactions, which provide stereocontrolled aldol transformations that allow the efficient synthesis of structurally complex natural products

La Universidad de Barcelona en el NO-DO (1943-1975): análisis de la educación superior a través de la verdad oficial del régimen franquista

Este artículo estudia la representación de la Universidad de Barcelona en uno de los instrumentos de propaganda más importantes de la dictadura franquista: el NO-DO (Noticiarios y Documentales Cinematográficos). Para ello, se han recopilado y analizado todas las noticias relativas a la institución universitaria aparecidas en él, llegando a identificar tres claves interpretativas del sentido de la verdad oficial: la lucha por el poder, la exaltación de la jerarquía y la vida académica

Numerical study of the aerodynamics of sound sources in a bass-reflex port

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The aim of this paper is to study the aerodynamics phenomena of a bass-reflex port that causes noise in the audible frequency range. After discarding structural and mechanical vibration issues, the hypothesis considered is that vortex shedding is the source of the noise. Experimental and numerical evidences of the vortex, an analysis of its noise and the similarities between real and simulated performance are presented. The numerically simulated cases with the original geometry are excited at different frequencies and with modifications of the port geometry. Likewise, the internal performance of an enclosure with a closed port was simulated. The simulations have been performed with axisymmetrical geometries using the open-source OpenFOAM® toolbox. Moreover, experimental measurements were carried out. First, acoustic signal experiments were done to analyse the response of the bass-reflex ports. Secondly, a structure vibration measurement was conducted in order to exclude the cabinet structure vibration as a source of the noise in question. A good agreement was found between numerical and experimental results, especially in the frequency band of the detected noise, i.e. the 1000–1500 Hz range. Despite no remarkable improvement being made with the geometry changes explored, the presented CFD approach has proved a useful and cost-effective tool to address this kind of phenomenon.Peer ReviewedPostprint (published version

‘One-pot’ engineering of 0D carbon-based inorganic nanoarchitectonics for boosting multitasking catalytic activity

[Abstract] Easy-to-make nanostructured materials that exhibit multitasking activity —while reducing the use of hazardous solvents throughout its architectural design— is a must to advance in the so-called Industry 4.0. Herein, a simple and eco-friendly ‘one-pot’ functionalization approach has been devised for synthesizing 0D carbon-based inorganic nanoarchitectonics made of carbon dots (CDs, as core carbon source) carrying two different inorganic building blocks, viz. quantum dots (CdSe@ZnS–QDs) and metal nanoparticles (Pt–NPs). As a proof-of-principle, the multi-catalytic activity of the resulting 0D Pt/QD/CD nanoarchitectonics by means of photoelectrocatalysis and sonocatalysis has been considered and compared with the pristine CD counterpart, demonstrating its suitability for boosting pivotal catalytic tasks like i) the photoelectrogeneration of hydrogen via hydrogen evolution reaction (HER), and ii) the sonodegradation of environmental pollutants (i.e., Rhodamine B) in water. Overall, this chemical approach is general and might be tailored for architecting alternative carbon-based heterostructures to enhance alternative multi-catalytic tasks.H. H. acknowledges the program of China Scholarships Council (No. 201908440337). X.S. thanks ICREA for the ICREA Academia Prize 2020. X.S. and J.G.-A. thank MINECO/FEDER for financial support (PID2019-104171RB-I00). J. M. is indebted to the Ramón y Cajal Program (RYC2021-033820-I Fellowship) funded by MCIN/AEI/10.13039/501100011033 and by the European Union “NextGenerationEU/PRTR”. I. J. G. acknowledges the Spanish Ministry of Universities for a Beatriz Galindo (BG22/000147) and Maria Zambrano funding (RSU.UDC.MZ09 [RSU.UDC.MZ11]) transferred by the European Union-Next GenerationEU

Degradation of fatty acid phase‐change materials (PCM): new approach for its characterization

The use of adequate thermal energy storage (TES) systems is an efficient way to achieve thermal comfort in buildings reducing the cooling and heating demand. Besides, deploy phase change materials (PCM) to meet and enhance the TES needs is highly effective and widely studied. In this paper, a study of the degradation of two fatty acids is presented, capric and myristic acids, in order to evaluate whether their thermo‐physical properties are affected throughout time during service. This was carried out by means of two different types of thermal treatments: degradation at constant temperature (thermal stability test), 60 °C during 100 h and 500 h, and degradation with heating and cooling cycling (thermal cycling stability), between a temperature range from 15 °C to 70 °C with 0.5 °C/min ramp during 500 and 1000 cycles. Despite no significant changes were meas‐ ured for myristic acid, experimental results revealed a decrease of melting enthalpy of 6.6% in capric acid thermally treated for 500 h. Evidences of chemical degradation were found that might explain the decrease in thermophysical properties during use