The wave equation for stiff strings and piano tuning

We study the wave equation for a string with stiffness. We solve the equation and provide a uniqueness theorem with suitable boundary conditions. For a pinned string we compute the spectrum, which is slightly inharmonic. Therefore, the widespread scale of 12 equal divisions of the just octave is not the best choice to tune instruments like the piano. Basing on the theory of dissonance, we provide a way to tune the piano in order to improve its consonance. A good solution is obtained by tuning a note and its fifth by minimizing their beats.Peer ReviewedPostprint (published version

The Gaudí-colon connection

Antonio Gaudí, a world-famous architect, was a leader of the artistic movement known as modernism, which is based on the use of natural forms

Briófitos ripícolas de ecossistemas aquáticos da Ilha da Madeira:biodiversidade, bioindicação e conservação

Tese de doutoramento, Biologia (Ecologia), Universidade de Lisboa, Faculdade de Ciências, 2010Disponível no documentoFundação para a Ciência e Tecnologia (SFRH/BD/12444/2003), III Quadro Comunitário de Apoio através do Programa Operacional CIência e Inovação 2010 (POCI 2010) e Fundo Social Europe

Nuevas aplicaciones de la imagen radiológica a la Antropología Física

Las nuevas técnicas de imagen de alta resolución (radiografía digital, TAC multicorte, resonancia magnética y escáner tridimensional), además de las posibilidades diagnóstico-médicas que ya se le conocen, permiten reconstruir y medir, presentándose como un instrumento de gran utilidad investigadora y docente. La aplicación de las nuevas técnicas de imagen es amplia, éstas son útiles en: 1) investigación antropológica y biomédica; 2) identificación forense; 3) realización de autopsias virtuales; 4) el paleodiagnóstico de muchas de las paleopatologías presentadas por restos esqueléticos arqueológicos de animales y humanos; y 5) en la docencia universitaria [...]

Analysis of solid state relay solutions based on different semiconductor technologies

This paper provides an analysis on the design, implementation and operation of Bi-Directional Switches (BDS) based on power semiconductor devices intended to replace Electro Mechanical Relays (EMR) in home appliances. Static and dynamic characterizations of test vehicles developed using different power device semiconductor technologies (TRIAC, Super Junction (SJ) MOSFET, IGBT...) are presented. At this time, emerging Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) seem to be very suitable for the mentioned applications. Actually, GaN HEMTs based BDS has demonstrated to be the best solution to replace EMRs, with a high expectation to a significant cost reduction

Estudio comparativo de la radiología y ecocardiografía en la detección de incrementos de atrio izquierdo en perros con insuficiencia mitral

Este estudio retrospectivo se basa en la comparación de la radiología y la ecocardiografía en la detección de incrementos de tamaño del atrio izquierdo en el perro. Para valorar la cardiomegalia, se han propuesto diversos criterios radiográficos y ecocardiográficos. Actualmente, los parámetros más objetivos de una y otra técnica son, respectivamente, el índice cardiaco vertebral (ICV) y la ratio entre las dimensiones del atrio izquierdo y la arteria Aorta (ratio LA/Ao). En este estudio aplicamos una nueva medida radiográfica, denominada bisectriz del atrio izquierdo (BAE), con el propósito de detectar incrementos del atrio izquierdo. Se constituyeron dos grupos: grupo A (14 perros con sintomatología de patología mitral espontánea) y grupo B (16 perros sin sintomatología cardiaca). La BAE la obtenemos realizando la bisectriz del ángulo de 90º que se forma entre los ejes cardiacos mayor y menor utilizados para calcular el ICV. La ratio LA/Ao se obtiene mediante el modo ecográfico bidimensional (Modo B). Se obtuvo un punto de corte (valor óptimo) de la BAE de 1.8 cuerpos vertebrales. Existió correlación positiva entre los tres parámetros, y en referencia a la BAE, se obtuvo una sensibilidad del 78.6% y una especificidad del 100%

Noise and charge discreteness as ultimate limit for the THz operation of ultra-small electronic devices

Altres ajuts: Consejería de Educación de la Junta de Castilla y León (project SA254P18)To manufacture faster electron devices, the industry has entered into the nanoscale dimensions and Terahertz (THz) working frequencies. The discrete nature of the few electrons present simultaneously in the active region of ultra-small devices generate unavoidable fluctuations of the current at THz frequencies. The consequences of this noise remain unnoticed in the scientific community because its accurate understanding requires dealing with consecutive multi-time quantum measurements. Here, a modeling of the quantum measurement of the current at THz frequencies is introduced in terms of quantum (Bohmian) trajectories. With this new understanding, we develop an analytic model for THz noise as a function of the electron transit time and the sampling integration time, which finally determine the maximum device working frequency for digital applications. The model is confirmed by either semi-classical or full- quantum time-dependent Monte Carlo simulations. All these results show that intrinsic THz noise increases unlimitedly when the volume of the active region decreases. All attempts to minimize the low signal-to-noise ratio of these ultra-small devices to get effective THz working frequencies are incompatible with the basic elements of the scaling strategy. One can develop THz electron devices, but they cannot have ultra-small dimensions. Or, one can fabricate ultra-small electron devices, but they cannot be used for THz working frequencies