Tema 11 de l'assignatura Sistemes estructurals.

Tema 9 de l'assignatura Introducció a les estructures. Grup tarda.

A methodology to retrieve the dielectric function of a nanocomposite from infrared spectroscopy is presented. The use of effective medium theories allows treating the optical response of a multi-phase composite as that of a single phase with an effective response that is a complex function of the components and their spatial arrangement. This methodology has been tested in a case study involving cerium oxide nanoparticles, whose vibrational properties are known to change significantly upon particle size reduction. Accurate values of its dielectric function in the infrared have been retrieved and used to analyse this phenomenon. The main goal of this study is to develop a systematic methodology for the study of the vibrational properties of nanomaterials. It is also intended that the development of effective medium models will be useful for designing new composite nanomaterials with improved optical properties (e.g., solar absorbers).

Red blood cells (RBCs) alterations can cause very severe blood diseases. In thalassemia, the production of hemoglobin polypeptide chains is unbalanced. This causes no symptoms or small blood count alterations in patients with less important genetic mutations, or severe anemia and high morbi-mortality in the most severe cases. Traditional techniques do not perfectly discriminate among different thalassemia degrees and most patients need to undergo genetic studies. Authors have tried alternatives to analyze RBCs, collecting their emission and absorption spectral traits with spectrometers and spectrofluorometers. Multispectral imaging with confocal microscopy allows capturing both tridimensional and spectral information. In this study we are using confocal spectral imaging to analyze RBCs from patients with different degrees of alpha-thalassemia and iron deficiencies. The instrument, a Leica TCS SP8 confocal microscope has high sensitivity hybrid cameras, a diode laser and a white laser combined with an acoustic-optic tunable filter. RBCs exhibited autofluorescence when excited at 405 nm. The mean emission intensities at 502 nm, 628 nm and 649 nm allowed us to discriminate between different etiologies.

En la industria del color es muy importante conocer la gama de colores de un dispositivo. Mediante la comparación de gamas podemos evaluar el efecto que tiene el uso de distintas tintas, papeles, fuentes de iluminación o dispositivos de impresión en el color obtenido. Existen diversos programas que realizan esta comparación, pero tienen inconvenientes. Por ello hemos desarrollado y validado un software para comparar gamas de color generadas por impresoras. El software representa las gamas simultáneamente en el espacio 3D CIELAB, además de calcular su volumen. Para validar nuestro software hemos realizado un doble análisis. Por un lado, hemos comparado los resultados obtenidos a partir de nuestro software y los obtenidos con otros métodos de comparación, como la representación en diferentes espacios de color. Por otro lado, hemos usado el programa ICC3D para comparar las representaciones de las gamas con las de nuestro programa, además del volumen. Con ambos programas las conclusiones fueron similares, aunque nuestro software presenta algunas ventajas, permitiendo distinguir diferencias entre las gamas que mediante otros métodos no se discriminaron. Este nuevo software va a permitir el estudio de la influencia de distintos factores en la reproducción del color, permitiendo conocer las condiciones para conseguir la mejor calidad posible

Imaging through nebulous media encountered in nature – like fog – is one
of the up-to-date research questions in the field of navigation. Among different
approaches to solve this problem, the use of polarimetric imaging has been proposed.
The aim of this research is to present a polarized light propagation model based on
Monte-Carlo simulations and Mie Theory for its use as a tool to study the feasibility and
characteristics of polarized light detection techniques in these kinds of media. Studying
and obtaining the backscattering Mueller matrix for a turbid environment allows to
completely characterize the backscattering characteristics of the media. Thus, it may be
used to select the combination of polarization components more useful for each
situation. On the other hand, it has been seen that when light first interact with fog,
generated backscatter directly blinds the sensor of the imaging device and hides
reflected signals of objects being imaged. Using a time-resolved variant of the model, it
has been possible to characterize the shape and the influence of the temporal response
of a backscattered light pulse, concluding that, apart from the greater light extinction in
a more scattering medium, media-backscattering and reflected-object signals are
independent

Complete characterization of biological samples is of potential interest in different industrial and research areas, as for instance, in biomedical applications, for the recognition of organic structures or for the early detection of some diseases. During the last decades, polarimetric methods are experiencing an increase of attention in the study of biomedical tissues, and they are nowadays used in such framework to provide qualitative (polarimetric imaging) and quantitative (data processing) information for the studied samples. Polarimetric methods are based on the analysis of polarization modifications produced by lightmatter interactions which can be triggered by a number of complex internal processes but can be roughly understood as the result of the combination of three pure polarimetric features of the sample: its diattenuation, retardance and depolarization. To describe the depolarization sample behavior, we use the Indices of Polarimetric Purity (IPP): related with the randomness of the scattering processes, IPPs provide more information of depolarizing systems than the widely used depolarization index, 𝑃∆, which further synthetizes the depolarization content of samples. As a result, IPPs allow the revelation of some structures from tissue samples (animal and vegetal) hidden in regular intensity images of even in the 𝑃∆ channel, leading to better tissue classification results.

The study of tissue optics is relevant for developing innovative non-invasive diagnostic and therapeutic techniques, and optical phantoms that simulate light propagation processes through soft biological tissue are required to evaluate the performance and calibrate different medical imaging modalities. Liquid lipid based low-cost phantoms were prepared, with cow’s milk as scattering material, Red India ink as the absorbing material and demineralized water as the matrix material since it provides a soft medium biologically compatible with the addition of organic molecules. Two experiments were carried out for characterization of this tissue model. First, collimated and diffuse transmittance and reflectance spectra were measured using phantoms with milk of different fat content. From the data, dependence between: total extinction coefficient, Kubelka Munk’s ratio, absorption and scattering coefficients on the wavelength were estimated. Second, using collimated transmittance measurements the effect of the phantom components was observed. The absorption peak, increases as ink was added to phantoms; and when lipid concentration was varied, by fixed ink, the scattering growths. The extinction coefficient’s dependence on the wavelength was determined, and fluorescence was observed. Results confirm the possibility of spectroscopic identification of milk kinds, as well as the feasibility of low-cost controllable phantom for preliminary biophotonic studies.

Electron-electron correlation is at the origin of complexity in multi-electron systems. Since the total response of a complex system is not the sum of its independent constituents, the many-electron problem remains a computational challenge even though understanding correlation mechanisms is essential for a full control of the electric and magnetic properties of matter. In this work, we disentangle the fingerprints of correlated electron dynamics in the strong laser-atom interaction of the simplest multi-electron system. The two electrons of the helium atom interacting with an intense electromagnetic field represent an extraordinary scenario to explore correlations from a fundamental view, since we can perform a numerical integration of the time-dependent Schrödinger equation. Our theoretical results predict a correlation mechanism of back-reaction showing a distinctive signature in high-order harmonic generation. An extension of the high-harmonic spectra towards higher frequencies encodes the information of back-reaction. This finding demonstrates that correlation phenomena can be tracked with high-harmonic spectroscopy, and opens the possibility to experimentally probe complex systems.

In this scientific work we developed a high-performance in vitro detection system for food allergy in a multiplex serologic IgE format which improves the specificity and selectivity of our biosensors, reducing the cross-reactivity and the matrix-effect in real serum assays. We demonstrated the effectivity of the system for one molecular allergen, with promising results to become a real alternative to existing CRD diagnostic tests based on specific IgE detection. We accomplished a novel assay framework inspired by the chemical and optical properties of SiO2 NPs and by the flexibility of the interferometric Fabry-Perot transducer used which helped us to solve the unspecific adsorption problem in diagnostic test based on specific IgE detection by separating the objective molecule, IgE, from the rest of the serum out of the sensor. The novelty of the methodology lies on the use of a given size of SiO2 NPs as filtering and signal amplification system to separate IgE from IgG and to improve the interferometric optical signal, respectively

La microscopía es una técnica ampliamente usada en multitud de ámbitos tales como la
investigación básica y aplicada en biomedicina o ingeniería. Muchas técnicas de
microscopía emplean luz estructurada junto con técnicas computacionales de
reconstrucción de imágenes. En este trabajo describimos un método de microscopía con
luz estructurada que consiste en acoplar un modulador espacial de luz basado en
microespejos (DMD, acrónimo de la expresión digital micromirror device) a un
microscopio invertido comercial. La fuente de iluminación es una lámpara con ancho de
banda en el visible. El mismo sistema de epi-iluminación del microscopio,
convenientemente desmontado, se utiliza para iluminar el DMD. Un sistema óptico
adicional proyecta los patrones luminosos codificados en el DMD sobre el diafragma de
campo del microscopio. Una cámara CCD convenientemente sincronizada actúa como
dispositivo fotodetector flexible. El objetivo principal del trabajo es validar tecnologías
asequibles para reconstruir imágenes con luz estructurada, realizar tomografía o lograr
otras mejoras en microscopía de fluorescencia. En particular, se desarrollarán técnicas
de imagen basadas en detección integrada con un solo píxel. También se explorarán
técnicas de microscopía de tipo SIM (structured illumination microscopy), que permiten
obtener seccionado óptico y resolución equiparables a las de la microscopía confocal.

Una de las principales aplicaciones de los moduladores espaciales de luz es la simulación de elementos ópticos difractivos, tal como la parte difractiva de las lentes intraoculares multifocales. Previamente, el grupo de investigación llevó a cabo el montaje de un sistema óptico con un modulador de cristal líquido sobre silíceo (LCoS SLM) calibrado para trabajar en régimen solo de fase, con el que se realizó la simulación en banco óptico de una lente bifocal comercial de manera satisfactoria. El presente trabajo utiliza el modulador para el análisis y simulación de una lente trifocal de perfil difractivo sinusoidal de reciente aparición en el mercado. Ya que la forma de este perfil es hasta el momento desconocida, se utiliza un microscopio confocal para obtener la topografía de los anillos difractivos y se caracteriza la eficiencia energética de la lente trifocal a lo largo del espacio imagen. A partir de la información obtenida de la lente comercial, se representa un modelo de perfil sinusoidal en el modulador y se analiza la eficiencia energética de la lente simulada en el banco óptico. La similitud entre los resultados obtenidos con la propia lente versus los obtenidos con el simulador en banco óptico permitirá verificar el modelo de perfil sinusoidal propuesto. Además, el uso del modulador permite modificar algunos parámetros de diseño de la lente, por lo que se podrá buscar suplir algunas de sus limitaciones o proponer un nuevo comportamiento óptico deseado.