Holography, tomography and 3D microscopy as linear filtering operations

In this paper we characterise 3D optical imaging techniques as 3D linear shift invariant filtering operations. From the Helmholtz equation that is the basis of scalar diffraction theory we show that the scattered field, or indeed a holographic reconstruction of this field, can be considered to be the result of a linear filtering operation applied to a source distribution. We note that if the scattering is weak, the source distribution is independent of the scattered field and a holographic reconstruction (or in fact any far-field optical imaging system) behaves as a 3D linear shift invariant filter applied to the refractive index contrast (which effectively defines the object). We go on to consider tomographic techniques that synthesise images from recordings of the scattered field using different illumination conditions. In our analysis we compare the 3D response of monochromatic optical tomography with the 3D imagery offered by confocal microscopy and scanning white light interferometry (using with quassi-monochromatic illumination) and explain the circumstances in which these approaches are equivalent. Finally, we consider the 3D response of polychromatic optical tomography and in particular the response of spectral optical coherence tomography and scanning white light interferometry

Optical diffraction tomography in fluid velocimetry: the use of a priori information

Holographic Particle Image Velocimetry (HPIV) has been used successfully to make threedimensional, three-component flow measurements from holographic recordings of seeded fluid. It is clear that measurements can only be made in regions that contain particles, but simply adding more seeding results in poor quality images that suffer from the effects of multiple scattering. Optical Diffraction Tomography provides a means to reconstruct a 3D map of refractive index from coherent recordings of scattered fields with different illumination conditions. Although the Born Approximation limits the applicability of the technique to weakscattering problems, this approach has been used to create three-dimensional images using a Digital Holographic Microscope (DHM). A non-linear optimization technique, the Conjugated Gradient optimisation Method (CGM) has been previously proposed in microwave imaging for strong scattering problems. In this paper we propose a modification of the CGM which uses apriori information to reduce the number of unknown variables that characterize the object to the position of the seeders. Some 2D numerical experiments have been computed, showing promising results and the value of these is fluid velocimetry is discussed

Comparative Analysis of Tolerances Allocation in Mechanical Assemblies based on Cost-tolerance Curves

El presente trabajo propone un método para la determinación de los valores de las tolerancias individuales de las piezas que forman un conjunto ensamblado a partir de valores de tolerancias especificados en el conjunto final, optimizando el coste total de fabricación de las piezas individuales a partir de funciones de coste-tolerancia basadas en el proceso de fabricación de cada una de ellas. Para ello se parte de los principales trabajos desarrollados en la línea de asignación de tolerancias y se realiza la propuesta del modelo de trabajo, basado en la optimización de costes a partir de la aplicación del método de los multiplicadores de Lagrange a diversas curvas de coste-toleranci

La poesía de cancionero en "La Celestina": 'oh, hideputa el trovador'

Resumen: La Celestina es una obra miscelánea en que las canciones, como los proverbios y otras citas cultas vienen «entrejeridas» de tal forma que el efecto final aparece difícilmente comprensible sin tener en cuenta el ambiente goliárdico universitario. Para entender el papel que los cancioneros desempeñan en la obra se observan las reacciones de los criados a los versos de Calisto y sus juicios y propuestas de otra forma de literatura.Palabras clave: Celestina. Miscelánea. Cancioneros. Goliárdico. Donaire.Abstract: La Celestina is a miscellaneous work, where you will find «entrejeridas» songs, as well as proverbs and literary quotes, where the final effect is barely comprehensible to the reader if they are taken out of universitary context. Observing the servants' reactions to Calisto's verses and their judgements and proposals for a different form of literature allows us to better understand what functions these songs fulfill.Keywords: Celestina. Miscellany. Cancioneros. Goliardic. Grace

High performance computing for a 3-D optical diffraction tomographic application in fluid velocimetry

Optical Diffraction Tomography has been recently introduced in fluid velocimetry to provide three dimensional information of seeding particle locations. In general, image reconstruction methods at visible wavelengths have to account for diffraction. Linear approximation has been used for three-dimensional image reconstruction, but a non-linear and iterative reconstruction method is required when multiple scattering is not negligible. Non-linear methods require the solution of the Helmholtz equation, computationally highly demanding due to the size of the problem. The present work shows the results of a non-linear method customized for spherical particle location using GPU computing and a made-to-measure storing format

Versatile hollow fluorescent metal-silica nanohybrids through a modified microemulsion synthesis route

Silica-metal nanohybrids are common materials for applications in biomedicine, catalysis or sensing. Also, hollow structures are of interest as they provide additional useful features. However, in these materials the control of the size and accessibility to the inner regions of the structure usually requires complex synthesis procedures. Here we report a simple colloidal procedure for synthesizing hollow silica-metal nanohybrids, driven by the diffusion of metal precursors through the porous silica shell and subsequent reduction in aqueous solutions. The formation of hollow nanoparticles is controlled by the colloidal conditions during synthesis, which affect the ripening of hollow nanoparticles in presence of organosilanes. The modification of the conditions during synthesis affected the growth of silica precursors in presence of fluorescein isothiocyanate (FITC). The limited access to water molecules during the hydrolysis of silica precursors is attributed to the hydrophobicity of organic fluorescent molecules linked to the condensing silica clusters at the initial stages of nanoparticle formation and to the limitation of water content in the microemulsion method used. Finally, the growth of metal nanoseeds at the core of hollow nanoparticles can be easily achieved though a simple method in aqueous environment. The pH and thermal conditions during the reduction process affect the formation of metal-silica nanohybrids and their structural features

Influence of the Lubrication Conditions on the Surface Finish of Turned Aeronautical Aluminium Alloys. A preliminary Study

Nowadays, one of the main objectives that affects the development of any new product is the respect for the environment. Until the late 80's, the development and manufacture of the most of the product were aimed to achieve maximum quality in time and costs with environmental issues relegated to secondary importance. On the other hand, in the 90's, the pressure from factors such as markets, financial and legislative factors, led to environmental considerations being taken into account. In this context, the current aeronautical industry strategies are based on the search for economic, environmental and energy efficiency considerations for all the processes involved in the aircraft manufacturing

Synthesis and characterization of fluorescent hollow silica nanoparticles: Control of size and metal incorporation for several nanotechnology applications

En el mundo de los nanomateriales la sílice es uno de los compuestos mas estudiados debido a sus propiedades y la versatilidad que ofrece en cuanto aplicaciones. En este proyecto se desarrolla un nuevo método de obtención de sílice funcionalizada con moléculas fluorescentes y nanoparticulas metálicas lo cual le confiere al material nuevas propiedades que lo hacen válido para uso como marcadores, catálisis, aplicaciones biómedicas..

Fast and simple assessment of surface contamination in operations involving nanomaterials

The deposition of airborne nanosized matter onto surfaces could pose a potential risk in occupational and environmental scenarios. The incorporation of fluorescent labels, namely fluorescein isotiocyanate (FITC) or tris-1, 3-phenanthroline ruthenium (II) chloride (Ru(phen)3Cl2), into spherical 80-nm silica nanoparticles allowed the detection after the illumination with LED light of suitable wavelength (365 or 405 nm respectively). Monodisperse nanoparticle aerosols from fluorescently labeled nanoparticles were produced under safe conditions using powder generators and the deposition was tested into different surfaces and filtering media. The contamination of gloves and work surfaces that was demonstrated by sampling and SEM analysis becomes immediately clear under laser or LED illumination. Furthermore, nanoparticle aerosols of about 105 nanoparticles/cm3 were alternatively fed through a glass pipe and personal protective masks to identify the presence of trapped nanoparticles under 405 nm or 365 nm LED light. This testing procedure allowed a fast and reliable estimation of the contamination of surfaces with nanosized matter, with a limit of detection based on the fluorescence emission of the accumulated solid nanoparticles of 40 ng of Ru(phen)3@SiO2 of silica per mg of non-fluorescent matter