Expanding the toolbox for nanoparticle trapping and spectroscopy with holographic optical tweezers

We have developed a workstation based on holographic tweezers to optically trap, move and characterize metal nanoparticles. Our advanced darkfield imaging system allows us to simultaneously image and take spectra of single trapped metal nanoparticles. We take advantage of the beamshaping abilities of the spatial light modulator and correct for aberrations of the trapping optics. We monitor the improvement of the optical trap with video-based nanoparticle tracking. Furthermore we theoretically assess the capabilities and limitations of video-based tracking for nanoparticle position detection, in particular with respect to acquisition frequencies below the corner frequency

Matrimonio y estructura de la élite en la Florencia Renacentista, 1282-1500

Este texto, derivado de una ponencia en una conferencia, es un informe preliminar de un proyecto a larga escala para trazar las transformaciones en las estructuras de las redes de la élite florentina a lo largo de dos siglos. En este artículo me limito únicamente a la descripción de tendencias anteriores, desconocidas en modelos amplios, de los matrimonios cruzados florentinos. Los lectores informados verán inmediatamente que dichas tendencias tienen implicaciones importantes para los debates en la historiografía florentina (que desarrollaré más adelante). En último término, estoy interesado en las implicaciones políticas de las tendencias aquí descritas. Pero por ahora no entro en una interpretación, explicación o argumentación. Trataré únicamente de mostrar hechos nuevos.This conference paper is an interim report from a large-scale project to trace transformations in Florentine elite network structures over two centuries. In this paper, I confine myself solely to a description of previously unknown trends in broad patterns of Florentine inter-marriage. Knowledgeable readers will immediately see that these trends have important implications for debates in Florentine historiography (which I will develop in the future). Ultimately, I am primarily interested in the political implications of the trends I herein describe. But for now I do not engage in interpretation, explanation, or argumentation. I intend simply to lay out some new facts

Introducción a "Matrimonio y Estructura de Élite en la Florencia Renacentista, 1282-1500"

El siguiente texto, salido de una ponencia de conferencia y escrito en 1994 es el primer borrador de un artículo publicado en 2010 en Renaissance Quarterly y llamado "Open Elite? Social Mobility, Marriage, and Family in Florence, 1282-1494." Esta introducción debate las justificaciones metodológicas para publicar un primer borrador, escrito seis años antes del artículo final, más sofisticado. Al descubrir algunos de los pasos del proceso de investigación permite examinar la relación entre los dos estilos de "interpretación" en la historia y el "test de hipótesis" en ciencias sociales.The following conference paper, written in 1994, is the first draft of an article eventually published in 2010 in Renaissance Quarterly, entitled "Open Elite? Social Mobility, Marriage, and Family in Florence, 1282-1494." This introduction discusses the methodological justifications for publishing a first draft, written sixteen years before the final, more sophisticated article. By unveiling some steps of the actual process of research, it allows a discussion of the relationships between the two styles of "interpretation" in history and "testing hypotheses" in social science

Introduction to "Marriage and Elite Structure in Renaissance Florence, 1282-1500"

El siguiente texto, salido de una ponencia de conferencia y escrito en 1994 es el primer borrador de un artículo publicado en el 2010 en Renaissance Quarterly y llamado "Open Elite? Social Mobility, Marriage, and Family in Florence, 1282-1494." Esta introducción debate las justificaciones metodológicas para publicar un primer borrador, escrito seis años antes del artículo final más sofisticado. Al descubrir algunos de los pasos del proceso de investigación permite examinar la relación entre los dos estilos de "interpretación" en la historia y el "test de hipótesis" en ciencias sociales.The following conference paper, written in 1994, is the first draft of an article eventually published in 2010 in Renaissance Quarterly, entitled "Open Elite? Social Mobility, Marriage, and Family in Florence, 1282-1494." This introduction discusses the methodological justifications for publishing a first draft, written sixteen years before the final, more sophisticated article. By unveiling some steps of the actual process of research, it allows a discussion of the relationships between the two styles of "interpretation" in history and "testing hypotheses" in social science

Generalised photon sieves: fine control of complex fields with simple pinhole arrays

Spatial shaping of light beams has led to numerous new applications in fields such as imaging, optical communication, and micromanipulation. However, structured radiation is less well explored beyond visible optics, where methods for shaping fields are more limited. Binary amplitude filters are often used in these regimes and one such example is a photon sieve consisting of an arrangement of pinholes, the positioning of which can tightly focus incident radiation. Here, we describe a method to design generalized photon sieves: arrays of pinholes that generate arbitrary structured complex fields at their foci. We experimentally demonstrate this approach by the production of Airy and Bessel beams, and Laguerre–Gaussian and Hermite–Gaussian modes. We quantify the beam fidelity and photon sieve efficiency, and also demonstrate control over additional unwanted diffraction orders and the incorporation of aberration correction. The fact that these photon sieves are robust and simple to construct will be useful for the shaping of short- or long-wavelength radiation and eases the fabrication challenges set by more intricately patterned binary amplitude masks

Holographic tracking and sizing of optically trapped microprobes in diamond anvil cells

We demonstrate that Digital Holographic Microscopy can be used for accurate 3D tracking and sizing of a colloidal probe trapped in a diamond anvil cell (DAC). Polystyrene beads were optically trapped in water up to Gigapascal pressures while simultaneously recording in-line holograms at 1 KHz frame rate. Using Lorenz-Mie scattering theory to fit interference patterns, we detected a 10% shrinking in the bead’s radius due to the high applied pressure. Accurate bead sizing is crucial for obtaining reliable viscosity measurements and provides a convenient optical tool for the determination of the bulk modulus of probe material. Our technique may provide a new method for pressure measurements inside a DAC

Probabilistic seismic demand modeling of local level response parameters of an RC frame

Probabilistic methods to evaluate the seismic vulnerability of reinforced concrete (RC) frames are largely used in the context of performance based design and assessment, often describing the structural response using global engineering demand parameters (EDPs) such as the maximum interstory drift. While such EDPs are able to synthetically describe the structural behavior, the use of local EDPs is necessary to provide a more realistic and thorough description of failure mechanisms of low-ductility frames lacking seismic details. The objective of this paper is to investigate viable probabilistic seismic demand models of local EDPs, which may be used in developing fragility curves for the assessment of the low-ductility RC frames. The present work explores adequate regression models, probability distributions and uncertainty variation of the demand models. In addition, the adequacy of several ground motion intensity measures (IMs) to be used for predictive modeling of local EDPs is investigated. A realistic benchmark three-story RC frame representative of non-ductile buildings is used as a case study to identify key considerations

Synthesis and Analysis of Entangled Photonic Qubits in Spatial-Parity Space

We present the novel embodiment of a photonic qubit that makes use of one continuous spatial degree of freedom of a single photon and relies on the the parity of the photon's transverse spatial distribution. Using optical spontaneous parametric downconversion to produce photon pairs, we demonstrate the controlled generation of entangled-photon states in this new space. Specifically, two Bell states, and a continuum of their superpositions, are generated by simple manipulation of a classical parameter, the optical-pump spatial parity, and not by manipulation of the entangled photons themselves. An interferometric device, isomorphic in action to a polarizing beam splitter, projects the spatial-parity states onto an even--odd basis. This new physical realization of photonic qubits could be used as a foundation for future experiments in quantum information processing.Comment: 6 pages, 5 figures, submitted to PR