Advantages of digital holographic microscopy for real-time full field absolute phase imaging

Different interferometric techniques were developed last decade to obtain full field, quantitative, and absolute phase imaging, such as phase-shifting, Fourier phase microscopy, Hilbert phase microscopy or digital holographic microscopy (DHM). Although, these techniques are very similar, DHM combines several advantages. In contrast, to phase shifting, DHM is indeed capable of single-shot hologram recording allowing a real-time absolute phase imaging. On the other hand, unlike to Fourier phase or Hilbert phase microscopy, DHM does not require to record in focus images of the specimen on the digital detector (CCD or CMOS camera), because a numerical focalization adjustment can be performed by a numerical wavefront propagation. Consequently, the depth of view of high NA microscope objectives is numerically extended. For example, two different biological cells, floating at different depths in a liquid, can be focalized numerically from the same digital hologram. Moreover, the numerical propagation associated to digital optics and automatic fitting procedures, permits vibrations insensitive full- field phase imaging and the complete compensation for a priori any image distortion or/and phase aberrations introduced for example by imperfections of holders or perfusion chamber. Examples of real-time full-field phase images of biological cells have been demonstrated. ©2008 COPYRIGHT SPIE

Review of quantitative phase-digital holographic microscopy: promising novel imaging technique to resolve neuronal network activity and identify cellular biomarkers of psychiatric disorders.

Quantitative phase microscopy (QPM) has recently emerged as a new powerful quantitative imaging technique well suited to noninvasively explore a transparent specimen with a nanometric axial sensitivity. In this review, we expose the recent developments of quantitative phase-digital holographic microscopy (QP-DHM). Quantitative phase-digital holographic microscopy (QP-DHM) represents an important and efficient quantitative phase method to explore cell structure and dynamics. In a second part, the most relevant QPM applications in the field of cell biology are summarized. A particular emphasis is placed on the original biological information, which can be derived from the quantitative phase signal. In a third part, recent applications obtained, with QP-DHM in the field of cellular neuroscience, namely the possibility to optically resolve neuronal network activity and spine dynamics, are presented. Furthermore, potential applications of QPM related to psychiatry through the identification of new and original cell biomarkers that, when combined with a range of other biomarkers, could significantly contribute to the determination of high risk developmental trajectories for psychiatric disorders, are discussed.

Methods of generating carrier-envelope-phase stabilized, intense, few-cycle laser pulses

Ultrafast laser pulses have become an integral part of the toolbox of countless laboratories doing physics, chemistry, and biological research. The work presented here is motivated by a section in the ever-growing, interdisciplinary research towards understanding the fundamental workings of light-matter interactions. Specifically, attosecond pulses can be useful tools to obtain the desired insight. However access to, and the utility of, such pulses is dependent on the generation of intense, few-cycle, carrier-envelope-phase stabilized laser pulses. The presented work can be thought of as a sort of roadmap towards the latter. From the oscillator which provides the broadband seed to amplification methods, the integral pieces necessary for the generation of attosecond pulses are discussed. A range of topics from the fundamentals to design challenges is presented, outfitting the way towards the practical implementation of an intense few-cycle carrier-envelope-phase stabilized laser source.

Quantitative characterization of multi-phase materials by digital image processing

An automatic image processing and analysis technique has been developed for quantitative characterization of multi-phase materials. For the development of this technique is used the Khoros system that offers the basic morphological tools and a flexible, visual programming language. These techniques are implemented in a highly user oriented image processing environment that allows the user to adapt each step of the processing to his special requirements.To illustrate the implementation and performance of this technique, images of two different materials are processed for microstructure characterization. The result is presented through the determination of volume fraction of the different phases or precipitates.

Simple and versatile heterodyne whole-field interferometer for phase optics characterization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Processamento digital de fotografias aéreas para análise do uso do solo

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Controle digital através de dispositivo FPGA aplicado a um retificador trifásico híbrido operando com modulação por histerese variável

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Processamento digital de imagens para identificação da sigatoka negra em bananais utilizando análise de componentes principais e redes neurais artificiais

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

On the equivalence between the wave-packet phase space representation (WPPSR) and the phase space generated by the squeezed states

We show that the parametrized Wave-Packet Phase Space representation, which has been studied earlier by one of the authors, is equivalent to a Squeezed States Phase Space Representation of quantum mechanics. © 1988.

Modulation Techniques for Multi-Phase Converters and Control Strategies for Multi-Phase Electric Drives

The ever-increasing spread of automation in industry puts the electrical engineer in a central role as a promoter of technological development in a sector such as the use of electricity, which is the basis of all the machinery and productive processes. Moreover the spread of drives for motor control and static converters with structures ever more complex, places the electrical engineer to face new challenges whose solution has as critical elements in the implementation of digital control techniques with the requirements of inexpensiveness and efficiency of the final product. The successfully application of solutions using non-conventional static converters awake an increasing interest in science and industry due to the promising opportunities. However, in the same time, new problems emerge whose solution is still under study and debate in the scientific community During the Ph.D. course several themes have been developed that, while obtaining the recent and growing interest of scientific community, have much space for the development of research activity and for industrial applications. The first area of research is related to the control of three phase induction motors with high dynamic performance and the sensorless control in the high speed range. The management of the operation of induction machine without position or speed sensors awakes interest in the industrial world due to the increased reliability and robustness of this solution combined with a lower cost of production and purchase of this technology compared to the others available in the market. During this dissertation control techniques will be proposed which are able to exploit the total dc link voltage and at the same time capable to exploit the maximum torque capability in whole speed range with good dynamic performance. The proposed solution preserves the simplicity of tuning of the regulators. Furthermore, in order to validate the effectiveness of presented solution, it is assessed in terms of performance and complexity and compared to two other algorithm presented in literature. The feasibility of the proposed algorithm is also tested on induction motor drive fed by a matrix converter. Another important research area is connected to the development of technology for vehicular applications. In this field the dynamic performances and the low power consumption is one of most important goals for an effective algorithm. Towards this direction, a control scheme for induction motor that integrates within a coherent solution some of the features that are commonly required to an electric vehicle drive is presented. The main features of the proposed control scheme are the capability to exploit the maximum torque in the whole speed range, a weak dependence on the motor parameters, a good robustness against the variations of the dc-link voltage and, whenever possible, the maximum efficiency. The second part of this dissertation is dedicated to the multi-phase systems. This technology, in fact, is characterized by a number of issues worthy of investigation that make it competitive with other technologies already on the market. Multiphase systems, allow to redistribute power at a higher number of phases, thus making possible the construction of electronic converters which otherwise would be very difficult to achieve due to the limits of present power electronics. Multiphase drives have an intrinsic reliability given by the possibility that a fault of a phase, caused by the possible failure of a component of the converter, can be solved without inefficiency of the machine or application of a pulsating torque. The control of the magnetic field spatial harmonics in the air-gap with order higher than one allows to reduce torque noise and to obtain high torque density motor and multi-motor applications. In one of the next chapters a control scheme able to increase the motor torque by adding a third harmonic component to the air-gap magnetic field will be presented. Above the base speed the control system reduces the motor flux in such a way to ensure the maximum torque capability. The presented analysis considers the drive constrains and shows how these limits modify the motor performance. The multi-motor applications are described by a well-defined number of multiphase machines, having series connected stator windings, with an opportune permutation of the phases these machines can be independently controlled with a single multi-phase inverter. In this dissertation this solution will be presented and an electric drive consisting of two five-phase PM tubular actuators fed by a single five-phase inverter will be presented. Finally the modulation strategies for a multi-phase inverter will be illustrated. The problem of the space vector modulation of multiphase inverters with an odd number of phases is solved in different way. An algorithmic approach and a look-up table solution will be proposed. The inverter output voltage capability will be investigated, showing that the proposed modulation strategy is able to fully exploit the dc input voltage either in sinusoidal or non-sinusoidal operating conditions. All this aspects are considered in the next chapters. In particular, Chapter 1 summarizes the mathematical model of induction motor. The Chapter 2 is a brief state of art on three-phase inverter. Chapter 3 proposes a stator flux vector control for a three- phase induction machine and compares this solution with two other algorithms presented in literature. Furthermore, in the same chapter, a complete electric drive based on matrix converter is presented. In Chapter 4 a control strategy suitable for electric vehicles is illustrated. Chapter 5 describes the mathematical model of multi-phase induction machines whereas chapter 6 analyzes the multi-phase inverter and its modulation strategies. Chapter 7 discusses the minimization of the power losses in IGBT multi-phase inverters with carrier-based pulse width modulation. In Chapter 8 an extended stator flux vector control for a seven-phase induction motor is presented. Chapter 9 concerns the high torque density applications and in Chapter 10 different fault tolerant control strategies are analyzed. Finally, the last chapter presents a positioning multi-motor drive consisting of two PM tubular five-phase actuators fed by a single five-phase inverter.

Thermoelectric performance of p-type TiCoSb half-Heusler compounds - Intrinsic phase separation and charge carrier concentration optimization as key to high efficiency

The world's rising demand of energy turns the development of sustainable and more efficient technologies for energy production and storage into an inevitable task. Thermoelectric generators, composed of pairs of n-type and p-type semiconducting materials, di¬rectly transform waste heat into useful electricity. The efficiency of a thermoelectric mate¬rial depends on its electronic and lattice properties, summarized in its figure of merit ZT. Desirable are high electrical conductivity and Seebeck coefficients, and low thermal con¬ductivity. Half-Heusler materials are very promising candidates for thermoelectric applications in the medium¬ temperature range such as in industrial and automotive waste heat recovery. The advantage of Heusler compounds are excellent electronic properties and high thermal and mechanical stability, as well as their low toxicity and elemental abundance. Thus, the main obstacle to further enhance their thermoelectric performance is their relatively high thermal conductivity.rn rnIn this work, the thermoelectric properties of the p-type material (Ti/Zr/Hf)CoSb1-xSnx were optimized in a multistep process. The concept of an intrinsic phase separation has recently become a focus of research in the compatible n-type (Ti/Zr/Hf)NiSn system to achieve low thermal conductivities and boost the TE performance. This concept is successfully transferred to the TiCoSb system. The phase separation approach can form a significant alternative to the previous nanostructuring approach via ball milling and hot pressing, saving pro¬cessing time, energy consumption and increasing the thermoelectric efficiency. A fundamental concept to tune the performance of thermoelectric materials is charge carrier concentration optimization. The optimum carrier concentration is reached with a substitution level for Sn of x = 0.15, enhancing the ZT about 40% compared to previous state-of-the-art samples with x = 0.2. The TE performance can be enhanced further by a fine-tuning of the Ti-to-Hf ratio. A correlation of the microstructure and the thermoelectric properties is observed and a record figure of merit ZT = 1.2 at 710°C was reached with the composition Ti0.25Hf0.75CoSb0.85Sn0.15.rnTowards application, the long term stability of the material under actual conditions of operation are an important issue. The impact of such a heat treatment on the structural and thermoelectric properties is investigated. Particularly, the best and most reliable performance is achieved in Ti0.5Hf0.5CoSb0.85Sn0.15, which reached a maximum ZT of 1.1 at 700°C. The intrinsic phase separation and resulting microstructure is stable even after 500 heating and cooling cycles.

Pupil phase apodization for achromatic imaging of extra-solar planets

Direct imaging of extra-solar planets in the visible and infrared region has generated great interest among scientists and the general public as well. However, this is a challenging problem. Diffculties of detecting a planet (faint source) are caused, mostly, by two factors: sidelobes caused by starlight diffraction from the edge of the pupil and the randomly scattered starlight caused by the phase errors from the imperfections in the optical system. While the latter diffculty can be corrected by high density active deformable mirrors with advanced phase sensing and control technology, the optimized strategy for suppressing the diffraction sidelobes is still an open question. In this thesis, I present a new approach to the sidelobe reduction problem: pupil phase apodization. It is based on a discovery that an anti-symmetric spatial phase modulation pattern imposed over a pupil or a relay plane causes diffracted starlight suppression sufficient for imaging of extra-solar planets. Numerical simulations with specific square pupil (side D) phase functions, such as ... demonstrate annulling in at least one quadrant of the diffraction plane to the contrast level of better than 10^12 with an inner working angle down to 3.5L/D (with a = 3 and e = 10^3). Furthermore, our computer experiments show that phase apodization remains effective throughout a broad spectrum (60% of the central wavelength) covering the entire visible light range. In addition to the specific phase functions that can yield deep sidelobe reduction on one quadrant, we also found that a modified Gerchberg-Saxton algorithm can help to find small sized (101 x 101 element) discrete phase functions if regional sidelobe reduction is desired. Our simulation shows that a 101x101 segmented but gapless active mirror can also generate a dark region with Inner Working Distance about 2.8L/D in one quadrant. Phase-only modulation has the additional appeal of potential implementation via active segmented or deformable mirrors, thereby combining compensation of random phase aberrations and diffraction halo removal in a single optical element.

Thickness measurement of dynamic thin liquid films generated by plug-annular flow in non-wetting microchannels

Surface tension forces are significant at millimeter length-scales, causing profoundly different flow morphologies in microchannels than in macroscale flows. The existence and morphology of thin liquid films is particularly relevant for predicting performance and operational stability of devices containing microscale two phase flows. Analytical, computational, and experimental methods previously employed in the study of thin liquid films are discussed. Thicknesses before and after a novel film morphology, referred to as a `shock,' are measured with a novel film thickness measurement technique that uses confocal microscopy. Film thicknesses predicted by previous work are compared to experimental results. Methods for increasing the accuracy of the confocal film thickness measurement technique are discussed.

Proyectos conjuntos entre grupos de investigación y bibliotecas para la preservación digital y la difusión. El caso de un archivo de fuentes primarias de autores destacados

El interés por preservar y difundir digitalmente los materiales de autores destacados de la cultura de un país es un buen motivo de reunión de investigadores humanistas y Bibliotecas universitarias. A partir del ejemplo de gestación del proyecto Archivo ARCAS de fuentes primarias de autores destacados, se muestra la riqueza de interacciones posibles en un escenario marcado por la sinergia que produce el desarrollo de proyectos conjuntos. Se exponen los antecedentes y se presentan los actores intervinientes. Se detallan las principales decisiones que la FaHCE (UNLP) / IdIHCS (UNLP-CONICET) y su Biblioteca han debido tomar teniendo en cuenta su organización, la disponibilidad de recursos humanos y la base tecnológica existente para que el proyecto pueda prosperar. Luego, a un nivel más técnico, se consignan las principales características del prototipo generado y de su primera fase de implementación. Finalmente, se concluye enunciando los desafíos a futuro que el proyecto demandará, considerando la construcción de una plataforma integrada de fuentes primarias que contemple las necesidades de grupos de investigación con perfiles heterogéneos