Hunting spectro-temporal information in unevenly spaced paleoclimate time series

18 p.

Design strategies for ultra-high efficiency photovoltaics

While concentrator photovoltaic cells have shown significant improvements in efficiency in the past ten years, once these cells are integrated into concentrating optics, connected to a power conditioning system and deployed in the field, the overall module efficiency drops to only 34 to 36%. This efficiency is impressive compared to conventional flat plate modules, but it is far short of the theoretical limits for solar energy conversion. Designing a system capable of achieving ultra high efficiency of 50% or greater cannot be achieved by refinement and iteration of current design approaches.

This thesis takes a systems approach to designing a photovoltaic system capable of 50% efficient performance using conventional diode-based solar cells. The effort began with an exploration of the limiting efficiency of spectrum splitting ensembles with 2 to 20 sub cells in different electrical configurations. Incorporating realistic non-ideal performance with the computationally simple detailed balance approach resulted in practical limits that are useful to identify specific cell performance requirements. This effort quantified the relative benefit of additional cells and concentration for system efficiency, which will help in designing practical optical systems.

Efforts to improve the quality of the solar cells themselves focused on the development of tunable lattice constant epitaxial templates. Initially intended to enable lattice matched multijunction solar cells, these templates would enable increased flexibility in band gap selection for spectrum splitting ensembles and enhanced radiative quality relative to metamorphic growth. The III-V material family is commonly used for multijunction solar cells both for its high radiative quality and for the ease of integrating multiple band gaps into one monolithic growth. The band gap flexibility is limited by the lattice constant of available growth templates. The virtual substrate consists of a thin III-V film with the desired lattice constant. The film is grown strained on an available wafer substrate, but the thickness is below the dislocation nucleation threshold. By removing the film from the growth substrate, allowing the strain to relax elastically, and bonding it to a supportive handle, a template with the desired lattice constant is formed. Experimental efforts towards this structure and initial proof of concept are presented.

Cells with high radiative quality present the opportunity to recover a large amount of their radiative losses if they are incorporated in an ensemble that couples emission from one cell to another. This effect is well known, but has been explored previously in the context of sub cells that independently operate at their maximum power point. This analysis explicitly accounts for the system interaction and identifies ways to enhance overall performance by operating some cells in an ensemble at voltages that reduce the power converted in the individual cell. Series connected multijunctions, which by their nature facilitate strong optical coupling between sub-cells, are reoptimized with substantial performance benefit.

Photovoltaic efficiency is usually measured relative to a standard incident spectrum to allow comparison between systems. Deployed in the field systems may differ in energy production due to sensitivity to changes in the spectrum. The series connection constraint in particular causes system efficiency to decrease as the incident spectrum deviates from the standard spectral composition. This thesis performs a case study comparing performance of systems over a year at a particular location to identify the energy production penalty caused by series connection relative to independent electrical connection.

Computational Predictions of G Protein-Coupled Receptor Structures and Binding Sites

G protein-coupled receptors (GPCRs) are the largest family of proteins within the human genome. They consist of seven transmembrane (TM) helices, with a N-terminal region of varying length and structure on the extracellular side, and a C-terminus on the intracellular side. GPCRs are involved in transmitting extracellular signals to cells, and as such are crucial drug targets. Designing pharmaceuticals to target GPCRs is greatly aided by full-atom structural information of the proteins. In particular, the TM region of GPCRs is where small molecule ligands (much more bioavailable than peptide ligands) typically bind to the receptors. In recent years nearly thirty distinct GPCR TM regions have been crystallized. However, there are more than 1,000 GPCRs, leaving the vast majority of GPCRs with limited structural information. Additionally, GPCRs are known to exist in a myriad of conformational states in the body, rendering the static x-ray crystal structures an incomplete reflection of GPCR structures. In order to obtain an ensemble of GPCR structures, we have developed the GEnSeMBLE procedure to rapidly sample a large number of variations of GPCR helix rotations and tilts. The lowest energy GEnSeMBLE structures are then docked to small molecule ligands and optimized. The GPCR family consists of five subfamilies with little to no sequence homology between them: class A, B1, B2, C, and Frizzled/Taste2. Almost all of the GPCR crystal structures have been of class A GPCRs, and much is known about their conserved interactions and binding sites. In this work we particularly focus on class B1 GPCRs, and aim to understand that family’s interactions and binding sites both to small molecules and their native peptide ligands. Specifically, we predict the full atom structure and peptide binding site of the glucagon-like peptide receptor and the TM region and small molecule binding sites for eight other class B1 GPCRs: CALRL, CRFR1, GIPR, GLR, PACR, PTH1R, VIPR1, and VIPR2. Our class B1 work reveals multiple conserved interactions across the B1 subfamily as well as a consistent small molecule binding site centrally located in the TM bundle. Both the interactions and the binding sites are distinct from those seen in the more well-characterized class A GPCRs, and as such our work provides a strong starting point for drug design targeting class B1 proteins. We also predict the full structure of CXCR4 bound to a small molecule, a class A GPCR that was not closely related to any of the class A GPCRs at the time of the work.

Collective behavior of asperities as a model for friction and adhesion

Understanding friction and adhesion in static and sliding contact of surfaces is important in numerous physical phenomena and technological applications. Most surfaces are rough at the microscale, and thus the real area of contact is only a fraction of the nominal area. The macroscopic frictional and adhesive response is determined by the collective behavior of the population of evolving and interacting microscopic contacts. This collective behavior can be very different from the behavior of individual contacts. It is thus important to understand how the macroscopic response emerges from the microscopic one. In this thesis, we develop a theoretical and computational framework to study the collective behavior. Our philosophy is to assume a simple behavior of a single asperity and study the collective response of an ensemble. Our work bridges the existing well-developed studies of single asperities with phenomenological laws that describe macroscopic rate-and-state behavior of frictional interfaces. We find that many aspects of the macroscopic behavior are robust with respect to the microscopic response. This explains why qualitatively similar frictional features are seen for a diverse range of materials. We first show that the collective response of an ensemble of one-dimensional independent viscoelastic elements interacting through a mean field reproduces many qualitative features of static and sliding friction evolution. The resulting macroscopic behavior is different from the microscopic one: for example, even if each contact is velocity-strengthening, the macroscopic behavior can be velocity-weakening. The framework is then extended to incorporate three-dimensional rough surfaces, long- range elastic interactions between contacts, and time-dependent material behaviors such as viscoelasticity and viscoplasticity. Interestingly, the mean field behavior dominates and the elastic interactions, though important from a quantitative perspective, do not change the qualitative macroscopic response. Finally, we examine the effect of adhesion on the frictional response as well as develop a force threshold model for adhesion and mode I interfacial cracks.

A fully-nonlocal energy-based formulation and high-performance realization of the quasicontinuum method

The quasicontinuum (QC) method was introduced to coarse-grain crystalline atomic ensembles in order to bridge the scales from individual atoms to the micro- and mesoscales. Though many QC formulations have been proposed with varying characteristics and capabilities, a crucial cornerstone of all QC techniques is the concept of summation rules, which attempt to efficiently approximate the total Hamiltonian of a crystalline atomic ensemble by a weighted sum over a small subset of atoms. In this work we propose a novel, fully-nonlocal, energy-based formulation of the QC method with support for legacy and new summation rules through a general energy-sampling scheme. Our formulation does not conceptually differentiate between atomistic and coarse-grained regions and thus allows for seamless bridging without domain-coupling interfaces. Within this structure, we introduce a new class of summation rules which leverage the affine kinematics of this QC formulation to most accurately integrate thermodynamic quantities of interest. By comparing this new class of summation rules to commonly-employed rules through analysis of energy and spurious force errors, we find that the new rules produce no residual or spurious force artifacts in the large-element limit under arbitrary affine deformation, while allowing us to seamlessly bridge to full atomistics. We verify that the new summation rules exhibit significantly smaller force artifacts and energy approximation errors than all comparable previous summation rules through a comprehensive suite of examples with spatially non-uniform QC discretizations in two and three dimensions. Due to the unique structure of these summation rules, we also use the new formulation to study scenarios with large regions of free surface, a class of problems previously out of reach of the QC method. Lastly, we present the key components of a high-performance, distributed-memory realization of the new method, including a novel algorithm for supporting unparalleled levels of deformation. Overall, this new formulation and implementation allows us to efficiently perform simulations containing an unprecedented number of degrees of freedom with low approximation error.

Technology for Single Cell Protein Analysis in Immunology and Cancer Prognostics

The first chapter of this thesis deals with automating data gathering for single cell microfluidic tests. The programs developed saved significant amounts of time with no loss in accuracy. The technology from this chapter was applied to experiments in both Chapters 4 and 5.

The second chapter describes the use of statistical learning to prognose if an anti-angiogenic drug (Bevacizumab) would successfully treat a glioblastoma multiforme tumor. This was conducted by first measuring protein levels from 92 blood samples using the DNA-encoded antibody library platform. This allowed the measure of 35 different proteins per sample, with comparable sensitivity to ELISA. Two statistical learning models were developed in order to predict whether the treatment would succeed. The first, logistic regression, predicted with 85% accuracy and an AUC of 0.901 using a five protein panel. These five proteins were statistically significant predictors and gave insight into the mechanism behind anti-angiogenic success/failure. The second model, an ensemble model of logistic regression, kNN, and random forest, predicted with a slightly higher accuracy of 87%.

The third chapter details the development of a photocleavable conjugate that multiplexed cell surface detection in microfluidic devices. The method successfully detected streptavidin on coated beads with 92% positive predictive rate. Furthermore, chambers with 0, 1, 2, and 3+ beads were statistically distinguishable. The method was then used to detect CD3 on Jurkat T cells, yielding a positive predictive rate of 49% and false positive rate of 0%.

The fourth chapter talks about the use of measuring T cell polyfunctionality in order to predict whether a patient will succeed an adoptive T cells transfer therapy. In 15 patients, we measured 10 proteins from individual T cells (~300 cells per patient). The polyfunctional strength index was calculated, which was then correlated with the patient's progress free survival (PFS) time. 52 other parameters measured in the single cell test were correlated with the PFS. No statistical correlator has been determined, however, and more data is necessary to reach a conclusion.

Finally, the fifth chapter talks about the interactions between T cells and how that affects their protein secretion. It was observed that T cells in direct contact selectively enhance their protein secretion, in some cases by over 5 fold. This occurred for Granzyme B, Perforin, CCL4, TNFa, and IFNg. IL- 10 was shown to decrease slightly upon contact. This phenomenon held true for T cells from all patients tested (n=8). Using single cell data, the theoretical protein secretion frequency was calculated for two cells and then compared to the observed rate of secretion for both two cells not in contact, and two cells in contact. In over 90% of cases, the theoretical protein secretion rate matched that of two cells not in contact.

Photochemical electron transfer at fixed distance : a synthetic model of the photosynthetic primary process

A series of meso-phenyloctamethylporphyrins covalently bonded at the 4'phenyl position to quinones via rigid bicyclo[2.2.2]octane spacers were synthesized for the study of the dependence of electron transfer reaction rate on solvent, distance, temperature, and energy gap. A general and convergent synthesis was developed based on the condensation of ac-biladienes with masked quinonespacer-benzaldehydes. From picosecond fluorescence spectroscopy emission lifetimes were measured in seven solvents of varying polarity. Rate constants were determined to vary from 5.0x10⁹sec^-1 in N,N-dimethylformamide to 1.15x10¹⁰ Sec^-1 in benzene, and were observed to rise at most by about a factor of three with decreasing solvent polarity. Experiments at low temperature in 2-MTHF glass (77K) revealed fast, nearly temperature-independent electron transfer characterized by non-exponential fluorescence decays, in contrast to monophasic behavior in fluid solution at 298K. This example evidently represents the first photosynthetic model system not based on proteins to display nearly temperature-independent electron transfer at high temperatures (nuclear tunneling). Low temperatures appear to freeze out the rotational motion of the chromophores, and the observed nonexponential fluorescence decays may be explained as a result of electron transfer from an ensemble of rotational conformations. The nonexponentiality demonstrates the sensitivity of the electron transfer rate to the precise magnitude of the electronic matrix element, which supports the expectation that electron transfer is nonadiabatic in this system. The addition of a second bicyclooctane moiety (15 Å vs. 18 Å edge-to-edge between porphyrin and quinone) reduces the transfer rate by at least a factor of 500-1500. Porphyrinquinones with variously substituted quinones allowed an examination of the dependence of the electron transfer rate constant κ_ET on reaction driving force. The classical trend of increasing rate versus increasing exothermicity occurs from 0.7 eV≤ |ΔG^0'(R)| ≤ 1.0 eV until a maximum is reached (κ_ET = 3 x 10⁸ sec^-1 rising to 1.15 x 10¹⁰ sec^-1 in acetonitrile). The rate remains insensitive to ΔG⁰ for ~ 300 mV from 1.0 eV≤ |ΔG^0’(R)| ≤ 1.3 eV, and then slightly decreases in the most exothermic case studied (cyanoquinone, κ_ET = 5 x 10⁹ sec^-1).

A multiple scattering problem

The present work deals with the problem of the interaction of the electromagnetic radiation with a statistical distribution of nonmagnetic dielectric particles immersed in an infinite homogeneous isotropic, non-magnetic medium. The wavelength of the incident radiation can be less, equal or greater than the linear dimension of a particle. The distance between any two particles is several wavelengths. A single particle in the absence of the others is assumed to scatter like a Rayleigh-Gans particle, i.e. interaction between the volume elements (self-interaction) is neglected. The interaction of the particles is taken into account (multiple scattering) and conditions are set up for the case of a lossless medium which guarantee that the multiple scattering contribution is more important than the self-interaction one. These conditions relate the wavelength λ and the linear dimensions of a particle a and of the region occupied by the particles D. It is found that for constant λ/a, D is proportional to λ and that |Δχ|, where Δχ is the difference in the dielectric susceptibilities between particle and medium, has to lie within a certain range.

The total scattering field is obtained as a series the several terms of which represent the corresponding multiple scattering orders. The first term is a single scattering term. The ensemble average of the total scattering intensity is then obtained as a series which does not involve terms due to products between terms of different orders. Thus the waves corresponding to different orders are independent and their Stokes parameters add.

The second and third order intensity terms are explicitly computed. The method used suggests a general approach for computing any order. It is found that in general the first order scattering intensity pattern (or phase function) peaks in the forward direction Θ = 0. The second order tends to smooth out the pattern giving a maximum in the Θ = π/2 direction and minima in the Θ = 0 , Θ = π directions. This ceases to be true if ka (where k = 2π/λ) becomes large (> 20). For large ka the forward direction is further enhanced. Similar features are expected from the higher orders even though the critical value of ka may increase with the order.

The first order polarization of the scattered wave is determined. The ensemble average of the Stokes parameters of the scattered wave is explicitly computed for the second order. A similar method can be applied for any order. It is found that the polarization of the scattered wave depends on the polarization of the incident wave. If the latter is elliptically polarized then the first order scattered wave is elliptically polarized, but in the Θ = π/2 direction is linearly polarized. If the incident wave is circularly polarized the first order scattered wave is elliptically polarized except for the directions Θ = π/2 (linearly polarized) and Θ = 0, π (circularly polarized). The handedness of the Θ = 0 wave is the same as that of the incident whereas the handedness of the Θ = π wave is opposite. If the incident wave is linearly polarized the first order scattered wave is also linearly polarized. The second order makes the total scattered wave to be elliptically polarized for any Θ no matter what the incident wave is. However, the handedness of the total scattered wave is not altered by the second order. Higher orders have similar effects as the second order.

If the medium is lossy the general approach employed for the lossless case is still valid. Only the algebra increases in complexity. It is found that the results of the lossless case are insensitive in the first order of k_imD where k_im = imaginary part of the wave vector k and D a linear characteristic dimension of the region occupied by the particles. Thus moderately extended regions and small losses make (k_imD)² ≪ 1 and the lossy character of the medium does not alter the results of the lossless case. In general the presence of the losses tends to reduce the forward scattering.

Activaciones patrimoniales e iniciativas museísticas: ¿por quién? y ¿para qué?

[ES] Se suele afirmar que hay dos tipos de patrimonio cultural. Uno, “eterno”, “riguroso”, “irremplazable” o “global”; otro, “contingente”, “flexible”; “sustituible” o “local”. El primero es de la “humanidad”; el segundo, de la “comunidad”. Los trabajos que se presentan en esta publicación, describen y analizan procesos de activación de ese segundo tipo de patrimonio: los intereses y las valorizaciones que han conducido a la patrimonialización o puesta en valor de unos bienes culturales; qué agentes han intervenido en ese proceso; por qué, para qué y cómo lo han llevado a cabo. Se interesan más por el modus operandi que por el opus operatum. Escritos por profesores, investigadores, especialistas y técnicos, los trabajos de esta publicación presentan un conjunto de experiencias europeas y americanas, mostrando un panorama diverso y complejo del campo patrimonial y museístico, así como distintas aproximaciones en función de la posición que ocupa el autor respecto a los bienes culturales.

La Tipología Analítica aplicada al estudio de materiales líticos de época histórica

Homenaje a Georges Laplace, realizado en Vitoria-Gasteiz el 13, 14 y 15 de noviembre de 2012. Edición a cargo de Aitor Calvo, Aitor Sánchez, Maite García-Rojas y Mónica Alonso-Eguíluz.

Análise comparativa dos instrumentos de gestão em Unidades de Conservação visando a gestão participativa no Cone Sul

A influência humana sobre as unidades de conservação (UCs) deve ser considerada a partir de modelos mais amplos, entendendo que há influência dos processos sociais nas mesmas e que essa é uma dimensão a ser discutida no âmbito das práticas de proteção da natureza. É importante que seja levado em consideração na criação, na ampliação e na gestão de uma UC a participação dos atores envolvidos direta e indiretamente, já que o quadro mundial indica ser uma tendência a criação de novas áreas e o envolvimento da sociedade neste processo. Ante esta realidade objetivou-se, nesta tese, contribuir para o fortalecimento da gestão participativa em UCs no Cone Sul, aqui definido como o conjunto de quatro países: Brasil, Argentina, Uruguai e Chile e tendo como estudo de caso quatro áreas protegidas: Parque Nacional do Itatiaia - Brasil, Parque Nacional Lago Puelo - Argentina, Santuário da Natureza Parque Pumalín - Chile e Paisagem Protegida Lagoa de Rocha Uruguai. Tendo por base os instrumentos de gestão em unidades de conservação no Brasil: plano de manejo, zona de amortecimento, educação ambiental e conselho gestor e sendo os mesmos determinados por normas legais (Leis, Decretos, Resoluções, Instruções Normativas) tais normas foram analisadas e comparadas com a finalidade de averiguar se nos países estudados estes instrumentos eram determinados legalmente, da mesma forma como são no Brasil, bem como se a vertente participativa estava presente nesta determinação. Após verificou-se se na Argentina, no Uruguai e no Chile havia a aplicação dos mesmos instrumentos de gestão em áreas protegidas que no Brasil; bem como foi averiguada a situação dos mesmos nos estudos de caso tendo por base a vertente participativa. Depois houve a contextualização e apresentação das dificuldades na gestão e das pressões sofridas pelas áreas protegidas buscando trazer à tona a realidade em que estão inseridas e das quais compartilham. Para tanto se utilizou de levantamentos bibliográficos, documentais, entrevistas semi-estruturadas com pessoas que tiveram experiências práticas com o problema pesquisado e os estudos de caso. Constatou-se que a determinação legal de instrumentos que propiciem a participação não é, via de regra, essencial para efetivar a gestão participativa da UC, mas a existência dos mesmos sim. Verificou-se que um bom resultado está atrelado às qualidades técnicas e subjetivas da gestão e também dos gestores, que podem ajudar e muito na gestão participativa, juntamente com uma parceria bem fortalecida.

Desarrollo de un prototipo de exoesqueleto básico activado con una señal cerebral.

[ES]En este documento se estudia el desarrollo de una aplicación electrónica para la ayuda a gente con movilidad reducida a través de unos sensores cerebrales que permitan el análisis de la iniciativa de la persona a realizar acciones que de otra manera no podría realizar. El concepto completo consiste en el diseño del sensor que el paciente se colocaría en la cabeza, el tratamiento de la información extraída y la actuación por medio de una solución mecánica, como un conjunto cilindro-pistón para el futuro desarrollo de un sistema de ayuda a la movilidad.

Jean-Jacques Rousseau: por uma ética das virtudes

No âmbito da discussão filosófica sobre a moral, é possível perceber, nas últimas três décadas, um novo interesse pela denominada ética das virtudes. A ética das virtudes diz respeito a uma longa tradição de investigação moral que tem no conceito de virtudes, por oposição aos conceitos de leis, princípios, ou direitos, uma de suas ideias mais fundamentais. O objetivo desta dissertação de mestrado é elucidar de que forma o pensamento político e moral de Jean-Jacques Rousseau, ainda no contexto do Iluminismo, preserva os argumentos centrais da tradição da ética das virtudes. Embora Alasdair MacIntyre tenha contribuído bastante para o ressurgimento do interesse filosófico pela ética das virtudes, mostro nesta dissertação que as críticas que ele dirige de maneira generalizada ao Iluminismo não se aplicam de modo inteiramente adequado à posição que Rousseau efetivamente defende em seus escritos filosóficos. A obra de Rousseau é bastante vasta e, ao considerarmos alguns textos isoladamente, os argumentos que Rousseau apresenta parecem pouco sistemáticos. No entanto, como mostro na presente dissertação, ao analisarmos a obra de Rousseau como todo, fica bastante claro o quão a filosofia moral de Rousseau permanece fundamentalmente uma investigação sobre virtudes.

Iventividade, atividade de trabalho e transtornos mentais graves: um ensaio no campo da cognição

Esta dissertação consiste em uma investigação acerca do conceito de atividade dirigida, pertencente à Clínica da Atividade e dos Meios de Trabalho, proposta por Y. Clot e D. Faïta, no sentido de verificar a sua pertinência para uma Psicologia da Inventividade. Trata-se da utilização da categoria de ritornelo para analisar os pressupostos teóricos do conceito de atividade dirigida, no que tange à cognição. A categoria ritornelo está relacionada a um conjunto de materiais apontados como relevantes para se pensar a questão da invenção: trata-se da Esquizoanálise, proposta por G. Deleuze & F. Guattari. A investigação foi realizada a partir de um caso clínico observado pelo pesquisador, que acompanhou um usuário de um Serviço de Saúde Mental, do município do Rio de Janeiro, Brasil, em seu trabalho como padeiro em uma cooperativa de culinária. Apesar de lidar bem com situações mais rotineiras, esse usuário demonstrava ter muita dificuldade em lidar com as variabilidades do meio, com situações que fugiam à sua rotina, apresentando um nível de ansiedade que o impedia de realizar quaisquer tarefas. Criou-se um projeto de atuação clínica que tinha como foco solicitar que ele explicitasse verbalmente o que o afligia, descrevendo todas as situações ansiogênicas, buscando, juntamente com esse paciente, encaminhamentos para tais situações. Ao final de seis meses, o paciente conseguia lidar com os imprevisíveis pertinentes à atividade, laborativa ou não. Foram realizadas duas análises deste caso clínico. Na primeira, utilizou-se a categoria de ritornelo e na segunda, o conceito de atividade dirigida. Finalmente, a segunda análise foi articulada à primeira, com o objetivo de investigar as possibilidades de sinergia entre uma e outra. Dentre as conclusões, observou-se que a construção de um dispositivo dialógico sobre as dificuldades de lidar com o não-rotineiro elemento inerente à vida, e à vida no trabalho pode ser terapeuticamente frutífero na medida em que sua atividade linguageira acerca das dificuldades vividas apresentou-se como objeto de co-análise, alimentando variações no processo de trabalho. Além disso, ritornelo e atividade dirigida articularam-se no nível dos processos de territorialização e desterritorialização propostos por Deleuze & Guattari. A atividade dirigida auxiliou no sentido de ser uma ferramenta relevante para encontrar outros modos de proceder, conectando distantes gêneros, de modo que o mais pleno faça crescer aquele que se encontra precário, atendendo ao 2 e 3 princípios do rizoma postulados por Deleuze & Guattari.

Mobilização do corpo-si na gestão da atividade de motoristas de ambulâncias

Esta tese busca explorar as possibilidades contidas do corpo na gestão da atividade de trabalho de motoristas de ambulâncias. Trata-se de uma concepção de corpo, não oponente a alma, que se notabiliza pelo pensamento, pela inteligência, pelo sistema nervoso, pela história: um corpo-si. O diálogo mantido com a perspectiva ergológica, aqui convocada, opera-se a partir da concepção de vida, saúde-doença em George Canguilhem, da contribuição ergonômica, dos referenciais da linguagem e trabalho e da etnografia. Para configuração do campo empírico, adotaram-se métodos e técnicas apropriados de pesquisa em situação concreta de trabalho, denominadas visitas, instrumentalizadas com técnicas de entrevistas dialógicas e observações da atividade, além de uma pesquisa bibliográfica e análise global do trabalho. A pesquisa contou com a participação de motoristas de UTI móvel de uma empresa de transportes de ambulâncias da cidade do Rio de Janeiro. A análise das situações de trabalho foi inspirada na ergonomia da atividade e nas contribuições da perspectiva dialógica. Dentre os resultados obtidos destacamos: problemas de comunicação na relação de trabalho entre motoristas e a Central de Atendimento (Call Center), estado de má conservação e de desconforto das ambulâncias, riscos de doenças no contato com o usuário, insuficiência salarial e atraso no pagamento, indeterminação de pausas durante a jornada, contraintes temporais decorrentes da pilotagem em casos de urgência e emergência, ameaças de multas por excesso de velocidade, além de obstáculos emanados do trânsito: engarrafamentos, barulhos, semáforos, etc. Enfim, um conjunto de variabilidades e infidelidades do meio de trabalho, que permite aos motoristas produzirem novos usos de si, porque mobilizam a integralidade do corpo para chegar a modos operatórios que deem conta dessas situações de trabalho, considerando, sobretudo, a gestão da dinâmica entre as exigências de produtividade e qualidade com saúde, segurança e fiabilidade.