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‣ As imagens em movimento e sua contribuição para o ensino das ciências físicas no Brasil - 1800 a 1960; The motion pictures and their contribution to physics sciences teaching in Brazil from 1800 through 1960

Bonetti, Marcelo de Carvalho
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/05/2013 Português
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Neste trabalho pretendemos apresentar elementos históricos dos caminhos percorridos pela educação e pelos audiovisuais no Brasil, dos que vieram importados e daquelas que foram produzidas aqui e, que retrataram temas correlatos ao ensino da Física, buscando elementos desta trajetória desde o Império com a chegada ao Brasil das primeiras imagens animadas, até aqueles produzidos especificamente para projetos de ensino de Física empregados no Brasil na década de 1960. Procuramos identificar as transformações e as políticas educacionais desde o império no Brasil até a década de 1960, quando são introduzidos no Brasil os projetos de ensino de física, e neles filmes educativos especificamente realizados como parte integrante do processo de ensino. Também identificamos as transformações dos programas de ensino de física do ensino secundário no colégio Pedro II, que serviram como referência para o ensino secundário em todo País, a fim de identificar os conteúdos presentes no ensino de física e que foram tratados em audiovisuais. Dedicamos atenção ao ensino primário de ciências físicas, com especial atenção ao método intuitivo, identificando possíveis contribuições dos primeiros filmes mudos. Foram investigadas as contribuições do Instituto Nacional do Cinema Educativo para o ensino das ciências físicas...

‣ The role of presynaptic activity in monocular deprivation: Comparison of homosynaptic and heterosynaptic mechanisms

Blais, Brian S.; Shouval, Harel Z.; Cooper, Leon N.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 02/02/1999 Português
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Although investigations in computational neuroscience have been extensive, the opportunity (that has made such a marked difference in physical sciences) to test detailed and subtle quantitative consequences of a theory against experimental results is rare. In this paper, we outline a testable consequence of two contrasting theories of synaptic plasticity applied to the disconnection in visual cortex of the closed eye in monocular deprivation. This disconnection is sometimes thought to be the consequence of a process that stems from a competition of inputs for a limited resource such as neurotrophin. Such a process leads to what we call spatial competition, or heterosynaptic synaptic modification. A contrasting view—exemplified by the Bienenstock, Cooper, and Munro (BCM) theory—is that patterns of input activity compete in the temporal domain. This temporal competition is homosynaptic and does not require a conserved resource. The two mechanisms, homosynaptic and heterosynaptic, are the distinguishing characteristics of two general classes of learning rules we explore by using a realistic environment composed of natural scenes. These alternative views lead to opposite dependence on the level of presynaptic activity of the rate of disconnection of the closed eye in monocular deprivation. This strong and testable consequence sets the stage for a critical distinguishing experiment. This experiment has been done and supports the second view. These results have important implications for the processes of learning and memory storage in neocortex.

‣ Drift and breakup of spiral waves in reaction–diffusion–mechanics systems

Panfilov, A. V.; Keldermann, R. H.; Nash, M. P.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Rotating spiral waves organize excitation in various biological, physical, and chemical systems. They underpin a variety of important phenomena, such as cardiac arrhythmias, morphogenesis processes, and spatial patterns in chemical reactions. Important insights into spiral wave dynamics have been obtained from theoretical studies of the reaction–diffusion (RD) partial differential equations. However, most of these studies have ignored the fact that spiral wave rotation is often accompanied by substantial deformations of the medium. Here, we show that joint consideration of the RD equations with the equations of continuum mechanics for tissue deformations (RD–mechanics systems), yield important effects on spiral wave dynamics. We show that deformation can induce the breakup of spiral waves into complex spatiotemporal patterns. We also show that mechanics leads to spiral wave drift throughout the medium approaching dynamical attractors, which are determined by the parameters of the model and the size of the medium. We study mechanisms of these effects and discuss their applicability to the theory of cardiac arrhythmias. Overall, we demonstrate the importance of RD–mechanics systems for mathematics applied to life sciences.

‣ Maps of random walks on complex networks reveal community structure

Rosvall, Martin; Bergstrom, Carl T.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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To comprehend the multipartite organization of large-scale biological and social systems, we introduce an information theoretic approach that reveals community structure in weighted and directed networks. We use the probability flow of random walks on a network as a proxy for information flows in the real system and decompose the network into modules by compressing a description of the probability flow. The result is a map that both simplifies and highlights the regularities in the structure and their relationships. We illustrate the method by making a map of scientific communication as captured in the citation patterns of >6,000 journals. We discover a multicentric organization with fields that vary dramatically in size and degree of integration into the network of science. Along the backbone of the network—including physics, chemistry, molecular biology, and medicine—information flows bidirectionally, but the map reveals a directional pattern of citation from the applied fields to the basic sciences.

‣ Annotating proteins with generalized functional linkages

Llewellyn, Richard; Eisenberg, David S.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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As genome sequencing outstrips the rate of high-quality, low-throughput biochemical and genetic experimentation, accurate annotation of protein function becomes a bottleneck in the progress of the biomolecular sciences. Most gene products are now annotated by homology, in which an experimentally determined function is applied to a similar sequence. This procedure becomes error-prone between more divergent sequences and can contaminate biomolecular databases. Here, we propose a computational method of assignment of function, termed Generalized Functional Linkages (GFL), that combines nonhomology-based methods with other types of data. Functional linkages describe pairwise relationships between proteins that work together to perform a biological task. GFL provides a Bayesian framework that improves annotation by arbitrating a competition among biological process annotations to best describe the target protein. GFL addresses the unequal strengths of functional linkages among proteins, the quality of existing annotations, and the similarity among them while incorporating available knowledge about the cellular location or individual molecular function of the target protein. We demonstrate GFL with functional linkages defined by an algorithm known as zorch that quantifies connectivity in protein–protein interaction networks. Even when using proteins linked only by indirect or high-throughput interactions...

‣ Individual identity and movement networks for disease metapopulations

Keeling, Matt J.; Danon, Leon; Vernon, Matthew C.; House, Thomas A.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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The theory of networks has had a huge impact in both the physical and life sciences, shaping our understanding of the interaction between multiple elements in complex systems. In particular, networks have been extensively used in predicting the spread of infectious diseases where individuals, or populations of individuals, interact with a limited set of others—defining the network through which the disease can spread. Here for such disease models we consider three assumptions for capturing the network of movements between populations, and focus on two applied problems supported by detailed data from Great Britain: the commuter movement of workers between local areas (wards) and the permanent movement of cattle between farms. For such metapopulation networks, we show that the identity of individuals responsible for making network connections can have a significant impact on the infection dynamics, with clear implications for detailed public health and veterinary applications.

‣ A general strategy for the evolution of bond-forming enzymes using yeast display

Chen, Irwin; Dorr, Brent M.; Liu, David R.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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The ability to routinely generate efficient protein catalysts of bond-forming reactions chosen by researchers, rather than nature, is a long-standing goal of the molecular life sciences. Here, we describe a directed evolution strategy for enzymes that catalyze, in principle, any bond-forming reaction. The system integrates yeast display, enzyme-mediated bioconjugation, and fluorescence-activated cell sorting to isolate cells expressing proteins that catalyze the coupling of two substrates chosen by the researcher. We validated the system using model screens for Staphylococcus aureus sortase A–catalyzed transpeptidation activity, resulting in enrichment factors of 6,000-fold after a single round of screening. We applied the system to evolve sortase A for improved catalytic activity. After eight rounds of screening, we isolated variants of sortase A with up to a 140-fold increase in LPETG-coupling activity compared with the starting wild-type enzyme. An evolved sortase variant enabled much more efficient labeling of LPETG-tagged human CD154 expressed on the surface of HeLa cells compared with wild-type sortase. Because the method developed here does not rely on any particular screenable or selectable property of the substrates or product...

‣ Insights into plant size-density relationships from models and agricultural crops

Deng, Jianming; Zuo, Wenyun; Wang, Zhiqiang; Fan, Zhexuan; Ji, Mingfei; Wang, Genxuan; Ran, Jinzhi; Zhao, Changming; Liu, Jianquan; Niklas, Karl J.; Hammond, Sean T.; Brown, James H.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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There is general agreement that competition for resources results in a tradeoff between plant mass, M, and density, but the mathematical form of the resulting thinning relationship and the mechanisms that generate it are debated. Here, we evaluate two complementary models, one based on the space-filling properties of canopy geometry and the other on the metabolic basis of resource use. For densely packed stands, both models predict that density scales as M−3/4, energy use as M0, and total biomass as M1/4. Compilation and analysis of data from 183 populations of herbaceous crop species, 473 stands of managed tree plantations, and 13 populations of bamboo gave four major results: (i) At low initial planting densities, crops grew at similar rates, did not come into contact, and attained similar mature sizes; (ii) at higher initial densities, crops grew until neighboring plants came into contact, growth ceased as a result of competition for limited resources, and a tradeoff between density and size resulted in critical density scaling as M−0.78, total resource use as M−0.02, and total biomass as M0.22; (iii) these scaling exponents are very close to the predicted values of M−3/4, M0, and M1/4, respectively, and significantly different from the exponents suggested by some earlier studies; and (iv) our data extend previously documented scaling relationships for trees in natural forests to small herbaceous annual crops. These results provide a quantitative...

‣ Global meta-analysis reveals no net change in local-scale plant biodiversity over time

Vellend, Mark; Baeten, Lander; Myers-Smith, Isla H.; Elmendorf, Sarah C.; Beauséjour, Robin; Brown, Carissa D.; De Frenne, Pieter; Verheyen, Kris; Wipf, Sonja
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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A major advance of the last 20 y at the interface of biological, environmental, and conservation sciences has been the demonstration that plant biodiversity positively influences ecosystem function. Linking these results to applied conservation efforts hinges on the assumption that biodiversity is actually declining at the local scale at which diversity–function relationships are strongest. Our compilation and analysis of a global database of >16,000 repeat survey vegetation plots from habitats across the globe directly contradict this assumption. We find no general tendency for local-scale plant species diversity to decline over the last century, calling into question the widespread use of ecosystem function experiments to argue for the importance of biodiversity conservation in nature.

‣ In vivo X-ray cine-tomography for tracking morphological dynamics

dos Santos Rolo, Tomy; Ershov, Alexey; van de Kamp, Thomas; Baumbach, Tilo
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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X-ray microtomography is a well-established tool to study the three-dimensional morphology of static biological samples. To capture motion in living specimen in real time, movies of X-ray projections are frequently used. However, the resulting loss of information about the third spatial dimension has limited the applicability of such acquisition protocols. Now, by combining ultrafast X-ray microtomography and sophisticated motion analysis, we developed X-ray cine-tomography as a tool to visualize the internal dynamics of nontranslucent millimeter-sized samples in three-dimensional space. We demonstrate the technique by analyzing the fast-moving screw-and-nut–type hip joint inside a living weevil. The method may be applied to a wide range of samples and processes across materials and life sciences.

‣ Physiology and applied sciences in Nepal: 1st annual conference

Thapa, Ghan Bahadur; Mahotra, Narayan Bahadur; Pun, Matiram
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 01/03/2014 Português
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With the increasing number of medical schools in Nepal, there is an expected increase in the number of Nepalese physiologists. The first medical school was established in the 1970s. We report here about the first annual conference of Nepalese physiologists on 27-28 September 2013 organized by the Department of Clinical Physiology of the Nepalese Army Institute of Health Sciences (NAIHS) and Kathmandu University School of Medical Sciences (KUMS). Nepalese physiologists are trying to form their own physiological society. In this regard, NAIHS and KUMS have played an important role to bring physiologists from different parts of Nepal involved in teaching, learning, and research activities in medical schools. There were a number of foreign invitees (India, Israel, Italy, Japan, and Sweden). There were plenary presentations on the topics that are relevant in Nepal, e.g., high-altitude physiology and wilderness medicine. The final session of the conference was an open session meeting of Nepalese physiologists. There was an open interaction about establishing Nepalese Physiological Society. After much deliberation, there was an agreement to register the society in Kathmandu with the current ad hoc committee which will elect the first executive body of the society.

‣ A Critical Evaluation of Cohesive Zone Models of Dynamic Fracture

Falk, Michael L.; Needleman, Alan; Rice, James R.
Fonte: EDP Sciences Publicador: EDP Sciences
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Finite element calculations of dynamic fracture based on embedding cohesive surfaces in a continuum indicate that the predictions are sensitive to the cohesive law used. Simulations were performed on a square block in plane strain with an initial edge crack loaded at a constant rate of strain. Cohesive laws that have an initial elastic response were observed to produce spontaneous branching at high velocity, but to modify the linear elastic properties of the body. As a consequence the cohesive surface spacing cannot be refined arbitrarily and becomes an important length scale in the simulations. Cohesive laws that are initially rigid do not alter the linear elastic response of the body. However, crack branching behavior was not observed when such a cohesive relation was implemented using a regular finite element mesh.; Earth and Planetary Sciences; Engineering and Applied Sciences

‣ Technical Perspective: Complex Financial Products: Caveat Emptor

Parkes, David C.
Fonte: Association for Computing Machinery Publicador: Association for Computing Machinery
Tipo: Commentary or Review
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Engineering and Applied Sciences

‣ Discovering Communities through Friendship

Morrison, Gregory C.; Mahadevan, Lakshminarayanan
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
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We introduce a new method for detecting communities of arbitrary size in an undirected weighted network. Our approach is based on tracing the path of closest‐friendship between nodes in the network using the recently proposed Generalized Erds Numbers. This method does not require the choice of any arbitrary parameters or null models, and does not suffer from a system‐size resolution limit. Our closest‐friend community detection is able to accurately reconstruct the true network structure for a large number of real world and artificial benchmarks, and can be adapted to study the multi‐level structure of hierarchical communities as well. We also use the closeness between nodes to develop a degree of robustness for each node, which can assess how robustly that node is assigned to its community. To test the efficacy of these methods, we deploy them on a variety of well known benchmarks, a hierarchal structured artificial benchmark with a known community and robustness structure, as well as real‐world networks of coauthorships between the faculty at a major university and the network of citations of articles published in Physical Review. In all cases, microcommunities, hierarchy of the communities, and variable node robustness are all observed...

‣ Discriminative, generative, and imitative learning

Jebara, Tony (Tony S.), 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 212 leaves; 21629727 bytes; 21629483 bytes; application/pdf; application/pdf
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I propose a common framework that combines three different paradigms in machine learning: generative, discriminative and imitative learning. A generative probabilistic distribution is a principled way to model many machine learning and machine perception problems. Therein, one provides domain specific knowledge in terms of structure and parameter priors over the joint space of variables. Bayesian networks and Bayesian statistics provide a rich and flexible language for specifying this knowledge and subsequently refining it with data and observations. The final result is a distribution that is a good generator of novel exemplars. Conversely, discriminative algorithms adjust a possibly non-distributional model to data optimizing for a specific task, such as classification or prediction. This typically leads to superior performance yet compromises the flexibility of generative modeling. I present Maximum Entropy Discrimination (MED) as a framework to combine both discriminative estimation and generative probability densities. Calculations involve distributions over parameters, margins, and priors and are provably and uniquely solvable for the exponential family. Extensions include regression, feature selection, and transduction. SVMs are also naturally subsumed and can be augmented with...

‣ Structure and evolution of the Australian continent : insights from seismic and mechanical heterogeneity and anisotropy

Simons, Frederik Jozef Maurits, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 261 p.; 20763345 bytes; 20763101 bytes; application/pdf; application/pdf
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In this thesis, I explore the geophysical structure and evolution of the Australian continental lithosphere. I combine insights from isotropic and anisotropic seismic surface-wave tomography with an analysis of the anisotropy in the mechanical properties of the lithosphere, inferred from the coherence between gravity anomalies and topography. With a new high-resolution waveform tomographic model of Australia, I demonstrate that the depth of continental high wave speed anomalies does not universally increase with age, but is dependent on the scale and the tectonic history of the region under consideration. I construct an azimuthally anisotropic three-dimensional model of the Australian upper mantle from Rayleigh-wave waveforms. I compare Bayesian inverse methods with discretely parameterized regularization methods, and explore the use of regular, tectonic and resolution-dependent tomographic grids. I advocate the use of multitaper spectral estimation techniques for coherence analysis of gravity and topography, applied to Australian isostasy. I investigate the importance of internal loading, the directional anisotropy of the gravitational response to loading, and the estimation bias affecting the long wavelengths of the coherence function. I develop a method for non-stationary coherence analysis which enables a complete characterization of continental strength by the dependency of gravity-topography coherence on wavelength...

‣ A laboratory study of the friction behavior of granular materials

Frye, Kevin M. (Kevin Michael), 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 145 leaves; 10401799 bytes; 10401555 bytes; application/pdf; application/pdf
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I report on laboratory experiments designed to investigate the microphysical processes that result in rate- and state-dependent friction behavior and experiments designed to match the boundary conditions used by numerical models of granular friction. The effect of relative humidity (RH from <5% to 100%) is investigated with velocity stepping tests (10-20 tm/s) and slide-hold-slide (SHS) tests (3-1000 s) on 3 mm thick layers of quartz powder, alumina powder, Westerly granite powder, and Westerly granite blocks sheared at 25 MPa normal stress. Powders are conditioned in situ under controlled RH to create new surface area before shearing. A transition from velocity-strengthening to velocity-weakening frictional behavior occurs as RH increases. Frictional healing is negligible at low humidity and increases with increasing RH for both materials. While the coefficient of sliding friction for powders is independent of humidity, bare surface data indicate that sliding friction decreases with increased RH. Normal stress vibrations in SHS tests can add compaction induced granular strengthening, but for constant normal force tests, chemically assisted healing mechanisms control the friction behavior. The chemically assisted contact junction processes can be reduced or turned off at low humidity at room temperature in quartz and alumina. Velocity stepping tests and SHS tests are also performed at different values of applied normal stress (5 to 45 MPa) after pre-conditioning at high normal stress (40 and 35 MPa) for powders and no pre-conditioning for bare surfaces. Time-dependent frictional healing decreases with increasing normal stress.; (cont.) For the powders...

‣ Actin remodeling in motile cells

Osborn, Eric A. (Eric Alan), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 142 leaves; 7801872 bytes; 7820724 bytes; application/pdf; application/pdf
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Non-muscle cell shape change and motility depend primarily on the dynamics and distributions of cytoplasmic actin. In cells, actin cycles between monomeric and polymeric phases tightly regulated by actin binding proteins that control cellular architecture and movement. Here, we characterize actin remodeling in shear stress stimulated endothelial cells and in actin networks reconstituted with purified proteins. Fluid shear stress stimulation induces endothelial cells to elongate and align in the direction of applied flow. Alignment requires 24 h of exposure to flow, but the cells respond within minutes to flow by diminishing their movements by 50%. Although movement slows, actin filament turnover times and the amount of polymerized actin in cells decreases, increasing actin filament remodeling in individual cells composing a confluent endothelial monolayer to levels used by disperse, non-confluent cells for rapid movement. Hours later, motility returns to pre-shear stress levels, but actin remodeling remains highly dynamic in many cells. We conclude that shear stress initiates a cytoplasmic actin remodeling response that is used to modify endothelial cell shape instead of bulk cell translocation. We determine the steady state dynamics of purified actin filament networks in the entangled state and after orthogonal cross-linking with filamins using a novel...

‣ Cenozoic tectonic and geomorphic evolution of the Red River Region, Yunnan Province, China

Schoenbohm, Lindsay M. (Lindsay Marie), 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 235 p.; 18752370 bytes; 18783216 bytes; application/pdf; application/pdf
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(cont.) Xianshuihe-Xiaojiang fault system during growth of the southeast plateau margin. Cosmogenic ²⁶A1 and ¹⁰Be basin-wide erosion rate and burial ages indicate a background incision rate of [approximately] 0.05 to 0.10 mm/a, lower than the long-term incision rate minimum of [approximately] 0.26 mm/a. Cosmogenically-determined incision rate approximately doubles to [approximately] 0.20 mm/a in the region of maximum dip-slip displacement on the Red River fault. This thesis also develops a new cosmogenic tool for quantitative landscape analysis: using depth dependence data for multiple cosmogenic nuclides from a single site to constrain an erosion history. This method is applied in the Dry Valleys region of Antarctica.; This thesis outlines the Cenozoic development of the Red River region, exploring regional landscape evolution and tectonic accommodation of the India-Eurasia collision, focusing on the Oligo-Miocene, left-lateral Ailao Shan shear zone and the active, right-lateral Red River fault on the northeast margin of the shear zone, along which the Red River has incised a deep valley. Oligo-Miocene fluvial and alluvial conglomerates in the valley record shear zone unroofing: pervasive, syn-depositional shortening indicates transpressional exhumation. A low-relief landscape...

‣ System identification of dynamic closed-loop cardiovascular control of total peripheral resistance by arterial and cardiopulmonary baroreceptors

Aljuri, A. Nikolai (Antony Nikolai), 1968-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 77 leaves; 3015933 bytes; 3015742 bytes; application/pdf; application/pdf
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Prolonged exposure to microgravity in space flight missions (days) impairs the mechanisms responsible for defense of cardiac output (CO) and arterial blood pressure (Pa) against orthostatic stress during re-entry and in the post-flight period. To date, available countermeasures have not been able to eliminate the observed orthostatic hypotension. The mechanisms responsible for the observed orthostatic intolerance are not yet completely understood. Pa is maintained by control pathways, which influence either total peripheral resistance (Ra) or CO. Central control of Ra is achieved by a complex closed-loop negative feedback system composed of the arterial and the cardiopulmonary baroreflexes. The aims of the doctoral research presented in this thesis were: 1) design and employ a novel conscious animal model for the examination of arterial and cardiopulmonary baroreceptors in the dynamic closed-loop short-term control of Ra. 2) develop and apply a system identification method for the analysis of fluctuations in Pa, right atrial pressure (Pra), and Ra to quantitatively characterize the physiologic mechanisms responsible for the couplings between these variables. For this purpose, eight conscious sheep were used, where both types of baroreceptors were simultaneously exposed to random independent beat pressure variations over a small range around their operating points...