Página 13 dos resultados de 9995 itens digitais encontrados em 0.061 segundos

‣ Social signaling in decision making

Caneel, Ron
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 60 p.; 2847072 bytes; 2848694 bytes; application/pdf; application/pdf
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Nonverbal communication is an important and often underestimated instrument in social interactions. The paralinguistic elements of speech, which are described in common speech as "tone of voice", are one channel of the nonverbal communication. They, together with conversational dynamics, are a very powerful measurement for interactions, without looking at the content of the conversation. A subset of these features, the social signaling measurements, are very useful when analyzing and quantifying conversation. The goal of this thesis is to better understand the framework of social signaling. We applied the social signaling measurements to negotiations as well as to small group interactions. For negotiation we were able to predict up to 30% of the variance in individual outcome. The use of automated algorithms enables to build real-time feedback mechanisms that can then help users to improve and achieve their objectives.; by Ron Caneel.; Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.; Includes bibliographical references (p. 55-60).

‣ Defining the human endothelial transcriptome

Natarajan, Sripriya, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 117 leaves; 6383991 bytes; 6391242 bytes; application/pdf; application/pdf
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Advances in microarray technology facilitate the study of biological systems at a genome-wide level. Meaningful analysis of these transcriptional profiling studies, however, demands the concomitant development of novel computational techniques that take into account the size and complexity of the data. We have devised statistical algorithms that use replicate microarrays to define a genome-wide expression profile of a given cell type and to determine a list of genes that are significantly differentially expressed between experimental conditions. Applying these algorithms to the study of cultured human umbilical vein endothelial cells (HUVEC), we have found approximately 54% of all genes to be expressed at a detectable level in HUVEC under basal conditions. The set of highest expressed genes is enriched in nucleic acid binding proteins, cytoskeletal proteins and isomerases as well as certain known markers of endothelium, and the complete list of genes can be found at ... We have also studied the effect of a 4-hour exposure of HUVEC to 10 U/mL of IL-1, and detected 491 upregulated and 259 downregulated statistically significant genes, including several chemokines and cytokines, as well as members of the TNFAIP3 family, the KLFfamily and the Notch pathway. Applying these rigorous statistical techniques to genome-wide expression datasets underscores known patterns of endothelial inflammatory gene regulation and unveils new pathways as well.; (cont.) Finally...

‣ Characterization of human expired breath by solid phase microextraction and analysis using gas chromatography-mass spectrometry and differential mobility spectrometry

Merrick, William (William F. W.)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 95 leaves; 4181829 bytes; 4185745 bytes; application/pdf; application/pdf
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Breath analysis has potential to become a new medical diagnostic modality. In this thesis, a method for the analysis of human expired breath was developed using gas chromatography-mass spectroscopy. It was subsequently adopted for gas chromatography-differential mobility spectroscopy, a modality not previously applied to this problem. Tedlar bags and solid-phase microextraction were used for breath sampling and concentration prior to analysis. Four fiber coatings were evaluated with respect to selectivity and sensitivity; extraction time, gas chromatography temperature programming, and sample storage stability were explored for optimization. The method entails extraction and preconcentration with a polydimethylsiloxane-divinylbenzene coated fiber for 30 min at 37⁰C, and extraction profiles for several compounds demonstrate competitive adsorption. 120 compounds were identified in breath with response variability between 23 - 117% about mean values. Feasibility of differential mobility spectroscopy for breath analysis was established, and this method will be the basis for future investigations on the diagnostic potential of breath analysis.; by William Merrick.; Thesis (M. Eng.)--Harvard-MIT Division of Health Sciences and Technology...

‣ Design of intelligent interiors

Bonanni, Leonardo Amerigo, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 112 p.; 5131962 bytes; 5136561 bytes; application/pdf; application/pdf
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Ubiquitous computing is transforming interior design by allowing utilities, goods and information to be delivered where and when we need them. How will new information technologies impact the design of interior spaces? Intelligent interiors can be more flexible and expressive than traditional spaces. Automation, personal fabrication and augmented reality can be applied to interior spaces with new interaction modes that operate at an architectural scale. Water, light, and other utilities can be automated in a way that empowers users by providing direct feedback, tangible benefit and being fail-soft. Appliances can make it possible to produce and recycle a large number of variable goods locally and on demand. Many of the objects and surfaces of interior spaces can serve as displays to provide information intuitively where and when it is needed. This thesis demonstrates how distributed intelligence can increase productivity and enrich the experience of interior spaces. Experiments with augmentations to the utilities, goods and information of a working kitchen suggest guidelines for interaction with intelligent interior spaces. The perceptual load and quality of interaction needs to be balanced; for example in our experiments projected text was almost always distracting.; (cont.) This work demonstrated that: information should behave at the scale of architectural space; an intelligent interior space should provide as much fidelity at the lowest bandwidth possible to support activity without distracting from tasks; the association of information to the tasks and objects referred to should be concrete and obvious; and appropriate feedback should accompany new interaction to increase the control and confidence of users. This thesis shows that new interaction modes for interior spaces can be intuitively understood and valued. In addition to being more flexible and functional...

‣ Microdamage accumulation in bovine trabecular bone

Moore, Tara L. Arthur (Tara Lee Arthur), 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 285 p.
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When bone is loaded beyond its failure point, it develops damage in the form of microcracks. Normally, microcracks are repaired by the remodeling process, limiting the number of in vivo microcracks. However, if the rate of microdamage accumulation increases or the rate of remodeling slows, microdamage can accumulate, reducing bone stiffness and strength and may lead to stress fractures or fragility fractures. A new technique for visualizing microdamage in vitro has been developed that uses chelating fluorochromes to label microcracks. Sequential staining is used to distinguish between microdamage that occurred before testing and damage created during testing. Microdamage parameters quantified include the total number of microcracks, total length of microcracks, damaged area, the number of trabeculae containing microcracks, the pattern of microcracking, the extent of microdamage across the thickness of the trabeculae, and the size of the damage-containing region in the specimen. The chelating fluorochrome marker technique was used to label and quantify microdamage in specimens of bovine trabecular bone damaged in uniaxial compression and compressive fatigue, and relationships between microdamage parameters and changes in mechanical properties (maximum compressive strain...

‣ Acoustic correlates of word stress in American English

Okobi, Anthony O. (Anthony Obiesie), 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 126 p.
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Acoustic parameters that differentiate between primary stress and non-primary full vowels were determined using two-syllable real and novel words and specially constructed novel words with identical syllable compositions. The location of the high focal pitch accent within a declarative carrier phrase was varied using an innovative object naming task that allowed for a natural and spontaneous manipulation of phrase-level accentuation. Results from male native speakers of American English show that when the high focal pitch accent was on the novel word, vowel differences in pitch, intensity prominence, and amplitude of the first harmonic, H1 * (corrected for the effect of the vocal tract filter), accurately distinguished full vowel syllables carrying primary stress vs. non-primary stress. Acoustic parameters that correlated to word stress under all conditions tested were syllable duration, HI*-A3*, as a measurement of spectral tilt, and noise at high frequencies, determined by band-pass filtering the F3 region of the spectrum. Furthermore, the results indicate that word stress cues are augmented when the high focal pitch accent is on the target word.; (cont.) This became apparent after a formula was devised to correct for the masking effect of phrase-level accentuation on the spectral tilt measurement...

‣ Using otoacoustic emissions to measure the transmission matrix of the middle-ear

Miller, Antonio John
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 41 leaves
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Here we describe an experimental method for measuring the acoustic transmission matrix of the middle-ear using otoacoustic emissions. The experiment builds on previous work that uses distortion product otoacoustic emissions (DPOAEs) as an intracochlear sound source to drive the middle-ear in reverse. This technique eliminates the complications introduced by needing to place an acoustic transducer inside the cochlea. Previous authors have shown how the complete 4x3 system response matrix, with its 12 unknowns, can be simplified to a 2x2 transmission matrix by de-coupling the middle-ear cavity and assuming the cochlear fluids are incompressible. This simplified description of middle-ear mechanics assumes that the input-output response at the tympanic membrane and stapes footplate is linear, one dimensional and time invariant. The technique allows for estimating the acoustic pressure and volume velocity at the tympanic membrane and the volume velocity of the stapes footplate, in both the forward and reverse direction, and under different boundary conditions at the stapes. The technique was applied to deeply anesthetized cats with widely opened middle-ear cavities over a frequency range of 200Hz to 10kHz. Results on three animals are reported and generally agree with previous data and a published middle-ear model.; by Antonio John Miller.; Thesis (S.M.)--Harvard-MIT Division of Health Sciences and Technology...

‣ Role of the precentral cortex in adapting behavior to different mechanical environments

Richardson, Andrew Garmory, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 171 p.
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We routinely produce movements under different mechanical contexts. All interactions with the physical environment, such as swinging a hammer or lifting a carton of milk, alter the forces experienced during movement. With repeated experience, sensorimotor maps are adapted to maintain a high level of movement performance regardless of the mechanical environment. This dissertation explored the contribution of the precentral cortex to this process of motor adaptation. In the first experiment, we recorded precentral neural activity in rhesus monkeys that were trained to perform visually-cued reaching movements while holding on to a robotic manipulandum capable of changing the forces experienced during the task. Preparation and control of the reaching movements were correlated with single cell activity throughout the precentral cortex, including the primary motor cortex and five different premotor areas. Precentral field potential activity was also modulated during the reaching behavior, particularly in the beta and high gamma frequency bands. When novel forces were introduced, single cell activity changed in a manner that specifically compensated for the applied forces and mirrored the time course of behavioral adaptation.; (cont.) Force-related changes were present in the field potential activity as well. Some of these changes were maintained following removal of the forces. Control data and simulations revealed that these residual changes were well described by a model of noisy adaptation in a redundant cortical network. In the second experiment...

‣ The structural determinants of media contagion

Marlow, Cameron Alexander, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166 p.
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Informal exchanges between friends, family and acquaintances play a crucial role in the dissemination of news and opinion. These casual interactions are embedded in a network of communication that spans our society, allowing information to spread from any one person to another via some set of intermediary ties. Weblogs have recently emerged as a part of our media ecology and incidentally engender this process of media contagion; because weblog authors are tied by social networks of readership, contagious media events happen frequently, and in a form that is immediately measurable. The generally accepted notion of media diffusion is that it occurs through two channels: externally, as applied by a constant force such as the mass media, and internally through socio-structural means. Sitting between our traditional notions of mass media and the public, weblogs problematize this classical theory of mass media influence. This thesis aims to elucidate the role of weblogs in media contagion through a sociological study of this community in two parts: First, I will address the issues of modeling the social structure of weblogs as observed through their readership network, and the various media events that occur therein.; (cont.) Using a large weblog corpus collected over a one-month period...

‣ Simulation methods and tissue property models for non-invasive transcranial focused ultrasound surgery

Connor, Christopher W
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 300 p.
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Many brain tumors are localized deeply and are currently surgically inaccessible without causing severe damage to the overlying structures of the brain. The current spectrum of non-invasive methods for treating such tumors includes radiotherapy, which requires exposure to ionizing radiation, and chemotherapy, which is systemically toxic. However, these tumors may also potentially be attacked by focusing highly intense ultrasound onto them. Focused ultrasound surgery is without the side effects of radiotherapy and chemotherapy, and the therapeutic effect of ultrasound therapy can be monitored in real- time using the proton chemical shift MRI technique. However, in order for brain tumors to be treated non-invasively, the ultrasound must be focused onto the targeted brain tissue through the intact cranium. Transcranial focusing of ultrasound is a longstanding and difficult problem as skull is a highly heterogeneous material. As the ultrasound field propagates through the bones of the skull, it undergoes substantatial distortion due to the variations in density and speed of sound therein. There is substantial individual variation in skull size, thickness and composition. Furthermore, the acoustic attenuation coefficient in bone is high...

‣ Fundamental and practical limits to image acceleration in parallel magnetic resonance imaging

Ohliger, Michael A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 160 leaves
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Imaging speed in conventional magnetic resonance imaging (MRI) is limited by the performance of magnetic field gradients and the rate of power deposition in tissue. Parallel MRI techniques overcome these constraints by exploiting information stored within the spatial sensitivity patterns of radiofrequency detector arrays to substitute for some of the spatial information that would normally be obtained using magnetic field gradients. Parallel MRI strategies have been applied clinically to increase patient comfort, enhance spatial resolution, expand anatomical coverage, and reduce image artifacts. The effectiveness of parallel MRI techniques is largely determined by the amount of spatial information that is stored in the detector coil sensitivities. This dissertation investigates the spatial encoding properties of coil arrays from three practical and fundamental perspectives. First, a novel array design is presented that enables spatial encoding in multiple directions simultaneously. Second, the impact of inductive coupling between array elements in parallel MRI is investigated theoretically and experimentally. Finally, electromagnetic calculations are described that permit computation of the ultimate intrinsic signal-to-noise ratio available to any physically realizable coil array for parallel MR. These calculations help to establish fundamental limits to the image accelerations that may be achieved using parallel MRI techniques. These limits are intrinsically related to the wavelengths of the electromagnetic fields at MR imaging frequencies. The sensitivity patterns that correspond to the ultimate intrinsic SNR also represent potential starting points for new coil designs.; by Michael A. Ohliger.; Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology...

‣ Ensemble : fluency and embodiment for robots acting with humans; Fluency and embodiment for robots acting with humans

Hoffman, Guy, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 234 p.
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This thesis is concerned with the notion of fluency in human-robot interaction (HRI), exploring cognitive mechanisms for robotic agents that would enable them to overcome the stop-and-go rigidity present in much of HRI to date. We define fluency as the ethereal yet manifest quality existent when two agents perform together at high level of coordination and adaptation, in particular when they are well-accustomed to the task and to each other. Based on mounting psychological and neurological evidence, we argue that one of the keys to this goal is the adaptation of an embodied approach to robot cognition. We show how central ideas from this psychological school are applicable to robot cognition and present a cognitive architecture making use of perceptual symbols, simulation, and perception-action networks. In addition, we demonstrate that anticipation of perceptual input, and in particular of the actions of others, are an important ingredient of fluent joint action. To that end, we show results from an experiment studying the effects of anticipatory action on fluency and teamwork, and use these results to suggest benchmark metrics for fluency. We also show the relationship between anticipatory action and a simulator approach to perception...

‣ Dissecting the eastern margin of the Tibetan plateau : a study of landslides, erosion and river incision in a transient landscape

Ouimet, William Burke
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 197 p.
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The eastern margin of the Tibetan plateau is characterized by large rivers dissecting regional topography that has been uplifted in association with the continued convergence of the Indian subcontinent and Eurasia. In this thesis, I utilize field observations, digital topographic data, cosmogenic isotope data, low-temperature thermochronology and numerical simulations to better understand the evolution of these rivers and tectonics of the region. The goals of this work are: 1) to characterize the rates and processes of river incision and erosion associated with major rivers dissecting the eastern margin; 2) to better understand and constrain the transient landscape evolution that defines regional topography; and 3) to move closer to understanding the relationships among tectonics, topography and erosion that apply directly to the eastern margin, and may be applied to other landscapes around the world. To accomplish these goals, I study the rates and processes of river incision and erosion on the eastern margin on a variety of spatial and temporal scales. I discuss local incision processes and related landforms by exploring the influence of large landslides and discussing epigenetic gorges, which are secondary bedrock-walled channels that form in relation to episodes of river blockage or afgradation. I quantify short-term (102-105 yr) erosion rates using cosmogenic isotopes ( Be) from river sand for 65 small river basins (typically <100 km2) throughout the eastern margin...

‣ Just build it! : a fully functional concept vehicle using robotic wheels; Fully functional concept vehicle using robotic wheels

Schmitt, Peter, S.M. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 64 p.
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Interest in electric vehicle drive units is resurging with the proliferation of hybrid and electric vehicles. Currently emerging key-technologies are: in-wheel motors, electric braking, integrated steering activators and active suspension combined with embedded sensors and real time computation. These electric vehicle drive units have the potential to go beyond current applications and lead to a novel vehicle architectures and a new vehicle culture. Building upon the research in the Smart Cities Group at the MIT Media Lab I propose to implement a novel mechanical and electric robotic wheel technology and the associated control and drive software in a fully functional concept vehicle. I will make use of a modular design for wheel robots which I developed through prior iterations at different scales combined with applied automotive technologies. This platform provides a realistic and scalable test-bed for evaluating the proposed technologies and will ultimately serve building a full scale concept vehicle.; by Peter Schmitt.; Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2007.; Page 64 blank.; Includes bibliographical references (p. [62]-[63]).

‣ Perturbation-based detection and prosthetic correction of vestibulopathic gait

Sienko, Kathleen Helen, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 158 p.
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While being able to balance is something most of us take for granted, each year approximately 400,000 Americans are diagnosed with a balance disorder. In order to prevent fall-related injuries due to postural instability, it is important to create both diagnosis techniques so that therapy can be applied before a fall occurs and devices which can aid the balance-impaired population. The aims of this research are twofold: 1) to develop metrics that quantify the locomotor stability of individuals with reduced vestibular function and 2) to assess the capability of a noninvasive vibrotactile balance prosthesis for improving postural and gait stability. The clinical standards of practice for assessing vestibular deficiency include testing postural stability while standing but not during locomotion. This research examines one prospective locomotor-based technique involving the analysis of postural recovery from controlled surface perturbations. The research also investigates the use of a novel wearable vibrotactile sensory substitution device for enhanced postural and locomotor stability. The balance prosthesis is composed of an inertial motion-sensing system mounted on the lower back, a vibrotactile display worn around the torso, and a computer controller.; (cont.) It can serve as a permanent or temporary replacement of motion cues...

‣ Advances in Optical Coherence Tomography and Microscopy for endoscopic applications and functional neuroimaging; Advances in OCT and OCM for endoscopic applications and functional neuroimaging

Aguirre, Aaron Dominic, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 250 p.
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Optical Coherence Tomography (OCT) is a developing medical imaging technology that generates micron resolution cross-sectional images of subsurface internal tissue structure in situ and in real time, without the need to remove and process specimens. Previous studies have suggested that OCT holds great potential for use in laparoscopic and endoscopic applications to detect early stage neoplastic pathologies. A minimally invasive imaging modality capable of identifying pre-malignant tissues in vivo could be used to guide conventional excisional biopsy and histology, thereby reducing sampling error and enabling earlier detection and treatment. One limitation of prior endoscopic OCT imaging methods is the inability to visualize cellular features characteristic of early disease states such as neoplasia. This thesis seeks to demonstrate that advances in OCT resolution and in miniaturized imaging devices will lead to enhanced visualization of pathologic changes in vivo at both the tissue architectural and cellular levels. Toward this goal, three technological advances are made. First, compact and portable laser light sources for clinical ultrahigh resolution OCT are demonstrated based on supercontinuum generation in highly nonlinear optical fibers. Second...

‣ Reservoir-based devices for the monitoring and treatment of disease

Kim, Grace Young
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 151 p.
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Cancer mortality still remains high despite significant investments in diagnostics, drug development, and treatment. The systemic route is convenient both for routine monitoring and for drug administration. Local cancer biomarker concentrations, however, are more indicative of the state of solid tumors and their response to therapy. Furthermore, local drug delivery can achieve efficacy where systemic treatments fail. This dissertation describes two reservoir-based devices to enable such local approaches. We are applying superparamagnetic crosslinked iron oxide nanoparticles (CLIO) for the quantitative measurements of soluble cancer biomarkers. These nanoparticles are functionalized to react specifically in the presence of their target analyte. An implanted device with a size-exclusion membrane was used to contain the CLIO and to expose them to the cancer milieu. The system was designed to be deployed deep within the body and indirectly detect cancer cells and their activity by their secreted products, which are produced at a very high copy number by each cell. A reservoir-based polymeric device has also been applied for local chemotherapy. A biodegradable polymer microchip was designed in our group to independently deliver more than one therapeutic agent. Only in vitro release of active compounds had been previously demonstrated. The work in this thesis achieves local drug therapy from the polymer microchip and demonstrates efficacy against an in vivo tumor model of brain cancer. The reservoir-based device approach has the potential to enable early detection of cancer recurrence...

‣ Advanced brachytherapy dosimetric considerations

Melhus, Christopher S. (Christopher Scott), 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 145 p.
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The practice of brachytherapy and brachytherapy dosimetry was investigated with emphasis on evaluations of dose distributions and shielding considerations for both photon- and neutron-emitting radionuclides. Monte Carlo simulation methods were employed to calculate dose distributions for virtual and commercial brachytherapy sources. Radionuclides studied were 103Pd, 1251, 131Cs, 137Cs, 169b, 192Ir, and 252Cf. 252Cf sources also emit neutrons from spontaneous fission. The brachytherapy dosimetry protocol recommended by the American Association of Physicists in Medicine was followed and evaluated for conditions of partial scatter (non-infinite media) and material inhomogeneities, both commonly encountered in brachytherapy treatment. Furthermore, energy-dependent characteristics of dosimetry parameters were evaluated and reference calculations performed for virtual photon and neutron sources. These findings were applied to three clinical brachytherapy cases: eye plaques using 103Pd, 125I, and 131Cs; high-dose rate 252Cf treatment; and, 2 Cf plaques for superficial lesions. For eye plaques, material heterogeneities were significant for each radionuclide with dose reduction at 5 mm of 18%, 11%, and 10% for P03pd, 125I, and 131Cs, respectively. For a proposed highdose rate 252Cf source (5mm length)...

‣ The functional role of the mammalian tectorial membrane in the cochlear mechanics

Ghaffari, Roozbeh, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 110 p.
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Sound-evoked vibrations transmitted into the mammalian cochlea produce traveling waves that provide the mechanical tuning necessary for spectral decomposition of sound. These traveling waves of motion propagate along the basilar membrane (BM) and ultimately stimulate the mechano-sensory receptors. The tectorial membrane (TM) plays a key role in this stimulation process, but its mechanical function remains unclear. Here we show that the TM supports traveling waves that are an intrinsic feature of its visco-elastic structure. Radial forces applied at audio frequencies (1-20 kHz) to isolated TM segments generate longitudinally propagating waves on the TM with velocities similar to those of the BM traveling wave near its best frequency (BF) place. We compute the dynamic shear storage modulus and shear viscosity of the TM from the propagation velocity of the waves and show that segments of the TM from the basal turn are stiffer than apical segments are. Analysis of loading effects of hair bundle stiffness, the limbal attachment of the TM, and viscous damping in the subtectorial space suggests that TM traveling waves can occur in vivo. To test how TM waves may participate in cochlear function, we investigated waves in genetically modified mice lacking beta-tectorin...

‣ Modular architecture in biological networks

Ramachandran, Gopal (Gopal Sebastian)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 207 p.
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In the past decade, biology has been revolutionized by an explosion in the availability of data. Translating this new wealth of information into meaningful biological insights and clinical breakthroughs will require a complete overhaul both in the questions being asked, and the methodologies used to answer them. One of the largest challenges in organizing and understanding the data coming from genome sequencing, microarray experiments, and other high-throughput measurements, will be the ability to find large-scale structure in biological systems. Ideally, this would lead to a simplified representation, wherein the thousands of genes in an organism can be viewed as a much smaller number of dynamic modules working in concert to accomplish cellular functions. Toward demonstrating the importance of higher-level, modular structure in biological systems, we have performed the following analyses: 1. Using computational techniques and pre-existing protein-protein interaction (PPI) data, we have developed general tools to find and validate modular structure. We have applied these approaches to the PPI networks of yeast, fly, worm, and human.; (cont.) 2. Utilizing a modular scaffold, we have generated predictions that attempt to explain existing system-wide experiments as well as predict the function of otherwise uncharacterized proteins. 3. Following the example of comparative genomics...