Thesis: B.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1981 / Lacks leaf 38. / by Eric Brian Shain. / B.S. / B.S. Massachusetts Institute of Technology, Department of Mechanical Engineering

Made available in DSpace on 2014-06-11T19:25:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-08Bitstream added on 2014-06-13T20:14:18Z : No. of bitstreams: 1 apolinario_jc_me_araca.pdf: 190197 bytes, checksum: 1aba6bb35b316b811a8b671145feab29 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A literatura apresenta que a resposta de reparo ósseo pode ser acentuada pela estimulação física, mecânica ou eletromagnética. Há evidências de que o ultra-som – US – de baixa potência pode acelerar a regeneração óssea. Este trabalho objetivou verificar o efeito do US no defeito ósseo, criado experimentalmente, em tíbias de ratos sob ausência de carga (suspenso pela cauda) por meio de análise densitométrica e biomecânica. Trinta Rattus novergicus albinus, Wistar, adultos, divididos em 3 grupos: G1 (n=10), não suspenso - experimento de 15 dias; G2 (n=10), suspenso pela cauda - experimento de 15 dias e, G3 (n=10), suspensos pela cauda, experimento de 36 dias. Os animais foram submetidos à osteotomia em ambas as tíbias e à aplicação do US (freqüência de 1,5 MHz, ciclo 1:4, 30mW/cm2) na direita (12 sessões de 20 minutos). O G3 somente foi osteotomizado após 21º dia de suspensão. Para análises densitométrica utilizou-se densitômetro DPXLunar ™, sistema digital Digora e o programa computacional Image J ; para ensaio mecânico usou máquina universal de ensaio EMIC . Os resultados do Conteúdo Mineral Ósseo (g), Área (cm²), Densidade Mineral Óssea (g/cm²) e da Densidade Óssea (mmAl) observadas nas tíbias, assim como a Força Máxima (N) e Rigidez (x103N/m) não demonstraram diferenças significantes (tratadas versus controle de cada grupo), possivelmente pelo menor tempo de tratamento com relação aos trabalhos encontrados na literatura. Concluindo que o Ultra-Som de baixa potência não acelerou o processo de consolidação óssea. / Literature shows that bone repair response can be accented by physical, mechanic or electromagnetic stimulation. There are evidences that low power ultrasound – US - can speed up bone regeneration. This work aimed at determining the effect of US in bone defects, experimentally created, in tibia from rats under load absence (suspended by the tail) by densitometric analysis and biomechanics. Thirty Rattus novergicus albinus, Wistar, adult, divided in 3 groups: G1 (n=10), not suspended – a 15 day experiment; G2 (n=10), suspended by the tail – a 15 day experiment and, G3 (n=10), suspended by the tail – a 36 day experiment. , The animals have been submitted to the osteotomy in both tibias and to the US application (1,5 MHz frequency, cycle 1:4, 30mW/cm2), on the right (twelve sessions of 20 minutes). G3 was only osteotomized after the 21st day of suspension. DPX-Lunar™ densitometer, Digora digital system and Image J computer program were used for densitometrical analysis; for the mechanical assay, the universal machine of EMIC assay was used. The results for Bone Mineral Content (g), Area (cm²), Bone Mineral Density (g/cm²) and Bone Density (mmAl) observed in tibias, as well as Maximum Power (N), and Rigidity (x103N/m) did not show any significant differences (treated versus control of each group), possibly due to shorter treatment time as regards the studies found in literature. Concluding that the low power ultrasound not accelerated the process of consolidating bone.

Attitude Determination and Control System (ADCS) is often a complex system on-board any  satellite  which  needs  validation  and  testing  to  prove  its  operability  and  verify  its software  compatibility  with  hardware  and  other  subsystems.    One  failure  in  orbit  is extremely expensive in terms of cost and time due to payload preparation and launch. The ideal test bench would be the one that perfectly simulates the space environment and all its main factors such as weightlessness, Earth’s Magnetic Field (EMF), vacuum, neutral particles, plasma and radiation, among others.  The target in this case was the Earth’s Magnetic Field (EMF), solved with a Helmholtz Cage in a Merritt Configuration, and weightlessness, not implemented but analysed in detail where different alternatives are proposed, similar to market solutions.As  derived  from  literature  and  simulations  executed  along  this  M.  Sc.    Thesis,  the Merritt Cage seems beneficial against any other configuration in terms of magnetic field uniformity and effective volume.  After the design and assembly of the test bench, both properties were verified and successfully achieved, despite the lack of calibration, not executed because of time limitation, and tiny issues encountered along the full evolutionof the project. / Attitude Determination and Control System (ADCS) är ofta ett komplicerat system ombord på alla satelliter som behöver validering och testning för att bevisa dess användbarhet och  verifiera dess  programvarukompatibilitet med  hårdvara och  andra delsystem.   Ett fel  i  omloppsbana  är  extremt  dyrt  med  avseende  på  kostnader  och  tid  på  grund  av förberedelse  och  lansering  av  nyttolast  Den  ideala  testbänken  skulle  vara  den  som perfekt  simulerar  rymdmiljön  och  alla  dess  huvudfaktorer  såsom  viktlöshet,  Earth’s Magnetic  Field  (EMF),  vakuum,  neutrala  partiklar,  plasma  och  strålning,  bland  andra. Målet  i  detta  fall  var  EMF,  löst  med  en  Helmholtz-bur  i  en  Merritt-konfiguration,  och viktlöshet,  inte  implementerad  men  analyserad  i  detalj  där  olika  alternativ  föreslås, liknande marknadslösningar.Som härstammar från litteratur och simuleringar utförda längs denna M. Sc. Avhandling verkar Merritt Cage vara gynnsam mot annan konfiguration när det gäller magnetfältens enhetlighet och effektiv volym.  Efter konstruktionen och montering av testbänken, var båda egenskaperna verifierade och framgångsrikt uppnådda, trots bristen på kalibrering, inte  genomförda  på  grund  av  tidsbegränsning,  och  små  problem  som  uppstod  underprojektets fulla utveckling.

La suppression du vecteur gravité lors des vols spatiaux normalement orienté de la tête vers les pieds en position debout agit sur les fluides de l’organisme par la perte du gradient de pression hydrostatique, ce qui aboutit à un syndrome de déconditionnement cardio-vasculaire. Cette absence de gravité perturbe également le système vestibulaire, particulièrement les otolithes qui perdent leur capacité à détecter les inclinaisons de la tête. Nous avons conduit nos études chez l’homme à l’aide du modèle d’immersion sèche durant 3 jours ainsi que du modèle d’alitement anti-orthostatique durant 60 jours.Le but de notre premier travail de recherche est d’étudier l’influence du système otolithique sur la régulation du système cardio-vasculaire au travers du réflexe vestibulo-sympathique. Il a pour cela été utilisé des expérimentations de stimulation galvanique pour évaluer la sensibilité otolithique ainsi que des manœuvres de flexion de cou associées à des mesures cardio-vasculaires conventionnelles et de pléthysmographie. Un accéléromètre a, de plus, été utilisé pour quantifier les phases d’activité et d’inactivité.Le but de notre second travail de recherche est d’étudier l’évolution du baroréflexe carotidien au cours des modèles de stimulation d’impesanteur et d’établir d’éventuelles hypothèses d’interaction avec les afférences otolithiques. Il a pour cela été utilisé des mesures de pression artérielle et de fréquence cardiaque en réponse à des stimulations mécaniques des barorécepteurs carotidiens appliquées de façon directe via la technique du collier de pression.Nos résultats ont confirmé que la manœuvre de flexion du cou est bien une stimulation otolithique avec l’apparition des modifications de réactivité otolitiques seulement en décubitus ventral et non en décubitus latéral. Néanmoins le rôle du réflexe vestibulo-sympathique sur la régulation cardio-vasculaire n’est pas clairement mis en évidence. Par ailleurs, la sensibilité du baroréflexe carotidien au cours de ces protocoles n’est pas modifiée.Notre hypothèse générale d’une modification du contrôle cardio-vasculaire en lien avec la réduction de la stimulation otolithique au cours de protocoles de simulation d’impesanteur n’est pas vérifiée. Il reste à comprendre la signification réelle de la manœuvre du head-down neck flexion et son lien avec l’authentique stimulation otolithique qu’elle provoque. Il est vraisemblable que de multiples systèmes sensoriels interviennent dans la régulation cardio-vasculaire en lien avec la gravité. Le rôle spécifique du système vestibulaire sera vraisemblablement mieux appréhendé dans des situations où sa plasticité est le mieux mise en jeu c’est-à-dire en impesanteur réelle. / The removal of the gravity vector during spaceflight normally directed from the head to the feet in the standing position acts on the body fluids by the loss of the hydrostatic pressure gradient, which results in a cardiovascular deconditioning syndrome. This lack of gravity also disturbs the vestibular system, particularly otoliths that lose their ability to detect head tilts. We conducted our studies in humans using the 3-day dry immersion model and the 60-day anti-orthostatic bed rest model. The aim of our first research work is to study the influence of the otolithic system on the regulation of the cardiovascular system through the vestibulo-sympathetic reflex. For this purpose, galvanic stimulation experiments were used to evaluate otolithic sensitivity as well as neck flexion maneuvers associated with conventional cardiovascular and plethysmography measurements. In addition, an accelerometer has been used to quantify the activity and inactivity phases. The aim of our second research project is to study the evolution of the carotid baroreflex during weightlessness simulation models and to establish possible hypotheses of interaction with otolithic afferents. For this purpose, blood pressure and heart rate measurements were used in response to mechanical stimulations of carotid baroreceptors applied directly via the pressure collar technique. Our results confirmed that the neck flexion maneuver is indeed an otolithic stimulation with the appearance of otolitic changes of reactivity only in ventral decubitus and not in lateral decubitus. Nevertheless, the role of vestibulo-sympathetic reflex on cardiovascular regulation is not clearly demonstrated. Moreover, the sensitivity of the carotid baroreflex during these protocols is not modified. Our general hypothesis of a change in cardiovascular control related to the reduction of otolithic stimulation during weightless simulation protocols is not verified. It remains to understand the real meaning of the head-down neck flexion maneuver and its connection with the authentic otolithic stimulation it causes. It is likely that multiple sensory systems are involved in cardiovascular regulation in relation to gravity. The specific role of the vestibular system is likely to be better understood in situations where its plasticity is best brought into play, that is to say in real weightlessness.