Multiple-mouse MRI (MMMRI) accelerates biomedical research by imaging multiple mice simultaneously. To date, MMMRI has been explored in three ways: shielded transmit-receive coils, shielded transmits coil with separate unshielded receive coils; and finally shielded transmit-receive coils with independent gradient coils. However alternative transmit coil configurations and possible benefits of eliminating shielding have not yet been explored. The goal of this thesis is to test possible radiofrequency configurations with and without shielding for the purpose of improving image quality for MMMRI. Results demonstrate that using an unshielded transmit-receive coil array provided a 20% improvement over an identical shielded coil. A new unshielded 7-coil MMMRI array is presented, minimizing the ghosting between image overlap using mutual inductance minimization and a sensitivity encoding (SENSE) reconstruction. The final array provided high resolution images (90µm) of up to seven live mice simultaneously with appropriate signal-to-noise for automated analysis.

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F. Bitter. / "March 2, 1949." / Signal Corps Contract no. W36-039-sc-32037. Project no. 102B Dept. of the Army Project no. 3-99-10-022

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Surface coil; Receiver coil; RF; MRI; High Input Reflection Coefficient Preamplifier. Includes bibliographical references (p. 86-88).

No description available.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Magnetic Resonance Imaging; Radio Frequency Coil; Breast Cancer; Imaging Systems. Includes bibliographical references (leaves 118-123).

Master of Science / Department of Electrical and Computer Engineering / Punit Prakash / The primary objective of this research is to implement an experimentally validated computational model to guide device design and selection of energy delivery strategies for treating chronic rhinitis by radiofrequency ablation. Chronic rhinitis is one of the most common global health problems. It is not life-threatening but has a severe impact on quality of life. Direct cost by chronic rhinitis is enormous and places a burden on societies. Radiofrequency ablation is proposed to be as an efficient treatment providing symptom relief and avoiding side effects compared to traditional therapies. Three-dimensional finite element method (FEM) models were developed to investigate RFA devices and energy delivery strategies. FEM computational models could provide vital variable profiles that are technically challenging to determine through experiments. Also, computer simulation could reduce the number of experimental procedures during the device design process. First, single pair bipolar RF ablation experiments were performed to validate FEM simulations using the same geometry as in experiments. The data from experiments and simulations had a high correlation (R = 0.91). Second, the Neurent basket electrode was employed in experimental ablations in egg white, for comparison against FEM simulations. Smaller lesion sizes were observed in experiments compared to simulations, attributed to thermal convection that was not accounted for in simulation. Finally, FEM simulations were used to investigate the effects of basket electrode diameter, length, and applied power on ablation zone formation. A shorter but wider electrode with a maximum spacing distance between two pairs of electrodes is preferable to create discontiguous ablation zones. 50% duty cycle was recommended to create thermal ablation zones with gradually increasing temperature and sufficiently large thermal lesion volumes.

Orientadores: Rosa Cristina Cecche Lintz, Luisa Andréia Gachet Barbosa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-26T02:21:25Z (GMT). No. of bitstreams: 1 Pfeifer_WeilaPacker_M.pdf: 2466874 bytes, checksum: 28fd415c46dbb96247c6b2f15fafae34 (MD5) Previous issue date: 2014 / Resumo: O crescente desenvolvimento tecnológico e a necessidade de comunicação entre as pessoas tem intensificado o aumento do número de equipamentos que se comunicam por meio de redes sem fio (wireless). As construções de alvenaria, ou seja, de paredes feitas de tijolos cerâmicos, blocos de concreto ou placas cimentícias são algumas das barreiras artificiais que podem influenciar na queda ou diminuição do sinal dessas redes, dificultando a comunicação entre os usuários de redes sem fio. A construção civil tem utilizado resíduos de diferentes naturezas para a produção de concretos e argamassas, tais como resíduos de construção e demolição, pó de mármore, pó de granito e de outras rochas, isoladores de porcelana para redes alta tensão, borracha, resíduos de lodo provenientes das Estações de Tratamento de Água (ETA) e Estação de Tratamento de Esgoto (ETE) como uma alternativa tecnicamente viável, tentando minimizar o consumo de materiais naturais e evitar a disposição inadequada dos resíduos no meio ambiente. Conciliando as necessidades tecnológicas e ambientais, esse trabalho objetiva estudar as características da pasta de cimento e do resíduo de borracha quanto à permissividade de ondas de radiofrequência. Visa-se com isso propor ao mercado a incorporação desse resíduo à fabricação de placas cimentícias ou divisórias, de modo que essas atenue o mínimo possível às ondas de radiofrequência das redes de wireless. Para tanto, foram caracterizados fisicamente o cimento e a borracha e moldados corpos de prova de pastas de cimento sem e com adição de borracha as quais foram ensaiadas à compressão. Amostras de pastas de cimento e amostras de resíduos de borracha foram caracterizadas quanto à permissividade de ondas de radiofrequência, utilizando equipamento analisador de redes e cavidade ressonante na faixa de frequência de 2,45 GHz que representa a faixa de frequência de utilização do wireless. Quanto aos resultados de compressão observa-se que se confirma a relação inversa entre o teor crescente de água/cimento e de borracha com a resistência à compressão. Quanto aos ensaios de radiofrequência, nota-se o aumento da tangente de perda para a pasta de cimento em relação ao resíduo de borracha, consequentemente a pasta de cimento possui uma menor permissividade das ondas de wireless. Para os ensaios de radiofrequência foi necessário desenvolver uma nova metodologia, adaptando para escalas reduzidas as exigências da Norma Técnica Brasileira para a fabricação de corpos de prova / Abstract: The increasing technological development and the need for communication between people has intensified the increasing number of devices that communicate through wireless networks (wireless). The masonry buildings, ie walls made of clay bricks, concrete blocks or cement slabs are some of the artificial barriers that can influence the fall or decrease the signal of these networks, hindering communication between users of wireless networks. The construction industry has used different kinds of waste for the production of concrete and mortar, such as construction and demolition waste, marble dust, granite dust and other rocks, porcelain insulators for high voltage networks, rubber, waste sludge from the Water Treatment Plants (WTP) and Sewage Treatment Plant (STP) as a technically viable alternative, trying to minimize the consumption of natural materials and avoid improper disposal of waste on the environment. Combining the technological and environmental needs, this work aims to study the characteristics of the cement paste and rubber residue as the permissiveness of radiofrequency waves. The aim is to propose it to the market to include this residue for the manufacture of cement slabs or partitions, so that these can attenuate the minimum radiofrequency waves to wireless networks. For that were physically characterized the cement and rubber and molded specimens of cement pastes with and without addition of rubber which were tested in compression. Samples of cement pastes and rubber waste samples were characterized as the permissiveness of radiofrequency waves, using network analyzer equipment and resonant cavity in the frequency band of 2.45 GHz that represents the range of the wireless frequency usage. Regarding the compression results it can be seen that confirms the inverse relationship between increasing water content / rubber cement and the compressive strength. For the tests, radio frequency, note the increase of loss tangent for the cement paste relative to residue of rubber, consequently the cement paste has a lower permittivity of the wireless waves. For testing radio frequency was necessary to develop a new methodology, adapting to the requirements of small scales Brazilian Technical Standard for the manufacture of test specimens / Mestrado / Tecnologia e Inovação / Mestra em Tecnologia

The increasing importance of narrow-band radiations is traced in the recent history of radio astronomy. The need for multi-channel spectrometers to observe these radiations is stressed. The theoretical basis of spectral analysis is given with particular emphasis on autocorrelation or interference methods. A twenty-channel radio-frequency spectrometer designed on interference principles has been constructed and found to perform in accordance with its theory of operation. When used in conjunction with a 25-metre telescope and a hydrogen receiver the spectrometer is capable of producing low-noise wideband spectra at high speed. The spectrometer output was recorded on punched cards, and subsequent data processing was by digital methods. A large area including the position of the spiral galaxy M31 was surveyed with the help of the spectrometer. One hundred and forty-three independent spectra of the 21-cm radiation of atomic hydrogen were obtained and are analyzed in terms of area, velocity, and shape. The major axis of the nebula is found to extend about 2.5° either side of the centre, in agreement with the work of van de Hulst, Raimond, and van Woerden (1957). The length of the minor axis, after correction for the effect of the antenna beamwidth, is only 40', a result which indicates a reduction in the inclination (of the plane of the galaxy to the line of sight) from 14.5° to 8.2°. This lower value leads to an upward revision of the optical axial ratio (of galactic thickness to galactic diameter) to 0.2, while maintaining a low ratio (0.07, Schmidt, 1957) for the distribution of atomic hydrogen. A high axial ratio would clear the way for a reinterpretation of the optical velocities of emission nebulae in M31 (Mayall, 1950), which have so far appeared to be in violent contradiction to the radio velocities (van de Hulst et al, 1957). It is suggested that many of these emission objects may lie some distance from the plane of the galaxy. The position angle of M31, as revealed by the spectrometer observations is distinctly less than the 38° established optically. A new value of 33° is proposed and it is suggested that the former value can be accounted for in terms of an increased axial ratio and the observed asymmetries in the light distribution. The velocity of the centre of gravity of M31 has been obtained by summation of all 143 spectra. The result, -295.6±0.4 km/sec with respect to the local standard of rest, is in complete agreement with that found by van de Hulst (ibid). Radial motions of a few km/sec are possible in the outer parts of M31 but their presence has not been established. Many of the spectra have multiple peaks, which may be interpreted in terms of spiral structure. The velocities of certain concentrations of atomic hydrogen are measurable but their positions are not resolved by the antenna beam. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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