Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on May 26, 2010. Major professor: Lanny Griffin, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering, with a Specialization in Biomedical Engineering." " 2010." Includes bibliographical references (p. ).

Diss. (sammanfattning) Göteborg : Univ. , 2010.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 110-116). Also available on the Internet.

Las redes de área corporal permiten la interconexión de nodos independientes situados dentro o fuera de la superficie corporal o, incluso, alejados de dicha superficie. En cuanto a las comunicaciones intracorporales, el establecimiento de un enlace robusto con una cápsula endoscópica o con un marcapasos, son ejemplos de los avances tecnológicos conseguidos en las últimas décadas. A pesar de estos desarrollos en asistencia sanitaria, los estándares actuales para este tipo de comunicaciones no permiten conexiones inalámbricas de alta velocidad de transmisión, las cuales son comunes en los servicios actuales de telecomunicaciones. Los sistemas UWB han surgido como potencial candidato para las futuras redes de comunicaciones inalámbricas intracorporales. No obstante, el principal obstáculo de la tecnología UWB para aplicaciones intracorporales es la alta atenuación que sufren las señales transmitidas al atravesar los distintos tejidos corporales, que aumenta drásticamente con el aumento de la frecuencia. Por tanto, es importante una caracterización precisa del canal UWB intracorporal a la hora de validar dicha banda como la adecuada para este propósito.Esta tesis se centra en el análisis de la tecnología UWB para posibilitar comunicaciones intracorporales inalámbricas desde un punto de vista experimental. Para conseguir este objetivo, se ha empleado un novedoso sistema de medidas experimental basado en fantomas en diversos escenarios de propagación intracorporal. De esta forma, se pueden comprobar las pérdidas de propagación en el medio así como la diversidad del canal de una forma fiable. Con el fin de validar los valores obtenidos en el laboratorio, se han comparado y analizado con los obtenidos en un experimento in vivo. Por otro lado, se han diseñado y fabricado nuevas antenas UWB candidatas para comunicaciones intracorporales, empleando técnicas existentes y nuevas de miniaturización y optimización. Finalmente, se han usado técnicas basadas en diversidad para mejorar el rendimiento del canal de propagación en dos escenarios intracorporales diferentes. / Wireless Body Area Networks allow the interconnection between independent nodes located either inside or over the body skin or further. Regarding in-body communications, establishing a proper link with a capsule endoscope or with a pacemaker are examples of technological advances achieved in the last decades. In spite of these healthcare developments, current standards for these kind of communications do not allow high data rate wireless connections, which are common in the current telecommunication services. UWB systems have emerged as a potential solution for future wireless in-body communications. Nevertheless, the main drawback of UWB for in-body applications is the high attenuation of human body tissues which increases dramatically with the increment of frequency. Hence, an accurate UWB in-body channel characterization is relevant in order validate UWB frequency band as the best candidate for future networks of implantable nodes. This thesis is devoted to test UWB technology for in-body communications from an experimental point of view. To achieve this goal, a novel spatial phantom-based measurement setup is used in several in-body propagation scenarios. Thus, the losses in the propagation medium and the channel diversity are checked in a reliable way. In order to check the values obtained in laboratory, they are compared and discussed with those obtained in an in vivo experiment. On the other hand, new UWB antenna candidates for inbody communications are designed and manufactured by using typical and new miniaturization and antenna optimization techniques for this purpose. Finally, diversity-based techniques are used to improve the performance of the propagation channel in two different in-body scenarios. / Les xarxes d'àrea corporal permeten la interconnexió de nodes independents situats, o bé dins, o bé sobre la pell, o inclús allunyats del propi cos. Pel que fa a les comunicacions intracorporals, l'establiment d'un bon enllaç amb una càpsula endoscòpica o amb un marcapassos, són exemples dels avanços tecnològics aconseguits les darreres dècades. A pesar d'aquests desenvolupaments en assistència sanitària, els estàndards actuals per a aquests tipus de comunicacions no permeten connexions sense fil d'alta velocitat de transmissió, que són habituals als serveis actuals de telecomunicacions. Els sistemes UWB han sorgit com una solució potencial per a les futures comunicacions sense fill intracorporals. No obstant, el principal obstacle de la tecnologia UWB per a les aplicacions intracorporals és l'alta atenuació dels teixits del cos humà, que augmenta dràsticament amb l'increment de freqüència. Per tant, és important una caracterització acurada del canal UWB intracorporal a l'hora de validar la banda de freqüència UWB com a la millor candidata per a les futures xarxes de nodes implantats.Aquesta tesi se centra en l'anàlisi de la tecnologia UWB per a comunicacions intracorporals des d'un punt de vista experimental. Per a aconseguir aquest objectiu s'ha emprat un sistema novedós de mesures experimentals, basat en fantomes, en diversos escenaris de propagació intracorporal. D'aquesta manera es poden comprovar les pèrdues de propagació en el medi i la diversitat del canal d'una forma fiable. Per tal d'avaluar els valors obtinguts al laboratori, s'han comparat i analitzat amb aquells obtinguts en un experiment in vivo. Per altra banda, s'han dissenyat i fabricat noves antenes UWB candidates per a comunicacions intracorporals emprant tècniques típiques i noves de miniaturització i optimització d'antenes per a aquest propòsit. Finalment s'han usat tècniques basades en diversitat per a millorar el rendiment del canal de propagació en dos escenaris intracorporals diferents. / Andreu Estellés, C. (2018). UWB radio channel and diversity characterization for wireless implanted devices [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/111836 / TESIS

One of two project reports: The other part is designated PART B: OFF-CAMPUS PROJECT. / <p> Ion implantation is investigated as a technique to fabricate solar cells on monocrystalline silicon. The electrical properties of the implanted layer, as determined using the Hall Effect, and solar cell performance have beep studied for varying implant species (As and P), implanted dopant concentration (10^18 - 10^21 cm^-3), implanted substrate temperature (55° to 300°K} and annealing temperature (700° to 900°C). Some progress has been made toward the optimization of the various parameters. </p> / Thesis / Master of Engineering (MEngr)

<p> Ion implanted Bragg gratings integrated in rib waveguide structures were simulated, fabricated and characterized for the silicon-on-insulator (SOI) photonics platform. After selective silicon self-implantation, to an amorphizing dose of 2x10^15 ions/cm^2, the approximately 0.3 damage-induced increase in the refractive index provided the modulation mechanism necessary for the formation of a Bragg grating. The benefits of implanted Bragg gratings compared to the more widely utilized surface relief type gratings include planar surface retention, desirable for subsequent processing and wafer bonding, and a smaller depth of the index modulation, important for minimizing filtering bandwidths. To our knowledge, this is the first time ion implantation has been utilized to produce Bragg gratings integrated in an SOI rib waveguide. The benefits of using SOI for an optoelectronics platform include: cost minimization, reduced device size, and compatibility with silicon based microelectronics.</p> <p> Device performance was simulated using coupled mode theory (CMT) in conjunction with beam propagation methods (BPM), to determine transverse modal profiles for computing coupling coefficients and to determine geometric dimensions suitable to achieve adequate grating strength and single-mode operation. The Monte Carlo ion implantation simulator SUSPREM4, implementing the binary collision approximation (BCA), was used to determine the amorphous silicon grating profiles. Implanted grating devices were then fabricated into SOI having a 2.5 μm device layer and were optically characterized. For a grating length of 2100 μm and an implant energy of 60 keV, the extinction ratio of the resonant wavelength was found to be -18.11 dB and -0.87 dB for TE and TM polarizations respectively. The excess loss per unit length was measured to be 1.2 dB/mm for TE polarization and 0.6 dB/mm for TM polarization. After annealing the gratings at temperatures of up to 300 °C, used to annihilate low energy point defects responsible for absorption, it was found that the excess loss per unit length was reduced to 0.3 dB/mm for TE polarization. Compared to etched gratings with similar dimensions, it was determined that the strength of the implanted gratings was approximately 2.5 times stronger for grating lengths one third the length as result of mode-shifting due to the higher index of refraction. This is of great consequence to the miniaturization and densification of Bragg grating based devices in silicon photonics.</p> / Thesis / Master of Applied Science (MASc)

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2006. / Existing thermoplastic polyurethanes (TPUs), used in the manufacturing of cardiovascular devices, still have unproven long-term biostability and may be prone to excessive plastic deformation when subjected to cyclic loading. These negative aspects can be attributed to, among other factors, the weak nature of virtual crosslinking through microphase separation. The modification and covalent crosslinking of existing medical grade polyurethanes with unsaturated acyl chlorides are thus proposed to improve these properties. A model compound study was used to find a suitable acyl chloride (4-pentenoyl chloride), confirm the intended carbamate nitrogen as successful reaction site and to optimize the chemistry of the reaction. Two medical grade polyurethanes, Pellethane® 2363- 80AE (Pellethane) and PurSil 35-80A (PurSil), were subsequently successfully modified with 4-pentenoyl chloride. The degree of modification could be accurately controlled (R2 = 0.99) to between 4.5% to 20.0% and between 11.5% to 18.5% for the respective polyurethanes. The degree of modification and method of crosslinking were then optimized to obtain the required mechanical properties (i.e. minimum hysteresis). The hysteresis and creep of the modified and crosslinked Pellethane were reduced by 42.5% and 44.0%, respectively, while the hysteresis of the modified and crosslinked PurSil was reduced by 12.9%. The chemical stability of Pellethane (control) modified Pellethane (15% modification) and crosslinked Pellethane (Pell15.0) was evaluated in an in vitro degradation study. The hysteresis of the crosslinked polymer was at least 27.5% better when compared to Pellethane, and showed a significant resistance to surface degradation (as studied with scanning electron microscopy). Although the soft phases in both polyurethanes are vulnerable toward degradation, it was not as pronounced in Pell15.0, mainly due to the restriction of chain movement resulting from the crosslinking. Small-diameter tubular constructs, with similar fiber and wall thicknesses, were electrospun from Pellethane and the 15% modified Pellethane. A standard electrospinning technique was used in the case of the former while in the case of the latter a novel “reactive” electrospinning technique was used for the in situ crosslinking of the novel material, while simultaneously forming the tubular constructs. It is suggested that the manufacturing of Pell15.0 be scaled up to produce adequate amounts of material to enable the extrusion and in vivo evaluation of e.g. pacemaker leads. A circulatory animal model, e.g. a senescent baboon model, could be used to evaluate and further optimize the electrospun tubular constructs.

No description available.

The electronic structure of some transition metal compounds, specifically, Ca-doped LaMnO3, fundamental Mn oxides (MnO, Mn2O3, Mn3O4, and MnO2), and Fe-doped ZnO is studied using a combination of soft X-ray spectroscopy and atomic multiplet calculations. X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) are used as experimental tools to probe the unoccupied and occupied partial density of electronic states,respectively.<p> Ca-doped LaMnO3 perovskites have attracted great attention due to their colossal magnetoresistance and a wide range of magnetic and structural transitions. The magnetic and charge transport properties of these perovskites are directly related with Mn 3d-occupancy or Mn-valency and therefore, an investigation of the Mn-valence at Ca-doped LaMnO3 system is important. In this system, the Mn-valency is generally considered as a mixture of Mn3+ and Mn4+. But my research suggests the presence of Mn2+ at the surface of Ca-doped LaMnO3 samples. It is observed that increasing Ca-doping decreases Mn2+ concentration, and conversely, increases Mn3+ concentration. High temperature annealing at 1000 °C in air leads to the full reduction of surface Mn2+. Mechanisms for these observations are proposed in this study.<p> Mn oxides (MnO, Mn2O3, Mn3O4, and MnO2) are often used as reference standards for determining the Mn-valency in Mn-related complex systems and therefore a detailed understanding of their electronic structure is necessary. The Mn L2,3 XAS and O K XAS are measured for the four Mn oxides consisting of three common Mn oxidation states (Mn2+ in MnO, Mn3+ in Mn2O3, mixture of Mn2+ and Mn3+ in Mn3O4, and Mn4+ in MnO2). A significant energy shift with a systematic trend is observed in measured Mn L2,3 and O K absorption edges. These energy shifts are identified as a characteristic shift for different Mn oxidation states. Mn L2,3 Resonant Inelastic X-ray Scattering (RIXS) spectroscopy is demonstrated as a powerful tool in describing low energy excitations, e.g. d-d excitations and charge-transfer excited states in Mn oxides. For the first time, a RIXS study of Mn2O3,Mn3O4, and MnO2 is accomplished. Atomic multiplet calculations are used to successfully reproduce the energy positions and intensity variations of d-d excitation peaks observed in the experiment, and thus to describe the experimental RIXS spectra.<p> Finally, the local electronic structure of Fe implanted ZnO samples, a useful diluted magnetic semiconductor for spintronics, is investigated to shed light on the existing debate about the origin of ferromagnetism in these materials. Fe L2,3 XAS reveals that doped Fe ions are present in both Fe2+ and Fe3+ valence states. A combined theoretical and experimental study shows that doped ions are incorporated into Zn-sites of ZnO in tetrahedral symmetry. Fe L3- RIXS measurements demonstrate that a high Fe-ion dose of 8 × 107 cm-2 causes formation of FeO clusters, while low dose samples exhibit more free carriers.

The electronic structure of some transition metal compounds, specifically, Ca-doped LaMnO3, fundamental Mn oxides (MnO, Mn2O3, Mn3O4, and MnO2), and Fe-doped ZnO is studied using a combination of soft X-ray spectroscopy and atomic multiplet calculations. X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) are used as experimental tools to probe the unoccupied and occupied partial density of electronic states,respectively.<p> Ca-doped LaMnO3 perovskites have attracted great attention due to their colossal magnetoresistance and a wide range of magnetic and structural transitions. The magnetic and charge transport properties of these perovskites are directly related with Mn 3d-occupancy or Mn-valency and therefore, an investigation of the Mn-valence at Ca-doped LaMnO3 system is important. In this system, the Mn-valency is generally considered as a mixture of Mn3+ and Mn4+. But my research suggests the presence of Mn2+ at the surface of Ca-doped LaMnO3 samples. It is observed that increasing Ca-doping decreases Mn2+ concentration, and conversely, increases Mn3+ concentration. High temperature annealing at 1000 °C in air leads to the full reduction of surface Mn2+. Mechanisms for these observations are proposed in this study.<p> Mn oxides (MnO, Mn2O3, Mn3O4, and MnO2) are often used as reference standards for determining the Mn-valency in Mn-related complex systems and therefore a detailed understanding of their electronic structure is necessary. The Mn L2,3 XAS and O K XAS are measured for the four Mn oxides consisting of three common Mn oxidation states (Mn2+ in MnO, Mn3+ in Mn2O3, mixture of Mn2+ and Mn3+ in Mn3O4, and Mn4+ in MnO2). A significant energy shift with a systematic trend is observed in measured Mn L2,3 and O K absorption edges. These energy shifts are identified as a characteristic shift for different Mn oxidation states. Mn L2,3 Resonant Inelastic X-ray Scattering (RIXS) spectroscopy is demonstrated as a powerful tool in describing low energy excitations, e.g. d-d excitations and charge-transfer excited states in Mn oxides. For the first time, a RIXS study of Mn2O3,Mn3O4, and MnO2 is accomplished. Atomic multiplet calculations are used to successfully reproduce the energy positions and intensity variations of d-d excitation peaks observed in the experiment, and thus to describe the experimental RIXS spectra.<p> Finally, the local electronic structure of Fe implanted ZnO samples, a useful diluted magnetic semiconductor for spintronics, is investigated to shed light on the existing debate about the origin of ferromagnetism in these materials. Fe L2,3 XAS reveals that doped Fe ions are present in both Fe2+ and Fe3+ valence states. A combined theoretical and experimental study shows that doped ions are incorporated into Zn-sites of ZnO in tetrahedral symmetry. Fe L3- RIXS measurements demonstrate that a high Fe-ion dose of 8 × 107 cm-2 causes formation of FeO clusters, while low dose samples exhibit more free carriers.