Application of Phase Imaging at High Field - MR Thermometry at 7 Tesla

The main purpose of this research was to develop improved methods for RF coil characterisation, and for non-invasive spatio-temporal mapping of temperature in the living body, in order to utilise the full potential of magnetic resonance imaging (MRI) at high magnetic fields by ensuring radiofrequency (RF) safety. Current RF power limits are often overly conservative, unnecessarily limiting the full potential of MRI, especially at high field. Thus it is useful to monitor tissue temperature while running MR imaging sequences which may deposit high RF power. Proton resonance frequency (PRF) MR thermometry can employ the phase of the complex MR signal to estimate temperature change over time. However, the shift of the water PRF with temperature is relatively small, making phase-based MR thermometry inherently sensitive to any extraneously caused changes of local frequency or MR phase. A potential source of error to PRF MR thermometry is a change in surround air susceptibility. The considerable impact of air susceptibility changes on PRF MR thermometry was demonstrated and quantified in experiments and magnetic field simulations. One way of correcting MR thermometry is to use a chemically shifted reference substance, in combination with a phase-sensitive chemical shift-selective MR thermometry sequence. The requirement of having a reliable separation of substances based on their resonance frequency was met by a novel frequency-selective phase-sensitive spin-echo (SE) MR thermometry sequence. This sequence was thoroughly tested in phantom and in-vivo experiments as well as in extensive Bloch simulations. The sequence limitations and advantages are discussed in detail. This technique acquires unsaturated water and fat images in rapid succession at the same position in space. The acquisition of a water and fat slice in less than 100 ms allows the correction of rapid field fluctuations in the brain caused by breathing and heartbeat, while still ensuring the correction of long term drift. With no assumptions required regarding temperature distribution in the tissue, this novel MR thermometry technique can measure brain temperature within a single (1.5 mm)3 voxel with a very low standard deviation (SD) of 0.3 K. Using an MRI phantom with a dimethyl sulfoxide reference, heating experiments achieved a MR temperature measurement with an SD of approximately 0.1 K in a single (1.5 mm)3 voxel. In conclusion, the work presented in this thesis assists the development of a real-time in-vivo temperature monitoring system that guarantees patient RF safety at high field

Nucleophilic substitution of nitrite in nitrobenzenes, nitrobiphenyls and nitronaphthalenes

Aromatic compounds, accessible only by multistep procedures, can be synthesized easily by nucleophilic substitution of nitrite in nitrobenzenes, nitrobiphenyls, and nitronaphthalenes. Thus, meta-substituted phenols 3, 4, and 7 are obtained from 1,3-dinitrobenzene (1) and meta-substituted nitrobenzenes 6, as well as 3,5-disubstituted phenols 10 and 5-substituted resorcinol derivatives 11 from 3,5-disubstituted nitrobenzenes 9. The unsymmetrically substituted nitrobiphenyls 13, 15, 17, 19, 21, 23, 24, and 26 are also available by nitrite exchange from the corresponding easily accessible dinitrobiphenyls 16, 18, 20, 22, and 25. A nitrite exchange with nucleophiles is easily possible in the 1,5-disubstituted naphthalenes 29, 34, while in the case of the 1,8-disubstituted naphthalenes 31, 36 only the chloro derivative 36 undergoes this exchange under much stronger conditions in low yield

Influence of head size on the development of metallic wear and on the characteristics of carbon layers in metal-on-metal hip joints

Background and purpose Particles originating from the articulating surfaces of hip endoprostheses often induce an inflammatory response, which can be related to implant failure. We therefore analyzed the metal content in capsular tissue from 44 McKee-Farrar metal-on-metal hip prostheses (with 3 different head sizes) and we also analyzed the morphological structure of layers located on articulating surfaces

Identifying service product features associated with visitor satisfaction and revisit intention: A focus on sports events

To date, it remains very challenging for managers to combine different features of sports events into compelling product/service offerings that meet visitors\u27 expectations. Yet, there is a scarcity of research that demonstrates how sport event managers can overcome this challenge, thereby leaving a gap in the sporting event literature. To fill part of this gap, this study used an in-depth bibliographic review to identify features commonly associated with product/service offerings at sports events and then used those features to create a new measuring instrument to examine different service offering scenarios. In this respect, seven key features were combined into 19 service offering scenarios. A total of 2229 responses were collected through structured questionnaires at six sports events in Taiwan. Then, this study used the collected responses to explore the associations amongst the 19 service offering scenarios, visitor satisfaction, and revisit intention using multiple regression equations. After examining the suitability of the models, the best fit models were then depicted with path analysis graphs for comparisons and contrasts. The findings of this study provide important insights on how sporting event marketers or destination managers can combine different product/service characteristics to build a set of product/service offering scenarios and then test the product/service offering scenarios that best meet visitors\u27 expectations and also increase visitors’ satisfaction level and their intention to come back

Understanding the Complexity of Reusing Knowledge across Contexts - A situated learning perspective

There is a prevailing belief today that knowledge is one of the most important sources of an organization’s competitive advantage. Through attempting to transfer and reuse knowledge organizations try to prevent the reinvention of the wheel. However, these attempts have proven to be problematic in the past. The purpose of our study is to contribute to the understanding of what makes the transfer and reuse of knowledge a difficult and complex task. We aim to do so through looking at an initiative to replicate Six Sigma results at a large Scandinavian manufacturing company. Taking a situated learning perspective, we analyze how people work and interact in communities of practice when carrying out improvement work. Results show that in such an environment, knowledge is contextual and has to go through a process of transformation to be understood and valued by another community. To enable such a process to take place it is important to shift emphasis from transferring knowledge through hierarchies and formal descriptions to activities that connect and expand communities of practice. Suggestions for such activities are given to management.International Managemen

Symposium: . Gerechtigkeit II: Moderatoren des Gerechtigkeitserlebens

Das Symposium soll einen Beitrag zu einem Verständnis dafür leisten, wann und unter welchen Bedingungen Gerechtigkeitserleben besonders bedeutsam ist. Die Gerechtigkeitsforschung der letzten Jahre hat sich zunehmend mit der Frage beschäftigt, warum Gerechtigkeit sehr weitreichende Wirkungen hat und unter welchen Bedingungen diese Wirkungen auftreten. Dieses Symposium geht daher der Frage nach, welche Variablen die Zusammenhänge zwischen Gerechtigkeitserleben und Variablen des Verhaltens und Erlebens in verschiedenen Handlungsfeldern moderieren. Die einzelnen Beiträge untersuchen dabei: kulturelle Unterschiede in der Machtdistanz und dem Zeitempfinden für die Einschätzung von Unfairness und der Bereitschaft zu Verzeihen; gruppenbezogene Variablen der Distinktheit von Eigen- und Fremdgruppe im Kontext von Sanktionen (retributive Gerechtigkeit); den Zusammenhang zwischen Gerechte-Welt-Glaube und spezifischen Bewältigungsreaktionen auf erlebte Ungerechtigkeit bzw. Bullying in Schulen; sowie Statusmotive und moralische Identität in Bezug auf den fair process effect

Symposium: Gerechtigkeit I: Entstehung und Bedeutsamkeit des Gerechtigkeitserlebens

Die Erforschung des Gerechtigkeitserlebens hat sich als eine wichtige Thematik der Sozialpsychologie in den letzten Jahren und Jahrzehnten etabliert. Die Effekte von verschiedenen Arten des Erlebens von Gerechtigkeit auf eine Vielzahl von Variablen in unterschiedlichen Handlungsfeldern erwiesen sich dabei als sehr robust. Das Symposium geht der Frage nach, wie Gerechtigkeitserleben entsteht und welche Bedeutsamkeit Gerechtigkeitsvorstellungen für das Erleben und Verhalten haben. Konkret beschäftigen sich die einzelnen Beiträge mit den Auswirkungen der Fairness von Auswahlverfahren auf spätere Mitarbeitereinstellungen und –verhalten; der Integration unterschiedlicher Gerechtigkeitsvorstellungen in Verteilungssituationen und der Berechnung einer fairen Ressourcenverteilung; der Abgrenzung von Gerechtigkeitstheorien von anderen Theorien, die Reaktionen in Bedrohungssituationen erklären (z.B. Reaktanztheorie); den Unterschieden zwischen impliziten und expliziten Gerechtigkeitseinstellungen bei der Aktivierung von Verteilungsprinzipien; und den kognitiven und affektiven Prozessen bei der Entwicklung von Ungerechtigkeitssensibilität

Application of Phase Imaging at High Field - MR Thermometry at 7 Tesla

The main purpose of this research was to develop improved methods for RF coil characterisation, and for non-invasive spatio-temporal mapping of temperature in the living body, in order to utilise the full potential of magnetic resonance imaging (MRI) at high magnetic fields by ensuring radiofrequency (RF) safety. Current RF power limits are often overly conservative, unnecessarily limiting the full potential of MRI, especially at high field. Thus it is useful to monitor tissue temperature while running MR imaging sequences which may deposit high RF power. Proton resonance frequency (PRF) MR thermometry can employ the phase of the complex MR signal to estimate temperature change over time. However, the shift of the water PRF with temperature is relatively small, making phase-based MR thermometry inherently sensitive to any extraneously caused changes of local frequency or MR phase. A potential source of error to PRF MR thermometry is a change in surround air susceptibility. The considerable impact of air susceptibility changes on PRF MR thermometry was demonstrated and quantified in experiments and magnetic field simulations. One way of correcting MR thermometry is to use a chemically shifted reference substance, in combination with a phase-sensitive chemical shift-selective MR thermometry sequence. The requirement of having a reliable separation of substances based on their resonance frequency was met by a novel frequency-selective phase-sensitive spin-echo (SE) MR thermometry sequence. This sequence was thoroughly tested in phantom and in-vivo experiments as well as in extensive Bloch simulations. The sequence limitations and advantages are discussed in detail. This technique acquires unsaturated water and fat images in rapid succession at the same position in space. The acquisition of a water and fat slice in less than 100 ms allows the correction of rapid field fluctuations in the brain caused by breathing and heartbeat, while still ensuring the correction of long term drift. With no assumptions required regarding temperature distribution in the tissue, this novel MR thermometry technique can measure brain temperature within a single (1.5 mm)3 voxel with a very low standard deviation (SD) of 0.3 K. Using an MRI phantom with a dimethyl sulfoxide reference, heating experiments achieved a MR temperature measurement with an SD of approximately 0.1 K in a single (1.5 mm)3 voxel. In conclusion, the work presented in this thesis assists the development of a real-time in-vivo temperature monitoring system that guarantees patient RF safety at high field

Application of Phase Imaging at High Field - MR Thermometry at 7 Tesla

The main purpose of this research was to develop improved methods for RF coil characterisation, and for non-invasive spatio-temporal mapping of temperature in the living body, in order to utilise the full potential of magnetic resonance imaging (MRI) at high magnetic fields by ensuring radiofrequency (RF) safety. Current RF power limits are often overly conservative, unnecessarily limiting the full potential of MRI, especially at high field. Thus it is useful to monitor tissue temperature while running MR imaging sequences which may deposit high RF power. Proton resonance frequency (PRF) MR thermometry can employ the phase of the complex MR signal to estimate temperature change over time. However, the shift of the water PRF with temperature is relatively small, making phase-based MR thermometry inherently sensitive to any extraneously caused changes of local frequency or MR phase. A potential source of error to PRF MR thermometry is a change in surround air susceptibility. The considerable impact of air susceptibility changes on PRF MR thermometry was demonstrated and quantified in experiments and magnetic field simulations. One way of correcting MR thermometry is to use a chemically shifted reference substance, in combination with a phase-sensitive chemical shift-selective MR thermometry sequence. The requirement of having a reliable separation of substances based on their resonance frequency was met by a novel frequency-selective phase-sensitive spin-echo (SE) MR thermometry sequence. This sequence was thoroughly tested in phantom and in-vivo experiments as well as in extensive Bloch simulations. The sequence limitations and advantages are discussed in detail. This technique acquires unsaturated water and fat images in rapid succession at the same position in space. The acquisition of a water and fat slice in less than 100 ms allows the correction of rapid field fluctuations in the brain caused by breathing and heartbeat, while still ensuring the correction of long term drift. With no assumptions required regarding temperature distribution in the tissue, this novel MR thermometry technique can measure brain temperature within a single (1.5 mm)3 voxel with a very low standard deviation (SD) of 0.3 K. Using an MRI phantom with a dimethyl sulfoxide reference, heating experiments achieved a MR temperature measurement with an SD of approximately 0.1 K in a single (1.5 mm)3 voxel. In conclusion, the work presented in this thesis assists the development of a real-time in-vivo temperature monitoring system that guarantees patient RF safety at high field