56 research outputs found
An integrated ultrasound-guided high intensity focused ultrasound system for in-vivo experiment
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What meaning do gay men on PrEP make of their sexuality: a phenomenological investigation
No full textThis study aims to explore what meaning gay men on pre-exposure prophylaxis (PrEP) make of their sexuality. PrEP is a medication that was approved in 2012 by the US Federal Drugs Agency (FDA) as an effective means of prophylaxis against contracting HIV.
Eight gay men in London who have been on PrEP for at least 6 months, and who do not participate regularly in chemsex were interviewed, and the data was analysed using a hybrid method, relying mainly on Interpretative Phenomenological Analysis (IPA), in addition to a heuristic first step. The results revealed how the participants made sense of their sexualities through lenses of being and doing something sexual, often through the identity and acts of sexual roles. Speaking about their sexualities and PrEP showed to be important to the participants, not only as a means of communication, but also as a manifestation of their sexualities. Despite the notion that PrEP neutralises the threat of contracting HIV, the fear of HIV was still prevalent amongst the participants, and casual sex was still perceived to be potentially dangerous. Finally, the results reveal how these participants constructed and valued ideas and fantasies of ‘good’ and ‘natural’ sex, which PrEP seems to help them uphold.
This study can contribute towards a deeper understanding of gay sexuality, particularly given the context of rapid changes in technology in the fight against HIV. The clinical significance of this research, especially for existential therapists, lies in the importance the participants placed on speaking about their sexualities, the insights gained from how these participants navigate their sexual lives, and the challenges and dilemmas they face regarding the choices they make and the risks they are willing or not willing to take as part of their sexuality
Deep localized hyperthermia with ultrasound-phased arrays using the pseudoinverse pattern synthesis method
No full textOne of the major limitations of hyperthermia as a cancer treatment modality is the lack of heating equipment and techniques capable of consistent therapeutic heating of deep-seated tumors. This thesis introduces a new pattern synthesis method capable of precisely controlling the power deposition level at a set of control points in the treatment volume using ultrasound phased arrays. This method, called the pseudoinverse pattern synthesis method, reduces the pattern synthesis problem to one of estimating the minimum-norm least-square solution to a matrix equation of the form, Hu = p, where u is the array excitation vector, p is the desired complex pressure at the control points, and H is a matrix propagation operator from the surface of the array to the control points. A useful solution to this problem is obtained when the number of control points is less than the number of elements of the array and the matrix H is full rank. This solution, called the minimum-norm solution, allows the array to be focused at several points simultaneously. This multiple-focus approach is important when ultrasound is used as a heating agent as it reduces the spatial-peak temporal-peak intensity required to generate a specified heating pattern. Furthermore, the minimum-norm solution allows the optimization of the array excitation efficiency and the intensity gain at the control points. These quantities are very significant for achieving deep localized heating with phased arrays. In fact, optimization of the intensity gain at the control points generally results in removal of high intensity interference patterns from the synthesized field. The removal of high intensity interference patterns eliminates one of the major disadvantages of multiple focusing. The pseudoinverse pattern synthesis method is introduced and discussed in detail. Simulation results are used to demonstrate its powerful capabilities as a pattern synthesis method. Its generality is demonstrated by the use of several different array structures to synthesize different multiple-focus patterns. Simulation results indicate that direct synthesis of multiple-focus patterns can provide an alternative to single-focus scanning. Finally, measured intensity profiles using a prototype cylindrical-section array agree well with theoretically predicted profiles.Made available in DSpace on 2011-05-07T14:03:32Z (GMT). No. of bitstreams: 2
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