Cause and Amelioration of MRI-Induced Heating Through Medical Implant Lead Wires

The RF fields present in magnetic resonance imaging (MRI) scanners can induce hazardous heating in patients wearing medical implants. The inherent design and locale of deep brain stimulators (DBS) and spinal cord stimulators (SCS) make them particularly susceptible. We apply antenna concepts and use electromagnetic (EM) simulation to explain the phenomenon and anticipate its sensitivity to lead wire length. We anticipate that a DC resistance of less than 50 Ω/m and an RF impedance of more than 1:23kΩ/m would be required for a safe electrode for SCS use. We investigate the possibility of manipulating wire conductivity and diameter in order to use the skin depth effect to achieve a safe electrode. The effect of the thickness and permittivity of insulation surrounding the wires is explored

Impulse TDR and its application to measurement of antennas

The traditional stimulus signal used in a time-domain reflectometer (TDR) is a voltage step. We propose an alternative technique, whereby an impulse generator is employed in place of the step generator in a TDR. The advantage conferred by “impulse TDR” is that more energy is available at higher frequencies than with conventional step TDR, and so a higher bandwidth and signal-to-noise ratio (SNR) is achieved. The theoretical result is compared with measurement

Measurement of antennas and microwave components using time-domain reflectometry of a voltage impulse

Band-pass microwave systems such as ultra-wideband antennas are traditionally characterized in the frequency-domain through a vector network analyzer in an anechoic chamber. A recent study proved antennas could be accurately measured in the time-domain using a step-function time-domain reflectometer (TDR), without the need for an anechoic chamber. We propose a new advance in the TDR characterization method. An impulse generator is employed in place of the step generator in a TDR set-up. The advantage conferred by this change is that more energy is available beyond a given frequency than with a step, and so a higher signal-to-noise ratio is achieved. The theoretical result is compared with measurement

Purposeful empiricism: how stochastic modeling informs industrial marketing research

It is increasingly recognized that progress can be made in the development of integrated theory for understanding, explaining and better predicting key aspects of buyer–seller relationships and industrial networks by drawing upon non-traditional research perspectives and domains. One such non-traditional research perspective is stochastic modeling which has shown that large scale regularities emerge from the individual interactions between idiosyncratic actors. When these macroscopic patterns repeat across a wide range of firms, industries and business types this commonality suggests directions for further research which we pursue through a differentiated replication of the Dirichlet stochastic model. We demonstrate predictable behavioral patterns of purchase and loyalty in two distinct industrial markets for components used in critical surgical procedures. This differentiated replication supports the argument for the use of stochastic modeling techniques in industrial marketing management, not only as a management tool but also as a lens to inform and focus research towards integrated theories of the evolution of market structure and network relationships

Social tourism and its contribution to sustainable tourism

Social Tourism has gained wide recognition for the benefits it brings to citizens who would otherwise not be able to participate in tourism. Social tourism also delivers benefits to the tourism industry, to destinations and to provide a positive return on investment for governments. However, whilst policy makers extol the virtues of social tourism, programmes have struggled to remain resilient under pressure on public finances caused by the Global Financial Crisis. This paper reviews the contributions of social tourism to sustainable tourism, critically assesses their potential to drive sustainable tourism in the future and makes recommendations for European policy makers

Theory in tourism

Tourism's relationship with theory is a vexed and complex issue. Previous research has examined the status of the academic study of tourism in disciplinary terms and the epistemological basis of knowledge production, yet very little examination of the conceptual structure of tourism has been undertaken. This conceptual article examines the presence of theory of tourism. It presents evidence, via the use of case study vignettes, of examples of theory/theorizing at the meta-, middle range and micro-levels. It articulates guidelines for theorising tourism and principles for developing a theoretical contribution to knowledge, critical to Annals of Tourism Research, whose mission is to advance knowledge of tourism phenomena at the conceptual level that can lead to progress in theory development

“Tourism for all?” Considering social tourism: a perspective paper

Social tourism concerns the inclusion of all members of a society in participation in tourism. Such participation is made possible through the provision of some form of system of social or welfare support (Minneart, Diekmann, and McCabe 2011). The interventions should have a well-defined social intention, such as to combat isolation and loneliness in older people, or to encourage family cohesion amongst low-income families or to support accessible tourism for people with disabilities. Social tourism is not a new concept, but it has in recent years attracted greater attention from researchers. This perspective article provides some background to the historical development of and progress made to improve inclusivity in access to tourism and points to the potential for the future

"Worlds of reason: the praxis of accounting for 'day visitor' behaviour in the Peak National Park" a qualititative investigation

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN039331 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Depression And Vulnerability: The Role Of Mood And Depression History On Cognitive Processing

Cognitive theorists hypothesize the existence of a causal cognitive vulnerability for depression that exists as either a continuously observable trait-like difference (i.e., the main-effects model) or a latent factor observable only in interaction with life events or mood (i.e., the interaction effects model). The current investigation examined the main-effects model and one form of the interaction-effects model that emphasizes current mood as the activator of latent cognitive vulnerability, the Differential Activation Hypothesis (DAH). When primed by sad mood, vulnerable individuals purportedly process environmental information in a manner similar to currently depressed individuals, making them more vulnerable for depression.;Studies of cognition in depressed, remitted and nondepressed subjects have been criticized for not priming subjects at test times or for using state-like symptom descriptor stimuli to assess trait-like differences. In the current investigation, depressed, remitted and never depressed women completed self-report questionnaires and two computerized tasks, a Stroop task and a deployment-of-attention task (DOAT). Care was taken to evaluate both stage-like and trait-like stimuli, as well as priming individuals, through mood inductions, before cognitive tasks.;Results indicated that subjects\u27 self-reports were predicted only by main effects of mood or diagnostic history, thereby supporting the main-effects hypothesis. When the Stroop task was presented following the DOAT, further support for the main-effects hypothesis was obtained. A weighted reaction time analysis using subjects\u27 self-referent ratings of stimuli was able to differentiate depressed and never depressed subjects\u27 performance, but not previously depressed subjects\u27 performance on the Stroop. Subjects\u27 responses to the DOAT conformed to predictions made from both the main-effects model and the DAH for trait-like but not for state-like stimuli. Never depressed subjects and unprimed remitted subjects evidenced a protective bias by focusing attention away from trait-like negative-content stimuli, while primed previously depressed subjects and currently depressed subjects were unbiased.;Overall, modest support for the DAH was obtained while studies more consistently pointed towards support for the main-effects hypothesis. Important stimulus characteristics were identified, implications for understanding depression and limitations of the current investigation were discussed

Emergence:Annals and the evolving research and publishing landscape in tourism

Annals of Tourism Research is a social sciences journal, which is celebrating its 50th anniversary in 2024. It holds a unique position in the field of tourism research and this article presents a discussion between its founding editor, Professor Jafar Jafari and one of its current co-editors, Professor Scott McCabe about its origins and emergence. The discussion covers the context and motivations for setting out the journal with a social sciences orientation, the ways that tourism research has expanded and developed as well as looks forward to the future, outlining a series of issues and topics that could be addressed in the coming decades to keep tourism research relevant and having impact on the industry and policy