Estimating anisotropy parameters and traveltimes in the tau-p domain

The presence of anisotropy influences many aspects of seismic wave propagation and has therefore implications for conventional processing schemes. To estimate the anisotropy, we need both forward modelling and inversion tools. Exact forward modelling in anisotropic media is generally done by raytracing. However, we present a new and fast method, using the tau-p transform, to calculate exact P and SV reflection moveout curves in stratified, laterally homogeneous, anisotropic media which requires no ray tracing. Results are exact even if the SV-waves display cusps. In addition, we show how the same method can be used for parameter estimation. Since inversion for anisotropic parameters is very nonunique, we develop expressions requiring only a reduced number of parameters. Nevertheless, predictions using these expressions are more accurate than Taylor series expansions and are also able to handle cusps in the SV traveltime curves. In addition, layer stripping is a linear process. Therefore, both effective (average) and local (interval) estimates can be obtained

The views of young people with congenital cardiac disease on designing the services for their treatment

Background and purpose: There is little documented evidence of young people with congenital cardiac disease being consulted as to what help, if any, they really need in relation to their condition. Most research concentrates on the medical aspects of the condition. There are studies of psychological and social functioning, but few have directly sought the opinions of the young people. More recent research has indicated a need for health professionals to develop services to meet both psychosocial and physical needs of young people with congenital cardiac disease. The findings of the recent Kennedy Report support this need. The purpose of this study was to explore the views of young people with a range of congenital cardiac conditions, on what would help them better deal with their condition, and when and how help might be provided. Methods: This was a qualitative study using semi-structured interviews. We interviewed 16 young people in their own home. Interviews were tape-recorded and transcribed. Analysis was conducted using the "Framework" method. Results: Whilst most of the young people interviewed actively manage their condition, they think more support from others would be beneficial. Issues of activity and communication were cited most often as areas requiring more understanding from people they interact with, for example teachers and peers. The discussion focuses on how health professionals might change or develop their practice to help young people better cope with their condition. Conclusions: Most of the young people interviewed in this study had developed their own strategies for coping with their condition. Although this is a small study, the young people provided important suggestions as to how health professionals could better develop current services

Factors associated with self-perceived state of health in adolescents with congenital cardiac disease attending paediatric cardiologic clinics

The purpose of our study was to determine the ways in which adolescents with congenital cardiac disease believed that the condition had affected their life, and how these views were related to their perceived health. Interviews were conducted with a series of 37 adolescents, 17 girls and 20 boys, aged from 11 to 18, as they attended the clinics of 4 paediatric cardiologists in a teaching hospital in the United Kingdom. Transcripts of the interviews were analysed for recurring themes. A questionnaire was formed consisting of a set of questions for each theme, and additional items eliciting “perceived health”, and administered to a second series of 74 adolescents, 40 boys and 34 girls, who were again aged from 11 to 18 years. Slightly less than half (46%) perceived their health as either “good” or “very good”, and one-third (33%) rated it as “average”. The majority (66%) felt themselves to be “the same” as, or only very slightly “different” from, their peers. The assessment of the seriousness of their condition by the adolescents, the degree to which they saw themselves as different from others, and their perceived health, were not related to the “complexity of the underlying medical condition” as rated by their physician. It was the psychosocial themes, such as exclusion from activities or the effect of the condition on relationships, that were most strongly related to the perception of their health by the adolescents. Improved education of parents, teachers and peers, and attendance at classes for cardiac rehabilitation, might help to ameliorate some of these problems

Locating and Quantifying Broadband Fan Sources Using In-Duct Microphones

In-duct beamforming techniques have been developed for locating broadband noise sources on a low-speed fan and quantifying the acoustic power in the inlet and aft fan ducts. The NASA Glenn Research Center's Advanced Noise Control Fan was used as a test bed. Several of the blades were modified to provide a broadband source to evaluate the efficacy of the in-duct beamforming technique. Phased arrays consisting of rings and line arrays of microphones were employed. For the imaging, the data were mathematically resampled in the frame of reference of the rotating fan. For both the imaging and power measurement steps, array steering vectors were computed using annular duct modal expansions, selected subsets of the cross spectral matrix elements were used, and the DAMAS and CLEAN-SC deconvolution algorithms were applied

Trends in cyclones in the high-latitude North Atlantic during 1979-2016

We report an increase in winter (DJF) cyclone densities in the areas around Svalbard and in northwestern Barents Sea and a decrease in cyclone densities in southeastern Barents Sea during 1979-2016. Despite high interannual variability, the trends are significant at the 90% confidence level. The changes appear as a result of a shift into a more meridional winter storm track in the high-latitude North Atlantic, associated with a positive trend in the Scandinavian Pattern. A significant decrease in the Brunt-Vaisala frequency east of Svalbard and a significant increase in the Eady Growth Rate north of Svalbard indicate increased baroclinicity, favouring enhanced cyclone activity in these regions. For the first time, we apply composite analysis to explicitly address regional consequences of these wintertime changes in the high-latitude North Atlantic. We find a tendency toward a warmer and more moist atmospheric state in the Barents Sea and over Svalbard with increased cyclone activity around Svalbard.Peer reviewe

Experimental support of the scaling rule for demographic stochasticity

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73613/1/j.1461-0248.2006.00903.x.pd

Highly variable friction and slip observed at Antarctic ice stream bed

The slip of glaciers over the underlying bed is the dominant mechanism governing the migration of ice from land into the oceans, with accelerating slip contributing to sea-level rise. Yet glacier slip remains poorly understood, and observational constraints are sparse. Here we use passive seismic observations to measure both frictional shear stress and slip at the bed of the Rutford Ice Stream in Antarctica using 100,000 repetitive stick-slip icequakes. We find that basal shear stresses and slip rates vary from 104 to 107 Pa and 0.2 to 1.5 m per day, respectively. Friction and slip vary temporally over the order of hours, and spatially over 10s of metres, due to corresponding variations in effective normal stress and ice–bed interface material. Our findings suggest that the bed is substantially more complex than currently assumed in ice stream models and that basal effective normal stresses may be significantly higher than previously thought. Our observations can provide constraints on the basal boundary conditions for ice-dynamics models. This is critical for constraining the primary contribution of ice mass loss in Antarctica and hence for reducing uncertainty in sea-level rise projections