Optimal path shape for range-only underwater target localization using a Wave Glider

Underwater localization using acoustic signals is one of the main components in a navigation system for an autonomous underwater vehicle (AUV) as a more accurate alternative to dead-reckoning techniques. Although different methods based on the idea of multiple beacons have been studied, other approaches use only one beacon, which reduces the system’s costs and deployment complexity. The inverse approach for single-beacon navigation is to use this method for target localization by an underwater or surface vehicle. In this paper, a method of range-only target localization using a Wave Glider is presented, for which simulations and sea tests have been conducted to determine optimal parameters to minimize acoustic energy use and search time, and to maximize location accuracy and precision. Finally, a field mission is presented, where a Benthic Rover (an autonomous seafloor vehicle) is localized and tracked using minimal human intervention. This mission shows, as an example, the power of using autonomous vehicles in collaboration for oceanographic research.Peer ReviewedPostprint (author's final draft

Evaluation of health outcomes in osteoarthritis patients after total knee replacement: a two-year follow-up

10.1186/1477-7525-8-87Health and Quality of Life Outcomes8

A review of health utilities across conditions common in paediatric and adult populations

<p>Abstract</p> <p>Background</p> <p>Cost-utility analyses are commonly used in economic evaluations of interventions or conditions that have an impact on health-related quality of life. However, evaluating utilities in children presents several challenges since young children may not have the cognitive ability to complete measurement tasks and thus utility values must be estimated by proxy assessors. Another solution is to use utilities derived from an adult population. To better inform the future conduct of cost-utility analyses in paediatric populations, we reviewed the published literature reporting utilities among children and adults across selected conditions common to paediatric and adult populations.</p> <p>Methods</p> <p>An electronic search of Ovid MEDLINE, EMBASE, and the Cochrane Library up to November 2008 was conducted to identify studies presenting utility values derived from the Health Utilities Index (HUI) or EuroQoL-5Dimensions (EQ-5D) questionnaires or using time trade off (TTO) or standard gamble (SG) techniques in children and/or adult populations from randomized controlled trials, comparative or non-comparative observational studies, or cross-sectional studies. The search was targeted to four chronic diseases/conditions common to both children and adults and known to have a negative impact on health-related quality of life (HRQoL).</p> <p>Results</p> <p>After screening 951 citations identified from the literature search, 77 unique studies included in our review evaluated utilities in patients with asthma (n = 25), cancer (n = 23), diabetes mellitus (n = 11), skin diseases (n = 19) or chronic diseases (n = 2), with some studies evaluating multiple conditions. Utility values were estimated using HUI (n = 33), EQ-5D (n = 26), TTO (n = 12), and SG (n = 14), with some studies applying more than one technique to estimate utility values. 21% of studies evaluated utilities in children, of those the majority being in the area of oncology. No utility values for children were reported in skin diseases. Although few studies provided comparative information on utility values between children and adults, results seem to indicate that utilities may be similar in adolescents and young adults with asthma and acne. Differences in results were observed depending on methods and proxies.</p> <p>Conclusions</p> <p>This review highlights the need to conduct future research regarding measurement of utilities in children.</p

Should Endovascular Repair Be Reimbursed for Low Risk Abdominal Aortic Aneurysm Patients? Evidence from Ontario, Canada

Background. This paper presents unpublished clinical and economic data associated with open surgical repair (OSR) in low risk (LR) patients and how it compares with EVAR and OSR in high risk (HR) patients with an AAA > 5.5 cm. Design. Data from a 1-year prospective observational study was used to compare EVAR in HR patients versus OSR in HR and LR patients. Results. Between 2003 and 2005, 140 patients were treated with EVAR and 195 with OSR (HR: 52; LR: 143). The 1-year mortality rate with EVAR was statistically lower than HR OSR patients and comparable to LR OSR patients. One-year health-related quality of life was lower in the EVAR patients compared to OSR patients. EVAR was cost-effective compared to OSR HR but not when compared to OSR LR patients. Conclusions. Despite a similar clinical effectiveness, these results suggest that, at the current price, EVAR is more expensive than open repair for low risk patients

Spatial and temporal evolution of Liassic to Paleocene arc activity in southern Peru unraveled by zircon U-Pb and Hf in-situ data on plutonic rocks

International audienceCordilleran-type batholiths are built by prolonged arc activity along active continental margins and provide detailed magmatic records of the subduction system evolution. They complement the stratigraphic record from the associated forearcs and backarcs. We performed in-situ U-Pb geochronology and Hf isotope measurements on zircon grains from a large set of plutonic rocks from the Coastal Batholith in southern Peru. This batholith emplaced into the Precambrian basement and the Mesozoic sedimentary cover. We identify two major periods of voluminous arc activity, during the Jurassic (200-175 Ma) and the Late Cretaceous-Paleocene (90-60 Ma). Jurassic arc magmatism mainly resulted in the emplacement of a dominantly mafic suite with εHf values ranging from − 9.5 to + 0.1. Published ages south of the Arequipa area suggest that the arc migrated southwestward out of the study area during the Middle Jurassic. After a magmatic gap of 85 Ma, arc activity abruptly resumed 90 Ma ago in Arequipa. Intrusive bodies emplaced into both basement and older Jurassic intrusions and strata. This activity culminated between 70 and 60 Ma with the emplacement of very large volumes of dominantly quartz-dioritic magmas. This last episode may be considered as a flare-up event, characterized by intense magmatic transfers into the crust and rapid relief creation. The Late Cretaceous-Paleocene initial εHf are shifted toward positive values (up to + 3.3 and + 2.6) compared to the Jurassic ones, indicating either a larger input of juvenile magmas, a lesser interaction with the ancient crust, or an increase of re-melting of young mantle-derived mafic lower crust. These magmatic fluxes with juvenile component are coeval with the onset of the crustal thickening at 90 Ma and represent a significant contribution to the formation of the continental crust in this area