DIP: Disruption-Tolerance for IP

Disruption Tolerant Networks (DTN) have been a popular subject of recent research and development. These networks are characterized by frequent, lengthy outages and a lack of contemporaneous end-to-end paths. In this work we discuss techniques for extending IP to operate more effectively in DTN scenarios. Our scheme, Disruption Tolerant IP (DIP) uses existing IP packet headers, uses the existing socket API for applications, is compatible with IPsec, and uses familiar Policy-Based Routing techniques for network management

Duality Theory for Robust Utility Maximisation

In this paper we present a duality theory for the robust utility maximisation problem in continuous time for utility functions defined on the positive real axis. Our results are inspired by -- and can be seen as the robust analogues of -- the seminal work of Kramkov & Schachermayer [18]. Namely, we show that if the set of attainable trading outcomes and the set of pricing measures satisfy a bipolar relation, then the utility maximisation problem is in duality with a conjugate problem. We further discuss the existence of optimal trading strategies. In particular, our general results include the case of logarithmic and power utility, and they apply to drift and volatility uncertainty

The impact of socioeconomic status on implant selection for patients undergoing hip arthroplasty

© 2015, UTMJ. All rights reserved. Hip resurfacing arthroplasty (HRA) is an alternative to total hip arthroplasty (THA) that preserves proximal femoral bone stock. Patient socioeconomic status (SES) has been demonstrated to impact access to care for numerous healthcare interventions but little is known about its impact on HRA when compared to THA. The aim of this study was to investigate whether there are disparities in SES for patients receiving HRA or THA. A retrospective database review was conducted comprising 617 hip arthroplasty patients (310 HRA, 307 THA). Patient postal code was used as a surrogate marker for patients’ SES and referenced against Canada Census Tract data to determine patient income. Patients greater than 70 years of age and those who underwent THA as revision or for fractures were excluded from the study. There were 465 patients included in the analysis comprised of 273 HRA and 192 THA patients. HRA patients ($33,240, SD$8,206) had a significantly higher mean income than THA patients ($29,365, SD$7,119, p\u3c0.001). The percentage of patients that underwent HRA compared to THA increased as patients’ SES increased. Patients with an income greater than $25,000 were significantly more likely to undergo HRA rather than THA (OR ≥1.76), compared to patients with an income less than$25,000 in whom THA was more likely. There appears to be a disparity in SES between patients who receive HRA and THA. Further work is needed to better understand the factors that influence the choice of hip replacement for patients requiring surgical intervention

Distribution of Water Vapor in Molecular Clouds

We report the results of a large-area study of water vapor along the Orion Molecular Cloud ridge, the purpose of which was to determine the depth-dependent distribution of gas-phase water in dense molecular clouds. We find that the water vapor measured toward 77 spatial positions along the face-on Orion ridge, excluding positions surrounding the outflow associated with BN/KL and IRc2, display integrated intensities that correlate strongly with known cloud surface tracers such as CN, C2H, 13CO J =5-4, and HCN, and less well with the volume tracer N2H+. Moreover, at total column densities corresponding to Av < 15 mag., the ratio of H2O to C18O integrated intensities shows a clear rise approaching the cloud surface. We show that this behavior cannot be accounted for by either optical depth or excitation effects, but suggests that gas-phase water abundances fall at large Av. These results are important as they affect measures of the true water-vapor abundance in molecular clouds by highlighting the limitations of comparing measured water vapor column densities with such traditional cloud tracers as 13CO or C18O. These results also support cloud models that incorporate freeze-out of molecules as a critical component in determining the depth-dependent abundance of water vapor