The great divergence between the USO fund and WTI spot prices

This paper discusses the concept of the ‘roll yield’ and its impact on the performance of ETFs that invest in futures contracts of storable commodities. It argues that comparing the returns of a futures position to the returns of a spot position can be quite misleading. As a case study, it examines the returns of the USO exchange traded fund whose investment objective is to mimic the performance of WTI prices using futures contracts. A simple regression model shows that the significant underperformance of the USO fund relative to WTI spot prices has been caused by the prolonged contango market and the steep WTI futures curve in the post-2009 period. © 2022 Informa UK Limited, trading as Taylor & Francis Group

A review of stochastic volatility processes: Properties and implications

The volatility of a financial asset is an important input for financial decision-making in the context of asset allocation, option pricing, and risk management. The authors compare and contrast four approaches to stochastic volatility to determine which is most appropriate to each of these various needs. © Emerald Backfiles 2007

Wear of congruent meniscal bearings in unicompartmental knee arthroplasty: a retrieval study of 16 specimens.

Many designs of unicompartmental knee replacement show early and mid-term failure due to polyethylene wear. We studied the wear rate of congruent polyethylene meniscal bearings retrieved from failed Oxford unicompartmental knee replacements. We examined 16 bearings, 0.8 to 12.8 years after implantation, measuring their thickness and comparing it with that of 14 unused bearings. The mean rate of penetration, which included the effects of wear at both upper and lower surfaces, was 0.036 mm per year (maximum 0.08). Bearings as thin as 3.5 mm wore no faster than thicker models, but ten with evidence of impingement had greater wear. The six bearings with no impingement showed a mean rate of penetration of 0.01 mm per year. In unicompartmental knee replacement, careful implantation of fully congruous meniscal bearings can avoid failure due to polyethylene wear

Incomplete cement mantles in the sagittal femoral plane: an anatomical explanation.

The influence of operative technique on the formation of incomplete cement mantles in the sagittal plane has been rarely considered in the literature. In this article, we discuss the influence of the anatomy of the proximal femur on the formation of incomplete cement mantles and discuss how their incidence can be reduced by correct component positioning

Serum levels of cobalt and chromium in a complex modular total hip arthroplasty system.

There is concern that modularity in a total hip arthroplasty system increases serum cobalt and chromium ion levels. This study measures the serum cobalt and chromium levels in patients with an Oxford Universal Hip (Corin, Cirencester, United Kingdom), which has a modular sliding mechanism; patients with a similarly manufactured hip with no sliding mechanism; and a control group. Loosening was excluded clinically and radiologically. Arthroplasty patients had statistically higher levels of serum cobalt and chromium than controls, but there was no significant difference in levels between the implanted groups