Food talk: 40-Hz fin whale calls are associated with prey biomass

Animals use varied acoustic signals that play critical roles in their lives. Understanding the function of these signals may inform about key life-history processes relevant for conservation. In the case of fin whales ( Balaenoptera physalus ), that produce different call types associated with different behaviours, several hypotheses have emerged regarding call function, but the topic still remains in its infancy. Here, we investigate the potential function of two fin whale vocalizations, the song-forming 20-Hz call and the 40-Hz call, by examining their production in relation to season, year and prey biomass. Our results showed that the production of 20-Hz calls was strongly influenced by season, with a clear peak during the breeding months, and secondarily by year, likely due to changes in whale abundance. These results support the reproductive function of the 20-Hz song used as an acoustic display. Conversely, season and year had no effect on variation in 40-Hz calling rates, but prey biomass did. This is the first study linking 40-Hz call activity to prey biomass, supporting the previously suggested food-associated function of this call. Understanding the functions of animal signals can help identifying functional habitats and predict the negative effects of human activities with important implications for conservation.

Challenges in approximating the Black and Scholes call formula with hyperbolic tangents

In this paper, we introduce the concept of standardized call function and we obtain a new approximating formula for the Black and Scholes call function through the hyperbolic tangent. Differently from other solutions proposed in the literature, this formula is invertible; hence, it is useful for pricing and risk management as well as for extracting the implied volatility from quoted options. The latter is of particular importance since it indicates the risk of the underlying and it is the main component of the option’s price. That is what trading desks focus on. Further we estimate numerically the approximating error of the suggested solution and, by comparing our results in computing the implied volatility with the most common methods available in the literature, we discuss the challenges of this approach.

Using video calling to simulate arthroscopic surgery in a resource-poor setting

There is high demand for arthroscopic procedures in the developing world. Simulation allows trainees to develop basic arthroscopic skills away from theatre, where there may be reduced surgical exposure compared with centres with established arthroscopic practice. Smartphones are widely available and accessible throughout the world. We propose a method to create a low-cost, low-fidelity arthroscopic simulator that can be used at home by using the video call function of smartphones. We used readily available materials from a local market. An adequately sized cardboard box was used to house exercises, LED head torch as a light source, bamboo skewers as probes and a smartphone with video call function allowed visualisation without the need to purchase additional equipment. The whole simulator was constructed using less than 50 ZAR (US$3) of new materials. The arthroscopic simulator can be built simply and is easily portable. Established training exercises can be practised and allow development of basic arthroscopic skills. Our home-made simulator is inexpensive, simple to construct and does not require additional hardware (or software) purchases by the trainee. It is a perfect solution for individuals who want to practise their arthroscopic skills, either at home or at the workplace.

NONPARAMETRIC ESTIMATES OF OPTION PRICES AND RELATED QUANTITIES

We propose a new nonparametric technique to estimate the call function based on the superhedging principle. This approach requires minimal assumptions on absence of arbitrage and other market imperfections. The estimates so obtained are then combined with SNP estimates of the actual density of market returns. This permits to investigate the time behavior of the relative distance between the two densities obtained. Our empirical findings suggest that the more the two densities differ, the shorter is time to maturity, suggesting a major role of uncertainty over shorter than longer horizons.