**The Centre for Mathematical Sciences**** research seminars and events are listed below.**

The four main seminar series are in applied mathematics, pure mathematics, statistics and theoretical physics. Visit the centre's webpages for the latest seminar updates and information.

**Wednesday 26 September (14:00-15:00, Room 101, Rolle Building): Flowing to minimal surfaces**

- Speaker: Melanie Rupflin (Oxford)

**Abstract:** Melanie will discuss the construction and properties of a geometric flow, the Teichmueller harmonic map flow, that is designed to change surfaces into minimal surfaces. As she will explain, this flow, which we defined as a natural gradient flow of the Dirichlet energy, succeeds in decomposing any closed surface in any compact target manifold into minimal surfaces. This is joint work with Peter Topping.

**Wednesday 3 October, 14:00-15:00 (Room 005, Babbage Building): Evolution of magnetic field structures in non-linear MHD dynamos**

- Speaker: Daniel Miller (Exeter)

**Abstract: **ABC flows are an exact solution to the MHD equation of motion. As such they provide an ideal testing ground for examining changes to the magnetic field during the saturation process. In this seminar I compare how the saturation process affects magnetic field structures in dynamos with and without stagnation points in their forcing.

Contact matthew.craven@plymouth.ac.uk for queries.

**Wednesday 17 October, 13:00-14:30 (Devonport Lecture Theatre, Portland Square Building): Mini-symposium in medical statistics**

**Practical issues in medical statistics**

- Speaker: Gavin Koh (GSK)

**Abstract: **Statistical methods provide a variety of options for designing a clinical trial: for example, superiority, equivalence and non-inferiority. Selecting a design depends not just on statistical considerations, but contradictory clinical, regulatory and ethical considerations. After completing a study, secondary multivariate analyses are often performed and further choices need to be made: Which exposure group should be chosen as comparator? Or should you fit a no-intercept model? How should the independent variables be parameterised?

Tafenoquine is a new chemical entity being developed as a novel treatment for malaria. Gavin will illustrate these questions using data from a recently completed phase III trial of tafenoquine in malaria. This will be an interactive seminar with the audience asked to suggest and justify design solutions.

**Dietary intake in the early years and its relationship to BMI in a bi-ethnic group: the Born in Bradford 1000 study**

- Speaker: Samuel Mahoney (Covance)

**Abstract: **The number of infants, toddlers and children who were overweight increased from 32 million globally in 1990 to 42 million in 2013. This figure is predicted to rise to 70 million by 2025. In the UK it is estimated by 2020 that 20% of all boys and 33% of all girls will be obese. Using data from the Born in Bradford 1000 cohort this study aimed to assess relationships between dietary intake at age 12, 18 and 36 months and BMI Z-scores at age 36 months in a bi-ethnic group. Results indicate that dietary intake at 18 and 36 months was somewhat related to BMI Z-score at age 36 months and suggest the importance of early interventions aimed at establishing healthy eating behaviours.

Contact Dr Yinghui Wei (yinghui.wei@plymouth.ac.uk) for any queries.

**Wednesday 24 October: Non-linear generation of infragravity waves in deep waters**

- Speaker: Teodor Vrecica (Tel Aviv University)

**Abstract: **Infragravity (IG) waves are commonly defined as sea surface gravity waves whose frequency is lower than that of the wind sea (0.05 Hz) and higher than that of the tides and internal waves (0.005 Hz). They are important for various aspects in oceanography and marine engineering such as: estimations of sediment transport and harbor resonances, altimetry measurements, the breaking of the ice sheet in the Pacific and Earth’s hum. Their primary known generation mechanism is the nonlinear shoaling of the wave field. Therefore, the focus of most previous related works was limited to coastal areas. Yet, details of the generation, and specially their directional properties, are still not fully understood. Results of recent field measurements confirmed the existence of IG wave climate in deeper waters. A common assumption is that the origin of deep water IG waves is the reflection from coastlines (leaky waves), however not every occurrence can be explained in this manner. Here, we present a new triad interaction mechanisms for IG wave generation in deep water. For steady homogeneous deep water wave fields, three wave interactions only produce steady non-resonant interactions. However, for evolving seas waves are able to resonate with changes of the wave field in time and space to yield mean energy transfer to the IG frequency range. The considered effects include simple growth of the wave field, effects of gustiness, and whitecapping. A new model for IG wave generation is constructed, which takes these effects into account. It is used to evaluate several storm events, where data obtained from archived reanalysis is used. Model results are compared to measurements of deep water pressure gauges with a good capability of describing the directional properties of the IG frequency range. The presented work sets the basis for future formulation of an IG wave source term for extending IG wave forecasting models to the deep waters.

This is a joint seminar with CPRG. Contact matthew.craven@plymouth.ac.uk for any queries.