An Assessment of Perceived Crop Damage in a Tanzanian Village Impacted by Human-Elephant Conflict and an Investigation of Deterrent Properties of African Elephant (Loxodonta Africana) Exudates Using Bioassays

Human-elephant conflict (HEC) is on the rise in East Africa as habitat that was formerly occupied by elephants and other wildlife is being converted to farmland. African elephants (Loxodonta africana) will raid agricultural fields to feed on crops, and many agriculturalists attribute the majority of their crop damage to elephants. The first two objectives of this study were to evaluate the accuracy of this perception by comparing perceived crop damage by elephants and other factors to the actual, quantified crop damage, as well as to evaluate the effectiveness of deterrent methods against wildlife used by local farmers in a Tanzanian village. From May to November 2008, farmers from Miti Mirefu in northern Tanzania were interviewed about both their perception of crop damage and effectiveness of deterrents used. During the same period, the actual damage to their corn fields was measured and compared to the perceived damage. Participants perceived elephants to cause the most damage. Damage from elephants was infrequent, but when it occurred it was on a larger scale than damage attributed to other factors, suggesting that farmers assess damage based on the maximal damage by a single event. Damage from a lack of water was much more frequent and more severe on average than elephant damage. Traditional deterrent methods have not been effective and innovative techniques are difficult to institute on a wide scale. The final objective of this study was to assess compounds that might be used for crop protection. Elephants use chemical signals to communicate keep-away and attractant signals to conspecifics. Compounds within the exudates of African elephants can be identified and used as deterrents around crop fields or to attract elephants to a safe haven. From July to September 2008, at Ndarakwai Ranch in northern Tanzania, (E,E)-farnesol and 3-pentanone were bioassayed with wild African elephants. The compounds tested did not elicit bioactivity, but the importance of continued research on biologically meaningful signals is essential to effectively reducing HEC

Non-rigid image registration to reduce beam-induced blurring of cryo-electron microscopy images

Microscopic imaging and technolog

Polarization-controlled evolution of light transverse modes and associated Pancharatnam geometric phase in orbital angular momentum

We present an easy, efficient and fast method to generate arbitrary linear combinations of light orbital angular momentum eigenstates $\ell=\pm 2$ starting from a linearly polarized TEM$_{00}$ laser beam. The method exploits the spin-to-orbital angular momentum conversion capability of a liquid-crystal-based $q$-plate and a Dove prism inserted in a Sagnac polarizing interferometer. The nominal generation efficiency is 100\%, being limited only by reflection and scattering losses in the optical components. When closed paths are followed on the polarization Poincar\'{e} sphere of the input beam, the associated Pancharatnam geometric phase is transferred unchanged to the orbital angular momentum state of the output beam.Comment: 5 pages and 5 figure

Quantifying Spatiotemporal Chaos in Rayleigh-B\'enard Convection

Using large-scale parallel numerical simulations we explore spatiotemporal chaos in Rayleigh-B\'enard convection in a cylindrical domain with experimentally relevant boundary conditions. We use the variation of the spectrum of Lyapunov exponents and the leading order Lyapunov vector with system parameters to quantify states of high-dimensional chaos in fluid convection. We explore the relationship between the time dynamics of the spectrum of Lyapunov exponents and the pattern dynamics. For chaotic dynamics we find that all of the Lyapunov exponents are positively correlated with the leading order Lyapunov exponent and we quantify the details of their response to the dynamics of defects. The leading order Lyapunov vector is used to identify topological features of the fluid patterns that contribute significantly to the chaotic dynamics. Our results show a transition from boundary dominated dynamics to bulk dominated dynamics as the system size is increased. The spectrum of Lyapunov exponents is used to compute the variation of the fractal dimension with system parameters to quantify how the underlying high-dimensional strange attractor accommodates a range of different chaotic dynamics