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

A methodological analysis of national models of integration: time to think without the models?

National models of integration are widely used to understand the relationship between nationalism and integration-immigration policies. In this methodological article, we highlight two key concerns. First, national models of integration emerged out of inductive and normative case studies. The analytical value of models which are based on inductive and normative reasoning is not directly generalisable beyond very similar cases. Second, and despite their inductive limitations, the generalisation and application of national models beyond these analytical limits have produced tautological and essentialist outcomes – fitting empirical data into the models and overlooking other possible correlations between nationalism and integration policies. Amid recent scholarly attempts at amending the national models, the question remains whether national models are truly useful tools for the comparative studies of the relationships between nationalism and integration-immigration policies. We argue that comparative examinations require a more robust theoretical and methodological approach that can be used across periods and contexts without becoming tautological and essentialist

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