Evidence that Adaptation in Drosophila Is Not Limited by Mutation at Single Sites

Adaptation in eukaryotes is generally assumed to be mutation-limited because of small effective population sizes. This view is difficult to reconcile, however, with the observation that adaptation to anthropogenic changes, such as the introduction of pesticides, can occur very rapidly. Here we investigate adaptation at a key insecticide resistance locus (Ace) in Drosophila melanogaster and show that multiple simple and complex resistance alleles evolved quickly and repeatedly within individual populations. Our results imply that the current effective population size of modern D. melanogaster populations is likely to be substantially larger (≥100-fold) than commonly believed. This discrepancy arises because estimates of the effective population size are generally derived from levels of standing variation and thus reveal long-term population dynamics dominated by sharp—even if infrequent—bottlenecks. The short-term effective population sizes relevant for strong adaptation, on the other hand, might be much closer to census population sizes. Adaptation in Drosophila may therefore not be limited by waiting for mutations at single sites, and complex adaptive alleles can be generated quickly without fixation of intermediate states. Adaptive events should also commonly involve the simultaneous rise in frequency of independently generated adaptive mutations. These so-called soft sweeps have very distinct effects on the linked neutral polymorphisms compared to the standard hard sweeps in mutation-limited scenarios. Methods for the mapping of adaptive mutations or association mapping of evolutionarily relevant mutations may thus need to be reconsidered

Departure from linearity of fibre Bragg grating temperature coefficients

We have measured the Bragg wavelength shift of three gratings from -30degreesC to +80degreesC. The observed deviation from linearity is a quadratic function of temperature, arising from the non-linear thermo-optic coefficient of silica glass

A fibre optic microsensor for measurement of temperature dynamics in gas turbine systems

The use of computational fluid dynamics (CFD) to model the temperature and pressure distributions which drive complex thermodynamic processes in gas turbine systems contributes to more cost efficient turbine design and development. However, experimental measurements are still required for validation of full-field CFD models, particularly in regions of highly unsteady flow where model stability is most severely tested. THis work concerns the development of fiber optic temperature and pressure microsensors for measurements combining high spatial resolution and high bandwidth in unsteady gas flows. The objective of the work presented in this paper was to measure gas total temperature in a large- scale turbomachinery test-rig at DERA Pyestock, known as the Isentropic Light Piston Facility. We have accordingly designed a dual sensor system, in which one of the elements is heated, so that gas total temperature can be measured independently of the convective heat transfer coefficient. While such dual element probes based on thin-film resistance gauges have been developed previously for aerodynamic studies, this is the first report of their development using optical sensors. ©2003 Copyright SPIE - The International Society for Optical Engineering

Application of Hilbert transforms to high resolution strain and temperature characterisation of fibre Bragg grating sensors

We report measurements of the strain and temperature coefficients of optical fibre Bragg gratings with similar to 1pm wavelength resolution using Fourier transform spectroscopy and Hilbert transform signal processing

Bend measurement using Bragg gratings in multicore fibre

We describe the measurements of curvature made using Bragg gratings written in separate cores of a multicore optical fibre. The gratings act as independent, but isothermal, strain gauges. Thus the difference in Bragg wavelength between the gratings provides a measurement of local curvature

Transverse loading of multicore fibre gratings

We report experimental measurements of the reflection spectra of Bragg gratings inscribed in 4-core fibres under transverse loading. Broadening and splitting of the Bragg peaks from each core are observed as a function of load and fibre orientation