107 research outputs found
Stabilising Lyme Regis â a strategic approach
Coastal erosion and landslides have been a constant threat to Lyme Regis in West Dorset, UK for over 250 years. By the 1980s, the frequency and scale of coastal erosion and land instability had reached a point whereby the local council realised that a change from the previous ad hoc repair and protection approach was needed to secure the long-term future of the town. An environmental improvements initiative was developed from then onwards to provide a strategic and integrated programme of coast protection and cliff stabilisation measures designed to mitigate the increasing threat of climate change, coastal erosion and landslides, while respecting the siteâs unique heritage and environmental interests. This paper outlines the background and principal phases of the project that have been successfully delivered over the period 1990â2015
Wide-field fluorescence lifetime imaging with optical sectioning and spectral resolution applied to biological samples
How Gaussian competition leads to lumpy or uniform species distributions
A central model in theoretical ecology considers the competition of a range
of species for a broad spectrum of resources. Recent studies have shown that
essentially two different outcomes are possible. Either the species surviving
competition are more or less uniformly distributed over the resource spectrum,
or their distribution is 'lumped' (or 'clumped'), consisting of clusters of
species with similar resource use that are separated by gaps in resource space.
Which of these outcomes will occur crucially depends on the competition kernel,
which reflects the shape of the resource utilization pattern of the competing
species. Most models considered in the literature assume a Gaussian competition
kernel. This is unfortunate, since predictions based on such a Gaussian
assumption are not robust. In fact, Gaussian kernels are a border case
scenario, and slight deviations from this function can lead to either uniform
or lumped species distributions. Here we illustrate the non-robustness of the
Gaussian assumption by simulating different implementations of the standard
competition model with constant carrying capacity. In this scenario, lumped
species distributions can come about by secondary ecological or evolutionary
mechanisms or by details of the numerical implementation of the model. We
analyze the origin of this sensitivity and discuss it in the context of recent
applications of the model.Comment: 11 pages, 3 figures, revised versio
Direct observation of Anderson localization of matter-waves in a controlled disorder
We report the observation of exponential localization of a Bose-Einstein
condensate (BEC) released into a one-dimensional waveguide in the presence of a
controlled disorder created by laser speckle . We operate in a regime allowing
AL: i) weak disorder such that localization results from many quantum
reflections of small amplitude; ii) atomic density small enough that
interactions are negligible. We image directly the atomic density profiles vs
time, and find that weak disorder can lead to the stopping of the expansion and
to the formation of a stationary exponentially localized wave function, a
direct signature of AL. Fitting the exponential wings, we extract the
localization length, and compare it to theoretical calculations. Moreover we
show that, in our one-dimensional speckle potentials whose noise spectrum has a
high spatial frequency cut-off, exponential localization occurs only when the
de Broglie wavelengths of the atoms in the expanding BEC are larger than an
effective mobility edge corresponding to that cut-off. In the opposite case, we
find that the density profiles decay algebraically, as predicted in [Phys. Rev.
Lett. 98, 210401 (2007)]. The method presented here can be extended to
localization of atomic quantum gases in higher dimensions, and with controlled
interactions
A mixed-methods needs assessment of adult diabetes mellitus (type II) and hypertension care in Toledo, Belize
Developments in the Photonic Theory of Fluorescence
Conventional fluorescence commonly arises when excited molecules relax to their ground electronic state, and most of the surplus energy dissipates in the form of photon emission. The consolidation and full development of theory based on this concept has paved the way for the discovery of several mechanistic variants that can come into play with the involvement of laser input â most notably the phenomenon of multiphoton-induced fluorescence. However, other effects can become apparent when off-resonant laser input is applied during the lifetime of the initial excited state. Examples include a recently identified scheme for laser-controlled fluorescence. Other systems of interest are those in which fluorescence is emitted from a set of two or more coupled nanoemitters. This chapter develops a quantum theoretical outlook to identify and describe these processes, leading to a discussion of potential applications ranging from all-optical switching to the generation of optical vortices
The COGs (context, object, and goals) in multisensory processing
Our understanding of how perception operates in real-world environments has been substantially advanced by studying both multisensory processes and âtop-downâ control processes influencing sensory processing via activity from higher-order brain areas, such as attention, memory, and expectations. As the two topics have been traditionally studied separately, the mechanisms orchestrating real-world multisensory processing remain unclear. Past work has revealed that the observerâs goals gate the influence of many multisensory processes on brain and behavioural responses, whereas some other multisensory processes might occur independently of these goals. Consequently, other forms of top-down control beyond goal dependence are necessary to explain the full range of multisensory effects currently reported at the brain and the cognitive level. These forms of control include sensitivity to stimulus context as well as the detection of matches (or lack thereof) between a multisensory stimulus and categorical attributes of naturalistic objects (e.g. tools, animals). In this review we discuss and integrate the existing findings that demonstrate the importance of such goal-, object- and context-based top-down control over multisensory processing. We then put forward a few principles emerging from this literature review with respect to the mechanisms underlying multisensory processing and discuss their possible broader implications
Long-distance seed dispersal by wind: disentangling the effects of species traits, vegetation types, vertical turbulence and wind speed
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