Sea anemones (Exaiptasia pallida) use a secreted adhesive and complex pedal disc morphology for surface attachment

Background The mechanism by which sea anemones attach to surfaces underwater remains elusive, which is surprising given their ubiquitous distribution in the world’s oceans and tractability for experimental biology. Their adhesion is mechanically interesting, bridging the interface between very hard and soft materials. The Cnidaria are thought to have evolved adhesion to surfaces at least 505 Ma ago implying that, among the Metazoa, only Porifera developed this capability earlier. The purpose of this study was primarily to address an existing hypothesis, that spirocysts (a sticky class of cnidocyst) facilitate adhesion to surfaces, as observed during prey capture. Results We demonstrated conclusively that spirocysts were not involved in the pedal disc adhesion of Exaiptasia pallida. Second, we applied a variety of imaging methods to develop an understanding of the true adhesion mechanism. Morphological studies using scanning electron microscopy identified a meshwork of adhesive material, unique to the pedal disc. Serial block-face SEM highlighted four classes of cells that could secrete the adhesive from the pedal disc ectoderm. A variety of histochemical techniques identified proteins, glycans and quinones in the cell contents and secreted adhesive, with variation in contents of specific cell-types in different areas of the body. Conclusions Spirocysts are not used by Exaiptasia pallida for adhesion to surfaces. Instead, a structurally and compositionally complex secreted glue was observed, firmly attaching the animals underwater. The results of this study provide a basis for further investigations of adhesion in Cnidaria, and establish E. pallida as a new model organism for bioadhesion research

Dimensions of coupling in middleware

It is well accepted that different types of distributed architectures require different degrees of coupling. For example, in client-server and three-tier architectures, application components are generally tightly coupled, both with one-another and with the underlying middleware. Meanwhile, in off-line transaction processing, grid computing and mobile applications, the degree of coupling between application components and with the underlying middleware needs to be minimised. Terms such as "synchronous", "asynchronous", "blocking", "non-blocking", "directed", and "non-directed" are often used to refer to the degree of coupling required by an architecture or provided by a middleware. However, these terms are used with various connotations. And while various informal definitions have been provided, there is a lack of an overarching formal framework to unambiguously communicate architectural requirements with respect to (de-)coupling. This article addresses this gap by: (i) formally defining three dimensions of (de-)coupling; (ii) relating these dimensions to existing middleware; and (iii) proposing notational elements to represent various coupling integration patterns. This article also discusses a prototype that demonstrates the feasibility of its implementation

Evaluation of problem-solving skills: what we really do

Abstract no. 1394published_or_final_versio

Wildlife Conservation

In this paper we consider how conservation has arisen as a key aspect of the reaction to human-initiated degradation and disappearance of ecosystems, wild lands. and wildlife. Concern over species extinction is given an historical perspective which shows the way in which pressure on wild and natural aspects of global ecology have changed in recent centuries. The role of conservation in the struggle to protect the environment is then analysed using underlying ethical arguments behind the economic, ecological and rights based justifications given for conservation. The moral considerability of species and individuals is reviewed and different positions contrasted, most importantly utilitarianism versus rights. A central argument with primary influence over economics is the utilitarian justification for action and this is explored with reflection upon the use of monetary valuation. Rights are then explored and the use of consequentialism in adjudicating different rights claims introduced. Human preferences can be seen as practically powerful in justifying conservation policy decisions. even when an animal-centred ethic has been adopted. Yet ecological and non-consequentialist expressions of concern characterise the entire problem in fundamentally different ways, e.g. biodiversity and ecosystems maintenance versus marginal species loss, designation of wilderness areas versus management of parklands. Leaving the wild in wilderness and the natural in Nature cannot then be reduced to preference utilitarianism as in the economic calculus

Wildlife Conservation

In this paper we consider how conservation has arisen as a key aspect of the reaction to human-initiated degradation and disappearance of ecosystems, wild lands. and wildlife. Concern over species extinction is given an historical perspective which shows the way in which pressure on wild and natural aspects of global ecology have changed in recent centuries. The role of conservation in the struggle to protect the environment is then analysed using underlying ethical arguments behind the economic, ecological and rights based justifications given for conservation. The moral considerability of species and individuals is reviewed and different positions contrasted, most importantly utilitarianism versus rights. A central argument with primary influence over economics is the utilitarian justification for action and this is explored with reflection upon the use of monetary valuation. Rights are then explored and the use of consequentialism in adjudicating different rights claims introduced. Human preferences can be seen as practically powerful in justifying conservation policy decisions. even when an animal-centred ethic has been adopted. Yet ecological and non-consequentialist expressions of concern characterise the entire problem in fundamentally different ways, e.g. biodiversity and ecosystems maintenance versus marginal species loss, designation of wilderness areas versus management of parklands. Leaving the wild in wilderness and the natural in Nature cannot then be reduced to preference utilitarianism as in the economic calculus

Extending a perfect matching to a Hamiltonian cycle

Graph TheoryInternational audienceRuskey and Savage conjectured that in the d-dimensional hypercube, every matching M can be extended to a Hamiltonian cycle. Fink verified this for every perfect matching M, remarkably even if M contains external edges. We prove that this property also holds for sparse spanning regular subgraphs of the cubes: for every d ≥7 and every k, where 7 ≤k ≤d, the d-dimensional hypercube contains a k-regular spanning subgraph such that every perfect matching (possibly with external edges) can be extended to a Hamiltonian cycle. We do not know if this result can be extended to k=4,5,6. It cannot be extended to k=3. Indeed, there are only three 3-regular graphs such that every perfect matching (possibly with external edges) can be extended to a Hamiltonian cycle, namely the complete graph on 4 vertices, the complete bipartite 3-regular graph on 6 vertices and the 3-cube on 8 vertices. Also, we do not know if there are graphs of girth at least 5 with this matching-extendability property

A Simplified Procedure for Sizing Vertical Ground Coupled Heat Pump Heat Exchangers for Residences in Texas

A simplified technique for the sizing of vertical U-tube ground coupled heat pump (GCHP) heat exchangers for Texas climates was developed utilizing a transient simulation model of a ground coupled heat pump and weather and soil data for Texas. The simulation model discretized the ground heat exchanger into elements and computed the temperature distribution surrounding the heat exchanger on a minute-by-minute basis. Hundreds of runs were made with the model for a wide range of ground temperatures, ground thermal properties (density, thermal conductivity, and specific heat), and outdoor weather. A set of sizing charts were developed from the model runs that could provide quick reference on the size of the ground heat exchanger. Corrections for ground temperature, ground density, ground thermal conductivity, and indoor air temperature were presented. Soil temperature and thermal conductivity were found to be the most important parameters for sizing GCHP heat exchangers. Results from the simplified method were compared to two available heat exchanger sizing methods: the National Water Well Association (NWWA) and the International Ground Source Heat Pump Association (IGSHPA). The simplified method predicted shorter lengths than those from either of these two methods