930 resultados para Nuclear matters


Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Whether animal signals convey honest information is a central evolutionary question, since selection pressures could, in some circumstances, favour dishonesty. A prior study of signalling in hermit crabs proposed that the cheliped extension display of Pagurus bernhardus might represent such an instance of dishonesty. A limitation of this conclusion, however, was that honesty was defined in the context of size assessment, neglecting the potential information that displays might transmit about signallers' variable internal states. Recent analyses of signalling in this same species have shown that its displays provide reliable information about the amount of risk crabs are prepared to tolerate, which therefore might enable signallers to use these displays to honestly convey their motivation to take such risks. Here we test this 'honest advertisement of motivation' hypothesis by varying crabs' need for food and analysing their signalling during simulated feeding conflicts against a model. When crabs were starved for 1-5 days, they dropped significantly in weight. Despite this decrement in resource-holding potential and energy reserves, crabs were more likely to perform cheliped extension displays the longer they were food deprived. Longer-starved crabs, whose subjective resource value was greater, also displayed at a higher rate and were more likely to risk seizing the food from the model. We conclude that cheliped extension is a reliable indicator of crabs' internal state and suggest how this honest signal might operate in conflicts over a variety of other resources in addition to food. We propose that future studies detecting apparent dishonesty should analyse many possible signal-state correlations before concluding a signal is actually dishonest. (c) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Northern Ireland is uniquely distinguished from England, Scotland and Wales, by being a society in transition, emerging from a prolonged period of civil conflict and political instability that has affected its infrastructure and has increased the need for co-ordinated and specialist research. The paper traces some of the systemic challenges and opportunities for educational research capacity-building that arise from Northern Ireland being uniquely positioned as a small polity and critically appraises how initiatives elsewhere, while providing valuable exemplars, are unlikely to transfer readily to this context. Rather, building on an expanded definition of research capacity, Northern Ireland needs to capitalize cautiously on the current climate of openness between policymaker and researcher communities to develop a shared, cohesive agenda, improve research support and harness the strengths and pockets of excellence that exist. All of these should simultaneously go towards meeting local priority research needs, addressing the developmental capacity building needs of local researcher, while at the same time contributing to local, national and international knowledge production.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Purpose: The runt-related transcription factor, Runx2 may have an oncogenic role in mediating metastatic events in breast cancer, but whether Runx2 has a role in the early phases of breast cancer development is not clear. We examined the expression of Runx2 and its relationship with oestrogen receptor (ER) and progesterone receptor (PR) in breast cancer cell lines and tissues.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

ABSTRACT Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful analytical techniques available to biology. This review is an introduction to the potential of this method and is aimed at readers who have little or no experience in acquiring or analyzing NMR spectra. We focus on spectroscopic applications of the magnetic resonance effect, rather than imaging ones, and explain how various aspects of the NMR phenomenon make it a versatile tool with which to address a number of biological problems. Using detailed examples, we discuss the use of 1H NMR spectroscopy in mixture analysis and metabolomics, the use of 13C NMR spectroscopy in tracking isotopomers and determining the flux through metabolic pathways (‘fluxomics’) and the use of 31P NMR spectroscopy in monitoring ATP generation and intracellular pH homeotasis in vivo. Further examples demonstrate how NMR spectroscopy can be used to probe the physical environment of a cell by measuring diffusion and the tumbling rates of individual metabolites and how it can determine macromolecular structures by measuring the bonds and distances which separate individual atoms. We finish by outlining some of the key challenges which remain in NMR spectroscopy and we highlight how recent advances— such as increased magnet field strengths, cryogenic cooling, microprobes and hyperpolarisation—are opening new avenues for today’s biological NMR spectroscopists.