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Defining Role (defining + role)

Distribution by Scientific Domains

Life Sciences	33%

Selected Abstracts

The brain weights body-based cues higher than vision when estimating walked distances

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2010
Jennifer L. Campos
Abstract Optic flow is the stream of retinal information generated when an observer's body, head or eyes move relative to their environment, and it plays a defining role in many influential theories of active perception. Traditionally, studies of optic flow have used artificially generated flow in the absence of the body-based cues typically coincident with self-motion (e.g. proprioceptive, efference copy, and vestibular). While optic flow alone can be used to judge the direction, speed and magnitude of self-motion, little is known about the precise extent to which it is used during natural locomotor behaviours such as walking. In this study, walked distances were estimated in an open outdoor environment. This study employed two novel complementary techniques to dissociate the contributions of optic flow from body-based cues when estimating distance travelled in a flat, open, outdoor environment void of distinct proximal visual landmarks. First, lenses were used to magnify or minify the visual environment. Second, two walked distances were presented in succession and were either the same or different in magnitude; vision was either present or absent in each. A computational model was developed based on the results of both experiments. Highly convergent cue-weighting values were observed, indicating that the brain consistently weighted body-based cues about twice as high as optic flow, the combination of the two cues being additive. The current experiments represent some of the first to isolate and quantify the contributions of optic flow during natural human locomotor behaviour. [source]

Managing Diversity? ,Community Cohesion' and Its Limits in Neoliberal Urban Policy

GEOGRAPHY COMPASS (ELECTRONIC), Issue 2 2008
Julie MacLeavy
The concept of ,community cohesion' has played a defining role in the institution of a new policy agenda for regenerating urban areas in many liberal welfare states. Its particular interpretation supports the installation of urban programmes that are based not on the improvement of the built environment, but rather investment in the social and cultural composition of cities. In particular, the economic and civic participation of individuals living within deprived urban areas is positioned as a key means of redressing situations of inequality and disadvantage. This article reviews the concept of ,community cohesion', its use in urban policy in the UK, and the recent literature on this subject. Through an indicative discussion of the New Deal for Communities programme, it explores the potential implications of ,community cohesion' for disadvantaged policy subjects and considers especially its provisions for ethnic minority groups: a constellation of community in which individuals are understood to experience a ,double disadvantage' as a result of their disproportionate concentration in deprived urban areas, and their subjection to the consequences of racial discrimination (as well as language and cultural barriers). [source]

The 550th Anniversary of the Universität Basel, 1460,,,2010: Paracelsian Beginnings and Chemistry

HELVETICA CHIMICA ACTA, Issue 9 2010
G. Wayne Craig
Abstract This year marks the 550th anniversary of the founding of the Universität Basel. After its inception, the development of chemistry has played a major role in its evolution as an academic institution to meet the needs of industry and the educational community. Chemistry evolved in Basel as a dominant industry because of its central location and connection to the Rhine. The dyestuff industry and later the pharmaceutical industry established the Basel location as a major center of distribution. Companies like Sandoz AG, Ciba AG, J.,R. Geigy AG, and F. Hoffmann-La Roche AG influenced the defining role of chemistry not only in Europe but throughout the world. This article highlights some of the academic personalities that contributed to the development of chemistry in the remarkable history of the Universität Basel since the time of Paracelsus. [source]

A review of host finding behaviour in the parasitic sea louse, Lepeophtheirus salmonis (Caligidae: Copepoda)

JOURNAL OF FISH DISEASES, Issue 1 2009
A J Mordue (Luntz)
Abstract Ectoparasitic sea lice are the most important parasite problem to date for the salmon farming industry in the northern and southern hemispheres. An understanding of host location in the specialist species, Lepeophtheirus salmonis, the most important louse species in the North Atlantic, is now being realized using behavioural in vitro and in vivo bioassays coupled with chemical analysis of fish conditioned waters. Both physical and chemical cues are important in host location. Responses of sea lice to physical cues such as light and salinity may enable them to gather in areas where host fish are likely to be found. Mechanoreception is an important sensory modality in host location and acts by switching on specific behaviours that enable landing on a fish. Chemoreception plays a defining role in host location and recognition. The detection of host kairomones switches on ,host search' behavioural patterns and also induces landing responses whereas non-host kairomones fail to induce attraction or significant landing behaviour. Semiochemicals derived from salmon and also non-host fish have been identified, and may prove useful for the development of integrated pest management strategies, by the introduction of odour traps for monitoring lice numbers, and by the use of stimulo-deterrent diversionary (push:pull) strategies in their control. [source]

Incongruent patterns of genetic connectivity among four ophiuroid species with differing coral host specificity on North Atlantic seamounts

MARINE ECOLOGY, Issue 2010
Walter Cho
Abstract Seamounts are considered to play a defining role in the evolution and diversity of marine fauna, acting as ,stepping-stones' for dispersal, regional centers of genetic isolation and speciation, and refugia for deep-sea populations. This study focused on the patterns of dispersal and genetic connectivity of four seamount ophiuroid species (Asteroschema clavigera, Ophiocreas oedipus, Ophioplinthaca abyssalis, and Ophioplinthaca chelys) displaying differing levels of associative (epifaunal) specificity to cold-water coral hosts inhabiting the New England and Corner Rise Seamount chains, and Muir Seamount in the Northwestern Atlantic. Analyses of mt16S and mtCOI revealed evidence for recent population expansion and high gene flow for all four species. However, species-specific genetic differentiation was significant based on seamount region and depth. Significant differences were found among regional seamount groups for A. clavigera, within seamount regions and seamounts for O. chelys, among 250-m depth intervals for A. clavigera, among 100-m depth intervals for O. oedipus, and there were indications of isolation by distance for A. clavigera and O. oedipus. In addition, A. clavigera and O. oedipus, broadcast spawners with high fidelity to specific coral hosts, displayed predominantly westward historical migration, whereas the ophioplinthacids, with lower host-specificity, displayed predominantly eastward migration. No congruent patterns of historical migration were evident among species and seamounts, yet these patterns can be correlated with species-specific host specificity, specific depth strata, and dispersal strategies. Conservation efforts to protect seamount ecosystems should promote multi-species approaches to genetic connectivity, and consider the impact of the ,dependence' of biodiversity on host fauna in these vulnerable marine ecosystems. [source]

What determines the molecular composition of abnormal protein aggregates in neurodegenerative disease?

NEUROPATHOLOGY, Issue 4 2008
Richard A. Armstrong
Abnormal protein aggregates, in the form of either extracellular plaques or intracellular inclusions, are an important pathological feature of the majority of neurodegenerative disorders. The major molecular constituents of these lesions, viz., ,-amyloid (A,), tau, and ,-synuclein, have played a defining role in the diagnosis and classification of disease and in studies of pathogenesis. The molecular composition of a protein aggregate, however, is often complex and could be the direct or indirect consequence of a pathogenic gene mutation, be the result of cell degeneration, or reflect the acquisition of new substances by diffusion and molecular binding to existing proteins. This review examines the molecular composition of the major protein aggregates found in the neurodegenerative diseases including the A, and prion protein (PrP) plaques found in Alzheimer's disease (AD) and prion disease, respectively, and the cellular inclusions found in the tauopathies and synucleinopathies. The data suggest that the molecular constituents of a protein aggregate do not directly cause cell death but are largely the consequence of cell degeneration or are acquired during the disease process. These findings are discussed in relation to diagnosis and to studies of to disease pathogenesis. [source]