988 resultados para Context heterogeneity
Resumo:
The results presented in this thesis show that all females of a given population do not necessarily choose similar mating partners. Specifically, partner preferences of a fish, the sand goby (Pomatoschistus minutus), varied among individual females and depended on the social context at the time of choice. I also show that females assess multiple mate choice cues simultaneously; partner preferences were based more strongly on an interaction effect between different choice cues than on any individual cue. Furthermore, I found that preferred matings involved fitness benefits in the form of increased offspring success, but these benefits were not significantly affected by mate compatibility. Hence, mate choice for partner compatibility does not appear to be an important determinant of the observed variation in female mate preferences in this species. The context-dependency of female mating preferences revealed is relevant to how genetic variation in sexually selected traits might be maintained: as the mating success of a certain male type varies according to the choice context, directional sexual selection on male traits is shown to be less intense than generally thought making for a slower loss of genetic variation in these traits. Mating preferences of sand gobies were assessed by giving females a binary choice between males that differed in body size and/or other focus traits. These association preferences were found to be sexually motivated, repeatable and to correspond to actual mating decisions.
Resumo:
Environmental variation is a fact of life for all the species on earth: for any population of any particular species, the local environmental conditions are liable to vary in both time and space. In today's world, anthropogenic activity is causing habitat loss and fragmentation for many species, which may profoundly alter the characteristics of environmental variation in remaining habitat. Previous research indicates that, as habitat is lost, the spatial configuration of remaining habitat will increasingly affect the dynamics by which populations are governed. Through the use of mathematical models, this thesis asks how environmental variation interacts with species properties to influence population dynamics, local adaptation, and dispersal evolution. More specifically, we couple continuous-time continuous-space stochastic population dynamic models to landscape models. We manipulate environmental variation via parameters such as mean patch size, patch density, and patch longevity. Among other findings, we show that a mixture of high and low quality habitat is commonly better for a population than uniformly mediocre habitat. This conclusion is justified by purely ecological arguments, yet the positive effects of landscape heterogeneity may be enhanced further by local adaptation, and by the evolution of short-ranged dispersal. The predicted evolutionary responses to environmental variation are complex, however, since they involve numerous conflicting factors. We discuss why the species that have high levels of local adaptation within their ranges may not be the same species that benefit from local adaptation during range expansion. We show how habitat loss can lead to either increased or decreased selection for dispersal depending on the type of habitat and the manner in which it is lost. To study the models, we develop a recent analytical method, Perturbation expansion, to enable the incorporation of environmental variation. Within this context, we use two methods to address evolutionary dynamics: Adaptive dynamics, which assumes mutations occur infrequently so that the ecological and evolutionary timescales can be separated, and via Genotype distributions, which assume mutations are more frequent. The two approaches generally lead to similar predictions yet, exceptionally, we show how the evolutionary response of dispersal behaviour to habitat turnover may qualitatively depend on the mutation rate.
Resumo:
This practice-led research investigated the negotiation processes informing effective models of transcultural collaboration. In a creative project interweaving the image-based physicality of the Japanese dance form of butoh with the traditional Korean vocal style of p'ansori, a series of creative development cycles were undertaken with a team of artists from Australia and Korea, culminating in Deluge, a work of physical theatre. The development of interventions at 'sites of transcultural potential' resulted in improvements to the negotiation of interpersonal relationships and assisted in the emergence of a productive working environment in transculturally collaborative artistic practice.
Resumo:
The pseudoproline residue (Psi Pro, L-2,2-dimethyl-1,3-thiazolidine-4-carboxylic acid) has been introduced into heterochiral diproline segments that have been previously shown to facilitate the formation of beta-hairpins, containing central two and three residue turns. NMR studies of the octapeptide Boc-Leu-Phe-Val-(D)Pro-Psi Pro-Leu-Phe-Val-OMe (1), Boc-Leu-Val-Val-(D)Pro-Psi Pro-Leu-Val-Val-OMe (2), and the nonapeptide sequence Boc-Leu-Phe-Val-(D)Pro-Psi Pro-(D)Ala-Leu-Phe-Val-OMe (3) established well-registered beta-hairpin structures in chloroform solution, with the almost exclusive population of the trans conformation for the peptide bond preceding the Psi Pro residue. The beta-hairpin conformation of 1 is confirmed by single crystal X-ray diffraction. Truncation of the strand length in Boc-Val-(D)Pro-Psi Pro-Leu-OMe (4) results in air increase in the population of the cis conformer, with a cis/trans ratio of 3.65. Replacement of Psi Pro in 4 by (L)Pro in 5, results in almost exclusive population of the trans form, resulting in an incipient beta-hairpin conformation, stabilized by two intramolecular hydrogen bonds. Further truncation of the sequence gives an appreciable rise in the population of cis conformers in the tripeptide piv-(D)Pro-Psi Pro-Leu-OMe (6). In the homochiral segment Piv-Pro Psi Pro-Leu-OMe (7) only the cis form is observed with the NMR evidence strongly supporting a type VIa beta-turn conformation, stabilized by a 4 -> 1 hydrogen bond between the Piv (CO) and Leu (3) NH groups. The crystal structure of the analog peptide 7a (Piv-Pro-Psi(H,CH3)Pro-Leu-NHMe) confirms the cis peptide bond geometry for the Pro-Psi(H,CH3)pro peptide bond, resulting in a type VIa beta-turn conformation.
Resumo:
The biodiversity of farmland ecosystems has decreased remarkably during the latter half of the 20th century, and this development is due to intensive farming with its various environmental effects. In the countries of the EU the Common Agricultural Policy (CAP) is the main determinant affecting farmland biodiversity, since the agricultural policy defines guidelines of agricultural practices. In addition to policies promoting intensive farming, CAP also includes national agri-environment schemes (AES), in which a part of subsidies paid to farmers is directed to acts that are presumed to promote environmental protection and biodiversity. In order to shape AES into relevant and powerful tools for biodiversity protection, detailed studies on the effects of agriculture on species and species assemblages are needed. In my thesis I investigated the importance of habitat heterogeneity and effects of different habitat and landscape characteristics on farmland bird abundance and diversity in typical cereal cultivation-dominated southern Finnish agricultural environments. The extensive data used were collected by territory mapping. My two main study species were the drastically declined ortolan bunting (Emberiza hortulana) and the phenomenally increased tree sparrow (Passer montanus); in addition I studied assemblages of 20 species breeding in open arable and edge/bush habitats. In light of my results I discuss whether the Finnish AES take into account the habitat needs of farmland birds, and I provide suggestions for improvement of the future AES. My results show that heterogeneity of both uncultivated and cultivated habitats increases abundance and species richness among farmland birds, but in this respect the amount and diversity of uncultivated habitats are essential. Ditches in particular are a keystone structure for farmland birds in boreal landscapes. Ditches lined by trees or bushes increased ortolan bunting abundance. Loss of that kind of ditches (and clearance of forest and bush patches), reduced breeding ortolan buntings, mainly by decreasing availability of song-posts that are important for the breeding groups of the species. Heterogeneity of uncultivated habitats, most importantly open ditches and the habitat patch richness, increased densities and species richnesses of species assemblages of open arable and edge/bush habitats. Human impact (winter-feeding, nest-boxes) affected favourably the tree sparrow s rapid range expansion in southern Finland, but any habitat types had no significant effects. At the moment the Finnish agri-environmental policy does not conserve farmland ditches as a habitat type. Instead, sub-surface drainage is financially promoted. This is a fatal mistake as far as farmland biodiversity is concerned. In addition to the maintenance of ditches, at least the following aspects should be included more than is done previously in the measures of the future AES: 1) promotion of diverse crop rotation (especially by promoting animal husbandry), 2) maintenance of tree and bush vegetation in islets and along ditches, 3) promotion of organic farming.
Resumo:
Health information technology (IT) can have a profound effect on the temporal flow and organisation of work. Yet research into the context, meaning and significance of temporal factors remains limited, most likely because of its complexity. This study outlines the role of communications in the context of the temporal and organizational landscape of seven Australian residential aged care facilities displaying a range of information exchange practices and health IT capacity. The study used qualitative and observational methods to identify temporal factors associated with internal and external modes of communication across the facilities and to explore the use of artifacts. The study concludes with a depiction of the temporal landscape of residential aged care particularly in regards to the way that work is allocated, prioritized, sequenced and coordinated. We argue that the temporal landscape involves key context-sensitive factors that are critical to understanding the way that humans accommodate to, and deal with health technologies, and which are therefore important for the delivery of safe and effective care.
Resumo:
Mental retardation due to fragile X syndrome is one of the genetic disorders caused by tripler repeat expansion, CGG repeat involved in this disease is known to exhibit polymorphism even among normal individuals. Here we describe the development of suitable probes for detection of polymorphism in CGG repeat at FMR1 locus as well as the diagnosis of fragile X syndrome. Using these methods polymorphism at the FMR1 locus has been examined in 161 individuals. Ninety eight patients with unclassified mental retardation were examined, of whom 7 were found to have the expanded (CGG) allele at the FMR1 locus, The hybridization pattern for two patients has been presented as representative data.
Resumo:
Elephants use vocalizations for both long and short distance communication. Whereas the acoustic repertoire of the African elephant (Loxodonta africana) has been extensively studied in its savannah habitat, very little is known about the structure and social context of the vocalizations of the Asian elephant (Elephas maximus), which is mostly found in forests. In this study, the vocal repertoire of wild Asian elephants in southern India was examined. The calls could be classified into four mutually exclusive categories, namely, trumpets, chirps, roars, and rumbles, based on quantitative analyses of their spectral and temporal features. One of the call types, the rumble, exhibited high structural diversity, particularly in the direction and extent of frequency modulation of calls. Juveniles produced three of the four call types, including trumpets, roars, and rumbles, in the context of play and distress. Adults produced trumpets and roars in the context of disturbance, aggression, and play. Chirps were typically produced in situations of confusion and alarm. Rumbles were used for contact calling within and among herds, by matriarchs to assemble the herd, in close-range social interactions, and during disturbance and aggression. Spectral and temporal features of the four call types were similar between Asian and African elephants.
Resumo:
This research examines how a tourist’s degree of psychological entitlement (sense of deservingness) influences their responses to hotels that differ in cultural distance. Using a visit to China by Western tourists as a context, an experiment shows that entitled tourists respond more negatively to high cultural distance hotel environments compared with low cultural distance environments. Results are mediated by tourist irritation. Research contributions include demonstrating how entitlement moderates cultural distance effects, revealing tourist irritation as a mechanism that explains these effects, and showing how psychological entitlement influences how tourists react to hotel environments when visiting a foreign destination.
Resumo:
This research has identified the trends apparent in service desk design and delivery literature. By doing archival analysis, this investigation has led to the development of a generic framework which has identified three themes in service desk design – User groups, Support models, and Technology types – and two themes in service desk delivery – Direction of delivery, and Executive support level. This research also aims to provide an understanding of service desk functions and the challenges faced by organisations in delivering those functions.
Resumo:
Despite tertiary institutions acknowledging that reflective practice is an essential component of undergraduate dance teacher training, there is often a disparity between the tertiary students’ reflective skills and the more sophisticated reflective ability needed to navigate the 21st century workforce (Silva 2008). This paper charts the evolution of a dance teaching reflective pedagogy within a suite of three units across a three-year undergraduate dance teacher-training course for school, community and studio dance teachers. This reflective pedagogy based on exploration, collaboration, critical questioning and connections with community forms the basis of a model of tertiary dance teacher- training; the Performance in Context Model (PCM). Over the past four years, through four cycles of action research, the PCM pedagogy, context and engagement with community has developed into a successful model integrating practical dance teaching skills, artistry and community engagement. The PCM represents a holistic collaborative approach to dance teacher education: the marrying of ‘teacher-as-artist’, ‘teacher-as-performer’ and ‘teacher-as-researcher’. More specifically, it emphasises the need for mature, reflective, receptive and flexible approaches in response to dance teaching and learning. These are enacted in a variety of contexts, with tertiary dance teaching students identifying as teaching artists, as well as researchers of their own practice.
Resumo:
In this paper, numerical modelling of fracture in concrete using two-dimensional lattice model is presented and also a few issues related to lattice modelling technique applicable to concrete fracture are reviewed. A comparison is made with acoustic emission (AE) events with the number of fractured elements. To implement the heterogeneity of the plain concrete, two methods namely, by generating grain structure of the concrete using Fuller's distribution and the concrete material properties are randomly distributed following Gaussian distribution are used. In the first method, the modelling of the concrete at meso level is carried out following the existing methods available in literature. The shape of the aggregates present in the concrete are assumed as perfect spheres and shape of the same in two-dimensional lattice network is circular. A three-point bend (TPB) specimen is tested in the experiment under crack mouth opening displacement (CMOD) control at a rate of 0.0004 mm/sec and the fracture process in the same TPB specimen is modelled using regular triangular 2D lattice network. Load versus crack mouth opening isplacement (CMOD) plots thus obtained by using both the methods are compared with experimental results. It was observed that the number of fractured elements increases near the peak load and beyond the peak load. That is once the crack starts to propagate. AE hits also increase rapidly beyond the peak load. It is compulsory here to mention that although the lattice modelling of concrete fracture used in this present study is very similar to those already available in literature, the present work brings out certain finer details which are not available explicitly in the earlier works.
Resumo:
We have used circular dichroism as a probe to characterize the solution conformational changes in RecA protein upon binding to DNA. This approach revealed that RecA protein acquires significant amounts of alpha-helix upon interaction with DNA. These observations, consistent with the data from crystal structure (Story, R. M., Weber, I., and Steitz, T. (1992) Nature 355, 318-325), support the notion that some basic domains including the DNA binding motifs of RecA protein are unstructured and might contribute to the formation of alpha-helix. A comparison of nucleoprotein filaments comprised of RecA protein and a variety of DNA substrates revealed important structural heterogeneity. The most significant difference was observed with poly(dG). poly(dC) and related polymers, rich in GC sequences, which induced minimal amounts of alpha-helix in RecA protein. The magnitude of induction of alpha-helix in RecA protein, which occurred concomitant with the production of ternary complexes, was 2-fold higher with homologous than heterologous duplex DNA. Most importantly, the stimulation of ATP hydrolysis by high salt coincided with that of the induction of alpha-helix in RecA protein. These conformational differences provide a basis for thinking about the biochemical and structural transitions that RecA protein experiences during the formal steps of presynapsis, recognition, and alignment of homologous sequences.