989 resultados para Birkhoff normal form


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Titanium dioxide nanocrystals are an important commercial product used primarily in white pigments and abrasives, however, more recently the anatase form of TiO2 has become a major component in electrochemical and photoelectrochemical devices. An important property of titanium dioxide nanocrystals for electrical applications is the degree of crystallinity. Numerous preparation methods exist for the production of highly crystalline TiO2 particles. The majority of these processes require long reaction times, high pressures and temperatures (450–1400 °C). Recently, hydrothermal treatment of colloidal TiO2 suspensions has been shown to produce quality crystalline products at low temperatures (<250 °C). In this paper we extend this idea utilising a direct microwave heating source. A comparison between convection and microwave hydrothermal treatment of colloidal TiO2 is presented. The resulting highly crystalline TiO2 colloids were characterised using Raman spectroscopy, XRD, TEM, and electron diffraction. The results show that the microwave treatment of colloidal TiO2 gives comparable increases in crystallinity with respect to normal hydrothermal treatments while requiring significantly less time and energy than the hydrothermal convection treatment.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

PURPOSE: To explore the effects of glaucoma and aging on low-spatial-frequency contrast sensitivity by using tests designed to assess performance of either the magnocellular (M) or parvocellular (P) visual pathways. METHODS: Contrast sensitivity was measured for spatial frequencies of 0.25 to 2 cyc/deg by using a published steady- and pulsed-pedestal approach. Sixteen patients with glaucoma and 16 approximately age-matched control subjects participated. Patients with glaucoma were tested foveally and at two midperipheral locations: (1) an area of early visual field loss, and (2) an area of normal visual field. Control subjects were assessed in matched locations. An additional group of 12 younger control subjects (aged 20-35 years) were also tested. RESULTS: Older control subjects demonstrated reduced sensitivity relative to the younger group for the steady (presumed M)- and pulsed (presumed P)-pedestal conditions. Sensitivity was reduced foveally and in the midperiphery across the spatial frequency range. In the area of early visual field loss, the glaucoma group demonstrated further sensitivity reduction relative to older control subjects across the spatial frequency range for both the steady- and pulsed-pedestal tasks. Sensitivity was also reduced in the midperipheral location of "normal" visual field for the pulsed condition. CONCLUSIONS: Normal aging results in a reduction of contrast sensitivity for the low-spatial-frequency-sensitive components of both the M and P pathways. Glaucoma results in a further reduction of sensitivity that is not selective for M or P function. The low-spatial-frequency-sensitive channels of both pathways, which are presumably mediated by cells with larger receptive fields, are approximately equivalently impaired in early glaucoma.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

It has been proposed that body image disturbance is a form of cognitive bias wherein schemas for self-relevant information guide the selective processing of appearancerelated information in the environment. This threatening information receives disproportionately more attention and memory, as measured by an Emotional Stroop and incidental recall task. The aim of this thesis was to expand the literature on cognitive processing biases in non-clinical males and females by incorporating a number of significant methodological refinements. To achieve this aim, three phases of research were conducted. The initial two phases of research provided preliminary data to inform the development of the main study. Phase One was a qualitative exploration of body image concerns amongst males and females recruited through the general community and from a university. Seventeen participants (eight male; nine female) provided information on their body image and what factors they saw as positively and negatively impacting on their self evaluations. The importance of self esteem, mood, health and fitness, and recognition of the social ideal were identified as key themes. These themes were incorporated as psycho-social measures and Stroop word stimuli in subsequent phases of the research. Phase Two involved the selection and testing of stimuli to be used in the Emotional Stroop task. Six experimental categories of words were developed that reflected a broad range of health and body image concerns for males and females. These categories were high and low calorie food words, positive and negative appearance words, negative emotion words, and physical activity words. Phase Three addressed the central aim of the project by examining cognitive biases for body image information in empirically defined sub-groups. A National sample of males (N = 55) and females (N = 144), recruited from the general community and universities, completed an Emotional Stroop task, incidental memory test, and a collection of psycho-social questionnaires. Sub-groups of body image disturbance were sought using a cluster analysis, which identified three sub-groups in males (Normal, Dissatisfied, and Athletic) and four sub-groups in females (Normal, Health Conscious, Dissatisfied, and Symptomatic). No differences were noted between the groups in selective attention, although time taken to colour name the words was associated with some of the psycho-social variables. Memory biases found across the whole sample for negative emotion, low calorie food, and negative appearance words were interpreted as reflecting the current focus on health and stigma against being unattractive. Collectively these results have expanded our understanding of processing biases in the general community by demonstrating that the processing biases are found within non-clinical samples and that not all processing biases are associated with negative functionality

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In architectural design and the construction industry, there is insufficient evidence about the way designers collaborate in their normal working environments using both traditional and digital media. It is this gap in empirical evidence that the CRC project, “Team Collaboration in High Bandwidth Virtual Environments” addresses. The project is primarily, but not exclusively, concerned with the conceptual stages of design carried out by professional designers working in different offices. The aim is to increase opportunities for communication and interaction between people in geographically distant locations in order to improve the quality of collaboration. In order to understand the practical implications of introducing new digital tools on working practices, research into how designers work collaboratively using both traditional and digital media is being undertaken. This will involve a series of empirical studies in the work places of the industry partners in the project. The studies of collaboration processes will provide empirical results that will lead to more effective use of virtual environments in design and construction processes. The report describes the research approach, the industry study, the methods for data collection and analysis and the foundation research methodologies. A distinctive aspect is that the research has been devised to enable field studies to be undertaken in a live industrial environment where the participant designers carry out real projects alongside their colleagues and in familiar locations. There are two basic research objectives: one is to obtain evidence about design practice that will inform the architecture and construction industries about the impact and potential benefit of using digital collaboration technologies; the second is to add to long term research knowledge of human cognitive and behavioural processes based on real world data. In order to achieve this, the research methods must be able to acquire a rich and heterogeneous set of data from design activities as they are carried out in the normal working environment. This places different demands upon the data collection and analysis methods to those of laboratory studies where controlled conditions are required. In order to address this, the research approach that has been adopted is ethnographic in nature and case study-based. The plan is to carry out a series of indepth studies in order to provide baseline results for future research across a wider community of user groups. An important objective has been to develop a methodology that will produce valid, significant and transferable results. The research will contribute to knowledge about how architectural design and the construction industry may benefit from the introduction of leading edge collaboration technologies. The outcomes will provide a sound foundation for the production of guidelines for the assessment of high bandwidth tools and their future deployment. The knowledge will form the basis for the specification of future collaboration products and collaboration processes. This project directly addresses the industry-identified focus on cultural change, image, e-project management, and innovative methods.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In today’s global design world, architectural and other related design firms design across time zones and geographically distant locations. High bandwidth virtual environments have the potential to make a major impact on these global design teams. However, there is insufficient evidence about the way designers collaborate in their normal working environments using traditional and/or digital media. This paper presents a method to study the impact of communication and information technologies on collaborative design practice by comparing design tasks done in a normal working environment with design tasks done in a virtual environment. Before introducing high bandwidth collaboration technology to the work environment, a baseline study is conducted to observe and analyze the existing collaborative process. Designers currently rely on phone, fax, email, and image files for communication and collaboration. Describing the current context is important for comparison with the following phases. We developed the coding scheme that will be used in analyzing three stages of the collaborative design activity. The results will establish the basis for measures of collaborative design activity when a new technology is introduced later to the same work environment – for example, designers using electronic whiteboards, 3D virtual worlds, webcams, and internet phone. The results of this work will form the basis of guidelines for the introduction of technology into global design offices

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Solar Cities Congress 2008 “Energising Sustainable Communities – Options for Our Future” THEME 3: Climate Change. Impact on Society and Culture. Sub Theme: planning and implementing holistic strategies for sustainable transport Abstract Promoting the use of cycling as an environmentally and socially sustainable form of transport. We need to reduce carbon emissions. We need to reduce fuel consumption. We need to reduce pollution. We need to reduce traffic congestion. As obesity levels and associated health problems in the developed nations continue to increase we need to adopt a healthier lifestyle. Few if any would argue with these statements. In fact many would consider these problems to be amongst the most urgent that our society faces. What if we had a vehicle that uses no fossil fuel to power it, creates no pollution, takes up far less space on the roads and promotes an active, healthy lifestyle. What if this machine would have energy efficiency levels 50 times greater than the car? This is a solution that is here, now and ready to go and many of us already own one. It is the humble bicycle. Although bicycle sales in Australia now outnumber car sales, bicycle use as a form of transport (as opposed to recreation) only constitutes around 3% to 4% of all trips. So, why are bicycles the forgotten form of transport if they promise to deliver the benefits that I have just outlined? This paper examines the underlying reasons for the relatively low use of bicycles as a means of transport. It identifies the areas of greatest potential for encouraging the use of the world’s most efficient form of transport. Tim Williams - May 2007

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Infection of plant cells by potyviruses induces the formation of cytoplasmic inclusions ranging in size from 200 to 1000 nm. To determine if the ability to form these ordered, insoluble structures is intrinsic to the potyviral cytoplasmic inclusion protein, we have expressed the cytoplasmic inclusion protein from Potato virus Y in tobacco under the control of the chrysanthemum ribulose-1,5-bisphosphate carboxylase small subunit promoter, a highly active, green tissue promoter. No cytoplasmic inclusions were observed in the leaves of transgenic tobacco using transmission electron microscopy, despite being able to clearly visualize these inclusions in Potato virus Y infected tobacco leaves under the same conditions. However, we did observe a wide range of tissue and sub-cellular abnormalities associated with the expression of the Potato virus Y cytoplasmic inclusion protein. These changes included the disruption of normal cell morphology and organization in leaves, mitochondrial and chloroplast internal reorganization, and the formation of atypical lipid accumulations. Despite these significant structural changes, however, transgenic tobacco plants were viable and the results are discussed in the context of potyviral cytoplasmic inclusion protein function.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This study used a 25-item questionnaire to examine the perceptions of 128 people with a close interest in bereavement and its literature. The study is part of a project to identify key aspects and the bereavement process. Subjects were asked to rate their perceptions of key bereavement phenomena with regards their frequency in the acute and later stages of bereavement. Descriptive results are presented and discussed, and a profile of phenomena perceived to be common to both stages is outlined.