995 resultados para Toxic elements


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While the internship unit in a public relations degree is often viewed as the foremost area of experiential learning it can fail to deliver significant learning outcomes for student and teacher. This paper explores the use of other activity-based learning (ABL) methods as implemented in the Deakin University public relations undergraduate degree. The paper applies Donald Schon's concept of the reflective practitioner to learning undertaken in an internship unit and compares this application to two other units where ABL is used and the focus is on creating a client-professional relationship. For the purpose of this paper information was analysed using the 2006 on-campus cohort only. The cohort was further refined to include those students who successfully completed the degree of BA in public relations. Student internship evaluation forms and unit records were viewed to gain statistical information.

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Role play is an increasingly popular technique in tertiary education, being student centred, constructivist and suitable for a range of subject areas. The choice of formats is wide open, with options ranging from the traditional face to face performance through to multi-user online computer games. Some teachers prefer to take advantage of features of both online and face to face formats and offer a blended form. This case study describes an innovative blended role play in which the online component plays a small but important part. The findings show that decisions on not only how to make the best use of technology but also how to design and facilitate a role play can have a profound effect on the creation of an engaging first-person story from which powerful learning can be drawn—in this case, learning outcomes including deep insights into strengths and weaknesses of participants' personal change management styles.

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A series of alloys have been produced with microalloying additions of rare-earth (RE) elements in the range of 0.1–0.4 wt.%. The alloys have been extruded to produce grain sizes of 23 ± 5 μm. The texture of the extruded alloys was measured, and it was found that the extrusion texture was weakened by the addition of RE elements. The samples with weakened extrusion textures exhibited an increase in the tensile elongation.

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Efficient and accurate finite elements are crucial for finite element analysis to provide adequate prediction of the structural behavior. A large amount of laminated plate elements have been developed for finite element analysis of laminated composite plates based on the various lamination theories. A recent and complete review of the laminated finite elements based on the higher-order shear deformation theories, including the global higher-order theories, zig-zag theories and the global-local higher-order theories is presented in this paper. Finally some points on the development of the laminated plate elements are summarized.

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A large amount of finite elements have been developed for finite element analysis of laminated composite plates. The laminated plate theories are reviewed and summarized in this paper. The focus of this review is on the recently developed laminated finite elements since 1990. The 2-D triangular and quadrilateral displacement-based and mixed/hybrid-based finite element models, which were developed based on the first-order shear deformation theories, the higher-order shear deformation theories, the zig-zag theories and the global-local higher-order deformation theories, and the layer-wise laminated plate theories are reviewed in this paper and also their related patents. Finally, some points on the development of the laminated finite elements are summarized.

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Throughout the world, many native species inhabit agricultural landscapes. While natural habitats will form the cornerstone of conservation efforts in production-oriented environments, the success of these efforts will be enhanced by a greater understanding of the potential contribution of the increasingly modified countryside (‘matrix’) elements in these landscapes. Here, we investigate the relative occurrence of birds in some landscape elements (i.e. land-uses, vegetation types) common to agricultural environments around the world. Twenty-seven study mosaics (1 km × 1 km in size), selected to incorporate variation in the cover of native vegetation and the richness of different landscape elements, were sampled in Gippsland, south-eastern Australia. Birds were surveyed in five main types of elements: native vegetation, linear vegetation, plantation, scattered trees and pasture. The greatest number of species was recorded in native vegetation, the most important element for the majority of birds in Australian agricultural landscapes. Nevertheless, most countryside elements had value for many species; particularly structurally complex elements. Ordination analyses (based on presence/absence data for 81 species) showed that the composition of bird communities differed between elements. The number of mosaics in which ‘all species’ and ‘woodland species’ were recorded was positively related to the breadth of elements they used; thus species using a greater number of elements occurred more frequently in the study region. Correlation analyses identified that the richness of woodland species (those of increased conservation concern in Australia) in different elements was influenced by features of the mosaic in which they occurred. Notably, the richness of woodland bird species recorded in scattered trees and pasture increased with local native vegetation cover. Key implications for conservation in Australian agricultural environments include: (1) native vegetation is vital for the persistence of birds in these landscapes, and thus is the primary element on which conservation efforts in agricultural landscapes depend; (2) countryside elements can enhance the conservation value of agricultural landscapes by (a) increasing structural complexity in largely cleared areas and (b) increasing the heterogeneity of the entire landscape; and (3) patches of different elements cannot be managed in isolation from their surroundings, as landscape properties affect the richness of bird assemblages in different elements.

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Laser beam spot-welding is widely applied to join sheet metals for automotive components especially for thinsheet components in automotive industries. The spot welds in such metallic structures contribute a lot to the integrated strength and fatigue life for the whole structures and they are responsible for their damage or collapse in some loading cases. In this paper, the 2-D hybrid special finite elements each containing an edge crack are employed to study the fracture behaviors of laser beam spot-welds. Hence the calculation accuracy in the vicinity of crack tips is ensured, and a better description of stress singularity with only one hybrid element surrounding one crack is provided. The numerical modeling for laser beam spot-welds subjected to three typical modes ofloadings including tension-lap, shear-lap and angle-clip can be greatly simplified with the applications of such elements. Three specimens under lap-shear, lap-tension and angle clip are devised and analyzed respectively, and main fracture parameters such as stress intensity factors and the initial direction of crack growth are obtained through tinite element analyses. The computed results ti'om numerical examples demonstrate the validity and versatility of the proposed modeling.

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Homeostasis in the intact organism is achieved implicitly by repeated incremental feedback (inhibitory) and feedforward (stimulatory) adjustments enforced via intermittent signal exchange. In separated systems, neurohormone signals act deterministically on target cells via quantifiable effector-response functions. On the other hand, in vivo interglandular signaling dynamics have not been estimable to date. Indeed, experimentally isolating components of an interactive network definitionally disrupts time-sensitive linkages. We implement and validate analytical reconstruction of endogenous effector-response properties via a composite model comprising (i) a deterministic basic feedback and feedforward ensemble structure; (ii) judicious statistical allowance for possible stochastic variability in individual biologically interpretable dose–response properties; and (iii) the sole data requirement of serially observed concentrations of a paired signal (input) and response (output). Application of this analytical strategy to a prototypical neuroendocrine axis in the conscious uninjected horse, sheep, and human (i) illustrates probabilistic estimation of endogenous effector dose–response properties; and (ii) unmasks statistically vivid (2- to 5-fold) random fluctuations in inferred target-gland responsivity within any given pulse train. In conclusion, balanced mathematical formalism allows one to (i) reconstruct deterministic properties of interglandular signaling in the intact mammal and (ii) quantify apparent signal-response variability over short time scales in vivo. The present proof-of-principle experiments introduce a previously undescribed means to estimate time-evolving signal-response relationships without isotope infusion or pathway disruption.

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Community-based interventions are an important component of obesity prevention efforts. The literature provides little guidance on priority-setting for obesity prevention in communities, especially for socially and culturally diverse populations. This paper reports on the process of developing prioritized, community-participatory action plans for obesity prevention projects in children and adolescents using the ANGELO (Analysis Grid for Elements Linked to Obesity) Framework. We combined stakeholder engagement processes, the ANGELO Framework (scans for environmental barriers, targeted behaviours, gaps in skills and knowledge) and workshops with key stakeholders to create action plans for six diverse obesity prevention projects in Australia (n = 3), New Zealand, Fiji and Tonga from 2002 to 2005. Some sites included sociocultural contextual analyses in the environmental scans. Target groups were under-5-year-olds (Australia), 4–12-year-olds (Australia) and 13–18-year-olds (all four countries). Over 120 potential behavioural, knowledge, skill and environmental elements were identified for prioritization leading into each 2-day workshop. Many elements were common across the diverse cultural communities; however, several unique sociocultural elements emerged in some cultural groups which informed their action plans. Youth were actively engaged in adolescent projects, allowing their needs to be incorporated into the action plans initiating the process of ownership. A common structure for the action plan promoted efficiencies in the process while allowing for community creativity and innovation. The ANGELO is a flexible and efficient way of achieving an agreed plan for obesity prevention with diverse communities. It is responsive to community needs, combines local and international knowledge and creates stakeholder ownership of the action plan.

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Accumulation of beta amyloid (Aβ) in the brain is central to the pathogenesis of Alzheimer's disease. Aβ can bind to membrane lipids and this binding may have detrimental effects on cell function. In this study, surface plasmon resonance technology was used to study Aβ binding to membranes. Aβ peptides bound to synthetic lipid mixtures and to an intact plasma membrane preparation isolated from vascular smooth muscle cells. Aβ peptides were also toxic to vascular smooth muscle cells. There was a good correlation between the toxic effect of Aβ peptides and their membrane binding. 'Ageing' the Aβ peptides by incubation for 5 days increased the proportion of oligomeric species, and also increased toxicity and the amount of binding to lipids. The toxicities of various Aβ analogs correlated with their lipid binding. Significantly, binding was influenced by the concentration of cholesterol in the lipid mixture. Reduction of cholesterol in vascular smooth muscle cells not only reduced the binding of Aβ to purified plasma membrane preparations but also reduced Aβ toxicity. The results support the view that Aβ toxicity is a direct consequence of binding to lipids in the membrane. Reduction of membrane cholesterol using cholesterol-lowering drugs may be of therapeutic benefit because it reduces Aβ-membrane binding.

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It has been consistently reported that vegetable oils including canola oil have a life shortening effect in Stroke-Prone Spontaneously Hypertensive Rats (SHRSP) and this toxic effect is not due to the fatty acid composition of the oil. Although it is possible that the phytosterol content or type of phytosterol present in vegetable oils may play some role in the life shortening effect observed in SHRSP rats this is still not completely resolved. Furthermore supercritical CO2 fractionation of canola oil with subsequent testing in SHRSP rats identified safe and toxic fractions however, the compounds responsible for life shortening effect were not characterised. The conventional approach to screen toxic substances in oils using rats takes more than six months and involves large number of animals. In this article we describe how rapid bioassay-guided screening could be used to identify toxic substances derived from vegetable oils and/or processed foods fortified with vegetable oils. The technique incorporates sequential fractionation of oils/processed foods and subsequent treatment of human cell lines that can be used in place of animal studies to determine cytotoxicity of the fractions with structural elucidation of compounds of interest determined via HPLC-MS and GC-MS. The rapid bioassay-guided screening proposed would require two weeks to test multiple fractions from oils, compared with six months if animal experiments were used to screen toxic effects. Fractionation of oil before bio-assay enhances the effectiveness of the detection of active compounds as fractionation increases the relative concentration of minor components.

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A family of simple, displacement-based and shear-flexible triangular and quadrilateral flat plate/shell elements for linear and geometrically nonlinear analysis of thin to moderately thick laminate composite plates are introduced and summarized in this paper.

The developed elements are based on the first-order shear deformation theory (FSDT) and von-Karman’s large deflection theory, and total Lagrangian approach is employed to formulate the element for geometrically nonlinear analysis. The deflection and rotation functions of the element boundary are obtained from Timoshenko’s laminated composite beam functions, thus convergence can be ensured theoretically for very thin laminates and shear-locking problem is avoided naturally.

The flat triangular plate/shell element is of 3-node, 18-degree-of-freedom, and the plane displacement interpolation functions of the Allman’s triangular membrane element with drilling degrees of freedom are taken as the in-plane displacements of the element. The flat quadrilateral plate/shell element is of 4-node, 24-degree-of-freedom, and the linear displacement interpolation functions of a quadrilateral plane element with drilling degrees of freedom are taken as the in-plane displacements.

The developed elements are simple in formulation, free from shear-locking, and include conventional engineering degrees of freedom. Numerical examples demonstrate that the elements are convergent, not sensitive to mesh distortion, accurate and efficient for linear and geometric nonlinear analysis of thin to moderately thick laminates.

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In 2003, Deakin University implemented a centralised learning management system (LMS) under the banner of Deakin Studies Online (DSO), as well as implementing policies requiring all its units of study to have at least a basic online presence from 2004. Given the scope of the university's commitment to online education, it was considered essential to evaluate the effectiveness of this investment. Based on more than 5400 responses obtained from students in 2004 and 2005 as part of the DSO evaluation survey, the analysis presented here identifies those elements of the online learning environment (OLE) that are most used and valued by students, those elements of the OLE that students most want to see improved, and, those factors that most contribute to students' perceptions that use of the OLE enhanced their learning experience. The most used and valued elements were core LMS functions, including accessing unit information, accessing lecture/tute/lab notes, interacting with unit learning resources, reading online discussions, contacting lecturers/tutors and submitting assignments online. The OLE elements identified as most needing attention were receiving feedback on assignments; viewing my marks; and reviewing unit progress. Students felt that using DSO enhanced their learning experience when they were adequately supported by unit teachers and technical support services; when they were able to find and use unit information; and when they were able to read the online contributions of other unit members. The retrospective analysis of data collected in the period 2004-2005 has been shaped by a forward-looking agenda. The array of elements available within, and in association with, traditional LMSs which has emerged since that time raises the future challenge of how to maximise and evidence educational value through the optimal combination of elements from the portfolio of e-learning technologies increasingly available to educators.