925 resultados para LIMITATIONS
Resumo:
Traction force microscopy (TFM) is commonly used to estimate cells’ traction forces from the deformation that they cause on their substrate. The accuracy of TFM highly depends on the computational methods used to measure the deformation of the substrate and estimate the forces, and also on the specifics of the experimental set-up. Computer simulations can be used to evaluate the effect of both the computational methods and the experimental set-up without the need to perform numerous experiments. Here, we present one such TFM simulator that addresses several limitations of the existing ones. As a proof of principle, we recreate a TFM experimental set-up, and apply a classic 2D TFM algorithm to recover the forces. In summary, our simulator provides a valuable tool to study the performance, refine experimentally, and guide the extraction of biological conclusions from TFM experiments.
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The Internet Corporation for Assigned Names and Numbers (ICANN) is an institution besieged. It has endeavored to be democratic but its attempts to do so have been disastrous. The typical explanation for this is that the problem is with ICANN: it fails to meet its democratic obligations. My view is that the problem is with our understanding of "democracy." Democracy is an empty concept that fails to describe few, if any, of our genuine political commitments. In the real world, the failings inherent in "democracy" have been papered over by some unusual characteristics of the physical political process. However, in online trans-national institutions like ICANN, democracy is exposed as a poor substitute for a number of other conceptions of our political commitments. This Article seeks to articulate these political commitments and to explain why democracy and ICANN are such a poor mix. It begins by charting the rise of ICANN and its attempts to be democratic. It then explains why democracy is an empty shell of a concept. It then explores some features of democracy and ICANN, explaining why the online world exposes limitations in implications of democracy such as the nature of the demos, the idea of constituencies, direct democracy, voting, and the like. It concludes that ICANN's example demonstrates that democracy is in fact anything but a coherent general theory of political action. We need to consider, then, whether we should continue to berate ICANN for its undemocratic actions.
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Road infrastructure has been considered as one of the most expensive and extensive infrastructure assets of the built environment globally. This asset also impacts the natural environment significantly during different phases of life e.g. construction, use, maintenance and end-of-life. The growing emphasis for sustainable development to meet the needs of future generations requires mitigation of the environmental impacts of road infrastructure during all phases of life e.g. construction, operation and end-of-life disposal (as required). Life-cycle analysis (LCA), a method of quantification of all stages of life, has recently been studied to explore all the environmental components of road projects due to limitations of generic environmental assessments. The LCA ensures collection and assessment of the inputs and outputs relating to any potential environmental factor of any system throughout its life. However, absence of a defined system boundary covering all potential environmental components restricts the findings of the current LCA studies. A review of the relevant published LCA studies has identified that environmental components such as rolling resistance of pavement, effect of solar radiation on pavement(albedo), traffic congestion during construction, and roadway lighting & signals are not considered by most of the studies. These components have potentially higher weightings for environment damage than several commonly considered components such as materials, transportation and equipment. This paper presents the findings of literature review, and suggests a system boundary model for LCA study of road infrastructure projects covering potential environmental components.
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This study is the first to examine the effectiveness of the Fun FRIENDS programme, a school-based, universal preventive intervention for early childhood anxiety and promotion of resilience delivered by classroom teachers. Participants (N = 488) included children aged 4–7 years attending 1 of 14 Catholic Education schools in Brisbane, Australia. The schools were randomly allocated to one of three groups, the intervention, active comparison and waitlist control group. Parents completed standardized measures of anxiety and behavioural inhibition (BI), resilience, social and emotional functioning and behaviour difficulties in addition to parental stress and anxiety, at pre- and post- and 12-month follow-up. Teachers also completed a parallel measure of social and emotional strength at the three time points. Comparable results were obtained for the intervention and comparison groups; however, the intervention group (IG) achieved greater reductions in BI, child behavioural difficulties and improvements in social and emotional competence. In addition, significant improvements in parenting distress and parent–child interactions were found for the IG, with gains maintained at 12-month follow-up. Teacher reports revealed more significant improvement in social and emotional competence for the IG. Clinical implications of the findings are discussed, along with limitations and directions for future research.
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Purpose This paper aims to identify, through a literature review, key issues regarding how online role plays can be designed and to apply them when designing a role play on conflict management. Design/methodology/approach By drawing on the key issues identified in the literature review, a role play on conflict management was designed and evaluated. Data were collected by developing a survey that focused on perceived learning, participation and satisfaction. Findings Overall, a majority of the students felt that they learned and participated in the role play. The most positive finding was that the students were satisfied with their role play experience. Research limitations/implications Researchers are urged to further develop the dimensions and measures of online role play success. The measures that were developed for evaluating perceived learning, participation and satisfaction with role plays can be further developed and tested. It is suggested that the effects on learning need to be further explored. Practical implications It is suggested that teachers take the identified key issues of online role play design into account. An important challenge seems to be to encourage students to reflect and do additional reading and research in relation with online role plays. Originality/value Online collaboration is commonly argued as beneficial from an e-learning perspective. However, a challenge for research and practice is to learn how collaborative e-learning activities may be developed. This paper contributes by focusing on how online role plays can be designed and evaluated.
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Gel dosimetry and plastic chemical dosimeters such as PresageTM are capable of very accurately mapping dose distributions in three dimensions. Combined with their near tissue equivalence one would expect that after several decades of development they would be the dosimeter of choice for dosimetry, however they have not achieve widespread clinical use. This presentation will include a brief description and history of developments in gels and 3D plastics for dosimetry, the limitations and advantages, and their role in the future.
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The general aim of designated driver programs is to reduce the level of drink driving by encouraging potential drink drivers to travel with a driver who has abstained from (or at least limited) consuming alcohol. Designated driver programs appear to be quite widespread around the world, however a limited number have been subject to rigorous evaluation. This paper reports results from an outcome evaluation of a designated driver program called ‘Skipper’, which was trialled in a provincial city in Queensland, Australia. The outcome evaluation included surveys three weeks prior to (baseline), four months following (1st follow-up), and 16 months following (2nd follow-up) the commencement of the trial in both the ‘intervention area’ (baseline, n = 202; 1st follow-up, n = 211; 2nd follow-up, n = 200) and a ‘comparison area’(baseline, n = 203; 1st follow-up, n = 199; 2nd follow-up, n = 201); and a comparison of random breath testing and crash data before and after the trial. The survey results indicate that awareness of the program in the intervention area was quite high four months following its introduction and that this was maintained at 16 months. The results also suggest that the ‘Skipper’ program and the related publicity had positive impacts on behaviour with an increase in the proportion of people participating in designated driver as a passenger. It is less clear, however, whether the ‘Skipper’ program impacted on other behaviours of interest, such as drink driving or involvement in alcohol-related crashes. Suggestions for further research and program improvement are discussed as well as limitations of the research.
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The authors conducted a theoretical review of the change readiness literature and identified two major limitations with this work. First, while there is substantial agreement about the key cognitions that underlie change readiness, researchers have not examined the affective element of this attitude. Second, researchers have not adopted a multilevel perspective when considering change readiness. The authors address these limitations and argue that it is important to incorporate affect into definitions of the change readiness construct and also when measuring this construct. They then develop a multilevel framework that identifies the antecedents and consequences of individual, work group, and organizational change readiness. Next, the authors outline the theoretical processes that lead to the development of individual and collective change readiness. They then review theoretical and empirical evidence to identify the antecedents of change readiness at the three levels of analysis. Finally, the authors identify a number of suggestions to guide future research seeking to adopt a multilevel approach to change readiness.
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Purpose Based on substitutes for leadership theory, the aim of this study is to examine followers' learning goal orientation as a moderator of relationships among transformational leadership, organizational citizenship behavior (OCB) and sales productivity. Design/methodology/approach Data came from 61 food and beverage attendants of a casino, and were analyzed using regression analyses. Findings Transformational leadership was positively related to both OCB and sales productivity. Learning goal orientation moderated the relationship between transformational leadership and OCB, such that transformational leadership was more strongly related to OCB among followers with a low learning goal orientation than among followers with a high learning goal orientation. Research limitations/implications Limitations of the study include the small sample size and cross-sectional research design. Practical implications Organizations could train supervisors to practice a transformational leadership style and to take followers' learning goal orientation into account. Originality/value The findings of this study suggest that, with regard to OCB, a high learning goal orientation of followers may act as a “substitute” for low levels of leaders' transformational leadership.
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Since the 1950s, X-ray crystallography has been the mainstay of structural biology, providing detailed atomic-level structures that continue to revolutionize our understanding of protein function. From recent advances in this discipline, a picture has emerged of intimate and specific interactions between lipids and proteins that has driven renewed interest in the structure of lipids themselves and raised intriguing questions as to the specificity and stoichiometry in lipid-protein complexes. Herein we demonstrate some of the limitations of crystallography in resolving critical structural features of ligated lipids and thus determining how these motifs impact protein binding. As a consequence, mass spectrometry must play an important and complementary role in unraveling the complexities of lipid-protein interactions. We evaluate recent advances and highlight ongoing challenges towards the twin goals of (1) complete structure elucidation of low, abundant, and structurally diverse lipids by mass spectrometry alone, and (2) assignment of stoichiometry and specificity of lipid interactions within protein complexes.
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The technical feasibility of roll motion control devices has been amply demonstrated for over 100 years. Performance, however, can still fall short of expectations because of deficiencies in control system designs, which have proven to be far from trivial due to fundamental performance limitations. This tutorial paper presents an account of the development of various ship roll motion control systems and the challenges associated with their design. The paper discusses how to assess performance, the applicability of different models, and control methods that have been applied in the past.
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Introduction Radiographer abnormality detection systems that highlight abnormalities on trauma radiographs (‘red dot’ system) have been operating for more than 30 years. Recently, a number of pitfalls have been identified. These limitations initiated the evolution of a radiographer commenting system, whereby a radiographer provides a brief description of abnormalities identified in emergency healthcare settings. This study investigated radiographers' participation in abnormality detection systems, their perceptions of benefits, barriers and enablers to radiographer commenting, and perceptions of potential radiographer image interpretation services for emergency settings. Methods A cross-sectional survey was implemented. Participants included radiographers from four metropolitan hospitals in Queensland, Australia. Conventional descriptive statistics, histograms and thematic analysis were undertaken. Results Seventy-three surveys were completed and included in the analysis (68% response rate); 30 (41%) of respondents reported participating in abnormality detection in 20% or less of examinations, and 26(36%) reported participating in 80% or more of examinations. Five overarching perceived benefits of radiographer commenting were identified: assisting multidisciplinary teams, patient care, radiographer ability, professional benefits and quality of imaging. Frequently reported perceived barriers included ‘difficulty accessing image interpretation education’, ‘lack of time’ and ‘low confidence in interpreting radiographs’. Perceived enablers included ‘access to image interpretation education’ and ‘support from radiologist colleagues’. Conclusions A range of factors are likely to contribute to the successful implementation of radiographer commenting in addition to abnormality detection in emergency settings. Effective image interpretation education amenable to completion by radiographers would likely prove valuable in preparing radiographers for participation in abnormality detection and commenting systems in emergency settings.
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Plant tissue has a complex cellular structure which is an aggregate of individual cells bonded by middle lamella. During drying processes, plant tissue undergoes extreme deformations which are mainly driven by moisture removal and turgor loss. Numerical modelling of this problem becomes challenging when conventional grid-based modelling techniques such as Finite Element Methods (FEM) and Finite Difference Methods (FDM) have grid-based limitations. This work presents a meshfree approach to model and simulate the deformations of plant tissues during drying. This method demonstrates the fundamental capabilities of meshfree methods in handling extreme deformations of multiphase systems. A simplified 2D tissue model is developed by aggregating individual cells while accounting for the stiffness of the middle lamella. Each individual cell is simply treated as consisting of two main components: cell fluid and cell wall. The cell fluid is modelled using Smoothed Particle Hydrodynamics (SPH) and the cell wall is modelled using a Discrete Element Method (DEM). During drying, moisture removal is accounted for by reduction of cell fluid and wall mass, which causes local shrinkage of cells eventually leading to tissue scale shrinkage. The cellular deformations are quantified using several cellular geometrical parameters and a favourably good agreement is observed when compared to experiments on apple tissue. The model is also capable of visually replicating dry tissue structures. The proposed model can be used as a step in developing complex tissue models to simulate extreme deformations during drying.
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Background Rapid developments in technology have encouraged the use of smartphones in physical activity research, although little is known regarding their effectiveness as measurement and intervention tools. Objective This study systematically reviewed evidence on smartphones and their viability for measuring and influencing physical activity. Data Sources Research articles were identified in September 2013 by literature searches in Web of Knowledge, PubMed, PsycINFO, EBSCO, and ScienceDirect. Study Selection The search was restricted using the terms (physical activity OR exercise OR fitness) AND (smartphone* OR mobile phone* OR cell phone*) AND (measurement OR intervention). Reviewed articles were required to be published in international academic peer-reviewed journals, or in full text from international scientific conferences, and focused on measuring physical activity through smartphone processing data and influencing people to be more active through smartphone applications. Study Appraisal and Synthesis Methods Two reviewers independently performed the selection of articles and examined titles and abstracts to exclude those out of scope. Data on study characteristics, technologies used to objectively measure physical activity, strategies applied to influence activity; and the main study findings were extracted and reported. Results A total of 26 articles (with the first published in 2007) met inclusion criteria. All studies were conducted in highly economically advantaged countries; 12 articles focused on special populations (e.g. obese patients). Studies measured physical activity using native mobile features, and/or an external device linked to an application. Measurement accuracy ranged from 52 to 100 % (n = 10 studies). A total of 17 articles implemented and evaluated an intervention. Smartphone strategies to influence physical activity tended to be ad hoc, rather than theory-based approaches; physical activity profiles, goal setting, real-time feedback, social support networking, and online expert consultation were identified as the most useful strategies to encourage physical activity change. Only five studies assessed physical activity intervention effects; all used step counts as the outcome measure. Four studies (three pre–post and one comparative) reported physical activity increases (12–42 participants, 800–1,104 steps/day, 2 weeks–6 months), and one case-control study reported physical activity maintenance (n = 200 participants; >10,000 steps/day) over 3 months. Limitations Smartphone use is a relatively new field of study in physical activity research, and consequently the evidence base is emerging. Conclusions Few studies identified in this review considered the validity of phone-based assessment of physical activity. Those that did report on measurement properties found average-to-excellent levels of accuracy for different behaviors. The range of novel and engaging intervention strategies used by smartphones, and user perceptions on their usefulness and viability, highlights the potential such technology has for physical activity promotion. However, intervention effects reported in the extant literature are modest at best, and future studies need to utilize randomized controlled trial research designs, larger sample sizes, and longer study periods to better explore the physical activity measurement and intervention capabilities of smartphones.
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This submission makes one simple yet powerful recommendation for law reform to promote justice for survivors of child sexual abuse. It is informed by extensive analyses of the phenomenon of child sexual abuse and its psychological sequelae, legislative time limits and case law across Australia and internationally, the policy reasons underpinning statutory time limits generally, and the need for fairness, certainty and practicability in the legal system. The recommendation is that legislative reform is required in all Australian States and Territories to remove time limitations for civil claims for injuries caused by child sexual abuse.