17 resultados para Life-times

em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast


Relevância:

60.00% 60.00%

Publicador:

Resumo:

The feasibility of large-scale implementation of Li-air batteries (LABs) hinges on understanding the thermodynamic and kinetic factors that control charge-discharge rates, efficiency and life times. Here, the kinetics of bias-induced reactions is explored locally on the surface of Li-ion conductive glass ceramics, a preferred electrolyte for LABs, using direct current-voltage and strain spectroscopies. Above a critical bias, particle growth kinetics were found to be linear in both the bias and time domains. Partial reversibility was observed for Li particles as evidenced by the presence of anodic peaks following the Li(+) reduction, as well an associated reduction in particle height. The degree of reversibility was highest for the smallest particles formed. These observations thus suggest the possibility of producing nanobatteries with an active anode volume of the order of 0.1 al.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

In the last 40 years a wide range of molecules, including neutrals, cations and anions, containing up to 13 atoms—in addition to detections of C60 and C70 — have been found in the harsh environment of the interstellar medium. The exquisite sensitivity and very high spectral and, more recently, spatial resolution, of modern telescopes has enabled the physics of star formation to be probed through rotational line emission. In this article, I review the basic properties of interstellar clouds and the processes that initiate the chemistry and generate chemical complexity, particularly in regions of star and planet formation. Our understanding of astrochemistry has evolved over the years. Before 1990, the general consensus was that molecules were formed in binary, gas-phase, or volume, reactions, most importantly ion-neutral reactions despite the very low ionization in clouds. Since then, observations have indicated unambiguously that there is also a contribution from surface processes, particularly on the icy mantles that form around refractory grain cores in cold, dense gas. The balance between these two processes depends on particular physical conditions and can vary during the life cycle of a particular volume of interstellar cloud.The complex chemistry that occurs in space is driven mostly through interaction of thegas with cosmic ray protons, a source of ionization that enables a rich ion-neutral chemistry. In addition, I show that the interaction between the gas and the dust in cold, dense regionsalso leads to additional chemical complexity through reactions that take place in ices at onlya few tens of degrees above absolute zero. Although densities are low compared to those in terrestrial environments, the extremely long life times of interstellar clouds and their enormous sizes, enable complex molecules to be synthesised and detected. I show that in some instances, particularly in reactions involving deuterium, the rotational populations of reactants, together with spin-selection rules, can determine the detailed abundances. Although the review is mainly focused on regions associated with star formation, I also consider chemistry in other interesting astronomical regions — in the early Universe and in the envelopes formed by mass loss during the final stages of stellar evolution.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Objective
To examine the psychometric properties of an internet version of a children and young person's quality of life measure originally designed as a paper questionnaire.

Methods
Participants were 3,440 10 and 11 year old children in Northern Ireland who completed the KIDSCREEN-27 online as part of a general attitudinal survey. The questionnaire was animated using cartoon characters that are familiar to most children and the questions appeared on screen and were read aloud by actors.

Results
Exploratory principal component analysis of the online version of the questionnaire supported the existence of five components in line with the paper version. The items loaded on the components that would be expected based on previous findings with five domains - physical well-being,psychological well-being, autonomy and parents, social support and peers and school environment.Internal consistency reliability of the five domains was measured using Cronbach's alpha and the results suggested that the scale scores were reliable. The domain scores were similar to those reported in the literature for the paper version.

Conclusions
These results suggest that the factor structure and internal consistency reliability scores of the KIDSCREEN-27 embedded within an online survey are comparable to those reported in the literature for the paper version.

Relevância:

40.00% 40.00%

Publicador:

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Background: After a volcano erupts, a lake may form in the cooled crater and become an isolated aquatic ecosystem. This makes fishes in crater lakes informative for understanding sympatric evolution and ecological diversification in barren environments. From a geological and limnological perspective, such research offers insight about the process of crater lake ecosystem establishment and speciation. In the present study we use genetic and coalescence approaches to infer the colonization history of Midas cichlid fishes (Amphilophus cf. citrinellus) that inhabit a very young crater lake in Nicaragua-the ca. 1800 year-old Lake Apoyeque. This lake holds two sympatric, endemic morphs of Midas cichlid: one with large, hypertrophied lips (~20% of the total population) and another with thin lips. Here we test the associated ecological, morphological and genetic diversification of these two morphs and their potential to represent incipient speciation.
Results: Gene coalescence analyses [11 microsatellite loci and mitochondrial DNA (mtDNA) sequences] suggest that crater lake Apoyeque was colonized in a single event from the large neighbouring great lake Managua only about 100 years ago. This founding in historic times is also reflected in the extremely low nuclear and mitochondrial genetic diversity in Apoyeque. We found that sympatric adult thin- and thick-lipped fishes occupy distinct ecological trophic niches. Diet, body shape, head width, pharyngeal jaw size and shape and stable isotope values all differ significantly between the two lip-morphs. The eco-morphological features pharyngeal jaw shape, body shape, stomach contents and stable isotopes (d15N) all show a bimodal distribution of traits, which is compatible with the expectations of an initial stage of ecological speciation under disruptive selection. Genetic differentiation between the thin- and thick-lipped population is weak at mtDNA sequence (FST = 0.018) and absent at nuclear microsatellite loci (FST < 0.001).
Conclusions: This study provides empirical evidence of eco-morphological differentiation occurring very quickly after the colonization of a new and vacant habitat. Exceptionally low levels of neutral genetic diversity and inference from coalescence indicates that the Midas cichlid population in Apoyeque is much younger (ca. 100 years or generations old) than the crater itself (ca. 1 800 years old). This suggests either that the crater remained empty for many hundreds of years after its formation or that remnant volcanic activity prevented the establishment of a stable fish population during the early life of the crater lake. Based on our findings of eco-morphological variation in the Apoyeque Midas cichlids, and known patterns of adaptation in Midas cichlids in general, we suggest that this population may be in a very early stage of speciation (incipient species), promoted by disruptive selection and ecological diversification.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Adopting and adapting musicology’s use of affect theories, specifically Jeremy Gilbert’s idea of an ‘affective analysis’ and David Epstein’s idea of ‘shaping affect’, this article looks at Martin Crimp’s Attempts on Her Life from a practitioner’s perspective. It investigates the challenges and benefits of adopting an ‘affective approach’ to directing recent theatre texts which stress the musicality and corporeality of language along with, and at times above, their signifying roles. Rather than locating Aristotelian dramatic climaxes based on narratological or characterological progression, an affective approach seeks to identify moments of affective intensity, which produce a different sort of impact by working on a ‘body-first’ methodology rather than the directly cerebral. That this embodied impact is not ultimately meaningless is one of affect theories most vital assertions. This approach has resonance in terms of how directors, performers and critics/theorists approach work of this type.

Relevância:

30.00% 30.00%

Publicador:

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Objective: The purpose of this study was to estimate costs and quality of life (QoL) of late-stage glaucoma patients in 4 European countries. Methods: Retrospective review of medical charts of patients with POAG who were followed in a low-vision or vision rehabilitation center in one of 4 countries for at least 1 year was used to determine patient characteristics, health status, and health care resource use. Visual impairment was measured by best-corrected visual acuity (Snellen score). Patients were also interviewed over the telephone in order to assess their health-related QoL (using EuroQol EQ-5D) and use of resources including: the number of visits to rehabilitation centers, visits to hospital and non-hospital specialists, the use of low-vision devices, medication, tests, and the use of hired home help. The costs associated with resource use were calculated from the perspective of a third-party payer of health and social care based on resource usage and unit costs in each country. Results: Patients undergoing visual rehabilitation in France (n=21), Denmark (n=59), Germany (n=60), and the United Kingdom (n=22) were identified, interviewed and had their medical charts reviewed. Annual maintenance costs of late-stage glaucoma amounted to €830 (±445) on average. Average home help costs were more than 3 times higher. QoL, on average, was 0.65 (±0.28). QoL was positively correlated with the level of visual acuity in the patients' best eye. On the other hand, visual acuity was also positively correlated to health care costs, but negatively correlated to costs of home help. Conclusions: The study was limited by its observational, uncontrolled design. The finding that late-stage glaucoma is associated with higher home help costs than health care maintenance costs suggests that potential savings from a better preventive treatment are to be found for social care payers rather than health care payers. © 2008 Informa UK Ltd All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Purpose This chapter explores the ideas of Alasdair MacIntyre and Vaclav Havel and what these two thinkers can contribute to green political theory. Design/methodology/approach This chapter includes examination of some of the key works of Havel and MacIntyre and analysis of these works from the point of view of green political theory. Findings The section ‘Havel and the Imperative to “Live in Truth”: Dissent and Green Politics’ explores Havel’s thought with a particular emphasis on his ethicised notion of political action and critique (‘living in truth’) and his focus on the centrality of dissent (both intellectually and in practice) as central to political critique and action. The section ‘MacIntyre as a Green Thinker: Vulnerability in Political and Moral Theory’ offers an overview of MacIntyre interpreted as a putative green thinker, with a particular emphasis on his ideas of dependence and vulnerability. The Conclusion attempts to draw some common themes together from both thinkers in terms of what they have to offer contemporary green political thought. Research limitations/implications What is presented here is introductory, ground clearing and therefore necessarily suggestive (as well as under-developed). That is, it is the start of a new area of exploration rather than an analysis based on any exhaustive and comprehensive knowledge of both thinkers. Practical implications This chapter offers some initial lines of exploration for scholars interested in the overlap between green thinking and the work of Havel and MacIntyre. Originality/value This is the first exploration of the connections between the works of Havel and MacIntyre and green political theory.