878 resultados para Critical current degradation


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Top-predators have been reported to have an important role in structuring food webs and maintaining ecological processes for the benefit of biodiversity at lower trophic levels. This is thought to be achieved through their suppressive effects on sympatric mesopredators and prey. Great scientific and public interest surrounds the potential use of top-predators as biodiversity conservation tools, and it can often be difficult to separate what we think we know and what we really know about their ecological utility. Not all the claims made about the ecological roles of top-predators can be substantiated by current evidence. We review the methodology underpinning empirical data on the ecological roles of Australian dingoes (Canis lupus dingo and hybrids) to provide a comprehensive and objective benchmark for knowledge of the ecological roles of Australia's largest terrestrial predator. From a wide variety of methodological flaws, sampling bias, and experimental design constraints inherent to 38 of the 40 field studies we assessed, we demonstrate that there is presently unreliable and inconclusive evidence for dingoes role as a biodiversity regulator. We also discuss the widespread (both taxonomically and geographically) and direct negative effects of dingoes to native fauna, and the few robust studies investigating their positive roles. In light of the highly variable and context-specific impacts of dingoes on faunal biodiversity and the inconclusive state of the literature, we strongly caution against the positive management of dingoes in the absence of a supporting evidence-base for such action.

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Wastewater-based epidemiology (WBE) applies advanced analytical methods to quantify drug residues in wastewater with the aim to estimate illicit drug use at the population level. Transformation processes during transport in sewers (chemical and biological reactors) and storage of wastewater samples before analysis are expected to change concentrations of different drugs to varying degrees. Ignoring transformation for drugs with low to medium stability will lead to an unknown degree of systematic under- or overestimation of drug use, which should be avoided. This review aims to summarize the current knowledge related to the stability of commonly investigated drugs and, furthermore, suggest a more effective approach to future experiments. From over 100 WBE studies, around 50 mentioned the importance of stability and 24 included tests in wastewater. Most focused on in-sample stability (i.e., sample preparation, preservation and storage) and some extrapolated to in-sewer stability (i.e., during transport in real sewers). While consistent results were reported for rather stable compounds (e.g., MDMA and methamphetamine), a varying range of stability under different or similar conditions was observed for other compounds (e.g., cocaine, amphetamine and morphine). Wastewater composition can vary considerably over time, and different conditions prevail in different sewer systems. In summary, this indicates that more systematic studies are needed to: i) cover the range of possible conditions in sewers and ii) compare results more objectively. To facilitate the latter, we propose a set of parameters that should be reported for in-sewer stability experiments. Finally, a best practice of sample collection, preservation, and preparation before analysis is suggested in order to minimize transformation during these steps.

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Over the past two decades neo liberalism has shaped global economic activity. The international reach of the current economic crisis propelled by the subprime mortgage meltdown in the United States has affected Indigenous communities in different ways to those whose investments were depleted by the Wall Street activities of an unregulated corporate and banking sector. Throughout this roller coaster economic ride the low socio-economic position of Indigenous peoples continued in Canada, the United States of America, New Zealand, Hawaii and Australia. The logic, or illogic of capital, failed to extend the boom of the economic upturn to Indigenous peoples, but is poised to extend the repercussions of the current downturn deep into Indigenous lives. The consistency of the Indigenous socio-economic position across these countries, even where treaties exist, indicates that the phenomenon is based on a shared Indigenous reality. In this special edition, the commonality in the way in which Indigenous people are engaged in and positioned by market forces and regulation by their respective nation states is proposed as one of the foundation plates of that Indigenous positioning...

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This edition of the International Journal of Critical Indigenous Studies marks the tenth since the journal’s launch in 2008. During that time, over forty articles and eleven book reviews have been published, which is testament to the continuing upward trajectory of Critical Indigenous Studies. Although there continues to be an increasing range of areas of Indigenous research to which a critical focus is brought to bear, a consistent issue for many of the journal’s contributors has been the delineation and application of Indigenous methods and methodologies in social research. The present edition is no exception, with two articles focussing on Indigenous-centred research. The first, by Krystal Summers, reflexively explores the author’s experiences as an undergraduate student undertaking Indigenous-centred research in Peru. As an Indigenous First Nations woman, Summers was mindful that her research practice was faithful to the ethics and protocols outlined in her original project proposal. Her subsequent ‘journey of critical reflexive understanding and storytelling’ supports the proposition of current literature in Indigenous research methodologies that a properly critical Indigenous ethnography will naturally enjoin with Indigenous epistemologies and methodologies.

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This chapter provides a critical legal geography of outer Space, charting the topography of the debates and struggles around its definition, management, and possession. As the emerging field of critical legal geography demonstrates, law is not a neutral organiser of space, but is instead a powerful cultural technology of spatial production. Drawing on legal documents such as the Outer Space Treaty and the Moon Treaty, as well as on the analogous and precedent-setting legal geographies of Antarctica and the deep seabed, the chapter addresses key questions about the legal geography of outer Space, questions which are of growing importance as Space’s available satellite spaces in the geostationary orbit diminish, Space weapons and mining become increasingly viable, Space colonisation and tourism emerge, and questions about Space’s legal status grow in intensity. Who owns outer Space? Who, and whose rules, govern what may or may not (literally) take place there? Is the geostationary orbit the sovereign property of the equatorial states it supertends, as these states argued in the 1970s? Or is it a part of the res communis, or common property of humanity, which currently legally characterises outer Space? Does Space belong to no one, or to everyone? As challenges to the existing legal spatiality of outer Space emerge from spacefaring states, companies, and non-spacefaring states, it is particularly critical that the current spatiality of Space is understood and considered.

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The idea of retinal cell transplantation as a potential treatment for age-related retinal degeneration, a leading cause of blindness in the Western world, has been around for a number of decades. To date, however, it has not been entirely successful; one of the main reasons for this is the lack of an ideal substratum for the retinal cells, specifically for the growth of retinal pigment epithelial cells prior to transplantation. This chapter reviews the reasoning behind this potential treatment, the development of animal transplantation models for human trials, the prerequisites of an ideal substratum, the past and current research on substratum materials, and the potential for future developments in this area.

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One of the major challenges in the treatment of lung cancer is the development of drug resistance. This represents a major obstacle in the treatment of patients, limiting the efficacy of both conventional chemotherapy and biological therapies. Deciphering the mechanisms of resistance is critical to further understanding the multifactorial pathways involved, and in developing more specific targeted treatments. To date, numerous studies have reported the potential role of microRNAs (miRNAs) in resistance to various cancer treatments. MicroRNAs are a family of small non-coding RNAs that regulate gene expression by sequence-specific targeting of mRNAs causing translational repression or mRNA degradation. More than 1200 validated human miRNAs have been identified to date. While as little as one miRNA can regulate hundreds of targets, a single target can also be affected by multiple miRNAs. Evidence suggests that dysregulation of specific miRNAs may be involved in the acquisition of resistance to a number of cancer treatments, thereby modulating the sensitivity of cancer cells to such therapies. Therefore, targeting miRNAs may be an attractive strategy for developing novel and more effective individualized therapies, improving drug efficiency, and for predicting patient response to different treatments. In this review, we provide an overview on the role of miRNAs in resistance to current lung cancer therapies and novel biological agents.

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Expression of the F-Box protein Leaf Curling Responsiveness (LCR) is regulated by microRNA, miR394, and alterations to this interplay in Arabidopsis thaliana produce defects in leaf polarity and shoot apical meristem (SAM) organisation. Although the miR394-LCR node has been documented in Arabidopsis, the identification of proteins targeted by LCR F-box itself has proven problematic. Here, a proteomic analysis of shoot apices from plants with altered LCR levels identified a member of the Major Latex Protein (MLP) family gene as a potential LCR F-box target. Bioinformatic and molecular analyses also suggested that other MLP family members are likely to be targets for this post-translational regulation. Direct interaction between LCR F-Box and MLP423 was validated. Additional MLP members had reduction in protein accumulation, in varying degrees, mediated by LCR F-Box. Transgenic Arabidopsis lines, in which MLP28 expression was reduced through an artificial miRNA technology, displayed severe developmental defects, including changes in leaf patterning and morphology, shoot apex defects, and eventual premature death. These phenotypic characteristics resemble those of Arabidopsis plants modified to over-express LCR. Taken together, the results demonstrate that MLPs are driven to degradation by LCR, and indicate that MLP gene family is target of miR394-LCR regulatory node, representing potential targets for directly post-translational regulation mediated by LCR F-Box. In addition, MLP28 family member is associated with the LCR regulation that is critical for normal Arabidopsis development.

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Preparing social work students for the demands of changing social environments and to promote student mobility and interest in overseas employment opportunities have resulted in an increasing demand for international social work placements. The literature describes numerous examples of social work programmes that offer a wide variety of international placements. However, research about the actual benefit of undertaking an overseas placement is scant with limited empirical evidence on the profile of students participating, their experience of the tasks offered, the supervisory practice and the outcomes for students' professional learning and career. This study contributes to the existing body of literature by exploring the relevance of international field placements for students and is unique in that it draws its sample from students who have graduated so provides a distinctive perspective in which to compare their international placement with their other placement/s as well as evaluating what were the benefits and drawbacks for them in terms of their careers, employment opportunities and current professional practice.

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This paper discusses various theoretical approaches to diversity management, analysing their similarities and differences. I start with a review of certain previously presented classifications, and then proceed to describing the different approaches in more detail. In this paper, I propose that the various viewpoints can be categorized into three groups: 1) practitioner/consultant approach, 2) mainstream approach, and 3) critical approaches. Although there are differences within these groups, in particular regarding the critical approaches, these differences appear less significant than those between the groups. Those representing the first group are mainly interested in how to get most out of a diverse workforce, while those in the second group focus on the effects of diversity on performance or work group functioning. While some of the mainstream writers can be rather critical towards earlier research, they hardly ever discuss or even recognize the wide ranging criticism put forward by critical scholars. The critical researchers, then, remain a rather scattered group who do not always share much more than a conviction that the mainstream research keeps missing highly significant issues. Nonetheless, in order to increase our understanding of how different persons can and do work together, more dialogue is required between the varying standpoints.

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We examine the exclusion limits set by the CDF and D0 experiments on the Standard Model Higgs boson mass from their searches at the Tevatron in the light of large theoretical uncertainties on the signal and background cross sections. We show that when these uncertainties are consistently taken into account, the sensitivity of the experiments becomes significantly lower and the currently excluded mass range M-H = 158-175 GeV could be entirely reopened. The necessary luminosity required to recover the current sensitivity is found to be a factor of two higher than the present one. (C) 2011 Elsevier B.V. All rights reserved.

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Ultrasonic degradation of poly(methyl methacrylate) (PMMA) was carried out in several solvents and some mixtures of solvents. The time evolution of molecular weight distribution (MWD), determined by gel permeation chromatography, is analysed by continuous distribution kinetics. The rate coefficients for polymer degradation are determined for each solvent. The variation of rate coefficients is correlated with the vapour pressure of the solvent, kinematic viscosity of the solution and solvent-polymer interaction parameters. The vapour pressure and the kinematic viscosity of the solution are found to be more critical than other parameters (such as the Huggins and Flory-Huggins constants) in determining the degradation rates. (C) 2001 Society of Chemical Industry.

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Technology scaling has caused Negative Bias Temperature Instability (NBTI) to emerge as a major circuit reliability concern. Simultaneously leakage power is becoming a greater fraction of the total power dissipated by logic circuits. As both NBTI and leakage power are highly dependent on vectors applied at the circuit’s inputs, they can be minimized by applying carefully chosen input vectors during periods when the circuit is in standby or idle mode. Unfortunately input vectors that minimize leakage power are not the ones that minimize NBTI degradation, so there is a need for a methodology to generate input vectors that minimize both of these variables.This paper proposes such a systematic methodology for the generation of input vectors which minimize leakage power under the constraint that NBTI degradation does not exceed a specified limit. These input vectors can be applied at the primary inputs of a circuit when it is in standby/idle mode and are such that the gates dissipate only a small amount of leakage power and also allow a large majority of the transistors on critical paths to be in the “recovery” phase of NBTI degradation. The advantage of this methodology is that allowing circuit designers to constrain NBTI degradation to below a specified limit enables tighter guardbanding, increasing performance. Our methodology guarantees that the generated input vector dissipates the least leakage power among all the input vectors that satisfy the degradation constraint. We formulate the problem as a zero-one integer linear program and show that this formulation produces input vectors whose leakage power is within 1% of a minimum leakage vector selected by a search algorithm and simultaneously reduces NBTI by about 5.75% of maximum circuit delay as compared to the worst case NBTI degradation. Our paper also proposes two new algorithms for the identification of circuit paths that are affected the most by NBTI degradation. The number of such paths identified by our algorithms are an order of magnitude fewer than previously proposed heuristics.