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Selected AbstractsIdentifying English Language Learners with Learning Disabilities: Key Challenges and Possible ApproachesLEARNING DISABILITIES RESEARCH & PRACTICE, Issue 1 2005Richard K. Wagner The need for effective approaches for identifying English language learners with learning disabilities is great and growing. Meeting this need is complicated by recent developments in the field of learning disabilities that are unrelated to the English language learning status, and by limitations in existing knowledge specific to the identification of English language learners with learning disabilities. We review recent developments in the field of learning disabilities concerning the need for earlier identification, the need for a more appropriate conceptualization of learning disability, and the need for more effective assessments and treatments. We discuss challenges to assessment and identification of English language learners with learning disabilities, provide examples of two approaches to meeting these challenges, and describe some remaining challenges. [source] Managing alliance relationships: Key challenges in the early stages of collaborationR & D MANAGEMENT, Issue 1 2002Mícheál J. Kelly Recent surveys indicate that executives of technology companies consider strategic alliances to be central to their competitive strategies. Yet the barriers to successful alliances are formidable. In many instances, these barriers develop in the early stages of an alliance. This study identifies and analyzes the types of challenges that companies face in the start,up phase of their alliances. It is based on a survey and interviews with executives in the Canadian high technology industry. The study finds that the principal challenges in the first year of an alliance relate to relationship issues between the partners. It suggests stronger attention to these issues in the design and implementation of an alliance. The paper concludes with guidelines to build and sustain effective working relationships between partners. [source] The Process of Fixing the British National Minimum Wage, 1997,2007BRITISH JOURNAL OF INDUSTRIAL RELATIONS, Issue 2 2009William Brown The British National Minimum Wage was introduced in 1999 under the guidance of a Low Pay Commission constructed on a basis of ,social partnership'. The article analyses its conduct over its first 10 years from diary data. Key challenges were for it to be independent of government, to have its advice accepted by government and to maintain internal unanimity. The changing internal dynamics of the Commission, and its major negotiations over the level of the minimum wage, are described and analysed. Conclusions are drawn for the social partnership process. [source] Seine: a dynamic geometry-based shared-space interaction framework for parallel scientific applicationsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2006L. Zhang Abstract While large-scale parallel/distributed simulations are rapidly becoming critical research modalities in academia and industry, their efficient and scalable implementations continue to present many challenges. A key challenge is that the dynamic and complex communication/coordination required by these applications (dependent on the state of the phenomenon being modeled) are determined by the specific numerical formulation, the domain decomposition and/or sub-domain refinement algorithms used, etc. and are known only at runtime. This paper presents Seine, a dynamic geometry-based shared-space interaction framework for scientific applications. The framework provides the flexibility of shared-space-based models and supports extremely dynamic communication/coordination patterns, while still enabling scalable implementations. The design and prototype implementation of Seine are presented. Seine complements and can be used in conjunction with existing parallel programming systems such as MPI and OpenMP. An experimental evaluation using an adaptive multi-block oil-reservoir simulation is used to demonstrate the performance and scalability of applications using Seine. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effects of Economic Prosperity on Numbers of Threatened SpeciesCONSERVATION BIOLOGY, Issue 4 2001Robin Naidoo We corrected for factors that might otherwise confound such a relationship. Our study was motivated by the continuing debate over the relationship between environmental degradation and per-capita income. Proponents of the environmental Kuznets-curve hypothesis argue that although environmental degradation may increase initially, increases in per-capita income will eventually result in greater environmental quality. Theoretical objections and the lack of widespread empirical evidence recently have thrown doubt on the existence of such a pattern. Treating threat to biodiversity as one potential indicator of environmental degradation, we divided threatened species into seven taxonomic groups ( plants, mammals, birds, amphibians, reptiles, fishes, and invertebrates) and analyzed each group separately. Count-data regression analysis indicated that the number of threatened species was related to per-capita gross national product in five of seven taxonomic groups. Birds were the only taxonomic group in which numbers of threatened species decreased throughout the range of developed countries' per-capita gross national product. Plants, amphibians, reptiles, and invertebrates showed increasing numbers of threatened species throughout this same range. If these relationships hold, increasing numbers of species from several taxonomic groups are likely to be threatened with extinction as countries increase in prosperity. A key challenge is to understand the interactions among consumer preferences, biology, and institutions that lead to the relationship observed for birds and to see whether this knowledge can be applied to conservation of other taxa. Resumen: Utilizamos datos de más de 100 países para investigar la relación entre números de especies amenazadas y el producto interno bruto per cápita. Hicimos ajustes para factores que pudieran confundir tal relación. Nuestro estudio fue motivado por el continuo debate sobre la relación entre la degradación ambiental y el ingreso per cápita. Proponentes de la hipótesis de la curva ambiental de Kuznets argumentan que, aunque la degradación ambiental puede aumentar inicialmente, el incremento en el ingreso per cápita eventualmente resultará en una mejor calidad ambiental. Recientemente, objeciones teóricas y la carencia de evidencia empírica generalizada hacen dudar de la existencia de ese patrón. Tratando la amenaza a la biodiversidad como un potencial indicador de la degradación ambiental, dividimos a las especies amenazadas en siete grupos taxonómicos (plantas, mamíferos, aves, anfibios, reptiles, peces e invertebrados) y analizamos cada uno por separado. El análisis de regresión de los datos de conteo indicó que el número de especies amenazadas se relacionó con el producto interno bruto per cápita en 5 de los 7 grupos taxonómicos. Las aves fueron el único grupo en el que el número de especies amenazadas decreció a lo largo del rango del producto interno bruto per cápita de los países desarrollados. Las plantas, anfibios, reptiles e invertebrados mostraron un incremento en el número de especies amenazadas en este mismo rango. Si estas relaciones persisten, es posible que aumente el número de especies, de varios grupos taxonómicos, amenazadas de extinción a medida que los países incrementen su prosperidad. Constituye un reto clave entender las interacciones entre la preferencia de los consumidores y los factores biológicos e institucionales que conducen a la relación observada en las aves, y ver si este conocimiento puede aplicarse en la conservación de otros taxones. [source] Priorities and paradigms: directions in threatened species recoveryCONSERVATION LETTERS, Issue 3 2009Sue V. Briggs Abstract Recovering threatened species is a key challenge for conservation managers, policy makers, and researchers. This article describes a practical framework for assigning priorities for recovery of threatened species according to cost-effectiveness of recovery strategies for species groups. The framework has the following steps: (1) determine the conservation goal,persistence in the wild of the largest number of threatened species with the funds available; (2) assign threatened species to species recovery groups according to their characteristics and threats,small-population species that require actions at sites and declining-population species that require actions across landscapes; (3) identify the recovery strategies and their component actions for the species groups; (4) cost the recovery strategies for the species groups; (5) determine the cost-effectiveness of the recovery strategies for the species groups,the number of species recovered divided by the cost of the strategies; (6) assign priorities to the recovery strategies according to their cost-effectiveness; (7) allocate funds to the recovery strategies that maximize the number of threatened species recovered for the funds available; and (8) undertake the funded recovery strategies and actions. The framework is illustrated with an example. [source] Customer Behavior in an Online Ordering Application: A Decision Scoring Model,DECISION SCIENCES, Issue 4 2005Kenneth K. Boyer ABSTRACT This research presents the development of behavioral scoring models to predict future customer purchases in an online ordering application. Internet retailing lowers many barriers for customers switching between retailers for repeat purchases; thus, retaining existing customers is a key challenge for achieving profitability. Survey data were collected from 1,089 online customers of two companies. The subjective survey data were then used to predict purchases over the ensuing 12 months based on data from the company databases. The analysis illustrates the general applicability of predictive models of future customer purchases while also demonstrating the need to develop specific models tailored for an individual company's operating and marketing environment. The models provide insight on how companies can target marketing dollars more effectively and allocate investment across multiple operational areas for maximum return. The research answers a call for rigorous research in the area of predictive marketing, an area in which many companies are excelling but where there is a scarcity of detailed knowledge regarding application of such models. [source] Phylogenetic beta diversity: linking ecological and evolutionary processes across space in timeECOLOGY LETTERS, Issue 12 2008Catherine H. Graham Abstract A key challenge in ecological research is to integrate data from different scales to evaluate the ecological and evolutionary mechanisms that influence current patterns of biological diversity. We build on recent attempts to incorporate phylogenetic information into traditional diversity analyses and on existing research on beta diversity and phylogenetic community ecology. Phylogenetic beta diversity (phylobetadiversity) measures the phylogenetic distance among communities and as such allows us to connect local processes, such as biotic interactions and environmental filtering, with more regional processes including trait evolution and speciation. When combined with traditional measures of beta diversity, environmental gradient analyses or ecological niche modelling, phylobetadiversity can provide significant and novel insights into the mechanisms underlying current patterns of biological diversity. [source] Ecological perspectives on the sequenced genome collectionECOLOGY LETTERS, Issue 12 2005Jennifer B. Hughes Martiny Abstract Our complete genome collection is one of our most valuable biological resources. A key challenge for the future is the interpretation of these genomes from an ecological perspective. In this review, we discuss current work at this increasingly important interface. In particular, we review ongoing work aimed at developing high quality data sets that combine ecological, environmental, evolutionary and genomic information. Such data will help to identify biases in the sequence collection and facilitate future discoveries about the nature of ecological adaptation at the genome level. These efforts will be greatly enhanced by the contributions of ecologists. [source] Disruption of dopamine homeostasis underlies selective neurodegeneration mediated by ,-synucleinEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2007Soon S. Park Abstract A key challenge in Parkinson's disease research is to understand mechanisms underlying selective degeneration of dopaminergic neurons mediated by genetic factors such as ,-synuclein (,-Syn). The present study examined whether dopamine (DA)-dependent oxidative stress underlies ,-Syn-mediated neurodegeneration using Drosophila primary neuronal cultures. Green fluorescent protein (GFP) was used to identify live dopaminergic neurons in primary cultures prepared on a marked photoetched coverslip, which allowed us to repeatedly access preidentified dopaminergic neurons at different time points in a non-invasive manner. This live tracking of GFP-marked dopaminergic neurons revealed age-dependent neurodegeneration mediated by a mutant human ,-Syn (A30P). Degeneration was rescued when ,-Syn neuronal cultures were incubated with 1 mm glutathione from Day 3 after culturing. Furthermore, depletion of cytoplasmic DA by 100 µm,-methyl- p -tyrosine completely rescued the early stage of ,-Syn-mediated dopaminergic cell loss, demonstrating that DA plays a major role in oxidative stress-dependent neurodegeneration mediated by ,-Syn. In contrast, overexpression of a Drosophila tyrosine hydroxylase gene (dTH1) alone caused DA neurodegeneration by enhanced DA synthesis in the cytoplasm. Age-dependent dopaminergic cell loss was comparable in ,-Syn vs dTH1-overexpressed neuronal cultures, indicating that increased DA levels in the cytoplasm is a critical change downstream of mutant ,-Syn function. Finally, overexpression of a Drosophila vesicular monoamine transporter rescued ,-Syn-mediated neurodegeneration through enhanced sequestration of cytoplasmic DA into synaptic vesicles, further indicating that a main cause of selective neurodegeneration is ,-Syn-induced disruption of DA homeostasis. All of these results demonstrate that elevated cytoplasmic DA is a main factor underlying the early stage of ,-Syn-mediated neurodegeneration. [source] Selective sampling for approximate clustering of very large data setsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 3 2008Liang Wang A key challenge in pattern recognition is how to scale the computational efficiency of clustering algorithms on large data sets. The extension of non-Euclidean relational fuzzy c-means (NERF) clustering to very large (VL = unloadable) relational data is called the extended NERF (eNERF) clustering algorithm, which comprises four phases: (i) finding distinguished features that monitor progressive sampling; (ii) progressively sampling from a N × N relational matrix RN to obtain a n × n sample matrix Rn; (iii) clustering Rn with literal NERF; and (iv) extending the clusters in Rn to the remainder of the relational data. Previously published examples on several fairly small data sets suggest that eNERF is feasible for truly large data sets. However, it seems that phases (i) and (ii), i.e., finding Rn, are not very practical because the sample size n often turns out to be roughly 50% of n, and this over-sampling defeats the whole purpose of eNERF. In this paper, we examine the performance of the sampling scheme of eNERF with respect to different parameters. We propose a modified sampling scheme for use with eNERF that combines simple random sampling with (parts of) the sampling procedures used by eNERF and a related algorithm sVAT (scalable visual assessment of clustering tendency). We demonstrate that our modified sampling scheme can eliminate over-sampling of the original progressive sampling scheme, thus enabling the processing of truly VL data. Numerical experiments on a distance matrix of a set of 3,000,000 vectors drawn from a mixture of 5 bivariate normal distributions demonstrate the feasibility and effectiveness of the proposed sampling method. We also find that actually running eNERF on a data set of this size is very costly in terms of computation time. Thus, our results demonstrate that further modification of eNERF, especially the extension stage, will be needed before it is truly practical for VL data. © 2008 Wiley Periodicals, Inc. [source] Pathogen fitness components and genotypes differ in their sensitivity to nutrient and temperature variation in a wild plant,pathogen associationJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2007A.-L. LAINE Abstract Understanding processes maintaining variation in pathogen life-history stages affecting infectivity and reproduction is a key challenge in evolutionary ecology. Models of host,parasite coevolution are based on the assumption that genetic variation for host,parasite interactions is a significant cause of variation in infection, and that variation in environmental conditions does not overwhelm the genetic basis. However, surprisingly little is known about the stability of genotype,genotype interactions under variable environmental conditions. Here, using a naturally occurring plant,pathogen interaction, I tested whether the two distinct aspects of the infection process , infectivity and transmission potential , vary over realistic nutrient and temperature gradients. I show that the initial pathogen infectivity and host resistance responses are robust over the environmental gradients. However, for compatible responses there were striking differences in how different pathogen life-history stages and host and pathogen genotypes responded to environmental variation. For some pathogen genotypes even slight changes in temperature arrested spore production, rendering the developing infection ineffectual. The response of pathogen genotypes to environmental gradients varied in magnitude and even direction, so that their rankings changed across the abiotic gradients. Hence, the variable environment of spatially structured host,parasite interactions may strongly influence the maintenance of polymorphism in pathogen life-history stages governing transmission, whereas evolutionary trajectories of infectivity may be unaffected by the surrounding environment. [source] Food consumption impacts of adherence to dietary norms in the United States: a quantitative assessmentAGRICULTURAL ECONOMICS, Issue 2-3 2007C. S. Srinivasan Dietary norms; Dietary adjustment; Food consumption impacts; Quadratic programming Abstract Promotion of adherence to healthy-eating norms has become an important element of nutrition policy in the United States and other developed countries. We assess the potential consumption impacts of adherence to a set of recommended dietary norms in the United States using a mathematical programming approach. We find that adherence to recommended dietary norms would involve significant changes in diets, with large reductions in the consumption of fats and oils along with large increases in the consumption of fruits, vegetables, and cereals. Compliance with norms recommended by the World Health Organization for energy derived from sugar would involve sharp reductions in sugar intakes. We also analyze how dietary adjustments required vary across demographic groups. Most socio-demographic characteristics appear to have relatively little influence on the pattern of adjustment required to comply with norms. Income levels have little effect on required dietary adjustments. Education is the only characteristic to have a significant influence on the magnitude of adjustments required. The least educated rather than the poorest have to bear the highest burden of adjustment. Our analysis suggests that fiscal measures like nutrient-based taxes may not be as regressive as commonly believed. Dissemination of healthy-eating norms to the less educated will be a key challenge for nutrition policy. [source] Buying peace or fuelling war: the role of corruption in armed conflictsJOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 4 2003Philippe Le Billon Although corruption may have a corrosive effect on economies and rule-based institutions, it also forms part of the fabric of social and political relationships. This endogenous character means that conflict may be engendered more by changes in the pattern of corruption than by the existence of corruption itself. Such changes, frequently associated with domestic or external shocks, can lead to armed conflict as increasingly violent forms of competitive corruption between factions ,fuel war' by rewarding belligerents. Controversially, ,buying-off' belligerents can facilitate a transition to peace; but ,sticks' such as economic sanctions, rather than ,carrots', have dominated international conflict resolution instruments. While ,buying peace' can present a short-term solution, the key challenge for peace-building initiatives and fiscal reforms is to shift individual incentives and rewards away from the competition for immediate corrupt gains. This may be facilitated by placing public revenues under international supervision during peace processes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Refining the P,T records of UHT crustal metamorphismJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2008S. L. HARLEY Abstract Ultra-high-temperature (UHT) metamorphism occurs when the continental crust is subjected to temperatures of greater than 900 °C at depths of 20,40 km. UHT metamorphism provides evidence that major tectonic processes may operate under thermal conditions more extreme than those generally produced in numerical models of orogenesis. Evidence for UHT metamorphism is recorded in mineral assemblages formed in magnesian pelites, supported by high-temperature indicators including mesoperthitic feldspar, aluminous orthopyroxene and high Zr contents in rutile. Recent theoretical, experimental and thermodynamic data set constraints on metamorphic phase equilibria in FMAS, KFMASH and more complex chemical systems have greatly improved quantification of the P,T conditions and paths of UHT metamorphic belts. However, despite these advances key issues that remain to be addressed include improving experimental constraints on the thermodynamic properties of sapphirine, quantifying the effects of oxidation state on sapphirine, orthopyroxene and spinel stabilities and quantifying the effects of H2O,CO2 in cordierite on phase equilibria and reaction texture analysis. These areas of uncertainty mean that UHT mineral assemblages must still be examined using theoretical and semi-quantitative approaches, such as P(,T),, sections, and conventional thermobarometry in concert with calculated phase equilibrium methods. In the cases of UHT terranes that preserve microtextural and mineral assemblage evidence for steep or ,near-isothermal' decompression P,T paths, the presence of H2O and CO2 in cordierite is critical to estimates of the P,T path slopes, the pressures at which reaction textures have formed and the impact of fluid infiltration. Many UHT terranes have evolved from peak P,T conditions of 8,11 kbar and 900,1030 °C to lower pressure conditions of 8 to 6 kbar whilst still at temperature in the range of 950 to 800 °C. These decompressional P,T paths, with characteristic dP/dT gradients of ,25 ± 10 bar °C,1, are similar in broad shape to those generated in deep-crustal channel flow models for the later stages of orogenic collapse, but lie at significantly higher temperatures for any specified pressure. This thermal gap presents a key challenge in the tectonic modelling of UHT metamorphism, with implications for the evolution of the crust, sub-crustal lithosphere and asthenospheric mantle during the development of hot orogens. [source] Visualizing feature evolution of large-scale software based on problem and modification report dataJOURNAL OF SOFTWARE MAINTENANCE AND EVOLUTION: RESEARCH AND PRACTICE, Issue 6 2004Michael Fischer Abstract Gaining higher-level evolutionary information about large software systems is a key challenge in dealing with increasing complexity and architectural deterioration. Modification reports and problem reports (PRs) taken from systems such as the concurrent versions system (CVS) and Bugzilla contain an overwhelming amount of information about the reasons and effects of particular changes. Such reports can be analyzed to provide a clearer picture about the problems concerning a particular feature or a set of features. Hidden dependencies of structurally unrelated but over time logically coupled files exhibit a good potential to illustrate feature evolution and possible architectural deterioration. In this paper, we describe the visualization of feature evolution by taking advantage of this logical coupling introduced by changes required to fix a reported problem. We compute the proximity of PRs by applying a standard technique called multidimensional scaling (MDS). The visualization of these data enables us to depict feature evolution by projecting PR dependence onto (a) feature-connected files and (b) the project directory structure of the software system. These two different views show how PRs, features and the directory tree structure relate. As a result, our approach uncovers hidden dependencies between features and presents them in an easy-to-assess visual form. A visualization of interwoven features can indicate locations of design erosion in the architectural evolution of a software system. As a case study, we used Mozilla and its CVS and Bugzilla data to show the applicability and effectiveness of our approach. Copyright © 2004 John Wiley & Sons, Ltd. [source] Eye tracking and online search: Lessons learned and challenges aheadJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 7 2008Lori Lorigo This article surveys the use of eye tracking in investigations of online search. Three eye tracking experiments that we undertook are discussed and compared to additional work in this area, revealing recurring behaviors and trends. The first two studies are described in greater detail in Granka, Joachims, & Gay (2004), Lorigo et al. (2006), and Pan et al. (2007), and the third study is described for the first time in this article. These studies reveal how users view the ranked results on a search engine results page (SERP), the relationship between the search result abstracts viewed and those clicked on, and whether gender, search task, or search engine influence these behaviors. In addition, we discuss a key challenge that arose in all three studies that applies to the use of eye tracking in studying online behaviors which is due to the limited support for analyzing scanpaths, or sequences of eye fixations. To meet this challenge, we present a preliminary approach that involves a graphical visualization to compare a path with a group of paths. We conclude by summarizing our findings and discussing future work in further understanding online search behavior with the help of eye tracking. [source] A review of penetrometers for subsurface access on comets and asteroidsMETEORITICS & PLANETARY SCIENCE, Issue 6 2008David L. GLASER Because they offer desirable scientific capabilities and relative mechanical simplicity, penetrators and penetrometers, which use only axial force to push beneath the surface, are a good choice for near-term missions. Penetrometers are instruments, generally deployed from a larger vehicle, that measure subsurface mechanical properties and may also contain additional scientific instruments. There are three basic types: "fast" penetrometers are released from above and plunge into the surface. Static and dynamic (collectively referred to as "slow") penetrometers use, respectively, a constant slow penetration speed and periodic hammering impulses. The low gravity environment of asteroids and comets presents a key challenge to instrument deployment and also greatly affects the mechanical properties of surface materials, and in turn penetrometer performance. The Rosetta mission, currently en route to comet 67P/Churyumov-Gerasimenko, will be the next mission to try both fast and slow, dynamic penetrometry, when it arrives in 2014. We present some new concepts of static penetrometers for small body exploration that are adapted to the low gravity environment. The low gravity environment also presents challenges for the testing of penetrometers on Earth and a number of previous solutions are described and new methods suggested. In the next generation of missions to study comets and asteroids, penetrometers could provide important data on their mechanical, seismic, thermal, electromagnetic, and chemical characteristics, as well as sample collection. [source] Democratic Deepening in Third Wave Democracies: Experiments with Participation in Mexico CityPOLITICAL STUDIES, Issue 1 2007Imke Harbers After the initial transition to democratic rule the question of how to improve the quality of democracy has become the key challenge facing Third Wave democracies. In the debate about the promotion of more responsive government, institutional reforms to increase direct participation of citizens in policy-making have been put on the agenda. The Federal District of Mexico City constitutes a particularly intriguing case in this debate. This article explores how political participation developed in Mexico City between 1997 and 2003 and what effects this has had on democratic deepening. It develops an ideal-type conceptual framework of citizen participation that outlines the conditions under which participation contributes to democratic deepening. Overall, the case of Mexico City highlights how the promotion of participation can fail to make the aspired contribution to democratic deepening and might even have negative effects on the quality of democracy. [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Mixed matrix materials comprising molecular sieve entities embedded in a polymer matrix can economically increase membrane permselectivity, thereby addressing a key challenge hindering the widespread use of membrane-based gas separations. Prior work has clarified the importance of proper selection of the dispersed sieve phase and the continuous matrix phase based on their intrinsic transport properties. Proper material selection for the two components, while necessary, is not sufficient since the interfacial contact zone appears to be equally important to achieve optimum transport properties. Specifically, it was found that chemical coupling of the sieve to the polymer can lead to better macroscopic adhesion but to even poorer transport properties than in the absence of the adhesion promoter. This counterintuitive behavior may be attributed to a nanometric region of disturbed packing at the polymer sieve interphase. The poor properties are believed to result from "leakage" of gas molecules along this nanometric interface. The Maxwell model was modified to take into account these complexities and to provide a first order quantification of the nanometric interphase. The analysis indicates that optimization of the transport properties of the interfacial region is key to the formation of ideal mixed matrix materials. This approach is used in the second part of this paper to form successful mixed matrix membrane materials. [source] From carbon nanotube coatings to high-performance polymer nanocompositesPOLYMER INTERNATIONAL, Issue 4 2008Stéphane Bredeau Abstract Since their discovery at the beginning of the 1990s, carbon nanotubes (CNTs) have been the focus of considerable research by both academia and industry due to their remarkable and unique electronic and mechanical properties. Among numerous potential applications of CNTs, their use as reinforcing materials for polymers has recently received considerable attention since their exceptional mechanical properties, combined with their low density, offer tremendous opportunities for the development of fundamentally new material systems. However, the key challenge remains to reach a high level of nanoparticle dissociation (i.e. to break down the cohesion of aggregated CNTs) as well as a fine dispersion upon melt blending within the selected matrices. Therefore, this contribution aims at reviewing the exceptional efficiency of CNT coating by a thin layer of polymer as obtained by an in situ polymerization process catalysed directly from the nanofiller surface, known as the ,polymerization-filling technique'. This process allows for complete destructuring of the native filler aggregates. Interestingly enough, such surface-coated carbon nanotubes can be added as ,masterbatch' in commercial polymeric matrices leading to the production of polymer nanocomposites displaying much better thermomechanical, flame retardant and electrical conductive properties even at very low filler loading. Copyright © 2007 Society of Chemical Industry [source] Challenges for donor agency country-level performance assessment: a review,PUBLIC ADMINISTRATION & DEVELOPMENT, Issue 5 2003Mark Ireland This review of country-level performance assessment in donor agencies is primarily based upon the experiences documented by bilateral donors to developing countries. The review suggests that four emerging themes can be identified in the literature on country-level performance review: ownership, decentralisation and leadership, accountability and learning and complexity. The review considers the implementation of ,results-based' approaches used by a number of international agencies and examines their relationship with ,evidence-based' approaches. A key challenge, in the development of performance assessment, is bringing in a stronger evidence-based approach into the planning and evaluation of donor country-level programmes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Forest Restoration in Urbanizing Landscapes: Interactions Between Land Uses and Exotic ShrubsRESTORATION ECOLOGY, Issue 2 2005Kathi L. Borgmann Abstract Preventing and controlling exotic plants remains a key challenge in any ecological restoration, and most efforts are currently aimed at local scales. We combined local- and landscape-scale approaches to identify factors that were most closely associated with invasion of riparian forests by exotic shrubs (Amur honeysuckle [Lonicera maackii] and Tatarian honeysuckle [L. tatarica]) in Ohio, U.S.A. Twenty sites were selected in mature riparian forests along a rural,urban gradient (<1,47% urban land cover). Within each site, we measured percent cover of Lonicera spp. and native trees and shrubs, percent canopy cover, and facing edge aspect. We then developed 10 a priori models based on local- and landscape-level variables that we hypothesized would influence percent cover of Lonicera spp. within 25 m of the forest edge. To determine which of these models best fit the data, we used an information-theoretic approach and Akaike's information criterion. Percent cover of Lonicera was best explained by the proportion of urban land cover within 1 km of riparian forests. In particular, percent cover of Lonicera was greater in forests within more urban landscapes than in forests within rural landscapes. Results suggest that surrounding land uses influence invasion by exotic shrubs, and explicit consideration of land uses may improve our ability to predict or limit invasion. Moreover, identifying land uses that increase the risk of invasion may inform restoration efforts. [source] Relevance of genetically modified crops in light of future environmental and legislative challenges to the agri-environmentANNALS OF APPLIED BIOLOGY, Issue 3 2009M. O'Brien Abstract A key challenge for countries like Ireland up to 2030 is to produce sufficient supplies of food, feed and fuel, without compromising on public health or negatively impacting the environment. As we progress through the technology era, certain agricultural technologies [e.g. genetically modified (GM) crops] have been championed to maximise production while minimising environmental impact. Yet, multiple arguments have been made to counter such a claim, which has led to a polarisation of opinions and a plethora of generic commentaries being made in regard to the impact of this technology. Yet, few studies within the European Union (EU) have conducted a critical needs analysis to assess the potential of specific GM traits in light of issues, such as climate change, increased environmental legislation (e.g. EU Water Framework, Nitrates Directive, proposed reform to the Pesticide Directive and Common Agricultural Policy reform), mitigating biodiversity loss and sustainable biofuel production. The goal of this study is to collate a register of GM traits such that a list of potential GM crops could be prioritised against the backdrop of the challenges facing the tillage sector. Clearly, the crops with the most significant potential for genetic modification are those that are grown widely and/or receive high applications of pesticides and fertilisers (e.g. potato, wheat, barley and maize). GM traits with significant agronomic potential include late blight resistant potato, Fusarium head blight resistant wheat and Septoria resistant wheat and herbicide-tolerant winter oilseed rape and maize. Following on from these, crops with enhanced nitrogen-use efficiency could provide significant input to the tillage sector in light of EU-based restrictions on nitrogen usage, crops with elevated protein content could offset the costs of imported animal feed and crops with modified oil content/lignocellulose composition could assist in biodiesel/bioenergy production at a regional level. This study is relevant to other European countries that cultivate similar crops and like Ireland, are facing multiple challenges to their tillage sector in the near future. [source] Independent living units: Managing and renewing an ageing stockAUSTRALASIAN JOURNAL ON AGEING, Issue 3 2007Sean McNelis Objectives:,To report on a key challenge (and its implications) that Australian not-for-profit organisations face as they manage and renew an ageing stock of independent living units (ILUs) for older people. Methods:,A national survey of ILU organisations complemented by 28 interviews with ILU managers, peak aged care organisations and government officers, and five workshops with ILU managers. Results:,ILUs are a policy response to the housing needs of older people with low income and limited assets. However, ILU organisations face significant challenges as the overall condition of ILUs deteriorates, as they seek to meet higher expectations and as they move into a phase of renewal. Conclusions:,The future of ILU organisations is at a watershed, with many reconsidering their role as providers of ILUs. Any extensive reduction in ILUs will have implications for older people, for public housing providers and for delivery of community care to older renters. [source] Approaches towards the Efficient Use of Resources in the IndustryCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2010M. Schmidt Abstract Resource efficiency in companies targets economic and efficient use of materials and energy in production. On the one hand, this aims to contribute towards sustainable development and, on the other hand, efficient use of resources can save costs and improve the competitiveness of a company. This aspect is becoming all the more important in the light of current developments in world market prices for natural resources. In Germany, the use of materials and energy currently accounts for about 46,% of the gross value of goods manufactured by companies. It is known from various sources that the average potential for savings here is 10,15,%. The material costs alone can be reduced by 2,3,% through efficient management. The potentials for saving lie less in the individual technologies applied and more in the interplay within and between the complex production systems. That is why one key challenge facing the industry is to ascertain the hidden costs that are in fact linked with inefficiencies in a company. Analysis methods and approaches are necessary for this, such as for example the material and energy flow analysis. [source] Roads, Development, and Conservation in the Congo BasinCONSERVATION BIOLOGY, Issue 6 2000David Wilkie Research in the Republic of Congo shows that roads established and maintained by logging concessions intensify bushmeat hunting by providing hunters greater access to relatively unexploited populations of forest wildlife and by lowering hunters' costs to transport bushmeat to market. Reconciling the contrary effects of roads on economic development and biodiversity conservation is one of the key challenges to wildlife managers in all nations. As the Democratic Republic of Congo prepares to reconstruct its almost completely collapsed road system, the government, donors, and conservation organizations have a unique opportunity to strategically prioritize investment in segments of the network that would maximize local and national economic benefits while minimizing adverse effects on forest wildlife. Resumen: La densidad de carreteras está estrechamente ligada al acceso a mercados, el crecimiento económico, la explotación de recursos naturales, la fragmentación del hábitat, la deforestación y la desaparición de tierras y vida silvestre. Investigación en la República del Congo muestra que las carreteras establecidas y mantenidas por las concesiones para tala de árboles intensifican la cacería al proveer a los cazadores un mayor acceso a poblaciones forestales de vida silvestre relativamente sin explotar y al disminuir el costo de transporte de la carne obtenida por la caza hacia el mercado. La reconciliación de los efectos contrarios de las carreteras en el desarrollo económico y la conservación de la biodiversidad es uno de los retos clave para los manejadores de vida silvestre en todas las naciones. A medida que la República Democrática del Congo se prepara para reconstruir su casi completamente colapsado sistema carretero, el gobierno, los donadores y las organizaciones no gubernamentales conservacionistas tienen una oportunidad única para priorizar estratégicamente las inversiones en segmentos de la red carretera que podrían maximizar los beneficios económicos locales y nacionales al mismo tiempo que se minimicen los impactos adversos sobre la vida silvestre forestal. [source] Industry responses to EU WEEE and ROHS Directives: perspectives from ChinaCORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 5 2006Jieqiong Yu Abstract The electrical and electronics (EE) industry has come under increasing pressure to adopt extended producer responsibility (EPR) policies through the introduction of the European Union's Directives on Waste Electrical and Electronic Equipment (WEEE) and the Restriction of Use of Certain Hazardous Substances (ROHS). Based on the findings of 50 questionnaires and in-depth interviews with China's EE manufacturers, this paper investigates the perception of and readiness of companies for implementation of WEEE and ROHS in China. It identifies key difficulties encountered by manufacturers in fulfilling the requirements and evaluates the effectiveness of these two directives in promoting environmental reform. The findings indicate that the extent of companies' responses largely depends on their market structure and client requirements. Supply chain management, raw material testing and cost implications appear to be key challenges in addressing issues surrounding the directives. There is little evidence to suggest that these directives have effectively driven China's EE manufacturers towards systematic eco-design. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment. [source] Characterization and uncertainty analysis of VOCs emissions from industrial wastewater treatment plantsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2010Kaishan Zhang Abstract Air toxics from the industrial wastewater treatment plants (IWTPs) impose serious health concerns on its surrounding residential neighborhoods. To address such health concerns, one of the key challenges is to quantify the air emissions from the IWTPs. The objective here is to characterize the air emissions from the IWTPs and quantify its associated uncertainty. An IWTP receiving the wastewaters from an airplane maintenance facility is used for illustration with focus on the quantification of air emissions for benzyl alcohol, phenol, methylene chloride, 2-butanone, and acetone. Two general fate models, i.e., WATER9 and TOXCHEM+V3.0 were used to model the IWTP and quantify the air emissions. Monte Carlo and Bootstrap simulation were used for uncertainty analysis. On average, air emissions from the IWTP were estimated to range from 0.003 lb/d to approximately 16 lb/d with phenol being the highest and benzyl alcohol being the least. However, emissions are associated with large uncertainty. The ratio of the 97.5th percentile to the 2.5th percentile air emissions ranged from 5 to 50 depending on pollutants. This indicates point estimates of air emissions might fail to capture the worst scenarios, leading to inaccurate conclusion when used for health risk assessment. © 2009 American Institute of Chemical Engineers Environ Prog, 2010 [source] The "Ductilities" in Single Phase Steels from Usual to Nanoscale MicrostructuresADVANCED ENGINEERING MATERIALS, Issue 10 2009Olivier Bouaziz Abstract The control and the improvement of the ductility of nanostructured structural steels is one of the key challenges in assessing the technological viability of this metallurgical strategy. In the present paper, it is shown that more rigorous definitions of the ductility are required in order to avoid possible confusions. After this preliminary work, a more transparent analysis is done concerning the effect of the microstructural scale showing clearly the weaknesses and the strengths of ultra-fine single phase steels. Finally, possible ways to overcome the main limitations are presented. [source] | |||||||||||||||||||||||||||||||||||||||||||