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Recent Decades (recent + decade)
Selected AbstractsGARDENS AND DWELLING: PEOPLE IN VERNACULAR GARDENS,GEOGRAPHICAL REVIEW, Issue 3 2004CLARISSA T. KIMBER ABSTRACT. Investigations of dooryard gardens, kitchen gardens, home gardens, and houselot gardens fall unequally into one of three groupings. The first are those that treat the plants in the gardens as biological entities and define a space considered a culturally controlled biological community or habitat. The second are those that consider plants cultural traits and the space defined by their positions a setting for household activities. The third conceives of plants as design elements within a garden or a landscape that frames a house or provides a setting for formal human performances. Recent decades have witnessed a broadening focus in the study of gardens, from spatial characteristics and biological content to social and cultural concerns such as reciprocity networks, contested spaces, and the concept of "dwelling." [source] Polymorphic microsatellite markers for paternity assessment in southern calamari Sepioteuthis australis (Cephalopoda: Loliginidae)MOLECULAR ECOLOGY RESOURCES, Issue 4 2003L. M. Van Camp Abstract Recent decades have seen the fast growth of cephalopod fisheries but their management is compromised by the critical gaps in our knowledge of cephalopod life histories. Molecular markers are invaluable tools for studying the evolutionary significance and management implications of variation in mating systems. We have developed seven polymorphic microsatellite loci for mating system analysis in the southern calamari Sepioteuthis australis Quoy & Gaimard 1833 using magnetic enrichment and colony hybridization techniques. Observed heterozygosities range from 32% to 100% and will have sufficient power to examine the relative success of alternate mating strategies in S. australis. [source] Biological and Cultural Anthropology of a Changing Tropical Forest: A Fruitful Collaboration across SubfieldsAMERICAN ANTHROPOLOGIST, Issue 2 2006REBECCA HARDIN In this article, we integrate approaches from biological and cultural anthropology to describe changing relationships between humans and animals in the Dzanga-Ndoki Park and Dzanga-Sangha Dense Forest Reserve (RDS), Central African Republic (CAR). Recent decades have seen a rapid proliferation of human activities, with striking tensions between logging and conservation economies. Our data suggest that certain animals and humans initially adapted successfully to these forest uses, and that local residents have crafted culturally rich new ways of living in the forest. However, our longitudinal data indicate animal declines and expanding frontiers of increasingly intensive human use. These trends are altering previous territorial arrangements and coming to undermine today's remarkably rich spectrum of human,animal encounters there. Our combined approach offers an alternative to increasingly distinct method and theory between anthropology's subfields. We sketch a research agenda for integrated anthropological attention to environmental change, especially to transformations in human,animal interactions and entanglements. [source] The globalisation of the nursing workforce: barriers confronting overseas qualified nurses in AustraliaNURSING INQUIRY, Issue 4 2001Lesleyanne HawthorneArticle first published online: 25 FEB 200 The globalisation of the nursing workforce: barriers confronting overseas qualified nurses in Australia Recent decades have coincided with the rapid globalisation of the nursing profession. Within Australia there has been rising dependence on overseas qualified nurses (OQNs) to compensate for chronic nurse shortages related to the continued exodus of Australian nurses overseas and to emerging opportunities in other professions. Between 1983/4 and 1994/5, 30 544 OQNs entered Australia on either a permanent or temporary basis, counter-balancing the departure overseas of 23 613 locally trained and 6519 migrant nurses (producing a net gain of just 412 nurses in all). The period 1995/6,1999/2000 saw an additional 11 757 permanent or long-term OQN arrivals, with nursing currently ranked third target profession in Australia's skill migration program, in the context of continuing attrition among local nurses. This pattern of reliance on OQNs is a phenomenon simultaneously occurring in the UK, the US, Canada and the Middle East , the globalisation of nursing reflecting not merely Western demand but the growing agency and participation of women in skilled migration, their desire for improved quality of life, enhanced professional opportunity and remuneration, family reunion and adventure. [source] Skin Care of the Diaper AreaPEDIATRIC DERMATOLOGY, Issue 4 2008Ralf Adam Ph.D. These needs include products such as diapers that absorb the excreta, as well as products for cleansing and conditioning the skin. A number of factors play a role in development of diaper dermatitis, including prolonged exposure to excreta, alterations in skin pH or increased hydration, and changes in skin microbial flora. Recent decades have seen great improvements in our understanding of these factors and our ability to develop new and better products to protect baby skin. Better diaper designs and the development of pH-buffered baby wipes have improved the care of skin in the diaper area. Continuing research offers the promise of new products with additional benefits for caregivers and infants. [source] Steps toward the ripening of relationship sciencePERSONAL RELATIONSHIPS, Issue 1 2007HARRY T. REIS Recent decades have seen remarkable growth in research and theorizing about relationships. E. Berscheid (1999) invigorated this growth by proclaiming "The Greening of Relationship Science," the emergence of a multidisciplinary science of interpersonal relationships with enormous potential to advance knowledge about human behavior and to provide an empirically informed framework for improving the human condition. Here I discuss several steps necessary to move the field from a green science toward a more mature, ripened one, including the need to be action oriented but in a theory-building way, to become more cumulative and collective, and to develop an integrated network of theories, constructs, and their observable manifestations. Perceived partner responsiveness is one possible central organizing theme for the diverse phenomena relationship scientists study. [source] What's in a Sector?PUBLIC ADMINISTRATION REVIEW, Issue 6 2003The Shifting Career Plans of Public Policy Students Recent decades have seen a trend in which public policy graduates shun government and enter private-sector employment. In part, the shift reflects changing sectoral opportunities, but its magnitude and consistency are puzzling,even troubling,in light of the need for public-sector talent. Data from a two-year series of surveys and interviews with policy students reveal that many begin their training with uncertain career goals and ambivalence about public-sector work. Interest in government declines from entry to graduation, and it appears that the policy curriculum,heavy on analytic methods and conveying cautions about policy making,does little to promote a public-sector orientation. Those planning to enter government are strongly motivated by a desire to have an impact, whereas those drawn to the private sector seek financial resources and professional development. Many anticipate fluid careers and choose positions expected to offer growth, a feature more commonly associated with private than public jobs. [source] Silence in the Context of ,Child Voice'CHILDREN & SOCIETY, Issue 1 2010Ann Lewis Recent decades have seen growing enthusiasm internationally for the concept and practice of ,child voice'. This was encapsulated in, and stimulated, by Article 12 of the 1989 United Nations Convention on the Rights of the Child. This article presents the case for incorporating the equally important concept of ,child silence' in both research and applied contexts. ,Child voice' has become a powerful moral crusade and consequently criticism of voice has been muted. This is despite the growing articulation of reservations about ,child voice' in various research and applied contexts. Two particular sets of emerging concerns are discussed: one set is around the purposes behind such engagement with children; and one set relates to the ethical protocols involved. Finally, the article makes a series of recommendations for researchers working in the fields of ,child voice'. These concern five methodological aspects: recognising, noting, responding to, interpreting and reporting silence from children. It is concluded that it is timely to take a step back from assumed support for ,child voice' as necessarily ,a good thing'. Rather, we need to consider more reflexively how, why and when ,child voice' is realised in co-constructed research and professional contexts. [source] Experience, Purpose, and the Value of Vagueness: On C. S. Peirce's Contribution to the Philosophy of CommunicationCOMMUNICATION THEORY, Issue 3 2009Mats Bergman Recent decades have witnessed a growth of interest in the contribution of pragmatism to the study of communication. Yet, it is striking that C. S. Peirce, the founder of pragmatism and the father of one of the major strands of modern semiotics, is often ignored by communication scholars sympathetic to pragmatism. In this article, I explore some of the reasons for this neglect, and put forward the case for a recovery of some of the philosophical tools that Peircean pragmatism can provide for communication theory. [source] Molecular markers of phase transition in locustsINSECT SCIENCE, Issue 1 2006ARNOLD DE LOOF Abstract The changes accompanying the transition from the gregarious to the solitary phase state in locusts are so drastic that for a long time these phases were considered as distinct species. It was Boris Uvarov who introduced the concept of polyphenism. Decades of research revealed that phase transition implies changes in morphometry, the color of the cuticle, behavior and several aspects of physiology. In particular, in the recent decade, quite a number of molecular studies have been undertaken to uncover phase-related differences. They resulted in novel insights into the role of corazonin, neuroparsins, some protease inhibitors, phenylacetonitrile and so on. The advent of EST-databases of locusts (e.g. Kang et al., 2004) is a most encouraging novel development in physiological and behavioral locust research. Yet, the answer to the most intriguing question, namely whether or not there is a primordial molecular inducer of phase transition, is probably not within reach in the very near future. [source] Wet and dry summers in Europe since 1750: evidence of increasing droughtINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2009K. R. Briffa Abstract Moisture availability across Europe is calculated based on 22 stations that have long instrumental records for precipitation and temperature. The metric used is the self-calibrating Palmer Drought Severity Index (scPDSI) which is based on soil moisture content. This quantity is calculated using a simplified water budget model, forced by historic records of precipitation and temperature data, where the latter are used in a simple parameterization for potential evaporation. The precipitation and temperature records are updated to include the 2003 summer and all records, except for one, span at least 200 years, with the record for Kew going back to 1697. The Kew record shows a significant clustering of dry summers in the most recent decade. When all the records are considered together, recent widespread drying is clearly apparent and highly significant in this long-term context. By substituting the 1961,1990 climatological monthly mean temperatures for the actual monthly means in the parameterization for potential evaporation, an estimate is made of the direct effect of temperature on drought. This analysis shows that a major influence on the trend toward drier summer conditions is the observed increase in temperatures. This effect is particularly strong in central Europe. Based on the 22 scPDSI records, a gridded scPDSI dataset covering a large part of Europe has been constructed and compared to a recent high-resolution scPDSI dataset spanning the twentieth century only. We again observe that a major cause for the large areal extent of summer drought in the last two decades is high temperatures. Temperatures in the 12 months preceding and including the summer of 2003 explain an increase in the areas experiencing slightly dry (or worse) conditions of 11.1%. Copyright © 2009 Royal Meteorological Society [source] Prediction of irritancy in the human skin irritancy model and occupational settingCONTACT DERMATITIS, Issue 2 2003R. A. Tupker It is of great importance to find ways to lower the incidence of chronic irritant contact dermatitis. In this process, it is crucial to have insight in the factors that can predict irritancy. This review offers a survey of recent findings in the field of skin irritancy testing, discussed in the context of renowned, older work. Extrinsic and intrinsic factors that may determine the outcome of irritancy testing in the human skin model are considered. In recent decades, there has been increasing interest in factors influencing the development of occupational dermatitis by means of prospective cohort studies. This promising new area of investigation is discussed separately. [source] ECONOMIC DEPRIVATION AND CHANGES IN HOMICIDE ARREST RATES FOR WHITE AND BLACK YOUTHS, 1967,1998: A NATIONAL TIME-SERIES ANALYSIS,CRIMINOLOGY, Issue 3 2001STEVEN F. MESSNER Using time-series techniques with national data for 1967,98, we model the effects on changes in age-race-specific arrest rates of changes in indicators of economic deprivation. A measure of child poverty is positively related to juvenile arrest rates for both races, whereas changing unemployment (lagged) yields a surprising negative effect on youth offending. Measures of intraracial income inequality are also associated with changes in juvenile arrest rates, but the effects differ by race. Between-race inequality is unrelated to changes in arrest rates for both races. Our general conclusion is that fluctuations in juvenile homicide offending over recent decades can be understood, at least in part, with reference to the macro-economic environment confronting young people and their families. [source] Education and Social Change: The Case of Israel's State CurriculumCURRICULUM INQUIRY, Issue 4 2007AMOS HOFMAN ABSTRACT The aim of this article is to explore, through the case of the official Israeli state curriculum, how the educational system is affected by social changes and how it responds to them, and to suggest curricular directions that go along with the new social reality that has emerged in Israel during the past decade. We offer a conceptual-theoretical analysis based on the examination of 10 subject areas taught at Israeli schools by leading experts who investigated the curriculum documents of the Ministry of Education in their disciplines. We identify three stages of curriculum development in Israel since its establishment: promotion of hegemonic national goals, emphasis on academic structure of knowledge, and in recent decades, multiple conflicting goals. Changes in the Israeli state curricula indeed reflect a response to broader social changes, yet these changes are partial, irresolute, and scattered. There is a need for a transcultural approach, promoting a core curriculum common to all groups in Israel, beyond which each group may express its uniqueness. [source] BRASSICALES , AN ORDER OF PLANTS CHARACTERISED BY SHARED CHEMISTRYCURTIS'S BOTANICAL MAGAZINE, Issue 3 2010Michael F. Fay Among the many advances in our understanding of angiosperm relationships in recent decades due to the advent of DNA sequence data is the confirmation that all plants (apart from Drypetes) that produce mustard oil precursors are related to each other and should be treated as one order, Brassicales. Due to the lack of obvious shared morphological characters, this is one of the more unexpected of these advances. Here we give the background to this development and introduce the families in Brassicales, including Tropaeolaceae, the subject of this issue. [source] Multinational Corporations and Patterns of Local Knowledge Transfer in Costa Rican High-Tech IndustriesDEVELOPMENT AND CHANGE, Issue 3 2008Elisa Giuliani ABSTRACT Over recent decades, governments in industrializing countries have promoted policies to attract foreign investors, anticipating the benefits of technology transfer to host economies. During the 1990s, Costa Rica adopted an industrialization strategy based on attracting high-tech multinational companies (MNCs). Using an original survey of a sample of high-tech MNC subsidiaries, this article shows that the new wave of efficiency-seeking subsidiaries tend not to transfer knowledge to domestic firms even when they establish backward linkages with them. Instead, most of the knowledge transfer occurs between high-tech foreign subsidiaries. This has clear policy implications for host country governments. [source] Global factors shaping the future of food aid: the implications for WFPDISASTERS, Issue 2007Daniel Maxwell Food aid is a key component of a humanitarian response but its use in other programming contexts is subject to numerous criticisms. Even in humanitarian emergencies food aid is often late, unreliable and out of proportion to other elements of the response. Three major factors will shape the future of food aid. First, mechanisms of food aid governance are being reviewed and may undergo major changes,particularly the Food Aid Convention now that hopes have diminished for an Agreement on Agriculture at the World Trade Organisation. The second significant factor is donor agency trends. Overall levels of food aid have dropped fairly steadily in recent decades and there are several discernible trends in resource allocation, procurement and the use of food aid. The third factor is an emerging body of best practice that will define acceptable standards of food aid programming in the future. [source] A redescription of the Early Carboniferous acanthodian Acanthodes lopatini Rohon, 1889ACTA ZOOLOGICA, Issue 2009Pavel Beznosov Abstract Investigation of numerous well-preserved specimens of Early Carboniferous acanthodians collected over recent decades from southern central Siberia allowed their redescription as Acanthodes lopatini Rohon, 1889. The morphological characteristics supporting this classification, some peculiarities of ontogeny and a new reconstruction of this species are given. The genus Carycinacanthus Miles 1966 is regarded as a junior synonym of Acanthodes. Homalacanthus bergi (Obruchev 1962) is regarded as a junior synonym of A. lopatini. [source] How can we preserve and restore species richness of pollinating insects on agricultural land?ECOGRAPHY, Issue 6 2008Markus Franzén During recent decades, concern about the loss of biodiversity on agricultural land has increased, and semi-natural grasslands have been highlighted as critical habitats. Temperate European agricultural landscapes require distinct and appropriate management to prevent further impoverishment of the flora and fauna. This is especially urgent for pollinating insects that provide important ecosystem services. Our aim was to examine how species richness of three important groups of pollinating insects; solitary bees, butterflies and burnet moths are related to different farm characteristics, and if there are any differences between these three groups. A further aim was to test if red-listed species are related to any farm characteristics. Species richness of solitary bees, butterflies and burnets was measured on all semi-natural grasslands at 16 farms in a forest-dominated area of 50 km2 in southern Sweden, using systematic transect walks in April to September 2003 (only butterflies and burnets) and 2005. Species richness of solitary bees and butterflies was intercorrelated, both before and after controlling for the area of semi-natural grassland. Species richness of solitary bees increased with the area of semi-natural grassland. After controlling for the effect of the area of semi-natural grassland species richness was strongly positively related with the density of the plant Knautia arvensis and negatively related with the proportion of grazed grassland. The results were similar for solitary bees and butterflies. The number of red-listed solitary bees was positively related to the proportion of meadows with late harvest (after mid-July) and decreased with increased farm isolation. The number of burnet species (all red-listed) was positively related to vegetation height, flower density and the proportion of meadows with late harvest on a farm. Areas with a high density of K. arvensis and with traditional hay-meadow with late harvest present, harbour most species. Promoting traditional hay-meadows, late extensive grazing and the herb K. arvensis, people managing agricultural biodiversity can encompass high species richness of pollinating insects and support red-listed species. Further, we suggest that the density of K. arvensis at a farm can be used as a biodiversity indicator, at least for pollinating insects. [source] The myth of plant species saturationECOLOGY LETTERS, Issue 4 2008Thomas J. Stohlgren Abstract Plant species assemblages, communities or regional floras might be termed ,saturated' when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties highest in native species richness appear increasingly invaded over time. Despite the possibility of some increased awareness and reporting of native and exotic plant species in recent decades, historical records show a significant, consistent long-term increase in exotic species (number and frequency) at county, state and regional scales in the Pacific Northwest. Here, as in other regions of the country, colonization rates by exotic species are high and extirpation rates are negligible. The rates of species accumulation in space in multi-scale vegetation plots may provide some clues to the mechanisms of the invasion process from local to national scales. [source] Hybrid Branch Plants: Japanese Lean Production in Poland's Automobile IndustryECONOMIC GEOGRAPHY, Issue 3 2008Tomasz Majek Abstract This article examines hybrid branch plants created by an interaction of the routines and conventions of the parent company with those of local institutions. We argue that hybridization is a search for an appropriate mix of practices that ensure viability in local circumstances, rather than necessarily the transfer of established "best" (parent-company) practices. Conceptually, hybridization is interpreted as learning-based (and bargaining) processes that are inherent in the evolution (internationalization) of firms in which alternative trajectories are possible. Empirically, the article examines the recent transfer of lean production to Poland's automobile industry and comparatively and qualitatively analyzes four hybrid branch plants in terms of six dimensions of shop-floor and factory management. Given the explosion of Japanese foreign direct investment in recent decades, its competitive strengths, and the importance that Japanese firms attach to learning processes, lean production is an important case study for hybridization. The four cases illustrate different types of hybrid behavior with different consequences for corporate and local performance. [source] The Changing Structure of the UK Economy: Implications for the Current AccountECONOMIC OUTLOOK, Issue 2 2005Article first published online: 4 MAY 200 In common with other developed countries, the UK has seen the relative importance of the service sector grow, accounting for an ever greater share of employment and output , a trend that has accelerated over recent decades. At the same time, globalisation means that international trade is of increasing importance as a share of UK expenditure. With the traded goods sector dwindling in importance, what are the implications for the current account? This paper examines the changing structure of the UK economy and prospects for the current account. Although the current account is expected to remain in deficit for the foreseeable future, the size of the deficit is likely to remain manageable as growing surpluses from trade in services and investment income offset a widening goods deficit. [source] Eyes Wide Shut: Recent Educational Policy in the Light of Changing Notions of English Identity,ENGLISH IN EDUCATION, Issue 3 2000Chris Kearney Abstract Although Curriculum 2000 includes some welcome changes, such as the inclusion of drama, it is essentially a missed opportunity. I argue that it fails to address the complexity of modern life. In many academic areas, including literature, issues of identity are central to fundamental debates. Such debates have been precipitated by increasing economic globalisation and the consequent increase in interdependence between people from diverse cultural heritages. Although this situation is not new, the social and technological changes of recent decades have altered the pace of such developments. In most cities school populations reflect such changes. In this paper I argue that there are substantial gaps in the curriculum which derive mainly from government policy being premised on crude and obsolete notions of English identity. Such notions lead to a confusion of the concepts of culture and citizenship as modes of belonging. In my view both of these factors severely constrain our ability to construct a critical curriculum which adequately addresses contemporary interests and dilemmas. [source] PERSPECTIVE: Linking concepts in the ecology and evolution of invasive plants: network analysis shows what has been most studied and identifies knowledge gapsEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2010Sonia Vanderhoeven Abstract In recent decades, a growing number of studies have addressed connections between ecological and evolutionary concepts in biologic invasions. These connections may be crucial for understanding the processes underlying invaders' success. However, the extent to which scientists have worked on the integration of the ecology and evolution of invasive plants is poorly documented, as few attempts have been made to evaluate these efforts in invasion biology research. Such analysis can facilitate recognize well-documented relationships and identify gaps in our knowledge. In this study, we used a network-based method for visualizing the connections between major aspects of ecology and evolution in the primary research literature. Using the family Poaceae as an example, we show that ecological concepts were more studied and better interconnected than were evolutionary concepts. Several possible connections were not documented at all, representing knowledge gaps between ecology and evolution of invaders. Among knowledge gaps, the concepts of plasticity, gene flow, epigenetics and human influence were particularly under-connected. We discuss five possible research avenues to better understand the relationships between ecology and evolution in the success of Poaceae, and of alien plants in general. [source] Regulation of natural genetic transformation and acquisition of transforming DNA in Streptococcus pneumoniaeFEMS MICROBIOLOGY REVIEWS, Issue 3 2009Ola Johnsborg Abstract The ability of pneumococci to take up naked DNA from the environment and permanently incorporate the DNA into their genome by recombination has been exploited as a valuable research tool for 80 years. From being viewed as a marginal phenomenon, it has become increasingly clear that horizontal gene transfer by natural transformation is a powerful mechanism for generating genetic diversity, and that it has the potential to cause severe problems for future treatment of pneumococcal disease. This process constitutes a highly efficient mechanism for spreading ,-lactam resistance determinants between streptococcal strains and species, and also threatens to undermine the effect of pneumococcal vaccines. Fortunately, great progress has been made during recent decades to elucidate the mechanism behind natural transformation at a molecular level. Increased insight into these matters will be important for future development of therapeutic strategies and countermeasures aimed at reducing the spread of hazardous traits. In this review, we focus on recent developments in our understanding of competence regulation, DNA acquisition and the role of natural transformation in the dissemination of virulence and ,-lactam resistance determinants. [source] Accounting, Modernity and Health Care PolicyFINANCIAL ACCOUNTABILITY & MANAGEMENT, Issue 4 2001Irvine Lapsley The National Health Service of the United Kingdom has been the subject of many reforms since it was established in 1948. This paper examines the process of reform in relation to significant changes to the NHS in recent decades. This reform process places ideas of the modern at the heart of these various initiatives. This paper also examines the intended or actual role of accounting in this modernisation process to examine its significance in the making of health care policy. [source] Changes in spawning stock structure strengthen the link between climate and recruitment in a heavily fished cod (Gadus morhua) stockFISHERIES OCEANOGRAPHY, Issue 3 2006GEIR OTTERSEN Abstract Atlantic cod (Gadus morhua) is one of the commercially most important fish species in the North Atlantic and plays a central role in several ecosystems. Fishing pressure has been heavy over a prolonged period and the recent decades have shown dramatic decline in abundance of many stocks. The Arcto-Norwegian (or North-east Arctic) cod stock in the Barents Sea is now the largest stock of Atlantic cod. Recruitment to this stock has varied extensively during the last 60 yr. There is evidence for fluctuations in climate, particularly sea temperature, being a main cause for this variability, higher temperatures being favourable for survival throughout the critical early life stages. Our studies of time series present compelling evidence for a strengthening of the climate,cod recruitment link during the last decades. We suggest this is an effect of the age and length composition of the spawning stock having changed distinctly. The age of the average spawner has decreased by more than 3 yr from between 10 and 11 in the late 1940s to 7,8 in the 1990s, average length from just above 90 cm to around 80 cm. The number of age classes contributing to the spawning stock has also decreased, while the number of length groups present increased slightly. Significant decrease in age of spawners has frequently been described for other heavily fished stocks worldwide. We therefore find it likely that the proposed mechanism of increased influence of climate on recruitment through changes in the spawning stock age and size composition is of a general nature and might be found in other systems. [source] High-Performance Alkaline Polymer Electrolyte for Fuel Cell ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Jing Pan Abstract Although the proton exchange membrane fuel cell (PEMFC) has made great progress in recent decades, its commercialization has been hindered by a number of factors, among which is the total dependence on Pt-based catalysts. Alkaline polymer electrolyte fuel cells (APEFCs) have been increasingly recognized as a solution to overcome the dependence on noble metal catalysts. In principle, APEFCs combine the advantages of and alkaline fuel cell (AFC) and a PEMFC: there is no need for noble metal catalysts and they are free of carbonate precipitates that would break the waterproofing in the AFC cathode. However, the performance of most alkaline polyelectrolytes can still not fulfill the requirement of fuel cell operations. In the present work, detailed information about the synthesis and physicochemical properties of the quaternary ammonia polysulfone (QAPS), a high-performance alkaline polymer electrolyte that has been successfully applied in the authors' previous work to demonstrate an APEFC completely free from noble metal catalysts (S. Lu, J. Pan, A. Huang, L. Zhuang, J. Lu, Proc. Natl. Acad. Sci. USA2008, 105, 20611), is reported. Monitored by NMR analysis, the synthetic process of QAPS is seen to be simple and efficient. The chemical and thermal stability, as well as the mechanical strength of the synthetic QAPS membrane, are outstanding in comparison to commercial anion-exchange membranes. The ionic conductivity of QAPS at room temperature is measured to be on the order of 10,2,S cm,1. Such good mechanical and conducting performances can be attributed to the superior microstructure of the polyelectrolyte, which features interconnected ionic channels in tens of nanometers diameter, as revealed by HRTEM observations. The electrochemical behavior at the Pt/QAPS interface reveals the strong alkaline nature of this polyelectrolyte, and the preliminary fuel cell test verifies the feasibility of QAPS for fuel cell applications. [source] APPLIED ISSUES: Size-dependent mortality of migratory silver eels at a hydropower plant, and implications for escapement to the seaFRESHWATER BIOLOGY, Issue 10 2010O. CALLES Summary 1.,The European eel population has decreased drastically during recent decades, and new EU-legislation calls for measures to change this negative trend. This decline has been attributed to a number of factors, including habitat fragmentation by structural barriers that prevent eels moving between freshwater and the sea. The success of downstream migrating adult silver eels migrating past a hydroelectric plant (HEP) in Sweden was examined by radio-telemetry, and the results were considered in a historical context by analysing catch data from the river for 1957,2006. 2.,The choice of routes and passage success were quantified for three treatment groups and one control group of silver eels. The first treatment, the reservoir group (n = 50), was released into the reservoir upstream of the HEP, and these fish could proceed downstream by passing through the HEP (20 mm rack and turbines) or by entering the spill gates into the former channel, bypassing the HEP. The second treatment group (inside rack, n = 15) was released downstream of the 20-mm rack and had to pass through the turbines to continue migration to the sea. The third treatment group consisted of dead radio-tagged eels (n = 6) that were released into the turbines to study the extent of drifting by dead individuals. Finally, the control group (n = 50) was released downstream of the HEP to test for effects of confounding factors. 3.,Most live individuals displayed migratory behaviour and continued to proceed downstream after release. Only 8% of the fish released in the reservoir or downstream of the HEP (control) did not migrate. The probability of reaching the next HEP, 24 km further downstream, was high for the control group (96%) and the reservoir-released individuals that passed the HEP via the spill gates and the former channel (83%). Survival was low and size-dependent for the individuals that passed the turbines (40%) and even lower for the individuals that had to pass through the rack and the turbines (26%). The overall passage success for eels released in the reservoir was 30%, including both routes. 4.,Annual catch data from 1957 to 2006 showed that the number of eels in the River Ätran has decreased. Despite this decrease, escapement biomass has remained unchanged, because of the fact that the mean size of eels has doubled. Passage data from 2007 show that changes in size and abundance have resulted in a reduction of relative escapement to the sea to values that are 21,24% of what they were in 1957,66. However, this low level of escapement could potentially be rectified if appropriate measures facilitating HEP passage are successfully implemented, since the potential escapement biomass in the river, owing to the large size of the eels, has changed little since the 1950s. [source] Phytoplankton production and growth rate in Lake Tanganyika: evidence of a decline in primary productivity in recent decadesFRESHWATER BIOLOGY, Issue 11 2007STEPHANE STENUITE Summary 1. This study focused on phytoplankton production in Lake Tanganyika. We provide new estimates of daily and annual primary production, as well as growth rates of phytoplankton, and we compare them with values published in former studies. 2. Chlorophyll- a (chl- a) in the mixed layer ranged from 5 to 120 mg chl- a m,2 and varied significantly between rainy and dry seasons. Particulate organic carbon concentrations were significantly higher in the south basin (with 196 and 166 mg C m,3 in the dry and the rainy season, respectively) than in the north basin (112 and 109 mg C m,3, respectively). 3. Carbon : phosphorus (C : P) ratios varied according to season. Phosphorus limitation seemed to occur more frequently than nitrogen limitation, especially during the rainy season. Severe P deficiencies were rare. 4. Measured particulate daily primary production ranged from 110 to 1410 mg C m,2 day,1; seasonal contrasts were well marked in the north basin, but less in the south basin, where primary production peaks occurred also in the rainy season. Estimates of annual primary production, based on daily primary production calculated from chl- a and water transparency, gave values lower than those reported in previous studies. Picophytoplankton accounted on average for 56% of total particulate production in the south basin during the wet season of 2003. 5. Phytoplankton growth rates, calculated from primary production, ranged from 0.055 to 0.282 day,1; these are lower than previously published values for Lake Tanganyika. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||