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Showing papers by "University of Leeds published in 2006"


Journal ArticleDOI
TL;DR: The Model of Emissions of Gases and Aerosols from Nature (MEGAN) is used to quantify net terrestrial biosphere emission of isoprene into the atmosphere as mentioned in this paper.
Abstract: . Reactive gases and aerosols are produced by terrestrial ecosystems, processed within plant canopies, and can then be emitted into the above-canopy atmosphere. Estimates of the above-canopy fluxes are needed for quantitative earth system studies and assessments of past, present and future air quality and climate. The Model of Emissions of Gases and Aerosols from Nature (MEGAN) is described and used to quantify net terrestrial biosphere emission of isoprene into the atmosphere. MEGAN is designed for both global and regional emission modeling and has global coverage with ~1 km2 spatial resolution. Field and laboratory investigations of the processes controlling isoprene emission are described and data available for model development and evaluation are summarized. The factors controlling isoprene emissions include biological, physical and chemical driving variables. MEGAN driving variables are derived from models and satellite and ground observations. Tropical broadleaf trees contribute almost half of the estimated global annual isoprene emission due to their relatively high emission factors and because they are often exposed to conditions that are conducive for isoprene emission. The remaining flux is primarily from shrubs which have a widespread distribution. The annual global isoprene emission estimated with MEGAN ranges from about 500 to 750 Tg isoprene (440 to 660 Tg carbon) depending on the driving variables which include temperature, solar radiation, Leaf Area Index, and plant functional type. The global annual isoprene emission estimated using the standard driving variables is ~600 Tg isoprene. Differences in driving variables result in emission estimates that differ by more than a factor of three for specific times and locations. It is difficult to evaluate isoprene emission estimates using the concentration distributions simulated using chemistry and transport models, due to the substantial uncertainties in other model components, but at least some global models produce reasonable results when using isoprene emission distributions similar to MEGAN estimates. In addition, comparison with isoprene emissions estimated from satellite formaldehyde observations indicates reasonable agreement. The sensitivity of isoprene emissions to earth system changes (e.g., climate and land-use) demonstrates the potential for large future changes in emissions. Using temperature distributions simulated by global climate models for year 2100, MEGAN estimates that isoprene emissions increase by more than a factor of two. This is considerably greater than previous estimates and additional observations are needed to evaluate and improve the methods used to predict future isoprene emissions.

3,746 citations


Journal ArticleDOI
TL;DR: The CASPAR criteria are simple and highly specific but less sensitive than the Vasey and Espinoza criteria and are confirmed as the validity of clinical diagnosis as the gold standard definition of "case"-ness.
Abstract: Objective To compare the accuracy of existing classification criteria for the diagnosis of psoriatic arthritis (PsA) and to construct new criteria from observed data. Methods Data were collected prospectively from consecutive clinic attendees with PsA and other inflammatory arthropathies. Subjects were classified by each of 7 criteria. Sensitivity and specificity were compared using conditional logistic regression analysis. Latent class analysis was used to calculate criteria accuracy in order to confirm the validity of clinical diagnosis as the gold standard definition of “case”-ness. Classification and Regression Trees methodology and logistic regression were used to identify items for new criteria, which were then constructed using a receiver operating characteristic curve. Results Data were collected on 588 cases and 536 controls with rheumatoid arthritis (n = 384), ankylosing spondylitis (n = 72), undifferentiated arthritis (n = 38), connective tissue disorders (n = 14), and other diseases (n = 28). The specificity of each set of criteria was high. The sensitivity of the Vasey and Espinoza method (0.97) was similar to that of the method of McGonagle et al (0.98) and greater than that of the methods of Bennett (0.44), Moll and Wright (0.91), the European Spondylarthropathy Study Group (0.74), and Gladman et al (0.91). The CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria consisted of established inflammatory articular disease with at least 3 points from the following features: current psoriasis (assigned a score of 2; all other features were assigned a score of 1), a history of psoriasis (unless current psoriasis was present), a family history of psoriasis (unless current psoriasis was present or there was a history of psoriasis), dactylitis, juxtaarticular new bone formation, rheumatoid factor negativity, and nail dystrophy. These criteria were more specific (0.987 versus 0.960) but less sensitive (0.914 versus 0.972) than those of Vasey and Espinoza. Conclusion The CASPAR criteria are simple and highly specific but less sensitive than the Vasey and Espinoza criteria.

2,797 citations


Journal ArticleDOI
21 Jul 2006-Science
TL;DR: Evidence of declines (pre-versus post-1980) in local bee diversity in Britain and the Netherlands is found and a causal connection between local extinctions of functionally linked plant and pollinator species is strongly suggested.
Abstract: Despite widespread concern about declines in pollination services, little is known about the patterns of change in most pollinator assemblages. By studying bee and hoverfly assemblages in Britain and the Netherlands, we found evidence of declines (pre-versus post-1980) in local bee diversity in both countries; however, divergent trends were observed in hoverflies. Depending on the assemblage and location, pollinator declines were most frequent in habitat and flower specialists, in univoltine species, and/or in nonmigrants. In conjunction with this evidence, outcrossing plant species that are reliant on the declining pollinators have themselves declined relative to other plant species. Taken together, these findings strongly suggest a causal connection between local extinctions of functionally linked plant and pollinator species.

2,616 citations


Journal ArticleDOI
26 Oct 2006-Nature
TL;DR: A formal meta-analysis of studies that have experimentally manipulated species diversity to examine how it affects the functioning of numerous trophic groups in multiple types of ecosystem suggests that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal Trophic group, leading to less complete depletion of resources used by that group.
Abstract: Over the past decade, accelerating rates of species extinction have prompted an increasing number of studies to reduce species diversityexperimentallyandexaminehowthisalterstheefficiency by which communities capture resources and convert those into biomass 1,2 . So far, the generality of patterns and processes observed in individual studies have been the subjects of considerable debate 3–7 .Here wepresent aformal meta-analysis of studies thathaveexperimentallymanipulatedspeciesdiversitytoexamine how it affects the functioning of numerous trophic groups in multiple types of ecosystem. We show that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal trophic group, leading to less complete depletion of resources used by that group. At the same time, analyses reveal that the standing stock of, and resource depletion by, the most species-rich polyculture tends to be no different from that of the single most productive species used in an experiment. Of the known mechanisms that might explain these trends, results are most consistent with what is called the ‘sampling effect’, which occurs when diverse communities are more likely to contain and become dominated by the most productive species. Whether this mechanism is widespread in natural communities is currently controversial. Patterns we report are remarkably consistent for four different trophic groups (producers, herbivores, detritivores and predators) and two major ecosystem types (aquatic and terrestrial). Collectively, ouranalysessuggestthat theaverage species loss does indeed affect the functioning of a wide variety of organisms and ecosystems, but the magnitude of these effects is ultimatelydeterminedbytheidentityofspeciesthataregoingextinct.

1,691 citations


Journal ArticleDOI
TL;DR: The IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry (IUPAC-GKDE) as mentioned in this paper has published a series of data sheets for organic halogen species.
Abstract: This article, the fourth in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of organic halogen species, which were last published in 1997, and were updated on the IUPAC website in 2006/07. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and four appendices containing the data sheets, which provide information upon which the recommendations are made.

1,623 citations


Journal ArticleDOI
TL;DR: Using a sample of U.K. wire makers, a model in which personality and work environment antecedents affect proactive work behavior via cognitive-motivational mechanisms was tested and positive self-reported proactive work behaviors were validated against rater assessments.
Abstract: Using a sample of U.K. wire makers (N = 282), the authors tested a model in which personality and work environment antecedents affect proactive work behavior via cognitive-motivational mechanisms. Self-reported proactive work behaviors (proactive idea implementation and proactive problem solving) were validated against rater assessments for a subsample (n = 60) of wire makers. With the exception of supportive supervision, each antecedent was important, albeit through different processes. Proactive personality was significantly associated with proactive work behavior via role breadth self-efficacy and flexible role orientation, job autonomy was also linked to proactive behavior via these processes, as well as directly; and coworker trust was associated with proactive behavior via flexible role orientation. In further support of the model, the cognitive-motivational processes for proactive work behavior differed from those for the more passive outcome of generalized compliance.

1,499 citations


Journal ArticleDOI
14 Dec 2006-Nature
TL;DR: The data suggest that SCN9A is an essential and non-redundant requirement for nociception in humans, and should stimulate the search for novel analgesics that selectively target this sodium channel subunit.
Abstract: The complete inability to sense pain in an otherwise healthy individual is a very rare phenotype. In three consanguineous families from northern Pakistan, we mapped the condition as an autosomal-recessive trait to chromosome 2q24.3. This region contains the gene SCN9A, encoding the alpha-subunit of the voltage-gated sodium channel, Na(v)1.7, which is strongly expressed in nociceptive neurons. Sequence analysis of SCN9A in affected individuals revealed three distinct homozygous nonsense mutations (S459X, I767X and W897X). We show that these mutations cause loss of function of Na(v)1.7 by co-expression of wild-type or mutant human Na(v)1.7 with sodium channel beta(1) and beta(2) subunits in HEK293 cells. In cells expressing mutant Na(v)1.7, the currents were no greater than background. Our data suggest that SCN9A is an essential and non-redundant requirement for nociception in humans. These findings should stimulate the search for novel analgesics that selectively target this sodium channel subunit.

1,474 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the heat transfer behavior of aqueous suspensions of multi-walled carbon nanotubes (CNT nanofluids) flowing through a horizontal tube.

1,334 citations


Journal ArticleDOI
TL;DR: In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats.
Abstract: Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

1,162 citations


Journal ArticleDOI
TL;DR: Loss-of-function mutations in a previously uncharacterized, predominantly neuronal P-type ATPase gene, ATP13A2, underlying an autosomal recessive form of early-onset parkinsonism with pyramidal degeneration and dementia are described.
Abstract: Neurodegenerative disorders such as Parkinson and Alzheimer disease cause motor and cognitive dysfunction and belong to a heterogeneous group of common and disabling disorders. Although the complex molecular pathophysiology of neurodegeneration is largely unknown, major advances have been achieved by elucidating the genetic defects underlying mendelian forms of these diseases. This has led to the discovery of common pathophysiological pathways such as enhanced oxidative stress, protein misfolding and aggregation and dysfunction of the ubiquitin-proteasome system. Here, we describe loss-of-function mutations in a previously uncharacterized, predominantly neuronal P-type ATPase gene, ATP13A2, underlying an autosomal recessive form of early-onset parkinsonism with pyramidal degeneration and dementia (PARK9, Kufor-Rakeb syndrome). Whereas the wild-type protein was located in the lysosome of transiently transfected cells, the unstable truncated mutants were retained in the endoplasmic reticulum and degraded by the proteasome. Our findings link a class of proteins with unknown function and substrate specificity to the protein networks implicated in neurodegeneration and parkinsonism.

1,112 citations


Journal ArticleDOI
TL;DR: Delirium is common in medical in-patients and has serious adverse effects on mortality, functional outcomes, LOS and institutionalisation.
Abstract: Background: Despite the acknowledged clinical importance of delirium, research evidence for measures to improve its management is sparse. A necessary first step to devising appropriate strategies is to understand how common it is and what its outcomes are in any particular setting. Objective: To determine the occurrence of delirium and its outcomes in medical in-patients, through a systematic review of the literature. Method: We searched electronic medical databases, the Consultation-Liaison Literature Database and reference lists and bibliographies for potentially relevant studies. Studies were selected, quality assessed and data extracted according to preset protocols. Results: Results for the occurrence of delirium in medical in-patients were available for 42 cohorts. Prevalence of delirium at admission ranged from 10 to 31%, incidence of new delirium per admission ranged from 3 to 29% and occurrence rate per admission varied between 11 and 42%. Results for outcomes were available for 19 study cohorts. Delirium was associated with increased mortality at discharge and at 12 months, increased length of hospital stay (LOS) and institutionalisation. A significant proportion of patients had persistent symptoms of delirium at discharge and at 6 and 12 months. Conclusion: Delirium is common in medical in-patients and has serious adverse effects on mortality, functional outcomes, LOS and institutionalisation. The development of appropriate strategies to improve its management should be a clinical and research priority. As delirium prevalent at hospital admission is a significant problem, research is also needed into preventative measures that could be applied in community settings.

Journal ArticleDOI
TL;DR: The purpose of this paper is to assess the impact of participatory processes on sustainability indicator identification and environmental management in three disparate case studies to draw three primary conclusions.

Journal ArticleDOI
TL;DR: This is the first estimate of the prevalence and distribution of pain of predominantly neuropathic origin in the general population, using a previously validated and reliable data collection instrument.

Book
Markus Haase1
14 Jun 2006
TL;DR: In this article, the basic theory of sectorial operators is developed along the lines of the abstract framework of Chapter 1 Fundamental properties like the composition rule are proved and a panorama of functional calculi is developed.
Abstract: In Section 21 the basic theory of sectorial operators is developed, including examples and the concept of sectorial approximation In Section 22 we introduce some notation for certain spaces of holomorphic functions on sectors A functional calculus for sectorial operators is constructed in Section 23 along the lines of the abstract framework of Chapter 1 Fundamental properties like the composition rule are proved In Section 25 we give natural extensions of the functional calculus to larger function spaces in the case where the given operator is bounded and/or invertible In this way a panorama of functional calculi is developed In Section 26 some mixed topics are discussed, eg, adjoints and restrictions of sectorial operators and some fundamental boundedness and some first approximation results Section 27 contains a spectral mapping theorem

Journal ArticleDOI
TL;DR: Pectin is a high value functional food ingredient widely used as a gelling agent and stabilizer and it is also an abundant, ubiquitous and multifunctional component of the cell walls of all land plants as mentioned in this paper.
Abstract: Pectin is a high value functional food ingredient widely used as a gelling agent and stabilizer. It is also an abundant, ubiquitous and multifunctional component of the cell walls of all land plants. Food scientists and plant scientists therefore share a common goal to better understand the structure and functionalities of pectic polymers at the molecular level. The basic properties of pectin have been known for nearly 200 years, but recently there has been tremendous progress in our understanding of the very complex fine structure of pectic polymers and pectinolytic enzymes. This has been made possible by synergies between plant and food research and by the application of a range of state-of-the-art techniques including enzymatic fingerprinting, mass spectrometry, NMR, molecular modelling, and monoclonal antibodies. With this increased knowledge comes the prospect of novel applications. Producers are beginning to develop a new generation of sophisticated designer pectins with specific functionalities. Moreover, the ability to manipulate pectin in planta would have a major impact on fruit and vegetable quality and processing, as well as on pectin production.

Journal ArticleDOI
TL;DR: The results indicate that targeted blockade of IL-6 signaling is a highly efficacious and promising means of decreasing disease activity in RA.
Abstract: Objective To establish the safety and efficacy of repeat infusions of tocilizumab (previously known as MRA), a humanized anti–interleukin-6 (IL-6) receptor antibody, alone and in combination with methotrexate (MTX), for the treatment of rheumatoid arthritis (RA). Methods The study group comprised 359 patients with active RA in whom the response to MTX was inadequate. During a stabilization period, these patients received their current dose of MTX for at least 4 weeks. Following stabilization, they were randomized to 1 of 7 treatment arms, as follows: tocilizumab at doses of 2 mg/kg, 4 mg/kg, or 8 mg/kg either as monotherapy or in combination with MTX, or MTX plus placebo. Results A 20% response (improvement) according to the American College of Rheumatology criteria (ACR20 response) was achieved by 61% and 63% of patients receiving 4 mg/kg and 8 mg/kg of tocilizumab as monotherapy, respectively, and by 63% and 74% of patients receiving those doses of tocilizumab plus MTX, respectively, compared with 41% of patients receiving placebo plus MTX. Statistically significant ACR50 and ACR70 responses were observed in patients receiving combination therapy with either 4 mg/kg or 8 mg/kg of tocilizumab plus MTX (P < 0.05). A dose-related reduction in the Disease Activity Score in 28 joints was observed from week 4 onward, in all patients except those receiving monotherapy with 2 mg/kg of tocilizumab. In the majority of patients who received 8 mg/kg of tocilizumab, the C-reactive protein level/erythrocyte sedimentation rate normalized, while placebo plus MTX had little effect on these laboratory parameters. Tocilizumab was mostly well tolerated, with a safety profile similar to that of other biologic and immunosuppressive therapies. Alanine transaminase and aspartate transaminase levels followed a sawtooth pattern (rising and falling between infusions). There were moderate but reversible increases in the nonfasting total cholesterol and triglyceride levels and reversible reductions in the high-density lipoprotein cholesterol and neutrophil levels. There were 2 cases of sepsis, both of which occurred in patients who were receiving combination therapy with 8 mg/kg of tocilizumab plus MTX. Conclusion These results indicate that targeted blockade of IL-6 signaling is a highly efficacious and promising means of decreasing disease activity in RA.

Journal ArticleDOI
TL;DR: Research findings from around the world are used to show how the proposed process can be used to develop quantitative and qualitative indicators that are both scientifically rigorous and objective while remaining easy to collect and interpret for communities.

Journal ArticleDOI
TL;DR: This unprecedented wood density data set yields consistent guidelines for estimating wood densities when species-level information is lacking and should significantly reduce error in Central and South American carbon accounting programs.
Abstract: Wood density is a crucial variable in carbon accounting programs of both secondary and old-growth tropical forests. It also is the best single descriptor of wood: it correlates with numerous morphological, mechanical, physiological, and ecological properties. To explore the extent to which wood density could be estimated for rare or poorly censused taxa, and possible sources of variation in this trait, we analyzed regional, taxonomic, and phylogenetic variation in wood density among 2456 tree species from Central and South America. Wood density varied over more than one order of magnitude across species, with an overall mean of 0.645 g/cm3. Our geographical analysis showed significant decreases in wood density with increasing altitude and significant differences among low-altitude geographical regions: wet forests of Central America and western Amazonia have significantly lower mean wood density than dry forests of Central and South America, eastern and central Amazonian forests, and the Atlantic forests of Brazil; and eastern Amazonian forests have lower wood densities than the dry forests and the Atlantic forest. A nested analysis of variance showed that 74% of the species-level wood density variation was explained at the genus level, 34% at the Angiosperm Phylogeny Group (APG) family level, and 19% at the APG order level. This indicates that genus-level means give reliable approximations of values of species, except in a few hypervariable genera. We also studied which evolutionary shifts in wood density occurred in the phylogeny of seed plants using a composite phylogenetic tree. Major changes were observed at deep nodes (Eurosid 1), and also in more recent divergences (for instance in the Rhamnoids, Simaroubaceae, and Anacardiaceae). Our unprecedented wood density data set yields consistent guidelines for estimating wood densities when species-level information is lacking and should significantly reduce error in Central and South American carbon accounting programs.

Journal ArticleDOI
TL;DR: Nucleic-acid aptamers have the molecular recognition properties of antibodies, and can be isolated robotically for high-throughput applications in diagnostics, research and therapeutics.
Abstract: Nucleic-acid aptamers have the molecular recognition properties of antibodies, and can be isolated robotically for high-throughput applications in diagnostics, research and therapeutics. Unlike antibodies, however, they can be chemically derivatized easily to extend their lifetimes in biological fluids and their bioavailability in animals. The first aptamer-based clinical drugs have recently entered service. Meanwhile, active research programmes have identified a wide range of anti-viral aptamers that could form the basis for future therapeutics.

Reference EntryDOI
15 Apr 2006
TL;DR: Volume 1 IRON Heme Proteins: Oxygen Storage and Oxygen Transport Proteinology Volume 2 IRON continued Non-Heme Protesins: Dinuclear Iron ProteINs Non-heme ProteINS: Iron Storage Non- Heme Protins: Iron Transport NICKEL MANGANESE COBALT MOLYBDENUM/TUNGSTEN COPPER Cupredoxins
Abstract: Volume 1 IRON Heme Proteins: Oxygen Storage and Oxygen Transport Proteins Heme Proteins: Cytochromes Heme Proteins: Cytochrome Peroxidases Heme Proteins: Cytochrome P-450 Heme Proteins: Oxidoreductases Non-Heme Proteins: Iron-Sulfur Clusters Non-Heme Proteins: Mononuclear Iron Proteins Volume 2 IRON continued Non-Heme Proteins: Dinuclear Iron Proteins Non-Heme Proteins: Iron Storage Non-Heme Proteins: Iron Transport NICKEL MANGANESE COBALT MOLYBDENUM/TUNGSTEN COPPER Cupredoxins (Type-1 Copper Proteins) Type-2 Copper Enzymes Binuclear Copper: Type-3 Copper Enzymes Binuclear Copper: CuA Copper Multicopper Enzymes Copper Storage and Transport VANADIUM.

Journal ArticleDOI
28 Sep 2006-Nature
TL;DR: By using the seven forest inventories complemented with trait and inventory data collected elsewhere, two dominant gradients in tree composition and function across the Amazon are shown, one paralleling a major gradient in soil fertility and the other paralleled a gradient in dry season length.
Abstract: The world's greatest terrestrial stores of biodiversity and carbon are found in the forests of northern South America, where large-scale biogeographic patterns and processes have recently begun to be described. Seven of the nine countries with territory in the Amazon basin and the Guiana shield have carried out large-scale forest inventories, but such massive data sets have been little exploited by tropical plant ecologists. Although forest inventories often lack the species-level identifications favoured by tropical plant ecologists, their consistency of measurement and vast spatial coverage make them ideally suited for numerical analyses at large scales, and a valuable resource to describe the still poorly understood spatial variation of biomass, diversity, community composition and forest functioning across the South American tropics. Here we show, by using the seven forest inventories complemented with trait and inventory data collected elsewhere, two dominant gradients in tree composition and function across the Amazon, one paralleling a major gradient in soil fertility and the other paralleling a gradient in dry season length. The data set also indicates that the dominance of Fabaceae in the Guiana shield is not necessarily the result of root adaptations to poor soils (nodulation or ectomycorrhizal associations) but perhaps also the result of their remarkably high seed mass there as a potential adaptation to low rates of disturbance.

Journal ArticleDOI
TL;DR: In this paper, the authors present an up-to-date guidance manual on the factors affecting the demand for public transport for use by public transport operators and planning authorities, and for academics and other researchers.

Journal ArticleDOI
TL;DR: In this paper, a novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described, which can be used to generate microstructures with martensites/austenite combinations giving attractive properties.
Abstract: A novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described. This involves quenching to below the martensite-start temperature and directly ageing, either at, or above, the initial quench temperature. If competing reactions, principally carbide precipitation, are suppressed by appropriate alloying, the carbon partitions from the supersaturated martensite phase to the untransformed austenite phase, thereby increasing the stability of the residual austenite upon subsequent cooling to room temperature. This novel treatment has been termed ‘quenching and partitioning’ (Q&P), to distinguish it from quenching and tempering, and can be used to generate microstructures with martensite/austenite combinations giving attractive properties. Another approach that has been used to produce austenite-containing microstructures is by alloying to suppress carbide precipitation during the formation of bainitic structures, and interesting comparisons can be made between the two approaches. Moreover, formation of carbide-free bainite during the Q&P partitioning treatment may be a reaction competing for carbon, although this could also be used constructively as an additional stage of Q&P partitioning to form part of the final microstructure. Amongst the ferrous alloys examined so far are medium carbon bar steels and low carbon formable TRIP-assisted sheet steels.

Journal ArticleDOI
TL;DR: In this paper, the authors argue that a necessary tension exists between authoritative and dialogic approaches as dialogic exchanges are followed by authoritative interventions, and the authoritative introduction of new ideas is followed by the opportunity for dialogic application and exploration of those ideas.
Abstract: In this paper, we draw upon a framework for analyzing the discursive interactions of science classrooms (Mortimer & Scott, 2003, Meaning Making in Secondary Science Classrooms, Maidenhead, UK: Open University Press), to probe the movement between authoritative and dialogic discourse in a Brazilian high school science class. More specifically, we argue the point that such shifts between communicative approaches are an inevitable part of teaching whose purpose is to support meaningful learning of scientific knowledge. We suggest that a necessary tension therefore exists between authoritative and dialogic approaches as dialogic exchanges are followed by authoritative interventions (to develop the canonical scientific view), and the authoritative introduction of new ideas is followed by the opportunity for dialogic application and exploration of those ideas. In these ways, one communicative approach follows from the other, authoritativeness acting as a seed for dialogicity and vice versa. We discuss how this analysis, in terms of shifts in communicative approach, offers a new and complementary perspective on supporting “productive disciplinary engagement” (Engle & Conant, 2002, Cognition and Instruction, 20, 399–484) in the classroom. Finally we consider some methodological issues arising from this study. © 2006 Wiley Periodicals, Inc. Sci Ed90:605–631, 2006

Journal ArticleDOI
TL;DR: This paper examined two groups of students at a Chinese University writing essays on the same topic, one receiving feedback from the teacher and one from their peers, and found that students used teacher and peer feedback to improve their writing but that teacher feedback was more likely to be adopted and led to greater improvements in the writing.

Journal ArticleDOI
TL;DR: In this paper, the authors presented a new synthesis and interpolation of the basal area and aboveground live biomass of old-growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished.
Abstract: The biomass of tropical forests plays an important role in the global carbon cycle, both as a dynamic reservoir of carbon, and as a source of carbon dioxide to the atmosphere in areas undergoing deforestation. However, the absolute magnitude and environmental determinants of tropical forest biomass are still poorly understood. Here, we present a new synthesis and interpolation of the basal area and aboveground live biomass of old-growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished. Forest biomass was analyzed in terms of two uncorrelated factors: basal area and mean wood density. Basal area is strongly affected by local landscape factors, but is relatively invariant at regional scale in moist tropical forests, and declines significantly at the dry periphery of the forest zone. Mean wood density is inversely correlated with forest dynamics, being lower in the dynamic forests of western Amazonia and high in the slow-growing forests of eastern Amazonia. The combination of these two factors results in biomass being highest in the moderately seasonal, slow growing forests of central Amazonia and the Guyanas (up to 350?Mg?dry weight?ha?1) and declining to 200-250?Mg?dry weight?ha?1 at the western, southern and eastern margins. Overall, we estimate the total aboveground live biomass of intact Amazonian rainforests (area 5.76 × 106?km2 in 2000) to be 93±23?Pg?C, taking into account lianas and small trees. Including dead biomass and belowground biomass would increase this value by approximately 10% and 21%, respectively, but the spatial variation of these additional terms still needs to be quantified

Journal ArticleDOI
TL;DR: In this paper, the authors draw from the work of the continental philosopher Martin Heidegger to articulate a relational theory of human agency that is better suited to explaining everyday purposive actions and practices, and argue that the dominant "building" mode of strategizing that configures actors as distinct entities deliberately engaging in purposeful strategic activities derives from a more basic "dwelling" mode in which strategy emerges non-deliberately through everyday practical coping.
Abstract: What strategic actors actually do in practice has become increasingly the focus of strategy research in recent years. This paper argues that, in furthering such practice-based views of strategy, we need a more adequate re-conceptualization of agency, action and practice and how they interrelate. We draw from the work of the continental philosopher Martin Heidegger to articulate a relational theory of human agency that is better suited to explaining everyday purposive actions and practices. Specifically, we argue that the dominant ‘building’ mode of strategizing that configures actors (whether individual or organizational) as distinct entities deliberately engaging in purposeful strategic activities derives from a more basic ‘dwelling’ mode in which strategy emerges non-deliberately through everyday practical coping. Whereas, from the building perspective, strategy is predicated upon the prior conception of plans that are then orchestrated to realize desired outcome, from a dwelling perspective strategy do...

Journal ArticleDOI
20 Jul 2006-Nature
TL;DR: A three-dimensional deformation field for the Dabbahu rifting episode derived from satellite radar data shows that the entire segment ruptured, making it the largest to have occurred on land in the era of satellite geodesy.
Abstract: Occurring mainly over a week in September 2005, a 60-km-long section of the Afar depression in Ethiopia was torn apart by the injection of over 2 cubic kilometres of molten rock into the plate: an 8-metre-wide gap appeared at the surface. Satellite radar imagery reveals that a series of fissures opened, the rift shoulders rose, and the ground surface dropped above the molten rock. A similarly large rift took place in Krafla in Iceland 25 years ago, but in a series of events over a ten year period. The Afar incident suggests that magma intrusion into a dyke, rather than faulting of the crust, may be responsible for the segmentation of continental rifts. Seafloor spreading centres show a regular along-axis segmentation thought to be produced by a segmented magma supply in the passively upwelling mantle1,2. On the other hand, continental rifts are segmented by large offset normal faults, and many lack magmatism. It is unclear how, when and where the ubiquitous segmented melt zones are emplaced during the continental rupture process. Between 14 September and 4 October 2005, 163 earthquakes (magnitudes greater than 3.9) and a volcanic eruption occurred within the ∼60-km-long Dabbahu magmatic segment of the Afar rift, a nascent seafloor spreading centre in stretched continental lithosphere3,4. Here we present a three-dimensional deformation field for the Dabbahu rifting episode derived from satellite radar data, which shows that the entire segment ruptured, making it the largest to have occurred on land in the era of satellite geodesy. Simple elastic modelling shows that the magmatic segment opened by up to 8 m, yet seismic rupture can account for only 8 per cent of the observed deformation. Magma was injected along a dyke between depths of 2 and 9 km, corresponding to a total intrusion volume of ∼2.5 km3. Much of the magma appears to have originated from shallow chambers beneath Dabbahu and Gabho volcanoes at the northern end of the segment, where an explosive fissural eruption occurred on 26 September 2005. Although comparable in magnitude to the ten year (1975–84) Krafla events in Iceland5, seismic data suggest that most of the Dabbahu dyke intrusion occurred in less than a week. Thus, magma intrusion via dyking, rather than segmented normal faulting, maintains and probably initiated the along-axis segmentation along this sector of the Nubia–Arabia plate boundary.

Journal ArticleDOI
TL;DR: In this article, the authors argue that climatic factors may not be the dominant drivers of dissolved organic carbon (DOC) change in surface waters across much of Europe and North America, and suggest that these systems may be recovering rather than destabilising.
Abstract: Since 1988, there has been, on average, a 91% increase in dissolved organic carbon (DOC) concentrations of UK lakes and streams in the Acid Waters Monitoring Network (AWMN). Similar DOC increases have been observed in surface waters across much of Europe and North America. Much of the debate about the causes of rising DOC has, as in other studies relating to the carbon cycle, focused on factors related to climate change. Data from our peat-core experiments support an influence of climate on DOC, notably an increase in production with temperature under aerobic, and to a lesser extent anaerobic, conditions. However, we argue that climatic factors may not be the dominant drivers of DOC change. DOC solubility is suppressed by high soil water acidity and ionic strength, both of which have decreased as a result of declining sulphur deposition since the 1980s, augmented during the 1990s in the United Kingdom by a cyclical decline in sea-salt deposition. Our observational and experimental data demonstrate a clear, inverse and quantitatively important link between DOC and sulphate concentrations in soil solution. Statistical analysis of 11 AWMN lakes suggests that rising temperature, declining sulphur deposition and changing sea-salt loading can account for the majority of the observed DOC trend. This combination of evidence points to the changing chemical composition of atmospheric deposition, particularly the substantial reduction in anthropogenic sulphur emissions during the last 20 years, as a key cause of rising DOC. The implications of rising DOC export for the carbon cycle will be very different if linked primarily to decreasing acid deposition, rather than to changes in climate, suggesting that these systems may be recovering rather than destabilising.

Journal ArticleDOI
TL;DR: The phylogeographic approach is illustrated with two case studies: the initial dispersal out of Africa, and the colonization of Europe, which show how modern humans spread across the authors' planet.