Showing papers by "Royal Holloway, University of London published in 2009"

Fire in the Earth System

Abstract: Fire is a worldwide phenomenon that appears in the geological record soon after the appearance of terrestrial plants. Fire influences global ecosystem patterns and processes, including vegetation distribution and structure, the carbon cycle, and climate. Although humans and fire have always coexisted, our capacity to manage fire remains imperfect and may become more difficult in the future as climate change alters fire regimes. This risk is difficult to assess, however, because fires are still poorly represented in global models. Here, we discuss some of the most important issues involved in developing a better understanding of the role of fire in the Earth system.

The Genome Sequence of Taurine Cattle: A Window to Ruminant Biology and Evolution

Abstract: To understand the biology and evolution of ruminants, the cattle genome was sequenced to about sevenfold coverage. The cattle genome contains a minimum of 22,000 genes, with a core set of 14,345 orthologs shared among seven mammalian species of which 1217 are absent or undetected in noneutherian (marsupial or monotreme) genomes. Cattle-specific evolutionary breakpoint regions in chromosomes have a higher density of segmental duplications, enrichment of repetitive elements, and species-specific variations in genes associated with lactation and immune responsiveness. Genes involved in metabolism are generally highly conserved, although five metabolic genes are deleted or extensively diverged from their human orthologs. The cattle genome sequence thus provides a resource for understanding mammalian evolution and accelerating livestock genetic improvement for milk and meat production.

What are the effects of fiscal policy shocks

Abstract: We propose and apply a new approach for analyzing the effects of fiscal policy using vector autoregressions. Specifically, we use sign restrictions to identify a government revenue shock as well as a government spending shock, while controlling for a generic business cycle shock and a monetary policy shock. We explicitly allow for the possibility of announcement effects, i.e., that a current fiscal policy shock changes fiscal policy variables in the future, but not at present. We construct the impulse responses to three linear combinations of these fiscal shocks, corresponding to the three scenarios of deficit-spending, deficit-financed tax cuts and a balanced budget spending expansion. We apply the method to US quarterly data from 1955 to 2000. We find that deficit-financed tax cuts work best among these three scenarios to improve GDP, with a maximal present value multiplier of five dollars of total additional GDP per each dollar of the total cut in government revenue 5 years after the shock. Copyright © 2009 John Wiley & Sons, Ltd.

The spread of awareness and its impact on epidemic outbreaks

Abstract: When a disease breaks out in a human population, changes in behavior in response to the outbreak can alter the progression of the infectious agent. In particular, people aware of a disease in their proximity can take measures to reduce their susceptibility. Even if no centralized information is provided about the presence of a disease, such awareness can arise through first-hand observation and word of mouth. To understand the effects this can have on the spread of a disease, we formulate and analyze a mathematical model for the spread of awareness in a host population, and then link this to an epidemiological model by having more informed hosts reduce their susceptibility. We find that, in a well-mixed population, this can result in a lower size of the outbreak, but does not affect the epidemic threshold. If, however, the behavioral response is treated as a local effect arising in the proximity of an outbreak, it can completely stop a disease from spreading, although only if the infection rate is below a threshold. We show that the impact of locally spreading awareness is amplified if the social network of potential infection events and the network over which individuals communicate overlap, especially so if the networks have a high level of clustering. These findings suggest that care needs to be taken both in the interpretation of disease parameters, as well as in the prediction of the fate of future outbreaks.

Inequality in Landownership, the Emergence of Human-Capital Promoting Institutions, and the Great Divergence

Abstract: This paper suggests that inequality in the distribution of landownership adversely affected the emergence of human-capital promoting institutions (e.g. public schooling), and thus the pace and the nature of the transition from an agricultural to an industrial economy, contributing to the emergence of the great divergence in income per capita across countries. The prediction of the theory regarding the adverse effect of the concentration of landownership on education expenditure is established empirically based on evidence from the beginning of the 20th century in the U.S.

Local restoration of dystrophin expression with the morpholino oligomer AVI-4658 in Duchenne muscular dystrophy: a single-blind, placebo-controlled, dose-escalation, proof-of-concept study

Abstract: Summary Background Mutations that disrupt the open reading frame and prevent full translation of DMD , the gene that encodes dystrophin, underlie the fatal X-linked disease Duchenne muscular dystrophy. Oligonucleotides targeted to splicing elements (splice switching oligonucleotides) in DMD pre-mRNA can lead to exon skipping, restoration of the open reading frame, and the production of functional dystrophin in vitro and in vivo, which could benefit patients with this disorder. Methods We did a single-blind, placebo-controlled, dose-escalation study in patients with DMD recruited nationally, to assess the safety and biochemical efficacy of an intramuscular morpholino splice-switching oligonucleotide (AVI-4658) that skips exon 51 in dystrophin mRNA. Seven patients with Duchenne muscular dystrophy with deletions in the open reading frame of DMD that are responsive to exon 51 skipping were selected on the basis of the preservation of their extensor digitorum brevis (EDB) muscle seen on MRI and the response of cultured fibroblasts from a skin biopsy to AVI-4658. AVI-4658 was injected into the EDB muscle; the contralateral muscle received saline. Muscles were biopsied between 3 and 4 weeks after injection. The primary endpoint was the safety of AVI-4658 and the secondary endpoint was its biochemical efficacy. This trial is registered, number NCT00159250. Findings Two patients received 0·09 mg AVI-4658 in 900 μL (0·9%) saline and five patients received 0·9 mg AVI-4658 in 900 μL saline. No adverse events related to AVI-4658 administration were reported. Intramuscular injection of the higher-dose of AVI-4658 resulted in increased dystrophin expression in all treated EDB muscles, although the results of the immunostaining of EDB-treated muscle for dystrophin were not uniform. In the areas of the immunostained sections that were adjacent to the needle track through which AVI-4658 was given, 44–79% of myofibres had increased expression of dystrophin. In randomly chosen sections of treated EDB muscles, the mean intensity of dystrophin staining ranged from 22% to 32% of the mean intensity of dystrophin in healthy control muscles (mean 26·4%), and the mean intensity was 17% (range 11–21%) greater than the intensity in the contralateral saline-treated muscle (one-sample paired t test p=0·002). In the dystrophin-positive fibres, the intensity of dystrophin staining was up to 42% of that in healthy muscle. We showed expression of dystrophin at the expected molecular weight in the AVI-4658-treated muscle by immunoblot. Interpretation Intramuscular AVI-4658 was safe and induced the expression of dystrophin locally within treated muscles. This proof-of-concept study has led to an ongoing systemic clinical trial of AVI-4658 in patients with DMD. Funding UK Department of Health.

Does contact reduce prejudice or does prejudice reduce contact? A longitudinal test of the contact hypothesis among majority and minority groups in three European countries.

Abstract: A widely researched panacea for reducing intergroup prejudice is the contact hypothesis. However, few longitudinal studies can shed light on the direction of causal processes: from contact to prejudice reduction (contact effects) or from prejudice to contact reduction (prejudice effects). The authors conducted a longitudinal field survey in Germany, Belgium, and England with school students. The sample comprised members of both ethnic minorities (n = 512) and ethnic majorities (n = 1,143). Path analyses yielded both lagged contact effects and prejudice effects: Contact reduced prejudice, but prejudice also reduced contact. Furthermore, contact effects were negligible for minority members. These effects were obtained for 2 indicators of prejudice: negative intergroup emotions and desire for social distance. For both majority and minority members, contact effects on negative emotions were stronger when outgroup contacts were perceived as being typical of their group. Contact effects were also mediated by intergroup anxiety. This mediating mechanism was impaired for minority members because of a weakened effect of anxiety on desire for social distance. Theoretical and practical implications of these findings are discussed.

Anxiety, Processing Efficiency, and Cognitive Performance New Developments from Attentional Control Theory

Abstract: There have been many attempts to account theoretically for the effects of anxiety on cognitive performance. This article focuses on two theories based on insights from cognitive psychology. The more recent is the attentional control theory (Eysenck, Derakshan, Santos, & Calvo, 2007), which developed from the earlier processing efficiency theory (Eysenck & Calvo, 1992). Both theories assume there is a fundamental distinction between performance effectiveness (quality of performance) and processing efficiency (the relationship between performance effectiveness and use of processing resources), and that anxiety impairs processing efficiency more than perfor- mance effectiveness. Both theories also assume that anxiety impairs the efficiency of the central executive component of the working memory system. In addition, attentional control theory assumes that anxiety impairs the efficiency of two types of attentional control: (1) negative attentional control (involved in inhibiting attention to task-irrelevant stimuli); and (2) positive attentional control (involved in flexibly switching attention between and within tasks to maximize performance). Recent (including unpublished) research relevant to theoretical predictions from attentional control theory is discussed. In addition, future directions for theory and research in the area of anxiety and performance are presented.

Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records

Abstract: The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in d 18 O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi-parameter annual layer counting provides an age of 11 700 calendar yr b2 k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene-Holocene boundary have also been recognised. Copyright # 2008 John Wiley & Sons, Ltd.

Media System, Public Knowledge and Democracy A Comparative Study

Abstract: ■ This article addresses the implications of the movement towards entertainment-centred, market-driven media by comparing what is reported and what the public knows in four countries with different media systems. The different systems are public service (Denmark and Finland), a `dual' model (UK) and the market model (US). The comparison shows that public service television devotes more attention to public affairs and international news, and fosters greater knowledge in these areas, than the market model. Public service television also gives greater prominence to news, encourages higher levels of news consumption and contributes to a smaller within-nation knowledge gap between the advantaged and disadvantaged. But wider processes in society take precedence over the organization of the media in determining how much people know about public life. ■

Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy

Abstract: We show that intermediate mass black holes conjectured to be the early precursors of supermassive black holes and surrounded by relic cold dark matter density spikes can act as particle accelerators with collisions, in principle, at arbitrarily high center-of-mass energies in the case of Kerr black holes. While the ejecta from such interactions will be highly redshifted, we may anticipate the possibility of a unique probe of Planck-scale physics.

The conservation of bees: a global perspective

Abstract: Bees are major pollinators of Angiosperms and therefore their apparent decline is of importance for humans and biodiversity. We synthesise results of 12 recent reviews to provide a global picture of the threats they face. Habitat loss is the major threat to bee diversity, whilst invasive species, emerging diseases, pesticide use, and climate change also have the potential to impact bee populations. We suggest that future conservation strategies need to prioritise (i) minimising habitat loss, (ii) making agricultural habitats bee-friendly, (iii) training scientists and the public in bee taxonomy and identification, (iv) basic autecological and population genetic studies to underpin conservation strategies, (v) assessing the value of DNA barcoding for bee conservation, (vi) determining the impact of invasive plants, animals, parasites and pathogens, and (vii) integrating this information to understand the potential impact of climate change on current bee diversity.

Escape of methane gas from the seabed along the West Spitsbergen continental margin

Abstract: More than 250 plumes of gas bubbles have been discovered emanating from the seabed of the West Spitsbergen continental margin, in a depth range of 150-400 m, at and above the present upper limit of the gas hydrate stability zone (GHSZ). Some of the plumes extend upward to within 50 m of the sea surface. The gas is predominantly methane. Warming of the northward-flowing West Spitsbergen current by 1°C over the last thirty years is likely to have increased the release of methane from the seabed by reducing the extent of the GHSZ, causing the liberation of methane from decomposing hydrate. If this process becomes widespread along Arctic continental margins, tens of Teragrams of methane per year could be released into the ocean.

Impacts of plant symbiotic fungi on insect herbivores: mutualism in a multitrophic context.

Abstract: We consider how fungi that form symbiotic associations with plants interact with insect herbivores attacking the same plants. Both endophytes and mycorrhizae have significant impacts on herbivores with which they are in relatively intimate contact, but weaker effects on those from which they are spatially separated. Generalist insects are usually adversely affected by the presence of endophytes and mycorrhizae, whereas specialist insects may often benefit. Effects on feeding guilds vary according to type of fungi; for example, aphids are often negatively affected by endophytes but respond positively to mycorrhizae, and leafchewers are usually negatively affected by both types of fungi. There is a strong taxonomic bias in the literature and many interactions remain little studied; laboratory studies predominate over field studies. Although some patterns emerge, there is a large amount of specificity and context dependency in the outcome of interactions, reflecting the influence of fungal and host genotype, fungal, host, and insect species, and environmental factors. Whereas some of the mechanisms underpinning these interactions are relatively well characterized, others remain unclear and await elucidation by molecular and metabolomic techniques.

Non-Euclidean statistics for covariance matrices, with applications to diffusion tensor imaging

Abstract: The statistical analysis of covariance matrix data is considered and, in particular, methodology is discussed which takes into account the non-Euclidean nature of the space of positive semi-definite symmetric matrices. The main motivation for the work is the analysis of diffusion tensors in medical image analysis. The primary focus is on estimation of a mean covariance matrix and, in particular, on the use of Procrustes size-and-shape space. Comparisons are made with other estimation techniques, including using the matrix logarithm, matrix square root and Cholesky decomposition. Applications to diffusion tensor imaging are considered and, in particular, a new measure of fractional anisotropy called Procrustes Anisotropy is discussed.

Wildfire responses to abrupt climate change in North America

Abstract: It is widely accepted, based on data from the last few decades and on model simulations, that anthropogenic climate change will cause increased fire activity. However, less attention has been paid to the relationship between abrupt climate changes and heightened fire activity in the paleorecord. We use 35 charcoal and pollen records to assess how fire regimes in North America changed during the last glacial–interglacial transition (15 to 10 ka), a time of large and rapid climate changes. We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indicated at any time during deglaciation. There are, however, clear links between large climate changes and fire activity. Biomass burning gradually increased from the glacial period to the beginning of the Younger Dryas. Although there are changes in biomass burning during the Younger Dryas, there is no systematic trend. There is a further increase in biomass burning after the Younger Dryas. Intervals of rapid climate change at 13.9, 13.2, and 11.7 ka are marked by large increases in fire activity. The timing of changes in fire is not coincident with changes in human population density or the timing of the extinction of the megafauna. Although these factors could have contributed to fire-regime changes at individual sites or at specific times, the charcoal data indicate an important role for climate, and particularly rapid climate change, in determining broad-scale levels of fire activity.

Global functional atlas of Escherichia coli encompassing previously uncharacterized proteins.

Abstract: One-third of the 4,225 protein-coding genes of Escherichia coli K-12 remain functionally unannotated (orphans). Many map to distant clades such as Archaea, suggesting involvement in basic prokaryotic traits, whereas others appear restricted to E. coli, including pathogenic strains. To elucidate the orphans' biological roles, we performed an extensive proteomic survey using affinity-tagged E. coli strains and generated comprehensive genomic context inferences to derive a high-confidence compendium for virtually the entire proteome consisting of 5,993 putative physical interactions and 74,776 putative functional associations, most of which are novel. Clustering of the respective probabilistic networks revealed putative orphan membership in discrete multiprotein complexes and functional modules together with annotated gene products, whereas a machine-learning strategy based on network integration implicated the orphans in specific biological processes. We provide additional experimental evidence supporting orphan participation in protein synthesis, amino acid metabolism, biofilm formation, motility, and assembly of the bacterial cell envelope. This resource provides a “systems-wide” functional blueprint of a model microbe, with insights into the biological and evolutionary significance of previously uncharacterized proteins.

Oceanic nickel depletion and a methanogen famine before the Great Oxidation Event

Abstract: It has been suggested that a decrease in atmospheric methane levels triggered the progressive rise of atmospheric oxygen, the so-called Great Oxidation Event, about 24 Gyr ago(1) Oxidative weathering of terrestrial sulphides, increased oceanic sulphate, and the ecological success of sulphate-reducing microorganisms over methanogens has been proposed as a possible cause for the methane collapse(1), but this explanation is difficult to reconcile with the rock record(2,3) Banded iron formations preserve a history of Precambrian oceanic elemental abundance and can provide insights into our understanding of early microbial life and its influence on the evolution of the Earth system(4,5) Here we report a decline in the molar nickel to iron ratio recorded in banded iron formations about 27 Gyr ago, which we attribute to a reduced flux of nickel to the oceans, a consequence of cooling upper-mantle temperatures and decreased eruption of nickel-rich ultramafic rocks at the time We measured nickel partition coefficients between simulated Precambrian sea water and diverse iron hydroxides, and subsequently determined that dissolved nickel concentrations may have reached similar to 400nM throughout much of the Archaean eon, but dropped below similar to 200nM by 25 Gyr ago and to modern day values(6) (similar to 9 nM) by similar to 550 Myr ago Nickel is a key metal cofactor in several enzymes of methanogens(7) and we propose that its decline would have stifled their activity in the ancient oceans and disrupted the supply of biogenic methane A decline in biogenic methane production therefore could have occurred before increasing environmental oxygenation and not necessarily be related to it The enzymatic reliance of methanogens on a diminishing supply of volcanic nickel links mantle evolution to the redox state of the atmosphere

An Ambidexterity Perspective Toward Multinational Enterprises From Emerging Economies

Abstract: Executive Overview In this article we present an ambidexterity perspective on the international expansion of emerging economy enterprises, highlighting the unique strategic behavior of emerging market multinational enterprises (EM MNEs). Specifically, we conceptualize ambidexterity as a multidimensional term comprising co-evolution, co-competence, co-opetition, and co-orientation. While all firms need and maintain some degree of ambidexterity, EM MNEs have stronger motives and abilities to build and leverage such ambidexterity to offset their late-mover disadvantages. They behave co-evolutionarily to deal with the external environment they face at home and abroad, leverage their co-competence (transactional and relational) to compete against their global rivals, develop co-opetitive (simultaneous cooperation and competition) ties with their business stakeholders, and maintain co-orientations (leveraging competitive advantages to bolster short-term survival and compensating competitive disadvantages for lo...

Inpainting and Zooming Using Sparse Representations

Abstract: Representing the image to be inpainted in an appropriate sparse representation dictionary, and combining elements from Bayesian statistics and modern harmonic analysis, we introduce an expectation maximization (EM) algorithm for image inpainting and interpolation. From a statistical point of view, the inpainting/interpolation can be viewed as an estimation problem with missing data. Toward this goal, we propose the idea of using the EM mechanism in a Bayesian framework, where a sparsity promoting prior penalty is imposed on the reconstructed coefficients. The EM framework gives a principled way to establish formally the idea that missing samples can be recovered/interpolated based on sparse representations. We first introduce an easy and efficient sparse-representation-based iterative algorithm for image inpainting. Additionally, we derive its theoretical convergence properties. Compared to its competitors, this algorithm allows a high degree of flexibility to recover different structural components in the image (piecewise smooth, curvilinear, texture, etc.). We also suggest some guidelines to automatically tune the regularization parameter.

The Effects of High Stakes High School Achievement Awards: Evidence from a Randomized Trial

Abstract: The Israeli matriculation certificate is a prerequisite for most postsecondary schooling. In a randomized trial, we attempted to increase certification rates among low-achievers with cash incentives. The experiment used a school-based randomization design offering awards to all who passed their exams in treated schools. This led to a substantial increase in certification rates for girls but had no effect on boys. Affected girls had a relatively high ex ante chance of certification. The increase in girls' matriculation rates translated into an increased likelihood of college attendance. Female matriculation rates increased partly because treated girls devoted extra time to exam preparation.

Effects of mycorrhizal fungi on insect herbivores: a meta-analysis.

Abstract: Mycorrhizal status of the host plant is often ignored in studies on plant-herbivore interactions, but mycorrhizal colonization is known to induce many morphological, physiological, and biochemical changes in host plants, which in turn may alter plant quality as a host for insect herbivores. Both positive and negative effects of mycorrhizal colonization of the host plant on performance and density of insect herbivores have been reported in previous studies. We have conducted a meta-analysis of 34 published and unpublished studies on this topic in order to find out the sources of variation in mycorrhizae effects on insect herbivores. Effects of mycorrhizae on chewing insects depended upon the parameter measured and the degree of herbivore feeding specialization. Density and consumption of chewing insects were higher on mycorrhizal plants, but this did not lead to greater plant damage, presumably because herbivore survival tended to be lower on mycorrhizal plants. Mono- and oligophagous chewers benefited from mycorrhizal colonization of their host plants, whereas performance of polyphagous chewers was reduced on mycorrhizal plants. Among sucking insects, phloem feeders benefited from mycorrhizal infection, but performance of mesophyll feeders was lower on mycorrhizal plants. The type of mycorrhiza was not important for chewing insects, but performance of sucking insects was increased more by arbuscular mycorrhizal fungi (AM) than by ectomycorrhizae (ECM). Among AM inoculation studies, the most commonly used fungal species, Glomus intraradices, tended to have a negative effect on chewer performance, whereas all other fungal species tended to have a positive effect. There was no significant difference in results between studies using inoculation and fungicides, field and laboratory studies, and published and unpublished studies. Mycorrhizal status of the host plant thus influences insect herbivore performance, but the magnitude and direction of the effect depend upon the feeding mode and diet breadth of the insect and the identity of fungi.

Addressing sustainable development through public procurement: the case of local government

Abstract: Purpose: While the contribution of supply chain management to sustainability is receiving increasing attention in the private sector, there is still a scarcity of parallel studies of public procurement. Hence the purpose of this paper is to explore the ways in which local government authorities in England use their procurement function to foster sustainable development. Design/methodology/approach: The paper uses an exploratory approach. Based on a review of the existing literature, qualitative research into leading local government authorities is undertaken to draw out the multiple ways in which public procurement can support sustainable development. Findings: At an aggregate level, local government procurers have adopted a wide range of initiatives to address all three aspects of sustainability. These are condensed into a typology of sustainable supply chain management for the public sector. Research limitations/implications: The study highlights the importance of supporting factors, like transparency, organisational culture and strategy as well as leeway in public policy, for sustainable supply chain management in the public sector. Practical implications: The experience of the best practice local authorities deserves wider recognition among practitioners, policy makers and academic researchers, not least given the objective of the UK government to be among the leaders in the European Union on sustainable procurement by 2009. Originality/value: The proposed typology of sustainable supply chain management for the public sector can serve as a basis for future research in this area.

Oceanic Nickel depletion and a methanogen famine before the Great Oxidation Event

Abstract: It has been suggested that a decrease in atmospheric methane levels triggered the progressive rise of atmospheric oxygen, the so-called Great Oxidation Event, about 2.4 Gyr ago(1). Oxidative weathering of terrestrial sulphides, increased oceanic sulphate, and the ecological success of sulphate-reducing microorganisms over methanogens has been proposed as a possible cause for the methane collapse(1), but this explanation is difficult to reconcile with the rock record(2,3). Banded iron formations preserve a history of Precambrian oceanic elemental abundance and can provide insights into our understanding of early microbial life and its influence on the evolution of the Earth system(4,5). Here we report a decline in the molar nickel to iron ratio recorded in banded iron formations about 2.7 Gyr ago, which we attribute to a reduced flux of nickel to the oceans, a consequence of cooling upper-mantle temperatures and decreased eruption of nickel-rich ultramafic rocks at the time. We measured nickel partition coefficients between simulated Precambrian sea water and diverse iron hydroxides, and subsequently determined that dissolved nickel concentrations may have reached similar to 400nM throughout much of the Archaean eon, but dropped below similar to 200nM by 2.5 Gyr ago and to modern day values(6) (similar to 9 nM) by similar to 550 Myr ago. Nickel is a key metal cofactor in several enzymes of methanogens(7) and we propose that its decline would have stifled their activity in the ancient oceans and disrupted the supply of biogenic methane. A decline in biogenic methane production therefore could have occurred before increasing environmental oxygenation and not necessarily be related to it. The enzymatic reliance of methanogens on a diminishing supply of volcanic nickel links mantle evolution to the redox state of the atmosphere.

Initial performance metrics of a new custom-designed ArF excimer LA-ICPMS system coupled to a two-volume laser-ablation cell

Abstract: A new custom-built excimer (193 nm) laser-ablation system with two-volume laser-ablation cell coupled to a quadrupole ICPMS is described, which combines rapid ( 10000 cps/ppm for mid-high m/z, 55 μm, 5 Hz). An application of reconstructing medieval Pb exposure highlights the need for rapid signal washout in unravelling strongly varying Pb peaks in well-preserved archaeological tooth enamel.

Long-lasting modulation of feature integration by transcranial magnetic stimulation

Abstract: The human brain analyzes a visual object first by basic feature detectors. On the objects way to a conscious percept, these features are integrated in subsequent stages of the visual hierarchy. The time course of this feature integration is largely unknown. To shed light on the temporal dynamics of feature integration, we applied transcranial magnetic stimulation (TMS) to a feature fusion paradigm. In feature fusion, two stimuli which differ in one feature are presented in rapid succession such that they are not perceived individually but as one single stimulus only. The fused percept is an integration of the features of both stimuli. Here, we show that TMS can modulate this integration for a surprisingly long period of time, even though the individual stimuli themselves are not consciously perceived. Hence, our results reveal a long-lasting integration process of unconscious feature traces.

Performance Pay and Teachers' Effort, Productivity and Grading Ethics

Abstract: This paper presents evidence about the effect of individual monetary incentives on English and math teachers in Israel. Teachers were rewarded with cash bonuses for improving their students' performance in high-school matriculation exams. The main identification strategy is based on measurement error in the assignment to treatment variable that produced a randomized treatment sample. The incentives led to significant improvements in test taking rates, conditional pass rates, and mean test scores. Improvements were mediated through changes in teaching methods, enhanced after-school teaching, and increased responsiveness to students' needs. No evidence was found of manipulation of test scores by teachers.

Measurement of the gamma gamma* --> pi0 transition form factor

Abstract: We study the reaction e+e- --> e+e-pi0 and measure the gamma gamma* --> pi0 transition form factor in the momentum transfer range from 4 to 40 GeV^2. The analysis is based on 442 fb^-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV.