Showing papers by "University of Sussex published in 2003"

Stable clustering, the halo model and non-linear cosmological power spectra

Abstract: We present the results of a large library of cosmological N-body simulations, using power-law initial spectra.

The Galaxy Luminosity Function and Luminosity Density at Redshift z = 0.1*

Abstract: Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS), we measure the galaxy luminosity density at z = 0.1 in five optical bandpasses corresponding to the SDSS bandpasses shifted to match their rest-frame shape at z = 0.1. We denote the bands 0.1u, 0.1g, 0.1r, 0.1i, 0.1z with λeff = (3216, 4240, 5595, 6792, 8111 A), respectively. To estimate the luminosity function, we use a maximum likelihood method that allows for a general form for the shape of the luminosity function, fits for simple luminosity and number evolution, incorporates the flux uncertainties, and accounts for the flux limits of the survey. We find luminosity densities at z = 0.1 expressed in absolute AB magnitudes in a Mpc3 to be (-14.10 ± 0.15, -15.18 ± 0.03, -15.90 ± 0.03, -16.24 ± 0.03, -16.56 ± 0.02) in (0.1u, 0.1g, 0.1r, 0.1i, 0.1z), respectively, for a cosmological model with Ω0 = 0.3, ΩΛ = 0.7, and h = 1 and using SDSS Petrosian magnitudes. Similar results are obtained using Sersic model magnitudes, suggesting that flux from outside the Petrosian apertures is not a major correction. In the 0.1r band, the best-fit Schechter function to our results has * = (1.49 ± 0.04) × 10-2 h3 Mpc-3, M* - 5 log10 h = -20.44 ± 0.01, and α = -1.05 ± 0.01. In solar luminosities, the luminosity density in 0.1r is (1.84 ± 0.04) × 108 h L0.1r,☉ Mpc-3. Our results in the 0.1g band are consistent with other estimates of the luminosity density, from the Two-Degree Field Galaxy Redshift Survey and the Millennium Galaxy Catalog. They represent a substantial change (~0.5 mag) from earlier SDSS luminosity density results based on commissioning data, almost entirely because of the inclusion of evolution in the luminosity function model.

Identification, Timing, and Signal Specificity of Pseudomonas aeruginosa Quorum-Controlled Genes: a Transcriptome Analysis

Abstract: There are two interrelated acyl-homoserine lactone quorum-sensing-signaling systems in Pseudomonas aeruginosa. These systems, the LasR-LasI system and the RhlR-RhlI system, are global regulators of gene expression. We performed a transcriptome analysis to identify quorum-sensing-controlled genes and to better understand quorum-sensing control of P. aeruginosa gene expression. We compared gene expression in a LasI-RhlI signal mutant grown with added signals to gene expression without added signals, and we compared a LasR-RhlR signal receptor mutant to its parent. In all, we identified 315 quorum-induced and 38 quorum-repressed genes, representing about 6% of the P. aeruginosa genome. The quorum-repressed genes were activated in the stationary phase in quorum-sensing mutants but were not activated in the parent strain. The analysis of quorum-induced genes suggests that the signal specificities are on a continuum and that the timing of gene expression is on a continuum (some genes are induced early in growth, most genes are induced at the transition from the logarithmic phase to the stationary phase, and some genes are induced during the stationary phase). In general, timing was not related to signal concentration. We suggest that the level of the signal receptor, LasR, is a critical trigger for quorum-activated gene expression. Acyl-homoserine lactone quorum sensing appears to be a system that allows ordered expression of hundreds of genes during P. aeruginosa growth in culture.

Catastrophe and impoverishment in paying for health care: with applications to Vietnam 1993–1998

Abstract: This paper presents and compares two threshold approaches to measuring the fairness of health care payments, one requiring that payments do not exceed a pre-specified proportion of pre-payment income, the other that they do not drive households into poverty. We develop indices for 'catastrophe' that capture the intensity of catastrophe as well as its incidence and also allow the analyst to capture the degree to which catastrophic payments occur disproportionately among poor households. Measures of poverty impact capturing both intensity and incidence are also developed. The arguments and methods are empirically illustrated with data on out-of-pocket payments from Vietnam in 1993 and 1998. This is not an uninteresting application given that 80% of health spending in that country was paid out-of-pocket in 1998. We find that the incidence and intensity of 'catastrophic' payments - both in terms of pre-payment income as well as ability to pay - were reduced between 1993 and 1998, and that both incidence and intensity of 'catastrophe' became less concentrated among the poor. We also find that the incidence and intensity of the poverty impact of out-of-pocket payments diminished over the period in question. Finally, we find that the poverty impact of out-of-pocket payments is primarily due to poor people becoming even poorer rather than the non-poor being made poor, and that it was not expenses associated with inpatient care that increased poverty but rather non-hospital expenditures.

The first data release of the sloan digital sky survey

Abstract: The Sloan Digital Sky Survey (SDSS) has validated and made publicly available its First Data Release. This consists of 2099 deg2 of five-band (u, g, r, i, z) imaging data, 186,240 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 1360 deg2 of this area, and tables of measured parameters from these data. The imaging data go to a depth of r ≈ 22.6 and are photometrically and astrometrically calibrated to 2% rms and 100 mas rms per coordinate, respectively. The spectra cover the range 3800–9200 A, with a resolution of 1800–2100. This paper describes the characteristics of the data with emphasis on improvements since the release of commissioning data (the SDSS Early Data Release) and serves as a pointer to extensive published and on-line documentation of the survey.

A splicing mutation affecting expression of ataxia–telangiectasia and Rad3–related protein (ATR) results in Seckel syndrome

Abstract: Seckel syndrome (OMIM 210600) is an autosomal recessive disorder characterized by intrauterine growth retardation, dwarfism, microcephaly and mental retardation. Clinically, Seckel syndrome shares features in common with disorders involving impaired DNA-damage responses, such as Nijmegen breakage syndrome (OMIM 251260) and LIG4 syndrome (OMIM 606593). We previously mapped a locus associated with Seckel syndrome to chromosome 3q22.1–q24 in two consanguineous Pakistani families1. Further marker analysis in the families, including a recently born unaffected child with a recombination in the critical region, narrowed the region to an interval of 5 Mbp between markers D3S1316 and D3S1557 (145.29 Mbp and 150.37 Mbp). The gene encoding ataxia–telangiectasia and Rad3–related protein (ATR) maps to this region2,3. A fibroblast cell line derived from an affected individual displays a defective DNA damage response caused by impaired ATR function. We identified a synonymous mutation in affected individuals that alters ATR splicing. The mutation confers a phenotype including marked microcephaly (head circumference 12 s.d. below the mean) and dwarfism (5 s.d. below the mean). Our analysis shows that UV-induced ATR activation can occur in non-replicating cells following processing by nucleotide excision repair.

The Broadband Optical Properties of Galaxies with Redshifts 0.02 < z < 0.22

Abstract: Using photometry and spectroscopy of 183,487 galaxies from the Sloan Digital Sky Survey, we present bivariate distributions of pairs of seven galaxy properties: four optical colors, surface brightness, radial profile shape as measured by the Sersic index, and absolute magnitude. In addition, we present the dependence of local galaxy density (smoothed on 8 h � 1 Mpc scales) on all of these properties. Several classic, well-known relations among galaxy properties are evident at extremely high signal-to-noise ratio: the color- color relations of galaxies, the color-magnitude relations, the magnitude-surface brightness relation, and the dependence of density on color and absolute magnitude. We show that most of the i-band luminosity density in the universe is in the absolute magnitude and surface brightness ranges used: � 23:5 < M0:1i < � 17:0 mag and 17 < l0:1i < 24 mag in 1 arcsec 2 (the notation z b represents the b band shifted blueward by a factor ð1 þ zÞ). Some of the relationships between parameters, in particular the color-magnitude relations, show stronger correlations for exponential galaxies and concentrated galaxies taken separately than for all galaxies taken together. We provide a simple set of fits of the dependence of galaxy properties on luminosity for these two sets of galaxies and other quantitative details of our results. Subject headings: galaxies: fundamental parameters — galaxies: photometry — galaxies: statistics On-line material: ASCII parameter files, color figure, FITS files 1. MOTIVATION There are strong correlations among the measurable physical properties of galaxies. The classification of galaxies along the visual morphological sequence described by Hubble (1936) correlates well with the dominance of their central bulge, their surface brightnesses, and their colors. These properties also correlate with other properties, such as metallicity, emission-line strength, luminosity in visual bands, neutral gas content, and the winding angle of the spiral structure (for a review, see Roberts & Haynes 1994). The surface brightnesses of giant galaxies classified morpho- logically as elliptical are known to be strongly correlated with their sizes (Kormendy 1977; Kormendy & Djorgovski 1989). Galaxy colors (at least of morphologically elliptical galaxies) are known to be strongly correlated with galaxy luminosity (Baum 1959; Faber 1973; Visvanathan & Sandage 1977; Terlevich et al. 2001). The gravitational mass of a galaxy is closely related to the luminosity and other galaxy properties. These galaxy relations manifest them-

Animal colour vision — behavioural tests and physiological concepts

Abstract: Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detection are colour blind. Having established the existence of colour vision, research focussed on the question of how many spectral types of photoreceptors are involved. Recently, data on photoreceptor spectral sensitivities have been combined with behavioural experiments and physiological models to study systematically the next logical question: 'what neural interactions underlie colour vision?' This review gives an overview of the methods used to study animal colour vision, and discusses how quantitative modelling can suggest how photoreceptor signals are combined and compared to allow for the discrimination of biologically relevant stimuli.

Enticing People to Interact with Large Public Displays in Public Spaces.

Abstract: Large displays are increasingly being placed in public places to support community and social activities. However, a major problem that has been observed with this new form of public interaction is the resistance by the public to participate. A main reason is due to the prominence of the affective aspect of the user experience. In particular, feelings of social embarrassment often act as a barrier. Our paper is concerned with understanding why this is the case and considering how we can attempt to overcome these aspects through improving the design of public interaction. Our focus is on how groups of people socialize around large public displays, the way they move towards them, congregate around them and change from being onlookers to participants and back again. We describe a system – the Opinionizer – which we designed and placed in two authentic social gatherings, intended to encourage socializing and interaction. We present our findings in terms of the patterns of physical and social engagement that take place around it. We then present a model of public interaction flow, which we use as the basis from which to provide design recommendations for encouraging public participation.

How Clonal Is Staphylococcus aureus

Abstract: Staphylococcus aureus is an important human pathogen and represents a growing public health burden owing to the emergence and spread of antibiotic-resistant clones, particularly within the hospital environment. Despite this, basic questions about the evolution and population biology of the species, particularly with regard to the extent and impact of homologous recombination, remain unanswered. We address these issues through an analysis of sequence data obtained from the characterization by multilocus sequence typing (MLST) of 334 isolates of S. aureus, recovered from a well-defined population, over a limited time span. We find no significant differences in the distribution of multilocus genotypes between strains isolated from carriers and those from patients with invasive disease; there is, therefore, no evidence from MLST data, which index variation within the stable “core” genome, for the existence of hypervirulent clones of this pathogen. Examination of the sequence changes at MLST loci during clonal diversification shows that point mutations give rise to new alleles at least 15-fold more frequently than does recombination. This contrasts with the naturally transformable species Neisseria meningitidis and Streptococcus pneumoniae, in which alleles change between 5- and 10-fold more frequently by recombination than by mutation. However, phylogenetic analysis suggests that homologous recombination does contribute toward the evolution of this species over the long term. Finally, we note a striking excess of nonsynonymous substitutions in comparisons between isolates belonging to the same clonal complex compared to isolates belonging to different clonal complexes, suggesting that the removal of deleterious mutations by purifying selection may be relatively slow.

A requirement for PARP‐1 for the assembly or stability of XRCC1 nuclear foci at sites of oxidative DNA damage

Abstract: The molecular role of poly (ADP-ribose) polymerase-1 in DNA repair is unclear. Here, we show that the single-strand break repair protein XRCC1 is rapidly assembled into discrete nuclear foci after oxidative DNA damage at sites of poly (ADP-ribose) synthesis. Poly (ADP-ribose) synthesis peaks during a 10 min treatment with H2O2 and the appearance of XRCC1 foci peaks shortly afterwards. Both sites of poly (ADP-ribose) and XRCC1 foci decrease to background levels during subsequent incubation in drug-free medium, consistent with the rapidity of the single-strand break repair process. The formation of XRCC1 foci at sites of poly (ADP-ribose) was greatly reduced by mutation of the XRCC1 BRCT I domain that physically interacts with PARP-1. Moreover, we failed to detect XRCC1 foci in Adprt1?/? MEFs after treatment with H2O2. These data demonstrate that PARP-1 is required for the assembly or stability of XRCC1 nuclear foci after oxidative DNA damage and suggest that the formation of these foci is mediated via interaction with poly (ADP-ribose). These results support a model in which the rapid activation of PARP-1 at sites of DNA strand breakage facilitates DNA repair by recruiting the molecular scaffold protein, XRCC1.

An efficient targeting strategy for multiobject spectrograph surveys: The Sloan digital sky survey "tiling" algorithm

Abstract: Large surveys using multiobject spectrographs require automated methods for deciding how to efficiently point observations and how to assign targets to each pointing. The Sloan Digital Sky Survey (SDSS) will observe around 10 6 spectra from targets distributed over an area of about 10,000 deg 2 , using a multiobject fiber spectrograph that can simultaneously observe 640 objects in a circular field of view (referred to as a ‘‘ tile ’’) 1=49 in radius. No two fibers can be placed closer than 55 00 during the same observation; multiple targets closer than this distance are said to ‘‘ collide.’’ We present here a method of allocating fibers to desired targets given a set of tile centers that includes the effects of collisions and that is nearly optimally efficient and uniform. Because of large-scale structure in the galaxy distribution (which form the bulk of the SDSS targets), a naive covering of the sky with equally spaced tiles does not yield uniform sampling. Thus, we present a heuristic for perturbing the centers of the tiles from the equally spaced distribution that provides more uniform completeness. For the SDSS sample, we can attain a sampling rate of greater than 92% for all targets, and greater than 99% for the set of targets that do not collide with each other, with an efficiency greater than 90% (defined as the fraction of available fibers assigned to targets). The methods used here may prove useful to those planning other large surveys.

How long before the end of inflation were observable perturbations produced

Abstract: We reconsider the issue of the number of e-foldings before the end of inflation at which observable perturbations were generated. We determine a plausible upper limit on that number for the standard cosmology which is around 60, with the expectation that the actual value will be up to 10 below this. We also note a special property of the $\ensuremath{\lambda}{\ensuremath{\varphi}}^{4}$ model which reduces the uncertainties in that case and favors a higher value, giving a fairly definite prediction of 64 e-foldings for that model. We note an extreme (and highly implausible) situation where the number of e-foldings can be even higher, possibly up to 100, and discuss the shortcomings of quantifying inflation by e-foldings rather than by the change in $\mathrm{aH}.$ Finally, we discuss the impact of nonstandard evolution between the end of inflation and the present, showing that again the expected number of e-foldings can be modified, and in some cases significantly increased.

The Semantics of English Prepositions: Spatial Scenes, Embodied Meaning, and Cognition

Abstract: Using a cognitive linguistics perspective, this book provides a comprehensive, theoretical analysis of the semantics of English prepositions. All English prepositions originally coded spatial relations between two physical entities; while retaining their original meaning, prepositions have also developed a rich set of non-spatial meanings. In this study, Tyler and Evans argue that all these meanings are systematically grounded in the nature of human spatio-physical experience. The original 'spatial scenes' provide the foundation for the extension of meaning from the spatial to the more abstract. This analysis articulates an alternative methodology that distinguishes between a conventional meaning and an interpretation produced for understanding the preposition in context, as well as establishing which of several competing senses should be taken as the primary sense. Together, the methodology and framework are sufficiently articulated to generate testable predictions and allow the analysis to be applied to additional prepositions.

The dissociation of word reading and text comprehension: Evidence from component skills

Abstract: In this paper, we discuss the relative contribution of several theoretically relevant skills and abilities in accounting for variance in both word reading and text comprehension. We present data from the first and second waves of a longitudinal study, when the children were 7 to 8 years, and 8 to 9 years old. In multiple regression analyses, we show that there is a dissociation between the skills and abilities that account for variance in word reading, and those that account for variance in text comprehension. The pattern of results is very similar at both time points. Significant variance in comprehension skill is accounted for by measures of text integration, metacognitive monitoring, and working memory. By contrast, these measures do not account for variance in word reading ability, which was best accounted for by a phoneme deletion task. The implications of these findings for our understanding of the development of reading ability, children’s problems in text comprehension and for remediation will be discussed.

The modern molecular clock.

Abstract: The discovery of the molecular clock — a relatively constant rate of molecular evolution — provided an insight into the mechanisms of molecular evolution, and created one of the most useful new tools in biology. The unexpected constancy of rate was explained by assuming that most changes to genes are effectively neutral. Theory predicts several sources of variation in the rate of molecular evolution. However, even an approximate clock allows time estimates of events in evolutionary history, which provides a method for testing a wide range of biological hypotheses ranging from the origins of the animal kingdom to the emergence of new viral epidemics.

University Research Evaluation and Funding: An International Comparison

Abstract: Many countries have introducedevaluations of university research, reflectingglobal demands for greater accountability. Thispaper compares methods of evaluation usedacross twelve countries in Europe and theAsia-Pacific region. On the basis of thiscomparison, and focusing in particular onBritain, we examine the advantages anddisadvantages of performance-based funding incomparison with other approaches to funding.Our analysis suggests that, while initialbenefits may outweigh the costs, over time sucha system seems to produce diminishing returns.This raises important questions about itscontinued use.

Structure and energetics of the vacancy in graphite

Abstract: We determine properties of the vacancy in graphite from first principles calculations. The ground-state structure is associated with a formation energy of 7.4 eV and arises through a combination of symmetric relaxation and symmetry-breaking Jahn-Teller distortion to one of three degenerate, symmetry-related structures. The distortion results in a weak reconstructed bond and small out-of-plane atomic displacements. Dynamic switching between degenerate structures is activated by a barrier of 0.1 eV and we interpret scanning tunneling microscopy observations on the basis of thermal averaging between structures. The calculated migration energy of 1.7 eV is lower than that widely accepted from experiment, and we propose that the discrepancy is explained by a revised picture of trapping during vacancy transport, dependent on concentration. We discuss the significance of these findings in understanding defect behavior in irradiated graphite and related graphitic materials, in particular single-walled nanotubes.

International student migration and the European ‘Year Abroad’: effects on European identity and subsequent migration behaviour

Abstract: This paper first draws attention to the scant literature in population geography on international student migration, or ISM. Yet students comprise an important element in global and European population mobility, especially of highly skilled movements. This study is set within the context of intra-European ISM and looks specifically at the ‘Year Abroad experience’ which has been subsidised over the past 15 years by the Erasmus and Socrates programmes. Empirical data come from questionnaire surveys to three groups of University of Sussex students, surveyed during 2000–01. The main survey was a large postal survey to graduates who had spent a year abroad (YA) in another European country as part of their Sussex degree. This questionnaire was designed to test two sets of hypotheses: firstly that the YA had given students/graduates a more ‘European’ identity or consciousness, and a greater insight into European issues; and secondly that YA graduates would be more likely to pursue their subsequent career/migration paths in continental Europe. These hypotheses were tested against a control sample of Sussex graduates who had not been on a YA, matched by degree type and time of graduation. A third sample was undertaken with second-year undergraduate students about to embark on their YA, in order to test pre- and post-YA perspectives. The results broadly confirm the research hypotheses, although with a variety of nuances and outcomes. Copyright © 2003 John Wiley & Sons, Ltd.

The σ70 family of sigma factors

Abstract: Members of the sigma70 family of sigma factors are components of the RNA polymerase holoenzyme that direct bacterial or plastid core RNA polymerase to specific promoter elements that are situated 10 and 35 base-pairs upstream of transcription-initiation points. Members of the sigma70 family also function as contact points for some activator proteins, such as PhoB and lambda(cl), and play a role in the initiation process itself. The primary sigma factor, which is essential for general transcription in exponentially growing cells, is reversibly associated with RNA polymerase and can be replaced by alternative sigma factors that co-ordinately express genes involved in diverse functions, such as stress responses, morphological development and iron uptake. On the basis of gene structure and function, members of the sigma70 family can broadly be divided into four main groups. Sequence alignments of the sigma70 family members reveal that they have four conserved regions, although the highest conservation is found in regions 2 and 4, which are involved in binding to RNA polymerase, recognizing promoters and separating DNA strands (so-called 'DNA melting'). The division of the linear sequence of sigma70 factors into four regions is largely supported by recent structural data indicating that primary sigma factors have three stable domains that incorporate regions 2, 3 and 4. Furthermore, structures of the RNA polymerase holoenzyme have revealed that these domains of sigma70 are spread out across one face of RNA polymerase. These structural data are starting to illuminate the mechanistic role of sigma factors in transcription initiation.

Decentralisation and poverty reduction in Africa: the politics of local–central relations

Abstract: Decentralisation advocates argue that decentralised governments are more responsive to the needs of the poor than central governments and thus are more likely to conceive and implement pro-poor policies. Recent evidence from a selected group of sub-Saharan African countries is reviewed in a comparative framework that highlights factors associated with success in poverty reduction. It is argued that the degree of responsiveness to the poor and the extent to which there is an impact on poverty are determined primarily by the politics of local–central relations and the general regime context—particularly the ideological commitment of central political authorities to poverty reduction. In most of the cases, ‘elite capture’ of local power structures has been facilitated by the desire of ruling elites to create and sustain power bases in the countryside. Popular perceptions of the logic of patronage politics, combined with weak accountability mechanisms, have reinforced this outcome. The conclusion from these African cases is that decentralisation has not empowered challenges to local elites who are resistant or indifferent to pro-poor policies. Thus, decentralisation is unlikely to lead to more pro-poor outcomes without a serious effort to strengthen and broaden accountability mechanisms at both local and national levels. Copyright © 2003 John Wiley & Sons, Ltd.

Policy discourses on women's land rights in sub-Saharan Africa: the implications of the re-turn to the customary.

Abstract: This article examines some contemporary policy discourses on land tenure reform in sub–Saharan Africa and their implications for women's interests in land. It demonstrates an emerging consensus among a range of influential policy institutions, lawyers and academics about the potential of so–called customary systems of land tenure to meet the needs of all land users and claimants. This consensus, which has arisen out of critiques of past attempts at land titling and registration, particularly in Kenya, is rooted in modernizing discourses and/or evolutionary theories of land tenure and embraces particular and contested understandings of customary law and legal pluralism. It has also fed into a wide–ranging critique of the failures of the post–colonial state in Africa, which has been important in the current retreat of the state under structural adjustment programmes. African women lawyers, a minority dissenting voice, are much more equivocal about trusting the customary, preferring instead to look to the State for laws to protect women's interests. We agree that there are considerable problems with so–called customary systems of land tenure and administration for achieving gender justice with respect to women's land claims. Insufficient attention is being paid to power relations in the countryside and their implications for social groups, such as women, who are not well positioned and represented in local level power structures. But considerable changes to political and legal practices and cultures will be needed before African states can begin to deliver gender justice with respect to land.

Diet of wild boar Sus scrofa in Western Europe, with particular reference to consumption of agricultural crops

Abstract: The diet of wild boar Sus scrofa in Western Europe is reviewed, paying particular attention to the consumption of agricultural crops and the implications of this from the point of view of crop damage. Data were taken mainly from 11 studies that provide quantitative informa- tion about the consumption of different food types, but we also list all the foods reported as being eaten by wild boar in a total of 21 studies. 2. Vegetable foods occurred more frequently in the diet than animal foods, and also consti- tuted the bulk of the food ingested. Overall, there were four major vegetable food categories: mast, roots, green plant matter and agricultural crops. Depending on the study area, wild boar always consumed at least one energy-rich plant food such as acorns, beechnuts, chest- nuts, pine seeds, olives, cereal grains or other crops. The number and types of agricultural crops consumed varied between study areas but crops represent an important component of wild boar diet throughout its Western European range. Among animal foods, insects, earthworms, birds and mammals were eaten most consistently but the diet also included amphibians, reptiles, gastropods and myriapods. 3. Seasonal, interannual and regional differences in the diet, together with its striking overall breadth, indicate that wild boar are opportunistic omnivores whose diet, in any particular instance, is largely determined by the relative availability of different food types. Dependence on energy-rich plant material as a major component of the diet, coupled with large body size and a propensity to trample crops as well as consume them, means that wild boar cause significant agricultural damage.

Ultraviolet modifications of dispersion relations in effective field theory

Abstract: The existence of a fundamental ultraviolet scale, such as the Planck scale, may lead to modifications of the dispersion relations for particles at high energies in some scenarios of quantum gravity. We apply effective field theory to this problem and identify dimension-5 operators that do not mix with dimensions 3 and 4 and lead to cubic modifications of dispersion relations for scalars, fermions, and vector particles. Further we show that, for electrons, photons and light quarks, clock comparison experiments bound these operators at ${10}^{\ensuremath{-}5}/{M}_{\mathrm{P}\mathrm{l}}$.

Group decision-making in animals

Abstract: Groups of animals often need to make communal decisions, for example about which activities to perform, when to perform them and which direction to travel in; however, little is known about how they do so. Here, we model the fitness consequences of two possible decision-making mechanisms: 'despotism' and 'democracy'. We show that under most conditions, the costs to subordinate group members, and to the group as a whole, are considerably higher for despotic than for democratic decisions. Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large. Democratic decisions are more beneficial primarily because they tend to produce less extreme decisions, rather than because each individual has an influence on the decision per se. Our model suggests that democracy should be widespread and makes quantitative, testable predictions about group decision-making in non-humans.