Showing papers by "University of Sussex published in 2005"

Simulations of the formation, evolution and clustering of galaxies and quasars

Abstract: The cold dark matter model has become the leading theoretical picture for the formation of structure in the Universe. This model, together with the theory of cosmic inflation, makes a clear prediction for the initial conditions for structure formation and predicts that structures grow hierarchically through gravitational instability. Testing this model requires that the precise measurements delivered by galaxy surveys can be compared to robust and equally precise theoretical calculations. Here we present a simulation of the growth of dark matter structure using 2,1603 particles, following them from redshift z = 127 to the present in a cube-shaped region 2.230 billion lightyears on a side. In postprocessing, we also follow the formation and evolution of the galaxies and quasars. We show that baryon-induced features in the initial conditions of the Universe are reflected in distorted form in the low-redshift galaxy distribution, an effect that can be used to constrain the nature of dark energy with future generations of observational surveys of galaxies.

The general self-efficacy scale: multicultural validation studies.

Abstract: General self-efficacy is the belief in one's competence to cope with a broad range of stressful or challenging demands, whereas specific self-efficacy is constrained to a particular task at hand. Relations between general self-efficacy and social cognitive variables (intention, implementation intentions, outcome expectancies, and self-regulation), behavior-specific self-efficacy, health behaviors, well-being, and coping strategies were examined among 1,933 respondents in 3 countries: Germany (n = 633), Poland (n = 359), and South Korea (n = 941). Participants were between 16 and 86 years old, and some were dealing with stressful situations such as recovery from myocardial events or tumor surgery. Perceived self-efficacy was measured by means of the General Self-Efficacy Scale (R. Schwarzer & M. Jerusalem, 1995). Meta-analysis was used to determine population effect sizes for four sets of variables. Across countries and samples, there is consistent evidence for associations between perceived self-efficacy and the variables under study confirming the validity of the psychometric scale. General self-efficacy appears to be a universal construct that yields meaningful relations with other psychological constructs.

Gender Equality and Women’s Empowerment: A Critical Analysis of the Third Millennium Development Goal

Abstract: This article discusses the third Millennium Development Goal (MDG), on gender equality and women's empowerment. It explores the concept of women's empowerment and highlights ways in which the indicators associated with this Goal – on education, employment, and political participation – can contribute to it.

An integrative theory of intergroup contact

Abstract: Publisher Summary This chapter begins with a re-presentation of Allport's classic hypothesis and shows—with reference to recent cross-sectional and longitudinal surveys— laboratory experiments, and meta-analysis, that many of his original propositions have capably withstood the test of time. It examines Brewer and Miller's, and Gaertner and Dovidio's attempts to extend the contact hypothesis, in both of which categorization processes play a key role. This approach sets the stage for the model, first published in 1986 by Hewstone and Brown. In that model, emphasis was given on identifying the conditions that would allow the generalization of attitudes and behavior change beyond the specific context in which the contact occurs. The chapter discusses the developments of contact theory that occurred in the 1980s and reviews the empirical research instigated by the Hewstone–Brown model. It also reviews the progress to date and attempts a theoretical integration of these models in the light of the large volume of research that they have stimulated.

Cosmological parameter analysis including SDSS Lyα forest and galaxy bias: Constraints on the primordial spectrum of fluctuations, neutrino mass, and dark energy

Abstract: We combine the constraints from the recent Ly$\ensuremath{\alpha}$ forest analysis of the Sloan Digital Sky Survey (SDSS) and the SDSS galaxy bias analysis with previous constraints from SDSS galaxy clustering, the latest supernovae, and 1st year WMAP cosmic microwave background anisotropies. We find significant improvements on all of the cosmological parameters compared to previous constraints, which highlights the importance of combining Ly$\ensuremath{\alpha}$ forest constraints with other probes. Combining WMAP and the Ly$\ensuremath{\alpha}$ forest we find for the primordial slope ${n}_{s}=0.98\ifmmode\pm\else\textpm\fi{}0.02$. We see no evidence of running, $dn/d\mathrm{ln} k=\ensuremath{-}0.003\ifmmode\pm\else\textpm\fi{}0.010$, a factor of $3$ improvement over previous constraints. We also find no evidence of tensors, $rl0.36$ ($95%$ c.l.). Inflationary models predict the absence of running and many among them satisfy these constraints, particularly negative curvature models such as those based on spontaneous symmetry breaking. A positive correlation between tensors and primordial slope disfavors chaotic inflation-type models with steep slopes: while the $V\ensuremath{\propto}{\ensuremath{\phi}}^{2}$ model is within the 2-sigma contour, $V\ensuremath{\propto}{\ensuremath{\phi}}^{4}$ is outside the 3-sigma contour. For the amplitude we find ${\ensuremath{\sigma}}_{8}=0.90\ifmmode\pm\else\textpm\fi{}0.03$ from the Ly$\ensuremath{\alpha}$ forest and WMAP alone. We find no evidence of neutrino mass: for the case of $3$ massive neutrino families with an inflationary prior, $\ensuremath{\sum}_{}^{}{m}_{\ensuremath{ u}}l0.42$ eV and the mass of lightest neutrino is ${m}_{1}l0.13$ eV at $95%$ c.l. For the 3 massless $+1$ massive neutrino case we find ${m}_{\ensuremath{ u}}l0.79$ eV for the massive neutrino, excluding at $95%$ c.l. all neutrino mass solutions compatible with the LSND results. We explore dark energy constraints in models with a fairly general time dependence of dark energy equation of state, finding ${\ensuremath{\Omega}}_{\ensuremath{\lambda}}=0.72\ifmmode\pm\else\textpm\fi{}0.02$, $\mathrm{w}(z=0.3)=\ensuremath{-}{0.98}_{\ensuremath{-}0.12}^{+0.10}$, the latter changing to $\mathrm{w}(z=0.3)=\ensuremath{-}{0.92}_{\ensuremath{-}0.10}^{+0.09}$ if tensors are allowed. We find no evidence for variation of the equation of state with redshift, $\mathrm{w}(z=1)=\ensuremath{-}{1.03}_{\ensuremath{-}0.28}^{+0.21}$. These results rely on the current understanding of the Ly$\ensuremath{\alpha}$ forest and other probes, which need to be explored further both observationally and theoretically, but extensive tests reveal no evidence of inconsistency among different data sets used here.

The Luminosity and Color Dependence of the Galaxy Correlation Function

Abstract: Westudytheluminosityandcolordependenceofthegalaxytwo-pointcorrelationfunctionintheSloanDigitalSky Survey, starting from a sample of � 200,000 galaxies over 2500 deg 2 . We concentrate our analysis on volume-limited subsamples of specified luminosity ranges, for which we measure the projected correlation function wp(rp), which is directly related to the real-space correlation function � (r). The amplitude of wp(rp) rises continuously with luminosity from Mr �� 17: 5t oMr �� 22:5, with the most rapid increase occurring above the characteristic luminosity L� (Mr �� 20:5). Over the scales 0:1 h � 1 Mpc � 22 can be approximated, imperfectly, by power-law three-dimensional correlation functions � (r) ¼ (r/r0) � � with � � 1:8 and r0(L� ) � 5:0 h � 1 Mpc. The brightest subsample, � 23 < Mr < � 22, has a significantly steeper � (r). When we divide samples by color, redder galaxies exhibit a higher amplitude and steeper correlation function at all luminosities. The correlation amplitude of blue galaxies increases continuously with luminosity, but the luminosity dependence for red galaxies is less regular, with bright red galaxies exhibiting the strongest clustering at large scales and faint red galaxies exhibiting the strongest clustering at small scales. We interpret these results using halo occupation distribution (HOD) models assuming concordance cosmological parameters. For most samples, an HOD model with two adjustable parameters fits the wp(rp) data better than a power law, explaining inflections at rp � 1 3 h � 1 Mpc as the transition between the one-halo and two-halo regimes of � (r). The implied minimum mass for a halo hosting a central galaxy more luminous than L grows steadily, with Mmin / L at low luminosities and a steeper dependence above L� . The mass at which a halo has, on average, one satellite galaxy brighter than L is M1 � 23Mmin(L), at all luminosities. These results imply a conditional luminosity function (at fixed halo mass) in which central galaxies lie far above a Schechter function extrapolation of the satellite population. The HOD model fits nicely explain the color dependence of wp(rp) and the cross correlation between red and blue galaxies. For galaxies with Mr < � 21, halos slightly above Mmin have blue central galaxies, while more massive halos have red central galaxies and predominantly red satellite populations. The fraction of blue central galaxies increases steadily with decreasing luminosity and host halo mass. The strong clustering offaint red galaxies follows from the fact that nearly all of them are satellite systems in high-mass halos. The HOD fitting results are in good qualitative agreement with the predictions of numerical and semianalytic models of galaxy formation. Subject headingg cosmology: observations — cosmology: theory — galaxies: distances and redshifts — galaxies: halos — galaxies: statistics — large-scale structure of universe

Consensus decision making in animals

Abstract: Individual animals routinely face decisions that are crucial to their fitness. In social species, however, many of these decisions need to be made jointly with other group members because the group will split apart unless a consensus is reached. Here, we review empirical and theoretical studies of consensus decision making, and place them in a coherent framework. In particular, we classify consensus decisions according to the degree to which they involve conflict of interest between group members, and whether they involve either local or global communication; we ask, for different categories of consensus decision, who makes the decision, what are the underlying mechanisms, and what are the functional consequences. We conclude that consensus decision making is common in non-human animals, and that cooperation between group members in the decision-making process is likely to be the norm, even when the decision involves significant conflict of interest.

The Third Data Release of the Sloan Digital Sky Survey

Abstract: This paper describes the Third Data Release of the Sloan Digital Sky Survey (SDSS). This release, containing data taken up through 2003 June, includes imaging data in five bands over 5282 deg2, photometric and astrometric catalogs of the 141 million objects detected in these imaging data, and spectra of 528,640 objects selected over 4188 deg2. The pipelines analyzing both images and spectroscopy are unchanged from those used in our Second Data Release.

Analysis of electromagnetic performance of flux-switching permanent-magnet Machines by nonlinear adaptive lumped parameter magnetic circuit model

Abstract: A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed.

The design of coiled-coil structures and assemblies

Abstract: Protein design allows sequence-to-structure relationships in proteins to be examined and, potentially, new protein structures and functions to be made to order. To succeed, however, the protein-design process requires reliable rules that link protein sequence to structure?function. Although our present understanding of coiled-coil folding and assembly is not complete, through numerous bioinformatics and experimental studies there are now sufficient rules to allow confident design attempts of naturally observed and even novel coiled-coil motifs. This review summarizes the current design rules for coiled coils, and describes some of the key successful coiled-coil designs that have been created to date. The designs range from those for relatively straightforward, naturally observed structures-including parallel and antiparallel dimers, trimers and tetramers, all of which have been made as homomers and heteromers-to more exotic structures that expand the repertoire of Nature's coiled-coil structures. Examples in the second bracket include a probe that binds a cancer-associated coiled-coil protein; a tetramer with a right-handed supercoil; sticky-ended coiled coils that self-assemble to form fibers; coiled coils that switch conformational state; a three-component two-stranded coiled coil; and an antiparallel dimer that directs fragment complementation of larger proteins. Some of the more recent examples show an important development in the field; namely, new designs are being created with function as well as structure in mind. This will remain one of the key challenges in coiled-coil design in the next few years. Other challenges that lie ahead include the need to discover more rules for coiled-coil prediction and design, and to implement these in prediction and design algorithms. The considerable success of coiled-coil design so far bodes well for this, however. It is likely that these challenges will be met and surpassed.

Autopoiesis, adaptivity, teleology, agency

Abstract: A proposal for the biological grounding of intrinsic teleology and sense-making through the theory of autopoiesis is critically evaluated. Autopoiesis provides a systemic language for speaking about intrinsic teleology but its original formulation needs to be elaborated further in order to explain sense-making. This is done by introducing adaptivity, a many-layered property that allows organisms to regulate themselves with respect to their conditions of viability. Adaptivity leads to more articulated concepts of behaviour, agency, sense- construction, health, and temporality than those given so far by autopoiesis and enaction. These and other implications for understanding the organismic generation of values are explored.

Using Emoticons to Reduce Dependency in Machine Learning Techniques for Sentiment Classification

Abstract: Sentiment Classification seeks to identify a piece of text according to its author's general feeling toward their subject, be it positive or negative. Traditional machine learning techniques have been applied to this problem with reasonable success, but they have been shown to work well only when there is a good match between the training and test data with respect to topic. This paper demonstrates that match with respect to domain and time is also important, and presents preliminary experiments with training data labeled with emoticons, which has the potential of being independent of domain, topic and time.

The Properties and luminosity function of extremely low luminosity galaxies

Abstract: We examine a sample of low-redshift (10 h-1 Mpc -18. The resulting slope at low luminosities in this sample is α2 ~ -1.3. However, we almost certainly miss a large number of galaxies at very low luminosities due to low surface brightness selection effects, and we estimate that the true low-luminosity slope may be as steep as or steeper than α2 ~ -1.5. The results here are consistent with previous SDSS results and, in the g band, roughly consistent with the results of the Two Degree Field Galaxy Redshift Survey. Extremely low luminosity galaxies are predominantly low surface brightness, exponential disks, the majority of which are red.

Compulsive buying--a growing concern? An examination of gender, age, and endorsement of materialistic values as predictors.

Abstract: Compulsive buying is an understudied, but growing, dysfunctional consumer behaviour with harmful psychological and financial consequences. Clinical perspectives treat it as a psychiatric disorder, whereas recent proposals emphasize the increasing endorsement of materialistic values as a cause of uncontrolled buying (e.g. Dittmar, 2004b; Kasser & Kanner, 2004). The present research aims to improve understanding of compulsive buying through examining gender, age, and endorsement of materialistic values as key predictors in three UK questionnaire studies, which sampled individuals who had contacted a self-help organization and residentially matched 'controls' (N = 330), consumer panelists from a multinational corporation (N = 250), and 16- to 18-year-old adolescents (N = 195). The results confirmed previously documented gender differences, and showed that younger people are more prone to compulsive buying. The central findings were that materialistic value endorsement emerged as the strongest predictor of individuals' compulsive buying, and that it significantly mediated the observed age differences.

Structures for amyloid fibrils.

Abstract: Alzheimer's disease and Creutzfeldt-Jakob disease are the best-known examples of a group of diseases known as the amyloidoses. They are characterized by the extracellular deposition of toxic, insoluble amyloid fibrils. Knowledge of the structure of these fibrils is essential for understanding the process of pathology of the amyloidoses and for the rational design of drugs to inhibit or reverse amyloid formation. Structural models have been built using information from a wide variety of techniques, including X-ray diffraction, electron microscopy, solid state NMR and EPR. Recent advances have been made in understanding the architecture of the amyloid fibril. Here, we describe and compare postulated structural models for the mature amyloid fibril and discuss how the ordered structure of amyloid contributes to its stability.

The life and death of DNA-PK

Abstract: Double-strand breaks (DSBs) arise endogenously during normal cellular processes and exogenously by genotoxic agents such as ionizing radiation (IR). DSBs are one of the most severe types of DNA damage, which if left unrepaired are lethal to the cell. Several different DNA repair pathways combat DSBs, with nonhomologous end-joining (NHEJ) being one of the most important in mammalian cells. Competent NHEJ catalyses repair of DSBs by joining together and ligating two free DNA ends of little homology (microhomology) or DNA ends of no homology. The core components of mammalian NHEJ are the catalytic subunit of DNA protein kinase (DNA-PKcs), Ku subunits Ku70 and Ku80, Artemis, XRCC4 and DNA ligase IV. DNA-PK is a nuclear serine/threonine protein kinase that comprises a catalytic subunit (DNA-PKcs), with the Ku subunits acting as the regulatory element. It has been proposed that DNA-PK is a molecular sensor for DNA damage that enhances the signal via phosphorylation of many downstream targets. The crucial role of DNA-PK in the repair of DSBs is highlighted by the hypersensitivity of DNA-PK-/- mice to IR and the high levels of unrepaired DSBs after genotoxic insult. Recently, DNA-PK has emerged as a suitable genetic target for molecular therapeutics such as siRNA, antisense and novel inhibitory small molecules. This review encompasses the recent literature regarding the role of DNA-PK in the protection of genomic stability and focuses on how this knowledge has aided the development of specific DNA-PK inhibitors, via both small molecule and directed molecular targeting techniques. This review promotes the inhibition of DNA-PK as a valid approach to enhance the tumor-cell-killing effects of treatments such as IR.

Computation of geometric partial differential equations and mean curvature flow

Abstract: This review concerns the computation of curvature-dependent interface motion governed by geometric partial differential equations. The canonical problem of mean curvature flow is that of finding a surface which evolves so that, at every point on the surface, the normal velocity is given by the mean curvature. In recent years the interest in geometric PDEs involving curvature has burgeoned. Examples of applications are, amongst others, the motion of grain boundaries in alloys, phase transitions and image processing. The methods of analysis, discretization and numerical analysis depend on how the surface is represented. The simplest approach is when the surface is a graph over a base domain. This is an example of a sharp interface approach which, in the general parametric approach, involves seeking a parametrization of the surface over a base surface, such as a sphere. On the other hand an interface can be represented implicitly as a level surface of a function, and this idea gives rise to the so-called level set method. Another implicit approach is the phase field method, which approximates the interface by a zero level set of a phase field satisfying a PDE depending on a new parameter. Each approach has its own advantages and disadvantages. In the article we describe the mathematical formulations of these approaches and their discretizations. Algorithms are set out for each approach, convergence results are given and are supported by computational results and numerous graphical figures. Besides mean curvature flow, the topics of anisotropy and the higher order geometric PDEs for Willmore flow and surface diffusion are covered.

Body Image and Self-Esteem Among Adolescent Girls: Testing the Influence of Sociocultural Factors

Abstract: In Western cultures, girls’ self-esteem declines substantially during middle adolescence, with changes in body image proposed as a possible explanation. Body image develops in the context of sociocultural factors, such as unrealistic media images of female beauty. In a study of 136 U.K. girls aged 11–16, experimental exposure to either ultra-thin or average-size magazine models lowered body satisfaction and, consequently, self-esteem. Selfesteem was also lower among older than among younger girls. Structural equation modeling showed that this age trend was partially accounted for by a corresponding downward trend in body satisfaction; this, in turn, was fully accounted for by upward age trends in awareness and internalization of sociocultural attitudes toward appearance, and in social comparison with media models. Results support calls for early educational interventions to help girls to deconstruct advertising and media images. Self-esteem is defined as a ‘‘positive or negative attitude toward . . . the self’’ (Rosenberg, 1965, p. 30), and can be viewed as a key indicator of psychological well-being, at least among people in Western cultures (Baumeister, Campbell, Krueger, & Vohs, 2003; Oishi, Diener, Lucas, & Suh, 1999). In Western cultures, self-esteem typically differs by gender. A recent meta-analysis of self-esteem studies, most conducted in Western industrialized nations, has confirmed that women’s self-esteem is moderately, but significantly, lower than men’s (d 5 .21); moreover the average

Defective DNA single-strand break repair in spinocerebellar ataxia with axonal neuropathy-1

Abstract: Spinocerebellar ataxia with axonal neuropathy-1 (SCAN1) is a neurodegenerative disease that results from mutation of tyrosyl phosphodiesterase 1 (TDP1). In lower eukaryotes, Tdp1 removes topoisomerase 1 (top1) peptide from DNA termini during the repair of double-strand breaks created by collision of replication forks with top1 cleavage complexes in proliferating cells. Although TDP1 most probably fulfils a similar function in human cells, this role is unlikely to account for the clinical phenotype of SCAN1, which is associated with progressive degeneration of post-mitotic neurons. In addition, this role is redundant in lower eukaryotes, and Tdp1 mutations alone confer little phenotype. Moreover, defects in processing or preventing double-strand breaks during DNA replication are most probably associated with increased genetic instability and cancer, phenotypes not observed in SCAN1 (ref. 8). Here we show that in human cells TDP1 is required for repair of chromosomal single-strand breaks arising independently of DNA replication from abortive top1 activity or oxidative stress. We report that TDP1 is sequestered into multi-protein single-strand break repair (SSBR) complexes by direct interaction with DNA ligase IIIalpha and that these complexes are catalytically inactive in SCAN1 cells. These data identify a defect in SSBR in a neurodegenerative disease, and implicate this process in the maintenance of genetic integrity in post-mitotic neurons.

National character does not reflect mean personality trait levels in 49 cultures

Abstract: Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity.

Photoreceptor spectral sensitivities in terrestrial animals: adaptations for luminance and colour vision.

Abstract: This review outlines how eyes of terrestrial vertebrates and insects meet the competing requirements of coding both spatial and spectral information. There is no unique solution to this problem. Thus, mammals and honeybees use their long-wavelength receptors for both achromatic (luminance) and colour vision, whereas flies and birds probably use separate sets of photoreceptors for the two purposes. In particular, we look at spectral tuning and diversification among ‘long-wavelength’ receptors (sensitivity maxima at greater than 500 nm), which play a primary role in luminance vision. Data on spectral sensitivities and phylogeny of visual photopigments can be incorporated into theoretical models to suggest how eyes are adapted to coding natural stimuli. Models indicate, for example, that animal colour vision—involving five or fewer broadly tuned receptors—is well matched to most natural spectra. We can also predict that the particular objects of interest and signal-to-noise ratios will affect the optimal eye design. Nonetheless, it remains difficult to account for the adaptive significance of features such as co-expression of photopigments in single receptors, variation in spectral sensitivities of mammalian L-cone pigments and the diversification of long-wavelength receptors that has occurred in several terrestrial lineages.

The health belief model

Abstract: Development of the health belief model (HBM) In the 1950s US public health researchers began developing psychological models designed to enhance the effectiveness of health education programmes (Hochbaum, 1958). Demographic factors such as socio-economic status, gender, ethnicity and age were known to be associated with preventive health behaviours and use of health services (Rosenstock, 1974), but these factors could not be modified through health education. Thus the challenge was to develop effective health education targeting modifiable, individual characteristics that predicted preventive health behaviour and service usage. Beliefs provided an ideal target because they are enduring individual characteristics which influence behaviour and are potentially modifiable. Beliefs may also reflect different socialization histories arising from demographic differences while, at the same time, differentiating between individuals from the same background. If persuasive methods could be used to change beliefs associated with health behaviours and such interventions resulted in health behaviour change then this would provide a theory-based technology of health education. An expectancy–value model was developed in which events believed to be more or less likely were seen to be positively or negatively evaluated by the individual. In particular, the likelihood of experiencing a health problem, the severity of the consequences of that problem, the perceived benefits of any particular health behaviour and its potential costs were seen as core beliefs guiding health behaviour (see ‘Expectations and health’). Rosenstock (1974) attributed the first health belief model (HBM) research to Hochbaum's (1958) studies of the uptake of tuberculosis X-ray screening.