9,756 research outputs found

    DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios

    Full text link
    The pseudo-conformal universe is an alternative to inflation in which the early universe is described by a conformal field theory on approximately flat space-time. The fields develop time-dependent expectation values, spontaneously breaking the conformal symmetries to a de Sitter subalgebra, and fields of conformal weight zero acquire a scale invariant spectrum of perturbations. In this paper, we show that the pseudo-conformal scenario can be naturally realized within theories that would ordinarily be of interest for DBI inflation, such as the world-volume theory of a probe brane in an AdS bulk space-time. In this approach, the weight zero spectator field can be associated with a geometric flat direction in the bulk, and its scale invariance is protected by a shift symmetry.Comment: 34 page

    Highly prevalent but not always persistent: undergraduate and graduate student's misconceptions about psychology.

    Get PDF
    Although past research has documented the prevalence of misconceptions in introductory psychology classes, few studies have assessed how readily upper-level undergraduate and graduate students endorse erroneous beliefs about the discipline. In Study 1, we administered a 30-item misconception test to an international sample of 670 undergraduate, Master’s and doctoral students. Analyses indicated that participants identified and rejected the majority of misconceptions, with doctoral students performing better than their Master’s or undergraduate peers. In Study 2, we administered a revised version of our questionnaire to a novel sample of 557 students while controlling for number of years spent at university, psychology courses completed and need for cognition. Once again, we found that graduate students rejected more, affirmed less and reported lower levels of uncertainty than their undergraduate counterparts. Educational implications and future research directions are discussed

    Protective actions of des-acylated ghrelin on brain injury and blood-brain barrier disruption after stroke in mice

    Get PDF
    The major ghrelin forms, acylated ghrelin and des-acylated ghrelin, are novel gastrointestinal hormones. Moreover, emerging evidence indicates that these peptides may have other functions including neuro- and vaso-protection. Here, we investigated whether post-stroke treatment with acylated ghrelin or des-acylated ghrelin could improve functional and histological endpoints of stroke outcome in mice after transient middle cerebral artery occlusion (tMCAo). We found that des-acylated ghrelin (1 mg/kg) improved neurological and functional performance, reduced infarct and swelling, and decreased apoptosis. In addition, it reduced blood-brain barrier (BBB) disruption in vivo and attenuated the hyper-permeability of mouse cerebral microvascular endothelial cells after oxygen glucose deprivation and reoxygenation (OGD + RO). By contrast, acylated ghrelin (1 mg/kg or 5 mg/kg) had no significant effect on these endpoints of stroke outcome. Next we found that des-acylated ghrelin's vasoprotective actions were associated with increased expression of tight junction proteins (occludin and claudin-5), and decreased cell death. Moreover, it attenuated superoxide production, Nox activity and expression of 3-nitrotyrosine. Collectively, these results demonstrate that post-stroke treatment with des-acylated ghrelin, but not acylated ghrelin, protects against ischaemia/reperfusion-induced brain injury and swelling, and BBB disruption, by reducing oxidative and/or nitrosative damage

    Single crystals of metal solid solutions

    Get PDF
    The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project

    Relationship of changes in total hip bone mineral density to vertebral and nonvertebral fracture risk in women with postmenopausal osteoporosis treated with once-yearly zoledronic acid 5 mg: The HORIZON-Pivotal Fracture Trial (PFT)

    Get PDF
    Measurements of change in bone mineral density (BMD) are thought to be weak predictors of treatment effect on the reduction of fracture risk. In this study we report an alternative year-on-year approach for the estimation of treatment effect explained by BMD in which we examine the relationship between fracture risk and the most recent change in BMD. We studied 7736 postmenopausal women (ages 65 to 89 years) who were participants in the Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly–Pivotal Fracture Trial (HORIZON-PFT) and were randomized to either intravenous administration of zoledronic acid or placebo. The percentage of treatment effect explained by change in total hip BMD was estimated using the alternative year-on-year approach and the standard approach of looking at change over 3 years. We also studied a subset of 1132 women in whom procollagen type 1 amino-terminal propeptide (PINP) was measured at baseline and 12 months, to estimate the percentage of treatment effect explained by change in PINP. Regardless of the method used, the change in total hip BMD explained a large percentage of the effect of zoledronic acid in reducing new vertebral fracture risk (40%; 95% CI, 30% to 54%; for the 3-year analysis). The treatment effects for nonvertebral fracture were not statistically significant for the year-on-year analysis but 3-year change in BMD explained 61% (95% CI, 24% to 156%) of treatment effect. Change in PINP explained 58% (95% CI, 15% to 222%) of the effect of zoledronic acid in reducing new vertebral fracture risk. We conclude that our estimates of the percentage of treatment effect explained may be higher than in previous studies because of high compliance with zoledronic acid (due to its once-yearly intravenous administration). Previous studies may have underestimated the relationship between BMD change and the effect of treatment on fracture risk. © 2012 American Society for Bone and Mineral Research

    Heparin Isomeric Oligosaccharide Separation Using Volatile Salt Strong Anion Exchange Chromatography

    Get PDF
    The complexity of heparin and heparan sulfate saccharides makes their purification, including many isomeric structures, very challenging and is a bottleneck for structure–activity studies. High-resolution separations have been achieved by strong anion exchange (SAX) chromatography on Propac PA1 and cetyltrimethylammonium (CTA)-C18 silica columns; however, these entail subsequent desalting methodologies and consequent sample losses and are incompatible with orthogonal chromatography methodologies and, in particular, mass spectrometry. Here, we present the CTA-SAX purification of heparin oligosaccharides using volatile salt (VS) buffer. In VSCTA-SAX, the use of ammonium bicarbonate buffer for elution improves resolution through both weaker dissociation and conformational coordination of the ammonium across the sulfate groups. Using ion mobility mass spectrometry, we demonstrate that isomeric structures have different structural conformations, which makes chromatographic separation achievable. Resolution of such structures is improved compared to standard SAX methods, and in addition, VSCTA-SAX provides an orthogonal method to isolate saccharides with higher purity. Because ammonium bicarbonate is used, the samples can be evaporated rather than desalted, preventing substantial sample loss and allowing more effective subsequent analysis by electrospray mass spectrometry. We conclude that VSCTA-SAX is a powerful new tool that helps address the difficult challenge of heparin/heparan sulfate saccharide separation and will enhance structure–activity studies

    What is a hologenomic adaptation? Emergent individuality and inter-identity in multispecies systems

    Get PDF
    Contemporary biological research has suggested that some host–microbiome multispecies systems (referred to as “holobionts”) can in certain circumstances evolve as unique biological individual, thus being a unit of selection in evolution. If this is so, then it is arguably the case that some biological adaptations have evolved at the level of the multispecies system, what we call hologenomic adaptations. However, no research has yet been devoted to investigating their nature, or how these adaptations can be distinguished from adaptations at the species-level (genomic adaptations). In this paper, we cover this gap by investigating the nature of hologenomic adaptations. By drawing on the case of the evolution of sanguivory diet in vampire bats, we argue that a trait constitutes a hologenomic adaptation when its evolution can only be explained if the holobiont is considered the biological individual that manifests this adaptation, while the bacterial taxa that bear the trait are only opportunistic beneficiaries of it. We then use the philosophical notions of emergence and inter-identity to explain the nature of this form of individuality and argue why it is special of holobionts. Overall, our paper illustrates how the use of philosophical concepts can illuminate scientific discussions, in the trend of what has recently been called metaphysics of biology

    Machiavellianism, emotional manipulation, and friendship functions in women's friendships

    Get PDF
    Machiavellianism and emotional manipulation has not been investigated in friendships. The current studies investigated Machiavellianism, emotional manipulation, and six friendship functions in women's same-sex friendships. For study 1, women (N = 221) completed the Mach IV, emotional manipulation measure (with reference to their own behaviour and their friend's behaviour), mood worsening and use of inauthentic displays from the managing emotions of others scale, and the friendship function measure. Machiavellianism predicted the self-perceived ability to employ emotional manipulation towards a same-sex friend and perceiving their friend to use emotional manipulation towards them. Machiavellianism predicted lower scores on all six friendship functions. For study 2, women (N = 186) completed the Mach IV, the modified emotional manipulation measure (with reference to their own behaviour and their friend's behaviour), and the friendship function measure. Women high on Machiavellianism reported using emotional manipulation more frequently towards their same-sex friend and perceived their same-sex friend to frequently use emotional manipulation towards them. Machiavellianism predicted lower scores on five of the friendship functions. These studies demonstrated that women higher on Machiavellianism employ emotional manipulation in their same-sex friendships. Women with higher Machiavellianism scores also perceived that they themselves were manipulated by their friend
    corecore