9,482 research outputs found

    Holocene Glaciation of the Arrigetch Peaks, Brooks Range, Alaska

    Get PDF
    Eleven cirque glaciers and associated deposits within the granitic Arrigetch Peaks of the west-central Brooks Range face north, minimizing insolation. Shading by surrounding mountainous terrain decreases insolation on these landforms even more significantly, favoring the formation of glacier-cored moraines. Comparison of glacier photographs taken in 1911, 1962, and 1979 reveals a record of decelerating recession. Geomorphic and lichenometric mapping suggests at least three to possibly eight phases of Holocene glacial expansion. These date between ~5000 and 300 yr B.P., based on the application of a central Brooks Range Rhizocarpon geographicum growth curve

    The Home Literacy Environment as a Predictor of the Early Literacy Development of Children at Family-Risk of Dyslexia

    Get PDF
    The home literacy environment (HLE) predicts language and reading development in typically developing children; relatively little is known about its association with literacy development in children at family-risk of dyslexia. We assessed the HLE at age 4Ā years, precursor literacy skills at age 5, and literacy outcomes at age 6, in a sample of children at family-risk of dyslexia (nĀ =Ā 116) and children with no known risk (nĀ =Ā 72). Developmental relationships between the HLE and literacy were comparable between the groups; an additional effect of storybook exposure on phoneme awareness was observed in the family-risk group only. The effects of socioeconomic status on literacy were partially mediated by variations in the HLE; in turn, effects of the HLE on literacy were mediated by precursor skills (oral language, phoneme awareness, and emergent decoding) in both groups. Findings are discussed in terms of possible geneā€“environment correlation mechanisms underpinning atypical literacy development

    Neurodegenerative brain changes are associated with area deprivation in the United Kingdom: findings from the Brains for Dementia Research study

    Get PDF
    Socioeconomic disadvantage is associated with greater risk of dementia. This has been theorised to reflect inequalities in cognitive reserve, healthcare access, lifestyle, and other health factors which may contribute to the clinical manifestation of dementia. We aimed to assess whether area deprivation in the United Kingdom was associated with greater risk or severity of the specific neurodegenerative diseases which lead to dementia in a multi-centre cohort with autopsy assessment. Participants underwent clinical assessment prior to brain tissue donation post-mortem. Each then underwent detailed, standardised neuropathological assessment. National area deprivation statistics were derived for each participantā€™s neighbourhood, for use as a predictor in binary and ordinal logistic models assessing the respective presence and severity of staging of key neuropathological changes, adjusting for theorised confounders. Individuals from among the 20% most deprived neighbourhoods in the United Kingdom had significantly higher neurofibrillary tangle and neuritic plaque staging, and increased risk of cerebral amyloid angiopathy. These findings were not explained by a greater risk of diabetes or hypertension, APOE genotype, alcohol misuse or tobacco smoking, sex, or age differences. A sensitivity analysis conditioning on baseline cognitive impairment did not meaningfully change the observed association. Socioeconomic disadvantage may contribute to dementia incidence through a greater severity of specific neuropathological changes (neurofibrillary tangles, neuritic plaques, and cerebral amyloid angiopathy), independent of other indirect influences. Mechanisms through which deprivation is associated with these require further exploration

    Herschel Observations of Cataclysmic Variables

    Get PDF
    We have used the PACS instrument on the Herschel Space Observatory to observe eight cataclysmic variables at 70 and 160 Ī¼m. Of these eight objects, only AM Her was detected. We have combined the Herschel results with ground-based, Spitzer, and WISE observations to construct spectral energy distributions for all of the targets. For the two dwarf novae in the sample, SS Cyg and U Gem, we find that their infrared luminosities are completely dominated by their secondary stars. For the two highly magnetic "polars" in our survey, AM Her and EF Eri, we find that their mid-infrared excesses, previously attributed to circumbinary dust emission, can be fully explained by cyclotron emission. The WISE light curves for both sources show large, orbitally modulated variations that are identically phased to their near-IR light curves. We propose that significant emission from the lowest cyclotron harmonics (n ā‰¤ 3) is present in EF Eri and AM Her. Previously, such emission would have been presumed to be optically thick, and not provide significant orbitally modulated flux. This suggests that the accretion onto polars is more complicated than assumed in the simple models developed for these two sources. We develop a model for the near-/mid-IR light curves for WZ Sge with an L2 donor star that shows that the ellipsoidal variations from its secondary star are detected. We conclude that none of the targets surveyed have dusty circumbinary disks

    Testing for Vertical Inequity in Property Tax Systems

    Get PDF
    Models for testing assessor performance have been widely discussed in the literature. Many have been used in practice. The purpose of this study are to evaluate the performance of existing models and to propose two new models. We find that existing models can be used correctly to test for inequity when their functional form is consistent with the pattern of the assessment-sales ratio data. Results from the application of different models show inconsistencies since the appropriate functional form may vary for different data sets. The new models have the ability to emulate the forms of the existing models as well as handle more complex relationships.

    Beyond locutionary denotations: exploring trust between practitioners and policy

    Get PDF
    This study reports the findings of a research on the trust relationship between practitioners in the Skills for Life (SfL) area and the policy that informs their practice. The exploration of this relationship was premised on an extended notion of trust relationship which draws from the Speech Act theory of Austin (1962; Searle 1969; Kissine 2008), leading to the claim that the existence of different layers of imports in textual analysis makes it possible for a trust relationship to exist between the human/physical and the non human/non physical. The study found that the majority of practitioners in the SfL field trust policy to deliver its inherent policy only to a limited extent. Amongst others, the study identified the impact of the perlocutionary import of policy text on practitioners as a viable reason for this limited level of trust. Such perlocutionary imports, it also found, have adverse impact on practitioners who are considered to have drawn from previous experience to mediate the import of contemporary policies

    Dehydrative etherification reactions of glycerol with alcohols catalyzed by recyclable nanoporous aluminosilicates: telescoped routes to glyceryl ethers

    Get PDF
    Catalytic strategies for the efficient transformation of abundant sustainable bioderived molecules, such as glycerol, into higher value more useful products is an important research goal. In this study, we demonstrate that atom efficient dehydrative etherification reactions of glycerol with activated alcohols are effectively catalyzed by nanoporous aluminosilicate materials in dimethylcarbonate (DMC) to produce the corresponding 1-substituted glyceryl ethers in high yield. By carrying out the reaction in acetone, it is possible to capitalize on the ability of these materials to catalyze the corresponding acetalization reaction, allowing for the development of novel, telescoped acetalization-dehydrative etherification reaction sequences to selectively produce protected solketal derivatives. These materials also catalyze the telescoped reaction of glycerol with <i>tert</i>-butanol (TBA) in acetone to produce the corresponding solketal mono <i>tert</i>-butyl ether product in high yield, providing a potential route to convert glycerol directly into a useful and sustainable fuel additive

    Clustering of photometric luminous red galaxies I : Growth of Structure and Baryon Acoustic Feature

    Full text link
    The possibility of measuring redshift space (RSD) distortions using photometric data have been recently highlighted. This effect complements and significantly alters the detectability of baryon acoustic oscillations (BAO) in photometric surveys. In this paper we present measurements of the angular correlation function of luminous red galaxies (LRGs) in the photometric catalog of the final data release (DR7) of the Sloan Digital Sky Survey II (SDSS). The sample compromise ~ 1.5 x 10^6 LRGs distributed in 0.45 < z < 0.65, with a characteristic photometric error of ~ 0.05. Our measured correlation centered at z=0.55 is in very good agreement with predictions from standard LCDM in a broad range of angular scales, 0.5āˆ˜<Īø<6āˆ˜0.5^\circ < \theta < 6^\circ. We find that the growth of structure can indeed be robustly measured, with errors matching expectations. The velocity growth rate is recovered as fĻƒ8=0.53Ā±0.42f \sigma_8 = 0.53 \pm 0.42 when no prior is imposed on the growth factor and the background geometry follows a LCDM model with WMAP7+SNIa priors. This is compatible with the corresponding General Relativity (GR) prediction fĻƒ8=0.45f \sigma_8 = 0.45 for our fiducial cosmology. If we adopt a parametrization such that f=Ī©mĪ³(z)f=\Omega ^\gamma_m(z), with Ī³ā‰ˆ0.55\gamma \approx 0.55 in GR, and combine our fĻƒ8f\sigma_8 measurement with the corresponding ones from spectroscopic LRGs at lower redshifts we obtain Ī³=0.54Ā±0.17\gamma=0.54 \pm 0.17. In addition we find evidence for the presence of the baryon acoustic feature matching the amplitude, location and shape of LCDM predictions. The photometric BAO feature is detected with 98 % confidence level at z=0.55.Comment: 16 pages, 19 figures, minor changes to text to match accepted version by MNRA

    Associations between multimorbidity and neuropathology in dementia: a case for considering functional cognitive disorders, psychiatric illness, and dementia mimics

    Get PDF
    Cognitive impairment in older people has a variety of underlying causes. In addition to neurodegenerative causes such as Alzheimer's disease, a dementia-like cognitive disorder may appear due to non-degenerative factors. Multimorbidity has been previously associated with clinical dementia risk, though whether this was due to greater risk of dementia-related neuropathology, or other factors that mimic dementia, was unclear. We provide evidence that physical multimorbidity is not associated with greater pathological changes at autopsy. Other factors related to multimorbidity and cognitive impairments may be important targets for investigation, such as functional cognitive disorders, primary psychiatric disorders (depression, anxiety, psychosis) and polypharmacy
    • ā€¦
    corecore