Lightweight piston architecture

The invention is an improvement in a lightweight carbon-carbon composite piston, the improvement uses near-net shape knitted or warp-interlock preforms to improve the structural qualities of the piston. In its preferred embodiment, a one piece, tubular, closed-ended, knitted preform (a sock) of carbon fibers embedded within the matrix of the piston structure forms the crown, side wall, skirt and inner surface of the piston, and wrap-interlock preforms strengthen the piston crown and wrist pin bosses

Why Do Delusions Persist?

Delusions are bizarre and distressing beliefs that characterize certain mental illnesses. They arise without clear reasons and are remarkably persistent. Recent models of delusions, drawing on a neuroscientific understanding of learning, focus on how delusions might emerge from abnormal experience. We believe that these models can be extended to help us understand why delusions persist. We consider prediction error, the mismatch between expectancy and experience, to be central. Surprising events demand a change in our expectancies. This involves making what we have learned labile, updating and binding the memory anew: a process of memory reconsolidation. We argue that, under the influence of excessive prediction error, delusional beliefs are repeatedly reconsolidated, strengthening them so that they persist, apparently impervious to contradiction

Mark-Recapture and Stochastic Population Models for Polar Bears of the High Arctic

We used mark-recapture data and population viability analysis (PVA) to estimate demographic parameters, abundance, and harvest risks for two adjacent populations of polar bears (Ursus maritimus) inhabiting Lancaster Sound and Norwegian Bay, Canada. Analyses were based on data from 1871 bears that were uniquely marked during the period 1972–97. Our best-fitting mark-recapture model specified sex and age effects on probabilities of survival and an effect of prior recapture (dependence) on capture probability. The most parsimonious solution in our analysis of survival was to assume the same rate for the Lancaster Sound and Norwegian Bay populations. Total (harvested) annual survival rates (mean ± 1 SE) for females included: 0.749 ± 0.105 (cubs), 0.879 ± 0.050 (ages 1–4), 0.936 ± 0.019 (ages 5– 20), and 0.758 ± 0.054 (ages 21+). Mean litter size was 1.69 ± 0.01 cubs for females of Lancaster Sound and 1.71 ± 0.08 cubs for females of Norwegian Bay. By age six, on average 0.31 ± 0.21 females of Lancaster Sound were producing litters (first age of reproduction was five years); however, females of Norwegian Bay did not reproduce until age seven or more. Total abundance (1995–97) averaged 2541 ± 391 bears in Lancaster Sound and 203 ± 44 bears in Norwegian Bay. The finite rate of increase (lambda) during the study period was estimated to be 1.001 ± 0.013 for bears of Lancaster Sound and 0.981 ± 0.027 for bears of Norwegian Bay. We incorporated demographic parameters into a harvest-explicit PVA to model short-term (15 yr) probabilities of overharvesting (i.e., 1997–2012). Our harvest simulations suggest that current levels of kill are approaching and perhaps exceeding the sustainable yield in both populations.Nous avons recouru aux données obtenues par marquage et recapture ainsi qu’aux analyses de viabilité de population pour estimer les paramètres démographiques, l’abondance et les risques liés à la récolte de deux populations adjacentes d’ours polaires (Ursus maritimus) évoluant dans le détroit de Lancaster et la baie Norwegian, au Canada. Les analyses reposaient sur les données relatives à 1 871 ours marqués de manière unique pendant la période allant de 1972 à 1997. Notre modèle de marquage et recapture le mieux ajusté tenait compte des effets du sexe et de l’âge sur les probabilités de survie, ainsi que de l’effet d’une recapture antérieure (dépendance) sur la probabilité de capture. La solution la plus parcimonieuse de notre analyse de survie consistait à assumer le même taux pour les populations du détroit de Lancaster et de la baie Norwegian. Les taux totaux de survie annuels (récoltés) (moyenne ± 1 SE) chez les femelles s’établissaient comme suit : 0,749 ± 0,105 (oursons), 0,879 ± 0,050 (âges 1-4), 0,936 ± 0,019 (âges 5-20), et 0,758 ± 0,054 (âges 21+). La grosseur moyenne des portées était de 1,69 ± 0,01 ourson dans le cas des femelles du détroit de Lancaster, et de 1,71 ± 0,08 ourson dans le cas des femelles de la baie Norwegian. Avant l’âge de six ans, en moyenne 0,31 ± 0,21 femelle du détroit de Lancaster produisait des portées (l’âge de reproduction le plus jeune était de cinq ans); cependant, les femelles de la baie Norwegian ne se reproduisaient pas avant l’âge de sept ans ou plus. L’abondance totale (1995-1997) atteignait en moyenne 2 541 ± 391 ours au détroit de Lancaster, et 203 ± 44 ours dans la baie Norwegian. Le taux fini d’augmentation (lambda) pendant la période d’étude était estimé à 1,001 ± 0,013 dans le cas des ours du détroit de Lancaster, et de 0,981 ± 0,027 dans le cas des ours de la baie Norwegian. Nous avons intégré les paramètres démographiques à une analyse de viabilité de population de récolte explicite pour modéliser les probabilités à court terme (15 ans) de surrécolte (i.e. 1997-2012). Nos simulations de récolte laissent croire que les taux d’ours tués approchent et peuvent même dépasser le rendement admissible des deux populations

The Evolution in the Faint-End Slope of the Quasar Luminosity Function

(Abridged) Based on numerical simulations of galaxy mergers that incorporate black hole (BH) growth, we predict the faint end slope of the quasar luminosity function (QLF) and its evolution with redshift. Our simulations have yielded a new model for quasar lifetimes where the lifetime depends on both the instantaneous and peak quasar luminosities. This motivates a new interpretation of the QLF in which the bright end consists of quasars radiating at nearly their peak luminosities, but the faint end is mostly made up of quasars in less luminous phases of evolution. The faint-end QLF slope is then determined by the faint-end slope of the quasar lifetime for quasars with peak luminosities near the observed break. We determine this slope from the quasar lifetime as a function of peak luminosity, based on a large set of simulations spanning a wide variety of host galaxy, merger, BH, and ISM gas properties. Brighter peak luminosity (higher BH mass) systems undergo more violent evolution, and expel and heat gas more rapidly in the final stages of quasar evolution, resulting in a flatter faint-end slope (as these objects fall below the observed break in the QLF more rapidly). Therefore, as the QLF break luminosity moves to higher luminosities with increasing redshift, implying a larger typical quasar peak luminosity, the faint-end QLF slope flattens. From the quasar lifetime as a function of peak luminosity and this interpretation of the QLF, we predict the faint-end QLF slope and its evolution with redshift in good agreement with observations. Although BHs grow anti-hierarchically (with lower-mass BHs formed primarily at lower redshifts), the observed change in slope and differential or luminosity dependent density evolution in the QLF is completely determined by the luminosity-dependent quasar lifetime and physics of quasar feedback.Comment: 13 pages, 4 figures, submitted to ApJ (Replacement with minor revisions and changed sign convention

Letter to the Editor concerning “A systematic review of controlled trials on visual stress using intuitive overlays or colorimeter"

yesWe read with interest the review written by Evans and Allen, and published in the Journal of Optometry, in July, 2016

An Abundance of K3 Fibrations from Polyhedra with Interchangeable Parts

Even a cursory inspection of the Hodge plot associated with Calabi-Yau threefolds that are hypersurfaces in toric varieties reveals striking structures. These patterns correspond to webs of elliptic-K3 fibrations whose mirror images are also elliptic-K3 fibrations. Such manifolds arise from reflexive polytopes that can be cut into two parts along slices corresponding to the K3 fibers. Any two half-polytopes over a given slice can be combined into a reflexive polytope. This fact, together with a remarkable relation on the additivity of Hodge numbers, explains much of the structure of the observed patterns.Comment: 30 pages, 15 colour figure

QTL and Drought Effects on Leaf Physiology in Lowland Panicum virgatum

Switchgrass is a key component of plans to develop sustainable cellulosic ethanol production for bioenergy in the USA. We sought quantitative trait loci (QTL) for leaf structure and function, using the Albany full-sib mapping population, an F1 derived from lowland tetraploid parents. We also assessed both genotype × environment interactions (G×E) in response to drought and spatial trends within experimental plots, using the mapping population and check clones drawn from the parent cultivars. Phenotypes for leaf structure and physiological performance were determined under well-watered conditions in two consecutive years, and we applied drought to one of two replicates to test for G×E. Phenotypes for check clones varied with location in our plot and were impacted by drought, but there was limited evidence of G×E except in quantum yield (ΦPSII). Phenotypes of Albany were also influenced by plant location within our plot, and after correcting for experimental design factors and spatial effects, we detected QTL for leaf size, tissue density (LMA), and stomatal conductance (gs). Clear evidence of G×E was detected at a QTL for intrinsic water use efficiency (iWUE) that was expressed only under drought. Loci influencing physiological traits had small additive effects, showed complex patterns of heritability, and did not co-localize with QTL for morphological traits. These insights into the genetic architecture of leaf structure and function set the stage for consideration of leaf physiological phenotypes as a component of switchgrass improvement for bioenergy purposes

Population Viability of Barren-ground Grizzly Bears in Nunavut and the Northwest Territories

We modelled probabilities of population decline as a function of annual kill for a population of barren-ground grizzly bears (Ursus arctos) inhabiting Nunavut and the Northwest Territories, Canada. Our results suggest that the population is at risk of decline, especially if annual removal rates increase from the 42-year mean of 13.4 bears per year. Adding six bears to the mean annual kill results in a greater than 40% chance of a decrease by one-quarter in population size over the next 50 years, compared to a 10% chance with the current level of human-caused mortality. Additional mortalities may result from increased problem behaviour by bears at mine sites or hunt and exploration camps, given recent increases in human activity in the region, and may already be present as unreported mortality. We believe any increase in current harvest quotas would considerably lessen conservation prospects for the population.On a simulé les probabilités de baisse de la population en fonction du prélèvement annuel dans le cadre de la chasse pour une population de grizzlis de la toundra (Ursus arctos) habitant le Nunavut et les Territoires du Nord-Ouest, au Canada. Nos résultats suggèrent que la population risque de décliner, surtout si les taux de prélèvement augmentent par rapport à la moyenne établie sur 42 ans qui est de 13,4 ours par an. Le fait d'ajouter 6 ours au prélèvement de chasse annuel augmente à plus de 40 % le risque que la population décline d'un quart au cours des prochains 50 ans, par rapport à 10 % dans le cas du niveau actuel de mortalité provoquée par les humains. Vu l'augmentation récente de l'activité anthropique dans la région, d'autres individus pourraient être abattus à cause du nombre croissant de comportements problématiques des ours résidant à des sites miniers et à des campements d'exploration, et il est possible que ce phénomène existe déjà mais que les morts ne soient pas rapportées. Notre opinion est que toute augmentation des quotas actuels de prélèvement réduirait considérablement les perspectives de conservation pour la population