14,300 research outputs found

    Self-injurious behaviour in individuals with autism spectrum disorder

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    Background: Autism spectrum disorder (ASD) has been identified as a risk marker for self-injurious behaviour. In this study we aimed to describe the prevalence, topography and correlates of self-injury in individuals with ASD in contrast to individuals with Fragile X and Down syndromes and examine person characteristics associated with self-injury across and within these groups.\ud \ud Method: Carers of individuals with ASD (N=149; mean age=9.98, SD=4.86), Fragile X syndrome (N=123; mean age=15.32, SD=8.74) and Down syndrome (N=49; mean age=15.84, SD=12.59) completed questionnaires relating to the presence and topography of self-injury Information was also gathered regarding demographic characteristics, affect, autistic behaviour, hyperactivity, impulsivity and repetitive behaviour.\ud \ud Results: Self-injurious behaviour was displayed by 50% of the ASD sample; a significantly higher prevalence than in the Down syndrome group (18.4%) but broadly similar to the prevalence in Fragile X syndrome (54.5%). Self-injury was associated with significantly higher levels of autistic behaviour within the Down and Fragile X syndrome groups. Within the ASD group, the presence of self-injury was associated with significantly higher levels of impulsivity and hyperactivity, negative affect and significantly lower levels of ability and speech.\ud \ud Conclusions: Self-injurious behaviour is prevalent in individuals with ASD and the presence of ASD phenomenology increases the risk of self-injury in individuals with known genetic disorders but without a diagnosis of idiopathic autism. Person characteristics associated with self-injury in ASD indicate a role for impaired behavioural inhibition, low levels of ability and negative affect in the development of self-injurious behaviour

    Dilepton Production at Fermilab and RHIC

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    Some recent results from several fixed-target dimuon production experiments at Fermilab are presented. In particular, we discuss the use of Drell-Yan data to determine the flavor structure of the nucleon sea, as well as to deduce the energy-loss of partons traversing nuclear medium. Future dilepton experiments at RHIC could shed more light on the flavor asymmetry and possible charge-symmetry-violation of the nucleon sea. Clear evidence for scaling violation in the Drell-Yan process could also be revealed at RHIC.Comment: 5 pages, talk presented at the RIKEN-BNL Workshop on 'Hard Parton Physics in Nucleus-Nucleus collisions, March 199

    Disturbances of Plant Communities : Spruce Bark Beetle Infestation

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    The spruce bark beetle (Dendroctonus rufipennis) is not new to the area, nor is it the only insect to affect the region\u27s forests. Epidemic scale outbreaks are known to have occurred on the lower Kenai Peninsula as far back as the mid-1800s. The recent epidemic, however, has certainly been the most significant terrestrial ecological disturbance to the area in recorded history (Wittwer et al. 1998). Notable outbreaks were not noted in the Kachemak Bay Watershed until the 1950s and early 1960s when the first outbreak was observed near Anchor Point. At approximately the same time, beetle outbreaks were growing outside of the Watershed. An extended period of drought is thought to have contributed to the surge in outbreaks by reducing trees\u27 ability to resist and recover from beetle attack. Increased rainfall in the late 1960s, however, dampened the drought conditions, curtailing a more widespread epidemic. By the late 1970s, beetle outbreaks had skyrocketed again on the Kenai Peninsula. Despite this outbreak, the Kachemak Bay Watershed remained healthy until 1984 when an outbreak in the Fox River drainage began to expand, and beetles commenced consuming forests along East Road on the northern side of the Bay. Meanwhile, a small infestation in Mallard Bay, on the southern side of the Watershed, expanded to 12,000 acres by 1988. In addition, more outbreaks were developing to the north of Homer, near Ninilchik and Crooked Creek. There was some thought that the maritime climate of the Bay area would keep the outbreaks from expanding throughout the area, but this was not to be the case

    Valuing Catastrophic Citrus Losses

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    Courts are often required to estimate changes in welfare to agricultural operations from catastrophic events. For example, courts must assign damages in lawsuits, such as with pesticide drift cases, or determine "just compensation" when the government takes private land for public use, as with the removal of dairy farms from environmentally sensitive land or destruction of canker-contaminated citrus trees. In economics, the traditional method of quantifying producer losses is estimating changes in producer welfare, but courts rarely use this method. Instead, they turn to substitute valuation methods that may not fully capture welfare changes, such as changes in land value, tree replacement value, and total revenue. This study examines various measures for valuing the back-to-back catastrophic freezes that occurred in the Florida citrus industry in the 1980s. We first use the traditional method to determine the welfare change due to a freeze (1) for a citrus grove that loses one crop and is able to return to full production the next year, and (2) the lower measure of welfare loss due to a citrus grove that loses all of its trees and is abandoned or is replanted. The lower measure is used to simulate the legal doctrine of avoidable consequences. These measures are then compared to substitute valuation measures that have been used by courts to determine welfare changes. For case 1, total revenue overestimates losses by 35.6%. For case 2, total revenue overestimates losses by 55.3%, tree replacement value underestimates losses by 93.6%, and changes in land value underestimates losses by 13.2%.citrus, perennial crops, catastrophic loss, damages, freeze, Crop Production/Industries,

    Valuing Catastrophic Losses for Perennial Agricultural Crops

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    Courts are often required to estimate changes in welfare to agricultural operations from catastrophic events. For example, courts must assign damages in lawsuits, such as with pesticide drift cases, or determine 'just compensation' when the government takes private land for public use, as with the removal of dairy farms from environmentally sensitive land or destruction of canker-contaminated citrus trees. In economics, the traditional method of estimating changes in producer welfare is the computation of lost producer surplus, but courts rarely use this method. Instead, they turn to substitute valuation methods that may not fully capture welfare change, such as changes in land value, tree replacement value, and total revenue. This study examines various measures for valuing the back-to-back catastrophic freezes that occurred in the Florida citrus industry in the 1980s. We first use the traditional method to determine the welfare change due to a freeze (1) for a citrus grove that loses one crop and is able to return to full production the next year (simulating destruction of annual crops), and (2)the lower measure of welfare loss due to a citrus grove that loses all of its trees and is abandoned or is replanted. The lower measure is used to simulate the legal doctrine of avoidable consequences. These measures are then compared to substitute valuation measures that have been used by courts to determine welfare changes. For case 1, total revenue overestimated losses by 35.6%. For case 2, total revenue overestimates losses by 55.3%, tree replacement value underestimates losses by 93.6%, and changes in land value underestimates losses by 13.2%.citrus, perennial crops, catastrophic loss, damages, freeze, Crop Production/Industries,

    Derived Demand for Food Nutrients as Welfare Indicator of Biofortified Crops: High-Iron Rice in the Philippines

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    The study estimates potential consumer gains from the introduction of High-Iron Rice in the Philippines. By deriving the demand for dietary iron from a national survey on household food consumption and expenditure, we project consumer welfare implications under both non-market and market analytical frameworks.Crop Production/Industries,

    The neural stem cell microenvironment

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    In mammals, neural stem cells appear early in development and remain active within the central nervous system for the whole life duration of the organism. During this developmental process they assume different cellular morphologies and reside within changing microenvironments whilst retaining the basic properties of a stem cell: multipotentiality and the ability to self renew. In this chapter, the basic morphological characteristics of neural stem cells will be reviewed, along with the fundamental structural components and signalling molecules of their microenvironments. In early neural development, when the patterning of the nervous system is established, neural stem cells are called neuroepithelial cells; they are situated among other neuroepithelial cells and they are exposed to various signals such as retinoic acid, sonic hedgehog and fibroblast growth factors. When neurogenesis commences, stem cells are transformed to radial glial cells and the complexity of their microenvironment increases due to the emergence of various types of neuronal progenitors, differentiated cells and extracellular signaling molecules. Finally, during adulthood, neural stem cells assume astroglial morphology and reside in specific microenvironments that are called neurogenic niches; small neurogenic islands where neurons and glia are continuously generated under the control of mechanisms largely similar to those operating during embryonic development
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