2,624 research outputs found

    A METHOD FOR CALCULATING DYNAMIC BREAST CENTRE OF MASS DURING RUNNING

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    This study aimed to develop a novel method for calculating breast centre of mass (COM) during running for use in musculoskeletal modelling. Magnetic resonance imaging (MRI) scans and kinematic data were collected from a female participant running at 2.6 m·s-1. A breast surface marker array was used to calculate the COM of 16 segments, based upon tissue composition from the MRI scan. The motion of the surface markers were used to calculate breast COM position during running. Breast COM was more superior, medial and posterior than the nipple marker. Breast COM range of motion was lower (~50%) in all directions during running when compared to the nipple marker. Results suggest that the localised breast deformation is the key factor in calculating breast COM during running

    What Do We Learn from the Weather? The New Climate-Economy Literature

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    A rapidly growing body of research applies panel methods to examine how temperature, precipitation, and windstorms influence economic outcomes. These studies focus on changes in weather realizations over time within a given spatial area and demonstrate impacts on agricultural output, industrial output, labor productivity, energy demand, health, conflict, and economic growth, among other outcomes. By harnessing exogenous variation over time within a given spatial unit, these studies help credibly identify (i) the breadth of channels linking weather and the economy, (ii) heterogeneous treatment effects across different types of locations, and (iii) nonlinear effects of weather variables. This paper reviews the new literature with two purposes. First, we summarize recent work, providing a guide to its methodologies, datasets, and findings. Second, we consider applications of the new literature, including insights for the "damage function" within models that seek to assess the potential economic effects of future climate change

    Temperature and Income: Reconciling New Cross-Sectional and Panel Estimates

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    This paper presents novel evidence and analysis of the relationship between temperature and income. First, using sub-national data from 12 countries in the Americas, we provide new evidence that the negative cross-country relationship between temperature and income also exists within countries and even within states. Second, we provide a theoretical framework for reconciling the substantial, negative association between temperature and income in the cross-section with the even stronger short-run effects of temperature estimated by panel models. The theoretical framework suggests that half of the negative short-term effects of temperature may be offset in the long run through adaptation.

    Climate Change and Economic Growth: Evidence from the Last Half Century

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    This paper uses annual variation in temperature and precipitation over the past 50 years to examine the impact of climatic changes on economic activity throughout the world. We find three primary results. First, higher temperatures substantially reduce economic growth in poor countries but have little effect in rich countries. Second, higher temperatures appear to reduce growth rates in poor countries, rather than just the level of output. Third, higher temperatures have wide-ranging effects in poor nations, reducing agricultural output, industrial output, and aggregate investment, and increasing political instability. Analysis of decade or longer climate shifts also shows substantial negative effects on growth in poor countries. Should future impacts of climate change mirror these historical effects, the negative impact on poor countries may be substantial.

    Archaeological Investigations at the Pettigrew Site on the University of North Carolina Campus, Chapel Hill, North Carolina

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    Research Report No. 20, Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. Reports in this series discuss the findings of archaeological excavations and research projects undertaken by the RLA between 1984 and present

    SOD1G93A transgenic mouse CD4+ T cells mediate neuroprotection after facial nerve axotomy when removed from a suppressive peripheral microenvironment

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    Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving motoneuron (MN) axonal withdrawal and cell death. Previously, we established that facial MN (FMN) survival levels in the SOD1G93A transgenic mouse model of ALS are reduced and nerve regeneration is delayed, similar to immunodeficient RAG2-/- mice, after facial nerve axotomy. The objective of this study was to examine the functionality of SOD1G93A splenic microenvironment, focusing on CD4+ T cells, with regard to defects in immune-mediated neuroprotection of injured MN. We utilized the RAG2-/- and SOD1G93A mouse models, along with the facial nerve axotomy paradigm and a variety of cellular adoptive transfers, to assess immune-mediated neuroprotection of FMN survival levels. We determined that adoptively transferred SOD1G93A unfractionated splenocytes into RAG2-/- mice were unable to support FMN survival after axotomy, but that adoptive transfer of isolated SOD1G93A CD4+ T cells could. Although WT unfractionated splenocytes adoptively transferred into SOD1G93A mice were able to maintain FMN survival levels, WT CD4+ T cells alone could not. Importantly, these results suggest that SOD1G93A CD4+ T cells retain neuroprotective functionality when removed from a dysfunctional SOD1G93A peripheral splenic microenvironment. These results also indicate that the SOD1G93A central nervous system microenvironment is able to re-activate CD4+ T cells for immune-mediated neuroprotection when a permissive peripheral microenvironment exists. We hypothesize that dysfunctional SOD1G93A peripheral splenic microenvironment may compromise neuroprotective CD4+ T cell activation and/or differentiation, which, in turn, results in impaired immune-mediated neuroprotection for MN survival after peripheral axotomy in SOD1G93A mice

    Yedoma permafrost genesis: Over 150 years of mystery and controversy

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    Since the discovery of frozen megafauna carcasses in Northern Siberia and Alaska in the early 1800s, the Yedoma phenomenon has attracted many Arctic explorers and scientists. Exposed along coastal and riverbank bluffs, Yedoma often appears as large masses of ice with some inclusions of sediment. The ground ice particularly mystified geologists and geographers, and they considered sediment within Yedoma exposures to be a secondary and unimportant component. Numerous scientists around the world tried to explain the origin of Yedoma for decades, even though some of them had never seen Yedoma in the field. The origin of massive ice in Yedoma has been attributed to buried surface ice (glaciers, snow, lake ice, and icings), intrusive ice (open system pingo), and finally to ice wedges. Proponents of the last hypothesis found it difficult to explain a vertical extent of ice wedges, which in some cases exceeds 40 m. It took over 150 years of intense debates to understand the process of ice-wedge formation occurring simultaneously (syngenetically) with soil deposition and permafrost aggregation. This understanding was based on observations of the contemporary formation of syngenetic permafrost with ice wedges on the floodplains of Arctic rivers. It initially was concluded that Yedoma was a floodplain deposit, and it took several decades of debates to understand that Yedoma is of polygenetic origin. In this paper, we discuss the history of Yedoma studies from the early 19th century until the 1980s—the period when the main hypotheses of Yedoma origin were debated and developed

    Facial Nerve Axotomy in Mice: A Model to Study Motoneuron Response to Injury

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    The goal of this surgical protocol is to expose the facial nerve, which innervates the facial musculature, at its exit from the stylomastoid foramen and either cut or crush it to induce peripheral nerve injury. Advantages of this surgery are its simplicity, high reproducibility, and the lack of effect on vital functions or mobility from the subsequent facial paralysis, thus resulting in a relatively mild surgical outcome compared to other nerve injury models. A major advantage of using a cranial nerve injury model is that the motoneurons reside in a relatively homogenous population in the facial motor nucleus in the pons, simplifying the study of the motoneuron cell bodies. Because of the symmetrical nature of facial nerve innervation and the lack of crosstalk between the facial motor nuclei, the operation can be performed unilaterally with the unaxotomized side serving as a paired internal control. A variety of analyses can be performed postoperatively to assess the physiologic response, details of which are beyond the scope of this article. For example, recovery of muscle function can serve as a behavioral marker for reinnervation, or the motoneurons can be quantified to measure cell survival. Additionally, the motoneurons can be accurately captured using laser microdissection for molecular analysis. Because the facial nerve axotomy is minimally invasive and well tolerated, it can be utilized on a wide variety of genetically modified mice. Also, this surgery model can be used to analyze the effectiveness of peripheral nerve injury treatments. Facial nerve injury provides a means for investigating not only motoneurons, but also the responses of the central and peripheral glial microenvironment, immune system, and target musculature. The facial nerve injury model is a widely accepted peripheral nerve injury model that serves as a powerful tool for studying nerve injury and regeneration
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