22 research outputs found

    Advances in samarium-neodymium geochronology: applications to early earth garnet, hydrothermal carbonate, and high temperature metamorphic systems

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    This study utilizes recent advances in the analysis of neodymium (Nd) and samarium (Sm) by thermal ionization mass spectrometry (TIMS) to constrain timescales of heating and fluid flow within the lithosphere. Garnet grows during metamorphism and can be linked to its pressure and temperature of growth, while carbonate mineralization ages can be linked to hydrothermal fluid flow. The ability to date these common minerals makes it possible to unravel the timing and duration of tectonometamorphic processes. Garnet from the Eoarchean Nuvvuagittuq Supracrustal Belt (NSB) in Québec, Canada yields an age of 2574.66 ± 0.72 Ma. This is the most precise Neoarchean age reported for this terrane and was achieved through a modified partial dissolution procedure designed to remove the effects of much older (up to 3.8 Ga) inherited mineral growth. An accurate age for the most recent metamorphic garnet in the NSB is critical, as the (controversial) Hadean Nd model age calculations for this terrane depend on the time at which the 147Sm/144Nd systematics were last altered. Carbonate mineralization ages are explored for a diverse group of thirty samples using a novel sequential acid extraction procedure. Through this procedure it is possible to constrain carbonate mineralization in a variety of geologic settings (metamorphic fluid flow, hydrothermal and ore-forming systems) to ± 20 Myr. Zoned and bulk garnet geochronology at ten sites within a unusually localized area (~5 km2) of high temperature granulite-facies metamorphism in Bristol, New Hampshire reveals multiple brief (<1 Myr) periods of garnet growth focused between 393 and 386 Ma, at peak temperatures of 730-850°C. Comparison with garnet growth ages and temperatures , in central Massachusetts (364 Ma at 950°C) and Connecticut (341 Ma at 1000°C) reveal a regional trend of pulsed high temperature garnet growth spanning ~60 Myr from north to south, the same time span bracketed by associated igneous rocks dated via zircon geochronology. Ultrahigh metamorphic temperatures were achieved during the Acadian Orogeny in New England in localized, short pulses, likely related to igneous heating and/or associated fluid flow above and beyond the regional heating due to tectonic overthickening

    Community-based physical activity interventions for adolescents and adults with complex cerebral palsy : A scoping review

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    Aim To identify implementation strategies and safety outcomes (adverse events) of community-based physical activity interventions for adolescents and adults with complex cerebral palsy (CP). Method Five electronic databases were systematically searched to April 2022. Data were extracted on the implementation and safety of physical activity interventions for adolescents and adults with CP, classified in Gross Motor Function Classification System (GMFCS) levels IV and V, delivered in a community setting. Results Seventeen studies with 262 participants (160 participants classified in GMFCS levels IV or V) were included. Community settings included schools (n = 4), participants' homes (n = 3), gymnasia (n = 2), swimming pools (n = 2), and other settings (n = 4). Most studies specified medical or safety exclusion criteria. Implementation strategies included pre-exercise screening, use of adapted equipment, familiarization sessions, supervision, physical assistance, and physiological monitoring. Attendance was high and attrition low. Nine studies reported non-serious, expected, and related events. Four studies reported minor soreness and four studies reported minor fatigue post-exercise. Serious adverse events related to exercise were infrequent (reported for 4 of 160 participants [<2%]: three participants withdrew from an exercise programme and one participant ceased exercise for a short period). Most frequently reported was pain, requiring temporary exercise cessation or programme change, or study withdrawal (three participants). Interpretation For most adolescents and adults with CP classified in GMFCS levels IV and V, physical activity interventions can be safely performed in a community setting, without post-exercise pain or fatigue, or serious adverse events

    CCR4-bearing T cells participate in autoimmune diabetes.

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    Chemokine receptor expression is exquisitely regulated on T cell subsets during the course of their migration to inflammatory sites. In the present study we demonstrate that CCR4 expression marks a pathogenic population of autoimmune T cells. CCR4 was found exclusively on memory CD4(+) T cells during the progression of disease in NOD mice. Cells expressing the CCR4 ligand TARC (thymus- and activation-regulated chemokine) were detected within infiltrated islets from prediabetic mice. Interestingly, neutralization of macrophage-derived chemokine (MDC) with Ab caused a significant reduction of CCR4-positive T cells within the pancreatic infiltrates and inhibited the development of insulitis and diabetes. Furthermore, enhanced recruitment of CCR4-bearing cells in NOD mice resulting from transgenic expression of MDC resulted in acceleration of clinical disease. Cumulatively, the results demonstrate that CCR4-bearing T cells participate in the development of such tissue-driven autoimmune reactions

    CCR4-bearing T cells participate in autoimmune diabetes

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    CCR4-bearing T cells participate in autoimmune diabetes

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    Chemokine receptor expression is exquisitely regulated on T cell subsets during the course of their migration to inflammatory sites. In the present study we demonstrate that CCR4 expression marks a pathogenic population of autoimmune T cells. CCR4 was found exclusively on memory CD4(+) T cells during the progression of disease in NOD mice. Cells expressing the CCR4 ligand TARC (thymus- and activation-regulated chemokine) were detected within infiltrated islets from prediabetic mice. Interestingly, neutralization of macrophage-derived chemokine (MDC) with Ab caused a significant reduction of CCR4-positive T cells within the pancreatic infiltrates and inhibited the development of insulitis and diabetes. Furthermore, enhanced recruitment of CCR4-bearing cells in NOD mice resulting from transgenic expression of MDC resulted in acceleration of clinical disease. Cumulatively, the results demonstrate that CCR4-bearing T cells participate in the development of such tissue-driven autoimmune reactions
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