755 research outputs found

    Analysis of the Socio-Economic Impacts of a Proposed Highway between Nuevo Italia and Puerto Breu, Peru

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    Road building is increasingly promoted in the borderlands shared by Peru and Brazil despite an incomplete understanding of the socio-environmental impacts of transportation infrastructure in the region. Amazonian roads often expand informally, without official government process, previous consultation by Indigenous populations, and environmental impact statements.. Amazonian road expansion also often follows a progressive feedback cycle, with new, unplanned roads begetting illegal logging pathways and agricultural expansion which in turn expands and formalizes road systems. One expanding road system is developing between the Ucayali River and the remote headwaters of the Yurua/Jurua River. The Carretera Yurua (officially trail UC-105), extended approximately300 km long in August 2020. Existing research suggests that the unplanned construction of the Yurua road, which originally began as informal logging roads extending off a road to explore fossil fuels, could result in significant land changes and will facilitate ranching, additional illegal timber harvesting, and coca farming, threatening global biodiversity hotspots and conservation areas, and endangered Indigenous cultures and territories. This research spatially analyzes the different waterways, cultural territories, conservation areas and other administrative units crossed by the proposed road. Additional analysis includes the deforestation footprint and downstream impacts of the road. Methods include GIS analysis and remote sensing along with document and internet research of news articles, legal documents, social media communications, interviews from key actors, and studies of similar infrastructure projects in the bio-culturally diverse Amazon borderlands

    A neuroepithelial wave of BMP signalling drives anteroposterior specification of the tuberal hypothalamus

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    The tuberal hypothalamus controls life-supporting homeostatic processes, but despite its fundamental role, the cells and signalling pathways that specify this unique region of the central nervous system in embryogenesis are poorly characterised. Here, we combine experimental and bioinformatic approaches in the embryonic chick to show that the tuberal hypothalamus is progressively generated from hypothalamic floor plate-like cells. Fate-mapping studies show that a stream of tuberal progenitors develops in the anterior-ventral neural tube as a wave of neuroepithelial-derived BMP signalling sweeps from anterior to posterior through the hypothalamic floor plate. As later-specified posterior tuberal progenitors are generated, early specified anterior tuberal progenitors become progressively more distant from these BMP signals and differentiate into tuberal neurogenic cells. Gain- and loss-of-function experiments in vivo and ex vivo show that BMP signalling initiates tuberal progenitor specification, but must be eliminated for these to progress to anterior neurogenic progenitors. scRNA-Seq profiling shows that tuberal progenitors that are specified after the major period of anterior tuberal specification begin to upregulate genes that characterise radial glial cells. This study provides an integrated account of the development of the tuberal hypothalamus

    Single-cell analysis of early chick hypothalamic development reveals that hypothalamic cells are induced from prethalamic-like progenitors

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    The hypothalamus regulates many innate behaviors, but its development remains poorly understood. Here, we used single-cell RNA sequencing (RNA-seq) and hybridization chain reaction (HCR) to profile multiple stages of early hypothalamic development in the chick. Hypothalamic neuroepithelial cells are initially induced from prethalamic-like cells. Two distinct hypothalamic progenitor populations then emerge and give rise to tuberal and mammillary/paraventricular hypothalamic cells. At later stages, the regional organization of the chick and mouse hypothalamus is highly similar. We identify selective markers for major subdivisions of the developing chick hypothalamus and many previously uncharacterized candidate regulators of hypothalamic induction, regionalization, and neurogenesis. As proof of concept for the power of the dataset, we demonstrate that prethalamus-derived follistatin inhibits hypothalamic induction. This study clarifies the organization of the nascent hypothalamus and identifies molecular mechanisms that may control its induction and subsequent development

    Rupture by damage accumulation in rocks

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    The deformation of rocks is associated with microcracks nucleation and propagation, i.e. damage. The accumulation of damage and its spatial localization lead to the creation of a macroscale discontinuity, so-called "fault" in geological terms, and to the failure of the material, i.e. a dramatic decrease of the mechanical properties as strength and modulus. The damage process can be studied both statically by direct observation of thin sections and dynamically by recording acoustic waves emitted by crack propagation (acoustic emission). Here we first review such observations concerning geological objects over scales ranging from the laboratory sample scale (dm) to seismically active faults (km), including cliffs and rock masses (Dm, hm). These observations reveal complex patterns in both space (fractal properties of damage structures as roughness and gouge), time (clustering, particular trends when the failure approaches) and energy domains (power-law distributions of energy release bursts). We use a numerical model based on progressive damage within an elastic interaction framework which allows us to simulate these observations. This study shows that the failure in rocks can be the result of damage accumulation
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