3,676 research outputs found

    Pedogenic Processes in Thick Sand Deposits on a Marine Terrace, Central California

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    Pedological studies in thick sedimentary sequences are generally limited to the upper few meters. Field investigation of thick (~50 m) sand deposits on an emergent Pleistocene marine terrace in central California showed morphological differences between the solum at the surface and the deep regolith. Based on morphological and geochemical features, four units were identified within the regolith. Two zones of active pedogenesis occur within three of these units. The surficial unit is in Holocene sand deposits (mixed, thermic, Argic Xeropsamments), and has darkened A horizons, a slightly reddened subsoil, and incipient lamellae at the depth of wetting front infiltration. These lamellae have slightly more day and Fe oxides than the soil above. Mineral weathering is intense at the surface. The other zone of active pedogenesis is at the base of the regolith, where a lithologic discontinuity above the terrace platform forms an aquitard, and throughflow occurs. Meteoric water percolates through thin regolith deposits above the shoreline angle, and at other locations on the terrace where sediment has been removed by erosion. Percolating water carries clay, organic matter, and solutes to the water table. Weathering is intense within this basal unit. Illuviation of clays and Fe oxides, and precipitation of Fe oxides and silica occur within this unit. As pore space is filled, fractures and channels become paths for saturated water flow. Eluviation of Fe occurs at these sites. Most of the intervening regolith is isolated from current pedogenesis by its great depth and a relatively dry Holocene climate. Well-developed lamellae are preserved as relicts of Pleistocene episodes of soil formation. These lamellae formed by illuviation of clay and Fe oxides, and were sites of silica precipitation. The conceptual model presented here is intended to facilitate understanding of pedogenic and geomorphological evolution of marine terrace deposits, and to assist with the interpretation of groundwater flow in these terrace systems

    Herbage Accumulation, Nutritive Value and Persistence of Mulato II in Florida

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    Grasses in the Brachiaria genus are the most widely grown forages in tropical America, occupying over 80 Mha (Boddey et al. 2004). Mulato II is apomictic and a vigorous, semi-erect cultivar resulting from 3 generations of crosses including original crosses between ruzigrass and signal-grass (cv. Basilisk, apomictic tetrapliod). According to Peters et al. (2003), Mulato produced 25% more herbage mass than palisadegrass (Brachiaria brizantha) and koroni-viagrass (Brachiaria humidicola) under similar management practices. Although Mulato II shows promise as a forage in tropical regions, herbage accumulation and persistence in subtropical areas is unknown. This publication summarises results of the research with Mulato II conducted in Florida in the last 5 years

    A 3D explainability framework to uncover learning patterns and crucial sub-regions in variable sulci recognition

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    Precisely identifying sulcal features in brain MRI is made challenging by the variability of brain folding. This research introduces an innovative 3D explainability frame-work that validates outputs from deep learning networks in their ability to detect the paracingulate sulcus, an anatomical feature that may or may not be present on the frontal medial surface of the human brain. This study trained and tested two networks, amalgamating local explainability techniques GradCam and SHAP with a dimensionality reduction method. The explainability framework provided both localized and global explanations, along with accuracy of classification results, revealing pertinent sub-regions contributing to the decision process through a post-fusion transformation of explanatory and statistical features. Leveraging the TOP-OSLO dataset of MRI acquired from patients with schizophrenia, greater accuracies of paracingulate sulcus detection (presence or absence) were found in the left compared to right hemispheres with distinct, but extensive sub-regions contributing to each classification outcome. The study also inadvertently highlighted the critical role of an unbiased annotation protocol in maintaining network performance fairness. Our proposed method not only offers automated, impartial annotations of a variable sulcus but also provides insights into the broader anatomical variations associated with its presence throughout the brain. The adoption of this methodology holds promise for instigating further explorations and inquiries in the field of neuroscience

    Identifying and managing patients at risk of severe allergic reactions to food: report from two iFAAM workshops

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    Food allergy affects a small but important number of children and adults. Much of the morbidity associated with food allergy is driven by the fear of a severe reaction, and fatalities continue to occur. Foods are the commonest cause of anaphylaxis. One of the aims of the European Union funded Integrated Approaches to Food Allergen and Allergy Risk Management (iFAAM) project was to improve the identification and management of children and adults at risk of experiencing a severe reaction. A number of interconnected studies within the project have focused on quantifying the severity of allergic reactions; the impact of food matrix, immunological factors on severity of reactions; the impact of co‐factors such as medications on the severity of reactions; utilising single dose challenges to understand threshold and severity of reactions; and community studies to understand the experience of patients suffering real‐life allergic reactions to food. Associated studies have examined population thresholds, and co‐factors such as exercise and stress. This paper summarises two workshops focused on the severity of allergic reactions to food. It outlines the related studies being undertaken in the project indicating how they are likely to impact on our ability to identify individuals at risk of severe reactions and improve their management

    Early Increase in Extrasynaptic NMDA Receptor Signaling and Expression Contributes to Phenotype Onset in Huntington's Disease Mice

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    SummaryN-methyl-D-aspartate receptor (NMDAR) excitotoxicity is implicated in the pathogenesis of Huntington's disease (HD), a late-onset neurodegenerative disorder. However, NMDARs are poor therapeutic targets, due to their essential physiological role. Recent studies demonstrate that synaptic NMDAR transmission drives neuroprotective gene transcription, whereas extrasynaptic NMDAR activation promotes cell death. We report specifically increased extrasynaptic NMDAR expression, current, and associated reductions in nuclear CREB activation in HD mouse striatum. The changes are observed in the absence of dendritic morphological alterations, before and after phenotype onset, correlate with mutation severity, and require caspase-6 cleavage of mutant huntingtin. Moreover, pharmacological block of extrasynaptic NMDARs with memantine reversed signaling and motor learning deficits. Our data demonstrate elevated extrasynaptic NMDAR activity in an animal model of neurodegenerative disease. We provide a candidate mechanism linking several pathways previously implicated in HD pathogenesis and demonstrate successful early therapeutic intervention in mice

    The Typical Flight Performance of Blowflies: Measuring the Normal Performance Envelope of Calliphora vicina Using a Novel Corner-Cube Arena

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    Despite a wealth of evidence demonstrating extraordinary maximal performance, little is known about the routine flight performance of insects. We present a set of techniques for benchmarking performance characteristics of insects in free flight, demonstrated using a model species, and comment on the significance of the performance observed. Free-flying blowflies (Calliphora vicina) were filmed inside a novel mirrored arena comprising a large (1.6 m1.6 m1.6 m) corner-cube reflector using a single high-speed digital video camera (250 or 500 fps). This arrangement permitted accurate reconstruction of the flies' 3-dimensional trajectories without the need for synchronisation hardware, by virtue of the multiple reflections of a subject within the arena. Image sequences were analysed using custom-written automated tracking software, and processed using a self-calibrating bundle adjustment procedure to determine the subject's instantaneous 3-dimensional position. We illustrate our method by using these trajectory data to benchmark the routine flight performance envelope of our flies. Flight speeds were most commonly observed between 1.2 ms−1 and 2.3 ms−1, with a maximum of 2.5 ms−1. Our flies tended to dive faster than they climbed, with a maximum descent rate (−2.4 ms−1) almost double the maximum climb rate (1.2 ms−1). Modal turn rate was around 240°s−1, with maximal rates in excess of 1700°s−1. We used the maximal flight performance we observed during normal flight to construct notional physical limits on the blowfly flight envelope, and used the distribution of observations within that notional envelope to postulate behavioural preferences or physiological and anatomical constraints. The flight trajectories we recorded were never steady: rather they were constantly accelerating or decelerating, with maximum tangential accelerations and maximum centripetal accelerations on the order of 3 g
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