24 research outputs found

    Pervasive gaps in Amazonian ecological research

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    Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

    Pervasive gaps in Amazonian ecological research

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    Conversion Discriminative Analysis on Mild Cognitive Impairment Using Multiple Cortical Features from MR Images

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    Neuroimaging measurements derived from magnetic resonance imaging provide important information required for detecting changes related to the progression of mild cognitive impairment (MCI). Cortical features and changes play a crucial role in revealing unique anatomical patterns of brain regions, and further differentiate MCI patients from normal states. Four cortical features, namely, gray matter volume, cortical thickness, surface area, and mean curvature, were explored for discriminative analysis among three groups including the stable MCI (sMCI), the converted MCI (cMCI), and the normal control (NC) groups. In this study, 158 subjects (72 NC, 46 sMCI, and 40 cMCI) were selected from the Alzheimer's Disease Neuroimaging Initiative. A sparse-constrained regression model based on the l2-1-norm was introduced to reduce the feature dimensionality and retrieve essential features for the discrimination of the three groups by using a support vector machine (SVM). An optimized strategy of feature addition based on the weight of each feature was adopted for the SVM classifier in order to achieve the best classification performance. The baseline cortical features combined with the longitudinal measurements for 2 years of follow-up data yielded prominent classification results. In particular, the cortical thickness produced a classification with 98.84% accuracy, 97.5% sensitivity, and 100% specificity for the sMCI–cMCI comparison; 92.37% accuracy, 84.78% sensitivity, and 97.22% specificity for the cMCI–NC comparison; and 93.75% accuracy, 92.5% sensitivity, and 94.44% specificity for the sMCI–NC comparison. The best performances obtained by the SVM classifier using the essential features were 5–40% more than those using all of the retained features. The feasibility of the cortical features for the recognition of anatomical patterns was certified; thus, the proposed method has the potential to improve the clinical diagnosis of sub-types of MCI and predict the risk of its conversion to Alzheimer's disease

    Quantitative 18F-AV1451 Brain Tau PET Imaging in Cognitively Normal Older Adults, Mild Cognitive Impairment, and Alzheimer's Disease Patients

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    Recent developments of tau Positron Emission Tomography (PET) allows assessment of regional neurofibrillary tangles (NFTs) deposition in human brain. Among the tau PET molecular probes, 18F-AV1451 is characterized by high selectivity for pathologic tau aggregates over amyloid plaques, limited non-specific binding in white and gray matter, and confined off-target binding. The objectives of the study are (1) to quantitatively characterize regional brain tau deposition measured by 18F-AV1451 PET in cognitively normal older adults (CN), mild cognitive impairment (MCI), and AD participants; (2) to evaluate the correlations between cerebrospinal fluid (CSF) biomarkers or Mini-Mental State Examination (MMSE) and 18F-AV1451 PET standardized uptake value ratio (SUVR); and (3) to evaluate the partial volume effects on 18F-AV1451 brain uptake.Methods: The study included total 115 participants (CN = 49, MCI = 58, and AD = 8) from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Preprocessed 18F-AV1451 PET images, structural MRIs, and demographic and clinical assessments were downloaded from the ADNI database. A reblurred Van Cittertiteration method was used for voxelwise partial volume correction (PVC) on PET images. Structural MRIs were used for PET spatial normalization and region of interest (ROI) definition in standard space. The parametric images of 18F-AV1451 SUVR relative to cerebellum were calculated. The ROI SUVR measurements from PVC and non-PVC SUVR images were compared. The correlation between ROI 18F-AV1451 SUVR and the measurements of MMSE, CSF total tau (t-tau), and phosphorylated tau (p-tau) were also assessed.Results:18F-AV1451 prominently specific binding was found in the amygdala, entorhinal cortex, parahippocampus, fusiform, posterior cingulate, temporal, parietal, and frontal brain regions. Most regional SUVRs showed significantly higher uptake of 18F-AV1451 in AD than MCI and CN participants. SUVRs of small regions like amygdala, entorhinal cortex and parahippocampus were statistically improved by PVC in all groups (p < 0.01). Although there was an increasing tendency of 18F-AV-1451 SUVRs in MCI group compared with CN group, no significant difference of 18F-AV1451 deposition was found between CN and MCI brains with or without PVC (p > 0.05). Declined MMSE score was observed with increasing 18F-AV1451 binding in amygdala, entorhinal cortex, parahippocampus, and fusiform. CSF p-tau was positively correlated with 18F-AV1451 deposition. PVC improved the results of 18F-AV-1451 tau deposition and correlation studies in small brain regions.Conclusion: The typical deposition of 18F-AV1451 tau PET imaging in AD brain was found in amygdala, entorhinal cortex, fusiform and parahippocampus, and these regions were strongly associated with cognitive impairment and CSF biomarkers. Although more deposition was observed in MCI group, the 18F-AV-1451 PET imaging could not differentiate the MCI patients from CN population. More tau deposition related to decreased MMSE score and increased level of CSF p-tau, especially in ROIs of amygdala, entorhinal cortex and parahippocampus. PVC did improve the results of tau deposition and correlation studies in small brain regions and suggest to be routinely used in 18F-AV1451 tau PET quantification

    Pervasive gaps in Amazonian ecological research

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    Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

    Mapping and Spatial Analysis of Aeolian Deposits, White River Badlands, South Dakota

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    The goal of this study is to determine the timing of the latest episode of aeolian dune activity in the White River Badlands (WRB) south of the North Unit of the Badlands National Park (BNP), South Dakota. Our previous results indicate that alluvial pediments in the BNP experienced an episode of fluvial incision initiated by approximately 1,000 AD. We hypothesize that incision was caused by a regional drought that destabilized pediment surfaces and enhanced erosive power of periodic storms sometime in the interval known as the Medieval Climatic Anomaly (approximately 900 to 1200 AD). We further hypothesized that a regional drought would have driven change in other geomorphic systems in the WRB. WRB aeolian dune fields occur north of the White River on approximately 400 km2 of dissected strath terraces. Aeolian features include aeolian cliff-top deposits (ACT), sand sheets, and stabilized parabolic dunes. Previous 14C analyses of paleosols indicated that ACT accumulated rapidly post 1300 radiocarbon years before present (Rawlings et al., 2003), approximately the same time as pediment incision in BNP. Further study of these aeolian deposits could determine whether a regional drought occurred in the WRB and shed light on climate changes on the northern Great Plains. In summer 2014, we made a reconnaissance trip the WRB dune fields in preparation for more detailed study. We are using digital mapping technology and remote sensing analysis to map dune forms on strath terraces in the WRB. Surficial maps will be used to establish cross-cutting relationships and relative ages of WRB dune forms, as well as wind direction. GIS 3D technology was used to convert digital elevation models to triangulated irregular networks (TIN) for analysis. Remote sensing analysis was accomplished using SPOT 5 imagery of the dune complex classified using Principle Component Analysis (PCA) and an unsupervised classification. Investigators will discuss results of the summer 2014 WRB reconnaissance and subsequent digital mapping and remote sensing analysis of the White River dune fields

    Assessing and Displaying Landslide Hazards, Badlands National Park, South Dakota

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    The goal of this study is to assess and communicate hazards associated with landslides in the Badlands National Park using geological mapping and innovative GIS data gathering and display techniques. The current geological map of the Badlands National Park (1:62,500 scale) was published in 1976. While an excellent map, it gives little information useful for hazard assessment other than distribution of slide deposits. The goal here is to create a detailed map of slide distribution together with information on slide mechanisms, timing, and bedrock geologic factors that contribute to hazards. These data are displayed in GIS formats that are interactive, can be quickly updated, and useful for analysis. Landslide zones in the Badlands are especially hazardous to park infrastructure; the main road through the park crosses three of the largest slide zones. At these crossings, road stabilization has been ongoing and expensive. Creep rates of 50 to 125 mm/week were recorded by geotechnical investigators at Cedar Pass prior to stabilization efforts in 2000. In addition to creep, there is significant danger of catastrophic slumping and rock toppling in these zones. Geologic conditions that contribute to slide formation include loosely consolidated strata, precipitation events, the presence of swelling clays, vertical jointing, and a structural dip towards the river valley. In addition to assessing hazards, we are attempting to use GIS techniques in innovative ways. In this first phase of the project, using data gathered in three field seasons, we created a digital base map of the project area in ESRI’s ArcGIS Software. Point, line and polygon vector data were gathered with the use of both sub-meter Trimble GeoXT and Garmin GPS units. Together with field notes, drawings and hyperlinked digital images at specific landslide locations, data was checked into the project Geodatabase and specific feature classes were created/updated and overlaid on high-resolution imagery. Analysis was then performed on the layers to create distinct spatial and temporal boundaries based on geologic beds and historic activity. This state of the art geospatial digital map allows the map user greater access to spatial/geologic information and interpretation of the field area than a traditional geologic map
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