5,183 research outputs found

    Review: Do the Different Sensory Areas within the Cat Anterior Ectosylvian Sulcal Cortex Collectively Represent a Network Multisensory Hub?

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    Current theory supports that the numerous functional areas of the cerebral cortex are organized and function as a network. Using connectional databases and computational approaches, the cerebral network has been demonstrated to exhibit a hierarchical structure composed of areas, clusters and, ultimately, hubs. Hubs are highly connected, higher-order regions that also facilitate communication between different sensory modalities. One region computationally identified network hub is the visual area of the Anterior Ectosylvian Sulcal cortex (AESc) of the cat. The Anterior Ectosylvian Visual area (AEV) is but one component of the AESc that also includes the auditory (Field of the Anterior Ectosylvian Sulcus - FAES) and somatosensory (Fourth somatosensory representation - SIV). To better understand the nature of cortical network hubs, the present report reviews the biological features of the AESc. Within the AESc, each area has extensive external cortical connections as well as among one another. Each of these core representations is separated by a transition zone characterized by bimodal neurons that share sensory properties of both adjoining core areas. Finally, core and transition zones are underlain by a continuous sheet of layer 5 neurons that project to common output structures. Altogether, these shared properties suggest that the collective AESc region represents a multiple sensory/multisensory cortical network hub. Ultimately, such an interconnected, composite structure adds complexity and biological detail to the understanding of cortical network hubs and their function in cortical processing

    Acoustic characterization of crack damage evolution in sandstone deformed under conventional and true triaxial loading

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    We thank the Associate Editor, Michelle Cooke, and the reviewers, Ze'ev Reches and Yves Guéguen, for useful comments which helped to improve the manuscript. We thank J.G. Van Munster for providing access to the true triaxial apparatus at KSEPL and for technical support during the experimental program. We thank R. Pricci for assistance with technical drawings of the apparatus. This work was partly funded by NERC award NE/N002938/1 and by a NERC Doctoral Studentship, which we gratefully acknowledge. Supporting data are included in a supporting information file; any additional data may be obtained from J.B. (e-mail: [email protected]).Peer reviewedPublisher PD

    Experimental and analytical study of cryogenic propellant boiloff to develop and verify alternate pressurization concepts for Space Shuttle external tank using a scaled down tank

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    Self pressurization by propellant boiloff is experimentally studied as an alternate pressurization concept for the Space Shuttle external tank (ET). The experimental setup used in the study is an open flow system which is composed of a variable area test tank and a recovery tank. The vacuum jacketed test tank is geometrically similar to the external LOx tank for the Space Shuttle. It is equipped with instrumentation to measure the temperature and pressure histories within the liquid and vapor, and viewports to accommodate visual observations and Laser-Doppler Anemometry measurements of fluid velocities. A set of experiments were conducted using liquid Nitrogen to determine the temperature stratification in the liquid and vapor, and pressure histories of the vapor during sudden and continuous depressurization for various different boundary and initial conditions. The study also includes the development and calibration of a computer model to simulate the experiments. This model is a one-dimensional, multi-node type which assumes the liquid and the vapor to be under non-equilibrium conditions during the depressurization. It has been tested for a limited number of cases. The preliminary results indicate that the accuracy of the simulations is determined by the accuracy of the heat transfer coefficients for the vapor and the liquid at the interface which are taken to be the calibration parameters in the present model

    Water use governance in a temperate region: Implications for agricultural climate change adaptation in the Northeastern United States

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    Climate change and access to water are interrelated concerns for agriculture and other sectors, even in temperate regions. Governance approaches and regulatory frameworks determine who has access to water, for what purpose, and when. In the northeastern United States, water governance has historically been conducted by states through a combination of statutory guidance and common law. However, it is unclear what effect if current governance approaches will be sufficient for achieving resource conservation and equitable allocation in a changing climate. To provide insight into these issues, we conducted the first review of freshwater governance in the 12 states that comprise the U.S. Northeast. Specifically, we examine their heterogeneous approaches to surface and groundwater use, permitting and reporting, and scarcity provisions. Using agriculture as the sector of focus, we show through narrative review and quantitative analysis that change in the proportion of cropland that is irrigated in each state does not differ based on governance approach. We also suggest that future decades may bring regulatory shifts relevant to agriculture, changes in enforcement, increased competition between agriculture and other users, and greater potential competition between states for water resources. This case study raises the question: how should we prepare for the time when competition for, or degradation of, a resource surpasses the ability of existing governance mechanisms to ensure conservation and equitable distribution

    Cerebral Amyloid and Hypertension are Independently Associated with White Matter Lesions in Elderly.

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    In cognitively normal (CN) elderly individuals, white matter hyperintensities (WMH) are commonly viewed as a marker of cerebral small vessel disease (SVD). SVD is due to exposure to systemic vascular injury processes associated with highly prevalent vascular risk factors (VRFs) such as hypertension, high cholesterol, and diabetes. However, cerebral amyloid accumulation is also prevalent in this population and is associated with WMH accrual. Therefore, we examined the independent associations of amyloid burden and VRFs with WMH burden in CN elderly individuals with low to moderate vascular risk. Participants (n = 150) in the Alzheimer's Disease Neuroimaging Initiative (ADNI) received fluid attenuated inversion recovery (FLAIR) MRI at study entry. Total WMH volume was calculated from FLAIR images co-registered with structural MRI. Amyloid burden was determined by cerebrospinal fluid Aβ1-42 levels. Clinical histories of VRFs, as well as current measurements of vascular status, were recorded during a baseline clinical evaluation. We tested ridge regression models for independent associations and interactions of elevated blood pressure (BP) and amyloid to total WMH volume. We found that greater amyloid burden and a clinical history of hypertension were independently associated with greater WMH volume. In addition, elevated BP modified the association between amyloid and WMH, such that those with either current or past evidence of elevated BP had greater WMH volumes at a given burden of amyloid. These findings are consistent with the hypothesis that cerebral amyloid accumulation and VRFs are independently associated with clinically latent white matter damage represented by WMHs. The potential contribution of amyloid to WMHs should be further explored, even among elderly individuals without cognitive impairment and with limited VRF exposure

    Sub-barrier fusion of the oxygen isotopes: A more complete picture

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    We have measured the sub-barrier fusion cross sections for 16,17,18O on 16O and we present the data and the experimental method in detail. The data were analyzed with a one-dimensional potential barrier inversion model, a two-dimensional incoming wave boundary condition model, and a two-dimensional Wentzel-Kramers-Brillouin model. We find that a multidimensional model is necessary to describe the enhanced fusion cross sections in oxygen and the two-dimensional incoming wave boundary condition model suggests that a complete description of the fusion, inelastic, and elastic cross sections is possible

    Bilateral Diffuse Uveal Melanocytic Proliferation Presenting as Small Choroidal Melanoma

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    Purpose. To describe a patient with Bilateral Diffuse Uveal Proliferation who presented initially with a clinical picture consistent with choroidal melanoma. Methods. Presentation of a clinical case with fundus photos, fluorescein angiography, and optical coherence tomography. Results. A 70-year-old Caucasian male with history of esophageal cancer presented with an asymptomatic pigmented choroidal lesion in his left eye initially diagnosed as choroidal nevus. This lesion enlarged over the course of a year and developed orange pigment and increased thickness. A metastatic workup was negative, and a radioactive iodine plaque was placed on the left eye. Over the next six months, the visual acuity in his left eye decreased. His clinical picture was consistent with unilateral Diffuse Uveal Proliferation. A recurrence of his esophageal carcinoma with metastasis was discovered and palliative chemotherapy was initiated. Although his visual acuity improved in the left eye, similar pigmentary changes developed in the right fundus. His visual acuity in both eyes gradually decreased to 20/200 until his death a year later. Conclusion. BDUMP should always be considered in the differential diagnosis of patients with pigmented fundus lesions and a history of nonocular tumors

    Text mining the food security literature reveals substantial spatial bias and thematic broadening over time

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    We conducted text mining analyses on nearly the entirety of academic literature related to food security. Assessing the literature\u27s spatial scope, we found a truly global body of research conducted across 187 different countries, but with significant spatial heterogeneities in where research is conducted. Comparing the spatial distribution of the literature to actual rates of food insecurity, we found only a slight association between where food security research is conducted and where food security needs are located. Using topic modeling to assess the thematic scope of the literature, we found that originally food security research focused on economic policy and global issues, and only later did the literature expand to encompass themes like livelihoods, health, and the environment. This analysis provides the first ever thematic scoping of the entire food security literature and the first assessment of spatial biases in where food security research is conducted
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