63 research outputs found

    Recent Advances in High-Resolution MR Application and Its Implications for Neurovascular Coupling Research

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    The current understanding of fMRI, regarding its vascular origins, is based on numerous assumptions and theoretical modeling, but little experimental validation exists to support or challenge these models. The known functional properties of cerebral vasculature are limited mainly to the large pial surface and the small capillary level vessels. However, a significant lack of knowledge exists regarding the cluster of intermediate-sized vessels, mainly the intracortical, connecting these two groups of vessels and where, arguably, key blood flow regulation takes place. In recent years, advances in MR technology and methodology have enabled the probing of the brain, both structurally and functionally, at resolutions and coverage not previously attainable. Functional MRI has been utilized to map functional units down to the levels of cortical columns and lamina. These capabilities open new possibilities for investigating neurovascular coupling and testing hypotheses regarding fundamental cerebral organization. Here, we summarize recent cutting-edge MR applications for studying neurovascular and functional imaging, both in humans as well as in animal models. In light of the described imaging capabilities, we put forward a theory in which a cortical column, an ensemble of neurons involved in a particular neuronal computation is spatially correlated with a specific vascular unit, i.e., a cluster of an emerging principle vein surrounded by a set of diving arteries. If indeed such a correlation between functional (neuronal) and structural (vascular) units exist as a fundamental intrinsic cortical feature, one could conceivably delineate functional domains in cortical areas that are not known or have not been identified

    Emergence of winner-takes-all connectivity paths in random nanowire networks

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    Nanowire networks are promising memristive architectures for neuromorphic applications due to their connectivity and neurosynaptic-like behaviours. Here, we demonstrate a self-similar scaling of the conductance of networks and the junctions that comprise them. We show this behavior is an emergent property of any junction-dominated network. A particular class of junctions naturally leads to the emergence of conductance plateaus and a “winner-takes-all” conducting path that spans the entire network, and which we show corresponds to the lowest-energy connectivity path. The memory stored in the conductance state is distributed across the network but encoded in specific connectivity pathways, similar to that found in biological systems. These results are expected to have important implications for development of neuromorphic devices based on reservoir computing

    Uncovering hidden in vivo resonances using editing based on localized TOCSY

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    A novel single-shot spectral editing technique for in vivo proton NMR is proposed to recover resonances of low-concentration metabolites obscured by very strong resonances. With this new method, editing is performed by transferring transverse magnetization to J-coupled spins from selected coupling partners using a homonuclear Hartmann-Hahn polarization transfer with adiabatic pulses. The current implementation uses 1D-TOCSY with single-voxel localization based on LASER to recover the H1 proton of beta-glucose at 4.63 ppm from under water and the lactate methyl resonances from beneath a strong lipid signal. The method can be extended to further spin systems where conventional editing methods are difficult to perform

    Person-centred Leadership: a relational approach to leadership derived through action research

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    Aims & Objectives: How does person-centred leadership manifest in clinical nursing. Background: Person-centred practice fosters healthful relationships and is gaining increasing attention in nursing and healthcare, but nothing is known about the influence of a person centred approach to leadership practice. Most leadership models used in nursing were originally developed outside of nursing. Design: A three year participatory action research study where participant leaders planned, researched and learned from their practice development. Methods: After an orientation phase, four action spirals focused on: critical and creative reflective inquiries into leadership practice change; leading the implementation and evaluation of a new nursing system; facilitating storytelling sessions with staff and annually reflecting on personal leadership change. Multiple data gathering methods offered insight into leadership development from several perspectives. Results: Critical and creative thematic data analysis revealed a set of attributes, relational processes and contextual factors that influenced the being and becoming of a person-centred leader. Comparing the findings with nursing leadership literature supports a conceptual framework for person-centred leadership. Conclusions: Person-centred leadership is a complex, dynamic, relational and contextualised practice that aims to enable associates and leaders achieve self-actualisation, empowerment and wellbeing.sch_nurpub5316pu

    Methodological consensus on clinical proton MRS of the brain: Review and recommendations

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    © 2019 International Society for Magnetic Resonance in Medicine Proton MRS (1H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good-quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi-adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use

    Biochars effects potentially toxic elements and antioxidant enzymes in Lactuca sativa L. grown in multi-metals contaminated soil

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    Geogenic and anthropogenic activities can leads to agriculture soil pollution and land degradation. Many cost-effective and environment friendly strategies are applied to improve soil fertility, reduce soil pollution and human health risks caused by consumption of metals contaminated vegetables. In this study we evaluate the effects of rice husk biochar (RHB), biochar from corn cob (CCB) and biochar from peanut shells (PNB) on the bioavailability of potentially toxic elements (PTEs) in soil, its bioaccumulation and antioxidant enzymes activities in Lactuca sativa L. plants. RHB, CCB and PNB amendments significantly (P≀0.05) increased Lactuca sativa L. biomass production (39%, 65% and 100%) as well as soil fertility. Amendments of PNB, RHB and CCB significantly (P≀0.05) increased soil available phosphorous (P), cation exchange capacity (CEC), pH, total nitrogen (TN), total carbon (TC) and dissolved organic carbon (DOC) concentration, but markedly reduced bioavailable concentrations of cadmium (Cd) (31%, 20% and 22%) arsenic (As) (33%, 22% and 27%), and lead (Pb) (46%, 24% and 32%). In addition, CCB and PNB amendments significantly (P≀0.01) decreased the shoot accumulation of Pb, Cd and As, while RHB amendment increased the shoot accumulations of nickel (Ni) and chromium (Cr). The reduction in PTEs accumulation may be linked with increased sorption of PTEs by biochars. Furthermore, amendments of CCB and PNB significantly (P≀0.05) suppressed the activities of SOD (53% and 69%), POD (22%, 31%) but stimulated (38% and 31%) with amendment of RHB. However, RHB, CCB and PNB amendments significantly (P≀0.05) suppressed the activity of CAT (21%, 41% and 48%) in Lactuca sativa L. plants. PNB was the most effective soil amendment as compared with RHB and CCB. However, to fully elucidate the effects of the tested biochars, long-term field trails are needed

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