864 research outputs found

    Spin and orbital states in La1.5 Sr0.5 CoO4 studied by electronic structure calculations

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    Electronic structure of the layered perovskite La1.5Sr0.5CoO4 with a checkerboard Co2+/Co3+ charge order is studied, using the local-spin-density approximation plus Hubbard U calculations including also the spin-orbit coupling and multiplet effect. Our results show that the Co2+ ion is in a high spin state (HS, t(2g)(5)e(g)(2)) and Co3+ low spin state (LS, t(2g)(6)). Due to a small Co2+ t(2g) crystal field splitting, the spin-orbit interaction produces an orbital moment of 0.26 mu(B) and accounts for the observed easy in-plane magnetism. Moreover, we find that the Co3+ intermediate spin state (IS, t(2g)(5)e(g)(1)) has a multiplet splitting of several tenths of eV and the lowest-lying one is still higher than the LS ground state by 120 meV, and that the Co3+ HS state (t(2g)(4)e(g)(2)) is more unstable by 310 meV. Either the IS or HS Co3+ ions would give rise to a wrong magnetic order and anisotropy

    High Force Unimanual Handgrip Contractions Increase Ipsilateral Sensorimotor Activation and Functional Connectivity

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    Imaging and brain stimulation studies seem to correct the classical understanding of how brain networks, rather than contralateral focal areas, control the generation of unimanual voluntary force. However, the scaling and hemispheric-specificity of network activation remain less understood. Using fMRI, we examined the effects of parametrically increasing right-handgrip force on activation and functional connectivity among the sensorimotor network bilaterally with 25%, 50%, and 75% maximal voluntary contractions (MVC). High force (75% MVC) unimanual handgrip contractions resulted in greater ipsilateral motor activation and functional connectivity with the contralateral hemisphere compared to a low force 25% MVC condition. The ipsilateral motor cortex activation and network strength correlated with relative handgrip force (% MVC). Increases in unimanual handgrip force resulted in greater ipsilateral sensorimotor activation and greater functional connectivity between hemispheres within the sensorimotor network. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved

    Feasibility of PROMIS CAT Administration in the Ambulatory Sports Medicine Clinic With Respect to Cost and Patient Compliance: A Single-Surgeon Experience.

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    Background: Pay-for-performance reimbursement models are becoming increasingly popular, but the implementation of a routine patient-reported outcome (PRO) collection system places additional burden on both the patient and the provider. The Patient-Reported Outcomes Measurement Information System (PROMIS) was developed in an effort to make PRO collection more practical and efficient, but providers may be reluctant to embrace a transition to a PROMIS-based clinical outcome registry. Hypothesis: PROMIS can be successfully incorporated into daily clinical practice, with an overall patient compliance rate of 80%. Study Design: Cross-sectional study; Level of evidence, 3. Methods: As part of routine practice, all patients presenting to a single surgeon\u27s sports medicine clinic for an appointment were asked to complete a series of PROMIS computerized adaptive tests (CATs), including PROMIS Physical Function, Physical Function-Upper Extremity, Pain Interference, and Depression subscales. Overall compliance was calculated by dividing the number of survey sets completed by the number of eligible clinic visits. Compliance rates were further assessed by patient age, type of clinic visit, and location of injury. Costs associated with this system of routine PRO collection were categorized as start-up or maintenance costs. Results: From August 7, 2017, to December 8, 2017, there were 581 patients (1109 clinic encounters) who met inclusion criteria for the study. Of the 1109 clinic encounters, there was an overall compliance rate of 91.3% (1013/1109 visits during which the patient completed the entire PROMIS survey set). Overall, the full survey set consisted of a mean 15.3 questions and took a mean of 2.6 minutes to complete. Patients who were aged ≥62 years had a significantly lower compliance rate (81.8%; Conclusion: The routine electronic collection of PROMIS scores in the ambulatory orthopaedic clinic resulted in a compliance rate of over 90%, although older patients were generally less compliant than younger patients. Our system of data collection is practical and efficient in a high-volume orthopaedic clinic and places minimal financial burden on the provider

    Visuospatial Processing Deficits Linked to Posterior Brain Regions in Premanifest and Early Stage Huntington's Disease

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    OBJECTIVES: Visuospatial processing deficits have been reported in Huntington’s disease (HD). To date, no study has examined associations between visuospatial cognition and posterior brain findings in HD. METHODS: We compared 119 premanifest (55> and 64<10.8 years to expected disease onset) and 104 early symptomatic (59 stage-1 and 45 stage-2) gene carriers, with 110 controls on visual search and mental rotation performance at baseline and 12 months. In the disease groups, we also examined associations between task performance and disease severity, functional capacity and structural brain measures. RESULTS: Cross-sectionally, there were strong differences between all disease groups and controls on visual search, and between diagnosed groups and controls on mental rotation accuracy. Only the premanifest participants close to onset took longer than controls to respond correctly to mental rotation. Visual search negatively correlated with disease burden and motor symptoms in diagnosed individuals, and positively correlated with functional capacity. Mental rotation (“same”) was negatively correlated with motor symptoms in stage-2 individuals, and positively correlated with functional capacity. Visual search and mental rotation were associated with parieto-occipital (pre-/cuneus, calcarine, lingual) and temporal (posterior fusiform) volume and cortical thickness. Longitudinally, visual search deteriorated over 12 months in stage-2 individuals, with no evidence of declines in mental rotation. Conclusions: Our findings provide evidence linking early visuospatial deficits to functioning and posterior cortical dysfunction in HD. The findings are important since large research efforts have focused on fronto-striatal mediated cognitive changes, with little attention given to aspects of cognition outside of these areas. (JINS, 2016, 22, 595–608
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