33 research outputs found

    Upper mantle velocity-temperature conversion and composition determined from seismic refraction and heat flow

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    International audience[1] We compile upper mantle P n velocities from seismic refraction/wide-angle reflection surveys in the southern Superior Province of the Canadian Shield and compare them with temperatures at the Moho deduced from heat flow data. Calculated Moho temperatures and P n velocities correlate well, showing that in this area, P n depends primarily on temperature. The obtained values of @V(P n)/@T depend weakly on the assumed value of Moho heat flow and are on the order of À6.0 Â 10 À4 ± 10% km s À1 K À1 , within the range of temperature derivatives obtained in laboratory studies of ultramafic rocks. Comparison between observed P n velocities and predicted values for several mineralogical models at Moho temperatures allows constraints on both the Moho heat flow and the shallow mantle composition. For all Moho heat flows, undepleted (clinopyroxene-rich) mantle compositions do not allow a good fit to the data. For depleted mantle compositions, temperatures consistent with the observed P n velocities correspond to values of Moho heat flow larger than 12 mW m À2. For our preferred Moho heat flow of 15 mW m À2 , the best fit mantle composition is slightly less depleted than models for average Archean subcontinental lithospheric mantle. This may be due to rejuvenation by melt-related metasomatism during the Keweenawan rifting event. The similarity in P n À T conversion factors estimated from this empirical large-scale geophysical study and those from laboratory data provides confidence in the absolute temperature values deduced from heat flow measurements and seismic studies. Citation: Perry, H. K. C., C. Jaupart, J.-C. Mareschal, and N. M. Shapiro (2006), Upper mantle velocity-temperature conversion and composition determined from seismic refraction and heat flow

    Abnormal connectivity in the sensorimotor network predicts attention deficits in traumatic brain injury

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    The aim of this study was to explore modifications of functional connectivity in multiple resting-state networks (RSNs) after moderate to severe traumatic brain injury (TBI) and evaluate the relationship between functional connectivity patterns and cognitive abnormalities. Forty-three moderate/severe TBI patients and 34 healthy controls (HC) underwent resting-state fMRI. Group ICA was applied to identify RSNs. Between-subject analysis was performed using dual regression. Multiple linear regressions were used to investigate the relationship between abnormal connectivity strength and neuropsychological outcome. Forty (93%) TBI patients showed moderate disability, while 2 (5%) and 1 (2%) upper severe disability and low good recovery, respectively. TBI patients performed worse than HC on the domains attention and language. We found increased connectivity in sensorimotor, visual, default mode (DMN), executive, and cerebellar RSNs after TBI. We demonstrated an effect of connectivity in the sensorimotor RSN on attention (p < 10−3) and a trend towards a significant effect of the DMN connectivity on attention (p = 0.058). A group-by-network interaction on attention was found in the sensorimotor network (p = 0.002). In TBI, attention was positively related to abnormal connectivity within the sensorimotor RSN, while in HC this relation was negative. Our results show altered patterns of functional connectivity after TBI. Attention impairments in TBI were associated with increased connectivity in the sensorimotor network. Further research is needed to test whether attention in TBI patients is directly affected by changes in functional connectivity in the sensorimotor network or whether the effect is actually driven by changes in the DMN

    Inhibition of THC-induced effects on the central nervous system and heart rate by a novel CB1 receptor antagonist AVE1625

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    CB1 antagonists such as AVE1625 are potentially useful in the treatment of obesity, smoking cessation and cognitive impairment. Proof of pharmacological action of AVE1625 in the brain can be given by antagonising the effects of delta-9-tetrahydrocannabinol (THC), a CB1/CB2 agonist. Inhibition of THC-induced effects by AVE1625 was observed on Visual Analogue Scales 'alertness', 'feeling high', 'external perception', 'body sway' and 'heart rate'. Even the lowest dose of AVE1625 20 mg inhibited most of THC-induced effects. AVE1625 did not have any effect on psychological and behavioural parameters or heart rate by itself. After THC and AVE1625 administration, changes on electroencephalography were observed. This study shows a useful method for studying the effects of CB1 antagonists. AVE1625 penetrates the brain and antagonises THC-induced effects with doses at or above 20 mg.Stress-related psychiatric disorders across the life spa

    The Effects of Standing Tutorials on Learning in Undergraduate Students: Study Protocol

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    Standing classrooms could potentially counteract excessive sedentary behavior. This paper describes the protocol for an exploratory longitudinal randomized controlled trial aimed at studying the effects of standing during tutorials on learning in undergraduate students. Learning is operationally defined as the use of interactions that are conducive to learning and an improved performance on concept tests. Final examination scores are also used as a measure of learning performance. The secondary aim is to explore the unintended effects of standing tutorials through the students’ subsequent physical activity, tutorial attendance, and affect. Participants were randomly recruited to a sitting or standing tutorial for nine weeks. This study addresses learning in a real-world setting and reveals insights on the effects of standing on learning

    The effects of standing in tutorial group meetings on learning: A randomized controlled trial

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    Background: Standing desks have been brought into the education environment to reduce sedentary behavior among students. The current study explored the effects of standing in tutorial group meetings on learning among undergraduate students. Methods: Ninety-six participants were randomly allocated to a Sit or Stand group, with 2 h tutorial group meetings scheduled, once or twice per week, for nine weeks. Learning was analyzed using exam grades, concept maps, and tutorial interactions. Results: Overall, the Sit and Stand groups did not differ from each other in terms of learning, measured through their exam, concept map, and the use of learning-oriented interactions. Conclusion: Standing in tutorial group meetings neither enhanced nor compromised learning. Considering the health risks associated with prolonged sedentary behavior, offering standing tutorial group meetings to undergraduate students is a recommended solution to break up prolonged sedentary behavior and encourage more physical activity, while maintaining the learning performance of students
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