796 research outputs found

    A copper-catalyzed asymmetric oxime propargylation enables the synthesis of the gliovirin tetrahydro-1,2-oxazine core

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    The bicyclic tetrahydro-1,2-oxazine subunit of gliovirin is synthesized through a diastereoselective copper-catalyzed cyclization of an N-hydroxyamino ester. Oxidative elaboration to the fully functionalized bicycle was achieved through a series of mild transformations. Central to this approach was the development of the first catalytic, enantioselective propargylation of an oxime to furnish a key N-hydroyxamino ester intermediate

    Soft systems methodology: a context within a 50-year retrospective of OR/MS

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    Soft systems methodology (SSM) has been used in the practice of operations research and management science OR/MS) since the early 1970s. In the 1990s, it emerged as a viable academic discipline. Unfortunately, its proponents consider SSM and traditional systems thinking to be mutually exclusive. Despite the differences claimed by SSM proponents between the two, they have been complementary. An extensive sampling of the OR/MS literature over its entire lifetime demonstrates the richness with which the non-SSM literature has been addressing the very same issues as does SSM

    Locomotor adaptability in persons with unilateral transtibial amputation

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    Background Locomotor adaptation enables walkers to modify strategies when faced with challenging walking conditions. While a variety of neurological injuries can impair locomotor adaptability, the effect of a lower extremity amputation on adaptability is poorly understood. Objective Determine if locomotor adaptability is impaired in persons with unilateral transtibial amputation (TTA). Methods The locomotor adaptability of 10 persons with a TTA and 8 persons without an amputation was tested while walking on a split-belt treadmill with the parallel belts running at the same (tied) or different (split) speeds. In the split condition, participants walked for 15 minutes with the respective belts moving at 0.5 m/s and 1.5 m/s. Temporal spatial symmetry measures were used to evaluate reactive accommodations to the perturbation, and the adaptive/de-adaptive response. Results Persons with TTA and the reference group of persons without amputation both demonstrated highly symmetric walking at baseline. During the split adaptation and tied post-adaptation walking both groups responded with the expected reactive accommodations. Likewise, adaptive and de-adaptive responses were observed. The magnitude and rate of change in the adaptive and de-adaptive responses were similar for persons with TTA and those without an amputation. Furthermore, adaptability was no different based on belt assignment for the prosthetic limb during split adaptation walking. Conclusions Reactive changes and locomotor adaptation in response to a challenging and novel walking condition were similar in persons with TTA to those without an amputation. Results suggest persons with TTA have the capacity to modify locomotor strategies to meet the demands of most walking conditions despite challenges imposed by an amputation and use of a prosthetic limb

    A systematic review of randomized and case‐controlled trials investigating the effectiveness of school‐based motor skill interventions in 3‐ to 12‐year‐old children

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    Background Research suggests that children identified with impaired motor skills can respond well to intensive therapeutic interventions delivered via occupational and physical therapy services. There is, however, a need to explore alternative approaches to delivering interventions outside traditional referral‐based clinic settings because limited resources mean such health services often struggle to meet demand. This review sets out to systematically assess the evidence for and against school‐based interventions targeted at improving the motor skills of children aged between 3‐12 years old. Method Five electronic databases were searched systematically (AMED, CINAHL, Cochrane, Medline & PsycINFO) for peer‐reviewed articles published between January 2012 and July 2018. Studies were eligible if they implemented a school‐based motor skill intervention with a randomised or case‐controlled trial design that objectively measured motor skills as an outcome, which were not specific to an athletic or sporting skill. Participants had to be aged between 3‐12 years old and free from neurological disorders known to affect muscle function. Risk of bias was assessed using the Cochrane risk of bias tool. Results Twenty‐three studies met the inclusion criteria. These studies encompassed interventions targeted at training: fundamental movement skills; handwriting; fine; and global motor skills. The majority of these studies reported beneficial impact on motor function specifically, but some interventions also assessed subsequent impacts on activity and participation (but not wellbeing). A number of the studies had methodological shortcomings that means these results need to be interpreted with caution. Conclusions Schools appear to be an effective setting for motor skill interventions, but the extent of benefit likely depends on the type of intervention. Moreover, confirmation is needed as to whether benefits extend beyond motor function into everyday activities, participation and wellbeing. Future research should include follow‐up measures to assess the longer‐term efficacy of school‐based interventions

    Synthesis, Characterization and Magnetic Susceptibility of the Heavy Fermion Transition Metal Oxide LiV_{2}O_{4}

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    The preparative method, characterization and magnetic susceptibility \chi measurements versus temperature T of the heavy fermion transition metal oxide LiV_{2}O_{4} are reported in detail. The intrinsic \chi(T) shows a nearly T-independent behavior below ~ 30 K with a shallow broad maximum at about 16 K, whereas Curie-Weiss-like behavior is observed above 50-100 K. Field-cooled and zero-field-cooled magnetization M measurements in applied magnetic fields H = 10 to 100 G from 1.8 to 50 K showed no evidence for spin-glass ordering. Crystalline electric field theory for an assumed cubic V point group symmetry is found insufficient to describe the observed temperature variation of the effective magnetic moment. The Kondo and Coqblin-Schrieffer models do not describe the magnitude and T dependence of \chi with realistic parameters. In the high T range, fits of \chi(T) by the predictions of high temperature series expansion calculations provide estimates of the V-V antiferromagnetic exchange coupling constant J/k_{B} ~ 20 K, g-factor g ~ 2 and the T-independent susceptibility. Other possible models to describe the \chi(T) are discussed. The paramagnetic impurities in the samples were characterized using isothermal M(H) measurements with 0 < H <= 5.5 Tesla at 2 to 6 K. These impurities are inferred to have spin S_{imp} ~ 3/2 to 4, g_{imp} ~ 2 and molar concentrations of 0.01 to 0.8 %, depending on the sample.Comment: 19 typeset RevTeX pages, 16 eps figures included, uses epsf; to be published in Phys. Rev.
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