928 research outputs found

    Perdeuterated cyanobiphenyl liquid crystals for infrared applications

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    Perdeuterated 4'-pentyl-4-cyanobiphenyl (D5CB) was synthesized and its physical properties evaluated and compared to those of 5CB. D5CB retains physical properties similar to those of 5CB, such as phase transition temperatures, dielectric constants, and refractive indices. An outstanding feature of D5CB is that it exhibits a much cleaner and reduced infrared absorption. Perdeuteration, therefore, extends the usable range of liquid crystals to the mid infrared by significantly reducing the absorption in the near infrared, which is essential for telecom applications

    Evolution of central pattern generators for the control of a five-link bipedal walking mechanism

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    Central pattern generators (CPGs), with a basis is neurophysiological studies, are a type of neural network for the generation of rhythmic motion. While CPGs are being increasingly used in robot control, most applications are hand-tuned for a specific task and it is acknowledged in the field that generic methods and design principles for creating individual networks for a given task are lacking. This study presents an approach where the connectivity and oscillatory parameters of a CPG network are determined by an evolutionary algorithm with fitness evaluations in a realistic simulation with accurate physics. We apply this technique to a five-link planar walking mechanism to demonstrate its feasibility and performance. In addition, to see whether results from simulation can be acceptably transferred to real robot hardware, the best evolved CPG network is also tested on a real mechanism. Our results also confirm that the biologically inspired CPG model is well suited for legged locomotion, since a diverse manifestation of networks have been observed to succeed in fitness simulations during evolution.Comment: 11 pages, 9 figures; substantial revision of content, organization, and quantitative result

    Schottky mass measurements of heavy neutron-rich nuclides in the element range 70\leZ \le79 at the ESR

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    Storage-ring mass spectrometry was applied to neutron-rich 197^{197}Au projectile fragments. Masses of 181,183^{181,183}Lu, 185,186^{185,186}Hf, 187,188^{187,188}Ta, 191^{191}W, and 192,193^{192,193}Re nuclei were measured for the first time. The uncertainty of previously known masses of 189,190^{189,190}W and 195^{195}Os nuclei was improved. Observed irregularities on the smooth two-neutron separation energies for Hf and W isotopes are linked to the collectivity phenomena in the corresponding nuclei.Comment: 10 pages, 9 figures, 2 table

    Hepatitis viral markers in patients undergoing primary liver transplants

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    The purpose of the study was to determine the prevalence in liver transplant (OLTx) patients of the hepatitis markers (anti-A, anti-B, anti-C, anti-D and HBsAg) and the interrelationships between markers and patients' sexes, ages, dates of transplant, clinicopathological diagnoses, and short-term survivals. Slightly more than half of the patients were male. Anti-A and anti-B were about evenly distributed between male and female. Anti-C, anti-D, and HBsAg were far more common in males. Age and year of transplant showed only a moderate increase in anti-A with increasing age. Anti-A was found in 57% of all patients, anti-B in 18%, anti-C in 17%, and HBsAg in 17%. Anti-D was tested only in patients who were positive for anti-B or HBsAg and occurred in 21 (11%) of 185. The poorest short-term survival occurred in males who showed both anti-A and HBsAg. © 1993 Plenum Publishing Corporation

    \b{eta}-delayed three-proton decay of 31Ar

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    The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880 MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a gaseous time projection chamber with optical readout allowing to record decay events with emission of protons. In addition to \b{eta}-delayed emission of one and two protons we have clearly observed the beta-delayed three-proton branch. The branching ratio for this channel in 31Ar is found to be 0.07(2)%.Comment: 5 pages, 3 figures, submitted to Physical Rev.

    Visual, Motor and Attentional Influences on Proprioceptive Contributions to Perception of Hand Path Rectilinearity during Reaching

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    We examined how proprioceptive contributions to perception of hand path straightness are influenced by visual, motor and attentional sources of performance variability during horizontal planar reaching. Subjects held the handle of a robot that constrained goal-directed movements of the hand to the paths of controlled curvature. Subjects attempted to detect the presence of hand path curvature during both active (subject driven) and passive (robot driven) movements that either required active muscle force production or not. Subjects were less able to discriminate curved from straight paths when actively reaching for a target versus when the robot moved their hand through the same curved paths. This effect was especially evident during robot-driven movements requiring concurrent activation of lengthening but not shortening muscles. Subjects were less likely to report curvature and were more variable in reporting when movements appeared straight in a novel “visual channel” condition previously shown to block adaptive updating of motor commands in response to deviations from a straight-line hand path. Similarly, compromised performance was obtained when subjects simultaneously performed a distracting secondary task (key pressing with the contralateral hand). The effects compounded when these last two treatments were combined. It is concluded that environmental, intrinsic and attentional factors all impact the ability to detect deviations from a rectilinear hand path during goal-directed movement by decreasing proprioceptive contributions to limb state estimation. In contrast, response variability increased only in experimental conditions thought to impose additional attentional demands on the observer. Implications of these results for perception and other sensorimotor behaviors are discussed

    First Results from the TOTEM Experiment

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    The first physics results from the TOTEM experiment are here reported, concerning the measurements of the total, differential elastic, elastic and inelastic pp cross-section at the LHC energy of s\sqrt{s} = 7 TeV, obtained using the luminosity measurement from CMS. A preliminary measurement of the forward charged particle η\eta distribution is also shown.Comment: Conference Proceeding. MPI@LHC 2010: 2nd International Workshop on Multiple Partonic Interactions at the LHC. Glasgow (UK), 29th of November to the 3rd of December 201

    Contribution of primary motor cortex to compensatory balance reactions

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    <p>Abstract</p> <p>Background</p> <p>Rapid compensatory arm reactions represent important response strategies following an unexpected loss of balance. While it has been assumed that early corrective actions arise largely from sub-cortical networks, recent findings have prompted speculation about the potential role of cortical involvement. To test the idea that cortical motor regions are involved in early compensatory arm reactions, we used continuous theta burst stimulation (cTBS) to temporarily suppress the hand area of primary motor cortex (M1) in participants prior to evoking upper limb balance reactions in response to whole body perturbation. We hypothesized that following cTBS to the M1 hand area evoked EMG responses in the stimulated hand would be diminished. To isolate balance reactions to the upper limb participants were seated in an elevated tilt-chair while holding a stable handle with both hands. The chair was held vertical by a magnet and was triggered to fall backward unpredictably. To regain balance, participants used the handle to restore upright stability as quickly as possible with both hands. Muscle activity was recorded from proximal and distal muscles of both upper limbs.</p> <p>Results</p> <p>Our results revealed an impact of cTBS on the amplitude of the EMG responses in the stimulated hand muscles often manifest as inhibition in the stimulated hand. The change in EMG amplitude was specific to the target hand muscles and occasionally their homologous pairs on the non-stimulated hand with no consistent effects on the remaining more proximal arm muscles.</p> <p>Conclusions</p> <p>Present findings offer support for cortical contributions to the control of early compensatory arm reactions following whole-body perturbation.</p

    The Practice of Immigration Health in Complex Emergency Situations - A Case Study of Kosovo from March to July 1999

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    The need to rapidly transport refugees, displaced as a result of evolving complex humanitarian emergencies creates challenges for those refugee-receiving nations that require formaI immigration medical screening of these populations. Balancing the need to expediently resettle the refugees with these legislative and regulatory medical requirements can be logistically and operationally difficult. During the 1999 Kosovo crisis, the Humanitarian Evacuation Programme from the Former Yugoslav Republic of Macedonia rapidly moved large numbers of Kosovar Albanian refugees to nations with existing formal immigration medical screening requirements. This paper describes the successful management and delivery of immigration health services during this complicated international event.La nécessité de transporter rapidement les réfugiés déplacés à cause d'urgences humanitaires complexes à évolution rapide représenteun défi pour les nations receveuses de réfugiés requérant un tamisage médical routinier de sa population immigrante. Des points de vue logistique et opérationnel, il peut s'avérer fort difficile pour ces états de concilier la nécessité de relocaliser rapidement les réfugiés avec les exigences de leurs lois et règlements en matière médicale et sanitaire. Lors de la crise du Kosovo de 1999, le Programme d'Évacuation Humanitaire de l'ancienne république yougoslave de Macédoine déplaça rapidement un grand nombre de réfugiés albanais kosovars vers des nations requérant formellement un tamisage médical de sa population immigrante. Cet article décrit la gestion et la distribution réussies de services de santé à l'immigration au cours de cet événement international complexe
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