65 research outputs found

    Seeing the last part of a hitting movement is enough to adapt to a temporal delay.

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    Being able to see the object that you are aiming for is evidently useful for guiding the hand to a moving object. We examined to what extent seeing the moving hand also influences performance. Subjects tried to intercept moving targets while either instantaneous or delayed feedback about the moving hand was provided at certain times. After each attempt, subjects had to indicate whether they thought they had hit the target, had passed ahead of it, or had passed behind it. Providing visual feedback early in the movement enabled subjects to use visual information about the moving hand to correct their movements. Providing visual feedback when the moving hand passed the target helped them judge how they had performed. Performance was almost as good when visual feedback about the moving hand was provided only when the hand was passing the target as when it was provided throughout the movement. We conclude that seeing the temporal relationship between the hand and the target as the hand crosses the target's path is instrumental for adapting to a temporal delay

    Perceptual judgments of duration of parabolic motions

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    In a 2-alternative forced-choice protocol, observers judged the duration of ball motions shown on an immersive virtual-reality display as approaching in the sagittal plane along parabolic trajectories compatible with Earth gravity effects. In different trials, the ball shifted along the parabolas with one of three different laws of motion: constant tangential velocity, constant vertical velocity, or gravitational acceleration. Only the latter motion was fully consistent with Newton's laws in the Earth gravitational field, whereas the motions with constant velocity profiles obeyed the spatio-temporal constraint of parabolic paths dictated by gravity but violated the kinematic constraints. We found that the discrimination of duration was accurate and precise for all types of motions, but the discrimination for the trajectories at constant tangential velocity was slightly but significantly more precise than that for the trajectories at gravitational acceleration or constant vertical velocity. The results are compatible with a heuristic internal representation of gravity effects that can be engaged when viewing projectiles shifting along parabolic paths compatible with Earth gravity, irrespective of the specific kinematics. Opportunistic use of a moving frame attached to the target may favour visual tracking of targets with constant tangential velocity, accounting for the slightly superior duration discrimination

    The Effects of Visuomotor Calibration to the Perceived Space and Body, through Embodiment in Immersive Virtual Reality

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    We easily adapt to changes in the environment that involve cross-sensory discrepancies (e.g., between vision and proprioception). Adaptation can lead to changes in motor commands so that the experienced sensory consequences are appropriate for the new environment (e.g., we program a movement differently while wearing prisms that shift our visual space). In addition to these motor changes, perceptual judgments of space can also be altered (e.g., how far can I reach with my arm?). However, in previous studies that assessed perceptual judgments of space after visuomotor adaptation, the manipulation was always a planar spatial shift, whereas changes in body perception could not directly be assessed. In this study, we investigated the effects of velocity-dependent (spatiotemporal) and spatial scaling distortions of arm movements on space and body perception, taking advantage of immersive virtual reality. Exploiting the perceptual illusion of embodiment in an entire virtual body, we endowed subjects with new spatiotemporal or spatial 3D mappings between motor commands and their sensory consequences. The results imply that spatiotemporal manipulation of 2 and 4 times faster can significantly change participants’ proprioceptive judgments of a virtual object’s size without affecting the perceived body ownership, although it did affect the agency of the movements. Equivalent spatial manipulations of 11 and 22 degrees of angular offset also had a significant effect on the perceived virtual object’s size; however, the mismatched information did not affect either the sense of body ownership or agency. We conclude that adaptation to spatial and spatiotemporal distortion can similarly change our perception of space, although spatiotemporal distortions can more easily be detected

    The holy grail:Environmental management, competitive advantage and business performance in the Spanish hotel industry

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    © Emerald Group Publishing Limited G959-6119. Purpose - This paper aims to analyse the influence of environmental proactivity on cost and differentiation competitive advantages, and to explore the double relationship between environmental proactivity and business performance. Design/methodology/approach - The population consists of all three- to five-star hotels in Spain. A sample of 350 hotels was classified according to environmental proactivity and performance levels, employing a two-step cluster analysis. Significant differences between groups were examined. Findings - The results show two types of environmental behaviour (reactive and proactive), with proactive hotels developing significantly better on both cost and differentiation competitive advantage and achieving significantly higher performance levels. Hotels which achieve above average business performance levels are significantly more environmentally proactive. Research limitations/implications - The present paper demonstrates that environmental management is related to competitive advantages and business performance. Environmental management systems are more developed in higher category, chain-affiliated and larger hotels. This could be due to having more resources to develop their environmental capability. The environmental proactivity scale employed in this study is presented as a reference measure for hotel managers to benchmark their current practices and implement environmental improvements. Originality/value - First, measuring environmental proactivity using four managerial systems (operative, information, strategic and technical) is innovative and provides a more detailed approach to measuring environmental proactivity. Second, demonstrating a double association between environmental proactivity and performance provides fresh insights into the relationship between these variables

    Intermittent inotropic support with levosimendan in advanced heart failure as destination therapy: The LEVO-D registry

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    Advanced heart failure; Inotropes; Palliative careInsuficiencia cardiaca avanzada; Inotropos; Cuidados paliativosInsuficiència cardíaca avançada; Inòtrops; Cures pal·liativesAim Patients with advanced heart failure (AHF) who are not candidates to advanced therapies have poor prognosis. Some trials have shown that intermittent levosimendan can reduce HF hospitalizations in AHF in the short term. In this real-life registry, we describe the patterns of use, safety and factors related to the response to intermittent levosimendan infusions in AHF patients not candidates to advanced therapies. Methods and results Multicentre retrospective study of patients diagnosed with advanced heart failure, not HT or LVAD candidates. Patients needed to be on the optimal medical therapy according to their treating physician. Patients with de novo heart failure or who underwent any procedure that could improve prognosis were not included in the registry. Four hundred three patients were included; 77.9% needed at least one admission the year before levosimendan was first administered because of heart failure. Death rate at 1 year was 26.8% and median survival was 24.7 [95% CI: 20.4–26.9] months, and 43.7% of patients fulfilled the criteria for being considered a responder lo levosimendan (no death, heart failure admission or unplanned HF visit at 1 year after first levosimendan administration). Compared with the year before there was a significant reduction in HF admissions (38.7% vs. 77.9%; P 12 g/dL (+1.5), amiodarone use (−1.5) HF visit 1 year before levosimendan (−1.5) and heart rate >70 b.p.m. (−2). Patients with a score less than −1 had a very low probability of response (21.5% free of death or HF event at 1 year) meanwhile those with a score over 1.5 had the better chance of response (68.4% free of death or HF event at 1 year). LEVO-D score performed well in the ROC analysis. Conclusion In this large real-life series of AHF patients treated with levosimendan as destination therapy, we show a significant decrease of heart failure events during the year after the first administration. The simple LEVO-D Score could be of help when deciding about futile therapy in this population

    Evaluación del impacto de una intervención para mejorar las coberturas de vacunación frente a neumococo en pacientes con VIH

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    Fundamentos: Las personas infectadas por el vi-rus de la inmunodeficiencia humana (VIH) presentan riesgo elevado de sufrir la enfermedad neumocócica invasiva, motivo por el que se recomienda su vacuna-ción frente al neumococo. El objetivo de este trabajo fue evaluar el impacto de implementar una consulta hospitalaria de vacunas en las coberturas de vacuna-ción de estos pacientes. Métodos: Se elaboró un estudio cuasiexperimental sin grupo control, de tipo antes/después, en el que se realizó un muestreo de casos consecutivos de pacientes con VIH remitidos a nuestra consulta entre el 1 noviembre de 2014 y el 30 junio de 2018. Las coberturas en el momento de la fecha de la cita para la valoración de su estado vacunal (en nuestra consulta) y después de ser atendido se compararon usando la prueba chi-cuadrado. Como referencia se utilizaron las del momento de la fecha de la primera cita. Resultados: Se analizaron 209 pacientes, en los que se obtuvieron mejoras estadísticamente signifi-cativas en sus coberturas vacunales: 2, 9% en el mo-mento de la fecha de la cita para la valoración en nuestra consulta y 88% después de ser atendidos en nuestra consulta (RR [IC95%]= 30, 7 [13, 92-67, 58]) para la vacuna antineumocócica conjugada 13-valen-te, y 16, 3% en el momento de la primera cita y 83, 7% después de ser atendidos en nuestra consulta (RR [IC95%]=5, 2 [3, 76-7, 04]) para la vacuna antineumo-cócica polisacárida 23-valente. Conclusiones: Implementar una consulta hospitalaria de vacunas representa una intervención efectiva para mejorar las coberturas de vacunación frente al neumococo en pacientes con VIH. Background: People affected by the human immunodeficiency virus (HIV) have a higher risk of invasive pneumococcal disease. Therefore, vaccination against streptococcus pneumoniae is recommended for that group. The objective of this study was to analyze the impact of implementing a hospital appointment to assess vaccination status as part of the vaccination schedule of HIV patients. Methods: We carried out a quasi-experimental uncontrolled before and after study with a sampling of consecutive cases of HIV patients referred to our department from November 1, 2014 to June 30, 2018. The study compared the vaccination coverage on the date of the appointment for an assessment of their vaccination status in our department and after the appointment. The analysis used the chi-squared test and the values on the date of the first appointment were taken as a reference. Results: 209 patients were analyzed, and a statistically significant improvement was observed regarding their vaccination coverage: 2.9% of the patients had been vaccinated on the date in which they made an appointment for assessment by our department, and 88.0% were vaccinated after they left (OR [95%CI]: 30.7 [13.92-67.58]) with the 13-valent pneumococcal conjugate vaccine; and 16.3% had been vaccinated on the date they made the first appointment vs. 83.7% after they came to the appointment (OR [95%CI]: 5.2 [3.76-7.04]) with the 23-valent polysaccharide pneumococcal vaccine. Conclusions: Implementing a hospital appointment for vaccination is an effective intervention to improve vaccination coverage against streptococcus pneumoniae in HIV patients

    Enzyme Promiscuity in Enolase Superfamily. Theoretical Study of o-Succinylbenzoate Synthase Using QM/MM Methods

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    The promiscuous activity of the enzyme o-succinylbenzoate synthase (OSBS) from the actinobacteria Amycolatopsis is investigated by means of QM/MM methods, using both density functional theory and semiempirical Hamiltonians. This enzyme catalyzes not only the dehydration of 2-succinyl-6R-hydroxy-2,4-cyclohexadiene-1R-carboxylate but also catalyzes racemization of different acylamino acids, with N-succinyl-R-phenylglycine being the best substrate. We investigated the molecular mechanisms for both reactions exploring the potential energy surface. Then, molecular dynamics simulations were performed to obtain the free energy profiles and the averaged interaction energies of enzymatic residues with the reacting system. Our results confirm the plausibility of the reaction mechanisms proposed in the literature, with a good agreement between theoretical and experimentally derived activation free energies. Our simulations unravel the role played by the different residues in each of the two possible reactions. The presence of flexible loops in the active site and the selection of structural modifications in the substrate seem to be key elements to promote the promiscuity of this enzyme.This work was supported by the Spanish Ministerio de Economia y Competitividad project CTQ2012-36253-C03-03 ́ and FEDER funds. K.S. thanks the Polish National Science Center (NCN) for Grant 2011/02/A/ST4/00246. The authors acknowledge computational facilities of the Servei d’Informatica ̀ de la Universitat de Valencia in the ̀ “Tirant” supercomputer, which is part of the Spanish Supercomputing Network

    Dosimetric Calibration of Radiochromic Film For Laser-accelerated Proton Beams

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    [Otros] When an ultra-intense and ultra-short laser pulse interacts with solid matter a fraction of the laser pulse can be converted into kinetic energy of a beam of charged particles. Radiochromic film (RCF), widely used as radiation detector in the field of conventional radiotherapy, can be used as detector for laser-accelerated protons. If used in stack configuration it is a useful and versatile tool to obtain 2D spatial distribution and energetic information of proton beams. In order to obtain dosimetric information from RCF it must be properly calibrated. Irradiating film pieces under well known conditions allows us to establish a relation between the optical density (OD) of the radiochromic film, which is measured through a flat bed scanner operating in transmission mode, and the deposited energy in the active layer. A calibration curve over a large dynamic range (3 orders of magnitude) has been obtained for few MeV protons. Our calibration process has been performed at the Spanish National Accelerator Center at Sevilla. We have irradiated several areas of a single RCF with a constant 50 pA beam current and fixed 4 MeV energy from a 3 MV tandem accelerator. We have calculated the deposited energy in the films under the same conditions. We demonstrate that this technique can be used to measure the spectrum and total energy of a laser-accelerated mixed-energy proton beam. This detector has been calibrated for a near future application at the Center of Pulsed, Ultra-short, Ultra-intense Lasers (CLPU) at Salamanca (Spain). We present the calibration procedure and results, the design optimization, and a comparison with similar experiments.Project funded by the Spanish Ministry of Economy and Competitiveness and co-funded with FEDERs funds within the INNPACTO 2011 program. This work was supported by the Spanish Plan Nacional de Investigacion Cientifica, Desarrollo e InnovacionTecnologica (I+D+i) under Grant No. FIS2010-21216-CO2-01 and the Valencian Local Government under Grants PROMETEOII/2013/010 and ISIC 2011/013.Bellido, P.; Seimetz, M.; Soriano, A.; Huertas, C.; García Lopez, J.; Jimenez-Ramos, MC.; Fernandez, B.... (2013). Dosimetric Calibration of Radiochromic Film For Laser-accelerated Proton Beams. IEEE. 20-23. https://doi.org/10.1109/NSSMIC.2013.6829806S202

    Time-of-Flight Detector for the Characterisation of Laser-Accelerated Protons

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    [Otros] Lasers of ultra-high intensity focused on thin targets can form plasmas and release large numbers of charged particles with kinetic energies in the MeV region. The characterization of the accelerated particles requires suitable detectors. We present a time-of-flight detector based on a plastic scintillator optimized for the spectral analysis of laser-accelerated protons. All details of the detector layout are adapted to the expected properties of the proton beam. Particle energies will be separated by the time-of-flight technique over 200 cm path length. The active area (25 mm width) corresponds to a few mrad opening angle. With 5 mm thickness the detector is capable of absorbing protons up to 22.5 MeV. A very thin, aluminized mylar foil shields the scintillator from outer light while absorbing very little particle energy. The scintillation photons are measured with a photomultiplier tube coupled through a bundle of optical fibres. The coupling of these fibres via a PMMA light guide has been previously optimized in simulations with Litrani. A critical aspect of the detection of virtually large numbers of protons emitted in femtosecond pulses is the saturation of the PMT. The latter can be avoided by use of appropriate optical filters. With these the effective dynamic range starts from single particles over several orders of magnitude. Our time-of-flight detector has been calibrated at the Spanish National Accelerator Centre at Sevilla. Proton beams from 0.46 to 5.6 MeV from a tandem accelerator have been used to measure the relation between particle energy and pulse heights. Further tests have been performed with a pulsed electron beam to simulate many-particle hits.Project funded by the Spanish Ministry of Economy and Competitiveness and co-funded with FEDER¿s funds within the INNPACTO 2011 program, Grant No. IPT-2011-0862- 900000. This work was supported by the Spanish Plan Nacional de Investigacion Científica, Desarrollo e Innovacion Tecnológica (I+D+i) under Grant No. FIS2010-21216-CO2-01 and the Valencian Local Government under Grants PROMETEOII/2013/010 and ISIC 2011/013Seimetz, M.; Bellido, P.; Soriano, A.; Huertas, C.; García Lopez, J.; Jimenez-Ramos, MC.; Fernandez, B.... (2013). Time-of-Flight Detector for the Characterisation of Laser-Accelerated Protons. IEEE. 25-28. https://doi.org/10.1109/NSSMIC.2013.6829804S252
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