Modeling tree-growth: Assessing climate suitability of temperate forests growing in Moncayo Natural Park (Spain)

In the past few decades, temperate forests have been negatively altered by numerous anthropogenic activities and by the impact of ongoing climate change. These changes may require management actions to help preserve some forest tree species. In this sense, highly-detailed knowledge of tree growth and survival across territorial and climatic gradients will be important for forest conservation. We developed a novel approach to determine the optimal zones of forest growth and expansion through climate suitability maps, using a dense tree-ring network of four forest species in Moncayo Natural Park and high-resolution climate data. Our results showed that the mixed-effects models developed using climate data and tree size were able to predict between 65 and 80% of growth variability along the climatic gradient. All studied species were influenced by climate, and the relationship between growth and climate significantly differed along the prevailing climate gradient. Moreover, the suitability maps showed that the current species distribution is limited, and their application may serve as a tool for adaptive management in forests subjected to climate change

Summer drought and spring frost, but not their interaction, constrain European beech and Silver fir growth in their southern distribution limits

Climate warming has lengthened the growing season by advancing leaf unfolding in many temperate tree species. However, an earlier leaf unfolding increases also the risk of frost damage in spring which may reduce tree radial growth. In equatorward populations of temperate tree species, both late frosts and summer droughts impose two constraints to tree growth, but their effects on growth are understudied. We used a tree-ring network of 71 forests to evaluate the potential influence of late frosts and summer droughts on growth in two tree species that reach their southern distribution limits in north-eastern Spain: the deciduous European beech (Fagus sylvatica L.) and the evergreen Silver fir (Abies alba Mill). The occurrence of late frost events and summer drought was quantified by using a high-resolution daily temperature and precipitation dataset considering the period 1950 2012. Late frosts were defined as days with average temperature below 0 °C in the site-specific frost-free period, whereas drought was quantified using the 18 month-long August Standardized Precipitation Evapotranspiration Index (SPEI). The growth of European beech and Silver fir was reduced by the occurrence of both late frost events and summer drought. However, we did not find a significant interaction on growth of these two climate extremes. Beech was more negatively impacted by late frosts, whereas Silver fir was more impacted by summer drought. Further studies could use remote-sensing information or in situ phenological records to refine our frost index and better elucidate how late frosts affect growth, whether they interact with drought to constrain growth, and how resilience mechanisms related to post-frost refoliation operate in beech. © 2019 Elsevier B.V

Neurophysiologic Assessment of Motor Imagery Training by Using Virtual Reality for Pediatric Population with Cerebral Palsy

[ES] Existen diversas evidencias que indican que los déficits motores en los pacientes de parálisis cerebral se asocian con problemas en la planificación motora que, a su vez, apuntan a una mermada capacidad para imaginar movimientos. La imaginación motora se ha revelado como una herramienta efectiva en el aprendizaje y la adquisición de habilidades motoras ya que comparte estructuras neuronales similares con la ejecución motora. En este trabajo se presenta un paradigma basado en un juego de realidad virtual para guiar la actividad mental del paciente que sirve a dos fines: estudiar su capacidad de imaginar movimientos e implicar y motivar al paciente en el entrenamiento de dicha capacidad. El estudio ha involucrado cuatro niños con parálisis cerebral espástica (edad media = 13.25 años, DS = 1.5) con lesión cerebral bilateral. Los resultados obtenidos del análisis de su actividad electroencefalográfica muestran que estos pacientes son capaces de emplear la imaginación motora en una tarea de marcha, indicada por la presencia del fenómeno ERD (Event Related Desynchronization) en zonas corticales motoras, independientemente de su nivel funcional y de los miembros afectados.[EN] There are several evidences showing that motor disorders in patients with cerebral palsy are associated with problems in motor planning, which, in turn, denote a diminished capability to imagine movements. Motor imagery appears like an effective means in learning and  acquiring motor skills since it shares similar neural structures to those ones used in motor execution. In this paper, a paradigm based on a virtual reality game that drives the patient’s electroencephalographic signal is presented. This study aims, on the one hand, to analyze the patients’ ability of imagining movements and, on the other hand, to involve and motivate them in order to implement this ability. The research work has engaged four children with spastic cerebral palsy (mean age = 13.25, SD = 1.5) with bilateral brain damage. After analyzing their electroencephalographic signal, the results show that these patients are able of using motor imagery in a walking task, as indicated by the presence of ERD (event related desynchronization) in cortical motor areas, regardless their functional impairment and affected body extremities.Este trabajo ha sido financiado parcialmente por los proyectos CP-WALKER (DPI2012-39133-C03-01), MD (PIE201650E055) y NeuroMOD (DPI2015-68664-C4-1-R)Del Castillo, M.; Serrano, J.; Lerma, S.; Martínez, I.; Rocon, E. (2018). Evaluación Neurofisiológica del Entrenamiento de la Imaginación Motora con Realidad Virtual en Pacientes Pediátricos con Parálisis Cerebral. Revista Iberoamericana de Automática e Informática industrial. 15(2):174-179. https://doi.org/10.4995/riai.2017.8819OJS174179152Bayón, C., Ramírez, O., Serrano, J.I., del Castillo, M.D., Pérez-Somarriba, A., Belda-Lois, J.M., Martínez-Caballero, I., Lerma-Lara, S., Cifuentes, C., Frizera, A., Rocon, E., 2017. Development and evaluation of a novel robotic platform for gait rehabilitation in patients with cerebral palsy: CPWalker. Robotics and Autonomous Systems, 91, 101-114. https://doi.org/10.1016/j.robot.2016.12.015Blair, E., 2010. Epidemiology of the cerebral palsies. Orthopedic Clinics of North America, 41, 441-55. https://doi.org/10.1016/j.ocl.2010.06.004Chang, M.C., Kim, D.Y., Park, D.H., 2015. Enhancement of cortical excitability and lower limb motor function in patients with stroke by transcranial direct current stimulation. Brain Stimulation, 8(3), 561-566. https://doi.org/10.1016/j.brs.2015.01.411Crajé, C., van Elk, M., Beeren, M., van Schie, H.T., Bekkering, H., Steenbergen, B., 2010. Compromised motor planning and motor imagery in right hemiparetic cerebral palsy. Research in Developmental Disabilities, 3186, 1313-1322. https://doi.org/10.1016/j.ridd.2010.07.010Iosa, M., Zocolillo, L., Montesi, M., Morelli, D., Paolucci, S., Fusco, A., 2014. The brain's sense of walking: a study on the intertwine between locomotor imagery and internal locomotor models in healthy adults, typically developing children and children with cerebral palsy. Frontiers in Human Neuroscience, 8(359), 1-9. https://doi.org/10.3389/fnhum.2014.00859Labruyère, R., Gerber, C.N., Birrer‐Brütsch, K., Meyer‐Heim, A., van Hedel, H., 2013. Requirements for and impact of a serious game for neuro‐pediatric robot‐assisted gait training. Research in Developmental Disabilities, 34, 3906-3915. https://doi.org/10.1016/j.ridd.2013.07.031Laver, K., George, S., Thomas, S., Deutsch, JE., Crotty, M., 2012. Cochrane review: virtual reality for stroke rehabilitation. European Journal of Physical and Rehabilitation Medicine, 48(3), 523-530.Lerma, S., del Castillo, M.D., Serrano, J.I., Rocon, E., Raya, R., Martínez, I., 2015. EEG control of gait in children with cerebral palsy. Preliminary data for the construction of a brain computer interface. Gait & Posture 42, S42. https://doi.org/10.1016/j.gaitpost.2015.06.082Meyer-Heim, A., van Hedel, HJA., 2013. Robot-assisted and computer-enhanced therapies for children with cerebral palsy: current state and slinical implementation. Seminars in Pediatric Neurology, 02, 139-145. https://doi.org/10.1016/j.spen.2013.06.006Mullen, T., Kothe, C., Chi, Y.M., Ojeda, A., Kerth, T., Makeig, S., Cauwenberghs, G., Jung, T.-P., 2013. Real-time modeling and 3d visualization of source dynamics and connectivity using wearable EEG. In Procceedings of IEEE EMBS, 2013, pp. 2184-2187.Mutsaarts, M., Steenbergen, B., Bekkering, H., 2007. Impaired motor imagery in right hemiparetic cerebral palsy. Experimental Brain Research, 172, 151-162. https://doi.org/10.1007/s00221-005-0327-0Niazi, I.K., Mrachacz-Kersting, N., Jiang, N., Dremstrup, K., Farina, D., 2012. Peripheral electrical stimulation triggered by self-paced detection of motor intention enhances motor evoked potentials. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 20(4), 595-604. https://doi.org/10.1109/TNSRE.2012.2194309Pfurtscheller, G., da Silva, F. H. L. 1999. Event-related EEG/EMG synchronization and desynchronization: basic principles, Clinical Neurophysiology, 110, 1842-1857. https://doi.org/10.1016/S1388-2457(99)00141-8Ridderinkhof, KR., Brass, M., 2015. How kinesthetic motor Imagery works: a predictive-processing theory of visualization in sports and motor expertise. Journal of Physiology, 109, 35-63. https://doi.org/10.1016/j.jphysparis.2015.02.003Rose, FD., Brooks, BM., Rizzo A., 2005. Virtual reality in brain damage rehabilitation: review. Cyberpsychology Behavior, 8(3), 241-62. https://doi.org/10.1089/cpb.2005.8.241Sharma, N., Baron, JC., 2013. Does motor imagery share neural networks with executed movement: a multivariate fMRI analysis. Frontiers in Human Neuroscience, 7:564. https://doi.org/10.3389/fnhum.2013.00564Shin, Y.K., Lee, D.R., Hwang, H.J., You, S.J., Im, C.H., 2012. A novel EEG-based brain mapping to determine cortical activation patterns in normal children and children with cerebral palsy during motor imagery tasks. Neurorehabilitation, 31(4), 349-355. DOI: 10.3233/NRE-2012-00803Spruijt, S., ven der Kamp, J., Steenbergen, B., 2015. Current insights in the development of children's motor imagery ability. Research in Developmental Disabilities, 34, 4154-60. https://doi.org/10.1016/j.ridd.2013.08.044Weiss, P.L., Keshner, EA., Levin, M.F. (eds.), 2014. Virtual Reality for Physical and Motor Rehabilitation, Springer. https://doi.org/10.1007/978-1-4939-0968-1Winkler, I., Haufe, S., Tangermann, M., 2011. Automatic classification of artifactual ICA-Components for artifact removal in EEG signals. Behavioral and Brain Functions, 7(30), 1-15. https://doi.org/10.1186/1744-9081-7-30You, S.H., Jang, S.H., Kim, Y.H., Hallett, M., Ahn, S.H., Kwon, Y.H., Kim, J.H, Lee, M.Y., 2005. Virtual reality-induced cortical reorganization and associated locomotor recovery in chronic stroke: an experimenter-blind randomized study. Stroke, 36(6), 1166-1171. https://doi.org/10.1161/01.STR.0000162715.43417.9

Annual cambial rhythm in Pinus halepensis and Pinus sylvestris as indicator for climate adaptation

To understand better the adaptation strategies of intra-annual radial growth in Pinus halepensis and Pinus sylvestris to local environmental conditions, we examined the seasonal rhythm of cambial activity and cell differentiation at tissue and cellular levels. Two contrasting sites differing in temperature and amount of precipitation were selected for each species, one typical for their growth and the other represented border climatic conditions, where the two species coexisted. Mature P. halepensis trees from Mediterranean (Spain) and sub-Mediterranean (Slovenia) sites, and P. sylvestris from sub-Mediterranean (Slovenia) and temperate (Slovenia) sites were selected. Repeated sampling was performed throughout the year and samples were prepared for examination with light and transmission electron microscopes. We hypothesized that cambial rhythm in trees growing at the sub-Mediterranean site where the two species co-exist will be similar as at typical sites for their growth. Cambium in P. halepensis at the Mediterranean site was active throughout the year and was never truly dormant, whereas at the sub-Mediterranean site it appeared to be dormant during the winter months. In contrast, cambium in P. sylvestris was clearly dormant at both sub-Mediterranean and temperate sites, although the dormant period seemed to be significantly longer at the temperate site. Thus, the hypothesis was only partly confirmed. Different cambial and cell differentiation rhythms of the two species at the site where both species co-exist and typical sites for their growth indicate their high but different adaptation strategies in terms of adjustment of radial growth to environmental heterogeneity, crucial for long-term tree performance and survival

Alternative symplectic structures for SO(3,1) and SO(4) four-dimensional BF theories

The most general action, quadratic in the B fields as well as in the curvature F, having SO(3,1) or SO(4) as the internal gauge group for a four-dimensional BF theory is presented and its symplectic geometry is displayed. It is shown that the space of solutions to the equations of motion for the BF theory can be endowed with symplectic structures alternative to the usual one. The analysis also includes topological terms and cosmological constant. The implications of this fact for gravity are briefly discussed.Comment: 13 pages, LaTeX file, no figure

Comprensión lectora y rendimiento académico en estudiantes de educación superior

Maestría en Educación desde la Diversidad, Facultad de Ciencias Sociales y Humanas.El artículo presenta los resultados de una investigación realizada con el objetivo de determinar la relación entre el rendimiento académico y el nivel de comprensión lectora de 60 estudiantes de quinto semestre de las carreras de Ingeniería de sistemas y Psicología de dos instituciones de Educación Superior de la ciudad de Pasto, a partir del promedio de calificaciones y de la aplicación de la Prueba de Comprensión Lectora, desarrollada exclusivamente para el presente estudio. Los resultados obtenidos indican que, en general, la muestra se encuentra en los niveles de rendimiento académico Aceptable y Bueno, y en el nivel 4 de comprensión lectora. Se encontró una relación débil, directa y significativa entre las variables de manera que es posible afirmar que existe una leve tendencia a presentar un mayor rendimiento académico si se tiene mayor capacidad de comprensión lectora. De esta manera, se propone que el nivel medio de comprensión lectora es el estándar mínimo requerido para que un estudiante permanezca en el sistema de educación superior. Este nivel trasciende la comprensión literal del texto pero no alcanza un grado complejo de reflexión y evaluación de textos. Así mismo, el rendimiento académico se presenta como una medida consistente que indica regularidad en el desempeño de los estudiantes a lo largo de su formación universitaria, que si bien se ve influenciado por procesos como la comprensión lectora, debe ser entendido como un fenómeno multifactorial que requiere del estudio de otros componentes que pueden determinarlo

Electrodynamics with Lorentz-violating operators of arbitrary dimension

The behavior of photons in the presence of Lorentz and CPT violation is studied. Allowing for operators of arbitrary mass dimension, we classify all gauge-invariant Lorentz- and CPT-violating terms in the quadratic Lagrange density associated with the effective photon propagator. The covariant dispersion relation is obtained, and conditions for birefringence are discussed. We provide a complete characterization of the coefficients for Lorentz violation for all mass dimensions via a decomposition using spin-weighted spherical harmonics. The resulting nine independent sets of spherical coefficients control birefringence, dispersion, and anisotropy. We discuss the restriction of the general theory to various special models, including among others the minimal Standard-Model Extension, the isotropic limit, the case of vacuum propagation, the nonbirefringent limit, and the vacuum-orthogonal model. The transformation of the spherical coefficients for Lorentz violation between the laboratory frame and the standard Sun-centered frame is provided. We apply the results to various astrophysical observations and laboratory experiments. Astrophysical searches of relevance include studies of birefringence and of dispersion. We use polarimetric and dispersive data from gamma-ray bursts to set constraints on coefficients for Lorentz violation involving operators of dimensions four through nine, and we describe the mixing of polarizations induced by Lorentz and CPT violation in the cosmic-microwave background. Laboratory searches of interest include cavity experiments. We present the theory for searches with cavities, derive the experiment-dependent factors for coefficients in the vacuum-orthogonal model, and predict the corresponding frequency shift for a circular-cylindrical cavity.Comment: 58 pages two-column REVTeX, accepted in Physical Review

Can robotic-based top-down rehabilitation therapies improve motor control in children with cerebral palsy? A perspective on the CPWalker project

[EN] Cerebral Palsy (CP) is one of the most severe disabilities in childhood, and it demands important costs in health, education, and social services. CP is caused by damage to or abnormalities inside the developing brain that disrupt the brain's ability to control movement and maintain posture. Furthermore, CP is often associated with sensory deficits, cognition impairments, communication and motor disabilities, behavior issues, seizure disorder, pain, and secondary musculoskeletal problems. According to the literature, motor modules are peripheral measurements related to automatic motor control. There is a lack of evidence of change in motor modules in children with CP when different treatment approaches have been evaluated. Thus, new strategies are needed to improve motor control in this population. Robotic-based therapies are emerging as an effective intervention for gait rehabilitation in motor disorders such as stroke, spinal cord injury, and CP. There is vast clinical evidence that neural plasticity is the central core of motor recovery and development, and on-going studies suggest that robot-mediated intensive therapy could be beneficial for improved functional recovery. However, current robotic strategies are focused on the peripheral neural system (PNS) facilitating the performance of repetitive movements (a bottom-up approach). Since CP affects primarily brain structures, both the PNS and the central nervous system (CNS) should to be integrated in a physical and cognitive rehabilitation therapy (a top-down approach). This paper discusses perspectives of the top-down approach based on a novel robot-assisted rehabilitative system. Accordingly, the CPWalker robotic platform was developed to support novel therapies for CP rehabilitation. This robotic platform (Smart Walker + exoskeleton) is controlled by a multimodal interface enabling the interaction of CP infants with robot-based therapies. The aim of these therapies is to improve the physical skills of infants with CP using a top-down approach, in which motor related brain activity is used to drive robotic physical rehabilitation therapies. Our hypothesis is that the CPWalker concept will promote motor learning and this improvement will lead to significant improvements in automatic motor control.Lerma Lara, S.; Martínez Caballero, I.; Bayón, C.; Del Castillo, M.; Serrano, I.; Raya, R.; Belda Lois, JM.... (2016). Can robotic-based top-down rehabilitation therapies improve motor control in children with cerebral palsy? A perspective on the CPWalker project. Biomedical Research and Clinical Practice. 22-26. doi:10.15761/BRCP.1000106S222

Spatio-temporal assessment of beech growth in relation to climate extremes in Slovenia – An integrated approach using remote sensing and tree-ring data

Climate change is predicted to affect tree growth due to increased frequency and intensity of extreme events such as ice storms, droughts and heatwaves. Yet, there is still a lot of uncertainty on how trees respond to an increase in frequency of extreme events. Use of both ground-based wood increment (i.e. ring width) and remotely sensed data (i.e. vegetation indices) can be used to scale-up ground measurements, where there is a link between the two, but this has only been demonstrated in a few studies. We used tree-ring data together with crown features derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) to assess the effect of extreme climate events on the growth of beech (Fagus sylvatica L.) in Slovenia. We found evidence that years with climate extremes during the growing season (drought, high temperatures) had a lower ring width index (RWI) but we could not find such evidence for the remotely sensed EVI (Enhanced Vegetation Index). However, when assessing specific events where leaf burning or wilting has been reported (e.g. August 2011) we did see large EVI anomalies. This implies that the impact of drought or heatwave events cannot be captured by EVI anomalies until physical damage on the canopy is caused. This also means that upscaling the effect of climate extremes on RWI by using EVI anomalies is not straightforward. An exception is the 2014 ice storm that caused a large decline in both RWI and EVI. Extreme climatic parameters explained just a small part of the variation in both RWI and EVI by, which could indicate an effect of other climate variables (e.g. late frost) or biotic stressors such as insect outbreaks. Furthermore, we found that RWI was lower in the year after a climate extreme occurred in the late summer. Most likely due to the gradual increase in temperature and more frequent drought we found negative trends in RWI and EVI. EVI maps could indicate where beech is sensitive to climate changes and could be used for planning mitigation interventions. Logical next steps should focus on a tree-based understanding of the short -and long-term effects of climate extremes on tree growth and survival, taking into account differential carbon allocation to the crown (EVI) and to wood-based variables. This research highlights the value of an integrated approach for upscaling tree-based knowledge to the forest level