Spin injection in Silicon at zero magnetic field

In this letter, we show efficient electrical spin injection into a SiGe based \textit{p-i-n} light emitting diode from the remanent state of a perpendicularly magnetized ferromagnetic contact. Electron spin injection is carried out through an alumina tunnel barrier from a Co/Pt thin film exhibiting a strong out-of-plane anisotropy. The electrons spin polarization is then analysed through the circular polarization of emitted light. All the light polarization measurements are performed without an external applied magnetic field \textit{i.e.} in remanent magnetic states. The light polarization as a function of the magnetic field closely traces the out-of-plane magnetization of the Co/Pt injector. We could achieve a circular polarization degree of the emitted light of 3 % at 5 K. Moreover this light polarization remains almost constant at least up to 200 K.Comment: accepted in AP

Variational Approach to Molecular Kinetics

The eigenvalues and eigenvectors of the molecular dynamics propagator (or transfer operator) contain the essential information about the molecular thermodynamics and kinetics. This includes the stationary distribution, the metastable states, and state-to-state transition rates. Here, we present a variational approach for computing these dominant eigenvalues and eigenvectors. This approach is analogous the variational approach used for computing stationary states in quantum mechanics. A corresponding method of linear variation is formulated. It is shown that the matrices needed for the linear variation method are correlation matrices that can be estimated from simple MD simulations for a given basis set. The method proposed here is thus to first define a basis set able to capture the relevant conformational transitions, then compute the respective correlation matrices, and then to compute their dominant eigenvalues and eigenvectors, thus obtaining the key ingredients of the slow kinetics

EXPOSICIÓN A Leptospira sp. EN ESTUDIANTES DE MEDICINA VETERINARIA AL INICIO Y TÉRMINO DE LA CARRERA

Leptospirosis is globally known as the most prevalent zoonotic disease, caused by different Leptospira sp. serovars. In urban areas, exposure is mainly related to certain occupational health groups, such as veterinary students. The objective of the research was to determine the rate of serorreactors to leptospira in veterinary students on two stages of their studies, at the beginning (sophomore students) and at the end (senior students). Pool serum samples were analized by the microagglutination test (MAT) for serovars canicola, icterohemorragiae, grippotyphosa, georgia, pomona and hardjo. Positive result were 18.4% (7/38) for sophomore students and 8.8% (7/80) for seniors. The positive serovars were georgia for the sophomore students, and georgia, icterohemorragiae and canicola for the seniors. The risk of infection was 2.4 (0.76 – 7.28) (p=0.137) comparing sophomore versus seniors. Exposure to Leptospira infection was demonstrated in veterinary students showing the need for more research on the main risk factors related to its presentation.La leptospirosis es la enfermedad zoonótica de mayor prevalencia a nivel mundial, la cual es causada por diferentes serovares de Leptospira sp. En el medio urbano, la población expuesta corresponde a grupos ocupacionales, entre los que se encuentran los estudiantes de ciencias veterinarias. Para determinar la frecuencia de serorreactores en estudiantes de medicina veterinaria en dos etapas de la carrera (ingresantes y prácticas finales), se tomaron muestras de sangre que fueron analizadas mediante la prueba de microaglutinación de grupos para los serovares canicola, icterohemorragiae, grippotyphosa, georgia, pomona y hardjo. El 18.4% (7/38) de ingresantes y 8.8% (7/ 80) de alumnos de prácticas finales resultaron seropositivos. Los serovares reactivos fueron georgia en ingresantes, y georgia, icterohemorragiae y canicola en alumnos de prácticas finales. El riesgo de infección fue de 2.4 (0.76 – 7.28) (p=0.137) cuando se comparó ingresantes versus prácticas finales. Se demostró la presencia de exposición a infecciones por leptospira en alumnos de veterinaria, lo que hace necesario investigar los potenciales factores de riesgo asociados a su presentación

Status of the Stony Brook Superconducting Heavy-Ion Linac

We describe the present status of the State University of New York at Stony Brook Superconducting Heavy-Ion LINAC (SUNYLAC). The LINAC will extend at very modest cost the capabilities of the existing FN tandem Van de Graaff into the energy range 5-10 MeV/A for light heavy-ions from oxygen to bromine. The active elements are 43 lead-plated copper superconducting resonators of the split-loop type optimized for either velocity ß=v/c=0.055 or ß=0.10. Phase and amplitude of each resonator is independently set through RF-feedback controllers interfaced to an overall computer control system. Full scale construction work began in July, 1979 following the in-beam demonstration of a prototype LINAC module containing 4 low-ß resonators, and the majority of the installation work on the beam transport and refrigeration systems was completed in the summer of 1980. The project is now well into its final assembly and testing phase, with the completion of assembly scheduled in early 1982. We describe details of the design of key elements of the LINAC and the initial operating experience with the injection beam path, helium refrigerator and first production accelerator module. The progress of a continuing program aimed at optimizing crucial aspects of the LINAC is also reviewed

The Free Energy Landscape of Small Molecule Unbinding

The spontaneous dissociation of six small ligands from the active site of FKBP (the FK506 binding protein) is investigated by explicit water molecular dynamics simulations and network analysis. The ligands have between four (dimethylsulphoxide) and eleven (5-diethylamino-2-pentanone) non-hydrogen atoms, and an affinity for FKBP ranging from 20 to 0.2 mM. The conformations of the FKBP/ligand complex saved along multiple trajectories (50 runs at 310 K for each ligand) are grouped according to a set of intermolecular distances into nodes of a network, and the direct transitions between them are the links. The network analysis reveals that the bound state consists of several subbasins, i.e., binding modes characterized by distinct intermolecular hydrogen bonds and hydrophobic contacts. The dissociation kinetics show a simple (i.e., single-exponential) time dependence because the unbinding barrier is much higher than the barriers between subbasins in the bound state. The unbinding transition state is made up of heterogeneous positions and orientations of the ligand in the FKBP active site, which correspond to multiple pathways of dissociation. For the six small ligands of FKBP, the weaker the binding affinity the closer to the bound state (along the intermolecular distance) are the transition state structures, which is a new manifestation of Hammond behavior. Experimental approaches to the study of fragment binding to proteins have limitations in temporal and spatial resolution. Our network analysis of the unbinding simulations of small inhibitors from an enzyme paints a clear picture of the free energy landscape (both thermodynamics and kinetics) of ligand unbinding

Roadmap on Machine learning in electronic structure

AbstractIn recent years, we have been witnessing a paradigm shift in computational materials science. In fact, traditional methods, mostly developed in the second half of the XXth century, are being complemented, extended, and sometimes even completely replaced by faster, simpler, and often more accurate approaches. The new approaches, that we collectively label by machine learning, have their origins in the fields of informatics and artificial intelligence, but are making rapid inroads in all other branches of science. With this in mind, this Roadmap article, consisting of multiple contributions from experts across the field, discusses the use of machine learning in materials science, and share perspectives on current and future challenges in problems as diverse as the prediction of materials properties, the construction of force-fields, the development of exchange correlation functionals for density-functional theory, the solution of the many-body problem, and more. In spite of the already numerous and exciting success stories, we are just at the beginning of a long path that will reshape materials science for the many challenges of the XXIth century

Validation of a low-cost virtual reality system for training street-crossing. A comparative study in healthy, neglected and non-neglected stroke individuals

Unilateral spatial neglect is a common consequence of stroke that directly affects the performance of activities of daily living. This impairment is traditionally assessed with paper-and-pencil tests that can lack correspondence to real life and are easily compensated. Virtual reality can immerse patients in more ecological scenarios, thus providing therapists with new tools to assess and train the effects of this impairment in simulated real tasks. This paper presents the clinical validation and convergent validity of a low-cost virtual reality system for training street-crossing in stroke patients with and without neglect. The performance of neglect patients was significantly worse than the performance of non-neglect and healthy participants. In addition, several correlations between the scores in the system and in the traditional scales were detected.This study was funded in part by Ministerio de Educacion y Ciencia Spain, Projects Consolider-C (SEJ2006-14301/PSIC), "CIBER of Physiopathology of Obesity and Nutrition, an initiative of ISCIII" and the Excellence Research Program PROMETEO (Generalitat Valenciana. Conselleria de Educacion, 2008-157).Navarro, MD.; Llorens Rodríguez, R.; Noé, E.; Ferri, J.; Alcañiz Raya, ML. (2013). Validation of a low-cost virtual reality system for training street-crossing. A comparative study in healthy, neglected and non-neglected stroke individuals. Neuropsychological Rehabilitation. 23(4):597-618. https://doi.org/10.1080/09602011.2013.806269S597618234Allegri, R. F. (2000). Atención y negligencia: bases neurológicas, evaluación y trastornos. Revista de Neurología, 30(05), 491. doi:10.33588/rn.3005.99645Appelros, P., Karlsson, G. M., Seiger, Åke, & Nydevik, I. (2002). Neglect and Anosognosia After First-Ever Stroke: Incidence and Relationship to Disability. Journal of Rehabilitation Medicine, 34(5), 215-220. doi:10.1080/165019702760279206Baheux, K., Yoshizawa, M., & Yoshida, Y. (2007). Simulating hemispatial neglect with virtual reality. Journal of NeuroEngineering and Rehabilitation, 4(1). doi:10.1186/1743-0003-4-27Boian, R. F., Burdea, G. C., Deutsch, J. E. and Winter, S. H. Street crossing using a virtual environment mobility simulator.Paper presented at 3rd Annual International Workshop on Virtual Reality. Lausanne, Switzerland.Broeren, J., Samuelsson, H., Stibrant-Sunnerhagen, K., Blomstrand, C., & Rydmark, M. (2007). Neglect assessment as an application of virtual reality. Acta Neurologica Scandinavica, 116(3), 157-163. doi:10.1111/j.1600-0404.2007.00821.xBuxbaum, L. J., Ferraro, M. K., Veramonti, T., Farne, A., Whyte, J., Ladavas, E., … Coslett, H. B. (2004). Hemispatial neglect: Subtypes, neuroanatomy, and disability. Neurology, 62(5), 749-756. doi:10.1212/01.wnl.0000113730.73031.f4Buxbaum, L. J., Palermo, M. A., Mastrogiovanni, D., Read, M. S., Rosenberg-Pitonyak, E., Rizzo, A. A., & Coslett, H. B. (2008). Assessment of spatial attention and neglect with a virtual wheelchair navigation task. Journal of Clinical and Experimental Neuropsychology, 30(6), 650-660. doi:10.1080/13803390701625821Castiello, U., Lusher, D., Burton, C., Glover, S., & Disler, P. (2004). Improving left hemispatial neglect using virtual reality. Neurology, 62(11), 1958-1962. doi:10.1212/01.wnl.0000128183.63917.02Conners, C. K., Epstein, J. N., Angold, A., & Klaric, J. (2003). Journal of Abnormal Child Psychology, 31(5), 555-562. doi:10.1023/a:1025457300409Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). «Mini-mental state». Journal of Psychiatric Research, 12(3), 189-198. doi:10.1016/0022-3956(75)90026-6Fordell, H., Bodin, K., Bucht, G., & Malm, J. (2011). A virtual reality test battery for assessment and screening of spatial neglect. Acta Neurologica Scandinavica, 123(3), 167-174. doi:10.1111/j.1600-0404.2010.01390.xGupta, V., Knott, B. A., Kodgi, S., & Lathan, C. E. (2000). Using the «VREye» System for the Assessment of Unilateral Visual Neglect: Two Case Reports. Presence: Teleoperators and Virtual Environments, 9(3), 268-286. doi:10.1162/105474600566790Hartman-Maeir, A., & Katz, N. (1995). Validity of the Behavioral Inattention Test (BIT): Relationships With Functional Tasks. American Journal of Occupational Therapy, 49(6), 507-516. doi:10.5014/ajot.49.6.507Jannink, M. J. A., Aznar, M., de Kort, A. C., van de Vis, W., Veltink, P., & van der Kooij, H. (2009). Assessment of visuospatial neglect in stroke patients using virtual reality: a pilot study. International Journal of Rehabilitation Research, 32(4), 280-286. doi:10.1097/mrr.0b013e3283013b1cJehkonen, M., Laihosalo, M., & Kettunen, J. (2006). Anosognosia after stroke: assessment, occurrence, subtypes and impact on functional outcome reviewed. Acta Neurologica Scandinavica, 114(5), 293-306. doi:10.1111/j.1600-0404.2006.00723.xKatz, N., Ring, H., Naveh, Y., Kizony, R., Feintuch, U., & Weiss, P. L. (2005). Interactive virtual environment training for safe street crossing of right hemisphere stroke patients with Unilateral Spatial Neglect. Disability and Rehabilitation, 27(20), 1235-1244. doi:10.1080/09638280500076079Kim, D. Y., Ku, J., Chang, W. H., Park, T. H., Lim, J. Y., Han, K., … Kim, S. I. (2010). Assessment of post-stroke extrapersonal neglect using a three-dimensional immersive virtual street crossing program. Acta Neurologica Scandinavica, 121(3), 171-177. doi:10.1111/j.1600-0404.2009.01194.xKim, J., Kim, K., Kim, D. Y., Chang, W. H., Park, C.-I., Ohn, S. H., … Kim, S. I. (2007). Virtual Environment Training System for Rehabilitation of Stroke Patients with Unilateral Neglect: Crossing the Virtual Street. CyberPsychology & Behavior, 10(1), 7-15. doi:10.1089/cpb.2006.9998Kim, K., Kim, J., Ku, J., Kim, D. Y., Chang, W. H., Shin, D. I., … Kim, S. I. (2004). A Virtual Reality Assessment and Training System for Unilateral Neglect. CyberPsychology & Behavior, 7(6), 742-749. doi:10.1089/cpb.2004.7.742Kim, Y. M., Chun, M. H., Yun, G. J., Song, Y. J., & Young, H. E. (2011). The Effect of Virtual Reality Training on Unilateral Spatial Neglect in Stroke Patients. Annals of Rehabilitation Medicine, 35(3), 309. doi:10.5535/arm.2011.35.3.309Krakauer, J. W. (2006). Motor learning: its relevance to stroke recovery and neurorehabilitation. Current Opinion in Neurology, 19(1), 84-90. doi:10.1097/01.wco.0000200544.29915.ccMcComas, J., MacKay, M., & Pivik, J. (2002). Effectiveness of Virtual Reality for Teaching Pedestrian Safety. CyberPsychology & Behavior, 5(3), 185-190. doi:10.1089/109493102760147150Myers, R. L., & Bierig, T. A. (2000). Virtual Reality and Left Hemineglect: A Technology for Assessment and Therapy. CyberPsychology & Behavior, 3(3), 465-468. doi:10.1089/10949310050078922Peskine, A., Rosso, C., Box, N., Galland, A., Caron, E., Rautureau, G., … Pradat-Diehl, P. (2010). Virtual reality assessment for visuospatial neglect: importance of a dynamic task. Journal of Neurology, Neurosurgery & Psychiatry, 82(12), 1407-1409. doi:10.1136/jnnp.2010.217513Romero, M., Sánchez, A., Marín, C., Navarro, M. D., Ferri, J., & Noé, E. (2012). Utilidad clínica de la versión en castellano del Mississippi Aphasia Screening Test (MASTsp): validación en pacientes con ictus. Neurología, 27(4), 216-224. doi:10.1016/j.nrl.2011.06.006Rose, F. D., Brooks, B. M., & Rizzo, A. A. (2005). Virtual Reality in Brain Damage Rehabilitation: Review. CyberPsychology & Behavior, 8(3), 241-262. doi:10.1089/cpb.2005.8.241Schwebel, D. C., & McClure, L. A. (2010). Using virtual reality to train children in safe street-crossing skills. Injury Prevention, 16(1), e1-e1. doi:10.1136/ip.2009.025288Simpson, G., Johnston, L., & Richardson, M. (2003). An investigation of road crossing in a virtual environment. Accident Analysis & Prevention, 35(5), 787-796. doi:10.1016/s0001-4575(02)00081-7Smith, J., Hebert, D., & Reid, D. (2007). Exploring the effects of virtual reality on unilateral neglect caused by stroke: Four case studies. Technology and Disability, 19(1), 29-40. doi:10.3233/tad-2007-19104Sugarman, H., Weisel-Eichler, A., Burstin, A. and Brown, R.Use of novel virtual reality system for the assessment and treatment of unilateral spatial neglect: A feasibility study. Paper presented at International Conference on Virtual Rehabilitation. Zürich.Tanaka, T., Sugihara, S., Nara, H., Ino, S., & Ifukube, T. (2005). Journal of NeuroEngineering and Rehabilitation, 2(1), 31. doi:10.1186/1743-0003-2-31Thomson, J. A., Tolmie, A. K., Foot, H. C., Whelan, K. M., Sarvary, P., & Morrison, S. (2005). Influence of Virtual Reality Training on the Roadside Crossing Judgments of Child Pedestrians. Journal of Experimental Psychology: Applied, 11(3), 175-186. doi:10.1037/1076-898x.11.3.175Weiss, P. L. (Tamar), Naveh, Y., & Katz, N. (2003). Design and testing of a virtual environment to train stroke patients with unilateral spatial neglect to cross a street safely. Occupational Therapy International, 10(1), 39-55. doi:10.1002/oti.176Witmer, B. G., & Singer, M. J. (1998). Measuring Presence in Virtual Environments: A Presence Questionnaire. Presence: Teleoperators and Virtual Environments, 7(3), 225-240. doi:10.1162/105474698565686Wu, H., Ashmead, D. H. and Bodenheimer, B.Using immersive virtual reality to evaluate pedestrian street crossing decisions at a roundabout. Paper presented at 6th Symposium on appied perception in Graphics and Visualization. Chania

Quasi-continuous Interpolation Scheme for Pathways between Distant Configurations

A quasi-continuous interpolation (QCI) scheme is introduced for characterizing physically realistic initial pathways from which to initiate transition state searches and construct kinetic transition networks. Applications are presented for peptides, proteins, and a morphological transformation in an atomic cluster. The first step in each case involves end point alignment, and we describe the use of a shortest augmenting path algorithm for optimizing permutational isomers. The QCI procedure then employs an interpolating potential, which preserves the covalent bonding framework for the biomolecules and includes repulsive terms between unconstrained atoms. This potential is used to identify an interpolating path by minimizing contributions from a connected set of images, including terms corresponding to minima in the interatomic distances between them. This procedure detects unphysical geometries in the line segments between images. The most difficult cases, where linear interpolation would involve chain crossings, are treated by growing the structure an atom at a time using the interpolating potential. To test the QCI procedure, we carry through a series of benchmark calculations where the initial interpolation is coupled to explicit transition state searches to produce complete pathways between specified local minima.This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/H042660/1]This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in the Journal of Chemical Theory and Computation, copyright © American Chemical Society after peer review. To access the final edited and published work see http://dx.doi.org/10.1021/ct300483

The Energy Landscape, Folding Pathways and the Kinetics of a Knotted Protein

The folding pathway and rate coefficients of the folding of a knotted protein are calculated for a potential energy function with minimal energetic frustration. A kinetic transition network is constructed using the discrete path sampling approach, and the resulting potential energy surface is visualized by constructing disconnectivity graphs. Owing to topological constraints, the low-lying portion of the landscape consists of three distinct regions, corresponding to the native knotted state and to configurations where either the N- or C-terminus is not yet folded into the knot. The fastest folding pathways from denatured states exhibit early formation of the N-terminus portion of the knot and a rate-determining step where the C-terminus is incorporated. The low-lying minima with the N-terminus knotted and the C-terminus free therefore constitute an off-pathway intermediate for this model. The insertion of both the N- and C-termini into the knot occur late in the folding process, creating large energy barriers that are the rate limiting steps in the folding process. When compared to other protein folding proteins of a similar length, this system folds over six orders of magnitude more slowly.Comment: 19 page

Coordination in climbing: effect of skill, practice and constraints manipulation

BACKGROUND: Climbing is a physical activity and sport involving many subdisciplines. Minimization of prolonged pauses, use of a relatively simple path through a route and smooth transitions between movements broadly define skilled coordination in climbing. OBJECTIVES: To provide an overview of the constraints on skilled coordination in climbing and to explore future directions in this emerging field. METHODS: A systematic literature review was conducted in 2014 and retrieved studies reporting perceptual and movement data during climbing tasks. To be eligible for the qualitative synthesis, studies were required to report perceptual or movement data during climbing tasks graded for difficulty. RESULTS: Qualitative synthesis of 42 studies was carried out, showing that skilled coordination in climbing is underpinned by superior perception of climbing opportunities; optimization of spatial-temporal features pertaining to body-to-wall coordination, the climb trajectory and hand-to-hold surface contact; and minimization of exploratory behaviour. Improvements in skilled coordination due to practice are related to task novelty and the difficulty of the climbing route relative to the individual's ability level. CONCLUSION: Perceptual and motor adaptations that improve skilled coordination are highly significant for improving the climbing ability level. Elite climbers exhibit advantages in detection and use of climbing opportunities when visually inspecting a route from the ground and when physically moving though a route. However, the need to provide clear guidelines on how to improve climbing skill arises from uncertainties regarding the impacts of different practice interventions on learning and transfer