506 research outputs found

    The twin paradox in compact spaces

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    Twins travelling at constant relative velocity will each see the other's time dilate leading to the apparent paradox that each twin believes the other ages more slowly. In a finite space, the twins can both be on inertial, periodic orbits so that they have the opportunity to compare their ages when their paths cross. As we show, they will agree on their respective ages and avoid the paradox. The resolution relies on the selection of a preferred frame singled out by the topology of the space.Comment: to be published in PRA, 3 page

    Exploración posturográfica de pacientes simuladores

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    Introduction: An aphysiological pattern in computerized dynamic posturography (CDP) may be produced by numerous causes. We analyze the results obtained in this test by a group of malingering patients. Patients and method: This study analyzes a particular group of 7 malingerers, ie patients simulating a false and unreal equilibrium disorder, without any a priori awareness of the gain expected from a pathological report. The condition can only be identified with the very complex postural disorder known as ‚Äúcontinuous imbalance.‚ÄĚ We analyze the results of the dynamic posturography test following the diagnostic criteria described by other authors. Results: Of the criteria analyzed, we found Cevette‚Äôs to be the most frequently positive for our study group. Conclusions: The wide diversity in the criteria used makes it necessary to apply them together, assuming a high level of suspicion and great care in the diagnostic process

    Resultados de la autotransfusión postoperatoria en artroplastia total de rodilla

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    Introducci√≥n. El prop√≥sito es evaluar si la utilizaci√≥n de los drenajes autotransfusores en la artroplastia total de rodilla primaria minimiza la ca√≠da de la hemoglobina en el postoperatorio, as√≠ como la necesidad de transfusiones sangu√≠neas alog√©nicas. Material y m√©todos. Estudio retrospectivo, anal√≠tico observacional que incluy√≥ 100 pacientes intervenidos de artroplastia de rodilla entre enero 2014 y enero 2015 en el Hospital Dr. Peset. Compara tanto los par√°metros anal√≠ticos de sangrado (hemoglobina y hematocrito) como la necesidad de transfusi√≥n sangu√≠nea entre pacientes reinfundidos y no reinfundidos. Resultados. Se reinfundieron 50 pacientes con un volumen medio de 505 ml. La necesidad de transfusi√≥n sangu√≠nea alog√©nica en los reinfundidos fue de 4% mientras que en los no reinfundidos fue de 24%. La ca√≠da media de hemoglobina postquir√ļrgica fue 1,12 g/ dl menor en el grupo reinfundido. Conclusiones. El red√≥n autotransfusor es una t√©cnica segura que mejora el rendimiento anal√≠tico postransfusional y, por consiguiente, reduce el n√ļmero de transfusiones alog√©nicas.Introduction. The purpose is to evaluate the use of autotransfusors drains in total knee arthroplasty primary minimizes the drop in hemoglobin in the postoperative period, and the need for allogeneic blood transfusions. Material and methods. A retrospective, analitic and observational study, have been included 100 patients undergoing knee arthroplasty between January 2014 and January 2015 at the Dr. Peset Hospital. Compare the analytical parameters of bleeding (hemoglobin and hematocrit) and the need for blood transfusion among patients and not reinfused reinfused. Results. Fifty patients with Total Knee Arthroplasty (TKA) were reinfused with a mean volume of 505 ml. The need for allogenic blood transfusions was 4%, while in patients not reinfused was 24%. The average drop in postoperative hemoglobin was 1.12 g / dl lower in the group reinfused. Conclusions. The autotransfusion drain is a safe technique which improves post-transfusional values and therefore reduces the number of allogenic blood transfusions

    Estudio baropodométrico en pacientes tratados mediante artroplastia total de rodilla

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    La patolog√≠a artr√≥sica de la rodilla condiciona una disminuci√≥n de la carga del miembro afecto y un patr√≥n de apoyo con predominio generalmente del arco externo. El prop√≥sito de este estudio es determinar si existe una modificaci√≥n significativa de este patr√≥n tras la implantaci√≥n de una artroplastia total de rodilla (ATR) primaria, recogiendo las presiones plantares de ambos pies mediante baropodometr√≠a electr√≥nica previamente y 4 meses tras la cirug√≠a, tanto en est√°tica como en din√°mica. As√≠, se analizan las presiones plantares de 30 pacientes, 21 mujeres y 9 hombres, intervenidos de ATR primaria en el Hospital Universitario Doctor Peset entre los a√Īos 2013 y 2015. Tambi√©n se ha determinado si existe una correcci√≥n del eje anat√≥mico tras la cirug√≠a. Utilizando test no param√©tricos (test de Wilcoxon para datos apareados, U de Mann-Whitney), observamos una modificaci√≥n significativa de dicho √°ngulo desde valores medianos de 1.2¬ļ de varo a 4.9¬ļ de valgo en el postoperatorio, una disminuci√≥n mediana de la presi√≥n plantar en ambos pies y una redistribuci√≥n de la carga axial, aumentando en el miembro intervenido. Concluimos que, 4 meses tras la cirug√≠a, se produce una tendencia a la ‚Äúnormalizaci√≥n‚ÄĚ de la pisada en pacientes en los que se ha implantado una ATR, condicionado tanto por la mejora del dolor y la funcionalidad como por la realineaci√≥n del eje.Knee osteoarthritis determines a decrease of the load of the affected limb and a pattern usually dominance of external support plantar arc. The purpose of this study is to determine whether a significant change in this pattern is? after implantation of a primary total knee arthroplasty (TKA), measuring plantar pressures in both feet by electronic baropodometry previously and 4 months after surgery, in static and dynamic. Plantar pressures of 30 patients are analyzed, who underwent primary TKA at the University Hospital Doctor Peset between 2013 and 2015. In addition, it has also been determined if there is a correction on the anatomical axis after surgery. Using nonparametric test (Wilcoxon test for paired data, U Mann Whitney), we observed a significant change in the angle from median values of 1.2¬ļ varus to 4.9¬ļ valgus postoperatively, a median decrease of plantar pressure in both feet and a redistribution of axial load, increasing in the operated limb. We conclude that, 4 months after surgery, there is a tendency to ‚Äúnormalization‚ÄĚ of the tread in patients undergoing TKA. This is conditioned by improving pain and function as axis realignment occurs

    Brane Decay and Death of Open Strings

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    We show how open strings cease to propagate when unstable D-branes decay. The information on the propagation is encoded in BSFT two-point functions for arbitrary profiles of open string excitations. We evaluate them in tachyon condensation backgrounds corresponding to (i) static spatial tachyon kink (= lower dimensional BPS D-brane) and (ii) homogeneous rolling tachyon. For (i) the propagation is restricted to the directions along the tachyon kink, while for (ii) all the open string excitations cease to propagate at late time and are subject to a collapsed light cone characterized by Carrollian contraction of Lorentz group.Comment: 19 pages, published version (typos corrected, a reference added

    Sialoendoscopia: una nueva alternativa en el tratamiento de la patología salival. Nuestra experiencia

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    Objectives: Sialoendoscopy is a procedure used to visualize the salivary ducts and their pathology. It can be used either as a diagnostic method to rule out inflammatory processes in the parotid and submandibular glands (diagnostic sialoendoscopy) or to treat pathological areas (stenosis, extract foreign bodies or sialolithiasis) through the use of appropriate instruments (interventionist sialoendoscopy). We attempt to prove a declining rate of salivary gland excision. Patients and method: Sialoendoscopy was performed in 8 patients. Results: Of these, 50 % of patients were diagnosed as having sialolithiasis and the other 50 % had chronic sialoadenitis. In patients with sialolithiasis, sialoendoscopy allowed the extraction of the calculus in two patients (50 %). In the remainder, sialoendoscopy provided confirmation of the diagnosis in all cases. Conclusions: Sialoendoscopy is a new technique for use in the diagnosis, treatment and post-operative management of sialolithiasis, sialoadenitis and other salivary gland pathologies

    Optimal behavior of viscoelastic flow at resonant frequencies

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    The global entropy generation rate in the zero-mean oscillatory flow of a Maxwell fluid in a pipe is analyzed with the aim at determining its behavior at resonant flow conditions. This quantity is calculated explicitly using the analytic expression for the velocity field and assuming isothermal conditions. The global entropy generation rate shows well-defined peaks at the resonant frequencies where the flow displays maximum velocities. It was found that resonant frequencies can be considered optimal in the sense that they maximize the power transmitted to the pulsating flow at the expense of maximum dissipation.Comment: Paper accepted to be published in Phys. Rev.

    Wess-Zumino Term in Tachyon Effective Action

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    We show that the source of RR field computed from the boundary state describing the decay of a non-BPS brane is reproduced by a particular form of the Wess-Zumino term in the tachyon effective action. We also obtain a simple expression of the S-charge associated with rolling tachyons.Comment: 10 pages, lanlma

    Rolling of Modulated Tachyon with Gauge Flux and Emergent Fundamental String

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    We investigate real-time tachyon dynamics of unstable D-brane carrying fundamental string charge. We construct the boundary state relevant for rolling of modulated tachyon with gauge fields excited on the world-volume, and study spatial distribution of the fundamental string charge and current as the D-brane decays. We find that, in contrast to homogeneous tachyon rolling, spatial modulation of the tachyon field triggers density wave of strings when electric field is turned on, and of string anti-string pairs when magnetic field is turned on. We show that the energy density and the fundamental string charge density are locked together, and evolve into a localized delta-function array (instead of evolving into a string fluid) until a critical time set by initial condition of rolling tachyon. When the gauge fields approach the critical limit, the fundamental strings produced become BPS-like. We also study the dynamics via effective field theory, and find agreement.Comment: 28 pages, Latex, 7 .eps figures v2: stability discussion update
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