Open strings in relativistic ion traps

Electromagnetic plane waves provide examples of time-dependent open string backgrounds free of $\alpha'$ corrections. The solvable case of open strings in a quadrupolar wave front, analogous to pp-waves for closed strings, is discussed. In light-cone gauge, it leads to non-conformal boundary conditions similar to those induced by tachyon condensates. A maximum electric gradient is found, at which macroscopic strings with vanishing tension are pair-produced -- a non-relativistic analogue of the Born-Infeld critical electric field. Kinetic instabilities of quadrupolar electric fields are cured by standard atomic physics techniques, and do not interfere with the former dynamic instability. A new example of non-conformal open-closed duality is found. Propagation of open strings in time-dependent wave fronts is discussed.Comment: 43 pages, 11 figures, Latex2e, JHEP3.cls style; v2: one-loop amplitude corrected, open-closed duality proved, refs added, miscellaneous improvements, see historical note in fil

Zooterapia amazônica: uso de gordura de sucuri ( Eunectes murinus ) como cicatrizante natural

Zootherapy (the use of the therapeutic potential of animals) is at least 6,000 years old, and has been kept active throughout generations until modern days. Animal fat is commonly used in the zootherapeutic folk medicine from South America, specially the green anaconda's fat, which is widely promoted as a natural medicine to treat wounds, even though there is no scientific evidence showing its efficacy. In this study we compared the total healing time and the proportional daily reduction of dorsal epithelial incisions in adult male Wistar rats treated with nitrofural (a commercial cicatrizing ointment) and with anaconda fat. We applied the treatments every two days and measured the incision diameter daily, during ten consecutive days. Differences among the groups in the total healing time and in the proportional daily reduction of the incision consistently showed that the fat-based treatment resulted in a faster healing process compared to the commercial ointment tested. The literature suggests that the efficacy of animal fat on healing may be primarily related to the presence of fatty acids, which have been widely demonstrated to be important for biochemical reactions involved in healing processes. Our findings are widely socially relevant, considering that traditional Amazonian communities that use anaconda fat in folk medicine do not have easy access to pharmacies and hospitals.Práticas ancestrais de zooterapia (uso das potencialidades terapêuticas da fauna) existem há pelo menos 6000 anos, e têm sido mantidas ao longo de gerações até os tempos modernos. Gordura de animais é comumente utilizada na zooterapia tradicional da América do Sul, e a gordura de serpentes sucuris é amplamente comercializada como cicatrizante natural, embora não existam evidências científicas que mostrem sua eficácia terapêutica. Neste estudo comparamos o tempo de cicatrização epitelial total e a redução proporcional diária de uma incisão dorsal em ratos Wistar machos adultos, entre um grupo controle, um grupo tratado com nitrofural (uma pomada cicatrizante comercial) e um grupo tratado com gordura de sucuri. Nós aplicamos os tratamentos a cada dois dias e medimos o diâmetro da incisão diariamente por dez dias consecutivos. Diferenças entre os grupos no tempo de cicatrização total e na redução proporcional diária da incisão consistentemente mostraram que gordura de sucuri teve ação cicatrizante mais eficiente que a pomada comercial testada. A literatura sugere que a eficácia de gordura animal em processos de cicatrização pode estar principalmente relacionada à presença de ácidos graxos, os quais têm sido amplamente demonstrados como importantes para reações bioquímicas envolvidas em processos de cicatrização. Os resultados têm ampla relevância social, considerando que as comunidades tradicionais amazônicas que utilizam a gordura de sucuris como zooterápico não têm acesso fácil a farmácias e hospitais

Automatic Balancing of a Rotor-Bearing System: On-line Algebraic Identifier for a Rotordynamic Balancing System

[ES] En este artículo, se presenta una metodología para balancear varios modos de vibración a la vez de un sistema rotor-cojinete mediante lo que se denomina discos de balanceo activo. Para determinar la magnitud del desbalance y su posición angular en el rotor, se propone un identificador en línea basado en la técnica de identificación algebraica. Para lo anterior, se desarrolló un modelo matemático en elemento finito para un sistema rotatorio de múltiples grados de libertad, donde se consideró un elemento viga con cuatro grados de libertad por nodo, en este modelo se consideran los efectos de inercia rotatoria, momentos giroscópicos, deformaciones por cortante y amortiguamiento interno y externo, así como la implementación al sistema rotor-cojinete de los discos de balanceo activo. Asimismo, se evaluó y analizó el comportamiento en el tiempo del identificador propuesto para una distribución de masas de desbalance en diferentes puntos a lo largo del rotor, tomando como dato de entrada la respuesta de vibración obtenida de la simulación de un sistema rotodinámico de múltiples grados de libertad, con diferentes rampas de excitación de tipo lineal. De los resultados obtenidos se demuestra, que con dos discos de balanceo activo se puede balancear hasta cuatro modos de vibración al mismo tiempo.[EN] A methodology for simultaneously balancing of several modes of vibration for a rotor bearing system by mean the so-called active balancing disk is presented in this paper. In order to determine the magnitude of the unbalance and its angular position on the rotor, it is proposed an on-line identifier based on algebraic identification. A mathematical model was developed for a multiple degrees-of-freedom rotational system for a beam-type finite element with 4 degrees of freedom per node. This model considers the effect of rotating inertia, gyroscope moments, shearing strains, internal-external damping and the presence of active balancing disks. Likewise, the time scale behavior of the proposed algebraic identifier was assessed and analyzed for an unbalanced mass distribution on different locations along the rotor. For this test, the vibration response was obtained from a multiple degrees-of-freedom rotor dynamic system simulation, with several linear coasting up and down. The results show that it is possible to simultaneously balance up to four vibration modes using two active balancing disks.Agradecemos a la DGEST por el apoyo recibido mediante el financiamiento al proyecto titulado “Diseño y Construcción de un Disco Balanceador Activo para Maquinaria Rotatoria” con clave 5294.14-P.Mendoza Larios, J.; Colín Ocampo, J.; Blanco Ortega, A.; Abúndez Pliego, A.; Gutiérrez Wing, E. (2016). Balanceo Automático de un Sistema Rotor-Cojinete: Identificador Algebraico en Línea del Desbalance Para un Sistema Rotodinámico. Revista Iberoamericana de Automática e Informática industrial. 13(3):281-292. https://doi.org/10.1016/j.riai.2016.03.004OJS281292133Arredondo, J.; Jugo, J.; Alonso-Quesada, S.; Lizárraga, I. y Etxebarria, V. (2008). Modelización, análisis y control de sistemas de cojinetes magnéticos activos. Revista Iberoamericana de Automática e Informática Industrial. Vol. 5, No. 4, (Octubre 2008), pp. 17-27, ISSN: 1697-7912. DOI: 10.4995/S1697-7912(08)70173-0Beltrán-Carbajal, F.; Silva-Navarro, G. and Arias-Montiel, M. (2013). Active unbalance control of rotor systems using on-line algebraic identification methods. Asian journal of control, Vol. 15, No. 6, 1627-1637. DOI: 10.1002/asjc.744Beltrán-Carbajal, F.; Silva-Navarro, G. y Arias-Montiel, M. (2014). Control activo de vibraciones en un rotor tipo Jeffcott con velocidad variable usando una suspensión electromecánica. Revista Iberoamericana de Automática e Informática Industrial. Vol. 11, No. 3, pp. 17-27, ISSN: 1697-7912. DOI: 10.1016/j.riai.2014.05.002Beltrán-Carbajal, F.; Silva-Navarro, G.; Sira-Ramírez, H. and Blanco-Ortega, A. (2008). Computación y Sistemas Vol. 13 No. 3, 2010, pp 313-330.Beltrán-Carbajal, F.; Silva-Navarro, G.; Sira-Ramírez, H. and QuezadaAndrade, J. (2005). Active vibration control using on-line algebraic identification of harmonic vibrations. 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