580 research outputs found
Discrete--time ratchets, the Fokker--Planck equation and Parrondo's paradox
Parrondo's games manifest the apparent paradox where losing strategies can be
combined to win and have generated significant multidisciplinary interest in
the literature. Here we review two recent approaches, based on the
Fokker-Planck equation, that rigorously establish the connection between
Parrondo's games and a physical model known as the flashing Brownian ratchet.
This gives rise to a new set of Parrondo's games, of which the original games
are a special case. For the first time, we perform a complete analysis of the
new games via a discrete-time Markov chain (DTMC) analysis, producing winning
rate equations and an exploration of the parameter space where the paradoxical
behaviour occurs.Comment: 17 pages, 5 figure
Wave-unlocking transition in resonantly coupled complex Ginzburg-Landau equations
We study the effect of spatial frequency-forcing on standing-wave solutions
of coupled complex Ginzburg-Landau equations. The model considered describes
several situations of nonlinear counterpropagating waves and also of the
dynamics of polarized light waves. We show that forcing introduces spatial
modulations on standing waves which remain frequency locked with a
forcing-independent frequency. For forcing above a threshold the modulated
standing waves unlock, bifurcating into a temporally periodic state. Below the
threshold the system presents a kind of excitability.Comment: 4 pages, including 4 postscript figures. To appear in Physical Review
Letters (1996). This paper and related material can be found at
http://formentor.uib.es/Nonlinear
Synchronization of Spatiotemporal Chaos: The regime of coupled Spatiotemporal Intermittency
Synchronization of spatiotemporally chaotic extended systems is considered in
the context of coupled one-dimensional Complex Ginzburg-Landau equations
(CGLE). A regime of coupled spatiotemporal intermittency (STI) is identified
and described in terms of the space-time synchronized chaotic motion of
localized structures. A quantitative measure of synchronization as a function
of coupling parameter is given through distribution functions and information
measures. The coupled STI regime is shown to dissapear into regular dynamics
for situations of strong coupling, hence a description in terms of a single
CGLE is not appropiate.Comment: 4 pages, LaTeX 2e. Includes 3 figures made up of 8, 4 (LARGE),and 2
postscript files. Includes balanced.st
Els alumnes de segon grau de formació professional fan pràctiques a les empreses
Abstract not availabl
At-home vital bleaching : a comparison of hydrogen peroxide and carbamide peroxide treatments
El blanqueamiento de los dientes vitales que realiza el/la paciente domiciliariamente con férulas bajo supervisión del/de la dentista es una alternativa interesante entre las que integran este tipo de terapéutica odontológica, ya sea, de forma aislada o combinada con alguna de las modalidades de tratamiento en la consulta. En este procedimiento blanqueador se usan peróxidos de baja concentración que se aplican sobre el esmalte dentario mediante una cubeta individualizada especialmente diseñada para ello. El objetivo del presente trabajo es analizar y comparar dos productos blanqueadores comerciales de diferente concentración indicados para esta técnica, VivaStyle (Vivadent) y FKD (Kin); el primero de ellos es un peróxido de carbamida al 10%, mientras que el segundo es un peróxido de hidrógeno al 3,5%. Se analizan los parámetros que deben ser controlados durante la puesta en práctica de este tipo de procedimiento y se presentan 6 casos (3 de ellos tratados con uno de los productos mencionados y los otros 3 con el otro) en los que se constata su capacidad blanqueadora y la aparición y la intensidad de hipersensibilidad postoperatoria. Los resultados obtenidos muestran que ambos productos son eficaces para la función para la que han sido desarrollados. En general, la hipersensibilidad dentaria es mínima
In vivo evaluation of the effects of 10% carbamide peroxide and 3.5% hydrogen peroxide on the enamel surface
Objetivos: El blanqueamiento de los dientes vitales que realiza el/la paciente en su domicilio bajo la supervisión del/de la dentista con férulas individualizadas especialmente diseñadas para ello y peróxidos de baja concentración, es una opción de entre las que integran esta terapéutica odontológica, ya sea, como tratamiento único o combinada con otra modalidad de blanqueamiento en la consulta. El objetivo del presente trabajo es analizar el efecto que producen sobre la superficie del esmalte dos productos blanqueadores indicados para esta técnica. Diseño del estudio: Se emplearon dos productos blanqueadores, el VivaStyle (Vivadent), peróxido de carbamida al 10%, y el FKD (Kin), peróxido de hidrógeno al 3,5%, que se aplicaron mediante férulas sobre los dientes anteriores de 20 pacientes (10 en cada grupo). El tiempo de aplicación de cada producto fue de 2 y 3 horas al día respectivamente durante 28-33 días. Se obtuvieron réplicas de las superficies dentales antes y después del tratamiento, las cuales fueron observadas con un microscopio electrónico de barrido. Resultados: Las imágenes obtenidas muestran la integridad de la superficie dental, con el mantenimiento de las estructuras normales de la superficie del esmalte. Conclusiones: Los resultados obtenidos muestran que ninguno de los dos productos alteran la superficie del esmalte, no observándose, pues, cambios postoperatorios
Downregulation of Fzd6 and Cthrc1 and upregulation of olfactory receptors and protocadherins by dietary beta-carotene in lungs of Bcmo1-/- mice.
An ongoing controversy exists on beneficial versus harmful effects of high beta-carotene (BC) intake, especially for the lung. To elucidate potential mechanisms, we studied effects of BC on lung gene expression. We used a beta-carotene 15,15'-monooxygenase 1 (Bcmo1) knockout mouse (Bcmo1-/-) model, unable to convert BC to retinoids, and wild-type mice (Bcmo1+/+) mice to dissect the effects of intact BC from effects of BC metabolites. As expected, BC supplementation resulted in a higher BC accumulation in lungs of Bcmo1-/- mice than in lungs of Bcmo1+/+ mice. Whole mouse genome transcriptome analysis on lung tissue revealed that more genes were regulated in Bcmo1-/- mice than Bcmo1+/+ mice upon BC supplementation. Frizzled homolog 6 (Fzd6) and collagen triple helix repeat containing 1 (Cthrc1) were significantly downregulated (fold changes -2.99 and -2.60, respectively, false discovery rate <0.05) by BC in Bcmo1-/-. Moreover, many olfactory receptors and many members of the protocadherin family were upregulated. Since both olfactory receptors and protocadherins have an important function in sensory nerves and Fzd6 and Cthrc1 are important in stem cell development, we hypothesize that BC might have an effect on the highly innervated pulmonary neuroendocrine cell (PNEC) cluster. PNECs are highly associated with sensory nerves and are important cells in the control of stem cells. A role for BC in the innervated PNEC cluster might be of particular importance in smoke-induced carcinogenesis since PNEC-derived lung cancer is highly associated with tobacco smoke
Downregulation of Fzd6 and Cthrc1 and upregulation of olfactory receptors and protocadherins by dietary beta-carotene in lungs of Bcmo1-/- mice.
An ongoing controversy exists on beneficial versus harmful effects of high beta-carotene (BC) intake, especially for the lung. To elucidate potential mechanisms, we studied effects of BC on lung gene expression. We used a beta-carotene 15,15'-monooxygenase 1 (Bcmo1) knockout mouse (Bcmo1-/-) model, unable to convert BC to retinoids, and wild-type mice (Bcmo1+/+) mice to dissect the effects of intact BC from effects of BC metabolites. As expected, BC supplementation resulted in a higher BC accumulation in lungs of Bcmo1-/- mice than in lungs of Bcmo1+/+ mice. Whole mouse genome transcriptome analysis on lung tissue revealed that more genes were regulated in Bcmo1-/- mice than Bcmo1+/+ mice upon BC supplementation. Frizzled homolog 6 (Fzd6) and collagen triple helix repeat containing 1 (Cthrc1) were significantly downregulated (fold changes -2.99 and -2.60, respectively, false discovery rate <0.05) by BC in Bcmo1-/-. Moreover, many olfactory receptors and many members of the protocadherin family were upregulated. Since both olfactory receptors and protocadherins have an important function in sensory nerves and Fzd6 and Cthrc1 are important in stem cell development, we hypothesize that BC might have an effect on the highly innervated pulmonary neuroendocrine cell (PNEC) cluster. PNECs are highly associated with sensory nerves and are important cells in the control of stem cells. A role for BC in the innervated PNEC cluster might be of particular importance in smoke-induced carcinogenesis since PNEC-derived lung cancer is highly associated with tobacco smoke
- …