<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0035-001X</journal-id>
<journal-title><![CDATA[Revista mexicana de física]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. fis.]]></abbrev-journal-title>
<issn>0035-001X</issn>
<publisher>
<publisher-name><![CDATA[Sociedad Mexicana de Física]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0035-001X2008000300001</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Noise-assisted synchronization of the transition times of a set of uncoupled bistable elements]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Cortés]]></surname>
<given-names><![CDATA[E]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Fujioka]]></surname>
<given-names><![CDATA[J]]></given-names>
</name>
<xref ref-type="aff" rid="A02"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rodríguez]]></surname>
<given-names><![CDATA[R.F]]></given-names>
</name>
<xref ref-type="aff" rid="A03"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Autónoma Metropolitana Departamento de Física ]]></institution>
<addr-line><![CDATA[Mexico D.F.]]></addr-line>
<country>México</country>
</aff>
<aff id="A02">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Física Departamento de Materia Condensada]]></institution>
<addr-line><![CDATA[México D.F.]]></addr-line>
<country>México</country>
</aff>
<aff id="A03">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Física Departamento de Física Química]]></institution>
<addr-line><![CDATA[México D.F.]]></addr-line>
<country>México</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>06</month>
<year>2008</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>06</month>
<year>2008</year>
</pub-date>
<volume>54</volume>
<numero>3</numero>
<fpage>176</fpage>
<lpage>179</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0035-001X2008000300001&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0035-001X2008000300001&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0035-001X2008000300001&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[We study the noise-induced synchronization of the transition times of a set of non-interacting bistable systems undergoing an activation process in the presence of an external periodic field. Starting from a collection of time series corresponding to these transition times, we first explore graphically the extent of the synchronization for different values of the noise intensity and the frequency of the periodic signal. Then we quantify this phenomenon by means of the fractional fluctuation of the transition times. We show that this quantity has an optimal behavior when we plot it as a function of the noise intensity and the frequency of the periodic external force. Three-dimensional plots of the fractional fluctuation versus these two parameters clearly exhibit the parameter region of optimal synchronization.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[En este trabajo se estudia la sincronización inducida por ruido, de los tiempos de transición de un conjunto de sistemas biestables. Estos sistemas llevan a cabo un proceso de activación en presencia de un campo periódico externo. Se parte de un conjunto de series de tiempo que corresponden a los tiempos de transición de los distintos sistemas y se explora en forma gráfica el grado de sincronización para diferentes valores de la intensidad del ruido, así como de la frecuencia de la señal periódica. Una vez hecho esto, se cuantifica este fenómeno por medio de la fluctuación fraccional de los tiempos de transición. Se muestra que esta cantidad tiene un comportamiento óptimo al graficarla contra la intensidad del ruido y la frecuencia de la fuerza periódica externa. En gráficas tridimensionales de la fluctuación fraccional contra estos dos parámetros, se observa con claridad la región de comportamiento óptimo en estos parámetros.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Synchronization]]></kwd>
<kwd lng="en"><![CDATA[noise]]></kwd>
<kwd lng="en"><![CDATA[activation processes]]></kwd>
<kwd lng="es"><![CDATA[Sincronización]]></kwd>
<kwd lng="es"><![CDATA[ruido]]></kwd>
<kwd lng="es"><![CDATA[procesos de activación]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <p align="justify"><font face="verdana" size="4">Carta</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="4"><b>Noise&#150;assisted synchronization of the transition times of a set of uncoupled bistable elements</b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="2"><b>E. Cort&eacute;s&ordf;, J. Fujioka<sup>b</sup> and </b><b>R.F. Rodr&iacute;guez<sup>c</sup></b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><i>&ordf; Departamento de F&iacute;sica, Universidad Aut&oacute;noma Metropolitana Iztapalapa, Apartado Postal 55&#150;534, Mexico D.F. 09340, M&eacute;xico,</i> e&#150;mail: <a href="mailto:emil@xanum.uam.mx">emil@xanum.uam.mx</a></font></p>     <p align="justify"><font face="verdana" size="2"><i><sup>b</sup> Departamento de Materia Condensada, Instituto de F&iacute;sica, Universidad Nacional Aut&oacute;noma de M&eacute;xico, Apartado Postal 20&#150;364, M&eacute;xico D.F. 01000, M&eacute;xico.</i></font></p>     <p align="justify"><font face="verdana" size="2"><i><sup>c</sup> Departamento de F&iacute;sica Qu&iacute;mica, Instituto de F&iacute;sica, Universidad Nacional Aut&oacute;noma de M&eacute;xico, Apartado Postal 20&#150;364, M&eacute;xico D.F. 01000, M&eacute;xico</i></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2">Recibido el 11 de septiembre de 2007    <br>   Aceptado el 23 de mayo de 2008</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Abstract</b></font></p>     <p align="justify"><font face="verdana" size="2">We study the noise&#150;induced synchronization of the transition times of a set of non&#150;interacting bistable systems undergoing an activation process in the presence of an external periodic field. Starting from a collection of time series corresponding to these transition times, we first explore graphically the extent of the synchronization for different values of the noise intensity and the frequency of the periodic signal. Then we quantify this phenomenon by means of the fractional fluctuation of the transition times. We show that this quantity has an optimal behavior when we plot it as a function of the noise intensity and the frequency of the periodic external force. Three&#150;dimensional plots of the fractional fluctuation versus these two parameters clearly exhibit the parameter region of optimal synchronization.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Keywords: </b>Synchronization; noise; activation processes.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Resumen</b></font></p>     <p align="justify"><font face="verdana" size="2">En este trabajo se estudia la sincronizaci&oacute;n inducida por ruido, de los tiempos de transici&oacute;n de un conjunto de sistemas biestables. Estos sistemas llevan a cabo un proceso de activaci&oacute;n en presencia de un campo peri&oacute;dico externo. Se parte de un conjunto de series de tiempo que corresponden a los tiempos de transici&oacute;n de los distintos sistemas y se explora en forma gr&aacute;fica el grado de sincronizaci&oacute;n para diferentes valores de la intensidad del ruido, as&iacute; como de la frecuencia de la se&ntilde;al peri&oacute;dica. Una vez hecho esto, se cuantifica este fen&oacute;meno por medio de la fluctuaci&oacute;n fraccional de los tiempos de transici&oacute;n. Se muestra que esta cantidad tiene un comportamiento &oacute;ptimo al graficarla contra la intensidad del ruido y la frecuencia de la fuerza peri&oacute;dica externa. En gr&aacute;ficas tridimensionales de la fluctuaci&oacute;n fraccional contra estos dos par&aacute;metros, se observa con claridad la regi&oacute;n de comportamiento &oacute;ptimo en estos par&aacute;metros.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Descriptores:</b> Sincronizaci&oacute;n; ruido; procesos de activaci&oacute;n.</font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2">PACS:05.40.&#150;a,05.45.Xt</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><a href="/pdf/rmf/v54n3/v54n3a1.pdf" target="_blank">DESCARGAR ART&Iacute;CULO EN FORMATO PDF</a></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Acknowledgments</b></font></p>     <p align="justify"><font face="verdana" size="2">We are grateful to Rafael Soto M. (Facultad de Ciencias, UNAM) for his valuable contribution to this work. RFR acknowledges partial support from grant DGAPA&#150;UNAM, IN108006.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>References</b></font></p>     <!-- ref --><p align="justify"><font face="verdana" size="2">1. O. Carrillo, M. Iba&ntilde;ez, J. Garcia&#150;Ojalvo, J. Casademunt, and J.M. Sancho, <i>Phys. Rev. E </i><b>67</b> (2003) 046110.</font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=8397883&pid=S0035-001X200800030000100001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p align="justify"><font face="verdana" size="2">2. H. Zhonghuai, Y. Lingfa, X. Zuo, and Xin Houwen, <i>Phys. Rev. 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