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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>Dear colleagues, <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>For the measurement of interdisciplinarity, one can use, for example, Rao-Stirling diversity which is defined as follows (Rao, 1982; Stirling, 2007): <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in;text-indent:.5in'><span style='font-size:11.0pt;color:#44546A'>Ä</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'> = </span><span style='font-size:11.0pt;color:#44546A'>Ó</span><sub><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>ij</span></sub><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'> p<sub>i</sub> p<sub>j</sub> d<sub>ij</sub> (1)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>where <i>d<sub>ij</sub> </i>is a disparity measure between two classes <i>i </i>and <i>j</i>—the categories are in the case below journals—and <i>p<sub>i </sub></i>is the proportion of elements assigned to each class <i>i</i>. As the disparity measure, we use the distances on an aggregated journal-journal citation map (Leydesdorff, Heimeriks, & Rotolo, in press; Leydesdorff, Rafols, & Chen, 2013). <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>For example, 23 publications can be retrieved as of today with the search string “au=Marijuan P*” at WoS. The journal map is as follows: <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal align=center style='text-align:center'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><img width=639 height=363 id="Picture_x0020_4" src="cid:image003.jpg@01D09217.0098C760" alt="cid:image001.gif@01D09216.E78CE210"></span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>and the Rao-Stirling diversity (“interdisciplinarity”) of this set is 01282.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>If I repeat the analysis with the search string “au=leydesdorff l*”, I retrieve 270 documents; Rao-Stirling diversity is 0.0805.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal align=center style='text-align:center'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><img width=639 height=362 id="Picture_x0020_3" src="cid:image004.jpg@01D09217.0098C760" alt="cid:image002.gif@01D09216.E78CE210"></span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>In other words, Leydesdorff is more prolific than Marijuan in terms of WoS publications, but Marijuan’s portfolio is more interdisciplinary than Leydesdorff’s. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>One finds the relevant software at <a href="http://www.leydesdorff.net/portfolio/index.htm">http://www.leydesdorff.net/portfolio/index.htm</a> <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>Reference:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#44546A'>Leydesdorff, L., Heimeriks, G., & Rotolo, D. (2015 (in press)). <a href="http://arxiv.org/abs/1502.05676">Journal Portfolio Analysis for Countries, Cities, and Organizations: Maps and Comparisons</a>. <i>Journal of the Association for Information Science and Technology</i>. <o:p></o:p></span></p></div></body></html>