inside front cover-19-2 EDITORIAL BOARD Editor-in-Chief Maricor N. Soriano, Ph.D. Associate Editors Mario A. Aurelio, Ph.D. Earth Sciences Jose Maria P. Balmaceda, Ph.D. Mathematics Zubaida U. Basiao, Ph.D. Biology Joel Joseph S. Marciano, Jr., Ph.D. Computer Science, Engineering Nemesio E. Montaño, Ph.D. Biochemistry Irene M. Villaseñor, Ph.D. Chemistry Corazon D. Villareal, Ph.D. Managing Editor Dercylis G. Mararac Editorial Assistant EDITORIAL ADVISORS Rigoberto C. Advincula, PhD Dept. of Chemistry University of Houston radvincula@uh.edu Alfonso M. Albano, PhD. Dept. of Physics Bryn Mawr College, Bryn Mawr, Pennsylvania aalbano@brynmawr.edu Jose B. Cruz, PhD. Dept. of Electrical and Computer Engineering Ohio State University cruz@ece.osu.edu. Victor C. Gavino, PhD. Dept. of Nutrition University of Montreal, Canada victor.gavino@umontreal.ca SCIENCE DILIMAN (ISSN 0115-7809) is published bi-annually by the Research Dissemination and Utilization Office (RDUO) of the Office of the Vice Chancellor for Research and Development (OVCRD), University of the Philippines Diliman. Address all communications to the Editor in Chief, SCIENCE DILIMAN, Research Dissemination and Utilization Office, Office of the Vice Chancellor for Research and Development, Lower Ground Floor, Phivolcs Bldg., C. P. Garcia Ave., University of the Philippines, Diliman, Quezon City 1101 Philippines. Subscription Rates: P300.00/year (two issues), exclusive of postage US$ 25.00/year (two issues), exclusive of postage Tel. No: (632) 981-85-00 loc. 4047 (632) 927-2567; 927-2309; 436-87-20 TelFax: (632) 927-2568 E-mail: rduo.ovcrd@up.edu.ph Website: http://www.ovcrd.upd.edu.ph SCIENCE DILIMAN A Journal of Pure and Applied Sciences COVER ART The illustration shows a multimedia server distributing content to different clients grouped according to how fast they receive the content (Tiglao et al. pp. 33-42, this issue.) Cover art courtesy of Engr. Nestor Michael Tiglao of the Electrical and Electronics Engineering Institute, University of the Philippines, Diliman. Contents of this journal may not be reproduced without the publisher’s written permission except for fair use, i.e., for personal, educational and research purposes, in accordance with Copyright law. Reprinting and re-publication in any other journal or compilation is likewise prohibited except as provided in the Copyright Agreement when the author reprints his/her article for inclusion in any publication where he/she is the author or editor, subject to giving proper credit to the original publication of the article in the journal. Kelvin S. Rodolfo, PhD. Dept. of Earth and Environmental Sciences University of Illinois, Chicago, Illinois krodolfo@uic.edu Rudolf A. Roemer, PhD. Centre for Scientific Computing and Dept. of Physics University of Warwick r.roemer@warwick.ac.uk Luis G. Sison, PhD. Electrical and Electronics Engineering Institute University of the Philippines, Diliman luis.sison@up.edu.ph Raul K. Suarez, PhD. Dept. of Ecology, Evolution and Marine Biology University of California, Sta. Barbara suarez@lifesci.ucsb.edu