SC I E N C E DI L I M A N is published semi-annually 
(June and December) by the University of 
the Philippines Diliman through the Office 
of the Vice Chancellor for Research and 
Development. The journal features articles of 
pure and applied sciences.

Editorial Board
Editor in Chief
 Jonas P. Quilang, Ph.D.

Associate Editors
 Jose Maria P. Balmaceda, Ph.D.
  University of the Philippines Diliman
 Louis Angelo M. Danao, Ph.D.
  University of the Philippines Diliman
 Carlos Primo C. David, Ph.D.
  University of the Philippines Diliman
 Christian N. Della, Ph.D.
  University of Glasgow Singapore
 Arnold M. Guloy, Ph.D.
  University of Houston
 Marie Antonette J. Meñez, Ph.D.
  University of the Philippines Diliman
 Dennis I. Merino, Ph.D.
  Southeastern Louisiana University
 Arnel A. Salvador, Ph.D.
  University of the Philippines Diliman
 Terence P. Tumolva, D.Eng.
  University of the Philippines Diliman
 Casiana Blanca J. Villarino, Ph.D.
  University of the Philippines Diliman
 Irene M. Villaseñor, Ph.D.
  University of the Philippines Diliman

Managing Editor
 Conchitina R. Cruz, Ph.D.
  University of the Philippines

Editorial Assistant
 Narita E.C. de las Alas

Layout Artist
 Mirriam M. Velasco

Copyeditor
 Jean Lau Wang

On the Cover:
A collage of shells of freshwater and land snails of UPLLG with 
UPLLG as the background.
Photographer: Kinsley Meg G. Perez and Julius A. Parcon
Layout artist: Sedney S. Mendoza

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 republication in any other journal or compilation is likewise 
prohibited except as provided in the Publication 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.

The views expressed in the articles are those of the authors and do not 
necessarily reflect the views of the publisher and the editors.

Science Diliman
July-December 2021 • Vol. 33 No. 2ISSN Print 0115-7809

ISSN Online 2012-0818

INTERNATIONAL ADVISORY BOARD

Teofilo A. Abrajano, Jr., Ph.D.
King Abdullah University of Science and Technology
Kingdom of Saudi Arabia

Rigoberto C. Advincula, Ph.D.
Case School of Engineering
Case Western Reserve University, USA

Kenneth A. Buckle, Ph.D.
Professor Emeritus
School of Chemical Engineering
The University of New South Wales, Australia

Jose B. Cruz, Jr., Ph.D.
Professor Emeritus
University of Illinois, USA
University of California, Irvine, USA
The Ohio State University, USA

John P. Encarnacion, Ph.D.
Department of Earth and Atmospheric Sciences
Saint Louis University, USA

Mihali A. Felipe, Ph.D.
Gerstein Lab, Bioinformatics
Yale University, USA

Robert J. Howell, Ph.D.
Department of Mechanical Engineering
The University of Sheffield, United Kingdom

Jeanmaire E. Molina, Ph.D.
Department of Biology
Long Island University, Brooklyn, USA

Rudolf A. Roemer, Ph.D.
Department of Physics
University of Warwick, United Kingdom

Raul K. Suarez, Ph.D.
Professor Emeritus
University of California, Sta. Barbara, USA

Myra O. Villareal, Ph.D.
Life and Environmental Sciences
Graduate School
University of Tsukuba, Japan