Volume 6 No. 2

March 2011
Characterization of Silver (Ag) Nanomaterials Synthesized by Horizontal Vapor Phase Crystal (HVPC) Growth Technique for Antimicrobial Applications

Characterization of Silver (Ag) Nanomaterials Synthesized by Horizontal Vapor Phase Crystal (HVPC) Growth Technique for Antimicrobial Applications

pp 30-39 (Vol 6 No 2 2011)

Wilfred V. Espulgar 1, Gil Nonato C. Santos 2, Reuben V. Quiroga 3
Solid State Physics Laboratory
DLSU Physics Department
espulgarw@dlsu.edu.ph,
gil.santos@dlsu.edu.ph,
3 reuben.quiroga@dlsu.edu.ph

ABSTRACT

Triangular silver nanoplates, of different orientations, and other nanostructures were successfully synthesized for antimicrobial purposes using the Horizontal Vapor Phase Crystal (HVPC) growth technique. The starting material for the synthesis was 35mg of 99.99% pure silver powder at varying growth temperatures from 800 °C, 900 °C, 1000 °C, and 1100 °C with growth times of 4 hours, 6 hours, or 8 hours at a fixed ramp time of 80 minutes were used as parameters in this study. Results from the SEM micrograph which was supported by EDX analysis showed that nanoparticles, triangular nanoplates, hexagonal nanoplates, nanowires, nanoribbons, nanorods, and nanocubes can be grown in the HVPC technique. The pour plate technique was employed to test the antimicrobial potency of the grown silver nanomaterials. Results revealed that the number of E. coli colonies grown when 105 CFU/mL of bacterial solution was exposed to a quartz tube with silver nanomaterials was decreased compared to when it was exposed to a quartz tube with or without silver powder.
Keywords: nanometerials, antimicrobial, Horizontal Vapor Phase Crystal (HVPC) growth technique, vacuum, pour plate technique

Geodesic Equation for an Acceleration-Dependent Metric

Geodesic Equation for an Acceleration-Dependent Metric

pp 19-29 (Vol 6 No 2 2011)

Emmanuel T. Rodulfo * and Ermys B. Bornilla
Physics Department, De La Salle University, 2401 Taft Avenue, Manila, Philippines *
*  
E-mail: emmanuel.rodulfo@dlsu.edu.ph

ABSTRACT

In Einstein’s General Relativity, a spacetime-dependent metric defines the curvature of the manifold. Some studies however propose to resolve various celestial anomalies by allowing some anomalous acceleration to modify the law of inertia. If higher-derivative dependencies are allowed in an otherwise monogenic Lagrangian, the usual variational technique leads to a higher-derivative extension of the Euler-Lagrange equations first presented by Ostrogradsky. Using this technique, to find the extremum of the spacetime interval, we derive the geodesic equation for a spacetime whose metric may have explicit dependence on the spacetime four-vector, four-velocity and four-acceleration. To exemplify its importance, we apply our result to some modified inertia models that accommodates some anomalous acceleration in their dynamics.

ON L-GROUPS

ON L-GROUPS

pp 16-18 (Vol 6 No 2 2011)

Rolando N. Paluga
Mathematics Department, Caraga State University rnpaluga@carsu.edu.ph

ABSTRACT

Let G be a group and H be a subgroup with H /= G. In this paper, we construct a group using G − H. This paper also presents several properties of this group.

Carrageenan-Ionic Liquid Composite:  Development of Polysaccharide-Based Solid  Electrolyte System

Carrageenan-Ionic Liquid Composite: Development of Polysaccharide-Based Solid Electrolyte System

pp 8-15 (Vol 6 No 2 2011)

D. H. Camacho,* S. J. M. Tambio, and M. I. A. Oliveros
Department of Chemistry, College of Science,
De La Salle University, 2401 Taft Avenue, Manila, Philippines
*Telephone/Fax: (+632)-5360230; E-mail: drexel.camacho@dlsu.edu.ph

ABSTRACT

Solid electrolyte system compared to a liquid electrolyte is desirable for some electrochemical applications. Natural polymers like polysaccharides were explored as polymer matrix in the development of solid electrolyte system. Among the polysaccharides screened, κ-carrageenan showed promising results. Cyclic voltammetry of the I3-/I- redox couple in κ-carrageenan gel showed improved performance compared to aqueous medium. Composite films of κ-carrageenan with KI and I2 as triiodide sources and polymer electrolytes based on κ-carrageenan and ionic liquid, 1,3-dimethyl imidazolium iodide (DMII) with I2 were prepared and characterized. The composite characterizations indicate that lower conductivity using Van der Pauw technique was observed with KI/I2 system owing to its porous surface. The κ-carrageenan/DMII/I2 system on the other hand showed a smooth surface and significantly higher conductivity making it a promising solid electrolyte system.

Triterpenes and Sterol from Pouteria campechiana

Triterpenes and Sterol from Pouteria campechiana

pp 1-7 (Vol 6 No 2 2011)

Consolacion Y. Ragasaa 1, Lynne M. Labacladoa, and John A. Rideoutb
a Chemistry Department, De La Salle University, 2401 Taft Avenue, Manila 1004, Philippines and
b School of Chemical and Biomedical Sciences, Central Queensland University, Queensland 4701, Queensland, Australia

1 Corresponding author: Tel/Fax: 062-5360230; E-mail: ragasac@dlsu.edu.ph

ABSTRACT

The ethyl acetate extract of the stem bark of Pouteria campechiana afforded 3β, 28-dihydroxy-olean-12-enyl fatty acid ester 1, a mixture of a fatty acid ester of oleanolic acid 2a and a fatty acid ester of betulinic acid 2b in a 0.3:1 ratio, and spinasterol 3 by silica gel chromatography. The structures of 1-2b were elucidated by extensive 1D and 2D NMR spectroscopy. The structure of 3 was identified by comparison of its 1H NMR data with spinasterol. Antimicrobial tests on 1 and a mixture of 2a and 2b indicated that they are slightly active against the bacteria, Escherichia coli and Pseudomonas areruginosa and the fungi, Candida albicans and Trichophyton mentagrophytes. They are inactive against Staphylococcus aureus, Bacillus subtilis, and Aspergillus niger.