Abstract

The megastigmane sesquiterpene vomifoliol (1) was isolated from the leaf extracts of Psychotria gitingensis and Villaria odorata, two Rubiaceae species endemic to the Philippines. The structure of 1 was determined by extensive NMR spectroscopy and comparison of its 1H and 13C NMR chemical shifts with those found in the literature.

Index Terms

Psychotria, Villaria, vomifoliol, sesquiterpene

Abstract

Strong light-matter interactions inside semiconductor microcavities have coherent and stimulated effects offering the possibility of developing new optical devices. Since most of the researches done in microcavities were gallium-based only a few for silicon-based, we therefore focused in the design of a strongly coupled silicon-based microcavity made possible using the transfer matrix program (TM), a tool for stimulating reflectance, transmittance and absorbance of layered structures. Validation of the TM program involved the comparison of the current experimental result to the simulated microcavity based on the theory and experiment on silicon-based microcavities. The TM program was also validated by simulating the reflectivity for multilayered structures sample from the National Institute of Physics (NIP), University of the Philippines (UP)-Diliman. This was made possible by comparing the results for the experiment, TM and UV-VIS. After validation, a silicon based microactivity was designed with three active mediums of crystalline Si3N4 sandwiched between two a-Si-N:H distributed Bragg reflectors (DBRs). Results of the study have shown that the general profile of a-Si-N:H microcavity for calculated transmission spectrum agrees well with the experimental results of Ballarini in 2004. Conversely, the calculated reflectivity spectra for multilayered structures such as MQW 318, HEMT 316 and HEMT 326 from NIP, UP-Diliman fairly fit the measured and the UV-VIS spectra. The transfer matrix program used to design silicon-based microcavities consisting of a crystalline silicon nitride (c-Si3N4) embedded between amorphous silicon nitride (a-Si-N:H) and distributed Bragg reflectors (DBRs) showed two dips in the reflectance spectrum as the cavity is coupled with light. These peaks are shifted as the cavity layer thickness is changed by a constant percentage. These two dips signify the upper and lower polariton branches. The anticrossing of these two polariton branches upon reaching resonance is the very signature of a strong coupling regime. Thus, a strongly coupled silicon-based microcavity was observed.

Index Terms

anticrossing, microcavities, semiconductors, silicon-based, transfer matrix program

Abstract

We demonstrated a low-cost, fast, and straightforward approach to a dimensional measurement applicable up to the micrometer level. The technique relies mainly on laser light deflected on a probe fixture, with a reflective surface, that varies its angle as a function of thickness. Changes in light intensity transmitted through a continuous gradient sunglass lens are then correlated with the changes in the sample thickness, calibrated using the micrometer stage. The advantages of the technique depend on the simplicity of the design and readily available materials. Manual data acquisition which is used in this technique reports a precision error of about ±1 µm.

Index Terms

calibration, metrology, optical technique, polydimenthysiloxane (PDMS)

Abstract

A conventional and most widely used geophysical method, called Wenner array, is used to investigate the relationship of the bulk soil electrical conductivity of loam and its water content. Loam is made up of relative proportions of sand, silt and clay and most of them contains nutrients which are needed by the plants. It can be seen that loam saturates at a certain range for this experiment and as the soil saturates it quickly decreases which shows that the probe reads the excess water physically seen in the set-up.

Index Terms

bulk electrical conductivity, loam, water content, Wenner array

Abstract

This study fabricated an ultrasonic device and its impact of sonication to inactivate microbes in wastewater was evaluated. Microbial inactivation and water quality assessment were also examined. An ultrasonic circuit was designed to have a tunable frequency of 40.5, 714.4, and 209.7kHz. The device power output was about 277mW. Wastewater was collected and analyzed. Samples were placed in a sterile beaker and ultrasonically exposed for 15 and 60 min. The device ability to inactivate microbes was performed thru pour plate method. Heterotrophic plate count was recorded for analysis. Total suspended solids (TSS) and pH value were determined. Results showed microbial reduction percentage both at 15min and 60min. Colony counts were observed to decrease as the frequency and exposure tine also increases. Physical analysis of water demonstrated that sonication promotes deagglomeration of large particulate matters. TSS data showed differences at 15min and at 60min using 40.5-209.7kHz. Chemical results showed an alkaline sample before and after sonication. This study therefore suggests that the fabricated ultrasonic device were able to inactivate microbes and proved to be a viable agent for water decontamination.

Index Terms

ultrasound, microbes, frequency, ultrasonication

Abstract

This study was conducted to compare the growth on varying polymerization time of silica modified-polyaniline (SM-PAni) nanostructures on glass substrate with varying polymerization time. Characterizations of the surface morphology and elemental composition of the grown nanostructures were done using scanning electron microscopy (SEM) equipped with energy dispersive x-ray spectroscopy (EDS). Fourier Transform Infrared (FTIR) Spectroscopy was employed to analyze the chemical structure of the films. The results revealed that longer polymerization time would yield longer polyaniline rod-like nanostructures as a result of longer reaction time of the grown polyaniline rod-like nanostructures with the reaction mixture. FTIR spectral analysis confirmed that the formation of emeraldine salt oxidation state of polyaniline exists.

Index Terms

Emeraldine salt, conducting polymers, oxidative polymerization, silica modified-polyaniline

Abstract

This paper explores the relationship of the change in the refractive index of water when chemical pollutants are mixed with it. Using the Mach-Zehnder interferometer, the refractive index of water was calculated from the number of fringe shifts of the bullseye pattern for every 1ml of chemical pollutant added in the water. As the concentration of the pollutants increases, the index of refraction increased exponentially. Our results suggest that there may be a connection between the two quantities for specific group of pollutants, e.g. nitrates and chlorides.

Index Terms

environmental pollutants, index of refraction, interferometer, Mach-Zehnder

Abstract

This paper is an attempt to assess the climate change risk and vulnerability index of he Panglao Island, Bohol, Philippines. Results have revealed that the overall vulnerability index of Panglao is 39.01% while the Municipality of Daius is 36.43%. Both estimates are in the moderate risk levels. Panglao's resiliency index can be deemed to be less resilient while Dauis can be considered to be more resilient.

Index Terms

climate change, coastal tourism, risk index, vulnerability index.

Abstract

We developed a robust and low-cost protocol for building microfluidic chambers by constructing the mold using sticker paper, which is several hundred microns thick. The chamber channel geometry was implemented using computer aided design (CAD) software, and was printed on the sticker paper using a commercial ink-jet printer. Precision laser cutting was used to remove the mold design, which was later fused onto a glass slide where the Polydimethylsiloxane (PDMS) was reconstituted, poured, and cured. We flowed in hydrochloric acid (HCI) and methyl orange at the inlet and based on color change (by chemical reaction) we characterized mixing homogeneity. Laminar flow was implemented by performing the procedure at low Reynolds Number (3.69 ±0.06 x 10^-2 and advective mixing conditions was controlled by keeping the P'eclet number high (62). We found that with the use of size-controlled filter paper as suction device at the outlet, a uniform flow was achieved as well as homogenous mixing.

Index Terms

advective mixing, homogenous mixing, laminar flow, polydimenthylsiloxane

Abstract

Unseeded and seeded growth of Zinc Oxide on glass substrate via Chemical Bath Deposition technique (CBD) were studied for hydrogen peroxide gas sensor application. Ammonium hydroxide (NH₄OH) and Zinc sulfate (ZnSO₄) were used as the precursor substances in the synthesis. The chemical compositions of the synthesized samples were examined by Fourier Transform InfraRed (FTIR) spectroscopy. IV curve and sensitivity measurements were carried out in order to examine its potential to be fabricated as Hydrogen peroxide (H₂O₂) gas sensor. Experimental results show that seeded samples favors greater growth than the unseeded ones. FTIR spectra verify that ZnO were indeed synthesized. IV curve and Sensitivity graph show that in the presence of H₂O₂ gas, the resistance of ZnO increase which can be used as the basis for the H₂O₂ detection.

Index Terms

Zinc oxide, Hydrogen peroxide, seeded growth, unseeded growth, Chemical bath deposition

Abstract

This work presented a Current-Mode CMOS Instrumentation Amplifier (IA) that can be used for neutral signal sensing. The IA has achieved a Common-Mode Rejection Ratio (CMRR) of 108dB and generates a noise of 17nV√Hz while dissipating only 550µW of power under a bipolar supply of +/-0.9V. The IA is based on a Differential Voltage-Current Conveyor (DVCC) using TSMC 0.18µm CMOS Mixed Mode Technology. The simulations are carried out using Linear Technology SPICE with the model file obtained from MOSIS.

Index Terms

CMOS, CMRR, DVCC, IA, Neuron

Abstract

This study was conducted to characterize and determine the applications of Zinc oxide nanorods as waste water disinfectant and gas sensor. ZnO nanoparticles were prepared from zinc sulfate and ammonium hydroxide thru chemical bath deposition. These were synthesized and dried at 100°C (Type-I), a portion of which was annealed at 400°C (Type-II). The particles were morphologically assessed using Scanning Electron Microscopy (SEM) and optical microscopy. X-ray Diffraction (XRD) was done to determine ZnO phases. To determine its applications as wastewater disinfectant, heterotrophic plate count on ZnO treated and untreated wastewater samples were utilized to evaluate microbial viability. Results revealed that ZnO nanorods were successfully synthesized. SEM images showed nanostructured ZnO with hexagonal tip of 10-250nm diameters. Increase in clustering and grain size was observed with increased heating temperature and time. XRD showed a highly crystalline ZnO with average crystal size of 54nm (Type-I) and 58nm (Type-II). Optical microscopy depicted films relatively flat the thickness of which range from 169.8-258.2µm. Microbiological analysis revealed that Type-I ZnO had reduced bacterial counts by 92% from 21,000 to 1,700cfu/mL, Type-II powder had bactericidal efficacy of 86% from 11,400 to 1,600cfu/mL. Type-I and Type-II film sensors have a sensitivity response of 10 and 6.5 percent with response time of both 25s. I-V curves showed Type-I had high surface recovery than Type-II sensor. This study have generally shown that promise of nanoparticles as disinfectants in wastewater treatment and the viability of films as acetic acid gas sensor.

Index Terms

zinc oxide, disinfection, sensor, nanoparticles, modified deposition-sedimentation, annealing technique, chemical bath deposition

Abstract

This study simulated an Elekta Compact 6-MV linear accelerator (Linac) using Geant4 Monte Carlo. The head assembly was constructed based from available machine data considering the projected dimension, relative position, and estimated material composition. The beam source was modeled by transporting 2 billion 6-MeV mono-energetic electrons to produce x-ray energy spectrum after hitting a tungsten target. The spatial energy of primary particles was set to 0.127 MeV and the gun radius to 0.5 mm. The EmLivermore physics list was chosen to consider low energy electromagnetic processes. The interest points were computed at depths 1.04 cm to 30 cm with varying field sizes along the central axis of voxelized water phantom with source to surface distance (SSD) of 100 cm. The validity of the simulated data has been verified by comparison with experimental measurements. There was a good agreement between the simulated and measured beam data. Normalization errors computed were 4.6% and 3.9% for 10 x 10 cm² and 15 x 15 cm² field sizes, respectively.

Index Terms

depth-dose, Elekta Compact, Geant4, linear accelerator, Monte Carlo, water phantom

Abstract

This study tackles about the possibility of modeling actual ear canals physically using materials with rigid walls. The materials being molded into tubes are engineering plastic and steel. These materials were specifically chosen because of their rigid property. Three samples for each material of ear canal models were produced having different lengths. Data on both the materials showed that they have similar frequency response curves with that of actual ear canals. However, in this experiment, the geometry of the ear canal has yet to be investigated.

Index Terms

actual ear canals, ear canal models and frequency response curves, lengths, geometry