Solar energy is free, clean, and virtually limitless; however, its conversion into a storable form presents technological challenges. Compared to batteries or other mechanical systems, fuels are more energy-dense, directly usable, and compatible with the current energy infrastructure. One scheme to produce “solar fuels” is the photoelectrochemical (PEC) reduction of CO2 to one- or two-carbon compounds, where a semiconductor configured as an electrode performs both the light absorption and electrochemical functionalities. A potential material for this application is the p-type copper bismuth oxide (CuBi2O4) with a band gap capable of visible light absorption and a conduction band edge position suitable for CO2 reduction. In this study, CuBi2O4 photocathodes were prepared via an electrodeposition-spray deposition-annealing route. By varying the number of spray cycles, films with varying Cu/Bi ratios (0.25, 0.51, 0.68, 0.94, 2.04) were synthesized. Where the ratio exceeded the stoichiometric value of 0.5, a bilayered film composed of a nanoparticulate copper (II) oxide (CuO) phase on top of CuBi2O4 was present, forming a heterojunction between the two oxide layers. With increasing Cu/Bi ratio, the light absorption range of the films broadened due to the CuO phase. Analysis of the photocurrent-potential behavior of the films under visible-light illumination showed a 4–7-fold increase in the photocurrent from an inert electrolyte to a CO2-saturated electrolyte, confirming activity for CO2 reduction of the CuBi2O4/CuO films. The transient photocurrent response of the films showed a 70-80% decrease in the photocurrent after only 15 mins of testing. However, when tested in an electrolyte with an electron scavenger, the percent decrease was lowered to <10%, indicating that the instability of the films resulted from poor interfacial kinetics. While the CuBi2O4/CuO films can accomplish CO2 reduction, further strategies to improve their efficiency and stability are needed to realize practical application.

Abaca fiber reinforced polymer composites hold immense potential for structural applications, necessitating a comprehensive understanding of their mechanical behavior. As the demand for environmental-friendly materials grows, this study endeavors to revolutionize the understanding of abaca fiber reinforced polymer composites through the development and validation of a finite element model (FEM) for a composite beam made from 30% abaca fiber reinforced polymer, with dimensions of 135 mm in length, 12.7 mm in width, and 3 mm in thickness. The FEM was developed using Ansys Composite PrepPost, incorporating accurate material properties and boundary conditions. Mesh independence analysis confirmed convergence at 312 elements. Structural responses were simulated under bending loads and pure moment, considering two fiber orientations: 0 deg/90 deg and +45 deg/-45 deg. Experimental validation involved fabricating the beam with the hand lay-up technique, and testing it under various loads to measure flexural and torsional deflections. The results showed that the FEM accurately predicted the beam's performance, with the 0o/90o orientation exhibiting higher flexural deflection and the +45deg/-45deg orientation showing greater torsional deflection. The trend of the results are also in agreement with the analytical calculations based on the Composite Lamination Theory (CLT). Statistical analysis confirmed that the differences between experimental data and FEM predictions were not significant, validating the model's reliability. While the findings are promising, caution should be exercised in generalizing the results due to the small sample size. Overall, this study underscores the FEM's potential for advancing the utilization of abaca fiber composites in engineering, ensuring reliable and efficient modeling for practical applications.

The decline in antibiotic discovery and increasing restrictiveness of antibiotics continue to strengthen antimicrobial resistance (AMR) as a potentially significant global threat. Of the many emerging solutions, antimicrobial peptides (AMP) are known for their efficiency in treating multi- drug resistant (MDR) organisms. However, drawbacks on its stability, bioavailability, and unwanted macromolecule interactions hamper its clinical use. Considering these limitations, the development of better drug delivery systems is needed to increase the stability, efficacy, and pharmacokinetics of AMPs. Chitosan-based hydrogels (CSH), known for their excellent therapeutic agent carrier performance, were synthesized via the pH-induced gelation method. Citropin 1.1 peptide (CIT) and varying concentrations of Doxycycline (DOX), Vancomycin (VCY), and Methylene blue dye (MB) were encapsulated into the CSH. Doxycycline was used to compare low molecular weight drug release behavior with AMP, while Vancomycin was used to compare high molecular weight drug release behavior with AMP. On the other hand, MB dye was used to compare an easily detectable agent’s release behavior with AMP. Additionally, the release profiles of the loaded CSH in phosphate-buffered saline (PBS) were investigated via a UV-VIS spectrophotometer. In vitro release data showed that the DOX-CSH, VCY-CSH, and MB-CSH followed a similar pattern: initial burst release, followed by a sustained release, and eventually reaching an equilibrium state, while CIT-CSH observed a different pattern of release: sustained release, followed by a burst release and eventually reaching equilibrium state. The highest overall efficiency reported for DOX-CSH, VCY-CSH, MB-CSH, and CIT-CSH are 16.86 ± 0.75%, 6.02 ± 0.26%, 6.77 ± 1.18% and 55.11 ± 4.71%, respectively. The release data of loaded hydrogels were modeled with Korsmeyer-Peppas (KP), Higuchi (H), and First-Order (FO) kinetic models. The best-fit model for CIT-CSH was observed with the KP model, having an average R-squared value of 0.9137 and n value of 0.9244, suggesting that the governing release mechanism is anomalous or non-Fickian diffusion. Furthermore, the best-fit model for DOX-CSH, VCY-CSH, and MB-CSH was observed with the FO model, having an average R-squared value of 0.9941, 0.9818, and 0.9848, respectively. This implies that the rate of release of the loaded agents of the mentioned loaded CS hydrogels is concentration-dependent, making the concentration gradient the primary driving force of the release mechanism. Overall, CSH poses promising therapeutic agent carrier properties for both antibiotics and antimicrobial peptides, which can be further modified and optimized for targeted therapeutic agent delivery.

Laguna de Bay is a multi-purpose lake adjacent to Metro Manila and has been classified as a Class C water resource in accordance with the DENR Administrative Order No. 2016-008. In this study, the nutrient loading and carrying capacity, along with its Carlson’s Trophic State Index (CTSI), were assessed using a two-dimensional numerical model implemented with the Hydrodynamic and ECO Lab Modules of DHI’s MIKE 21. The hydrodynamic model was calibrated with respect to water levels observed at the Angono Station (mean error of 0.1858 m). The water quality component on the other hand (ECO Lab) which simulated temperature, salinity, BOD, DO, Chl-a, NH3, NO3, and PO4 among others, ended with average mean errors of -0.167 mg/L for NO3-N and -0.0596 mg/L for PO4 when compared to LLDA’s lake monitoring stations. Based on simulation results, nitrates and phosphates spread in the lake coming mostly from the west bay (San Pedro to Metro Manila), and the central bay (Angono and Baras), demonstrating that much of the lake’s pollution originate from land-based sources (anthropogenic). Through various scenarios, it was found that the lake fails for various water quality parameters even with its tributary rivers being able to satisfy the upper limits of the Class C surface water standards. PO4, NO3-N, and BOD on the other hand need to be set at 0.35 mg/L, 6.3 mg/L, and 3 mg/L, respectively for all draining tributaries to achieve the water quality requirements for Class C waters any time of the year. Also, based on the Carlson’s Trophic State Index (CTSI), Laguna de Bay can be classified as a hypereutrophic lake with values increasing during the wet season.

Metro Manila’s Road network comprises more than two hundred major road intersections, with more than a third being under elevated structures (flyovers, bridges, etc.). With vehicles idling, accelerating, and decelerating, traffic-related air pollution can be thrice as high at intersections. This makes intersections a hotspot for urban air pollution, a main health concern for commuter groups. This study examines the effect of elevated structures (e.g., flyovers, bridges, and rail stations) as covers and barriers to the TRAP exposure rate of pedestrians, bicycle lane users, and public utility vehicle (PUB, PUJ, and UVE) commuters at six (6) intersections in Metro Manila. The study implemented air dispersion modeling using US EPA’s AERMOD to estimate TRAP concentrations. The results showed that there were higher TRAP concentrations at intersections with full (35.94 ug/min ± 20 ug/min, 95%CL) and partial cover (34.26 ug/min ± 30.14 ug/min, 95%CL) than those intersections without cover (14.70 ug/min ± 5.35 ug/min, 95%CL). In terms of time variability, average TRAP concentrations for intersections with full cover were higher three hours after rush hours (classified as post-rush hours) (48.18 ug/min ± 22 ug/min 95%CL) compared to off-peak hours (25.97 ± 12.91 ug/min, 95%CL) and rush hours (31.17 ± 18.39 ug/min, 95%CL). On the other hand, average TRAP concentrations for intersections with partial cover were higher during rush hours (45.63 ± 26.66 ug/min, 95%CL) than post-rush hours (28.06 ± 12.40 ug/min, 95%CL) and off-peak hours (31.12 ± 16.43 ug/min, 95%CL). Last, average TRAP concentrations for intersections without cover have no significant peaking time. The higher average TRAP concentrations at intersections with cover were attributed to the lower wind speeds (0.83 m/s ± 0.36 m/s, 95%CL) recorded compared to intersections with no cover (1.43 m/s ± 0.21 m/s, 95%CL). The study hypothesizes that the elevated structures at these sites act as barriers that impede wind speed, therefore slowing the dispersion process. The model results were validated by in-situ survey sensors, with a correlation coefficient equal to 0.77. Five (5) commuter groups were identified, and TRAP exposure was calculated for each group, intersection, and time. Cyclists under intersections with full cover during the post-rush period (0.675 ug/min ± 0.14 ug/min, 95%CL) and cyclists under intersections with partial cover during rush hours (0.650 ug/min ± 0.2 ug/min, 95%CL) were found to have the highest TRAP exposure per unit time.