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Scholarly Works, Physical Sciences and Mathematics

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14583/177

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    Transmittance Properties of Healthy and Infected Coffee Robusta Leaves with Coffee Leaf Miner (CLM) Pests
    bulan, Jejomar; Cadondon, Jumar; Lesidan, James Roy; Vallar, Edgar; Galvez, Maria Cecilia (Multidisciplinary Digital Publishing Institute (MDPI), 2023)
    Coffee Robusta (Coffea canephora) increased its total production by 73.5% during the first quarter of 2023. In this study, twenty (20) samples each of healthy and infected coffee leaves were measured for their transmittance properties in the UV-Vis and NIR regions. Coffee Leaf Miner (CLM)-infected leaves were identified based on translucent patches on the plant foliage. The results showed that a healthy coffee leaf has a mean transmittance of 41.53 µW for the NIR region, while for the infected leaves, the mean transmittance is 47.06 µW. Healthy coffee Robusta leaves showed significant differences in their transmittance properties compared to infected coffee Robusta leaves in the UV (r = −0.15, p = 0.021, F = 5.8, t = −0.286), visible (r = −0.15, p = 0.018, F = 6.11, t = −2.88), and NIR (r = −0.14, p = 0.027, F = 5.28, t = −2.99) regions. A CLM index was introduced based on the intensity ratio of green and red wavelengths. I535/575 showed positive correlation with the estimated chlorophyll-a concentration for healthy (r = 0.94, p = 0.227) and infected (r = 0.56, p = 0.622) leaves. This method leads to the development of portable sensors for the early detection of CLM pests in plants. © 2023 by the author. Licensee MDPI, Basel, Switzerland.
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    Characterization of porcine skin using a portable time-domain optical coherence tomography system
    Galvez, Maria Cecilia; Cadondon, Jumar; Mandia, Paulito; Macalalad, Ernest; Vallar, Edgar; Shiina, Tatsuo (Multidisciplinary Digital Publishing Institute (MDPI), 2023)
    Optical coherence tomography (OCT) is an imaging tool used to visualize the cross-section of a sample. Additionally, this device can measure the sample’s physical properties. This experiment used a portable version to measure the epidermal thickness and dermal extinction coefficient of porcine skin obtained from different anatomical sites. The thinnest epidermis was found to be from the ear region, while the thickest is from the leg. Meanwhile, the lowest dermal extinction coefficient was from the ear, while the highest was from the belly. These measured properties can be used as aids for diagnosing various skin conditions in humans and animals.
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    Stock market returns and climate risk in the U.S.
    Chen, Yiyang; Mamon, Rogemar; Spagnolo, Fabio; Spagnolo, Nicola (Elsevier, 2025)
    Using a data set for all companies forming the S&P 500 index, we investigate the stock price responses to acute physical risks, chronic physical risks, and transition risks. Our findings reveal that certain sectors are more vulnerable to climate risks, whereas others appear to be relatively unaffected. In addition, our results show that listed firms with poor environmental performance scores are more exposed to climate risk, as indicated by their stock returns being negatively affected, compared to firms with higher environmental performance scores. This suggests that improving environmental performance may help companies to better cope with climate risks and improve their financial performances. Our analysis provides evidence that the short-term systematic risk is more vulnerable to the climate risk events, whereas effects on long-term systematic risk do not appear to be statistically significant. These findings indicate that investors and firms should pay a particular attention to short-term systematic risk when considering the potential impact of climate risk on stock market performances.
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    Algal organic matter fluorescence analysis of Chlorella sp. for biomass estimation
    Cadondon, Jumar; Lesidan, James Roy; Bulan, Jejomar; Vallar, Edgar; Shiina, Tatsuo; Galvez, Maria Cecilia (Multidisciplinary Digital Publishing Institute (MDPI), 2023-11-15)
    Algal Organic Matter (AOM) is derived from the dissolved organic matter composition of the algal species being observed. In this study, excitation–emission fluorescence spectroscopy was used to determine Chlorella sp.’s AOM and pigment characteristics in varying algal biomass concentrations. The AOM and pigment characteristics were observed at 400–600 nm and 600–800 nm fluorescence emission, respectively, with an excitation spectrum of 300–450 nm. F450/680 was computed based on the ratio between the dissolved organic matter contribution at 450 nm and chlorophyll-a at 680 nm. F450/680 positively correlated with algal biomass (r = 0.96) at an excitation wavelength of 405 nm. This study is a good reference for those interested in algal biomass estimation and production in natural waters.
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    Structural, electronic, and optical properties of copper doped monolayer molybdenum disulfide: A density functional theory study
    Ducut, Melsa Rose D.; Rojas, Kurt Irvin M.; Bautista, Reilly V.; Arboleda, Nelson B. Jr. (Elsevier, 2025)
    We conducted first-principles calculations to investigate the effect of doping monolayer molybdenum disulfide (MoS2) with Cu in its structural, electronic, and optical properties. We found that Cu doping changes the material from an n-type semiconductor into a p-type semiconductor by shifting the Fermi energy level towards the valence band in all variations of concentration and site. The absorption coefficient, photoconductivity, and reflectivity calculations indicate that Cu-doped MoS2 is sensitive to violet light. In addition, Cu doping elevates the sensitivity of the material to low-energy light. These results show that Cu-doped MoS2 can be used in optoelectronic applications.