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Faculty Publication (2020)

Biology logo

1. Bejar, S.G.F., Duya, M.R.M., Duya, M.V., Galindon, J.M.M., Pasion, B.O., Ong, P.S. (2020). Living in small spaces: Forest fragment characterization and its use by Philippine tarsiers (Tarsius syrichta Linnaeus, 1758) in Mindanao Island, Philippines (Article in press)Primates. https://doi.org/10.1007/s10329-020-00798-2 more

Abstract:

The Philippine tarsier (Tarsius syrichta) is a charismatic species that is threatened by illegal hunting and deforestation. Although they occur in forest and disturbed habitats, ecological information about them is still considerably lacking, which consequently hampers our ability to effectively protect tarsiers from further endangerment. Here, we characterized a 36-ha forest fragment in Mindanao Island where a population of tarsiers persist, and assessed the factors that could have influenced their distribution within the area. We sampled trees (> 1 cm DBH) within 10 × 10-m sampling plots (N = 54), which were established within 1-ha grids (N = 32) and locations where tarsiers were captured (N = 22). The habitat was characterized as a regenerating forest over limestone, with a generally homogeneous structure in terms of tree species richness, abundance, mean DBH, and height. In both sampling plots, we found an abundance of trees below 5 cm in DBH (> 50%) and between 2.6 and 5 m in height (> 40%), which, accordingly, the tarsiers appeared to prefer to use when foraging or sleeping. Lianas were among the most important features of the forest, possibly being a keystone structure in such habitats. Community assemblage, species richness, and mean height of trees, as well as distance to the forest edge, were found to be significant factors that influenced tarsier distribution in the fragment. Our study provides basic yet critical information on the habitat and ecology of Philippine tarsiers in Mindanao, and highlights the importance of forest fragments with rich flora diversity to the survival of the species.

 

2. Francisco, J.C.E., Rivera, W.L., Vital, P.G. (2020). Influences of carbohydrate, nitrogen, and phosphorus sources on the citric acid production by fungal endophyte Aspergillus fumigatus P3I6Preparative Biochemistry and Biotechnology, 50 (3), Pages 292-301. DOI: 10.1080/10826068.2019.1689510 more

Abstract:

Fungi are ecologically ubiquitous organisms on earth and regarded as one of the prolific sources of natural products. Fungal endophytes may provide essential prerequisite molecules to plant biochemical pathways which allow the efficient synthesis of primary and secondary metabolites. This study characterized the influences of various combinations of process parameters namely, carbohydrate, nitrogen, and phosphorus sources on citric acid (CA) production by the isolated fungal endophyte Aspergillus fumigatus P3I6 from Citrus microcarpa. Aspergillus fumigatus P3I6 had higher CA concentration of 9.2 (± 0.9) g L−1 and 9.0 (± 5.0 × 10−15) g L−1 when supplemented with sucrose and white refined sugar, respectively, than A. niger NRRL 599. Response Surface Methodology (RSM) had shown that A. fumigatus P3I6 produced the highest CA (23.8 g L−1) in Combination 4 (18.0% sucrose, 0.3 g L−1 ammonium sulfate, and 5.0 g L−1 dipotassium phosphate (K2HPO4)). Analysis of variance showed that when K2HPO4 concentrations were increased, CA content in fermentation media was significantly elevated. Hence, K2HPO4 was the most critical variable in the quadratic model (p < 0.05); however, sucrose concentration still has its role in production. Aside from using A. niger in most fermentation processes, this discovered fungal strain can be potentially used in biotechnological applications.

 

3. Garcia, L.M.B., Sayco, M.J.P., Aya, F.A. (2020). Point-of-no-return and delayed feeding mortalities in first-feeding larvae of the silver therapon Leiopotherapon plumbeus (Kner) (Teleostei: Terapontidae)Aquaculture Reports, 16, Article number 100288. https://doi.org/10.1016/j.aqrep.2020.100288 more

Abstract:

This study examined the incidence of mortalities among first-feeding post-yolk sac silver therapon Leiopotherapon plumbeus (Kner) larvae deprived of live food in the hatchery. Starting after their yolk was consumed at 40 h post-hatch (hph) and every 2 h thereafter until 54 hph, larvae were fed and exposed to live food for an hour only and their performance was observed after initial feeding at 25 °C. Feeding incidence progressively increased until 48 hph as larval mouth gape increased during exogenous feeding, but oil globule volume progressively declined until full exhaustion at 52 hph. All starved larvae fed at 48 hph but feeding incidence progressively declined until larvae ceased to feed at 54 hph to coincide with a significant reduction in survivorship, indicating that larvae have reached their point-of-no-return (PNR) at 50 hph despite the availability of food. Delayed initial feeding of un-fed post-yolk sac larvae starting at 46 hph until 54 hph resulted in significantly higher feeding incidence among 46−48 hph larvae than those fed after 50 hph, which did not survive longer than 10 h after initial feeding. These results demonstrate that silver therapon larvae have a very brief transitional or mixed-feeding period of 12 h after yolk exhaustion so that initial feeding beyond 50 hph when larvae have reached their PNR results in early onset of death.

 

4. Leonardo, L., Hernandez, L., Magturo, T.C., Palasi, W., Rubite, J.M., de Cadiz, A., Moendeg, K., Fornillos, R.J., Tabios, I.K., Mistica, M., Fontanilla, I.K. (2020). Current status of neglected tropical diseases (NTDs) in the PhilippinesActa Tropica, 203, Article number 105284. ttps://doi.org/10.1016/j.actatropica.2019.105284 more

Abstract:

In the Philippines, ten NTDs are prevalent, but only six namely LF, schistosomiasis, STH, food-borne trematodiases, rabies and leprosy are considered to be of public health importance. The 81 provinces in the country are endemic for at least one of these NTDs. Others may be endemic for two or even more of these diseases. Since 2000, after the Philippines accepted and implemented the WHO guidelines for NTDs prevention, control and elimination, significant progress has been achieved in reducing the magnitude of NTDs endemic in the country. Since 2009, out of 46 filariasis-endemic provinces, the number of provinces that has eliminated LF has progressively increased so that by 2015, 76% are already LF-free. By 2019, only four provinces remain endemic for LF. For schistosomiasis, as of 2012, report from the Department of Health (DOH) put the number of high endemic provinces at 10, moderately endemic at 6 and low to elimination levels at 12. For STH, results of the National Parasite Survey in the Philippines among school-aged children conducted in 2015 by the Research Institute for Tropical Medicine, the research arm of the Philippine DOH, however, showed that the overall cumulative prevalence was 28.4% with a prevalence range between 7.1% and 67.4%. The figures are way above the <20% prevalence standard set by the World Health Organization. Control and prevention efforts for FBTs just gained traction with the call of WHO for elimination of NTDs in 2015. There is an urgent need to update information by an intensive national baseline survey that can validate previous data as well as generate new information on the magnitude of the FBT problem in the Philippines. For leprosy, elimination activities have been intensified in high prevalence areas and from 2009 to 2013, case detection and prevalence were sustained at <1.0 per 10,000 population. Rabies elimination activities have been effective that by 2011, only five regions out of 16 remained with the highest number of rabies cases. In a period of seven years from 2010 to 2017, the number of rabies-free provinces and municipalities increased from 3 to 49. Problems continue to hound the NTD programmes in the Philippines as priorities shift to more urgent health problems in a country that is weighed down not only by the triple burden of disease but serious health consequences of emergencies and disasters and the fast-growing population itself. Paradigm shifts are suggested to replace the traditional and conventional perspectives of control. These include change from disease approach to intervention approach to allow for integration of strategies targeting several NTDs and multisectoral, multidisciplinary approach requiring strong, viable and sustainable partnerships involving various agencies of the government, public and private sector, pharmaceuticals, academe, researchers, local government units and the endemic communities themselves.

 

5. Santos, B.S., Torres, S.K.M. (2020). Species identification among morphologically-similar caranx speciesTurkish Journal of Fisheries and Aquatic Sciences, 20 (2), Pages 159-169. http://doi.org/10.4194/1303-2712-v20_2_08 

Abstract:

Accurate identification of species is important in assessing biodiversity and in conservation and population management strategies. Species with similar morphology, however, could be difficult to identify correctly. Published papers have reported on Caranx species that have been incorrectly identified and careful analysis is needed when identifying these species. In this study, 21 specimens from the genus Caranx were identified using DNA barcoding. Specimens were collected from Batangas, Philippines, where freshwater Caranx, which are about 50% more expensive, are present. Using morphological characteristics, C. ignobilis and C. sexfasciatus were identified correctly while one C. papuensis specimen was identified as C. sexfasciatus. Barcodes for three species, namely C. ignobilis, C. sexfasciatus, and C. papuensis, were detected based on cytochrome c oxidase I (COI) sequences. With the addition of Caranx COI sequences from GenBank, the calculated average K2P distance among species (8.19%), was higher than the average K2P distance within species (0.30%). Analysis of all available COI sequences of C. sexfasciatus from GenBank showed multiple cases of likely misidentification in other studies. Geometric morphometric analyses revealed morphological differences between specimens barcoded as C. papuensis and C. sexfasciatus that could aid in identifying the species. 

 

6. Singer, G.A., Loya, F.P., Lapsley, W.D., Tobar, B.Z., Carlos, S., Carlos, R.S., Carlos, E.T., Adao, D.E.V., Rivera, W.L., Jaffe, D.A., Mazet, J.A.K., Chomel, B.B. (2020). Detection of Bartonella infection in pet dogs from Manila, the PhilippinesActa Tropica, 205, Article number 105277. http://doi.org/10.1016/j.actatropica.2019.105277more

Abstract:

Dogs can be infected by a wide range of Bartonella spp., but studies regarding the prevalence of Bartonella infection in dogs in the Philippines have not been conducted. This study aimed at determining the prevalence of Bartonella infection in pets dogs from two veterinary clinics in Metro Manila, The Philippines, using both serology and polymerase chain reaction (PCR). Blood samples from 116 dogs from two different groups, one of 60 mainly “healthy dogs” and the other one of 56 dogs enrolled in a tick-borne disease suspect group, were tested for presence of B. henselae antibodies and to detect Bartonella DNA using primers specific for the citrate synthase gene. Seroprevalence for B. henselae was very low (2.6%), as the only three (5%) seropositive dogs (titer 1:64) where among the healthy pet dog group. Following subsequent sequencing, 13 samples, all from the tick-borne disease group, were determined positive for B. henselae (11.2%). This is the first study to report dog infection with B. henselae in the Philippines. 

 

 Chemistry logo

1. Custodio, K.K.S., Claudio, G.C. and Nellas, R.B.(2020). Structural Dynamics of Neighboring Water Molecules of N-Isopropylacrylamide PentamerACS Omega, 5 (3), Pages 1408-1413. more

Abstract:

Poly(N-isopropylacrylamide) (PNIPAM) is a popular polymer widely used in smart hydrogel synthesis due to its thermo-responsive behavior in aqueous medium. Aqueous PNIPAM hydrogels can reversibly swell and collapse below and above their lower critical solution temperature (LCST), respectively. The present work used molecular dynamics simulations to explore the behavior of water molecules surrounding the side chains of a NIPAM pentamer in response to temperature changes (273-353 K range) near its experimental LCST (305 K). Results suggest a strong inverse correlation of temperature with water density and hydrophobic hydration character of the first coordination shell around the isopropyl groups. Integrity of the first and second coordination shells is further characterized by polygon ring analysis. Predominant occurrence of pentagons suggests clathrate-like behavior of both shells at lower temperatures. This predominance is eventually overtaken by 4-membered rings as temperature is increased beyond 303 and 293 K for the first and second coordination shells, respectively, losing their clathrate-like property. It is surmised that this temperature-dependent stability of the coordination shells is one of the important factors that controls the reversible swell-collapse mechanism of PNIPAM hydrogels.

 

2. Espiritu, R, Tan, JL, Lim, LH, Arco, S. (2020). Density functional theory study on the degradation of fuel cell anion exchange membranes via removal of vinylbenzyl quaternary ammonium head groupJournal of Physical Organic Chemistry. e4049. more

Abstract:

The alkaline stability of different tethered amine functional groups of fuel cell anion exchange membranes (AEMs), namely, trimethyl amine (TMA), 1‐azabicyclo[2.2.2]octane (ABCO), 1,4‐diazabicyclo[2.2.2]octane (DABCO), and N‐methylpiperidine (NMP), is investigated using density functional theory (DFT). Among the amine functional groups investigated, ABCO emerged as the most stable exhibiting the highest energy of barrier (EOB) of 33.5 kcal/mol, while DABCO has the lowest EOB of 30.0 kcal/mol due to the presence of an additional electron‐withdrawing nitrogen. The calculated lowest unoccupied molecular orbital (LUMO) energy revealed the trend of increasing alkaline stability against nucleophilic attack, consistent with their measured barrier energies: DABCO < TMA < NMP < ABCO. Most importantly, the DFT calculations confirmed the proposed multistep AEM degradation mechanism via the detachment of the whole vinylbenzyl quaternary ammonium group through the following steps: (1) nucleophilic attack leading to the loss of aromaticity with subsequent transformation to a quinodimethane moiety, (2) detachment of the quinodimethane‐like intermediate from the polymer backbone by the attack of superoxide and/or peroxy radicals via oxidative cleavage, and (3) the rearomatisation of the reaction intermediate.

 

3. Perez, S.J.LP., Atayde, E.C. and Arco, S.D. (2020). Synthesis and biological evaluation of some novel 1‐alkyl‐3‐methylimidazolium carboxylate ionic liquids as potential antifungal agentsJournal of the Chinese Chemical Society. https://doi.org/10.1002/jccs.201900366 more

Abstract:

In an effort to discover lead compounds that may be of importance as potent antifungal agents, a series of novel 1‐alkyl‐3‐methylimidazolium carboxylate ionic liquids were efficiently synthesized through a solvent‐free ultrasound‐assisted quaternization reaction of 1‐methylimidazole and alkyl bromides RBr (R = hexyl, octyl) followed by an anion exchange process with selected carboxylate anions (cinnamate, salicylate, crotonate, and oxalate). Quantitative yields obtained were in the range of 86–94%. Structure characterization was done using FT‐IR, 1H‐NMR, and 13C‐NMR spectroscopic techniques. All the synthesized compounds showed in vitro antifungal activity against the fungus Candida albicans with the minimum inhibitory concentrations found to be less than or equal to 1%. Preliminary cytotoxicity assays (trypan blue exclusion and MTT) were performed on all ionic liquids and findings revealed higher lymphocyte viability in 1‐hexyl‐3‐methylimidazolium carboxylate ionic liquids than in 1‐octyl‐3‐methylimidazolium counterparts. No extensive toxicity effect was observed with the carboxylate anion variation. Among the tested compounds, 1‐hexyl‐3‐methylimidazolium crotonate and 1‐hexyl‐3‐methylimidazolium oxalate exhibited the lowest cytotoxicity in the trypan blue exclusion and MTT assays, respectively. Together, our results highlight the potential of carboxylate‐based ionic liquids in the development of next‐generation antifungal drugs.

 

4. Regulacio, M.D., Yang, D.-P. and Ye, E. (2020). Toward greener methods of producing branched metal nanostructuresCrystEngComm, 22 (3), Pages 399-411. more

Abstract:

The continuous drive to develop green and sustainable production methods has prompted scientists into exploring the use of biogenic resources (e.g. plant extracts, microorganisms, and biomolecules) as environmentally benign reagents for the synthesis of functional metal nanomaterials. An emerging class of metal nanomaterials is branched metal nanostructures, which display tremendous potential in diverse technological areas, including biomedicine, catalysis, and sensing. In the biogenic synthesis of branched metal nanostructures, biological systems often take on multiple roles as reducing, capping, and shape-directing agents. Furthermore, the reaction typically proceeds at relatively lower temperatures, sometimes even at room temperature, and water is conveniently used as a solvent. This greatly simplifies the synthetic procedure, aside from lowering the production cost and rendering the process greener. Herein, we review different biogenic methods of preparing metal nanostructures having distinctively branched architectures (e.g. flowers, stars, and dendrites). We highlight reports that provide critical insights that are pertinent to the elucidation of the formation mechanisms. However, a more rigorous understanding is still necessary to establish exact mechanisms, and so, further research on this matter is encouraged. Advancing our mechanistic understanding will help us improve existing bioinspired methodologies to create high-quality branched metal nanostructures with optimal performance for envisioned applications.

 

5. Sacdal, R., Madriaga, M., and Espino, M.P. (2020). Overview of the analysis, occurrence and ecological effects of hormones in lake waters in AsiaEnvironmental Research, 182, (109091). more

Abstract:

Hormones are natural and synthetic compounds that are now being detected in the aquatic environment. Many lakes in Asia are important water sources that may be affected by these emerging contaminants. Lakes are drains and reservoirs of watersheds that are altered by changing land use and environmental conditions. While there are several studies on the detection of hormones in lakes, these studies were mostly done in China. Limited information is available on the presence of these contaminants in the lakes in other Asian countries. Hormones in the lake water come from discharge waters in urban areas, farm runoffs, and effluents of wastewater and sewage treatment plants. Hormones contamination in water has been shown to affect the reproduction and growth of certain aquatic organisms. In this review, a background on the chemical nature and physiological functions of hormones is provided and the existing knowledge on the occurrence and ecological impacts of hormones in lakes is described. The available analytical methods for sampling, analyte extraction and instrumental analysis are outlined. This overview provides insights on the current conditions of lakes that may be impacted by hormones contamination. Understanding the levels and possible ecological consequences will address the issues on these emerging contaminants especially in the Asian environment. This will elicit discussions on improving guidelines on wastewater discharges and will drive future research directions.

 

IESM logo

1. Bagtasa, G. (2020). 118-year climate and extreme weather events of Metropolitan Manila in the PhilippinesInternational Journal of Climatology, 40 (2), Pages 1228-1240. more

Abstract:

Metropolitan Manila, the Philippines, is a megacity with a population of 12.9 million people. Unabated urbanization and disorganized infrastructure build‐up, coupled with a large urban poor population have made many of its population vulnerable to climate change. This study presents the 118‐year urban climate and extreme weather events of Metropolitan Manila. Daily average and minimum temperature are on the rise comparable to countrywide trends. Consequently, there are more warm and less cold nights. Total annual precipitation is also increasing at a rate of 77.99 mm/decade. Decreasing simple daily intensity index implies that higher observed precipitation is due to the increase in wet days count rather than intensity. Tropical cyclones (TCs) are critical in producing most extreme rainfall events in the metropolis. Extreme precipitation is induced either by a TC's immediate rainbands or remote precipitation effects by enhancing the prevailing summer monsoon flow. TC‐induced rain modulates annual rainfall variability and is estimated to contribute 45.2% to Metropolitan Manila mean total rainfall.

 

2. Manuel, A., C. Blanco, A.C., Tamondong, M.,  Jalbuena, R., Cabrera, O., Gege, P. (2020). Optimization of Bio-Optical model parameters for turbid lake water quality estimation using LANDSAT8 and WASI-2DInternational Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives, 42 (3/W11), Pages 67-72. more

Abstract:

Laguna Lake, the Philippines’ largest freshwater lake, has always been historically, economically, and ecologically significant to the people living near it. However, as it lies at the center of urban development in Metro Manila, it suffers from water quality degradation. Water quality sampling by current field methods is not enough to assess the spatial and temporal variations of water quality in the lake. Regular water quality monitoring is advised, and remote sensing addresses the need for a synchronized and frequent observation and provides an efficient way to obtain bio-optical water quality parameters. Optimization of bio-optical models is done as local parameters change regionally and seasonally, thus requiring calibration. Field spectral measurements and in-situ water quality data taken during simultaneous satellite overpass were used to calibrate the bio-optical modelling tool WASI-2D to get estimates of chlorophyll-a concentration from the corresponding Landsat-8 images. The initial output values for chlorophyll-a concentration, which ranges from 10–40 μg/L, has an RMSE of up to 10 μg/L when compared with in situ data. Further refinements in the initial and constant parameters of the model resulted in an improved chlorophyll-a concentration retrieval from the Landsat-8 images. The outputs provided a chlorophyll-a concentration range from 5–12 μg/L, well within the usual range of measured values in the lake, with an RMSE of 2.28 μg/L compared to in situ data. 

 

3. Perez, G.J., Felix, M.J., Namuco, S., Felicio, F., Merida, H., Vergel, K.K., Castro, E., Marciano, J.J.S., Jr. (2020). Environmental monitoring using Philippines' DIWata-2: A case study in Laguna de Bay40th Asian Conference on Remote Sensing, ACRS 2019, 40th Asian Conference on Remote Sensing: Progress of Remote Sensing Technology for Smart Future, ACRS 2019; Daejeon Convention Center (DCC)Daejeon; South Korea, Code 157736.

Abstract:

The Philippines extensive coastline, fertile land and high species diversity makes the country abundant in natural resources. Protection of the environment and sustainable use of resources is of paramount importance, especially with the continuous increase in population and exposure of the country to natural hazards. This has been one of the primary motivations for the development of the Philippines' microsatellites, Diwata-1 and Diwata-2, with missions focusing on environmental monitoring and disaster assessment. This paper highlights the improvements made in the second satellite mission which makes it more effective for spatiotemporal change analysis. Launched in 29 October 2018, Diwata-2 is deployed at 621 km sun-synchronous orbit with 8°inclination, allowing 11-day revisit period and 3 to 5 years expected mission lifetime. This, together with wider image swaths and improved signal-to-noise ratio of its imaging cameras, make Diwata-2 capable for more in-depth studies of water quality in high-value coastal and inland waters. This is demonstrated through the retrievals of turbidity in Laguna de Bay, which at ~900 km2 area, is considered as the largest lake in the country. Using Diwata-2 Spaceborne Multispectral Imager (SMI) with Liquid Crystal Tunable Filter (LCTF), series of images of the lake were captured within the period of March to June 2019. The highest turbidity values were observed in April, which coincides with the peak months of dry season. The turbidity of the lake then gradually drops at the end of the dry season. Large spatial variability is also observed across the lake's major bays. This detailed information is valuable to fish pen and cage operators, lake managers, local and national government, and other stakeholders in ensuring the sustainable use of the lake. Through the improved capabilities of Diwata-2, images can be captured and analyzed to track the spatiotemporal changes of different geophysical variables that are relevant for the management of the country's natural resources and environment.

 

4. Veloria, A., Perez, G.J., Tapang, G., Comiso, J. (2020). Comparison between GPM and gridded precipitation product from interpolated rain gauge measurements40th Asian Conference on Remote Sensing: Progress of Remote Sensing Technology for Smart Future, ACRS 2019; Daejeon Convention Center (DCC)Daejeon; South Korea, Code 157736.

Abstract:

Due to sparsely distributed synoptic stations in the Philippines, representation of precipitation is inadequate. Satellite-derived products, such as the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM), are available to complement synoptic data for more precise and robust measurements. However, these products tend to over- or underestimate rainfall depending on the season. Precipitation measurements from a dense network of rain gauges in the Philippines are available courtesy of the Department of Science and Technology - Advance Science and Technology Institute (DOST-ASTI). This study aims to create a gridded precipitation data over the Philippines from interpolated rain gauge measurements and validate its performance through comparison with GPM. Comparison of rain gauge data with overlapping synoptic measurements in a 0.25° grid showed distance-dependent likelihood. Thus, inverse distance weighting (IDW) was performed to combine multiple rain gauge measurements representative of precipitation over 0.1° grid. Strong positive correlations (r = 0.58 to 0.97) were obtained from comparing IDW values and monthly synoptic measurements suggesting that rain gauge measurements may be used as complimentary ground data. IDW values were then subjected to kriging and iterative method to create a monthly gridded precipitation. Results showed that the interpolated precipitation follows the wet and dry season as well as monsoon seasonality in the Philippines. The calculated differences between the interpolated precipitation and GPM monthly product revealed that the interpolated precipitation have lower estimates with respect to GPM regardless of season. This is in contrast with the strong positive relationship between monthly synoptic measurements and GPM (r = 0.856). Low estimates from the interpolated precipitation is due to isolated zero measurements from various rain gauges. This may be attributed to maintenance issues of the sensors where the data do not report broken and erroneous instruments. Further filtering of the dataset and regular maintenance of the sensors must be done to better incorporate the use of dense rain gauge network for the creation of a Philippine gridded precipitation.

 

5. Valete, M.A.P., Perez, G.J.P., Enricuso, O.B., Comiso, J.C. (2020). Spatiotemporal evaluation of historical drought in the Philippines40th Asian Conference on Remote Sensing: Progress of Remote Sensing Technology for Smart Future, ACRS 2019; Daejeon Convention Center (DCC)Daejeon; South Korea, Code 157736.

Abstract:

Negative impacts of drought on agriculture and water resources vary according to different timescales and intensity. In this paper, the historical droughts in the Philippines were examined using the Standardized Precipitation Index (SPI) at different timescales (SPI-1, SPI-3, and SPI-12). SPI is derived from the monthly rainfall data of Tropical Rainfall Measuring Mission (TRMM) 3B43 v7 from 1998 to 2018. A total of 384 TRMM grids in the Philippines were used in the time series analysis to investigate the spatiotemporal dynamics of drought. Results showed that the Philippines was frequently hit by different types of drought. It also showed that the spatial distribution of the past drought events varied through timescales. Particularly, more variation was observed in the entire land area using the shorter SPI timescales, i.e. SPI-1 and SPI-3. With longer timescales, values tend to be more similar and closer to each other resulting in smoother trends. The affected areas in terms of percentage were also examined. Each drought event's severity, duration, and intensity for the areal average of the Philippines was also investigated. These results demonstrate the viability of satellite-derived SPI for drought evaluation at a national level, which is important in the decision-making for drought mitigation in the Philippines.

 

IM

1. Afable, E. A., de la Cruz, R. J., Paras, A. T., & Segui, M. E. (2020). Diagonalizability with respect to perplectic and pseudo-unitary similarity transformations. Linear Algebra and its Applications, 591, Pages 61-71. doi:10.1016/j.laa.2020.01.010 more

Abstract:

Let Rn be the n-by-n backward identity matrix and let Ln,k:=Ik−In−k. Suppose ACn×n is nonsingular. We say that A is perplectic if RnATRn=A−1; and A is pseudo-unitary if Ln,kALn,k=A−1. We give necessary and sufficient conditions for a matrix to be diagonalizable via a perplectic or a pseudo-unitary matrix.

 

2. Agapito, T. D., & Paras, A. T. (2020). ψS-orthogonal matrices and ψS-symmetries. Linear Algebra and its Applications, 584, Pages 185-196. doi:10.1016/j.laa.2019.09.017 more

Abstract:

Let GLn(C) denote the set of n-by-n nonsingular matrices with entries from the field C of complex numbers. For any SGLn(C), define the map ψS:GLn(C)→GLn(C) by ψS(A)=SA−1‾S−1. A matrix AGLn(C) is said to be ψS-orthogonal if ψS(A)=A−1. A ψS-orthogonal H is called a ψS-symmetry if rank(H−I)=1. We give conditions on S so that ψS-symmetries exist. Moreover, we determine conditions on S such that the ψS-symmetries generate the ψS-orthogonal matrices, and the minimum number of ψS-symmetries needed to express a ψS-orthogonal.

 

3. Awa, D., & de la Cruz, R. J. (2020). Every real symplectic matrix is a product of real symplectic involutions. Linear Algebra and its Applications, 589, Pages 85-95. doi:10.1016/j.laa.2019.12.003 more

Abstract:

A 2n-by-2n matrix A is symplectic if AT[0I−I0]A=[0I−I0]. It is known that if n>1, then every 2n-by-2n complex symplectic matrix is a product of four symplectic involutions. We consider the real case. We give an example of a real symplectic matrix which is a product of two complex symplectic involutions but is not a product of two real symplectic involutions. We show that every 4-by-4 real symplectic matrix is a product of four real symplectic involutions. We use this result to show that for n>1, every 2n-by-2n real symplectic matrix is a product of a finite number of real symplectic involutions. 

 

4. Balmaceda, J. M. P., & Datu, J. P. P. (2020). Idempotents in certain matrix rings over polynomial rings. International Electronic Journal of Algebra, 27, Pages 1-12. doi:10.24330/ieja.662942 more

Abstract:

We determine the forms of the nontrivial idempotents in the ring of 2 × 2 matrices over the polynomial rings Zpq[x] and Zp2[x], where p and q are any primes. Any such idempotent in the stated rings will be of a form in our list. Our work generalizes the results of Kanwar, Khatkar and Sharma (2017) who identified the forms of idempotents in M2(Z2p [x]) and M2(Z3p [x]).

 

5. Caalim, J. V., Futorny, V., Sergeichuk, V. V., & Tanaka, Y. (2020). Isometric and selfadjoint operators on a vector space with nondegenerate diagonalizable form. Linear Algebra and its Applications, 587, Pages 92-110. doi:10.1016/j.laa.2019.11.004 more

Abstract:

Let V be a vector space over a field F with scalar product given by a nondegenerate sesquilinear form whose matrix is diagonal in some basis. If F=C, then we give canonical matrices of isometric and selfadjoint operators on V using known classifications of isometric and selfadjoint operators on a complex vector space with nondegenerate Hermitian form. If F is a field of characteristic different from 2, then we give canonical matrices of isometric, selfadjoint, and skewadjoint operators on V up to classification of symmetric and Hermitian forms over finite extensions of F.

 

6. Cajayon, Raquel C., Lucilo, Jayson A., Pilar-Arceo, Carlene PC., & Mendoza, Eduardo R. (2020). Comparison of Two Nature-Inspired Algorithms for Parameter Estimation of S-system Models.  Philippine Journal of Science, 149 (1), Pages 63-78. more

Abstract:

Parameter estimation for models of biochemical systems is computationally expensive due to the nonlinearity and high dimensionality of the coupled systems of ordinary differential equations underlying the models. Hence, it is important to apply novel methods to the problem and evaluate their performance. We consider the Bat algorithm (BA) and the Firefly algorithm (FA) with respect to parameter estimation of S-system models. Using three S-systems of increasing complexity from the MADMan benchmarking framework, we assess and compare the relative performance of the two algorithms relative to various data sets, initial conditions, and noise levels. Simulation results show that both algorithms can be effectively used in estimating parameters of the S-system models. In particular, in all three S-systems used, the FA performed better than the BA based on the final cost function values and relative estimate errors. The introduction of noise to data significantly affected the convergence of both algorithms.

 

7. Galvez, L., & Kim, J. (2020). Projection decoding of some binary optimal linear codes of lengths 36 and 40. Mathematics, 8 (1). doi:10.3390/MATH8010015 more

Abstract:

Practically good error-correcting codes should have good parameters and efficient decoding algorithms. Some algebraically defined good codes, such as cyclic codes, Reed–Solomon codes, and Reed–Muller codes, have nice decoding algorithms. However, many optimal linear codes do not have an efficient decoding algorithm except for the general syndrome decoding which requires a lot of memory. Therefore, a natural question to ask is which optimal linear codes have an efficient decoding. We show that two binary optimal [36,19,8] linear codes and two binary optimal [40,22,8] codes have an efficient decoding algorithm. There was no known efficient decoding algorithm for the binary optimal [36,19,8] and [40,22,8] codes. We project them onto the much shorter length linear [9,5,4] and [10,6,4] codes over GF(4) , respectively. This decoding algorithm, called projection decoding, can correct errors of weight up to 3. These [36,19,8] and [40,22,8] codes respectively have more codewords than any optimal self-dual [36,18,8] and [40,20,8] codes for given length and minimum weight, implying that these codes are more practical.

 

8. Galvez, L. E., & Kim, J. (2020). Construction of self-dual matrix codes. Designs, Codes, and Cryptography. doi:10.1007/s10623-020-00740-z more

Abstract:

Matrix codes over a finite field FqFq are linear codes defined as subspaces of the vector space of m×nm×n matrices over FqFq. In this paper, we show how to obtain self-dual matrix codes from a self-dual matrix code of smaller size using a method we call the building-up construction. We show that every self-dual matrix code can be constructed using this building-up construction. Using this, we classify, that is, we find a complete set of representatives for the equivalence classes of self-dual matrix codes of small sizes. In particular we have classifications for self-dual matrix codes of sizes 2×42×42×52×5 over F2F2, of size 2×32×32×42×4 over F4F4, of size 2×22×22×32×3 over F8F8, and of size 2×22×22×32×3 over F13F13, all of which have been left open from K. Morrison’s classification.

 

9. Hernandez, B. S., Mendoza, E. R., & Reyes V, A. A. (2020). A computational approach to multistationarity of power-law kinetic systems. Journal of Mathematical Chemistry, 58 (1), Pages 56-87. doi:10.1007/s10910-019-01072-7 more

Abstract:

This paper presents a computational solution to the multistationarity problem for any power-law kinetic system, i.e., to determine if such a system can have multiple positive equilibria within a stoichiometric class. The approach combines (i) the extension of the "Higher Deficiency Algorithm" of Ji and Feinberg for mass action systems to power-law kinetic systems with reactant-determined interactions (i.e., reactions branching from the same reactant complex have identical kinetic order vectors) and (ii) the CF-RM method which transforms any power-law system to a dynamically equivalent one with reactant-determined interactions. We apply the approach to models of anaerobic yeast fermentation and monolignol biosynthesis in populus xylem, both in the GMA (generalized mass action) format of Biochemical Systems Theory. We establish their monostationarity, i.e., for any set of rate constants, the systems have at most one positive steady state. We also provide examples of the broader scope of our approach for deficiency one power-law kinetic systems in comparison to the extension of Feinberg's Deficiency One Algorithm to such systems. Such examples have the capacity for multistationarity for particular rate constants.

 

10. Paras, A. T., & Salinasan, J. R. (2020). The product of an involution and a skew-involution. Linear Algebra and its Applications, 584, Pages 431-437. doi:10.1016/j.laa.2019.09.035 more

Abstract:

We give necessary and sufficient conditions for a matrix over a field to be the product of an involution (A2=I) and a skew-involution (A2=−I).

 

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1. Afalla, J., Catindig, G., De Los Reyes, A., Prieto, E., Faustino, M.A.,  Vistro, V., Gonzales, K.C., Bardolaza, H., Mag-Usara, V.K., Husay, H.A., Muldera, J., Cabello, N.I., Ferrolino, J.P., Kitahara, H., Somintac, A., Salvador, A., Tani, M., Estacio, E. (2020). Ultrafast carrier dynamics and THz conductivity in epitaxial-grown LT-GaAs on silicon for development of THz photoconductive antenna detectorsJournal of Physics D: Applied Physics, 53 (9), article number 095105. more

Abstract:

Carrier dynamics and photoconductivity in epitaxial-grown low-temperature GaAs on nominal and vicinal Si(1 0 0) substrates ('LT-GaAs/Si') were studied to predict their actual performance as THz photoconductive antenna (PCA) detectors. An optical-pump terahertz-probe technique was used to obtain the transmittance, carrier lifetime and photoconductivity of two LT-GaAs/Si samples, grown using different substrates and different growth protocols. The LT-GaAs grown on Si(1 0 0) substrate with a 4° tilt to 1 1 0 has better crystallinity, in agreement with other reports; while the LT-GaAs layer grown on nominal Si(1 0 0) substrate, though more structurally defective, has a much faster electron trapping time. Fabricated test PCAs with either dipole or bowtie geometries confirm the characterization results. The photoconductivity and carrier lifetime results manifest in the PCA performance, in responsivity, and in detection bandwidth. The prototypes' sensitivities, bandwidths and dynamic ranges show that with some growth optimization, LT-GaAs/Si can be tailored to create economical, broadband THz detectors.

 

2. De Los Reyes, A., Bardolaza, H., Vasquez, J. D., Cabello, N. I., Lopez, L., Chang, C. Y., Somintac, A., Salvador, A., Jang, D. J., & Estacio, E. (2020). Temperature-dependent terahertz time-domain spectroscopy of 3D, 2D, and 0D semiconductor heterostructuresJournal of Materials Science: Materials in Electronics0123456789. https://doi.org/10.1007/s10854-020-03188-y more

Abstract:

Carrier transport in semiconductors with different dimensionalities, i.e., 3D (bulk), 2D (QW), and 0D (QD), were investigated via temperature-dependent terahertz time-domain spectroscopy (THz-TDS). The optical properties and recombination dynamics in the samples were probed via photoluminescence spectroscopy. The temperature-dependence of the THz emission from the samples was explained in the context of the drift-diffusion model using the dominant THz radiation mechanism. The THz emission from diffusion-type THz emitters such as p- and n-InAs decreases as temperature increases due to mobility decrease. Conversely, the THz emission from drift-type THz emitters such as SI-GaAs, GaAs QW, and InAs QD was found to increase with temperature due to the increase in the driving electric field. In summary, THz-TDS can be utilized to gain qualitative insights on the temperature-dependent transport characteristics and establish dominant THz radiation mechanisms.

 

3. De Los Reyes, A.E., Vasquez, J.D., Bardolaza, H.R., Lopez, L.P., Jr., Chang, C.-Y., Somintac, A.S., Salvador, A.A., Jang, D.-J., Estacio, E.S. (2020). Low-temperature carrier dynamics in MBE-grown InAs/GaAs single-and multi-layered quantum dots investigated via photoluminescence and terahertz time-domain spectroscopyOptical Materials Express, 10 (1), Pages 178-188. more

Abstract:

The photocarrier dynamics in molecular beam epitaxy (MBE)-grown single-(SLQD) and multi-layered (MLQD) InAs/GaAs quantum dots were studied. Photoluminescence (PL) spectroscopy has shown that the MLQD has more uniform QD size distribution as compared to the bimodal SLQD. Correlation between PL and THz-TDS has shown that photocarrier transport is more favored in the MLQD owing to this uniform QD size distribution, resulting to higher THz emission. The THz emission from the QD samples were found to be proportional to temperature. A drift-related photocarrier transport mechanism is proposed, wherein photocarriers generated in the QDs are accelerated by an interface electric field.

 

4. Escaño, M.C., Balgos, M.H., Nguyen, T.Q., Prieto, E.A., Estacio, E.,  Salvador, A., Somintac, A., Jaculbia, R., Hayazawa, N., Kim, Y.b., Tani, M. (2020). True bulk As-antisite defect in GaAs(1 1 0) identified by DFT calculations and probed by STM/STS measurementsApplied Surface Science, Volume 511, Article number 145590. more

Abstract:

We reveal the As-antisite (AsGa) defect close to the surface of GaAs(1 1 0) with bulk characteristics using first-principles methods with experimental verifications. We found that the AsGa in the third-layer mimics the geometry, partial charge density and more importantly, the density of states of AsGa in bulk GaAs. Notably, the mid-gap state induced by AsGa in bulk GaAs is well-reproduced by the AsGa in the third layer of GaAs(1 1 0). Simulated and experimental STM images show an “asymmetric two-lobe” feature in the region around the defect. Using local density of states (LDOS) and STS spectra, we propose three prominent peaks with characteristic energy levels corresponding to the third layer AsGa. The above results present the first report of surface electronic signatures of true bulk defect near the surface of GaAs(1 1 0).

 

5. Sanchez, J.R.G.,  Joson, P.R.S., Vega, M.M. (2020). Studying absorbance properties and mercury remediation capabilities of gold–graphene oxide–iron oxide (Au–GO–Fe3O4) nanoparticle systemsJournal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering, 55 (3), Pages 216-223. more

Abstract:

Mercury pollution is a rampant problem in many economically significant Philippine freshwater ecosystems. Communities dependent on these freshwater sources are therefore at risk for exposure to harmful levels of mercury. Various formulations of a novel gold–graphene oxide–iron oxide (Au–GO–Fe3O4) hybrid nanoparticle system were created and subjected to UV–Vis spectroscopy to determine optimal formulations that would best serve as potential substrates for Surface-Enhanced Raman Spectroscopy (SERS) detection of mercury. Optimal formulations of Au–GO–Fe3O4 were also introduced into mercury-polluted environments to evaluate its ability to remove mercury from both water and biological tissues. Spectroscopic analysis revealed that Fe3O4-rich formulations of Au–GO–Fe3O4 had the greatest potential to boost Raman signal intensities of mercury due to red shifting of absorbance peaks and overall increased absorbance across visible wavelengths resulting in the inclusion of greater areas underneath absorbance peaks. Mercury remediation experiments likewise demonstrated Au–GO–Fe3O4 to significantly reduce average concentrations of mercury from 1.67 to 0.82 ppm in polluted water samples–corresponding to a mercury removal efficiency of 50.9% and a mercury adsorption capacity of 5.89 mg/g. The results highlight the viability of Au–GO–Fe3O4 to function as both substrate for SERS detection of mercury and as effective adsorbent for mercury remediation.

 

6. Santos-Putungan, A.B., Stojić, N., Binggeli, N., Paraan, F.N.C. (2020). Selective capture of CO2 over N2 and CH4: B clusters and their size effectsMaterials Today Communications, 22, article number 100712. more

Abstract:

Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO2 over N2 and CH4 on planar-type B clusters, based on our previous finding of strong chemisorption of CO2 on the B10−13 planar and quasiplanar clusters. We consider the prototype B8 and B12 planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature, CO2 can be separated from N2 by selective binding to the B12 cluster and not to the B8 cluster. Selective adsorption of CO2 over CH4 at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for N2 on the planar-type B36 cluster, we discuss the selectivity trend of CO2 adsorption over N2 and CH4 with planar-cluster size, showing that it extends over sizes including B10-13 clusters and significantly larger.

 

 

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1. Cardenas, M. B., Rodolfo, R. S., Lapus, M. R., Cabria, H. B., Fullon, J., Gojunco, G. R., . . . Zhang, T. (2020). Submarine groundwater and vent discharge in a volcanic area associated with coastal acidificationGeophys Res Lett, 47 (1), e2019GL085730. 3.

 

2. Conaco C, Cabaitan PC. (2020). Influence of salinity and temperature on the surivival and settlement of Helipora coerulea larvae. Mar. Pollut. Bull., 150, 110703.

 

3. Jackisch D, Yeo B-X, Switzer AD, He S, Cantarero DLM, Siringan FP, Goodkin NF. (2020). Precipitation stable isotopic signatures of tropical cyclones in Metropolitan Manila, Philippines show significant negative isotopic excursionsEarth Syst. Sci. Discuss. DOI: https://doi.org/10.5194/nhess-2019-352. Article in Review.

 

4. Li T, Lin X, Yu L, Lin S, Rodriguez IB, Ho T-Y. (2020). RNA-seq profiling of Fugacium kawagutii reveals strong responses in metabolic processes and symbiosis potential to deficiencies of iron and other trace metalsSci Total Environ, 705, 135767.

 

5. Ligson CA, Tabalanza TD, Villanueva RD, Cabaitan PC. (2020). Feasibility of early outplanting of sexually propagated Acropora verweyi for coral reef restoration demonstrated in the PhilippinesRestoration Ecology, 28 (1), Pages 244-251.

 

6. Millwer BW, Torres JP, Flores MS, FOrteza I, Rosenber G, Haygood MG, Schmidt EW, Concepcion GP. (2020). Synergistic anti-methicillin-resistant Staphylococcus aureus (MRSA) activity and absolute stereochemistry of 7,8-dideoxygriseorhodin CJournal of Antibiotics. Article in Press.

 

7. Olano DEB, Salvador-Reyes LA, Montaño MNE, Azanza RV. (2020). Sorpiton of paralytic shellfish toxins (PSTs) in algal polysaccharide gelsAlgal Research 45, 101655.

 

8. Onda DFL, Gomez NC. (2020). Marine microbes and plastic debris research status and opportunities in the PhilippinesPhilippine Journal of Science, 149 (1), Pages 89-100.

 

9. Quimpo TJR, Cabaitan PC, Hoey AS. (2020). Detachment of Porites cylindrica nubbins by herbivorous fishesRestor Ecol, 28 (2), Pages 418-426.

 

10. Reich HG, Rodriguez IB, LaJeunesse TC, Ho T-Y. (2020). Endosymbiotic dinoflagellates pump iron: differences in iron and other trace metal needs among the SymbiodiniaceaeCoral Reefs. Article in Review. DOI:10.1007/s00338-020-01911-z

 

11. Torres JP, Lin Z, Fenton DS, Leavitt LU, Niu C, Lam P-Y, Robes JM, Pterson RT, Concepcion GP, Haygood MG, Olivera BM, Schmidt EW. (2020). Boholamide A, an APD-Class, Hypoxia-Selective CyclodepsipeptideJournal of Natural Products. Article in Press.

 

12. Tuo S -, Rodriguez IB, Ho T-. (2020). H2 accumulation and N2 fixation variation by ni limitation in cyanotheceLimnology and Oceanography, 65 (2), Pages 377-386.

 

13. Yñiguez AT, Lim PT, Leaw CP, Jipanin SJ, Iwataki M, Benico G. (2020). Over 30 years of HABs in the Philippines and Malaysia: What have we learned? Harmful Algae, 101776. Article in Press.

 

14. Yñiguez AT, Ottong ZJ. (2020). Predicting fish kills and toxic blooms in an intensive mariculture site in the Philippines using a machine learning model. Sci Total Environ, 707, 136173.

 

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1. Dimalanta, C. B., Faustino-Eslava, D. V., Gabo-Ratio, J. A. S., Marquez, E. J., Padrones, J. T., Payot, B. D., Queaño, K. L., Ramos, N. T., Yumul, G. P. Jr. (2020). Characterization of the proto-Philippine Sea Plate: Evidence from the emplaced oceanic lithosphere fragments along eastern PhilippinesGeoscience Frontiers, 11 (1), Pages 3-21. https://doi.org/10.1016/j.gsf.2019.01.005 more

Abstract:

The proto-Philippine Sea Plate (pPSP) has been proposed by several authors to account for the origin of the Mesozoic supra-subduction ophiolites along the Philippine archipelagoIn this paper, a comprehensive review of the ophiolites in the eastern portion of the Philippines is undertaken. Available data on the geology, ages and geochemical signatures of the oceanic lithospheric fragments in Luzon (Isabela, Lagonoy in Camarines Norte, and Rapu-Rapu island), Central Philippines (Samar, Tacloban, Malitbog and Southeast Bohol), and eastern Mindanao (Dinagat and Pujada) are presented. Characteristics of the Halmahera Ophiolite to the south of the Philippines are also reviewed for comparison. Nearly all of the crust-mantle sequences preserved along the eastern Philippines share Early to Late Cretaceous ages. The geochemical signatures of mantle and crustal sections reflect both mid-oceanic ridge and supra-subduction signatures. Although paleomagnetic information is currently limited to the Samar Ophiolite, results indicate a near-equatorial Mesozoic supra-subduction zone origin. In general, correlation of the crust-mantle sequences along the eastern edge of the Philippines reveal that they likely are fragments of the Mesozoic pPSP.

 

2. Rodrigo, J. D., Gabo-Ratio, J. A. S., Queaño, K. L., Fernando, A. G. S., de Silva, L.P. Jr., Yonezu, K. Zhang, Y. (2020). Geochemistry of the late Cretaceous Pandan formation in Cebu Island, Central Philippines: sediment contributions from the Australian plate margin during the MesozoicThe Depositional Record (The journal of the International Association of Sedimentologists. https://doi.org/10.1002/dep2.103more

Abstract:

The Late Cretaceous Pandan Formation in Cebu Island is one of the oldest sedimentary units in the Central Philippines. The inconsistencies in geological descriptions and interpretation of the depositional environment of the Pandan Formation complicated efforts to determine the origin and tectonic history of the basement of Cebu Island. This study therefore looks into the petrological and geochemical characteristics of the Pandan Formation and their implications for the tectonic development of the Philippine Arc during the late Mesozoic. Petrographic analyses indicate significant contribution from mafic sources with additional inputs from felsic rocks, siliciclastics and metamorphic sources. Enrichment of detrital quartz from felsic volcanic and plutonic rocks, as well as from siliciclastic and metamorphic sources, has shifted the SiO2 composition of the Pandan clastics from a mafic to a more intermediate source. Whole‐rock geochemical analyses revealed low SiO2/Al2O3 = 4.21, low K2O/Na2O = 1.16, low Th/Sc = 0.13, low Th/U = 2.78, high La/Th = 4.51, significantly low REEs = ca 76.45 ppm and low LaN/YbN = 4.28. A slight negative chondrite‐normalized Eu/Eu* (0.91) anomaly and significantly high PAAS‐normalized positive Eu/Eu* (1.39) values are consistent with derivation from a young undissected magmatic arc terrane. Tectonic discrimination diagrams suggest formation in an oceanic island arc to active margin/collision zone modelled to be located at the oceanic leading edge of Australia. Rapid uplift and erosion of the magmatic arc and older allochthonous blocks gave way to the rapid deposition of the Pandan Formation in the Late Cretaceous at the subequatorial region.

 

3. Yumul. G. P. Jr., Dimalanta, C. B., Gabo-Ratio, J. A. S., Armada, L. T., Queaño, K. L., Jabagat, K. D. (2020). Mineralization parameters and exploration targeting for gold – copper deposits in the Baguio (Luzon) and Pacific Cordillera (Mindanao) Mineral Districts, Philippines: A reviewJournal of Asian Earth Sciences, 191.  https://doi.org/10.1016/j.jseaes.2020.104232more

Abstract:

The Baguio Mineral District in Luzon, Philippines is known to host several world-class epithermal gold – porphyry copper deposits. The interplay of tectonic setting, magma composition, structural control and hydrothermal systems contributed to the generation of these deposits. Ridge subduction (Scarborough seamount) resulting to flat subduction and a transpressional regime could also be related to the formation of epithermal gold - porphyry copper deposits in Baguio. Subduction processes leading to the formation of calc-alkaline rocks associated with high water pressure, oxygen fugacity and late sulfur saturation are almost always associated with the gold-copper deposits in the district. Compared to the Baguio Mineral District, less exploration work, mine development and production were done in the Pacific Cordillera Mineral District, Mindanao in southern Philippines. It is worth noting, however, that both mineral districts show similarities and overlapping features in terms of geological, geophysical and geochemical characteristics. This leads one to conclude that the Pacific Cordillera Mineral District has ore deposits waiting to be discovered.

 

4. Yumul, G. P., Jr., Dimalanta, C. B., Salapare, R. C., Queño, K. L., Faustino-Eslava, D. V., Marquez, E. J., Ramos, N. T., Payot, B. D., Guotana, J. M. R., Gabo-Ratio, J. A. S., Armada, L. T., Padrones, J. T., Ishida, K., Suzuki, S. (2020). Slab rollback and microcontinent subduction in the evolution of the Zambales Ophiolite Complex (Philippines): A reviewGeoscience Frontiers, 11 (1), Pages 22-36. https://doi.org/10.1016/j.gsf.2018.12.008more

Abstract:

New radiolarian ages show that the island arc-related Acoje block of the Zambales Ophiolite Complex is possibly of Late Jurassic to Early Cretaceous age. Radiometric dating of its plutonic and volcanic-hypabyssal rocks yielded middle Eocene ages. On the other hand, the paleontological dating of the sedimentary carapace of the transitional mid-ocean ridge – island arc affiliated Coto block of the ophiolite complex, together with isotopic age datings of its dikes and mafic cumulate rocks, also yielded Eocene ages. This offers the possibility that the Zambales Ophiolite Complex could have: (1) evolved from a Mesozoic arc (Acoje block) that split to form a Cenozoic back-arc basin (Coto block), (2) through faulting, structurally juxtaposed a Mesozoic oceanic crust with a younger Cenozoic lithospheric fragment or (3) through the interplay of slab rollback, slab break-off and, at a later time, collision with a microcontinent fragment, caused the formation of an island arc-related ophiolite block (Acoje) that migrated trench-ward resulting into the generation of a back-arc basin (Coto block) with a limited subduction signature. This Meso-Cenozoic ophiolite complex is compared with the other oceanic lithosphere fragments along the western seaboard of the Philippines in the context of their evolution in terms of their recognized environments of generation.

 

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1. Boonchuen, P., Maralit, B.A., Jaree, P., Tassanakajon, A., Somboonwiwat, K. (2020). MicroRNA and mRNA interactions coordinate the immune response in non-lethal heat stressed Litopenaeus vannamei against AHPND-causing Vibrio parahaemolyticusScientific Reports, 10 (787), https://doi.org/10.1038/s41598-019-57409-4 more

Abstract:

While Vibrio parahaemolyticus (VPAHPND) has been identified as the cause of early mortality syndrome (EMS) or acute hepatopancreatic necrosis disease (AHPND) in shrimp, mechanisms of host response remain unknown. Understanding these processes is important to improve farming practices because this understanding will help to develop methods to enhance shrimp immunity. Pre-treatment of shrimp with 5-minute chronic non-lethal heat stress (NLHS) for 7 days was found to significantly increase Litopenaeus vannamei survival against VPAHPND infection. To elucidate the mechanism involved, mRNA and miRNA expression profiles from the hemocyte of L. vannamei challenged with VPAHPND after NLHS with corresponding control conditions were determined by RNA-Seq. A total of 2,664 mRNAs and 41 miRNAs were differentially expressed after the NLHS treatment and VPAHPND challenge. A miRNA-mRNA regulatory network of differentially expressed miRNAs (DEMs) and differentially expressed genes (DEGs) was subsequently constructed and the interactions of DEMs in regulating the NLHS-induced immune-related pathways were identified. Transcriptomic data revealed that miRNA and mRNA interactions contribute to the modulation of NLHS-induced immune responses, such as the prophenoloxidase-activating system, hemocyte homeostasis, and antimicrobial peptide production, and these responses enhance VPAHPND resistance in L. vannamei.

 

2. Itang, L.A.M., Stec, D., Mapalo, M.A., Mirano-Bascos, D. & Michalczyk, L. (2020). An integrative description of Mesobiotus dilimanensis, a new tardigrade species from the Philippines (Eutardigrada: Macrobiotidae: furciger group)Raffles Bulletin of Zoology, 68, Pages 19–31 DOI:10.26107/RBZ-2020-0003 more

Abstract:

In this study, a new species of the Mesobiotus furciger group from Diliman, Quezon City, Philippines was identified using an integrative taxonomy approach. Morphological and morphometric data obtained through phase and Nomarski contrast microscopy and scanning electron microscopy along with molecular analyses of the DNA sequences of four molecular markers (18S rRNA, 28S rRNA, ITS-2, and COI) support the erection of Mesobiotus dilimanensis, new species. The new species is the third limno-terrestrial tardigrade species from the Philippines described as new to science and is the first member of the Mesobiotus furciger species complex described using an integrative taxonomy approach in the country.

 

3. Galvez, L.C., Barbosa, C.F.C., Koh, R.B.L., Aquino, V.M. (2020). Loop-mediated isothermal amplification (LAMP) assays for the detection of abaca bunchy top virus and banana bunchy top virus in abacaCrop Protection, 131. DOI: 10.1016/j.cropro.2020.105101 more

Abstract:

Abaca bunchy top virus (ABTV) and banana bunchy top virus (BBTV) are pathogens that infect abaca in the Philippines causing significant reduction in abaca fiber yield and quality. In this study, a sensitive loop-mediated isothermal amplification (LAMP) assay was developed for detecting ABTV and BBTV in abaca, Musa textilis Nee. Five primer sets were designed and tested to detect ABTV while three primer sets were designed and tested to detect BBTV. Out of which only one primer set for each virus was specific to their respective targets that is DNA-N for ABTV and DNA-S for BBTV for successful LAMP based detection applications. The concentrations of Bst DNA polymerase, dNTPs, incubation time and temperature were optimized for both viruses using either GelRed™ or SYBR™ Green I as detection dyes. The ABTV and BBTV LAMP assays were more sensitive than conventional PCR and were able to detect ABTV or BBTV in asymptomatic abaca samples. The developed LAMP protocols provide a simple, fast and accurate detection method that will be indispensable for the production of ABTV- and BBTV-free abaca tissue cultured plantlets. This is the first report of a LAMP-based assay for detection of ABTV and BBTV in abaca.

 

4. Galvez, L. C., Koh, R. B. L., Barbosa, C. F. C., Aquino, V. M. (2020). Multiplex reverse transcription-polymerase chain reaction for simultaneous detection of banana bract mosaic virus (BBrMV) and sugarcane mosaic virus (SCMV) in abacaCanadian Journal of Plant Pathology, DOI: 10.1080/07060661.2019.1708810 more

Abstract:

The abaca (Musa textilis Nee) is an important fibre crop in the Philippines. Its fibre yield and quality is severely impacted by two potyviruses, namely, banana bract mosaic virus (BBrMV) and sugarcane mosaic virus (SCMV). A multiplex RT-PCR assay was developed for the simultaneous detection of these two RNA viruses in abaca. Primer sets were designed to amplify fragments of BBrMV coat protein (743 bp), SCMV coat protein (595 bp) and Musa sp. elongation factor 1 (219 bp) as an internal control. The specificity of each primer pair was confirmed by cloning and sequencing of the RT-PCR products. The multiplex RT-PCR assay was optimized by varying primer concentration combinations, dNTP concentration, Mg2+ concentration, Taq polymerase concentration, annealing temperature and extension temperature. The developed multiplex RT-PCR protocol has the same level of sensitivity and specificity when compared with uniplex RT-PCR detection for each virus and internal control. The inclusion of internal control amplification eliminates the risk of obtaining false negative results. The use of the optimized multiplex RT-PCR in simultaneous detection of BBrMV and SCMV from field samples proves that it is reliable, robust and faster than uniplex RT-PCR detection of each virus. This method will be useful for large-scale surveys of these two RNA viruses in abaca and will be vital for epidemiological studies and disease prevention.

 

5. Koh, R.B.L., Zaulda, F.A.D.L.C.,  Barbosa, C.F.C., Aquino, V.M., Galvez, L.C. (2020). Immunodiagnosis of bunchy top viruses in abaca with polyclonal antibodies against their recombinant coat proteinsArchives of Phytopathology and Plant Protection, DOI: 10.1080/03235408.2020.1727106 more

Abstract:

Polyclonal antibodies against abaca bunchy top virus (ABTV) and banana bunchy top virus (BBTV) proteins are necessary for immuno-based detection of these two viruses in abaca (Musa textilis Nee). In this study, recombinant bunchy top viral coat proteins fused with a 6xHis tag at the N-terminus were expressed in E. coli BL21StarTM(DE3)pLysS strain and purified under denaturing conditions. Purified recombinant ABTV and BBTV coat proteins were used as antigens for the production of rabbit polyclonal antibodies. IgG was purified and evaluated by Direct Antigen Coating (DAC)-ELISA and further optimized by testing primary to secondary antibody dilution combinations. Analysis of ABTV and BBTV-infected abaca samples using the optimized DAC-ELISA assay showed that the anti-ABTV CP IgG can react to BBTV and that anti-BBTV CP IgG can react to ABTV, hence, a cross-reaction. The study demonstrates the advantage of using recombinant DNA technology for mass production of antigens for antibody production. Although specificity of the polyclonal antibodies may have been compromised when renatured recombinant proteins were used as immunogens, the ability of the purified IgGs to detect positive abaca samples reveals that the DAC-ELISA can be routinely used for screening disease-free abaca planting materials.

 

6. Kregel, S., Bagamasbad, P., He, S., LaPensee, E., Raji, Y., Brogley, M., Chinnaiyan, A., Cieslik, M., Robins, D.M. (2020). Differential modulation of the androgen receptor for prostate cancer therapy depends on the DNA response elementNucleic Acids Research, gkaa178, https://doi.org/10.1093/nar/gkaa178 more

Abstract:

Androgen receptor (AR) action is a hallmark of prostate cancer (PCa) with androgen deprivation being standard therapy. Yet, resistance arises and aberrant AR signaling promotes disease. We sought compounds that inhibited genes driving cancer but not normal growth and hypothesized that genes with consensus androgen response elements (cAREs) drive proliferation but genes with selective elements (sAREs) promote differentiation. In a high-throughput promoter-dependent drug screen, doxorubicin (dox) exhibited this ability, acting on DNA rather than AR. This dox effect was observed at low doses for multiple AR target genes in multiple PCa cell lines and also occurred in vivo. Transcriptomic analyses revealed that low dox downregulated cell cycle genes while high dox upregulated DNA damage response genes. In chromatin immunoprecipitation (ChIP) assays with low dox, AR binding to sARE-containing enhancers increased, whereas AR was lost from cAREs. Further, ChIP-seq analysis revealed a subset of genes for which AR binding in low dox increased at pre-existing sites that included sites for prostate-specific factors such as FOXA1. AR dependence on cofactors at sAREs may be the basis for differential modulation by dox that preserves expression of genes for survival but not cancer progression. Repurposing of dox may provide unique opportunities for PCa treatment.

 

7. Mapalo, M.A., Arakawa, K., Baker, C.M., Persson, D.K., Mirano-Bascos, D., Giribet, G. (2020). The Unique Antimicrobial Recognition and Signaling Pathways in Tardigrades with a Comparison Across EcdysozoaG3: Genes, Genomes, Genetics, 10 (1), DOI: 10.1534/g3.119.400734 more

Abstract:

Tardigrades are microscopic animals known to withstand unfavorable abiotic conditions. These animals are also constantly exposed to biotic stresses, including parasites and internal microbiomes. However, the tardigrade immune mechanisms against these biotic stresses are largely uncharacterized. Due to the contentious phylogenetic position of tardigrades, it is not intuitive whether they possess an immune system more similar to that of arthropods (e.g., Toll, Imd, and JNK pathways of the Drosophila melanogaster antimicrobial response) or to that of nematodes (e.g., the Tir-1/Nsy-1/Sek-1/Pmk-1/Atf-7 signaling cassette [called Tir-1 pathway here]) in Caenorhabditis elegans). In this study, comparative genomic analyses were conducted to mine homologs of canonical D. melanogaster and C. elegans immune pathway genes from eight tardigrades (Echiniscoides cf. sigismundi, Echiniscus testudo, Hypsibius exemplaris, Mesobiotus philippinicus, Milnesium tardigradum, Paramacrobiotus richtersi, Richtersius cf. coronifer, and Ramazzottius varieornatus) and four non-arthropod ecdysozoans (two onychophorans: Epiperipatus sp. and Opisthopatus kwazululandi; one nematomorph: Paragordius varius; and one priapulan: Priapulus caudatus) in order to provide insights into the tardigrade antimicrobial system. No homologs of the intracellular components of the Toll pathway were detected in any of the tardigrades examined. Likewise, no homologs of most of the Imd pathway genes were detected in any of the tardigrades or any of the other non-arthropod ecdysozoans. Both the JNK and Tir-1 pathways, on the other hand, were found to be conserved across ecdysozoans. Interestingly, tardigrades had no detectable homologs of NF-κB, the major activator of antimicrobial response gene expression. Instead, tardigrades appear to possess NF-κB distantly related NFAT homologs. Overall, our results show that tardigrades have a unique gene pathway repertoire that differs from that of other ecdysozoans. Our study also provides a framework for future studies on tardigrade immune responses.

 

8. Roquid, K.R., Alcantara, K.M., Garcia, R.L. (2020). Identification and validation of mRNA 3'untranslated regions of DNMT3B and TET3 as novel competing endogenous RNAs of the tumor suppressor PTENInternational Journal of Oncology, 56, Pages 544-558. https://doi.org/10.3892/ijo.2019.4947 more

Abstract:

PTEN inactivation is a frequent event in oncogenesis. Multiple regulatory mechanisms such as promoter hypermethylation, antisense regulation, histone modifications, targeting by microRNAs (miRNAs/miRs) and regulation by transcription factors have all been shown to affect the tumor suppressor functions of PTEN. More recently, the functional involvement of competing endogenous RNAs (ceRNAs) in miRNA‑dependent and coding‑independent regulation of genes shed light on the highly nuanced control of PTEN expression. The present study has identified and validated DNA methyltransferase 3β (DNMT3B) and TET methylcytosine dioxygenase 3 (TET3) as novel ceRNAs of PTEN, with which they share multiple miRNAs, in HCT116 colorectal cancer cells. miR‑4465 was identified and characterized as a miRNA that directly targets and regulates all 3 transcripts via their 3'untranslated regions (3'UTRs) through a combination of luciferase reporter assays, abrogation of miRNA response elements (MREs) via site‑directed mutagenesis, target protection of MREs with locked nucleic acids, RT‑qPCR assays and western blot analysis. Competitive miRNA sequestration was demonstrated upon reciprocal 3'UTR overexpression and siRNA‑mediated knockdown of their respective transcripts. Overexpression of DNMT3B or TET3 3'UTR promoted apoptosis and decreased migratory capacity, potentially because of shared miRNA sequestration and subsequent activation of PTEN expression. Knockdown of TET3 and DNMT3B decoupled their protein‑coding from miRNA‑dependent, coding‑independent functions. Furthermore, the findings suggested that the phenotypic outcome of ceRNAs is dictated largely by the number of shared miRNAs, and predictably, by the existence of other ceRNA networks in which they participate. Taken together, the findings of the present study identified DNMT3B and TET3 as novel ceRNAs of PTEN that may impact its dose‑sensitive tumor suppressive function.

 

nip 

1. Afalla, J., Catindig, G., Delos Reyes, A., Prieto, E., Faustino, M. a., Vistro, V., Gonzales, K. C., Bardolaza, H., Mag-usara, V., Husay, H. A., Muldera, J., Cabello, N., Ferrolino, J. P., Kithara, H., Somintac, A., Salvador, A., Tani, M., & Estacio, E. (2020). Ultrafast carrier dynamics and THz conductivity in epitaxial-grown LT-GaAs on silicon for development of THz photoconductive antenna detectorsJournal of Physics D: Applied Physics53 (9). https://doi.org/10.1088/1361-6463/ab5aa7 more

Abstract:

Carrier dynamics and photoconductivity in epitaxial-grown low-temperature GaAs on nominal and vicinal Si(1 0 0) substrates ('LT-GaAs/Si') were studied to predict their actual performance as THz photoconductive antenna (PCA) detectors. An optical-pump terahertz-probe technique was used to obtain the transmittance, carrier lifetime and photoconductivity of two LT-GaAs/Si samples, grown using different substrates and different growth protocols. The LT-GaAs grown on Si(1 0 0) substrate with a 4° tilt to 1 1 0 has better crystallinity, in agreement with other reports; while the LT-GaAs layer grown on nominal Si(1 0 0) substrate, though more structurally defective, has a much faster electron trapping time. Fabricated test PCAs with either dipole or bowtie geometries confirm the characterization results. The photoconductivity and carrier lifetime results manifest in the PCA performance, in responsivity, and in detection bandwidth. The prototypes' sensitivities, bandwidths and dynamic ranges show that with some growth optimization, LT-GaAs/Si can be tailored to create economical, broadband THz detectors.

2. Bernardo, R. C., Celestial, J., & Vega, I. (2020). Stealth black holes in shift symmetric kinetic gravity braidingPhysical Review D101 (2), 24036. https://doi.org/10.1103/PhysRevD.101.024036 more

Abstract:

We derive all hairy stealth black holes in the most general second-order, shift symmetric, scalar-tensor theory with luminally propagating gravitational waves, often called kinetic gravity braiding. Our approach exploits a loophole in a recently obtained no-go statement which claims shift symmetry breaking to be necessary for stealth solutions to exist in kinetic gravity braiding. We highlight the essential role played by a covariantly constant kinetic density in obtaining these solutions. Lastly, we propose a parametrization of the theories based on the asymptotics of its stealth solutions and comment on the intriguing singular effective metric for scalar perturbations in stealth black holes.

 

3. De Los Reyes, A., Bardolaza, H., Vasquez, J. D., Cabello, N. I., Lopez, L., Chang, C. Y., Somintac, A., Salvador, A., Jang, D. J., & Estacio, E. (2020). Temperature-dependent terahertz time-domain spectroscopy of 3D, 2D, and 0D semiconductor heterostructuresJournal of Materials Science: Materials in Electronics0123456789. https://doi.org/10.1007/s10854-020-03188-y more

Abstract:

Carrier transport in semiconductors with different dimensionalities, i.e., 3D (bulk), 2D (QW), and 0D (QD), were investigated via temperature-dependent terahertz time-domain spectroscopy (THz-TDS). The optical properties and recombination dynamics in the samples were probed via photoluminescence spectroscopy. The temperature-dependence of the THz emission from the samples was explained in the context of the drift-diffusion model using the dominant THz radiation mechanism. The THz emission from diffusion-type THz emitters such as p- and n-InAs decreases as temperature increases due to mobility decrease. Conversely, the THz emission from drift-type THz emitters such as SI-GaAs, GaAs QW, and InAs QD was found to increase with temperature due to the increase in the driving electric field. In summary, THz-TDS can be utilized to gain qualitative insights on the temperature-dependent transport characteristics and establish dominant THz radiation mechanisms.

 

4. De Los Reyes, A. E., Vasquez, J. D., Bardolaza, H. R., Lopez, L. P., Chang, C.-Y., Somintac, A. S., Salvador, A. A., Jang, D.-J., & Estacio, E. S. (2020). Low-temperature carrier dynamics in MBE-grown InAs/GaAs single- and multi-layered quantum dots investigated via photoluminescence and terahertz time-domain spectroscopyOptical Materials Express10 (1), 178. https://doi.org/10.1364/ome.380909 more

Abstract:

The photocarrier dynamics in molecular beam epitaxy (MBE)-grown single- (SLQD) and multi-layered (MLQD) InAs/GaAs quantum dots were studied. Photoluminescence (PL) spectroscopy has shown that the MLQD has more uniform QD size distribution as compared to the bimodal SLQD. Correlation between PL and THz-TDS has shown that photocarrier transport is more favored in the MLQD owing to this uniform QD size distribution, resulting to higher THz emission. The THz emission from the QD samples were found to be proportional to temperature. A drift-related photocarrier transport mechanism is proposed, wherein photocarriers generated in the QDs are accelerated by an interface electric field.

 

5. Flores, M., Kar, D., & Kim, J. S. (2020). Constraining Stealth SUSY with illuminated fat jets at the LHCPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics801, 135151. https://doi.org/10.1016/j.physletb.2019.135151 more

Abstract:

We investigate the discovery potential of a Stealth SUSY scenario involving squark decays by reconstructing the lightest neutralino decay products using a large-radius jet containing a high transverse momentum photon. Requirements on the event topology, such as photon and large-radius jet multiplicity result in less background than signal. We also estimated the sensitivity of our analysis and found that it has a better exclusion potential compared to the strongest existing search for the specific benchmark points considered here.

 

6. Manaoat, N. M., Bantang, J. Y., & Bo-ot, L. M. (2020). Diurnal Temperature Variation in an Idealized Room for Different Wall Materials Using a Thermal Load Model in the Philippine Setting1st International Conference on Human Interaction and Emerging Technologies, IHIET 2019; Nice; France; 22 August 2019 through 24 August 2019; Code 229139, 110–116. 

Abstract:

A simple thermal model is used to simulate the heat load received by an idealized room incorporating climatological factors and daily weather patterns in the Philippine setting. The model provides diurnal temperature variation of the idealized room with varying wall materials situated in Quezon City during the cool-dry and hot-dry seasons in the country. The model was used to calculate the heat load to keep the temperature of the room less than 25 °C. Rooms with walls made of bamboo and oak were demonstrated to perform better than those which are made of concrete, bricks and sandstone. The room with oak walls were shown to provide up to 3 × savings in terms of computed daily energy consumption during the hot-dry season. This study can help us provide design and structural considerations in relation to energy utilization and possibly conservation.

 

7. Pablico, D. A. L., & Galapon, E. A. (2020). Quantum traversal time across a potential wellPhysical Review A101 (2), Pages 1–13. https://doi.org/10.1103/PhysRevA.101.022103 more

Abstract:

We consider the quantum traversal time of an incident wave packet across a potential well using the theory of quantum time of arrival (TOA) operators. This is done by constructing the corresponding TOA operator across a potential well via quantization. The expectation value of the potential-well TOA operator is compared to the free-particle case for the same incident wave packet. The comparison yields a closed-form expression of the quantum well traversal time which explicitly shows the classical contributions of the positive and negative momentum components of the incident wave packet and a purely quantum-mechanical contribution significantly dependent on the well depth. An incident Gaussian wave packet is then used as an example. It is shown that for shallow potential wells, the quantum well traversal time approaches the classical traversal time across the well region when the incident wave packet is spatially broad and approaches the expected quantum free-particle traversal time when the wave packet is localized. For deep potential wells, the quantum traversal time oscillates from positive to negative, implying that the wave packet can be advanced or delayed.

 

8. Santos-putungan, A. B., Binggeli, N., & Paraan, F. N. C. (2020). Selective capture of CO 2 over N 2 and CH 4 : B clusters and their size effects. Materials Today Communications, 22Article number 100712. https://doi.org/10.1016/j.mtcomm.2019.100712 more

Abstract:

Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO2 over  and  on planar-type B clusters, based on our previous finding of strong chemisorption of  on the B planar and quasiplanar clusters. We consider the prototype B and B planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature,  can be separated from  by selective binding to the B cluster and not to the B cluster. Selective adsorption of  over CH4 at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for  on the planar-type B36 cluster, we discuss the selectivity trend of  adsorption over  and CH4 with planar-cluster size, showing that it extends over sizes including B10-13 clusters and significantly larger.

 

9. Simon, R. C., Sagisi, J. L. B., Zambale, N. A. F., & Hermosa, N. (2020). Is a single layer graphene a slab or a perfect sheetCarbon157, Pages 486–494. https://doi.org/10.1016/j.carbon.2019.10.044 more

Abstract:

We show that graphene is best described as a slab with finite thickness based on our reflectivity analysis for five different wavelengths. We perform fine-scan angular reflectivity on a single layer graphene on top of SiO2/Si and determine its crossing angle. The experimental data were then compared to the predictions of the three most common models for a single layer graphene. We find that the slab model gives good predictions for the crossing angle in all our experiments. This implies that (1) the real part of the electric permittivity of graphene has a crucial role in the electromagnetic wave propagation, (2) the field across a single layer graphene is continuous, and (3) the dispersionless refractive index of graphite can describe the optical index of graphene in the visible regime.

 

10. Veloria, A., Perez, G.J., Tapang, G., Comiso, J. (2020). Comparison between GPM and gridded precipitation product from interpolated rain gauge measurements40th Asian Conference on Remote Sensing: Progress of Remote Sensing Technology for Smart Future, ACRS 2019; Daejeon Convention Center (DCC)Daejeon; South Korea; 14 October 2019 through 18 October 2019; Code 157736

Abstract:

Due to sparsely distributed synoptic stations in the Philippines, representation of precipitation is inadequate. Satellite-derived products, such as the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM), are available to complement synoptic data for more precise and robust measurements. However, these products tend to over- or underestimate rainfall depending on the season. Precipitation measurements from a dense network of rain gauges in the Philippines are available courtesy of the Department of Science and Technology - Advance Science and Technology Institute (DOST-ASTI). This study aims to create a gridded precipitation data over the Philippines from interpolated rain gauge measurements and validate its performance through comparison with GPM. Comparison of rain gauge data with overlapping synoptic measurements in a 0.25° grid showed distance-dependent likelihood. Thus, inverse distance weighting (IDW) was performed to combine multiple rain gauge measurements representative of precipitation over 0.1° grid. Strong positive correlations (r = 0.58 to 0.97) were obtained from comparing IDW values and monthly synoptic measurements suggesting that rain gauge measurements may be used as complimentary ground data. IDW values were then subjected to kriging and iterative method to create a monthly gridded precipitation. Results showed that the interpolated precipitation follows the wet and dry season as well as monsoon seasonality in the Philippines. The calculated differences between the interpolated precipitation and GPM monthly product revealed that the interpolated precipitation have lower estimates with respect to GPM regardless of season. This is in contrast with the strong positive relationship between monthly synoptic measurements and GPM (r = 0.856). Low estimates from the interpolated precipitation is due to isolated zero measurements from various rain gauges. This may be attributed to maintenance issues of the sensors where the data do not report broken and erroneous instruments. Further filtering of the dataset and regular maintenance of the sensors must be done to better incorporate the use of dense rain gauge network for the creation of a Philippine gridded precipitation.

 

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