Physical Sciences and Mathematics Commons^™

Tooth Position Determination By Automatic Cutting And Marking Of Dental Panoramic X-Ray Film In Medical Image Processing, Yen-Cheng Huang, Chiung-An Chen, Tsung-Yi Chen, He-Sheng Chou, Wei-Chi Lin, Tzu-Chien Li, Jia-Jun Yuan, Szu-Yin Lin, Chun-Wei Li, Shih-Lun Chen, Yi-Cheng Mao, Patricia Angela R. Abu, Wei-Yuan Chiang, Wen-Shen Lo

Department of Information Systems & Computer Science Faculty Publications

This paper presents a novel method for automatic segmentation of dental X-ray images into single tooth sections and for placing every segmented tooth onto a precise corresponding position table. Moreover, the proposed method automatically determines the tooth’s position in a panoramic X-ray film. The image-processing step incorporates a variety of image-enhancement techniques, including sharpening, histogram equalization, and flat-field correction. Moreover, image processing was implemented iteratively to achieve higher pixel value contrast between the teeth and cavity. The next image-enhancement step is aimed at detecting the teeth cavity and involves determining the segment and points separating the upper and lower jaw, …

Visualizing Phytochemical-Protein Interaction Networks: Momordica Charantia And Cancer, Yumi L. Briones, Alexander T. Young, Fabian M. Dayrit, Armando Jerome De Jesus, Nina Rosario L. Rojas

Chemistry Faculty Publications

The in silico study of medicinal plants is a rapidly growing field. Techniques such as reverse screening and network pharmacology are used to study the complex cellular action of medicinal plants against disease. However, it is difficult to produce a meaningful visualization of phytochemical-protein interactions (PCPIs) in the cell. This study introduces a novel workflow combining various tools to visualize a PCPI network for a medicinal plant against a disease. The five steps are 1) phytochemical compilation, 2) reverse screening, 3) network building, 4) network visualization, and 5) evaluation. The output is a PCPI network that encodes multiple dimensions of …

Influence Of Boreal Summer Intraseasonal Oscillation On Rainfall Extremes In The Philippines, Lyndon Mark P. Olaguera, John A. Manalo, Jun Matsumoto

Physics Faculty Publications

This study investigates the impact of the northward/northwestward propagating 30–60-day mode of the boreal summer intraseasonal oscillation (BSISO) on the extreme rainfall events in the Philippines during the June–September (JJAS) season from 1979 to 2018. The Philippines domain is divided into the three latitudinal regions: Luzon region (13°–22°N), Visayas region (10°–13°N), and Mindanao region (5°–10°N) to account for the regional differences in the timing of extreme rainfall events. The probability density functions of JJAS rainfall are skewed towards higher values relative to the non-BSISO days in BSISO Phases 6–8, Phases 5–7, and Phases 4–6 over the Luzon, Visayas, and Mindanao …

Comparative Toxicity, Phytochemistry, And Use Of 53 Philippine Medicinal Plants, Lydia M. Clemen-Pascual, Rene Angelo S. Macahig, Nina Rosario L. Rojas

Chemistry Faculty Publications

The study compares the toxicity of 53 selected medicinal plants commonly used in the Philippines to treat various diseases. It uses as a benchmark Vitex negundo L., which was approved by the Philippine Food and Drug Administration as an herbal drug for cough and asthma after passing clinical trials for safety and efficacy. The methods were chosen for their simplicity and accessibility even for resource-limited laboratories. Extracts (95 % ethanol) of the medicinal parts of the plants were (1) chemically profiled using qualitative phytochemical tests that detect the presence of key classes of bioactive compounds; and (2) evaluated for toxicity …

A Global Agenda For Advancing Freshwater Biodiversity Research, Alain Maasri, Sonja C. Jähnig, Hendrik Freitag, 93 Co-Authors

Biology Faculty Publications

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.

Survey Data On Energy And Fuel Use Of Firms In Economic Zones In The Philippines, Majah-Leah V. Ravago, Raul V. Fabella, Karl Robert L. Jandoc, Renzi G. Frias, J. Kathleen P. Magadia

Economics Department Faculty Publications

The data describe characteristics, operations, utilities, and fuels used in the production of 115 manufacturing and agro-industrial firms in Philippine special economic zones. The data include information on the firm's production, sales, and schedules; electricity sources, requirements, and uses; the importance of various conventional fuels, and the firms’ fuel expenditure in their major production processes. The data also include their employee's aptitude, knowledge, considerations, and opinions on alternative fuels and primary energies, and experiences in using them. The data were gathered through a series of focus group discussions (FGDs) in June 2019 and an online survey conducted in August to …

Teaching And Learning Under Covid-19 Public Health Edicts: The Role Of Household Lockdowns And Prior Technology Usage, Neil Guppy, David Boud, Tania Heap, Dominique Verpoorten, Uwe Matzat, Joanna Tai, Louise Lutze-Mann, Mary Roth, Patsie Polly, Jamie-Lee Burgess, Jenilyn L. Agapito, Silvia K. Bartolic

Department of Information Systems & Computer Science Faculty Publications

Public health edicts necessitated by COVID-19 prompted a rapid pivot to remote online teaching and learning. Two major consequences followed: households became students' main learning space, and technology became the sole medium of instructional delivery. We use the ideas of "digital disconnect" and "digital divide" to examine, for students and faculty, their prior experience with, and proficiency in using, learning technology. We also explore, for students, how household lockdowns and digital capacity impacted learning. Our findings are drawn from 3806 students and 283 faculty instructors from nine higher education institutions across Asia, Australia, Europe, and North America. For instructors, we …

Classifying Mosquito Presence And Genera Using Median And Interquartile Values From 26-Filter Wingbeat Acoustic Properties, Hernan S. Alar, Proceso L. Fernandez Jr

Department of Information Systems & Computer Science Faculty Publications

Mosquitoes are known to be one of the deadliest creatures in the world. There have been several studies that aim to identify mosquito presence and species using various techniques. The most common ones involve automatic identification of mosquito species from the sounds produced by flapping its wings. The development of these important concepts and technologies can help reduce the spread of mosquito-borne diseases. This paper presents a simple model based on mean and interquartile values that aim to solve the mosquito classification. Despite its simplicity, the proposed model significantly outperforms a Convolutional Neural Network (CNN) model in identifying the mosquito …

Automated Classification Model With Otsu And Cnn Method For Premature Ventricular Contraction Detection, Liang-Hung Wang, Lin-Juan Ding, Chao-Xin Xie, Su-Ya Jiang, I-Chun Kuo, Xin-Kang Wang, Jie Gao, Pao-Cheng Huang, Patricia Angela R. Abu

Department of Information Systems & Computer Science Faculty Publications

Premature ventricular contraction (PVC) is one of the most common arrhythmias which can cause palpitation, cardiac arrest, and other symptoms affecting the work and rest activities of a patient. However, patients hardly decipher their own feelings to determine the severity of the disease thus, requiring a professional medical diagnosis. This study proposes a novel method based on image processing and convolutional neural network (CNN) to extract electrocardiography (ECG) curves from scanned ECG images derived from clinical ECG reports, and segment and classify heartbeats in the absence of a digital ECG data. The ECG curve is extracted using a comprehensive algorithm …

Improvised Centrifugal Spinning For The Production Of Polystyrene Microfibers From Waste Expanded Polystyrene Foam And Its Potential Application For Oil Adsorption, Marco Laurence M. Budlayan, Jonathan N. Patricio, Jeanne Phyre B. Lagare, Susan D. Arco, Arnold C. Alguno, Antonio M. Basilio, Felmer S. Latayada, Rey Y. Capangpangan

Physics Faculty Publications

A straightforward approach to recycle waste expanded polystyrene (EPS) foam to produce polystyrene (PS) microfibers using the improvised centrifugal spinning technique is demonstrated in this work. A typical benchtop centrifuge was improvised and used as a centrifugal spinning device. The obtained PS microfibers were characterized for their potential application for oil adsorption. Fourier transform infrared spectroscopy results revealed similarity on the transmission bands of EPS foam and PS microfibers suggesting the preservation of the EPS foam’s chemical composition after the centrifugal spinning process. Scanning electron microscopy displayed well-defined fibers with an average diameter of 3.14 ± 0.59 μm. At the …

Detection Of Dental Apical Lesions Using Cnns On Periapical Radiograph, Chun-Wei Li, Szu-Yin Lin, He-Sheng Chou, Tsung-Yi Chen, Yu-An Chen, Sheng-Yu Liu, Yu-Lin Liu, Chiung-An Chen, Yen-Cheng Huang, Shih-Lun Chen, Yi-Cheng Mao, Patricia Angela R. Abu, Wei-Yuan Chiang, Wen-Shen Lo

Department of Information Systems & Computer Science Faculty Publications

Apical lesions, the general term for chronic infectious diseases, are very common dental diseases in modern life, and are caused by various factors. The current prevailing endodontic treatment makes use of X-ray photography taken from patients where the lesion area is marked manually, which is therefore time consuming. Additionally, for some images the significant details might not be recognizable due to the different shooting angles or doses. To make the diagnosis process shorter and efficient, repetitive tasks should be performed automatically to allow the dentists to focus more on the technical and medical diagnosis, such as treatment, tooth cleaning, or …

Particulate Oxalate-To-Sulfate Ratio As An Aqueous Processing Marker: Similarity Across Field Campaigns And Limitations, Miguel Ricardo A. Hilario, Ewan Crosbie, Paola Angela Bañaga, Grace Betito, Rachel A. Braun, Maria Obiminda L. Cambaliza, Andrea F. Corral, Melliza Templonuevo Cruz, Jackie E. Dibb, Genevieve Rose Lorenzo, Alexander B. Macdonald, Claire E. Robinson, Michael Shook, James Bernard Simpas, Connor Stahl, Edward Winstead, Luke Ziemba, Armin Sorooshian

Physics Faculty Publications

Leveraging aerosol data from multiple airborne and surface-based field campaigns encompassing diverse environmental conditions, we calculate statistics of the oxalate-sulfate mass ratio (median: 0.0217; 95% confidence interval: 0.0154 – 0.0296; R = 0.76; N = 2948). Ground-based measurements of the oxalate-sulfate ratio fall within our 95% confidence interval, suggesting the range is robust within the mixed layer for the submicrometer particle size range. We demonstrate that dust and biomass burning emissions can separately bias this ratio towards higher values by at least one order of magnitude. In the absence of these confounding factors, the 95% confidence interval of the ratio …

Managing The Energy Trilemma In The Philippines, Josef Teofisto T. Yap, Aaron Joseph P. Gabriola, Chrysogonus F. Herrera

Ateneo School of Government Publications

Background

The transition to an energy mix with lower carbon emissions is hampered by the existence of the so-called Energy Trilemma. The primary consequence is a trade-off between various objectives of energy policy, e.g., equity and sustainability. This conflict can lead to policy gridlock if policymakers are unable to prioritize the goals. This paper proposes a framework and methodology to manage the trilemma by applying methods related to multi-criteria decision-making in order to assign weights to the various components of the trilemma.

Results

Following the International Energy Agency (IEA), an expanded concept of energy security is adopted and translates to …

Total Organic Carbon And The Contribution From Speciated Organics In Cloud Water: Airborne Data Analysis From The Camp2ex Field Campaign, Connor Stahl, Ewan Crosbie, Paola Angela Bañaga, Grace Betito, Rachel A. Braun, Zenn Marie Cainglet, Maria Obiminda L. Cambaliza, Melliza Templonuevo Cruz, Julie Mae Dado, Miguel Ricardo Hilario, Gabrielle Leung, Alexander B. Macdonald, Angela Monina T. Magnaye, Jeffrey S. Reid, Claire E. Robinson, Michael Shook, James Bernard Simpas, Shane Marie Visaga, Edward Winstead, Luke Ziemba, Armin Sorooshian

Physics Faculty Publications

This work focuses on total organic carbon (TOC) and contributing species in cloud water over Southeast Asia using a rare airborne dataset collected during NASA’s Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex), in which a wide variety of maritime clouds were studied, including cumulus congestus, altocumulus, altostratus, and cumulus. Knowledge of TOC masses and their contributing species is needed for improved modeling of cloud processing of organics and to understand how aerosols and gases impact and are impacted by clouds. This work relies on 159 samples collected with an axial cyclone cloudwater collector at altitudes of 0.2–6.8 km that …

Publication-Driven Research Experience For Undergraduates (Reu) Program In Optics And Photonics In The Philippines Using Circuit Analogue-Based Research Experiments, Benjamin Dingel, Clint Dominic Bennett

Physics Faculty Publications

We summarize a unique publication-driven Research Experience for Undergraduates program in optics/photonics that uses electronic circuit analogue-based research to strengthen students’ engagement in research. At present, we have published 4 journal and conference papers.

Synoptic Conditions And Potential Causes Of The Extreme Heavy Rainfall Event Of January 2009 Over Mindanao Island, Philippines, Lyndon Mark P. Olaguera, Michelle Español Caballar, Joseph Cabacungan De Mata, Loida Ann Torres Dagami, Jun Matsumoto, Hisayuki Kubota

Physics Faculty Publications

This study investigates the synoptic conditions that led to the heavy rainfall/flood (HRF) event in Mindanao Island, Philippines (122 −127°E; 5 −10°N), on January 2009 (JAN2009 HRF) that are less emphasized in previous works. Extensive flooding was reported over Cagayan de Oro City in the northern part of Mindanao, where the rainfall on January 10, 11, and 13, 2009, exceeded the 99th percentile of daily rainfall records of all January of the city from 1979 to 2017 by almost two times. A similar exceedance was also felt in Hinatuan station over the eastern coast of Mindanao Island on January 15, …

Understanding Covid-19 Dynamics And The Effects Of Interventions In The Philippines: A Mathematical Modelling Study, Jamie M. Caldwell, Elvira P. De Lara-Tuprio, Timothy Robin Y. Teng, Ma. Regina Justina E. Estuar, Raymond Francis R. Sarmiento, Milinda Abayawardana B. Eng, Robert Neil F. Leong, Richard T. Gray, James G. Wood, Linh-Vi Le, Emma S. Mcbryde, Romain Ragonnet, James M. Trauer

Mathematics Faculty Publications

Background

COVID-19 initially caused less severe outbreaks in many low- and middle-income countries (LMIC) compared with many high-income countries; possibly because of differing demographics; socioeconomics; surveillance; and policy responses. Here; we investigate the role of multiple factors on COVID-19 dynamics in the Philippines; a LMIC that has had a relatively severe COVID-19 outbreak.

Methods

We applied an age-structured compartmental model that incorporated time-varying mobility; testing; and personal protective behaviors (through a “Minimum Health Standards” policy; MHS) to represent the first wave of the Philippines COVID-19 epidemic nationally and for three highly affected regions (Calabarzon; Central Visayas; and the National Capital …

The Incubation Effect Among Students Playing An Educational Game For Physics, May Marie P. Talandron-Felipe, Ma. Mercedes T. Rodrigo

Department of Information Systems & Computer Science Faculty Publications

The incubation effect (IE) is a problem-solving phenomenon composed of three phases: pre-incubation where one fails to solve a problem; incubation, a momentary break where time is spent away from the unsolved problem; and post-incubation where the unsolved problem is revisited and solved. Literature on IE was limited to experiments involving traditional classroom activities. This initial investigation showed evidence of IE instances in a computer-based learning environment. This paper consolidates the studies on IE among students playing an educational game called Physics Playground and presents further analysis to examine the incidence of post-incubation or the revisit to a previously unsolved …

Caries And Restoration Detection Using Bitewing Film Based On Transfer Learning With Cnns, Yi-Cheng Mao, Tsung-Yi Chen, He-Sheng Jhou, Szu-Yin Lin, Sheng-Yu Liu, Yu-An Chen, Yu-Lin Liu, Chiung-An Chen, Yen-Cheng Huang, Shih-Lun Chen, Chun-Wei Li, Patricia Angela R. Abu, Wei-Yuan Chiang

Department of Information Systems & Computer Science Faculty Publications

Caries is a dental disease caused by bacterial infection. If the cause of the caries is detected early; the treatment will be relatively easy; which in turn prevents caries from spreading. The current common procedure of dentists is to first perform radiographic examination on the patient and mark the lesions manually. However; the work of judging lesions and markings requires professional experience and is very time-consuming and repetitive. Taking advantage of the rapid development of artificial intelligence imaging research and technical methods will help dentists make accurate markings and improve medical treatments. It can also shorten the judgment time of …

Climate-Induced Stressors To Peace: A Review Of Recent Literature, Ayyoob Sharifi, Dahlia Simangan, Chui Ying Lee, Rose Reyes, Tarek Katramiz, Jairus Carmela C. Josol, Leticia Dos Muchangos, Hassan Virji, Shinji Kaneko, Thea Kersti Tandog, Leorence Tandog, Moinul Islam

Environmental Science Faculty Publications

Climate change is increasingly recognized as a threat to global peace and security. This paper intends to provide a better understanding of the nature of interactions between climate change and events that undermine peace through a systematic review of recent literature. It highlights major methodological approaches adopted in the literature, elaborates on the geographic focus of the research at the nexus of climate change and peace, and provides further information on how various climatic stressors, such as extreme temperature, floods, sea-level rise, storms, and water stress may be linked to different events that undermine peace (e.g. civil conflict, crime, intercommunal …

The Effect Of Urbanization On Temperature Indices In The Philippines, John A. Manalo, Jun Matsumoto, Hiroshi G. Takahashi, Marcelino Q. Villafuerte Ii, Lyndon Mark P. Olaguera, Guoyu Ren, Thelma Cinco

Physics Faculty Publications

This paper presents a comprehensive analysis of the effect of urbanization on the surface air temperature (SAT) from 1951 to 2018 in the Philippines. The daily minimum temperature (T_min) and daily maximum temperature (T_max) records from 34 meteorological stations were used to derive extreme temperature indices. These stations were then classified as urban or rural based on satellite night-lights. The results showed a significant difference in the SAT trends between urban and rural stations, indicative of the effect of urbanization in the country. Larger and more significant warming trends were observed in indices related …

Formulating 3-Chloropropyltriethoxysilane Modified Silica Nanoparticle Sprays As Hydrophobic Transparent Coatings Onto Cotton Textiles, Mikaela C. S. Mendoza, Gilbert U. Yu

Chemistry Faculty Publications

Cotton textiles were transformed into hydrophobic fabrics via the application of 3-chloropropylthriethoxysilane-functionalized silica nanoparticle spray coatings. Silica particles were measured to be < 50 nm, as determined by dynamic light scattering (DLS). The incorporation of hexadecyltrimethylammonium bromide (HTAB), a surfactant, into the nanosilica alcohol-based sprays resulted in a suspension that was stable for at least a week. Stability and turbidity tests of samples point to smaller particle size (silica nanoparticles = 24.3 ± 8.5 nm) as the main contributor to possibly providing transparency, as evidenced when sprayed in colored (black) textiles, while still contributing to hydrophobicity/ superhydrophobicity of the cloth.

Enhanced Electrochemical Performances Of Hollow-Structured N-Doped Carbon Derived From A Zeolitic Imidazole Framework (Zif-8) Coated By Polydopamine As An Anode For Lithium-Ion Batteries, Da-Won Lee, Achmad Yanuar Maulana, Chaeeun Lee, Jungwook Song, Cybelle M. Futalan, Jongsik Kim

Environmental Science Faculty Publications

Doping heteroatoms such as nitrogen (N) and boron (B) into the framework of carbon materials is one of the most efficient methods to improve the electrical performance of carbon-based electrodes. In this study, N-doped carbon has been facilely synthesized using a ZIF-8/polydopamine precursor. The polyhedral structure of ZIF-8 and the effective surface-coating capability of dopamine enabled the formation of N-doped carbon with a hollow structure. The ZIF-8 polyhedron served as a sacrificial template for hollow structures, and dopamine participated as a donor of the nitrogen element. When compared to ZIF-8-derived carbon, the HSNC electrode showed an improved reversible capacity of …

Measurement Report: Firework Impacts On Air Quality In Metro Manila, Philippines, During The 2019 New Year Revelry, Genevieve Rose Lorenzo, Paola Angela Bañaga, Maria Obiminda L. Cambaliza, Melliza Templonuevo Cruz, Mojtaba Azadi Aghdam, Avelino Arellano, Grace Betito, Rachel A. Braun, Andrea F. Corral, Hossein Dadashazar, Eva-Lou Edwards, Edwin Eloranta, Robert Holz, Gabrielle Leung, Lin Ma, Alexander B. Macdonald, Jeffrey S. Reid, James Bernard Simpas, Connor Stahl, Shane Marie Visaga, Armin Sorooshian

Physics Faculty Publications

Fireworks degrade air quality, reduce visibility, alter atmospheric chemistry, and cause short-term adverse health effects. However, there have not been any comprehensive physicochemical and optical measurements of fireworks and their associated impacts in a Southeast Asia megacity, where fireworks are a regular part of the culture. Size-resolved particulate matter (PM) measurements were made before, during, and after New Year 2019 at the Manila Observatory in Quezon City, Philippines, as part of the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex). A high-spectral-resolution lidar (HSRL) recorded a substantial increase in backscattered signal associated with high aerosol loading ∼440 m above the …

Ethics Of Ai In Education: Towards A Community-Wide Framework, Wayne Holmes, Kaska Poraysa-Pomsta, Ken Holstein, Emma Sutherland, Toby Baker, Simon Buckingham Shum, Olga C. Santos, Ma. Mercedes T. Rodrigo, Mutlu Cukurova, Ig Ibert Bittencourt, Kenneth R. Koedinger

Department of Information Systems & Computer Science Faculty Publications

While Artificial Intelligence in Education (AIED) research has at its core the desire to support student learning, experience from other AI domains suggest that such ethical intentions are not by themselves sufficient. There is also the need to consider explicitly issues such as fairness, accountability, transparency, bias, autonomy, agency, and inclusion. At a more general level, there is also a need to differentiate between doing ethical things and doing things ethically, to understand and to make pedagogical choices that are ethical, and to account for the ever-present possibility of unintended consequences. However, addressing these and related questions is far …

Vlsi Implementation Of A Cost-Efficient Loeffler-Dct Algorithm With Recursive Cordic For Dct-Based Encoder, Rih-Lung Chung, Chen-Wei Chen, Chiung-An Chen, Patricia Angela R. Abu, Shih-Lun Chen

Department of Information Systems & Computer Science Faculty Publications

This paper presents a low-cost and high-quality; hardware-oriented; two-dimensional discrete cosine transform (2-D DCT) signal analyzer for image and video encoders. In order to reduce memory requirement and improve image quality; a novel Loeffler DCT based on a coordinate rotation digital computer (CORDIC) technique is proposed. In addition; the proposed algorithm is realized by a recursive CORDIC architecture instead of an unfolded CORDIC architecture with approximated scale factors. In the proposed design; a fully pipelined architecture is developed to efficiently increase operating frequency and throughput; and scale factors are implemented by using four hardware-sharing machines for complexity reduction. Thus; the …

On The Sigma Value And Sigma Range Of The Join Of A Finite Number Of Even Cycles Of The Same Order, Marie Cris A. Bulay-Og, Agnes Garciano, Reginaldo M. Marcelo

Mathematics Faculty Publications

Let c be a vertex coloring of a simple; connected graph G that uses positive integers for colors. For a vertex v of G; the color sum of v is the sum of the colors of the neighbors of v. If no two adjacent vertices of G have the same color sum; then c is called a sigma coloring of G. The sigma chromatic number of G is the minimum number of colors required in a sigma coloring of G. Let max(c) be the largest color assigned to a vertex of G by a coloring c. The sigma value of …

The Set Chromatic Numbers Of The Middle Graph Of Graphs, Gerone Russel J. Eugenio, Mari-Jo P. Ruiz, Mark Anthony C. Tolentino

Mathematics Faculty Publications

For a simple connected graph G; let c : V (G) → N be a vertex coloring of G; where adjacent vertices may be colored the same. The neighborhood color set of a vertex v; denoted by NC(v); is the set of colors of the neighbors of v. The coloring c is called a set coloring provided that NC(u) neq NC(v) for every pair of adjacent vertices u and v of G. The minimum number of colors needed for a set coloring of G is referred to as the set chromatic number of G and is denoted by χ_s(G). In …

On The Sigma Chromatic Number Of The Zero-Divisor Graphs Of The Ring Of Integers Modulo N, Agnes Garciano, Reginaldo M. Marcelo, Mari-Jo P. Ruiz, Mark Anthony C. Tolentino

Mathematics Faculty Publications

The zero-divisor graph of a commutative ring R with unity is the graph Γ(R) whose vertex set is the set of nonzero zero divisors of R; where two vertices are adjacent if and only if their product in R is zero. A vertex coloring c : V (G) → Bbb N of a non-trivial connected graph G is called a sigma coloring if σ(u) = σ(ν) for any pair of adjacent vertices u and v. Here; σ(χ) denotes the sum of the colors assigned to vertices adjacent to x. The sigma chromatic number of G; denoted by σ(G); is defined …

Stabilization Of Cultural Innovations Depends On Population Density: Testing An Epidemiological Model Of Cultural Evolution Against A Global Dataset Of Rock Art Sites And Climate-Based Estimates Of Ancient Population Densities, Richard Walker, Anders Eriksson, Camille Ruiz, Taylor Howard Newton, Francesco Casalegno

Department of Information Systems & Computer Science Faculty Publications

Demographic models of human cultural evolution have high explanatory potential but weak empirical support. Here we use a global dataset of rock art sites and climate and genetics-based estimates of ancient population densities to test a new model based on epidemiological principles. The model focuses on the process whereby a cultural innovation becomes endemic in a population; predicting that this cannot occur unless population density exceeds a critical threshold. Analysis of the data; using a Bayesian statistical framework; shows that the model has stronger empirical support than a proportional model; where detection is directly proportional to population density; or a …