Physical Sciences and Mathematics Commons^™

Modeling And Counteracting Exposure Bias In Recommender Systems, Sami Khenissi, Olfa Nasraoui

Faculty and Staff Scholarship

What we discover and see online, and consequently our opinions and decisions, are becoming increasingly affected by automated machine learned predictions. Similarly, the predictive accuracy of learning machines heavily depends on the feedback data that we provide them. This mutual influence can lead to closed-loop interactions that may cause unknown biases which can be exacerbated after several iterations of machine learning predictions and user feedback. Machine-caused biases risk leading to undesirable social effects ranging from polarization to unfairness and filter bubbles. In this paper, we study the bias inherent in widely used recommendation strategies such as matrix factorization. Then we …

Galaxy And Mass Assembly (Gama): Properties And Evolution Of Red Spiral Galaxies, Smriti Mahajan, Kriti Kamal Gupta, Rahul Rana, M. J.I. Brown, S. Phillipps, Joss Bland-Hawthorn, M. N. Bremer, S. Brough, Benne W. Holwerda, A. M. Hopkins, J. Loveday, Kevin Pimbblet, Lingyu Wang

Faculty and Staff Scholarship

We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 < z < 0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) that has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long time-scales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The specific star formation rate (sSFR) and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average 0.9 dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination angles to support these as the major causes for the red optical colours seen in ≳47 per cent of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies that are detected in H I, we find that the SFR of gas-rich red spiral galaxies is lower by ∼1 dex than their blue counterparts.

A Validated Uplc-Ms/Ms Method For The Determination Of Aliphatic And Aromatic Isocyanate Exposure In Human Urine, Maggy Lépine, Lekha Sleno, Jacques Lesage, Sébastien Gagné

Études primaires

4,4′-Methylenediphenyldiisocyanate (MDI), toluenediisocyanate (2,4-TDI and 2,6-TDI), and 1,6′-hexamethylenediisocyanate (HDI) are all commonly used in the production of polyurethane-containing materials in different application areas. Workers exposed occupationally to these compounds may develop sensitization with the potential to lead to asthma. Isocyanates are metabolized in vivo by conjugation to macromolecules and/or by acetylation prior to being eliminated in urine. The hydrolysis of urine samples releases free amine compounds from these metabolites as biomarkers of exposure, specific to each parent isocyanate: 4,4′-methylenedianiline (MDA), toluenediamine (2,4-TDA and 2,6-TDA), and hexamethylenediamine (HDA). To address the need for a validated method that could be used for …

Internal Sorting Of Streaming Numbers Constrained By Limited Memory Size, Suluk Chaikhan

Chulalongkorn University Theses and Dissertations (Chula ETD)

Due to technological advancements, data consumption is exponentially increasing. However, the size of memory storage increases linearly. Therefore, memory storage is insufficient to store big data. Besides, all existing sorting algorithms cannot sort big data in the memory storage with limited capacity, which is much smaller than the data size. Although external sorting algorithms can sort big data, they cannot keep a sorting result on limited memory storage. This dissertation proposed two new sorting algorithms to handle the sorting issue of streaming data in limited memory storage, namely, streaming data sort, and fast streaming data sort. Both sorting algorithms are …

Synthesis Of Guanidines From Thioureas Using Photocatalyst, Trin Sae-Tan

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this study, a photo catalytic guanylation is investigated using Ru(bpy)3Cl2 as a photocatalyst under visible light irradiation. The reaction can be performed in green solvent such as ethanol and water and non-toxic K2CO3 base using 1-5% of Ru(bpy)3Cl2 under 19W white LED irradiation. Under optimized condition, this method can be applied for guanylation of various thioureas carrying a variety of functional groups with morpholine. Moreover, the amine scope includes primary and secondary amine carrying various functional groups. As the result, more than twenty examples of guanidine products can be produced in fair to excellent yields. Moreover, the reaction can …

Benzoporphyrin-Based Photosensitizing Nanocomposites For Optoelectronic Applications, Wittawat Keawsongsaeng

Chulalongkorn University Theses and Dissertations (Chula ETD)

A new series of meso-bifunctionalized benzoporphyrin derivatives bearing a p-diphenylaminophenylethynyl and a p-carboxylphenylethynyl meso-groups, and 2 p-carboxyl groups in a trans-fashion on a benzoporphyrin core is successfully synthesized and characterized by spectroscopic techniques. Impact of electron-donating diphenylamino and electron-withdrawing surface-anchoring carboxyl groups on photophysical and electrochemical properties of the target benzoporphyrins was investigated in comparison with those of their benchmark analog containing one carboxylphenylethylnyl and three phenyl meso-groups by UV-visible spectrophotometry and cyclic voltammetry. The results show that while the p-carboxylphenylethynyl group give electronic contribution to the molecules by lowering energy gap, a role of the p-diphenylaminophenylethynyl group is found …

Digilego For Peripartum Depression: A Novel Patient-Facing Digital Health Instantiation, J Rodin, C Timko, S Harris

Faculty, Staff and Student Publications

Digital health technologies offer unique opportunities to improve health outcomes for mental health conditions such as peripartum depression (PPD), a disorder that affects approximately 10-15% of women in the U.S. every year. In this paper, we present the adaption of a digital technology development framework, Digilego, in the context of PPD. Methods include mapping of the Behavior Intervention Technology (BIT) model and the Patient Engagement Framework (PEF) to translate patient needs captured through focus groups. This informs formative development and implementation of digital health features for optimal patient engagement in PPD screening and management. Results show an array ofPPD-specific Digilego …

ผลของแอโรมาติกพอลิเอสเทอร์พอลิออลต่อสมบัติของโฟมพอลิไอโซไซยานูเรตแบบแข็ง, สุวมิตร เชื่อมชิต

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้ศึกษาผลจากการใช้แอโรมาติกพอลิเอสเทอร์พอลิออลสองชนิด คือ พอลิออล A และพอลิออล B เป็นองค์ประกอบหลักต่อสมบัติของโฟมพอลิไอโซไซยานูเรตแบบแข็ง โดยพอลิออล A และพอลิออล B มีค่าหมู่ไฮดรอกซิลต่างกัน คือ 220 และ 350 mg.KOH/g ตามลำดับ เตรียมโฟมด้วยดัชนีไอโซไซยาเนตที่ 250, 280 และ 300 ศึกษาเวลาที่ใช้ในการเกิดปฏิกิริยา คือ เวลาที่สารผสมเป็นครีม เวลาที่สารผสมเป็นเจล เวลาที่โฟมหยุดฟู และเวลาที่ผิวหน้าของโฟมไม่เกาะติดกับผิวสัมผัสของวัสดุ สมบัติเชิงกายภาพและสมบัติเชิงกลของโฟมที่ศึกษามีดังนี้ คือ ความหนาแน่น การเปลี่ยนแปลงของหมู่ไอโซไซยาเนตและอัตราส่วนระหว่างหมู่ไอโซไซยานูเรตและหมู่ยูรีเทน ความต้านทานต่อแรงกดอัด สัณฐานวิทยา เสถียรภาพทางความร้อน ค่าการนำความร้อน และสมบัติการป้องกันการลามไฟ จากการศึกษาพบว่าโฟมพอลิไอโซไซยานูเรตที่เตรียมจากพอลิออล B สูตร F6 ที่ดัชนีไอโซไซยาเนต 280 มีสมบัติที่ใกล้เคียงกับเป้าหมายที่ต้องการ คือ ความหนาแน่น 35-40 kg/m3 ค่าการนำความร้อนที่น้อยกว่าหรือเท่ากับ 0.023 W/mK และผ่านการทดสอบมาตรฐานการลามไฟ DIN 4102-B2 ดังนั้น สูตรการผลิตโฟมจากพอลิออล B สูตร F6 ที่ดัชนี 280 มีความเป็นไปได้ที่จะนำไปใช้ในงานเชิงอุตสาหกรรม

Historical Trends In Air Temperature, Precipitation, And Runoff Of A Plateau Inland River Watershed In North China, Along Zhang, Ruizhong Gao, Xixi Wang, Tingxi Liu, Lijing Fang

Civil & Environmental Engineering Faculty Publications

Understanding historical trends in temperature, precipitation, and runoff is important but incomplete for developing adaptive measures to climate change to sustain fragile ecosystems in cold and arid regions, including the Balagaer River watershed on the Mongolian Plateau of northeast China. The objective of this study was to detect such trends in this watershed from 1959 to 2017. The detection was accomplished using a Mann-Kendall sudden change approach at annual and seasonal time scales. The results indicated that the abrupt changes in temperature preceded that in either runoff or precipitation; these abrupt changes occurred between 1970 and 2004. Significant (α = …

Computational Fluid Dynamics Study Of The Effects Of Secondary Flows In 90-Degree Pipe Elbow Erosion, O. Ayala, G. Rivera-Hernández, C. Knight

Engineering Technology Faculty Publications

Computational fluid dynamics (CFD) of particle-laden fluid flows through a 90-degree pipe elbow at Reynolds numbers 1,000 and 10,000 were completed; for different dimensionless elbow curvature ratios of 1.0, 1.5, and 2.5; and for particles with different Stokes numbers of 0.01, 0.1, 0.5, 1.0, 5.0, and 10.0. There were two scenarios in the study. For the first, the particles felt drag from the primary (or the axial) flow as well as from the secondary fluid flows in the elbow. For the second, the secondary fluid flow in the 90-degree bend was suppressed from the particle drag, thus the particles only …

Singlet Fission In A Hexacene Dimer: Energetics Dictate Dynamics, Samuel N. Sanders, Elango Kumarasamy, Kealan J. Fallon, Matthew Y. Sfeir, Luis M. Campos

Publications and Research

Singlet fission (SF) is an exciton multiplication process with the potential to raise the efficiency limit of single junction solar cells from 33% to up to 45%. Most chromophores generally undergo SF as solid-state crystals. However, when such molecules are covalently coupled, the dimers can be used as model systems to study fundamental photophysical dynamics where a singlet exciton splits into two triplet excitons within individual molecules. Here we report the synthesis and photophysical characterization of singlet fission of a hexacene dimer. Comparing the hexacene dimer to analogous tetracene and pentacene dimers reveals that excess exoergicity slows down singlet fission, …

Double Inclusive Small-X Gluon Production And Their Azimuthal Correlations In A Biased Ensemble, Gary Kapilevich

Publications and Research

We consider double gg → g production in the presence of a bias on the unintegrated gluon distribution of the colliding hadrons or nuclei. Such bias could be due to the selection of configurations with a greater number of gluons or higher mean transverse momentum squared or, more generally, due to a modified spectral shape of the gluon distribution in the hadrons. Hence, we consider reweighted functional averages over the stochastic ensemble of small-x gluons. We evaluate explicitly the double inclusive gluon transverse momentum spectrum in high-energy collisions, and their azimuthal correlations, for a few simple examples of biases.

"Lagrangian Disks" In M-Theory, Sebastián Franco, Sergei Gukov, Sangmin Lee, Rak-Kyeong Seong, James Sparks

Publications and Research

While the study of bordered (pseudo-)holomorphic curves with boundary on Lagrangian submanifolds has a long history, a similar problem that involves (special) Lagrangian submanifolds with boundary on complex surfaces appears to be largely overlooked in both physics and math literature. We relate this problem to geometry of coassociative submanifolds in G₂ holonomy spaces and to Spin(7) metrics on 8-manifolds with T² fibrations. As an application to physics, we propose a large class of brane models in type IIA string theory that generalize brane brick models on the one hand and 2d theories T[M₄] on …

Investigating The Time Scales Of Electromechanical Motion In Graphene Drumheads Using Pump-Probe Spectroscopy With Stm, Alana P. Gudinas

Honors Theses and Capstones

Scanning tunneling microscopy (STM) has transformed the field of condensed matter physics over the past few decades, allowing scientists to image materials at the atmomic scale, manipulate individual atoms, and probe electronic states on the surface of materials. In recent years, there have been numerous developments to introduce time-resolved measurements to STM in order to probe atomic-scale dynamic processes and combine spatial and temporal resolution. Advances like THz-STM setups achieve femtosecond resolution, but require complex external setups. All-electronic pump-probe spectroscopy for STM (directly analogous to optical pump-probe spectroscopy) has been pioneered by Loth et al., and newer applications (Natterer et …

Decreasing Uncertainty In Nuclear Magnetic Resonance Measurements Through The Application Of Pappus Chains, Ryan Williams

Honors Theses and Capstones

To make further advancements in nuclear polarization, the Dynamic Nuclear Polarization Group at the University of New Hampshire requires an accurate measurement of the polarization of their materials. Through a non-traditional method of data analysis, the uncertainty in this polarization measurement via Nuclear Magnetic Resonance (NMR) was reduced. To extract the polarization, we measure an NMR signal through the real impedance of our circuitry, whose area is proportional to the polarization. However, our signal size depends on how in-tune our circuitry is with a specific frequency, with the signal growing smaller the less in-tune it becomes. A new method of …

Quantifying Electron Precipitation In The Van Allen Radiation Belts, Timothy Raeder

Honors Theses and Capstones

The spatial and temporal distribution of high energy electron precipitation from the Van Allen radiation belts is not currently well-understood. The FIREBIRD-II mission (2015-present) and the Van Allen Probes (2012-2019) provide a unique opportunity to examine the behaviors and drivers of high energy electron precipitation. This study quantifies electron precipitation observed by FIREBIRD-II as a function of radial distance (L-shell), magnetic local time (MLT), hemisphere, and geomagnetic indices (Kp). Electron precipitation was observed to peak at L-shell 4.5-5. Regions of elevated electron precipitation were identified at L-shell 4-6 at dawn (MLT 6-9) and dusk (MLT 15-21). Hemisphere filtering indicated very …

A Content Analysis-Based Approach To Explore Simulation Verification And Identify Its Current Challenges, Christopher J. Lynch, Saikou Y. Diallo, Hamdi Kavak, Jose J. Padilla

VMASC Publications

Verification is a crucial process to facilitate the identification and removal of errors within simulations. This study explores semantic changes to the concept of simulation verification over the past six decades using a data-supported, automated content analysis approach. We collect and utilize a corpus of 4,047 peer-reviewed Modeling and Simulation (M&S) publications dealing with a wide range of studies of simulation verification from 1963 to 2015. We group the selected papers by decade of publication to provide insights and explore the corpus from four perspectives: (i) the positioning of prominent concepts across the corpus as a whole; (ii) a comparison …

Method Development For The Analysis Of Fatty Acids In Adipose Tissue Using Stir Bar Sorptive Extraction Coupled With Gas Chromatography-Mass Spectrometry, Angela Marisol Encerrado Manriquez

Open Access Theses & Dissertations

The project was aimed to develop an easy and sensitive analytical tool to study the role of fatty acids (FAs) profile in periprostatic adipose tissue (PPAT) and prostate cancer (PCa). PCa is the second leading cause of cancer-related death among American men. Although obesity has been mostly ruled out by many researchers as a risk factor for developing PCa, it has shown to be associated with PCa metastasis and progression. Periprostatic adipose tissue, which was present on 48% of prostatic surfaces, has been reported to act as energy sources for facilitating a positive microenvironment for PCa tumor progression. To understand …

Mathematical Modeling Of Microemulsification Processes, Numerical Simulations And Applications To Drug Delivery, Ogochukwu Nneka Ifeacho

Open Access Theses & Dissertations

Microemulsion systems are a great pharmaceutical tool for the delivery of formulations containing multiple hydrophilic and hydrophobic ingredients of varying physicochemical properties. These systems are gaining popularity because of its long shelf life, improved drug solubilisation capacity, easy preparation and improvement of bioavailability. Despite the advantages associated with the use of microemulsion systems in pharmaceutical industries, the major challenge impeding their use has been and continues to be the lack of understanding of these systems.

Microemulsions can be mathematically modeled by an initial boundary value problem involving a sixth order nonlinear time dependent equation. In this Thesis, we present a …

Reconciling Carbon Flux Discrepancies In A Desert Environment: Characterizing Influences Of Soil Processes Using Automated Co2 Flux Chambers, Alejandro Lara

Open Access Theses & Dissertations

Dryland ecosystems play a fundamental role in controlling the balance of carbon on a global scale. These ecosystems dominate the inter-annual variability of carbon uptake by terrestrial ecosystems, and this is driven by temperature and precipitation patterns. Despite this global importance, there are some important discrepancies that have been reported between CO2 fluxes measured with differing techniques, particularly between eddy covariance tower measurements of net ecosystem exchange (NEE) of carbon (C) versus on-the-ground methods such as chambers and biomass surveys. The discrepancy is a consequence of instrumentation and measurement technique differences; yet, its biological origins remain unknown. The goal of …

Using Machine Learning On An Imbalanced Cancer Dataset, James Ekow Arthur

Open Access Theses & Dissertations

With an estimated 1.4 million cancer diagnosis worldwide and the increasing death of cancer patients. It is prudent to investigate methods, approaches and smarter ways of predicting and diagnosing of cancer so that a holistic techniques can be used to curb or reduce false predictions , increase exact predictions and also meticulos prognosis information .

Can a feasible technique be developed for the general problem of prognosis and diagnosis of cancer be developed ?

We will show here that this problem of cancer prognosis and diagnosis can be efficiently tackled with the aid of machine learning techniques and the best, …

Development Of Software Tools And Experimental In Situ Electron Spin Resonance For Characterizing The Magnetic And Electrocatalytic Properties Of Transition Metal Chalcogenide Crystals, Jose Armando Delgado

Open Access Theses & Dissertations

Studying the magnetic properties and crystal defects of transition metal chalcogenide crystals is of paramount importance for utilizing them for next generation spintronics devices and hydrogen evolution reaction catalysts. Hydrothermally grown transition metal chalcogenide nanocrystals (MoS2, Ru2S3, Rh2S3, Co2S8) were chosen as catalysts for the hydrogen evolution reaction due to their low dimensionality and previous utilization as catalysts for hydrodesulfurization. The relationship between crystal defect sites and catalytic activity must be discerned to maximize the efficiency of hydrogen production during the hydrogen evolution reaction. ESR spectroscopy was utilized as a spin sensitive technique to study the defects and local changes …

Active Seismic Studies In Lemon Creek Valley Glacier, Juneau, Alaska: Characterization Of Subglacial Sediments To Understand Glacier Dynamics, Lucia Fernanda Gonzalez

Open Access Theses & Dissertations

Deformation and flow properties of subglacial sediments as well as the presence and volume of water at the ice/bed interface strongly influence glacier dynamics. Studies of Lemon Creek Glacier, a small temperate valley glacier in the Juneau Icefield, near Juneau, Alaska, have shown that the glacier is rapidly retreating, with a negative mass balance every year since 1957. However, the bed topography and properties of subglacial sediments at the base of Lemon Creek Glacier remained unknown until now. In this project, we process and interpret ~1-km-long NW-SE trending active-source seismic reflection profiles collected during June and July 2017 near the …

Development On Of An Unmanned Aerial Vehicle-Based Orangutan Population Assessment And Monitoring Method For The Multifunctional Landscape Of East Kalimantan, Indonesia, Muhammad Sugihono Hanggito

Open Access Theses & Dissertations

Deforestation, habitat degradation, and other forms of land conversion are threatening the existence of orangutans (Pongo spp.), the critically endangered great apes that only live on the two large Sunda-shelf islands of Sumatra and Borneo. Currently, orangutan populations persist not only within conservation or protected areas but also in other functional landscapes such as forest/acacia plantations, oil palm plantations, and mining concessions. The presence of orangutan populations in this recently modified multifunctional landscape has the potential to exacerbate human-orangutan conflict, which could further threaten orangutan populations. Lack of information about the distribution and size of orangutan populations hampers long term …

Benchmarking Machine Learning Methods For Molecular Property Prediction, Govinda Bahadur Kc

Open Access Theses & Dissertations

Machine learning (ML) techniques have been widely applied in a variety of areas ranging from pattern recognition, natural language processing, and computer games to self-driving cars, clinical diagnostics, and molecular structure prediction easing day to day life of human beings. Drug discovery is an expensive, complex, and time taking process. Currently, the pharma industry is hoping to leverage machine learning methods in expediting the drug discovery process. Molecular property prediction is one of the most important tasks in drug discovery. While developing a new drug relies on a proper understanding of molecular properties, there has been great interest in the …

Planar Motion Control Of A Cube Satellite Using Cold Gas Thrusters, Christian Lozoya

Open Access Theses & Dissertations

This Thesis presents a mathematical model developed for the computational simulation ofCubeSat movement using four thrusters that permit uniaxial translation and rotation. Arbitrary functions are fit to boundary conditions to simulate the force, acceleration, velocity, and displacement of the CubeSat along a plane. The model is used to derive a motion control algorithm assuming constant pressure and mass. A single model describes both translation and rotation. This Thesis also explores the relationship between propellant consumption and the time required to complete a displacement implied by the model.

Optimization Of Regional Scale Numerical Weather Prediction & Air Quality Model For The Paso Del Norte Region, Suhail Mahmud

Open Access Theses & Dissertations

Improvement of the Accuracy and Forecast capability of the Numerical Weather Prediction (NWP) models and Air Quality Models (AQM) are critical issues in today's scientific study of Meteorology and Air Pollution. The models for these predictions are dependent on topography, climate, initial and boundary conditions, domain size, and computational efficiency. Different techniques such as Data Assimilation, Ensemble Methods, Increased Computing Capacity to achieve higher model resolution, and Improved Physics Schemes can be used to address this problem. In this study, the NWP models, the Weather and Research Forecast (WRF), and the HYSPLIT models, were enhanced for the Paso Del Norte …

Towards The Development Of A Cohesive Design-Driven Code Quality Metrics, Omar Masmali

Open Access Theses & Dissertations

Software complexity is an indicator of expected future maintenance and sustainability. Excessive complexity suggests that software or a component of software has a design or implementation that is difficult to understand, modify, and maintain. Several complexity measures have been developed by researchers to identify and characterize degrees of complexity. Code smells are widely adopted as indicators for low code quality. Many studies have adopted fixed threshold values for code smells and other quality metrics. These fixed threshold values often ignore the uniqueness of each software system and the unique roles each component play. Moreover, these thresholds are largely fixed throughout …

Expression, Purification, And Characterization Of Recombinant Human Npas2, Brenda Moreno

Open Access Theses & Dissertations

Many living organisms have biological clocks known as circadian rhythms that control various physiological and behavioral processes, tailored with the day and night. At the cellular level, the circadian clock drives daily rhythms with a transcriptional-translational feedback loop (TTFL) established by multiple transcription factors and genes under their regulation. Circadian Locomotor Output Cycles Kaput (CLOCK) and Brain and Muscle ARNT-like protein 1 (BMAL1) are two of those transcription factors, initiating the TTFL by forming a heterodimeric complex that bind to DNA promoters. Neuronal PAS domain protein 2 (NPAS2) is a functional analog to CLOCK. Less knowledge about NPAS2, in contrast …

Discovery Of Glycan-Based Biomarkers For Cutaneous Leishmaniasis And Chagas Disease By Reversed Immunoglycomics, Alba Lucia Montoya

Open Access Theses & Dissertations

Protozoa are the causative agents of a number of diseases that affect humans and mammalian animals. Several forms of leishmaniasis are caused by different Leishmania species (Leishmania spp.), while Chagas disease (CD) is caused by the parasite Trypanosoma cruzi (T. cruzi). These members of the Trypanosomatidae family have characteristic glycoconjugates broadly distributed on their cell surfaces, which can be useful for diagnosis and follow-up of chemotherapy for the diseases.

Leishmania spp. expresses an “exotic” surface glycocalyx mainly composed of a number of glycosyl-phosphatidylinositol (GPI)-anchored proteins, a complex lipophosphoglycan (LPG) and a family of low-molecular mass glycoinositol-phospholipids (GIPLs), some of them …