Digital Commons Network^™

Flow Reorganization In An Anthropogenically Modified Tidal Channel Network: An Example From The Southwestern Ganges-Brahmaputra-Meghna Delta, R. L. Bain, Rip P. Hale, S. L. Goodbred

OES Faculty Publications

We examine variations in discharge exchange between two parallel, 1‐ to 2‐km‐wide tidal channels (the Shibsa and the Pussur) in southwestern Bangladesh over spring‐neap, and historical timescales. Our objective is to evaluate how large‐scale, interconnected tidal channel networks respond to anthropogenic perturbation. The study area spans the boundary between the pristine Sundarbans Reserved Forest, where regular inundation of the intertidal platform maintains the fluvially abandoned delta plain, and the anthropogenically modified region to the north, where earthen embankments sequester large areas of formerly intertidal landscape. Estimates of tidal response to the embankment‐driven reduction in basin volume, and hence tidal prism, …

Internal Waves Influence The Thermal And Nutrient Environment On A Shallow Coral Reef, Emma C. Reid, Thomas M. Decarlo, Anne L. Cohen, George T.F. Wong, Steven J. Lentz, Aryan Safaie, Austin Hall, Kristen A. Davis

OES Faculty Publications

Internal waves can influence water properties in coastal ecosystems through the shoreward transport and mixing of subthermocline water into the nearshore region. In June 2014, a field experiment was conducted at Dongsha Atoll in the northern South China Sea to study the impact of internal waves on a coral reef. Instrumentation included a distributed temperature sensing system, which resolved spatially and temporally continuous temperature measurements over a 4‐km cross‐reef section from the lagoon to 50‐m depth on the fore reef. Our observations show that during summer, internal waves shoaling on the shallow atoll regularly transport cold, nutrient‐rich water shoreward, altering …

Dinitrogen Fixation Across Physico-Chemical Gradients Of The Eastern Tropical North Pacific Oxygen Deficient Zone, C. R. Selden, M. R. Mulholland, P.W. Bernhardt, B. Widner, A. Macías-Tapia, Q. Ji, A. Jayakumar

OES Faculty Publications

The Eastern Tropical North Pacific Ocean hosts one of the world's largest oceanic oxygen deficient zones (ODZs). Hot spots for reactive nitrogen (N_r) removal processes, ODZs generate conditions proposed to promote N_r inputs via dinitrogen (N₂) fixation. In this study, we quantified N₂ fixation rates by ¹⁵N tracer bioassay across oxygen, nutrient, and light gradients within and adjacent to the ODZ. Within subeuphotic oxygen‐deplete waters, N₂ fixation was largely undetectable; however, addition of dissolved organic carbon stimulated N₂ fixation in suboxic (μmol/kg O₂) waters, suggesting that diazotroph communities are …

Bomb Radiocarbon Age Validation For The Long-Lived, Unexploited Arctic Fish Species Coregonus Clupeaformis, John M. Casselman, Cynthia M. Jones, Steven E. Campana

OES Faculty Publications

The growth rates of freshwater fish in the Arctic would be expected to be very low, but some previous studies of lake whitefish (Coregonus clupeaformis) have reported relatively rapid growth and longevity estimates of less than 15 years. We used bomb radiocarbon chronologies to validate an ageing method based on otolith sections for lake whitefish in both an unexploited Arctic lake (MacAlpine Lake; longevity 50 years) and a lightly exploited temperate population (Lake Simcoe; longevity 49 years). Our results confirm previous suggestions that other ageing methods can seriously underestimate lake whitefish age after ~5–8 years. A Chapman–Robson estimate …

Spatial Structuring And Life History Connectivity Of Antarctic Silverfish Along The Southern Continental Shelf Of The Weddell Sea, Jilda Alicia Caccavo, Julian R. Ashford, Svenja Ryan, Chiara Papetti, Michael Schröder, Lorenzo Zane

OES Faculty Publications

A multi-disciplinary approach was employed to examine a physical-biological population hypothesis for a critical forage species, the Antarctic silverfish Pleuragramma antarctica. Caccavo et al. (2018; Sci Rep 8:17856) had shown strong gene flow along the westward Antarctic Slope Current, in addition to spatially recurring length modes that provided evidence for episodic connectivity. In this paper, otolith nucleus chemistry from a subset of fish collected in the southern Weddell Sea as part of a hydrographic survey of the Filchner Trough system was used to test between connectivity scenarios. Nucleus chemistry, which reflects environmental exposure during early life, showed significant …

Synthesis And Bioactivity Of Sulfide Derivatives Containing 1,3,4-Oxadiazole And Pyridine, Gang Yu, Shunhong Chen, Feng He, Dexia Luo, Yu Zhang, Jian Wu

Turkish Journal of Chemistry

A series of novel sulfide derivatives containing 1,3,4-oxadiazole and pyridine were synthesized, characterized, and tested for their antibacterial activity against tobacco bacterial wilt and rice bacterial blight and for insecticidal activity toward diamondback moth. The results showed that some compounds had good insecticidal and bactericidal activity, e.g., the activities of compounds 6e and 6g-6j toward tobacco bacterial wilt were much better than those of commercial thiodiazole-copper, and some of the synthesized compounds possessed good insecticidal activity against Plutella xylostella. Compounds 6d, 6h, 6j, 6l, 6p, 6r, and 6p displayed over 93% activity at 500 mg L$^{-1}$.

Targeting Human Telomeric Dna With Azacyanines, Ayça Küçükakdağ Doğu, Özgül Persi̇l Çeti̇nkol

Turkish Journal of Chemistry

Small molecules targeting telomeric DNA or its interactions with telomerase have been an active area of cancer research. In the present study, we investigated the interactions of six benzimidazole compounds, called azacyanines, differing from each other in alkyl chain length and branching in the benzimidazole ring (azamethyl, azaethyl, azapropyl, azaisopropyl, azabutyl, and azaisobutyl) with human telomeric DNA (tel24) in 1:1 and 1:6 ratio (tel24:azacyanine) using UV-Vis, circular dichroism (CD), and fluorescence spectroscopy. All the compounds were binding to tel24 as indicated by the formation of the weak induced CD band between 320 nm and 360 nm. A substantial red shift …

Optical Characterization Of Salt-Induced Swelling Behavior Of Poly($N$-Isopropylacrylamide) Terpolymer Hydrogel Layers, İlke Anaç, Anil Bozdoğan

Turkish Journal of Chemistry

This study reports for the first time the effect of different sodium halide salts (NaClO$_{4}$, NaI, and Na$_{2}$CO$_{3})$ in the low concentration range (in the range of 10$^{-7}$-1 M) on the swelling behavior of photo-crosslinked, surface-immobilized poly($N$-isopropyl acrylamide) (PNIPAAm) terpolymer layers. PNIPAAm terpolymer (consisting of $N$-isopropylacrylamide, methacrylic acid, and 4-methacryloxybenzophenone) was synthesized via free radical polymerization. The PNIPAAm terpolymer layers were prepared on gold substrates via spin coating and crosslinked and surface attached via UV radiation. The swelling behavior of the layers in monovalent (NaClO$_{4}$ and NaI) and divalent (Na$_{2}$CO$_{3})$ solutions was monitored by surface plasmon/optical waveguide spectroscopy. The terpolymer …

Molecular Dynamics Simulations Of Adsorption Of Long Pyrene-Peg Chains On A Thin Carbon Nanotube, Peli̇n Deni̇z Akkuş, Ayşe Özge Kürkçüoğlu Levi̇tas

Turkish Journal of Chemistry

Carbon nanotubes have emerged as highly promising theranostic agents due to their unique structural/physical features, high surface area, and high drug-loading capacity. The high cytotoxicity of carbon nanotubes can be eliminated by noncovalent coating using hydrophilic polymers. We investigated the adsorption of long pyrene functionalized polyethylene glycol (PEG) chains, PEG$_{2000}$ and PEG$_{5000}$, on a single-walled carbon nanotube (SWNT) from a crowded solution. Full-atom molecular dynamics simulations in explicit water were used to mimic the experimental conditions of noncovalent PEGylation with a stoichiometry of one SWNT to ten pyrene-PEG. Although the diffusional behavior of the pyrene molecules still attached to the …

Acetyl- And Butyrylcholinesterase Inhibitory Activity Of Selected Photochemically Synthesized Polycycles, Ivana Sagud, Irena Skoric, Dragana Vuk, Ana Ratkovic, Franko Burcul

Turkish Journal of Chemistry

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the main cause of dementia in the elderly population. Since the treatment of AD has been associated with the activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), their inhibitors remain the main focus of AD investigations. In this study we evaluated cholinesterase inhibitory activity of 14 bicyclo[3.2.1]octene/octadiene derivatives and naturally occurring sesquiterpene alcohol cedrol. These 14 compounds have been efficiently and ecologically prepared by a photochemical approach in batch photochemical reactors. Various compounds with the bicyclo[3.2.1]octene skeleton have already been successfully evaluated for treatment of central nervous system disorders and AD. Among …

Reduced Graphene Oxide Supported Tin Oxide-Boron Oxide Flexible Paper Anodes For Li-Ion Batteries, Hi̇lal Köse, Şeyma Dombaycioğlu, Hatem Akbulut, Ali̇ Osman Aydin

Turkish Journal of Chemistry

Freestanding tin oxide-boron oxide/reduced graphene oxide (SnO$_{2}$-B$_{2}$O$_{3}$/rGO) nanocomposite anode was produced for Li-ion cells. This binder-free flexible paper anode structure was fabricated by combining SnO$_{2}$-B$_{2}$O$_{3}$ composite and graphene oxide which were synthesized through the sol-gel method and Hummers' method, respectively. Field emission gun scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectrometer, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction were utilized to characterize anode materials. The Williamson-Hall (W-H) analysis was applied using XRD data to determine crystal size and strain of the lattice. Electrochemical tests, cyclic voltammetry, and electrochemical impedance spectroscopy measurements were performed to determine …

Anticancer And Antiangiogenesis Activities Of Novel Synthesized 2-Substituted Benzimidazoles Molecules, Adem Güner, Eli̇fsu Polatli, Tamer Akkan, Hakan Bektaş, Canan Albay

Turkish Journal of Chemistry

In this study, novel 2-substituted benzimidazoles molecules having triazole, thiadiazole, and oxadiazole rings were synthesized and were evaluated by anticancer, antioxidant/oxidant status, genotoxicity, and antiangiogenesis assays. Anticancer activity of the compounds was determined by MTT (0.5, 5, and 50 $\mu $g/mL) and lactate dehydrogenase (LDH) release assays against human prostate and breast cancer cells. Oxidative status of cells was elicited by total oxidative stress and total antioxidant capacity methods. Chick chorioallantoic membrane assay was used to evaluate the antiangiogenic activity. Genotoxicity was evaluated by the sister chromatid exchange (SCE) and micronucleus (MN) tests in lymphocyte cultured human blood. Our results …

Ionic Liquid-Based Graphene Oxide-Coated Fiber For Headspace-Solid Phase Microextraction Of Polycyclic Aromatic Hydrocarbons In Water Samples, Peli̇n Erdem, Paniz Tashakkori, Melek Merdi̇van, Serap Seyhan Bozkurt

Turkish Journal of Chemistry

Ionic liquid (IL) containing amino and vinyl terminated imidazolium cation and bis[(trifluoromethyl)sulfonyl] imide anion-functionalized graphene oxide (GO) coating material was prepared and coated on a stainless steel wire by a sol-gel technique for headspace-solid phase microextraction (HS-SPME). Its extraction performance was checked by HS-SPME of polycyclic aromatic hydrocarbons (PAHs) coupled to gas chromatography with mass spectrometry (GC-MS). The extraction capability of the IL-functionalized GO-coated fiber was comparable with that of the commercial fibers of polydimethylsiloxane (PDMS) and polydimethylsiloxane/carboxen/divinylbenzene (PDMS/CAR/DVB). Under the optimized conditions, such as extraction temperature, extraction time, and salting-out, the proposed HS-SPME-GC-MS method presented a wide working range …

Glucose Oxidase Immobilized Biofuel Cell Flow Channel Geometry Analysis By Cfd Simulations, Sali̇h Obut, Tahsi̇n Bahar

Turkish Journal of Chemistry

Glucose oxidase was covalently immobilized to a porous electrode, which was developed by using ferrocene functionalized polyethyleneimine, multiwall carbon nanotubes, and carbon cloth for biofuel cell applications in our recent studies. The kinetics parameters (i.e. k$_{M}$, V$_{max})$ and other parameters required for the modeling study were determined experimentally. Fuel cell flow channel geometry was analyzed by a computational fluid dynamics modeling approach. Substrate flow rate and mass transfer for each proposed channel type were considered in the simulations. The results showed that serpentine type flow channels are advantageous over pin type or parallel flow channels to acquire sufficient performance from …

Synthesis And Characterization Of Novel Mussel-Inspired Benzoxazines By Thiol-Benzoxazine Chemistry, Mustafa Arslan

Turkish Journal of Chemistry

A catechol-based benzoxazine copolymer is reported via a new approach using an oxazine-thiol reaction. The main chain benzoxazine precursor was obtained via the classic benzoxazine synthesis methodology using the raw chemicals catechol, formaldehyde, and 4,7,10-trioxa-1,13-tridecanediamine. The countercomponent was synthesized from poly(ethylene glycol) methyl ether via the Fischer esterification reaction. The obtained reactive catechol-based benzoxazine was then reacted in mild conditions with polymeric thiol precursor to obtain a copolymer structure. The precursors and the resulting structure were characterized by thermal and spectral analyses using DSC, TGA, FT-IR,$^{\, 1}$H NMR, and GPC. Film formation was also demonstrated with unreacted oxazine ring units …

Stability Improvement By Crosslinking Of Previously Immobilized Glucose Oxidase On Carbon Nanotube-Based Bioanode, Tahsi̇n Bahar

Turkish Journal of Chemistry

Bioanode stability with glucose oxidase was enhanced significantly by covalent crosslinking without substantial enzymatic activity and affinity loss. Initially, glucose oxidase was immobilized by aldehyde groups on the electrode that was developed using ferrocenecarboxaldehyde, polyethyleneimine, multiwall carbon nanotubes, and carbon cloth for biofuel cell applications. The glucose oxidase half-life was extended by more than 4 times, from 27.2 to 124.7 h, after the electrode was crosslinked. Enzymatic kinetic parameters were determined for the crosslinked enzyme and they were compared to the noncrosslinked immobilized enzyme parameters on the electrode. The apparent substrate affinity of the crosslinked enzyme electrode was decreased (i.e. …

Teaching Hidden History: A Case Study Of Dialogic Scaffolding In A Hybrid Graduate Course, Amy K. Swan, Nathan M. Sleeter, Kelly Schrum

International Journal for the Scholarship of Teaching & Learning

Using an expanded version of Alexander’s (2008) theory of dialogic teaching developed by Rojas-Drummond, Torreblanca, Pedraza, Vélez, and Guzmán (2013), this case study explored how instructors and students in a hybrid graduate course engaged in the process of dialogic teaching and learning (DTL). In particular, we examined the ways in which scaffolding strategies used in the course supported inquiry-based learning. Our findings suggest that instructors and students engaged in all five dimensions of DTL as defined by Rojas-Drummond et al. (2013), and illuminate the ways in which scaffolding can facilitate inquiry-based learning in interdisciplinary instructional settings.

Georgia Journal Of College Student Affairs, Georgia College Personnel Association (Gcpa)

Journal of Higher Education & Student Affairs

Complete issue for volume 35, number 1 (Fall 2019).

Indoor Positioning Using Multiple Signal Sources (Modes), Vishal Chummar Perekadan

Theses

Computation of accurate indoor positioning information is important in several application areas like mobile robotics, navigation, virtual reality and ubiquitous computing. In spite of its importance we still do not have an indoor positioning system equivalent to the Global Positioning System~(GPS), which is the standard for large scale outdoor positioning, but is unreliable or unavailable in indoor environments. In this work, we present a multi-source radio frequency(RF) based system for automatic indoor positioning using the received signal strength (RSS) and demonstrate its efficacy by simultaneously using broadcast FM radio & GSM signals for position estimation. This method is data driven …

A Geometric Approach For Global Stability Of A Predator-Prey Model With An Ivlev-Type Functional Response, Soniykha Dhevi Murukan

Theses

In this paper, using a geometric approach, we study the global stability for a class of predator-prey model with an Ivlev-type functional response. We obtained this by sufficient conditions on the systems parameters, which guarantee that the positive equilibrium point of the presented system is globally asymptotically stable. Our results improve the previously obtained results from Xiaoqin Wang and Huihai Ma [1]. We conjecture that the local and global stability of the positive equilibrium are equivalent. Our conjecture is supported by numerical simulations. The theoretical proof will be our future research effort.

Complexity Assessment Using Systems Modelling Language Models, Victor Emmanuel Pierre Lopez

Theses

A complexity metric was proposed for the quantification of system complexity using information about the composition of a system and its interactions depicted in a System Modelling Language (SysML) model. The proposed metric was adapted from the complexity metric developed by Sinha and Suh for design structure matrix (DSM) applications, and was modified to allow the proposed metric to be applied at different decomposition levels and to accommodate the inclusion of external interactions. The metric was applied to three case studies: an aircraft engine, a Mars lander, and a spacecraft thermal control system. The proposed metric attributed a higher amount …

Effects Of Non-Uniform Temperature Distribution On Degradation Of Lithium-Ion Batteries, Gabriel M. Cavalheiro

Theses

The effects of non-uniform temperature distribution on degradation of Lithium-ion (Li-ion) batteries are investigated in this study. A Li-ion battery stack consisting of five 3 Ampere hour (Ah) pouch cells connected in parallel was tested for 2215 cycles and compared with a single baseline cell. The behaviors of temperature distribution, degradation, and current distribution of the stack were characterized and discussed. Results supported the hypothesis that non-uniform temperature distribution causes non-uniform and accelerated degradation. All cells in the stack experienced higher temperature rise and degraded faster than the baseline cell. In particular, capacity retention of the middle cell in the …

Charging Management Of Plug-In Electric Vehicles Applying Monte Carlo Markov Chain And Quantum-Inspired Optimization Algorithm, Mehdi Rahmani-Andebili

Theses

The transportation sector is responsible for almost one-third of energy consumption and greenhouse gas emissions. To mitigate the above-mentioned issues, plug-in electric vehicles (PEV) are being encouraged by governments and environmentalists to replace internal combustion engine (ICE) vehicles, since PEVs can be charged by renewable energy sources. Based on the predictions performed by the research organizations, the PEV sales will surpass the ICE car sales in the next two decades. Thus, the PEV drivers will consume a considerable portion of electricity soon. However, the uncontrolled and simultaneous charging of PEVs can put the power system under stress. Therefore, the charging …

Seeding Hydrogen Propellant In Nuclear Thermal Propulsion Engines, Daria Nikitaeva

Theses

Using the NASA Design Reference Architecture, Nuclear Thermal Propulsion engine and Mars transfer vehicle models were developed to numerically examine the effects of adding heavy noble gases into the hydrogen propellant stream (seeding) on round trip transit times (baseline of 357 days). Seeded hydrogen, up to maximum seed mass concentration (MSMC) 55.85%, increased engine and vehicle performance by reducing pressure losses, decreasing reactor power, and increasing the overall change in velocity while assuming constant vehicle volume and dry mass. The tradeoff was lowered specific impulse and increased net propellant mass, resulting in increased vehicle wetted mass. Vehicle performance increased at …

A Numerical Model Of The High-Temperature Supercritical Tube Flow Produced By The Ntrees Nuclear Thermal Propulsion Test Facility, Connor T. Pierce

Theses

No abstract provided.

Stabilize Chaotic Flows In A Coupled Triple-Loop Thermosyphon System, Haley N. Anderson

Honors College Theses

This study addresses the control of chaotic dynamic systems represented by three coupled Lorenz systems. In application, Lorenz systems are commonly used to describe the one-dimensional motion of fluids in a tube when heated below and cooled above. This system, in particular, reflects the fluid motion in a coupled triple-loop thermosyphon system. The goal is to derive a system of nonlinear differential equations to help us study various flow patterns governed by such a high-dimensional nonlinear model numerically. Once the driving parameter (Rayleigh number) values are identified corresponding to the chaotic regime, a minimal number of proportional controllers are designed …

Honors @ Georgia Southern, University Honors Program Students And Staff, Georgia Southern University

Honors College: News & Publications (2008-2020)

• Emily Pressler Selected for Fulbright
• Katherine Barrs Recieves the Barry Goldwater Scholarship
• Carolynn Nixon is Named a Rangel Fellow
• 2018-2019 Graduates

Fostering Students' Civic Skills: Education For Sustainable Democracy, Atakan Ata

Georgia Educational Researcher

This qualitative study explored factors that supported teachers in their efforts to promote students’ critiquing, communicating, and collaborating skills. Despite the various challenges that public schools face today, they are most likely the very institutions to play a critical role in individuals’ civic skills development. Individual in-depth interviews were the primary method used to understand the participants’ perspectives on instruction and the factors that foster students’ civic skills. Factors that supported the participants in their efforts to promote civic skills among their students were found to be teacher collaboration, planning, and teacher motivation. Details and the implications of the findings …

When Human Cognitive Modeling Meets Pins: User-Independent Inter-Keystroke Timing Attacks, Ximing Liu, Yingjiu Li, Robert H. Deng, Bing Chang, Shujun Li

Research Collection School Of Computing and Information Systems

This paper proposes the first user-independent inter-keystroke timing attacks on PINs. Our attack method is based on an inter-keystroke timing dictionary built from a human cognitive model whose parameters can be determined by a small amount of training data on any users (not necessarily the target victims). Our attacks can thus be potentially launched on a large scale in real-world settings. We investigate inter-keystroke timing attacks in different online attack settings and evaluate their performance on PINs at different strength levels. Our experimental results show that the proposed attack performs significantly better than random guessing attacks. We further demonstrate that …

Global Inference For Aspect And Opinion Terms Co-Extraction Based On Multi-Task Neural Networks, Jianfei Yu, Jing Jiang, Rui Xia

Research Collection School Of Computing and Information Systems

Extracting aspect terms and opinion terms are two fundamental tasks in opinion mining. The recent success of deep learning has inspired various neural network architectures, which have been shown to achieve highly competitive performance in these two tasks. However, most existing methods fail to explicitly consider the syntactic relations among aspect terms and opinion terms, which may lead to the inconsistencies between the model predictions and the syntactic constraints. To this end, we first apply a multi-task learning framework to implicitly capture the relations between the two tasks, and then propose a global inference method by explicitly modelling several syntactic …