Physical Sciences and Mathematics Commons^™

Factors Affecting Dimensional Precision Of Consumer 3d Printing, David D. Hernandez

International Journal of Aviation, Aeronautics, and Aerospace

This paper investigates the factors affecting dimensional precision of consumer-grade 3D printing, attempting to isolate and mitigate sources of error. The focus is on creating engineering prototypes of, tooling for, or finalized instances of mechanical devices. A specific fused deposition modeling printer – the Ultimaker 2 – is analyzed in terms of meeting precise physical dimensions, consistent shapes, and predictable surface finish. Extensive trial and error resulted in removal of several sources of bias, with square test articles exhibiting a lower-than-anticipated mean percentage error of -0.387% (SD = 0.559), a value comparable to other modern manufacturing techniques. A full …

Ionospheric Response To Infrasonic-Acoustic Waves Generated By Natural Hazard Events, M. D. Zettergren, J. B. Snively

Publications

"Recent measurements of GPS-derived total electron content (TEC) reveal acoustic wave periods of ∼1–4 min in the F region ionosphere following natural hazard events, such as earthquakes, severe weather, and volcanoes. Here we simulate the ionospheric responses to infrasonic-acoustic waves, generated by vertical accelerations at the Earth’s surface or within the lower atmosphere, using a compressible atmospheric dynamics model to perturb a multifluid ionospheric model. Response dependencies on wave source geometry and spectrum are investigated at middle, low, and equatorial latitudes. Results suggest constraints on wave amplitudes that are consistent with observations and that provide insight on the geographical variability …

Probabilistic Reasoning In Cosmology, Yann Benétreau-Dupin

Electronic Thesis and Dissertation Repository

Cosmology raises novel philosophical questions regarding the use of probabilities in inference. This work aims at identifying and assessing lines of arguments and problematic principles in probabilistic reasoning in cosmology.

The first, second, and third papers deal with the intersection of two distinct problems: accounting for selection effects, and representing ignorance or indifference in probabilistic inferences. These two problems meet in the cosmology literature when anthropic considerations are used to predict cosmological parameters by conditionalizing the distribution of, e.g., the cosmological constant on the number of observers it allows for. However, uniform probability distributions usually appealed to in such arguments …

Pre-Breakdown Arcing As A Proxy For Dc Dielectric Breakdown Testing Of Polymeric Insulators, Allen Andersen, Jr Dennison

Journal Articles

Pre-breakdown arcing is proposed as a key indicator of DC breakdown properties of polymeric dielectric materials. Voltage step-up tests were performed for films of low-density polyethylene (LDPE) at ramp rates significantly lower than is common in most studies, allowing for the observation of both breakdown and transient pre-breakdown current spikes. The distributions of the breakdowns versus applied field were compared with the more frequent pre-breakdown arcs. A strong correlation was observed for LDPE between the distribution of breakdowns in step-up tests and the distribution of pre-breakdown arcing. Pre-breakdown arcing distributions are much easier to obtain than breakdown distributions and may …

Dr. Linda French: Don’T Limit Yourself (Interview With Kelsi Singer), Linda French

Linda French

Dr. Linda French is Professor of Physics and past Chair of the Physics Department at Illinois Wesleyan University, where she has been a professor since 2002. She received her A.B. in astronomy from Indiana University and a Ph. D. in planetary astronomy from Cornell University. Her scientific research, funded by the National Science Foundation, concerns the study of the shapes and surfaces of asteroids and comets. She is a frequent guest observer at Lowell Observatory in Arizona and at Cerro Tololo Interamerican Observatory in Chile, and is often accompanied by students on these research trips.

Physical, Thermal, And Spectroscopic Characterization Of Biofield Energy Treated Methyl-2-Naphthyl Ether, Mahendra Kumar Trivedi, Alice Branton, Dahryn Trivedi, Gopal Nayak, Khemraj Bairwa, Snehasis Jana

Mahendra Kumar Trivedi

Convergence Rates And Hölder Estimates In Almost-Periodic Homogenization Of Elliptic Systems, Zhongwei Shen

Mathematics Faculty Publications

For a family of second-order elliptic systems in divergence form with rapidly oscillating, almost-periodic coefficients, we obtain estimates for approximate correctors in terms of a function that quantifies the almost periodicity of the coefficients. The results are used to investigate the problem of convergence rates. We also establish uniform Hölder estimates for the Dirichlet problem in a bounded C^1,α domain.

Effects Of Interferons And Double-Stranded Rna On Human Prostate Cancer Cell Apoptosis, Haiyan Tan, Chun Zeng, Junbo Xie, Norah J. Alghamdi, Ya Song, Hongbing Zhang, Aimin Zhou, Di Jin

Chemistry Faculty Publications

Prostate cancer is the second most commonly diagnosed cancer among men in the United States. Prostate cancer therapy is severely hampered by lack of response and development of resistance to conventional chemotherapeutic drugs in patients. Therefore, the development and discovery of new drugs have become an urgent clinical need. Interferons (IFNs), a family of pleiotropic cytokines, exert antitumor activities due to their anti-proliferative, immunomodulatory and proapoptotic functions. Here, we report that pretreatment of prostate cancer PC-3 cells with IFNs sensitized these cells to double-stranded RNAs (dsRNAs)-induced apoptosis. The enhancement effect of IFN treatment was dependent on IFN subtypes, in particular, …

First Observation Of Cp Violation In ¯B0→D(*)Cph0 Decays By A Combined Time-Dependent Analysis Of Babar And Belle Data, A. Abdesselam Et Al

Faculty Articles

We report a measurement of the time-dependent CP asymmetry of ¯B0→D(*)CPh0 decays, where the light neutral hadron h0 is a π0, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K+K−, K0Sπ0, or K0Sω. The measurement is performed combining the final data samples collected at the Υ(4S) resonance by the BABAR and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×106B¯B pairs recorded by the BABAR detector and (772±11)×106B¯B pairs recorded by the Belle detector. We measure the CP asymmetry parameters −ηfS=+0.66±0.10(stat)±0.06(syst) and …

Emergence Of Room-Temperature Ferroelectricity At Reduced Dimensions, D. A. Tenne

Physics Faculty Publications and Presentations

The enhancement of the functional properties of materials at reduced dimensions is crucial for continuous advancements in nanoelectronic applications. Here, we report that the scale reduction leads to the emergence of an important functional property – ferroelectricity, challenging the long-standing notion that ferroelectricity is inevitably suppressed at the scale of a few nanometers. A combination of theoretical calculations, electrical measurements, and structural analyses provides evidence of room-temperature ferroelectricity in strain-free epitaxial nanometer-thick films of otherwise non-ferroelectric SrTiO₃. We show that electrically-induced alignment of naturally existing polar nanoregions is responsible for the appearance of a stable net ferroelectric polarization …

Modeling, Designing, And Implementing An Ad-Hoc M-Learning Platform That Integrates Sensory Data To Support Ubiquitous Learning, Hien M. Nguyen

FIU Electronic Theses and Dissertations

Learning at any-time, at anywhere, using any mobile computing platform learning (which we refer to as “education in your palm”) empowers informal and formal education. It supports the continued creation of knowledge outside a classroom, after-school programs, community-based organizations, museums, libraries, and shopping malls with under-resourced settings. In doing so, it fosters the continued creation of a cumulative body of knowledge in informal and formal education. Anytime, anywhere, using any device computing platform learning means that students are not required to attend traditional classroom settings in order to learn. Instead, students will be able to access and share learning resources …

Differential Effects Of Munc18s On Multiple Degranulation-Relevant Trans-Snare Complexes, Hao Xu, Matthew Grant Arnold, Sushmitha Vijay Kumar

Faculty Publications

Mast cell exocytosis, which includes compound degranulation and vesicle-associated piecemeal degranulation, requires multiple Q- and R- SNAREs. It is not clear how these SNAREs pair to form functional trans-SNARE complexes and how these trans-SNARE complexes are selectively regulated for fusion. Here we undertake a comprehensive examination of the capacity of two Q-SNARE subcomplexes (syntaxin3/SNAP-23 and syntaxin4/SNAP-23) to form fusogenic trans-SNARE complexes with each of the four granule-borne R-SNAREs (VAMP2, 3, 7, 8). We report the identification of at least six distinct trans-SNARE complexes under enhanced tethering conditions: i) VAMP2/syntaxin3/SNAP-23, ii) VAMP2/syntaxin4/SNAP-23, iii) VAMP3/syntaxin3/SNAP-23, iv) VAMP3/syntaxin4/SNAP-23, v) VAMP8/syntaxin3/SNAP-23, and vi) VAMP8/syntaxin4/SNAP-23. …

Geology & Geography News, Georgia Southern University

School of Earth, Environment, and Sustainability News (2013-2021)

• Georgia Southern Faculty Research Receives National Attention

Cosm News, Georgia Southern University

College of Science and Mathematics News (2012-2019)

• Georgia Southern Faculty Research Receives National Attention

Molecular Helices As Electron Acceptors In High-Performance Bulk Heterojunction Solar Cells, Yu Zhong, M. Tuan Trinh, Rongsheng Chen, Geoffrey E. Purdum, Petr P. Khlyabich, Melda Sezen, Seokjoon Oh, Haiming Zhu, Brandon Fowler, Boyuan Zhang, Wei Wang, Chang-Yong Nam, Matthew Y. Sfeir, Charles T. Black, Michael L. Steigerwald, Yueh-Lin Loo, Fay Ng, X.-Y. Zhu, Colin Nuckolls

Publications and Research

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed …

Antimalarial Drug Discovery Using Triazoles To Overcome Chloroquine Resistance, Elias Sibhatu Tesfaselassie

Dissertations and Theses

Malaria is considered as one of the most prevalent and debilitating diseases affecting humans. Plasmodium falciparum is the most virulent form of the parasite which developed resistance to several antimalarial drugs. Chloroquine is one of the most successful antimalarials developed that is safe, effective, and cheap. However, its use has been limited due to the emergence of drug resistance. Click chemistry, particularly, the copper(I)-catalyzed reaction between azides and alkynes has shown to have a cutting-edge advantage in medicinal chemistry by its reliability, selectivity and biocompatibility.

Triazole-based antimalarials were synthesized via copper(I)-catalyzed alkyne-azide cycloaddition reaction by modifying the aliphatic chains terminal …

The Firece Green Fire: Vol. 6 Issue 2, Wofford College Environmental Studies Program

The Fierce Green Fire

No abstract provided.

The Effect Of Foam Rolling Duration On Hamstring Range Of Motion, Grace Couture, Dustin Karlik, Stephen C. Glass, Brian M. Hatzel

Funded Articles

Musculoskeletal health benefits from flexibility training and maintaining a functional, or sport specific, range of motion is important to one’s overall fitness. Commercial foam rollers are commonly used in gyms, therapy clinics and homes, yet data are lacking on the optimal rolling duration and effect on range of motion.

Comprehensive Analysis Of Emerging New Psychoactive Substances By Ion Mobility Spectrometry And Mass Spectrometry, Seongshin Gwak

FIU Electronic Theses and Dissertations

In the new era of drug abuse, the proliferation of new psychoactive substances (NPS), commonly referred to as designer drugs or legal highs, has been a global concern. These substances are produced to circumvent current legislation for controlled substances with minor modifications in their chemical structure. Although many efforts have been made previously, the characterization of such substances are still challenging because of (1) the continual emergence of newly identified substances, (2) the lack of a universal screening test for NPS that are structurally similar to each other, and (3) the complex and time-consuming chromatographic techniques currently used. Therefore, it …

Adaptive Automation Design And Implementation, Jason M. Bindewald

Theses and Dissertations

Automations allow us to reduce the need for humans in certain environments, such as auto-pilot features on unmanned aerial vehicles. However, some situations still require human intervention. Adaptive automation is a research field that enables computer systems to adjust the amount of automation by taking over tasks from or giving tasks back to the user. This research develops processes and insights for adaptive automation designers to take theoretical adaptive automation ideas and develop them into real-world adaptive automation system. These allow developers to design better automation systems that recognize the limits of computers systems, enabling better designs for systems in …

A System-Level Throughput Model For Quantum Key Distribution, Robert C. Cernera

Theses and Dissertations

Quantum Key Distribution (QKD) is an innovative technology which exploits the laws of quantum mechanics to generate and distribute shared secret keying material. QKD systems generate and distribute key by progressing through a number of distinct phases, typically in a serial manner. The purpose of this research is to identify these phases, their relationships to each other, as well as their relationship to time, memory space, computational requirements, and hardware resources. A mathematical model is developed which enables the study of critical system parameters, identifies and demonstrates potential bottlenecks that affect the overall key generation rate of serial implementations, and …

Modeling Radiation Effectiveness For Inactivation Of Bacillus Spores, Emily A. Knight

Theses and Dissertations

This research models and analyzes the inactivation of Bacillus spores following a radiation exposure and the process enacted by the Bacillus spore to repair the resulting damage. Irradiation of a spore and the medium surrounding the spore induces chemical reactions that produce reactive oxygen species (ROS). This research will consider the reaction- diffusion of these ROS throughout the spore. These ROS can react with the spore's DNA and enzymes to degrade them to such an extent that the DNA cannot be repaired or replicated, thus causing spore death. In order to survive a dose of radiation, a spore must repair …

Testing The Adequacy Of A Semi-Markov Process, Richard S. Seymour

Theses and Dissertations

Due to the versatility of its structure, the semi-Markov process is a powerful modeling tool used to describe complex systems. Though similar in structure to continuous time Markov chains, semi-Markov processes allow for any transition time distribution which enables these processes to t a wider range of problems than the continuous time Markov chain. While semi-Markov processes have been applied in fields as varied as biostatistics and finance, there does not exist a theoretically-based, systematic method to determine if a semi-Markov process accurately fits the underlying data used to create the model. In fields such as regression and analysis of …

Experimental And Theoretical Basis For A Closed-Form Spectral Brdf Model, Samuel D. Butler

Theses and Dissertations

The microfacet class of BRDF models is frequently used to calculate optical scatter from realistic surfaces using geometric optics, but has the disadvantage of not being able to consider wavelength dependence. This dissertation works toward development of a closed-form approximation to the BRDF that is suitable for hyperspectral remote sensing by presenting measured BRDF data of 12 different materials at four different incident angles and up to seven different wavelengths between 3.39 and 10.6 micrometer. The data was intended to be fit to various microfacet BRDF models to determine an appropriate form of the wavelength scaling. However, when fitting the …

How To Make Business Processes "Socialize"?, Zakaria Maamar, Noura Faci, Ejub Kajan, Sherif Sakr, Mohamed Boukhebouze, Ahmed Barnawi

All Works

This paper presents an approach that builds upon social computing principles to make business processes; "socialize". First the approach identifies the main components of a business process that are task, person, and; machine. A task is a work unit that forms with other tasks a business process and that a person and/ormachine; execute. Afterwards the approach enriches a business process with details captured from the (execution; and social) relations that connect tasks together, persons together, and machines together. While execution; relations are widely reported in the literature, there is a growing interest in studying the role of social; relations in …

Temperature Dependent Rubidium-Helium Line Shapes And Fine Structure Mixing Rates, Wooddy S. Miller

Theses and Dissertations

Diode Pumped Alkali Lasers (DPALs) are a new type of laser that uses alkali metal vapor as a gain medium and a buffer gas to control the line shape and kinetics. While these systems were first demonstrated in 2003 [48] they have just recently been scaled to the kilowatt power levels in 2012 [18]. To achieve these powers, the design of the gain cell relied on a set of incomplete line shape and kinetic data. The current focus areas of DPAL research are the continued power scaling of the systems and basic science research into the rates involved within the …

An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena

Theses and Dissertations

The Global Positioning System (GPS) developed and operated by the United States Air Force (USAF) provides a way for users to determine position, navigation and timing (PNT). GPS provides an extraordinary capability that has become instrumental in all aspects of our day to day lives. As new technologies such as automated vehicles and unmanned aircraft continue to be developed, a reliable back up to GPS is required to ensure the PNT data generated in these systems is accurate. This research studies a potential architecture for deploying a nationwide network of ground based pseudolites that would act to supplement and backup …

Dynamic Studies Of Guest Molecules In Metal-Organic Frameworks Using Solid-State Nmr, Yuanjun Lu

Electronic Thesis and Dissertation Repository

Metal-organic frameworks (MOFs) are a new class of porous materials that possess large three-dimensional voids in their structures. In this work, Solid-state NMR (SSNMR) is used to examine the dynamics of guest molecules at various temperatures in MOFs that possess different types of channels. Chapter 2 introduces the ¹³CO₂ adsorption behavior in α-Mg formate studied by ¹³C SSNMR in conjunction with molecular dynamic simulation. ¹H-¹³C cross polarization technique has successfully determined the adsorption sites of CO₂ in this type of MOF to be hydrogen atoms. The dynamic analysis detects that at low temperature, …

Field Observations And Novel Methodologies For Carbon System Assessments In Coastal Waters, Bo Yang

USF Tampa Graduate Theses and Dissertations

Coastal zones receive massive terrestrial inputs of nutrients and organic matter, and play an important role in biogeochemical cycles. The interactions of river inputs, ocean currents, atmospheric exchanges, anthropogenic influences, and biologically active ecosystems make CO₂ system studies in coastal waters highly challenging. This work focuses on improving our understanding of the CO₂ system in coastal waters through (1) development of a new methodology for measurements of CO₂ system parameters in the field; (2) observations of large spatial and temporal CO₂ system variations in coastal waters; and (3) characterization of the influence of organics on CO …

Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center And Reaction Center Plus Light Harvesting Complexes, Houman Yaghoubi

USF Tampa Graduate Theses and Dissertations

Harvesting solar energy can potentially be a promising solution to the energy crisis now and in the future. However, material and processing costs continue to be the most important limitations for the commercial devices. A key solution to these problems might lie within the development of bio-hybrid solar cells that seeks to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. The bio-photoelectrochemical cell technologies exploit biomimetic means of energy conversion by utilizing plant-derived photosystems which can be inexpensive and ultimately the most sustainable alternative. Plants and photosynthetic …