Digital Commons Network^™

Methodologies For Improvement Of Metal Fatigue Life, Ali Haghshenas

LSU Doctoral Dissertations

A methodology is proposed to identify the onset of crack initiation that utilizes the material damping. The damping is measured using the impulse excitation technique (IET). The damping is also used to correlate fatigue life of additively manufactured (AM) specimens to their damping characteristics. Results reveal that the damping value is inversely proportional to the fatigue life of the specimens.

To detect the damage accumulation and crack initiation in metals due to cyclic loading, another methodology based on the measurement of the surface roughness parameters is introduced. Results presented reveal that the evolution of the surface roughness parameters can be …

The Roles Of Host Species, Geographic Scale And Environmental Stressors In Shaping The Composition Of Coral Microbiomes, Alicia Marie Riegel Parker

LSU Doctoral Dissertations

Reef-building corals are long-lived and may take many centuries to adapt, making them especially susceptible to climate change. However, corals host microbial symbionts that can change quickly, potentially speeding acclimation. My dissertation aimed to determine the degree of coevolution and flexibility between corals and their microbiomes among hosts, across space, and in response to stress.

Microbial communities are usually surveyed by sequencing the 16S rRNA gene, however the PCR primers used also amplify coral DNA, thereby limiting prokaryotic read coverage. To mitigate this contamination, I designed a peptide nucleic acid clamp that increased the recovery of bacterial reads by 2-11x …

Exploring The Fmn Binding Site In The Mitochondrial Outer Membrane Protein Mitoneet, Homyra Tasnim, Aaron P. Landry, Chelsey R. Fontenot, Huangen Ding

Faculty Publications

© 2020 Elsevier Inc. MitoNEET is a mitochondrial outer membrane protein that hosts a redox active [2Fe-2S] cluster in the C-terminal cytosolic domain. Increasing evidence has shown that mitoNEET has an essential role in regulating energy metabolism in human cells. Previously, we reported that the [2Fe-2S] clusters in mitoNEET can be reduced by the reduced flavin mononucleotide (FMNH2) and oxidized by oxygen or ubiquinone-2, suggesting that mitoNEET may act as a novel redox enzyme catalyzing electron transfer from FMNH2 to oxygen or ubiquinone. Here, we explore the FMN binding site in mitoNEET by using FMN analogs and find that lumiflavin, …

Erratum: Searches For Gravitational Waves From Known Pulsars At Two Harmonics In 2015-2017 Ligo Data (Astrophysical Journal (2019) 879 (10) Doi: 10.3847/1538-4357/Ab20cb), B. P. Abbott, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, C. Adams, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, G. Allen, A. Allocca, M. A. Aloy, P. A. Altin, A. Amato, A. Ananyeva, S. B. Anderson, W. G. Anderson, S. V. Angelova, S. Antier, S. Appert, K. Arai, M. C. Araya, J. S. Areeda, M. Arène, N. Arnaud

Faculty Publications

Two analysis errors have been identified that affect the results for a handful of the high-value pulsars given in Table 1 of Abbott et al. (2019). One affects the Bayesian analysis for the five pulsars that glitched during the analysis period, and the other affects the 5n-vector analysis for J0711-6830. Updated results after correcting the errors are shown in Table 1, which now supersedes the results given for those pulsars in Table 1 of Abbott et al. (2019). Updated versions of figures can be seen in Figures 1-4. Bayesian analysis.-For the glitching pulsars, the signal phase evolution caused by the …

A Cryogenic Silicon Interferometer For Gravitational-Wave Detection, R. X. Adhikari, K. Arai, A. F. Brooks, C. Wipf, O. Aguiar, P. Altin, B. Barr, L. Barsotti, R. Bassiri, A. Bell, G. Billingsley, R. Birney, D. Blair, E. Bonilla, J. Briggs, D. D. Brown, R. Byer, H. Cao, M. Constancio, S. Cooper, T. Corbitt, D. Coyne, A. Cumming, E. Daw, R. Derosa, G. Eddolls, J. Eichholz, M. Evans, M. Fejer, E. C. Ferreira, A. Freise, V. V. Frolov, S. Gras

Faculty Publications

The detection of gravitational waves from compact binary mergers by LIGO has opened the era of gravitational wave astronomy, revealing a previously hidden side of the cosmos. To maximize the reach of the existing LIGO observatory facilities, we have designed a new instrument able to detect gravitational waves at distances 5 times further away than possible with Advanced LIGO, or at greater than 100 times the event rate. Observations with this new instrument will make possible dramatic steps toward understanding the physics of the nearby Universe, as well as observing the Universe out to cosmological distances by the detection of …

Multilayer Inse-Te Van Der Waals Heterostructures With An Ultrahigh Rectification Ratio And Ultrasensitive Photoresponse, Fanglu Qin, Feng Gao, Mingjin Dai, Yunxia Hu, Miaomiao Yu, Lifeng Wang, Wei Feng, Bin Li, Ping An Hu

Faculty Publications

Multilayer van der Waals (vdWs) semiconductors have promising applications in high-performance optoelectronic devices. However, photoconductive photodetectors based on layered semiconductors often suffer from sizeable dark currents and high external driving bias voltages. Here, we report vertical van der Waals heterostructures (vdWHs) consisting of multilayer indium selenide (InSe) and tellurium (Te). The multilayer InSe-Te vdWH device shows a record high forward rectification ratio greater than 107 at room temperature. The vdWH device achieves an ultrasensitive and broadband photoresponse photodetector with an ultrahigh photo/dark current ratio over 104 and a high detectivity of 1013 Jones under visible light illumination with weak incident …

Influence Of External Nacl Salt On Membrane Rigidity Of Neutral Dopc Vesicles, Judith U. De Mel, Sudipta Gupta, Rasangi M. Perera, Ly Ngo, Piotr Zolnierczuk, Markus Bleuel, Sai Venkatesh Pingali, Gerald J. Schneider

Faculty Publications

Copyright © 2020 American Chemical Society. Sodium chloride (NaCl) is a very common molecule in biotic and abiotic aqueous environments. In both cases, variation of ionic strength is inevitable. In addition to the osmotic variation posed by such perturbations, the question of whether the interactions of monovalent ions Na+ and Cl-, especially with the neutral head groups of phospholipid membranes are impactful enough to change the membrane rigidity, is still not entirely understood. We investigated the dynamics of 1,2-di-(octadecenoyl)-sn-glycero-3-phosphocholine (DOPC) vesicles with zwitterionic neutral head groups in the fluid phase with increasing external salt concentration. At higher salt concentrations, we …

General Product Formula Of Multiple Integrals Of Lévy Process, Nishant Agrawal, Yaozhong Hu, Neha Sharma

Journal of Stochastic Analysis

No abstract provided.

Continuous Dependence On The Coefficients For Mean-Field Fractional Stochastic Delay Evolution Equations, Brahim Boufoussi, Salah Hajji

Journal of Stochastic Analysis

No abstract provided.

Using Stable Isotopes To Disentangle Marine Sedimentary Signals In Reactive Silicon Pools, Rebecca A. Pickering, Lucie Cassarino, Katharine R. Hendry, Xiangli L. Wang, Kanchan Maiti, Jeffrey W. Krause

Faculty Publications

Many studies use sedimentary biogenic silica (bSiO2) stable isotopes (e.g., δ³⁰Si) as paleoproxies but neglect signals from other sedimentary reactive SiO2 phases. We quantified δ³⁰Si for multiple reactive Si pools in coastal river-plume sediments, revealing up to −5‰ difference between acid-leachable and alkaline-digestible amorphous SiO2. Thus, previous studies have missed valuable information on early diagenetic products and, in cases where sediments were not cleaned, potentially biased bSiO2 δ³⁰Si values. Acid-leachable δ³⁰Si, that is, from authigenic products, are the result of either multistep fractionation from a bSiO2 source or an ~2‰ fractionation (consistent …

Gw190412: Observation Of A Binary-Black-Hole Coalescence With Asymmetric Masses, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, C. Adams, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, A. Aich, L. Aiello, A. Ain, P. Ajith, S. Akcay, G. Allen, A. Allocca, P. A. Altin, A. Amato, S. Anand, A. Ananyeva, S. B. Anderson, W. G. Anderson, S. V. Angelova, S. Ansoldi, S. Antier, S. Appert, K. Arai, M. C. Araya, J. S. Areeda

Faculty Publications

We report the observation of gravitational waves from a binary-black-hole coalescence during the first two weeks of LIGO's and Virgo's third observing run. The signal was recorded on April 12, 2019 at 05â¶30â¶44 UTC with a network signal-to-noise ratio of 19. The binary is different from observations during the first two observing runs most notably due to its asymmetric masses: A ∼30 M⊙ black hole merged with a ∼8 M⊙ black hole companion. The more massive black hole rotated with a dimensionless spin magnitude between 0.22 and 0.60 (90% probability). Asymmetric systems are predicted to emit gravitational waves with stronger …

Observational Consequences Of Bianchi I Spacetimes In Loop Quantum Cosmology, Ivan Agullo, Javier Olmedo, V. Sreenath

Faculty Publications

Anisotropies generically dominate the earliest stages of expansion of a homogeneous universe. They are particularly relevant in bouncing models, since shears grow in the contracting phase of the cosmos, making the isotropic situation unstable. This paper extends the study of cosmological perturbations in loop quantum cosmology (LQC) to anisotropic Bianchi I models that contain a bounce followed by a phase of slow-roll inflation. We show that, although the shear tensor dilutes and the universe isotropizes soon after the bounce, cosmic perturbations retain memory of this short anisotropic phase. We develop the formalism needed to describe perturbations in anisotropic, effective LQC, …

Do Ground Layer Microhabitats In Old-Growth Pine Savanna Influence Recruitment Of Longleaf Pine?, Matthew Blanchard

LSU Master's Theses

Savanna tree populations typically share two demographic characteristics, high mortality of juvenile stages and low mortality of established trees. Juvenile savanna tree species escape demographic bottlenecks when they reach a safe size and annual mortality becomes low. Longleaf pine (Pinus palustris Mill.) is the dominant tree species in pine savannas of the southeastern United States. The seeds and juvenile seedlings experience bottlenecks to recruitment to a safe size, the grass stage. Low intensity, frequent savanna fires facilitate establishment of seedlings, but also kill juvenile seedlings that have not grown sufficient above ground biomass. We hypothesized that juvenile seedlings escape the …

Development Of Artificial Intelligence Approach To Nowcasting And Forecasting Vibrio Prevalence In Coastal Waters, Peyman Hosseinzadeh Namadi

LSU Doctoral Dissertations

Vibrio parahaemolyticus (V.p) is an epidemiologically significant pathogen that poses high risks to the human health and shellfish industry, calling for predictive models for management interventions. This study presents an Artificial Intelligence(AI)-based approach to predicting and reducing the risks. The AI-based approach involves the identification of environmental indicators and their optimum variation ranges favoring V.p prevalence, the development of nowcasting and forecasting models for predicting V.p prevalence, and the creation of remote sensing algorithms for mapping concentrations of V.p and its environmental indicators by synergistically combining the Deep Neural Network (DNN) modeling technique, Genetic Programming (GP) method, R …

Transition Metal Complexes Of Pyridyltriazole And Bipyridine Ligands, Sen Gao

LSU Doctoral Dissertations

Four Ni(II) complexes have been obtained with the pyridyltriazole ligand, bpt, or the bis(pyridyltriazole) ligand, m-xpt, in chapter 2. This work was carried out as a comparison with the previously established coordination chemistry of copper(II) with bpt and m-xpt. Initially, the reaction between Ni(II) and bpt only produced one mononuclear compound, [Ni(bpt)₂(H₂O)₂](NO₃)₂ (1). In order to study the formation of Ni-bpt and Ni-m-xpt complexes in solution, mixtures of Ni(NO₃)₂ and ligand (m-xpt or bpt) were prepared in different ratios and …

Modifications To Gravitational Wave Equation From Canonical Quantum Gravity, Andrea Dapor, Klaus Liegener

Faculty Publications

It is expected that the quantum nature of spacetime leaves its imprint in all semiclassical gravitational systems, at least in certain regimes, including gravitational waves. In this paper we investigate such imprints on gravitational waves within a specific framework: space is assumed to be discrete (in the form of a regular cubic lattice), and this discrete geometry is quantised following Dirac's canonical quantisation scheme. The semiclassical behavior is then extracted by promoting the expectation value of the Hamiltonian operator on a semiclassical state to an effective Hamiltonian. Considering a family of semiclassical states representing small tensor perturbations to Minkowski background, …

Second Harmonic Generation Spectroscopy And Microscopy Of Liposomes, Nanoparticles, And Cells, Prakash Hamal

LSU Doctoral Dissertations

Second harmonic generation (SHG) is used to investigate the factors that impact nanoparticle-based drug-delivery applications. In the first study, molecular adsorption and transport kinetics of a positively-charged dye, malachite green isothiocyanate (MGITC), is characterized at the surface of different colloidal liposomes in water using SHG spectroscopy. The molecular interactions of MGITC is compared to our previous investigations with malachite green (MG). In comparison to MG, MGITC demonstrates stronger adsorption and faster transport through lipid membranes. Correspondingly, the SHG experimental results are in excellent agreement with the molecular dynamics (MD) simulations results. A key finding illustrates the importance of functional groups, …

The Value Of Information Under Partial Information For Exponential Utility, Farai Julius Mhlanga, Mbakisi Dube

Journal of Stochastic Analysis

No abstract provided.

Isolation And Characterization Of Bacteria In A Toluene-Producing Enrichment Culture Derived From Contaminated Groundwater At A Louisiana Superfund Site, Madison Mikes

LSU Master's Theses

In an effort to better understand the role that various microbes may play in toluene production, bacteria from a toluene-producing enrichment culture derived from contaminated groundwater at a Superfund site were cultivated and isolated on low nutrient solid media. A total of 14 solid medium formulations containing varying pH ranges, carbon sources, solidifying agents, and incubation gas headspaces were used to obtain 278 isolates in pure culture. Isolated bacteria, identified using partial 16S rRNA gene sequences, were most closely related with the genera Anoxybacillus, Azospira, Bacillus, Bradyrhizobium, Cellulosimicrobium, Micrococcus, and Propionicimonas.

Further attempts …

Water-Redispersible Cellulose Nanofiber And Polyanionic Cellulose Hybrids For High-Performance Water-Based Drilling Fluids, Mei Chun Li, Zhengjie Tang, Chaozheng Liu, Runzhou Huang, Meen S. Koo, Guoqiang Zhou, Qinglin Wu

Faculty Publications

Cellulose nanofibers (CNFs) with nanoscale dimension, high aspect ratio, and easily modified surface chemistry show great potential as novel rheological and filtration modifiers in bentonite water-based drilling fluids (BT-WDFs). However, CNFs would suffer from poor redispersibility in an aqueous suspension if they were fully dried for transportation, storage, and field application. Herein, we report a simple, versatile, and scalable strategy to prepare water-redispersible CNFs through compounding them with a water-soluble, commercially available drilling fluid additive, polyanionic cellulose (PAC), and subsequent drying. The results revealed that the water redispersibility of CNF/PAC hybrids was dependent on the PAC's viscosity (i.e., low viscosity, …

Antarctica And The Southern Ocean, Jessica Blunden, Derek S. Arndt, E. Povl Abrahamsen, Sandra Barreira, Cecilia M. Bitz, Amy Butler, Kyle R. Clem, Steve Colwell, Lawrence Coy, Jos De Laat, Marcel D. Du Plessis, Ryan L. Fogt, Helen Amanda Fricker, John Fyfe, Alex S. Gardner, Sarah T. Gille, Tessa Gorte, L. Gregor, Will Hobbs, Bryan Johnson, Eric Keenan, Linda M. Keller, Natalya A. Kramarova, Matthew A. Lazzara, Jan T.M. Lenaerts, Jan L. Lieser, Hongxing Liu, Craig S. Long, Michelle Maclennan, Robert A. Massom, François Massonnet, Matthew R. Mazloff

Faculty Publications

No abstract provided.

Viola Fragments: Contextualizing And Interpreting Selections From György Kurtág's Signs, Games And Messages, Mounir Nessim

LSU Doctoral Dissertations

The viola came to prominence as a solo instrument relatively late compared to the violin and cello. As a result, the standard repertoire is more recent, consisting largely of twentieth century works. The standard repertoire continues to expand as new works are written and embraced by performers. One such work is the Hungarian composer György Kurtág's open ended collection of pieces for solo viola Signs, Games and Messages (1987-). Kurtág, born in 1926, is one of the most important composers of the twentieth and twenty-first centuries. His music is characterized by its brevity, fragmentation, ambiguity, and intertextuality. The painstaking scrutiny …

Characterizing The Epigenetic And Transcriptomic Responses To Perkinsus Marinus Infection In The Eastern Oyster Crassostrea Virginica, Kevin M. Johnson, K. A. Sirovy, Sandra M. Casas, Jerome F. La Peyre, Morgan W. Kelly

Faculty Publications

© Copyright © 2020 Johnson, Sirovy, Casas, La Peyre and Kelly. Eastern oysters in the northern Gulf of Mexico are routinely infected with the protistan parasite Perkinsus marinus, the cause of the disease commonly known as dermo. Recent experimental challenges among Atlantic coast populations have identified both resistant and susceptible genotypes using comparative transcriptomics. While controlled experimental challenges are essential first assessments, expanding this analysis to field reared individuals provides an opportunity to identify key genomic signatures of infection that appear both in the laboratory and in the field. In this study we combined reduced representation bisulfite sequencing with 3′ …

Characterizing The Epigenetic And Transcriptomic Responses To Perkinsus Marinus Infection In The Eastern Oyster Crassostrea Virginica, Kevin M. Johnson, K. A. Sirovy, Sandra M. Casas, Jerome F. La Peyre, Morgan W. Kelly

Faculty Publications

© Copyright © 2020 Johnson, Sirovy, Casas, La Peyre and Kelly. Eastern oysters in the northern Gulf of Mexico are routinely infected with the protistan parasite Perkinsus marinus, the cause of the disease commonly known as dermo. Recent experimental challenges among Atlantic coast populations have identified both resistant and susceptible genotypes using comparative transcriptomics. While controlled experimental challenges are essential first assessments, expanding this analysis to field reared individuals provides an opportunity to identify key genomic signatures of infection that appear both in the laboratory and in the field. In this study we combined reduced representation bisulfite sequencing with 3′ …

Overcoming Salt Contamination Of Bentonite Water-Based Drilling Fluids With Blended Dual-Functionalized Cellulose Nanocrystals, Mei Chun Li, Qinglin Wu, Jingquan Han, Changtong Mei, Tingzhou Lei, Sun Young Lee, Jaegyoung Gwon

Faculty Publications

The depletion of onshore oil reserves along with a rapid increase in the global energy demand has driven the oil industry to explore and produce oil from deepwater fields. However, because of high salinity in the subsea formation, salt contamination is becoming one of the most critical challenges to bentonite water-based drilling fluids (BT-WDFs), causing undesirable changes in density, rheology, and filtration performance of the fluids. Herein, we reveal the mechanisms of the negative influence of salt cations on BT-WDFs and demonstrate the function of biomass-derived cellulose nanocrystals (CNCs) as anti-salt agents in the fluids through rational dual surface functionalization …

Global Health In Preconception, Pregnancy And Postpartum Alliance: Development Of An International Consumer And Community Involvement Framework, Heidi J. Bergmeier, Virginia Vandall-Walker, Magdalena Skrybant, Helena J. Teede, Cate Bailey, Jo Anna B. Baxter, Ana Luiza Vilela Borges, Jacqueline A. Boyle, Ayesha Everitt, Cheryce L. Harrison, Margely Herrera, Briony Hill, Brian Jack, Samuel Jones, Laura Jorgensen, Siew Lim, Cynthia Montanaro, Leanne M. Redman, Judith Stephenson, Hildrun Sundseth, Shakila Thangaratinam, Paula Thynne, Ruth Walker, Helen Skouteris

Clinical Research Faculty Publications

Background: The goal of the Global Health in Preconception, Pregnancy and Postpartum (HiPPP) Alliance, comprising consumers and leading international multidisciplinary academics and clinicians, is to generate research and translation priorities and build international collaboration around healthy lifestyle and obesity prevention among women across the reproductive years. In doing so, we actively seek to involve consumers in research, implementation and translation initiatives. There are limited frameworks specifically designed to involve women across the key obesity prevention windows before (preconception), during and after pregnancy (postpartum). The aim of this paper is to outline our strategy for the development of the HiPPP Consumer …

Simulated Field-Modulated X-Ray Absorption In Titania, Pragathi Darapaneni, Alexander M. Meyer, Mykola Sereda, Adam Bruner, James A. Dorman, Kenneth Lopata

Faculty Publications

© 2020 Author(s). In this paper, we present a method to compute the x-ray absorption near-edge structure (XANES) spectra of solid-state transition metal oxides using real-time time-dependent density functional theory, including spin-orbit coupling effects. This was performed on bulk-mimicking anatase titania (TiO2) clusters, which allows for the use of hybrid functionals and atom-centered all electron basis sets. Furthermore, this method was employed to calculate the shifts in the XANES spectra of the Ti L-edge in the presence of applied electric fields to understand how external fields can modify the electronic structure, and how this can be probed using x-ray absorption …

Sediment Transport Near Ship Shoal For Coastal Restoration In The Louisiana Shelf: A Model Estimate Of The Year 2017–2018, Haoran Liu, Kehui Xu, Yanda Ou, Robert Bales, Zhengchen Zang, Z. George Xue

Faculty Publications

No abstract provided.

Cost-Effectiveness Analysis Of Advanced Radiotherapy Techniques For Post-Mastectomy Breast Cancer Patients, Yibo Xie, Beibei Guo, Rui Zhang

Faculty Publications

Background: Prior cost-effectiveness studies of post-mastectomy radiotherapy (PMRT) only compared conventional radiotherapy versus no radiotherapy and only considered tumor control. The goal of this study was to perform cost-effectiveness analyses of standard of care (SOC) and advanced PMRT techniques including intensity-modulated radiotherapy (IMRT), standard volumetric modulated arc therapy (STD-VMAT), non-coplanar VMAT (NC-VMAT), multiple arc VMAT (MA-VMAT), Tomotherapy (TOMO), mixed beam therapy (MIXED), and intensity-modulated proton therapy (IMPT). Methods: Using a Markov model, we estimated the cost-effectiveness of various techniques over 15 years. A cohort of women (55-year-old) was simulated in the model, and radiogenic side effects were considered. Transition probabilities, …

A Systematic Review Of Children’S Physical Activity Patterns: Concept, Operational Definitions, Instruments, Statistical Analyses, And Health Implications, Thayse Natacha Gomes, Peter T. Katzmarzyk, Sara Pereira, Mabliny Thuany, Martyn Standage, José Maia

Population and Public Health Science Faculty Publications

Despite the widespread use of the expression “physical activity pattern” (PAP), there apparently is no general consensus regarding its definition. This systematic review aimed to examine available research focussing on (1) definitions of PAP, (2) instruments/techniques used to describe PAP, (3) statistical approaches used to analyse PAP, and (4) implications of PAP on children’s health. A systematic review of the available literature was done to identify studies published up to October 2019, and 76 studies were eligible. None of the studies presented a formal definition of PAP; a wide range of instruments were used to investigate children’s PAP, and most …