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Fish And Macroinvertebrate Response To Restoration And Conservation Efforts, Madison C. Cogar Dec 2020

Fish And Macroinvertebrate Response To Restoration And Conservation Efforts, Madison C. Cogar

MSU Graduate Theses

Fish and macroinvertebrate response to restoration and conservation efforts varies in regards to the size and structure of the system (e.g. headwater streams in WV versus large rivers such as the Mississippi River). This project reviews fish and macroinvertebrate rebound in treated acid mine drainage (AMD) streams in WV as well as macroinvertebrate drift patterns in the Mississippi and Missouri Rivers. AMD is a product of a chemical reaction resulting in an acidic water outflow from mining sites, which may harm aquatic life. As a response, passive AMD treatment systems have been installed. I tested the effectiveness of remediation by …


Assessing Grassed Waterway Implementation Using Acpf And Swat Models, Kirsten Schaefer Dec 2020

Assessing Grassed Waterway Implementation Using Acpf And Swat Models, Kirsten Schaefer

MSU Graduate Theses

Agriculture is the most significant contributor of nonpoint source pollutants in US waterways, with sediment being the most prevalent cause of impairments. Sediment loss mitigation occurs through Best Management Practices (BMPs), such as grassed waterways. Federal and state agencies incentivize the implementation of BMPs through cost-share programs for farmers. The investment of public funds has increased pressure to demonstrate the effectiveness and value of individual projects, necessitating the development of strategies for prioritizing projects based on the sensitivity of sites to sediment erosion and optimal locations for implementation. This study has three primary objectives: (i) document existing locations of grassed …


Developing A Tourism Opportunity Index Regarding The Prospective Of Overtourism In Nepal, Susan Phuyal Dec 2020

Developing A Tourism Opportunity Index Regarding The Prospective Of Overtourism In Nepal, Susan Phuyal

MSU Graduate Theses

This research explores Nepal's overtourism scenario based on the capacity of a locality to manage sustainable tourism practices. Environmental degradation, local infrastructure degradation, negative tourist experience and local resident responses regarding visitors are the four main variables used in this study to analyze overtourism. In order to analyze the case study of overtourism, we select the three top touristic cities of Nepal, Kathmandu, Pokhara, and Chitwan based on the number of annual visitors. Nepal's case analysis of overtourism conditions reviews the overall threat of over-tourism and establishes a metric by which tourism can be viewed as potentially detrimental to sustainability. …


The Legacy Of Contamination By Lead Smelters In Missouri, Robert S. Armstrong Dec 2020

The Legacy Of Contamination By Lead Smelters In Missouri, Robert S. Armstrong

MSU Graduate Theses

Missouri has a rich history of lead mining. In the smelting process lead particles are emitted, which may be toxic to plants and animals. This study focuses on two primary lead smelters, Herculaneum and Glover, in Missouri. Smelting operations have ceased at these two sites, and unlike Herculaneum, Glover has no reported lead concentrations. Findings from air and sediments of these two sites were compared to background conditions and to each other. Thirty-three samples were collected from Herculaneum and Glover (thirty samples and three replicates) and eleven samples (ten samples and one replicate) for background. For Herculaneum sediment, lead levels …


Raman Spectroscopic Investigation Of The Speciation Of Uranyl (Vi) And Thorium (Iv) Ions In Chloride-Bearing Aqueous Solutions Under Hydrothermal Conditions, Nadib Akram Dec 2020

Raman Spectroscopic Investigation Of The Speciation Of Uranyl (Vi) And Thorium (Iv) Ions In Chloride-Bearing Aqueous Solutions Under Hydrothermal Conditions, Nadib Akram

MSU Graduate Theses

Raman spectra were acquired for a uranyl chloride aqueous solution at temperatures ranging from 25°C to 500°C at the chloride concentration of 6M and uranium (vi) concentration of 0.05M. The measurements were taken by sealing the sample in a hydrothermal diamond anvil cell (HDAC) which enabled spectra acquisition at non-ambient conditions. The pressure inside the cell was measured by estimating the liquid-vapor homogenization temperature (TH) and using the isochoric equation of state diagram of water. The acquired spectra were then fitted to determine the speciation distribution of the various uranyl chloride species for the mentioned concentration. The developed …


Kinetic Monte Carlo Investigations Involving Atomic Layer Deposition Of Metal-Oxide Thinfilms, David Tyler Magness Dec 2020

Kinetic Monte Carlo Investigations Involving Atomic Layer Deposition Of Metal-Oxide Thinfilms, David Tyler Magness

MSU Graduate Theses

Atomic Layer Deposition is a method of manufacturing thin film materials. Metal-oxides such as zinc-oxide and aluminum-oxide are particularly interesting candidates for use in microelectronic devices such as tunnel junction barriers, transistors, Schottky diodes, and more. By adopting a 3D Kinetic Monte Carlo model capable of simulating ZnO deposition, the effect of parameters including deposition temperature, chamber pressure, and composition of the initial substrate at the beginning of deposition can be investigated. This code generates two random numbers: One is used to select a chemical reaction to occur from a list of all possible reactions and the second is used …


Lightweight Deep Learning For Botnet Ddos Detection On Iot Access Networks, Eric A. Mccullough Dec 2020

Lightweight Deep Learning For Botnet Ddos Detection On Iot Access Networks, Eric A. Mccullough

MSU Graduate Theses

With the proliferation of the Internet of Things (IoT), computer networks have rapidly expanded in size. While Internet of Things Devices (IoTDs) benefit many aspects of life, these devices also introduce security risks in the form of vulnerabilities which give hackers billions of promising new targets. For example, botnets have exploited the security flaws common with IoTDs to gain unauthorized control of hundreds of thousands of hosts, which they then utilize to carry out massively disruptive distributed denial of service (DDoS) attacks. Traditional DDoS defense mechanisms rely on detecting attacks at their target and deploying mitigation strategies toward the attacker …


Computational Elucidation Of The "Coloring Problem" In Rhenium Aluminum Silicon Compounds, Alec George Neeson Aug 2020

Computational Elucidation Of The "Coloring Problem" In Rhenium Aluminum Silicon Compounds, Alec George Neeson

MSU Graduate Theses

Re1Si1Al1 and its related compounds are potential thermoelectric materials. Previously, it was reported to adopt a MoSi2-type structure with Si and Al atoms statistically sharing the same crystallographic sites. This recent study indicates otherwise – Si and Al are segregated and occupy different sites when mixed with a 1:1:1 stoichiometry. To confirm and rationalize the segregation between Si and Al, this research studied this compound with first-principle calculations. Several model structures have been constructed for Re1Si1Al1 including a number of different super-cell models. Energy analysis confirmed that the …


In Silico Investigation For The Conversion Of Methyl Oleate To Gasoline, Arkanil Roy Aug 2020

In Silico Investigation For The Conversion Of Methyl Oleate To Gasoline, Arkanil Roy

MSU Graduate Theses

Petroleum products are found in all walks of life. From the plastic casing on a cell phone to the gasoline that runs most vehicles, a lot is derived from petroleum. Ubiquitous use of petroleum has adversely affected the environment. Toxic substances such as SOx and NOx are released into the atmosphere during the processing and usage of petroleum products, which contributes to global warming. Inevitable oil spills cause devastating effects to marine ecosystems. The rate of regeneration of petroleum is much slower than the rate of usage that would lead to it being exhausted in the recent future. Hence, a …


Application Of Carbon Nanoparticles As Dna Detection Probe And Fluorescent Ink, Luckio Frank Owuocha Aug 2020

Application Of Carbon Nanoparticles As Dna Detection Probe And Fluorescent Ink, Luckio Frank Owuocha

MSU Graduate Theses

There is a significant interest in developing a sensitive, selective, efficient, and inexpensive method for rapid molecular diagnostic tests. This research aims to develop an inexpensive nucleic acid detection method by using DNA-conjugated carbon nanoparticles that exhibit fluorescence in the visible region. Carbon nanoparticles of this class can be detected without specialized equipment and have great promise toward the development of analytical methods that can be used in resource-limited environments with a lack of access to proper diagnostic and healthcare. We employed EDC-NHS (two-step) and EDC (one-step) coupling techniques to prepare DNA-conjugated carbon nanoparticles. The dot blotting method was adapted …


Stream Bank And Bar Erosion Contributions And Land Use Influence On Suspended Sediment Loads In Two Ozark Watersheds, Southeast Missouri, Kayla Ann Coonen Aug 2020

Stream Bank And Bar Erosion Contributions And Land Use Influence On Suspended Sediment Loads In Two Ozark Watersheds, Southeast Missouri, Kayla Ann Coonen

MSU Graduate Theses

In-channel sources and storages of fine-sediment such as in banks and bars can influence sediment loads and overall geomorphic activity in stream systems. However, in-channel processes and effects on sediment load are rarely quantified in geomorphic or water quality studies. This study uses a sediment budget approach to assess the influence of bank erosion and bar deposition on fine sediment loads in Mineral Fork (491 km2) and Mill Creek (133 km2) watersheds located in the Ozark Highlands in Washington County, Missouri. These watersheds were disturbed by historical lead and barite mining which included the construction of …


Heterostructure Of 2d Materials: Hfs2/Hfo2/Si, Christopher J. Robledo Aug 2020

Heterostructure Of 2d Materials: Hfs2/Hfo2/Si, Christopher J. Robledo

MSU Graduate Theses

Heterostructures have been utilized in electronic devices for over 50 years with the proposal for the first heterostructure transistor in 1957. With the scaling of devices, it is necessary to create new heterostructures that will comply with Moore’s Law, as well as make devices faster and consume less power. Novel 2D materials, such as hafnium disulfide, have shown promise as an active channel layer, while hafnium dioxide is already proven to be a replacement of silicon dioxide for the gate insulating layer. However, fabrication techniques for wide-scale integration of these heterostructures have not yet been achieved. Also, the dielectric properties …


A Geochemical And Statistical Investigation Of The Big Four Springs Region In Southern Missouri, Jordan Jasso Vega Aug 2020

A Geochemical And Statistical Investigation Of The Big Four Springs Region In Southern Missouri, Jordan Jasso Vega

MSU Graduate Theses

The Big Four Springs region hosts four major first-order magnitude springs in southern Missouri and northern Arkansas. These springs are Big Spring (Carter County, MO), Greer Spring (Oregon County, MO), Mammoth Spring (Fulton County, AR), and Hodgson Mill Spring (Ozark County, MO). Based on historic dye traces and hydrogeological investigations, these springs drain an area of approximately 1500 square miles and collectively discharge an average of 780 million gallons of water per day. The rocks from youngest to oldest that are found in Big Four Springs region are the Cotter and Jefferson City Dolomite (Ordovician), Roubidoux Formation (Ordovician), Gasconade Dolomite …


Evaluating Particulate Matter 2.5 In The Yangtze River Delta, Muhammad Abdullah Aug 2020

Evaluating Particulate Matter 2.5 In The Yangtze River Delta, Muhammad Abdullah

MSU Graduate Theses

Particulate Matter 2.5 (PM2.5) is a growing concern in industrialized countries. In China, high concentrations of PM2.5 are causing devastating health and environmental effects for the people living there. Coal-burning for domestic and industrial purposes is the main culprit for decreasing air quality in China. The focus of this paper is on the Yangtze River Delta (YRD) located on the eastern coast of China. Hourly PM2.5 readings from March 2015 to June 2016 were obtained from 125 air quality monitoring stations (AQMS) in 23 cities in the YRD. In this study, PM2.5 readings were examined …


Cloud Resource Prediction Using Explainable And Cooperative Artificial Neural Networks, Nathan R. Nelson Aug 2020

Cloud Resource Prediction Using Explainable And Cooperative Artificial Neural Networks, Nathan R. Nelson

MSU Graduate Theses

This work proposes a system for predicting cloud resource utilization by using runtime assembled cooperative artificial neural networks (RACANN). RACANN breaks up the problem into smaller contexts, each represented by a small-scale artificial neural network (ANN). The relevant ANNs are joined together at runtime when the context is present in the data for training and predictions. By analyzing the structure of a complete ANN, the influence of inputs is calculated and used to create linguistic descriptions (LD) of model behavior, so RACANN becomes explainable (eRACANN). The predictive results of eRACANN are compared against its prototype and a single deep ANN …


Doping Effects On Transition-Metal Silicides: Crystal Structures And Physical Properties Of Aluminium Doped Rhenium Silicide, Victoria Decocq Aug 2020

Doping Effects On Transition-Metal Silicides: Crystal Structures And Physical Properties Of Aluminium Doped Rhenium Silicide, Victoria Decocq

MSU Graduate Theses

Semiconductive transition-metal silicides (e.g., ReSi) express weak thermoelectric properties. These properties can improve through n-type or p-type doping (e.g., Al), resulting in altered crystal structures. Binary rhenium silicide (ReSi1.75) exhibits promising thermoelectric properties and an intriguing crystal structure. Previous research has shown ReSi1.75 changes from a commensurate supercell MoSi2-type structure to an incommensurate superspace group structure, when doped with aluminium to ReAl0.074Si1.67. ReSi1.75 expresses a figure of merit (ZT) of 0.70 at 800°C, which improves to a ZT of 0.95 at 150°C for ReAl0.02Si1.75. Because of …


Investigating Chitosan Modified With Triethylammonium Butanamide And Triethylphosphonium Butanamide As Non-Viral Gene Delivery Vectors By Examining Cytotoxicity And Transfection Efficiency, Deborah C. Ehie Aug 2020

Investigating Chitosan Modified With Triethylammonium Butanamide And Triethylphosphonium Butanamide As Non-Viral Gene Delivery Vectors By Examining Cytotoxicity And Transfection Efficiency, Deborah C. Ehie

MSU Graduate Theses

Gene therapy is a very challenging field, especially with new emerging genetic disorders. Chitosan (CS), due to chitosan’s flexibility, biocompatibility, and biodegradability, has been of interest in the world of gene therapy especially as researchers are gravitating towards non-viral vectors due to the problems caused by viral vectors. Nevertheless, there are still issues regarding solubility, cellular uptake of cargos being transported in vitro or in vivo, increased cytotoxicity levels, as well as many other things that prevent chitosan from being an efficient gene delivery agent. Here I present five derivatives of chitosan, which were all modified with either triethylphosphonium …


Detrital Zircon Petrochronology For Sedimentary Provenance Analysis: Source To Sink Of The Mississippi/Missouri River Drainage Basin, Sage Denali Muttel Aug 2020

Detrital Zircon Petrochronology For Sedimentary Provenance Analysis: Source To Sink Of The Mississippi/Missouri River Drainage Basin, Sage Denali Muttel

MSU Graduate Theses

Detrital petrochronology can provide a detailed look into sedimentary provenance through integrated mineral radioisotopic ages with corresponding mineral chemistry. By combining U-Pb ages and Th/U values of detrital zircon from 13 samples collected from Quaternary sand deposits in the Upper Missouri, Yellowstone, Bighorn, Platte, Kansas, Arkansas, Mississippi, Red and Brazos Rivers, an interpretation of detailed signatures that record evidence of the evolution of the Mississippi/Missouri River drainage and the tectonic events that shaped it were observed. Low Th/U values in zircon correlate temporally to convergent magmatism, whereas, higher and more variable Th/U zircon are coeval with known extensional tectonism. Using …


Toward Development Of A Paper-Based Microanalytical Device For Heavy Metal Ion Detection By Enzyme Inhibition, Adjoa Otubea Adams Aug 2020

Toward Development Of A Paper-Based Microanalytical Device For Heavy Metal Ion Detection By Enzyme Inhibition, Adjoa Otubea Adams

MSU Graduate Theses

In recent years, paper-based microanalytical devices have attracted great attention in broad application areas including the colorimetric detection of heavy metal ions. The simplicity, portability, and low cost of the devices offer unique advantages over conventional instrumental analysis. This project utilizes the inhibition of an enzyme-catalyzed reaction by metal ions to develop a paper-based analytical device for the detection of heavy metal contaminants such as mercury. I selected alkaline phosphatase for this study. This enzyme possesses Mg and Zn ions in its active site. Therefore, the competitive displacement of these metal ions and/or denaturation of the enzyme by heavy metal …


Synthesis, Characterization, And Biological Studies Of Novel Organoantimony(V) Cyanoximates, Kevin Anthony Pinks Aug 2020

Synthesis, Characterization, And Biological Studies Of Novel Organoantimony(V) Cyanoximates, Kevin Anthony Pinks

MSU Graduate Theses

The requirement of new antimicrobial treatments has become an urgent field recently. Multi-drug resistant (MDR) bacteria are now resistant to common antibiotics. To antagonize such bacteria 8 novel organoantimony(V) cyanoximates were synthesized to be characterized and submitted for biological activity studies. Eight organoantimony(V) cyanoximates were characterized by elemental analysis, thermal analysis, IR-, 13C{1H} NMR, some with UV-visible spectroscopy, and single crystal X-ray analysis. Antimicrobial Disk studies indicated Sb(Ph)4(ACO) and Sb(Ph)4(ECO) had significant antimicrobial effect against all three strains: two gram-negative a) Escherichia coli strain S17 and b) Pseudomonas aeruginosa strain PAO1, alongside a …


Transitioning From The Abstract To The Concrete: Reasoning Algebraically, Andrea Lynn Martin Aug 2020

Transitioning From The Abstract To The Concrete: Reasoning Algebraically, Andrea Lynn Martin

MSU Graduate Theses

Why are students not making a smooth transition from arithmetic to algebra? The purpose of this study was to understand the nature of students’ algebraic reasoning through tasks involving generalizing. After students’ algebraic reasoning had been analyzed, the challenges they encountered while reasoning were analyzed. The data was collected through semi-structured interviews with six eighth grade students and analyzed by watching recorded interviews while tracking algebraic reasoning. Through data analysis of students’ algebraic reasoning, three themes emerged: 1) it was possible for students to reach stage two (informal abstraction) and have an abstract understanding of the mathematical pattern even if …


Applications Of Artificial Intelligence And Graphy Theory To Cyberbullying, Jesse D. Simpson Aug 2020

Applications Of Artificial Intelligence And Graphy Theory To Cyberbullying, Jesse D. Simpson

MSU Graduate Theses

Cyberbullying is an ongoing and devastating issue in today's online social media. Abusive users engage in cyber-harassment by utilizing social media to send posts, private messages, tweets, or pictures to innocent social media users. Detecting and preventing cases of cyberbullying is crucial. In this work, I analyze multiple machine learning, deep learning, and graph analysis algorithms and explore their applicability and performance in pursuit of a robust system for detecting cyberbullying. First, I evaluate the performance of the machine learning algorithms Support Vector Machine, Naïve Bayes, Random Forest, Decision Tree, and Logistic Regression. This yielded positive results and obtained upwards …


Synthesis And Characterization Of Carbon Coated Barium Titanate Core-Shell Nanoparticles, Moudip Nandi Aug 2020

Synthesis And Characterization Of Carbon Coated Barium Titanate Core-Shell Nanoparticles, Moudip Nandi

MSU Graduate Theses

Core-shell nanoparticles (CSNP) with fascinating ferroelectric properties have diverse applications in biotechnology and the electronic field of studies. Among so many perovskites, barium titanate (BTO) nanoparticles draw much interest due to their distinct electronic and ferroelectric features. Additionally, the incorporation of carbon in the shell of CSNP makes it suitable for application in many fields due to its innocuous nature. Carbon not only increases the biocompatible properties of an element but also gives mechanical stability to the CSNP. This thesis is targeted towards the synthesis of oxide-carbide CSNP, where the core is made of BTO and the shell is made …


Performance Of Pld Grown Zno Thin Film As A Thin Film Transistor, Shahidul Asif Aug 2020

Performance Of Pld Grown Zno Thin Film As A Thin Film Transistor, Shahidul Asif

MSU Graduate Theses

The performance of ZnO thin film (grown in different parameters) as a thin film transistor (TFT) is the focus of this study. ZnO is renowned for being n-type semiconductor naturally which was utilized in fabricating a thin film transistor here. This thesis is compared the performance of ZnO thin film transistor by growing the thin film using pulsed laser deposition (PLD) on two slightly different substrates at different temperatures in an optimal 0.1 milli bar oxygen pressure which was later analyzed using other material characterization methods. The substrates were both Si (100) but had different resistivity due to different amount …


Field Measurements Of Bed-Load Transport Distances Using Painted Sediment Tracers In An Urban Stream In The Missouri Ozarks, Kristen E. Breckenridge Aug 2020

Field Measurements Of Bed-Load Transport Distances Using Painted Sediment Tracers In An Urban Stream In The Missouri Ozarks, Kristen E. Breckenridge

MSU Graduate Theses

Predictions of bed-load mobility and transport in stream channels are useful for restoration and management purposes. This study uses native gravel tracers to determine transport distances for bed-load in an urban stream in the Ozark Highlands. The objectives of this project are to: (i) determine downstream transport distances of painted tracers of different sizes over a range of flow conditions; (ii) evaluate the influence of channel morphology and thalweg location on transport; and (iii) compare field results to those predicted by mobility equations. The study site is located on South Creek, which drains Springfield, Missouri. The study reach is 132 …


The Legacy Of Mining In Southwest Missouri: Past And Present Conditions Of The Tri-State Mining District, Anastasia M C Mcclanahan Aug 2020

The Legacy Of Mining In Southwest Missouri: Past And Present Conditions Of The Tri-State Mining District, Anastasia M C Mcclanahan

MSU Graduate Theses

The historic Tri-State Mining District (TSMD) of southwestern Missouri, southeastern Kansas, and northeastern Oklahoma has a history of lead and zinc mining that extended over a hundred years. During the district’s peak production period, the TSMD was one of the world’s largest producers of lead and zinc. The mining activities in the TSMD produced economic growth that supported the local communities and were essential to the victory of the Allied Forces during World War I and World War II. Beginning in the 1920s, the mining activities in the district slowly began to cease due to depletion of metal ores and …


Improving Biodiesel Through Pyrolysis: Direct Dynamics Investigations Into Thermal Decomposition Of Methyl Linoleate, Michael Bakker May 2020

Improving Biodiesel Through Pyrolysis: Direct Dynamics Investigations Into Thermal Decomposition Of Methyl Linoleate, Michael Bakker

MSU Graduate Theses

Dependence on petroleum and petrochemical products is unsustainable as it is both a finite resource and environmentally hazardous. Biodiesel is a proposed alternative, but has complications including possessing poor cold weather operability and lacking the ability to supplement other petrochemical products (e.g., ethylene, hexane, etc.) relied upon in society. Pyrolysis of biodiesel has demonstrated the formation of smaller hydrocarbons comprising many of these petrochemical products. Our aim is to computationally simulate the pyrolysis of methyl linoleate, the most prevalent component in biodiesel formed in the US (from soybean). We make use of unimolecular direct dynamics describing intramolecular processes, introducing Temperature …


Determining Particle Size Of Polymeric Micelles In Thermothickening Aqueous Solutions, Jessica Diane Bruer May 2020

Determining Particle Size Of Polymeric Micelles In Thermothickening Aqueous Solutions, Jessica Diane Bruer

MSU Graduate Theses

Many active pharmaceutical ingredients (APIs) are poorly soluble and cause inadequate drug absorption. Soluplus®, a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer, is a commercial excipient (BASF Corp) that enhances the solubility and bioavailability of many APIs. The mechanism of enhancement is related to the ability to form polymeric micelles in solution. These micelles store insoluble APIs in their hydrophobic interior and transport them to targeted sites in the body. An important characteristic of solubility enhancers is the particle size exhibited in solution before and after loading with APIs. This is most commonly determined by dynamic light scattering (DLS) …


A Software Source Code Recommendation System For Code Reuse From Private Repositories, Md Mazharul Islam May 2020

A Software Source Code Recommendation System For Code Reuse From Private Repositories, Md Mazharul Islam

MSU Graduate Theses

Motivated by the idea of reusing existing source code from previous projects within a software company, in this thesis, I present a new source code recommendation technique to help programmers find relevant implementations or sample code based on software requirement specifications. My proposed technique assists programmers to search existing code repositories using natural language query. My approach summarizes the uploaded code into sentences or phrases to match them against user queries. This version of my proposed technique extracts and analyzes the content of Python code (such as variables, functions, docstrings, and comments) to generate code summary for each function which …


Geochemistry Of The Lazufre Volcanic Complex: Determining The Geometries And Processes Of The Magmatic Sources In The Central Andean Volcanic Zone, Brooke Erin Benz May 2020

Geochemistry Of The Lazufre Volcanic Complex: Determining The Geometries And Processes Of The Magmatic Sources In The Central Andean Volcanic Zone, Brooke Erin Benz

MSU Graduate Theses

The Central Andes in South America contain many active volcanoes and volcano complexes due to constant subduction producing extrusive rocks varying in composition. The Lazufre Complex, Chile-Argentina border, consists of two Pleistocene volcanic centers, Lastarria and Cordon del Azufre andesite and dacite lava flows and domes. Whole-rock K-Ar dates of lavas from Cordon del Azufre place the most recent eruptions at 0.6-0.3 Ma ±0.3 Ma. Major-element data of plagioclase and pyroxene show homogeneous compositions between the centers, which is consistent with whole rock major- and trace-element compositions. The primary composition of the pyroxenes are augite and diopsides for cpx and …