Lead Doped Carbon Nanofibers in Li-ion Batteries

Lead acid batteries have been a very reliable rechargeable battery since its inception in the mid-1800s. Lithium-Ion batteries have been sought out for their light-weight and capacity of holding large amounts of energy in a small amount of space. Few studies have been conducted in the use of lead in lithium-ion batteries. In this thesis, lead-doped carbon nanofibers were produced by using the Forcespinning® method and used as an anode on a lithium-ion battery. The morphology, material characterization and thermal properties of the anode material were analyzed using the Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Thermogravimetric Analysis (TGA) and X-Ray Photoelectron Spectroscopy (XPS). Electrochemical studies on the batteries cells were cycle performance, cyclic voltammetry and rate performance

Phylogenetic systematics of South American lizards of the genus Stenocercus (Squamata: Iguania)

The South American iguanian lizard genus Stenocercus includes 58 species occurring mostly in the Andes and adjacent lowland areas from northern Venezuela and Colombia to central Argentina at elevations of 0--4000 m. Limited taxon or character sampling have characterized all previous phylogenetic analyses of Stenocercus, which has repeatedly been proposed as sister taxon to the Tropidurus Group. In this study, I use molecular and morphological data to (1) infer the phylogenetic relationships among most species of Stenocercus, (2) perform explicit statistical tests of previous phylogenetic hypotheses, and (3) infer the ancestral distribution of Stenocercus. Using parsimony and Bayesian analyses, monophyly of this genus is strongly supported with a dataset of 32 species of Stenocercus, 12 outgroup taxa, and 1641 bp of mtDNA. Molecular data also are used to analyze evolutionary relationships within Stenocercus with a Bayesian approach based on mixture models, which accommodate variability in the parameters of the rate matrix across sites. Morphological data were obtained from 55 species of Stenocercus and one outgroup taxon; polymorphic and continuous morphological characters were coded using step matrices with frequency parsimony and gap-weighting methods, respectively. Parsimony and Bayesian analyses were performed with a combined dataset of 55 ingroup taxa, one outgroup taxon, and 1764 characters. All analyses support a basal split of Stenocercus into two clades. When all 55 ingroup taxa are included, these clades are composed of 26 (clade A) and 29 (clade B) species. In general, species in clade A have small scales and granular scales on the posterior surface of thighs, whereas species in clade B have large scales and non-granular, imbricate scales on posterior surface of thighs. Clade A is restricted to the central Andes except for a few species occurring in the northern Andes in Ecuador and Colombia. Clade B is more widespread and includes species occurring in the northern, central, and southern Andes, as well as species in the Amazon Basin and lowlands in southeastern South America. A dispersal-vicariance analysis suggests that the most recent common ancestor of species of Stenocercus occurred in the central Andes. Four new species of Stenocercus are described from the northern Andes of Colombia, southern Andes of Ecuador, northern and central Andes of Peru, and Cerrado forest in Brazil. In addition, S.torquatus is resurrected and S.variabilis is redescribed

The cranial osteology of the iguanid lizard Stenocercus guentheri (Squamata: Iguanidae) and its postembryonic development

Thesis (M.A.)--University of Kansas, Ecology and Evolutionary Biology, 2001.In spite of the great diversity of iguanid lizards, detailed descriptions of their osteocrania and postembryonic development are rare. Herein, the adult cranial osteology of the iguanid lizard Stenocercus guentheri and its postembryonic development are described based on cleared and double-stained and dry skeletal specimens from a single Ecuadorian population. The amphikinetic skull of S. guentheri is short and elevated, and bears teeth on the premaxilla, maxillae, and pterygoids. Mandibular teeth are present on the dentaries. Males having wider skulls than females, no other sexual dimorphism in the cranial osteology was found. Ossification of the articular from Meckel's cartilage, and growth of the parietal (ossification and investment of the frontoparietal fontanelle), are the most significant ontogenetic changes of the splanchnocranium and dermatocranium, respectively. The ossification of the cartilage separating the bones of the braincase is the most relevant postembryonic ontogenetic event of the neurocranium. The number of teeth does not vary ontogenetically and replacement teeth are present throughout postembryonic life. This study includes a list of the osteocranial characters of Stenocercus that have been used in systematic studies·, as well as a discussion of functional morphology and kinesis

A new species of Stenocercus (Squamata, Iguania) from central-western Brazil with a key to Brazilian Stenocercus

A new species of Stenocercus from centralwestern Brazil differs from other Stenocercus by the following combination of characters: head and body scales strongly keeled, posthumeral and postfemoral mite pockets absent, nostrils laterally oriented, supraciliary scales not enlarged or projected, and caudal fracture planes absent. Morphologically, the new species more closely resembles S. prionotus and S. caducus. The latter species has been reported in Brazil based on misidentified specimens from Mato Grosso that correspond to the new species described herein. However, it is very likely that S. caducus occurs in Brazil because it has been reported from geographically close areas. Therefore, I recognize seven species of Stenocercus from Brazil and provide a dichotomous key to assist in the identification of specimens

Preliminares al modelo de estocásticos para la formación tecnológica

Se presenta una parte de una investigación que examinó la implementación de la propuesta para estocásticos del bachillerato tecnológico en un aula de Matemáticas I (DEMS, 2014), a fin de caracterizar la formación respectiva del estudiante bachiller. Mediante la aplicación de un cuestionario de diagnóstico y la observación durante la enseñanza (Wittrock, 1986), se analizaron los desempeños de 88 estudiantes de nuevo ingreso y de tercer semestre. Entrevistamos a tres de ellos para profundizar en su comprensión de las ideas de estocásticos implicadas en el cuestionario y las que fueron objeto de la enseñanza. Los resultados revelaron el predominio de un pensamiento determinista y de una formación matemática básica deficiente

Experimental Evaluation Of A Precast Concrete Beam-To-Column Prototype Design Under A Column Removal Scenario

Precast concrete multistory buildings are used in an attempt to optimize the available construction space and reduce costs. However, little is known about predicting their capacity in a brittle response mode due to the sudden loss of a critical element that could induce a Progressive Collapse Scenario. Therefore, the National Institute for Standards and Technology (NIST) developed an explicit approach in the design of precast concrete systems that is intended to mitigate a progressive collapse by enhancing the rotational capacity of joints and the robustness of the structural system. A full-scale experiment was conducted to investigate the structural performance of a prototype design under a column-removal scenario. The test assembly frame, consisting of three columns and two beams, was subjected to a displacement controlled vertical force acting at the center to characterize the failure modes and collapse mechanisms. Brittleailures of critical structural elements were observed and significantly impacted the performance

Experimental Evaluation Of A Precast Concrete Beam-To-Column Prototype Design Under A Column Removal Scenario

Precast concrete multistory buildings are used in an attempt to optimize the available construction space and reduce costs. However, little is known about predicting their capacity in a brittle response mode due to the sudden loss of a critical element that could induce a Progressive Collapse Scenario. Therefore, the National Institute for Standards and Technology (NIST) developed an explicit approach in the design of precast concrete systems that is intended to mitigate a progressive collapse by enhancing the rotational capacity of joints and the robustness of the structural system. A full-scale experiment was conducted to investigate the structural performance of a prototype design under a column-removal scenario. The test assembly frame, consisting of three columns and two beams, was subjected to a displacement controlled vertical force acting at the center to characterize the failure modes and collapse mechanisms. Brittleailures of critical structural elements were observed and significantly impacted the performance

Temporal Characterization of Dust Activity in the Central Patagonia Desert (years 1964-2017)

Like a peninsula into the Southern Ocean, the vast Patagonia desert in the southern tip of South America is exposed to extreme winds. Dust blown from this region has important impacts thousands of kilometers away, but these impacts are very difficult to assess. Questions such as the sources of dust found in snow in East Antarctica as well as the provenance of nutrients in the Southern Ocean remain unanswered. While the Patagonia desert is the likely source of dust, there is a dearth of observational records of dust activity from this desert. This study fills the gap in observations by providing a record of 50 years of surface and satellite observations of the largest and most active dust source in Patagonia: lake Colhu Huapi. The seasonality, frequency and periods of major dust activity are identified from meteorological records at a station located 100km downwind from the lake. Collocated satellite observations confirmed the major periods of dust activity in the last 30 years. This dataset provides information on how to interpret records of recent dust found in East Antarctica snow as well as help to understand the CO2 cycle in the Southern Ocean

Aprendizaje de estocásticos en primer semestre de ingeniería

Este estudio se dirige a la cuestión de si la formación del ingeniero satisface los requerimientos de conocimientos de estocásticos para un desarrollo satisfactorio en su futuro desempeño profesional y/o académico tecnológico. Para ello, se interesa en la comprensión de las ideas fundamentales de estocásticos en los alumnos del primer semestre de ingeniería y en las dificultades que pueden tener para aprender probabilidad y estadística; se enfoca en la propuesta para estocásticos de los institutos tecnológicos. En la primera etapa de la investigación, el objeto de análisis fue el programa de estudio y los medios que recomienda el sistema de institutos tecnológicos, así como su correspondencia con las ideas fundamentales de estocásticos para un currículo en espiral. En la segunda etapa se considera la simultaneidad de la introducción de probabilidad y de estadística y del cálculo diferencial e integral. La tercera etapa se centra en el examen de la comprensión de estocásticos de los estudiantes