1925 research outputs found
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Assessing fire impacts to a spring-fed riparian ecosystem during a dry climate cycle in Grand Canyon National Park, USA
No full textRecent threats to long term functionality of springs and their dependent ecosystems throughout the Grand Canyon ecoregion have surfaced as the current climate cycle continues to shift seasonal regimes to hotter and dryer conditions. Increasing fire disturbance is an emerging consequence. This study assessed ecosystem resilience to ongoing climate stressors, scouring disturbance, and novel fire disturbance throughout ~20,000 meters² of a burned spring-fed riparian ecosystem in Grand Canyon National Park for one year following the fire. Findings highlighted complex internal relationships between parameters of hydrology, geology, geomorphology, and vegetation composition that influenced ecosystem recovery to disturbances and climate stressors on a reach-scale basis. Temporally dry stream reaches were less resilient to changing hydrologic regimes induced by climate change and displayed low rates of vegetation regrowth during recovery from fire. Temporally wet reaches displayed higher rates of vegetation regrowth following fire, suggesting reaches more resilient to climate stressors were able to sustain higher rates vegetation recovery following novel fire disturbance. Scouring and significant alluvial erosion were identified as disturbances that caused ecosystem composition and structure changes that may increase in frequency following fire removal of channel-stabilizing root systems. Seasonal flooding regimes were identified as a critical disturbance required for Fremont cottonwood (Populus fremontii) sapling establishment, however flood intervals and climate impact to flood regimes were not quantified in this study. Overarching ecosystem changes to composition and structure were identified by the short-term removal of Fremont cottonwood from the system, the previously dominant phreatic species. Recommendations were made to better constrain long-term fire influences on resilience, and to rehabilitate heavily impacted ecosystem reaches. As fire in spring ecosystems is likely to increase throughout semi-arid regions, an interdisciplinary monitoring and response plan should be refined to guide management plans
Case Study of Dual Certification Practicum: Focusing on Students' Perceptions of Field Placements
No full textThis descriptive case study delved into the perceptions of Dual Certification Practicum students. The researcher examined the insight of the preservice teachers with regards to the practicum course. The Participants are three Southwestern University students that are enrolled in the Bachelor of Science Elementary Education program. The students selected have completed three semesters of practicum. Data was collected through a Venn Diagram, focused questionnaire, interview and artifacts from the student’s practicum experiences. The data analysis process utilized first cycle coding for the Venn Diagram. The focused questionnaire, artifacts and the interview were analyzed through multiple cycles of coding.The data collection tools scaffold the Participants’ memories of their different practicum courses to expose the results. The findings revealed that the mentor teacher is influential when it comes to the perceptions of the practicum course. Each student had different experiences during their practicum course but in the end the mentor teachers’ approach to the student outlined how the course proceeded. This document provides a narrative of the students’ individual experiences in practicum and the multiple connections that lead back to the mentor teacher’s influence
Governments' use of fear appeals and accessible language in COVID-19 outreach: comparing Florida and New York’s messages, March 2020-September 2020
No full textThe United States has struggled throughout the COVID-19 pandemic to effectively reduce the impacts of the virus. This is largely due to the drastically different responses from state-level leadership; two states that demonstrate such opposing reactions are New York and Florida. In March 2020, NY officials implemented complete shutdowns of public spaces and prohibited social gatherings, whereas FL officials introduced little to no restrictions. The official outreach from these states are key sources for constituents to learn about health threats and necessary safety precautions. Current health communication research argues that effectively conveying risks and mitigation strategies can be accomplished through the combined use of fear appeals and efficacy promotion. This research applies the recommendations of the Extended Parallel Process and Elaboration Likelihood Models to identify how successful NY and FL's COVID-19 messages were in arousing fear and promoting behavior change. Recognizing the cognitive needs and diverse backgrounds of constituents is also key in motivating them to attend to health messages and make necessary changes. Because of the disproportionate impacts of COVID-19 on those of low socioeconomic status and racial and ethnic minorities, this study analyzes the literacy levels of FL and NY's messages and the frequency of their references to minority groups. The results suggest that neither state holistically applied the aforementioned models nor demonstrated a consideration of the literacy levels and demographic backgrounds of constituents. As health inequities have been exacerbated during the COVID-19 pandemic, it has become more important than ever to identify and alleviate current gaps in public health outreach. Further research can test how other states used fear appeals and catered communication towards high-risk constituents to identify the magnitude of persuasive discontinuity in public health messages across the U.S
On codes and matroids: minors, self-orthogonality, cycle nested and doubly-even matroids
No full textThe strong interplay between codes and matroids has generated a considerable interest in the discrete mathematics literature over several decades. While the main starting point in this interplay was the connection between the weight enumerator of a code and the Tutte polynomial of a matroid, many more connections have been established since. In this thesis, we explore these connections further, and introduce new notions for matroids using concepts from coding theory. Our main contributions can be summarized in two parts. In the first part, we consider the code-minor problem, which is something that has been inspired by matroid operations, but has not been properly investigated. We find necessary and sufficient conditions for a binary code to be a minor of another binary code, together with the corresponding results for matroids. We focus on special matrices for binary codes to get further results, using strings and substrings. In particular, we focus on establishing conditions for self-dual binary codes to have the extended binary Hamming or the extended binary Golay code as a minor. In the second part, we introduce the notions of cycle nested and doubly-even matroids using concepts of self-orthogonality from coding theory. In the binary case, we characterize the cocycle nested matroids and describe some properties of doubly-even matroids by relating them to doubly-even codes
Computational Analysis of Flow Topology and Targeted Drug Delivery in Coronary Artery
No full textNanotechnology has introduced novel diagnostic and therapeutic solutions in the field of medical sciences for the improvement and optimization of conventional methods. In this script, we focus on nano-scale therapeutic particles, which have a pivotal role in the invention of targeted drug delivery systems. Targeted drug delivery is a promising technique to direct the drug to specific diseased regions. Nanoparticles have provided an attractive approach for this purpose. In practice, the major focus of targeted delivery has been on targeting cell receptors. However, the complex fluid mechanics in diseased biomedical flows questions if a sufficient number of nanoparticles can reach the desired region. In this thesis, we present our study on a shear-sensitive drug delivery system and investigate the relationship between the topology of the flow and coherent structures defining ridges in the flow field with the dispersed particles' concentration maps in the left anterior descending artery (LAD). We propose that hidden topological structures in cardiovascular flows identified with Lagrangian coherent structures (LCS) control drug transport and provide valuable information for optimizing targeted drug delivery efficiency. We couple image-based computational fluid dynamics (CFD) with continuum transport models to study nanoparticle transport in coronary artery disease. We simulate nanoparticle transport as well as the recently proposed shear targeted drug delivery system that couples micro-carriers with nanoparticle drugs. The role of the LCS formed near the stenosed artery in controlling drug transport is discussed. Furthermore, we demonstrate the drug transport in the coronary artery wall targeting the vascular smooth muscle cells. Finally, we review some potential applications of nanoparticles in the treatment of cancer. Our results motivate the design of smart micro-needles guided by flow topology, which could achieve optimal drug delivery efficiency
In vitro neurovascular model development for liquid embolic implant simulation
No full textCerebral aneurysms are responsible for the death of 500,000 people each year with half of the victims less than 50 years old.1 Aneurysm rupture results in 50% mortality and a 66% chance of permanent disability. Current aneurysm treatment devices are delivered by making an incision in the femoral artery of a patient, and delivered to the brain using microcatheters. A novel liquid embolic device, PPODA-QT poly (propylene glycol) diacrylate and pentaerythritol tetrakis (3-mercaptopropionate) (PPODA-QT), is under development for the occlusion and treatment of cerebral aneurysms. Benchtop testing may be utilized to augment in vivo biocompatibility tests.The first aim of this thesis involved the creation of a vessel phantom that mimics the physiological properties and tortuosity of human vasculature. In the second aim, a flow loop was designed to replicate and monitor physiological flows within the circle of Willis. In the last aim, the resultant system was utilized to monitor a simulated balloon occlusion and long term data acquisition.
A clinically relevant SolidWorks® model of human vasculature was designed. A biomimetic material, printed using a Connex® 3 Objet 260 printer, was selected to match human vessel properties. An in vitro model was created, using a ViVitro® Superpump and LabVIEW® VI with sensors to monitor pressure and flow. Lastly, a simulated use in a mock procedure and long term monitoring evaluation were performed. This thesis presents a methodology of developing and adapting an in vitro flow loop for clinical simulation and empirical procedural validation
The role of host identity in high latitude moss-associated nitrogen fixation
Get PDFMosses make up a significant portion of primary plant productivity in Arctic and boreal ecosystems and are important regulators of biogeochemical cycling. In addition to producing recalcitrant litter and insulating soils, mosses often host epiphytic microbes capable of fixing nitrogen (N) from the air at rates which make it the largest source of a limiting nutrient in these environments. Since the availability of N is linked to carbon (C) fixation and decomposition, the current and future rates of N2 fixation are important topics of research in an area which stores large amounts of C belowground. Past evidence indicates that host moss identity and environmental conditions can alter rates of moss-associated N2 fixation. However, past studies often focus on a limited number of species and use indirect methods to measure N2 fixation. This dissertation employs 15N2 incubations to measure rates of moss-associated fixation at sites ranging from 60° to 68° N in Alaska in both natural surveys and manipulative experiments in the field. We found that N2 fixation is almost ubiquitous among mosses and that moss identity is consistently an important predictor of associated N2 fixation rates. In subsequent analyses related to C stable isotopes and a reciprocal transplant, we also found a significant interaction between host identity and environment. The strength of the interaction term was typically host specific. As temperature and other abiotic conditions change along with climate and cause changes in moss biomass and diversity, it is critical to incorporate the interaction term into predictions of future N inputs
Virtual education in K-12 for at-risk students: a school analysis answering questions pertaining to preparedness, environment, and performance
No full textThis study included quantitative and qualitative methods to provide an in-depth exploration of the parameters of at-risk student virtual education environment. Surveys were administered to teachers, students, and support staff. The connection between school resources and learning are discussed in this study. The results of the study provide insights into how students struggling through adverse situations can be transformed into successful high school graduates. The study makes a lucid understanding of how virtual schools can enable students in at-risk situations to graduate from high school, contrary to views in literature
Photovoltaic characterization and trans-oceanic sub-surface photovoltaic performance
No full textUtilization of marine photovoltaic energy is primarily focused on surfaceharvesting with limited photovoltaic cell implementation in a submarine
environment. To obtain estimations of photovoltaic energy in the
submarine environment, an experimental deployment of solar cells was utilized.
This deployment involved the development of custom photovoltaic
assessment modules (CPAMs). These CPAMs were affixed to four adult
female northern elephant seals (Mirounga angustirostris) with deployment
times between 76 and 107 days. These deployments encompassed a large
geographic area between Santa Cruz, California and the Aleutian Islands
of Alaska. This work discusses the calibration, dive shifting, and power
calculations of these oceanic deployments. Deployment results, including
power results and energy predictions from the CPAM data record, are
presented up to 22 meters in depth. Past this depth, depths fell below
the sensitivity of the data resulting in a non-uniform distribution of high,
medium, and low irradiances. However, this deployment relied on nonlinear
regression to obtain power at depth and in low-light conditions,
this regression did not produce accurate estimations of power. To include
these low-light level cases, experimental laboratory characterization was
conducted. While photovoltaic cells have been deployed in the marine environment
in the past to assess performance at depth, unfortunately, these applied
studies have been somewhat limited in their scope due to the environmental
conditions at the test location. The results of silicon solar cell
testing in a laboratory setting wherein the spectra produced by various
water types are simulated over a wide range of depth and temperature are
also presented. Spectra at depth were generated based on Bird's Clear
Sky model and Jerlov's spectral absorption coefficients. These spectra
were used in conjunction with a tunable solar simulator, source meter,
and cold plate. This work discusses the spectra generation, experimental
testing, and current-voltage curve parameters of silicon solar cells. The
results include short circuit current, open circuit voltage, and maximum
power at ten different water types with depths up to 30 m. While deeper
depths could have been conducted, only depths up to 30 m were considered
to limit the number of testing cases. This laboratory characterization
provided an interpolation table to obtain power estimations for low-light
conditions within the field deployment. It was found that there was a
roughly 70-85% reduction in power within the first 5 m and 85-95% reduction
in power at 15 m, comparable to previously published literature.
Depending on solar cell size, energy requirements, and energy behavior
of a bio-logger, solar energy can be a primary or supplementary energy
source
Development and optimization of an injectable liquid-to-solid polymer gelation system for treatment of large and wide-neck intracranial aneurysms
No full textAn intracranial aneurysm is an abnormal enlargement or pouch that forms from a weakened vessel segment in the brain. Often going unnoticed and untreated, these aneurysms can rupture and cause a sudden and catastrophic hemorrhagic stroke. Approximately 15% of patients die from an intracranial aneurysm rupture even before receiving medical attention and 25% of patients die despite medical treatment. Patients that survive typically suffer from various levels of morbidity such as neurological deficits. Thus, only one in four patients who suffer a ruptured intracranial aneurysm will fully recover. It is estimated that between 3 million and 6 million Americans have intracranial aneurysms, and approximately 30,000 people in the United States suffer a rupture event each year.1–6There are a number of endovascular aneurysm treatment devices currently on the market, as well as a few more under investigation. However, all of these devices have significant shortcomings such as limited biocompatibility and efficacy that can potentially be addressed with a new device or devices.
This proposal details the development of a novel liquid embolic (PPODA-QT) that quickly solidifies into a stable and biocompatible cast of any aneurysm shape and size. This material could provide surgeons with a novel approach for aneurysm treatment, especially for large and wide-neck aneurysms that current devices have limited efficacy in treating. Preliminary in vitro modeling and in vivo aneurysm studies have demonstrated that PPODA-QT allows for precise delivery control, vessel protection, and complete and durable occlusion of larger side-wall and bifurcation aneurysms with small-, medium-, and wide-necks, while eliminating the issues encountered with past liquid embolics like Onyx such as biocompatibility, device migration during delivery, and catheter adhesion.1,7,8 Gross and histological evaluation of PPODA-QT injected into in vivo aneurysm models has also suggested that the material is highly biocompatible, making PPODA-QT an exciting material candidate for endovascular intracranial aneurysm treatment.