Repository logo

Browsing by Author "Li, Yan Vivian, committee member"

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Anthropometric fit evaluation of structural firefighters' protective pants: a gender comparison study
    (Colorado State University. Libraries, 2014) Langseth-Schmidt, Kirian, author; Park, Juyeon, advisor; Li, Yan Vivian, committee member; Rosecrance, John, committee member
    This study identified fit issues associated with the female firefighter's station and turnout pants, in comparison to male firefighters. Fifteen firefighters (9 females, 6 males) participated in a multi-dimensional fit evaluation protocol; including a survey, 3D body scanning, joint angle measurement and an exit interview. Female firefighters showed, through the survey, significantly lower ratings on overall satisfaction, comfort, mobility, and performance of their protective pants. Anthropometric data, generated from 3D body scanning, confirmed a congruent trend of the fit issues to the survey data. The joint angle measurement determined decreased range of motion (ROM) for females during simulated occupational activities. Results affirmed that female firefighters experience poorer fit and a higher level of discomfort than male firefighters, while wearing uniform pants designed for the male physique. This study suggests important implications to the firefighting industry, policy makers, and researchers involved in improving protective clothing to enhance occupational safety of firefighters.
  • Thumbnail Image
    ItemOpen Access
    Correlated electron microscopy with electro-optical imaging of hexagonal tungsten oxide nanorods
    (Colorado State University. Libraries, 2019) Cashen, Christina J., author; Sambur, Justin B., advisor; Prieto, Amy, committee member; Li, Yan Vivian, committee member
    Fundamental understanding of the dynamics of ion insertion into a host material are essential to accommodate the rising demand for energy storage technology. It has been established that single nanoparticle electrodes greatly improve the kinetics of the ion insertion reaction, however the heterogeneous behavior of single particles correlated to the structure of the particle has been challenging to determine. This work takes on this challenge by developing a method that implements optical microscopy to study the optical modulations of electrochromic single particle hexagonal tungsten oxide (h-WO3) nanorods with transmission electron microscopy (TEM). Heightened resolution provided by TEM reveals sub-atomic structural details which would be impossible to observe with other techniques. This work introduces a method of measuring correlated single particle optical activity of WO3 with TEM resolution images of the same particle. This study found heterogeneous optical modulations of the carbon film considerably influenced the optical activity of WO3. Bearing in mind this behavior is vital for future experiments using this method. After this is accounted, we compare the optical activity of two single particles using the common parameters: maximum optical density (max OD) and the time it takes to reach 90% of the max OD (t90). This comparison provides further evidence that the presence of nanosized step-edge gradients contribute to the ion insertion dynamics of this electrochromic host material. Further study using this method can reveal a understanding of how the presence of step-edges contributes to the local lattice dynamics upon lithiation of a nanorod.
  • Thumbnail Image
    ItemOpen Access
    Design and application of strongly reducing photoredox catalysts for small molecule and macromolecular synthesis
    (Colorado State University. Libraries, 2019) Pearson, Ryan Michael, author; Miyake, Garret, advisor; McNally, Andy, committee member; Szamel, Grzegorz, committee member; Li, Yan Vivian, committee member
    The synthesis and application of new families of strongly reducing organic photoredox catalysts are described in this dissertation. These compounds provide a platform on which catalytically relevant properties including redox potentials and absorption profiles can be tuned, as well as predicted in silico. The critical photophysical and electrochemical characteristics have been established for both dihydrophenazine and phenoxazine catalysts which enable their ability to be used as green alternatives to commonly used transition metal photocatalysts. Specifically, phenoxazines have been utilized to mediate organocatalyzed atom transfer radical polymerization (O-ATRP) for the production of well-defined polymers using visible light. To this end, a catalyst system able to synthesize acrylic polymers with predictable molecular weights and dispersities less than 1.10 has been developed. In addition, dihydrophenazines were shown to mediate trifluoromethylation and atom transfer radical addition reactions, while phenoxazines were able to mediate C-N and C-S cross coupling reactions in the presence of a nickel co-catalyst.
  • Thumbnail Image
    ItemOpen Access
    Development of surface modifications on titanium for biomedical applications
    (Colorado State University. Libraries, 2021) Maia Sabino, Roberta, author; Popat, Ketul C., advisor; Martins, Alessandro F, advisor; Herrera-Alonso, Margarita, committee member; Li, Yan Vivian, committee member; Wang, Zhijie, committee member
    For decades, titanium-based implants have been largely employed for different medical applications due to their excellent mechanical properties, corrosion resistance, and remarkable biocompatibility with many body tissues. However, even titanium-based materials can cause adverse effects which ultimately lead to implant failure and a need for revision surgeries. The major causes for implant failure are thrombus formation, bacterial infection, and poor osseointegration. Therefore, it is essential to develop multifunctional surfaces that can prevent clot formation and microbial infections, as well as better integrate into the body tissue. To address these challenges, two different surface modifications on titanium were investigated in this dissertation. The first one was the fabrication of superhemophobic titania nanotube (NT) surfaces. The second approach was the development of tanfloc-based polyelectrolyte multilayers (PEMs) on NT. The hemocompatibility and the ability of these surfaces to promote cell growth and to prevent bacterial infection were investigated. The results indicate that both surface modifications on titanium enhance blood compatibility, and that tanfloc-based PEMs on NT improve cell proliferation and differentiation, and antibacterial properties, thus being a promising approach for designing biomedical devices.
  • Thumbnail Image
    ItemOpen Access
    Nitric oxide-releasing or generating surfaces for blood-contacting medical devices
    (Colorado State University. Libraries, 2020) Zang, Yanyi, author; Reynolds, Melissa, advisor; Kipper, Matt, committee member; Li, Yan Vivian, committee member; Zabel, Mark, committee member
    Medical device-induced thrombosis is a major complication that impairs the expected performance of blood-contacting medical devices. Traditional anticoagulation therapies are used to reduce thrombus formation; however, systemic anticoagulants such as heparin increase the risk of thrombocytopenia or even bleeding, which are detrimental to patients who already have injuries. To address these issues, surface modification has been widely studied to improve the performance of blood-contacting medical devices, ranging from biopassive surfaces to biomimetic surfaces. To date, such modifications are not sufficient to prevent blood clotting alone. Supplementary anticoagulation remains necessary to maintain clot-free surfaces. Nitric oxide (NO) is a well-known signaling molecule that has antiplatelet properties. Our approach is to use surfaces that can either release NO via NO donors or promote NO production via an NO catalyst. In this work, a NO-releasing polyelectrolyte multilayer coating effectively reduces platelet adhesion, platelet activation and delay blood clotting on titania nanotube array surfaces. In addition, NO-releasing polymeric surfaces mediate blood serum protein deposition in a manner that prevents platelet adhesion and platelet activation. However, the NO donors used in these two coatings are photo- and thermo- sensitive, and the NO release is limited by the amount of NO donor added to the coating. To overcome these shortcomings, a copper-based metal organic framework (MOF) was used to infinitely promote NO production from NO donors in the blood. The copper-based MOF polymer coating was successfully applied to the surfaces of extracorporeal life support catheters and circulation tubing via custom coating systems. These copper-based MOF-coating also exhibited inherent antibacterial properties under both static and dynamic flow conditions.
  • Thumbnail Image
    ItemOpen Access
    The right ventricle—the forgotten chamber that deserves more love
    (Colorado State University. Libraries, 2022) Nguyen-Truong, Michael, author; Wang, Zhijie, advisor; Chicco, Adam, committee member; Li, Yan Vivian, committee member; McGilvray, Kirk, committee member; Popat, Ketul, committee member
    Right ventricle failure (RVF) is associated with serious cardiac and pulmonary diseases that contribute significantly to the morbidity and mortality of patients. The prevalence of RVF is significantly increased in the later stages of pulmonary hypertension, congenital heart disease, and left heart failure with preserved ejection fraction. Moreover, the mortality rate of these patients has not improved with currently limited treatment options. The persistent clinical challenge is mainly due to an incomplete understanding of the structure-function relationships of the RV, partly attributed to the lack of large animal models, as well as the lack of RV-specific therapies. Therefore, the overall goal of the study is to fill knowledge gaps in the biomechanics of right ventricle failure secondary to pressure overload and in the regenerative potential of mesenchymal stromal cells (MSCs) regulated by RV mechanics. The specific aims are: 1. Assess the unique ex vivo biomechanics of the RV free wall in contrast to the LV free wall. 2. Assess the ex vivo biomechanics of the "significant other" of the RV chamber – the septum wall. 3. Establish a novel ovine model of RV failure and investigate RV biomechanical changes during RV failure progression. 4. Investigate the pro-angiogenic paracrine effect in the context of mesenchymal stromal cell mechanobiology to ultimately improve RV therapy. From ovine models, there was distinct anisotropic mechanical behavior of the RV compared to the left side in healthy adults, and the low-strain mechanical behavior was correlated to collagen III. Multiscale computational model indicated softer collagen fibers in the RV. The investigation on the septal wall originally revealed transmural biomechanical changes and a significantly more compliant wall than the ventricular free walls. A new adult RV failure was established, and there was stiffening of the RV in the outflow tract direction and altered tissue anisotropy with RV failure progression. Finally, from prior and our own RV mechanical data, biomimetic scaffolds that represent healthy and diseased RV mechanics were fabricated for the first time. The pro-angiogenic potentials of MSCs on these scaffolds were assessed by cytokine production and neovessel formation. There were synergistic effects of matrix stiffness and anisotropy on MSC pro-angiogenic functionality.