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- Title
- SOLAR AND FUEL CELL CIRCUIT MODELING, ANALYSIS AND INTEGRATIONS WITH POWER CONVERSION CIRCUITS FOR DISTRIBUTED GENERATION.
- Creator
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Krishnamurthy, Smitha, Yuan, Jiann, University of Central Florida
- Abstract / Description
-
Renewable energy is considered to be one of the most promising alternatives for the growing energy demand in response to depletion of fossil fuels and undesired global warming issue. With such perspective, Solar Cells and Fuel Cells are most viable, environmentally sound, and sustainable energy sources for power generation. Solar and Fuel cells have created great interests in modern applications including distributed energy generation to provide clean energy. The purpose of this thesis was to...
Show moreRenewable energy is considered to be one of the most promising alternatives for the growing energy demand in response to depletion of fossil fuels and undesired global warming issue. With such perspective, Solar Cells and Fuel Cells are most viable, environmentally sound, and sustainable energy sources for power generation. Solar and Fuel cells have created great interests in modern applications including distributed energy generation to provide clean energy. The purpose of this thesis was to perform a detailed analysis and modeling of Solar and Fuel cells using Cadence SPICE, and to investigate dynamic interactions between the modules and power conversion circuits. Equivalent electronic static and dynamic models for Solar and Fuel Cells, their electrical characteristics, and typical power loss mechanisms associated with them are demonstrated with simulation results. Power conversion circuits for integration with the dynamic models of these renewable low voltage sources are specifically chosen to boost and regulate the input low dc voltage from the modules. The scope of this work was to analyze and model solar and fuel cells to study their terminal characteristics, power loss mechanisms, modules and their dynamics when interfaced with power converters, which would lead to better understanding of these renewable sources in power applications.
Show less - Date Issued
- 2009
- Identifier
- CFE0002815, ucf:48100
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002815
- Title
- Establishment of Methods for Isolation of Pnmt+ Cardiac Progenitor Cells.
- Creator
-
Varudkar, Namita, Ebert, Steven, Parthasarathy, Sampath, Muller, Mark, University of Central Florida
- Abstract / Description
-
Cardiovascular disease is the leading cause of death in the United States. Millions of patients suffer each year from endothelial dysfunction and/or debilitating myocardial damage resulting in decreased quality of life and increased risk of death or disablement. Current pharmacological approaches are only partly effective at treating cardiovascular disease, and hence, better strategies are needed to provide significant improvements in treatment options. Cardiac stem/progenitorcells have the...
Show moreCardiovascular disease is the leading cause of death in the United States. Millions of patients suffer each year from endothelial dysfunction and/or debilitating myocardial damage resulting in decreased quality of life and increased risk of death or disablement. Current pharmacological approaches are only partly effective at treating cardiovascular disease, and hence, better strategies are needed to provide significant improvements in treatment options. Cardiac stem/progenitorcells have the potential to regenerate myocardial tissue and repair damaged heart muscle. There are many different types of cardiac progenitor cells, and each may have certain unique properties and characteristics that would likely be useful for particular clinical applications. A current challengein the field is to identify, isolate, and test specific cardiac stem/progenitor cell populations for their ability to repair/regenerate myocardial tissue. Our laboratory has discovered a new type of cardiac progenitor cell that expresses the enzyme, Phenylethanolamine-n-methyltransferase (Pnmt). My initial studies focused on identification of Pnmt+ cells based on knock-in of a nuclear-localized Enhanced Green Fluorescent Protein (nEGFP) reporter gene into exon 1 of the Pnmt gene in a stable recombinant Pnmt-nEGFP mouse embryonic stem cell (mESC) line. These cells were differentiated into cardiomyocytes, and I identified nEGFP+ cells using fluorescence, immunofluorescence, and phase-contrast microscopy techniques. Our results showed that only about 0.025% ( 1 per 4000) of the cardiac-differentiating stem cells expressed the nEGFP+ marker. Because of the relative rarity of these cells, optimization of isolation methods proved initially challenging. To overcome this technical barrier, I used a surrogate cell culture system to establish the methodsof isolation based on expression of either a fluorescent cell marker (EGFP), or a unique cell surface receptor represented by an inactivated (truncated) version of the human low-affinity nerve growth factor receptor (LNGFR). Plasmid DNA containing these reporter genes was transiently transfected into a permissive cell line (RS1), and reporter gene expression was used to identify and isolate transfected from non-transfected cells using either Fluorescence-Activated Cell Sorting(FACS) or Magnetic-Activated Cell Sorting (MACS) methods. The main objective of the study was to establish the isolation techniques based on the expression of reporter genes (EGFP and LNGFR) in RS1 cells. Following transfection, EGFP+ cells were successfully isolated via FACS as verified by flow cytometric and microscopic analyses, which showed that approximately 96% of the isolated cells were indeed EGFP+. Despite the relative purity of the isolated cell population, however, their viability in culture following FACS was substantially compromised ( 50% attrition). In contrast, MACS enabled efficient isolation of LNGFR+ cells, and the vast majority of these ( 90%) retained viability in culture following MACS. The LNGFR expression was verified using RT-PCR. Further, MACS methods enabled isolation of marked cells in about 5-7 mins, whereas it took 2-4 hours to using FACS to perform similar isolations from the same amount of starting material (10^6 cells). In addition, MACS is a more economical method in that it does not require the use of an expensive laser-based instrument to perform the sorting. These results suggest that MACS was a more efficient, gentle, and feasible technique than FACS for isolation of reporter-tagged mammalian cells. Consequently, future studies aimed at isolation of Pnmt+ cardiac progenitor cells will thus primarily focus on MACS methods.
Show less - Date Issued
- 2014
- Identifier
- CFE0005558, ucf:50287
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005558
- Title
- PREPARATION AND CHARACTERISATION OF STABILIZED NAFION/PHOSPHOTUNGSTIC ACID COMPOSITE MEMBRANES FOR PROTON EXCHANGE MEMBRANE FUEL CELL (PEMFC) AUTOMOBILE ENGINES.
- Creator
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Agarwal, Rohit, Fenton, James, University of Central Florida
- Abstract / Description
-
Membrane durability is one of the limiting factors for proton exchange membrane fuel cell (PEMFC) commercialisation by limiting the lifetime of the membrane via electrochemical / mechanical / thermal degradation. Lower internal humidity in the membrane at high temperature (>100 oC) and low relative humidity (25-50 %RH) operating conditions leads to increased resistance, lowering of performance and higher degradation rate. One of the promising candidates is composite proton exchange membranes ...
Show moreMembrane durability is one of the limiting factors for proton exchange membrane fuel cell (PEMFC) commercialisation by limiting the lifetime of the membrane via electrochemical / mechanical / thermal degradation. Lower internal humidity in the membrane at high temperature (>100 oC) and low relative humidity (25-50 %RH) operating conditions leads to increased resistance, lowering of performance and higher degradation rate. One of the promising candidates is composite proton exchange membranes (CPEMs) which have heteropoly acid (HPA) e.g. Phosphotungstic acid (PTA) doped throughout the Nafion® matrix. HPA is primarily responsible for carrying intrinsic water which reduces the external water dependence. The role of relative humidity during membrane casting was studied using surface analysis tools such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermo-gravimetric analysis (TGA), and Scanning electron microscopy (SEM) / Energy dispersive spectrometer (EDS). Membrane casting at lower relative humidity (30% approx.) results in finer size, and better PTA incorporation in the composite membrane. The effect of increase in PTA concentration in the Nafion matrix was studied with regards to conductivity, performance and durability. In-plane conductivity measurements were performed at 80 oC and 120 oC. During theses measurements, relative humidity was varied from 20% to 100% RH. Membrane conductivity invariably increases on increasing the relative humidity or operating temperature of the cell. Membrane conductivity increases with increasing PTA content from 3% to 25% PTA but never reaches the conductivity of membrane with 0% PTA. Possible explanation might be the role of cesium in PTA stabilisation process. Cesium forms a complex compound with PTA inside host matrix, rendering the PTA incapable of holding water. In plane conductivity measurements only measure surface conductivity, hence another reason might be the existence of a PTA skin on the membrane surface which is not truly representative of the whole membrane. XRD revealed that the structure of the composite membrane changes significantly on addition of PTA. Membrane with 3% PTA has structure similar to Nafion® and does not exhibit the characteristic 25o and 35o 2Ө peaks while membrane with 15% PTA and 25% PTA have strong characteristic PTA peaks. Also the membrane structure with 25% PTA matches well with that of PTA.6H2O. By applying the Scherer formula, PTA particle size was calculated from Full width half maximum (FWHM) studies at 17o 2Ө peak of the membranes. Particles coalesce on increasing the PTA concentration in the membrane leading to larger particles but still all particles were in nanometer range. Also the FWHM of membranes decreased at 17o 2Ө peak on increasing the PTA concentration, leading to higher crystallinity in the membrane. Structure analysis by FTIR indicated increase in PTA signature intensity dips, as the PTA concentration in membrane increases from 0-25%. Also by FTIR studies, it was found that some PTA is lost during the processing step as shown by comparison of as cast and protonated spectra. Possible reasoning might be that some amount of PTA does not gets cesium stabilized which gets leached away during processing. TGA studies were performed which showed no signs of early thermal degradation (temperature >300 oC); hence the assumption that all membranes are thermally robust for intended fuel cell applications. The membranes with different amounts of PTA were then catalyst coated and tested for 100-hour at open circuit voltage (OCV), 30% RH and 90 oC. By increasing the PTA in the host Nafion® matrix, the percent change in fuel crossover decreases, percent change in ECA increases, cathode fluoride emission rate decreases, and percent change in OCV decreases after the 100 hour test. Possible reasons for decreasing percentage of fuel crossover might be the increased internal humidity of the membrane due to increasing PTA incorporation. It is reported that during higher relative humidity operation, there is decrease in fuel crossover rate. Increasing ECA percentage loss might be due to the fact that HPA in the membrane can get adsorbed on the catalyst sites, rendering the sites inactive for redox reaction. Decrease in cathode fluorine emission rate (FER) might be due to the fact that there is more water available internally in the membrane as compared to Nafion®. It is reported that at higher relative humidity, FER decreases. ECA and crossover both contribute to the OCV losses. Higher component of OCV is crossover loss, which results in mixed potentials. Hence decreasing percentage of crossover might be the reason behind the decreasing OCV loss. Initial performance of fuel cell increases with increasing PTA concentration, but after the 100 hour test, higher PTA membrane exhibited highest performance loss. Increasing initial fuel cell performance can be due to the lowering of resistance due to PTA addition. Increasing ECA losses might be responsible for the increasing performance losses on adding more PTA to host membrane.
Show less - Date Issued
- 2008
- Identifier
- CFE0002486, ucf:47677
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002486
- Title
- A NOVEL BINDING INTERACTION FOR THE PAXILLIN LD3 MOTIF: PAXILLIN LD3 MEDIATES MERLIN-PAXILLIN BINDING AT PAXILLIN BINDING DOMAIN 1.
- Creator
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Geden, Sandra, Fernandez-Valle, Cristina, University of Central Florida
- Abstract / Description
-
Neurofibromatosis type 2, an autosomal dominant genetic disorder, causes predisposed individuals to develop various benign central and peripheral nervous system tumors. The characteristic tumors of this disease are schwannomas, which are tumors of the Schwann cells, typically on the vestibular nerve. These and the other associated tumors slowly compress nervous system structures causing deafness and loss of balance, resulting in an average life-span of less than 40 years. The product of the...
Show moreNeurofibromatosis type 2, an autosomal dominant genetic disorder, causes predisposed individuals to develop various benign central and peripheral nervous system tumors. The characteristic tumors of this disease are schwannomas, which are tumors of the Schwann cells, typically on the vestibular nerve. These and the other associated tumors slowly compress nervous system structures causing deafness and loss of balance, resulting in an average life-span of less than 40 years. The product of the Nf2 gene is the protein named merlin or schwannomin. In individuals diagnosed with NF2, merlin is either absent or mutated to the point of inactivation. As such, merlin functions as a negative growth regulator in that it suppresses tumor growth. Being that NF2 is predominately a disease of the Schwann cells, merlin's functional role within the signal transduction pathways of Schwann cell growth and differentiation are being investigated. This thesis explores the molecular relationships between merlin and its various interactors within Schwann cells, and illuminates one step in elucidating merlin's functional mechanism of action. Merlin has been shown to associate with paxillin in a density-dependant manner and to bind directly to paxillin through two specific paxillin binding domains. Individual paxillin LD domain fusion proteins were produced, as well as recombinant merlin lacking the paxillin binding domains. Direct binding assays were performed in order to determine which specific paxillin domains merlin might interact with directly. The results indicate that, in vitro, merlin binds, through its PBD1 domain, to the paxillin LD3 motif. Supporting this data, the results also demonstrate that when the merlin PBD1 domain is deleted, merlin binding to paxillin LD3 is abrogated. The direct binding shown here between paxillin and merlin, coupled with research demonstrating that merlin is present in â1 integrin immuno-precipitations, leads to the question of whether merlin binds directly to â1 integrin or associates with â1 integrin through paxillin. Using direct binding assays, this research shows that the merlin C-terminus binds directly to the cytoplasmic domain of â1 integrin, in vitro. Lastly, since merlin is an ERM family protein and has been shown to dimerize with ezrin (another ERM family member), and because merlin has been shown to bind directly to paxillin, the question asked is whether paxillin can interact directly with ezrin. The results indicate that paxillin can bind directly to the N-terminus of ezrin, in vitro. The findings presented here, when examined together, provide a framework for the proposal of a model in which paxillin LD3 mediates the localization of merlin to the plasma membrane, where it associates with the â1 integrin cytoplasmic domain and ezrin. These results and the proposed model offer additional insight into the mechanism of action of merlin's negative growth regulating function in Schwann cells.
Show less - Date Issued
- 2005
- Identifier
- CFE0000654, ucf:46499
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000654
- Title
- STUDY OF THE INTERACTIONS OF PROTEINS, CELLS AND TISSUE WITH BIOMATERIALS.
- Creator
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Bhalkikar, Abhijeet, Hickman, James, University of Central Florida
- Abstract / Description
-
Bioengineering is the application of engineering principles to address challenges in the fields of biology and medicine. Biomaterials play a major role in bioengineering. This work employs a three level approach to study the various interactions of biomaterials with proteins, cells and tissue in-vitro. In the first study, we qualitatively and quantitatively analyzed the process of protein adsorption of two enzymes to two different surface chemistries, which are commonly used in the field. In...
Show moreBioengineering is the application of engineering principles to address challenges in the fields of biology and medicine. Biomaterials play a major role in bioengineering. This work employs a three level approach to study the various interactions of biomaterials with proteins, cells and tissue in-vitro. In the first study, we qualitatively and quantitatively analyzed the process of protein adsorption of two enzymes to two different surface chemistries, which are commonly used in the field. In the second study, we attempted to engineer a tissue construct to build a biocompatible interface between a titanium substrate and human skin. In the third study, an in-vitro model of the motoneuron-muscle part of the stretch reflex arc circuit was developed. Using a novel silicon based micro-cantilever device, muscle contraction dynamics were measured and have shown the presence of a functional neuro-muscular junction (NMJ). These studies have potential applications in the rational design of biomaterials used for biosensors and other implantable devices, in the development of a functional prosthesis and as a high-throughput drug-screening platform to study various neuro-muscular disorders.
Show less - Date Issued
- 2010
- Identifier
- CFE0003347, ucf:48433
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003347
- Title
- USER-DEFINED PATTERNING OF NEURAL PROGENITOR CELLS ON 3D MICROPILLAR ARRAYS USING ROUND CROSS-SECTIONAL GEOMETRY, SPECIFIC DIMENSIONS AND THIOL-BASED CHEMICAL ADHESION.
- Creator
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Wesser, Andrea, Cho, Hyoung Jin, University of Central Florida
- Abstract / Description
-
The ability to control stem cell functions, particularly neuronal progenitors, has long since been believed to be the key to successful treatment of neurodegenerative disorders such as Alzheimer's, Parkinson's and accidents involving head trauma. The neurology field calls for many new solutions to address the controlled neural stem cell seeding and placement of cells for neural tissue regeneration. Self-assembled monolayers (SAM) from the alkanethiol group provide a straightforward...
Show moreThe ability to control stem cell functions, particularly neuronal progenitors, has long since been believed to be the key to successful treatment of neurodegenerative disorders such as Alzheimer's, Parkinson's and accidents involving head trauma. The neurology field calls for many new solutions to address the controlled neural stem cell seeding and placement of cells for neural tissue regeneration. Self-assembled monolayers (SAM) from the alkanethiol group provide a straightforward applicable, reliable treatment for cell adhesion. An ODT/gold treatment was used to adhere the cells to patterned areas, due mainly to a high confluence of cells attracted to it, as well as the viable environment it produced for the cells. Arrays of micropillars, made of SU-8 photoresist, then covered with a thin film of gold and treated with the ODT, created scaffolding allowing manipulation of neural stem cells. Based on multiple trials of observing varying cross-sectional geometric parameters, metal layer thicknesses and the ODT/Gold treatment, this study explores seeding density control, base and circumferential cell population dependence on those parameters.
Show less - Date Issued
- 2008
- Identifier
- CFE0002054, ucf:47563
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002054
- Title
- CELL PHONE DISTRACTION: ANALYSIS OF MOTOR RESPONSE IN A SIMULATED DRIVING ENVIRONMENT.
- Creator
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Ravishankar, Anusha, Kincaid, Dr.J.Peter, University of Central Florida
- Abstract / Description
-
Does the use of a cell phone while driving influence the driver's ability to execute a proper turn?Is there difference between genders pertaining to motor skill while driving in a simulated driving environment? To find the answers to these questions, three groups of ten participants (5 women and 5 men)each were tested using a scripted test scenario focusing on left and right turns. The participantswere made to drive through a test scenario to get used to the driving simulator. The scenario...
Show moreDoes the use of a cell phone while driving influence the driver's ability to execute a proper turn?Is there difference between genders pertaining to motor skill while driving in a simulated driving environment? To find the answers to these questions, three groups of ten participants (5 women and 5 men)each were tested using a scripted test scenario focusing on left and right turns. The participantswere made to drive through a test scenario to get used to the driving simulator. The scenario for the experimental group was an inner-city training scenario with the presence of vehicular trafficand the main focus area was on six critical turns (3 left and 3 rights). The apparatus used for this study was the "Patrol Simulator" built by GE Driver Development. A 2 (Gender) x 3 (Cell phone condition) between subjects design was used to assess the differences in mean driving performance between gender (male and female) at 3 cell phone conditions (No Phone, Phone No Conversation, Phone with Conversation). The study verified that cell phone use while driving would adversely affects a driver's ability to perform turns, and showed that gender plays a role in this effect. However, it did confirm that gender does not play any role in a person's overall ability to drive.
Show less - Date Issued
- 2004
- Identifier
- CFE0000084, ucf:46149
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000084
- Title
- INVESTIGATING THE ROLE OF NEURONAL AGING IN FRAGILE X-ASSOCIATED TREMOR/ATAXIA SYNDROME.
- Creator
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Hencak, Katlin Marie, von Kalm, Laurence, Southwell, Amber, University of Central Florida
- Abstract / Description
-
Fragile X-associated tremor/ataxia syndrome (FXTAS) is an X-linked late-onset neurodegenerative disorder caused by a noncoding trinucleotide repeat expansion in the FMR1 gene. This gene produces fragile x mental retardation protein (FMRP), an RNA binding protein whose targets are involved in brain development and synaptic plasticity. One of the proposed mechanisms of FXTAS pathogenesis is an RNA gain-of-function in which the repeat expansion causes toxic mRNA that sequesters important...
Show moreFragile X-associated tremor/ataxia syndrome (FXTAS) is an X-linked late-onset neurodegenerative disorder caused by a noncoding trinucleotide repeat expansion in the FMR1 gene. This gene produces fragile x mental retardation protein (FMRP), an RNA binding protein whose targets are involved in brain development and synaptic plasticity. One of the proposed mechanisms of FXTAS pathogenesis is an RNA gain-of-function in which the repeat expansion causes toxic mRNA that sequesters important proteins in the cell, interfering with their functions. Another suggested method of pathogenesis is through a mutant protein called FMRpolyG. This protein results from repeat-associated non-AUG (RAN) translation, in which the expanded repeats are translated where they otherwise would not be. This protein co-localizes with intranuclear inclusions and nuclear membrane proteins, causing disorganization of the nuclear lamina in FXTAS patient brain samples and neurons differentiated from FXTAS patient-derived induced pluripotent stem cells (iPSCs). iPSC technology involves reprogramming an adult somatic cell back to an embryonic-like state, allowing it to be differentiated into all cell types. A limit with iPSCs, though, is modeling late-onset disorders because the cells lose all age-related features during reprogramming. Progerin, a truncated form of the lamin A protein, has been used to age neurons differentiated from Parkinson Disease (PD) patient-derived iPSCs. Progerin-mediated aging was found to unmask PD-like phenotypes in those neurons, making it a promising technology for modeling late-onset disorders such as FXTAS. In this study, we investigated the link between the aging process and FXTAS pathogenesis in neurons differentiated from FXTAS patient-derived iPSCs with the use of progerin. Progerin transduction was successful in aging the FXTAS neurons. The presence of FMRpolyG was confirmed and an interaction with Lap2b was observed. In some neurons, there was also an observed interaction between FMRpolyG and progerin. Overall, this data suggests that there is an interaction between the mutant FMRpolyG protein and the nuclear membrane during aging, which may contribute to the cell death that causes neurodegeneration in FXTAS patients.
Show less - Date Issued
- 2019
- Identifier
- CFH2000554, ucf:45678
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000554
- Title
- STEM CELL BIOLOGY AND STRATEGIES FOR THERAPEUTIC DEVELOPMENT IN DEGENERATIVE DISEASES AND CANCER.
- Creator
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Alvarez, Angel, Sugaya, Kiminobu, University of Central Florida
- Abstract / Description
-
Stem cell biology is an exciting field that will lead to significant advancements in science and medicine. We hypothesize that inducing the expression of stem cell genes, using the embryonic stem cell gene nanog, will reprogram cells and dedifferentiate human mesenchymal stem cells into pluripotent stem cells capable of neural differentiation. The aims of initial studies are as follows: Aim 1: Demonstrate that forced expression of the embryonic stem cell gene nanog induces changes in human...
Show moreStem cell biology is an exciting field that will lead to significant advancements in science and medicine. We hypothesize that inducing the expression of stem cell genes, using the embryonic stem cell gene nanog, will reprogram cells and dedifferentiate human mesenchymal stem cells into pluripotent stem cells capable of neural differentiation. The aims of initial studies are as follows: Aim 1: Demonstrate that forced expression of the embryonic stem cell gene nanog induces changes in human mesenchymal stem cells to an embryonic stem cell-like phenotype. Aim 2: Demonstrate that induced expression of nanog up-regulates the expression of multiple embryonic stem cell markers and expands the differentiation potential of the stem cells. Aim 3: Demonstrate that these nanog-expressing stem cells have the ability to differentiate along neural lineages in vitro and in vivo, while mock-transfected cells have an extremely limited capacity for transdifferentiation. Alternatively, we hypothesize that embryonic stem cell genes can become activated in malignant gliomas and differentially regulate the subpopulation of cancer stem cells. This study examines the role of embryonic stem cell genes in transformed cells, particularly cancer stem cells. These studies explore has the following objectives: Aim 1: Isolate different sub-populations of cells from tumors and characterize cells with stem cell-like properties. Aim 2: Characterize the expression of embryonic stem cell markers in the sub-population of cancer stem cells. Aim 3: Examine the effects of histone deacetylase inhibitors at inhibiting the growth and reducing the expression of stem cell markers. Our research has demonstrated the potential of the embryonic transcription factor, nanog, at inducing dedifferentiation of human bone marrow mesenchymal stem cells and allowing their recommitment to a neural lineage. Specifically, we used viral and non-viral vectors to induce expression of NANOG, which produced an embryonic stem cell-like morphology in transduced cells. We characterized these cells using real-time PCR and immunohistochemical staining and find an up-regulation of genes responsible for pluripotency and self-renewal. Embryonic stem cell markers including Sox2, Oct4 and TERT were up-regulated following delivery of nanog. The role of nanog in the expression of these markers was further demonstrated in our induced-differentiation method where we transfected embryonic stem cell-like cells, that have been transduced with nanog flanked by two loxP sites, with a vector containing Cre-recominase. We tested the ability of these nanog-transfected cells to undergo neural differentiation in vitro using a neural co-culture system or in vivo following intracranial transplantation. Our next study characterized patient-derived glioblastoma cancer stem cells. We found that cells isolated from serum-free stem cell cultures were enriched for stem cell markers and were more proliferative than the bulk population of cells grown in convention serum-supplemented media. These cancer stem cells expressed embryonic stem cell markers NANOG and OCT4 whereas non-tumor-derived neural stem cells do not. Moreover, the expression of stem cell markers was correlated with enhanced proliferation and could serve as a measure of drug effectiveness. We tested two different histone deacetylase inhibitors, trichostatin A and valproic acid, and found that both inhibited proliferation and significantly reduced expression of stem cell markers in our cancer stem cell lines. These data demonstrate the potential use of stem cell genes as therapeutic markers and supports the hypothesis that cancer stem cells are a major contributor to brain tumor malignancy.
Show less - Date Issued
- 2011
- Identifier
- CFE0003641, ucf:48845
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003641
- Title
- Development of Cytotoxic Natural Killer Cells for Ovarian Cancer Treatment.
- Creator
-
Pandey, Veethika, Altomare, Deborah, Zhao, Jihe, Khaled, Annette, Estevez, Alvaro, University of Central Florida
- Abstract / Description
-
Ovarian cancer is a leading cause of gynecological malignancy. Cytoreductive surgery and frontline platinum/taxane-based chemotherapy provides good initial efficacy in the treatment, but poor long-term patient survival. This is mainly caused by tumor relapse due to intraperitoneal spreading and ineffective alternate therapies to treat these resistant tumors. The challenge in the field is to develop strategies that would prove effective in these patients and extend overall survival.Over the...
Show moreOvarian cancer is a leading cause of gynecological malignancy. Cytoreductive surgery and frontline platinum/taxane-based chemotherapy provides good initial efficacy in the treatment, but poor long-term patient survival. This is mainly caused by tumor relapse due to intraperitoneal spreading and ineffective alternate therapies to treat these resistant tumors. The challenge in the field is to develop strategies that would prove effective in these patients and extend overall survival.Over the years, various treatments have been developed for the treatment of cancer amongst which, adoptive cell immunotherapy has shown promising results. But despite the efficacy seen in the clinic, there are concerns with the complexity of treatment and associated side effects. Therefore, there is still a need for better understanding of how different components of the immune system react to the presence of tumor. In this study, healthy human peripheral blood mononuclear cells (PBMCs) were used to examine the immune response in a mouse model with residual human ovarian tumor, where natural killer (NK) cells were found to be the effector cells that elicited an anti-tumor response. Presence of tumor was found to stimulate NK cell expansion and cytotoxicity in mice treated intraperitoneally (IP) with PBMCs+Interleukin-2 (IL- 2). Intravenous (IV) adoptive transfer of isolated NK cells has been attempted in ovarian cancer patients before, but showed lack of persistence in patients resulting in lack of anti-tumor efficacy. Experiments in this study highlight the significance of NK cell-cytotoxic response to tumor, which may be attributed to interacting immune cell types in the PBMC population (when treated IP), as opposed to clinically used isolated NK cells showing lack of anti-tumor efficacy in ovarian cancer patients (when treated IV).iiiNK cell immunotherapy is mainly limited by insufficient numbers generated for adoptive transfer, limited in vivo life span after adoptive transfer, lack of cytotoxicity and some logistical concerns that impede its widespread implementation. Therefore there is a need to develop methods of NK cell expansion that provide stimulation similar to other immune cell types in the PBMC population. The second part of this study utilizes a method of in vivo NK cell expansion using a particle-based approach in which plasma membranes of K562-MB21-41BBL cells (K562 cells expressing membrane-bound IL-21 and 41BB ligand) are used for specific NK cell expansion from PBMCs. NK cells expanded with this method were cytotoxic, showed in vivo persistence and biodistribution in different organs.Collectively, these studies show that NK cells are a major innate immune component that can recognize and kill the tumor. Their cytotoxic ability, using particle-based stimulation, can be enhanced for a second-line treatment of relapsed tumors such as in ovarian cancer as well as other cancer types.
Show less - Date Issued
- 2015
- Identifier
- CFE0006369, ucf:51531
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006369
- Title
- AUTOLOGOUS SKIN CELL SPRAY-TRANSPLANTATION AS AN INNOVATIVE ALTERNATIVE TO AUTOLOGOUS SPLIT- THICKNESS SKIN GRAFTS FOR DEEP PARTIAL THICKNESS BURN WOUNDS: AN INTEGRATIVE LITERATURE REVIEW.
- Creator
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Beaudet, Alexandria M, Bushy, Angeline, University of Central Florida
- Abstract / Description
-
Burn wounds tend to be a critical problem with a complicated healing process. Although advancements have been made and the treatment of burn wounds has improved significantly, the healing process for deep-partial thickness burn wounds remains problematic. The purpose of this thesis is to review the available literature on an innovate biotechnology, autologous skin cell-spray transplantation, to more effectively treat burn wounds and potentially other injuries in the future. This study was...
Show moreBurn wounds tend to be a critical problem with a complicated healing process. Although advancements have been made and the treatment of burn wounds has improved significantly, the healing process for deep-partial thickness burn wounds remains problematic. The purpose of this thesis is to review the available literature on an innovate biotechnology, autologous skin cell-spray transplantation, to more effectively treat burn wounds and potentially other injuries in the future. This study was conducted by critically researching and comparing (N=7) peer-reviewed research articles focusing not only on burn wounds using traditional treatments, but also the treatment of burn wounds using revolutionary cell-spray autographing technologies. The findings in this thesis show significant enhancement using this innovative approach for the treatment of burn injuries, and presents pivotal information for future nursing research, clinical practice as well as policy and education.
Show less - Date Issued
- 2019
- Identifier
- CFH2000576, ucf:45658
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000576
- Title
- VARIABLE FLUID FLOW REGIMES ALTER ENDOTHELIAL ADHERENS JUNCTIONS AND TIGHT JUNCTIONS.
- Creator
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Ranadewa, Dilshan, Steward, Robert, Gou, Jihua, Mansy, Hansen, University of Central Florida
- Abstract / Description
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Variable blood flow regimes influence a range of cellular properties ranging from cell orientation, shape, and permeability: all of which are dependent on endothelial cell-cell junctions. In fact, cell-cell junctions have shown to be an integral part of vascular homeostasis through the endothelium by allowing intercellular signaling and passage control through tight junctions (TJs), adherens junctions (AJs), and gap junctions (GJs). It was our objective to determine the structural response of...
Show moreVariable blood flow regimes influence a range of cellular properties ranging from cell orientation, shape, and permeability: all of which are dependent on endothelial cell-cell junctions. In fact, cell-cell junctions have shown to be an integral part of vascular homeostasis through the endothelium by allowing intercellular signaling and passage control through tight junctions (TJs), adherens junctions (AJs), and gap junctions (GJs). It was our objective to determine the structural response of both AJs and TJs under steady and oscillatory flow. Human brain microvascular endothelial cells (HBMECs) were cultured in a parallel plate flow chamber and exposed to separate trails of steady and oscillatory fluid shear stress for 24 hours. Steady flow regimes consisted of a low laminar flow (LLF) of 1 dyne/cm2, and a high laminar flow (HLF) of 10 dyne/cm2 and oscillatory flow regimes consisted of low oscillatory flow (LOF) +/- 1 dyne/cm2 and high oscillatory flow (HLF) of +/- 10 dyne/cm2. We then imaged the TJs ZO-1 Claudin-5 and AJs JAM-A VE-Cadherin and subsequently analyzed their structural response as a function of pixel intensity. Our findings revealed an increase in pixel intensity between LLF and LOF along the boundary of the cells in both TJs ZO1 Claudin 5. Therefore, our results demonstrate the variable response of different cell-cell junctions under fluid shear, and for the first time, observes the difference in cell-cell junctional structure amongst steady and oscillatory flow regimes
Show less - Date Issued
- 2019
- Identifier
- CFE0007518, ucf:52618
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007518
- Title
- MECHANISMS PROMOTING PHOSPHORYLATION OF THE NF2 TUMOR SUPPRESSOR AND ITS EFFECTS ON SCHWANN CELL DEVELOPMENT.
- Creator
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Thaxton, Courtney, Fernandez-Valle, Cristina, University of Central Florida
- Abstract / Description
-
Neurofibromatosis type 2 is an autosomal dominant disease characterized by the formation of schwannomas and other peripheral neuropathies. The nf2 gene encodes the protein Schwannomin, or merlin. Schwannomin (Sch) is a membrane-cytoskeletal linking protein that suppresses cell proliferation at high cell density and modulates cell shape. Sch's tumor suppressive activity is regulated by its localization, conformation, and phosphorylation at serine 518 (S518). Sch's localization is...
Show moreNeurofibromatosis type 2 is an autosomal dominant disease characterized by the formation of schwannomas and other peripheral neuropathies. The nf2 gene encodes the protein Schwannomin, or merlin. Schwannomin (Sch) is a membrane-cytoskeletal linking protein that suppresses cell proliferation at high cell density and modulates cell shape. Sch's tumor suppressive activity is regulated by its localization, conformation, and phosphorylation at serine 518 (S518). Sch's localization is dependent on binding the scaffold protein, paxillin. Phosphorylation of Sch at S518 regulates its conformation and tumor suppressor function. In a negative feedback loop, unphosphorylated Sch restricts cell proliferation downstream of Rac and p21-activated kinase (Pak), whereas Pak-induced phosphorylation inactivates Sch's ability to inhibit Pak and cell proliferation. Little is known about the function of the phosphorylated form of Sch, or the molecular mechanisms leading to its phosphorylation. Here we demonstrate that Sch-S518 phosphorylation is dependent on paxillin-binding and plasma membrane localization in SCs. Phosphorylation of Sch at the plasma membrane is mediated by Cdc42-Pak and results in altered SC morphology and polarity. Moreover, we have identified two extracellular stimuli that trigger Sch-S518 phosphorylation; these are neuregulin (NRG) and laminin, two potent activators of SC proliferation and myelination. NRG promotes Sch-S518 phosphorylation downstream of ErbB2/ErbB3 through PKA, whereas laminin-1 stimulation of β1 integrin promotes Pak- dependent phosphorylation of Sch-S518. Additionally, we find that Sch promotes process formation and elongation in primary and myelinating SCs, independent of Sch S518 phosphorylation. However, Sch phosphorylation was found to influence SC differentiation, as expression of an unphosphorylatable variant, Sch-S518A, facilitated SC myelination, whereas expression of a phospho-mimicking variant, Sch-S518D, reduced the SC's ability to myelinate. Together, these findings have identified receptor-mediated and paxillin-dependent pathways that regulate phosphorylation and inactivation of Sch's tumor suppressor function. Additionally, these results have elucidated novel normal functions for Sch during peripheral nerve development and myelination, and identify novel therapeutic targets for treatment of NF2 and other peripheral neuropathies.
Show less - Date Issued
- 2007
- Identifier
- CFE0001898, ucf:47393
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001898
- Title
- ON MODELING HIV INFECTION OF CD4+ T CELLS.
- Creator
-
Comerford, Amy, Mohapatra, Ram, University of Central Florida
- Abstract / Description
-
We examine an early model for the interaction of HIV with CD4+ T cells in vivo and define possible parameters and effects of said parameters on the model. We then examine a newer, more simplified model for the interaction of HIV with CD4+ T cells that also considers four populations: uninfected T cells, latently infected T cells, actively infected T cells, and free virus. The stability of both the disease free steady state and the endemically infected steady state are examined utilizing...
Show moreWe examine an early model for the interaction of HIV with CD4+ T cells in vivo and define possible parameters and effects of said parameters on the model. We then examine a newer, more simplified model for the interaction of HIV with CD4+ T cells that also considers four populations: uninfected T cells, latently infected T cells, actively infected T cells, and free virus. The stability of both the disease free steady state and the endemically infected steady state are examined utilizing standard methods and the Routh-Hurwitz criteria. We show that if N, the number of infectious virions produced per actively infected T cell, is less than a critical value, , then the uninfected state is the only steady state in the non negative orthant, and this state is stable. We establish an expression for . If , then the uninfected steady state is unstable, and the endemically infected state can be stable or unstable, depending on the value of the parameters utilized.
Show less - Date Issued
- 2006
- Identifier
- CFE0001093, ucf:46769
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001093
- Title
- INCREASED LEVELS OF ANXIETY REVEALING CHARACTERISTICS OF SOCIAL PHOBIA ELUCIDATED BY SMART PHONE USE.
- Creator
-
Richardson , Mark, Beidel, Deborah, University of Central Florida
- Abstract / Description
-
Students at the University of Central Florida completed two self-report inventories: the SPAI-23, (Social Phobia and Anxiety Inventory - 23) and MPPUS (Mobile Phone Problem Use Scale) to determine if there is a relationship between social phobia and problematic mobile phone use. Fifty one students (N = 51) completed both surveys and the results indicated that there was a small but positive relationship between problematic cell phone use and social phobia symptoms, r=.28, p=.05. The results...
Show moreStudents at the University of Central Florida completed two self-report inventories: the SPAI-23, (Social Phobia and Anxiety Inventory - 23) and MPPUS (Mobile Phone Problem Use Scale) to determine if there is a relationship between social phobia and problematic mobile phone use. Fifty one students (N = 51) completed both surveys and the results indicated that there was a small but positive relationship between problematic cell phone use and social phobia symptoms, r=.28, p=.05. The results are discussed in terms of how social phobia might increase problematic phone use.
Show less - Date Issued
- 2012
- Identifier
- CFH0004241, ucf:44931
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004241
- Title
- GENERATION OF RECOMBINANT MOUSE EMBRYONIC STEM CELL LINES AND THEIRAPPLICATION FOR IN VIVO BIOLUMINISCENCE IMAGING IN THE HEART.
- Creator
-
KAMMILI, RAMANA, Ebert, Steve, University of Central Florida
- Abstract / Description
-
ABSTRACT Cardiovascular disease is the major cause of death in the United States, with 80 million people suffering from some form of heart disease each year. One major limitation is the inability of the heart to repair the damaged tissue. Stem cell therapy holds enormous promise to repair and regenerate the damaged myocardium, but there are many technical difficulties that must first be overcome. One such difficulty is the present lack of ability to track and assess transplanted stem cells...
Show moreABSTRACT Cardiovascular disease is the major cause of death in the United States, with 80 million people suffering from some form of heart disease each year. One major limitation is the inability of the heart to repair the damaged tissue. Stem cell therapy holds enormous promise to repair and regenerate the damaged myocardium, but there are many technical difficulties that must first be overcome. One such difficulty is the present lack of ability to track and assess transplanted stem cells over time in vivo. The central hypothesis of this thesis is that in vivo bioluminescence imaging is a safe and useful method for monitoring transplanted stem cells in mouse hearts. To evaluate this hypothesis, two aims were performed. In aim 1, stable recombinant mES cell lines expressing the firefly luciferase (fLUC) reporter gene under the control of constitutive and cardiac-specific promoters were generated and characterized in vitro. In aim 2, these fLUC-expressing recombinant cell lines were evaluated following transplantation into neonatal mouse hearts. The major findings are: (1) Novel stable recombinant mES reporter cell lines were developed for in vivo bioluminescence imaging; (2) One of these cell lines was created using the glyceraldehyde 3-phosphodehydrogenase (GAPDH) promoter fused to the fLUC reporter and it showed similar levels of fLUC expression in undifferentiated (pluripotent) compared to cardiac-differentiated mES cells; (3) Another cell line was produced using the cardiac-specific sodium-calcium exchanger 1 (NCX1) promoter fused to the fLUC reporter and this cell line showed markedly increased fLUC expression following induction of cardiac differentiation in culture when compared to the pluripotent cells. (4) Transplantation of the recombinant fLUC-expressing cells into neonatal mouse hearts produced bioluminescent signals that persisted for at least 24 days, the maximum timepoint analyzed in this study; (5) Transplantation of 100,000 or more mES cells to the heart consistently produced teratoma and tumor formations, regardless of which recombinant clone was used or whether the mES cells were injected as pluripotent or cardiac-differentiated cells, (6) Transplantation of between 10,000 and 50,000 cardiac-differentiated NCX1-fLUC mES cells(containing mixed population of other cells) per heart resulted in measurable bioluminescent image signals in vivo with low incidence of tumor formation, and (7) Some of the transplanted NCX1-fLUC mES cells were identified in ventricular muscle tissue in postmortem histological sections where it was found that they had developed cardiomyocyte characteristics. In summary, I developed stable recombinant mES cell lines suitable for non-invasive bioluminescence imaging to study the survival and proliferation of the cells in vivo. These results demonstrate that bioluminescence imaging in the neonatal mouse heart model is an effective strategy for non-invasive monitoring of transplanted stem cells over time in vivo, and minimizes animal usage through elimination of the need for animal sacrifice at multiple timepoints.
Show less - Date Issued
- 2008
- Identifier
- CFE0002304, ucf:47827
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002304
- Title
- nanoengineered energy harvesting and storage devices.
- Creator
-
Li, Chao, Thomas, Jayan, Zhai, Lei, Yang, Yang, Gesquiere, Andre, Dong, Yajie, Sun, Wei, University of Central Florida
- Abstract / Description
-
Organic and perovskite solar cells have recently attracted significant attention due to itsflexibility, ease of fabrication and excellent performance. In order to realize even betterperformance for organic and perovskite solar cells, rejuvenated effort towards developingnanostructured electrodes and high quality active layer is necessary.In this dissertation, several strategic directions of enhancing the performance of organicand perovskite solar cells are investigated. An introduction and...
Show moreOrganic and perovskite solar cells have recently attracted significant attention due to itsflexibility, ease of fabrication and excellent performance. In order to realize even betterperformance for organic and perovskite solar cells, rejuvenated effort towards developingnanostructured electrodes and high quality active layer is necessary.In this dissertation, several strategic directions of enhancing the performance of organicand perovskite solar cells are investigated. An introduction and background of organic andperovskite solar cells, which includes motivation, classification and working principles,nanostructured electrode materials and solvent effect on active materials, and devices fabrication,are presented. A facile method, called Spin-on Nanoprinting (SNAP), to fabricate highly orderedZnO-AgNW-ZnO electrode is introduced to enhance the performance of organic solar cell.Subsequently, a ternary solvent method is developed to fabricate high Voc thieno[3,4-b]thiophene/benzodithiophene (PTB7) and indene-C60 bisadduct (ICBA)solar cells. Theperformance of the devices improved about 20% compared to those made by binary solventmethod. In order to understand the fundamental properties of the materials ruling theperformance of the PSCs tested, AFM-based nanoscale characterization techniques includingPulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFM (MSAFM) are introduced.These methods are used to study the morphology and physical properties of the structuresconstitutive of the active layers of the PSCs. Conductive-AFM (cAFM) studies reveal localvariations in conductivity in the donor and acceptor phases as well as an increase in photocurrentmeasured in the PTB7:ICBA sample obtained with the ternary solvent processing technique.Moreover, efficient perovskite solar cells with good transparency in the visible wavelength rangehave been developed by a facile and low-temperature PCBM-assisted perovskite growth method.This method results in the formation of perovskite-PCBM hybrid material at the grain boundaries which is observed by EELS mapping and confirmed by steady-state photoluminescence (PL)spectra and transient photocurrent (TP) measurements. This method involves fewer steps andtherefore is less expensive and time consuming than other reported methods. In addition, wereport an all solid state, energy harvesting and storing (ENHANS) filament which integratesperovskite solar cell (PSC) on top of a symmetric supercapacitor (SSC) via a copper filamentwhich works as a shared electrode for direct charge transfer. Developing ENHANS on a copperfilament provides a low-cost solution for flexible self-sufficient energy systems for wearablesand other portable devices. Finally, a summary of this dissertation as well as some potentialfuture directions are presented.
Show less - Date Issued
- 2016
- Identifier
- CFE0006693, ucf:51912
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006693
- Title
- Excellent Surface Passivation for High Efficiency C_Si Solar Cells.
- Creator
-
Bakhshi, Sara, Schoenfeld, Winston, Abdolvand, Reza, Sundaram, Kalpathy, Davis, Kristopher, University of Central Florida
- Abstract / Description
-
Semiconductor surface clean is sometimes perceived as costly but long recognized as pivotal in determining the final semiconductor device performance and yield. In this contribution, we investigated the effectiveness of crystalline silicon surface cleaning by a simple UV-ozone process in comparison to the industry standard RCA clean for silicon photovoltaic applications. We present a unique method of processing the silicon surface effectively by UV-ozone cleaning. Despite being simple, UV...
Show moreSemiconductor surface clean is sometimes perceived as costly but long recognized as pivotal in determining the final semiconductor device performance and yield. In this contribution, we investigated the effectiveness of crystalline silicon surface cleaning by a simple UV-ozone process in comparison to the industry standard RCA clean for silicon photovoltaic applications. We present a unique method of processing the silicon surface effectively by UV-ozone cleaning. Despite being simple, UV-ozone cleaning results in a superior surface passivation quality that is comparable to high-quality RCA clean. When used as a stack dielectric(-)UV-ozone oxide overlaid by aluminum oxide(-)the thickness of UV-ozone oxide plays an important role in determining the passivation quality. Of all treatment times, 15 min of UV-ozone treatment results in an outstanding passivation quality, achieving the effective carrier lifetime of 3 ms and saturation current density of 5 fA/cm2. In addition, we present a simple and effective technique to extract values of electron/hole capture cross-section for the purpose of analyzing the interface passivation quality from already measured surface recombination parameters of saturation current density, interfacial trap density and total fixed charge, instead of measuring on the separately prepared metal-insulated-semiconductor (MIS) samples by the techniques: frequency-dependent parallel conductance or deep-level transient spectroscopy.
Show less - Date Issued
- 2018
- Identifier
- CFE0007154, ucf:52313
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007154
- Title
- Embryonic Stem Cell Derived Exosomes Enhance Cardiac Stem Cell Differentiation into Heart Cells.
- Creator
-
Hammond, Jamillah, Singla, Dinender, Masternak, Michal, Davidson, Victor, University of Central Florida
- Abstract / Description
-
Transplantation of embryonic stem (ES) cells into the ischemic and infarcted heart has proven to repopulate cardiac cell populations, attenuate structural cardiac remodeling, and rescue cardiac function. Unfortunately, the pluripotency of ES cells increases risk of teratoma formation in vivo. Exosomes, smaller in comparison to ES cells, are cell free carriers of miRNA, proteins, and lipids, and do not suggest risk of teratoma formation. Exosomes have been proposed to mediate and attenuate...
Show moreTransplantation of embryonic stem (ES) cells into the ischemic and infarcted heart has proven to repopulate cardiac cell populations, attenuate structural cardiac remodeling, and rescue cardiac function. Unfortunately, the pluripotency of ES cells increases risk of teratoma formation in vivo. Exosomes, smaller in comparison to ES cells, are cell free carriers of miRNA, proteins, and lipids, and do not suggest risk of teratoma formation. Exosomes have been proposed to mediate and attenuate regeneration following myocardial infarction (MI), however, the role of exosomes derived from ES cells (ES-Exo) in activating resident cardiac stem cells (CSCs) to undergo cardiac differentiation is not established. In the present study, Stem cell antigen 1 positive (Sca-1+ve) CSCs were isolated, incubated with exosomes, and evaluated for differentiation into the major heart cell types in vitro. Observations of in vitro cardiac differentiation were further established in an in vivo model of MI. Ligation of the coronary artery, or a sham surgery was performed in C57BL/6 mice 8-12 weeks of age. Mice were split among four study groups: sham, MI, MI + H9c2-Exo (a cell line control), (&) MI + ES-Exo. ES-Exo were transplanted via intramyocardial (IM) injection immediately following coronary artery ligation. At day 14 (D14), echocardiography was used to evaluate cardiac function. Differentiation into the major heart cells was determined by sarcomeric ?-actin (cardiomyocytes) and smooth muscle ?-actin (vascular smooth muscle cells) immunostaining. Hematoxylin and Eosin and Masson's Trichrome staining assessed cardiomyocyte hypertrophy and fibrosis, respectively. Immunostaining for major heart cellular markers revealed significant activation of resident Sca-1+ve CSCs to undergo cardiac differentiation after ES-Exo treatment. Cardiomyocyte hypertrophy and myocardial fibrosis were significantly increased following coronary artery ligation. Results from histological staining revealed significantly decreased levels of hypertrophy and fibrosis in hearts transplanted with ES-Exo following coronary ligation. In summary, our findings advocate ES-Exo as a viable treatment option to repopulate the myocardium with viable heart cells, attenuate cardiac remodeling, and rescue cardiac function.
Show less - Date Issued
- 2018
- Identifier
- CFE0007188, ucf:52254
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007188
- Title
- OPTIMIZATION OF PROCESS PARAMETERS FOR REDUCED THICKNESS CIGSES THIN FILM SOLAR CELLS.
- Creator
-
Pethe, Shirish, Dhere, Neelkanth, University of Central Florida
- Abstract / Description
-
With the advent of the 21st century, one of the serious problems facing mankind is harmful effects of global warming. Add to that the ever increasing cost of fuel and the importance of development of clean energy resources as alternative to fossil fuel has becomes one of the prime and pressing challenges for modern science and technology in the 21st century. Recent studies have shown that energy related sources account for 50% of the total emission of carbon dioxide in the atmosphere. All...
Show moreWith the advent of the 21st century, one of the serious problems facing mankind is harmful effects of global warming. Add to that the ever increasing cost of fuel and the importance of development of clean energy resources as alternative to fossil fuel has becomes one of the prime and pressing challenges for modern science and technology in the 21st century. Recent studies have shown that energy related sources account for 50% of the total emission of carbon dioxide in the atmosphere. All research activities are focused on developing various technologies that are capable of converting sunlight into electricity with high efficiency and can be produced using a cost-effective process. One of such technologies is the CuIn1-xGaxSe2 (CIGS) and its alloys that can be produced using cost-effective techniques and also exhibit high photo-conversion efficiency. The work presented here discusses some of the fundamental issues related to high volume production of CIGS thin film solar cells. Three principal issues that have been addressed in this work are effect of reduction in absorber thickness on device performance, micrononuniformity involved with amount of sodium and its effect on device performance and lastly the effect of working distance on the properties of molybdenum back contact. An effort has been made to understand the effect of absorber thickness on PV parameters and optimize the process parameters accordingly. Very thin (<1 µm) absorber film were prepared by selenization using metallorganic selenium source in a conventional furnace and by RTP using Se vapor. Sulfurization was carried out using H2S gas. Devices with efficiencies reaching 9% were prepared for very thin (<1 µm) CIGS and CIGSeS thin films. It was shown through this work that the absorber thickness reduction of 64% results in the efficiency drop of only 32%. With further optimization of the reaction process of the absorber layer as well as the other layers higher efficiencies can be achieved. The effect of sodium on the device performance is experimentally verified in this work. To the best of our knowledge the detrimental effect of excess sodium has been verified by experimental data and effort has been made to correlate the variation in PV parameter to theoretical models of effect of sodium. It has been a regular practice to deposit thin barrier layer prior to molybdenum deposition to reduce the micrononuniformities caused due to nonuniform out diffusion of sodium from the soda lime glass. However, it was proven in this work that an optimally thick barrier layer is necessary to reduce the out diffusion of sodium to negligible quantities and thus reduce the micrononuniformities. Molybdenum back contact deposition is a bottleneck in high volume manufacturing due to the current state of art where multi layer molybdenum film needs to be deposited to achieve the required properties. In order to understand and solve this problem experiments were carried out. The effect of working distance (distance between the target and the substrate) on film properties was studied and is presented in this work. During the course of this work efforts were taken to carry out a systematic and detailed study of some of the fundamental issues related to CIGS technology and particular for high volume manufacturing of CIGS PV modules and lay a good foundation for further improvement of PV performance of CIGS thin film solar cells prepared by the two step process of selenization and sulfurization of sputtered metallic precursors.
Show less - Date Issued
- 2010
- Identifier
- CFE0003517, ucf:48940
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003517
