High Fidelity Detection Of Defects In Polymer Films Using Surface-Modified Nanoparticles,
2014
University of Akron
High Fidelity Detection Of Defects In Polymer Films Using Surface-Modified Nanoparticles, Matthew Becker
Matthew Becker
Surface defects are ubiquitous for most thin films, yet their systematic detection poses one of the most difficult challenges even to modern day technology. Polymer thin films are no exception to these problems. We address this issue by developing a novel, efficient method for the optical detection of surface topographical features using fluorescent nanoprobes, which are surface-modified CdSe quantum dots whose ability to detect surface features can be tuned via size and chemical properties. We have successfully applied this approach to detect numerous types of artificial and natural defects in polymer films including lines, pinholes, sharp edges, and chemically variant …
Computational Modeling Of In Vitro Biological Responses On Polymethacrylate Surfaces,
2014
The University of Akron
Computational Modeling Of In Vitro Biological Responses On Polymethacrylate Surfaces, Abraham Joy
Abraham Joy
The objective of this research was to examine the capabilities of QSPR (Quantitative Structure Property Relationship) modeling to predict specific biological responses (fibrinogen adsorption, cell attachment and cell proliferation index) on thin films of different polymethacrylates. Using 33 commercially available monomers it is theoretically possible to construct a library of over 40,000 distinct polymer compositions. A subset of these polymers were synthesized and solvent cast surfaces were prepared in 96 well plates for the measurement of fibrinogen adsorption. NIH 3T3 cell attachment and proliferation index were measured on spin coated thin films of these polymers. Based on the experimental results …
Poly (Ethylene Glycol) As A Sensitive Regulator Of Cell Survival Fate On Polymeric Biomaterials: The Interplay Of Cell Adhesion And Pro-Oxidant Signaling Mechanisms,
2014
The University of Akron
Poly (Ethylene Glycol) As A Sensitive Regulator Of Cell Survival Fate On Polymeric Biomaterials: The Interplay Of Cell Adhesion And Pro-Oxidant Signaling Mechanisms, Abraham Joy
Abraham Joy
Poly(ethylene glycol) (PEG) is one of the most widely used compounds across a variety of platforms and is increasingly found in medical applications. Polycarbonates containing varying mol% of PEG (Mw 1000) were used to probe the effects of PEG on cell adhesion, proliferation, spreading, and survival. Two contrasting PEG-mediated cell signaling elements affected these cellular behaviors: (i) integrin α5 receptor mediated cellular focal adhesions to the biomaterial surface and (ii) modulation of cellular redox and apoptosis through generation of reactive oxygen species (ROS). At lower PEG1k mol% (5% and 8%) cell attachment and spreading decreased concomitantly due to ROS, whereas …
Simple, Rapid, And Highly Sensitive Detection Of Diphosgene And Triphosgene By Spectrophotometric Methods,
2014
The University of Akron
Simple, Rapid, And Highly Sensitive Detection Of Diphosgene And Triphosgene By Spectrophotometric Methods, Abraham Joy
Abraham Joy
Methods for the detection and estimation of diphosgene and triphosgene are described. These compounds are widely used phosgene precursors which produce an intensely colored purple pentamethine oxonol dye when reacted with 1,3-dimethylbarbituric acid (DBA) and pyridine (or a pyridine derivative). Two quantitative methods are described, based on either UV absorbance or fluorescence of the oxonol dye. Detection limits are approximately 4 micromol/L by UV and <0.4 micromol/L by fluorescence. The third method is a test strip for the simple and rapid detection and semi-quantitative estimation of diphosgene and triphosgene, using a filter paper embedded with dimethylbarbituric acid and poly(4-vinylpyridine). Addition …
Predicting Biomaterial Property-Dendritic Cell Phenotype Relationships From The Multivariate Analysis Of Responses To Polymethacrylates,
2014
The University of Akron
Predicting Biomaterial Property-Dendritic Cell Phenotype Relationships From The Multivariate Analysis Of Responses To Polymethacrylates, Abraham Joy
Abraham Joy
Dendritic cells (DCs) play a critical role in orchestrating the host responses to a wide variety of foreign antigens and are essential in maintaining immune tolerance. Distinct biomaterials have been shown to differentially affect the phenotype of DCs, which suggested that biomaterials may be used to modulate immune response towards the biologic component in combination products. The elucidation of biomaterial property-DC phenotype relationships is expected to inform rational design of immuno-modulatory biomaterials. In this study, DC response to a set of 12 polymethacrylates (pMAs) was assessed in terms of surface marker expression and cytokine profile. Principal component analysis (PCA) determined …
Long-Range Radical Cation Migration In Dna: Investigation Of The Mechanism,
2014
The University of Akron
Long-Range Radical Cation Migration In Dna: Investigation Of The Mechanism, Abraham Joy
Abraham Joy
During the past decade, long-range radical cation migration in DNA has been an area of extensive experimental and theoretical examination. The motivations for the vigorous investigation of this topic are its potential to yield a deeper understanding of the processes that cause oxidative damage of genomic DNA and the potential for use of DNA architectures in molecular electronics. This investigation has revealed the mechanisms of charge transport and the limitations of DNA as a functional element in devices. In this article we discuss various aspects of the radical cation migration process and present the plausible mechanism by which this process …
Photoinduced Polymer Chain Scission Of Alkoxyphenacyl Based Polycarbonates,
2014
The University Of Akron
Photoinduced Polymer Chain Scission Of Alkoxyphenacyl Based Polycarbonates, Shuangyi Sun, Elaheh Chamsaz, Abraham Joy
Abraham Joy
We report the design and development of a new class of alkoxyphenacyl based photodegradable polycarbonates. These polymers incorporate the photoactive moiety in the backbone and, when irradiated at 300 nm, undergo controlled chain scission. Micropatterned thin films of these polymers were fabricated by photolithographic techniques. The use of these photodegradable polymers for controlled release applications was demonstrated by the release of Nile Red from polymeric nanoparticles. In addition, these polymers are mechanically robust, thermally stable, and hydrolytically degradable.
Oxidative Damage To Dna: Counterion-Assisted Addition Of Water To Ionized Dna,
2014
The University of Akron
Oxidative Damage To Dna: Counterion-Assisted Addition Of Water To Ionized Dna, Abraham Joy
Abraham Joy
Oxidative damage to DNA, implicated in mutagenesis, aging, and cancer, follows electron loss that generates a radical cation that migrates to a guanine, where it may react with water to form 8-oxo-7,8-dihydroguanine (8-OxoG). Molecular dynamics and ab initio quantum simulations on a B-DNA tetradecamer reveal activated reaction pathways that depend on the local counterion arrangement. The lowest activation barrier, 0.73 eV, is found for a reaction that starts from a configuration where a Na+ resides in the major groove near the N7 atoms of adjacent guanines, and evolves through a transition state where a bond between a water oxygen atom …
Selective One-Electron Oxidation Of Duplex Dna Oligomers: Reaction At Thymines,
2014
The University of Akron
Selective One-Electron Oxidation Of Duplex Dna Oligomers: Reaction At Thymines, Abraham Joy
Abraham Joy
The one-electron oxidation of duplex DNA generates a nucleobase radical cation (electron “hole”) that migrates long distances by a hopping mechanism. The radical cation reacts irreversibly with H2O or O2 to form oxidation products (damaged bases). In normal DNA (containing the four common DNA bases), reaction occurs most frequently at guanine. However, in DNA duplexes that do not contain guanine (i.e., those comprised exclusively of A/T base pairs), we discovered that reaction occurs primarily at thymine and gives products resulting from oxidation of the T-C5 methyl group and from addition to its C5–C6 double bond. This surprising result shows that …
One-Electron Oxidation Of Dna Oligomers That Lack Guanine: Reaction And Strand Cleavage At Remote Thymines By Long-Distance Radical Cation Hopping,
2014
The University of Akron
One-Electron Oxidation Of Dna Oligomers That Lack Guanine: Reaction And Strand Cleavage At Remote Thymines By Long-Distance Radical Cation Hopping, Abraham Joy
Abraham Joy
The anthraquinone (AQ) photosensitized one-electron oxidation of DNA introduces a radical cation (electron “hole”) that migrates through the duplex by hopping. The radical cation normally is trapped irreversibly by reaction at guanine. We constructed AQ-linked DNA oligomers composed exclusively of A/T base pairs. Their irradiation led to reaction and strand cleavage primarily at thymines. Long-distance radical cation hopping to distant thymines was demonstrated by the distance dependence of the process and by experiments with DNA oligomers that contain a single remote GG step. The reaction of the radical cation at thymine was shown to involve its 5-methyl group by the …
Role Of Cations And Confinement In Asymmetric Photochemistry: Enantio-And Diastereo-Selective Photocyclization Of Tropolone Derivatives Within Zeolites,
2014
The University of Akron
Role Of Cations And Confinement In Asymmetric Photochemistry: Enantio-And Diastereo-Selective Photocyclization Of Tropolone Derivatives Within Zeolites, Abraham Joy
Abraham Joy
Asymmetric induction in photochemical reactions has been explored using the photochemistry of tropolones as a model. Three approaches have been examined: chiral inductor, chiral auxiliary and [chiral inductor + chiral auxiliary]. All three methods gave excellent asymmetric induction in zeolite and very little or zero induction in solution. Results presented on tropolones clearly illustrate the remarkable influence that a confined space studded with cations can have on asymmetric induction. Tropolone derivatives, upon irradiation undergo 4π-electron electrocyclization to yield a bicyclic product and a rearranged product. Enantiomeric excess up to 68% has been achieved in the cyclized product. In systems where …
Polaronic Semiconductor Behavior Of Long-Range Charge Transfer In Dna Oligomers In Solution: Controlling Barriers To Long-Distance Radical Cation Migration In Dna With Thymine Analogs,
2014
The University of Akron
Polaronic Semiconductor Behavior Of Long-Range Charge Transfer In Dna Oligomers In Solution: Controlling Barriers To Long-Distance Radical Cation Migration In Dna With Thymine Analogs, Abraham Joy
Abraham Joy
A series of anthraquinone-linked DNA oligonucleotides was prepared and the efficiency of long-distance radical cation migration was measured. In one set of oligonucleotides, two GG steps are separated by either a TATA or an ATAT bridge. In these two compounds, the efficiency of radical cation migration from GG to GG differs by more than an order of magnitude. Replacement of the thymines in the TATA or ATAT bridges with 3-methyl-2-pyridone (t, a thymine analog) results in the much more efficient radical cation migration across the bridge in both cases. This is attributed to a decrease in the oxidation potential of …
Chiral Photochemistry Within Zeolites,
2014
The University of Akron
Chiral Photochemistry Within Zeolites, Abraham Joy
Abraham Joy
Chiral induction of chemical reactions continues to be one of the main concerns of chemists. While basic rules of chiral induction of thermal reactions have been reasonably established, the same is not true of photochemical reactions. Short excited state lifetime and low activation energies for reactions in the excited state(s) leave very little room for manipulating the diastereomeric transition states. Yet impressive chiral induction of photochemical reactions in the solid state has been achieved. On the other hand, chiral induction of photoreactions of organic molecules in solution continues to be inefficient at ambient conditions. We are exploring the possibility of …
Control Of Surface Chemistry, Substrate Stiffness, And Cell Function In A Novel Terpolymer Methacrylate Library,
2014
The University of Akron
Control Of Surface Chemistry, Substrate Stiffness, And Cell Function In A Novel Terpolymer Methacrylate Library, Abraham Joy
Abraham Joy
A focused library of methacrylate terpolymers was synthesized to explore the effects of varying surface chemistry and adhesive peptide ligands on cell function. The chemical diversity of methacrylate monomers enabled construction of a library of polymers in which one can systematically vary the chemical composition to achieve a wide range of contact angle, Young's modulus, and Tg values. Furthermore, the materials were designed to allow surface immobilization of bioactive peptides. We then examined the effects of these material compositions on protein adsorption and cell attachment, proliferation, and differentiation. We observed that chemical composition of the polymers was an important determinant …
Chiral Photochemistry,
2014
The University of Akron
Chiral Photochemistry, Abraham Joy
Abraham Joy
Chiral induction of chemical reactions continues to be one of the main concerns of chemists. While basic rules of chiral induction of thermal reactions have been reasonably established, the same is not true of photochemical reactions. Short excited state lifetime and low activation energies for reactions in the excited state(s) leave very little room for manipulating the diastereomeric transition states. Yet impressive chiral induction of photochemical reactions in the solid state has been achieved. On the other hand, chiral induction of photoreactions of organic molecules in solution continues to be inefficient at ambient conditions. We are exploring the possibility of …
Halogenated Squaraine Dyes As Potential Photochemotherapeutic Agents. Synthesis And Study Of Photophysical Properties And Quantum Efficiencies Of Singlet Oxygen Generation*,
2014
The University of Akron
Halogenated Squaraine Dyes As Potential Photochemotherapeutic Agents. Synthesis And Study Of Photophysical Properties And Quantum Efficiencies Of Singlet Oxygen Generation*, Abraham Joy
Abraham Joy
The photophysical properties of two pairs of squaraine molecules where two oxygen atoms in a squaraine bridge are replaced with sulfur atoms are investigated. This substitution leads to an inversion of the lowest singlet π−π* electronic transition by an n−π* transition, effectively reducing the energy difference between singlet and triplet states and significantly increasing the intersystem crossing efficiency without the use of “heavy atoms”. Experimental results, in agreement with quantum chemical calculations, show near-unity values for triplet quantum yield and singlet oxygen generation quantum yield for sulfur-containing squaraines, which are potentially useful for two-photon photodynamic therapy.Keywords (keywords): squaraine dyes; intersystem …
Calculated Vs. Experimental Values For Volume And Surface Resistivity In Various Polymer Compounds,
2014
University of Wisconsin - Whitewater
Calculated Vs. Experimental Values For Volume And Surface Resistivity In Various Polymer Compounds, Megan Webster
Pursuit - The Journal of Undergraduate Research at The University of Tennessee
Versatile due to their resistance to high stress environments including but not limited to extreme temperature, pressure, and stress, polymers additionally have many uses in electrical applications wherein antistatic or conductive properties are preferential, i.e. conductive seals, oil pipeline spheres, and gaskets, to name a few. Being a complex material, many factors may affect the electrical resistivity of a given polymer compound including type and amount of carbon black, type of rubber, cure time and temperature, and dispersion, amongst other factors. External conditions such as relative humidity and temperature also play key roles. This paper will analyze five different rubber …
Sticky Gecko Feet: The Role Of Temperature And Humidity,
2014
University of Akron Main Campus
Sticky Gecko Feet: The Role Of Temperature And Humidity, Peter H. Niewiarowski, Stephanie Lopez, Liehui Ge, Emily Hagan, Ali Dhinojwala
Dr. Peter H. Niewiarowski
Gecko adhesion is expected to be temperature insensitive over the range of temperatures typically experienced by geckos. Previous work is limited and equivocal on whether this expectation holds. We tested the temperature dependence of adhesion in Tokay and Day geckos and found that clinging ability at 12 degrees C was nearly double the clinging ability at 32 degrees C. However, rather than confirming a simple temperature effect, our data reveal a complex interaction between temperature and humidity that can drive differences in adhesion by as much as two-fold. Our findings have important implications for inferences about the mechanisms underlying the …
Mechanism Of Insulin Aggregation: Applied To Alzheimer's Disease,
2014
University of Connecticut
Mechanism Of Insulin Aggregation: Applied To Alzheimer's Disease, Milos Atz
Honors Scholar Theses
Alzheimer’s disease, a debilitating neurodegenerative illness, is caused by the irreversible aggregation of beta-amyloid proteins in the brain. In Alzheimer’s brains, the protein can become disfigured, causing it to aggregate into long, insoluble fibers that deposit on brain tissue. Studying the aggregation mechanisms of amyloid proteins can lead to a deeper understanding of the progression of Alzheimer’s disease and possibly point towards a potential cure or treatment for the disease. Heat induced aggregation of insulin provides a model system to study the aggregation of amyloidogenic proteins. This study investigates the early stages of heat induced insulin aggregation using dynamic light …
Ab Initio Studies Of Proton Transport In Proton Exchange Membranes,
2014
University of Tennessee - Knoxville
Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark
Doctoral Dissertations
A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …
