42 research outputs found
Antioxidant activity of synthetic polymers of phenolic compounds
No full textIn recent years, developing potent antioxidants has been a very active area of research. In this context, phenolic compounds have been evaluated for their antioxidant activity. However, the use of phenolic compounds has also been limited by poor antioxidant activity in several in vivo studies. Polymeric phenols have received much attention owing to their potent antioxidant properties and increased stability in aqueous systems. To be truly effective in biological applications, it is important that these polymers be synthesized using benign methods. In this context, enzyme catalyzed synthesis of polymeric phenols has been explored as an environmentally friendly and safer approach. This review summarizes work in enzymatic syntheses of polymers of phenols. Several assays have been developed to determine the antioxidant potency of these polymeric phenols. These assays are discussed in detail along with structure-property relationships. A deeper understanding of factors affecting antioxidant activity would provide an opportunity for the design of versatile, high performing polymers with enhanced antioxidant activity
Polymer dynamics and fluctuations probed with fluorescence methods
No full textThe arc of the thesis is direct measurement of polymer chain properties with potent fluorescence methods imported from other interdisciplinary sciences and applied successfully to polymer physics problems for the first time.
The focus is an important theme in equilibrium polymer physics - chain structure and dynamics at solid-liquid interfaces and confined geometries, respectively. The role of polymer dynamics and fluctuations on the topological confinement formed by entanglement strands in a polymer solution, as experienced by a particle of comparable size is also investigated. These questions are fundamental in many scientific and technical applications, including adhesion, interdiffusion, friction, the mechanical behavior of composite and nanocomposite materials, and functional properties of other kinds. The experimental investigations involve development of novel fluorescence techniques of spectroscopy, microscopy and image analysis with single molecule sensitivity and/or single particle accuracy. Use of these techniques allow access to phenomena occurring at a wide range of length scales and time scales, characteristic of problems in macromolecular physics. Single particle tracking experiments also show advantages of unearthing distribution of individual particle dynamics within an ensemble.Item withdrawn by Laura Spradlin ([email protected]) on 2014-11-13T16:56:56Z
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University of Illinois Theses & Dissertations (ID: 1)
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Particle Dance Floor
No full textNavigating a crowded dance floor is just like a particles journey within a cell; both require complex science and great artistry. Whilst humans rely on our senses to move through crowds, particles 10000 times smaller than a human hair move randomly among obstacles, in bursts of caged transport. At the molecular level, particles bump and jostle and diffuse randomly to the rhythm of thermal energy. The crowding elements also fluctuate randomly, but to a different beat because they are usually of dissimilar size. This makes the space between dancing bodies ever-changing and spontaneous. My graduate research aims to uncover the nature of single-particle motion on this molecular dance floor which is important for future design of advanced materials, in drug delivery and cellular biology. I use fluorescence microscope to visualize the dynamics of thousands of 140 nanometer latex particles within a labyrinth of long and intertwined polymer molecules. The image shows their trajectories over a minute; each particle undergoes cycles of obstruction until it escapes and moves a short distance. The movement of particles at times 0s (dark blue), 10s (blue), 20s (green), 30s (yellow), 40s (orange), 50s (red) to 60s (maroon) makes this piece of obstruct expressionism.Ope
Particle Dance Floor
No full textNavigating a crowded dance floor is just like a particles journey within a cell; both require complex science and great artistry. Whilst humans rely on our senses to move through crowds, particles 10000 times smaller than a human hair move randomly among obstacles, in bursts of caged transport. At the molecular level, particles bump and jostle and diffuse randomly to the rhythm of thermal energy. The crowding elements also fluctuate randomly, but to a different beat because they are usually of dissimilar size. This makes the space between dancing bodies ever-changing and spontaneous. My graduate research aims to uncover the nature of single-particle motion on this molecular dance floor which is important for future design of advanced materials, in drug delivery and cellular biology. I use fluorescence microscope to visualize the dynamics of thousands of 140 nanometer latex particles within a labyrinth of long and intertwined polymer molecules. The image shows their trajectories over a minute; each particle undergoes cycles of obstruction until it escapes and moves a short distance. The movement of particles at times 0s (dark blue), 10s (blue), 20s (green), 30s (yellow), 40s (orange), 50s (red) to 60s (maroon) makes this piece of obstruct expressionism.Submitted by Kayla Hays ([email protected]) on 2015-04-20T22:35:54Z
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Kumar_Subhalakshmi.pdf: 876780 bytes, checksum: 438802d5b7ff78d239934a95375a8487 (MD5)Made available in DSpace on 2015-04-20T22:35:55Z (GMT). No. of bitstreams: 1
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Previous issue date: 2015-04Ope
DEVELOPMENT OF SMART ANTI-CORROSION COATINGS WITH METAL ION END CAPPED NANOCONTAINER LOADED WITH SINGLE AND DUO GREEN CORROSION INHIBITORS
No full textThe cost incurred by the direct and indirect damages of corrosion are immense. Even if we apply all the control measures available to prevent corrosion, it is not possible to cut down the damage completely. Hence, new and efficient methods to prevent corrosion are in demand. The objective of the current work is to synthesize a smart coating that is not only efficient but also environmentally friendly. For the first time, two green corrosion inhibitors are loaded into the halloysite nanotubes and end capped using metal ions. Vanillin and thyme oil were loaded individually and together into halloysite nanotubes and was end capped using copper ions to form VHNTES, THNTES, and VTHNT-ES. The loading of the halloysite nanotubes with the green corrosion inhibitors were characterized by ultraviolet visible spectroscopy (UV-vis) and confirmed by the characteristic peaks in the spectrum obtained from fourier-transform infrared (FTIR) spectroscopy
Variable-range hopping: role of Coulomb interactions
No full textThe effect of Coulomb interactions on hopping conduction in the variable-range hopping regime is analyzed within a linear-response formalism. Here the conductivity and the dielectric function are related to the density-density response function for which a generalized master equation (GME) can be derived using the Mori-Zwanzig projector formalism. The GME can be thought of as a random resistor network with frequency-dependent internode conductances, whose values can be determined from a function related to the current-current correlator at the two nodes. We evaluate the internode conductances using a diagrammatic perturbation formalism. For a single electron hop with all the other charges frozen, we obtain hop rates correct to all orders in Coulomb interaction. This gives us a finite temperature generalization of existing results for the interacting system. We then incorporate relaxation effects that accompany electron hops, using a dynamical model of the Coulomb gap. We argue that the parameter that governs the local relaxation is related to the conductivity itself. These internode conductances are then used to calculate the dc conductivity of the network by effective- medium approximation. We show that a crossover from Efros-Shklovskii's T½ behavior to Mott's T¼ behavior occurs due to the relaxation effects, as the temperature is increased. At low temperatures the relaxation is slow so that electrons hop in a frozen charge background and thereby sense the Coulomb gap. This gives the T½ behavior. At higher temperatures the relaxation gets faster and the Coulomb gap is alleviated leading to Mott's behavior
Dielectric properties of the electron glass
No full textThe dielectric-constant matrix of a system of electrons that have been localized by disorder is calculated as a function of frequency and distance. It is shown that the basic polarization process in these systems is quite different from those with extended electrons, as the electronic transitions can only occur by phonon-mediated hops between localized states. It is also argued that the random-phase approximation is not adequate for such systems, as the correct account for the excitation energies of the system requires inclusion of electron-hole interaction. Our analysis provides an expression for screening length that shows a basic departure from the Thomas-Fermi approximation. On the basis of our results for polarizability, we also argue that a soft Coulomb gap for electron-hole excitations should exist to provide dielectric stability to the system
Traditional method of catching crab and fish from Bonai Forest Division, Odisha, India
No full textDocumentation of traditional knowledge is an important task in contemporary situation where we are facing a lot of health problems. Keeping this in view an attempt has been taken to document the most common traditional practices to catch food from perennial streams of Bonai Forest Division. During the survey in December 2022, we observed two common but unique techniques to catch crab in Koira range & fish in Sole Range. It was observed that crab was caught after removing of stone from the streams & fishes were caught using sound. The present communication discusses two traditional practices to get food in details & the ecological situation in current days
Ferromagnetism of anderson localized electrons: application to cluster compounds
No full textA study of the electrical transport and magnetic properties of a series of cluster compounds with the generic formula A0.5M2X4 suggests that the electrons at the Fermi surface are localized, and the ferromagnetism seen in these compounds arises from these electrons. The magnetism of these compounds shows some features characteristic of itinerant models and others which are characteristic of localized models. We construct a model which has a nondegenerate band of localized states with on-site repulsion. Further, the singly occupied states interact via direct exchange interaction which is ferromagnetic. Using a mean-field approximation we calculate the various magnetic properties, which are in qualitative accord with the observed behavior. In particular, we find that the single-particle excitations play a dominant role in the magnetism of these compounds, even though the electrons are localized. We also analyze the spin-wave excitations in this model and discuss their effect on low-temperature thermodynamics
