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Articles 1 - 11 of 11

Full-Text Articles in Physical Sciences and Mathematics

Single Molecule Studies Of A Short Rna, Peker Milas Nov 2014

Single Molecule Studies Of A Short Rna, Peker Milas

Doctoral Dissertations

The material related with orientation of Cyanine dyes and their behavior at the ends of duplex RNA is also documented in [110]. Cyanine dyes are widely used to study the folding and structural transformations of nucleic acids using fluorescence resonance energy transfer (FRET). The extent to which FRET can be used to extract inter- and intra-molecular distances has been the subject of considerable debate in the literature; the contribution of dye and linker dynamics to the observed FRET signal is particularly troublesome. We used molecular dynamics (MD) simulations to study the dynamics of the indocarbocyanine dyes Cy3 and Cy5 attached …


Introducing The Newton-Poisson-Brillouin Model In The Quest For Plasmons In Metallic Carbon Nanotubes, Richard P. Zannoni Nov 2014

Introducing The Newton-Poisson-Brillouin Model In The Quest For Plasmons In Metallic Carbon Nanotubes, Richard P. Zannoni

Doctoral Dissertations

A new method is presented to model carbon nanotubes (CNT) of micron length. The Newton-Poisson-Brillouin (NPB) model uses Newtonian physics to model the interaction of a population of thermally excited quasi-particles. The NPB model is self-consistent with Poisson’s equation, and the quasi-particles are confined to the CNT’s band structure. In this work, we explore the parameter space of the model.


Measurement Of The Parity Violating Asymmetry In Elastic Electron Scattering Off 208pb, Jonathan W. Wexler Nov 2014

Measurement Of The Parity Violating Asymmetry In Elastic Electron Scattering Off 208pb, Jonathan W. Wexler

Doctoral Dissertations

The Lead Radius Experiment (PREX) was carried out in order to provide a model independent measurement of the RMS radius √ < r2 >of the neutron distribution in the 208Pb nucleus. The parity-violating scattering asymmetry for longitudinally polarized 1.06 GeV electrons from an unpolarized 208Pb target was measured at Q2 = 0.00880 GeV2. This measurement was performed by the PREX collaboration in Hall A at Jefferson Laboratory in Newport News, VA, between March and June, 2010. The electron detectors used in this measurement were designed and fabricated by University of Massachusetts-Amherst and Smith College. The resulting …


Studies On The Wrinkling Of Thin Polymer Films Floating On Liquid, Kamil B. Toga Nov 2014

Studies On The Wrinkling Of Thin Polymer Films Floating On Liquid, Kamil B. Toga

Doctoral Dissertations

This dissertation aims to broaden our understanding on wrinkling instabilities occurring on floating polymeric sheets, and tries to establish innovative methods that exploit these patterns in studies on material behavior and interfacial phenomena. We will address three major topics in this thesis including, i) characterization of the conditions required to buckle an annular disc, ii) characterization of wrinkles occurring around a droplet/bubble placed on a membrane that is kept taut at the liquid-air interface, and iii) using wrinkling patterns as a probe to understand the interfacial behavior and dynamics of ultrathin films. The first project in this thesis is about …


The Impact Of Membrane Tension On Phase Separation And Solid Domain Properties In Model Multicomponent Vesicles, Dong Chen Nov 2014

The Impact Of Membrane Tension On Phase Separation And Solid Domain Properties In Model Multicomponent Vesicles, Dong Chen

Doctoral Dissertations

Multicomponent phospholipid membranes provide an ideal model to study the complex phase behavior of biological membranes. Giant unilamellar vesicles (GUV) formed by mixtures of two or more phospholipids have particular merit as model membranes because of their simplicity, operability, and ease of viewing phase separation and testing membrane mechanics. Until the research in this thesis, biochemistry and biophysical studies of phase separation in phospholipid membranes primarily addressed the influence of membrane composition on the transition temperatures and domain shapes. This thesis focuses on a commonly neglected variable - membrane tension, analogous to pressure in bulk materials, as an important parameter …


On The Crumpling Of Thin Sheets, Anne Dominique Cambou Nov 2014

On The Crumpling Of Thin Sheets, Anne Dominique Cambou

Doctoral Dissertations

The inner walls of mitochondria, cabbage leaves, and even the Himalayas are all examples of thin sheets: objects with a thickness much smaller than their length and width. Despite their differences in size and in material composition, similar patterns emerge when sheets are crumpled or forced into a small three-dimensional space. As the compaction progresses, the deformations focus into increasingly sharper features that look like the network of peaks and creases found on the surface of a balled up piece of paper. In this regime, external forces are straining the membrane, causing the elastic energy to localize while leaving most …


Direct Measurement Of The Pp Solar Neutrino Interaction Rate In Borexino, Keith Otis Aug 2014

Direct Measurement Of The Pp Solar Neutrino Interaction Rate In Borexino, Keith Otis

Doctoral Dissertations

This dissertation presents the first direct detection of pp solar neutrinos within Borexino, the underground liquid-scintilator detector located at the Gran Sasso National Labratory(LNGS) in Italy, designed to measure the interaction of neutrinos through neutrino-electron elastic scattering. The rate of scattering in Borexino from the pp solar neutrino spectrum is measured to be 155 +/- 16(stat) +/- 13(sys) counts per day per 100 tonnes. With this measurement we are able to rule out the no oscillation hypothesis at the 2-sigma C.L. and the results agree with Standard Solar Model predictions within 1.1-sigma. These neutrinos are from the keystone proton-proton fusion …


Morphology Characterization Of Low Band Gap Polymer-Based Organic Photovoltaics, Feng Liu Aug 2014

Morphology Characterization Of Low Band Gap Polymer-Based Organic Photovoltaics, Feng Liu

Doctoral Dissertations

In bulk heterojunction (BHJ) thin film organic photovoltaics (OPV), morphology control is critical to obtain good device efficiency. Nanoscale phase separation that creates bicontinuous interpenetrating structure on a size scale commensurate with exciton diffusion length (~10 nm) is thought to be the ideal morphology. Results obtained from this work indicate that morphology can be affected by chemical structure of the polymer, processing conditions, blending ratio and post treatments. Physical properties of the material, such as crystallinity, crystal orientation, material interactions and miscibility, surface energy and particle aggregations are critical for determining the morphology and thus the device performance. Previous investigations …


Creasing Instability Of Hydrogels And Elastomers, Dayong Chen Aug 2014

Creasing Instability Of Hydrogels And Elastomers, Dayong Chen

Doctoral Dissertations

CREASING INSTABILITY OF HYDROGELS AND ELASTOMERS MAY 2014 DAYONG CHEN, B.S., TIANJIN UNIVERISTY M.S., TIANJIN UNIVERSITY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Ryan C. Hayward Soft polymers placed under compressive stress can undergo an elastic creasing instability in which sharp folds spontaneously form on the free surfaces. This process may play an important role in contexts as diverse as brain morphogenesis, failure of tires, and electrical breakdown of soft polymer actuators. While the creasing instability has been used for collotype printing since as early as the 1850s, the scientific appreciation of this instability …


Optical And Scanning Probe Studies Of Isolated Poly (3-Hexylthiophene) Nanofibers, Mina Baghgarbostanabad Aug 2014

Optical And Scanning Probe Studies Of Isolated Poly (3-Hexylthiophene) Nanofibers, Mina Baghgarbostanabad

Doctoral Dissertations

Plastic electronics have an essential role in the future technologies owing to their compelling characteristics such as light weight, biocompatibity, low cost fabrication, and tunable optoelectronic properties. However, the performance of polymer-based devices strongly depends on the efficiency of exciton formation and dynamics that are themselves strongly sensitive to polymer molecular packing and structural order. Therefore, the current challenge in achieving high efficiency is establishing a correlation between molecular packing and exciton coupling. P3HT nanofibers represent an attractive platform for studying optical and electronic properties of exciton coupling because their nominal (highly crystalline) internal chain packing structure is known. A …


Biophysical Studies Of Axonal Transport, Leslie Cyle Conway Apr 2014

Biophysical Studies Of Axonal Transport, Leslie Cyle Conway

Doctoral Dissertations

Intracellular transport provides a mechanism by which cellular material, such as organelles, vesicles, and protein, can be actively transported throughout the cell. This process relies on the activity of the cytoskeletal filament, microtubules, and their associated motor proteins. These motors are able to walk along microtubule tracks while carrying cellular cargos to enable the fast, regulated transport of these cargos. In cells, these microtubule filaments act as a binding platform for numerous different motor species as well as microtubule-associated proteins (MAPs). In addition, these filaments often form higher order structures, such as microtubule bundles. How motors navigate such complex, crowded …