Thesis (Ph.D.)--Lehigh University, 2008. / Adviser: John Huennekens.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6474. Adviser: Enrico Gratton. Includes bibliographical references (leaves 98-111). Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6250. Adviser: Taekjip Ha. Includes bibliographical references (leaves 114-119) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0880. Adviser: Nigel Goldenfeld. Includes bibliographical references (leaves 158-176) Available on microfilm from Pro Quest Information and Learning.

The design of new materials and chemicals derived entirely from computation has long been a goal of computational chemistry, and the governing equation whose solution would permit this dream is known. Unfortunately, the exact solution to this equation has been far too expensive and clever approximations fail in critical situations. Quantum computers offer a novel solution to this problem. In this work, we develop not only new algorithms to use quantum computers to study hard problems in chemistry, but also explore how such algorithms can help us to better understand and improve our traditional approaches. In particular, we first introduce a new method, the variational quantum eigensolver, which is designed to maximally utilize the quantum resources available in a device to solve chemical problems. We apply this method in a real quantum photonic device in the lab to study the dissociation of the helium hydride (HeH$^{+}$) molecule. We also enhance this methodology with architecture specific optimizations on ion trap computers and show how linear-scaling techniques from traditional quantum chemistry can be used to improve the outlook of similar algorithms on quantum computers. We then show how studying quantum algorithms such as these can be used to understand and enhance the development of classical algorithms. In particular we use a tool from adiabatic quantum computation, Feynman's Clock, to develop a new discrete time variational principle and further establish a connection between real-time quantum dynamics and ground state eigenvalue problems. We use these tools to develop two novel parallel-in-time quantum algorithms that outperform competitive algorithms as well as offer new insights into the connection between the fermion sign problem of ground states and the dynamical sign problem of quantum dynamics. Finally we use insights gained in the study of quantum circuits to explore a general notion of sparsity in many-body quantum systems. In particular we use developments from the field of compressed sensing to find compact representations of ground states. As an application we study electronic systems and find solutions dramatically more compact than traditional configuration interaction expansions, offering hope to extend this methodology to challenging systems in chemical and material design. / Chemical Physics

Abstract not available.

Nanotechnology is now a reality although it is still very much in its infancy. This being said much work still needs to be done. During the last past few decades, new experimental tools such as videomicroscopy and optical tweezers, which allow us to both visualize and manipulate in real time the dynamics of macromolecules, have emerged. These two tools alone provide endless possibilities. For example, it is now possible to tether a polymer at one end with optical tweezers while a constant flow of solvent extends it. If the chain is fluorescently labeled, dynamical properties can be extracted via videomicroscopy. In this thesis, we study a similar problem. With the help of Molecular Dynamics (MD) simulations, we examine the physics of a Freely Jointed Chain (FJC) tethered by one end to a hard surface while being submitted to a Poiseuille flow. A good solvent is used during the first part of this thesis, while for the second part, we look at the dynamics of the chain in poor solvents. In both cases, we compare actual stretching theories to our simulation data and extract the effects of Hydrodynamic Interactions (HI). For good solvents, we propose a new empirical equation which relates the unstretched fraction of the chain to the full range of shear rates. We also observe a peculiar cyclic motion of the chain which was first reported experimentally. For poor solvents, we study the collapsed chain properties while changing the strength of the shear flow linearly in time. A novel hysteretic effect for the chain extension as a function of shear rate is observed in our simulations.

Capillary electrophoresis (CE) is the workhorse of countless analytical laboratories and is used routinely in various industries including pharmaceutical, forensic and clinical applications. Basically, CE is a method for separating charged molecular species in a buffer-filled capillary by the application of an electric field; the analytes move from one end of the capillary to the detector at the other end at speeds determined by their charge, size and shape. Generally, in free solution CE uniformly charged polyelectrolytes (such as DNA) are free-draining, meaning that their speed is independent of their size. Hence, until recently, a gel or other sieving medium has been necessary for the separation of polyelectrolytes; however, modifying uniformly charged polymers on the molecular level, via conjugation to uncharged polymers, allows for separation in free solution CE. In this thesis, advancements to the theory of free solution electrophoresis of polyelectrolytes, in particular, to the theories for two new free solution electrophoresis methods relying on conjugation, are presented. The first method, called End Labelled Free Solution Electrophoresis (ELFSE), can be used to sequence DNA, a negatively charged polymer in solution. Two different means of improving the resolution of ELFSE are predicted, one based on the molecular end effect, the other based on using a controlled electro-osmotic flow. In addition, a theory for the segregation of the DNA and label coils in ELFSE is presented. The second method is called Free Solution Conjugate Electrophoresis (FSCE); it allows for characterization of a sample of neutral polymers differing in length. The relevant theory, developed herein, elucidates how to accurately determine the molar mass distribution of the sample through FSCE measurements. In addition, supporting theories are developed that clarify the correct equation for the diffusion coefficient of molecules undergoing free solution electrophoresis, as well as illustrate that under ideal conditions, a viscosity gradient within the capillary serves only to decrease resolution and hence can not be used to improve performance. These theoretical studies constitute the six articles presented in this thesis. In addition, a comprehensive review article covering the development of ELFSE over the last decade, the theoretical concepts used to predict the ultimate performance of ELFSE for DNA sequencing, and the technological advances that are needed to speed the development of competitive ELFSE-based sequencing and separation technologies, is given in Appendix A. The predicted improvement in ELFSE resolution based on the end effect theory was also proven experimentally; the article with these findings is provided in Appendix B.