A Geometrical Derivation of a Family of Quantum Speed Limit Results

We derive a family of quantum speed limit results in time independent systems with pure states and a finite dimensional state space, by using a geometric method based on right invariant action functionals on SU(N). The method relates speed limits for implementing quantum gates to bounds on orthogonality times. We reproduce the known result of the Margolus-Levitin theorem, and a known generalisation of the Margolis-Levitin theorem, as special cases of our method, which produces a rich family of other similar speed limit formulas corresponding to positive homogeneous functions on su(n). We discuss the general relationship between speed limits for controlling a quantum state and a system's time evolution operator.Comment: 12 page

Quantitative Study of the Antimicrobial Effects of Silver on the Motility of Escherichia coli

In recent decades, the number of antibiotic-resistant bacterial infections has grown to become a serious global threat. This rise can be attributed to the widespread misuse of antibiotics and the lack of newly developed drugs to fight resistant organisms. Novel bactericidal substances have, therefore, garnered significant research interest. Silver, due to its powerful antimicrobial effects, is one such substance. Silver is typically most effective in cationic form; however, advancements in nanotechnology have paved the way for the controlled fabrication of nano-silver. Silver nanoparticles have been shown to have increased antibacterial potency for a variety of reasons, including the release of silver ions into aqueous media. Nonetheless, the entire antimicrobial mechanism of silver nanoparticles has not been completely elucidated. One such unexplored interaction is with bacterial motility. Motility allows bacterial cells to navigate their environment and steer themselves in favorable directions. Furthermore, motility has been shown to play an important role in virulence and biofilm-formation. In this research, I investigated the interactions between silver ions and motility of Escherichia coli. By performing and collecting data from a series of phase-contrast microscopy experiments, I was able to show, through quantitative modeling and results, that silver ions cause a decrease in swimming velocity, an increase in tumbling frequency, and an increase in tumbling dwell time, all while not killing the cell. The experiments I performed included free-swimming experiments, in which bacteria swam in the 2-D focal plane, and tethering assay experiments, where a cell was trapped to a glass coverslip by a single flagellum. By modeling the rotational velocity of the tethered cells using hidden Markov models, I was able to show that silver ions cause a significant change to the tumble-to-run probabilities of treated cells. These results are of great importance for furthering the understanding of silver as a bactericide

Postglacial Sandy Hill: A Regional Manifestation of the Gulf of Maine Archaic Tradition

Over twenty years of archaeological excavations at Sandy Hill, in Mashantucket, CT, have provided an incredibly rich assemblage of artifacts. Yet some of the most basic questions about Sandy Hill\u27s Early Archaic inhabitants remain unanswered. This thesis will synthesize the results of major excavations at Sandy Hill by analyzing site morphology, lithics, and hard tissue macrobotanical remains from several radiocarbon dated contexts. Macrobotanical artifacts recovered from Sandy Hill indicate a preference for hazelnut as well as wetland roots and tubers. The lithic assemblage is related to the Gulf of Maine Archaic Tradition and the predominance of quartz flakes technology and the uniform size and shape of these flakes suggest systematic production for a specific purpose, perhaps grater boards. Sandy Hill is a regional manifestation of the Gulf of Maine Archaic Tradition where people exploited dependable wetland resources in a time of ecological stress

The message of Hebrew prophecy

Thesis (Ph.D.)--Boston Universit

Direct band gap gallium antimonide phosphide (GaSbxP1-x) for solar fuels.

Photoelectrochemical water splitting has been identified as a promising route for achieving sustainable energy future. However, semiconductor materials with the appropriate optical, electrical and electrochemical properties have yet to be discovered. In search of an appropriate semiconductor to fill this gap, GaSbP, a semiconductor never tested for PEC performance is proposed here and investigated. Density functional theory (DFT+U) techniques were utilized to predict band gap and band edge energetics for GaSbP alloys with low amount of antimony. The overall objective of this dissertation is to understand the suitability of GaSbxP1-x alloys for photoelectrochemical water splitting application. Specifically, the goals are to develop synthesis methods, grow GaSbxP1-x alloys, understand their optical and photoelectrochemical properties, and compare experimental values with theoretical predictions. DFT+U calculations suggested that with less than 1% Sb incorporated into GaP, an indirect to direct band gap transition should occur. Furthermore, predictions with band edge positions for GaSbxP1-x alloys with small amount of Sb composition suggest band edge straddling of the water splitting reaction. Preliminary experiments were performed using reactive vapor transport in a microwave plasma reactor. The experiments primarily resulted in growing GaSbxP1-x nanowires. Extensive characterization using electron microscopy and X-ray diffraction and photoluminescence spectroscopy corroborated the predictions using DFT+U calculations. Initial experimentation utilized a plasma transport scheme of Ga and Sb metals with di-tert-butyl-phosphine gas on the reactor to synthesis GaSbxP1-x nanowires. Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) confirmed ternary alloying of these GaSbxP1-x nanowires. Direct band gaps were observed between 1.7 eV and 2.2eV with GaSbxP1-x compositions between 3% and 6%. However, the method used here is not suitable for growing single crystal films. In order to grow single crystal films on silicon substrates, a new reactor was designed and built for halide vapor phase epitaxy method. Experiments using Halide Vapor Phase Epitaxy (HVPE) reactor were conducted using silicon and sapphire substrates. Experiments using excessive Gallium yielded microwire morphologies. Further experiments with reduced Gallium precursor temperature allowed for growth of quality crystalline films on silicon substrate. The films grown at different temperatures exhibited different amounts of antimonide alloying. The resulting samples exhibited direct band gaps of 1.7 to 2.1 eV evidenced by UV-Vis diffuse reflectance spectroscopy.. Room temperature photoluminescence corroborated these findings. Photoelectrochemical studies of the HVPE grown samples show that they can be highly photoactive materials under the proper growth conditions. The best performing sample had saturated photovoltages of .75 eV and a photoactivity of 8 mA/cm2 under unbiased conditions and 4 suns illumination. This photocurrent saturated to 11 mA/cm2 at 1 V vs. Ag/AgCl external bias. In summary, the work presented here provides fundamental insight into growth and properties of GaSbP alloy samples with low amount of Sb incorporation. The experimental data corroborates predictions by DFT+U technique in terms of indirect to direct band gap transition, band gap as a function of Sb incorporation and band edge energetics for photoelectrochemical water splitting. This work also provides first of its kind use of halide vapor phase epitaxy technique for the growth of GaSbP alloys. Photoactivity data suggests that these materials are highly promising for photoelectrochemical devices