Radio Pulsar Searching and Timing Follow-up

Pulsars provide some of the richest laboratories for studying the behavior of ultra-dense matter. As such, they have been utilized for decades to place stringent limits on gravitation and as probes of the material that fills our Galaxy. These tests benefit greatly from a catalog of pulsars that is as complete as possible, which in turn requires thorough searches of the Galaxy and precise timing of discoveries. These searches are informed by the continued characterization of the pulsar population, and so searching techniques develop in tandem with the analysis of their discoveries. Large scale pulsar surveys find pulsars; small scale follow-up on those discoveries uncover the pulsars\u27 potential for continued science. In this way, both techniques are crucial to the future of pulsar experimentation. In this dissertation, I discuss the continued analysis of two pulsar surveys utilizing the Green Bank Telescope and subsequent follow-up on the sources from them. In Chapter 1, I provide an overview on the behavior and evolution of pulsars. Aside from the pulsars themselves, I discuss modern pulsar searching techniques and some of the complexities inherent in pulsar timing. In Chapter 2, discussion focuses on the largest radio survey conducted to date: the Green Bank North Celestial Cap survey. This survey has discovered many pulsars that have led to seminal papers in gravitation and neutron star equations of state, but also provides an unprecedented snapshot of the pulsar population at 350 MHz. I utilize these data to assess the survey\u27s sensitivity to pulsars, an analysis that impacts Galactic population models. In Chapter 3, I shift focus to the GBT 820 MHz Cygnus survey, which covers a much smaller region of the Galactic plane that hosts an abundance of active stellar formation. Deep scans of this dense region uncovered several new pulsars, including a source in a relativistic orbit with a massive white dwarf companion. I discuss this source and its follow-up in detail, and utilize the survey results to highlight deficiencies in Galactic models commonly used for pulsar searching. In Chapter 4, I return to the GBNCC survey, but in the context of long-term timing follow-up of its discoveries. Through the use of a pipeline developed to maintain pulsar solutions as high-cadence data are continually collected from observatories like CHIME, I have updated timing solutions for 128 pulsars. This procedure has given rise to many newly measured parameters and updates to those that were previously published; it also provides a framework for iterative pulsar timing that will be essential in the era of dedicated, regular observations of large groups of pulsars. In Chapter 5, I provide an overview of the results from these studies and briefly discuss the future in pulsar searching and timing

Receipt for the Sale of 7 Enslaved Persons

Receipt for the sale from Alexander C. and Eliza M. McEwen to their daughter Elizabeth M. Featherston of seven enslaved persons named Julia Ann, Cornelius, Ilay Ann, Ellen, John, William, and Frances.https://egrove.olemiss.edu/lanternproject/1051/thumbnail.jp

Obituaries for Alexander Calvin McEwen

One of the earliest settlers to Holly Springs, Mississippi, McEwen died December 6, 1869.https://egrove.olemiss.edu/ciwar_clip/1036/thumbnail.jp

Receipt for the Sale of 7 Enslaved Persons

Receipt for the sale from Alexander C. and Eliza M. McEwen to their daughter Elizabeth M. Featherston of seven enslaved persons named Julia Ann, Cornelius, Ilay Ann, Ellen, John, William, and Frances.https://scholarsjunction.msstate.edu/lantern-um/1052/thumbnail.jp

A Mean Field Model for the Quadrupolar Phases of UPd3_3

UPd$_3$ is known to exhibit four antiferroquadrupolar ordered phases at low temperatures. We report measurements of the magnetisation and magnetostriction of single crystal UPd$_3$, along the principal symmetry directions, in fields up to 33 T. These results have been combined with recent inelastic neutron and x-ray resonant scattering measurements to construct a mean field model of UPd$_3$ including up to fourth nearest neighbour interactions. In particular we find that anisotropic quadrupolar interactions must be included in order to explain the low temperature structures derived from the scattering data.Comment: 9 pages, 6 figures, 3 table

Integration of EndNote Online in information literacy instruction designed for small and large chemistry courses

The blended model for information literacy instruction described in this article introduces students not only to efficient techniques for finding scientific literature and properties of chemical compounds, but also to managing this information with a bibliographic management program (EndNote Online). The model blends face-to-face instruction with online tutorials posted on a LibGuide page prepared for each course. A graded online assignment designed in SurveyMonkey was used to assess student learning. During the instruction, students learned to find literature in Google Scholar, PubMed, Scopus, SciFinder, and Web of Science. They also searched for properties of chemical compounds in ChemSpider, PubChem, Reaxys, and SciFinder using a chemical name, molecular formula, CAS Registry Number, or by drawing a molecular structure. The results from the assignments showed that students learned how to find literature and chemical property information efficiently and use a bibliographic management program to store, organize, share, and cite references. This article presents the implementation of the model in two small (40–60 students) and one large (380–460 students) undergraduate chemistry courses. The information literacy instruction described in this article was carried out in more than 20 undergraduate and graduate courses at the University of Maryland College Park. It provided more than 5000 students with versatile skills that they can use throughout their college education and even later in their professional life. The design of the model and its implementation was a result of a close collaboration between the chemistry librarian and the course instructors

Localization of Mad2 to Kinetochores Depends on Microtubule Attachment, Not Tension

A single unattached kinetochore can delay anaphase onset in mitotic tissue culture cells (Rieder, C.L., A. Schultz, R. Cole, G. Sluder. 1994. J. Cell Biol. 127:1301–1310). Kinetochores in vertebrate cells contain multiple binding sites, and tension is generated at kinetochores after attachment to the plus ends of spindle microtubules. Checkpoint component Mad2 localizes selectively to unattached kinetochores (Chen, R.-H., J.C. Waters, E.D. Salmon, and A.W. Murray. 1996. Science. 274:242–246; Li, Y., and R. Benezra. Science. 274: 246–248) and disappears from kinetochores by late metaphase, when chromosomes are properly attached to the spindle. Here we show that Mad2 is lost from PtK1 cell kinetochores as they accumulate microtubules and re-binds previously attached kinetochores after microtubules are depolymerized with nocodazole. We also show that when kinetochore microtubules in metaphase cells are stabilized with taxol, tension at kinetochores is lost. The phosphoepitope 3f3/2, which has been shown to become dephosphorylated in response to tension at the kinetochore (Nicklas, R.B., S.C. Ward, and G.J. Gorbsky. 1995. J. Cell Biol. 130:929–939), is phosphorylated on all 22 kinetochores after tension is reduced with taxol. In contrast, Mad2 only localized to an average of 2.6 out of the 22 kinetochores in taxol-treated PtK1 cells. Therefore, loss of tension at kinetochores occupied by microtubules is insufficient to induce Mad2 to accumulate on kinetochores, whereas unattached kinetochores consistently bind Mad2. We also found that microinjecting antibodies against Mad2 caused cells arrested with taxol to exit mitosis after ∼12 min, while uninjected cells remained in mitosis for at least 6 h, demonstrating that Mad2 is necessary for maintenance of the taxol-induced mitotic arrest. We conclude that kinetochore microtubule attachment stops the Mad2 interactions at kinetochores which are important for inhibiting anaphase onset