259 research outputs found

    Magnetic Anisotropy of Co2MnSn1−xSbx Thin Films Grown on GaAs (001)

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    Heusler alloy Co2MnSn1−xSbx (x = 0.0, 0.5, and 1.0) thin films were grown on GaAs (001) substrates using pulsed laser deposition techniques. Growth parameters have been determined that result in highly magnetically anisotropic, crystalline, and oriented (001) films. The angular dependences, relative to the GaAs (001) crystallographic directions, of the coercive field Hc(θ) and the remanence Mr(θ) were determined from angle dependent magneto-optic Kerr effect (MOKE) measurements. It was found that Hc(θ) revealed higher order symmetry contributions to the magnetic anisotropy than did Mr(θ). The Fourier analysis of rotational MOKE data was used to determine the symmetry contributions to the total anisotropy

    Counts-in-Cylinders in the Sloan Digital Sky Survey with Comparisons to N-body Simulations

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    Environmental statistics provide a necessary means of comparing the properties of galaxies in different environments and a vital test of models of galaxy formation within the prevailing, hierarchical cosmological model. We explore counts-in-cylinders, a common statistic defined as the number of companions of a particular galaxy found within a given projected radius and redshift interval. Galaxy distributions with the same two-point correlation functions do not necessarily have the same companion count distributions. We use this statistic to examine the environments of galaxies in the Sloan Digital Sky Survey, Data Release 4. We also make preliminary comparisons to four models for the spatial distributions of galaxies, based on N-body simulations, and data from SDSS DR4 to study the utility of the counts-in-cylinders statistic. There is a very large scatter between the number of companions a galaxy has and the mass of its parent dark matter halo and the halo occupation, limiting the utility of this statistic for certain kinds of environmental studies. We also show that prevalent, empirical models of galaxy clustering that match observed two- and three-point clustering statistics well fail to reproduce some aspects of the observed distribution of counts-in-cylinders on 1, 3 and 6-Mpc/h scales. All models that we explore underpredict the fraction of galaxies with few or no companions in 3 and 6-Mpc/h cylinders. Roughly 7% of galaxies in the real universe are significantly more isolated within a 6 Mpc/h cylinder than the galaxies in any of the models we use. Simple, phenomenological models that map galaxies to dark matter halos fail to reproduce high-order clustering statistics in low-density environments.Comment: 17 pages, 10 figures. Accepted, Ap

    Magnetic and Transport Properties of Co2MnSnxSb1−x Heusler Alloys

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    We present the magnetic, structural, and transport properties of the quaternary Heusler alloys Co2MnSnxSb1−x (x = 0, 0.25, 0.50, 0.75, and 1.0), which have been theoretically predicted to be half-metallic. Magnetization measurements as a function of applied field show that the saturation moment for x = 1 (Co2MnSn) is near the Slater–Pauling value of 5μB; however, the moment for x = 0 (Co2MnSb) falls far short of its predicted value of 6μB. Resistivity as a function of temperature was measured from 5 to 400 K, and a phase transition from a half-metallic ferromagnetic phase to a normal ferromagnetic phase was observed between 50 and 80 K for all of the alloys. At low temperature (10 K\u3cT\u3c40 K), the resistivity ratio was found to vary as R(T)/R(T = 5 K) = A+BT2+CT9/2, where the T2 term results from electron-electron scattering, whereas the T9/2 term is a consequence of double magnon scattering

    Sedimentary deformation relating to episodic seepage in the last 1.2 million years: a multi-scale seismic study from the Vestnesa Ridge, eastern Fram Strait

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    Seafloor hydrocarbon seepage is a natural fluid release process that occurs worldwide on continental shelves, slopes, and in deep oceanic basins. The Vestnesa sedimentary ridge in the eastern Fram Strait hosts a deep-water gas hydrate system that became charged with hydrocarbons ~2.7 Ma and has experienced episodic seepage along the entire ridge until a few thousand years ago, when seepage activity apparently ceased in the west but persisted in the east. Although it has been documented that faults and fractures play a key role in feeding the seeps with thermogenic gases, the mechanisms controlling seepage periodicity remain poorly understood. Here we integrate highresolution P-cable 3D seismic and Chirp data to investigate the spatial and temporal evolution of high-resolution fractures and fluid flow features in the west of the Vestnesa Ridge. We characterize sediment deformation using a fracture density seismic attribute workflow revealing two highly deformed stratigraphic intervals and associated small-scale pockmarks (<20 m diameter). Chronostratigraphic constraints from the region show that these two highly deformed intervals are influenced by at least three major climatic and oceanic events during the last 1.2 million years: the Mid-Pleistocene Transition (~1.25–0.7 Ma), the penultimate deglaciation (~130 ka) and the last deglaciation (Heinrich Stadial 1: ~16 ka). These periods of deformation appear associated with seismic anomalies potentially correlated with buried methane-derived authigenic carbonate and have been sensitive to shifts in the boundary of the free gas-gas hydrate interface. Our results show shifts (up to ~30 m) in the depth of the base of the gas hydrate stability zone (GHSZ) associated with major changes in ocean bottom water temperatures. This ocean-driven effect on the base of the GHSZ since the Last Glacial Maximum coincides with the already highly deformed Mid-Pleistocene Transition sedimentary interval and likely enhanced deformation and gas leakage along the ridge. Our results have implications for understanding how glacial cycles impact fracture formation and associated seepage activity

    The Grizzly, May 2, 2000

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    Asbestos Mess Hits Helfferich Hard • Commencement Set for UC Seniors • Douglass Davis, UC Alumnus and Faculty Member, Dead at 81 • Annual Spring Fling a High-Flying Success • Students Selected to Speak at 2000 Ursinus Graduation Ceremonies • Letters from the Editors • Final Exam Schedule • UC Female Reflects on the Horrors of the Freshman Fifteen • The Poet-Tree Grows at Ursinus • A New Chapter in the History Books: Newmaster Hurls the First Perfect Game in Centennial Conference History • UC Track Gears Up for Last Meet • Profile: Lisa Newmaster • Bears Capture Back-to-Back CC Title • Unpredicted Ending for UC Lacrossehttps://digitalcommons.ursinus.edu/grizzlynews/1468/thumbnail.jp

    Investigating the Heart of a Community: Archaeological Excavations at the African Meeting House, Boston, Massachusetts

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    In collaboration with the Museum of African American History, an archaeological research team from the University of Massachusetts Boston carried out a data recovery excavation at the African Meeting House on Beacon Hill. The African Meeting House was a powerful social institution for 19thcentury Boston’s free black community. The site played an important role in the abolition movement, the creation of educational opportunity, and other community action for social and political equality. The Meeting House was originally built in 1806, and renovations in preparation for the 2006 bi-centennial celebration prompted an investigation of areas of the property to be impacted by the proposed construction. Archaeological fieldwork, conducted under Massachusetts Historical Commission Permit Number 2750, was spread over seven weeks in May through July 2005. The field team opened and explored about 19 m2 of the site in the backlot south of the Meeting House and alley to the west. These excavations recorded information about a series of significant features and deposits, and collected over 38,000 artifacts and a series of soil samples for a detailed archaeobiological research program. These excavations met the requirements of the data recovery program as outlined in 950 CMR 70.00 and in the Memorandum of Agreement for the project, and the proposed renovation work proceeded with a finding of no adverse effect (36 CFR 800.5(b)). The depositional history and the nature of the archaeological record allow us to separate the overall excavation into three sub-areas: 1) the west alley between the AMH and 2 Smith Court; 2) the historic Meeting House backlot; and 3) the south yard, which originally belonged to the 44 Joy Street property. In terms of significant features and deposits, the west alley was almost entirely a series of builders’ trenches reflecting the historic sequence of construction and remodeling of the Meeting House and adjacent buildings to the west. In the backlot, the units against the south wall of the Meeting House contained similar builders’ trenches. The backlot also contained a series of stone and brick drains and a trash-rich midden layer. The vast majority of artifacts in the Meeting House backlot date from about 1806–1840. The ceramics assemblage is particularly large, and reflects both community meals at the Meeting House and business of Domingo Williams, a caterer who rented a basement apartment. Finally, only one feature was studied in the south yard, a privy (outhouse) that was for the 44 Joy Street property. The bottommost layer of the privy was an artifact rich nightsoil layer, dating to about 1811–1838, and containing the trash of African American tenants living at 44 Joy Street. Together, the archaeological deposits in the backlot provide a variety of insights into living conditions, economic opportunity, foodways, health, and daily life for 19th-century Boston’s free black community. These results thus provide information to help further the research, interpretation, and public education goals of the Museum of African American History

    The Grizzly, April 12, 2001

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    Airband 2001: \u27Case to the Ex\u27 Claims Victory • CAB, RHA, USGA and Class Officer Elections to be Held • Religion Forum Engages Students in Faith-based Discussion • The Big Test: Redefining the SATs • Opinions: Dispelling the Rumors: National Greeks Respond; Questioning the National Greek Approval Process; Purpose of Nationals: To Build up, not Destroy, Existing Greek Life on Campus; Why I Wanted to Bring Tri Sigma to Ursinus College; Tri Sigma Sorority Members Respond to Controversy; Phi Kappa Sigma Fraternity: The Brotherhood of Gentlemen; Why AOL Instant Messenger Will be the Demise of Society • Berman Exhibit \u27Zelda: By Herself\u27 on Display Until Apr. 19 • Women\u27s LAX Remains Undefeated, in First Placehttps://digitalcommons.ursinus.edu/grizzlynews/1488/thumbnail.jp
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