Toxoplasma gondii major surface antigen (SAG1): in vitro analysis of host cell binding

Previous studies have indicated that SAG1, the major surface molecule of the protozoan parasite Toxoplasma gondii, is an important attachment ligand for the host cell. However, the research data that supports this claim comes largely from studies investigating tachyzoite binding, and not SAG1 binding per se. In this study we successfully developed an in vitro attachment assay to directly evaluate the mechanism of SAG1-host cell binding. Competition experiments were then performed using SAG1 that had been pre-treated with the neoglycoprotein BSA-glucosamide or with antibody. Soluble BSA-glucosamide blocked SAG1 attachment to MDBK cells in a dose-dependent manner, implying that SAG1 binding is mediated, in part, via attachment to host cell surface glucosamine. Interestingly, pre-incubation of SAG1 in polyclonal sera from chronically infected mice failed to block binding. This challenges the assumption that anti-SAG1 antibodies block parasite attachment through the masking of SAG1 host cell binding domains. Taken together, this evidence presents new strategies for understanding SAG1-mediated attachment

Metric Perturbation Approach to Gravitational Waves in Isotropic Cosmologies

Gravitational waves in isotropic cosmologies were recently studied using the gauge-invariant approach of Ellis-Bruni. We now construct the linearised metric perturbations of the background Robertson-Walker space-time which reproduce the results obtained in that study. The analysis carried out here also facilitates an easy comparison with Bardeen.Comment: 29 pages, Latex file, accepted for publication in Physical Review

Shear-Free Gravitational Waves in an Anisotropic Universe

We study gravitational waves propagating through an anisotropic Bianchi I dust-filled universe (containing the Einstein-de-Sitter universe as a special case). The waves are modeled as small perturbations of this background cosmological model and we choose a family of null hypersurfaces in this space-time to act as the histories of the wavefronts of the radiation. We find that the perturbations we generate can describe pure gravitational radiation if and only if the null hypersurfaces are shear-free. We calculate the gauge-invariant small perturbations explicitly in this case. How these differ from the corresponding perturbations when the background space-time is isotropic is clearly exhibited.Comment: 32 pages, accepted for publication in Physical Review

Mineral investigations of D-2 lands in the Philip Smith Mountains and Chandler Lake quadrangles

Eight hundred and sixty-five stream sediment samples were collected over an area of approximately 2,120 square kilometers (828 square miles) in the Chandler Lake and Philip Smith Mountains quadrangles (Fig. 1). The samples were analyzed by atomic absorption methods for Cu, Pb, Zn, Ag and Mo. Statistical reduction of the data resulted in the definition of 86 anomalous samples. The majority of the anomalous samples were from streams draining either the Hunt Fork Shale, Kanayut Conglomerate, or the Lisburne Group. The anomalous samples are grouped in ten separate areas; eight of these areas warrant additional field examination. The number of geochemical anomalies within the area indicates that region has good potential for copper, lead and zinc sulfide mineral deposits.Introduction -- Objective -- Previous investigations -- Regional geology and petrology -- Structural geology -- Geochemistry -- Mining activity and economic geology -- Summary and conclusions -- References cited -- Appendix

Evaluation of the mineral resources of the pipeline corridor, phases i and ii

In accordance with U. S. Bureau of Mines (U.S.B.M.) Grant No. G0166180 entitled, “Evaluation of the Mineral Resources of the Pipeline Corridor”, the Mineral Industry Research Laboratory (M.I.R.L.), of the University of Alaska, completed an examination of the mineral resource potential of the federal utility corridor established for the trans-Alaska pipeline. The contract was completed under the direction of the Principal Investigator, Paul A. Metz and the Associate Investigator, Mark S. Robinson.Introduction -- Section I. Geology and mineral resources of the Valdez quadrangle -- Section II. Geology and mineral resources of the Gulkana quadrangle -- Section III. Geology and mineral resources of the Mt. Hayes quadrangle -- Section IV. Geology and mineral resources of the Big Delta quadrangle -- Section V. Geology and mineral resources of the Fairbanks quadrangle -- Section VI. Geology and mineral resources of the Livengood quadrangle -- Section VII. Geology and mineral resources of the Tanana quadrangle --Section VIII. Geology and mineral resources of the Bettles quadrangle -- Section IX. Geology and mineral resources of the Wiseman quadrangle -- Section X. Geology and mineral resources of the Chandalar quadrangle -- Section XI. Geology and mineral resources of the Philip Smith Mountains quadrangle -- Section XII. Geology and mineral resources of the Sagavanirktok quadrangle

Bernstein modes in a weakly relativistic electron-positron plasma

The kinetic theory of weakly relativistic electron-positron plasmas, producing dispersion relations for the electrostatic Bernstein modes was addressed. The treatment presented preserves the full momentum dependence of the cyclotron frequency, albeit with a relaxation on the true relativistic form of the distribution function. The implications of this new treatment were confined largely to astrophysical plasmas, where relativistic electronpositron plasmas occur naturally

Baseline geochemical studies for resource evaluation of D-2 Lands - geophysical and geochemical investigations at the Red Dog and Drenchwater Creek mineral occurrences

Major zinc, lead and barite mineralization has been discovered at Red Dog and Drenchwater Creeks in the DeLong Mountains of north-western Alaska. The host rocks for the mineral occurrences are carbonates, cherts, shales, and dacitic volcanic rocks of the Mississippian Lisburne Group. The host rocks are deformed in a narrow belt of imbricate thrust sheets that extend from the Canadian border to the Chukchi Sea. The rocks strike generally east-west and dip to the south. The sulfide minerals occur as stratiform mineralization parallel to bedding planes, as breccia fillings and vein replacements, and as disseminations in the various host rocks. The primary ore minerals are sphalerite, pyrite, pyrrhotite, and galena. Barite occurs as massive beds up to 90 meters (300 feet) thick at Red Dog Creek and as nodules, veinlets, and disseminations at Drenchwater Creek. Close spaced soil sampling, mercury vapor sampling, and magnetic and radiometric surveys were conducted over the areas of exposed sulfide mineralization to test the response of these techniques to these types of deposits in northern Alaska. There is potential for additional deposits of this type in the Lisburne Group of the entire northern Brooks Range. These techniques provide a rapid low cost method for the discovery and preliminary evaluation of these types of mineral occurrences in northern Alaska.Introduction -- Objectives -- General geology of the Red Dog Creek and Drenchwater Creek mineral occurrences -- Red Dog Creek mineral occurrence -- Location and previous investigations -- Regional geology and petrology -- Geochronology and structural geology -- Economic geology -- Drenchwater Creek mineral occurrence -- Location and previous investigations -- Regional geology and petrology -- Geochronology and structural geology -- Economic geology -- Geophysical and geochemical data collection, analysis, and reduction - Red Dog Creek -- Geophysical and geochemical data collection, analysis, and reduction - Drenchwater Creek -- Summary and conclusions -- References cited -- Appendices

Performativity and a microbe: Exploring Mycobacterium bovis and the political ecologies of bovine tuberculosis

Mycobacterium bovis, the bacterium responsible for causing bovine tuberculosis (bTB) in cattle, displays what I call ‘microbial performativity’. Like many other lively disease-causing microorganisms, it has an agency which is difficult to contain, and there is a need for fresh thinking on the challenges of dealing with this slippery and indeterminate microbe. As a practising veterinary scientist who side-stepped mid-career into a parallel training in the social sciences to view bTB from an alternative perspective, I create an interdisciplinary coming-together where veterinary science converges with a political ecology of (animal) health influenced by science and technology studies (STS) and social science and humanities scholarship on performativity. This suitably hybridized nexus creates a place to consider the ecologies of a pathogen which could be considered as life out of control. I consider what this means for efforts to eradicate this disease through combining understandings from the published scientific literature with qualitative interview-based fieldwork with farmers, veterinarians and others involved in the statutory bTB eradication programme in a high incidence region of the UK. This study demonstrates the value of life scientists turning to the social sciences to re-view their familiar professional habitus—challenging assumptions, and offering alternative perspectives on complex problems