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Molecular characterization of infectious mouse mammary tumor viruses (MMTVs) has been hampered due to the problem of cloning a full-length exogenous virus into a plasmid. The present report describes our strategy for obtaining a full-length clone of an exogenous MMTV from a mouse mammary tumor that arose spontaneously in a wild Chinese mouse free of endogenous MMTV and shows that the cloned virus (JYG-MMTV) is expressed in rat RBA cells. Four-week-old C58/J x CBA/CaJ female mice, free of both endogenous and exogenous MMTVs, were injected with virus-secreting RBA cells. The progeny of these mice were bred, and their offspring were tested for the presence of MMTV. These third-generation mice were found to actively produce MMTV that was shed in their milk and transmitted to their offspring. The virus was detected not only in the mammary glands of these young mice, but also in their spleens and bone marrow. These results suggest that our plasmid-cloned exogenous JYG-MMTV is infectious. This virus can now be used effectively in manipulating the various genes of JYG-MMTV and other MMTV strains to understand their structure/function relationships.
Research Article| June 01, 1999 Chronostratigraphy of the Miocene–Pliocene Sagantole Formation, Middle Awash Valley, Afar rift, Ethiopia Paul R. Renne; Paul R. Renne 1Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 947092Department of Geology and Geophysics, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar Giday WoldeGabriel; Giday WoldeGabriel 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Search for other works by this author on: GSW Google Scholar William K. Hart; William K. Hart 4Department of Geology, Miami University, Oxford, Ohio 45056 Search for other works by this author on: GSW Google Scholar Grant Heiken; Grant Heiken 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Search for other works by this author on: GSW Google Scholar Tim D. White Tim D. White 5Laboratory for Human Evolutionary Studies, Museum of Vertebrate Zoology6Department of Integrative Biology, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar Author and Article Information Paul R. Renne 1Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 947092Department of Geology and Geophysics, University of California, Berkeley, California 94720 Giday WoldeGabriel 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 William K. Hart 4Department of Geology, Miami University, Oxford, Ohio 45056 Grant Heiken 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Tim D. White 5Laboratory for Human Evolutionary Studies, Museum of Vertebrate Zoology6Department of Integrative Biology, University of California, Berkeley, California 94720 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1999) 111 (6): 869–885. https://doi.org/10.1130/0016-7606(1999)111<0869:COTMPS>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Paul R. Renne, Giday WoldeGabriel, William K. Hart, Grant Heiken, Tim D. White; Chronostratigraphy of the Miocene–Pliocene Sagantole Formation, Middle Awash Valley, Afar rift, Ethiopia. GSA Bulletin 1999;; 111 (6): 869–885. doi: https://doi.org/10.1130/0016-7606(1999)111<0869:COTMPS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Sagantole Formation comprises more than 200 m of lacustrine, alluvial, and volcaniclastic sediments, plus compositionally bimodal tephras and basaltic lavas, exposed in a domelike horst named the Central Awash Complex in the southwestern Afar rift of Ethiopia. The Sagantole Formation is widely known for abundant vertebrate faunas, including the 4.4 Ma primitive hominid Ardipithecus ramidus. New lithostratigraphic data are used to subdivide the Sagantole Formation into the Kuseralee, Gawto, Haradaso, Aramis, Beidareem, Adgantole, and Belohdelie Members, in ascending order. The members are defined on the basis of lithologic differences and laterally continuous bounding tephras.40Ar/39Ar dating of 12 intercalated volcanic units firmly establishes the age of the Sagantole Formation to be 5.6 to 3.9 Ma, significantly older than previous proposals based on erroneous correlations. Magnetostratigraphic data reveal eight paleomagnetic polarity zones, which can be correlated unambiguously with the Thvera, Sidufjall, Nunivak, and Cochiti Subchrons of the Gilbert Chron. Thus, by reference to the geomagnetic polarity time scale, seven additional chronological datums can be placed in the Sagantole Formation. With a total of 19 such datums, the age resolution anywhere in the Sagantole Formation is better than ±100 k.y., making this the best-dated Miocene–Pliocene succession in Africa. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Characteristics of fatigue-crack propagation behavior are reviewed for recently developed commercial aluminum-lithium alloys, with emphasis on the underlying micromechanisms associated with crack advance and their implications to damage-tolerant design. Specifically, crack-growth kinetics in Alcoa 2090-T8E41, Alcan 8090 and 8091, and Pechiney 2091 alloys, and in certain powder-metallurgy alloys, are examined as a function of microstructure, plate orientation, temperature, crack size, load ratio and loading sequence. In general, it is found that growth rates for long (> 10 mm) cracks are nearly 2--3 orders of magnitude slower than in traditional 2000 and 7000 series alloys at comparable stress-intensity levels. In additions, Al-Li alloys shown enhanced crack-growth retardations following the application of tensile overloads and retain superior fatigue properties even after prolonged exposure at overaging temperatures; however, they are less impressive in the presence of compression overloads and further show accelerated crack-growth behavior for microstructurally-small (2--1000 {mu}m) cracks (some three orders of magnitude faster than long cracks). These contrasting observations are attributed to a very prominent role of crack-tip shielding during fatigue-crack growth in Al-Li alloys, promoted largely by the tortuous and zig-zag nature of the crack-path morphologies. Such crack paths result in locally reduced crack-tip stress intensities, due to crack deflection and consequent crack wedging from fracture-surface asperities (roughness-induced crack closure); however, such mechanisms are far less potent in the presence of compressive loads, which act to crush the asperities, and for small cracks, where the limited crack wake severely restricts the shielding effect. 50 refs., 21 figs.
Public demand for clean and sustainable water sources drives the need for skilled hydrogeologist who specialize in surface and subsurface water flow. Hydrogeologists must integrate three-dimensional data from maps, wells, field sites, and geologic models to predict the movement of water through the subsurface. Research in other STEM disciplines has shown that targeted training of relevant spatial thinking skills can improve student persistence and retention, especially among women and students of color. Because the specific spatial thinking skills relevant to practicing hydrogeology have not yet been documented, best practices to inform hydrogeology curricula are lacking. This situation hampers efforts to train students for careers in hydrogeology and our response to the need for clean and sustainable water. Our project seeks to identify and characterize the specific spatial thinking skills and knowledge that hydrogeologists use when solving water and contaminant flow problems, and to understand how students use (or do not use) these skills when learning hydrogeology in the classroom. Characterizing these skills is a critical first step toward creating curricular materials that will improve the preparation of diverse and capable hydrogeologists ready to respond to the challenges of a changing world. This presentation will present our work and findings from the first year of our project and focus on characterization of spatial thinking skills relevant to practicing hydrogeology using data collected from expert hydrogeologists from government, consulting, industry, and academia.
This paper represents a sequel to an earlier paper, where a unified study of the applications of Volterra functional series to nonlinear analysis is presented. The same philosophy is followed here, giving special emphasis on frequency-domain results which either have not been published before, or where rigour had been lacking. Some of the results presented include generalisations or rigorous formalisations of wellknown special cases. Explicit and recursive formulas for obtaining n th-order transfer functions of composite nonlinear systems are presented. A recursive method for obtaining the n th-order output of a nonlinear circuit by solving a linear circuit n times is derived. Each time different input sources arc used. Recursive formulas for obtaining the n th-order transfer functions of nonlinear circuits are then generated. These results are used to obtain formulas for n th-order transfer functions of cascade systems, as well as inverse systems. Methods for synthesising nonlinear circuits and inverse systems via feedback configurations are given. Finally, the general structures of transfer functions for a large class of nonlinear systems are also derived.
