25,565 research outputs found

    La sombra del tiempo: el realismo de Felipe Cooper

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    Felipe Cooper expone, revela, el tiempo del espacio, el tiempo de la pintura

    Induction and repression of mammalian achaete-scute homologue (MASH) gene expression during neuronal differentiation of P19 embryonal carcinoma cells

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    MASH1 and MASH2, mammalian homologues of the Drosophila neural determination genes achaete-scute, are members of the basic helix-loop-helix (bHLH) family of transcription factors. We show here that murine P19 embryonal carcinoma cells can be used as a model system to study the regulation and function of these genes. MASH1 and MASH2 display complementary patterns of expression during the retinoic-acid-induced neuronal differentiation of P19 cells. MASH1 mRNA is undetectable in undifferentiated P19 cells but is induced to high levels by retinoic acid coincident with neuronal differentiation. In contrast, MASH2 mRNA is expressed in undifferentiated P19 cells and is repressed by retinoic acid treatment. These complementary expression patterns suggest distinct functions for MASH1 and MASH2 in development, despite their sequence homology. In retinoic-acid-treated P19 cells, MASH1 protein expression precedes and then overlaps expression of neuronal markers. However, MASH1 is expressed by a smaller proportion of cells than expresses such markers. MASH1 immunoreactivity is not detected in differentiated cells displaying a neuronal morphology, suggesting that its expression is transient. These features of MASH1 expression are similar to those observed in vivo, and suggest that P19 cells represent a good model system in which to study the regulation of this gene. Forced expression of MASH1 was achieved in undifferentiated P19 cells by transfection of a cDNA expression construct. The transfected cells expressing exogenous MASH1 protein contained E-box-binding activity that could be super-shifted by an anti-MASH1 antibody, but exhibited no detectable phenotypic changes. Thus, unlike myogenic bHLH genes, such as MyoD, which are sufficient to induce muscle differentiation, expression of MASH1 appears insufficient to promote neurogenesis

    Minding the Middle: Insights, from Hezbollah and Hamas; Strategic Insights, v. 10, Special issue (October 2011), 124-137. Part III: New Actors and Belligerents

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    This article appeared in Strategic Insights, v.10, Special issue (October 2011), 124-137. Part III: New Actors and BelligerentsThis paper examines the relevance of Hezbollah and Hamas to current and future forms of warfare. A brief review of the literature, however, makes it clear that Hezbollah, particularly during its 2006 war with Israel, has already had a significant impact on US military thinking.Approved for public release; distribution is unlimited

    STABILIZATION OF UPLAND RICE PRODUCTION UNDER SHORTENED FALLOW IN WEST AFRICA: RESEARCH PRIORITY SETTING IN A DYNAMIC ENVIRONMENTAL AND ECONOMIC CLIMATE

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    This paper presents a dynamic model of land resource degradation and shifting rice cultivation in West Africa based upon Boserup and Dvorak. The model indicates the ex ante impact of research strategies to maximize the economic benefits of host plant resistance and land resource management and thereby stabilize yield decline and reduce land degradation.Land Economics/Use, Resource /Energy Economics and Policy,

    Interview with David Johnson by Andrea L’Hommedieu

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    Biographical NoteDavid E. Johnson was born on July 20, 1947, to Evelyn Irene (Hale) and Frank Tivis Johnson in Hardtner, Kansas. His father operated a grain elevator and his mother worked at a department store. He was raised in Enid, Oklahoma, attending Enid High School, where he excelled at debate, and was graduated from the University of Oklahoma with a degree in journalism. He worked for Ed Muskie’s 1972 presidential campaign in the “boiler room” and on his Intergovernmental Relations Committee from 1972 to 1978, working with Al From. He then worked for the Carter administration and for the Department of Health and Human Services. He was administrative assistant to George Mitchell from 1981 to 1984. After a period of a few months in the governmental relations office of the Pharmaceutical Manufacturers Association, he became executive director of the Democratic Senatorial Campaign Committee (DSCC). Since 1987 until the time of this interview, worked in a Washington, D.C. lobbying firm; he also held the position of chair of the Board of Directors of the Mitchell Institute. SummaryInterview includes discussion of: the Muskie 1972 presidential race; working for the Carter administration; his interview with Senator Mitchell for the administrative assistant position in the coffee shop of the Portland Airport; arriving in the Senate office without anyone having been informed that he was hired; hired as executive director of the Democratic Senatorial Campaign Committee (DSCC); the 1982 U.S. Senate campaign; the challenges that Mitchell’s schedule and travel back to Maine presented; anecdote about Mitchell and a senator’s ID card; the tradition for the Senate staff to relax with a few beers in the office after their senator was safely out of the office for the weekend; the familial nature of the Senate staffs when members of the staff had long tenures; smoking in the office; Gayle Cory, how she took to “raising” Johnson, her expertise, and her role in holding the office together; the atmosphere of Mitchell’s office and his leadership style; Johnson’s role as chief of staff; criticism of Mitchell as a tax-and-spend Democrat and Mitchell’s index card response; answering the mail and how Mitchell enjoyed calling some of those who had written his office; Mitchell’s overall strategy of piecing many small elements together to accomplish his goals; and the development of the working relationship between Johnson and Mitchell

    Improvements to the missile aerodynamic prediction code DEMON3

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    The computer program DEMON3 was developed for the aerodynamic analysis of nonconventional supersonic configurations comprising a body with noncircular cross section and up to two wing or fin sections. Within a wing or fin section, the lifting surfaces may be cruciform, triform, planar, or low profile layouts; the planforms of the lifting surfaces allow for breaks in sweep. The body and fin sections are modeled by triplet and constant u-velocity panels, respectively, accounting for mutual body-fin interference. Fin thickness effects are included for the use of supersonic planar source panels. One of the unique features of DEMON3 is the modeling of high angle of attack vortical effects associated with the lifting surfaces and the body. In addition, shock expansion and Newtonian pressure calculation methods can be optionally engaged. These two dimensional nonlinear methods are augmented by aerodynamic interference determined from the linear panel methods. Depending on the geometric details of the body, the DEMON3 program can be used to analyze nonconventional configurations at angles of attack up to 25 degrees for Mach numbers from 1.1 to 6. Calculative results and comparisons with experimental data demonstrate the capabilities of DEMON3. Limitations and deficiencies are listed
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