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Now showing items 1 - 16 of 509

  • On Invariant Semisimple CR Structures of Maximal Rank on the Compact Lie Groups SUn(C) and SOn(R)

    Ounaies-Khalgui, H.   Yu, R. W. T.  

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  • The atmosphere of the sun: C. J. Durrant Adam Hilger £23.50 168 pages

    Alec MacKinnon  

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  • The Sun: A User\"s Manual, By C. Vita-Finzi

    Rogel-Salazar   J.  

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  • Rounding Numbers: Ptolemy\"s Calculation of the Earth—Sun Distanceby Christián C. Carman

    Review by: Tanya Leise  

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  • JDN11 delivers sea, sun, and science on the C?te d\"Azur

    Dianoux   A. J.  

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  • Short-term variability of comet C/2012 S1 (ISON) at 4.8 AU from the Sun

    Santos-Sanz, P.   Ortiz, J. L.   Morales, N.   Duffard, R.   Pozuelos, F.   Moreno, F.   Fernández-Valenzuela, E.  

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  • Sun Dogs and Eagle down: The Indian Paintings of Bill Holmby Steven C. Brown

    Review by: Bill Mercer  

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  • A new ent-kaurane deterpenoid from Isodon excisoides (Sun ex C. H. Hu) C. Y. Wu et H. W. Li

    Ding, Lan   Wang, Han   Liu, Guoan   Yang, Dongjuan  

    A new ent-kaurane diterpenoid, excisoidesin (1), was isolated from the acetone extract of the leaves of Isodon excisoides (Sun ex C. H. Hu) C. Y. Wu et H. W. Li, along with kamebacetal B (2), glaucocalyxin A (3), leukamenin E (4), kamebanin (5) and wangzaozin A (6). The structure of the new compound was determined as 7α,14β,18-trihydroxy-ent-kaur-16-en-3,15-dione by spectroscopic methods. Compound 1-6 showed significant cytotoxic activity against human tumor Bel-7402 cells.
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  • THE INNER COMA OF COMET C/2012 S1 (ISON) AT 0.53 AU AND 0.35 AU FROM THE SUN

    Bonev, Boncho P.   DiSanti, Michal A.   Villanueva, Geronimo L.   Gibb, Erika L.   Paganini, Lucas   Mumma, Michael J.  

    Using long-slit spectroscopy at the NASA Infrared Telescope Facility, we extracted H2O production rates and spatial profiles of gas rotational temperature and molecular column abundance in comet C/2012 S1 ISON, observed at heliocentric distances of 0.53 and 0.35 AU. These measurements uniquely probed the physical environment in the inner collisional coma of this comet during its first (and last) approach to the Sun since being emplaced in the Oort Cloud some 4.5 billion years ago. Our observations revealed a comet evolving on various timescales, both over hours and days. At 0.35 AU, ISON showed a considerable decrease in water production rate in less than 2 hr, likely declining from a major outburst. Our measured temperature spatial distributions reflect the competition between the processes that cause heating and cooling in the coma, and also provide insight about the prevalent mechanism(s) of releasing gas-phase H2O. The observed temperatures suggest that the comet was likely ejecting icy material continuously, which sublimated in the coma and heated the ambient gas, augmenting fast H-atoms produced by H2O photolysis. ISON adds to the very limited sample of comets for which spatial-spectral studies of water temperatures have been conducted. These studies are now feasible and can be extended to comets having a variety of gas production rates. Continued synergy of such observations with both space missions like Rosetta and with physical models is strongly encouraged in order to gain a deeper understanding of the processes in the inner collisional zone of the cometary coma.
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  • CHARACTERIZING THE DUST COMA OF COMET C/2012 S1 (ISON) AT 4.15 AU FROM THE SUN

    Li, Jian-Yang   Kelley, Michael S. P.   Knight, Matthew M.   Farnham, Tony L.   Weaver, Harold A.   A\"Hearn, Michael F.   Mutchler, Max J.   Kolokolova, Ludmilla   Lamy, Philippe   Toth, Imre  

    We report results from broadband visible images of comet C/2012 S1 (ISON) obtained with the Hubble Space Telescope Wide Field Camera 3 on 2013 April 10. C/ISON's coma brightness follows a 1/rho (where rho is the projected distance from the nucleus) profile out to 5000 km, consistent with a constant speed dust outflow model. The turnaround distance in the sunward direction suggests that the dust coma is composed of sub-micron-sized particles emitted at speeds of tens of ms(-1). A(theta)f rho, which is commonly used to characterize the dust production rate, was 1340 and 1240 cm in the F606W and F438W filters, respectively, in apertures <1".6 in radius. The dust colors are slightly redder than solar, with a slope of 5.0% +/- 0.2% per 100 nm, increasing to >10% per 100 nm 10,000 km down the tail. The colors are similar to those of comet C/1995 O1 (Hale-Bopp) and other long-period comets, but somewhat bluer than typical values for short-period comets. The spatial color variations are also reminiscent of C/Hale-Bopp. A sunward jet is visible in enhanced images, curving to the north and then tailward in the outer coma. The 1."6 long jet is centered at a position angle of 291 degrees., with an opening angle of similar to 45 degrees.. The jet morphology remains unchanged over 19 hr of our observations, suggesting that it is near the rotational pole of the nucleus, and implying that the pole points to within 30 degrees of (R.A., decl.) = (330 degrees., 0 degrees.). This pole orientation indicates a high obliquity of 50 degrees-80 degrees.
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  • The Old Men of C(uba): Will the Sun Also Rise (on Cuba)?

    Ira Sohn   Juan Villeta Trigo  

    Cuba is approaching a crossroads regarding the future of its economic system. The paper begins with an overview of Cuba's vital statistics and then discusses the country's changing political landscape that has already triggered some selected -- albeit very modest -- changes. We review the long history of foreign country involvement in Cuba's affairs in order to put the tortured relations with the United States into sharper focus. Part 3 describes the methodological framework used to highlight Cuba's major weaknesses, and we conclude that the distortions that have been compounded over fifty years can be unwound only by introducing a comprehensive reform program that embraces new leadership and new thinking.
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  • T. H. Hyde, W. Sun, and C. J. Hyde: Applied Creep Mechanics. McGraw Hill Education, New York et al. 2013

    Altenbach   Holm  

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  • Nomadic Art of the East Eurasian Steppesby Emma C. Bunker; James C. Watt; Zhixin Sun

    Review by: Francis Allard  

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  • Use of class A and class C stellar engines to control sun movement in the galaxy

    Viorel Badescu and Richard B. Cathcart  

    Two particular stellar engines of class A and C, respectively, are described. When the Sun is the energy source, both of them provide practically the same thrust force. A simple dynamic model for Sun motion in the Galaxy is developed. It takes into account the (perturbation) thrust force provided by a stellar engine, which is superposed on the usual gravitational forces. Two different Galaxy gravitational potential models were used to describe Sun motion. The results obtained in both cases are in reasonably good agreement. Three simple strategies of changing the Sun trajectory are considered. For a single Sun revolution the maximum deviation from the usual orbit is of the order of 35–40 pc. Thus, stellar engines of the kind envisaged here may be used to control to a certain extent, the Sun movement in the Galaxy. However, under the constraints of present day technology this solution is not yet realistic.
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  • Use of class A and class C stellar engines to control sun movement in the galaxy

    Viorel Badescu   Richard B. Cathcart  

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  • Placing the Sun and Mainstream S[CLC]i[/CLC]C Particles in Galactic Chemodynamic Evolution

    Clayton   D. D.  

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