4,050 research outputs found

    Space Trajectory Error Analysis Program (STEAP) for halo orbit missions. Volume 2: Programmer's manual

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    The six month effort was responsible for the development, test, conversion, and documentation of computer software for the mission analysis of missions to halo orbits about libration points in the earth-sun system. The software consisting of two programs called NOMNAL and ERRAN is part of the Space Trajectories Error Analysis Programs. The program NOMNAL targets a transfer trajectory from earth on a given launch date to a specified halo orbit on a required arrival date. Either impulsive or finite thrust insertion maneuvers into halo orbit are permitted by the program. The transfer trajectory is consistent with a realistic launch profile input by the user. The second program ERRAN conducts error analyses of the targeted transfer trajectory. Measurements including range, doppler, star-planet angles, and apparent planet diameter are processed in a Kalman-Schmidt filter to determine the trajectory knowledge uncertainty

    Increased H2_2CO production in the outer disk around HD 163296

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    Three formaldehyde lines were observed (H2_2CO 303_{03}--202_{02}, H2_2CO 322_{22}--221_{21}, and H2_2CO 321_{21}--220_{20}) in the protoplanetary disk around the Herbig Ae star HD 163296 with ALMA at 0.5 arcsecond (60 AU) spatial resolution. H2_2CO 303_{03}--202_{02} was readily detected via imaging, while the weaker H2_2CO 322_{22}--221_{21} and H2_2CO 321_{21}--220_{20} lines required matched filter analysis to detect. H2_2CO is present throughout most of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of the H2_2CO emission is likely caused by an optically thick dust continuum. The H2_2CO radial intensity profile shows a peak at 100 AU and a secondary bump at around 300 AU, suggesting increased production in the outer disk. Different parameterizations of the H2_2CO abundance were compared to the observed visibilities with χ2\chi^2 minimization, using either a characteristic temperature, a characteristic radius or a radial power law index to describe the H2_2CO chemistry. Similar models were applied to ALMA Science Verification data of C18^{18}O. In all modeling scenarios, fits to the H2_2CO data show an increased abundance in the outer disk. The overall best-fit H2_2CO model shows a factor of two enhancement beyond a radius of 270±\pm20 AU, with an inner abundance of 2 ⁣ ⁣5×10122\!-\!5 \times 10^{-12}. The H2_2CO emitting region has a lower limit on the kinetic temperature of T>20T > 20 K. The C18^{18}O modeling suggests an order of magnitude depletion in the outer disk and an abundance of 4 ⁣ ⁣12×1084\!-\!12 \times 10^{-8} in the inner disk. The increase in H2_2CO outer disk emission could be a result of hydrogenation of CO ices on dust grains that are then sublimated via thermal desorption or UV photodesorption, or more efficient gas-phase production beyond about 300 AU if CO is photodisocciated in this region

    NEW RECORDS FOR \u3ci\u3eACERIA ANTHOCOPTES\u3c/i\u3e (ACARI: ERIOPHYIDAE) OCCURRING ON CANADA THISTLE IN COLORADO, NEBRASKA, AND WYOMING, U.S.A.

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    Canada thistle [Cirsium arvense (L.) Scop.] growing in eastern Colorado, Wyoming and western Nebraska were surveyed for the presence and distribution of Aceria anthocoptes (Nal.). Of the 34 sites surveyed in 2004, mites were abundant at 42%, present in lesser numbers at 52%, and not present at 6% of the sites. In 2005, two new sites were added and ten sites sampled in 2004 were revisited. Of these 12 sites, mites were abundant at 17%, present to a lesser extent at 58%, and not present at 25% of the sites. The results demonstrate that Canada thistle growing in this region commonly harbor A. anthocoptes. How long A. anthocoptes has been present in this region is unknown, however, anecdotal evidence demonstrating a dramatic decline in the population of Canada thistle at one Colorado site from 2000 to 2007 suggests that the mite may have been present since 2002

    Synthetic Mudscapes: Human Interventions in Deltaic Land Building

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    In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are denied by traditional inhabitation. Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The social, economic, and ecological evolution of the region are defended by an expanded web of growing land

    Why witnesses of bullying tell: Individual and interpersonal factors

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    The reactions of those who witness bullying are important because they can stop the bullying and prevent further harm. Factors associated with telling behavior were investigated with 477 elementary school students who witnessed bullying. Approximately seventy percent of the students talked to someone about bullying incidents, most often, teachers. Chi-square and logistic regression analyses demonstrated that gender, frequency of witnessing, cognitive empathy, and social skills were found to be associated with telling behavior of witnesses, whereas affective empathy and school connectedness were not significantly related. Findings from this research are important for future practice and studies on bystander intervention

    Stars of extragalactic origin in the solar neighborhood

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    We computed the spatial velocities and the galactic orbital elements using Hipparcos data for 77 nearest main-sequence F-G-stars with published the iron, magnesium, and europium abundances determined from high dispersion spectra and with the ages estimated from theoretical isochrones. A comparison with the orbital elements of the globular clusters that are known was accreted by our Galaxy in the past reveals stars of extragalactic origin. We show that the relative elemental abundance ratios of r- and \alpha- elements in all the accreted stars differ sharply from those in the stars that are genetically associated with the Galaxy. According to current theoretical models, europium is produced mainly in low mass Type II supernovae (SNe II), while magnesium is synthesized in larger amounts in high mass SN II progenitors. Since all the old accreted stars of our sample exhibit a significant Eu overabundance relative to Mg, we conclude that the maximum masses of the SNII progenitors outside the Galaxy were much lower than those inside it are. On the other hand, only a small number of young accreted stars exhibit low negative ratios [Eu/Mg]<0[Eu/Mg] < 0. The delay of primordial star formation burst and the explosions of high mass SNe II in a relatively small part of extragalactic space can explain this situation. We provide evidence that the interstellar medium was weakly mixed at the early evolutionary stages of the Galaxy formed from a single proto-galactic cloud and that the maximum mass of the SN II progenitors increased in it with time simultaneously with the increase in mean metallicity.Comment: Accepted for 2004, Astronomy Letters, Vol. 30, No. 3, P.148-158 15 pages, 3 figure

    Spectroscopy of high proper motion stars in the ground--based UV

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    Based on high quality spectral data (spectral resolution R>60000) within the wavelength range of 3550-5000 AA we determined main parameters (effective temperature, surface gravity, microturbulent velocity, and chemical element abundances including heavy metals from Sr to Dy) for 14 metal-deficient G-K stars with large proper motions. The stars we studied have a wide range of metallicity: [Fe/H]=-0.3 \div -2.9. Abundances of Mg, Al, Sr and Ba were calculated with non-LTE line-formation effects accounted for. Abundances both of the radioactive element Th and r-process element Eu were determined using synthetic spectrum calculations. We selected stars that belong to different galactic populations according to the kinematical criterion and parameters determined by us. We found that the studied stars with large proper motions refer to different components of the Galaxy: thin, thick disks and halo. The chemical composition of the star BD+80 245 located far from the galactic plane agrees with its belonging to the accreted halo. For the giant HD115444 we obtained [Fe/H]=-2.91, underabundance of Mn, overabundance of heavy metals from Ba to Dy, and, especially high excess of the r-process element Europium: [Eu/Fe]=+1.26. Contrary to its chemical composition typical for halo stars, HD115444 belongs to the disc population according to its kinematic parameters.Comment: 16 pages, 4 figures, 5 tables, "UV Universe-2010 (2nd NUVA Symposium) conference

    Optical/IR from ground

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    Optical/infrared (O/IR) astronomy in the 1990's is reviewed. The following subject areas are included: research environment; science opportunities; technical development of the 1980's and opportunities for the 1990's; and ground-based O/IR astronomy outside the U.S. Recommendations are presented for: (1) large scale programs (Priority 1: a coordinated program for large O/IR telescopes); (2) medium scale programs (Priority 1: a coordinated program for high angular resolution; Priority 2: a new generation of 4-m class telescopes); (3) small scale programs (Priority 1: near-IR and optical all-sky surveys; Priority 2: a National Astrometric Facility); and (4) infrastructure issues (develop, purchase, and distribute optical CCDs and infrared arrays; a program to support large optics technology; a new generation of large filled aperture telescopes; a program to archive and disseminate astronomical databases; and a program for training new instrumentalists
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