Reusable Centaur study. Volume 1: Executive summary

A study of the Reusable Centaur for use as an initial upper stage with the space shuttle was conducted. The currently operative Centaur stage, with modifications for space shuttle orbiter compatibility and for improved performance, represents a cost effective development solution. The performance needs and available development funds are discussed. The main features of three Reusable Centaur configurations with increasing capability at increasing development costs are summarized

The impact of historical land use change from 1850 to 2000 on particulate matter and ozone

Anthropogenic land use change (LUC) since pre-industrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation. The general trend of expansion of managed ecosystems (croplands and pasturelands) at the expense of natural ecosystems has led to an 11 % decline in global mean biogenic volatile organic compound emissions. Concomitant growth in agricultural activity has more than doubled ammonia emissions and increased emissions of nitrogen oxides from soils by more than 50 %. Conversion to croplands has also led to a widespread increase in ozone dry deposition velocity. Together these changes in biosphere-atmosphere exchange have led to a 14 % global mean increase in biogenic secondary organic aerosol (BSOA) surface concentrations, a doubling of surface aerosol nitrate concentrations, and local changes in surface ozone of up to 8.5 ppb. We assess a global mean LUC-DRF of +0.017 Wm−2, −0.071 Wm−2, and −0.01 Wm−2 for BSOA, nitrate, and tropospheric ozone, respectively. We conclude that the DRF and the perturbations in surface air quality associated with LUC are substantial and should be considered alongside changes in anthropogenic emissions and climate feedbacks in chemistry-climate studies.https://www.atmos-chem-phys.net/16/14997/2016/acp-16-14997-2016.pdfhttps://www.atmos-chem-phys.net/16/14997/2016/acp-16-14997-2016.pdfPublished versio

Reusable Centaur study. Volume 2: Final report

For abstract, see N74-31346

Carpentered World Hypothesis vs. Piaget: Revisiting the Illusions of Segall, Campbell and Herskovits

Individual and group differences in susceptibility to various visual illusions have interested psychologists at least since Binet (1895). At present, there appear to be at least two more-or-less competing explanations of the ontogeny of illusion suscpetibility: Piaget\u27s (1969) Law of Relative Centrations and Segall, Campell and Herskovits\u27 91966) Carpentered World hypothesis. While these theories sometimes produce similar predications, they may also lead to contradictory ones

Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model

The heating of solar chromospheric inter-network regions by means of the absorption of electromagnetic (EM) waves that originate from the photospheric blackbody radiation is studied in the framework of a plasma slab model. The absorption is provided by the electron-neutral collisions in which electrons oscillate in the EM wave field and electron-neutral collisions damp the EM wave. Given the uncertain nature of the collision cross-section due to the plasma micro-turbulence, it is shown that for plausible physical parameters, the heating flux produced by the absorption of EM waves in the chromosphere is between $20 - 45$ % of the chromospheric radiative loss flux requirement. It is also established that there is an optimal value for the collision cross-section, $5 \times 10^{-18}$ m$^{2}$, that produces the maximal heating flux of 1990 W m$^{-2}$.Comment: Physics of Plasmas, in press, April 2011 issue (final printed version, typos in proofs corrected