Study of low acceleration space transportation systems. Volume I - Summary Phase II STUDY report

Technical feasibility of electric-nuclear propulsion system for manned Mars missio

Triton: A hot potato

The effect of sunlight on the surface of Triton was studied. Widely disparate models of the active geysers observed during Voyager 2 flyby were proposed, with a solar energy source almost their only feature. Yet Triton derives more of its heat from internal sources (energy released by the radioactive decay) than any other icy satellite. The effect of this relatively large internal heat on the observable behavior of volatiles on Triton's surface is investigated. The following subject areas are covered: the Global Energy Budget; insulation polar caps; effect on frost stability; mantle convection; and cryovolcanism

The role of nonuniform internal heating in Triton's energy budget

Triton's large heliocentric distance and high albedo, combined with its unusually large silicate mass fraction, make internal heating more important in its energy budget than in that of any other icy satellite. Brown et al. have recently estimated that the average radiogenic heat flux (which is probably between 3.3 and 6.6 mW/sq m depending on core size and composition) may equal 5 to 20 pct. of the average absorbed insolation. On a global scale, this additional energy input appreciably increases the thermal emissivity required to be consistent with the observed surface temperature. Brown et al. also speculated that spatial variations of the internal flux may change the local sublimation deposition balance enough to lead to observable modifications of the distribution of volatiles on Triton's surface. An attempt is made to estimate the magnitude of internal heat flux variations due to the insulating effect of the polar caps, to mantle convection, and to cryovolcanism; the importance is evaluated of these variations in modifying the volatile distribution

Detection And Mapping (DAM) package. Volume 2a: Software user manual (part 1)

For abstract, see N77-18516

Single molecule photon counting statistics for quantum mechanical chromophore dynamics

We extend the generating function technique for calculation of single molecule photon emission statistics [Y. Zheng and F. L. H. Brown, Phys. Rev. Lett., 90,238305 (2003)] to systems governed by multi-level quantum dynamics. This opens up the possibility to study phenomena that are outside the realm of purely stochastic and mixed quantum-stochastic models. In particular, the present methodology allows for calculation of photon statistics that are spectrally resolved and subject to quantum coherence. Several model calculations illustrate the generality of the technique and highlight quantitative and qualitative differences between quantum mechanical models and related stochastic approximations. Calculations suggest that studying photon statistics as a function of photon frequency has the potential to reveal more about system dynamics than the usual broadband detection schemes.Comment: Submitted to the Journal of Physical Chemistr

Control of laminar-instability waves using a new technique

A new technique using surface-film activators has been developed to induce and control laminar-instability waves by periodic heating. A flat plate was instrumented and installed in the GALCIT High-speed Water Tunnel with flush-mounted surface heaters and probes. Extremely two-dimensional naturally occurring Tolmien-Schlichting (TS) waves were observed along with the subsequent formation of turbulent spots. Laminar-instability waves were then excited in a controlled fashion using the surface-mounted heaters. A preliminary experiment on cancellation of excited laminar-instability waves was carried out. Finally, turbulent spots were produced using amplitude-modulated bursts to form Gaussian TS wave packets. Flow visualization, along with wall shear measurements, was used to infer the velocity and vorticity field near the wall

Social Entrepreneurship and Social Transformation

This study provides a comparative analysis of seven cases of social entrepreneurship that have been widely recognized as successful. The paper suggests factors associated with successful social entrepreneurship, particularly with social entrepreneurship that leads to significant changes in the social, political and economic contexts for poor and marginalized groups. It generates hypotheses about core innovations, leadership, organization, and scaling up in successful social entrepreneurship. The paper concludes with a discussion of the implications for the practice of social entrepreneurship, for further research, and for the continued development of support technologies and institutions that will encourage future social entrepreneurship.This publication is Hauser Center Working Paper No. 15. The Hauser Center Working Paper Series was launched during the summer of 2000. The Series enables the Hauser Center to share with a broad audience important works-in-progress written by Hauser Center scholars and researchers

Food Preservation by Freezing

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Reactions of Na/plus/, K/plus/, and Ba/plus/ ions with O2, NO, and H2O molecules

Investigating ion molecule reactions of sodium, potassium, and barium ions with oxygen, nitric oxide, and water in drift tube mass spectromete

Effects of prolonged acceleration with or without clinostat rotation on seedlings of Arabidopsis thaliana (L.) Heynh

Three 21-day tests of the effects of chronic centrifugation were carried out on populations of Arabidopsis thaliana. In addition to 1 g the resultant g-forces tested were: 2,4,6,8,16, and 20 g. Observed end points included gross morphological characters such as size of plant organs and, at the other extreme, features of sub-cellular structure and ultrastructure. Plants were grown on banks of clinostats. The acceleration vector was directed either parallel with the plants' axes or transverse to the axes. Plant responses to chronic axial acceleration and to transverse acceleration with clinostated plants were determined. From the data obtained it was possible in some cases: (1) to determine the g-functions of specific plant developmental characters; (2) to extrapolate those functions to the hypothetical value at zero g in order to predict (tentatively) the morphology of a plant grown in space, (3) to describe morphological effects of clinostat rotation, (4) to determine which of those effects was influenced by the prevailing g-force, and (5) to put to direct test the assumption that clinostat rotation nullifies or compensates for the influence of gravity