Interrelationships between interstellar and interplanetary grains

The relationship between solar system dust (SSD) and interstellar dust particles (ISMD) is being reconsidered because of the discovery of isotopic anomalies in meteorites. Meteoritic, circumstellar/meteoritic, interstellar/meteoritic, planetary, and cometary data are reviewed

Preliminary studies of the time-dependent shear and uniaxial tensile behaviour of oriented polymers

Summary The work reported in this memo is the initial stages of an investigation of the time-dependent behaviour of certain anisotropic polymers. In the first instance low density polyethylene with a transversely isotropic symmetry is being examined. Different degrees of anisotropy have been induced by cold drawing and the time dependent material parameters necessary to describe the stiffness of the anisotropic polyethylene have been determined. This involved the measurement of uniaxial tensile creep: lateral contraction creep, and torsional creep under conditions of constant load at 20°C ± 0.5°C. The tensile creep and contraction creep apparatus has been described elsewhere (Darlington (a) 1968) and only the principle of the apparatus is discussed here. The torsional creep apparatus is described in detail. Analysis of the experimental data is not yet complete. The data is tabulated in section 5 and a preliminary analysis is presented in section G. Details of proposed future work are discussed in section 7

Interstellar Al-26 and excess Mg-26

Evidence of a possible supernova explosion that occured very near the Earth is presented by the presence of radioactive 26 Aluminum (26 Al). The time of the supernova explosion is placed at approximately 100,000 years ago and is partially supported by cosmic gamma ray measurements from both HEAO 3 and the Solar Maximum Mission

Isospin Effects on Astrophysical S-Factors

We estimate the ratios of bare astrophysical S-factors at zero incident energy for proton and deuteron induced reactions in a model which assumes a compound nucleus formation probability plus a statistical decay. The obtained ratios agree well with available experimental values, as far as the reactions which have dominant s-wave entrance channel components are investigated. Due to its simplicity the model could be used as a guidance for predictions on reactions which have not been investigated yet.Comment: 12 pages, 1 figure

Field operations with cesium clocks in HF navigation systems

Networks of HF phase comparison marine navigation stations employing cesium clocks are discussed. The largest permanent network is in the Gulf of Mexico where some fourteen base stations are continuously active and others are activated as needed. These HF phase comparison systems, which operate on a single transmission path, require a clock on the mobile unit as well. Inventory consists of upwards of 70 clocks from two different manufacturers. The maintenance of this network as an operating system requires a coordinated effort involving clock preparation, clock environment control, station performance monitoring and field service

Final report of the Support to Regional Aquatic Resources Management (STREAM): a NACA networking initiative

The governing council of Naca has resolved to effect a shift in emphasis from aquaculture development to aquaculture for development. This will require engaging partners from a broad spectrum of government and development agencies, the nature of the information that will need to be gathered and the strategies used for disseminating information and initiating action. The vehicle for operationalising this shift is STREAM - Support to Regional Aquatic Resources Management. This report outlines the nature of the STREAM network, its relationship to NACA's vision, mission, objectives and operating principles, and how STREAM differs from previous NACA's networks. Because STREAM is different, a theoretical basis for network communication is presented along with an outline of the preliminary steps in getting the network up and running. (Pdf contains 33 pages)

Supernova Reverse Shocks and SiC Growth

We present new mechanisms by which the isotopic compositions of X-type grains of presolar SiC are altered by reverse shocks in Type II supernovae. We address three epochs of reverse shocks: pressure wave from the H envelope near t = 10$^6$s; reverse shock from the presupernova wind near 10$^8-10^9$s; reverse shock from the ISM near 10$^{10}$s. Using 1-D hydrodynamics we show that the first creates a dense shell of Si and C atoms near 10$^6$s in which the SiC surely condenses. The second reverse shock causes precondensed grains to move rapidly forward through decelerated gas of different isotopic composition, during which implantation, sputtering and further condensation occur simultaneously. The third reverse shock causes only further ion implantation and sputtering, which may affect trace element isotopic compositions. Using a 25M$_{\odot}$ supernova model we propose solutions to the following unsolved questions: where does SiC condense?; why does SiC condense in preference to graphite?; why is condensed SiC $^{28}$Si-rich?; why is O richness no obstacle to SiC condensation?; how many atoms of each isotope are impacted by a grain that condenses at time t$_0$ at radial coordinate r$_0$? These many considerations are put forward as a road map for interpreting SiC X grains found in meteorites and their meaning for supernova physics.Comment: 28 pages, 14 figures, animation for Figure 3 and machine-readable Table 3 can be found at http://antares.steelangel.com/~edeneau/supernova/DHC_2003, Submitted to Ap