The Composition of the Solar Wind in Polar Coronal Holes

The solar wind charge state and elemental compositions have been measured with the Solar Wind Ion Composition Spectrometers (SWICS) on Ulysses and ACE for a combined period of about 25 years. This most extensive data set includes all varieties of solar wind flows and extends over more than one solar cycle. With SWICS the abundances of all charge states of He, C, N, O, Ne, Mg, Si, S, Ar and Fe can be reliably determined (when averaged over sufficiently long time periods) under any solar wind flow conditions. Here we report on results of our detailed analysis of the elemental composition and ionization states of the most unbiased solar wind from the polar coronal holes during solar minimum in 1994–1996, which includes new values for the abundance S, Ca and Ar and a more accurate determination of the ²⁰Ne abundance. We find that in the solar minimum polar coronal hole solar wind the average freezing-in temperature is ∼1.1×10⁶ K, increasing slightly with the mass of the ion. Using an extrapolation method we derive photospheric abundances from solar wind composition measurements. We suggest that our solar-wind-derived values should be used for the photospheric ratios of Ne/Fe=1.26±0.28 and Ar/Fe=0.030±0.007.     

Isotopic Composition of H,HE and NE in the Protosolar Cloud

Observations and measurements in the solar wind, the Jovian atmosphere and the gases trapped in lunar surface material provide the main evidence from which the isotopic composition of H, He and Ne in the Protosolar Cloud (PSC) is derived. These measurements and observations are reviewed and the corrections are discussed that are needed for obtaining from them the PSC isotopic ratios. The D/H, ³He/⁴He (D+³He)/H, ²⁰Ne/²²Ne and ²¹Ne/²²Ne ratios adopted for the PSC are presented. Protosolar abundances provide the basis for the interpretation of isotopic ratios measured in the various solar system objects. In this article we discuss constraints derived from the PSC abundances on solar mixing, the origin of atmospheric neon, and the nature of the “SEP” component of neon trapped at the lunar surface. We also discuss constraints on the galactic evolution provided by the isotopic abundances of H and He in the PSC. This revised version was published online in August 2006 with corrections to the Cover Date.     

Automatic Inspection and Diagnostic System for Army Tactical Vehicles

A tactical system designed to inspect and diagnose malfunctions in all army tactical vehicles including jeeps, trucks, and tanks is known as Ready Multipurpose Automatic Inspection and Diagnostic System (READYMAIDS). The laboratory model developed to prove the feasibility of design is discussed together with design problems such as instrumenting a vehicle without modifications. The system uses a small digital computer in addition to switching, measurement, and loading devices. These devices are integrated into a small transportable unit. Results to date, problem areas, and possible solutions are described.     

G2-chromosome aberrations induced by high-LET radiations.

We report measurement of initial G2-chromatid breaks in normal human fibroblasts exposed to various types of high-LET particles. Exponentially growing AG 1522 cells were exposed to gamma rays or heavy ions. Chromosomes were prematurely condensed by calyculin A. Chromatid-type breaks and isochromatid-type breaks were scored separately. The dose response curves for the induction of total chromatid breaks (chromatid-type + isochromatid-type) and chromatid-type breaks were linear for each type of radiation. However, dose response curves for the induction of isochromatid-type breaks were linear for high-LET radiations and linear-quadratic for gamma rays. Relative biological effectiveness (RBE), calculated from total breaks, showed a LET dependent tendency with a peak at 55 keV/micrometer silicon (2.7) or 80 keV/micrometer carbon (2.7) and then decreased with LET (1.5 at 440 keV/micrometer). RBE for chromatid-type break peaked at 55 keV/micrometer (2.4) then decreased rapidly with LET. The RBE of 440 keV/micrometer iron particles was 0.7. The RBE calculated from induction of isochromatid-type breaks was much higher for high-LET radiations. It is concluded that the increased production of isochromatid-type breaks, induced by the densely ionizing track structure, is a signature of high-LET radiation exposure.     

Reflections on the quest for international cooperation

Changed political objectives, straitened economic circumstances and an altered balance of capability and expertise in space endeavours have together produced more discussion of the need for international cooperation than ever before, but the meaning of the term has subtly shifted. Insisting on US ‘leadership’ is self-defeating; what is instead firmly desired by the USA's potential partners is a balanced relationship in which each nation makes an identifiable contribution and takes the lead in at least one of a package of projects. If this is going to happen, there must be an international forum or framework in which projects can be discussed and agreed. This in turn requires initiative at governmental level.     

Cytogenetic effects of energetic ions with shielding

In order to understand the effects of shielding on the induction of biological damages by charged particles, we conducted experiments with accelerated protons (250 MeV) and iron particles (1 GeV/u). Human lymphocytes in vitro were exposed to particle beams through polyethylene with various thickness, and chromosomal aberrations were determined using FISH technique. Dose response curves for chromosome aberrations were obtained and compared for various particle types. Experimental results indicated that for a given absorbed dose at the cell, the effectiveness of protons and iron particles in the induction of chromosomal aberrations was not significantly altered by polyethylene with thickness up to 30-cm and 15-cm respectively. Comparing with gamma rays, charged particles were very effective in producing complex chromosomal damages, which may be an important mechanism in alterating functions in nondividing tissues, such as nervous systems.     

Microsatellite instability in human mammary epithelial cells transformed by heavy ions

We analyzed DNA and proteins obtained from normal and transformed human mammary epithelial cells for studying the neoplastic transformation by high-LET irradiation in vitro. We also examined microsatellite instability in human mammary cells transformed to various stages of carcinogenesis, such as normal, growth variant and tumorigenic, using microsatellite marker D5S177 on the chromosome 5 and CY17 on the Chromosome 10. Microsatellite instabilities were detected in the tumorigenic stage. These results suggest that microsatellite instability may play a role in the progression of tumorigenecity. The cause of the genomic instability has been suggested as abnormalities of DNA-repair systems which may be due to one of the three reasons: 1) alterations of cell cycle regulating genes. 2) mutations in any of the DNA mismatch repair genes. 3) mutation in any of the DNA strand breaks repair genes. No abnormality of these genes and encoded proteins, however was found in the present studies. These studies thus suggest that the microsatellite instability is induced by an alternative mechanism.     

Moon first versus flexible path exploration strategies: Considering international contributions

This paper analyses potential future collaborative space exploration architectures in terms of 1) the technical capabilities of contributing partners; and 2) the constraints imposed by internal and international politics. We find that when international partners are considered endogenously, the argument for a “flexible path” approach is weakened substantially. This is because international contributions can make “Moon first” economically feasible; and characteristics of proposed “flexible path” approaches may preclude international involvement because of the disproportionate risk that those contributions inherently bear. This could have serious implications for future collaborations. We also note that while there are multiple feasible collaborative architectures, there is currently substantial overlap among the potential niche contributions identified by the international partners.     

The Origin of Primary Cosmic Rays: Constraints from ACE Elemental and Isotopic Composition Observations

Cosmic-ray isotope observations from NASAs Advanced Composition Explorer (ACE) mission have been used to investigate the composition of cosmic-ray source material. Source abundances relative to ⁵⁶Fe are reported for eleven isotopes of Ca, Fe, Co, and Ni, including the very rare isotopes ⁴⁸Ca and ⁶⁴Ni. Although the source abundances range over a factor 10⁴, most of the ratios to ⁵⁶Fe are consistent with solar-system values to within 20%. However, there are some notable differences, the most significant being an excess of (70±30)% relative to the solar system for the cosmic-ray source ratio ⁵⁸Fe/⁵⁶Fe. The possible association of such an excess with a contribution to the cosmic-ray source from Wolf–Rayet star ejecta is discussed.