International Space Station as an Observation Platform for Hypersonic Re-Entry of its Visiting Vehicles

The International Space Station (ISS) will receive an armada of visiting supply vehicles during its life in orbit. Over 500 tons of material will be destroyed in targeted re-entries of these vehicles. Because all such re-entries lie in the same orbital plane of the station, and because the visiting vehicles typically deorbit within a few hours of departure, the ISS will usually be within sight of the re-entry process, at a range of only 300-600 kilometers. This vantage point offers an unprecedented opportunity for systematically measuring hypersonic destructive processes. This paper examines the integrated operational constraints of the ISS, its supply vehicles, and candidate sensors which can be employed in the scientific observation of the re-entry process. It is asserted the ISS program has the potential to reduce the worldwide risks from future deorbiting spacecraft, through systematic experimental characterization of the factors which affect the rupture, debris survival, and footprint size of its visiting vehicle fleet

Systematics of Nama (Hydrophyllaceae): Seed Coat Morphology of Lemmonia californica ajd Nama Species allies with Nama demissum

Seed coat morphology of Lemmonia californica. long held to be a relative of Nama, was examined using scanning electron microscopy. Its seed coat exhibits reticulum cells with undulate cell walls and columnar radial wall thickenings. Seed coat structure in nine species of Nama, N. demissum, N. aretioides, N. densum, N. parviflorumm, N. pusillum, N. depressum, N. dichotomum, N. sericeum and N. origanifolium, members forming one of six seed groups in Nama, also exhibit reticulum cells with undulate walls and columnar wall thickenings. The Nama species and Lemmonia are remarkably similar in testa organization, suggesting that the relationship of the two may well be closer than the generic status accorded Lemmonia would indicate

Molecular characterization of a cytotoxic porin protein from Campylobacter jejuni and its role in campylobacteriosis

Campylobacter jejuni is a major cause of enteritis in developed and developing countries. A cytotoxic complex was isolated from organism-free filtrates of broth grown organisms by screening for activity in HEp-2 cells following high performance liquid chromatography using a combination of size exclusion and DEAE column chromatography. The toxin was found to coincide with a 45 kDa protein possessing an N-terminus sequence indicative of a bacterial outer membrane porin protein together with a high molecular weight carbohydrate which was determined to be lipopolysaccharide (LPS). The carbohydrate portion of the LPS had reactivity for the lectins Galanthus nivalis agglutinin, Maakia amurensis agglutinin and Datura stromonium agglutinin. The cytotoxicity of the porin-LPS complex was heat-labile at 70\sp\circC within 30 min. It was also found to be resistant to trypsin and to degradation by the enzymes neuriminidase and glycosidase F as well as to oxidation with sodium meta-periodate. The complex induced DNA fragmentation, cytoplasmic blebbing and nuclear condensation in HEp-2 cells after 24 h of intoxication possibly indicating that the cells were becoming apoptotic. Oligonucleotides were generated from the N-terminus of the porin protein. Using a combination of vectorette and inverse polymerase chain reaction (PCR) and cloning, a 1.45 kb fragment was sequenced and found to contain a 1275 base pair (bp) open reading frame (ORF). The ORF, designated porA encoded a 424 amino acid protein with a 22 residue leader sequence and had a calculated molecular weight of 45.6 kDa and pI of 4.44. The mature protein was 402 amino acids in length and had a molecular weight of 43.5 kDa and a pI of 4.35. The translated PorA protein had a 50% sequence homology with Haemophilis influenzae major outer membrane protein P2. Thirty-two strains of Campylobacter sp. and closely related organisms were screened for the porA gene and expression of cytotoxin in cell culture. Although all strains examined produced a cytotoxin, 21 of the 32 strains (66%) were genotypically positive for porA and of these 21 of 23 (91%) were C. jejuni strains. It is postulated that this cytotoxic protein is a major virulence factor for C. jejuni and may be responsible for the clinical symptoms usually associated with campylobacteriosis

Minimum dV for Targeted Spacecraft Disposal

The density scale height of the Earth's atmosphere undergoes significant reduction in the final phases of a natural decay. It can be shown that for most realistic ballistic numbers, it is possible to exploit this effect to amplify available spacecraft dV by using it at the penultimate perigee to penetrate into higher drag regions at final apogee. The drag at this lower pass can more effectively propel a spacecraft towards the final target region than applying the same dV direct Hohmann transfer at that final apogee. This study analyzes the potential use of this effect-- in combination with small phasing burns--to calculate the absolute minimum delta-V that would be required to reliably guide a spacecraft to any specified safe unoccupied ocean region as a function of ballistic number, orbit inclination, and initial eccentricity. This calculation is made for controllable spacecraft in several orbit inclinations and eccentricities with arbitrary initial LAN and ArgP one week before final entry, under three-sigma atmospheric perturbations. The study analyzes the dV required under varying levels of final controllable altitude at which dV may be imparted, and various definitions of the length and location of a "safe" disposal area. The goal of such research is to improve public safety by creating assured safe disposal strategies for low-dV and/or low-thrust spacecraft that under more traditional strategies would need to be abandoned to a fully random decay

Systematics of Nama (Hydrophyllaceae)

Lemmonia has been maintained as a monotypic genus, despite the fact that it is morphologically very similar to several species of Nama. The major basis for this separation resides in the reportedly coalescent filament bases of Lemmonia as contrasted with the distinct filaments of Nama. Examination of corollas of Lemmonia with the scanning electron microscope has revealed that the filaments of the taxon are distinct. There is, then, no qualitative basis upon which to found Lemmonia, and the taxon is transferred to Nama

Introductory Address: Delivered November 3d, 1858, to the Medical Class of Harvard University, and Communicated to the Boston Medical and Surgical Journal

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