Performance of an ablator for Space Shuttle inorbit repair in an arc-plasma airstream

An ablator patch material performed well in an arc plasma environment simulating nominal Earth entry conditions for the Space Shuttle. Ablation tests using vacuum molded cones provided data to optimize the formulation of a two part polymer system for application under space conditions. The blunt cones were made using a Teflon mold and a state of the art caulking gun. Char stability of formulations with various amounts of catalyst and diluent were investigated. The char was found to be unstable in formulations with low amounts of catalyst and high amounts of diluent. The best polymer system determined by these tests was evaluated using a half tile patch in a multiple High Temperature Reusable surface Insulation tile model. It was demonstrated that this ablator could be applied in a space environment using a state of the art caulking gun, would maintain the outer mold line of the thermal protection system during entry, and would keep the bond line temperature at the aluminum tile interface below the design limit

Phenolics, depsides and triterpenes from the chilean lichen pseudocyphellaria nudata (zahlbr.) D.J. Galloway

Indexación: ScieloThe lichen Pseudocyphellaria nudata is a species endemic to southern South América. From the lichen tallus, methyl orsellinate, 2-methoxy-3,6-dimethyl-4-hydroxybenzaldehyde, methyl-evernate, tenuiorin, hopan-6ß,22-diol and hopan-6α,76,22-triol were isolated and identified as the main lichen constituents. This is the first report of the occurrence of 2-methoxy-3,6-dimethyl-4-hydroxybenzaldehyde in lichens.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=s0717-97072008000300017&nrm=is

The Organization of Agricultural Production in the Emergence of Chiefdoms in the Quijos Region, Eastern Andes of Ecuador

This dissertation examines the emergence of the ethnohistorically documented Quijos chiefdoms, in the eastern Ecuadorian Andes. It evaluates different alternatives that link the rise of centralized leadership with the organization of agricultural production. To this end I reconstructed the demographic history of a 137 km² region through a full coverage systematic survey, and the patterns of food production and consumption through the analysis of pollen, phytoliths and macroremains from the excavation of 31 tests at locations representing different environmental setting and settlement types. Based on a ceramic chronology established for this project (through the analysis of ceramic materials from 15 test pits and associated carbon dates) I propose a sequence starting at about 600 B.C., with the first manifestations of a regional system of centralized authority appearing after about 500 A.D. The most distinctive expression of this is what appear to be central places in each one of the three subregions encompassed by the survey. The analysis of botanical remains at these locations, and at others representing smaller and peripheral settlements did not show, however, signs of economic differentiation in terms of production or consumption patterns. Thus neither the varying local environmental conditions nor social status, alone or combined, produced distinctive agrarian practices or foodways. Along the same lines, the central places do not seem to have emerged as a strategic move towards controlling agricultural resources, and evidence of staple mobilization or trade networks involving the circulation of local or foreign durable prestige goods is null. Additionally, an analysis of a sample of obsidian artifacts collected through survey and excavations suggests that closeness to source, rather than status, determined the abundance of obsidian materials, while manufacture technology seems to have been standard across settlement types. I propose that frameworks that emphasize the control of economic resources or the importance of specialization of production in the development of complex societies are not useful for characterizing the social and political dynamics of the emerging Quijos chiefdoms, and that current understandings of this region as a hub of exchange activity can be readdressed in light of these findings

Biopesticide activity from drimanic compounds to control tomato pathogens

Indexación: Scopus.Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 μg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 μg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens. © 2018 by the authors.https://www.mdpi.com/1420-3049/23/8/205

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