1,627 research outputs found
The continuing materials analysis of the thermal control surfaces experiment (S0069)
The long term effects of the natural and induced space environment on spacecraft surfaces are critically important to future spacecraft - including Space Station Freedom. The damaging constituents of this environment include thermal vacuum, solar ultraviolet radiation, atomic oxygen, particulate radiation, and the spacecraft induced environment. The behavior of materials and coatings in the space environment continues to be a limiting technology for spacecraft and experiments. The Thermal Control Surfaces Experiment (TCSE) was flown on the National Aeronautics and Space Administration (NASA) Long Duration Exposure Facility (LDEF) to study these environmental effects on surfaces-particularly on thermal control surfaces. The TCSE was a comprehensive experiment that combined in-space measurements with extensive pre- and post-flight analyses of thermal control surfaces to determine the effects of exposure to the low Earth orbit space environment. The TCSE is the first space experiment to directly measure the total hemispherical reflectance of thermal control surfaces in the same way they are routinely measured in the laboratory. The trend analyses of selected coatings performed as part of the continuing post-flight analysis of the TCSE are described. A brief description of the TCSE and its mission on LDEF are presented. There are several publications available that describe the TCSE, it's mission on LDEF, and initial results in greater detail. These are listed in the TCSE Bibliography
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Controlling sapstain : trial of strong stain-preventive solutions on selected western softwoods in storage prolonged for 12 months
Environmental restrictions have induced many sawmills to seek alternatives to pentachiorophenol (penta) and similar chlorinated phenols for controlling mold and fungal stains on green lumber during storage and shipment. For that purpose, ten alternative stain preventives were evaluated against a traditional penta product (Permatox 101) on studs of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], hem-fir [Tsuga heterophylla (Raf.) Sarg.; Abies sp.], and sugar pine [Pinus lambertiana (Dougl.)] in field trials over a 12-month period. Strong solutions of most preventives provided good to excellent protection for 2 months. Efficacy decreased substantially after the studs were stored 6 months through warm weather. Hem-fir, and to a lesser degree, Douglas-fir, were adequately protected for 12 months only by Permatox 101. None of the treatments protected sugar pine for 1 year
Homogeneous Nucleation Rate Measurements for Water Over a Wide Range of Temperature and Nucleation Rate
An expansion cloud chamber was used to measure the homogeneous nucleation rate for water over a wide range of temperature from 230-290 K and nucleation rates of 1-106 drops cm-3 s-1. The comprehensive and extensive nature of this data allows a much more detailed comparison between theory and experiment than has previously been possible. The expansion chamber technique employs continuous pressure measurement and an adiabatic pulse of supersaturation to give the time history of supersaturation and temperature during the nucleation. The resulting drop concentration is determined using photographic techniques. The experimental observations are presented in tabular form and from them an empirical nucleation rate formula is determined: J=S2 exp[328.124-5.582 43T+0.030 365T2-5. 0319E-5T3-(999.814-4.100 87T+3.010 84E-3 T2)ln -2S], where J is the nucleation rate in units of drops cm -1 s-1 is the supersaturation ratio and T is the temperature in K
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Controlling hardwood sapstain : trials of stain-preventive products on red alder lumber
Production of hardwood lumber (mostly red alder) has been a small but growing part of the forest products industry in the Pacific Northwest. In laboratory tests, Rodewod® 200 EC plus borax protected alder at nearly all levels tested. Eight other chemicals provided some protection at the highest level tested. Fungal-stain preventive treatments were evaluated on red alder lumber in both an accelerated 6-week test on small specimens In the laboratory and on bundled boards (1 inch x 4 inches x 8 feet) exposed outdoors for 2 or 6 months. Strong solutions of RODEWOD® 300. PQ-8 plus borax, and Permatox 101 protected freshly sawed red alder lumber that was solid-piled and stored for 2 months during which summer temperatures peaked. None of the treatments provided good protection through 6 months of storage that included summer weather
Fluorescence of thermal control coatings on S0069 and A0114
Many of the thermal control surfaces exposed to the space environment during the 5.8 year LDEF mission experienced changes in fluorescence. All of the thermal control coatings flown on LDEF experiments S0069 and A0114 were characterized for fluorescence under ambient conditions. Some of the black coatings, having protective overcoats, appear bright yellow under ultraviolet exposure. Urethane based coatings exhibited emission spectra shifts toward longer wavelengths in the visible range. Zinc oxide pigment based coatings experienced a quenching of fluorescence, while zinc orthotitanate pigment based and other ceramic type coatings had no measurable fluorescence
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Controlling sapstain : trials of product group I on selected western softwoods
Environmental restrictions have induced many sawmills to seek alternatives to pentachlorophenol (penta) or similar chlorinated phenols to control fungal sapstains on green lumber. Five alternative preventives were evaluated against a traditional penta product (Permatox 101) on Douglas-fir, hem-fir, and pine lumber in an accelerated 6-week test on small specimens in the laboratory and in field trials on bundled studs (2 inch x 4 inch x 8 ft) exposed outdoors for 2 and 6 months. Strong solutions of most alternative preventives provided good protection of Douglas-fir and hem-fir studs for at least 2 months during warming spring weather; some also protected pine studs. Permatox 101 provided superior protection during prolonged outdoor storage, but may permit surface growth of brown mold
A TRADE LIBERALIZATION IN INTERNATIONAL DAIRY MARKETS
International dairy industries remain among the most distorted agricultural sectors. Dairy average bound tariffs remain among the highest of all agricultural commodities, and dairy trade is characterized by a large number of megatariffs and tariff-rate quotas (TRQs). The objective of our study is to examine how the international dairy markets might respond to policy changes under various assumptions, using a partial equilibrium, multiple-commodity, multiple-region model of agricultural policy and trade. Our results indicate that liberalization will reduce supplies, increase dairy trade, and raise world prices.Dairy Markets, Trade Liberalization, Model, Policy, International Relations/Trade,
Transient in utero knockout (TIUKO) of C-MYC affects late lung and intestinal development in the mouse
BACKGROUND: Developmentally important genes often result in early lethality in knockout animals. Thus, the direct role of genes in late gestation organogenesis cannot be assessed directly. In utero delivery of transgenes was shown previously to result in high efficiency transfer to pulmonary and intestinal epithelial stem cells. Thus, this technology can be used to evaluate late gestation development. RESULTS: In utero gene transfer was used to transfer adenovirus with either an antisense c-myc or a C-MYC ubiquitin targeting protein to knockout out c-myc expression in late gestation lung and intestines. Using either antisense or ubiquitin mediated knockout of C-MYC levels in late gestation resulted in similar effects. Decreased complexity was observed in both intestines and lungs. Stunted growth of villi was evident in the intestines. In the lung, hypoplastic lungs with disrupted aveolarization were observed. CONCLUSIONS: These data demonstrated that C-MYC was required for cell expansion and complexity in late gestation lung and intestinal development. In addition they demonstrate that transient in utero knockout of proteins may be used to determine the role of developmentally important genes in the lungs and intestines
Whisker/Cone growth on the thermal control surfaces experiment no. S0069
An unusual surface 'growth' was found during scanning electron microscope (SEM) investigations of the Thermal Control Surface Experiment (TCSE) S0069 front thermal cover. This 'growth' is similar to the cone type whisker growth phenomena as studied by G. K. Wehner beginning in the 1960's. Extensive analysis has identified the most probable composition of the whiskers to be a silicate type glass. Sources of the growth material are outgassing products from the experiment and orbital atomic oxygen, which occurs naturally at the orbital altitudes of the LDEF mission in the form of neutral atomic oxygen. The highly ordered symmetry and directionality of the whiskers are attributed to the long term (5.8 year) stable flight orientation of the LDEF
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