Development of polyisocyanurate pour foam formulation for space shuttle external tank thermal protection system

Four commercially available polyisocyanurate polyurethane spray-foam insulation formulations are used to coat the external tank of the space shuttle. There are several problems associated with these formulations. For example, some do not perform well as pourable closeout/repair systems. Some do not perform well at cryogenic temperatures (poor adhesion to aluminum at liquid nitrogen temperatures). Their thermal stability at elevated temperatures is not adequate. A major defect in all the systems is the lack of detailed chemical information. The formulations are simply supplied to NASA and Martin Marietta, the primary contractor, as components; Part A (isocyanate) and Part B (poly(s) and additives). Because of the lack of chemical information the performance behavior data for the current system, NASA sought the development of a non-proprietary room temperature curable foam insulation. Requirements for the developed system were that it should exhibit equal or better thermal stability both at elevated and cryogenic temperatures with better adhesion to aluminum as compared to the current system. Several formulations were developed that met these requirements, i.e., thermal stability, good pourability, and good bonding to aluminum

The economic viability of biomass crops versus conventional agricultural systems and its potential impact on farm incomes in Ireland

Ireland is currently importing 90 percent of its energy. The burning of domestically produced nonrenewable peat provides 4.9 percent of Ireland’s total primary energy supply while renewable biomass crops currently account for only 1 percent of the domestically produced energy supply. The Irish government have set a target of 30% of peat (approximately 0.9 million tonnes) used for electricity generation to be replaced by renewable energy crops. This would be equivalent to approximately 0.6 million tonnes of biomass crops or approximately 45,000 hectares of biomass. Direct payments and subsidies accounted for over 100 percent of average family farm income on beef and sheep farms in 2006. Therefore there appears to be significant potential for Irish farmers to replace conventional agricultural enterprises with biomass crops. A probit model was built to identify the socio-economic characteristics of farmers who may be willing to adopt energy crop production. The results from this were used in the construction of a linear programming model to determine the optimal enterprise for each farmer at varying energy prices.Willow, Miscanthus, Co-firing, Net present value, Probit, Linear programming, Agricultural Finance, Institutional and Behavioral Economics, Resource /Energy Economics and Policy,

Valuing the risk associated with willow and miscanthus relative to conventional agricultural systems

The agronomic characteristics of willow and miscanthus make these crops highly susceptible to risk. This is particularly true in a country such as Ireland which has limited experience in the production of these crops. Issues such as soil and climate suitability have as yet to be resolved. The lengthy production lifespan of energy crops only serve to heighten the level of risk that affects key variables. The uncertainty surrounding the risk variables involved in producing willow and miscanthus, such as the annual yield level and the energy price, make it difficult to accurately calculate the returns of such a project. The returns from willow and miscanthus are compared with those of conventional agricultural enterprises using Stochastic Efficiency with Respect to a Function (SERF). A risk premium is calculated which farmers would need to be compensated with in order for them to be indifferent between their current enterprise and switching to biomass crop production. With the exception of spring barley, a risk premium is required if farmers are to be indifferent between their current enterprise and willow or miscanthus. The value of the risk premium required to entice farmers to switch to miscanthus production is significantly less than that required for willow. This suggests that a greater level of risk is associated with willow than with miscanthus.Biomass, SERF, Risk Premium, Resource /Energy Economics and Policy, Risk and Uncertainty,

The effect of non-prescription ocular decongestants on intraocular pressure, anterior angle and pupil diameter

This study compares the effects of three sympathomimetic agents used in over-the-counter ocular decongestants, tetrahydrozoline, phenylephrine and naphazoline on intraocular pressure, anterior chamber angle and pupil diameter in normal healthy adult eyes. Both short term effects, monitored at 15 minutes, 30 minutes and 45 minutes following initial drop instillation, and long term effects measured for 96 hours during habitual use were studied. Only one product, Visine, which contains tetrahydrozoline, produced a significant change in the measured parameters. Visine lowered the intraocular pressure an average of 1.9 mmHg thirty minutes after instillation

Metal-ligand interplay in strongly-correlated oxides: a parametrized phase diagram for pressure induced spin transitions

We investigate the magnetic properties of archetypal transition-metal oxides MnO, FeO, CoO and NiO under very high pressure by x-ray emission spectroscopy at the K\beta line. We observe a strong modification of the magnetism in the megabar range in all the samples except NiO. The results are analyzed within a multiplet approach including charge-transfer effects. The pressure dependence of the emission line is well accounted for by changes of the ligand field acting on the d electrons and allows us to extract parameters like local d-hybridization strength, O-2p bandwidth and ionic crystal field across the magnetic transition. This approach allows a first-hand insight into the mechanism of the pressure induced spin transition.Comment: 5 pages, 3 figure

The Long Road to Developing Native Herbaceous Summer Forage Legume Ecotypes

Only a handful of well-adapted herbaceous summer forage legumes are currently marketed for drier regions of North America and even fewer are true natives. There is a growing demand for native germplasm in the region as a new generation of landowner attempts to return grasslands to a semblance of their original species and diversity. The objective of this paper is to describe preliminary research results of a grasslands team collecting, studying and promulgating native leguminous germplasm in Texas

Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672

We have found a very faint companion to the active solar analog HR 7672 (HD 190406; GJ 779; 15 Sge). Three epochs of high resolution imaging using adaptive optics (AO) at the Gemini-North and Keck II Telescopes demonstrate that HR 7672B is a common proper motion companion, with a separation of 0.79" (14 AU) and a 2.16 um flux ratio of 8.6 mags. Using follow-up K-band spectroscopy from Keck AO+NIRSPEC, we measure a spectral type of L4.5+/-1.5. This is the closest ultracool companion around a main sequence star found to date by direct imaging. We estimate the primary has an age of 1-3 Gyr. Assuming coevality, the companion is most likely substellar, with a mass of 55-78 Mjup based on theoretical models. The primary star shows a long-term radial velocity trend, and we combine the radial velocity data and AO imaging to set a firm (model-independent) lower limit of 48 Mjup. In contrast to the paucity of brown dwarf companions at <~4 AU around FGK dwarfs, HR 7672B implies that brown dwarf companions do exist at separations comparable to those of the giant planets in our own solar system. Its presence is at variance with scenarios where brown dwarfs form as ejected stellar embryos. Moreover, since HR 7672B is likely too massive to have formed in a circumstellar disk as planets are believed to, its discovery suggests that a diversity of physical processes act to populate the outer regions of exoplanetary systems.Comment: Astrophysical Journal, in pres

Method and system for measurement of mechanical properties of molecules and cells

Mechanical stresses and deformations are applied directly to cell surface receptors or molecules and measured using a system including a magnetic twisting device in combination with ferromagnetic microbeads coated with ligands for integrins or any other surface receptors. The system can be used diagnostically to characterize cells and molecules and to determine the effect of transformation and compounds, including drugs, on the cells and molecules. The system can also be used to induce cells to grow or alter production of molecules by the cells

Estimation of groundwater consumption by phreatophytes using diurnal water table fluctuations: A saturated-unsaturated flow assessment

This is the published version. Copyright American Geophysical Union[1] Groundwater consumption by phreatophytes is a difficult-to-measure but important component of the water budget in many arid and semiarid environments. Over the past 70 years the consumptive use of groundwater by phreatophytes has been estimated using a method that analyzes diurnal trends in hydrographs from wells that are screened across the water table (White, 1932). The reliability of estimates obtained with this approach has never been rigorously evaluated using saturated-unsaturated flow simulation. We present such an evaluation for common flow geometries and a range of hydraulic properties. Results indicate that the major source of error in the White method is the uncertainty in the estimate of specific yield. Evapotranspirative consumption of groundwater will often be significantly overpredicted with the White method if the effects of drainage time and the depth to the water table on specific yield are ignored. We utilize the concept of readily available specific yield as the basis for estimation of the specific yield value appropriate for use with the White method. Guidelines are defined for estimating readily available specific yield based on sediment texture. Use of these guidelines with the White method should enable the evapotranspirative consumption of groundwater to be more accurately quantified