Impact of uncertainty on modeling and testing

A thorough understanding of the uncertainties associated with the modeling and testing of the Space Shuttle Main Engine (SSME) Engine will greatly aid decisions concerning hardware performance and future development efforts. This report will describe the determination of the uncertainties in the modeling and testing of the Space Shuttle Main Engine test program at the Technology Test Bed facility at Marshall Space Flight Center. Section 2 will present a summary of the uncertainty analysis methodology used and discuss the specific applications to the TTB SSME test program. Section 3 will discuss the application of the uncertainty analysis to the test program and the results obtained. Section 4 presents the results of the analysis of the SSME modeling effort from an uncertainty analysis point of view. The appendices at the end of the report contain a significant amount of information relative to the analysis, including discussions of venturi flowmeter data reduction and uncertainty propagation, bias uncertainty documentations, technical papers published, the computer code generated to determine the venturi uncertainties, and the venturi data and results used in the analysis

Association of Restriction Fragment Length Polymorphisms among Maize Inbreds with Agronomic Performance of Their Crosses

Restriction fragment length polymorphisms (RFLPs) have been suggested as molecular markers to facilitate improvement of agronomic traits in maize (Zea mays L.). The objective of this study was to evaluate the utility of RFLP data in elucidating heterotic patterns among maize lines. Eight maize inbred lines and their 28 singlecross hybrids werevaluated for grain yield at two Iowa locations in each of 2 yr in a randomized-complete block design. The diallel mating design permitted estimation of general and specific combining ability effects. Restriction fragment length polymorphism analysis of inbred lines included five restriction enzymes and five eDNA and 28 genomic clones distributed over the maize genome. Restriction fragment length polymorphism patterns of crosses were predicted from analysis of the inbred parents. Genetic distances between inbred lines were estimated as modified Rogers\u27 distance (MRD). Grain yield and specific combining ability were significantly correlated with MRD for six of the 10 chromosomes. Dispersion of inbred lines and hybrids for RFLP allele frequencies was generally consistent with expectations based on known pedigrees. Results from this study suggest RFLP analysis as a potential alternative to field testing when attempting to assign maize inbred lines to heterotic groups

Spreading of Latex Particles on a Substrate

We have investigated both experimentally and theoretically the spreading behavior of latex particles deposited on solid substrates. These particles, which are composed of cross-linked polymer chains, have an intrinsic elastic modulus. We show that the elasticity must be considered to account for the observed contact angle between the particle and the solid substrate, as measured through atomic force microscopy techniques. In particular, the work of adhesion computed within our model can be significantly larger than that from the classical Dupr\'{e} formula.Comment: 7 pages, 7 figures, to appear in Europhys. Let

Hardy-Weinberg and linkage equilibrium estimates in the BSSS and BSCB1 random mated populations

Because maize (Zea mays) is an annual species those working with it must frequently make crosses to preserve and periodically maintain populations. Random mating is performed either using hand-pollination techniques or in wind-pollinated isolated blocks. Eighty-two restriction fragment length polymorphism (RFLP) markers were used to examine samples of random mated, hand-pollinated BSSS(R) and BSCB1(R) maize populations to find out whether their genotypic proportions conformed to predicted outcomes of random mating. The majority of loci conformed to expectations for Hardy-Weinberg equilibrium (HWE). Excess homozygosity was observed at 87% of the loci where the null hypothesis of HWE was rejected. For pairs of polymorphic loci, linkage equilibrium was observed in the BSSS(R) and BSCB1(R) progenitor populations (fewer than 5% of all tests rejected the null hypothesis of equilibrium at the P≤0.05 significance level). The BSSS(R)CO, BSCB1(R)CO and BSCB1(R)C12 populations showed slight increases in the proportion of pairs of loci in linkage disequilibrium compared to the progenitors (approximately 8.4% of all pairs of loci rejected the null hypothesis at the P≤0.05 significance level). BSSS(R)C12 was an extreme outlier with 25.0% of all pairs of polymorphic loci displaying significant (P≤0.05) linkage disequilibrium. This result was likely caused by the artificial grouping of three BSSS(R)CO plants with 97 BSSS(R)C12 plants during sampling. Results from principal components analysis of all individuals based on RFLP alleles supported this interpretation. Overall, most of the observed deviations from equilibrium were likely to have been caused by positive assortative mating in the case of HWE, and natural selection for epistatic effects between unlinked loci in the case of linkage disequilibrium

Drying and cracking mechanisms in a starch slurry

Starch-water slurries are commonly used to study fracture dynamics. Drying starch-cakes benefit from being simple, economical, and reproducible systems, and have been used to model desiccation fracture in soils, thin film fracture in paint, and columnar joints in lava. In this paper, the physical properties of starch-water mixtures are studied, and used to interpret and develop a multiphase transport model of drying. Starch-cakes are observed to have a nonlinear elastic modulus, and a desiccation strain that is comparable to that generated by their maximum achievable capillary pressure. It is shown that a large material porosity is divided between pore spaces between starch grains, and pores within starch grains. This division of pore space leads to two distinct drying regimes, controlled by liquid and vapor transport of water, respectively. The relatively unique ability for drying starch to generate columnar fracture patterns is shown to be linked to the unusually strong separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments

Drying and cracking mechanisms in a starch slurry

Starch-water slurries are commonly used to study fracture dynamics. Drying starch-cakes benefit from being simple, economical, and reproducible systems, and have been used to model desiccation fracture in soils, thin film fracture in paint, and columnar joints in lava. In this paper, the physical properties of starch-water mixtures are studied, and used to interpret and develop a multiphase transport model of drying. Starch-cakes are observed to have a nonlinear elastic modulus, and a desiccation strain that is comparable to that generated by their maximum achievable capillary pressure. It is shown that a large material porosity is divided between pore spaces between starch grains, and pores within starch grains. This division of pore space leads to two distinct drying regimes, controlled by liquid and vapor transport of water, respectively. The relatively unique ability for drying starch to generate columnar fracture patterns is shown to be linked to the unusually strong separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments

Genetic Diversity for Restriction Fragment Length Polymorphisms: Relation to Estimated Genetic Effects in Maize Inbreds

Restriction fragment length polymorphisms (RFLPs) have been proposed for investigating relationships among inbred lines and predicting heterosis and performance of single-cross hybrids in maize (Zea mays L.). Such use was evaluated in 20 maize inbreds classified as first-cycle, second-cycle, good, and poor lines, and in diallel crosses within types. Eight generations (parents, F1, F2, F3, backcrosses, and backcrosses selfed) from 67 crosses were evaluated for grain yield in five Iowa environments. Genetic effects were estimated from generation means by ordinary diallel analyses and the Eberhart-Gardner genetic model. Poor inbreds showed significantly greater average heterosis than did good lines. Estimates of additive ✕ additive epistatic effects were negative and highly significant in all except first-cycle lines. Using two restriction enzymes and 82 genomic) DNA probes distributed throughout the maize genome, all but one probe revealed polymorphisms with at least one enzyme (~4.5 variants per RFLP locus). Genetic distances between lines within types were estimated as Rogers\u27 distances (RD). Within diallel sets, RD values were partitioned into general (GRD)and specific (SRD). All four types of lines showed similar means and substantial variation for RD; GRD explained ~40% of the variation among RD values. Cluster analyses revealed associations among lines generally consistent with expectations based on known pedigrees. Correlations of RD and SRD with F1 yield heterosis, specific heterosis, and specific combining ability were positive but small (r = ≤ 0.50) when combined for all crosses. Results indicated that RFLPs can be used to investigate pedigree relationships among maize inbreds, but also suggest that RFLP-based genetic distance measures are of limited use in predicting heterotic performance of single crosses between unrelated lines

Population Genetics of Increased Hybrid Performance between Two Maize Populations under Reciprocal Recurrent Selection

Heterosis, the superiority in one or more characteristics of crossbred organisms relative to their inbred parents, is the basis of the modern cultivars utilized in maize (Zed mays L.). Heterosis is of interest in nondomesticated species due to its relevance to the question how much polymorphism is maintained in natural populations due to selection? (Berger, 1976). For maize and certain other domesticated species that employ inbred lines to produce commercial hybrids, knowledge of the mechanisms of gene action producing heterosis could contribute to advances in breeding techniques

Middle-up-down and top-down approaches: Strategy implementation, uncertainty, structure, and foodservice segment

This study explores the relationship between various profiles of the strategy implementation process and managers\u27 perception of the task environment, complexity and dynamism. This study addresses the following research questions: Do differences exist between levels of perceived environmental change/uncertainty and users of middle-up-down and top-down strategy implementation approaches? And, does this relationship become more meaningful when ownership, firm structure and foodservice segment characteristics are considered? There has been very little research on the food service industry that assesses the relationship between eleven task environment measures of complexity and dynamism and the use of a predominately top-down or middle-up-down approach to the implementation of strategies. Using a sample of food industry managers, multiple discriminate analysis (MDA) was used to predict the use of implementation strategies. Substantive differences appear to exist between levels of perceived environmental change/uncertainty and users of middle-up-down and top-down strategy implementation approaches for foodservice firms. The ability to correctly classify users of middle-up-down and top-down approaches using a multivariate combination of environmental variables is improved radically when ownership, firm structure, and market segment classifications were are considered. Taken as a whole, the findings are most convincing and support the basic hypotheses. Study findings indicate that a broad brushstroke approach to determining whether a middle-updown or top-down is used or appropriate based on the perceived task environment may not be valuable. The results support previous findings in other industries in that the prediction is better for market segments served and the public versus private nature of the firms involved