Evaluation of high temperature structural adhesives for extended service, phase 4

The evaluation of three phenylquinoxaline polymers as high temperature structural adhesives is presented. These included an experimental crisskubjabke oiktner (X-PQ) and two experimental materials (PPQ-2501) and (PPQ-HC). Lap shear, crack extension, and climing drum peel specimens were fabricated from all three polymers, and tested after thermal, combined thermal/humidity, and stressed Skydrol exposure. All three polymers generally performed well as adhesives at initial test temperatures from 219K (-67 F) to 505K (450 F) and after humidity exposure. The 644K (700 F) cured test specimens exhibited superior Skydrol resistance and thermal stability at 505K (450 F) when compared to the 602K (625 F) cured test specimens

Correlations between heterozygosity and measures of genetic similarity: implications for understanding mate choice

There is currently considerable interest in testing the effects of genetic compatibility and heterozygosity on animal mate preferences. Evidence for either effect is rapidly accumulating, although results are not always clear-cut. However, correlations between mating preferences and either genetic similarity or heterozygosity are usually tested independently, and the possibility that similarity and heterozygosity may be confounded has rarely been taken into account. Here we show that measures of genetic similarity (allele-sharing, relatedness) may be correlated with heterozygosity, using data from 441 human individuals genotyped at major loci in the major histocompatibility complex, and 281 peafowl (Pavo cristatus) individuals genotyped at 13 microsatellite loci. We show that average levels of allele-sharing and relatedness are each significantly associated with heterozygosity in both humans and peafowl, that these relationships are influenced by the level of polymorphism, and that these similarity measures may correlate with heterozygosity in qualitatively different ways. We discuss the implications of these inter-relationships for interpretation of mate choice studies. It has recently become apparent that mating preferences for'‘good genes' and 'compatible genes' may introduce discordant choice amongst individuals, since the optimal mate for one trait may not be optimal for the other, and our results are consistent with this idea. The inter-relationship between these measures of genetic quality also carries implications for the way in which mate choice studies are designed and interpreted, and generates predictions that can be tested in future research

Mucosal Thickening of Maxillary Sinuses of CLP vs non-CLP patients

poster abstractObjectives: The objective of this retrospective radiographic study was to compare mucosal thickening of maxillary sinuses of patients with cleft lip and palate (CLP) vs. non-CLP. Methods: Following IRB approval, three-dimensional cone beam computerized tomographs (CBCT; i-CAT) of children with unilateral CLP and children without CLP (age and gender matched; 8-14yoa; n=15ea) were selected randomly from pre-existing orthodontic records. Following reliability studies, one investigator segmented both sinuses from each CBCT using Dolphin-3D Imaging software. The sinuses were separated coronally into .4mm slices anterioposteriorly. Bony sinuses and airspaces were outlined manually on each slice. Software calculated total sinus and airspace area. Areas were summed and multiplied by slice thickness to determine volume. Mucosal thickening was the difference between total sinus and airspace volumes. Percent mucosal thickening was calculated. Since no significant differences existed between cleft (left) and noncleft (right) sides of either patient group (p>.05), sinuses for each group were pooled (n=30 ea). Significant differences in total sinus, airspace, mucosal thickening volumes and % mucosal thickening were determined using paired t-tests, accepting p<0.05 as significant. Principal Component Analysis (PCA) scatterplots were used to determine patterns of multivariate variation based on group, age, and sex. MANOVA was used to confirm PCA findings. Reliability was determined using Intraclass Correlations (ICC). Results: Reliability was excellent (ICC>0.99). The CLP total sinus and airspace volume were significantly smaller and mucosal thickening and % mucosal thickening were significantly greater than non-CLP sinuses (all p<.024). PCA showed that 89.6% of sample variance was explained by PC axis 1 and 2 (group and age). Age group 8-9yrs showed more separation with 13-14yrs than with 10-12yrs. MANOVA confirmed a significant effect of sample (p=.001) and age (p=.007)

Effects Of Iron Implantation On The Aqueous Corrosion Of Magnesium

The influence of the implantation of iron ions on the corrosion of magnesium and an AlZn-rich magnesium alloy (AZ91C) has been studied. Anodic polarization measurements in a dilute chloride-containing alkaline solution were used to evaluate corrosion resistance. A range of ion energies (50-180 keV) and doses (1016-2 x 1017 Fe+ ions cm-2) have been evaluated. Both the iron-implanted pure magnesium and the alloy AZ91C gave improved polarization measurements. A systematic positive shift of the open-circuit potential with increasing iron dose was found. In AZ91C at a dose of 1017 Fe+ ions cm-2, there was a + 0.6 V more noble shift in the open-circuit potential and a nearly equivalent shift of the pitting potential. In addition, there was a reduction of more than an order of magnitude in the current densities at all potentials. The ion energy did not have a large effect on the corrosion behavior. Annealing the samples did not further improve the corrosion resistance. The results from characterizing the corroded samples using Auger spectroscopy and scanning electron microscopy are also presented. © 1985

All-solid-state electrochromic reflectance device for emittance modulation in the far-infrared spectral region

All-solid-state electrochromic reflectance devices for thermal emittance modulation were designed for operation in the spectral region from mid- to far-infrared wavelengths (2–40 μm). All device constituent layers were grown by magnetron sputtering. The electrochromic (polycrystalline WO3), ion conductor (Ta2O5), and Li+ ion-storage layer (amorphous WO3), optimized for their infrared (IR) optical thicknesses, are sandwiched between a highly IR reflecting Al mirror, and a 90% IR transmissive Al grid top electrode, thereby meeting the requirements for a reversible Li+ ion insertion electrochromic device to operate within the 300 K blackbody emission range. Multicycle optical switching and emittance modulation is demonstrated. The measured change in emissivity of the device is to 20%

Exponential decay for the damped wave equation in unbounded domains

We study the decay of the semigroup generated by the damped wave equation in an unbounded domain. We first prove under the natural geometric control condition the exponential decay of the semigroup. Then we prove under a weaker condition the logarithmic decay of the solutions (assuming that the initial data are smoother). As corollaries, we obtain several extensions of previous results of stabilisation and control

Engineering Properties of Kentucky Oil Shales

Excavation, handling, and the environmentally safe disposal of spent oil shale and overburden materials require a knowledge of their geotechnical engineering properties. To determine these properties a laboratory investigation of the physical and geotechnical engineering properties was made. The physical tests consisted of mechanical analyses, Atterberg Limits, and specific gravity determinations. Geotechnical properties were determined by moisture-density analyses, triaxial compression, permeability tests, slake-durability, one-dimensional compression tests, and Los Angeles abrasion. A one-dimensional compression test was devised to address the problem of placement, loading, and saturation of the spent shales and overburden materials. The compacted, unprocessed oil shales were more susceptible to inundation and compression than compacted specimens of retorted shales and chars. Comparisons of the geotechnical properties of the unprocessed oil shales and processed shales are made

Assessing an Extension Plant Pest Diagnostic Center for Commercial Clients: Satisfaction, Savings, and Success

The descriptive-correlational study reported here sought to assess the effectiveness of the Extension Plant Pest Diagnostic Center (PPDC) for Tennessee\u27s commercial clients. These clients are served through one-on-one consultation regarding their individual plant or household and structural pest problems through submitted samples. The results from a mailed questionnaire showed that the majority of PPDC clients felt that the information was quick enough for their needs. While one-third of the 61 respondents stated that the PPDC recommendations saved them money, only one in 10 estimated the amount of money they saved. Suggestions for future PPDC evaluation studies are discussed

Mean field approximation of two coupled populations of excitable units

The analysis on stability and bifurcations in the macroscopic dynamics exhibited by the system of two coupled large populations comprised of $N$ stochastic excitable units each is performed by studying an approximate system, obtained by replacing each population with the corresponding mean-field model. In the exact system, one has the units within an ensemble communicating via the time-delayed linear couplings, whereas the inter-ensemble terms involve the nonlinear time-delayed interaction mediated by the appropriate global variables. The aim is to demonstrate that the bifurcations affecting the stability of the stationary state of the original system, governed by a set of 4N stochastic delay-differential equations for the microscopic dynamics, can accurately be reproduced by a flow containing just four deterministic delay-differential equations which describe the evolution of the mean-field based variables. In particular, the considered issues include determining the parameter domains where the stationary state is stable, the scenarios for the onset and the time-delay induced suppression of the collective mode, as well as the parameter domains admitting bistability between the equilibrium and the oscillatory state. We show how analytically tractable bifurcations occurring in the approximate model can be used to identify the characteristic mechanisms by which the stationary state is destabilized under different system configurations, like those with symmetrical or asymmetrical inter-population couplings.Comment: 5 figure