Properties of three graphite/toughened resin composites

Results are presented from an experimental evaluation of IM7/977-2, IM7/F655, and T800/F3900. Data presented include ply-level (unidirectional laminate) strength and moduli, unnotched and notched (open hole) tension and compression properties of quasi-isotropic laminates, and compression-after-impact strengths. These data are compared with properties of other toughened (IM7/8551-7 and IM6/18081) and brittle (T300/5208) graphite-epoxy materials. The IM7/977-2, IM7/F655, and T800/F3900 materials are substantially stronger and more damage tolerant than widely used first generation composite materials such as T300/5208. The T800/F3900 outperforms IM7/977-2 and IM7/F655 materials in tolerance to projectile impacts. Compression-after-impact strengths were found to be dependent on impactor velocity for a given impact energy. The open hole compression properties of all three materials are degraded by the combination of heat and moisture

Collective Choice and Control Rights in Firms

Recent writers have asserted that firms controlled by workers are rare because workers have diverse preferences over firm policies, and thus suffer from high transaction costs in making collective decisions. This is contrasted with firms controlled by investors, who all support the goal of wealth maximization. However, the source of the asymmetry between capital and labor has not been clearly identified. For example, firms could attract labor inputs by selling transferable shares, and well-known unanimity theorems from the finance literature carry over to models of this kind. We resolve this puzzle by arguing that because financial capital is exceptionally mobile, capital markets are sufficiently competitive to induce unanimity. The lower mobility of human capital implies that labor markets are monopolistically competitive and hence that unanimity cannot be expected in labor-managed firms. Moreover, such firms are vulnerable to takeover by investors while capital-managed firms are substantially less vulnerable to takeover by workers.capitalist firms, labor-managed firms, collective choice, preference heterogeneity, unanimity, voting, membership markets, control rights

Properties of two composite materials made of toughened epoxy resin and high-strain graphite fiber

Results are presented from an experimental evaluation of IM7/8551-7 and IM6/18081, two new toughened epoxy resin, high strain graphite fiber composite materials. Data include ply-level strengths and moduli, notched tension and compression strengths and compression-after-impact assessments. The measured properties are compared with those of other graphite-epoxy materials

An Observational Study in a Playground Situation of Differences in Artistic Personality at the Child Level

The amount of activity and the type of play on playgrounds possessing equipment and on playgrounds lacking equipment were compared for six artistic and five non-artistic children, aged five to eight. Modifications were used of (1) the Barker technique of recording child\u27s movements from place to place, and (2) the Goodenough technique of repeated short samples. The results indicate that artistic children differ primarily from the non-artistic in that they devote more time to play materials and are consequently less active physically and less social. Where play materials are absent the differences tend to disappear

Development of stitching reinforcement for transport wing panels

The NASA Advanced Composites Technology (ACT) program has the objective of providing the technology required to obtain the full benefit of weight savings and performance improvements offered by composite primary aircraft structures. Achieving the objective is dependent upon developing composite materials and structures which are damage tolerant and economical to manufacture. Researchers are investigating stitching reinforcement combined with resin transfer molding to produce materials meeting the ACT program objective. Research is aimed at materials, processes, and structural concepts for application in both transport wings and fuselages, but the emphasis to date has been on wing panels. Empirical guidelines are being established for stitching reinforcement in structures designed for heavy loads. Results are presented from evaluation tests investigating stitching types, threads, and density (penetrations per square inch). Tension strength, compression strength, and compression after impact data are reported

Affirmative Action: New Interpretations and Realities

Affirmative action emerged during the 1960s as a government-mandated strategy for rectifying the effects of past discrimination. Although the goal of providing equal opportunity for all citizens regardless of race or gender has never been questioned seriously, controversy has swirled around affirmative action with claims by nonminorities of reverse discrimination and complaints by employers of coercion to hire unqualified job applicants. This paper examines the relevance of affirmative action for the 1990s in light of changes in public policy and changes in society. It suggests that the judicious use of affirmative action can increase a company\u27s competitiveness in increasingly diverse product and labor markets

Characterization of the free energy dependence of an interprotein electron transfer reaction by variation of pH and site-directed mutagenesis

AbstractThe interprotein electron transfer (ET) reactions of the cupredoxin amicyanin, which mediates ET from the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase to cytochrome c-551i have been extensively studied. However, it was not possible to perform certain key experiments in that native system. This study examines the ET reaction from reduced amicyanin to an alternative electron acceptor, the diheme protein MauG. It was possible to vary the ΔG° for this ET reaction by simply changing pH to determine the dependence of kET on ΔG°. A P94A mutation of amicyanin significantly altered its oxidation–reduction midpoint potential value. It was not possible to study the ET from reduced P94A amicyanin to cytochrome c-551i in the native system because that reaction was kinetically coupled. However, the reaction from reduced P94A amicyanin to MauG was a true ET reaction and it was possible to determine values of reorganization energy (λ) and electronic coupling for the reactions of this variant as well as native amicyanin. Comparison of the λ values associated with the ET reactions between amicyanin and the TTQ of methylamine dehydrogenase, the diheme center of MauG and the single heme of cytochrome c-551i, provides insight into the factors that dictate the λ values for the respective reactions. These results demonstrate how study of ET reactions with alternative redox partner proteins can complement and enhance our understanding of the reactions with the natural redox partners, and further our understanding of mechanisms of protein ET reactions

Detection of Mycobacterium avium ss. Paratuberculosis in Blau Syndrome Tissues

Background and Aim of the Work. Blau syndrome is an inherited granulomatous inflammatory disorder with clinical findings of uveitis, arthritis, and dermatitis. Although rare, Blau syndrome shares features with the more common diseases sarcoidosis and Crohn's disease. The clinical findings of Blau syndrome are indistinguishable from juvenile sarcoidosis; the mutations of Blau syndrome are on the same gene of chromosome 16 (CARD15) that confers susceptibility to Crohn's disease. The product of this gene is part of the innate immune system. Mycobacterium avium ss. paratuberculosis (MAP) is the putative cause of Crohn's disease and has been implicated as a causative agent of sarcoidosis. Methods. Archival tissues of individuals with Blau syndrome were tested for the presence of MAP. Results. DNA evidence of MAP was detected in all of the tissues. Conclusions. This article finds that MAP is present in Blau syndrome tissue and postulates that it has a causal role. The presence of MAP in Blau syndrome—an autosomal dominant, systemic inflammatory disease—connects genetic and environmental aspects of “autoimmune” disease