Effect of Phenolic Matrix Microcracking on the Structural Response of a 3-D Woven Thermal Protection System

The effect of microcracking in the phenolic matrix of a three-dimensional woven thermal protection system (TPS) and the resulting material stiffness reduction was studied via a comparison of finite element analysis results from a linear analysis and an iterative linear analysis. A TPS is necessary to protect space vehicles from the aerodynamic heating of planetary entry. The Heatshield for Extreme Entry Environment Technology (HEEET) project has developed a TPS for use in high heat-flux and pressure missions. The material is a dual-layer continuous dry weave, which is then infiltrated with a low-density phenolic resin matrix to form a rigid ablator. The phenolic resin matrix does not have structural load transfer requirements, and testing has shown that the phenolic resin can fully satisfy thermal requirements when the matrix contains microcracks. Due to high stresses in the through-the-thickness direction of the material, phenolic microcracks may form in the matrix material, which would result in a reduction of stiffness. An exploratory study was conducted to determine if reduction in material stiffness would change the load paths and/or decrease the structural margins. A comparison was performed between a linear finite element analysis that did not take into account phenolic microcracking and an iterative linear finite element analysis that accounted for propagation of phenolic microcracking. Four subcases using varying assumptions were analyzed and the results indicate that the assumed strength at which the phenolic microcracking propagates was the critical parameter for determining the extent of microcracking in the phenolic matrix. Phenolic microcracking does not have an adverse effect on the structural response of the test article and is not a critical failure

Preliminary results of the University of California X-ray experiment on the OSO-3

Cosmic and solar X ray data obtained by Orbiting Solar Observatory /OSO-3

When Mediation Confidentiality and Substantive Law Clash: An Inquiry into the Impact of \u3cem\u3eIn Re Marriage of Kieturakis\u3c/em\u3e on California\u27s Confidentiality Law

Mediation confidentiality laws play a critical role in allowing mediation to remain a viable process for parties to discuss the issues involved in their dispute, exchange information, and potentially reach a settlement before trial. Without certain guarantees as to the confidential nature of such a meeting, no savvy party or attorney would agree to provide information that could later be turned against him at trial, and many valuable opportunities (as measured in time, cost, reputation, relationship, etc.) for resolution would be lost. However, some parties to mediated disputes either do not reach resolution, or later contest a mediated agreement in court. In these situations, what happens when the rules that govern mediation confidentiality are incompatible with the substantive law governing the case, to the point of being mutually exclusive? Is there a framework for judges to use in determining whether one set of laws should trump the other? Must the outcome always be at the expense or benefit of either substantive law or mediation confidentiality? In March of 2006, the California Court of Appeal faced this scenario in deciding In re Marriage of Kieturakis, a case in which mediation confidentiality law was in conflict with the state\u27s substantive law regarding marital dissolution settlements. Parts II and III of this article will begin by considering California\u27s mediation confidentiality law, the exceptions that have developed thereto, and the outcome of the Kieturakis case. Part IV will discuss the likely impact of the case on California law and the practice of mediation. Part V will examine how other jurisdictions and the Uniform Mediation Act (UMA) have approached similar conflicts between mediation confidentiality and substantive law. Finally, Part VI will question whether holdings such as Kieturakis increase mediator responsibility for ensuring the fairness of a settlement, as traditional safeguards against nequality may no longer apply to parties contesting a mediated settlement

Hard X-ray imaging facility for space shuttle: A scientific and conceptual engineering study

A shuttle-accommodated instrument for imaging hard X-rays in the study of nonthermal particles and high temperature particles in various solar and cosmic phenomena was defined and its feasibility demonstrated. The imaging system configuration is described as well as the electronics, aspect systems, mechanical and thermal properties and the ground support equipment

The Effect of Impurities on the Physical Properties of Oxychloride Cements

The rapidly increasing use of Stucco, a cement made by mixing magnesite with a solution of magnesium chloride, as an exterior for dwelling houses has given rise to an interesting study of its chemical and physical properties. As usually applied, the stucco is made according to the specifications of the Committee on Specifications for Plastic Magnesite, which recommended the following mixture to be standard: One part by weight of plastic calcined Magnesite; Two parts by weight of Standard Ground Silica; Five parts by weight of Standard Ottawa Sand. This is then mixed with a 22 degree Baume solution of magnesium chloride to the proper consistency. Various colored oxides may be added to color the cement as desired. The cementing properties of such mixture are due to the formation of an oxychloride compound of magnesium by the interaction between magnesite and the magnesium chloride solution, the sand acting only as a filler or as an attachment for the cement crystals

Expression of the Thyroid Hormone Receptor Gene, erbAα, in B Lymphocytes: Alternative mRNA Processing is Independent of Differentiation but Correlates with Antisense RNA Levels

The erbAα gene encodes two α-thyroid hormone receptor isoforms, TRα1 and TRα2, which arise from alternatively processed mRNAs, erbAα1 (α1) and erb α2 (α2). The splicing and alternative polyadenylation patterns of these mRNAs resemble that of mRNAs encoding different forms of immunoglobulin heavy chains, which are regulated at the level of alternative processing during B cell differentiation. This study examines the levels of erbAα mRNA in eight B cell lines representing four stages of differentiation in order to determine whether regulation of the alternatively processed α1 and α2 mRNAs parallels the processing of immunoglobulin heavy chain mRNAs. Results show that the pattern of α1 and α2 mRNA expression is clearly different from that observed for immunoglobulin heavy chain mRNAs. B cell lines display characteristic ratios of α1/α2 mRNA at distinct stages of differentiation. Furthermore, expression of an overlapping gene, Rev-ErbAα (RevErb), was found to correlate strongly with an increase in the ratio of α1/α2 mRNA. These results suggest that alternative processing of erbAα mRNAs is regulated by a mechanism which is distinct from that regulating immunoglobulin mRNA. The correlation between RevErb and erbAα mRNA is consistent with negative regulation of α2 via antisense interactions with the complementary RevErb mRNA

A Variational Approach for Minimizing Lennard-Jones Energies

A variational method for computing conformational properties of molecules with Lennard-Jones potentials for the monomer-monomer interactions is presented. The approach is tailored to deal with angular degrees of freedom, {\it rotors}, and consists in the iterative solution of a set of deterministic equations with annealing in temperature. The singular short-distance behaviour of the Lennard-Jones potential is adiabatically switched on in order to obtain stable convergence. As testbeds for the approach two distinct ensembles of molecules are used, characterized by a roughly dense-packed ore a more elongated ground state. For the latter, problems are generated from natural frequencies of occurrence of amino acids and phenomenologically determined potential parameters; they seem to represent less disorder than was previously assumed in synthetic protein studies. For the dense-packed problems in particular, the variational algorithm clearly outperforms a gradient descent method in terms of minimal energies. Although it cannot compete with a careful simulating annealing algorithm, the variational approach requires only a tiny fraction of the computer time. Issues and results when applying the method to polyelectrolytes at a finite temperature are also briefly discussed.Comment: 14 pages, uuencoded compressed postscript fil

Topological Properties of Citation and Metabolic Networks

Topological properties of "scale-free" networks are investigated by determining their spectral dimensions $d_S$, which reflect a diffusion process in the corresponding graphs. Data bases for citation networks and metabolic networks together with simulation results from the growing network model \cite{barab} are probed. For completeness and comparisons lattice, random, small-world models are also investigated. We find that $d_S$ is around 3 for citation and metabolic networks, which is significantly different from the growing network model, for which $d_S$ is approximately 7.5. This signals a substantial difference in network topology despite the observed similarities in vertex order distributions. In addition, the diffusion analysis indicates that whereas the citation networks are tree-like in structure, the metabolic networks contain many loops.Comment: 11 pages, 3 figure

Morphological Variations in Developing Ectomycorrhizae of Dryas integrifolia and Five Fungal Species

A comparative study of ectomycorrhiza formation between the host species Dryas integrifolia and four fungal species belonging to the Basidiomycotina ( Laccaria bicolor, L. laccata, Hebeloma cylindrosporum, Paxillus involutus) and one species in the Ascomycotina (Cenococcum geophilum) showed that patterns in ectomycorrhizal development were distinctive enough to characterize each fungal symbiont. Several aspects of hyphal growth on the plant root during colonization were studied in order to demonstrate the usefulness of SEM in observing the ontogeny of ectomycorrhizae. Each fungal species had a different rate of colonization, and varying root and root hair interactions. As a consequence mantle morphology and the overall appearance of mature ectomycorrhizal apices were also characteristic for each fungal species. Results indicate that the mycobiont plays a major role in determining the morphology of mature ectomycorrizae

Scanning Electron Microscopy of Ectomycorrhizae Potential and Limitations

Scanning electron microscopy (SEM) has added considerably to an understanding of the morphology of ectomycorrhizae. Features of the mantle of mature ectomycorrhizae have been studied most frequently. There is considerable variation in arrangement of hyphae and therefore in the appearance of the outer mantle. This variation is due primarily to the fungal symbiont although the host genome may also influence this feature. The Hartig net has been studied from fractured ectomycorrhizal roots and, in the present study, from fractured cryopreserved specimens; general features of the interaction between Hartig net hyphae and contiguous root cells have been described. There are few published accounts of using SEM techniques to study the ontogeny of ectomycorrhizae. This study demonstrates the usefulness of such techniques in studying the initial interaction of hyphae with root hairs and root surfaces, including the extramatrical phase which is normally very difficult to study using other techniques