Predicting fully plastic mode II crack growth from an asymmetric defect

Asymmetrically cracked specimens fail with considerably less ductility than symmetrically cracked ones, due to the crack progressing along a shear band into pre-damaged material. A formulation for the accumulation of damage ahead of an asymmetric crack is presented, based on strain increments following a power law relation. These results are integrated both numerically and approximately.The crack growth per unit displacement increases approximately as the logarithm of the total crack advance per inclusion spacing , and varies inversely as the critical fracture strain c. This provides a basis for predicting large-scale, fully plastic fracture from asymmetric weld defects, using small-scale laboratory specimens.

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Résumé Les éprouvettes fissurées de manière asymétrique se rompent avec beaucoup moins de ductilité que celles qui sont fissurées de manières symétrique, en raison du fait que la fissure se développe suivant une bande de cisaillement dans un matériau préendommagé. On Présente une formulation de l'accumulation du dommage en avant d'une fissure asymétrique, en se basant sur des gradients de déformations répartis selon une loi quadratique. L'interprétation des résultats est effectuée par voie numérique et par approximation.On constate que le croissance d'une fissure par unité de déplacement est sensiblement proportionnelle au logarithme de l'avancement total de la fissure rapporté à l'espacement entre deux inclusions , et en raison inverse de la déformation critique à la rupture c. Ceci fournt une base pour prédire une rupture à plus grande échelle et en conditions tout à fait plastiques, qui résulteront de défauts de soudage asymétriques, et ce en utilisant des éprouvettes réduites de laboratoire.

     

Molecular Genetics of Conjunctival Melanoma and Prognostic Value of TERT Promoter Mutation Analysis

The aim of this study was exploration of the genetic background of conjunctival melanoma (CM) and correlation with recurrent and metastatic disease. Twenty-eight CM from the Rotterdam Ocular Melanoma Study group were collected and DNA was isolated from the formalin-fixed paraffin embedded tissue. Targeted next-generation sequencing was performed using a panel covering GNAQ, GNA11, EIF1AX, BAP1, BRAF, NRAS, c-KIT, PTEN, SF3B1, and TERT genes. Recurrences and metastasis were present in eight (29%) and nine (32%) CM cases, respectively. TERT promoter mutations were most common (54%), but BRAF (46%), NRAS (21%), BAP1 (18%), PTEN (14%), c-KIT (7%), and SF3B1 (4%) mutations were also observed. No mutations in GNAQ, GNA11, and EIF1AX were found. None of the mutations was significantly associated with recurrent disease. Presence of a TERT promoter mutation was associated with metastatic disease (p-value = 0.008). Based on our molecular findings, CM comprises a separate entity within melanoma, although there are overlapping molecular features with uveal melanoma, such as the presence of BAP1 and SF3B1 mutations. This warrants careful interpretation of molecular data, in the light of clinical findings. About three quarter of CM contain drug-targetable mutations, and TERT promoter mutations are correlated to metastatic disease in CM.     

Association of seed size with genotypic variation in the chemical constituents of soybeans

Ten soybean genotypes grown in 1992 with seed size ranging from 7.6 to 30.3 g/100 seeds and maturity group V or VI were selected and tested for oil and protein content and for fatty acid composition. In these germplasm, protein varied from 39.5 to 50.2%, oil, 16.3 to 21.6%, and protein plus oil, 59.7 to 67.5%. Percentages of individual fatty acids relative to total fatty acids varied as follows: palmitic, 11.0 to 12.8; stearic, 3.2 to 4.7; oleic, 17.6 to 24.2; linoleic, 51.1 to 56.3 and linolenic, 6.9 to 10.0. Seed size showed no significant correlations with individual saturated fatty acids, protein or oil content. However, significant correlations were found between seed size and individual unsaturated fatty acids: positive with oleic, and negative with linoleic and linolenic. Oil and protein content were negatively correlated with each other. Among the major fatty acids, only the unsaturated were significantly correlated with each other: negative between oleic and linoleic or linolenic, and positive between linoleic and linolenic. A subsequent study with soybeans grown in 1993 generally confirmed these findings. Variation in relative percentages of unsaturated fatty acids andr values for most pairs of relationships were even higher than those obtained from the 1992 crop. Presented at the 85th AOCS Annual Meeting and Expo, Atlanta, Georgia, May 8–12, 1994.     

An ionene with spirane structure (spiroionene)

The secondary diamine 1,3,5,7-tetrahydro[1,2c:4,5c'] benzodipyrrole (3) and 1,2,4,5-tetrabromomethylbenzene (1) form a polymeric ionene with spirane structure through a repetitive alkylation reaction. The structure of the product could be proven by¹³C-NMR spectroscopy by comparison with suitable reference compounds. Solutions in aqueous methanol exhibit a typical polyelectrolyte effect. Variation of the counterions produces sufficient solubility in organic solvents. From the crystal structure of a similar model compound one can conclude that the synthesized polymer has a rod-like shape.     

Internal structure of coalitions in competitive and altruistic graphical coalitional games

This paper introduces a certain graphical coalitional game where the internal topology of the coalition depends on a prescribed communication graph structure among the agents. The game Value Function is required to satisfy four Axioms of Value. These axioms make it possible to provide a refined study of coalition structures on graphs by defining a formal graphical game and by assigning a Positional Advantage, based on the Shapley value, to each agent in a coalition based on its connectivity properties within the graph. Using the Axioms of Value the graphical coalitional game can be shown to satisfy properties such as convexity, fairness, cohesiveness, and full cooperativeness. Three measures of the contributions of agents to a coalition are introduced: marginal contribution, competitive contribution, and altruistic contribution. The mathematical framework given here is used to establish results regarding the dependence of these three types of contributions on the graph topology, and changes in these contributions due to changes in graph topology. Based on these different contributions, three online sequential decision games are defined on top of the graphical coalitional game, and the stable graphs under each of these sequential decision games are studied. It is shown that the stable graphs under the objective of maximizing the marginal contribution are any connected graph. The stable graphs under the objective of maximizing the competitive contribution are the complete graph. The stable graphs under the objective of maximizing the altruistic contribution are any tree.     

Methods for the determination of cyclopropenoid fatty acids. VII. The dilution-HBr-titration technique as a general method

The stepwise HBr titration method for the cyclopropenoid analysis of cottonseed oils is subject to serious inaccuracies when applied to samples containing higher cyclopropenoid concentrations, particularly if they contain appreciable amounts of alumina-adsorbable materials. A modification of the method is described which eliminates these sources of error. Its validity has been established by the analysis of a wide range of synthetic compositions including compositions containing massive amounts of interfering HBr-reactive substances and other alumina-adsorbable materials. The method with further modification can be used to analyze glycerides with the same high degree of accuracy. Presented at the AOCS Meeting in Houston, April 1965. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Viscoelastic Effects in a Phosphate Glass-Metal Seal

A family of phosphate glasses has been developed with thermal expansion behavior in the elastic range that nearly matches the response of 304 stainless steel. Attempts to make concentric pin-shell seals consistently have yielded fractures between 400° and 300°C during cooling. Elastic stress analyses which neglect glass transitional behavior and utilize constant glassy ("elastic") thermal expansion coefficients predict a residual stress state that is compressive. However, viscoelastic computations which include the effects of structural relaxation during glass transtion show that tensile stresses sufficient to cause failure arise during cooldown of the seal.     

Epoxy fatty acid ester plasticizers. Preparation and properties

Summary The preparation of epoxy fatty acid ester plasticizers has been reviewed. These plasticizers can be prepared by epoxidation reactions, utilizing a preformed peracid or anin-situ technique. A newin-situ epoxidation process, utilizing hydrogen peroxide and acetic acid in the presence of strong acid catalyst, has been described. Excellent conversions to epoxide have been achieved with a series of monounsaturated and polyunsaturated esters. Epoxy fatty acid esters are excellent plasticizers for vinyl resins. Their performance in a series of additional epoxy plasticizers of vegetable and marine origin is described. Novel epoxy plasticizers based upon mixed acetylated mono- and di-glyceride have been prepared and are found to have excellent plasticizer performance. Presented at the 28th fall meeting, American Oil Chemists’ Society, October 1954, Minneapolis, Minn.     

Recent studies of self-condensation and co-condensation of melamine-formaldehyde resins; cure at low temperatures

Self-condensation: recent research on the chemical pathways by which alcoholated melamine-formaldehyde (MF) resins react with themselves and on the product structures is summarized. Model compound studies suggest that bridges are less stable than widely thought unless they are in hexahydro-1,3,5-triazine ring structures. In acyclic structures they are probably less stable than bridges. Co-condensation: studies of how the composition of MF resins influences the rates of reaction with poly(ol) co-reactant show that MF resins that contain very low levels of and/or functionality are quite reactive. Reactivities of a variety of poly(ester) and acrylic coreactants were studied. By combining reactive MF resins with reactive co-reactants one can formulate high solids enamels that cure by co-condensation in 30 min at 50 to 65 °C with 0.5 parts per hundred (phr) of p-toluenesulfonic acid (p-TSA) catalyst. Cure at 25 °C appears feasible with higher catalyst levels.     

Uric Acid: The Sperm-Release Pheromone of the Marine Polychaete Platynereis dumerilii

In the marine polychaete, Platynereis dumerilii, reproductive behavior in the two sexes is synchronized by the consecutive discharge of male and female sex-specific pheromones. After the female releases the eggs into the free water column, immediate fertilization is achieved by several males circling around the eggs emitting sperm clouds. We report the isolation and identification of the sperm-release pheromone present in the coelomic fluid of sexually mature females. Each step in isolation was guided by bioassay. Isolation methods included extraction and solvent partitioning and separation methods included ultrafiltration and high-performance liquid chromatography. Uric acid was identified as the sperm-release pheromone that is discharged by the female with release of the eggs. The threshold concentration for sperm release by males was determined as 0.6 M.