Photoelastic concrete similutide with CR-39 reinforced with epoxy and glass

This investigation was undertaken to study the similitude of models for reinforced concrete beams by photoelasticity. All previous attempts of model analysis have not maintained the correct modular ratio of reinforcing rod to the beam material. The material problem of obtaining the necessary rods was solved. The material exploratory investigation revealed suitable reinforcing plastics that have opened a wide range of model analyses for reinforced concrete. The models fabricated provided a study in correlation of models and prototype. A sample of the stresses obtained with a photoelastic interferometer is given to demonstrate the practical application of the model analysis.     

Erratic behavior of CAT(0) geodesics under G-equivariant quasi-isometries

We show that, given any connected, compact space ${Z \subset \mathbb{R}^n}$ , there exists a group G acting geometrically on two CAT(0) spaces X and Y, a G-equivariant quasi-isometry ${f\colon X\rightarrow Y}$ , and a geodesic ray c in X such that the closure of f (c), intersected with ${\partial Y}$ , is homeomorphic to Z. This characterizes all homeomorphism types of ??geodesic boundary images?? that arise in this manner.     

Structure of an unsymmetrical isomer from the attempted synthesis of 1,8-dicyclooctatetraenylnaphthalene.

Attempted synthesis of 1,8-dicyclooctatetraenylnaphthalene (1) by the palladium(0)-catalyzed coupling of 1,8-dibromonaphthalene with cyclooctatetraenyltrimethylstannane afforded a single unsymmetrical isomer of 1 in 88% yield. Two-dimensional NMR methods and spectral synthesis were employed to assign the structure of the isomer (2). AM1 geometry-optimized structures of 2 and its isomers showed that the unexpected unsymmetrical structure of 2 results from the minimization of repulsive inter-ring H-H interactions. Compound 2 is postulated to arise via tandem [2 + 2] cycloaddition and 6 pi --> 4 pi + 2 sigma electrocyclization reactions of 1.     

Stereoselectivity in the reductive cleavage of vinylcyclopropane

Treatment of vinylcyclopropane (6) with lithium in liquid ammonia at 0° or 25° slowly effects reductive cleavage to afford a mixture of cis-2-pentene (7), trans-2-pentene (8), and 1-pentene (9). The major product is 7 and the ratio 7:8 is greater at 0° (4·25) than at 25° (3·2). Control experiments have established that the products are stable in lithium amide-liquid ammonia at 25°. In contrast, product ratios for cleavage of 6 with sodium in liquid ammonia at 0° or 25° are somewhat variable due to equilibration under the reaction conditions, and 8 is the major product at longer reaction times at 25°. It is suggested that the predominant cis-stereoselectivity is greatest in solvent-separated ion pair transition states.