Selective Phenol Alkylation: An Improved Preparation of Efaproxiral

An improved, two‐step synthesis of efaproxiral, used in breast cancer therapy, is described, utilizing inexpensive commodity chemicals for starting materials. Selective amide formation and O‐alkylation in the presence of multireactive functional groups is demonstrated, thus avoiding protection/deprotection steps.     

A reexamination ofSU(6) symmetry breaking in high-energy phenomenology

A permutationally-symmetric form for the nucleon wave function consisting of a linear combination of the56 ground state and the70 excited state is used to reexamine the nucleon structure functions and form factors. This form of wave function reproduces the results of the successful Carlitz-Kaur model, differing only in the addition of a term that is proportional to the square of the mixing coefficient between the56 and the70 states. Values of this mixing coefficient are obtained from the structure functions and from the initial slope of the neutron electric form factor using relativistic wave functions constructed by Henriques, Kellett, and Moorhouse. The signs of these values are in agreement, so that the model avoids the contradiction noted by Le Yaouanc et al. This result is due to the dependence of the neutron electric form factor calculation on the spin wave function and associated matrix elements.     

Regiospecific opening of oxetanes with trimethylsilyl cyanide - zinc iodide. a general approach to γ-amino alcohols.

Trimethylsilyl ethers of γ-hydroxy isonitriles were formed regiospecifically in the opening of oxetanes with trimethylsilyl cyanide - zinc iodide. Deprotection and hydrolysis of the initially formed ring cleavage products gave γ-amino alcohols.     

Plant delta(15)N associated with arbuscular mycorrhization, drought and nitrogen deficiency

It has long been evident that plant (15)N chiefly reflects the processes which fractionate (15)N/(14)N rather than the (15)N of plant N source(s). It has emerged recently that one of the most important fractionating processes contributing to the whole plant (15)N is the presence/absence, type or species of mycorrhiza, especially when interacting with nutrient deficiency. Ecto- and ericoid mycorrhizas are frequently associated with (15)N-depleted foliar (15)N, commonly as low as -12 per thousand. As shown by the present study, plants having no mycorrhiza, or those infected with various species of arbuscular mycorrhiza (AM)-forming fungi, interact with varying concentrations of soil nitrogen [N] and moisture to enrich plant (15)N by as much as 3.5 per thousand. Hence the lack of a mycorrhiza, or variation in the species of AM-forming fungal associations, can account for about 25% of the usually reported variations of foliar (15)N found in field situations and do so by (15)N enrichment rather than depletion. Copyright 1999 John Wiley & Sons, Ltd.     

Design,Manufacture, and Quasi-Static Testing of Metallic Negative Stiffness Structures within a Polymer Matrix

A composite material system comprised of a monostable negative stiffness (NS) structure within a polymer matrix was designed, fabricated, and experimentally evaluated. The monostable negative stiffness (NS) structure was designed using a combination of analytical and numerical models and manufactured in stainless steel. The NS structure was arranged in parallel with different polymer matrices to experimentally evaluate the effects of the matrix properties on the overall stiffness and energy dissipation of the composite NS-matrix system when loaded in uniaxial compression. A strong influence of the matrix properties on the stiffness and energy absorption capacity of the composite system was observed. Unlike conventional composites for which there is a natural tradeoff between stiffness and energy absorption capacity, the composite NS-matrix system enhanced stiffness while simultaneously improving energy absorption relative to a neat matrix, but only when the stiffness of the matrix was carefully matched to the stiffness of the NS structure.     

Critical Layers m Parallel Flows

Finite amplitude neutrally stable two-dimensional disturbances in parallel flows are determined for large Reynolds numbers when both nonlinearity and viscosity are important in the critical layer. The phase shift across the critical layer depends on the local vertical Reynolds number in the critical layer, and it varies monotonically between the value zero of the nonlinear theory and — π of the viscous theory. An O(?^½) distortion of both the mean and fundamental harmonic is shown to be necessary. The eigenvalue problem is solved for long waves yielding neutral modes which link the two previous theories. In particular certain difficulties of the nonlinear theory are resolved.