N-methylaniline formaldehyde: Its synthesis and use as an epoxy curing agent

A series of poly-secondary aromatic amines was prepared by the acid-catalyzed condensation of N-methylaniline with formaldehyde. These condensation products were evaluated as curing agents for a standard epoxy prepolymer, namely bis(2,3-epoxypropoxyphenyl)propane. Various molar ratios of N-methylaniline to formaldehyde were used to produce polyamine condensation products with varying degrees of polymerization. These molar ratios ranged from 1.60 to 1.30. Dielectric properties of the cured epoxy resins at temperatures above 100°C. were highly dependent upon these ratios. Lower-ratio condensation products produced resins with optimum dielectric properties at the higher temperature and also with good physical properties.     

Line-Integral Approach to Computing Impedance Matrix Elements

We present a line-integral approach for computing the impedance-matrix elements in the traditional Rao-Wilton-Glisson formulation of the moment method for electromagnetic problems. The line integral extends over the perimeter of a triangle and can be computed numerically using a Gauss-Legendre quadrature. We present the conversion of the surface integral to a line integral, and we perform calculations where we compare the present method to a surface quadrature approach.     

Synthesis and polymerization of tris(alkylamino)-silance with epoxy prepolymers

Phenyltris(methylamino)silane, phenyltris(ethylamino)silane, and vinyltris(hexylamino)silane were synthesized and evaluated as curing agents for epoxy resins. Cured resins derived therefrom have very good physical and dielectric properties. The moisture resistance of the resins evaluated was especially good for those derived from the vinyltris(hexylamino)silane. Typical dielectric properties of a phenyltris(ethylamino)silane-cured epoxy specimen include a dielectric constant of 3.7 at 25°C. and a dissipation factor of 0.8%. Elevated temperature data are also presented.     

Scattering by an infinite wedge with tensor impedance boundaryconditions-a moment method/physical optics solution for thecurrents

Plane wave scattering by an infinite, two-dimensional wedge whose faces are characterized by impedance tensors is discussed. A combination of the moment method (MM) and physical optics (PO) is used to obtain a solution for the equivalent electric currents. The currents near the edge on each face are expanded with a set of basis functions consisting of pulse functions, defined on a meshed region, plus a function spanning the whole face. The currents outside the meshed region are taken to be the sum of physical optics currents, taken to be known, plus the whole-face basis function current. Expressing the equivalent magnetic currents in terms of the electric currents through the impedance tensors, the expansion coefficients for the electric current expansion are determined through an MM solution of the magnetic field integral equation. Sample results for wedges with isotropic and anisotropic face impedances are presented     

The Anionic [1,3]‐H‐Shift Applied in Synthesis: A Novel Access to (+)‐Citreoviral

In this paper we present a highly stereoselective and concise synthesis of the tetrahydrofuran derivative 3 and thus, a formal synthesis of the mycotoxin metabolite (+)‐citreoviral ( 2 ). In our route we made use of a novel anionic [1,3]‐H‐shift to convert the homoallylic alcohol 9 into the allylic benzyl ether 10 . Another key step was the regio‐ and stereocontrolled cyclization of epoxide 18b to tetrahydrofuran 19b , which was then converted into ester 3 .     

Reduction of surface integrals to contour integrals

The closed-form reduction of surface integrals to contour integrals has potential applications to the numerical solution of scattering problems. The standard mathematical technique for the reduction of a general surface integral requires the solution of a partial differential equation of the Poisson type. In this paper, we show how the reduction can be accomplished by calculating an indefinite integral of type ∫ f (t) dt, where f = f (t) is a known function in a single variable t