Approximation of certain functions given by integrals with highlyoscillatory integrands

There is often a need to approximate integrals of highly oscillatory functions when studying scattering and diffraction of electromagnetic waves. This paper presents a method of estimating certain types of these integrals by evaluating one interpolating function and performing one or two relatively easy numerical integrations. The method is demonstrated for the case of a Fresnel integral     

The molecular mechanism of membrane proteins probed by evanescent infrared waves

The catalytic action of membrane proteins is vital to many cellular processes. Yet the molecular mechanisms remain poorly understood. We describe here the technique of evanescent infrared difference spectroscopy as a tool to decipher the structural changes associated with the enzymatic action of membrane proteins. Functional changes as minute as the protonation state of individual amino acid side chains can be observed and linked to interactions with a ligand, agonist, effector, or redox partner.     

A note on the mixed potential representation of electric fields inlayered media

A mixed potential formulation is given for electrical fields in layered environments. Contributions to the field from charges are identified explicitly through a scalar Green's function for layered media. The outcome is a computationally expedient Sommerfeld integral representation     

Radar target discrimination using the extinction-pulse technique

An aspect independent radar target discrimination scheme based on the natural frequencies of the target is considered. An extinction-pulse waveform upon excitation of a particular conducting target results in the elimination of specified natural modal content of the scattered field. Excitation of a dissimilar target produces a noticeably different late-time response. Construction of appropriate extinction-pulse waveforms is discussed, as well as the effects of random noise on their application to thin cylinder targets. Also presented is experimental verification of this discrimination concept using simplified aircraft models.     

Accurate evaluation of Sommerfeld integrals using the fast Fouriertransform

It is shown that the fast Fourier transform (FFT) combines naturally with Simpson's rule for Sommerfeld-type integral computation. The principal advantage of using the FFT is that a single subroutine call yields a set of sample values of an integral (i.e. the integral for various values of an integrand parameter). Such samples could be useful in themselves. In other applications Sommerfeld integrals represent Green's functions nested within other spatial integrals, so samples from the FFT might be useful in approximating the outernested integral. Several examples are provided to illustrate the process     

Frequency domain E-pulse synthesis and target discrimination

A frequency domain approach to theE-pulse radar target discrimination scheme is introduced. This approach is shown to allow easier interpretation ofE-pulse convolutions via theE-pulse spectrum, and leads to a simplified calculation of pulse basis function amplitudes in theE-pulse expansion. Experimental evidence obtained using aircraft models verifies the single-mode discrimination scheme, as well as the aspect-independent nature of theE-pulse technique. This leads to an integrated technique for target discrimination combining theE-pulse with single mode extraction waveforms.     

New progress on E/S pulse techniques for noncooperative targetrecognition

Experimental results obtained using the ground-plane time-domain scattering ranges are presented. An experimental demonstration of the noise-insensitivity of the E/S pulse technique is also presented     

E-pulse diagnostics of simple layered materials

The feasibility of using the E-pulse technique to diagnose changes in the properties of simple layered materials is undertaken. Numerical results for a conductor-backed lossy slab and a Salisbury screen show that changes in permittivity, conductivity and thickness can be diagnosed in the presence of white Gaussian noise.     

Thiophosphoester analogs of phosphatidic acids: Spectrophotometric substrates for phosphomonoesterases

Thiophosphoester analogs of dioctanoyl and didecanoyl phosphatidic acids were synthesized for use as substrates in spectrophotometric assays. These substrates are easily dispersable in aqueous media and release thiodiacylglycerols after phosphomonoesterase catalyzed hydrolysis. The free sulfhydryl of these thiodiacylglycerols reacts with the colorimetric reagent 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB), allowing the reaction to be followed. These analogs were shown to be good substrates for calf intestine alkaline phosphatase (highest activity at alkaline pH) and phosphomonoesterases of partially purified beef brain cytosol (highest activity at physiologic pH). Cationic amphiphilic drugs inhibit the actions of alkaline phosphatase on the dioctanoyl analog, but did not inhibit enzymatic hydrolysis ofp-nitrophenyl phosphate. In contrast, the beef brain cytosolic fractionp-nitrophenyl phosphate hydrolysis was mildly inhibited, and the phosphatidic acid analog hydrolysis was increased slightly. Tetramisole inhibited all enzyme activities withp-nitrophenyl phosphate, but was inhibitory only to the alkaline-phosphatase activity with the phosphatidic acid analog. This research was completed as partial fulfillment of the Ph.D. degree, awarded August, 1987, at Northern Illinois University, DeKalb, IL.     

Broad-band reduction of back-scattering from a thin cylinder

A theoretical and experimental study is made on the wide-band minimization of backscattering from a thin cylinder with a purely reactive central loading. It is concluded that relatively wide minimization bandwidths can be achieved by implementing the reactance loading by a coaxial cavity of high characteristic impedance.