Infrared multiphoton chemistry: Comparison of theory and experiment,solution of the master equation

An energy-grained master equation has been used to model the multiphoton pumping process in SF₆. It was found that an energy-dependent absorption cross section that was approximately inversely dependent on the level of excitation was needed to reproductive experimental data on the fraction decomposed per pulse.     

The hearing aid feedback path: mathematical simulations and experimental verification

Acoustic feedback in hearing aids has received little attention in the literature. Feedback occurs when stability conditions of the open-loop transfer function of an in situ hearing aid are violated. Solving the feedback problem will first require knowledge of the open-loop transfer function. Included in the open-loop transfer function is the acoustical path by which sound emanating from the earmold vent returns to the microphone (i.e., the feedback path). Reported herein are two different mathematical procedures for simulating transfer functions of the feedback path of an eyeglass-type hearing aid. In one procedure the vent exit was modeled as a point source of sound located on a flat plane, while it was treated as a point source on a sphere in the other. Results of laboratory experiments indicate that the mathematical models accurately predict those acoustic phenomena for which they were intended: point sources on plane and spherical baffles. Results of manikin experiments showed both models to be less accurate for simulating the feedback path around the human head. The maximum difference between experiment and theory was 6 dB at one frequency. Surprisingly, the flat-baffle model produced better agreement with experimental results than did the sphere model.     

Infrared multiphoton dissociation yields via a versatile new technique: intensity,fluence, and wavelength dependence for CF3I

Intensity, fluence, and wavelength dependence of the collisionless infrared multiphoton dissociation yield for CF₃I have been determined via “titration” of radical photoproducts and molecular-beam-sampling-mass spectrometry. The importance of nonlinear effects in the pumping of this molecule is confirmed.     

Oxindoles from α-acyloxyamides

Oxindoies have been obtained in good yields from the reaction of several a-acyloxy-α,α-diphenylacetanilides and boron trifluoride etherate. The reaction probably occurs by hydrolysis of the ester followed by electrophilic substitution of the resultant carbonium ion on the anilide ring.     

Semiautomated quality assurance for quantitative magnetic resonance imaging.

It is now well established that MRI can be used for quantitative (as opposed to simply qualitative) measurements, and good accuracy and precision have been obtained in phantom experiments. To make routine quantitative measurements as part of a clinical scanning protocol, however, quality assurance (QA) methods particularly suited to quantification must be developed. We describe a set of QA tests using clinical protocols on test phantoms, with which we have assessed quantitative performance of our Picker 0.5-T scanner (Picker International, Cleveland, OH) over 2 years. We also describe the automated data processing methods we have developed to deal with the large amounts of data generated by these tests.     

A quasi-classical formulation of the Wigner function approach to quantum ballistic transport

The time evolution of Wigner's function is shown to be a linear superposition of classical distributions unfolded by a family of classical hamiltonians.     

Acceleration-dependent lagrangians and equations of motion

Acceleration terms in a lagrangian are sometimes eliminated by substituting into the lagrangian the equations of motion which were obtained from the lagrangian. We show that, in general this is an incorrect procedure. In addition, we present a new correct procedure, which we call the method of the double zero.     

Importance of the polarization forces in He-metal surface interaction potential

In this paper we describe coupled channel calculation for atom-surface scattering for arbitrary potentials. We study, for the first time, the effect of the polarization-van der Waals forces. It is concluded that these forces are important for defining the repulsive part of the atom-metal surface potential. We study the He-Ni (110) system and present good agreement with experimental data for energies between 20 and 250 meV.