Advancing our understanding of human coronary artery disease requires new methods that can be used in patients for studying atherosclerotic plaque microstructure in relation to the molecular mechanisms that underlie its initiation, progression, and clinical complications, including myocardial infarction and sudden cardiac death. Here we report a dual-modality intra-arterial catheter for simultaneous microstructural and molecular imaging in vivo using a combination of optical frequency domain imaging (OFDI) and near-infrared fluorescence (NIRF) imaging. By providing simultaneous molecular information in the context of the surrounding tissue microstructure, this novel catheter could provide new opportunities for investigating coronary atherosclerosis and stent healing, and for identifying high-risk biological and structural coronary arterial plaques in vivo.

A new model equation has been obtained which permits a kinetic description of gases possessing internal degrees of freedom. The collision term of the model equation is related to the Wang-Chang and Uhlenbeck results for polyatomic gases much in the same manner as the Bhatnagar, Gross, and Krook model is related to the Boltzmann collision integral. A modified perturbation technique utilizing the various time scales of the flow situation has been employed in closing the equations of change. (This has been shown to be asymptotically equivalent to the Chapman-Enskog expansion of the time derivative.) From the model equation and its moments, depending upon the ratio of a ``flow through'' time to the inelastic relaxation time, one directly obtains either the bulk viscosity as a term modifying the pressure tensor, or a relaxation equation for the internal temperature. The model also accounts for the contribution to the heat transfer vector due to the presence of internal degrees of freedom. In this theory, the inelastic relaxation time appears as a parameter of the system. It is hoped that this model may serve the same function for aerodynamic and kinetic boundary value problems for gases with internal degrees of freedom that the Bhatnagar, Gross, and Krook model has for the simple gas.

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The energy and momentum relaxation of a nonequipartition gas mixture is considered. It is assumed that each component of the mixture has a Maxwellian distribution at a temperature Ti, with the peculiar velocity of the Maxwellian measured relative to the mean velocity of the ith species. For the case in which a ``diffusion'' Mach number is not too large, the results have a particularly simple form. The calculations were carried out for the hard sphere, Coulomb, and Maxwell force laws of interaction. It is also noted how these results may be used to construct kinetic model equations for the case of hard sphere and Coulomb interaction, in a manner similar to that proposed by Sirovich.