Raman Spectroscopy and Fluorescence Photon Migration for Breast Cancer Diagnosis and Imaging

We are developing optical methods based on near infra-red Raman spectroscopy and fluorescence photon migration for diagnosis and localization of breast cancer. We demonstrate the ability of Raman spectroscopy to classify accurately normal, benign and malignant breast tissues, an important step in developing Raman spectroscopic needle probes as a tool for improving the accuracy of needle biopsy. We also show that photon migration imaging can be used to localize accurately small fluorescent objects imbedded in a thick turbid medium with realistic optical properties, thus demonstrating the potential of this technique for optical imaging.     

A critical investigation of the effects of the radio frequency potential on the trapping of externally injected ions in ion trap mass spectrometry

The sensitivity of all ion trap mass spectrometry (ITMS) methods is dependent on the trapping efficiency of the instrument. For ITMS instruments utilizing external ion sources, such as laser desorption, trapping efficiency is known to depend on the phase and amplitude of the radio frequency (RF) potential applied to the ring electrode at the time of ion introduction. It is remarkable that, in a considerable body of literature, no consensus exists regarding the effects of these parameters on the efficacy of trapping externally generated ions. In this paper, a summary of the literature is presented in order to highlight significant discrepancies. New laser desorption ion trap mass spectrometry (LD-ITMS) data are also presented, from which conclusions are drawn in our effort to clarify some of the confusion. Copyright 1999 John Wiley & Sons, Ltd.     

Advancing the chromatography of GC/FT-IR to WCOT capillary columns

By the use of a wide-bore WCOT capillary column, it was possible to obtain the first on-the-fly GC/FT-IR spectra with a WCOT column. This wide-bore WCOT column gave improved separation, as compared to a SCOT column, and yielded identifiable infrared spectra for a real sample.     

Gaussian to flat-top intensity distributing lens

A system has been designed to convert the Gaussian intensity profile of a laser beam into a more uniform distribution. This paper postulates a number of afocal lens arrangements for this purpose and details the effect of one particular combination in balancing the higher-order terms and achieving collimation of a diffraction limited output between the l/e points.     

Photoelastic determination of stresses in multiple-pin connectors

The design, fabrication, and testing of photoelastic models of double-lap, multiple-pin connectors are discussed. Interest is in the stresses in the inner laps. These stresses are determined by constructing models with photoelastic inner laps and transparent-acrylic outer laps. The connectors have two pins, in tandem, parallel to the load direction. A photoelastic-isotropic point is shown to permit the evaluation of load sharing between the two pins. A numerical scheme, utilizing the isochromatic- and isoclinic-photoelastic data and a finite-difference representation of the planestress equilibrium equations, is used to compute the stresses around the two pins. Representative stress distributions and stress-concentration factors are shown.     

Raman spectra of several layer compounds with charge density waves

Raman scattering studies of the transition metal dichalcogenide layer compounds 1TTaS₂, 1TTaSe₂, 2H-TaSe₂ and 1TVSe₂ are reported. The materials were studied with commensurate and incommensurate charge density waves (CDWs) as well as in the absence of CDWs. Large qualitative changes observed in the Raman spectra are associated with the formation of CDWs and the change from an incommensurate to a commensurate phase.     

Raman measurements of the superionic conductor AgI

Using the Raman technique, we have observed large abrupt reversible changes in the phonon spectrum at the transition temperature, T_c = 147°C, of the superionic conductor AgI. The defect nature of the high temperature phase completely breaks down the selection rules and allows the Raman measurements to give a measure of the frequency dependent conductivity, σ(ω), assuming a frequency independent matrix element. Similarities as well as differences in σ(ω) above and below T_c are shown.     

Vertices of planar curves under the action of linear transformations

The number of vertices of a smooth Jordan curve with nowhere vanishing curvature can change under the action of a nonsingular real linear transformation. We examine the bifurcation set in the space of linear transformations for the number of vertices on the image curve, showing that generally there is a codimension-one set of linear transformations making an arbitrary point into a vertex, and obtaining conditions that the point be capable of being transformed into a higher vertex. We demonstrate that there is always an open set of linear transformations such that the image curves have at least six vertices. Received 23 July 1999; revised 17 March 2000.