Spectroscopic Depth Profiling Using Thermal Waves

Miller, Richard M.

doi:10.1007/978-3-642-83945-0_7

Topics in Current Physics

1989

DOI: 10.1007/978-3-642-83945-0_7

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Spectroscopic Depth Profiling Using Thermal Waves

Richard M. Miller¹

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Cited by 2 publications

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FT-IR photoacoustic depth profiling spectroscopy of enamel

Sowa

Mantsch

1994

Calcif Tissue Int

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Photoacoustic Fourier transform infrared (PA-FT-IR) depth profiling spectra of the enamel of an intact human tooth are obtained in a completely nondestructive fashion. The compositional and structural changes in the tissue are probed from the enamel surface to a depth of about 200 microns. These changes reflect the state of tissue development. The subsurface carbonate gradient in the enamel could be observed over the range of about 10-100 microns. The carbonate-to-phosphate ratio increases in the depth profile. The depth profile also reveals changes in the substitutional distribution of carbonate ions. Type A carbonates (hydroxyl substituted) increase relative to type B carbonates (phosphate substituted) with increasing thermal diffusion length. In addition to the changes in the carbonate ion distribution and content, the PA-FT-IR depth profile clearly indicates a dramatic increase in the protein content relative to the phosphate content with increased depth. The changes in the carbonate content and distribution, along with the changes in the protein content, may be responsible for the changes observed in the apatitic structure in the depth profile of the enamel.

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FT-IR photoacoustic depth profiling spectroscopy of enamel

Sowa

Mantsch

1994

Calcif Tissue Int

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Expectation Minimum (EM): A New Principle for the Solution of Ill-Posed Problems in Photothermal Science

Power

Prystay

1995

Appl Spectrosc

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The expectation-minimum (EM) principle is a new strategy for recovering robust solutions to the ill-posed inverse problems of photothermal science. The expectation-minimum principle uses the addition of well-characterized random noise to a model basis to be fitted to the experimental response by linear minimization or projection techniques. The addition of noise to the model basis improves the conditioning of the basis by many orders of magnitude. Multiple projections of the data onto the basis in the presence of noise are averaged, to give the solution vector as an expectation value which reliably estimates the global minimum solution for general cases, while the conventional approaches fail. This solution is very stable in the presence of random error on the data. The expectation-minimum principle has been demonstrated in conjunction with several projection algorithms. The nature of the solutions recovered by the expectation minimum principle is nearly independent of the minimization algorithms used and depends principally on the noise level set in the model basis.

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Spectroscopic Depth Profiling Using Thermal Waves

Cited by 2 publications

References 69 publications

FT-IR photoacoustic depth profiling spectroscopy of enamel

FT-IR photoacoustic depth profiling spectroscopy of enamel

Expectation Minimum (EM): A New Principle for the Solution of Ill-Posed Problems in Photothermal Science

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