The authors evaluated images obtained with a prototypic thermoacoustic computed tomographic (CT) scanner constructed for use at 434 MHz, a promising radio frequency for detecting breast cancer. In one excised porcine kidney, acoustic energy emanating from the kidney was detected with transducers. The resultant electric signals were used to create a three-dimensional data set. Two-dimensional images reconstructed in multiple planes were compared with state-of-the-art T1- and T2-weighted magnetic resonance images. The renal outline, parenchyma, and collecting system were clearly delineated on the thermoacoustic CT images.

Thermoacoustic CT with radio waves: a medical imaging paradigm.

Static secondary ion mass spectroscopy (fast atom bombardment mass spectroscopy), (SIMS (FABMS)) and Fourier transform infrared-photo-acoustic spectroscopy (FTIR-PAS) studies have been performed on samples of polypropylene subjected to different numbers of flame treatments. SIMS spectra allowed us to identify unambiguously the site of oxidation in the methyl pendant groups, because of the striking decrease in the intensity of the methyl fragment in positive-ion spectra. The behaviour of the surface concentrations of hydroxyl, formyl and carboxyl groups as a function of the number of flame treatments has also been observed, leading us to an hypothesis supporting the effectiveness of hydroxyl groups in promoting paint adhesion. FTIR-PAS spectra did not show evident changes on passing from untreated to flame-treated samples. This negative evidence is also important: it implies a limited depth of oxidation. In the light of previous XPS results and FTIR-PAS characteristics (thickness of the observed layer and sensitivity) we suggest a depth of oxidation of some 10 to 20 nm.

Surface effect of flame treatments on polypropylene

Surface effect of flame treatments on polypropylene: Part 2 SIMS (FABMS) and FTIR-PAS studies

6 – Analysis of Surfaces Exposed to Plasmas by Nondestructive Photoacoustic and Photothermal Techniques

Atmospheric chemical reactions are often initiated by ultraviolet (UV) solar radiation since absorption in that wavelength range coincides to typical chemical bond energies. In this review, we present an alternative process by which chemical reactions occur with the excitation of vibrational levels in the ground electronic state by red solar photons. We focus on the O–H vibrational manifold which can be an atmospheric chromophore for driving vibrationally mediated overtone-induced chemical reactions. Experimental and theoretical O–H intensities of several carboxylic acids, alcohols, and peroxides are presented. The importance of combination bands in spectra at chemically relevant energies is examined in the context of atmospheric photochemistry. Candidate systems for overtone-initiated chemistry are provided, and their lowest energy barrier for reaction and the minimum quanta of O–H stretch required for reaction are calculated. We conclude with a discussion of the major pathways available for overtone-induced reactions in the atmosphere.

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Sunlight-Initiated Photochemistry: Excited Vibrational States of Atmospheric Chromophores

During the past decade, photoacoustic spectroscopy has become a widely used spectroscopic tool. It has proved to be valuable in the investigation of the thermal and optical properties of a wide variety of samples, and in probing nonradiative deexcitations that follow a variety of excitations in matter.

Mohammadreza Hadjmohammadi

Papers

Use and Applications of Photoacoustic Spectroscopy