The specificity of molecular and functional photoacoustic (PA) images depends on the accuracy of the photoacoustic absorption spectroscopy. The PA signal is proportional to the product of the optical absorption coefficient and local light fluence; quantitative PA measurements of the optical absorption coefficient therefore require an accurate estimation of optical fluence. Light-modeling aided ...

Being able to heat and cool the absorption cell of a spectrometer has many benefits. Cooling simplifies the spectrum of the gas in the cell by freezing out rotational and vibrational motion of the gas molecules, while heating increases the population of the excited ro-vibrational states. We designed and prototyped a heating and cooling system for the absorption cell of the FASSST spectrometer [...

When naval mine-hunting sonars and side-scan surveying sonars operating at 20~60 kHz are working in shallow coastal waters, the visco-thermal absorption of sound by suspended mud in the water may greatly decrease their detection properties. This kind of water is also characterized as turbid seawater. However, the research on measuring the coefficient of sound absorption in turbid seawater has l...

The optical properties of turbid media were calculated from the curvature at the radial distance ρ(O) and the slope at the radial distance ρ* of simulated spatially resolved reflectance curves (ρ(O) (ρ*) denotes a decrease of the spatially resolved reflectance curve of 0.75 (2.4) orders of magnitude relative to the reflectance value at 1.2 mm). We found correlations between the curvature at ρ(O...

This paper reports on the effect of fiber crimp frequency on sound absorption capability of staple polypropylene nonwoven batts. Stuffer box was used to impart crimp to spun tow. Crimping of the tow renders the fibers the required textile applicability. In this work, polypropylene batts composed of staple fibers with linear densities of 9, 14, and 18 denier were employed. Three crimp frequency ...

National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 With the recent developments in Fourier transform infrared (FTIR) spectrometers it is becoming more feasible to place these instruments in field environments. As a result, there has been enormous increase in the use of FTIR techniques for a variety of qualitative and quantitative chemical measurements. These methods off...