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Noninvasive monitoring of cardiac development can potentially prevent cardiac anomalies in adulthood. Mouse models provide unique opportunities to study cardiac development and disease in mammals. However, high‐resolution noninvasive functional analyses of murine embryonic cardiac models are challenging because of the small size and fast volumetric motion of the embryonic heart, which is deeply embedded inside the uterus. In this study, a real time volumetric optoacoustic spectroscopy (VOS) platform for whole‐heart visualization with high spatial (100 µm) and temporal (10 ms) resolutions is developed. Embryonic heart development on gestational days (GDs) 14.5–17.5 and quantify cardiac dynamics using time‐lapse‐4D image data of the heart is followed. Additionally, spectroscopic recordings enable the quantification of the blood oxygenation status in heart chambers in a label‐free and noninvasive manner. This technology introduces new possibilities for high‐resolution quantification of embryonic heart function at different gestational stages in mammalian models, offering an invaluable noninvasive method for developmental biology. [ABSTRACT FROM AUTHOR]

Model studies of the optimal phase matching conditions are performed for the implementation of an optical parametric oscillator (OPO) in the mid-infrared range (IR) based on promising nonlinear crystals, such as: cadmium selenide CdSe, barium selenogallates BaGa4Se7 and BaGa2GeSe6, mercury thiogallate HgGa2S4 and zinc germanium phosphide ZnGeP2 (ZGP). To pump OPOs, it is necessary to use a laser source with a wavelength in the spectral range of 1.9–2.2 μm, since for the combination of physical properties of the listed above nonlinear crystals, it is optimal for achieving the maximum efficiency of parametric frequency conversion. Despite the high values of the effective nonlinear susceptibility and thermal conductivity, the transparency range of the ZGP crystal in the mid-IR range does not exceed 10.4 μm, and the achieved OPO generation wavelength range does not exceed 9 μm in the nanosecond mode. The HgGa2S4 and BaGa4Se7 crystals have lower values of nonlinear coefficients and thermal conductivity and wider transparency ranges and, as a consequence, make it possible to obtain lasing up to a wavelength of 12 μm. When using a BaGa4Se7 crystal, the lasing range can be extended up to 17 μm. The CdSe crystal has the widest transparency range. However, its other parameters do not allow solving the set tasks. [ABSTRACT FROM AUTHOR]

Optoacoustic signals induced by pulsed laser radiation (pulse width at half maximum 14 ns) with a wavelength of 532 nm are experimentally obtained in pressed cyclotrimethylenetrinitramine (RDX)–ultrafine nickel particle composites, and the observed parameters of radiation absorption at average particle radii of 40, 60, 80, and 140 nm are determined. It is shown that the dependence of the experimental absorption index on the particle radius with a constant mass fraction is a nonmonotonic function. The results are interpreted within the framework of the theory of monochromatic radiation transfer. It is shown that the agreement between the experimental and calculated absorption index values of pressed RDX–ultrafine nickel particle tablets with different radii is achieved when the residual porosity of the sample is taken into account. The mean pore radius and the concentration of pores are estimated. [ABSTRACT FROM AUTHOR]

Determination of chromophores of various classes—rosaniline (fuchsine), cyanidin-3-O-glucoside, tris (1,10-phenanthroline) iron(II), and phenol red — in their concentrated solutions near their solubility limits is performed with the optoacoustic technique for optically dense solutions; light-absorption coefficients of samples range from 0.5 to 500 cm –1 . The assessment of these substances in organo-aqueous and organic solvents is possible up to ca. 0.1 mol L –1 . Characteristic stability and rate constants of the chelation of iron(II) with 1,10-phenanthroline are determined. It was found that turbidities up to 200 FTU and dynamic viscosities up to 20 mPa s do not affect the determination. The determination of total anthocyanins (as cyanidin-3-O-glucoside) in bilberry and sweet-cherry juices agrees with the reference spectrophotometric method and demonstrates the possibilities of the optoacoustic technique for the analysis of real samples without dilution and with almost no sample preparation. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a spectroscopic characterisation method based on the optoacoustic technique has been used to investigate the optical properties of two separate spherical gold nanoparticle (SGNP) solutions where an absorption peak located at 520nm has been observed. This analysis has been carried out over the visible wavelength range from 410 to 650nm using a Q-switched Nd:YAG pumped optical parametric oscillator (OPO). To verify the reliability of optoacoustic spectroscopy (OAS), the results obtained have been compared to those from more standard and limited spectrophotometer and reference collimated optical transmission schemes, where good agreement is shown. The experimental procedure presented here demonstrates the potential of this technique for integration along with optoacoustic imaging methods to identify physiological information for non-destructive in-vivo applications. [ABSTRACT FROM AUTHOR]

Abstract: As a primary aim, several approaches to photothermal (thermal-lens) and optoacoustic determination of exogenous pyrogens (lipopolysaccharides) based on photometric procedures for their determination at the microgram level and below are compared. The limits of detection of lipopolysaccharides by thermal-lens spectrometry and optoacoustic spectroscopy are at a level of 2–100ng/mL, and the conditions of optoacoustic and photothermal procedures are the same. Optoacoustic spectroscopy is advantageous in determining suspensions, while thermal lensing is superior in determining lipopolysaccharides from homogenous aqueous solutions. As a secondary aim, photometric procedures for lipopolysaccharides by the formation of their ion pairs with several dyes and by the reaction of 2-keto-3-deoxyoctulosonic acid as a part of a lipopolysaccharide molecule with thiobarbituric acid are optimized. In the case of the 2-keto-3-deoxyoctulosonic acid reaction, the sampling stage time is decreased twofold, and the possibility of substitution of the toxic metaarsenite for sulfite with better sensitivity is shown. [Copyright &y& Elsevier]

In this work we present results of an investigation on Doppler limited infrared absorbing transitions of CHD2OH by optoacoustic detection. It is an alternative and attractive technique to be applied to this methanol isotopomer, in comparison to Fourier transform spectroscopy. Using a waveguide CO2 laser of 290 MHz tunability on each line, we were able to observe 60 IR absorptions, most of them of large offset. The data will be useful in the theoretical analysis of this molecule, as well as in the generation of far-infrared (FIR) laser radiation in optically pumped molecular lasers. [ABSTRACT FROM AUTHOR]

The propagation of ultrasound in a one-dimensional model and actual periodic structures (PSs) is studied experimentally by the method of optoacoustic spectroscopy based on the laser thermooptical excitation and wide-band piezodetection of short acoustic pulses. It is shown that the ultrasound transmission spectrum of a PS has stop and pass bands, and the greater the number of layers in the PSs, the deeper the stop bands. The case where the thickness, density, and ultrasound velocity of one or several layers in the PS are modified is studied in detail. In this case, a narrow local maximum of ultrasound transmission appears in the stop band, whose location depends considerably on the position of the “defective” layer in the PS. The experimental data obtained coincide well with the theoretical calculation. The nondestructive evaluation of actual PSs consisting of two epoxy-glued identical aluminum plates is carried out by the optoacoustic method. Such materials are widely used in aircraft industry. It is shown that the ultrasound transmission spectrum for these materials depends considerably on the thickness of the epoxy-glue layer. [ABSTRACT FROM AUTHOR]

In this work we present the results of an investigation about Doppler limited infrared absorbing transitions of the in-plane methyl-rocking and the asymmetric methyl deformation modes of 13CD3OD by means of optoacoustic detection. This is an alternative and attractive technique to be applied to this methanol isotopomer, in comparison to Fourier transform spectroscopy. In fact the contamination problem associated with the fast exchange of OD by OH in the molecule limits the use of the Fourier transform technique. Using a waveguide CO2 laser of 290 MHz tunability on each line we were able to observe 20 IR absorptions, most of them of large offset. The data will be useful in theoretical analysis of this molecule, as well as in the generation of FIR laser radiation in optically pumped molecular laser. [ABSTRACT FROM AUTHOR]

After briefly reviewing the theory and instrumentation, results from a variety of experiments carried out by the authors on the photoacoustic spectroscopy of solids and surfaces by employing an indigenous spectrometer are discussed in the light of the recent literature. Some of the important findings discussed are, phase angle spectroscopy, anomalous behaviour of monolayers, unusual frequency dependence in small cell volumes, spectra of a variety of solids including amorphous arsenic chalcogenides, photoacoustic detection of phase transitions and determination of surface areas and surface acidities of oxides. Recent developments such as piezoelectric photoacoustic spectroscopy, depth profiling and subsurface imaging are also presented. [ABSTRACT FROM AUTHOR]