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Fast Photoacoustic Imaging Technology
Published in Sihua Yang, Da Xing, Biomedical Photoacoustics, 2020
PAI technology of in vitro rat cardiac lesion group applied in ex vivo organs of small animals [19]. We used PAT to visualize infarcted areas within mouse hearts and compared it to other imaging techniques (MRI and CT). In order to induce ischemia, an in vivo ligation of the Ramus interventricularis anterior (RIVA, left anterior descending, LAD] was performed on nine wild type C41 mice. After varying survival periods, the mice were sacrificed. The hearts were excised and immediately transferred into a formaldehyde solution for conservation. Various wavelengths in the visible and near infrared region (500-1000 nm) had been tested to find the best representation of the ischemic regions [19]. Samples were exposed by nanosecond laser pulses delivered by an Nd:YAG pumped optical parametric oscillator. Ultrasound detection was achieved by an optical Mach-Zehnder interferometer, working as an integrating line detector. The samples were located inside a water tank. The voxel data are computed from the measurement data by a Fourier domain-based reconstruction algorithm, followed by a sequence of inverse Radon transforms. Results clearly indicate the capability of PAI to detect pathological tissue and the possibility to produce three-dimensional images with resolutions below 100 |im. Different wavelengths allow the representation of structure inside an organ or on the surface even without contrast-enhancing tracers.
Matrix Isolation Spectroscopy in Helium Droplets
Published in Leonid Khriachtchev, Physics and Chemistry at Low Temperatures, 2019
Kirill Kuyanov-Prozument, Dmitry Skvortsov, Mikhail N. Slipchenko, Boris G. Sartakov, Andrey Vilesov
Schematic of a helium droplet experiment is shown in Fig. 1. Helium droplets are produced in free jet expansion of gaseous He at temperature T0 = 20–6 K and at source pressure of P0 = 5–20 bar through a 5-μm diameter nozzle. The expanding He gas in the jet is cooled and condenses into droplets. The formed droplets enter the high-vacuum part of the apparatus, where they undergo further cooling by evaporation until they reach the measured temperature of 0.37 K.7,8 After the droplets have captured one or more molecules in the pickup cell they are exposed to the laser beam, which enters the apparatus coaxially and counter-propagates to the beam of droplets, providing an optimal overlap of the two beams. Upon the absorption of a laser photon, the droplet size decreases due to evaporative loss of helium atoms as the photon energy, deposited in the chromophore, relaxes and temporarily heats the droplet. The absorption signal is detected as a decrease (depletion) of the mass spectrometer signal. Most of the infrared spectra shown in this chapter are obtained using a pulsed optical parametric oscillator–amplifier laser setup.
Imaging Based on Absorption and Ion Detection Methods
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
In a similar type of study, Tang et al. (2016) used IR-AFM to investigate the compositions of nanodomains of another copolymer material, the so-called high-impact polypropylene (HIPP). In HIPP alloys, “rubber” particles with multilayered core–shell structure are dispersed in the polypropylene (PP) matrix. The rubber particles (size submicrometers to a few micrometers) have a “rigid” core and a “soft” (rubbery) intermediate layer. In their study, the authors used an optical parametric oscillator laser system (OPO, tunable over the range ν˜ = 900–2000 cm−1 and with spectral resolution Δν˜ = 4 cm−1) as the excitation source. The thermal expansion of the sample following absorption by specific molecular vibrational bands was measured with the AFM tip, raster scanning the sample area of interest.
The hygroscopic properties of biomass burning aerosol from Eucalyptus and cow dung under different combustion conditions
Published in Aerosol Science and Technology, 2023
Megan Mouton, Kotiba A. Malek, Markie’Sha H. James, Rudra P. Pokhrel, Marc N. Fiddler, Akua A. Asa-Awuku, Solomon Bililign
Aerosol sampled from the chamber entered a ring-down cavity (170 cm long, stainless steel, ½" OD) and the aerosol light extinction was measured at 550 nm. The laser components of the system included a Continuum Surelite I-20 Nd:YAG laser running at 20 Hz. The 355-nm beam pumped an optical parametric oscillator (OPO) laser. Additional details of the CRDS and set-up are described in our previous work (Singh et al. 2014; Singh, Fiddler, and Bililign 2016; Smith et al. 2019). The CRDS was operated under four different conditions to subtract background and calculate the change in ringdown time. Each condition was conducted for approximately three minutes and rotated through for each RH measurement. Specifically, (a) whole chamber air was sampled, (b) air was sampled via a drier (water vapor was removed), (c) air was sampled via a drier and a high efficiency particle air (HEPA) filter (water vapor and particles were removed), and (d) air was sampled via a HEPA filter (particles were removed). Extinction measurements were taken at 0% RH, 40% RH, and then several measurements between 78–92% RH. Zero and 40% RH measurements are representative of dry conditions (as defined by the World Meteorological Organization (WMO 2016)).
Controlled preparation and vibrational excitation of single ultracold molecular hydrogen ions
Published in Molecular Physics, 2022
Christian Wellers, Magnus R. Schenkel, Gouri S. Giri, Kenneth R. Brown, Stephan Schiller
Finally, we point out that a major improvement in MHI spectroscopy would be the introduction of a nondestructive state detection technique that consequently allows to reuse the same molecular ion for multiple spectroscopy cycles, effectively reducing the spectroscopic data acquisition time. This will also reduce the number of loading events and hence the total experimentation time. Evidence that a heteronuclear MHI in an MHI-Be ion pair is in a particular rovibrational state should be obtainable by coherently exciting the motion of the ion pair using an intense standing-wave near-resonantly tuned to a fundamental or low-overtone vibrational transition [23,34]. A suitable laser for this purpose appears to be a high-power continuous-wave optical parametric oscillator.
Study of the 71Π u state of sodium dimer by polarisation labelling spectroscopy
Published in Molecular Physics, 2022
P. Kowalczyk, A. Grochola, W. Jastrzebski
The pump beam originated from the optical parametric oscillator and amplifier system (OPO/OPA, Sunlite Ex, Continuum) equipped with a frequency doubler (FX-1) and pumped with the third harmonic of an injection seeded Nd:YAG laser (Powerlite 8000). This system delivered UV pulses of 3 mJ energy, 10 ns duration and spectral width below 0.16 cm. The pump pulses, tuned in the spectral range 34, 600−39, 400 cm, induced transitions from the ground state of Na to the excited state under investigation, but only transitions originating from the labelled levels were detected. The frequency of the pump beam was calibrated by measuring two additional signals: optogalvanic spectrum of argon and transmission fringes of a Fabry–Pérot interferometer with a free spectral range of 1 cm (for this purpose the fundamental frequency of tuneable OPO/OPA radiation was employed). In this way, we could determine absolute wave numbers of spectral lines with an uncertainty below 0.1 cm.