Using a low-cost infrared light source and a selection of narrowband filters, the non-resonant photoacoustic device is able to detect CO, SO₂ and CF₄ in SF₆ down to a few ppm.

The concentration of trace gases in the atmospheric environment is extremely low, but it has a great impact on the living environment of organisms. Photoacoustic spectroscopy has attracted extensive attention in the field of trace gas detection because of its high sensitivity, good selectivity, and fast response. As the core of a photoacoustic detection setup, the photoacoustic cell has a significant impact on detection performance. To improve detection sensitivity, a sphere-tube coupled photoacoustic cell (STPAC) was developed, which was mainly composed of a diffuse-reflective sphere and an acoustic resonance tube. Modulated light was reflected multiple times in the sphere to increase optical path, and photoacoustic (PA) signals were further amplified by the tube. Based on STPAC, a PA gas detection setup was built with a laser diode (LD) at 450 nm as the light source. The experimental results showed that the minimum detection limit (noise equivalent concentration, NEC) of NO₂ was ~0.7 parts per billion (ppb). Compared with the T-type PA cell (TPAC) in which the modulated light passed through the sphere, the signal-to-noise ratio of STPAC was increased by an order of magnitude at the same concentration of the NO₂ sample.

In this paper, CO was taken as an example to analyze the impact mechanism of temperatures and the temperature correction formula of its response factor was derived. The real temperature properties of SF₆ and CO were studied using a non-resonant PA spectroscopy device designed by our team.

Atmospheric aerosols play a pivotal role in the earth-atmospheric system. Analyzing their optical properties, specifically absorption and scattering coefficients, is essential for comprehending the impact of aerosols on climate. When different optical properties of aerosols are individually measured using multiple devices, cumulative errors in the detection results inevitably occur. To address this challenge, based on photoacoustic spectroscopy (PAS) and integrating sphere (IS) scattering enhancement, a compact gas cell (PASIS-Cell) was developed. The PASIS-Cell comprises a dual-T-type photoacoustic cell (DTPAC) and an IS. IS is coupled with DTPAC through a transparent quartz tube, thereby enhancing the scattering signal without compromising the acoustic characteristics of DTPAC. Concurrently, DTPAC can realize high-performance photoacoustic detection of absorption signal. Experimental results demonstrate that PASIS-Cell can simultaneously invert atmospheric aerosol absorption and scattering coefficients, with a minimum detection limit of less than 1 Mm^-1, showcasing its potential in the analysis of aerosol optical properties.

To detect non-polar, infrared-inactive hydrogen, a Differential Photoacoustic-Stimulated Raman Spectroscopy (DPA-SRS) method is proposed. Utilizing the SRS process, a portion of the pump light is converted into intense Stokes light corresponding to the hydrogen Raman shift, eliminating complex dual-laser configurations. The nonlinear thermoacoustic effect is excited by this dual-color light field, endowing Photoacoustic Spectroscopy with the capability for hydrogen fingerprint identification. Raman cell pressure was optimized to achieve a synergistic enhancement of the Stokes conversion efficiency and the Four-Wave Mixing effect. Furthermore, an acoustic mode-optimized differential H-type resonant photoacoustic cell was designed, which effectively enhances anti-interference capability through the differential detection mechanism. Distinct from traditional lock-in amplification methods, a time-frequency transformation algorithm was employed to precisely extract the frequency-domain photoacoustic signal from the broadband time-domain acoustic signal. Experimental results demonstrate that the DPA-SRS system exhibits excellent linearity and achieves a Limit of Detection of 0.65 ppm under atmospheric conditions.

To investigate the protective effects of Notch1 on myocardial ischemia reperfusion injury and explore underlying molecular mechanism. H9c2 cells were exposed to hypoxia/reoxygenation (H/R), ischemic preconditioning (IPC) and ischemic postconditioning (IPost) treatment following infection with lentiviral vector-Notch1 intracellular domain (Lv-N1ICD) or Lv-N1ICD-shRNA, and divided into control group, H/R group, H/R+ N1ICD group, IPC group, IPC+ N1ICD-shRNA group, IPost group, IPost+ N1ICD-shRNA group, respectively. Apoptosis was detected by Annexin V/propidium iodide (PI), and reactive oxygen species (ROS) was detected by 2', 7'dichlorofluorescin-diacetate (DCFH-DA). The expression of p-glycogen synthase kinase-3β (p-GSK-3β)/GSK-3β were detected by Western blot analysis. The apoptosis rate of cardiomyocytes in control group, H/R group, H/R+ N1ICD group, IPC group, IPC+ N1ICD-shRNA group, IPost group, IPost+ N1ICD-shRNA group was (5.34±1.70)%, (47.03±4.10)%, (33.89±12.25)%, (35.85±3.17)%, (51.12±8.22)%, (37.35±3.82)%, (47.90±3.08)%, respectively, showing significant differences in all group (F=18.47, P<0.05). ROS in control group, H/R group, H/R+ N1ICD group, IPC group, IPC+ N1ICD-shRNA group, IPost group, IPost+ N1ICD-shRNA group was 624.66±79.52, 1 221.87±63.66, 913.12±115.82, 935.85±201.62, 1 204.03±113.82, 967.15±106.11, 1 296.59±222.38, respectively, showing significant differences in all group (F=8.77, P<0.05). The ratio of p-GSK-3β to GSK-3β in control group, H/R group, H/R+ N1ICD group, IPC group, IPC+ N1ICD-shRNA group, IPost group, IPost+ N1ICD-shRNA group was 0.58±0.12, 0.62±0.20, 1.24±0.09, 1.16±0.12, 0.72±0.15, 1.16±0.12, 0.75±0.12, respectively, showing significant differences in all group (F=11.21, P<0.05). As an endogenous cardioprotective factor, Notch1 reduces myocardial ischemia reperfusion injury by promoting GSK-3β phosphorylation, inhibiting cardiomyocyte apoptosis and reducing ROS formation.