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Oxygen (O₂) concentration inside the substrate is an important measurement for silage-research and-practical management. In the laboratory gas chromatography is commonly employed for O₂ measurement. Among sensor-based techniques, accurate and reliable in situ measurement is rare because of high levels of carbon dioxide (CO₂) generated by the introduction of O₂ in the silage. The presented study focused on assessing three types of commercial O₂ sensors, including Clark oxygen electrodes (COE), galvanic oxygen cell (GOC) sensors and the Dräger chip measurement system (DCMS). Laboratory cross calibration of O₂ versus CO₂ (each 0-15 vol.%) was made for the COE and the GOC sensors. All calibration results verified that O₂ measurements for both sensors were insensitive to CO₂. For the O₂ in situ measurement in silage, all O₂ sensors were first tested in two sealed barrels (diameter 35.7 cm; height: 60 cm) to monitor the O₂ depletion with respect to the ensiling process (Test-A). The second test (Test-B) simulated the silage unloading process by recording the O₂ penetration dynamics in three additional barrels, two covered by dry ice (0.6 kg or 1.2 kg of each) on the top surface and one without. Based on a general comparison of the experimental data, we conclude that each of these in situ sensor monitoring techniques for O₂ concentration in silage exhibit individual advantages and limitations.

Highlights • The accuracy and dynamic range of a dual-wavelength laser-based DIAL measurement extend with simultaneously transmission and detection the spectrally closed "on" and "off" wavelengths; in addition to size, weight, and cost reduction. • Differential absorption lidar (DIAL) equipped with the dual-wavelength laser at 762 nm (on-wavelength) and 773 nm (off-wavelength) on 3D remote measurement of oxygen molecules, O 2. • A concentration of less than 1 ppm by volume is detectable by the system if a path length of 1 km is used. • The system can be used from a satellite to quickly characterize O 2 in H 2 O matrices on outer solar system bodies. • The wavelengths 762 nm and 773 nm lay in the water-window region (650–1350 nm) enabling system for laser remote sensing dissolved oxygen in water. Abstract Recently, we have demonstrated a longitudinally pumped tunable dual-wavelength Ti:sapphire laser that can operate at simultaneous dual-wavelength (765.0, 771.3 nm), (763.9, 772.2 nm), (763.5, 772.2 nm) and (762.4, 773.7 nm) with a pulse width of ∼20 ns and a maximum average power of ∼2.98 W at 1-kHz pulse repetition rate, corresponding to a slope efficiency of ∼34.7% [1]. In this paper, the feasibility of the contactless differential absorption lidar (DIAL) equipped with the dual-wavelength laser emitting at 762 nm (on-wavelength) and 773 nm (off-wavelength) on remote 3D-measurement of molecular oxygen, O 2 , has been investigated. Absorption by atmospheric oxygen A-band at 761.9 nm corresponds to the magnetic dipole transition b 1 Σ b + (v ′ = 0) ← X 3 Σ g − (v ″ = 0) with absorption cross section of 5.749 × 10−3 cm−2 atm−1 at STP. The accuracy and dynamic range of the DIAL measurement can be extended by simultaneous transmission and detection the spectrally close "on" and "off" wavelengths generated in a compact single laser, in addition to reduce the cost, volume, and weight of the system. The results demonstrate that a concentration of less than 1 ppm by volume is detectable by the system if a path length of 1 km is used. It is noticeable that the wavelengths 762 nm and 773 nm in the near-infrared window spectral range (650–950 nm) allow lidar system to monitor dissolved oxygen in ambient water. This system can also be used from a satellite to quickly characterize O 2 in H 2 O matrices in the outer solar system bodies. [ABSTRACT FROM AUTHOR]

Three-dimensional periodic molecular models of amorphous cis-1,4-polybutadiene ( cis-PBD) were constructed using the Materials Studio (MS)® software to study the effects of temperature on the diffusion of oxygen (O2). The radial distribution function, solubility parameter and others clearly proved the three-dimensional periodic molecular model was able to reproduce bulk experimental data of the authentic materials. The volume fraction of accessible oxygen was reckoned by fractional free volume with a probe radius of 1.8 Å. The diffusion coefficients (D) of O2 were calculated, and researches on the diffusion mechanism were made. Data obtained corresponded with the trend from available experiments and previously published simulation work. The results confirmed the accelerating effect of high temperatures on the diffusion of O2 and meanwhile suggested the favourable binding sites of thermo-oxidative aging reactions. Our findings have an important significance for promoting the development of membrane separation technology and provide valuable guidance for further research on thermo-oxidative aging of cis-PBD. [ABSTRACT FROM AUTHOR]

Highlights: [•] Impact of CO2 on dissolution rate under conditions emulating wine fermentations. [•] CO2 bubbling increases the volumetric mass transfer coefficient. [•] CO2 bubbling reduces oxygen solubility. [•] Overall, CO2 bubbling reduces oxygen dissolution rate. [ABSTRACT FROM AUTHOR]

Abstract: We observed electric quadrupole transitions in the O2 A-band, b 1Σg +←X 3Σg −(0,0), in high solar zenith angle atmospheric spectra recorded with the high-resolution solar-viewing Fourier transform spectrometer at Park Falls, WI. We identified 12 ΔN=±3 transitions for the first time, including the first detection of N O-branch transitions and extended the T S-branch observations of Brault [J Mol Spectrosc 1980;80:384–8] up to N″=23. Additionally, we observed six electric quadrupole transitions of the ΔN=−1 P O-branch. These observations demonstrate the excellent sensitivity and long-term stability of the new generation of solar-viewing Fourier transform spectrometers. [Copyright &y& Elsevier]

Abstract: The reaction mechanisms of CF and CCl with O2 have been investigated theoretically on the doublet potential energy surfaces (PESs). The QCISD/6-311++G(d,p) single-point calculations are performed using the B3LYP/6-311++G(d,p) optimized geometries to accurately determine the energetics. The two product channels, F+CO2 and FCO+O, have been found in the CF+O2 reaction. The former is more competitive because the formation pathway of it undergoes fewer reaction steps and lower barriers than that of FCO+O. In the case of the CCl+O2 reaction, the two similar channels of Cl+CO2 and ClCO+O have also been identified, and the first is less preferable. The title reactions in question are of practical significance in high-temperature processes, because the initial associations are barrier-present. This paper also discusses the effects of halogenations on the reactivity, the reaction pathways, the product channels and the reaction enthalpies of the three CX+O2 reactions (X=H, F or Cl). The reactivity of CX+O2 decreases in the order of CH, CF and CCl. [Copyright &y& Elsevier]