Effect of a Hypoxia-Controlled Atmosphere Box on Egg Respiration Intensity and Quality

Egg preservation is an important factor during storage and transportation. Fresh eggs were stored in boxes in a controlled atmosphere with an O2 concentration of 0% O2 + 100% nitrogen (N2), 5% O2 + 95% N2, 10% O2 + 90% N2, 15% O2 + 85% N2, and 20% O2 + 80% N2, and the effects of these storage conditions on large quantities of eggs were studied. The respiratory intensity and quality of eggs during storage were measured. We chose the weight loss rate of eggs, Haugh unit, pH, and the egg white total plate count as the characteristic indices of egg quality. We compared the changes in egg quality during and after storage at different O2 concentrations versus that at 25 °C. The stages were evaluated using the TOPSIS method to sort egg quality, and the optimal O2 concentration was selected. FLUENT was used to simulate and control the atmospheric requirements. Our findings showed that eggs stored in an air-conditioning chamber with O2 concentration ≤10% exhibited weak respiratory intensity (0–1 mg/(kg·h)). The rates of decrease in loss of egg weight and Haugh units were smaller. There were significant differences in the pH of egg white stored in different O2 concentrations (p < 0.05). Reducing the O2 concentration in the egg-storage environment reduced the number of colonies in eggs and had a positive effect on egg preservation. Simulations using FLUENT revealed that only 1200 s were required to achieve the low-oxygen environment in the controlled atmosphere box (1.5 m × 1 m × 1 m). The storage environment of 5% O2 + 95% N2 had the best preservation effect on eggs. This approach is associated with low costs in practical application and can potentially be used for egg storage and transport.

Technical note: Novel triple O₂ sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands

The aquatic eddy covariance technique stands out as a powerful method for benthic O2 flux measurements in shelf environments because it integrates effects of naturally varying drivers of the flux such as current flow and light. In conventional eddy covariance instruments, the time shift caused by spatial separation of the measuring locations of flow and O2 concentration can produce substantial flux errors that are difficult to correct. We here introduce a triple O2 sensor eddy covariance instrument (3OEC) that by instrument design eliminates these errors. This is achieved by positioning three O2 sensors around the flow measuring volume, which allows the O2 concentration to be calculated at the point of the current flow measurements. The new instrument was tested in an energetic coastal environment with highly permeable coral reef sands colonised by microphytobenthos. Parallel deployments of the 3OEC and a conventional eddy covariance system (2OEC) demonstrate that the new instrument produces more consistent fluxes with lower error margin. 3OEC fluxes in general were lower than 2OEC fluxes, and the nighttime fluxes recorded by the two instruments were statistically different. We attribute this to the elimination of uncertainties associated with the time shift correction. The deployments at ∼ 10 m water depth revealed high day- and nighttime O2 fluxes despite the relatively low organic content of the coarse sediment and overlying water. High light utilisation efficiency of the microphytobenthos and bottom currents increasing pore water exchange facilitated the high benthic production and coupled respiration. 3OEC measurements after sunset documented a gradual transfer of negative flux signals from the small turbulence generated at the sediment–water interface to the larger wave-dominated eddies of the overlying water column that still carried a positive flux signal, suggesting concurrent fluxes in opposite directions depending on eddy size and a memory effect of large eddies. The results demonstrate that the 3OEC can improve the precision of benthic flux measurements, including measurements in environments considered challenging for the eddy covariance technique, and thereby produce novel insights into the mechanisms that control flux. We consider the fluxes produced by this instrument for the permeable reef sands the most realistic achievable with present-day technology.

Thermogravimetric Analysis of Coal Semi-Char Co-Firing with Straw in O2/CO2 Mixtures

For coal semi-char as a by-produced of low-temperature pyrolysis, combustion for power generation is one of the effective utilization methods to realize its clean and efficient utilization. However, the coal semi-char combustion process has a difficult ignition, unstable combustion and low burnout rate. The co-firing of the semi-char with biomass under oxy-fuel conditions can improve the combustion behavior and reduce fossil CO2 emissions. In this paper, the combustion behavior of Shenhua coal semi-char (SHC) co-firing with straw (ST) in O2/CO2 mixture is investigated using thermogravimetric analysis. The results show that each curve lays between those of the individual fuels and presents three peaks (i.e., three stages). The thermogravimetric curves of SHC co-firing with ST can be divided into three stages: the volatile combustion of ST, the co-combustion of SHC and ST fixed-carbons and the SHC fixed-carbon combustion and the decomposition of the difficult pyrolytic material of ST. Blending ST into the SHC can significantly decrease the ignition temperature and improve the comprehensive combustion behavior of blended samples. In increasing the proportion of ST from 25 to 100%, the change of the blended ignition temperature is slight, but the burnout temperature decreases greatly. Kinetic parameters of combustion are calculated by using the Coats–Redfern integral method. Compared to that of stage I and stage III, the activation energy of stage II is significantly lower. As increasing blending ratio from 25% to 100%, the activation energy increases at stage I and decreases at stage III. Furthermore, the O2 concentration obviously affects stage III of 50% SHC + 50% ST, and the thermogravimetric curves at this stage are obviously shifted to the lower temperature zone as the O2 concentration increases. The activation energy of 50% SHC + 50% ST increases as the oxygen concentration increases. Besides, the activation energy shows that the combustion characteristics cannot be determined only by the activation energy obtained by the Coats–Redfern method. These findings can provide useful information for semi-char co-firing with biomass.

Effect of in vitro growth on mouse oocyte competency, mitochondria and transcriptome

In vitro generation of fertile oocytes has been reported in several mammalian species. However, oocyte integrity is compromised by in vitro culture. Here, we aimed to understand the factors affecting oocyte competency by evaluating mitochondrial function and transcriptome as well as lipid metabolism in in vivo-derived oocytes and in vitro grown and matured (IVGM) oocytes under atmospheric (20%) and physiological (7%) O2 concentration. We used single-cell RNA-sequencing as well as Gene Ontology and KEGG analyses to identify the molecular pathways affecting developmental competence of oocytes. Oocytes grown under 20% O2 conditions showed significant decrease in mitochondrial membrane potential, upregulation of ceramide synthesis pathway-associated genes, and high ceramide accumulation compared with oocytes grown under 7% O2 conditions and in vivo-grown oocytes. This suggests that excess ceramide level causes mitochondrial dysfunction and poor developmental ability of the oocytes. Mitochondrial DNA copy number was lower in IVGM oocytes irrespective of O2 concentration in culture, although there was no common abnormality in the expression of genes related to mitochondrial biosynthesis. In contrast, some oocytes produced under 7% O2 conditions showed gene expression profiles similar to those of in vivo-grown oocytes. In these oocytes the expression of transcription factors, including Nobox, was restored. Nobox expression correlated with the expression of genes essential for oocyte development. Thus, Nobox may contribute to the establishment of oocyte competency before and after the growth phase. The comprehensive analysis of IVGM oocytes presented here provides a platform for elucidating the mechanism underlying functional oocyte production in vivo.

Stator Leakage Monitoring System in Water-Cooled Generators: Problems and Solutions

An electrical generator is one of the most efficient large-scale machines. It converts mechanical to electrical energy with an efficiency coefficient of approximately 99%. The remaining 1% can mainly be contributed to heat losses. Direct cooling is only necessary for larger turbogenerators with more than 250 MVA where the cooling media is introduced via hollow conductors within the stator bars. Turbogenerators of approximately up to 700 MVA nowadays use exclusively hydrogen (H2) gas as a cooling media. Even larger turbogenerators have to introduce direct water cooling. The water chemistry of the stator cooling water is typically of neutral pH and has a conductivity of less than 0.1 μS/cm. Two zones of the oxygen (O2) concentration have been established through the last 50 years, one at low dissolved O2 concentration with less than 20 ppb, the other with high concentrations of more than 2 ppm. The latter has to continuously inject CO2 free air to ensure to always keep the oxygen concentration above 2 ppm. The first part of this publication shows several incidents with the air injection system in different Nuclear Power Plants in the US, resulting in unfavorable stator cooling water chemistry. This led to a reduced cooling efficiency, resulting in several chemical online cleanings being necessary. The second part of this work presents a technical solution to overcome the issues associated with the reduced stator cooling. It continuously injects and monitors the air injected into the system. Additionally, it also measures the hydrogen leakage rate.

Study on Diesel Low-Nitrogen or Nitrogen-Free Combustion Performance in Constant Volume Combustion Vessels and Contributory

This paper studies the combustion performance of diesel in constant volume combustion vessels under different conditions of mixed low-nitrogen (O2 and N2) or non-nitrogen (O2 and CO2) in varying proportions. The high-speed camera is used to shoot the combustion flame in the constant volume combustion vessel. The process and morphology of the combustion flame are amplified in both time and space to study and analyze the effects of different compositions and concentrations in gases on the combustion performance of diesel and conduct a study on the contributory factors in the performance of diesel with no nitrogen. According to the study, in the condition of low nitrogen, the O2 concentration is more than 60%, the ignition delay period is shortened, the combustion flame is bright and slender, it spreads quickly, and the blue flame appears when the O2 concentration reaches 70%; While for nitrogen-free combustion, only when the O2 concentration reaches 30% is the combustion close to the air condition; when the O2 concentration reaches 40%, the combustion condition is optimized obviously and the combustion flame is relatively slender compared to the air working condition. Similarly, with the increase of the O2 concentration, the ignition delay period of nitrogen-free diesel is shortened, the duration is extended, and the combustion performance is optimized. In addition, when the O2 concentration reaches 50%, with the decrease of the initial temperature, the ignition delay period is prolonged, and the duration is shortened obviously. When the temperature is lower than 700 K, there is no ignition. The increase of the diesel injection pressure is beneficial to optimize the ignition performance of diesel non-nitrogen combustion and shorten its ignition delay period and combustion duration. Related research has important guiding significance to optimize nitrogen-free combustion technology, which produces no NOx of the diesel engine.

Distribution Law of Three Spontaneous Combustion Zones in the Goaf Area of a Fully Mechanized Working Face under High Ground Temperature

To figure out the distribution law of three spontaneous combustion zones in the goaf area of fully mechanized working face under high ground temperature, this study took the 11501# fully mechanized mining face of Zhujixi Coal Mine as the research object, and employed software Fluent to perform numerical simulations on the O2 concentration distribution in the goaf; then, combining with the actual situations on the site, the high-location boreholes and grout holes of the roof gas drainage roadway of the 11501# working face were selected as measuring points to measure the O2 concentration changes in a few positions such as in middle part of the goaf, on the air intake side, and on the air return side. The results show that, the numerical simulation results were basically consistent with the field measurement results, in the middle part of the goaf, the scope of the oxidation zone was 26.4m-62m; on the air intake side, the scope of the oxidation zone was 32m-96m; on the air return side, the scope of the oxidation zone was 28.4m-91m. The research findings of this paper provided a scientific reference for formulating fire-prevention and fire-extinguishing technical plans for mines.

A Simple Sensor System for Onsite Monitoring of O2 in Vacuum-Packed Meats during the Shelf Life

Vacuum packaging (VP) is used to reduce exposure of retail meat samples to ambient oxygen (O2) and preserve their quality. A simple sensor system produced from commercial components is described, which allows for non-destructive monitoring of the O2 concentration in VP raw meat samples. Disposable O2 sensor inserts were produced by spotting small aliquots of the cocktail of the Pt–benzoporphyrin dye and polystyrene in ethyl acetate onto pieces of a PVDF membrane and allowing them to air-dry. These sensor dots were placed on top of the beef cuts and vacuum-packed. A handheld reader, FirestinGO2, was used to read nondestructively the sensor phase shift signals (dphi°) and relate them to the O2 levels in packs (kPa or %). The system was validated under industrial settings at a meat processing plant to monitor O2 in VP meat over nine weeks of shelf life storage. The dphi° readings from individual batch-calibrated sensors were converted into the O2 concentration by applying the following calibration equation: O2 (%) = 0.034 * dphi°2 − 3.413 * dphi° + 85.02. In the VP meat samples, the O2 levels were seen to range between 0.12% and 0.27%, with the sensor dphi signals ranging from 44.03° to 56.02°. The DIY sensor system demonstrated ease of use on-site, fast measurement time, high sample throughput, low cost and flexibility.