Air Saturation Research Articles

Scale-down of oxygen and glucose fluctuations in a tubular photobioreactor operated under oxygen-balanced mixotrophy.

Oxygen-balanced mixotrophy (OBM) is a novel type of microalgal cultivation that improves autotrophic productivity while reducing aeration costs and achieving high biomass yields on substrate. The scale-up of this process is not straightforward, as non-ideal mixing in large photobioreactors might have unwanted effects in cell physiology. We simulated at lab scale dissolved oxygen and glucose fluctuations in a tubular photobioreactor operated under OBM where glucose is injected at the beginning of the tubular section. We ran repeated batch experiments with the strain Galdieria sulphuraria ACUF 064 under glucose pulse feeding of different lengths, representing different retention times: 112, 71 and 21 minutes. During the long and medium tube retention time simulations, dissolved oxygen was depleted 15 to 25 minutes after every glucose pulse. These periods of oxygen limitation resulted in the accumulation of coproporphyrin III in the supernatant, an indication of disruption in the chlorophyll synthesis pathway. Accordingly, the absorption cross section of the cultures decreased steeply, going from values of 150 - 180 m2 ·kg-1 at the end of the first batch down to 50 - 70 m2 ·kg-1 in the last batches of both conditions. In the short tube retention time simulation, dissolved oxygen always stayed above 10% air saturation and no pigment reduction nor coproporphyrin III accumulation were observed. Concerning glucose utilization efficiency, glucose pulse feeding caused a reduction of biomass yield on substrate in the range of 4 to 22% compared to the maximum levels previously obtained with continuous glucose feeding (0.9 C-g·C-g-1 ). The missing carbon was excreted to the supernatant as extracellular polymeric substances constituted by carbohydrates and proteins. Overall, the results point out the importance of studying large-scale conditions in a controlled environment and the need for a highly controlled glucose feeding strategy in the scale-up of mixotrophic cultivation. This article is protected by copyright. All rights reserved.

Assessing the CO2 concentration at the surface of photosynthetic mesophyll cells.

We present a robust estimation of the CO2 concentration at the surface of photosynthetic mesophyll cells (cw ), applicable under reasonable assumptions of assimilation distribution within the leaf. We used Capsicum annuum, Helianthus annuus and Gossypium hirsutumas model plants for our experiments. We introduce calculations to estimate cw using independent adaxial and abaxial gas exchange measurements, and accounting for the mesophyll airspace resistances. The cw was lower than adaxial and abaxial estimated intercellular CO2 concentrations (ci ). Differences between cw and the ci of each surface were usually larger than 10 μmol mol-1 . Differences between adaxial and abaxial ci ranged from a few μmol mol-1 to almost 50 μmol mol-1 , where the largest differences were found at high air saturation deficits (ASD). Differences between adaxial and abaxial ci and the ci estimated by mixing both fluxes ranged from -30 to +20 μmol mol-1 , where the largest differences were found under high ASD or high ambient CO2 concentrations. Accounting for cw improves the information that can be extracted from gas exchange experiments, allowing a more detailed description of the CO2 and water vapor gradients within the leaf.

The climate niche of the invasive tick species Hyalomma marginatum and Hyalomma rufipes (Ixodidae) with recommendations for modeling exercises

The finding of immature stages of some Hyalomma spp. feeding on migratory birds in Europe is unexceptional. The reports of adults of Hyalomma in Europe (incl. the British Isles) after successful molting from immatures have increased in recent years. It has been claimed that the warming of the target territory could favor the populations of these invasive ticks. Although evaluations of the impact on health or measures of adaptation are on their way, the climate niches of these species remain undefined, preventing preventive policies. This study delineates such niches for both Hyalomma marginatum (2,729 collection points) and Hyalomma rufipes (2,573 collections) in their distribution area, together with 11,669 points in Europe where Hyalomma spp. are believed to be absent in field surveys. Niche is defined from daily data of temperature, evapotranspiration, soil humidity and air saturation deficit (years 1970–2006). A set of eight variables (annual/seasonal accumulated temperature and vapor deficit) has the maximum discriminatory power separating the niches of both Hyalomma and a negative dataset, with an accuracy near 100%. The sites supporting H. marginatum or H. rufipes seem to be controlled by the joint action of the amount of water in the air (accounting for mortality) and the accumulated temperature (regulating development). The use of accumulated annual temperature as the only variable for predictive purposes of colonization of Hyalomma spp. looks unreliable, as far as values of water in air are excluded.

Warming and hypoxia reduce the performance and survival of northern bay scallops (Argopecten irradians irradians) amid a fishery collapse.

Warming temperatures and diminishing dissolved oxygen (DO) concentrations are among the most pervasive drivers of global coastal change. While regions of the Northwest Atlantic Ocean are experiencing greater than average warming, the combined effects of thermal and hypoxic stress on marine life in this region are poorly understood. Populations of the northern bay scallop, Argopecten irradians irradians across the northeast United States have experienced severe declines in recent decades. This study used a combination of high-resolution (~1km) satellite-based temperature records, long-term temperature and DO records, field and laboratory experiments, and high-frequency measures of scallop cardiac activity in an ecosystem setting to quantify decadal summer warming and assess the vulnerability of northern bay scallops to thermal and hypoxic stress across their geographic distribution. From 2003 to 2020, significant summer warming (up to ~0.2°C year-1 ) occurred across most of the bay scallop range. At a New York field site in 2020, all individuals perished during an 8-day estuarine heatwave that coincided with severe diel-cycling hypoxia. Yet at a Massachusetts site with comparable DO levels but lower daily mean temperatures, mortality was not observed. A 96-h laboratory experiment recreating observed daily temperatures of 25 or 29°C, and normoxia or hypoxia (22.2% air saturation), revealed a 120-fold increased likelihood of mortality in the 29°C-hypoxic treatment compared with control conditions, with scallop clearance rates also reduced by 97%. Cardiac activity measurements during a field deployment indicated that low DO and elevated daily temperatures modulate oxygen consumption rates and likely impact aerobic scope. Collectively, these findings suggest that concomitant thermal and hypoxic stress can have detrimental effects on scallop physiology and survival and potentially disrupt entire fisheries. Recovery of hypoxic systems may benefit vulnerable fisheries under continued warming.

Influence of Oxygen Management on Color and Phenolics of Red Wines.

Winemaking involves contact at different stages with atmospheric oxygen, the consumption of which determines its final properties. The chemical analysis of red wines subjected to consecutive cycles of air saturation has been extensively researched; however, the capacity to consume different doses of oxygen before bottling is an aspect that has been little studied. In this work, the effect of saturation of different levels of oxygen on the final characteristics of different wines made from Tempranillo and Garnacha grape extracts was studied. For this purpose, the wines were subjected to controlled oxygen saturation levels to simulate their possible oxygenation before bottling. The only difference was the phenolic composition of grape extracts that were reconstituted under the same conditions to avoid the interferences inherent to the fermentation process and the additives added in the winery. The kinetics of oxygen consumption was then evaluated and its effect on the color, antioxidant capacity, and phenols of three different wines was analyzed. This work shows the relationship between the oxidation state of wine and changes in its chemical composition. In addition, it provides insight into the effect of oxygen consumption before bottling on the properties of wines subjected to high and single doses of oxygen.

Evaluation of an intermittent mist spray cooling system for improving greenhouse eggplant cultivation

Cultivation of crops in greenhouses faces the issue of overheating, which can harm yields. A low-cost solution is evaporative cooling, which also reduces the vapor pressure deficit. Fine mist sprays can significantly reduce temperature and vapor deficit. However, the fast evaporation rate could cause air saturation and wetting of plants, causing damage. A simple method to control the effect is intermittent spraying. In this research, air temperature was continuously measured at 20 locations for a misted 98m2 greenhouse during eggplant cultivation, as well as a control greenhouse without mist, while also evaluating the resulting crops. An array of 28 high pressure hydraulic nozzles, spraying 2.6kg/h each, intermittently sprayed 20 seconds on, then 10 seconds off throughout the day. The temperature in the misted greenhouse averaged 2.2K to 4.8K cooler than the control greenhouse. In the misted greenhouse, the total yield (+26%) and marketable fruits (+143%) were higher than the control. The cooling effect of the misted greenhouse compared to the control case tended to correlate with outdoor wind speed. The comparison of the misted greenhouse to its own initial condition did not. Evaluations of evaporation cooling may yield better understanding if compared to a control greenhouse at the same site.

Research of technical parameters and microbiological efficiency of the ultraviolet bactericidal air purification system applying

Purpose. Establishment of technical parameters and microbiological efficiency of ultraviolet bactericidal air purification systems based on ultraviolet radiation and ozonation. Methods. Methods of analysis, mathematical modeling, engineering methods of calculation and generally accepted experimental studies of electrical equipment for air purification are used. Results. To ensure the regulatory parameters of air and purification from pathogenic microflora and most types of harmful impurities of chemical and biological origin in industrial, agricultural, medical, educational, public and other premises, an experimental sample of a universal air purification system with the implementation of photooxidation has been developed and manufactured. Experimental studies of technical parameters and microbiological efficiency of the developed system were carried out, the dynamics of ozone concentration in the room under different modes of operation of the ozonator was established and the concentration of the total number of microorganisms, including fungi in the working area of the office space, was reduced. Conclusions 1. It was found that in an office space with a volume of 81 m3, air saturation with ozone to a concentration of 0.3 mg/m3 occurred after 30 minutes in the ozonizer operating mode: operating time 3 s, idle time 10 minutes, average rate of ozone reduction in air within a concentration of 0.007–0.053 mg/m3 is 0.001 mg/min. In case of intervals , reduction and accordingly the deviation of the ozone concentration from the average is reduced. 2. According to the results of microbiological studies, it was found that the total number of aerobic microorganisms in the air, CFU/m3, for 3 hours of operation of the SOP decreased by 91.4%, the total number of fungi – by 88.3%, the total number of microorganisms, including fungi – by 87.1%. Keywords: ultraviolet light, ozonation, photo oxidation, air purification, microclimate.

Safety and pulmonary function impact of surgical mask usage in stable COPD patients during the COVID-19 pandemic

There are hesitations about the use of surgical face masks, which are the main tools in protection from the COVID-19 pandemic, one of the biggest disasters of our age, in chronic airway diseases. The purpose of the study was to examine how stable patients with chronic obstructive pulmonary disease (COPD) responded to short-term surgical mask use in terms of in-mask air quality, oxygen saturation, and pulmonary function. Forty-one patients with stable COPD, by clinical presentation and pulmonary function tests (PFTs), were included in a quasi-experimental study. Stable COPD patients' PFTs, in-mask air quality, and pollution measures were collected before and after wearing surgical masks for two hours at rest. The findings of simultaneous tests of peripheral-blood-oxygen saturation were also recorded. The mean age of participants was 67.1 years and 87.8% were male. The pre- and post-mask PFTs parameters for GOLD (A+B) group were FEV1 (ml), FEV1 (%), FVC (ml), FVC (%), FEV1/FVC (%) and DLCO (%) (p=0.067, p=0. 065, p=0.062, p=0.083, p=0.083, p=0.269, p=0.956, respectively), whereas in GOLD (C+D) group (p=0.340, p=0.538, p=0.728, p=0.044, p=0.105, p=0.054, respectively). In post-mask measurements, the respiratory function was not impaired in GOLD-2022 (A-B-C-D) COPD subgroups. Oxygen and carbon-monoxide concentrations in exhaled air and oxygen saturation decreased after surgical mask use. The difference was statistically significant, but the difference was unimportant in terms of clinical implications. Surgical masks don’t appear to have a negative effect on pulmonary function and clinical parameters in stable COPD. This study may help provide evidence-based data to overcome hesitations in use of surgical masks in chronic airway diseases.

Cough, with a sac of marbles in the chest.

A 48-year-old male patient presented with productive cough, dyspnea and abdominal pain of 2 months duration. He was diagnosed with diabetes mellitus 6 months ago and had not been regular with his medications. Clinical examination revealed a respiratory rate of 18 per min with room air saturation of 95%, and a paucity of movements with bronchial breath sounds identified on inspection and auscultation, respectively, over the right hemithorax. Chest skiagram and computed tomography images of his thorax are shown below [Figure 1].Figure 1: (a) shows chest skiagram and (b–d) shows high-resolution computed tomography images of the chest. A description of the images is in the accompanying textQuestion: What is the diagnosis? Answer: Pulmonary and hepatic hydatid disease. DISCUSSION The chest skiagram [Figure 1a] revealed a well-defined round radio-opacity in the right mid zone with a crescentic hyperlucent medial margin, called the crescent sign (white arrow). Figure 1b is a coronal view of high-resolution computed tomography (HRCT) scan of the chest lung window, which shows a large cyst in the right lung, with multiple small rounded opacities with fluid attenuation, some of which appear to be floating within it, appearing like a sac of marbles. This is consistent with a diagnosis of a hydatid cyst with multiple daughter cysts within it. There are pockets of air seen between the outer pericyst and inner endocyst, aptly named ‘air-crescent sign’ (blue arrow) and ‘signet ring sign’ (red arrow), which suggest a ruptured or complicated hydatid cyst. Figure 1c, the sagittal section of the HRCT scan of the chest lung window at the level of the aortic outflow tract, shows the ruptured hydatid cyst in the right lung. The daughter cysts have collected in the dependent area of the larger cyst, with some appearing to ‘rise’ over the rest, or the ‘rising-sun sign’ (blue arrow). Also seen is a small air pocket inferiorly (red arrow) between the pericyst and endocyst, called the ‘air-bubble sign’. The presence of air on either side of the endocyst (red arrowheads) gives the appearance of an ‘onion-peel sign’, or the ‘cumbo sign’. Figure 1d shows a large well-defined homogenous cyst in the right lobe of the liver.[1] Blood investigations revealed uncontrolled blood sugar levels. Armed with the characteristic radiology above, and supplemented by a positive serum latex agglutination test for Echinococcus antigen, he was diagnosed with pulmonary and hepatic hydatid disease. He was started on oral albendazole and subsequently underwent pericystectomy of lung cyst along with partial pericystectomy of cyst in the liver. Post-surgery, he is at present asymptomatic and is on regular follow-up. Hydatid disease is a zoonosis, commonly caused by the accidental ingestion of ova of the tapeworm Echinococcusgranulosus, which subsequently develop into larvae in the host intestine and migrate to other parts of the body where they develop into embryos, with the liver and lung being the most commonly involved organs.[1] Characteristic thoracic radiology should lead clinicians to suspect pulmonary hydatid disease, especially when dealing with patients with non-resolving pneumonia or lung mass. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Stream‐Lake Connectivity Is an Important Control of Fluvial CO2 Concentrations and Emissions in Catchments

AbstractStreams in cultivated lowlands are commonly supersaturated with CO2 and are a source of CO2 to the atmosphere. Great uncertainties exist regarding the spatiotemporal variations of CO2 concentrations and emission rates in stream‐lake fluvial networks and small streams with variable plant cover. We studied this variability and the underlying mechanisms in 40 small, high‐alkalinity Danish streams, including 5 catchments with lakes. Generally CO2 concentrations were, on average, 9.2 times those of the atmosphere, declining downstream with rising water temperature, chlorophyll a concentration, and decreasing groundwater inputs. We furthermore observed that the concentrations of CO2 in stream waters declined at the outlet of lakes to values close to or below air saturation due to phytoplankton uptake and atmospheric loss during the long water retention time in the lakes. Downstream, CO2 concentrations were observed to decrease in summer and in the afternoons, which indicate plant uptake of CO2. Sites with deeper water and few plants and low gas transfer velocity retained high CO2 concentrations. Among 38 fluvial networks where emission could be calculated, it varied 10‐fold (0.41–4.06 g C m−2 d−1), but the overall mean was constrained to a narrow confidence interval (1.75–2.50 g C m−2 d−1). Our results highlight that a complex of physical, chemical and biological processes cause highly variable carbon dynamics and CO2 emissions in fluvial networks at local and catchment scales making upscaling challenging.

A new exponential model for predicting soil gas diffusivity with varying degree of saturation

AbstractSoil gas diffusivity (Dp/Do, gas diffusion coefficients in soil and in free air, respectively) and its relation to soil moisture is of great importance for describing and quantifying essential provisional and regulatory functions associated with terrestrial ecosystems such as soil aeration and greenhouse gas (GHG) emissions. Because gas migration in terrestrial soil systems is predominantly diffusion controlled, soil gas diffusivity becomes a fundamental prerequisite to quantify diffusive gas fluxes. Descriptive–predictive models are often used to estimate Dp/Do from easily measurable soil physical properties. Most of the available models take the form of power‐law functions and often tend to mischaracterize soil moisture effects at high moisture regimes. Based on a wide range Dp/Do data available in literature representing both intact and repacked soils, this study developed a novel air‐saturation‐dependent exponential (ASEX) gas diffusivity model to model Dp/Do in relation to soil air saturation. The model variable α, which represents the diffusivity at half air saturation normalized by the same in complete soil air saturation, could potentially differentiate moisture effects on different soil structural states. For specific applications in intact soils, we propose corresponding α values for upper‐limit (α = .6) and lower‐limit (α = .05) estimates of diffusivity, while an average value (α = .3) for general applications in both intact and repacked soils. As expected, our model based on a few a priori measured supportive data showed a better performance over the classical predictive models that do not use such measurements. The new model was further used to derive useful implications to showcase soil density effects on Dp/Do.

A pore-scale investigation of microplastics migration and deposition during unsaturated flow in porous media

Microplastics are ubiquitous in the natural environment and have the potential to endanger the natural environment, ecology and even human health. A series of microfluidic experiments by using soft lithography technology were carried out to investigate the effect of flow rate, particle volume fraction, particle size and pore/throat ratio on microplastics migration and deposition at the pore scale. We discovered a range of deposition patterns of the spherical microplastics from no particle deposition, to discontinuous particle layer, and to continuous particle layers in the retained liquid in the pores, depending on the particle size and volume fraction. Several metrics, including air saturation, probability of particle detainment, expansion ratio and thickness of residual liquid, were quantified to examine the role of various parameters on particle migration and retention of microplastics. At low flow rate (Q = 0.05 μL/min), microplastics migration and deposition were sensitive to changes in particle volume fraction, particle size and pore/throat ratio. In contrast, at high flow rates (Q > 5 μL/min), the migration and retention of particles were mainly controlled by strongly channelized air invasion pattern, while the particle volume fraction, particle size and pore/throat size ratio have only secondary influence. At intermediate range of flow rates, microplastics migration and deposition were dramatically impacted by flow rate, particle volume fraction, particle size and pore/throat ratio. This work improves the understanding of the mechanisms of particle migration and retention in porous media and can provide a reference for more accurate assessment of the exposure levels and times of microplastics in soil and groundwater systems.

Experimental hyperoxia (O2 supersaturation) reveals a gill diffusion limitation of maximum aerobic performance in fish.

Several studies have demonstrated that hyperoxia increases the maximal O2 consumption rate (ṀO2max) in fish, but exactly how this occurs remains to be explained. Here, we tested the hypothesis that hyperoxia improves arterial oxygenation in rainbow trout during exhaustive exercise. We demonstrate a 35% higher ṀO2max in hyperoxia (200% air saturation) relative to normoxia, which was achieved through a combined 15% increase in cardiac output due to elevated peak heart rate, and a 19% increase of the arterial-venous (A-V) O2 content difference. While arterial O2 partial pressure (PaO2) and O2 saturation of haemoglobin declined post-exhaustive exercise in normoxia, this did not occur in hyperoxia. This protective effect of hyperoxia on arterial oxygenation led to a 22% higher arterial O2 content post-exhaustive exercise, thereby allowing a higher A-V O2 content difference. These findings indicate that ṀO2max is gill diffusion limited in exhaustively exercised rainbow trout. Moreover, as previous studies in salmonids have demonstrated collapsing PaO2 in normoxia at maximal swimming speed and at acutely high temperatures, a diffusion limitation may constrain ṀO2 in other situations eliciting peak metabolic demand. These findings, along with the fact that hyperoxia increases ṀO2max in several other fishes, suggest that gill diffusion limitations of ṀO2max may be widespread in fishes.

A natural systemic to pulmonary artery shunt.

Isolation of the left subclavian artery is a rare anomaly associated with right aortic arch. We report a case in which this subclavian artery was supplying the pulmonary circulation in a patient with tetralogy of Fallot (TOF) which effectively acted as a natural systemic to pulmonary artery shunt. The patient had good room air saturation and no features of vertebrobasilar insufficiency or left upper limb ischemia. She underwent a total correction of TOF and ligation of the aberrant left subclavian artery.

Hypersaline produced water clarification by dissolved air flotation and sedimentation with ultrashort residence times

Treatment and reuse of some produced waters is made difficult due to their hypersalinity, high concentrations of myriad other dissolved and suspended components, specialized technology requirements (modularity, portability, and short residence times), and lack of existing information on their processing. In this work, produced water containing ∼100,000 mg/L total dissolved solids from the Permian Basin was coagulated with aluminum chlorohydrate (ACH) and flocculated with an anionic high molecular weight organic polymer prior to dissolved air flotation (DAF) and sedimentation to reduce turbidity to < 4 NTU and iron < 0.8 mg/L (>95% removal in both cases) with a total coagulation-flocculation-sedimentation/flotation residence time of only 5 min. Two advantages of DAF over sedimentation were noted: (i) DAF required only half the dosage of the pre-hydrolyzed ACH coagulant to remove ∼90% of turbidity and iron even without the organic polymeric flocculant and (ii) DAF even operated successfully without ACH coagulation (i.e., using only the organic polymeric flocculant) evidencing its lower chemical dosing needs. Further, DAF attained all water quality and operational goals at a recycle ratio of only 12% demonstrating that it outperformed sedimentation to generate clean brine at relatively reduced excess energies necessary for air saturation. Higher DAF recycle ratios reduced turbidity and iron removal possibly due to floc breakage. Colloids were effectively destabilized by double layer compression (due to high water salinity), charge neutralization (via adsorption of Al13 polycations), and enmeshment (precipitation of amorphous aluminum). They were flocculated via interparticle bridging (by the anionic organic polymeric flocculant) to create large, compact flocs facilitating ultrashort flotation/sedimentation times. Direct evidence for these individual coagulation and flocculation mechanisms were obtained using electrophoretic mobility measurements, thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, optical microscopy, computational image and video analysis, and scanning electron microscopy – energy dispersive X-ray spectroscopy.

Влияние концентратов сывороточных белков на технологические и органолептические показатели качества мороженого

The demand for protein-fortified foods is increasing, and so is the necessity of the complete utilization of milk constituents in the food industry. The research objective was to study various technological and sensory indicators of ice cream fortified with whey protein concentrate.&#x0D; The study featured ice cream samples with 8% of mass fraction of fat and 10% of nonfat milk solids with whey protein concentrations of 1–5 %. The dynamic viscosity was studied by rotational viscosimetry, dispersion – by microstructural methods, thermal stability – by thermostatic methods, and titratable acidity – by standard methods.&#x0D; Whey protein concentrate in amount of 1–5 % increased the titratable acidity by 1.05–1.90 times and the dynamic viscosity – by 1.16–2.90 times. With an extra addition of 4% whey protein concentrate, the viscosity of the mix exceeded the technologically permissible values. The consistency coefficient increased by 19.4 times, and the flow index decreased by 4.8 times. During freezing, the mix revealed the high capability to air saturation with mass fraction of melt whey protein concentrate of 1 and 2%. Thermal stability also increased: mass fraction of melt after 60 min of retention decreased by 3 times. After adding 1–3% whey protein concentrate, the dispersion of air bubbles and ice crystals improved. It was determined in accordance with the density of distribution by their sizes. The hardness of ice cream decreased 1.4–8.3 times as whey protein concentrate increased. A greater mass fraction of whey protein enhanced the creamy taste and improved the texture. &#x0D; Based on the main technological and sensory quality indicators, the mass fraction of whey protein concentrates should be under 3%. The results may be used in protein-fortified ice cream production.

Chronic experimental hyperoxia elevates aerobic scope: a valid method to test for physiological oxygen limitations in fish.

Experimental hyperoxia has been shown to enhance the maximum oxygen uptake capacity of fishes under acute conditions, potentially offering an avenue to test prominent physiological hypotheses attempting to explain impacts of climate warming on fish populations (e.g., gill-oxygen limitation driving declines in fish size). Such benefits of experimental hyperoxia must persist under chronic conditions if it is to provide a valid manipulation to test the relevant hypotheses, yet the long-term benefits of experimental hyperoxia to oxygen uptake capacity have not been examined. Here, the authors measured aerobic metabolic performance of Galaxias maculatus upon acute exposure to hyperoxia (150% air saturation) and after 5months of acclimation, at both 15°C and 20°C. Acute hyperoxia elevated aerobic scope by 74%-94% relative to normoxic controls, and an elevation of 58%-73% persisted after 5months of hyperoxia acclimation. When hyperoxia-acclimated fish were acutely transitioned back to normoxia, they maintained superior aerobic performance compared with normoxic controls, suggesting an acclimation of the underlying metabolic structures/processes. In demonstrating the long-term benefits of experimental hyperoxia on the aerobic performance of a fish, the authors encourage the use of such approaches to disentangle the role of oxygen in driving the responses of fish populations to climate warming.

Modulation of the oxygen sensing properties of iridium (III) complexes by changing their substitution groups

In this study, new bis-cyclometalated iridium (III) complexes bearing different ligated groups (–H, –OCH3, –F, –CH3) at the aryl moiety (Ir-1, Ir-2, Ir-3 and Ir-4) were synthesized and characterized. Then oxygen sensing properties of corresponding complexes were investigated in EC film. The complexes showed room temperature phosphorescence spectra in the range of 562–590 nm in THF and 546–554 nm in ethyl cellulose (EC) matrix. When they were incorporated in an ethyl cellulose matrix, the probes showed optimal dynamics of luminescence for oxygen monitoring in the range from 0 % to 100 % air saturation. The I0/I100 values of Ir-1, Ir-2, Ir-3 and Ir-4 in EC thin film were calculated as 10.9, 5.0, 7.3 and 22.7, respectively. The results showed that the oxygen sensitivity accomplishment of the complex core can be fine-tuned by varying these ligated groups, and the weak electron-donating properties of the methyl groups at the aryl moiety improve remarkably the optical oxygen sensing abilities of the Iridium (III) complexes.

Prevalence and mechanisms of environmental hyperoxia-induced thermal tolerance in fishes.

Recent evidence has suggested environmental hyperoxia (O2 supersaturation) can boost cardiorespiratory performance in aquatic ectotherms, thereby increasing resilience to extreme heat waves associated with climate change. Here, using rainbow trout (Oncorhynchus mykiss) as a model species, we analysed whether improved cardiorespiratory performance can explain the increased thermal tolerance of fish in hyperoxia (200% air saturation). Moreover, we collated available literature data to assess the prevalence and magnitude of hyperoxia-induced thermal tolerance across fish species. During acute warming, O2 consumption rate was substantially elevated under hyperoxia relative to normoxia beyond 23°C. This was partly driven by higher cardiac output resulting from improved cardiac contractility. Notably, hyperoxia mitigated the rise in plasma lactate at temperatures approaching upper limits and elevated the critical thermal maximum (+0.87°C). Together, these findings show, at least in rainbow trout, that hyperoxia-induced thermal tolerance results from expanded tissue O2 supply capacity driven by enhanced cardiac performance. We show 50% of the fishes so far examined have increased critical thermal limits in hyperoxia (range: 0.4–1.8°C). This finding indicates environmental hyperoxia could improve the ability of a large number of fishes to cope with extreme acute warming, thereby increasing resilience to extreme heat wave events resulting from climate change.

How do temperature, humidity, and air saturation state affect the COVID-19 transmission risk?

Environmental parameters have a significant impact on the spread of respiratory viral diseases (temperature (T), relative humidity (RH), and air saturation state). T and RH are strongly correlated with viral inactivation in the air, whereas supersaturated air can promote droplet deposition in the respiratory tract. This study introduces a new concept, the dynamic virus deposition ratio (α), that reflects the dynamic changes in viral inactivation and droplet deposition under varying ambient environments. A non-steady-state-modified Wells-Riley model is established to predict the infection risk of shared air space and highlight the high-risk environmental conditions. Findings reveal that a rise in T would significantly reduce the transmission of COVID-19 in the cold season, while the effect is not significant in the hot season. The infection risk under low-T and high-RH conditions, such as the frozen seafood market, is substantially underestimated, which should be taken seriously. The study encourages selected containment measures against high-risk environmental conditions and cross-discipline management in the public health crisis based on meteorology, government, and medical research.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-21766-x.