Decrease In Oxygen Concentration Research Articles

Design and Fabrication of Heart Rate and Oxygen Saturation Measurement Device using LED-LED Configuration and to Study Correlation of PPG Signal Amplitude with Breathing Rate

we present an approach for non-invasive signal acquisition in healthcare applications, specifically aiming the measurement of oxygen saturation (SpO2) and heart rate (HR) using photoplethysmography (PPG). Our proposed project emphasis on the design of a circuit that uses light-emitting diodes (LEDs) both as emitters and detectors. Through the use of a Field Programmable Gate Array (FPGA), we are able to effectively control the LEDs. By employing three LEDs, with two serving as emitters and one as a detector, we successfully obtain PPG signal after removing the noise. This work also demonstrates the correlation between PPG signal amplitudes and changes in breathing rate, showing lower amplitudes with decreased oxygen concentration and higher amplitudes with increased breathing rates. This proposed circuit design gives a cost-effective solution with low power consumption, making it highly suitable for practical implementation.

Impact of Functional Groups in Reduced Graphene Oxide Matrices for High Energy Anodes in Lithium-Ion Batteries

Most high capacity anode materials for lithium-ion batteries (LiB) require a carbonaceous matrix. In this context one promising material is reduced graphene oxide (rGO). Herein, we present the influence of different reduction degrees of rGO on its physico-chemical properties, such as crystallinity, specific surface area, electrical conductivity and electrochemical lithiation/delithiation behavior. It is found that a heat treatment under inert and reducing atmospheres increases the long-range order of rGO up to a temperature of 700 °C. At temperatures around 1000 °C, the crystallinity decreases. With decreasing oxygen content, a linear decrease in irreversible capacity during cycle 1 can be observed, along with a significant increase in electrical conductivity. This decrease in irreversible capacity can be observed despite an increase in specific surface area indicating the more significant influence of the oxygen content on the capacity loss. Consequently, the reversible capacity increases continuously up to a carbon content of 84.4 at% due to the thermal reduction. Contrary to expectations, the capacity decreases with further reduction. This can be explained by the loss of functional groups that will be lithiated reversibly, and a simultaneous reduction of long-range order, as concluded from dq/dU analysis in combination with XRD analysis.

Optimizing selective withdrawal strategies to mitigate hypoxia under water-level reduction in Germany's largest drinking water reservoir

Water-level reduction frequently occurs in deep reservoirs, but its effect on dissolved oxygen concentration is not well understood. In this study we used a well-established water quality model to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir, Germany. We then systematically elucidated the potential of selective withdrawal to control hypoxia under changing water levels. Our results documented a gradual decrease of hypolimnetic oxygen concentration under decreasing water level, and hypoxia occurred when the initial level was lower than 410 m a.s.l (71 m relative to the reservoir bottom). We also suggested that changes of hypoxic region, under increasing hypolimnetic withdrawal discharge, followed a unimodal trajectory with the maximum hypoxic area projected under the discharge between 3 m3/sec and 4 m3/sec. Besides, our results illustrated the extent of hypoxia was most effectively inhibited if the withdrawal strategy was applied at the end of stratification with the outlet elevation at the deepest part of the reservoir. Moreover, hypoxia can be totally avoided under a hybrid elevation withdrawal strategy using surface withdrawal during early and mid stratification, and deep withdrawal at the end of stratification. We further confirmed the decisive role of thermal structure in the formation of hypoxia under water-level reduction and withdrawal strategies. We believe the conclusions from this study can be applied to many deep waters in the temperate zone, and the results should guide stakeholders to mitigate negative impacts of hypoxia on aquatic ecosystems.

MFN2-mediated mitochondrial fusion facilitates acute hypobaric hypoxia-induced cardiac dysfunction by increasing glucose catabolism and ROS production

BackgroundRapid ascent to high-altitude environment which is characterized by acute hypobaric hypoxia (HH) may increase the risk of cardiac dysfunction. However, the potential regulatory mechanisms and prevention strategies for acute HH-induced cardiac dysfunction have not been fully clarified. Mitofusin 2 (MFN2) is highly expressed in the heart and is involved in the regulation of mitochondrial fusion and cell metabolism. To date, however, the significance of MFN2 in the heart under acute HH has not been investigated. Methods and resultsOur study revealed that MFN2 upregulation in hearts of mice during acute HH led to cardiac dysfunction. In vitro experiments showed that the decrease in oxygen concentration induced upregulation of MFN2, impairing cardiomyocyte contractility and increasing the risk of QT prolongation. Additionally, acute HH-induced MFN2 upregulation promoted glucose catabolism and led to excessive mitochondrial reactive oxygen species (ROS) production in cardiomyocytes, ultimately resulting in decreased mitochondrial function. Furthermore, co-immunoprecipitation (co-IP) and mass spectrometry analyses indicated that MFN2 interacted with the NADH-ubiquinone oxidoreductase 23 kDa subunit (NDUFS8). Specifically, acute HH-induced MFN2 upregulation increased NDUFS8-dependent complex I activity. ConclusionsTaken together, our studies provide the first direct evidence that MFN2 upregulation exacerbates acute HH-induced cardiac dysfunction by increasing glucose catabolism and ROS production. General significanceOur studies indicate that MFN2 may be a promising therapeutic target for cardiac dysfunction under acute HH.

Box Behnken design application for optimization of bio-oil yield from catalytic pyrolysis of agro-residue

A Response Surface Methodology (RSM) was used to investigate the effect of reaction temperature and biomass to catalyst (b/c) ratio on the catalytic pyrolysis of three wood sawdust samples in a fixed bed reactor using Green zeolite-Y catalyst synthesized from Ficus exasperate (L.) leaf particles. Temperature (400–700 °C), biomass percentage (60–100%), and catalyst (0–40%) were the independent variables with a total of 15 experimental runs, including 3 center runs, were generated via the Box-Behnken experimental design. The results reveal that biomass/ catalyst (b/c) ratio of 80/20% at 550 °C yielded optimum pyrolytic liquid for Melicia excelsa (Me), Diospyros crassiflora (Dc) and Entada Africana (Ea) as 31 wt.%, 31 wt.%, 30 wt.%, respectively while with the attendance of catalysts at 20% increased the yield of pyrolytic liquid for Me (45 wt.%), Dc (42 wt.%), and Ea (43 wt.%). GCMS analysis of Me (80.81 wt.%), Dc (73.96 wt.%), and Ea (70.26 wt.%) pyrolytic oil reveals the dominance of phenols, ethers, alcohols, ketones, alkanes, and acids. Reduction in acidity, decrease in oxygen content, increase in viscosity of the bio-oil were noticed in biomass/catalyst (b/c) ratio of 80/20 at 550 °C. These measurements show enhanced pyrolysis oil characteristics, which is a boost to its bioenergy potential.

Corrosion form transition of mooring chain in simulated deep-sea environments: Remarkable roles of dissolved oxygen and hydrostatic pressure

The corrosion form and mechanical properties deterioration of mooring chain steel in simulated deep-sea environments were investigated. With the increase of ocean depth, not only the pressure increases, but also the dissolved oxygen content decreases. These two factors affect corrosion evolution of mooring chain steel in simulated deep-sea environments, which was studied for the first time. Compared with uniform corrosion of mooring chain steel in shallow sea with sufficient oxygen, low dissolved oxygen leads to the corrosion dominated by pitting with pit covers. Meanwhile, hydrostatic pressure distinctly accelerates pitting initiation and propagation. The higher the hydrostatic pressure is, the more serious the pitting is. For failure mechanism of unstressed mooring chain steel serving in simulated deep-sea environments, both absorbed hydrogen and corrosion morphology can degrade the ductility of mooring chain steel, in which the leading factor depends on the service time. The severe pitting is the main factor and causes remarkable ductility loss of the steel after long-term immersion. But hydrogen plays an important role on elongation loss in early stage.

The Thermochemical Conversion of Municipal Solid Waste by Torrefaction Process

In this work, the thermochemical properties of municipal solid waste (MSW) are studied using the torrefaction process as the main method for investigation. Torrefaction experiments were carried out using an electric laboratory furnace, at temperatures of 200, 250, and 300 °C. The residence time was set to 90 min. Proximate and ultimate analysis were performed on the torrefied MSW samples and compared with the properties of the raw MSW samples. In addition, the thermal properties of the obtained torrefied MSW samples were evaluated by thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The following could be stated: the obtained results showed that mass and energy yields (MY and EY, respectively) decrease with increasing when torrefaction temperature, while the heating values (HHV) increased under the same conditions (from 24.3 to 25.1 MJ/kg). Elemental analysis showed an increase in carbon content (C), from 45.7 ± 0.9 to 52.8 ± 1.05 wt.%, and decrease in oxygen content (O), from 45.6 ± 0.9 to 39.5 ± 0.8 wt.%, when torrefaction temperature is increased, which is consistent with the general definition of the torrefaction process. In addition, enhancement factors (EFs) and fuel ratios (FRs) were calculated, which ranged from 1.00 to 1.02 and 0.16 to 0.23, respectively. Some anomalies were observed during the thermal analysis, which are assumed to be related to the composition of the selected MSW. This study therefore shows that torrefaction pretreatment can improve the physicochemical properties of raw MSW to a level comparable to coal, and could contribute to a better understanding of the conversion of MSW into a valuable, solid biofuel.

Lab- and pilot-scale photo-biofilter performance with algal–bacterial beads in a recirculation aquaculture system for rearing rainbow trout

AbstractIndustrial aquaculture has proliferated due to increased world demand for fish and seafood. Aerobic bacterial biofilters typically perform the nitrogen abatement of wastewater. Recirculation aquaculture systems (RAS) require nitrifying microorganisms developed in the biofilter. Despite the advantages of these biofilters, there are disadvantages, such as the time needed to mature, decrease in oxygen concentration, accumulation of organic matter and difficulty of backflushing, among others. On the other hand, microalgae effectively eliminate nutrients-pollutants, consuming inorganic carbon, nitrogen, and phosphorus and balancing soluble oxygen, conditions not attributable to nitrifying biofilters. The current study used a photo-biofilter to determine the depuration capacity of an immobilized co-culture of microalga Tetradesmus dimorphus and nitrifying bacteria isolated from a Salmon RAS. Bacteria frorm genera Flavobacterium, Microbacterium, Raoultella, Sphingobacterium, and Pseudomonas were identified. Biofilters were tested in sequential batch (lab-scale; 2.85 L) and continuous mode (pilot-plant scale; 120 L) attached to a RAS system for rearing rainbow trout. The algal–bacterial community structure was studied using 16S rRNA gene sequencing. Results showed that at typical loading rates, the algal–bacterial community could simultaneously remove ammonium, total ammonium nitrogen (TAN), nitrate and phosphate. Moreover, the system evaluated removed TAN daily, at an average of 1.18 kg per m3 of beads. Graphical Abstract

Deposition and characterisation of c-axis oriented AlScN thin films via microwave plasma-assisted reactive HiPIMS

In this work, we demonstrate that highly oriented c-axis aluminium scandium nitride (AlScN) piezoelectric thin films can be deposited via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS), without the necessity of substrate heating. A combination of in situ plasma diagnostics, i.e. time-of-flight mass spectrometry (ToF-MS), modified quartz crystal microbalance (m-QCM), and magnetic field measurements allowed to optimise the deposition conditions, in turn maximising the nitrogen supply and ionic flux at the substrate region, while maintaining stable discharge conditions. The AlScN thin films synthesised in this study were deposited as chemically gradient coatings with varying levels of scandium doping, and were characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Obtaining highly textured films was made possible with the addition of microwave plasma to the optimised HiPIMS discharge, where the wurtzite AlScN films (with up to 20 at. % Sc) exhibited a stronger texture in the (0002) orientation compared to films prepared without microwave plasma. Additionally, the use of a microwave plasma led to a significant decrease in oxygen content in the films and increase in nitrogen content, ensuring stoichiometric compositions. Based on the results mentioned above, it is expected that the AlScN thin films fabricated via MAR-HiPIMS would exhibit a strong piezoelectric response.

Threads of microbial activity on quasi-anoxic environments: Case studies from Oligocene to Miocene of the Central Paratethys

Microbial activity can be expressed in a wide range of products and forms including boring structures, biofilm-like subproducts, and framboidal pyrite precipitates. Microendolithic structures, in particular, are found in carbonate hardgrounds including tests of planktonic and benthic foraminifera and their traces can provide an extra paleoenvironmental marker of relative paleobathymetry, oxygenation, and environmental stress. Variegated traces of microbial activity including microborings, framboidal pyrite bacterial subproducts, and probable biofilms were herein studied in tests of benthic foraminifera from dysphotic to aphotic, shelf to an upper bathyal hypoxic environment. Collected material is from 6 localities in the Central Paratethys area, the Czech Republic (LOM-1 Mikulov, Hevlín), Slovakia (DNV, LKŠ-1), and Hungary (Rozalia), ranging from Rupelian to Serravalian. Microendolithic morphology was examined from resin casts obtained from the tests resulting in a total of ten ichnospecies and four other forms for which it was only possible to establish affinity on higher ranks. Levels of oxygen depletion were estimated from Benthic Foraminifera Oxygen index (BFOI). The bacterial origin of pyrite was inferred by morphology, grain size, and ẟS34 values. The number of observed microboring structures gradually reduce with the decrease of oxygen content, while the precipitation of framboidal pyrite were increasing at the same time. Biofilm-like structures, apart from the suggestive morphology, also showed an enriched content of elemental iron, sulfur, and phosphorus. Raman spectroscopy shows similarities with organic pigment spectra and is still under investigation.

Validation of non-equilibrium kinetics in CO2–N2 plasmas

This work explores the effect of N2 addition on CO2 dissociation and on the vibrational kinetics of CO2 and CO under various non-equilibrium plasma conditions. A self-consistent kinetic model, previously validated for pure CO2 and CO2–O2 discharges, is further extended by adding the kinetics of N2. The vibrational kinetics considered include levels up to v = 10 for CO, v= 59 for N2 and up to v 1= 2 and v 2= v 3= 5, respectively for the symmetric stretch, bending and asymmetric stretch modes of CO2, and account for electron-impact excitation and de-excitation (e–V), vibration-to-translation (V–T) and vibration-to-vibration energy exchange (V–V) processes. The kinetic scheme is validated by comparing the model predictions with recent experimental data measured in a DC glow discharge operating in pure CO2 and in CO2–N2 mixtures, at pressures in the range 0.6–4 Torr (80.00–533.33 Pa) and a current of 50 mA. The experimental results show a higher vibrational temperature of the different modes of CO2 and CO and an increased dissociation fraction of CO2, that can reach values as high as 70%, when N2 is added to the plasma. On the one hand, the simulations suggest that the former effect is the result of the CO2–N2 and CO–N2 V–V transfers and the reduction of quenching due to the decrease of atomic oxygen concentration; on the other hand, the dilution of CO2 and dissociation products, CO and O2, reduces the importance of back reactions and contributes to the higher CO2 dissociation fraction with increased N2 content in the mixture, while the N2(B3Πg) electronically excited state further enhances the CO2 dissociation.

Energetics and structure of SiC(N)(O) polymer‐derived ceramics

AbstractThis study presents new experimental data on the thermodynamic stability of SiC(O) and SCN(O) ceramics derived from the pyrolysis of polymeric precursors: SMP‐10 (polycarbosilane), PSZ‐20 (polysilazane), and Durazane‐1800 (polysilazane) at 1200°C. There are close similarities in the structure of the polysilazanes, but they differ in crosslinking temperature. High‐resolution X‐ray photoelectron spectroscopy shows notable differences in the microstructure of all polymer‐derived ceramics (PDCs). The enthalpies of formation (∆H°f, elem) of SiC(O) (from SMP‐10), SCN(O) (from PSZ‐20), and SCN(O) (from Durazane‐1800) are −20 ± 4.63, −78.55 ± 2.32, and −85.09 ± 2.18 kJ/mol, respectively. The PDC derived from Durazane‐1800 displays greatest thermodynamic stability. The results point to increased thermodynamic stabilization with addition of nitrogen to the microstructure of PDCs. Thermodynamic analysis suggests increased thermodynamic drive for forming SiCN(O) microstructures with an increase in the relative amount of SiNxC4−x mixed bonds and a decrease in silica. Overall, enthalpies of formation suggest superior stabilizing effect of SiNxC4−x compared to SiOxC4−x mixed bonds. The results indicate systematic stabilization of SiCN(O) structures with decrease in silicon and oxygen content. The destabilization of PDCs resulting from higher silicon content may reach a plateau at higher concentrations.

Oxygen and pCO2 in the Surface Waters of the Atlantic Southern Ocean in 2021–2022

The carbon dioxide concentration in the atmosphere has progressively risen since pre-industrial times. About one-third of the anthropogenically generated CO2 is absorbed by the waters of the World Ocean, whereas the waters of the Southern Ocean take up about 40% of this CO2. The concentrations of oxygen and carbon dioxide dissolved in seawater are sensitive to climate changes, transferring anthropogenic pressures with consequences for the biogeochemical cycles in the World Ocean. The Southern Ocean is a key region for the exchange of oxygen and carbon between the surface water and the atmosphere and for their transfer with cold water masses to the deep layers of the Ocean. In this paper, we discuss the dynamics of the carbon dioxide partial pressure (pCO2) and dissolved oxygen (O2) in the surface waters of the Atlantic Southern Ocean based on data collected during the 87th cruise of the R/V “Academik Mstislav Keldysh”. The study area includes the Bransfield Strait, Antarctic Sound, the Powell Basin, the Weddell, and Scotia Seas. We have analyzed the spatial distribution of pCO2 and oxygen for the areas of transformation of water masses and changes in biogeochemical processes. In the zone of Scotia and Weddell Seas, we have observed an increase in pCO2 and a decrease in oxygen concentrations at the transect from the Weddell Sea at 56° W to the Powell Basin. From the Antarctic Sound to the Bransfield Strait, a decrease in oxygen saturation and an increase in pCO2 has been traced. The surface waters of the Bransfield Strait have revealed the greatest variability of hydrochemical characteristics due to a complex structure of currents and intrusions of different water masses. In general, this area has been characterized by the maximum pCO2, while the surface waters are undersaturated with oxygen. The variability of the AOU/ΔpCO2 (w-a) ratio has revealed a pCO2 oversaturation and an O2 undersaturation in the waters of the Bransfield Strait. It is evidence of active organic carbon decomposition as the major controlling process. Yet, photosynthesis is the major biogeochemical process in the studied areas of the Weddell and Scotia seas, and their waters have been undersaturated with pCO2 and oversaturated with O2. As it comes from the analysis of the distribution and correlation coefficients of AOU and the sea-air gradient of pCO2 with other physical and biogeochemical properties, the predominance of the biotic processes to the dynamics of O2 and pCO2 in the surface water layer has been demonstrated for the studied areas. Yet, there is evidence of additional sources of CO2 not associated with the production and destruction processes of organic matter.

Impact of hypoxia conditions on the Mnemiopsis leidyi A. Agassiz, 1865 bioluminescence.

The findings of the study on the impact of hypoxia on the glow of the Black Sea ctenophore Mnemiopsis leidyi A. Agassiz, 1865 of three size groups (20-30, 30-45, and 45-60 mm) were obtained under experimental conditions. Peculiarities of ctenophore bioluminescence were studied during mechanical and chemical stimulation under the conditions of normoxia (at an oxygen concentration of 5.6-6.7 mg O2 ·L-1 ), moderate hypoxia (2.5-2.8 mg O2 ·L-1 ), and acute hypoxia (1.2-1.5 mg O2 ·L-1 ). An increase in the amplitude and energy of luminescence of the ctenophores mechanically and chemically stimulated was observed at an oxygen concentration of 1.2-1.5 mg O2 ·L-1 (acute hypoxia) in two size groups in the lobate form (30-45 and 45-60 mm). The inhibition of amplitude, energy, and duration of the signal was registered in M. leidyi ctenophores at the transitional stage from larva to the lobate form under conditions of acute hypoxia. It was noted that in normoxia, the values of the amplitude and energy of the bioluminescent signal of M. leidyi increase along with a size growth of an individual. This phenomenon was observed both during mechanical and chemical stimulations. Under conditions of acute hypoxia, this trend was mainly preserved. The universality of the relation between the bioluminescence of the organisms and their bioenergetics is obvious. The bioluminescent system of ctenophores has the role of an antioxidant system and is engaged in the neutralization of reactive oxygen species, that is the process during which photons are emitted. The response of the bioluminescent system to a decrease in О2 concentration can be associated with an increase in the production of ROS that provides high values of the ctenophore luminescence under hypoxic conditions.

Effect of hypoxia on HIF-1α and NOS3 expressions in CD34+ cells of JAK2V617F-positive myeloproliferative neoplasms

PurposeMyeloproliferative neoplasms (MPN) are a heterogeneous group of hematopoietic stem-cell diseases with excessive proliferation of one or more blood cell lines. In this study, we evaluated the effect of different oxygen concentrations on HIF-1α and NOS3 gene expression to determine the effect of the bone marrow microenvironment on JAK2V617F positive Philadelphia chromosome negative (Ph−) MPNs. Patients and methodsPeripheral blood mononuclear cells (MNC) of 12 patients with Ph− MPN were collected. The presence of JAK2V617F allele status was determined with allele-specific nested PCR analysis. MPN CD34+ and CD34depleted populations were isolated from MNC by magnetic beads. Separate cell cultures of CD34+/depleted populations were managed at different oxygen concentrations including anoxia (∼0%), hypoxia (∼3%), and normoxia (∼20%) conditions for 24 ​h. HIF-1α and NOS3 gene expression changes were examined in each population related to JAK2V617F status with real time RT-PCR. ResultIt was revealed that relative HIF-1α and NOS3 expressions were significantly increased in response to decreased oxygen concentration in all samples. Relative HIF-1α and NOS3 expressions were found to be higher especially in CD34+ and CD34depleted populations carrying JAK2V617F mutations compared to MPN patients carrying wild-type JAK2. ConclusionJAK2V617F might have specific role in HIF-1α and NOS3 regulations with respect to low oxygen concentrations in Ph− MPN. Further evaluations might reveal the effect of JAK2V617F on Ph− MPN pathogenesis in bone marrow microenvironment.

Impact of atmospheric pressure variations on aerobic biodegradation test.

Biodegradation rate is an important index to evaluate the environmental risk of chemicals, which is usually determined by measuring oxygen consumption through respirometer in a biodegradation test. However, atmospheric pressure variations affect reactor oxygen concentration and oxygen volume recorded by respirometer in biodegradation test, and the parameters of reactor volume and test material amount amplify its effect. Atmospheric pressure variation >1 kPa could introduce >20% underestimation in biodegradation rate when a small amount of test material (0.04-0.2 g per 100 g of inoculum) and high reactor volume (2-4 L) were used according to the international standards. A 5 kPa drop in atmospheric pressure leads to a 6% decrease in headspace oxygen concentration in the reactor, which could subsequently inhibit biodegradation microbials and decrease the biodegradation rate by 30%. Moreover, the biodegradation process (oxygen consumption rate) could be accelerated/delayed several times by atmospheric pressure variations compared to the process without variations when the oxygen consumption rate was <5 mL h-1 in a 0.5 or 1 L reactor and <10 mL h-1 in a 2-L reactor. Mitigating the effects of atmospheric pressure variations on biodegradation test includes lowering the reactor volume, increasing the test material amount and recording atmospheric pressure for further modification.

Pacific Decadal Oscillation Influences Tropical Oxygen Minimum Zone Extent and Obscures Anthropogenic Changes

AbstractObservations suggest that the tropical Pacific Ocean has lost oxygen since the 1960s leading to the expansion of its oxygen minimum zone (OMZ). Attribution to anthropogenic forcing is, however, difficult because of limited data availability and the large natural variability introduced by the Pacific Decadal Oscillation (PDO). Here, we evaluate the PDO influence on oxygen dynamics and OMZ extent using observations and hindcast simulations from two global ocean circulation models (NEMO‐PISCES, MOM6‐COBALT). In both models, the tropical Pacific oxygen content decreases by about 30 Tmol.decade−1 and the OMZ volume expands by 1.3 × 105 km3.decade−1 during PDO positive phases, while variations of similar magnitude but opposite sign are simulated during negative phases. Changes in equatorial advective oxygen supply, partially offset by biological demand, control the oxygen response to PDO. Observations which cover 39% of the tropical Pacific volume only partially capture spatio‐temporal variability, hindering the separation of anthropogenic trend from natural variations.

Human thermal physiological response of wearing personal protective equipment: An educational building semi-open space experimental investigation

With the outbreak and spread of the COVID-19 epidemic, HCWs are frequently required to wear personal protective equipment (PPE) for nucleic acid sample collection in semi-open transition spaces. Wearing PPE causes significant psychological and physical stress in HCWs. In this study, operative temperature (Top) and wet-bulb globe temperature (WBGT) were used to assess thermal conditions through field experiments, while multiple physiological parameters were measured in the subjects. The results indicated that the subjects showed statistically significant differences in thermal perception and physiological parameters with and without PPE. Using observed increases in heart rate (HR), auditory canal temperature (Tac), mean skin temperature (MST), and end-tidal CO2 pressure, subjects were shown to have an increased metabolic rate and heat storage while wearing PPE. Additionally, a decrease in oxygen concentration was also observed, and this decrease may be linked to fatigue and cognitive impairment. Moreover, HR, MST, and Tac showed a significant linear relationship, which increased with temperature and operative temperature, and the HR response was stronger with PPE than without PPE. The neutral, preferred, and acceptable temperatures were significantly lower with PPE than without PPE, and the deviations for neutral Top/WBGT were 9.5/7.1 °C and preferred Top/WBGT was 2.2/4.0 °C, respectively. Moreover, the upper limits of acceptable WBGT, 29.4 °C with PPE and 20.4 °C without PPE, differed significantly between the two phases. Furthermore, the recorded physiological parameter responses and thermal perception responses of the subjects while wearing PPE indicated that they were at risk of thermal stress. Overall, these results suggest that people who wear PPE should focus on their health and thermal stress. This study provides a reference for the development of strategies to counteract heat stress and improve thermal comfort.

Intrinsic Smoke Properties and Prediction of Smoke Production in National Bureau of Standards (NBS) Smoke Chamber

Smoke production in a smoke chamber is characterized by the accumulation of smoke and the continuous consumption of oxygen leading to a vitiated atmosphere. However, a method is proposed to predict the smoke evolution in a smoke chamber at 25 kW/m2 by using material properties calculated from a cone calorimeter, as already shown in a previous article. These properties represent the ability of a material to produce smoke at a specific mass loss rate. The influence of a flame retardant on these properties can be used as a quantitative measurement of its action on smoke production. These properties can be calculated at another heat flux than 25 kW/m2. The knowledge of the curve “mass loss rate = f(time)” in a smoke chamber is still required, but this curve is close to that measured in a cone calorimeter at the same heat flux. The results prove that the smoke production in a smoke chamber and cone calorimeter is qualitatively similar, i.e., the decrease of oxygen content in a smoke chamber has no influence on smoke (at least as long as optical density does not exceed 800).

Migration of lattice oxygen during chemical looping dry reforming of methane with Ca2Fe2O5/Zr0.5Ce0.5O2 oxygen carrier

Ca2Fe2O5/Zr0.5Ce0.5O2 exhibits excellent reactivity in chemical looping dry reforming of methane. The migration of lattice oxygen is crucial to the cyclic stability of oxygen carrier, but the lattice oxygen migration in Ca2Fe2O5/Zr0.5Ce0.5O2 were not extensively explored. This work explored the lattice oxygen migration of Ca2Fe2O5/Zr0.5Ce0.5O2 during redox process. During the reduction process, the lattice oxygen reacted with the hydrogen radical, resulting in the decrease of lattice oxygen content and the increase of oxygen vacancy. As the lattice oxygen released, the spatial structure of Ca2Fe2O5 was destroyed and transferred into Fe8Ca8O20 with oxygen defects due to lattice distortion. The exothermic reaction between H2 and Ca2Fe2O5 promoted the formation of FeH with hexagonal close-packed structure. After reduction for 160 min, the unstable FeH completely converted into FeC with stable structure and the complete reduction was reached. As for the oxidation process, Fe and CaO reacted with the oxygen radical to form Ca2Fe2O5, leading to the complete recovery of lattice oxygen within 40 min. However, crystalline phase transformation could lead to the spatial structure instability and sintering after multiple redox cycles. Overall, the migration of oxygen during redox process is clarified in detail, providing a reference for improving the cyclic stability of Ca2Fe2O5/Zr0.5Ce0.5O2.