O2 Mixture Research Articles

Elevated ozone and carbon dioxide affects the composition of volatile organic compounds emitted by Vicia faba (L.) and visitation by European orchard bee (Osmia cornuta).

Recent studies link increased ozone (O3) and carbon dioxide (CO2) levels to alteration of plant performance and plant-herbivore interactions, but their interactive effects on plant-pollinator interactions are little understood. Extra floral nectaries (EFNs) are essential organs used by some plants for stimulating defense against herbivory and for the attraction of insect pollinators, e.g., bees. The factors driving the interactions between bees and plants regarding the visitation of bees to EFNs are poorly understood, especially in the face of global change driven by greenhouse gases. Here, we experimentally tested whether elevated levels of O3 and CO2 individually and interactively alter the emission of Volatile Organic Compound (VOC) profiles in the field bean plant (Vicia faba, L., Fabaceae), EFN nectar production and EFN visitation by the European orchard bee (Osmia cornuta, Latreille, Megachilidae). Our results showed that O3 alone had significant negative effects on the blends of VOCs emitted while the treatment with elevated CO2 alone did not differ from the control. Furthermore, as with O3 alone, the mixture of O3 and CO2 also had a significant difference in the VOCs' profile. O3 exposure was also linked to reduced nectar volume and had a negative impact on EFN visitation by bees. Increased CO2 level, on the other hand, had a positive impact on bee visits. Our results add to the knowledge of the interactive effects of O3 and CO2 on plant volatiles emitted by Vicia faba and bee responses. As greenhouse gas levels continue to rise globally, it is important to take these findings into consideration to better prepare for changes in plant-insect interactions.

Lung-gut axis of microbiome alterations following co-exposure to ultrafine carbon black and ozone

BackgroundMicrobial dysbiosis is a potential mediator of air pollution-induced adverse outcomes. However, a systemic comparison of the lung and gut microbiome alterations and lung-gut axis following air pollution exposure is scant. In this study, we exposed male C57BL/6J mice to inhaled air, CB (10 mg/m3), O3 (2 ppm) or CB + O3 mixture for 3 h/day for either one day or four consecutive days and were euthanized 24 h post last exposure. The lung and gut microbiome were quantified by 16 s sequencing.ResultsMultiple CB + O3 exposures induced an increase in the lung inflammatory cells (neutrophils, eosinophils and B lymphocytes), reduced absolute bacterial load in the lungs and increased load in the gut. CB + O3 exposure was more potent as it decreased lung microbiome alpha diversity just after a single exposure. CB + O3 co-exposure uniquely increased Clostridiaceae and Prevotellaceae in the lungs. Serum short chain fatty acids (SCFA) (acetate and propionate) were increased significantly only after CB + O3 co-exposure. A significant increase in SCFA producing bacterial families (Ruminococcaceae, Lachnospiraceae, and Eubacterium) were also observed in the gut after multiple exposures. Co-exposure induced significant alterations in the gut derived metabolite receptors/mediator (Gcg, Glp-1r, Cck) mRNA expression. Oxidative stress related mRNA expression in lungs, and oxidant levels in the BALF, serum and gut significantly increased after CB + O3 exposures.ConclusionOur study confirms distinct gut and lung microbiome alterations after CB + O3 inhalation co-exposure and indicate a potential homeostatic shift in the gut microbiome to counter deleterious impacts of environmental exposures on metabolic system.

Hydrogen sulfide measurement of combustion gaseous product using ultraviolet absorption spectroscopy

Measurement of hydrogen sulfide (H2S) in gaseous product can provide direct reference for high-temperature corrosion of industrial combustion equipment. Aiming at the interference effect of overlapping measurement of absorption spectrum for H2S and other combustion gas components in UV absorption spectroscopy, the simulation calculation of ultraviolet band absorption spectrum of the typical gaseous products of coal combustion were carried out. The cross interference effects of combustion gaseous products were analyzed in detail. Due to the SO2 and H2S gas under typical combustion condition have equivalent absorption strength in the 228 nm-233 nm band, the influence of SO2 on H2S concentration inversion must be emphatically considered, and the inversion algorithm of H2S gas concentration under the background interference of combustion gaseous products SO2 was put forward. In order to validate the measurement accuracy by the inversion algorithm, the measurement experiments of gas mixture of H2S and SO2 were carried out. The results show that the algorithm can effectively solve the problem of cross interference between the detection of H2S and SO2 in the combustion gaseous products by UV absorption spectroscopy. On this basis, the sampling, pre-treatment and H2S gas concentration measurement system for boiler flue gas near the wall was developed and applied to measure H2S concentration of flue gas near the wall in a 1000 MW ultra-supercritical coal-fired power generation boiler. The results can provide important references for combustion adjustment and high-temperature corrosion prevention of boiler.

Metrology of Ar-N2/O2 Mixture Atmospheric Pressure Pulsed DC Jet Plasma and its Application in Bio-Decontamination.

Atmospheric pressure plasma jets are gaining a lot of attention due to their widespread applications in the field of bio-decontamination, polymer modification, material processing, deposition of thin film, and nanoparticle fabrication. Herein, we are reporting the disinfection of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli bacteria using plasma jet. In this regard, Ar-O2, Ar-N2, and Ar-O2-N2 mixture plasma is generated and characterized using optical and electrical characterization. Variation in plasma parameters like electron temperature, electron density, and reactive species production is monitored with discharge parameters such as applied voltage and feed gas concentration. Results show that the peak average power consumed in Ar-O2, Ar-N2, and Ar-O2-N2 mixture plasma is found to be 4.45, 2.93, and 4.35 W respectively, at 8 kV. Moreover, it is noted that by increasing applied voltage, the electron temperature, electron density, and reactive species production also increases. It is worth noting that electron temperature increases with increase in oxygen concentration in the mixture (, while it decreases with increase in nitrogen concentration in the mixture (Ar-N2). Similarly, a decreasing trend in electron temperature is noted for Ar-O2-N2 mixture plasma. On the other hand, a decreasing trend in electron density is noted for all the mixtures. Reduction in viable colonies of Pseudomonas aeruginosa, Staphylococcus Aureus, and Escherichia coli were confirmed by the serial dilution method. The inactivation efficiency of pulsed DC plasma generated, in the Ar-N2 mixture at 8 kV and 6 KHz, was evaluated against P. aeruginosa, S. aureus and E. coli bacteria by measuring the number of surviving cells versus plasma treatment time. Results showed that after 240 s of plasma treatment, the number of survival colonies of the mentioned bacteria was reduced to less than 30 CFU/mL.

Determination of the apparent effective ionization coefficient in mixtures of He and O2 using steady-state Townsend discharge: effect of penning ionization and attachment

He:O2 gas mixtures are popular in many non-thermal plasma applications because of the good thermal conductivity of He and high production of reactive oxygen species. The applications utilizing reactive oxygen species, in particular, applications in biomedicine require accurate knowledge of the fundamental ionization parameters of gases such as the ionization coefficient. This study was focused on experimental determination of the reduced apparent effective ionization coefficient α ea /N in He:O2 mixtures. Experiments were conducted in the absolute pressure range of 10–800 Torr and reduced electric field E/N range of 40–1000 Td utilizing a steady-state non-self-sustaining Townsend discharge. Experimental results were compared with a theoretical model which was based on BOLSIG + calculation of ionization and attachment coefficients and additionally considered the ion conversion of O− to O2 −, detachment from O2 − and formation of O3 − and Penning ionization by He metastable species. The measurements agreed reasonably well with model calculations. Comparison with model suggest that He metastable species affect net ionization in He:O2 mixtures with O2 concentrations up to 10% often encountered in the applications and thus should be included in models of atmospheric pressure plasmas. The attachment of electrons became important at O2 concentrations above 10% and is therefore less important in most applications.

A redox model for NO oxidation, NH3 oxidation and high temperature standard SCR over Cu-SSZ-13

A kinetic model is developed to predict the influence of temperature and hydrothermal aging on the redox of active Cu sites under standard SCR, NO oxidation and NH3 oxidation conditions over a practically relevant fully-formulated Cu-SSZ-13 catalyst. NO2/N2 production during NO/NH3 titration of CuII sites is utilized to identify rate parameters associated with NO-only RHC (reduction half cycle) and NH3-only RHC respectively. Integral N2 formation during subsequent NO + NH3 titration is consistent with the production of one NO2 per two CuII sites reduced during NO-only RHC and one N2 per six CuII sites reduced during NH3-only RHC. Decreased reduction of CuII sites by NO/NH3 upon hydrothermal aging, along with the production of one NO2 per two CuII sites during NO-only RHC, is accordant with the involvement of proximal ZCuOH and oxygen-bridged dimeric CuII sites. Oxidation of partially solvated and framework coordinated ZCu (CuI) sites occurs in presence of O2, does not produce N2 and can lead to the consumption of Brønsted acid sites. A global OHC kinetic model is developed to predict transient and integral N2 formation during exposure of CuI sites to a mixture of NO and O2. The resulting redox kinetic model quantitatively predicts NO and NH3 consumption during isothermal transient response Cu redox (TRCR) protocols, along with temperature and age dependent steady-state standard SCR and oxidation conditions. The redox model presented in this work synthesizes recent kinetic, spectroscopic and computational findings to provide a foundational description of active site redox during standard SCR, NO oxidation and NH3 oxidation over Cu-SSZ-13.

Mixed gas concentration inversion based on the hierarchical feature fusion convolutional neural network

Recently, the detection of gas mixtures has attracted considerable attention due to its promising application in disease diagnosis, environmental monitoring and so on. However, the detection of gas mixtures is inevitably subject to the cross-interference between different components. Herein, we propose a hierarchical feature fusion convolutional neural network (CNN) model for mixed gas concentration inversion. In our experiment, mixtures of SO2, NO2 and NH3 were analyzed. SO2 and NO2 were the detected gases while NH3 was the interfering gas. The proposed model can be applied to low-resolution spectra. Compared with the model without hierarchical structure and feature fusion, the mean absolute errors of SO2 and NO2 decreased by 80.3% and 87.0% in the simulated spectral samples. The experimental results also demonstrate that the proposed model could effectively reduce the cross-interference and improve the accuracy of gas concentration inversion. This model would have a promising application in the field of gas detection and low-resolution spectra.

Effects of confinement on detonation in H2–O2 mixture with transverse concentration gradient

Since hydrogen has wide flammability limit and low ignition energy, it could be easily ignited and be easy for the transition to a detonation, leading to extremely serious impacts in explosion accidents or extremely high combustion effeciency in the propulsion. In the field of explosion accidents and the combustion chamber of propulsion systems, hydrogen mixtures are more likely to be highly non-uniform and a detonation usually propagates in a non-homogeneous medium. The work studies behaviors of detonations in non-homogenous medium by a high-resolution simulations. We widen computational domain and steepen the gradient to weaken the role of transverse wave on cellular detonations propagating in the medium with transverse concentration gradient and to reveal the interaction of longitudinal shock with reaction wave. The results show that characteristics of detonations in nonuniform medium is controlled by coupling role of gradient and confinement. As a domain is sufficient wide, the reflection wave is rather weak so that the detonation takes on galloping propagation, with a single-head mode. As the width is mediate, detonation cell takes on highly irregularity, similar to that of highly unstable detonation. However, in the narrow domain, steepening gradient plays a key role while confinement becomes minor in detonation propagation.

Selective Sulfation Roasting for Cobalt and Lithium Extraction from Industrial LCO-Rich Spent Black Mass

The extraction of cobalt from secondary resources has become crucial, as cobalt has been identified as a strategically important and critical raw material due to the high risks of supply chain disruptions. In this work, selective sulfation roasting was investigated as a potential recycling strategy to extract cobalt and lithium from an industrial lithium cobalt oxide (LCO)-rich black mass. Additionally, the effect of graphite on metal extraction was studied. In the first set of experiments, the sieved black mass fraction containing both cathode and anode materials was directly roasted in a predetermined composition of gas mixtures of SO2, O2, and Ar for 1 h at 850 °C. The gas composition was determined from Kellogg’s diagram to allow for the selective sulfation of Co and Li. In another set of experiments, the carbon present in the black mass was first removed by roasting the material in Ar for 2 h and then in an Ar and O2 gas mixture for five hours at 600 °C. Afterward, selective sulfation roasting was performed in mixtures of SO2, O2, and Ar gas similar to the previous set of experiments. For comparison, similar experiments were performed at 800 °C. The sulfation roasted black mass was leached in water to study the efficiency of Co extraction into the solution. Interestingly, the presence of carbon was found to be beneficial for Co extraction. The extraction efficiency for the first case (with carbon present in the raw material) was observed to be more than three times higher than in the second case (with carbon removed) for sulfation at 850 °C. The extraction efficiency and purity of the extracted Co were found to be better for higher temperature sulfation roasting conditions due to faster reaction kinetics. It was also found that almost all of the Li could be recovered while extracting Co. The maximum efficiency of the extraction was 99.51% Li and 61.21% Co for roasting under a gas flow of 10% SO2-10% O2-Ar at 850 °C for 60 min. These results suggest that Co and Li can be selectively extracted from the black mass by sulfation roasting pre-treatment followed by leaching in water. In holistic processing, the leach residue can then be further subjected to battery metal processing by state-of-the-art methods.

Photoluminescence of SiO2:Eu and SiON:Eu films: Color selection through activating emissions from SiOx, Eu3+, and Eu2+

Photoluminescence (PL) from Eu-doped SiO2 (SiON) thin films sputter-deposited in O2, H2O vapor, or a mixture of O2 and N2 gases was characterized by excitation at a wavelength of 325 nm. The SiO2 films deposited at 500 °C with O2 contained small amount of α-quartz nanocrystals. The primary condition for either or both of the Eu3+ and Eu2+ emissions to appear was Eu content between 1 and 3 at.%, and 2.5 at.% gave the maximum emission intensity of Eu3+. The PL spectra showed only the Eu3+ emission when the films were deposited at room temperature (RT) and subsequently post annealed in an O2 atmosphere. Changing the annealing atmosphere from O2 to a vacuum and annealing at temperatures above 600 °C resulted in an intense broad violet emission signal peaking at 390 nm along with the Eu3+ emission signal. This violet emission originated from reduced SiOx species. When deposited at RT, similar temperature-dependent emission properties were obtained regardless of the reactive gas (H2O vapor or a mixture of O2 and N2). Complete transformation of Eu3+ into Eu2+ occurred when deposition was carried out at temperatures between 400 and 500 °C; a blue emission at around 467 nm was predominant from the SiO2:Eu2+ films. Deposition in the O2 and N2 gas mixture at elevated temperatures produced SiON:Eu2+ films, from which an intense white emission band peaking at 525 nm and ranging between 400 and 650 nm was observed.

Optical diagnosis of an inductively coupled plasma source for atmosphere-breathing electric propulsion system

Atmosphere-breathing electric propulsion (ABEP) systems capture atmospheric particles for use as propellant. In the best-case scenario, such systems can undertake long-life space missions without carrying propellant from the ground. The present research mainly focuses on plasma discharge processes based on inductively coupled plasma generation from atmospheric particles in very low Earth orbit (120–250 km). The optical diagnosis is done when the N2 and O2 mixture is injected into the low-pressure discharge chamber. Numerous active groups can be identified from the emission spectra, including excited molecules, molecular ions, atoms, and excited atoms. The generation mechanism of active groups is also clarified to understand the ionization process. The variations of plasma parameters are analyzed for different ratios of N2 to O2, which can also be expanded to describe the potential behavior of ABEP systems in low Earth orbit. Note that this research is only a preliminary study and is not fully representative of the potential of ABEP systems. However, to develop ABEP systems, it is essential to understand the plasma behavior of discharge systems.

In situ diffraction monitoring of nanocrystals structure evolving during catalytic reaction at their surface

With decreasing size of crystals the number of their surface atoms becomes comparable to the number of bulk atoms and their powder diffraction pattern becomes sensitive to a changing surface structure. On the example of nanocrystalline gold supported on also nanocrystalline {text{CeO}}_2 we show evolution of (a) the background pattern due to chemisorption phenomena, (b) peak positions due to adsorption on nonstoichiometric {text{CeO}}_{2-x} particles, (c) Au peaks intensity. The results of the measurements, complemented with mass spectrometry gas analysis, point to (1) a multiply twinned structure of gold, (2) high mobility of Au atoms enabling transport phenomena of Au atoms to the surface of ceria while varying the amount of Au in the crystalline form, and (3) reversible {text{CeO}}_2 peaks position shifts on exposure to He–X–He where X is O2, H2, CO or CO oxidation reaction mixture, suggesting solely internal alternations of the {text{CeO}}_2 crystal structure. We found no evidence of ceria lattice oxygen being consumed/supplied at any stage of the process. The work shows possibility of structurally interpreting different contributions to the multi-phase powder diffraction pattern during a complex physico-chemical process, including effects of physi-, chemisorption and surface evolution. It shows a way to structurally interpret heterogeneous catalytic reactions even if no bulk phase transition is involved.

The Use of E-Peroxone to Neutralize Wastewater from Medical Facilities at a Laboratory Scale

The treatment of medical wastewater by the peroxone (AOP) and electro-peroxone (E-peroxone) processes was analyzed. The E-peroxone process is based on the production of hydrogen peroxide electrochemically from an O2 and O3 gas mixture produced in sparged ozone generator effluent using graphite-polytetrafluorethylene cathodes. The electrogenerated H2O2 reacts with sparged ozone to produce hydroxyl radicals. All advanced oxidation processes presented in this study effectively removed chemical oxygen demand (COD) by up to 87%. The use of E-peroxone showed 15% better results in COD reduction than conventional peroxone. The research suggests that E-peroxone is more sufficient at removing pollutants in wastewater than peroxone. Hence, E-peroxone was found to be more cost-effective than AOP in this case.

Microchip Employing Short Period Thermal Modulation for the Detection of H₂S and SO₂ Mixtures

Most of the previous works used to improve the performance of single gas sensors by forming the array. However, more discrete sensors would bring higher cost, larger volume, and power consumption. With the technique of micro-electro-mechanical systems (MEMS), a microchip with three sensitive materials (ZIF8-WO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , ZIF8-In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , and ZIF8-SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) has been fabricated to detect the mixtures of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . By combining the short-period thermal modulation with the periodic sampling, the response curve could be split into several sub-curves, and each sub-curve was regarded as the virtual device operated at a constant temperature. It can reduce power consumption without increasing the physical volume. Based on the fluctuation and distinction of the descriptors, the optimal 24 features were extracted from the initial 144 features. A stacked denoising autoencoder (SDAE) was employed to enhance the generalization ability of Bagging neural networks. Toward the unknown 30 mixtures of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , the recognition model under short-period thermal modulation (SPT, 78.67 %) had better performance than that under constant temperature (CT, 62.67 %). SPT (92.63 %) has a smaller non-overlapping area of feature buffers than CT (50.45 %), which might be the physics behind the performance improvement. Certainly, this work has broad application prospects in the future.

Study on the concentration retrieval of SO2 and NO2 in mixed gases based on the improved DOAS method.

NO2 and SO2 are important components of air pollutants, and their absorption spectra are superimposed at 193-253 nm. The superposed spectra affect the gas concentration retrieval based on the ultraviolet differential optical absorption spectroscopy (DOAS) method. In this study, a suitable wavelength band was chosen for concentration retrieval, moreover, the characteristics of the quasi-periodic variation of absorption cross-section with wavelength was given sufficient attention and then the superposed spectra were separated by the Fast Fourier transform (FFT) method. The concentration of the gases to be measured was calculated according to the relationship between the amplitude of absorbance after FFT and the gas concentration. The experimental results prove that by using an absorption cell with a 700 mm optical path, the relative deviation absolute value of the retrieval concentration of SO2 in a NO2 and SO2 gas mixture is less than 1.471%, and that of NO2 in a NO2 and SO2 gas mixture is less than 7.207%. The method has good adaptability, high detection precision, whether single SO2, NO2 or a mixture of both, and important reference value for the development of DOAS and future research on the high-precision detection of more types of mixed gases in the ultraviolet band, such as gas mixtures of NO2, SO2 and NO in flue gas.

2D-imaging of absolute OH and H2O2 profiles in a He–H2O nanosecond pulsed dielectric barrier discharge by photo-fragmentation laser-induced fluorescence

Pulsed dielectric barrier discharges (DBD) in He–H2O and He–H2O–O2 mixtures are studied in near atmospheric conditions using temporally and spatially resolved quantitative 2D imaging of the hydroxyl radical (OH) and hydrogen peroxide (H2O2). The primary goal was to detect and quantify the production of these strongly oxidative species in water-laden helium discharges in a DBD jet configuration, which is of interest for biomedical applications such as disinfection of surfaces and treatment of biological samples. Hydroxyl profiles are obtained by laser-induced fluorescence (LIF) measurements using 282 nm laser excitation. Hydrogen peroxide profiles are measured by photo-fragmentation LIF (PF-LIF), which involves photo-dissociating H2O2 into OH with a 212.8 nm laser sheet and detecting the OH fragments by LIF. The H2O2 profiles are calibrated by measuring PF-LIF profiles in a reference mixture of He seeded with a known amount of H2O2. OH profiles are calibrated by measuring OH-radical decay times and comparing these with predictions from a chemical kinetics model. Two different burst discharge modes with five and ten pulses per burst are studied, both with a burst repetition rate of 50 Hz. In both cases, dynamics of OH and H2O2 distributions in the afterglow of the discharge are investigated. Gas temperatures determined from the OH-LIF spectra indicate that gas heating due to the plasma is insignificant. The addition of 5% O2 in the He admixture decreases the OH densities and increases the H2O2 densities. The increased coupled energy in the ten-pulse discharge increases OH and H2O2 mole fractions, except for the H2O2 in the He–H2O–O2 mixture which is relatively insensitive to the additional pulses.

Oxygen-Ozone Therapy in Cervicobrachial Pain: A Real-Life Experience.

This prospective, open-label clinical study was carried out to evaluate both the efficacy and safety of intramuscular paravertebral injections of an oxygen−ozone (O2−O3) mixture in patients with cervicobrachial pain. We enrolled 540 subjects affected by cervicobrachial pain referred to the Ozone Therapy Ambulatory at the Mater Domini Hospital of Catanzaro (Italy) and to the Center of Pain in Taurianova (Reggio Calabria, Italy). All the subjects (n = 540) completed the treatment and the follow-up visits. The subjects received a mean of 11 cervical intramuscular treatments with an O2−O3 mixture (5 mL) with an O3 concentration of 10 μg/mL bis a week. The improvement of pain was measured by a change in the mean of the Visual Analog Scale (VAS) score from baseline to the end of treatment and during follow-ups. Patient satisfaction was assessed at the end of treatment using the SF-36 Questionnaire. The development of adverse drug reactions was recorded. The mean (±standard deviation) VAS pain score at baseline, at the end of treatment, and during follow-ups showed a significant reduction in pain over time (p < 0.001). All the patients who were enrolled (n: 540) were pain-free after one year. According to the pain distribution, all subjects showed a significant reduction in pain over time in each group (p < 0.05). No significant differences were observed with respect to sex or age. No adverse events were observed during the study. In conclusion, we documented that the intramuscular injection of an O2−O3 mixture is an effective and safe treatment option for patients with cervicobrachial pain.

Cardiovascular Effects of Adding Epinephrine to Bupivacaine in Children Undergoing Caudal Block: A Double-blind Randomized Clinical Trial

Background: Caudal block is a common, safe, and effective anesthetic technique for lower abdominal, urological, and lower extremity surgeries in pediatrics. Objectives: This study aimed to evaluate the cardiovascular effects of adjuvant epinephrine in the caudal block on heart rate and blood pressure changes in children. Methods: This double-blind, randomized clinical trial was performed on 60 children who underwent elective infra-umbilical surgeries. They were under general anesthesia with midazolam, fentanyl, lidocaine, and propofol. The patients were ventilated through laryngeal mask airway (LMA), and anesthesia was maintained with sevoflurane in O2 and N2O mixture. The intervention group received a caudal block with 0.2% bupivacaine and 1/200000 epinephrine (1 mL/kg), while the control group received a caudal block without epinephrine. Heart rate, blood pressure, and ECG were monitored before the block and in the first, fifth, and 20th minutes after surgery. Results: The two groups showed no statistically significant differences in demographics and systolic and diastolic blood pressures. However, sinus arrhythmia was more prevalent in the study group in the first minute after the block (P &lt; 0.001). No differences were observed in the incidence of arrhythmia in the fifth and 20th minutes after the block. Conclusions: It appears that epinephrine as an adjuvant to the caudal block does not have long-lasting effects after the block, except sinus tachycardia in the first minute. Considering that no changes in blood pressure and other hemodynamic parameters were observed, it seems that epinephrine can be used safely in the caudal block in pediatric patients.

Combustion characteristics of liquid carbon dioxide-dried coal at different pressures of CO2–O2 mixture

In this study, the coal combustion behavior was determined at different combustion pressures, including supercritical CO2–O2 conditions. The coal mass and mass ratio of oxygen-to-coal remained constant. The drying impact of liquid carbon dioxide (LCO2) on supercritical combustion was investigated using raw coal with a high moisture content (20%). The extent of combustion (i.e., coal conversion) and particle temperature were measured using a weighing method and a two-color pyrometer, respectively. The effects of oxygen diffusion and volatile release on the extent of combustion were explored as pressures varied from subcritical to supercritical conditions. The temperature was further increased at the same supercritical pressure to study the effect of oxygen diffusivity on combustion. The phase change behavior of CO2–O2 mixture is identified and visualized. The kinetic and diffusion data were used to determine the Thiele modulus and the resultant effectiveness factor. The role of the hydrophobic surface groups in coal in the LCO2 drying process was investigated using Fourier Transform Infrared (FTIR) spectroscopy. In addition, the time-resolved water contact angle with the LCO2-treated coal sample was determined using the in-situ pendent drop method at atmospheric pressure.

Adsorption processes on a carbonaceous surface: Electron spin resonance study

The effect of pyrolysis at T ∼700 °C of the low-rank coal samples was studied using scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), and Raman scattering of light methods. The kinetics of adsorption-desorption processes on a carbon surface was first investigated based on the dynamics of the spin characteristics of paramagnetic defects (carbon dangling bonds). The EPR signals of these defects in the air are characterized by the anomalously large broadening up to ΔBpp = 32 mT, nearly two orders of magnitude in comparison with the initial samples. It is established that broadening is caused by the interaction of the spins of defects with molecular oxygen. The latter is adsorbed on the surface of the samples in a high concentration because the samples have a high porosity formed with the participation of ash nanoclusters, including FexOy. The observed EPR dynamics are very complex. It depends on the initial conditions of signal observation, the occurrence of other gases, e.g. nitrogen, and drastically on the humidity of the environment. For example, holding samples in the water vapor at T = 100 °C reduces the ΔBpp from ∼17.5 mT to 3.2 mT for a time of nearly t ∼24 s. Using the strong effect of oxygen on the broadening of the studied samples, the kinetics of competitive processes of adsorption/desorption of N2↔O2↔H2O on the carbon surface is studied in detail. The unusual adsorption kinetics for the mixture of O2 and N2 gases, caused by a difference in the diffusion rates, was found.