Low Partial Pressure Research Articles

Kinetics of Liquid-Phase 1-Butene Hydroisomerization over Pd/Al2O3 Catalysts

Liquid-phase 1-butene hydroisomerization to 2-butene is an important approach to utilize cheap and abundant C4 olefins (normally as by-products from refinery processes), and the reaction kinetics is critical to the development of its reactors and catalysts. Herein, kinetics experiments are performed to understand the characteristics of liquid-phase 1-butene hydroisomerization over a commercial Pd/Al2O3 catalyst, and three intrinsic kinetics models are proposed to describe the rates of the hydroisomerization and hydrogenation reactions. The results show that the selectivity toward 2-butene increases with temperature, indicating the hydrogenation reactions are suppressed due to the low partial pressure of hydrogen under high temperature. The fraction of hydrogen in reactants significantly affects 1-butene conversion and 2-butene selectivity, and thus, this effect should be included in kinetics models. Comparing the proposed power-law, dual-site Langmuir–Hinshelwood, and single-site Langmuir–Hinshelwood models, the single-site Langmuir–Hinshelwood model is the best in predicting the experiments, implying that hydroisomerization and hydrogenation reactions may occur at the same type of active sites under the reaction conditions in this work. The activation energies of the hydroisomerization reactions are lower than those of the hydrogenation reaction, and the adsorption enthalpy of butenes is smaller than that of hydrogen.

The effect of ammonia partial pressure on the growth of semipolar (11–22) InGaN/GaN MQWs and LED structures

This paper presents the effect of ammonia partial pressure at a relatively low fixed V/III (∼765) growth atmosphere on the growth of multi-quantum well (MQW) structures and the light emitting diode (LED) emission wavelength. At fixed V/III ratio, ammonia partial pressure together with the consequent group III partial pressures are shown to influence the growth of InGaN/GaN MQWs in term of growth rate and the indium incorporation for the quantum well. It is also observed that the growth of InGaN quantum well (QW) behaves differently as compared to GaN quantum barrier (QB) at low V/III ambient. For the growth of InGaN QW, the data collected shows the existence of threshold point for ammonia partial pressure of ∼300 Pa. In the regime below the threshold value, the decomposition of InGaN due to severe dissociation of In-N bonds caused the growth rate to be extremely low. As the ammonia partial pressure increases above the threshold value, the growth rate of InGaN QW increases sharply together with an improvement in indium incorporation, as proven by the XRD and (11–24) asymmetric reciprocal space mapping (RSM) results. The XRD result is consistent with the atomic force microscopy (AFM) results. As the partial pressures increases, the RMS and peak-to-valley roughness increases which is credited to the increment in indium incorporation. Furthermore, “needle-like” structures can be observed over all samples when the MQWs were grown with limited ammonia partial pressure. During the growth for the LED structure with thin layers of InGaN/GaN, the partial pressure of ammonia became a dominating factor in the formation of well-abrupt layer interfaces. Through the XRD and room-temperature photoluminescence (RTPL) results, it is shown that abrupt layers can be formed at higher ammonia partial pressures, while indium clusters tend to form at a lower partial pressure, which are most probably due to the insufficient N concentration, while the electroluminescence (EL) results were consistent as well. Therefore, it is once again confirmed that the performance of the InGaN/GaN LED is highly governed by the partial pressures of the ammonia.

Experimental Analysis of Reaction Heat of CO2 Absorption of Phase Change Absorber AEP-DPA at Low Partial Pressure

The reaction heat of CO2 absorption by organic amines is directly related to the regenerative heat consumption of absorbers. Therefore, it is necessary to study and determine the heat of absorption reaction and heat of regeneration reaction of CO2 capture solvent before its industrial validation and application. According to the law of thermodynamics, a computer model of the heat of absorption reaction and desorption reaction is established and verified. The heat of reaction of the AEP-DPA phase transition absorption system was studied under different ratios, absorption temperatures, reaction concentrations and reaction pressures. The heat of reaction increases with concentration and decreases with pressure. The reaction heat of the AEP-DPA phase transition absorption system and MEA were compared. The optimum reaction conditions were as follows: AEP-DPA ratio 6:4, absorption temperature 40 °C. The reduction rate of absorption heat and regenerative heat of the AEP-DPA phase change absorption system is more than 35% and 31%, respectively.

Trace level of atomic copper in N-doped graphene quantum dots switching the selectivity from C1 to C2 products in CO electroreduction

To unravel the relationship between trace Cu on the metal-free catalysts toward CO/CO2 reduction reaction (CO/CO2RR), we investigated the effect of trace Cu loading in N-doped graphene quantum dots (NGQDs) on CO/CO2RR. A general trend is that increasing the Cu loading in NGQDs switches the selectivity from C1 (CH4) to C2 products in CORR. When 2.5 μg/cm2 Cu with the atomic size is loaded on NGQDs, the selectivity shifts from 62% Faradaic efficiency (FE) of CH4 to 52% FE of C2 products in CORR. Further increasing the atomic Cu loading to 3.8 μg/cm2 promotes the FE of C2 products to 78%. CO2RR requires one order of magnitude higher Cu loading than CORR to switch the selectivity from C1 to C2 products due to the low partial pressure of CO. This study clarifies the distinct impact of trace (ppm level) Cu on the activity/selectivity between CORR and CO2RR.

Improvement of NO adsorptive selectivity by the embedding of Rh in MOF‐177 as carrier

In this paper, MOF‐177 was embedded with Rh for the improvement of NO adsorptive selectivity at room temperature. The results showed that the experimental NO saturated adsorption capacity of MOF‐177 was very limited value of 1.35 mL·g−1 with a negligible selectivity, but the embedded 3 wt % Rh/MOF‐177 improved it to 16 mL·g−1 with higher maximal selectivity of NO to CO2 (352) and to O2 (600) under low partial pressure. In the simulated mixture gas, the adsorption capacity of NO atmosphere was about 9–18 times higher than that of O2 and CO2, and the adsorptive selectivity was up to near 18. The reductive Rh particles in MOF‐177 were basically nanometer‐sized higher dispersion state by great carrier function of MOF‐177. The pulse adsorption experiments verified that one reduced Rh0 adsorbed three NO molecules, indicating that the NO adsorption form in Rh/MOF‐177 should be a trinitro‐group (Rh (NO)3) adsorbed species in low pressure. This work firstly illustrated that the MOFs materials embedded with metal particle such as Rh can obviously improve NO adsorption selectivity and also provided a reference way for functionalized modification of MOFs materials to enhance the adsorptive separation performance of pollutant NO in flue gas.

Gender differences in clinical characteristics of patients with non-cystic fibrosis bronchiectasis in different age groups in northern China.

Patient gender has clinical and prognostic implications in non-cystic fibrosis bronchiectasis, yet the potential effect of gender on clinical characteristics of patients with non-cystic fibrosis bronchiectasis is still unclear. This study aimed to investigate the gender differences in clinical characteristics of patients with bronchiectasis in different age groups in northern China. A total of 777 patients diagnosed with bronchiectasis were retrospectively included in Beijing Chaoyang Hospital and divided into two groups by gender: the male group and the female group. Each group was then subdivided into two according to their age (≤65 and >65 years). Gender differences in clinical characteristics were compared in all patients with bronchiectasis in the two age groups, respectively. A total of 777 bronchiectasis patients were included. Of these patients, the prevalence of female non-smokers was substantially higher than that of male non-smokers (94.0% vs. 36.8%). There were gender differences in etiology of bronchiectasis, with more post-measles and connective tissue disease in females (p = 0.006 and 0.002 separately) and more chronic obstructive pulmonary disease (COPD) in males (p < 0.001). The male group had a significantly higher C-reactive protein (CRP) on admission (p = 0.03). Female patients showed a higher forced expiratory volume in 1 s as percentage of predicted volume (FEV1%pred) and forced vital capacity rate of 1 s (FEV1/FVC) (p < 0.001), lower partial pressure of carbon dioxide (PaCO2 ) (p = 0.04) and hospital costs (p = 0.02) than males, and a higher prevalence of infection with Pseudomonas aeruginosa in >65-year-old group (p = 0.019). There were many differences between male and female patients in smoking status, etiology, lung function, blood gas analysis, and hospital costs in all patients or different age groups.

Logistic Regression Analysis of Clinical Characteristics for Differentiation of Chronic Obstructive Pulmonary Disease Severity.

This study aimed to investigate the predictive value of general clinical data, blood test indexes, and ventilation function test indexes on the severity of chronic obstructive pulmonary disease (COPD). A total of 141 clinical characteristics of COPD patients admitted to our hospital were collected. A mild-to-moderate group and a severe group were classified depending on the severity of COPD, and their baseline data were compared. The predictive factors of severe COPD were analyzed by univariate and multivariate logistic regression, and the nomogram model of severe COPD was constructed. The clinical variables, including gender, height, weight, body mass index (BMI), age, course, diabetes, hypertension, smoking history, WBC, NEUT, lymphocyte count (LY), MONO, eosinophil count (EOS), PLT, mean platelet volume (MPV), platelet distribution width (PDW), partial pressure of oxygen (PaO2), and PaCO2, were collected. There were 67 mild-to-moderate COPD patients and 74 severe COPD patients in this study cohort. Severe COPD had a higher white blood cell count (WBC), neutrophil count (NEUT), monocyte count (MONO), platelet count (PLT), neutrophil to lymphocyte ratio (NLR), and a lower partial pressure of carbon dioxide (PaCO2). Univariate logistic regression analysis showed that WBC, NEUT, MONO, PLT, and NLR were contributing factors of severe COPD, while PaCO2 was an unfavorable factor of severe COPD. Enter, forward, backward, and stepwise multivariate logistic regression analyses all showed that NEUT and PLT were independent contributing factors to severe COPD. Moreover, the nomogram model had good predictive ability, with an area under the curve (AUC) of the receiver operating characteristic (ROC) curve being 0.881. Good calibration and clinical utility were validated through the calibration plot and the decision curve analysis (DCA) plot, respectively. The severity of COPD was correlated with NEUT and PLT, and the nomogram model based on these factors had good predictive performance.

An international survey exploring the adoption and utility of diagnostic lung ultrasound by physiotherapists and respiratory therapists in intensive care.

Lung ultrasound (LUS) is an emerging assessment tool for intensive care unit (ICU) therapists (physiotherapists, physical therapists and respiratory therapists) to aid pathology identification, intervention selection, clinical reasoning and as an outcome measure to assess intervention efficacy. However, the extent of LUS adoption and use by ICU therapists internationally has not been described in the literature. This survey explored the interest in LUS amongst ICU therapists internationally. In addition, LUS training, use in clinical practice and barriers to implementation were also explored. The survey findings were used to facilitate recommendations for future adoption. International ICU therapists were invited to answer a 37 question cross-sectional open e-survey, distributed using the online survey tool REDCap®. The exact sample size of eligible ICU therapists from around the world is unknown, therefore the participant responses received were a representative convenience sample of the international ICU therapist population. Survey links were posted on the relevant web pages and social media forums utilised by various ICU therapist associations and professional organisations worldwide. A snowballing technique was used to encourage survey participants to forward the survey link within their professional networks. The survey was open on REDCap® for an 8-week period between March and May 2021. Three hundred twenty ICU therapists from 30 countries responded with most respondents coming from either the United Kingdom (n = 94) or Australia (n = 87). Eighty-nine of the ICU therapist respondents (30%) reported being users of LUS, however, 40 of those 89 respondents reported having no formal accreditation. The top clinical indications to perform a LUS scan were changes on chest radiograph, altered findings on auscultation and a low partial pressure of arterial oxygen/fraction of inspired oxygen ratio. The 71% of LUS users reported that their ICU does not have a local policy in place to guide ICU therapists' use of LUS. Most LUS users (82%) only document their LUS findings in the patient's medical notes and (73%) only store the LUS clips on the ICU's ultrasound machine. The 85% of respondents perceive LUS becoming an increasing part of their objective assessment in the future and 96% report that they have other ICU therapist colleagues interested in adopting LUS. Main reasons why respondents believe that ICU therapists are not adopting LUS in their ICU are a difficulty in access to appropriate training, mentorship, and a lack of local governance policy guiding their use of LUS. To the authors' knowledge this is the first study to explore the international adoption and utility of LUS by ICU therapists. LUS is a growing technique with widespread interest from ICU therapists internationally with a desire to adopt LUS into their assessments and upskill their practice. ICU therapists' use of LUS could allow more targetted and appropriate treatment for patients on ICU. Barriers to LUS adoption could be mitigated by having access to quality training programmes and mentorship. Development of profession specific guidance and policies within local infrastructure should facilitate growth and ensure robust quality assurance and governance processes.

Reticular Design of Precise Linker Installation into a Zirconium Metal–Organic Framework to Reinforce Hydrolytic Stability

Reticular chemistry allows for the rational assembly of metal-organic frameworks (MOFs) with designed structures and desirable functionalities for advanced applications. However, it remains challenging to construct multi-component MOFs with unprecedented complexity and control through insertion of secondary or ternary linkers. Herein, we demonstrate that a Zr-based MOF, NU-600 with a (4,6)-connected she topology, has been judiciously selected to employ a linker installation strategy to precisely insert two linear linkers with different lengths into two crystallographically distinct pockets in a one-pot, de novo reaction. We reveal that the hydrolytic stability of these linker-inserted MOFs can be remarkably reinforced by increasing the Zr6 node connectivity, while maintaining comparable water uptake capacity and pore-filling pressure as the pristine NU-600. Furthermore, introducing hydrophilic -OH groups into the linear linker backbones to construct multivariate MOFs can effectively shift the pore-filling step to lower partial pressures. This methodology demonstrates a powerful strategy to reinforce the structural stability of other MOF frameworks by increasing the connectivity of metal nodes, capable of encouraging developments in fundamental sciences and practical applications.

Cyclic CO2 capture behavior of slag-derived Li4SiO4: A kinetic analysis of CO2 desorption

Two slag-derived Li4SiO4 were synthesized using metallurgical slags as silica sources and used as CO2 sorbents. The CO2 desorption process was studied using a fixed temperature during the sorption step, with different CO2 partial pressures and several desorption temperatures. The kinetic parameters of the CO2 desorption were studied using the Avrami-Erofeev and zero-order models. With the latter, it was possible to calculate the activation energy of the desorption during the first minutes of the process, while with the Avrami-Erofeev model, only the energy associated with the second stage of the model was obtained. The calculated energies with the Avrami model were at least three orders of magnitude greater than the sorption stages reported values. Moreover, both models showed that the Li4SiO4 derived from the electric arc furnace (EAF) slag is less dependent on temperature than the derived from the blast furnace (BF). The kinetic parameters of desorption were also calculated for several regeneration cycles, where it was found that the k values diminish when lower partial pressures of CO2 (PCO2) were used. Finally, the structural evolution after the cyclic study showed the formation of secondary phases in the slag-derived silicates.

Pulmonary ventilation and gas exchange during prolonged exercise in humans: Influence of dehydration, hyperthermia and sympathoadrenal activity.

What is the central question of the study? Ventilation increases during prolonged intense exercise, but the impact of dehydration and hyperthermia, with associated blunting of pulmonary circulation, and independent influences of dehydration, hyperthermia and sympathoadrenal discharge on ventilatory and pulmonary gas exchange responses remain unclear. What is the main finding and its importance? Dehydration and hyperthermia led to hyperventilation and compensatory adjustments in pulmonary CO2 and O2 exchange, such that CO2 output increased and O2 uptake remained unchanged despite the blunted circulation. Isolated hyperthermia and adrenaline infusion, but not isolated dehydration, increased ventilation to levels similar to combined dehydration and hyperthermia. Hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise, partly via sympathoadrenal activation. The mechanisms driving hyperthermic hyperventilation during exercise are unclear. In a series of retrospective analyses, we evaluated the impact of combined versus isolated dehydration and hyperthermia and the effects of sympathoadrenal discharge on ventilation and pulmonary gas exchange during prolonged intense exercise. In the first study, endurance-trained males performed two submaximal cycling exercise trials in the heat. On day 1, participants cycled until volitional exhaustion (135± 11min) while experiencing progressive dehydration and hyperthermia. On day 2, participants maintained euhydration andcore temperature (Tc ) during a time-matched exercise (control). At rest and during the first 20min of exercise, pulmonary ventilation ( ), arterial blood gases, CO2 output and O2 uptake were similar in both trials. At 135±11min, however, was elevated with dehydration and hyperthermia, and this was accompanied by lower arterial partial pressure of CO2 , higher breathing frequency, arterial partial pressure of O2 , arteriovenous CO2 and O2 differences, and elevated CO2 output and unchanged O2 uptake despite a reduced pulmonary circulation. The increased was closely related to the rise in Tc and circulating catecholamines (R2 ≥0.818, P≤0.034). In three additional studies in different participants, hyperthermia independently increased to an extent similar to combined dehydration and hyperthermia, whereas prevention of hyperthermia in dehydrated individuals restored to control levels. Furthermore, adrenaline infusion during exercise elevated both Tc and . These findings indicate that: (1) adjustments in pulmonary gas exchange limit homeostatic disturbances in the face of a blunted pulmonary circulation; (2) hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise; and (3) sympathoadrenal activation might partly mediate the hyperthermic hyperventilation.

Impact of the Si/Al ratio on the ethanol/water coadsorption on MFI zeolites revealed using original quantitative IR approaches.

Advanced IR vibrational spectroscopic techniques, e.g., using a coupled gravimetric-IR surface analyzer (AGIR) and a high-throughput in situ IR cell (Carroucell), have been used for the quantitative studies of the adsorption and coadsorption of ethanol and water on MFI zeolites with different Si/Al ratios. The AGIR coupling is a powerful tool for the accurate determination of the molar adsorption coefficients during coadsorption experiments since their evaluation is based on the measurement of the exact amount of adsorbed species. The use of the Carroucell set up allows characterizing all the samples simultaneously, strictly in the same gaseous and temperature environment. The molar absorption coefficients of pure adsorbed ethanol and water are determined: their values are constant whatever the Si/Al ratio of the MFI zeolites. Moreover, these coefficients are found to be identical in the case of the water-ethanol coadsorption experiments. Their use allows obtaining the exact quantity of each adsorbate specie in the binary system. At low partial pressures, the unary water adsorption experiments suggest that the amount of adsorbed water results mainly from the preferential adsorption on Brønsted acid sites in tetrameric clusters. In contrast, the adsorption of EtOH occurs on both silanol groups and Brønsted acid sites (BASs). The effect of the Si/Al ratio is only observed at relatively low partial pressures. The effect of the Si/Al ratio on the ethanol adsorption capacity is also investigated. This study directs the choice of an appropriate zeolite once it is used in membranes for drying ethanol.

Effects of Argon Partial Pressure Variations on Wettability and Anti-icing Characteristics of Aluminum Doped ZnO Thin Films

When ice forms on solid surfaces, it can cause issues in many different sectors (aircraft, electricity lines, etc.). Surfaces and coatings with hydrophobic qualities may be used in anti-icing applications. The purpose of this work is to utilize RF Magneton Sputtering to deposit AZO thin coatings, which will slow the accumulation of ice on the surface. The effects of changes in argon partial pressure on the anti-icing, wettability, optical, and structural properties of the resulting thin films have been experimentally investigated. X-ray diffraction demonstrated a (002) peak of ZnO, the intensity of the peak diminishes with an increase in partial pressure. The band gap was measured to be between 2.98 and 3.15 eV, and the average maximum transmittance was observed to be around 82% for 50% partial pressure and 71% for 33% partial pressure, confirming the transparency of the thin films. Wettability studies revealed that the films are hydrophobic with a maximum contact angle of 127.5°, which was deposited at lower partial pressure. Films deposited at 33% partial pressure delayed the formation of ice on the surface by 4.5 folds when compared to an uncoated substrate.

THE INFLUENCE OF PLASMA ASSISTANCE MODES ON CHARACTERISTICS AND COMPOSITION OF PVD ZIRCONIUM NITRIDE COATINGS

Zirconium nitride coatings are deposited by a vacuum-arc method at a low (0.01-0.04 Pa) nitrogen partial pressure in the modes without and with plasma assistance. The plasma assistance is provided by the operation of a gas plasma source based on a non-self-sustained arc discharge with thermionic and hollow cathodes. This new low-inertia method has not been practically studied in terms of formation of nitride coatings with different architecture (single-layer, multi-layer, gradient coatings). We note that the effect of plasma assistance (an increase of the nitrogen concentration in the nitride coating with the increasing nitrogen ion fraction in the gas-metal plasma) is practically unobservable in the ZrN coatings formed under the selected conditions. Furthermore, their phase compositions do not noticeably change and their physical, mechanical and tribological properties are not significantly improved.

Effect of transversus abdominis plane block combined with low-dose dexmedetomidine on elderly patients undergoing laparoscopic colectomy.

Colon cancer is a common malignancy, for which surgery is currently the preferred therapy. To assess the effect of transversus abdominis plane block (TAPB) combined with low-dose dexmedetomidine on elderly patients undergoing laparoscopic colectomy. Sixty-two elderly patients undergoing laparoscopic colectomy between March 2021 and March 2022 were randomly selected and equally divided into Group A (low-dose dexmedetomidine) and Group B (TAPB + low-dose dexmedetomidine) by the randomized double-blind method. The treatment outcomes were compared. The resting and active Visual Analogue Scale and Pittsburgh Sleep Quality Index scores were lower in Group B than those in Group A at 6 h, 1 day, 2 days and 3 days after operation (p < 0.05). The two groups had no significant differences in the levels of cluster of differentiation 4+ (CD4+), CD8+ and free Cor, CD4+/CD8+ ratio and NK cell level before anesthesia (p > 0.05). At 24 h after the operation, the level of CD4+, CD4+/CD8+ ratio and NK cell level were higher in Group B than those in Group A, and the levels of CD8+ and free Cor were lower in Group B (p < 0.05). Group B had higher partial pressure of oxygen ((45.52 ±11.14) mm Hg) and pH (7.42 ±0.06) (p < 0.05) and lower partial pressure of carbon dioxide ((4.05 ±0.32) mm Hg) than those of Group A (p < 0.05). TAPB combined with low-dose dexmedetomidine can exert better anesthetic, analgesic and sedative effects, and ameliorate stress responses.

Mechanical power ratio and respiratory treatment escalation in COVID-19 pneumonia: a secondary analysis of a prospectively enrolled cohort.

Under the hypothesis that mechanical power ratio could identify the spontaneously breathing patients with higher risk of respiratory failure, we assessed lung mechanics in non-intubated patients with COVID-19 pneumonia aimed at: 1) describe their characteristics; 2) compare lung mechanics between patients who received respiratory treatment escalation and those who did not; 3) identify variables associated with the need for respiratory treatment escalation. Secondary analysis of prospectively enrolled cohort involving 111 consecutive spontaneously breathing adults receiving continuous positive airway pressure, enrolled from September 2020 to December 2021. Lung mechanics, other previously reported predictive indices were calculated, as well as a novel variable: the mechanical power ratio (the ratio between the actual and the expected baseline mechanical power). Patients were grouped according to the outcome: 1) no-treatment escalation (patient supported in continuous positive airway pressure until improvement); 2) treatment escalation (escalation of the respiratory support to non-invasive or invasive mechanical ventilation); and the association between lung mechanics/predictive scores and outcome was assessed. At day 1, patients undergoing treatment escalation had similar spontaneous tidal volume than patients who did not (7.1 ± 1.9 vs 7.1 ± 1.4 mL/KgIBW; p=0.990). In contrast, they showed higher respiratory rate (20 ± 5 vs 18 ± 5 bpm; p=0.028), minute ventilation (9.2 ± 3.0 vs 7.9 ± 2.4 L/min; p=0.011), tidal pleural pressure (8.1 ± 3.7 vs 6.0 ± 3.1 cmH2O; p=0.003), mechanical power ratio (2.4 ± 1.4 vs 1.7 ± 1.5; p=0.042) and lower PaO2/FiO2 (174 ± 64 vs 220 ± 95; p=0.007). Mechanical power (AUC 0.738 [95%CI 0.636-0.839] p<0.001), the mechanical power ratio (AUC 0.734 [95%CI 0.625-0.844] p <0.001) and the pressure-rate index (AUC 0.733 [95%CI 0.631-0.835] p <0.001) showed the highest AUC. In this COVID-19 cohort, tidal volume was similar in patients undergoing treatment escalation and in patients who did not; mechanical power, its ratio, and pressure-rate index were the variables presenting the highest association with the clinical outcome.

Low partial pressure CO2 capture in packed tower by EHA+Diglyme water-lean absorbent

The results of beaker experiments (Fu et al., 2021, 2022) showed that water-lean 2-ethylhexan-1-amine (EHA) + diglyme absorbent has more advantages than the commercial water-based ethanolamine (MEA) absorbent in terms of characteristics of carbon dioxide (CO2) absorption and desorption.Verifying CO2 capture characteristics in a tower facility is essential to absorbents development. In this work, a pilot packed tower was set up and the Dg16 type polypropylene step ring was taken as packing to test the capture efficiency and mass transfer performance of EHA + diglyme water-lean absorbent for low partial pressure CO2, and then the effects of gas-liquid ratio, CO2 partial pressure and packing height on the capture performance were clarified. The results showed that the absorption of CO2 by EHA + diglyme water-lean absorbent was dominated by liquid-phase mass transfer in the packed tower. Compared with aqueous 30 wt%MEA, the water-lean EHA + diglyme achieved much higher CO2 capture efficiency and overall volumetric mass transfer coefficient. This work demonstrated the transition from water-free absorption to water-lean absorption under the existence of water vapor in flue gas. It can provide basic data for the design of the CO2 capture process based on water-lean absorption in packed towers.

Multiscale responses and recovery of soils to wildfire in a sagebrush steppe ecosystem

Ecological theory predicts a pulse disturbance results in loss of soil organic carbon and short-term respiration losses that exceed recovery of productivity in many ecosystems. However, fundamental uncertainties remain in our understanding of ecosystem recovery where spatiotemporal variation in structure and function are not adequately represented in conceptual models. Here we show that wildfire in sagebrush shrublands results in multiscale responses that vary with ecosystem properties, landscape position, and their interactions. Consistent with ecological theory, soil pH increased and soil organic carbon (SOC) decreased following fire. In contrast, SOC responses were slope aspect and shrub-microsite dependent, with a larger proportional decrease under previous shrubs on north-facing aspects compared to south-facing ones. In addition, respiratory losses from burned aspects were not significantly different than losses from unburned aspects. We also documented the novel formation of soil inorganic carbon (SIC) with wildfire that differed significantly with aspect and microsite scale. Whereas pH and SIC recovered within 37 months post-fire, SOC stocks remained reduced, especially on north-facing aspects. Spatially, SIC formation was paired with reduced respiration losses, presumably lower partial pressure of carbon dioxide (pCO2), and increased calcium availability, consistent with geochemical models of carbonate formation. Our findings highlight the formation of SIC after fire as a novel short-term sink of carbon in non-forested shrubland ecosystems. Resiliency in sagebrush shrublands may be more complex and integrated across ecosystem to landscape scales than predicted based on current theory.

Descriptors of Failed Extubation in Norwood Patients Using Physiologic Data Streaming

The objective of this study is to evaluate the utility of high-frequency physiologic data during the extubation process and other clinical variables for describing the physiologic profile of extubation failure in neonates with hypoplastic left heart syndrome (HLHS) post-Norwood procedure. This is a single-center, retrospective analysis. Extubation events were collected from January 2016 until July 2021. Extubation failure was defined as the need for re-intubation within 48h of extubation. The data included streaming heart rate, respiratory rate, blood pressure, arterial oxygen saturation, and cerebral/renal near-infrared spectroscopy (NIRS). The most recent blood laboratory results before extubation were also included. These markers, demographics, clinical characteristics, and ventilatory settings were compared between successful and failed extubations. The analysis included 311 extubations. The extubation failure rate was 10%. According to univariable analyses, failed extubations were preceded by higher respiratory rates (p = 0.029), lower end-tidal CO2 (p = 0.009), lower pH (p = 0.043), lower serum bicarbonate (p = 0.030), and lower partial pressure of O2 (p = 0.022). In the first 10min after extubation, the failed events were characterized by lower arterial (p = 0.028) and cerebral NIRS (p = 0.018) saturations. Failed events were associated with persistently lower values for cerebral NIRS 2h post-extubation (p = 0.027). In multivariable analysis, vocal cord anomaly, cerebral NIRS at 10min post-extubation, renal NIRS at pre-extubation and post-extubation, and end-tidal CO2 at pre-extubation remained as significant co-variables. Oximetric indices before, in the 10min immediately after, and 2h after extubation and vocal cords paralysis are associated with failed extubation events in patients with parallel circulation.

Ceria-Supported Cobalt Catalyst for Low-Temperature Methanation at Low Partial Pressures of CO2.

The direct catalytic conversion of atmospheric CO2 to valuable chemicals is a promising solution to avert negative consequences of rising CO2 concentration. However, heterogeneous catalysts efficient at low partial pressures of CO2 still need to be developed. Here, we explore Co/CeO2 as a catalyst for the methanation of diluted CO2 streams. This material displays an excellent performance at reaction temperatures as low as 175 °C and CO2 partial pressures as low as 0.4 mbar (the atmospheric CO2 concentration). To gain mechanistic understanding of this unusual activity, we employed in situ X-ray photoelectron spectroscopy and operando infrared spectroscopy. The higher surface concentration and reactivity of formates and carbonyls-key reaction intermediates-explain the superior activity of Co/CeO2 as compared to a conventional Co/SiO2 catalyst. This work emphasizes the catalytic role of the cobalt-ceria interface and will aid in developing more efficient CO2 hydrogenation catalysts.