Predictive performance of the variation rate of the driving pressure on the outcome of invasive mechanical ventilation in patients with acute respiratory distress syndrome.

PURPOSE: To assess the value of the driving pressure variation rate (ΔP%) in predicting the outcome of weaning from invasive mechanical ventilation in patients with acute respiratory distress syndrome. METHODS: In this case-control study, a total of 35 patients with moderate-severe acute respiratory distress syndrome were admitted to the intensive care unit between January 2022 and December 2022 and received invasive mechanical ventilation for at least 48 h were enrolled. Patients were divided into successful weaning group and failed weaning group depending on whether they could be removed from ventilator support within 14 days. Outcome measures including driving pressure, PaO2:FiO2, and positive end-expiratory pressure, etc. were assessed every 24 h from day 0 to day 14 until successful weaning was achieved. The measurement data of non-normal distribution were presented as median (Q1, Q3), and the differences between groups were compared by Wilcoxon rank sum test. And categorical data use the Chi-square test or Fisher's exact test to compare. The predictive value of ΔP% in predicting the outcome of weaning from the ventilator was analyzed using receiver operating characteristic curves. RESULTS: Of the total 35 patients included in the study, 17 were successful vs. 18 failed in weaning from a ventilator after 14 days of mechanical ventilation. The cut-off values of the median ΔP% measured by Operator 1 vs. Operator 2 in the first 4 days were ≥ 4.17% and 4.55%, respectively (p < 0.001), with the area under curve of 0.804 (sensitivity of 88.2%, specificity of 64.7%) and 0.770 (sensitivity of 88.2%, specificity of 64.7%), respectively. There was a significant difference in mechanical ventilation duration between the successful weaning group and the failure weaning group (8 (6, 13) vs. 12 (7.5, 17.3), p = 0.043). The incidence of ventilator-associated pneumonia in the successful weaning group was significantly lower than in the failed weaning group (0.2‰ vs. 2.3‰, p = 0.001). There was a significant difference noted between these 2 groups in the 28-day mortality (11.8% vs. 66.7%, p = 0.003). CONCLUSION: The median ΔP% in the first 4 days of mechanical ventilation showed good predictive performance in predicting the outcome of weaning from mechanical ventilation within 14 days. Further study is needed to confirm this finding.

Similar electronic state effect enables excellent activity for nitrate-to-ammonia electroreduction on both high- and low-density double-atom catalysts.

Double-atom catalysts (DACs) for harmful nitrate (NO3-) electroreduction to valuable ammonia (eNO3RR) is attractive for both environmental remediation and energy transformation. However, the limited metal loading in most DACs largely hinders their applications in practical catalytic applications. Therefore, exploring ultrahigh-density (UHD) DACs with abundant active metal centers and excellent eNO3RR activity is highly desired under the site-distance effect. Herein, starting from the experimental M2N6 motif deposited on graphene, we firstly screened the low-density (LD) Mn2N6 and Fe2N6 DACs with high eNO3RR activity and then established an appropriate activity descriptor for the LD-DAC system. By utilizing this descriptor, the corresponding Mn2N6 and Fe2N6 UHD-DACs with dynamic, thermal, thermodynamic, and electrochemical stabilities, are identified to locate at the peak of activity volcano, exhibiting rather-low limiting potentials of -0.25 and -0.38 V, respectively. Further analysis in term of spin state and orbital interaction, confirms that the electronic state effect similar to that of LD-DACs enable the excellent eNO3RR activity to be maintained in the UHD-DACs. These findings highlight the promising application of Mn2N6 and Fe2N6 UHD-DACs in nitrate electroreduction for NH3 production and provide impetus for further experimental exploration of ultrahigh-density DACs based on their intrinsic electronic states.

Theoretical insights into the electroreduction of nitrate to ammonia on graphene-based single-atom catalysts.

Electrocatalytic reduction of harmful nitrate (NO3-) to valuable ammonia (eNO3RR) is critical and attractive for both environmental remediation and energy transformation. A single atom catalyst (SAC) based on graphene represents one of the most promising eNO3RR catalysts. However, the underlying catalytic mechanism and the intrinsic factors dictating the catalytic activity trend remain unclear. Herein, using first-principles calculations, eNO3RR on TMN3 and TMN4 (TM = Ti-Ni) doped graphene was thoroughly investigated. Our results reveal that FeN4 doped graphene exhibits excellent eNO3RR performance with a low limiting potential of -0.38 V, agreeing with the experimental finding, which can be ascribed to the effective adsorption and activation of NO3-via the charge "acceptance-donation" mechanism and its moderate binding due to the occupation of the d-p antibonding orbital. In particular, we found that eNO3RR activities are well correlated with the intrinsic properties of TM centers and their local environments. With the established activity descriptor, several other graphene-based SACs were efficiently screened out with excellent eNO3RR performance. Our studies could not only provide an atomic insight into the catalytic mechanism and activity origin of eNO3RR on graphene-based SACs, but also open an avenue for the rational design of SACs for eNO3RR towards ammonia by regulating the metal center and its local coordination environment.

Single-atom catalysts based on TiN for the electrocatalytic hydrogen evolution reaction: a theoretical study.

The electrocatalytic hydrogen evolution reaction (HER) for water splitting is crucial for the sustainable production of clean hydrogen fuel, while the high cost of Pt catalysts impedes its commercialization. Herein, we have performed a systematic theoretical study on the electrocatalytic HER over single-atom catalysts (SACs) based on low-cost TiN. Specifically, the TiN(100) surface with a Ti or N vacancy has been considered as the support. 20 transition-metal (TM) atoms and 3 nonmetallic atoms are embedded into the Ti or N vacancy, accordingly denoted as M@Tiv or M@Nv. All the single atoms can be stabilized by the surface vacancies, controlled by the adjustable chemical potential. Interestingly, for TM-embedded TiN(100), the hydrogen binding is much stronger over M@Nv than M@Tiv, which can be attributed to the more localized d states of the TM atoms anchored by the N vacancies, indicating a strong coordination effect. Among 43 catalysts, 10 (Ni, Zn, Nb, Mo, Rh@Tiv, and Au, Pd, W, Mo, B@Nv) were predicted to have high HER catalytic activity with near-zero hydrogen adsorption free energy. For the further gaseous hydrogen evolution, Zn@Tiv can adopt both Tafel (with an energy barrier of 0.68 eV) and Heyrovsky mechanisms, while the others may prefer the Heyrovsky mechanism. This work provides a promising strategy to realize cost-efficient electrocatalysts for the HER, and highlights the important role of the local coordination environment for SACs.

Study of water adsorption on graphene edges.

Water adsorption on graphene edges was studied by field emission (FE) experiments and first principles simulation. By analyzing the FE current change with temperature, it was concluded that the intrinsic FE of a graphene edge is consistent with Fowler-Nordheim (FN) theory. The noise of IV and non-linearity of FN curves at room-temperature can be interpreted by the adsorption effects. Water is speculated as the most responsible gas specie. We have calculated the work function of graphene by VASP. The results show that water adsorption will lower the work function of the graphene edge, while increasing the work function of the graphene surface.