RESUMO
H2 has been comprehensively deemed a promising potential candidate to replace traditional fossil fuel-based energy. Typically, the hydrolysis of most hydrogen-rich boron hydrides (e.g. NaBH4, NH3BH3 and Me2NHBH3) catalyzed by nanomaterials generates H2 with only one H atom supplied by water and the other one by a hydrogen-rich boron hydride. Interestingly, both H atoms of produced H2 are provided by water upon hydrolysis of B2(OH)4. Herein, the catalytic mechanisms of H2 evolution upon water splitting at the expense of B2(OH)4 in its hydrolysis reactions catalyzed by acid, base or metal nanoparticles have been investigated by density functional theory (DFT) calculations. By computational studies, the mechanisms of catalysis by base and metal nanoparticles are basically the same as those speculated from our previous experiments. The previously proposed acid catalytic mechanism has been overturned, however. This study not only provides important insights into the catalytic mechanism for water splitting at the expense of B2(OH)4, but also opens up an exciting opportunity to use water to store H2.
RESUMO
Importance: Organ transplant is a life-saving procedure for patients with end-stage organ failure. In the US, organ procurement organizations (OPOs) are responsible for the evaluation and procurement of organs from donors who have died; however, there is controversy regarding what measures should be used to evaluate their performance. Objective: To evaluate OPO performance metrics using combined mortality and donation data and quantify the associations of population demographics with donation metrics. Design, Setting, and Participants: This national cohort study includes data from the US organ transplantation system from January 2008 through December 2017. All individuals who died within the US, as reported by the National Death index, were included. Exposures: Death, organ donation, and donation eligibility. Main Outcomes and Measures: Evaluation of the variation in donation metrics and the use of ineligible donors by OPO and demographic subgroup. Results: This study included 17â¯501â¯742 deaths and 75â¯769 deceased organ donors (45â¯040 men [59.4%]; 51â¯908 White individuals [68.5%]). Of these donors, 15â¯857 (20.9%) were not eligible, as defined by the OPOs. The median donation metrics by OPO were 0.004 (range, 0.002-0.012) donors per death, 0.89 (range, 0.68-1.30) donors per eligible death, and 0.72 (range, 0.57-0.86) eligible donors per eligible death. The OPOs in the upper quartile of the overall eligible donors per eligible death metric were in the upper quartile of annual rankings on 90 of 140 occasions (64.3%). There was little overlap in top-performing OPOs between metrics; an OPO in the upper quartile for 1 metric was also in the upper quartile for the other metrics on 37 of 570 occasions (6.5% of the time). The median donor eligibility rate, defined as the number of eligible donors per donor, was 0.79 (range, 0.61-0.95) across OPOs. Age (eg, 65 to 84 years, coefficient, -0.55 [SE, 0.03]; P < .001; vs those aged 18 to 34 years), sex (male individuals, -0.09 [SE, 0.02]; P < .001; vs female individuals), race (eg, Black individuals, 0.35 [SE, 0.02]; P < .001; vs White individuals), cause of death (eg, central nervous system tumor, 0.48 [SE, 0.08]; P < .001; vs anoxia), year (eg, 2016-2017: -0.10 [SE, 0.03]; P < .001; vs 2008-2009), and OPO were associated with the use of ineligible donors; OPO was a significant factor associated with performance in all metrics (χ256, 500.5; P < .001; coefficient range across individual OPOs, -0.15 [SE, 0.09] to 0.75 [SE, 0.09]), even after accounting for population differences. Female and non-White individuals were significantly less likely to be used as ineligible donors. Conclusions and Relevance: We demonstrate significant variability in OPO performance rankings, depending on which donation metric is used. There were significant differences in OPO performance, even after accounting for differences in potential donor populations. Our data suggest significant variation in use of ineligible donors among OPOs, a source for increased donors. The performance of OPOs should be evaluated using a range of donation metrics.